JP2021134065A - Sheet discrimination device, control method and image formation device - Google Patents

Abstract

To provide a sheet discrimination device for discriminating a kind of a conveyed sheet.SOLUTION: This sheet discrimination device comprises: a gate which changes from a first attitude of maintaining a direction for regulating traveling of a sheet by being energized by an energization member to a second attitude of retreating from a conveyance passage of the sheet by rushing of the sheet, and, by the change of the strength of the stiffness of the sheet applied to the energization member during passage of the sheet, restores from the second attitude to the first attitude; a sensor for detecting the change of the attitude of the gate; and a sheet discrimination circuit 112 which measures time to a time point of restoring to the first attitude with a time point where the gate changes from the first attitude to the second attitude as a reference during conveyance of the sheet, and discriminates a kind of the sheet in accordance with the length of the measured time.SELECTED DRAWING: Figure 8

Description

The present disclosure relates to a technique for determining the type of sheet.

As a sheet to be conveyed along the transfer path of the image forming apparatus, there are sheets having different basis weights such as plain paper and thick paper. When transporting different types of sheets, it is necessary to adjust the image formation conditions according to the type of sheet in order to avoid deterioration of image quality, poor fixing, and the like.

According to Patent Document 1, when passing paper through a curved transport path, the sheet is transported in the curved transport path by utilizing the characteristic that the thick thick paper is transported along the outer peripheral side of the curved transport path. A sheet detection device having a sheet detection flag for detecting each of a plurality of transport areas to be transported and a CPU for determining the type of sheet to be transported based on the result detected by the sheet detection flag is disclosed.

In this way, the image formation conditions are set according to the type of the determined sheet.

JP-A-2017-206383

However, according to Patent Document 1, the sheet discriminating device must be arranged in the curved transport path, and the degree of freedom in design is low. Therefore, for example, there is a problem that it cannot be applied to an image forming apparatus that does not have a curved transport path.

One aspect of the present disclosure is a sheet discriminating device capable of discriminating the type of sheet to be transported regardless of whether or not the arranged transport path is curved, a control method for controlling the sheet discriminating device, and a sheet discriminating device. It is an object of the present invention to provide an image forming apparatus provided with the apparatus.

One aspect of the present disclosure is a sheet discriminating device for discriminating the type of sheet to be conveyed, from a first posture in which the seat is urged by an urging member to maintain a direction for restricting the progress of the sheet, and by plunging the sheet. , A gate that changes to a second posture that retracts from the transport path of the seat and returns from the second posture to the first posture due to a change in the waist strength of the seat that is given to the urging member while the seat is passing. , The sensor that detects the change in the posture of the gate, and the time until the gate returns to the first posture with reference to the time when the gate changes from the first posture to the second posture while the seat is being conveyed. It is characterized by including a measuring unit for measuring the number of sheets and a discriminating unit for discriminating the type of sheet according to the length of the measured time.

Here, the discriminating unit compares the calculated length calculated by multiplying the conveying speed of the sheet by the measured time with the paper type threshold value according to the size set for the sheet. The type of sheet may be determined.

Here, when the calculated length is larger than the paper type threshold value, the discriminating unit determines that the sheet is the first type of thick paper, and when the calculated length is smaller than or equal to the paper type threshold value. It may be determined that the sheet is a second type of plain paper.

Here, further, there is an upper limit threshold value, and the upper limit threshold value is larger than the paper type threshold value, and the discriminating unit determines whether the calculated length is larger than the paper type threshold value and the calculated length is smaller than the upper limit threshold value. Alternatively, if they are equal, it may be determined that the sheet is the first type of thick paper, and if the calculated length is larger than the upper threshold value, it may be determined that there is a size error.

Here, further, there is a lower limit threshold value, the lower limit threshold value is smaller than the paper type threshold value, and the discriminant unit determines whether the calculated length is larger than the lower limit threshold value and the calculated length is smaller than the paper type threshold value. Alternatively, if they are equal, it may be determined that the sheet is a second type of plain paper, and if the calculated length is smaller than or equal to the lower threshold value, it may be determined that there is a size error.

Here, there are further an upper limit threshold value and a lower limit threshold value, the upper limit threshold value is larger than the paper type threshold value, the paper type threshold value is larger than the lower limit threshold value, and the discriminating unit has the calculated length of the paper type threshold value. When it is larger and the calculated length is smaller than or equal to the upper limit threshold value, it is determined that the sheet is the first type of thick paper, the calculated length is larger than the lower limit threshold value, and the calculated length is larger. If it is smaller than or equal to the paper type threshold value, it is determined that the sheet is a second type of plain paper, and the calculated length is larger than the upper limit threshold value, or the calculated length is smaller than the lower limit threshold value. Or, if they are equal, it may be determined that there is a size error.

Further, one aspect of the present disclosure is an image forming apparatus for forming an image, characterized in that the sheet discriminating apparatus is provided.

Here, the image forming apparatus includes a plurality of cassettes accommodating the sheets and a resist unit for correcting the skew of the sheets to be conveyed, and from a position where the plurality of paper feed paths from the plurality of cassettes merge. The gate and the sensor included in the sheet discriminating device may be arranged between the resist portion and the resist portion.

Here, the image forming apparatus includes a resist unit having a gate for correcting the skew of the conveyed sheet, and the gate of the resist unit and the gate of the sheet discriminating device are integrated. It may be.

Further, one aspect of the present disclosure is an image forming apparatus for forming an image, which includes the above-mentioned sheet discriminating device, a cassette for accommodating sheets, and an operation panel for receiving input from a user. , The operation panel receives an input of the sheet size from the user, and the sheet discriminating device stores the paper type threshold value corresponding to the sheet size. The discriminating unit is characterized by reading out a paper type threshold value corresponding to the size of the detected or input sheet.

Further, one aspect of the present disclosure is an image forming apparatus for forming an image, in which a size sensor for detecting the size of a sheet in a sheet conveying path, the above-mentioned sheet discriminating device, and an inclination of the conveyed sheet. A resist unit having a gate for correcting rows is provided, and the gate of the resist unit and the gate of the sheet discriminating device are integrated, and the sheet discriminating device corresponds to the size of the sheet. The paper type threshold is stored, and the discriminating unit reads out the paper type threshold corresponding to the sheet size detected by the size sensor.

