Sheet feeding device and image forming apparatus

Abstract

When a double-feed sheet is detected by the double-feed detection means and transported to the discharge section, depending on the speed at which the sheet is transported, it may take time, potentially delaying the start of transport of subsequent sheets. [Solution] The system comprises a first loading section for loading sheets, a feeding means for feeding sheets, a double-feed detection means for detecting double feeding, a first conveying means provided downstream of the double-feed detection means for transporting sheets, a first conveying path through which sheets pass from the feeding means to the first conveying means, a second conveying path branching off from the first conveying path and through which sheets detected by the double-feed detection means pass, a second conveying means provided on the second conveying path, a second loading section for loading sheets detected by the double-feed detection means, and a control means for controlling the speed of sheets transported by the second conveying means toward the second loading section based on information on the basis weight of the sheets detected by the double-feed detection means.

Description

[Technical Field]

[0001] The present invention relates to a sheet feeding device and an image forming apparatus equipped with a sheet feeding device. [Background technology]

[0002] In general, in image forming machines such as printers that form images on sheets, a phenomenon called "double feeding" is known to occur when multiple sheets are fed together while overlapping. When double feeding occurs, the overlapping sheets (hereinafter referred to as double-feed sheets) are discharged as blank sheets on which no image is formed.

[0003] In particular, when binding or stapling is performed on a sheet on which an image has been formed, a blank sheet is interposed within the bound or stapled product. Therefore, Patent Document 1 discloses a method in which a double-feed detection means is installed on the transport path through which the fed sheets pass, and when a double-feed sheet is detected, the double-feed sheet is discharged onto an escape transport path that branches off from the normal transport path leading to the image forming unit. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2011-42469 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] However, when a double-feed sheet is detected by the double-feed detection means and transported to the escape transport path, the process can take time depending on the sheet transport speed, potentially delaying the start of transport for subsequent sheets. In the worst-case scenario, the double-feed sheet may stop within the transport path of the image forming machine, requiring the operator to remove the stopped sheet. As a result, it takes a considerable amount of time for the machine to resume operation. In particular, productivity in the field of commercial printing presses is considered important, and it is necessary to reduce downtime caused by the handling of double-feed sheets and the operator's recovery process.

[0006] Therefore, the object of the present invention is to provide a sheet feeding device that reduces the downtime of the device by changing the sheet transport control that discharges the double-feed sheet to the escape tray based on the sheet information of the double-feed sheet. [Means for solving the problem]

[0007] One aspect of the present invention is characterized by comprising: a first loading section for loading sheets; a feeding means for feeding sheets loaded in the first loading section at a first speed; a double-feed detection means for detecting double-feeding of sheets fed from the feeding means; a first transport means provided downstream of the double-feed detection means in the sheet transport direction for transporting sheets; a first transport path through which sheets pass from the feeding means to the first transport means in the sheet transport direction; a second transport path branching off from the first transport path for which sheets detected by the double-feed detection means pass; a second transport means provided in the second transport path for transporting sheets; a second loading section provided downstream of the second transport means in the sheet transport direction for loading sheets detected by the double-feed detection means; and a control means for controlling the speed of sheets transported by the second transport means toward the second loading section based on information on the basis weight of the sheets detected by the double-feed detection means. [Effects of the Invention]

[0008] According to the present invention, it is possible to reduce the downtime of the equipment by changing the sheet transport control that discharges the double-feed sheet to the escape tray based on the sheet information of the double-feed sheet. [Brief explanation of the drawing]

[0009] [Figure 1] Cross-sectional view showing the overall configuration of the printer according to Embodiment 1 [Figure 2] Diagram showing the configuration of the control unit of the paper deck according to Embodiment 1 [Figure 3] Enlarged view of the feed unit to the transport roller pair according to Embodiment 1 [Figure 4] A diagram showing the ultrasonic reception level according to Embodiment 1. [Figure 5] Flowchart of the double feed detection process by the control unit according to Embodiment 1 [Figure 6] Flowchart of double-feed processing by the control unit according to Embodiment 1 [Figure 7] Timing chart of double feed detection processing by the control unit according to Embodiment 1 [Figure 8] Diagram showing the relationship between the basis weight of the sheet and the speed and torque of the drive motor according to Embodiment 1. [Figure 9] Flowchart of double-feed processing by the control unit according to Embodiment 2 [Figure 10] Diagram showing the relationship between the required torque and drive current of the drive motor according to Embodiment 2. [Modes for carrying out the invention]

[0010] <Embodiment 1> The best mode for carrying out the present invention will be described below with reference to the drawings.

