Image forming apparatus

Abstract

To improve the detection accuracy of seat characteristics or the like using sensors.SOLUTION: An image forming apparatus includes: an image forming unit 15 for forming an image on a sheet S; a manual feed tray 200 for placing a manually fed sheet S; a feed unit 201 for feeding the sheet S placed on the manual feed tray 200; a conveyance roller pair 205 arranged in succession with the feed unit 201 for conveying the sheet S fed by the feed unit 201 toward the image forming unit 15; a flat-surface first conveyance path P1 arranged between the feed unit 201 and the conveyance roller pair 205; and a sensor unit 220 for reading reflected light of light irradiated on the sheet S being conveyed in the first conveyance path P1.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an image forming apparatus for forming an image on a sheet. [Background technology]

[0002] In recent years, the types of recording media that can be output by image forming devices such as printers, facsimiles, and copiers have been expanding, and sheets with smoother surfaces than high-quality paper, such as coated paper made of pulp with a coating, are becoming standard. In addition, the range of sheet weights that can be handled is also expanding, both for thick and thin paper. In order to turn these sheets into high-quality products in an image forming device, it is necessary to set transport conditions, transfer conditions, and the like that are suited to the characteristics of each sheet. However, it is not easy for a user of an image forming device to appropriately set detailed conditions that are suited to these sheet characteristics.

[0003] In response to these issues, image forming devices that support settings using detection means such as sensors are being developed. For example, in a vertical path machine, an image forming device has been proposed in which a sheet type sensor is provided between the sheet cassette and the registration roller unit, and the sheet characteristics are detected using this sheet type sensor (see Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] U.S. Patent No. 7,783,211 Summary of the Invention [Problem to be solved by the invention]

[0005] In general, the posture of a sheet conveyed along a conveying path may change near the sensor due to, for example, resistance from a guide member that guides the sheet, or the sheet being loosened due to the conveying speed relationship between a conveying roller upstream of the sensor and a conveying roller downstream of the sensor. In contrast, in order to obtain highly accurate detection results using a sensor that detects sheet characteristics, it is necessary to stably convey the sheet at a position that matches the focal length of the sensor, and therefore it is desirable to suppress the change in posture during sheet conveyance.

[0006] However, in the image forming apparatus described in the above-mentioned Patent Document 1, the suppression of the change in the position of the sheet during conveyance is not taken into consideration, and the conveyance path from the sheet cassette to the registration roller is configured as a curved conveyance path in a vertical path machine. When the guide portion that guides the sheet is curved, it is difficult to suppress the change in the position of the sheet during conveyance. In addition, in the registration roller portion, the sheet is abutted against the registration roller portion to intentionally generate a slack (loop) in the sheet, thereby restricting the leading edge of the sheet. In such a registration roller portion, it is necessary to provide a degree of freedom in the conveyance path so that the sheet can form a loop, and it is difficult to obtain an arrangement that allows the sheet to be conveyed in a stable position, and it is difficult to suppress the change in the position of the sheet during conveyance. For these reasons, it has been difficult to detect the sheet characteristics, etc., using a sensor with high accuracy.

[0007] SUMMARY OF THE PRESENT EMBODIMENT An object of the present invention is to provide an image forming apparatus capable of improving the detection accuracy of sheet characteristics and the like using a sensor. [Means for solving the problem]

[0008] One aspect of the present invention is an image forming apparatus comprising an image forming unit that forms an image on a sheet, a manual feed tray for placing a manually fed sheet, a feeding unit that feeds the sheet placed on the manual feed tray, a transport unit arranged adjacent to the feeding unit and transporting the sheet fed by the feeding unit toward the image forming unit, a planar first transport path arranged between the feeding unit and the transport unit, and a detection unit that reads reflected light of light irradiated onto the sheet transported along the first transport path. Effect of the Invention

[0009] According to the present invention, it is possible to improve the detection accuracy of sheet characteristics and the like using a sensor. [Brief description of the drawings]

