Image forming device

Abstract

To provide an image forming device having a switching mechanism for transporting paper to multiple transport paths, and preventing false detection of abnormalities in the switching mechanism without increasing costs due to additional hardware, even in a configuration in which the user can contact a sensor at the destination of the transport path.SOLUTION: The image forming device has a discharge port, a discharge transport path 26 for transporting a sheet 2, a double-sided reversing path 29 for transporting the sheet 2 in a different direction from the discharge transport path 26, and a reverse flapper 32 that switches between a first state for leading the sheet 2 to the discharge transport path 26 and a second state for leading it to the double-sided reversing path 29, a full-load sensor 39 located at the discharge port for detecting the sheet 2, an engine control unit 303 for controlling the reverse flapper 32, a switching abnormality determination unit 315 that determines that an abnormality exists in the reverse flapper 32 when the sheet 2 is detected by the full-load sensor 39 after the engine control unit 303 controls the reverse flapper 32 to switch to the second state.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to an image forming apparatus, and more particularly to a method for detecting an abnormality in a switching mechanism in an image forming apparatus having a plurality of transport paths for transporting paper and a switching mechanism for switching the destination of paper. [Background technology]

[0002] Conventionally, image forming apparatuses such as printers and copiers have a configuration having multiple transport paths, such as an outlet for discharging paper outside the machine and a transport path for inverting paper. In order to transport paper to a specified transport path, the image forming apparatus uses a transport path switching mechanism to switch the transport destination. This switching mechanism switches the transport destination of the paper by switching the state of the switching mechanism at a position on the transport path where the transport path branches into multiple transport paths. If this switching mechanism is broken, the paper may be transported to a transport path other than the specified transport path. In addition, the designated transport path is notified of a paper jam because no paper arrives. Therefore, there is a problem that a paper jam is notified to a user or a serviceman even when the switching mechanism is broken. It is difficult for a user or a serviceman to identify that the transport path switching mechanism is broken from the content of the notification. In addition, an instruction to clear the paper jam is given from the operation panel of the image forming apparatus, but there is no paper in the specified transport path, and the user must check the transport path unnecessarily. This leads to a decrease in usability due to a false detection of a paper jam. In response to this, for example, Patent Document 1 proposes a control method in which it is determined that a sheet has been transported to a transport path different from a designated transport path based on a change in a sensor located at the end of the transport path. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 10-157920 Summary of the Invention [Problem to be solved by the invention]

[0004] However, when the sensor at the end of the transport path is located at the discharge outlet, the detection result of the sensor also changes when the user touches it. For example, the full sensor that detects the full state of the discharge tray is located at the discharge outlet, and is in a position where the user can touch it. In this case, the detection result of the full sensor also changes when the paper lifted by the user to remove the stacked paper comes into contact with the full sensor. When it is determined that the paper has been transported to a transport path different from the designated transport path only based on the change in the sensor located at the end of the transport path, there is a risk that the change in the sensor output due to the user's operation is mistakenly determined to be the change in the sensor output due to the transport of the paper. Therefore, even though the switching mechanism is normal, the sensor output has changed, resulting in a false detection of an abnormality in the switching mechanism. In addition, if a paper jam occurs at the timing when an abnormality in the switching mechanism is falsely detected, there is a problem that the paper jam is not notified because the failure of the switching mechanism is notified first. In addition, even if the switching mechanism is not broken and there is a delay between the instruction to drive and the completion of the switching operation, the paper may be transported to a transport path that is not designated. In this case, the switching operation can be performed, but the switching mechanism may be determined to be broken and the paper may be determined to be unable to be transported. Therefore, if the switching operation takes longer than usual, a user or a service technician must replace the switching mechanism, which is a problem.

[0005] The present invention has been made under these circumstances, and has an object to prevent erroneous detection of an abnormality in a switching mechanism for transporting paper to multiple transport paths, even in a configuration in which a user can contact a sensor at the end of a transport path, without increasing costs by adding hardware, etc. [Means for solving the problem]

[0006] In order to solve the above-mentioned problems, the present invention has the following configuration.

[0007] (1) An image forming apparatus comprising: a first conveyance path having a discharge port for conveying a recording medium; a second conveyance path for conveying the recording medium in a direction different from that of the first conveyance path; switching means for switching between a first state in which the recording medium is guided to the first conveyance path and a second state in which the recording medium is guided to the second conveyance path; detection means disposed at the discharge port for detecting the recording medium; and control means for controlling the switching means, wherein the image forming apparatus further comprises determination means for determining an abnormality of the switching means when the detection means detects the recording medium after the switching means is controlled by the control means to switch to the second state.

Advantages of the Invention

[0008] According to the present invention, even in a configuration having a switching mechanism for conveying paper through a plurality of conveyance paths and allowing a user to contact a sensor at the end of the conveyance path, it is possible to prevent misdetection of an abnormality in the switching mechanism without increasing costs such as adding hardware.

Brief Description of the Drawings

[0009] [Figure 1] Front schematic cross-sectional view showing the overall configuration of the image forming apparatuses of Examples 1 and 2 [Diagram 2] Hardware configuration diagrams of Examples 1 and 2 [Diagram 3] Control block diagrams of Examples 1 and 2 [Figure 4] Diagram for explaining the outline of the conveyance path switching unit of Examples 1 and 2 [Diagram 5] Timing chart for explaining switching abnormality determination in Example 1 [Figure 6] Flowchart showing the switching abnormality determination process of Example 1 [Figure 7] Diagram for explaining the control to be performed when the conveyance path switching unit of Example 2 is abnormal [Figure 8] Diagram for explaining the control to be performed when the conveyance path switching unit of Example 2 is abnormal [Figure 9] Flowchart showing the switching abnormality determination process of Example 2 DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS EXAMPLES

[0010] A first embodiment to which the present invention can be applied will be described below. The overall configuration of a laser printer engine as an image forming apparatus will be outlined with reference to FIG.

