JPH03174176A - Pressurized contact cylindrical member pair of image forming device - Google Patents

Abstract

PURPOSE:To obtain the pressurized contact force uniform over the entire length without curving by providing a magnetic field generating means on one cylindrical member and a member to be attracted by the magnetic field of the magnetic field generating means on the other cylindrical member and providing a magnetic material surface layer on at least one of a pair of the cylindrical members. CONSTITUTION:A roller 20 and roller 30 which have shaft parallel with each other are in pressurized contact with each other over the entire length and are constituted rotatable. The roller 20 is constituted by forming an elastic layer 22 on the outer peripheral surface of a cylindrical core material 21 made of a material, such as iron, having magnetism. On the other hand, the roller 30 is formed by holding a permanent magnet 32 in a magnet guide 33 provided in a cylinder 31 made of a nonmagnetic material, such as aluminum. The magnetic cylinder 21 is attracted to the magnet of the permanent magnet 32 via the nonmagnetic cylinder 31 of the roller 30 in-between so that the roller 20 and the roller 30 are attracted to each other by the uniform attraction force over the entire length and are brought into pressurized contact by the resilient elastic roller 22 on the surface of the roller 20. The uniform pressing force is obtd. in this way without curving over the entire length.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a pair of cylindrical members that are used in an image forming apparatus and rotate while being pressed against each other.

2. Description of the Related Art Image forming apparatuses using an electrostatic photographic process, such as conventional electrophotographic copying machines, printers, and facsimile machines, are provided with pairs of rollers that rotate while being pressed against each other.

FIG. 5 is a diagram showing an example of a photosensitive drum and a developing device of an image forming apparatus using an electrostatic photographic process. , an agitator 5 that stirs the toner 3 stored in the housing 4, a developing roller 6,
a toner supply roller 7 that supplies toner to the developing roller 6;
A toner layer thickness regulating roller 8 is provided to regulate the layer thickness of the toner that adheres to the developing roller 6 and is conveyed.

Agitator 5 is fixed to rotating shaft 5a. The developing roller 6 has an elastic rubber layer 6c laminated on the outer periphery of a non-magnetic stainless steel core 6b that rotates around a shaft 6a, is in pressure contact with the developing roller 6, and rotates around a shaft 7a in the direction of the arrow. Toner is supplied to the outer periphery of the developing roller 6 by the toner supply roller ruff, and is transported toward a position where it comes into pressure contact with the photosensitive drum 9, which rotates in the direction of the arrow around the shaft 9a as the developing roller 6 rotates. Ru. On the way, the thickness of the toner layer is regulated by a rotating toner layer thickness regulating roller 8 in pressure contact with the developing roller 6, and a uniform thin layer is conveyed to a position in pressure contact with the photoreceptor drum 9 and developed.

In this way, the developing roller 6 includes the toner supply roller 7, the toner layer regulating roller 8. The photosensitive drum 9 rotates while being pressed against it. It is necessary for these pairs of rollers that press against each other to rotate in contact with uniform pressure in the axial direction. Therefore, at least one of the roller pairs has an elastic surface layer, and the bearings at both ends of either roller are equipped with springs. The roller is biased in the direction of pressing against the end of the other roller.

For example, the above-mentioned developing roller 6 and toner layer thickness regulating roller 8
Regarding the pair of rollers, the developing roller 6 has a rubber surface layer 6c, and a bearing 10 that pivotally supports both ends of the shaft 8a of the toner layer thickness regulating roller 8 is moved in the direction toward the developing roller 6 (arrow) by a spring 10a. B), the developing roller 6 and the toner layer thickness regulating roller 8 move in the axial direction -
It rotates while being pressed together with various pressure forces. Further, the entire developing device 1 is moved in the direction toward the photosensitive drum 9 by the spring 3 (
The developing roller 6 having a rubber surface layer is pressed against the photosensitive drum 9 in the axial direction by a -like shore force.

Means for bringing a pair of parallel rollers into pressure contact with each other include the method of pressing both ends of the shaft of one roller against the ends of the other roller with a compression spring as described above, and, for example, the method of
As shown in Japanese Patent No. 148949, there is also a method in which bearings that support the shaft ends of both rollers are pulled together by a tension spring.

Both rollers will be rotating anyway, so if you want to use a spring to press them together,
The force of the spring must be applied to the bearings at both ends. In this case, if the surface layer of one roller is an elastic layer, a nearly uniform pressure contact force can be obtained over the entire length in the axial direction, but the pressure points at both ends serve as fulcrums, and the reaction force is uniform over the entire length of the contact part. To hang,
The shape is similar to the model of a beam with uniformly distributed loads supported at both ends, and when exaggerated as shown in Figure 6, it bends into a curved shape in which both ends are pulled together and the center line is separated in the middle, and the roller has low rigidity. There is a risk that the center portions may escape from each other and the pressure contact force may decrease. In FIG. 6, collar number 14 is a row having an elastic layer.

