JP2017129667A - Image formation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image formation device that can easily detect a material and thickness of a sheet.SOLUTION: An image formation device 100 forms an image on a sheet R. The image formation device 100 comprises: a sensor 32; a pose change unit 31; and a detection unit 5. The sensor is arranged so as to have a gap with respect to the sheet, is configured to project the sheet with light and receive the light reflected upon the sheet. The pose change unit is configured to change a pose of the sensor between a first pose and a second pose. Then, the detection unit is configured to detect a material and thickness TH of the sheet on the basis of a first light reception signal of the first pose to be output by the sensor and a second light reception signal of the second pose to be output by the sensor.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an image forming apparatus.

  In the image recording apparatus described in Patent Document 1, the material (paper quality) of the recording paper is detected based on the voltage value indicated by the output signal of the reflective optical sensor. In the image recording apparatus described in Patent Document 1, the reflective optical sensor is rotated by the link mechanism by an angle corresponding to the thickness (paper thickness) of the recording paper. The voltage value indicated by the output signal fluctuates by the angle at which the reflective optical sensor is rotated, and the paper thickness is detected by the amount of fluctuation in the voltage value. Therefore, Patent Document 1 describes that both the paper quality and the paper thickness can be detected by a single reflective optical sensor.

JP 2006-151560 A

  In the image forming apparatus described in Patent Document 1, the paper thickness is not directly detected based on the output signal of the reflective optical sensor. The paper thickness is converted into an angle change of the sensor by the link mechanism, the angle change is detected by the sensor, and the paper thickness is calculated from the detected angle change. Therefore, complicated calculation is required to detect the paper thickness.

  The present invention has been made in view of the above problems, and an object thereof is to provide an image forming apparatus capable of easily detecting the material and thickness of a sheet.

  The image forming apparatus according to the present invention forms an image on a sheet. The image forming apparatus includes a sensor, a posture change unit, and a detection unit. The sensor is disposed at a position that can face the surface of the sheet that passes through the conveyance path or is stopped on the conveyance path, projects light onto the sheet, and receives light reflected by the sheet. The posture changing unit changes the posture of the sensor between the first posture and the second posture. The detection unit detects the material and thickness of the sheet based on the first light reception signal output from the sensor in the first posture and the second light reception signal output from the sensor in the second posture. .

  According to the image forming apparatus of the present invention, the material and thickness of the paper can be easily detected.

1 is a diagram illustrating an image forming apparatus according to an embodiment of the present invention. It is a side view which expands and shows a part of conveyance unit shown in FIG. It is sectional drawing which shows the displacement sensor shown in FIG. It is a graph which shows the characteristic of the displacement sensor shown in FIG. It is a side view which shows the attitude | position change part of the conveyance unit shown in FIG. FIG. 6 is a side view of a conveyance path illustrating a front end portion of a sheet when double feeding occurs. FIG. 6 is a side view of a conveyance path showing a rear end portion of a sheet when double feeding occurs. FIG. 6 is a side view of a conveyance path showing a front end of a sheet at a reference timing. FIG. 6 is a side view of a conveyance path showing a rear end portion of a sheet at a first timing. FIG. 10 is a side view of a conveyance path showing a rear end portion of a sheet at a second timing. It is a flowchart which shows operation | movement of a control part.

  Embodiments of the present invention will be described below with reference to the drawings (FIGS. 1 to 11). In the drawings, the same or corresponding parts are denoted by the same reference numerals and description thereof is not repeated.

  An image forming apparatus 100 according to an embodiment of the present invention will be described with reference to FIG. As shown in FIG. 1, the image forming apparatus 100 is, for example, a multifunction machine. Specifically, the image forming apparatus 100 includes an image forming unit 1, a fixing unit 16, an image reading unit 2, a document transport unit 3, an operation panel 4, a feeding unit 11, a transport unit 13, a discharge unit 15, and a control unit. 5 (detector).

  The image forming unit 1 forms an image on a sheet R (sheet). The fixing unit 16 fixes the image formed on the paper R onto the paper R. Specifically, the fixing unit 16 includes a heating roller 161 and a pressure roller 162. The heating roller 161 and the pressure roller 162 fix the image on the paper R by heating and pressurizing the paper R passing through the nip portion N. The nip portion N is formed between the heating roller 161 and the pressure roller 162. The document transport unit 3 transports the document U to the image reading unit 2. The image reading unit 2 reads an image formed on the document U. The operation panel 4 receives an operation from the user for the image forming apparatus 100. The operation panel 4 includes a display unit 41.

  The feeding unit 11 includes one or a plurality of cassettes 111 on which the paper R is stacked, and feeds the paper R to the transport unit 13. The transport unit 13 includes one or a plurality of transport roller pairs 131 and a registration roller pair 132, and transports the paper R to the image forming unit 1. The transport unit 13 transports the paper R on which the image is formed to the fixing unit 16. The transport unit 13 transports the paper R on which the image is fixed to the discharge unit 15. The discharge unit 15 discharges the paper R on which the image is fixed.

