JP3825976B2 - Image forming apparatus - Google Patents

Description

[0001]
[Technical field to which the invention belongs]
The present invention relates to an electrophotographic image forming apparatus such as a copying machine, a facsimile machine, and a printer, and more particularly, to an image carrier and a configuration of a transfer roller disposed with a predetermined positional relationship with the image carrier.
[0002]
[Prior art]
An image forming apparatus is an apparatus for transferring a toner image formed on a photosensitive drum onto a recording sheet to form an image on the recording sheet. Conventionally, an image forming apparatus capable of obtaining a high-quality print image has been demanded. It has been.
[0003]
FIG. 6 shows a part of a conventional image forming apparatus 1, FIG. 6 (1) shows a cross-sectional view, and FIG. 6 (2) shows a simplified model. As shown in FIG. 6A, the photosensitive drum 2 is formed by a photosensitive drum base tube portion 43 formed in a hollow cylindrical shape and a pair of drum flanges 6 that block the openings at both ends of the photosensitive drum base tube portion 43. Is done. A drum shaft 8 penetrating the photosensitive drum 2 in the axial direction is formed coaxially with the photosensitive drum 2, and the drum shaft 8 is rotatably supported by a pair of drum-side bearings 40 provided at both ends.
[0004]
The transfer roller 3 is formed in a cylindrical shape, and its axis A2 is arranged in parallel with the axis A1 of the photosensitive drum 2. A roller shaft 7 penetrating the transfer roller 3 in the axial direction is formed coaxially with the transfer roller 3, and the roller shaft 7 is rotatably supported by a pair of roller-side bearings 42 provided at both ends. The roller shaft 7 is connected with a pair of elastic urging members 5 in the axial direction, and is provided with a pair of tracking rolls 4 in the axial direction, and a regulating means referred to in the present invention. The roller shaft 7 is pressed toward the drum shaft 8 by the urging member 5, and each tracking roll 4 comes into contact with the photosensitive drum 2, whereby a predetermined amount of space is provided between the photosensitive drum 2 and the transfer roller 3. A gap H is formed. Such a conventional image forming apparatus 1 is disclosed in Japanese Patent Laid-Open No. 9-218549.
[0005]
In such an image forming apparatus 1, since a gap is formed between the photosensitive drum peripheral surface and the transfer roller peripheral surface, the photosensitive drum and the transfer roller do not slide, and the photosensitive drum peripheral surface The photosensitive layer is prevented from being worn and peeled off, and the toner image can be satisfactorily transferred to the recording paper to prevent image distortion.
[0006]
In addition to the image forming apparatus configured to form a predetermined amount of gap between the circumferential surface of the photosensitive drum and the peripheral surface of the transfer roller by the regulating means such as the tracking roll as described above, the photosensitive body is regulated by the regulating means. There is an image forming apparatus configured to press-contact the peripheral surface of the drum and the peripheral surface of the transfer roller with a predetermined pressing force. Such a conventional technique is disclosed in Japanese Patent Laid-Open No. 2-165173.
[0007]
In such an image forming apparatus, the circumferential surface of the photosensitive drum and the circumferential surface of the transfer roller are in contact with each other, and the circumferential surface of the photosensitive drum and the circumferential surface of the transfer roller are pressed against each other with a stable predetermined pressure. Therefore, it is not necessary to increase the transfer electric field (or potential difference) acting between the peripheral surface of the photosensitive drum and the peripheral surface of the transfer roller, and a problem such as a lack of characters occurs due to a high pressure contact force. Therefore, the toner image can be satisfactorily transferred to the recording paper.
[0008]
[Problems to be solved by the invention]
The positional relationship between the outer peripheral surface of an image carrier that carries a toner image, such as a photosensitive drum, a photosensitive belt, and an intermediate transfer member, and the peripheral surface of a transfer roller that transfers the toner image on the image carrier onto a recording sheet is predetermined. In the conventional technology as described above that is regulated by the urging member and the regulating means so as to have the positional relationship, there are the following problems.
