JP7775638B2 - Image forming device - Google Patents

Description

The present invention relates to an image forming apparatus.

In electrophotographic image forming devices, residual toner and other deposits on the surface of an image carrier (e.g., a photosensitive drum) that carries a toner image are removed by bringing a cleaning member (e.g., a blade member) into contact with the surface of the image carrier.

In recent years, there has been a demand for image forming units (e.g., photosensitive units) that are highly reliable and have a long lifespan. The lifespan of an image forming unit is primarily determined by image defects resulting from wear on the image carrier and poor cleaning caused by wear on the cleaning member.

The wear rate of the image carrier and the cleaning member depend on the contact force of the cleaning member on the image carrier. As the contact force of the cleaning member increases, the above speeds also increase. Therefore, if the contact force of the cleaning member can be properly managed, it is possible to improve the reliability of the image forming unit by detecting the end of its lifespan and adjusting the contact force of the cleaning member.

For example, Patent Documents 1 and 2 disclose a configuration in which polarized light is incident on a cleaning member to measure the internal stress of the cleaning member.

Japanese Patent Application Laid-Open No. 2006-189327 Japanese Patent Application Laid-Open No. 2003-5580

However, the configurations described in Patent Documents 1 and 2 are complex, including the inclusion of a light source, polarizer, analyzer, and observation device, and therefore leave room for improvement in the configuration for detecting the state (contact force) of the cleaning member.

The object of the present invention is to provide an image forming apparatus that is capable of detecting the contact force of a cleaning member with a simple configuration.

The image forming apparatus according to the present invention comprises:
An image forming apparatus including an image carrier that carries a toner image, and a cleaning member that comes into contact with and cleans the surface of the image carrier,
a control unit that performs measurement control to measure a parameter related to a contact force of the cleaning member with the image carrier by rotating the image carrier while supplying toner to the image carrier during non-image formation ; and
a charging roller for charging the image carrier;
Equipped with
The parameter is the amount of change in the charging current between the image carrier and the charging roller .

According to the present invention, the contact force of the cleaning member can be detected using a simple configuration.

1 is a diagram illustrating an overall configuration of an image forming apparatus according to an embodiment of the present invention; FIG. 2 is a diagram illustrating a main part of a control system of the image forming apparatus. FIG. 10 is a diagram showing the relationship between the number of rotations of the photosensitive drum and the amount of change in charging current. FIG. 10 is a diagram showing the relationship between the contact force of the cleaning member and the wear rate of the photosensitive drum. FIG. 10 is a diagram showing the relationship between the film thickness of the photosensitive drum and the charging current. FIG. 10 is a diagram showing the relationship between the rotation speed of the photosensitive drum and the measured value of the charging current. FIG. 10 is a diagram showing the relationship between the number of printed sheets and the contact force of the cleaning member. FIG. 4 is a diagram illustrating a contact portion between the photosensitive drum and the cleaning member. FIG. 10 is a diagram showing the relationship between the amount of supplied toner and the contact force of the cleaning member. 10 is a diagram showing the relationship between the contact force of the cleaning member and the amount of change in temperature of the photosensitive drum. FIG. FIG. 4 is a diagram illustrating an example of the arrangement of a temperature detection unit. 10 is a diagram showing the relationship between the contact force of the cleaning member and the amount of distortion of the cleaning member. FIG. FIG. 10 is a diagram showing an example of the arrangement of strain gauges. FIG. 10 is a diagram showing the relationship between the amount of toner patch and the amount of distortion of the cleaning member. FIG. 10 is a diagram showing the relationship between the output voltage of the distance sensor and the contact force of the cleaning member. FIG. 10 is a diagram illustrating an example of the arrangement of distance sensors. 10A and 10B are diagrams illustrating an example of the positional relationship between a biasing member and an imaging unit. 10A and 10B are diagrams illustrating the relationship between the length of the urging member and the contact force of the cleaning member.

Embodiments of the present invention will now be described in detail with reference to the accompanying drawings. Figure 1 is a diagram showing the overall configuration of an image forming apparatus 1 according to an embodiment of the present invention. Figure 2 is a diagram showing the main components of the control system of image forming apparatus 1.

As shown in Figure 1, image forming apparatus 1 is an intermediate transfer color image forming apparatus that uses electrophotographic process technology. Specifically, image forming apparatus 1 primarily transfers the Y (yellow), M (magenta), C (cyan), and K (black) color toner images formed on photosensitive drum 413 onto intermediate transfer belt 421, overlays the four color toner images on intermediate transfer belt 421, and then performs secondary transfer onto paper S delivered from paper feed tray units 51a to 51c, thereby forming an image.

