JP2002287441A - Image forming device and toner concentration control method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device and a toner concentration control method therefore, whereby even when an environmental factor changes, toner concentration can be appropriately controlled without decreasing the operating rate of the device and performing excessive correction, and the appropriate toner concentration can be maintained. SOLUTION: It is determined that whether the correction of an output voltage of a toner concentration sensor is required or not (S1 to S7). Only when the correction is required, the output voltage of the toner concentration sensor is corrected. In order to correct the output voltage, a control voltage is corrected (S8), and the output voltage is corrected while the correction intensity of the control voltage thereafter is decreased (S8 to S13). When the correction is not required, the step immediately proceeds to an image forming operation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an image forming apparatus such as an electrophotographic copying machine and a method for controlling a toner density thereof.

[0002]

2. Description of the Related Art In an image forming apparatus such as an electrophotographic copying machine or a facsimile machine, an original is irradiated with light, and an electrostatic latent image is formed on a photoreceptor by light reflected from the original. A visible image is recorded on a recording sheet as a visual image, or a visible image is formed by similar processing using an electric signal representing an image sent from the outside and recorded on the recording sheet.

In this type of image forming apparatus, a two-component developer comprising a toner and a magnetic carrier is used for forming a visible image. This toner density affects the density of a copied image. Therefore, the image forming apparatus detects the toner density in order to always obtain a copy image with a constant density,
When the toner density decreases, the toner is replenished and the toner density is controlled so as to fall within an appropriate range.

[0004] A toner density sensor for detecting the toner density is provided in the developing device. The developing device is disposed adjacent to a photoconductor drum having a photoconductor provided on a surface thereof, and develops an electrostatic latent image formed on the photoconductor drum into a visible image.

Known toner density sensors used in copiers, printers, and the like include, for example, a method of detecting a toner concentration in a two-component developer composed of a magnetic carrier and a toner, and a method of detecting the remaining amount of magnetic toner or the magnetic toner. There is a differential transformer type that detects the presence or absence of toner, and a differential transformer type toner density sensor is often used.

[0006] The toner density sensor of the differential transformer type is
As shown in FIG. 4, an AC power supply 44 is supplied to the primary coil 41 of the differential transformer. On its secondary side, two coils of substantially the same number of turns and of opposite polarity are wound in series. One of the secondary side coils is a reference coil 4
2. The other coil is a detection coil 43.

A screw core 45 having a high magnetic permeability is inserted near the primary coil 41 and the reference coil 42 so as to function as a magnetic core. By adjusting the position of the screw core 45, the inductance between the primary coil 41 and the reference coil 42 can be adjusted. Primary coil 41
The developer 46 or the magnetic toner to be measured flows near the detection coil 43 and the developer 4.
6 or the magnetic toner acts as a magnetic core and the primary coil 4
1 and the inductance between the detection coil 43 is changed. Since the magnitude of this inductance is determined by the amount of magnetic powder of the developer 46 or the magnetic toner working as a magnetic core, the amount of magnetic powder, that is, the toner concentration can be measured by the output voltage of the detection coil 43.

The reference coil 42 and the detection coil 43 have substantially the same number of turns, and have opposite polarities. Further, since the reference coil 42 and the detection coil 43 are connected in series, a difference between the two coils can be obtained as an output. The phase comparison circuit 47 performs an exclusive OR operation on the AC voltage supplied to the coil 41 and the outputs of the reference coil 42 and the detection coil 43, which are the secondary side coils. After that, the output signal is smoothed by the smoothing circuit 48 and taken out as a DC voltage, and toner is supplied in accordance with the output voltage.

Generally, in an image forming apparatus using a two-component developer (hereinafter, referred to as a developer), toner is charged by friction when stirring the developer, and the charged toner is transferred onto a photosensitive drum. A visible image is formed by electrostatically adhering to the electrostatic latent image formed on the substrate.

The toner density sensor in such an image forming apparatus is a magnetic permeability sensor, that is, a magnetic carrier (hereinafter, referred to as a magnetic carrier).
(Referred to as a carrier). Therefore, as shown in FIG. 5, when the toner density is low, the output voltage of the toner density sensor becomes high, and when the toner density is high, the output voltage of the toner density sensor becomes low. That is, since the toner density sensor reflects the density of the carrier in the space, the air contained in the developer may be erroneously detected as the toner.

As shown in FIG. 1, even when the toner density is the same, the output voltage of the toner density sensor differs depending on whether the developer is moist but dry. Here, A in FIG. 5 shows the relationship between the toner density and the output voltage of the toner density sensor when the humidity is 80%, B when the humidity is 60%, and C when the humidity is 15%. It is. As described above, even when the toner concentration is the same, the higher the humidity, the higher the output voltage of the toner concentration sensor.

In general, a temperature sensor for detecting temperature and a humidity sensor for detecting humidity can immediately follow a change in temperature or humidity, and can detect the change. On the other hand, the developer is capacitive, and even if environmental factors such as ambient temperature and humidity change, the state of the developer cannot immediately change following environmental factors.

For example, in winter, after the operation of the image forming apparatus is finished, the user turns off the heating and goes out of the office. Also, when the operation of the image forming apparatus is started the next morning before the heating is not effective yet, the temperature rises around the apparatus. The temperature rise of the developer is slow. In other words, even if the temperature around the image forming apparatus increases, it takes time for the temperature of the developer to rise following the surrounding temperature.

Similarly, during the rainy season, the room is dehumidified,
It takes time from the state in which the developer has absorbed moisture to the time in which the developer is dehumidified similarly to the surroundings. As described above, when the environmental factors greatly change between the end of the previous operation and the start of the operation of the image forming apparatus, a deviation occurs between the change of the environmental factors around and the change of the state of the developer.

In the image forming apparatus, for example, when the humidity is high, the charge holding amount of the carriers decreases, and the repulsive force between the carriers also decreases. As a result, the distance between the carriers is reduced, the number of carriers per unit volume of the developer is increased, and the magnetic permeability per unit volume is increased. For this reason, the toner density sensor automatically detects an increase in the magnetic permeability of the developer due to an increase in the number of carriers as a decrease in the apparent toner density (hereinafter referred to as a detected toner density Td). As a result, the actual toner density (hereinafter referred to as the actual toner density Tc)
Will increase.

Conversely, when the developer is dry or the like, the humidity of the developer is low, so that the charge holding amount of the carrier increases, and the repulsive force between the carriers also increases. Accordingly, the distance between the carriers is increased, and the number of carriers per unit volume of the developer is reduced, thereby decreasing the magnetic permeability per unit volume. Therefore, the toner density sensor detects a decrease in the magnetic permeability of the developer due to a decrease in the number of carriers.
, The supply of toner is stopped, and the actual toner concentration Tc is reduced.

