JPH1063058A - Controller for image forming process - Google Patents

Abstract

PROBLEM TO BE SOLVED: To maintain the color stability and density stability in detecting the reflection density of a test patch formed by toner having all of wave length characteristics, irrespective of reflection method by providing a switch for switching the voltage gain of a non-inverting amplifier corresponding to the wavelength of a light emission element and transmittance of the toner. SOLUTION: In this device, an image formation process controlling circuit 200 is composed of a patch data generating circuit 210, an image density sensor 220, a patch data detecting circuit 230 and a CPU 240. The patch data detecting circuit 230 is a circuit for converting an output signal from the image density sensor 220 to a voltage, and composed of the non-inverting amplifier OP, resistive elements R1 to R6, and diode switches S1 and S2. Then, by selectively connecting the resistive elements R5 and R6 with the resistive element R4 by the diode switches S1 and S2, the voltage gain of the non-inverting amplifier OP is switched corresponding to the light wavelength of the light emission element 221 and transmittance of the toner.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of transferring a color toner image formed by superimposing a single color toner image on an image carrier sequentially by a plurality of developing devices arranged on the peripheral surface of the image carrier onto a recording sheet. The present invention relates to an image forming process control device that controls image forming process conditions for color image formation.

[0002]

2. Description of the Related Art In recent years, as an electrophotographic image forming apparatus, a semiconductor laser, 600 nm or more and 850 nm has been used.
LE with a main energy peak in the wavelength range below m
D, EL (electroluminescence), LCD (liquid crystal shutter) or the like is used as a writing light source, and the surface of the photoreceptor is exposed to laser light, for example, yellow (Y), magenta (M), cyan (C) and black (BK). A color toner image is formed by superimposing a single-color toner image formed by reversal development by four developing devices containing the respective developers on an image carrier, and transferring the color toner image onto recording paper to form a color image. Color copiers and color printers that perform recording have been proposed.

[0003] Since color stability is important for a color toner image formed by superposition in such a color image process, each single-color toner image has a well-balanced toner adhesion amount in terms of the structure of the color image. The image quality, that is, the reproducibility of the color balance is greatly affected by whether the image is developed in the same manner as described above, and whether the toner adhesion amount is stably maintained even when copying a large amount. The color stability of a color image is different from that of a monochrome image.
It is necessary to maintain a predetermined adhesion amount. The above-described color image forming apparatus is provided with control means for managing the amount of toner attached to each single color.

As a means for controlling the amount of toner adhesion,
Forming a test patch of a specific density corresponding to each single-color toner image in a non-image area of the image carrier, including an image density sensor including a plurality of light emitting elements and light receiving elements having different emission wavelengths, A light-emitting element that has a complementary color relationship is selectively emitted, and the reflected light of the test patch of each color is detected by a light-receiving element to control the bias voltage or toner concentration of the developing unit for each color, or according to the humidity in the device. A method of controlling the number of revolutions of the developing sleeve of the developing device by using a method disclosed in Japanese Patent Application Laid-Open Nos. 57-40279, 62-239180 and 2-186368. Has already been disclosed.

In response to recent demands for downsizing image forming apparatuses,
The image density sensor has to be simplified. The image density sensor employs either a reflection method or a diffuse reflection method. The present applicant has studied the improvement for detecting the reflection density from the test patches of all colors with a single light emitting element regardless of the reflection method or the irregular reflection method, and found the following technical problem. .

[0006]

FIG. 15 is a schematic diagram showing the concept of a regular reflection type image density sensor.
(A) is a schematic diagram showing an optical arrangement of a regular reflection type image density sensor.

An image density sensor adopting a regular reflection method is
As shown in FIG. 15A, a phototransistor, which is a light receiving element, is arranged at a position where reflected light that is regularly reflected from an incident point at which an incident light from an LED, which is a light emitting element, intersects a test patch surface. If the point where the incident ray intersects with the test patch surface is the incident point, the plane including the normal of the plane at the incident point and the incident ray is the incident plane, and the angle formed by the incident ray and the reflected ray with the normal is within 90 °. Sometimes Fresnel's law of reflection is applied, the reflected ray is in the plane of incidence and on the opposite side of the normal to the incident ray, and the angles of incidence and reflection are equal.

FIG. 15B is a graph showing an output characteristic when a test patch is formed with toner absorbing the emission wavelength from the light emitting element, and FIG. 15C is a graph showing the transmission of the emission wavelength from the light emitting element. 6 is a graph showing output characteristics when a test patch is formed with a toner. From the output characteristics shown in FIGS. 15B and 15C, the output of the image density sensor fluctuates due to the wavelength characteristics of the toner forming the test patch. If the toner absorbs the wavelength of the light-emitting element, the toner absorbs light, so if the amount of adhered toner increases, the amount of reflected light decreases. The output becomes 0. In the case of toner transmitting the wavelength of the light emitting element, the toner scatters light. Therefore, if the amount of adhered toner increases, the amount of scattered light increases and the amount of light reflected on the light receiving element decreases. However, when the amount of the scattered light exceeds the amount of toner that covers the entire surface of the image carrier with the toner, the amount of reflected light does not change even if the amount of toner adhered fluctuates from the amount of adhesion where the ratio of the scattered light becomes almost constant. The output saturates at a certain value.

FIG. 16 is a schematic view showing the concept of an irregular reflection type image density sensor, and FIG. 16 (a) is a schematic view showing the optical arrangement of an irregular reflection type image density sensor.

An image density sensor employing the diffuse reflection method is
As shown in FIG. 16A, a phototransistor, which is a light receiving element, is disposed at a position for receiving outgoing light that is irregularly reflected from an incident point where an incident light from an LED, which is a light emitting element, intersects a test patch surface.

FIG. 16B is a graph showing the output characteristics when a test patch is formed with toner absorbing the emission wavelength from the light emitting element, and FIG. 16C shows the transmission characteristics of the emission wavelength from the light emitting element. 6 is a graph showing output characteristics when a test patch is formed with a toner. From the output characteristics shown in FIGS. 16B and 16C, the output of the image density sensor fluctuates due to the wavelength characteristics of the toner forming the test patch. When the toner absorbs the wavelength of the light emitting element, the amount of reflected light decreases as the amount of toner adhered increases, and the output becomes 0 when the amount of toner adheres to the entire surface of the image bearing member. If the toner scatters light and the amount of toner adhesion increases, the amount of scattered light increases and the amount of light reflected on the light receiving element increases. However, the ratio of scattered light becomes substantially constant when the amount of toner adhered to the surface of the image bearing member exceeds the amount of toner that covers all of the toner. Becomes smaller, and the output from the image density sensor saturates at a constant value.

