JPH0453981A - Contact charging device and image forming device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention provides a method for carrying out charging processing (including static elimination processing) on the surface of a charged object by bringing a contact charging member to which a voltage including an oscillating voltage is applied to the charged object into contact with the charged object. This invention relates to a contact type charging device.

The present invention also relates to an image forming apparatus using the contact charging device.

(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, images are used as charged objects such as photoreceptors and dielectric materials. Generally, a corona charger is widely used as a device for charging the surface of a carrier.

A corona charger 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,
Requires an expensive high voltage transformer (approximately 6 to 8 KV)
There are problems in that a relatively large amount of undesirable ozone is generated due to corona discharge, and it is necessary to devise a countermeasure structure.

In contrast to such corona chargers, there is a contact charging device that charges the surface of the charged object by bringing a contact charging member to which a voltage is applied into contact with the surface of the charged object. Because it has the advantage of having an extremely small amount, for example, it has attracted attention as an alternative device to a corona charger for charging the surface of an image carrier such as a photoreceptor or dielectric in an image forming apparatus. Research on its practical application is underway (Japanese Patent Application Laid-open No. 57-178267, 56-1043
51・58-40566・58-139156・58-
150975, etc.).

The present applicant has also proposed various improvements regarding contact charging for the purpose of uniform charging processing and the like.

For example, DC voltage V. C, and an oscillating voltage VAC (alternating voltage, pulsating voltage: sine wave, rectangular wave, triangular wave) having a peak-to-peak voltage vPp that is more than twice the charging start voltage of the charged object when a DC voltage is applied to the charged object. A voltage V in which a voltage whose voltage value changes periodically over time (hereinafter referred to as an AC voltage or an AC voltage component) is superimposed. A contact charging method or device based on applying C+VAC or a contact charging member surface to prevent charging failures caused by current leakage at surface defects such as pinholes that may exist on the surface of the charged object. (
JP-A-63-149668, 149669, etc.).

FIG. 5 shows a schematic configuration of an example of an image forming apparatus using a contact charging device as a primary charging means for the surface of an image carrier.

Reference numeral 1 denotes an image carrier as an object to be charged, and the image carrier in this example is rotated at a predetermined circumferential speed (process speed) in the clockwise direction of arrow A.
This is a drum-shaped electrophotographic photosensitive member (hereinafter referred to as a photosensitive drum) that is rotationally driven.

2 is a charging roller as a contact charging member, and a core metal 28
and a conductive elastic roller portion 2 integrally formed concentrically around its outer periphery.
b, and is disposed substantially parallel to the surface of the photosensitive drum 1 in pressure contact with the drum with a predetermined pressing force, and rotates as the photosensitive drum 1 rotates.

Reference numerals 3 and 4 denote power supplies for applying a bias to the charging roller 2, which have a predetermined DC voltage V. By applying a superimposed voltage vDc+vAc of C and an alternating current voltage vAc to the charging roller 2 via the core metal 28, the surface of the rotating photosensitive drum 1 is uniformly primary charged to a predetermined polarity and potential by a contact charging method.

Exposure 5 (laser dome scanning exposure, imaging exposure of a document image, etc.) of target image information is performed on the primary charging surface of the photosensitive drum 1 by an exposure means (not shown). An electrostatic latent image is formed on the surface that covers the target image information.

Next, the formed latent image is reversely developed or normally developed by the toner developer 6, and the developed toner image is transferred to the pressure nip portion between the photosensitive drum 1 and the transfer roller 8 that is in contact with the surface of the photosensitive drum 1 with a predetermined pressing force. Transfer material 7 fed to (transfer section) from a paper feed section (not shown) at appropriate timing
The images are transferred one after another onto the surface of the screen.

The transfer roller 8 is made up of a core bar 8a and a conductive elastic roller part 8b integrally formed concentrically around the outer periphery of the core bar 8a.The transfer roller 8 is supplied with a bias voltage from a power source via the core bar 8a to the transfer roller 8 with a polarity opposite to that of the toner of the toner image. A transfer DC bias voltage of is applied, and the toner image on the side of the photosensitive drum 8 is electrostatically attracted to the side of the transfer material 7 and transferred.