[0011] <Image forming apparatus> FIG. 1 is a cross-sectional view showing the overall configuration of a printer 1 which is an image forming apparatus according to the present embodiment. As shown in FIG. 1, the printer 1 which is an image forming apparatus includes an apparatus main body 100 which is an image forming apparatus main body for forming an image on a sheet, and a paper deck 101 for feeding the sheet to the apparatus main body 100. The paper deck 101 is connected to the apparatus main body 100, and includes large-capacity stackers 110a to 110c capable of stacking a larger amount of sheets than the sheet cassettes 61 to 64 in the apparatus main body 100.

[0012] The apparatus main body 100 is provided with an image reading unit 21 having a scanning optical system for reading an image at the upper part of the apparatus main body, and an image forming unit 22 for forming an image on a sheet is provided at the lower part thereof. Further, a plurality of stages of sheet cassettes 61 to 64 for accommodating front-loading type sheets that can be taken in and out from the front side of the apparatus main body are provided below the image forming unit 22.

[0013] The image forming unit 22 includes image forming stations 23Y, 23M, 23C, and 23K for forming images of respective colors of yellow (Y), magenta (M), cyan (C), and black (K). The image forming stations 23Y to 23K are tandem type image forming units arranged side by side along the intermediate transfer belt 31. The yellow image forming station 23Y is configured to include a photosensitive drum 11Y, and a charging device 12Y, an exposure device 13Y, a developing device 14Y, a primary transfer roller 35Y, a cleaning blade 15Y, etc. around the photosensitive drum 11Y.

[0014] The above charging device 12Y charges the surface of the photosensitive drum 11Y to a predetermined potential, and the exposure device 13Y forms an electrostatic latent image on the surface of the photosensitive drum 11Y uniformly charged by this charging device 12Y. Further, the developing device 14Y develops the electrostatic latent image formed on the photosensitive drum 11Y with toner to form a toner image. The primary transfer roller 35Y forms a primary transfer nip between the photosensitive drum 11Y and the intermediate transfer belt 31, and is configured to transfer the toner image on the photosensitive drum 11Y onto the intermediate transfer belt 31 by applying a transfer bias. Also, the cleaning blade 15Y is configured to contact the surface of the photosensitive drum 11 on the downstream side of the primary transfer nip and remove the residual toner remaining on the photosensitive drum 11Y after the primary transfer.

[0015] Note that the other image forming stations 23M to 23K have basically the same configuration as the above-described yellow image forming station 23Y except for the toner color used, and thus the description thereof is omitted.

[0016] The intermediate transfer belt 31 forms a secondary transfer portion T2 that transfers the image formed on the intermediate transfer belt 31 to the sheet together with the secondary transfer inner roller 32 and the secondary transfer outer roller 41 on the downstream side of the black image forming station 23K. Further, a fixing device 5 is provided downstream in the sheet conveyance direction of the secondary transfer portion T2, and the unfixed image on the sheet is fixed to the sheet by being pressurized and heated by this fixing device 5.

[0017] As described above, when the printer 1 prints an image read by, for example, the image reading unit 21, the read image information is photoelectrically converted, and images of each color are formed at the image forming stations 23Y to 23K. Then, the images formed at the image forming stations 23Y to 23K are primarily transferred so as to be superimposed on the intermediate belt, and this image is secondarily transferred to the sheet fed from the sheet cassettes 61 to 64 or the paper deck 101 at the secondary transfer portion T2.

[0018] Next, the sheet onto which the image has been transferred in the secondary transfer section T2 is subjected to heat and pressure in the fixing device 5 to fuse the toner image, and if the user specifies single-sided image formation mode, it is discharged from the discharge port 50 to the outside of the device. If double-sided image formation mode is selected, the sheet is transported to the inversion transport path 52, where the front and rear ends of the sheet are reversed in order to invert the front and back sides of the sheet. After that, the inverted sheet is transported again to the image formation section 22 via the double-sided transport path 85, and an image is formed on the back side of the sheet.

