JP7625967B2 - Image forming device, image forming condition adjustment method - Google Patents

Description

The present invention relates to an electrophotographic image forming apparatus and a method for adjusting image forming conditions performed in the image forming apparatus.

Image forming devices are known that form images using a developer containing toner and a carrier. In this type of image forming device, an adjustment process may be performed to adjust image formation conditions such as the development bias voltage applied to the development roller. For example, an image forming device is known that acquires the charge amount of the toner and determines whether or not the timing to perform the adjustment process has arrived based on the acquired charge amount of the toner (see Patent Document 1). In this image forming device, a measurement toner image is formed, and the charge amount of the toner is acquired based on the detection result of the density of the measurement toner image.

JP 2020-34799 A

However, when the measurement toner image is formed to determine whether the timing for performing the adjustment process has arrived, the toner is consumed accordingly.

The object of the present invention is to provide an image forming device and an image forming condition adjustment method that can determine whether the timing has arrived to perform an adjustment process to adjust image forming conditions without consuming toner.

An image forming apparatus according to one aspect of the present invention includes an image carrier, a developing member, a detection processing unit, and a judgment processing unit. An electrostatic latent image is formed on the image carrier. The developing member is provided opposite the image carrier and transports a developer containing toner and a carrier to an area facing the image carrier. The detection processing unit detects a non-developing current that flows when a specific electric field that moves the toner toward the developing member is formed in the facing area where the developer is present. The judgment processing unit judges whether or not the timing for performing an adjustment process to adjust image formation conditions has arrived based on the non-developing current detected by the detection processing unit.

An image formation condition adjustment method according to another aspect of the present invention is executed by an image forming apparatus including an image carrier on which an electrostatic latent image is formed, and a developing member that is disposed opposite the image carrier and transports a developer containing toner and a carrier to an opposing area with the image carrier, and includes the following detection step and judgment step. In the detection step, a non-development current that flows when a specific electric field that moves the toner toward the developing member is formed in the opposing area where the developer is present is detected. In the judgment step, it is judged whether or not the timing for performing an adjustment process to adjust the image formation conditions has arrived based on the non-development current detected by the detection step.

According to the present invention, it is possible to determine whether the timing has come to perform an adjustment process to adjust image formation conditions without consuming toner.

FIG. 1 is a cross-sectional view showing the configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a block diagram showing a system configuration of the image forming apparatus according to the embodiment of the present invention. FIG. 3 is a cross-sectional view showing the configuration of an image forming unit of the image forming apparatus according to the embodiment of the present invention. FIG. 4 is a cross-sectional view taken along the line IV-IV in FIG. FIG. 5 is a flowchart showing an example of an image forming condition adjustment process executed in the image forming apparatus according to the embodiment of the present invention. FIG. 6 is a block diagram showing a system configuration of an image forming apparatus according to another embodiment of the present invention.

The following describes an embodiment of the present invention with reference to the attached drawings. Note that the following embodiment is an example of the present invention and does not limit the technical scope of the present invention.

[Configuration of image forming apparatus 100]
First, the configuration of an image forming apparatus 100 according to an embodiment of the present invention will be described with reference to FIGS.

For ease of explanation, the vertical direction in the installed state (as shown in FIG. 1) in which the image forming device 100 can be used is defined as the up-down direction D1. The left side of the paper surface of the image forming device 100 shown in FIG. 1 is defined as the front (front face) as the front direction D2. The left-right direction D3 is defined based on the front face of the image forming device 100 in the installed state.

The image forming device 100 is a multifunction device that has multiple functions, such as a scanning function for reading an image of an original document, a printing function for forming an image based on image data, a fax function, and a copy function. The present invention may also be applied to image forming devices such as printers, fax machines, and copy machines that are capable of forming images using an electrophotographic method.

As shown in FIG. 1 and FIG. 2, the image forming device 100 includes an ADF (Auto Document Feeder) 1, an image reading unit 2, an image forming unit 3, a paper feed unit 4, an operation display unit 5, a memory unit 6, and a control unit 7.

The ADF1 transports documents to be read by the scanning function. The ADF1 includes a document setting section, multiple transport rollers, a document holder, and a paper ejection section.

The image reading unit 2 realizes the scanning function. The image reading unit 2 includes a document table, a light source, multiple mirrors, an optical lens, and a CCD (Charge Coupled Device).

The image forming unit 3 realizes the printing function. Specifically, the image forming unit 3 forms a color or monochrome image on a sheet supplied from the paper feed unit 4 according to an electrophotographic method.

The paper feed unit 4 supplies sheets to the image forming unit 3. The paper feed unit 4 includes a paper feed cassette, a manual feed tray, and multiple transport rollers.

The operation display unit 5 is a user interface of the image forming device 100. The operation display unit 5 has a display unit such as a liquid crystal display that displays various information in response to control instructions from the control unit 7, and an operation unit such as operation keys or a touch panel that inputs various information to the control unit 7 in response to user operations.

