JPH10207183A - Voltage applying device and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To bring the arm part of a spring as an elastic member for applying a voltage to a voltage applying member (electrifying roller) into stable contact with the conductive shaft part of the voltage applying member (electrifying roller), at a fixed position. SOLUTION: The vicinity of the root part of the arm part 36a of the spring 36 is abutted on a spring stopper part 40a formed in the end part, of an electrode 40, to regulate the movement of the spring 36 and attain positioning, so that the arm part 36a of the spring 36 comes into stable contact with a core metal 31 as the conductive shaft part of the electrifying roller 30, at the fixed position, to obtain the excellent application of the voltage.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a voltage applying device for applying a voltage to a member to be charged, such as an electrophotographic photosensitive member or a dielectric, and a copy utilizing an electrophotographic process provided with the voltage applying device. And image forming apparatuses such as laser beam printers and facsimile machines.

[0002]

2. Description of the Related Art In a conventional image forming apparatus utilizing an electrophotographic process, a corona charger is frequently used as a means for charging a drum-type electrophotographic photosensitive member (hereinafter simply referred to as a photosensitive member) as an image carrier. I was In this method, a corona charger is arranged so as to face a photoreceptor in a non-contact manner, and the surface of the photoreceptor is charged to a predetermined polarity and potential by exposing the surface of the photoreceptor to a discharge corona generated by the corona charger.

In recent years, contact charging devices (direct charging devices) have been put to practical use because they have advantages such as lower ozone and lower power than corona chargers. In this method, a charging member to which a voltage has been applied is brought into contact with the photoconductor to charge the surface of the photoconductor to a predetermined polarity and potential. A contact charging device using a rotatable charging roller as the charging member is:
It is preferably used from the viewpoints of charging and contact safety.

As a voltage application method for applying a charging bias voltage to a charging roller, conventionally, as shown in FIG. 10, for example, a voltage is applied to a power supply side of a coil-shaped spring 36 for pressing a charging roller 30 against a photosensitive member (not shown). An arm portion 36a extending from one end side in contact with the electrode 40 electrically connected,
A method has been proposed in which a voltage is applied by bringing the core metal 31 of the charging roller 30 into contact with the metal core 31. The charging roller 30 has a core 31
Is rotatably supported by a bearing 35 that rotatably supports the spring 35, and the other end of the spring 36 is in contact with the bearing 35.
Reference numeral 42 denotes a thrust stopper that restricts movement of the charging roller 30 in the longitudinal direction.

[0005]

However, in the above-described conventional method of applying a voltage to the charging roller, the position of the arm 36a extending from one end of the spring 36 in contact with the metal core 31 is not regulated. In addition, the position of the arm 36a is not stable, and has the following problems.

Since the position of the arm portion 36a is not stable, the contact pressure between the arm portion 36a and the metal core 31 varies, and if the contact pressure is low, poor conduction is likely to occur. In this case, the rotation of the charging roller 30 driven by the photosensitive member is hindered, and good charging performance cannot be obtained.

Further, since the position of the arm portion 36a is not constant, the tip of the arm portion 36a pierces the rubber portion of the charging roller 30 when the charging roller 30 is assembled or the charging operation is performed. The leading end of the portion 36a contacts the side end surface of the charging roller 30, and the charging roller 30
Or hurt.

Accordingly, the present invention provides a voltage applying device which can always apply a stable voltage by stably bringing an arm portion of a spring, which is an elastic member, into contact with a predetermined position at a voltage applying member (charging roller). And an image forming apparatus.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has an elastic member having one end electrically connected to a power supply side, wherein the elastic member includes a coil spring portion, and the coil spring. A conductive arm portion extending from one end of the portion, and a pressurizing contact between a rotatable voltage applying member and an object to be applied by an elastic force of the coil spring portion, and the arm portion directly or through a conductive member. A voltage applying device that applies a voltage to the voltage applying member by contacting the conductive shaft that is a rotation axis of the voltage applying member with a regulating member that regulates the position of the arm; The position of the arm portion that contacts the arm is regulated.

[0010] Further, it is preferable that the arm portion is brought into contact with the conductive shaft portion at a substantially right angle or near a right angle with respect to the axial direction of the conductive shaft portion by the regulating member. Further, it is preferable that a tip portion of the arm portion is bent in a direction opposite to the voltage applying member along an axial direction of the conductive shaft portion.

