JP3244731B2 - Charging device, process unit, and image forming apparatus - 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 apparatus having a charging member for charging an object to be charged in contact with the object, a process unit having the charging apparatus, and a process unit applicable to an electrophotographic apparatus. The present invention relates to an image forming apparatus using a process unit.

[0002]

2. Description of the Related Art Heretofore, it has been known to use a corona discharger having a wire electrode facing a photoreceptor and a shield electrode surrounding the wire electrode as a charging device of an image forming apparatus such as an electrophotographic copying machine. .

[0003] However, when such a corona discharger is used, the voltage applied to the wire electrode is 4KV to 8K.
V, high current flows from the wire electrode to the shield electrode, so that the charging efficiency is low, a large amount of ozone is generated by corona discharge, and discharge unevenness occurs due to contamination of the discharge wire electrode. Was.

In order to solve such a problem, the present applicant has already proposed charging means for bringing a charging member into contact with a member to be charged.

FIG. 5 shows an example of an electrophotographic apparatus using a contact charging device. The photoreceptor 1 rotates in the direction of the arrow, and the charging roller 2 is pressed by a spring 3 to form a contact portion (nip portion) n with the photoreceptor 1. After the photoconductor 1 is charged by applying a bias voltage to the roller 2 from the power supply 19, an electrostatic latent image is formed by exposure 14. The electrostatic latent image on the photoreceptor 1 is applied with toner powder by a developing unit 15 to obtain a visualized image, and then the visualized image is transferred to a transfer paper 16 as a transfer material by a transfer unit 17. Thereafter, the transfer paper 16 is heated by a fixing device (not shown) to permanently fix the toner image. The toner powder remaining on the photoreceptor 1 after the transfer is cleaned by the cleaner 18 and the photoreceptor 1 is again subjected to image formation.

[0006]

However, it has been found that the conventional example shown in FIG. 5 has a problem that electrostatic noise due to charging is emitted outside the machine. That is,
Although charging is performed in the vicinity of the nip portion n in FIG. 5, electrostatic noise due to charging is radiated from the vicinity of the nip to the opposite side (upward in the figure) of the charging roller 2 from the photosensitive member 1 side. .

[0007] Radio interference due to radiation (electrostatic) noise sometimes causes electronic equipment to malfunction due to radio noise. In that sense, it is indispensable for the recording apparatus to reduce radiation noise outside the apparatus.

For example, in the conventional example shown in FIG. 5, the radiation noise may be 45 dB (μV / m).

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above problems, and has as its object to provide a charging device which reduces the generation of electrostatic noise radiated from a charging member and a charging device provided with the charging device. An object of the present invention is to provide a process unit and an image forming apparatus using the process unit.

Another object of the present invention is to provide a low-cost, high-charging-efficiency charging device, a process unit provided with the charging device, and an image forming apparatus using the process unit.

A further object of the present invention is to provide a charging device which generates less ozone, a process unit provided with the charging device, and an image forming apparatus using the process unit.

Further objects and features of the present invention will become more apparent from the following detailed description when read in conjunction with the accompanying drawings.

According to the present invention, which achieves the above object, there is provided an image carrier, a charging member to which a voltage is applied to contact the image carrier and charge the image carrier; A cleaning blade for cleaning the carrier, an image forming apparatus comprising: a conductive member that covers the charging member and is grounded;
The conductive member includes a holder for the cleaning blade.

According to another aspect of the present invention, there is provided a process unit detachable from an image forming apparatus, comprising: an image carrier; and a charging member to which a voltage can be applied to contact the image carrier and charge the image carrier. And a cleaning blade for cleaning the image carrier, wherein the process unit comprises: a conductive member that covers the charging member and is grounded;
The conductive member includes a holder for the cleaning blade.

[0015]

[0016]

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

FIG. 1 is a schematic side view of the image forming apparatus.

In FIG. 1, a photosensitive member 1 serving as an image carrier as a member to be charged is provided with a photosensitive layer 1a on a conductive substrate 1b made of aluminum, iron, or the like.
Is connected to the ground. The charging roller 2 serving as a charging member is in contact with the surface of the photoconductor 1 and is connected to a power supply 19 that supplies power between the charging roller 2 and the photoconductor.

