Paper sheet conveyance device, and image forming apparatus

Abstract

To make it possible to reset a paper sheet characteristic, after abnormality such as jam or the like is generated.SOLUTION: An image forming apparatus comprises: a medium sensor 280 for detecting a paper sheet characteristic of a paper sheet conveyed by a conveyance roller C155; UI 330 for inputting the paper sheet characteristic, a first conveyance sensor 160 for detecting abnormality concerning the paper sheet conveyed by the conveyance roller C155; and a control part 300 for switching between a medium sensor mode of setting the paper sheet characteristic based on a detection result of the medium sensor 280, and a user setting mode of setting the paper sheet characteristic based on information input from the UI 330. The control part 300 switches from the medium sensor mode to the user setting mode, when it is detected by the first conveyance sensor 160 that abnormality is generated when conveying the paper sheet in the medium sensor mode.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a paper transport device equipped with a media sensor that detects paper characteristics such as the surface texture and thickness of the paper being transported, and to an image forming apparatus such as a printer, copier, or multifunction machine equipped with such a paper transport device. [Background technology]

[0002] An electrophotographic image forming apparatus feeds paper one sheet at a time from a paper feed section such as a paper feed cassette or manual feed tray, and forms an image on the fed paper. Each type of paper has different paper characteristics such as surface properties and thickness. The image forming apparatus performs image formation control (paper feed / transport / development / transfer / fixing control, etc.) according to the paper characteristics. In addition to being manually set by the user, the paper characteristics can also be automatically set using a media sensor installed on the paper transport path. An image forming apparatus equipped with a media sensor can use the media sensor to determine the paper characteristics of the transported paper, and determine the operating conditions for image formation control based on the paper characteristics (Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2022-62122 Summary of the Invention [Problem to be solved by the invention]

[0004] In paper feed control, paper is transported by multiple rollers arranged on a transport path. Therefore, the load acting on the rollers changes depending on, for example, the characteristics of the paper (surface properties, basis weight, etc.). The image forming device performs feed control by determining the motor speed and current value, which are the operating conditions for image formation control, depending on the characteristics of the paper.

[0005] In Patent Document 1, the paper characteristics are determined by a media sensor on the transport path, and the operating conditions for image formation control, including feeding control, are determined based on the determined paper characteristics. However, if the paper characteristics determined by the media sensor do not match the paper characteristics of the paper actually transported, there is a risk of an abnormality, such as a jam, occurring.

[0006] SUMMARY OF THE PRESENT DISCLOSURE In view of the above problems, a primary object of the present invention is to enable the resetting of paper characteristics after the occurrence of an abnormality such as a jam. [Means for solving the problem]

[0007] The paper transport device of the present invention comprises a feeding means for transporting paper, a detection means for detecting paper characteristics of the paper transported by the feeding means, an input means for inputting the paper characteristics, an abnormality detection means for detecting abnormalities related to the paper transported by the feeding means, and a control means for switching between a first mode in which first paper characteristics are set based on the detection results of the detection means and a second mode in which second paper characteristics are set based on information input to the input means, wherein in the first mode, the control means transports the paper under operating conditions based on the first paper characteristics, and in the second mode, the control means transports the paper under operating conditions based on the second paper characteristics, and when the abnormality detection means detects the occurrence of an abnormality while transporting the paper in the first mode, the control means switches from the first mode to the second mode. The image forming apparatus of the present invention comprises a feeding means for transporting paper, an image forming means for forming an image on the paper transported by the feeding means, a detection means for detecting paper characteristics of the paper transported by the feeding means, an input means for inputting the paper characteristics, an abnormality detection means for detecting abnormalities related to the paper transported by the feeding means, and a control means for switching between a first mode in which first paper characteristics are set based on the detection results of the detection means and a second mode in which second paper characteristics are set based on information input to the input means, wherein in the first mode, the control means transports the paper under operating conditions based on the first paper characteristics, and in the second mode, the control means transports the paper under operating conditions based on the second paper characteristics, and when the abnormality detection means detects the occurrence of an abnormality while transporting the paper in the first mode, the control means switches from the first mode to the second mode. Effect of the Invention

[0008] According to the present invention, it is possible to reset the paper characteristics after the occurrence of an abnormality such as a jam. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram illustrating the configuration of an image forming apparatus. [Diagram 2] FIG. [Diagram 3] FIG. 4 is a configuration diagram of a media sensor. [Figure 4] FIG. [Diagram 5] FIG. [Figure 6] Top view of the manual feed tray. [Figure 7] FIG. 4 is an explanatory diagram of a jam detection method. [Figure 8] 6 is a flowchart showing a process for setting paper characteristics. [Figure 9] 11 is a flowchart showing a setting process. [Figure 10] FIG. [Figure 11] 4 is a flowchart showing a printing process. [Figure 12] FIG. 4 is a diagram illustrating the relationship between paper characteristics and the paper conveying speed. [Figure 13] 4 is a flowchart showing a feeding operation. [Figure 14] FIG. [Figure 15] 6 is a flowchart showing a process for manually setting paper characteristics. [Figure 16] FIG. 13 is a view showing an example of a paper characteristics determination method setting screen. [Figure 17] FIG. 13 is another configuration diagram of the media sensor. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

[0011] 1 is a configuration diagram of an image forming apparatus according to the present embodiment. The image forming apparatus 100 includes a scanner unit 101 and a UI (User Interface) 330 at its upper portion. Such an image forming apparatus 100 can be realized by, for example, a copier, a multifunction machine, or an MFP (Multi Function Peripheral).

[0012] The scanner unit 101 reads an image of an original document, for example, when copying or sending a facsimile. The scanner unit 101 transmits image data indicating the read original image to the image forming apparatus 100. When copying, the image forming apparatus 100 prints an image on paper based on the image data acquired from the scanner unit 101.

[0013] The UI 330 is an operation unit having an input interface and an output interface. The UI 330 includes various key buttons such as a numeric keypad 331, a start key 332, and a stop key 333, and a touch panel as an input interface. The UI 330 includes a display 334 and a speaker as an output interface. The user can input various instructions and settings to the image forming apparatus 100 through the UI 330. The UI 330 can display on the display 334 a screen for inputting instructions and settings to the image forming apparatus 100 and a screen showing the status of the image forming apparatus 100.

[0014] The image forming apparatus 100 includes a laser scanner unit 110, a process unit 120, a primary transfer section 121, a transfer belt 130, a secondary transfer section 140, a fixing section 170, paper feed cassettes 150 and 220 for storing paper, and a feed mechanism for feeding paper. The image forming apparatus 100 transfers an image (toner image) formed by the process unit 120 and the laser scanner unit 110 to paper fed by the feed mechanism by the primary transfer section 121, the transfer belt 130, and the secondary transfer section 140. The image forming apparatus 100 fixes the toner image to the paper by the fixing section 170. The paper on which the image has been printed in this manner is discharged to the paper discharge port A200, the paper discharge port B196, or the paper discharge port C199.