As described above, the image density sensor has a technical problem that the light intensity incident on the light receiving element by the reflection method varies depending on the wavelength of the light emitting element and the wavelength characteristic of the toner forming the test patch.

An object of the present invention is to solve the above technical problems,
An image forming process control device capable of maintaining the color stability and the density stability by detecting the reflection density of a test patch formed of a toner having all wavelength characteristics with a set of a light emitting element and a light receiving element regardless of the reflection method. To provide.

[0014]

The above object is achieved by the following constitution.

(1) A test patch is formed on an image carrier by reversal development using toner of two or more colors, and a light emitting element for irradiating the test patch surface with light of a specific wavelength and receiving reflected light thereof. A light receiving element that outputs a signal corresponding to the light intensity, a non-inverting amplifier that amplifies an output signal from the light receiving element to a predetermined level, and a control unit that controls an image forming process based on the output signal from the non-inverting amplifier An image forming process control device comprising: a switch for switching a voltage gain of the non-inverting amplifier according to a wavelength of the light emitting element and a transmittance of toner. With the above configuration, a detection output can be stably obtained from a test patch formed of toner having all wavelength characteristics, so that color stability and density stability can be maintained.

(2) A test patch is formed on the image carrier by reversal development using toner of two or more colors, and a light emitting element for irradiating the test patch surface with light of a specific wavelength and receiving diffusely reflected light thereof. A light receiving element that outputs a signal corresponding to the light intensity, a non-inverting amplifier that amplifies an output signal from the light receiving element to a predetermined level, and a control unit that controls an image forming process based on the output signal from the non-inverting amplifier An image forming process control device comprising: a switch for switching a voltage gain of the non-inverting amplifier according to a wavelength of the light emitting element and a transmittance of toner. With the above configuration,
Since a detection output can be stably obtained from a test patch formed of a toner having all wavelength characteristics, color stability and density stability can be maintained.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred image forming process to which the image forming process control apparatus of the present embodiment is applied and a schematic configuration of an image forming apparatus capable of performing such a process will be described with reference to FIG.

FIG. 1 is a schematic sectional view showing an image forming apparatus to which the image forming process control apparatus according to the present embodiment can be applied.

Prior to the description of each component, a color image forming process will be described.

The image carrier 10 is driven and rotated clockwise while being grounded. Scorotron charger 12 and the grid held at a uniform potential V _G for applying a potential of V _H to the peripheral surface of the image carrier 10, provided with ion by corona discharge by a corona discharge wire. Prior to the charging by the scorotron charger 12, in order to eliminate the history of the photoconductor of the image carrier 10 up to the previous printing, exposure by PCL using a light emitting diode or the like is performed to eliminate the charge on the peripheral surface of the image carrier 10.

After the surface of the image carrier 10 is uniformly charged, the writing device 13 performs image exposure based on the image signal.
The writing device 13 (see FIG. 2)
The optical path is bent by a reflection mirror 137 through a polygon mirror 134, an fθ lens 135, etc., which emits and rotates light 1 for scanning. A rotation (sub-scan) of the image carrier 10 forms a latent image. The image portion is exposed to form a reversal latent image such that the image portion has a lower potential.

First, development of yellow (Y) of the first color is performed by a developing sleeve 141 which rotates while holding a developer with a built-in magnet. The developer whose layer thickness is regulated on the developing sleeve 141 by the layer forming means is transported to the developing area.

The gap between the developing sleeve 141 and the image carrier 10 in the developing area is 0.2 to 1.0 mm, which is larger than the layer thickness of the developer held on the developing sleeve 141.
AC bias V _AC and the DC bias V _DC is applied to overlap therebetween. Because the charge amount of the toner is the same polarity as the DC bias V _DC, the portion of the AC bias the toner given the opportunity to leave from the carrier by V _AC DC bias V _DC high potential than the electrostatic latent image V _H Does not adhere
The toner adheres to the electrostatic latent image _{VL having} a lower potential than the DC bias _VDC, and is visualized (reversal development).

After the visualization of the first color is completed, the image forming process for the second color is started, and the uniform charging is again performed by the scorotron charger 12, and the latent image based on the image data of the second color is formed by the writing device 13. You. At this time, the charge elimination by the PCL performed in the image forming process of the first color is not performed because the toner attached to the image portion of the first color scatters due to a sharp drop in the surrounding potential.

Again, V _H is applied over the entire surface of the image carrier 10.
A latent image similar to that of the first color is formed and developed on a portion of the photoconductor having the potential of not having the image of the first color, but development is performed again on a portion of the photoconductor having the image of the first color. in part, V _M by the charge possessed by the shading and toner itself by the toner of the first color attached 'latent image is formed, V _DC and V _M' development according to the potential difference between is performed. When the development of the first color and the first color in the overlapping portion of the second color image performed by creating a latent image of VL, the first color and for collapsing the balance of the second color, V _H to reduce the exposure amount of the first color > V _M ′> V
_L become the intermediate potential, sometimes developed with the latent image potential of V _M '.

For the third color and the fourth color, the same image forming process as that for the second color is performed, and a visible image of four colors is formed on the peripheral surface of the image carrier 10.

In the transfer area, a transfer roller 18 is pressed against the peripheral surface of the image carrier 10 in synchronization with the transfer timing.
A multicolor image is collectively transferred by sandwiching the fed recording paper.

Next, the recording paper is discharged at the same time by the separation brush 19 brought into pressure contact, separated by the peripheral surface of the image carrier 10 and conveyed to a fixing device (not shown). After the toner is fused by pressurization, the toner is discharged to the outside of the apparatus via a paper discharge roller. After the recording paper passes through the transfer roller 18 and the separation brush 19, the transfer roller 18 and the separation brush 19 are retracted from the peripheral surface of the image carrier 10 to prepare for the formation of the next toner image.

