JP2015016931A - Image formation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To secure flexibility of double-sided printing control even number of motors is reduced.SOLUTION: An image formation device comprises a switching unit 100 having a pendulum gear 101 to which rotary drive force of a motor is transmitted and which is engaged to a first gear train or a second gear train. The pendulum gear 101 is movable to a normal rotation position where it is engaged to the first gear train (91, 92, 93, 94, 96) and rotates a switch back roller 52 in a normal rotation direction, a reverse rotation position where it is engaged to the second gear train (91, 92, 95, 96) and rotates the switch back roller in a reverse rotation direction, and to a non-engagement position where it is not engaged to the first gear train and the second gear train. The switching unit 100 has a switching mechanism 200 which can initialize the position of the pendulum gear at all positions of the normal rotation position, the reverse rotation position, and the non-engagement position when starting power supply of the image formation device.

Description

  The present invention relates to an image forming apparatus, and more particularly to a technique for performing duplex printing in an image forming apparatus.

  Conventionally, as a capacitor-insulated small-capacity power supply, for example, one described in Patent Document 1 is known. Japanese Patent Application Laid-Open No. 2004-228688 discloses a technique for providing a motor for driving a paper discharge roller in addition to a motor for driving a photoconductor and the like, and performing double-sided printing by rotating the paper discharge roller in the reverse direction.

JP 2011-048328 A

  However, in Patent Document 1, since the number of motors increases, there is a possibility that noise due to motor noise increases. For this reason, there has been a demand for a technique that can reduce the number of motors to suppress noise caused by motor noise and ensure flexibility of double-sided printing control even when the number of motors is reduced.

  The present invention provides a technique capable of ensuring the flexibility of double-sided printing control even when the number of motors is reduced.

  An image forming apparatus disclosed in this specification includes an image forming unit that forms an image on a recording medium, a motor that generates a rotational driving force in one direction, and a rotation direction for switching a recording medium conveyance direction. A switchback roller that is switched between a forward rotation direction and a reverse rotation direction; and a first gear train that transmits the rotational driving force of the motor to the switchback roller so that the rotation direction of the switchback roller is the forward rotation direction. A second gear train that transmits the rotational driving force of the motor to the switchback roller so that the rotational direction of the switchback roller is a reverse direction; and the first gear train that is transmitted the rotational driving force of the motor. Or a switching unit having a pendulum gear meshing with the second gear train, the pendulum gear meshing with the first gear train, and the switchback roller A forward rotation position that rotates in the rotation direction, meshes with the second gear train, a reversal position that rotates the switchback roller in the reverse direction, and a non-engagement with neither the first gear train nor the second gear train The switching unit can move any of the normal rotation position, the reverse position, and the non-meshing position when initializing the position of the pendulum gear when power supply to the image forming apparatus is started. A switching mechanism that enables initialization even at the position is included.

  According to this configuration, the position of the pendulum gear can be moved to the forward rotation position, the reverse rotation position, and the non-meshing position by one motor. Further, the initial position of the pendulum gear is possible at any of the forward rotation position, the reverse position, and the non-meshing position by the switching mechanism. Therefore, even when the number of motors is reduced, it is possible to ensure flexibility in duplex printing.

In the image forming apparatus, the switching unit is a switching gear having a holder that rotatably supports the pendulum gear, and a cam that rotates the holder by pressing the holder. A switching gear that switches the forward rotation position, the reverse rotation position, and the non-meshing position of the pendulum gear by rotating, and a driving gear that transmits a rotational driving force from the motor to the switching gear, The switching mechanism is configured to switch the position of the pendulum gear, and a fixing mechanism that fixes the switching gear in a non-rotatable manner at positions corresponding to the forward rotation position, the reverse rotation position, and the non-meshing position of the pendulum gear. And an opening mechanism that rotatably opens the switching gear fixed by the fixing mechanism.
According to this configuration, the switching mechanism can be suitably configured by the fixing mechanism and the opening mechanism.

In the image forming apparatus, the opening mechanism includes a solenoid, and the fixing mechanism rotates an intermediate gear that transmits the rotational driving force from the motor to the switching gear via the driving gear. A first link that is supported by the switching gear and that rotatably supports the intermediate gear, and a first link that is movably coupled to the first link and that engages with the switching gear. Two links, an engaging portion that is formed on the switching gear, engages with the engaging protrusion and fixes the switching gear, and is connected to the second link, and the second link is on the engaging portion side. A biasing spring, and the engagement portion engages with the engagement protrusion to fix the switching gear at a position corresponding to the forward rotation position, and the engagement The protrusion engages and moves forward to the position corresponding to the reverse position. A second engagement portion that fixes the switching gear; and a third engagement portion that engages with the engagement protrusion and fixes the switching gear at a position corresponding to the non-meshing position. When the position of the pendulum gear is changed, the engagement between the engagement protrusion and the engagement portion may be released against the urging force of the spring by acting on the second link. .
According to this configuration, the opening mechanism and the fixing mechanism can be preferably configured.

Further, in the image forming apparatus, each of the engaging portions has the first engaging portion, the second engaging portion, and the second engaging portion in the rotation direction of the switching gear when the position of the first engaging portion is used as a reference. And you may make it form in order of the said 3rd engaging part.
According to this configuration, it is possible to switch the normal rotation position → reverse position → stack position → normal rotation position (three quadrants) regarding the position of the pendulum gear.

Further, in the image forming apparatus, the third engaging portion is formed at two positions on the switching gear, and each of the engaging portions has a position of the switching gear when the position of the first engaging portion is used as a reference. The first engagement portion, the third engagement portion, the second engagement portion, and the third engagement portion may be formed in this order in the rotation direction.
According to this configuration, it is possible to switch the normal rotation position → stack position → reverse position → stack position → normal rotation position (four quadrants) regarding the position of the pendulum gear.

In the image forming apparatus, the first engagement portion and the second engagement portion are formed on the switching gear at a position where an angle of rotation of the switching gear forms 180 °. The first engaging portion and the third engaging portion may be formed at a position where the rotation angle forms 90 °.
According to this configuration, when the position of the pendulum gear is changed in three quadrants or four quadrants, the rotation of the switching gear can be simply controlled in units of 90 °. That is, switching between the three quadrants or the four quadrants can be performed easily and suitably. Here, the rotation angles “180 °” and “90 °” are not necessarily limited to just “180 °” and “90 °”. For example, 181 ° or 179 ° is included in “180 °”.

In the image forming apparatus, when the intermediate gear is retracted from the drive gear, the intermediate gear may be retracted in the direction opposite to the rotation direction of the drive gear with the rotation shaft of the switching gear as the rotation center.
According to this configuration, since the degree of contact with the drive gear is reduced when retracting from the drive gear, compared to when the drive gear is retracted in the same direction as the rotation direction, abnormal noise due to contact with the drive gear is reduced. Can be suppressed.

In the image forming apparatus, the switching gear includes a toothed portion that meshes with the intermediate gear when the pendulum gear is located at the reverse position and the non-meshing position, and the pendulum gear is located at the normal rotation position. And the switching gear is integrally formed with the switching gear on the surface opposite to the surface on which the cam is formed, and the intermediate gear and the toothless portion facing the intermediate gear. The first engaging portion corresponds to the missing tooth portion from a circumferential portion corresponding to the toothed portion of the cylindrical portion. It is formed as a guide groove that guides to a circumferential portion, and the second and third engaging portions are formed as locking grooves that lock the engaging projections at the circumferential portion of the cylindrical portion. Good.
According to this configuration, when the pendulum gear is initialized at the normal rotation position, the intermediate gear can be initialized in a state where the intermediate gear is located at the missing tooth portion of the switching gear. Therefore, even if the intermediate gear rotates accidentally in the initialization state, the switching gear does not rotate, and the initialization state at the normal rotation position can be stabilized.

  Further, in the image forming apparatus, a discharge port that can discharge the recording medium on which an image is formed, and a conveyance that is arranged upstream of the image forming unit in the conveyance direction and receives a rotational driving force from the motor. A first conveyance path configured to be conveyed to the conveyance roller and to pass through the image forming unit to reach the switchback roller; a roller; a paper feeding unit on which the recording medium is placed; And switching the position of the pendulum gear with the second transport path configured such that the recording medium merges from the switchback roller to the upstream side of the image forming unit of the first transport path in the transport direction. And a control unit that controls the opening mechanism, and the control unit is capable of executing a double-sided image forming process for forming an image on the recording medium. And a first recording medium having a second surface and a second recording medium having a first surface and a second surface, the first recording medium being a process of forming an image on each surface of the two recording media. Is supplied from the sheet feeding unit to the first conveying path by the conveying roller, and an image is formed on the first surface of the first recording medium by the image forming unit and conveyed to the switchback roller. A first step of holding the forward rotation position, and switching the position of the pendulum gear from the forward rotation position to the reverse position so that the first recording medium is transported through the second transport path. A second step of holding the position, a third step of switching the position of the pendulum gear from the reverse position to the non-meshing position, and holding the non-meshing position, and a position of the pendulum gear from the non-meshing position. The image forming unit forms an image on the first surface of the second recording medium, and the second recording medium holds the forward rotation position so that the second recording medium is conveyed to the switchback roller. A fourth step, a fifth step of switching the position of the pendulum gear from the normal rotation position to the reverse position, and holding the reverse position so that the second recording medium is transported to the second transport path; The position of the pendulum gear is switched from the reverse position to the forward rotation position, an image is formed on the second surface of the first recording medium, and an image is formed on the second surface of the second recording medium. As described above, a sixth step of holding the forward rotation position may be included.

