JP2007009969A - Electromagnetic clutch and paper conveyance mechanism equipped with it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electromagnetic clutch capable of increasing a meshing rate by a simple and compact configuration without generating force in the thrust direction to suppress occurrence of noise and vibration and to provide a paper conveyance mechanism using it. <P>SOLUTION: This electromagnetic clutch 20 is provided with a driving output shaft 21, a ring-like driving input gear 22 arranged so as to surround at least a part of the driving output shaft 21, and an electromagnetic clutch part 23 incorporated on the same shaft between the driving output shaft 21 and the driving input gear 22 to attract the driving output shaft 21 and the driving input gear 22 magnetically or release an attraction condition. The driving input gear 22 is a double helical gear forming two helical gear parts 22a, 22b on the same shaft to make the direction of torsion of gear teeth symmetrical on the left and right sides, and phase deviation by 0.5 teeth is provided in the helical gear parts 22a, 22b. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an electromagnetic clutch that controls transmission of rotational driving force by ON / OFF of a current, and a sheet conveying mechanism including the electromagnetic clutch.

  Conventionally, in the case where the driving of a plurality of driven members is controlled separately, the number of driven members such as motors provided for the number of driven members increases the cost of the apparatus. Therefore, it is general to provide a clutch mechanism that drives and drives each driven member using one driving means and transmits and interrupts driving force between the driving means and each driven member. The clutch mechanism consists of a mechanical clutch that engages and disengages the driving force using gear meshing, friction of the clutch plate, centrifugal force, etc., and a driving force by adsorbing the clutch plate by electromagnetic force. Are classified as electromagnetic clutches that are intermittent.

  The electromagnetic clutch includes, for example, a first rotation shaft composed of an inner shaft and the like, and a drive input gear arranged coaxially with the first rotation shaft so as to surround at least a part of the first rotation shaft. And a second rotating shaft made of a movable member such as a coupling, and an electromagnetic clutch portion incorporated between the first rotating shaft and the second rotating shaft. The first rotating shaft and the second rotation When the shaft and the shaft are integrally driven, the current, which is a movable piece engaged with the second rotating shaft, is engaged with the first rotating shaft by passing a current through the coil in the electromagnetic clutch section. The rotor is attached by suction pressure using electromagnetic force.

  Such an electromagnetic clutch is used as a drive connecting means for electrically controlling the drive timing of the paper feed unit and the paper transport unit of the image forming apparatus. When a directional force is applied, variations in clutch engagement time and clutch release (disconnection) time become large, which may adversely affect the performance of the electromagnetic clutch. Therefore, a conventional electromagnetic clutch employs a spur gear that does not generate a thrust force (hereinafter referred to as a thrust force) as a drive input gear.

  When a spur gear is used as the drive input gear, all gears connected to the gear train in the same plane as the drive input gear are spur gears. Here, since the spur gear has a low meshing rate (see Non-Patent Document 1) compared to a helical gear whose gear teeth are helical, a gear train from a drive source such as a motor to a drive input gear. , Gear meshing noise is likely to occur. In addition, when such an electromagnetic clutch is used in the paper transport unit, there is a problem that the paper vibrates at the meshing frequency and image defects such as transfer deviation occur.

  Many drive transmission means using helical gears having a high meshing rate instead of spur gears have already been proposed. For example, FIG. 1 of Patent Document 1 shows a journal paper (roll paper) winding mechanism. In this printer, a method is disclosed in which a helical gear is used as a drive transmission system to the spool of the journal mechanism, and when the roll paper is taken up by the spool, the positional deviation in the rotational direction is prevented when the spool is started. Further, in Patent Document 2, a plurality of helical gears that rotate integrally with an image carrier are provided at both ends of the image carrier, and a roller that rotates together with the image carrier and a helical gear are meshed well to form a pitch. An image forming apparatus that prevents unevenness is disclosed.

  However, when a helical gear is used as the drive input gear of the electromagnetic clutch, the thrust force acts on the electromagnetic clutch although the meshing noise and the vibration of the meshing frequency are reduced. The direction of this thrust force is determined by the torsional direction of the gear teeth of the helical gear, but if the torsional direction is set so that the thrust force acts against the electromagnetic clutch against the electromagnetic clutch, When the setting is made so that the thrust (actuation) time varies and the thrust force acts in the opposite direction, the variation of the clutch connection time increases.

