JPS61215573A - Controller for toner density - Google Patents

Abstract

PURPOSE:To detect accurately supplied toner decreasing below a specific amount and to simplify the structure of a toner hopper by digitizing the output signal of a density detecting means into multistage toner density data and comparing it with reference data, and thus detecting toner empty state. CONSTITUTION:The multistage toner density data B obtained by converting the output voltage of a magnetic sensor 23 as a density detecting means into digital data by an A/D converting circuit 35 is compared with the reference data read out of a RAM 41; when A<=B (namely, when toner density is low or reference density), the density data is compared with toner empty data C in a ROM 40. Then when C>B, a solenoid 39 is turned on to supply toner and when C<=B, it is judged that the toner in a toner hopper 25 decreases below a specific amount and a toner empty display 43 is turned on to indicate that. Consequently, toner empty detection is performed accurately and a mechanical mechanism is eliminated to simplify the structure of the toner hopper.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] One aspect of the present invention is a toner concentration control method for controlling the toner concentration of a developer contained in a developing device in an image forming/forming apparatus such as a copying machine. Regarding equipment.

[Technical Background of the Invention] Generally, for example, in a copying machine, a developer is often used to develop an electrostatic latent image on a photoreceptor by a magnetic brush method using a two-component developer consisting of toner and carrier. In a copying machine using such a developing device, a density detector detects the toner concentration of the developer contained in the developing device, and a toner replenishing means is operated according to the detection result to replenish toner. The toner concentration in the developer is controlled to a constant value.

Further, when the amount of replenishing toner in the toner replenishing means falls below a predetermined amount (toner empty), this is detected and notified. That is, as the amount of toner decreases, an actuator installed inside a toner hopper that stores replenishment toner approaches a reed switch installed on the side of the toner hopper, and a magnet attached to the tip of the actuator turns on the reed switch. This causes the toner empty indicator to light up with the on signal.

[Problems with the Background Art] However, in the conventional toner empty detection method described above, the reed switch is turned on before the toner in the toner hopper is completely exhausted, making it impossible to accurately detect empty toner in the toner hopper. In addition, when converting the toner hopper into a cartridge, it is difficult to simplify the shape of the toner hopper, leading to an increase in costs. Furthermore, since it is a mechanical detection method, there is also the problem that many parts are required.

[Object of the Invention] The present invention has been made in view of the above circumstances, and its purpose is to accurately detect when the amount of replenishing toner in a toner replenishing means has fallen below a predetermined amount (toner empty). It is an object of the present invention to provide a toner concentration control device which can simplify the structure of a toner hopper of a toner replenishing means.

[Summary of the Invention] In order to achieve the above object, the present invention digitizes the output signal of the density detection means to convert it into multi-stage toner density data, and converts the toner density data into preset reference data. The system is configured to detect toner empty through comparison.

[Embodiment of the Invention] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

FIG. 5 shows a copying machine as an example of an image forming apparatus according to the present invention. That is, 1 is a housing, and a photosensitive drum 2 that rotates in the direction of arrow a in the figure is provided approximately at the center of the housing. Further, in the upper part of the housing 1, a document table 3 for supporting a document is provided so as to be able to reciprocate in the direction indicated by the arrow in the figure. By moving the document table 3 in synchronization with the rotation of the photoreceptor drum 2, the light emitted from the exposure lamp 4 is reflected by the document on the document table 3, and the reflected light is transmitted through convergent light transmission. An image is formed on the photoreceptor drum 2 by the body 5, and is reflected on the photoreceptor drum 2 as an inverted image of the document. At this time, by charging the surface of the photoreceptor drum 2 with the charging device 6, an inverted image of the original is formed on the photoreceptor drum 2 as an electrostatic latent image, and this electrostatic latent image is developed. It is configured to be visualized by applying toner with a container 7.

