JP2024078810A - Image forming apparatus and image forming method - Google Patents

Abstract

An image forming apparatus and an image forming method are provided that are capable of setting execution conditions for image forming processing for each sheet according to the ease with which a developer penetrates into the sheet.
[Solution] The image forming device includes an acquisition processing unit 81 that acquires a specific value indicating the ease of ink penetration into the sheet based on the amount of reflected light that is emitted from the light emitting unit and reflected on an image-formed first surface of a sheet on one side of which an image is formed by an image forming unit 3, and the amount of transmitted light that is emitted from the light emitting unit and passes through the sheet, and a setting processing unit 82 that sets execution conditions for an image formation process that forms an image on an unformed second surface of the sheet based on the specific value.
[Selected figure] Figure 3

Description

The present invention relates to an image forming apparatus and an image forming method.

Image forming devices such as printers that form images on sheets using a developer such as ink are known. Image forming devices that set the execution conditions for the image formation process based on the type of sheet are also known (see, for example, Patent Document 1).

Japanese Patent Application Laid-Open No. 5-16462

However, the ease with which the developer penetrates into a sheet may differ for each individual sheet, even if the sheets are of the same type. However, in a conventional configuration in which the execution conditions for the image formation process are set based on the type of sheet, it is not possible to set the execution conditions for the image formation process for each sheet according to the ease with which the developer penetrates into that sheet.

The object of the present invention is to provide an image forming apparatus and an image forming method that can set the execution conditions of the image forming process for each sheet according to the ease with which the developer penetrates into that sheet.

An image forming apparatus according to one aspect of the present invention includes an image forming unit, a reflected light detection unit, a transmitted light detection unit, an acquisition processing unit, and a setting processing unit. The image forming unit forms an image on one side of a sheet using a developer. The reflected light detection unit includes a first light emission unit that emits light toward an image-formed first side of a single-sided image forming sheet on one side of which an image has been formed by the image forming unit, and detects the amount of reflected light emitted from the first light emission unit and reflected by the single-sided image forming sheet. The transmitted light detection unit includes a second light emission unit that emits light toward an irradiation area of the first side of the single-sided image forming sheet that is irradiated with light emitted from the first light emission unit, and detects the amount of transmitted light emitted from the second light emission unit and transmitted through the single-sided image forming sheet. The acquisition processing unit acquires a specific value indicating the ease of penetration of the developer into the single-sided image forming sheet based on the amount of reflected light detected by the reflected light detection unit and the amount of transmitted light detected by the transmitted light detection unit. The setting processing unit sets the execution conditions of the image forming process for forming an image on the unformed second side of the single-sided image forming sheet based on the specific value acquired by the acquisition processing unit.

The image forming method according to another aspect of the present invention is executed by an image forming apparatus including an image forming unit that forms an image on one side of a sheet using a developer, a first light emitting unit that emits light toward an image-formed first side of a single-sided image forming sheet on one side of which an image has been formed by the image forming unit, a reflected light detection unit that detects the amount of reflected light emitted from the first light emitting unit and reflected by the single-sided image forming sheet, and a second light emitting unit that emits light toward an irradiation area of the first side of the single-sided image forming sheet that is irradiated with light emitted from the first light emitting unit, and a transmitted light detection unit that detects the amount of transmitted light emitted from the second light emitting unit and transmitted through the single-sided image forming sheet, and includes an acquisition step and a setting step. In the acquisition step, a specific value indicating the ease of penetration of the developer into the single-sided image forming sheet is acquired based on the amount of reflected light detected by the reflected light detection unit and the amount of transmitted light detected by the transmitted light detection unit. In the setting step, the execution conditions of the image forming process for forming an image on the unformed second side of the single-sided image forming sheet are set based on the specific value acquired in the acquisition step.

According to the present invention, it is possible to set the execution conditions of the image formation process for each sheet according to the ease with which the developer penetrates into that sheet.

FIG. 1 is a diagram showing the configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a diagram showing the configuration of the image forming unit of the image forming apparatus according to the embodiment of the present invention. FIG. 3 is a block diagram showing a system configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 4 is a diagram showing the configuration of a media sensor of the image forming apparatus according to the embodiment of the present invention. FIG. 5 is a flowchart showing an example of an execution condition setting process executed by the image forming apparatus according to the embodiment of the present invention.

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

[Configuration of Image Forming Apparatus 10]
First, the configuration of an image forming apparatus 10 according to an embodiment of the present invention will be described with reference to Figures 1 to 4. Here, Figure 1 is a cross-sectional view showing the configuration of the image forming apparatus 10. Also, Figure 2 is a plan view showing the configuration of the image forming unit 3. Also, Figure 4 is a side view showing the configuration of the media sensor 5 and a sheet SH1 passing through a detection position P4. In Figure 1, the paper feed path R1, paper discharge path R2, reverse transport path R3, and re-transport path R4 are indicated by two-dot chain lines.