When the photoreceptor 1 rotates in the direction of arrow A, the photoreceptor 1 is primarily charged by a charging roller 2 which is driven and rotated by the photoreceptor 1. An electrostatic latent image is formed on the photoconductor 1 by laser exposure 14 from a laser scanning device (not shown), and a regulating member that regulates the toner powder on a developing sleeve 25 which is a carrier for carrying the toner powder of the developing device 15. The photoreceptor 1 is developed with the toner powder whose layer thickness is regulated by the developing blade 26, and is visualized. The visualized toner powder on the photoreceptor 1 is transferred by the transfer roller 31 onto the transfer material 16 made of paper which is fed by the feed roller 29 and conveyed at the timing by the registration roller pair 30 and the like. You. The transfer material 16 onto which the toner image has been transferred is fixed by a fixing device including a fixing roller 32 and a pressure roller 33. The toner remaining on the photoconductor 1 after the transfer is cleaned by a cleaner device 18.

The power supply 19 has a vibration component (a peak-to-peak voltage of 1500 V) whose voltage value changes periodically and a DC component (70 V).
0V) is applied to the metal core of the charging roller 2. The peak-to-peak voltage of the vibration component is set to be twice or more the charging start voltage of the photoreceptor 1, which is a charged body, as disclosed in Japanese Patent Application Laid-Open No. 63-149668 filed by the present applicant. Thereby, the charging of the photoconductor 1 becomes uniform. As the waveform of the vibration component, a sine wave, a rectangular wave, and a triangular wave can be used. The oscillating voltage may be formed by turning on and off a DC power supply. The vibration component supplied to the charging roller 2 serving as a charging member is controlled by the control means 20 so as to have a constant current (560 μA). By controlling the vibration component at a constant current, a constant alternating electric field is formed between the photosensitive drum 1 and the charging roller 2 even when the atmosphere environment of the apparatus changes, such as temperature and humidity. Regardless, the photosensitive drum 1 can always be uniformly charged. Here, in order to make the charging uniform regardless of the environment, the voltage between the peaks of the oscillating voltage is always equal to the charging start voltage value of the photosensitive drum 1 at 2
It is desirable that the constant current control is performed so as to be twice or more.
The current value at this time was 560 μA.

In this embodiment, the cleaning blade 34 of the cleaner device 18 includes a rubber chip 35 having an elastic end, and a holder 36 supporting the rubber chip 35 and made of a conductive member. It has an L-shape covering the charging roller 2. The holder is connected to the ground and is made of a metal such as iron. The holder covers the nip between the photoconductor 1 and the charging roller 2 and is opposite to the photoconductor 1 with respect to the charging roller 2, that is, is connected to the photoconductor 1. The charging roller 2 is provided so as to sandwich the charging roller 2 therebetween.

As a result, the photosensitive member 1 and the charging roller 2
Cleaner 1 for electrostatic noise generated near the nip
It is possible to suppress radiation to the 8 side. Also,
By making the holder portion 36 of the cleaning blade 34 L-shaped, the rigidity of the holder 36 itself is improved.

On the other hand, the developing blade 26 of the developing device 15
A rubber blade portion made of urethane or the like for regulating the thickness of the toner on the developing sleeve 25 made of aluminum; and a blade holder portion 27 supporting the rubber blade portion,
The blade holder 27 is a conductive member connected to the ground and made of metal such as iron. The holder 27 covers the nip between the photoconductor 1 and the charging roller 2. Accordingly, the blade holder 27 can suppress the radiation of electrostatic noise generated near the nip between the photosensitive member 1 and the charging roller 2 to the developing device 15 side.

The radiation of electrostatic noise toward the photosensitive drum 1 from the nip is suppressed by the fact that the base of the photosensitive drum 1 is grounded by a conductor such as aluminum.

In this embodiment, the cleaning blade holder 36 and the developing blade holder 27 are grounded in order to reliably reduce radiation noise. Holder 36
And 27 are longer than the roller 2 in the longitudinal direction of the charging roller 2, that is, in the generatrix direction (the direction perpendicular to the plane of FIG. 1). In this example, when the electromagnetic field intensity indicating the magnitude of the radiation noise was measured, it was less than 30 dB.

As in this embodiment, since the conductive member covering the charging roller 2 is constituted by the cleaning blade holder 36 and the developing blade holder 27, there is no need to provide a new shield member, and the shielding effect can be obtained at low cost. And
Further, a space for installing the shield member is not required.

FIG. 2 is a side view of a process unit detachable from an image forming apparatus for explaining a reference example of the present invention.