An image carrier for carrying an image; a charging roller for contacting and charging the image carrier; an exposing means for forming an electrostatic latent image on the image carrier; Developing means for forming a toner image, a transfer roller for contact-transferring the toner image to a transfer material at a transfer portion, and an elastic member having one end electrically connected to a power supply, wherein the elastic member is a coil spring portion. And a conductive arm portion extending from one end of the coil spring portion, and the charging roller and / or the transfer roller, which are rotatable by the elastic force of the coil spring portion, are brought into pressure contact with the image carrier. A bias voltage is applied to the charging roller and / or the transfer roller by bringing the arm into contact with the charging roller and / or a conductive shaft that is a rotation shaft of the transfer roller directly or via a conductive member. In the image forming apparatus is characterized in that for regulating the position of the arm portion provided with a regulating member for regulating the position of the arm portion in contact with the conductive shaft portion. (Operation) According to the configuration of the present invention, the position of the arm portion of the spring is regulated by the regulating member, so that the arm portion of the spring comes into stable contact with the conductive shaft portion of the voltage applying member at a fixed position. And good voltage application can be performed.

[0012]

Embodiments of the present invention will be described below with reference to the drawings.

(First Embodiment) FIG. 1 is a schematic configuration diagram showing an image forming apparatus in which a voltage applying device according to the present embodiment is applied to a charging device. The image forming apparatus according to the present embodiment is a laser beam printer using a detachable electrophotographic process with a process unit (process cartridge). FIG. 2 is an enlarged cross-sectional view of the process unit.

In FIG. 1, reference numeral 1 denotes a lower housing of a laser beam printer (image forming apparatus), and 2 denotes an upper housing thereof. The upper housing 2 includes a lower housing 1 around a hinge support shaft 3.
Is freely openable and closable between a closed state shown by a solid line and an opened state shown by a two-dot chain line.

Reference numeral 4 denotes a process unit. In this embodiment, a drum type photosensitive member 5, a charging device 6, a developing device 7, and a cleaning device 8 are assembled to a frame 9 and are detachable from a printer main body. As a unit. The process unit 4 opens the upper housing 2 of the printer from the lower housing 1, inserts it into the unit mounting part 10 inside the printer, and stores it therein. It will be in the state of being attached to.

Numeral 11 denotes a laser scanner unit (exposure device), numeral 12 denotes a cassette, numeral 13 denotes a paper feed roller, numeral 14 denotes a pair of registration rollers, numeral 15 denotes a transfer guide, numeral 16 denotes a transfer charger, numeral 17 denotes a conveying member, and numeral 18 denotes a fixing unit. These are provided on the upper housing 2 side of the printer.

In the above-described laser beam printer (image forming apparatus), at the time of forming an image, the photosensitive member 5 is rotationally driven at a predetermined peripheral speed (process speed) clockwise as indicated by an arrow based on a print start signal. A charging roller (charging member) of the charging device 6 to which a bias voltage obtained by superimposing an AC voltage on a DC voltage in contact with the peripheral surface of the charging device 6 is applied.
Due to 30, the surface of the photoconductor 5 is uniformly and uniformly charged.

A laser beam L modulated according to the time-series electric digital pixel signal of the target image information is output from the laser scanner unit 11, and the laser beam L
Is reflected by the mirror 11a and is exposed to the exposure window 9a of the frame 9.
Then, the light enters the process unit 4 and hits the charged surface of the photoconductor 5, and the surface of the photoconductor 5 is scanned by the laser beam L. As a result, an electrostatic latent image corresponding to the target image information is formed on the surface of the photoconductor 5. This electrostatic latent image is developed on a developing sleeve 7a of a developing device 7 with toner applied with a layer thickness regulated by a developing blade 7b.

On the other hand, the paper feed rollers 13
Transfer paper P such as paper is fed one by one, and the transfer position between the photoconductor 5 and the transfer charger 16 is transferred through the transfer guide 15 through the transfer guide 15 in accordance with the timing of the emission of the laser light L by the registration roller pair 14. Transported to As a result, the formed toner image on the photoconductor 5 side is sequentially transferred to the surface of the transfer material P.

The transfer material P on which the toner image has been transferred is a photosensitive member 5
After being separated from the front surface, the sheet is conveyed to a fixing device 18 by a conveying member 17 and passes through a nip portion between a fixing roller 18a and a pressure roller 18b to undergo a toner image fixing process.
Is discharged to the paper discharge tray 20. Photoreceptor 5 after transfer
Is subjected to image formation starting from charging repeatedly after the residual toner is removed by the blade 8a of the cleaning device 8.

