Recording medium conveying device, image forming apparatus, recording medium conveying method, and recording medium conveying program

Abstract

To provide a recording medium conveying device that can prevent deterioration of light sources of light with respective wavelengths in an end detection sensor.SOLUTION: A recording medium conveying device comprises: an end detection sensor that has a plurality of light sources of light with various wavelengths for detecting an end of a recording medium conveyed along a predetermined conveyance direction; and a light source selection unit that, on the basis of information on the recording medium, selects the light source of light with a wavelength to be used for detection of the end of the recording medium from the light sources of light with various wavelengths.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a recording medium transport device, an image forming apparatus, a recording medium transport method, and a recording medium transport program. [Background technology]

[0002] A recording medium transport device installed in an image forming apparatus adjusts the image formation position on the recording medium by detecting the edge of the recording medium in a direction perpendicular to the recording medium transport direction using an optical sensor such as a CIS sensor. Patent Document 1 (Japanese Patent Laid-Open No. 2006-222221) describes a technique for such a recording medium transport device. This technique involves performing multiple position determinations on the same sheet of paper, changing the light emission intensity of the LED in the CIS sensor during these multiple position determinations, and determining the optimal light intensity of the LED based on the different outputs of the CIS sensor resulting from the changes in light emission intensity. This technique is said to automatically adjust the light intensity of the LED to detect the edge of the paper, whether it is white or colored paper, without shortening the life of the LED. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-87934 Summary of the Invention [Problem to be solved by the invention]

[0004] The optical sensor has light sources (LEDs) of different wavelengths for each of the RGB colors to enable detection of the edges of recording media (paper) of different colors. When detecting the edge of a recording medium, all light sources are turned on. However, depending on the color of the recording medium, some light from each light source has a wavelength that has low reflectivity on the recording medium and contributes little to recording medium edge detection. Therefore, when detecting the edge of a recording medium using an optical sensor, light sources of colors that do not contribute to edge detection may be turned on, which can accelerate deterioration of such light sources.

[0005] Therefore, an object of the present invention is to provide a recording medium conveying device, an image forming apparatus, a recording medium conveying method, and a recording medium conveying program that are capable of suppressing deterioration of the light source of each wavelength light in an edge detection sensor. [Means for solving the problem]

[0006] To achieve this objective, the present invention provides a recording medium transport device that includes an edge detection sensor having a plurality of light sources of different wavelengths for detecting the edge of a recording medium transported along a predetermined transport direction, and a light source selection unit that selects a light source of wavelength light to be used for detecting the edge of the recording medium from among the light sources of different wavelengths based on information about the recording medium. [Effects of the Invention]

[0007] The present invention can provide a recording medium transport device, an image forming apparatus, a recording medium transport method, and a recording medium transport program that can suppress deterioration of the light source of each wavelength light in the edge detection sensor. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram showing the overall configuration of an image forming apparatus including a recording medium conveying device according to the first embodiment. [Figure 2] FIG. 2 is a block diagram of an image forming apparatus including a recording medium conveying device according to the first embodiment. [Figure 3]FIG. 3 is a flowchart showing the recording medium transport method according to the first embodiment. [Figure 4] FIG. 4 is a timing chart for explaining light source selection (part 1) in the recording medium conveying method according to the first embodiment. [Figure 5] FIG. 5 is a timing chart for explaining light source selection (part 2) in the recording medium conveying method according to the first embodiment. [Figure 6] FIG. 6 is a timing chart for explaining light source selection (part 3) in the recording medium conveying method according to the first embodiment. [Figure 7] FIG. 7 is a graph showing the cumulative lighting time of the light source, illustrating the light source selection (part 4) in the recording medium conveying method according to the first embodiment. [Figure 8] FIG. 8 is a timing chart for explaining light source selection (part 4) in the recording medium conveying method according to the first embodiment. [Figure 9] FIG. 9 is a flowchart showing a recording medium transport method according to the second embodiment. [Figure 10] FIG. 10 is a timing chart for explaining light source selection in the recording medium conveying method according to the second embodiment. [Figure 11] FIG. 11 is a flowchart showing a recording medium transport method according to the third embodiment. [Figure 12] FIG. 12 is a timing chart for explaining light source selection in the recording medium conveying method according to the third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, each embodiment of the present invention will be described in detail with reference to the drawings. In each embodiment, elements having substantially the same function or configuration are designated by the same reference numerals, and redundant description will be omitted.

