JPH04213474A - Electrifier - Google Patents

Abstract

PURPOSE:To reduce the longitudinal dimension of a device by regulating a movement in the shaft direction of an electrifying roller without preventing the rotating movement of the electrifying roller and having no play in the device passing an electrifying roller to a photosensitive drum as a body to be electrified, and electrifying the photosensitive drum. CONSTITUTION:The pressing force f1 of a pressing spring 4a and the pressing force f2 of a pressing spring 4b which act on both end parts of the electrifying roller for pressing it top the photosensitive drum 1 are made different in sizes (f1>f2), so that the electrifying roller 2 has the occurrence of meandering/ moving force to the longitudinal one end side direction R of the electrifying roller 2. The electrifying roller 2 meandering/moving is received/stopped by an end part regulating plate 72 as a positioning member, and positioning in the longitudinal direction of the electrifying roller 2 is carried out.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention is a method of charging the surface of a charged object (including static elimination processing) by bringing a charging roller into contact with the charged object.
The present invention relates to a charging device (roller charging device).

0002

[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 surfaces such as photoreceptors and dielectric materials, transfer materials, etc. Conventionally, corona discharge devices have been widely used as devices for charging the surface of a body to be charged, such as the back surface.

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

On the other hand, a contact type charging device, which charges the surface of the charged object by bringing a charging member to which a voltage is applied into contact with the charged object, can reduce the voltage of the power supply and generates only a very small amount of ozone. Because of these advantages, it has attracted attention as a charging treatment device to replace the above-mentioned corona discharge device, and research on its practical application is progressing (Japanese Patent Laid-Open No. 57-17826
7.56-104351.58-40566.58-1
39156.58-150975, etc.).

FIG. 5 is a cross-sectional side view of an example in which a roller-type contact charging member (hereinafter referred to as a charging roller) is used as a charging device for an image carrier in an image forming apparatus, and FIG.
A vertical cross-sectional view taken along line A-A of FIG.

1 is a part of a rotating drum-type electrophotographic photosensitive member (hereinafter referred to as a photosensitive drum) as an object to be charged;
Specified circumferential speed (process speed) in the clockwise direction of arrow N
It is rotationally driven with.

A charging roller 2 is arranged approximately parallel to the photosensitive drum 1 and pressed into contact with the surface of the photosensitive drum. It consists of a conductive elastic layer 2a made of carbon-containing EPDM or the like, which is coated in the form of a roller.

Reference numeral 7 denotes a housing with an open bottom side in which the charging roller 2 is housed, and is fixedly supported by a stationary member (not shown) at a constant distance from the photosensitive drum 1.

Reference numerals 71 and 71 are spring insert/bearing guides provided downward at both ends in the housing 7, and 5 and 5 are bearings that are movable up and down within these bearing guides, and are attached to both ends of the core metal 3 of the charging roller 2. The parts are rotatably supported by the bearings 5. Reference numerals 4 and 4 designate pressure springs compressed between the housing ceiling surface and the bearing 5 in each of the above-mentioned bearing guides 71 and 71. Therefore, the charging roller 2 charges the photosensitive drum 1 with pressing spring forces f and f acting on both ends of the core metal 3 via the movable bearings 5, respectively.
The photosensitive drum 1 rotates as the photosensitive drum 1 rotates. The charging roller 2 can also be configured to be actively rotated.

The housing ceiling surface portion corresponding to the upper end of the pressing spring 4 on one end side of the charging roller 2 is provided as an electrode plate 6, and a voltage applying power supply S to the charging roller 2 is connected to the electrode plate 6.
By making the pressing spring 4, bearing 5, and charging roller core metal 3 conductive, a bias is applied from the power source S to the charging roller 2 via the electrode plate 6 → pressing spring 4 → bearing 5 → core metal 3. A voltage is applied, and the peripheral surface of the rotating photosensitive drum 1 is charged to a desired polarity and potential by a contact method. Since the charging mechanism is already known, its explanation will be omitted.

Each process means (not shown in the figure) such as image exposure, development, and transfer is applied to the charged surface of the photosensitive drum, and a recording material (transfer material) is formed after the image is transferred.
is outputted via the image fixing means. After the image has been transferred, the surface of the photosensitive drum is cleaned by a cleaning means (not shown) to remove adhered contaminants such as residual toner, and is then charged again by a charging roller 2 and used for image formation repeatedly. be done.

