JP3386231B2 - Image forming device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic image forming apparatus applied to copying machines, facsimiles, printers and the like.

[0002]

2. Description of the Related Art Conventionally, the surface of a photoconductor is uniformly charged to a predetermined potential by a charging means, and the surface of the photoconductor is irradiated with a light image to form an electrostatic latent image. An image forming apparatus that forms a toner image by developing with a developing unit using a two-component developer including at least a toner and a carrier is well known. However, in a developing system using such a two-component developer, the toner density is Has a great influence on the developing characteristics, it is necessary to properly maintain the toner concentration in the developer, and various types of methods have been proposed in the past, but they can be roughly classified into the following two types. . A. A method that detects the toner concentration or its substitute characteristics and keeps the toner concentration constant. B. A method that detects the developing ability of the developer or its substitute characteristics and controls the toner concentration so that the developing ability becomes constant.

As the method A, for example, a change in the bulk density of the developer is detected (JP-A-47-5487), and a change in the bulk density of the developer is detected as permeability → reactance change. (Japanese Patent Application Laid-Open No. 47-5138) and one that detects a change in volume of the developer (Japanese Patent Application Laid-Open No. 50-
No. 19459), one that detects a volume change of the developer by a torque change (JP-A-47-6589), and one that detects a color change of the developer (JP-A-48-69527).
(Japanese Patent Laid-Open No. 1988), a device for detecting a change in electric resistance of a developer (Japanese Patent Laid-Open No. 48-38157), and a device for detecting a dielectric voltage due to a counter charge (on a carrier) of a developed toner (Japanese Patent Laid-Open No. 2004-38157). JP-A-48-57638 and JP-A-48-42739). Next, as the method of B, as shown in, for example, Japanese Patent Laid-Open No. 48-29448, a density of a toner image after a charge pattern which is independent of a photoconductor is created and developed is optically detected. There are things I tried to do.

A method of forming a predetermined latent image pattern on an image carrier, developing the latent image pattern to form a toner pattern, detecting the toner pattern by an optical sensor, and detecting the image forming condition based on the result. Also known are JP-A-54-134635 and JP-A-58-13915.
Although many techniques are disclosed, such as Japanese Patent Laid-Open No. 8 and Japanese Patent Laid-Open No. 58-190966, all of these techniques produce a sensor pattern under a constant image forming condition, and only one information can be obtained from one pattern. .

There is also known one which controls the toner density and image forming parameters other than the toner density by using an optical sensor, and is disclosed in JP-A-58-190966 and JP-A-4.
Although there is JP-A-96076, etc., each of them can obtain only one information from one pattern, so that a plurality of patterns must be created in order to control a plurality of parameters. Therefore, when multiple patterns are created between sheets during continuous copying, the copy speed decreases,
If the pattern image interval is increased, the control information becomes insufficient,
Concentration fluctuations are large (not real-time control).

[0006]

In each of the above-mentioned prior arts, since only one information is obtained from one pattern, only the number of pieces of information desired (in some cases, more than the number of pieces of information desired) can be obtained. It was necessary to image the pattern and detect this. However, when a plurality of patterns are imaged during continuous copying, the copy speed is reduced and the toner consumption is increased accordingly. Therefore, normally, when there is a time margin such as when the power is turned on, a plurality of patterns are imaged, the proper values of the charging potential, the developing bias, and the exposure amount are obtained by using them, and the proper value of the toner density is obtained during copying. Only asking is done. However, in order to stably obtain a higher-quality image, it is necessary to know the potential of the photosensitive member, the proper developing bias, and the developing ability (≈toner concentration) that change momentarily even during continuous copying.

The present invention has been made in view of the above circumstances, and a plurality of information can be obtained by one pattern,
An object of the present invention is to provide an image forming apparatus provided with a means capable of maintaining proper copy quality without reducing copy speed. Further, in addition to the above-mentioned object, an image provided with means capable of suppressing side effects such as carrier adhesion when forming a sensor pattern and easily forming a distribution (gradient) of the exposure amount of the P sensor pattern An object is to provide a forming device.

[0008]

In order to achieve the above object, the invention of claim 1 forms a predetermined latent image pattern on an image carrier and develops it with a developer containing toner to form a toner pattern. Created, this toner pattern is detected by an optical sensor, and the charger current and grid
Mode voltage, the toner supply amount, the image forming apparatus to control the image forming conditions such as developing bias, the toner pattern is made of different conditions continuously in the moving direction of the image bearing member
The optical sensor measures the reflection density of the toner pattern.
Is continuously detected, and the sensor output is a predetermined threshold value Vth1.
At time t _{1 at} which it intersects, and after t ₁ , a predetermined threshold value Vth
Detect time t ₂ −t ₁ until time t ₂ that intersects 1
Alternatively, after the time t ₂ , the sensor output has another predetermined value.
Time t ₃ −t ₂ until time t _{3 at} which the threshold value Vth2 of
Is detected, and t ₂ −t ₁ or t ₃ −t ₂ is set to a predetermined value.
It is characterized in that the image forming condition is controlled by comparison .

