Post-processing device and image forming system

Abstract

To punch a sheet at a prescribed position regardless of a deviation of a diameter of a conveyance roller in a post-processing device provided with punching means for punching the currently conveyed sheet.SOLUTION: A period sensor for detecting a rotation period of an upstream roller is provided. A post-processing control unit adjusts a rotational speed ((iii) timings t4, t11, t12, etc.) of a conveyance motor so as to roughly match the peripheral speed of the upstream roller with the speed component of a punch unit at a punching position in a tangential direction on the basis of the rotation period ((i) rounded numerals 1-4, etc.) of the upstream roller detected by the period sensor.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to a post-processing device and an image forming system. For example, it relates to a post-processing device provided with a punching device for punching binding holes in a sheet on which an image is formed by an image forming device such as a copying machine or a printer.

Background Art

[0002] Conventionally, a post-processing device having a rotary punch has been proposed. For example, a technique related to punching means for punching a sheet at a predetermined position while conveying the sheet by rotating a punch by conveying the sheet to a punch unit by a conveying roller disposed on a conveyance path (see, for example, Patent Document 1). In addition, it is common to use a rubber roller for the conveying roller to apply a conveying force to the sheet.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, due to wear of the surface of the rubber roller, variations in component tolerances, thermal expansion, etc., the diameter of the roller deviates from the ideal diameter. Due to the deviation of the diameter of the roller, the conveyance speed of the sheet changes, and there is a risk that the punching position on the sheet (the position of the first hole, the interval between holes, etc.) may deviate.

[0005] The present invention has been made under such circumstances, and an object of the present invention is to punch a sheet at a predetermined position regardless of the deviation of the diameter of a conveying roller in a post-processing device provided with punching means for punching a conveyed sheet.

Means for Solving the Problems

[0006] In order to solve the above problems, the present invention has the following configuration. (1) Punching means for punching at a punching position while rotating on a conveyed sheet, a first motor for driving the punching means, a first rotating body disposed upstream of the punching means in the conveyance direction of the sheet for conveying the sheet, a second motor for driving the first rotating body, and control means for controlling the driving of the first motor and the second motor, which is a post-processing device for performing post-processing on a sheet on which an image has been formed by an image forming apparatus, and includes first detection means for detecting the surface speed of the first rotating body, and the control means adjusts the rotational speed of the second motor so that the surface speed of the first rotating body detected by the first detection means substantially coincides with the tangential component of the rotational speed of the punching means at the punching position. A post-processing device characterized by this. (2 ) An image forming apparatus for forming an image on a sheet, and the post-processing apparatus described in (1 ) to An image forming system characterized by comprising.

Effects of the Invention

[0007] According to the present invention, in a post-processing apparatus provided with punching means for punching a conveyed sheet, punching can be performed at a predetermined position of the sheet regardless of the deviation of the diameter of the conveyance roller.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Mode for Carrying Out the Invention

[0009] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Example

[0010] <Explanation of the configurations of the post-processing apparatus and the image forming apparatus> FIG. 1 is a cross-sectional view showing the configurations of an electrophotographic image forming apparatus 1 and a post-processing apparatus 4, which are the image forming system of Example 1. In FIG. 1, the vertical direction is indicated by double-headed arrows. The post-processing apparatus 4 performs various post-processing such as punching and stapling on the sheet P on which an image has been formed by the image forming apparatus 1. The image forming apparatus 1 includes a paper feeding device 6 that accommodates a plurality of sheets P and feeds the sheets P one by one. The paper type of the sheet P fed from the paper feeding device 6 (thin paper, plain paper, thick paper, basis weight, etc.) is discriminated by a paper type sensor 151 disposed in the conveyance path. The sheet P is conveyed to a photosensitive drum 9, which is an image carrier rotatably supported by a cartridge 8, and a transfer roller 10, which is a transfer means to which a predetermined voltage is applied. In the cartridge 8, a toner image is formed on the surface of the photosensitive drum 9 through the steps of exposure, charging, latent image formation, and development. The latent image formation is performed by a laser scanner unit 15 that scans laser light in a direction (main scanning direction) orthogonal to the conveyance direction of the sheet P by a rotating polygon mirror and a lens to form a latent image.

[0011] The sheet P on which an unfixed toner image is formed is discharged to the discharge tray 7 through a fixing unit 11 that heats and presses the toner on the sheet P for fixing. When the sheet P is discharged to the post-processing device 4, it is sent to the horizontal conveyance unit 14 after passing through the fixing unit 11. A conveyance sensor 135 is arranged in the horizontal conveyance unit 14. The conveyance sensor 135 is a sensor for detecting the presence or absence of the sheet P in the horizontal conveyance unit 14 and for detecting the interval between the previously conveyed sheet P and the subsequent sheet P to be conveyed subsequently. The sheet P is delivered from the horizontal conveyance unit 14 to the post-processing device 4 and is conveyed by the upstream rollers 21 (21a, 21b) and the downstream rollers 22 (22a, 22b), which are the conveyance rollers of the post-processing device 4.

[0012] (upstream rollers 21, downstream rollers 22) The upstream roller 21, which is the first rotating body, is arranged on the upstream side of the punching unit 62 in the conveyance direction of the sheet P. The downstream roller 22, which is the second rotating body, is arranged on the downstream side of the punching unit 62 in the conveyance direction of the sheet P. The upstream roller 21 and the downstream roller 22 are each composed of a pair of two rollers having the same diameter. The two rollers refer to the roller that is driven via a gear (not shown) by a conveyance motor 104 (Fig. 2) described later and the roller that is driven in a driven manner in contact with that roller. Hereinafter, the symbol a is attached to the roller that is driven in a driven manner, and the symbol b is attached to the roller that receives the drive of the conveyance motor 104. In addition, when there is no need for particular distinction and explanation, they are collectively referred to as the upstream roller 21 and the downstream roller 22. It is assumed that the drive is transmitted between the upstream roller 21 and the downstream roller 22 via a belt (belt) and they rotate at the same speed.

[0013] Between the upstream roller 21 and the downstream roller 22, an entrance sensor 27 for detecting the presence or absence of the sheet P and a rotary punch unit 62 are arranged. The entrance sensor 27, which is the second detection means, detects the leading edge of the sheet P, and after a predetermined time has elapsed since the timing of detecting the leading edge of the sheet P, the punch unit 62 is rotationally driven to punch the sheet P while it is being conveyed. Details of the punching operation of the punch unit 62 will be described in <Sheet Conveyance Control and Punching Control of the Punch Unit>.

