JP2021056299A - Image forming apparatus - Google Patents

Abstract

To accurately detect the characteristics of a recording medium.SOLUTION: An image forming apparatus 10 comprises: a transmission type first optical sensor 60 having a light emitting unit 61 that irradiates, with light, a recording medium conveyed to a first irradiation area of a conveyance path 143, and a light receiving unit 64 that receives light transmitting through the recording medium; a reflection type second optical sensor 50 having a light emitting unit 51 that irradiates, with light, the recording medium conveyed to a second irradiation area of the conveyance path, and a light receiving unit 52 that receives light reflected on a surface of the recording medium; and a determination unit 11 that determines the paper type of the recording medium by using detection results from measurement performed by the first and second optical sensors. The first and second optical sensors 50, 60 are arranged side by side in a width direction orthogonal to a conveyance direction of the recording medium, and includes a pressing mechanism 70 that includes a pressing part 71 and urges the recording medium against a guide plate 1431 during the measurement performed by the second optical sensor 60 to hold the recording medium.SELECTED DRAWING: Figure 3

Description

The present invention relates to an image forming apparatus.

In recent years, in the color printing industry, image forming devices such as electrophotographic printers have been widely used. In the field of PP (production printing) corresponding to the color printing industry, adaptation to various types of paper is required as compared with the case of being used in the office. Then, in order to perform high-quality printing on these various types of paper, the paper characteristics stored in the paper feed tray are set for a plurality of items, and the image is printed under the image forming conditions according to the set items. There is a forming device.

In order to make such various paper settings, there is an image forming apparatus including a sensor that automatically detects the characteristics of the paper used for printing. For example, in Patent Document 1, in order to accurately detect and discriminate the type of paper, an ultrasonic detection unit that detects the basis weight of the paper and the surface property of the paper are determined from the reflected light from the surface of the paper by irradiating it with light. An image forming apparatus is disclosed in which a surface detection unit for detection is juxtaposed in the width direction of the paper, and the type of the paper is detected and discriminated from the measurement result. Further, in the image forming apparatus of Patent Document 1, the paper is pressed by the pressing members arranged so as to face the surface detection unit, and the paper is pressed by the pressing members arranged on both sides in the width direction of the ultrasonic detection unit. ing.

Japanese Unexamined Patent Publication No. 2016-055933

However, in Patent Document 1, the ultrasonic detection unit and the optical surface detection unit are juxtaposed in the width direction of the paper, and the influence of light between the optical sensors is not considered.

The present invention has been made in view of the above circumstances, and can stabilize the surface position of the recording medium at the time of measurement by the reflection type optical sensor, and the other by the irradiation light of one of the two optical sensors. It is an object of the present invention to provide an image forming apparatus capable of measuring with high accuracy by preventing the influence on the image forming apparatus.

The above object of the present invention is achieved by the following means.

(1) Paper tray and
A transport unit that includes a transport path formed by a pair of guide plates arranged to face each other and transports a recording medium fed from the paper feed tray to the transport path.
A transmissive first optical sensor having a light emitting unit that irradiates the recording medium conveyed to the first irradiation region of the transport path with light and a light receiving unit that receives the light transmitted through the recording medium. When,
A reflective second optical unit having a light emitting unit that irradiates the recording medium transported to the second irradiation region of the transport path with light and a light receiving unit that receives the light reflected on the surface of the recording medium. Expression sensor and
A determination unit for determining the paper type of the recording medium by using the detection results measured by the first and second optical sensors is provided.
The first and second optical sensors are arranged side by side in the width direction orthogonal to the transport direction of the recording medium.
An image forming apparatus including a pressing member and comprising a pressing mechanism for pressing the recording medium by urging the recording medium on the guide plate at the time of measurement by the second optical sensor.

(2) The second irradiation region is in the opening of the first guide plate among the first and second guide plates constituting the pair of guide plates.
The pressing mechanism has a pressing surface that comes into contact with the recording medium.
The above (1), wherein the pressing surface includes the opening and covers the entire circumference of the opening when the recording medium is pressed when viewed from a direction perpendicular to the transport surface of the transport path. Image forming device.

(3) The above (1) or the above (2), wherein the light receiving portion of the first optical sensor and the light receiving portion of the second optical sensor are arranged on the same side with respect to the transport path. The image forming apparatus according to.

(4) The image forming apparatus according to any one of (1) to (3) above, wherein the measurement by the first optical sensor is also performed at the time of measurement by the second optical sensor.

(5) The measurement of the first and second optical sensors is performed by stopping the recording medium in the first and second irradiation regions, according to any one of (1) to (4) above. Image forming device.

(6) The image forming apparatus according to any one of (1) to (5) above, wherein the irradiation direction of the irradiation light by the light emitting portion of the second optical sensor is along the width direction.

(7) The second irradiation region is in the opening of the first guide plate among the first and second guide plates constituting the pair of guide plates.
The pressing mechanism is arranged in the opening of the second guide plate.
The pressing surface of the pressing mechanism is substantially in the same plane as the transport surface of the second guide plate when the measurement by the second optical sensor is not performed, and the pressing mechanism is used when the measurement is performed. However, by moving toward the first guide plate, the recording medium is pressed between the pressing surface and the conveying surface of the first guide plate, any of the above (1) to (6). The image forming apparatus according to.

(8) Provided with an opening / closing mechanism that allows a part or all of the first guide plate to be opened / closed by a user's operation.
A light receiving portion of the first optical sensor, a light emitting portion of the second optical sensor, and a light receiving portion are arranged on the first guide plate that is opened and closed.
The image forming apparatus according to any one of (1) to (7) above, wherein the light emitting portion of the first optical sensor and the pressing mechanism are arranged on the side of the fixed second guide plate.

(9) The opening / closing mechanism makes the first guide plate rotatable about a rotation axis extending in the width direction as a rotation center.
In the transport direction, the rotation axis is on the downstream side in the opening direction of the first guide plate, and the first and second optical types arranged on the first guide plate on the upstream side in the opening direction. The image forming apparatus according to (8) above, wherein the center of gravity of the sensor is located.

(10) A paper thickness sensor that detects the thickness of the recording medium and
Further, a transport roller separating mechanism for switching one of two sets of transport roller pairs adjacent to each other on the upstream side and the downstream side of the first and second irradiation regions in the transport direction is provided.
Depending on the detection result of the paper thickness sensor,
The image forming apparatus according to any one of (1) to (9) above, wherein the transfer roller pair is separated by the transfer roller separation mechanism at the time of measurement of the second optical sensor.

(11) When a paper thicker than a predetermined value is detected by the detection of the paper thickness sensor,
The image forming apparatus according to (10) above, wherein the transport roller pair is separated by the transport roller separation mechanism at the time of measurement of the second optical sensor.