[0010] [Figure 1] 1 is a cross-sectional view showing an image forming apparatus according to an embodiment. [Diagram 2] 4 is a cross-sectional view showing a range from a feeding unit to a pair of conveying rollers when a pressing unit according to the embodiment is located at a standby position; FIG. [Diagram 3] 3 is a cross-sectional view showing a state cut along line AA in FIG. 2. [Figure 4] FIG. 2A is a perspective view showing a pressing roller, and FIG. 2B is a perspective view showing a slider. [Diagram 5] FIG. 2 is a plan view showing a feed roller to a pair of transport rollers according to the embodiment; [Figure 6] 4 is a cross-sectional view showing a portion from a feeding unit to a pair of conveying rollers when a pressing unit according to an embodiment is located at a pressing position. FIG. [Figure 7] 7 is a cross-sectional view showing a state cut along line BB in FIG. 6. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] The present embodiment will be described below with reference to the drawings. First, the schematic configuration of an image forming apparatus 1 according to the present embodiment will be described with reference to FIG. 1. The dimensions, materials, and relative positions of the components of the image forming apparatus 1 are not intended to limit the scope of the present invention unless otherwise specified. In addition, in the present embodiment, a full-color copying machine having multiple photosensitive drums is applied as the image forming apparatus 1. However, the present embodiment is not limited to this, and can also be applied to monochrome or mono-color copying machines and printers having one photosensitive drum.

[0012] [Image forming equipment] 1 is a schematic diagram of an image forming apparatus 1 according to the present embodiment. The image forming apparatus 1 forms an image on a sheet used as a recording medium based on image information input from an external PC or image information read from an original. The sheets used as recording media include various sheet materials of different materials and sizes, such as paper with different basis weights, such as thick paper, plain paper, and thin paper, envelopes, plastic films for overhead projectors, and cloth.

[0013] The image forming apparatus 1 includes an apparatus main body 1A that houses an image forming unit 15 that forms an image on a sheet S, and an image reading device 300 that is disposed above the apparatus main body 1A and reads image information from a document. The image forming unit 15 is an intermediate transfer type electrophotographic unit that includes four image forming stations PY, PM, PC, and PK, an intermediate transfer belt 155, and a fixing unit 160.

[0014] Each of the image forming stations PY to PK executes an electrophotographic process to form a toner image on the surface of a photosensitive drum 151, which is an image carrier. That is, when the image forming stations PY to PK are requested to form a toner image, the photosensitive drum 151, which is a photosensitive member, is rotated and a charging device uniformly charges the surface of the photosensitive drum 151. An exposure device 152 provided at the bottom of the apparatus main body 1A irradiates the photosensitive drum 151 with laser light based on image information to expose the drum surface, and writes an electrostatic latent image on the photosensitive drum 151. A developing device 153 supplies charged toner particles to the photosensitive drum 151 and develops the electrostatic latent image on the drum surface into a toner image.

[0015] The toner images of each color formed on the surface of each photosensitive drum 151 in the image forming stations PY to PK are finally transferred onto the sheet S via the intermediate transfer belt 155 and secondary transfer rollers 159. First, the toner images carried on each photosensitive drum 151 are primarily transferred onto the intermediate transfer belt 155 by the primary transfer rollers 154. Adherents such as toner remaining on the photosensitive drums 151 are removed by cleaning devices provided in each of the image forming stations PY to PK.

[0016] An intermediate transfer belt 155, which is an intermediate transfer body, is wound around a secondary transfer inner roller 156, a tension roller 157, and a tension roller 158, and is driven to rotate in the direction R1 in the figure. The toner image carried on the intermediate transfer belt 155 is secondarily transferred to a sheet S at a secondary transfer section 161 formed between the intermediate transfer belt 155 and a secondary transfer roller 159 facing the secondary transfer inner roller 156. Adherents such as toner remaining on the intermediate transfer belt 155 are removed by a belt cleaning device.

[0017] The sheet S onto which the toner image has been transferred is delivered to a fixing device 160. The fixing device 160, which is a fixing means in this embodiment, has a fixing roller as a rotating body that transports the sheet S, a pressure roller that holds the sheet S together with the fixing roller, and a heat source (e.g., a halogen lamp) that heats the toner image on the sheet. The fixing device 160 applies heat and pressure to the toner image while transporting the sheet S to melt the toner, and then the toner is fixed to the sheet S.