[0010] First Embodiment FIG. 1 is a diagram illustrating the overall configuration of an image forming apparatus 1 according to a first embodiment, including a recording medium transport unit. The image forming apparatus 1 shown in FIG. 1 forms an image on a sheet-like recording medium 100. The image forming apparatus 1 includes a medium supply unit 10, a medium inspection unit 20, an image forming unit 30, and an image inspection unit 40, arranged in this order from upstream to downstream along the transport direction [FD] of the recording medium 100. The image forming apparatus 1 also includes multiple medium transport rollers 1a arranged within these components. These medium transport rollers 1a form a transport path 1b that transports the recording medium 100 supplied from the medium supply unit 10 through the medium inspection unit 20, the image forming unit 30, and the image inspection unit 40, in that order. The image forming apparatus 1 also includes a control unit 50 and an operation unit 60. Each of these components that make up the image forming apparatus 1 will be described below.

[0011] <Media supply section 10> The medium supply unit 10 can store a large number of sheet-like recording media 100, and sequentially supplies the stored recording media 100 one by one to the media inspection unit 20. The medium supply unit 10 can store a plurality of different types of recording media 100. The medium supply unit 10 also sends out a type of recording media 100 selected based on instructions from the control unit 50, which will be described later, to the media inspection unit 20.

[0012] <Media Inspection Department 20> The media inspection unit 20 includes media characteristic detection sensors 21 for detecting the physical properties of the recording medium 100. The media characteristic detection sensors 21 detect, for example, the color of the recording medium 100 as a physical property of the recording medium 100. The media inspection unit 20 sends the recording medium 100 whose physical properties have been detected to the image forming unit 30 in accordance with instructions from the control unit 50, which will be described later. The media characteristic detection sensors 21 are also one of the components that make up the recording medium transport device.

[0013] <Image forming unit 30> The image forming unit 30 forms an image on the recording medium 100 sent from the medium inspection unit 20 based on instructions from a control unit 50, which will be described later. Here, as an example, the image forming unit 30 is assumed to be an electrophotographic image forming device that forms a toner image. The image forming unit 30 includes a medium swinging unit 31, an edge detection sensor 32, a toner image forming unit 33, and a medium reversing path 34.

[0014] [Medium swinging unit 31] The medium rocking unit 31 is one of the components that make up the recording medium transport device. The medium rocking unit 31 has a pair of rollers that nip the recording medium 100 transported from the media inspection unit 20. One of the pair of rollers is a drive roller that is movable in the axial direction of the roller, that is, the transport width direction [CD]. As this drive roller moves, the recording medium 100 nipped by the pair of rollers rocks in the transport width direction [CD], which is perpendicular to the transport direction [FD]. The medium rocking unit 31 moves the drive roller based on, for example, the edge position of the recording medium 100 detected by an edge detection sensor 32, which will be described next, and moves the recording medium 100 to a predetermined position in the transport width direction [CD].

[0015] [Edge detection sensor 32] The edge detection sensor 32 is one of the components that make up the recording medium transport device. The edge detection sensor 32 is used to detect the edge of the recording medium 100 that is nipped between the roller pair of the medium rocking unit 31. For this reason, the edge detection sensor 32 is disposed immediately downstream of the medium rocking unit 31 in the transport direction [FD]. Such an edge detection sensor 32 is, for example, an optical sensor such as a CIS (Contact Image Sensor).

[0016] The edge detection sensor 32 has light sources of light of different wavelengths—red (R), green (G), and blue (B)—and multiple light-receiving elements that receive the reflected light of each color emitted from the light-emitting elements. The light sources of each color are light-emitting elements, such as LEDs (light-emitting diodes), that emit pulses of light of each wavelength. These light sources and light-receiving elements for each wavelength are each arranged along the transport width direction [CD], which is parallel to the axes of the roller pairs that make up the medium rocking unit 31. This allows the position of the edge of the recording medium 100 in the transport width direction [CD] to be detected based on the light intensity received by each light-receiving element.

