JPH0387882A - Transfer device - Google Patents

Abstract

PURPOSE:To easily fit a transfer material support member to the frame body of a transfer material carrier with an uniform tensile force and to reduce the size of the device by providing a friction member to the contact part of the frame body of the transfer material carrier which contacts the transfer material support member. CONSTITUTION:At the position of the drum frame body 35 which contacts the transfer material carrier sheet 34, the friction member 70 which has a specific frictional force such as urethane foam or rubber is stuck. The frame body 35 is wound with the sheet 34 only by fitting the rotation-directional head part 34a and tail part 34b of the sheet 34 to a coupling member 33 with screws. Consequently, the sheet 34 is easily fitted in a specific tension state, an area where transfer is disabled becomes small, and the device is reduced in size.

Description

[Detailed Description of the Invention] No. 1 The present invention is used to transfer a toner image formed on an image carrier onto a transfer material in an image forming apparatus using electrophotography, electrostatic recording, etc. The present invention relates to a transfer device, and specifically relates to a transfer device that performs transfer by supporting a transfer material on a flexible transfer material support member.

Traditionally, various types of transfer devices have been used to transfer toner images formed on image carriers onto transfer materials in image forming apparatuses using electrophotography, electrostatic recording, etc. have been proposed and put into practical use.

The transfer material is supported on an endlessly moving transfer material support member, and a transfer corona discharge is applied from the back side of the support member to transfer the toner image on an image carrier such as a photosensitive drum onto the transfer material. The transfer device is extremely suitable for forming color images because it can effectively perform multiple transfers of toner images of multiple colors onto a transfer material.

However, in this case, the image carrier and the transfer material must be in uniform contact with each other to prevent transfer failure. For this purpose, generally, a notch opening is provided in the cylindrical drum, and a flexible transfer material supporting member (transfer material carrying sheet) made of a substantially rectangular sheet-shaped insulating screen is stretched over the drum surface of the opening. The transfer material support member is synchronized with the image carrier. Then, the flexible transfer material support member is pasted near the four sides of the support member to the vicinity of the four sides of the opening on the outer peripheral surface of the cylindrical drum using double-sided tape or the like.

Although this method allows the transfer material to be brought into uniform contact with the image carrier, it has the following drawbacks.

That is, when attaching the four sides of a flexible transfer material support member, it is difficult and time-consuming to attach the support member without curling, bending, or tilting, and the workability is poor. This also applies when the rigid body presses the tip of the transfer material support member along the axial direction of the transfer drum. In particular, it takes a considerable amount of time to install it without tilting or bending.

The transfer material support member is cylindrically stretched over an opening in the outer peripheral surface of the frame of the cylindrical drum (consisting of a pair of cylindrical rings and a band-like connecting member connecting them). For,
When the transfer material support member expands and contracts due to changes in temperature and humidity, repeated transfers, etc., unevenness occurs on the surface of the transfer material support member. If such unevenness occurs, when the transfer material is supported on the transfer material supporting member, it may cause poor adsorption or misalignment of the adsorption material, and the transfer material may not be the same for each color of the toner image on the image carrier. There have been drawbacks such as color shift of the image due to positional deviation in upward transfer, image unevenness due to transfer failure, and image transfer omission.

As a countermeasure to this problem, it is conceivable to separate the transfer area from the fixed portion of the transfer material support member, but in that case, the cylindrical outer diameter of the transfer material support member becomes large, and the transfer device becomes large. In a type of transfer device that attracts multiple sheets of transfer material onto a transfer drum, it is recommended to avoid increasing the outer diameter of the cylinder of the transfer material support member as much as possible by reducing the distance between the transfer materials. Preferably, in this case, if a non-transferable area is created by separating the transfer area from the fixed part of the transfer material as described above, a space for this will be required in addition to the space for the fixed part of the transfer material support member. , an increase in the cylindrical outer diameter of the transfer support member is unavoidable.

As another countermeasure, as known from Japanese Patent Publication No. 63-34468, one or both of the front end and the rear end in the rotational direction of the flexible transfer material support member are elastically connected using a 6-tension spring or the like. However, in this method, the degree of freedom of the transfer material supporting member in the circumferential direction is too large, resulting in color misregistration during multiple transfer. In addition, the transfer material support member is likely to shift in the axial direction, and even if a length is provided on the transfer material support member side and a bottle is provided on the ring side for positioning, due to the structure,
There are many inconveniences, such as being able to position only either the transfer material support member side or the ring side, and if the pin protrudes from the transfer material support member, it will come into contact with the image carrier.