[0018] In parallel with such an image forming process, sheets S are fed one by one from the cassette feeding section 10 or the manual feeding section 20 toward the image forming section 15. The cassette feeding section 10 has two upper and lower feeding cassettes 100, 100 that store sheets S inside the apparatus main body 1A, and a feeding unit 101 that feeds the sheets S from each feeding cassette 100. The feeding unit 101 has a pickup roller 102, a feeding roller 103, and a separation roller 104. In the case of feeding the sheets S from the feeding cassette 100 during image formation, when the control section 30 issues a print signal, the pickup roller 102 feeds the sheets S stored in the feeding cassette 100. Thereafter, the sheets S are sent out to the conveying path in a single sheet state by the roller pair of the feeding roller 103 and the separation roller 104, and are conveyed to the registration roller pair 12 via the conveying roller pair 11.

[0019] The manual feed section 20 has a manual tray 200 on which a user stacks sheets S outside the apparatus main body 1A, and a feed unit 201 that feeds the sheets S from the manual tray 200. The feed unit 201 is an example of a feed section that feeds the sheets S placed on the manual tray 200, and has a pickup roller 202, a feed roller 203, and a separation roller 204. When feeding the sheets S from the manual tray 200 during image formation, when the control unit 30 issues a print signal, the pickup roller 202 feeds the sheets S stacked on the manual tray 200. Thereafter, the sheets S are sent out to a conveyance path in a single sheet state by the roller pair of the feed roller 203 and the separation roller 204, and are conveyed to the registration roller pair 12 via the conveyance roller pair 205 and the conveyance roller pair 11. The feeding units 101 and 201 may employ other mechanisms such as a separation pad system or an air feeding system.

[0020] Thus, the conveying roller pair 205 is an example of a conveying section, and is disposed adjacent to the feeding unit 201, and conveys the sheet S fed by the feeding unit 201 toward the image forming unit 15 via the conveying roller pair 11 and the registration roller pair 12. In this embodiment, among the conveying paths of the sheet S from the manual feed tray 200 to the image forming unit 15, a planar area disposed between the feeding unit 201 and the conveying roller pair 205 is defined as a first conveying path P1. That is, in the first conveying path P1, a nip line between the feeding roller 203 and the separation roller 204 and a nip line between the conveying roller pair 205 coincide with each other.

[0021] In this embodiment, the first conveying path P1 is arranged so as to be horizontal. Here, "arranged so as to be horizontal" refers not only to the strict horizontality of the design, but also to a range of ±3 degrees from the strict horizontality in consideration of errors such as tolerances. The range of ±3 degrees is, for example, the maximum range in which the first conveying path P1 can oscillate while maintaining its planarity in the space between the guide member 210a of the upper frame 210 and the guide member 211a of the lower frame 211, which will be described later. In addition, "arranged so as to be horizontal" includes not only the case where the nip line of the feed roller 203 and the separation roller 204 and the nip line of the conveying roller pair 205 are completely aligned, but also the case where they are inclined to each other at an angle of up to 3 degrees. Furthermore, "arranged so as to be horizontal" also includes the case where the nip line of the feed roller 203 and the separation roller 204 and the nip line of the conveying roller pair 205 are parallel to each other but not aligned, while being located in the space between the guide member 210a and the guide member 211a.

[0022] In this embodiment, the first transport path P1 is arranged so as to be horizontal, but this is not limited to this. That is, the first transport path P1 only needs to be flat, and the inclination angle may be changed appropriately depending on the inclination angles of the upstream and downstream transport paths, the installation space, etc. For example, the inclination angle may be set to a range of ±10 degrees with respect to the horizontal in accordance with the inclination angles of the upstream and downstream transport paths.

[0023] A second conveying path P2 is provided downstream of the conveying roller pair 205 in the sheet conveying direction, so as to be continuous with the first conveying path P1. In this embodiment, the second conveying path P2 conveys the sheet S to the image forming unit 15, and is provided with the sheet conveying direction being the upward direction in at least a part of the region. Thus, in this embodiment, the image forming apparatus 1 has a vertical path conveying configuration. That is, the nip line of the registration roller pair 12 is provided so that the smaller angle formed with the horizontal line when viewed from the axial direction of the registration roller pair 12 is 45 degrees or more. In this embodiment, the conveying path from the cassette feeding unit 10 and the conveying path from the manual feeding unit 20 are arranged so as to merge at the conveying roller pair 11.

