JP2018177446A - Image forming apparatus, method and program for determining paper kind - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus or the like capable of performing skew-correction and paper-kind determination with a simple configuration by providing a member for determining a paper kind to a member for performing skew-correction.SOLUTION: An image forming apparatus comprises: a plurality of shutter members 210a, 210b that are provided in a main scanning direction of a sheet so that a sheet being fed is stopped for skew-correction; abutment detection means 220, 250 respectively attached on the shutter members and for detecting an abutment of a sheet P; push-force detection means 211, 240, 250 provided on at least one of the plurality of shutter members and for detecting a push force upon feeding of a sheet; and paper-kind determination means 300 that determines a paper kind on the basis of a push force detected by the push-force detection means.SELECTED DRAWING: Figure 3

Description

  The present invention relates to an image forming apparatus such as MFP (Multi Function Peripherals) which is a multifunction digital multifunction machine, a paper type determination method and a paper type determination program executed by the apparatus.

  In the image forming apparatus as described above, when the paper type such as the paper thickness of the printing paper is different, the optimum process conditions at the time of image formation are also different. Therefore, the paper type of the paper is determined and the process conditions are determined according to the determination result. It is desirable to change.

  Conventionally, there is known an image forming apparatus that corrects a skew, which is an inclination of a sheet, by providing a plurality of sheet shutter members and bringing a conveyed sheet into contact with the plurality of shutter members (for example, patent documents 1). However, in the technology described in Patent Document 1, the movement amount of the gate is the same for any paper type, and therefore, the paper type can not be determined.

  Therefore, according to Patent Document 2, when the sheet is stopped and bent by the registration roller pair, the sensor shaft of the load sensor is pushed in by the loop portion of the sheet, and a voltage corresponding to the amount of pushing of the sensor shaft is output from the load sensor. An image forming apparatus has been proposed which determines the sheet thickness based on the output voltage value.

JP, 2013-154979, A JP 2007-144666 A

  However, in the image forming apparatus described in Patent Document 2, it is necessary to separately provide a member for performing skew correction and a member for detecting the paper type in the sheet conveyance unit before image formation, and the configuration is complicated. There is a problem that it becomes expensive.

  This invention was made in order to solve such a subject, and is provided with the member for determining a paper type in the member for performing a skew correction, and skew correction is also a paper type by simple structure. SUMMARY OF THE INVENTION It is an object of the present invention to provide an image forming apparatus capable of performing the above determination, a paper type determination method to be executed by the same apparatus, and a paper type determination program.

The above-mentioned subject is solved by the following means.
(1) A plurality of shutter members provided in the main scanning direction of the sheet for stopping the conveyed sheet for skew correction, and contact detection means for detecting contact between the sheets attached to the respective shutter members And a pressing force detection unit provided on at least one of the plurality of shutter members for detecting a pressing force at the time of sheet feeding, and determining the paper type based on the pressing force detected by the pressing force detection unit. An image forming apparatus comprising: paper type determination means.
(2) After detecting the contact of the sheet by the contact detection means, the contact state of the sheet is held and the pressing force is detected by the pressing force detecting means, and the sheet passes the shutter member after the detection of the pressing force The image forming apparatus according to item 1 above, characterized in that
(3) The paper type judging means is characterized in that the pressing force is detected and the paper type is judged from the timing when it is detected that the paper has come into contact with the shutter member by all of the plurality of contact detection means. The image forming apparatus according to claim 1 or 2.
(4) The image according to any one of items 1 to 3, wherein the pressing force detection means detects the pressing force at the time of sheet feeding based on the amount of movement of the shutter member due to contact with the shutter member. Forming device.
(5) The shutter member has a predetermined shutter holding force that regulates the sheet conveyance when the sheet is in contact, and the shutter holding force is the first of the time until the sheet abuts on the shutter member and skew correction is completed. The image forming apparatus according to claim 4, wherein the image forming apparatus is a shutter holding force and a second shutter holding force until a pressing force of a sheet after skew correction is detected.
(6) The image forming apparatus according to (5), wherein the first holding force is a holding force in which the shutter member does not move by a pressing force of the sheet.
(7) The image forming apparatus according to (5), wherein the second holding force is a holding force corresponding to a load amount that changes in accordance with the movement amount of the shutter member.
(8) The image writing position setting means for setting the writing position of the image from the movement amount of the shutter member at the time of the paper type determination by the pressing force detecting means is further provided with any of the above 4 to 7 An image forming apparatus according to claim 1.
(9) The image forming apparatus according to any one of the above items 4 to 8, wherein the amount of movement of the shutter member is calculated by pulse counting by an optical sensor and a slit member.
(10) The image forming apparatus according to any one of the above items 1 to 9, wherein the contact detection of the sheet by the contact detection unit is performed by an electrostatic sensor.
(11) The image forming apparatus according to any one of (1) to (10), wherein the pressing force detection unit detects the pressing force based on the amount of pressure of the sheet in contact with the shutter member.
(12) The image forming apparatus according to item 11, wherein the paper type determination unit determines the paper type based on at least two pressure amounts detected by the pressing force detection unit.
(13) The image forming apparatus according to item 11 or 12, wherein the pressure amount is measured by a piezoelectric sensor.
(14) The shutter member, in the case where there is a contact detection means for which the contact detection has not been performed within a predetermined time after the contact is first detected by any of the plurality of contact detection means 14. The image forming apparatus according to any one of the above 1 to 13, wherein the stop of the sheet due to the release of the sheet is released.
(15) When the stop of the sheet by the shutter member is released, the sheet type determination means determines that the sheet type of the sheet determined immediately before is the sheet type of the sheet from which the stop has been released. The image forming apparatus according to item 14 above.
(16) The image forming apparatus according to any one of items 1 to 15, wherein process conditions for image formation are set according to the determination result after the paper type determination by the paper type determination unit.
(17) The image forming apparatus according to item 16, wherein the process condition is a transfer output.
(18) The image forming apparatus according to item 16, wherein the process condition is sheet separation output.
(19) The image forming apparatus according to item 16, wherein the process condition is a fixing temperature.
(20) A step in which the image forming apparatus stops the skewed sheet for skew correction with a plurality of shutter members provided in the main scanning direction of the sheet, and a contact detection attached to each shutter member Means for detecting the contact of the sheet, the step of detecting the pushing force at the time of sheet feeding by the pushing force detecting means provided on at least one of the plurality of shutter members, and the step of detecting the pushing force And a paper type determination step of determining a paper type based on the pressing force detected by the control unit.
(21) A step of stopping the conveyed sheet for skew correction by the plurality of shutter members provided in the main scanning direction of the sheet on the computer of the image forming apparatus, and the steps attached to the respective shutter members The step of detecting the contact of the sheet by the contact detecting means, the step of detecting the pushing force at the time of sheet feeding by the pushing force detecting means provided on at least one of the plurality of shutter members, the pushing force is detected A paper type determination program for executing a paper type determination step of determining a paper type based on a pressing force detected in the step of performing.