[0011] <Image forming device> A laser printer 100 (hereinafter, simply referred to as the printer 100) forms an electrostatic latent image by image light formed based on an image signal sent from a controller unit (not shown), develops the electrostatic latent image, and transfers a visible image in a superimposed manner to form a color visible image. The printer 100 transfers a color visible image to a sheet 2 as a recording medium fed from a cassette 1 by a paper feed roller 40, and fixes the color visible image on the sheet 2. The image forming unit is composed of photosensitive drums 5Y, 5M, 5C, 5K, charging units 7Y, 7M, 7C, 7K, developing units 8Y, 8M, 8C, 8K, and an intermediate transfer belt 12, which are arranged in parallel for each developing color. The photosensitive drums 5Y, 5M, 5C, 5K, charging units 7Y, 7M, 7C, 7K, and developing units 8Y, 8M, 8C, 8K are mounted in process cartridges 22Y, 22M, 22C, 22K that are detachable from the printer 100 main body.

[0012] The photosensitive drums 5Y, 5M, 5C, and 5K are configured by coating the outer periphery of an aluminum cylinder with an organic photoconductive layer, and are rotated by the driving force of a drive motor (not shown). The drive motor rotates the photosensitive drums 5Y, 5M, 5C, and 5K in a clockwise direction in response to an image forming operation. Exposure light to the photosensitive drums 5Y, 5M, 5C, and 5K is sent from scanner units 10Y, 10M, 10C, and 10K, and is configured to selectively expose the surfaces of the photosensitive drums 5Y, 5M, 5C, and 5K to form electrostatic latent images.

[0013] The printer 100 is configured to have four charging units (injection chargers) 7Y, 7M, 7C, and 7K for charging the photosensitive drums 5Y, 5M, 5C, and 5K of yellow (Y), magenta (M), cyan (C), and black (K) at each station. The charging units 7Y, 7M, 7C, and 7K are provided with sleeves 7YS, 7MS, 7CS, and 7KS. The printer 100 is configured to have four developing units 8Y, 8M, 8C, and 8K for developing yellow (Y), magenta (M), cyan (C), and black (K) at each station in order to visualize the electrostatic latent image. The developing units 8Y, 8M, 8C, and 8K are provided with sleeves 8YS, 8MS, 8CS, and 8KS. The developing units 8Y, 8M, 8C, and 8K are detachably attached.

[0014] The intermediate transfer belt 12 is in contact with the photosensitive drums 5Y, 5M, 5C, and 5K, and rotates counterclockwise during color image formation, rotating with the rotation of the photosensitive drums 5Y, 5M, 5C, and 5K. The intermediate transfer belt 12 receives a visible image transferred thereto by a primary transfer voltage applied to the primary transfer rollers 4Y, 4M, 4C, and 4K (primary transfer). The intermediate transfer belt 12 transfers a color visible image onto the sheet 2 in a superimposed manner by sandwiching and conveying the sheet 2 at the position of the secondary transfer roller 9 (secondary transfer). The intermediate transfer belt 12 is sandwiched between the secondary transfer roller 9 and an opposing roller 18 at the secondary transfer section.

[0015] The fixing section 13 fixes the transferred unfixed color visible image while conveying the sheet 2, and includes a fixing roller 14 for heating the sheet 2 and a pressure roller 15 for pressing the sheet 2 against the fixing roller 14. The fixing roller 14 and the pressure roller 15 are formed in a hollow shape, and a heater is built in the fixing roller 14. That is, the sheet 2 holding the color visible image is conveyed by the fixing roller 14 and the pressure roller 15, and the toner is fixed to the surface by applying heat and pressure. After the visible image is fixed, the sheet 2 is conveyed to a discharge conveying path 26 as a first conveying path, and is discharged to the discharge section by a discharge conveying roller 31, and the image forming operation is completed. In addition, a full-load sensor 39 as a detection means (first detection means) located in the discharge section is a sensor that detects that the sheet stack on the discharge tray 27 is in a full-load state. Here, the full-load state means a state in which the stack height of the sheet stack on the discharge tray 27 exceeds the height allowed for the discharge tray 27. When the sheet is not fully loaded, the full load sensor 39 detects the leading edge to the trailing edge of the sheet 2 every time the sheet 2 is discharged. In addition, in the conveying path, a registration sensor 19 capable of detecting the leading edge and trailing edge of the conveyed sheet 2, a fixing discharge sensor 20, and a double-sided conveying sensor 28 as a second detection means are arranged. A registration roller 3 is arranged upstream of the registration sensor 19 in the conveying direction.

[0016] (Double-sided printing) Next, a description will be given of duplex conveyance control when printing on the front and back sides of the sheet 2. The sheet 2 that has been printed on the front side and passed through the fixing unit 13 is conveyed to the position of the conveyance path switching unit 36. The conveyance path switching unit 36 ​​switches the inversion flapper 32 as a switching means, and conveys the sheet 2 to the duplex inversion path 29 as the second conveyance path (duplex inversion path). Note that in FIG. 1, the inversion flapper 32 when conveying the sheet 2 to the discharge conveyance path 26 is indicated by a solid line, and the inversion flapper 32 when conveying the sheet 2 to the duplex inversion path 29 is indicated by a dashed line. Switching the position of the inversion flapper 32 from the solid line position to the dashed line position, or from the dashed line position to the solid line position, will hereinafter also be expressed as switching the state of the inversion flapper 32.

[0017] When the rear end of the sheet 2 reaches the double-sided reversing path 29, the rotation direction of the reversing rollers 30 is switched by a motor (not shown), and the sheet 2 is conveyed to a double-sided conveying path 33 serving as a third conveying path. The sheet 2 whose conveying direction has been reversed is conveyed along the double-sided conveying path 33 by a double-sided conveying roller 37 and a double-sided re-feed roller 35. Then, the sheet 2 enters the print conveying path 25 again in an inverted state, where a toner image is transferred and fixed onto the back side, and the sheet is discharged to the discharge section.

