JPH06148973A - Image forming device - Google Patents

Abstract

PURPOSE:To obtain stable image quality even when the electrostatic charge quantity of toner is fluctuated according to the using state of a copying machine. CONSTITUTION:By a mode set control means 1, one among the image forming modes such as a continuous running mode and plural low duty modes is selected based on the temperature of a fixing roller at the turning off/on time of the copying machine, the rising time of the heater 4 of a fixing roller or the set time of a preheating mode so as to set the optimum developing bias voltage impressed on a developing sleeve from a developing bias power source 6. It is good that one among the image forming modes is selected based on the copying amount (CV) of the copying machine per one month scheduled in the past or the future, a value(Cth) obtained by dividing the number of all the copied sheets by the total turning-on time of the copying machine from a new state or a value(Crh(H)) obtained by dividing the number of copied sheets within a concerned time by H hours last before a present time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine, a facsimile and a printer, and more specifically, an image carrier and a latent image forming means for forming a latent image on the image carrier. The present invention relates to an image forming apparatus provided with a developing device that supplies a two-component developer carried on a developer carrying body onto the image carrying body to visualize the latent image.

[0002]

2. Description of the Related Art In an image forming apparatus such as a copying machine equipped with a developing device using a two-component developer (hereinafter referred to as a developer), in order to obtain stable image quality, the developer in the developing device must be It is desirable to stabilize the toner charge amount and toner concentration. However, the toner charge amount of the developer changes depending on the stirring time and the standing time of the developer, and the change of the toner charge amount may change the toner adhesion amount to the latent image formed on the image carrier. Are known. FIG. 2 shows an example in which the time variation of the toner charge amount differs depending on the usage mode of the image forming apparatus. When a new developer whose initial toner charge amount is Q0 is set in the image forming apparatus and a conventionally known initial startup operation is performed, the toner charge amount rises to a predetermined value Q1. Go. After that, in the case of the continuous run use mode in which the power of the image forming apparatus main body is constantly turned on and the image forming operation is continuously performed, the toner charge amount further increases as shown by the curve A1, and the predetermined stable value is obtained. (Q2 in FIG. 2), the image forming operation is performed in a state where the toner charge amount is maintained at a substantially stable value Q2. On the other hand, the power of the image forming apparatus main body is intermittently turned off.
In addition, in the case of a low duty duty mode in which the frequency of the image forming operation is small even when the power source is ON, the ON / OFF of the power source is repeated, so that the toner charge amount becomes as shown by the curve A2. fluctuate. For example, during the period indicated by the symbol T1, the power is turned on, the developer is stirred by the image forming operation, and the toner charge amount is increased. In addition, during the period indicated by the symbols T2 and T3, the power source is turned off during the night, holidays such as Saturday and Sunday,
The developer is left standing and the toner charge amount is low.

[0003]

As shown in FIG. 2, the toner charge amount of the developer in the low duty use mode shown by the curve A2 is the toner charge amount of the developer in the continuous run use mode shown by the curve A1. When the value is lower than the stable value Q2 (for example, the toner charge amount Q3 in FIG. 2), the toner is apparently stable. Further, in the low-duty usage mode indicated by the curve A2, the apparent stable value (Q3) of the toner charge amount differs due to the length of the OFF time of the power source of the image forming apparatus main body, and the OFF time is long. As shown in the period T3, the toner charge amount is extremely reduced. Further, in the low duty use mode, the toner charge amount also varies depending on the frequency of performing the image forming operation in the ON state of the power supply.

When the toner charge amount of the developer becomes lower than a predetermined value, the toner is likely to adhere to the image carrier, resulting in poor halftone image reproducibility and a dark image. I will end up. Further, when the image forming operation is repeated in the state where the toner charge amount of the developer is reduced, the toner density is rapidly reduced and the toner is rapidly replenished,
When the toner is replenished, background stains and toner scattering occur.
As described above, when the toner charge amount of the developer varies depending on the usage mode of the image forming apparatus, the desired image quality cannot be obtained depending on the usage mode, and stability of the image quality is impaired. is there.

The present invention has been made in view of the above problems, and an object thereof is to provide an image forming apparatus capable of obtaining stable image quality even when the toner charge amount varies depending on the usage state of the apparatus. That is.

[0006]

In order to achieve the above-mentioned object, an image forming apparatus according to a first aspect of the present invention comprises an image carrier, a latent image forming means for forming a latent image on the image carrier, and a developing device. The two-component developer carried on the agent carrier is supplied onto the image carrier,
An image forming apparatus provided with a developing device for converting the latent image into a visible image, having a plurality of image forming modes in which image forming process conditions are set corresponding to a plurality of different toner charge amounts of the developer. A mode setting control means for selecting and setting any one of the plurality of image forming modes based on a past usage pattern of the image forming apparatus or a future usage pattern of the image forming apparatus. To do. This mode setting control means, based on a past usage pattern of the image forming apparatus or a future usage pattern, for example,
It can be configured to be set manually or automatically.

An image forming apparatus according to a second aspect is the image forming apparatus according to the first aspect, in which the fixing member heated by the heating means fixes the image transferred onto the transfer material, and the fixing device. Temperature setting means for detecting the temperature of the member, and the mode setting control means changes the setting of the image forming mode based on the temperature of the fixing member when the power source of the image forming apparatus main body is turned on. It is characterized in that it is configured to.

