JP2007119236A - Sheet material conveyance device and image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize a silent mechanism of a switching means while increasing durability of parts of the switching means by proper operation timing of a flapper without using an elastic member in an image forming device capable of switching conveyance passages for paper. <P>SOLUTION: Concerning the flapper 42 constituted to rotate by turning current carrying to a solenoid on and off, the flapper 42 is operated while a rear end of paper passes through along the flapper 42 by using a time counting means for measuring predetermined time after the paper conveyance passage is switched. The paper S itself absorbs rotary movement inertia force of the flapper 42 to reduce vibration of the flapper 42. The sound that the flapper 42 hits the paper S is suppressed by a mechanism that the flapper 42 pushes up the paper S together with reduction of vibration. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a sheet material conveying apparatus and an image forming apparatus, and is particularly suitable for application to a technique for switching a conveyance path of a sheet as a sheet material.

  2. Description of the Related Art Conventionally, in a paper transport path switching device provided in an image forming apparatus, a method of controlling a paper transport destination by providing a flapper at a branch point of the transport path and driving the flapper is generally used. In many image forming apparatuses, a paper conveyance path switching device using a flapper is mounted (see Patent Document 1).

  FIG. 1 shows the structure of a conventional image forming apparatus including a paper transport path switching device. The structure shown in FIG. 1 is a structure in which the transport destination of the sheet fed from the F direction is arbitrarily switched to the transport path A as the first transport path or the transport path B as the second transport path.

  As shown in FIG. 1, a flapper 42 as a switching unit is a member that determines a sheet conveyance direction. A sheet, which is a type of sheet material that has been conveyed, is guided by the flapper 42 and travels. When the position of the flapper 42 is in the state shown in FIG. 2A, the paper advances to the transport path A. On the other hand, when the position of the flapper 42 is in the state shown in FIG. Here, the flapper 42 has a structure interlocking with the movement of the solenoid, and its state is controlled by turning on / off the energization of the solenoid.

In recent image forming apparatuses, it is inevitable to increase the speed of the transport path switching operation in order to meet the need for higher throughput. Under such circumstances, the weight reduction of the flapper has been adopted in order to suppress the rotational operation inertia force of the flapper under high speed driving and to perform a stable operation. In many cases, the material of the flapper and the flapper rotating shaft is formed as a mold-integrated part, and the material cost is reduced by reducing the thickness.
JP-A-3-279157

  However, with regard to the transport path switching mechanism described above, the rotational driving force of the flapper, which is a switching means by turning on / off the energization of the solenoid, is generally input from one side of the flapper end because of space or the like. Thereby, torsional stress acts on the flapper. Since the lighter flapper has reduced rigidity, after the use period of the image forming apparatus becomes longer and the number of operations of the flapper advances, fatigue failure is caused by repeated torsional stress on the flapper. There was a case.

  As a method corresponding to this, there is means for increasing rigidity by increasing the thickness of the flapper. However, this method is often difficult in part due to space reasons due to downsizing of the apparatus.

  Moreover, if the rigidity is increased by increasing the thickness of the flapper, the rotational inertia force increases, which may lead to the generation of noise or fatigue failure due to vibration. That is, at the end of the flapper operation, noise due to vibration contact between the flapper and the support member that supports the flapper is generated, or fatigue failure of the flapper itself due to vibration occurs.

For this reason, from the viewpoint of noise reduction and high durability, even if the space saving is sacrificed, an elastic member such as a sponge or a spring is arranged to absorb the inertia force of the flapper rotation operation until the end of the flapper operation. Or had to be relaxed.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a sheet material conveying apparatus and an image forming apparatus capable of stabilizing the power drive by suppressing the rotational operation inertia force of the flapper with a thin flapper corresponding to high speed.

  Another object of the present invention is to provide a sheet material conveying apparatus capable of reducing a rotational operation inertia force without using an elastic member by using an appropriate flapper operation timing, having excellent durability, and realizing a silent mechanism. An object is to provide an image forming apparatus.

