JPH0256577A - Toner concentration controller - Google Patents

Abstract

PURPOSE:To control concentration easily and stably even if a detector is stained by controlling the quantity of light emission of an optical detector by a control circuit so that the output level of the optical detector is constant. CONSTITUTION:This controller has the optical detector 2 which detects a mark for toner concentration control formed in a noimage area on a latent image formation medium 1 optically and the control circuit 3 which controls toner supply to a developing device 4 according to the detected level of the mark for toner concentration control by the optical detector 2. Then the control circuit 3 controls the quantity of light emission of the optical detector 2 so that the output level of the optical detector 2 is constant. Namely, the photodetection level of the optical detector 2 is monitored and the quantity of light emission is adjusted automatically so that the photodetection level is a certain constant value. Consequently, even if the detector 2 is stained, the output is made constant and the toner concentration control is performed stably and easily.

Description

[Detailed Description of the Invention] [Table of Contents] (Field of Application in the Renovation Industry) Conventional Technology Means for Solving Problems to be Solved by the Invention (Fig. 1) Working Example (a) Description of one Example (Fig. 2, Fig. 3) (b) Description of another embodiment (Fig. 4, Fig. 5) (c) Description of another embodiment Effect of the invention [Summary] A latent image formed on a latent image forming medium Regarding toner density control devices that detect toner density control marks with optical detectors and control toner density in developing devices, the purpose is to easily and stably control the density even if the detector is dirty. an optical detector that optically detects a toner concentration control mark formed in a non-image area of a forming medium; - a toner concentration control device having a control circuit for controlling toner replenishment, the control circuit being configured to control the amount of light emitted by the optical detector so that the output level of the optical detector is a constant value; Configured.

[Industrial application field]

The present invention relates to a toner density control device that controls the toner density of a developing device by detecting toner density control marks formed on a latent image forming medium using an optical detector.

In devices such as electrophotographic devices that form a latent image on a medium and develop it to form a toner image, toner is controlled to be supplied to the developing device in order to maintain the toner density of the toner image at a predetermined level. .

In order to detect this toner concentration, a method is used in which a toner concentration control mark is formed on the medium and the mark is detected by an optical detector.

Since such an optical detector needs to be mounted at a position close to the medium, the light receiving and emitting surfaces of the detector become dirty due to toner scattering and the like.

Therefore, there is a need for a technique that does not affect the toner concentration detection performance even due to such an error.

[Conventional technology]

Conventionally, air has been blown onto the detector in order to prevent the detector from being contaminated by toner or the like.

Conventionally, when the reflection level of the medium excluding the toner mark area drops to a certain value, an error is reported as the detector is dirty, and cleaning of the extractor is requested.

Furthermore, as seen in Patent Application Publication No. 14348/1983, there was also a method of detecting toner concentration using differential outputs of a pair of detectors.

[Problem to be solved by the invention]

However, with the method of blowing air, since the gap between the medium and the detector is small, it is difficult to blow the air directly onto the receiving and emitting surfaces of the detector. There is a problem in that it disturbs the toner image, making it virtually impossible to control the toner density stably.

Furthermore, the method of monitoring the reflection level of the detector has the problem that as the amount of printing increases, the detector becomes dirty more quickly, which shortens the regular cleaning cycle and requires more effort.

Furthermore, the method of providing a pair of detectors has the problem that not only an extra detector is required, but also an extra mounting area is required.

Therefore, an object of the present invention is to provide a toner concentration control device that can easily and stably control the concentration even if the detector is dirty.

Another object of the present invention is to provide a concentration control device that can easily and stably control the concentration even if the detector is dirty, and that makes it easy to adjust the position of the detector.

[Means to solve the problem]

FIG. 1 is a diagram showing the principle of the present invention.

In the present invention, as shown in FIG. 1(A), a latent image forming medium 1
an optical detector 2 that optically detects a mark for toner density control etc. formed in a non-image area of the developing device 4 based on the detection level of the mark for toner density control by the optical detector 2; In a toner density control device having a control circuit 3 for controlling toner replenishment, the control circuit 3 controls the amount of light emitted from the optical detector 2 so that the output level of the optical detector 2 is a constant value. Configured to control.

As shown in FIG. 1(B), the present invention also provides an optical detector 2 for optically detecting a toner density control mark formed in a non-image area of a latent image forming medium 1; target detection 2
In a toner density control device having a control circuit 3 that controls toner replenishment of the developing device 4 based on the detection level of the toner density control mark of S2, the control circuit 3 is configured to control the output level of the optical detector 2. The optical detector 2 is configured to control the amount of light emitted from the optical detector 2 such that A switch 9b is provided to connect either one of the control circuit 3 and the level generation source 9a.

[Effect]

In the present invention, the light receiving level Din of the optical detector 2 is monitored, and the amount of light emitted is automatically adjusted each time the light receiving level Din becomes a certain constant value.

Even if dirt occurs on the toner 2, the output can be kept constant, and toner density control can be achieved stably and easily.