The storage unit 6 is a non-volatile storage device. For example, the storage unit 6 is a storage device such as a non-volatile memory such as a flash memory or an EEPROM (registered trademark), an SSD (Solid State Drive), or an HDD (Hard Disk Drive).

The control unit 7 performs overall control of the image forming apparatus 100. As shown in FIG. 2, the control unit 7 includes a CPU 11, a ROM 12, and a RAM 13. The CPU 11 is a processor that executes various arithmetic processes. The ROM 12 is a non-volatile storage device in which information such as control programs for causing the CPU 11 to execute various processes is stored in advance. The RAM 13 is a volatile or non-volatile storage device used as a temporary storage memory (work area) for the various processes executed by the CPU 11. The CPU 11 performs overall control of the image forming apparatus 100 by executing the various control programs stored in advance in the ROM 12.

The control unit 7 may be a control unit provided separately from a main control unit that performs overall control of the image forming device 100. The control unit 7 may also be configured with an electronic circuit such as an application specific integrated circuit (ASIC).

[Configuration of image forming unit 3]
Next, the configuration of the image forming section 3 will be described with reference to Figures 1 to 3. Here, Figure 3 is a cross-sectional view showing the configuration of the image forming unit 24. In Figure 3, the current path between the charging roller 32 and the first voltage application section 37, and the current path between the developing roller 44 and ground are indicated by dashed lines.

As shown in FIG. 1, the image forming unit 3 includes a plurality of image forming units 21 to 24, an optical scanning device 25, an intermediate transfer belt 26, a secondary transfer roller 27, a fixing device 28, and a paper discharge tray 29. As shown in FIGS. 2 and 3, the image forming unit 3 also includes a density sensor 30.

Image forming unit 21 forms a Y (yellow) toner image. Image forming unit 22 forms a C (cyan) toner image. Image forming unit 23 forms an M (magenta) toner image. Image forming unit 24 forms a K (black) toner image. As shown in FIG. 1, image forming units 21-24 are arranged side by side in the order of yellow, cyan, magenta, and black from the front side of image forming device 100 along the front-to-rear direction D2 of image forming device 100.

As shown in FIG. 3, the image forming unit 24 includes a photoconductor drum 31, a charging roller 32, a developing device 33, a primary transfer roller 34, and a drum cleaning unit 35. In addition, each of the image forming units 21 to 23 has a similar configuration to the image forming unit 24.

An electrostatic latent image is formed on the surface of the photoreceptor drum 31. For example, the photoreceptor drum 31 has a photosensitive layer 31A formed from amorphous silicon. The photoreceptor drum 31 receives a rotational driving force supplied from a motor (not shown) and rotates in a rotational direction D4 shown in FIG. 3. This causes the photoreceptor drum 31 to transport the electrostatic latent image formed on the surface. The photoreceptor drum 31 is an example of an image carrier of the present invention. Note that the photoreceptor layer 31A may be formed from other photosensitive materials, such as an organic photosensitive material.

The charging roller 32 charges the surface of the photoconductor drum 31 by applying a preset charging voltage. For example, the charging roller 32 charges the surface of the photoconductor drum 31 to a positive polarity. The surface of the photoconductor drum 31 charged by the charging roller 32 is irradiated with light based on image data emitted from the optical scanning device 25. As a result, an electrostatic latent image is formed on the surface of the photoconductor drum 31.

The developing device 33 uses a developer containing toner and carrier to develop the electrostatic latent image formed on the surface of the photoconductor drum 31. This forms a toner image on the surface of the photoconductor drum 31.

The primary transfer roller 34 transfers the toner image formed on the surface of the photoconductor drum 31 by the developing device 33 onto the intermediate transfer belt 26.

The drum cleaning unit 35 removes the toner remaining on the surface of the photoconductor drum 31 after the toner image is transferred by the primary transfer roller 34.

The image forming section 3 includes a toner container 36 (see FIG. 1) corresponding to each of the image forming units 21 to 24. The image forming section 3 also includes a first voltage application section 37 (see FIG. 2 and FIG. 3), a second voltage application section 38 (see FIG. 2 and FIG. 3), and a current detection section 39 (see FIG. 2 and FIG. 3) corresponding to each of the image forming units 21 to 24.

Here, we will explain the toner container 36, the first voltage application unit 37, the second voltage application unit 38, and the current detection unit 39 that correspond to the image forming unit 24. Note that FIG. 2 shows the first voltage application unit 37, the second voltage application unit 38, and the current detection unit 39 that correspond to the image forming unit 24.

The toner container 36 contains the K (black) toner. The toner container 36 supplies the K (black) toner to the developing device 33.