In order to achieve the above object, the first invention of the present invention provides:
A conveying means for conveying the sheet material; a switching means provided at a branching position for branching the sheet material into a plurality of conveying paths on the downstream side in the conveying direction of the conveying means; Driving means for switching the driving state of the switching means from the off state to the on state so as to switch the first conveying path from the first conveying path to the second conveying path different from the first conveying path. When the sheet material is conveyed to the second conveyance path, the driving unit changes the driving state of the switching unit from the on state to the off state while the rear end of the sheet material passes along the switching unit. The sheet material conveying device is configured to be switched.

In addition, the second invention of this invention,
A conveying means for conveying the sheet material; a switching means provided at a branching position for branching the sheet material into a plurality of conveying paths on the downstream side in the conveying direction of the conveying means; and disposed downstream of the switching means, The sheet material detecting means for detecting the sheet material and the switching means are driven, and the sheet material conveying path is changed from the first conveying path among the plurality of conveying paths to the second conveying path different from the first conveying path. Driving means for switching the driving state of the switching means from the OFF state to the ON state so that the sheet material is conveyed to the second conveying path, the driving means is configured such that the leading edge of the sheet material is the sheet material detecting means. The sheet material conveying apparatus is configured to switch the driving state of the switching unit from the on state to the off state after a predetermined time has passed.

  Further, the present invention provides a roller pair for conveying a sheet, a switching means provided at a branching position for branching a sheet material conveyed by the roller pair to a plurality of conveying paths, driving the switching means, and a sheet. The drive state of the switching means is changed from the off state to the on state so as to switch the material transport path from the first transport path of the plurality of transport paths to a second transport path different from the first transport path. Switching means, and after the rear end of the sheet material has passed through the roller pair, while the sheet material is passing along the switching means, the drive state of the switching means A sheet material conveying device configured to switch from an on state to an off state.

  According to the present invention, there is provided a sheet material conveying apparatus and an image forming apparatus having a conveyance switching mechanism capable of reducing a rotating operation inertia force, excellent in durability, realizing a silent mechanism, and corresponding to speeding up and downsizing. Can be provided.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In all the drawings of the following embodiment, the same or corresponding parts are denoted by the same reference numerals.

(One embodiment)
First, an image forming apparatus according to an embodiment of the present invention will be described. FIG. 1 shows a color image forming apparatus according to an embodiment of the present invention.

  As shown in FIG. 1, the color image forming apparatus according to this embodiment includes four photosensitive drums 1 (photosensitive drums 1a, 1b, 1c, and 1d). Around these photosensitive drums 1, a charging unit 2, an exposure unit 3, a developing unit 4, a transfer member 5 as a transfer unit, and a cleaning unit 6 are arranged in order according to the rotation direction. It is configured.

  The charging means 2 (2a, 2b, 2c, 2d) uniformly charges the surface of the photosensitive drum 1. The exposure means 3 (3a, 3b, 3c, 3d) irradiates a laser beam based on the image information, and forms an electrostatic latent image on the photosensitive drum 1. The developing means 4 (4a, 4b, 4c, 4d) attaches toner to the electrostatic latent image and visualizes it as a toner image. Transfer rollers 5 (5a, 5b, 5c, 5d) as transfer means transfer the toner image on the photosensitive drum 1 to a sheet. The cleaning means 6 (6a, 6b, 6c, 6d) removes post-transfer toner remaining on the surface of the photosensitive drum 1 after transfer.

  In this embodiment, the photosensitive drum 1, the charging means 2, the developing means 4, and the cleaning means 6 are integrated into a cartridge and can be attached to and detached from the apparatus main body as a process cartridge 7 (7a, 7b, 7c, 7d). It is configured.

