JPS6370261A - Driving device for image carrier drum - Google Patents

Abstract

PURPOSE:To prevent a photosensitive body from rotating irregularly even if its load varies by coupling one of two worms engaging a worm wheel with a driving shaft through a spring and also energizing it in the rotating direction of the driving shaft. CONSTITUTION:A worm engaging the worm wheel 3 coupled directly with the rotating shaft of a photosensitive body is divided into 1st and 2nd worms 4 and 5 and one end of the spring 12 inserted into the groove 10b of a support member 10 fixed on the shaft 7 is fixed to the worm 5, which is energized in the rotating direction of the shaft 7. The worm 4 is fixed on the shaft 7, the worm 5 is supported rotatably through a bearing 9, and the shaft 7 is rotated to drive the wheel 3 by the spring 12 without any play originating from the engagement with the wheel 3 and worms. Therefore, even if the photosensitive body varies in load or is shocked externally, the irregularity in rotation is eliminated and an image which is neither distorted nor shifts in position is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a driving device for an image bearing drum used in an image forming apparatus such as a copying machine, a facsimile machine, and a printer.

[Conventional technology]

Conventionally, image forming apparatuses such as copying machines, facsimile machines, and printers have been known to have various configurations.
FIG. 9 is a perspective view showing an example of its configuration, and FIG. 9 is a schematic perspective view showing a driving device for the image carrier drum. In FIG.
A dielectric layer or a photoreceptor layer such as an electrophotographic photoreceptor is provided on the surface. A recording head 102, which is a latent image forming device, is provided above the image carrier drum 101. When the image bearing drum 101 is a dielectric drum, the recording head 102 may be an ion dot projection matrix head (for example, see Japanese Patent Application Publication No. 57-501348) that forms a charge image directly on the FW body layer, or a multilayer head. In the case of an electrophotographic photoreceptor drum, it is a needle electrode head, and in the case of an electrophotographic photoreceptor drum, a light emitting diode array head, a liquid crystal matrix head, and a laser beam that form a charge image by scanning and projecting a light image after being uniformly charged by a charger. scanning head.

These include a cathode ray tube scanning head or an original image scanning optical system head which is an optical system of a normal copying machine.

The image carrier drum 101 has its support shaft 101
' is the machine frame 103 of the image forming apparatus as shown in FIG.
A pulley 104 is rotatably supported on a bearing (not shown) provided at one end thereof, and a pulley 104 is attached to one end thereof, and the pulley 104 is driven by a motor 107 via a reduction gear box 105 and a belt or chain 106. The image carrier drum 101 is driven to rotate in the direction of arrow A. In FIG. 9, 108 is a tension adjustment device for the belt or chain 106.

Further, in the drawing of the image carrier drum 101, on the right side is a toner powder image developing device 110, on the lower side is a transfer/fixing roller 111 that performs fixing at the same time as transfer, and on the left side is the image carrier drum 1.
A cleaner 113 consisting of a blade 112 that contacts the circumferential surface of the drum 01 and its support, and a static eliminator 114 for erasing the residual latent image on the image bearing drum 101 are provided.

The transfer/fixing roller 111 is constituted by a roller made of a metal material whose surface is coated with a highly elastic polysecure resin, and support shafts 115 at both ends thereof are each supported substantially at the center of a pressure arm 116 . The pressure arm 116 has a support shaft 117 provided at its base end that is rotatably supported by a bearing provided on the machine frame 103 of the image forming apparatus, and a pressure spring at the other end. 118 is installed. The other end of the pressure spring 118 is hung on the machine frame 103 and urges the tip of the pressure arm 116 upward.

The support shaft 115 that supports the transfer/fixing roller Ill is provided at the intermediate portion of the pressure arm 116, so that the transfer/fixing roller 111 forming the pressure roller is attached to the image carrier drum 1.
01, and the pressure contact force is applied almost evenly.

A recording paper 119 such as a transfer paper is inserted between the image carrier drum 101 and the transfer/fixing roller 111, and is conveyed while being held between the image carrier drum 101 and the transfer/fixing roller 111. At this time, the toner image on the image carrier drum 101 is transferred and fixed onto the recording paper 119 by the pressure contact force of the transfer/fixing roller 111 . After this toner image is transferred and fixed, the recording paper 119 is discharged.

A peeling claw 120 is provided in the ejection section, and a peeling claw 120 is provided to remove the recording paper 12.
0 is discharged without being wrapped around the image carrier drum 101 or the transfer/fixing roller 111.