According to the image forming apparatus according to the present invention, a transmissive unit having a light emitting unit that irradiates the recording medium conveyed to the first irradiation region of the transport path with light and a light receiving unit that receives the light transmitted through the recording medium. It has a first optical sensor of the mold, a light emitting unit that irradiates the recording medium conveyed to the second irradiation region of the transport path with light, and a light receiving unit that receives the light reflected on the surface of the recording medium. The first and second optical sensors are provided with a reflective second optical sensor and a determination unit for determining the paper type of the recording medium by using the detection results measured by the first and second optical sensors. The optical sensors are arranged side by side in the width direction orthogonal to the transport direction of the recording medium, have a pressing portion, and urge the recording medium on the guide plate at the time of measurement of the second optical sensor, thereby urging the recording medium. It is provided with a pressing mechanism for pressing. As a result, the surface position of the recording medium during measurement by the reflective optical sensor can be stabilized, and the influence of the irradiation light of one of the two optical sensors on the other can be prevented, resulting in high accuracy. An image forming apparatus capable of measurement can be provided.

It is a figure which shows the schematic structure of the image formation system which includes the image formation apparatus which concerns on this embodiment. It is a side view which shows the structure of the media sensor arranged in the transport path. It is a perspective view which shows the structure of the basis weight sensor and the surface sensor. It is a schematic diagram which shows the structure of the basis weight sensor. It is sectional drawing of the surface sensor. It is a perspective view which shows the internal structure of the surface sensor. It is sectional drawing of the surface sensor which shows the state which the shutter is open. It is a perspective view which shows the structure of the pressing mechanism. It is a schematic diagram which shows the arrangement position of a light emitting part and a light receiving part. It is a top view which shows the positional relationship between an irradiation area and a pressing area. It is sectional drawing which shows the position of the rotation axis of the opening / closing mechanism, and the rotation direction. It is a block diagram which shows the structure of an image forming apparatus. It is a flowchart which shows the printing process of an image forming apparatus. It is a subroutine flowchart which shows the paper setting process (step S10). This is an example of an operation screen showing the determination result (paper type / basis weight classification).

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the description of the drawings, the same elements are designated by the same reference numerals, and duplicate description will be omitted. In addition, the dimensional ratios in the drawings are exaggerated for convenience of explanation and may differ from the actual ratios. In the drawings, the vertical direction is the Z direction, the front and back directions of the image forming apparatus are the X directions, and the directions orthogonal to these X and Z directions are the Y directions. The X direction is also referred to as a width direction or a rotation axis direction. Further, in the vicinity of the media sensor (media sensor 15 described later), the transport direction of the recording medium parallel to the plane of the transport path (transport path 143 described later) inclined with respect to the horizontal plane and orthogonal to the X direction is the Y'direction. , The direction orthogonal to this is called the Z'direction (see FIG. 2 etc.). Further, the XY'plane is a plane parallel to the transport surface, and Z'is a direction perpendicular to the transport surface. In the present embodiment, the recording medium includes printing paper (hereinafter, simply referred to as paper) and various films. In particular, the paper includes those produced using plant-derived mechanical pulp and / or chemical pulp. The types of recording media include coated glossy paper and matte paper, and uncoated plain paper and high-quality paper.

FIG. 1 is a diagram showing a schematic configuration of an image forming system 1 including an image forming apparatus 10 according to the present embodiment. As shown in FIG. 1, the image forming system 1 includes an image forming device 10, a paper feeding device 20, and a post-processing device 30 that are mechanically and electrically connected to each other.

(Image forming apparatus 10)
The image forming apparatus 10 includes a control unit 11, a storage unit 12, an image forming unit 13, a paper feed transport unit 14, a media sensor 15, an operation panel 18, a communication unit (not shown), and the like. These are connected to each other via a signal line such as a bus for exchanging signals. FIG. 2 is a side view showing the configuration of the media sensor 15 arranged in the transport path 143. The media sensor 15 includes a paper thickness sensor 40, a basis weight sensor 50, a surface sensor 60, and a pressing mechanism 70 for pressing the paper, and measures the paper characteristics. The basis weight sensor 50 is a transmission type first optical sensor, and the surface sensor 60 is a reflection type second optical sensor. Details of these media sensors 15 will be described later.

(Control unit 11)
The control unit 11 is composed of a CPU, ROM, RAM, etc., and executes various processes by executing a program stored in the ROM or the storage unit 12 described later, and controls each unit of the device and various types according to the program. Performs arithmetic processing. The control unit 11 functions as a determination unit that determines the paper type based on the detection results of the two optical sensors or the media sensor 15 including the two optical sensors.

(Memory unit 12)
The storage unit 12 includes an auxiliary storage unit such as a ROM for storing various programs and various data in advance, a RAM for temporarily storing programs and data as a work area, and a hard disk for storing various programs and various data. Further, the storage unit 12 stores the paper information stored in each paper feed tray. Paper information includes information on paper brand, size (paper width, paper length), basis weight (weight), paper type (coated paper, plain paper, woodfree paper, rough paper, etc.), and the paper type described later. It is set by the judgment process. Further, the storage unit 12 may store the paper brand, the learned model used for determining the paper type, and the paper profile (both described later).

(Image forming unit 13)
The image forming unit 13 forms an image by, for example, an electrophotographic method. The image forming unit 13 is composed of a writing unit 131 corresponding to each of the basic colors of Y (yellow), M (magenta), C (cyan), and K (black), a photoconductor drum 132, and toners and carriers of each color. A developer 133, etc., which accommodates a two-component developer, and the like are provided. Further, the image forming unit 13 further includes an intermediate transfer belt 134, a secondary transfer unit 135, and a fixing unit 136. The toner images formed on the photoconductor drum 132 by the developer 133 of each color are superposed on the intermediate transfer belt 134 and transferred to the paper S conveyed by the secondary transfer unit 135. The toner image on the paper S is fixed on the paper S by being heated and pressurized by the fixing portion 136 on the downstream side.

(Paper feed transport unit 14)
The paper feed transport unit 14 includes a plurality of paper feed trays 141, 142, transport paths 143, 144, and the like. The transport paths 143 and 144 include a plurality of transport roller pairs provided along these transport paths and a drive motor (not shown) for driving these transport roller pairs. It is equipped with a delivery roller that feeds out the highest-ranked paper among the plurality of sheets S loaded and placed in the paper feed trays 141 and 142, and feeds the paper S in the paper feed tray one by one to the transport path on the downstream side. .. The media sensor 15 is arranged on the upstream side of the resist roller on the transport path 143. As shown in FIG. 2, in the vicinity of the media sensor 15, the transport path 143 includes an upper guide plate 1431 formed of sheet metal and a lower guide plate 1432, and the transport path 143 between these guides facing each other at predetermined intervals. Paper S passes through. In the present embodiment, the upper guide plate 1431 and the lower guide plate 1432 correspond to the first and second guide plates, respectively, but the present invention is not limited to this, and vice versa.