  For this reason, when an electromagnetic clutch whose driving input gear is a helical gear is used, for example, as a driving connection means of a registration roller, the sheet conveying performance becomes unstable and the image writing position varies. In addition, in order to eliminate the variation in the writing position, it is necessary to set a larger amount of slack of the sheet with respect to the registration roller, and there is a problem that a rush sound is increased when the sheet is conveyed again from the registration roller.

  As a gear that increases the meshing rate without generating a thrust force, there is a known YAMAGA gear in which two helical gears are coaxially overlapped so that the torsional direction of gear teeth is symmetrical. FIG. 2 of Patent Document 1 discloses an example in which a thrust force is suppressed by using a blind gear in the drive transmission system of the journal mechanism. Further, Patent Document 3 discloses a method of improving the image quality by increasing the meshing rate without generating a thrust force by using a blind gear as the drive input gear of the fixing unit of the image forming apparatus. .

However, due to recent demands for downsizing and downsizing of image forming apparatuses, electromagnetic clutches used in the paper transport unit are required to be further downsized and thinned. Usually, the gear thickness of the YAMAGA gear is the gear thickness of two helical gears, so when using the YAMAGA gear as the drive input gear of the electromagnetic clutch, an arrangement space for two gears is required. However, there are cases where sufficient space cannot be secured due to restrictions on the size of the apparatus. In addition, if the gear thickness of the lintel gear is reduced, the meshing rate is reduced by that amount.
Takahisa Tsukamoto, “Design Technology for Plastic Gears for Power Transmission” (Gihodo Publishing, P.73-74) Japanese Patent Laid-Open No. 11-35198 Japanese Patent Laid-Open No. 2-166470 JP 2003-91184 A

  SUMMARY OF THE INVENTION In view of the above problems, the present invention provides an electromagnetic clutch that increases the engagement rate with a simple and compact configuration without generating thrust force and suppresses the generation of noise and vibration, and a paper transport mechanism using the electromagnetic clutch. The purpose is to do.

In order to achieve the above object, the present invention comprises a rotatable drive output shaft, a drive input gear arranged coaxially with the drive output shaft, and coaxial with the drive output shaft and the drive input gear. An electromagnetic clutch part incorporated between the drive output shaft and the drive input gear,
In the electromagnetic clutch that allows the drive output shaft and the drive input gear to be rotated integrally or separately by energizing or shutting off the electromagnetic clutch portion, the twist direction of the gear teeth as the drive input gear A helical gear composed of two helical gear portions symmetrical to each other is used, and the gear teeth of the helical gear portion have a phase shift.

  In the electromagnetic clutch having the above-described configuration, the drive input gear may be configured by superimposing two helical gears on the same axis while shifting the phase so that the torsional direction of the gear teeth is symmetrical. It is characterized by being.

  The present invention also provides a paper transport mechanism in which the electromagnetic clutch having the above-described configuration is mounted.

  According to the first configuration of the present invention, the use of a spurious gear as the drive input gear can increase the meshing rate as compared with the case where a spur gear is used. In addition, the thrust force is not generated as in the case of using a helical gear, so that variations in the connection time and release time of the electromagnetic clutch are reduced. Furthermore, since the gear teeth of the helical gear portion have a phase shift, a sufficient meshing rate can be ensured even if the gear thickness of the blind gear is reduced, and the electromagnetic clutch can be made thinner.

  According to the second configuration of the present invention, in the electromagnetic clutch having the first configuration, the two helical gears are coaxially shifted in phase so that the twisting directions of the gear teeth are symmetric. By configuring the drive input gear so as to overlap with each other, the phase shift amount of the helical gear portion can be easily adjusted.

  Further, according to the third configuration of the present invention, by mounting the electromagnetic clutch having the above first or second configuration on the paper transport mechanism, image defects due to vibration of the gear meshing cycle do not occur, and noise is generated. And a compact image forming apparatus.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a side sectional view of an image forming apparatus on which an electromagnetic clutch of the present invention is mounted. In FIG. 1, an image forming unit P is disposed above the transport belt 8 in the image forming apparatus 1. The image forming unit P forms a predetermined image through each process of charging, exposure, development, and transfer.