Further, one aspect of the present disclosure changes from a first posture in which the seat is urged by an urging member to maintain a direction for restricting the progress of the seat to a second posture in which the seat is retracted from the transport path due to the rushing of the seat. A gate that returns from the second posture to the first posture due to a change in the waist strength of the seat given to the urging member while the seat is passing, and a sensor that detects the change in the posture of the gate. It is a control method used in a sheet discriminating device for discriminating the type to which a sheet to be transported belongs, and is based on a time point at which the gate changes from the first posture to the second posture during sheet transportation. It is characterized in that the time until the time when the posture returns to the first posture is measured, and the type of the seat is determined according to the measured length of the time.

According to the above aspect, it is possible to determine the type of sheet to be conveyed regardless of whether or not the conveyed transfer path to be arranged is curved, which is an excellent effect.

It is a figure which shows the schematic structure of the image forming apparatus 10 as one Embodiment. It is a perspective view which shows the structure of the skew correction part 40. It is an exploded view of the skew correction part 40 when the 2nd resist roller 52 is removed. (A) It is sectional drawing of the movable claw part 640. (B) It is sectional drawing of the movable claw part 630. (C) It is sectional drawing of the movable claw part 630 before the tip of the sheet reaches. (D) It is sectional drawing of the movable claw part 630 while passing a sheet. (E) It is sectional drawing of the movable claw part 630 after the rear end of a sheet has passed. (F) Indicates a state in which the shielding portion 634 does not exist in the gap 556. (G) Indicates a state in which the shielding portion 634 exists in the gap 556. (A), (b) shows the process of correcting the skew of the sheet. (A) to (f) Show the state (posture) of the stopper 632 according to the passage of the sheet. The sensor ON time in each case of (a) and (b) plain paper and thick paper is shown. It is a block diagram which shows the structure of the control circuit 100. The first threshold value, the second threshold value and the third threshold value used for determining the type of the sheet are shown. It is a flowchart which shows the whole operation in an image forming apparatus 10. It is a flowchart which shows the operation of the print processing in an image forming apparatus 10.

1 Embodiment An embodiment of the present disclosure will be described with reference to the drawings.

1.1 Image forming apparatus 10
As shown in FIG. 1, the image forming apparatus 10 is a tandem type color multifunction device (MFP: Multifunction Peripheral) having the functions of a scanner, a printer, and a copier.

In the figure, the left-right direction when the image forming apparatus 10 is viewed from the front is the X-axis direction, the vertical direction is the Y-axis direction, and the direction orthogonal to both the X-axis and the Y-axis is the Z-axis direction.

As shown in this figure, the image forming apparatus 10 is configured by providing a paper feeding unit 13 for accommodating and feeding a sheet at the bottom of the housing. A printer 12 that forms an image by an electrophotographic method is provided above the paper feed unit 13. Above the printer 12, an image reader 11 that reads a document and generates image data, and an operation panel 19 that displays an operation screen and accepts an input operation from a user are provided.

The image reader 11 has an automatic document transfer device. The automatic document transfer device transfers the documents set in the document tray one by one to the document glass plate. The image reader 11 reads the document transported to a predetermined position on the document glass plate by the automatic document transport device or the image placed on the document glass plate by the user by moving the scanner, and red (R). Image data composed of multi-valued digital signals of green (G) and blue (B) is obtained.

The image data of each color component obtained by the image reader 11 undergoes various data processing in the control circuit 100, and further, the reproduced colors of yellow (Y), magenta (M), cyan (C), and black (K) are reproduced. Converted to image data.

The printer 12 has an intermediate transfer belt 21, a drive roller for tensioning the intermediate transfer belt 21, a driven roller, a backup roller 25, a secondary transfer roller 22, a belt cleaning device 26, and an intermediate transfer belt 21 facing the intermediate transfer belt 21. The image forming portions 20Y, 20M, 20C, 20K, the fixing portion 30, the control circuit 100, and the like are arranged at predetermined intervals along the traveling direction X of the above.

Each image forming unit includes a photoconductor drum which is an image carrier, an LED array for exposure-scanning the surface of the photoconductor drum, a charging charger, a developing device, a cleaner, a primary transfer roller, and the like.

The paper feed unit 13 includes paper feed cassettes 60, 61, 62 for accommodating sheets of different sizes, and pickup rollers 63, 64, 65 for feeding the sheets from the paper feed cassettes to the transport path. .. Various sheets such as plain paper and thick paper are housed in the paper feed cassettes 60, 61, and 62. Here, the basis weight of plain paper is, for example, 60 g / m ² , and the basis weight of thick paper is, for example, 100 g / m ² .

In each of the image forming portions 20Y to 20K, each photoconductor drum is uniformly charged by a charging charger and exposed by an LED array to form an electrostatic latent image on the surface of the photoconductor drum. Each electrostatic latent image was developed by a developer of each color, a toner image of colors Y to K was formed on the surface of each photoconductor drum, and the toner image was arranged on the back surface side of the intermediate transfer belt 21. By the electrostatic action of each primary transfer roller, the intermediate transfer belt 21 is sequentially transferred onto the surface.

On the other hand, for example, the pickup roller 63 for feeding out the sheets one by one from the paper feed cassette 60 and the sheet skewing according to the image drawing operation by the image forming units 20Y to 20K from any of the paper feed cassettes 13. The sheet is fed via the skew correction unit 40 for correcting (skew) and other transport rollers, and the secondary transfer roller 22 and the backup roller 25 face each other with the intermediate transfer belt 21 interposed therebetween. Will be transported to. When the user accommodates the sheet in the paper feed cassette, the size of the sheet is detected by the rear end regulation plate provided on the paper feed cassette.

The sheet on which the Y to K color toner images are secondarily transferred is further conveyed to the fixing portion 30. When the toner image transferred to the surface of the sheet passes through the fixing nip formed between the heating roller 31 of the fixing portion 30 and the pressure roller 32 pressed against the heating roller 31, the sheet is heated and pressed. The sheet is fused and fixed to the surface of the sheet, and after passing through the fixing portion 30, the sheet is sent to the discharge tray 15.

An inversion tray 16 is installed above the output tray 15. When double-sided printing is performed, the sheet whose front surface is printed is switched back on the reversing tray 16. The sheet is conveyed to the skew correction unit 40 in a posture in which the front surface and the back surface are reversed via the transfer path 39, and then an image is formed on the back surface of the sheet.

