JP2006276630A - Toner concentration controller - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a toner concentration controller which can accurately detect the concentration of toner regardless of the use condition and environment of an image forming apparatus and avoid erroneous detection of emptiness of toner. <P>SOLUTION: The toner concentration controller is provided with: an inductance detection type toner concentration sensor 28 which is attached to the developing unit of an electrophotographic system image forming apparatus and provided with a signal processing part which adjusts an output voltage without changing a sensitivity grade, on the basis of a control voltage applied to a control terminal; a toner replenishing mechanism which replenishes the toner to the developing unit; and a toner concentration control part 40 which controls the toner replenishing mechanism, based on the toner concentration detected by the toner concentration sensor. Further, a correction processing part 43 which corrects the output voltage on the basis of the correlation between the output voltages before/after the control voltage is switched is provided. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention is an inductance detection type equipped with a signal processing unit which is attached to a developing device of an electrophotographic image forming apparatus and adjusts an output voltage without changing a sensitivity gradient based on a control voltage applied to a control terminal. The present invention relates to a toner density control device including a toner density sensor, a toner supply mechanism that supplies toner to the developing device, and a toner density control unit that controls the toner supply mechanism based on a toner density detected by the toner density sensor.

  A conventional image forming apparatus is mounted such that a toner density sensor is provided in a developing unit, and a detection signal is input to a toner density control unit via a relay substrate on which a variable resistor for adjusting the control voltage is mounted. The variable resistor provided on the relay board is adjusted so that the sensitivity characteristic is improved before and after the target control density by absorbing the sensitivity variation of the toner density sensor attached to the developing device and the sensitivity variation due to machine difference. Calibration work was underway.

  The adjustment voltage by the variable resistor described above is input to the toner density control unit, and a predetermined control voltage corresponding to the voltage input value is set and input from the toner density control unit to the signal processing unit. The calibration work is normally performed at the time of manufacture, and after shipping, it is adjusted to the degree of maintenance by a maintenance engineer.

On the other hand, a charging member made of magnetic particles is brought into contact with the image carrier and a charging bias is applied to the charging member to charge the image carrier, and toner particles and the magnetic material used for the charging member. In an image forming apparatus using a two-component developer composed of magnetic carrier particles having different magnetic permeability and particles, different values may be output even at the same toner concentration due to the influence of magnetic particles having different magnetic permeability. In some cases, a technique for adjusting the above-described control voltage in order to maintain a proper toner density has been proposed.
JP 2003-295598 A

  However, according to the above-described conventional toner concentration control device, the toner charge amount varies depending on the use state and use environment of the image forming apparatus even under a constant control voltage, and the toner concentration is accordingly changed. Since the output value of the sensor fluctuates, there is a problem that accurate detection is difficult due to a shift to the saturation region of the sensitivity characteristic adjusted by the control voltage. For example, when the toner charge amount decreases, the carrier bulk density increases and approaches the saturation region where the output voltage is high, and conversely when the toner charge amount increases, the carrier bulk density decreases and the output voltage is low. It approaches the saturation region. Further, even when the toner concentration is lowered, the bulk density of the carrier is increased and approaches the saturation region on the higher output voltage side.

  Also, when the output voltage becomes higher than a certain threshold that is normally set in a region with good sensitivity characteristics, the toner replenishment mechanism is controlled by the toner density control unit to replenish the toner to the developer, and the toner replenishment mechanism is activated for a predetermined time. If the value of the toner density sensor does not decrease, it is determined that the toner cartridge of the toner replenishment mechanism has no toner, but toner replenishment is performed when the output voltage approaches the high saturation region. Even if the mechanism is operated, the value of the toner density sensor does not easily decrease, and there is a problem that it may be erroneously detected as toner empty.

  Therefore, it is conceivable to control the control voltage. However, if the control voltage is changed, there is a problem in that the output voltage is different even if the toner density is the same, so that the control cannot be properly performed.

  SUMMARY OF THE INVENTION In view of the above-described conventional drawbacks, the present invention is to provide a toner concentration control device that can accurately detect the toner concentration regardless of the use state and use environment of the image forming apparatus and can avoid erroneous detection of toner empty. .