[0014] After the sheet P is punched by the punch unit 62, it is conveyed by the downstream roller 22 and the roller 24 that are rotated by a drive source (not shown) and discharged onto the upper tray 25. Inside the post-processing device 4, in addition to the upper tray 25, a lower tray 37 is also arranged, and there are a plurality of trays as discharge destinations for the sheet P. These two trays are configured to move up and down according to the amount of the bundle of sheets P (the thickness of the bundle consisting of a plurality of sheets P, hereinafter also referred to as a sheet bundle) loaded on the tray by a drive source (not shown). When the discharge destination of the sheet P is the lower tray 37, the conveyance of the sheet P is temporarily stopped before it is discharged onto the upper tray 25. The sheet P is switched back by the roller 24 and conveyed to the roller 26. The sheet P is conveyed to the intermediate stacking unit 39 by the roller 26, the roller 28, and the roller 29 that are rotated by a drive source (not shown). In the intermediate stacking unit 39, alignment operations in the conveyance direction and the width direction (a direction substantially orthogonal to the conveyance direction) of the sheet P are performed, and after the alignment of a predetermined number of sheets P is completed, a stapling operation is performed by a stapler (not shown). Thereafter, the discharge guide 34 connected to the guide drive unit 35 moves parallel in the direction of the discharge roller 36 to push out the sheet bundle, and the sheet bundle is discharged onto the lower tray 37. The operation panel 110 is for the user to manually set the size and type (paper type) of the sheet P. It is assumed that the control of the image forming apparatus 1 and the post-processing apparatus 4 is performed based on the information set using the operation panel 110. The configurations of the image forming apparatus 1 and the post-processing apparatus 4 have been described above.

[0015] <Functions of the Image Forming Apparatus and the Post-Processing Apparatus> FIG. 2 is a block diagram for explaining the functions and configurations of the image forming apparatus 1 and the post-processing apparatus 4 shown in FIG. 1. Here, only the parts related to the punching control and the conveyance control of the sheet P are extracted and explained. The image forming control unit 111 performs image forming control of the image forming apparatus 1. The image forming control unit 111 performs an image forming operation according to the paper type information and the print mode information input to the operation panel 110. Further, the image forming control unit 111 transmits the obtained paper type information, print mode information, etc. to the post-processing control unit 101. The post-processing control unit 101, which is a control means, controls the punching operation and the conveyance operation of the post-processing apparatus 4. The post-processing control unit 101 controls the punching operation and the conveyance operation according to the paper type information, print mode information, etc. transmitted from the image forming control unit 111.

[0016] The post-processing control unit 101 is composed of a motor control unit 105, a driver circuit 115 of the punching motor 102, a driver circuit 103 of the conveyance motor 104, and a sensor control unit 108. The motor control unit 105 controls the driver circuit 115 of the punching motor 102 by outputting a drive instruction to drive and control the punching motor 102. The motor control unit 105 controls the driver circuit 103 of the conveyance motor 104 to drive and control the conveyance motor 104. Hereinafter, the punching motor 102, which is the first motor of the first embodiment, is a stepping motor. On the other hand, the conveyance motor 104, which is the second motor, will be described as a DC brushless motor integrated with a hall element that outputs a pulse signal at a period proportional to the rotation speed. The conveyance motor 104 outputs an FG pulse signal to the driver circuit 103 of the conveyance motor 104. The driver circuit 115 of the punching motor 102 rotates the punch unit 62, which is a punching means, by driving the punching motor 102. Here, the punch unit 62 has a punch 202 and a die 205. The driver circuit 103 of the conveyance motor 104 rotates the upstream roller 21b and the downstream roller 22b by driving the conveyance motor 104.

[0017] The sensor control unit 108 performs three operations. The first operation is to detect the presence or absence of the sheet P from the change in the output signal of the entrance sensor 27 (hereinafter referred to as the entrance sensor signal). When the leading edge of the sheet P reaches the entrance sensor 27, the entrance sensor signal rises from, for example, a low level to a high level. When the trailing edge of the sheet P passes through the entrance sensor 27, the entrance sensor signal falls from, for example, a high level to a low level. The low level and high level of the entrance sensor signal may be reversed.

[0018] The second operation is as follows. First, the surface speed of the upstream roller 21a is detected based on the rotation period detected from the pulse signal output from the upstream roller cycle sensor 114 (hereinafter simply referred to as the cycle sensor 114), which is the first detection means for detecting the surface speed of the upstream roller 21a. Then, the rotational speed of the conveyance motor 104 is calculated based on the detected surface speed of the upstream roller 21a. The method for detecting the rotation period of the upstream roller 21a and calculating the rotational speed of the conveyance motor 104 will be described in detail in <Method for Calculating and Adjusting the Speed of the Conveyance Motor 104> described later. The third operation is to detect the signal of the home position sensor 130 that outputs a pulse signal for each rotation period of the punch 202. The home position sensor 130 is configured to repeatedly output a pulse signal by alternately blocking and transmitting light when a photointerrupter (not shown) cuts a flag (not shown). A pulse signal is also output from the downstream roller cycle sensor 131 (hereinafter simply referred to as the cycle sensor 131), which is the third detection means for detecting the surface speed of the downstream roller 22a, to the sensor control unit 108. The functions of the image forming apparatus 1 and the post-processing apparatus 4 have been described above.

[0019] <Punching Section of the Punch Unit> Next, the punch unit 62 will be described with reference to FIG. 3. In FIG. 3, the conveyance direction of the sheet P is also indicated by an arrow. In FIG. 3, in the punch unit 62, a punch 202 and a die 205 are each pivotally supported by a casing (not shown). Gears (not shown) fixed to one end of a support shaft 65 of the punch 202 and one end of a support shaft 66 of the die 205 mesh with a gear (not shown) provided on the output shaft of the punching motor 102. Then, by the rotational drive of the punching motor 102, the punch 202 is configured to be rotatable synchronously in the clockwise direction in FIG. 3, and the die 205 is configured to be rotatable synchronously in the counterclockwise direction. A die hole 206 is provided in the die 205 at a position for receiving the punch 202 when punching is performed. FIGS. 3(a), (b), (c), and (d) show how the sheet P being conveyed is punched by the punch unit 62, which is a punching device, as time elapses.

[0020] FIG. 3(a) shows that the rotational position of the punch 202 is at the home position. Here, the position shown in (c) where the sheet P is punched is referred to as the punching position, and the position of an imaginary line connecting the support shaft 65 and the support shaft 66 is referred to as the punching center position 75. The punch 202 in FIG. 3(a) is at a position in front in the rotational direction by an angle indicated by the arrow 67 from the punching center position 75. Usually, the punch 202 is stopped at this position, and the conveyance of the incoming sheet P is awaited. Even when the punch 202 is stopped at the home position, it does not interfere with the conveyance of the sheet P. FIG. 3(b) shows that the rotational position of the punch 202 is at the punching start position 70, which is the first position where punching of the sheet P begins. FIG. 3(c) shows the position where the punch 202 and the die hole 206 are exactly meshed and the sheet P is punched, which is the above-described punching position. The punching position is the punching center position 75. FIG. 3(d) shows that the rotational position of the punch 202 is at the punching end position 71, which is the second position where punching ends. Here, the acute angle θ between the punching start position 70 and the punching end position 71 shown in FIG. 3(d) is the punching section. The other angle (360° - θ) is the non-punching section excluding the punching section.