An image forming apparatus according to a third aspect is the image forming apparatus according to the first aspect, in which the fixing member heated by the heating means fixes the image transferred onto the transfer material, and the image forming apparatus. A time measuring means for measuring the rising time of the heating means until the fixing member reaches a predetermined temperature when the power of the forming apparatus main body is turned on, and the mode setting control means is measured by the time measuring means. The configuration is such that the setting of the image forming mode is changed based on the rising time.

An image forming apparatus according to a fourth aspect of the present invention is the image forming apparatus according to the first aspect, wherein preheating setting means sets the image forming apparatus to a preheating mode which is a predetermined standby state.
The image forming apparatus is provided with a time measuring unit for measuring a preheat mode setting time set in the preheating mode, and the mode setting control unit is configured to operate the preheating mode setting time based on the preheating mode setting time measured by the time measuring unit. It is characterized in that the configuration of the image forming mode is changed.

[0010]

According to the image forming apparatus of the present invention, the image forming apparatus has a plurality of image forming modes in which the image forming process conditions are set corresponding to a plurality of different toner charge amounts of the developer. For example, in accordance with the usage pattern as shown by the curve A1 in FIG. 2, that is, the usage pattern of the continuous run in which the image forming apparatus main body is constantly turned on to continuously perform the image forming operation, the toner charge amount Continuous run mode in which the image forming process conditions are set so as to be suitable for the saturation value Q2 of the image forming apparatus, or a usage mode as shown by the curve A2 in FIG. 2, that is, the power source of the image forming apparatus main body is intermittently turned off, and A low duty mode or the like in which the image forming process condition is set so as to be suitable for the apparent stable value Q3 of the toner charge amount in response to the low duty usage mode in which the frequency of the image forming operation is small even when the power is turned on. Has a plurality of image forming modes. Further, the low duty mode may be divided into a plurality of image forming modes more finely in consideration of the variation of the toner charge amount of the developer in the usage mode of the low duty.

Then, by the mode setting control means,
Based on past usage of the image forming apparatus or expected usage in the future, one of the plurality of image forming modes, for example, the continuous run mode or the plurality of low duty modes is selected and set. . For example, when the continuous run mode is selected and set by the mode setting control means, the image forming process condition set based on the stable value Q2 of the toner charge amount shown by the curve A1 in FIG. 2 is used. The subsequent image forming operation is performed. Here, the image forming process conditions include a developing bias voltage applied to the developer carrier of the developing device, a charging potential of the image carrier uniformly charged by the charging device, and an exposure device. The exposure amount and the like when forming a latent image on the image bearing member may be mentioned. Further, for example, when the toner charge amount of the developer in the past usage mode of the image forming apparatus or in the future expected usage mode fluctuates as shown by a curve A2 in FIG. 2, the mode setting control is performed. When one of the plurality of low duty modes is set by the means, the toner charge amount value in the apparent stable region of the curve A2 (for example, the average value Q3 of the peak values of the curve A2) is set. Subsequent image forming operations are performed using the image forming process conditions. Therefore, even when the usage mode of the image forming apparatus is different such as the continuous run or the low duty and the toner charge amount of the developer is different, the image forming process condition is set to be suitable for the toner charge amount. The selected image forming mode is selected and set.

In the image forming apparatus of the second aspect, the temperature of the fixing member is detected by the temperature detecting means. The temperature of the fixing member is set to 0 when the power source of the image forming apparatus main body is 0.
After the FF, the temperature decreases toward room temperature as the OFF time elapses. Therefore, if the temperature of the fixing member immediately after the power is turned on is detected, the image forming apparatus is turned off. The time, that is, the time during which the developer has been left alone can be known, and the amount of decrease in the toner charge amount of the developer can be known. Therefore, by configuring the mode setting control unit so that the subsequent image forming mode is selected and set based on the temperature of the fixing member when the power is turned on, the image forming mode is set more finely. Therefore, in the low duty duty mode, the difference in image quality between before the power is turned off and when the power is turned on becomes small. Further, according to this configuration, it is not necessary to provide a time measuring unit for measuring the OFF time in the state where the power source is OFF in order to know the time when the developer is left.

According to another aspect of the image forming apparatus of the present invention, the rise time of the heating means until the fixing member reaches a predetermined temperature is measured when the power source of the image forming apparatus main body is turned on by the time measuring means. . The temperature of the fixing member decreases toward room temperature as the OFF time elapses after the power of the image forming apparatus main body is turned off. Then, when the power is turned on, the heating means is activated until the temperature of the fixing member whose temperature is lowered reaches a predetermined temperature. If the start-up time of the heating means is detected, the time during which the power supply is off, that is,
The time during which the developer has been left is known, and the amount of decrease in the toner charge amount of the developer is known. Therefore, by configuring the mode setting control means so as to select and set the subsequent image forming mode based on the rising time measured by the time measuring means, the image forming mode can be set more finely, In the low-duty usage mode, the difference in image quality between before the power is turned off and after it is turned on is small. Further, according to this configuration, it is not necessary to provide a time measuring unit for measuring the OFF time in the state where the power source is OFF in order to know the time when the developer is left.

