JPS6337381B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a toner concentration detection device suitable for detecting the mixing ratio of toner and carrier in a developer used in a developing device in electrostatic recording or electrophotography.

2. Description of the Related Art In electrostatic recording and electrophotography, a mixture of a magnetic carrier and a toner (colored powder) in a certain ratio is used as a developer for visualizing an electrical latent image. When developing an electrical latent image using such a developer, it is desirable that the mixing ratio of the magnetic carrier and toner (toner concentration) be controlled within a substantially constant range. For this purpose, it is necessary to accurately detect the toner concentration of the developer. The toner concentration detection means may be one that responds to changes in magnetic permeability, magnetic flux density, electrical conductivity, electrical loss surface color, etc.
Here, an example will be described in which toner concentration is detected based on a change in inductance (sensitive to a change in magnetic permeability) of a detection coil.

FIG. 1 shows the installation configuration of a conventional developer toner concentration detection device. A developer 1 containing a mixture of magnetic carrier and toner contained in a developer container (not shown) is attracted to the outer circumference of a rotating sleeve 3 by the magnetic force of a fixed magnet roll 2, and as the rotating sleeve 3 rotates, the developer 1 is mixed with a magnetic carrier and toner. It is transported in the direction of the arrow. While being conveyed, the developer 1 comes into contact with the surface of the recording medium 4 having an electrical latent image, and develops the latent image with toner. The developer 1 is returned to the developer container,
It is mixed and stirred with new toner and reused. A portion of the developer 1 on the rotary sleeve 3 is diverted from the surface of the rotary sleeve 3 by a hopper 5 having an opening at the lower end in an area past the contact area with the recording medium 4 . The flow rate of the developer 1 that naturally falls from the opening at the lower end of the hopper 5 is almost constant, and is supplied into a detection container 7 in which a flat detection coil 6 is attached. A rotating discharge magnet roll 8 is provided at the lower end opening of the detection container 7, and discharges the developer 1 in the container 7 to the outside at a constant flow rate. In this way, the magnetic permeability of the developer 1 affects the inductance of the detection coil 6, so that the toner concentration of the developer 1 can be detected from the inductance of the detection coil 6. That is, when the toner concentration of the developer 1 decreases, the mixing ratio of the magnetic carrier increases and the magnetic permeability of the developer 1 increases, so that the inductance of the detection coil 6 increases. Moreover, it decreases as the concentration increases.

Such toner concentration detection can be performed with high precision under optimal conditions.

By the way, in the detection device having the above configuration, most of the developer 1 led out of the detection container 7 by the rotating discharge magnet roll 8 is scraped off at the A portion of the detection container 7. Magnetic roll 8 for its discharge
When the surface of the developer 1 advances into the detection container 7, the developer 1 within the range covered by the magnetic force (5 to 15 mm depending on the magnetic flux density, approximately 10 mm at 1000G) is attracted and transported to the bottom part of the detection container 7, where it is Since the developer 1 is limited to an appropriate amount (for example, 2 mm) and is led out of the container 7, most of the developer 1 that has been adsorbed and conveyed to the RO portion remains within the container 7, and moreover, it tends to be pushed upward as shown by the arrow in the figure. be. Therefore, in FIG. 1, the developer 1 in the left flow path of the detection coil 6 stagnates, and almost only the developer 1 in the right flow path is discharged to the outside of the container 7. In addition, in order to satisfy the optimum amount of discharge to the outside of the detection container 7 for measuring toner concentration with high precision, the opening width of the bottom part of the container 7 is narrow, about 2 mm. If a large foreign substance gets mixed into the container 7, the foreign substance cannot be easily discharged from the container 7, and the developer 1 becomes stagnant inside the container 7. As mentioned above, in the conventional device, the container 7
There is a drawback that the developer 1 stagnates inside the printer, making it impossible to accurately detect changes in toner density.

SUMMARY OF THE INVENTION An object of the present invention is to provide an apparatus that eliminates the conventional drawbacks and can accurately detect toner concentration.

The present invention prevents the developer from stagnation in the area where the toner concentration of the developer is measured and keeps the flow uniform and constant at all times by using the outlet end of the area and the circumferential surface of the discharge magnet roll. Openings with widths a and b through which a portion of the developer to be adsorbed and conveyed passes are formed on the developer discharge side and the scraping side, respectively, so that the relationship a>b>0 holds, and furthermore, a discharge mag is formed in the area. A means is provided for restricting the flow rate of the developer that is adsorbed and conveyed by the net roll.

FIG. 2 shows an embodiment of a developer toner concentration detection device to which the present invention is applied. The same numbers as in FIG. 1 in the drawings indicate the same parts, and the other configurations are the same as in FIG. 1.

A part of the developer 1 overflows from the upper edge of the hopper 5, and the other part naturally falls from the opening at the lower end, and is supplied at an approximately constant flow rate into the flat-shaped detection container 7 in which the detection coil 6 is attached. . Detection container 7
The developer 1 inside is mounted approximately at the center of the lower end opening of the detection container 7 so as to have a width greater than the range of the magnetic force of the discharge magnet roll 8, and to avoid electromagnetic coupling with the detection coil 6. While the outflow amount is limited by the passage width c of the outflow restriction plate 9 and the opening width a of the lower end portion of the detection container 7, the outflow amount is led out of the detection container 7 by the rotating discharge magnet roll 8, and the outflow amount of the detection container 7 is The developer 1 that has been adsorbed and conveyed by the roll 8 over this width is scraped off by the opening width b at the lower end A portion, and the developer 1 that is adsorbed on the roll 8 and is equal to the opening width b advances into the detection container 7 again. . however,
The aperture width b is smaller than a and is greater than or equal to zero, so that a portion of the developer 1 adsorbed to the discharge magnet roll 8 is always left, and the optimum discharge amount for highly accurate measurement is the width of both apertures. It is determined by the value of the difference a-b.
In addition, the restricted passage width c by the outflow restriction plate 9 is a-
It is configured to have a value of (a-b/2) or b+(a-b/2). For example, if the opening widths a and b are each 4 mm,
If it is 2 mm, the c value is 3 mm, and in this case container 7
The amount discharged to the outside is 2mm.