[0018] <Hardware configuration diagram> 2 is a diagram showing the hardware configuration in the first embodiment. The printer 100 has a CPU (Central Processing Unit) 201, a timer 202, a ROM (Read Only Memory) 203, a RAM (Random Access Memory) 204, and an I / O port 206. The CPU 201 controls the entire printer 100. The timer 202 generates control timing. The ROM 203 stores a control program. The RAM 204 stores data and the like. The I / O port 206 is connected to the CPU 201, the timer 202, the ROM 203, and the RAM 204 via a bus 205.

[0019] The I / O port 206 is connected to a drive circuit 211 for a reversing solenoid 221, an input circuit 212 for the fixing and ejection sensor 20, an input circuit 213 for the double-sided conveyance sensor 28, and an input circuit 214 for the full-load sensor 39. The drive circuit 211 for the reversing solenoid 221 drives the reversing solenoid 221 which is linked to the reversing flapper 32. The input circuit 212 for the fixing and ejection sensor 20 inputs the logic of the fixing and ejection sensor 20 to the I / O port 206. The input circuit 213 for the double-sided conveyance sensor 28 inputs the logic of the double-sided conveyance sensor 28 to the I / O port 206. The input circuit 214 for the full-load sensor 39 inputs the logic of the full-load sensor 39 to the I / O port 206.

[0020] The CPU 201 drives the reversing solenoid 221 by operating the I / O port 206 via the bus 205. The CPU 201 also checks the logic of the I / O port 206 via the bus 205 to check the logic of the fixing discharge sensor 20, the duplex conveying sensor 28, and the full-load sensor 39.

[0021] <Function block diagram> 3 is a block diagram showing the functional configuration of the first embodiment. The engine control unit 303 as a control unit has the functions of a double-sided inversion unit 311, a first detection unit 312, a second detection unit 313, a full-load determination unit 314, and a switching abnormality determination unit 315 and a conveyance abnormality determination unit 316 as a determination unit. The double-sided inversion unit 311 switches the state of the inversion flapper 32 by controlling the inversion solenoid 221 according to a predetermined switching timing based on the detection result of the fixing discharge sensor 20. The first detection unit 312 detects the sheet 2 conveyed to the discharge conveyance path 26 by the full-load sensor 39. The second detection unit 313 detects the sheet 2 conveyed to the double-sided conveyance path 33 by the double-sided conveyance sensor 28. The full-load determination unit 314 determines whether the sheet 2 stacked on the discharge tray 27 is full or not based on the detection result of the first detection unit 312.

[0022] The switching abnormality determination unit 315 determines whether or not the conveying path switching unit 36 ​​is abnormal based on the detection results of the first detection unit 312 and the second detection unit 313. When the second detection unit 313 does not detect the sheet 2, the conveying abnormality determination unit 316 determines whether or not an abnormality has occurred in the conveying of the sheet 2 based on the determination result of the switching abnormality determination unit 318. When the conveying abnormality determination unit 316 determines that an abnormality has occurred in the conveying of the sheet 2, it notifies the user by displaying information that an abnormality (failure) has occurred on the operation panel 301 via the controller 302. The operation panel 301 functions as a notification unit that notifies the user of various information by the engine control unit 303.

[0023] <Transport path switching mechanism> Next, the conveying path switching unit 36 ​​of the first embodiment will be described. FIG. 4(a) is a cross-sectional view of the conveying path switching unit 36, and shows a state (first state) in which the inversion flapper 32 is switched so as to guide the sheet 2 in the direction of the discharge conveying path 26. Hereinafter, the state of FIG. 4(a) is also referred to as a state in which the inversion flapper 32 is switched to the direction of the discharge conveying path 26. FIG. 4(b) shows a state (second state) in which the inversion flapper 32 is switched so as to guide the sheet 2 in the direction of the double-sided inversion path 29. Hereinafter, the state of FIG. 4(b) is also referred to as a state in which the inversion flapper 32 is switched to the direction of the double-sided inversion path 29. The conveying path switching unit 36 ​​has the inversion flapper 32, a spring 401, a flapper arm 402, a flapper arm rotating shaft 402a, a link arm 403, a link arm rotating shaft 403a, and an inversion solenoid 221. The inversion flapper 32 operates in conjunction with the flapper arm 402.

[0024] 4(a), the reversing flapper 32 receives a counterclockwise force around a flapper arm rotation shaft 402a due to the elastic force of a spring 401, and the counterclockwise rotation of the flapper arm 402 is restricted by a link arm 403. As a result, the reversing flapper 32 is in a state where it guides the sheet 2 in the direction of the discharge conveying path 26. In addition, in FIG. 4(a), the reversing solenoid 221 is in an OFF state.

[0025] As shown in FIG. 4B, when the inversion flapper 32 is switched to the double-sided inversion path 29, the inversion solenoid 221 receives a signal from the drive circuit 211 of the inversion solenoid 221 and turns ON. When the inversion solenoid 221 is in the ON state, it attracts the link arm 403 in the direction of the arrow N. This causes the link arm 403 to rotate about the link arm rotation shaft 403a and push up the flapper arm 402. The flapper arm 402 rotates clockwise about the flapper arm rotation shaft 402a, and the accompanying inversion flapper 32 switches to the direction of the double-sided inversion path 29. After the tip 32t of the inversion flapper 32 reaches the branch position 32a, the sheet 2 to be conveyed is conveyed to the double-sided inversion path 29. Here, if the timing at which the tip 32t of the inversion flapper 32 reaches the branch position 32a is earlier than the timing at which the tip of the sheet 2 reaches the branch position 32a, the sheet 2 is conveyed to the double-sided inversion path 29.