FIG. 6 is a graph showing the relationship between humidity and the output voltage of the toner density sensor. The horizontal axis represents humidity (%), and the vertical axis represents the output voltage (V) of the toner density sensor. FIG. 7 is a graph showing the relationship between the control voltage of the toner density sensor and the output voltage of the toner density sensor. The horizontal axis represents the control voltage (V) of the toner density sensor, and the vertical axis represents the output voltage of the toner density sensor (V). V). The toner density is controlled by replenishing the toner so that the output voltage of the toner density sensor approaches the control voltage.

6 and 7, for example, when the control voltage is adjusted so that the output voltage of the toner density sensor becomes 2.2 V under an environment of 40% humidity, (a) the humidity of the developer becomes 20%
In this case, the output voltage of the toner density sensor is reduced from 2.2 V by 0.30 V to 1.9 V, and (b) humidity 8
At 0%, the output voltage increases from 2.2V by 0.2V to 2.4V.

However, the sensitivity of the toner density sensor is set to 0.6.
Assuming that V / weight%, the detected toner density Td is increased by 0.50% in (a) and the detected toner density Td is reduced by 0.33% in (b), so that recording on the recording paper is performed. Density changes (fading or darkening)
Resulting in. In addition, when the output voltage changes depending on the humidity, a shift occurs in the control voltage. For example, as shown in FIG. 7, when the humidity is 40%, the output voltage is 2.2V.
Is 0.22 V when the humidity reaches 20%,
When the humidity reaches 80%, the voltage shifts by 0.18V.

When the temperature inside the image forming apparatus rises due to use at high temperatures, frequent use, or installation near a window exposed to direct sunlight, the toner density sensor increases the toner density (detected toner density Td). Therefore, the toner supply is stopped, and the actual toner density Tc is reduced.

Conversely, when the temperature inside the image forming apparatus drops due to use at a low temperature or installation of the apparatus near the outlet of the cooling device, the toner density sensor detects the toner density (detected toner density Td). ) Is detected as a decrease. As a result, when toner is replenished, the actual toner density Tc increases, and it may not be possible to print an image with a normal density. This is because the varicap (variable capacitance diode) used in the oscillation circuit for generating the magnetic field of the toner concentration sensor increases the capacitance when the temperature increases, and decreases the capacitance when the temperature decreases. This is due to characteristics.

FIG. 8 is a graph showing the relationship between the temperature in the copying machine and the output voltage of the toner density sensor. The horizontal axis represents the temperature (° C.), and the vertical axis represents the output voltage (V) of the toner density sensor.
And FIG. 9 is a graph showing the relationship between the control voltage of the toner density sensor and the output voltage of the toner density sensor.
The horizontal axis represents the control voltage (V), and the vertical axis represents the output voltage (V) of the toner density sensor.

According to FIGS. 8 and 9, when the control voltage is adjusted so that the output voltage of the toner density sensor becomes 2.0 V under the environment of 20 ° C., (c) the temperature in the copying machine becomes 10 ° C.
In this case, the output voltage increases by 0.133 V to 2.133 V, and (d) at 30 ° C., the output voltage decreases by 0.106 V to 1.894 V.

Assuming that the sensitivity of the toner density sensor is 0.6 V /% by weight, in (c), the real toner density Tc is reduced by 0.22%, and in (d), the real toner density is 0.18%. In some cases, the density Tc becomes too large to record an image at a normal density. In addition, when the output voltage changes depending on the temperature, a shift occurs in the control voltage. For example, as shown in FIG.
In the case of ° C., the control voltage at which the output voltage becomes 2.0 V is shifted by 0.12 V when the temperature becomes 10 ° C. and 0.10 V when the temperature becomes 30 ° C.

Further, the temperature sensor and the humidity sensor detect only the temperature or the humidity in the area in contact with the detection surface for detecting the temperature or the humidity. For this reason, a location where the humidity is high or where the temperature is high is detected locally, which may affect the outputs of the temperature sensor and the humidity sensor.

Furthermore, even if the developer is agitated, the state of the developer, that is, the detected toner concentration becomes uniform,
As shown in FIG. 10, there is a time lag until the output voltage of the toner density sensor becomes constant. As shown in the figure, for example, it takes about 5 minutes for the output voltage of 3.2 V to become constant at 2.5 V.

As described above, the speed at which the state of the developer changes is delayed with respect to the speed at which the value detected by the temperature sensor or the humidity sensor changes. That is, the developer has a reaction delay with respect to the temperature sensor and the humidity sensor. When correcting the output voltage of the toner density sensor to reduce this reaction delay, if it is assumed that a constant correction value is continuously provided, do not replenish the toner excessively or supply the toner for an excessively long time. And may be overcorrected. Further, when a high-temperature developer is instantaneously detected, correct correction cannot be performed even if correction is performed using a correction value adjusted to the locally high temperature. In addition, since there is a time lag until the state of the developer is stabilized, correct correction cannot be performed even if correction is performed using a correction value adjusted to a state before the state of the developer is stabilized.

Therefore, in order to appropriately control the toner density regardless of changes in environmental factors, it is taken into consideration that the toner density will be uniform during use even without correction. Correction is necessary, and in order to prevent overcorrection and appropriately control the toner density, even if the correction is performed, the correction value initially used is not used continuously but gradually. The intensity of the correction needs to be reduced.

Japanese Patent Application Laid-Open No. 11-202605 describes an image forming apparatus capable of maintaining a toner density within an appropriate range by switching values used for correction, regardless of changes in environmental factors. . In this image forming apparatus, switching between toner replenishment control based on the estimated toner consumption and toner concentration control based on the estimated toner consumption and the actual measurement value of the toner density sensor is performed. Until the number of prints reaches the initial control number, toner supply control based on the estimated toner consumption is performed. After the number of prints reaches the initial control number, toner density control is performed based on the estimated toner consumption and the actual measurement value of the toner density sensor. The initial control number is calculated based on the temperature, the humidity, and the time during which the operation of the image forming apparatus is stopped. The estimated toner consumption is calculated from a dot count value that is image density information.

[0030]

In the image forming apparatus described in the above publication, toner supply control is always performed. That is,
Each time a print command is issued and the temperature, the humidity, and the time during which the operation of the apparatus is stopped are calculated, the initial control sheet number and the estimated toner consumption are calculated.

However, when the temperature or humidity changes or when the operation of the apparatus is stopped for a short time, toner supply may not be necessary. In such a case, there is no need to calculate the initial control number and the estimated toner consumption.

As described above, even though it is not necessary to replenish the toner, it takes a long time to shift to the image forming operation by calculating the initial control number and the estimated toner consumption. As a result, the operation rate of the image forming apparatus is reduced.

Further, in order to appropriately control the toner density, it is necessary to perform correction in consideration of the fact that the toner density becomes uniform during use without correction.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a method for appropriately controlling the toner density without lowering the operation rate of the apparatus and causing overcorrection even when environmental factors change. It is an object of the present invention to provide an image forming apparatus capable of controlling the toner density and maintaining an appropriate toner density, and a method for controlling the toner density.