The first voltage application unit 37 is a power source that applies the charging voltage to the charging roller 32. Specifically, the charging voltage is a voltage that includes a first DC component. Here, the first DC component is a DC voltage having a voltage value set by the control unit 7. For example, the first DC component is a DC voltage having positive polarity.

The second voltage application unit 38 applies a predetermined development bias voltage to the development roller 44 (see FIG. 3) of the development device 33. Specifically, the development bias voltage is a voltage including a second DC component and a specific AC component. Here, the second DC component is a DC voltage having a voltage value set by the control unit 7. For example, the second DC component is a DC voltage having positive polarity and a lower voltage value than the first DC component. In addition, the specific AC component is a rectangular wave, and is an AC voltage having an amplitude value, duty ratio, and frequency set by the control unit 7.

The current detection unit 39 detects the current flowing through the developing roller 44 (see FIG. 3) of the developing device 33. As shown in FIG. 3, the current detection unit 39 is provided in the current path that runs from the developing roller 44 through the second voltage application unit 38 to ground. For example, the current detection unit 39 includes a resistor, and outputs the voltage across the resistor to the control unit 7.

The optical scanning device 25 emits light based on image data toward the surface of the photoconductor drum 31 of each image forming unit 21 to 24.

The intermediate transfer belt 26 is an endless belt member onto which the toner images formed on the surfaces of the photoconductor drums 31 of the image forming units 21 to 24 are transferred. The intermediate transfer belt 26 is stretched at a predetermined tension by a drive roller and a tension roller. The intermediate transfer belt 26 rotates in the rotation direction D5 shown in FIG. 3 as the drive roller rotates in response to a rotational driving force supplied from a motor (not shown).

The secondary transfer roller 27 transfers the toner image transferred onto the surface of the intermediate transfer belt 26 onto a sheet supplied from the paper feed unit 4.

The fixing device 28 fixes the toner image transferred to the sheet by the secondary transfer roller 27 onto the sheet.

The sheet on which the toner image has been fixed by the fixing device 28 is discharged onto the discharge tray 29.

The density sensor 30 detects the density of the toner image transferred to the outer peripheral surface of the intermediate transfer belt 26. For example, the density sensor 30 is a reflective photosensor that includes a light-emitting section that emits light toward the outer peripheral surface of the intermediate transfer belt 26, and a light-receiving section that receives the light emitted from the light-emitting section and reflected by the outer peripheral surface of the intermediate transfer belt 26. As shown in FIG. 3, the density sensor 30 is disposed downstream of the image forming unit 24 in the rotation direction D5 of the intermediate transfer belt 26 and upstream of the secondary transfer roller 27 in the rotation direction D5.

[Configuration of developing device 33]
3 and 4, the configuration of the developing device 33 of the image forming unit 24 will be described. The developing device 33 of each of the image forming units 21 to 23 also has the same configuration as the developing device 33 described below.

As shown in Figures 3 and 4, the developing device 33 includes a housing 41, a first transport member 42, a second transport member 43, a developing roller 44, a regulating member 45, and a toner sensor 46.

As shown in FIG. 3, the housing 41 houses a first transport member 42, a second transport member 43, a developing roller 44, and a regulating member 45. The housing 41 also houses the developer including the toner and the carrier. Specifically, the housing 41 houses the developer in an internal space formed by a bottom surface 51 and side walls erected on the bottom surface 51. The housing 41 is formed long in the left-right direction D3. The developing device 33 uses the developer housed in the housing 41 to develop an electrostatic latent image formed on the surface of the photosensitive drum 31.

As shown in Figures 3 and 4, the housing 41 has a first transport path 52 and a second transport path 53 through which the developer is transported. Specifically, a partition wall 54 (see Figure 4) extending in the left-right direction D3 is provided on the bottom surface 51 of the housing 41. The first transport path 52 and the second transport path 53 extending in the left-right direction D3 are formed by the bottom surface 51, the side walls, and the partition wall 54 of the housing 41.

The first transport member 42 is rotatably provided in the housing 41. As shown in FIG. 4, the first transport member 42 is provided in the first transport path 52. The first transport member 42 transports the developer contained in the first transport path 52 in the transport direction D6 shown in FIG. 4. The first transport member 42 also stirs the developer to frictionally charge the toner and the carrier. For example, the toner is positively charged by frictional charging with the carrier. For example, the first transport member 42 is a screw-shaped member that is rotatably provided around a rotation axis along the left-right direction D3 in the first transport path 52. The first transport member 42 rotates by receiving a rotational driving force supplied from a motor (not shown). The first transport member 42 is not limited to a screw-shaped member, and may be any member that can stir and transport the developer.

