JPH07122766B2 - Toner concentration detector - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a toner concentration detecting device, and more particularly to a toner concentration detecting device used in a wet type color electrophotographic copying machine or the like.

(Prior Art) Optically detecting the density of a monochrome toner (mainly black toner) in a developer is already known from JP-A-56-78861. However, in a liquid developer used for color electrophotography or the like, since the colors of the liquid developers taken into the developing area are switched, the liquid developers are often mixed with each other. At this time, if black or another color liquid developer is mixed with one color liquid developer, a toner concentration detection error is likely to occur. The reason is that a general color toner has a detection capability of about 1/10 to 1/50 of black toner. For example, as shown in FIG. 7, when the black toner and the blue toner of the color toner are compared, the light resistance value (vertical axis) with respect to the toner density (horizontal axis)
The characteristic curves of are completely different. Therefore, in the above-described conventional toner density detecting device, even when a small amount of black toner of color toner is mixed, the color toner is detected at an abnormally high density, and the density of the color trailer is actually reduced. Color toner may not be replenished. As a result, the transferred image on the recording paper after development becomes very deteriorated.

(Object) It is an object of the present invention to solve the above-mentioned drawbacks, to eliminate a color toner density detection error, and to provide a toner density detecting device capable of preventing deterioration of a color image.

(Structure) In order to achieve the above object, the present invention provides a toner concentration detection in which a light emitting element and a light receiving element are arranged with a predetermined gap, and the toner concentration of the developer in this gap is optically detected. In the device, a color filter of a plurality of colors arranged in the gap to color-separate the detection light from the light-emitting element, and based on the toner density detection value for each color obtained from the detection light color-separated by the color filter, And a density control circuit for calculating a color mixing characteristic.

In the apparatus having such a configuration, the toner density of the liquid developer is detected for each of a plurality of colors through the interposition of color filters of a plurality of colors, and based on the toner density detection value for each color obtained by this. The color mixing characteristics are calculated by the density control circuit, and the toner density control taking into consideration the color mixing is performed.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a basic circuit configuration of the toner concentration detecting device according to the present invention. The lamp L of the probe 2 which emits light when an output voltage from the lamp lighting circuit 1 is applied and the lamp L is compared with the lamp L. The color filter 3 is placed between the photodiode PD and the photodiode PD which are arranged to face each other with a certain gap.
Is installed. The output signal from the photodiode PD of the probe 2 is amplified by the amplifier circuit 5 of the concentration control circuit 4, and then an arithmetic circuit 6 for performing arithmetic operation as described later.
Applied to. The output from the amplifier circuit 5 is taken into the arithmetic circuit 6 at regular intervals based on the signal from the timer circuit 7. The calculated value obtained by the arithmetic circuit 6 is compared with the reference value in the comparison circuit 8, and the solenoid valve control circuit 9 is driven based on the deviation value obtained thereby. An output signal from the electromagnetic valve control circuit 9 activates a solenoid that opens and closes the valve of the contactor bottle in which the liquid developer is stored. The comparison result of the comparison circuit 8 is displayed on the monitor display circuit 10.

Further, the probe 2 has the configuration shown in FIG. That is, for example, a tubular body made of a stainless steel tube or the like.
A side hole 12 is formed in the tube body 11, and a lamp L and a photodiode PD are installed in the tube body 11 so as to face the side hole 12 and face each other with a certain distance therebetween. The lamp L and the photodiode PD are arranged at a position slightly decentered from the axis of the tube body 11 and moved to the inner wall side.

A disc-shaped color filter 3 is rotatably provided between the lamp L and the photodiode PD. The color filter 3 is arranged coaxially with the tube body 11. One half of the color filter 3 is arranged between the lamp L and the photodiode PD, and the other half is held by the guide member 13. There is. Furthermore, from the center of the color filter 3, the rotary drive shaft
The color filter 2 is extended, and the color filter 2 is rotated at an arbitrary angle by the rotational force transmitted through the rotary drive shaft 14.