[0019] <Paper Deck> Next, the configuration of the paper deck 101 will be explained in detail. As shown in Figure 1, the paper deck 101 is equipped with sheet loading sections 110a to 110c, which are first loading sections with a larger capacity than the sheet cassettes 61 to 64 provided on the main body 100 of the device. It is also equipped with feeding sections 120a to 120c, which are feeding means corresponding to each sheet loading section 110a to 110c. The feeding sections 120a to 120c are suction conveying means that use a fan (not shown) to handle the sheets on the sheet loading sections 110a to 110c, and then use a belt to suction and convey them, thus constituting a feeding means for feeding the sheets loaded on the sheet loading sections 110a to 110c.

[0020] Furthermore, the paper deck 101 is equipped with a sheet transport path 250, which is a first transport path that guides sheets fed from the sheet loading sections 110a to 110c to the main body of the device 100. It is also equipped with an escape transport path 251, which is a second transport path that branches off from the sheet transport path 250 and guides sheets to an escape tray 232 provided on the upper surface of the paper deck 101. Multiple transport roller pairs 205 to 214 are arranged in the sheet transport path 250 to transfer the fed sheets to the main body of the device 100.

[0021] In this embodiment, the sheet transport path refers to the path through which the sheet passes, as shown below. This path is from when the sheet is fed from the sheet loading sections 61-64 or 110a-110c, until the image is formed on the sheet, and until the sheet is discharged outside the device (in this embodiment, until the sheet is discharged from the discharge port 50). The sheet transport path 250 constitutes the sheet transport path in the paper deck 101.

[0022] On the other hand, the escape transport path 251 branches upward from the sheet transport path 250 at a branching point 231 downstream of the transport roller pair 214, which is the first transport means, and a transport roller pair 215, which is the second transport means, is arranged on the escape transport path 251. The sheets transported by the transport roller pair 215 are discharged into an escape tray 232 provided on the upper surface of the paper deck 101 at the end of the escape transport path 251.

[0023] Furthermore, the paper deck 101 is equipped with transport roller pairs 216-220, and another paper deck can be connected to the right side of the paper deck 101, allowing for paper feeding from the extended paper deck as well.

[0024] Furthermore, downstream of the transport roller pairs 205, 206, and 207 that feed the sheets from the feeding sections 120a, 120b, and 120c to the sheet transport path 250, there are double-feed detectors 233a, 233b, and 233c, which serve as double-feed detection means for detecting double feeding of sheets. The escape tray 232 is a double-feed sheet discharge section to which sheets in which double feeding has been detected are discharged via an escape transport path that branches off from the middle of the sheet transport path. Sheets in which double feeding has been detected by the double-feed detectors 233a, 233b, and 233c are discharged to the escape tray 232.

[0025] In this embodiment, the double-feed detectors 233a, 233b, and 233c are composed of an ultrasonic transmitting sensor and an ultrasonic receiving sensor, and when sheets overlap, they determine that a double-feed has occurred based on the degree of attenuation of the ultrasonic waves passing through the sheets. Furthermore, the double-feed detection method does not necessarily have to use an ultrasonic sensor; for example, it may be composed of an optical sensor or the like.

[0026] <Paper Deck Control Unit> The configuration of the control device 300, which serves as the control unit for the paper deck 101, will be explained using Figure 2. As shown in Figure 2, the control device 300 includes a CPU 301 as a calculation means for performing various calculations, and a ROM 302 and RAM 303 that constitute storage means. The RAM 303 functions as the working area of ​​the CPU 300, and the ROM 302 stores various programs used to control the paper deck 101. Here, the CPU 301, ROM 302, and RAM 303 are connected by a bus 304. The control device 300 is equipped with an input unit, the operation unit 305, which is used by the operator to register various sheet information (size, basis weight, type, etc.) and set and execute print jobs.