On the other hand, the image carrier 10 from which the recording paper has been separated removes and cleans the residual toner by pressing the blade of the cleaning device 22 and receives the charge by the PCL and the charge by the charger 12 again to form the next image forming process. to go into. The blade moves immediately after the cleaning of the surface of the photoconductor and is retracted from the peripheral surface of the image carrier 10.

Next, the function and performance characteristics of the main components of the image forming apparatus for executing the above-described color image forming process will be described with reference to FIGS.

The image carrier 10 forms an intermediate layer by applying a coating liquid for an intermediate layer on a conductive support and drying and curing the coating solution.
An electrophotographic photosensitive member having a photosensitive layer formed thereon;
The radius is set to 40 mm or more in order to transport in the longitudinal (297 mm) direction using a medium-sized transfer material. Such a radius of 40 mm or more may be used during image writing or when the transfer roller 18 is used.
Is also required to prevent the image from being displaced even if is pressed or released. Note that the conductive support is grounded. The image carrier 10 is about 75-100 mm /
An encoder for detecting the phase on the rotation axis of the image carrier 10 is a drum-shaped photoconductor of φ80 to φ120 mm composed of a (-) charged coating type OPC that rotates in the direction indicated by the arrow at a linear velocity of sec. (Not shown), and an encoder (not shown) outputs a phase signal indicating the phase of the image carrier 10 to C
It is sent to the PU 240 (see FIG. 1).

Examples of the conductive support include conventionally known ones, for example, a metal substrate such as aluminum or stainless steel, or a conductive layer in which a conductive powder such as a metal oxide is dispersed in a resin layer. The one with the height is used. There is no particular limitation on the processing method for imparting roughness to the surface of the support. For example, for metal substrates, chemical etching,
Examples include chemical methods such as electroplating, physical methods such as vapor deposition and sputtering, and mechanical methods such as lathe processing. Also, like certain types of resin conductive layers,
The layer may have irregularities due to the shape and presence of the constituent material such as conductive powder contained in the layer and have a surface roughness. The cross-sectional shape of the irregularities on the surface of the support may be a V-shaped shape, a U-shaped shape, a saw blade shape, or any other irregular shape, and is not particularly limited.

For the intermediate layer, a coating solution is prepared by dissolving an organic metal compound such as a metal alkoxide compound and a silane coupling agent as main components in a solvent. This liquid is applied, dried and cured to form a liquid.

The charge generating material (CGM) has a sufficient spectral sensitivity even in a long wavelength region and generates a charge faithfully in response to a minute difference in exposure amount, thereby forming an image having excellent contrast and resolution. can do. Considering these characteristics, titanyl phthalocyanine is most suitable as CGM.

The charger 12 includes, for example, a scorotron charger employing a platinum wire (cladding or alloy) as a charging wire, or a saw-tooth electrode or a brush electrode disposed between the developing device 14 and the transfer roller 18. Prior to the latent image forming process, the image carrier 10 is uniformly charged to V _H -750 V to adjust the gradation reproducibility and the like to thereby prevent fog.

FIG. 2 is a plan view showing a schematic configuration of the writing device.

The writing device 13 sends image data from a formatter that decodes a printer command to a laser diode (LD) modulation circuit, causes the semiconductor laser 131 to emit light based on the modulated image signal, and generates an image carrier with a dot clock of 20 MHz. A latent image is formed by line-scanning on the semiconductor laser 10, a semiconductor laser 131, a collimator lens 132, a polygon mirror 134, and an fθ lens 135.
And a first cylindrical lens 133 and a second cylindrical lens 136. The semiconductor laser 131 is oscillated by a pulse width modulated modulation signal, and the laser light is deflected by a polygon mirror 134 rotating at a predetermined speed. The first cylindrical lens 133 and the second cylindrical lens 136 allow the image carrier 1
The scanning is performed by focusing on a spot corresponding to 600 DPI (about 60 × 80 μm) on the zero.

As the semiconductor laser 131, GaAlAs or the like is used, the maximum output is 10 mW, the light efficiency is 25%, and the divergence angle is 8 to 16 ° in the direction parallel to the bonding surface and 20 to 36 ° in the direction vertical to the bonding surface. is there. Since color toners (yellow, magenta, and cyan) may be sequentially superimposed, it is preferable to use light having a wavelength of little absorption by the color toner. In this case, the wavelength is 780 nm.
It is.

The polygon mirror 134 is equivalent to a deflecting optical system. The polygon mirror 134 condenses the beam and reduces the Pepper's sum and the astigmatic difference in order to realize a flat scanning surface. A polygon surface is provided, and rotates at 23600 (rpm) at a writing density of 600 dpi.

The fθ lens 135 reduces the Pepperl sum and the astigmatic difference in order to realize the flattening of the scanning surface, and removes the field curvature.

The first cylindrical lens 133 and the second
The cylindrical lens 136 corresponds to a correction optical system, and reduces unevenness of the scanning line pitch due to a surface tilt error of the polygon mirror 134. Thus, the polygon tilt angle is 120 seconds PP, and the tilt angle correction rate is 1'20.
That is all. The second cylindrical lens 136 focuses the beam on the image carrier 10.

The image data output section includes a modulation circuit (not shown), an LD drive circuit (not shown), an index sensor 138 and an index detection circuit (not shown) as a synchronous system, and a polygon driver (not shown). Is provided.

The modulation circuit compares the reference signal with a D / A-converted analog recording signal of a recording signal composed of predetermined bits to convert the signal into a multi-value signal. The modulation signal obtained in this manner becomes a drive signal for the LD drive circuit. LD drive circuit,
The semiconductor laser 131 is oscillated by the modulation signal. A signal corresponding to the light amount of the beam from the semiconductor laser 131 is fed back to drive the semiconductor laser 131 so that the light amount becomes constant. It can be changed. Thereby, the latent image potential can be adjusted. The synchronization system enters the index sensor 138 via a mirror that reflects a beam from the deflection optical system. Index sensor 13
Reference numeral 8 outputs a current in response to the beam, and the current is subjected to current / voltage conversion by an index detection circuit and output as an index signal. Based on the index signal, the surface position of the polygon mirror 134 rotating at a predetermined speed is detected, and optical scanning is performed by a modulation signal in a raster scanning method at a cycle in the main scanning direction.