According to this configuration, even when the number of motors is reduced, “2 → 4 → 1 → 3 printing” can be suitably performed when images are formed on both sides of a sheet with one set of two sheets. In the image forming apparatus, the control unit may perform the switching in the sixth step for a longer time than in the second step to the fifth step. The opening mechanism may be controlled to open the gear rotatably.
According to this configuration, when the position of the pendulum gear is switched from the reverse position to the normal rotation position, it can be performed directly without using the stack position. Therefore, switching control can be simplified.

  In the image forming apparatus of the present invention, the position of the pendulum gear can be moved to the normal rotation position, the reverse rotation position, and the non-meshing position by one motor. Further, the initial position of the pendulum gear is possible at any of the forward rotation position, the reverse position, and the non-meshing position by the switching mechanism. Therefore, even when the number of motors, that is, the number of motors is reduced, it is possible to ensure flexibility in duplex printing.

1 is a schematic side sectional view of an image forming apparatus according to an embodiment. Block diagram showing electrical configuration of image forming apparatus Explanatory drawing explaining the gear arrangement concerning the forward rotation position of the pendulum gear Explanatory drawing explaining the gear arrangement concerning the reverse position of the pendulum gear Explanatory drawing explaining the gear arrangement | positioning which concerns on the non-meshing position of a pendulum gear Front view of switching gear Perspective view of switching gear Perspective view of first link Perspective view of second link Front view showing a switching mechanism including a fixing mechanism and an opening mechanism Explanatory drawing showing the switching operation to the initial position of the pendulum gear Explanatory drawing showing the switching operation to the initial position of the pendulum gear Explanatory drawing showing the switching operation of the pendulum gear from the forward rotation position to the reverse rotation position Explanatory drawing showing the switching operation of the pendulum gear from the forward rotation position to the reverse rotation position Explanatory drawing showing the switching operation from the reverse position of the pendulum gear to the stack position Explanatory drawing showing the switching operation from the reverse position of the pendulum gear to the stack position Explanatory drawing showing the switching operation from the stack position of the pendulum gear to the forward rotation position Explanatory drawing showing the switching operation from the stack position of the pendulum gear to the forward rotation position Explanatory drawing explaining conveyance of paper in double-sided image formation processing Explanatory drawing explaining conveyance of paper in double-sided image formation processing Time chart schematically showing the signal of each sensor in double-sided image formation processing Front view showing another switching gear Explanatory drawing showing the switching operation from the forward rotation position of the pendulum gear to the stack position Explanatory drawing showing the switching operation from the forward rotation position of the pendulum gear to the stack position Explanatory drawing showing the switching operation from the stack position of the pendulum gear to the reverse position Explanatory drawing showing the switching operation from the stack position of the pendulum gear to the reverse position

1. Overall Configuration of Printer <Embodiment>
One embodiment will be described with reference to FIGS.

1. Internal Configuration of Printer The internal configuration of the printer 10 will be described with reference to FIG.

  The printer 10 is, for example, a direct tandem color LED printer that forms a color image using toners of four colors (black K, yellow Y, magenta M, and cyan C). In the following description, the left side in the horizontal direction (X-axis direction) in FIG. The image forming apparatus is not limited to a direct tandem color LED printer, and may be, for example, a color laser printer, a monochrome laser printer, or a complex machine having a copy function. Further, an electrophotographic printer or an ink jet printer may be used.

  As shown in FIG. 1, the printer 10 mainly includes an image forming unit 17, a fixing device 18, a transport mechanism 20, a tray paper feeding unit (an example of a paper feeding unit) 30, a manual paper feeding unit 40, and a discharging unit 50. , Rotation direction variable gear train 90, switching unit 100, first transport path P1, second transport path P2, and third transport path P3.

  The tray paper feeding unit 30 is provided at the bottom in the main body casing 2 of the printer 10 and includes a tray 31, a pickup roller 32, and a paper feeding roller 33. The tray paper feeding unit 30 feeds the paper ST set on the plurality of trays 31 by the user to the first transport path P1 indicated by the solid line. The first transport path P <b> 1 is a transport path from the tray 31 through the image forming unit 17 to the discharge unit 50. The first conveyance path P1 merges with the second conveyance path P2 at the merge point G1, and merges with the third conveyance path P3 at the merge point G2.

  The image forming unit 17 forms an image on the paper ST conveyed from the tray paper supply unit 30 or via the second conveyance path P2 or the third conveyance path P3. The image forming unit 17 includes, for example, well-known configurations such as an exposure unit, a developer storage unit, a developing unit, an image carrying unit, and a transfer unit for each color, and forms an image on the paper ST by a known electrophotographic method. To do. That is, the image forming unit 17 forms an image (monochrome image, color image) based on print data received from a PC, for example, on the paper ST conveyed by the belt 23. The sheet ST on which the image is formed is heat-fixed by the fixing device 25 and discharged onto the sheet discharge tray 51 through the first transport path P1.

  The discharge unit 50 includes a discharge tray 51, a switchback roller 52, and a discharge port 53. The paper ST on which the image is formed by the image forming unit 17 is discharged to the paper discharge tray 51. In addition, when the paper ST is printed on both sides, the discharge unit 50 feeds the paper ST to the second transport path P2, which is the reverse transport path, by reversing the switchback roller 52.

  The switchback roller 52 is supported by the main casing 2 so that the rotation direction of the switchback roller 52 can be switched between the normal rotation direction and the reverse rotation direction at the upper and rear portions of the main casing 2. More specifically, the switchback roller 52 forwards the paper ST toward the paper discharge tray 51 via the discharge port 53 and the paper ST conveyed toward the paper discharge tray 51 in the main casing 2. The rotation direction can be switched by a switching unit 100 to be described later in the reversing direction to be drawn in.

  The transport mechanism 20 transports the paper ST in the transport paths P1, P2, and P3. As shown in FIG. 1, the transport mechanism 20 includes an auxiliary paper feed roller (an example of a transport roller) 21, a registration roller (hereinafter referred to as “registration roller”) 22, a transport belt 23, a heating roller 25, an intermediate discharge. A paper roller 26, a reversing mechanism 70, and the like are included.

  The auxiliary paper feed roller 21 conveys the paper ST taken out from the tray 31 by the pickup roller 32 to the registration roller 22. The registration rollers 22 adjust the posture of the conveyed paper ST and send it out onto the belt 23 at a predetermined timing.

  The reversing mechanism 70 includes a flapper 71, a plurality of reversing transport rollers 72, a second transport path (an example of a second transport path) P <b> 2 as a reverse transport path indicated by a dotted line, and a switchback roller 52. In addition, as FIG. 1 shows, the 1st conveyance path | route P1 and the 2nd conveyance path | route P2 merge at the junction G1. That is, from the junction point G1 to the junction point G2, the first conveyance path P1 and the second conveyance path P2 are a common conveyance path. Further, from the flapper 71 to the switchback roller 52, the first transport path P1 and the second transport path P2 are a common transport path.

  The rotational direction variable gear train 90 is connected to the intermediate paper discharge roller 26 and the switchback roller 52. The rotation direction variable gear train 90 switches the rotation direction of the intermediate paper discharge roller 26 and the switchback roller 52 between the normal rotation direction and the reverse rotation direction by a switching operation by the switching unit 100 as will be described later (FIG. 3).

  The switching unit 100 includes a pendulum gear 101 and a solenoid 104 (see FIG. 3). As will be described later, the switching unit 100 sets the position of the pendulum gear 101 with respect to the rotation direction variable gear train 90 in accordance with the operation of the solenoid 104, such as a normal rotation position (see FIG. 3), a reverse position (see FIG. 4), And it switches to either position of a non-meshing position (refer to Drawing 5). Thereby, the rotation direction of the intermediate paper discharge roller 26 and the switchback roller 52 is switched between the normal rotation direction and the reverse rotation direction.

  Further, the manual paper feed unit 40 is provided on the front surface of the printer 10, and the paper ST inserted by the user at the time of manual printing is transferred to the first transport path via the third transport path P3 indicated by a one-dot chain line. Paper is fed to P1. The third transport path P3 is a path used when an image is formed on the paper ST fed from the manual paper feed unit 40, that is, when manual printing is performed on the paper ST. As shown in FIG. 1, the third transport path P3 substantially corresponds to the junction point G2 from the manual sheet feeder 40 to the first transport path P1.

  For example, when double-sided printing is performed on the paper ST from the tray paper supply unit 30 by a double-sided continuous method, which will be described later, the paper ST is imaged by the image forming unit 17 on the back surface (the bottom surface when stored in the tray 31). Is printed and then conveyed to the switchback roller 52. Then, by reverse rotation of the switchback roller 52 and the intermediate paper discharge roller 26, the paper ST passes through the flapper 71, the second transport path P2, the plurality of reverse transport rollers 72, the auxiliary paper feed roller 21, and the registration roller 22. It is conveyed and sent out on the belt 23 with the front and back being reversed. Then, the sheet ST is discharged onto the discharge tray 51 after the image is printed on the front surface (upper surface when stored in the tray 31) by the image forming unit 17.

