JP2006072206A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus with which increased reliability of image quality is assured by securely causing a timing belt section to diminish shock or vibrations, caused by drive systems other than a drum. <P>SOLUTION: The image forming apparatus comprises a drive unit for driving the rotatory parts of devices used for recording images, formed by a series of image forming processes, onto a recording material. The drive unit includes: a motor as a drive source; a drive pulley for an image carrier; an image carrier drive belt; a drive pulley for rotatory parts other than the image carrier; a drive belt for the rotatory parts other than the image carrier; a motor fixing plate for holding the motor; one position regulating means 1 for the motor fixing plate, which is disposed on the bisecting line of an angle formed by the center of the pulley for the image carrier and the center of a drive pulley for the motor and the center of the drive pulley for the other rotatory parts; and a motor tension load means disposed on the bisecting line. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus, and more particularly to a configuration for improving image quality and reducing noise during image formation.

  In a drive system of a conventional image forming apparatus, drive transmission by gears is usually used as in Patent Document 1. Drum / developer from main motor. A plurality of gears are arranged side by side to the paper conveyance system.

Japanese Patent Laid-Open No. 11-38715

  However, in the case of drive transmission by such a gear, there is a problem that the impact of the clutch ON of the developing device or the shock when the rear end of the paper passes through the roller during paper conveyance is transmitted to the drum via the gear and deteriorates the image. there were.

  In order to reduce vibration, measures such as increasing the strength of the structure or changing the material of the gear are taken, but the effect is insufficient for the cost increase.

  As another countermeasure, there has been proposed a method in which all driving is performed by a timing belt as disclosed in JP-A-7-160082. However, even with such a configuration, the belt can absorb shocks and vibrations when the accuracy of parts such as the length of the timing belt is optimal, but if the tolerance is too long or too short, In some cases, tooth jumping occurs when the load is high, or the effect of damping shock / vibration becomes insufficient due to excessive tension, resulting in insufficient reliability.

  In order to stabilize the belt tension, there are cases where measures such as attaching a tensioner are taken, but vibration due to the tensioner rubbing against the belt is still transmitted to the drum driving unit, which deteriorates the image.

  Furthermore, since the main motor and the drum drive were not directly, but via a pulley serving as an idler, the fitting play generated at the idler portion still appeared on the drum in the form of shock and vibration.

  The present invention has been made in view of the above problems, and the object of the present invention is to improve the reliability of image quality by reliably attenuating shocks and vibrations by a drive system other than the drum at the timing belt portion. An object is to provide an image forming apparatus.

  In order to achieve the above object, the present invention according to claim 1 is a drive unit that rotationally drives a rotating unit of an apparatus for recording an image formed by a series of image forming processes on a recording material, the drive unit comprising: A motor, an image carrier driving pulley, an image carrier driving belt, a driving pulley for a rotating part other than the carrier, a rotating part driving belt other than the image carrier, and a motor fixing plate for holding the motor A position regulating means for the motor fixing plate provided on a bisector of an angle formed by the pulley center of the image carrier, the center of the driving pulley of the motor, and the center of the other driving part driving pulley; The image forming apparatus includes a motor tension loading unit provided on an equipartition line.

  The invention according to claim 2 is the invention according to claim 1, characterized in that the belt material is a timing belt made of rubber.

  According to a third aspect of the present invention, in the first or second aspect of the present invention, the image carrier driving pulley is a large-diameter pulley having a diameter twice or more that of the image carrier.

  According to a fourth aspect of the present invention, in the invention according to any one of the first to third aspects, the tooth profile of the drive belt has a helical shape.

  According to the present invention, in the main drive unit of the image forming apparatus, the drum belt drive unit that directly drives the drum by the timing belt from the main motor and the drive other than the drum such as the paper conveyance system are directly driven from the main motor in the same manner. A belt drive system other than the drum drive, and on the bisector of the angle formed by the center of the pulley of the drum, the center of the drive pulley of the motor, and the center of the other rotation part drive pulley; By providing the motor tension loading means, the belt tension other than the drum and the drum can be applied evenly regardless of variations in the dimensions of the belt and frame, and the shock and vibration caused by the drive system other than the drum can be reliably ensured at the timing belt section. Can be attenuated, improving the reliability of image quality.

  Further, since the belt material of the drive unit is a rubber timing belt, shocks and vibrations other than the drum drive can be absorbed more and image quality can be improved.

  In the drive system, the drum-driven pulley is a large-diameter pulley, so that the meshing frequency by the belt can be reduced and the image quality is further improved.

  Further, in the drive system, the tooth profile of the drive belt has a helical shape, so that it becomes a polygonal shape when the timing belt is tensioned, and image quality deterioration and noise generation can be prevented.