[0027] Furthermore, the control device 300 is connected to double-feed detection devices 233a, 233b, and 233c, which serve as double-feed detection means. The control device 300 is also connected to a first drive motor 234a that drives a conveyor belt that picks up and conveys the sheets of the conveyor roller pairs 205-214 and the feeding sections 120a, 120b, and 120c. The control device 300 is also connected to a second drive motor 234b that drives the conveyor roller pairs 216-220, and a third drive motor 234c that drives the conveyor roller pair 215. In addition, the control device 300 is also connected to a conveyor switch 235. This conveyor switch 235 is provided at the branching section 231 so as to be movable between a first and second position, and has a solenoid as a drive source to change the posture of the switching member. When the switching member is in the first position, it guides the sheet to the sheet conveyor path 250, and when it is in the second position, it guides the sheet to the escape conveyor path 251.

[0028] Here, the ROM 302 stores a double-feed processing program P1 that is executed when the double-feed detectors 236a to 236c detect a double-feed sheet. In this embodiment, the double-feed detector 233a detects a double-feed of a sheet fed from the sheet loading unit 110a. Similarly, the double-feed detector 233b detects a double-feed of a sheet fed from the sheet loading unit 110b, and the double-feed detector 233c detects a double-feed of a sheet fed from the sheet loading unit 110c.

[0029] <Double feed detection in the paper deck's feeding section> Figure 3 is an enlarged view of the vicinity from the feeding unit 120a to the transport roller pair 212. Figures 3(a), 3(b), and 3(c) show the process of the sheet 400 being fed and transported from the feeding unit 120a in chronological order.

[0030] As described above, the double feed detector 233a consists of an ultrasonic oscillating sensor and an ultrasonic receiving sensor. The ultrasonic waves emitted from the ultrasonic oscillating sensor are received by the ultrasonic receiving sensor, and the CPU 301 determines whether or not a double feed has occurred based on the attenuation level of the ultrasonic waves. Therefore, since it is necessary to emit, receive, and determine ultrasonic waves, a predetermined amount of time is required for one double feed detection. In this embodiment, this series of times (sampling time) is set to 25 ms. In addition, the transport speed of the sheet 400 in this embodiment is set to 1000 mm / sec. Figure 3(a) shows the timing of starting double feed detection. Double feed detection starts when the leading edge of the sheet 400 in the transport direction has moved a predetermined distance past the double feed detector 233a. The leading edge of the sheet is prone to excessive flapping due to transport vibrations, making it highly likely to falsely detect a double feed. Therefore, double feed detection starts when the sheet 400 has moved a predetermined distance (flapping stabilization distance) past the double feed detector. In this embodiment, this predetermined distance is set to 20 mm.

[0031] While a double feed is being detected, the sheet 400 continues to be transported, passing through the state shown in Figure 3(b), and finally reaching the double feed detector 233a with respect to the transport direction of the sheet 400, as shown in Figure 3(c). The time it takes to go from the state in Figure 3(a) to the state in Figure 3(c) varies depending on the length of the sheet 400 with respect to the transport direction, so the number of double feed detections Cmax varies depending on the length of the sheet 400 with respect to the transport direction. Cmax can be calculated using equation (1).

[0032]

number

[0033] In equation (1), in this embodiment, Cmax is the number of double feed detections, L is the length of the sheet 400 in the transport direction (mm), b is the flutter stabilization distance (20 mm), V is the transport speed (1000 mm / sec), and S is the sampling time (25 msec).

[0034] Next, Figure 4 shows the received ultrasonic level for each detection count C by the double-feed detectors 233a, 233b, and 233c. In single-feed mode, i.e., when there is no double-feeding, the ultrasonic is received at a high level with little attenuation (single-feed level region in the figure). In double-feed mode, the ultrasonic is attenuated and received at a low level (double-feed level region in the figure). Therefore, a threshold is set for the received level (dotted line in the figure), and the CPU 301 determines that a reception level above this threshold is single-feed, and a reception level below this threshold is double-feed. In other words, Figure 4 shows that the CPU determines that the sheet is double-feeding on the third double-feed detection (C=3).

[0035] Next, the operation of the double-feed detection process performed by the CPU 301 will be explained using Figure 5. This flow is executed each time a sheet is fed from the sheet stacking units 110a, 110b, and 110c. In this embodiment, the explanation will be given for the case where a sheet is fed from the sheet stacking unit 110a.