[0024] When the sheet S abuts against the nip portion of the registration roller pair 12 while the registration roller pair 12 is stopped, the conveying roller pair 11 pushes the sheet S into this nip portion, causing the sheet S to bend between the conveying roller pair 11 and the registration roller pair 12. As a result, the orientation of the sheet S is corrected so that the leading ends of the sheet S are aligned, and in this state, the registration roller pair 12 rotates, and the sheet S is conveyed to the image forming unit 15 after skew correction. The registration roller pair 12 is a registration roller pair, and is located upstream of the image forming unit 15 in the conveying path of the sheet S, and conveys the sheet S to the image forming unit 15 in accordance with the timing for forming an image on the sheet S.

[0025] The sheet S on which an image has been formed by passing through the secondary transfer unit 161 and the fixing device 160 is conveyed to discharge rollers 171 by a post-fixing conveying unit 170. The discharge rollers 171 discharge the sheet S on which the image has been formed, and stack it on a discharge tray 180 provided on the upper part of the apparatus main body 1A. Note that this embodiment employs a so-called internal discharge type configuration in which a discharge space (above the discharge tray 180) for stacking the sheet S is provided between the apparatus main body 1A and the image reading device 300 in the vertical direction.

[0026] The discharge roller 171 is an example of a reversing section that reverses and conveys the sheet S, on which an image has been transferred to a first surface in the image forming section 15, so that the image can be transferred to a second surface opposite to the first surface. That is, in the case of double-sided printing, the discharge roller 171 conveys the sheet S, on which an image has been formed on the first surface, and when the rear end of the sheet S passes the branching section 172, reverses the conveying direction and switches back the sheet S. As a result, the sheet S is delivered to the double-sided conveying section 190, and is conveyed by the re-conveying roller pairs 193 and 194 of the double-sided conveying section 190 through the double-sided path 192 toward the registration roller pair 12. The double-sided path 192 is an example of a double-sided conveying path in which the sheet S reversed by the discharge roller 171 is conveyed again from the re-conveying roller pair 194 toward the registration roller pair 12. The re-conveying roller pair 194 is located upstream of the registration roller pair 12 in the conveying path, and is an example of an upstream roller pair that conveys the sheet S to the registration roller pair 12. Then, after the skew is corrected again by the pair of registration rollers 12, the sheet S, which has an image formed on its second side by passing through the secondary transfer section 161 and the fixing device 160, is discharged by the discharge rollers 171 and loaded onto the discharge tray 180.

[0027] In the above description, the image forming section 15 may be an electrophotographic unit of a direct transfer type, or an image forming unit of an inkjet type or an offset printing type.

[0028] The control unit 30 has a CPU, RAM, and ROM, and controls each unit in the image forming apparatus 2. The CPU outputs an output signal to each electric component to operate the electric component at the desired timing and with the required amount of control based on the detection signals input from each sensor and the information stored in the ROM. Therefore, it is the CPU that actually controls the electric components. The ROM and RAM store information data required for controlling each unit, and the CPU reads the information data stored in the ROM and writes it to the RAM.

[0029] [Manual feed section] 2 is a schematic cross-sectional view of the manual feed section 20 according to this embodiment. In the manual feed section 20, the sheet S fed by the pickup roller 202 from the manual feed tray 200 is held by a nip portion 203N formed by a feed roller 203 and a separation roller 204. At this time, the direction in which the sheet is fed by the nip portion 203N is defined as a first conveying direction D1. Downstream of the nip portion 203N in the sheet conveying direction, a first conveying path P1 formed by a guide member 210a of the upper frame 210 and a guide member 211a of the lower frame 211 is provided toward the conveying roller pair 205.

[0030] The conveying roller pair 205 has a driving roller 205a that rotates when driven, and a driven roller 205b that rotates following the driving roller 205a. When the sheet S enters the conveying roller pair 205, the sheet S is sandwiched and conveyed by a nip portion 205N formed by the conveying roller pair 205. At this time, the direction in which the sheet S is sent out by the nip portion 205N is defined as a second conveying direction D2.

[0031] Between the nip portion 203N and the nip portion 205N, a sensor unit 220 is supported by the lower frame 211 by a fixing portion (not shown). The sensor unit 220 is provided to detect the sheet characteristics in a state where it is exposed to a part of the guide member 211a of the lower frame 211. On the opposite side of the sensor unit 220 across the first conveying path P1, a pressing unit 230 for pressing the sheet S toward the sensor unit 220 is provided. In this manner, the sensor unit 220, which is a media sensor, is disposed on the horizontal first conveying path P1 between the feed roller 203 and the pair of conveying rollers 205 in the conveying path fed from the manual feed tray 200. The sensor unit 220 is also disposed upstream of the pair of conveying rollers 11 where the conveying path from the cassette feeding unit 10 and the conveying path from the manual feed unit 20 join.

