JPH0335276A - Image forming device - Google Patents

Abstract

PURPOSE:To prevent the permanent strain of a transfer member by separating the transfer member from a material to be transferred at the time of other than image formation. CONSTITUTION:At the time of other than the image formation, a transfer roller 1 is held by a holding member 3, which can rotate centering on a supporting point 2 and serves also as a paper guide, and a spring (not shown in figure) which energizes the roller 1 on the side of a photosensitive body 4. At the time of image forming operation, the transfer roller 1 is made press-contact with the photosensitive body 4 by a solenoid 7, a link member 8 and an elastic member 9. Thus, it is prevented that the permanent strain arises in the transfer roller 1 and that remarkable deterioration such as transfer skipping arises in an image.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to an image forming apparatus with an improved structure for transferring an image to a transfer material.

(Prior Art) Some image forming apparatuses, such as electronic photographic machines, are equipped with a contact-type transfer device.

A contact-type transfer device includes an elastic transfer roller, and presses the elastic transfer roller against a photosensitive drum through a sheet of paper to transfer the image on the photosensitive drum to the sheet of paper.

(Problem to be Solved by the Invention) However, in the past, the elastic transfer roller was kept in pressure contact with the photosensitive drum even when the image was not being formed. There is a problem in that this causes uneven transfer and makes it impossible to obtain a clear image.

Therefore, it is an object of the present invention to provide an image forming apparatus that does not cause permanent distortion in the transfer member.

Furthermore, in the past, since the photosensitive drum and the elastic transfer roller were rotationally driven by independent drive sources, there was a problem that jitter occurred in the transferred image due to speed differences, load fluctuations, and the like.

SUMMARY OF THE INVENTION Therefore, it is an object of the present invention to provide an image forming apparatus that does not cause permanent distortion in a transfer member or jitter in a transferred image.

(Example) Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

An embodiment of the present invention is shown in FIGS. 1 to 6.

FIG. 1 is a diagram showing a transfer device according to the present invention, and shows a state other than the image forming operation.

In the figure, 1 is a transfer roller as a transfer member, and this transfer roller 1 is rotatable around a fulcrum 2 when not in an image forming operation, and is attached to a holding member 3 that also serves as a paper guide and a photoreceptor 4 side. It is held by a spring (not shown) for biasing. This transfer roller 1 includes a spring 5 and an end portion 3 of the holding member 3.
It is supported by a cs housing 6 at a first position away from the photoreceptor 4 .

Also, during the image forming operation, a solenoid 7, a link member 8, and an elastic member 9 are used to press the transfer roller l against the photoreceptor 4.
is included.

FIG. 2 shows the state during the image forming operation, and when the solenoid 7 is energized, the elastic member 9 attached to the link member 8 and the end portion 3 a S housing 6 of the transfer roller holding member 3 The transfer roller 1 is supported at a second position positioned so as to receive an appropriate pressure from the photoreceptor 4.

FIG. 3 is a flowchart showing the operating state of the solenoid 7 of the transfer roller 1.

To explain according to the flowchart below, the transfer roller 1
Solenoid 7 is normally “OFF” (i.e. transfer roller 1
is in the first position where it is not in pressure contact with the photoconductor 4), and even when the power of the device is turned on and the photoconductor 4 begins to rotate, the solenoid 7 remains "ON" during warming up.
(that is, the transfer roller 1 is in the second position where it is in pressure contact with the photoreceptor 4), and when the warming-up is completed and the main motor (photoreceptor drum motor) is turned on by the print ON signal. First time using solenoid 7
In other words, the transfer roller 1 is not brought into pressure contact with the photoreceptor 4 except when an image forming operation is performed.

This makes it possible to prevent the disadvantage that if the transfer roller 1 remains in pressure contact, permanent distortion is likely to occur in the transfer roller 1, and significant deterioration such as transfer missing occurs in the image.

Furthermore, as shown in the flowchart of Fig. 3, when the transfer paper jams, the transfer roller 1 is turned off by the jam detection signal.
F' to prevent the transfer roller 1 from being scratched or destroyed.

FIG. 4 is a cross-sectional view schematically showing the transfer device according to this embodiment.

In the figure, 4 is a photosensitive drum, for example, an OPC drum is used. A transfer roller 1 holds guide rollers la and lb at both ends thereof. The transfer roller 1 is guided and supported by a base 14 via bearings 12 and bushings 13 at both ends of a shaft 11, and a compression coil 15 protruding from the base 14 causes the guide rollers la and lb to be connected to the photoreceptor. 4, they are in contact with each other with the nip width.