[0036] In S500, the CPU 301 initializes the double-feed detection count C and Cmax. C is the count value of the current detection number and is stored in RAM 303. C is initially set to 1. Cmax is the maximum number of double-feed detections. In this embodiment, since double-feed detection is performed multiple times in the transport direction of the fed sheet, this number becomes Cmax. For example, if it is A4 paper, substituting the transport direction length of 297 mm into equation (1), Cmax becomes 11 times.

[0037] In S501, CPU301 waits until the sheet is transported to a position where double-feed detection can begin. Specifically, it waits until the sheet 400 is transported to the state shown in Figure 3(a).

[0038] In S502, the CPU301 starts reading using the double-feed detection sensor. As described above, the ultrasonic waves emitted from the ultrasonic oscillation sensor are received by the ultrasonic receiving sensor, and the reception level of the ultrasonic waves received by the receiving sensor is read.

[0039] In S503, CPU301 determines whether or not it is a double feed. As mentioned above, it determines whether or not it is a double feed based on the ultrasonic attenuation level.

[0040] If a double feed is determined in S503 (Yes in the diagram), CPU301 performs double feed post-processing in S504. The double feed post-processing will be explained later. If it is determined in S503 that there is no double feed (No in the diagram), CPU301 increments C in S505. Then, in S506, CPU301 determines whether C has become greater than Cmax. If it is determined in S506 that C has become greater than Cmax (Yes in the diagram), CPU301 terminates the double feed detection process. If it is determined in S506 that C is less than or equal to Cmax (No in the diagram), CPU301 performs double feed detection again.

[0041] <Control flow when sheet double feeding occurs> Next, we will explain in detail the double-feed processing that occurs when sheets are fed twice. As an example, we will assume that the sheets being handled have different basis weights: thin paper, regular paper, and thick paper. Figure 6 shows the operation of the double-feed processing performed by CPU 301.

[0042] First, in S600, the CPU 301 performs a sheet transport path switch. Specifically, it switches the orientation of the switching member of the branching section 231 to a second position that transports the sheet to the escape transport path 251.

[0043] In S601, the CPU 301 determines the basis weight of the sheet. For example, one way to determine the basis weight of the sheet is by using the sheet information set by the operation unit 305 when the operator places the sheet in the sheet cassettes 61-64 or the sheet loading sections 110a-110c.

[0044] In S602, if the basis weight of the sheet is greater than a predetermined first value (Yes in the diagram), the double-feed sheet is determined to be ordinary paper or thick paper and the process proceeds to S603. If the basis weight is less than the first predetermined value (No in the diagram), the double-feed sheet is determined to be thin paper and the process proceeds to S606.

[0045] In S603, if the basis weight of the sheet is greater than a predetermined second value (greater than the first predetermined value) (Yes in the diagram), the double-feed sheet is determined to be cardboard and the process proceeds to S604. If it is less than the second predetermined value (No in the diagram), the double-feed sheet is determined to be plain paper and the process proceeds to S605.

[0046] In S604, since the double-feed sheet is determined to be thick paper, the speeds of the drive motors 234a, 234b, and 234c are set to the second speed, which is lower than the first speed, which is the speed at which the sheet is transported during single-feed operation. In S605, since the double-feed sheet is determined to be plain paper, the speeds of the drive motors 234a, 234b, and 234c are set to the third speed, which is higher than the first speed. In S606, since the double-feed sheet is determined to be thin paper, the speeds of the drive motors 234a, 234b, and 234c are set to the fourth speed, which is higher than the third speed. In other words, the relationship of the sheet transport speeds after double-feed detection is fourth speed > third speed > first speed > second speed.

[0047] This is because thin and regular paper have more torque available for transport compared to thick paper, and the excess torque resources can be used to increase speed when double-feeding, allowing for a higher speed than the first speed. On the other hand, thick paper may have insufficient torque available for transport, so the speed should be lower than the first speed (details regarding speed and torque based on sheet basis weight are described in Figure 8).