  In addition, when performing double-sided printing of the paper ST from the manual paper feed unit 40, only the printing order of the paper ST on the front and back surfaces is different from that when the paper ST is fed from the tray paper feed unit 30. That is, in the case of duplex printing from the manual paper feed unit 40, an image is printed first on the upper surface of the paper ST when inserted from the manual paper feed unit 40.

2. Next, the electrical configuration of the printer 10 will be described with reference to FIG.

  The printer 10 includes a CPU (an example of a control unit) 11, a ROM 12, and a RAM 13. A timer 14, an operation unit 15, a display unit 16, an image forming unit 17, a fixing unit 18, a network interface 19, a main motor 60, a process motor 61, various sensors, and the like are connected to these.

  Various programs for controlling the operation of the printer 10 are recorded in the ROM 12, and the CPU 11 controls the operation of the printer 10 while storing the processing results in the RAM 13 according to the program read from the ROM 12. The timer 14 measures various times related to the processing of the CPU 11.

  The operation unit 15 includes a plurality of buttons and allows various input operations such as a print instruction on the paper ST by the user. The display unit 16 includes a liquid crystal display, a lamp, and the like, and can display various setting screens, operation states, and the like. The network interface 19 is connected to an external device such as a PC via the communication line NT, and mutual data communication is possible.

  As various sensors, a paper feed sensor 3, a pre-registration sensor 4, a post-registration sensor 5, a post-fixing sensor 6, a paper discharge sensor 7, a reverse path sensor 8, and a manual feed for detecting the position of the paper ST. A sensor 9 is provided in the main casing 2. As shown in FIG. 1, the paper feed sensor 3 is provided in the vicinity of the paper feed roller 33 in the first transport path P1.

  Further, the pre-registration sensor 4 is provided in the first transport path P1 on the downstream side in the transport direction of the paper ST with respect to the auxiliary paper feed roller 21 and on the upstream side in the transport direction of the paper ST with respect to the registration roller 22. ing. The post-registration sensor 5 is provided downstream of the registration rollers 17 in the transport direction of the paper ST and upstream of the image forming unit 17 in the transport direction of the paper ST in the first transport path P1.

  Further, the post-fixing sensor 6 is provided in the first transport path P1 downstream of the fixing unit 18 in the transport direction of the paper ST and upstream of the intermediate paper discharge roller 26 in the transport direction of the paper ST. ing. The paper discharge sensor 7 is provided near the switchback roller 52 upstream of the switchback roller 52 in the transport direction of the paper ST. Further, the reverse path sensor 8 is provided in the vicinity of the reverse reverse transport roller 72 in the main body casing 2 in the second transport path P2. The manual feed sensor 9 is provided in the third transport path P3.

  Each of the paper feed sensor 3, the pre-registration sensor 4, the post-registration sensor 5, the post-fixing sensor 6, the paper discharge sensor 7, the reverse path sensor 8, and the manual feed sensor 9 includes a swingable actuator, and the paper ST Is in contact with the actuator, and the actuator is tilted and turned on. When the paper ST is separated, the actuator is turned off. Then, this ON / OFF detection signal is transmitted to the CPU 11. Thereby, the CPU 11 can recognize the position of the paper ST.

  The main motor 60 (an example of a motor) is configured to generate a rotational driving force in one direction when driven. The main motor 60 transmits the rotational driving force to each of the intermediate paper discharge roller 26, the switchback roller 52, the paper feed roller 33, the auxiliary paper feed roller 21, the registration roller 22, the heating roller 25, the reverse conveyance roller 72, and the like. It is configured.

  Further, the process motor 61 is configured to generate a rotational driving force in one direction when driven. The process motor 61 is configured to transmit a rotational driving force to, for example, a photosensitive drum and a developing roller included in the image forming unit 17 and a belt cleaning roller (not shown).

  A solenoid (an example of an opening mechanism) 104 is controlled by the CPU 11 when the position of the pendulum gear 101 is switched, as will be described later.

3. Configuration of Driving Force Transmission Mechanism The printer 10 transmits a driving force that can switch the rotation direction of the switchback roller 52 and the intermediate paper discharge roller 26 between the normal rotation direction and the reverse rotation direction in order to form images on both sides of the paper ST. A mechanism 80 is provided.

  The normal rotation direction of the switchback roller 52 and the intermediate paper discharge roller 26 is a rotation direction in which the paper ST is rotated so as to be conveyed toward the paper discharge tray 51. The reverse direction of the switchback roller 52 and the intermediate paper discharge roller 26 is a rotation direction in which the paper ST is rotated so as to be conveyed from the discharge port 53 toward the second conveyance path P2.

  More specifically, the forward rotation direction of the switchback roller 52 is clockwise in FIG. 1 and counterclockwise in FIG. 3, and the forward rotation direction of the intermediate paper discharge roller 26 is counterclockwise in FIG. It is clockwise in FIG. 3 in the clockwise direction. 1 and 4, the reverse direction of the switchback roller 52 is the counterclockwise direction in FIG. 1 and the clockwise direction in FIG. 4. The reverse direction of the intermediate paper discharge roller 26 is the reverse direction in FIG. This is clockwise and counterclockwise in FIG.

  The driving force transmission mechanism 80 is located, for example, in the rear part of the main casing 2 and includes an input gear 81, a rotation direction variable gear train 90, and a switching unit 100.

3-1. Input Gear The input gear 81 forms a lower part of the driving force transmission mechanism 80 as shown in FIG. The input gear 81 is configured to rotate clockwise by receiving a rotational driving force to one of the main motors 60 via a plurality of gears (not shown) in the main body casing 2. The input gear 81 is, for example, a two-stage gear composed of a small-diameter gear and a large-diameter gear, and the small-diameter gear meshes with a drive gear 103 described later, and the large-diameter gear is the main casing 2. It meshes with one of a plurality of gears (not shown).

3-2. Rotational direction variable gear train The rotational direction variable gear train 90 constitutes a rear upper portion of the driving force transmission mechanism 80 as shown in FIG. A rotational driving force to one side of the main motor 60 is transmitted to the rotation direction variable gear train 90 via the input gear 81 and the switching unit 100. The rotational direction variable gear train 90 includes a switchback roller gear 96 positioned at the upper end of the rotational direction variable gear train 90, an intermediate discharge roller gear 97 positioned at the lower end of the rotational direction variable gear train 90, and a switchback roller gear. The first idle gear 91, the second idle gear 92, the third idle gear 93, the fourth idle gear 94, and the fifth idle gear 95 positioned between the 96 and the intermediate paper discharge roller gear 97 are included.

  The switchback roller gear 96 is provided so as to rotate integrally with the switchback roller 52. The switchback roller gear 96 meshes with the first idle gear 91. As shown in FIG. 3, the first idle gear 91 is positioned below the switchback roller gear 96 and is rotatably supported. The first idle gear 91 meshes with the switchback roller gear 96 and the second idle gear 92.

  The second idle gear 92 is positioned below the first idle gear 91 and is rotatably supported by the main casing 2. The second idle gear 92 is a two-stage gear composed of a small diameter gear and a large diameter gear, the small diameter gear meshes with the first idle gear 91 and the third idle gear 93, and the large diameter gear is It meshes with the fifth idle gear 95.

  The third idle gear 93 is positioned below the second idle gear 92 and is rotatably supported by the main casing 2. The third idle gear 93 is a two-stage gear composed of a small diameter gear and a large diameter gear. The small diameter gear meshes with the second idle gear 92, and the large diameter gear meshes with the fourth idle gear 94. doing.

  The fourth idle gear 94 is located below the third idle gear 93 and above the intermediate discharge roller gear 97, and is rotatably supported. The fourth idle gear 94 meshes with the third idle gear 93 and the intermediate paper discharge roller gear 97. Further, the fourth idle gear 94 is configured to transmit the rotational driving force generated from the main motor 60 via the switching unit 100.

  The fifth idle gear 95 is positioned in front of and below the second idle gear 92 and is rotatably supported. The fifth idle gear 95 meshes with the second idle gear 92. Further, the fifth idle gear 95 is configured such that the rotational driving force generated from the main motor 60 is transmitted via the switching unit 100.

  The intermediate paper discharge roller gear 97 is provided so as to rotate integrally with the intermediate paper discharge roller 26. The intermediate paper discharge roller gear 97 is engaged with the fourth idle gear 94.

  Here, in the arrangement of the fourth idle gear 94, the third idle gear 93, the second idle gear 92, the first idle gear 91, and the switchback roller gear 96, the rotation direction of the switchback roller 52 is the normal rotation direction. In this manner, the rotational driving force of the motor is transmitted to the switchback roller 52 as an example of a first gear train. Further, the arrangement of the fifth idle gear 95, the second idle gear 92, the first idle gear 91, and the switchback roller gear 96 is such that the rotation direction of the motor is such that the rotation direction of the switchback roller 52 is the reverse direction. 3 is an example of a second gear train that transmits a driving force to a switchback roller 52. FIG.

3-3. Switching unit The switching unit 100 constitutes a portion between the input gear 81 and the rotation direction variable gear train 90 in the driving force transmission mechanism 80. The switching unit 100 includes a pendulum gear 101 that meshes with a first gear train or a second gear train that transmits the rotational driving force of the main motor 60. The switching unit 100 includes a holder 102, a drive gear 103, a sector gear 120, and a switching mechanism 200.