[0026] <Switching abnormality judgment control> Next, a method for determining whether the conveying path switching unit 36 ​​is abnormal or not by the switching abnormality determination unit 315 will be described. FIG. 5 is a timing chart showing the leading edge position of the sheet 2, the state of the inverting flapper 32, and the state changes of the driving unit and the detection unit when the switching of the inverting flapper 32 is not in time for the conveyance of the sheet 2. More specifically, (i) is a graph showing time on the horizontal axis and positions on the conveying path on the vertical axis, and the vertical axis shows the fixing discharge sensor 20 position, the branch position 32a, and the full-load sensor 39 position in that order from upstream to downstream in the conveying direction. The leading edge (paper leading edge) and trailing edge (paper trailing edge) of the conveyed sheet 2 are also shown in the graph. (ii) shows the state of the inverting flapper 32, and shows the change over time in whether it has been switched to the discharge conveying path (FIG. 4(a)) or the double-sided inverting path 29 (FIG. 4(b)). (iii) shows the change over time in the logic (high level or low level) of the signal output from the fixing and discharge sensor 20, and (iv) shows the change over time in the logic (on (high level) or off (low level)) of the reversing solenoid 221. (v) shows the change over time in the logic (high level or low level) of the signal output from the full-load sensor 39. The outputs of the fixing and discharge sensor 20 and the full-load sensor 39 switch from low level to high level when the leading edge of the sheet 2 arrives, and switch from high level to low level when the trailing edge of the sheet 2 passes by.

[0027] After passing the fixing and discharging sensor 20, the sheet 2 is transported to the branching position 32a. The duplex reversing section 311 sets the reversing solenoid 221 to ON at a predetermined timing P501, starting from the time when the fixing and discharging sensor 20 detects the leading edge of the sheet 2 (timing A), and switches the reversing flapper 32 to the direction of the duplex reversing path 29. Here, the timing when the leading edge of the sheet 2 reaches the branching position 32a is defined as timing P502, and the timing when the direction of the reversing flapper 32 switches from the discharging and conveying path 26 to the duplex reversing path 29 is defined as timing P503.

[0028] Usually, the sheet 2 reaches the branch position 32a after the reversing flapper 32 switches to the double-sided reversing path 29. That is, under normal conditions, the timing P502 is later than the timing P503. Then, the sheet 2 is conveyed to the double-sided reversing path 29, so it is detected by the double-sided conveying sensor 28, and the full-load sensor 39 does not change (is not detected). However, when an assembly error in manufacturing or a delay in a drive instruction occurs in the conveying path switching unit 36, it may take longer than usual for the reversing flapper 32 to switch to the double-sided reversing path 29. In this case, as shown in FIG. 5, the timing P502 may be earlier than the timing P503. That is, the sheet 2 reaches the branch position 32a before the reversing flapper 32 switches to the double-sided reversing path 29, so the sheet 2 may be conveyed to the discharge conveying path 26. The sheet 2 conveyed to the discharge conveying path 26 is discharged to the discharge tray 27, and is detected by the full-load sensor 39 without being detected by the double-sided conveying sensor 28.

[0029] Therefore, the switching abnormality determination unit 315 can determine whether or not the conveying path switching unit 36 ​​is abnormal based on a change in the full load sensor 39. The switching abnormality determination unit 315 measures the number of times it has determined that the conveying path switching unit 36 ​​is abnormal (hereinafter referred to as the number of determinations), and stores the number of times it has determined that the conveying path switching unit 36 ​​is abnormal in the RAM 204. If the number of determinations is equal to or greater than a predetermined number Y (the predetermined number or more), the engine control unit 303 notifies the user by displaying on the operations panel 301 that a malfunction has occurred. If the number of determinations is less than the predetermined number Y (less than the predetermined number), the engine control unit 303 notifies the user by displaying on the operations panel 301 that a misprint has occurred during the image forming operation.

[0030] On the other hand, the full-load sensor 39 is located at the discharge outlet of the discharge conveying path 26, and can be touched by the user. When the user removes the sheet 2 stacked on the discharge tray 27, the sheet 2 may come into contact with the full-load sensor 39, causing a change in the output of the full-load sensor 39. In such a case, it is necessary to determine whether the change in the output of the full-load sensor 39 is caused by the user's actions or not. When determining whether the conveying path switching unit 36 ​​is abnormal based on the change in the full-load sensor 39, the switching abnormality determination unit 315 uses the time T during which the full-load sensor 39 detects the sheet 2. This time T is the time during which the full-load sensor 39 continues to detect the sheet 2 during the period (the period BA) from when the measurement is started at the timing A to when the measurement is ended at the timing B. More specifically, the time T is the time from when the full-load sensor 39 is switched from the low level to the high level to when it is switched from the high level to the low level.

[0031] As described above, timing A is the timing when the fixing discharge sensor 20 detects the leading edge of the sheet 2, and timing B is the timing when the predetermined time X has elapsed without the sheet 2 being detected by the duplex conveying sensor 28. The predetermined time X is a time determined in advance including a margin in addition to the time when the sheet 2 is estimated to arrive. Here, the variation of the measured time T will be explained. The measured time T is calculated based on the length of the conveying direction of the sheet 2 to be conveyed and the conveying speed (conveying speed), and also includes variation elements such as the variation of the conveying time due to the assembly error in manufacturing and the variation of the paper feeding operation. Therefore, the measured time T changes within a range including the above-mentioned variation elements. The range including this variation element is set to be equal to or greater than the predetermined period Tmin and equal to or less than Tmax (predetermined period).

[0032] When the time T is equal to or greater than the predetermined period Tmin and equal to or less than Tmax (within the predetermined period) (Tmin≦T≦Tmax), the switching abnormality determination unit 315 can determine that the change in the full load sensor 39 is due to the conveyance of the sheet 2. Therefore, it can be determined that the sheet 2 has been conveyed to the discharge conveyance path 26, and the switching abnormality determination unit 315 can determine that the conveyance path switching unit 36 ​​is abnormal.