The image forming device 10 is a printer capable of forming images on both sides of a sheet using an inkjet method. The present invention may also be applied to image forming devices such as facsimile machines, copy machines, and multifunction machines that are capable of forming images using an inkjet method.

As shown in Figures 1 and 3, the image forming device 10 includes a housing 1, a sheet conveying section 2, an image forming section 3, a conveying unit 4, a media sensor 5, an operation display section 6, a memory section 7, and a control section 8.

The housing 1 houses each of the components of the image forming device 10. A paper feed cassette 11 is removably provided in the housing 1. The paper feed cassette 11 houses sheets on which images are to be formed. For example, the paper feed cassette 11 houses sheets such as paper, coated paper, postcards, envelopes, and overhead projector sheets. A paper output tray 12 is provided on the outer surface of the housing 1. Sheets on which images have been formed by the image forming unit 3 are output to the paper output tray 12.

Inside the housing 1, there are provided a paper feed path R1, a paper discharge path R2, a reversing conveying path R3, and a re-conveying path R4 that guide the sheet conveyed by the sheet conveying unit 2. The paper feed path R1 is a path through which the sheet moves from the paper feed cassette 11 (an example of a paper feed source of the sheet of the present invention) to the image forming unit 3. The paper discharge path R2 is a path through which the sheet moves from the image forming unit 3 to the paper discharge tray 12. The reversing conveying path R3 is used to reverse a one-sided image forming sheet on one side of which an image is formed by the image forming unit 3. The reversing conveying path R3 branches off from a first branching position P1 (see FIG. 1) on the paper discharge path R2. The re-conveying path R4 is used to re-convey the one-sided image forming sheet that has been reversed using the reversing conveying path R3 to the image forming unit 3. The re-conveying path R4 branches off from a second branching position P2 (see FIG. 1) on the reversing conveying path R3 and merges at a merging position P3 (see FIG. 1) on the paper feed path R1. The portion of the paper feed path R1 where it merges with the re-conveying path R4 is an example of a junction in the present invention. In addition, the reversing path R3 and the re-conveying path R4 are examples of the reversing path in the present invention.

The sheet transport unit 2 transports a sheet inside the housing 1. As shown in FIG. 1, the sheet transport unit 2 includes a pick-up roller 21, a first transport roller pair 22, a second transport roller pair 23, a third transport roller pair 24, and a fourth transport roller pair 25.

The pickup roller 21 picks up sheets one by one from the paper feed cassette 11 and sends the sheets to the paper feed path R1. The first transport roller pair 22 is provided in the paper feed path R1 and transports the sheet in the transport direction D1 (see FIG. 1) toward the image forming unit 3. The second transport roller pair 23 is provided in the paper discharge path R2 and transports the single-sided image formation sheet in the transport direction D2 (see FIG. 1) toward the paper discharge tray 12. The third transport roller pair 24 is provided in the reverse transport path R3 and transports the single-sided image formation sheet in the transport direction D3 (see FIG. 1) from the first branch position P1 toward the second branch position P2, and then transports the single-sided image formation sheet in the opposite direction to the transport direction D3 to send the single-sided image formation sheet to the re-transport path R4. The fourth transport roller pair 25 is provided in the re-transport path R4 and transports the single-sided image formation sheet in the transport direction D4 (see FIG. 1) toward the junction position P3.

The image forming unit 3 uses ink as a developer to form an image based on image data on one side of a sheet supplied from the sheet conveying unit 2. As shown in FIG. 1, the image forming unit 3 includes line heads 31, 32, 33, and 34 corresponding to the colors black, cyan, magenta, and yellow, and a head frame 35 that supports these. The head frame 35 is supported by the housing 1. The number of line heads included in the image forming unit 3 may be one or multiple, excluding four.

The line heads 31 to 34 are so-called line head type recording heads. In other words, the image forming device 10 is a so-called line head type image forming device. As shown in FIG. 2, the line heads 31 to 34 are long in a width direction D6 perpendicular to the sheet transport direction D5 by the transport unit 4. Specifically, each of the line heads 31 to 34 has a length in the width direction D6 that corresponds to the width of the largest size sheet that can be accommodated in the paper feed cassette 11. Each of the line heads 31 to 34 is fixed to the head frame 35 at a predetermined interval along the transport direction D5.

