JP2005147310A - Driving device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a driving device, simple in constitution, preventing increase in engagement noise and abnormality of rotation transmitting accuracy due to inclination of axis of a large-bore gear, compact and having high durability. <P>SOLUTION: When a driving motor 1 is rotated in the direction of an arrow A, a drum driving gear 2 is rotated in the direction of an arrow B by meshing of a gear part 4a of a rotating shaft 4 and a gear part 2a of a drum driving gear 2. The vicinity of the meshing part of the drum driving gear 2 receives the force in the direction of approaching the driving motor 1 by the thrust force caused by an angle of torsion of a helical gear. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a drive device using gears, and more particularly to a drive device suitable for use on a photosensitive drum in an image forming apparatus such as a copying machine or a printer that requires high accuracy.

  2. Description of the Related Art Conventionally, image forming apparatuses such as copiers, printers, facsimiles, and multi-function machines of these types have been provided with a driving device that rotates, for example, a photosensitive drum with high accuracy. FIG. 5 is a perspective view showing the vicinity of a driving device in such a conventional image forming apparatus. In FIG. 1, the drum unit 100 includes a drum holding frame 106, a drum drive shaft 108 that is rotatably supported, and a photosensitive drum 110 that is supported so as to be able to rotate integrally with the drum drive shaft 108.

  The drum holding frame 106 is integrally formed of an appropriate synthetic resin. The drum holding frame 106 is provided with a main charger, a cleaning device, etc. (not shown). A holding cylindrical portion 112 is integrally formed on the unit rear side wall 104. The holding cylindrical portion 112 is formed concentrically with the drum drive shaft 108 and extends horizontally outward from the unit rear side wall 104.

  Further, the positioning member 10 is detachably disposed on the outer side of the main body rear side wall 104. An annular positioning member 10 formed integrally from a suitable synthetic resin has a positioning cylindrical portion 12 extending outward in the axial direction. The outer peripheral surface at the distal end portion of the positioning cylindrical portion 12 is fitted with the inner peripheral surface of the holding cylindrical portion 112 of the unit rear side wall 104. Outside these, a support frame 560 is detachably attached to a main body housing side (not shown).

  The support frame 560 is formed of an appropriate metal plate, for example, a steel plate, and has a substantially rectangular flat substrate portion 562 and a plurality of legs extending from the peripheral portion of the substrate portion 562 to the same single side by the same length. And a mounting flange portion 564 formed at the tip of the portion. The front outer surface of each of the mounting flange portions 564 is positioned on a virtual plane that is substantially parallel to the substrate portion 562. Further, a support shaft (not shown) is fixed to the substrate portion 562 of the support frame 560 so that the support shaft (not shown) extends to the one surface side. A drum drive gear 570 is rotatably supported on the support shaft.

  An electric motor M that is a drive source such as the photosensitive drum 110 is attached to the outside of the substrate portion 562 in the support frame 560. An output gear 590 is rotatably supported inside the substrate portion 562 of the support frame 560. The output gear 590 is connected to a drive shaft (not shown) of the electric motor M and meshed with the drum drive gear 570. . In the figure, a case where spur gears are employed for these gears is illustrated. The boss 572 of the drum drive gear 570 is fitted to the positioning member 10 so as to be rotatable and detachable.

  Further, in the positioning cylindrical portion 12 and the holding cylindrical portion 112, a driving side coupling and a drum side coupling (not shown) constitute coupling means between the drum driving gear 570 and the drum driving shaft 108, respectively. . When the electric motor M rotates, the rotation is transmitted to the drum driving shaft 108 by the coupling means while being decelerated by the output gear 590 and the drum driving gear 570, and the photosensitive drum 110 rotates.

  In the conventional driving device as described above, in order to prevent the shaft from collapsing, for example, a gear pursuing the accuracy of the gear mounting portion is disclosed (for example, see Patent Document 1). Specifically, it includes a pair of parallel substrates, a plurality of support shafts that hold the substrates at a predetermined interval, and a drive member that engages with the support shafts, and one end of the support shaft is a pair. The other end of the support shaft is fixed by being fitted and positioned in a hole formed in the second substrate of the pair of substrates. One of the plurality of holes drilled in the second substrate is set as a reference hole tolerance, and the other hole is set as a hole tolerance capable of detecting the planting fall of the support shaft.