[0033] On the other hand, when the user removes the sheet 2 loaded on the discharge tray 27, since the measured time T is generally shorter compared to the time Tmin (T < Tmin), the switching abnormality determination unit 315 can determine that there is no abnormality. Further, when the sheet 2 loaded on the discharge tray 27 is in a full load state, the full load sensor 39 continues to detect the sheet 2. Therefore, the measured time T is longer than the time Tmax (T > Tmax), and the switching abnormality determination unit 315 can determine that it is not due to a change caused by the conveyance of the sheet 2.

[0034] <Conveyance Abnormality Determination Control> Next, the conveyance abnormality determination unit 316 that makes a determination according to the determination result of the switching abnormality determination unit 315 will be described. The conveyance abnormality determination unit 316 notifies of a conveyance abnormality when the sheet 2 conveyed to the duplex reversal path 29 is not detected by the duplex conveyance sensor 28 after a lapse of a predetermined time X. However, as described above, even when the conveyance path switching unit 36 is abnormal, the duplex conveyance sensor 28 cannot detect the sheet 2. In this case, after the user is notified of the conveyance abnormality and checks the conveyance path, since the sheet 2 does not exist in the duplex conveyance path 33, it becomes a false detection by the conveyance abnormality determination unit 316. Therefore, in the first embodiment, when the switching abnormality determination unit 315 determines that the conveyance path switching unit 36 is abnormal, the conveyance abnormality determination unit 316 does not notify of a conveyance abnormality to prevent false notification.

[0035] <Flowchart Regarding Abnormality Determination Control> FIG. 6 is a flowchart regarding the switching abnormality determination unit 315. In step (hereinafter referred to as S) 601, the engine control unit 303 determines whether the fixing discharge sensor 20 is detecting the sheet 2, that is, whether the sheet 2 has reached the fixing unit 13. If the engine control unit 303 determines in S601 that the sheet 2 has reached the fixing unit 13, the process proceeds to S602. If it determines that it has not reached, the process returns to S601. Note that the timing at which the leading edge of the sheet 2 is detected by the fixing discharge sensor 20 is the timing A described above.

[0036] In S602, the engine control unit 303 determines whether the designated destination of the sheet 2 is the duplex reversal path 29. If in S602 the engine control unit 303 determines that the destination of the sheet 2 is the duplex reversal path 29, the process proceeds to S603. If it determines that it is not the duplex reversal path 29, the process ends.

[0037] In S603, the engine control unit 303 switches the reversing flapper 32 in the direction of the duplex reversal path 29 by the duplex reversing unit 311. In S604, the engine control unit 303 starts measuring the time T when the full-load sensor 39 detects the sheet 2 with the timer 202. In S605, the engine control unit 303 determines whether a predetermined time X has elapsed since the process of S601 by the conveyance abnormality determination unit 316. If in S605 the engine control unit 303 determines that the predetermined time X has not elapsed, the process returns to S605. If it determines that the predetermined time X has elapsed, the process proceeds to S606. The timing when the predetermined time X has elapsed corresponds to the timing B described above.

[0038] In S606, the engine control unit 303 ends the measurement of the time T started in S604. In S607, the engine control unit 303 determines whether the duplex conveyance sensor 28 has not detected (not detected) the sheet 2 by the conveyance abnormality determination unit 316. If in S607 the engine control unit 303 determines that the sheet 2 has not been detected, the process proceeds to S608. If it determines that the sheet 2 has been detected, since the sheet 2 has been normally conveyed to the duplex conveyance path 33, the process ends. Note that when the sheet 2 is detected in S607, the engine control unit 303 may use the measured time T and determine that the user has touched the discharge tray 27 when the time T is less than the time Tmin (T < Tmin). Also, the engine control unit 303 may determine that the sheet 2 loaded on the discharge tray 27 is in a full-load state when the measured time T is longer than the time Tmax (T > Tmax).

[0039] In S608, the engine control unit 303 judges whether the time T at which the full load sensor 39 detects the sheet 2 is equal to or greater than the predetermined period Tmin and equal to or less than Tmax (Tmin≦T≦Tmax). If the engine control unit 303 judges in S608 that the time T is equal to or greater than the predetermined period Tmin and equal to or less than Tmax, the process proceeds to S609, and if the engine control unit 303 judges that the time T is not equal to or greater than the predetermined period Tmin and equal to or less than Tmax, the process proceeds to S614.

[0040] In S609, the engine control unit 303 determines that the conveying path switching unit 36 ​​is abnormal using the switching abnormality determination unit 315. In S610, the engine control unit 303 stores the number of determinations measured by the switching abnormality determination unit 315 in the RAM 204. At this time, the conveying abnormality determination unit 316 does not detect the sheet 2 by the duplex conveying sensor 28, but does not notify the user that an abnormality has occurred in the conveying.

[0041] In S611, the engine control unit 303 determines whether the number of determinations stored in S610 is equal to or greater than the predetermined number Y. If the engine control unit 303 determines in S611 that the number of determinations is equal to or greater than the predetermined number Y, the process proceeds to S612. In S612, the engine control unit 303 notifies the user on the operations panel 301 of the failure state of the transport path switching unit 36, and ends the process. If the engine control unit 303 determines in S611 that the number of determinations is less than the predetermined number Y, the process proceeds to S613. In S613, the engine control unit 303 notifies the user on the operations panel 301 that a misprint has occurred, and ends the process.

[0042] If the time T is not equal to or greater than the predetermined period Tmin and equal to or less than Tmax in S608, the engine control unit 303 determines through the conveyance abnormality determination unit 316 that the sheet 2 remains on the conveyance path from the fixing discharge sensor 20 to the double-sided conveyance sensor 28. In S614, the engine control unit 303 notifies the user that an abnormality has occurred in the conveyance, and ends the process.