In FIG. 2, when the process unit is mounted on the main body of the image forming apparatus and an image signal is input, the photosensitive member 1 rotates in the direction of the arrow, and the power supply 1 provided in the main body of the apparatus is rotated.
9 and the charging roller 2 connected to the constant current control means 20. An electrostatic latent image is formed on the photoreceptor 1 by laser exposure 14 from a laser scanning device (not shown). Further, the photoreceptor 1 is formed on a developing sleeve 25 of a developing unit 15 by toner powder whose layer thickness is regulated by a developing blade 26.
Is developed and visualized. The visualized toner image is fed by a paper feed roller (not shown), and is transferred by a transfer roller (not shown) onto a transfer material conveyed at a timing adjusted by a pair of registration rollers (not shown). . The transfer material onto which the toner image has been transferred is fixed by a fixing device including a fixing roller and a pressure roller (not shown). The toner remaining on the photoconductor 1 after the transfer is transferred to a cleaner device 18.
Is cleaned by

In the present embodiment, the charging roller 2 which comes into contact with the photoreceptor 1 is held by a holder 7 which supports an insulating bearing of a core shaft of the charging roller.
Is made of a metal such as iron which is a conductive member. Further, the holder 7 is grounded to the image forming apparatus main body. The holder 7 is longer than the roller 2 in the generatrix direction of the charging roller 2 (the direction perpendicular to the plane of FIG. 2), and is provided so as to cover the roller 2 at both ends of the roller. That is, at both ends of the roller 2, a holder wall is also provided in a direction intersecting with the generatrix direction (a direction parallel to the paper surface). Therefore, radiation noise generated near the nip portion between the photoconductor 1 and the charging roller 2 can be suppressed by the charging roller holder 7 and the photoconductor 1 that are grounded.

In this embodiment, the electromagnetic field strength is 30 dB.
Radiated noise was significantly reduced as compared with the electromagnetic field intensity of 45 dB when a non-conductive resin holder was used as the holder.

FIG. 6 shows a preferred example of the structure of the charging roller 2 in the above embodiment.

A conductive elastic layer 22 is provided on the metal core 21, a high-resistance elastic layer 23 is provided thereon, and a protective film 2 is provided on the surface.
4 The conductive elastic layer 22 is made of a material obtained by dispersing carbon in EPDM (a terpolymer of ethylene propylene diene), and serves to guide a bias voltage supplied to the metal core 21. The high-resistance elastic layer 23 is made of urethane rubber or the like, and includes a small amount of conductive fine powder (for example, carbon) as an example. The high-conductive part such as a pinhole of the photoconductor 1 is charged. Even when the rollers 2 are opposed to each other, the leakage current to the photoreceptor 1 is limited to prevent the bias voltage from dropping sharply. Surface protective film 24
Is made of N-methylmethoxylated nylon, and has a protective effect such that the composition of the conductive elastic layer 22 and the high-resistance elastic layer 23 does not touch the photoconductor 1 and deteriorate the surface of the photoconductor 1. Make

FIG. 3 shows another embodiment of a process unit detachable from the image forming apparatus of the present invention.

Parts common to FIG. 2 are denoted by the same reference numerals, and in this embodiment, only the charging member is different. FIG. 7 is a side view when the process unit of FIG. 3 is mounted on the image forming apparatus main body. The operation will be described with reference to FIGS.

The photoreceptor 1 rotates in the direction of the arrow, is connected to a power supply 19 and a constant current control means 20 provided in the apparatus main body, and is charged by the charging blade 4 in contact with the photoreceptor 1. When a laser beam 46a emitted from the laser scanner unit 46 after being modulated by an image signal is reflected by the mirror 47 and irradiated on the charged surface of the photoconductor 1, an electrostatic latent image is formed on the photoconductor 1. You. The electrostatic latent image on the photoreceptor 1 is developed on a developing sleeve 25 of a developing unit 15 with toner powder whose layer thickness is regulated by a developing blade 26. On the other hand, the transfer material 16 made of paper placed on the cassette 41 is fed by a feed roller 42, conveyed by a pair of registration rollers 43, 43 in synchronization with the laser emission timing, and transferred by a transfer guide 44. You will be guided to the location. The toner image formed on the photoconductor 1 is transferred to the transfer material 16 conveyed to the transfer position by the corona discharger 45 for transfer as described above. Transfer material 16 after transfer
After the toner image is fixed by a fixing device including a fixing roller 51 and a pressure roller 52, the toner image is discharged to a tray 48 outside the apparatus by a paper discharge roller 49. On the other hand, the photoreceptor 1 after the transfer
The remaining toner is cleaned by the cleaning device 18.

As shown in FIG. 3, the photosensitive member 1, the developing device 15, the cleaning device 18, and the charging devices 4, 5, 6
Is provided in one frame 8 as a process unit, and is detachably provided in the image forming apparatus main body. The process unit 8 may be formed of at least a photoconductor and a charging device. In FIG. 7, the apparatus main body can be divided into an upper housing and a lower housing at a transfer material conveyance path, that is, between the photoconductor 1 and the transfer charger 45. The upper housing is rotatable counterclockwise around the center. Then, the process unit 8 can be attached and detached from the upper housing in a state where the apparatus is divided and opened.