On the other hand, a paper feed device 8 is provided at a lower portion of the housing 1 to supply paper to the lower part of the photoreceptor drum 2 (image transfer section 14). The paper feed device 8 includes a paper feed cassette 9 which is removable and stores a plurality of sheets of paper on the left side of the housing 1, and a manual feed cassette 9 which is protruded from the right side of the housing 1 and is used to manually feed paper. One sheet of paper is loaded from the paper feed table 10 and the paper feed cassette 9.
It has a paper feed roller 511 that feeds sheets one by one, and a transport roller 12 that transports the paper sent out by the paper feed roller 11. At the same time as stopping the
The configuration includes a registration roller 13 that corrects the inclination of the leading edge of the paper and sends the paper to the image transfer unit 14 at a timing such that the leading edge of the paper and the leading edge of the toner image on the photoreceptor drum 2 coincide. There is.

The paper conveyed by the registration rollers 13 is sent to the image transfer section 14. The paper sent to the image transfer unit 14 comes into close contact with the surface of the photoreceptor drum 2 at the transfer charger 15, and the toner image on the photoreceptor drum 2 is then charged by the charger 15. is transcribed. After the transfer, the photosensitive drum 2 is configured so that residual toner on the surface thereof is removed by a cleaner 16 and the photosensitive drum 2 returns to its initial state. On the other hand, the transfer pattern paper is transferred to the transport roller 51.
7 to a heat roller 18 as a fixing device,
By passing through the fixing roller 18, the transferred image is heated and fixed. Then, the paper after fixing is transferred to the paper ejection roller 1.
9 so that the paper is discharged onto a tray 20 outside the housing 1.

The developing device 7 performs development using a two-component developer consisting of toner and carrier, and by forming a magnetic brush of the developer on the surface, the developer is applied to the area to be developed, that is, the photosensitive drum 2. A magnetic roller (
(developing roller) 21. In addition, 22 is the developing device 7
A developer agitator is used to agitate the developer inside. A magnetic sensor 2 as a density detection means is mounted on the side wall of the developing device 7.
3 is mounted with its detection head 24 portion exposed inside the developing device 7, and the toner concentration of the developer in the developing device 7 is detected by a change in the magnetic permeability of the developer. Further, a toner hopper 25 containing replenishment toner is provided above the developing device 7, and as a toner replenishing roller 26 provided at the bottom thereof rotates, the toner in the toner hopper 25 is transferred to the developing device 7. It is designed to be replenished internally. The toner supply roller 26 is rotatably driven by a solenoid (not shown) via a rotation mechanism (not shown).

FIG. 1 shows the toner control circuit.

That is, the magnetic sensor 23 includes a detection head 24 that includes an adjustment coil and a detection coil that come into contact with the developer in the developing device 7 and detect the magnetic permeability of the developer.
an oscillator 31 that drives the oscillator and outputs a reference phase signal, an amplifier 32 that amplifies the minute output signal from the detection head 24, and a detection signal amplified by this amplifier 32 and a reference phase signal output from the oscillator 31. a phase comparator 33 that compares the phase difference between the two, and a low-pass filter 34 that shapes the waveform of the signal output from the phase comparator 33.
It consists of The characteristics of the output voltage with respect to the toner concentration of this magnetic sensor 23 are shown in FIG.
The output voltage increases as the toner concentration decreases. The output voltage of the magnetic sensor 23 is supplied as an analog signal to an 8-bit A/D conversion circuit 35. This A
The /D conversion circuit 35 starts a conversion operation when a conversion command signal is supplied from a microcomputer (hereinafter simply referred to as microcomputer) 36 that controls the entire copying machine, and converts the input analog signal into digital data. The data is then supplied to the microcomputer 36 as multi-stage toner density data. Further, an auto toner set mode switch 37 is connected to the microcomputer 36, and by turning on this switch 37, the auto toner set mode is set. Further, a solenoid drive circuit 38 is connected to the microcomputer 36, and this drive circuit 38 drives a toner replenishment solenoid 39. The toner replenishment solenoid 39 is for rotationally driving the toner replenishment roller 26.