[0021] The motor control unit 105 starts the rotational drive of the punch unit 62, which has been waiting at the home position, by the punching motor 102 at a predetermined timing in synchronization with the timing when the leading end of the sheet P is detected by the entrance sensor 27 via the sensor control unit 108. Also, the motor control unit 105 can punch at a desired position on the sheet P without stopping the conveyance of the sheet P by matching the conveyance speed of the sheet P and the rotational speed of the punch unit 62. Let the component in the tangential direction of the rotational speed due to the rotational motion of the punch 202 and the die 205 shown in FIG. 3(c) be V p be.

[0022] In the range (punching section) from the punching start position 70 where the punch unit 62 starts punching the sheet P to the punching end position 71, it is assumed that the home position sensor 130 is in a light-shielded state. In the range other than this (non-punching section) of the punch unit 62, it is assumed that the home position sensor 130 is in a light-transmitting state. In the operation of stopping the punch 202 before the above-described sheet P is conveyed, the motor control unit 105 controls as follows. That is, the motor control unit 105 stops the punch unit 62 by driving the punching motor 102 by a predetermined number of steps from the timing when the home position sensor 130 transitions from the light-shielded state to the light-transmitting state. In this way, the motor control unit 105 rotates the punch unit 62 from the position in FIG. 3(d) to the position in FIG. 3(a) and stops it at the home position. The above describes the punching section, which is the first section from the first position to the second position of the punch unit 62.

[0023] <Sheet Conveyance Control and Punching Control of Punch Unit> The conveyance control of the sheet P and the punching control of the punch unit 62 will be described with reference to FIG. 4. FIG. 4(a) is a diagram showing a main part of the vicinity of the punch unit 62 of the post-processing apparatus 4 as viewed from above. FIG. 4(a) shows a state where the leading end of the sheet P has reached the upstream roller 21, and FIG. 4(b) is a plan view of the post-processing apparatus 4 in a state where the entrance sensor 27 has detected the leading end of the sheet P. In the first embodiment, the punch unit 62 punches at the left end in the direction substantially orthogonal to the conveyance direction of the sheet P (width direction), and is assumed to be arranged at the position shown in FIG. 4. Note that the punch may be made at the right end of the sheet P. 119, 120, and 121 indicated by the dashed circles show the ideal hole positions when three holes are punched in the sheet P. The holes drawn with dashed lines indicate that they are to be punched hereafter, and the holes drawn with solid lines that appear later indicate that they have already been punched.

[0024] The signs indicated by "L" in FIG. 4 all indicate distances in the conveyance direction. The distance L1 is the distance between the punching center position 75 of the punch unit 62 and the entrance sensor 27 (the center position in the conveyance direction; the same applies hereinafter). The distance L2 is the distance between the entrance sensor 27 and the center position in the conveyance direction of the ideal hole position 119. The distance L3 is the distance between the center of the ideal hole position 119 (or hole position 120) and the center of the next hole position 120 (or hole position 121), that is, the interval between the holes. The distance L4 is the distance between the end (rear end) of the hole position 119 (or hole position 120) and the end (front end) of the next hole position 120 (or hole position 121). Also, in FIG. 4, two upstream rollers 21 and downstream rollers 22 are respectively arranged at a predetermined interval in a direction substantially orthogonal to the conveyance direction. Further, in FIG. 4, the upstream roller 21 and the downstream roller 22 are respectively represented by the driven-side upstream roller 21a and downstream roller 22a.

[0025] When a print instruction in the punch mode, which is a mode for performing a punching operation on the sheet P, is sent from the image formation control unit 111 to the post-processing control unit 101, the post-processing control unit 101 causes the motor control unit 105 to perform control in the punch mode. The motor control unit 105 drives the conveyance motor 104 and controls the rotational speed of the conveyance motor 104 so that the period of the FG pulse signal input from the conveyance motor 104 becomes an ideal period. The upstream roller 21 and the downstream roller 22 rotate under the drive of the conveyance motor 104 and convey the sheet P. The conveyance speed of the sheet P is obtained from the rotational speed of the conveyance motor 104, the reduction ratio of the drive gear (not shown), and the diameters of the upstream roller 21 and the downstream roller 22. For example, let the conveyance speed of the sheet P be V s [mm / sec], and the rotational speed (number of revolutions) of the conveyance motor 104 be V smotor [rpm]. Also, let the reduction ratio of the drive gear connecting the conveyance motor 104 to the upstream roller 21 be K s , and the radius of both the upstream roller 21 and the downstream roller 22 be R s . At this time, the conveyance speed V s of the sheet P is obtained by the following formula (1). V s = R s × 2πV smotor × K s ···(1) The sheet P supplied from the horizontal conveyance unit 14 to the upstream roller 21 is conveyed to the punch unit 62 at the conveyance speed V s .

[0026] On the other hand, the punch unit 62 waits at the punching start position 70 (which is also the standby position) until the leading edge of the sheet P reaches the entrance sensor 27. When the entrance sensor 27 detects the leading edge of the sheet P and a predetermined time has elapsed, the motor control unit 105 starts driving the punching motor 102. At this time, the time (hereinafter referred to as the waiting time) to wait until driving the punching motor 102 is T stopLet it be so. The punching motor 102 is controlled to reach a predetermined rotational speed based on a predetermined speed profile, and the first punching is performed at the ideal hole position 119 on the sheet P (hereinafter, also referred to as the planned hole position 119 of the first hole). The rotational speed of the punching motor 102 is the tangential speed V of the rotational motion of the punch 202 and the die 205 shown in Fig. 3(c). p is set to a speed that matches the conveyance speed V of the sheet P s (V p = V s ). Here, the conveyance speed V of the sheet P s is the ideal conveyance speed assuming that the diameter of the upstream roller 21b does not change. That is, the punch unit 62 is controlled at a rotational speed that matches the ideal conveyance speed of the sheet P.

[0027] Here, let the time from when the entrance sensor 27 detects the leading end of the sheet P until the planned hole position 119 of the first hole reaches the punching center position 75 be T s . Let the time for the punch 202 and the die 205 to rotate at a predetermined speed profile between Fig. 3(a) and Fig. 3(c) be T p . The waiting time T stop is determined from the time T s and the time T p . Assuming that the conveyance speed V of the sheet P s is constant, using the distances L1 and L2, the time T s is obtained by the following formula (2). T s = (L1 + L2) / V s ···(2) Also, the waiting time T stop is obtained by the following formula (3). T stop = T s - T p ···(3)

[0028] For example, substituting the distance L1 = 20 [mm], the distance L2 = 31.7 [mm], and V s = 314 [mm / sec] into formula (2), T s = 164.6 [msec]. The time T pTaking it as 50 [msec], time T s and time T p Substituting into Equation (3), waiting time T stop = 114.6 [msec]. The waiting time T stop varies according to the number of holes to be punched in the sheet P and the length (sheet size) in the conveyance direction of the sheet P. In Example 1, for example, taking the condition of punching 3 holes in a LETTER size sheet P as an example, the method for obtaining the waiting time T stop was explained.

[0029] When continuously punching holes in the sheet P, the motor control unit 105 drives the punching motor 102 with a predetermined speed profile between the punching end position 71 and the punching start position 70 in FIG. 3. Thereby, the second hole and the third hole can be punched at the ideal hole positions 120 and 121 on the sheet P.