As shown in FIG. 2, each of the line heads 31 to 34 has a plurality of recording heads 30. The recording heads 30 eject ink toward a sheet transported by the transport unit 4. Specifically, a number of nozzles 30A (see FIG. 2) having openings for ejecting ink are provided on the surface of the recording head 30 facing the sheet transported by the transport unit 4. The recording head 30 also includes pressure chambers (not shown) corresponding to each of the nozzles 30A, piezoelectric elements (not shown) corresponding to each of the pressure chambers, and communication channels (not shown) communicating with each of the pressure chambers. The piezoelectric elements eject ink from the nozzles 30A in response to application of a predetermined drive voltage. Specifically, the piezoelectric elements pressurize the ink contained in the pressure chambers to eject ink from the nozzles 30A.

In this embodiment, the line head 31 has three recording heads 30 arranged in a staggered pattern along the width direction D6. Similarly to the line head 31, each of the other line heads 32 to 34 also has three recording heads 30 arranged in a staggered pattern along the width direction D6. Each of the line heads 31 to 34 is supplied with ink of the same color as the color corresponding to that line head from an ink container (not shown). Note that FIG. 2 shows the image forming unit 3 as viewed from the top of FIG. 1.

As shown in FIG. 1, the transport unit 4 is disposed below the line heads 31 to 34. The transport unit 4 transports the sheet in a transport direction D5 (see FIG. 2) toward the discharge path R2 while facing the recording head 30. Specifically, the transport unit 4 transports the sheet by a predetermined transport amount each time the recording head 30 ejects ink. The transport unit 4 also stops transporting the sheet while the recording head 30 ejects ink. As shown in FIG. 1, the transport unit 4 includes a transport belt 41 on which the sheet is placed, tension rollers 42 to 44 that stretch the transport belt 41, and a transport frame 45 that supports them. The gap between the transport belt 41 and the recording head 30 is adjusted so that the gap between the surface of the sheet and the recording head 30 during image formation is 1 mm, for example.

The tension roller 42 is rotated by a rotational driving force supplied from a motor (not shown). This causes the conveyor belt 41 to rotate in a direction that allows the sheet to be conveyed in the conveying direction D5 (see FIG. 2). The conveyor unit 4 is also provided with a suction unit (not shown) that draws air through a number of through holes formed in the conveyor belt 41 to adhere the sheet to the conveyor belt 41. A pressure roller 46 is provided opposite the tension roller 42 to press the sheet against the conveyor belt 41 for conveyance.

The media sensor 5 is used to detect various pieces of information related to the sheet. As shown in FIG. 1, the media sensor 5 is provided at a detection position P4 (see FIG. 1) downstream of the junction position P3 in the paper feed path R1 in the transport direction D1 and upstream of the image forming unit 3 in the transport direction D1.

The media sensor 5 includes a reflective optical sensor 51, a transmissive optical sensor 52, and a displacement sensor 53, as shown in FIG. 3.

The reflective optical sensor 51 includes a first light emitting section 51A, a specular reflected light receiving section 51B, and a diffuse reflected light receiving section 51C, as shown in FIG. 4. The reflective optical sensor 51 is an example of a reflected light detection section of the present invention.

The first light emitting unit 51A emits the first emitted light L1 (see FIG. 4) toward the back surface of the sheet SH1 passing through the detection position P4. The sheet SH1 is an unimaged sheet on which no image is formed on both sides of the sheet, or the one-sided image-formed sheet. The back surface of the sheet SH1 is the surface opposite to the surface (front surface) facing the recording head 30. In other words, when the sheet SH1 is the one-sided image-formed sheet, the back surface is the surface on which an image has been formed (an example of the first surface of the present invention). The first light emitting unit 51A emits the first emitted light L1 toward the back surface of the sheet SH1. In FIG. 4, the first emitted light L1 is indicated by a thick line with an arrow. For example, the first light emitting unit 51A is a light emitting element such as a light emitting diode that emits light of a predetermined wavelength. In addition, the first light emitting unit 51A may be provided with a light guiding member that guides the light emitted from the light emitting element to the back surface of the sheet SH1.

The specularly reflected light receiving unit 51B detects the amount of specularly reflected light L2 (see FIG. 4) (one example of the reflected light of the present invention) from the light emitted from the first light emitting unit 51A and reflected by the rear surface of the sheet SH1. In FIG. 4, the specularly reflected light L2 is indicated by a solid line with an arrow. For example, the specularly reflected light receiving unit 51B is a light receiving element such as a phototransistor that receives the specularly reflected light L2 and outputs an electrical signal according to the amount of light received.

The diffuse reflected light receiving unit 51C detects the amount of diffuse reflected light L3 (see FIG. 4) from the light emitted from the first light emitting unit 51A and reflected by the rear surface of the sheet SH1. In FIG. 4, the diffuse reflected light L3 is indicated by a dashed line with an arrow. For example, the diffuse reflected light receiving unit 51C is a light receiving element such as a phototransistor that receives the diffuse reflected light L3 and outputs an electrical signal according to the amount of light received.