  Further, the sheet fed from the sheet feeding section 8 is conveyed to a sheet conveying belt 9a which is a sheet carrier through a cassette conveying roller 8a2 and a registration roller 8d, and each color toner image is sequentially transferred to the sheet by an image forming unit. After being transferred and a color image recorded on the paper, the image is fixed by the fixing unit 10 as a fixing unit, and is discharged to the discharge stacking unit 13 by the discharge rollers 11 and 12.

  On the other hand, in the case of double-sided printing, after the image is fixed on the paper by the fixing unit 10 and before being discharged to the discharge stacking unit by the discharge rollers 11 and 12, the conveyance path is switched by the flapper 42 serving as a conveyance path switching unit. Switches. The sheet S is nipped and conveyed by a forward / reverse conveying roller 40 serving as a sheet material reversing unit, and passes through a sheet detection sensor 43 serving as a sheet material detecting unit.

  The sheet detection sensor 43 drives the forward / reverse transport roller 40 in reverse by a control means (not shown) attached thereto after a predetermined time. As a result, the sheet is nipped and conveyed by the conveying roller 41. Thereafter, the sheet is conveyed again to the image forming unit by the U-turn roller 17 and the registration roller 8d through the skew feeding roller 16 on the front surface of the apparatus main body, and image formation is performed on the second surface.

  The paper feeding unit 8 includes a feeding cassette 8a, a multi feeding tray 8b which is a multi feeding device, a multi feeding unit 8c, and a registration roller 8d.

  The feeding cassette 8a is configured to be able to store a plurality of sheets S and to be loaded on the inner bottom portion of the apparatus main body. When an image is formed from the feeding cassette 8a, the sheets S are separated and conveyed one by one by the cassette pickup roller 8a1. It is conveyed to the image forming unit by the cassette conveying roller 8a2 and the registration roller 8d.

In addition, the multi-feed tray 8b is normally stored in the front of the apparatus main body. The multi-feed tray 8b is rotated and opened from the apparatus main body when used, and a plurality of sheets S are set. At the time of image formation from the multi-feed tray 8b, the paper S is separated and conveyed one by one by the multi-pickup roller 8c1, and the multi-conveying roller 8c2 and the registration roller 8 are conveyed.
It is conveyed to the image forming unit by d.

  Separation and conveyance of sheets in the feeding cassette 8a and the multi-feed tray 8b are performed via a gear drive train by a feeding motor (not shown) provided in the sheet feeding unit.

  The photosensitive drum 1 as an image carrier is configured by applying an organic optical conductor layer (OPC) to the outer peripheral surface of an aluminum cylinder. Both ends of the photosensitive drum 1 are rotatably supported by flanges, and a driving force is transmitted to one end from a driving motor (not shown), thereby counterclockwise indicated by an arrow in FIG. It is rotationally driven in the direction.

  Each charging unit 2 is a conductive roller formed in a roller shape. The roller is brought into contact with the surface of the photosensitive drum 1 and a charging bias voltage is applied by a power source (not shown) to thereby form a photosensitive member. The surface of the drum 1 is uniformly charged.

  The exposure means 3 has a polygon mirror. The polygon mirror is irradiated with image light corresponding to an image signal from a laser diode (not shown).

  The developing means 4 is adjacent to the toner storage portion storing the toners of the respective colors of black, cyan, magenta, and yellow and the surface of the photoreceptor. The developing unit 4 is rotationally driven by a driving unit (not shown). The developing unit 4 includes a developing roller that performs development by applying a developing bias voltage from a developing bias power source (not shown).

  In addition, transfer members 5a, 5b, 5c, and 5d are provided inside the electrostatic conveyance belt 9a in contact with the electrostatic conveyance belt 9a. These transfer members 5a, 5b, 5c, and 5d face the four photosensitive drums 1a, 1b, 1c, and 1d, respectively. These transfer members 5 are connected to a transfer bias power source (not shown). Then, a positive electric field is applied to the sheet from the transfer member 5 via the electrostatic conveyance belt 9a. By this electric field, the respective negative color toner images on the photosensitive drum 1 are sequentially transferred onto the sheet in contact with the photosensitive drum 1, and a color image is formed on the sheet.

