JP2780030B2 - Image forming device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Object of the Invention (Industrial Application Field) The present invention relates to an image forming apparatus such as an electrostatic copying machine and a printer which utilizes an electrostatic transfer process, and in particular, a rotating cylindrical shape as an image carrier. The present invention relates to an image forming apparatus provided with a photoreceptor and a transfer roller which is a transfer member pressed against the photoreceptor.

(Prior Art and Problems to be Solved) A rotating cylindrical photoreceptor as an image carrier and a transfer roller as a transfer member which presses against and rotates in synchronization with the photoreceptor are provided. There is already proposed an image forming apparatus configured to transfer a toner image previously formed on the surface of a photoreceptor to a transfer material by passing through a transfer member.

As a method of driving the photoconductor and the transfer roller of such an apparatus, a gear disposed at one end of the photoconductor receives an input from the outside to rotate the photoconductor, and the other end of the photoconductor is rotated. The transfer roller is driven by a gear provided at the end of the transfer roller, which meshes with the gear provided at the end of the photoreceptor, by a gear provided at one end of the photoconductor. While driving the photoconductor,
Some transfer rollers are configured to receive a driving force from the outside by a gear disposed at the end.

FIG. 6 is a view showing only a photosensitive member and a transfer roller portion of a known device corresponding to the former, and shows a photosensitive member 1;
And a transfer roller 8 pressed against the transfer roller 8. A spur gear 3 is disposed at an end of the photosensitive member and is driven to rotate. A spur gear 22 provided at the other end is connected to an end of the transfer roller 8 by an end. The roller 8 is driven by meshing with the gear 29 of the section.

FIG. 7 shows an example of the latter type, in which the photosensitive member 1 is housed in a process cartridge, which is driven by a gear 3,
The transfer roller 8 on the main body side obtains torque from the helical gear 29 side.

By the way, in this type of apparatus, in order to smoothly rotate the photosensitive member and the transfer roller,
Normally, a slight gap is provided in the thrust direction. However, in the configuration shown in FIG. 6, as can be seen immediately, the positions of both the photoconductor and the transfer roller are not fixed in the axial direction. Transfer blur occurs in that direction, which may cause deterioration in image quality.

As shown in FIG. 7, the photosensitive member 1 is provided in the process cartridge, the transfer roller 8 is provided on the main body side, and the transfer roller 8 is separately driven. The transfer roller 8 is provided with a helical gear 29. When the first process cartridge is mounted, the transfer roller 8 automatically moves to the reference surface by the start of operation when the first process cartridge is mounted. An axial force is applied, and the photoconductor stabilizes at a certain position irrespective of whether the position is maintained or moved by this force, so if this position is set in advance as a normal position, Good.

However, when the process cartridge is replaced, by this time, the transfer roller 8 is in a position where it cannot be further moved in the thrust direction, so that the photoconductor cannot move to the normal position, and some force is applied to the photoconductor. If it does, the position in the axial direction is not stable, so that there is a possibility that the transfer blur occurs as in the case described above.

This is the same even if the torsion angle of the drive gear of the transfer roller 8 is reversed. If the spur gear is used, the same problem as in the case of FIG. 6 occurs.

The present invention has been made in order to cope with the above situation, and in an image forming apparatus including an image carrier and a transfer roller pressed against the image carrier, the above-described transfer blur,
It is an object of the present invention to provide an image forming apparatus that does not cause deterioration in image quality due to this.

(2) Configuration of the Invention (Technical Means for Solving the Problems, Action of the Invention) In order to achieve the above object, the present invention provides a rotatable image carrier, and a nip portion between the image carrier and the nip. A transfer roller for transferring an image from the image bearing member to a transfer material at a portion, wherein a first helical gear provided on the image bearing member and receiving a driving force from a driving helical gear; A second helical gear provided on the image carrier and meshing with a helical gear provided on the transfer roller, wherein the first helical gear is arranged in the generatrix direction of the image carrier. The direction of the force that the gear receives from the driving helical gear is
The image forming apparatus (1), wherein the second helical gear has the same direction as the direction of a force received from the helical gear provided on the transfer roller, or the image forming apparatus (1). Wherein the apparatus has a process cartridge detachably attached to the entire apparatus, and the process cartridge includes the image carrier and image forming means acting on the image carrier. Device (2).

With this configuration, when the image carrier and the transfer roller are driven, the image carrier and the transfer roller are automatically moved to the reference position, and thereafter, the positions can be stably maintained. Image forming work can be performed.

