JP6058099B2 - Driving device and image forming apparatus having the same - Google Patents

Description

  The present invention relates to a driving device that transmits a rotation of a driving motor to a driven shaft through a coupling that can be connected to and disconnected from at least a pair of helical gears that mesh with each other, and an image forming apparatus including the driving device.

  For example, in an image forming apparatus such as a copying machine or a printer that forms an image on paper by an electrophotographic method, a latent image formed on an image carrier such as a photosensitive drum is developed with toner in a developing device, and the toner The toner image is visualized and the toner image is transferred onto a sheet. The sheet onto which the toner image has been transferred is conveyed to a fixing device, where the toner image is fixed by being heated and pressed in the process of passing through the fixing nip between the heating roller and the pressure roller of the fixing device. In response, the paper on which the toner image has been fixed is discharged to a paper discharge unit outside the apparatus, and a series of image forming operations is completed.

  In such an image forming apparatus, for example, a driving device that rotationally drives the photosensitive drum transmits the rotation of the driving motor to the photosensitive drum through the reduction gear train and the coupling. In this case, the coupling / disconnection between the drive motor and the driven shaft is generally performed by coupling. However, in Patent Document 1, the gear can be rotated on the fixed shaft and slidable in the axial direction. Supports and urges the gear in the connecting direction with the driven shaft by the compression spring, and if necessary, the gear is slid along the axial direction of the fixed shaft by the slide lever to release the connection between the gear and the driven shaft. A configuration has been proposed.

JP-A-5-017040

  However, in the conventional drive device including the mechanism proposed in Patent Document 1, when the rotation on the driven side is locked, an overload is generated in the drive system component such as a gear and the drive system component Problem occurs.

  The present invention has been made in view of the above problems, and the purpose of the invention is to protect the drive system parts such as gears from overload and damage them even when the rotation on the driven side is locked. It is an object of the present invention to provide a drive device that can be prevented and an image forming apparatus including the drive device.

  The drive device according to the present invention is a device that transmits the rotation of the drive motor to the driven shaft through a coupling that can be connected to and disconnected from at least a pair of helical gears that mesh with each other. The driving device supports one of the pair of helical gears so as to be rotatable and slidable in the axial direction. The urging means urges the helical gear in a direction in which the coupling is coupled. Then, when the drive motor is rotating, a thrust force is generated at the meshing portion of the pair of helical gears in a direction to release the coupling. The urging force of the urging means is greater than the thrust force when the driven shaft is rotating. When the rotation of the driven shaft is locked, the thrust force larger than the urging force of the urging means is generated, and one of the pair of helical gears resists the urging force of the urging means. By sliding with respect to the fixed shaft, the coupling is released.

  According to the present invention, a thrust force in the axial direction (direction in which the coupling is released) is generated at the meshing portion of the pair of helical gears by the rotation of the pair of helical gears. Thereby, when the driven shaft is rotating normally, the thrust force generated by the meshing of the pair of helical gears is smaller than the urging force of the urging means, so that the coupling is maintained in the connected state. As a result, the rotation of the drive motor is transmitted to the driven shaft through the coupling. When the rotation of the driven shaft is locked, a thrust force larger than the urging force of the urging means is generated at the meshing portion of the pair of helical gears. Due to this thrust force, one helical gear slides on the fixed shaft against the biasing force of the biasing means. For this reason, the coupling is released, and the rotation of the drive motor is not transmitted to the driven shaft. As a result, the drive system parts such as the helical gear are protected from overload and their damage is prevented.

  Also, when the rotation of the driven shaft is locked and one helical gear rotates and slides in the axial direction, the male thread formed on the boss portion of the helical gear is connected to the inner circumference of the fixed cylindrical member. The axial position of the helical gear is fixed by being screwed into the female screw portion formed in the above, and the non-coupled state of the coupling is maintained. When the drive motor is reversed and the helical gear is also reversed, the male screw portion formed on the boss portion of the gear is disengaged from the female screw portion of the cylindrical member, and the helical gear is removed. Since the coupling is reconnected by sliding on the fixed shaft by the biasing force of the biasing means, the rotation of the driven shaft by the drive motor is resumed.

FIG. 1 is a longitudinal sectional view of an image forming apparatus according to an embodiment. FIG. 2 is a perspective view illustrating a state during normal operation of the drive device according to the embodiment. FIG. 3 is a plan sectional view showing a state during normal operation of the drive device according to the embodiment. FIG. 4 is a perspective view of a gear unit of the drive device according to the embodiment. FIG. 5 is a perspective view illustrating a state when the driving apparatus according to the embodiment is locked. FIG. 6 is a plan sectional view showing a state when the driving apparatus according to the embodiment is locked.

