JP7025909B2 - Image forming device - Google Patents

Description

The present invention relates to an image forming apparatus that forms an image using an electrophotographic method.

Conventionally, electrophotographic image forming devices are widely used as, for example, copiers, printers, facsimile machines, etc. because high-quality images can be formed with simple operations in a short time and maintenance management is easy. is doing.

The electrophotographic image forming apparatus includes, for example, a photoconductor, a charging device, an exposure device, a developing device, a transfer device, and a fixing device. The charging device receives a voltage to charge the surface of the photoconductor to a predetermined potential. The exposure apparatus irradiates the surface of the photoconductor in a charged state with signal light corresponding to the image information to form an electrostatic latent image. The developing device supplies toner to the electrostatic latent image on the surface of the photoconductor to develop the toner image. The transfer device transfers the toner image on the surface of the photoconductor to a recording medium. The fixing device, for example, fixes a toner image on a recording medium. As a result, an image is formed on the recording medium.

Here, the developing means includes a developing roller that supplies toner to the electrostatic latent image on the surface of the photoconductor to form a toner image, and a two-component developer containing toner is stored in the developing roller and the two components are stored in the developing roller. A developing device including a developing tank for supplying a developing agent and a toner concentration sensor for detecting the toner concentration in the developing tank is used.

The replenishment of toner into the developing tank is controlled according to the detection result of the toner concentration sensor.
The toner concentration sensor usually outputs the detection result as a voltage. In determining whether or not the toner concentration is appropriate, the differential transformer type toner concentration sensor used as the conventional toner concentration sensor uses an abnormal range at the time of registering the toner concentration reference value, which is a fixed value.

Here, the differential transformer type toner concentration sensor will be described.
In the conventional differential transformer type toner concentration sensor, the sensor output value when the standard developing tank is put into the developing tank to be used in advance and the predetermined stirring operation is performed is 1.65V, which is a center value of 0 to 3.3V, for example. Rough adjustment of the coil is performed so that there is no variation in each sensor.

In the developer concentration adjustment (automatic debate adjustment) performed when the image forming apparatus is installed or when the developer is replaced, the image is formed using the toner concentration sensor output value when the standard developer is stirred for a predetermined time as the toner concentration reference value. This is an operation of storing (registering) in the main body of the device.

If the toner concentration of the developer becomes an output value in an abnormal under-toner state or an output value in an abnormal over-toner state when the developer concentration is adjusted, a trouble is detected as an error in registering the toner concentration reference value. Since the conventional sensor roughly adjusts the overtoner state and the undertoner state with a standard developer, a predetermined fixed value is used for the threshold value (abnormal range).

Since the conventional differential transformer type toner concentration sensor has a small variation in the output value for each product, the abnormal range at the time of registering the toner concentration reference value can be dealt with by a predetermined fixed value, but the non-contact type toner concentration sensor Since the output value varies greatly from product to product, it was necessary to change the threshold value at the time of registration of the standard developer standard value for each product in order to maintain the image quality.

As a means for setting the data necessary for adjusting the developer concentration corresponding to each toner concentration sensor, as a conventional technique, for example, in a toner concentration sensor that detects a toner concentration from a change in magnetic permeability, the toner concentration sensor is unique to the sensor. A storage means for storing data in a rewritable manner has been proposed (see Reference 1).

With this configuration, the control value unique to the sensor can be writably held in the toner concentration detection sensor that detects the toner concentration of the developer, so that various data unique to the sensor can be obtained for each toner concentration detection sensor. Based on this, the developer density can be adjusted to maintain the image quality.

Japanese Unexamined Patent Publication No. 2006-293282

However, in the conventional technique proposed in Patent Document 1, the developer concentration can be adjusted for each toner concentration sensor based on the sensor-specific information, but the output value varies greatly for each toner concentration sensor. The countermeasures for the standard value of the standard developer have not been solved.

An object of the present invention is to provide an image forming apparatus capable of improving the accuracy of a toner density detection result, supplying an appropriate toner, and improving the image quality of an image formed by realizing an image density. ..

