JPH0527609A - Transfer drum for image forming device - Google Patents

Abstract

PURPOSE:To prevent a change in roundness caused by the expansion of a supporting film member composing the form supporting surface of a transfer drum with heat, in a color electrophotographic copying machine adopting a system for transferring a color toner image formed on a form by a developing device in a state where the form is supported by tone transfer drum. CONSTITUTION:The frame of the transfer drum 30 is composed of side rings 31 and 32 on both sides, and a tie-bar 34 connecting both rings, and the supporting film member 40 is arranged on the surface of the transfer drum 30, to constitute the supporting surface of the form. The supporting film member 40 used for the transfer drum is composed of a member having properties that the coefficient of thermal expansion in the transverse direction of X-X, is high, and low in the longitudinal (circumferential) direction of Y-Y, and even if the member 40 is heated with the heat from the fixing device, the roundness of the transfer drum can not be changed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a supporting film member for a transfer drum which carries a sheet in a color electronic copying machine using a plurality of developing devices and one photosensitive drum, and more particularly, the supporting film member is not affected by heat or the like. Even when affected
The present invention relates to a device that can maintain the circular shape of a holding surface of a sheet without expanding in the circumferential direction.

[0002]

2. Description of the Related Art In a commonly used image forming apparatus such as an electronic copying machine, one developing device is arranged in an image forming section, and a toner image formed on a photosensitive drum of the developing device is transferred onto a sheet. Then, the sheet is fixed through a fixing device to obtain a copy. On the other hand, a color electronic copying machine is provided with a developing device that forms a color toner image using each of yellow, magenta, cyan, and black toners, and is formed by these developing devices. The color toner image is transferred onto a sheet to make a color copy. As the color electronic copying machine, for example, as shown in Japanese Patent Laid-Open No. 59-155870, a plurality of developing devices are arranged in a straight line, and a sheet is formed along an image transfer portion from these developing devices. It is known to use a method in which a color toner image is transferred onto a sheet while being moved while being moved.

As in the prior art example, in addition to linearly forming the sheet conveying path, as shown in Japanese Patent Laid-Open No. 107280/1989, a plurality of developing devices are provided around the transfer drum carrying the sheet. There is also a case where a system is used in which a color toner image is transferred by rotating the transfer drum once every time a toner image is formed by each developing device. In an electronic copying machine that uses a system in which a color toner image is transferred onto a sheet while the sheet is supported by the transfer drum, in addition to disposing a plurality of developing devices around the transfer drum, Japanese Patent Laid-Open No. Hei 2 As shown in Japanese Patent Laid-Open No. 238480, one photoconductor drum is arranged with respect to the transfer drum,
A method of arranging a plurality of developing devices with respect to the photosensitive drum may be used.

In the color electronic copying machine disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 2-238480, electrostatic holding means is used to hold the paper on the transfer drum. A charging means is disposed on the back side of the charging means to electrostatically hold the paper on the surface of the film. At the peeling portion for peeling the paper from the transfer drum, a means for peeling the paper from the drum surface and sending it to the fixing device is used by scooping up the leading end of the paper using a swinging claw member. There is. As the transfer drum, for example, a member as disclosed in Japanese Patent Laid-Open No. 2-6983 is used, and two metal ring-shaped members are connected by a tie bar.
By attaching both sides of the supporting film member to one side ring and fixing the front and rear ends of the supporting film member to the tie bar part, the supporting means by the substantially cylindrical supporting film member is configured. ..

When the transfer drum as described above is used, as shown in FIGS. 6 and 7, both sides of the supporting film member 40 in the width direction are connected to the side rings 31 and 32 to be supported. Then, the front end portion and the rear end portion in the length direction of the supporting film member 40 are fixedly held to the tie bar 34 by using the fixing member 36, thereby forming a cylindrical member having the same diameter as the side ring. A support film member can be constructed.

