JP2966796B2 - Method and apparatus for controlling toner concentration - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a toner density control method.
And its device . 2. Description of the Related Art In recent years, a plurality of developing units have been arranged around a photoreceptor, and any one of the above-mentioned developing units can be selected by a user's designation, so that a latent image on the photoreceptor can be arbitrarily selected. There has been proposed an electrophotographic apparatus that develops (visualizes) with a toner of the following color. That is, for example, in the electrophotographic apparatus shown in FIG. 4, a first developing device A containing red toner and a second developing device B containing black toner are arranged around the photosensitive member 1 respectively. When the user operates a mode selection switch (not shown) on the operation panel, the selected one of the developing units A and B is changed to the photosensitive member 1 in accordance with the designated mode. , And obtains a copy of a designated color according to a known copying process such as charging, exposure, development, and transfer. When the first developing device A and the second developing device B use a two-component developer composed of toner and carrier, the toner and carrier are used to make the density of the copied image uniform. , I.e., toner concentration control to keep the toner concentration constant. In the above-described conventional toner density control method in an electrophotographic apparatus, for example, in FIG. 4, a density pattern (test image) of a designated toner is formed on a non-image portion of the photosensitive member 1 at a predetermined cycle. The density difference of the density pattern is detected as a reflected light amount difference by the well-known optical detecting means 2, and the reflected light amount is photoelectrically converted by the P sensor, thereby erasing, for example, the front and rear of the density pattern, and the surface of the photoconductor 1 The toner density is detected and controlled by comparing the P sensor output Vsg (approximately constant) obtained by viewing and the P sensor output Vsp (changed in accordance with the toner density) obtained by viewing the density pattern. Further, in the conventional toner density control, the detection timing of the toner density is performed at a predetermined cycle (for example, the first sheet after the main switch is turned on and every ten sheets thereafter), and when it is detected that the toner density is low, For example, until the next toner concentration detection timing, for example, up to the tenth sheet, the toner replenishing solenoid is turned on and off for each sheet, and the toner is continuously supplied to a predetermined developing device. In this toner density control method, if the detection light of the P sensor is selected to be infrared, the control level can be controlled irrespective of the color of the toner, as shown in FIG. Have been. Therefore, in a conventional electrophotographic apparatus, a method of controlling the toner density by using the same optical detecting means (including sharing of one detecting means) has been adopted. [0007] However, as shown in FIG. 4, for example, the above-mentioned conventional electrophotographic apparatus includes a second developing device B containing a frequently used black toner and a red developing device B which is rarely used. Since there is a difference in the developer capacity between the first developing device A containing the toner and the deterioration with time of the red toner having a small capacity is more easily promoted than that of the black toner having a large capacity. When the toner density is controlled by the same optical detection means, the red toner is detected by the P sensor as having a low toner density due to its deterioration over time, despite the proper toner density, as shown in FIG. As described above, the red toner is excessively supplied, and there is a problem that a mechanical trouble occurs due to background smearing of the copy and scattering of the toner. SUMMARY OF THE INVENTION An object of the present invention is to provide a toner density control method for an electrophotographic apparatus capable of avoiding an excessive supply of toner caused by a difference in toner color or capacity. According to the present invention, a latent image on a photoreceptor is visualized by attaching toner to a latent image by a plurality of developing units having different amounts of developer consisting of toner and carrier. In the toner concentration control device for detecting the toner concentration of the developing device containing a large amount of the developer, the toner concentration is detected by detecting the amount of the toner attached to the photoconductor, and the developing device containing the small amount of the developer is detected. The toner concentration is detected from the ratio of the toner and the carrier in the developing device. An embodiment of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows an example of a toner density control device controlled based on a toner density control method according to the present invention. This toner density control device detects the toner density of the first developing device A, which is less frequently used and has a smaller capacity, among the developing devices A and B disposed around the photoreceptor 1 by using the inductance detecting means 3. It is configured to detect the toner density of the second developing unit B, which is frequently used and has a large capacity, by using the same optical detecting means 2 as in the related art. As shown in FIG. 2, for example, the inductance detecting means 3 includes a detection coil 3a, a reference coil 3b, a detection oscillator 3c, a reference oscillator 3d, a gate 3e, an integrating amplifier 3f, a multivibrator 3g, a detector 3h, and a DC amplifier. 3i and a comparator 3j. When the developer passes through the detecting coil 3a, the inductance detecting means 3 changes the magnetic permeability and the inductance of the detecting coil 3a due to a change in the toner density, that is, a change in the ratio between the carrier and the toner. Using
The toner density is detected. That is, in FIG. 2, the detection coil 3a
The oscillation frequency of the detection oscillator 3c changes due to the change in the inductance of the detection oscillator 3c. On the other hand, the reference coil 3b is set in advance so that its inductance matches the value at the time of proper toner density. Then, the oscillation frequency of the reference oscillator 3d based on the reference coil 3b and the oscillation frequency of the detection oscillator 3c are added, and this is integrated, amplified, detected, and DC amplified by the integrating amplifier 3f, the detector 3h, and the DC amplifier 3i. Here, when the toner density of the first developing device A is high, the inductance L of the detection coil 3a becomes small, and the detection oscillator 3c