  Further, there is disclosed one that prevents vibration, step-out, and noise of the motor by eliminating the shaft tilt of the motor and suppressing the deformation of the damper (see, for example, Patent Document 2). Specifically, the image bearing member includes a cylindrical developing unit that supplies a developer to the latent image formed on the image bearing member for development, and a driving unit that drives the developing unit. In the image forming apparatus, the shaft of the driving unit is configured to be supported by a bearing on the opposite side of the developing unit across the driving unit.

Moreover, what provided the auxiliary member fitted coaxially to the small diameter part of a gear is disclosed (for example, refer patent document 3). Specifically, a gear having a large-diameter portion whose periphery is a tooth surface and a small-diameter portion erected from the large-diameter portion and having a hole portion at the center of the large-diameter portion to form a bearing portion is provided. The gear device includes an auxiliary member that has a fitting portion that fits into the small diameter portion and that has a hole portion at the center to form a bearing portion, and the gear in a state in which the small diameter portion and the fitting portion are fitted. And the rotation center shaft is inserted into the bearing portion of the auxiliary member.
JP 2001-082587 A JP 2003-076092 A JP 2002-227968 A

  However, in the conventional configuration as described above, when a resin gear is used as a gear in the driving device, a thermal expansion is applied to this when a clearance is provided in consideration of variation in dimensions. The backlash of the bearing portion becomes large, and the shaft falls easily. In particular, this phenomenon tends to appear in a large-diameter gear having a large gear outer diameter with respect to the gear shaft length. The shaft length of the gear is the length of the portion of the gear that fits with the shaft.

  For example, the drum drive gear, which is the large-diameter gear shown in FIG. 5, has a diameter of the tooth tip circle that is about four times the shaft length. However, to prevent the shaft from collapsing, the shaft length is set to the gear outer diameter. If it is extended by an appropriate amount, the entire drive device will be enlarged accordingly. In addition, when a helical gear is used for the drum drive gear and the motor output gear, the thrust force caused by the torsion angle causes the shaft to move by the backlash of the drum drive gear bearing that is a large-diameter gear. The fall is noticeable.

  In view of the above-described problems, the present invention provides a driving device that has a simple configuration, prevents an increase in meshing noise due to a shaft collapse of a large-diameter gear and an abnormality in rotation transmission accuracy, and is compact and highly durable. The purpose is to do.

  In order to achieve the above object, the present invention has a drive side gear, a spacer member fitted to the root of the drive side gear, and a driven side gear having a diameter of the tooth tip circle larger than the axial length. The drive-side gear and the driven-side gear are helical gears, and the side surface of the driven-side gear is moved by the force in the thrust direction caused by the twist angle of the meshing portion of the drive-side gear and the driven-side gear. It is made to contact | abut on the front surface of a spacer member.

  Further, a protrusion is provided on the inner peripheral surface of the spacer member, and the protrusion is engaged with the drive side gear so that the spacer member rotates integrally with the drive side gear.

  The spacer member is made of a resin material.

  According to the present invention, it is possible to provide a compact and highly durable drive device with a simple configuration that prevents an increase in meshing noise and an abnormality in rotation transmission accuracy due to a shaft fall of a large-diameter gear.

  Specifically, in the driven gear having a large diameter of the tip circle with respect to the shaft length, a portion in which the dimensional variation due to the shaft tilt is the largest and a thrust force due to the helical angle of the helical gear is applied. The shaft collapse is regulated by bringing the vicinity of the tooth base, which is a part, into contact with the spacer member. As a result, it is possible to prevent the meshing abnormality due to the shaft collapse, to achieve accurate drive transmission, to prevent noise generation, and to improve durability.

  Further, a protrusion is provided on the inner peripheral surface of the spacer member, and the protrusion engages with the drive side gear so that the spacer member rotates integrally with the drive side gear. As a result, the circumferential speed at the contact portion between the driven gear side surface and the spacer member front surface during rotation is relatively close to zero, so that noise and accuracy degradation due to friction and wear can be reduced. it can.

  Further, by using a resin material for the spacer member, the contact portion between the driven gear side surface and the spacer member front surface is smoothly rubbed.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the present invention, in a large-diameter gear whose tip circle has a large diameter with respect to the shaft length, the portion where the dimensional variation due to shaft tilt is the largest and where the thrust force due to the twist angle of the helical gear is applied. The vicinity of the tooth base is brought into contact with the spacer member to thereby prevent the shaft from collapsing and prevent the meshing abnormality due to the shaft collapsing.