  The control unit 5 controls the image forming unit 1, the fixing unit 16, the image reading unit 2, the document conveying unit 3, the operation panel 4, the feeding unit 11, the conveying unit 13, and the discharging unit 15. The control unit 5 includes, for example, a processor and a memory. The processor includes, for example, a CPU (Central Processing Unit). The memory stores data and computer programs. The memory includes, for example, a semiconductor memory, and may further include an HDD (Hard Disk Drive).

  Next, the transport unit 13 will be described with reference to FIG. As shown in FIG. 2, the transport unit 13 has a transport path 21. The transport unit 13 transports the paper R along the transport path 21 in the transport direction XT. The conveyance path 21 has a reference surface 211. The reference surface 211 is a surface on which one main surface (hereinafter referred to as “back surface”) of the pair of main surfaces of the paper R is in sliding contact.

  Specifically, the transport roller pair 131 transports the paper R in the transport direction XT. The registration roller pair 132 temporarily stops the paper R and sends the paper R to the image forming unit 1 at a predetermined timing. The conveyance roller pair 131 and the registration roller pair 132 are driven by a conveyance motor. When the control unit 5 rotates the transport motor in the first rotation direction, the transport roller pair 131 and the registration roller pair 132 rotate normally. As a result, the transport roller pair 131 and the registration roller pair 132 transport the paper R in the transport direction XT. On the other hand, when the control unit 5 rotates the transport motor in the second rotation direction opposite to the first rotation direction, the transport roller pair 131 and the registration roller pair 132 are reversed. As a result, the transport roller pair 131 and the registration roller pair 132 transport the paper R in the direction opposite to the transport direction XT.

  The transport unit 13 further includes a paper sensor 22, a displacement sensor 23, and a paper sensor 112. Output signals of the paper sensor 22, the displacement sensor 23, and the paper sensor 112 are input to the control unit 5.

  The paper sensor 22 detects the paper R. Specifically, the paper sensor 22 is disposed upstream of the registration roller pair 132 in the transport direction XT. The displacement sensor 23 is disposed at the first specified position PR1 of the transport path 21. The paper sensor 22 is disposed downstream of the displacement sensor 23 in the transport direction XT. The sheet sensor 22 and the registration roller pair 132 are arranged at a predetermined distance in the transport direction XT. When a predetermined time elapses after the paper sensor 22 detects the front end of the paper R in the transport direction XT, the control unit 5 stops the transport roller pair 131. As a result, the sheet R hits the registration roller pair 132 and is skew-corrected.

  The paper sensor 112 detects the paper R. The paper sensor 112 is disposed at the second specified position PR2 of the transport path 21. Specifically, the paper sensor 112 is disposed upstream of the displacement sensor 23 in the transport direction XT. The paper sensor 112 can also detect a paper R jam. Each of the paper sensor 22 and the paper sensor 112 includes, for example, an optical sensor. Each of the paper sensor 22 and the paper sensor 112 may include, for example, an optical sensor and an actuator.

  Next, the displacement sensor 23 will be described with reference to FIG. As shown in FIG. 3, the displacement sensor 23 is a laser displacement sensor including a PSD (Position Sensitive Detector).

  Specifically, the displacement sensor 23 includes a light projecting unit 231 and a light receiving unit 232. The light projecting unit 231 projects spot light (light) onto the object R1 along the light projecting axis L1. The light projecting unit 231 includes, for example, an LED (Light Emitting Diode). The light receiving unit 232 has a light receiving surface 232a. A PSD is disposed on the light receiving surface 232a. The spot light is reflected by the surface of the object R1, and enters the light receiving surface 232a as reflected light (light). The reflected light includes regular reflected light and scattered light. The specularly reflected light is light that is specularly reflected from the surface of the object R1 in the spot light. The scattered light is light scattered on the surface of the object R1 among the spot light. The direction in which specularly reflected light travels (reflection angle) is different from the direction in which scattered light travels (reflection angle). In FIG. 3, the approximate direction in which reflected light including regular reflected light and scattered light travels is indicated by the reflected light axis L2. The same applies to FIGS. 5 to 9. In the present embodiment, the object R1 is the paper R or the reference surface 211.

  The light receiving unit 232 of the displacement sensor 23 receives the reflected light and outputs a light reception signal having a voltage value WV. Hereinafter, the received reflected light may be referred to as received light reflected light. Specifically, the voltage value WV changes according to the intensity distribution of the received and reflected light on the light receiving surface 232a. Since the PSD is linear, the intensity distribution of the received / reflected light is formed along a certain direction on the light receiving surface 232a.