The paper feed transport unit 14 transports the paper S fed from the paper feed tray 141 or the like. The paper S conveyed through the transport path 143 is ejected onto the output tray 342 via the subsequent post-processing device 30 after the image is formed by the image forming unit 13. When performing double-sided printing in which an image is also formed on the back surface of the paper S, the paper S having an image formed on one side is conveyed to a transport path 144 for forming a double-sided image at the lower part of the main body of the apparatus. The paper S transported to the transport path 144 is inverted on the front and back by the switchback path, then merges with the transport path 143 for one side, and the image forming unit 13 again forms an image on the other side of the paper S. To.

(Operation panel 18)
The operation panel 18 is provided with a touch panel, a numeric keypad, a start button, a stop button, etc., displays the status of the image forming apparatus 10 or the image forming system 1, and is a type of paper placed on the paper feed tray 141 or the like from the user. It is used for setting etc. and inputting instructions.

(Paper Feeding Device 20)
As shown in FIG. 1, the paper feed device 20 includes a paper feed transfer unit 24. Further, the paper feed device 20 includes a control unit, a storage unit, and a communication unit (none of which are shown) in addition to the paper feed transport unit 24, and these include signal lines such as a bus for exchanging signals. They are connected to each other via. The paper feed transport unit 24 includes a plurality of paper feed trays 241, 242, 243, and a transport path 244. The paper S conveyed from each paper feed tray is conveyed to the image forming apparatus 10 on the downstream side, and the paper characteristics are measured by the media sensor 15 and the image is formed by the image forming unit 13.

(Post-processing device 30)
As shown in FIG. 1, the post-processing device 30 includes a post-processing unit 31, a transport path 341, and a paper ejection tray 342. The post-processing unit 31 performs processing such as stapling processing, cutting processing, punching processing (punching holes), and the like on the paper S conveyed from the image forming apparatus 10. Further, the post-processing device 30 includes a control unit, a storage unit, and a communication unit (none of which are shown) in addition to these components, and these include a signal line such as a bus for exchanging signals. To be connected to each other.

(Media sensor 15)
As described above, the media sensor 15 includes a paper thickness sensor 40, a basis weight sensor 50, a surface sensor 60, and a paper pressing mechanism 70. With reference to FIG. 2, among these components, the paper thickness sensor 40 is arranged on the most upstream side in the transport direction. The paper thickness sensor 40 includes a pair of transport rollers 411 and 412, and a pressing mechanism 42 including an actuator, an encoder, and a light emitting / receiving unit. The upper transport roller 411 is urged toward the lower transport roller 412 by the pressing mechanism 42. By transporting the paper S to the nips of the transport rollers 411 and 412, the transport roller 411 moves upward by a height corresponding to the thickness of the paper S. The pressing mechanism 42 detects the paper thickness of the paper S based on the amount of displacement of the transport roller 411 in the height direction (thickness direction).

FIG. 3 is a perspective view showing the configurations of the basis weight sensor 50 and the surface sensor 60. As shown in FIGS. 2 and 3, the basis weight sensor 50 and the surface sensor 60 are arranged side by side in the X direction (width direction) between the transport roller pairs 1433 and 1434. Further, a pressing mechanism 70 is arranged below the surface sensor 60 (minus side in the Z'direction). The pressing mechanism 70 will be described later. The upper guide plate 1431 is composed of three partial guide plates 1431a, 1431b, and 1431c, and a part of the basis weight sensor 50 (light receiving portion) and a surface sensor 60 are on the central partial guide plate 1431b. Is placed. Further, as will be described later (FIG. 11 described later), the central partial guide plate 1431b constitutes a unit together with a part of the basis weight sensor 50 and the surface sensor 60, and these units are centered on the rotation shaft 146. To make it rotatable. The rotation shaft 146 extends along the X direction (width direction) and forms a part of the opening / closing mechanism.

Further, a transport roller separation mechanism that releases pressure contact between the transport rollers and separates them from the transport roller pair 1434 on the downstream side of the two sets of transport roller pairs 1433 and 1434 adjacent to the basis weight sensor 50 and the surface sensor 60. 145 is connected. The transfer roller separation mechanism 145 includes a drive motor, a cam, and the like, and switches to a release state by moving the position of the upper roller of the transfer roller pair 1434. The transport roller separating mechanism 145 may be configured to separate the transport roller pair 1433 on the upstream side instead of the transport roller pair 1434 on the downstream side.

(Basis weight sensor 50)
FIG. 4 is a schematic view showing the configuration of the basis weight sensor 50. The basis weight sensor 50 is a transmissive optical sensor that detects the basis weight of paper, includes a light emitting unit and a light receiving unit, and measures the amount of attenuation (transmittance) of light transmitted through the paper S.

As shown in FIG. 4, the basis weight sensor 50 includes a plurality of light emitting units 51 and a single light receiving unit 52. The light emitting unit 51 includes a first light emitting unit 51a, a second light emitting unit 51b, and a third light emitting unit 51c. From the first, second, and third light emitting units, the first, second, and third irradiation lights are irradiated to the irradiation region, respectively. This irradiation region (second irradiation region) is an inner region in the opening a12 when viewed from the Z'direction. The opening a12 is provided in the upper guide plate 1431. Further, the lower guide plate 1432 is also provided with an opening a22 at a position facing the opening a12. The openings a11 and a12 have the same shape, and are, for example, rectangular. A transparent sheet made of PET or the like and transmitting the wavelength of each irradiation light in order to prevent foreign matter such as paper dust from the paper S passing through the transport path 143 from adhering to the openings a12 and a22. 54a and 54b are attached. As described above, the opening a11 for the surface sensor 60 is not attached with any sheet, and the shutter 651 prevents foreign matter from adhering to the opening a11.