[0035]

In order to solve the above-mentioned problems, an image forming apparatus according to the present invention comprises: a toner density sensor for detecting a toner density of a developer; an environmental factor measuring means for measuring an environmental factor; In an image forming apparatus comprising: a toner control unit configured to control a toner concentration of a developer based on an output voltage of the toner concentration sensor, an environmental factor and an image measured by an environmental factor measuring unit immediately before the image forming apparatus is stopped. The difference between the environmental factor measured by the environmental factor measuring means after the image forming apparatus is restarted, the output voltage of the toner density sensor immediately before the image forming apparatus is stopped, and the output voltage of the toner density sensor after the image forming apparatus is restarted A determination unit that determines whether or not the output voltage of the toner density sensor needs to be corrected based on the difference between the determination unit and the toner control unit. It is characterized by controlling the toner density of the developer according to the determination result of.

According to the above configuration, the output voltage of the toner density sensor is corrected based on environmental factors (for example, temperature and humidity) immediately before the image forming apparatus is stopped and environmental factors after the image forming apparatus is restarted. There is provided a determination means for determining the necessity of. This makes it possible to appropriately correct the output voltage of the toner density sensor when the environmental factors change greatly immediately before the image forming apparatus stops and after the restart. Therefore, the toner concentration can be appropriately controlled,
Thereby, an appropriate toner density can be maintained.

Further, for example, when it is determined that the correction of the output voltage of the toner density sensor is not necessary, it is possible to immediately shift to the image forming operation, and it is possible to prevent a reduction in the apparatus operation rate in the image forming apparatus. .

In the above-described image forming apparatus, the determining unit determines whether the environmental factor measured by the environmental factor measuring unit immediately before the image forming apparatus is stopped and the environmental factor measured by the environmental factor measuring unit after the image forming apparatus is restarted. If the difference from the above is less than an environment setting value set in advance to a predetermined value, it is preferable to determine that the correction of the output voltage of the toner density sensor is unnecessary.

According to the above arrangement, the amount of change in the environmental factor when the image forming apparatus is restarted is small compared to the environmental factor immediately before the image forming apparatus is stopped, and the output voltage of the toner density sensor is corrected. If it is not necessary, it is possible to immediately shift to the image forming operation without correcting the output of the toner density sensor. As a result, it is possible to prevent a decrease in the apparatus operation rate and the image forming efficiency.

In the above-described image forming apparatus, the determining unit determines whether the environmental factor measured by the environmental factor measuring unit immediately before the image forming apparatus is stopped and the environmental factor measured by the environmental factor measuring unit after the image forming apparatus is restarted. Is greater than or equal to the environment setting value, and the difference between the output voltage of the toner density sensor immediately before the image forming apparatus is stopped and the output voltage of the toner density sensor after the image forming apparatus is restarted is a predetermined value. If the value is equal to or greater than the toner set value set for
While it was determined that the output voltage of the toner density sensor needed to be corrected, the environmental factors measured by the environmental factor measuring means immediately before the image forming apparatus was stopped and the environmental factors measured by the environmental factor measuring means after the image forming apparatus was restarted were measured. The difference between the environmental factors is equal to or greater than the environment setting value, and the difference between the output voltage of the toner density sensor immediately before the image forming apparatus is stopped and the output voltage of the toner density sensor after the image forming apparatus is restarted is When the value is smaller than the toner set value, it is preferable that it is determined that the correction of the output voltage of the toner density sensor is unnecessary.

According to the above configuration, the amount of change in the environmental factor when the image forming apparatus is restarted is the amount of change required to correct the output of the toner density sensor with respect to the environmental factor immediately before the image forming apparatus is stopped. If so, the actual toner density is detected. Since the final correction of the output of the toner density sensor is determined based on the actual toner density, it is possible to shift to the image forming operation in the shortest apparatus stop time without performing the output correction of the toner density sensor. . Therefore, it is possible to prevent a reduction in the apparatus operation rate and the image forming efficiency.

A toner density control method for an image forming apparatus according to the present invention is a method for controlling a toner density of an image forming apparatus in which a toner density of a developer is controlled by correcting an output voltage of a toner density sensor for detecting a toner density of the developer. In the method,
The output of the toner density sensor according to a comparison result between a difference between an environmental factor immediately before the image forming apparatus is stopped and an environmental factor after the image forming apparatus is restarted, and an environmental setting value set to a predetermined value in advance. It is characterized in that the necessity of voltage correction is determined, and the toner concentration of the developer is controlled based on the determination result.

According to the above configuration, even when environmental factors greatly change between when the operation of the image forming apparatus was stopped last time and when the operation was started, it is possible to appropriately correct the output voltage of the toner density sensor. it can. Further, when it is determined that the correction of the output voltage of the toner density sensor is not necessary, it is possible to immediately shift to the image forming operation, and it is possible to prevent a decrease in the apparatus operation rate in the image forming apparatus.

The above-described method of controlling the toner density of the image forming apparatus is configured such that when the difference between the environmental factor immediately before the image forming apparatus is stopped and the environmental factor after the image forming apparatus is restarted is less than the above environment setting value. It is determined that the correction of the output voltage of the toner density sensor is unnecessary, and it is preferable to shift to the image forming operation.

According to the above configuration, when the amount of change of the environmental factor at the time of restarting the apparatus with respect to the environmental factor immediately before the stop of the apparatus is small and the correction is not required, the output correction of the toner density sensor is performed. It is possible to immediately shift to the image forming operation without performing. Therefore, it is possible to prevent a reduction in the apparatus operation rate and the image forming efficiency.

In the above-described toner density control method for an image forming apparatus, the difference between the environmental factor immediately before the image forming apparatus is stopped and the environmental factor after the image forming apparatus is restarted is equal to or more than the environmental setting value. The difference between the output voltage of the toner density sensor immediately before the image forming apparatus is stopped and the output voltage of the toner density sensor when the image forming apparatus is restarted is
When the toner value is less than a predetermined toner value, it is determined that the correction of the output voltage of the toner density sensor is unnecessary, and it is preferable to shift to the image forming operation.

According to the above arrangement, the amount of change in the environmental factor when the image forming apparatus is restarted is the amount of change required to correct the output of the toner density sensor with respect to the environmental factor immediately before the image forming apparatus is stopped. Even if there is, the final correction of the output of the toner density sensor is determined by detecting the actual toner density. Therefore, it is possible to shift to the image forming operation in the shortest apparatus stop time without performing the output correction of the toner density sensor. As a result, it is possible to prevent a decrease in the apparatus operation rate and the image forming efficiency.

In the above-described method for controlling the toner density of the image forming apparatus, it is preferable that the detection is started after the output voltage of the toner density sensor is delayed by a predetermined time from the start of the image forming apparatus.

