JP2011237467A - Image formation apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To lengthen a product life of a transfer roller in an image formation apparatus.SOLUTION: An image formation apparatus 1 includes a photoreceptor drum 40, a transfer roller 44, a high voltage power supply for transfer 39, an environment condition sensor 38, an environment history storage section 71, and a transfer bias control section 72. The environment condition sensor 38 measures environment information around the transfer roller 44. The environment history storage section 71 stores the environment information measured by the environment condition sensor 38 in an environment history information DB 82. The transfer bias control section 72 determines transfer bias that is applied from the high voltage power supply for transfer 39 to the transfer roller 44 on the basis of the latest environment information stored in the environment history information DB 82 and at least one piece of past environment information.

Description

  The present invention relates to an image forming apparatus, and more particularly to an electrophotographic image forming apparatus.

  2. Description of the Related Art An electrophotographic image forming apparatus such as a copying machine, a facsimile machine, or a multifunction machine includes a charger, an exposure device, a developing device, and a transfer device around a photosensitive drum. In such an image forming apparatus, the photosensitive drum is charged and further exposed to form an electrostatic latent image on the surface of the photosensitive drum. Thereafter, the electrostatic latent image is developed to form a toner image, and the toner image is further transferred onto a predetermined sheet.

Conventionally, a transfer roller made of a conductive resin has been used as the transfer device. However, the resistance value of the transfer roller made of conductive resin varies depending on environmental conditions such as temperature and humidity. Therefore, it is necessary to control the transfer bias applied to the transfer roller in accordance with a change in the environment in the image forming apparatus.
In view of this, an image forming apparatus has been proposed that estimates a resistance value of a transfer roller by applying a transfer bias to the transfer roller when a transfer operation is not performed, and predicts the value of the transfer bias. In such an image forming apparatus, a transfer bias value corresponding to an environmental change is determined by comparing the predicted transfer bias value with a transfer bias value estimated based on environmental information or the like (for example, , See Patent Document 1).

JP 2003-66743 A

  In Patent Document 1, as described above, in order to determine the value of the transfer bias corresponding to the environmental change, the transfer bias is applied to the transfer roller in a state where the transfer operation is not executed. However, since the number of operations of the transfer roller increases when a transfer bias is applied during a non-transfer operation, there has been a problem that the life of the transfer roller is shortened.

  An object of the present invention is to extend the life of a transfer roller in an image forming apparatus.

  Hereinafter, a plurality of modes will be described as means for solving the problems. These aspects can be arbitrarily combined as necessary.

An image forming apparatus according to an aspect of the present invention includes an image carrier, a transfer roller, a power supply unit, an environmental condition sensor, an environmental history storage unit, and a transfer bias control unit.
The image carrier carries an image made of a developer. The transfer roller transfers the developer on the image carrier onto the recording paper. The power supply unit applies a transfer bias to the transfer roller. The environmental condition sensor measures environmental information around the transfer roller. The environment history storage unit stores environment information measured by the environmental condition sensor in the environment history storage area. The transfer bias control unit determines a transfer bias to be applied from the power supply unit to the transfer roller based on the latest environment information stored in the environment history storage area and at least one past environment information.

As described above, the transfer bias controller is configured to transfer the transfer roller from the power supply unit based on the latest environment information and at least one past environment information measured by the environmental condition sensor and stored in the environment history storage area by the environment history storage unit. The transfer bias applied to the is determined.
Since the transfer bias is determined based on the environmental information stored in the environment history storage area in this way, it is not necessary to apply the transfer bias to the transfer roller during the non-transfer operation of the transfer roller. Accordingly, it is possible to prevent an increase in the number of operations of the transfer roller resulting from the application of the transfer bias to the transfer roller during the non-transfer operation, thereby extending the life of the transfer roller.
Further, the transfer bias is determined not only based on the latest environment information stored in the environment history storage area but also based on at least one past environment information. Here, “at least one past environment information” means at least one environment among the past environment information measured before the latest environment information and stored in the environment history storage area by the environment history storage unit. Information. As a result, it is possible to determine an optimum transfer bias corresponding to a change in the resistance value of the transfer roller caused by a change in physical properties of the transfer roller and surrounding environment.

  The environmental condition sensor may include a temperature detection sensor and a humidity detection sensor. Here, the environmental history storage unit stores environmental information including temperature and humidity measured by the temperature detection sensor and the humidity detection sensor in the environmental history storage area, and the transfer bias control unit stores environmental information including temperature and humidity. Based on this, the transfer bias may be determined.

