JPH04268584A - Contact electrifier - Google Patents

Abstract

PURPOSE:To provide a contact electrifier which can secure uniform abutting with respect to the surface of the body to be electrified of an electrifying member, easily, and to remove electrification unevenness caused by ununiform abutting, has durabilities, and further, is reduced in cost, as a contact electrifier which electrify-controls the surface of the body to be electrified by abutting the electrifying member on the body to be electrified and relatively moving both of them. CONSTITUTION:The electrifying member 2 is composed of a conductive member 2a on which a voltage is applied, and a tube-like resistant layer member 2b rotatively, armoring the conductive member 2a. Then, the conductive member 2a is abutted on the body to be electrified via the resistant layer member 2b armoring the conductive member 2a.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a contact charging device that charges (including neutralizes) the surface of an object to be charged by bringing a charging member into contact with an object and moving the two relative to each other.

0002

[Prior Art] For example, in image forming devices such as electrophotographic devices (copying machines, printers, image display devices, etc.) and electrostatic recording devices, image carriers (charged objects) such as photoreceptors and dielectric materials are charged. Conventionally, corona discharge devices have been widely used as processing devices.

A corona discharge device is effective as a device for uniformly charging the surface of an object to be charged to a predetermined polarity and potential.
It has problems such as requiring a high-voltage power supply and generating a relatively large amount of undesirable corona products such as ozone due to corona discharge.

On the other hand, the contact charging device as described above, which charges the object by bringing the charging member into contact with the object, can lower the applied voltage power source and minimize the generation of corona products such as ozone. For example, in image forming apparatuses, its use as a charging device for charging an image bearing member is progressing.

[0005] The present applicant also basically sets the voltage applied to the charging member to be a superimposed voltage (oscillating voltage) of the DC voltage Vdc and the AC voltage Vac, for the purpose of uniformly charging the object to be charged. A contact charging method or device is proposed (Japanese Patent Application Laid-open No. 149668/1986/63-
149669, etc.).

As a specific example, as shown in FIG. 7, for example, an electrophotographic photosensitive drum 1, which is rotationally driven, serves as an object to be charged.
(hereinafter referred to as a photosensitive drum), for example, a roller-shaped conductive member 20 as a charging member (hereinafter referred to as a charging roller) is pressed by a spring 20d and brought into contact with the charging roller 2.
By applying a superimposed voltage (oscillating voltage) of a DC voltage Vdc and an AC voltage Vac having a peak-to-peak voltage Vpp that is more than twice the charging start voltage of the photoreceptor from the power supply 4 to can be uniformly charged by contact. The charged potential of the photosensitive drum 2 is determined by the applied DC voltage. The applied alternating current voltage acts to equalize the charged potential. 21 indicates the charged area, and A is its width (approximately 10 to 3
0 μm).

The charging roller 20 of this example has a conductive core metal 20a.
A conductive elastic layer 20b made of conductive rubber or the like is formed concentrically with the core metal into a roller shape by molding or the like, and rotates as the photosensitive drum 1 rotates. A voltage is applied from the power source 4 to the core metal 20a of the charging roller 20 via the contact spring 20c. The charging member is not limited to the roller type described above, but may also be a blade type. FIG. 8 shows an example using a blade-type charging member (charging blade) 22.

[0008]

[Problems to be Solved by the Invention] One of the problems with contact charging devices is that the charging member is connected to a charging roller 20 as shown in FIG.
In this case, it is difficult to uniformly contact the charging roller 20 with the surface of the charged object, and uneven charging may occur due to uneven contact. The charging blade 22 as shown in FIG. 8 requires a considerable amount of cost due to material costs and processing costs for the layers, and wear progresses due to relative movement and friction with the surface of the charged object, resulting in a relatively short life. Can be mentioned.

The present invention improves the structure of the charging member so that it is easy to ensure that the charging member is in uniform contact with the surface of the object to be charged, thereby eliminating uneven charging due to uneven contact, and is durable. The purpose is to provide a low-cost contact charging device.

0010

[Means for Solving the Problems] The present invention is a contact charging device characterized by the following configuration.