Furthermore, as shown in Japanese Utility Model Application Publication No. 59-1419157, a first member having a low frictional force toward the transfer material support member through the first member of the elastic member is provided between the outer circumferential surface of the ring and the transfer material support member. There is also a method of providing two parts, but in this case,
As described above, problems and color shift when attaching the transfer material support member to the outer peripheral surface of the cylindrical drum cannot be prevented.

Therefore, an object of the present invention is to enable a flexible transfer material support member to be easily attached to the frame of a transfer material carrier with uniform tension without the need for an operator, and to be able to easily attach the flexible transfer material support member to the frame body of a transfer material carrier over time and under the environment. It is an object of the present invention to provide a transfer device in which there is no unevenness of a transfer material support member due to factors and the size of the device can be reduced by reducing a non-transferable area.

The above-mentioned object is achieved by the transfer device according to the present invention. In summary, the present invention provides a structure in which one end of a flexible transfer material support member is attached to the frame of an endlessly rotating transfer material carrier via an elastic member, so that the transfer material support is attached to the frame. The transfer device is characterized in that a friction member having a predetermined frictional force is provided at a contact portion of the frame body with the transfer material supporting member.

Oihohoku Examples of the present invention will be described in detail below.

FIG. 1 is a configuration diagram showing a color image forming apparatus equipped with a transfer device according to an embodiment of the present invention.

In this embodiment, an image bearing member, that is, an electrophotographic photosensitive drum 1 which is rotatably supported and rotates in the direction of the arrow, is provided with a negative charger 2.
The electrostatic latent image is formed on the photosensitive drum 1 by uniformly charging the photosensitive drum 1 and irradiating the photosensitive drum 1 with a light image 3 according to image information using an exposure means such as a laser beam exposure device. The electrostatic latent image is visualized as a toner image on the photosensitive drum 1, for example, by the mobile developing device 4.

The mobile developing device 4 includes four developing units 4M and 4C14Y that specifically accommodate four color developers: magenta developer, cyan developer, yellow developer, and black developer.
, 4B, and a guide (not shown) that holds these four developing devices and is movable in the horizontal direction. The mobile developing device 4 transports a desired developing device to a developing position facing the outer peripheral surface of the photosensitive drum 1, and develops the electrostatic latent image on the photosensitive drum 1.

The visible image, that is, the toner image, on the photosensitive drum 1 is carried by a transfer device 30, which will be described in detail later, and is conveyed by the transfer device 30 in the direction of the arrow in the figure.Then, a transfer material is brought into contact with the photosensitive drum 1. Transferred to P. The transfer material P is transferred to the transfer device 30 in synchronization with the image by the registration rollers 6a.
supplied to.

After the residual toner on the surface of the photosensitive drum 1 is cleaned by a cleaning device 20, the photosensitive drum 1 is subjected to a color image process again.

Furthermore, to explain the transfer device 30, in this embodiment, the transfer device 30 transfers the transfer material P fed to the transfer device 3o.
It has a transfer material adsorption means 50 for adsorbing and holding the transfer material on the transfer material carrying sheet 34 as a flexible transfer material supporting member. As shown in FIG. 1, the transfer material adsorption means 50 is provided inside the transfer drum 30D as a transfer material carrier, and applies an electric charge of opposite polarity to the toner image on the photosensitive drum 1 to the transfer material. It has an adsorption corona charger 51 applied to the back surface of the carrier sheet 34, and a conductive roller 52 provided outside the transfer drum 30D. This conductive roller 52 is grounded, serves as a counter electrode to the adsorption corona charger 51, and also functions to inject charges into the transfer material P and cause the transfer material P to be electrostatically attracted to the transfer material carrying sheet 34.

