JP7786288B2 - Image forming system - Google Patents

Description

The present invention relates to an image forming system.

Traditionally, in the commercial printing industry, ensuring the quality of images printed on paper has been a major challenge. The condition of the paper used changes depending on the environment in which the customer uses it, but even if the condition of the paper in relation to the customer's environment is understood, it is difficult to ensure image quality unless the printing machine (image forming device) used by the customer is properly controlled.

In response, technology has been proposed that automatically inspects printed images to determine whether the output meets the customer's needs. For example, when whiteouts and density unevenness occur simultaneously due to component deterioration or changes over time, technology has been proposed that can detect not only the density unevenness, which occurs over a wide area and is easy to detect, but also the whiteouts themselves (see, for example, Patent Document 1).

JP 2011-137895 A

However, with the configuration described in Patent Document 1, while it is possible to detect blank areas depending on the state of the printing press, it is not possible to determine which unit (fixing unit or transfer unit) is causing the blank areas. Furthermore, with the configuration described in Patent Document 1, it is not possible to determine which printing conditions should be changed for which unit, so image quality cannot be guaranteed.

The present invention aims to provide an image forming system that can reduce the occurrence of image defects and ensure image quality.

The invention described in claim 1 has been made to achieve the above object,
In an image forming system,
an image forming apparatus including a transfer unit that transfers an image onto a sheet of paper and a fixing unit that fixes the image transferred by the transfer unit onto the sheet of paper, and forming an image on the sheet of paper;
an image inspection device that inspects the paper on which the image is formed by the image forming device;
a media detection device disposed downstream of the image inspection device and including a media detection unit that detects the physical properties of the paper;
a control unit that controls the image forming device, the image inspection device, and the media detection device;
Equipped with
The control unit is characterized in that when the image inspection device detects an abnormality in the image formed on the paper, it determines whether to change the image formation conditions in the image forming device based on the physical properties detected by the media detection unit, and feeds back the determination result to the image formation control of the image forming device.

The invention described in claim 2 is the image forming system described in claim 1,
The media detection unit detects the physical properties of a blank area of the paper on which no image is formed.

The invention described in claim 3 is the image forming system described in claim 1,
The media detection unit detects the physical property when the abnormality detected by the image inspection device is a white spot.

The invention described in claim 4 is the image forming system described in claim 3,
the control unit, when the abnormality detected by the image inspection device is a white spot, causes the sheet on which the image formation has not been performed to be discharged from the image forming device;
The media detection unit detects the physical properties of a sheet of paper that has been discharged from the image forming apparatus and on which no image has been formed.

The invention described in claim 5 is the image forming system described in claim 3,
the media detection unit detects the moisture content of the paper when the abnormality detected by the image inspection device is a white spot;
The control unit determines whether to change the image forming conditions in the image forming apparatus based on the moisture content detected by the media detection unit, and feeds back the determination result to the image formation control of the image forming apparatus.

The invention described in claim 6 is the image forming system described in claim 5,
The control unit is characterized in that it determines that the temperature of the fixing unit needs to be lowered if the moisture content detected by the media detection unit is less than a first threshold, and determines that the output value of the transfer unit needs to be lowered if the moisture content detected by the media detection unit is equal to or greater than the first threshold.

The invention described in claim 7 is the image forming system described in claim 5,
The media detection device is characterized in that the media detection unit detects the moisture content of the paper while the paper is being transported.

The invention described in claim 8 is the image forming system described in claim 1,
a second media detection device disposed in front of the image forming device and including a second media detection unit that detects physical properties of the paper before the image is formed;
When the image inspection device detects an abnormality in the image formed on the paper, the control unit determines whether to change the image formation conditions in the image forming device based on the difference between the physical properties detected by the media detection unit and the physical properties detected by the second media detection unit, and feeds back the determination result to the image formation control of the image forming device.

The invention described in claim 9 is the image forming system described in claim 8,
the media detection unit and the second media detection unit both detect the moisture content of the paper;
The control unit determines whether to change the image formation conditions in the image forming device based on the difference between the moisture content detected by the media detection unit and the moisture content detected by the second media detection unit, and feeds back the determination result to the image formation control of the image forming device.

The invention described in claim 10 is the image forming system described in claim 9,
The control unit is characterized in that it determines that the temperature of the fixing unit needs to be lowered when the difference between the moisture content detected by the media detection unit and the moisture content detected by the second media detection unit is less than a first threshold value, and determines that the output value of the transfer unit needs to be lowered when the difference between the moisture content detected by the media detection unit and the moisture content detected by the second media detection unit is equal to or greater than the first threshold value.

The invention described in claim 11 is the image forming system described in claim 1,
The media detection unit is characterized in that it is disposed on a path for discharging a sheet of paper for which the image inspection device has detected an abnormality.

