JP3977938B2 - Development device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device using a two-component developing system in electrophotographic systems such as copying machines, printers, and fax machines, and in particular, by improving toner density control using a toner density sensor, The present invention relates to a technology for detecting a failure of a concentration sensor.
[0002]
[Prior art]
Conventionally, a color image forming apparatus for forming a color image using a plurality of different developing containers containing four different types of toners is known, and the four types of developing containers are to be easily maintained and inspected. It is designed to be removed and inspected for each developer container.
[0003]
Since there are a plurality of such developing containers, they are likely to be detached during maintenance and inspection. In order to solve this problem, as disclosed in JP-A-6-51625, the detection signal from the toner density sensor is shaped into a pulse signal, and density detection is performed based on the number of pulse signals generated within a predetermined gate period. There has been disclosed a technique for detecting the presence or absence of wearing by using a device that performs the above-described operation so as to determine that no wearing is performed when a pulse signal is not generated within the gate period.
[0004]
[Problems to be solved by the invention]
However, such a technique only detects whether or not a pulse signal is generated within the gate period. For example, even if the stirring member of the developer container fails due to stress such as developer, the pulse is electrically pulsed. Since the signal is shaped, a pulse signal is generated due to detection of the developer, resulting in poor agitation, and even if the toner sensor fails, it may be determined that it is not installed, so accurate detection cannot be performed. .
[0005]
In recent years, an image forming apparatus having a long life has been developed using an a-Si photosensitive member. However, when the configuration is such as the density detection of such a technique, the detection surface of the toner density detection sensor in a long-term use. In some cases, the developer stays in the vicinity or the toner adheres to the detection surface of the toner concentration detection sensor, resulting in a toner concentration detection error. Therefore, the concentration detection cannot be performed stably for a long time.
[0006]
The present invention has been made in view of the above-mentioned problems, and it is possible to discover in detail the mounting state of the developing container and the defects in the developing device with a simple configuration, and it can be used for a long time and is stable. An object of the present invention is to provide a developing device capable of controlling the toner density.
[0007]
[Means for Solving the Problems]
In order to solve the above-described problems, the present invention provides a developer container in which a developer composed of a carrier and toner is stored, toner density detecting means for magnetically detecting toner density information in the developer container, and the toner density detection. Waveform forming means for forming a waveform in which the output value from the toner density detecting means is lowered by mechanical means for periodically scraping the developer present on the detection surface of the means, and vibration formed by the waveform forming means In a developing device that controls toner density based on an output value of a waveform, a sampling unit that samples the vibration waveform at regular intervals, a sampling number setting unit that sets the number of samplings within a predetermined period of the vibration waveform, and the sampling unit It is determined whether the value sampled by the step is a region that is lower than the reference value T / Cref by a predetermined value Va. Comprising the minimum value output detecting means for detecting a predetermined output value decreases, and the case where even a number of times set by the sampling times setting means by sampling does not detect the output value decreases by the minimum value output detecting means It is characterized by determining as a malfunction.
By adopting such a configuration, the developer on the detection surface is periodically scraped by mechanical means, so that the staying toner can be used for a long time without adhering. Since the output value decreases at the period of, it can be easily understood that the decreased output value cannot be detected because it is not installed, the mechanical means is faulty, or the toner density sensor is faulty.
[0008]
Further, the minimum value output detecting means may be configured to detect the minimum value of the output value reduced by the sampling means or the vicinity thereof. Thus, by detecting the minimum value of the development density or the vicinity thereof, it is possible to reliably detect that the output value is lowered, and it is possible to improve the accuracy.
[0009]
Further, the detection of the minimum value or the vicinity thereof may be configured such that a predetermined detection area is provided for the decreasing output value, and the minimum value or the vicinity thereof is detected from the output value in the detection area. good. Since the detection area is thus provided for detection, it becomes strong against noise and does not malfunction.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram for explaining the outline of a color image forming apparatus of the present invention. Reference numeral 1 denotes a color image forming apparatus main body. Reference numeral 2 denotes a photosensitive drum, and an OPC or a-Si photosensitive member is used. A charging roller 3 is configured to be able to apply a predetermined bias voltage to the surface of the photosensitive drum 2 from a power source (not shown). Reference numeral 4 denotes an exposure unit, and image information from an external terminal is irradiated with a laser beam on the surface side charged on the photosensitive drum 1 to form a latent image. In this case, LED light may be used.