[0015] The process unit 120 includes a photosensitive drum, a developing unit, a charging roller, a photosensitive drum cleaner, etc. In the process unit 120, the surface of the photosensitive drum is charged by the charging roller, and then a latent image is formed on the photosensitive drum by a laser beam irradiated from the laser scanner unit 110. The laser scanner unit 110 irradiates the photosensitive drum with a laser beam modulated based on image data acquired from the scanner unit 101 or an external personal computer, etc. As a result, a latent image based on the image data is formed on the photosensitive drum.

[0016] The latent image formed on the photosensitive drum is developed by toner in a developing device. By developing, an image (toner image) is formed on the photosensitive drum. The process unit 120 of this embodiment has four photosensitive drums to form a color image. Toner images of different colors are formed on the four photosensitive drums. In this embodiment, toner images of yellow (Y), magenta (M), cyan (C), and black (K) are formed on the four photosensitive drums. When a monochrome image is formed, only a black toner image is formed.

[0017] A primary transfer voltage is applied to the toner images on the photosensitive drums in the primary transfer section 121, and the toner images are transferred to the transfer belt 130. The four photosensitive drums sequentially transfer the toner images onto the transfer belt 130. The toner images of each color are superimposed on the transfer belt 130. The toner images of each color transferred to the transfer belt 130 are transported to the secondary transfer section 140 by the rotation of the transfer belt 130. The photosensitive drums are used for the next image forming operation after the toner remaining on the photosensitive drums after transfer is removed by a photosensitive drum cleaner.

[0018] When the process unit 120 starts an image forming operation, a sheet is fed from the sheet feed cassettes 150 and 220 and the manual feed tray 210, which are sheet feed units. The fed sheet is conveyed to the secondary transfer unit 140 via a conveyance path 40. The sheet stored in the sheet feed cassette 150 is fed to the conveyance path 41 by a pickup roller 151. The conveyance paths 40 and 41 from the sheet feed cassette 150 to the secondary transfer unit 140 are provided with conveyance rollers A153, B154, C155, and pre-registration conveyance rollers 161 for conveying the fed sheet. The sheet placed on the manual feed tray 210 is fed to the conveyance path 42 by the pickup roller 211. The conveyance paths 40 and 42 from the manual feed tray 210 to the secondary transfer unit 140 are provided with conveyance rollers C155 and pre-registration conveyance rollers 161 for conveying the fed sheet. The pre-registration transport rollers 161 transport the paper to the secondary transfer unit 140 in accordance with the timing at which the toner image carried by the transfer belt 130 is transported to the secondary transfer unit 140 .

[0019] A pickup sensor 152 is provided between the pickup roller 151 and the transport roller A 153. A manually-fed paper presence / absence detection sensor 214 is provided at the base end of the manual feed tray 210. A first transport sensor 160 and a media sensor 280 are provided on the transport path 40 between the transport roller C 155 and the pre-register transport roller 161.

[0020] The secondary transfer unit 140 transfers the toner images of each color to the paper all at once by applying a secondary transfer voltage to the paper and the toner images. The paper onto which the toner images have been transferred by the secondary transfer unit 140 is transported to the fixing unit 170. A transport belt 190 is provided between the secondary transfer unit 140 and the fixing unit 170, and the paper is transported to the fixing unit 170 by the transport belt 190.

[0021] The fixing unit 170 heats and presses the paper with the transferred toner image at a predetermined fixing temperature while pinching and transporting the paper, thereby melting and fixing the toner image to the paper. This fixes the image to the paper. The paper with the fixed image is transported to one of the transport paths C234, B231, and A230. For this purpose, flappers A172 and B182 are provided downstream of the fixing unit 170 in the transport direction of the paper. Transport roller D162 and second transport sensor 171 are provided between the fixing unit 170 and flappers A172 and B182.

[0022] The conveying path C234 is provided with a paper discharge roller 180. The paper discharge roller 180 discharges the paper to the paper discharge port A200. The conveying path B231 is connected to a conveying path D181. The conveying path D181 branches into a paper discharge path A193 to the paper discharge port B196 and a paper discharge path B184 to the paper discharge port C199. A flapper 183 is provided at the branch point between the paper discharge path A193 and the paper discharge path B184. The conveying path B231 and the conveying path D181 are provided with a conveying roller E232, a paper discharge roller A241, and a paper discharge roller B242.

[0023] The discharge path A193 is provided with discharge rollers C243 and a first discharge sensor 195. The paper transported to the discharge path A193 by the flapper 183 is discharged to the discharge outlet B196 by the discharge rollers C243. The discharge path B184 is provided with discharge rollers D244, E245, F246, and a second discharge sensor 197. The paper transported to the discharge path B184 by the flapper 183 is discharged to the discharge outlet C199 by the discharge rollers D244, E245, and F246.

[0024] The conveying path A230 is provided with a reversing roller 163, a double-sided conveying roller A164, a double-sided conveying roller B165, a double-sided conveying roller C166, a double-sided conveying roller D179, and a double-sided conveying roller E168. A double-sided reversing conveying path 233 is connected to the conveying path A230.

[0025] For example, when discharging a sheet of paper to the paper outlet A200 with the print side facing down during single-sided printing, the reversing roller 163 reverses its rotation direction just before the rear end of the sheet of paper guided by the flapper A172 to the transport path A230 passes through the reversing roller 163. This transports the sheet toward the paper discharge roller 180. Also, when discharging a sheet of paper after printing on its first side has been completed during double-sided printing, the reversing roller 163 transports the sheet of paper without reversing its rotation direction. The sheet of paper is transported to the double-sided reversing transport path 233 via the reversing roller 163, double-sided transport roller A164, double-sided transport roller B165, double-sided transport roller C166, double-sided transport roller D179, and double-sided transport roller E168.

[0026] A duplex conveying path 235 for conveying paper to the conveying path 41 is connected to the duplex reversing conveying path 233. After being conveyed to the duplex reversing conveying path 233, the conveying direction of the paper is reversed and the paper is conveyed to the duplex conveying path 235. For this purpose, a flapper 178 is provided at a branching point of the duplex conveying path 235. The duplex conveying path 235 is provided with duplex conveying rollers F169, G175, H176, and I177. Note that the duplex reversing conveying path 233 and the duplex conveying path 235 are also provided with a plurality of sensors for detecting paper.

[0027] When the paper is conveyed to the double-sided reversing conveyance path 233 during double-sided printing, the conveyance is temporarily stopped when the rear end passes the double-sided conveyance roller D179. The double-sided conveyance roller E168 reverses the rotation direction and conveys the paper in the opposite direction. The flapper 178 guides the paper to the double-sided conveyance path 235. The paper guided to the double-sided conveyance path 235 is conveyed to the conveyance path 41 by the double-sided conveyance roller F169, the double-sided conveyance roller G175, the double-sided conveyance roller H176, and the double-sided conveyance roller I177. Through this series of operations, the print side of the paper is reversed, and the second side opposite to the first side becomes the print side. The paper conveyed to the conveyance path 41 is conveyed to the secondary transfer unit 140, and an image is printed on the second side in the same manner as on the first side.

