JPS6115372B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an AC surface potentiometer for measuring the surface potential of a charged object.

In a conventional AC surface potentiometer, for example, as shown in FIG.
A rotating sector 4 made of metal was provided between the sensing electrode 6 and the aperture 2, and the rotating sector 4 was configured to be rotated by a motor 5.
For example, as shown in FIG. However, this electrostatic field changes, and an alternating current voltage is generated at the detection electrode 6. By detecting this AC voltage with the detection device 7, the surface potential of the object to be measured 8 can be measured.

The surface potential is measured as described above, but at this time, high-pressure air is sent from the air inlet 3 to increase the pressure inside the shield case 1, and at the same time, the air is exhausted from the aperture 2 to remove dust, etc. from inside the shield case 1. was preventing the intrusion of

Also, instead of the rotating sector shown in Figure 1,
Some use a tuning fork or solenoid to vibrate a metal disc or the like.

However, such conventional AC surface potentiometers require a rotating sector to generate fluctuations in the electric field, a motor to drive the metal disk, a tuning fork,
Since a drive source such as a solenoid and a device such as an air pump that sends an air flow to prevent the intrusion of dirt and the like are provided independently, it is difficult to miniaturize the device. Furthermore, since the drive source must be installed near the detection electrode, there are also drawbacks such as the tendency to generate noise due to vibrations from the vibration source.

This invention improves the above-mentioned conventional drawbacks, and eliminates either the drive source for the device that uses a fan to fluctuate the electric field or the drive source for the device that generates airflow. The object of the present invention is to reduce the size of the surface electrometer as a whole, reduce noise generation, reduce failures, and improve reliability.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 is a diagram showing an embodiment of the present invention. In the figure, 1 is a shield case, and an aperture 2 is formed in a part of the surface facing the object to be measured 8, and an air pump or the like is connected to the upper part of the shield case. An air inlet 3 is provided for introducing air. Reference numeral 6 denotes a detection electrode, which is arranged at a position to receive the electric field entering from the aperture 2. 7 is a detection device for detecting the alternating current voltage induced on the detection electrode 6; 9 is a fan; as shown in the perspective view of FIG. 9a, 9b,
9c, 9d, . . . The fan 9 is mounted on the shield case 1 so that a part of the blade is located between the aperture 2 and the detection electrode 6.
It is rotatably attached to the A light source 10 such as an LED is arranged so as to reflect light on a part of the blade of the fan, and a light receiving element 1 such as a phototransistor is placed at a position where this irradiated light is received by the light reflected by the blade.
1 is placed.

Next, the operation of this embodiment will be explained. When the aperture 2 is arranged to face the object to be measured 8 and air is supplied into the shield case 1 from the air inlet 3 using an air pump or the like, this air flow is exhausted from the aperture 2. Therefore, it is also possible to prevent dust and the like from entering the shield case 1 from the aperture 2. Further, as in the conventional case, by increasing the air pressure inside the shield case 1, it is possible to prevent dust and the like from entering through gaps other than the aperture 2.

At the same time as the above action, the fan 9 is
is rotated, the electrostatic field entering from the aperture 2 causes the blades 9a, 9b, 9c, 9 of the fan 9 to
Fluctuations are generated by d,... Therefore, since an alternating current voltage is generated in the detection electrode 6, the surface potential of the object to be measured 8 can be measured by detecting this alternating voltage using the detection device 7 in the same manner as in the conventional method. While this measurement is being made
The number of rotations of the fan 9 can be detected by emitting light from a light source 10 such as an LED, reflecting it off the blades of the fan 9, and detecting the reflected light using a light receiving element 11 such as a photo transistor.