As shown in FIG. 1, a developing device 14 loaded with a two-component developer composed of a toner such as yellow, magenta, cyan, and black and a carrier is provided on the periphery of the image carrier 10.

FIG. 3 shows a schematic configuration of the developing device.

The developing device 14 combines a toner made of a polyester-based material having an average particle diameter of about 8.5 μm and a ferrite-based coating carrier having an average particle diameter of 30 μm with a toner concentration of 7 to 7 μm.
After the developer controlled to 9% is stirred by rotating the stirring screw 142 to set a predetermined charge amount (Q / M), the developer is applied to the image carrier 10 outside the magnet roller at a predetermined rotation speed. On the other hand, a magnetic brush whose layer is regulated by the layer thickness regulating member 144 is formed on the outer periphery of the developing sleeve 141 which rotates in the forward direction.
A KHz AC bias and a DC bias of -650 V are applied to visualize the latent image in the development area facing the image carrier 10 into a toner image. The developing gap is 0.4
6 mm.

The developing device 14 has a developing sleeve 141 having a diameter of 20 (mm) near the opening of the housing facing the image carrier 10.
The rotating shaft is fitted into the side wall of the housing, and a stirring screw 142 having a diameter of 16 (mm) and a supply roller 14 are provided behind the rotating shaft.
3 is inserted into the side wall of the housing, and the developing sleeve 141, the stirring screw 142, the supply roller 14
The number of rotations can be changed by connecting the drive shaft 3 to a drive system (not shown) via a gear, for example. This control operation is performed by the CPU 240. For example, by using this function, the image density is adjusted based on the output signal from the image density sensor by adjusting the rotation axis of the developing sleeve 141 to, for example, 200 (rpm) or 250 (rpm).
(Rpm), 300 (rpm) and controlling the supply amount of the developer during a certain development time.

FIG. 4 is a graph showing the toner characteristics of each color. As shown in FIG. 4, the vertical axis represents transmittance (%), and the horizontal axis represents wavelength.

Since the light transmittance of yellow (Y), magenta (M), cyan (C), and black (BK) of each toner greatly varies depending on the wavelength, the image density of the test patch is constant. However, a difference occurs in the detected density signal.

The transfer roller 18 has a shaft made of a stainless steel rod, and a resin material such as polyurethane rubber, silicone rubber, styrene-butadiene copolymer elastomer, olefin-based elastomer or the like on the outer periphery of which has a cell size of 10 to 30.
Formed with a firing type or open cell type of about 0 μm,
Further, it is composed of the above-mentioned resin material mixed with an inorganic material such as carbon black as a conductivity-imparting material and / or an organic conductive agent, and a conductive elastic member capable of being supplied with electrification. As the elastic member, a ruby cell roller made of foamed polyurethane resin containing carbon black (manufactured by Toyo Polymer Co., Ltd.) was used. The electric resistance of the transfer roller 18 is 2 × 10 ⁸
Ω and rubber hardness are preferably about 25 ° in Asker C scale. The outer shape of the elastic member is 16 mm, and the outer shape of the shaft is 8
mm.

Immediately after the transfer process, the separation brush 19 removes static electricity from the recording paper with an AC corona or a high-voltage current to reduce the electrostatic attraction of the recording paper to the image carrier 10 and to utilize the rigidity and weight of the paper. The recording paper is easy to separate, and if it is weak, the thinner the recording paper is, the harder the rigidity becomes.

The cleaning device 22 contacts the surface of the image carrier 10 with a blade or the like, thereby
The toner and dust adhering to the surface of No. 0 are scraped off and captured in a waste toner box.

Next, an image forming process control circuit 200 employed in the image forming apparatus of the present embodiment will be described with reference to FIGS.

The image forming process control circuit 200 is similar to that shown in FIG.
As shown in the figure, the patch data generation circuit 210, the image density sensor 220, the patch detection circuit 230, and the CPU 240 are provided.

The patch data generation circuit 210 has a nonvolatile R
The OM stores test patch data for each of the primary colors of yellow, magenta, and cyan. Such test patch data is read out when correcting image forming process conditions.

The image density sensor 220 detects the reflection density from the test patch of each color, and includes a regular reflection system and a diffuse reflection system.

FIG. 5 is a sectional view showing the arrangement of an image density sensor employing the regular reflection method.

Image density sensor 220 based on regular reflection method
As shown in FIG. 5, a groove is formed in the casing such that the centers of the light receiving surfaces of the light emitting diode 221 and the phototransistor 222 form an angle of 40 ° and 40 °, and the light emitting diode 221 and the phototransistor 222 are formed in the groove. The photocoupling is constituted by fitting into the. The casing is provided in the vicinity of the cleaning device 22 with a gap of 6 mm from the surface of the image carrier 10 so as to face the center of the image carrier 10 so as to be horizontal with the surface of the image carrier 10 via the substrate. Thus, the test patches are arranged at an angle of 40 ° with respect to the center line O at the position where the test patch is detected at θ1 and θ2. Therefore, the image density sensor 220
An electric signal corresponding to the intensity of light reflected from the test patch carried on the surface 10b of the rotating image carrier 10 while maintaining the light emitting / receiving relationship by reflection shown in FIG. 5 is obtained.

FIG. 6 is a sectional view showing an arrangement state of an image density sensor adopting the irregular reflection method.

Image density sensor 220 using diffuse reflection method
As shown in FIG. 6, a groove was formed in the casing such that the center of the light receiving surface of the light emitting diode 221 and the phototransistor 222 formed an angle of 40 °, and fitted into the light emitting diode 221 and the phototransistor 222 in the groove. This constitutes a photocoupling. The casing is provided in the vicinity of the cleaning device 22 with a gap of 6 mm from the surface of the image carrier 10 so as to face the center of the image carrier 10 so as to be horizontal with the surface of the image carrier 10 via the substrate. Thus, θ is arranged at an angle of 40 ° with respect to the center line O at the position where the test patch is detected. Therefore, the image density sensor 220 maintains the relationship of light projection and light reception by reflection shown in FIG.
An electrical signal corresponding to the intensity of light reflected from the test patch carried by b is obtained.

FIG. 7 is a circuit diagram showing a patch detection circuit.