The invention described in claim 12 is the image forming system described in claim 11,
The media detection device is characterized in that the media detection unit detects the surface properties of the paper while the paper is stopped.

The invention described in claim 13 is the image forming system described in claim 12,
The control unit determines that it is necessary to increase the temperature of the fixing unit when the surface property detected by the media detection unit exceeds a second threshold value.

The invention described in claim 14 is the image forming system described in claim 1,
The control unit feeds back the judgment result to the image formation control of the image forming device, and if the image inspection device again detects an abnormality in the image formed on the paper, stops the image formation operation by the image forming device, estimates the location of the defect based on the physical properties detected by the media detection unit, and notifies a service call.

This invention makes it possible to reduce the occurrence of image defects and ensure image quality.

1 is a diagram showing a schematic configuration of an image forming system according to an embodiment of the present invention; FIG. 2 is a diagram illustrating a schematic configuration of a media detection device. 10A and 10B are diagrams for explaining an area where the physical properties of paper are to be detected; FIG. 2 is a functional block diagram showing a control structure of the image forming system according to the present embodiment. 4 is a flowchart showing the operation of the image forming system according to the present embodiment. 10 is a flowchart illustrating an example of an image forming condition determination process. 10 is a flowchart showing another example of the image formation condition determination process. 10 is a flowchart showing another example of the image formation condition determination process. FIG. 10 is a diagram showing a schematic configuration of an image forming system according to a first modified example. 10 is a flowchart illustrating an example of an image formation condition determination process according to Modification 1. 10A and 10B are diagrams for explaining how the media detection unit detects the physical properties of a sheet of paper on which an image has not yet been formed. 10A and 10B are diagrams for explaining how feedback is performed from a sheet that is to be newly fed from the sheet feeding device;

Embodiments of the present invention will be described in detail below with reference to the drawings.

As shown in FIG. 1, the image forming system 1 according to this embodiment is configured to include a paper feeder 10, an image forming device 20 connected downstream of the paper feeder 10 and forming an image on paper based on print data, a relay unit 30 connected downstream of the image forming device 20, an image inspection device 40 connected downstream of the relay unit 30, a media detection device 50 connected downstream of the image inspection device 40, and a finisher 60 connected downstream of the media detection device 50.

The paper feed device 10 is equipped with a paper feed mechanism consisting of multiple paper feed trays, paper feed rollers, separation rollers, paper feed/separation rubber, and feed rollers. Each paper feed tray stores paper by type (paper type, basis weight, paper size, etc.), and the paper is transported one sheet at a time, starting from the top, to the image forming device 20.

The image forming device 20 is comprised of an endless, circular intermediate transfer belt 21, image forming units 22 arranged along the intermediate transfer belt 21 that form toner images of the colors C (cyan), M (magenta), Y (yellow), and K (black), a transfer unit 23 that transfers the toner images (images) to paper, and a fixing unit 24 that fixes the transferred toner images (images) to the paper. The image forming device 20 forms a full-color toner image by superimposing the CMYK toner images on the intermediate transfer belt 21 using the image forming units 22. The transfer unit 23 then transfers the toner image formed on the intermediate transfer belt 21 to paper transported from the paper feed device 10. The fixing unit 24 then thermally fixes the toner image to the paper, and the paper is then output to a downstream device (here, relay unit 30).

The relay unit 30 relays and transports the paper output from the image forming device 20 to a downstream device (here, the image inspection device 40). The relay unit 30 has the function of synchronizing with the transport speed of the paper transported from the image forming device 20.

The image inspection device 40 is equipped with a sensor (such as a line sensor) that optically reads the paper transported from the relay unit 30. The image inspection device 40 uses the sensor to read and inspect the paper on which the image is formed, and after determining whether there are any image abnormalities (white spaces), transports the paper to the downstream media detection device 50.

1 and 2, the media detection device 50 is configured to include a moisture content detection unit (media detection unit) 51 that detects the moisture content of the paper P, a paper surface property detection unit (media detection unit) 52 that detects the surface property of the paper P, and a paper resistance detection unit (media detection unit) 53 that detects the resistance of the paper P. For paper P that has been determined to have an image abnormality (whiteout) by the image inspection device 40, the media detection device 50 causes the moisture content detection unit 51 to detect the moisture content of the paper P while transporting the paper P. Since the moisture content of paper P detected by the moisture content detection unit 51 has an image abnormality (whiteout), the paper P is transported to a path that ejects (purges) the paper P as abnormal paper (waste paper) onto a purge tray T2 provided above the media detection device 50. A paper surface property detection unit 52 and a paper resistance detection unit 53 are provided on the discharge path to the purge tray T2, and when the media detection device 50 discharges the paper P to the purge tray T2, the transport of the paper P is stopped and the paper surface property detection unit 52 detects the surface property of the paper P and the paper resistance detection unit 53 detects the resistance of the paper P. In Figure 2, symbol A1 indicates the stop position when the surface property of the paper P is detected, and symbol A2 indicates the stop position when the resistance of the paper P is detected.
On the other hand, for paper P that is not determined to have an image abnormality (white space), the media detection device 50 discharges the paper P to the downstream finisher 60 without detecting the physical properties (moisture content) of the paper P using the moisture content detection unit 51.