  In the present invention, since the transfer bias is determined based on the latest environmental information and at least one past environmental information without applying the transfer bias during the non-transfer operation, the life of the transfer roller can be extended.

1 is a schematic diagram illustrating a configuration of a main body of an image forming apparatus. FIG. 3 is a schematic diagram illustrating a configuration of an image forming unit and its periphery. Block diagram showing functional configuration of image forming apparatus The figure which shows an example of an environment area | region table. The figure which shows an example of environmental history information DB. The figure which shows an example of a transfer bias table. 6 is a graph (part 1) illustrating an example of an environment change characteristic of a resistance value in a transfer roller. 6 is a graph (2) showing an example of an environmental change characteristic of a resistance value in a transfer roller. The flowchart which shows the control processing of an environmental condition sensor. 7 is a flowchart showing transfer bias determination processing.

(1) Overall Image Forming Apparatus The image forming apparatus 1 will be described with reference to FIGS. 1 and 2. FIG. 1 is a schematic diagram of the entire image forming apparatus according to the present embodiment. FIG. 2 is a schematic diagram illustrating the configuration of the image forming unit and its periphery. Hereinafter, in order to clarify the directional relationship in the image forming apparatus 1, the directions for the worker standing on the front surface (front side in FIG. 1) of the image forming apparatus 1 are defined as the left-right direction and the front-rear direction.

The image forming apparatus 1 includes an image reading device 2 and an image forming device main body 3.
The image reading apparatus 2 includes an image reading unit 21 and a document cover 22. The image reading unit 21 is a device that reads image data of a document, and is a so-called flatbed scanner. The image reading unit 21 includes a light source 23, a plurality of reflecting mirrors 24, and a scanner unit 25. In the image reading unit 21, the light irradiated and reflected from the light source 23 onto the original on the platen glass 26 is guided to the scanner unit 25 while being reflected by the plurality of reflecting mirrors 24. The document cover 22 is rotatably disposed on the image reading unit 21.

  The image forming apparatus main body 3 includes a housing 31, and an image forming unit 32, a fixing unit 33, a paper transport unit 34, a paper feed cassette 35, a manual paper feed tray 36, and a paper delivery provided inside the housing 31. A section 37, an environmental condition sensor 38, and a high-voltage power supply 39 for transfer.

  The image forming unit 32 forms an image on the paper P based on the image data of the original read by the image reading device 2 and the image data sent from the personal computer. The image forming unit 32 includes a photosensitive drum 40, a charger 41, an exposure head 42, a developing device 43, a transfer roller 44, and a cleaning roller 45.

  The photosensitive drum 40 is a cylindrical device that is provided with an electrostatic latent image formed on a surface thereof and is rotatably provided. The photosensitive drum 40 is rotated counterclockwise in FIGS. 1 and 2 about a rotation axis perpendicular to the paper surface direction of FIGS. 1 and 2 by a driving device (not shown). The charger 41, the exposure head 42, the developing device 43, the transfer roller 44, and the cleaning roller 45 are provided in this order in the rotation direction of the photosensitive drum 40.

The charger 41 uniformly charges the surface of the photosensitive drum 40. The charger 41 is, for example, a corona discharge type device. A predetermined charging voltage is applied to the charger 41 by a charging voltage application circuit (not shown).
The exposure head 42 draws an electrostatic latent image along the image data by irradiating the surface of the charged photosensitive drum 40 with light. The exposure head 42 includes, for example, an LED (Light Emitting Diode) as a light source.

The developing device 43 supplies toner to the electrostatic latent image on the photosensitive drum 40 and develops the electrostatic latent image.
As shown in FIG. 2, the developing device 43 includes a developing device main body 50, a developing roller 51, a supply roller 52, a first toner chamber 53, a second toner chamber 54, and a first agitation disposed in the developing device main body 50. A member 55, a second stirring member 56, a blade 57, and a toner end sensor 58 are provided.

The developing roller 51 is rotatably disposed at a position in the developing device main body 50 and in contact with the photosensitive drum 40. The rotation axis of the developing roller 51 is parallel to the rotation axis of the photosensitive drum 40.
A predetermined developing voltage is applied to the developing roller 51 by a developing voltage applying circuit (not shown). The developing roller 51 supplies the toner received from the supply roller 52 to the photosensitive drum 40 and develops the latent image on the photosensitive drum 40 with the toner.
The supply roller 52 is rotatably disposed at a position in the developing device main body 50 and in contact with the developing roller 51. A predetermined supply voltage is applied to the supply roller 52 by a development voltage application circuit (not shown). The supply roller 52 supplies the toner stored in the first toner chamber 53 to the developing roller 51.