0012

Problems to be Solved by the Invention The following problems can be raised with such a charging device. In other words, the movement of the charging roller 2 in the axial direction causes the end of the core metal 3 to move toward the housing 7.
The material of the core metal 3 and the end regulating plates 72 are as follows.
Usually, the former 3 is a metal such as iron, and the latter 72 is a metal such as A.
There are different plastics such as BS resin, and each has a different coefficient of thermal expansion. For this reason, core metal 3
If the end face of the charging roller 2 is configured to be in contact with the end regulating plates 72, 72, when the ambient temperature changes, the end face end regulating plates 72, 72 will interfere with the core bar 3, preventing smooth rotation of the charging roller 2. The core bar 3 and the end regulating plates 72, 7
A gap a, a must be provided between the two. Furthermore, when setting the gaps a, a, it is necessary to take into account the variations in the longitudinal dimensions that occur during the manufacturing of the core metal 3 and the housing 7, and to set them to values sufficient to prevent interference.

As a result, the area B of the surface of the photosensitive drum 1 charged by the charging roller 2 has a variation of only the sum of the gaps a and a (hereinafter referred to as backlash) a+a when viewed in the axial direction. Become.

FIG. 7 shows the relationship between the required charging area B on the photosensitive drum 1 and the length L of the charging roller 2. what if,
If the above-mentioned variation is zero, the length L of the charging roller 2 will be long if it is only B, as shown in FIG. 7(1). However, when L=B, if there is backlash a+a, then
If the position of the charging roller 2 shifts as shown in (2) and (3), the required charging area B on the photosensitive drum 1 will be in the gap a.
, a is no longer charged.

In order to prevent such problems, (4) in FIG.
), it is necessary to increase the length L of the charging roller 2 by the amount of backlash a+a, so that L=B+a+a. In other words, the width of the device increases by the amount of backlash a+a, which creates a problem in that image forming elements such as the charging roller 2 and the photosensitive drum 1 must also be increased in size.

[0016] Furthermore, the bias application to the charging roller 2 is
Since this is carried out via the electrode plate 6, pressing spring 4, conductive bearing 5, and core metal 3, there are many contact points, which increases contact resistance during long-term use, which may result in charging failure.

Furthermore, although the manufacturing lot number of the charging roller 2 is generally printed on the end face of the core metal 3, during long-term use, contact and friction between both end faces and the surface of the end regulating plate 72 must be avoided. Therefore, there is a problem in that the printing is rubbed off and becomes unreadable, making it impossible to trace the production lot of the charging roller 2. To prevent this, it has been necessary to use costly markings instead of printing.

The object of the present invention is to rationally solve the problems of the conventional device as described above.

[0019]

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

(1) In a charging device that charges the surface of a charged object by pressing a charging roller against the surface of the charged object, a shifting force is applied to the charging roller in the direction of one longitudinal end of the charging roller, and the charging roller is shifted. A contact charging device comprising a charging roller positioning member that receives the charging roller against force.

(2) A pressing force for pressing the charging roller against the surface of the object to be charged is applied to both ends of the charging roller, and the pressing forces applied to one end and the other end are set to different values, so that the charging roller is The charging device according to (1), wherein the charging device generates a shifting force toward one longitudinal end.

(3) Charging is performed by placing the charging roller against the surface of the object to be charged so that the virtual normal drawn to the axis of the charging roller does not coincide with the direction of movement of the surface of the object to be charged. The charging device according to (1), characterized in that the charging device generates a shifting force in the direction of one longitudinal end of the roller.

(4) The charging roller is a tapered roller whose diameter gradually increases in the longitudinal direction, and is pressed against the surface of the object to be charged, thereby generating a force to move the charging roller in the direction of one longitudinal end. The charging device according to (1).

(5) The charging roller positioning member is an electrode for applying voltage to the charging roller (1)
) described charging device.

[0025]

[Function] A shifting force is applied to the charging roller in the direction of one of its longitudinal ends, and the positioning member receives the charging roller against the shifting force of the charging roller, thereby positioning the charging roller, thereby eliminating backlash. As a result, the charging roller does not need to be made longer to accommodate play, and the entire device can be made more compact.