The color filter 3 is divided into three as shown in FIG. 3, and a red filter 3a, a green filter 3b and a blue filter 3c are attached to each divided area.
Then, by rotating the color filter 3 as described above, any one of the three color filters 3a, 3b and 3c is arranged in a portion between the lamp L and the photodiode PD. Note that the gap g between the lamp L and the color filter 3 is arranged so as to be substantially in the center of the side hole 12.

The arithmetic circuit 6 has a function of calculating the color mixture characteristic based on the toner density detection value for each color obtained from the detection light color-separated by the color filter 3. As an example of the color mixing characteristics, a color circle as shown in FIG. 4 is used. In the method using the color circle, the hue error and the grayness (turbidity) are calculated based on the toner density detection value for each color obtained from the color-separated detection light based on the following expressions. That is, the highest toner density detection value for each color is H,
Hue error = {(ML) / (HL)} × 100 (%) Grayness = (L / H) × 100 (%) where M is the middle and L is the lowest. The results are plotted on the color circle shown in FIG. 4, and the state is displayed on the monitor display circuit 10.

In such an embodiment, the toner density is detected while the color filter 3 of the probe 2 is rotated, and the toner density detection signal for each color separated into three colors is output from the probe 2. The hue error and the grayness are calculated by the arithmetic circuit 6 of the density control circuit 4 based on the toner density detection signal for each color. For example, in the case of yellow toner, with respect to the reference area shown in FIG.
When the position indicated by the above calculation result is moving in each of the arrow E _C direction, the arrow D direction, and the arrow E _M direction, color mixing with other colors is progressing, and noise due to color mixing causes noise. The original toner density is obtained after cutting. Further, when the toner is moved in the H direction, the density of the yellow toner has decreased, so the valve of the toner conch bottle is opened through the solenoid valve control circuit 9 to replenish the concentrated toner. This operation is repeated until the calculated value returns to the area A.

As another embodiment of the present invention, three filters having complementary colors such as yellow, magenta and cyan can be used as the color filters.

Further, as in the embodiment shown in FIG. 5, one lamp L
Alternatively, three photodiodes PD may be arranged to face each other, and the color filters 13a, 13b and 13c of different colors may be adhered to the light receiving portions of the photodiodes PD. Furthermore, in the embodiment shown in FIG. 6, the lamp L
There are 3 pairs of a photo diode PD and a photodiode PD. According to such an embodiment, the rotary driving mechanism for the color filter as in the first embodiment can be omitted.

(Effects) As described above, the toner density detecting device according to the present invention uses the density control circuit to mix color characteristics based on the toner density detection value for each color obtained through the color filter that separates the detection light from the light emitting element. Therefore, the original color toner density can be detected while eliminating noise due to color mixing, and a stable color toner density can always be maintained to maintain a good image.

[Brief description of drawings]

FIG. 1 is a block diagram of a toner concentration detecting device according to an embodiment of the present invention, and FIG. 2 is a partially enlarged side view of a probe.
FIG. 3 is a front view of a color filter, FIG. 4 is a diagram showing a color circle, FIGS. 5 and 6 are partially enlarged side views of a probe in another embodiment of the present invention, and FIG. 7 is a toner. 6 is a diagram showing the density detection characteristics of FIG. 2 ... Probe, 3 ... Color filter, 4 ... Density control circuit, L ... Lamp, PD ... Photodiode.

Claims (1)

[Claims] 1. A toner concentration detecting device in which a light emitting element and a light receiving element are arranged with a predetermined gap interposed therebetween to optically detect the toner concentration of a developer in the gearup. Color filters of multiple colors arranged in the gap to separate the detected light,
A toner density detecting device comprising: a density control circuit for calculating a color mixing characteristic based on a toner density detection value for each color obtained from detection light color-separated by the color filter.