3-3-1. Drive Gear, Holder, and Pendulum Gear The drive gear 103 transmits the rotational driving force from the main motor 60 to the sector gear 120. The drive gear 103 is positioned on the rear upper side of the input gear 81, and the drive gear shaft 103 </ b> A is supported by the main body casing 2 to be rotatably supported. Further, the drive gear 103 supports the holder 102 rotatably by the drive gear shaft 103 </ b> A being inserted into the drive gear shaft insertion hole 102 </ b> A of the holder 102. The drive gear 103 meshes with the input gear 81 and the pendulum gear 101. Further, the drive gear 103 meshes with the intermediate gear 105 as the intermediate gear 105 moves.

  The holder 102 supports the pendulum gear 101 rotatably. Holder 102 includes a gear support portion 102B and a switching power receiving portion 102C. The gear support portion 102B includes a pendulum gear shaft insertion hole 102D through which the pendulum gear shaft 101A of the pendulum gear 101 is inserted. The switching power receiving portion 102 </ b> C constitutes a front portion of the holder 102.

  The pendulum gear 101 is supported rotatably with respect to the holder 102 by supporting the pendulum gear shaft 101 </ b> A in the pendulum gear shaft insertion hole 102 </ b> D of the holder 102. The pendulum gear 101 is always meshed with the drive gear 103. The pendulum gear 101 is configured to be selectively meshed with the fourth idle gear 94 or the fifth idle gear 95 when the holder 102 swings around the drive gear shaft 103A as a fulcrum.

  Specifically, as shown in FIG. 3, the pendulum gear 101 is a positive gear that meshes with the fourth idle gear 94 by rotating the holder 102 counterclockwise about the drive gear shaft 103A. Located in the turning position. In this case, the rotational driving force of the main motor 60 includes the input gear 81, the drive gear 103, the pendulum gear 101, and the first gear train (fourth idle gear 94, third idle gear 93, second idle gear 92, first gear It is transmitted to the switchback roller 52 via the idle gear 91 and the switchback roller gear 96). As a result, the switchback roller 52 rotates in the forward direction. The rotational driving force of the main motor 60 is transmitted to the intermediate paper discharge roller 26 via the input gear 81, the drive gear 103, the pendulum gear 101, the fourth idle gear 94, and the intermediate paper discharge roller gear 97. As a result, the intermediate paper discharge roller 26 rotates in the forward rotation direction. The forward rotation direction of the switchback roller 52 and the intermediate paper discharge roller 26 is opposite. For example, if the forward rotation direction of the switchback roller 52 is counterclockwise, the forward rotation direction of the intermediate paper discharge roller 26 is clockwise (see FIG. 3).

  In this manner, the state in which the holder 102 is rotated counterclockwise, the pendulum gear 101 is positioned at the normal rotation position, and the pendulum gear 101 is held at the normal rotation position that meshes with the first gear train is switched as follows. This is called the normal rotation mode of the unit 100.

  On the other hand, as shown in FIG. 4, the pendulum gear 101 is positioned at a reverse rotation position where the holder 102 meshes with the fifth idle gear 95 by rotating clockwise with the drive gear shaft 103 </ b> A as a fulcrum. . Thereby, the rotational driving force of the main motor 60 is the input gear 81, the drive gear 103, the pendulum gear 101, and the second gear train (the fifth idle gear 95, the second idle gear 92, the first idle gear 91, the switchback. It is transmitted to the switchback roller 52 via the roller gear 96). As a result, the switchback roller 52 rotates in the reverse direction. Further, the rotational driving force of the main motor 60 includes an input gear 81, a drive gear 103, a pendulum gear 101, a fifth idle gear 95, a second idle gear 92, a third idle gear 93, a fourth idle gear 94, and an intermediate sheet discharge. This is transmitted to the intermediate paper discharge roller 26 via the roller gear 97. As a result, the intermediate paper discharge roller 26 rotates in the reverse direction. For example, if the reverse direction of the switchback roller 52 is clockwise, the reverse direction of the intermediate paper discharge roller 26 is counterclockwise (see FIG. 4).

  In this manner, the state in which the holder 102 is rotated clockwise, the pendulum gear 101 is positioned at the reverse position, and the pendulum gear 101 is held at the reverse position where the pendulum gear 101 meshes with the second gear train will be described below. This is called reverse mode.

  Further, as shown in FIG. 5, the pendulum gear 101 is positioned at an intermediate position between the fourth idle gear 94 and the fifth idle gear 95 with the drive gear shaft 103A as a fulcrum, so that the fourth idle gear 94 and the Both of the five idle gears 95, that is, in the non-meshing position where they do not mesh with either the first gear train or the second gear train. In this way, the pendulum gear 101 is prevented from rotating the driving force of the main motor 60 to either the first gear train or the second gear train and preventing the switchback roller 52 and the intermediate paper discharge roller 26 from rotating. The state held at the non-engagement position is referred to as a stack mode of the switching unit 100.

3-3-2. As shown in FIG. 6, the sector gear 120 has a cam 122 and a sector gear shaft 123 that rotate the holder 102 by pressing the holder 102, and the cam 122 is rotated by its own rotation about the sector gear shaft 123. By rotating, the forward rotation position, the reverse position and the non-meshing position (hereinafter referred to as the stack position) of the pendulum gear 101 are switched.

  The sector gear 120 includes a missing tooth gear 121. The sector gear 120, that is, the toothless gear 121, has a toothed portion 121 </ b> A that meshes with an intermediate gear 105 (see FIG. 10) described later when the pendulum gear 101 is in the reverse position and the non-engagement position, When located at the rolling position, the intermediate gear 105 and the missing tooth portion 121B are provided.

  Further, the sector gear 120 includes engagement portions (141 to 143) that engage with an engagement protrusion (see FIG. 9) 161 described later to fix the sector gear 120. Further, the sector gear 120 includes a cylindrical portion 140 that is integrally formed with the sector gear 120 on the surface opposite to the surface on which the cam 122 is formed, and in which the engaging portions (141 to 143) are formed.

  The engaging portions (141 to 143) are engaged with the engaging protrusion 161, and guide grooves (an example of a first engaging portion) 141 that fixes the sector gear 120 at a position corresponding to the forward rotation position. The first engaging groove (an example of the second engaging portion) 142 that fixes the sector gear 120 at a position corresponding to the reverse position when the 161 is engaged and the engaging protrusion 161 are engaged to correspond to the non-engaging position. And a second locking groove (an example of a third engaging portion) 143 that fixes the sector gear 120 at the position.

  In the present embodiment, the first engaging portion 141 guides the engaging protrusion 161 from the circumferential portion corresponding to the toothed portion 121A of the cylindrical portion 140 to the circumferential portion corresponding to the missing tooth portion 121B. 141. As shown in FIG. 6, the guide groove 141 has a bent portion 141 </ b> A in which an engagement protrusion 161 (see FIG. 9) of the second link 160 described later is positioned when the pendulum gear 101 is positioned in the forward rotation position. Is formed.

  The second and third engaging portions (142, 143) are formed as second and third locking grooves (142, 143) for locking the engaging protrusion 161 at the circumferential portion of the cylindrical portion 140. Yes.

  In addition, as shown in FIG. 6, the engaging portions (141 to 143) are arranged in the rotational direction of the sector gear 120 (the clockwise direction in FIG. 6) when the position of the first engaging portion 141 is used as a reference. The first engaging portion (guide groove) 141, the second engaging portion (first locking groove) 142, and the third engaging portion (second locking groove) 143 are formed in this order. Therefore, the position of the pendulum gear 101 can be switched in the order of normal rotation position → reverse position → stack position → normal rotation position.

  At this time, in the present embodiment, as shown in FIG. 6, the first engaging portion 141 and the second engaging portion 142 are positioned on the sector gear 120 at an angle where the rotation angle of the sector gear 120 forms 180 °. The first engagement portion 141 and the third engagement portion 143 are formed at positions where the rotation angle of the sector gear 120 forms 90 °. Further, the third engaging portion 143 and the second engaging portion 142 are formed at positions where the rotation angle of the sector gear 120 forms 90 °. Therefore, when the position of the pendulum gear 101 is changed in three quadrants, the rotation of the sector gear 120 can be simply controlled in units of 90 °. That is, the switching of the three quadrants of the pendulum gear 101 can be performed easily and suitably. Note that the positions and the number of engaging portions formed in the cylindrical portion 140 are not limited to those shown in FIG. For example, the third engagement portion 143 and the second engagement portion 142 may be formed at a position where the rotation angle of the sector gear 120 forms 60 °.

  Further, as shown in FIG. 6, the sector gear 120 has a columnar extension portion 145 for forming a guide groove 141 formed in a part of the columnar portion 140. The columnar expansion portion 145 has an abutting portion 145A with which an engaging projection 161 (see FIG. 9) of a second link 160 described later abuts.

3-3-3. Switching mechanism The switching mechanism 200 enables initialization at any of the forward rotation position, the reverse rotation position, and the non-meshing position when initializing the position of the pendulum gear 101 at the start of power supply to the printer 10. That is, in the present embodiment, the initial position of the pendulum gear 101 can be any of the forward rotation position, the reverse position, and the non-meshing position. The switching mechanism 200 includes a fixing mechanism 300 and an opening mechanism 104 for that purpose.

  The fixing mechanism 300 fixes the sector gear 120 so as not to rotate at each position corresponding to the forward rotation position, the reverse rotation position, and the non-meshing position of the pendulum gear 101. The fixing mechanism 300 includes an intermediate gear 105, a first link 150, a second link 160, a spring 170, and the engaging portions (141 to 143).