The transfer material P attracted by the transfer device 30 is transferred to the transfer charger 1
The transfer material carrying sheet 3 is conveyed to the transfer area where the transfer material holding sheet 3 is arranged, and in order to transfer the first color toner image, for example, a magenta toner image, on the photosensitive drum L onto the first transfer material P.
An electric charge having a polarity opposite to that of the toner is applied to the back side of the image forming apparatus 4 using a transfer corona charger 15. Subsequently, the same latent image is created on the photosensitive drum 1 again and developed with the first color toner, and the second image is similarly formed.
A toner image of the first color is transferred onto a sheet of transfer material. By the time the first transfer material comes to the position of the conductive roller 52 for the second time, the conductive roller 52 is released and the toner image transferred onto the transfer material P is not disturbed! , for example, the transfer material carrying sheet 3
It is separated by more than 2 mm from 4.

Next, a second color toner image formed on the photosensitive drum 1 in synchronization with the first transfer material to which the first color toner image has been transferred is transferred to a second color toner image using a transfer corona charger 15. The toner image of the second color is transferred onto the second transfer material P, and the toner image of the second color is also transferred to the second transfer material to which the toner image of the first color has been transferred. Thereafter, toner images of four colors are transferred to each of the two transfer materials P in the same manner.

Regarding the transfer device 30 of this embodiment, Section 2.3.4.5.
This will be further explained using FIGS. 6 and 7.

2 and 3 respectively show a transfer device 30 of this embodiment.
FIG. 3 is a cross-sectional view and a perspective view showing the transfer material carrying sheet in a stretched state.

Transfer material carrying sheet 34 as a flexible transfer material supporting member
One end portion (the leading end portion in the rotational direction of the sheet 34) 34a is,
It is adhered onto the rigid body 61 with double-sided tape or the like. The rigid body 61 has holes for screw fixing and counterbore holes for hiding the screw heads. Further, the opposite end portion 34b of the transfer material carrying sheet 34 (the rear end portion in the rotational direction of the sheet 34) is adhered onto a rigid body 63 via an elastic member 62 such as foamed urethane or rubber. In this embodiment, escape holes for hiding the screw heads are formed in the elastic member 62, and screw holes are formed in the rigid body 63. Furthermore, screw clearance holes 34c and 34d are also provided at the ends 34a and 34b of the transfer material carrying sheet 34.

As shown in FIG. 4, the transfer device 30 includes cylindrical rings 31 and 32 provided at both ends and a connecting member 33 that connects the rings 31 and 32, and the drum frame 35 of the transfer drum 30D. is formed. The connecting member 33 is provided with two rows of screw holes 33a in the longitudinal direction thereof. Furthermore, a friction member 70 having a predetermined friction force, such as urethane foam or rubber, is attached to the upper inner region of the outer circumferential surface of the rings 31, 32 at a position where it contacts the transfer material carrying sheet 34.

In order to wind the transfer material carrying sheet 34 around the drum frame 35, as shown in FIG. The rigid bodies 61 and 63 may be screwed to the connecting member 33 using screws that are inserted into the screw holes of the rigid bodies 61 and 62 provided in the connecting member 33 and screwed into the screw holes 33a of the connecting member 33.

The distance βa between the screw holes of the rigid body 61 and the screw holes of the rigid body 63 (same as the distance between the screw relief holes 34c and 34d of the transfer material carrying sheet 34) is determined by the transfer shown in FIG. Screw hole 33 of connecting member 33 when wrapping material carrying sheet 34
For the interval gb between a, ffa=nb+α(α〉0)
The margin α in this relational expression is determined in consideration of expansion and contraction of the transfer material carrying sheet 34 due to environmental changes, color shift during multiple transfer of transfer materials, and the like.

In this embodiment, as described above, by eliminating the adhesion of the transfer material carrying sheet 34 to the connecting member 33, the sheet 3
The tension state during winding of the sheet 34 can be controlled by the above margin α, and the workability when replacing the sheet 34 is improved.

According to this, the transfer material carrying sheet 34 can be easily attached to a predetermined tension state (tension) without depending on the operator, so that the attachment of the transfer material carrying sheet 34 can be easily carried out without depending on the operator. The difference in the degree of freedom of deformation of the sheet 34 between other locations is reduced, and image defects are less likely to occur. Furthermore, since a friction member 70 having a predetermined frictional force is interposed between the rings 31, 32 and the transfer material carrying sheet 34, the sheet 34 does not shift in the axial direction of the drum 30D.

Here, the friction force of the friction member 70 will be explained.