The patch detection circuit 230 is a circuit for converting an output signal from the image density sensor 220 into a voltage, and includes an operational amplifier OP, resistance elements R1 to R6, and diode switches S1 and S2.
It can be used in common regardless of the arrangement of the regular reflection system or the irregular reflection system.

The maximum output 1 is applied to the anode terminal of the light emitting diode 221 and the anode terminal of the phototransistor 222.
A variable direct-current power supply V _CC of 0 (V) is connected, for example, a resistance element R1 is connected to the cathode terminal of the light emitting diode 221 and an operational amplifier OP, resistance elements R2 to R6 and a diode switch are connected to the cathode terminal of the phototransistor 222. An output detection circuit composed of S1 and S2 is provided.
The output detection circuit is a non-inverting amplifier in which an input is applied to the non-inverting terminal of the operational amplifier OP and a part of the output voltage is fed back to the inverting terminal of the operational amplifier through the resistors R4 to R6. The resistance elements R5 and R6 can be selectively connected to the resistance element R4 by diode switches S1 and S2 so that the voltage gain can be changed. In the present embodiment, the gain A _fb of the output detection circuit is 1 + R4 / R5 or 1 + R4 / R6.
It is. Since the output detection circuit is a non-inverting amplifier circuit, its gain is independent of the loop gain of the operational amplifier, and is determined only by the resistance of the feedback circuit. R4 to 560
kΩ, and R5 is 560 k depending on the emission wavelength of the light emitting element.
If Ω, 5.6 kΩ and 1.2 kΩ and R6 is 36 kΩ, the voltage gain A _fb is switched between 2,100,500 and 16.6. The voltage gain A _fb is switched by C
This is performed by a control signal from the PU 240.

The patch detection circuit 220 detects the voltage corresponding to the light intensity of the light from the light emitting diode 221 received by the phototransistor 222 via the patch by having the above-described configuration.

In the following, the toner adhesion amount M / A is set to 0.4 to 0.5.
The detectability is examined from the output voltage of the image density sensor when it is changed to 6 mg / cm ² with reference to Tables 1 to 12 and FIGS.

First, output characteristics from the image density sensor when a regular reflection type image density sensor is employed will be described.

FIG. 8 is a graph showing output characteristics when a light emitting device having an emission wavelength of 950 nm is used. In each graph, the vertical axis shows the output voltage from the patch detection circuit 220, and the horizontal axis shows Toner adhesion amount M / A (mg / cm
² ) is shown.

FIG. 8A shows the output characteristics when the voltage gain A _fb of the patch detection circuit 220 is set to 16.6 by changing the amount of the test patch adhered with the yellow, magenta, cyan, and black toners. FIG. By changing the amount of test patch attached with black toner,
Although the output voltage decreases with an increase in the toner adhesion amount, even if the test patch is formed by changing the adhesion amount of the yellow, magenta, and cyan toners, the voltage gain of the patch detection circuit 220 is large because the amount of reflected light is large. Since A _fb is large, it indicates that the output voltage is saturated.

[0069]

[Table 1]

Table 1 shows the detectability based on the output voltage from the patch detection circuit 220 when the toner adhesion amount M / A was changed to 0.4 to 0.6 mg / cm ^{2 under the} same conditions as in FIG. Is considered. If a test patch is formed with black toner, the amount of toner attached to the test patch can be reduced to 0.4 to
If it is changed at 0.6 mg / cm ² , it can be detected because an output difference ΔV occurs. However, when a test patch is formed with yellow, magenta, and cyan toners, the toner adhesion amount of the test patch is 0.4 to 0.6 mg / cm ^2.
Cannot be detected because the output difference .DELTA.V does not occur even if it is changed by.

Therefore, in this embodiment, when a test patch is formed with yellow, magenta, and cyan toners, the voltage gain A _fb of the patch detection circuit 220 is reduced to 2 to detect the reflection density.

FIG. 8B is a graph showing output characteristics when the voltage gain A _fb of the patch detection circuit 220 is set to 2 by changing the amount of the test patch attached with the yellow, magenta, and cyan toners. . If the test patch is formed with yellow, magenta, and cyan toners while changing the amount of adhesion, the output voltage decreases as the amount of toner adhesion increases.

[0073]

[Table 2]

Table 2 shows that a test patch was formed with yellow, magenta, and cyan toners when the toner adhesion amount M / A was changed from 0.4 to 0.6 mg / cm ^{2 under the} same conditions as in FIG. 8B. The output voltage from the patch detection circuit 220 and the toner adhesion amount M / A are set to 0.4 under the same conditions as in FIG.
This is to examine the detectability from the output voltage from the patch detection circuit 220 when a test patch is formed with the black toner when the density is changed to 0.6 mg / cm ² . 0.4-0.6mg of toner adhesion amount for test patches of all colors
/ Cm ² , there is an output difference, which improves the detectability.

FIG. 9 is a graph showing output characteristics when a light emitting element having an emission wavelength of 650 nm is used. In each graph, the vertical axis shows the output voltage from the patch detection circuit 220, and the horizontal axis shows Toner adhesion amount M / A (mg / cm
² ) is shown.

FIG. 9A shows output characteristics when the voltage gain A _fb of the patch detection circuit 220 is set to 16.6 by changing the amount of test patch adhered with yellow, magenta, cyan, and black toners. FIG. If the test patch is formed by changing the adhesion amount of cyan and black toner, the output voltage will decrease as the amount of toner adhesion increases, but the toner patch of yellow and magenta will be used to change the adhesion amount of the test patch. However, since the amount of reflected light is large and the voltage gain A _fb of the patch detection circuit 220 is large, this indicates that the output voltage is saturated.

[0077]

[Table 3]

Table 3 shows the detectability based on the output voltage from the patch detection circuit 220 when the toner adhesion amount M / A was changed from 0.4 to 0.6 mg / cm ^{2 under the} same conditions as in FIG. 9A. Is considered. If a test patch is formed with cyan and black toners, the output difference Δ is obtained by changing the toner adhesion amount of the test patch by 0.4 to 0.6 mg / cm ^2.
V can be detected. However, when a test patch is formed with yellow and magenta toners, the toner adhesion amount of the test patch is 0.4 to 0.6 mg / cm.
^{Even if} it is changed in ² , it cannot be detected because the output difference ΔV does not occur.