Reference numeral 16 denotes a cleaning device including a cleaning member for removing toner and paper dust adhering to the transfer roller 105. This cleaning device 16 is supported by the bushing 13 on which the transfer roller 1 is supported. , the cleaning device 16 is positioned integrally with the transfer roller 1. That is, even when the transfer roller 1 presses the photoreceptor 4, the relative position between the transfer roller 1 and the cleaning device 16 does not change.

The transfer roller 1 is driven by a first roller provided at the end of the photoreceptor 4.
This is done by transmitting the image from the gear 17 to the second gear 18 provided at the end of the transfer roller 1.

Further, the pitch circle diameter of the second gear 18 of the transfer roller 1 is approximately equal to the diameter of the guide rollers la and lb of the transfer roller 1, and the pitch circle diameter of the first gear 17 of the photoconductor 4 is approximately equal to the diameter of the guide rollers la and lb of the transfer roller 1. It is approximately equal to the diameter of 4.

FIG. 5 is a sectional view showing details of the transfer roller 1.

As shown in FIG. 5, the transfer roller 1 in this embodiment includes a resiliently deformable elastic layer 19, a conductive layer 20, and a resistive layer 2.
1 and a support shaft 22.

The resistance layer 21 is made by dispersing conductive carbon in a polyester resin and has a volume resistivity of 108 Ω.
, 1 am thick is used.

The conductive layer 20 is made of, for example, the same material as the resistive layer 21 and has a volume resistivity of about 10'Ω·(maximum), and has a thickness of 0.1 m.

The elastic layer 19 is made of, for example, foamed urethane with a rubber hardness of 20 @, and conductive members 23 made of, for example, conductive urethane and having a volume resistivity of 10'Ω, which will be described later, are formed at both ends of the elastic layer in the axial direction. .

Next, the operation of the transfer roller 1 according to this embodiment will be explained.

The toner image 24 on the photoreceptor 4 is transferred to the toner transfer section (between K and J) according to the rotation direction of the photoreceptor 4 (direction of arrow R). At the image transfer section 25, the toner image 24 is pressed against the paper P, which is a transfer material.

During this time, a transfer voltage having a polarity opposite to the charge (negative polarity in this figure) of the toner image supplied by the high voltage generation circuit 26 acts on the toner image 24, and the toner image 24 is electrostatically transferred to the paper P. , forms an image on paper P.

At this time, in the image transfer section (between K and J), the photoreceptor 1 and the paper P come into close contact with each other due to the elastic deformation of the elastic layer 19 of the transfer roller 1, forming a wide nip width.

In roller transfer, if the transfer pressure is too high, the toner image 24
A phenomenon occurs in which the toner in the center of the image is not transferred to the transfer material. For example, when recording characters, only blank characters, that is, only the irregularities of character shapes are recorded.

Since the transfer pressure also depends on the rubber hardness of one elastic layer,
Unless the settings are made under appropriate conditions, good images cannot be obtained.

Furthermore, if the volume resistance value of the resistive layer 21 is too low, discharge may occur between the resistive layer 21 and the photoreceptor 4 when a transfer voltage is applied, or unipolar toner may be generated due to charge injection, resulting in a significant reduction in transfer efficiency.

FIG. 6 shows a schematic configuration of an electrophotographic monochrome laser printer.

This laser printer is electrically connected to a computer or a host system (external device) such as a word processor via a transmission device (not shown), receives dot image data from the external device, and emits a laser beam. By modulating it, writing is performed on the photoreceptor, and the written dot image data is developed and transferred onto paper.

That is, 31 is an apparatus main body, and a drum-shaped photoreceptor 4 is disposed within this main body 100, and this photoreceptor 4 is rotated in the direction of arrow R by a drive source (not shown).

The peripheral portion of the photoconductor 4 was provided with a charge control type charging charger 32, an electrostatic latent image forming section 33, a developing section 34 having a guide roller (not shown), and a cleaning device 16 along the rotational direction of the photoconductor 4. A transfer roller 1, a cleaner 35 for cleaning residual toner on the photoreceptor 4, and a discharge lamp 36 are arranged in this order.

The main body 31 is provided with a paper feed cassette 37, and a paper P as a recording medium taken out from the paper feed cassette 37 by a paper feed roller 38 is fed between the photoreceptor 4 and the transfer roller 1. After passing through the image transfer section 25 and the fixing device 39, the face-up/face-down switching section 49
As a result, the paper is guided to the respective paper discharge rollers 46 and 47, and is discharged to the paper discharge section.