The first toner chamber 53 and the second toner chamber 54 store toner replenished from a toner cartridge 60 that is detachably attached to the developing device main body 50. The first stirring member 55 and the second stirring member 56 are provided in each of the first toner chamber 53 and the second toner chamber 54 and send the toner toward the supply roller 52 while stirring the toner.
The blade 57 is in elastic contact with the outer peripheral surface of the developing roller 51 and makes the thickness of the toner layer attached to the outer peripheral surface of the developing roller 51 uniform. A predetermined bias voltage is applied to the blade 57 by a development voltage application circuit (not shown).
The toner end sensor 58 is provided at the bottom of the first toner chamber 53 and monitors the remaining amount of toner in the first toner chamber 53.

The transfer roller 44 is a conductive sponge rubber roller in which a rubber layer is formed on a conductive core material. The transfer roller 44 is disposed to face the photosensitive drum 40 and transfers the toner image on the photosensitive drum 40 onto the paper P. A transfer bias determined by the transfer bias controller 72 is applied to the transfer roller 44 from a high-voltage power supply 39 for transfer, which will be described in detail later.
The cleaning roller 45 removes the toner remaining on the photosensitive drum 40 after the transfer.

  The fixing unit 33 includes a heating roller and a pressure roller. The fixing unit 33 fixes the toner image on the paper P by applying heat and pressure to the paper P after the transfer.

  The paper transport unit 34 includes a transport path and a plurality of rollers. The paper transport unit 34 transports the paper P along the transport path by rollers, so that a paper discharge unit passes through the image forming unit 32 and the fixing unit 33 from a paper feed cassette 35 or a manual paper feed tray 36 described later. Up to 37, the paper P is conveyed.

The paper feed cassette 35 accommodates a bundle of paper P before image formation. The paper feed cassette 35 is provided so as to be able to be taken in and out of the housing 31.
The manual paper feed tray 36 has a manual paper feed function for special paper such as backing paper.
The paper discharge unit 37 is a part for discharging the paper P on which an image is formed. The paper discharge unit 37 is provided on the upper surface of the housing 31.

The environmental condition sensor 38 is disposed in the vicinity of the transfer roller 44 and measures environmental information around the transfer roller 44. The environmental condition sensor 38 is connected to a printer control unit 70 described later, and its operation is controlled by the sensor control unit 73. The measurement result by the environmental condition sensor 38 is stored in the environmental history information DB 82 of the memory unit 80 by the environmental history storage unit 71.
The environmental condition sensor 38 in this embodiment includes a temperature detection sensor 381 and a humidity detection sensor 382. The temperature detection sensor 381 measures the temperature around the transfer roller 44. The humidity detection sensor 382 measures the relative humidity around the transfer roller 44.

  A high-voltage power supply 39 for transfer as a power supply unit applies a transfer bias to the transfer roller 44. A printer control unit 70 is connected to the transfer high-voltage power supply 39, and the operation is controlled by the transfer bias control unit 72. Further, the transfer bias applied to the transfer roller 44 is determined by the transfer bias controller 72.

(2) Configuration of Control System of Image Forming Apparatus The configuration of the control system of the image forming apparatus 1 will be described with reference to FIG. FIG. 3 is a block diagram illustrating a functional configuration of the image forming apparatus.
As shown in FIG. 3, the image forming apparatus 1 includes an operation unit 90, a printer control unit 70, a memory unit, in addition to the image reading unit 21, the image forming unit 32, the environmental condition sensor 38, and the transfer high-voltage power supply 39 described above. 80 and a timer 91 are provided.

  The operation unit 90 is configured with a hard key or the like for inputting various instructions to the image forming apparatus 1.

  The printer control unit 70 includes, for example, a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory). The CPU can execute various programs and execute programs. The ROM stores programs and data necessary for the CPU to operate. The RAM stores temporary data and a program created when the program is executed. When the CPU reads and executes a program in a recording medium such as a ROM, various functions of the printer control unit 70 are realized, and each unit constituting the image forming apparatus 1 is controlled. Note that the control of each unit constituting the image forming apparatus 1 may be performed by, for example, an MPU instead of being performed by the CPU.