  The toner image detection sensor 20 detects a toner pattern formed on the belt in order to measure the color misregistration amount. Further, the toner image detection sensor 20 calculates a color misregistration amount based on the detection result, and corrects the image forming position based on the calculation result of the color misregistration amount.

  Further, the sheet S is conveyed from the sheet feeding unit 8 to the image forming area by the conveying unit 9. An electrostatic conveyance belt 9a as a sheet carrier constituting the conveyance unit 9 is disposed to face all the photosensitive drums 1a, 1b, 1c, and 1d. That is, the electrostatic conveyance belt 9a is stretched and supported by four rollers, that is, a driving roller 9b and driven rollers 9c, 9d, and 9e. Then, the electrostatic conveying belt 9a flows by the rotation of the driving roller 9b, whereby the sheet is conveyed to the transfer position, and the toner image on the photosensitive drum 1 is transferred.

  At the most upstream position of the electrostatic conveyance belt 9a, an attracting roller 9f that holds the sheet together with the electrostatic conveyance belt 9a and attracts the sheet to the electrostatic conveyance belt 9a is disposed. During the conveyance of the sheet, a voltage is applied to the suction roller 9f. As a result, an electric field is formed between the attracting roller 9f and the grounded driven roller 9c opposite to the attracting roller 9f, and dielectric polarization occurs between the electrostatic transport belt 9a and the paper, and electrostatic attracting to both of them. Produce power.

A fixing unit 10 as a fixing unit applies heat and pressure to an image formed on a sheet and fixes the image. The fixing belt 10a has a cylindrical shape having an electromagnetic induction heat generating layer, and includes a belt guide member 10c having a built-in magnetic field generating unit including an exciting coil and a T-shaped magnetic core.
Guided by The elastic pressure roller 10b sandwiches the fixing belt 10a and forms a fixing nip portion N having a predetermined width with a predetermined pressure contact force with the belt guide member 10c.

  The elastic pressure roller 10b is rotationally driven by driving means (not shown). Along with this rotation drive, the cylindrical fixing belt 10a rotates, and electromagnetic induction heat generation of the fixing belt 10a is performed by supplying power from an excitation circuit (not shown) to the excitation coil.

  In a state where the fixing nip N rises at a predetermined temperature and is temperature-controlled, the sheet S on which the unfixed toner image conveyed from the image forming unit is formed is introduced into the fixing nip N. At this time, the sheet S is introduced between the fixing belt 10a and the elastic pressure roller 10b with the image surface facing upward, that is, facing the surface of the fixing belt 10a. Thereafter, the sheet S is nipped and conveyed through the fixing nip N together with the fixing belt 10a with the image surface closely contacting the outer surface of the fixing belt 10a at the fixing nip N.

  The sheet S is heated by electromagnetic induction heat generated by the fixing belt 10a in the process of being nipped and conveyed through the fixing nip portion N. As a result, the unfixed toner image on the paper S is heated and fixed. Thereafter, the sheet S is fed to the switching mechanism.

  Next, the switching mechanism for switching a plurality of transport paths according to the present invention will be described in detail. FIG. 2 shows the flow of paper in the paper conveyance path switching unit according to this embodiment, and FIG. 3 shows the conveyance path switching mechanism according to one embodiment of the present invention.

  As shown in FIG. 2A, during single-sided printing, the paper S fixed by the fixing unit 10 (not shown in FIG. 2) is discharged to the discharge stacking unit by the discharge rollers 11 and 12. Therefore, the flapper 42 does not operate (the flapper is closed), and the paper is conveyed in the direction of arrow A and stacked on the paper discharge tray.

  On the other hand, as shown in FIG. 2B, in the case of double-sided printing, the flapper 42 is turned on / off by a solenoid (not shown in FIG. 2) before being discharged to the discharge stacking portion by the discharge rollers 11 and 12. Driven in rotation (flapper open state) and transported in the direction of arrow B.