[0009]
When the recording paper is inserted between the surface of the image carrier and the surface of the transfer roller, the positional relationship between the photosensitive drum and the transfer roller is such that the recording paper is between the surface of the image carrier and the surface of the transfer roller. Therefore, the recording paper is discharged from between the surface of the image carrier and the surface of the transfer roller, and then returned to the original positional relationship by the urging member. At this time, an impact force acts on the image carrier by inserting and ejecting the recording paper. In particular, when a thick recording paper or an uneven recording paper is inserted, this impact force becomes large.
[0010]
Due to such an impact force, the image carrier is displaced in a short time, and the toner image carried on the image carrier and the unfixed toner image transferred to the recording paper are vibrated, and the image blurs. In addition, there is a problem that image blurring occurs and a high-quality image cannot be obtained. In particular, when the image carrier, the transfer roller, and the like are formed of a hollow body, the vibration of the image carrier is further increased when an impact force is applied to the outer peripheral surface of the hollow portion.
[0011]
Accordingly, the object of the present invention has been made in view of the above problems, and even if there is an impact generated during insertion and ejection of the recording paper, the image carrier and the recording paper are not vibrated and good transfer can be achieved. An object of the present invention is to provide an image forming apparatus that can be used.
[0012]
[Means for Solving the Problems]
The present invention comprises an image carrier that is formed in a cylindrical shape and carries a toner image, and a gear groove is formed on the outer peripheral portion of one axial end portion;
A drum shaft fixed coaxially with the image carrier and protruding from both ends of the image carrier;
Drum side bearings that are respectively provided at both ends of the drum shaft and rotatably support the drum shaft;
A transfer roller that is formed in a cylindrical shape and whose axis is arranged in parallel with the axis of the image carrier, can be rotated around the axis, and can move toward and away from the image carrier;
A roller shaft fixed coaxially with the transfer roller and protruding from both ends of the transfer roller;
Roller-side bearings provided at both ends of the roller shaft, respectively, for rotatably supporting the roller shaft;
An urging member that presses the transfer roller toward the image carrier;
A gear fixed to the roller shaft and meshing with a gear groove formed in the image carrier;
At a location spaced axially outward from the image bearing member, provided on the respective axes of the drum shaft and the roller shaft to form a predetermined gap between the image carrier and the transfer roller by contact with each other look including a regulating means,
The restricting means is an image forming apparatus formed of a shock absorbing material having elasticity .
[0013]
According to the present invention, the image carrier and the transfer roller are positioned in a predetermined positional relationship by the restricting means, and the restricting means is provided axially outward from the image carrier. Therefore, the amount of displacement of the image carrier due to the impact force when inserting and ejecting the recording paper can be reduced. This will be described with reference to FIGS.
[0014]
FIG. 1 shows a part of an image forming apparatus 10 according to an embodiment of the present invention. FIG. 1 (1) shows a cross-sectional view and FIG. 1 (2) shows a simplified model.
[0015]
As shown in FIGS. 1 (1) and 6 (1), in order to compare the conventional apparatus and the apparatus of the present invention, other than the position of the restricting means disposed on the axis of the image carrier, for example, the photosensitive drum The dimensions, the bearing position, the characteristics of the biasing means, the dimensions of the drum shaft, and the material of each member are the same in the conventional apparatus and the apparatus of the present invention. In the conventional apparatus 1, the regulating means 4 abuts on the outer periphery of the photosensitive drum 2 and is provided with the roller-side bearing 40 and predetermined dimensions L 1 and L 2. On the other hand, in the apparatus 10 of the present invention, the regulating means 50 is separated from the photosensitive drum 12, and is provided with the roller side bearing 28 and the predetermined dimensions L3 and L4. Therefore, the dimensions L3 and L4 of the apparatus of the present invention are shorter than the dimensions L1 and L2 of the conventional apparatus as the dimension between the roller side bearing and the regulating means.
[0016]
The magnitude of the impact force generated when inserting and ejecting the recording paper depends on how much the transfer roller is displaced from the shaft of the photosensitive drum. Therefore, when the thickness of the recording paper is the same, the magnitude of the impact force generated in the prior art and the image forming apparatus of the present invention is the same. However, since an impact force is generated at the position of the restricting means for restricting the positions of the photosensitive drum and the transfer roller, the position at which the impact force is applied differs between the case of the prior art and the case of the present invention.
