JP4085819B2 - Image forming apparatus and image forming method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electrophotographic image forming apparatus in which an imaging unit that includes at least a developing device and performs image formation is attached to and detached from a main body. The present invention also relates to an image forming method in such an image forming apparatus.
[0002]
In this specification, the image forming apparatus includes a printer, a FAX (facsimile) apparatus, an MFP (multifunctional peripheral device), etc., and is a color type, a monochrome type, a stand-alone type, or connected to a network. Whether or not
[0003]
[Prior art]
Conventionally, this type of image forming apparatus includes a predicting unit that predicts toner consumption based on density information included in an image signal, and a test toner formed on a photoconductor under a certain image forming condition. Means for detecting the image density of the image to estimate the toner density in the developer, and calculating a difference between the toner density estimated by the estimation means and a predetermined reference toner density, and the prediction means There has been proposed a method in which the toner consumption is determined by correcting the predicted toner consumption (see, for example, Patent Document 1).
[0004]
A theoretical value calculating means for calculating a theoretical value of the amount of toner to be replenished from the toner hopper to the developer tank; and a means for detecting an actual value of the replenished toner amount based on the theoretical value. Based on the measured value and the measured value, there has been proposed one that corrects the driving time of the replenishing means for replenishing toner (see, for example, Patent Document 2).
[0005]
[Patent Document 1]
JP-A-8-248760 (Claim 1)
[Patent Document 2]
Japanese Patent Laid-Open No. 11-202604 (Claim 1)
[0006]
[Problems to be solved by the invention]
By the way, in recent image forming apparatuses, for the purpose of reuse of resources, for example, an image carrier, a charger, an exposure device, a developing device, a transfer unit, a cleaning unit, and a toner reservoir are integrated as an imaging unit. In some cases, the imaging unit is attached to and detached from the image forming apparatus main body.
[0007]
However, in the above conventional technique, process conditions (development bias value, etc.) are set regardless of individual variations (including variations in developer characteristics) of the imaging unit. For this reason, when the imaging unit is replaced, there is a problem that the toner density in the developing device becomes too high or too low due to individual variations of the imaging unit. For example, when an imaging unit is used in which the density of an image to be formed (this is simply referred to as “image density”) is difficult to increase, the image density is difficult to increase, so that excessive toner is supplied. As a result, the toner density in the developing device is kept high, which causes a problem that fog and dust increase. On the other hand, when using an imaging unit or the like in which the image density tends to be high, the toner density in the developing device is kept low, so that the total amount of developer is reduced and the supply to the developing roller is uniform. This causes a problem that the image is lost and an image defect occurs.
[0008]
If a toner concentration detection sensor is provided to manage the toner concentration in the developing device, the above problem can be avoided. However, providing a toner concentration detection sensor increases the cost.
[0009]
SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus and an image forming method capable of stabilizing the toner density and improving the image quality without using a high-cost toner density detection sensor.
[0010]
[Means for Solving the Problems]
  In order to solve the above problem, an image forming apparatus according to claim 1 is provided.
  An image forming apparatus in which an imaging unit that includes at least a developing device and performs image formation is attached to and detached from a main body,
  An imaging unit loading detector for detecting that the imaging unit is loaded on the main body;
  A development bias output variable section that variably sets the development bias output for the developing unit of the imaging unit;
  An image density detector for detecting an image density of an image formed by the imaging unit;
  An environment information acquisition unit that acquires environment information representing the environment in which the main body exists;
  A storage unit that prestores characteristic candidate information representing a pattern or a general relational expression in which a reference characteristic representing a correspondence relationship between the development bias output and the image density changes according to the environment information;
  According to the detection result indicating that the imaging unit is loaded, the imaging unitBased on the output of the detection result of the density of the image by the image density detection unit.A correspondence information acquisition unit for acquiring correspondence information indicating a correspondence relationship between the development bias output for the developing device and the image density;
  Based on the correspondence information acquired by the correspondence information acquisition unit and the environment information acquired by the environment information acquisition unit at the time of acquisition of the correspondence information, a reference characteristic obtained from the characteristic candidate information stored in the storage unit As a reference characteristic when the imaging unit is loadedEquipped with a reference characteristic setting section to set,
  The development bias output variable unit obtains a reference characteristic at the time of image formation based on the reference characteristic at the time of loading the imaging unit and the environment information acquired by the environment information acquisition unit at the time of image formation, and the reference at the time of image formation Set development bias output based on characteristicsIt is characterized by that.