  In order to achieve the above object, a first characteristic configuration of a toner concentration control device according to the present invention is attached to a developing unit of an electrophotographic image forming apparatus as described in claim 1 of the claims. And an inductance detection type toner density sensor having a signal processing unit for adjusting an output voltage without changing a sensitivity gradient based on a control voltage applied to a control terminal, and a toner supply mechanism for supplying toner to the developer And a toner concentration control device comprising a toner concentration control unit that controls the toner replenishment mechanism based on the toner concentration detected by the toner concentration sensor, based on a correlation between output voltages before and after switching of the control voltage. Thus, a correction processing unit for correcting the output voltage is provided.

  According to the above-described configuration, even if the control voltage is changed, the output voltage is corrected based on the correlation between the output voltages before and after the correction processing unit, so that the continuity of the detected voltage is ensured and the toner density varies. Can be accurately grasped. Therefore, by adjusting the control voltage when the output voltage of the toner concentration sensor approaches the saturation region, the toner concentration can always be monitored in a region with good sensitivity characteristics.

  As described in claim 2, the second feature configuration is that, in addition to the first feature configuration described above, the control voltage is switched based on humidity, whereby the surrounding environment changes. Even if it exists, the toner density can be accurately detected.

  In the third feature configuration, in addition to the first or second feature configuration described above, the control voltage is switched based on an operating time of the developing device or an image forming volume. Accordingly, it is possible to accurately detect a change in toner density due to the operation time of the developing device.

  The fourth characteristic configuration is that, in addition to any of the first to third characteristic configurations described above, the control voltage is switched based on toner density. As a result, the toner density can always be detected in a sensitive area.

  In the fifth feature configuration, as described in claim 5, in addition to any of the first to fourth feature configurations described above, a plurality of developing devices to which the toner density sensor is attached are installed. This is because the control voltage can be switched independently for each developing device, so that the toner concentration can be accurately detected for each developing device, and each toner concentration can be controlled appropriately.

  As described above, according to the present invention, it is possible to provide a toner concentration control device that can accurately detect the toner concentration regardless of the use state and use environment of the image forming apparatus and can avoid erroneous detection of toner empty. It became so.

  Embodiments of a toner concentration control apparatus according to the present invention will be described below. As shown in FIGS. 1 and 2, the electrophotographic developing device includes a toner cartridge 10 filled with replenishing toner, a developing device 20 to which toner is supplied from the toner cartridge 10, and a toner connecting them. A supply path 30 is provided, and the toner is dropped and supplied from the toner cartridge 10 to the developing device 20 via the toner supply path 30.

  On the back side of the toner cartridge 10, there is provided a driven gear mechanism that is engaged with and driven by a drive gear of a toner supply motor (not shown) provided on the back side of the main body of the image forming apparatus. ), The screw conveyor mechanism 8a rotating in the opposite direction around the axis P in conjunction with the driven gear mechanism, and the screw conveyor mechanism 8a rotating around the axis parallel to the axis P1. The toner supply mechanism 8 is constituted by stirring mechanisms 8b and 8c that supply toner while stirring the toner toward the inside. The stirring mechanisms 8a and 8b are provided by stirring blades 81 and 82 protruding in the circumferential direction of the roller. The toner filled inside is supplied toward the conveying blades of the screw conveyor mechanism 8a.

  A toner supply port 10a that is openable and closable so as to face the upper opening of the vertical supply path 2 is formed at the bottom of the case of the toner cartridge 10 at the end of the toner conveyance by the screw conveyor mechanism 8a. The toner conveyed by the screw conveyor mechanism 8a is dropped and supplied from the toner supply port 10a to the developing device 20 through the toner supply path 30. That is, the toner cartridge 10 and the toner supply motor constitute a toner supply mechanism.

  The toner cartridge 10 is slidably held by a guide rail mechanism 11 provided on the image forming apparatus main body side, and is provided in the guide rail 11 when being inserted along the guide rail mechanism 11. A lid body (not shown) of the toner supply port 10a is engaged with and released from the engaged portion (not shown), and the lid body is closed when performing a detachment operation. As a result, it is possible to prevent the toner filled during the replacement operation of the toner cartridge 10 or the operation of adding toner to the toner cartridge 10 from flowing out of the toner supply port 10a.