  In this image forming portion P, a photosensitive drum 2 carrying a visible image (toner image) is disposed, and the toner image formed on the photosensitive drum 2 moves adjacent to the image forming portion. The sheet is transferred onto a sheet (recording medium) 6 carried and conveyed by the conveying belt 8, and after being fixed on the sheet 6 in the fixing unit 7, the sheet is discharged from the apparatus main body. While the photosensitive drum 2 is rotated clockwise in FIG. 8, an image forming process for the photosensitive drum 2 is executed.

  Next, the image forming unit P will be described in detail. Around and around the photosensitive drum 2 rotatably disposed, a charger 3 for charging the photosensitive drum 2, an exposure unit 4 for exposing image information to the photosensitive drum 2, and the photosensitive drum 2 A developing device 5 for forming a toner image and a cleaning unit 9 for removing the developer (toner) remaining on the photosensitive drum 2 are provided.

  First, the surface of the photosensitive drum 2 is uniformly charged by the charger 3 and then irradiated by the exposure unit 4 to form an electrostatic latent image corresponding to the image signal on the photosensitive drum 2. The developing device 5 is filled with a predetermined amount of toner by a toner container 10. This toner is supplied onto the photosensitive drum 2 by the developing device 5 and electrostatically adheres, whereby a toner image corresponding to the electrostatic latent image formed by exposure from the exposure unit 4 is formed.

  The sheet 6 on which the toner image is transferred is accommodated in a plurality of paper feed cassettes 11a, 11b, and 11c for storing paper and a stack bypass (manual feed tray) 11d provided above the paper feed cassettes 11a, 11b and 11c. The toner is supplied onto the conveyor belt 8 via the roller 13 and is conveyed to the position of the photosensitive drum 2. A sheet made of dielectric resin is used for the conveyor belt 8, and a belt in which both ends thereof are overlapped and joined to form an endless shape or a seamless belt is used.

  The conveyance belt 8 is stretched between a downstream drive roller 14 and an upstream driven roller 15. When the conveyance belt 8 starts to rotate counterclockwise, the sheet 6 is transferred from the registration roller 13 to the conveyance belt 8. It is transported up. At this time, the image writing signal is turned on, and an image is formed on the photosensitive drum 2 at a predetermined timing. The toner image on the photosensitive drum 2 is transferred onto the sheet 6 by applying an electric field to the lower portion of the photosensitive drum 2 with the transfer roller 16 to which a predetermined transfer voltage is applied. The sheet 6 is held on the conveyor belt 8 with an electrostatic adsorption force.

  The sheet 6 on which the toner image has been transferred is separated from the conveyance belt 8 and conveyed to the fixing unit 7. In addition, the photosensitive drum 2 after the toner image is transferred is removed by the cleaning unit 9 in preparation for the subsequent formation of a new electrostatic latent image. The sheet 6 conveyed from the conveying belt 8 to the fixing unit 7 is heated and pressed by the fixing roller 7a, and the toner image is fixed on the surface of the sheet 6 to form a predetermined image. The sheet 6 on which the image is formed is then discharged to a discharge tray 18 by a discharge roller 17.

  FIG. 2 is a perspective view showing an external configuration of the electromagnetic clutch of the present invention mounted on a paper transport mechanism such as the paper feed roller 12, registration roller 13, discharge roller 17 and the like shown in FIG. 1, and FIG. It is sectional drawing of an electromagnetic clutch. The electromagnetic clutch 20 includes a drive output shaft 21, a ring-shaped drive input gear 22 arranged coaxially with the drive output shaft 21 and surrounding at least a part of the drive output shaft 21, and the drive output shaft 21 and the drive. An electromagnetic clutch portion 23 is provided coaxially between the input gear 22 and magnetically attracts the drive output shaft 21 and the drive input gear 22 or releases the attracted state.

  The drive output shaft 21 is composed of, for example, a shaft, and a drive output gear 24 to which a rotated member such as a sheet conveying roller of an image forming apparatus (not shown) is connected is fixed to the drive output shaft 21. . The drive output shaft 21 is fitted with an armature 41, a rotor 42, an electromagnetic coil portion 43, and an exterior 26 which will be described later, and movement in the thrust direction is restricted by a stopper 50.