[0011]
Here, the phrase “loaded” with respect to the main body of the imaging unit includes a case where the imaging unit is initially loaded or a case where it is loaded by replacement. The imaging unit loaded in the main body may be not only a new product but also a reuse product.
[0012]
The “reference characteristic” is determined by, for example, the slope of the straight line and the threshold value at which the image density rises when the development bias output value and the image density have a substantially linear (linear) correspondence.
[0013]
  The reference characteristic setting section“From the characteristic candidate information stored in the storage unit” to obtain the reference characteristicIn order tothe aboveOne reference characteristic may be selected from a plurality of reference characteristics (candidate characteristics) stored in advance in the storage unit based on the environment information at the time of obtaining the correspondence information, or under the environment represented by the environment information. The correspondence relationship between the development bias output and the image density in FIG.
[0014]
  In the image forming apparatus of the present invention, when the imaging unit is loaded in the main body, the correspondence information acquisition unit is configured to detect the imaging unit loading detection unit according to the detection result indicating that the imaging unit is loaded.Based on the output of the detection result of the density of the image by the image density detection unit.Correspondence information representing the correspondence between the development bias output to the developing device and the image density is acquired. Then, the reference characteristic setting unitBased on the correspondence information acquired by the correspondence information acquisition unit and the environment information acquired by the environment information acquisition unit at the time of acquisition of the correspondence information, a reference characteristic obtained from the characteristic candidate information stored in the storage unit As a reference characteristic when the imaging unit is loadedSet.The development bias output variable unit obtains a reference characteristic at the time of image formation based on the reference characteristic at the time of loading the imaging unit and the environment information acquired by the environment information acquisition unit at the time of image formation, and the reference at the time of image formation The development bias output is set based on the characteristics.
[0015]
  Therefore, the aboveAt the time of image formationBased on the reference characteristics, the developing bias output variable unit can set the developing bias output for the developing device in accordance with the density of the image to be formed (this is called “target image density”). With the development bias output set as described above, toner is supplied to the developing device by a predetermined toner supply unit (for example, a known toner hopper) so that the image density by the imaging unit matches the target image density. Alternatively, the drive time of the toner replenishing unit is controlled so that the toner density in the developing device becomes constant according to the detection result of a predetermined print amount detection unit (for example, that detects density information included in the image signal). To do. As a result, even when the imaging unit is replaced, it is possible to set conditions so as to cancel out variations in the individual imaging units during image formation. Therefore, the toner density can be stabilized and the image quality can be improved.
[0016]
In the present invention, among the elements included in the imaging unit, a developer composed of toner and carrier and having a toner density suitable for image formation (referred to as “starter”) is replaced. It works particularly effectively in cases.
[0017]
  According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the developing bias output variable unit is configured to generate the image at the time of image formation.,A developing bias output for the developing device is set according to a target image density.
[0018]
  In the image forming apparatus according to claim 2, the developing bias output variable section,A developing bias output for the developing device is set according to the target image density. As a result, the toner density can be stabilized as described above, and the image quality can be improved.
[0019]
  According to a third aspect of the present invention, in the image forming apparatus according to the first aspect, the image forming apparatus further includes a durability information acquisition unit that acquires information regarding durability of the image forming apparatus, and the development bias output variable unit includes the durability According to the information aboutReference characteristics at the time of image creationChange the coefficientRukoAnd features.
[0020]
The “durability” information of the image forming apparatus includes a wide variety of factors that change the “correspondence between the developing bias output to the developing device and the image density”.
[0021]
  In the image forming apparatus according to the third aspect, the durability information acquisition unit acquires information regarding the durability of the image forming apparatus. Then, the development bias output variable unit responds to the information on the durability.Reference characteristics at the time of image creationChange the coefficientTheTherefore, even if the actual “correspondence between the development bias output to the developing device and the image density” changes as a result of, for example, long-term use of the image forming apparatus, the development bias output always changes according to the change. Set appropriately. Therefore, the image quality can be maintained.
[0022]
According to a fourth aspect of the present invention, there is provided the image forming apparatus according to the second aspect, wherein a toner replenishing unit that supplies toner as a developer component to the developer and an image density by the imaging unit is a target. A control unit is provided for driving the toner replenishing unit so as to match the image density or based on the output of the print amount detection unit for detecting the print amount so that the toner density in the developing device becomes constant. And
[0023]
According to another aspect of the image forming apparatus of the present invention, the controller controls the toner in the developer so that the image density by the imaging unit matches the target image density or based on the output of the print amount detection unit that detects the print amount. The toner replenishing unit is driven so that the density becomes constant. Therefore, the effect that the toner density can be stabilized and the quality of the image can be improved is specifically obtained.