Furthermore, in the present invention, when the detector 2 and the toner concentration control mark are aligned in opposing positions at the time of shipment or replacement in the field, when such automatic adjustment is activated, the output level fluctuates and the optimal position adjustment is not possible. Since this is not possible, the light is emitted at a constant level, and the optimal facing position can be determined by monitoring the output level.

〔Example〕

(a) Description of one embodiment FIG. 2 is a configuration diagram of an embodiment of the present invention.

In the figure, the same parts as those shown in FIG. 4b is a toner replenishing section that replenishes toner into the developing device 4 according to instructions from the control circuit 3; 5 is a pre-charger that charges the photosensitive drum 1;

6 is a transfer charger, which transfers the toner image on the photosensitive drum 1 onto the paper PP; 7 is a cleaner, which cleans the photosensitive drum 1; 8 is a feed roller, which transfers the toner image from the photosensitive drum 1 onto the paper PP. It is meant to be transported.

In FIG. 2(B), 2a is a light emitting diode that irradiates the photosensitive drum 1, 2b is a phototransistor that receives reflected light from the photosensitive drum 1, and 20 is a voltage-current exchanger. 21 is a current-voltage conversion circuit that converts the drive voltage of the control circuit 3 into a drive current id to drive the light emitting diode 2a, and 21 is a current-voltage conversion circuit that converts the output current 1j2 of the phototransistor 2b into a voltage. It outputs the drum surface level VDRM and mark level VMRK.

30 is a D/A (digital/analog) converter, which converts the digital drive voltage Dout of the control circuit 3 into an analog world and outputs it to the voltage-current conversion circuit 20; 31 is an A/D' (analog/digital) converter; ) converter, and the output level of the current-voltage conversion circuit 21 VDRM%
It converts VMIIK into a digital value Din and outputs it to the control circuit 3.

In this embodiment, the control circuit 3 is constituted by a microprocessor, and controls toner density and automatically adjusts the amount of light of the detector by executing a program.

Then, with respect to the photosensitive drum 1 rotating in the direction of the arrow in the figure,
Pre-charging is performed by the pre-charging device 5, a light image is exposed, and an electrostatic latent image is formed.

The toner image formed on the photosensitive drum 1 is developed by the Mag I cola 4a to which a developing bias voltage is applied, and the developed toner image is transferred by the transfer charger 6 to the paper PP fed by the feed roller 8, and after the transfer, the photosensitive drum 1 is cleaned by cleaner 7.

FIG. 3 is a detailed explanatory diagram of the present invention, FIG. 3(A) is a process flow diagram, and FIG. 3(B) is an explanatory diagram of automatic adjustment operation.

(2) The control circuit (hereinafter referred to as MPU) 3 reads the photosensitive drum reflection level VflRM obtained by integrating the output of the light receiver (phototransistor) 2b from the A/D converter 31, and compares it with the initial value VDRMO.

■ If V IIRM and V DRMO do not match, MPU3 will detect that VDRM is larger than VDRMO (V DI
IM > V DRMO), and V DIl+4
> If it is V DIINO, reduce the output Dout to the D/A Koni/Herta 30 to (Dout 1), and
If RM<V DRMO, the output Dout to the D/A converter 30 is increased to (Dout+1), and the process returns to step.

In this way, before starting printing, that is, when starting the drum, A
The output of the /D converter 31, that is, the light receiving level Dout of the light receiver 2b, is adjusted repeatedly until it reaches the initial value VDMMO, and the value of the output Dout is determined as shown in FIG. 3(B) before toner mark detection. and fix it.

(2) When the adjustment is completed in this way, printing starts, and toner marks TNM are written on the photosensitive drum 1 in the non-printing area for each page.

The MPU 3 reads the toner mark level VHRK obtained by peak-holding the output of the phototransistor 2b from the A/D converter 31, and compares it with a predetermined threshold value Vs.

As shown in FIG. 3(B), if VMRlt is less than Vs, the density is low, so the toner replenisher 4b is instructed to replenish 1-toner.

If VMRK is less than Vs, the toner replenisher 4b is not instructed to replenish toner.

In this way, toner density control can be performed while automatically adjusting the reflection level of the drum 1 to a constant value, and accurate toner density control is possible regardless of whether the detector is dirty.

Since the light emitting current has a limit depending on the detector, if the light emitting current is controlled to its maximum value and the detector is then cleaned, the cleaning cycle will be significantly longer.

Furthermore, since the reflectance of the photosensitive drum 1 differs for each photosensitive drum 1, the level has conventionally been adjusted for each tram.
That adjustment is also unnecessary.

Furthermore, the control level Vs of the 1-ner mark is shifted in accordance with the decrease in the reflection level of the drum, but with this method, there are many variations in print density between devices.
In the present invention, since the reflection level of the drum is kept constant, no variation occurs.

(b) Description of other embodiments FIG. 4 is a block diagram of another embodiment of the present invention.