  As shown in FIGS. 2B and 2C, the developing device 20 has an N pole and an S pole alternately in the longitudinal direction of a developing container containing a two-component developer 27 composed of toner and carrier. A rotating sleeve 22 including a fixed magnet roller 51 magnetized on the rotating sleeve 22 and a sleeve 23 disposed on the upstream side of the developing position of the rotating sleeve 22 in the rotation direction. The developer held on the sleeve 23 is brought into contact with the peripheral surface of the sleeve 23 to regulate the layer thickness and then guided to the developing position A. The sleeve 23 is provided with a rotatable one-pole magnet 24. The The developing device 20 is configured to switch the stop or allowance of the development by controlling the rotation position of the magnet 24 by an actuator such as a motor, and the magnet 24 is fixed to the fixed magnet roller 21 as shown in FIG. The developer 25 carried on the rotating sleeve 22 is brought into contact with the peripheral surface of the sleeve 23 by the magnetic force of the fixed magnet roller 21 and the layer thickness is regulated by the magnetic force of the fixed magnet roller 21. As shown in FIG. 2C, when the magnet 24 is rotated to the vicinity of the layer thickness regulating position B, the N pole that is the magnetic pole of the opposed fixed magnet roller 21 A magnetic bridge is formed by the S pole, which is the magnetic pole of the magnet 24, the supply of the developer 25 is shut off, and development is stopped.

  As shown in FIG. 3B, a toner concentration sensor 28 is provided on the bottom surface of the developing container 26 so that the detection unit 28a faces the inside, and the detection signal is sent to a toner concentration control unit described later. It is configured to be entered.

  As shown in FIG. 3A, the toner density sensor 28 has a drive coil L1, a detection coil L3, and a reference coil L2 provided in the same core, and the oscillation output from the oscillator 1 is applied to the drive coil 2. In addition, a differential transformer type sensor that detects the toner density by the differential output of the detection coil L3 and the reference coil L2, and the output of the detection coil L3 and the applied voltage of the drive coil L1 are input to the signal processing circuit 5 and the toner density signal It is configured to be output as. A capacitor 4 and a variable capacitance diode 2 are connected in series to the middle point of the reference coil L2 and the detection coil L3, and control is applied to the variable capacitance diode 2 via a resistor 3 (connected to the control terminal 7). A signal processing unit 6 is provided in which the output voltage is adjusted without changing the sensitivity gradient according to the voltage. The signal processing unit 6 of such an inductance detection type toner density sensor can be appropriately configured by using techniques described in Japanese Patent No. 2894754, Japanese Patent Laid-Open No. 2-156150, and the like.

  As shown in FIG. 4, the toner density control device according to the present invention is based on the above-described toner density sensor 28, a toner supply mechanism for supplying toner to the developing device 20, and the toner density detected by the toner density sensor 28. A toner density control unit 40 that controls the toner replenishing mechanism and a correction processing unit 43 that corrects the output voltage based on the correlation of the output voltage before and after the switching of the control voltage are configured.

  As shown in FIG. 6, the toner density controller 40 sets the normal control voltage to 7V and operates the toner replenishment motor when the voltage detected by the toner density sensor 28 rises to a reference value of 2.5V or more. As a result, the toner density in the developing device 20 is controlled to fall within a predetermined range.

  However, if the humidity increases and the charge amount of the toner in the developing device 20 decreases, or if the high density copying operation is continued well, the carrier bulk density increases relatively and the output voltage becomes higher in the saturated region. If the toner charge level increases due to a large number of copying operations, etc., the carrier bulk density decreases relatively, approaches the saturation region on the lower output voltage side, and the toner density decreases. The bulk density of the carrier increases and approaches the saturation region on the higher output voltage side. In such a case, the change in the detection voltage is small with respect to the change in the toner concentration, and there is a possibility that the toner concentration cannot be detected accurately. For example, when the output voltage approaches a high saturation region, a change in voltage cannot be detected even when the toner supply mechanism is operated, and it may be erroneously detected that the toner in the toner cartridge 10 has been consumed.