[0028] 2 is an explanatory diagram of a control unit that controls the operation of image forming apparatus 100 having such a configuration. Control unit 300 is built into image forming apparatus 100. Control unit 300 is an information processing device including a central processing unit (CPU) 301, a read only memory (ROM) 302, a random access memory (RAM) 303, and a non-volatile memory 304. In addition to these, control unit 300 includes a network interface (I / F) 314, a fax interface (I / F) 315, and an image processing unit 316. To control unit 300, an image forming unit 320, the above-mentioned UI 330, and an I / O 307 are connected.

[0029] The I / O 307 is connected to various sensors and various motors serving as drive sources provided in the image forming apparatus 100. The various motors are, for example, a pre-fixing conveyance motor 145, a fixing motor 173, a post-fixing conveyance motor 146, a manual feed conveyance motor 147, a first paper discharge conveyance motor 148, and a second paper discharge conveyance motor 149. The various sensors are, for example, the above-mentioned first conveyance sensor 160, second conveyance sensor 171, pickup sensor 152, first paper discharge sensor 195, second paper discharge sensor 197, manual feed paper presence / absence detection sensor 214, and media sensor 280. The I / O 307 is connected to other various sensors, such as a fixing motor stable rotation detection sensor 174, a first paper length detection sensor 218, a second paper length detection sensor 219, and a manual feed paper width volume sensor 217.

[0030] CPU 301 controls the operation of image forming apparatus 100 by executing a computer program stored in ROM 302. RAM 303 provides a working area when CPU 301 executes processing. CPU 301 acquires detection results from various sensors via I / O 307, and controls the operation of various motors via I / O 307 based on the acquired detection results. In this way, CPU 301 controls paper feeding and fixing unit 170.

[0031] CPU 301 of control unit 300 starts a print operation when, for example, an instruction to start a print operation (hereinafter, referred to as a "job") is input from UI 330. CPU 301 can also accept jobs via network I / F 314 and fax I / F 315. Network I / F 314 accepts jobs from an external device such as a personal computer via a network. Fax I / F 315 accepts jobs via facsimile communication.

[0032] The CPU 301 performs image processing on the image to be printed in accordance with the job using the image processing unit 316. The image processing unit 316 performs image processing such as image development and rotation. The CPU 301 performs print processing of the image on the paper by controlling the operation of each component in the image forming apparatus 100 described above using the image forming unit 320. The image forming unit 320 can control the application of high voltage to the process unit 120, the transfer belt 130, the secondary transfer unit 140, etc. in FIG. 1, drive control, and control the laser scanner unit 110. The image forming unit 320 can also control the heater of the fixing unit 170 in FIG. 1.

[0033] The CPU 301 that has acquired the job interprets the acquired job and starts a printing operation. After starting the printing operation, the CPU 301 performs a paper feed operation. When feeding paper from paper feed cassette 150, CPU 301 drives pre-fixing conveyance motor 145 via I / O 307 to rotate pickup roller 151. As pickup roller 151 rotates, paper sheets in paper feed cassette 150 are fed one by one. At this time, CPU 301 determines whether the paper feeding operation was performed normally based on the detection result of pickup sensor 152. When feeding paper from manual feed tray 210, with paper placed on manual feed tray 210, an instruction to transport paper on manual feed tray 210 is input by UI 330. CPU 301 determines whether paper is placed on the manual feed tray based on the detection result of manual feed paper presence / absence detection sensor 214. CPU 301 drives manual feed motor 147 via I / O 307 to rotate pickup roller 211. As pickup roller 211 rotates, the paper on manual feed tray 210 is fed one sheet at a time.

[0034] The fed paper has its paper characteristics, such as surface property and thickness, detected by the media sensor 280. The CPU 301 detects the paper characteristics based on the detection result of the media sensor 280, and sets the operating conditions for image formation control, such as the fixing temperature, transfer voltage, and paper conveyance speed, according to the detected paper characteristics, to perform image formation.

[0035] In parallel with the paper feeding operation, the CPU 301 starts the image forming operation by the process unit 120 so as to be in time for the paper to reach the secondary transfer unit 140. The image forming operation by the process unit 120 is as described above.

[0036] CPU 301 detects the position of the paper conveyed by conveyance rollers A 153, B 154, and C 155 based on the detection result of first conveyance sensor 160. CPU 301 controls the conveyance of the paper based on the timing at which first conveyance sensor 160 detects the leading edge of the paper so that the leading edge of the paper and the leading edge of the toner image on transfer belt 130 coincide with each other at secondary transfer unit 140. For example, if first conveyance sensor 160 detects the paper earlier than the toner image, CPU 301 stops the paper at the position of pre-registration conveyance rollers 161 for a predetermined time and then resumes conveyance.

[0037] CPU 301 transfers the toner image onto the paper by applying a secondary transfer voltage to the paper and toner image that have reached secondary transfer unit 140. The paper onto which the toner image has been transferred is transported to fixing unit 170 via transport belt 190. CPU 301 drives a fixing roller of fixing unit 170 using fixing motor 173 to heat and fix the toner image onto the paper. The paper onto which the image has been fixed is then transported further downstream in the paper transport direction.

[0038] When the second conveyance sensor 171 detects the leading edge of the paper after the image is fixed, the CPU 301 judges whether the paper is to be conveyed to the conveyance path A230, the conveyance path B231, or the conveyance path C234 according to the job contents specified in advance from the UI 330. The CPU 301 controls the flapper A172 and the flapper B182 according to the judgment result to switch the guide destination of the paper. Specifically, in the case of double-sided printing and when the paper is discharged to the paper discharge port A200 with the print side facing down, the CPU 301 switches the flapper A to guide the paper to the conveyance path A230. When single-sided printing or double-sided printing is completed on both sides, the CPU 301 guides the paper to either the conveyance path B231 or the conveyance path C234. When the paper is discharged to the paper discharge port B196 or the paper discharge port C199, the CPU 301 switches the flapper B182 to guide the paper to the conveyance path B231. When discharging the paper to the paper discharge port A200, the CPU 301 switches between the flapper A172 and the flapper B182 to guide the paper to the transport path C234.

[0039] The CPU 301 drives the conveying rollers D162 and E232 by the post-fixing conveying motor 146 to convey the paper conveyed to the conveying path B231 to the conveying path D181. The CPU 301 drives the paper discharge rollers A241 and B242 by the first paper discharge conveying motor 148 to convey the paper in the direction of the paper discharge outlet B196 and the paper discharge outlet C199.