The present invention comprises a developing device that supplies toner to a photoconductor that forms an electrostatic latent image to form a toner image, and develops the developing device in an image forming device that forms an image using an electrophotographic method. A non-contact type toner concentration detecting means provided on the outer wall of the developing tank for detecting the toner concentration in the tank, and a toner concentration reference value are set based on the detection results of the toner concentration detecting means, and the inside of the developing tank is set. It is provided with a control means for controlling the toner concentration of the above, and as a configuration of the toner concentration detecting means, a storage means (IC memory) for storing the detection result of the toner concentration detecting means is provided. In addition to detecting the empty state inside, the toner concentration in the developing tank in which the developer is present is detected, the detection result of the toner concentration detecting means is output as a frequency, and the storage means is used for other correction elements in advance. The correction value of the control value for determining whether or not to register the toner concentration reference value set corresponding to each is stored, and the detection result of the toner concentration detecting means is stored as a frequency output value by the control means. Using the frequency output value stored in the storage means when the developer is not added, the registered value abnormality range for determining whether or not to register the toner concentration reference value is variable. be.

According to the image forming apparatus of the present invention, an image forming apparatus comprising a developing apparatus for supplying toner to a photoconductor forming an electrostatic latent image to form a toner image and forming an image by using an electrophotographic method. , A non-contact type toner concentration detecting means provided on the outer wall of the developing tank for detecting the toner concentration in the developing tank of the developing device, and a toner concentration reference value are set based on the detection results of the toner concentration detecting means. A control means for controlling the toner concentration in the developing tank is provided, and as a configuration of the toner concentration detecting means, a storage means (IC memory) for storing the detection result of the toner concentration detecting means is provided, and a developer is provided. The empty state in the developing tank when not charged is detected, the toner concentration in the developing tank in which the developer is present is detected, the detection result of the toner concentration detecting means is output as a frequency, and the storage means is used. The correction value of the control value for determining whether or not to register the toner concentration reference value set in advance corresponding to each of the other correction elements is stored, and the detection result of the toner concentration detecting means is stored as a frequency output value. Then, the control means can change the registered value abnormality range for determining whether or not to register the toner concentration reference value by using the frequency output value stored in the storage means when the developer is not charged. Then, the frequency output value from the toner concentration detecting means when the developer is not added, that is, the value called the aerial frequency is stored in advance, the variation of each sensor product is grasped, and the specified stirring is performed when the standard developer is added. It is possible to accurately set the abnormal range when registering the toner concentration reference value after operation.

It is a block diagram which shows the structure of the image forming apparatus which concerns on 1st Embodiment. It is sectional drawing which shows the structure of the developing apparatus which constitutes the image forming apparatus. It is a flowchart of the automatic developer density adjustment mode in the image forming apparatus. It is a graph which showed the relationship of the frequency output value with respect to the toner density detected by the toner density sensor of the automatic developer density adjustment mode in the image forming apparatus. It is a graph which showed that the relationship of the frequency output value with respect to the toner density detected by the toner density sensor of the automatic developer density adjustment mode in the image forming apparatus varies from product to toner density sensor. It is a block diagram which shows the structure of the image forming apparatus which concerns on 2nd Embodiment. 6. It is a flowchart which shows the automatic developer density adjustment mode in the image forming apparatus. It is a graph which shows the environment correction value with respect to the environment area value given from the temperature and humidity in the image forming apparatus. It is a graph which shows the change by the influence of temperature and humidity of the output frequency value with respect to the toner density | concentration from the toner density sensor used in the image forming apparatus. It is a flowchart at the time of operation of toner reference value registration in the image forming apparatus which concerns on 3rd Embodiment. It is a graph which shows the change by the influence of the printing speed of the output frequency value with respect to the toner density from the toner density sensor used in the image forming apparatus for each model.

(First Embodiment)
Hereinafter, the first embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram showing the configuration of the image forming apparatus according to the first embodiment, and FIG. 2 is a cross-sectional view showing the configuration of the developing apparatus constituting the image forming apparatus.

As shown in FIG. 2, the image forming apparatus 1 according to the first embodiment includes a developing apparatus 5 that supplies toner to a photoconductor drum (photoreceptor) 2 that forms an electrostatic latent image to form a toner image. Further, in an image forming apparatus that forms an image using an electrophotographic method, a toner density sensor (toner density detecting means) 140 that detects the toner concentration in the developing tank of the developing apparatus 5 is provided, and the toner density sensor 140 is detected. A toner concentration reference value is set based on the result to provide a good quality image.