In general, since the developer has a capacity, the state does not change immediately in response to a change in an environmental factor, and there is a time lag until the state changes in accordance with the environmental factor. On the other hand, for example, since environmental factor measuring means such as a temperature sensor and a humidity sensor have good sensitivity, they respond quickly to changes in environmental factors. For this reason, when controlling the toner density, the speed delay of the change in the state of the developer, that is, the time lag, becomes an obstacle to the fluctuation speed of the environmental factor. If the factors (for example, temperature and humidity) of the environmental factors having a fast variation speed are reflected in the toner density control of the developer having a slow variation speed, an overcorrection tendency occurs.

According to the above configuration, however, the output voltage of the toner density sensor is delayed by a predetermined time from the start of the image forming apparatus, and the detection is started. After the adjustment, the detection of the output voltage of the toner density sensor can be started. As a result, the correction can be performed by reflecting the difference in the length of the stop time of the image forming apparatus, and a decrease in image quality due to the influence of overcorrection can be avoided.

In the above-described toner density control method of the image forming apparatus, the output voltage of the toner density sensor is corrected after the detection of the output voltage of the toner density sensor is started and before the image forming operation is performed. Is preferred.

According to the above configuration, the output voltage of the toner density sensor is corrected from the time when the detection of the output voltage of the toner density sensor is started until the image forming operation is performed, that is, during the pre-rotation. Thus, after the correction of the output voltage of the toner density sensor, it is possible to immediately shift to the image forming operation. Therefore, there is no effect on the image forming operation, and
It is possible to prevent a decrease in the device operation rate.

In the above-described method of controlling the toner density of the image forming apparatus, it is preferable that the intensity of the correction for the output voltage of the toner density sensor be reduced with time during the execution of the image forming operation.

For example, when the image forming operation and the correction for the output voltage of the toner density sensor are performed separately, the time before the image forming operation becomes longer by the time for correcting the output voltage of the toner density sensor. The downtime of the image forming apparatus becomes longer.

However, according to the above configuration, the image forming operation and the correction for the output voltage of the toner density sensor proceed at the same time, so that the stop time of the image forming apparatus can be reduced. Therefore, it is possible to avoid stopping the apparatus only for correcting the output voltage of the toner density sensor, and to prevent a decrease in the apparatus operation rate.

In the above-described toner density control method of the image forming apparatus, a toner image is formed by applying toner to the electrostatic latent image formed on the surface of the photosensitive member based on the image signal after the image forming operation. It is preferable that the cumulative rotation time of the motor that drives the developing means is counted, and the correction intensity for the output voltage of the toner density sensor is sequentially reduced as the counted cumulative rotation time elapses.

According to the above arrangement, the intensity of correction for the output voltage of the toner density sensor is gradually reduced as the cumulative rotation time of the motor for driving the developing means shifts to the image forming operation with the lapse of time. The toner density can be controlled.

For example, when the size of the paper is different, even if the same number of images are formed, the rotation time of the developing means is different, and the toner concentration in the developer in the developing device is also different. As described above, the number of sheets on which an image is formed is not directly related to the toner density in the developer. Similarly, for example, the time elapsed since the start of the image forming apparatus and the rotation time of the photoconductor are not directly related to the toner concentration in the developer.

However, since the accumulated rotation time of the motor for driving the developing means after shifting to the image forming operation is directly related to the toner concentration in the developer, the accumulated rotation time is used to determine the output voltage of the toner density sensor. By performing the correction, it is possible to perform the correction with higher precision than by using the number of images formed, the time elapsed since the start of the image forming apparatus, the rotation time of the photoconductor, and the like.

[0060]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS.

The image forming apparatus according to this embodiment is similar to the image forming apparatus shown in FIG.
As shown in FIG. 1, a photosensitive drum 22 and a developing device (developing means) 20 are provided. The photosensitive drum 22 is driven to rotate. A photoconductor is provided on the surface of the photoconductor drum 22. The surface of the photoconductor drum 22 is uniformly charged to a predetermined potential by a charging roller (not shown), and is exposed by, for example, a laser beam from an LSU (laser beam scanner unit) not shown. Thus, an electrostatic latent image is formed on the surface of the photosensitive drum 22 according to image data (image signal) input from the outside.

The developing device 20 develops the electrostatic latent image formed on the photosensitive drum 22 into a visible image.

The developing device 20 includes a toner container 23 containing toner, a toner density sensor 21 and a developing roller 2.
4 and a stirring roller 25, and a two-component developer (hereinafter, referred to as a toner) comprising a toner and a magnetic carrier.
And a developing tank 26 filled with the developer. The toner stored in the toner container 23 is supplied to the developer in the developing tank 26 as needed.

The developing roller 24 is disposed in contact with the photosensitive drum 22. Further, the toner density sensor 21 is disposed at a position where its detection surface 21 a is always in contact with the developer and is separated from the developing roller 24. Since the toner density sensor 21 is a magnetic permeability sensor, it is easily affected by a magnetic field. Therefore, by disposing the toner density sensor 21 at a position distant from the developing roller 24, the toner density sensor 21 is hardly affected by the magnetic field. The toner density sensor 21 is connected to, for example, a substrate provided with a memory for storing the output voltage of the toner density sensor 21 and the like.

The developing tank 26 is a storage tank for storing the developer.

The stirring roller 25 charges the toner minutely by stirring the developer in the developing tank 26.

The developing roller 24 is a rotating roller provided so as to face the photosensitive drum 22, and is driven to rotate while contacting the photosensitive drum 22 at the same speed as the photosensitive drum 22. I have. As a result, toner is attached to the electrostatic latent image on the photosensitive drum 22, and the electrostatic latent image is developed to form a toner image.

Further, a temperature sensor (environmental factor measuring means) such as a process control thermistor (not shown) is disposed in the image forming apparatus, for example, in the vicinity of the photosensitive drum 22, for example. ) Is measured.

The environmental factors are not limited to temperature, but may be factors affecting image formation, for example, humidity. Therefore, a humidity sensor may be provided in the image forming apparatus.

With the development, the toner in the developing tank 26 is consumed. Therefore, in order to always obtain a copy image having a constant density, the image forming apparatus needs to appropriately supply toner from the toner container 23 to the developing tank 26 so that the toner concentration of the developer is maintained in an appropriate range. is there. The toner is supplied in accordance with the output voltage of the toner density sensor 21. That is, the toner supply is controlled such that the output voltage of the toner density sensor 21 approaches the control voltage as the target value, thereby controlling the toner density. Therefore, the output voltage of the toner density sensor 21 is corrected so as to approach the control voltage. The control voltage is
For example, when a new developing device 20 is installed in the image forming apparatus, the toner concentration sensor 21
The output voltage detected by the above is initialized.