The electrostatic latent image forming section 33 includes a semiconductor laser oscillator (not shown) (such as a laser diode) that generates a laser beam modulated according to dot image data from an external device (not shown), and a laser output from this laser oscillator. A lens system such as a collimator lens that focuses the beam light (
(not shown), for example, a four-sided rotating mirror (polygon mirror) that scans the laser beam focused by this lens system.
, a mirror motor 4 that rotates this rotating mirror 40 at high speed.
1. A lens 42 that correctly guides the laser beam scanned by the rotating mirror 40 to the photoconductor 4, Reflection mirrors 43 and 44 that reflects the laser beam toward the photoconductor 4, and a laser beam scanned by the rotating mirror 40. It consists of a beam photodetector (not shown) that detects the

In such a configuration, when a print start signal is received from an external device, the photoreceptor 4 rotates, and the photoreceptor 4 is charged with a surface potential of about 0600 V by the charging device 32.
It is uniformly charged so that

Next, when receiving dot image data from an external device,
The electrostatic latent image forming section 33 outputs a laser beam modulated according to the dot image data, and scans and exposes the charged surface of the photoreceptor 4 with the laser beam, thereby changing the surface of the photoreceptor 4. forms an electrostatic latent image. The electrostatic latent image formed on the photoreceptor 4 is reversely developed by a developing device 50 having a developing roller 45, thereby becoming a visualized toner image. The toner image on the photoreceptor 4 is transferred to the image transfer section 25 by the action of the transfer roller 1 driven by a gear attached to the photoreceptor 4 (not shown).
The image is transferred onto the paper P conveyed from the paper feed cassette 31.

The paper P on which the toner image has been transferred is conveyed to the fixing device 39, where the toner image is fixed, and then transferred to the paper ejection rollers 46, 47.
The paper is ejected by

Further, the transfer roller 1 is provided with a cleaning device 16 for removing toner and paper powder, so that the image transfer portion 25 can always perform the transfer in a clean state.

After the toner image is transferred by the transfer roller 1, the remaining toner on the photoreceptor 4 is cleaned by a cleaner 35 disposed around the photoreceptor 4, and is removed by a static elimination lamp 48 such as a red LED. Static electricity is removed uniformly.

Note that, as shown in FIG. 7, the drive of the transfer roller 1 is not transmitted from a gear (not shown) of the photoreceptor 4, but is driven by a nip in contact with the photoreceptor 4. It may also be made to rotate at a constant speed. This can prevent image deterioration (such as synchronization blur) caused by driving the transfer roller 1.

Further, since the transfer roller 1 is made of an elastic material, it can also absorb vibrations caused by the rotation of the photoreceptor 4, and a good image without synchronization blur can be obtained. Also, the longitudinal dimension of the transfer roller 1 is A+B than C of the maximum transfer paper used in the device.
The transfer paper is larger than the photoreceptor 4 and the transfer roller 1.
The driven rotation of the transfer roller 1 is smooth without slipping even when the transfer roller 1 is in between. Also, the larger the dimensions A and B are, the better; however, if they are too large, the photoreceptor 4 will become large and the entire device will not be compact.
+B dimension is 5 to 50 mm, preferably 10 to 30 mm
It is best to keep it to a certain level.

Although the above embodiment has been described with respect to an electrophotographic laser printer, the present invention is not limited thereto, and can be similarly applied to other image forming apparatuses.

[Effects of the Invention] As explained above, according to the present invention, good images can be obtained for a long period of time without causing damage such as permanent distortion to the transfer member.

Further, the transfer member can be rotated at a constant speed by following the rotation of the image carrier, and it is possible to prevent image deterioration due to synchronization blur and the like.

[Brief explanation of drawings]

FIGS. 1 to 6 show an embodiment of the present invention. FIG. 1 is a configuration diagram showing a state in which the transfer roller is separated from the photosensitive drum, and FIG. 2 is a state diagram in which the transfer roller is in pressure contact with the photosensitive drum. 3 is a flowchart showing the operation of the solenoid for positioning the transfer roller, FIG. 4 is a block diagram showing the transfer device, FIG. 5 is a side sectional view showing the transfer roller, and FIG. FIG. 7 is a schematic block diagram showing a laser printer, and FIG. 7 is a block diagram showing another embodiment of the transfer device. 1... Transfer roller (transfer member) 4... Photoreceptor (image bearing member) 7... Solenoid (M hearing means), 24...
- Toner image (developer image).

Claims (2)

[Claims] (1) In an image forming apparatus that forms an image by bringing a transfer member into pressure contact with an image carrier through a transfer material to transfer a developer image on the image carrier to the transfer material, during image formation. The image forming apparatus is characterized in that the image forming apparatus further includes a separating means for separating the transfer member from the transfer target material. (2) Image formation in an image forming apparatus that forms an image by bringing a transfer member into pressure contact with a rotating image carrier through a transfer material to transfer the developer image on the image carrier to the transfer material. An image forming apparatus characterized in that: the transfer member is rotated in accordance with the rotation of the image carrier.