In the image forming apparatus of the fourth aspect, the preheating mode setting time during which the image forming apparatus is set in the preheating mode which is the predetermined standby state is measured by the time measuring means. Even in the preheating mode setting time, the developer is left according to the length of the preheating mode setting time, and the toner charge amount is reduced. Therefore, if the preheating mode setting time is measured, the developer is left unattended. The time is known, and the amount of decrease in the toner charge amount of the developer is known. Therefore, by further configuring the mode setting control means so as to select and set the image forming mode when the preheating mode is released based on the preheating mode setting time measured by the timing means, The image forming mode can be set finely, and in the use mode of the low duty, the difference in image quality between before starting the preheating mode and after canceling the preheating mode becomes small.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to an electrophotographic copying machine (hereinafter referred to as a copying machine) which is an image forming apparatus will be described below. FIG. 3 is a front view showing a schematic configuration of the copying machine according to the present embodiment. First, an outline of the entire copying machine will be described. A contact glass 10 for placing an original is provided on the upper part of the copying machine, and an openable / closable original cover 11 is attached so as to cover the contact glass 10. Below the contact glass 10, a document irradiation lamp 12 and an irradiation mirror 12 are provided.
An optical unit as an exposure device including a, a reflection mirror 13, a moving lens system 14, and the like is provided. And
The photoconductor drum 20 is arranged at a position where the imaging light from the optical unit is irradiated. This photoconductor drum 20
Is rotated clockwise by an unillustrated drive system. Around the photosensitive drum 20, a charging charger 21 as a charging device, an eraser 22, a developing unit 23 as a developing device, a transfer charger 24,
A separation charger 25, a separation claw 26, a cleaning unit 27, a discharge lamp 28, etc. are arranged.

As shown in FIG. 3, the developing unit 23 comprises a hopper portion 40 for accommodating toner and a developing device portion 42 rotatably provided with a developing sleeve 41 as a developer carrying member. The both parts 40 and 42 are integrated by, for example, screwing. A toner delivery member 43 is provided in the casing 40a of the hopper portion 40. Further, in the casing 42a of the developing device section 42, a mixing roller 44 for mixing the toner replenished from the hopper section 40 into the two-component developer from the carrier and the toner, the developer from the mixing roller 44 Agitating paddle 45 for supplying to developing sleeve 41 while agitating
The developing doctor 4 that regulates the amount of developer on the developing sleeve 41
6. A separator 47 for circulating the developer regulated by the developing doctor 46 on the mixing roller 44 is provided.

Then, from the mounting portion A of the sheet feeding cassette (not shown) formed on the right side surface of the copying machine, the photosensitive drum 2
The transfer path of the transfer paper 6 through the lower facing portion of 0 to the paper discharge section B formed on the left side of the copying machine is the paper feed roller 30,
The delivery roller pair 31, the registration roller pair 32, the conveyance belt device 33, the fixing roller pair 34 as a fixing member of the fixing device, the paper discharge roller pair 35, and the like.

In the above structure, the contact glass 1
When the document 9 is set on the document 0 and the copy start button of the operation unit (not shown) is pressed, the light emitted from the document irradiation lamp 12 is applied to the document 9, and the reflected light is reflected by the reflection mirror 1.
3, an image is formed on the photosensitive drum 20 via the moving lens system 14 and the like. The surface of the photosensitive drum 20 is uniformly charged by the charging charger 21, and this charge is selectively erased by the reflected light from the document to form an electrostatic latent image. Then, the eraser 22 erases the charges around the image area, and the rotation of the photosensitive drum 20 causes the developing unit 2 to rotate.
It passes through the facing part of 3. At this time, the electrostatic latent image is made into a toner image by the developing unit 23 having the developing sleeve 41 to which a predetermined developing bias voltage is applied from the developing bias power source 6, and a toner image corresponding to the original image is formed on the photosensitive drum 20. It is formed. This toner image is fed from a paper feed cassette (not shown) by the paper feed roller 30 and the delivery roller pair 31, and is transferred to the transfer paper 6 which is conveyed to the surface of the photoconductor drum 20 by the registration roller pair 32 at a timing. It is transferred by the transfer charger 24. The transfer paper 6 on which the toner image has been transferred is neutralized by the separation charger 24, separated from the surface of the photoconductor drum 20 with the aid of the separation claw 26 if necessary, and sent to the fixing roller pair 34 by the conveyor belt device 33. To be Then, the toner image is fixed on the transfer sheet 6 by the fixing roller pair 34, and the sheet is discharged onto a sheet discharge tray (not shown) of the sheet discharge section B by the sheet discharge roller pair 35. On the other hand, on the surface of the photoconductor drum 20 after the toner image is transferred to the transfer paper 6, after the residual toner is removed by the cleaning unit 27, the residual charge is removed by the charge removal lamp 28 to prepare for the next image formation. .

By the way, in the copying machine having the above-mentioned structure, for example, a usage pattern of continuous runs as shown by the curve A1 in FIG.
If the toner charge amount varies depending on the usage mode of the copying machine, such as the low duty usage mode as indicated by the curve A2, desired image quality cannot be obtained depending on the usage mode, and the image density varies. However, there was a problem that the stability of the image quality was affected, such as the deterioration of halftone reproducibility.