As shown in Figure 3, the media detection device 50 detects the physical properties of the blank portion of the paper P where no image is formed (blank area E2), rather than the image area E1 where an image is formed on the paper P.

The finisher 60 performs the specified post-processing on the paper sent from the media detection device 50 (normal paper with no image abnormalities) and then discharges it onto the paper output tray T1.

As shown in FIG. 4, the image forming system 1 is configured to include a control unit 110, a memory unit 120, a paper feeder 10, an image forming device 20, a relay unit 30, an image inspection device 40, a media detection device 50, and a finisher 60.

The control unit 110 is configured to include a CPU, a ROM, and a memory.
The CPU reads out various processing programs stored in the ROM, and performs centralized control of the operations of the various parts of the image forming system 1 in accordance with the programs.
The ROM is configured from a non-volatile semiconductor memory or the like, and stores various processing programs, parameters and files required for executing the programs, and the like.
The memory is configured by a DRAM (Dynamic Random Access Memory) or the like, and temporarily stores various data such as programs and image data related to various image processes.
For example, when an abnormality in the image formed on paper is detected by the image inspection device 40, the control unit 110 determines whether to change the image formation conditions (e.g., transfer control and fixing control) in the image forming device 20 based on the physical properties detected by the media detection device 50, and feeds back the determination result to the image formation control of the image forming device 20.

The storage unit 120 is a non-volatile storage device such as a hard disk drive (HDD) or semiconductor memory that stores various data such as programs and image data. The storage unit 120 stores data such as program data and various setting data in a manner that allows it to be read and written by the control unit 110.

Next, the operation of the image forming system 1 according to this embodiment will be described with reference to the flowcharts in Figures 5 to 8.

First, as shown in FIG. 5, the control unit 110 causes the image forming device 20 to form an image on paper (step S101).

Next, the control unit 110 causes the image inspection device 40 to perform image inspection on the paper on which the image was formed in step S101 (step S102).

Next, the control unit 110 determines whether or not an image abnormality (white spot) has been detected by the image inspection device 40 in step S102 (step S103).
When the control unit 110 determines that an image abnormality (white area) has been detected (step S103: YES), the process proceeds to the next step S104.
On the other hand, if the control unit 110 determines that no image abnormality (white space) has been detected (step S103: NO), the control unit 110 proceeds to step S106 and discharges the paper directly to the paper discharge tray T1 (normal discharge).

Next, the control unit 110 performs a process to determine whether the image formation conditions are appropriate (image formation condition determination process) (step S104).

Here, an example of the image formation condition determination process (processing to determine whether the image formation conditions are appropriate based on the moisture content of the paper) will be described with reference to the flowchart in Figure 6.

First, as shown in FIG. 6, the control unit 110 causes the moisture content detection unit 51 of the media detection device 50 to detect the moisture content of the paper after image formation (paper on which an image abnormality has been detected), and acquires the detected moisture content of the paper after image formation (step S201). Specifically, the control unit 110 causes the moisture content detection unit 51 to detect the moisture content of the blank area E2 (see FIG. 3) of the paper P, and acquires the detected moisture content.

Next, the control unit 110 determines whether the moisture content obtained in step S201 is less than a first threshold value α (step S202). Here, the first threshold value α is a moisture content value below which the fixing temperature is estimated to be high enough to cause white voids.
When the control unit 110 determines that the fixing temperature is less than the first threshold value α (step S202: YES), it determines that the fixing temperature is high, and proceeds to the next step S203.
On the other hand, if the control unit 110 determines that the temperature is not less than the first threshold value α (i.e., is equal to or greater than the first threshold value α) (step S202: NO), it determines that the fixing temperature is normal and that an image abnormality (white space) has occurred due to other factors (i.e., the output value for transferring toner to paper is high), and proceeds to step S205.

In step S203, the control unit 110 determines that the unit for which image formation control is to be changed (image formation control change unit) is the "fixing unit (fixing section 24)."

Next, the control unit 110 determines to lower the target temperature of the fixing unit (fixing section 24), which is the image formation control change unit, by X [°C] (step S204), and proceeds to step S105 in Figure 5.

In step S205, the control unit 110 determines the image formation control change unit to be the "transfer unit (transfer unit 23)."

