JP3100423B2 - Roller transfer device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a roller transfer device used in an image recording apparatus utilizing an electrostatic transfer process, such as a laser printer, an electrostatic copying machine, and the like.

[0002]

2. Description of the Related Art As a device for transferring a toner image formed on a toner image carrier by an electrophotographic image forming method such as a so-called Carlson method onto a transfer medium, a corona transfer method and a bias roller transfer method have been well known. ing. The corona transfer method is widely used in printers and copiers due to its simple structure.However, when the humidity is high, the recording paper absorbs moisture and has low resistance, resulting in poor transfer and ozone harmful to the human body. In addition, there is a problem that when the recording paper is separated from the image carrier, the toner scatters and a sharp image cannot be obtained. On the other hand, in the roller transfer method, since the toner is transferred by pressure, a stable transfer image can be obtained even at high humidity without being influenced by the moisture absorption state of the paper, and a sharp image with little toner scattering can be obtained. In addition, since no ozone is generated by corona discharge, the roller transfer method can be said to be a transfer method that compensates for the above-mentioned disadvantages of the corona transfer method.

[0003]

The conventional roller transfer method has the following problems, which has been an obstacle to practical use. FIG. 4 is an enlarged view of a transfer portion for roller transfer. 1 is a photosensitive drum, 5 is a transfer roller, 10 is a recording paper, and 11 is a toner image. A is the contact surface between the photosensitive drum and the toner image, B is the contact surface between the toner layers between the toner layers, C is the contact surface between the toner image and the recording paper 10, and D is the contact surface between the recording paper 10 and the transfer roller 5. Surface. The photosensitive drum 1 receives power from a motor or the like (not shown), which is a driving unit, and rotates in a direction indicated by an arrow. Further, a drive system is not connected to the transfer roller 5, and can be driven by the photosensitive drum 1, and the transfer roller 5
, And rotates in the direction of the arrow. Therefore, if there is a portion having a small friction coefficient among the surface A, the surface B, the surface C, and the surface D, the slip is likely to occur. The slipperiness varies depending on the photoreceptor drum 1, toner, recording medium 10 (paper, OHP sheet, etc.), material and surface shape of the transfer roller 5, and the like.
Is set to be relatively high, and slipping is relatively likely to occur partially or simultaneously at any of the surfaces A, B, and C. If a slip occurs on any of the surfaces A, B, and C, the transferred image will have a so-called transfer deviation.
Transfer loss or image shrinkage is likely to occur.

In order to avoid such a problem, a drive system may be connected to the transfer roller 5, but at this time, an unnecessary force is generated and a stable transfer image cannot be obtained. This will be described with reference to FIG. In the drawing, 1 is a photosensitive drum, 5 is a transfer roller, 12 is a gear directly connected to the shaft of the transfer roller, and 13 is a motor (not shown) which is driven by a transfer roller 5.
Is a gear that transmits the driving force to the motor. Α is the pressure angle of the gear. The transfer roller 5 is adjusted by a spring or the like (not shown) so that an appropriate pressure F1 acts in the normal direction of the drum 1. The transmission gear 13 is disposed at a position forming an angle α with the normal line of the drum. This is because the force F2 generated when transmitting the driving force from the gear 13 to the gear 12 is in a direction perpendicular to the normal line of the drum. That is, the arrangement is intended to eliminate the fluctuation of the transfer pressure F1.

In practice, however, the transfer roller moves in the direction of the drum normal in accordance with the thickness of the recording medium, so that the meshing position between the gears 12 and 13 fluctuates, and therefore the direction of the rotation transmitting force F2 also fluctuates. Then, a force was generated in the normal direction of the drum. As a result, only the transfer pressure F1 of the transfer roller 5 on the side of the gear 12 is increased, and uneven transfer or missing transfer occurs. In addition, when the fluctuation of the meshing position between the gear 12 and the gear 13 is relatively large, the rotational load is increased or the meshing of the teeth is deteriorated, so that the rotational fluctuation of the transfer roller 5 is caused. Such rotation fluctuation causes pitch unevenness of the transferred image. In addition, even when the transfer roller 5 is disposed, the transfer roller is elastically deformed by pressure, so that the gear 12
It is difficult to set the meshing position of the gear 13 and the gear 13 at an optimum position.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to improve the image quality of a transferred image by preventing the pressing force of the transfer roller from being applied to the toner image carrier when transmitting the rotational force to the transfer roller.