[0017]
Therefore, as shown in FIGS. 1 (2) and 6 (2), the dimensions L3 and L4 between the bearing and the regulating member in the case of the present invention are shorter than the dimensions L1 and L2 in the conventional case. The moment around the bearing is smaller in the present invention. Therefore, the deflection of the drum shaft due to the impact force F is smaller in the present invention, and the displacement amount and vibration of the surface carrying the toner image of the photosensitive drum are smaller in the present invention than in the prior art.
[0018]
As described above, the present invention can reduce the amount of displacement and vibration of the image carrier when an impact force due to the passage of the recording paper is applied, and can satisfactorily transfer the toner image on the image carrier onto the recording paper. . In addition, since the restricting means is provided to be spaced outward from the end of the transfer roller in the axial direction, the amount of displacement of the transfer roller due to the impact force can be reduced when the recording paper is inserted and removed. Further, since the restricting means is formed of an elastic shock absorbing material, even when the recording material is ejected, a portion of the restricting means provided on the drum shaft and a portion provided on the roller shaft collide with each other. The impact can be absorbed, and the impact on the image carrier and recording paper during image transfer can be reduced.
[0019]
In addition to this, in the image forming apparatus of the present invention, it is not necessary to lengthen the size of the image carrier in the axial direction for the contact of the regulating member, so the axial size of the image carrier is reduced. As a result, the cost of an expensive image carrier that is a consumable item can be reduced.
Further, when the gear groove formed on the image carrier and the gear fixed to the roller shaft mesh with each other, when the image carrier is rotated, the transfer roller rotates together with the image carrier. Therefore, the transfer roller rotates in synchronization with the image carrier, and the inserted recording paper can be pinched and discharged.
[0020]
In the present invention, the regulating means is
A first regulating member provided loosely fitted on the drum shaft;
A second regulating member provided loosely fitted on the roller shaft,
A first regulating member and the second regulating member, characterized that you contact with each other.
[0021]
According to the present invention, since the first restricting member and the second restricting member are provided loosely on the drum shaft and the roller shaft, respectively , the first restricting member and the transfer roller are rotated even if the image bearing member and the transfer roller rotate. The member and the second restricting member can always be stationary without rotating in a state where they are in contact with each other. Therefore, each regulating member does not rotate with the image carrier and the transfer roller, and the contact surface of each regulating member is prevented from being worn. Further, it becomes difficult for foreign matters such as toner to adhere to the contact surface of each regulating member, and an accurate predetermined positional relationship can be formed between the image carrier and the transfer roller .
[0022]
The present invention, the first regulating member and the second regulating member, characterized by forming Rukoto resin or hard rubber having elasticity.
[0023]
According to the present invention, the restricting member that is formed of a resin or hard rubber having elasticity, it is possible to have a shock absorption.
[0026]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 2 is a cross-sectional view illustrating a main configuration of the image forming apparatus 10 according to the present embodiment. The image forming apparatus 10 is an apparatus that forms an image on recording paper by an electrophotographic system such as a copying machine or a printer, and is used to form an image on the recording paper around a photosensitive drum 12 that is an image carrier. A mechanism is provided. In order from the upstream side in the rotation direction of the photosensitive drum 12, a charging mechanism 13 for uniformly charging the surface of the photosensitive drum 12, an exposure mechanism 14 for irradiating light for forming an electrostatic latent image on the surface of the photosensitive drum, and photosensitive A developing mechanism 15 for supplying toner to the electrostatic latent image formed on the surface of the photosensitive drum to form a toner image, and a transfer for transferring the toner image formed on the surface of the photosensitive drum to recording paper as a recording medium A roller 16, a cleaning blade 17 for cleaning the surface of the photosensitive drum, and a slow-power lamp 18 for removing residual charges on the surface of the photosensitive drum are arranged side by side.