The operation panel 19 is provided with a display unit composed of a liquid crystal display board or the like, and displays contents set by the user and various messages. The operation panel 19 receives an instruction to start copying, a setting of the number of copies, a setting of copying conditions, a setting of a data output destination, a setting of a sheet size, etc. from the user, and notifies the control circuit 100 of the received contents. ..

1.2 Skew correction unit 40
The skew correction unit 40 corrects the skew of the sheet to be conveyed.

FIG. 2 is a perspective view showing the configuration of the skew correction unit 40 when the skew correction unit 40 is viewed from the direction of arrow A in FIG.

As shown in FIG. 2, the skew correction unit 40 is composed of a first resist roller 51 and a second resist roller 52 provided so as to be parallel to the axial direction of the first resist roller 51. It is provided with a pair of 50, and further includes a gate portion 600 (FIG. 3) attached to the shaft of the first resist roller 51.

FIG. 3 is an exploded view of the skew correction unit 40 when the second resist roller 52 is removed.

(1) First resist roller 51 and second resist roller 52
As shown in FIG. 2, in the first resist roller 51, the roller bodies 511, 512, and 513 are fixed around the rotating shaft 510 rotatably supported by the bearing 514. Further, in the second resist roller 52, the roller main bodies 521, 522, and 523 are fixed around the rotating shaft 520 rotatably supported by the bearing 524.

The second resist roller 52 is urged in the direction of arrow F (FIG. 2) by a compression coil spring (not shown). By this urging, each of the roller bodies 521, 522, and 523 of the second resist roller 52 is pressed against the corresponding roller bodies 511, 512, and 513 of the first resist rollers 51. The roller bodies 511, 512, 513 and the roller bodies 521, 522, and 523 come into contact with each other to form the nip 341. The sheet fed and conveyed by the pickup roller 63 passes through the nip 341.

The first resist roller 51 rotates by transmitting the rotational driving force of the drive motor 81 shown in FIG. 1 via the electromagnetic clutch 82. When each color toner image superimposed on the intermediate transfer belt 21 moves toward the secondary transfer nip 23 due to the orbital running of the intermediate transfer belt 21, the resist roller pair 50 moves the resist roller pair 50 to the drive motor 81 via the electromagnetic clutch 82. The rotational drive is started by receiving the rotational drive force, and the sheet engaged in the nip 341 is sent out toward the secondary transfer nip 23.

(2) Gate 600
As shown in FIG. 3, the set of the movable claw portion 610 and the movable claw portion 620 attached to the mounting plate 615 and urged by the torsion spring 616 is rotatably freed on the rotating shaft 510 of the first resist roller 51. It is inserted. Further, between the movable claw portion 610 and the movable claw portion 620, a pair of the movable claw portion 630 and the movable claw portion 640 attached to the mounting plate 617 and urged by the torsion spring 618 is rotatably placed. 1 It is loosely inserted into the rotating shaft 510 of the resist roller 51. The mounting plate 615, the torsion spring 616, the mounting plate 617, the torsion spring 618, and the movable claw portions 610 to 640 constitute the gate portion 600.

(A) Movable claws 610 to 640
The movable claw portion 610 is a gate resist type gate member.

As shown in FIG. 3, in the movable claw portion 610, a claw-shaped stopper 612 that protrudes in the radial direction from the outer peripheral surface of the annular shape portion 611 is provided, and on the outer peripheral surface, on the side opposite to the stopper 612. , A protruding plate-shaped holding portion 613 is provided.

From the inner peripheral surface of the ring-shaped portion 611, a ring-shaped rib (not shown) projects toward the center of the through hole 611a of the ring-shaped portion 611. The ring-shaped rib makes contact with the rotating shaft 510 without a gap while keeping the contact area of the first resist roller 51 with the outer peripheral surface of the rotating shaft 510 small. By reducing the contact area between the ring-shaped portion 611 and the rotating shaft 510, the ring-shaped portion 611 functions as a slide bearing for the rotating shaft 510 of the resist roller pair 50. The stopper 612 is formed with a contact surface for the seat. When the sheet comes into contact with the stopper 612, the ring-shaped portion 611 of the movable claw portion 610 rotates around the rotation axis 510 of the first resist roller 51, so that the stopper 612 has a transport path as shown in FIG. It protrudes to 38 and retracts from the transport path 38.

The movable claw portions 620 and 640 have the same configuration as the movable claw portion 610. The movable claw portion 620 includes a ring-shaped portion 621, a stopper 622, and a holding portion 623. Further, the movable claw portion 640 also includes an annular shape portion 641, a stopper 642, and a holding portion 643 (FIG. 4A).

On the other hand, of the movable claw portions 610 to 640, the movable claw portion 630 arranged at the center of the rotation shaft 510 of the first resist roller 51 has an annulus-shaped portion 631 and a stopper 632 as shown in FIG. 4 (b). In addition to the holding portion 633, a shielding portion 634 that protrudes in the circumferential direction from the holding portion 633 of the ring-shaped portion 631 is provided. The shielding portion 634 blocks the light emitted from the light emitting element 551 of the sensor 550, which will be described later, by rotating the movable claw portion 630 around the rotation shaft 510 of the first resist roller 51 during the transfer of the sheet. Or, make it transparent.

The stopper 632 (gate) is urged by the torsion spring 618 (urging member) to maintain the first posture and hinder the advance of the seat, that is, regulate the advance of the seat (FIGS. 4 (c), (e). )etc). Further, the stopper 632 allows the seat to advance when the pressing force received from the advancing seat exceeds the urging force of the torsion spring 618 due to the entry of the seat, that is, the posture is changed to the second posture in which the stopper 632 retracts from the transport path of the seat. (Fig. 4 (d), etc.). Further, the stopper 632 increases the waist strength of the seat to the torsion spring 618 due to the change in the waist strength of the seat given to the torsion spring 618 which is a biasing member during the passage of the seat, particularly in the latter half of the seat. When it falls below the urging force of, it returns to the first posture (Fig. 6 (d), etc.). The stoppers 642, 612, and 622 (gates) are the same as those of the stopper 632.

(B) Mounting plates 615, 617
As shown in FIG. 3, the mounting plate 615 is attached to the holding portions 613 and 623 by the screws 613a and 623a. The mounting plate 615 holds the movable claws 610 and 620 in the same direction, and the movable claws 610 and 620 keep the angles around the rotation shaft 510 common to each other.