It has already been mentioned that if the frictional force of the friction member 70 is small, it may cause color misregistration or the like. However, if the frictional force of the friction member 70 is too large, the situation is equivalent to that of fixing both ends of the transfer material carrying sheet 34 with double-sided tape or the like, and this also causes the above-mentioned transfer failure. For this reason, an experimental investigation revealed that the frictional force obtained from the surface properties of urethane rubber, neobra rubber, etc. is generally preferable. Therefore, the material of the friction member 70 is selected from these urethane rubbers.

In this embodiment, by using the elastic member 62 at the rear end portion 34b of the transfer material carrying sheet 34 in the rotation direction,
The degree of freedom of deformation of the seat 34 near the fixed portion of the seat 34 is improved, but if the elastic member 62 is used at both the front end and the rear end of the seat 34 in the rotational direction, the degree of freedom of the seat 34 can be further improved. I can do it.

When there is no transfer material P on the sheet 34, the transfer material carrying sheet 34 is cleaned by the cleaning brush 72 as shown in FIG. A gap 76 is created between the oscillating member 70 and the seat 34 at the portion where the oscillating member 70 is moved. This gap 76 is small, and the transfer material carrying sheet 34
The other portions do not shift due to the frictional force between the friction member 70 and the sheet 34.

However, the above-mentioned gap 76 gradually advances from the starting point 34A to the ending point 34B in the rotational direction of the transfer material carrying sheet 34 due to the rotation of the transfer drum 30D, and the distortion of the sheet 34 due to the above-mentioned factors such as temperature and humidity is prevented. Absorb. Therefore, unevenness and expansion/contraction of the transfer material carrying sheet 34 do not occur in the axial direction and circumferential direction of the transfer drum 30D.

FIG. 9 is a perspective view showing a transfer drum in another embodiment of the transfer device of the present invention, and FIG. 10 is a longitudinal sectional view of the transfer drum of FIG. 9. In addition, in Figures 9 and 10, 2nd to 8th
The same reference numerals as those attached to the figures indicate the same members.

In the transfer device of this embodiment, the rotational direction leading end 34a of the transfer material carrying sheet 34 of the transfer drum 30D is connected to the drum frame body 3.
A connecting member 33 that connects rings 31 and 32 that constitute 5
The rear end portion 34b of the seat 34 in the rotational direction is fixed to a holding member 37 at the side of the seat 34. The retaining member 37 is wound around the ring 31, 32 under tension, such as by a tension spring 38.

As in the previous embodiment, a friction member 70 having a predetermined friction force, such as foamed urethane or rubber, is attached to the upper inner area of the outer peripheral surface of the rings 31 and 32 at the position where it contacts the transfer material carrying sheet 34. It is attached.

Even with the above configuration, the same effects as described above can be obtained.

FIG. 11 is a longitudinal cross-sectional view showing the mounting portion of the transfer material carrying sheet in still another embodiment of the transfer device of the present invention.

The transfer device of this embodiment is characterized in that the attachment of the transfer material carrying sheet in the transfer device shown in FIGS. 1 to 8 and the transfer device shown in FIGS. 9 to 10 is performed using a combination of methods. In FIG. 11, the same reference numerals as in FIGS. 1 to 8 and 9 to 10 indicate the same members.

That is, the leading end portion 34a in the rotational direction of the transfer material carrying sheet 34 is attached to the rigid body 61 to the connecting member 33 that connects the rings 31, 32 (see FIGS. 5, 10, etc.) that constitute the drum frame 35 of the transfer drum 30D. The rear end portion 34b of the seat 34 in the rotational direction is attached via an elastic member 62 to a rigid body 63 that is tensioned by a tension spring 38 or the like.

As in the previous embodiment, a friction member 70 having a predetermined friction force, such as foamed urethane or rubber, is placed at a position in contact with the transfer material carrying sheet 34 in the upper inner region of the outer peripheral surface of the rings 31 and 32. It is pasted.

Even with the above configuration, the same effects as described above can be obtained.

FIG. 12 is a cross-sectional view showing a transfer drum in yet another embodiment of the transfer device of the present invention.

In the transfer device of this embodiment, friction members 70a and 70b having different frictional forces are provided at the positions in contact with the transfer material carrying sheet 34 on the inner side region of the outer peripheral surface of the rings 31 and 32 constituting the drum frame 35 of the transfer drum 30D. is provided, and the frictional force of the friction member 70a corresponding to the side including the leading end 34a of the transfer material carrying sheet 34 in the rotational direction (the leading end side of the image) is greater than the friction force of the friction member 70a that includes the rear end 34b of the transfer material carrying sheet 34 in the rotational direction. side(
The friction force of the friction member 70b corresponding to the rear end of the image is larger.