[0011]
A developing unit 5 develops color toner on the formed latent image. The developing unit 5a develops yellow from the upstream side in the rotation direction of the photoreceptor 2, the developing unit 5b develops magenta, and the developing unit 5c develops cyan. The developing devices 5d for developing black are arranged. Each developing device 5 has a toner container 50a containing yellow toner, a developing container 51a for developing toner supplied by a supply roller 52a, and a toner container 50b containing magenta toner and a supply roller 52b. A developing container 51b for developing the replenished toner, a toner container 50c containing cyan toner and a developing container 51c for developing toner replenished by the replenishing roller 52c, and a toner container 50d containing black toner are replenished. A developing container 51d for developing the toner replenished by the roller 52d is disposed in the upper part of the color image forming apparatus. A nonmagnetic toner is used for each color toner of the present invention. Reference numeral 31 denotes a cleaning unit which removes toner that has not been transferred on the intermediate transfer drum 6 described below from the photosensitive drum 2.
[0012]
An intermediate transfer drum 6 performs color superposition by sequentially repeating the operation of transferring the toner developed on the photosensitive drum 2 by applying a predetermined bias in order for each toner. 6a is a secondary transfer roller, and 6b is a cleaning fur brush. In this color superposition, although not shown, the secondary transfer roller 6a and the cleaning fur brush 6b are provided with a retreat mechanism that is retracted from the intermediate transfer drum 6 until each color is completely superposed.
[0013]
Reference numeral 7 denotes a paper feeding means, which is loaded with a large capacity paper disposed below the color image forming apparatus 1 and feeds the uppermost paper by a paper feed roller 70, and paper one by one. It consists of a manual feed unit that transports it. The sheet fed from the sheet feeding means 7 is conveyed to the registration roller 60, and after being aligned and timed, is fed to the secondary transfer roller 6a at the timing of the toner superimposed on the intermediate transfer drum 6. After the transfer, the sheet is conveyed toward the exit side by the conveyance belt 8. Reference numeral 9 denotes a fixing unit which fixes the toner, which is arranged near the outlet side and is secondarily transferred, to the sheet by heat and pressure.
[0014]
Reference numeral 10 denotes a paper discharge unit, which includes a face-up tray 10a that discharges the paper heat-fixed by the fixing unit 9 with the print surface facing up, and a face-down tray 10b that discharges the paper with the print surface down. .
[0015]
Here, the configuration of the developing device of the present invention will be described. FIG. 2 illustrates the internal mechanism of the developing device. As shown in the figure, each color toner is supplied to each developing container 51a to 51d from toner supply containers 50a to 50d (not shown), and the magnetic carrier mixed in each developing container 51a to 51d is each color. It has a mechanism that can be mixed with toner. For the sake of brevity, only the mechanism of the developing container 5a will be described, and other same developing devices have the same functions and are omitted.
[0016]
A developing roller 53 (not shown) is provided with a magnet inside, and can be rotated by carrying a developer mixed with toner and carrier mixed in the developing container 51a around by the magnetic force. It is configured. Reference numeral 54 denotes a developer regulating member, which is configured so that a magnet is disposed therein to form a magnetic shield, and the developer is transferred to a position facing the photosensitive drum 2 only when developing. Reference numeral 55 denotes a first mixer, which includes an outer mixer 56 and a screw-type inner mixer 57 in order to increase the stirring ability. The outer mixer 56 is provided with a scraper 56a which is a feature of the present invention.
The scraper 56a is configured by attaching a urethane foam member to a rubber member. This is because the urethane foam member alone is deformed by the pressure of the developer, and the surface of the toner density sensor cannot be scraped out sufficiently. Configure as follows.
58 is a toner concentration sensor (detection means), and a magnetic permeability sensor is used. The toner density sensor is configured to magnetically detect a change in the toner density (volume) of the developer that has been conveyed onto the detection surface 58a and stayed. The toner staying on the detection surface 58a is scraped off by the elastic member 56a. Reference numeral 59 denotes a second mixer, which is configured to transfer the developer to the developing roller 53 side while stirring the developer.
With the above configuration, the developer can be agitated at a constant cycle by the rotation of the scraper 56 a as the first mixer 55 rotates, and when this state is detected by the toner density sensor 58, the constant cycle. Can be detected.