Therefore, the present embodiment has a plurality of image forming modes in which the image forming process conditions are set corresponding to a plurality of different toner charge amounts of the two-component developer, and the copying machine has been used in the past. , Or mode setting control means for selecting and setting any one of the plurality of image forming modes on the basis of a usage pattern expected in the future.

First, the configuration of the mode setting control means 1 will be described with reference to FIG. The mode setting control means 1 comprises an I / O unit 1a, a main body control unit 1b having a CPU, a timer as a time measuring unit, and a storage unit 1 having a RAM, a ROM, and the like. Main body control unit 1b
Is a user operation unit 2, a fixing roller thermometer 3 as a temperature detecting unit, a heater 4 as a heating unit, a copy number counter 5, a developing bias power source 6, and a charging charger power source 7 through the I / O unit 1a. , And the exposure control unit 8 and the like.

Here, the user operation unit 2 sets the image forming mode desired by the user and the copy amount predicted in the past or in the future (for example, the number of copies per month,
Hereinafter, it will be referred to as CV). The fixing roller thermometer 3 is composed of a thermistor or the like so as to detect the temperature of the fixing roller pair 34, and the measured value of the temperature is sent to the main body control unit 1b via the I / O unit 1a as necessary. . Further, the heater 4 heats the fixing roller pair 34 to a predetermined temperature when the main power of the copying machine is turned on, and maintains the temperature, and in the preheating mode of the copying machine. Is configured to be maintained at a temperature lower than the above predetermined temperature. The developing bias power source 6 applies a predetermined developing bias voltage to the developing sleeve 41 for image density adjustment and the like, and the charging charger power source 7 applies a predetermined high voltage to the discharge wire and the grid electrode of the charging charger 21. The application control unit 8 is configured so that the exposure amount by the document irradiation lamp 12 can be controlled. The developing bias voltage,
The high voltage and the set value of the exposure amount are set by the main body control unit 1.
Each can be changed as required by b.

Next, a specific example of the mode setting control of the image forming mode by the mode setting control means will be described with reference to the flowcharts of FIGS. [Specific Example 1] This example is based on whether the past usage mode of the copying machine or the usage mode expected in the future is the continuous run or the low duty, or the CV (copy amount per month). 2) is a specific example in which the mode control means is configured so as to manually select and set the optimum image forming mode depending on the difference.

Hereinafter, description will be given based on the flowchart of the mode setting control 1 in FIG. First, the user operates the user operation unit 2 based on the past usage of the copying machine or the usage expected in the future (step 1). When the use mode is the continuous run, the key input from the user operation unit 2 is not performed, and the developing bias voltage in the continuous run mode defined in advance is set (step 2), and the present flowchart ends. . That is, this continuous run mode is the priority mode.

On the other hand, when the usage mode is the low duty, the past CV of the copying machine or the CV expected in the future is keyed in from the user operation unit 2 (step 1). Then, in the main body control unit 1b, the preset storage unit 1c
Are compared with the plurality of comparison reference values K _{1 to} Kn stored in (steps 3, 5, 7, 9). For example, step 3
When the input CV value is larger than K ₁ sheets in the comparison of ₁ ), the developing bias voltage L ₁ (V) is selected,
The developing bias control data is sent from the main body controller 1b to the developing bias power source 6 via the I / O unit 1a, and the developing bias voltage applied from the developing bias power source 6 to the developing sleeve 41 at the time of image formation is L ₁ ( V) is set in the image forming mode (step 4), and the present flowchart ends.

In the comparison of the above step 3, if the input CV value is less than or equal to K ₁ , the process proceeds to the next step 5. In the comparison in step 5, if the input CV value is less than or equal to K ₁ sheets and greater than K ₂ sheets, the developing bias voltage L ₂ (V) is selected, and the main body control unit 1b is selected.
The developing bias control data is sent from the developing bias power source 6 to the developing bias power source 6 via the I / O unit 1a, and the developing bias voltage applied from the developing bias power source 6 to the developing sleeve 41 during image formation is L ₂ (V). The image forming mode is set (step 6), and this flowchart ends. In the comparison in step 5 above, if the input CV value is K
If the number of sheets is _two or less, go to the next step 7.

Hereinafter, the preset reference comparison value K _{1 is} set in advance.
~ The above comparison is repeated up to n times corresponding to the number of Kn,
The image forming mode is set such that the optimum developing bias voltage is applied (steps 7 to 10), and the present flowchart ends.

The apparent stable value of the toner charge amount of the developer and the value of the developing bias voltage suitable for the stable value with respect to each range of the CV are obtained in advance by experiments or the like, and are stored in the storage unit 1c. Remembered in. Here, for example, when the CV changes and the toner charge amount decreases, the image density becomes high. Therefore, it is necessary to correct it and decrease the developing potential according to the toner charge amount decrease amount. And the developing bias voltage is set lower.