[0030] Also, between the preceding sheet P and the subsequent sheet P, the motor control unit 105 drives the punching motor 102 with a predetermined speed profile to rotate it to the home position, and temporarily stops the punch 202 and the die 205 at that position. When the leading end of the next sheet P reaches the entrance sensor 27, the post-processing control unit 101 waits for the waiting time T stop again and then drives the punching motor 102. The above is the explanation of the sheet conveyance control and the punching control of the punch unit 62.

[0031] <Deviation in the diameters of the upstream roller and the downstream roller> Next, the deviation in the diameters of the upstream roller 21b and the downstream roller 22b will be described. In Example 1, in order to apply a conveyance force to the sheet P, rubber rollers with relatively large friction with the sheet P are used for the upstream roller 21b and the downstream roller 22b. On the other hand, for the upstream roller 21a and the downstream roller 22a on the driven side, in order not to impede the conveyance of the sheet P by the upstream roller 21b and the downstream roller 22b on the driving side, rollers made of a resin material with less friction with the sheet P are used. The period sensor 114 detects the rotation period of the upstream roller 21a, that is, the roller.

[0032] The rubber roller will have its diameter changed due to, for example, the wear of its surface or the expansion caused by receiving the heat carried by the sheet P heat-fixed by the fixing unit 11. Also, there are manufacturing tolerance variations in the diameter of the rubber roller. Due to these factors, the deviation in the diameters of the upstream roller 21b and the downstream roller 22b causes the conveying speed V of the sheet P s to deviate from the ideal conveying speed, resulting in a deviation in the position of the first hole with respect to the leading end of the sheet P and the interval between holes (hereinafter referred to as the hole interval). Hereinafter, in the first embodiment, a system in which the downstream roller 22b also has the same diameter deviation as the upstream roller 21b will be described. The deviation in the diameter of the upstream roller 21b has been described above.

[0033] <Measures against the deviation between the diameters of the upstream roller and the downstream roller> Next, measures against the deviation in the diameter of the upstream roller 21b will be described. By detecting the rotation period of the upstream roller 21a with the period sensor 114 and adjusting the rotation speed of the conveying motor 104, it becomes possible to convey the sheet P at an ideal conveying speed regardless of the deviation in the diameter of the upstream roller 21b.

[0034] The rotation period of the upstream roller 21a is detected using the period sensor 114 and the flag 125 in FIG. 4. As shown in FIG. 4, the flag 125 is fixed to the shaft of the upstream roller 21a and rotates in synchronization with the upstream roller 21a. The period sensor 114 is, for example, a photo interrupter. When the flag 125 rotates to block or transmit light, a pulse signal corresponding to the rotation period of the upstream roller 21a is output to the sensor control unit 108. Here, for example, when the flag 125 blocks the light, the pulse signal becomes low level, and when the light is transmitted, the pulse signal becomes high level. Note that the level of the pulse signal may be reversed.

[0035] For example, when the diameter of the upstream roller 21b is larger than the ideal value, the rotation period becomes longer. The post-processing control unit 101 increases the rotation speed of the conveying motor 104 so that the rotation period obtained based on the pulse signal becomes an ideal period, thereby adjusting the conveying speed V of the sheet P sIt becomes possible to control it to an ideal conveyance speed. As a result, it is possible to reduce the deviation in the position of the first hole and the hole interval with respect to the tip of the sheet P. Above, the countermeasure for the deviation in the diameter of the upstream roller 21 has been described. Note that it is also possible to apply it to the deviation in the diameter of the downstream roller 22b, and the same process may be performed using the period sensor 131 of the downstream roller 22 in FIG. 2.

[0036] <Method for calculating and adjusting speed of conveyance motor> Next, the method for calculating and adjusting the rotational speed of the conveyance motor 104 will be specifically described. FIG. 5 is a diagram showing the rotational speeds of the respective motors and the output signals of the respective sensors with respect to time when three LETTER size sheets are perforated with three holes. FIG. 5(i) shows the pulse signal (shown as the upstream roller period sensor signal) output from the period sensor 114 of the upstream roller 21, and (ii) shows the entrance sensor signal output from the entrance sensor 27. (iii) shows the rotational speed of the conveyance motor 104, (iv) shows the signal (shown as the home position sensor signal) output from the home position sensor 130, and (v) shows the rotational speed of the perforation motor 102. The home position sensor signal in (iv) is at a high level in the perforation section and at a low level in the non-perforation section, but it may be the reverse. The circled numbers 1 to 4 indicate the number of rotation periods starting from the rising edge of the pulse signal of the period sensor 114 counted by the sensor control unit 108. For example, the first circled numbers 2 and 1 in FIG. 5(i) represent the two most recent periods among the plurality of measured rotation periods when the post-processing control unit 101 adjusts the rotational speed of the conveyance motor 104. Similarly, the circled numbers 4 to 1 represent the four most recent periods among the plurality of measured rotation periods when the post-processing control unit 101 adjusts the rotational speed of the conveyance motor 104. The horizontal axis in each case indicates time. Note that V smotor1 is the rotational speed of the conveyance motor 104 obtained from the rotation period, and V smotor2 is the adjusted rotational speed described later.

[0037] Timing t1 is the timing when the conveyance motor 104 is started, and a pulse signal of the cycle sensor 114 is also output in synchronization with the driving of the conveyance motor 104. For example, the post-processing control unit 101 starts (initiates driving) the conveyance motor 104 by the motor control unit 105 at the timing when it receives the punching mode information from the image formation control unit 111. Further, the post-processing control unit 101 may start the conveyance motor 104 by the motor control unit 105 based on the signal output from the conveyance sensor 135 via the image formation control unit 111. Between timing t1 and timing t2, the sensor control unit 108 waits for the time from when the conveyance motor 104 is started until the rotation speed stabilizes.

[0038] The post-processing control unit 101 starts measuring the rotation period by the sensor control unit 108 at timing t2. Note that it is assumed that the post-processing control unit 101 continues to measure the rotation period by the cycle sensor 114 until the processing is completed. The plurality of measured rotation periods may be temporarily stored in a storage unit (not shown), for example, the most recent plurality of rotation periods. Timing t3 is the timing when the rotation period of the upstream roller 21a has been measured for two cycles. The sensor control unit 108 averages the values for the two measured cycles and calculates the rotation speed of the conveyance motor 104 at the time of punching corresponding to the first sheet P using the averaged value. Here, averaging is for leveling the variation in the rotation behavior of the upstream roller 21b.

[0039] Let the ideal rotation period and the measured rotation period be T r1 , T r2 respectively, and let the current speed of the conveyance motor 104 be V smotor1 . Then, the adjusted speed V smotor2 of the conveyance motor 104 is obtained by the following formula (4). V smotor2 = T r2 / T r1 × V smotor1 ···(4) For example, when the ideal rotation period T r1 is 100 [msec], the measured rotation period T r2 is 105 [msec], and the current rotation speed V of the conveyance motor 104smotor1 Substitute it into Equation (3) with 1000 [rpm]. Then, the rotational speed V of the conveying motor 104 after adjustment smotor2 becomes 1050 [rpm].