  According to the invention described in the preceding paragraph (1), the plurality of shutter members provided in the main scanning direction of the sheet and stopping the conveyed sheet for skew correction detect a plurality of contact of the sheet. Since the contact detection means are respectively attached, skew correction of the sheet can be performed by the shutter member. Moreover, since at least one of the plurality of shutter members is provided with pressing force detection means for detecting the pressing force at the time of paper feeding for determining the paper type, the shutter member and the pressing force detection means are separately provided. The image forming apparatus is not necessary, and can perform skew correction and sheet type determination with a simple configuration.

  According to the invention described in the preceding paragraph (2), after the contact detection means detects the contact of the sheet, the contact state of the sheet is held and the pressing force is detected by the pressing force detecting means. After detection, the sheet passes through the shutter member.

  According to the invention described in the preceding paragraph (3), the paper type determination means detects the pressing force and determines the paper type from the timing when it is detected that the paper abuts against the shutter member by all of the plurality of contact detection means. Therefore, the paper type can be accurately determined with the skew corrected.

  According to the invention described in the preceding paragraph (4), the pressing force detection means detects the pressing force at the time of sheet feeding based on the movement amount of the shutter member due to the contact with the shutter member. The pressing force can be detected.

  According to the invention described in item (5), when the sheet is in contact with the shutter member, the pressing force of the sheet after the skew correction is performed by the first shutter holding force until the sheet is in contact with the shutter member and the skew correction is completed. The second shutter holding force restricts the sheet conveyance until it detects.

  According to the invention described in the preceding paragraph (6), the shutter member regulates the sheet conveyance with a holding force such that the shutter member can not move by the pressing force of the sheet until the sheet abuts on the shutter member and the skew correction is completed. .

  According to the invention described in the preceding paragraph (7), until the shutter member detects the pressing force of the sheet after skew correction, the shutter force is a holding force corresponding to the load amount (effect) that changes according to the movement amount of the shutter member. , Regulate paper transport.

  According to the invention described in the preceding paragraph (8), the writing position of the image is set from the movement amount of the shutter member at the time of the sheet type determination by the pressing force detecting means. Therefore, the writing position of the image by the movement of the shutter member Deviations of the image can be corrected, and the image can be exported from the same writing position as in the case where the pressing force detection is not performed.

  According to the invention described in (9), the movement amount of the shutter member can be accurately calculated by pulse counting by the optical sensor and the slit member.

  According to the invention described in (10), since the contact detection of the sheet by the contact detection means is performed by the electrostatic sensor, the contact of the sheet can be reliably detected with a simple configuration.