[0040] When discharging the paper to paper discharge port B196, CPU 301 switches flapper 183 to guide the paper to paper discharge path A193, and drives paper discharge rollers C243 with first paper discharge conveyance motor 148 to discharge the paper to paper discharge port B196. When discharging the paper to paper discharge port C199, CPU 301 switches flapper 183 to guide the paper to paper discharge path B184, and drives paper discharge rollers D244, E245, and F246 with second paper discharge conveyance motor 149 to discharge the paper to paper discharge port C199.

[0041] When the paper is discharged to the paper outlet A200 with the print side facing down in single-sided printing, the CPU 301 switches the flapper A172 and controls the rotation of the reversing roller 163 to transport the paper as described above. When the printing on the first side is completed in double-sided printing, the CPU 301 switches the flapper A172 to guide the paper to the double-sided reversing transport path 233. To transport the paper to the double-sided reversing transport path 233, the CPU 301 controls the rotation of the reversing roller 163, the double-sided transport roller A164, the double-sided transport roller B165, the double-sided transport roller C166, the double-sided transport roller D179, and the double-sided transport roller E168. After that, the CPU 301 reverses the rotation of the double-sided transport roller E168 and controls the rotation of the double-sided transport roller G175, the double-sided transport roller H176, and the double-sided transport roller I177 as described above to transport the paper to the transport path 41.

[0042] The image specified in the job is printed on the specified number of sheets of paper. When all the sheets of paper with the printed image have been ejected, the printing operation for the job is completed. When the entire job is completed, the CPU 301 displays the completion of the job on the UI 330.

[0043] (Media Sensor) 3 is a configuration diagram of the media sensor 280. The media sensor 280 of this embodiment is used to detect the surface properties and thickness of the paper as paper characteristics. The media sensor 280 includes a media sensor unit 54, an external LED (Light Emitting Diode) 55b as an external light source, a light collecting guide 57d, and an arithmetic and control unit 58. The media sensor unit 54 includes an LED 55a as a light source, phototransistors 56a and 56b as light receiving units, and slits 57a, 57b, and 57c therein. The arithmetic and control unit 58 controls the operation of the media sensor 280 and performs arithmetic operations according to the output values ​​of the phototransistors 56a and 56b.

[0044] When detecting the surface property of the paper S, the media sensor 280 operates as follows. Light emitted from the LED 55a is irradiated via the slit 57a onto the surface of the paper S transported along the transport path 40. The phototransistor 56a receives the reflected light that is reflected by the surface of the paper S and concentrated via the slit 57b. The phototransistor 56b receives the reflected light that is reflected by the surface of the paper S and concentrated via the slit 57c.

[0045] The surface quality of the paper S is judged as follows. The phototransistor 56a receives light diffusely reflected by the paper S from the light source LED 55a and outputs a diffuse reflection output value corresponding to the amount of diffusely reflected light received. The phototransistor 56b receives light specularly reflected by the paper S from the light source LED 55a and outputs a specular reflection output value corresponding to the amount of specularly reflected light received. The surface roughness x of the paper S is expressed by the following equation based on the output values ​​of the phototransistors 56a and 56b. Surface roughness x = specular reflection output value / diffuse reflection output value ... (Equation 1)

[0046] Equation 1 utilizes the characteristic that the amount of specularly reflected light increases when the surface of the paper S is "smooth" and "fine". The calculation control unit 58 performs calculation processing of Equation 1 and transmits a numerical value (surface property x) that quantifies the surface property of the paper S to the CPU 301. The CPU 301 uses the acquired surface property x and a threshold value for determining the surface property to determine the surface property. If the surface property x is larger than the threshold value, the surface property is determined to be "smooth" and "fine". If the surface property x is smaller than the threshold value, the surface property is determined to be "rough" and "coarse". Although one threshold value is used in this embodiment, the CPU 301 may use multiple threshold values ​​to determine the surface property in more detail.

[0047] The thickness of the paper S is determined as follows: The conveyance path 40 is provided with an opening for irradiating the rear surface of the paper S with light from the external LED 55b. Light emitted from the external LED 55b as a light source passes through the light collecting guide 57d and is irradiated onto the back surface of the paper S. At least a portion of this light passes through the paper S. The transmitted light that passes through the paper S is received by the phototransistor 56a via the slit 57b. The phototransistor 56a outputs a specular transmission output value according to the amount of transmitted light received. The calculation control unit 58 detects the transmittance of the paper S from the specular transmission output value. The calculation control unit 58 sends the detected transmittance to the CPU 301. The thicker the paper S, the lower the transmittance value, and the thinner the paper S, the higher the transmittance value. The thickness of the paper S is determined by this transmittance characteristic.

[0048] The CPU 301 determines the thickness of the sheet S using the obtained transmittance and a threshold value for determining thickness. In this embodiment, the thickness of the sheet S is classified into three types: "thick," "normal," and "thin." To this end, the CPU 301 uses a thickness / thin discrimination threshold value A and a thickness / thin discrimination threshold value B as threshold values ​​for determining the thickness. Here, the thickness / thin discrimination threshold value A is a value greater than the thickness / thin discrimination threshold value B.

[0049] The CPU 301 judges the thickness of the sheet S to be "thin" if the transmittance is higher than the thickness / thin discrimination threshold A, and judges the thickness of the sheet S to be "thick" if the transmittance is lower than the thickness / thin discrimination threshold B. The CPU 301 judges the thickness of the sheet S to be "normal" if the transmittance is lower than the thickness / thin discrimination threshold A and higher than the thickness / thin discrimination threshold B. Note that, although two thickness / thin discrimination thresholds are used in this embodiment, the CPU 301 may use one thickness / thin discrimination threshold, or may use three or more thickness / thin discrimination thresholds to more finely classify the thickness of the sheet S.

[0050] Although the media sensor 280 of this embodiment has been described taking an optical sensor as an example, the sensor is not limited to this as long as it is capable of detecting paper characteristics such as the surface property and thickness of the paper S. For example, the media sensor 280 may be another type of sensor such as an ultrasonic sensor that uses reflection or transmission of ultrasonic waves. The surface property and thickness of the paper S may be manually set by the user using the UI 330 without using the media sensor 280. Furthermore, the paper characteristics detected by the media sensor 280 may be at least one of the surface property and the thickness, or a characteristic other than the surface property and the thickness.

[0051] (Setting paper characteristics using UI330) 4 is an example diagram of a setting screen for setting the surface properties of paper S using the UI 330. A setting screen 600 is displayed on the display 334 of the UI 330. The setting screen 600 displays selection buttons 601, 602, and 603 for selecting the surface property, and a confirmation button 604 for confirming the selection result. The selection button 601 is selected when the surface property of the paper is fine (smooth). The selection button 602 is selected when the surface property of the paper is standard. The selection button 603 is selected when the surface property of the paper is coarse (rough).