In FIG. 2, reference numeral 9c denotes an opening / closing cover for the exposure opening 9b of the photoreceptor surface of the process unit 4. When the process unit 4 is removed from the printer or when the upper housing 2 is opened, the closed position is set. To cover and protect the photoreceptor surface.

FIG. 3 is a sectional view of the charging roller 30.
The charging roller 30 includes a conductive elastic layer 32 on a conductive metal core 31 such as SUS, and a high-resistance elastic layer 3 on the conductive elastic layer 32.
Third, a protective film 34 is provided on the surface. The conductive elastic layer 32 is made of a material obtained by dispersing carbon in EPDM, and functions to guide a bias voltage supplied to the metal core 31. The high-resistance elastic layer 33 is made of urethane rubber or the like, and a layer containing a small amount of conductive fine powder (for example, carbon) is given as an example. Even in this case, the leak current to the photosensitive member 5 is limited to prevent the bias voltage from dropping sharply. The protective film 34 is made of N-methylmethoxylated nylon, and has a conductive elastic layer 32 and a high-resistance elastic layer 3.
The composition material 3 serves to protect the surface of the photoconductor 5 from being deteriorated by touching the photoconductor 5.

FIG. 4 is a schematic diagram showing a voltage application device for applying a voltage to the charging roller 30. Although not shown in the figure, the photosensitive member 5 is rotatably held at both ends between side plates of the frame 9. In this figure, G is a drum gear provided concentrically and integrally on one end side of the photoconductor 5. When the process unit 4 is mounted in the printer main body in a predetermined manner, the drum gear G is engaged with a driving gear (not shown) on the printer main body side, and the rotational force of the driving gear is transmitted to the photoconductor 5 via the drum gear G. Then, the photosensitive member 5 is driven to rotate.

Both ends of a core metal 31 (only one side is shown in the figure), which is a rotating shaft, are respectively supported by insulating bearings 35, and both bearings 35 are placed between the bearing 35 and the frame 9 (not shown). The charging roller 30 is brought into contact with the photoreceptor 5 in a predetermined pressure by being deflected in the direction of the photoreceptor 5 by a coiled spring 36 as a conductive elastic member such as SUS which is contracted. The charging roller 30 rotates following the rotation of the photoconductor 5. Both end surfaces of the metal core 31 in the axial direction of the charging roller 30 abut against a thrust stopper 42 integrally formed with the bearing 35, and the axial movement of the charging roller 30 is restricted. The thrust stopper 42 is formed of an insulating resin together with the bearing 35. An arm 36a extending from the root of the spring 36 is in pressure contact with the shaft peripheral surface 31b of the metal core 31. The arm 36a is positioned by a spring stopper 40a provided on the electrode 40.

The electrode 40 has one end extending toward the upper end of the spring 36, and the upper end of the spring 36 is brought into contact with the extended portion of the electrode 40 and received. The spring 36 is conductive, and the bearing 35 is insulative, so that the electrode 40 and the core 31 are electrically connected via the spring 36. The base end of the electrode 40 is fixedly supported by the process unit 4 by a heat cascade or the like. The electrode 40 and the power receiving terminal 41a of the process unit 4 are also in contact with each other and are electrically connected. When the process unit 4 is mounted at a predetermined position on the print main body, the power receiving terminal 41a on the process unit 4 and the power supply terminal 41b on the print main body come into contact, and the power supply 38 on the print main body side and the process unit 4 side Is electrically connected to the electrode 40. Next, the configuration of the spring 36 for applying a voltage to the charging roller 30 will be described in detail with reference to FIGS.

FIGS. 5A, 5B and 5C show a spring 36.
Is a triangular diagram, and the spring 36 is a coil spring 3
6c and an arm portion 36a extending from a root portion 36a1 of the coil spring portion 36c.

The arm portion 36a of the spring 36 is provided in a direction substantially perpendicular to the central axis CL1 of the charging roller 30 or at a direction not so much inclined from the perpendicular direction when pressure is generated (see FIG. 7). The distal end portion 36b of the arm portion 36a is bent in a direction substantially parallel to the central axis CL1 of the charging roller 30 and in a direction opposite to the charging roller 30 when the spring 36 is assembled (FIG. 7).
reference). Accordingly, the tip end portion 36b of the spring 36 does not stick into the rubber portion on the surface of the charging roller 30 at the time of assembling or the like, and does not damage the side end surface 30a of the charging roller 30. The arm 36a has a base 36a1.
And the coil spring portion 3 from the root portion 36a1.
6c.