Similarly, the mounting plate 617 is also attached to the holding portions 633 and 643 by the screws 633a and 643a. The mounting plate 617 holds the movable claws 630 and 640 in the same direction, and the movable claws 630 and 640 keep the angles around the rotation shaft 510 common to each other.

(C) Twist springs 616, 618
As shown in FIG. 2, the torsion spring 616 has a coil one end 616a fixed to the frame 54a of the housing bottom plate in a state where one end of the rotating shaft 510 is loosely inserted inside the coil of the torsion spring 616, and the coil other end 616b. Is fixed to the hook 615f of the mounting plate 615.

When the movable claw portions 610 and 620 and the mounting plate 615 are integrated and rotate around the rotating shaft 510, the torsion spring 616 expands and contracts with the displacement of the mounting plate 615. The restoring force of the torsion spring 616 acts in the direction of rotating the movable claws 610 and 620 in the clockwise direction of the arrow G in FIG. When the movable claws 610 and 620 are rotated by the restoring force of the torsion spring 616, the axial one end 615a of the mounting plate 615 hits the frame 54b of the side wall of the housing, so that further rotation is prevented and the movable claws 610 are prevented from further rotation. , 620 is stationary.

Like the torsion spring 616, the torsion spring 618 has one end of the rotating shaft 510 loosely inserted inside the coil, one end of the coil 618a is fixed to the frame 54d erected on the bottom plate of the housing, and the other end of the coil 618b is attached. It is fixed to the hook 617f of the plate 617. When the movable claws 630 and 640 are rotated by the restoring force of the torsion spring 618, the axial one end 617a of the mounting plate 617 hits the frame 54c of the side wall of the housing, so that further rotation is prevented and the movable claws 630 are prevented from further rotation. , 640 is in a stationary state.

Here, the force at the time of mounting the torsion springs 616 and 618 may be, for example, 0.5N.

(D) Sensor 550
The sensor 550 detects a posture change between the first posture and the second posture at the stopper 632 (gate) as shown below.

As shown in FIGS. 4 (f) and 4 (g), the sensor 550 is fixed to the frame 553 of the housing and emits light at a position where the light emitting element 551 and the light emitted by the light emitting element 551 are received. It is fixed to the frame 554 of the housing and includes a light receiving element 552 that receives the light emitted by the light emitting element 551.

The distance between the light emitting element 551 and the light receiving element 552 is provided to be larger than the thickness of the shielding portion 634 of the movable claw portion 630.

As shown in FIG. 4 (g), when the shielding unit 634 exists in the gap 556 between the light emitting element 551 and the light receiving element 552, the light emitted from the light emitting element 551 is blocked by the shielding unit 634. Therefore, the light receiving element 552 does not detect light. On the other hand, as shown in FIG. 4 (f), when the shielding unit 634 does not exist in the gap 556 between the light emitting element 551 and the light receiving element 552, the light emitted from the light emitting element 551 is blocked by the shielding unit 634. Without the light receiving element 552, the light receiving element 552 detects the light.

As shown in FIG. 4C, the light receiving element 552 detects the light emitted from the light emitting element 551 before the tip of the conveyed sheet S reaches the stopper 632.

Generally, as shown in FIG. 4D, when the tip of the sheet abuts on the stopper 632 and the movable claw portion 630 starts rotating around the rotation axis 510 in the counterclockwise direction of the figure, the light emitting element The light emitted from 551 is blocked by the shielding unit 634, and the light receiving element 552 does not detect the light.

As shown in FIG. 4 (e), when the rear end of the seat passes through the stopper 632, the movable claw portion 630 rotates around the rotation axis 510 in the opposite direction (counterclockwise in the figure), and the stopper 632 Returns to its original position. At this time, the light receiving element 552 detects the light emitted from the light emitting element 551.

The position (posture) of the stopper 632 in FIGS. 4 (c) and 4 (e) is referred to as a first position (first posture). On the other hand, the position (posture) of the stopper 632 in FIG. 4D is referred to as a second position (second posture).

The sensor 550 transmits a detection signal that changes with time to the sheet discrimination circuit 112 of the printer control circuit 109, which will be described later. The detection signal is ON in the time zone when the light receiving element 552 is detecting light, and is OFF in the time zone when the light receiving element 552 is not detecting light.

1.3 Sheet skew correction The sheet skew correction will be described with reference to FIGS. 5 (a) and 5 (b). 5 (a) and 5 (b) are schematic views when the first resist roller 51 is viewed from a direction orthogonal to the sheet transport path, and the rotary shaft 510, the roller main bodies 511 to 513, and the movable claw portion are shown. 610, 620, 630 and 640 are extracted and shown.

FIG. 5A shows a state in which the right corner R1 of the seat S1 is about to enter in the preceding oblique posture as compared with the left corner L1.

As shown in FIG. 5B, when the right corner R1 of the sheet S1 abuts against the stopper 642, the sheet S1 receives a transfer resistance from the movable claw portion 640, and the transfer speed of the right corner R1 decreases. Therefore, the seat S1 advances so that the left corner L1 catches up with the right corner R1. As a result, in FIG. 5B, the oblique posture of the sheet S1 is corrected, and the sheet S1 faces the transport direction as shown by the alternate long and short dash line.

As described above, the skew of the sheet is corrected.

1.4 State (posture) of stopper 632 according to the passage of the sheet
The state (posture) of the stopper 632 that changes according to the passage of the sheet will be described with reference to FIGS. 6 (a) to 6 (f).

As shown in FIG. 6A, the stopper 632 is in the first position before the plain paper S3 reaches the stopper 632.

Further, as shown in FIGS. 6 (b) and 6 (c), the stopper 632 is in the second position while the plain paper S3 passes through the stopper 632.

Next, as shown in FIG. 6D, the stopper 632 is in the first position immediately before the rearmost end S3a of the plain paper S3 passes through the stopper 632. This is because the plain paper S3 has a weak waist, and the rearmost end S3a of the plain paper S3 cannot withstand the restoring force of the torsion spring 618. The stopper 632 restores from the second position to the first position.

In this case, as shown in FIG. 7A, when the stopper 632 is restored from the second position to the first position (time 201b), the detection signal of the sensor 550 is turned off. Therefore, the time 201 from the time 201a to the time 201b is measured as the ON time (required time) of the sensor 550.