[0006]

However, as described above, in the transfer drum in which the supporting film member 40 is formed into a cylindrical shape by the supporting means by the side rings on both sides and the tie bar, as described above, during the use of the color electronic copying machine. When the transfer drum is heated by another member, the supporting film member expands, and the sheet supporting surface of the supporting film member is deformed from a perfect circle. in this way,
When the paper-supporting surface of the support film member is deformed, the color toner image transferred onto the paper is misaligned, which causes a problem that the image quality of the color copy is deteriorated. As described above, the reason why the cylindrical shape of the support film member is deformed is that the support film member is particularly affected when the expansion coefficients in the vertical and horizontal directions are different. Therefore, in the conventional transfer drum, it has been attempted to cope with the above-mentioned deformation of the sheet supporting surface by using a material having a small thermal expansion as the supporting film member.

However, as the performance of the color electronic copying machine is improved, the number of color copies to be made per unit time is increased, and when a fixing device having a large heat capacity is used, the fixing device and other fixing devices are used. The amount of heat output from the device increases. Further, when the color electronic copying machine is downsized, it is necessary to dispose the transfer drum close to the heat source such as a fixing device. The degree of surface deformation increases, and it becomes difficult to maintain the roundness of the support film member.

In addition to the above-mentioned problems, in the portion where the supporting film member is attached to the tie bar, a concave portion having a shape in which a part of the supporting film member is cut out is formed corresponding to the concave portion 35 for the peeling claw provided in the tie bar. In order to prevent the strain from concentrating on the recessed portion, as shown in FIG.
As shown in FIG. 7, a reinforcing member 37 is provided. The reinforcing member 37 is formed by attaching a plastic plate-like member to the back surface of the front end of the support film member 40 using a double-sided tape 39 to reinforce the front end of the support film member 40 on the tie bar side. .. However, by providing the reinforcing member 37, when the leading end of the paper is electrostatically attached to the portion of the reinforcing member, charging due to the discharge action from the back surface is not favorably performed, and the paper supporting ability is improved. The problem of weakening occurs. Therefore, by providing a large number of holes 38 ... In the reinforcing member 37, a means for sufficiently charging the supporting portion at the leading end of the sheet by the discharge from the charging corotron is used. However, even if such a means is used, the sheet supporting force is not sufficiently exerted in the reinforcing member portion, and there is a problem that the sheet moves toward the photosensitive drum in the image transfer portion. It was

[0009]

SUMMARY OF THE INVENTION The present invention solves the problems of the conventional transfer drum as described above. The heat applied to the transfer drum causes the support film member to expand, so that the roundness of the paper support surface is reduced. It is an object of the present invention to prevent the change and to provide a supporting means by which the supporting film member can be sufficiently charged at the tip of the supporting film member supported by the tie bar.

[0010]

SUMMARY OF THE INVENTION According to the present invention, a sheet of paper is supported on a transfer drum, a toner image formed on a photosensitive drum is transferred onto the sheet of paper, and then the sheet of paper is separated from the transfer drum. Then, the present invention relates to a device for fixing, and making a color copy. In the present invention, the transfer drum,
It is composed of cylindrical side rings arranged on both sides, a tie bar connecting the side rings, and a supporting film member forming a paper supporting surface. Further, in the transfer drum of the present invention, both side portions in the width direction of the support film member are supported by side rings, and both side portions in the length direction are supported by tie bars, respectively, and the support film member has a width of A material having a large coefficient of expansion in the direction and a small coefficient of expansion in the circumferential direction is used. In addition to the above-mentioned structure, in the transfer drum of the present invention, a plastic reinforcing piece is attached to the recess provided in the supporting film member at a position where the tip of the supporting film member in the circumferential direction is supported by the tie bar. In addition to reinforcing the recess, it is possible to reduce the size of the member that blocks the discharge from the back surface.