The image forming device 1 also employs a tandem system in which photosensitive drums 413 corresponding to the four colors YMCK are arranged in series in the direction of travel of the intermediate transfer belt 421, and each color toner image is transferred sequentially to the intermediate transfer belt 421 in a single step.

As shown in FIG. 2, the image forming device 1 includes an image reading unit 10, an operation display unit 20, an image processing unit 30, an image forming unit 40, a paper conveying unit 50, a fixing unit 60, and a control unit 101.

The control unit 101 includes a CPU (Central Processing Unit) 102, a ROM (Read Only Memory) 103, and a RAM (Random Access Memory) 104. The CPU 102 reads a program corresponding to the processing content from the ROM 103, loads it into the RAM 104, and works with the loaded program to centrally control the operation of each block of the image forming device 1. At this time, various data stored in the memory unit 72 is referenced. The memory unit 72 is configured, for example, from a non-volatile semiconductor memory (so-called flash memory) or a hard disk drive.

The control unit 101 transmits and receives various data to and from external devices (e.g., personal computers) connected to a communication network such as a LAN (Local Area Network) or WAN (Wide Area Network) via the communication unit 71. The control unit 101 receives, for example, image data (input image data) transmitted from an external device and forms an image on paper S based on this image data. The communication unit 71 is configured, for example, by a communication control card such as a LAN card.

As shown in FIG. 1, the image reading unit 10 is configured with an automatic document feeder 11, also known as an ADF (Auto Document Feeder), and an original image scanning device 12 (scanner).

The automatic document feeder 11 transports documents D placed on the document tray using a transport mechanism and sends them to the document image scanning device 12. The automatic document feeder 11 makes it possible to continuously read the images (including both sides) of multiple documents D placed on the document tray all at once.

The document image scanning device 12 optically scans a document transported from the automatic document feeder 11 onto the contact glass or a document placed on the contact glass, and forms an image of the light reflected from the document on the light-receiving surface of a CCD (Charge Coupled Device) sensor 12a to read the document image. The image reading unit 10 generates input image data based on the reading results from the document image scanning device 12. This input image data is subjected to predetermined image processing in the image processing unit 30.

As shown in FIG. 2, the operation display unit 20 is composed of, for example, a liquid crystal display (LCD) with a touch panel, and functions as a display unit 21 and an operation unit 22. The display unit 21 displays various operation screens, image status, and the operating status of each function in accordance with display control signals input from the control unit 101. The operation unit 22 has various operation keys such as a numeric keypad and start key, and accepts various input operations by the user and outputs operation signals to the control unit 101.

The image processing unit 30 includes circuits that perform digital image processing according to initial settings or user settings. For example, under the control of the control unit 101, the image processing unit 30 performs gradation correction based on gradation correction data (gradation correction table). In addition to gradation correction, the image processing unit 30 also performs various correction processes such as color correction and shading correction, as well as compression processing. The image forming unit 40 is controlled based on the image data that has undergone these processes.

As shown in FIG. 1, the image forming unit 40 forms an image on paper S based on the settings of a print job. The image forming unit 40 includes image forming units 41Y, 41M, 41C, and 41K, an intermediate transfer unit 42, and the like, for forming images using color toners of the Y, M, C, and K components based on input image data.

Image forming units 41Y, 41M, 41C, and 41K for the Y, M, C, and K components have the same configuration. For ease of illustration and explanation, common components are indicated by the same reference numerals, and when distinguishing between them, the reference numerals are followed by Y, M, C, or K. In Figure 1, only the components of image forming unit 41Y for the Y component are designated with reference numerals, and the components of the other image forming units 41M, 41C, and 41K are not designated with reference numerals.

The image forming unit 41 includes an exposure device 411, a development device 412, a photosensitive drum 413, a charging device 414, a drum cleaning device 415, and a current detection unit 416.

The photosensitive drum 413 is made of an organic photosensitive material, for example, a drum-shaped metal substrate, with a photosensitive layer made of a resin containing an organic photoconductor formed on the outer surface.

The control unit 101 controls the drive current supplied to the drive motor (not shown) that rotates the photosensitive drum 413, thereby rotating the photosensitive drum 413 at a constant peripheral speed.

The charging device 414 is a charging roller that comes into contact with the photosensitive drum, and generates a corona discharge to uniformly charge the photoconductive surface of the photosensitive drum 413 to a negative polarity.

The exposure device 411 is composed of, for example, a semiconductor laser, and irradiates the photosensitive drum 413 with laser light corresponding to the image of each color component. As a result, an electrostatic latent image of each color component is formed in the image area of the surface of the photosensitive drum 413 irradiated with the laser light due to the potential difference with the background area.