The second transport member 43 is rotatably provided in the housing 41. As shown in FIG. 4, the second transport member 43 is provided in the second transport path 53. The second transport member 43 transports the developer contained in the second transport path 53 in the transport direction D7 shown in FIG. 4. The second transport member 43 also stirs the developer to frictionally charge the toner and the carrier. For example, the second transport member 43 is a screw-shaped member that is rotatably provided around a rotation axis along the left-right direction D3 in the second transport path 53. The second transport member 43 rotates by receiving a rotational driving force supplied from a motor (not shown). The second transport member 43 is not limited to a screw-shaped member, and may be any member that can stir and transport the developer.

As shown in FIG. 4, a first passage 55 leading to the second transport path 53 is provided at the downstream end of the first transport path 52 in the transport direction D6. For example, the first passage 55 is formed at the right end of the partition 54. Also, as shown in FIG. 4, a second passage 56 leading to the first transport path 52 is provided at the downstream end of the second transport path 53 in the transport direction D7. For example, the second passage 56 is formed at the left end of the partition 54. In other words, inside the housing 41, a circulating transport path in which the developer circulates is formed by the first transport path 52, the first passage 55, the second transport path 53, and the second passage 56.

The developing roller 44 is disposed opposite the photosensitive drum 31. The developing roller 44 transports the developer containing the toner and the carrier to an opposing region R1 (see FIG. 3) with the photosensitive drum 31. The developing bias voltage is applied to the developing roller 44. The developing roller 44 is an example of a developing member of the present invention.

As shown in FIG. 3, the developing roller 44 is disposed opposite the second transport member 43 and the photosensitive drum 31. The developing roller 44 scoops up the developer from the second transport path 53. The developer scooped up by the developing roller 44 forms a magnetic brush on the outer circumferential surface of the developing roller 44 due to the magnetic force of the magnetic poles disposed inside the developing roller 44.

The developing roller 44 is rotatably supported by the housing 41, and rotates in the rotation direction D8 shown in FIG. 3 upon receiving a rotational driving force supplied from a motor (not shown). As a result, the developing roller 44 transports the magnetic brush formed on the outer peripheral surface to the facing region R1 (see FIG. 3).

The electrostatic latent image formed on the surface of the photoconductor drum 31 is transported to the opposing region R1 by the rotation of the photoconductor drum 31. Here, the electrostatic latent image formed on the surface of the photoconductor drum 31 includes a visualized region that is visualized by the toner and a non-visualized region that is not visualized by the toner. The visualized region is a region of the charged region on the surface of the photoconductor drum 31 that is charged by the charging roller 32 and is irradiated with light emitted by the optical scanning device 25. The non-visualized region is a region of the charged region that is not irradiated with light emitted by the optical scanning device 25.

When the developing bias voltage is applied to the developing roller 44, a first electric field that moves the toner toward the photoconductor drum 31 is formed between the developing roller 44 and the visualization area, which face each other in the opposing region R1. When the developing bias voltage is applied to the developing roller 44, a second electric field that moves the toner toward the developing roller 44 is formed between the developing roller 44 and the non-visual area, which face each other in the opposing region R1. The toner contained in the magnetic brush transported to the opposing region R1 is selectively moved to the visualization area of the electrostatic latent image formed on the surface of the photoconductor drum 31 by the action of the first electric field and the second electric field formed in the opposing region R1. As a result, the electrostatic latent image formed on the surface of the photoconductor drum 31 is developed (visualized).

The visualized area may be an area of the charged area that is not irradiated with the light emitted by the optical scanning device 25. In this case, the non-visualized area may be an area of the charged area that is irradiated with the light emitted by the optical scanning device 25, or an area on the surface of the photosensitive drum 31 that is not charged by the charging roller 32. When the visualized area is an area of the charged area that is not irradiated with the light from the optical scanning device 25, the toner is charged with a polarity opposite to the charging polarity of the charged area.

The regulating member 45 regulates the layer thickness of the magnetic brush formed on the outer peripheral surface of the developing roller 44. As shown in FIG. 3, the regulating member 45 is provided downstream of the opposing region between the second transport member 43 and the developing roller 44 in the rotation direction D8 and upstream of the opposing region R1 in the rotation direction D8. The regulating member 45 is provided facing the outer peripheral surface of the developing roller 44 so that a predetermined gap is formed between the regulating member 45 and the outer peripheral surface of the developing roller 44.

An opening 57 is provided above the first transport path 52. As shown in FIG. 3, the opening 57 is provided on the upper surface of the housing 41 that covers the first transport path 52 above the first transport path 52. The opening 57 is provided opposite the upstream end of the first transport path 52 in the transport direction D6. The opening 57 is used to transport the toner supplied from the toner container 36 to the first transport path 52. Specifically, the toner supplied from the toner container 36 is transported through the opening 57 to the loading position P1 (see FIG. 4) of the first transport path 52. The loading position P1 is a position opposite the opening 57 in the bottom surface 51.