Therefore, in this embodiment, when a test patch is formed with yellow and magenta toners, the voltage gain A _fb of the patch detection circuit 220 is reduced to 2 to detect the reflection density.

FIG. 9B is a graph showing the output characteristic when the voltage gain A _fb of the patch detection circuit 220 is set to 2 by changing the amount of the test patch attached with the yellow and magenta toners. When the test patch is formed with yellow and magenta toners while changing the amount of adhesion, the output voltage decreases as the amount of toner adhesion increases.

[0081]

[Table 4]

Table 4 shows that a test patch was formed with yellow and magenta toners when the toner adhesion amount M / A was changed to 0.4 to 0.6 mg / cm ^{2 under the} same conditions as in FIG. 9B. The output voltage from the patch detection circuit 220 of FIG.
Under the same conditions as in FIG.
This is an examination of the detectability from the output voltage from the patch detection circuit 220 when a test patch is formed with cyan and black toner when the density is changed to 0.6 mg / cm ² . 0.4-toner adhesion amount for all color test patches
If it is changed at 0.6 mg / cm ² , an output difference ΔV is generated, so that the detectability is improved.

FIG. 10 is a graph showing output characteristics when a light emitting element having an emission wavelength of 570 nm is used. In each graph, the output voltage from the patch detection circuit 220 is shown on the vertical axis, and the horizontal axis is shown on the horizontal axis. Toner adhesion amount M / A (mg / c
m ² ).

FIGS. 10 (a) and 10 (b) show the case where the voltage gain A _fb of the patch detection circuit 220 is set to 16.6 by changing the adhesion amount of the test patch with yellow, magenta, cyan and black toners. 4 is a graph showing output characteristics. If the test patch is formed by changing the amount of adhesion of the test patch using yellow toner, the output voltage will decrease as the amount of toner adhesion increases, but the test patch will be formed by changing the amount of test patch adhesion using magenta, cyan, and black toner. Even when the light-emitting element at 570 nm has a smaller light quantity than the light-emitting elements at 950 nm and 860 nm, the light-emitting element absorbs the emission wavelength and the output voltage becomes zero.

[0085]

[Table 5]

Table 5 shows the detectability based on the output voltage from the patch detection circuit 220 when the toner adhesion amount M / A was changed from 0.4 to 0.6 mg / cm ^{2 under the} same conditions as in FIG. Things. If a test patch is formed with yellow toner, the amount of toner adhered to the test patch is 0.4 to 0.5.
If it is changed at 6 mg / cm ² , it can be detected because an output difference ΔV occurs. However, if a test patch is formed using magenta, cyan, and black toners, even if the amount of toner attached to the test patch is changed in the range of 0.4 to 0.6 mg / cm ² , it cannot be detected because the output difference ΔV does not occur.

Therefore, in this embodiment, when a test patch is formed with magenta, cyan, and black toners, the voltage gain A _fb of the patch detection circuit 220 is increased to 100 to detect the reflection density.

FIG. 10C is a graph showing output characteristics when the voltage gain A _fb of the patch detection circuit 220 is set to 100 by changing the amount of the test patch attached with magenta, cyan, and black toners. . If the test patch is formed with magenta, cyan, and black toners while changing the amount of adhesion, the output voltage decreases as the amount of toner adhesion increases.

[0089]

[Table 6]

Table 6 shows a patch when a test patch was formed with yellow toner when the toner adhesion amount M / A was changed to 0.4 to 0.6 mg / cm ^{2 under the} same conditions as in FIG. Under the same conditions as the output voltage from the detection circuit 220 and the same conditions as in FIG.
magenta when changing the cm ^2, cyan, black patch detection when forming test patches with toner circuits 2
In this figure, the detectability is examined based on the output voltage from the reference numeral 20.
The toner adhesion amounts of the test patches of all colors are set to 0.4 to 0.
If it is changed at 6 mg / cm ² , an output difference ΔV is generated, so that the detectability is improved.

Next, output characteristics from the image density sensor when an irregular reflection type image density sensor is employed will be described.

FIG. 11 is a graph showing output characteristics when a light emitting element having an emission wavelength of 950 nm is used. In each case, the vertical axis shows the output voltage from the patch detection circuit 220, and the horizontal axis shows Toner adhesion amount M / A (mg / c
m ² ).

FIG. 11A shows that the voltage gain A _fb of the patch detection circuit 220 is changed to 16.6 by changing the adhesion amount of the test patch with yellow, magenta, cyan and black toners.
6 is a graph showing the output characteristics when the setting is made. If the test patch is formed by changing the amount of test patch attached with black toner, the output voltage will decrease with an increase in the amount of toner attached.However, the test patch is formed by changing the amount of test patch attached with yellow, magenta and cyan toner. However, since the amount of reflected light is large and the voltage gain A _fb of the patch detection circuit 220 is large, this indicates that the output voltage is saturated.

[0094]

[Table 7]

Table 7 shows the detectability based on the output voltage from the patch detection circuit 220 when the toner adhesion amount M / A was changed to 0.4 to 0.6 mg / cm ^{2 under the} same conditions as in FIG. Is considered. If a test patch is formed with black toner, the amount of toner attached to the test patch will be 0.4
If it is changed at ０．６0.6 mg / cm ² , it can be detected because an output difference ΔV occurs. However, when a test patch is formed with yellow, magenta, and cyan toners, the toner adhesion amount of the test patch is 0.4 to 0.6 mg / cm.
^{Even if} it is changed in ² , it cannot be detected because the output difference ΔV does not occur.

Therefore, in this embodiment, when a test patch is formed with yellow, magenta, and cyan toners, the voltage gain A _fb of the patch detection circuit 220 is reduced to 2 to detect the reflection density.

FIG. 11B is a graph showing output characteristics when the voltage gain A _fb of the patch detection circuit 220 is set to 2 by changing the amount of the test patch adhered with the yellow, magenta, and cyan toners. . If the test patch is formed with yellow, magenta, and cyan toners with varying amounts of adhesion, the output voltage increases as the amount of toner adhesion increases.

