JP2017161585A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To downsize an image forming apparatus, and appropriately control image forming conditions without preventing cost reduction.SOLUTION: An image forming apparatus includes an image forming section 105 that forms a toner patch P; an intermediate transfer belt 24 that carries the toner patch P formed by the image forming section 105; and detection electrodes 41a and 41b. The image forming apparatus also includes a toner image sensor 40 that detects the amount of charge induced between the intermediate transfer belt 24 and the detection electrodes 41a and 41b or between the toner patch P carried on the intermediate transfer belt 24 and the detection electrodes 41a and 41b; and a control operation section 10 that controls image forming conditions according to the amount of charge detected by the toner image sensor 40.SELECTED DRAWING: Figure 5

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, and a facsimile machine using an electrophotographic system.

  In recent years, image forming apparatuses using an electrophotographic system have been improved in speed and image quality. In order to satisfy these performances, for example, when a toner image is transferred to a recording material, the impedance of the recording material is detected, and the transfer voltage corresponding to the detection result is controlled. Thus, the image forming conditions are controlled according to the characteristics of the recording material, the installation environment of the image forming apparatus, and the like, such as transferring the toner image while suppressing the occurrence of image defects. Further, in addition to such control, the color image forming apparatus requires accurate color reproducibility and density stability, and thus has a function of automatically controlling image density.

  In image density control, in general, a plurality of test toner images formed on a rotating body carrying a toner image while changing image forming conditions are detected by an optical detection means provided in the image forming apparatus. From this, the toner adhesion amount (toner concentration, hereinafter, toner adhesion amount) is calculated. Based on the calculation result, optimum image forming conditions for development, transfer, fixing, etc. are determined, or density gradation control is performed. The detection principle in the optical detection means is that the test toner image for the light emitted from the light emitting element and the reflected light from the base of the rotating body are respectively acquired by the light receiving element, and the output (reflected output) from the acquired light receiving element is obtained. Based on the comparison result, the toner adhesion amount is calculated. In recent years, the sensitivity of capacitive proximity sensors has been increasing, and application to the detection of toner adhesion amount that needs to capture minute changes in adhesion amount is expected (for example, Patent Documents). 1). Furthermore, for the purpose of speeding up the image forming apparatus and improving the image quality, it has been proposed to detect the charge amount of the toner image in addition to the above-described toner adhesion amount and reflect it in the image forming conditions (for example, Patent Documents). 2).

JP 2010-276524 A JP 2009-098038 A

  However, the method of calculating the toner adhesion amount by comparing the test toner image and the amount of reflected light from the background of the rotating body by the optical detection means decreases the detection sensitivity when the adhesion amount of the test toner image is large. Resulting in. For this reason, there are cases where sufficient control of image forming conditions cannot be performed. In order to measure not only the toner adhesion amount but also the charge amount of the toner image, it is necessary to newly provide a sensor for measuring the charge amount of the toner image, which may hinder downsizing and cost reduction of the image forming apparatus. There is.

  The present invention has been made under such circumstances, and an object of the present invention is to appropriately control image forming conditions without hindering downsizing and cost reduction of an image forming apparatus.

  In order to solve the above-described problems, the present invention has the following configuration.

  (1) A forming unit that forms a toner image, an image carrier that carries the toner image formed by the forming unit, and an electrode, and between the image carrier and the electrode, or the image carrier Detection means for detecting the amount of charge induced between the toner image carried on the electrode and the electrode; and control means for controlling image forming conditions based on the amount of charge detected by the detection means. An image forming apparatus comprising the image forming apparatus.

  According to the present invention, it is possible to appropriately control image forming conditions without hindering downsizing and cost reduction of the image forming apparatus.

Sectional view of the image forming apparatus of Example 1 Schematic diagram of the toner image sensor of Example 1. Circuit diagram of charge amount detection unit of embodiment 1 FIG. 6 is a diagram illustrating the operation of the toner image sensor according to the first embodiment. The block diagram of the control calculating part of Example 1 Schematic diagram of the toner image sensor of Example 1. Schematic diagram of the toner image sensor of Example 2

  Embodiments of the present invention will be described below with reference to the drawings.

[Image forming apparatus]
In the first embodiment, a configuration in which the adhesion amount and the charge amount of a toner image formed on an image carrier are detected and the image forming conditions are controlled according to the detection result will be described. FIG. 1 is a schematic cross-sectional view of the image forming apparatus of this embodiment. In this embodiment, a color image forming apparatus employing an intermediate transfer belt is used as an example of the image forming apparatus. The image forming apparatus of this embodiment is a printer equipped with an automatic duplex printing mechanism in a 4-drum full color system. An image forming unit that performs image formation is configured for each color of toner, and yellow (Y) and magenta (M) in order from the upstream side of the rotation direction (counterclockwise direction) indicated by the arrow of the intermediate transfer belt 24 in the drawing. , Cyan (C) and black (K) stations are arranged. In the figure, suffixes Y, M, C, and K at the end of the reference numerals represent toner colors, and will be omitted in the following description unless necessary.