As described above, according to the present example, the apparent stable value of the toner charge amount of the developer at the low duty is lowered unlike the stable value of the toner charge amount of the developer at the continuous run. Even in such a case, a low development bias voltage is set to correct the change in image quality due to the decrease in the toner charge amount, so the image density becomes higher than a predetermined level and the halftone image reproducibility is improved. Can be prevented, and the image quality can be stabilized.
Further, at the time of the low duty, the image forming mode is selected and set more finely based on the past CV value of the copying machine or the CV value expected in the future. It is possible to stabilize the image quality according to the usage mode. Further, the user can freely and timely select and set a desired continuous run mode, a plurality of low duty modes, and other image forming modes by manual key input from the user operation unit 2. .

[Specific Example 2] In this example, when the toner charge amount of the developer is reduced when the power source of the copying machine main body is OFF as in the periods T2 and T3 of FIG. Based on the length of the power-off state period, that is, the degree of decrease in the toner charge amount due to leaving the developer, the mode setting control is performed to select and set the image forming mode when the developer is turned on thereafter. This is one of the concrete examples of the means. In this example, the length of the period in which the power of the copying machine main body is in the OFF state is obtained from the degree of decrease in the temperature of the fixing roller pair 34 from the fixable temperature when the copying machine is turned on. The temperature of the fixing roller pair 34 is detected by the fixing roller thermometer 3 including a thermistor or the like.

Hereinafter, description will be given based on the flowchart of the mode setting control 2 in FIG. First, the fixing roller pair 34 when the power of the copying machine main body is changed from the OFF state to the ON state
Is determined to be a fixable temperature (step 1), and if it is the fixable temperature, that is, the continuous run use mode in which the copying machine is almost in the ON state, it is defined in advance. The developing bias voltage in the continuous run mode is set (step 2), and this flowchart ends.

On the other hand, when the usage mode is the above-mentioned low duty, the fixing roller pair 3 is set in the main body control section 1b.
The temperature of _No. 4 is compared with a plurality of comparison reference values K1 to Kn stored in advance in the storage unit 1c (steps 3, 5, 7). For example, in the comparison of step 3, when the temperature of the fixing roller pair 34 is higher than K ₁ degree, the developing bias voltage L ₁ (V) is selected, and the main body control unit 1b outputs the I / O unit 1a. The developing bias control data is sent to the developing bias power source 6, and the image forming mode is set such that the developing bias voltage applied from the developing bias power source 6 to the developing sleeve 41 at the time of image formation is L ₁ (V) (step 4) The flow chart ends.

When the temperature of the fixing roller pair 34 is equal to or lower than K ₁ degree in the comparison of the step 3, the process proceeds to the next step 5. And in the comparison of step 5,
When the temperature of the fixing roller pair 34 is lower than K ₁ degree and higher than K ₂ degree, the developing bias voltage L ₂ (V) is selected and the developing bias power source is supplied from the main body control section 1b through the I / O section 1a. The developing bias control data is sent to the image forming device 6, and the image forming mode is set such that the developing bias voltage applied from the developing bias power source 6 to the developing sleeve 41 during image formation is L ₂ (V) (step 6). This flowchart ends.

Hereinafter, the preset reference comparison value K _{1 is set.}
~ The above comparison is repeated up to n times corresponding to the number of Kn,
The image forming mode is set so that the optimum developing bias voltage is applied (steps 7 to 9), and the present flowchart ends.

For each temperature range of the fixing roller pair 34, the degree of decrease in the toner charge amount due to the developer being left and the value of the developing bias voltage suitable for the decreased toner charge amount were previously tested. And is stored in the storage unit 1c. Here, for example, when the toner charge amount decreases, the image density increases, so that the developing bias voltage is lowered according to the decrease amount of the toner charge amount so as to correct it and reduce the developing potential. Is set to.

As described above, according to the present embodiment, the temperature of the fixing roller pair 34 is kept in the OFF state of the power source of the copying machine main body,
That is, since the developer is lowered in an approximately inverse proportion to the leaving time, the temperature of the fixing roller pair 34 when the power of the copying machine is turned on causes the developer to be left to a certain extent and the toner charge amount to a lower extent. I know what I did. Therefore, at the time of the above low duty, the power of the copying machine main body is turned off.
Even if the toner charge amount decreases over time, the power source is turned off.
The difference in image quality between before being turned on and after being turned on becomes small, and even if the amount of decrease in the toner charge amount varies due to the length of the OFF time of the power source, depending on the variation. By automatically setting the developing bias voltage
It is possible to prevent the image quality from varying and to stabilize the image quality according to the usage of the copying machine. Further, in this example, it is not necessary to provide a timer or the like for measuring the time of the OFF state when the power of the copying machine main body is OFF.

Specific Example 3 In this example, when the toner charge amount of the developer is reduced when the power of the copying machine main body is OFF as in the periods T2 and T3 of FIG. Based on the length of the power-off state period, that is, the degree of decrease in the toner charge amount due to leaving the developer, the mode setting control is performed to select and set the image forming mode when the developer is turned on thereafter. This is one of the concrete examples of the means. In this example, the length of the power-off period of the copying machine main body is set to the preheating mode setting time from when the copying machine is set to the preheating mode to when it is released, or when the copying machine is powered on. It is obtained from the rising time of the heater 4. The preheating mode setting time and the rising time are measured by a timer provided in the main body control unit 1b.