  According to the invention described in the preceding paragraph (11), since the pressing force detection means detects the pressing force by the pressure amount of the sheet in contact with the shutter member, the pressing force at the time of sheet feeding can be detected relatively easily. it can.

  According to the invention described in the preceding paragraph (12), the paper type judging means judges the paper type by the pressure amount of at least two places detected by the pushing force detecting means, so that the local variation of the pressure amount is alleviated Thus, highly accurate paper type determination can be performed.

  According to the invention described in the preceding paragraph (13), the pressure amount can be reliably measured by the piezoelectric sensor.

  According to the invention described in the preceding paragraph (14), after any contact is first detected by any of the plurality of contact detecting means, the contact detecting means is not detected within a predetermined time. If it is determined that the skew correction can not be performed, the stop of the sheet by the shutter member is released.

  According to the invention described in the preceding paragraph (15), when the stop of the sheet by the shutter member is released, it is determined that the sheet type of the sheet determined immediately before is the sheet type of the sheet of which the stop is released. It is possible to avoid the presence of a sheet whose type is not specified and to smoothly execute the subsequent image forming process and the like.

  According to the invention described in the preceding paragraph (16), after the determination of the paper type by the paper type determination means, the process conditions at the time of image formation are set according to the determination result, so appropriate process conditions according to the paper type Image formation can be performed.

  According to the invention described in (17), transfer can be performed with an appropriate transfer output according to the paper type.

  According to the invention described in the preceding paragraph (18), it is possible to separate the paper with the proper paper separation output according to the paper type.

  According to the invention described in (19), it is possible to perform fixing at an appropriate fixing temperature according to the paper type.

  According to the invention described in (20), the skew detection of the sheet can be performed by detecting the contact of the sheet by the contact detection means, and it is necessary to separately provide the shutter member and the pressing force detection means. Instead, skew correction and paper type detection can be performed with a simple configuration.

  According to the invention described in the preceding paragraph (21), the plurality of shutter members provided in the main scanning direction of the sheet stop the conveyed sheet for skew correction, and attach to the plurality of shutter members, respectively. Detecting the contact of the sheet by the plurality of contact detecting means, and detecting the pressing force at the time of sheet feeding by the pressing force detecting means provided on at least one of the plurality of shutter members; The computer of the image forming apparatus can execute a paper type determination step of determining a paper type based on the pressing force detected in the step of detecting the pressing force.

FIG. 1 is an overall configuration diagram of an image forming apparatus according to an embodiment of the present invention. FIG. 6 is a view showing the details of a skew correction / paper type detection unit. (A)-(C) is a sectional view in the state where a sheet was conveyed by skew correction and pushing force detection unit. FIG. 6 is a flowchart showing an operation of the image forming apparatus in the case of performing paper type determination using the skew correction and pressing force detection unit shown in FIG. 2 and FIG. 3. (A)-(C) show other embodiment of this invention, and are sectional drawings of the state in which the paper was conveyed by the skew correction and the pushing force detection unit. FIG. 6 is a flowchart showing an operation of the image forming apparatus in the case of performing paper type determination using the skew correction / pushing force detection unit shown in FIG. 5; FIG. 6 is a flowchart showing another operation of the image forming apparatus in the case of performing paper type determination using the skew correction / push force detection unit shown in FIG. 5; FIG.

  Hereinafter, an embodiment of the present invention will be described based on the drawings.

  FIG. 1 is an overall configuration diagram of an image forming apparatus 1 according to an embodiment of the present invention.

  The image forming apparatus 1 includes one or more sheet feeding cassettes 100 for storing sheets. The sheet pulled out of the sheet feeding cassette 100 is conveyed upward by the conveyance roller disposed at a predetermined position of the conveyance path 700 along the sheet conveyance path 700 directed upward.

  In the vicinity of the center position in the vertical direction of the conveyance path 700, a skew correction / push force detection unit 200 for performing skew correction which is the inclination of the sheet and detection of the sheet push force is disposed. The skew correction / push force detection unit 200 is disposed on the upstream side (lower side) of the pair of registration rollers 202 and 203 disposed on both sides of the conveyance path 700 and the registration rollers 202 and 203 on both sides of the conveyance path 700. A pair of transport rollers 201, 201 is provided. Details of the skew correction / push force detection unit 200 will be described later.

  At the downstream side of the skew correction and pressing force detection unit 200, an image forming unit for forming an image on a sheet is provided. Specifically, a rotatable photosensitive drum 401 is provided, and around the rotation of the photosensitive drum 401, a charging roller 402 for charging the photosensitive drum 401 and a charged photosensitive drum 401 are used as image data. In accordance with the above, an exposure unit 403 for exposing, a developing device 404 for developing the surface of the photosensitive drum 401 to form a toner image, a transfer roller 405 for transferring the formed toner image onto paper, and a photosensitive drum 401 after transfer. A cleaner 406 or the like for removing electricity from the surface of the substrate is disposed.

