JPH0444060A - contact charging device - Google Patents

Abstract

PURPOSE:To eliminate an electrifying sound generated between a contact electrifying member and a charged body by providing a sound source for generating a sound wave which is opposite in phase from a vibration sound due to an applied pulsating voltage component nearby the contact electrifying member. CONSTITUTION:The outer peripheral surface of a photosensitive drum is charged (or discharged) electrostatically by an electrostatic charging roller 1 while a power source 7 applies a roller 6 for a sound source with an AC voltage(pulsating voltage component) Vac' which is 180 deg. out of frequency phase with an AC voltage component (pulsating voltage component) Vac to the electrifying roller 1. Consequently, the electrifying sound is superposed on the opposite-phase sound source wave and then the electrifying sound and sound source wave cancel each other. Namely, the electrifying sound is eliminated. Consequently, the uncomfortable electrifying sound is eliminated and not generated and this device is applicable to fast electrification.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a contact charging device that charges (including neutralizes) the surface of a charged object by bringing a contact charging member to which a voltage is applied into contact with the charged object. It's about improvement.

(Prior art) For example, in image forming devices such as electrophotographic devices (copying machines, laser beam printers, image display devices, etc.) and electrostatic recording devices, image bearing materials such as photoreceptors and dielectric materials are used as charged objects. Corona discharge devices have been widely used as devices for charging the body surface.

A corona discharge device is effective as a means for uniformly charging the surface of an object to be charged, such as an image carrier, to a predetermined potential. but,
It requires a high-voltage power supply and has problems such as relatively large amounts of undesirable ozone being generated due to corona discharge.

In contrast to such a corona discharge device, a contact charging device, which charges the surface of the charged object by bringing a charging member to which a voltage is applied as described above into contact with the charged object, can reduce the voltage of the power source, and
Because it has the advantage of generating only a very small amount of ozone, it is used, for example, in image forming apparatuses, where corona is used to charge the surface of image carriers such as photoreceptors and dielectrics, and other objects to be charged. It has attracted attention as an alternative device to electric discharge devices, and research on its practical use is progressing (Japanese Patent Application Laid-Open No. 1782-1982).
67・56-104351・58-40566・58-
139] 5B・58150975, etc.).

The present applicant also applied a DC voltage Vdc to a charging member and a pulsating current voltage Va having a peak-to-peak voltage VpP that is twice or more the charging start voltage of the charged object, for the purpose of uniform charging processing, etc.
Contact charging is based on applying a voltage Vdc + Vac superimposed with c (voltage whose voltage value changes periodically over time, such as a sine wave, rectangular wave, or triangular wave, hereinafter referred to as AC voltage or AC voltage component). He has proposed many methods and devices (Japanese Patent Application Laid-open No. 63-149668).
・Publication No. 149669, etc.).

FIG. 5 shows a schematic configuration of an example in which a roller type contact charging member is used as a charging processing means for an image carrier in an image forming apparatus.

2 is a rotating drum-type electrophotographic photoreceptor (
The photosensitive drum is a part of the photosensitive drum (hereinafter referred to as a photosensitive drum), and is rotated at a predetermined circumferential speed (process speed) in the clockwise direction of the arrow. 2b shows a grounded aluminum drum as a base layer of the photosensitive drum, and 2a shows a photosensitive layer formed on the outer peripheral surface of the aluminum drum.

1 is a charging roller as a contact charging member, for example,
Conductive core metal 1a made of iron, stainless steel (SUS), etc.
The conductive charging roller 1 is made of a conductive rubber layer 1b made of carbon-containing EPDM or the like, which is coated on the outer periphery of the roller. The conductive rubber layer 1b is arranged approximately parallel to the photosensitive drum 1 with free bearings, and the conductive rubber layer 1b is brought into contact with the surface of the photosensitive drum 2 with a predetermined pressing force by a pressure means such as a spring 5. In this case, the photosensitive drum 2 rotates as the photosensitive drum 2 rotates.

3 is an external power supply that applies voltage to the charging roller 1;
Preset for the charging roller 1 by the power source 3,
DC voltage Vdc and photosensitive layer 2 when applying DC voltage
A superimposed voltage Vdc+Vac with AC voltage Vac having a peak-to-peak voltage vpp that is more than twice the charging start voltage of a is applied via the contact plate spring 4 and the core metal 1a, so that the photosensitive drum 2 which is being rotationally driven is The outer peripheral surface is charged to a predetermined potential.

Image exposure, development, and transfer process means (not shown in the figure) are applied to the two surfaces of the charged photosensitive drum.
The recording material (transfer material) to which the image has been transferred is outputted through an image fixing process means.