The memory unit 80 is a storage area configured by, for example, an HDD.
The timer 91 operates regardless of the image forming processing operation, and is constituted by a clock circuit, for example. A printer control unit 70 is connected to the timer 91. The sensor control unit 73 of the printer control unit 70 controls the environmental condition sensor 38 so as to measure environmental information at intervals of a timer value to be described later based on the time signal output from the timer 91. Further, the transfer bias controller 72 acquires the environmental information measured by the environmental condition sensor 38 based on the timer up signal output from the timer 91 at the same timer value interval.

  Since the printer control unit 70 performs processing based on data in the memory unit 80, the memory unit 80 will be described first, and then each functional unit of the printer control unit 70 will be described.

(2-1) Memory Unit The memory unit 80 includes an environment area table 81, an environment history information DB 82, a transfer bias table 83, and a timer value storage area 84. The memory unit 80 is not limited to the HDD, and may be a RAM.

(2-1-1) Environment Area Table The environment area table 81 is a table showing the relationship between temperature, relative humidity, and absolute humidity, as shown in FIG. FIG. 4 is a diagram illustrating an example of the environment area table. In FIG. 4, the vertical axis represents relative humidity, and the horizontal axis represents temperature. In addition, the absolute humidity calculated in advance from the relative humidity and the temperature is expressed by a region number that is an integer value of 1 to 13 assigned for each section using a known mathematical formula or the like. For example, if the temperature is 19 ° C. and the relative humidity is 20%, the absolute humidity is indicated by the area number “4”.

(2-1-2) Environmental history information DB
In the environment history information DB 82, the environment information acquired by the environmental condition sensor 38 is stored in time series by the environment history storage unit 71. In the environment history information DB 82 in the present embodiment, the environment information is stored in association with at least the measurement time of the environment information and the area number corresponding to the environment information.
The environment history information DB 82 will be described with reference to FIG. FIG. 5 is a diagram illustrating an example of the environment history information DB. In this example, one record includes a record number, time, temperature and relative humidity as environment information, and an area number.

The record number is an arbitrary number that identifies each record. The time is the time when the environmental information is measured by the environmental condition sensor 38. The temperature is the temperature around the transfer roller 44 measured by the temperature detection sensor 381. The relative humidity is the relative humidity around the transfer roller 44 measured by the humidity detection sensor 382. The area number indicates the absolute humidity corresponding to the environmental information measured by the environmental condition sensor 38 and is a number acquired from the environmental area table 81 described above.
FIG. 5 shows an example in which the environment information with the record number 33 is stored as the latest environment information. The environmental information to which the record number 33 is attached has a temperature of 19 ° C. and a relative humidity of 20%, and is associated with T33 as the measurement time and “4” as the area number. As described above, FIG. 5 shows an example in which new environment information is sequentially written under the table. However, this is only an example, and other modes may be used as long as the temperature and relative humidity as environment information, the measurement time, and the region number are associated with each other and shown in time series.

(2-1-3) Transfer Bias Table The transfer bias table 83 stores area numbers and transfer bias in association with each other. The transfer bias table 83 will be described with reference to FIG. FIG. 6 is a diagram illustrating an example of the transfer bias table.
The area number is an area number indicated in the environment area table 81 and is represented by an integer value of 1 to 13. The transfer bias is a value of a transfer current applied from the transfer high-voltage power supply 39 to the transfer roller 44. The transfer current value corresponds to each of the absolute humidity indicated by the region number so that an appropriate transfer bias can be applied to the transfer roller 44 according to a change in the resistance value of the transfer roller 44 due to a change in the surrounding environment. It is a set value. The transfer current value corresponding to the area number is changed depending on the type of the transfer roller 44 and the type of paper used. Accordingly, the transfer current value is set according to the type of the transfer roller 44 and the type of paper, for example, at the start of use of the image forming apparatus 1 or when the transfer roller 44 is replaced, and is stored in the transfer bias table 83.
Here, for convenience of explanation, the transfer current value of the transfer bias is indicated by “A” to “M”. However, actually, the transfer current value (μA) set in accordance with the type of the transfer roller 44 and the type of paper is stored in the transfer bias table 83.

(2-1-4) Timer Value Storage Area The timer value storage area 84 stores a timer value used for controlling the environmental condition sensor 38. The timer value is a value indicating the measurement interval of the environmental condition sensor 38. Based on the time signal output from the timer 91, the sensor control unit 73 causes the environmental condition sensor 38 to measure ambient environmental information at intervals of the timer value stored in the timer value storage area 84. Further, the transfer bias controller 72 acquires the environmental information measured by the environmental condition sensor 38 based on the timer up signal output from the timer 91 at the same timer value interval.