[0032] [Sensor unit] FIG. 3 is a cross-sectional view showing a state cut along the line AA shown in FIG. 2, and shows the sensor unit 220 and the pressing unit 230 viewed from the downstream side in the conveying direction. The sensor unit 220 has a line sensor 221, a receiver 222 of an ultrasonic sensor 228, and a chip (driver) for performing image processing and ultrasonic analysis. The sensor unit 220 here is an example of a media sensor for measuring the characteristics of the sheet S and determining the type of the sheet S. The sensor unit 220 uses light or ultrasonic waves that can be used to detect or estimate, for example, the basis weight correlated with the thickness of the sheet S, the surface properties of the sheet S, and even the moisture content. The control unit 30 detects (determines) the type of the sheet S based on the detection result (detection signal) of the sensor unit 220. A transmitter 223 of the ultrasonic sensor 228 is provided on the opposite side of the sensor unit 220 across the first conveying path P1. The transmitter 223 is attached to a guide member 210a of the upper frame 210.

[0033] The line sensor 221 is disposed facing the first transport path P1. The line sensor 221 is an example of an optical sensor that detects the surface property of the sheet S, and is formed of, for example, a CIS. In this embodiment, the line sensor 221 has a light emitting unit 224 that emits light to irradiate the sheet S transported on the first transport path P1, and a detection unit 225 that receives reflected light of the light irradiated on the sheet S. Furthermore, the detection unit 225 has a glass plate 226 that is an example of a transparent member that transmits the reflected light, and a light receiving element 227 that receives the reflected light that has transmitted through the glass plate 226.

[0034] Light emitted from a light emitting unit 224, which is a light source, passes through a glass plate 226 and is collected on the sheet S, and the reflected light passes through the glass plate 226 and is received by a light receiving element 227 via a lens (not shown), so that the surface property of the sheet S can be detected. In addition, a signal transmitted from a transmitter 223 of an ultrasonic sensor 228 is received by a receiver 222 via the sheet S, so that the thickness (basis weight) of the sheet S can be detected. The accuracy of both the line sensor 221 and the ultrasonic sensor 228 is improved by stably positioning the sheet S at an intended position relative to the sensor, particularly at a position in the vertical direction. For this reason, a pressing unit 230, which is an example of a pressing unit, presses the sheet S conveyed in the first conveying path P1 so as to abut against the glass plate 226.

[0035] [Press unit] The pressing unit 230 is provided to stabilize the position of the sheet S. The pressing unit 230 has a pressing holder 235 that can swing relative to the sheet S, a slider 233 that is slidably held by the pressing holder 235 and can move toward and away from the sheet S, pressing rollers 231 and 232, and an urging member 234 (see FIG. 4). The slider 233 rotatably holds the pressing rollers 231 and 232. The pressing rollers 231 and 232 can press the sheet S. The urging member 234 is made of, for example, a compression coil spring, and is provided between the pressing holder 235 and the slider 233, and presses the slider 233 toward the sheet S relative to the pressing holder 235.

[0036] 4(a) and (b), the pressing roller 231 has a roller-shaped pressing portion 231a that presses the sheet S and a shaft portion 231b that rotatably supports the pressing portion 231a. Both ends of the shaft portion 231b are rotatably supported by holes 233a of the slider 233, so that the pressing roller 231 is rotatably supported by the pressing holder 235 via the two sliders 233. The pressing roller 232 has a similar configuration, so a detailed description will be omitted.

[0037] The slider 233 has a claw-shaped stopper portion 233b. The stopper portion 233b restricts movement of the slider 233 in a direction D3 in which the slider 233 abuts against the sheet S by engaging with an engagement portion (not shown) of the pressing holder 235. The slider 233 has a slide portion 233c. The slide portion 233c is held by the pressing holder 235 so as to be movable in the direction D3 in which the slider 233 abuts against the sheet S. The slider 233 has an engagement portion 233d. The engagement portion 233d holds, between the pressing holder 235 and the biasing member 234 that presses the slider 233 in the direction D3 in which the slider 233 abuts against the sheet S.