Hereinafter, description will be given based on the flowchart of the mode setting control 3 in FIG. First, it is judged whether or not the rising time of the heater 4 when the power of the copying machine main body is turned from the OFF state to the ON state or the preheating mode setting time is zero time (step 1). That is, in the case of the continuous run use mode in which the copying machine is almost in the ON state, the developing bias voltage in the continuous run mode defined in advance is set (step 2), and this flow chart ends.

On the other hand, when the usage mode is the low duty, the rise time or the preheating mode setting time is set in the main body control unit 1b in advance and stored in the storage unit 1c. It is compared with K _{1 to} Kn (steps 3, 5, 7). For example, in the comparison of step 3, when the rising time or the preheating mode setting time is shorter than K ₁ hour, the developing bias voltage L
₁ (V) is selected, and main body control unit 1b to I / O unit 1a
The developing bias control data is sent to the developing bias power source 6 via the developing bias power source 6, and the developing bias voltage applied from the developing bias power source 6 to the developing sleeve 41 at the time of image formation is L.
_The image forming mode such as ₁ (V) is set (step 4), and this flowchart ends.

In the comparison of the above step 3, if the rising time or the preheating mode setting time is K ₁ hour or more, proceed to the next step 5. Then, in the comparison of step 5, in the case where the rising time or the preheating mode setting time is K ₁ hour or more and shorter than K ₂ hours, the developing bias voltage L ₂ (V) is selected, and the main body control section 1b is selected. The developing bias control data is sent to the developing bias power source 6 through the I / O unit 1a, and the developing bias voltage applied from the developing bias power source 6 to the developing sleeve 41 during image formation is L ₂ (V). The image forming mode is set (step 6), and this flowchart ends.

Hereinafter, the reference comparison value K ₁ set in advance is set.
~ The above comparison is repeated up to n times corresponding to the number of Kn,
The image forming mode is set so that the optimum developing bias voltage is applied (steps 7 to 9), and the present flowchart ends.

The degree of reduction of the toner charge amount due to the developer being left for each range of the rise time or the preheat mode setting time, and the value of the developing bias voltage suitable for the lowered toner charge amount are as follows: It is obtained in advance by experiments or the like and stored in the storage unit 1c. Here, for example, when the toner charge amount decreases, the image density increases, so that the developing bias voltage is lowered according to the decrease amount of the toner charge amount so as to correct it and reduce the developing potential. Is set to.

As described above, according to the present embodiment, the rise time or the preheat mode setting time is equal to the O of the power source of the copying machine main body.
During the FF state, that is, the developer is left in a substantially inverse proportion to the time for which the developer is left. Therefore, depending on the temperature of the fixing roller pair 34 when the power source of the copying machine is turned on, how much the developer is left and the toner is charged. You can see how much the amount has decreased.
Therefore, at the low duty, even if the toner charge amount decreases during the OFF time of the power source of the copying machine main body or the preheating mode setting time, it is turned on before the power source is turned off or before the preheating mode is started and thereafter. The difference in image quality between after the preheating mode is released and after the preheating mode is released, and even if the amount of decrease in the toner charge amount varies due to the length of the power OFF time or the preheating time, By automatically setting the image forming process conditions according to the variations, it is possible to prevent the variations in the image quality and further to stabilize the image quality according to the usage mode of the copying machine.

[Specific Example 4] The past or expected future usage of the copying machine can be known or predicted from the total number of copies in the total ON time from the new state of the copying machine. can do. Therefore, in this example, a value (hereinafter referred to as Cth) obtained by dividing the total number of copies by the total ON time is obtained and used for the mode setting control.

Hereinafter, description will be given based on the flowchart of the mode setting control 4 in FIG. First, in the main body control unit 1b, the total number of copies input from the copy number counter 5 and the total ON time measured by a timer provided in the main body control unit 1b and stored in the storage unit 1c are used. , Cth is calculated, and Cth is compared with a preset reference value Ko for the continuous run mode (step 1). If Cth is larger than Ko,
The developing bias voltage in the continuous run mode defined in advance is set (step 2), and this flow chart ends.

On the other hand, when the usage mode is the above-mentioned low duty, in the main body control section 1b, the calculated value of Cth is set to a plurality of comparison reference values K _{1 to} Kn which are preset and stored in the storage section 1c. It is compared (steps 3 and 5). For example, in the comparison in step 3, when the calculated value of Cth is larger than K ₁ , the developing bias voltage L ₁ (V) is selected, and the developing bias power source 6 is supplied from the main body control unit 1b via the I / O unit 1a. developing bias control data is sent, the developing bias voltage applied to the developing sleeve 41 from a developing bias power source 6 at the time of image formation is set in the image forming mode such as a L ₁ (V) (step 4), book The flowchart ends.

In the comparison of step 3, if the calculated value of Cth is K ₁ or less, the process proceeds to the next step. Hereinafter, the comparison is repeated up to n times corresponding to the preset number of reference comparison values K _{1 to} Kn, and the image forming mode is set such that the optimum developing bias voltage is applied (step 5). ~ 7), this flow chart ends.

Incidentally, an apparent stable value of the toner charge amount of the developer with respect to each range of the calculated value of Cth,
And the value of the developing bias voltage suitable for the stable value are obtained in advance by experiments or the like and are stored in the storage unit 1c.
Here, for example, when Cth is changed and the toner charge amount is decreased, the image density is increased. Therefore, it is corrected according to the decrease amount of the toner charge amount so as to correct it and reduce the developing potential. And the developing bias voltage is set lower.