  The drive input gear 22 is a spur gear in which two helical gear portions 22a and 22b are formed on the same axis so that the torsional direction of the gear teeth is symmetrical. The helical gear portions 22a and 22b The phases are integrally formed with a shift of 0.5 teeth. The drive input gear 22 is connected to a gear 25 that transmits a drive force of a motor (not shown) that is a drive source of the rotated member. As the gear 25, a spur gear formed by shifting the phases of the two helical gear portions 25a and 25b by 0.5 teeth so as to mesh with the gear teeth of the drive input gear 22 is used.

  31 is a gear receiver with which the drive input gear 22 is engaged. A plurality of claw portions 32 are erected on the surface of the gear receiver 31 that contacts the drive input gear 22, and a plurality of claw portions (not shown) are also provided on the surface that contacts the armature 41. By these claw portions, the drive input gear 22, the gear receiver 31, and the armature 41 are engaged so as to rotate integrally.

  The electromagnetic clutch unit 23 serves as an armature 41 that is a movable piece, a rotor 42 that is opposed to the armature 41, an electromagnetic coil unit 43 that forms a magnetic circuit that penetrates the rotor 42 in the radial direction, and serves as, for example, a yoke and an electromagnetic wave. It is comprised from the exterior 26 which protects the coil part 43. FIG. Further, the electromagnetic clutch portion 23 is made of, for example, a disc spring or the like, and urges the armature 41 in a direction away from the rotor 42, so that an appropriate space is provided between the vertical surface of the armature 41 and the bottom surface 42b of the rotor 42. A separation spring (not shown) for holding the is also disposed.

  The amateur 41 is formed in a ring shape, and a plurality of engaging portions 41a to which the claw portions 32 of the gear receiver 31 are engaged are provided on the outer peripheral end thereof. The rotor 42 is made of a magnetic material, and has a cylindrical outer tube portion and a bottom surface that contacts the armature 41. An engagement hole (not shown) that engages with the drive output shaft 21 is formed at the center of the bottom surface so that the drive output shaft 21 and the rotor 42 rotate integrally. A through hole 42 a is formed on the bottom surface of the rotor 42, and a magnetic circuit that bypasses the magnetic circuit generated by the electromagnetic coil unit 43 (divides) and passes between the rotor 42 and the armature 41 is formed. Configured to promote.

  The electromagnetic coil unit 43 includes a bobbin 27, a coil 28 wound around the bobbin 27, and a connection terminal unit 29 that connects an end of the coil 28 and an external lead wire (not shown). Arranged in the internal space and fixed to the exterior 26.

  With the above-described configuration, the electromagnetic clutch 20 energizes the electromagnetic coil unit 43 from an external power source (not shown) to magnetically attract the armature 41 and the rotor 42 against the separation spring, thereby driving the drive output shaft 21. The drive input gear 22 is connected and the electromagnetic coil unit 43 is de-energized to release the magnetic attraction, and the drive is performed while holding the space between the armature 41 and the rotor 42 by the biasing force of the separation spring. The output shaft 21 and the drive input gear 22 are separated.

  The present invention is characterized in that a helical gear is used as the drive input gear 22 and that the phases of the two helical gear portions 22a and 22b constituting the helical gear are shifted. Thereby, compared with the case where a spur gear is used, a meshing rate can be raised and generation | occurrence | production of a meshing noise and the generation | occurrence | production of the vibration of a meshing frequency are prevented. In addition, since no thrust force is generated as in the case of using a helical gear, it is possible to reduce variations in the connection time and release time of the electromagnetic clutch 20.

  Furthermore, since the phase shifts are provided in the helical gear portions 22a and 22b, the meshing rate is higher than when there is no phase shift. Therefore, a sufficient meshing rate can be ensured even if the gear thickness of the lintel gear is reduced, so that the dimension in the thrust direction of the electromagnetic clutch 20 is shortened, and the electromagnetic clutch 20 can be made thinner. The amount of phase shift between the two helical gears is not limited to 0.5 teeth, the amount of shift between the drive input gear 22 and the gear 25 is equal, and the meshing rate of each gear is the highest. It should be set so that.

  If the electromagnetic clutch according to the present invention is mounted on the sheet conveying mechanism of the image forming apparatus shown in FIG. 1, an image forming apparatus with no noise caused by vibration of the gear meshing cycle is generated. Further, since the thrust force does not act on the sheet transport rollers such as the paper feed roller 12, the registration roller 13, and the discharge roller 17, it is not necessary to take measures such as reinforcing the housing and the roller bearing, which is advantageous in terms of cost. Furthermore, since the gear thickness of the drive input gear 22 can be reduced, the image forming apparatus can be reduced in size and size.