[0024]
  The image forming method according to claim 5 is an image forming method in an image forming apparatus in which an imaging unit that includes at least a developing device and performs image formation is attached to and detached from the main body.
  Characteristic candidate information representing a pattern or a general relational expression in which a reference characteristic representing a correspondence relationship between the development bias output and the image density changes according to the environment information is stored in the storage unit in advance.
  Detecting that the imaging unit is loaded into the main body,
  According to the detection result indicating that the imaging unit is loaded, the imaging unitOutput images with multiple development bias outputsLet meThe density of the image is detected, and based on the density detection result,Acquires correspondence information indicating the correspondence between the development bias output to the developer and the image densityAnd
  Obtain environment information representing the environment in which the image forming apparatus exists,
  Based on the environmental information and the correspondence information, the reference characteristic obtained from the characteristic candidate information stored in the storage unit is used as the reference characteristic when the imaging unit is loaded.SettingAnd
  At the time of image formation, environmental information representing the environment in which the image forming apparatus exists is acquired, and reference characteristics at the time of image formation are obtained based on the environment information and the reference characteristics at the time of loading the imaging unit. Set development bias output based on reference characteristicsIt is characterized by that.
[0025]
  According to the image forming method of claim 5, when the imaging unit is loaded on the main body, the imaging unit is selected according to a detection result indicating that the imaging unit is loaded.Output images with multiple development bias outputsLet meThe density of the image is detected, and based on the density detection result,Acquires correspondence information indicating the correspondence between the development bias output to the developer and the image densityAt the same time, environment information representing the environment in which the image forming apparatus exists is acquired.AndBased on the environmental information and the correspondence information, the reference characteristic obtained from the characteristic candidate information stored in the storage unit is used as the reference characteristic when the imaging unit is loaded.Set.At the time of image formation, environment information representing the environment in which the image forming apparatus exists is acquired, and reference characteristics at the time of image formation are obtained based on the environment information and the reference characteristics at the time of loading the imaging unit. The development bias output is set based on the reference characteristics.
[0026]
  Therefore, the aboveAt the time of image formationBased on the reference characteristics, the development bias output to the developing device can be set by the development bias output variable unit according to the target image density. With the development bias output set as described above, toner is supplied to the developing device by a predetermined toner supply unit (for example, a known toner hopper) so that the image density by the imaging unit matches the target image density. Alternatively, the drive time of the toner replenishing unit is controlled so that the toner density in the developing device becomes constant according to the detection result of a predetermined print amount detection unit (for example, that detects density information included in the image signal). To do. As a result, even when the imaging unit is replaced, it is possible to set conditions so as to cancel out variations in the individual imaging units during image formation. Therefore, the toner density can be stabilized and the image quality can be improved.
  In another aspect, the image forming apparatus of the present invention provides:
  An image forming apparatus in which an imaging unit that includes at least a developing device and performs image formation is attached to and detached from a main body,
  An imaging unit loading detector for detecting that the imaging unit is loaded on the main body;
  A development bias output variable section for variably setting a plurality of development bias outputs to the developing unit of the imaging unit;
  An image density detector for detecting an image density of an image formed by the imaging unit;
  An environment information acquisition unit that acquires environment information representing the environment in which the main body exists;
  Under a plurality of environments, a storage unit that stores a pattern representing a correspondence relationship between the development bias output to the developing device and the image density for each environment;
  By operating the imaging unit in accordance with a detection result indicating that the imaging unit is loaded under a certain environment, the development bias output variable unit is configured to variably set a plurality of development bias outputs, thereby storing the memory. A correspondence information acquisition unit for acquiring a pattern representing a correspondence relationship between the development bias output for the developing unit and the image density based on the pattern stored in the unit;
  A reference characteristic setting unit that sets the pattern as a reference characteristic under the environment represented by the environmental information at the time of pattern acquisition,
  The development bias output variable unit shifts the reference characteristic according to the difference between the environment information representing the environment at the time of image formation and the environment information at the time of pattern acquisition at the time of image formation. Based on this, the developing bias output to the developing device is set according to the target image density.
[0027]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the illustrated embodiments.
[0028]
FIG. 1 schematically shows a cross-sectional structure of an electrophotographic image forming apparatus according to an embodiment. The image forming apparatus is roughly divided into a main body 100 having a box-like outer shape, and an imaging unit 20 that is detachably mounted on the main body 100. FIG. 1 shows a state in which the imaging unit 20 is loaded on the main body 100.