Next, a charging device in the process unit 8 will be described with reference to FIG.

The charging blade 4 as a contact charging member includes:
For example, a rubber blade having a thickness of 1 to 2 mm, such as hydrin, EPDM, urethane, or NBR, whose resistance is controlled to about 10 ⁵ to 10 ⁸ Ωcm, is provided on a conductive rigid support member (support) 5 such as a steel plate. Side is integrally attached and held by a conductive adhesive 13, the free length l of the blade (the distance between the tip of the support member of the blade and the contact portion of the blade with the photosensitive drum) is about 5 to 20 mm, and the photosensitive drum 1 (The angle between the tip of the blade and the line of the tangent line of the drum at the point where the blade is in contact with the drum on the downstream side in the drum surface moving direction from the blade contact point)
Is set to about 8 ° to 25 ° and the contact pressure is about 4 to 40 gr / cm, and the tip of the blade is brought into contact with the rotation of the photosensitive drum 1 in the counter direction (the contact angle is an acute angle). The contact of the charging blade 4 with the photosensitive drum 1 may be in the forward direction (the contact angle is acute) with respect to the rotation of the drum 1.

Reference numeral 9 denotes a surface resistance layer provided at a contact portion of the charging blade 4 with the photosensitive drum 1, and 10 ⁸ to 10 ¹²
The resistance blade 4 is printed on the charging blade 4 as a thin layer of about 2 to 100 μm in thickness, such as nylon or urethane, having a resistance of about Ωcm.

As described above, reference numeral 19 denotes a power supply for applying a voltage to the charging blade 4. The power supply 19 supplies a DC voltage corresponding to a required potential of the photosensitive drum 1 to the conductive rigid supporting member 5 of the charging blade 4. Voltage or peak-to-peak voltage that is at least twice the charging start voltage (applied DC voltage V _TH at which the photoconductor starts charging when a DC voltage is applied) determined by the charging blade and the photosensitive drum to obtain charging uniformity When an oscillating voltage obtained by superimposing the alternating voltage and the DC voltage is supplied, power is supplied to the charging blade 4 via the support member 5, and a contact portion between the charging blade 4 having the surface resistance layer 8 and the photosensitive drum 1 is provided. The surface of the photosensitive drum 1 is uniformly charged to a predetermined polarity and a predetermined potential.

On the other hand, as shown in FIG. 3, a copper foil (conductive member) 6 having a thickness of about 0.3 mm is formed on the inner wall of the process unit.
Is attached by a double-sided tape so as to cover the charging blade 4, and this copper foil is grounded. In addition, the support 5
Although not shown, it is fixed to the frame 7 with screws. Further, the holder portion 36 of the cleaning blade 35
Is made of a conductive member and grounded together with the copper foil.
The copper foil 6 and the holder 36 are provided longer than the blade 4 in the longitudinal direction of the charging blade 4 (the direction perpendicular to the plane of FIG. 3).

When the electromagnetic field strength was measured also in this example, it was less than 30 dB. As a result, even in the contact charging method using the charging blade, as in the above-described embodiment, the entire area around the nip portion of the contact charging, which generates radiation noise, is covered with a grounded conductor, which is a conventional problem. It has become possible to solve the radiation noise problem that had been occurring.

In the embodiment shown in FIG. 3, a double-sided tape made of copper foil is used as the conductive member. However, it is a matter of course that the inner wall of the process unit may be coated with copper foil instead.

Further, in the above embodiments, the preferable volume resistance value of the conductive member was 10 ³ Ωcm or less in order to reduce radiation noise.

The process unit 8 shown in FIG. 2 is also detachable from the image forming apparatus main body shown in FIG. 7, as in this embodiment.

In order to perform charging uniformly and stably, for example, an oscillating voltage is applied to the contact charging member so that the charging member and the photosensitive member 1 are charged.
When an alternating electric field is formed between the charging member and the DC voltage, the radiation noise is particularly larger than when a DC voltage is applied to the charging member. Therefore, the provision of the conductive member as described above is particularly effective.

In the above-described embodiments, the charging of the photosensitive member is not limited to the case where the potential of the photosensitive member is increased, but includes the case where the potential of the photosensitive member is reduced, that is, so-called static elimination.