[0026] Also, since only the side of the charging roller that moves closer is received and positioned by the positioning member, and the opposite side is left open without any abutting member, the charging roller does not thermally expand due to an increase in ambient temperature. Even if the dimensions change in the longitudinal direction, rotation will not be hindered.

If the lot number is written on the open end surface of the charging roller, the marking will not be erased due to rubbing against the regulating plate as in the conventional case, and an expensive marking process will not be required. There's no need.

Furthermore, by using the positioning member that receives the charging roller and makes contact with the charging roller as an electrode for applying voltage to the charging roller, power can be supplied to the charging roller with one contact point, and charging failures due to contact resistance can be avoided. It can be prevented.

[0029]

【Example】

<First Embodiment> (FIG. 1) FIG. 1 is a longitudinal cross-sectional view of the apparatus of the first embodiment. Figures 5 and 6 above
The same parts as those of the conventional device shown in FIG.

In the apparatus of this embodiment, the pressing springs 4a and 4b at both ends of the core bar 3 for pressing the charging roller 2 against the surface of the photosensitive drum are the springs 4 at the left end in the drawing.
The pressing force f1 of a is the pressing force f2 of the pressing spring 4b on the right end side.
Springs with different elastic modulus are used to increase the elasticity.

In this configuration, the charging roller 1 is moved toward the right side R in its longitudinal direction as the photosensitive drum 1 rotates N, and is subjected to a moving force, so that the right end surface 32 of the core metal 3 serving as a charging roller positioning member is aligned with the right end of the housing 7. The charging roller 2 is positioned in the longitudinal direction by coming into contact with and being received by the side end regulating plate 72.

Therefore, it is sufficient to have the end regulating plate 72 only on the moving direction side of the charging roller 2, and no end regulating plate is required on the other side, which is the left side of the charging roller. Therefore, even if the longitudinal dimension of the charging roller 2 becomes longer due to thermal expansion, the problem that the charging roller 2 stops rotating does not occur, so there is no need to provide play a+a. In other words, it is only necessary to design the length L of the charging roller 2 based on the position of the end regulating plate 72 without allowing play, and the length of the charging roller 2 can be made shorter than in the conventional device, and the width of the device can be reduced. Can be made smaller.

Furthermore, at least the core bar 3 of the end regulating plate 72
By using the end surface abutting portion as a conductive electrode 6 made of metal or the like for applying voltage to the charging roller 2, the right end surface 32 of the core metal 3 is attached to this electrode 6 at least while the photosensitive drum is rotating, on the right side of the charging roller 2. The bias voltage can be supplied from the power source S to the charging roller 2 with only this one contact point, and charging failures due to contact resistance may occur even during long-term use. The probability of doing so is greatly reduced. In this case, since the bearing 5 does not need to be electrically conductive, an inexpensive material with excellent mutual sliding properties with the bearing guide 71 can be selected.

Furthermore, since the left end surface 31 of the core metal on the side not in contact with the end regulating plate 72 is open and will not be rubbed at all, the manufacturing lot number of the charging roller 2 is printed with indestructible ink on this end surface. If this is done, the lot number can be clearly read even after long-term use, which has the advantage of eliminating the need for costly markings.

<Second Embodiment> (FIG. 2) FIG. 2 shows a plan view of the main parts of the apparatus of the second embodiment. In this embodiment, the charging roller 2 is arranged so that its axis C has an intersection angle θ with respect to the generatrix D of the photosensitive drum 1. When the photosensitive drum 1 is rotated in the direction of the arrow N, the pressing spring 4 - The charging roller 2, which is pressed against the photosensitive drum 1 by the roller 4, is moved to the right side R in the longitudinal direction and receives a moving force, and as in the case of the first embodiment, the right end surface 32 of the core bar 3 is moved to the right side of the charging roller. The charging roller is positioned in the longitudinal direction by contacting the electrode plate 6 surface of the end regulating plate 72 as a positioning member. Therefore, play can be eliminated to zero, and the longitudinal dimension of the device can be reduced compared to conventional devices. Further, a voltage is applied to the charging roller 2 via the electrode plate 6 and the core metal 3.