[0017]
FIG. 3 shows output characteristics obtained from the toner density sensor 58 with such a configuration. FIG. 3 shows the output voltage when the toner concentration is 4%, 5%, and 6%. As shown in FIG. 3, the output voltage increases as the mixing ratio (concentration) increases depending on the mixing ratio of the toner and the carrier. Will decline. Under such circumstances, the toner is replenished with the toner density reference value T / Cref as a reference to keep the density constant. Here, the voltage drop in the region で occurs at a constant cycle because the developer staying on the detection surface of the toner density detection sensor is scraped off by the scraper 56a, and the normal output value is obtained by the periodic rotation of the scraper 56a. The output value output from the toner density sensor 58 is lowered by superimposing an intentional vibration waveform component on the. Since this region IV intentionally decreases the output value, the toner concentration detection in this region cannot detect the true toner concentration. Accordingly, the present invention is configured to detect the T / C detection data Xi in the stable region B, which is an output value obtained from the original developer, without detecting the toner density in such a region.
[0018]
Since the stable region B is configured such that the position where the scraper 56a is attached is always fixed and the output voltage hardly fluctuates, the stable region B can be easily understood. Further, the detection in the stable region B can detect the toner density at a position where the scraper 56a is sufficiently separated from the toner density sensor 58, and can obtain a more stable toner density regardless of mechanical fluctuations. . In this case, the detection is performed once within the cycle Tc of the scraper 56a, but the present invention is not limited to this.
[0019]
The time when the toner density detection is not performed is started from a predetermined time when the output value of the toner density sensor 58 is lowered. The predetermined time in this case is not particularly limited, and the predetermined time may be started from any point in the unstable region where the output value of the toner density sensor has decreased. As shown in FIG. 4, the minimum value is measured by sampling the output value, and the time for entering the stable region B determined in advance by the timer from that point may be measured to delay the toner control for Td time. In this case, if a minimum point detection area is provided and minimum point detection is performed only in an area lower than the reference value T / Cref by Va, the minimum point can be detected stably without being affected by noise.
When such density detection is performed, only Va is changed even in the case of a large design change in which the toner density reference value T / Cref is changed, and the method for detecting the minimum point is not greatly affected.
Since the minimum value cannot be reliably detected unless the toner concentration sampling period Ts at this time is sufficiently short with respect to the scraper period Tc, the sampling period Ts is 1/10 of the scraper period Tc although it depends on the detected waveform of the scraper region. In the following, it is desirable to set it to 1/20 or less. In addition, since the scraper has a periodic output, by measuring the period, whether or not the developing device, which is a feature of the present invention, is attached, a sensor failure of the toner concentration sensor, a failure of the scraper, etc. Can be determined.
[0020]
Next, the control block of the present invention is shown in FIG. The control configuration includes a CPU 514 incorporating a RAM 515, a timer 516, an AD converter 517, etc., a DC motor for replenishing toner, and a driver 513 for driving it. The timer 516 interrupts at a constant cycle Ts, and the output from the toner density sensor 58 is digitized by the AD converter 517 by this interrupt. The digitized toner density value is processed by software to calculate the ON time of the DC motor 512, and ON / OFF control is performed by the port output. The ON / OFF output is actually driven by the driver 513 to drive the DC motor 512 to replenish toner. For the DC motor 512, it is more desirable to use a speed-controlled motor such as a governor motor because the replenishment amount of toner can be kept constant. The CPU 514 does not need to include the RAM 515, timer 516, AD converter 517, etc., and may be configured externally.
[0021]
Next, the control flow of the present invention will be described with reference to FIGS. FIG. 6 is a flowchart showing overall control of toner density according to the present invention, and FIG. 7 is a flowchart for measuring toner density according to the present invention.
After power-on, the CPU 514 clears the RAM 515, initializes variable initial values, sets the timer 516, etc. (S1), enables interrupts (S2), and then waits for a print request (S3). When a print request is generated, variables in the RAM 515 are initialized, the scanner, main, development motor, etc. are turned on and rotated to permit toner density control (S4 to S6). Next, a printing process is performed (S7), the motor is turned off to prohibit toner density control, and a print request is waited (S9).
[0022]
Next, a flowchart in the interrupt process will be described with reference to FIG. Only the toner density control delay means of the present invention that measures and controls the minimum point (control in FIG. 4) will be described.
In the toner density control interruption process, it is checked whether or not the control is permitted (S21). If the control is not permitted, the toner motor is turned off and the process is terminated. If permitted, the AD converter 517 digitizes the toner density sensor output (S22).