[0052] The user selects the surface property of the paper to be fed from among selection buttons 601, 602, and 603 through the input interface, and presses decision button 604. By pressing decision button 604, the selection is notified from UI 330 to CPU 301. CPU 301 sets the surface property of the paper to be fed based on the notified selection.

[0053] 5 is an example diagram of a setting screen for setting the thickness of paper S using the UI 330. A setting screen 700 is displayed on the display 334 of the UI 330. The setting screen 700 displays selection buttons 701, 702, and 703 for selecting a thickness, and a confirmation button 704 for confirming the selection result. The selection button 701 is selected when the paper is thin paper, which has a thin thickness. The selection button 702 is selected when the paper is plain paper, which has a medium thickness. The selection button 703 is selected when the paper is thick cardboard, which has a thick thickness.

[0054] The user selects the thickness of the paper to be fed from selection buttons 701, 702, and 703 using the input interface, and presses decision button 704. By pressing decision button 704, the selection is notified from UI 330 to CPU 301. CPU 301 sets the thickness of the paper to be fed based on the notified selection.

[0055] (Manual feed tray) 6 is a top view of the manual feed tray 210. When a stack of multiple sheets of paper is placed on the manual feed tray 210, the pickup roller 211 separates and transports each sheet from the stack. At this time, the manual feed paper presence / absence detection sensor 214 outputs a detection result that paper is present. The stack of sheets is narrowed by the regulation guides 212 and 213 provided on the upper surface of the manual feed tray 210. The regulation guides 212 and 213 prevent the sheets from skewing when they are transported by the pickup roller 211. The regulation guides 212 and 213 are slidable in the directions of the arrows 215 and 216, and can change their positions according to the length of the sheets in the width direction (sheet width) that intersects with the transport direction. Therefore, the sheets are prevented from skewing regardless of the sheet width.

[0056] The restriction guides 212 and 213 are connected to a manual paper width volume sensor 217 via a link (not shown). The manual paper width volume sensor 217 transmits a detection value according to the position of the restriction guide 212 to the CPU 301. The CPU 301 detects the paper width based on the detection value acquired from the manual paper width volume sensor 217.

[0057] First paper length detection sensor 218 and second paper length detection sensor 219 are configured as flag-type sensors. First paper length detection sensor 218 and second paper length detection sensor 219 are provided at different positions in the paper transport direction and are used to detect the length in the transport direction (paper length) of paper placed on manual feed tray 210. First paper length detection sensor 218 and second paper length detection sensor 219 detect the presence or absence of paper and transmit the detection results to CPU 301. CPU 301 detects the paper length based on the detection results obtained from first paper length detection sensor 218 and second paper length detection sensor 219.

[0058] For example, when A4 size paper, as shown by the solid line in Fig. 6, is placed, neither the first paper length detection sensor 218 nor the second paper length detection sensor 219 detects the paper. When B4 size paper, as shown by the dashed line, is placed, the first paper length detection sensor 218 detects the paper, but the second paper length detection sensor 219 does not detect the paper. In this way, the paper length is determined based on the detection results of the first paper length detection sensor 218 and the second paper length detection sensor 219. CPU 301 can detect the size of the paper placed on manual feed tray 210 based on the detection results of first paper length detection sensor 218 and second paper length detection sensor 219 and the detection value of manual feed paper width volume sensor 217.

[0059] (Jam detection) 7 is an explanatory diagram of a jam detection method for detecting a jam of paper during transport. Here, detection of a jam such as a paper jam by the first transport sensor 160 will be described. In this case, the first transport sensor 160 functions as an abnormality detection sensor that detects abnormality in the transport of paper. Note that jam detection can also be performed by other sensors provided on the transport path in a similar manner.

[0060] 7 shows the detection result (ON / OFF state) of the first conveyance sensor 160 and the rotation speed of the conveyance roller C 155. When a sheet is conveyed to the detection position of the first conveyance sensor 160, the first conveyance sensor 160 detects the sheet and the detection result becomes the ON state. When the first conveyance sensor 160 does not detect a sheet, the detection result becomes the OFF state.

[0061] Time T_d0 is a theoretical value of the time required for a sheet to be transported from the transport roller C155 to the detection position of the first transport sensor 160. Time T_d0 is calculated from the distance from the transport roller C155 to the first transport sensor 160 and the rotation speed v of the transport roller C155. Time T_dm is an allowable delay time from when the first transport sensor 160 detects a sheet to when the detection result transitions to an ON state. Time T_dm is determined by the transport interval of the sheet, etc., and is calculated from the allowable delay distance and the rotation speed v of the transport roller C155.

[0062] When the CPU 301 starts rotating the conveyance roller C155, it starts monitoring the detection result of the first conveyance sensor 160 and starts a timer for measuring time T_dj. Time T_dj is the time obtained by adding time T_dm to time T_d0. Time T_dj is a reference time for detecting the occurrence of a jam, and if the first conveyance sensor 160 does not detect the paper before the time T_dj has elapsed, it is determined that a jam has occurred.

[0063] During normal operation, the detection result of the first transport sensor 160 transitions to the ON state before the timer that measures the time T_dj times out. When the detection result of the first transport sensor 160 transitions to the ON state, the CPU 301 determines that the transport of the paper is normal, cancels the timer, and continues the transport of the paper. When a jam occurs, the timer that measures the time T_dj times out before the detection result of the first transport sensor 160 transitions to the ON state. The CPU 301 determines that a paper transport jam has occurred because the detection result of the first transport sensor 160 does not transition to the ON state within a predetermined time (within the time T_dj).

[0064] (Setting paper characteristics) 8 is a flowchart showing a process for setting paper characteristics, which is a process for setting the paper characteristics such as the surface texture and thickness of the paper placed on manual feed tray 210.

[0065] CPU 301 determines whether or not paper is placed on manual feed tray 210 based on the detection result of manual feed paper presence / absence detection sensor 214 (S601). CPU 301 waits until paper is placed on manual feed tray 210 (S601: N). If paper is placed on manual feed tray 210 (S601: Y), CPU 301 sets the paper characteristics (S602) and ends the process. Note that if paper is stored in paper feed cassette 150, 220, CPU 301 performs the process of S602 without performing the process of S601.

[0066] FIG. 9 is a flowchart showing the setting process of S602. When the CPU 301 starts the processing of S602, it determines whether the paper characteristic determination mode has already been set (S301). The paper characteristic determination mode determines whether the paper characteristics are automatically set using the media sensor 280 or manually set by the user using the UI 330. When automatically set using the media sensor 280, the paper characteristic determination mode is set to the "media sensor mode." When manually set using the UI 330, the paper characteristic determination mode is set to the "user setting mode." Whether the paper characteristic determination mode has already been set is determined, for example, by whether information indicating the paper characteristic determination mode is stored in the RAM 303.