Embodiments of the present invention will be described below with reference to the accompanying drawings.
[Image forming apparatus]
An image forming apparatus 1 shown in FIG. 1 is a monochrome copying machine, and includes an image reading device 2 on an upper portion of the apparatus main body 1A. A paper discharge tray 3 is provided below the image reading device 2. An image forming unit 4 is disposed inside the apparatus main body 1A, and a paper feeding unit 5 is disposed below the image forming unit 4.

  The image reading device 2 includes two light guides 6 arranged in the main scanning direction (left-right direction in FIG. 1) and positions facing the incident surfaces of the outer end surfaces of the light guides 6 in the main scanning direction. LED7 which is a light source arrange | positioned is provided. The image reading device 2 employs a side light system in which light from both LEDs 7 is incident from the incident surface of each light guide 6 and guided in the main scanning direction. In the image reading apparatus 2, the light guide 6 and the LED 7 are supported so as to be able to reciprocate in the sub-scanning direction (the direction perpendicular to the paper in FIG. 1). Although not shown, the image reading device 2 includes an imaging lens that forms an image of the reflected light reflected from the document, and a CCD that converts the optical image formed by the imaging lens into an electrical signal and reads it. A photoelectric conversion element is provided.

  The image forming unit 4 forms an image by electrophotography. The image forming unit 4 includes a photosensitive drum 8 as an image carrier that is rotatably arranged, a charger 9 arranged around the photosensitive drum 8, a laser scanner unit (LSU) 10, a developing device 11, a transfer roller 12, and a cleaning device. A device 13 is provided.

  The paper feed unit 5 includes a detachable paper feed cassette 14 and a pick roller 15 and a paper feed roller 16 disposed in the vicinity thereof. Here, a plurality of sheets S are stacked and accommodated in the sheet feeding cassette 14. The sheets S in the sheet feeding cassette 14 are sequentially picked up one by one from the upper one by the pick roller 15 and further fed out to the sheet conveying path P by the sheet feeding roller 16.

  The paper conveyance path P extends upward from the paper supply unit 5 to the paper discharge tray 3. In the paper transport path P, a registration roller 17, the transfer roller 12, the fixing device 18, a transport roller 19, and a paper discharge roller 20 are sequentially arranged from below.

  Next, an image forming operation of the image forming apparatus 1 configured as described above will be described.

  When the image forming operation is started, in the image forming unit 4, the photosensitive drum 8 is rotationally driven in a direction indicated by an arrow (clockwise) in FIG. Further, the surface of the photosensitive drum 8 is uniformly charged to a predetermined potential by the charger 9. In the image reading device 2, the original image is read as will be described later, and a laser beam based on an electric signal transmitted from the image reading device 2 is output from the laser scanner unit (LSU) 10 to be the photosensitive drum 8. When the surface is exposed and scanned, an electrostatic latent image corresponding to image information is formed on the photosensitive drum 8. Then, the electrostatic latent image formed on the photosensitive drum 8 is developed by the developing device 11 using toner as a developer to be visualized as a toner image.

  Further, the paper S accommodated in the paper feed cassette 14 of the paper feed unit 5 is picked up from the uppermost one by the pick roller 15 and is sent out to the paper transport path P by the paper feed roller 16. The paper S sent out to the paper transport path P in this way is transported to the registration roller 17 along the paper transport path P. Further, the sheet S is temporarily set in the registration roller 17 and then supplied to the image forming unit 4 at a predetermined timing synchronized with the toner image on the photosensitive drum 8.

  In the image forming unit 4, the paper S is supplied to a transfer nip between the photosensitive drum 8 and the transfer roller 12. Further, the sheet S is conveyed while being pressed against the photosensitive drum 8 by the transfer roller 12. As a result, the toner image on the photosensitive drum 8 is transferred to the surface of the paper S. Then, the sheet S on which the toner image is transferred is conveyed to the fixing device 18. The sheet S is heated and pressurized in the process of passing through the fixing nip of the fixing device 18 and receives the fixing of the toner image. The toner remaining on the surface of the photosensitive drum 8 (transfer residual toner) after the transfer of the toner image onto the paper S is removed by the cleaning device 13. The photosensitive drum 8 whose surface has been cleaned is prepared for the next image forming operation.

Thus, the sheet S having the toner image fixed on the surface thereof by the fixing device 18 is conveyed by the conveying roller 19 along the sheet conveying path P to the paper discharge roller 20. Further, the paper S is discharged to the paper discharge tray 3 by the paper discharge roller 20. This completes a series of image forming operations.
[Driver]
Next, details of the drive device according to the present invention will be described below with reference to FIGS.