In view of the above-mentioned drawbacks of the conventional pair of rollers in image forming apparatuses that rotate while being pressed against each other, the present invention aims to achieve a uniform pressing force over the entire length without any particular reinforcement and without bending. An object of the present invention is to provide a pair of rollers that provides the following.

In order to solve the above problems, we propose two inventions.

The pair of rollers (pair of cylindrical members) according to the first invention is a pair of cylindrical members that rotate in pressure contact with each other with a uniform pressure contact force over the entire length in the axial direction, and have axes parallel to each other. has a magnetic field generating means, and the other cylindrical member has a member attracted by the magnetic field of the magnetic field generating means over its entire length, and at least one of the pair of cylindrical members has an elastic surface layer. It is characterized by having.

In the roller pair according to the second invention, instead of at least one of the pair of cylindrical members having an elastic surface layer as in the first invention, at least one of the rollers is arranged in the axial direction. It is characterized by moderate flexibility.

Function: Since the roller pair of the present invention is constructed as described above,
The pair of cylindrical members has a magnetic field generating means provided over the entire length inside each member and a member attracted by the magnetic field generating means, which attracts each other, so that they contact each other with a uniform pressing force over the entire length, and the shaft fulcrums at both ends Since the concentrated load applied to the first and second eye tube members can be ignored, the first and second eye tube members will not curve even if no particular reinforcement is required.
In the invention, the elastic surface layer provided on at least one roller, and in the second invention, at least one roller has appropriate flexibility in the axial direction, so that the pair of rollers can be stretched over the entire length. Close contact is achieved, the uniformity of the pressing force is not impaired, and good image formation is achieved over the entire surface.

Hereinafter, embodiments of the present invention will be described in detail based on the drawings.

FIG. 1 is a diagram showing an embodiment of a pair of rollers that are in pressure contact with each other in an image forming apparatus to which the first invention is applied.

The rollers 20 and 30 have axes parallel to each other, are pressed against each other over their entire lengths, and are rotatable.

The roller 20 has an elastic layer 22 made of flexible rubber or the like on the outer peripheral surface of a cylindrical core material 2L made of a magnetic material such as iron.
is formed and configured.

On the other hand, the roller 30 has a permanent magnet (ferrite) 3 attached to a magnet guide 33 made of resin or the like, which is provided non-rotatably with respect to the device inside a cylinder 31 made of a non-magnetic material such as aluminum.
2 is held and formed. The permanent magnet 32 is provided so that one magnetic pole faces the roller 20, and the lines of magnetic force coming out of the magnetic pole penetrate the non-magnetic cylinder 31, pass through the magnetic cylinder 21 of the roller 20, and return to the magnetic pole on the opposite side of the magnet.

As a result, the a-type cylinder 21 becomes the non-magnetic cylinder 31 of the roller 30.
The rollers 20 and 30 are attracted to each other by the magnetic poles of the permanent magnet 32, and the rollers 20 and 30 are attracted to each other with a uniform attraction force over the entire length, and the flexible elastic layer 22 on the surface of the roller 20 presses them together with a uniform contact force over the entire length. Ru.

For this purpose, the permanent magnet 32 is made of ferrite-dispersed EP
A rubber magnet with low rigidity such as DM rubber is suitable.

According to this configuration, the rollers 20 and 30 are attracted to each other with a uniform suction force over their entire length, so they do not curve over their entire length, and the flexible elastic layer on the surface of one roller allows a uniform pressing force to be applied. Since a concentrated load is not applied only to both ends, the magnetic cylinder 21 and the non-magnetic cylinder 31 will not curve in the longitudinal direction even if they are thin.

FIG. 2 is a diagram showing an embodiment in which the present invention is applied to the photosensitive drum 9 and the rollers of the developing device 1 explained in FIG.

The photosensitive drum 9 is constructed by forming a photosensitive layer on the outer surface of an aluminum core 9b, and is supported by a shaft 9a fixed to the frame of the main body of the apparatus. The developing roller 6 in the developing device 1 is constructed by forming an elastic rubber layer 6c on the outer peripheral surface of a non-magnetic stainless steel core 6b, and has a shaft 6 fixed to the developing device frame.
Rotate around a. In this embodiment, as a means for bringing the developing roller 6 and the photosensitive drum 9 into pressure contact, a permanent magnet 11a is placed inside the developing roller 6, and a permanent magnet 12 is placed inside the photosensitive drum 9, so that the a-poles of opposite polarities face each other. The roller is fixed to the machine frame over its entire length. or,
The developing device 1 is provided so as to be movable in the direction of arrow A.

As a result, the permanent magnet 11a in the developing roller 6 and the permanent magnet 12 in the photoreceptor drum 9 are attracted to each other, and the developing roller 6 and the photoreceptor drum 9 are attracted to each other with a uniform attraction force over the entire length.
The elastic rubber layer 6c on the surface of the developing roller 6 makes it possible to rotate the developing roller 6 by uniformly contacting it with pressing force over the entire length. Developing roller 6
As a means for bringing the toner layer thickness regulating roller 8 into pressure contact with the toner layer thickness regulating roller 8, a permanent magnet 11b is provided within the developing roller 6 over its entire length.