[0040] When the current rotation period is longer than the ideal rotation period like this, that is, when the rotational speed of the upstream roller 21 is 5% slower than the ideal speed, it is possible to approach the ideal rotation period by increasing the rotational speed of the conveying motor 104 by 5%. On the other hand, when the current rotation period is shorter than the ideal rotation period, for example, when the rotational speed is 5% faster, a similar effect can be obtained by reducing the rotational speed of the conveying motor 104 by 5% using Equation (4).

[0041] The timing t4 is the timing at which the motor control unit 105 changes from the rotational speed V obtained based on the rotation period smotor1 to the adjusted rotational speed V smotor2 The timing t5 is the timing at which the entrance sensor 27 detects the leading edge of the sheet P. Here, since the punching motor 102 is driven at a predetermined speed profile, if the conveying speed Vs of the sheet P is changed after the timing t5 when the leading edge of the sheet P is detected by the entrance sensor 27, the position for punching the first hole will shift. Therefore, it is desirable that the adjustment of the rotational speed of the conveying motor 104 is completed by the time it reaches the state (timing t5) shown in FIG. 4(b) where the entrance sensor 27 detects the leading edge of the sheet P as in the first embodiment (for example, the state shown in FIG. 4(a)). That is, it is desirable that the post-processing control unit 101 adjusts the rotational speed of the conveying motor 104 before the entrance sensor 27 detects the leading edge of the sheet P.

[0042] The timing t6 is the timing at which the punching motor 102 is started after the time T stop has elapsed from the timing t5. The timing t7 is the timing when punching of the first hole in the sheet P starts, the timing t8 is the timing when the punch 202 and the die 205 are at the punching center position 75, and the timing t9 is the timing when punching of the first hole in the sheet P is completed. The timing t 10is the timing to start punching the second hole in the sheet P. The time from timing t7 to timing t 10 is the time for the sheet P to pass through a distance corresponding to the ideal hole interval. The punching motor 102 rotates at a speed profile such that the punch 202 and the die 205 make one revolution during this time. The home position sensor 130 outputs a high-level signal between timing t7 and timing t9.

[0043] Timing t 11 is the timing when punching of the third hole in the sheet P is completed. At this point, the post-processing control unit 101 substitutes the average value of the detection results of the last four (from round number 1 to round number 4) rotation cycles into the time T in Equation (4) r2 and calculates the rotational speed V of the conveying motor 104 after adjustment corresponding to the second sheet. Then, the post-processing control unit 101 changes the rotational speed of the conveying motor 104 to the adjusted rotational speed V smotor2 . In FIG. 5, the adjustment of the rotational speed of the conveying motor 104 is performed before the rear end of the first sheet P passes through the entrance sensor 27. However, since the punching operation for three holes in the first sheet P has been completed, there is no impact on the punching operation of the first sheet P. In this way, when there is a subsequent sheet P being continuously conveyed on the sheet P, the post-processing control unit 101 adjusts the rotational speed for conveying the subsequent sheet P by the upstream roller 21 after the punching operation by the punch unit 62 is completed. smotor2

[0044] ​Here, the reason for changing the acquisition frequency of the rotation period between the first sheet P (acquisition frequency of the rotation period: 2 times) and the subsequent sheets P (acquisition frequency of the rotation period: 4 times) is as follows. The first reason is that in the subsequent sheets P, the rotation period varies more than that of the first sheet P where the sheet P is not being conveyed due to the load fluctuations that occur when the upstream roller 21 and the downstream roller 22 convey the sheet P. The second reason is that before punching the first sheet P, a waiting time (in the range of timing t1 to timing t2) is required for the rotation speed of the conveyance motor 104 to stabilize, so the time available for measurement is short. The acquisition frequency for obtaining the average value of the detection results of the rotation period is not limited to these, and it may be changed according to the degree of variation in the rotation period and the accuracy of the punching position to be obtained.

[0045] Timing t 12 is the timing when the third hole of the second sheet P has been punched. At this point, the post - processing control unit 101 calculates the rotation speed V of the conveyance motor 104 corresponding to the third sheet P in the same manner as the second sheet P smotor2 and changes it to V after adjusting the rotation speed. smotor2

[0046] In the first embodiment, a printing job for three sheets P was used as an example for explanation. However, for a long - term printing job, by using the same method, it is possible to approach the ideal surface speed (peripheral speed) of the upstream roller 21b regardless of the expansion or wear of the diameter of the upstream roller 21b. Also, being able to approach the ideal surface speed of the upstream roller 21b means that it is also possible to make the speed V in the tangential direction of the rotation speed of the punch unit 62 p substantially coincide. The method for calculating and adjusting the speed of the conveyance motor 104 has been described above.

[0047] <Flowchart of speed adjustment> Next, a flowchart for adjusting the rotational speed of the conveyance motor 104 will be described with reference to FIG. 6. In step (hereinafter referred to as S) 601, the post-processing control unit 101 receives an instruction for a print job in the punch mode from the image formation control unit 111. In S602, the post-processing control unit 101 activates the conveyance motor 104 via the driver circuit 103 by the motor control unit 105. In S603, the post-processing control unit 101 waits for the rotation of the conveyance motor 104 to stabilize based on the FG pulse signal output from the conveyance motor 104 (waiting for rotation stabilization). In S604, the post-processing control unit 101 starts measuring the rotation period of the upstream roller 21a by the period sensor 114. In S605, the post-processing control unit 101 calculates the rotational speed of the conveyance motor 104 based on the rotation period of the upstream roller 21a started to be measured in S604. For example, the post-processing control unit 101 averages a plurality of (for example, two) most recent periods among the measured plurality of rotation periods and uses them for calculating the rotational speed. In S606, the post-processing control unit 101 changes the rotational speed of the conveyance motor 104 to the rotational speed corresponding to the first sheet P calculated in S605 (adjusted rotational speed V smotor2 ). In S607, the post-processing control unit 101 determines whether there is a subsequent sheet P (subsequent paper) based on the information received from the image formation control unit 111. If the post-processing control unit 101 determines in S607 that there is a subsequent paper, the process proceeds to S608. In S608, the post-processing control unit 101 confirms that the final hole has been punched for the current sheet P and returns the process to S605. In S605, the post-processing control unit 101, for example, averages a plurality of (for example, four) most recent periods among the measured plurality of rotation periods and uses them for calculating the rotational speed. If the post-processing control unit 101 determines in S607 that there is no subsequent sheet P of the paper, the process ends. The flowchart for speed adjustment has been described above.

