JPH0614078B2 - Method and apparatus for measuring charge amount of toner for two-component developer - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for accurately, quickly and easily measuring the charge amount of a two-component developer toner in a state that matches the usage state of an electrophotographic apparatus. .

2. Description of the Related Art Generally, a so-called two-component developer is widely used as a developer in the field of electrophotographic apparatus. This two-component developer is composed of an electrically insulating toner and a magnetic carrier, and by stirring the developer, triboelectric charging is caused between the toner and the carrier to retain a charge of a predetermined polarity. Toner is supplied together with a carrier onto a non-magnetic sleeve containing a magnet to form a magnetic brush, and the magnetic brush is brought into contact with a photoconductor on which a predetermined electrostatic latent image is formed, thereby forming a latent image on the latent image. The development is performed by forming a corresponding toner image. Therefore, it will be understood that measuring the charge amount of the toner in the agitated state has a very important meaning in adjusting the density of the toner image formed.

Conventionally, for example, a blow-off powder charge amount measuring device or a magnet blow-off method is known as such a toner charge amount measuring device or measuring method.

The former device measures the charge amount of toner by using a blow-off Faraday cage that uses a mesh. However, it is caused by the collision of toner or carrier whose charge amount should be measured with the mesh. Since it is accompanied by triboelectrification, the measured value of the charge amount changes depending on the measurement conditions and the like, and it has a drawback that the absolute value is difficult to measure.

The latter method is a blow-off method that does not use a mesh, in which a magnetic brush of developer is formed on a magnet, and the difference between the attraction force of the carrier and toner to the magnet is used to separate the two to separate the charge amount. It is to measure. According to this method, the developer for which the toner charge amount is to be measured is not present in the Faraday cage, so that not all the electric force generated from the sample is captured by the magnet. Therefore, all of the charge amount cannot be measured accurately, and it is difficult to set the blow condition that blows only the toner without blowing the carrier in the magnetic brush. Of.

Object of the Invention That is, the object of the present invention is to eliminate the drawbacks inherent in the known means described above, and to accurately, quickly and easily measure the charge amount of toner in a state that matches the actual use state. Another object of the present invention is to provide a method and an apparatus for measuring the charge amount of a toner for a two-component developer.

According to the present invention, a magnet is disposed adjacent to a container formed of a conductive material and provided with a toner and an outlet for airflow, and a two-component developer including toner and a magnetic carrier is provided.
A magnetic brush of the developer is formed by being housed in the container, and an air stream is blown into the container under the condition of being electrically shielded from the outside, and at the same time, the magnet is rotated to move the magnetic brush. Only the toner component in the brush,
A method of calculating the charge amount of a two-component developer toner by removing the charge from the container through the discharge port and measuring the charge amount of the carrier remaining in the container is provided. It

According to the present invention, further, a developer accommodating container formed of a conductive material and provided with an outlet for toner and an air flow, an air flow supply pipe, and an electric insulating material provided at the tip of the pipe. An airflow blowing device for supplying an airflow into the developer container under the condition of being electrically disconnected from the outside through the nozzle, which is adjacent to the developer container. And a measuring device for measuring the amount of charge of the carrier contained in the developer accommodating container. A charge amount measuring device is provided.

That is, in the present invention, the two-component developer is contained in the container, and the air flow for removing the toner whose charge amount is to be measured is supplied under the condition of being electrically cut off from the outside. . Therefore, when measuring the charge amount, the electrical influence from the outside can be ignored, and the charge amount of the toner can be measured with extremely high accuracy.

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below in detail based on specific examples shown in the accompanying drawings.

In FIG. 1 schematically showing a measuring apparatus for suitably carrying out the method of the present invention, the measuring apparatus is roughly equipped with an air flow blowing device 1, a Faraday cage 2, and a magnet provided adjacent to the Faraday cage 2. 3 and a charge amount measuring device 4 connected to the Faraday cage 2.

The airflow spraying device 1 is composed of a nozzle 6 made of an electrically insulating material such as Teflon and a gas supply tube 5, and the tip of the nozzle 6 is connected to the inside of the Faraday cage 2. Further, one end of the tube 5 is connected to a gas storage member such as a gas cylinder (not shown) or a supply device. Therefore, the compressed gas can be supplied into the Faraday cage 2 while being electrically disconnected from the outside.

The Faraday cage 2 is made of a conductive material such as brass, and is for accommodating therein a two-component developer whose toner charge amount is to be measured. Further, the Faraday cage 2 is provided with a discharge port 7 so that the toner component in the developer is discharged to the outside of the Faraday cage 2 through the discharge port 7 by the gas blow by the air flow spraying device 1 described above. There is. In this case, it is preferable to coat the inner wall of the Faraday cage 2 with a dielectric or the like in order to prevent frictional electrification between the inner wall of the Faraday cage 2 and the developer.

