JPH043315Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a toner concentration detection device for a dry two-component developer used in a magnetic brush developing device.

In a magnetic brush developing device that uses a dry two-component developer (a mixture of magnetic carrier and toner),
As the number of copies increases, only the toner in the developer is consumed, so the toner density decreases, and the copy density decreases accordingly. Therefore, a method has been proposed in which toner concentration is detected and toner is automatically replenished.

FIG. 1 shows an example of a magnetic brush developing device that is equipped with an optical toner concentration detection device that detects the intensity of scattered light from the developer and controls the toner concentration based on the output of the above method. It is a line diagram.
This magnetic brush developing device 1 includes a developer container 2,
A two-component developer 3 prepared at the bottom of the container, a magnetic brush roller 4 that conveys the developer, a doctor blade 5 that regulates the amount of developer conveyed, and a scraper 6 that removes the developer from the magnetic brush roller 4. ,
It is composed of a stirring member 7 for stirring the developer, a toner hopper 8 containing replenishing toner, a toner replenishing roller 9 for supplying toner, and the like. The magnetic brush roller 4 further includes a large number of magnetic pole parts (first
In the figure, it is composed of a fixed magnet roller 10 having N1, S1, N2...Sn) and a cylindrical non-magnetic sleeve 11 that is rotatable relative to the magnet roller 10. At the portion where the magnetic brush roller 4 faces the photoreceptor 12, there is a developing magnetic pole portion (N1 in FIG. 1) of the magnet roller 10.
position. Further, in a portion where the magnetic brush roller 4 faces an optical toner concentration detection device 13 that is installed above the magnetic brush roller 4 and measures the toner concentration of the developer, a magnetic roller 1 is provided.
0 concentration detection magnetic pole part (S1 in FIG. 1) is positioned.

Therefore, the dry two-component developer 3 placed in the developer container 2 is conveyed in the direction of the arrow as the non-magnetic sleeve 11 rotates while remaining attached to the non-magnetic sleeve 11 by the magnetic force of the magnet roller 10. , the layer thickness is made constant by the doctor blade 5. Thereafter, at the position of the developing magnetic pole N1, the ears of the developer are made to stand up, and the part where the ears stand up (hereinafter referred to as the standing part) is brought into contact with the photoreceptor 12, and the part formed in advance on the photoreceptor 12 is brought into contact with the photoreceptor 12. Develop the electrostatic latent image. The developer that has contributed to the development is removed from the non-magnetic sleeve 11 by the scraper 6, falls onto the stirring member 7, is stirred and conveyed, and adheres to the non-magnetic sleeve 11 again.

On the other hand, the optical toner concentration detecting device 13 disposed in the magnetic brush developing device 1 is rubbed by the standing portion at the position of the magnetic pole portion S1 for detecting the concentration. This toner concentration detection device 13
Under this control, the toner supply roller 9 rotates only when necessary, and toner is supplied from the toner hopper 8. The supplied toner is stirred and mixed with the developer scraped off by the scraper 6 to maintain the toner concentration.

FIG. 2 shows a case where the toner concentration detection device 13a, which was previously studied by the inventor of the present invention, is used as the toner concentration detection device of the magnetic brush developing device 1.
This is a cross section taken along the line XX in the figure, that is, a plane including the rotation axis of the magnetic brush roller 4. This toner concentration detection device 13a is connected to a transparent plate 17 disposed at a position in contact with the above-mentioned spike portion.
, the light emitting element 14 and the light receiving element 15 provided on the side of the transparent plate 17 opposite to the magnetic brush roller 4, and the light emitting element 14 and the light receiving element 1.
5, and a holder 16a for holding the holder 5.

The optical axis of the light-emitting element 14 and the axis indicating the maximum sensitivity of the light-receiving element 15 (hereinafter referred to as the axis) are aligned with an imaginary line perpendicular to the cylindrical surface of the magnetic brush roller 4 in a plane that includes the rotation axis of the magnetic brush roller 4. They are arranged so as to be inclined and symmetrically intersect with each other. Further, the holder 16a forms a light emitting optical path of the light emitting element 14 and a light receiving optical path of the light receiving element 15 along the optical axis and the axis, and also projects the light emitting element 14 at a spaced apart position facing the transparent plate 17. It has a light aperture and a light receiving aperture for the light receiving element 15 . It should be noted that lenses 18a,
18b is attached.

Therefore, the light emitted from the light emitting element 14 passes through the transparent plate 17 and reaches the surface 11 of the magnetic brush roller 4.
After being scattered by the spikes 19 formed on a,
The light passes through the transparent plate 17 again and enters the light receiving element 15, where it is converted into an output voltage corresponding to the incident light flux.