(1) In a contact charging device in which a charging member is brought into contact with an object to be charged and the two are moved relative to each other to charge the surface of the object to be charged, the charging member includes a conductive member to which a voltage is applied, and a conductive member to which a voltage is applied. The contact comprises a tubular resistance layer member that is fitted onto a conductive member and is rotatable, and the electrically conductive member is brought into contact with a charged object via the resistance layer member that is fitted onto the conductive member. Charging device.

(2) The contact charging device according to (1), wherein the tubular resistance layer member rotates as a result of relative movement between the object to be charged and the charging member.

[0013]

[Function] (a) The charged object is activated by the voltage applied to the conductive member brought into contact with the charged object through the resistance layer member, which acts on the charged object through the resistance layer member. Contact charging processing is performed in the same way as when the sexual member is brought into direct contact with the object to be charged.

(b) Since the resistance layer member is interposed between the object to be charged and the conductive member to which a voltage is applied, even if there is a low voltage defect such as a pinhole on the surface of the object to be charged, the defect can be removed. This prevents the charging current from leaking to the parts and causing charging defects.

(c) The conductive member can be a flexible member such as a wire member that can be easily placed along the surface of the object to be charged, and is uniformly brought into contact with the surface of the object to be charged at each longitudinal portion through the resistance layer member. Therefore, it is possible to prevent charging defects such as uneven charging due to uneven contact of the charging member.

(d) Since the resistance layer member is a freely rotatable tube-shaped member that is fitted onto the conductive member, it rotates as it moves relative to the charged object, thereby causing wear due to friction with the charged object. is reduced and the durability of the device is improved. If a lubricant is interposed between the conductive member and the tubular resistance layer member, the frictional wear between the conductive member and the tubular resistance layer member is also reduced, and the durability is further improved.

(e) Even when the voltage applied to the conductive member is a voltage containing an alternating current component, the so-called charging noise generated due to the alternating current component can be avoided because the resistance layer member does not vibrate together with the conductive member. On the contrary, the vibration of the conductive member is greatly reduced because the resistance layer member acts as an absorbing layer for the vibration of the conductive member.

(f) As described above, the charging member composed of the conductive member and the tubular resistance layer member fitted around the conductive member so as to be rotatable thereon has a higher charging capacity than conventional charging members such as roller type or blade type. This is actually advantageous in terms of material cost, manufacturing, and required processing accuracy, and it becomes possible to construct a contact charging device at a low cost overall.

[0019]

[Example] <Example 1> (FIGS. 1 to 3) FIG. 1 shows an electronic device in which a photosensitive drum 1 as an image carrier (charged body) is subjected to primary charging using a contact charging device according to the present invention. 1 is a schematic configuration diagram of an example of a laser beam printer or a copying machine using a photographic process.

The photosensitive drum 1 in this example has an outer diameter of 30φ and consists of an aluminum drum base 1b and an organic photosensitive layer (OPC) 1a formed on the outer peripheral surface of the drum base. It is rotated in the direction at a predetermined peripheral speed (process speed) of 40 mm/sec in this example.

Reference numeral 2 denotes a contact charging member, which is composed of a conductive wire 2a as a conductive member, and a tubular resistance layer member 2b that is freely rotatably fitted on the outside of the conductive wire. In this example, the conductive wire 2a is a gold-plated tungsten wire with an outer diameter of 60 μm.

The tubular resistance layer member 2b is a thin resistance layer tube whose inner diameter is larger than the outer diameter of the conductive wire 2a as a conductive member, as shown in an enlarged cross-sectional model view in FIG. The resistance value of the resistance layer tube 2b is determined when a low voltage defect such as a pinhole exists on the surface of the photosensitive drum 1 and the defect corresponds to the charging member 2, and the voltage is applied from the conductive wire 2a to the defect. It is desirable that the resistance be 105Ω to 107Ω so as to suppress sudden current flow.

Specific materials constituting the resistance layer tube 2b include N-methylmethoxylated nylon (trade name: Torezin: Teikoku Kagaku Sangyo Co., Ltd.), polyvinyl butyral resin, polyurethane resin, ethylene/vinyl acetate resin, styrene/vinyl acetate resin, etc. Examples include resins such as butadiene resin, fluorocarbon resin in which a low-resistance material such as carbon is dispersed (trade name: Emlaron: Nippon Addison Co., Ltd.), regenerated cellulose, and furthermore, epichlorohydrin, urethane, chloroprene, acrylonitrile-butadiene-based rubber, and the like. The resistance layer tube 2b has at least the effective charging width L of the photosensitive drum 1 (FIG. 3).
The conductive wire 2a is made to have a length that covers the length range corresponding to the conductive wire 2a, and is fitted over the length range of the conductive wire 2a. Then, as shown in FIG. 3, a charging member 2 consisting of a conductive wire 2a and a resistance layer tube 2b is stretched on the outer surface of the photosensitive drum 1 approximately parallel to the drum generatrix direction O-O, and the resistance layer tube 2b By pressing the conductive wire portions exposed to the outside at both ends of the photosensitive drum 1 with the presser members 3, the conductive wire 2a is brought into contact with the photosensitive drum 1 via the resistance layer tube 2b that is fitted onto the conductive wire 2a. I've let it happen.

Reference numeral 4 denotes a power source for applying voltage to the conductive wire 2a. Although the voltage applied to the conductive wire 2a may be only a DC voltage, in this embodiment, an oscillating voltage in which a DC voltage Vdc and an AC voltage Vac are superimposed is applied in order to uniformly charge the surface of the photosensitive drum. An oscillating voltage is a voltage whose voltage value changes periodically over time. Preferably, an oscillating voltage is used in which an AC voltage Vac having a peak-to-peak voltage that is twice or more the charging start voltage of the photoreceptor and a DC voltage Vdc are superimposed. The waveform of the oscillating voltage is not limited to a sine wave, but may be a rectangular wave, a triangular wave, or a pulse wave.

As described above, by applying a voltage from the power supply 4 to the conductive wire 2a, the surface of the rotating photosensitive drum 1 is uniformly charged using a contact charging method. In this example, Vdc: -7
00V Vac: Peak-to-peak voltage Vpp=1800V, frequency f=
By applying a superimposed voltage of Vdc+Vac at 250 Hz, one surface of the photosensitive drum could be uniformly charged to approximately -700V.

As described above, the charging member 2 is stretched approximately parallel to the generatrix direction of the photosensitive drum, and both ends thereof are held by pressing members 3, 3.
By pressing the conductive wire 2a between the holding members 3 and 3 against the photosensitive drum 1, the entire length of the conductive wire 2a is brought into uniform contact with the surface of the photosensitive drum 1 via the tubular resistance layer member 2b fitted on the outside of the holding member 3. The contact state is maintained stably, and uneven charging due to uneven contact is not observed.

The tubular resistance layer member 2b fitted over the conductive wire 2a rotates as the photosensitive drum 1 rotates, so there is less friction with the rotating photosensitive drum surface, thereby reducing wear and damage to the photosensitive drum surface. Good chargeability and image quality were maintained even after passing 3000 sheets of A4 size paper. Also, the generation of charging noise has been reduced.

The surface of the photosensitive drum that has been uniformly charged by the charging member 2 as described above is subjected to scanning exposure 5 or an original with a laser beam modulated in accordance with the desired image information by an image exposure means (not shown). An image is formed and exposed, and an electrostatic latent image is formed on the surface of the photosensitive drum.

The electrostatic latent image is developed as a toner image by the developing device 6, and the toner image is fed to a sheet (not shown) at the pressure contact portion (transfer portion) between the photosensitive drum 1 and the transfer roller 7 to which a transfer bias is applied. The images are transferred onto the transfer material 8 that is conveyed at the same timing.

The transfer material 8 passes through the transfer section and is transferred to the photosensitive drum 1.
The image is sequentially separated from the surface and output as an image-formed product (print copy) via a fixing device (not shown). After the toner image has been transferred, the surface of the photosensitive drum is cleaned by a cleaning device 9 to remove residual toner and is repeatedly used for image formation.