The microcomputer 36 also includes a ROM for storing reference data.
(Read-only memory) 40 and RAM (Random Access Memory) 41 are connected, and the RAM 41 is backed up by a backup power source 42 such as a battery. The ROM 40 stores toner empty data C and toner empty copy stop data D as reference data. In addition,
The toner empty copy stop data D is set to toner density data lower than the toner empty data C. In general, a toner empty indicator 43 is connected to the microcomputer 36 to notify that the amount of supplied toner in the toner hopper 25 has fallen below a predetermined amount.

Next, the operation in the above configuration will be explained. First, the operation of the main program will be explained with reference to the flowchart shown in FIG. Now, when the copy key (not shown) is turned on, the process proceeds to step A1, where it is determined whether the mode is normal copy mode or auto toner set mode based on the state of switch 37. If it is normal copy mode (if switch 37 is off) Proceed to step A2. In step A2, an external interrupt timer is set to permit external interrupts at intervals of 10 m5ec, for example, and the process proceeds to step A3 for normal copy control. Note that when an interrupt is permitted by the external interrupt timer, an interrupt program for the automatic toner detection mode, which will be described later, is executed. On the other hand, in step A1, if the auto toner set mode is selected (if the switch 37 is in the on state), step A
The process proceeds to Step 4, where a timer is set for, for example, 3 minutes to stir the developer, and the process proceeds to Step A5. In step A5, it is determined whether 3 minutes have elapsed or not, and when the 3 minutes have elapsed, the process proceeds to step 86. In step A6, for example, 350
Set the m5ec timer and proceed to step A7. In step A7, it is determined whether 350 m5ec has elapsed, and if 35QmSeC has elapsed, the process proceeds to step 88. In step 88, the microcomputer 36 starts A/D conversion by supplying a conversion command signal to the A/D conversion circuit 35, and the process proceeds to step A9. In step A9, the above A
The toner density data obtained by /D conversion is stored in the RAM 41 as reference data A, and the process proceeds to step AIO. In step A10, it is determined whether or not the mode is auto toner set mode. If the mode is not the auto toner set mode (if the switch 37 is off), the process returns to step A2, and if the mode is the auto toner set mode, the process returns to step A6. Go back and repeat the same operation as above. In this case, R
The reference data stored in AM41 will be sequentially rewritten with new data. After repeating this a predetermined number of times every 350 m5ec, the operation of the auto toner set mode is ended by turning off the switch 37, and the RAM 41
Reference data A is stored in . In this mode, an initial developer serving as a reference is stored in the developing device 7 in advance, and the toner density thereof is detected as described above and used as the reference data A.

Next, the operation of the interrupt program will be explained with reference to the flowchart shown in FIG. As described above, this operation is performed every time an interrupt is enabled by the external interrupt timer at intervals of 10 m5ec. If the interrupt is permitted, the process proceeds to step B1 to start A/D conversion, and the process proceeds to step B2. In step B2, reference data A in the RAM 41 is read out, and the process proceeds to step B3. Step B
In step 3, the toner density data B obtained by the A/D conversion is compared with the reference data A read from the RAM 41, and when A>8 (that is, when the toner density is high), the process proceeds to step B4. In step B4, the solenoid 39 is turned off and the process returns to the main program. In step B3, if A≦B (that is, when the toner density is low or the standard density), the process proceeds to step B5. In step B5, the density data B is compared with toner empty data C in the ROM 40, and if C>8, the process advances to step B6. In step B6, the solenoid 39 is turned on to replenish toner, and the process returns to the main program. In step B5, if C50, it is determined that the amount of toner in the toner hopper 25 has fallen below a predetermined amount, and the process proceeds to step B7. In step B7, the toner empty indicator 43 is turned on to notify that the amount of toner has fallen below a predetermined amount, and the process proceeds to step B8. In step B8, the density data B and the ROM 40 are
The comparison is made with the toner empty copy stop data D in
If so, it is determined that the toner in the toner hopper 25 has run out, and the process proceeds to step B9. In step B9, the copying operation is stopped and the process returns to the main program. −
In this way, the output voltage of the magnetic sensor 23 is converted into multi-stage digital data B by A/D conversion, and the data B is stored in the ROM 40 and compared with the toner empty data C, thereby detecting toner empty. It is something to do. As a result, Bettner empty detection can be performed more accurately than conventional mechanical detection methods.