[0017] [Toner image forming unit 33] Toner image forming unit 33 forms a toner image by electrophotography, transfers the formed toner image to one main surface of recording medium 100, and fixes the transferred toner image on recording medium 100. Such toner image forming unit 33 is disposed downstream of edge detection sensor 32 in the transport direction [FD], and transfers a toner image to a predetermined position on recording medium 100 that has been moved to a predetermined position in the transport width direction [CD] by the drive of medium swinging unit 31.

[0018] [Media reversal path 34] The medium inversion path 34 switches the front and back sides of the recording medium 100 that has passed through the toner image forming unit 33. The medium inversion path 34 also supplies the recording medium 100, whose front and back sides have been switched, to the conveyance path 1b upstream of the medium swinging unit 31 in the conveyance direction [FD]. This allows toner images to be formed on both the front and back sides of the recording medium 100.

[0019] The image forming unit 30 is not limited to an electrophotographic type. The image forming unit 30 may be any type that includes the medium shaking unit 31 and the edge detection sensor 32, and may include another type, such as an inkjet type, instead of the toner image forming unit 33.

[0020] <Image Inspection Department 40> The image inspection unit 40 inspects the image formed on the recording medium 100 in the image forming unit 30. This image inspection unit 40 includes an image detection sensor 41 arranged across the transport width direction [CD] perpendicular to the transport direction [FD] of the recording medium 100. The image detection sensor 41 is a sensor for inspecting the toner image formed on the recording medium 100. This image detection sensor 41 captures an image of the entire surface of the recording medium 100 across the transport width direction [CD] and transmits the captured image data to the control unit 50. The image detection sensor 41 is also one of the components that make up the recording medium transport device.

[0021] The image inspection unit 40 also has a discharge path 42 for separating and discharging, from the conveyance path 1b, the recording medium 100 that has been determined to have a defect in the image detected by the image detection sensor 41. This determination is made by the control unit 50.

[0022] <Control unit 50> The control unit 50 is one of the components that make up the recording medium conveying device. The control unit 50 is configured by a computer and is usually mounted as a circuit board inside the main body of the image forming unit 30. The computer includes memories such as a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory). The computer also includes a non-volatile storage unit and a network interface. The control unit 50 comprehensively controls the operation of each unit of the image forming apparatus 1 by having the CPU read a predetermined program from the ROM, load it into the RAM, and execute the loaded program. In particular, the control unit 50 executes a recording medium conveying program for controlling the recording medium conveying device provided in the image forming apparatus 1.

[0023] 2 is a block diagram of an image forming apparatus 1 including a recording medium conveying device according to the first embodiment. As shown in this diagram, a control unit 50 includes functional units, namely, a drive control unit 51, a storage unit 52, and a light source selection unit 53.

[0024] [Drive control unit 51] The drive control unit 51 is a part that comprehensively controls the operation of each unit that constitutes the image forming apparatus 1. This drive control unit 51 performs control based on information input from the operation unit 60 and information acquired from the medium characteristic detection sensor 21, edge detection sensor 32, and image detection sensor 41. Details of the control performed by this drive control unit 51 will be described below in the recording medium conveyance method section.

[0025] [Storage unit 52] The memory unit 52 stores the accumulated lighting time of the light sources of light of different wavelengths of each color that the edge detection sensor 32 has. The accumulated lighting time is the accumulated value of the time that the light sources of light of different wavelengths of each color, red (R), green (G), and blue (B), are turned on. This accumulated lighting time is the accumulated time since the light source of the edge detection sensor 32 was replaced. Note that the accumulated lighting time may also be stored as the usage ratio of each light source.