[0048] In S607, the drive motors 234a, 234b, and 234c are driven at the speed set in S604, S605, or S606, and the double-feed sheet is discharged to the escape tray 232 via the escape transport path 251. In S608, when the rear end of the sheet is detected by the sheet rear end detection sensor 240, it is assumed that the double-feed sheet has been discharged to the escape tray 232, and the process proceeds to S609 (Yes in the figure). In S609, since the transport process for the double-feed sheet is completed, the speeds of the drive motors 234a, 234b, and 234c are set to the first speed, and preparations are made for the start of transporting the next sheet. In S610, a transport path switch (250) is performed. This returns the orientation of the switching member of the branching section 231 to the first position for transporting to the sheet transport path 250. After that, the CPU 301 terminates the double-feed process.

[0049] <Effects of processing after sheet double feeding occurs> Next, Figure 7 shows the timing chart for when thin paper and regular paper are double-fed. As an example, we assume that sheets are fed from the sheet loading section 110a. Figure 7(a) shows the case when no double-feed occurs, and Figure 7(b) shows the case when a double-feed occurs.

[0050] First, let's explain Figure 7(a) when no double feed occurs. The CPU 301 starts the sheet transport operation based on the ENABLE signal (not transporting: Low, transporting start: High) which indicates the instruction to start transporting the sheet. If no double feed occurs, the logic of the double feed detection signal (normal: Low, double feed detected: High) from the double feed detector 233a is Low. Since the sheet is not discharged to the escape tray, the sheet rear end detection signal (when transport to the escape tray is not yet complete: Low, when transport to the escape tray is complete: High) from the sheet rear end detection sensor 240 in the escape transport path 251 also remains Low. Therefore, the timing of sheet transport (T700, T701, T702) is at approximately equal intervals.

[0051] Next, we will explain Figure 7(b) when a double feed occurs. After the Nth sheet is successfully transported in T700, the transport operation of the (N+1)th sheet in T701 is started by the ENABLE signal (Low when not transporting, High when transport has started), which is a transport start instruction. In T703, the double feed detector 233a detects a double feed, and when the double feed detection signal becomes High, the double feed process is started. In T704, when the sheet rear end detection signal becomes High by the sheet rear end detection sensor 240 in the escape transport path 251, it is considered that the sheet has been discharged to the escape tray. Here, the sheet rear end detection signal is Low when transport to the escape tray is not yet complete and High when transport to the escape tray is complete. In other words, the double feed process is complete. Then, in T705, since the double feed process is complete, the transport operation of the next (N+2)th sheet is started.

[0052] Here, as shown in Figure 6, if the double-feed sheet is thin paper or plain paper, the drive motors 234a, 234b, and 234c are increased in speed to quickly discharge it into the escape tray 232. This shortens the time from the detection of double feeding in T703 to the completion of the double-feed process in T704, making it possible to start transporting the next sheet earlier. In single-feed mode, the next sheet is transported at least at the interval of T702, so the downtime can be reduced by at least ΔT.

[0053] Next, Figure 8 shows the relationship between sheet basis weight and speed. For example, thin paper (50 g / m²) 2 ) · Plain paper (81g / m 2 ) · Cardboard (325g / m²) 2 Three types are assumed. In addition, during single-pass feeding, in order to maintain the same productivity regardless of the sheet weight, the speeds of the drive motors 234a, 234b, and 234c are not switched, and the speed is unified to V to match the cardboard that requires the most torque.

[0054] The formula for calculating the torque of the drive motor is shown in equation (2). T = (ma)α ... Equation (2) In equation (2), T is the required output torque of the drive motor, m is the basis weight of the paper, a is the acceleration, and α is the margin (1.4 to 1.5). Since there is a correlation between the motor's rotational speed and the acceleration a, which increases as the motor's rotational speed increases, it is defined in Figure 8 using the motor's rotational speed.

[0055] When thin paper is fed in double feed, the basis weight is the same as the standard basis weight of thick paper when fed in single feed (325 g / m²). 2 ) compared to the basis weight of two sheets of thin paper (100g / m²) 2 ) Because the basis weight is reduced to less than 1 / 3, there is ample output torque required for the drive motor, allowing it to be driven at 3V, which is three times the speed during single-pass transport.

[0056] The basis weight of plain paper when fed in double feed is the same as the basis weight of thick paper when fed in single feed (325 g / m²). 2 ) compared to the basis weight of two sheets of plain paper (162g / m²) 2 ) . Because the basis weight is reduced to less than half, there is ample output torque required for the drive motor, allowing it to be driven at 2V, which is twice the speed during single-pass transport.