[0029]
In this example, the imaging unit 20 includes an image carrier 1, a charging unit 2, a developing device 8, an image density sensor 5, a transfer unit 6, a cleaning unit 9, and a toner reservoir that are sequentially arranged around the image carrier 1. 11 and the EEPROM 10 are integrally combined. In this example, the image carrier 1 is composed of a photosensitive drum. The charging unit 2 includes a charging roller for uniformly charging the surface of the image carrier 1. The developing device 8 forms an image (toner image) on the surface of the image carrier 1 using a developer composed of toner and carrier by a developing roller 4 that rotates counterclockwise in the drawing. The image density sensor 5 detects the density (image density) of an image formed on the surface of the image carrier 1 as an image density detection unit. The transfer unit 6 includes a transfer roller, and transfers an image onto a sheet supplied between the image carrier 1 and the transfer unit 6. The cleaning unit 9 has a cleaning blade and cleans the surface of the image carrier 1. A toner hopper 12 serving as a toner replenishing portion made of a spiral screw member is provided below the toner reservoir 11. By driving the toner hopper 12, toner is supplied from the toner reservoir 11 to the developing device 8 as a component of the developer. The EEPROM 10 stores unit history information (including new product information) representing the history of the imaging unit 20.
[0030]
  The main body 100 includes a control unit 90 including a CPU (Central Processing Unit) that controls the operation of the entire apparatus, and a paper supply unit (not shown) that supplies paper between the image carrier 1 and the transfer unit 6 described above. An exposure unit 3 that irradiates the surface of the image carrier 1 with a laser beam corresponding to an image signal, and an environmental sensor as an environmental information acquisition unit30And a power supply unit (not shown) for supplying a necessary voltage (power supply) to each unit including the developing roller 4. Environmental sensor30Acquires temperature and humidity as environment information representing the environment in which the main body 100 (that is, the present image forming apparatus) exists, and outputs the data to the control unit 90.In addition, in a storage unit (not shown), characteristic candidate information (described later) representing a pattern in which a reference characteristic representing a correspondence relationship between the development bias output and the image density changes according to environmental information or a general relational expression is stored. .
[0031]
This image forming apparatus performs image formation (image formation) by executing a known electrophotographic process including a charging step, an exposure step, a development step, and a transfer step according to control by the control unit 90. Specifically, the surface of the image carrier 1 is first charged to a uniform potential by the charging unit 2 while rotating the image carrier 1 clockwise (indicated by an arrow in the drawing). Subsequently, the surface of the image carrier 1 is exposed by the exposure unit 3 according to an image signal (representing an image to be formed), and an electrostatic latent image is formed there. Subsequently, the electrostatic latent image is developed by the developing device 4 to form an image (toner image) on the surface of the image carrier 1. The formed image is transferred by the transfer unit 6 to a sheet supplied between the image carrier 1 and the image. The toner remaining on the surface of the image carrier 1 without being transferred is cleaned by the cleaning unit 9.
[0032]
When the imaging unit 20 is loaded into the main body 100, the control unit 90 operates as an imaging unit loading detection unit, acquires unit history information from the EEPROM 10 mounted on the imaging unit 20, and the imaging unit 20 It is detected that the main body 100 is loaded. Here, the unit history information represents the history of the imaging unit 20, and includes new information indicating that the imaging unit 20 is new. The control unit 90 determines that “the imaging unit 20 has been loaded into the main body 100” when a new or reusable imaging unit 20 is loaded for the first time or when it is loaded by replacement.
[0033]
The control unit 90 functions as a development bias output variable unit, and variably sets the development bias output Vb for the developing device 8 of the imaging unit 20. The set value of the development bias output Vb is stored in a Vb table described later. The developing bias output Vb set by the control unit 90 is applied to the developing device 8 via the power supply unit (not shown).
[0034]
FIG. 2 shows a processing flow in the image forming apparatus when a new imaging unit 20 is loaded into the main body 100.
[0035]
First, when a new imaging unit 20 is loaded into the main body 100, the control unit 90 acquires unit history information from the EEPROM 10 mounted on the imaging unit 20, and the new imaging unit 20 is loaded into the main body 100. On the other hand, it is detected that it has been loaded (S21).