[0038] The pressing holder 235 is rotatably held by a holder rotation shaft 236 fixedly supported by a support portion (not shown) of the upper frame 210. As shown in Fig. 3, a biasing member 237 made of, for example, a tension coil spring is provided between the pressing holder 235 and the upper surface portion 210b of the upper frame 210. The biasing member 237 has one end supported by the upper surface portion 210b of the upper frame 210 and the other end supported by the pressing holder 235, and is provided so as to pull the pressing holder 235 upward D4.

[0039] The pressing holder 235 is biased upward D4 by the biasing member 237, while the upper surface of the pressing holder 235 abuts against the cam member 238, thereby restricting the upward movement. The cam member 238 is fixed to a cam shaft 239 that is rotatably supported by the support part 210c of the upper frame 210. A cam drive gear 240 is fixed to an end of the cam shaft 239, and the cam drive gear 240 rotates when the drive motor M is driven based on a signal from the control part 30, thereby rotating the cam member 238 and controlling the position of the pressing holder 235.

[0040] 5 is a plan view showing the positional relationship between the sensor unit 220, the feed roller 203 and the separation roller 204 on the upstream side in the conveying direction, and the conveying roller pair 205 on the downstream side in the conveying direction. The conveying roller pair 205 has a plurality of roller portions 207, 208, and 209, which are an example of a plurality of conveying rollers arranged on the same axis. In the sheet width direction W perpendicular to the first conveying direction D1 and the second conveying direction D2, the roller portion 207 provided at one end of the plurality of roller portions 207, 208, and 209 has one end surface 207a. In addition, in the sheet width direction W, the roller portion 209 provided at the other end of the plurality of roller portions 207, 208, and 209 has the other end surface 209a. In this embodiment, the sensor unit 220 is disposed in an area W1 between an extension surface of the end surface 207a of the roller portion 207 and an extension surface of the end surface 209a of the roller portion 209 in the sheet width direction W when viewed from the second conveying direction D2 in the first conveying path P1. That is, the sensor unit 220 is disposed in the maximum area W1 in which the conveying roller pair 205 holds the sheet. As a result, the sensor unit 220 is disposed in the area W1 where a pulling force acts on the sheet S pulled out by the conveying roller pair 205, so that the sensor unit 220 can stably detect the conveyed sheet S.

[0041] [Sheet detection operation] Next, the operation of detecting the sheet characteristics by the sensor unit 220 will be described. As shown in FIG. 2, before the sheet S is fed, the pressing unit 230 waits at a position where the pressing rollers 231 and 232 are retracted from the first conveying path P1. The control unit 30 drives a feeding motor (not shown) to rotate the feeding roller 203, and drives a conveying motor (not shown) to rotate the conveying roller pair 205. When the sheet S is conveyed and the conveying sensor 241 detects that the sheet S has reached the conveying roller pair 205, the control unit 30 stops conveying the sheet S. When the sheet S stops, the control unit 30 drives the driving motor M to rotate the cam member 238 and lower the pressing unit 230. Then, the control unit 30 presses the sheet S located above the sensor unit 220 by the pressing rollers 231 and 232 so as to abut against the sensor unit 220. That is, when the leading edge of the sheet S transported in the first transport path P1 has passed through the glass plate 226 and the trailing edge of the sheet S has not yet passed through the glass plate 226, the pressing unit 230 presses the sheet S to abut against the glass plate 226. This makes it possible to prevent the sheet S from passing between the pressing rollers 231, 232 and the glass plate 226 and applying excessive force to the sheet S when the pressing unit 230 is abutting against the glass plate 226 before the leading edge of the sheet S passes through the glass plate 226.

[0042] The operation of the pressing unit 230 after it has descended will be described with reference to Figs. 6 and 7. Fig. 6 is a schematic cross-sectional view showing a state in which the pressing unit 230 is located at a lowered pressing position in the manual feed section 20 according to this embodiment. Fig. 7 is a cross-sectional view showing a state cut along line BB shown in Fig. 6. As shown in Figs. 6 and 7, when the sheet S stops, the pressing holder 235 descends and the pressing rollers 231 and 232 press the sheet S toward the sensor unit 220. At this time, the pressing rollers 231 and 232 come into contact with the sensor unit 220 and are pressed upward D4 relative to the pressing holder 235, and the urging member 234 is compressed.