[0026] [Light source selection section 53] The light source selection unit 53 selects which color (wavelength) of light source to use and at what timing from among the multiple light sources possessed by the edge detection sensor 32 when the edge detection sensor 32 detects the edge of the recording medium 100. The light source selection unit 53 makes its selection based on information input from the operation unit 60 and information acquired from the medium characteristic detection sensor 21, edge detection sensor 32, and image detection sensor 41. Details of the selection procedure performed by this light source selection unit 53 will be described below in the recording medium transport method section. <Operation unit 60> The operation unit 60 is a section for inputting job information related to image formation performed using this image forming apparatus 1, information related to each recording medium 100 stored in the medium supply unit 10, and various settings. The information and settings input from the operation unit 60 are registered in the control unit 50. Such operation unit 60 may be an external device such as a personal computer or printer controller that is capable of communicating with the control unit 50 to exchange data. The operation unit 60 also serves as one of the components that make up the recording medium transport device.

[0027] <Recording medium transport method> Next, a recording medium conveying method implemented in the image forming apparatus 1 described above will be described. FIG. 3 is a flowchart showing the recording medium conveying method according to the first embodiment, illustrating the steps implemented by the functional units of the control unit 50 of the image forming apparatus 1 as they execute a recording medium conveying program. This step is related to edge detection of the recording medium 100, which is fed to the image forming unit 30 along the conveying direction [FD], to move the recording medium 100 to a predetermined position in the conveying width direction [CD], and is a step for selecting a light source for the edge detection sensor 32 to be used in this detection. The recording medium conveying method according to the first embodiment will be described below in the order shown in the flowchart of FIG. 3, with reference to FIGS. 1 and 2 and other necessary figures. Note that this flowchart starts when an image formation job is started by the image forming apparatus 1.

[0028] [Step S101] In step S101, the light source selection unit 53 acquires medium information. The acquired medium information is job information input from the operation unit 60. The job information includes information indicating whether the image formation performed in this job is overprinting on the recording medium 100, and color information of the recording medium 100. Overprinting here refers to forming an image by overwriting an image on the recording medium 100 on which an image has already been formed. The color information of the recording medium 100 is the a* value and b* value in the L*a*b* color space. Note that this color information of the recording medium 100 may be color information acquired from the medium characteristic detection sensor 21. The color information may also be information registered in advance in the control unit 50.

[0029] [Step S102] In step S102, the light source selection unit 53 determines, based on the medium information acquired in step S101, whether the image formation performed in this job is overprinting on the recording medium 100. If the light source selection unit 53 determines that it is overprinting (YES), it proceeds to step S102a, and if it determines that it is not overprinting (NO), it proceeds to step S103.

[0030] [Step S102a] In step S102a, the light source selection unit 53 selects simultaneous lighting of all red (R), green (G), and blue (B) light sources of the edge detection sensor 32. Figure 4 is a timing chart illustrating light source selection (part 1) in the recording medium conveyance method according to the first embodiment. This timing chart shows the timing for turning on / off the red (R) light source LED.R, green (G) light source LED.G, and blue (B) light source LED.B, and this is the same for the timing charts shown below.

[0031] As shown in Fig. 4, turning on all light sources simultaneously means turning on light sources of all colors simultaneously when detecting the edge of each recording medium 100 that is conveyed one by one sequentially to the edge detection sensor 32 (see Fig. 1). This makes it possible to detect the edge of the recording medium 100 regardless of the color of the image already formed on the recording medium 100.

[0032] [Step S103] On the other hand, in step S103, the light source selection unit 53 determines whether the recording medium 100 is a white medium based on the color information of the recording medium 100 acquired in step S101. If it is determined that the recording medium 100 is a white medium (YES), the process proceeds to step S104, and if it is determined that the recording medium 100 is not a white medium (NO), the process proceeds to step S103a.

[0033] [Step S103a] In step S103a, the light source selection unit 53 selects a light source color based on the a* and b* values ​​of the color information of the recording medium 100 acquired in step S101. For example, if the color profile of the recording medium 100 has a*=30 and b*=35 values, the light source selection unit 53 selects green (G) and blue (B) light sources that have high reflectance on the recording medium 100 as the light source color. Figure 5 is a timing chart illustrating light source selection (part 2) in the recording medium conveying method according to the first embodiment.