The transfer material 7 that has passed through the transfer section and has received the toner image is separated from the surface of the photosensitive drum, is introduced into a fixing device (not shown), undergoes image fixation, and is output as an image-formed product (print/copy). Ru.

After the image has been transferred, the surface of the photosensitive drum is cleaned by a cleaning device 10 to remove residual toner and other contaminants that have adhered to the drum surface, and is then subjected to an image forming process below primary charging to turn it green and use it for image forming. be done.

(Problems to be Solved by the Invention) One problem with contact charging is that when a voltage including an oscillating voltage is applied to a contact charging member to perform charging or neutralization processing on the surface of the charged object, the oscillating voltage component An example of this is the generation of a more or less unpleasant so-called electrification noise due to this.

Taking the image forming apparatus shown in FIG. 5 as an example, photosensitive tram 1: An organic optical semiconductor layer is formed to a thickness of 50 μm on the outer peripheral surface of an aluminum cylinder with an outer diameter of 30 mm, a wall thickness of 1 mm, and a length of 320 mm. (OPC photosensitive drum).

Contact charging roller 2: Core metal 2a = stainless steel core metal conductive elastic roller portion 2b = outer diameter 16 mm, length 300 mm carbon particle-dispersed EPDM rubber roller. Hardness is approximately 30 degrees (Asker-C).

DC voltage component of applied bias v0° =-500V -Next charging voltage = -450V.

Under the conditions, when the process speed (peripheral speed of the photosensitive tram 1) is 25 mm/sec, when it is 50 mm/sec, it is 100 m
The alternating current voltage component vAc of the bias applied to the contact charging roller 2, which can obtain a sufficient charging state on one surface of the photosensitive drum, was measured for three cases where m/sec. The results are shown in the table below.

In this state, noises other than the charging noise of the charging roller 2, such as device drive sounds and paper feeding parts, come in, so the photosensitive drum 1 is stopped and a voltage including the above AC voltage component VAC is applied to the charging roller 2. This was measured using a sound level meter.

As the process speed of the photosensitive drum is increased, unless the AC frequency of the AC voltage component vAc is increased, so-called cycle marks will occur on the image. ,1
As the AC frequency increases to 00mm/sec, it is necessary to increase the AC frequency.As long as the frequency is low, the charging sound and noise are small, or as the frequency increases, the charging sound and noise increase, and when the frequency becomes high, it exceeds the difference in the sound level meter value. To the human ear, it sounds uncomfortable or increased.

In the above case, the charging noise is not noticeable when the process speed is 25 mm/sec, but at 50 mm/sec.
/ s e c becomes a disturbing noise, 100 mm /
sec, it becomes an unpleasant irritating noise.

In the case of the above-mentioned image forming apparatus, the charging noise is caused by the photosensitive drum 1.
The applied AC voltage component vA of the charging roller 2 which is brought into contact with
By applying periodic vibrations to the photosensitive drum 1 as an object to be charged by c, as shown in the model diagram of FIG. This causes the air around the drum to vibrate and is propagated as charging noise.

An object of the present invention is to substantially eliminate, or significantly reduce, the generation of charging sound and noise as described above regarding contact charging.

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

(1) In a contact charging device that charges the surface of the charged object by bringing a contact charging member to which a voltage including an oscillating voltage is applied to the charged object, the contact charging member contacts the charged object separately from the contact charging member and vibrates. It has another member to which a voltage is applied, and the stationary vibration generated in the charged object due to the contact of the contact charging member to which a voltage including an oscillating voltage is applied, and the contact of the other member to which an oscillating voltage is applied. A contact charging device characterized in that a phase relationship between an oscillating voltage applied to a contact charging member and an oscillating voltage applied to other members is set so that standing vibrations generated in a charged body cancel each other out.