As shown in FIGS. 6 and 7, the electrode 40 has a positioning hole 40b near the contact portion with the spring 36, and a spring stopper portion 40a having a bent end portion.

The spring stopper 40a of the electrode 40 is formed slightly larger than the outer diameter of the projection 4a provided on the process unit 4. The electrode 40 is assembled so that the positioning hole 40b fits into the projection 4a. I have. Projection 4
Since a is projected from the positioning hole 40b even after the electrode 40 is assembled, and the outer diameter of the projection 4a is smaller than the inner diameter of the coil spring portion 36c, the spring 36 is positioned by the projection 4a ( The protrusion 4a and the positioning hole 40b are positioned on the center line CL2 of the coil spring 36c).

Then, the spring 36 is connected to the projection 4a of the electrode 40.
6 (from the state of FIG. 6 to the state of FIG. 7), and the spring 36 is deflected by a predetermined amount to generate a pressing force (a state when the apparatus is used). At this time, as shown in FIG. 8, the arm 36a of the spring 36 moves from the position indicated by the broken line to the position indicated by the solid line in the direction of the arrow a1 by being pushed by the metal core 31 of the charging roller 30.

The force in the direction of the arrow a1 is as shown in FIG.
When represented by (b) and (c), respectively, arrow a1 and arrow a
2 and an arrow a3. In FIG. 5B, the force in the direction of the arrow a2 causes the spring 36 to move the center line CL2 of the coil spring portion 36c.
Generate a clockwise turning moment around. This moment is in the direction of arrow m in FIGS. 6 and 7, and a force is applied to the spring 36 so as to rotate in the direction of arrow m.

On the other hand, the root 36 of the arm 36a of the spring 36
By contacting a1 with the spring stopper 40a at the end of the electrode 40, the rotation of the spring 36 in the direction of the arrow m is suppressed, and the arm 36a of the spring 36 is positioned. Further, even when the arm portion 36a of the spring 36 slides on the core metal 31 of the charging roller 30 in a state when the apparatus is used, the arm portion 36a of the spring 36
7, the arm 36a of the spring 36 is connected to the center line CL1 of the core metal 31 of the charging roller 30 in FIG.
The bearing 35 is slightly bent in the direction, and comes into contact with the surface of the bearing 35 facing the rubber portion 30a on the side of the charging roller 30.

As described above, in the present embodiment, the spring 36
Is reliably and stably positioned between the spring stopper portion 40a at the end of the electrode 40 and the surface of the bearing 35 facing the rubber portion 30a on the side of the charging roller 30, so that the spring 3
The arm 36a of the sixth roller 6 can slide on the core metal 31 of the charging roller 30 stably, and can apply a voltage to the charging roller 30.

Further, at the time of assembling the spring 36, the arm 36a of the spring 36 is positioned by the spring stopper portion 40a, so that it is not necessary to assemble the spring 36 accurately while positioning it. Can be improved.

The tip 36 of the arm 36a of the spring 36
b faces outward on the opposite side of the charging roller 30,
When incorporating the charging roller 30 or using the device, the arm 36
a is prevented from sticking into the rubber portion on the surface of the charging roller 30 or damaging the side end surface 30a, thereby improving the yield. By reducing the possibility of damaging the device, it is possible to protect the worker, and at the same time, to improve the ease of handling and the productivity.

Although the bearing 35 is made of an insulating resin, one or more power supply paths may be added by using a conductive resin as the bearing on the power supply side. As a result, the reliability of power supply can be dramatically increased with a slight increase in cost.

In the above embodiment, the charging roller is used as the charging member. However, the present invention is not limited to this. For example, a transfer member used for a transfer unit may be used, and a bias voltage may be applied using another roller. The present invention can be applied to any device that performs the above.

(Second Embodiment) In the first embodiment described above, a spring stopper for positioning the arm 36a of the spring 36 is provided on the electrode 40, but in this embodiment, FIG.
As shown in FIG. 7, a spring stopper 4b is provided integrally with the process unit 4 side. Another configuration is the first embodiment.

