JPH026455Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a toner concentration detection device for an electrostatic copying machine for detecting the concentration of toner in an electrostatic copying machine that uses mixed particles of carrier and toner.

FIG. 1 shows a schematic configuration of a general electrostatic copying machine. In this figure, an image of light from a light source 2 reflected by a document 3 is projected onto a photoreceptor drum 1 through an optical system of mirrors 4, 5 and a lens 6. The toner powder in the toner box 7 is supplied to a developing section 8 that is in contact with the drum 1, and the transfer paper 9 is supplied to the peripheral surface of the drum 1 via a paper feeding mechanism. On the circumferential surface of the drum 1, there is a first charging device 10 that charges the drum in advance, and a transfer paper 9 that transfers an electrostatic latent image on the drum surface.
A second charging device 11 for transferring the toner to the toner, and a third charging device 12 for separating the toner from the drum side are provided, respectively. The transfer paper 9 on which the toner image has been transferred is discharged onto a paper discharge tray 14 through a fixing section 13.

Incidentally, the developing section 8 stirs a carrier (usually iron powder) and toner (resin powder) to generate frictional electrification, and faces the photoreceptor drum 1 with the toner attracted around the carrier. It has a function of attracting them with a rotating magnetic brush 15 and bringing them into contact with the circumferential surface of the drum 1. As a result, the toner is attracted to the electrostatic latent image formed on the circumferential surface of the drum 1 to perform development. In this case, while the toner is absorbed by the drum 1 and consumed as it is used, the amount of carrier remains unchanged. Therefore, since the toner concentration decreases with use, it is necessary to appropriately detect the toner concentration and supply toner so that the toner concentration does not fall below the lower limit.

Conventionally, toner concentration detection devices for this type of electrostatic copying machine have been a mechanical method that detects the amount of toner in the developing section 8 using mechanical contacts, an L detection method that uses changes in coil inductance, or a transfer method. There is an optical method that detects the density of toner transferred to paper 9. However, although the unit price of the mechanical method is low, since it uses contacts, there is a risk of malfunction due to intrusion of toner. The L detection method requires a complicated control circuit and is expensive. Furthermore, the optical method has the disadvantage of slow feedback for concentration detection. Therefore, it is difficult for these conventional techniques to be applied to high-speed compact copying machines in terms of cost, reliability, or detection speed.

In view of the above points, the present invention has been developed to provide a developing section of an electrostatic copying machine that uses mixed particles of carrier and toner.
A piezoelectric vibrator in which a piezoelectric element is fixed to a magnetic diaphragm is disposed, and a magnetic core having a coil is disposed so that the carrier in the developing section and the magnetic diaphragm constitute a part of a magnetic circuit. By utilizing the fact that the magnetic resistance of the magnetic circuit changes when toner adheres to a certain carrier, toner concentration can be detected quickly and with high reliability, and the total amount of mixed particles of carrier and toner can also be detected. An object of the present invention is to provide a toner concentration detection device for an electrostatic copying machine that is capable of performing the following steps.

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a toner concentration detection device for an electrostatic copying machine according to the present invention will be described below with reference to the drawings.

2 to 5, the toner concentration detection device for an electrostatic copying machine includes a piezoelectric vibrator 22 in which a piezoelectric element 20 is bonded to a magnetic diaphragm 21 which is a thin plate of magnetic material such as permalloy, and a magnetic diaphragm 22. A magnetic core 23 with a center pole and a magnetic ring 25 facing 21
a bottomed cylindrical magnetic core structure having a center pole with an annular coil 24 provided in the center; and an insulator for supporting the magnetic diaphragm 21 inside the magnetic ring 25. A support body 26 is provided. Here, a magnetic ring 25 is magnetically bonded to the outer edge of the magnetic core 23 with a center pole, and an insulating support 2 is placed inside the magnetic ring 25.
6 is fixed. The periphery of the magnetic diaphragm 21 is elastically supported by an insulating support 26 via an elastic body 27 such as silicone adhesive. And magnetic ring 2
5 is arranged so as to penetrate the side wall of the container 30 of the developing section 8A of the electrostatic copying machine. That is, the detection surface of the piezoelectric vibrator 22 (the surface of the magnetic diaphragm 21 on which the piezoelectric element is not provided) is exposed inside the container 30. A magnetic brush 15A and a stirring rod (not shown) are rotatably provided in the container 30, and a toner box 7 containing toner is arranged above the container 30.