FIG. 3 is a diagram for explaining the surface potential detection principle of the embodiment shown in FIG. 2, and the same parts as those in FIG. 2 are designated by the same reference numerals. In the figure, Vi is a voltage that equivalently represents the potential on the surface of the object to be measured.
If the electric field generated at the position of the sensing electrode 6 by this voltage Vi is integrated over the area of the sensing electrode 6 as E, the permittivity is εo, the output voltage generated across the resistor R is Vo, and the time is t, then Vo=Rεo ∂E/∂t, (εo∴permittivity). Further, when the rotational speed n of the fan 9 changes, the output voltage Vo changes as shown in FIG. Therefore, as can be seen from FIG. 4, variations in the rotational speed n cause variations in the output voltage Vo, resulting in measurement errors. Therefore, if the rotation speed n of the fan 9 is detected by the light receiving element 11 as described above and further converted into a voltage proportional to the rotation speed by the frequency-voltage converter 10, the output voltage Vo' of this converter 10 is changes as shown in FIG. 5 with respect to the rotational speed n. Therefore, when this output voltage Vo' and the output voltage Vo' are input to the differential amplifier 11, the difference between the input voltages Vo and Vo' is amplified to generate an output Vo'' (see FIG. 2). This output voltage Vo'' remains constant as shown in FIG. 6 with respect to changes in the rotational speed n. That is, even if the rotational speed n of the fan 9 changes due to changes in the airflow, there is no substantial effect on the measurement output, and sufficient compensation can be achieved.

Figure 7 shows the voltage when the above compensation is performed.
This shows the relationship between Vi and the output voltage Vo'', and as can be seen from this figure, the rotation speed n of the fan 9 is ±Δ
This shows that even if the rotation speed n varies by n, it has no effect on the output voltage at all.If such compensation is not performed, as shown in Figure 8, when the rotational speed n fluctuates by ±Δn, the output voltage Vo will fluctuate within the shaded range, making it impossible to make accurate measurements. Therefore, in this embodiment, the above compensation is performed.

As described above with respect to the embodiments, according to the present invention, there is no need to separately provide a drive source used to generate fluctuations in the electric field, making it possible to downsize the device and reduce failures. ,
This has many effects such as improving reliability.

In the above embodiment, the fan 9 may be driven directly by a motor, and in that case, the fan itself takes in air from the air inlet 3 and exhausts it from the aperture 2, so there is no need to use an air pump or the like. There is no need to supply air, and effects substantially equivalent to those of the previous embodiment can be obtained.

FIG. 9 shows the main parts of a copying machine as an example of a device in which the surface electrometer according to the present invention is used.
A is a charged corona generator, B is a light for forming a latent image,
C is a surface electrometer according to the present invention, D is a developing machine, and E is a
is transfer paper, F is transfer device, G is static elimination corona generator,
H indicates a photosensitive drum.

In a copying machine with such a configuration, a surface electrometer C is installed as shown in the figure to measure the latent image potential, and calculate the charging corona voltage, the bias voltage applied to the developing device, the transfer device voltage, the neutralizing corona voltage, and the latent image potential. The amount of light B for image formation is controlled to the optimum value for copying.

When a surface electrometer is used in such a location, developer is constantly scattered during copying, which may reduce the functionality of the surface electrometer. Furthermore, the installation space for the surface electrometer is also limited and narrow.

Therefore, when using a surface electrometer as described above, if the one according to the present invention is used, it is possible to downsize it, so it is possible to easily secure the installation space, and it is completely protected against the intrusion of dust, etc. It can be prevented from occurring and can provide sufficient functionality over a long period of time without deteriorating functionality.

[Brief explanation of the drawing]

Figures 1A and 1B are a schematic diagram showing an example of a conventional cross-over type surface potentiometer and a plan view of its rotating sector.
Figures A and B are a schematic diagram showing an embodiment of the present invention and a perspective view of its fan, Figure 3 is a circuit diagram for explaining the principle of surface potential detection in the embodiment of Figure 2, and Figures 4 to 4 are FIG. 8 is a diagram for explaining the operation of the embodiment shown in FIG. 2, and FIG. 9 is an explanatory diagram showing an example of application of the AC surface electrometer according to the present invention. 1... Shield case, 2... Aperture, 3
...Air inlet, 4...Rotating sector, 5...Motor, 6...Detection electrode, 7...Detection device, 8...Measurement object, 9,9'...Fan, 10...Light source,
11... Light receiving element, 12... Rotation axis.

Claims (1)

[Claims] 1. A detection electrode and a device that enters from the aperture and changes an electric field that induces a voltage in the detection electrode are provided in a shield case in which an aperture and an air inlet are formed, and the voltage induced in the detection electrode is detected. 1. An AC surface potentiometer that uses a fan to measure surface potential, characterized in that a fan is disposed between the aperture and the detection electrode as a device for varying the electric field.