<Third Embodiment> (FIGS. 3 and 4) FIG. 3 is a front view of the charging roller 2 used in the device of the third embodiment;
FIG. 4 is a longitudinal sectional view of a device using the charging roller 2. As shown in FIG. The charging roller 2 in this embodiment is tapered in the axial direction, and has an outer diameter of d1 at the left end and a larger outer diameter d2 at the right end.

When this tapered charging roller 2 is brought into contact with the photosensitive drum 1 as shown in FIG. 4, and both ends of the core metal 3 are pressed with equal pressing force f3 by pressing springs 4, 4,
When the photosensitive drum 1 rotates in the direction of the arrow N, the charging roller 2 receives a shifting force to the right in its longitudinal direction, and the right end surface 32 of the core bar 3 abuts against the end regulating plate 72 on that side, causing the charging roller 2 to move in the longitudinal direction R. Directional positioning is performed. Therefore, play can be eliminated to zero, and the longitudinal dimension of the device can be reduced compared to conventional devices.

It should be noted that the left end side of the housing 7 may have a structure in which no wall is provided at all as in the device shown in FIG.
In order to maintain strength depending on the material of the housing 7, a side wall 72L may be provided as necessary, as in the third embodiment shown in FIG.

In each of the apparatuses of the above embodiments, the case where the charging roller 2 is driven to rotate by the photosensitive drum 1 has been described. However, when the charging roller 2 is driven to rotate, the present invention can be applied and the same method as the apparatus of the above embodiments can be applied. be effective.

Furthermore, although the above-described apparatuses in each of the embodiments have been described in terms of charging the photosensitive drum 1, they can also be used as a transfer charging device for transferring an image on the photosensitive drum to a recording medium such as paper.

[0041]

As described above, according to the present invention, the backlash of the charging roller can be reduced, the longitudinal dimension of the device can be shortened, and the width of the entire device can be made smaller. Since the other end of the charging roller is open, there will be no problem even if the longitudinal dimension of the charging roller changes due to thermal expansion. Even if you write the lot number on the open end with ink, etc., the lot number will not change. The number will not become unreadable due to scratches. In addition, the charging roller receiving part of the positioning member is used as an electrode, and since the charging roller can be brought into good contact with this electrode by the force of the charging roller's shifting, power can be reliably supplied to the charging roller through the electrode at one contact point. can do.

[Brief explanation of the drawing]

[Figure 1] Figure 1 is a vertical cross-sectional view of the first embodiment device.

[Figure 2]
FIG. 2 is a plan view of the main parts of the device of the second embodiment.

[Figure 3]
FIG. 3 is a front view of the charging roller used in the device of the third embodiment.

[Fig. 4] Fig. 4 is a vertical cross-sectional view of the device of the third embodiment

[Figure 5]
Figure 5 is a cross-sectional view of the conventional device.

[Figure 6] Figure 6 is Figure 5
A vertical cross-sectional view along line A-A of

[Figure 7] (1) in Figure 7
(2) and (3) are illustrations of the positional relationship between the required charging area and the charging roller.

[Explanation of symbols] 1 Photosensitive drum (charged object) 2　Charging roller 6　Electrode plate 72 End regulation plate (positioning member)

Claims (5)

[Claims] 1. A charging device that charges the surface of a charged object by pressing a charging roller against the surface of the charged object, wherein a shifting force is applied to the charging roller in the direction of one longitudinal end thereof;
A contact charging device comprising a charging roller positioning member that receives the charging roller against the shifting force of the charging roller. [Claim 2] A pressing force for pressing the charging roller against the surface of the charged object is applied to both ends of the charging roller, and the pressing forces applied to one end and the other end are set to different values, so that the charging roller has a longitudinal direction. 2. The charging device according to claim 1, wherein the charging device generates a shifting force toward one end. 3. The charging roller is arranged so that the charging roller is pressed against the surface of the charged object so that the virtual normal drawn to the axis of the charging roller does not coincide with the direction of movement of the surface of the charged object. 2. The charging device according to claim 1, wherein the charging device generates a shifting force toward one longitudinal end. 4. The charging roller is a tapered roller whose diameter gradually increases in the longitudinal direction, and is pressed against the surface of the object to be charged, thereby generating a force to move the charging roller toward one longitudinal end. The charging device according to claim 1. 5. The charging device according to claim 1, wherein the charging roller positioning member is an electrode for applying voltage to the charging roller.