  The sheet on which the toner image has been transferred by the transfer roller 405 is fixed by the fixing device 500, and then discharged to the sheet discharge unit 600. The fixing device 500 includes a heating roller 501 and a pressing roller 502, and performs fixing by heating and pressing a sheet by both rollers.

  The entire operation including the image forming operation of the image forming apparatus 1 is controlled by the control unit 300. The control unit 300 includes a CPU 301, a ROM 302 for storing an operation program of the CPU 301, and a RAM 303 as a work area when the CPU 301 operates. Each process is executed by the CPU 301 operating according to the operation program.

  FIG. 2 is a view showing details of the skew correction / push force detection unit 200, and FIG. 3 is a cross-sectional view of a state in which the sheet is conveyed to the skew correction / push force detection unit 200.

  As described above, the skew correction / push force detection unit 200 includes the pair of registration rollers 202 and 203 and the conveyance rollers 201 and 201.

  The registration rollers 202 and 203 are composed of a plurality of rollers supported at an interval on a drive shaft 202a and a driven shaft 202b (shown in FIG. 3) arranged in a horizontal state, and the main drive shaft 202a is rotated by a drive unit not shown. By driving, one of the registration rollers 202 is rotated, and the other registration roller 203 is rotated around the driven shaft 203 a as the registration roller 202 rotates. Further, the transport rollers 201, 201 are composed of a plurality of rollers supported at intervals on the respective shaft portions 201a arranged in a horizontal state, and one shaft 202a is rotationally driven by a drive unit (not shown), and paper to be described later The pressing force at the time of type determination is applied to the sheet P.

  The registration rollers 202 and 203 play the role of supplying the sheet P conveyed in the X direction (upward direction) by the conveyance rollers 201 and 201 in accordance with the operation timing of the image forming unit. The skew correction of the sheet is performed before the toner bites into the registration rollers 202 and 203.

  That is, a plurality of (two in this example) shutter members 210a and 210b are provided in total between some adjacent resist rollers among the plurality of resist rollers 202 and 203, and the sheet P is resist The leading edge of the sheet P is in contact with the end of the shutter members 210 a and 210 b before it is inserted into the rollers 202 and 203. An abutment sensor 220 for detecting the abutment of the sheet P is provided at the upstream end of each of the shutter members 210a and 210b in the sheet conveyance direction. The contact sensor 220 is formed of, for example, an electrostatic sensor that detects a contact state based on a change in capacitance of the sheet presence or absence.

  The shutter members 210a and 210b are rotatably provided independently on the driven shaft 203a of the registration roller 203 on the driven side. Further, in the rotational direction of the shutter members 210a and 210b, the lever 231 is connected to the end other than the end where the contact sensor 220 of the shutter members 210a and 210b is disposed, The other end is locked to the stopper member 230.

  Further, biasing force in a direction in which each lever 231 is pressed toward the shutter members 210a and 210b by the spring member 232 is always applied. The biasing force of the spring member 232 is transmitted to the shutter members 210a and 210b via the lever 231, and in each shutter member 210a and 210b, in the counterclockwise direction of FIG. The biasing force that is pushed to the side is always applied. When the sheet P is fed after skew correction, the shutter members 210a and 210b can be rotated clockwise in FIG. 3 against the biasing force by the pressing force of the sheet P.

  The stopper member 230 is connected to a support device (not shown) that supports the stopper member 230 in a fixed and releasable manner. In this embodiment, the stopper members 250 are fixed until the skew correction is completed, whereby the shutter members 210a and 210b apply holding forces to the shutter members 210a and 210b, which do not move by the pressing force of the sheet P. After the skew correction is completed, the fixing of the stopper member 230 is released, and the pressing force of the sheet P enables the rotation of each of the shutter members 210a and 210b. When the shutter members 210a and 210b rotate by a predetermined amount, the locking of the lever 231 with the stopper member 230 is released.

  FIG. 3A shows a standby state in which the leading edge of the sheet P is not yet in contact with the contact sensor 220, and the contact surface of the contact sensor 220 at the end of the shutter members 210a and 210b is the drive resist roller 202. The leading end of the sheet P is in contact with the contact surface before it enters the nip portion. In this state, the shutter members 210a and 210b are prevented from rotating by the stopper member 230. Therefore, when the sheet P is skewed as shown in FIG. 2A, the leading end of the sheet P abuts against one of the shutter members 210a and 210b, but does not abut against the other shutter member. The advancing side of the skew of the leading end of the sheet P waits for the delay side, and as shown in FIG. 2B, the skew (skew) of the sheet is corrected.

  After the skew correction is completed, that is, when all the contact sensors 220 of the shutter members 210a and 210b detect the contact of the sheet P (turned ON), the fixing of the stopper member 230 is released. Then, as shown in FIG. 3B, the shutter members 210a and 210b rotate clockwise in FIG. 3 by the pressing force of the leading end of the sheet caused by the feeding of the sheet P by the conveyance roller 201, and then the sheet P The front end of the roller pushes into the nip portion of the pair of registration rollers 202 and 203 while pushing the shutter members 210a and 210b.