On the other hand, as shown in FIG. 6E, the stopper 632 is in the second position immediately before the rearmost end S4a of the thick paper S4 passes through the stopper 632. This is because the thick paper S4 is stiff and the stopper 632 does not return to the first position even by the restoring force of the torsion spring 618.

As shown in FIG. 6 (f), after the rearmost end S4a of the thick paper S4 has passed through the stopper 632, the stopper 632 is restored from the second position to the first position.

In this case, as shown in FIG. 7B, when the stopper 632 is restored from the second position to the first position (time 202b), the detection signal of the sensor 550 is turned off. Therefore, the time 202 from the time 202a to the time 202b is measured as the ON time (required time) of the sensor 550.

As described above, the timing at which the stopper 632 is restored from the second position to the first position differs on the rear end side of the sheet depending on whether the sheet is plain paper or thick paper.

In other words, the time required from the time when the stopper 632 changes from the first position to the second position to the time when the stopper 632 is restored from the second position to the first position differs depending on whether the sheet is plain paper or thick paper. ..

Here, regardless of whether the sheet is plain paper or thick paper, the length of the sheet in the transport direction does not change as long as it has the same size.

However, when the sheet transport speed is constant, the length of the sheet in the transport direction is calculated by multiplying the transport speed by the required time, and the calculated length depends on whether the sheet is plain paper or thick paper. It will be different. Here, the length in the transport direction of the sheet calculated by the transport speed × the required time using the detected required time and the transported speed is referred to as a detected sheet length in order to distinguish it from the actual sheet length.

1.5 Control circuit 100
As shown in FIG. 8, the control circuit 100 includes a CPU 101, a ROM 102, a RAM 103, an image memory 104, an image processing circuit 105, a network communication circuit 106, a scanner control circuit 107, an input / output circuit 108, a printer control circuit 109, and a storage circuit 110. And so on.

The CPU 101, ROM 102, and RAM 103 constitute the main control unit 101a.

The RAM 103 temporarily stores various control variables, the number of copies set by the operation panel 19, and provides a work area when the program is executed by the CPU 101.

The ROM 102 stores a control program for executing various jobs such as a copy operation.

The CPU 101 operates according to the control program stored in the ROM 102.

When the CPU 101 operates according to the control program, the main control unit 101a has an image memory 104, an image processing circuit 105, a network communication circuit 106, a scanner control circuit 107, an input / output circuit 108, a printer control circuit 109, a storage circuit 110, and the like. Is controlled in a unified manner.

As described above, the control circuit 100 is a computer system including a microprocessor and a memory. The memory stores the computer program, and the microprocessor operates according to the computer program. Here, a computer program is configured by combining a plurality of instruction codes indicating instructions to a computer in order to achieve a predetermined function.

Further, the main control unit 101a receives the user's operation from the operation panel 19. When the user's operation is, for example, a print instruction, the main control unit 101a causes the printer control circuit 109 to execute the image forming process. When the user's operation is to set the sheet size, the main control unit 101a writes the sheet size for which the setting has been received to the storage circuit 110. When the user's operation is another instruction, the main control unit 101a causes the other processing to be executed.

The image memory 104 temporarily stores image data such as a print job.

The image processing circuit 105, for example, performs various data processing on the image data of each color component obtained by the image reader 11 and converts the image data into image data of each reproduced color of Y, M, C, and K.

The network communication circuit 106 accepts a print job from an external terminal device such as a PC (personal computer) via a network such as a LAN.

The scanner control circuit 107 controls the image reader 11 to execute the operation of reading the image of the original.

The input / output circuit 108 relays the transmission and reception of information between the operation panel 19 and the main control unit 101a.

The printer control circuit 109 and the storage circuit 110 will be described below.

1.6 Storage circuit 110
The storage circuit 110 includes an area for storing the sheet size 121. Further, the storage circuit 110 has a first threshold value (upper limit threshold value), a second threshold value (paper type threshold value), and a third threshold value (lower limit threshold value) for each length (set sheet length) in the transport direction of a plurality of types of sheets. I remember. As an example, the first threshold value 122, the second threshold value 123, and the third threshold value 124 stored in the storage circuit 110 shown in FIG. 8 correspond to the length “297 mm” of the “A4” size sheet in the transport direction. There is.

Here, the sheet size 121 is the size of the sheet selected by the user on the setting screen displayed on the operation panel 19. The sheet size 121 is, for example, "A3", "A4", "B4", "B5", or the like. Further, the sheet size 121 may be the size of the sheet detected by the rear end regulation plate provided on the paper feed cassette when the user accommodates the sheet in the paper feed cassette.

Further, the first threshold value 122, the second threshold value 123, and the third threshold value 124 are threshold values used for determining whether the type of the sheet is plain paper or thick paper by using the above-mentioned detection sheet length. ..

FIG. 9 shows a first threshold value, a second threshold value, and a third threshold value used for determining the type of sheet. In this figure, the vertical axis indicates the detection sheet length.

As shown in this figure, the second threshold value 123 (paper type threshold value) is a boundary value for separating plain paper and thick paper. The first threshold value 122 (upper limit threshold value) is a boundary value that distinguishes between thick paper and a size error. Further, the third threshold value 124 (lower limit threshold value) is a boundary value that distinguishes between plain paper and a size error. Further, the size 221 is the size of plain paper as an example, and the size 222 is the size of thick paper as an example.

If the detection sheet length is larger than the first threshold value 122, it is a size error.

When the detection sheet length is equal to or smaller than the first threshold value 122 and the detection sheet length is larger than the second threshold value 123, the sheet is thick paper.

When the detection sheet length is equal to or smaller than the second threshold value 123 and the detection sheet length is larger than the third threshold value 124, the sheet is plain paper.

If the detection sheet length is equal to or smaller than the third threshold value 124, it is a size error.

1.7 Printer control circuit 109
As shown in FIG. 8, the printer control circuit 109 includes a printer main control circuit 111, a sheet discrimination circuit 112, and the like.

Like the control circuit 100, the printer control circuit 109 is also composed of a CPU, a ROM, a RAM, and the like.

The RAM temporarily stores various control variables and the like, and provides a work area when a program is executed by the CPU. The ROM and RAM store a control program for executing various jobs such as a print operation. The CPU operates according to a control program stored in the ROM or RAM.