According to the second aspect of the invention, there is provided a specified reflection density.
A certain place with a degree (this is called P sensor patch)
Exposed and by an optical device having at least one lens
Form a P-sensor patch image on the photoconductor, and
To develop a toner pattern by developing with a developer containing
The toner pattern of the
Depending on the resultCharger current, grid voltage, toner replenishment
Quantity, development bias, etc.Image forming device for controlling image forming conditions
The P sensor patchToner patternAnti
The radiation density differs in the scanning directionAnd its toner pattern
The optical sensor continuously detects the reflection density of the screen,
Time t at which the sensor output crosses a predetermined threshold value Vth1
₁ And t ₁ After that, the time at which the predetermined threshold value Vth1 is crossed again
t _Two Time to _Two -T ₁ To detect or
Time t _Two After that, the sensor output crosses another predetermined threshold value Vth2.
Time t _Three Time to _Three -T _Two Is detected and t _Two −
t ₁ Or t _Three -T _Two By comparing
Control image forming conditionsIt is characterized by

According to a third aspect of the present invention, a P sensor patch is exposed on a predetermined location having a certain reflection density (this is called a P sensor patch), and the P sensor patch is formed on the photoconductor by an optical device having at least one lens. An image is formed, this is developed with a developer containing toner to create a toner pattern, this toner pattern is detected by an optical sensor, and the result is the charger current, grid voltage, and toner replenishment.
In an image forming apparatus for controlling image forming conditions such as amount and developing bias, the toner pattern of the P sensor patch is formed by a mixture of a high density portion and a low density portion of a minute area.
One of the distribution densities (for example, in the high density area) differs in the scanning direction, and the reflection density of the toner pattern is
The optical sensor continuously detects and the sensor output
At time t _{1 at} which the constant threshold value Vth1 is crossed, and after t ₁ , again
Time t ₂ until the time t _{2 at which the} predetermined threshold value Vth1 is crossed −
After detecting t ₁ , or after the time t ₂ , the sensor
Until time t ₃ when the output crosses another predetermined threshold Vth2
Detecting a time _{t 3 -t 2, t 2 -t} 1 or _t 3 -t
_The image forming condition is controlled by comparing ₂ with a predetermined value .

According to a fourth aspect of the present invention, a P sensor patch is exposed on a predetermined place having a predetermined reflection density (this is called a P sensor patch), and the P sensor patch is formed on the photoconductor by an optical device having at least one lens. An image is formed, this is developed with a developer containing toner to create a toner pattern, this toner pattern is detected by an optical sensor, and the result is the charger current, grid voltage, and toner replenishment.
In an image forming apparatus that controls image forming conditions such as amount and developing bias , the P sensor patch image is formed with different illuminance in the moving direction of the photoconductor , and the P sensor patch image is displayed.
The reflection density of the imaged toner pattern differs in the scanning direction.
The optical sensor measures the reflection density of the toner pattern.
The sensor output is continuously detected by the
At time t _{1 at} which th1 is crossed, and after t ₁ , a predetermined threshold value is set again.
Detecting a time _t 2 -t ₁ up to time _{t 2} which intersects with Vth1
Either, or the time t ₂ after the sensor output is different
Time t ₃ until the time t _{3 at which the} predetermined threshold value Vth2 is crossed −
detecting a t _2, a t 2 -t ₁ or _t 3 -t ₂ given
The image forming condition is controlled by comparing with the value .

According to a fifth aspect of the present invention, there is provided a digital optical system for exposing the photoconductor for each pixel, and a predetermined latent image pattern is formed on the photoconductor by the digital optical system. To develop a toner pattern, detect this toner pattern with an optical sensor, and use the result to detect the charger current, grid voltage, toner replenishment amount, and development bar.
In an image forming apparatus that controls image forming conditions such as noise , the toner pattern is formed under different conditions in the moving direction of the photoconductor, and the reflection density of the toner pattern is changed.
The optical sensor continuously detects and the sensor output
At time t _{1 at} which the constant threshold value Vth1 is crossed, and after t ₁ , again
Time t ₂ until the time t _{2 at which the} predetermined threshold value Vth1 is crossed −
After detecting t ₁ , or after the time t ₂ , the sensor
Until time t ₃ when the output crosses another predetermined threshold Vth2
Detecting a time _{t 3 -t 2, t 2 -t} 1 or _t 3 -t
_The image forming condition is controlled by comparing ₂ with a predetermined value .

[0013]

In any of the image forming apparatuses according to the first to fifth aspects, since the toner pattern (sensor pattern) is formed under continuously different conditions in the moving direction of the photoconductor as an image carrier, the toner pattern is formed. The reflectance (density) of the (sensor pattern) can be continuously changed in the moving direction of the photoconductor, and this is detected by an optical sensor, and the change in the output intensity depending on the position or time change is detected. It becomes possible to obtain a plurality of information from one sensor pattern.