  The intensity distribution of the received and reflected light depends on the distance D1 between the light projecting unit 231 and the object R1. Therefore, the thickness of the paper R can be detected based on the voltage value WV. The voltage value WV increases as the interval D1 increases. In addition, you may employ | adopt the displacement sensor 23 with which the voltage value WV becomes small, so that the space | interval D1 becomes large. The intensity distribution of the received / reflected light also depends on the material of the object R1. Therefore, the material of the paper R can be detected based on the voltage value WV.

  In the present embodiment, as the displacement sensor 23, the displacement sensor 23 formed by the light projection axis L1 and the surface of the object R1 is smaller than 90 degrees. However, the present invention is not limited thereto, and a displacement sensor in which the light projection axis L1 and the surface of the object R1 form a substantially right angle may be used as the displacement sensor 23.

  Next, the characteristics of the displacement sensor 23 will be described with reference to FIGS. FIG. 4 is a graph showing the characteristics of the displacement sensor 23. The horizontal axis X1 in FIG. 4 indicates the position P along a certain direction on the light receiving surface 232a, and the vertical axis Y1 indicates the intensity of the received and reflected light at the position P. The light receiving unit 232 detects an intensity distribution along a certain direction of the received and reflected light, and outputs a light reception signal having a voltage value WV corresponding to the intensity distribution.

  Specifically, the voltage value WV changes according to the barycentric position P1 of the intensity distribution of the received and reflected light. The center of gravity position P1 is a position corresponding to the center of gravity PG in the figure F1. The figure F1 is a figure surrounded by a straight line L3 passing through the position P0, a straight line L4 passing through the position P2, the graph G1, and the horizontal axis X1. The position P0 indicates the position of one end point of the pair of end points of the light receiving unit 232. The position P2 indicates the position of the other end point of the pair of end points of the light receiving unit 232. The displacement sensor 23 may be a laser displacement sensor including a CCD (Charge Coupled Device) image sensor or a CMOS (Complementary Metal-Oxide Semiconductor) image sensor.

  Next, with reference to FIG. 5, the attitude change of the displacement sensor 23 for detecting the material of the paper R will be described. As shown in FIG. 5, the transport unit 13 further includes a posture changing unit 31. The control unit 5 controls the posture changing unit 31. As a result, the posture changing unit 31 rotates the displacement sensor 23 in the rotation direction XR to change the posture of the displacement sensor 23 between the first posture and the second posture. In FIG. 5, the displacement sensor 23 in the first posture is indicated by a solid line, and the displacement sensor 23 in the second posture is indicated by a two-dot chain line. The angle θ2 formed by the light projection axis L11 of the displacement sensor 23 in the first posture and the paper R is different from the angle θ3 formed by the light projection axis L12 of the displacement sensor 23 in the second posture and the paper R.

  Specifically, the posture changing unit 31 includes a rotation shaft 311, an actuator 312, and a magnetic member 313. The rotation shaft 311 supports the displacement sensor 23 in a rotatable manner. The actuator 312 rotates the displacement sensor 23 in the rotation direction XR, and determines the position of the displacement sensor 23 as one of the first position and the second position. The magnetic member 313 is a thin plate-like member (for example, a metal plate), and is provided on the surface of the displacement sensor 23 opposite to the surface facing the object R1.

  The actuator 312 includes a first electromagnet 312a and a second electromagnet 312b. The first electromagnet 312a and the second electromagnet 312b are arranged at positions where the magnetic member 313 can be attracted. The controller 5 turns on the first electromagnet 312a and turns off the second electromagnet 312b. As a result, the first electromagnet 312a attracts the magnetic member 313, and the attitude of the displacement sensor 23 is set to the first attitude. On the other hand, the control unit 5 turns off the first electromagnet 312a and turns on the second electromagnet 312b. As a result, the second electromagnet 312b attracts the magnetic member 313, and the posture of the displacement sensor 23 is set to the second posture. The displacement sensor 23 in the second posture is rotated by an angle θ1 with respect to the displacement sensor 23 in the first posture. As a result, the light projecting axis L12 is also rotated by an angle θ1 from the light projecting axis L11. The angle θ1 is greater than 0 degree and is preferably 5 degrees or less, and more preferably 1 degree or more and 2 degrees or less.

  Next, the material detection process, the paper thickness detection process, the double feed detection process, and the size abnormality detection process will be described in order with reference to FIGS. In the material detection process, the material of the paper R is detected. In the paper thickness detection process, the thickness of the paper R is detected. In the double feed detection process, it is detected that two or more sheets R are transported in an overlapping state, that is, the occurrence of double feed is detected. In the size abnormality detection process, it is detected that the size of the paper R is different from the input size.