[0067] If the paper characteristics determination mode is not set (S301: N), the CPU 301 displays a selection screen for the paper characteristics determination mode on the display 334 of the UI 330 (S302). The CPU 301 waits until the selection of the paper characteristics determination mode on the selection screen is completed (S303: N). If the paper characteristics determination mode is selected (S303: Y), the CPU 301 saves the selection in the RAM 303 (S304).

[0068] 10 is a diagram showing an example of a selection screen for the paper characteristics determination mode. A selection button 801 for setting the media sensor mode, a selection button 802 for setting the user setting mode, and a decision button 803 are displayed on the selection screen 800. The user selects either the selection button 801 or the selection button 802 through the input interface of the UI 330 and presses the decision button 803. This causes the selection to be transmitted from the UI 330 to the CPU 301. The CPU 301 sets the paper characteristics determination mode by saving the selection acquired from the UI 330 in the RAM 303. When the selection button 801 is selected, the desensor mode is saved as the paper characteristic determination mode in the RAM 303. When the selection button 802 is selected, the user setting mode is saved as the paper characteristic determination mode in the RAM 303.

[0069] If the paper characteristics determination mode has already been set (S301: Y), or if the paper characteristics determination mode has been set in the processes of S302 to S304, the CPU 301 determines whether the paper characteristics determination mode is the media sensor mode (S305). The CPU 301 makes this determination by referring to the paper characteristics determination mode stored in the RAM 303. If the paper characteristics determination mode is the media sensor mode (S305: Y), the CPU 301 ends this process.

[0070] If the paper characteristic determination mode is the user setting mode (S305: N), the CPU 301 displays the setting screen 700 of FIG. 5 for setting the paper thickness on the display 334 of the UI 330 (S306). The CPU 301 waits until the selection of the paper thickness on the setting screen 700 is completed (S307: N). If the paper thickness has been selected (S307: Y), the CPU 301 saves the selected paper thickness in the RAM 303 (S308). The details of the selection of the paper thickness are as described above.

[0071] After setting the paper thickness, CPU 301 displays setting screen 600 of FIG. 4 for setting the paper surface properties on display 334 of UI 330 (S309). CPU 301 waits until selection of the paper surface properties on setting screen 600 is complete (S310: N). If the paper surface properties have been selected (S310: Y), CPU 301 saves the selected paper surface properties in RAM 303 (S311). Details of the selection of the paper surface properties are as described above.

[0072] This completes the process of S602. If the paper characteristic determination mode is the user setting mode, the paper characteristics (surface property, thickness) are set at this point. If the paper characteristic determination mode is the media sensor mode, the paper characteristics are not set at this point. In the media sensor mode, the paper characteristics are set by the media sensor 280 detecting the paper. Note that the order of the processes of S306 to S308 and S309 to S311 may be reversed. In this embodiment, an example has been described in which surface property and thickness are set as paper characteristics in the user setting mode, but the paper characteristic that is set may be at least one of surface property and thickness, or a characteristic other than surface property and thickness.

[0073] (Job Processing) FIG. 11 is a flowchart showing the print process when a job instructing a print operation is acquired.

[0074] CPU 301 waits until a job is acquired (S1001: N). When a job is acquired (S1001: Y), CPU 301 sets a cumulative counter to 0 (S1002). The cumulative counter is a variable for counting the cumulative number of jams that have occurred, including recoveries, within the same job, and is stored in RAM 303. CPU 301 starts a paper feed operation and prints an image specified by the job on paper (S1003).

[0075] FIG. 12 is an explanatory diagram of the relationship between paper characteristics and paper conveying speed. FIG. 12 shows the conveying speed corresponding to the surface property and thickness of the paper. The image forming apparatus 100 of this embodiment can set the conveying speed to two speeds, for example, 340.0 [mm / sec] and 137 [mm / sec]. Note that these conveying speeds are only examples, and other speeds may be used. Furthermore, the conveying speed may be set to three or more speeds.

[0076] Paper with fine surface properties tends to stick to each other. This can easily cause a double-feed jam, where multiple sheets overlap during transport. For this reason, paper with fine surface properties is transported at a slow transport speed of 137.0 [mm / sec] to prevent double-feed jams and ensure reliable transport. Paper with coarse surface properties may get caught in the transport path. For this reason, paper with coarse surface properties is also transported at a slow transport speed of 137.0 [mm / sec]. Paper with standard surface properties that is thick paper may jam due to high resistance at the bend in the transport path. For this reason, paper with standard surface properties that is thick paper is transported at a slow transport speed of 137.0 [mm / sec]. Paper with standard surface properties that is thin paper or normal paper is transported at a fast transport speed of 340.0 [mm / sec].

[0077] FIG. 13 is a flow chart showing the feeding operation in S1003. The CPU 301 judges whether the paper characteristics determination mode is the media sensor mode or not by referring to the RAM 303 (S550). If the paper characteristics determination mode is the user setting mode (S550: N), the CPU 301 starts paper feeding at a conveying speed corresponding to the paper characteristics that have already been set (S553).

[0078] If the paper characteristics determination mode is the media sensor mode (S550: Y), CPU 301 determines whether the paper characteristics have been determined (S551). If the paper characteristics have been determined (S551: N), CPU 301 starts paper feeding at a transport speed corresponding to the determined paper characteristics (S553). If the paper characteristics have not been determined (S552: Y), CPU 301 starts paper feeding at a slow transport speed (S552).

[0079] After performing the paper feed operation as described above, the CPU 301 judges whether or not a jam has occurred (S1004). The occurrence of a jam is detected as described above. A jam occurs when, for example, a paper sheet whose characteristics cannot be determined by the media sensor 280 is conveyed, or when the media sensor 280 malfunctions and erroneously determines the characteristics of the paper sheet, and the operating conditions such as the conveying speed are not set appropriately. If a jam has not occurred (S1004: N), the CPU 301 judges whether or not the paper characteristics determination mode is the media sensor mode (S1005). If the paper characteristics determination mode is the media sensor mode (S1005: Y), the CPU 301 reads the paper sheet being conveyed by the media sensor 280 and obtains the reading result (S1006). The CPU 301 detects the paper characteristics based on the reading result obtained from the media sensor 280, and stores the detected characteristics in the RAM 303. The CPU 301 newly determines the operating conditions of the image formation control, including the feeding control, based on the detected paper characteristics.

[0080] If the paper characteristics determination mode is the user setting mode (S1005: N), or after the operating conditions are determined, the CPU 301 resumes paper feeding and determines whether a jam has occurred (S1007) in the same manner as in the process of S1004. If the mode is the media sensor mode, the CPU 301 resumes paper feeding under the operating conditions newly determined in the process of S1006.

[0081] If no jam has occurred (S1007: N), CPU 301 determines whether there is a sheet to be fed next (S1008). If there is no sheet to be fed next (S1008: Y), CPU 301 ends the print process according to the job. If there is a sheet to be fed next (S1008: N), CPU 301 returns to the process of S1003 and performs the feeding operation of the next sheet.