[0043] 7, the pressing roller 232 has a width in the width direction equal to or greater than the detection area of ​​the opposing line sensor 221, and is configured to regulate the position of the sheet S that it abuts over the entire detection surface of the line sensor 221. The pressing roller 231 is disposed on the opposite side of the pressing roller 232 across the transmitter 223 of the ultrasonic sensor 228, in the vicinity of the transmitter 223. This allows the position of the sheet S between the transmitter 223 and receiver 222 of the ultrasonic sensor 228 to be stably regulated.

[0044] When the pressing unit 230 is located at the pressing position and stops descending, the sheet S starts to be conveyed again, and the sensor unit 220 starts to detect the sheet S being conveyed. When the conveyance is resumed, the driving of the feed roller 203 is stopped and the sheet S is conveyed only by the pair of conveying rollers 205. That is, when the leading edge of the sheet S conveyed on the first conveying path P1 reaches the pair of conveying rollers 205, the feeding unit 201 stops driving and rotates idly. This makes it possible to prevent the sheet S from being pushed by the feed roller 203 on the upstream side of the pair of conveying rollers 205 and causing the sheet S to become loose. After the conveyance is resumed, when the sheet S is conveyed by a predetermined distance required for detecting the sheet characteristics, the control unit 30 again rotates the cam member 238 to raise the pressing holder 235, and moves the pressing unit 230 to the standby position shown in FIG. 2, thereby completing the detection operation.

[0045] In this way, with the configuration of this embodiment, since there is no influence of bending of the sheet S, the pressing force of the pressing unit 230 on the sheet S can be small to stabilize the posture of the sheet S. This makes it possible to avoid problems such as a decrease in the conveying force, rotation of the sheet S, and damage to the sheet S due to an increase in resistance caused by the pressing of the sheet S. Furthermore, when a special sheet such as coated paper is fed using the manual feed tray 200, the type of sheet can be automatically identified and applied to subsequent processing.

[0046] As described above, according to the image forming apparatus 1 of the present embodiment, the first transport path P1 is disposed in a plane between the feeding unit 201 and the pair of transport rollers 205, and the sensor unit 220 reads the reflected light of the light irradiated on the sheet S transported on the first transport path P1. That is, the sensor unit 220, which is a media sensor, is disposed on the first transport path P1 between the feed roller 203 and the pair of transport rollers 205 on the transport path for feeding the sheet S from the manual feed tray 200. This makes it possible to suppress changes in the posture of the sheet S during transport, thereby improving the detection accuracy of the sheet characteristics using the sensor unit 220.

[0047] Moreover, in this embodiment, the first transport path P1 is installed horizontally. Therefore, the angle change from the sheet S fed from the manual feed tray 200 is reduced, and the change in the posture of the sheet S during transport can be more effectively suppressed. Furthermore, in this embodiment, the second transport path P2 is a vertical path. Therefore, the first transport path P1 and the second transport path P2 form a route at a substantially right angle, but the sensor unit 220 is disposed in a horizontal area avoiding the bends and curves of the route, and therefore the detection accuracy of the sheet characteristics, etc. can be improved.

[0048] In this embodiment, the pressing unit 230 presses the sheet S being conveyed in the first conveying path P1 so as to abut against the glass plate 226 of the line sensor 221. Therefore, the line sensor 221 can improve the detection accuracy since the sheet S is stably positioned at the intended position (glass surface).

[0049] In the above embodiment, a media sensor is used as the sensor unit 220, but the present invention is not limited to this, and for example, a double feed detection sensor may be used. In this case, the detection accuracy of the sensor can be improved. In the above embodiment, the pressing unit 230 is provided, but if the position of the sheet S relative to the sensor unit 220 is stable, the pressing unit 230 does not need to be provided. [Explanation of symbols]

[0050] 1...image forming apparatus, 15...image forming section, 30...control section, 200...manual feed tray, 201...feeding unit (feeding section), 205...pair of transport rollers (transport section), 207...roller section (transport roller), 207a...one end surface, 208...roller section (transport roller), 209...roller section (transport roller), 209a...other end surface, 220...sensor unit (media sensor), 221...line sensor (optical sensor), 224...light emitting section, 225...detection section, 226...glass plate (transparent member), 227...light receiving element, 228...ultrasonic sensor, 230...pressing unit (pressing section), D1...first transport direction (sheet transport direction), D2...second transport direction (sheet transport direction), P1...first transport path, P2...second transport path