  The timer value stored in the timer value storage area 84 is preferably changed according to the type of the transfer roller 44, for example. This is because the resistance value of the transfer roller 44 changes according to the surrounding environment, but the change characteristics vary depending on the type of transfer roller as shown in FIGS. 7A and 7B. FIG. 7A and FIG. 7B are graphs showing an example of the environmental change characteristic of the resistance value in the transfer roller. Specifically, FIGS. 7A and 7B show environmental change characteristics of the resistance value of the transfer roller when the surrounding environment changes from a low temperature and low humidity environment (LL) to a high temperature and high humidity environment (HH). 7A and 7B, the vertical axis represents the resistance value of the transfer roller, and the horizontal axis represents time.

As shown in FIG. 7A, in a certain transfer roller, the resistance value changes abruptly according to the change in the ambient environment from LL to HH. For a transfer roller having such an environment change characteristic, it is preferable to set the timer value short and shorten the measurement interval of environmental information by the environmental condition sensor 38.
Further, as shown in FIG. 7B, in a certain transfer roller, the resistance value gradually changes according to the change in the ambient environment from LL to HH. For the transfer roller having such an environmental change characteristic, in order to save power consumption due to the operation of the environmental condition sensor 38, the timer value is set long and the measurement interval of the environmental information by the environmental condition sensor 38 is lengthened. It is preferable to do.

Therefore, when the environmental change characteristic of the resistance value of the transfer roller is known in advance, a timer value corresponding to the environmental change characteristic of the resistance value of the transfer roller is set and stored in the timer value storage area 84.
On the other hand, when the environmental change characteristic of the resistance value of the transfer roller is unknown, for example, a timer value based on the environmental change per unit time may be set and stored in the timer value storage area 84 as described later. Good.

(2-2) Printer Control Unit Next, the printer control unit 70 will be described. As shown in FIG. 3, the printer control unit 70 includes an environment history storage unit 71, a transfer bias control unit 72, and a sensor control unit 73.

(2-2-1) Environmental History Storage Unit When the environmental condition sensor 38 measures the environmental information under the control of the sensor control unit 73, the environmental history storage unit 71 acquires the environmental information measured by the environmental condition sensor 38, The acquired environment information is stored in the environment history information DB 82 in time series. Specifically, the environment history storage unit 71 acquires environment information measured by the environmental condition sensor 38 and acquires an area number corresponding to the measured environment information from the environment area table 81. Subsequently, the environment history storage unit 71 associates the acquired environment information with the measurement time and area number of the environment information and writes them in the environment history information DB 82 in time series.
For example, when the temperature acquired from the environmental condition sensor 38 is 19 ° C. and the relative humidity is 20%, the environmental history storage unit 71 refers to the environmental region table 81 and acquires the region number “4”. Then, a record number 33 is attached to the bottom of the environment history information DB 82 shown in FIG. 5 in association with the temperature 19 ° C. and the relative humidity 20%, which is environment information, the measurement time T33 and the region number “4”. Write.

(2-2-2) Transfer Bias Control Unit The transfer bias control unit 72 is based on the latest environment information stored in the environment history information DB 82 by the environment history storage unit 71 and at least one past environment information. A transfer bias applied from the power source 39 to the transfer roller 44 is determined. The transfer bias controller 72 controls the operation of the transfer high-voltage power supply 39.

When determining the transfer bias, the transfer bias controller 72 first determines whether or not a predetermined number or more of environment information is stored in the environment history information DB 82, that is, the environment information stored in the environment history information DB 82 is equal to or more than a predetermined number of records. Monitor whether it is.
The predetermined number may be at least two or more including the latest environment information and at least one past environment information. Here, the at least one past environmental information is at least one environmental information among the past environmental information measured before the latest environmental information and stored in the environmental history information DB 82 by the environment history storage unit 71. That means. Here, an example in which the predetermined number is three is given below. Also, an example will be described in which the transfer bias is determined based on three pieces of environmental information that are continuous in time series. However, the three pieces of environmental information may not be continuous in time series as long as they include the latest environmental information and past environmental information.

  When three or more pieces of environment information are stored in the environment history information DB 82, the transfer bias control unit 72 is based on three pieces of environment information including the latest environment information and two pieces of past environment information. Determine the transfer bias.