FIG. 1 is a schematic view of a main part of a reference example, in which a cylindrical photosensitive member 1 disposed in a process cartridge 4 has a flange 2 at one end and a flange at the other end. And helical gears 3 integral with the cartridge 4, and positioning pins 5a and 5b fixed to both side surfaces of the cartridge engage with the center of the flange 2 and the helical gear 3 to Thus, the photosensitive member 1 is rotatably supported.

In the present embodiment, the process cartridge 4 includes a charger, a developing device, a cleaner, and the like (not shown).
It also includes a drum cartridge composed of a photoreceptor, a charger (not shown), a cleaner, and the like, a toner cartridge composed of a developing device (not shown), a toner hopper, and the like.

Support member attached to both sides of the cartridge
A conductive shaft 6 is pivotally mounted on bearings 7a and 7b provided on the transfer roller 10. A conductive urethane sponge is wound around a position facing the photoreceptor 1 to form a transfer roller 8. doing.

The pins 5a and 5b supporting the photoreceptor 1 are inserted into the concave portions 10a and 10b formed in the support member 10 to determine the vertical position, so that the weight of the cartridge, the surface hardness of the transfer roller 8, and the like are determined. By appropriately setting, the photosensitive member 1 and the transfer roller 8 can be pressed against each other so that an appropriate nip portion is formed.

A helical gear 9 is attached to the shaft 6, meshes with the gear 3, and is transferred via a transfer roller 8 and gears 9 and 3 by an input from the shaft 6 by a drive source (not shown). The photoconductor 1 rotates.

As described above, since the helical gear is used, an axial thrust acts between the two gears, so that the thrust is smaller than the maximum static friction force between the photosensitive member 1 and the transfer roller 8. Coefficient of friction of the transfer roller 8 so as to increase the force,
By setting the pressure contact force on the photoreceptor and the like, the photoreceptor 1 can be moved together with the cartridge 4 and thereafter maintained at a predetermined position in the axial direction, and the transfer roller 8 can also be maintained at a predetermined position in the axial direction. There is no blur in the thrust direction at the time of exposure and transfer, and the use of a helical gear can reduce pitch unevenness as compared with the case of using a spur gear.

Further, the apparatus main body is provided with a sheet feeding unit, a conveying unit, a fixing unit, an exposure unit, and the like (not shown), and performs image formation in the same manner as a known image forming apparatus.

FIG. 2 shows the apparatus shown in FIG. 1 as viewed from the left in the figure. Reference numeral 11 denotes a member for supporting the cartridge housing 4, and the process cartridge is applied in the direction F by a spring (not shown). It is pressed and fixed to the support member. The gear 9 is disposed so as to be substantially inclined by a pressure angle α of the gear with respect to the vertical direction, and the gear 9 is configured such that the force in the pressure angle direction applied to the gear 3 is perpendicular to the gravity. It is.

By the way, the photoreceptor rotates while contacting the surface of the photoreceptor with the cleaning blade and the spacer of the sleeve installed in the developing device. Therefore, the photoreceptor receives loads from these members, but there is always the possibility that these loads fluctuate. However, the fluctuation may cause the photosensitive member to vibrate and generate pitch unevenness.

For this reason, in the above-described apparatus, the transfer roller 8 rotates while slipping with respect to the photoconductor 1.

To explain this, the radius of the transfer roller 8 when not pressed against the photoconductor 1 is
R ₀ , the radius of the pressed portion upon pressure contact is R _t , the radius of the photoconductor 1 is R _d , the angular velocity of the transfer roller 8 is ω _t , and the angular velocity of the photoconductor 1 is ω _d , When the ratio of the peripheral speed of the transfer roller 8 to the circumferential speed of the _{X, R d · ω d ·} X = R t · ω t (1) the number of teeth of gear 9 for driving the photosensitive member 1 Z _9, photoconductor Gear 3
Of the number of teeth and _{Z 3, R d / Z 3} · X = R t / Z 9 (2) Also, the reference pitch circle radius R ₉ of the gear 9, it R ₃ of the gear 3, the center distance Assuming that L and the backlash are δ, L = R _d + R _t (3) L = R ₉ + R ₃ + δ (4) The gears 9 and 3 are selected so as to satisfy the above equations.