[0036]
When it is detected that the imaging unit 20 is loaded, the control unit 90 operates as the correspondence information acquisition unit and operates the imaging unit 20 to perform image formation. At this time, the control unit 90 variably sets a plurality of development bias outputs Vb for the developing device 8 according to the values stored in the Vb table, and is formed on the surface of the image carrier 1 by each development bias output Vb. The density of the obtained image (image density) is acquired according to the output of the image density sensor 5. As a result, correspondence information representing the correspondence relationship between the value stored in the Vb table (that is, the development bias output Vb for the developing device 8) and the image density at the development bias output Vb is acquired (S22).
[0037]
On the other hand, the control unit 90 acquires environmental information (including humidity) at the time of acquiring the correspondence information from the environmental sensor 30 (S23).
[0038]
  And the control part 90 works as a reference | standard characteristic setting part, and limits the correspondence information with the environmental information at the time of the correspondence information acquisition.When the imaging unit is loadedReference characteristics are set (S24).At this time, the control unit 90 refers to the patterns shown in FIG. 3A to FIG. 3E as the characteristic candidate information.
[0039]
3A to 3E, the relative humidity, which is one of the environments of this apparatus, is 75% or more, 60 to 75%, 40 to 60%, 25 to 40%, or 25% or less, respectively. In this case, various patterns (candidate characteristics) assumed for the reference characteristics are shown. The reference characteristic is determined by the slope of the straight line and the threshold value at which the image density rises because the development bias output Vb value and the image density have a substantially linear (linear) correspondence. For example, as shown in FIG. 3 (a), in an environment where the relative humidity is 75% or more, a characteristic such as (1) (indicated by a thin solid line) with a large slope and a small threshold value, and (2) (medium thickness) A characteristic with a small slope / threshold value such as (3) (represented by a thick solid line) and a characteristic (4) (represented by a thin broken line) A characteristic with a large slope and a medium threshold value, a characteristic with a medium slope and a medium threshold value such as (5) (represented by a medium-thick broken line), and a characteristic with a small gradient such as (6) (represented by a thick broken line) Characteristics with a medium threshold value, large slope such as (7) (represented by a thin one-dot chain line) and characteristics with a large threshold value, and characteristics such as (8) (indicated by a one-dot chain line having a medium thickness) Nine types of patterns are assumed: characteristics with a large threshold and characteristics with a small slope and a large threshold, such as {circle over (9)} (represented by a thick one-dot chain line). In this example, as the pattern moves from FIG. 3A to FIG. 3E, that is, as the relative humidity decreases, the slope of the straight line gradually decreases and the threshold value gradually increases as the entire pattern. In this example, the patterns in FIGS. 3A to 3E are stored in a storage unit (not shown).
[0040]
In this example, the control unit 90 selects one of the patterns in FIGS. 3A to 3E as the reference characteristic. For example, when the relative humidity is 50% and the slope of the correspondence relationship between the value of the developing bias Vb table and the image density is large (closest to {circle around (1)}), the pattern (tilt) of {circle around (1)} in FIG. Level and threshold level) are selected as reference characteristics.
[0041]
FIG. 4 shows a flow corresponding to FIG. 2 in the processing during normal image formation using the imaging unit 20 loaded in the main body 100.
[0042]
First, the control unit 90 acquires the current environmental information (including the humidity) from the environmental sensor 30 (including humidity) (S41).
[0043]
Next, the control unit 90 operates as a development bias output variable unit, and sets the target image density based on the current environment information and the reference characteristics (tilt level and threshold level) acquired when the imaging unit is loaded (S42). Accordingly, the developing bias output Vb for the developing device 8 is set (S43). For example, if the reference characteristic acquired when the imaging unit is loaded is the pattern (1) in FIG. 3C, and the current relative humidity is 65%, the relative humidity is 60 to 75% in FIG. Shift to select the pattern (1) in FIG. Then, the value of the developing bias output Vb corresponding to the target image density is set on the pattern (1) in FIG.
[0044]
At the same time, the control unit 90 sets the value of the voltage Vc applied to the charging unit 2. This Vc value is set such that the surface potential of the image carrier 1 has a certain potential difference with respect to the set developing bias Vb value.
[0045]
In this way, an image forming operation is performed in a state where the developing bias Vb for the developing device 8 and the applied voltage Vc to the charging unit 2 are set.
[0046]
Thereafter, for example, the output of the image density sensor 5 is detected at a frequency of once for the image formation of five sheets (S44). Then, the toner hopper 12 is driven to supply toner from the toner reservoir 11 to the developing device 8 so that the actual image density matches the target image density. For example, when the actual image density is lower than the target image density, the toner hopper 12 is driven.