  The intermediate gear 105 transmits the rotational driving force from the main motor 60 to the sector gear 120 via the driving gear 81.

  As shown in FIG. 8, the first link 150 has a first circular hole 151, a long hole 152, and a second circular hole 153. The first link 150 is rotatably supported by the sector gear 120 by fitting the first circular hole 151 to the sector gear shaft 123. Further, the first link 150 supports the intermediate gear 105 rotatably by fitting the second circular hole 153 to the rotation shaft of the intermediate gear 105.

  As shown in FIG. 9, the second link 160 includes an engagement protrusion 161, an engagement column 162, a rotation shaft 163, a coupling portion 164, and a spring locking portion 165. The engaging protrusion 161 engages with the engaging portions (141 to 143) of the sector gear 120. The second link 160 is supported by the caging 2 so that the second link 160 can rotate about the rotation shaft 163. Further, the engagement column 162 is fitted into the long hole 152 of the first link 150, and the engagement column 162 can move in the long hole 152. Thereby, the second link 160 is movably coupled to the first link 150.

  One end of the spring 170 is locked to the spring locking portion 165 of the second link 160 and the other end is supported by the caging 2 to urge the spring locking portion 165 downward. Accordingly, a counterclockwise rotational force is applied to the second link 160, and the engagement protrusion 161 of the second link 160 is urged toward the engagement portion side of the sector gear 120.

  When the position of the pendulum gear 101 is switched, the opening mechanism 104 opens the sector gear 120 fixed by the fixing mechanism 300 in a rotatable manner. In the present embodiment, the opening mechanism 104 is configured by a solenoid 104. Note that the opening mechanism 104 is not limited to a solenoid. For example, a mechanism that rotates the second link 160 about the rotation center using a motor may be used.

  The solenoid 104 includes a main body 104A including an electromagnet and a movable iron core 104B. As shown in FIG. 10, the distal end portion of the movable iron core 104 </ b> B is coupled to the coupling portion 164 of the second link 160. The solenoid 104 is a so-called pull solenoid. When the electromagnet is excited, that is, when the solenoid 104 is turned on, the movable iron core 104B is attracted to the inside of the main body and moves upward in FIG. With the suction of the movable iron core 104B, the end of the second link 160 on the spring locking portion 165 side is pulled upward, and the second link 160 rotates clockwise about the rotation shaft 163 as the rotation center. Accordingly, when the engaging portions (141 to 143) of the sector gear 120 and the engaging protrusion 161 of the second link 160 are engaged, the engagement is released.

  That is, in this embodiment, the position of the pendulum gear 101 is changed to the normal rotation position, the reverse position, and the stack position by switching the solenoid 104 between the excited state and the non-excited state, in other words, the mode of the switching unit 100 is set to the normal position. It is possible to switch to a rotation mode, an inversion mode, and a stack mode. Specifically, the engagement between the engagement protrusion 161 of the second link 160 and the engagement portions (141 to 143) of the sector gear 120 is released by the solenoid 104, and the engagement protrusion 161 is moved to the desired engagement portion (141). To 143), the position of the pendulum gear 101 can be set to a desired position. Thereby, the initial position of the pendulum gear 101 can be set to any one of the normal rotation position, the reverse position, and the stack position (non-meshing position).

  In the present embodiment, the solenoid 104, the intermediate gear 105, the engaging portions (141 to 143), the first link 150, the second link 160, and the spring 170 constitute the switching mechanism 200. The switching mechanism 200 is not limited to this.

4). Next, a position switching operation of the pendulum gear 101, in other words, a mode switching operation of the switching unit 100 will be described with reference to FIGS. In the following description, it is assumed that the main motor 60 is always driven and the input gear 81 is rotated in one direction, unless otherwise specified. Moreover, the description regarding the overlapping position and operation is simplified. In addition, the rotation angle of the sector gear 120 (toothless gear 121) is controlled by the rotation angle (the number of drive steps) of the main motor 60, for example, where the main motor 60 is configured by a stepping motor. Further, it is assumed that the number of drive steps corresponding to the desired rotation angle of the sector gear 120 is determined in advance.

4-1. Initial Switching Operation when the Power is On First, an initial switching operation when the printer 10 is powered on will be described with reference to FIGS. Here, it is assumed that the position of the pendulum gear 101 at the time of power on is indefinite, for example, the case where the power is turned off at the reverse position of the pendulum gear 101.

  When the pendulum gear 101 is in the reverse position, that is, when the switching unit 100 is in the reverse mode, the engagement protrusion 161 of the second link 160 has the first locking groove 142 as shown in FIG. Is engaged. Further, the intermediate gear 105 is separated from the drive gear 103.

  11B, when the solenoid 104 is turned on and the movable iron core 104B is attracted, the end of the second link 160 on the spring locking portion 165 side is pulled upward, thereby The second link 160 rotates clockwise about the rotation shaft 163 as a rotation center. As a result, the engagement between the engagement protrusion 161 of the second link 160 and the first locking groove 142 of the sector gear 120 is released, and the engagement column 162 of the second link 160 is elongated by the elongated hole 152 of the first link 150. Move in. Thereby, the intermediate gear 105 meshes with the drive gear 103. Then, with the rotation of the drive gear 103, the sector gear 120 starts to rotate in the same direction (clockwise direction) as the drive gear 103 via the intermediate gear 105.

  Next, by rotating the sector gear 120 with the solenoid 104 turned on, the engagement protrusion 161 of the second link 160 engages with the second locking groove 143 of the sector gear 120 as shown in FIG. The sector gear 120 continues to rotate without being stopped.

  Then, as the sector gear 120 continues to rotate, the engagement protrusion 161 of the second link 160 comes into contact with the contact portion 145A of the cylindrical expansion portion 145, as shown in FIG. At this time, the intermediate gear 105 reaches the missing tooth portion 121B of the sector gear 120.

  At this time, when the solenoid 104 is turned off, the end portion of the second link 160 on the spring locking portion 165 side is pulled downward by the contraction force of the spring 170, whereby the second link 160 has the rotation shaft 163 as the center of rotation. Rotate counterclockwise. As a result, as shown in FIG. 12B “fixed to the initial position”, the engagement protrusion 161 of the second link 160 moves in the guide groove 141. Accordingly, the engaging column 162 of the second link 160 moves in the elongated hole 152 of the first link 150, so that the intermediate gear 105 moves along the missing tooth portion 121B until it contacts the toothed portion 121A. Thereby, the intermediate gear 105 is disengaged from the drive gear 103. At this time, the engagement column 162 of the second link 160 moves in the guide groove 141 to the bent portion 141A.

  When the intermediate gear 105 is disengaged from the drive gear 103, as shown in FIG. 12B, the intermediate gear 105 retreats around the sector gear shaft 123 as the rotation center in the direction opposite to the rotation direction of the drive gear 103 (see thick arrows). That is, when the intermediate gear 105 is retracted from the drive gear 103, in FIG. 12B, the intermediate gear 105 is retracted counterclockwise with the sector gear shaft 123 via the first link 150 as the rotation center. Therefore, the contact degree with the drive gear 103 is reduced when the intermediate gear 105 is retracted from the drive gear 103 as compared with the case where the intermediate gear 105 is retracted in the same direction as the rotation direction of the drive gear 103 (clockwise in FIG. 12B). . Thereby, the generation of abnormal noise due to contact with the drive gear 103 can be suppressed.

  Then, for example, by stopping the rotation of the drive motor 103 by stopping the rotation of the main motor 60, the initial switching operation is completed as shown in FIG. 12C corresponds to the normal rotation mode of the switching unit 100, that is, the normal rotation position of the pendulum gear 101. In this embodiment, the initial position of the pendulum gear 101 is normal rotation. It is considered as a position.

  Note that the initial position of the pendulum gear 101 is not limited to the normal rotation position, and the switching mechanism 200 allows the initial position of the pendulum gear 101 to be any of the normal rotation position, the reverse position, and the non-meshing position. . As a result, it is possible to ensure flexibility regarding the initial position of the pendulum gear 101, and thus flexibility in duplex printing.

4-2. Switching Operation from Forward Rotation Position (Initial Position) to Reverse Position Next, referring to FIGS. 13 and 14, the switching operation from the forward rotation position (initial position) of the pendulum gear 101 to the reverse position, that is, the switching unit 100 is performed. The switching operation from the normal rotation mode to the reverse mode will be described.

  When the pendulum gear 101 is located at the normal rotation position (initial position), the intermediate gear 105 abuts on the toothed portion 121A of the sector gear 120 by the contraction force of the spring 170 as shown in FIG. The engagement protrusion 161 of the second link 160 is fixed to a bent portion 141A in the guide groove 141. Therefore, in the “transition start” shown in FIG. 13B, the solenoid 104 is turned on, and the end portion of the second link 160 on the spring locking portion 165 side is pulled upward, and as a result, the second link 160 has a rotation axis. It rotates clockwise around 163 as the center of rotation.

  As a result, the engaging protrusion 161 of the second link 160 moves further in the guide groove 141 toward the toothless portion 121B, and the engaging column 162 of the second link 160 moves in the elongated hole 152 of the first link 150. Moving. Further, the sector gear 120 also rotates clockwise by the engagement protrusion 161. Thereby, the intermediate gear 105 meshes with the toothed portion 121A of the sector gear 120 and the drive gear 103 (see thick arrows). Then, as shown in FIG. 13C “in transition”, as the drive gear 103 rotates, the sector gear 120 rotates in the same direction (clockwise direction) as the drive gear 103 via the intermediate gear 105. To start. At this time, the solenoid 104 is turned off.

  Next, the sector gear 120 continues to rotate in the clockwise direction (see “in transition” in FIG. 14A). When the sector gear 120 rotates approximately 180 ° from the “transition start” position shown in FIG. The engaging protrusion 161 moves to a position facing the first locking groove 142 of the sector gear 120. Then, as the second link 160 rotates counterclockwise by the contraction force of the spring 170, the engagement protrusion 161 of the second link 160 is moved to the first locking position as shown in FIG. 14B “fixed to the reverse position”. While engaging with the groove 142, the engaging column 162 of the second link 160 moves in the long hole 152 of the first link 150. Thereby, the intermediate gear 105 is disengaged from the drive gear 103 in a state where the intermediate gear 105 is engaged with the toothed portion 121 </ b> A of the sector gear 120. At that time, the intermediate gear 105 retracts in the direction opposite to the rotation direction of the drive gear 103. This completes the switching operation of the pendulum gear 101 from the forward rotation position (initial position) to the reverse position (see “Switching Complete” in FIG. 14C).

4-3. Switching Operation from Reverse Position to Stack Position Next, referring to FIGS. 15 and 16, the switching operation of the pendulum gear 101 from the reverse position to the stack position, that is, the switching operation of the switching unit 100 from the reverse mode to the stack mode. Will be described.

  To switch the pendulum gear 101 from the “reverse position” shown in FIG. 15A to the “stack position” shown in FIG. 16B, first, the solenoid 104 is turned on to turn on the engagement protrusion 161 of the second link 160 and the sector gear 120. The engagement with the first locking groove 142 is released, and the intermediate gear 105 and the drive gear 103 are engaged (see “transition start” in FIG. 15B).

  Next, rotation of the sector gear 120 in the clockwise direction is continued with the solenoid 104 turned off (see “transition” in FIG. 15C), and when the sector gear 120 rotates approximately 90 ° from the “transition start” position in FIG. 15B. The engagement protrusion 161 of the second link 160 moves to a position facing the second locking groove 143 of the sector gear 120. Then, the contraction force of the spring 170 causes the engagement protrusion 161 of the second link 160 to engage with the second locking groove 143 and the intermediate gear 105 as shown in FIG. In a state where it is engaged with the toothed portion 121 </ b> A of the sector gear 120, it is disengaged from the drive gear 103. At that time, the intermediate gear 105 retracts in the direction opposite to the rotation direction of the drive gear 103. This completes the switching operation of the pendulum gear 101 from the reverse position to the stack position (see “switching complete” in FIG. 16B).

4-4. Next, referring to FIGS. 17 and 18, the switching operation of the pendulum gear 101 from the stack position to the normal rotation position, that is, the switching unit 100 from the stack mode to the normal rotation mode. The switching operation will be described.

  In order to switch the pendulum gear 101 from the “stack position” shown in FIG. 17A to the “forward rotation position” shown in FIG. 18C, first, as shown in FIG. 17B “transition start”, the solenoid 104 is turned on. As a result, the engagement between the engagement protrusion 161 of the second link 160 and the second locking groove 143 of the sector gear 120 is released, and the intermediate gear 105 and the drive gear 103 are engaged with each other.

  Next, the rotation of the sector gear 120 in the clockwise direction is continued with the solenoid 104 turned off (see “in transition” in FIG. 17C), and when the sector gear 120 rotates by approximately 90 ° from the “transition start” position in FIG. 17B. Then, the engagement protrusion 161 of the second link 160 moves to a position facing the guide groove 141 of the sector gear 120 (see “reaching the forward rotation position” in FIG. 18A). Then, the engagement protrusion 161 of the second link 160 moves in the guide groove 141 as shown in FIG. 18B “fixed in the forward rotation position” by the contraction force of the spring 170, and the intermediate gear 105 is moved to the sector gear 120. It moves along the missing tooth portion 121B and contacts the toothed portion 121A. As a result, the intermediate gear 105 is disengaged from the drive gear 103. At that time, the intermediate gear 105 retracts in the direction opposite to the rotation direction of the drive gear 103. This completes the switching operation of the pendulum gear 101 from the stack position to the forward rotation position (see “switching completion” in FIG. 18C).

5. Double-sided image forming process The double-sided image forming process by the CPU 11 for a plurality of sheets ST will be described with reference to FIGS.

  The double-sided image forming process by the CPU 11 for a plurality of sheets ST is executed with two sheets as one set. Of the two sheets ST in one set, a sheet ST on which an image is formed on the first sheet is a preceding sheet ST1, and a sheet ST on which an image is formed on the second sheet is a succeeding sheet ST2.

  Further, in the preceding paper ST1, a surface on which an image is formed first is a second printing surface, and a surface on which an image is formed later is a first printing surface. In the succeeding paper ST2, a surface on which an image is formed first is a fourth printing surface, and a surface on which an image is formed later is a third printing surface. In a state where the preceding paper ST1 is placed on the tray 31, the first printing surface corresponds to the front surface of the preceding paper ST1, and the second printing surface corresponds to the back surface of the preceding paper ST1. Further, in a state where the succeeding sheet ST2 is placed on the tray 31, the third printing surface corresponds to the front surface of the succeeding sheet ST2, and the fourth printing surface corresponds to the back surface of the succeeding sheet ST2.

  In this embodiment, when forming an image with two sheets as a set in the double-sided image forming process, the image is formed in the order of the second printing surface → the fourth printing surface → the first printing surface → the third printing surface. Is done. Hereinafter, this is referred to as “2 → 4 → 1 → 3 printing”.

  When performing “2 → 4 → 1 → 3 printing”, the CPU 11 first supplies the preceding paper ST1 from the tray paper supply unit 30 to the first conveyance path P1 by the paper supply roller 33, and the second side is an image. The first step is executed to maintain the forward rotation mode so that the image is formed by the forming unit 17 and conveyed to the switchback roller 52.

  Specifically, in order to execute the first step, the process motor 61 is driven after the position of the pendulum gear 101 is initialized to the normal rotation position by the initial switching operation. Next, the CPU 11 controls the switching unit 100 to be held in the normal rotation mode.

  Then, the preceding sheet ST1 on the sheet feeding tray 31 is conveyed toward the image forming unit 17. Subsequent paper ST2 is stacked on the paper feed tray 31. As a result, as shown at time t1 in FIG. 21, the paper feed sensor 3, the pre-registration sensor 4, and the post-registration sensor 5 are turned on.

  Next, when the preceding sheet ST1 is conveyed along the first conveying path P1, an image is formed by the image forming unit 17 on the second printing surface of the preceding sheet ST1, and the preceding sheet ST1 passes through the fixing unit 18, The intermediate paper discharge roller 26 and the switchback roller 52 are conveyed so that the front ends thereof are positioned in the vicinity of the discharge port 53. Subsequent paper ST2 is stacked on the paper feed tray 31. At this time, as shown at time t2 in FIG. 21, the paper feed sensor 3, the pre-registration sensor 4, and the post-registration sensor 5 are turned off, and the post-fixing sensor 6 and the paper discharge sensor 7 are turned on.

  Next, based on the ON / OFF state of the paper discharge sensor 7 for the preceding sheet ST1, the CPU 11 causes the preceding sheet ST1 to be conveyed to the second conveying path P2 after a predetermined time has elapsed, as shown at time t3 in FIG. The second step of holding the reverse mode is executed. The positions of the sheets ST1 and ST2 according to the second step are shown in FIG. 19A.

  In order to execute the second step, the sheet discharge sensor 7 is turned from ON to OFF. For example, at time t3 when 1.00 sec elapses, the solenoid 11 is controlled by the switching operation shown in FIGS. 104 is turned ON, and the switching unit 100 is switched from the normal rotation mode to the reverse mode. As a result, the transport direction of the preceding sheet ST1 is reversed, and the preceding sheet ST1 is transported toward the second transport path P2. Then, the preceding paper ST1 is transported so that the leading end is positioned in the vicinity of the reverse reverse transport roller 72.

  The CPU 11 drives the paper feed roller 33 a predetermined time after switching the switching unit 100 from the normal rotation mode to the reverse mode. Thus, the succeeding sheet ST2 is conveyed toward the image forming unit 17 after a predetermined time has elapsed from time t3. Then, at time t4 in FIG. 21, the paper discharge sensor 7 is in an OFF state, and the paper feed sensor 3, the pre-registration sensor 4, and the post-registration sensor 5 are in an ON state.

  Next, at time t4 in FIG. 21, the CPU 11 switches the switching unit 100 from the inversion mode to the stack mode by the switching operation shown in FIGS. 15 and 16 (third step). Thus, preparation for switching to the forward rotation mode is made next.

  Next, at a time t5 in FIG. 21 after a lapse of a predetermined time from the ON / OFF of the pre-registration sensor 4 for the subsequent sheet ST2, the CPU 11 maintains the normal rotation mode so that the subsequent sheet ST2 is conveyed to the switchback roller 52. The fourth step is executed. The positions of the sheets ST1 and ST2 according to the fourth step are shown in FIG. 19B.

  Specifically, when the preceding sheet ST1 is conveyed toward the second conveying path P2 and the reversing path sensor 8 is turned on and a predetermined time has elapsed, the preceding sheet ST1 is entirely within the second conveying path P2. Since it enters and passes between the intermediate paper discharge rollers 26, the switching unit 100 is switched from the stack mode to the normal rotation mode by the switching operation shown in FIGS.

  In the fourth step, an image is formed on the fourth printing surface of the subsequent sheet ST2, and the subsequent sheet ST2 is conveyed toward the discharge port 53 by the intermediate sheet discharge roller 26 that rotates in the normal rotation direction. At this time, the preceding sheet ST1 is transported to a position where the trailing edge of the preceding sheet ST1 exceeds the rearmost reverse transporting roller 72.

  Further, the succeeding sheet ST2 is conveyed to a position where the leading end thereof is in the vicinity of the discharge port 53 by the intermediate discharge roller 26 and the switchback roller 52 that rotate in the forward direction. At this time, the reverse path sensor 8 is turned OFF, and the post-fixing sensor 6 and the paper discharge sensor 7 are in the ON state.

  Further, the preceding paper ST1 is conveyed so that the leading edge of the preceding paper ST1 is positioned in the vicinity of the auxiliary paper feeding roller 21. Further, the succeeding sheet ST2 is conveyed so that the rear end thereof is positioned in the vicinity of the discharge port 53. At this time, as shown at time t6 in FIG. 21, the paper discharge sensor 7 remains ON, and the post-fixing sensor 6 is OFF.

  Next, the CPU 11 executes a fifth step in which the reverse mode is maintained so that the subsequent sheet ST2 is transported to the second transport path P2. Specifically, in order to execute the fifth step, the discharge sensor 7 is turned from ON to OFF, and for example, at the timing of time t6 in FIG. The switching unit 100 is switched from the normal rotation mode to the reverse mode by the switching operation shown in FIG. As a result, the conveyance direction of the subsequent sheet ST2 is reversed, and the subsequent sheet ST2 is conveyed toward the second conveyance path P2. The positions of the sheets ST1 and ST2 according to the fifth step are shown in FIG. 19C.

  Then, the succeeding paper ST2 is transported so that the leading end is positioned in the vicinity of the reverse reverse transport roller 72. Further, the preceding sheet ST1 is conveyed again into the first conveying path P1 by the rotation of the auxiliary sheet feeding roller 21, and is conveyed toward the image forming unit 17, and the image forming unit is formed on the first printing surface of the preceding sheet ST1. 17 forms an image.

  Then, at a time t7 after a predetermined time has elapsed since the reverse path sensor 8 is turned on by the succeeding paper ST2, the CPU 11 executes a sixth step for maintaining the normal rotation mode. The positions of the sheets ST1 and ST2 according to the sixth step are shown in FIG. 20A.

  In the sixth step, the preceding sheet ST1 is discharged from the main body casing 2 through the discharge port 53 in the first transport path P1. Further, the succeeding sheet ST2 is transported from the second transport path P2 to the first transport path P1 by the auxiliary paper feeding roller 21, and an image is formed on the third printing surface of the succeeding sheet ST2 by the image forming unit 17. Then, the succeeding sheet ST2 is discharged from the main body casing 2 through the discharge port 53.

  Specifically, the subsequent sheet ST2 is conveyed toward the second conveyance path P2, and at time t7 when the reverse path sensor 8 is turned on and a predetermined time has elapsed, the subsequent sheet ST2 is entirely in the second conveyance path. It is in P2 and passes between the intermediate paper discharge rollers 26. Therefore, under the control of the CPU 11, the switching unit 100 is switched from the inversion mode to the normal rotation mode without going through the stack mode by the switching operation shown in FIGS.

  As a result, the preceding sheet ST1 forms an image on the first printing surface and is conveyed toward the discharge port 53 by the intermediate discharge roller 26. Then, the preceding sheet ST1 is conveyed by the intermediate sheet discharge roller 26 and the switchback roller 52 to a position where the leading end is near the discharge port 53.

  On the other hand, the succeeding paper ST2 is conveyed to a position where the trailing edge thereof exceeds the reverse reverse conveying roller 72. Then, at time t8 in FIG. 21, the reverse path sensor 8 is in the OFF state, and the post-fixing sensor 6 and the paper discharge sensor 7 are in the ON state.

  Next, the preceding sheet ST1 is conveyed so that the rear end thereof is positioned in the vicinity of the discharge port 53. Subsequent paper ST2 is conveyed so that the leading edge is positioned in the vicinity of auxiliary paper feed roller 21. At this time, at time t9 in FIG. 21, the paper discharge sensor 7 remains in the ON state, and the post-fixing sensor 6 is in the OFF state.

  Next, the preceding sheet ST1 is discharged from the discharge port 53 to the discharge tray 51. The succeeding sheet ST2 is conveyed again into the first conveyance path P1 by the rotation of the auxiliary sheet feeding roller 21, and is conveyed toward the image forming unit 17, and an image is formed on the third printing surface by the image forming unit 17. The At this time, as shown at time t10 in FIG. 21, the paper discharge sensor 7 is in the OFF state, and the pre-registration sensor 4 and the post-registration sensor 5 are in the ON state.

  Next, the succeeding paper ST2 is conveyed by the intermediate paper discharge roller 26 and the switchback roller 52 so that the leading end thereof is positioned in the vicinity of the discharge port 53. Accordingly, at time t11 in FIG. 21, the post-fixing sensor 6 and the paper discharge sensor 7 are in the ON state.

  Next, the subsequent sheet ST2 is discharged from the discharge port 53 to the discharge tray 51 so as to be placed on the preceding sheet ST1. Thus, at time t12 in FIG. 21, the post-fixing sensor 6 and the paper discharge sensor 7 are in the OFF state. Thus, the double-sided image forming process for the first set of two sheets ST, that is, “2 → 4 → 1 → 3 printing” is completed.

  Note that the paper conveyance timing related to “2 → 4 → 1 → 3 printing” is not limited to that shown in FIG. For example, as shown in FIG. 20B, when the leading edge of the preceding sheet ST1 is conveyed so as to be positioned in the vicinity of the discharge port 53, that is, when the preceding sheet ST1 reaches the reverse position, the stacking is performed for a predetermined time. A mode may be provided. In other words, the stack mode may be provided when shifting from the first step in the normal rotation mode to the second step in the reverse mode. Thus, by temporarily stopping the conveyance of the preceding sheet ST1, the conveyance start timing of the subsequent sheet ST2 can be adjusted as appropriate.

6). Effects of the Embodiment According to this embodiment, the position of the pendulum gear 101 can be moved to the normal rotation position, the reverse position, and the stack position (non-meshing position) by one main motor 60. Further, the switching mechanism 200 enables the initial position of the pendulum gear 101 at any one of the forward rotation position, the reverse position, and the stack position. Therefore, even when the number of motors is reduced, it is possible to ensure flexibility in duplex printing.
Further, “2 → 4 → 1 → 3 printing” is possible by switching the normal rotation position → stack position → reverse position → stack position → normal rotation position (three quadrants) regarding the position of the pendulum gear 101. At that time, when the position of the pendulum gear 101 is changed in three quadrants, the rotation of the sector gear 120 can be simply controlled in units of 90 °. That is, the switching of the three quadrants can be performed easily and suitably.

<Other embodiments>
The present invention is not limited to the embodiments described with reference to the above description and drawings. For example, the following embodiments are also included in the technical scope of the present invention.

  (1) In the above embodiment, the example in which the pendulum gear 101 is switched in three quadrants has been described, but the present invention is not limited to this. For example, as shown in FIG. 22, in the sector gear 120, when the engaging portions (141 to 143, 143A) are based on the position of the first engaging portion 141, the rotation direction of the sector gear 120 (clockwise in FIG. 22). Direction), the first engaging portion (guide groove) 141, the third engaging portion (third locking groove) 143A, the second engaging portion (first locking groove) 142, and the third engaging portion ( The second locking groove) 143 may be formed at positions where the rotation angle of the sector gear 120 forms 90 °. In this case, the position of the pendulum gear 101 can be switched between four quadrants by simply controlling the rotation of the sector gear 120 in units of 90 ° in the order of normal rotation position → stack position → reverse position → stack position → normal rotation position. It is.

  That is, the switching operation from the normal rotation position to the reversal position shown in FIGS. 13 and 14 is the switching operation from the normal rotation position to the stack position shown in FIGS. 23 and 24, and FIGS. 25 and 26. It is possible to change to a switching operation from the stack position to the reverse position.

  In order to switch the pendulum gear 101 from the “forward position” shown in FIG. 23A to the “stack position” shown in FIG. 24C, first, the engagement projection 161 of the second link 160 and the sector gear are turned on by turning on the solenoid 104. The engagement with the 120 guide grooves 141 is released, and the intermediate gear 105 and the drive gear 103 are engaged (see “transition start” in FIG. 23B). Next, the rotation of the sector gear 120 in the clockwise direction is continued with the solenoid 104 turned off (see “in transition” in FIG. 23C and FIG. 24A), and the sector gear 120 is almost from the “transition start” position in FIG. 23B. When rotated 90 °, the engagement protrusion 161 of the second link 160 moves to a position facing the third locking groove 143A of the sector gear 120. Then, due to the contraction force of the spring 170, the engagement protrusion 161 of the second link 160 is engaged with the third locking groove 143A as shown in FIG. In a state where it is engaged with the toothed portion 121 </ b> A of the sector gear 120, it is disengaged from the drive gear 103. At that time, the intermediate gear 105 retracts in the direction opposite to the rotation direction of the drive gear 103. This completes the switching operation of the pendulum gear 101 from the forward rotation position to the stack position (see “switching completion” in FIG. 24C).