[0043] As described above, according to the first embodiment, even in a configuration where the user can contact the sensor at the end of the conveyance path, it is possible to correctly determine an abnormality in the conveyance path switching unit. In the first embodiment, the duplex reversal path is described as an example of one of a plurality of conveyance paths. However, the plurality of conveyance paths are not limited to the duplex reversal path, and may be a conveyance path from a discharge port provided in the image forming apparatus to a post-processing apparatus. Further, in the first embodiment, the conveyance path switching unit of the laser beam printer has been described. However, the present invention is not limited to this, and can be applied to an entire sheet conveyance apparatus having a conveyance path switching unit that switches the conveyance path on the sheet conveyance path.

[0044] As described above, according to the first embodiment, even in a configuration having a switching mechanism for conveying sheets to a plurality of conveyance paths and allowing the user to contact the sensor at the end of the conveyance path, it is possible to prevent false detection of an abnormality in the switching mechanism without increasing costs such as adding hardware.

Embodiment

[0045] Next, a second embodiment to which the present invention can be applied will be described. In the second embodiment, when the conveyance path switching unit 36 is abnormal, control for conveying the sheet 2 to the duplex reversal path by engine control will be described. Note that the same reference numerals are used for the same parts as those in the first embodiment, and the description thereof will be omitted.

[0046] <Control to be performed when the switching unit is abnormal> Control for conveying the sheet 2 to the duplex reversal path 29 by engine control when the conveyance path switching unit 36 is abnormal will be described. FIG. 7 shows the leading edge position of the sheet 2, the state of the reversal flapper 32, the driving unit, and the state change of the detection unit when the number of times of determining that the conveyance path switching unit 36 is abnormal is less than the predetermined number Z, and FIG. 8 shows the same when the number of times of determination is equal to or greater than the predetermined number Z. (i) to (v) are the same as (i) to (v) in FIG. 5. In the second embodiment, the predetermined number Z defined is described as 1 (Z < Y). Also, the conveyance destination of the preceding sheet 2 (preceding sheet) is the discharge conveyance path 26, and the conveyance destination of the subsequent sheet 2 (subsequent sheet) is the duplex reversal path 29.

[0047] (The number of judgments is less than the specified number Z: Figure 7) First, the control of conveying the sheet 2 to the double-sided reversing path 29 when the number of times that the conveying path switching unit 36 ​​is judged to be abnormal is less than the predetermined number Z and it takes longer than usual for the reversing flapper 32 to switch will be described with reference to Fig. 7. In the case of Fig. 7, the number of times that the judgment is made is 0, which is less than the predetermined number Z, so printing starts as usual. The preceding sheet 2 reaches the position of the fixing and discharging sensor 20, the logic of the fixing and discharging sensor 20 turns ON, and the sheet passes the branch position 32a and the position of the full-load sensor 39.

[0048] Next, the succeeding sheet 2 is conveyed following the preceding sheet 2. Here, the interval at which the trailing edge of the preceding sheet 2 and the leading edge of the succeeding sheet 2 are detected at the position of the fixing and ejection sensor 20 is defined as interval T701. Since the number of judgments is less than the predetermined number Z, the duplex inversion unit 311 turns the inversion solenoid 221 ON at a timing P702 that is determined in advance with the detection of the succeeding sheet 2 by the fixing and ejection sensor 20 as the starting point. After the inversion solenoid 221 turns ON, the inversion flapper 32 switches to the direction of the duplex inversion path 29. Here, the timing at which the succeeding sheet 2 arrives at the branch position 32a is defined as timing P703, and the timing at which the direction of the inversion flapper 32 switches from the ejection and conveyance path 26 to the duplex inversion path 29 is defined as timing P704.

[0049] As described in the first embodiment, when an assembly error occurs in manufacturing or a drive instruction delay occurs, the conveying path switching unit 36 ​​may take longer than usual for the reversing flapper 32 to switch to the direction of the double-sided reversing path 29. In this case, the timing P703 may be earlier than the timing P704, and the succeeding sheet 2 is detected by the full-load sensor 39 after being conveyed to the discharge conveying path 26. Here, similar to the first embodiment, the switching abnormality determination unit 315 determines that the succeeding sheet 2 has been conveyed to the discharge conveying path 26 based on the change in the full-load sensor 39. Therefore, the switching abnormality determination unit 315 determines that the conveying path switching unit 36 ​​is abnormal. Here, the number of determinations (=1) that the conveying path switching unit 36 ​​has been judged to be abnormal is stored in the RAM 204, but the occurrence of a misprint is notified on the operation panel 301, and the user is prompted to print again.

[0050] (The number of judgments is Z or more: Figure 8) Next, when the number of times the transport path switching unit 36 ​​is determined to be abnormal is equal to or greater than the predetermined number Z, and it takes longer than usual for the reversing flapper 32 to switch, the control for transporting the succeeding sheet 2 to the double-sided reversing path 29 will be described with reference to Fig. 8. Here, it is assumed that the process shown in Fig. 7 is carried out, i.e., the number of times the transport path switching unit 36 ​​is determined to be abnormal is 1, and the predetermined number Z is 1.

[0051] 8, since the number of times that the transport path switching unit 36 ​​has been determined to be abnormal is one, which is equal to or greater than the predetermined number Z, the engine control unit 303 starts printing by making the interval at which to print an image on the sheet 2 wider than normal. Here, the interval at which the trailing edge of the preceding sheet 2 and the leading edge of the succeeding sheet 2 are detected at the position of the fixing discharge sensor 20 is set to interval T705. Interval T705 is determined to be longer than interval T701 (T705>T701).