[0047]
As a result, even when the imaging unit is replaced, it is possible to set conditions so as to cancel out variations in the individual imaging units during image formation. Therefore, the toner density can be stabilized and the image quality can be improved.
[0048]
FIG. 5 shows another flow of processing during normal image formation using the imaging unit 20 loaded on the main body 100.
[0049]
First, as in the example of FIG. 4 described above, current (normal image forming) environment information is acquired (S51), and based on the reference characteristics (inclination level and threshold level) acquired when the imaging unit is loaded (S52). ), A developing bias output Vb for the developing device 8 and an applied voltage Vc to the charging unit 2 are set (S53).
[0050]
In this example, during the image forming operation, the control unit 90 functions as a print amount detection unit, counts density information included in the image signal, and detects the print amount (S54). A toner consumption amount is predicted based on the print amount detection result, and toner is replenished by the toner hopper 12 (S55). The toner replenishment amount is controlled by the driving time of the toner hopper 12.
[0051]
Further, for example, every time the accumulated value (cumulative density information) of the counted printing amount reaches 10 images on the entire surface, the output of the image density sensor 5 is detected once (S56). When the actual image density is higher than the target image density, the driving time of the toner hopper 12 for the density information counted from the image signal is shortened. If the actual image density is lower than the target image density, the driving time of the toner hopper 12 for the density information counted from the image signal is lengthened (S57).
[0052]
As a result, even when the imaging unit is replaced, it is possible to set conditions so as to cancel out variations in the individual imaging units during image formation. Therefore, the toner density can be stabilized and the image quality can be improved.
[0053]
FIG. 6 shows another flow of processing in the image forming apparatus when a new imaging unit 20 is loaded into the main body 100.
[0054]
First, as in the example of FIG. 2 described above, when a new imaging unit 20 is loaded on the main body 100, the controller 90 determines that the new imaging unit 20 is loaded on the main body 100. Is detected (S61). Then, the correspondence information acquisition unit operates the imaging unit 20 in accordance with the detection result indicating that the imaging unit 20 is loaded, and indicates the correspondence between the development bias output Vb for the developing device 8 and the image density. Information is acquired (S62). On the other hand, the control unit 90 acquires environmental information (including humidity) at the time of acquiring the corresponding information from the environmental sensor 30 (S63).
[0055]
Then, in order to limit the correspondence information with the environment information at the time of obtaining the correspondence information and set the reference characteristics, the control unit 90 sets the development bias output Vb and the image under the environment represented by the environment information in this example. The correspondence relationship with the density is formulated by calculation (S64).
[0056]
  Here, since the development bias output Vb value and the image density are in a substantially linear (linear) correspondence relationship, the mathematical expression representing the reference characteristic is generallyAs characteristic candidate informationIt is represented by the following formula (1).
[0057]
Y = AX + B (1)
[0058]
Here, Y is the toner adhesion amount acquired by the image density detection sensor 5, and X is the developing bias Vb table (value). A and B are coefficients.
[0059]
The coefficient A is expressed by the following equation (2).
[0060]
A = Ao × (relative humidity / 50) / EXP (−0.002K) (2)
[0061]
Here, K is the number of printed sheets as information relating to durability, and 1K is set to 1000 (the value of K is 0 when a new product is loaded).
[0062]
The coefficients to be set are Ao and B according to equations (1) and (2). The value of B is determined from the relationship between the acquired development bias Vb table and the image density. Further, the value of Ao is determined from the relative humidity at the time of obtaining the correspondence information based on the equation (2).
[0063]
In this way, the control unit 90 formulates the correspondence relationship between the development bias output Vb and the image density under the environment represented by the environment information by calculation.
[0064]
FIG. 7 shows a flow corresponding to FIG. 6 in the normal image forming process using the imaging unit 20 loaded in the main body 100.
[0065]
First, the current environmental information (at the time of normal image formation) is acquired (S71), and based on the reference characteristics (formula coefficients Ao, B) acquired when the imaging unit is loaded (S72), the development bias output Vb for the developing unit 8 and An applied voltage Vc to the charging unit 2 is set (S73).
[0066]
Specifically, the A value is obtained by the equation (2) from the coefficient Ao acquired when the imaging unit is loaded, and the relative humidity and durability information K during normal image formation. Furthermore, from the A value and the coefficient B acquired when the imaging unit is loaded, the X value for setting the target image density Y, that is, the developing bias Vb value (Vb table) is set by Equation (1).