≪Material detection process≫
With reference to FIG. 5, the material detection process of the paper R will be described. In FIG. 5, the conveyance of the paper R is stopped by the registration roller pair 132. In the displacement sensor 23 in the first posture shown by the solid line in FIG. 5, the light projecting unit 231 projects spot light onto the paper R along the light projecting axis L11. That is, the displacement sensor 23 is disposed at a position that can face the surface of the paper R that is stopped on the transport path 21. The spot light is reflected by the surface of the paper R, and the reflected light of the spot light travels along the reflection optical axis L21. The light receiving unit 232 receives the reflected light, and the light receiving unit 232 outputs a first light reception signal. In the displacement sensor 23 in the second posture indicated by the two-dot chain line in FIG. 5, the light projecting unit 231 projects spot light onto the paper R along the light projecting axis L12. The spot light is reflected by the surface of the paper R, and the reflected light of the spot light travels along the reflection optical axis L22. The light receiving unit 232 receives the reflected light, and the light receiving unit 232 outputs a second light receiving signal. The controller 5 detects the material of the paper R based on the first light receiving signal and the second light receiving signal.

  Specifically, the control unit 5 calculates a voltage difference WL1 (WL1 = | WV2−WV1 |) between the voltage value WV1 of the first light reception signal and the voltage value WV2 of the second light reception signal. As shown in Table 1, the control unit 5 has a first table in which the range of the voltage difference WL1 is associated with the material of the paper R. In Table 1, a numerical range Q1, a numerical range Q2, and a numerical range Q3 are numerical ranges that do not overlap each other. The control unit 5 detects the material of the paper R by comparing the voltage difference WL1 with the first table.

  When the material of the paper R changes, the ratio of scattered light included in the reflected light changes. When the ratio of the scattered light changes, the amount of movement of the barycentric position P1 changes with respect to the change of the constant angle θ1 of the light projection axis L1, and the voltage difference WL1 changes. For example, when the ratio of scattered light increases, the amount of movement of the gravity center position P1 increases, and the voltage difference WL1 increases. Therefore, the material of the paper R can be detected based on the voltage difference WL1.

≪Paper thickness detection process≫
Next, the principle of the paper thickness detection process will be described with reference to FIG. In FIG. 5, the conveyance of the paper R is stopped by the registration roller pair 132. In a state where the sheet R does not exist on the reference surface 211, the light projecting unit 231 of the displacement sensor 23 in the first posture projects the spot light onto the reference surface 211 along the light projecting axis L13 indicated by a one-dot chain line in FIG. To do. The spot light is reflected by the reference surface 211, and the reflected light of the spot light travels along the reflection optical axis L23. The light receiving unit 232 receives the reflected light, and the light receiving unit 232 outputs a third light receiving signal. The control unit 5 detects the thickness of the paper R (hereinafter referred to as paper thickness TH) based on the material of the paper R, the first light receiving signal, and the third light receiving signal.

  Specifically, the control unit 5 calculates a voltage difference WL2 (WL2 = | WV3−WV1 |) between the voltage value WV1 of the first light reception signal and the voltage value WV3 of the third light reception signal. As shown in Tables 2 to 4, the control unit 5 includes second to fourth tables in which the range of the voltage difference WL2 is associated with the paper thickness TH. The second table in Table 2 corresponds to plain paper, the third table in Table 3 corresponds to thick paper, and the fourth table in Table 4 corresponds to glossy paper. The control unit 5 compares the voltage difference WL2 with a table corresponding to the material of the paper R, and detects the paper thickness TH.

  In Table 2, a numerical range Q11, a numerical range Q12,... Are numerical ranges that do not overlap each other. The numerical value H11, the numerical value H12,... Are different from each other. In Table 3, a numerical range Q21, a numerical range Q22,... Are numerical ranges that do not overlap each other. The numerical value H21, the numerical value H22,... Are different from each other. In Table 4, a numerical range Q31, a numerical range Q32,... Are numerical ranges that do not overlap each other. The numerical value H31, the numerical value H32,... Are different from each other.

  As described above, when the material of the paper R changes, the ratio of the scattered light included in the reflected light changes. When the ratio of scattered light changes, the voltage difference WL2 changes for the same paper thickness TH. Therefore, the control unit 5 can detect the paper thickness TH more precisely by including the second table to the fourth table for each material of the paper R.

≪Temperature / nip pressure setting≫
Based on the material of the paper R detected by the material detection processing and the paper thickness TH detected by the paper thickness detection processing, the control unit 5 (fixing control unit) detects the temperature and pressure (nip pressure) of the nip portion N. To control. The controller 5 may control both the temperature and the pressure of the nip portion N based on one of the material of the paper R and the paper thickness TH, or may control one of the temperature and the pressure of the nip portion N. Good.