Here, before the output voltage of the toner density sensor 21 is corrected, whether or not the correction is necessary is determined by, for example, a determination circuit (determination means). And
The correction is performed only when the determination circuit determines that the correction is necessary. This determination is based on a difference value ΔT between the temperature Ta detected by the temperature sensor immediately before the image forming apparatus is stopped and the temperature Tb detected by the temperature sensor after the image forming apparatus is restarted, and a predetermined value in advance. A comparison result of comparing the temperature with the specified temperature T (environment setting value), the output voltage Va of the toner density sensor 21 immediately before the image forming apparatus is stopped, and the output voltage Vb after the image forming apparatus is restarted. This is performed based on a comparison result obtained by comparing a difference value ΔV, which is an output difference between the above, and a set value VX (toner set value) preset to a predetermined value.

The above-described determination circuit determines that the output voltage of the toner density sensor 21 needs to be corrected when the temperature changes greatly immediately before the image forming apparatus is stopped and after the image forming apparatus is restarted. I have. On the other hand, if the temperature does not change much immediately before the image forming apparatus stops and after the restart, the correction of the output voltage of the toner density sensor is determined to be unnecessary.

Therefore, when environmental factors greatly change immediately before the image forming apparatus stops and after the restart, the output voltage of the toner density sensor can be appropriately corrected. Therefore, the toner concentration can be appropriately controlled,
Thereby, an appropriate toner density can be maintained.

When the temperature has not changed much between immediately before the image forming apparatus is stopped and after the restart, the operation can immediately proceed to the image forming operation, and the operation rate of the image forming apparatus can be reduced. Can be prevented.

Hereinafter, a toner density control method will be described with reference to FIG.

For example, at the time of warm-up rotation of the image forming apparatus, at the time of returning from the paper conveyance jam, at the time of releasing the interlock, etc.
The temperature Tb in the developing tank 26 immediately after the power is turned on is detected using a temperature sensor (S1).

The temperature Ta in the developing tank 26 detected by the temperature sensor and stored in the memory immediately before the image forming apparatus was stopped and the temperature Ta detected immediately after the current power supply of the image forming apparatus were turned on. A difference value ΔT from the temperature Tb in the developing tank 26 is calculated (S2). Then, the difference value ΔT is equal to or higher than a specified temperature T which is a set value, that is, ΔT = | Ta−T
The determination circuit determines whether b | ≧ T (S
3).

When the difference value ΔT is ΔT = | Ta−Tb | ≧ T
In the case of (3), that is, in the case of YES in S3, the pre-rotation is started with a delay of a predetermined time, for example, 1.5 seconds from the power-on, and the detection of the toner density (output voltage) by the toner density sensor 21 is started (S4) ). Here, the pre-rotation means that the developer is stirred by the stirring roller 25 without performing the development.

When the detection of the toner density is started and the output voltage Vb of the toner density sensor 21 is read (S5),
A difference value ΔV between the output voltage Vb and the output voltage Va of the toner density sensor 21 which is read immediately before the image forming apparatus is stopped last time and stored in the memory is calculated (S
6) The difference value ΔV is compared with a preset set value VX (S7). In this S7, the toner density sensor 21
Is to be determined. The correction of the output voltage of the toner density sensor 21 is performed based on a control voltage that is preset in advance. Toner density sensor 21
When the output voltage is corrected, the control voltage preset in advance is corrected, and the output voltage of the toner density sensor 21 is corrected so as to approach the corrected control voltage value. Here, the initially set control voltage is defined as a voltage Vref.

When the difference value ΔV is ΔV = | Vb−Va | ≧ V
When X is satisfied, that is, in the case of YES in S7, as shown in FIG. 3, after providing a time interval X necessary for the state of the developer to shift to the stable state, the toner density sensor 21 described later is used. Correct the output voltage. During the time interval X, the developer stirring is continued. Since the stirring speed varies depending on the model, the stirring time also varies, but usually from 180 seconds to 30 minutes.
The developer is stirred for about 0 seconds. Accordingly, it is possible to prevent the toner density sensor 21 from locally detecting a value different from the other portions. Therefore, the image forming operation can be started after the state of the developer is stabilized, and a decrease in image quality can be prevented.

If the difference value ΔT is lower than the specified temperature T, that is, if NO in S3, it is determined that there is no change in the state of the environmental factor, and the output voltage of the toner density sensor 21 is not corrected and immediately. Since the operation shifts to the image forming operation, the operation rate of the apparatus can be maintained.

Also, in the case of NO in S7, that is, when the difference value ΔT is equal to or higher than the specified temperature T but the difference value ΔV is smaller than the set value VX, the operation immediately shifts to the image forming operation. That is, even if it is determined that the environmental factor has changed, if it is determined that the output voltage of the toner density sensor 21 has not changed much, the output voltage of the toner density sensor 21 is not corrected.

Next, a method of correcting the output voltage of the toner density sensor 21 in the toner density control method will be described with reference to FIGS.

Here, for example, in a high temperature state, the toner density sensor 21 determines that the toner density (detected toner density) has increased despite the fact that the actual toner density is an appropriate value or lower. Since there is a tendency to detect, toner supply is stopped. For this reason, the actual toner density decreases.

Therefore, in the high temperature state, the voltage Vref, which is the control voltage of the toner density sensor 21 which is initially set, is changed to the high side (as shown in FIG. 3) in order to replenish the toner. The correction is performed), the voltage Vref2 is set (S8), and the execution of image formation is started (S9). In addition,
The control voltage is a voltage required for the detected toner density to become a normal density, and the output voltage of the toner density sensor 21 is corrected so as to approach the control voltage. Therefore, for example, when the control voltage is corrected to the voltage Vref2, the output voltage of the toner density sensor 21 becomes the voltage Vre2.
It is corrected to approach f2.

As described above, the voltage Vref2 is the voltage Vref stored in the image forming apparatus when the image forming apparatus is initialized.
Is subjected to a plus correction. The width of the plus correction is programmed in advance at the time of manufacturing the image forming apparatus and stored in the image forming apparatus as a constant used for correcting the output value, or a special value is set when the image forming apparatus is installed so as to individually correspond to each image forming apparatus. The input is made by an engineer through an operation panel or the like.

When the execution of image formation is started, the rotation time of the developing device drive motor (motor for driving the developing means) for driving the developing device 20 is detected (S10). Then, it is determined whether or not the rotation time is equal to or longer than a set value (S11).

When the rotation time is equal to or longer than the set value, that is,
If YES in S11, the voltage Vref2 is gradually corrected, and the toner density sensor 21 is corrected based on the corrected control voltage.
, That is, the toner density is controlled. This correction of the control voltage is performed until the voltage Vref2 is released (the correction level is reduced) in steps of Vs every time the rotation time of the developing device drive motor elapses T1 and the voltage returns to the voltage Vref. That is, after the control voltage is changed from the voltage Vref to the higher voltage Vref2, the voltage Vre
Lower Vs from f2. Thereafter, every time the time T1 elapses, the correction is made so as to decrease by Vs with the previous control voltage as a reference voltage (S12).