The magnet 3 is a U-shaped plate whose N pole and S pole are opposed to each other at the tip as shown in the figure, and the shaft is connected to a motor 9 via a pulley 8 or the like, and has a predetermined length. It can rotate at speed.

The charge amount measuring device comprises a condenser 10, a potentiometer 11 and a recorder 12.

That is, in the present invention, the two-component developer, which has been stirred under the same conditions as those used in an electrophotographic apparatus such as a copying machine, is housed in the Faraday cage 2 and the nitrogen is blown by the airflow spraying apparatus 1 while rotating the magnet 3. Supply compressed gas such as gas.

That is, a magnetic brush of developer is formed in the Faraday cage 2, but the magnetic force of the magnet 3 acts on the carrier in the magnetic brush, and the toner is mainly attached to the carrier by electrostatic force. Therefore, only the toner is discharged from the Faraday cage 2 by the gas flow. In this case, since the magnet 3 is rotating, the relative movement of the magnetic brush with respect to the magnet 3 is promoted, and as a result, even the toner at the base portion of the magnetic brush is effectively and quickly discharged from the Faraday cage. .

Thus, all the toner in the Faraday cage 2 is discharged, so the absolute value of the charge amount of the remaining carrier corresponds to that of the toner charge amount. Since the electric charge of the carrier is held in the capacitor 10, by measuring the potential difference between both ends of the capacitor 10 with the potentiometer 11,
The following formula: Q = CVC where C is the electric capacity of the capacitor 10, V is the potential difference measured, and the charge amount of the carrier is calculated. The toner charge amount is calculated as the opposite polarity of the above value.

In this case, if the weight of the toner is calculated by measuring the weight of the Faraday cage before and after discharging the toner, the charge amount per gram of toner, that is, the toner specific charge is calculated.

Incidentally, FIG. 2 shows a simplified diagram of a conventionally known measuring apparatus of the magnet blow-off method. In this case, even if the magnet is rotated, the magnetic brush is directly formed on the magnet, so that the relative movement of the magnetic brush with respect to the magnet is performed. Therefore, it is difficult to discharge the toner existing at the base portion of the magnetic brush, and it is difficult to accurately measure the charge amount.

On the other hand, according to the present invention, since the magnetic brush is formed so as to be separated from the magnet 3, the rotation of the magnet 3 causes relative movement with respect to the magnet 3 of the magnetic brush, and thus the root portion of the magnetic brush. Since the toner existing in the toner moves, the remarkable effect that the toner is also easily discharged by the gas flow is achieved.

In the present invention, the gas flow for discharging the toner in the Faraday cage varies depending on the volume of the Faraday cage 2, the magnetic force of the magnet 3 and the like, but is generally 0.1 to 2.0, particularly 0.5 to 1. It is preferable to supply at a pressure in the range of 5 Kg / cm ² gauge. When the pressure is larger than this range, it is easy to cause the problem that the carrier is blown and discharged together with the toner, and when the pressure is smaller than the above pressure, it is difficult to blow all the toner.

Further, it is desirable to bring the magnet and the sample close to each other in order to obtain a favorable magnetic brush formation and blow condition in the Faraday cage, but the surface magnetic flux density of the magnet 3 is in the range of 500 to 4000, particularly 1000 to 2000 gauss. The magnet 3 and the Faraday cage 2 are 0.
It can be used at a distance of 001 to 10, especially 0.01 to 1.0 mm. Further, in order to prevent the leakage of charges stored in the Faraday cage 2, it is preferable that the surface of the magnet 3 is covered with an electrically insulating material such as resin and the pulley 8 and the like are also formed with an electrically insulating material. is there.

In the present invention, the rotation speed of the magnet 3 is preferably in the range of 1 to 240 rpm, particularly 10 to 60 rpm. Even if the magnetic brush is rotated at a speed higher than the above range or at a speed lower than the above range, suitable movement of the magnetic brush is not exhibited, and it becomes difficult to discharge the toner at the base portion of the magnetic brush.

The shape of the magnet 3 itself is not limited to that shown in FIG. 1, and various types such as those in which N poles and S poles are alternately arranged in a plate shape or a column shape are also used. obtain. However, if a magnetic pole having an excessively high magnetic pole density is used with respect to the Faraday cage, the effect of moving the magnetic brush due to the rotation of the magnet 3 is less likely to appear, and therefore the embodiment shown in the accompanying drawings is most preferable.