≪Double feed detection process≫
Next, the double feed detection process will be described with reference to FIGS. FIG. 6 is a side view of the transport path showing the front end RP1 of the paper R when double feeding occurs. FIG. 7 is a side view of the transport path showing the rear end RP2 of the paper R when double feeding occurs. As shown in FIG. 6, the displacement sensor 23 can project light onto the paper R on the reference surface 211 by the light projecting unit 231 at the first specified position PR1 of the transport path 21. In FIG. 6, when the light projecting unit 231 projects light onto the paper R, the paper R is moving on the conveyance path 21. That is, the displacement sensor 23 is disposed at a position that can face the surface of the paper R that passes through the conveyance path 21. The same applies to FIG.

  The displacement sensor 23 shown in FIG. 6 is in the first posture, and the light projecting unit 231 of the displacement sensor 23 projects spot light along the light projection axis L1 to the front end RP1 of the paper R. The spot light is reflected by the front end RP1, and the reflected light of the spot light travels along the reflection optical axis L2. The light receiving unit 232 receives the reflected light, and the light receiving unit 232 outputs a fourth light reception signal. The fourth light reception signal has a voltage value WV4.

  The displacement sensor 23 shown in FIG. 7 is in the first posture, and the light projecting unit 231 of the displacement sensor 23 projects spot light along the light projecting axis L1 to the rear end RP2 of the paper R. The spot light is reflected by the rear end RP2, and the reflected light of the spot light travels along the reflection optical axis L2. The light receiving unit 232 receives the reflected light, and the light receiving unit 232 outputs the fifth light reception signal. The fifth light reception signal has a voltage value WV5.

  Based on the fourth light reception signal and the fifth light reception signal, the control unit 5 detects that two or more sheets R are conveyed in an overlapping manner.

  Specifically, the control unit 5 acquires size information indicating the size of the paper R along the transport direction XT, speed information indicating the transport speed VT of the paper R, and trigger timing information indicating the trigger timing. The trigger timing is a timing at which the front end RP1 of the paper R being conveyed has passed the second specified position PR2 shown in FIG. The passage of the front end RP1 through the second specified position PR2 is detected by the paper sensor 112. The trigger timing may be a timing at which the rear end portion RP2 of the paper R being conveyed has passed the second specified position PR2.

  The control unit 5 acquires information indicating the paper size (for example, A4 size, B5 size) of the paper R. Information indicating the paper size is input to the memory of the control unit 5 by, for example, a paper size setting operation on the operation panel 4. The control unit 5 reads information indicating the paper size from the memory. The vertical and horizontal dimensions of the paper R are stored in the memory of the control unit 5 in correspondence with the paper size. For example, for “A4 size” paper, “297 mm” is stored as the vertical dimension, and “210 mm” is stored as the horizontal dimension. Based on the information indicating the paper size, the control unit 5 reads, as size information, the dimension along the transport direction XT of the paper R among the vertical and horizontal dimensions of the paper R. Further, the transport speed VT of the paper R is stored in the memory of the control unit 5 as speed information. The control unit 5 reads the transport speed VT of the paper R from the memory.

  Based on the size information, the speed information, and the trigger timing information, the control unit 5 determines that the front end RP1 passes the first specified position PR1 and the rear end RP2 passes the first specified position PR1. The rear end passage timing is calculated. The light projecting unit 231 projects spot light to the front end RP1 at the front end passage timing, and the light receiving unit 232 outputs a fourth light reception signal. The light projecting unit 231 projects spot light to the rear end RP2 at the rear end passage timing, and the light receiving unit 232 outputs the fifth light reception signal. Based on the voltage value WV4 of the fourth light reception signal and the voltage value WV5 of the fifth light reception signal, the control unit 5 confirms that two or more sheets R are conveyed in an overlapped state, that is, double feed. Detect that is occurring.

  As shown in FIG. 6, when two sheets of paper R are double-fed, the front end RP1 of the upper sheet R2 is located downstream in the transport direction XT from the front end of the lower sheet R3. Accordingly, at the front end passage timing, only the front end portion RP1 of the upper sheet R2 exists at the first specified position PR1. As a result, the light receiving unit 232 of the displacement sensor 23 outputs a fourth light receiving signal having a voltage value WV4 corresponding to the thickness of one sheet of paper R (described as a paper thickness TH1).

  On the other hand, as shown in FIG. 7, at the rear end passage timing, the rear end portion RP2 of the upper sheet R2 and the lower sheet R3 overlap each other at the first specified position PR1. As a result, the light receiving unit 232 of the displacement sensor 23 outputs a fifth light reception signal having a voltage value WV5 corresponding to the thickness of two sheets of paper R (described as paper thickness TH2).

  When the paper thickness TH2 is greater than the paper thickness TH1, the control unit 5 determines that double feeding has occurred. For example, if the paper thickness TH2 is equal to or greater than 1.5 times the paper thickness TH1 (TH2 ≧ 1.5 × TH1), the control unit 5 determines that double feeding has occurred. If the paper thickness TH2 is equal to the paper thickness TH1, the control unit 5 determines that no double feed has occurred. For example, if the paper thickness TH2 is smaller than 1.5 times the paper thickness TH1 (TH2-TH1 <1.5 × TH1), the control unit 5 determines that no double feed has occurred.