The toner sensor 46 detects the amount of toner at a detection position P2 (see FIG. 4) downstream in the transport direction D6 from the loading position P1 in the first transport path 52. For example, the toner sensor 46 is provided on the bottom surface of the housing 41 as shown in FIG. 3. For example, the toner sensor 46 is a magnetic permeability sensor including an LC oscillator circuit that outputs an electric signal according to the magnetic permeability of the developer contained in the housing 41. The toner sensor 46 is used by the control unit 7 to control the supply of the toner from the toner container 36 to the developing device 33.

There is known an image forming device that acquires the charge amount of the toner and determines whether or not it is time to execute an adjustment process to adjust the image formation conditions based on the acquired charge amount of the toner. In this image forming device, a measurement toner image is formed, and the charge amount of the toner is acquired based on the detection result of the density of the measurement toner image.

Here, when the measurement toner image is formed to determine whether the timing for performing the adjustment process has arrived, the toner is consumed accordingly.

In contrast, in the image forming device 100 according to an embodiment of the present invention, as described below, it is possible to determine whether the timing to perform the adjustment process has arrived without consuming the toner.

[Configuration of control unit 7]
Next, the configuration of the control unit 7 will be described with reference to FIG.

As shown in FIG. 2, the control unit 7 includes a processing execution unit 61, a detection processing unit 62, a judgment processing unit 63, and a first update processing unit 64.

Specifically, the ROM 12 of the control unit 7 prestores an image formation condition adjustment program for causing the CPU 11 to function as the processing execution unit 61, the detection processing unit 62, the judgment processing unit 63, and the first update processing unit 64. The CPU 11 then executes the image formation condition adjustment program stored in the ROM 12 to function as each of the above-mentioned units.

The image formation condition adjustment program may be recorded on a computer-readable recording medium such as a CD, DVD, or flash memory, and may be read from the recording medium and stored in a storage device such as the memory unit 6. The process execution unit 61, the detection processing unit 62, the determination processing unit 63, and the first update processing unit 64 may be configured as electronic circuits such as an application specific integrated circuit (ASIC).

In the following, of the image forming units 21 to 24, the sections included in the image forming unit 24 and the sections provided corresponding to the image forming unit 24 will be described as examples. The following description also applies to each of the image forming units 21 to 23.

The process execution unit 61 executes the adjustment process to adjust the image formation conditions.

For example, the adjustment process includes a development bias adjustment process that forms a predetermined specific toner image and adjusts the development bias voltage based on the density of the specific toner image.

For example, the development bias adjustment process is a process for adjusting the second DC component. For example, the development bias adjustment process is performed in the following manner. First, the image forming unit 24 is used to sequentially form a plurality of the specific toner images, and the voltage value of the second DC component included in the development bias voltage is increased or decreased by a predetermined change amount each time the specific toner image is formed. In other words, a plurality of the specific toner images corresponding to a plurality of different voltage values of the second DC component are formed. Next, a density sensor 30 is used to detect the density of each of the specific toner images transferred to the outer peripheral surface of the intermediate transfer belt 26. Next, a relational expression showing the relationship between the voltage value of the second DC component and the density of the specific toner image is calculated based on the voltage values of the plurality of second DC components and the detection results of the densities of the specific toner images corresponding to each of the voltage values. Next, based on the calculated relational expression, a voltage value of the second DC component that can make the density of the specific toner image a predetermined target density is obtained. Then, the second DC component is adjusted based on the obtained voltage value. The developing bias adjustment process may be a process of adjusting the specific AC component. The developing bias adjustment process may be a process of adjusting both the second DC component and the specific AC component.

The adjustment process may include a light amount adjustment process that adjusts the amount of light emitted from the optical scanning device 25. The adjustment process may also include a charging voltage adjustment process that adjusts the charging voltage. The adjustment process may also include a primary transfer voltage adjustment process that adjusts the primary transfer voltage applied to the primary transfer roller 34. The adjustment process may also include a secondary transfer voltage adjustment process that adjusts the secondary transfer voltage applied to the secondary transfer roller 27. The adjustment process may also include one or more of the development bias adjustment process, the light amount adjustment process, the charging voltage adjustment process, the primary transfer voltage adjustment process, and the secondary transfer voltage adjustment process.

The detection processing unit 62 detects the non-development current that flows when the second electric field (an example of the specific electric field of the present invention) that moves the toner toward the developing roller 44 is formed in the opposing region R1 where the developer is present.

The non-development current is a current that is generated when the toner contained in the magnetic brush transported to the opposing region R1 moves toward the developing roller 44 due to the action of the second electric field formed in the opposing region R1, and is a current that flows through the developing roller 44.

Here, the greater the charge on the toner contained in the magnetic brush transported to the opposing region R1, the stronger the electrostatic force acting between the toner and the carrier, making it more difficult for the toner to leave the carrier and move. In other words, the non-development current becomes smaller.