  FIG. 1 is a schematic cross-sectional view of an image forming apparatus equipped with a driving device of the present invention, and shows an example of a digital copying machine. In the figure, the surface of the photosensitive drum 70 is uniformly charged positively or negatively by a charging device 71. On the other hand, a document (not shown) is placed on a document placing table 90 covered with a lid 91, and the image data is read by a reading device (not shown). The read image data is written on the surface of the photosensitive drum 70 by a laser scanner (exposure device) 72, and an electrostatic latent image is formed on the surface of the photosensitive drum 70.

  Specifically, in the case of the reverse development method, the charge corresponding to the image is removed, and in the case of the regular development method, the charge corresponding to the background is removed to form an electrostatic latent image. . Next, the electrostatic latent image on the photosensitive drum 70 is visualized with toner by the developing device 73. At this time, the charging polarity of the toner is the same as the charging polarity of the photosensitive drum 70 in the case of the reversal development method, and is opposite to the charging polarity of the photosensitive drum 70 in the case of regular development.

  On the other hand, the paper P stored in the paper feed cassette S is pulled out by the pickup roller 82, sandwiched between the paper feed roller 83 and the separating roller 84, and sent to the conveyance path. Then, the registration roller pair 81 feeds the paper P to the transfer unit at the timing when the toner image on the photosensitive drum 70 reaches the transfer unit. In the transfer portion, the sheet P is sandwiched between the photosensitive drum 70 and the transfer roller 74, and a charge having a polarity opposite to the toner charging polarity is applied to the transfer roller 74. Toner image moves onto the paper P. The toner remaining on the photosensitive drum 70 without moving onto the paper P is removed and collected by the cleaning roller 75.

  On the other hand, the paper P on which the toner image is placed is conveyed to the fixing roller pair 85. Here, the toner image is heated and pressurized by the fixing roller pair 85 and fixed on the paper P. Then, the paper P is discharged to the paper discharge unit 87 by the discharge roller pair 86. The paper P placed on the manual feed tray 88 is sent to the registration roller pair 81 by the paper feed roller 89, and thereafter passes through the same path as the above-described transport path.

  FIG. 2 is a perspective view of the drive device according to the first embodiment of the present invention. This figure shows a state seen from the photosensitive drum side. In the figure, reference numeral 1 denotes a driving motor for driving a photosensitive drum (not shown). The rotating shaft 4 of the drive motor 1 is integrally formed with a gear portion 4a around it. Reference numeral 2 denotes a substantially disc-shaped drum drive gear. A gear portion 2a is provided on the entire outer peripheral surface of the drum drive gear 2, and a cylindrical bearing portion 2b extending in the axial direction is provided at the center portion. In the drum drive gear 2, the diameter of the tip circle is about 3 to 4 times the axial length. Further, the gear portion 4a of the rotating shaft 4 of the drive motor 1 and the gear portion 2a of the drum drive gear 2 are helical gears, and are directly meshed with each other. Note that the teeth of the gear portion 2a are simplified.

  A hatched portion 3 is a spacer member which is a molded product of PBT, PP, ABS or the like, and is inserted into the root of the rotating shaft 4 of the drive motor 1. The rotating shaft 4 passes through a bearing hole 5a opened at the center of a bearing plate 5 which is a substantially square plate member. The spacer member 3 is interposed between the outer surface of the rotating shaft 4 and the inner surface of the bearing hole 5a. The bearing plate 5 is attached to the outer surface of a member corresponding to the support frame 560 described with reference to FIG. Reference numeral 6 denotes a bracket plate for attaching the driving motor 1 to the main body housing side (not shown). The material of the drum drive gear 2 may be a molded product made of the same resin material as that of the spacer member 3.

  FIG. 3 is an enlarged perspective view of the spacer member 3 as seen from the photosensitive drum side. As shown in the figure, the spacer member 3 includes a cylindrical main body 3a, a flange 3b that extends in the outer peripheral direction from the peripheral edge of the tip, and forms a ring shape. A plurality of protrusions 3c are arranged at equal angular intervals and extend inward. When the spacer member 3 is inserted into the root of the rotating shaft 4 of the driving motor 1, the protrusion 3 c meshes with the gear portion 4 a of the rotating shaft 4, so that the spacer member 3 rotates integrally with the rotating shaft 4. ing. Although it is conceivable to form the spacer member 3 integrally with the rotating shaft 4, this increases the diameter of the rotating shaft and increases the cost.