The determination of the transfer bias will be described again with reference to FIG. When the latest environment information is the environment information of the record number 33, the transfer bias control unit 72 acquires the area numbers corresponding to the environment information of the record number 33, the record number 32, and the record number 31 from the environment history information DB 82. . Here, the transfer bias control unit 72 acquires the region numbers “4”, “6”, and “8”.
When the three area numbers are acquired, the transfer bias controller 72 calculates an average value of the three area numbers. Here, since the region numbers are “4”, “6”, and “8”, “6” that is the average value of these region numbers is calculated. When the calculated average value is a numerical value including a decimal point, the portion after the decimal point is rounded down.

After calculating the average value “6” of the area numbers, the transfer bias control unit 72 refers to the transfer bias table 83 to acquire a transfer current value corresponding to the average value, and determines that value as the transfer bias. In the transfer bias table 83 shown in FIG. 6, since it is “F”, which is the transfer current value corresponding to the average value “6”, “F” is acquired as the transfer current value, and that value is determined as the transfer bias.
Thereafter, the transfer bias controller 72 controls the transfer high-voltage power supply 39 so as to apply the transfer current “F” of the transfer bias to the transfer roller 44.

  As described above, by determining the transfer bias based on the environment information stored in the environment history information DB 82 by the environment history storage unit 71, it is possible to appropriately select the transfer bias according to the surrounding environmental conditions without applying the transfer bias during the non-transfer operation. Transfer bias can be determined. Accordingly, since it is not necessary to apply a transfer bias during the non-transfer operation of the transfer roller 44, the number of operations of the transfer roller 44 can be reduced and the life of the transfer roller 44 can be extended.

Further, by determining the transfer bias based on not only the latest environment information but also three pieces of environment information including two pieces of past environment information, the transfer roller 44 caused by changes in physical properties of the transfer roller 44 and the surrounding environment. It is possible to determine the optimum transfer bias corresponding to the change in the resistance value.
That is, since the transfer roller 44 is a conductive sponge rubber roller in which a rubber layer is formed on a conductive core material, its resistance value is changed according to the surrounding environmental conditions as described above. However, the resistance value does not change immediately under the influence of changes in ambient environmental conditions. For example, even if the surrounding environmental conditions change abruptly, the resistance value of the transfer roller 44 starts to change in response to changes in the environmental conditions after a predetermined time. Further, the resistance value of the transfer roller 44 is different when the surrounding environment changes from the high temperature and high humidity state to the latest environmental condition and when the surrounding environment changes from the low temperature and low humidity state to the latest environmental condition.
Therefore, in this embodiment, the transfer bias is determined using not only the current environment information but also the past environment information. As a result, a more appropriate transfer bias can be applied to the transfer roller 44 corresponding to the change in the physical properties of the transfer roller 44 and the surrounding environmental conditions.

(2-2-3) Sensor Control Unit The sensor control unit 73 is connected to the environmental condition sensor 38 at intervals of the timer value stored in the timer value storage area 84 based on the time signal output from the timer 91. Control to measure environmental information.
For example, when the timer value is to be changed when the transfer roller 44 is replaced, the sensor control unit 73 can newly set the timer value and store it in the timer value storage area 84.

  The operation control of the environmental condition sensor 38 by the sensor control unit 73 will be described with reference to FIG. FIG. 8 is a flowchart showing control processing of the environmental condition sensor.

  The sensor control unit 73 accepts a timer value change request in step S1. The timing of the timer value change request is arbitrarily determined, and may be, for example, when the transfer roller 44 is replaced, at a certain time interval, or when environmental information is measured by the environmental condition sensor 38.

If it is determined in step S1 that there is a timer value change request (Yes in step S1), the sensor control unit 73 sets a new timer value in steps S2 to S6 and stores it in the timer value storage area 84. Let
First, if there is already a timer value to be changed in step S2, the sensor control unit 73 receives the timer value. For example, when the environmental change characteristic of the resistance value of the transfer roller 44 is already known when the transfer roller 44 is replaced, and the timer value corresponding to the environmental change characteristic is known in advance, the timer value An input is received through the operation unit 90, for example. Thereafter, the sensor control unit 73 stores the received timer value in the timer value storage area 84 in step S3.