Oscillation frequency increases. As a result, the output of the comparator 3j becomes “L” level, and the comparator 3j outputs the toner supply signal “L”. On the other hand, when the toner concentration is low, the inductance L of the detection coil 3a increases, and the oscillation frequency of the detection oscillator 3c decreases. This allows
The output of the comparator 3j becomes "H" level,
Outputs a toner supply signal “H”. The toner supply signal, that is, the output of the inductance detecting means 3 is given to the toner density controlling means 4. Further, the toner density control means 4 has an output of a color designation input means 5 for outputting a mode selection signal by operating a mode selection switch for designating (designating by a user) a color of toner to be used, and optical detection. The outputs of the means 2 are each provided. On the other hand, an output terminal of the toner density control means 4 includes a first toner supply driving means 7 for driving the first toner supply roller 6 of the first developing device A, and a second developing device B
The second toner supply driving means 9 for driving the second toner supply roller 8 is connected to each other. Here, each of the toner supply driving means 7 and 9 is constituted by a mechanism for rotating each of the toner supply rollers 6 and 8 for a predetermined time by turning on and off a well-known toner supply solenoid. The toner density control unit 4 controls the first and second toner supply driving units 7 and 9 according to the outputs of the optical detection unit 2, the inductance detection unit 3, and the color designation input unit 5. That is, as shown in FIG. 3, for example, when the copy switch of the electrophotographic apparatus is turned on, the toner density control means 4 first determines which of the first developing unit A and the second developing unit B It is determined whether or not an image is to be formed. This judgment is determined by the input from the color designation input unit 5. Here, when the user designates the red toner, the first developing device A is moved to the vicinity of the photoreceptor 1 when the black toner is designated, and the developing device is brought into a developable state. Next, when the first developing device A is selected in the above determination, the inductance detection mode is turned on, and the output of the inductance detection means 3, that is, the toner replenishment signal is "L" according to a predetermined program.
It is determined whether it is "H". Thus, when the toner supply signal is "H", the first toner supply driving means 7
Is turned on, and the red toner is supplied into the first developing device A. Next, when predetermined toner replenishment (a preprogrammed number of toner replenishments) is completed, the first toner replenishment driving means 7 is turned off, and it is determined whether or not copying is completed, and then the operation is stopped. On the other hand, when the second developing device B is selected in the above judgment, the optical detection mode is turned on, and the output of the optical detection means 2 is set to "H" according to a predetermined program.
Based on “L”, the second toner supply driving unit 9 is turned on, and black toner is supplied into the second developing device B. Hereinafter, similarly to the case of the red toner, when the predetermined toner replenishment is completed according to a unique program, the second toner replenishment drive unit 9 is turned off, and the operation is stopped when the copy is completed. As described above, the toner density control device embodying the present invention controls the toner density control of the first developing device A and the toner density control of the second developing device B by different toner density control means. The toner supply can be controlled according to a unique program. Therefore, according to the toner density control method of the present invention, an excessive supply of toner caused by a difference in toner color or capacity is avoided. According to the present invention, the toner concentration of a developing device containing a large amount of developer is detected from the amount of toner adhering to the photoreceptor, and the developing device containing a small amount of developer is detected. The toner concentration is detected from the ratio of toner and carrier in the developing device. By increasing the load on the same carrier, even if carrier deterioration over time occurs, an accurate toner concentration in consideration of carrier deterioration can be detected, and background contamination and toner scattering due to excessive replenishment can be avoided.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram of one embodiment of the present invention. FIG. 2 is a block diagram of an inductance detecting unit in the embodiment shown in FIG. FIG. 3 is a flowchart showing an example of the operation of the embodiment shown in FIG. 1; FIG. 4 is a schematic view of a conventional electrophotographic apparatus. FIG. 5 is a diagram showing a relationship between a toner adhesion amount on a photoconductor and a reflected light amount. FIG. 6 is a diagram illustrating a relationship between the number of copies and a toner density. DESCRIPTION OF SYMBOLS A First developing unit B Second developing unit 1 Photoconductor 2 Optical detection unit 3 Inductance detection unit 4 Toner density control unit 5 Color designation input unit 6 First toner supply roller 7 First toner supply drive unit 8 Second toner supply roller 9 Second toner supply drive unit

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-61-132969 (JP, A) JP-A-57-136668 (JP, A) JP-A-59-124359 (JP, A) 45278 (JP, A) JP-A-59-165081 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G03G 13/01 G03G 15/01-15/01 117 G03G 15/08 -15/095

Claims (1)

(57) [Claims] A large amount of developer is accommodated in a toner concentration control device for developing a latent image on a photoreceptor by applying toner to a latent image on a photoreceptor with a plurality of developing devices having different amounts of developer composed of toner and carrier. The toner concentration of the developing device is detected by detecting the amount of toner adhering to the photoconductor, and the toner concentration of the developing device containing a small amount of the developer is detected from the ratio of the toner and the carrier in the developing device. A toner concentration control device characterized by the above-mentioned. 2. A large amount of developer is accommodated in a toner concentration control device for developing a latent image on a photoreceptor by applying toner to a latent image on a photoreceptor with a plurality of developing devices having different amounts of developer composed of toner and carrier. The toner concentration of the developing device is detected by detecting the amount of toner adhering to the photoconductor, and the toner concentration of the developing device containing a small amount of the developer is detected from the ratio of the toner and the carrier in the developing device. A toner density control method characterized by the above-mentioned.