  FIG. 4 is a schematic main part longitudinal cross-sectional view of the drive device of the present embodiment. As described above, the drum drive gear 2 has a substantially disk shape, and the gear portion 2a is provided on the entire outer peripheral surface thereof. A cylindrical bearing 2b extending in the axial direction is provided at the center. The dimension C, which is the length of the bearing portion 2b, is the axial length of the drum drive gear 2. The gear portion 2 a meshes with the gear portion 4 a of the rotating shaft 4 of the drive motor 1. The spacer member 3 is inserted into the rotating shaft 4 while the protrusion 3c of the spacer member 3 is engaged with the gear portion 4a.

  Further, on the side of the drum driving gear 2 on the side of the driving motor 1 (right side in the figure), a thin ring-shaped rib 2c having an outer diameter slightly smaller than the root circle is 0.5 mm in height in the vicinity of the outer peripheral edge. It is provided over the entire circumference. The rib 2 c is in contact with the front surface of the flange 3 b of the spacer member 3. In this configuration, since each circumferential speed at the contact portion between the side surface of the drum drive gear 2 and the front surface of the spacer member 3 is relatively close to 0 during rotation, noise and accuracy degradation due to friction and wear are reduced. Can be reduced.

  When the driving motor 1 rotates in the direction of arrow A in FIG. 2 in a state where a load torque from the photosensitive drum (not shown) is applied to the drum driving gear 2, the gear portion 4a of the rotating shaft 4 and the drum driving gear 2 are rotated. The drum drive gear 2 rotates in the direction of arrow B by meshing with the gear portion 2a. The vicinity of the meshing portion of the drum drive gear 2 receives a force in a direction approaching the drive motor 1 due to a thrust force caused by the twist angle of the helical gear. On the other hand, the spacer member 3 rotates while restricting the axis fall of the drum drive gear 2 with the rib 2c on the side surface of the drum drive gear 2 in contact with the front surface of the flange 3b of the spacer member 3.

  Thus, when a rotational load torque is applied to the drum drive gear 2, the direction of the twist angle is such that the thrust force on the drum drive gear 2 due to the twist angle of the meshing portion is on the spacer member 3 side. Is specified, the spacer member 3 regulates the shaft fall of the drum drive gear 2. As a result, it is possible to prevent the meshing abnormality due to the shaft collapse, to achieve accurate drive transmission, to prevent noise generation, and to improve durability.

  The drive side gear referred to in the claims corresponds to the rotating shaft 4 having the gear portion 4a in the embodiment, and the driven side gear corresponds to the drum drive gear 2 having the gear portion 2a.

  Although an example of a copying machine has been described in the embodiment, the present invention is not limited to this, and can be applied to all drive devices using a large-diameter gear.

1 is a schematic cross-sectional view of an image forming apparatus equipped with a drive device of the present invention. 1 is a perspective view of a driving apparatus according to Embodiment 1 of the present invention. FIG. 3 is an enlarged perspective view of a spacer member viewed from the photosensitive drum side. The principal part longitudinal cross-sectional view of the drive device of a present Example. FIG. 10 is a perspective view showing the vicinity of a driving device in a conventional image forming apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Drive motor 2 Drum drive gear 3 Spacer member 4 Rotating shaft 5 Bearing plate 6 Bracket plate

Claims (3)

  A drive-side gear, a spacer member fitted to the root of the drive-side gear, and a driven-side gear having a diameter of a tooth tip circle larger than an axial length, and the drive-side gear and the driven-side gear are A helical gear, characterized in that a side surface of the driven gear is brought into contact with the front surface of the spacer member by a force in a thrust direction caused by a twist angle of a meshing portion of the driving gear and the driven gear. To drive.   2. The spacer member according to claim 1, wherein a protrusion is provided on an inner peripheral surface of the spacer member, and the protrusion is engaged with the driving side gear so that the spacer member rotates integrally with the driving side gear. The drive device described.   The drive device according to claim 1, wherein the spacer member is made of a resin material.

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