The transmissive optical sensor 52 includes a second light emitting section 52A and a transmitted light receiving section 52B shown in FIG. 4. The transmissive optical sensor 52 is an example of a transmitted light detection section of the present invention.

The second light emitting unit 52A emits the second emitted light L4 (see FIG. 4) toward the rear surface of the sheet SH1 passing through the detection position P4. The second light emitting unit 52A emits the second emitted light L4 toward an area of the rear surface of the sheet SH1 that is irradiated with the first emitted light L1 emitted from the first light emitting unit 51A. In FIG. 4, the second emitted light L4 is indicated by a thick line with an arrow. For example, the second light emitting unit 52A is a light emitting element such as a light emitting diode that emits light of a predetermined wavelength. In addition, the second light emitting unit 52A may be provided with a light guiding member that guides the light emitted from the light emitting element to the rear surface of the sheet SH1.

In the media sensor 5, the first light emitting section 51A also functions as the second light emitting section 52A. In other words, the first emitted light L1 and the second emitted light L4 are the same light. Note that the second light emitting section 52A may be provided separately from the first light emitting section 51A.

The transmitted light receiving unit 52B detects the amount of transmitted light L5 (see FIG. 4) that is emitted from the second light emitting unit 52A and transmitted through the sheet SH1. In FIG. 4, the transmitted light L5 is indicated by a dotted line with an arrow. For example, the transmitted light receiving unit 52B is a light receiving element such as a phototransistor that receives the transmitted light L5 and outputs an electrical signal according to the amount of light received.

The displacement sensor 53 includes a lever member 53A shown in FIG. 4. The displacement sensor 53 also includes a displacement amount detection unit (not shown).

The lever member 53A is provided so that it can be displaced from a predetermined reference position by contact with the sheet SH1. In FIG. 4, the lever member 53A installed at the reference position is indicated by a dashed line. For example, the lever member 53A is provided so that it can swing about the swing shaft 53B shown in FIG. 4. The swing shaft 53B is an axis that extends in the width direction of the sheet SH1, perpendicular to the conveying direction D1 (see FIG. 4). By contacting the sheet SH1, the lever member 53A is displaced from the reference position in the swing direction about the swing shaft 53B by an amount according to the thickness of the sheet SH1.

The displacement amount detection unit detects the amount of displacement of the lever member 53A from the reference position. For example, the displacement amount detection unit is an electric circuit that includes a variable resistor whose electrical resistance changes in response to the rotation of the pivot shaft 53B and outputs an electric signal in response to the electrical resistance of the variable resistor.

The operation display unit 6 has a display unit such as a liquid crystal display that displays various information in response to control instructions from the control unit 8, and an operation unit such as operation keys or a touch panel that inputs various information to the control unit 8 in response to user operations. The operation display unit 6 is provided on the top surface of the housing 1.

The storage unit 7 is a non-volatile storage device. For example, the storage unit 7 is a flash memory. The storage unit 7 may also be an SSD (solid state drive) or an HDD (hard disk drive).

The control unit 8 includes control devices such as a CPU 8A, a ROM 8B, and a RAM 8C. The CPU 8A is a processor that executes various arithmetic operations. The ROM 8B is a non-volatile storage device in which information such as a control program for causing the CPU 8A to execute various processes is stored in advance. The RAM 8C is a volatile or non-volatile storage device used as a temporary storage memory (work area) for various processes executed by the CPU 8A. In the control unit 8, the CPU 8A executes various control programs stored in the ROM 8B in advance. As a result, the image forming device 10 is comprehensively controlled by the control unit 8. The control unit 8 may be configured with an electronic circuit such as an integrated circuit (ASIC), or may be a control unit provided separately from the main control unit that comprehensively controls the image forming device 10.

However, the ease with which ink penetrates into sheets can differ for each individual sheet, even if the sheets are of the same type. However, in a conventional configuration in which the execution conditions for the image formation process are set based on the type of sheet, it is not possible to set the execution conditions for the image formation process for each sheet according to the ease with which ink penetrates into that sheet.

In contrast, in the image forming device 10 according to an embodiment of the present invention, as described below, it is possible to set the execution conditions of the image forming process for each sheet according to the ease with which the ink penetrates into that sheet.

Specifically, an execution condition setting program for causing the CPU 8A of the control unit 8 to execute the execution condition setting process described below (see the flowchart in FIG. 5) is prestored in the ROM 8B of the image forming device 10. The execution condition setting program may be recorded on a computer-readable recording medium such as a CD, DVD, or flash memory, and may be read from the recording medium and installed in the storage unit 7.