According to the above configuration, when the rotating discharge magnet roll 8 adsorbing the developer 1 equal to the opening width b of the lower end portion A of the detection container 7 advances into the detection container 7, the area covered by its magnetic force is The developer 1 is further adsorbed onto the layer of the developer 1 on the magnet roll 8 and is conveyed to the outflow restriction plate 9. Then, the amount of adsorption is limited to be approximately equal to a-(a-b/2) or b+(a-b/2), and when it passes through the outflow amount limiting plate 9, the amount of adsorbed developer layer is On top of this, the developer within the range of the magnetic force is further attracted, as described above. Then, the opening width a of the lower end portion of the detection container 7 is
Then, the amount of adsorption is limited to be approximately equal to the amount obtained by adding a-b/2 to the restriction by the outflow restriction plate 9,
It is led out of the detection container 7. Therefore, the amount of developer 1 flowing out of the detection container 7 in the flow paths on both sides of the flow rate limiting plate 9, that is, in the flow paths on both sides of the detection coil 6, is approximately equal to a-b/2, and the detection The developer in the container 7 is uniformly discharged in a fixed amount, and the opening width a at the lower end (discharge side) of the container 7 can be made large, so even if a large foreign object gets into the container 7, it can be easily removed. This has the effect that the toner concentration can be accurately measured without the developer 1 stagnating in the same container.

FIG. 3 shows another embodiment, which differs from FIG. 2 in that a part of the hopper 5 is formed on one of the upper opening side plates of the flat detection container 10, the lower opening is flat, and the side plate is One side of the discharge magnet roll 8 is extended beyond the axis of the discharge magnet roll 8, and a concave portion is provided leaving a portion of both ends. It is installed so that the peripheral surfaces are in contact with each other.
The opening widths b and a of portions A and B of the lower end opening of the detection container 10 and the passage width c due to the outflow restriction plate 9 installed approximately in the center of the lower end opening of the detection container 10
The setting conditions, etc. are exactly the same as in FIG.

In this case as well, the same effect as in FIG. 2 is obtained. Furthermore,
The shape of the outflow restriction plate 9 can be made into a flat plate that is easy to manufacture, the detection container 10 and the discharge magnet roll 8 can be easily connected, and the opening accuracy of each opening width a, b, and c is improved. There is.

FIG. 4 shows an example of an electrical circuit of such a toner concentration detection device. The detection coil 6 constitutes a series resonant circuit with a capacitor 11, and is connected to a constant frequency oscillator 12. In a range where the toner concentration of the developer acting on the detection coil 6 includes a specified value, the terminal voltage of the detection coil 6 is made to increase or decrease in direct proportion to the toner concentration. The terminal voltage of the detection coil 6 is rectified by a diode 13, and is rectified by a capacitor 14.
The smoothed signal is then applied to the input of the comparator 15. Comparator 1
5 is a detection coil 6 which inputs a reference voltage from a reference power supply 16 and obtains the toner concentration when it is below the lower limit value.
Set to output at the terminal voltage of . In this way, by monitoring the output of the comparator 15, it can be known that the toner concentration in the developer has fallen below the specified value.

As described above, according to the present invention, since the developer is always discharged without being stagnated in the detection container, the toner concentration of the developer can be measured with high precision, which has a great practical effect.

[Brief explanation of the drawing]

FIG. 1 is a vertical side view of a conventional developer toner concentration detection device, FIGS. 2 and 3 are vertical side views of a developer toner concentration detection device of the present invention, and FIG. 4 is an electrical connection diagram. be. DESCRIPTION OF SYMBOLS 1... Developer, 3... Rotating sleeve, 5... Hopper, 6... Detection coil, 7, 10... Detection container, 8... Discharge magnet roll, 9... Outflow rate restriction plate.

Claims (1)

[Scope of Claims] 1. A developer containing a mixture of carrier and toner is supplied into a detection container, is attracted to a discharge magnet roll provided at an outlet of the detection container, and is discharged to the outside of the detection container, while the developer is detected. The toner concentration of the developer passing through the container is measured by a detection coil disposed in the detection container, and the developer is discharged by the outlet end of the detection container and the circumferential surface of the discharge magnet roll. Openings with widths a and b are formed on the side and the scraping side, respectively, through which a portion of the adsorbed developer passes, and a developer flow path is formed on the developer discharge side and the scraping side of the detection coil. and further, located approximately at the center in the rotational direction of the discharge magnet roll in the detection container, and having a width greater than the range of the magnetic force of the discharge magnet roll;
Further, a restricting means is provided so as not to form an electromagnetic coupling with the detection coil, and forms a passage with a width c through which the adsorbed developer passes through the circumferential surface of the discharge magnet roll, and a>c>b>0. A toner concentration detection device for a developer, characterized in that it is configured so that the following relationship holds true. 2. The limiting means is configured to allow passage of an amount of adsorbed developer of approximately a-(a-b/2) or b+(a-b/2). A toner concentration detection device for a developer as described in Section 1.