[0027]
In order to form an image in the image forming apparatus 10, first, the surface of the photosensitive drum 12 is uniformly charged by the charging mechanism 13, and the charged photosensitive drum surface is irradiated with laser light by the exposure mechanism 14. An electrostatic latent image is formed, toner is supplied to the electrostatic latent image by the developing mechanism 15 to form a toner image, and the toner image is sent between the transfer roller 16 and the photosensitive drum 12. The image is transferred onto the recording paper, and the recording paper is heated by a heat fixing mechanism (not shown) to fix the toner image on the recording paper.
[0028]
The toner remaining on the surface of the photoconductive drum after the image transfer is removed by the cleaning blade 17, and the electric charge remaining on the surface of the photoconductive drum is gradually discharged by the gradual discharge lamp, and the image forming apparatus prepares for the next image formation. It is done.
[0029]
FIG. 3 is a cross-sectional view showing the vicinity of the transfer roller of the image forming apparatus 10 as viewed from the recording paper insertion side. As shown in FIGS. 1 and 3, the image forming apparatus 10 includes a photosensitive drum 12, a flange 20, a transfer roller 16, a first restricting member 22, a second restricting member 23, and an urging member 24.
[0030]
The photoconductor drum 12 is formed by a photoconductor drum base tube portion 12a formed in a hollow cylindrical shape and a pair of drum flanges 20 that block openings at both ends of the photoconductor drum base tube portion 12a. A drum shaft 21 penetrating the photosensitive drum 2 in the axial direction is formed coaxially with the photosensitive drum 12, and the drum shaft 21 is rotatably supported by a pair of drum-side bearings 28 provided at both ends.
[0031]
The transfer roller 16 is formed in a cylindrical shape, and its axis A4 is arranged in parallel with the axis A3 of the photosensitive drum 12. A roller shaft 25 penetrating the transfer roller 16 in the axial direction is formed coaxially with the transfer roller 16, and the roller shaft 25 is rotatably supported by a pair of roller-side bearings 29 provided at both ends. The roller side bearing 29 is mounted in the long hole 30 of the frame 27 of the image forming apparatus 1. The roller-side bearing 29 can be displaced toward the drum shaft 21 by the long hole 30, whereby the roller shaft 25 supported by the roller-side bearing 29 is supported so as to be close to and away from the drum shaft 21. Therefore, in the embodiment, the transfer roller 16 is disposed below the photosensitive drum 12 and supported so as to be movable up and down.
[0032]
A gear b is fixed to one end of the drum shaft 21 and meshes with a gear a to which a rotational force is transmitted from a rotation transmission mechanism (not shown). As a result, the rotational force from the rotation transmission mechanism is transmitted to the photosensitive drum 12 via the gear a, the gear b, and the drum shaft 21. Further, a gear groove 40 is formed on the peripheral surface of one flange attached to the photosensitive drum 12, that is, the flange 20 on the side where the gear b is formed.
[0033]
A gear d is fixed to one end of the roller shaft 25. The gear d meshes with the gear groove 40 formed in the aforementioned flange. As a result, the rotation of the photosensitive drum 12 is transmitted to the transfer roller 16. Therefore, the transfer roller 16 rotates in synchronization with the photosensitive drum 12, and can hold and insert the inserted recording paper.
[0034]
A biasing member 24 is provided on each of the pair of roller shaft side bearings 29. The urging member 24 has elasticity and is constituted by, for example, a spring. As a result, the urging member 24 presses the transfer roller 16 toward the photosensitive drum 12.
[0035]
FIG. 4 is a front view showing a part of the image forming apparatus 10 of FIG. The first restricting member 22 and the second restricting member 23, which are the restricting means 50, are formed in a disc shape, and are provided in pairs on both sides with respect to the photosensitive drum 12 and the transfer roller 16. The roller shaft 25 is urged toward the drum shaft 21 by the urging member 24, and the first restricting member 22 and the second restricting member 23 come into contact with each other. A predetermined gap H is formed between the two. This predetermined gap H is set smaller than the thickness of the recording paper.
[0036]
The first regulating member 22 is loosely fitted in a rotatable state with respect to the drum shaft 21 at a position separated from the photosensitive drum 12. Similarly, the second regulating member 23 is loosely fitted in a rotatable state with respect to the roller shaft 25 at a position separated from the transfer roller 16. The first restricting member 22 and the second restricting member 23 have impact absorbing means, and are formed of an impact absorbing material having elasticity such as resin or hard rubber.