As an electrical configuration, the image forming apparatus 1 is characteristic in addition to a control unit (control means) 100, a storage means 110, an operation display unit 120, and various image forming mechanisms 130, as shown in FIG. It is configured to include a toner concentration sensor 140.

The control unit 100 controls the operation display unit 120 and various image forming mechanisms 130 based on a predetermined program stored in the storage means 110 and data stored in the storage means 110 by executing the program. In addition, the automatic developer concentration adjustment mode is also controlled based on the detection result of the toner concentration by the toner concentration sensor 140.

The toner concentration sensor 140 is a non-contact type toner concentration sensor, and includes a toner concentration detection unit 142 for detecting the toner concentration and an IC memory (storage means) 144 for storing the detection result of the toner concentration detection unit 142. ..

The toner concentration detection unit 142 detects the empty state in the developing tank when the developer is not charged, detects the toner concentration in the developing tank in which the developing agent is present, and determines the detection result of the toner concentration detecting means as a frequency. Is output as.

The IC memory 144 stores the correction value of the control value for determining whether or not to register the toner density reference value set in advance corresponding to each of the other correction elements, and also stores the detection result of the toner concentration detecting means. Store as a frequency output value.

As an operation in the automatic developer concentration adjustment mode, the reference value of the toner concentration detected by the toner concentration detection unit 142 is registered in the IC memory 144 independently provided by the toner concentration sensor 140. The control unit 100 determines whether or not the data is suitable for registration, and if appropriate, controls the data up to the registration in the IC memory 144.

Further, the control unit 100 uses the frequency output value stored in the IC memory 144 when the developer is not applied to change the registered value abnormality range for determining whether or not to register the toner concentration reference value. It is a feature.

(Overall configuration of image forming device)
First, a schematic configuration of the image forming apparatus 1 according to the present embodiment will be described.
As shown in FIG. 2, the image forming apparatus 1 in the present embodiment includes a photoconductor drum 2 on which an electrostatic latent image is formed on the surface and a charger 3 which is a charging device for charging the surface of the photoconductor drum 2. An exposure unit (not shown), which is an exposure device that forms an electrostatic latent image on the surface of the photoconductor drum 2, and a two-component developer containing toner in the electrostatic latent image on the surface of the photoconductor drum 2. It is a device including a developing device 5 that supplies and forms a toner image, and a developing agent replenishing device 6 that supplies the developing agent to the developing device 5, and forms an image using the developing agent by an electrophotographic method. , An image is formed on a predetermined sheet (recording paper, recording medium, etc.) which is a recording medium according to the image data output from the outside.

A non-contact toner concentration sensor 30 is provided at the bottom of the developing device 5.

The photoconductor drum 2 is formed in a cylindrical shape. The charger 3 functions to uniformly charge the surface of the photoconductor drum 2 to a predetermined potential. As the charger 3, in addition to the contact roller type shown in FIG. 2, a contact brush type, a non-contact charger type, or the like is appropriately used.

As the exposure unit (not shown), a laser scanning unit (LSU) including a laser irradiation unit and a reflection mirror is used. However, in addition to the laser scanning unit, an EL (electroluminescence) in which light emitting elements are arranged in an array or an LED writing head can be used as an exposure unit. Such an exposure unit functions to form an electrostatic latent image according to the image data on the surface of the photoconductor drum 2 by exposing the charged photoconductor drum 2 according to the input image data. ..

The developing device 5 functions to visualize (develop) the electrostatic latent image formed on the photoconductor drum 2 with the toner of the developing agent. A developer replenishing device 6 is arranged adjacent to the developing device 5.
The developer replenishing device 6 is configured to store an unused developer (powdered developer) and replenish toner from above the developing tank 8. The developer supply device 6 supplies the developer to the developer tank 8 via the developer transfer mechanism 7.

As described above, the electrostatic latent image on the photoconductor drum 2 is visualized by the developer to become a toner image, and the toner image is transferred to the conveyed sheet and transferred onto the sheet by the transfer roller 4. Toner. Then, the toner image is heat-fixed on the sheet by a fixing unit composed of a heat roller and a pressure roller (not shown).

Then, the sheet on which the toner image is fixed is conveyed by a transfer roller (not shown) and discharged onto the paper output tray.