  The image forming apparatus includes a photosensitive drum 1 as a photoreceptor, a charging roller 2 as a charging unit, a scanner unit 11 as an exposure unit, a developing unit 8 as a developing unit, a toner container 7 as a replenishing unit, and a drum cleaner 16. doing. Further, the image forming apparatus drives the intermediate transfer belt 24 that is an image carrier, the secondary transfer roller 25 that is a second transfer unit, and a drive that functions as a counter roller of the secondary transfer roller 25 while driving the intermediate transfer belt 24. A roller 26, a tension roller 13 and an auxiliary roller 23 are provided. Further, the image forming apparatus includes a primary transfer roller 4 as a first transfer unit, a fixing unit 21 as a fixing unit, and a control calculation unit 10 as a control unit that controls these. Although not shown, the image forming apparatus is a power source that is a first application unit that applies a development voltage to the developing device 8 and a power source that is a second application unit that applies a primary transfer voltage to the primary transfer roller 4. A power supply is provided as third application means for applying a secondary transfer voltage to the secondary transfer roller 25. The photosensitive drum 1 is configured by applying an organic optical transmission layer to the outer periphery of an aluminum cylinder, and rotates by receiving a driving force of a driving motor (not shown). The driving motor drives the photosensitive drum 1 in accordance with an image forming operation. Rotate clockwise.

  When the control arithmetic unit 10 receives the image signal, the recording material S is fed into the image forming apparatus by the pickup roller 14 and the paper feeding rollers 17 and 18 from the paper feeding cassette 15A. The recording material S conveyed from the paper supply rollers 17 and 18 to the conveyance path is a roller-like synchronous rotating body for synchronizing an image forming operation described later and the conveyance of the recording material S, that is, a registration roller 19a, and It is pinched by the registration facing roller 19b, stops and waits. Hereinafter, the registration roller 19a and the registration counter roller 19b are simply referred to as a registration roller pair 19a and 19b. Then, the control calculation unit 10 forms an electrostatic latent image corresponding to the received image signal on the surface of the photosensitive drum 1 charged to a constant potential by the action of the charging roller 2 by the scanner unit 11.

  The developing unit 8 is a means for visualizing the electrostatic latent image formed on the photosensitive drum 1 (on the photosensitive member), and develops each color of YMCK for each station. The developing device 8 is provided with a developing roller 5 to which a developing voltage for visualizing the electrostatic latent image is applied. Thus, the electrostatic latent image formed on the surface of the photosensitive drum 1 is developed as a single color toner image by the action of the developing device 8.

  The intermediate transfer belt 24 is in contact with the photosensitive drum 1, is stretched around the drive roller 26, the stretch roller 13, and the auxiliary roller 23, and the drive roller 26 is rotationally driven by a drive source (not shown). As a result, the intermediate transfer belt 24 rotates in the counterclockwise direction in synchronism with the rotation of the photosensitive drum 1 during color image formation. The developed single color toner image is sequentially transferred by the action of the primary transfer voltage applied to the primary transfer roller 4, and becomes a multicolor toner image on the intermediate transfer belt 24 (on the image carrier). The intermediate transfer belt 24 of this embodiment uses an endless film member having a thickness of 70 μm in which carbon black is dispersed in a polyimide material. Super engineering plastics such as PEEK, PPS, PVdF, and PEN, and general-purpose engineering plastics such as PET may be used as the material. The tension roller 13 and the auxiliary roller 23 that stretch the intermediate transfer belt 24 are both formed of a metal conductive core and are at a ground potential. The drive roller 26 is also a metal conductive core bar provided with a low-resistance rubber layer for driving transmission, and has a ground potential similar to the tension roller 13 and the auxiliary roller 23. The toner not transferred onto the intermediate transfer belt 24 but remaining on the photosensitive drum 1 is collected by a drum cleaner 16 installed in contact with the photosensitive drum 1. Each color drum cleaner 16 includes a cleaner blade 161 and a toner recovery container 162.

  The multicolor toner image formed on the intermediate transfer belt 24 is conveyed to a secondary transfer nip portion formed by a secondary transfer roller 25 and a driving roller 26. The recording material S waiting in a state of being sandwiched between the registration roller pair 19a and 19b is synchronized with the conveyance of the multicolor toner image on the intermediate transfer belt 24 by the action of the registration roller pair 19a and 19b. It is conveyed to the next transfer nip. A secondary transfer voltage is applied to the secondary transfer roller 25, and multicolor toner images are transferred onto the recording material S at a time.

  The fixing unit 21 includes a rotating pressure roller 21a having an elastic layer, a pressure roller 21a that rotates, and a fixing nip portion N formed in pressure contact with the pressure roller 21a, and a heating rotator 21b having a heating unit that heats the fixing nip portion N. Consists of The recording material S holding the multicolor toner image is conveyed by the pressure roller 21a, and heat and pressure are applied at the fixing nip portion N to fix the toner on the surface. The recording material S after the toner image is fixed is discharged to the paper discharge tray 30 by the discharge rollers 20a and 20b, and the image forming operation is completed. The belt cleaner 28 cleans the toner remaining on the intermediate transfer belt 24 by the action of the cleaner blade 281, and the collected toner is stored in the cleaner container 282.