When the CPU operates according to the control program stored in the ROM or RAM, the CPU, ROM, and RAM functionally constitute the printer main control circuit 111 and the sheet discrimination circuit 112.

(1) Printer main control circuit 111
The printer main control circuit 111 uniformly controls the feeding operation from the paper feeding unit 13 and the image forming operation of the image forming units 20Y to 20K of the printer 12, and executes the image forming operation.

Further, the printer main control circuit 111 controls the sheet discrimination circuit 112.

Further, the printer main control circuit 111 receives the detection result of the sheet type from the sheet discrimination circuit 112. The detection results include thick paper, plain paper, and size errors as sheet types.

Upon receiving the detection result that the sheet type is plain paper from the sheet discrimination circuit 112, the printer main control circuit 111 sets the image formation conditions in the case of plain paper. For example, the secondary transfer voltage, fixing temperature, etc. are set as image formation conditions in the case of plain paper. When the post-processing device is connected to the image forming device 10, the post-processing (matching, staple, punch) setting in the post-processing device may be set to the conditions for plain paper. The printer main control circuit 111 causes the printer 12 to perform image formation according to the set image formation conditions and the like.

Further, when the sheet discrimination circuit 112 receives the detection result that the sheet type is thick paper, the printer main control circuit 111 sets the image formation condition in the case of thick paper. For example, the secondary transfer voltage, fixing temperature, etc. are set as image formation conditions in the case of thick paper. When the post-processing device is connected to the image forming device 10, the post-processing (matching, staple, punch) setting in the post-processing device may be set to the conditions for thick paper. The printer main control circuit 111 causes the printer 12 to perform image formation according to the set image formation conditions.

On the other hand, when a size error is received from the sheet discrimination circuit 112 as a detection result, the printer main control circuit 111 performs processing at the time of the size error. Specifically, the printer main control circuit 111 causes the printer 12 to stop the sheet transfer, stop the image formation, and display an error message indicating a size error on the operation panel 19.

(2) Sheet discrimination circuit 112
The sheet discrimination circuit 112 stores the length of the sheet in the transport direction (set sheet length) for each of a plurality of types of sheet sizes. For example, when the sheet size is "A4", the sheet discrimination circuit 112 stores "297 mm" as the set sheet length.

The sheet discrimination circuit 112 includes a time measuring device for measuring time.

The sheet discrimination circuit 112 reads the sheet size 121 from the storage circuit 110, and detects the set sheet length corresponding to the read sheet size 121. For example, when the sheet size 121 is "A4", the sheet discrimination circuit 112 detects the set sheet length "297 mm" corresponding to the size "A4" from the stored set sheet length.

The sheet discrimination circuit 112 selects three sets of threshold values from the storage circuit 110 according to the detected set sheet length. For example, the sheet discrimination circuit 112 selects the first threshold value 122, the second threshold value 123, and the third threshold value 124 for the set sheet length “297 mm”.

The seat discrimination circuit 112 receives a detection signal from the sensor 550 while the seat is being conveyed. The sheet discrimination circuit 112 (measurement unit) is the time required from the first time point when the detection signal is changed from OFF to ON to the second time point when the time measurement device is changed from ON to OFF (sensor 550). ON time) is measured. That is, the seat discrimination circuit 112 measures the time required from the time when the stopper 632 (gate) changes its posture from the first posture to the second posture to the time when it returns to the first posture while the seat is being conveyed.

Next, the sheet discrimination circuit 112 discriminates the type of the sheet according to the length of the measured required time as shown below.

The sheet discrimination circuit 112 calculates the detection sheet length from the sheet transport speed and the measured required time.

When the detection sheet length = transport speed × required time is calculated, the sheet discrimination circuit 112 (discrimination unit) compares the detection sheet length with the first threshold value 122, the second threshold value 123, and the third threshold value 124.

When the detection sheet length is larger than the first threshold value 122, the sheet determination circuit 112 determines that a size error has occurred.

When the detection sheet length is equal to or smaller than the first threshold value 122 or smaller than the first threshold value 122 and the detection sheet length is larger than the second threshold value 123, the sheet discrimination circuit 112 determines that the sheet is thick paper.

When the detection sheet length is equal to or smaller than the second threshold value 123 or smaller than the second threshold value 123 and the detection sheet length is larger than the third threshold value 124, the sheet discrimination circuit 112 determines that the sheet is plain paper.

When the detection sheet length is equal to or smaller than the third threshold value 124, the sheet determination circuit 112 determines that a size error has occurred.

Here, the sheet discriminating circuit 112, the sensor 550, and the movable claw portion 630 constitute a sheet discriminating device that discriminates the type of the sheet to be conveyed.

1.8 Operation in the image forming apparatus 10 The operation in the image forming apparatus 10 will be described.

(1) Overall Operation of Image Forming Device 10 The overall operation of the image forming apparatus 10 will be described with reference to the flowchart shown in FIG.

The main control unit 101a receives a user's operation from the operation panel 19 (step S101).

When the user's operation is to set the sheet size (“sheet size setting” in step S101), the main control unit 101a writes the sheet size for which the setting has been received to the storage circuit 110 (step S102). Next, the main control unit 101a returns the control to step S101.

When the user's operation is a print instruction (“print instruction” in step S101), the main control unit 101a causes the printer control circuit 109 to execute a print process (image formation process) (step S103). When the print process is completed, the main control unit 101a returns the control to step S101.

When the user's operation is another instruction (“other instruction” in step S101), the main control unit 101a executes the other process (step S104). When the other processing is completed, the main control unit 101a returns the control to step S101.

(2) Operation of print processing The operation of print processing will be described with reference to the flowchart shown in FIG.

The sheet discrimination circuit 112 reads the sheet size 121 from the storage circuit 110, and detects the set sheet length corresponding to the read sheet size 121. The sheet discrimination circuit 112 selects three sets of threshold values from the storage circuit 110 according to the detected set sheet length (step S121).

The sheet discrimination circuit 112 measures the required time (ON time of the sensor 550) from the first time point when the sensor 550 changes from OFF to ON to the second time point when the sensor 550 changes from ON to OFF. (Step S122).