The first light emitting unit 51a irradiates the first irradiation light having the first wavelength. The first wavelength is, for example, a wavelength of near infrared rays that is longer than the wavelength of visible light. More specifically, the first wavelength includes, for example, wavelengths between 750 nm and 900 nm. The second light emitting unit 51b irradiates the second irradiation light having the second wavelength. The second wavelength is, for example, the wavelength of a blue ray included in visible light. More specifically, the second wavelength includes, for example, wavelengths between 400 nm and 470 nm. Both the first light emitting unit 51a and the second light emitting unit 51b are arranged on the opposite side of the transport path 143 from the light receiving unit 52, and the third light emitting unit 51c is on the same side as the light receiving unit 52. Therefore, it is provided in the vicinity of the light receiving unit 52. The third light emitting unit 51c irradiates the third irradiation light having a third wavelength toward the irradiation region (aperture a12). The third wavelength is, for example, the wavelength of the green ray of the visible light. More specifically, the third wavelength includes, for example, wavelengths between 495 nm and 570 nm. The third wavelength is different from the first wavelength (eg, wavelength between 750 nm and 900 nm) and the second wavelength (eg, 400 nm to 470 nm).

The third irradiation light is emitted toward the transport path 143 in the upper and lower guide plates 1431 and 1432. A reflection unit 53 is provided inside the lower guide plate 1432 provided in the vicinity of the first light emitting unit 51a and the second light emitting unit 51b. The reflecting portion 53 is, for example, painted in green, which is the same color as the third irradiation light, and reflects the third irradiation light. The reflecting unit 53 does not reflect the first irradiation light (near infrared rays) and the second irradiation light (blue rays) that are not the same color.

In the present embodiment, the control unit 11 controls the first light emitting unit 51a and the second light emitting unit 51b at the time of measurement, and irradiates the first irradiation light and the second irradiation light at different timings, respectively. The light receiving unit 52 receives the first irradiation light and the second irradiation light, detects the light amount of each irradiation light, and transmits the detected light amount of the first irradiation light and the light amount of the second irradiation light to the control unit 11. Output. Further, the paper S conveyed to the position of the opening a12 is also irradiated with the first irradiation light and the second irradiation light in the same manner. The light receiving unit 52 receives the transmitted light (first transmitted light, second transmitted light) of the first irradiation light and the second irradiation light, detects the amount of each irradiation light, and detects the first transmitted light. The amount of light and the amount of light of the second transmitted light are output to the control unit 11. That is, the light receiving unit 52 detects the first irradiation light and the second irradiation light when there is no paper S, and the first transmitted light and the second transmitted light when the paper S is in the opening a12.

Similarly, regarding the third light emitting unit 51c, the light receiving unit 52 reflects the first reflected light reflected by the reflecting unit 53 when there is no paper S, and is reflected by the surface of the paper S when the paper S is in the opening a12. The second reflected light is detected.

The control unit 11 calculates the first transmittance by dividing the amount of light of the first transmitted light by the amount of light of the first irradiation light. Similarly, the second transmittance is calculated by dividing the amount of the second transmitted light by the amount of the second irradiation light. Then, the type of paper S is determined from these first and second transmittances and the determination criteria stored in the storage unit 12.

Further, the control unit 11 calculates the reflectance by dividing the amount of light of the second reflected light by the amount of light of the first reflected light in addition to the first and second transmittances, and takes this reflectance into consideration. , The type of paper S may be determined. In this embodiment, the third light emitting unit 51c and the reflecting unit 53 are provided, but these may be omitted.

(Surface sensor 60)
Next, the configuration of the surface sensor 60 will be described with reference to FIGS. 5 to 9 together with FIGS. 2 and 3. FIG. 5 is a cross-sectional view of the surface sensor 60, and FIG. 6 is a perspective view showing the internal configuration of the surface sensor 60. In FIG. 6, the description of the cover (housing 61) that covers the entire surface sensor 60 is omitted.

As shown in these figures, the surface sensor 60 includes a housing 61, a light emitting unit 62, a collimating lens 63, a plurality of light receiving units 64 (light receiving units 641, 642), and an opening / closing mechanism 65. The housing 61 covers other components and shields external light. The housing 61 is not on the bottom surface, and when attached, the upper guide plate 1431 functions as a member that covers the bottom surface of the surface sensor 60. Details of the light emitting unit 62, the collimating lens 63, and the plurality of light receiving units 64 (light receiving units 641, 642) will be described later.

The opening / closing mechanism 65 includes a shutter 651, a connection portion 652, a rotating shaft 653, a worm gear 654, and a drive motor 655. The power of the drive motor 655 is transmitted to the shutter 651 through the worm gear 654, the rotating shaft 653, and the connecting portion 652. The shutter 651 moves around the rotation axis 653 in the direction of the arrow. The upper guide plate 1431 is provided with an opening a11, and the lower guide plate 1432 is provided with an opening a21. 5 and 6 show a state in which the paper characteristics of the paper S in the normal state are not measured. At this time, the opening a11 is closed by the plate-shaped shutter 651 which is a flat plate member. The opening / closing operation of the opening a11 of the shutter 651 is performed by the control unit 11 controlling the drive motor 655.

FIG. 7 is a schematic cross-sectional view of the surface sensor 60 showing a state in which the shutter is open. FIG. 7 shows the state of the measurement of the paper characteristics, that is, the measurement mode. Note that in FIG. 7, the description of the configuration of the opening / closing mechanism 65 other than the shutter 651 is omitted. The opening a11 has a substantially rectangular shape, and the hole size is, for example, several tens of mm in the horizontal direction (X direction) and several tens of mm in the vertical direction (Y'direction). The size of the opening a11 and the arrangement positional relationship with other components will be described later (FIG. 10 described later). A plurality of ribs r1 (see FIG. 7) are provided on the lower surface of the shutter 651 so as not to interfere with the transport of the paper S in the transport path 143. Each rib r1 is inclined along the transport direction so that the lower surface of the upper guide 1431 is retracted on the upstream side in the transport direction and slightly protrudes on the downstream side. With such a rib r1, the paper S can be smoothly conveyed. Further, a reference plate 6501 as a member for calibration is attached to the upper surface of the shutter 651. The reference plate 6501 is, for example, a white plate having a predetermined surface property, and the surface property sensor 60 can be calibrated by measuring the reference plate 6501 of the closed shutter 651 before measuring the paper characteristics. Do.