After the image has been transferred, the surface of the photosensitive drum 2 is cleaned by a cleaning process means (not shown) to remove adhered contaminants such as residual toner after transfer, and is then charged again by the charging roller 1 for repeated image formation. Served.

The contact charging member 1 is not limited to a roller type, but may have any other suitable shape such as a play type, a rod type, a horizontally long pad type, or a horizontally long flock type.

(Problems to be Solved by the Invention) One of the problems with such a contact charging device is as follows.

That is, when a voltage including an alternating current (pulsating current) voltage component Vac is applied to the charging member 1 brought into contact with the surface of the charged object 2 to perform charging (or neutralization) processing on the surface of the charged object, during the execution process. , between the contact charging member 1 and the object to be charged 2, a vibration sound called a "charging table" is generated to a greater or lesser extent due to the applied AC voltage component Vac, and the vibration sound is unpleasant and jarring to the ears. This is one of the problems.

Figures 6 (A), (B), and (C) are explanatory diagrams of the generation mechanism of the charging table, in which the contact charging member is the charging roller 1 in Figure 5 described in ))0, and the charged object is the photosensitive tram 2. do.

■Since the AC voltage component Vac is applied to the charging roller 1, when the AC electric field reaches a positive peak,
(A) As shown by the solid line in the figure, a positive charge +e is applied to the charging roller 1 side with the photosensitive layer 2a in between, and the base layer 2 of the photosensitive drum
A negative charge -〇 is induced on the b side. Since these positive and negative charges attract each other, the surface portion of the charging roller 1 near the photosensitive drum is attracted toward the photosensitive drum 2 against elasticity, and moves from position a shown by the solid line to the position shown by the two-dot chain line. Move to.

■Next, when the AC electric field starts to reverse, charging roller 1
The positive charge +e on the side and the negative charge -e on the drum substrate 2b side begin to be canceled by the induced charges of opposite polarity.

Then, when the AC electric field just changes from positive to negative, the positive charge on the charging roller 1 side and the drum base layer 2
The negative charge on the b side disappears (Figure (B)).

As a result, the surface portion of the charging roller that has moved to the position returns to the position a shown by the two-dot chain line in Figure (B) due to the restoring force.

(2) Furthermore, when the alternating current electric field changes from negative to negative, a negative charge -e is induced on the charging roller 1 side and a positive charge +e is induced on the drum base layer 2b side, as shown in Figure (C). Ru.

Therefore, the surface portion of the charging roller 1 in the vicinity of the photosensitive tram is moved again against elasticity from the position a shown by the solid line to the position shown by the two-dot chain line due to the attraction of both charges.

Since the following cycle phenomena are repeated repeatedly, the charging roller 1 vibrates due to the applied alternating current component Vac, and as a result, it is considered that a "charging table" is generated.

Furthermore, if the frequency of the AC voltage Vac is f and the vibration frequency of the charging roller 1 is F, as is clear from the above explanation, the charging roller 1 will vibrate twice during one period of the AC voltage Vac. Therefore, the following relationship exists between both f and F.

2f (Hz)=F (C/S) (1) Charging table also occurs when the contact charging member has a blade type other than a roller type or other shapes.

If the voltage VPP between the edges of the applied AC voltage component Vac is made smaller than twice the charging start voltage of the member to be charged, the number of charging tables can be reduced considerably.

However, in this case, the uniform charging property on the surface of the photosensitive drum 2, which is the object to be charged, may deteriorate, resulting in spot-like charging unevenness. Even if a normal electrophotographic image forming process is applied to the surface of a photosensitive drum with spotty charging unevenness, the output image will be a spotty black dot image corresponding to the spotty unevenness, and a high-quality image cannot be obtained.

The contact surface between the charging roller 1 and the photosensitive drum 2 is microscopically uneven, making it difficult to obtain an ideal bonding surface, and the peak-to-peak voltage VPp of the AC voltage component Vac nevertheless performs uniform charging. Although a so-called "leveling effect" is obtained, lowering the peak-to-peak voltage indicates that the leveling effect disappears.

Furthermore, in order to reduce the number of charging tables, it has been proposed to insert a vibration-proofing member made of rubber inside the photosensitive drum 2, but this method causes new problems such as deformation of the photosensitive drum, weight increase, and manufacturing cost. It causes problems and lacks practicality.

An object of the present invention is to rationally solve the problem of charging noise as described above.

