JP2001265166A - Electrophotographic image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an effect for reducing uneven rotation and also to provide superior image quality in respective speed modes even in an image forming device equipped with plural speed modes. SOLUTION: In a driving device, provided with a photoreceptor 10 fixed on a drive shaft 22 rotated by a drive motor, and an inertial rotating body attached to the shaft 22 and integrally rotating with the photoreceptor 10 so as to drive and rotate the photoreceptor 10 by switching two kinds of speed, the inertial rotating body is constituted of a 1st fly wheel 26 rotatably fixed on the drive shaft 22 and a 2nd fly wheel 27 with respect to the shaft 22. Then, it is equipped with an electromagnetic clutch 29 for integrally rotating them between the wheel 27 and the shaft 22. By engaging/disengaging the clutch 29 in accordance with the rotating speed of the photoreceptor 10, the strength of the inertial force acting on the photoreceptor 10 is switched to an optimum value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a copying machine, a printer,
It relates to image forming devices such as facsimile machines.Especially, it repeats the electrophotographic process of charging, writing, development, transfer and cleaning, transfers the image formed on the image carrier, and finally records on paper, OHP sheet etc. The present invention relates to an electrophotographic image forming apparatus that records an image on a medium.

[0002]

2. Description of the Related Art In an image forming apparatus of this type, a developing device, a cleaning device, and the like are driven together with an image carrier by transmitting rotation of a driving motor. For this reason,
When there is a torque fluctuation in a developing device, a cleaning device, or the like, there is a case where the fluctuation causes a rotation unevenness in the image carrier.

[0003] When the rotation unevenness occurs, there have been problems in that the image on the image carrier is disturbed, and when the image is transferred to a recording medium, the disturbance is caused.

In particular, in an image forming apparatus for forming a halftone image such as a color copying machine or a color printer, it is essential to improve the rotational drive performance of a photoreceptor or the like, that is, to reduce rotational unevenness. An important issue is how to suppress rotation unevenness with high accuracy.

Therefore, in a conventional image forming apparatus,
For example, the rotation unevenness of the image carrier is prevented by attaching an inertial rotating body called a flywheel to the drive shaft of the image carrier, or improving the performance of a gear for driving the image carrier rotation.

[0006]

By the way, in such an image forming apparatus, vibrations are sometimes generated in the rotation direction of the drive shaft of the image carrier. When a flywheel is used, for example, the vibrations are mainly In the case of a frequency band such as tens Hz to several hundreds Hz, the rotation unevenness is effectively reduced. On the other hand, in a low frequency band such as several Hz to tens of Hz, the reduction effect of the rotation unevenness is reduced by half. Inconvenience.

On the other hand, for example, in a color image forming apparatus, the image quality is lowered to obtain high productivity, but the high speed mode for increasing the image forming speed and the image forming speed for increasing the image quality are obtained. Some speed modes have a plurality of speed modes, such as a low speed mode.

However, in such an image forming apparatus having a plurality of speed modes, when the rotation speed changes, the range in which the effect of reducing rotational unevenness can be obtained also changes. Must be prioritized to one of the speed modes, or tuning of the inertial mass according to the rotational speed must be performed every time. However, it was actually difficult to perform optimal tuning for all speed modes.

In view of the above circumstances, the present invention provides an image forming apparatus having a plurality of speed modes, in which the effect of reducing rotation unevenness can be obtained for each speed mode. An object is to provide good image quality.

According to the second aspect of the present invention, it is an object of the present invention to compact such an image forming apparatus.

It is an object of the invention according to claims 3 and 5 to make it possible to electrically quickly change the inertial force according to the speed mode.

A fourth object of the present invention is to make it possible to change the inertial mass even if there is not enough room in the axial direction of the drive shaft.

[0013]

According to the present invention, there is provided a semiconductor device comprising:
The invention according to the invention relates to an electrophotographic image forming apparatus in which an inertial rotator is provided on a drive shaft of an image carrier, and the rotational speed of the image carrier can be switched to a plurality of stages. It is characterized in that it comprises a contact / separation means for selectively switching some of them depending on the rotation speed of the carrier and not switching them integrally with the drive shaft.

According to a second aspect of the present invention, in the first aspect of the present invention, a first flywheel and a second flywheel having the same outer diameter are provided as inertial rotating bodies, and these are arranged close to each other on a drive shaft. It is characterized by being attached.

The invention according to claim 3 is the invention according to claim 1 or 2
In the invention described in (1), an electromagnetic clutch is provided as the contact / separation means.

According to a fourth aspect of the present invention, in the first aspect of the present invention, the first flywheel fixed on the drive shaft and the ring-shaped second second ring provided on the outer periphery thereof are used as the inertial rotating body.
And a flywheel, wherein the second flywheel is attached to the drive shaft via a plate-like flange.

According to a fifth aspect of the present invention, in the invention according to the fourth aspect, the flange is made of a magnetic material, is rotatably provided on the drive shaft, and the first flywheel supports an electromagnet for attracting the flange. It is characterized by that.

[0018]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a schematic configuration diagram of a main part in an electrophotographic image forming apparatus according to the present invention.

In FIG. 1, reference numeral 10 denotes a drum-shaped photosensitive member as an image carrier. On the upper side of the photoconductor 10, the photoconductor 10
, And a charging charger 11 is provided in parallel with it.
From the charging charger 11 in the rotation direction of the photoconductor 10,
Around the photoreceptor 10, a developing device 12, a transfer charger 13, a cleaning device 14, and the like are sequentially provided.

A writer 15 is arranged on the charger 11. Further, a fixing device 16 is provided on the left side of the cleaning device 14.

Along with the rotation of the photoreceptor 10, a bias voltage is applied by a charging charger 11 to uniformly charge the surface, and a writing unit 15 irradiates writing light to perform optical writing. An electrostatic latent image is formed thereon.

Subsequently, with the further rotation of the photosensitive member 10, toner is attached to the latent image portion by the developing device 12 to form a visible image, and a toner image is formed on the photosensitive member 10. Thereafter, a bias voltage is applied by the transfer charger 13 to
The toner image is transferred to a recording medium 17 such as a sheet, which has been conveyed below.

The surface of the photoreceptor 10 after the image transfer is cleaned by removing the residual toner by a cleaning device 14, and then, for example, is discharged by a not-shown discharging lamp to prepare for the next image formation starting from charging.

On the other hand, the recording medium 17 after the image transfer is conveyed to a fixing device 16, where the transferred image is fixed by the fixing device 16, and then discharged out of the main body of the image forming apparatus by a discharge roller (not shown). Stack on paper tray.

FIG. 2 shows a longitudinal section along the drive shaft of the photosensitive member 10 in the above-described image forming apparatus. As can be seen from FIG. 2, the photoconductor 10 is mounted on the drive shaft 22. The drive shaft 22 includes a drive gear train 25 that transmits a driving force from a drive motor (not shown), first and second flywheels 26 and 27 that are inertial rotating bodies, and an electromagnetic clutch that forms a contact / separation unit. 29.

The drive shaft 22 is provided on a pair of side plates 24a and 24b provided at the front and rear of the main body of the image forming apparatus.
3a, it is attached to the latter via bearings 23b, 23c and a holder 23d, and is rotated by a drive torque from a motor via a drive gear train 25.

The drive gear train 25 is fixed on a drive shaft 22 and a drive gear 25a that is rotated by a drive force from the motor. The drive gear train 25 transmits the drive force from the drive gear 25a to rotate the drive shaft 22. And a driven gear 25b to be driven.

The first flywheel 26 has a specific mass m
1 and is fixed to the drive shaft 22 with screws and is always rotated integrally. The mass m1 is such that when the first flywheel 26 is rotated at high speed together with the photoconductor 10 at a first speed (ω1) described later, the rotation unevenness can be effectively reduced. .

On the other hand, the second flywheel 27 is formed in a disk shape having substantially the same outer diameter as the first flywheel 26, and is provided on the shaft end side of the first flywheel 26 in proximity to the first flywheel 26. Have been. The second flywheel 27 has a specific mass m2 and the bearing 2
8 and a rotating electromagnetic clutch 29 to the drive shaft 22. The mass m2 can effectively reduce the rotation unevenness when the second flywheel 27 is rotated at a low speed together with the photoconductor 10 and the first flywheel 26 at a second speed (ω2) described later. It is the size that can be done.

The electromagnetic clutch 29 is driven by the electromagnetic force
The inertial force of the flywheel 27 is additionally applied to the photoreceptor 10. For example, according to the operation of a mode setting switch (not shown), a “disconnected state” when off and a “connected state” when on. Can be switched. Further, the electromagnetic clutch 29 of this example is interposed between the outer ring portion 29a and the inner ring portion 29b, and the outer ring portion 29a is
It is fixed to the flywheel 27. On the other hand, the inner ring 2
9b is fixed to the drive shaft 22 with a screw. Note that this mode setting switch operates the drive shaft 2 at the first speed (ω1).
2 and the photoconductor 10 are rotated at a high speed to form a high-speed image, and the second mode (ω2, where ω1> ω) is set.
When a high quality image is formed by rotating the drive shaft at a low speed in 2), the second mode is set.

Next, the operation of this example will be described. For example, when the first (high-speed) mode is set, the state between the electromagnetic clutch 29 and a power source (not shown) is in a “non-conductive state”, and the transmission of power from the inner ring portion 29b to the outer ring portion 29a is performed. Is in the “disconnected state”.

Here, it is assumed that, for example, a start button (not shown) is turned on to operate the image forming apparatus. Then, the rotational driving force on the motor side is transmitted to the drive shaft 22 via the drive gear train 25, and the drive shaft 22 rotates. For this reason,
The first flywheel 26 fixed integrally with the drive shaft 22 also rotates at the same angular velocity.

On the other hand, the second flywheel 27 is attached to the drive shaft 22 via a bearing 28 on the first flywheel 26 side, and is free to rotate. Also,
An outer ring portion 29a is fixed to the shaft end side of the second flywheel 27, and is in a state free of rotation with respect to the drive shaft 22. Further, the outer ring portion 29a and the electromagnetic clutch 29
The inner ring portion 29b opposed to the outer ring 29b is screwed to the drive shaft 22 and thus rotates integrally with the drive shaft 22. However, since the electromagnetic clutch 29 is in the "disconnected state", the rotation of the inner ring portion 29b causes the outer ring to rotate. The second flywheel 27 through the portion 29a
Is not transmitted to

Therefore, in the case of "non-conduction state", the second
No rotational force is transmitted to the flywheel 27, and the inertial force does not act on the photoconductor 10. That is, the photoconductor 10
, Only the inertial force of the first flywheel 26 acts. Accordingly, when the photoreceptor 10 is rotated at a high speed at the first speed (ω1) to form a high-speed image, the rotation unevenness can be reduced only by the inertial force of the first flywheel 26, so that high-speed image formation can be performed. Even in the case of performing, the image quality can be improved.

On the other hand, when the mode is set to the second (high image quality) mode, the state between the electromagnetic clutch 29 and the power supply (not shown) is "conductive", and the inner ring portion 29b moves from the outer ring portion 29a to the outer ring portion 29a. Is in the “connected state”.

Here, it is assumed that, for example, the start button is turned on to operate the image forming apparatus. In this case, the first
The flywheel 26 rotates integrally with the drive shaft 22 at the same angular speed regardless of whether the electromagnetic clutch 29 is "conductive" or "non-conductive", as in the previous speed mode.

On the other hand, the second flywheel 27 is attached to the drive shaft 22 via the bearing 28 on the first flywheel 26 side, and is free to rotate.
The shaft end of the second flywheel 27 is
Is in the “connected state”, the rotation of the inner ring portion 29b is transmitted to the second flywheel 27 via the outer ring portion 29a.

Accordingly, the electromagnetic clutch 29 is in the "conductive state".
In the case of (2), the second flywheel 27 also rotates, so that its inertial mass acts on the photoconductor 10. as a result,
A large inertial force acts on the photoreceptor 10. Thereby, when the photoreceptor 10 is rotated at a low speed at the second speed (ω2) to form a high-quality image, the rotation unevenness is reduced by the inertial force of both the first flywheel 26 and the second flywheel 27. Will be able to
Further, a good image quality can be stably obtained.

Next, a second embodiment according to the present invention will be described. In this example, the same parts as those in the first example are denoted by the same reference numerals, and redundant description will be avoided.

FIG. 3 shows a longitudinal section along the drive shaft of the photosensitive member 10 of the second example. As can be seen from FIG. 3, a drive shaft 22 to which the photoconductor 10 is attached has a drive gear train 25 for transmitting a driving force from a motor (not shown), and first and second flywheels which are inertial rotating bodies. The vehicle includes wheels 30 and 34 and an electromagnet 31 constituting a contact / separation unit.

The first flywheel 30 has a unique mass m
3 and a substantially disk shape having an outer diameter D, and is fixed to the drive shaft 22 with screws and attached integrally. It should be noted that the mass m3 has such a size that when the first flywheel 30 is rotated at high speed together with the photoconductor 10 at the third speed (ω3), the rotation unevenness can be effectively reduced.

Also, the first flywheel 30 has
As shown in FIG. 4, the side surface 30 opposite to the drive gear train 25
b (see FIG. 4), a plurality of magnet chambers 30a are formed concentrically. One end face 31a of the electromagnet 31 is fixed to each of the magnet chambers 30a, and the magnetic force F1 generated by the wound coil 31c allows the flange 32 to be attracted to the opposite side face 31b. Has become.

On the other hand, as shown in FIG. 3, the second flywheel 34 has a specific mass m4, and the bearing 33 and the flange 33 are closer to the shaft end of the drive shaft 22 than the first flywheel 30 is. 32. The second flywheel 34 has a ring shape,
The inner diameter is formed to be larger than the outer diameter of the first flywheel 30 so that the first flywheel 30 is extrapolated from the shaft end side while keeping a certain gap. The mass m4 is such that when the second flywheel 34 is rotated at low speed together with the photoconductor 10 and the first flywheel 30 at the fourth speed (ω4), the rotation unevenness can be effectively reduced. It has become.

The flange 32 is formed in a thin disk shape by using a magnetic material such as steel, for example, and is integrally attached to the bearing 33. As a result, the flange 32 is free to rotate with respect to the drive shaft 22.

The shaft end of the drive shaft 22 has a side surface 30 b (see FIG. 4) of the first flywheel 30 and a bearing 33.
Between them, a spring washer 35 is interposed,
Due to the spring force F2 (where F1> F2), the bearing 33 is constantly pushed toward the shaft end. And drive shaft 2
A suitable retaining member such as a washer 36 is attached near the end of the second shaft, for example, to prevent the second flywheel 34 from falling off the drive shaft 22. When the electromagnet 31 is energized, the flange 32 is attracted, and as shown in FIG. 5, a gap h is formed between the electromagnet 31 and the retaining member in the thrust direction.

Next, the operation of this example will be described. For example, it is assumed that a start button (not shown) is turned on to operate the image forming apparatus. Then, the rotational driving force on the motor side is transmitted to the drive shaft 22 via the drive gear train 25, and the drive shaft 22 rotates. Therefore, the first flywheel 26 fixed integrally with the drive shaft 22 also rotates at the same angular velocity.

Here, for example, when the first (high-speed) mode is set, the electromagnet 31 is in a "non-conductive state" with a power source (not shown), and generates a magnetic force. Absent. Therefore, only the spring force F <b> 2 of the spring washer 35 acts on the flange 32 to which the second flywheel 34 is attached, and the flange 32 is separated from the first flywheel 30. Further, the flange 32 is attached to the bearing 3.
3 is attached to the drive shaft 22 with the interposition of the rotary shaft 3, so that the rotational drive force from the drive shaft 22 is not transmitted.

Therefore, even if the drive shaft 22 rotates, the rotational force is not transmitted to the second flywheel 34, so that no inertial force is generated in the second flywheel 34. As a result, only the inertial force of the first flywheel 30 acts on the drive shaft 22. As a result, the third
When the photoreceptor 10 is rotated at a high speed (ω3) to form a high-speed image, rotation inertia can be reduced by the inertia force of the first flywheel 30, so that even when performing a high-speed image formation. Thus, the image quality can be improved.

On the other hand, when the mode is set to the second (high image quality) mode, the electric connection between the electromagnet 31 and the power supply (not shown) is "conductive", and the magnetic force F1 is generated. Since the flange 32 facing the electromagnet 31 is formed of a magnetic material, the flange 32 is attracted by the magnetic force F1 and is attracted to the side surface 31b of the electromagnet 31. As a result, the first flywheel 30 and the second flywheel 34
Integrally rotate around the drive shaft 22 with a large inertial mass. Thereby, a larger inertial force can be generated as compared with the case where the electromagnet 31 is in the “non-conductive state”.

Therefore, when the photoreceptor 10 is rotated at a low speed at the fourth speed (ω4) to form a high quality image, uneven rotation is caused by the inertial force of both the first flywheel 30 and the second flywheel 34. Since the image quality can be reduced, more excellent image quality can be stably obtained.

In the above example, the image carrier is
The case where the present invention is applied to the electrophotographic image forming apparatus using the drum-shaped photoconductor 10 and the rotation unevenness of the drive shaft which is the central axis of the photoconductor 10 is removed has been described. However, the present invention relates to an electrophotographic image forming apparatus using a belt-shaped photoreceptor as an image carrier, in a case where rotation unevenness of a drive shaft for rotating and transporting the photoreceptor by rotating the photoreceptor is removed. Can also be applied.

In an electrophotographic color image forming apparatus, a single color image formed on a photosensitive member is sequentially transferred to form a composite color image on an intermediate transfer member, and the composite color image is transferred. Although recording is performed on paper or the like, the invention is similarly applied to such a color image forming apparatus, and rotation unevenness of a photosensitive member or an intermediate transfer member as an image carrier can be eliminated. Since most of the color image forming apparatuses have a high-speed mode and a low-speed mode, this type of color image forming apparatus is particularly useful.