[0034] 5 shows a case where green (G) and blue (B) light sources are selected based on the color information of the recording medium. In this case, the green (G) light source LED.G and the blue (B) light source LED.B are simultaneously turned on to detect the edges of each recording medium 100 that is conveyed one by one sequentially to the edge detection sensor 32 (see FIG. 1). This makes it possible to prevent unnecessary lighting of the light source of red (R) wavelength light, which has a weak reflection intensity from the recording medium 100 and therefore makes little contribution to edge detection of the recording medium 100.

[0035] [Step S104] On the other hand, in step S104, the light source selection unit 53 determines whether the integrated lighting times of the light sources of light of each wavelength stored in the storage unit 52 are uniform. If the light source selection unit 53 determines that they are uniform (YES), the process proceeds to step S104a, and if the light source selection unit 53 determines that they are not uniform (NO), the process proceeds to step S105. Note that the determination of whether the integrated lighting times are uniform may have a certain degree of latitude.

[0036] [Step S104a] In step S104a, the light source selection unit 53 selects sequential lighting of the light sources of light of each wavelength possessed by the edge detection sensor 32. FIG. 6 is a timing chart illustrating light source selection (part 3) in the recording medium conveying method according to the first embodiment. As shown in FIG. 6, sequential lighting of the light sources of light of each wavelength refers to switching the light sources of light of each wavelength and sequentially lighting them for each recording medium 100 in order to detect the edge of each recording medium 100 conveyed one by one to the edge detection sensor 32 (see FIG. 1). By sequentially lighting the light sources of light of each wavelength in this way, it is possible to suppress an increase in the cumulative lighting time of all the light sources.

[0037] [Step S105] Meanwhile, in step S105, the light source selection unit 53 selects the light source of the wavelength light having the shortest cumulative turn-on time based on the cumulative turn-on times of the light sources of each wavelength light stored in the storage unit 52. Fig. 7 is a graph showing the cumulative turn-on times of the light sources, explaining light source selection (part 4) in the recording medium transport method according to the first embodiment. Fig. 8 is a timing chart explaining light source selection (part 4) in the recording medium transport method according to the first embodiment.

[0038] As shown in Fig. 7, assume that the cumulative lighting time of the red (R) light source LED.R is the shortest among the cumulative lighting times of the light sources of each color stored in memory unit 52. In this case, as shown in Fig. 8, only the selected red (R) light source LED.R is turned on each time the edge of each recording medium 100 is detected as it is conveyed one by one sequentially to edge detection sensor 32 (see Fig. 1). This averages the cumulative lighting times of light sources of different wavelengths, making it possible to prevent accelerated deterioration of light sources of specific wavelengths.

[0039] [Step S106] In step S106, the drive control unit 51 turns on the light source of the color selected by the light source selection unit 53 from the light sources of each color equipped in the edge detection sensor 32 at the selected timing to detect the edge of the recording medium 100.

[0040] This also causes the drive control unit 51 to drive the medium rocking unit 31 based on the detected position of the end of the recording medium 100, and moves the recording medium 100, which is nipped by the medium rocking unit 31, to a predetermined position in the transport width direction [CD].

[0041] Note that step S106 is repeatedly performed until the job for which information was acquired in step S101 is completed. However, if it is determined in step S103 that the recording medium 100 is a white medium, edge detection is performed on a predetermined number of recording media 100 (for example, one sheet), and then the process returns to step S104. Then, in step S104, it is preferable to repeatedly determine whether the accumulated lighting times are uniform.

[0042] In addition, the drive control unit 51 drives the toner image forming unit 33 to form a toner image on the recording medium 100 that has passed through the medium shaking unit 31, and drives the image detection sensor 41 to capture an image of the entire surface of the recording medium 100 on which the toner image has been formed.

[0043] <Effects of the first embodiment> According to the first embodiment described above, in the edge detection sensor 32 having light sources of different wavelengths, it is possible to reduce the cumulative lighting time of all light sources and suppress lighting of light sources of wavelengths that do not contribute to edge detection without accelerating deterioration of light sources of specific wavelengths. As a result, it is possible to suppress deterioration of the light sources of each wavelength in the edge detection sensor 32, reduce the frequency of light source replacement, and reduce the running costs of the image forming apparatus 1.