  In this embodiment, after skew correction of the sheet P which has been conveyed obliquely, the sheet pressing force is detected by the amount of movement of the shutter members 210a and 210b before the leading end of the sheet P enters the nip portion. There is.

  That is, as shown in FIG. 3, each shutter member 210a, 210b is provided with a slit member 211 which is rotatable integrally with the shutter members 210a, 210b at an intermediate position in the rotation direction. A large number of slits are formed on the slit member 211 in the rotational direction, and the slit of the slit member 211 is read by an optical sensor 240 including light emitting elements and light receiving elements disposed on both sides of the slit member 211. The amount of rotation of the shutter members 210a and 210b is detected by a pulse count value corresponding to the number of slits when read.

  More specifically, after the skew correction, as shown in FIG. 3B, the fixing of the stopper member 230 is released and the shutter members 210a and 210b are rotated by the pressing force of the sheet P. The shutter members 210a and 210b are applied with a biasing force in the direction opposite to the pressing force of the sheet P by the spring member 232, so the shutter members 210a and 210b have a holding force that resists the pressing force of the sheet P. And rotates while changing the load amount (drag force) according to the pressing amount of the sheet P. The pressing force of the sheet P is larger as the thickness of the sheet is thicker, and as the pressing force is larger, the amount of rotation of the shutter members 210a and 210b is larger and the amount of rotation of the slit member 211 is larger. The pushing force of the sheet P is detected by counting the number of slits of the slit member 211 corresponding to the amount of rotation by the optical sensor 240. If necessary, when the pressing force of the sheet P is detected, after the sheet P is fed by a fixed amount, the driving of the conveyance roller 201 may be stopped for a predetermined time until the pressing force end.

  After the detection of the pressing force of the sheet P, when the sheet P is conveyed to the nip portion of the registration rollers 202 and 203, the conveyance force by the registration rollers 202 and 203 is also added, and the shutter members 210a and 210b are in the state of FIG. The sheet P is transported. The conveyed sheet has the toner image transferred by the transfer roller 405, is fixed by the fixing device 500, and is discharged to the sheet discharge unit 600.

  When the sheet P completely passes through the skew correction / pushing force detection unit 200, the shutter members 210a and 210b return to the standby state of FIG. 3A by the biasing force of the spring member 232.

  Although the fixing and holding of the shutter members 210a and 210b and the release after the skew correction are performed by the stopper member 230 at the time of skew correction, the shutters at the time of skew correction are directly related to the shutter members 210a and 210b. The members 210a and 210b are held in the rotation preventing state, and when detecting the amount of rotation of the shutter members 210a and 210b, the holding is released and the shutter members 210a and 210b are rotated against the biasing force of the spring member 232 3A. After detection, the shutter members 210a and 210b are forced to rotate clockwise in FIG. 3 to be in the state of FIG. 3C, and after passing the sheet P, the biasing force of the spring member 232 causes FIG. It may be configured to return to the standby state of (A).

  FIG. 4 is a flow chart showing the operation of the image forming apparatus 1 when the paper type determination is performed using the skew correction / pushing force detection unit 200 shown in FIGS. 2 and 3.

  The operations shown in the flowcharts of FIG. 4 and the subsequent drawings are executed by the CPU 301 of the control unit 300 operating according to the operation program stored in the ROM 302 or the like.

  In step S01, it is determined whether conveyance of the sheet by the conveyance roller 201 is started, and if it is not started (NO in step S01), the process waits for the start. If it is started (YES in step S01), the stopper member 230 is fixed in step S12, and the shutter members 210a and 210b are not moved by the pressing force of the sheet P in the shutter members 210a and 210b (retention force 1 Hold).

  Next, in step S03, whether all the contact sensors 220 provided on the sheet contact portion of the shutter members 210a and 210b detect contact of the sheet P (whether all contact sensors 220 are on) to decide. If all the contact sensors 220 are not ON (NO in step S03), the process waits until all contact sensors 220 are ON.

  If all the contact sensors 220 are ON (YES in step S03), it is determined that skew correction is complete, and the process advances to step S04 to release fixing by the stopper member 230 and hold based on the biasing force of the spring member 232 The force (holding force 2) is held by the shutter members 210a and 210b. The holding force 2 is a holding force corresponding to a load amount that changes according to the movement amount (rotation amount) of the shutter members 210a and 210b, which is urged by the spring member 232. 210a and 210b become rotatable.