[0057] As described above, the speed can be tripled when thin paper is fed in doubles, and doubled when regular paper is fed in doubles, and the drive motors 234a, 234b, and 234c can be driven with less torque than when thick paper is fed in singles.

[0058] On the other hand, the basis weight when cardboard is fed in double feed is the same as the basis weight of cardboard when fed in single feed (325 g / m²).2 ) With respect to this, the basis weight is for two sheets of cardboard (650 g / m 2 ). Since the basis weight is doubled and exceeds the required output torque of the drive motors 234a, 234b, and 234c, by driving at 1 / 2V which is half the speed during single feed, the torque becomes equivalent to that during single feed. As a result, even when thick paper is double-fed, the drive motors 234a, 234b, and 234c can be driven and stably discharged to the escape tray 232.

[0059] As described above, as in Embodiment 1, when thin paper or plain paper is double-fed, by increasing the speed of the drive motors 234a, 234b, and 234c and quickly discharging them to the escape tray, the time until the conveyance of the subsequent paper is started can be reduced, and productivity can be improved. Also, when thick paper is double-fed, the drive motors 234a, 234b, and 234c can be driven, and it is possible to avoid the double-fed sheet from stopping inside the apparatus. By reducing the operator's recovery process, productivity is significantly improved.

[0060] <Embodiment 2> Next, Embodiment 2 in which the drive current applied to the drive motor is increased when thick paper is double-fed will be described. When compared with Embodiment 1, the processing when double-fed thick paper occurs is different. In Embodiment 1, the sheet conveyance speed was decreased, but in Embodiment 2, the current applied to the drive motor is increased.

[0061] The details of the double-feed process of Embodiment 2 are shown in FIG. 9. FIG. 9 shows the operation of the double-feed process performed by the CPU 301.

[0062] First, the CPU 301 performs conveyance path switching in S900. Specifically, the posture of the switching member of the branch portion 231 is switched to the second position for conveyance to the escape conveyance path 251.

[0063] In S901, the CPU 301 determines the basis weight of the sheet. For example, as a means for determining the basis weight of the sheet, there is the information of the sheet set by the operation unit 305 when the operator installs the sheet on the sheet stacking unit 110a.

[0064] In S902, if the basis weight of the sheet is greater than a second predetermined value (Yes in the diagram), the double-feed sheet is determined to be cardboard and the process proceeds to S903. If the basis weight is less than the second predetermined value (No in the diagram), the double-feed sheet is determined to be something other than cardboard and the process proceeds to S904.

[0065] In S903, since the double-feed sheet is made of cardboard, the drive current of the drive motors 234a, 234b, and 234c is set to a second current value which is greater than the first current value which is the drive current used for single-feed transport.

[0066] In S904, since the double-feed sheet is not cardboard, the first current value of the drive motors 234a, 234b, and 234c is set. This is because the torque required for transporting cardboard is insufficient, and the torque is increased by increasing the drive current (details regarding sheet basis weight and drive current are described in Figure 10).

[0067] In S907, the drive motors 234a, 234b, and 234c are driven by the drive current set in either S903 or S904, and the double-feed sheet is discharged to the escape tray 232 via the escape transport path 251.

[0068] In S908, when the rear end of the sheet is detected by the sheet rear end detection sensor 240, it is assumed that the double-feed sheet has been discharged into the escape tray 232, and the process proceeds to S907 (Yes in the diagram). In S907, since the double-feed sheet transport process is complete, the drive currents of the drive motors 234a, 234b, and 234c are set to the first current value, and preparations are made for the start of transporting the next sheet. In S908, the transport path is switched. The orientation of the switching member of the branching section 231 is returned to the first position for transporting to the sheet transport path 250. After that, the CPU 301 terminates the double-feed process.

[0069] Next, Figure 10 shows the relationship between the required torque and drive current when feeding cardboard in single and double passes.

[0070] The output torque of the motor is shown in equation (3). Tm=βI...Equation (3) In equation (3), β is the motor torque constant and I is the drive current.