According to this, the spring 38 causes the friction members 70a, 70b to
The gripping force of the transfer material carrying sheet 34 is different between the sheets 3 and 3.
The leading end of 4 is gripped strongly, and the trailing end is gripped weakly.

Therefore, there is no misalignment of the transfer material carrying sheet 34 on the leading edge side of the image, which is important for color misregistration, etc., and the rear end side of the sheet 34 is deflected in the circumferential direction, but the overall deflection of the sheet 34 is reduced. , it will absorb the unevenness.

FIG. 13 is a cross-sectional view showing a transfer drum in yet another embodiment of the transfer device of the present invention.

In the transfer device of this embodiment, the frictional force of the friction member 70 provided at the position in contact with the transfer material carrying sheet 34 on the upper inner region of the outer peripheral surface of the rings 31 and 32 constituting the drum frame 35 of the transfer drum 30D is It is characterized in that the transfer material carrying sheet 34 is continuously enlarged from the leading end 34a in the rotational direction toward the rear end 34b, as indicated by arrow G.

In order to form a friction member 70 with a varying frictional force in this way, for example, when forming the friction member 70 on the ring 31, 32, the latter is moved in the direction of arrow G.
The member 70 may be formed so that the surface roughness of the material is reduced.

According to the friction member 70 as described above, since the friction force of the member 70 is continuously changed, the transfer material carrying sheet 34
The effect of taking up the deflection can be further improved.

As explained above, in the transfer device of the present invention, one end of the flexible transfer material support member is attached to the endlessly rotating frame of the transfer material carrier via the elastic member. In this way, the transfer material support member is stretched over the frame, and a friction member having a predetermined frictional force is provided at the contact portion of the frame with the transfer material support member, so that the transfer material support member can be stretched without depending on the operator. The flexible transfer material support member can be easily attached to the frame of the transfer material carrier with uniform tension, and there is no unevenness of the transfer material support member due to aging or environmental factors, and the transfer can be easily performed. By reducing the disabled area, it is also possible to downsize the device.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing a color image forming apparatus equipped with a transfer device according to an embodiment of the present invention. FIG. 2 is a sectional view showing the transfer material carrying sheet in the transfer device of FIG. 1 in an expanded state. FIG. 3 is a perspective view showing the transfer material carrying sheet in a stretched state. 4 is a perspective view showing the drum frame of the transfer device of FIG. 1. FIG. 5 is a perspective view showing a curved transfer material carrying sheet attached to the drum frame shown in FIG. 4. FIG. FIG. 6 is a perspective view showing a transfer drum to which the transfer material carrying sheet of FIG. 5 is attached. FIG. 7 is an explanatory diagram showing the dimensional relationship in the transfer drum of FIG. 6. FIG. 8 is a cross-sectional view of the transfer drum of FIG. 6. FIG. 9 is a perspective view showing a transfer drum in another embodiment of the transfer device of the present invention. FIG. 10 is a cross-sectional view similarly showing the transfer drum. FIG. 1 is a longitudinal cross-sectional view showing the mounting portion of the transfer material carrying sheet in still another embodiment of the transfer device of the present invention. FIG. 12 is a cross-sectional view showing a transfer drum in yet another embodiment of the transfer device of the present invention. FIG. 13 is a cross-sectional view showing a transfer drum in yet another embodiment of the transfer device of the present invention. 30D: Transfer drum 31, 32: Ring 33: Connecting member 34: Transfer material carrying sheet 35 Ni drum frame 38: Tension spring Figure 4B 4Y 4+, : 4M Figure 2 34 Figure 3 Figure 7 Figure 8 Figure 10 Figure 70 Figure 11 JUL) Figure 12 Figure 13

Claims (1)

[Claims] 1) One end of a flexible transfer material support member is attached to the frame of an endlessly rotating transfer material carrier via an elastic member, so that the transfer material support member is stretched over the frame. A transfer device, characterized in that a friction member having a predetermined frictional force is provided at a contact portion of the frame with the transfer material support member.