[0082] If a jam occurs in the process of S1004 or S1007 (S1004: Y or S1007: Y), the CPU 301 performs jam stop processing (S1009). In the jam stop processing, the CPU 301 ejects the paper downstream of the paper that caused the jam, and stops the transport of the paper that caused the jam and the paper upstream of the paper that caused the jam.

[0083] After the jam stop processing, the CPU 301 displays a guide screen on the display 334 of the UI 330 to guide the user through the jam processing procedure (S1010). Fig. 14 is an example of a guide screen. The guide screen 500 guides the user to remove the remaining paper remaining inside the image forming apparatus 100. The guide screen 500 displays the position of the sensor that detected the jam and the position of the remaining paper. The remaining paper is the paper that caused the jam and the paper that is upstream of the paper whose transport was stopped by the jam stop processing.

[0084] CPU 301 waits until all the remaining sheets are removed (S1011: N). CPU 301 detects that the remaining sheets have been removed, for example, when second transport sensor 171, first transport sensor 160, and pickup sensor 152 no longer detect the sheets. Alternatively, CPU 301 may display a button on guide screen 500 for reporting that the removal of the remaining sheets has been completed, and detect that the remaining sheets have been removed when this button is pressed via the input interface of UI 330. When all the remaining sheets are removed (S1011: Y), CPU 301 refers to RAM 303 to determine whether the paper characteristic determination mode is the media sensor mode (S1012).

[0085] If the paper characteristics determination mode is the user setting mode (S1012: N), the CPU 301 returns to the process of S1003 and resumes the paper feeding operation. If the paper characteristics determination mode is the media sensor mode (S1012: Y), the CPU 301 increments the cumulative counter stored in the RAM 303 by 1 (S1013). The CPU 301 compares the cumulative counter with the reset threshold (S1014).

[0086] The reset threshold is stored in advance in RAM 303 by the user before execution of a job, and is a threshold for determining whether or not the user needs to manually set the paper characteristics depending on the number of times jams have occurred. If the paper characteristics are not set appropriately, the paper transport speed will not be set appropriately and the frequency of jams will increase. For this reason, the reset threshold is provided since it may be necessary to reset the paper characteristics depending on the number of times jams have occurred within the same job. When the number of times jams have occurred exceeds the reset threshold, the paper characteristics are reset. In other words, the paper characteristics are reset by detecting a jam a predetermined number of times or more. In this embodiment, the reset threshold is set to "2", but this value is merely an example and other values ​​may be used.

[0087] If the cumulative counter is less than the reset threshold (S1014: N), CPU 301 returns to the process of S1003 and resumes the paper feed operation. If the cumulative counter is equal to or greater than the reset threshold (S1014: Y), CPU 301 performs manual paper characteristic setting processing (S1015). The manual paper characteristic setting processing switches the paper characteristic determination mode from the media sensor mode to the user setting mode. When the manual paper characteristic setting processing ends, CPU 301 returns to the process of S1003 and resumes the paper feed operation.

[0088] FIG. 15 is a flowchart showing the manual setting process of paper characteristics in S1015. When the CPU 301 starts the manual setting process of the paper characteristics, it displays a paper characteristics determination method setting screen on the display 334 of the UI 330 (S101). The CPU 301 waits until an instruction to manually set the paper characteristics is input through the paper characteristics determination method setting screen (S102: N). FIG. 16 is an example of the paper characteristics determination method setting screen. A set button 901 for manually setting the paper characteristics and a confirm button 902 for confirming the setting result are displayed on the paper characteristics determination method setting screen 900. The user selects the set button 901 and presses the confirm button 902. By pressing the confirm button 902, the setting contents (an instruction to manually set the paper characteristics) are input from the UI 330 to the CPU 301.

[0089] The CPU 301 acquires the setting contents (S102: Y) and stores the acquired setting contents in the RAM 303 (S103). As a result, the paper characteristics determination mode is set to the user setting mode.

[0090] The CPU 301 displays the setting screen 700 of FIG. 5 for setting the paper thickness on the display 334 of the UI 330 (S104). The CPU 301 waits until the selection of the paper thickness on the setting screen 700 is completed (S105: N). If the paper thickness has been selected (S105: Y), the CPU 301 saves the selected paper thickness in the RAM 303 (S106). The details of the selection of the paper thickness are as described above.

[0091] After setting the paper thickness, CPU 301 displays setting screen 600 of FIG. 4 for setting the paper surface properties on display 334 of UI 330 (S107). CPU 301 waits until selection of the paper surface properties on setting screen 600 is complete (S108: N). If the paper surface properties have been selected (S108: Y), CPU 301 stores the selected paper surface properties in RAM 303 (S109). Details of the selection of the paper surface properties are as described above.

[0092] This completes the manual setting process of the paper characteristics in S1015. CPU 301 determines the operating conditions for image formation control, including feeding control, based on the re-set paper characteristics, and resumes the paper feeding operation. Note that the order of the processes in S104 to S106 and S107 to S109 may be reversed.

[0093] In the image forming apparatus 100 of the present embodiment described above, when a jam occurs, the user manually resets the paper characteristics. In other words, when an abnormality such as a jam occurs under operating conditions based on automatically set paper characteristics, the image forming apparatus 100 manually resets the paper characteristics and updates the operating conditions. After the abnormality is resolved, the image forming apparatus 100 resumes the printing operation under the updated operating conditions.

[0094] Therefore, even if the paper characteristics automatically set based on the detection result of the media sensor 280 are not appropriate and an abnormality occurs, the user can reset the appropriate paper characteristics to perform normal printing. In other words, in this embodiment, the paper characteristics are automatically set using the media sensor 280 instead of manually setting them, so that user convenience is not impaired. If the automatically set paper characteristics are not appropriate, the frequency of occurrence of abnormalities can be reduced by switching the paper characteristics determination mode from the media sensor mode to the user setting mode after the abnormality occurs and having the user manually reset the paper characteristics.

[0095] Although the configuration of the image forming apparatus 100 has been described above, the present invention is applicable to any apparatus having a paper transport device that transports paper. The paper transport device has a media sensor 280 and a UI 330, and is equipped with the paper feed mechanism described in the image forming apparatus 100. The paper transport device sets paper characteristics based on the detection result of the media sensor 280. The paper transport device determines the operating conditions (transport speed, transport interval, etc.) for paper transport control based on the set paper characteristics, and transports paper under the determined operating conditions. When an abnormality such as a jam occurs, the paper transport device prompts the user to reset the paper characteristics using the UI 330. By resuming paper transport under operating conditions based on the reset paper characteristics, the occurrence of abnormalities is reduced.