Next, the control unit 110 determines to reduce the paper transfer output of the transfer unit (transfer unit 23), which is the image formation control change unit, by Y [μA] (step S206), and proceeds to step S105 in Figure 5.

Furthermore, another example of the image formation condition determination process (processing to determine whether the image formation conditions are appropriate based on the surface properties of the paper) will be described with reference to the flowchart in Figure 7.

First, as shown in FIG. 7, the control unit 110 causes the paper surface property detection unit 52 of the media detection device 50 to detect the surface property of the paper after image formation, and acquires the detected surface property of the paper after image formation (step S301). Specifically, the control unit 110 causes the paper surface property detection unit 52 to detect the surface property of the blank area E2 (see FIG. 3) of the paper P, and acquires the detected surface property.

Next, the control unit 110 determines whether the surface texture acquired in step S301 exceeds a second threshold value β (step S302). Here, the surface texture is an index showing the degree of roughness of the paper surface. High surface texture indicates a smooth surface on which an image is not easily fixed (a non-rough state), while low surface texture indicates a rough surface on which an image is easily fixed (a rough state). The second threshold value β is a surface texture value above which an image is not easily fixed and white spots may occur.
If the control unit 110 determines that the second threshold value β is exceeded (step S302: YES), it determines that the fixing temperature needs to be increased in a state where the image is difficult to fix on the paper, and proceeds to the next step S303.
On the other hand, if the control unit 110 determines that the second threshold value β is not exceeded (i.e., is equal to or less than the second threshold value β) (step S302: NO), it determines that the image can be sufficiently fixed to the paper and that an image abnormality (white space) has occurred due to a factor other than the surface properties (i.e., the output value for transferring toner to the paper is high), and proceeds to step S305.

In step S303, the control unit 110 determines the image formation control change unit to be the "fixing unit (fixing unit 24)."

Next, the control unit 110 determines to increase the target temperature of the fixing unit (fixing section 24), which is the image formation control change unit, by Z [°C] (step S304), and proceeds to step S105 in Figure 5.

In step S305, the control unit 110 determines the image formation control change unit to be the "transfer unit (transfer unit 23)."

Next, the control unit 110 determines to reduce the paper transfer output of the transfer unit (transfer unit 23), which is the image formation control change unit, by Y [μA] (step S306), and proceeds to step S105 in Figure 5.

Next, another example of the image formation condition determination process (a process for determining whether the image formation conditions are appropriate based on the moisture content and surface properties of the paper) will be described with reference to the flowchart in Figure 8. Note that, since moisture content generally changes more significantly than surface properties during image formation operations, in the example shown in Figure 8, moisture content is given priority before surface properties are determined.

First, as shown in FIG. 8, the control unit 110 causes the moisture content detection unit 51 and paper surface property detection unit 52 of the media detection device 50 to detect the moisture content and surface property of the paper after image formation, and obtains the detected moisture content and surface property of the paper after image formation (step S401).

Next, the control unit 110 determines whether the moisture content obtained in step S401 is less than a first threshold value α (step S402).
If the control unit 110 determines that the difference is less than the first threshold value α (step S402: YES), the process proceeds to the next step S403.
On the other hand, if the control unit 110 determines that the difference is not less than the first threshold value α (that is, is equal to or greater than the first threshold value α) (step S402: NO), the control unit 110 proceeds to step S405.

In step S403, the control unit 110 determines the image formation control change unit to be the "fixing unit (fixing unit 24)."

Next, the control unit 110 determines to lower the target temperature of the fixing unit (fixing section 24), which is the image formation control change unit, by X [°C] (step S404), and proceeds to step S105 in Figure 5.

In step S405, the control unit 110 determines whether the surface texture acquired in step S401 exceeds a second threshold value β.
If the control unit 110 determines that the second threshold value β is exceeded (step S405: YES), the process proceeds to the next step S406.
On the other hand, if the control unit 110 determines that the second threshold value β is not exceeded (that is, the second threshold value β or less) (step S405: NO), the control unit 110 proceeds to step S408.

In step S406, the control unit 110 determines the image formation control change unit to be the "fixing unit (fixing unit 24)."

Next, the control unit 110 determines to increase the target temperature of the fixing unit (fixing section 24), which is the image formation control change unit, by Z [°C] (step S407), and proceeds to step S105 in Figure 5.

In step S408, the control unit 110 determines the image formation control change unit to be the "transfer unit (transfer unit 23)."

Next, the control unit 110 determines to reduce the paper transfer output of the transfer unit (transfer unit 23), which is the image formation control change unit, by Y [μA] (step S409), and proceeds to step S105 in Figure 5.

In step S105 of FIG. 5, the control unit 110 feeds back the determination result (determined image formation conditions) in step S105 to the image formation control of the image forming device 20.