The control unit 8 includes an acquisition processing unit 81, a setting processing unit 82, and a judgment processing unit 83, as shown in FIG. 3. Specifically, the control unit 8 executes the execution condition setting program stored in the ROM 8B using the CPU 8A. As a result, the control unit 8 functions as the acquisition processing unit 81, the setting processing unit 82, and the judgment processing unit 83. Note that some or all of the functional units included in the control unit 8 may be configured with electronic circuits. The execution condition setting program may also be a program for causing multiple processors to function as each functional unit included in the control unit 8.

The acquisition processing unit 81 acquires a specific value indicating the ease of ink penetration into the single-sided image forming sheet based on the amount of specularly reflected light L2 detected by the reflective optical sensor 51 and the amount of transmitted light L5 detected by the transmissive optical sensor 52.

Specifically, the acquisition processing unit 81 acquires the specific value in the following manner.

First, the acquisition processing unit 81 uses a reflective optical sensor 51 and a transmissive optical sensor 52 to detect the amount of specularly reflected light L2 reflected by the rear surface of the non-image-formed sheet and the amount of transmitted light L5 transmitted through the non-image-formed sheet.

Next, the acquisition processing unit 81 uses a reflective optical sensor 51 and a transmissive optical sensor 52 to detect the amount of specularly reflected light L2 reflected by a specific image on the back surface of the single-sided image forming sheet, and the amount of transmitted light L5 that has passed through the specific image.

Here, the specific image is an image formed with ink of a predetermined specific color. For example, the specific color is black. The specific color may be cyan, magenta, or yellow. The specific image may be an image formed with ink of the specific color, and the density of the specific color may exceed a predetermined reference density.

Next, the acquisition processing unit 81 calculates the amount of ink that adheres to the back surface of the single-sided image forming sheet, out of the ink used to form the specific image, based on the amount of specularly reflected light L2 reflected by the back surface of the unimaged sheet and the amount of specularly reflected light L2 reflected by the specific image on the back surface of the single-sided image forming sheet.

For example, the acquisition processing unit 81 can calculate the amount of ink that is adhered to the back surface of the single-sided image forming sheet out of the ink used to form the specific image by the following formula (1). In formula (1), X is a symbol indicating the amount of ink that is adhered to the back surface of the single-sided image forming sheet out of the ink used to form the specific image. In formula (1), A is a symbol indicating the amount of specularly reflected light L2 reflected by the back surface of the unimaged sheet. In formula (1), B is a symbol indicating the amount of specularly reflected light L2 reflected by the specific image on the back surface of the single-sided image forming sheet. In formula (1), C is a symbol indicating the amount of first emitted light L1 absorbed by a predetermined unit amount of ink of the specific color.

X = (A - B) ÷ C... (1)

Next, the acquisition processing unit 81 calculates the amount of ink used to form the specific image based on the amount of transmitted light L5 that has passed through the unimaged sheet and the amount of transmitted light L5 that has passed through the specific image on the back surface of the single-sided image-forming sheet. Here, the amount of ink used to form the specific image includes the amount of ink that adheres to the back surface of the single-sided image-forming sheet and the amount of ink that has permeated from the back surface in the thickness direction of the sheet.

For example, the acquisition processing unit 81 can calculate the amount of ink used to form the specific image by the following formula (2). In formula (2), Y is a symbol indicating the amount of ink used to form the specific image. In formula (2), D is a symbol indicating the amount of transmitted light L5 that has passed through the unimaged sheet. In formula (2), E is a symbol indicating the amount of transmitted light L5 that has passed through the specific image on the back surface of the single-sided image-formed sheet. In formula (2), F is a symbol indicating the amount of second emitted light L4 absorbed by the unit amount of ink of the specific color.

Y = (D - E) ÷ F... (2)

Then, the acquisition processing unit 81 acquires the ratio of the amount of ink that adheres to the back surface of the single-sided image forming sheet to the amount of ink used to form the specific image as the specific value.

The determination processing unit 83 determines whether the specific image is present in the irradiation area of the first emitted light L1 on the back surface of the single-sided image forming sheet.

For example, the judgment processing unit 83 judges whether or not the specific image is present in the irradiation area based on the image data used to form an image on the single-sided image forming sheet.

Here, when the determination processing unit 83 determines that the specific image does not exist in the irradiation area, the acquisition processing unit 81 does not acquire the specific value. This avoids unnecessary driving of the reflective optical sensor 51 and the transmissive optical sensor 52 when it is difficult to acquire the specific value.

Based on the specific value acquired by the acquisition processing unit 81, the setting processing unit 82 sets the execution conditions of a second image forming process (an example of an image forming process of the present invention) that forms an image on the front side of the single-sided image forming sheet, i.e., the side on which an image is not formed (an example of the second side of the present invention).