[0098]

[Table 8]

Table 8 shows that test patches were formed with yellow, magenta, and cyan toners when the toner adhesion amount M / A was changed from 0.4 to 0.6 mg / cm ^{2 under the} same conditions as in FIG. 11B. The test was performed with the black toner when the toner adhesion amount M / A was changed to 0.4 to 0.6 mg / cm ^{2 under the} same conditions as in FIG. This is to examine the detectability from the output voltage from the patch detection circuit 220 when a patch is formed. 0.4-toner adhesion amount for all color test patches
If it is changed at 0.6 mg / cm ² , an output difference ΔV is generated, so that the detectability is improved.

FIG. 12 is a graph showing output characteristics when a light emitting device having an emission wavelength of 650 nm is used. In each graph, the vertical axis shows the output voltage from the patch detection circuit 220, and the horizontal axis shows Toner adhesion amount M / A (mg / c
m ² ).

FIG. 12A shows that the voltage gain A _fb of the patch detection circuit 220 is changed to 16.6 by changing the amount of adhesion of the test patch with yellow, magenta, cyan and black toners.
6 is a graph showing the output characteristics when the setting is made. If the test patch is formed by changing the adhesion amount of cyan and black toner, the output voltage will decrease as the amount of toner adhesion increases, but the toner patch of yellow and magenta will be used to change the adhesion amount of the test patch. However, since the amount of reflected light is large and the voltage gain A _fb of the patch detection circuit 220 is large, this indicates that the output voltage is saturated.

[0102]

[Table 9]

Table 9 shows the detectability based on the output voltage from the patch detection circuit 220 when the toner adhesion amount M / A was changed to 0.4 to 0.6 mg / cm ^{2 under the} same conditions as in FIG. Is considered. If a test patch is formed with cyan and black toners, the output difference ΔV can be detected by changing the toner adhesion amount of the test patch by 0.4 to 0.6 mg / cm ² . However, when a test patch is formed with yellow and magenta toners, the toner adhesion amount of the test patch is 0.4 to 0.6 mg / cm.
^{Even if} it is changed in ² , it cannot be detected because the output difference ΔV does not occur.

Therefore, in this embodiment, when a test patch is formed with yellow and magenta toners, the voltage gain A _fb of the patch detection circuit 220 is reduced to 2 to detect the reflection density.

FIG. 12B is a graph showing the output characteristic when the voltage gain A _fb of the patch detection circuit 220 is set to 2 by changing the amount of the test patch attached with the yellow and magenta toners. When the test patch is formed with yellow and magenta toners while changing the amount of adhesion, the output voltage increases as the amount of toner adhesion increases.

[0106]

[Table 10]

Table 10 shows that a test patch was formed with yellow and magenta toners when the toner adhesion amount M / A was changed to 0.4 to 0.6 mg / cm ^{2 under the} same conditions as in FIG. Output voltage from the patch detection circuit 220 of FIG.
Under the same conditions as in 2 (a), the toner adhesion amount M / A is set to 0.4 to
This is an examination of the detectability from the output voltage from the patch detection circuit 220 when a test patch is formed with cyan and black toner when the density is changed to 0.6 mg / cm ² . 0.4-toner adhesion amount for all color test patches
If it is changed at 0.6 mg / cm ² , an output difference ΔV is generated, so that the detectability is improved.

FIG. 13 is a graph showing output characteristics when a light emitting element having an emission wavelength of 570 nm is used. In each graph, the vertical axis shows the output voltage from the patch detection circuit 220, and the horizontal axis shows Toner adhesion amount M / A (mg / c
m ² ).

FIGS. 13A and 13B show the case where the voltage gain A _fb of the patch detection circuit 220 is set to 16.6 by changing the adhesion amount of the test patch with the yellow, magenta, cyan, and black toners. 4 is a graph showing output characteristics. If the test patch is formed by changing the amount of adhesion of the test patch with yellow toner, the output voltage will increase as the amount of toner adhesion increases.However, the test patch is formed by changing the amount of test patch adhesion with magenta, cyan and black toner. Even if the light-emitting element at 570 nm has a smaller light amount than the light-emitting elements at 950 nm and 860 nm, the light-emitting element absorbs the emission wavelength, and the output voltage becomes zero.

[0110]

[Table 11]

Table 11 shows that the toner adhesion amount M / A was 0.4 to 0.6 mg / cm ^{2 under the} same conditions as in FIGS. 13 (a) and 13 (b).
In this example, the detectability is examined based on the output voltage from the patch detection circuit 220 when the voltage is changed to. If a test patch is formed with yellow toner, an output difference ΔV can be detected by changing the toner adhesion amount of the test patch by 0.4 to 0.6 mg / cm ² . However, if a test patch is formed with magenta, cyan, and black toners, the amount of toner attached to the test patch is 0.4 to 0.6.
Even if it is changed at mg / cm ² , it cannot be detected because the output difference ΔV does not occur.

Therefore, in this embodiment, when a test patch is formed with magenta, cyan, and black toners, the voltage gain A _fb of the patch detection circuit 220 is increased to 500, and the reflection density is detected.

FIG. 13C is a graph showing output characteristics when the voltage gain A _fb of the patch detection circuit 220 is set to 500 by changing the amount of the test patch attached with magenta, cyan, and black toners. . If the test patch is formed with magenta, cyan, and black toners while changing the amount of adhesion, the output voltage decreases as the amount of toner adhesion increases.

[0114]

[Table 12]

Table 12 shows the patches formed when the test patches were formed with yellow toner when the toner adhesion amount M / A was changed to 0.4 to 0.6 mg / cm ^{2 under the} same conditions as in FIG. The toner adhesion amount M / A is set to 0.4 to 0.6 mg under the same conditions as the output voltage from the detection circuit 220 and FIG.
/ Cm ² , the sensitivity is examined based on the output voltage from the patch detection circuit 220 when a test patch is formed with magenta, cyan, and black toners. 0.4-toner adhesion amount for all color test patches
If it is changed at 0.6 mg / cm ² , an output difference ΔV is generated, so that the detectability is improved.

Next, the operation of the image forming process control circuit 200 according to the present embodiment will be described with reference to FIG.
FIG. 14 is a timing chart showing the operation of the image forming process control circuit according to the present embodiment.

FIG. 14 (a) shows the drive timing of the PCL, FIG. 14 (b) shows the drive timing of the charger 12, and FIG. FIG. 14 shows the timing.
FIGS. 14D to 14G show the drive timing of the developing device, and FIG. 14H shows the patch detection timing. FIGS. 14A to 14H show the ON state at the high level and the OFF state at the low level.