The control unit 110 then feeds back the judgment result to the image formation control of the image forming device 20, and if the image inspection device 40 again detects an abnormality in the image formed on the paper, it stops the image formation operation by the image forming device 20, estimates the location of the defect based on the physical properties detected by the media detection unit, and notifies the user or service technician of a service call (including information on the estimated location of the defect).

As described above, the image forming system 1 according to this embodiment includes an image forming device 20 that forms an image on paper and includes a transfer unit 23 that transfers an image onto paper and a fixing unit 24 that fixes the image transferred by the transfer unit 23 onto the paper, an image inspection device 40 that inspects the paper on which the image has been formed by the image forming device 20, a media detection device 50 that is disposed downstream of the image inspection device 40 and includes media detection units (moisture content detection unit 51, paper surface property detection unit 52, paper resistance detection unit 53) that detect the physical properties of the paper, and a control unit 110 that controls the image forming device 20, the image inspection device 40, and the media detection device 50. Furthermore, when an abnormality is detected in the image formed on the paper by the image inspection device 40, the control unit 110 determines whether to change the image formation conditions in the image forming device 20 based on the physical properties detected by the media detection unit and feeds back the determination result to the image formation control of the image forming device 20.
Therefore, according to the image forming system 1 of this embodiment, appropriate image formation can be performed according to the customer's usage environment (condition of the image forming device and paper), thereby reducing the occurrence of image defects and ensuring image quality.

Furthermore, according to the image forming system 1 of this embodiment, the media detection unit detects the physical properties of the blank area of the paper where no image is formed.
Therefore, according to the image forming system 1 of this embodiment, the physical properties of the paper can be detected with high accuracy, which makes it possible to perform more appropriate image formation and improve image quality.

Furthermore, according to the image forming system 1 of this embodiment, the media detection unit detects the physical property when the abnormality detected by the image inspection device 40 is a white spot.
Therefore, according to the image forming system 1 of this embodiment, when a white spot is detected, appropriate image formation can be automatically performed, so that image quality can be easily ensured.

Furthermore, according to the image forming system 1 of this embodiment, when the abnormality detected by the image inspection device 40 is a white spot, the media detection unit detects the moisture content of the paper, and the control unit 110 determines whether to change the image formation conditions in the image forming device 20 based on the moisture content detected by the media detection unit and feeds back the determination result to the image formation control of the image forming device 20.
Therefore, according to the image forming system 1 of this embodiment, it is possible to perform appropriate image formation depending on the state of the paper, thereby reducing the occurrence of image defects and ensuring image quality.

Furthermore, according to the image forming system 1 of this embodiment, the control unit 110 determines that the temperature of the fixing unit 24 needs to be lowered if the moisture content detected by the media detection unit is less than the first threshold value, and determines that the output value of the transfer unit 23 needs to be lowered if the moisture content detected by the media detection unit is equal to or greater than the first threshold value.
Therefore, according to the image forming system 1 of this embodiment, it is possible to perform appropriate image formation depending on the state of the paper, thereby reducing the occurrence of image defects and ensuring image quality.

Furthermore, according to the image forming system 1 of this embodiment, the media detection device 50 detects the moisture content of the paper by the media detection unit while the paper is being transported.
Therefore, according to the image forming system 1 of this embodiment, the moisture content can be detected without stopping the paper, making it possible to quickly change to appropriate image forming conditions and quickly suppress the occurrence of image defects.

Furthermore, in the image forming system 1 according to this embodiment, the media detection unit is disposed on the path along which a sheet of paper on which an abnormality has been detected by the image inspection device 40 is discharged.
Therefore, according to the image forming system 1 of this embodiment, since the paper does not have to be stopped to detect its physical properties on the path along which it is normally discharged, normal paper can be discharged without delay, thereby improving productivity related to image formation.

Furthermore, according to the image forming system 1 of this embodiment, the media detection device 50 detects the surface properties of the paper with the media detection unit while the paper is stopped.
Therefore, according to the image forming system 1 of this embodiment, the surface properties of the paper can be detected with high accuracy, which makes it possible to form more appropriate images and improve image quality.

Furthermore, according to the image forming system 1 of this embodiment, the control unit 110 determines that it is necessary to increase the temperature of the fixing unit 24 if the surface property detected by the media detection unit exceeds the second threshold value.
Therefore, according to the image forming system 1 of this embodiment, it is possible to perform appropriate image formation depending on the state of the paper, thereby reducing the occurrence of image defects and ensuring image quality.