[0007]

Means for Solving the Problems] In view of the above objects the present invention, with pressing the transcription medium for transferring to a transfer medium the toner image formed on the toner image bearing member to a toner image carrier
And a transfer roller which is concentrically fixed to the transfer roller.
A rotational force receiving apparatus, between the rotational force receiving device and a power source
A transmission device stretched over the power source, wherein the driving force of the power source is
A roller transfer device that is transmitted to the rotational force receiving device via the transmission device , wherein the power source and the rotational force receiving device are
The transmitting direction of the driving force to the rotational force receiving device of the transmitting device stretched between the transmitting device and the transmitting device is orthogonal to the direction in which the transfer roller presses and biases the toner image carrier. The power source is arranged so that the driving force from the power source
-Do not affect the pressing force of the transfer roller against the image carrier.
An improved roller transfer device is provided.

[0008]

[Function] The direction of the force for directly rotating the transfer roller is
Since the transfer roller is orthogonal to the direction in which the transfer roller is pressed against the toner image carrier, the transfer pressure is not affected.
In addition, since the transfer roller moves smoothly in the pressing direction, the pressing force always has an appropriate value, and the setting of the transfer roller becomes easy.

[0009]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows an embodiment of an electrophotographic apparatus using the present invention. In the figure, 1 is a photosensitive drum, 2 is a charger, 3 is an exposure device, 4 is a developing device, 5 is a transfer roller, 6 is a bearing, 7 is a spring, 8 is a bias power supply,
9 is a cleaner, 10 is a recording paper, 14 is a bearing guide for the transfer roller 5, 15 is a drive motor, 16 is a coaxial pulley directly connected to the transfer roller 5, 17 is a pulley directly connected to the motor 15, and 18 is a timing belt. is there. In the figure, a transfer roller 5 applies a pressure to a photosensitive drum 1 to a bearing 6.
And received by the spring 7. The bearing is adapted to move smoothly in the pressing direction by the guide. Since the transfer pressure affects the transfer characteristics, particularly the transfer efficiency, the transfer pressure is adjusted by changing the displacement of the spring 7 so that a good transfer characteristic can be obtained in the range of 1 to 500 × 10 ⁻³ kgW / cm ^2. Have been. The bias power supply 8 applies a bias voltage to the transfer roller 5.
When the toner is transferred from the photosensitive drum 1 to the recording paper 10, a voltage having a polarity opposite to that of the toner is generated. Since the bias voltage greatly affects the transfer characteristics as well as the pressure, the voltage at which good transfer characteristics can be obtained in the range of 0.1 to 4 kV during transfer is always considered, taking into account the transfer roller resistivity and the transfer medium resistivity. Has been adjusted.

As shown in a sectional view of FIG. 2, the transfer roller 5 is a conductive continuous porous body having fine pores as an elastic layer 5b on a metal core 5a (outer diameter 8 mm) of a metal such as stainless steel. It is lining. In this embodiment, a polyurethane sponge made of Toyo Polymer, Rubicel (registered trademark) is used as the continuous pore body, and a conductivity-imparting agent such as carbon black is added to impart conductivity. Since the volume resistivity of the elastic layer 5b greatly affects the transfer characteristics, it is adjusted in the range of 10 ² to 10 ¹³ Ωcm, and is set to 10 ⁶ to 10 ⁹ Ωcm in this embodiment. Further, the hardness affects the transfer characteristics in relation to the adhesion between the paper and the toner image at the time of transfer.
(ASKER-C) is adjusted to a relatively low hardness, and is set to 30 degrees (ASKER-C) in this embodiment. The thickness of the elastic layer 5b is appropriately determined in the range of about 1 to 15 mm, and is set to 6 mm in the present embodiment, because the thickness of the elastic layer 5b affects the adhesion between the paper and the toner image at the time of transfer similarly to the hardness.