  Exemplary embodiments of the present invention will be described below in detail with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention only to those unless otherwise specified. Absent.

<Embodiment 1>
FIG. 9 is a cross-sectional view of an image forming apparatus showing an embodiment of the present invention. As shown in FIG. 9, an image forming apparatus main body 900 includes a document table 906, a light source 907, a reading element (CIS: contact image sensor). 908, a paper feeding unit 909, an image forming unit 902, and the like.

  The sheet feeding unit 909 includes cassettes (storage containers) 910 and 911 that store the sheet material S and are detachable from the apparatus main body 900. Each cassette 910 and 911 includes a sheet feeding roller (sheet feeding unit). Are arranged respectively.

  The image forming unit 902 is provided with a cylindrical photosensitive drum 13, a developing device 27, a transfer charger 916, a separation charger 917, a cleaner 918, a primary charger 919, and the like. A conveyance guide 920, a fixing device 904, a discharge roller 905, and the like are disposed on the downstream side of the image forming unit 902.

  Next, the operation of this image forming apparatus will be described.

  When a paper feed signal is output from a control device (not shown) provided in the apparatus main body 900, the light reflected from the light source 907 and applied to the document D placed on the document placement table 906 is read by a reading element ( It is replaced with an electrical image signal via a CIS (contact image sensor) 908, transmitted to a laser scanner device 921, and irradiated to a photosensitive drum 13 from a laser light emitting element (not shown) via a polygon mirror 922 and lenses 923 and 924. Is done. The photosensitive drum 13 is charged in advance by a primary charger 919, and an electrostatic latent image is formed when irradiated with light. The electrostatic latent image is developed by a developing device 27 and visualized as a toner image. Is done.

  On the other hand, the sheet material S fed from the sheet feeding unit 909 is corrected for skew by the registration rollers 910 and further sent to the image forming unit 902 at a proper timing. In the image forming unit 902, the toner image on the photosensitive drum 13 is transferred to the sheet material S by the transfer charger 27, and the sheet material S that has received the transfer of the toner image is opposite in polarity to the transfer charger 916 by the separation charger 917. To be separated from the photosensitive drum 13.

  The sheet material S separated from the photosensitive drum 13 as described above is conveyed to the fixing device 904 by the conveying device 920, and the unfixed transfer image is permanently fixed to the sheet material S by pressurization and heating in the fixing device 904. . Then, the sheet material S on which the image is fixed is discharged into the body of the apparatus main body 900 by the discharge roller 905.

  Next, the configuration near the drive unit according to the present invention will be described.

  The drive is arranged on the back side of the main body so as to be connected to the photosensitive drum 13 and the developing unit 27. In FIG. 9, it is arranged on the back side of the photosensitive drum 13.

  1 and 2 are a perspective view and a plan view of an embodiment of a drive system according to the present invention.

  1 and 2, reference numeral 1 denotes a main motor which is a DC brushless motor as a driving source, 2 denotes a motor mounting plate to which the main motor is attached, and 3 denotes a tension spring which applies tension to the motor mounting plate 2. The main motor 1 is fixed to the motor mounting plate 2 at four locations by screws 4. Further, the motor mounting plate 2 is fixed on the driving upper plate 6 by four screws 5 in a state where the motor mounting plate 2 is urged in the arrow direction by the tension spring 3 described above.

  FIG. 3 is a view in which the main motor 1 and the driving upper plate 6 are removed and only the motor pulley 7 fixed to the shaft of the main motor 1 is left.

  The motor pulley 7 includes a large-diameter drum pulley 8 that drives only the photosensitive drum 13 and a driving pulley 9 that drives other registration rollers, a developing device, and manual feed driving. The drive of the drum pulley 8 is directly transmitted from the motor pulley 7 by a Hasuba timing belt 10.

  Similarly, the drive pulley 9 is also directly driven from the motor pulley 7 by a Hasuba timing belt 11. That is, the two drive systems are directly driven from the main motor 1 through the motor pulley 7 press-fitted into the main motor 1 without a tensioner.

  Next, the driving of the photosensitive drum 13 will be described with reference to FIG.

FIG. 4 shows only the drive part of the photosensitive drum 13 taken out, and only the part related to the drum drive is displayed. Reference numeral 12 denotes a drum cartridge, and reference numeral 13 denotes a photosensitive drum. The power from the main motor 1 is connected to the Hasuba timing belt 20 via the press-fitted motor pulley 7 and transmitted to the large-diameter pulley 8. Naturally, a helical shape is also formed on the large-diameter pulley 8 side, the twist direction is the direction indicated by 20, and the twist angle is 5 °.