Next, the sheet discrimination circuit 112 calculates the detection sheet length from the sheet transfer speed and the measured required time. Detection sheet length = transport speed x required time (step S123)
When the detection sheet length is calculated, the sheet discrimination circuit 112 compares the detection sheet length with the first threshold value 122, the second threshold value 123, and the third threshold value 124 (steps S124 to S126).

When the detection sheet length is larger than the first threshold value 122 (“YES” in step S124), the sheet determination circuit 112 determines that a size error has occurred. The printer main control circuit 111 performs processing when a size error occurs (step S127). This ends the print process.

When the detection sheet length is equal to or smaller than the first threshold value 122 (“NO” in step S124) and the detection sheet length is larger than the second threshold value 123 (“YES” in step S125), the sheet is determined. The circuit 112 determines that the sheet is thick paper. The printer main control circuit 111 sets the image formation conditions and forms the image in the case of thick paper (step S128). This ends the print process.

When the detection sheet length is equal to or smaller than the second threshold value 123 (“NO” in step S125) and the detection sheet length is larger than the third threshold value 124 (“YES” in step S126), the sheet is determined. The circuit 112 determines that the sheet is plain paper. The printer main control circuit 111 sets the image formation conditions and forms the image in the case of plain paper (step S129). This ends the print process.

When the detection sheet length is equal to or smaller than the third threshold value 124 (“NO” in step S126), the sheet determination circuit 112 determines that a size error has occurred. The printer main control circuit 111 performs processing when a size error occurs (step S130). This ends the print process.

1.9 Summary As described above, according to the above aspect, the sheet discrimination circuit 112 has changed from ON to OFF from the first time point when the detection signal received from the sensor 550 has changed from OFF to ON. Measure the time required up to two points in time. Next, the sheet discrimination circuit 112 calculates the detection sheet length from the sheet transfer speed and the measured required time. The sheet discrimination circuit 112 compares the detection sheet length with the first threshold value 122, the second threshold value 123, and the third threshold value 124. This has an excellent effect that the type of sheet can be discriminated.

2. Other Modifications The aspects of the present disclosure have been described based on the above embodiments, but are not limited to the above embodiments. It may be as shown below.

(1) The transport path 38 shown in FIG. 1 may be provided with a size detection sensor (size sensor) for detecting the size of the sheet, and the sheet discrimination circuit 112 may be used to determine whether the paper is plain paper or thick paper.

Specifically, for example, a size detection sensor for detecting the size of the sheet may be provided on the downstream side in the transport direction of the sheet from the pickup roller 63 (or 64, 65) shown in FIG. The sheet discrimination circuit 112 detects the sheet length (set sheet length) in the sheet conveying direction from the sheet size detected by the size detection sensor. The sheet discrimination circuit 112 selects three sets of threshold values from the storage circuit 110 according to the detected set sheet length. The sheet discrimination circuit 112 measures the time required from the first time point when the sensor 550 changes from OFF to ON to the second time point when it changes from ON to OFF, and measures the sheet transfer speed. The detection sheet length is calculated from the required time. Next, the sheet discrimination circuit 112 compares the detection sheet length with the first threshold value 122, the second threshold value 123, and the third threshold value 124, and discriminates whether the paper is plain paper or thick paper.

According to this configuration, even if the sheet size setting received from the operation panel 19 by the user's operation is incorrect, the sheet size can be correctly detected and it can be determined whether the paper is plain paper or thick paper. ..

(2) In the above embodiment, the seat discriminating device includes a seat discriminating circuit 112, a sensor 550, and a movable claw portion 630. Further, the sensor 550 and the movable claw portion 630 are provided on the first resist roller 51 of the skew correction portion 40. That is, the image forming apparatus 10 includes a resist unit having a gate for correcting the skew of the sheet to be conveyed, and the gate of the resist unit and the gate of the sheet discriminating device are integrated.

However, this configuration is not limited to this.

The skew correction unit 40 (resist unit) of the embodiment may not include the sensor 550. That is, the skew correction unit without the sensor performs skew correction, but does not determine whether the sheet is plain paper or thick paper.

In this case, one transport roller may be provided on both sides of the transport path 38 with the transport path 38 sandwiched in the middle of the transport path 38 shown in FIG. As a result, two transport rollers are provided. The two transfer rollers form a nip when the peripheral surfaces of the rollers are in contact with each other, and the sheet is passed through the nip so that the two transfer rollers transfer the sheet. Of the two transport rollers, one transport roller may be provided with a sensor and a movable claw portion similar to the sensor 550 and the movable claw portion 630 of the embodiment. This movable claw portion does not perform skew correction. These sensors, the movable claw portion, and the seat discrimination circuit 112 of the embodiment may constitute a seat discrimination device. This sheet discriminating device determines whether the sheet is plain paper or thick paper.

As described above, the sheet discriminating device does not have to be configured integrally with the skew correction unit, and can be provided, for example, in the transport path 38 shown in FIG. That is, the gate and the sensor provided in the sheet discriminating device may be arranged in the transport path from the position where the plurality of paper feed paths from the plurality of cassettes merge to the resist unit.

As a result, it is possible to increase the degree of freedom in designing the arrangement position of the sheet discriminating device in the transport path.

(3) In the above embodiment, the image forming apparatus 10 discriminates between thick paper and plain paper. The storage circuit 110 stores a second threshold value (paper type threshold value) for each length of the plurality of types of sheets in the transport direction. Here, the second threshold value 123 (paper type threshold value) is a boundary value for separating plain paper and thick paper.

However, it is not limited to this form. The image forming apparatus 10 may discriminate between thick paper, plain paper, and thin paper. Here, the basis weight of the thin paper is, for example, 40 g / m ² .

The storage circuit 110 may store the first paper type threshold value and the second paper type threshold value for each length of the plurality of types of sheets in the transport direction. The first paper type threshold value is a boundary value that distinguishes between plain paper and thick paper. The second paper type threshold is a boundary value that distinguishes between plain paper and thin paper.

The sheet discrimination circuit 112 discriminates between thick paper, plain paper, and thin paper by comparing the detected sheet length with the first paper type threshold value and the second paper type threshold value 123.

Further, the image forming apparatus 10 may discriminate more types of sheets.

(4) In the above embodiment, the seat discrimination circuit 112 returns to the first posture from the time when the stopper 632 (gate) changes its posture from the first posture to the second posture while the seat is being conveyed. The time required to complete the process is being measured. However, it is not limited to this form.