Here, the second image forming process is a process in which an image is formed on the front side of the single-sided image forming sheet that has passed through the reversing transport path R3 and the re-transport path R4 using the image forming unit 3.

For example, the execution conditions of the second image forming process include both a first condition related to the transport speed of the single-sided image forming sheet and a second condition related to the amount of ink ejected onto the single-sided image forming sheet.

For example, when the specific value acquired by the acquisition processing unit 81 is equal to or less than a predetermined threshold value, the setting processing unit 82 increases the amount of ink ejected onto the single-sided image forming sheet from a predetermined reference amount to 1.2 times the reference amount. For example, the threshold value is 0.8. For example, the setting processing unit 82 switches the waveform of the driving voltage applied to the piezoelectric element from a first waveform corresponding to the reference amount to a second waveform corresponding to 1.2 times the reference amount. This makes it possible to suppress variations in image density from sheet to sheet due to the ease of ink penetration from sheet to sheet. Note that the amount of ink ejected onto the single-sided image forming sheet when the specific value is equal to or less than the threshold value may be determined arbitrarily.

Furthermore, when the specific value acquired by the acquisition processing unit 81 is equal to or less than the threshold value, the setting processing unit 82 reduces the transport speed of the single-sided image formation sheet from a predetermined reference speed to half the reference speed. As a result, when the sheet stored in the paper feed cassette 11 is one into which ink easily permeates, even if the ink ejected onto the front side of the single-sided image formation sheet permeates to the back side, transport before the ink dries is suppressed. Therefore, contamination of the inside of the housing 1 by the ink is suppressed. Note that the transport speed of the single-sided image formation sheet when the specific value is equal to or less than the threshold value may be set arbitrarily.

The execution conditions for the second image forming process may include only one of the first condition and the second condition.

[Execution condition setting process]
5, an example of the procedure of the execution condition setting process executed by the control unit 8 in the image forming apparatus 10 and the procedure of the image forming method according to the present invention will be described. Here, steps S11, S12, ... represent the numbers of the processing procedures (steps) executed by the control unit 8. Note that the execution condition setting process is executed every time a sheet is conveyed from the paper feed cassette 11 when a double-sided image forming process is executed to form images on both sides of a sheet.

<Step S11>
First, in step S11, the control unit 8 detects the amount of specularly reflected light L2 reflected by the rear surface of the non-image-formed sheet and the amount of transmitted light L5 transmitted through the non-image-formed sheet, using the reflective optical sensor 51 and the transmissive optical sensor 52. Here, the process of step S11 is executed by the acquisition processing unit 81 of the control unit 8.

<Step S12>
In step S12, the control unit 8 determines whether or not the specific image is present in the irradiation area of the first emitted light L1 on the back surface (the surface on which the image has been formed) of the single-sided image forming sheet. Here, the process of step S12 is executed by the determination processing unit 83 of the control unit 8.

Specifically, the control unit 8 determines whether the specific image is present in the irradiation area based on the image data used to form an image on the single-sided image forming sheet.

<Step S13>
In step S13, the control unit 8 branches the process depending on the result of the process in step S12. Specifically, when it is determined that the specific image is present in the irradiation area on the back surface of the single-sided image forming sheet (Yes in S13), the control unit 8 shifts the process to step S14. Also, when it is determined that the specific image is not present in the irradiation area on the back surface of the single-sided image forming sheet (No in S13), the control unit 8 ends the execution condition setting process.

<Step S14>
In step S14, the control unit 8 detects the amount of specular reflected light L2 reflected by the specific image on the back surface of the single-sided image forming sheet and the amount of transmitted light L5 transmitted through the specific image, using the reflective optical sensor 51 and the transmissive optical sensor 52. Here, the process of step S14 is executed by the acquisition processing unit 81 of the control unit 8.

<Step S15>
In step S15, the control unit 8 acquires the specific value. Here, the process of step S15 is executed by the acquisition processing unit 81 of the control unit 8. The process of step S15 is an example of an acquisition step of the present invention.

Specifically, the control unit 8 calculates the amount of ink that adheres to the rear surface of the single-sided image forming sheet from the ink used to form the specific image based on the amount of specularly reflected light L2 detected in the processing of step S11 and the amount of specularly reflected light L2 detected in the processing of step S14.

The control unit 8 also calculates the amount of ink used to form the specific image based on the amount of transmitted light L5 detected in step S11 and the amount of transmitted light L5 detected in step S14.

Then, the control unit 8 obtains the specific value as the ratio of the amount of ink that adheres to the back surface of the single-sided image forming sheet to the amount of ink used to form the specific image.