(Automatic development density adjustment mode)
Next, in the image forming apparatus 1 of the first embodiment, the step of executing the automatic developer concentration adjusting mode will be described with reference to the flowchart.
FIG. 3 is a flowchart of the automatic developer density adjustment mode in the image forming apparatus of the first embodiment.

When the automatic developer concentration adjustment mode is started in the image forming apparatus 1, the stirring operation of the developer is started as shown in FIG. 3 (step S102). Then, the toner concentration sensor 140 detects the toner concentration according to the defined procedure, and outputs the detection result as a frequency output value (step S104).

Then, the processes of steps S104 to S106 are repeated until it is determined that the stirring screw in the developing tank has made one rotation (step S106). Then, a frequency average value that is a value of the toner concentration detected by the toner concentration sensor 140 is calculated (step S108).

Then, until it is determined that the predetermined stirring time in the automatic developer concentration adjustment has elapsed (step S110), the frequency measurement (step S104), which is the value of the toner concentration by the toner concentration sensor 140, is performed, and the stirring screw is rotated once. The calculation of the frequency average value (step S108), which is the value of the toner concentration between the two, is repeated.

Then, after the lapse of the predetermined stirring time, the toner stirring operation in the developing tank is stopped (step S112), and the toner is not present in the developing tank which has been measured in advance by the toner concentration sensor 140 and stored in the IC memory 144. The aerial frequency of the state is read out (step S114), and the difference value from the frequency average value when the toner is present in the developing tank is calculated (step S116). Then, it is determined whether or not the difference value is smaller than the undertoner threshold value (step S118).

If it is determined in step S118 that the difference value is smaller than the undertoner threshold value, it is determined whether or not the difference value is larger than the overtoner threshold value (step S120).

If it is determined in step S120 that it is larger than the overtoner threshold value, the frequency average value is registered as the toner concentration reference value (step S122).

On the other hand, if it is determined in step S118 that the difference value is not smaller than the undertoner threshold value, it is treated as an undertoner trouble (step S124), and the automatic developer concentration is not registered as the frequency average value as the density reference value. Exit the adjustment mode.

Further, in step S120, if it is determined that the difference value is not larger than the overtoner threshold value, it is processed as an overtoner trouble (step S126), and in this case as well, the frequency average value is not registered as the density reference value and is automatically processed. Exit the developer concentration adjustment mode.

Here, the relationship between the frequency output value detected by the toner concentration sensor 140 and the toner density is shown in the bluff.
FIG. 4 is a graph showing the relationship between the frequency output value and the toner concentration detected by the toner concentration sensor in the automatic developer concentration adjustment mode in the image forming apparatus of the first embodiment.

As shown in FIG. 4, the vertical axis of the graph is the average frequency output value (kHz) and the horizontal axis is the toner concentration (%), which are measured in advance by the toner concentration sensor 140 when the toner is not charged into the developing tank. The frequency output value is shown as air frequency: f _B.

In the toner concentration, the range of the toner concentration is classified as the under toner boundary value B _{1 and the} over toner boundary value B ₂ . Then, the region where the toner concentration is smaller than the under toner boundary value B ₁ is defined as the under toner region R ₁ , and the region R ₂ where the toner concentration is appropriate between the under toner boundary value B ₁ and the over toner boundary value B ₂ is the over toner. The region larger than the boundary value B ₂ is the overtoner region R ₃ .

The difference between the aerial frequency and the frequency output value at the concentration of the overtoner boundary value B2 is shown by the _two -dot chain line double-headed arrow in FIG. 4, which is the _overtoner threshold value TO.
Further, it is the difference between the air frequency and the frequency output value at the concentration of the undertoner boundary value B1, and the _one -dot chain line double-headed arrow indicates the _undertoner threshold value TU.

On the other hand, for example, when the toner concentration is measured on the overtoner side, the difference value _DO obtained by subtracting the frequency from the aerial frequency is indicated by a long dashed double arrow in FIG.
If it is determined in step S118 in FIG. 3 that the difference value DO is smaller than the _undertoner threshold value _TU , that is, the long dashed double arrow is shorter than the one-dot chain line double arrow, the process proceeds to step S120.

However, if it is determined in step S120 that it is smaller than the _overtoner threshold TO, that is, the long dashed double arrow is shorter than the two-dot chain line double arrow, it is determined that the frequency measurement is performed under the overtoner condition. It is treated as an overtoner trouble in step S126.