  Next, in step S05, the amount of movement of the shutter members 210a and 210b due to the pressing force of the sheet P is detected in a state where the sheet P is in contact, and then in step S06 the sheet type is determined based on the amount of movement. A table in which the correspondence relationship between the movement amount and the paper type is defined is stored in advance in a storage unit (not shown) in the image forming apparatus 1, and based on this table, the paper type corresponding to the detected movement amount is determined. Be done. The detection of the amount of movement may be performed for all the shutter members 210a and 210b, and the detection results may be averaged, or only one of the detection results may be used.

  Next, in step S07, process conditions for image formation are set according to the determined paper type. The process conditions may include, but not limited to, at least one of a transfer output at the time of transfer by the transfer roller 405, a sheet separation output, and a fixing temperature of the fixing device 500.

  In this embodiment, since the pressing force of the sheet P is detected as the amount of movement of the shutter members 210a and 210b and the sheet type is determined, the sheet P is immediately conveyed by the registration rollers 202 and 203 after skew correction. Compared to the case, the image writing position is shifted in the delay direction. Therefore, in step S08, in order to correct the deviation of the image position transferred to the sheet due to the movement of the shutter members 210a and 210b, the image writing position is set according to the movement amount of the shutter members 210a and 210b. By this correction, it is possible to write out the image from the same writing position as in the case where the pressing force detection of the paper P is not performed.

  Thereafter, in step S09, the sheet is conveyed by the registration rollers 202 and 203.

  FIG. 5 shows another embodiment of the present invention and is a cross-sectional view corresponding to FIG. In this embodiment, a pressure sensor 250 is provided at the sheet contact portion of the shutter members 210a and 210b, and the pressure sensor 250 detects contact of the sheet P and detects pressing force of the sheet P. .

  In the embodiment shown in FIG. 5, compared with the embodiment shown in FIG. 3, the slit member 211 in the shutter members 210a and 210b, the point that the optical sensor 240 is not provided, and the tips of the shutter members 210a and 210b. Since the configuration is the same as that of the embodiment of FIG. 3 except that the piezoelectric sensor 250 is provided instead of the contact sensor 220, the same components are denoted by the same reference numerals and detailed descriptions thereof will be omitted. . However, the pressing force detection of the sheet P performed by the piezoelectric sensor 250 can be performed even in the rotation preventing state of the shutter members 210a and 210b, and it is necessary to apply the holding force 2 to the shutter members 210a and 210b after skew correction. Because there is not, the biasing force of the spring member 232 may be weaker as compared with the embodiment of FIG.

  FIG. 5A shows a standby state in which the leading end of the sheet P is not yet in contact with the piezoelectric sensor 250, and the contact surface of the piezoelectric sensor 250 at the end of the shutter members 210a and 210b is driven by the drive resist roller 202 The sheet P is located on the upstream side of the nip portion of the registration roller 203 in the sheet conveyance direction, and the leading end of the sheet P abuts on the contact surface before it enters the nip portion. In this state, the shutter members 210a and 210b are prevented from rotating by the stopper member 230. Therefore, when the sheet P is skewed, the leading edge of the sheet P first comes in contact with either of the shutter members 210a and 210b, but not with the other shutter member. The leading side of the line waits for the late side, and the skew of the sheet is corrected.

  After completion of the skew correction, that is, when all the piezoelectric sensors 250 of the shutter members 210a and 210b detect the pressing force by the sheet P (turned on), the piezoelectric sensor 250 measures the pressing force of the sheet P. The pressure on the piezoelectric sensor 250 is larger as the thickness of the sheet is thicker, and the output of the piezoelectric sensor 250 is larger as the pressing force is larger.

  Thereafter, when the fixing of the stopper member 250 is released, as shown in FIG. 5B, the leading end of the sheet P pushes into the nip portion of the pair of registration rollers 202 and 203 while pushing the shutter members 210a and 210b. The conveyance force by 203 is also added, and the shutter members 210a and 210b are pushed up to the state of FIG. 5C, and the sheet P is conveyed. The conveyed sheet has the toner image transferred by the transfer roller 405, is fixed by the fixing device 500, and is discharged to the sheet discharge unit 600.

  When the sheet P completely passes through the skew correction / push force detection unit 200, the shutter members 210a and 210b return to the standby state shown in FIG. 3A by the biasing force of the spring member 232.

  FIG. 6 is a flow chart showing the operation of the image forming apparatus 1 when the paper type determination is performed using the skew correction / pushing force detection unit 200 shown in FIG.

  In step S11, it is determined whether conveyance of the sheet by the conveyance roller 201 or the like has been started. If it has not been started (NO in step S11), the process waits for the start. If it has been started (YES in step S11), in step S12, the stopper members 230 are fixed to hold the holding force that the shutter members 210a and 210b do not move by the pressing force of the sheet P.

  Next, in step S13, it is determined whether the contact of the sheet P is detected by all the piezoelectric sensors 250 provided on the sheet contact portion of the shutter members 210a and 210b (whether all the piezoelectric sensors 250 are on). . If all the piezoelectric sensors 250 are not on (NO in step S13), the process waits until all the piezoelectric sensors 250 are on.