In the configuration of the above embodiment, when the concentration of toner in the container 30 decreases below the set value, the amount of toner adhering to the carrier decreases, and as a result, the magnetic force between the magnetic ring 25 and the magnetic diaphragm 21 decreases. The gap is magnetically short-circuited by the carrier C as shown in FIG. 5, and the magnetic resistance of the gap becomes low. Therefore, the magnetic diaphragm 21 starts to vibrate due to the alternating current magnetic field corresponding to the alternating current voltage supplied to the coil 24, thereby notifying the user that the toner concentration has decreased.

Furthermore, when the total amount of carrier and toner decreases significantly, the carrier and toner no longer come into contact with the detection surface of the piezoelectric vibrator 22. As a result, the Q of the piezoelectric vibrator 22 becomes high. Therefore, if an oscillator having the piezoelectric vibrator 22 as an oscillation element is connected, the oscillator will start oscillating, and the reduction in the total amount of carrier and toner mixed particles can be detected.

On the other hand, when the total amount of carrier and toner is sufficient and the toner concentration is higher than the set value, the amount of toner adhering to the carrier increases, and as a result,
The magnetic gap between the magnetic ring 25 and the magnetic diaphragm 21 has a high magnetic resistance. Therefore, the attractive force of the magnetic core with center pole 23 is weak, and the magnetic diaphragm 21 does not vibrate. Further, the carrier and toner come into contact with the detection surface of the piezoelectric vibrator 22 and apply pressure thereto. As a result, the Q of the piezoelectric vibrator 22 decreases, and the oscillator using this as an oscillation element does not oscillate.

According to the above embodiment, the following effects can be achieved.

(1) The diaphragm of the piezoelectric vibrator 22 is made of a magnetic material, and the magnetic core 23 with a center pole is placed opposite to it, so that magnetic flux passes through the carrier in the developing section 8A of the electrostatic copying machine. Therefore, by utilizing the fact that magnetic resistance changes depending on the amount of toner attached to the carrier, which is a magnetic material, toner concentration can be adjusted at high speed.
Can be detected with high reliability.

(2) The total amount of mixed particles of carrier and toner can be detected at high speed and with high reliability by the contact pressure of the carrier and toner on the detection surface of the piezoelectric vibrator 22.

Note that the mounting position on the developing section can be changed as appropriate depending on the type of copying machine.

As explained above, according to the present invention, a piezoelectric vibrator in which a piezoelectric element is fixed to a magnetic diaphragm is disposed in the developing section of an electrostatic copying machine that uses mixed particles of carrier and toner, and By arranging a magnetic core having a coil so that the carrier and the magnetic diaphragm in the section constitute a part of the magnetic circuit, toner concentration can be detected at high speed and with high reliability. A toner concentration detection device for an electrostatic copying machine capable of detecting the total amount of mixed particles of toner and toner can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing an example of a general electrostatic copying machine, and FIG. 2 is an embodiment of the toner concentration detection device for an electrostatic copying machine according to the present invention. Side sectional view showing the state installed in the developing section, No. 3
The figure is a side sectional view of the embodiment, Figure 4 is a front view of the same, and Figure 5 is a side sectional view of the embodiment.
The figure is a side sectional view for explaining the operation of the embodiment. 8...Development section, 20...Piezoelectric element, 21...Magnetic diaphragm, 22...Piezoelectric vibrator, 23...Magnetic core with center pole, 24...Coil, 25...Magnetic ring, 26... Insulating support, 30... container.

Claims (1)

[Scope of utility model registration request] A bottomed cylinder comprising a piezoelectric vibrator in which a piezoelectric element is fixed to a magnetic diaphragm, a magnetic core with a center pole facing the magnetic diaphragm, and a magnetic ring, the center pole having a coil in the center. and an insulating support that supports the magnetic diaphragm inside the magnetic ring, and the magnetic vibration is applied to a developing section of an electrostatic copying machine using mixed particles of carrier and toner. A surface of the plate on which the piezoelectric element is not arranged is exposed, and the carrier and the magnetic diaphragm constitute a part of a magnetic circuit, and an alternating current voltage is supplied to the coil to drive the piezoelectric element. A toner concentration detection device for an electrostatic copying machine characterized by being connected to an oscillator.