In this configuration example, the diameter of the drum forming the image bearing drum 101 is looml, and the diameter of the transfer/fixing roller 111 is 65 mm.
1 (the polyacetal coating layer is 10 mm thick), and the total pressure applied to the transfer/fixing roller 111 is 1000 kg.
and the circumferential speed of the image carrier drum 101 is 150 tss.
/5et (A4 size 28 sheets/min), good recording can be obtained.

[Problem that the invention seeks to solve]

Incidentally, in the image forming apparatus configured as described above, the rotation of the image bearing drum 101 is detected by a low-resolution encoder, and the signal from the encoder is used as a reference synchronization signal to determine the timing of image formation by the recording nozzle 102. is controlled. That is, a reference synchronization signal is generated every time the image carrier drum 101 moves one dot line,
This synchronization signal controls the readout timing of the image signal from the buffer memory so that successive dot lines are formed at accurate intervals.

However, with a belt or chain 106
The rotation of the image carrier drum 101 driven by the motor 107 via the image bearing drum 4 is not necessarily constant and may vary. That is, as mentioned earlier, the image carrier drum 1
When the transfer/fixing roller 111 is pressed against the recording paper 11 with a large force of about 1 ton, for example, the recording paper 11
The belt or chain tension adjustment device 108 is displaced due to large load fluctuations and external shocks that occur when the image carrier drum 9 enters between them and is ejected from between them, causing the rotation of the image carrier drum 101 to be prevented. There is a problem in that the speed fluctuates, causing rotational unevenness, which tends to cause image distortion or misalignment during image formation or transfer onto the image carrier drum 101.

In particular, when the trailing edge of the recording paper 119 is ejected from between the image carrier drum 101 and the transfer/fixing roller 111,
The image carrier drum 101 begins to spin idly due to the sudden load reduction, and the synchronization signal is generated from the low reencoder at an earlier timing than in the normal case. In this way, if a dot line recording start signal is generated at an early timing while a certain dot line is being formed,
The recorded image becomes extremely disturbed, and this disturbance affects the subsequent formation of dot lines.

In other words, since it takes a certain amount of time to scan a dot line, if the rotational speed of the image carrier drum 101 increases above a certain value, a write signal for the next dot line will be generated while the dot line is being scanned, which will cause the image to become normal. This makes it impossible to record images.

Such image disturbances are called jolts, and the possibility of jolts occurring increases as the interval between dot lines becomes narrower and the resolution in the vertical direction becomes higher.

The present invention has been made in order to solve the above-mentioned problems in conventional image forming apparatuses. The purpose is to provide equipment.

[Failure to solve the problem]

In order to solve the above problems, the present invention provides a rotational drive source,
a drive shaft that rotates in response to the driving force of the rotational drive source; a first worm that is fixed to the drive shaft and rotates; a second worm that is rotatably supported on the drive shaft; an elastic member having one end coupled to the drive shaft and the other end coupled to a second worm to apply an elastic urging force to the second worm in the rotational direction of the drive shaft; A worm wheel meshing with the worm and an image carrier drum fixed to the rotation shaft of the worm wheel constitute a drive device for the image carrier drum.

[For production]

In the image carrier drum drive device configured as described above, the second worm does not move in the axial direction with respect to the first worm, but is rotatable relative to the rotational direction of the drive shaft. Moreover, since it is elastically biased in the rotational direction of the drive shaft, the tooth surfaces of the worm wheel that are engaged with the first and second worms are always pinched or pushed apart by the first and second worms. Therefore, the worm wheel is driven without backlash or rattling. Therefore, even if the load on the rotation of the image bearing drum fixedly attached to the worm wheel fluctuates, or even if an external shock is received, there is almost no backlash between the worm wheel and each worm, so the drive Since the rotational force from the source is transmitted through the worm to the image bearing drum with almost no uneven rotation, the drum can maintain stable rotation and an image with almost no distortion or deviation is formed.

〔Example〕

Examples will be described below. FIG. 1 is a schematic diagram showing an embodiment of an image bearing drum driving device according to the present invention.
FIG. 2 is a cross-sectional view of the main part thereof, and FIG. 3 is a perspective view thereof. In FIG. flame,
3 is a worm wheel attached to one end of the support shaft 1a of the image carrier drum 1; 4.5 is a first and second worm disposed on a drive shaft 7 connected to a motor 6;
It is designed to mesh with the worm wheel 3.

The first worm 4 is fitted onto the drive shaft 7 and fixed to the drive shaft 7 with a set screw 8, as shown in FIG.