When the transfer drum of the image forming apparatus of the present invention is affected by heat by forming the paper supporting surface of the transfer drum by using the supporting film member having the above-mentioned properties, However, since the supporting film member expands in the width direction but hardly expands in the circumferential direction, it is possible to prevent the condition of the perfect circle of the supporting surface by the supporting film member from changing. Further, by using the supporting film member having the above-mentioned properties, a transfer drum similar to that of the conventional color electronic copying machine can be constructed, and the heat shield mechanism for the transfer drum can be simplified. Will also be possible. Then, the color toner images transferred in a superposed state on the paper supported by the transfer drum are accurately transferred, so that the image quality of the color copy can be improved.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A transfer drum of an image forming apparatus of the present invention will be described with reference to the illustrated example. The example shown in FIG.
1 shows a configuration of a color electronic copying machine to which the transfer drum of the present invention can be applied. The color electronic copying machine 1 includes a plurality of developing devices 2y, 2m, 2c, and 2b for one photosensitive drum 3. The developing device 2 arranged is provided. In addition, around the photosensitive drum 3, as in the case of an image forming apparatus using a general electrophotographic system, a charging corotron 4,
A transfer corotron 5, a cleaning device 6 and the like are arranged. Then, one developing device in the developing device is moved to a position corresponding to the photoconductor drum, image information corresponding to the designated color is written on the photoconductor drum, a color toner image is formed, and a paper sheet is formed. To be transferred to.

A transfer drum 30 carrying a sheet is arranged at a position corresponding to the image transfer portion of the photosensitive drum, and each time the transfer drum 30 is rotated once, one color toner image is printed on the sheet. Causes the action of transcription. Then, after the color toner images of a plurality of colors are transferred in an overlapping manner, the peeling claw 22 of the peeling section 20 with respect to the transfer drum 30 is transferred.
Is peeled off by using, and is sent out toward the fixing device 9 and fixed to make a color copy. Further, in the paper peeling portion from the transfer drum 30, the above-mentioned JP-A-2-23848 is used.
A peeling means similar to the peeling portion shown in Japanese Patent Publication No. 0-52 is used, and the inner roller 21 arranged inside the drum is used.
And a peeling claw 22 that is pressed from the outside.

In the color electronic copying machine 1, as in the case of a general image forming apparatus, the paper feed tray 1 is provided in the paper feed section.
0 is arranged, and the sheets accommodated in the sheet feed tray 10 are fed while being separated one by one by using the sheet feeding device 11, and are directed to the registration section 15 by using the conveying roller device 13 provided in the sheet conveying path 12. To feed. The registration unit 15 is provided with a paper conveyance path formed as a curved path, and pre-registration rollers 16 and registration rollers 17 arranged in the upstream and downstream portions of the paper conveyance path. By this, a slight additional feeding action is given, and a loop is formed in the paper stopped at the registration portion.

After that, when a command for supplying a sheet to the transfer drum 30 is output, the register roller 17 is driven to cause the sheet to adhere to the transfer drum 30. At that time, the paper pressing roller 23 is pressed against the transfer drum 30, and the charging corotron 19 provided inside the transfer drum
The paper discharge surface charges the paper support surface of the transfer drum so that the paper is electrostatically attached and held.

As described above, the transfer drum 30 for transferring the color toner image from the photoconductor drum onto the paper while supporting the paper is constructed as shown in FIG. .. The transfer drum 30 is
The schematic structure is almost the same as that of the conventional example, but as its frame, it is composed of metal side rings 31 and 32 arranged on both sides and a tie bar 34 connecting both rings, A supporting film member 40 is attached around the frame to form a transfer drum.

In the transfer drum 30, the tie bar 3
4 is provided with a recess 35 substantially in the center thereof, and one side ring 31
A groove 33 is arranged in the groove. The peeling claw 22 is inserted into the concave portion 35 so as to perform the peeling action of the sheet, and the guide roller provided on the side portion of the member supporting the peeling claw 22 is engaged with the concave groove 33. , To swing the peeling claw in the paper peeling direction.