Therefore, when we actually investigated the relationship between the toner concentration and the output voltage by keeping the distance between the toner concentration detection device 13a and the non-magnetic sleeve 11 constant, we found that the third
As shown by curve A in the figure, a downwardly convex characteristic curve was obtained in which the output voltage of the light receiving element had a minimum value at a toner concentration of approximately 7.5%.

By the way, the output voltage obtained by the light receiving element 15 passes through an amplifier and a filter, and then is compared with a reference voltage Vc corresponding to a generally used set toner concentration of 7% by a comparator. If the voltage is higher than the reference voltage Vc, it is determined that the toner concentration is lower than the set toner concentration of 7%, and control is performed to supply toner. The following problems occurred.

With respect to the reference voltage Vc, there are at least two toner concentrations, namely the set toner concentration of 7% and the toner concentration of approximately 8% that exceeds the minimum value, and even in the vicinity of the set toner concentration of 7%, there is a slope of the output voltage. is extremely small. Therefore, the response of the output voltage to changes in toner concentration deteriorates, making accurate control difficult. Further, the toner supply roller 9
If the toner concentration exceeds approximately 8% due to the time delay between toner supply and toner concentration detection, the output voltage will be higher than the reference voltage Vc, so if the toner concentration is lower than the set toner concentration of 7%. As a result, toner is supplied without limit, making it impossible to control the copy density. Therefore, control in curve A could only be achieved at fairly low concentrations.

SUMMARY OF THE INVENTION An object of the present invention is to provide a toner concentration detection device that eliminates the above-mentioned problems and allows stable control over a wider range of toner concentrations.

The present invention is a toner concentration detection device for a dry two-component developer used in a magnetic brush developing device. , provided on the side of the transparent plate opposite to the magnetic brush roller, the axis of the light-receiving element is substantially perpendicular to the cylindrical surface of the magnetic brush roller in a plane that includes the rotation axis of the magnetic brush roller, and the light emitting element is provided on the side opposite to the magnetic brush roller. a light-receiving element and a light-emitting element arranged such that the optical axis of the element obliquely intersects with the axis on the magnetic brush roller side of the transparent plate; the transparent plate supporting the light-emitting element and the light-emitting element therein; The light emitting light path and light receiving path of the light emitting element are formed along the optical axis of the light emitting element and the axis of the light receiving element such that the light emitting aperture of the light emitting element and the light receiving aperture of the light receiving element are formed at spaced apart positions facing the light emitting element. a holder having a light receiving optical path of the element, the light emitting element projects the light from the light emitting element through the transparent plate onto the spiked part of the developer, and the light reflected inside the spiked part passes through the transparent plate and receives the light. The device is characterized in that it is configured to measure the toner concentration in the developer based on the photoelectric output of the light-receiving element by receiving light with the element.

An embodiment of the toner concentration detection device of the present invention will be described below.

In the description, the same names and symbols are used for the same parts as in the example of FIG. 2.

FIG. 4 shows the case where the toner concentration detection device of the present invention is used as the toner concentration detection device of the magnetic brush developing device shown in FIG. The explanation will be given using a cross section cut along a plane including the above. The toner concentration detection device 13b of the present invention includes a transparent plate 17 disposed in contact with the stand-up portion, and a light emitting element 14 and a light receiving element 15 provided on the side of the transparent plate 17 opposite to the magnetic brush roller 4. and a holder 1 that holds these light emitting elements 14 and light receiving elements 15.
6b.

The optical axis of the light emitting element 14 and the axis of the light receiving element 15 are
In a plane including the rotation axis of the magnetic brush roller 4, the axis of the light receiving element 15 is substantially perpendicular to the cylindrical surface of the magnetic brush roller 4, and the optical axis of the light emitting element 14 is aligned with this axis on the magnetic brush roller side of the transparent plate. They are arranged at an angle and intersect. In addition, holder 1
6b is a light emitting element 1 along the optical axis and axis.
4 and a light receiving optical path of the light receiving element 15, and a light emitting aperture of the light emitting element 14 and a light receiving aperture of the light receiving element 15 are provided at spaced apart positions facing the transparent plate 17. Note that lenses 18a and 18b are attached to the projection optical path of the light emitting element 14 and the light receiving optical path of the light receiving element 15, respectively.

Therefore, the light emitted from the light emitting element 14 passes through the transparent plate 17 and reaches the surface 11 of the magnetic brush roller 4.
After being scattered inside the spikes 19 formed on the surface a, the light passes through the transparent plate 17 again and enters the light receiving element 15, where it is converted into an output voltage according to the incident light flux.