For example, set the peripheral speed of the transfer roller to 3
When% and to increase, (2) from _{R d / Z 3 · 1.03 =} R 9 / Z 5 photoconductor 30mm outside diameter of 30 the number of teeth, if the number of teeth 15 of the gear 9, (2) Assuming that R _t = 7.725 mm from the equation, L = 22.725 mm from equation (3) and δ = 0.15 mm from the backlash, R ₉ + R ₃ = 22.575 mm from equation (4).

In the case of a helical gear, as is well known, the reference pitch circle radius can be changed by changing the torsion angle β. When the number of teeth is Z and the module is m, the reference pitch circle radius d _os is d _os = Z · m / _cosβ Therefore, (4) L-δ = R 5 + R 11 = (Z 9 + Z 3) · m / 2cosβ next from equation equal to 1 the module, beta = 4.67 ° becomes, thereby, The specifications of the gears 9 and 3 are determined so that the peripheral speed of the transfer roller is 3% higher than that of the photoconductor.

It should be noted that, even in spur gears, the outer diameter can be changed by dislocation, but this is also limited by the module. In addition, when the dislocation is in the plus direction, the tooth tip becomes thin, and the impact when the teeth mesh with each other is easily transmitted, which causes pitch unevenness. In the case of the above device, if a spur gear is used, the reference pitch circle diameter of the gear 3 is
It is 30mm and that of gear 9 is 15mm.

Assuming now that R _t = 7.725 mm and the backlash is 0.15 mm, the dislocation amount of the gear 9 is −0.0375, which is a negative dislocation.

It is generally known that when the number of teeth is about 15 or less, applying a minus dislocation decreases the strength of the root, and thus applying a positive dislocation to strengthen the root.

When the gear 3 of the photoconductor is configured to mesh with a sleeve gear that rotates integrally with a developing sleeve (not shown), the distance between the shaft of the gear 3 and the sleeve gear is determined based on the peripheral speed of the sleeve, the distance between the surface of the photoconductor and the surface of the sleeve. Since the distance is determined, it may be necessary to perform dislocation. Sleeve gear has 15 teeth
Since there are many cases in which the number of sheets is about one, it is not preferable to apply a negative dislocation as described above, and a positive dislocation is also not preferable since the tooth tip becomes thin. If you make the module smaller,
Although the number of teeth can be increased without increasing the reference pitch circle radius, if the module is small, the strength of the teeth is reduced and vibrations are likely to occur. In short, the use of spur gears in the above devices is not practical.

FIG. 3 is a schematic view of a main part of an embodiment of the present invention, and is an end view showing a photosensitive member, a transfer roller and their driving relation, and the same portions as those shown in FIG. The reference numerals are attached.

At one end of the photoreceptor 1, a helical gear 9 for receiving an input from the shaft 16 is provided.
A helical gear 3 is disposed at the other end, and a helical gear 22 whose helix angle is opposite to that of the helical gear 3 is provided at the other end. The helical gear 22 meshes with a helical gear 29 attached to one end of the transfer roller 8, and the transfer roller 8 pressed against the photoreceptor 1 is rotated by an appropriate means (not shown) such as a spring.

The input from the shaft 16 causes the photoconductor 1 to rotate in a counterclockwise direction as viewed from the left side of the drawing.
The photosensitive member 1 receives the thrust D ₁ of the the leftward, the transfer roller 8 by the rotation of the gear 29 receiving the illustrated thrust T, since the photosensitive member 1 is subjected to a force D ₂ leftward in the figure as a reaction force,
After all the photosensitive member 1 will be subjected to resultant force D ₃ of these forces D _1, D _2.

At this time, by the than the maximum static frictional force in the thrust direction between the photosensitive member 1 and the transfer roller 8, is set so that the resultant force D ₃ increases, as in the case of the above-described reference example, The photosensitive member 1 can be moved to the reference position, and when the photosensitive member 1 is driven, the position can be prevented from fluctuating. At the same time, the position of the transfer roller 8 is also stabilized, so that transfer blur and deterioration of image quality due to this can be prevented. It is possible.

Note that this is the same in the apparatus shown in FIG. 1 and in the reference example described later. However, even if the direction of the torsion angle of the helical gear is opposite to that shown in FIG. It is out of the question that the same action can be achieved only by reversing the biasing direction of.

Note When an additional note, when the direction of the helix angle of the gear 3 and the 22 in the same direction, the thrust D ₁ and the reaction force D ₂ and is smaller force D ₃ is in the opposite direction, which is the maximum static friction The possibility that the force becomes smaller than the force is increased, and the position of the photoconductor 1 in the thrust direction may not be maintained at a fixed position.