≪Reverse paper feed≫
The control unit 5 (conveyance control unit) controls the conveyance unit 13 so that the sheet R is conveyed in the direction opposite to the conveyance direction XT when it is detected that two or more sheets R are conveyed in an overlapping manner. To control. For example, the transport motor is rotated in the reverse direction, the registration roller pair 132 and the transport roller pair 131 are rotated in the opposite directions, and the paper R is transported in the direction opposite to the transport direction XT. By transporting the paper R in the direction opposite to the transport direction XT, for example, the operation of removing the paper R that has been double fed can be facilitated.

≪Size abnormality detection processing≫
Next, the size abnormality detection process will be described with reference to FIGS. FIG. 8 is a side view of the transport path 21 showing the front end RP1 of the paper R at the reference timing. The reference timing is a timing at which the front end RP1 passes through the first specified position PR1. FIG. 9 is a side view of the transport path 21 showing the rear end RP2 of the paper R at the first timing. The first timing indicates the timing when the first predetermined time has elapsed from the reference timing. The first predetermined time is determined based on the input size and the conveyance speed VT. In FIG. 9, the case where the rear end RP2 of the paper R is not located at the first specified position PR1 is indicated by a solid line, and the case where the rear end RP2 of the paper R is located at the first specified position PR1 is indicated by a two-dot chain line. .

  FIG. 10 is a side view of the transport path 21 showing the rear end RP2 of the paper R at the second timing. The second timing is a timing when a second predetermined time has elapsed from the first timing. The second predetermined time corresponds to the time required to feed the paper R by 2 cm to 3 cm. In FIG. 10, the case where the paper R is located at the first specified position PR1 is indicated by a solid line, and the case where the paper R is not located at the first specified position PR1 is indicated by a two-dot chain line.

  The displacement sensor 23 shown in FIGS. 8 to 10 is in the first posture. The displacement sensor 23 in the first posture faces the reference surface 211 at the first specified position PR1 of the transport path 21. The light projecting unit 231 of the displacement sensor 23 can project light onto the reference surface 211 and the paper R on the reference surface 211. 8 to 10, when the light projecting unit 231 projects light onto the paper R, the paper R is moving along the conveyance path 21. That is, the displacement sensor 23 is disposed at a position that can face the surface of the paper R that passes through the conveyance path 21.

  In the size abnormality detection process, when the size of the paper R is input, the control unit 5 acquires information indicating the size. Then, the control unit 5 determines whether or not the size of the paper R is different from the input size. For example, when glossy paper is used as the paper R, the size of the paper R may be input by the operation panel 4. The control unit 5 determines whether the size of the paper R conveyed by the conveyance unit 13 matches the input paper R size.

  As shown in FIG. 8, at the reference timing, the light projecting unit 231 of the displacement sensor 23 projects spot light onto the front end RP1 of the paper R along the light projecting axis L1. The spot light is reflected by the front end RP1, and the reflected light of the spot light travels along the reflection optical axis L2. The light receiving unit 232 receives the reflected light, and the light receiving unit 232 outputs a fourth light reception signal.

  As shown in FIG. 9, at the first timing, the light projecting unit 231 of the displacement sensor 23 projects spot light along the light projecting axis L1 toward the reference surface 211. When the paper R is not positioned at the first specified position PR1, the spot light is reflected by the reference surface 211. When the paper R is positioned at the first specified position PR1, the spot light is reflected by the paper R. The reflected light of the spot light reflected by the reference surface 211 travels along the reflected optical axis L24. The reflected light of the spot light reflected by the paper R travels along the reflected optical axis L25. The light receiving unit 232 receives the light reflected by the reference surface 211 or the paper R, and outputs a sixth light reception signal.

  As shown in FIG. 10, at the second timing, the light projecting unit 231 of the displacement sensor 23 projects spot light along the light projecting axis L1 toward the reference surface 211. When the paper R is not positioned at the first specified position PR1, the spot light is reflected by the reference surface 211. When the paper R is positioned at the first specified position PR1, the spot light is reflected by the paper R. The reflected light of the spot light reflected by the reference surface 211 travels along the reflected optical axis L26. The reflected light of the spot light reflected by the paper R travels along the reflected optical axis L27. The light receiving unit 232 receives the light reflected by the reference surface 211 or the paper R, and outputs a seventh light reception signal.

  The control unit 5 (detection unit) determines that the paper size is different from the input size based on the third light receiving signal, the fourth light receiving signal, the sixth light receiving signal, and the seventh light receiving signal (size abnormality). ) Is detected.

  More specifically, in the control unit 5, the voltage value WV4 of the fourth light reception signal and the voltage value WV5 of the sixth light reception signal are substantially equal, and the voltage value WV3 of the third light reception signal and the voltage value WV7 are substantially equal. In this case, it is determined that no size abnormality has occurred. For example, when the size abnormality of the actual paper R is smaller than the input size, the voltage value WV6 corresponds to the reflected optical axis L24 in FIG. On the other hand, the voltage value WV4 corresponds to the reflected optical axis L2 in FIG. As a result, the voltage value WV6 and the voltage value WV4 are greatly different.

  When the size abnormality of the actual paper R is larger than the input size, the voltage value WV7 corresponds to the reflected optical axis L27 in FIG. On the other hand, the voltage value WV3 corresponds to the reflected optical axis L23 in FIG. As a result, the voltage value WV7 and the voltage value WV3 are greatly different.

  Next, the size abnormality process will be described in detail with reference to FIGS. FIG. 11 is a flowchart showing the operation of the control unit 5. For example, when the size of the paper R is input from the operation panel 4, the control unit 5 acquires information indicating the size (S 101). The information indicating the size includes a size along the transport direction XT of the paper R.

  Next, the control unit 5 calculates the reference timing, the first timing, and the second timing based on the size information, the speed information, and the trigger timing information (S102). And the control part 5 acquires each voltage value of a 3rd light reception signal, a 4th light reception signal, a 6th light reception signal, and a 7th light reception signal (S103).

  Next, the control unit 5 calculates a voltage difference WL3 (WL3 = | WV6−WV4 |) that is an absolute value of a difference between the voltage value WV4 and the voltage value WV6 (S104). Then, the voltage difference WL3 is compared with the threshold value WR (S105). If the voltage difference WL3 is equal to or greater than the threshold WR (Yes in S105), the control unit 5 determines that a size abnormality that is smaller than the input size of the paper R has occurred (S106). Then, the process proceeds to step S107.

  Next, the control unit 5 displays a message indicating that a size abnormality has occurred on the display unit 41 (S107), stops the conveyance of the paper R, and ends the process. On the other hand, if the voltage difference WL3 is smaller than the threshold value WR (No in S105), the process proceeds to step S108.

  Next, the control unit 5 calculates a voltage difference WL4 (WL4 = | WV7−WV3 |) that is an absolute value of the difference between the voltage value WV7 and the voltage value WV3 (S108). Then, the voltage difference WL4 is compared with the threshold value WR (S109). If the voltage difference WL4 is greater than or equal to the threshold WR (Yes in S109), the control unit 5 determines that a size abnormality has occurred that is larger than the input size of the paper R (S110). Then, the process proceeds to step S107. On the other hand, if the voltage difference WL4 is smaller than the threshold WR (No in S109), the control unit 5 determines that no size abnormality has occurred, and the process ends.

  As described above with reference to FIGS. 1 to 11, according to the present embodiment, by changing the posture of the displacement sensor 23 between the first posture and the second posture by the posture changing unit 31, The material of the paper R and the paper thickness TH are detected. Since the angle change during the posture change is constant, it is not necessary to use a parameter indicating the angle change in order to detect the paper thickness TH, and the paper thickness TH can be easily detected.

  Further, the control unit 5 can accurately detect the paper thickness TH by detecting the paper thickness TH based on the material of the paper R, the first light reception signal, and the third light reception signal.

  Further, the control unit 5 controls at least one of the temperature and the pressure of the nip portion N based on at least one of the detected material of the paper R and the paper thickness TH. Therefore, it is possible to form an image on the paper R satisfactorily.

  Further, the control unit 5 detects that two or more sheets R are conveyed in an overlapping manner based on the fourth light reception signal and the fifth light reception signal. Therefore, the output signal of one displacement sensor 23 can detect not only the material of the paper R and the paper thickness TH but also the double feed of the paper R. As a result, it is not necessary to provide another sensor to detect double feeding of the paper R, and an increase in manufacturing cost of the image forming apparatus 100 can be suppressed.

  Then, when it is detected that two or more sheets R are transported in an overlapping manner, the control unit 5 controls the transport unit 13 so that the sheet R is transported in the direction opposite to the transport direction XT. . Therefore, by feeding the paper R back to a position where it can be easily accessed from the outside, for example, it becomes easy to take out the paper R transported in an overlapping manner from the transport unit 13. Further, if the sheets R transported in an overlapping manner are fed back to the feeding unit 11, post-processing when a double feed occurs is further facilitated.

  Further, the control unit 5 detects that the size of the paper R is different from the input size based on the third light receiving signal, the fourth light receiving signal, the sixth light receiving signal, and the seventh light receiving signal. Accordingly, in addition to the material of the paper R, the paper thickness TH, and the double feeding of the paper R, the size abnormality of the paper R can be detected. As a result, it is not necessary to provide another sensor for detecting an abnormal size of the paper R, and an increase in manufacturing cost of the image forming apparatus 100 can be suppressed.