  In this embodiment, as shown in FIG. 3, the flapper 42 and drive means (not shown) for driving the flapper 42 are configured by a link 47 as a link mechanism. The driving force by the driving means is input from one end side in the longitudinal direction of the flapper 42.

  Specifically, the flapper 42 is connected to the solenoid 46 by a link 47. Thereby, it is comprised so that rotation operation | movement is possible by ON / OFF of the electricity supply with respect to the solenoid 46. FIG.

  FIG. 3B shows a view of FIG. 3A viewed from the direction of the arrow α. As shown in FIG. 3B, when energization of the solenoid 46 is turned on, the solenoid core rod moves in the direction of arrow C while pulling the tension spring 49 whose one end is fixed by a rib (not shown). As a result, the link 47 connected to the solenoid core rod rotates in the arrow D direction. As the link 47 rotates, the flapper 42 connected to the link 47 rotates in the direction of arrow E in the figure and moves to the position indicated by the broken line (flapper open state).

  On the other hand, when the energization of the solenoid 46 is turned off, the solenoid core rod is pulled back by the spring force of the tension spring 49 as an urging spring. As a result, the flapper 42 returns to the initial position (solid line in FIG. 3) (the flapper closed state).

  As shown in FIG. 2B, the image surface side of the paper is transported along the flapper 42 in the paper transport path during duplex printing. For this reason, the surface of the flapper 42 has a streamlined shape that does not cause image quality deterioration such as scratches on the paper image surface side. The sheet S scooped up by the flapper 42 is conveyed by the forward / reverse conveying roller 40. Then, the leading edge of the paper S passes through a paper detection sensor 43 provided in the transport path switching device 44.

  The paper detection sensor 43 is for returning the position of the flapper 42 to a closed state by turning off the power supply to a solenoid (not shown) after a predetermined time by an accompanying control means. Subsequently, before the sheet S passes through the forward / reverse transport roller 40, the transport roller is driven in reverse. In this way, the sheet S is guided to another conveyance path by the flapper 42 in the closed state, returned to the image forming recording unit while being nipped and conveyed by the conveyance roller 41, and a preparation state for image formation on the second surface It becomes.

  By the way, in order to increase the torsional rigidity, the rotation of the flapper 42 is performed by transmitting a driving force to one end in the longitudinal direction of the flapper 42, so that a torsional stress is generated in the flapper 42. Therefore, it is preferable to adopt a structure with high torsional rigidity as the flapper 42.

  However, if the thickness of the flapper 42 is increased too much, the rotational operation inertia force of the flapper 42 increases. Therefore, at the stop position of the flapper 42 shown in FIG. 2A or FIG. 2B, the vibration of the flapper 42 that occurs in a certain time from the moment when the stop position is first reached until the operation inertia force is consumed to become a complete stationary state is large. Become. At this time, since the flapper 42 is supported by the support member in the transport path switching device, the flapper 42 causes vibration contact with the support member and becomes a source of abnormal noise.

  Thus, repeated torsional stress and vibration contact with the flapper 42 not only cause unpleasant noise for the user, but also may cause fatigue failure of the flapper 42. Therefore, the operation timing of the flapper according to the present invention will be described below.

  In other words, when the sheet is conveyed to one of the plurality of conveyance paths, the driving unit performs a predetermined time after the leading edge of the sheet passes through the sheet detection sensor 43 disposed on the downstream side of the flapper 42. After elapses, the driving state is switched from the on state to the off state.

（各動作タイミングにおけるフラッパ先端の挙動） Specifically, FIGS. 4A to 4C show the states of three different paper positions. Table 1 below shows the behavior of the tip of the flapper when the flapper 42 is stopped when the flapper 42 is operated in each state. In the measurement, a high-speed camera was used, and the behavior of the tip of the flapper 42 was investigated in units of 4 ms. In Table 1 below, the time when the flapper first reached the original stop position was defined as 0 on the horizontal axis. Further, the position of the tip of the flapper in a state where the flapper is completely stationary (a state where the rotational motion inertia force is 0) is set to 0 on the vertical axis.