 FIG. 4 is a schematic view of a main part of another reference example.

This device is different from the device shown in FIG. 3 only in that the input gears 9 and 3 of the photoreceptor 1 are spur gears.

The rotation of the photoconductor 1 causes the helical gear 22 integral therewith to rotate.
The transfer roller 8 is rotated via the helical gear 29.

At this time, the transfer roller 8 receives the thrust of the arrow T direction, the photosensitive member 1 as a reaction force will be subjected to force D ₂ to the left in the figure.

In this case, than the maximum static frictional force in the thrust direction between the photosensitive member 1 and the transfer roller 8, by leaving defined as the force D ₂ is increased, in the same manner as the embodiments described above, the photosensitive member 1 And the position of the transfer roller in the thrust direction does not fluctuate.

It will be readily understood that the position of the photoconductor in the thrust direction does not fluctuate even if the gears 3 and 9 are configured as helical gears and the gears 22 and 29 are configured as spur gears.

FIG. 5 is a schematic view of a main part of another reference example, in which a helical gear 3 is attached to the left end of the photosensitive member 1 in the drawing, and a helical gear 9 on the driving side is attached thereto. Are engaged with each other, and the gear 9 receives a driving force from the shaft 16, so that the photosensitive member 1
Viewed from the left in the figure, it is assumed that a thrust of the code D ₁ direction rotated counterclockwise.

A transfer roller 8 is pressed against the photosensitive member 1 by a spring (not shown) or the like.
Helical were attached to the gear 32, this was rotated via the gears 29 helical transcriptionally roller end meshing, a thrust T ₁ in a direction shown by the arrow this time.

At this time, by setting the thrust forces D ₁ and T _{1 to} be larger than the maximum static friction force in the thrust direction acting between the photoreceptor 1 and the transfer roller 8, as in the above-described embodiments, The photoconductor 1 and the transfer roller 8 can be moved to the reference position, and the photoconductor 1 does not fluctuate its position irregularly when it is rotationally driven thereafter.

If the directions of the torsion angles of the helical gear 3 provided on the photoconductor 1 and the helical gear 29 provided on the transfer roller 8 are set to be opposite to each other, the photoconductor 1 and the transfer roller 8 are Since they tend to be displaced in the same direction, they can move more easily even if the frictional force between them is large.

The transfer roller side of the gear 29, the 32 can achieve the same effect as described above because the thrust D ₁ acts on the photosensitive member 1 even spur gear.

In the case of this apparatus, when the photosensitive member 1 and the transfer roller 8 move while contacting each other, a kinetic frictional force is generated. However, this friction disappears after the photosensitive member 1 and the transfer roller 8 reach the reference position. Does not change in the thrust direction.

(3) Effects of the Invention As described above, according to the present invention, the direction of the force that the first helical gear receives from the driving helical gear in the generatrix direction of the image carrier is the second helical gear. Since the helical gear is in the same direction as the direction of the force received from the helical gear provided on the transfer roller, the position of the image carrier in the thrust direction can be stably set at the predetermined position. Therefore, transfer blurring and deterioration of the image quality caused by the transfer blur can be prevented, which greatly contributes to obtaining a high-quality image.

[Brief description of the drawings]

1 is an end view showing a reference example, FIG. 2 is an upper side view of the same, FIGS. 3 to 5 are end views showing an embodiment, a reference example, and a reference example of the present invention, FIG. FIG. 7 is an end view of a known device. 1 photoreceptor, 3, 9, 29, 32 helical gear, 8
Transfer roller.

Claims (2)

(57) [Claims] 1. An image forming apparatus comprising: a rotatable image carrier; and a transfer roller that forms a nip with the image carrier and transfers an image from the image carrier to a transfer material at the nip. A first helical gear provided on the image carrier and receiving a driving force from a driving helical gear, and provided on the image carrier;
A second gear meshing with a helical gear provided on the transfer roller;
The first helical gear receives a force from the driving helical gear in the generatrix direction of the image carrier, and the direction of the force received by the second helical gear is that of the second helical gear. The image forming apparatus according to claim 1, wherein the direction of the force received from the helical gear provided on the transfer roller is the same as the direction of the force. 2. The apparatus according to claim 1, wherein said apparatus has a process cartridge detachable from said apparatus main body, said process cartridge including said image carrier and image forming means acting on said image carrier. The image forming apparatus according to claim 1.