  2 is a perspective view showing a state of the drive device according to the present invention during normal operation, FIG. 3 is a cross-sectional view of the same, FIG. 4 is a perspective view of a gear unit of the drive device according to the present invention, and FIG. FIG. 6 is a cross-sectional view of the same, in a perspective view showing a state when the device is locked.

  As shown in FIG. 2, a drive motor 22 as a drive source is attached to the sheet metal frame 21. A small-diameter pinion gear 23 is attached to an end of an output shaft (not shown) that penetrates the frame 21 of the drive motor 22. A fixed shaft 24 is fixed in parallel to the pinion gear 23 on the side of the pinion gear 23 of the frame 21. A helical gear 25 that meshes with the pinion gear 23 is rotatably supported on the fixed shaft 24.

  Further, a gear unit U as shown in FIG. 4 is detachably incorporated in the frame 21. A cylindrical member 27 and a long cylindrical positioning boss 28 are integrally formed on the base member 26 of the gear unit U at an appropriate interval in the lateral direction. The base member 26 is fixed with a fixed shaft 29 concentrically penetrating the cylindrical member 27. A helical gear 30 is supported at the tip of the fixed shaft 29 so as to be rotatable and slidable in the axial direction. An internal thread portion 27 a is formed on the inner periphery of the cylindrical member 27 in the vicinity of the opening.

  The helical gear 30 meshes with the helical gear 25 as shown in FIG. A cylindrical boss portion 30 b integrally penetrates the center portion of the helical gear 30. One end (front end) of the boss portion 30b is formed with one engagement piece 31a of a coupling 31 for connecting / disconnecting (connecting / disconnecting) the photosensitive drum 8 and the helical gear 30 as described later. Has been. Further, a male screw portion 30 a is formed on the outer periphery of the other end portion (rear end portion) of the boss portion 30 </ b> A of the helical gear 30. The male screw portion 30a is selectively screwed into the female screw portion 27a formed on the cylindrical member 27 as described later.

  Incidentally, the rotating shaft (driven shaft) 32 of the photosensitive drum 8 and the helical gear 30 can be connected / disconnected (connected / disconnected) by the coupling 31. The coupling 31 is configured by engaging the engagement piece 31b and the engagement piece 31a. The engaging piece 31 b is bonded to the rotating shaft 32 of the photosensitive drum 8. The engagement piece 31 a is formed on the boss portion 30 b of the helical gear 30.

  Here, the helical gear 30 is slidably supported on the fixed shaft 29. The helical gear 30 is urged forward by a spring 33 (to the right in FIG. 3 and in the direction in which the coupling 31 is coupled). The spring 33 is an urging means that is contracted between the helical gear 30 and the cylindrical member 27.

  Thus, the gear unit U configured as described above is incorporated in the frame 21. Positioning of the gear unit U with respect to the frame 21 is performed by inserting and engaging a positioning pin 34 protruding from the frame 21 with a positioning boss 28 as shown in FIG.

  Next, the operation of the drive device configured as described above will be described.

  When the drive motor 22 is activated in a normal state where the rotation of the photosensitive drum 8 is not locked, the rotation of the drive motor 22 is caused by the pinion gear 23, the pair of helical gears 25 and 30, and the cup in the connected state. The light is transmitted to the rotating shaft 32 of the photosensitive drum 8 through the ring 31. Thereby, the photosensitive drum 8 is rotationally driven at a predetermined speed. At this time, a thrust force in the direction of the arrow in FIG. 3 (the direction in which the coupling 31 is released) is generated at the meshing portion of the pair of helical gears 25 and 30. Further, the biasing force of the spring 33 that biases the helical gear 30 in the reverse direction is set to be larger than the normal thrust force. Therefore, the helical gear 30 rotates at the initial position without sliding in the axial direction on the fixed shaft 29. Therefore, the engagement of the one engagement piece 31a of the coupling 31 formed on the boss 30b of the helical gear 30 with the other engagement piece 31b is maintained. Thereby, the coupling 31 maintains a connection state. Accordingly, in this state, the rotation of the drive motor 22 is transmitted to the rotating shaft 32 of the photosensitive drum 8 through the pinion gear 23, the pair of helical gears 25, 30 and the coupling 31, as described above. As a result, the photosensitive drum 8 is normally rotated at a predetermined speed.