  A series of image forming operations as described above is controlled by the control arithmetic unit 10 provided in the image forming apparatus. The voltage applied to the charging roller 2, the developing roller 5, the primary transfer roller 4, and the secondary transfer roller 25, the temperature control of the heating rotator 21b, and the like are also controlled by the control calculation unit 10.

  The toner image sensor 40 serving as a detection unit is disposed opposite to the intermediate transfer belt 24 at the position where the tension roller 13 is stretched, and detects the adhesion amount and charge amount of toner formed on the intermediate transfer belt 24. It is configured to Generally, in an electrophotographic color image forming apparatus, the characteristics of the toner and each of the above-described members vary depending on various conditions such as replacement of consumables, changes in the environment used (temperature, humidity, deterioration of the apparatus, etc.), the number of printed sheets, and the like. Change. Changes in the properties of the toner and each member are manifested as image defects and image density fluctuations accompanying changes in the optimum conditions for image formation. Then, due to image defects and image density fluctuations, an appropriate image that should originally be output and correct color reproducibility cannot be obtained. Therefore, in this embodiment, the following operation is performed in order to always properly form an image desired by the user under optimum image forming conditions. In the present exemplary embodiment, a plurality of toner patches P (see FIG. 2) that are test images are changed on the intermediate transfer belt 24 while changing the image forming conditions at a timing other than when the user issues an image formation instruction. Form on top. The toner image sensor 40 detects the toner adhesion amount and the toner charge amount.

[Toner image sensor]
FIG. 2A shows a schematic diagram of the toner image sensor 40 of the present embodiment. The toner image sensor 40 includes detection electrodes 41a and 41b that are capacitively coupled to face the intermediate transfer belt 24, and a charge amount detection unit 42 that detects the amount of charge electrostatically induced in the detection electrodes 41a and 41b. ing. Further, the toner image sensor 40 is installed on the back side of the detection electrodes 41a and 41b via the insulating substrate 44, and vibration that gives mechanical vibration so that the spatial distance between the detection electrodes 41a and 41b and the intermediate transfer belt 24 varies. A portion 43 is provided.

  FIG. 2B is a schematic diagram showing the arrangement of the detection electrode 41a that is the first electrode and the detection electrode 41b that is the second electrode. The detection electrodes 41 a and 41 b have a rectangular shape with long sides having substantially the same length in the direction orthogonal to the moving direction of the intermediate transfer belt 24. The short sides of the detection electrodes 41a and 41b are configured such that the detection electrode 41b is shorter than the detection electrode 41a. The two detection electrodes 41 a and 41 b are arranged on the insulating substrate 44 in close proximity to each other in a state of being aligned in the moving direction of the intermediate transfer belt 24. In this embodiment, the short side of the detection electrode 41a is 5 mm, the short side of the detection electrode 41b is 1 mm, and the long side is 50 mm. The toner patch P is a toner image that is formed on the intermediate transfer belt 24 and whose adhesion amount and charge amount are measured by the toner image sensor 40, and will be described in detail later.

[Charge amount detection unit]
FIG. 3 is a circuit diagram of the charge amount detection unit 42 incorporated in the toner image sensor 40 of the present embodiment shown in FIG. Ca indicates a capacitance formed between the detection electrode 41 a and the intermediate transfer belt 24 or between the detection electrode 41 a and the toner patch P on the intermediate transfer belt 24. Cb indicates a capacitance formed between the detection electrode 41 b and the intermediate transfer belt 24 or between the detection electrode 41 b and the toner patch P on the intermediate transfer belt 24. The detection electrode 41a is connected to the contact 421a-1 of the switch 421a that is the first connection means, and the detection electrode 41b is connected to the contact 421b-1 of the switch 421b that is the third connection means. In the first state where the contact 421a-1 and the contact 421a-2 are connected, the switch 421a connects the detection electrode 41a and the inverting input terminal (−) of the operational amplifier 422a that is the first amplifier. In the second state in which the contacts 421a-1 and 421a-3 are connected, the switch 421a opens the connection of the detection electrode 41a. The switch 421a grounds the detection electrode 41a in the third state in which the contact 421a-1 and the contact 421a-4 are connected.

  The switch 421b connects the detection electrode 41b and the inverting input terminal (−) of the operational amplifier 422b, which is the second amplifier, in the fourth state in which the contact 421b-1 and the contact 421b-2 are connected. In the fifth state in which the contact 421b-1 and the contact 421b-3 are connected, the switch 421b opens the connection of the detection electrode 41b. The switch 421b grounds the detection electrode 41b in the sixth state in which the contact 421b-1 and the contact 421b-4 are connected.