The developing device 412 is a two-component reverse development device that visualizes the electrostatic latent image by depositing developer of each color component onto the surface of the photosensitive drum 413, forming a toner image.

To the developing device 412, for example, a DC developing bias of the same polarity as the charging polarity of the charging device 414, or a developing bias in which an AC voltage is superimposed with a DC voltage of the same polarity as the charging polarity of the charging device 414, is applied. As a result, reversal development occurs, in which toner adheres to the electrostatic latent image formed by the exposure device 411.

The drum cleaning device 415 is in contact with the surface of the photosensitive drum 413 and has a flat cleaning member 417 (drum cleaning blade) made of an elastic material, and removes toner remaining on the surface of the photosensitive drum 413 without being transferred to the intermediate transfer belt 421.

The control unit 101 also performs estimation control to estimate the contact force of the cleaning member 417 on the photosensitive drum 413 when no image formation is occurring. Details of the estimation control performed by the control unit 101 will be described later.

Current detection unit 416 is a measuring device capable of measuring the current (hereinafter referred to as charging current) flowing between charging device 414 and photosensitive drum 413. While photosensitive drum 413 is rotating, current detection unit 416 counts up each time the charging current changes by a predetermined value.

The intermediate transfer unit 42 includes an intermediate transfer belt 421, a primary transfer roller 422, multiple support rollers 423, a secondary transfer roller 424, and a belt cleaning device 426.

The intermediate transfer belt 421 is an endless belt that is stretched in a loop around multiple support rollers 423. At least one of the multiple support rollers 423 is a drive roller, and the others are driven rollers. For example, it is preferable that roller 423A, which is located downstream in the belt running direction from primary transfer roller 422 for the K component, is the drive roller. This makes it easier to maintain a constant belt running speed at the primary transfer section. As drive roller 423A rotates, intermediate transfer belt 421 runs at a constant speed in the direction of arrow A.

The intermediate transfer belt 421 is a conductive and elastic belt with a high-resistance layer on its surface. The intermediate transfer belt 421 is driven to rotate by a control signal from the control unit 101.

The primary transfer roller 422 is positioned on the inner circumferential surface of the intermediate transfer belt 421, facing the photosensitive drum 413 for each color component. The primary transfer roller 422 is pressed against the photosensitive drum 413 with the intermediate transfer belt 421 sandwiched between them, forming a primary transfer nip for transferring the toner image from the photosensitive drum 413 to the intermediate transfer belt 421.

The secondary transfer roller 424 is positioned on the outer circumferential surface of the intermediate transfer belt 421, facing the backup roller 423B, which is positioned downstream of the drive roller 423A in the belt running direction. The secondary transfer roller 424 is pressed against the backup roller 423B with the intermediate transfer belt 421 sandwiched between them, forming a secondary transfer nip for transferring a toner image from the intermediate transfer belt 421 to the paper S.

When the intermediate transfer belt 421 passes through the primary transfer nip, the toner image on the photosensitive drum 413 is sequentially superimposed and primarily transferred onto the intermediate transfer belt 421. Specifically, a primary transfer bias is applied to the primary transfer roller 422, and a charge of the opposite polarity to the toner is applied to the back side of the intermediate transfer belt 421, i.e., the side that contacts the primary transfer roller 422, thereby electrostatically transferring the toner image onto the intermediate transfer belt 421.

Then, when the paper S passes through the secondary transfer nip, the toner image on the intermediate transfer belt 421 is secondarily transferred to the paper S. Specifically, a secondary transfer bias is applied to the secondary transfer roller 424, and a charge of the opposite polarity to the toner is applied to the back side of the paper S, i.e., the side that contacts the secondary transfer roller 424, thereby electrostatically transferring the toner image to the paper S. The paper S with the transferred toner image is transported toward the fixing unit 60.

The belt cleaning device 426 removes residual toner remaining on the surface of the intermediate transfer belt 421 after secondary transfer.

The fixing unit 60 includes an upper fixing unit 60A having a fixing surface side member arranged on the fixing surface of the paper S, i.e., the surface on which the toner image is formed, a lower fixing unit 60B having a back surface side support member arranged on the back surface of the paper S, i.e., the surface opposite the fixing surface, and a heat source. The back surface side support member is pressed against the fixing surface side member to form a fixing nip that clamps and transports the paper S.

The fixing unit 60 fixes the toner image onto the paper S by applying heat and pressure to the paper S, which has been transported after the toner image has been secondarily transferred, in the fixing nip. The fixing unit 60 is arranged as a unit within the fixing device F.

The upper fixing section 60A has an endless fixing belt 61, which is a fixing surface side member, a heating roller 62, and a fixing roller 63. The fixing belt 61 is stretched between the heating roller 62 and the fixing roller 63.