Furthermore, according to the image forming system 1 of this embodiment, the control unit 110 feeds back the judgment result to the image forming control of the image forming device 20, and if the image inspection device 40 again detects an abnormality in the image formed on the paper, it stops the image forming operation by the image forming device 20, estimates the location of the defect based on the physical properties detected by the media detection unit, and notifies a service call.
Therefore, according to the image forming system 1 of this embodiment, if an image abnormality is not resolved even after changing the image forming conditions, information including the defective part can be notified to the user or service person, so that the image defect will not continue to occur and the waste of materials can be reduced.

The above provides a detailed explanation based on an embodiment of the present invention, but the present invention is not limited to the above embodiment and can be modified without departing from the spirit of the invention.

(Variation 1)
For example, in the above embodiment, a configuration including a media detection device 50 having media detection units (moisture content detection unit 51, paper surface property detection unit 52, paper resistance detection unit 53) that detect the physical properties of paper after image formation is described as an example, but the present invention is not limited to this. For example, in addition to the media detection device 50, a second media detection device 70 may be provided that is disposed before the image forming device 20 and has a second media detection unit that detects the physical properties of paper before an image is formed on it.

As shown in FIG. 9, the image forming system 1A according to variant example 1 comprises a paper feeder 10, a second media detection device 70 connected downstream of the paper feeder 10, an image forming device 20 connected downstream of the second media detection device 70 and forming an image on paper based on print data, a relay unit 30 connected downstream of the image forming device 20, an image inspection device 40 connected downstream of the relay unit 30, a media detection device 50 connected downstream of the image inspection device 40, and a finisher 60 connected downstream of the media detection device 50.

The second media detection device 70 is configured with a moisture content detection unit (second media detection unit) 71 that detects the moisture content of the paper, a paper surface property detection unit (second media detection unit) 72 that detects the surface property of the paper, and a paper resistance detection unit (second media detection unit) 73 that detects the resistance of the paper. The moisture content detection unit 71 detects the moisture content of the paper transported from the paper feeder 10 while the paper is transported to the image forming device 20.

Next, we will explain the operation of the image forming system 1 according to Modification 1. Note that the operation of the image forming system 1 according to Modification 1 is the same as the operation of the image forming system 1 according to the embodiment (see FIG. 5 ), except for the difference in the content of the image formation condition determination process.
An example of the image formation condition determination process according to the first modification (processing for determining whether the image formation conditions are appropriate based on the moisture content of the paper) will be described below with reference to the flowchart of FIG.

First, as shown in FIG. 10, the control unit 110 causes the moisture content detection unit 71 of the second media detection device 70 to detect the moisture content of the paper before image formation, and the moisture content detection unit 51 of the media detection device 50 to detect the moisture content of the paper after image formation, and obtains the detected moisture contents of the paper before and after image formation (step S501).

Next, the control unit 110 calculates the difference in moisture content of the paper before and after image formation obtained in step S501 (the difference between the moisture content of the paper before image formation and the moisture content of the paper after image formation) (step S502).

Next, the control unit 110 determines whether the difference in moisture content calculated in step S502 is less than a first threshold value α (step S503).
If the control unit 110 determines that the difference is less than the first threshold value α (step S503: YES), the process proceeds to the next step S504.
On the other hand, if the control unit 110 determines that the difference is not less than the first threshold value α (that is, is equal to or greater than the first threshold value α) (step S503: NO), the control unit 110 proceeds to step S506.

In step S504, the control unit 110 determines the image formation control change unit to be the "fixing unit (fixing unit 24)."

Next, the control unit 110 determines to lower the target temperature of the fixing unit (fixing section 24), which is the image formation control change unit, by X [°C] (step S505), and proceeds to step S105 in Figure 5, where it feeds back the determination result (determined image formation conditions) to the image formation control of the image forming device 20.

In step S506, the control unit 110 determines the image formation control change unit to be the "transfer unit (transfer unit 23)."

Next, the control unit 110 determines to reduce the paper transfer output of the transfer unit (transfer unit 23), which is the image formation control change unit, by Y [μA] (step S507), and proceeds to step S105 in Figure 5, where it feeds back the determination result (determined image formation conditions) to the image formation control of the image forming device 20.

As described above, the image forming system 1A according to the first modification includes the second media detection device 70, which is disposed upstream of the image forming device 20 and includes a second media detection unit (moisture content detection unit 71, paper surface property detection unit 72, paper resistance detection unit 73) that detects the physical properties of the paper before an image is formed on it. Furthermore, when the image inspection device 40 detects an abnormality in the image formed on the paper, the control unit 110 determines whether to change the image formation conditions in the image forming device 20 based on the difference between the physical properties detected by the media detection unit and the physical properties detected by the second media detection unit, and feeds back the determination result to the image formation control of the image forming device 20.
Therefore, according to the image forming system 1A of variant example 1, it is possible to accurately detect changes in the physical properties of paper due to image formation, making it possible to perform more appropriate image formation and improve image quality.