  If all the piezoelectric sensors 250 are ON (YES in step S13), it is determined that the skew correction is completed, and the process proceeds to step S14, and the pressing force of the sheet P by the piezoelectric sensor 250 is detected.

  Next, in step S15, the paper type is determined based on the detected pressing force. A table in which the correspondence relationship between the pressing force and the paper type is defined is stored in advance in a storage unit (not shown) in the image forming apparatus 1, and based on the table, the paper type corresponding to the pressing force is determined. The detection of the pressing force is performed in the piezoelectric sensors 250 of all the shutter members 210a and 210b, the detection results are added or the average value is determined, and the paper type is determined based on these values. It is desirable in that it can absorb measurement variations and the like, and can perform highly accurate paper type determination. Also, the paper type may be determined based on the pressure transition within the measurement time.

  Next, in step S16, process conditions for image formation, such as transfer output, sheet separation output, fixing temperature of fixing device 500, etc., are set according to the determined paper type, and then fixing by stopper member 230 is performed in step S17. , And conveys the sheet by the resist rollers 202 and 203. The opening of the stopper member 230 may be performed after the measurement of the pressing force of the sheet at step S14 and before the sheet conveyance at step S17.

  FIG. 7 is a flowchart showing another operation of the image forming apparatus 1 when the paper type determination is performed using the skew correction / pushing force detection unit 200 shown in FIG. In this example, processing is included when skew correction can not be performed within a fixed time.

  In step S21, it is determined whether conveyance of the sheet by the conveyance roller 201 or the like is started, and if it is not started (NO in step S21), the process waits for the start. If it has been started (YES in step S21), in step S22, the stopper members 230 are fixed, and the holding force that the shutter members 210a and 210b do not move by the pressing force of the sheet P is held in the shutter members 210a and 210b.

  Next, in step S23, it is determined whether the contact of the sheet P is detected by all the piezoelectric sensors 250 provided on the sheet contact portion of the shutter members 210a and 210b (whether all the piezoelectric sensors 250 are on). .

  If all the piezoelectric sensors 250 are ON (YES in step S23), it is determined that the skew correction is completed, and the process proceeds to step S27, and the pressing force of the sheet P by the piezoelectric sensor 250 is detected.

  Next, in step S28, the paper type is determined based on the detected pressing force. The detection of the pressing force is performed in the piezoelectric sensors 250 of all the shutter members 210a and 210b, the detection results are added or the average value is determined, and the paper type is determined based on these values. It is desirable in that it can absorb measurement variations and the like, and can perform highly accurate paper type determination. Also, the paper type may be determined based on the pressure transition within the measurement time.

  Next, in step S29, process conditions for image formation, such as transfer output, sheet separation output, fixing temperature of fixing device 500, etc., are set according to the determined paper type, and then fixing by stopper member 230 in step S30. , And conveys the sheet by the resist rollers 202 and 203.

  In step S23, if all the piezoelectric sensors 250 are not ON (NO in step S23), the process proceeds to step S24, and it is determined whether any first piezoelectric sensor 250 is ON. If the first piezoelectric sensor 250 is not ON (NO in step S24), it is considered that the sheet P has not reached the shutter members 210a and 210b yet, so the process returns to step S23.

  If the first piezoelectric sensor 250 is ON (YES in step S24), it is checked in step S25 whether or not a predetermined time has elapsed since the first piezoelectric sensor 250 was turned ON. If the predetermined time has not elapsed (NO in step S25), the process returns to step S23.

  If the predetermined time has elapsed (YES in step S25), the process proceeds to step S26, the fixing by the stopper member 230 is released, and the sheet type for the immediately preceding sheet is set as the main sheet for the sheet, and then in step S29. move on. Therefore, in this case, the process conditions are set based on the sheet type of the previous sheet.

  Thus, in this embodiment, if all the piezoelectric sensors 250 do not turn on even after a predetermined time has passed since the first piezoelectric sensor 250 was turned on, the fixing by the stopper member 230 is released, and Since the sheet type of the sheet is set as the sheet type of the sheet, it is possible to prevent the occurrence of problems such as a sheet jam due to the skew correction exceeding the skew limit.

  As described above, in the embodiment of the present invention, the sheet P is applied to the plurality of shutter members 210a and 210b provided in the main scanning direction of the sheet P and stopping the conveyed sheet P for skew correction. Since a plurality of contact sensors 220 and piezoelectric sensors 250 for detecting contact are respectively attached, skew correction of the sheet P can be performed by the shutter members 210a and 210b. Moreover, the slit member 211 and the optical sensor 240 or the piezoelectric sensor 250 are pressing force detection means for detecting the pressing force at the time of sheet feeding to at least one of the plurality of shutter members 210a and 210b. Since it is not necessary to separately provide the shutter members 210a and 210b and the pressing force detection unit, the image forming apparatus can perform skew correction and sheet type determination with a simple configuration.