Here, as means for continuously forming the toner pattern in the moving direction of the photosensitive member as the image carrier under different conditions, the potential of the latent image pattern is kept substantially constant and the developing bias at the time of development is continuous. To change the reflection density of the P sensor patch in the scanning direction to continuously change the potential of the latent image pattern formed on the photoconductor in the moving direction of the photoconductor. As in claim 3, the P sensor patch is made of a mixture of a high density portion and a low density portion, and one of them (for example, in the high density area).
5. A method of varying the distribution density in the scanning direction so as to continuously vary the potential of the latent image pattern formed on the photoconductor in the moving direction of the photoconductor, and moving the P sensor pattern image of the photoconductor as in claim 4. There is a method in which images are formed with different illuminance in different directions and the potential of the latent image pattern formed on the photoconductor is made different continuously in the moving direction of the photoconductor. When optical writing is performed by a digital optical system as in claim 5, a certain area of the photoconductor is exposed with a constant density and intensity to form a latent image pattern of a constant potential, and the latent image pattern is developed. A method of continuously changing the bias, in which when forming a latent image pattern, each pixel is exposed with different intensities in the moving direction of the image carrier to continuously change the potential of the latent image pattern in the moving direction of the photoconductor. How to make
There is a method of exposing each pixel at different densities in the moving direction of the image carrier at the time of forming the latent image pattern to continuously change the potential of the latent image pattern in the moving direction of the photoconductor.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below based on the illustrated embodiments. [Embodiment 1] FIG. 1 is a diagram showing a schematic configuration of an image forming apparatus showing an embodiment of the present invention. In the drawing, reference numeral 1 is a photoconductor as an image carrier, and 2 is a photoconductor uniformly. A charging device for charging 3 is an eraser for removing unnecessary charges outside the image forming area on the photoconductor, and 4 is a constituent member of a developing device (the entire structure is not shown) and is formed on the photoconductor. A developing sleeve carrying a developer for developing the formed electrostatic latent image, 5 is a developer containing at least toner carried on the developing sleeve (for example, a two-component developer composed of toner and carrier), and 6 is photosensitive. An optical sensor for detecting a toner pattern (sensor pattern) formed on the body (for example, a reflection type photosensor including a light emitting element and a light receiving element, and detecting the reflectance (density) of the toner pattern) ,
Reference numeral 7 is a developing bias power source for applying a developing bias voltage to the developing sleeve 4, 8 is a transfer charger for transferring the toner image formed on the photoconductor to a transfer sheet fed by a sheet feeding means (not shown), 9 is a separation charger for separating the transfer sheet after transfer from the photoconductor, 10 is a transport unit for transporting the transfer sheet after separation to a fixing device (not shown), and 11 and 12 are for transporting the toner image. A cleaning brush and a cleaning blade of a cleaning device for cleaning the photoconductor, and a quenching lamp 13 for removing charge from the photoconductor after cleaning, respectively. Although not shown, a document exposure optical system including a document exposure lamp, a mirror, an imaging lens and the like is provided as an exposure unit, and after the charge is removed by the eraser 3, the document is exposed before reaching the developing sleeve 4. The exposure optical system forms an optical image of the original on the surface of the photoconductor.

Next, an embodiment of claim 1 will be described.
In the image forming apparatus having the configuration shown in FIG. 1, in this embodiment, as one of methods for forming a predetermined toner pattern on the photoconductor 1, a certain area on the photoconductor, which is a charger, is charged to a constant potential. Areas where static electricity is eliminated by the eraser 3 except for the area (this is called a sensor latent image pattern)
Is developed with the toner of the developer 5 carried on the developing sleeve 4 while continuously changing the developing bias to form a toner pattern in which the toner adhesion amount continuously changes in the moving direction of the photoconductor. Then, the reflectance of the formed toner pattern (sensor pattern) is detected by the optical sensor 6, and the image forming condition is controlled according to the result. The term "continuously" as used herein means that the step of changing the developing bias is sufficiently small and the difference between the average values of the detection voltages of adjacent portions is smaller than the standard deviation of the detection voltages of the respective portions. To tell.

Next, FIG. 2 shows a toner pattern forming method and detection results according to this embodiment. In the present embodiment, as shown in the lower part of FIG. 2, the latent image pattern portion potential is VS,
The developing bias (developing sleeve potential) is continuously increased above a certain value VB ₁ which is smaller than the normal value of VS, and is continuously increased when the developing bias reaches a certain value VB ₂ which is larger than the normal value of VS. Stop and return to VB ₁ . At this time, the toner adhesion amount on the toner pattern portion is as shown in the middle part of FIG. 2, and the output of the optical sensor 6 is as shown in the upper part of FIG. As an example of controlling the image forming conditions of the image forming apparatus based on the detection result of FIG. 2, the process control system includes a time t _{1 at} which the sensor output becomes a certain threshold Vth ₁ or less, and a threshold V again after t _1.
to detect the time of the larger until the time t ₂ than th1, "t
₂ -t ₁ "is to reduce the charger current is larger than the predetermined value," t ₂ -t ₁ "is the case smaller than a predetermined value to increase the charger current. Incidentally, the charger grid the case of the scorotron charger having, "t ₂ -t _1" is reduced grid voltage is larger than the predetermined value, "t ₂
If −t ₁ ″ is smaller than a predetermined value, the grid voltage may be increased. If another threshold value different from the threshold value Vth1 is set to Vth2, the same time t is set in this embodiment.
_{At 1} , the detection voltage of the optical sensor becomes Vth1 and Vth2 or less. After this, time t at which the detection voltage becomes higher than Vth1 again
₂ and detects the time t ₃ when exceeds Vth2, "t ₃ -t ₂ 'is increased toner supply amount is larger than the predetermined value,"
When t ₃ −t ₂ ″ is smaller than a predetermined value, toner replenishment is suppressed. As described above, in the present embodiment, the toner whose toner adhesion amount continuously changes in the moving direction of the photoconductor 1 is used. Since a pattern is formed, a plurality of pieces of information can be obtained by detecting this with the optical sensor 6, and a plurality of image forming conditions can be controlled.