[0071] The drive current in Figure 10 is calculated from equation (3). The drive current during single transmission is I m This is defined as follows. When double-feeding cardboard, the required output torque of drive motors 234a, 234b, and 234c is twice that of single-feeding, so the drive current is twice that of single-feeding, 2 × I, according to equation (3). m Therefore, driving the drive motors 234a, 234b, and 234c with twice the drive current value used for single-pass feeding will provide the necessary motor output torque for double-pass feeding of cardboard. This allows the drive motors 234a, 234b, and 234c to be driven even when double-passing cardboard is performed, enabling stable discharge into the escape tray 232.

[0072] In summary, when cardboard is double-feeded, the drive motors 234a, 234b, and 234c can be driven, preventing the double-feed sheet from stopping within the device. By reducing the operator's recovery process, productivity is significantly improved. [Explanation of symbols]

[0073] 110a, 110b, 110c Sheet loading section (first loading section) 120a, 120b, 120c Feeding section (feeding means) 233a, 233b, 233c Double feed detector (double feed detection means) 214 Conveyor roller (first conveying means) 215 Conveyor roller (second conveying means) 232 Escape Tray (Second Loading Section) 250-sheet conveying path (first conveying path) 251 Escape transport path (second transport path) 300 Control device (control means) 234 Drive motor (third drive motor) 305 Operation section

Claims

1. The first loading section for loading the sheets, A feeding means for feeding the sheet loaded in the first loading section at a first speed, A double-feed detection means for detecting double feeding of sheets fed from the feeding means, A first conveying means is provided downstream of the double-feed detection means in the sheet conveying direction and conveys the sheet, A first transport path through which the sheet passes from the feeding means to the first transport means in the sheet transport direction, A second transport path is provided, branching off from the first transport path, through which the sheet detected by the double-feed detection means passes. A second conveying means is provided in the second conveying path for conveying the sheet, A second loading section is provided downstream of the two transport means in the sheet transport direction and loads sheets detected by the double-feed detection means, A control means that controls the speed of the sheet being transported by the second transport means toward the second loading section based on the basis weight information of the sheet detected by the double-feed detection means, A sheet feeding device characterized by comprising the following features.

2. The control means controls the speed of the sheet being transported by the second transport means to a second speed that is lower than the first speed when the basis weight of the sheet is a first basis weight, and controls the speed of the sheet being transported by the second transport means to a third speed that is higher than the second speed when the basis weight of the sheet is a second basis weight that is lower than the first basis weight. The sheet feeding device according to feature 1.

3. The control means controls the speed of the sheet being transported by the second transport means to a fourth speed greater than the third speed when the basis weight of the sheet is a third basis weight which is smaller than the second. The sheet feeding device according to feature 2.

4. The third speed and the fourth speed are greater than the first speed. The sheet feeding device according to feature 3.

5. An input unit for inputting the basis weight of the sheets loaded in the first loading unit, The system includes a storage means for storing information on the basis weight of the sheet input by the input unit, The control means controls the speed of the sheet being transported by the second transport means toward the second loading section based on the basis weight information of the sheet stored by the storage means. The sheet feeding device according to feature 1.

6. The first loading section for loading the sheets, A feeding means for feeding the sheets loaded in the first loading section, A double-feed detection means for detecting double feeding of sheets fed from the feeding means, A first conveying means is provided downstream of the double-feed detection means in the sheet conveying direction and conveys the sheet, A first transport path through which the sheet passes from the feeding means to the first transport means in the sheet transport direction, A second transport path is provided, branching off from the first transport path, through which the sheet detected by the double-feed detection means passes. A second conveying means provided in the second conveying path for conveying sheets, A drive motor that provides drive to the second transport means, A second loading section is provided downstream of the two transport means in the sheet transport direction and loads sheets detected by the double-feed detection means, A control means that controls the current value supplied to the drive motor based on the sheet basis weight information detected by the double-feed detection means, A sheet feeding device characterized by comprising the following features.

7. The control means controls the current value supplied to the drive motor to a first current value when the basis weight of the sheet is a first basis weight, and controls the current value supplied to the drive motor to a second current value which is greater than the first current value when the basis weight of the sheet is a second basis weight which is greater than the first current value. The sheet feeding device according to feature 6.

8. A sheet feeding device according to any one of claims 1 to 7, An image forming apparatus comprising: an image forming unit that forms an image on a sheet fed by the sheet feeding device.

Images