  Further, power is transmitted from the large-diameter pulley 8 to a metal (iron) shaft 15 by a parallel pin (not shown), and rotation is transmitted to the photosensitive drum 13 through a coupling 14 made of zinc die cast. The photosensitive drum 13 can be attached and detached at the coupling 14 portion so as to be exchangeable integrally with the drum cartridge 12. Reference numeral 16 denotes a driving lower plate, which supports a shaft 15 so as to be rotatable up and down through a bearing 17 together with a driving upper plate 6 (not shown).

  The drum pulley 8 is incorporated by light press-fitting with respect to the shaft 15, and the pulley at the time of rotation moves up and down due to backlash to prevent the rotation from being disturbed and the image from being disturbed.

  The large-diameter pulley 8 has flanges 18 formed on both sides so that the belt does not come off.

  The parts are formed of two parts and are integrated by a snap joint portion 19.

  In particular, in the case of a helical belt, such a configuration is essential because the belt 10 generates a thrust force in the thrust direction.

  Next, driving of the developing device 27 will be described.

  FIG. 5 shows only the driving part of the developing device as in FIG. 4. In the figure, the power is transmitted from the main motor 1 to the driving belt 11 via the coaxial motor pulley 7 and then to the driving pulley 9. Here again, the belt 11 is a helical belt, and teeth are formed in the direction shown by 28 with a twist angle of 5 °. Like the drum pulley 8, since a biasing force is generated by the Hasuba belt 11, flanges 29 are provided on both sides and integrated by a snap joint portion 30.

  Similarly to the drum pulley 8, a metal (iron) shaft is lightly press-fitted into the drive pulley 9, and the pulley during the rotation moves up and down due to backlash, thereby preventing the rotation from being disturbed and the image from being disturbed.

  Further, the rotational force is transmitted to the shaft by a parallel pin (not shown), and the rotational force is transmitted to the coaxial sleeve / multi-stage gear 21 via the parallel pin.

  Further, the rotation of the sleeve / multi-stage gear 21 is transmitted to the gear of the developing clutch 23 through three idlers 22. The developing clutch 23 and the idler 22 are helical gears having a torsion angle of 10 °, and the sleeve / multi-stage gear 21 increases the meshing rate and smoothly rotates the sleeve. Also, because it is a helical rod, a load is applied in the thrust direction, and it slides with the driving lower plate 16 that is supported and the driving middle plate 31 shown in FIG. 3, and the twist angle is made too large to prevent abnormal noise due to wear. The end face 32 of the idler gear 22 is further coated with grease to improve slidability.

  When power is transmitted to the developing clutch 23, the coaxial sleeve drive gear 24 transmits power to the sleeve gear 25 in accordance with ON / OFF of the clutch. Reference numeral 27 denotes a current organ unit, and the internal sleeve 26 is driven by a coaxial sleeve gear 25.

  The ON / OFF timing of the sleeve 26 is controlled so as to be ON during image formation and OFF between sheets, thereby improving the life of the developer.

  Next, driving of the manual sheet feeder will be described.

  FIG. 6 is a diagram in which a manual paper feed drive and a registration roller drive system are added to the drum drive, and shows the entire drive system.

  In the figure, like the driving of the developing device, the power from the main motor 1 is transmitted to the helical belt 11 via the motor pulley 7 and to the driving pulley 9. Further, it is transmitted to the sleeve / multi-stage gear 21 which is a coaxial stage gear, meshed with the multi-idler gear 33 with a gear different from the drive transmission of the developing device, and finally to the clutch gear formed integrally with the multi-clutch 34. Rotation is transmitted. Further, at the time of the multi-clutch 34, it is transmitted to the multi-drive gear 35 via a metal shaft, and the paper feed roller and the like are driven as a power source for a manual feed section (not shown).

  Next, the driving of the registration roller will be described with reference to FIG.

  In the figure, like the driving of the developing device, the power from the main motor 1 is transmitted to the helical belt 11 via the motor pulley 7 and to the driving pulley 9. Further, driving is transmitted to a registration driving pulley 36 provided on the same axis, and driving is transmitted to a registration clutch 38 via a belt 37.

  The registration clutch 38 is on the same axis as the registration roller 39, and the roller rotates by ON / OFF of the clutch.

  Next, the configuration of the belt tension of the main motor pulley 7 according to the present invention will be described with reference to FIG.