When the relationship between the toner concentration and the output voltage obtained by the above-mentioned embodiment of the present invention is measured, the result is a curve B shown in FIG. 3, which shows a linear characteristic in which the output voltage decreases as the toner concentration increases. The relative sensitivity of toner concentration detection is good when compared with the device shown in FIG. 2, and even at relatively high toner concentrations, a downward convex characteristic curve with a minimum value like curve A in FIG. I found out that it doesn't happen. Furthermore, in one embodiment described above, the set toner density is 7.
% and a reference voltage Vc', it was found that the toner density could be controlled within the range of 7%±0.5% even when the number of copies was about 30,000.

In the above embodiment, if a transparent electrode 20 is provided on the contact surface between the transparent plate 17 and the spiked portion 19, and this transparent electrode 20 is grounded or a bias voltage of opposite polarity to the charge of the toner is applied, the transparent electrode 20 becomes transparent. It is preferable that no undesired toner adheres to the electrode surface. Further, as the light emitting element, a tungsten lamp, an LED, etc. can be used, and as the light receiving element, a phototransistor, a photodiode, etc. can be used. Furthermore, although lenses 18a and 18b are shown attached to the light emitting aperture of the light emitting element 14 and the light receiving aperture of the light receiving element 15, respectively, the same effect is not limited to this, and the same effect can be obtained even if a transparent flat plate is attached. .

In addition, in order to detect toner concentration, the magnetic brush roller facing the toner concentration detection device is not limited to a developing magnetic brush roller for developing an electrostatic latent image, but also a separate magnetic brush provided for toner concentration detection. It's okay to be a roller.

Regarding the configuration of the magnetic brush roller, in the above embodiment, the magnetic brush roller is fixed and the non-magnetic sleeve rotates, but the present invention is not limited to this. In magnetic brush rollers in which the brush roller is fixed, and in magnetic brush rollers in which the magnet roller and non-magnetic sleeve rotate in opposite directions, the developer is brought into direct contact with the magnet roller without using a non-magnetic sleeve. Even with a magnetic brush roller that rotates, the same effect can be obtained by timing the toner concentration measurement when the magnetic pole part of the magnet roller reaches the position on the axis of the light receiving element of the toner concentration detection device of the present invention. You can get the following effect.

As is clear from the above, according to the present invention, the characteristic curve showing the relationship between the toner concentration and the output voltage of the light receiving element is linear over a wide range of toner concentration, so that stable toner concentration control can be achieved over a long period of time. It is something that can be done.

[Brief explanation of the drawing]

FIG. 1 is a diagram of a general magnetic brush developing device in which a toner concentration detection device is arranged, and FIG. 1 is a sectional view taken along the line X-X in FIG. 1, FIG. 3 is a characteristic curve diagram showing the relationship between output voltage and toner concentration by the toner concentration detection device previously studied by the present inventor and the toner concentration detection device of the present invention, and FIG. 4 1 is a sectional view taken along line XX in FIG. 1 when the toner concentration detection device of the present invention is arranged as shown in FIG. 1. 1... Magnetic brush developing device, 4... Magnetic brush roller, 13, 13a, 13b... Toner concentration detection device, 14... Light emitting element, 15... Light receiving element,
19...Standing part.

Claims (1)

[Scope of Claim for Utility Model Registration] A toner concentration detection device for a dry two-component developer used in a magnetic brush developing device, disposed at a position in contact with the spikes of developer held and conveyed by a magnetic brush roller within the developing device. a transparent plate provided on a side of the transparent plate opposite to the magnetic brush roller, the axis of the light-receiving element being substantially perpendicular to the cylindrical surface of the magnetic brush roller in a plane that includes the rotational axis of the magnetic brush roller; and a light-receiving element and a light-emitting element arranged such that the optical axis of the light-emitting element obliquely crosses the axis on the magnetic brush roller side of the transparent plate, the light-emitting element and the light-receiving element being supported inside;
and a projection of the light-emitting element formed along the optical axis of the light-emitting element and an axis of the light-receiving element such that a light-emitting aperture of the light-emitting element and a light-receiving aperture of the light-receiving element are formed at separated positions facing the transparent plate. a holder having a light optical path and a light-receiving optical path of a light-receiving element, the light emitting element projects the light from the light emitting element onto the spiked part of the developer through the transparent plate, and the reflected light inside the spiked part is transmitted to the transparent plate. A toner concentration detection device characterized in that the toner concentration detection device is configured to measure the toner concentration in the developer based on the photoelectric output of the light receiving element by receiving the light with the light receiving element.