In this embodiment, the pulley 16 and the motor 15 are arranged so that the line connecting the center of the pulley 16 and the center of the pulley 17 is perpendicular to the normal line of the photosensitive drum 1. The rotation speed of the motor is adjusted so that the peripheral speed of the photosensitive drum 1 and the peripheral speed of the transfer roller 5 substantially match.
In the apparatus having the above configuration, first, the photosensitive drum 1
Are uniformly charged by the charger 2. Next, an electrostatic latent image is formed by the exposure device 3 and visualized by the developing device 4 to become a toner image. When the toner image on the photoreceptor reaches the contact area with the transfer roller 5, the toner image is pressed against the recording paper 10 conveyed in synchronization therewith, and at the same time, the transfer roller 5
, A voltage is applied from a bias power supply 8, and the toner image is transferred from the photosensitive drum 1 to the recording paper side. The toner remaining on the photosensitive drum without being transferred is cleaned by the cleaner 9 to prepare for the next cycle starting from charging.

In this apparatus, the timing belt 18 serves as a drive transmitting means for the transfer roller 5, that is, a rotational force transmitting device to the pulley 16 which is a rotational force receiving device.
Since the line connecting the center of the pulley 16 and the center of the pulley 17 concentric with each other is perpendicular to the common normal line (the direction of F1) of the transfer roller 5 and the photosensitive drum 1, the force F2 generated at the time of driving is The direction is perpendicular to the pressing direction (F1 direction) of the transfer roller 5. Further, even when recording media having different thicknesses pass, the transfer roller 5 can smoothly move in the pressing direction (F1 direction), so that a constant transfer pressure can always be applied. Here, the transfer roller 5 theoretically moves in an arc around the rotation axis of the pulley 17 which is fixed, but the transfer distance of the transfer roller 5 is the distance between the pulley 16 and the pulley 17. Since the transfer roller is considerably smaller, it can be considered that the transfer roller makes a linear motion approximately.

In this apparatus, when printing was evaluated by the above-described process, transfer unevenness, transfer omission, and transfer image pitch unevenness, which occurred when the transfer roller 5 was driven, did not occur. In this embodiment, the timing belt 18 is used as the drive transmission unit of the transfer roller 5.
The drive transmission means may be a chain-shaped one or a belt-shaped one having holes, projections, irregularities, and the like.

[0014]

As described above, according to the present invention, the drive transmission means is provided so that the direction of the force generated when driving the transfer roller is always perpendicular to the pressing direction of the transfer roller. Therefore, transfer unevenness and transfer omission caused by transfer pressure fluctuation do not occur, and transfer image pitch unevenness caused by transfer roller rotation fluctuation can be prevented. Further, the setting of the transfer roller can be easily performed because there is no need to care about the amount of elastic deformation.

[Brief description of the drawings]

FIG. 1 is a schematic view of a roller transfer device according to the present invention.

FIG. 2 is a sectional view of a transfer roller used in the apparatus of FIG.

FIG. 3 is an operation explanatory view of a main part of a conventional roller transfer device.

FIG. 4 is an enlarged view of a transfer area by a roller transfer device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Photoreceptor drum 5 ... Transfer roller 10 ... Recording paper 15 ... Drive motor 16 ... Pulley coaxial with a transfer roller 18 ... Timing belt

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G03G 15/16

Claims (3)

(57) [Claims] 1. A toner image bearing member (1) transfer medium the toner image formed on the (10) the transfer medium to transfer onto
(10) a toner image bearing member (1) transfer roller that presses and biases the (5), is fixed concentrically the transfer roller (5)
Receiving rotational force device (16) receives the rotating force device (1
6) and the transmission device (1) suspended between the power source (15).
8) , wherein the driving force of the power source (15) is
Via the device (18) to the rotational force receiving device (16).
In the roller transfer device to be reached , the power source (15) and the rotational force receiving device (16)
The rotational force receiving device of the transmission device (18) stretched between the devices;
Direction of transmission of driving force to the (16) (F2) is, the toner
The transfer roller (5) is the power source to be perpendicular to <br/> direction urging pressed (F1) to the image bearing member (1) (1
5), and the driving force from the power source (15) is
Pressing of the transfer roller (5) against the toner image carrier (1)
A roller transfer device characterized in that force is not affected . 2. The method according to claim 1, wherein the rotational force receiving device is a toothed pulley (1).
6), wherein the transmission device is a timing belt (18).
2. The roller transfer device according to claim 1, wherein a stretching direction of the timing belt is orthogonal to the urging force direction (F1). 3. The roller transfer device according to claim 1, wherein the rotational force receiving device is a sprocket, the transmission device is a chain, and a stretching direction of the chain is orthogonal to the urging force direction (F1). apparatus.