  As described above, the main motor 1 is fixed to the motor mounting plate 2 at four locations with the screws 4. The main motor 1 is hung on two belts at the motor pulley 7 and is placed on the driving upper plate 6. The position of the motor mounting plate on the drive upper plate 6 is on an angle equidistant line 41 (27 ° in the figure) formed by the center of the drum pulley 8, the center of the motor pulley 7, and the center of the drive pulley 8. An embossing 42 is formed for regulation, and a long hole that allows movement in the direction of the equidistant line 41 is provided at one position on the motor mounting plate at a position that matches the embossing 42.

  Further, in this state, the tension spring 3 also provided on the equipartition line is hung on a bending raising 46 provided on the driving upper plate 6, and the other is hung on a bending raising 45 formed on the motor mounting plate 2. Then, the pressure is applied straight in the direction indicated by the arrow 44 in the drawing, that is, toward the motor pulley 7.

  At this time, as described above, there is only one embossment for positioning 42, and since it is fitted with a long hole, there is no restriction on the position of the motor pulley 7, and there are two timings. The position of the motor pulley 7 is determined at a position balanced by the belts 10 and 11 and pressure. At this time, since the motor pulley 7 is on the equipartition line 41 and the tension spring 3 is also directed in the same direction, the belt tension is equally applied to the two pulleys. In this state, the main motor 1 is rotated by one turn by hand in order to securely engage the teeth of the belt with the pulley, and then the screw 5 is tightened to fix the position of the motor.

  Thus, only one position restricting portion for determining the spring pressing direction is provided on the equipartition line 41, and further, a pressure spring is provided on the equipartition line 41, and the position of the motor is a position where the two timing belts are balanced. By determining the position of the motor pulley 7 with the belt tension, for example, even if the length of the timing belt varies, the location of the two belts is automatically corrected to a position where the lengths of the two belts are balanced. Can be applied evenly and image unevenness due to skipping of the belt and durability abrasion of the belt can be prevented. According to this configuration, it is not necessary to use a tensioner even if two belts are used simultaneously, and there is no deterioration of the image due to vibration of the tensioner.

  In addition, since the tension is stable, it is possible to prevent the belt damper effect from being lowered due to variations in tension.

  Further, as a feature of this driving system as described above, the driving of the drum and the driving of the other developing / manual feeding portion / registration roller are directly divided into two systems from the main motor 1. Furthermore, these two drive systems are performed in a form without a tensioner by a timing belt instead of a gear.

  With this configuration, vibration and shock due to driving of the development, manual feed section, registration roller, etc. are less likely to be transmitted to the drum side than when the drive system is connected with a gear. In other words, even when the development / manual section / registration roller is driven, for example, when the development clutch is turned on, when the registration clutch is turned on, or when the development idler gear 22 is engaged, the drive timing belt 11 is cushioned. To absorb vibration and shock. The belt used here is optimally made of rubber, and has a higher vibration absorbing effect than a chain or SUS belt.

  Further, since the drive system is directly connected to the main motor 1 that is the drive source and the timing belt 11, the shock and vibration that is attenuated by the timing belt 11 is relayed by the motor that is the drive source that does not have backlash.・ Vibration is blocked by the main motor and is not easily transmitted to the belt 10 on the drum side.

  Further, since the drive is transmitted directly from the main motor 1 by the rubber timing belt 10 to the drum side, the effect of absorbing vibration and shock is further generated, and the vibration and shock are not transmitted to the drum side.

  In addition, by directly driving from the main motor 1 without passing through the idler in the next stage of the main motor 1 in this way, compared to the case where the drive is once transmitted from the motor through the idler, the engagement play of the idler portion is reduced. Since the influence can be removed, the image quality is further improved.

  Further, in this drive system, two systems of drive are connected to the main motor 1 without a tensioner. As described above, in general, when tension is applied to the belt, the tensioner is applied with a pressure of about 50 to 500 gf on the tooth surface side or back surface side of the belt to prevent loosening and tooth skipping. If the tensioner is used near the rotating part of the drum, which is the image creating part as in the form, the vibration of the tensioner sliding with the belt is directly transmitted to the drum, so that the image is significantly deteriorated. Even when the drum side is not provided with a tensioner and the tensioner is attached only on the development drive side, the vibration of the belt sliding with the tensioner is large and the influence remains. For the reasons as described above, in the present embodiment, the belts are directly driven without any tensioner in the present embodiment.