[0037]
5 is a side view of FIG. 4. FIG. 5 (1) shows a state before the recording paper 19 is inserted, and FIG. 5 (2) shows a state where the recording paper 19 is inserted. As shown in FIG. 5A, the recording paper 19 is conveyed toward the gap H between the photosensitive drum 12 and the transfer roller 16, and as shown in FIG. It is inserted between the transfer roller 16. At this time, since the thickness of the recording paper 19 is larger than the gap H between the photosensitive drum 12 and the transfer roller 16, the transfer roller 12 is separated from the photosensitive drum 12 and between the photosensitive drum 12 and the transfer roller 16. , And the first restricting member 22 and the second restricting member 23 are separated from each other. The transfer roller 16 is pressed by the biasing member 24 so as to be close to the photosensitive drum 12, and the recording paper 19 passes between the photosensitive drum 12 and the transfer roller 16 against this pressing force. . At the time of discharging, the first restricting member 22 and the second restricting member 23 come into contact again by the spring force of the biasing member 24, and the distance between the photosensitive drum 12 and the transfer roller 16 becomes a predetermined gap dimension H. Return.
[0038]
That is, an impact is generated when the recording paper is inserted and ejected, but the first restricting member 22 and the second restricting member 23 are mounted at positions separated from the photosensitive drum 12 and the transfer roller 16, respectively. The moment to be applied can be reduced, and the stagnation of the photosensitive drum and the transfer roller can be reduced. Furthermore, since the first and second regulating members are made of an impact absorbing material, the impact force and the vibration due to the impact force are absorbed. By reducing the vibration applied to the photosensitive drum 12 and the recording paper 19 in this way, the toner image formed on the photosensitive drum 12 and the unfixed toner image transferred to the recording paper are not subjected to vibration. Further, it is possible to prevent image bleeding and image blurring and form a good image.
[0039]
Further, since the first restricting member 22 and the second restricting member 23 are loosely fitted to the drum shaft 21 and the roller shaft 25, respectively, the first restricting member 22 and the roller shaft 25 are rotated even if the drum shaft 21 and the roller shaft 25 rotate. The member 22 and the second restricting member 23 can be stationary in a contact state without rotating. Accordingly, the first restricting member 22 and the second restricting member 23 do not rotate together with the photosensitive drum 12 and the transfer roller 16, and the contact surfaces of the first restricting member 22 and the second restricting member 23 are worn. It is prevented. Further, no foreign matter such as toner adheres to the contact surface, and an accurate and constant gap H can be formed between the photosensitive drum 12 and the transfer roller 16.
[0040]
The above-described embodiments are merely examples of the invention, and the configuration can be changed within the scope of the invention. For example, in this embodiment, the restricting means is used to form a predetermined gap H between the photosensitive drum as the image carrier and the transfer roller. However, the present invention is not limited to this. In addition, for example, an image forming apparatus that restricts the image carrier with the transfer roller so as to come into contact with the image carrier with a predetermined pressure is also included.
[0041]
In the present embodiment, the first restricting member and the second restricting member are brought into contact with each other to restrict the photosensitive drum and the transfer roller to a predetermined positional relationship. However, the predetermined position is determined using one restricting member. You may regulate on the relationship. For example, the photosensitive drum and the transfer roller are regulated to a predetermined positional relationship by contacting the first regulating member and the shaft of the transfer roller, or contacting the second regulating member and the shaft of the image carrier. Also good.
[0042]
The at least one of the first and second regulating members, only to be arranged between the axis of the well photoreceptor drum and the transfer roller may not be provided directly to the shaft, the other to be coaxial with the axis e.g. A member may be provided and provided between the axes via this member. Further, the first and second restricting members do not necessarily have to be disk-shaped and may have other shapes.
[0043]
The image bearing member has been described as an example of a photosensitive drum, but a photosensitive belt and an intermediate transfer member may also be used. In the case of the photosensitive belt, a regulating means is provided between the axis of the shaft facing the transfer roller and the axis of the transfer roller among the plurality of shafts that rotate the photosensitive belt without loosening.