On the other hand, the smaller the charge amount of the toner contained in the magnetic brush transported to the opposing region R1, the weaker the electrostatic force acting between the toner and the carrier, making it easier for the toner to separate from the carrier and move. In other words, the non-development current becomes larger.

In this way, the non-development current changes depending on the charge amount of the toner contained in the magnetic brush transported to the opposing region R1. Therefore, by detecting the non-development current, it is possible to estimate the charge amount of the toner.

Here, in the image forming device 100, the photosensitive layer 31A of the photosensitive drum 31 is formed from amorphous silicon. This makes it possible to reduce the electrical resistance of the photosensitive layer 31A compared to a configuration in which the photosensitive layer 31A is formed from an organic photosensitive material. When the electrical resistance of the photosensitive layer 31A is reduced, the non-developing current increases. Therefore, it is possible to reduce the detection error of the non-developing current.

For example, when a continuous printing process is performed in which an image is formed on each of the sheets that are transported in succession, the detection processing unit 62 detects the non-development current each time the developing roller 44 faces the inter-sheet area on the photoconductor drum 31 that corresponds to the area between two sheets that are transported in succession. This makes it possible to monitor the change in the charge amount of the toner during the execution of the continuous printing process.

In addition, the detection processing unit 62 may detect the non-development current at any timing when the second electric field is formed in the opposing region R1 during the execution of the continuous printing process. For example, the detection processing unit 62 may detect the non-development current at a timing when the non-visualized region corresponding to a non-printed region such as a margin region included in the image data to be printed faces the developing roller 44.

The detection processing unit 62 may also detect the non-development current at any timing when the second electric field is formed in the opposing region R1 during execution of a non-continuous printing process that forms an image on a single sheet.

The detection processing unit 62 may also detect the non-development current at any timing when the second electric field is formed in the opposing region R1 where the developer is present during operation of the image forming device 100.

The judgment processing unit 63 judges whether the timing to execute the adjustment process for adjusting the image formation conditions has arrived based on the non-development current detected by the detection processing unit 62.

Specifically, the determination processing unit 63 determines that the execution timing has arrived when the difference between the non-development current detected by the detection processing unit 62 and a preset reference current exceeds a predetermined threshold. In other words, the determination processing unit 63 determines that the execution timing has arrived when the non-development current detected by the detection processing unit 62 is greater than the sum of the reference current and the threshold, or when the non-development current is less than the remainder obtained by subtracting the threshold from the reference current.

The threshold value may be a value that is set unchangeably during the manufacture of the image forming device 100, or may be a value that can be set arbitrarily according to a predetermined setting operation.

The process execution unit 61 executes the adjustment process when the determination processing unit 63 determines that the execution timing has arrived.

When the judgment processing unit 63 judges that the execution timing has arrived, the first update processing unit 64 updates the reference current based on the non-development current used in the judgment.

Specifically, the first update processing unit 64 sets the non-development current used by the determination processing unit 63 to determine that the execution timing has arrived as the new reference current. This makes it possible to determine whether the execution timing has arrived based on the change in the charge amount of the toner since the adjustment process was performed.

The first update processing unit 64 may set the sum of the non-development current used by the judgment processing unit 63 to judge that the execution timing has arrived and an adjustment value corresponding to the change in the charge amount of the toner due to the execution of the development bias adjustment process as the new reference current. This makes it possible to reflect the change in the charge amount of the toner due to the execution of the development bias adjustment process in the reference current when the adjustment process is the development bias adjustment process. Therefore, compared to a configuration in which the change in the charge amount of the toner due to the execution of the development bias adjustment process is not reflected in the reference current, it is possible to delay the arrival of the execution timing without causing a deterioration in image quality. In other words, it is possible to reduce the frequency of execution of the development bias adjustment process without causing a deterioration in image quality.

The control unit 7 may not include the first update processing unit 64. In this case, the reference current may be a value that is unchangeably set during the manufacture of the image forming apparatus 100. The adjustment process may include a charge amount adjustment process that adjusts the charge amount of the toner contained in the developing device 33. In other words, the image formation conditions of the present invention may include the charge amount of the toner used in image formation. The charge amount adjustment process includes a toner replacement process that supplies the toner from the toner container 36 to the developing device 33 and moves the toner from the developing roller 44 to the photoconductor drum 31 to replace the toner in the developing device 33, and a developer stirring process that stirs the developer while the developer is retained in the developing device 33.

The determination processing unit 63 may also determine that the execution timing has arrived when the amount of change in the non-development current detected by the detection processing unit 62 in a predetermined unit time exceeds a predetermined allowable value.

[Image Forming Condition Adjustment Processing]
5, the image formation condition adjustment method of the present invention will be described together with an example of the procedure of the image formation condition adjustment process executed by the control unit 7 in the image forming apparatus 100. Here, steps S11, S12, ... represent the numbers of the process procedures (steps) executed by the control unit 7.

The image formation condition adjustment process is started when the continuous printing process starts, and is ended when the continuous printing process ends.