[0052] Since the number of judgments is equal to or greater than the predetermined number Z, the double-sided reversing unit 311 turns on the reversing solenoid 221 at timing P706 earlier than the predetermined timing P702. This timing P706 is determined so that the reversing flapper 32 switches before the conveyed sheet 2 reaches the branching position 32a in a case where it takes longer than usual for the reversing flapper 32 to switch to the direction of the double-sided reversing path 29. For example, the timing P706 is set 10 msec earlier than the timing P702, assuming that the distance from the position of the fixing discharge sensor 20 to the branching position 32a is 40 mm and the conveying speed of the sheet 2 is 100 mm / sec.

[0053] After the reversing solenoid 221 becomes ON, the reversing flapper 32 switches to the direction of the duplex reversing path 29. Here, the timing when the succeeding sheet 2 arrives at the branching position 32a is defined as timing P707, and the timing when the direction of the reversing flapper 32 switches from the discharge conveying path 26 to the duplex reversing path 29 is defined as timing P708. Compared to the normal case, the reversing flapper 32 switches at timing P708 earlier than timing P707 when the sheet 2 arrives at the branching position 32a. Also, since the interval between the preceding sheet 2 and the succeeding sheet 2 is widened by the interval T705, the reversing flapper 32 does not switch earlier than timing P709 when the rear end of the preceding sheet 2 passes through the branching position 32a. In other words, timing P709 is earlier than timing P708. Therefore, timing P707 is later than timing P708. Therefore, the succeeding sheet 2 is conveyed to the duplex reversing path 29. Since the succeeding sheet 2 is not conveyed to the discharge conveying path 26 downstream of the branch position 32a, the position of the succeeding sheet 2 in FIG. 8 is indicated by a dotted line.

[0054] Therefore, even if it takes longer than usual for the reversing flapper 32 to switch due to an abnormality in the conveying path switching unit 36, the succeeding sheet 2 can be conveyed to the double-sided reversing path 29 by engine control.

[0055] <Flowchart of control performed when the transport path switching unit is abnormal> 9 is a flowchart related to the control of conveying the sheet 2 to the double-sided reversing path 29 by engine control when the conveying path switching unit 36 ​​is abnormal. A case where the number of judgments stored in the RAM 204 is 0, the predetermined number of times Y is 2, and the predetermined number of times Z is 1 will be described using the flowchart.

[0056] In S801, the engine control unit 303 judges whether or not a print instruction has been received from the controller 302. If the engine control unit 303 judges in S801 that a print instruction has not been received, the process returns to S801, and if the engine control unit 303 judges that a print instruction has been received, the process proceeds to S802. In S802, the engine control unit 303 acquires the number of times that an abnormality has been judged to be present, which is stored in the RAM 204, and judges whether or not the number is less than a predetermined number Z. If the engine control unit 303 judges in S802 that the number of times that an abnormality has been judged to be present is less than the predetermined number Z, the process proceeds to S804. In S804, the engine control unit 303 starts printing. As a result, the sheet 2 is conveyed. Note that S805 and S806 are the same processes as S601 and S602 in FIG. 6, and therefore description thereof will be omitted.

[0057] If the destination of sheet 2 is the double-sided reversing path 29 in S806, the engine control unit 303 determines in S807 whether the number of abnormality determinations stored in the RAM 204 is less than the predetermined number Z. If the engine control unit 303 determines in S807 that the number of abnormality determinations is less than the predetermined number Z, the process proceeds to S809. If the number of abnormality determinations stored in the RAM 204 is 0, the above process is performed. Note that the processes from S809 to S820 are the same as the processes from S603 to S614 in Fig. 6, and therefore description thereof will be omitted. Note that if the number of abnormality determinations is less than the predetermined number Y in S819, the engine control unit 303 notifies the operation panel 301 of the occurrence of a misprint and prompts the user to print again.

[0058] If the engine control unit 303 determines in S802 that the number of determinations stored in the RAM 204 is equal to or greater than the predetermined number Z, the process proceeds to S803. In S803, the engine control unit 303 delays the timing to start printing, and the process proceeds to S804. This makes it possible to widen the gap between the rear end of the preceding sheet 2 and the front end of the succeeding sheet 2 more than a predetermined gap.

[0059] If the engine control unit 303 determines in S807 that the number of determinations stored in the RAM 204 is equal to or greater than the predetermined number Z, the process proceeds to S808. In S808, the engine control unit 303 determines the switching timing so as to advance the timing at which the double-sided inversion unit 311 switches the inversion flapper 32, which is determined in advance, and the process proceeds to S809. As a result, the double-sided inversion unit 311 switches the inversion flapper 32 to the double-sided inversion path 29 direction according to the timing determined in S808. If the number of determinations stored in the RAM 204 is 1, the above process is performed. By performing S803 and S808, the inversion flapper 32 is switched earlier than the succeeding sheet 2 reaches the branch position 32a. Therefore, the double-sided conveying sensor 28 detects the sheet 2 in S813, and the control is terminated.

[0060] As described above, according to the second embodiment, even if the transport path switching unit is abnormal, the sheet can be transported to the double-sided transport path. In addition, in the present embodiment, the transport path switching unit of the laser beam printer is described, but the present invention is not limited to this, and can be applied to all paper transport devices having a transport path switching unit that switches the transport path on the paper transport path.

[0061] As described above, according to the second embodiment, even if a switching mechanism for transporting paper to multiple transport paths is provided and a configuration is configured in which a user can contact a sensor at the end of a transport path, it is possible to prevent erroneous detection of an abnormality in the switching mechanism without increasing costs, such as by adding hardware.

[0062] <Other embodiments> The present invention can also be realized by a process in which a program for realizing one or more functions of the above-mentioned embodiments is supplied to a system or device via a network or a storage medium, and one or more processors in a computer of the system or device read and execute the program. Also, the present invention can be realized by a circuit (e.g., ASIC) for realizing one or more functions.