[0053]

As described above, according to the present invention, a plurality of inertia rotators are provided, and some of them are selectively rotated integrally with the drive shaft according to the rotation speed of the image carrier. Since there is provided contact / separation means for switching the image carrier, the optimal inertial force is applied to the image carrier according to the speed mode when the image carrier is switched to at least two types of speed modes and rotated. You can do it. Therefore, even in an image forming apparatus having a plurality of speed modes, the effect of reducing the rotation unevenness can be obtained for each speed mode, and thus, a good image quality can be provided.

According to the second aspect of the present invention, the first flywheel and the second flywheel having the same outer diameter are provided as the inertial rotating bodies and are mounted adjacent to each other on the drive shaft. Can be compacted.

According to the third aspect of the present invention, an electromagnetic clutch is provided as the contact / separation means. According to the fifth aspect of the present invention, the flange is made of a magnetic material, and is rotatably provided on the drive shaft. Since one flywheel supports the electromagnet that attracts the flange, the inertia force can be electrically and promptly and reliably changed according to the speed mode, and a highly reliable product can be provided. Moreover, claim 3
According to the invention according to the present invention, in addition, an electromagnetic clutch is used for the contacting / separating means. For example, it is necessary to use a magnetic material as a material of the drive shaft and the inertial rotating body, such as when an electromagnet is used. Since there is no such material, the degree of freedom in selecting materials used for these is increased, which is convenient.

Further, according to the fourth aspect of the present invention, the inertial rotating body includes the first flywheel fixed on the drive shaft and the ring-shaped second flywheel provided on the outer periphery of the first flywheel. The flywheel is attached to the drive shaft via a plate-like flange. Therefore, since these inertial rotators can be installed within the range of both thicknesses, they can be compactly accommodated in a narrow space where there is no margin in the axial direction of the drive shaft, so that the driving device of the image carrier can be reduced in size and lengthened. Is effective for reducing the size of the image forming apparatus.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a main part of an electrophotographic image forming apparatus according to the present invention.

FIG. 2 is a longitudinal sectional view along a drive shaft of a photoconductor in the image forming apparatus.

FIG. 3 is a longitudinal sectional view along a drive shaft of a photoconductor in another image forming apparatus.

FIG. 4 is a partially enlarged sectional view of the vicinity of the electromagnet in a state where power is not supplied to the electromagnet.

FIG. 5 is a partially enlarged sectional view of FIG. 3 in a state where the electromagnet is energized.

[Explanation of symbols]

 REFERENCE SIGNS LIST 10 photoconductor (image carrier) 11 charging charger 12 developing device 13 transfer charger 14 cleaning device 15 writing device 22 drive shaft 23a bearing 23b bearing 23c bearing 23d holder 24a side plate 24b side plate 25 drive gear train 26 first flywheel (inertial rotation) Body) 27 Second flywheel (inertial rotating body) 28 Bearing 29 Electromagnetic clutch (contacting / separating means) 30 First flywheel (inertial rotating body) 31 Electromagnet (contacting / separating means) 32 Flange (contacting / separating means) 33 Bearing 34 2 flywheel (inertia rotating body) 35 sprig washer

Claims (5)

[Claims] 1. An electrophotographic image forming apparatus in which an inertial rotator is provided on a drive shaft of an image carrier and a rotational speed of the image carrier can be switched to a plurality of stages. An electrophotographic image forming apparatus, comprising: a contacting / separating means for selectively switching some of them selectively in accordance with the rotation speed of the image carrier and not to rotate them integrally with the drive shaft. 2. The first inertial rotating body has a first outer diameter having the same outer diameter.
The electrophotographic image forming apparatus according to claim 1, wherein a flywheel and a second flywheel are provided, and they are mounted close to each other on the drive shaft. 3. The electrophotographic image forming apparatus according to claim 1, further comprising an electromagnetic clutch as said contacting / separating means. 4. An inertia rotating body comprising: a first flywheel fixed on the drive shaft; and a ring-shaped second flywheel provided on an outer periphery of the first flywheel. The second flywheel is provided with a plate-shaped flange. The electrophotographic image forming apparatus according to claim 1, wherein the electrophotographic image forming apparatus is attached to the drive shaft through a shaft. 5. The electrophotograph according to claim 4, wherein the flange is made of a magnetic material, is rotatably provided on the drive shaft, and the first flywheel supports an electromagnet for attracting the flange. Image forming apparatus.