<Embodiment 2> (FIGS. 4 and 5) In this embodiment, the charging member 2 is applied to the conductive wire 2a after applying silicone oil 2c (FIG. 4) as a lubricant to the conductive wire 2a. A tubular resistance layer member 2b is fitted onto the outside of the tubular resistance layer member 2b,
Both ends of the external tubular resistance layer member 2b are heat-shrinkable 2
d.2d (FIG. 5) to substantially eliminate the gap between the conductive wire 2a and the photosensitive drum 1 due to leakage of the silicone oil 2c from both ends of the tubular resistance layer member 2b.
This is to prevent surface contamination.

Then, as shown in FIG. 5, the charging member 2 is placed in a tensioned state at an intersection angle α with respect to the generatrix direction O-O of the photosensitive drum 1, with both ends being held down by pressing members 3. There is. By bringing the charging member 2 into contact with the photosensitive drum 1 with the intersection angle α, the contact of the charging member 2 with the photosensitive drum 1 along its length can be made more uniform. Both ends of the charging member 2, in which the tubular resistance layer member 2b is heat-shrinked 2d and 2d, are located outside the effective charging width L of the photosensitive drum 1 surface, and are floated above the photosensitive drum 1 surface.

In this case as well, the tubular resistance layer member 2b fitted around the conductive wire 2a rotates as the photosensitive drum 1 is driven to rotate. At this time, the silicone oil 2c as a lubricant applied to the conductive wire 2a reduces the friction between the conductive wire 2a and the tubular resistance layer member 2b fitted over it, further improving the durability of the device. size paper 500
Good charging properties and image properties were maintained even after passing 0 sheets.

<Embodiment 3> (FIG. 6) In this embodiment, the number of conductive wires 2a as a conductive member is not one but a plurality (four in this example), and a tubular resistance layer member 2b is provided over the entirety. The plurality of conductive wires 2a are fitted around the outside so that they can rotate freely, and the plurality of conductive wires 2a are arranged substantially parallel to each other and brought into contact with the surface of the photosensitive drum 1 via the tubular resistance layer member 2b. Each conductive wire 2a
A predetermined voltage is applied to.

[0035] With this configuration, the charged area width W can be widened,
Even if foreign matter adheres to one conductive wire portion or the wire is broken, charging of the surface of the photosensitive drum can be reliably continued by the remaining conductive wire contact area.

The conductive member 2a may be in the form of a conductive rod member, block member, pad member, etc. other than a conductive wire.

[0037]

As described above, according to the present invention, it is easy to ensure that the charging member is in uniform contact with the surface of the object to be charged, and therefore uneven charging due to uneven contact can be eliminated, and durability is achieved. Moreover, there is an effect that a low-cost contact charging device can be constructed.

[Brief explanation of the drawing]

FIG. 1 A schematic configuration diagram of an example of an image forming apparatus using a contact charging device according to the present invention.

[Figure 2] Enlarged cross-sectional model diagram of charging member

[Figure 3]
A cutaway plan view of the charging member placed in contact with the photosensitive drum

[Figure 4] Enlarged cross-sectional model diagram of a charging member with a lubricant-filled structure

[Fig. 5] A cutaway plan view of the charging member placed in contact with the photosensitive drum.

[Figure 6] An enlarged cross-sectional model diagram of a charging member configured with a plurality of conductive wires as conductive members.

[Figure 7] Schematic diagram of the configuration of an example of a contact charging device using a charging roller

[Figure 8] Schematic diagram of the configuration of an example of a contact charging device using a charging blade

[Explanation of symbols]

1 Photosensitive drum 2 as a charged object Charging member 2a Conductive wire 2b as a conductive member Tubular resistance layer member 3 Pressing member 4 Voltage applying power source

Claims (2)

[Claims] 1. A contact charging device in which a charging member is brought into contact with an object to be charged and the two are moved relative to each other to charge the surface of the object to be charged, wherein the charging member includes a conductive member to which a voltage is applied, and a Contact charging comprising a tube-shaped resistance layer member fitted onto the outside of the member and freely rotatable, and the conductive member is brought into contact with the object to be charged via the resistance layer member fitted onto the outside of the member. Device. 2. The contact charging device according to claim 1, wherein the tubular resistance layer member rotates as a result of relative movement between the object to be charged and the charging member.