[Embodiment 2] FIG. 3 is a view showing another embodiment of claim 1, which is a view showing a toner pattern forming method and a detection result. In this embodiment, an apparatus configuration similar to that shown in FIG. 1 is used, and as a method for forming a predetermined latent image pattern on the photoconductor 1, although not shown in FIG. 1, an image of a document is formed on the photoconductor. Reflected light from a reference reflector (not shown) (outside of the document placement area (contact glass) of the document table and installed near the standby position of the document exposure lamp) by the document exposure optical system After the charge is removed by the eraser 3, an image is formed on the photoconductor 1 to form a latent image pattern. The reference reflector is made of a relatively dark white material having an optical reflectance of about 0.3, which does not change with time. As shown in the lower part of FIG. 3, the potential of the latent image pattern is lower than that of FIG. It becomes low (because the reflectance of the reference reflector is small, the potential difference between the exposed portion and the non-exposed portion of the reflected light from the reference reflector is small). Next, the latent image pattern thus formed is developed with the toner of the developer 5 carried on the developing sleeve 4 while continuously changing the developing bias (developing sleeve potential), and the latent image pattern is moved in the moving direction of the photoconductor. A toner pattern in which the amount of adhered toner changes continuously is formed. Then, the reflectance of the developed toner pattern (sensor pattern) is detected by the optical sensor 6. FIG. 3 shows the development bias with respect to the latent image pattern potential, the toner adhesion amount, and the detection result by the optical sensor 6 at this time. In this embodiment, since the latent image pattern potential is lower than that in the first embodiment, the amount of change in the developing bias is small.

[0019] Control example of image forming condition of an image forming apparatus according to the detection results of Figure 3, the process control system, the time t ₁ to equal to or less than the threshold value Vth1 which is the sensor output, t ₁ after greater than threshold again Vth1 detecting a time until t ₂ comprising, "t ₂ -t _1" is increased amount of the original exposure lamp is greater than a predetermined value, when the "t ₂ -t _1" is smaller than a predetermined value Reduces the light intensity of the original exposure lamp. Also,
If another threshold which is different from the threshold value Vth1 and a Vth2, the detection voltage of the optical sensor is less than Vth1 and Vth2 substantially the same time t ₁ in the present embodiment. Again the detection voltage after this detects the time t ₃ when exceeding the time t ₂ and Vth2 larger than Vth1, "t ₃ -t _2" increases the amount of toner supply in the case larger than the predetermined value, "t ₃ When −t ₂ ″ is smaller than a predetermined value, toner supply is suppressed. As described above, in this embodiment, since the toner pattern in which the toner adhesion amount continuously changes in the moving direction of the photoconductor 1 is formed, a plurality of information can be obtained by detecting this with the optical sensor 6. It is possible to control a plurality of image forming conditions.

[Embodiment 3] FIG. 4 is a plan view of a reference reflector (P sensor patch) showing an embodiment of claim 2, and the structure of the image forming apparatus is the same as that of FIG. In this embodiment,
A reference reflector (P sensor patch) whose reflectance changes in the scanning direction (scanning direction of the document exposure optical system) is installed (on the back side outside the document mounting area (contact glass) of the document table and on the document exposure lamp). Installed in the vicinity of the standby position), and after the reflected light from the reference reflection plate is eliminated by the eraser 3, it is formed on the photoconductor 1 by the document exposure optical system for forming the image of the document on the photoconductor. An image is formed to form a latent image pattern, and the potential of the latent image pattern formed on the photoconductor is continuously changed in the moving direction of the photoconductor. Then, this latent image pattern is developed with the toner of the developer 5 carried on the developing sleeve 4 while keeping the developing bias (developing sleeve potential) constant, so that the toner adhesion amount is continuously increased in the moving direction of the photoconductor. Form a changing toner pattern. And
The reflectance (density) of the developed toner pattern (sensor pattern) is detected by the optical sensor 6. FIG. 5 is a diagram showing a toner pattern forming method and detection results according to the present embodiment, in which the lower image shows the latent image pattern and the developing bias, the middle image shows the toner adhesion amount, and the upper image shows the detection result of the optical sensor 6. As shown in FIG. 5, in this embodiment, since the latent image pattern potential itself continuously changes in the moving direction of the photoconductor, the photoconductor moves even if the developing bias is constant (normal image forming condition). It is possible to easily form the toner pattern in which the toner adhesion amount continuously changes in the direction.