(Pressing mechanism 70)
The opening a21 is wider than the opening a11 and is at substantially the same position in the XY'plane, and the opening a21 includes the opening a11. A pressing mechanism 70 is arranged below the lower guide plate 1432. FIG. 8 is a perspective view showing the configuration of the pressing mechanism 70. As shown in the figure, the pressing mechanism 70 includes a pressing plate 71, a support member 72, a working shaft 73, a spring 74, a cam 75, a rotating shaft 76, a gear series 77, and a drive motor 78. The pressing plate 71 as a pressing member has an upper surface (pressing surface 711 (shown in gray in the figure)) parallel to the XY'plane. At the time of measurement when the cam 75 is not acting, the pressing force of the spring 74 causes the pressing plate 71 and the integrated support member 72 supporting the pressing plate 71 to move in the upward direction (plus side of Z') indicated by an arrow, that is, The paper S is moved toward the upper guide plate 1431 which is the first guide plate, and the paper S is sandwiched and pressed between the upper guide plate 1431 and the upper guide plate 1431. As a result, the surface of the paper S can be stably arranged on the reference surface. On the other hand, when the measurement by the surface sensor 60 is not performed, the drive motor 78 rotates by a predetermined angle, and the driving force is the cam 75 by rotating the cam 75 via the gear series 77 and the rotation shaft 76. Pushes the action shaft 73 downward. As a result, the pressing plate 71 and the support member 72 are lowered downward against the urging force of the spring 74. The height of the pressing plate 71 can be detected by an encoder attached to the end of the rotating shaft 76. When the measurement by the surface sensor 60 is not performed, the pressing surface 711 of the pressing plate 71 is located in substantially the same plane as the conveying surface (upper surface) of the lower guide plate 1432 so as not to interfere with the transportation of the paper S. That is, both planes are located on the same plane or at a height where the pressing surface 711 is slightly lower.

The pressing surface 711 of the pressing plate 71 is sufficiently larger than the opening a11. In the measurement mode of FIG. 7, the tip of the paper S is transported to a position beyond the openings a11 and a20 in the transport direction, and then the paper S is temporarily stopped. After that, the pressing plate 71 is lifted by the driving mechanism of the pressing mechanism 70. As a result, the paper S is pressed and fixed by a predetermined urging force (the urging force of the spring 74) between the pressing surface 711 of the pressing plate 71 and the lower surface (reference surface) which is also the transport surface of the upper guide plate 1431. .. For example, the upper surface of the pressing plate 71 has a size larger than a dozen mm width or more over the entire circumference of the opening a11, and the paper S is pressed in the width region around the pressing plate 71.

FIG. 9 is a schematic view showing the arrangement positions of the light emitting unit 62 and the plurality of light receiving units 64. The arrangement angle of the light emitting unit 62 is set so that the incident angle of the irradiation light with respect to the reference plane is 75 °. The incident angle of 75 ° is an angle used for measuring the glossiness of blank paper according to JIS, and is an angle that is less affected by the color of the object to be measured. The reference surface is a virtual surface including the lower surface of the upper guide plate 1431 as described above, and at the time of measurement, the surface of the paper S to be measured is arranged on the reference surface. The light emitting unit 62 is arranged on the substrate b1. The light emitting unit 62 includes a light emitting element as a light source such as an LED that emits light having a predetermined wavelength, and the irradiation light emitted from the light source (point light source) becomes substantially parallel light by the collimating lens 63 and irradiates the irradiation region. Will be done. In the present embodiment, the wavelength of the light source of the light emitting unit 62 is preferably in the range of more than 405 nm and less than 525 nm, more preferably in the range of 445 nm or more and 500 nm or less, and the most preferable wavelength is around 465 nm. The irradiation region (first irradiation region) is an inner region in the opening a11 when viewed from the Z'direction, and the center (optical axis) of the irradiation region and the reference plane parallel to the XY'plane intersect at the intersection p1. Intersection at. As the light emitting unit 62, a surface light emitting type LED may be used, or a bullet type LED may be used. Further, when a bullet-shaped LED is used, a desired irradiation diameter (also referred to as a beam diameter) can be obtained by designing a lens suitable for the bullet-shaped directivity. Further, the light emitting unit 62 and the light receiving unit 64 are arranged along the X direction (width direction), that is, they are on the same XZ'plane, and the irradiation light from the light emitting unit 62 is along the width direction. ..

Each of the plurality of light receiving units 64 includes a light receiving element such as a photodiode, a phototransistor, etc., and a first light receiving unit 64 (light receiving unit 641) that receives specularly reflected light from the irradiation region and diffuse reflection from the irradiation region. Includes one or more second light receiving units 64 (light receiving units 642) that receive light. The first light receiving unit 641 is arranged at a position having a reflection angle of 75 ° corresponding to an incident angle of 75 ° of the light emitting unit 62, and receives specularly reflected light. Further, the second light receiving unit 642 can be arranged at any position of the reflection angle except the position of 75 ° within the range of the reflection angle of 0 ° or more and less than 90 °, and receives diffuse reflected light. The arrangement positions are preferably reflection angles of 60 °, 30 °, and 0 °, and more preferably two locations of 60 ° and 30 °, or one location of 60 °. In the examples of FIGS. 5, 7 and 9, a first light receiving unit 641 for receiving specular reflected light having a reflection angle of 75 ° and a second light receiving unit 642 for receiving diffuse reflected light having a reflection angle of 30 ° are arranged. An example of this is shown. In these figures, the light receiving unit 641 is arranged on the substrate b2, and the light receiving unit 642 is arranged on the substrate b3.

The housing 61 is provided with openings a3 and a4 on the light receiving path of the light receiving portions 641 and 642. The openings a3 and a4 have a similar structure. The openings a3 and a4 are circular slits having a diameter of, for example, φ3 mm when viewed from the intersection p1 side.

The irradiation diameter in the irradiation region is set to 6 mm or more, which is larger than the maximum length of the pulp fibers of the paper to be measured. For example, the irradiation diameter is 13 mm. The irradiation diameter referred to here is the diameter of the light (beam) in a plane orthogonal to the optical axis at the intersection p1 where the optical axis intersects the irradiation surface (reference plane).

(Irradiation area and pressing area)
FIG. 10 is a schematic top view showing the positional relationship between the irradiation region and the pressing region. As described above, the basis weight sensor 50 and the surface sensor 60 are arranged side by side in the paper width direction (X direction). That is, the irradiation region in the opening a11 and the irradiation region in the opening a12 are aligned in the width direction. The top view of the openings a11 and a12 (in the Y'direction (direction perpendicular to the transport surface); the same applies hereinafter) is preferably rectangular as shown in FIG. 10, but is trapezoidal or otherwise arbitrary. Can take the shape of. The length of the opening a11 in the vertical direction (Y'direction) is larger than the irradiation diameter (minor diameter). For example, it is in the range of 10 to 30 m, preferably about 20 mm. The lateral length (X direction) of the opening a11 is preferably a length close to the irradiation diameter (major axis). For example, it is in the range of 30 to 60 mm, preferably 40 mm.

In top view, the pressing surface 711 is sufficiently larger than the opening a11 of the upper guide plate 1431, the center of which substantially coincides with the center of the opening a11, and the pressing surface 711 includes the opening a11. Further, the opening a21 of the lower guide plate 1432 is slightly larger than the pressing plate 71 as long as it does not hinder the vertical movement of the pressing plate 71. For example, the opening a21 is set to a size such that a gap of about 0.5 to 2 mm is formed over the entire circumference.