In this case, the frequency output value is inappropriate as the toner concentration reference value, and the frequency average value in step S122 is not registered as the toner concentration reference value, and the automatic developer concentration adjustment mode causes an overtoner trouble. finish.

FIG. 5 is a graph showing that the relationship between the frequency output value and the toner concentration detected by the toner concentration sensor in the automatic developer concentration adjustment mode in the image forming apparatus of the first embodiment varies depending on the product of the toner concentration sensor. Is.

As shown in FIG. 5, there is a range of frequency output values from the upper limit product plotted by the diamond to the lower limit product plotted by the triangle with respect to the standard product plotted by the square.
This width has the width indicated by the dotted double-headed arrow in FIG. 5, but is clearly larger than the width of the solid double-headed arrow, which is the frequency range corresponding to the appropriate range _R2 of the toner concentration. Therefore, it is necessary to make corrections in consideration of variations in the toner concentration sensor for each product.

According to the first embodiment, the image forming apparatus includes a toner concentration sensor 140 and a control unit 100 for controlling the toner concentration in the developing tank, and the toner concentration sensor 140 is configured. As a storage means, the IC memory 144 is provided, and the empty state in the developing tank when the developer is not charged is detected, and the toner concentration in the developing tank in which the developer is present is detected to detect the toner concentration sensor 140. The detection result is output as a frequency output value, and the correction value of the control value for determining whether or not to register the toner concentration reference value set in advance corresponding to each of the other correction elements is stored in the IC memory 144. At the same time, the detection result of the toner concentration sensor 140 is stored as a frequency output value, and the control unit 100 registers the toner concentration reference value using the frequency output value stored in the IC memory 144 when the developer is not charged. By varying the registered value abnormality range to determine whether or not it is, the variation in each sensor product can be grasped, and the abnormality range at the time of adding the standard developer and registering the toner concentration reference value after the specified stirring operation can be accurately determined. Can be set.

(Second Embodiment)
Next, the second embodiment will be described with reference to the drawings.
For convenience of explanation, the same number is given to the configuration having the same function as that of the first embodiment, and the description thereof will be omitted.

6 is a block diagram showing the configuration of the image forming apparatus according to the second embodiment, FIG. 7 is a flowchart showing the automatic developer concentration adjusting mode in the image forming apparatus, and FIG. 8 is given from the temperature and humidity in the image forming apparatus. FIG. 9 is a graph showing an environmental correction value with respect to the environmental area value, and FIG. 9 is a graph showing a change in the output frequency value with respect to the toner concentration from the toner concentration sensor used in the image forming apparatus due to the influence of temperature and humidity.

The image forming apparatus according to the second embodiment is characterized in that the registration abnormality range in the automatic development density adjustment mode is changed according to the temperature and humidity.

As shown in FIG. 6, the image forming apparatus 201 according to the second embodiment is characterized by an electrical configuration in addition to a control unit 100, a storage means 110, an operation display unit 120, and various image forming mechanisms 130. The toner concentration sensor 140 is provided, and the temperature / humidity sensor 240 is further provided.

In the second embodiment, the environment area in the automatic development density adjustment mode is calculated based on the temperature and humidity detected by the temperature / humidity sensor 240, and the environment correction value is obtained from this environment area.

(Automatic development density adjustment mode)
Next, in the second embodiment, the step of executing the automatic development density adjustment mode according to the temperature and humidity will be described.

In the second embodiment, as shown in FIG. 7, the steps from steps S102 to S126, which are common to the first embodiment, have the same numbering. The difference from the first embodiment is that the step S202, which applies the correction value based on the environmental area determined by the temperature / humidity sensor in the step before the step S114, is provided.

When the toner, which is an insulator, is agitated, the toner particles are charged by rubbing against each other. However, the lower the temperature and the lower the humidity, the easier the charge, and conversely, the higher the temperature and the humidity, the less the charge.
Since the degree of charge changes depending on the temperature and humidity conditions, the apparent toner concentration changes even if the same toner concentration sensor is used, and the frequency output value changes with the change.

Therefore, in step S202, by applying the correction value to the overtoner threshold value TO or the _undertoner threshold value _TU , it is possible to accurately determine whether or not the toner concentration is appropriate.