The lower fixing unit 60B has a pressure roller 64, which is a backside support member. The pressure roller 64 forms a fixing nip between itself and the fixing belt 61, which holds and transports the paper S.

The paper transport unit 50 includes a paper feed unit 51, a paper discharge unit 52, and a transport path unit 53. The three paper feed tray units 51a to 51c that make up the paper feed unit 51 store paper S (standard paper, special paper) identified based on basis weight, size, etc., by pre-set type.

The transport path section 53 includes multiple transport roller pairs, such as a registration roller pair 53a, and a normal transport path 53b that passes the paper S through the image forming section 40 and the fixing section 60 and discharges it outside the image forming apparatus 1.

Paper sheets S stored in paper feed tray units 51a to 51c are fed one by one from the top and transported to image forming unit 40 via transport path unit 53. In image forming unit 40, the toner image on intermediate transfer belt 421 is secondary-transferred all at once onto one side of paper S, and then the toner image is fixed in fixing unit 60. Paper S with the image formed on it is discharged outside the machine via paper discharge unit 52, which is equipped with paper discharge rollers 52a.

Next, we will explain how the control unit 101 estimates and controls the contact force of the cleaning member 417.

The drum cleaning device 415 performs a cleaning operation to remove residual toner from the surface of the photosensitive drum 413, but because the cleaning member 417 contacts the photosensitive drum 413, both the photosensitive drum 413 and the cleaning member 417 wear out. As these wear out, poor image quality due to improper cleaning of the photosensitive drum 413 occurs, which leads to the end of the image forming unit's life.

For this reason, it is necessary to properly manage the contact force of cleaning member 417 on photosensitive drum 413. If the contact force of cleaning member 417 can be properly managed, it will be possible to properly detect the end of the life of the image forming unit and properly adjust the contact force of cleaning member 417, thereby improving the reliability of the image forming unit.

In this embodiment, the control unit 101 performs estimation control of the contact force of the cleaning member 417, thereby enabling appropriate management of the contact force of the cleaning member 417. Specifically, the control unit 101 performs measurement control to measure parameters related to the contact force of the cleaning member 417 on the photosensitive drum 413 by rotating the photosensitive drum 413 while supplying toner to the photosensitive drum 413. The control unit 101 then estimates the contact force of the cleaning member 417 based on the measurement results (parameters) of the current detection unit 416 during the measurement control.

It has been confirmed that the amount of change in charging current between charging device 414 and photosensitive drum 413, detected by current detection unit 416, increases as the rotation speed of photosensitive drum 413 increases. Figure 3 shows the relationship between the rotation speed of photosensitive drum 413 and the amount of change in charging current. Figure 3 shows the amount of change in charging current when photosensitive drum 413 is rotated while a fixed amount of toner (10 mg of toner per sheet of paper) is supplied to photosensitive drum 413.

From Figure 3, it can be seen that the greater the contact force of the cleaning member 417, the greater the change in charging current.

Furthermore, as shown in Figure 4, it has been confirmed that the greater the contact force of the cleaning member 417, the greater the wear rate of the photosensitive drum 413. Furthermore, as shown in Figure 5, it has been confirmed that the greater the film thickness on the photosensitive drum 413, the smaller the charging current. In other words, it has been confirmed that there is a relationship between the amount of wear on the photosensitive drum 413 and the amount of film thickness decreasing, and the amount of charging current increasing.

Considering these relationships, the amount of change in charging current and the contact force of the cleaning member 417 are correlated with the wear rate of the photosensitive drum 413, so by obtaining the measurement results of the current detection unit 416, it is possible to estimate the contact force of the cleaning member 417.

The amount of change in current shown in Figure 3 can be measured, for example, using a digital electrometer (product name: 5350, manufactured by ADC Corporation) and can be calculated, for example, using the following equations (1) to (5).

Q=CV=ε ₀ ε _p SV/D _p ...(1)
Q represents the surface charge of the photosensitive drum 413, C represents the electrostatic capacitance of the photosensitive drum 413, V represents the surface potential of the photosensitive drum 413, ε ₀ represents the dielectric constant of a vacuum, ε _p represents the dielectric constant of the photosensitive drum 413, S represents the area charged by the charging device 414, and D _p represents the film thickness of the photosensitive drum 413.

A(0)=ε ₀ ε _p LvV/D _p0 ...(2)
A(0) indicates the initial charging current, L indicates the charging width of the charging roller (charging device), v indicates the rotation speed of the photosensitive drum 413, and D _p0 indicates the initial film thickness of the photosensitive drum 413. Note that the "initial stage" here refers to, for example, the start of measurement control during non-image formation.