As described above, according to this example, the apparent stable value of the toner charge amount of the developer at the low duty is lowered unlike the stable value of the toner charge amount of the developer at the continuous run. Even in such a case, the developing bias voltage is set based on the calculated value of Cth so as to correct the change in the image quality due to the decrease in the toner charge amount.
It is possible to prevent the image density from becoming higher than a predetermined level and the reproducibility of the halftone image from deteriorating, and to stabilize the image quality. Further, at the time of the low duty, the image forming mode is selected and set more finely based on the past calculated value of Cth of the copying machine, so that the image quality according to the usage mode of the copying machine is further improved. Stabilization can be achieved.

[Embodiment 5] The past usage state of the copying machine or the expected usage state in the future can be known from the number of copies in the period from the present time of the copying machine to a predetermined H hours before, or Can be expected. Therefore, in this example, a value obtained by dividing the number of copies by the H time (hereinafter, Crh
(Referred to as (H)) and used for mode setting control.

Hereinafter, description will be given based on the flowchart of the mode setting control 5 in FIG. First, in the main body control unit 1b, the number of copies input from the copy number counter 5 and the period from the present time to the H hour before measured by the timer provided in the main body control unit 1b are used for the above Crh (H ) Is calculated and compared with Crh (H) and a preset reference value Ko for the continuous run mode (step 1). If Crh (H) is larger than Ko,
The developing bias voltage in the continuous run mode defined in advance is set (step 2), and this flow chart ends.

On the other hand, when the usage mode is the above-mentioned low duty, the calculated value of Crh (H) is set in the main body control section 1b in advance as a plurality of comparison reference values K ₁ stored in the storage section 1c. ~ Kn are compared (steps 3, 5).
For example, in the comparison of step 3, when the calculated value of Crh (H) is larger than K ₁ , the developing bias voltage L ₁ (V)
Is selected, the developing bias control data is sent from the main body control unit 1b to the developing bias power source 6 via the I / O unit 1a, and the developing bias voltage applied from the developing bias power source 6 to the developing sleeve 41 at the time of image formation is changed. The image forming mode such as L ₁ (V) is set (step 4), and this flowchart ends.

In the comparison of the above step 3, Crh (H)
If the calculated value of is less than or equal to K ₁ , proceed to the next step.
Hereinafter, the comparison is repeated up to n times corresponding to the preset number of reference comparison values K _{1 to} Kn, and the image forming mode is set such that the optimum developing bias voltage is applied (step 5). ~ 7), this flow chart ends.

For each range of the calculated value of Crh (H), the apparent stable value of the toner charge amount of the developer and the value of the developing bias voltage suitable for the stable value are:
It is obtained in advance by experiments or the like and stored in the storage unit 1c. Here, for example, when Crh (H) is changed and the toner charge amount is reduced, the image density is increased, so that the toner charge amount is reduced so as to correct it and reduce the development potential. The developing bias voltage is set to be low according to the amount. Further, the above-mentioned mode setting control can be performed every time a predetermined time elapses while the power of the copying machine main body is turned on.

As described above, according to this example, the apparent stable value of the toner charge amount of the developer at the low duty is lowered unlike the stable value of the toner charge amount of the developer at the continuous run. Even in such a case, the developing bias voltage is automatically set based on the calculated value of Crh (H) so as to correct the change in the image quality due to the decrease in the toner charge amount, so that the image density is It is possible to prevent the density from becoming higher than a predetermined level and the reproducibility of the halftone image from deteriorating, and to stabilize the image quality.

Further, at the time of the above low duty, the image forming mode is selected and set more finely based on the past calculated value of Crh (H) of the copying machine. It is possible to stabilize the image quality according to the above. For example, as shown by T1 in FIG. 2, the toner charge amount of the developer is gradually increased when the power source of the copying machine main body is turned on at the low duty. In such a case, the developing bias voltage can be set according to the change in the toner charge amount, and the image quality can be stabilized.

In this embodiment, in the above mode setting control, in order to suppress the change in image quality due to the change in toner charge amount, the developing bias power source 6 to the developing sleeve 4 are used.
1 has a plurality of image forming modes with different developing bias voltages applied to it, and controls so as to select and set an optimal developing bias voltage from among them, but as shown in the block diagram of FIG. It is configured to have a plurality of image forming modes in which a high voltage applied to the discharge wire or the grid electrode of the charger 21 by the charger power source 7 and the exposure amount of the document irradiation lamp 12 by the exposure controller 8 are different. Good.

Further, in the above-mentioned specific example 3, a timer having a backup power source that operates even when the power source of the copying machine main body is turned off is provided, and the time during which the power source is off is directly measured. Good.

Further, in the above-mentioned specific example 4, the total ON time from the new state of the copying machine is used to calculate the above Cth, but instead of this total ON time, from the new state of the copying machine. The total elapsed time of may be used.