The openings a12 and a22 for the basis weight sensor 50 have substantially the same size in the top view, and their centers coincide with each other. The vertical and horizontal lengths of the openings a12 and a12 are set to be equal to or slightly shorter than the openings a11.

The upper limit of the distance between the center of the opening a12 (opening a22) for the basis weight sensor 50 and the opening a11 for the surface sensor 60 in the X direction is limited. Even the smallest size of paper that can be fed by the image forming apparatus 10 is set to be less than or equal to the range that can be measured by both optical sensors. For example, the distance between the center of the opening a12 and the opening a11 in the X direction is one hundred and several tens of mm or less.

The area outside the opening a11 of the pressing surface 711 of the surface sensor 60 is a “pressing area” that presses the paper S against the upper guide plate 1431. This pressing region is an region that covers the entire circumference of the opening a11. The width of the surrounding square frame-shaped pressing region may be several mm or more, preferably within the range of 5 to 20 mm.

(Effect of this embodiment)
Since the paper S is pressed by the pressing region formed around the opening a11 between the pressing surface 711 of the pressing plate 71 and the upper guide plate 1431, the surface position of the paper S is stabilized and the reference surface. It can be positioned at, and by extension, measurement can be performed with high accuracy. Further, two optical sensors (basis sensor 50 and surface sensor 60) are formed by pressing the paper S so as to seal the irradiation area (opening a11) in the pressing area that covers the entire circumference of the opening a11. ) Are arranged side by side in the width direction and brought close to each other, it is possible to prevent light from leaking from the irradiation area of one optical sensor and entering the irradiation area of the other, and thus measurement can be performed with high accuracy.

Further, the roller spacing of adjacent transfer roller pairs (for example, transfer roller pairs 1433 and 1434) is limited to an upper limit value because it is necessary to set so that even the minimum paper size can be conveyed. In the present embodiment, by arranging the two optical sensors side by side in the width direction, the two optical sensors can be arranged even with a narrow roller spacing. Further, by doing so, the measurement by the two optical sensors can be executed at the same time, and the measurement related to the paper type discrimination can be performed in a short time.

Further, in the present embodiment, the irradiation light from the light emitting portion 62 of the surface sensor 60 is along the width direction. The paper S may loosen slightly when being conveyed through the transport path 143, but by setting the irradiation direction of such irradiation light to the width direction, the influence on the measurement of the looseness of the paper S can be reduced.

(Opening / closing mechanism of upper guide plate 1431)
FIG. 11 is an enlarged view of a part of FIG. 2, and is a side view showing the configuration of the media sensor. As also shown in FIG. 3, the upper guide plate 1431 is composed of three partial guide plates 1431a, 1431b, and 1431c. The unit (partial guide 1431b, basis weight sensor 50, surface sensor 60) attached to the central partial guide plate 1431b is counterclockwise with the direction indicated by the arrow in the figure centered on the rotation shaft 146 by manual operation by the user. Rotate clockwise. The rotating shaft 146 functions as a part of the opening / closing mechanism. As shown in FIG. 11, the rotating shaft 146 is located substantially in the center of the adjacent transport roller pairs 1433 and 1434 in the transport direction (Y'direction), and is located downstream in the opening direction (plus side in the Y'direction). There is a rotating shaft 146, and the center of gravity (or the center position of the partial guide 1431b in the Y'direction) of the two optical sensors arranged on the partial guide plate 1431b is located on the upstream side. The user can manually rotate these units in the open orientation shown by manipulating the handles, removing them from the hooks (neither shown) and lifting them up. As a result, the user can access the transport path 143, so that maintenance work for cleaning the two optical sensors and replacing parts can be easily performed. Further, when a transport jam of the paper S occurs in the transport path 143, the user can remove the jammed paper. The light emitting portions 51 (51a, 51b) of the basis weight sensor 50 and the pressing mechanism 70 are arranged on the fixed lower guide plate 1432 (second guide plate) side.

(Paper type judgment processing)
Next, the paper type determination process performed by the image forming apparatus 10 will be described with reference to FIGS. 12 to 15. FIG. 12 is a block diagram showing a configuration of an image forming apparatus. FIG. 13 is a flowchart showing a printing process of the image forming apparatus.

As shown in FIG. 12, the image forming apparatus 10 is connected to the server 80 and other image forming apparatus 10b and 10c through the network 90. In the figure, since the configurations other than the control unit 11 of the image forming apparatus 10 have already been described in FIG. 1 and the like, the description will be omitted by adding the same reference numerals.

The control unit 11 functions as an overall control unit 110, an engine control unit 120, a media sensor control unit 130, a post-processing option control unit 140, a paper feed option control unit 150, and a transfer control unit 160.

When a print job is input by an instruction sent from an operation panel 18 or an external terminal such as a network-connected PC operated by the user, the overall control unit 110 is based on the input print setting information of the print job. , The engine control unit 120 executes a print job. The overall control unit 110 executes the paper type determination process by using the paper type determination engine (learned model) stored in the storage unit 12 and the paper profile. Here, the "paper profile" associates a certain paper with the measured value of the media sensor 15 of the paper, the characteristic data input from the user, the paper size, an arbitrary identification name (for example, a paper brand), and the like. It is registered in advance. The "paper type discrimination engine" is also called a learned model, and a teacher using teacher data with the detection output by the media sensor 15 of the paper S as an input value and the paper type information set by the user of the paper S as a correct label. It is a trained model generated by Yes training. As the teacher data, the data of other image forming devices 10b, 10c, etc. connected to the network 90 may be aggregated by the server 80. The learning machine (not shown) can generate a trained model by a learning method using a neural network constructed by combining perceptrons. The learning method is not limited to this, and various methods can be adopted in the case of supervised learning. For example, a random forest, a support vector machine (SVM), a boosting method, a Bayesian network linear discrimination method, a non-linear discrimination method, and the like can be applied. Further, as a learning machine, it can be performed by using a stand-alone high-performance computer using a CPU and a GPU (Graphics Processing Unit) processor, or a cloud computer.

The engine control unit 120 performs processing related to image formation by controlling the post-processing option control unit 140, the paper feed option control unit 150, and the transport control unit 160. The post-processing option control unit 140 controls the post-processing device 30. Specifically, the paper transport timing, post-processing setting information of the paper to be transported, and the like are transmitted to the post-processing device 30. The paper feed option control unit 150 controls the paper feed device 20. Specifically, by communicating with the paper feed device 20, the paper feed tray to be used, the paper transfer timing, and the like are transmitted and received.