As an example of controlling the image forming condition of the image forming apparatus based on the detection result of FIG. 5, the process control system has a time t _{1 at} which the sensor output becomes a certain threshold value Vth1 or less, and after t ₁ again becomes larger than the threshold value Vth1. detecting a time until t ₂ comprising, "t ₂ -t _1" is to increase the developing bias is larger than a predetermined value, when the "t ₂ -t _1" is smaller than the predetermined value development Reduce the bias. Also, the threshold Vth1
Different if another threshold was Vth2, the detection voltage of the optical sensor is less than Vth1 and Vth2 substantially the same time t ₁ in the present embodiment. Again the detection voltage after this detects the time t ₃ when exceeding the time t ₂ and Vth2 larger than Vth1, "t ₃ -t _2" increases the amount of toner supply in the case larger than the predetermined value, "t ₃ When −t ₂ ″ is smaller than a predetermined value, toner supply is suppressed. As described above, in this embodiment, since the toner pattern in which the toner adhesion amount continuously changes in the moving direction of the photoconductor 1 can be easily formed,
By detecting this with the optical sensor 6, a plurality of pieces of information can be obtained and a plurality of image forming conditions can be controlled.

[Embodiment 4] FIG. 6 is a plan view of a reference reflection plate (P sensor patch) showing an embodiment of claim 3, and the structure of the image forming apparatus is the same as that of FIG. In the present embodiment, P in which the high density part and the low density part of the micro area are mixed in the reference reflector.
The sensor patch is printed, and the distribution density of one of them (for example, in the high-density area) is different in the scanning direction.
Further, the position of the P sensor patch is set to be displaced from the image forming position of the document exposure optical system for forming the image of the document on the photoconductor. That is, although the P sensor patch is a mixture of minute regions of high density portion and low density portion when viewed microscopically, since the position of the P sensor patch is displaced from the image forming position of the optical system, the P sensor patch Image is exposed on the photoconductor in an appropriately blurred manner, and the illuminance distribution of the P sensor patch image on the photoconductor has a smooth inclination in the moving direction of the photoconductor. Therefore, if the reflected light from the reference reflector (P sensor patch) is discharged by the eraser 3 and then imaged on the photoconductor 1 by the document exposure optical system to form a latent image pattern, it is formed on the photoconductor. The electric potential of the latent image pattern can be continuously changed in the moving direction of the photoconductor. Then, this latent image pattern is developed with the toner of the developer 5 carried on the developing sleeve 4 while keeping the developing bias (developing sleeve potential) constant, so that the toner adhesion amount is continuously increased in the moving direction of the photoconductor. A changing toner pattern can be formed. The latent image pattern potential in this case is substantially the same as that of the third embodiment shown in FIG. 5, and therefore, the toner adhesion material of the toner pattern (sensor pattern) developed with the developing bias kept constant and its reflectance are shown. The result detected by the optical sensor 6 is substantially the same as that in the third embodiment, and the control of the image forming condition of the image forming apparatus based on the detection result can be performed as in the third embodiment.

[Embodiment 5] FIG. 7 is an explanatory view of a main part of a document exposure optical system showing an embodiment of claim 4. In this example,
Attach the reference reflector (P sensor patch) 17 to the original exposure lamp 1
4, a light shield plate 15 is provided in a part of the exposure scanning range, and a part or all of the illumination light from the document exposure lamp 14 is shielded by the light shield plate 15 so that the P sensor pattern image is moved in the moving direction of the photoconductor 1. The images are formed with different illuminances, and the configuration of the image forming apparatus is the same as in FIG. That is, in this embodiment, the reference reflector (P sensor patch)
Even if the reflectance or the density of 17 is constant, as shown in FIG. 7, by providing the light shielding plate 15 in a part of the scanning range of the document exposure lamp 14 of the reference reflection plate (P sensor patch) 17, During scanning of the reflection plate 17, the illumination light from the document exposure lamp 14 is gradually shielded by the light shielding plate 15 as the document exposure lamp 14 moves.
The P sensor pattern image reflected by the reference reflection plate 17 and exposed on the photoconductor 1 via the mirror 16 and the imaging lens (not shown) is also imaged with different illuminance in the moving direction of the photoconductor 1. Will be. Therefore, if the reflected light from the reference reflector (P sensor patch) is discharged by the eraser 3 and then imaged on the photoconductor 1 by the document exposure optical system to form a latent image pattern, it is formed on the photoconductor. The electric potential of the latent image pattern can be continuously changed in the moving direction of the photoconductor. Then, this latent image pattern is developed with the toner of the developer 5 carried on the developing sleeve 4 while keeping the developing bias (developing sleeve potential) constant, so that the toner adhesion amount is continuously applied in the moving direction of the photoconductor 1. It is possible to form a toner pattern in which Incidentally, the latent image pattern potential in this case is also substantially the same as that of the third embodiment shown in FIG. 5, and therefore, the toner adhesion material of the toner pattern (sensor pattern) developed with the developing bias kept constant, and its reflectance are shown. The result detected by the optical sensor 6 is substantially the same as that in the third embodiment, and the control of the image forming condition of the image forming apparatus based on the detection result can be performed as in the third embodiment.