D _p (R) = D _p0 - αR... (3)
R is the number of rotations of the photosensitive drum 413 , D _p (R) is the film thickness of the photosensitive drum 413 when it has rotated R times, and α is the wear rate of the photosensitive drum 413 .

A(R)=ε ₀ ε _p LvV/(D _p0 -αR)...(4)
A(R) indicates the charging current when rotating R times.

ΔA=A(R)-A(0)=ε ₀ ε _p LvV(1/(D _p0 -αR)-1/D _p0 )...(5)
ΔA indicates the amount of change in the charging current.

In this way, the amount of change in the charging current can be determined from the measurement results of the current detection unit 416.

However, the current detection unit 416 has a detection limit for the charging current based on its resolution. As described above, the current detection unit 416 is configured to count up each time the charging current changes by a predetermined value while the photosensitive drum 413 is rotating.

The detection limit of the charging current can be calculated, for example, using the following equation (6):

LimA=ε ₀ ε _p LvV(1/(D _p0 -αLimR)-1/D _p0 )...(6)
LimA is the detection limit of the current detection unit 416, and LimR is the number of rotations of the photosensitive drum 413 when the charging current fluctuates by LimA.

In this configuration, each time the current detection unit 416 counts up, the control unit 101 acquires the charging current measured by the current detection unit 416 and the number of rotations of the photosensitive drum 413 at the time of counting up, and stores these in correspondence with each other in the memory unit 72, etc. In other words, each time the charging current changes by a predetermined value, the control unit 101 stores the charging current and the number of rotations of the photosensitive drum 413 in correspondence with each other in the memory unit 72.

When measuring the wear rate of the photosensitive drum 413, the control unit 101 can calculate the wear rate α (= LimA/LimR) of the photosensitive drum 413 using the charging current stored in the memory unit 72 or the like and the rotation speed of the photosensitive drum 413. Specifically, the control unit 101 calculates the wear rate of the photosensitive drum 413 using the amount of change in the charging current after the current detection unit 416 has counted up two or more times.

In other words, the control unit 101 calculates the wear rate of the photosensitive drum 413 based on two or more combinations of charging currents and the rotation speed of the photosensitive drum 413 stored in the memory unit 72, and estimates the contact force of the cleaning member 417. The control unit 101 corresponds to the "estimation unit" and "calculation unit" of the present invention.

For example, as shown in Figure 6, the photosensitive drum 413 starts to rotate when the charging current is not zero, but the charging current at this time is a value that does not reach the detection limit (LimA). In this case, the current detection unit 416 performs the first count-up at a value that does not cause the amount of change in the charging current to reach LimA. The rotation speed R1 of the photosensitive drum 413 at this time will be different from LimA.

As a result, it may not be possible to accurately detect the wear speed (contact force of the cleaning member 417) using the measurement value from only the first count-up, so the control unit 101 uses the amount of change in the charging current after the current detection unit 416 has counted up two or more times.

For example, the timing when the current detection unit 416 counts up next after R1 is when the number of rotations of the photosensitive drum 413 is R2. By doing this, the difference between R2 and R1 can be used as LimR, making it possible to accurately determine LimR.

Furthermore, from the perspective of improving reliability, it is preferable to use the amount of change in charging current after the photosensitive drum 413 has been rotated for a certain long period of time (for example, counting up 10 times) to estimate the contact force.

In this way, the detected wear rate of the photosensitive drum 413 can be stored in advance in a memory unit or the like, for example, as data such as that shown in Figure 4, and by referencing this data, it is possible to estimate the contact force of the cleaning member 417. In other words, the control unit 101 estimates the contact force of the cleaning member 417 based on the measurement results of the current detection unit 416.

The control unit 101 also detects, for example, the lifespan of the image forming unit 41 based on the estimated contact force of the cleaning member 417. The control unit 101 determines the wear rate of the photosensitive drum 413 from the estimated contact force of the cleaning member 417 by referring to a table, such as that shown in Figure 4, which shows the relationship between the contact force of the cleaning member 417 and the wear rate of the photosensitive drum 413.

The control unit 101 then detects the lifespan of the image forming unit 41 by dividing the estimated wear rate by the limit wear rate of the photosensitive drum 413. For example, if the limit wear rate of the photosensitive drum 413 is 15 μm and the wear rate of the photosensitive drum 413 is 2 μm/100k sheets, the lifespan of the image forming unit 41 is 750k sheets.

The wear rate of cleaning member 417 may also be calculated from the estimated contact force of cleaning member 417. In this case, control unit 101 similarly detects the life of image forming unit 41 by dividing the estimated wear rate by the limit wear rate of cleaning member 417. If the limit wear rate of cleaning member 417 is 500 μm ² and the wear rate of cleaning member 417 is 100 μm ² /100k sheets, the life of image forming unit 41 is 500k sheets.