The process of returning the control voltage of the toner density sensor 21 from the voltage Vref2 to the voltage Vref, ie, the above-described S1
2, before reaching the voltage Vref, the toner density sensor 21
It is determined whether the difference value ΔV3 between the output voltage V2 and the previous output voltage V1 is equal to or more than the set value VX (see S7) again, that is, ΔV3 = | V2−V1 | ≧ VX ( S13).

When the difference value ΔV3 is equal to or larger than the set value VX, that is, when YES in S13, the control voltage is corrected,
The voltage is returned to the voltage Vref2 at which the correction level becomes maximum. here,
Even while the output voltage correction of the toner density sensor 21 is being performed, that is, while the correction of the control voltage is being performed, the previous detection result (V1) is constantly updated, and the control voltage is corrected and the voltage Vre is corrected.
Until returning to f, the previous detection result is adopted.

If the difference value ΔV3 is smaller than the set value VX, that is, if NO in S13, the toner density sensor 21
Is gradually returned from the voltage Vref2 to the voltage Vref (correction is performed).

If the rotation time of the developing device drive motor is shorter than the set time, that is, if NO in S11, the process returns to before the execution of the image forming operation (before S9), and the rotation speed counter of the developing device 20 is reset. Unless the correction is performed, the output voltage of the toner density sensor 21 is not corrected.

The toner density sensor 21 as described above
Even after the correction of the output voltage is once completed, the difference value Δ
When it is detected that V3 is ΔV3 = | V2−V1 | ≧ VX, the correction of the output voltage of the toner density sensor 21 is repeated in the same procedure as described above. That is, the process returns to before the execution of the image forming operation (before S9), and the output voltage of the toner density sensor 21 is corrected again. In this correction, the process of returning the correction stepwise in S12 is repeated, and all the settings corrected in S8 are released, that is, the control voltage of the toner density sensor 21 returns to the voltage Vref (S12).
Repeated up to 14).

As described above, in S4, the detection of the output voltage of the toner density sensor 21 is started after a predetermined time delay from the start of the image forming apparatus.

In general, since the developer has a capacity, the state does not change immediately in response to a change in the temperature, but there is a time lag until the state changes in accordance with the temperature change. on the other hand,
Because the temperature sensor has good sensitivity, it responds quickly to temperature changes. For this reason, when controlling the toner concentration, the speed delay of the change in the state of the developer with respect to the speed of the temperature change detected by the temperature sensor, that is, a time lag, becomes an obstacle. Therefore, if the temperature detected by the temperature sensor is reflected on the toner density control of the developer having a slow fluctuation speed, the correction tends to be overcorrected.

However, in S4, detection of the output voltage of the toner density sensor 21 is started after a predetermined time delay from the start of the image forming apparatus. As a result, the detection of the output voltage of the toner density sensor 21 can be started after the developer adapts to changes in the surrounding environment. Therefore, it is possible to perform the correction by reflecting the difference in the length of the stop time of the image forming apparatus, and as a result, it is possible to avoid a decrease in the image quality due to the influence of the overcorrection.

In S12, the level of correction of the control voltage is gradually reduced. Toner density sensor 21
Since the correction of the output voltage is corrected according to the control voltage,
The level of correction of the output voltage of the toner density sensor 21 can be gradually reduced. If the control voltage is continuously maintained at the voltage Vref2, excessive toner replenishment may occur, resulting in overtoning and overcorrection. However, overcorrection is prevented by gradually reducing the level of correction. can do.

The correction of the output voltage of the toner density sensor 21 and the execution of the image forming operation may be performed in this order.
The execution of the image forming operation may be performed at the same time. At this time, during the execution of the image forming operation, the toner density sensor 2
It is preferable to reduce the intensity of the correction for the output voltage of No. 1 over time.

For example, when the image forming operation and the correction for the output voltage of the toner density sensor 21 are performed separately, the time before the image forming operation is lengthened by the time for correcting the output voltage of the toner density sensor 21. As a result, the downtime of the image forming apparatus becomes longer.

However, since the image forming operation and the correction for the output voltage of the toner density sensor 21 proceed simultaneously, the stop time of the image forming apparatus can be reduced.
Therefore, it is possible to avoid stopping the apparatus only for correcting the output voltage of the toner density sensor 21, and to prevent a reduction in the apparatus operation rate.

In general, since the developer has a capacity, the state does not change immediately in response to a change in temperature, and there is a time lag until the state changes in accordance with the change in temperature. on the other hand,
Since the sensors have good sensitivity, they respond quickly to a temperature change. For this reason, when controlling the toner concentration, the speed delay of the change in the state of the developer, that is, the time lag, becomes an obstacle to the speed at which the temperature changes.

When the temperature at which the fluctuation speed is high is reflected in the toner density control of the developer whose fluctuation speed is low, the correction tends to be overcorrected. Here, the intensity of the correction to the output voltage of the toner density sensor 21 is changed over time. By reducing with it,
It is possible to immediately shift to the image forming operation while avoiding the deterioration of the image quality due to the influence of the overcorrection. As a result, a decrease in the operation rate of the apparatus can be prevented. Then, when the image forming operation is performed, the state of the developer is stabilized with the passage of time, so that overcorrection can be prevented.

The control voltage is changed from the voltage Vref to the higher V
The control voltage correction for changing to ref2 may be performed during the pre-rotation. As a result, the image formation can be executed immediately after the output voltage is corrected while correcting the control voltage, and the influence on the image forming operation, that is, the reduction of the apparatus operation rate is not caused.

At S11, the rotation time of the developing device drive motor is used as a reference for a time scale. As a criterion of the time scale, for example, the number of images formed can be considered. However, for example, even with one A3 sheet,
Similarly, even one A4 sheet is calculated as one sheet. As described above, when the size of the paper is different, the developing roller 2
4 and the toner concentration in the developer in the developing device 20 is also different. The state of the developer will also be different.

As described above, the number of sheets on which an image is formed is not directly related to the toner density in the developer. Similarly, for example, the time elapsed since the start of the image forming apparatus and the rotation time of the photosensitive drum 22 are not directly related to the toner concentration in the developer.

However, since the accumulated rotation time of the developing device drive motor after shifting to the image forming operation is directly related to the toner concentration in the developer, the accumulated rotation time is used to correct the output voltage of the toner density sensor 21. , The correction can be performed with higher accuracy than when the correction is performed using the number of images formed, the time elapsed since the start of the image forming apparatus, the rotation time of the photoconductor, and the like.

[0107]

As described above, in the image forming apparatus of the present invention, the environmental factors measured by the environmental factor measuring means immediately before the image forming apparatus is stopped and the environmental factors measured by the environmental factor measuring means after the image forming apparatus is restarted are measured. The output of the toner density sensor is determined based on the difference between the environmental factor and the difference between the output voltage of the toner density sensor immediately before the image forming apparatus is stopped and the output voltage of the toner density sensor after the image forming apparatus is restarted. A determination unit is provided for determining whether voltage correction is necessary, and the toner control unit is configured to control the toner concentration of the developer according to the determination result of the determination unit.