[Sixth Embodiment] FIG. 8 is a view showing the schematic arrangement of an image forming apparatus according to the fifth embodiment of the present invention. Reference numerals 1 to 13 in the drawing denote the same constituent members as those shown in FIG. Therefore, the description is omitted. The image forming apparatus of this embodiment has a digital optical system that exposes the photoconductor 1 for each pixel, forms a predetermined latent image pattern on the photoconductor 1 by the digital optical system, and forms the latent image pattern on the developing sleeve 4. A toner pattern is created by developing with the developer 5 containing the carried toner, and this toner pattern is detected by the optical sensor 6, and the image forming conditions such as toner density replenishment are controlled according to the result. As a digital optical system, a light beam from a laser light source (not shown) such as a semiconductor laser is deflected and scanned by a deflector 19 such as a polygon mirror, and a photoconductor is provided via an imaging optical system (not shown), a mirror 18 and the like. For example, a laser scanner that exposes light on the first surface is used.

The present invention is also characterized in that, in the digital writing type image forming apparatus, the toner patterns are formed under different conditions in the moving direction of the photoconductor. Here, as means for continuously forming the toner pattern in the moving direction of the photoconductor under different conditions, a certain area of the photoconductor is exposed with a constant density and intensity when optical writing is performed by the digital optical system. To form a latent image pattern of a constant potential, and continuously change the developing bias during development,
When forming a latent image pattern, a method in which each pixel is exposed by a digital optical system with different intensities in the moving direction of the photoconductor to continuously change the potential of the latent image pattern in the moving direction of the photoconductor, latent image pattern There is a method in which each pixel is exposed at different densities in the moving direction of the photosensitive member by a digital optical system to form the latent image pattern potential continuously different in the moving direction of the photosensitive member.

The above embodiment will be described here. First, a certain area of the photoconductor 1 is exposed with a digital optical system at a constant density and intensity to form a latent image pattern of a constant potential. Then, the latent image pattern is developed with the toner of the developer 5 carried on the developing sleeve 4 while continuously changing the developing bias, so that the toner adhesion amount continuously changes in the moving direction of the photoconductor 1. A pattern (sensor pattern) is formed. The term "continuously" as used herein means that the step of changing the developing bias is sufficiently small and the difference between the average values of the detection voltages of adjacent portions is smaller than the standard deviation of the detection voltages of the respective portions. To tell.

In the image forming apparatus shown in FIG. 8, the optical sensor 6 detects the reflectance of the toner pattern (sensor pattern) formed as described above, and the image forming condition is controlled based on the result. FIG. 9 is a diagram showing a toner pattern forming method and detection results according to the above-described embodiment. The lower image shows the latent image pattern and the developing bias, the middle image shows the toner adhesion amount, and the upper image shows the detection result of the optical sensor 6. . As an example of controlling the image forming conditions of the image forming apparatus based on the detection result of FIG. 9, the process control system is configured such that the sensor output becomes a threshold value Vth1 or less at time t ₁ and after t ₁ again the threshold value Vth.
to detect the time of the larger until the time t ₂ than th1, "t
₂ -t ₁ "is to increase the charger current and the developing bias is larger than a predetermined value," when t ₂ -t ₁ "is smaller than a predetermined value to reduce the charger current and the developing bias.
Also, if another threshold which is different from the threshold value Vth1 and a Vth2, the detection voltage of the optical sensor is less than Vth1 and Vth2 substantially the same time t ₁ in the present embodiment. Again the detection voltage after this detects the time t ₃ when exceeding the time t ₂ and Vth2 larger than Vth1, "t ₃ -t _2" increases the amount of toner supply in the case larger than the predetermined value, "t ₃ When −t ₂ ″ is smaller than a predetermined value, toner supply is suppressed. As described above, in the present embodiment, even in the case of the image forming apparatus using the digital optical system, the toner pattern in which the toner adhesion amount continuously changes in the moving direction of the photoconductor 1 can be easily formed. By detecting with the optical sensor 6, a plurality of information can be obtained and a plurality of image forming conditions can be controlled.

[0028]

As described above, in the image forming apparatus of the present invention, the toner pattern (sensor pattern) is formed continuously under different conditions in the moving direction of the photoconductor as an image carrier, so that the toner pattern is formed. Pattern (sensor pattern)
The reflectance (concentration) of the sensor can be continuously changed in the moving direction of the photoconductor, and this can be detected by an optical sensor, and the change in the output intensity depending on the position and time can be detected. Multiple pieces of information can be obtained from the pattern. As described above, in the image forming apparatus of the present invention, since a plurality of information can be obtained by one sensor pattern, it is possible to control a plurality of image forming conditions at the same time, and to obtain an appropriate copy quality without reducing the copy speed. It can be maintained.

Here, as means for forming the toner pattern continuously in different directions in the moving direction of the photoconductor as the image carrier, the potential of the latent image pattern is kept substantially constant and the developing bias at the time of development is continuously made. However, in this case, the amount of change in the developing bias is large, and carrier adhesion may occur depending on the design of the developer and the developing sleeve. Therefore, in the invention of claim 2, the optical density of the P sensor patch is changed so that the amount of light reflected from the P sensor patch is changed in the scanning direction so that the potential of the latent image pattern formed on the photoconductor is changed to that of the photoconductor. The movement direction is continuously different. In this case, since the potential distribution itself of the latent image pattern has an inclination in the moving direction of the photoconductor, the developing bias may be constant (normal image forming condition), and problems such as carrier adhesion do not occur.