The seat discrimination circuit 112 determines the time required from the time when a predetermined time elapses from the time when the stopper 632 changes its posture from the first posture to the second posture during the transfer of the seat to the time when the stopper 632 returns to the first posture. You may measure. In other words, the seat discrimination circuit 112 may measure the time required until the return time of returning to the first posture is based on the change time of the stopper 632 changing the posture from the first posture to the second posture.

(5) In the above embodiment, the image forming apparatus 10 forms an image by an electrophotographic method. However, it is not limited to this form. The image forming apparatus may form an image by, for example, an inkjet method.

(6) The above-described embodiment and the above-described modification may be combined.

The sheet discriminating device according to the aspect of the present disclosure is useful as a technique for discriminating the type of sheet to be conveyed.

10 Image forming device 11 Image reader 12 Printer 13 Paper feed unit 40 Skew correction unit 50 Resist roller vs. 51 Resist roller 52 Resist roller 100 Control circuit 101 CPU
101a Main control unit 102 ROM
103 RAM
104 Image memory 105 Image processing circuit 106 Network communication circuit 107 Scanner control circuit 108 Input / output circuit 109 Printer control circuit 110 Storage circuit 111 Printer main control circuit 112 Sheet detection circuit 550 Sensor 551 Light emitting element 552 Light receiving element 600 Gate part 630 Movable claw part 631 Ring-shaped part 632 Stopper 633 Holding part 634 Shielding part

Claims (12)

A sheet discriminating device that discriminates the type of sheet to be transported.
The first posture, which is urged by the urging member to maintain the direction of restricting the progress of the seat, changes to the second posture, which is retracted from the transport path of the seat due to the rushing of the seat, and the urging is performed while the seat is passing. A gate that returns from the second posture to the first posture due to a change in the waist strength of the seat given to the member.
A sensor that detects changes in the posture of the gate and
A measuring unit that measures the time until the gate returns to the first posture based on the time when the gate changes from the first posture to the second posture during the transfer of the sheet.
A sheet discriminating device including a discriminating unit for discriminating the type of sheet according to the measured length of time. The discriminating unit compares the calculated length calculated by multiplying the transport speed of the sheet by the measured time with the paper type threshold value according to the size set for the sheet to obtain the type of the sheet. The sheet discriminating device according to claim 1, wherein the sheet discriminating device is characterized in that. When the calculated length is larger than the paper type threshold value, the discriminating unit determines that the sheet is the first type of thick paper, and when the calculated length is smaller than or equal to the paper type threshold value, the sheet is The sheet discriminating device according to claim 2, wherein it discriminates as a second type of plain paper. Further, there is an upper limit threshold, and the upper limit threshold is larger than the paper type threshold.
When the calculated length is larger than the paper type threshold value and the calculated length is smaller than or equal to the upper limit threshold value, the discriminating unit determines that the sheet is the first type of thick paper, and determines that the calculated length is the first type. The sheet discriminating device according to claim 2, wherein if is larger than the upper limit threshold value, it is determined that there is a size error. Further, there is a lower limit threshold, and the lower limit threshold is smaller than the paper type threshold.
When the calculated length is larger than the lower limit threshold value and the calculated length is smaller than or equal to the paper type threshold value, the discriminating unit determines that the sheet is a second type of plain paper, and performs the calculation. The sheet discriminating device according to claim 2, wherein if the length is less than or equal to the lower limit threshold value, it is determined that the size is an error. Further, there are an upper limit threshold value and a lower limit threshold value, the upper limit threshold value is larger than the paper type threshold value, and the paper type threshold value is larger than the lower limit threshold value.
The discriminating unit
When the calculated length is larger than the paper type threshold value and the calculated length is smaller than or equal to the upper limit threshold value, it is determined that the sheet is the first type of thick paper.
When the calculated length is larger than the lower limit threshold value and the calculated length is smaller than or equal to the paper type threshold value, it is determined that the sheet is a second type of plain paper.
The sheet discriminating device according to claim 2, wherein when the calculated length is larger than the upper limit threshold value, or when the calculated length is smaller than or equal to the lower limit threshold value, it is determined that the error is a size. An image forming device that forms an image
An image forming apparatus comprising the sheet discriminating apparatus according to any one of claims 1 to 6. The image forming apparatus
Multiple cassettes to accommodate the seats
It is equipped with a resist section that corrects the skew of the sheet to be conveyed.
The seventh aspect of claim 7, wherein the gate and the sensor included in the sheet discriminating device are arranged between a position where a plurality of paper feed paths from the plurality of cassettes merge and a resist portion. Image forming device. The image forming apparatus
A resist portion having a gate for correcting the skew of the conveyed sheet is provided.
The image forming apparatus according to claim 7, wherein the gate included in the resist unit and the gate included in the sheet discriminating apparatus are integrated. An image forming device that forms an image
The sheet discriminating device according to claim 2 and
A cassette that houses the seat and
Equipped with an operation panel that accepts input from users
The cassette detects the size of the contained sheet, or the operation panel accepts an input of the sheet size from the user.
The sheet discriminating device stores a paper type threshold value corresponding to the size of the sheet.
The discriminating unit is an image forming apparatus, characterized in that it reads out a paper type threshold value corresponding to the size of a sheet that has been detected or received an input. An image forming device that forms an image
A size sensor that detects the size of the sheet in the sheet transport path, and
The sheet discriminating device according to claim 2 and
A resist portion having a gate for correcting the skew of the conveyed sheet is provided.
The gate of the resist unit and the gate of the sheet discriminating device are integrated.
The sheet discriminating device stores a paper type threshold value corresponding to the size of the sheet.
The discriminating unit is an image forming apparatus that reads out a paper type threshold value corresponding to a sheet size detected by the size sensor. The first posture, which is urged by the urging member to maintain the direction of restricting the progress of the seat, changes to the second posture, which is retracted from the transport path of the seat due to the entry of the seat, and the urging member is changed while the seat is passing. A seat that is equipped with a gate that returns from the second posture to the first posture according to the change in the waist strength of the seat and a sensor that detects the change in the posture of the gate, and determines the type to which the seat to be transported belongs. This is a control method used in the discriminator.
During the transfer of the sheet, the time until the gate returns to the first posture is measured with reference to the time when the gate changes from the first posture to the second posture.
A control method characterized in that the type of sheet is determined according to the measured length of time.

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