  In addition, the present invention can be variously modified without departing from the spirit of the present invention. For example, in the above-described embodiment, a helical gear in which two helical gear portions 22a and 22b are integrally formed is used. However, two helical gears in which the torsion directions of the gear teeth are symmetrical are connected to a predetermined phase. A gap gear may be formed by providing a shift and fixing on the same axis. In this case, the phase shift amount of the drive input gear 22 that is a sparse gear can be easily adjusted when the two helical gears are fixed. Also, here, an example in which the electromagnetic clutch is applied to the connection between the paper transport mechanism such as the paper feed roller 12, the registration roller 13 and the discharge roller 17 and the drive input shaft has been described. It can also be applied to the connection between the rotating member and the drive input shaft.

  In addition, the electromagnetic clutch and paper transport mechanism of the present invention can be applied to various image forming apparatuses such as digital multifunction peripherals, tandem color copying machines, copying machines such as analog monochrome copying machines, facsimiles, laser printers, and the like. It is.

  The present invention includes a rotatable drive output shaft, a drive input gear disposed coaxially and outside the drive output shaft, a drive output shaft and a drive input gear coaxially and the drive output shaft and the drive input gear. A drive input gear in an electromagnetic clutch that is capable of rotating the drive output shaft and the drive input gear integrally or separately by energizing or interrupting the electromagnetic clutch portion. As described above, a helical gear composed of two helical gear portions in which the twisting direction of the gear teeth is symmetrical is used, and the gear teeth of the helical gear portion have a phase shift.

  As a result, there is no meshing noise or meshing frequency vibration when using a spur gear, and no thrust force is generated when using a helical gear. And an electromagnetic clutch with little variation in opening time can be provided. Further, since the gear thickness of the drive input gear can be reduced, the electromagnetic clutch is thinner than the conventional one.

  In addition, if the lintel gear, which is the drive input gear, is formed by superimposing the two helical gears whose gear teeth twist directions are symmetrical, the phase shift amount can be easily adjusted to the optimum phase shift amount. be able to.

  In addition, by using the electromagnetic clutch of the present invention, a paper conveyance mechanism that does not cause image defects due to vibration of the meshing period of the gear and has less noise can be obtained. In addition, since the thrust force does not act on the paper transport mechanism, the cost for measures against the thrust force can be reduced. Furthermore, the thin electromagnetic clutch contributes to the downsizing and compactness of the paper transport mechanism and the image forming apparatus including the same.

These are schematic sectional drawings of the image forming apparatus in which the electromagnetic clutch of this invention is mounted. These are the perspective views of the electromagnetic clutch of this invention. These are side surface sectional drawings which show the structure of the electromagnetic clutch of this invention.

Explanation of symbols

12 Paper feed roller (paper discharge mechanism)
13 Registration roller (paper discharge mechanism)
17 Discharge roller (paper discharge mechanism)
20 Electromagnetic clutch 21 Drive output shaft 22 Drive input gear (Yamaba gear)
22a, 22b Helical gear portion 23 Electromagnetic clutch portion 27 Bobbin 28 Coil 29 Connection terminal portion 41 Amateur 42 Rotor 43 Electromagnetic coil portion 100 Image forming apparatus

Claims (3)

A rotatable drive output shaft, a drive input gear disposed coaxially and outwardly with the drive output shaft, and coaxial with the drive output shaft and drive input gear and between the drive output shaft and the drive input gear. An electromagnetic clutch part incorporated in between,
In the electromagnetic clutch that allows the drive output shaft and the drive input gear to be rotated integrally or separately by energizing the electromagnetic clutch portion or cutting off the energization,
As the drive input gear, a spur gear composed of two helical gear portions in which the twist direction of the gear teeth is symmetrical is used, and the gear teeth of the helical gear portion have a phase shift. And electromagnetic clutch.   2. The drive input gear is configured by superimposing two helical gears on the same axis while shifting the phase so that the torsional direction of the gear teeth is symmetrical. Electromagnetic clutch.   A paper transport mechanism, wherein the electromagnetic clutch according to claim 1 is mounted.

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