In this way, the contact force of the cleaning member 417 can be estimated to detect the lifespan of the image forming unit 41.

The control unit 101 may also adjust the contact force of the cleaning member 417 based on the estimated contact force of the cleaning member 417.

For example, in a configuration in which the cleaning member 417 is a fixed load, as shown in Figure 7A, the contact force of the cleaning member 417 may gradually decrease over time or over the number of sheets it can handle. In this case, the contact force may decrease and fall below the threshold value corresponding to the contact force at which poor cleaning is likely to occur.

Therefore, the control unit 101 adjusts the contact force of the cleaning member 417 so that the contact force increases. For example, if the member 417A (see FIG. 7B) that supports the cleaning member 417 is movable by a motor (not shown), the contact force of the cleaning member 417 is increased by moving the cleaning member 417 toward the photosensitive drum 413.

In this way, by estimating the contact force of the cleaning member 417, the contact force of the cleaning member 417 can be adjusted to prevent poor cleaning and image defects caused by poor cleaning.

The control unit 101 may also change the amount of toner supplied during toner patch supply control based on the estimated contact force of the cleaning member 417. Toner patch supply control is a control for reducing torque and ensuring toner cleaning performance by supplying toner to the photosensitive drum 413 outside of print jobs, between sheets during print jobs, and in areas outside the image area during print jobs. The control unit 101 corresponds to the "change unit" of the present invention.

In conventional toner patch supply control, the amount of toner supplied is constant, regardless of the contact force of the cleaning member 417, as shown in Figure 8. Therefore, if the contact force of the cleaning member 417 is weak, supplying a toner patch during this type of toner patch supply control may result in poor cleaning.

In this embodiment, therefore, if the estimated contact force of the cleaning member 417 is weak, the control unit 101 controls the amount of toner supplied to decrease accordingly. For example, in Figure 8, the amount of toner supplied is controlled to decrease as the contact force becomes smaller than P, and if the contact force is P or greater, the amount of toner supplied remains constant.

In this way, by estimating the contact force of the cleaning member 417, it is possible to prevent poor cleaning and image defects caused by poor cleaning.

In addition, even if the current detection unit 416 measures the charging current multiple times, there may be situations where the amount of change in charging current per rotation remains the same for a given number of rotations. This is expected to occur, for example, when light fatigue or an increase in residual potential of the photosensitive drum 413 occurs. In such a situation, the increase in current due to wear of the photosensitive drum 413 may be negated.

Therefore, if there is no change in the charging current after rotating the photosensitive drum 413 for a predetermined time (e.g., 3 minutes), the control unit 101 may interrupt measurement of the charging current by the current detection unit 416 and interrupt estimation control.

Furthermore, since the charged state of the photosensitive drum 413 may not stabilize for several minutes after the photosensitive drum 413 starts to rotate, the change in charging current during the first few minutes does not need to be used to estimate the contact force of the cleaning member 417. In this case, the measurement results of the charging current after the first few minutes may be used to detect the wear rate of the cleaning member 417.

In this embodiment configured as described above, the contact force of the cleaning member 417 can be estimated by providing a measuring device capable of measuring the charging current. This makes it possible to detect the contact force of the cleaning member 417 without the need for a complex configuration such as a light source, polarizer, analyzer, or observation device, as in Patent Documents 1 and 2. In other words, in this embodiment, the contact force of the cleaning member can be detected with a simple configuration.

In the above embodiment, the number of rotations of the photosensitive drum 413 was measured each time the charging current changed by a predetermined value, but the present invention is not limited to this. For example, it would also be possible to measure the amount of change in charging current while the photosensitive drum 413 rotates a predetermined number of times.

The predetermined number of rotations is, for example, the number of rotations required to measure the amount of change in charging current when the film thickness of the photosensitive drum 413 is at its thickest. This predetermined number of rotations may be varied depending on the film thickness of the photosensitive drum 413 when measuring the charging current.

By doing this, the number of rotations of the photosensitive drum 413 can be reduced.

Furthermore, in the above embodiment, the wear rate of the photosensitive drum 413 was calculated, but the present invention is not limited to this, and the wear rate of the cleaning member 417 may also be calculated.

Furthermore, in the above embodiment, the amount of change in charging current was used as a parameter related to the contact force of the cleaning member 417, but the present invention is not limited to this. For example, the amount of change in temperature of the photosensitive drum 413 may also be used as the above parameter.

It has been confirmed that there is a correlation between the amount of temperature change near the photosensitive drum 413 and the contact force of the cleaning member 417, such that as the contact force increases, the amount of temperature change increases, as shown in Figure 9A.