<Step S11>
First, in step S11, the control section 7 determines whether or not the timing for detecting the non-development current has arrived.

Specifically, the control unit 7 determines that the detection timing has arrived when, during execution of the continuous printing process, the inter-sheet area on the photosensitive drum 31 that corresponds to the area between two sheets whose transport order is consecutive faces the developing roller 44.

Here, if the control unit 7 determines that the detection timing has arrived (Yes side of S11), it transitions the process to step S12. If the detection timing has not arrived (No side of S11), the control unit 7 waits for the arrival of the detection timing in step S11.

<Step S12>
In step S12, the control section 7 detects the non-development current. The process of step S12 is an example of a detection step of the present invention, and is executed by the detection processing section 62 of the control section 7.

Specifically, the control unit 7 detects the non-development current using the current detection unit 39.

<Step S13>
In step S13, the control unit 7 judges whether or not the execution timing has arrived. The process of step S13 is an example of a judgment step of the present invention, and is executed by the judgment processing unit 63 of the control unit 7.

Specifically, the control unit 7 determines that the execution timing has arrived when the difference between the non-development current detected in step S12 and the reference current exceeds the threshold value.

Here, if the control unit 7 determines that the execution timing has arrived (Yes in S13), it shifts the process to step S14. If the execution timing has not arrived (No in S13), the control unit 7 shifts the process to step S11.

<Step S14>
In step S14, the control unit 7 executes the adjustment process. The process in step S14 is executed by the process execution unit 61 of the control unit 7.

Specifically, the control unit 7 executes the development bias adjustment process.

<Step S15>
In step S15, the control unit 7 updates the reference current. The process of step S15 is executed by the first update processing unit 64 of the control unit 7. The process of step S15 may be executed together with step S14, or may be executed prior to step S14.

Specifically, the control unit 7 sets the non-development current detected in the immediately preceding step S12 as the new reference current.

In this way, in the image forming device 100, the non-development current that flows when the second electric field that moves the toner toward the developing roller 44 is formed in the opposing region R1 where the developer is present is detected. Then, based on the detected non-development current, it is determined whether the execution timing has arrived. This makes it possible to determine whether the execution timing has arrived without consuming the toner.

The detection processing unit 62 may detect the non-development current after the development bias adjustment process executed as the adjustment process is completed. For example, the detection processing unit 62 may detect the non-development current at the end of the development bias adjustment process or at the start of the continuous printing process or the non-continuous printing process that is executed for the first time after the end of the development bias adjustment process.

In this case, the image forming device 100 may be provided with a second update processing unit 65 shown in FIG. 6 instead of the first update processing unit 64.

The second update processing unit 65 updates the reference current based on the non-development current detected by the detection processing unit 62 after the development bias adjustment process is completed.

This makes it possible to reduce the frequency with which the development bias adjustment process is performed without causing a deterioration in image quality, similar to the configuration in which the adjustment value is used to update the reference current.

1 ADF
2 Image reading section 3 Image forming section 4 Paper feeding section 5 Operation display section 6 Memory section 7 Control section 24 Image forming unit 25 Optical scanning device 26 Intermediate transfer belt 27 Secondary transfer roller 30 Density sensor 31 Photoconductor drum 32 Charging roller 33 Developing device 34 Primary transfer roller 37 First voltage application section 38 Second voltage application section 39 Current detection section 41 Housing 42 First transport member 43 Second transport member 44 Developing roller 61 Processing execution section 62 Detection processing section 63 Determination processing section 64 First update processing section 65 Second update processing section 100 Image forming apparatus

Claims (7)