The subject of claim 2 is the difficulty of forming a reference pattern (P sensor patch) having a constant density gradient. Therefore, in the third aspect of the invention, the P sensor patch is made of a mixture of a high density portion and a low density minute area, and one of the distribution density (for example, the high density area) is made different in the scanning direction. By doing so, an arbitrary density gradient can be easily created, and the average amount of reflected light can be changed in the scanning direction. Therefore, a desired illuminance distribution can be easily formed on the photoconductor, and the potential of the latent image pattern formed on the photoconductor can be continuously made different in the moving direction of the photoconductor. Also,
According to the invention of claim 4, by forming the P sensor pattern image in the moving direction of the photoconductor with different illuminance, a latent image pattern having an inclination in the moving direction of the photoconductor is formed with a simple configuration. be able to.

According to the fifth aspect of the present invention, even in the case of an image forming apparatus which performs optical writing with a digital optical system, the toner pattern (sensor pattern) is continuously different in the moving direction of the photoconductor as an image carrier. The reflectance (density) of the toner pattern (sensor pattern) can be continuously changed in the moving direction of the photoconductor, and this is detected by the optical sensor to change the output intensity depending on the position. Since a plurality of pieces of information can be obtained from one sensor pattern by detecting a change with time or the like, it is possible to maintain an appropriate copy quality without reducing the copy speed.

In an image forming apparatus using a digital optical system, a means for forming a toner pattern continuously under different conditions in the moving direction of a photoconductor as an image carrier is as follows.
There is a method in which a certain area of the photoconductor is exposed at a constant density and intensity to form a latent image pattern having a constant potential, and the developing bias at the time of development is continuously changed to change the toner adhesion amount. Also, when the development bias is kept constant, each pixel is exposed with different intensities in the moving direction of the photoconductor when the latent image pattern is formed (the average exposure amount is changed in the scanning direction), and the desired illuminance is obtained. A method of creating a distribution and continuously changing the potential of the latent image pattern in the moving direction of the photoconductor, or exposing each pixel in the moving direction of the photoconductor at different densities when forming the latent image pattern (average There is a method of creating a smooth illuminance distribution and continuously changing the potential of the latent image pattern in the moving direction of the photoconductor. In this case, the potential distribution of the latent image pattern itself is exposed. Since the body has an inclination in the moving direction, the developing bias may be constant (normal image forming condition), and the toner pattern can be easily formed.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an image forming apparatus showing an embodiment of the present invention.

FIG. 2 is a diagram showing an embodiment of claim 1, and is an explanatory diagram of a toner pattern forming method and a detection result by an optical sensor.

FIG. 3 is a diagram showing another embodiment of claim 1, and is an explanatory diagram of a toner pattern forming method and a detection result by an optical sensor.

FIG. 4 is a plan view of a reference reflector (P sensor patch) showing an embodiment of claim 2;

FIG. 5 is a diagram showing an embodiment of claim 2 and is an explanatory diagram of a toner pattern forming method and a detection result by an optical sensor.

FIG. 6 is a plan view of a reference reflection plate (P sensor patch) showing an embodiment of claim 3;

FIG. 7 is an explanatory view of a main part of a document exposure optical system showing an embodiment of claim 4;

FIG. 8 is a schematic configuration diagram of an image forming apparatus showing an embodiment of claim 5.

FIG. 9 is a diagram showing an embodiment of claim 5, and is an explanatory diagram of a toner pattern forming method and a detection result by an optical sensor.

[Explanation of symbols]

1: Image carrier (photoreceptor) 2: Charger 3: Eraser 4: Development sleeve 5: developer 6: Optical sensor 7: Development bias power supply 8: Transfer charger 9: Separation charger 10: Transport unit 11: Cleaning brush 12: Cleaning blade 13: Quenching lamp 14: Original exposure lamp 15: Shading plate 16: Mirror 17: Reference reflector (P sensor patch) 18: Mirror 19: Deflector (polygon mirror, etc.)

Continuation of the front page (56) References JP-A-5-232769 (JP, A) JP-A-58-154862 (JP, A) JP-A-60-73654 (JP, A) JP-A-59-174862 (JP , A) JP-A-6-51604 (JP, A) JP-A-4-86762 (JP, A) JP-A-5-113723 (JP, A) JP-A-5-257353 (JP, A) 60-78049 (JP, U) (58) Fields surveyed (Int.Cl. ⁷ , DB name) G03G 15/00 G03G 15/08 G03G 21/00

Claims (5)