  In order to switch the pendulum gear 101 from the “stack position” shown in FIG. 25A to the “reverse position” shown in FIG. 26B, first, the solenoid 104 is turned on to engage the engaging protrusion 161 of the second link 160 and the sector gear. The engagement with the third locking groove 143A of 120 is released, and the intermediate gear 105 and the drive gear 103 are engaged (see “transition start” in FIG. 25B). Next, rotation of the sector gear 120 in the clockwise direction is continued with the solenoid 104 turned off (see “transition” in FIG. 25C), and when the sector gear 120 rotates approximately 90 ° from the “transition start” position in FIG. 25B. Then, the engaging protrusion 161 of the second link 160 moves to a position facing the first locking groove 142 of the sector gear 120. Then, due to the contraction force of the spring 170, the engagement protrusion 161 of the second link 160 engages with the first locking groove 142 as shown in FIG. In a state where it is engaged with the toothed portion 121 </ b> A of the sector gear 120, it is disengaged from the drive gear 103. At that time, the intermediate gear 105 retracts in the direction opposite to the rotation direction of the drive gear 103. This completes the switching operation of the pendulum gear 101 from the stack position to the reverse position (see “switching completion” in FIG. 26B).

DESCRIPTION OF SYMBOLS 10 ... Printer, 17 ... Image forming part, 21 ... Auxiliary paper feed roller, 26 ... Intermediate paper discharge roller, 30 ... Tray paper feed part, 52 ... Switchback roller, 53 ... Ejection port, 60 ... Main motor, 90 ... Rotation Direction variable gear train, 91 ... first idle gear, 92 ... second idle gear, 93 ... third idle gear, 94 ... fourth idle gear, 95 ... fifth idle gear, 96 ... switchback roller gear, 100 ... switch Unit: 101 ... Pendulum gear, 102 ... Holder, 103 ... Drive gear, 104 ... Solenoid (opening mechanism), 120 ... Sector gear, 121 ... No-tooth gear, 121A ... Tooth portion, 121B ... No-tooth portion, 122 ... Cam, 141 ... guide groove, 142 ... first locking groove, 143 ... second locking groove, 170 ... spring, 200 ... switching mechanism, 300 ... fixing mechanism, P1 ... first transport path, P2 ... first Transport route,

Claims (10)

An image forming unit for forming an image on a recording medium;
A motor that generates rotational driving force in one direction;
A switchback roller whose rotation direction is switched between a normal rotation direction and a reverse direction in order to switch the conveyance direction of the recording medium;
A first gear train that transmits the rotational driving force of the motor to the switchback roller such that the rotation direction of the switchback roller is a forward rotation direction;
A second gear train that transmits the rotational driving force of the motor to the switchback roller such that the rotation direction of the switchback roller is a reverse direction;
A switching unit having a pendulum gear that receives the rotational driving force of the motor and meshes with the first gear train or the second gear train;
The pendulum gear meshes with the first gear train and rotates the switchback roller in the forward rotation direction, and the reverse rotation position meshes with the second gear train and rotates the switchback roller in the reverse direction. , Movable to a non-meshing position that does not mesh with either the first gear train or the second gear train,
The switching unit is
A switching mechanism that enables initialization at any of the forward rotation position, the reverse position, and the non-meshing position when initializing the position of the pendulum gear at the start of power supply to the image forming apparatus; , Image forming apparatus. The image forming apparatus according to claim 1.
The switching unit is
A holder for rotatably supporting the pendulum gear;
A switching gear having a cam that rotates the holder by pressing the holder, and the normal rotation position, the reverse position, and the non-engagement position of the pendulum gear by rotating the cam by its own rotation. A switching gear to be switched,
A driving gear that transmits a rotational driving force from the motor to the switching gear, and
The switching mechanism is
A fixing mechanism that non-rotatably fixes the switching gear at each position corresponding to the forward rotation position, the reverse rotation position, and the non-meshing position of the pendulum gear;
An image forming apparatus comprising: an opening mechanism that rotatably opens the switching gear fixed by the fixing mechanism when the position of the pendulum gear is switched. The image forming apparatus according to claim 2.
The opening mechanism includes a solenoid;
The fixing mechanism is
An intermediate gear that transmits the rotational driving force from the motor to the switching gear via the driving gear;
A first link rotatably supported by the switching gear and rotatably supporting the intermediate gear;
A second link that is movably coupled to the first link and has an engaging projection that engages the switching gear;
An engaging portion that is formed on the switching gear and engages with the engaging protrusion to fix the switching gear;
A spring connected to the second link and biasing the second link toward the engaging portion,
The engaging portion is
A first engagement portion that engages with the engagement protrusion and fixes the switching gear at a position corresponding to the forward rotation position;
A second engagement portion that engages with the engagement protrusion and fixes the switching gear at a position corresponding to the reverse position;
A third engagement portion that engages with the engagement protrusion and fixes the switching gear at a position corresponding to the non-engagement position;
When the position of the pendulum gear is changed, the solenoid acts on the second link to release the engagement between the engagement protrusion and the engagement portion against the biasing force of the spring. Forming equipment. The image forming apparatus according to claim 3.
When each of the engaging portions is based on the position of the first engaging portion, the first engaging portion, the second engaging portion, and the third engaging portion in the rotation direction of the switching gear. An image forming apparatus formed in order. The image forming apparatus according to claim 3.
The third engagement portion is formed at two locations on the switching gear,
When each of the engaging portions is based on the position of the first engaging portion, the first engaging portion, the third engaging portion, the second engaging portion, and An image forming apparatus formed in the order of the third engaging portion. The image forming apparatus according to claim 3 or 4, wherein:
The first engaging portion and the second engaging portion are formed on the switching gear at a position where an angle of rotation of the switching gear forms 180 °, and the first engaging portion and the third engaging portion. The engagement portion is an image forming apparatus formed at a position where the rotation angle is 90 °. The image forming apparatus according to any one of claims 3 to 6,
When the intermediate gear is retracted from the drive gear, the intermediate gear is retracted in the direction opposite to the rotation direction of the drive gear with the rotation shaft of the switching gear as the rotation center. The image forming apparatus according to any one of claims 1 to 7,
The switching gear is
A toothed portion that meshes with the intermediate gear when the pendulum gear is located at the reverse position and the non-meshing position, and a missing portion that faces the intermediate gear when the pendulum gear is located at the forward rotation position. A toothless gear including a tooth portion;
The switching gear includes a cylindrical portion that is integrally formed with the switching gear on a surface opposite to a surface on which the cam is formed, and on which the engaging portion is formed.
The first engagement portion is formed as a guide groove that guides the engagement protrusion from a circumferential portion of the cylindrical portion corresponding to the toothed portion to a circumferential portion corresponding to the missing tooth portion,
The image forming apparatus, wherein the second and third engaging portions are formed as locking grooves that lock the engaging protrusions at a circumferential portion of the cylindrical portion. The image forming apparatus according to any one of claims 2 to 8,
A discharge port capable of discharging the recording medium on which an image is formed;
A transport roller disposed upstream of the image forming unit in the transport direction and to which a rotational driving force is input from the motor;
A paper feeding unit on which the recording medium is placed;
A first conveyance path configured to convey the recording medium to the conveyance roller and pass through the image forming unit to reach the switchback roller;
A second transport path configured to join the recording medium from the switchback roller to the upstream side in the transport direction with respect to the image forming unit of the first transport path;
A control unit for controlling the opening mechanism when switching the position of the pendulum gear,
The control unit can execute double-sided image formation processing for forming an image on the recording medium,
The double-sided image forming process includes:
A process of forming an image on each surface of two recording media, a first recording medium having a first surface and a second surface, and a second recording medium having a first surface and a second surface,
The first recording medium is supplied from the paper feeding unit to the first conveying path by the conveying roller, and an image is formed on the first surface of the first recording medium by the image forming unit, and the switchback roller A first step of holding the forward rotation position so as to be conveyed to
A second step of switching the position of the pendulum gear from the forward rotation position to the reverse position and holding the reverse position so that the first recording medium is transported along the second transport path; and the position of the pendulum gear. A third step of switching from the reverse position to the non-meshing position and holding the non-meshing position;
The position of the pendulum gear is switched from the non-engagement position to the forward rotation position, and an image is formed on the first surface of the second recording medium by the image forming unit, and the second recording medium is the switchback roller. A fourth step of holding the forward rotation position so that
A fifth step of switching the position of the pendulum gear from the normal rotation position to the reverse position, and holding the reverse position so that the second recording medium is transported to the second transport path;
The position of the pendulum gear is switched from the reverse position to the forward rotation position so that an image is formed on the second surface of the first recording medium and an image is formed on the second surface of the second recording medium. A sixth step of maintaining the forward rotation position in
An image forming apparatus. The image forming apparatus according to claim 9.
In the sixth step, the control unit controls the opening mechanism to rotatably open the switching gear for a longer time than in the second step to the fifth step.

Images