If there is no timer value to be changed in step S2, the sensor control unit 73 sets the timer value. Hereinafter, an example in which a timer value is set based on a change in temperature per unit time will be described.
First, in step S <b> 4, the sensor control unit 73 reads θ _i−1 and θ _i as the latest two temperature values and T _i−1 and Ti that are the measurement times from the environment history information DB 82. Next, in step S5, the sensor control unit 73 calculates Δθ, which is the difference between θ _i−1 and θ _i, and ΔT, which is the difference between T _i−1 and T _i . After calculating Δθ and ΔT, in step S6, the sensor control unit 73 calculates Δθ / ΔT, calculates a temperature change per unit time, and sets a timer value corresponding to the calculated temperature change. Thereafter, the process proceeds to step S 3, where the sensor control unit 73 stores the set timer value in the timer value storage area 84.

  In this example, after Δθ and ΔT are calculated, Δθ / ΔT is calculated and the timer value is set based on a change in temperature per unit time. However, the value of Δθ / ΔT may be stored in advance in the lookup table, and the timer value may be set by referring to it. Further, a timer value may be set based on a change in relative humidity per unit time.

(2-3) Transfer Bias Determination Processing Hereinafter, transfer bias determination processing by the printer controller 70 will be described with reference to FIG. FIG. 9 is a flowchart showing the transfer bias determination process.

In step S10, it waits for the timer 91 to be up.
When the timer 91 is up (Yes in step S10), the environmental history storage unit 71 of the printer control unit 70 acquires the environmental information measured by the environmental condition sensor 38 under the control of the sensor control unit 73 in step S11. To do.
Next, the environment history storage unit 71 acquires an area number corresponding to the environment information acquired in step S <b> 12 from the environment area table 81.
After acquiring the area number from the environment area table 81, the environment history storage unit 71 stores the acquired environment information in the environment history information DB 82 in time series in step S13. Specifically, the environment history storage unit 71 associates the environment information including the measured temperature and relative humidity, the measurement time of the environment information, and the acquired area number, and attaches the record number to the environment history information DB 82. Write in chronological order.

The transfer bias controller 72 of the printer controller 70 monitors whether or not the number of environment information stored in the environment history information DB 82, that is, the number of records of environment information is equal to or greater than a predetermined number (hereinafter referred to as N). . If the number of environmental information is N or more (Yes in step S14), the process proceeds to step S15. If the number of environmental information is N or less (No in step S14), the process returns to step S10.
In step S15, the transfer bias controller 72 updates the latest environment information stored in the environment history information DB 82 and N-1 pieces of past environment information among the environment information stored before the latest environment information. N region numbers respectively corresponding to. When the N area numbers are acquired, the transfer bias controller 72 calculates an average value R of the N area numbers in step S16.

Next, in step S17, the transfer bias controller 72 refers to the transfer bias table 83, acquires a transfer current value corresponding to the average value R, and determines that value as the transfer bias.
When the transfer bias is determined in step S17, the process returns to step S10.

(3) Features Features of the above-described embodiment will be described.
The image forming apparatus 1 according to the present embodiment includes a photosensitive drum 40, a transfer roller 44, a transfer high-voltage power supply 39, an environmental condition sensor 38, an environment history storage unit 71, and a transfer bias control unit 72. Prepare.
The photosensitive drum 40 carries an image made of a developer. The transfer roller 44 transfers the developer on the photosensitive drum 40 to a recording sheet. The transfer high-voltage power supply 39 applies a transfer bias to the transfer roller 44. The environmental condition sensor 38 measures environmental information around the transfer roller 44. The environment history storage unit 71 stores the environment information measured by the environmental condition sensor 38 in the environment history information DB 82. The transfer bias controller 72 determines the transfer bias applied to the transfer roller 44 from the transfer high-voltage power supply 39 based on the latest environment information and at least one past environment information stored in the environment history information DB 82.

Here, the transfer bias controller 72 determines a transfer bias applied to the transfer roller 44 from the high-voltage power supply 39 for transfer based on the latest environment information stored in the environment history information DB 82 and at least one past environment information. To do.
Since the transfer bias is determined based on the environment information stored in the environment history information DB 82 as described above, it is necessary to apply the transfer bias to the transfer roller 44 during the non-transfer operation of the transfer roller 44 in order to determine the transfer bias. Absent. Accordingly, it is possible to prevent an increase in the number of operations of the transfer roller 44 resulting from the application of the transfer bias to the transfer roller 44 during the non-transfer operation, thereby extending the life of the transfer roller 44.
Further, the transfer bias is determined based on the latest environment information stored in the environment history information DB 82 and at least one past environment information. Accordingly, it is possible to determine an optimum transfer bias corresponding to a change in the resistance value of the transfer roller 44 caused by a change in physical properties of the transfer roller 44 and the surrounding environment.