  On the other hand, when the rotation of the photosensitive drum 8 is locked for some reason, a large load is generated on the pair of helical gears 25 and 30. Due to this large load, a large thrust force in the direction of the arrow in FIGS. 5 and 6 (the direction in which the coupling 31 is released) is generated at the meshing portions of the helical gears 25 and 30. This thrust force is larger than the urging force of the spring 33. Therefore, the helical gear 30 slides on the fixed shaft 29 in the direction of the thrust force against the urging force of the spring 33. Further, one engagement piece 31a of the coupling 31 formed on the boss 30b of the helical gear 30 is disengaged from the other engagement piece 31b. As a result, the engagement pieces 31a and 31b are disengaged and the coupling 31 is released. In this case, the rotation of the drive motor 22 is not transmitted to the photosensitive drum 8, and the drive system components such as the helical gears 25 and 30 are protected from overload and the damage is prevented. For this reason, in the image forming apparatus 1 shown in FIG. 1, even when the rotation of the photosensitive drum 8 is locked, damage to the rotational drive system components such as the helical gears 25 and 30 is prevented. As a result, maintenance such as replacement of parts becomes unnecessary.

  As described above, when the helical gear 30 rotates and slides on the fixed shaft 29, the male screw portion 30a formed on the boss portion 30b of the helical gear 30 is fixed as shown in FIG. It is screwed into a female screw portion 27a formed on the inner periphery of the cylindrical member 27 on the side. As a result, the axial position of the helical gear is fixed, the coupling 31 is not connected, and the rotation of the drive motor 22 is stopped. Thereafter, when the drive motor 22 is reversed and the helical gear 30 is also reversed, the male screw portion 30a formed on the boss portion 30b of the helical gear 30 is screwed with the female screw portion 27a of the cylindrical member 27. Mismatch. Further, the helical gear 30 slides on the fixed shaft 29 by the urging force of the spring 33, and the coupling 31 is connected again as shown in FIGS. Therefore, the rotation of the photosensitive drum 8 by the drive motor 22 is resumed, and an image forming operation is possible.

  In the above description, the embodiment in which the present invention is applied to a monochrome copying machine and a driving device for rotationally driving a photosensitive drum provided thereon has been described. However, it is needless to say that the present invention can be similarly applied to a driving device for driving a rotational driving component other than the image forming apparatus.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 1A Image forming apparatus main body 2 Image reading apparatus 3 Paper discharge tray 4 Image forming part 5 Paper feeding part 6 Light guide 7 LED
8 Photosensitive drum 9 Charger 10 Laser scanner unit (LSU)
DESCRIPTION OF SYMBOLS 11 Developing device 12 Transfer roller 13 Cleaning device 14 Paper feed cassette 15 Pick roller 16 Paper feed roller 17 Registration roller 18 Fixing device 19 Transport roller 20 Paper discharge roller 21 Frame 22 Drive motor 23 Pinion gear 24 Fixed shaft 25 Helical gear 26 Base Member 27 Cylindrical member 27a Female threaded portion 28 of cylindrical member Positioning boss 29 Fixed shaft 30 Helical gear 30a Helical gear male threaded portion 30b Helical gear boss portion 31 Couplings 31a, 31b Coupling engagement Piece 32 Rotating shaft 33 of photosensitive drum Spring (biasing means)
34 Positioning pin P Paper transport path S Paper U Gear unit

Claims (3)

In the drive device that transmits the rotation of the drive motor to the driven shaft through a coupling that can be connected to and disconnected from at least a pair of helical gears that mesh with each other,
A fixed shaft that supports one of the pair of helical gears rotatably and slidably in the axial direction;
Biasing means for biasing one helical gear supported by the fixed shaft in a direction in which the coupling is coupled,
A male screw part is formed on the outer periphery of the end opposite to the coupling in the boss part of the one edge gear supported by the fixed shaft,
A cylindrical member is fixed around the fixed end of the fixed shaft,
On the inner periphery of the opening end of the cylindrical member, a female screw portion is formed, on which the male screw portion formed on the boss portion of the one edge gear can be screwed,
When the drive motor is rotating, a thrust force in a direction to release the coupling is generated at the meshing portion of the pair of helical gears,
The urging force of the urging means is greater than the thrust force when the driven shaft is rotating,
When the rotation of the driven shaft is locked, the thrust force larger than the urging force of the urging means is generated, and the one helical gear resists the urging force of the urging means, and the fixed shaft maintaining by sliding, the connection of the coupling is released Rutotomoni, the state of connection is released in the coupling by the male screw portion and female screw portion is screwed against the drive unit .   When the male screw portion and the female screw portion are screwed together, the drive motor rotates reversely, so that the male screw portion and the female screw portion are unscrewed, and the coupling is connected again. The drive device according to claim 1. The toner image formed in the image forming unit is transferred onto the paper supplied from the paper feeding unit, and the paper on which the toner image is transferred is fixed by the fixing device and then discharged to the paper discharging unit. In an image forming apparatus for forming
An image forming apparatus comprising the rotation drive system according to claim 1 or 2 .

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