[0044] Second Embodiment FIG. 9 is a flowchart showing a recording medium conveying method according to a second embodiment, illustrating the steps performed by the functional units of the control unit 50 of the image forming apparatus 1 described with reference to FIGS. 1 and 2 when the units execute a recording medium conveying program. This step is related to edge detection of the recording medium 100, which is fed to the image forming unit 30 along the conveying direction [FD], in order to move the recording medium 100 to a predetermined position in the conveying width direction [CD]. This step is another step for selecting a light source for the edge detection sensor 32 to be used in this process. The recording medium conveying method according to the second embodiment will be described below in the order shown in the flowchart of FIG. 9, with reference to FIGS. 1 and 2 and other necessary figures. This flowchart starts when an image formation job is started by the image forming apparatus 1.

[0045] [Step S201] In step S201, the drive control unit 51 instructs the edge detection sensor 32 to measure the reflectance of light of each wavelength on the recording medium 100. As a result, the edge detection sensor 32 sequentially irradiates one sheet of recording medium 100 with light of each wavelength from each light source, and receives the reflected light at the light receiving unit.

[0046] 10 is a timing chart illustrating light source selection in a recording medium conveyance method according to the second embodiment. As shown in FIG. 10, the drive control unit 51 sequentially turns on light sources of red (R), green (G), and blue (B) wavelengths at different timings for the edge detection sensor 32. The edge detection sensor 32 then measures the reflection intensity (VOUT level) on the recording medium 100. In this case, the edge detection sensor 32 may irradiate one sheet of recording medium 100 with light from each light source continuously without any intervals.

[0047] [Step S202] Next, in step S202, the light source selection unit 53 selects the light source that generates the wavelength light with the highest reflectance based on the measurement result in step S201. In the example shown in Fig. 10, the reflection intensity (VOUT level) is highest when the blue (B) light source LED.B is turned on, so the light source selection unit 53 selects at least the blue (B) light source LED.B. Note that the light source selection unit 53 may also simultaneously select the red (R) light source LED.R, which has the next highest reflection intensity (VOUT level).

[0048] [Step S203] In step S203, the drive control unit 51 turns on the light source selected by the light source selection unit 53 from among the light sources of light of each wavelength equipped in the edge detection sensor 32 to detect the edge of the recording medium 100. At this time, the edge detection sensor 32 turns on the selected light source to detect the edge of each recording medium 100 that is transported one by one sequentially to the edge detection sensor 32 (see FIG. 1). In addition, the drive control unit 51 drives the medium rocking unit 31 based on the detected position of the edge of the recording medium 100, and moves the recording medium 100 nipped by the medium rocking unit 31 to a predetermined position in the transport width direction [CD].

[0049] Note that step S203 is repeatedly performed until the same job using the recording medium 100 whose reflectance was measured in step S201 is completed.

[0050] <Effects of the second embodiment> Even in the second embodiment described above, it is possible to suppress the lighting of light sources of wavelengths that do not contribute to edge detection, and therefore it is possible to obtain the same effects as in the first embodiment.

[0051] Third Embodiment FIG. 11 is a flowchart showing a recording medium conveying method according to a third embodiment, illustrating the steps performed by the functional units of the control unit 50 of the image forming apparatus 1 described with reference to FIGS. 1 and 2 when the units execute a recording medium conveying program. This step is related to edge detection of the recording medium 100, which is fed to the image forming unit 30 along the conveying direction [FD], in order to move the recording medium 100 to a predetermined position in the conveying width direction [CD]. This step is yet another step for selecting a light source for the edge detection sensor 32 to be used in this process. The recording medium conveying method according to the third embodiment will be described below in the order shown in the flowchart of FIG. 11, with reference to FIGS. 1 and 2 and other necessary figures. This flowchart starts when an image formation job is started by the image forming apparatus 1.

[0052] [Step S301] In step S301, the drive control unit 51 turns on all wavelength light sources provided in the edge detection sensor 32 and starts edge detection of the recording medium 100. Fig. 12 is a timing chart illustrating light source selection in a recording medium conveyance method according to the third embodiment. As shown in Fig. 12, the drive control unit 51 turns on all color light sources to start edge detection for each recording medium 100 that is conveyed one by one sequentially to the edge detection sensor 32 (see Fig. 1).

[0053] The drive control unit 51 also drives the medium rocking unit 31 based on the detected position of the edge of the recording medium 100, and moves the recording medium 100 nipped by the medium rocking unit 31 to a predetermined position in the transport width direction [CD]. Furthermore, the drive control unit 51 drives the toner image forming unit 33 to form a toner image on the recording medium 100 that has passed through the medium rocking unit 31, and drives the image detection sensor 41 to capture an image of the entire surface of the recording medium 100 on which the toner image has been formed.

[0054] [Step S302] In the next step S302, the light source selection unit 53 acquires color information of the recording medium 100 from the image detection sensor 41. Here, the image detection sensor 41 is a sensor for inspecting the toner image formed on the recording medium 100, and captures an image of the entire surface of the recording medium 100 across the conveyance width direction [CD]. Therefore, the light source selection unit 53 acquires color information of areas where no image is formed from the image information of the entire surface of the recording medium 100 acquired from the image detection sensor 41. This color information is acquired as a* values ​​and b* values ​​in the L*a*b* color space, and this color information is used as the color information of the recording medium 100. Note that areas where no image is formed may also be detected based on job information related to image formation.

[0055] [Step S303] In step S303, the light source selection unit 53 selects the color of the light source based on the color information of the recording medium 100 acquired in step S302. At this time, the light source selection unit 53 selects the light source color based on the a* value and the b* value of the color information of the recording medium 100 acquired in step S302. The selection of the light source here is performed in the same manner as the procedure in step S103a of the first embodiment, and it is possible to prevent unnecessary lighting of a light source of wavelength light that has a weak reflection intensity on the recording medium 100 and makes a small contribution to edge detection of the recording medium 100.

[0056] [Step S304] In step S304, the drive control unit 51 stops the edge detection of the recording medium 100, which has been performed by turning on the light source of all wavelengths provided in the edge detection sensor 32.

[0057] [Step S305] In step S305, the drive control unit 51 turns on the light source of the wavelength light selected by the light source selection unit 53 in step S303 from among the light sources of light of each wavelength light equipped in the edge detection sensor 32, and detects the edge of the recording medium 100. At this time, the edge detection sensor 32 turns on the selected light source to detect the edge of the nth and subsequent recording media 100 that are transported one by one to the edge detection sensor 32 (see FIG. 1). In addition, the drive control unit 51 drives the medium rocking unit 31 based on the detected position of the edge of the recording medium 100, and moves the recording medium 100 nipped by the medium rocking unit 31 to a predetermined position in the transport width direction [CD].

[0058] <Effects of the third embodiment> Even in the third embodiment described above, it is possible to suppress the lighting of light sources of wavelengths that do not contribute to edge detection, and therefore it is possible to obtain the same effects as in the first embodiment.

[0059] In each of the above-described embodiments, an image is formed on only one side of the recording medium 100. However, the image forming unit 30 in this image forming apparatus 1 has a medium reversing path 34 that swaps the front and back sides of the recording medium 100 and resupplies the recording medium 100 to the transport path 1b upstream of the medium swinging unit 31. In this case, the light source selection unit 53 selects a light source individually for the back side of the recording medium 100 resupplied to the transport path 1b, just as it does for the front side of the recording medium 100 supplied from the medium supply unit 10. [Explanation of symbols]

[0060] 1...Image forming device 21...Media characteristic detection sensor (recording medium transport device) 30...Image forming unit 31...medium swinging unit (recording medium transport device) 32...End detection sensor (recording medium transport device) 33...Toner image forming unit 34...Media inversion path 41...Image detection sensor 50...Control unit (recording medium conveying device) 51...Drive control unit (recording medium conveying device) 52...Memory unit (recording medium transport device) 53...Light source selection unit (recording medium transport device) 60...Operation unit (recording medium transport device) 100...Recording media [FD]...Transport direction

Claims

1. an edge detection sensor having a light source of a plurality of different wavelengths for detecting an edge of a recording medium transported along a predetermined transport direction; a light source selection unit that selects a light source of light of a wavelength to be used for detecting the edge of the recording medium from among the light sources of light of different wavelengths based on information about the recording medium. Recording medium transport device.