  The environmental condition sensor 38 includes a temperature detection sensor 381 and a humidity detection sensor 382. Here, the environment history storage unit 71 stores environment information including the temperature and humidity measured by the temperature detection sensor 381 and the humidity detection sensor 382 in the environment history storage DB 82. The transfer bias controller 382 determines the transfer bias based on environmental information including temperature and humidity.

(4) Other Embodiments Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications can be made without departing from the scope of the invention. In particular, a plurality of embodiments and modifications described in this specification can be arbitrarily combined as necessary.

(A) In the above embodiment, the image forming apparatus having both the image reading apparatus 2 and the image forming unit 32 has been described. However, the present invention is not limited to this, and may be an image forming apparatus that does not have the image reading apparatus 2. Further, the image forming apparatus may be a multifunction machine having a facsimile function, a communication function, and the like.

(B) In the above embodiment, the process of calculating the average value R obtained by averaging the region numbers and determining the transfer bias has been described as an example. However, the present invention is not limited to this. For example, the transfer bias may be determined by adding three region numbers.
Specifically, a transfer bias table in which a transfer current value corresponding to the total value of the three area numbers is set is prepared. Then, the transfer bias controller 72 may acquire a transfer current value corresponding to the total value of the three area numbers from the transfer bias table and determine it as a transfer bias.

(C) In the above embodiment, an example in which the transfer bias is determined based on the area number stored in the environment history information DB 82 has been described. However, the environment information may be stored in the environment history information DB 82 without being associated with the area number.
Further, instead of the transfer bias table 83, a table in which the temperature and relative humidity are associated with the transfer current value that is optimum for the environmental information having the temperature and relative humidity may be prepared. In this case, the transfer bias control unit 72 acquires a predetermined number or more of temperatures and relative humidity stored in the environment history information DB 82, calculates an average value of each temperature and relative humidity, and a transfer current corresponding to the average value. The transfer bias may be determined by obtaining a value from the above table.

(D) The transfer bias controller 72 may not always perform the transfer bias determination process during the operation of the transfer roller 44. For example, it may be performed only when the image forming unit 32 starts the image forming process from the sleep state. Further, when the image forming unit 32 performs a continuous printing operation and the environmental temperature around the transfer roller 44 has already reached the high temperature region, the transfer bias determination process need not be performed.

(E) The timer value may be set by calculating the rate of change per time of the resistance value of the transfer roller 44 due to a change in the surrounding environment. In this case, a resistance value measuring device for measuring the resistance value of the transfer roller 44 and a region for storing the resistance value measured by the resistance value measuring device may be further provided. And the sensor control part 73 may calculate the change of the resistance value per unit time from the transition of the resistance value measured by the resistance value measuring device, and may determine the timer value based on the calculation result.

  The present invention can be applied to an electrophotographic image forming apparatus such as a copying machine, a printer, a facsimile machine, and a multifunction machine.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 3 Image forming apparatus main body 31 Case 32 Image forming part 33 Fixing part 34 Paper conveyance part 35 Paper feed cassette 36 Manual paper feed tray 37 Paper discharge part 38 Environmental condition sensor 381 Temperature detection sensor 382 Humidity detection sensor 39 Transfer High-voltage power supply (power supply)
40 Photosensitive drum (image carrier)
41 Charging Device 42 Exposure Head 43 Developing Device 44 Transfer Roller 45 Cleaning Roller 70 Printer Control Unit 71 Environmental History Storage Unit 72 Transfer Bias Control Unit 73 Sensor Control Unit 80 Memory Unit 81 Environmental Area Table 82 Environmental History Information DB (Environmental History Storage Area) )
83 Transfer bias table 91 Timer

Claims (2)

An image carrier that carries an image made of a developer;
A transfer roller for transferring the developer on the image carrier to a recording sheet;
A power supply for applying a transfer bias to the transfer roller;
An environmental condition sensor for measuring environmental information around the transfer roller;
An environmental history storage unit that stores environmental information measured by the environmental condition sensor in an environmental history storage area;
A transfer bias controller for determining a transfer bias applied to the transfer roller from the power supply unit based on the latest environment information stored in the environment history storage area and at least one past environment information;
An image forming apparatus comprising: The environmental condition sensor includes a temperature detection sensor and a humidity detection sensor,
The environmental history storage unit stores environmental information including temperature and humidity measured by the temperature detection sensor and the humidity detection sensor in the environmental history storage area,
The image forming apparatus according to claim 1, wherein the transfer bias control unit determines a transfer bias based on environmental information including temperature and humidity.

Images