Furthermore, in the image forming system 1A relating to variant example 1, the media detection unit and the second media detection unit both detect the moisture content of the paper, and the control unit 110 determines whether to change the image forming conditions in the image forming device 20 based on the difference between the moisture content detected by the media detection unit and the moisture content detected by the second media detection unit, and feeds back the determination result to the image formation control of the image forming device 20.
Therefore, according to the image forming system 1A of the first modification, it is possible to perform appropriate image formation depending on the state of the paper, thereby reducing the occurrence of image defects and ensuring image quality.

Furthermore, according to the image forming system 1A relating to variant example 1, the control unit 110 determines that the temperature of the fixing unit 24 needs to be lowered if the difference between the moisture content detected by the media detection unit and the moisture content detected by the second media detection unit is less than the first threshold value, and determines that the output value of the transfer unit 23 needs to be lowered if the difference between the moisture content detected by the media detection unit and the moisture content detected by the second media detection unit is equal to or greater than the first threshold value.
Therefore, according to the image forming system 1A of the first modification, it is possible to perform appropriate image formation depending on the state of the paper, thereby reducing the occurrence of image defects and ensuring image quality.

(Other Modifications)
In addition, in the above embodiment, when the physical properties of paper are detected using the media detection unit (moisture content detection unit 51, paper surface property detection unit 52, paper resistance detection unit 53) of the media detection device 50, the physical properties of the paper after image formation (paper on which an image abnormality has been detected) are detected, but this is not limited to this.
For example, instead of detecting the physical properties of paper after image formation, the physical properties of paper before image formation may be detected. Compared to paper before image formation, paper after image formation contains image information, which causes variations in the physical properties of the paper, resulting in a problem of reduced accuracy in detecting the physical properties. However, by detecting the physical properties of paper before image formation, the accuracy of detecting the physical properties can be improved. Specifically, first, if the abnormality detected by the image inspection device 40 is a blank area, the control unit 110 ejects paper before image formation (paper that has been fed but on which image formation has not started) from the image forming device 20. At this time, the ejected paper is transported to the media detection device 50 without image formation (however, fixing control is performed). Then, the media detection unit of the media detection device 50 detects the physical properties of the paper before image formation that was ejected from the image forming device 20. That is, the paper whose physical properties are to be detected is the paper being conveyed through the second media detection device 70 (=paper P4 on which image formation has not yet been performed), as shown in Fig. 11. Note that reference symbol P1 in Fig. 11 indicates a paper on which a blank spot has been detected, reference symbol P2 indicates a paper on which an image has already been formed, and reference symbol P3 indicates a paper on which image formation has already started.
As described above, when the abnormality detected by the image inspection device 40 is a white area, the control unit 110 causes the paper on which an image has not been formed to be discharged from the image forming device 20, and the media detection unit detects the physical properties of the paper on which an image has not been formed that has been discharged from the image forming device 20.This makes it possible to accurately detect the physical properties of the paper, thereby making it possible to perform more appropriate image formation and improve image quality.

In addition, in the above embodiment, the physical properties to be detected by the media detection device 50 and the second media detection device 70 are described as examples of moisture content, which is the moisture contained in the paper, and surface properties, which is the roughness of the paper surface, but are not limited to these.
For example, instead of moisture content or surface properties, the paper resistance value, which is the resistance of the paper, or physical properties such as grain direction, stiffness, thickness, basis weight, and size of the paper may be detected and used.

Furthermore, in the above embodiment, the moisture content detection unit 51 of the media detection device 50 is positioned upstream (in front of) the discharge path to the purge tray T2, and the moisture content of the paper is detected when an image abnormality (white space) is detected by the image inspection device 40, but this is not limited to this.
For example, the moisture content of the paper may be detected regardless of whether or not the image inspection device 40 detects an image abnormality (white space).
Furthermore, the moisture content detector 51 may be arranged on the discharge path to the purge tray T2, similar to the paper surface property detector 52 and the paper resistance detector 53.

In addition, in the above embodiment, at the timing when the image formation conditions are determined in the image formation condition judgment process, the determined image formation conditions are fed back to the image formation control of the image forming device 20, but this is not limited to this.
For example, as shown in FIG. 11, feedback may be performed from a sheet of paper that has already started to be transported within the image forming system 1, for which image formation has not yet been performed, and for which image formation using the changed parameters of the image formation conditions (image formation using the image formation conditions after feedback) is possible in time (for example, sheet P4 in FIG. 11).
12, all sheets that have already started to be conveyed in the image forming system 1 may be discharged to the purge tray T2, and feedback may be performed starting with sheet P6 that will newly start to be fed from the sheet feeding device 10. In particular, when changing the image forming conditions, if it is necessary to stop and restart the image forming unit depending on the feedback content, it is preferable to perform feedback starting with sheet P6 that will newly start to be fed from the sheet feeding device 10. Note that reference symbol P5 in FIG. 12 indicates a sheet that has already started to be conveyed at the timing when the image forming conditions were determined, and is then discharged to the purge tray T2.