Claims

1. An image forming unit that forms an image on a sheet, A manual feed tray for placing manually inserted sheets, A feeding unit that feeds the sheet placed on the manual feed tray, A transport unit is arranged in conjunction with the feeding unit and transports the sheet fed by the feeding unit toward the image forming unit, A planar first transport path is arranged between the feeding unit and the transport unit, A detection unit for reading reflected light from light irradiated onto a sheet being transported along the first transport path, comprising: a light-transmitting member that transmits the reflected light; and a light-receiving element that receives the reflected light that has passed through the light-transmitting member. A pressing unit that presses the sheet being transported in the first transport path so as to come into contact with the permeable member, Equipped with, An image forming apparatus characterized by the following features.

2. The pressing unit presses the sheet against the permeable member when the leading edge of the sheet being transported in the first transport path has passed through the permeable member, and the rear end of the sheet has not passed through the permeable member. The detection unit reads the reflected light of the light irradiated onto the sheet while the pressing unit is pressing the sheet against the transparent member. The image forming apparatus according to feature 1.

3. The pressing portion is rotatable with respect to the sheet width direction perpendicular to the sheet conveying direction when viewed from the sheet conveying direction in the first conveying path, and has a pressing roller that presses against the transparent member, With respect to the sheet width direction, the length of the pressing roller is greater than or equal to the length of the detection area of ​​the detection unit. The image forming apparatus according to claim 1 or 2.

4. The pressing portion is movable between a pressing position that presses the permeable member and a separated position that is separated from the permeable member, The system further includes a displacement unit that displaces the pressing portion between the pressing position and the separated position. The image forming apparatus according to claim 1 or 2.

5. The displacement unit is A biasing means for biasing the pressing portion toward the separated position, A drive source and drive mechanism for moving the pressing portion to the pressing position against the biasing force of the biasing means, Having, The image forming apparatus according to feature 4.

6. When the leading edge of the sheet being transported along the first transport path reaches the transport unit, the feeding unit stops driving and rotates freely. The image forming apparatus according to claim 1 or 2.

7. When the leading edge of the sheet being transported along the first transport path reaches the transport unit, the transport unit and the feeding unit stop driving, the pressing unit presses the sheet so as to come into contact with the permeable member, and the transport unit restarts driving to transport the sheet. The detection unit reads the reflected light of the light irradiated onto the sheet while the pressing unit is pressing the sheet against the transparent member and the transport unit has resumed driving and is transporting the sheet. The image forming apparatus according to claim 1 or 2.

8. The conveying unit has a plurality of conveying rollers arranged coaxially, The detection unit is positioned between the one end face of a transport roller provided at one end of the plurality of transport rollers and the other end face of a transport roller provided at the other end of the plurality of transport rollers, in the sheet width direction perpendicular to the sheet transport direction when viewed from the sheet transport direction in the first transport path. The image forming apparatus according to claim 1 or 2.

9. The first transport path is arranged to be horizontal. The image forming apparatus according to claim 1 or 2.

10. The feeding unit comprises a feeding roller and a separating member that abuts against the feeding roller, The transport unit has a pair of transport rollers, The nip line between the feeding roller and the separating member of the feeding section and the nip line between the pair of conveying rollers of the conveying section coincide and overlap with the first conveying path. The image forming apparatus according to claim 1 or 2.

11. The nip line between the feeding roller and the separating member of the feeding section and the nip line between the transport roller pair of the transport section are arranged to be horizontal. The image forming apparatus according to feature 10.

12. The conveying unit is provided with a second conveying path that is continuous with the first conveying path downstream in the sheet conveying direction and conveys the sheet to the image forming unit. The image forming apparatus according to claim 1 or 2.

13. The second transport path has the sheet transport direction upward in at least a portion of its area. The image forming apparatus according to feature 12.

14. The media sensor includes a light-emitting unit that emits light to irradiate the sheet being transported in the first transport path, and a detection unit that receives reflected light from the light irradiated onto the sheet, and comprises an optical sensor for detecting the surface properties of the sheet and an ultrasonic sensor for detecting the basis weight of the sheet. The image forming apparatus according to claim 1 or 2.

15. The system includes a control unit that detects the type of sheet based on the detection result of the media sensor. The image forming apparatus according to feature 14.

Images