[0067]
Thereafter, as in FIG. 5 described above, during the image forming operation, the control unit 90 operates as a print amount detection unit, counts density information included in the image signal, and detects the print amount (S74). . A toner consumption amount is predicted based on the print amount detection result, and toner is replenished by the toner hopper 12 (S75). The toner replenishment amount is controlled by the driving time of the toner hopper 12.
[0068]
Further, for example, every time the accumulated value (cumulative density information) of the counted printing amount reaches 10 images on the entire surface, the output of the image density sensor 5 is detected once (S76). When the actual image density is higher than the target image density, the driving time of the toner hopper 12 for the density information counted from the image signal is shortened. If the actual image density is lower than the target image density, the driving time of the toner hopper 12 for the density information counted from the image signal is lengthened (S77).
[0069]
As a result, even when the imaging unit is replaced, it is possible to set conditions so as to cancel out variations in the individual imaging units during image formation. Therefore, the toner density can be stabilized and the image quality can be improved. In addition, in this example, the developing bias output Vb is variably set by changing the A value included in the reference characteristic equation at the time of image formation according to the information K relating to the durability of the image forming apparatus. Even if the actual “correspondence between the developing bias output Vb for the developing device 8 and the image density” changes as a result of, for example, the image forming apparatus being used for a long period of time, the developing bias output Vb is always appropriate according to the change Is set. Therefore, the image quality can be maintained.
[0070]
In this embodiment, toner replenishment corresponds to the case where the development system is a two-component system, but the portion other than the toner supply may be a single component.
[0071]
The configuration of the imaging unit 20 is not limited to this embodiment. It may be a combination with other elements.
[0072]
The image carrier 1 described above may be a photosensitive belt, an intermediate transfer member, a transfer carrier, or the like, instead of the photosensitive drum. The charging unit 2 may be a charging magnetic brush, a charging belt, a charging corona charger / scorotron charger, a charging brush, a charging film, or the like instead of the charging roller. The transfer unit 6 may be a transfer belt, a transfer corona charger, a transfer brush, or the like instead of the transfer roller.
[0073]
The toner replenishing unit is not limited to the toner hopper, and other methods may be used.
[0074]
Further, the manner in which the control unit 90 detects that “the imaging unit 20 has been loaded into the main body 100” is not limited to that of the present embodiment. Instead of the EEPROM 10, the unit history information may be stored in an IC chip to which an antenna is connected, and the control unit 90 may perform wireless communication to acquire the unit history information from the IC chip without contact. Further, a fuse may be provided in the imaging unit 20, and new product information may be expressed by whether or not the fuse is blown.
[0075]
Moreover, what the environmental sensor 30 detects as environmental information is not restricted to temperature and humidity, Other environmental factors may be included, and the detection method is not limited.
[0076]
Further, the information on durability is not limited to the number of printed sheets K, and may be information on other consumable elements.
[0077]
【The invention's effect】
As is clear from the above, according to the image forming apparatus and the image forming method of the present invention, it is possible to stabilize the toner concentration and improve the image quality without using a high-cost toner concentration detection sensor.
[Brief description of the drawings]
FIG. 1 is a diagram schematically showing an overall configuration of an image forming apparatus according to an embodiment of the present invention.
FIG. 2 is a diagram illustrating a processing flow in the image forming apparatus when a new imaging unit is loaded in the main body.
FIG.
FIGS. 3A to 3E show that the relative humidity, which is one of the environments of the apparatus, is 75% or more, 60 to 75%, 40 to 60%, 25 to 40%, or 25% or less, respectively. It is a figure which shows the various patterns (property characteristic) by which the reference | standard characteristic is assumed in the case.
FIG. 4 is a diagram illustrating a flow corresponding to FIG. 2 in a process during normal image formation using an imaging unit loaded in the main body.
FIG. 5 is a diagram showing another flow corresponding to FIG. 2 in the processing at the time of normal image formation using the imaging unit loaded in the main body.
FIG. 6 is a diagram showing another flow of processing in the image forming apparatus when a new imaging unit is loaded in the main body.
FIG. 7 is a diagram illustrating a flow corresponding to FIG. 6 in a process during normal image formation using an imaging unit loaded in the main body.