[0048] As described above, according to the first embodiment, by measuring the rotation period of the upstream roller 21a and adjusting the rotation speed of the conveyance motor 104, even when the diameter of the upstream roller 21b deviates from the ideal diameter, it is possible to accurately punch the sheet P. Specifically, based on the rotation period of the upstream roller 21a detected by the period sensor 114, the following adjustment is performed. That is, the rotation speed of the conveyance motor 104 is adjusted so that the peripheral speed of the upstream roller 21b and the tangential velocity component at the punching position of the rotation speed of the punch unit 62 substantially coincide. In the first embodiment, the punching motor 102 is a stepping motor and the conveyance motor 104 is a DC brushless motor, but the configuration is not limited to this. For example, the conveyance motor 104 may also be a stepping motor. The punching motor 102 may use a DC brushless motor, and any means may be used as long as it can finely control the punching motor using an encoder to accurately control the rotation of the punch 202 and the die 205.

[0049] Also, in the first embodiment, the first detection means has been described using a sensor that detects the rotation period of the upstream roller 21a, but the configuration is not limited to this. For example, a general non-contact speed sensor using a semiconductor laser and a light receiving sensor may be used to detect the surface speed of the upstream roller 21a. The same effect can be obtained by irradiating two lasers at the same position on the upstream roller 21a, receiving the reflected scattered light with a light receiving sensor, and detecting the surface speed of the upstream roller 21a from the wavelength of the scattered light.

[0050] As described above, according to the first embodiment, in a post-processing apparatus including punching means for punching a conveyed sheet, it is possible to punch a predetermined position of the sheet regardless of the deviation of the diameter of the conveyance roller.

Embodiment

[0051] In Example 1, a system in which the diameters of the upstream roller 21b and the downstream roller 22b deviate from the ideal diameter together was described. In Example 2, a system that deviates from the ideal diameter and in which the diameters of the two rollers are different will be described. In Example 2, the rotation periods of both the upstream roller 21a and the downstream roller 22a are measured, and a method for adjusting the rotation speed of the conveyance motor 104 will be described. By this method, even when the diameters of both the upstream roller 21a and the downstream roller 22a deviate from their respective ideal diameters, it is possible to accurately punch the first hole and the third hole in the sheet P. In Example 2, since the configuration of the post-processing device 4 and the punching section are the same as those in Example 1, the description thereof is omitted, and the same reference numerals are used for the same configurations for description.

[0052] <Detection configuration of rotation periods of upstream roller and downstream roller> The detection configuration of the rotation periods of the upstream roller 21 and the downstream roller 22 will be described with reference to FIG. 7. FIG. 7(a) is a plan view showing a state in which the leading end of the sheet P has reached the upstream roller 21, similar to FIG. 4(a), and FIG. 7(b) is a plan view showing a state in which the trailing end of the sheet P has passed through the upstream roller 21. FIG. 7(c) is a plan view of the post-processing device 4 in a state where the trailing end of the sheet P has passed through the downstream roller 22, and the conveyance operation of the sheet P is depicted in order. The period sensor 131 detects the rotation period of the downstream roller 22a, that is, the roller. Note that the same reference numerals are given to the same configurations as in FIG. 4, and the description thereof is omitted.

[0053] The rotation period of the downstream roller 22a is measured using the period sensor 131 and the flag 134 of the downstream roller 22 in FIG. 7. The flag 134 is fixed to the axis of the downstream roller 22a and rotates in synchronization with the downstream roller 22a. The period sensor 131 also uses a photointerrupter similar to the period sensor 114. The period sensor 131 outputs a pulse signal corresponding to the rotation period to the sensor control unit 108 as shown in FIG. 2 when light is transmitted or blocked by the rotation of the flag 134.

[0054] <Measures against deviation of diameters of upstream roller and downstream roller> Next, countermeasures against the diameter deviation between the upstream roller 21 and the downstream roller 22 will be described. In the state of Fig. 7(b) where the rear end of the sheet P has passed through the upstream roller 21, since the sheet P will be conveyed only by the downstream roller 22, even if the conveyance speed corresponding to the diameter of the upstream roller 21 is set as in the first embodiment, the punching position of the third hole with respect to the sheet P will deviate. Therefore, at the timing when the rear end of the sheet P passes through the upstream roller 21, the rotation speed of the conveyance motor 104 corresponding to the diameter of the downstream roller 22 is changed. As a result, at the timing when the rear end of the sheet P has passed through the downstream roller 22, the holes that have not been punched yet, that is, the punching position of the third hole of the sheet P in Fig. 7, can be brought closer to the ideal position of the sheet P.

[0055] Fig. 8 is a diagram showing, in the configuration of the second embodiment, the rotation speeds of the respective motors and the signals output from the respective sensors when punching three holes each in three sheets P of LETTER size on the time axis. Figs. 8(i), (iii) to (vi) are the same graphs as Figs. 5(i) to (v) described in the first embodiment, and the description thereof will be omitted. From timing t1 to timing t 12 up to are the same as Fig. 5, and the description thereof will be omitted. Fig. 8(ii) shows a pulse signal (shown as the downstream roller period sensor signal) output from the period sensor 131 of the downstream roller 22. It is assumed that the post-processing control unit 101 continues to measure the rotation period by the period sensor 131 until the processing is completed. The measured plurality of rotation periods may be temporarily stored in a storage unit (not shown), for example, the plurality of most recent rotation periods.

[0056] The post-processing control unit 101 measures the rotation period of the upstream roller 21a by the period sensor 114 in the same manner as in the first embodiment, and changes the rotation speed of the conveyance motor 104 at timing t4. The post-processing control unit 101 measures the most recent four rotation periods of the pulse signal output from the period sensor 131 by the sensor control unit 108 at the timing t 22 when the rear end of the first sheet P has passed through the upstream roller 21, and averages the measured values. Timing t 22For example, it is advisable to determine it using the ideal time from when the entrance sensor 27 detects the leading edge of the sheet P (at timing t5) until the trailing edge of the sheet P passes through the upstream roller 21. In this way, after the trailing edge of the sheet P has passed through the upstream roller 21, the post-processing control unit 101 adjusts the rotational speed of the conveyance motor 104.

[0057] The post-processing control unit 101 substitutes the measurement result into time T using the formula (4) of the first embodiment r2 to calculate the adjusted rotational speed V smotor2 of the conveyance motor 104, and changes the rotational speed of the conveyance motor 104 to the adjusted rotational speed V smotor2 . At the timing t 11 when the punching of the third hole in the sheet P is completed, the post-processing control unit 101 acquires the most recent four rotation periods of the signal output from the periodic sensor 114 by the sensor control unit 108. Thereafter, the post-processing control unit 101 changes the rotational speed of the conveyance motor 104 corresponding to the second sheet in the same manner as in the first embodiment. As a result, the hole position of the first hole of the second sheet P can be punched at the ideal position 119.

[0058] The timing t 23 is the timing when the trailing edge of the second sheet P passes through the upstream roller 21. The post-processing control unit 101 changes the rotational speed of the conveyance motor 104 based on the detection result of the periodic sensor 131 of the downstream roller 22. The timing t 12 is the timing when the punching of the third hole in the second sheet P is completed. The post-processing control unit 101 changes the rotational speed of the conveyance motor 104 based on the detection result of the periodic sensor 114 of the upstream roller 21. The timing t 25 is the timing when the trailing edge of the third sheet P passes through the upstream roller 21. The post-processing control unit 101 changes the rotational speed of the conveyance motor 104 based on the detection result of the periodic sensor 131 of the downstream roller 22. Similar to the first sheet P, by changing the rotational speed of the conveyance motor 104 based on the rotation period of the pulse signal output from the periodic sensor 114 and the periodic sensor 131, punching can be performed at an ideal position with respect to the sheet P. The countermeasure for the deviation in the diameters of the upstream roller 21 and the downstream roller 22 has been described above.

[0059] <Flowchart of speed adjustment in Example 2> Next, a flowchart for adjusting the rotational speed of the conveyance motor 104 will be described with reference to FIG. 9. The same steps as those in Example 1 are assigned the same step numbers and the description thereof is omitted. The post-processing control unit 101 starts measuring the rotation period of the upstream roller 21a by the period sensor 114 in S604, and starts measuring the rotation period of the downstream roller 22a by the period sensor 131 in S609. In S606, after the post-processing control unit 101 changes the rotational speed of the conveyance motor 104 based on the detection result of the rotation period of the upstream roller 21a, it determines in S622 whether or not the rear end of the sheet P has passed through the upstream roller 21. If the post-processing control unit 101 determines in S622 that the rear end of the sheet P has not passed through the upstream roller 21, the process returns to S622, and if it determines that it has passed through, the process proceeds to S610. In S610, the post-processing control unit 101 calculates the rotational speed of the conveyance motor 104 based on the average value of a plurality of most recent periods (for example, four) among the rotation periods of the plurality of downstream rollers 22a measured by the period sensor 131. In S611, the post-processing control unit 101 changes the rotational speed of the conveyance motor 104 to the rotational speed calculated in S611. The flowchart of the speed adjustment in Example 2 has been described above.

[0060] As described above, according to Example 2, the rotation periods of the upstream roller 21a and the downstream roller 22a are measured, and the rotational speed of the conveyance motor 104 is adjusted. Thereby, even when the diameters of the upstream roller 21b and the downstream roller 22b are deviated from the ideal diameters and the diameters of each other are deviated, it is possible to accurately punch the sheet P. In this way, based on the rotation period of the downstream roller 22a detected by the period sensor 131, the rotational speed of the conveyance motor 104 is adjusted so that the peripheral speed of the downstream roller 22b and the velocity component in the tangential direction at the punching position of the punch unit 62 substantially coincide.

[0061] As described above, according to Example 2, in a post-processing apparatus provided with a punching means for punching a conveyed sheet, it is possible to punch a predetermined position of the sheet regardless of the deviation of the diameter of the conveyance roller.

Example

[0062] In Example 1, the rotational speed of the conveyance motor 104 was changed as a countermeasure against the deviation in the diameter of the upstream roller 21b. In Example 3, based on the measured rotational period of the upstream roller 21a, a method of changing the drive start timing of the punching motor 102 and the rotational speed of the hole interval (corresponding to the non-punched section) will be described. Specifically, in FIG. 5 of Example 1, the waiting time Tstop from when the entrance sensor 27 detects the leading end of the sheet P until the punching motor 102 is driven is changed to adjust the hole position 119 of the first hole. Also, the hole interval is adjusted by changing the speed profile of the punching motor 102 from the timing t9 when punching of the first hole is completed to the timing t 10 until punching of the second hole starts. Similar to Example 1, Example 3 will be described assuming that the upstream roller 21b and the downstream roller 22b are displaced by the same amount with respect to the ideal diameter. Also, since the configuration, functions, punching section, and deviation in roller diameter of the post-processing device 4 are the same as those in Example 1, the description will be omitted.

[0063] <Measures against the deviation in the diameter of the upstream roller and the downstream roller> Next, measures against the deviation in the diameter of the upstream roller 21b and the downstream roller 22b in Example 3 will be described. FIG. 10 is a timing chart of the rotational speed of each motor and the output signal of each sensor according to Example 3, and (i) to (v) are the same as those in FIG. 5(i) to (v), so the description will be omitted. Also, since the meaning of each timing is the same as that in FIG. 5, the description will be omitted.

[0064] At the timing t5 when the entrance sensor 27 detects the leading end of the sheet P, the sensor control unit 108 obtains the rotational period T of the upstream roller 21a in the same manner as in Example 1. Here, the post-processing control unit 101 calculates the predicted conveyance speed V of the sheet P from when the entrance sensor 27 detects the leading end of the sheet P until the sheet P reaches the punching center position 75. Here, the current rotational speed V of the conveyance motor 104, the ideal rotational period T, the measured rotational period T r2 is obtained. Here, the post-processing control unit 101 calculates the predicted conveyance speed V of the sheet P from when the entrance sensor 27 detects the leading end of the sheet P until the sheet P reaches the punching center position 75. Here, the current rotational speed V of the conveyance motor 104, the ideal rotational period T, the measured rotational period T s2 of the conveyance motor 104, the ideal rotational period T smotor1、 the measured rotational period T r1 r2 ​, the reduction ratio K of the drive gear connecting the conveying motor 104 to the upstream roller 21 s , the radius R of the upstream roller 21 s Let these be. The predicted conveying speed V s2 is obtained by the following formula (5). V s2 =R s ×2πV smotor1 ×K s ×T r1 / T r2 ···(5)

[0065] Let the predicted sheet conveying time until the punch 202 reaches the punching center position 75 after the entrance sensor 27 detects the tip of the sheet P be T s2 . The predicted sheet conveying time T s2 is the distance L1 from the entrance sensor 27 to the punching center position 75, and the distance L from the entrance sensor 27 to the center position of the hole position 119 of the first hole 2、 The predicted conveying speed V of the sheet P s2 is obtained by the following formula (6). T s2 =(L1 + L2) / V s2 ···(6)

[0066] Let the time T when the punch 202 and the die 205 rotate at a predetermined speed profile between FIGS. 3(a) and 3(c) be p . The time T from when the entrance sensor 27 detects the tip of the sheet P until the punching motor 102 is driven stop2 is obtained by formula (7) using the predicted sheet conveying time T s2 obtained by formula (6) and the time T p . T stop2 =T s2 -T p ···(7)

[0067] The motor control unit 105 waits for the time T stop2 obtained by formula (7) from the timing t5 when the entrance sensor 27 detects the tip of the sheet P, and drives the punching motor 102 at the timing t6. The rotational speed V of the punching motor 102 in FIG. 10 pmotor1By being driven by the target speed profile, the hole position 119 of the first hole with respect to the sheet P can be brought closer to the ideal position.

[0068] From the timing t9 when punching of the first hole is completed to the timing t when punching of the second hole starts 10 During this period, the post-processing control unit 101 causes the punching motor 102 to be controlled for acceleration and deceleration by the motor control unit 105. From this timing t9 to the timing t 10 Let the time until be the acceleration / deceleration time T accdec Using the predicted conveyance speed V s2 of the sheet P obtained by Equation (5) and the distance L4 from the ideal hole end (rear end) to the hole end (front end), the acceleration / deceleration time T accdec is obtained by Equation (8). T accdec = L4 / V s2 ···(8)

[0069] Table 1 shows the conversion table between the acceleration / deceleration time T accdec of the punching motor 102 and the target speed V pmotor2 In Table 1, the first column shows the acceleration / deceleration time T accdec (msec), and the second column shows the target speed V pmotor2 (pps). The information in Table 1 is assumed to be stored in a storage unit (not shown) of the post-processing control unit 101, for example.

Table 1

[0070] At the timing t when punching of the third hole in the first sheet P is completed 11 the sensor control unit 108 determines the rotation period T r2 Similarly, for the second and subsequent sheets P, the rotation speed V r2 which becomes the target speed is determined from the rotation period T pmotor2 Then, the sensor control unit 108 changes the rotation speed of the punching motor 102 from the timing when punching of the sheet P is completed to the timing when punching starts to the rotation speed V pmotor2 which becomes the target speed. Thereby, the same effect as that of the first sheet P can be obtained. The above is the description of the countermeasure for the deviation between the diameter of the upstream roller 21 and the downstream roller 22 in the third embodiment.

[0071] <Velocity adjustment flowchart of the third embodiment> Following the flowchart of FIG. 11, a series of processes for obtaining the waiting time T r2 and the rotation speed V stop2 of the punching motor 102 from the above-described rotation period T pmotor2 will be described using specific values. The same step numbers are assigned to the processes having the same content as those in the first embodiment, and the description thereof is omitted.

[0072] In S604, after the post-processing control unit 101 starts measurement of the rotation period of the upstream roller 21a by the sensor control unit 108, in S612, based on the average value of, for example, the four most recent rotation periods, the predicted conveyance speed V s2 of the sheet P and the waiting time T stop2 are obtained. For example, substituting R s = 10 [mm], K s = 0.3, V smotor1 = 1000 [rpm], T r1 = 100 [msec], T r2 = 105 [msec] into Equation (5), the predicted conveyance speed V s2 becomes 299 [mm / sec].

[0073] Also, with the distance L1 being 20 [mm] and the distance L2 being 31.7 [mm], substituting the obtained predicted conveyance speed V s2 , the distance L1, and the distance L2 into Equation (6), the predicted sheet conveyance time T s2 = 172.8 [msec]. Taking the time T p as 50 [msec], substituting the time T p and the obtained predicted sheet conveyance time T s2 into Equation (7), the waiting time T stop2 = 122.8 [msec].

[0074] With the distance L4 being 100 [mm], substituting the distance L4 and the obtained predicted conveyance speed V s2 into Equation (8), the acceleration / deceleration time T accdec is 334 [msec]. Seeking the target speed V accdec corresponding to the acceleration / deceleration time T pmotor2 obtained from the conversion table in Table 1, the rotational speed V pmotor2 as the target speed is 634 [pps]. In this way, the post-processing control unit 101 calculates the waiting time T stop2 and the rotational speed V pmotor2 of the punching motor 102.

[0075] In S613, the post-processing control unit 101 refers to a timer (not shown) and waits for the waiting time T stop2 (e.g., 122.8 [msec]) obtained in S612 after the entrance sensor 27 detects the leading edge of the sheet P. Thereafter, the post-processing control unit 101 drives the punching motor 102 at the rotational speed V pmotor1 as the target speed. In S614, after the post-processing control unit 101 finishes punching, it changes the target speed of the punching motor 102 to the rotational speed V pmotor2 (e.g., 634 [pps]) obtained in S612 as the target speed. In S615, the post-processing control unit 101 determines whether the final hole has been punched in the sheet P. If the post-processing control unit 101 determines in S615 that the final hole has been punched, the process proceeds to S607. If it determines that the hole has not been punched, the process returns to S613. Note that after the process of S608 is completed, the post-processing control unit 101 returns the process to S612. The flowchart of the speed adjustment in the third embodiment has been described above.

[0076] In Example 3, the post-processing control unit 101 makes the following adjustments based on the rotation period of the upstream roller 21a detected by the period sensor 114. That is, the post-processing control unit 101 adjusts the timing at which the driving of the punching motor 102 is started and the rotation speed of the punching motor 102 during the non-punching section between a predetermined punching operation and a punching operation performed subsequent to the predetermined punching operation. As described above, according to Example 3, in a post-processing apparatus including a punching means for punching a conveyed sheet, it is possible to punch a predetermined position of the sheet regardless of the deviation in the diameter of the conveying roller. Note that the adjustment of the rotation speed of the punching motor 102 may be applied to Example 2.

Explanation of Signs

[0077] 21 Upstream roller 62 Punch unit 101 Post-processing control unit 102 Punching motor 104 Conveying motor

Claims

1. Punching means for punching at a punching position while rotating on a conveyed sheet; A first motor for driving the punching means; A first rotating body disposed upstream of the punching means in the conveyance direction of the sheet and for conveying the sheet; A second motor for driving the first rotating body; Control means for controlling the driving of the first motor and the second motor; A post-processing device for performing post-processing on a sheet on which an image has been formed by an image forming apparatus, the post-processing device comprising: First detection means for detecting the surface speed of the first rotating body; The control means adjusts the rotational speed of the second motor so that the surface speed of the first rotating body detected by the first detection means substantially coincides with the component in the tangential direction at the punching position of the rotational speed of the punching means. A post-processing device characterized by this.

2. Second detection means for detecting the presence or absence of the sheet; The control means adjusts the rotational speed of the second motor before the second detection means detects the leading edge of the sheet. The post-processing device according to claim 1, characterized by this.

3. When there is a subsequent sheet continuously conveyed on the sheet, after the punching operation on the sheet by the punching means is completed, the control means adjusts the rotational speed of the second motor to convey the subsequent sheet by the first rotating body. The post-processing device according to claim 1 or claim 2, characterized by this.

4. A second rotating body disposed downstream of the punching means in the conveyance direction and for conveying the sheet by being driven by the second motor; Third detection means for detecting the surface speed of the second rotating body; The control means adjusts the rotational speed of the second motor so that the surface speed of the second rotating body detected by the third detection means substantially coincides with the component in the tangential direction at the punching position of the rotational speed of the punching means. The post-processing apparatus according to any one of claims 1 to 3.

5. The control means adjusts the rotational speed of the second motor after the rear end of the sheet has passed through the first rotating body. The post-processing apparatus according to claim 4.

6. The second rotating body has a rubber roller and a resin roller. The third detection means detects the rotation period of the roller. The post-processing apparatus according to claim 4 or claim 5.

7. The first rotating body has a rubber roller and a resin roller. The first detection means detects the rotation period of the roller. The post-processing apparatus according to any one of claims 1 to 6.

8. The first motor is a stepping motor. The second motor is a DC brushless motor. The post-processing apparatus according to any one of claims 1 to 7.

9. The punching means includes a punch that rotates in a predetermined direction and punches the sheet when driven by the first motor, and a die that rotates in a direction opposite to the predetermined direction and has a hole that meshes with the punch at the punching position. The post-processing apparatus according to any one of claims 1 to 8.

10. An image forming apparatus that forms an image on a sheet. The post-processing apparatus according to any one of claims 1 to 9. An image forming system comprising the same.

Images