  Thus, the detection electrodes 41a and 41b are connected to any one of the inverting input terminal (−), the high impedance open position (Open), and the ground potential (GND) of the operational amplifier 422a by the switches 421a and 421b. It is configured to be switched. The operational amplifiers 422a and 422b have a non-inverting input terminal (+) connected to a predetermined reference potential Vr and a capacitive element 424a that is a first capacitive element between the inverting input terminal (−) and the output terminal. The capacitor element 424b, which is the second capacitor element, is connected. The capacitors 424a and 424b are connected in parallel with a switch 423a as a second connection means and 423b as a fourth connection means, respectively.

  A voltage obtained by dividing the voltage Va output from the operational amplifier 422a by the resistors R1a and R2a is input to the non-inverting input terminal (+) of the difference detection amplifier 425. A voltage obtained by dividing the voltage Vb output from the operational amplifier 422b by the resistors R1b and R2b is input to the inverting input terminal (−) of the difference detection amplifier 425. The difference detection amplifier 425 outputs the difference (= Va−Vb) between the measured voltages Va and Vb output from the operation amplifiers 422a and 422b to the control operation unit 10 as Vout. The control calculation unit 10 detects the adhesion amount of the toner image formed on the intermediate transfer belt 24 based on the voltage Vout input from the difference detection amplifier 425 (hereinafter also referred to as the difference voltage Vout).

[Time variation of switch operation and output voltage]
FIG. 4A is a schematic diagram illustrating the operation of the switch 421a (or switch 421b) and the switch 423a (or switch 423b) and the time change of the output voltage. FIG. 4A shows a reference clock when the charge amount detector 42 operates. 4B, the switch 421a (or the switch 421b) indicates which position of the inverting input terminal (−), the open position (Open), and the ground potential (GND) of the operational amplifier 422a (or the operational amplifier 422b). Is connected. FIG. 4C shows the connection state (ON, OFF) of the switch 423a (or switch 423b). 4D shows the output voltage Vout output from the charge amount detection unit 42 (specifically, the difference detection amplifier 425) to the control calculation unit 10. FIG. The horizontal axis is time.

  At timing t1, the detection electrodes 41a and 41b are connected to the inverting input terminals (−) of the operational amplifiers 422a and 422b via the switches 421a and 421b, and the switches 423a and 423b are turned off, and the state shown in FIG. Become. At timing t1, a voltage Va corresponding to the ratio between the capacitance Ca formed between the detection electrode 41a and the intermediate transfer belt 24 and the capacitance of the capacitive element 424a is output from the output terminal of the operational amplifier 422a. (See FIG. 3). At timing t1, the voltage Vb corresponding to the ratio between the electrostatic capacitance Cb formed between the detection electrode 41b and the intermediate transfer belt 24 and the electrostatic capacitance of the capacitive element 424b is output from the output terminal of the operational amplifier 422b. Is output (see FIG. 3). When the switches 421a and 421b are connected to the open position (Open) at timing t2, the voltages Va and Vb at the output terminals of the operational amplifiers 422a and 422b are held. Therefore, the voltage Vout (for example, the voltage Vt) output from the difference detection amplifier 425 (see FIG. 3) that is the third amplifier is also held.

  At timing t3, the switches 423a and 423b are switched from the off state to the on state. Then, the capacitive elements 424a and 424b are short-circuited, and the charges charged in the capacitive elements 424a and 424b are discharged, and the voltages at the output terminals of the operational amplifiers 422a and 422b are reset. At this time, by switching the switches 421a and 421b to the ground potential (GND), the detection electrodes 41a and 41b are also discharged and the voltage is reset. Thereafter, at timing t4, with the switches 423a and 423b turned off again, the switches 421a and 421b are switched again so that the detection electrodes 41a and 41b and the inverting input terminals (−) of the operational amplifiers 422a and 422b are connected.

  By this operation, the capacitances Ca and Cb formed between the detection electrodes 41a and 41b and the intermediate transfer belt 24 and the capacitances of the capacitive elements 424a and 424b are output from the output terminals of the operational amplifiers 422a and 422b. The voltages Va and Vb corresponding to the ratio are output again. By repeating the operation from the timing t1 to the timing t4, the capacitances Ca and Cb are periodically measured, and the measured voltages are periodically updated and output from the operational amplifiers 422a and 422b.

  Electromagnetic wave noise having the same phase, amplitude, and the like is induced in the detection electrodes 41a and 41b that are close to each other in the same length and are arranged substantially in parallel. The difference detection amplifier 425 subtracts the output (Vb) of the operational amplifier 422b connected to the detection electrode 41b having a small electrode area from the output (Va) of the operational amplifier 422a connected to the detection electrode 41a having a large electrode area. (Va-Vb). This can be regarded as equivalent to removing electromagnetic noise from the output of the operational amplifier 422a. Therefore, by configuring the toner image sensor 40 as described above, it is possible to obtain high environmental noise resistance, and the electrostatic capacitance formed between the detection electrode 41a and the intermediate transfer belt 24 can be reduced. It is possible to capture a minute change according to the difference in the toner adhesion amount.