[Explanation of symbols]
1 Image carrier
5 Image density sensor
8 Developer
11 Toner reservoir
12 Toner Hopper
30 Environmental sensor
90 Control unit

Claims (6)

An image forming apparatus in which an imaging unit including at least a developing device and performing image formation is attached to and detached from a main body,
An imaging unit loading detector for detecting that the imaging unit is loaded on the main body;
A development bias output variable section that variably sets the development bias output for the developing unit of the imaging unit;
An image density detector for detecting an image density of an image formed by the imaging unit;
An environment information acquisition unit that acquires environment information representing the environment in which the main body exists;
A storage unit that prestores characteristic candidate information representing a pattern or a general relational expression in which a reference characteristic representing a correspondence relationship between the development bias output and the image density changes according to the environment information;
According to the detection result indicating that the imaging unit is loaded, the imaging unit outputs an image with a plurality of development bias outputs, and based on the output of the density detection result of the image by the image density detection unit , A correspondence information acquisition unit for acquiring correspondence information representing a correspondence relationship between the development bias output to the developing device and the image density;
Based on the correspondence information acquired by the correspondence information acquisition unit and the environment information acquired by the environment information acquisition unit at the time of acquisition of the correspondence information, a reference characteristic obtained from the characteristic candidate information stored in the storage unit Is provided with a reference characteristic setting unit for setting as a reference characteristic when the imaging unit is loaded ,
The development bias output variable unit obtains a reference characteristic at the time of image formation based on the reference characteristic at the time of loading the imaging unit and the environment information acquired by the environment information acquisition unit at the time of image formation, and the reference at the time of image formation An image forming apparatus, wherein a development bias output is set based on characteristics . The image forming apparatus according to claim 1,
The developing bias output variable section sets a developing bias output for the developing device according to a target image density at the time of image formation. The image forming apparatus according to claim 1,
A durability information acquisition unit that acquires information regarding durability of the image forming apparatus is provided.
The developing bias output variables are, the image forming apparatus, wherein the benzalkonium changing the coefficients including the reference characteristic during the image formation in accordance with the information on the endurance. The image forming apparatus according to claim 2.
A toner replenishing section for supplying toner as a developer component to the developing device;
The toner replenishing unit is driven so that the image density by the imaging unit matches the target image density, or based on the output of the print amount detection unit that detects the print amount, so that the toner concentration in the developing device becomes constant. An image forming apparatus comprising a control unit. An image forming method in an image forming apparatus in which an imaging unit including at least a developing device and performing image formation is attached to and detached from a main body,
Characteristic candidate information representing a pattern or a general relational expression in which a reference characteristic representing a correspondence relationship between the development bias output and the image density changes according to the environment information is stored in the storage unit in advance.
Detecting that the imaging unit is loaded into the main body,
According to the detection result indicating that the imaging unit is loaded, the imaging unit outputs an image with a plurality of development bias outputs , detects the density of the image, and based on the detection result of the density, the developing unit acquires the correspondence information representing the correspondence between the developing bias output and the image density with respect to,
Obtain environment information representing the environment in which the image forming apparatus exists,
Based on the environmental information and the correspondence information, the reference characteristic obtained from the characteristic candidate information stored in the storage unit is set as the reference characteristic when the imaging unit is loaded ,
During image formation, acquires the environment information indicating an environment in which the image forming apparatus exists, it determined Me a reference characteristic during image formation based on the reference characteristic at the time of environmental information and the imaging unit loading, during the image formation A developing bias output is set based on the reference characteristics of the image forming method. An image forming apparatus in which an imaging unit that includes at least a developing device and performs image formation is attached to and detached from a main body,
An imaging unit loading detector for detecting that the imaging unit is loaded on the main body;
A development bias output variable unit configured to variably set a plurality of development bias outputs for the developing unit of the imaging unit;
An image density detector for detecting an image density of an image formed by the imaging unit;
An environment information acquisition unit that acquires environment information representing the environment in which the main body exists;
Under a plurality of environments, a storage unit that stores a pattern representing a correspondence relationship between the development bias output to the developing device and the image density for each environment;
By operating the imaging unit in accordance with a detection result indicating that the imaging unit is loaded under a certain environment, the development bias output variable unit is configured to change and set a plurality of development bias outputs. A correspondence information acquisition unit that acquires a pattern representing a correspondence relationship between the development bias output to the developer and the image density based on the pattern stored in the unit;
A reference characteristic setting unit that sets the pattern as a reference characteristic under the environment represented by the environmental information at the time of pattern acquisition,
The development bias output variable unit shifts the reference characteristic according to the difference between the environment information representing the environment at the time of image formation and the environment information at the time of pattern acquisition at the time of image formation. An image forming apparatus characterized in that, based on a target image density, a developing bias output for the developing device is set.

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