[0023]
Next, it is checked whether it is currently within the T / C detection delay time Td, that is, the toner density reading timing (S23). If it is not the reading timing, a determination is made by subtracting the digitized value X _j from the reference value T / Cref and comparing it with the eigenvalue Va to determine whether it is the minimum value check region (S24). If it is not the minimum value check area, it is skipped, and if it is the minimum value check area, the minimum value is determined by comparing it with the previous value X _j-1 (S25). If it is not the minimum value, it is skipped, and if it is the minimum value, the previously written delay counter in the RAM 515 is cleared (S26).
[0024]
Returning to S23, in the case where the toner density is read out outside the T / C detection delay time Td, the process proceeds to S231, where a deviation between the reference value T / Cref and the read value is first obtained and multiplied by the feedback gain Ka. The feedback amount y is obtained. Next, the feedback amount y is converted into the motor ON time, and the motor ON time Y is calculated by applying the upper limit and the lower limit (S232).
[0025]
After each processing is completed, the delay counter in the RAM 515 is incremented (S27). Next, the toner density sensor is checked based on the delay counter value.
When the delay counter cannot find the minimum value, the counter value is successively increased. Therefore, the presence or absence of the developing device or the sensor error can be determined based on whether the number of samplings n in the sampling period Ts exceeds the scraper period Tc (S28). ). In this case, the sampling number n of one cycle is set in advance in the RAM 516, and the set number is compared with the actual sampling number. If it is determined that an error has occurred, that is, if the set number of times has been exceeded, the toner supply motor is turned off and stopped, and an error processing routine is executed (S281). As a result, it is determined whether the toner density sensor 58 is faulty, the scraper 56a is faulty and no vibration waveform is obtained, or the developing device is not installed.
[0026]
If there is no error in the toner density sensor check, the ON time of the toner replenishment motor is determined (S29). The toner supply motor determines whether the ON time Y is zero or more. If Y is greater than or equal to zero, the toner replenishing motor is turned on (S30), and then the Y value in the RAM 515 is decremented and the process ends (S31). If Y is less than or equal to zero, the toner replenishing motor is turned off and the process ends (S291). The toner replenishment motor ON time Y can set the toner replenishment motor ON time at intervals of the sampling period Ts.
[0027]
【The invention's effect】
With the above-described configuration, the present invention makes it possible to discover in detail the mounting state of the developing container and the malfunction in the developing device with a simple configuration, and can be used for a long period of time, thereby enabling stable toner density control. It has remarkable effects such as.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating an outline of a color image forming apparatus of the present invention. FIG. 2 is a diagram illustrating an internal mechanism of a developing device of the present invention. FIG. 3 is an output characteristic obtained from a toner density sensor. FIG. 5 is a control block diagram of the present invention. FIG. 6 is a flowchart showing overall control of the developing device of the present invention. FIG. 7 is a flowchart of measuring toner density according to the present invention.
1: color image forming apparatus main body 2: photosensitive drum 3: charging roller 4: exposure unit 5: developing unit 31: cleaning unit 6: intermediate transfer drum 6a: secondary transfer roller 6b: cleaning fur brush 7: paper supply unit 8 : Conveying belt 9: Fixing means 10: Paper discharging means

Claims (3)

A developer container containing a developer composed of a carrier and toner;
Toner density detecting means for magnetically detecting toner density information in the developing container;
Waveform forming means for forming a waveform in which the output value from the toner density detecting means is reduced by mechanical means for periodically scraping the developer present on the detection surface of the toner density detecting means;
In the developing device for controlling the toner density based on the output value of the vibration waveform formed by the waveform forming means,
Sampling means for sampling the vibration waveform at regular intervals;
Sampling frequency setting means for setting the sampling frequency within a predetermined period of the vibration waveform;
Minimum value output detection means for determining whether the value sampled by the sampling means is a region lower than a reference value T / Cref by a predetermined value Va, and detecting a predetermined output value that decreases only in the low region;
A developing device, wherein even if the number of times set by the sampling number setting means is sampled, if the output value that decreases by the minimum value output detecting means is not detected, it is determined as a malfunction. 2. The developing device according to claim 1, wherein the minimum value output detection unit is configured to detect the minimum value of the output value lowered by the sampling unit or the vicinity thereof. A determination unit configured to determine whether the value detected by the minimum value output detection unit is a minimum value; the determination unit compares the value detected by the output value detection unit with a value determined as the previous minimum value; 3. The developing device according to claim 2, wherein minimum value determination is performed.

Images