  The change in the toner adhesion amount means that the thickness of the toner layer and the thickness of the air layer interposed between the intermediate transfer belt 24 and the detection electrodes 41a and 41b change. The electrostatic capacitances Ca and Cb change according to the thickness of the toner layer and the thickness of the air layer, and the voltages Va and Vb measured by the operational amplifiers 422a and 422b also change. Based on the reference clock, the control calculation unit 10 according to the present embodiment is connected to the open position (Open) and the voltages Va and Vb are held (timing t2 to t3), based on the reference clock. The output voltage Vout of the difference detection amplifier 425 is detected. The control calculation unit 10 measures the value of the output voltage Vout output from the difference detection amplifier 425 as the voltage Vt at the timing when the voltages Va and Vb are held. Information in which the voltage Vt from the difference detection amplifier 425 is associated with the toner adhesion amount, for example, information that the difference voltage Vt increases as the toner adhesion amount increases is measured at the design stage, factory shipment, or the like. It is assumed that it is stored in advance in the control calculation unit 10. Thus, in this embodiment, the control calculation unit 10 can measure a change in the toner adhesion amount.

[Charge amount of toner]
Next, a method for estimating the charge amount of the toner formed on the intermediate transfer belt 24 will be described with reference to FIG. 4A shows a reference clock similar to that shown in FIG. 4A. 4B shows a drive signal for driving the vibration unit 43 incorporated in the toner image sensor 40, which is a divided signal of the reference clock. When the drive signal as shown in FIG. 4B (b) is input to the vibration unit 43, the vibration unit 43 vibrates with a constant amplitude according to the input drive voltage. As a result, the spatial distance between the detection electrodes 41a and 41b and the intermediate transfer belt 24 varies with a constant amplitude, and the capacitances Ca and Cb formed between the detection electrodes 41a and 41b and the intermediate transfer belt 24 also. It changes accordingly.

  First, the detection electrodes 41a and 41b and the inverting input terminals (−) of the operational amplifiers 422a and 422b are connected by the switches 421a and 421b. In this state, when the switches 423a and 423b are turned off, the voltage Va corresponding to the ratio between the capacitances Ca and Cb and the capacitances of the capacitors 424a and 424b is output from the output terminals of the operational amplifiers 422a and 422b. , Vb are output. And according to the vibration of the vibration part 43, the voltages Va and Vb also change.

  FIG. 4B schematically shows a temporal change in the voltage Va (or Vb) output from the operational amplifier 422a (or 422b) in correspondence with FIG. 4B (b). . 4B is a schematic diagram, and the output Va from the operational amplifier 422a and the output Vb from the operational amplifier 422b have different absolute values. As shown in (c) of FIG. 4B, the voltage Va output from the operational amplifier 422a corresponds to the vibration of the spatial distance between the detection electrode 41a and the intermediate transfer belt 24 due to the vibration of the vibration part 43. Oscillate with a constant amplitude Vppa. Here, the amplitude Vppa is a difference (Va1-Va2) between the voltage Va1 and the voltage Va2. Similarly, the voltage Vb output from the operational amplifier 422b vibrates with a constant amplitude Vppb in response to the spatial distance between the detection electrode 41b and the intermediate transfer belt 24 due to the vibration of the vibration unit 43. Here, the amplitude Vppb is a difference (Vb1-Vb2) between the voltage Vb1 and the voltage Vb2.

  For example, regarding the voltage Va output from the operational amplifier 422a due to the vibration of the vibration unit 43, the voltage Va when it is the largest is Va1, and the voltage Va when it is the smallest is Va2. The difference detection amplifier 425 outputs the difference between the voltages Va and Vb output from the operational amplifiers 422a and 422b to the control arithmetic unit 10 as the output voltage Vout. Here, regarding the output voltage Vout output from the difference detection amplifier 425, the maximum output voltage Vout is Vc1, and the minimum output voltage Vout is Vc2. The control calculation unit 10 detects the difference between the output voltages Vc1 and Vc2 output from the difference detection amplifier 425 as the amplitude Vpp (Vc1−Vc2). The control calculation unit 10 detects the charge amount of the toner formed on the intermediate transfer belt 24 based on the input output voltage Vout.

  The change in the charge amount of the toner means that the electric field intensity distribution between the intermediate transfer belt 24 and the detection electrodes 41a and 41b changes, and outputs from the operational amplifiers 422a and 422b according to the change in the electric field intensity distribution. The amplitudes Vppa and Vppb of the applied voltage also change. Then, the amplitude Vpp of the voltage output from the difference detection amplifier 425 also changes. In the present embodiment, based on the reference clock, the value of the difference voltage Vout from the difference detection amplifier 425 is measured as the voltage Vc1 at the timing T1 shown in FIG. 4B, and the difference from the difference detection amplifier 425 at the timing T2. The value of the voltage Vout is measured as the voltage Vc2. Information relating the amplitude Vpp, which is the difference between the voltage Vc1 and the voltage Vc2, and the charge amount of the toner, for example, information that the amplitude Vpp increases as the charge amount of the toner increases, is measured at the design stage or at the time of factory shipment. It is assumed that it is stored in advance in the control calculation unit 10. Thus, in this embodiment, the control calculation unit 10 can measure a change in the charge amount of the toner.