2. The light source selection unit selects the timing of turning on the light sources of the different wavelengths. The recording medium transport device according to claim 1 .

3. The information about the recording medium is color information about the recording medium. The recording medium transport device according to claim 1 .

4. When the recording medium is white, the light source selection unit sequentially selects the light sources of the different wavelengths in response to detection of edges of the recording medium that are sequentially transported one by one along the transport direction. The recording medium transport device according to claim 3 .

5. a storage unit that stores an integrated lighting time for each of the light sources of light of different wavelengths, When the recording medium is white, the light source selection unit selects the light sources so that the integrated lighting time for each of the light sources is uniform. The recording medium transport device according to claim 3 .

6. a storage unit that stores an integrated lighting time for each of the light sources of light of different wavelengths, When the recording medium is white, the light source selection unit selects a light source of light of a wavelength having the shortest cumulative lighting time. The recording medium transport device according to claim 3 .

7. The light source selection unit selects a light source of light with a wavelength that has the highest reflectance on the recording medium. The recording medium transport device according to claim 1 .

8. a drive control unit that controls the edge detection sensor to sequentially irradiate the recording medium with the light sources of the different wavelengths; The light source selection unit selects a light source of light of a wavelength to be used for detecting the edge of the recording medium based on the intensity of the reflected light from the recording medium sequentially obtained from the edge detection sensor under the control of the drive control unit. The recording medium transport device according to claim 1 .

9. a medium characteristic detection sensor that detects characteristics of the recording medium, in addition to the edge detection sensor; The light source selection unit acquires information about the recording medium from the medium characteristic detection sensor. The recording medium transport device according to claim 1 .

10. The medium characteristic detection sensor is disposed upstream of the edge detection sensor in the conveying direction of the recording medium. The recording medium transport device according to claim 9 .

11. the information about the recording medium includes information about whether or not the recording medium is an image-formed one; The light source selection unit selects simultaneous lighting of the light sources of light of different wavelengths when the recording medium has an image formed thereon. The recording medium transport device according to claim 1 .

12. The information about the recording medium is pre-registered information. The recording medium transport device according to claim 1 .

13. An operation unit for registering information about the recording medium is provided. The recording medium transport device according to claim 12.

14. The edge detection sensor is disposed along one main surface side of the recording medium in a conveyance width direction perpendicular to the conveyance direction. The recording medium transport device according to claim 1 .

15. a medium swinging unit that moves the recording medium in a transport width direction perpendicular to the transport direction along one main surface side of the recording medium based on the detection result of the edge detection sensor; The recording medium transport device according to claim 1 .

16. A recording medium transport device according to any one of claims 1 to 15; an image forming unit that is disposed downstream of the edge detection sensor in the conveyance direction of the recording medium and that forms an image on the recording medium; Image forming device.

17. an image detection sensor for capturing an image of one main surface of the recording medium on which an image has been formed in the image forming unit; The light source selection unit selects the light source based on information from the image detection sensor. The image forming apparatus according to claim 16.

18. a medium inversion path that switches the front and back sides of the recording medium on which the image has been formed in the image forming unit and supplies the recording medium again to a path on which the edge detection sensor is disposed; The light source selection unit selects the light source individually for the front and back surfaces of the recording medium. The image forming apparatus according to claim 16.

19. A recording medium conveying method using an edge detection sensor having a light source of a plurality of different wavelengths for detecting an edge of a sheet-shaped recording medium conveyed along a predetermined conveying direction, comprising: A light source selection unit selects a light source of light of a wavelength to be used for detecting an edge of the recording medium from among the light sources of light of different wavelengths based on information about the recording medium. Recording medium transport method.

20. A recording medium transport program for transporting a sheet-like recording medium by using an edge detection sensor having a light source of a plurality of different wavelengths for detecting an edge of the recording medium transported along a predetermined transport direction, the program comprising: a light source selecting unit for selecting a light source of light of a wavelength to be used for detecting an edge of the recording medium from among the light sources of light of different wavelengths based on information about the recording medium; Recording medium transport program.

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