The process of step S11 may be executed only when the sheet on which the image is first formed is transported in the double-sided image forming process. In this case, the control unit 8 may use the result of the process of step S11 executed when the first sheet is transported to obtain the specific value corresponding to each of the second and subsequent sheets transported.

<Step S16>
In step S16, the control unit 8 sets an execution condition for the second image forming process based on the specific value acquired in the process of step S15.

Specifically, when the specific value acquired by the processing of step S15 is equal to or less than the threshold value, the control unit 8 increases the amount of ink ejected onto the single-sided image forming sheet from the reference amount to an amount 1.2 times the reference amount.

In addition, when the specific value acquired by the processing of step S15 is equal to or less than the threshold value, the control unit 8 reduces the conveying speed of the single-sided image forming sheet from the reference speed to a speed that is half the reference speed.

In this way, in the image forming device 10, the specific value indicating the ease of ink penetration into the sheet is acquired for each sheet on which an image is formed. Then, the execution conditions of the second image forming process are set based on the acquired specific value. This makes it possible to set the execution conditions of the image forming process for each sheet according to the ease of ink penetration into the sheet.

The media sensor 5 may be provided on the re-transport path R4. In this case, the control unit 8 may transport a sheet with both sides blank through the re-transport path R4 before executing the double-sided image formation process, and then execute the process of step S11.

The image forming device 10 may not have the reverse transport path R3 and the re-transport path R4. In this case, the second image forming process may be a process that is executed in response to a predetermined user operation on the operation display unit 6 after the single-sided image forming sheet is placed in the paper feed cassette 11 by the user.

The developer of the present invention may also be a toner. In other words, the present invention may be applied to an image forming apparatus that forms an image by an electrophotographic method. In this case, the execution conditions of the image forming process of the present invention may include a third condition related to the amount of toner supplied to the single-sided image forming sheet. For example, when the specific value acquired by the acquisition processing unit 81 is equal to or less than the threshold value, the control unit 8 may adjust the developing bias voltage, etc., so that the amount of toner supplied to the single-sided image forming sheet is increased by a predetermined amount.

[Notes on the invention]
The following will provide an overview of the invention extracted from the above-described embodiment. Note that the configurations and processing functions described in the following supplementary notes can be selected and combined as desired.

<Appendix 1>
an image forming unit that forms an image on one side of a sheet using a developer; a reflected light detection unit that includes a first light emission unit that emits light toward an image-formed first side of a single-sided image forming sheet on one side of which an image has been formed by the image forming unit, and detects an amount of reflected light emitted from the first light emission unit and reflected by the single-sided image forming sheet; a transmitted light detection unit that includes a second light emission unit that emits light toward an irradiation area of the first side of the single-sided image forming sheet that is irradiated with light emitted from the first light emission unit, and detects an amount of transmitted light that is emitted from the second light emission unit and transmitted through the single-sided image forming sheet; an acquisition processing unit that acquires a specific value that indicates the ease of penetration of the developer into the single-sided image forming sheet based on the specific value acquired by the acquisition processing unit and the amount of transmitted light detected by the transmitted light detection unit; and a setting processing unit that sets execution conditions for an image formation process that forms an image on a second side of the single-sided image forming sheet on which an image has not been formed, based on the specific value acquired by the acquisition processing unit.

<Appendix 2>
An image forming apparatus as described in Appendix 1, further comprising a judgment processing unit that judges whether or not a specific image formed by the developer exists in the irradiation area of the single-sided image forming sheet, and the acquisition processing unit does not acquire the specific value when the judgment processing unit judges that the specific image does not exist in the irradiation area.

<Appendix 3>
The image forming apparatus of claim 1 or 2, wherein the developer is ink, and the execution conditions of the image forming process include either or both of a first condition related to the transport speed of the single-sided image forming sheet and a second condition related to the amount of ink ejected onto the single-sided image forming sheet.

<Appendix 4>
3. The image forming apparatus according to claim 1, wherein the developer is a toner, and the execution conditions of the image forming process include a third condition related to an amount of the toner supplied to the single-sided image forming sheet.

<Appendix 5>
An image forming apparatus as described in any of Appendices 1 to 4, comprising an inversion transport path used to invert the single-sided image forming sheet and re-transport the inverted single-sided image forming sheet to the image forming unit, and in the image forming process, an image is formed on the second side of the single-sided image forming sheet that has passed through the inversion transport path using the image forming unit.

<Appendix 6>
An image forming apparatus as described in Appendix 5, comprising a paper feed path extending from a paper feed source of the sheet via a junction with the inversion transport path to the image forming unit, and the reflected light detection unit and the transmitted light detection unit are provided between the junction in the paper feed path and the image forming unit.