(57) [Claims] 1. A predetermined latent image pattern is formed on an image carrier,
This is developed with a developer containing toner to create a toner pattern, and this toner pattern is detected by an optical sensor, and the result of the detection results in the charger current, grid voltage,
Toner supply amount, the image forming apparatus to control the image forming conditions such as developing bias, are made under the condition where the toner pattern is different continuously in the moving direction of the image carrier, the
The reflection density of the toner pattern is continuously measured by an optical sensor.
And the sensor output crosses a predetermined threshold value Vth1.
At time t ₁ and after t ₁ , the predetermined threshold value Vth1 is crossed again.
Or to detect the time _t 2 -t ₁ up to time _{t 2} that, there have
After the time t ₂ , the sensor output is another predetermined threshold Vth.
Detecting a time _t 3 -t ₂ until time _{t 3} when crossing the 2,
Comparison child to t ₂ -t ₁ or _t 3 -t ₂ and the predetermined value
An image forming apparatus characterized in that an image forming condition is controlled by and. 2. A predetermined place having a certain reflection density (this is called a P sensor patch) is exposed, and a P sensor patch image is formed on a photoconductor by an optical device having at least one lens. This is developed with a developer containing toner to create a toner pattern, this toner pattern is detected by an optical sensor, and the result is used as a charger.
Current, grid voltage, toner supply amount, development bias, etc.
In the image forming apparatus for controlling the image forming conditions of the above , the reflection density of the toner pattern of the P sensor patch is different in the scanning direction, and the reflection density of the toner pattern is optically determined.
It is continuously detected by the sensor and the sensor output
At time t _{1 at} which the threshold value Vth1 is crossed, and after t ₁ , a predetermined value is set again.
Time t ₂ −t ₁ until time t _{2 at} which the threshold value Vth1 of
Or the sensor output after the time t ₂
Until time t ₃ when V crosses another predetermined threshold Vth2
detecting a t ₃ -t _2, the t 2 -t ₁ or _t 3 -t ₂
An image forming apparatus characterized by controlling an image forming condition by comparing with a predetermined value . 3. A predetermined place having a certain reflection density (this is called a P sensor patch) is exposed, and a P sensor patch image is formed on a photoconductor by an optical device having at least one lens. This is developed with a developer containing toner to create a toner pattern, this toner pattern is detected by an optical sensor, and the result is used as a charger.
Current, grid voltage, toner supply amount, development bias, etc.
In the image forming apparatus for controlling the image forming condition, the toner pattern of the P sensor patch is formed by a mixture of minute areas of high density area and low density area, and one of them (for example, high density area) has a distribution density. Is different in the scan direction ,
The reflection density of the toner pattern is linked by an optical sensor.
Continuously detect and the sensor output crosses a predetermined threshold Vth1
At time t ₁ and after t ₁ again crosses the predetermined threshold value Vth ₁ .
Or to detect the time _t 2 -t ₁ up to time _{t 2} to be the difference, Oh
Or, after the time t ₂ , the sensor output is another predetermined threshold value.
Time up to the time _{t 3} that intersects with the Vth2 _t 3 -t ₂ detection
Then, t ₂ −t ₁ or t ₃ −t ₂ is compared with a predetermined value.
An image forming apparatus characterized in that the image forming condition is controlled by the above. 4. A predetermined place having a certain reflection density (this is called a P sensor patch) is exposed, and a P sensor patch image is formed on a photoconductor by an optical device having at least one lens. This is developed with a developer containing toner to create a toner pattern, this toner pattern is detected by an optical sensor, and the result is used as a charger.
Current, grid voltage, toner supply amount, development bias, etc.
In the image forming apparatus for controlling the image forming conditions, the P sensor patch image is formed with different illuminance in the moving direction of the photoconductor , and the P sensor patch image is developed into a toner pattern.
The reflection density of the
The reflection density of the pattern is continuously detected by the optical sensor
Then, the time t at which the sensor output crosses the predetermined threshold value Vth1
₁ and a time after t _{1 at} which the predetermined threshold value Vth1 is crossed again.
or detecting the time _t 2 -t ₁ to t _2, or the
Time t ₂ after the sensor output is different predetermined threshold Vth2 and exchange
Detecting a time _t 3 -t ₂ until time _{t 3} when differentially, _{t 2} -
By comparing t ₁ or t ₃ −t ₂ with a predetermined value
An image forming apparatus characterized by controlling image forming conditions . 5. A toner having a digital optical system for exposing a photoconductor for each pixel, forming a predetermined latent image pattern on the photoconductor by the digital optical system, and developing the latent image pattern with a developer containing toner. A pattern is created, this toner pattern is detected by an optical sensor, and the charger current,
In an image forming apparatus that controls image forming conditions such as a lid voltage, a toner replenishment amount, and a developing bias , the toner pattern is formed under different conditions in the moving direction of the photoconductor ,
The reflection density of the toner pattern is linked by an optical sensor.
Continuously detect and the sensor output crosses a predetermined threshold Vth1
At time t ₁ and after t ₁ again crosses the predetermined threshold value Vth ₁ .
Or to detect the time _t 2 -t ₁ up to time _{t 2} to be the difference, Oh
Or, after the time t ₂ , the sensor output is another predetermined threshold value.
Time up to the time _{t 3} that intersects with the Vth2 _t 3 -t ₂ detection
Then, t ₂ −t ₁ or t ₃ −t ₂ is compared with a predetermined value.
An image forming apparatus characterized in that the image forming condition is controlled by the above.