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

(1) In a contact charging device that performs charging by bringing a contact charging member to which a voltage including a pulsating voltage component is applied to a charged object into contact with the charged object, a contact charging member is placed between the contact charging member and the charged object in the vicinity of the contact charging member and the charged object. A contact charging device comprising a sound source that generates a sound wave having a phase substantially opposite to that of the vibration sound caused by the applied pulsating voltage component.

(2) The contact charging device according to (1), characterized in that the sound pressure level of the sound source is variable.

(3) The contact charging device according to (1), characterized in that the relationship between the vibrational sound wave phase of the contact charging member and the sound wave phase of the sound source can be made variable.

(4) The contact charging device according to (1), wherein the contact charging member and the sound source share a power source, and opposite phase components are supplied.

(5) The sound source is a member separate from the charging member that is brought into contact with the object to be charged and applies a pulsating voltage component that is approximately in opposite phase to the pulsating voltage component applied to the charging member, and this member itself also faces the object to be charged. (1)
Contact charging device as described.

(Function) In other words, the generated vibration sound, that is, the charging sound, overlaps with the sound wave that is generated from the sound source and has a phase substantially opposite to that of the charging sound, so that the charging sound and the sonic sound cancel each other out, resulting in charging. Sound is effectively muffled.

(Example) <Example 1> (FIG. 1) This example uses the device shown in FIG. As a sound source roller, the tram 2 is pressed against and opposed to the charging roller 1 with the wall thickness of the tram 2 interposed therebetween. The sound source roller 6 is also disposed and supported within the drum 1 on a bearing so that it rotates as the photosensitive drum 2 rotates. 6a is a core metal portion, and 6b is a conductive rubber roller portion.

Reference numeral 7 denotes a voltage application power source for this sound source roller, and this power source 7 applies a voltage to the sound source roller with a frequency phase shifted by 180 degrees from the AC voltage component (pulsating current voltage component) Vac applied to the charging roller 1. AC voltage with opposite phase (same)
In the state where VaC' is applied, photosensitive l by the charging roller 1
・Perform charging (or neutralization) processing on the outer peripheral surface of the ram.

As described above, a vibration sound, that is, a charging noise is generated between the charging roller 1 and the photosensitive drum 2 due to the AC voltage component Vac applied to the charging roller 1.

On the other hand, a vibration sound caused by the AC voltage component Vac'' applied to the roller 6 is also generated between the sound source roller 6 and the photosensitive drum 2 for the same reason. In other words, the roller 6 functions as a sound source.

Therefore, the vibration noise generated by the roller 6 with respect to the charging noise generated by the charging roller 1 is different from the AC voltage Vac applied to the roller 6.
Since the frequency phase of ' and the alternating current voltage component Vac applied to the charging roller 1 are in a relationship of opposite phases and shifted by 180 degrees from each other, the sound waves are of opposite phases. Therefore, the charging sound overlaps with this sound source sound wave with an opposite phase, so that the charging sound and the sound source sound wave cancel each other out. In other words, the charging sound is muted.

In fact, in the device shown in FIG. 5 which is not provided with the sound source roller 6, the peak-to-peak voltage of the charging roller 1 is maintained at twice the charging start voltage of the photosensitive layer 2a, and an AC voltage component with a frequency of 300 Hz is applied. Vac was applied, and the sound pressure level of the generated charging sound was measured using an anechoic method. The measuring device is Br1ier
A Kyaer Type 2230 was used, and the distance between the charging sound generation position and the probe was set to about 15 cm. The result was a sound pressure level of 63db.

On the other hand, regarding the apparatus shown in FIG. 5, which is provided with the sound source roller 6 as in this embodiment, the power supply 7 shifts the frequency phase difference by 180 degrees from the AC voltage component Vac applied to the charging roller 1, and the frequency An AC voltage VaC' having the same peak-to-peak voltage was applied to cause the charging roller 1 to charge the photosensitive drum 2. Similarly, when we measured the sound pressure level of the charging table, the sound pressure level was 53db.
It declined to . Further, the charging process of the photosensitive drum 1 is performed stably and uniformly without charging unevenness (Example 2) (Figure 2). The photosensitive drum 1 is disposed approximately parallel to the charging roller 1 and in contact with the outer surface of the photosensitive drum. The sound source roller 6 has the same structure as the charging roller 1, and rotates as the photosensitive drum 2 rotates.

When the charging roller 1 performs the charging process on the surface of the photosensitive drum 2, the power source 7 supplies an AC voltage Vac' with an opposite phase and the same frequency that is 180 degrees different in phase from the AC voltage component Vac applied to the charging roller 1 to the sound source roller 6. By applying the voltage, the same charging sound effect as in the first embodiment described above can be obtained.