(2) In an image forming apparatus that performs image formation on an image carrier through an image forming process that includes a step of charging the surface of the image carrier, the charging processing means includes a contact charging member to which a voltage including an oscillating voltage is applied. This is a contact-type charging device that charges the surface of the image carrier by bringing the image carrier into contact with the image carrier, and applies an oscillating voltage to the transfer means that contacts the image carrier. The contact charging member is adjusted so that the standing vibrations generated in the image carrier due to the contact of the contact charging member and the standing vibrations generated in the image carrier due to the contact of the transfer means to which an oscillating voltage is applied cancel each other out. An image forming apparatus characterized in that a phase relationship between an oscillating voltage and a transfer means is set.

(3) In an image forming apparatus that performs image formation by applying an image forming process to an image carrier including a step of charging the surface of the image carrier, the charging processing means includes a contact charging member to which a voltage including an oscillating voltage is applied. This is a contact-type charging device that charges the surface of the image carrier by bringing it into contact with the image carrier, and applies an oscillating voltage to the image carrier surface cleaning means that comes into contact with the image carrier. The standing vibration generated in the image carrier due to the contact of the contact charging member applied thereto and the standing vibration generated in the image carrier due to the contact of the image carrier surface cleaning means to which the oscillating voltage is applied cancel each other out. An image forming apparatus characterized in that a phase relationship between an oscillating voltage applied to the contact charging member and an oscillating voltage applied to the image carrier surface cleaning means is set.

(Function) As mentioned above, by providing a contact charging device with another member that contacts the charged object and applies an oscillating voltage to the charged object separately from the contact charging member, the charged object can also be applied to the charged object by the other member. The oscillating voltage is applied to each of the contact charging member and other members so that a standing vibration is generated, and in this case, the standing vibration and the standing vibration generated in the charged object by the contact charging member cancel each other out. By setting the phase relationship to be appropriately shifted, it is possible to suppress the vibration of the object to be charged, and thereby the generation of charging noise can be substantially eliminated or significantly reduced.

In an image forming apparatus that uses a contact charging device as a charging processing means for an image carrier as a charged object, other image forming process means equipment disposed in contact with the image forming apparatus, specifically, By applying an oscillating voltage to the image transfer means, image carrier surface cleaning means, etc. in the above-mentioned relationship, generation of charging noise and noise due to the contact charging member of the image carrier can be substantially reduced. It is possible to construct a quiet image forming apparatus by eliminating or significantly reducing the noise.

(Embodiments) <Embodiment 1> FIG. 1 shows a schematic diagram of the configuration of an image forming apparatus according to an embodiment of the present invention. Components common to those of the image forming apparatus shown in FIG. 5 will be designated by the same reference numerals and will not be described again.

The configurations of the photosensitive drum 1 and charging roller 2 are the same as in the case of noise measurement described above. The transfer roller 8 is made of the same material and hardness as the charging roller 2.

T is the primary winding of the transformer, T is the winding of the direct current (DC) power supply 4 for the charging roller 2, and the boosted alternating current (AC) voltage is passed through the diode D, capacitor C,
Convert to -500v by

T2 is a winding of the DC power supply 9 for the transfer roller 8;
+600V D by diode D2 and capacitor C2
C voltage is obtained.

T3 and T3' are windings for AC power supply 3 and 3',
Both have the same number of turns to obtain an output voltage of Vpp=1600V.

C3 is the AC applied to the charging roller 2 and the transfer roller 8.
This is a capacitor installed to shift the phase angles of voltages from each other.

Therefore, the primary winding T. When a 1200Hz AC voltage is applied to both ends of the charging roller 2, the following DC+A voltage is applied to the charging roller 2.
A superimposed voltage of C is applied.

■Charging roller 2 DC knee 5oov AC: 1200Hz, 1600Vpp ■Transfer roller 8 DC: +600V AC: 1200Hz, 1600Vpp However, the AC voltage component applied to the charging roller 2 and transfer roller 8 is the second
As shown in the figure, in this embodiment, the phase angles are shifted by 90° from each other due to the capacitor 03.

When the AC voltage component was also applied to the transfer roller 8 that was in contact with the photosensitive drum 1 and the noise was measured in the same way as the noise measurement described above, it was found that in the noise measurement described above, the AC voltage component was applied across the charging roller. Voltage component 1200Hz -16
00V,.