In addition, the detailed configuration and operation of each device that makes up the image forming system may be modified as appropriate without departing from the spirit and scope of the present invention.

1 Image forming system 10 Paper feed device 20 Image forming device 21 Intermediate transfer belt 22 Image forming unit 23 Transfer section 24 Fixing section 30 Relay unit 40 Image inspection device 50 Media detection device 51 Moisture content detection section (media detection section)
52 Paper surface detection unit (media detection unit)
53 Paper resistance detection unit (media detection unit)
60 Finisher 70 Second media detection device 71 Moisture content detection unit (second media detection unit)
72 Paper surface detection unit (second media detection unit)
73 Paper resistance detection unit (second media detection unit)
110 Control unit 120 Memory unit T1 Paper output tray T2 Purge tray P Paper

Claims (14)

an image forming apparatus including a transfer unit that transfers an image onto a sheet of paper and a fixing unit that fixes the image transferred by the transfer unit onto the sheet of paper, and forming an image on the sheet of paper;
an image inspection device that inspects the paper on which the image is formed by the image forming device;
a media detection device disposed downstream of the image inspection device and including a media detection unit that detects the physical properties of the paper;
a control unit that controls the image forming device, the image inspection device, and the media detection device;
Equipped with
The control unit, when an abnormality in the image formed on the paper is detected by the image inspection device, determines whether to change the image formation conditions in the image forming device based on the physical properties detected by the media detection unit, and feeds back the determination result to the image formation control of the image forming device. The image forming system of claim 1, wherein the media detection unit detects the physical properties of blank areas of the paper on which no image is formed. The image forming system of claim 1, wherein the media detection unit detects the physical property when the abnormality detected by the image inspection device is a white area. the control unit, when the abnormality detected by the image inspection device is a white spot, causes the sheet on which the image formation has not been performed to be discharged from the image forming device;
4. The image forming system according to claim 3, wherein the media detection unit detects physical properties of a sheet of paper that has been discharged from the image forming apparatus and on which no image has been formed. the media detection unit detects the moisture content of the paper when the abnormality detected by the image inspection device is a white spot;
The image forming system according to claim 3, wherein the control unit determines whether to change the image forming conditions in the image forming device based on the moisture content detected by the media detection unit, and feeds back the determination result to the image forming control of the image forming device. The image forming system of claim 5, wherein the control unit determines that the temperature of the fixing unit needs to be lowered if the moisture content detected by the media detection unit is less than a first threshold, and determines that the output value of the transfer unit needs to be lowered if the moisture content detected by the media detection unit is equal to or greater than the first threshold. The image forming system of claim 5, wherein the media detection device detects the moisture content of the paper using the media detection unit while the paper is being transported. a second media detection device disposed in front of the image forming device and including a second media detection unit that detects physical properties of the paper before the image is formed;
The image forming system described in claim 1, characterized in that when the image inspection device detects an abnormality in the image formed on the paper, the control unit determines whether to change the image forming conditions in the image forming device based on the difference between the physical properties detected by the media detection unit and the physical properties detected by the second media detection unit, and feeds back the determination result to the image formation control of the image forming device. the media detection unit and the second media detection unit both detect the moisture content of the paper;
The image forming system according to claim 8, wherein the control unit determines whether to change the image forming conditions in the image forming device based on the difference between the moisture content detected by the media detection unit and the moisture content detected by the second media detection unit, and feeds back the determination result to the image formation control of the image forming device. The image forming system of claim 9, wherein the control unit determines that the temperature of the fixing unit needs to be lowered if the difference between the moisture content detected by the media detection unit and the moisture content detected by the second media detection unit is less than a first threshold, and determines that the output value of the transfer unit needs to be lowered if the difference between the moisture content detected by the media detection unit and the moisture content detected by the second media detection unit is equal to or greater than the first threshold. The image forming system described in claim 1, characterized in that the media detection unit is located on a path for ejecting paper for which the abnormality has been detected by the image inspection device. The image forming system described in claim 11, characterized in that the media detection device detects the surface property of the paper using the media detection unit while the paper is stopped. The image forming system described in claim 12, characterized in that the control unit determines that the temperature of the fixing unit needs to be increased if the surface property detected by the media detection unit exceeds a second threshold. The image forming system described in claim 1, characterized in that, after the control unit feeds back the judgment result to the image formation control of the image forming device, if the image inspection device again detects an abnormality in the image formed on the paper, it stops the image formation operation of the image forming device, estimates the location of the defect based on the physical properties detected by the media detection unit, and notifies a service call.