The transport control unit 160 controls the paper feed transport by controlling the paper feed transport unit 14. In addition, the image forming unit 13 is controlled to control the image forming conditions and the image forming timing.

The media sensor control unit 130 controls the paper thickness sensor 40, the basis weight sensor 50, and the surface sensor 60 in response to an execution instruction request from the engine control unit 120 to execute measurement of paper characteristics. The media sensor control unit 130 also controls the operation of the pressing mechanism 70.

Next, the paper type determination process will be described with reference to FIG. Steps S10 to S30 are print preparation processes. The user performs this print preparation process before performing the main printing of the print job.

(Step S10)
The user operates the paper setting button on the operation screen (not shown) displayed on the operation panel 18. The control unit 11 starts the paper setting by accepting this operation from the user. The start instruction of the paper setting includes selection information of one or more paper feed trays (paper feed trays 141, 142, 241 to 243) in which the target paper is loaded. Details of this paper setting process will be described later with reference to FIG.

(Step S20)
When the paper setting is completed, the image formation conditions are set according to the set paper characteristics, and test printing (test printing) of the print job is performed.

(Step S30)
When the user is unsatisfied with the result of the test print, or when a plurality of types of paper are used in one print job, the user repeats the process of step S10 or less for another paper (step S30: NO). On the other hand, when the result of the test print is satisfactory and the confirmation regarding all the paper types is completed (YES), the control unit 11 advances the process to step S40 by accepting the operation of the preparation completion by the user. ..

(Step S40)
The control unit 11 controls the image forming unit 13 and the like to execute a print job (main printing), thereby completing the printing process (end).

(Paper setting process)
(Step S101)
FIG. 14 is a subroutine flowchart showing the paper setting process (step S10). The transport control unit 160 of the control unit 11 feeds the paper S from the paper feed tray (for example, the paper feed tray 141 (hereinafter, simply referred to as “selection tray”) selected by the user) and transports the paper S to the transport path 143. ..

(Step S102)
When the tip of the paper S passes the detection positions of the predetermined amount, the basis weight sensor 50, and the surface sensor 60, the paper transport is stopped at one end.

(Step S103)
The media sensor control unit 130 detects the paper thickness of the paper S by the paper thickness sensor 40, and passes the detection data (hereinafter, referred to as “measured value 1”) to the overall control unit 110. This measurement may be performed before step S102, or may be performed after the paper S is stopped.

(Step S104)
The overall control unit 110 determines the thickness of the paper S based on the detection data of the paper thickness sensor 40. If the thickness is equal to or greater than a predetermined value (YES), the process proceeds to step S105. On the other hand, if it is less than the predetermined value (NO), step S105 is skipped and the process proceeds to step S106.

(Step S105)
The overall control unit 110 switches the transport roller pair 1434 to the separated state by controlling the transport roller separating mechanism 145.

(Steps S106, S107)
The media sensor control unit 130 simultaneously detects the basis weight and surface quality of the paper by the basis weight sensor 50 and the surface surface sensor 60, and collects the detection data (hereinafter referred to as “measured values 2 and 3”, respectively) as a whole. It is passed to the control unit 110. Note that simultaneous does not have to be completely simultaneous, and there may be a difference of about several seconds. After the paper S is stopped, the paper S is used to measure multiple times (N times) of the pair. It may be done during the cycle of transporting again. Before this first measurement, the surface sensor 60 may be calibrated by the reference plate 6501.

(Step S108)
If the measurement has not been performed a predetermined number of N times, the processes of steps S106 and S107 are repeated. Before the next measurement is performed, the pressing mechanism 70 is moved up and down and the paper S is conveyed for a predetermined distance (for example, an arbitrary distance of several mm to 50 mm) to obtain the same paper S. Make another measurement of the position. Further, when transporting, the transport roller pair 1434 is returned to the pressure contact state by the transport roller separating mechanism 145. The N times is, for example, 5 times, and when the measurement for 5 times is completed (YES), the process proceeds to step S109.

(Step S109)
Here, averaging processing is performed on the detection data (measured values 2 and 3) of the basis weight and surface properties of N times acquired in steps S106 and S107.

(Step S120)
The overall control unit 110 uses the measured values 1 to 3 (or the average data thereof) acquired in steps S103, S106, and S107, the trained model (paper type determination engine), and the paper profile to determine the paper type. And determine the basis weight classification.

(Step S121)
Here, the overall control unit 110 displays the determination result.

FIG. 15 is an example of the operation screen 181 showing the determination result (paper type / basis weight classification) displayed on the operation panel 18. On the operation screen 181, two paper type / basis weight candidates are displayed in descending order of score. When the user accepts the determination result of the first candidate column 81 (coated paper / basis weight 177 to 216), the user is selected for the tray 1 (paper feed tray 141) by operating the button 84. The determination result in column 81 is applied. When applying the second candidate column 82 (plain paper / basis weight 172 to 216), the user operates the button 84 after selecting the column 82. On the other hand, when it is desired to apply the selected determination result to both trays 1 and 2, the user operates the button 85. Further, by operating the button 83, the determination result can be discarded without being adopted. The determination result selected by the user may be stored in the server 80 or the like as correct answer data, and may be used as teacher data for subsequent machine learning.

(Step S122)
If the user changes the paper type (YES), the process proceeds to step S123, and if the determination result is accepted without the change (NO), the process proceeds to step S124.

(Step S123)
The overall control unit 110 accepts an input operation from the user through the operation panel 18, and sets the accepted changed paper type as the paper type information of the selection tray.

(Step S124)
When the setting is not changed (for example, when the operation of the button 84 is accepted in FIG. 15), the overall control unit 110 sets the determination result performed in step S120 as the paper type information of the selection tray.

(Step S125)
The print condition of the selected tray is set to the print condition corresponding to the set paper type, and the process returns to the process of FIG. 13 and the process of step S10 or less is performed (return).

As described above, the image forming apparatus 10 according to the present embodiment determines the paper type of the recording medium by using the detection result from the media sensor 15. This makes it possible to accurately determine the paper type. In particular, when it is determined from the detection data of the paper thickness sensor 40 that the thick paper has a thickness equal to or greater than a predetermined value, the transport roller pair is separated. In the case of thick paper, it is difficult to flatten the paper S (in the irradiation region) by the pressing mechanism 70 because the rigidity (strain) of the paper is too high. By separating the transport roller pairs 1434 by the transport roller separating mechanism 145, the paper S can escape in the transport direction even when the paper S is loosened, so that the paper S can be easily leveled flat. be able to. On the other hand, in the case of thin paper with a small thickness, the paper S is pulled by the adjacent transport rollers 1433 and 1434 to give tension, and then pressed by the pressing mechanism 70 to prevent wrinkles and stabilize. The paper S can be flattened.