  Therefore, when the toner concentration control unit 40 approaches the saturation region on the higher output voltage side, the control voltage is reduced to, for example, 6 V to detect the toner concentration in a sensitive region, and approaches the saturation region on the lower output voltage side. Then, the control voltage is increased to 8 V, for example, and the control voltage is controlled to change so that the toner density is detected in a sensitive region.

  By changing the control voltage in this way, even a slight change in toner density can be detected sufficiently. However, if the control voltage changes, the output voltage will be different even at the same toner density. The output voltage is corrected based on the correlation between the output voltages before and after the voltage switching. More specifically, the correction processing unit 43 is preliminarily provided with the output characteristics of the toner density sensor 28 in the control voltage adjustment range as table data, and can be converted into an accurate toner density at any control voltage. It is. With this configuration, the toner density can always be accurately detected even when the control voltage is changed. For example, the problem of erroneously detecting that the toner in the toner cartridge 10 has been consumed is eliminated. Become so.

  Specifically, a humidity sensor 41 is provided in the image forming apparatus, and the control voltage is lowered when the humidity rises above a predetermined humidity, and the control voltage is lowered when the detected toner density falls below a predetermined value. The control voltage can be appropriately controlled by increasing the control voltage when a predetermined number of continuous copies are made. As the copy number counter 42 for detecting the image forming volume, a counter for counting the number of pixels to be printed can be used in place of the counter for counting the number of copies. Further, the control voltage may be switched when the operation time of the developing device 20 that affects the charging amount of the toner is detected and the continuous operation time elapses a predetermined time.

  Further, in the case of a color image forming apparatus, the toner density of each developing device can be accurately controlled by performing such control voltage switching control for each developing device corresponding to each color.

  Switching of the control voltage by the toner density control unit 40 described above can normally be configured by a microcomputer that controls the image forming apparatus and a part of its control program. However, as shown in FIG. It can also be configured. That is, the comparison circuit CMP1 that compares the output of the humidity sensor with a predetermined voltage, the switching transistor TR1 that turns on and off as a result, the comparison circuit CMP2 that compares the output of the toner sensor with a predetermined voltage, the switching transistor TR2 that turns on and off as a result, and the number counter The switching transistor TR1 that is turned on / off according to the value of and the operational amplifier AMP1 that adjusts the control voltage according to the resistance value connected to the switching transistor TR1.

  The above-described embodiment is an example of the present invention, and the control voltage value is merely an example, and is not limited to these values, and can be set as appropriate. Further, the above-described control block configuration and hardware circuit are not particularly limited, and can be appropriately changed and designed within a range where the effects of the present invention can be achieved.

Explanatory drawing of developing device (A) is a cross-sectional view of the toner cartridge, (b) is an explanatory view of the main part of the developing device (A) is a circuit diagram of the toner density sensor, (b) is an explanatory view of the installation of the toner density sensor. Functional block diagram of toner concentration control device Circuit diagram for control voltage adjustment Characteristics diagram of toner density sensor

Explanation of symbols

28: Toner density sensor 40: Toner density control unit 41: Humidity sensor 42: Number counter 43: Correction processing unit

Claims (5)

An inductance detection type toner density sensor equipped with a signal processing unit that is attached to a developing device of an electrophotographic image forming apparatus and that adjusts an output voltage without changing a sensitivity gradient based on a control voltage applied to a control terminal; A toner concentration control device comprising a toner replenishing mechanism for replenishing toner to the developing device, and a toner concentration control unit for controlling the toner replenishing mechanism based on a toner concentration detected by the toner concentration sensor,
A toner concentration control device provided with a correction processing unit that corrects the output voltage based on a correlation between output voltages before and after switching of the control voltage.   The toner density control device according to claim 1, wherein the control voltage is switched based on humidity.   The toner density control device according to claim 1, wherein the control voltage is switched based on an operation time of the developing device or an image forming volume.   4. The toner concentration control device according to claim 1, wherein the control voltage is switched based on a toner concentration.   The toner density control apparatus according to claim 1, wherein a plurality of developing devices to which the toner density sensor is attached are installed, and the control voltage is switched independently for each developing device.

Images