(Flapper tip behavior at each operation timing)

  FIG. 4A shows a point in time when a predetermined time has elapsed after the flapper 42 scoops up the paper and is nipped and conveyed by the forward / reverse conveying roller 40. At this time, the trailing edge of the paper S is completely separated from the flapper 42. From Table 1, it can be seen that when the flapper 42 is closed in the state of FIG. 4A, the initial amplitude at the tip of the flapper is the largest, and it takes about 300 ms until the amplitude is attenuated. In addition, since the contact vibration between the flapper support member (not shown) and the flapper 42 is large, the sound becomes annoying for the user. Further, in the flapper rotation operation endurance test under these conditions, a fatigue failure phenomenon due to repeated stress on the flapper 42 was confirmed at about 70% of the sheet material transport device life.

  On the other hand, in the state shown in FIG. 4C, the leading edge of the sheet S scooped up by the flapper 42 is sandwiched between the forward and reverse transport rollers 40. However, the trailing edge of the sheet S does not pass through the discharge rollers 11 and 12. When the flapper 42 is closed in this state, the sheet S is in a state close to the one-dot chain line shown in FIG. 4C and is conveyed while being rubbed by the flapper 42. At this time, the vibration of the flapper 42 is absorbed by the paper S, and thus is suppressed most. On the other hand, the sound of the flapper 42 being hit by the paper S increases. Further, since the sheet S is conveyed while being rubbed by the flapper 42 and a conveyance path in the vicinity of the flapper 42, a phenomenon of image quality deterioration due to scratches due to sliding with the flapper 42 or the like appears on the image surface of the sheet S. There is also.

  Based on such earnest studies by the present inventors, as shown in FIG. 4B, in this embodiment, the flapper 42 is closed in a state where the rear end of the sheet S is passing along the flapper 42. Therefore, the energization of the solenoid 46 is switched to the off state.

That is, at the time shown in FIG. 4B, the flapper 42 is closed. Thus, the sheet S is brought into contact with the flapper 42 within a time period from when the flapper 42 first reaches the operation completion position until the rotational inertia force of the flapper 42 is consumed and becomes completely stationary. To do. As a result, the rotational operation inertia force of the flapper 42 is absorbed by the paper S. The vibration of the flapper 42 is suppressed to a sufficient level from the viewpoint of durability, and the sound of hitting the paper S is suppressed by a mechanism that pushes up the paper S. As a result, as shown in FIG. 4C, the sheet S is not sandwiched between the conveyance path and no sliding scratch is formed on the image surface. Note that after the trailing edge of the sheet S passes through the discharge rollers 11 and 12 that are a pair of rollers provided immediately upstream of the flapper 42, the sheet S is passing along the flapper 42. In addition, the energization of the solenoid may be turned off in order to close the flapper 42.

  In addition, it was confirmed that the fatigue failure phenomenon of the flapper 42 due to repeated stress does not occur even after the operation durability of the flapper 42 has advanced by adopting the above-described method.

  This is based on the following reason according to the knowledge of the present inventors. That is, in the flapper according to the prior art, since driving is input from one end side, torsional stress is repeatedly applied to the flapper. On the other hand, by adopting the above-described operation timing, the flapper 42 is moved within the time from the initial arrival of the flapper 42 to the operation completion position until the complete stationary state in which the rotary operation inertia force of the flapper is consumed. The sheet S contacts almost the entire width. As a result, torsional stress generated in the flapper 42 is absorbed by the paper S and relaxed.