In this embodiment, the sound source roller 6 applies an AC voltage Vac to record uneven residual charge history (electrical memory) on the surface of the photosensitive drum 2 before the charging roller 1 charges the surface of the photosensitive drum 2.
' has an erasing (cancellation) effect and has the effect of improving the uniform charging process of the surface of the photosensitive drum 2 by the next charging roller 1.

In addition, the sound source roller 6 captures foreign matter such as toner that has slipped through the photosensitive drum surface cleaning device 11 located upstream of the roller in the direction of movement of the photosensitive drum surface before it reaches the charging roller 1. It also functions as a cleaning means for the photosensitive drum surface to prevent the charging roller 1 from becoming dirty.

It is preferable to remove foreign matter captured on the surface of the roller 6 by bringing a cleaning member 12 such as a plate into contact with the roller 6, so that the roller 6 itself is always maintained in a clean state.

Furthermore, by applying to the sound source roller 6 a voltage Vac'+Vdc which is a superposition of a DC voltage Vdc of the same polarity as the DC voltage component Vdc for the charging roller 1 in addition to the above-mentioned AC voltage VaC', the roller 6 is also It functions as a charging member for the two surfaces of the photosensitive drum, and works together with the charging roller 1 to select uniform charging characteristics, and by selecting the relationship between the distance between the roller 6 and the charging roller 1 and the frequency of the AC voltage component. It is also convenient as a charging device for high-speed recording.

<Embodiment 3> (Fig. 3) In this embodiment, the charging roller 1 as the charging member and the roller 6 as the sound source in Embodiment 2 are each replaced with a plate blade I.
A (charging blade) and 6A (sound source blade).

The charging plate IA and the sound source plate 6A are each made of the same conductive rubber material as the charging roller 6.

By applying the same voltage to these plates IA and 6A as to the roller toro, it is possible to obtain the same charging table noise reduction effect as in the second embodiment.

In the first to third embodiments, the power source 3 and the power source 7 may be shared, and the circuit configuration may be such that AC voltage components Vac and Vac' having opposite phases are applied to the charging members 1 and IA and the sound source members 6 and 6A, respectively.

It is also possible to make the voltage applied to the sound source members 6 and 6A variable so that the sound pressure can be adjusted to a minimum.

<Embodiment 4> (Fig. 4) In this embodiment, the charging sound of the charging roller 1 as a charging member is detected by a microphone 13 and inputted to the control circuit 14, and a signal sound having an opposite phase to the signal sound obtained by the microphone is detected. The sound is amplified and produced by a sound source 15 such as a speaker, which cancels out the charging sound and silences the charging sound.

(Effects of the Invention) As described above, according to the present invention, it is possible to effectively muffle the charging noise that occurs in a contact charging device with a simple configuration, and the frequency of the pulsating voltage component applied to the charging member can be effectively suppressed. Even if the current is increased, unpleasant charging noise is suppressed and does not occur, making it applicable to high-speed charging.

[Brief explanation of drawings]

1 to 4 are schematic configuration diagrams of the embodiment apparatus shown in FIGS. 1 to 4, respectively. FIG. 5 is a schematic configuration diagram of an example of a contact charging device. Figures 6 (A), (B), and (C) are explanatory diagrams of the mechanism by which charging noise occurs. 1.IA is a charging roller or charging blade as a contact charging member, 2 is a photosensitive drum as a charged object, and 6.6A is a roller or plate for a sound source. cry

Claims (5)

[Claims] (1) In a contact charging device that performs charging by bringing a contact charging member to which a voltage including a pulsating voltage component is applied to a charged object into contact with the charged object, a contact charging member is placed between the contact charging member and the charged object in the vicinity of the contact charging member and the charged object. A contact charging device comprising a sound source that generates a sound wave having a phase substantially opposite to that of the vibration sound caused by the applied pulsating voltage component. (2) The contact charging device according to claim (1), characterized in that the sound pressure level of the sound source is variable. (3) The contact charging device according to claim (1), wherein the relationship between the vibrational sound wave phase of the contact charging member and the sound wave phase of the sound source can be made variable. (4) The contact charging device according to claim (1), wherein the contact charging member and the sound source use a common power source, and opposite phase components are supplied. (5) The sound source is a member separate from the charging member that is brought into contact with the object to be charged and applies a pulsating voltage component that is approximately in opposite phase to the pulsating voltage component applied to the charging member, and this member itself also faces the object to be charged. The contact charging device according to claim 1, characterized in that it has a contact charging function.