an image carrier on which an electrostatic latent image is formed;
a developing member provided opposite to the image carrier and configured to transport a developer including a toner and a carrier to an area facing the image carrier;
a detection processing unit that detects a non-development current that flows when a specific electric field that moves the toner toward the developing member is formed in the opposing region where the developer is present;
a determination processing unit that determines whether or not a timing for executing an adjustment process for adjusting an image forming condition has arrived based on the non-development current detected by the detection processing unit;
An image forming apparatus comprising:
the determination processing unit determines that the execution timing has arrived when a difference between the non-development current detected by the detection processing unit and a preset reference current exceeds a predetermined threshold value;
The image forming apparatus includes:
a first update processing unit that updates the reference current based on the non-development current used in the determination when the determination processing unit determines that the execution timing has arrived;
the adjustment process includes a development bias adjustment process for forming a predetermined specific toner image and adjusting the development bias voltage based on a density of the specific toner image;
the first update processing unit sets, as a new reference current, a sum of the non-development current used in the determination by the determination processing unit that the execution timing has arrived and an adjustment value corresponding to a change in the charge amount of the toner due to execution of the development bias adjustment process;
Image forming device . an image carrier on which an electrostatic latent image is formed;
a developing member provided opposite to the image carrier and configured to transport a developer including a toner and a carrier to an area facing the image carrier;
a detection processing unit that detects a non-development current that flows when a specific electric field that moves the toner toward the developing member is formed in the opposing region where the developer is present;
a determination processing unit that determines whether or not a timing for performing an adjustment process for adjusting an image forming condition has arrived based on the non-development current detected by the detection processing unit;
An image forming apparatus comprising:
the determination processing unit determines that the execution timing has arrived when a difference between the non-development current detected by the detection processing unit and a preset reference current exceeds a predetermined threshold value;
the adjustment process includes a development bias adjustment process for forming a predetermined specific toner image and adjusting the development bias voltage based on a density of the specific toner image;
the detection processing unit detects the non-development current after the development bias adjustment process is completed,
The image forming apparatus includes:
a second update processing unit that updates the reference current based on the non-development current detected by the detection processing unit after the development bias adjustment process is completed;
Image forming device . an image carrier on which an electrostatic latent image is formed;
a developing member provided opposite to the image carrier and configured to transport a developer including a toner and a carrier to an area facing the image carrier;
a detection processing unit that detects a non-development current that flows when a specific electric field that moves the toner toward the developing member is formed in the opposing region where the developer is present;
a determination processing unit that determines whether or not a timing for performing an adjustment process for adjusting an image forming condition has arrived based on the non-development current detected by the detection processing unit;
Equipped with
the detection processing unit detects the non-development current every time a paper-interval area corresponding to a space between two sheets that are consecutively transported in the image carrier faces the developing member when a continuous printing process is performed in which an image is formed on each of the sheets that are consecutively transported.
Image forming device . The image carrier has a photosensitive layer formed of amorphous silicon.
4. The image forming apparatus according to claim 1 . 1. A method for adjusting image forming conditions, which is carried out in an image forming apparatus including an image carrier on which an electrostatic latent image is formed, and a developing member provided opposite the image carrier and configured to transport a developer containing a toner and a carrier to an area facing the image carrier, comprising:
a detection step of detecting a non-development current that flows when a specific electric field that moves the toner toward the developing member is formed in the opposing region where the developer is present;
a determination step of determining whether or not a timing for performing an adjustment process for adjusting an image forming condition has arrived based on the non-development current detected in the detection step;
Including,
In the determination step, it is determined that the execution timing has arrived when a difference between the non-development current detected in the detection step and a preset reference current exceeds a predetermined threshold value;
The image forming condition adjusting method includes the steps of:
an updating step of updating the reference current based on the non-development current used in the determination step when it is determined that the execution timing has arrived,
the adjustment process includes a development bias adjustment process for forming a predetermined specific toner image and adjusting the development bias voltage based on a density of the specific toner image;
An image forming condition adjustment method in which, in the update step, the sum of the non-development current used in determining that the execution timing has arrived by the judgment step and an adjustment value corresponding to the change in the charge amount of the toner due to execution of the development bias adjustment process is set as the new reference current . 1. A method for adjusting image forming conditions, which is carried out in an image forming apparatus including an image carrier on which an electrostatic latent image is formed, and a developing member provided opposite the image carrier and configured to transport a developer containing a toner and a carrier to an area facing the image carrier, comprising:
a detection step of detecting a non-development current that flows when a specific electric field that moves the toner toward the developing member is formed in the opposing region where the developer is present;
a determination step of determining whether or not a timing for performing an adjustment process for adjusting an image forming condition has arrived based on the non-development current detected in the detection step;
Including,
In the determination step, it is determined that the execution timing has arrived when a difference between the non-development current detected in the detection step and a preset reference current exceeds a predetermined threshold value;
the adjustment process includes a development bias adjustment process for forming a predetermined specific toner image and adjusting the development bias voltage based on a density of the specific toner image;
In the detection step, the non-development current is detected after the development bias adjustment process is completed,
The image forming condition adjusting method includes the steps of:
an updating step of updating the reference current based on the non-development current detected by the detecting step after the end of the developing bias adjustment process;
Image forming condition adjustment method. 1. A method for adjusting image forming conditions, which is carried out in an image forming apparatus including an image carrier on which an electrostatic latent image is formed, and a developing member provided opposite the image carrier and configured to transport a developer containing a toner and a carrier to an area facing the image carrier, comprising:
a detection step of detecting a non-development current that flows when a specific electric field that moves the toner toward the developing member is formed in the opposing region where the developer is present;
a determination step of determining whether or not a timing for performing an adjustment process for adjusting an image forming condition has arrived based on the non-development current detected in the detection step;
Including,
In the detection step, when a continuous printing process is performed in which an image is formed on each of sheets that are continuously transported, the non-development current is detected every time the developing member faces an inter-sheet area corresponding to a space between two sheets that are continuously transported in an order on the image carrier.
Image forming condition adjustment method.

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