Reference Signs List 1 image forming apparatus 200 skew correction and pressing force detection unit 201 conveyance roller 202, 203 registration roller 210a, 210b shutter member 211 slit member 220 contact sensor 230 stopper member 231 lever 232 spring member 240 optical sensor 250 piezoelectric sensor 300 control unit 301 CPU
302 ROM
401 photosensitive drum 405 transfer roller 500 fixing device P paper

Claims (21)

A plurality of shutter members provided in the main scanning direction of the sheet and stopping the conveyed sheet for skew correction;
Contact detection means for detecting the contact of the sheet attached to each of the shutter members;
Pushing force detection means provided on at least one of the plurality of shutter members for detecting a pushing force at the time of sheet feeding;
A paper type determination unit that determines a paper type based on the pressing force detected by the pressing force detection unit;
An image forming apparatus comprising:   After detecting the contact of the sheet by the contact detecting means, the pressing state of the sheet is held and the pressing force is detected by the pressing force detecting means, and the sheet is allowed to pass through the shutter member after detecting the pressing force. The image forming apparatus according to claim 1, characterized in that   The paper type determination means performs the detection of the pressing force and the paper type determination from the timing when it is detected that the paper has abutted against the shutter member by all of the plurality of abutment detection means. The image forming apparatus according to 1 or 2.   The image forming apparatus according to any one of claims 1 to 3, wherein the pressing force detection unit detects the pressing force at the time of sheet feeding based on the amount of movement of the shutter member due to contact with the shutter member. .   The shutter member has a predetermined shutter holding force that regulates the sheet conveyance when the sheet is in contact, and the shutter holding force is a first shutter holding force until the sheet comes in contact with the shutter member and skew correction is completed. 5. The image forming apparatus according to claim 4, wherein the second shutter holding force until the pressing force of the sheet after skew correction is detected.   The image forming apparatus according to claim 5, wherein the first holding force is a holding force that does not move the shutter member by a pressing force of a sheet.   The image forming apparatus according to claim 5, wherein the second holding force is a holding force corresponding to a load amount that changes in accordance with a movement amount of the shutter member.   The image writing position setting means for setting the writing position of the image from the movement amount of the shutter member at the time of the paper type determination by the pressing force detecting means is further provided. Image forming apparatus as described.   The image forming apparatus according to any one of claims 4 to 8, wherein the movement amount of the shutter member is calculated by pulse counting by an optical sensor and a slit member.   The image forming apparatus according to any one of claims 1 to 9, wherein the contact detection of the sheet by the contact detection unit is performed by an electrostatic sensor.   The image forming apparatus according to any one of claims 1 to 10, wherein the pressing force detection unit detects the pressing force based on an amount of pressure of the sheet in contact with the shutter member.   12. The image forming apparatus according to claim 11, wherein the paper type determination unit determines the paper type based on at least two pressure amounts detected by the pressing force detection unit.   The image forming apparatus according to claim 11, wherein the amount of pressure is measured by a piezoelectric sensor.   After a contact is first detected by any of the plurality of contact detection means, if there is a contact detection means for which the contact detection has not been performed within a predetermined time, the sheet by the shutter member The image forming apparatus according to any one of claims 1 to 13, wherein the stop is released.   When the stop of the sheet by the shutter member is released, the sheet type determination means determines that the sheet type of the sheet determined immediately before is the sheet type of the sheet of which the stop has been released. 15. The image forming apparatus according to 14.   The image forming apparatus according to any one of claims 1 to 15, wherein process conditions for forming an image are set in accordance with a determination result after determination of a paper type by the paper type determination unit.   The image forming apparatus according to claim 16, wherein the process condition is a transfer output.   The image forming apparatus according to claim 16, wherein the process condition is a sheet separation output.   The image forming apparatus according to claim 16, wherein the process condition is a fixing temperature. The image forming apparatus
Stopping the conveyed sheet for skew correction by a plurality of shutter members provided in the main scanning direction of the sheet;
Detecting contact of the sheet by contact detection means attached to each of the shutter members;
Detecting a pressing force at the time of sheet feeding by pressing force detecting means provided on at least one of the plurality of shutter members;
A paper type determination step of determining a paper type based on the pressing force detected in the step of detecting the pressing force;
A paper type determination method characterized in that: To the computer of the image forming apparatus,
Stopping the conveyed sheet for skew correction by a plurality of shutter members provided in the main scanning direction of the sheet;
Detecting contact of the sheet by contact detection means attached to each of the shutter members;
Detecting a pressing force at the time of sheet feeding by pressing force detecting means provided on at least one of the plurality of shutter members;
A paper type determination step of determining a paper type based on the pressing force detected in the step of detecting the pressing force;
Paper type judgment program to execute.

Images