The parameter for assigning the numerical value to be corrected for each temperature / humidity band is the parameter defined as the environment area used in the second embodiment.

In the second embodiment, as shown in Table 1, the humidity is 0 (%) to 100 (%) every 10 (%) and the temperature is 0 (° C) every 10 (° C) depending on the temperature and humidity bands. From 40 (° C.), a numerical value from 1 to 8 is practically assigned.

On the other hand, as shown in Table 2, corresponding to the environment area, the threshold value of the environment area is assigned a numerical value from 1 to 8, and the correction value for each numerical value is -7, -4, -2, 0, 1, 3. , 5, 8

FIG. 8 is a bluff plotting threshold correction values for the environment area based on Table 2. As shown in the graphs of Table 2 and FIG. 8, when the environment area value is 4, it can be seen that the threshold correction value is 0.

The region where the environmental area value is 4 is allocated so as to be centered at 20 to 30 ° C., which is near room temperature, and around 50%, which is neither extremely dry nor wet. Centering on the environment area value 4, the threshold value is sequentially corrected to the positive side up to the environment area value 8, or the threshold value is sequentially corrected to the negative side up to the environment area value 1.

FIG. 9 is a graph showing how the relationship between the output frequency and the toner concentration changes when the environmental area values 1, 4, and 7 are used.

As shown in FIG. 9, when the environment area value is 4, it is plotted as a square, but even if the correction value for the threshold value, that is, 0 is applied in step S202 in the flowchart of FIG. 7, the IC memory 144 is applied in step S114. The difference between the aerial frequency output value read from the above and the frequency at the _overtoner boundary value B2, the overtoner threshold value TO, and the _undertoner threshold value TU, which is the difference between the frequency at the _undertoner boundary value _B1 . There is no.

Since the lines plotted by the triangle corresponding to the environment area value 8 are shifted toward the smaller frequency, the difference from the aerial frequency read from the storage means becomes large.

For example, when making a judgment by comparing the overtoner threshold value and the difference, the difference value may exceed the overtoner threshold value even in a region where the toner concentration is actually too large, and it may be determined that the toner concentration is appropriate. On the contrary, even if the toner concentration is appropriate, it may be judged as under toner. Therefore, by correcting the threshold value correction value to the positive side in step 202, an error in determination can be avoided.

Similarly, the lines plotted in a diamond shape corresponding to the environmental area value 1 are shifted toward the larger frequency, so that even if the toner concentration is appropriate, it is determined to be overtoner or undertoner. Although it may be determined that the toner concentration is appropriate, the determination error can be avoided by correcting the threshold value correction value to the negative side in step S202 in the flowchart of FIG. 7.

In the second embodiment, the temperature and humidity around the developing device are detected by the temperature / humidity sensor 240.
The temperature / humidity sensor 240 is electrically connected to the control unit 100, and the detection result is input to the control unit 100. Then, in the control unit 100, the environmental area value is corrected according to the temperature and humidity around the developing device.

As the temperature / humidity sensor 240, a general sensor can be used. For example, a button-type temperature / humidity recorder (trade name: Hygrocron, manufactured by KN Laboratories, a limited partnership company) may be used.

According to the second embodiment, the temperature / humidity sensor 240 is provided in the configuration of the image forming apparatus 201, and the trouble is detected by adding the environmental correction value to the overtoner threshold value and the undertoner threshold value. By making the determination, it is possible to improve the accuracy of the toner concentration by considering the frequency output change due to the environmental difference factor in the automatic developer concentration adjustment mode.

(Third Embodiment)
Next, the third embodiment will be described with reference to the drawings.
For convenience of explanation, the same number is given to the configuration having the same function as that of the first embodiment, and the description thereof will be omitted.

FIG. 10 is a flowchart during the operation of toner reference value registration in the image forming apparatus according to the third embodiment, and FIG. 11 is a model having a different printing speed of an output frequency value with respect to the toner density from the toner density sensor used in the image forming apparatus. It is a graph which shows the change by each influence.

The third embodiment is characterized in that the registration abnormality range in the automatic development density adjustment mode is controlled so as to be variable for each image forming apparatus model having a different printing speed.

(Automatic development density adjustment mode)
Hereinafter, in the third embodiment, a step in which the automatic development density adjustment mode is executed according to the printing speed (process speed) will be described.