EFFECTS OF THE INVENTION According to the present invention, since the charge amount of toner is measured without using a mesh, frictional electrification due to mutual friction between the mesh and toner does not occur, and a compression for removing toner is performed. Since the gas supply is performed while being electrically disconnected from the outside, it is possible to accurately measure the charge amount without performing an operation such as correction.

In addition, since the toner is effectively discharged by the gas flow by the movement of the magnetic brush caused by the rotation of the magnet, it is possible to measure the amount of charge of the toner without error.

Further, in the present invention, since the movement of the magnetic brush similar to the developing method of a copying machine or the like is exhibited in the measurement, there is an additional advantage that the charge amount of the toner that matches the actual use state is measured. ing.

The invention is illustrated by the following example.

Example 1 Approximately 200 mg of a commercially available two-component developer was placed in the container of the present invention, precisely weighed with a direct reading balance (L-160DTP manufactured by Shimadzu Corp.), and then installed in a blow system to have a surface magnetic flux density of 1600 Gauss.
A horseshoe-shaped magnet (made by ECLIPSE, UK) was placed at a distance of 0.2 mm from the container, and a nozzle having a diameter of 1.0 mm was installed at a distance of 6.5 mm from the bottom surface of the container. The blow pressure was set to 1.0 kg / cm ² and the rotation speed of the magnet was set to 10 r in advance.
・ Adjusted to p ・ m, then press the start button to start measurement. At this time, a 0.1 μF capacitor was connected to the container, and the voltage applied to the capacitor was measured. On the other hand, after stopping the blowing, the container was removed from the blowing system and precisely weighed by a balance, and the difference from the value before the blowing was taken as the weight M of the toner separated from the carrier. The toner specific charge Q is calculated by taking the ratio with the charge amount Q calculated from the voltage measurement.
/ M.

Further, under the above conditions, instead of the developer, the toner and the carrier, which are components of the developer, were individually used as measurement samples and similarly measured.

The above results are shown in Table 1.

From this table, each measured charge amount of the carrier and toner alone is very small compared to that of the developer and can be ignored. Therefore, it is easily understood that the measured value of the developer was the amount of electric charge due to the friction between the carrier and the toner, which was latent in the developer.

Furthermore, when the sample remaining in the Faraday cage after the measurement was observed with a microscope, it was confirmed that almost all the toner particles were blown off.

Example 2 A developer for comparing the magnet blow-off method for measuring the charge amount of carrier particles remaining on the surface of a magnet with the present invention for measuring the charge amount of carrier particles remaining in a cage using a Faraday cage. When A and the developer B were measured by the respective methods, the results shown in Table 2 were obtained.

From this table, the measured value of the charge amount by the method of the present invention showed a large value as compared with that of the magnet blow-off method. This is the difference between whether or not the measurement sample is in the Faraday cage, and in the method of the present invention, since all the electric forces generated from the sample are captured in the cage, it is eloquent that the measurement is more accurate. Shows.

The magnet used in the magnet blow-off method is
Since the magnetic field was directed from the upper surface to the lower surface at the edge portion, the sample was attached so as to surround the edge of the magnet along the direction of the magnetic field. Therefore, the toner at the root of this portion remained without receiving the flow of compressed gas.

[Brief description of drawings]

FIG. 1 is a schematic view showing a specific example of a measuring device for carrying out the method of the present invention, in which 1 is an air flow spraying device, 2
Is a Faraday cage, 3 is a magnet, 4 is a charge amount measuring device, 6 is a nozzle, and 7 is an outlet. FIG. 2 is a diagram schematically showing a conventionally known measuring device of the magnet blow-off method.

Claims (2)

[Claims] 1. A two-component developer comprising a toner and a magnetic carrier, wherein a magnet is disposed adjacent to a container formed of a conductive material and provided with a toner and an air outlet.
A magnetic brush of the developer is formed by being housed in the container, and an air stream is blown into the container under the condition of being electrically shielded from the outside, and at the same time, the magnet is rotated to move the magnetic brush. Only the toner component in the brush,
A method of calculating the charge amount of a toner for two-component developer by removing the charge from the inside of the container through the discharge port and measuring the charge amount of the carrier remaining in the container. 2. A developer accommodating container formed of an electrically conductive material and provided with an outlet for discharging toner and an air flow, an air flow supply pipe, and a large size provided at an end of the pipe and made of an electrically insulating material. A nozzle having a diameter, and an air flow blowing device for supplying an air flow into the developer accommodating container under the condition of being electrically cut off from the outside through the nozzle, and adjacent to the developer accommodating container. A rotatable magnet provided, and a measuring device for measuring the charge amount of the carrier contained in the developer container, and the charging of the two-component developer toner. Quantity measuring device.