Further, in the above embodiment, the distance between the conductive member covering the nip portion between the photosensitive member 1 and the charging member and the charging member is smaller as the distance between the conductive member and the charging member becomes smaller. It is possible to prevent radiation noise. However, if they are too close, the charging member and the conductive member leak, and the charging ability of the photoreceptor 1 is reduced.
Image defects may occur. For this reason, the charging member and the conductive member need to be kept at a minimum distance so as to maintain an insulating state. Here, when the DC voltage applied to the charging member was about 2.0 kV, the distance between the charging member and the conductive member required about 3 mm or more.

In general, the ground includes a signal ground in the circuit and a frame ground connected to the ground. Here, in this embodiment, the conductive member is directly connected to the frame ground. Because, even if it is directly connected to the signal ground, it is effective in preventing radiation noise, but when dropped to the frame ground via the signal ground on the circuit in the image forming apparatus, the noise generated in the charging device becomes This is because there is a possibility of entering the circuit and causing a malfunction in the image forming apparatus main body. Therefore, it is more desirable to connect directly to the frame ground.

Further, in the charging device of the contact charging system, when the charging member primarily charges the photoreceptor 1, a considerable amount of radiation noise is generated. Therefore, the present invention is effective in preventing radiation noise of the contact charging device. However, in particular, as in the above-described embodiment, the current value having the vibration component applied to the charging member maintains the charging uniformity regardless of the environment. 560μ
Since the radiation noise generated when the constant current control is performed at A is relatively large and tends to leak out of the apparatus, it is particularly effective to provide the conductive member.

Further, when the current flowing to the charging member is controlled to be constant as described above, the current is prevented from flowing between the charging member and the conductive member so that the charging member and the photosensitive drum are always controlled. This is desirable because a constant electric field is formed between them.

[0052]

As described above, according to the present invention,
It is possible to use contact charging which has many advantages as compared with the corona discharger, and it was possible to greatly reduce electrostatic radiation noise which has been a problem in contact charging. In addition, by using the holder of the cleaning blade as the conductive member, the number of components is reduced and the size can be reduced.

[Brief description of the drawings]

FIG. 1 is a side view showing a first embodiment of a process unit of the present invention.

FIG. 2 is a side view showing a second embodiment of the process unit of the present invention.

FIG. 3 is a side view showing a third embodiment of the process unit of the present invention.

FIG. 4 is a side view of a charging device used in the process unit of FIG.

FIG. 5 is a side view illustrating a conventional charging device.

FIG. 6 is a side view illustrating an example of a charging roller.

FIG. 7 is a side view of the image forming apparatus equipped with the process unit of FIG. 3;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photoconductor 2 Charging roller 4 Charging blade 8 Process unit 6, 7, 27, 36 Conductive member

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yoshiya Nomura 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Shinichi Sasaki 3-30-2 Shimomaruko, Ota-ku, Tokyo (56) References JP-A-55-19727 (JP, A) JP-A-2-91666 (JP, A) JP-A-60-195562 (JP, A) JP-A-4-162068 (JP) , A) JP-A-2-163779 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 15/02 101 G03G 15/16 G03G 21/06

Claims (10)

(57) [Claims] 1. An image having an image carrier, a charging member to which a voltage is applied to contact the image carrier and charge the image carrier, and a cleaning blade for cleaning the image carrier. An image forming apparatus, comprising: a conductive member that covers the charging member and is grounded; and the conductive member includes a holder portion of the cleaning blade. 2. The image forming apparatus according to claim 1, wherein the conductive member covers a side of the charging member opposite to the image carrier. 3. The image forming apparatus according to claim 1, wherein the conductive member is longer than the charging member in a longitudinal direction of the charging member. 4. The image forming apparatus according to claim 1, wherein the charging member and the conductive member are provided at a predetermined distance so that no current flows between the charging member and the conductive member. 5. The image forming apparatus according to claim 1, wherein the charging member has a roller shape. 6. A process unit detachable from an image forming apparatus, comprising: an image carrier; a charging member capable of applying a voltage to contact the image carrier and charge the image carrier; A cleaning blade for cleaning the image carrier, comprising: a conductive member that covers the charging member and is grounded; and the conductive member includes a holder portion of the cleaning blade. Process unit. 7. The process unit according to claim 6, wherein the conductive member covers a side of the charging member opposite to the image carrier. 8. The process unit according to claim 6, wherein the conductive member is longer than the charging member in a longitudinal direction of the charging member. 9. The process unit according to claim 6, wherein the charging member and the conductive member are provided at a predetermined distance so that no current flows between the charging member and the conductive member. 10. The process unit according to claim 6, wherein the charging member has a roller shape.