Thus, even when the environmental factors greatly change immediately before the image forming apparatus is stopped and after the image forming apparatus is restarted, the output voltage of the toner density sensor can be appropriately corrected. Therefore, the toner density can be appropriately controlled, and the appropriate toner density can be maintained. Further, when it is determined that the correction of the output voltage of the toner density sensor is not necessary, it is possible to immediately shift to the image forming operation, and it is possible to prevent the operation rate of the image forming apparatus from being lowered. Play.

In the image forming apparatus according to the present invention, the determining means determines whether the environmental factors measured by the environmental factor measuring means immediately before the image forming apparatus is stopped and the environmental factors measured by the environmental factor measuring means after the image forming apparatus is restarted. When the difference from the factor is smaller than an environment setting value set in advance to a predetermined value, it is determined that the correction of the output voltage of the toner density sensor is unnecessary.

Thus, the amount of change in the environmental factor when the image forming apparatus is restarted is small compared to the environmental factor immediately before the image forming apparatus is stopped, so that it is not necessary to correct the output voltage of the toner density sensor. In such a case, it is possible to immediately shift to the image forming operation without performing the output correction of the toner density sensor. Therefore, there is an effect that it is possible to prevent a reduction in the apparatus operation rate and the image forming efficiency.

In the image forming apparatus according to the present invention, the determining means determines whether the environmental factors measured by the environmental factor measuring means immediately before the image forming apparatus is stopped and the environmental factors measured by the environmental factor measuring means after the image forming apparatus is restarted. The difference between the factor and the factor is equal to or more than the above environment setting value, and the difference between the output voltage of the toner density sensor immediately before the image forming apparatus is stopped and the output voltage of the toner density sensor after the image forming apparatus is restarted is determined in advance. If the toner setting value is equal to or more than the toner setting value, it is determined that the output voltage of the toner density sensor needs to be corrected, while the environmental factor and the image measured by the environmental factor measuring unit immediately before the image forming apparatus is stopped. The difference between the environmental factor measured by the environmental factor measuring unit after the restart of the image forming apparatus is equal to or more than the above environment setting value, and the toner concentration immediately before the image forming apparatus is stopped If the difference between the output voltage of the sensor and the output voltage of the toner density sensor after the image forming apparatus is restarted is smaller than the toner set value, it is determined that the correction of the output voltage of the toner density sensor is unnecessary. Configuration.

Thus, even if the amount of change in the environmental factor at the time of restarting the image forming apparatus is such that the output correction of the toner density sensor needs to be corrected with respect to the environmental factor immediately before the stop of the image forming apparatus. Since the final correction of the output of the toner density sensor is determined by detecting the actual toner density, the operation proceeds to the image forming operation without performing the output correction of the toner density sensor in the shortest apparatus stop time. be able to. Therefore, there is an effect that it is possible to prevent a reduction in the apparatus operation rate and the image forming efficiency.

A toner density control method for an image forming apparatus according to the present invention is directed to a toner density control method for an image forming apparatus for controlling a toner density of a developer by correcting an output voltage of a toner density sensor for detecting a toner density of the developer. In the method,
The output of the toner density sensor according to a comparison result between a difference between an environmental factor immediately before the image forming apparatus is stopped and an environmental factor after the image forming apparatus is restarted, and an environmental setting value set to a predetermined value in advance. In this configuration, the necessity of voltage correction is determined, and the toner density of the developer is controlled based on the determination result.

Thus, even when environmental factors greatly change between when the operation of the image forming apparatus was stopped last time and when the operation was started, the output voltage of the toner density sensor can be appropriately corrected. Further, when it is determined that the correction of the output voltage of the toner density sensor is not necessary, it is possible to immediately shift to the image forming operation, and it is possible to prevent a decrease in the apparatus operation rate in the image forming apparatus.

The toner density control method for an image forming apparatus according to the present invention provides a method for controlling the toner density when the difference between the environmental factor immediately before the image forming apparatus is stopped and the environmental factor after the image forming apparatus is restarted is smaller than the above-mentioned environment setting value. Is a configuration in which it is determined that the correction of the output voltage of the toner density sensor is unnecessary, and the process shifts to the image forming operation.

Thus, when the amount of change of the environmental factor at the time of restarting the apparatus with respect to the environmental factor immediately before the stop of the apparatus is small and the correction is not required, it is possible to immediately shift to the image forming operation. Therefore, there is an effect that it is possible to prevent a reduction in the apparatus operation rate and the image forming efficiency.

In the toner density control method for an image forming apparatus according to the present invention, a difference between an environmental factor immediately before the image forming apparatus is stopped and an environmental factor after the image forming apparatus is restarted is equal to or more than the above environment setting value. When the difference between the output voltage of the toner density sensor immediately before the image forming apparatus is stopped and the output voltage of the toner density sensor when the image forming apparatus is restarted is smaller than a predetermined toner set value. In this configuration, the correction of the output voltage of the toner density sensor is determined to be unnecessary, and the process proceeds to the image forming operation.

Thus, even if the amount of change in the environmental factor when the image forming apparatus is restarted is such that the output correction of the toner density sensor needs to be corrected with respect to the environmental factor immediately before the stop of the image forming apparatus. In the shortest apparatus stop time, it is possible to shift to the image forming operation without performing the output correction of the toner density sensor. Therefore, there is an effect that it is possible to prevent a reduction in the apparatus operation rate and the image forming efficiency.

The toner density control method for an image forming apparatus according to the present invention has a configuration in which detection is started after the output voltage of the toner density sensor is delayed by a predetermined time from the start of the image forming apparatus.

As a result, the detection of the output voltage of the toner density sensor can be started after the developer adapts to changes in the surrounding environment. Thereby, the correction can be performed by reflecting the difference in the length of the stop time of the image forming apparatus,
There is an effect that the deterioration of the image quality due to the influence of the overcorrection can be avoided.

According to the toner density control method of the image forming apparatus of the present invention, the output voltage of the toner density sensor is corrected between the time when the detection of the output voltage of the toner density sensor is started and the time when the image forming operation is performed. Configuration.

As a result, it is possible to immediately shift to the image forming operation after the correction of the output voltage of the toner density sensor. Therefore, there is an effect that there is no influence on the image forming operation and that a reduction in the apparatus operation rate can be prevented.

The toner density control method of the image forming apparatus according to the present invention is configured such that the intensity of correction for the output voltage of the toner density sensor is reduced with time during the execution of the image forming operation.

As a result, the image forming operation and the correction for the output voltage of the toner density sensor can proceed simultaneously, and the stop time of the image forming apparatus can be reduced. Therefore, it is possible to avoid stopping the apparatus only for correcting the output voltage of the toner density sensor, and to prevent a reduction in the apparatus operation rate.