Compared to the noise of 50 dB (A) generated when AC voltage component is applied and no AC voltage component is applied to the transfer roller 2, a significant noise reduction of 35 dB (A) was observed in this example.

As described above, the photosensitive drum 1 is subjected to periodic vibrations by the charging roller 2, which is in contact with an AC voltage component applied thereto, thereby causing standing vibrations. In addition, in this embodiment, an AC voltage component is also applied to the transfer roller 8 that is in contact with the photosensitive drum 1, so that standing vibrations caused by the transfer roller 2 are generated on the photosensitive drum 1.

However, the AC voltage components applied to the charging roller 2 and the transfer roller 8 have the same frequency but different phase angles, and the standing vibrations generated on the photosensitive drum l by the charging roller 2 and the transfer roller 8 cancel each other out. As a result, the vibration of the photosensitive drum was reduced, and charging noise was significantly reduced.

In this embodiment, the charging roller 2 and the transfer roller 8 are set at positions facing approximately 18 degrees with the photosensitive drum 1 in between, and both are at the antinode of the standing vibration of the photosensitive drum 1. Under the conditions that the rollers 8 are made of the same material and have approximately the same hardness, the AC for both rollers 2 and 8 is
The silencing effect was greatest when the voltage component phase difference was around 90°.

Regarding the above phase difference, the optimum phase difference can be determined depending on the arrangement position of the other contact members for canceling the standing vibration of the photosensitive tram caused by the charging roller 2, the transfer roller 8 in this embodiment, its material, etc. Although the value differs from case to case, the optimum amount of phase shift can be determined by varying the capacitance of the capacitor C3 and measuring the soundproofing effect.

<Embodiment 2> In this embodiment (FIG. 3), charging noise is reduced by applying an AC voltage to a cleaning roller (cleaner roller) 12 that rotates in contact with the photosensitive drum 1 in the cleaning device IO for the photosensitive drum 1. This is designed to suppress noise generation.

In this embodiment, the transfer means is a transfer corona charger 11 that does not contact the photosensitive drum 1. Reference numeral 9' indicates the voltage applying power source.

The cleaning device 10 includes a cleaning roller 12 made of conductive urethane rubber, a scraper 13 in contact with the surface of the roller 12, a cleaning blade 14, etc.
4 is in contact with the surface of the photosensitive drum 1 with a predetermined pressing force.

The cleaning roller 12 maintains the rotational circumferential speed of the photosensitive tram 1 (
The photosensitive drum 1 is rotated at a circumferential speed slower than the process speed) and passes through the transfer section by rubbing the surface of the photosensitive drum.
Scrape off any contaminants such as residual developer on the surface.

The residual toner and the like that have adhered to and transferred to the surface of the cleaning roller 12 are scraped off from the surface of the cleaning roller 12 by the scraper 13 and stored in the cleaning container 10a.

Toner and the like that have passed through the cleaning roller 12 are removed from the surface of the photosensitive drum by the next cleaning plate 14.

AC voltage is supplied to the cleaning roller 12 via the core metal 12a. This AC voltage is applied to the charging roller 2 by a capacitor 03 so that the cleaning roller 12 generates a standing vibration on the photosensitive drum 1 that cancels out the standing vibration generated on the photosensitive drum 1 due to the AC voltage component applied to the charging roller 2. The AC voltage component is out of phase with the AC voltage component, thereby reducing charging noise.

In this embodiment, the AC voltage supplied to the charging roller 2 and the cleaning roller 12 are both taken from the same winding T3, and the AC voltage waveforms are also the same. , T3', the interference effect (silence effect) of the vibrations caused by both rollers 2 and 12 can be produced more effectively than in the case where the rollers are supplied from the respective rollers 2 and 12.

Further, in this embodiment, by applying an AC voltage to the cleaning roller 12, the remaining toner on the photosensitive drum 1 is loosened by the vibration of the cleaning roller 12 to which the AC voltage is applied, and The charge is removed by the bias and easily transferred from the photosensitive drum 1 side to the cleaning roller 12 side and removed, resulting in the effect of improving cleaning performance.