Another feature of this drive system is that a large-diameter pulley 8 is used in the drum drive system. Specifically, the number of teeth of the motor pulley 7 is 18, and the drum pulley 8 has 271 teeth. The drive pulley is 91 teeth although it is not a large diameter. The reason for using a large-diameter pulley for driving the drum in this way is to reduce the influence of pitch unevenness due to meshing by minimizing the meshing pitch of the teeth on the image.
In this embodiment, the process speed is 237 mm / sec, and it is driven at 2200 rpm in consideration of the high efficiency of the rotation speed motor of the main motor that is a DC motor. In general, if the rotational speed is too slow, the rotation unevenness of the motor is poor, and if the rotational speed is increased too much, noise becomes a problem, and the motor is set at around 2000 rpm where the output efficiency of the motor itself is good. In this case, the meshing pitch of the teeth on the image is
237 / ((2200/60) × (271/19)) = 0.45 mm
It becomes. In general, as the meshing pitch is smaller, it is harder to see as unevenness, and when it is about 0.5 mm or less, it is difficult to visually discriminate and the problem does not occur. Here, since it is set to 0.45 mm and 0.5 mm or less, unevenness is hardly noticeable.

  As another feature, a Hasuba belt is used. In the present embodiment, since the belt is hung directly on the main motor 1, the number of pulley teeth on the main motor side cannot be increased too much. If it is increased, the number of teeth of the large-diameter pulley will increase unnecessarily to ensure the reduction ratio, and accuracy will not be achieved due to the influence of warpage on molding.

For this reason, in this embodiment, two identical 18-tooth pulleys 7 are press-fitted into the shaft of the main motor 1 while being arranged side by side. However, if the number of teeth is small, as shown in FIG. When the timing belt is wound around a pulley, the difference in rubber thickness in the longitudinal direction of the belt itself (difference between the toothed portion and the non-toothed portion) does not become circular, and polygonal driving occurs during rotation, resulting in uneven feeding. If the pulley diameter is large, it will be approximately circular, so it will not be a problem. However, if it is about 18 teeth, it will become an 18-sided shape with the belt wrapped around it, causing unevenness in feeding as well as noise. Become.

  In order to solve this problem, the Hasuba timing belt is used as described above. By using a lotus, the teeth have an angle in the width direction of the belt, and a plurality of teeth exist in the length direction, so that the rubber thickness is almost uniform as a whole. As a result, polygon driving is eliminated and image deterioration and noise due to uneven feeding are prevented. In particular, it is optimal when the belt is driven directly from the motor as in this embodiment.

<Embodiment 2>
In the first embodiment, the tension is applied from the upper left direction of the motor pulley 7 using a tension spring. However, if the direction is the same and approximately on the equidistant line 41, the compression spring is also applied to the lower right side of the motor pulley 7. It may be used. In the above-described embodiment, the pressurization direction is completely coincident with the equipartition line 41. However, if the load is small and the margin for the tooth jump of the belt is sufficient, the pressurization direction slightly deviates from the equipartition line 41. May be. However, in that case, the tensions of the two belts are not uniform and are somewhat unbalanced.

  In the present embodiment, in order to enable the replacement of the main motor 1 in the market, the screw 3 is left attached even after fixing with the spring 3 as a component. After fixing the motor, it may be removed and used only during assembly as a jig.

  Further, a hole or the like may be provided in the motor mounting plate 2 without using a dedicated spring, and it may be screwed while pulling on the equisegmentation line 41 using a tension gauge or the like. In that case, dedicated parts are not required.

It is an Example perspective view. It is an Example top view. It is detail drawing of a drive train pulley. It is a drum drive detailed drawing. FIG. It is a detailed view of a drive system. It is a figure which shows the polygon drive of a straight-tooth belt. It is detail drawing of two belt tension. 1 is a cross-sectional view of an image forming apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Main motor 2 Motor attachment plate 3 Tension spring 4,5 Screw 6 Driving upper plate 7 Motor pulley 8 Large diameter drum pulley 9 Driving pulley 10, 11 Timing belt 12 Drum cartridge 13 Photosensitive drum 27 Developer

Claims (4)

  A drive unit that rotationally drives a rotating portion of a device for recording an image formed by a series of image forming processes on a recording material, and a motor serving as a drive source, a drive pulley of an image carrier, and an image carrier A driving belt, a driving pulley for a rotating part other than the carrier, a rotating part driving belt other than the image carrier, a motor fixing plate for holding the motor, a pulley center of the image carrier, a driving pulley center of the motor, and others And a motor tension loading means provided on the bisector, and a position restricting means for the motor fixing plate provided on the bisector of the angle formed at the center of the rotating part driving pulley. An image forming apparatus.   2. The image forming apparatus according to claim 1, wherein the belt material is a rubber timing belt.   3. The image forming apparatus according to claim 1, wherein the image carrier driving pulley is a large-diameter pulley having a diameter twice or more that of the image carrier.   The image forming apparatus according to claim 1, wherein a tooth shape of the drive belt has a helical shape.

Images