The toner layer thickness regulating roller 8 is made of rust-proofed iron.

As a result, the toner layer thickness regulating roller 8 is attracted to the developing roller 6 with a uniform suction force over its entire length, and is brought into close contact with the rubber layer 6c of the developing roller 6 with a uniform pressing force.

Pressure contact between the developing roller 6 and the toner supply roller 7 can be performed in a similar manner.

In addition, when a peeling roller that peels off toner adhering to the developing roller after development is provided in pressure contact with the developing roller, it can be brought into pressure contact with the developing roller in a similar manner.

FIG. 3 is a diagram showing an embodiment of a pair of rollers that are in pressure contact with each other in an image forming apparatus to which the second invention is applied. In this embodiment, unlike the embodiment of the first invention shown in FIG. It has moderate flexibility in the direction. The rest of the structure is the same as the embodiment shown in FIG.

The flexibility, or in other words the rigidity, of the rollers 20 and 30 must satisfy the following requirements.

(a) When a wear device (not shown) activates the rollers via a pulley, gear, etc. connected to one end of one roller, a torsion force is generated on the roller due to the frictional force between the rollers. The roller needs to have enough rigidity to withstand this torsional force.

(b) If the rigidity of both rollers is sufficiently high, a small gap will partially occur between the two rollers depending on the cylindricity determined in the production process of the rollers. In order to compensate for this minute gap, at least one of the rollers needs to have a weak rigidity to the extent that it bends due to the pressing force, in other words, it needs to have flexibility.

By satisfying the above requirements, the rollers 2o and 30 are attracted with a uniform suction force over their entire length, and are not bent.
In addition, minute gaps are filled and a uniform pressing force allows for tight contact without any gaps. Furthermore, the rollers are not twisted by torsional force generated by friction between the rollers during cantering.

FIG. 4 shows the photosensitive drum 9 of the second invention explained in FIG.
FIG. 3 is a diagram showing an example in which the present invention is applied to various rollers of the developing bag layer 1. The difference from the embodiment of the first invention explained in FIG. 2 is that the developing roller 6 is a thin-walled aluminum cylinder having moderate flexibility in the axial direction, and no elastic rubber layer is provided on the outer periphery. There are only points.

With the above configuration, the permanent magnet 11a in the developing roller 6 and the permanent magnet 12 in the photoreceptor drum 9 are attracted to each other, and the developing roller 6 and the photoreceptor drum 9 are attracted to each other with a uniform attraction force over the entire length. Due to its flexibility, it can be rotated in close contact with no gaps over the entire length.

As an example, the photoreceptor drum 9 has an outer diameter of 60IIIn and a thickness of 1
．． A photosensitive layer is provided and formed on a 5 mm aluminum core bar 9b, and a magnetic material provided therein is formed into a coil spring shape of a piano wire with an outer diameter of about 60 Im, which is stretched once and placed inside the photoreceptor core bar 9b. Insert and place. The developing roller 6 is a thin aluminum cylinder with an outer diameter of 20III11, and a rubber magnet is used as the magnetic field generating means (lla) to obtain a magnetic attraction force of 10 to 20 gf per axial length lan. Under the above conditions, the thickness of the developing roller 6 is 0.1m
When an experiment was conducted by changing n+, 0.3 mm, 0.5 no, and 1 m, good rigidity could be obtained with 0.3 rrrn and 0.5 mm.

Note that the material of the developing roller is not limited to aluminum; for example, non-magnetic materials such as stainless steel and plastic can be used.

Furthermore, since the elastic coefficient varies depending on the material, it is necessary to select the section modulus accordingly.

Note that, as in the embodiment shown in FIG. 2, the present invention can be applied not only to the photosensitive drum and the developing roller but also to other pairs of rollers.

Effects As described above, according to the present invention, the pair of rollers in pressure contact with each other in an image forming apparatus can be pressed with a uniform pressing force even if the length of the roller pair is long.
Since the rollers can be brought into close contact and pressed together without curving, a uniform image can be obtained, and there is no need to increase the rigidity of the roller to prevent it from curving, which is also effective in preventing increases in cost. can get.

[Brief explanation of the drawing]

Claims (2)

[Claims] (1) In a pair of cylindrical members used in image forming apparatuses, which rotate while being pressed against each other with a uniform pressure force over the entire axial length, and having axes parallel to each other, a magnetic field is generated inside one of the cylindrical members. and the other cylindrical member has, within its entire length, a member that is attracted by the magnetic field of the magnetic field generating means, and at least one of the pair of cylindrical members has an elastic surface layer. A pair of cylindrical members. (2) In a pair of cylindrical members used in image forming apparatuses, which rotate while being pressed against each other with a uniform pressure force over the entire axial length, and having mutually parallel axes, a magnetic field is generated inside one of the cylindrical members. and the other cylindrical member has, within its entire length, a member that is attracted by the magnetic field of the magnetic field generating means, and at least one of the pair of cylindrical members has appropriate flexibility in the axial direction. A pair of cylindrical members characterized by having: