JP2806334B2 - Charging device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charging device,
In particular, the present invention relates to a contact-charging type charging device that is provided in an electrophotographic printer and applies a vibration voltage to a charging brush that is in contact with a photosensitive member to charge the drum surface.

[0002]

2. Description of the Related Art Conventionally, a main charging system of an electrophotographic printer includes a contact charging system and a corona charging system. The contact charging system is superior in that the applied voltage can be suppressed lower than that of the corona charging system and ozone generation is small. For this reason,
Recently, a contact charging system has been widely used. In the case of the contact charging system, if the applied voltage is DC, charging unevenness easily occurs. Therefore, it is general to apply an oscillating voltage to which an AC component is added.

FIG. 4 shows a conventional example of such a charging device.

In FIG. 4, a charging means 52 includes a conductive charging brush 52a provided in a band shape along the width direction of a drum-shaped photosensitive member 51, and the tip of the charging brush 52a is attached to the surface of the photosensitive member 51. And a conductive brush holding member 52b integrally held so as to be in contact with the brush. Among these, a voltage application circuit 52c for applying a periodic vibration voltage is connected to the brush holding member 52b.

[0005] The charging brush 52a is made up of a bundle of a plurality of filaments, which are thin fibrous wires, and is implanted in a brush holding member 52b. The voltage application circuit 52 c
As shown in, the AC component V _AC DC component V _DC to the frequency f
Is applied.

When an oscillating voltage is applied from the voltage application circuit 52c to the brush holding member 52b, the tip of the charging brush 52a set to a predetermined potential is rubbed against the surface of the rotating photosensitive member 51. Then, the surface of the photoconductor 51 is charged.

Here, since the charges generated on the surfaces of the charging brush 52a and the brush holding member 52b and the photoreceptor 51 are always of opposite signs, the electrostatic force becomes an attractive force and the charging brush 52a and the brush holding member 52b and the photoreceptor 51 are separated. Attract each other. At this time, since the charging voltage has an AC component, the attraction has strength. An approximate expression representing the time change of the attractive force is shown below. Here, A, B, C, φ ₁ and φ ₂ are constants and ω = 2πf.

F = Asin (ωt + φ ₁ ) + Bsin (2ωt + φ ₂ ) + C (1)

[0009]

However, in the above conventional example, the attractive force is a periodic force having a charging voltage frequency (hereinafter referred to as a charging frequency) and a frequency twice as high as the charging voltage. , A complex vibration of the frequency f and the frequency 2f is generated in the charging brush 52a and the brush holding member 52b, and the vibration is propagated to the surrounding air, and the frequency component f
And 2f mainly. Of the frequency components that cause such noise, the noise of the frequency component 2f has a high frequency and therefore has a large attenuation effect inside the housing and does not become a large noise source to the outside of the printer, but the noise of the frequency component f has a low frequency. However, there is a disadvantage that the attenuation effect inside the housing is small, and the noise becomes a significant noise source outside the printer.

[0010] Such noise is roughly classified into radiation noise and vibration noise. The radiation noise is a noise generated when the charging brush strikes the surface of the photoreceptor by generating minute vibrations. Is a sound transmitted by the vibrations of the photosensitive member, the charging brush, and the brush holding member, which are inconsistent in the contact charging method in which a vibration voltage is applied.

In order to cope with such inconveniences, measures have been taken to affix a vibration damping material or a sound absorbing material in the vicinity of the photosensitive drum, but it is difficult to select an affixing location in a limited space. In addition, there is a disadvantage that the manufacturing cost is high.

[0012]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned disadvantages of the prior art, and in particular, to provide a photosensitive member, a charging brush, and a charging device which suppresses vibration of the charging brush due to an electrostatic force generated at the time of charging to reduce noise. Is its purpose.

[0013]

In order to achieve the above object, according to the first aspect of the present invention, there is provided a conductive charging brush provided in a band along the width direction of a photoreceptor, and the charging brush is provided at the tip thereof. There are provided two sets of a conductive brush holding member for integrally holding the brush holding member so as to be in contact with the surface of the photoreceptor, and two voltage application circuits for applying a periodic vibration voltage to the brush holding member. Then, a configuration is adopted in which the phases of the oscillation voltages applied by the two sets of voltage application circuits are set so as to be shifted from each other by a half wavelength.

According to the present invention, the photosensitive member is vibrated by an attractive force acting between one of the brush holding members and the photosensitive member, and the photosensitive member is vibrated by the attractive force acting between the other brush holding member and the photosensitive member. The vibration urged by the body is simultaneously transmitted to the entirety of the photoreceptor hollow inside. Here, the vibration by the one brush holding member and the vibration by the other brush holding member include both the same frequency component as the charging frequency and the frequency component twice the same, but the same frequency component as the charging frequency. Are opposite to each other, so that when both vibrations are transmitted simultaneously, the same frequency component as the charging frequency is removed (Equations (2) to (4)).

Further, in the first aspect of the present invention, two sets of brush holding members are arranged in a straight line along the width direction of the photosensitive member. For this reason , the arrangement area of the charging device around the photoconductor can be reduced to the same size as that of the conventional example.

According to the second aspect of the present invention, a configuration is adopted in which two sets of brush holding members are juxtaposed via a joining member formed of an insulating material. In the present invention, the vibration applied to one brush holding member is also transmitted to the other brush holding member. Further, a leak that may occur between the brush holding members is prevented.

With these, the above-mentioned object is achieved.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIG.
A description will be given based on FIG.

The charging device shown in FIG. 1 has a conductive charging brush 1a, which is provided in a strip shape along the width direction of the photosensitive member 51.
2a, conductive brush holding members 1b, 2b for holding the charging brushes 1a, 2a integrally so that their tips come into contact with the surface of the photoreceptor 51, and periodic brush holding members 1b, 2b. Voltage application circuits 1c and 2c for applying an oscillating voltage are provided. That is, the charging brush, the brush holding member, and the voltage applying circuit
Each pair is provided. In particular, each charging brush 1a, 2a
Are the same, and the brush holding members 1b and 2b are formed symmetrically. Also, two sets of voltage applying circuits 1c and 2
The phases of the oscillating voltages applied by c are set to be shifted from each other by a half wavelength.

More specifically, in the present embodiment, the charging brushes 1a and 2a are configured as a bundle of fiber materials (filaments) planted on the brush holding members 1b and 2b as in the conventional example. Further, the two sets of brush holding members 1b, 2b are respectively arranged in a straight line along the width direction of the photoconductor. For this reason, each charging brush 1
The arrangement width of a and 2a is set to be slightly shorter than half the width of the photoconductor 51. Also, two sets of brush holding members 1
b and 2b are juxtaposed via a joining member 3 formed of an insulating material. Thereby, one brush holding member 1
The vibration applied to b (2b) is also transmitted to the other brush holding member 2b (1b).
Here, the thickness of the joining member 3 is desirably as thin as possible, but may be set according to the voltage applied to each of the brush holding members 1b and 2b.

As shown in FIGS. 2A and 2B, the oscillating voltage applied to the brush holding members 1b and 2b by the voltage applying circuits 1c and 2c is obtained by adding the _AC component VAC of the frequency f to the DC component _VDC. The oscillating voltage applied by one of the voltage applying circuits 1c and the oscillating voltage applied by the voltage applying circuit 2c are set such that their AC components are shifted in phase by half a wavelength (1 / 2f).

Next, the charging operation of the above embodiment will be described.

The drum-shaped photoreceptor 51 rotates, and from each of the voltage application circuits 1c and 2c to each of the brush holding members 1b and 2b.
When the oscillating voltage shown in FIG. 2 is applied, the charging brushes 1a,
2a is set to a potential corresponding to the oscillation voltage, and the surface of the photoconductor 51 rubbed with the brush is charged.

Here, since the potential of the brush holding members 1b and 2b and the electric charge induced on the surface of the photoreceptor 51 always have opposite signs, the electrostatic force acting between them becomes an attractive force, and the brush holding members 1b and 2b The photoconductors 51 attract each other. Also,
Since the oscillating voltage (charging voltage) has an AC component, this attractive force is accompanied by high and low.

In this embodiment, the time change of the attractive force differs depending on the brush holding members 1b and 2b. If attractive force and F ₂ acting, time each attraction F _1, F ₂ changes between the attractive force acting F _1, and the brush holding member 2b and the photosensitive member 51 between the brush holding member 1b and the photoconductor 51 Is represented by the following approximate expression (where A, B, C, φ ₁ ,
φ ₂ is a constant: ω = 2πf).

[0026]

(Equation 1)

In the above equation, the coefficient の of each term takes into account that the longitudinal width of each of the charging brushes 1a and 2a is approximately half that of the conventional example.

The photosensitive member 51 is vibrated by the action of the attractive forces F ₁ and F ₂ . The drum-shaped photoconductor 51 is
Generally, it is formed as a hollow inside with a material having a predetermined hardness so as to be lightweight. For this reason, the brush holding member 1b
The attractive force F ₁ acting on the half of the applied high voltage receiving photosensitive member 51 surface, the whole of the photoconductor 51 is approximately uniform vibration. On the other hand, the attractive force F ₂ also exerts vibration on the entire photoconductor 51. According to this, in effect, the photoconductor 51
The attractive force F that imparts vibration to the force F ₁ , F ₂
Given as the sum of Therefore, the attractive force F is represented by the following equation.

F = F ₁ + F ₂ = Bsin (2ωt + φ ₂ ) + C (4)

According to this, the attractive force F causing the photosensitive member 51 to vibrate is equivalent to the attractive force having only the frequency 2f twice the charging frequency f, and the photosensitive member 5 receiving the attractive force F
1 is oscillated at twice the charging frequency f. For this reason, according to the present embodiment, in an ideal state of the photoconductor 51, a frequency component corresponding to the charging frequency f can be removed from noise generated by vibration of the photoconductor 51, and
Harsh noise leaking out of the printer device can be suppressed. On the other hand, each attractive force F depends on the characteristics of the photoconductor 51.
_{Even when 1} and F ₂ do not uniformly act on the entire photoreceptor 51, noise can be effectively reduced, despite differences in effects.

In particular, there is no need to attach other components such as a vibration damping material or a sound absorbing material in the vicinity of the photosensitive drum, and the voltage application circuit increased compared to the conventional example is a problem in circuit design, and is a problem. It does not involve increasing the number of parts, and furthermore, there is almost no need to add new manufacturing technology to the processing of the charging brush and the holding member, so the manufacturing cost can be reduced compared to the means of attaching vibration damping materials and sound absorbing materials. Can be planned.

As for the so-called radiated sound generated by the charging brushes 1a and 2a hitting the photoreceptor surface, the radiated sound from the charging brush 1a and the radiated sound from the charging brush 2a have the charging frequency and twice the charging frequency, respectively. Since the light propagates in the air, the charge frequency component can be suppressed to some extent during the propagation, as in the case shown in the equation (4), and the propagation of the radiated sound to the outside of the printer can be reduced to some extent. .

Further, the respective attractive forces F ₁ and F ₂ act on the brush holding members 1b and 2b in the same manner as on the photoreceptor 51. In the present embodiment, since the brush holding members 1b and 2b are connected by the joining member 3, the vibrations urged by the brush holding members 1b and 2b by the attractive forces F ₁ and F _{2 respectively} cause the vibration from one brush holding member to the other. , And the noise caused by the vibration of the brush holding members 1b and 2b can be suppressed as in the case of the photoconductor 51 described above.

In addition, since the joining member 3 is formed of an insulating material, even when the brush holding members 1b and 2b are set to different potentials, it is possible to effectively prevent the occurrence of unexpected leaks and the like. can do.

Further, since the brush holding members 1b and 2b are arranged in a straight line along the width direction of the photoconductor 51, the brush holding members 1b and 2b can be mounted around the photoconductor on the same physical scale as the conventional example.

Here, the present invention is not limited to the above embodiment, and as shown in FIG.
b and 12b may be shifted in the direction of movement of the photoconductor surface (arrow B), and the ends of the charging brushes 11a and 12a may be set at the center position in the width direction of the photoconductor (arrow A). Even in this case, the same operation and effect as those of the above-described embodiment can be obtained, and the surface of the photoconductor can be uniformly charged without unevenness by removing the uncharged portion. Reference numeral 13 denotes a joining member.

As shown in FIG. 3B, each of the charging brushes 21a and 22a and the brush holding members 21b and 22b are provided to the full width of the photosensitive member, and are arranged side by side along the moving direction of the photosensitive member surface. You may. Even in this case, the same operation and effect as the above embodiment can be obtained. Symbol 23
Indicates a joining member.

Further, as shown in FIG. 3C, a plurality of charging brushes 31a, 32a, 33a, 34a and a plurality of brush holding members 31b, 32b, 33b, 34b may be arranged in a straight line. In this case, the voltage application circuits 1c and 2c
Are two brush holding members 31b, 33b (3
2b, 34b). The voltage application circuits 1c and 2c are provided with the brush holding members 31b, 32b and 3 respectively.
It is desirable that the connection is alternately made with 3b and 34b. Even in this case, the same operation and effect as in the above embodiment can be obtained, and vibration between the brush holding members is easily transmitted, so that noise can be more efficiently suppressed as compared with the above embodiment. it can.