Further, in the above-described specific example 1, the user manually inputs the CV from the user operation unit 2, but the CV may be automatically measured and calculated. Further, in the above-mentioned specific examples 3 to 5, the temperature of the fixing roller 34 when the copying machine is turned off / on, the rising time of the heater 4 of the fixing roller 34, the preheating mode setting time, and the total turning on of the copying machine from the new state. Value obtained by dividing the total number of copies by time (Ct
h), or a value (Crh (H)) obtained by dividing the number of copies within the time from the present time to H hours before is automatically measured and used for the above mode setting control. The user may manually input from the unit 2.

[0061]

According to the image forming apparatus of the first aspect, even when the usage mode is different such as the continuous run and the low duty, and the toner charge amount of the developer is different, the usage mode can be changed. The image forming mode suitable for the corresponding toner charge amount, that is, the image forming process condition is always set, so that the image density does not become higher than a predetermined density and the halftone reproducibility does not deteriorate, and it is stable. It is possible to obtain the desired image quality.

According to the image forming apparatus of claim 2, the mode setting control means sets the subsequent image forming mode based on the temperature of the fixing member when the power source of the image forming apparatus main body is turned on. With this configuration, the image forming mode can be set more finely, and in the above-mentioned low duty use mode, the difference in image quality between before the power is turned off and after it is turned on is small. Further, even if the amount of decrease in the toner charge amount varies due to the length of the power-off time, the image quality variation can be prevented by automatically setting the image forming process conditions according to the variation. The effect is that the stability of can be achieved. Further, there is also an effect that it is not necessary to provide a time measuring means for measuring the OFF time in a state where the power source is OFF in order to know the time when the developer is left.

According to the image forming apparatus of the third aspect, the mode setting control means is configured to set the subsequent image forming mode based on the rising time measured by the time measuring means. The image forming mode can be set finely, and the power source of the image forming apparatus main body is turned off in the above low duty use mode.
The difference in image quality between before the FF and after the ON is reduced, and even if the decrease amount of the toner charge amount varies due to the length of the OFF time of the power supply, the variation depends on the variation. By automatically setting the image forming process conditions, it is possible to prevent the image quality from varying and to stabilize the image quality. Also,
In order to know the time the developer is left unattended, the power supply
There is also an effect that it is not necessary to provide a time measuring means for measuring the OFF time in the FF state.

According to the image forming apparatus of the fourth aspect, the mode setting control means is provided so as to set the image forming mode when the preheating mode is released based on the preheating time measured by the timing means. By configuring, in the use mode of the low duty, the difference in image quality between before starting the preheating mode and after releasing the preheating mode is small, and the set time of the preheating mode is small. Even if there is a variation in the amount of decrease in the toner charge amount due to the length of the image, it is possible to prevent the variation in the image quality and further stabilize the image quality by automatically setting the image forming process conditions according to the variation. effective.

[Brief description of drawings]

FIG. 1 is a block diagram of mode setting control of a copying machine according to this embodiment.

FIG. 2 is a characteristic diagram showing a difference in a change in toner charge amount with time according to a usage mode of a copying machine.

FIG. 3 is a front view showing a schematic configuration of a copying machine according to the present embodiment.

FIG. 4 is a flowchart of mode setting control 1 according to the present embodiment.

FIG. 5 is a flowchart of mode setting control 2 according to the present embodiment.

FIG. 6 is a flowchart of mode setting control 3 according to the present embodiment.

FIG. 7 is a flowchart of mode setting control 4 according to the present embodiment.

FIG. 8 is a flowchart of mode setting control 5 according to the present embodiment.

[Explanation of symbols]

 1 mode setting control means 1a I / O section 1b main body control section 1c storage section 2 user operation section 3 fixing roller thermometer 4 heating heater 5 copy number counter 6 developing bias power supply 34 fixing roller pair 41 developing sleeve

Claims (4)

[Claims] 1. An image carrier, a latent image forming means for forming a latent image on the image carrier, and a two-component developer carried on the developer carrier are supplied onto the image carrier. An image forming apparatus having a developing device for visualizing the latent image, having a plurality of image forming modes in which image forming process conditions are set corresponding to a plurality of different toner charge amounts of the developer. A mode setting control means for selecting and setting any one of the plurality of image forming modes based on a past usage pattern of the image forming apparatus or an expected usage pattern in the future. Image forming apparatus. 2. A fixing member heated by heating means,
A fixing device for fixing the image transferred onto the transfer material and a temperature detecting means for detecting the temperature of the fixing member are provided, and the mode setting control means is used when the power source of the image forming apparatus main body is turned on. The image forming apparatus according to claim 1, wherein the setting of the image forming mode is changed based on the temperature of the fixing member. 3. A fixing member heated by heating means,
A fixing device for fixing the image transferred onto the transfer material; and a timer for measuring the rising time of the heating device until the fixing member reaches a predetermined temperature when the power source of the image forming apparatus main body is turned on. 2. The image forming apparatus according to claim 1, wherein the mode setting control means is configured to change the setting of the image forming mode based on the rising time measured by the time measuring means. 4. A preheating setting means for setting the image forming apparatus to a preheating mode which is a predetermined standby state, and a timing means for measuring a preheating mode setting time when the image forming apparatus is set to the preheating mode. 2. The image forming apparatus according to claim 1, further comprising: the mode setting control unit configured to change the setting of the image forming mode based on the preheating mode setting time measured by the time measuring unit. .