<Appendix 7>
a first light emitting section that emits light toward an image-formed first side of a single-sided image forming sheet on one side of which an image has been formed by the image forming section, a reflected light detection section that detects an amount of reflected light emitted from the first light emitting section and reflected by the single-sided image forming sheet, and a second light emitting section that emits light toward an irradiation area of the first side of the single-sided image forming sheet that is irradiated with the light emitted from the first light emitting section, and a transmitted light detection section that detects an amount of transmitted light emitted from the second light emitting section and transmitted through the single-sided image forming sheet. and a transmitted light detection unit that detects the amount of light emitted by the developer through the single-sided image forming sheet, the image forming method including: an acquisition step of acquiring a specific value indicating the ease of penetration of the developer into the single-sided image forming sheet based on the amount of reflected light detected by the reflected light detection unit and the amount of transmitted light detected by the transmitted light detection unit; and a setting step of setting execution conditions for an image formation process that forms an image on a second side of the single-sided image forming sheet on which an image has not been formed, based on the specific value acquired by the acquisition step.

Reference Signs List 1: Housing 2: Sheet conveying section 3: Image forming section 4: Conveying unit 5: Media sensor 6: Operation display section 7: Storage section 8: Control section 10: Image forming device 51: Reflective optical sensor 51A: First light emitting section 52: Transmissive optical sensor 52A: Second light emitting section 81: Acquisition processing section 82: Setting processing section 83: Determination processing section

Claims (7)

an image forming section for forming an image on one side of a sheet using a developer;
a first light emitting section that emits light toward a first surface of a single-sided image forming sheet on one side of which an image has been formed by the image forming section, and a reflected light detecting section that detects an amount of reflected light emitted from the first light emitting section and reflected by the single-sided image forming sheet;
a second light emitting section that emits light toward an irradiation area of the first surface of the single-sided image forming sheet that is irradiated with the light emitted from the first light emitting section, and a transmitted light detecting section that detects an amount of transmitted light that is emitted from the second light emitting section and transmitted through the single-sided image forming sheet;
an acquisition processing unit that acquires a specific value indicating the ease of penetration of the developer into the single-sided image forming sheet based on the amount of reflected light detected by the reflected light detection unit and the amount of transmitted light detected by the transmitted light detection unit;
a setting processing unit that sets an execution condition of an image forming process for forming an image on a second side of the single-sided image forming sheet based on the specific value acquired by the acquisition processing unit;
An image forming apparatus comprising: a determination processing unit that determines whether or not a specific image formed by the developer is present in the irradiation area of the single-sided image forming sheet,
The acquisition processing unit does not acquire the specific value when the determination processing unit determines that the specific image does not exist in the projection area.
The image forming apparatus according to claim 1 . The developer is an ink,
the execution conditions of the image forming process include one or both of a first condition related to a transport speed of the single-sided image forming sheet and a second condition related to an ejection amount of the ink onto the single-sided image forming sheet;
3. The image forming apparatus according to claim 1 or 2. The developer is a toner,
the execution conditions of the image forming process include a third condition related to an amount of the toner supplied to the single-sided image forming sheet;
3. The image forming apparatus according to claim 1 or 2. a reversing conveying path used for reversing the single-sided image forming sheet and re-conveying the inverted single-sided image forming sheet to the image forming unit,
In the image forming process, an image is formed on the second side of the single-sided image-formed sheet that has passed through the reversing transport path by using the image forming unit.
The image forming apparatus according to claim 1 . a sheet feed path extending from a sheet feed source of the sheet through a junction with the reverse conveyance path to the image forming unit,
the reflected light detection unit and the transmitted light detection unit are provided between the junction and the image forming unit in the paper feed path;
The image forming apparatus according to claim 5 . an image forming method executed by an image forming apparatus including: an image forming unit that uses a developer to form an image on one side of a sheet; a first light emitting unit that emits light toward an imaged first side of a single-sided image forming sheet on one side of which an image has been formed by the image forming unit, and a reflected light detection unit that detects an amount of reflected light that is emitted from the first light emitting unit and reflected by the single-sided image forming sheet; and a transmitted light detection unit that includes a second light emitting unit that emits light toward an irradiation area of the first side of the single-sided image forming sheet that is irradiated with the light emitted from the first light emitting unit, and detects an amount of transmitted light that is emitted from the second light emitting unit and transmitted through the single-sided image forming sheet,
an acquisition step of acquiring a specific value indicating the ease of penetration of the developer into the single-sided image forming sheet based on the amount of the reflected light detected by the reflected light detection unit and the amount of the transmitted light detected by the transmitted light detection unit;
a setting step of setting an execution condition of an image forming process for forming an image on a second side of the single-sided image forming sheet on the basis of the specific value acquired by the acquisition step;
An image forming method comprising the steps of:

Images