[0063] The disclosure of this embodiment includes the following configuration. (Configuration 1) a first transport path having an outlet and for transporting the recording medium; a second transport path for transporting the recording medium in a direction different from that of the first transport path; a switching means for switching between a first state in which the recording medium is guided to the first transport path and a second state in which the recording medium is guided to the second transport path; a detection means disposed at the discharge port for detecting the recording medium; A control means for controlling the switching means; An image forming apparatus comprising: an image forming apparatus comprising: a judgment means for judging that an abnormality has occurred in the switching means when the detection means detects the recording medium after the control means controls the switching means to switch to the second state. (Configuration 2) The image forming apparatus according to configuration 1, wherein the judgment means judges that an abnormality has occurred in the switching means when the time from when the detection means starts to detect the recording medium to when the detection means finishes is within a predetermined period. (Configuration 3) 3. The image forming apparatus according to claim 2, wherein the predetermined period is a time period determined based on a length of the recording medium in a transport direction and a speed at which the recording medium is transported. (Configuration 4) The image forming apparatus according to any one of configurations 1 to 3, further comprising a notification unit that notifies the user that the switching unit is in a faulty state when the determination unit determines that the switching unit is in an abnormal state. (Configuration 5) a notification unit that notifies the user that the switching means is in a fault state when the determination unit determines that the switching means is in an abnormal state, The image forming apparatus according to any one of configurations 1 to 4, wherein the determination unit counts the number of times that the switching unit is determined to be abnormal, and when the number of times is equal to or greater than a predetermined number of times, notifies the notification unit that the switching unit is in a faulty state. (Configuration 6) The image forming apparatus according to configuration 5, wherein the determining unit notifies the notifying unit that a misprint has occurred during an image forming operation when the number of times is less than the predetermined number of times. (Configuration 7) The image forming apparatus according to any one of configurations 1 to 6, wherein when the determination unit determines that the switching unit is abnormal, the control unit causes the switching unit to switch to the second state earlier than a predetermined timing. (Configuration 8) The image forming apparatus according to configuration 7, wherein the control means increases an interval at which the recording medium is fed from a predetermined interval when the determination means determines that an abnormality has occurred in the switching means. (Configuration 9) 9. The image forming apparatus according to any one of configurations 1 to 8, wherein the second transport path is a double-sided reversing path that reverses the recording medium. (Configuration 10) When the detection means is a first detection means, a third transport path along which the recording medium inverted in the double-sided inversion path is transported; A second detection means is disposed on the third transport path and detects the recording medium; Equipped with The image forming apparatus according to configuration 9, wherein the judgment means judges whether or not there is an abnormality in the switching means when the second detection means does not detect the recording medium after the control means controls the switching means to switch to the second state. (Configuration 11) The image forming apparatus according to configuration 10, characterized in that the control means determines that an abnormality has occurred in the transportation of the recording medium when the second detection means has not detected the recording medium and the time from when the first detection means starts to detect the recording medium to when it finishes detecting the recording medium is not within a predetermined period. [Explanation of symbols]

[0064] 26 Discharge conveying path 29 Double-sided inversion path 32 Inverted Flapper 39 Full Load Sensor 100 Laser Printer 303 Engine control unit 303 315 Switching Abnormality Judgment Unit

Claims

1. a first transport path having an outlet and for transporting the recording medium; a second transport path for transporting the recording medium in a direction different from that of the first transport path; a switching means for switching between a first state in which the recording medium is guided to the first transport path and a second state in which the recording medium is guided to the second transport path; a detection means disposed at the discharge port for detecting the recording medium; A control means for controlling the switching means; An image forming apparatus comprising: An image forming apparatus characterized in that it further comprises a judgment means for judging that an abnormality exists in the switching means when the detection means detects the recording medium after the control means controls the switching means to switch to the second state.

2. 2. The image forming apparatus according to claim 1, wherein the determining means determines that an abnormality has occurred in the switching means when a time from when the detection means starts to detect the recording medium to when the detection means finishes detecting the recording medium is within a predetermined period.

3. 3. The image forming apparatus according to claim 2, wherein the predetermined period is determined based on a length of the recording medium in a transport direction and a speed at which the recording medium is transported.

4. 4. The image forming apparatus according to claim 1, further comprising a notification unit that notifies the user that the switching unit is in a faulty state when the determination unit determines that the switching unit is in an abnormal state.

5. a notification unit that notifies the user that the switching means is in a fault state when the determination unit determines that the switching means is in an abnormal state, 4. The image forming apparatus according to claim 1, wherein the determination unit counts the number of times that the switching unit is determined to be abnormal, and when the count is equal to or greater than a predetermined number of times, the determination unit notifies the notification unit that the switching unit is in a faulty state.

6. 6. The image forming apparatus according to claim 5, wherein the determining unit notifies the notifying unit that a misprint has occurred during an image forming operation when the number of times is less than the predetermined number of times.

7. 4. The image forming apparatus according to claim 1, wherein the control unit causes the switching unit to switch to the second state earlier than a predetermined timing when the judgment unit judges that the switching unit is abnormal.

8. 8. The image forming apparatus according to claim 7, wherein the control means increases an interval at which the recording medium is fed from a predetermined interval when the determination means determines that the switching means is abnormal.

9. 4. The image forming apparatus according to claim 1, wherein the second transport path is a double-sided reversing path for reversing the recording medium from front to back.

10. When the detection means is a first detection means, a third transport path along which the recording medium inverted in the double-sided inversion path is transported; a second detection means disposed on the third transport path for detecting the recording medium; Equipped with The image forming apparatus according to claim 9, wherein the judgment means judges whether or not there is an abnormality in the switching means when the second detection means does not detect the recording medium after the control means controls the switching means to switch to the second state.

11. The image forming apparatus according to claim 10, characterized in that the control means determines that an abnormality has occurred in the transportation of the recording medium when the second detection means has not detected the recording medium and when the time from when the first detection means starts to detect the recording medium to when it finishes detecting the recording medium is not within a predetermined period.

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