On the other hand, the second worm 5 has its end surface joined to one end surface of the first worm 4, and is rotatably fitted and supported on the drive shaft 7 via a bearing 9. A spring support member 10 having a hollow shaft 10a is fitted onto the drive shaft 7 with one end surface of the hollow shaft 10a in contact with the inner ring of the bearing 9, and fixed to the drive shaft 7 with a screw 11. , a thin line provided on the circumferential surface of the cough spring support member 10. The other end of the spring 12, one end of which is fitted and held in the Jtlob, is fixed to one end of the second worm 5 with a screw so as to elastically urge the second worm 5 in the direction of rotation of the drive shaft 7. ing.

A protruding small-diameter portion 4a is formed on the other end surface of the first worm 4, and the inner ring of a bearing 13 fitted and fixed to the drive shaft 7 is brought into contact with the small-diameter portion 4a. The bearing 14 is fitted and fixed to the drive shaft 7 so that the inner ring is in contact with the other end surface of the hollow shaft 10a of the spring support member 10, which is in contact with the inner ring of the bearing 9 that pivotally supports the second worm 5. are doing. The outer ring of the cough bearing 14 is fixedly held on the worm support frame 15a by a bearing receiver 16.

On the other hand, the bearing 13 is supported by a worm support frame 15b and a bearing receiver 17, and the outer ring of the bearing 13 is pressed by the tip end surface of a pressing screw 16 screwed into a central threaded hole formed in the bearing receiver 17. The two bearings 13 and 14 are tightly held between the support frames 15a and 15b to prevent play.

When the tooth tip 3a of the worm wheel 3 is to be engaged with the first and second worms 4.5 configured in this way, first fix the spring holding member 10 to the drive shaft 7 using the screw 11.
The second worm wheel 3 is rotated to adjust the distance between the threaded part of the second worm 5 and the threaded part of the first worm 4.
Then, rotate the second worm 5 together with the spring holding member 10 to insert the tooth surface 3a of the worm wheel 3 between the threads of both worms 4 and 5, and then insert the spring holding member 10. The second worm 5 is rotated by a predetermined angle, and the spring 12 applies a spring biasing force to the second worm 5 in the direction of rotation of the drive shaft 7, so that the threads of the second worm 5 are pressed against the tooth surface 3a of the worm wheel 3. The spring holding member 10 is tightened and fixed to the drive shaft 7 with the screw 11 in such a manner that an appropriate spring pressure is applied. Note that a lubricant is applied in advance to the joint surfaces of the worms 4 and 5, the screw surfaces of each worm 4 and 5, and the tooth surface of the worm wheel 3.

In the image carrier drum drive device configured as described above, when the drive shaft 7 is rotationally driven by the motor 6, the first worm 4 is fixed to the drive shaft 7, while the second worm 5 is fixed to the drive shaft 7. The spring 12 is rotatably supported via a bearing 9 and is elastically biased in the direction of rotation of the drive shaft 7 by a spring 12 whose one end is held by a spring support member 10 fixed to the drive shaft 7. 4. Warm of both sides.
The worm wheel 3 meshing with the tooth surface 3a
is driven while being constantly held between both worms 4 and 5. In other words, it is rotated without bank lash or rattling.

Therefore, the recording paper enters between the image bearing drum 1 connected to the worm wheel 3 and the transfer/fixing roller.
Even when a load is suddenly applied, as shown by the dotted line in Figure 3, the image carrier may be damaged if a conventional drive device using a chain or belt or a drive system with backlash is used. The vibration phenomenon of the rotational speed of the drum 1 also disappears as shown by the solid line in FIG.
is rotated with a relatively smooth transition to the rotational speed of the loaded state, and rotational unevenness is extremely small.

Even when the recording paper is ejected from the image carrier drum 1 and the load suddenly decreases, the image carrier drum 1 idles and a vibration phenomenon in the rotational speed occurs, as in the case of using a conventional drive device. As shown by the solid line in FIG. 3, the rotational speed smoothly shifts to the light load state. Therefore, generation of jolt due to idle rotation of the image bearing drum 1 can be prevented. In addition, in Figure 3,
The part indicated by a shows a vibrating part where the rotational speed suddenly increases, which causes ditelt when a conventional drive device is used.

Furthermore, by configuring as in this embodiment, a reduction ratio of only about 1/20 can be obtained with a conventional drive system using a belt or chain and a reduction gear box, whereas a reduction ratio of only about 1/20 can be obtained.
Since a large reduction ratio of about 1/100 can be easily obtained with a worm gear, the diameter of the worm wheel 3 can be made equal to or smaller than the outer diameter of the image carrier drum 1 without the need for other reduction means or transmission means. In addition, since the motor can be placed horizontally, the entire drive device can be configured compactly and space can be saved. Further, the drive device and the image carrier drum can be integrated into a unit, and can be easily removed from the image forming apparatus and reinstalled.