In the figure, the same parts as those shown in FIGS. 1 and 2 are shown with the same symbols, and 22 is an integrating circuit, and
It integrates the output voltage of the voltage conversion circuit 21 and outputs the tram reflection level VDR14, and includes a capacitor CI, a resistor R7, an integrating amplifier M3, and input resistors R6 and R8.
23 is a mark peak hold circuit which holds the peak of the output voltage of the current-voltage conversion circuit 21 and outputs a toner mark level VMRK.

The voltage-current conversion circuit 20 includes an amplifier M1 that amplifies the command voltage from the switch 9b, a transistor Tr that causes a current Id to flow through the light emitting diode 2a according to the output of the amplifier M1, and a resistor R2.

Further, the current-voltage conversion circuit 21 is composed of a resistor R3 that generates a voltage according to the detected current IA of the transistor 2b, and an amplifier M2, and the level generation source 9a is connected to the potential source v3. It is composed of voltage dividing resistors R9 and R10.

In this embodiment, when the switch 9b is connected to the a side, automatic adjustment at the time of starting the drum and subsequent mark level detection operation are performed as in FIG. 2.

On the other hand, when manufacturing the apparatus or replacing the detector 2 in the field, it is necessary to adjust the detector 2 to face the toner mark TNM.

This will be explained using FIG. 5, which is an explanatory diagram of another embodiment of the present invention.

As shown by the circle in FIG. 5(A), adjusting the light emitting position and the detection position of the detector 2 so that they face the 1-ner mark TNM is the opposing position adjustment, which cannot be performed visually. Generally, the toner mark level is adjusted by checking the toner mark level eight times with a synchroscope.

That is, in the positional relationship as shown by the dotted line in FIG. 5(A), the toner mark level becomes VMRK in FIG. 5(B), and in the positional relationship as shown in the solid line at just right, the toner mark level becomes 1. as shown in the solid line. It looks like 1RK, and you can adjust the position just right while checking the toner mark level on the synchroscope.

At this time, when the automatic adjustment of the reflection level described in i;7 is activated, the drum reflection level ■DR,4 is
Because of the integral value of , it varies depending on the toner mark TNM,
Since an attempt is made to correct this to a constant value, the toner mark level and drum reflection level constantly fluctuate on the synchroscope, making it difficult to adjust the position optimally.

Therefore, when adjusting the position, the maintenance person must set switch 9b to b.
The detector 2 and the toner mark are adjusted to face each other by manually switching to the side so that the automatic adjustment does not work, and by setting the level i9a to drive the light emitting diode 2a with a constant current so that it emits light at a constant amount of light at all times. This is a simplified version of

(c) Description of another embodiment In the above embodiment, an electrophotographic printer using a laser beam was explained, but an electrophotographic printer using an LED array, an electrophotographic copying machine, and a transfer using an electrostatic recording method are also applicable. It can also be used in devices that use electrostatic toner images, such as electrostatic recording devices.

Although the present invention has been described above using examples, the present invention can be modified in various ways according to the gist of the present invention, and these are not excluded from the present invention.

〔Effect of the invention〕

As explained above, according to claim 11 of the present invention, even if the detector becomes dirty, the reflection level is automatically adjusted to a constant level, so there is no need to blow air and separate detection is performed. In addition to being able to accurately control the toner density, it also has the effect of significantly lengthening the cleaning cycle and eliminating the need for level adjustment for each latent image forming medium. play.

Further, according to claim (2) of the present invention, in addition to the effect of claim 1), there is an effect that alignment adjustment between the detector and the toner mark is facilitated.

[Brief explanation of the drawing]

Figure 1 is a diagram of the principle of the present invention. FIG. 2 is a configuration diagram of an embodiment of the present invention. FIG. 3 is a detailed explanatory diagram of the present invention, FIG. 4 is a configuration diagram of another embodiment of the present invention, FIG. 5 is an explanatory diagram of another embodiment of the present invention. latent image forming medium (photosensitive drum), ・-optical detector, ・-control plate circuit, ・Developer, b.-Switch. 9a.-level source, Patent applicant: Fujitsu Limited Representative Patent Attorney Akira Yamatani Principle diagram of the present invention 11th!1 (A) Ichigo-deidendensei-ku Figure 2 f’A)

Claims (1)

[Claims] (1) an optical detector (2) that optically detects a toner density control mark formed in a non-image area of the latent image forming medium (1); and the toner density of the optical detector (2). A toner density control device comprising: a control circuit (3) that controls toner replenishment of a developing device (4) based on a detection level of a control mark; 1. A toner concentration control device characterized in that the amount of light emitted by the optical detector (2) is controlled so that the output level of the optical detector (2) becomes a constant value. (2) an optical detector (2) that optically detects a toner density control mark formed in a non-image area of the latent image forming medium (1); and the toner density of the optical detector (2). A toner density control device comprising a control circuit (3) that controls toner replenishment of a developing device (4) based on a detection level of a control mark, the control circuit (3) being connected to the optical detector (2). a level generation source configured to control the amount of light emitted from the optical detector (2) so that the output level of the optical detector (2) is constant; (9a); and a switch (9b) connecting either the control circuit (3) or the level source (9a) to the optical detector (2).
) is provided.