In the third embodiment, as shown in FIG. 10, the steps from steps S102 to S126, which are common to the first embodiment, have the same numbering. It is different from the first embodiment that the step S302 for applying the correction value based on the process speed is provided in the step before the step S114.

The process speed in the image forming apparatus is the printing speed depending on the model.
As the process speed increases, the speed at which the toner is agitated in the developing tank also increases, so that friction between the toner particles occurs more frequently and violently. As a result, the toner particles are more likely to be charged.

Therefore, as in the case of the influence of air temperature and humidity, the output frequency value changes even if the toner concentration is the same. Therefore, by correcting the _undertoner threshold value _TU and the overtoner threshold value TO corresponding to the difference in the process speed, the accuracy of the determination is improved.

FIG. 11 is a graph showing the difference in the output frequency value with respect to the toner concentration caused by the difference in the process speed for each image forming apparatus.

As shown in FIG. 11, from the standard process speed model A (180 mm / s) plotted with diamonds to the model B (230 mm / s) plotted with squares and the model C (260 mm / s) plotted with triangles. It shows that as the process speed increases, the output frequency shifts to the larger one.

According to this, at the time of image formation, it may be determined that the toner density is appropriate even if the toner density is appropriate, or it may be determined that the toner density is appropriate even though it is under toner. By correcting the threshold value correction value to the negative side in step S302, it is possible to avoid a determination error.

Further, when the developing apparatus uses a two-component developer of color toner, the effect is more remarkable by making corrections. This is because when forming a color image, it is necessary to slow down the printing speed due to the relationship between color superposition and hue, and there is a strict requirement for accuracy in controlling the toner density.

Since the configuration is as described above, according to the third embodiment, the registration abnormality range in the automatic development density adjustment mode of the image forming apparatus is controlled so as to be variable for each image forming apparatus model having a different printing speed, for example. , Consider the frequency output change for each model with different printing speed so that the trouble detection judgment is made by adding the process speed difference to the image forming device with slow printing speed for the overtoner threshold and undertoner threshold. Therefore, the accuracy of the toner concentration can be improved.

As described above, the present invention is not limited to the above-described embodiment, and various modifications can be made within the scope of the claims. It is clear that a person skilled in the art can come up with various modifications or modifications within the scope of the claims, that is, the modifications are made as appropriate without departing from the gist of the present invention. Embodiments obtained by combining technical means are also included in the technical scope of the present invention.

1,201 Image forming apparatus 2 Photoreceptor drum (photoreceptor)
5 Developing equipment 8 Developing tank 100 Control unit (control means)
140 Toner concentration sensor (toner concentration detecting means)
142 Toner concentration detector 144 IC memory (storage means)
240 temperature / humidity sensor

Claims (3)

In an image forming apparatus that forms an image by using an electrophotographic method, a developing apparatus that supplies toner to a photoconductor that forms an electrostatic latent image to form a toner image is provided.
A non-contact type toner concentration detecting means provided on the outer wall of the developing tank for detecting the toner concentration in the developing tank of the developing device, and
A control means for controlling the toner concentration in the developing tank by setting a toner concentration reference value based on the detection result of the toner concentration detecting means.
Equipped with
The toner concentration detecting means is
A storage means for storing the detection result of the toner concentration detecting means is provided.
The empty state in the developing tank when the developer is not charged is detected, the toner concentration in the developing tank in which the developing agent is present is detected, and the detection result of the toner concentration detecting means is output as a frequency.
The storage means
The correction value of the control value for determining whether or not to register the toner concentration reference value set in advance corresponding to each of the other correction elements is stored, and the detection result of the toner concentration detecting means is stored as the frequency output value. death,
The control means is
The difference value between the frequency output value stored in the storage means when the developer is not charged and the frequency when the developer is present in the developing tank is obtained, and the difference value is set to a predetermined undertoner threshold and overtoner. An image forming apparatus, characterized in that it is determined whether or not to register the frequency as the toner concentration reference value by comparing with a threshold value. Equipped with a temperature / humidity sensor
The control means is
The undertoner threshold and the overtoner threshold are corrected according to the environmental conditions detected by the temperature / humidity sensor.
The image forming apparatus according to claim 1. The control means is
The undertoner threshold value and the overtoner threshold value are corrected according to the printing speed of the image forming apparatus.
The image forming apparatus according to claim 1 or 2.

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