[0044]
【The invention's effect】
According to the present invention, it is possible to reduce the amount of displacement of the image carrier and the vibration applied to the image carrier itself when an impact force due to the passage of the recording paper is applied. As a result, it is possible to prevent image blurring or the like that has occurred at the time of inserting and ejecting recording paper, and to obtain good image quality.
[0045]
Further, since the dimension of the image carrier for contacting the regulating means is not increased in the axial direction, the dimension of the image carrier in the axial direction can be reduced, and it is a consumable but expensive image carrier. The cost can be reduced.
In addition, the gear groove formed on the image carrier and the gear fixed to the roller shaft mesh with each other, so that the transfer roller rotates in synchronization with the image carrier, pinches and inserts the inserted recording paper. Can be made.
[0046]
Since or regulation means capable of absorbing shocks, it is possible to further reduce the impact on the image bearing member and the recording sheet during image transfer. Thereby, better image quality can be obtained.
[0047]
In addition, according to the present invention, wear of the contact surfaces where the first and second restricting members are in contact with each other and adhesion of foreign matter are prevented, so that an accurate and constant gap is provided between the image carrier and the transfer roller. Can be formed. As a result, a stable pressing force can be applied to the recording paper during image transfer, and the toner image can be transferred to the recording paper without unevenness.
Further, according to the present invention, each regulating member can be made of an elastic resin or hard rubber, so that it can have a shock absorbing property.
[Brief description of the drawings]
FIG. 1 shows a part of an image forming apparatus 10 according to an embodiment of the present invention, FIG. 1 (1) shows a cross-sectional view, and FIG. (2) shows a model diagram.
FIG. 2 is a cross-sectional view showing a main configuration of an image forming apparatus 10 according to an embodiment of the present invention.
3 is a cross-sectional view showing the vicinity of a transfer roller of the image forming apparatus 10. FIG.
4 is a front view showing a part of the image forming apparatus 10 of FIG. 3. FIG.
FIG. 5 is a side view of FIG. 4;
6 shows a part of a conventional image forming apparatus 1. FIG. 6A is a cross-sectional view, and FIG. 6B is a model diagram.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Image forming apparatus 12 Photosensitive drum 16 Transfer roller 19 Recording paper 20 Flange 21 Drum shaft 22 1st control member 23 2nd control member 24 Energizing member 25 Roller shaft 27 Frame 28, 29 Bearing 30 Long hole 50 Control means A3 Photosensitive drum axis A4 Transfer roller axis

Claims (3)

An image carrier that is formed in a cylindrical shape and carries a toner image, and a gear groove is formed on the outer peripheral portion of one end in the axial direction;
A drum shaft fixed coaxially with the image carrier and protruding from both ends of the image carrier;
Drum side bearings that are respectively provided at both ends of the drum shaft and rotatably support the drum shaft;
A transfer roller that is formed in a cylindrical shape and whose axis is arranged in parallel with the axis of the image carrier, can be rotated around the axis, and can move toward and away from the image carrier;
A roller shaft fixed coaxially with the transfer roller and protruding from both ends of the transfer roller;
Roller-side bearings provided at both ends of the roller shaft, respectively, for rotatably supporting the roller shaft;
An urging member that presses the transfer roller toward the image carrier;
A gear fixed to the roller shaft and meshing with a gear groove formed in the image carrier;
At a location spaced axially outward from the image bearing member, provided on the respective axes of the drum shaft and the roller shaft to form a predetermined gap between the image carrier and the transfer roller by contact with each other look including a regulating means,
The image forming apparatus according to claim 1, wherein the restricting means is formed of a shock absorbing material having elasticity . The regulating means is
A first regulating member provided loosely fitted on the drum shaft;
A second regulating member provided loosely fitted on the roller shaft,
The image forming apparatus according to claim 1, wherein the first regulating member and the second regulating member, characterized that you contact with each other. The first regulating member and the second regulating member, an image forming apparatus according to claim 2, wherein the formed Rukoto resin or hard rubber having elasticity.

Images