  Also in the fatigue fracture test by the present inventor, according to the above-described method, the conventional fatigue fracture phenomenon of the flapper is not recognized even at the stage of about 150% of the operating life (opening / closing operation about 300,000 times). It was. Further, it is possible to achieve a silent mechanism by reducing noise due to vibration of the flapper 42 without using an elastic body such as a sponge or a spring. Specifically, as a result of measuring the sound pressure level under the conditions according to this embodiment and in a semi-anechoic environment, a reduction of about 3 dB was confirmed.

  The paper detection sensor 43 shown in FIG. 4B also functions as a time measurement unit that measures the time for switching the flapper drive state from the on state to the off state at a predetermined time after the paper S passes through the flapper 42. Since the paper detection sensor 43 is disposed in the vicinity of the downstream side in the conveyance direction of the flapper 42, the flapper 42 can be operated with high timing accuracy. Further, it is desirable to dispose the paper detection sensor 43 as close as possible to the front and back of the flapper 42 in the transport path.

  For example, it is assumed that the paper detection sensor 43 is arranged on the upstream side of the conveyance path far from the flapper 42. In this case, the arrival time of the sheet S to the sheet conveyance path switching unit slightly changes due to the tolerance of each part interposed in the conveyance path or the change in the usage environment of the image forming apparatus. Due to this change in arrival time, the operation timing of the flapper 42 may deviate from a predetermined timing.

  Here, in this embodiment, the transport distance required until the paper S passes through the flapper 42 and is detected by the paper detection sensor 43 is about 50 mm. The number of intervening parts between the flapper 42 and the paper detection sensor 43 is three. That is, a frame 50 that also serves as a flapper support member 48 that supports both ends of the flapper, a cover 51 that is rotatably attached to the frame 50, and a flag (not shown) that is rotatably attached to the cover 51 and turns on / off the paper detection sensor 43. )).

  Further, since the sheet detection sensor 43 is disposed on the conveyance path where the sheet S is regulated and conveyed by a conveyance guide (not shown), the leading edge of the sheet S passes through the sheet detection sensor 43 with a stable behavior. As a result, it is possible to minimize the accumulated component tolerance and sufficiently increase the accuracy of the operation timing of the flapper 42.

  The rotation operation timing of the flapper 42 described above can be changed according to the type of the paper S (paper type) and the usage environment. In this case, detection of the type (paper type) of the paper S includes a method of directly inputting by the user or a method of automatically detecting using a sensor. In addition to these methods, it is also desirable to set various appropriate timings and control the operation timing of the flapper 42 to be changed. The effect of suppressing the sound of the flapper 42 hitting the paper S and the effect of suppressing the vibration of the flapper 42 can be obtained by appropriate rotation operation timing in the flapper.

  As described above, according to this embodiment, even if an extra elastic member such as a sponge or a spring is not used, fatigue failure due to vibration of the flapper 42 or torsional stress, and between the flapper 42 and its supporting member. Noise due to vibration contact can be prevented.

  Further, according to this embodiment, in a thin flapper that is thinned to cope with the recent increase in speed and downsizing, the rotational driving inertia force can be suppressed and the power drive can be stabilized. Further, by adopting an appropriate flapper operation timing, a sheet material conveying apparatus having a conveyance path switching mechanism capable of realizing a silent mechanism while improving the durability of a flapper component without using an elastic member, and image formation A device can be provided.

  Although one embodiment of the present invention has been specifically described above, the present invention is not limited to the above-described embodiment, and various modifications based on the technical idea of the present invention are possible. For example, the number, interval, and configuration of the image forming apparatus described in the above-described embodiment are merely examples, and a different number, interval, and configuration of the image forming apparatus can be adopted as necessary. It is.

1 is an image forming apparatus including a conveyance path switching device according to a conventional technique. It is sectional drawing for demonstrating the conveyance path | route of the conveyance path switching apparatus by one Embodiment of this invention. It is a basic diagram which shows the conveyance path switching mechanism by one Embodiment of this invention. It is sectional drawing explaining the flapper opening / closing timing in this invention.

Explanation of symbols

1, 1a, 1b, 1c, 1d Photosensitive drum 2, 2a, 2b, 2c, 2d Charging means 3, 3a, 3b, 3c, 3d Exposure means 4, 4a, 4b, 4c, 4d Developing means 5, 5a, 5b , 5c, 5d Transfer roller 6, 6a, 6b, 6c, 6d Cleaning means 7, 7a, 7b, 7c, 7d Process cartridge 8 Paper feed unit 8a Feed cassette 8a1 Cassette pick-up roller 8a2 Cassette transport roller 8b Multi feed tray 8c Multi-feeding unit 8c1 Multi-pickup roller 8c2 Multi-conveying roller 8d Registration roller 9 Conveying means 9a Electrostatic conveying belt 9b Driving roller 9c, 9d, 9e Driven roller 9f Adsorption roller 10 Fixing unit 10a Fixing belt 10b Elastic pressure roller 10c Belt Guide member 11, 12 Discharge roller 13 Discharge Loading part 16 skew roller 17 U-turn roller 20 the toner image detection sensor 40 forward and reverse conveying rollers 41 conveying roller 42 flapper 43 sensor 43 the paper detection sensor 44 conveying path switching unit 46 solenoid 47 link 48 flapper support member 49 spring 50 frame 51 cover

Claims (5)

Conveying means for conveying the sheet material;
Switching means provided at a branching position for branching the sheet material into a plurality of conveying paths on the downstream side in the conveying direction of the conveying means;
The switching unit drives the switching unit, and switches the sheet material conveyance path from the first conveyance path among the plurality of conveyance paths to a second conveyance path different from the first conveyance path. Driving means for switching the driving state from the off state to the on state,
When the sheet material is transported to the second transport path, the driving unit switches the driving state of the switching unit from the on state to the off state while the rear end of the sheet material passes along the switching unit. It is comprised so that it may switch to a state. The sheet | seat material conveying apparatus characterized by the above-mentioned. Conveying means for conveying the sheet material;
Switching means provided at a branching position for branching the sheet material into a plurality of conveying paths on the downstream side in the conveying direction of the conveying means;
A sheet material detecting means that is disposed downstream of the switching means and detects a sheet material;
The switching unit drives the switching unit, and switches the sheet material conveyance path from the first conveyance path among the plurality of conveyance paths to a second conveyance path different from the first conveyance path. Driving means for switching the driving state from the off state to the on state,
When the sheet material is transported to the second transport path, the driving unit switches the driving state of the switching unit from the on state to the off state after a predetermined time after the leading edge of the sheet material passes through the sheet material detecting unit. It is comprised so that it may switch to a state. The sheet | seat material conveying apparatus characterized by the above-mentioned. A pair of rollers for conveying the sheet;
Switching means provided at a branching position for branching the sheet material conveyed by the roller pair into a plurality of conveying paths;
The switching means drives the switching means and switches the sheet material conveyance path from the first conveyance path of the plurality of conveyance paths to a second conveyance path different from the first conveyance path. Driving means for switching the driving state from the off state to the on state,
The drive state of the switching means is switched from the on state to the off state after the trailing edge of the sheet material has passed through the roller pair and while the sheet material is passing along the switching means. It is comprised in the sheet material conveying apparatus characterized by the above-mentioned. The switching means and the driving means are constituted by a link mechanism,
The sheet material conveying apparatus according to any one of claims 1 to 3, wherein a driving force by the driving unit is configured to act on one end side along a longitudinal direction of the switching unit. . The sheet material conveying device according to any one of claims 1 to 4,
Image forming means for forming an image on a sheet material;
In an image forming apparatus having sheet material reversing means for reversing the sheet material image-formed by the image forming means,
The first conveying path is a conveying path for discharging the image-formed sheet material out of the image forming apparatus, and the second conveying path is the sheet material image-formed by the image forming means. An image forming apparatus, wherein the image forming apparatus is a conveyance path for conveying the sheet material to the sheet reversing unit.

Images