The configuration of the image forming apparatus 10 including the media sensor described above is not limited to the above configuration, and various configurations are described within the scope of the claims, as the main configuration has been described in explaining the features of the above-described embodiment. It can be modified. Further, the configuration provided in the general image forming apparatus is not excluded. For example, the light receiving portion 52 of the basis weight sensor 50 is arranged above the transport path 143, and the light emitting portions 51a and 51b that emit the irradiation light for transmission are arranged below the transport path 143, whereby the light receiving portion of the basis weight sensor 50 is arranged. An example in which the surface sensor 60 and the surface sensor 60 are arranged on the same side (upper side) with respect to the transport path 143 is shown, but the present invention is not limited to this, and the light emitting portion 51a of the basis weight sensor 50 with respect to the transport path 143. The 51b may be arranged on the same upper side as the surface sensor 60, and the light receiving portion 52 may be arranged on the lower side.

Further, although the example of opening and closing the partial guide plate 1431b which is a part of the upper guide plate 1431 by the opening / closing mechanism is shown, the upper guide plate 1431 may be configured to be fully opened / closed.

Further, although the example in which the overall control unit 110 has the trained model is shown, the present invention is not limited to this, and the server 80 may have the trained model and the server 80 may determine the paper type. In this case, the image forming apparatus 10 transmits the measured paper characteristic data to the server 80, and the server 80 that receives the data determines the paper type based on the data and sends the determination result back to the image forming apparatus. .. Further, in FIG. 1 and the like, the image forming apparatus 10 shows a configuration in which the image forming apparatus 10 is connected to the optional paper feeding apparatus 20 and the post-processing apparatus 30, but the image forming apparatus 10 may be a single image forming apparatus 10 without these options.

1 Image formation system 10 Image formation device 11 Control unit 110 Overall control unit 14 Transport unit 141, 142 Paper feed tray 143, 144 Transport path 1431 Upper guide plate a11, a12 Opening 1432 Lower guide plate a21, a22 Opening 145 Transport roller separation mechanism 146 Rotating shaft (opening and closing mechanism)
15 Media sensor 40 Paper thickness sensor 50 Basis weight sensor (first optical sensor)
60 Surface sensor (second optical sensor)
61 Housing a3, a4 Aperture b1, b2, b3 Substrate 62 Light emitting part 63 Collimating lens 64, 641, 642 Light receiving part 70 Pressing mechanism 71 Pressing plate (pressing member)
711 Pressing surface 72 Support member 73 Action shaft 74 Spring 75 Cam 76 Rotation shaft 77 Gear series 78 Drive motor 18 Operation panel 20 Paper feed device 30 Post-processing device 80 Server

Claims (11)

Paper tray and
A transport unit that includes a transport path formed by a pair of guide plates arranged to face each other and transports a recording medium fed from the paper feed tray to the transport path.
A transmissive first optical sensor having a light emitting unit that irradiates the recording medium conveyed to the first irradiation region of the transport path with light and a light receiving unit that receives the light transmitted through the recording medium. When,
A reflective second optical unit having a light emitting unit that irradiates the recording medium transported to the second irradiation region of the transport path with light and a light receiving unit that receives the light reflected on the surface of the recording medium. Expression sensor and
A determination unit for determining the paper type of the recording medium by using the detection results measured by the first and second optical sensors is provided.
The first and second optical sensors are arranged side by side in the width direction orthogonal to the transport direction of the recording medium.
An image forming apparatus including a pressing member and comprising a pressing mechanism for pressing the recording medium by urging the recording medium on the guide plate at the time of measurement by the second optical sensor. The second irradiation region is in the opening of the first guide plate among the first and second guide plates constituting the pair of guide plates.
The pressing mechanism has a pressing surface that comes into contact with the recording medium.
The first aspect of the present invention, wherein the pressing surface includes the opening and covers the entire circumference of the opening when the recording medium is pressed when viewed from a direction perpendicular to the transport surface of the transport path. Image forming device. The image forming according to claim 1 or 2, wherein the light receiving portion of the first optical sensor and the light receiving portion of the second optical sensor are arranged on the same side with respect to the transport path. apparatus. The image forming apparatus according to any one of claims 1 to 3, wherein the measurement by the first optical sensor is also performed at the time of measurement by the second optical sensor. The image forming apparatus according to any one of claims 1 to 4, wherein the measurement of the first and second optical sensors is performed by stopping the recording medium in the first and second irradiation regions. The image forming apparatus according to any one of claims 1 to 5, wherein the irradiation direction of the irradiation light by the light emitting unit of the second optical sensor is along the width direction. The second irradiation region is in the opening of the first guide plate among the first and second guide plates constituting the pair of guide plates.
The pressing mechanism is arranged in the opening of the second guide plate.
The pressing surface of the pressing mechanism is substantially in the same plane as the transport surface of the second guide plate when the measurement by the second optical sensor is not performed, and the pressing mechanism is used when the measurement is performed. However, the recording medium is pressed between the pressing surface and the conveying surface of the first guide plate by moving toward the first guide plate, according to any one of claims 1 to 6. Image forming device. An opening / closing mechanism that allows a part or all of the first guide plate to be opened / closed by a user's operation is provided.
A light receiving portion of the first optical sensor, a light emitting portion of the second optical sensor, and a light receiving portion are arranged on the first guide plate that is opened and closed.
The image forming apparatus according to any one of claims 1 to 7, wherein a light emitting unit of the first optical sensor and the pressing mechanism are arranged on the fixed second guide plate side. The opening / closing mechanism makes the first guide plate rotatable about a rotation axis extending in the width direction as a rotation center.
In the transport direction, the rotation axis is on the downstream side in the opening direction of the first guide plate, and the first and second optical types arranged on the first guide plate on the upstream side in the opening direction. The image forming apparatus according to claim 8, wherein the position of the center of gravity of the sensor is located. A paper thickness sensor that detects the thickness of the recording medium and
Further, a transport roller separating mechanism for switching one of two sets of transport roller pairs adjacent to each other on the upstream side and the downstream side of the first and second irradiation regions in the transport direction is provided.
Depending on the detection result of the paper thickness sensor,
The image forming apparatus according to any one of claims 1 to 9, wherein the transport roller pair is separated by the transport roller separation mechanism at the time of measurement of the second optical sensor. When a paper thicker than a predetermined value is detected by the detection of the paper thickness sensor,
The image forming apparatus according to claim 10, wherein the transport roller pair is separated by the transport roller separation mechanism at the time of measurement of the second optical sensor.

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