According to the toner density control method of the image forming apparatus of the present invention, the toner image is formed by applying toner to the electrostatic latent image formed on the surface of the photosensitive member based on the image signal after the image forming operation. The configuration is such that the cumulative rotation time of a motor for driving the developing means to be formed is counted, and the intensity of correction for the output voltage of the toner density sensor is sequentially reduced as the counted cumulative rotation time elapses.

As a result, the correction can be performed with higher accuracy than when the correction is performed by using the number of the formed images, the time elapsed since the start of the image forming apparatus, the rotation time of the photosensitive member, and the like. To play.

[Brief description of the drawings]

FIG. 1 is a flowchart illustrating a toner density control method of an image forming apparatus according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view illustrating a schematic configuration of the image forming apparatus.

FIG. 3 is an explanatory diagram illustrating toner density control based on a control voltage.

FIG. 4 is a circuit diagram illustrating an example of a configuration of a toner density sensor.

FIG. 5 is a graph showing a relationship between a toner density and an output voltage of a toner density sensor.

FIG. 6 is a graph showing a relationship between humidity and an output voltage of a toner density sensor.

FIG. 7 is a graph showing a relationship between a control voltage and an output voltage of a toner density sensor.

FIG. 8 is a graph showing a relationship between a temperature and an output voltage of a toner density sensor.

FIG. 9 is a graph showing a relationship between a control voltage and an output voltage of a toner density sensor.

FIG. 10 is a graph showing a relationship between a developer and an output voltage of a toner density sensor.

[Explanation of symbols]

 Reference Signs List 20 developing device 21 toner concentration sensor 21a detection surface 23 toner container 24 developing roller 25 stirring roller 26 developing tank

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Hiroo Naoi 22-22, Nagaikecho, Abeno-ku, Osaka-shi, Osaka F-term (reference) 2H027 DA13 DA14 DA33 DA35 DA46 DD07 DE04 DE07 DE09 EA06 EC06 EC08 EC09 EC18 EC20 ED10 EE07 EE08 EF04 EF06 EF10 JA11 JA12 JC06 ZA07 2H077 AA15 AB21 AD06 AD13 AE06 DA10 DA18 DA42 DA47 DA54 DA78 DA82 DA83 DA86 DB02 DB18 DB21 EA03 GA02 GA03 GA17

Claims (10)

[Claims] A toner density sensor for detecting a toner density of the developer; an environmental factor measuring means for measuring an environmental factor; and a toner control means for controlling a toner density of the developer based on an output voltage of the toner density sensor. A difference between an environmental factor measured by the environmental factor measuring means immediately before the image forming apparatus is stopped and an environmental factor measured by the environmental factor measuring means after the image forming apparatus is restarted, The necessity of correcting the output voltage of the toner density sensor is determined based on the difference between the output voltage of the toner density sensor immediately before the image forming apparatus is stopped and the output voltage of the toner density sensor after the image forming apparatus is restarted. Determining means for controlling the toner concentration of the developer according to the determination result of the determining means. Forming apparatus. 2. The image processing apparatus according to claim 1, wherein the difference between the environmental factor measured by the environmental factor measuring means immediately before the image forming apparatus is stopped and the environmental factor measured by the environmental factor measuring means after the image forming apparatus is restarted. 2. The image forming apparatus according to claim 1, wherein when the value is less than an environment setting value set in advance to a predetermined value, it is determined that correction of the output voltage of the toner density sensor is unnecessary. apparatus. 3. The method according to claim 1, wherein the determining step determines the difference between the environmental factor measured by the environmental factor measuring unit immediately before the image forming apparatus is stopped and the environmental factor measured by the environmental factor measuring unit after the image forming apparatus is restarted. The difference between the output voltage of the toner density sensor immediately before the image forming apparatus is stopped and the output voltage of the toner density sensor after the image forming apparatus is restarted is set to a predetermined value. If the toner setting is greater than
While it was determined that the output voltage of the toner density sensor needed to be corrected, the environmental factors measured by the environmental factor measuring means immediately before the image forming apparatus was stopped and the environmental factors measured by the environmental factor measuring means after the image forming apparatus was restarted were measured. The difference between the environmental factor is equal to or more than the above environment setting value, and the difference between the output voltage of the toner density sensor immediately before the image forming apparatus is stopped and the output voltage of the toner density sensor after the image forming apparatus is restarted is 3. The image forming apparatus according to claim 2, wherein when the value is smaller than the toner set value, it is determined that the correction of the output voltage of the toner density sensor is unnecessary. 4. A toner density control method for an image forming apparatus for controlling a toner density of a developer by correcting an output voltage of a toner density sensor for detecting a toner density of the developer. The necessity of correcting the output voltage of the toner density sensor is determined based on a result of comparing a difference between an environmental factor and an environmental factor after the image forming apparatus is restarted and an environmental setting value set to a predetermined value in advance. And controlling the toner concentration of the developer based on the determination result. 5. When the difference between an environmental factor immediately before the image forming apparatus is stopped and an environmental factor after the image forming apparatus is restarted is smaller than the above-mentioned environment setting value, the output voltage of the toner density sensor is corrected. 5. The method according to claim 4, wherein it is determined that the image density is unnecessary, and the process proceeds to an image forming operation. 6. A method according to claim 1, wherein a difference between an environmental factor immediately before the image forming apparatus is stopped and an environmental factor after the image forming apparatus is restarted is equal to or more than the environment setting value and the toner immediately before the image forming apparatus is stopped. If the difference between the output voltage of the density sensor and the output voltage of the toner density sensor when the image forming apparatus is restarted is less than a predetermined toner set value, the output of the toner density sensor is The toner density control method for an image forming apparatus according to claim 4, wherein it is determined that voltage correction is unnecessary, and the process shifts to an image forming operation. 7. The method according to claim 4, wherein the detection of the output voltage of the toner density sensor is started after a predetermined time delay from the start of the image forming apparatus. A toner density control method for an image forming apparatus. 8. A period from when the detection of the output voltage of the toner density sensor is started to when the image forming operation is executed.
8. The method according to claim 4, wherein the output voltage of the toner density sensor is corrected. 9. The image forming apparatus according to claim 4, wherein the intensity of correction for the output voltage of the toner density sensor is reduced with time during execution of the image forming operation.
12. The toner density control method for an image forming apparatus according to any one of the above items. 10. A cumulative rotation of a motor for driving developing means for applying toner to an electrostatic latent image formed on the surface of a photosensitive member based on an image signal to form a toner image after shifting to an image forming operation. 5. The method according to claim 4, wherein time is counted, and the intensity of correction for the output voltage of the toner density sensor is sequentially reduced as the counted cumulative rotation time elapses.
10. The toner density control method for an image forming apparatus according to any one of claims 9 to 9.