[Toner image detection operation, control of image forming conditions]
Next, the toner image detection operation of the image forming apparatus using the toner image sensor 40 and the control of the image forming conditions according to the detection result will be described. FIG. 5 is a block diagram illustrating an example of the configuration of the control calculation unit 10 in the image forming apparatus according to the present exemplary embodiment. The CPU 101 uses the RAM 103 as a work area based on various control programs stored in the ROM 102 and forms an image while controlling each part of the image forming apparatus. The ROM 102 stores various control programs, various data, and tables, and also stores information that associates the above-described differential voltage Vt with the toner adhesion amount and information that associates the amplitude Vpp with the toner charge amount. ing. The RAM 103 includes a program load area, a work area for the CPU 101, a storage area for various data, and the like. The pattern generating unit 104 generates an image data signal of the toner patch P as a test toner image. The image forming unit 105 serving as a forming unit includes the photosensitive drum 1, the charging roller 2, the scanner unit 11, the developing device 8, the primary transfer roller 4, and the like described above.

When calibration of the image forming apparatus is started by a user instruction from an external device or the like, the image forming apparatus first performs an initialization operation of the toner image sensor 40. In the initialization operation, the toner image sensor 40 described above is operated in a state where there is no toner image on the intermediate transfer belt 24. That is, the toner image sensor 40 detects the surface of the intermediate transfer belt 24. Specifically, the switches 421a and 421b shown in FIG. 4A are switched, and the toner adhesion amount is measured by the operation of detecting the differential voltage Vt. Thereafter, as shown in FIG. 4B, the vibration amount 43 is driven, and the charge amount of the toner image is measured by the operation of detecting the amplitude Vpp. Here, it is assumed that the differential voltage Vt measured in the initialization operation is Vt0 and the amplitude Vpp is Vpp0. The differential voltage Vt0 and the amplitude Vpp0 in the initialization operation are stored in the RAM 103 as output values at a toner adhesion amount of 0 mg / cm ² and a toner charge amount of 0 μC, respectively.

  Next, the image forming unit 105 experimentally forms a belt-like toner patch P on the intermediate transfer belt 24 while changing the image forming conditions in accordance with the image data signal output from the pattern generating unit 104. As shown in FIG. 2B, the toner patch P formed by the image forming unit 105 is formed at a position facing the detection electrode 41a with a width of 55 mm so as to cover the entire long sides of the detection electrodes 41a and 41b. The The formed toner patch P is detected by the operation of the toner image sensor 40 in a state where the intermediate transfer belt 24 is rotated, and an output value (differential voltage Vt, amplitude depending on the toner adhesion amount and the toner charge amount). Vpp) is measured sequentially.

The CPU 101 detects the difference (Vt−Vt0, Vpp) between the output value of the toner image sensor 40 when the toner patch P is detected and the output value when the toner adhesion amount is 0 mg / cm ² and the toner charge amount is 0 μC stored in the RAM 103. -Vpp0) is calculated. The CPU 101 uses the information (for example, a table) that associates the difference value stored in advance in the ROM 102 with the adhesion amount and the charge amount of the toner, and applies the adhesion amount and the charge of the toner image formed on the intermediate transfer belt 24. Find the amount. The CPU 101 determines image forming conditions of the image forming unit 105 according to various image control programs stored in the ROM 102 based on the obtained toner image adhesion amount and charge amount.

  Examples of the image forming conditions include a development voltage, a primary transfer voltage, a secondary transfer voltage, or a temperature of the heating rotator 21b of the fixing unit 21. The CPU 101 determines these image forming conditions based on the obtained adhesion amount and charge amount of the toner image, and executes an image forming operation. For example, in the case of the temperature of the heating rotator 21b of the fixing unit 21, the temperature is set higher as the toner image adhesion amount is larger. Further, for example, in the case of the primary transfer voltage and the secondary transfer voltage, the primary transfer voltage and the secondary transfer voltage are set higher as the adhesion amount of the toner image is larger. For example, in the case of the primary transfer voltage and the secondary transfer voltage, the primary transfer voltage and the secondary transfer voltage are set higher as the charge amount of the toner image is larger. Further, in the case of the development voltage, the development voltage is set in consideration of other characteristics and the like on the adhesion amount and charge amount of the toner image.

  As described above, according to this embodiment, it is possible to measure the toner adhesion amount and the charge amount with one toner image sensor 40, and it is possible to perform image formation under appropriate image formation conditions. In this embodiment, the two detection electrodes are used as the detection electrodes of the toner image sensor 40, and the difference between them is measured to enhance the resistance to electromagnetic noise. However, when used in an environment that is not easily affected by electromagnetic noise, it is not always necessary to measure the difference between the two detection electrodes. In that case, only one detection electrode is required.

  On the other hand, when it is desired to remove the influence of electromagnetic noise as much as possible, for example, as shown in FIG. 6A, the two electrodes are controlled to have the same potential around the two detection electrodes 41a and 41b as the detection electrodes 41a and 41b. It is good also as a structure covered with the shielding electrode 50 which is a shielding means. Further, as shown in FIG. 6B, a shielding electrode 51 which is a shielding means controlled to have the same potential as that of the detection electrodes 41a and 41b is provided between the two detection electrodes 41a and 41b and the vibrating portion 43. It may be provided. In the present embodiment, the toner image sensor 40 is configured such that the vibrating portion 43 is provided on the back side of the detection electrodes 41a and 41b so that both the toner adhesion amount and the charge amount can be measured. However, the vibration unit 43 may not be installed and may be operated so as to measure only the toner adhesion amount.

  As described above, according to the present embodiment, it is possible to appropriately control the image forming conditions without hindering the downsizing and cost reduction of the image forming apparatus.

[Toner image sensor]
FIG. 7A is a schematic diagram of the toner image sensor 45 of the second embodiment. The toner image sensor 45 includes detection electrodes 46 a and 46 b, a charge amount detection unit 47, an insulating substrate 49, and a vibration unit 48. The detection electrodes 46 a and 46 b are capacitively coupled to face the intermediate transfer belt 24. The charge amount detection unit 47 detects the amount of charge electrostatically induced in the detection electrodes 46a and 46b. The vibration unit 48 is installed on the back side of the detection electrodes 46a and 46b via an insulating substrate 49, and applies mechanical vibration so that the spatial distance between the detection electrodes 46a and 46b and the intermediate transfer belt 24 varies.

  FIG. 7B is a schematic diagram showing the arrangement of the detection electrodes 46a and 46b. The detection electrodes 46a and 46b have a substantially rectangular shape with long sides extending in a direction orthogonal to the moving direction of the intermediate transfer belt 24, and the two detection electrodes 46a and 46b have a moving direction of the intermediate transfer belt 24. They are arranged close to each other on the insulating substrate 49 in a state of being arranged in a direction orthogonal to each other. In this embodiment, the detection electrodes 46a and 46b are configured such that the short side is 5 mm and the long side is 50 mm. Note that the configuration and operation of the charge amount detection unit 47 are the same as those described in the first embodiment, and a description thereof will be omitted. The configuration of the image forming apparatus and the configuration of the control calculation unit 10 are the same as those described in the first embodiment, and a description thereof is omitted.

[Toner image detection operation, control of image forming conditions]
Next, using the toner image sensor 45 of the present embodiment configured as described above, the toner image detection operation in the image forming apparatus similar to the configuration described in the first embodiment and the control of the image forming conditions according to the detection result are performed. The method of performing will be described. When calibration of the image forming apparatus is started by a user instruction from an external device or the like, the next operation is started. The image forming unit 105 of the image forming apparatus forms a belt-like toner patch P on the intermediate transfer belt 24 on a trial basis while changing the image forming conditions in accordance with the signal output from the pattern generating unit 104. The toner patch P formed at this time is formed with a width of 55 mm so as to cover the entire long side of the detection electrode 41a at a position facing the detection electrode 41a and to avoid a position facing the detection electrode 41b (see FIG. (Refer FIG.7 (b)). In the formed toner patch P, output values corresponding to the toner adhesion amount and the toner charge amount are sequentially measured by the same operation as the toner image sensor 40 while the intermediate transfer belt 24 is rotated.

Here, the output from the operational amplifier 422a in FIG. 3 is an output corresponding to the amount of charge electrostatically induced in the detection electrode 46a facing the toner patch P. On the other hand, the output from the operational amplifier 422b in FIG. 3 is an output corresponding to the amount of charge electrostatically induced on the detection electrode 46b not facing the toner patch P, in other words, on the surface of the intermediate transfer belt 24 and the detection electrode 46b. It becomes. Therefore, the output from the difference detection amplifier 425 of this embodiment is the output value at the toner adhesion amount 0 mg / cm ² and the charge amount 0 μC stored in the RAM 103 from the output when the toner patch P is detected in the first embodiment. Is equivalent to computing the difference between

  That is, in this embodiment, the toner patch P is formed facing the detection electrode 46a, and the toner patch P is not formed at the position facing the detection electrode 46b, so that the difference detection amplifier 425 generates Vt−Vt0, Vpp−. Vpp0 is output. For this reason, in this embodiment, the toner adhesion amount and the charge amount can be measured without performing the initialization operation (operation for obtaining Vt0 and Vpp0) performed in the first embodiment. In this embodiment, when the toner patch P is formed, the toner charge amount is detected by the switching operation of the switches 421a and 421b in FIG. 4A, and the charge of the toner is driven by the vibration unit 43 in FIG. 4B. Performs the same operation as the amount detection. Therefore, in this embodiment, it is possible to shorten the time required for calibration of the image forming apparatus. Based on the measured output value, the CPU 101 determines the image forming conditions of the image forming unit 105 according to various image control programs stored in the ROM 102, and executes the image forming operation, as in the first embodiment. The image forming conditions are the same as those in the first embodiment, and a description thereof is omitted.

  As described above, also in this embodiment, it is possible to measure the toner adhesion amount and the charge amount with one toner image sensor 45, and it is possible to perform image formation under appropriate image formation conditions. In the present exemplary embodiment, the vibration unit 48 is provided on the back side of the detection electrodes 46a and 46b as the toner image sensor 45 so that both the toner adhesion amount and the charge amount can be measured. However, the vibration unit 48 may not be installed and the operation may be performed so as to measure only the toner adhesion amount. Also in this embodiment, when it is desired to remove the influence of electromagnetic wave noise as much as possible, the two detection electrodes 46a and 46b are covered with a shielding electrode controlled to have the same potential as the detection electrodes 46a and 46b. It is also possible (see FIG. 6A). In addition, a shielding electrode controlled to have the same potential as the detection electrodes 46a and 46b may be provided between the two detection electrodes 46a and 46b and the vibrating portion 48 (see FIG. 6B).

  As described above, according to the present embodiment, it is possible to appropriately control the image forming conditions without hindering the downsizing and cost reduction of the image forming apparatus.

DESCRIPTION OF SYMBOLS 10 Control calculating part 24 Intermediate transfer belt 40 Toner image sensor 41a, 41b Detection electrode 105 Image formation part

Claims (10)

Forming means for forming a toner image;
An image carrier that carries the toner image formed by the forming unit;
A detecting means having an electrode and detecting an amount of charge induced between the image carrier and the electrode or between a toner image carried on the image carrier and the electrode;
Control means for controlling image forming conditions based on the charge amount detected by the detection means;
An image forming apparatus comprising:   2. The control unit according to claim 1, wherein a toner adhesion amount of the toner image is obtained based on the charge amount detected by the detection unit, and the image forming condition is controlled based on the adhesion amount. The image forming apparatus described in 1.   The control unit obtains the toner charge amount of the toner image based on the charge amount detected by the detection unit, and controls the image forming condition based on the charge amount. The image forming apparatus described in 1. The electrode comprises a first electrode and a second electrode,
Vibrations that vibrate the electrodes so as to change the distance between the first electrode and the second electrode and the image carrier or between the first electrode and the second electrode and the toner image. With means,
4. The control unit according to claim 3, wherein the control unit obtains the charge amount of the toner based on a result detected by the detection unit by vibrating the first electrode and the second electrode by the vibration unit. The image forming apparatus described. The first electrode and the second electrode are rectangular, and are provided in close proximity to the moving direction with a long side in a direction orthogonal to the moving direction of the image carrier,
The lengths of the long sides of the first electrode and the second electrode are substantially equal,
The image forming apparatus according to claim 4, wherein a length of the second electrode in the moving direction is shorter than a length of the first electrode in the moving direction.   The control means detects the amount of charge detected by the detection means when no toner image is formed on the image carrier and the detection means when a toner image is formed on the image carrier. 6. The image forming apparatus according to claim 4, wherein the image forming condition is controlled based on the amount of electric charge. The first electrode and the second electrode are rectangles having substantially the same shape, and are arranged side by side in a direction perpendicular to the moving direction with a direction perpendicular to the moving direction of the image carrier as a long side,
The forming means forms a toner image at a position facing the first electrode of the image carrier, and does not form a toner image at a position facing the second electrode of the image carrier. The image forming apparatus according to claim 4.   And a shielding means disposed so as to surround the first electrode and the second electrode, and controlled to be substantially the same potential as the potential of the first electrode and the second electrode. The image forming apparatus according to any one of claims 4 to 7.   Shielding means disposed between the first electrode and the second electrode and the vibration means and controlled to be substantially the same potential as the potential of the first electrode and the second electrode. The image forming apparatus according to claim 4, wherein the image forming apparatus is an image forming apparatus. The forming means includes a photoconductor, a charging means for charging the photoconductor, an exposure means for exposing the photoconductor charged by the charging means to form a latent image, and a latent image formed by the exposure means. A developing means for developing an image with toner and forming a toner image; and a first transfer means for transferring a toner image on the photosensitive member formed by the developing means to the image carrier,
First application means for applying a voltage to the developing means;
Second application means for applying a voltage to the first transfer means;
Second transfer means for transferring the toner image transferred onto the image carrier by the first transfer means to a recording material;
Third application means for applying a voltage to the second transfer means;
Fixing means for fixing the toner image transferred by the second transfer means to the recording material;
With
The image forming conditions include at least one of a voltage applied by the first applying unit, a voltage applied by the second applying unit, a voltage applied by the third applying unit, and a temperature of the fixing unit. The image forming apparatus according to claim 1, wherein the number is one.

Images