The CPU 240 turns on the main motor (not shown) at time t1. As a result, the image carrier 10 starts rotating in the direction of the arrow (see FIG. 1), so that the phase signal changes from the encoder (not shown). Thereby, the CPU 240 can detect the rotation phase of the image carrier 10. The CPU 240 applies a predetermined output voltage from the high voltage power supply (not shown) to the charger 12 at the same time as the rotation of the image carrier 10 and starts the discharge of the image carrier. Ten image forming areas are uniformly charged.

On the other hand, the CPU 240 sends a test patch signal representing a gray scale from the patch data generation circuit 210 to the writing device 13 after time t2. The writing device 13 sends the recording signal to the pulse width modulation circuit as shown in FIG. The pulse width modulation circuit sends a modulation signal obtained by pulse width modulation of the test patch signal for one scanning line to the LD driving circuit. The LD drive circuit emits a laser beam by oscillating the semiconductor laser 131 with the modulation signal. Such a laser beam is deflected by a polygon mirror 134 rotating at a predetermined speed, and focused to a minute spot on the image carrier 10 by an fθ lens 135, a first cylindrical lens 133, and a second cylindrical lens 136. 3 sec exposure time and 0.2 sec
The scanning is repeated by repeating the off time of 4 times. by this,
For example, an electrostatic latent image is formed on the non-image area of the image carrier 10 at four intervals of about 20 mm × 30 mm × 12 mm. CPU
When detecting the end of the latent image forming operation, 240
14D to 14G, after detecting the phase of the image carrier 10 from a phase signal sent from an encoder (not shown), the developing device 14 is moved to a position synchronized with the electrostatic latent image. Drive. Specifically, the rotating developing sleeve 141 applies an AC bias after a lapse of 3 msec after applying a DC bias first, so that the latent image formed on the image carrier 10 is, for example, 20 × 30 mm square and about 12 mm apart. Thus, the patch toner image is continuously visualized four times. Thereby, yellow, magenta, cyan, and black patch toner images are formed. At this time, the exposure level for creating the test patch is the maximum exposure amount of PWM25.
Use 5 The latent image created in this way is 100
The image is visualized by the developing sleeve 141 which rotates at any one of rpm to 450 rpm.

The CPU 240 samples the data of 20 points or more by the image density sensor 220 at the timing shown in FIG. 14 (h) by sampling the portions of the test patch formed on the surface of the image carrier 10 except for 1 mm at both ends.
It is input via the patch detection circuit 230. Accordingly, the photodiode 222 outputs a signal corresponding to the intensity of light reflected from the test patch visualized on the image carrier 10 to C.
The output is output to the PU 240 to determine the rotation speed of the developing sleeve 141, the light emission intensity of the semiconductor laser 131, and the developing bias.

Therefore, the image forming process control circuit 200 according to the present embodiment can stably obtain a detection output from a test patch formed with toner having all wavelength characteristics, so that color stability and density stability can be obtained. Could be maintained.

[0122]

According to the first aspect of the present invention, by providing the above configuration, a detection output can be stably obtained from a test patch formed with toner having all wavelength characteristics, so that color stability and density stability can be obtained. Can maintain sex.

According to the second aspect of the present invention, by providing the above configuration, a detection output can be stably obtained from a test patch formed of a toner having all wavelength characteristics, so that color stability and density stability can be improved. Can be maintained.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view showing an image forming apparatus to which the image forming process control device according to the present embodiment can be applied.

FIG. 2 is a plan view showing a schematic configuration of a writing device.

FIG. 3 shows a schematic configuration of a developing device.

FIG. 4 is a graph showing toner characteristics of each color.

FIG. 5 is a cross-sectional view showing an arrangement state of an image density sensor employing a regular reflection method.

FIG. 6 is a cross-sectional view showing an arrangement state of an image density sensor employing a diffuse reflection method.

FIG. 7 is a circuit diagram showing a patch detection circuit.

FIG. 8 is a graph showing output characteristics when a light emitting device having an emission wavelength of 950 nm is used.

FIG. 9 is a graph showing output characteristics when a light emitting device having an emission wavelength of 650 nm is used.

FIG. 10 is a graph showing output characteristics when a light emitting element having a light emission wavelength of 570 nm is used.

FIG. 11 is a graph showing output characteristics when a light emitting element having an emission wavelength of 950 nm is used.

FIG. 12 is a graph showing output characteristics when a light emitting device having an emission wavelength of 650 nm is used.

FIG. 13 is a graph showing output characteristics when a light emitting element having a light emission wavelength of 570 nm is used.

FIG. 14 is a timing chart showing an operation of the image forming process control circuit according to the present embodiment.

FIG. 15 is a schematic diagram showing the concept of a regular reflection type image density sensor.

FIG. 16 is a schematic diagram illustrating the concept of an image density sensor of a diffuse reflection type.

[Explanation of symbols]

 Reference Signs List 10 image carrier 13 writing device 14 developing device 141 developing sleeve 200 image forming process control circuit 210 patch data generating circuit 230 patch detecting circuit 231 light emitting diode

Claims (2)

[Claims] 1. A test patch is formed on an image carrier by reversal development using two or more colors of toner, and a light emitting element for irradiating the test patch surface with light of a specific wavelength and receiving reflected light thereof to receive light. A light receiving element that outputs a signal corresponding to the intensity, a non-inverting amplifier that amplifies an output signal from the light receiving element to a predetermined level, and a control unit that controls an image forming process based on the output signal from the non-inverting amplifier. An image forming process control apparatus comprising: a switch for switching a voltage gain of the non-inverting amplifier according to a wavelength of the light emitting element and a transmittance of toner. 2. A light emitting element for forming a test patch on an image carrier by reversal development using toner of two or more colors, irradiating the test patch surface with light of a specific wavelength, and receiving light diffusely reflected by the light emitting element. A light-receiving element that outputs a signal according to the intensity,
A non-inverting amplifier for amplifying an output signal from the light receiving element to a predetermined level, and an image forming process control device having a control unit for controlling an image forming process based on the output signal from the non-inverting amplifier; An image forming process control device, comprising: a switch for switching a voltage gain of the non-inverting amplifier according to a wavelength and a transmittance of toner.