  Further, when it is detected that the size of the paper R is different from the input size, the control unit 5 stops the conveyance of the paper R, for example, and displays a message notifying the size difference on the display unit 41. indicate. Therefore, it is possible to avoid an image formation defect in which all the original images are not formed on the paper R and a problem that the size of the paper R is disproportionately larger than that of the original image.

  The embodiments of the present invention have been described above with reference to the drawings. However, the present invention is not limited to the above-described embodiment, and can be implemented in various modes without departing from the gist thereof. In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the above embodiments. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined. In order to facilitate understanding, the drawings schematically show each component as a main component, and the thickness, length, number, interval, etc. of each component shown in the drawings are actual for convenience of drawing. May be different. In addition, the material, shape, dimensions, and the like of each component shown in the above embodiment are merely examples, and are not particularly limited, and various changes can be made without departing from the effects of the present invention. is there.

  The present invention can be used in the field of image forming apparatuses.

1: Image forming unit 5: Control unit 13: Conveying unit 21: Conveying path 22: Paper sensor 23: Displacement sensor 112: Paper sensor 31: Attitude changing unit 100: Image forming apparatus 131: Conveying roller pair 132: Registration roller pair 161 : Heating roller 162: Pressure roller 211: Reference surface 231: Projecting unit 232: Light receiving unit 232a: Light receiving surface 311: Support unit

Claims (7)

An image forming apparatus for forming an image on a sheet,
A sensor that is disposed at a position that can face the surface of the sheet that passes through the conveyance path or is stopped on the conveyance path, projects light on the sheet, and receives light reflected by the sheet;
A posture changing unit that changes the posture of the sensor between a first posture and a second posture;
A detection unit configured to detect a material and a thickness of the sheet based on a first light reception signal output from the sensor in the first posture and a second light reception signal output from the sensor in the second posture; Image forming apparatus. The sensor in the first posture projects light onto the transport path, receives light reflected by the transport path, and outputs a third light reception signal;
The detector is
Based on the first light receiving signal and the second light receiving signal, the material of the sheet is detected,
The image forming apparatus according to claim 1, wherein the thickness of the sheet is detected based on the material of the sheet, the first light reception signal, and the third light reception signal. A fixing unit for fixing the image formed on the sheet to the sheet;
A fixing control unit for controlling the fixing unit;
The fixing unit has a nip portion through which the sheet passes,
The image forming apparatus according to claim 1, wherein the fixing controller controls at least one of a temperature and a pressure of the nip portion based on at least one of a material and a thickness of the sheet. The sensor in the first posture is
Projecting light to the front end in the sheet conveying direction, receiving light reflected by the front end, and outputting a fourth light reception signal;
Projecting light to a rear end portion of the sheet in the transport direction, receiving light reflected by the rear end portion, and outputting a fifth light reception signal;
The detection unit according to any one of claims 1 to 3, wherein the detection unit detects that two or more sheets are conveyed while being overlapped based on the fourth light reception signal and the fifth light reception signal. The image forming apparatus described in 1. A transport unit for transporting the sheet in the transport direction;
A conveyance control unit for controlling the conveyance unit;
The conveyance control unit controls the conveyance unit so that the sheet is conveyed in a direction opposite to the conveyance direction when it is detected that two or more sheets are conveyed in an overlapping manner. Item 5. The image forming apparatus according to Item 4. The sheet is conveyed at a predetermined conveyance speed,
When the size of the sheet is input, the detection unit acquires information indicating the size, and calculates a reference timing, a first timing, and a second timing,
The reference timing indicates a timing when a front end portion in the sheet conveyance direction reaches a specified position in the sheet conveyance path,
The first timing indicates a timing when a first predetermined time has elapsed from the reference timing,
The first predetermined time is determined based on the input size and the transport speed,
The second timing indicates a timing when a second predetermined time has elapsed from the first timing,
The sensor in the first posture is
Facing the transport path at the defined position;
Projecting light onto the transport path, receiving light reflected by the transport path, and outputting a third light reception signal;
In the reference timing, light is projected onto the front end portion of the sheet, light reflected by the front end portion is received, and a fourth light reception signal is output,
In the first timing, light is projected toward the conveyance path, the light reflected by the sheet or the conveyance path is received, and a sixth light reception signal is output,
In the second timing, light is projected toward the conveyance path, the light reflected by the conveyance path or the sheet is received, and a seventh light reception signal is output,
The detection unit is configured such that the size of the sheet is different from the input size based on the third light receiving signal, the fourth light receiving signal, the sixth light receiving signal, and the seventh light receiving signal. The image forming apparatus according to claim 1, wherein the image forming apparatus is detected. A display unit;
A display control unit for controlling the display unit,
When it is detected that the size of the sheet is different from the input size, the display control unit controls the display unit to display a message notifying the difference in size. Item 7. The image forming apparatus according to Item 6.