[0096] Such a paper transport device can also be used in an image reading device that reads an image printed on a paper while transporting the paper. The image reading device includes an automatic document feeder (ADF). By incorporating the paper transport device in the ADF, it is possible to achieve the same effect as the present invention.

[0097] In addition, in this embodiment, detection of a paper jam has been described as an example of detecting an abnormality, but even if another abnormality, such as an abnormality in the fixing temperature of the fixing unit 170, is detected, the operating conditions can be reset by a similar process to reduce the occurrence of the abnormality. In this case, the abnormality is detected based on the detection result of a temperature detection sensor that detects the fixing temperature, for example. In other words, the present invention is applicable to any abnormality in a component that operates under operating conditions set by paper characteristics.

[0098] (Another example of a media sensor) FIG. 17 is another configuration diagram of the media sensor 280. The control unit 300 can detect the characteristics of the paper sheet using this media sensor 280. FIG. 17 is a diagram seen from the conveying direction of the paper sheet S (the conveying roller C155 side). This media sensor 280 has an ultrasonic sensor 281 and an optical sensor 282, and detects the paper characteristics (for example, the surface property and basis weight) of the paper sheet S. The ultrasonic sensor 281 is composed of an ultrasonic transmitter 2811 and an ultrasonic receiver 2812. The optical sensor 282 is configured as a CIS (Contact Image Sensor) having, for example, a light source 1501 and a line sensor 1502. For example, an LED is used as the light source 1501.

[0099] When the optical sensor 282 detects the brightness value, it is necessary to hold the paper at the optical focal position. When detecting the paper S by ultrasonic waves, it is necessary to reduce the effect of fluttering of the paper S being transported. In order to stabilize the posture of the paper S, the media sensor facing roller 260 and the paper pressing roller 261 are provided between the transport roller C155 and the pre-registration transport roller 161. The media sensor facing roller 260 is provided opposite the optical sensor 282 and is configured to press the paper S against the optical sensor 282. This reduces the variation in the position and posture of the paper S when the media sensor 280 measures the surface of the paper S. Therefore, the media sensor 280 can stably measure the surface properties and basis weight of the paper S.

[0100] 5, the ultrasonic transmitter 2811 is disposed on the upper block 401 side, and the ultrasonic receiver 2812 is disposed on the lower block 402 side, with the transport path 40 of the paper S sandwiched between them. The ultrasonic sensor 281 is configured to transmit and receive ultrasonic waves via the paper S, thereby outputting information (output voltage) for determining the basis weight of the paper S. The basis weight here is the mass per unit area of ​​the paper S, and is expressed in [gsm].

[0101] Both the ultrasonic transmitter 2811 and the ultrasonic receiver 2812 are composed of a piezoelectric element (also called a piezo element) which is an element for mutual conversion between mechanical displacement and an electric signal, and an electrode terminal. When a pulse voltage of a predetermined frequency is inputted from the electrode terminal of the ultrasonic transmitter 2811, the piezoelectric element of the ultrasonic transmitter 2811 oscillates to generate an ultrasonic wave. The generated ultrasonic wave propagates through the air. When the ultrasonic wave reaches the paper S, the paper S vibrates due to the ultrasonic wave. In this manner, the ultrasonic wave generated by the ultrasonic transmitter 2811 propagates to the ultrasonic receiver 2812 via the paper S. The piezoelectric element of the ultrasonic receiver 2812 receives the ultrasonic wave propagated via the paper S, and generates an output voltage according to the amplitude of the received ultrasonic wave at the electrode terminal of the ultrasonic receiver 2812. The ratio of the output voltage when there is no paper S between the ultrasonic transmitter 2811 and the ultrasonic receiver 2812 and the output voltage when there is paper S is the transmittance. Since the ultrasonic transmittance changes depending on the basis weight (area density) of the paper S, the basis weight of the paper S can be estimated using the ultrasonic transmission coefficient-paper basis weight conversion formula.

Claims

1. A feeding means for conveying paper; a detection means for detecting paper characteristics of the paper conveyed by the feeding means; an input means for inputting paper characteristics; an abnormality detection means for detecting an abnormality regarding the paper conveyed by the feeding means; a control means for switching between a first mode in which a first paper characteristic is set based on a detection result of the detection means and a second mode in which a second paper characteristic is set based on information input to the input means, the control means, in the first mode, causes the sheet to be transported under operating conditions based on the first sheet characteristics, and in the second mode, causes the sheet to be transported under operating conditions based on the second sheet characteristics; The control means switches the mode from the first mode to the second mode when the abnormality detection means detects an occurrence of an abnormality while the paper is being transported in the first mode. Paper transport device.

2. The control means switches from the first mode to the second mode when the abnormality detection means detects the abnormality a predetermined number of times or more.

2. The paper transport device according to claim 1.

3. and when the abnormality detection means detects the abnormality, if the number of detected abnormalities is not equal to or greater than the predetermined number of times, the control means resumes conveying of the paper under the operating conditions based on the paper characteristics set in the first mode.

3. The paper transport device according to claim 2.

4. When the control means switches to the second mode, the control means determines new operating conditions based on the paper characteristics set in the second mode, and causes the feeding means to resume transport of the paper under the new operating conditions.

2. The paper transport device according to claim 1.

5. When the abnormality detection means detects the abnormality a predetermined number of times or more and switches to the second mode, the control means determines new operating conditions based on the paper characteristics set in the second mode, and causes the feeding means to resume transport of the paper under the new operating conditions.

5. The paper transport device according to claim 4.

6. The control means determines a transport speed of the paper by the feeding means based on the paper characteristics.

2. The paper transport device according to claim 1.

7. The abnormality detection means detects a jam of the paper conveyed by the feeding means.

2. The paper transport device according to claim 1.

8. The detection means detects at least one of the surface property and the thickness of the paper as the paper characteristic.

2. The paper transport device according to claim 1.

9. At least one of the surface property and the thickness of the paper is inputted as the paper characteristic from the input means.

2. The paper transport device according to claim 1.

10. A feeding means for conveying paper; an image forming means for forming an image on the paper conveyed by the feeding means; a detection means for detecting paper characteristics of the paper conveyed by the feeding means; an input means for inputting paper characteristics; an abnormality detection means for detecting an abnormality regarding the paper conveyed by the feeding means; a control means for switching between a first mode in which a first paper characteristic is set based on a detection result of the detection means and a second mode in which a second paper characteristic is set based on information input to the input means, the control means, in the first mode, causes the sheet to be transported under operating conditions based on the first sheet characteristics, and in the second mode, causes the sheet to be transported under operating conditions based on the second sheet characteristics; The control means switches the mode from the first mode to the second mode when the abnormality detection means detects an occurrence of an abnormality while the paper is being transported in the first mode. Image forming device.

11. the control means, when switching to the second mode, determines new operating conditions based on the paper characteristics set in the second mode, and resumes control of the feeding means and the image forming means under the new operating conditions. The image forming apparatus according to claim 10.

Images