As described above, in this embodiment, since the spring stopper 4b is provided integrally with the process unit 4, the positional accuracy between the projection 4a on the process unit 4 and the spring stopper 4b is further improved. The voltage can be applied while the sliding position between the arm portion 36a of the spring 36 and the metal core 31 of the charging roller 30 is more stable.

[0040]

As described above, according to the present invention, good power supply can be performed by the arm portion of the spring stably coming into contact with the conductive shaft portion at a fixed position.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram illustrating an image forming apparatus according to a first embodiment of the present invention.

FIG. 2 is a schematic diagram showing a process unit of the image forming apparatus according to the first embodiment of the present invention.

FIG. 3 is a cross-sectional view illustrating a charging roller of the image forming apparatus according to the first embodiment of the present invention.

FIG. 4 is a schematic diagram illustrating a voltage application device that applies a voltage to a charging roller of the image forming apparatus according to the first embodiment of the present invention.

FIGS. 5A, 5B, and 5C are diagrams illustrating a spring for applying a voltage to a charging roller by a triangular method.

FIG. 6 is a diagram showing a configuration around a spring for applying a voltage to a charging roller.

FIG. 7 is a diagram showing a positional relationship around a spring for applying a voltage to a charging roller before assembly.

FIG. 8 is a diagram illustrating a bending direction of an arm portion of a spring for applying a voltage to a charging roller during assembly.

FIG. 9 is a schematic diagram illustrating a voltage application device that applies a voltage to a charging roller of an image forming apparatus according to a second embodiment of the present invention.

FIG. 10 is a schematic diagram illustrating a voltage application device that applies a voltage to a charging roller of an image forming apparatus according to a conventional example.

[Explanation of symbols]

 4 Process Unit 4a Projection 4b, 40a Spring Stopper (Regulator) 5 Photoconductor (Image Carrier) 6 Charging Device 7 Developing Device (Developing Means) 11 Laser Scanner Unit (Exposing Means) 16 Transfer Charger 18 Fixing Device 30 Charging Roller 31 Core (conductive shaft) 36 Spring (elastic member) 36a Arm 36b Tip 36c Coil spring 40 Electrode

Claims (6)

[Claims] An elastic member having one end electrically connected to a power supply side; the elastic member having a coil spring portion and a conductive arm extending from one end of the coil spring portion; The elastic force of the rotatable voltage applying member is brought into pressure contact with the object to be applied, and the arm portion is brought into contact with a conductive shaft portion which is a rotation axis of the voltage applying member directly or via a conductive member. In a voltage application device that applies a voltage to a voltage application member, a regulating member that regulates the position of the arm is provided to regulate the position of the arm that contacts the conductive shaft. apparatus. 2. The voltage applying device according to claim 1, wherein the arm portion is brought into contact with the conductive shaft portion at a substantially right angle or an angle close to a right angle with respect to an axial direction of the conductive shaft portion by the regulating member. apparatus. 3. The voltage application device according to claim 1, wherein a tip portion of the arm portion is bent in a direction opposite to the voltage application member along an axial direction of the conductive shaft portion. 4. An image carrier for carrying an image, a charging roller for contacting and charging the image carrier, an exposure unit for forming an electrostatic latent image on the image carrier, and developing the electrostatic latent image. Developing means for forming a toner image, a transfer roller for contact-transferring the toner image to a transfer material at a transfer portion, and an elastic member having one end electrically connected to a power supply, wherein the elastic member is a coil spring portion. And a conductive arm portion extending from one end of the coil spring portion, and the charging roller and / or the transfer roller, which are rotatable by the elastic force of the coil spring portion, are brought into pressure contact with the image carrier. And applying a bias voltage to the charging roller and / or the transfer roller by bringing the arm into contact with the charging roller and / or a conductive shaft that is a rotation shaft of the transfer roller directly or via a conductive member. The image forming apparatus according to claim 1, wherein a regulating member that regulates the position of the arm is provided to regulate the position of the arm that contacts the conductive shaft. 5. The image forming apparatus according to claim 4, wherein the arm is brought into contact with the conductive shaft at a substantially right angle or an angle close to a right angle with respect to an axial direction of the conductive shaft by the regulating member. apparatus. 6. The image forming apparatus according to claim 4, wherein a tip portion of the arm portion is bent in a direction opposite to the charging roller and / or the transfer roller along an axial direction of the conductive shaft portion. apparatus.