Figure 9A shows the measurement results of temperature detection unit 416A (see Figure 9B) placed inside photosensitive drum 413, when a fixed amount of toner (10 mg of toner per sheet of paper S) is supplied to photosensitive drum 413 while rotating photosensitive drum 413 and the contact force of cleaning member 417 is changed. The temperature change amount is the amount of temperature change after photosensitive drum 413 has rotated a certain amount from the start of rotation.

The data shown in Figure 9A can be stored in advance in the memory unit 72, etc., and when estimating the contact force, the detected temperature change can be compared with this data to estimate the contact force of the cleaning member 417.

Furthermore, the temperature detection unit 416A only needs to be located near the photosensitive drum 413. Furthermore, the amount of temperature change may be measured with cooling fans and other devices inside the image forming apparatus 1 stopped.

The amount of distortion of the cleaning member 417 may also be used as a parameter. The amount of distortion of the cleaning member 417 is the amount by which the cleaning member 417 is drawn into the rotation of the photosensitive drum 413.

It has been confirmed that the amount of distortion of the cleaning member 417 and the contact force of the cleaning member 417 are correlated such that the greater the contact force, the greater the amount of distortion of the cleaning member 417, as shown in Figure 10A.

Figure 10A shows the measurement results of strain gauge 416B (see Figure 10B) when a strain gauge 416B is placed on the surface of cleaning member 417 facing photosensitive drum 413, and the photosensitive drum 413 is rotated while a fixed amount of toner (10 mg of toner per sheet of paper S) is supplied to photosensitive drum 413, changing the contact force of cleaning member 417. The amount of strain is the amount of change in the strain of cleaning member 417 compared to when cleaning member 417 is not in contact with photosensitive drum 413.

The data shown in Figure 10A can be stored in advance in the memory unit 72, etc., and when estimating the contact force, the detected amount of distortion can be compared with this data to estimate the contact force of the cleaning member 417.

In addition, while Figure 10A shows the amount of distortion of the cleaning member 417 when toner of a constant density is supplied, the contact force of the cleaning member 417 can also be estimated using the measurement results of the amount of distortion of the cleaning member 417 when toner patches of multiple densities are supplied to the photosensitive drum 413 as shown in Figure 11 and the contact force of the cleaning member 417 is set to 20 N/m and 10 N/m.

L1 is an approximation line of the measurement results of the amount of distortion when the contact force of the cleaning member 417 is 20 N/m, and L2 is an approximation line of the measurement results of the amount of distortion when the contact force of the cleaning member 417 is 10 N/m.

The intercept values at L1 and L2 are the amount of strain at each contact force. In this way, by comparing the measurement results of strain gauge 416B when estimating the contact force of cleaning member 417 with the amount of strain obtained from Figure 11, it is possible to estimate the contact force of cleaning member 417.

The distance between the cleaning member 417 and the photosensitive drum 413 may also be used as a parameter.

It has been confirmed that the distance between the cleaning member 417 and the photosensitive drum 413 and the contact force of the cleaning member 417 are correlated such that the distance decreases as the contact force increases, as shown in Figure 12A.

Figure 12A shows the measurement results of distance sensor 416C (see Figure 12B) when the distance sensor 416C is placed on the surface of cleaning member 417 facing photosensitive drum 413, and the photosensitive drum 413 is rotated while a fixed amount of toner (10 mg of toner per sheet of paper S) is supplied to photosensitive drum 413, changing the contact force of cleaning member 417. A high-resolution capacitance type, for example, is preferably used as distance sensor 416C.

The data shown in Figure 12A can be stored in advance in the memory unit 72, etc., and when estimating the contact force, the detected distance can be compared with this data to estimate the contact force of the cleaning member 417.

Furthermore, as shown in Figure 13A, in a configuration having a urging member 418 that urges the cleaning member 417 against the photosensitive drum 413, the length of the urging member 418 may be used as a parameter.

It has been confirmed that there is a correlation between the length of the biasing member 418 that applies a load to the cleaning member 417 and the contact force of the cleaning member 417, such that the length increases as the contact force increases, as shown in Figure 13B.

Figure 13B shows the length of the urging member 418 based on the measurement results of the imaging unit 416D (see Figure 13A) when the imaging unit 416D (see Figure 13A) is positioned at a location where it can image the urging member 418, and the photosensitive drum 413 is rotated while supplying a fixed amount of toner (10 mg of toner per sheet of paper S) to the photosensitive drum 413, and the contact force of the cleaning member 417 is changed.

The data shown in Figure 13B can be stored in advance in the memory unit 72, etc., and when estimating the contact force, the detected length of the biasing member 418 can be compared with this data to estimate the contact force of the cleaning member 417.

In addition, in each of the above embodiments, parameters related to contact force are measured using a measuring unit such as a current detection unit, but the present invention is not limited to this. For example, the present invention may be configured to acquire and measure measurement results obtained using an external measuring device. For example, if a high-precision device such as a current detection unit cannot be installed in the image forming apparatus 1, a service engineer or the like may connect a measuring unit to the image forming apparatus and measure parameters when estimating contact force during maintenance, etc.

Furthermore, in the above embodiment, the control unit 101 is configured to include an estimation unit, a calculation unit, etc., but the present invention is not limited to this, and the estimation unit, calculation unit, etc. may be provided separately from the control unit 101.

In addition, while the above embodiment estimates the contact force of the cleaning member 417, the present invention is not limited to this, and a configuration may be adopted in which only parameters related to the contact force of the cleaning member 417 are measured. However, in this configuration, for example, a user or an external device would be able to determine the level of the contact force of the cleaning member based on only these parameters.

In addition, in the above embodiment, the charging device is a charging roller, but the present invention is not limited to this and may also be a charging charger. However, in a configuration for measuring the amount of change in charging current, if a charging charger is provided as the charging device, it is sufficient to simply install a roller member for measuring the charging current.

Furthermore, the above-described embodiments are merely examples of specific embodiments of the present invention, and the technical scope of the present invention should not be interpreted as being limited by them. In other words, the present invention can be embodied in various forms without departing from its gist or main features.

REFERENCE SIGNS LIST 1 Image forming apparatus 40 Image forming unit 101 Control unit 413 Photosensitive drum 414 Charging device 415 Drum cleaning device 416 Current detection unit 417 Cleaning member

Claims (12)

An image forming apparatus including an image carrier that carries a toner image, and a cleaning member that comes into contact with and cleans the surface of the image carrier,
a control unit that performs measurement control to measure a parameter related to a contact force of the cleaning member with the image carrier by rotating the image carrier while supplying toner to the image carrier during non-image formation ; and
a charging roller for charging the image carrier;
Equipped with
the parameter is a change in charging current between the image carrier and the charging roller;
Image forming device. a storage unit that stores the charging current and the number of rotations of the image carrier in association with each other every time the charging current changes by a predetermined value;
a calculation unit that calculates a wear rate of the image carrier or the cleaning member, the wear rate having a correlation with the contact force, based on two or more combinations of the charging current and the rotation speed stored in the storage unit; and
Equipped with
The image forming apparatus according to claim 1 . An image forming apparatus including an image carrier that carries a toner image, and a cleaning member that comes into contact with and cleans the surface of the image carrier,
a control unit that performs measurement control to measure a parameter related to a contact force of the cleaning member with the image carrier by rotating the image carrier while supplying toner to the image carrier during non-image formation; and
a temperature detection unit that detects a change in temperature of the image carrier as the parameter ;
Equipped with
Image forming device. An image forming apparatus including an image carrier that carries a toner image, and a cleaning member that comes into contact with and cleans the surface of the image carrier,
a control unit that performs measurement control to measure a parameter related to a contact force of the cleaning member with the image carrier by rotating the image carrier while supplying toner to the image carrier during non-image formation; and
a distance detection unit that measures a distance between the cleaning member and the image carrier as the parameter ;
Equipped with
Image forming device. the distance detection unit is disposed on a surface of the cleaning member facing the image carrier;
The image forming apparatus according to claim 4 . An image forming apparatus including an image carrier that carries a toner image, and a cleaning member that comes into contact with and cleans the surface of the image carrier,
a control unit that performs measurement control to measure a parameter related to a contact force of the cleaning member with the image carrier by rotating the image carrier while supplying toner to the image carrier during non-image formation; and
a biasing member that biases the cleaning member against the image carrier;
a length measuring unit for measuring the length of the biasing member;
Equipped with
Image forming device. The length measuring unit is an imaging unit capable of imaging the urging member.
The image forming apparatus according to claim 6 . an estimation unit that estimates the contact force based on the parameters;
The image forming apparatus according to any one of claims 1 to 7. a life detection unit that detects the life of the image carrier or the cleaning member based on the parameter;
The image forming apparatus according to any one of claims 1 to 8 . an adjustment unit that adjusts the contact force of the cleaning member based on the parameter;
The image forming apparatus according to any one of claims 1 to 9 . a change unit that changes the amount of toner supplied in accordance with the parameter;
The image forming apparatus according to any one of claims 1 to 10 . the changing unit supplies the toner to the image carrier at times other than when a print job is being performed, between sheets during the print job, and in an area outside an image area during the print job.
The image forming apparatus according to claim 11 .