In addition, the configuration of FIG.
As shown in (a), the charging brushes may be provided to be shifted along the moving direction B of the photoconductor surface.

In order to further improve the noise suppression effect of each of these embodiments, it is an effective means to attach a vibration damping material or a sound absorbing material to each member. In this case, it is sufficient that the place and area of the vibration damping material and the sound absorbing material to be applied are smaller than those of the conventional example.

[0041]

According to the present invention, the charging brush, the brush holding member, and the voltage application circuit are provided in two sets, and the phase of the applied voltage of each voltage application circuit is reduced by half. Since the wavelength is set to be shifted, it is possible to remove or suppress the same frequency component as the charging frequency in the vibration applied to the photosensitive member from the attractive force generated between each brush holding member and the photosensitive member, Can eliminate or suppress a frequency component that matches the charging frequency of the noise caused by the noise, and can suppress harsh noise leaking outside the printer device.

In particular, there is no need to attach another component such as a vibration damping material or a sound absorbing material in the vicinity of the photosensitive drum, and the voltage application circuit increased compared to the conventional example is a problem in circuit design, and is a problem. It does not involve increasing the number of parts, and furthermore, there is almost no need to add new manufacturing technology to the processing of the charging brush and the holding member, so the manufacturing cost can be reduced compared to the means of attaching vibration damping materials and sound absorbing materials. Can be planned.

Also, with respect to the so-called radiated sound generated by the charging brush striking the photoreceptor surface, the radiated sound from one charging brush and the radiated sound from the other charging brush are air-charged at the charging frequency and twice the charging frequency, respectively. Since the light propagates through the inside, the charging frequency component can be suppressed to some extent during the propagation, and the propagation of radiation sound to the outside of the printer device can be reduced to some extent.

Further , since the brush holding members are arranged in a straight line along the width direction of the photoreceptor, they can be provided around the photoreceptor on a physical scale equivalent to that of the conventional example.

According to the second aspect of the present invention, since the brush holding members are connected by the joining member, the vibrations urged by the brush holding members by the attraction force are transmitted from one brush holding member to the other brush holding member. The noise caused by the vibration of these brush holding members can be suppressed in the same manner as the above-described vibration of the photoconductor. In addition, since the joining member is formed of an insulating material, it is possible to effectively prevent the occurrence of unexpected leaks and the like even when each brush holding member is set to a different potential. An excellent charging device can be provided.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention.

FIG. 2 is a waveform diagram of a voltage applied to a brush holding member by each voltage application circuit of FIG. 1, and FIG. 2 (a) shows a voltage waveform applied from one voltage application circuit to one brush holding member; FIG. 2B shows a voltage waveform applied from the other voltage application circuit to the other brush holding member.

FIG. 3 is a schematic configuration diagram showing another embodiment of the present invention in a direction in which a surface of a photoreceptor equipped with a charging device is viewed;
3A to 3C show different embodiments.

FIG. 4 is a configuration diagram showing a conventional example.

5 is a voltage waveform diagram applied to the brush holding member by the voltage application circuit of FIG.

[Explanation of symbols]

1a, 2a, 11a, 12a, 21a, 22a, 31
a, 32a, 33a, 34a Charging brush 1b, 2b, 11b, 12b, 21b, 22b, 31
b, 32b, 33b, 34b Brush holding member 1c, 2c Voltage application circuit 3, 13, 23, 33 Joining member 51 Photoconductor

Claims (2)

(57) [Claims] A conductive brush provided in a band along the width direction of the photoreceptor, and a conductive brush for integrally holding the charging brush such that a tip of the brush contacts the surface of the photoreceptor. Two sets of a holding member and a voltage application circuit for applying a periodic oscillation voltage to the brush holding member are provided, and the phases of the oscillation voltages applied by the two sets of voltage application circuits are set to be shifted from each other by a half wavelength. in a static-apparatus, the width direction of each of the two sets of brush holding member and the photosensitive member
Charging device characterized by being arranged in a straight line along the direction
Place. 2. The two brush holding members are made of an insulating material.
It is characterized by being juxtaposed via the formed joining member
The charging device according to claim 1.