Further, the mechanical mechanisms provided inside and outside of the conventional toner hopper can be eliminated, so the structure of the toner hopper can be simplified and it can be prevented from being touched by users or service personnel. In general, even if the toner hopper is made into a cartridge, toner empty detection can be performed using a device other than the cartridge mechanism, making it possible to simplify the cartridge section and reduce costs.

In the above embodiment, a ROM was provided separately from the microcomputer and the toner empty data and toner empty stop data were stored in this ROM, but the ROM was not provided and the data was stored in the ROM within the microcomputer. Good too.

Further, in the above embodiment, the case where the toner concentration of the developer is controlled in a copying machine has been explained, but the present invention is not limited to this, and development is performed using a two-component developer consisting of toner and carrier. The present invention can be applied to any image forming apparatus (for example, a laser printer or an electronic printer) equipped with a developing device that performs this process, as long as it controls the toner concentration of the developer.

[Effects of the Invention] As described in detail above, according to the present invention, it is possible to accurately detect when the amount of replenished toner in the toner replenishing means is less than a predetermined amount (toner empty), and the toner hopper of the toner replenishing means can be accurately detected. It is possible to provide a toner concentration control device whose structure can be simplified.

[Brief explanation of drawings]

The figures are for explaining one embodiment of the present invention, and FIG. 1 is a configuration diagram of a toner concentration control circuit, FIG. 2 is a diagram showing characteristics of output voltage with respect to toner concentration of a magnetic sensor, and FIG. FIG. 4 is a flowchart for explaining the operation of the main program, FIG. 4 is a flowchart for explaining the operation of the interrupt program, and FIG. 5 is a side view schematically showing the configuration of the copying machine. 2... Photosensitive drum, 7... Developing device, 21... Magnetic roller, 23... Magnetic sensor (density detection means), 2
4...Detection head, 25...Toner hopper, 26.
... Toner supply roller, 35 ... A/D conversion circuit, 3
6... Microcomputer, 38... Solenoid drive circuit, 3
9... Toner replenishment solenoid, 40... ROM,
43...Toner empty indicator.

Claims (5)

[Claims] (1) In an image forming apparatus that performs image formation using a developing device equipped with a developer conveying means for conveying a two-component developer consisting of toner and carrier to a developing area, a developing device housed in the developing device A concentration detection means for detecting the toner concentration of the agent and converting it into an analog electric signal, a conversion means for obtaining multi-level toner concentration data by converting the output signal of the concentration detection means into digital data, and the conversion means a first comparing means for comparing the toner density data obtained with first reference data set in advance; a toner replenishing means for replenishing toner to the developing device according to the comparison result of the first comparing means; a second comparing means for comparing the toner density data obtained by the converting means with second reference data having a density lower than the first reference data set in advance; and replenishing the toner according to the comparison result of the second comparing means. 1. A toner concentration control device comprising a notification means for notifying that the amount of supplied toner in the device has fallen below a predetermined amount. (2) The toner concentration control device according to claim 1, wherein the concentration detection means is a magnetic sensor that detects the toner concentration of the developer by magnetically detecting a change in the magnetic permeability of the developer. (3) The toner density control device according to claim 1, wherein the developer conveying means is a magnetic roller that conveys the developer while rotating. (4) The toner density control device according to claim 1, wherein the image forming device is a copying machine. (5) The toner density control device according to claim 4, wherein the developing area is a surface of a photoreceptor on which an electrostatic latent image is formed.