<Embodiment 3> In this embodiment (FIG. 4), a plate-type member (charging plate) 15 made of conductive urethane elastomer is used as the contact charging member, and a cleaning plate 16 of the cleaning device 10 of the photosensitive tram l is used. By applying AC voltage, charging noise can be suppressed.

The cleaning blade 16 is made of the same material as the charging plate 15, and is brought into contact with the surface of the photosensitive drum with a predetermined pressing force.

This cleaning plate 16 is supplied with AC voltage. This AC voltage is the AC voltage applied to the charging plate 15.
The capacitor 03 is arranged out of phase with the AC voltage component of the charging plate 15 so that the cleaning plate 16 generates a standing vibration in the photosensitive drum 1 that cancels out the standing vibration generated in the photosensitive drum 1 due to the voltage component. Charging sound noise is reduced.

The charging roller 2 and cleaning roller 12 like the devices shown in FIG. 1 and FIG. The plate 15 and cleaning blade 16 have a simple device configuration and are suitable for small and simple devices that do not require a particularly long life.

(Effects of the Invention) As described above, according to the present invention, charging noise and noise, which are problems in contact charging in which a voltage including an oscillating voltage component is applied to a contact charging member to charge the surface of a charged object, can be solved. This makes it possible to substantially eliminate or significantly reduce the occurrence of noise, making it possible to construct a quiet image forming apparatus or the like.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram of an image forming apparatus according to an embodiment. FIG. 2 is a diagram showing the phase difference between AC voltage components applied to the charging roller and the transfer roller. FIGS. 3 and 4 are schematic configuration diagrams of image forming apparatuses of other embodiments, respectively. FIG. 5 is a schematic configuration diagram of an example of an image forming apparatus using a contact charging device. FIG. 6 is a model diagram of standing vibrations occurring in the photosensitive drum. 1 is an image carrier (photosensitive drum) as a charged body, 2.
15 is a charging roller or charging plate as a contact charging member; 8 and 12 are transfer rollers or cleaning rollers as other members to which AC voltage is applied to prevent generation of charging noise and noise. Patent applicant Canon Co., Ltd.

Claims (3)

[Claims] (1) In a contact charging device in which a contact charging member to which a voltage including an oscillating voltage is applied is brought into contact with a charged object to charge the surface of the charged object, the contact charging member that contacts the charged object separately from the contact charging member and vibrates. It has another member to which a voltage is applied, and the stationary vibration generated in the charged object due to the contact of the contact charging member to which a voltage including an oscillating voltage is applied, and the contact of the other member to which an oscillating voltage is applied. A contact charging device characterized in that a phase relationship between an oscillating voltage applied to a contact charging member and an oscillating voltage applied to other members is set so that standing vibrations generated in a charged body cancel each other out. (2) In an image forming apparatus that performs image formation by applying an image forming process to an image carrier including a step of charging the surface of the image carrier, the charging processing means includes a contact charging member to which a voltage including an oscillating voltage is applied. This is a contact-type charging device that charges the surface of the image carrier by bringing the image carrier into contact with the image carrier, and applies an oscillating voltage to the transfer means that contacts the image carrier. The contact charging member is adjusted so that the standing vibrations generated in the image carrier due to the contact of the contact charging member and the standing vibrations generated in the image carrier due to the contact of the transfer means to which an oscillating voltage is applied cancel each other out. An image forming apparatus characterized in that a phase relationship between an oscillating voltage and a transfer means is set. (3) In an image forming apparatus that performs image formation by applying an image forming process to an image carrier including a step of charging the surface of the image carrier, the charging processing means includes a contact charging member to which a voltage including an oscillating voltage is applied. This is a contact-type charging device that charges the surface of the image carrier by bringing it into contact with the image carrier, and applies an oscillating voltage to the image carrier surface cleaning means that comes into contact with the image carrier. The standing vibration generated in the image carrier due to the contact of the contact charging member applied thereto and the standing vibration generated in the image carrier due to the contact of the image carrier surface cleaning means to which the oscillating voltage is applied cancel each other out. An image forming apparatus characterized in that a phase relationship between an oscillating voltage applied to the contact charging member and an oscillating voltage applied to the image carrier surface cleaning means is set.