In the above embodiment, a linear tension spring 12 is used as the spring for elastically urging the second worm 5, but a coil spring 21 as shown in FIG. 5 is used as the urging spring. It is also possible to use a temporary spring 22, as shown in Fig. 6^, ■). Leaf spring 2
2, both ends of the leaf spring 22 are fitted into the spring support members 11 and the springs 23 and 24 formed on the second worm 5 to support them. Also, each slit 2
3.24 has cutout openings 23a on opposite sides, respectively;
24a is preferably provided to increase the effective length of the leaf spring 22.

Further, in the above embodiment, two worms are fitted on the same drive shaft, but the two worms may be fitted on separate drive shafts that are linked to each other. FIG. 7 is a schematic sectional view showing such an embodiment, and the same or equivalent members as those in the embodiment shown in FIG. 2 are designated by the same reference numerals. That is, the first worm 4 is fitted onto the first drive shaft 7a and fixed with a set screw 8, and the second worm 5 is rotatably fitted onto the second drive shaft 7b via a bearing 9. The first and second drive shafts 7a, 7b are connected by universal joints 25a, 25b, etc., and are configured to be elastically biased in the rotation direction of the drive shaft 7b by a spring 12. They are designed to be driven in conjunction with each other.

Then, the tips of the teeth of the worm wheel 3 are engaged with the first and second worms 4 and 5, and the spring 12 is used so that the tooth surfaces of the tips are always held between the threads of the two worms 4 and 5. The second worm 5 is elastically urged in the rotational direction of the second drive shaft 7b.

With this configuration, the worm wheel 3 is rotated without backlash or rattling, as in the first embodiment, and rotational irregularities hardly occur due to load fluctuations or the like.

In each of the above embodiments, the tooth surface 3a of the worm wheel 3 is held between the first and second worms 4°5, and the first worm 4 is used for backlash prevention and the second worm 5 is used for driving. However, even if the threads of the first and second worms are brought into pressure contact with the tooth surfaces of the worm wheel so as to push them apart, the worm wheel cannot be rotated without buffing and crushing. can. In this case, the first worm 4 is connected to the drive shaft 7 (7a
), and is elastically biased by a spring in the direction of rotation of the drive shaft 7 (7a), while the second worm 5 is rotatably supported on the drive shaft 7 (7a). (7b), the first worm 4 functions as a drive and the second worm 5 functions as a backlash prevention function, eliminating backlash and preventing rotational irregularities due to load fluctuations as in each of the above embodiments. You can almost eliminate it.

〔Effect of the invention〕

As described above based on the embodiments, according to the present invention, elastic displacement is caused between the two worms in the rotational direction of the worms by an elastic member, so that the worms are attached to the image carrier drum. Since the tips of the teeth of the connected worm wheels are meshed, rotational drive is transmitted with almost no uneven rotation due to load fluctuations or external shocks on the image carrier drum, and almost no distortion or displacement. Image formation can be performed.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an embodiment of an image bearing drum driving device according to the present invention, FIG. 2 is a sectional view showing the main parts thereof, and FIG. 3 is a perspective view of the main parts. , FIG. 4 is a diagram showing fluctuations in the rotational speed of the image carrier drum due to load fluctuations, FIG. 5 is a perspective view of main parts showing a modification of the embodiment shown in FIGS. 1 to 3, FIG. 6 (Al, (Bl) is a sectional view and a plan view of another modified example, FIG. 7 is a schematic sectional view showing another embodiment, and FIG. 8 is a configuration of a conventional image forming apparatus. FIG. 9, a perspective view showing an example, is a schematic diagram showing a driving device for the image carrier drum. In the figure, 1 is an image carrier drum, 2 is a frame, 3 is a worm wheel, and 4 is a first worm, 5 is a second worm, 6 is a motor, 7 is a drive shaft, 9 is a bearing, 10 is a spring support member, 12 is a spring, 13.14 is a bearing, 15a, 15
b is the support frame, 16.17 is the bearing receiver, 18
indicates a set screw. Patent Applicant: Olympus Optical Industry Co., Ltd. Attorney General 10 Volumes Volume 1 II Osamu - Figure 1 Figure 4 Image 5 Figure 5a

Claims (1)

[Claims] a rotary drive source, a drive shaft that rotates in response to the driving force of the rotary drive source, a first worm that is fixed to the drive shaft and rotates, and a first worm that is rotatably supported on the drive shaft. an elastic member that applies an elastic biasing force to the second worm in the rotational direction of the drive shaft by coupling one end to the drive shaft and the other end to the second worm; a worm wheel meshing with the first and second worms;
An image carrier drum driving device comprising: an image carrier drum fixed to a rotating shaft of the worm wheel.