Transfer drum 30 constructed as described above
On the other hand, in the state in which the paper is supported, as shown in FIG. 3, the leading end of the paper P1 is positioned at the portion of the tie bar 34, and the tip of the peeling claw is placed in the recess 35 shown in FIG. When the part enters, it will be picked up by the peeling claw. When the transfer drum 30 carries two sheets of paper P1 and P2, the second sheet of paper P2
When peeling, the peeling claw 22 is pressed against the surface of the drum as shown in FIG. At that time, the inner roller 2 is provided at the upstream side in the rotation direction of the drum.
1, the supporting film member is supported from the inside, and the pressing roller 23 of the peeling claw 22 forms a recess on the surface of the supporting film member, and the tip of the peeling claw is inserted into the recessed portion to separate the sheet. To do.

Transfer drum 30 constructed as described above
As shown in FIG. 1, since it is arranged at a position very close to a heat source such as the fixing device 9, even if a heat shielding means or the like is provided between both members, It is unavoidable that the supporting film member is affected by heat. When the supporting film member expands due to heat, a large deformation occurs in the circumferential direction,
Problems occur such that the surface supporting the paper cannot maintain a perfect circle. Therefore, in the transfer drum 30 of the present invention, a support film member 40 having a large thermal expansion coefficient in the width direction but a small thermal expansion coefficient in the circumferential direction (length direction) is used as the support film member 40. There is. As the support film member, for example, a polyvinylidene fluoride (PVDF) film or the like can be used, and a commercially available KF film (trade name) can be used.

In the so-called KF film, the coefficient of thermal expansion in the longitudinal direction (circumferential direction ... YY direction) is about 2.5 times in the lateral direction (width direction ... XX direction). Even if a heating effect is applied, the circularity of the drum surface supporting the paper can be maintained to the extent that practically no problem occurs in the circumferential direction. Therefore, when the sheet supporting surface is formed by the supporting film member, even if the supporting film member expands due to the heat from the fixing device,
Since the expansion greatly affects only in the width direction, the position of the paper with respect to the photosensitive drum does not change, and the transfer position of the image with respect to the paper does not deviate.

Even when a plurality of color toner images are sequentially transferred onto the paper in a superposed state, the transfer positions of the color toner images are accurately set, so that a clear color copy can be made. Can be done. The support film member used in the transfer drum of the present invention is not limited to the above KF film, and may have a property that the expansion coefficient in the vertical direction is very small and the expansion coefficient is large only in the horizontal direction. For example, any other film member can be used.

(Example of Providing Reinforcing Pieces in Recesses of Support Film Member) In a transfer drum using a support film member having the above-described properties, the recesses of the support film member to be attached to the tie bars are shown in FIG. Figure 5
The reinforcing piece 45 as shown in FIG.
The reinforcing piece 45 is provided as an alternative to the reinforcing member shown in the conventional example of FIG. As shown in FIG. 4, the support film member 40 has side portions of the support film member with respect to the rings 31 and 32 on both sides forming the frame of the transfer drum and the tie bar 35 connecting the side rings. And the tip are attached. Then, with respect to the concave portion 41 formed in the central portion of the tip portion of the supporting film member 40, the reinforcing piece 4 is formed on the back surface thereof by using an adhesive means.
5 is attached, and the periphery of the recess 41 of the support film member is reinforced by the reinforcing piece at the recess 35 of the tie bar 34.

As shown in FIG. 5, the reinforcing piece 45 has a shape in which a concave groove 47 inclined in the central portion is surrounded by a flange 46 arranged around the concave groove 47. The shape of the concave groove 47 is matched with the concave portion 35 formed in the tie bar. Then, the reinforcing piece 45
Is made to correspond to the recess 41 of the support film member 40, and the portion of the flange 46 thereof is bonded using a double-sided tape or the like,
By reinforcing the periphery of the recess 41, stress is prevented from concentrating on the tip of the support film member. The reinforcing piece 45 can be made of any plastic material, and can be molded using a material having good workability such as vinyl chloride or polypropylene.

As shown in FIG. 2, the supporting film member 40 to which the reinforcing piece 45 is applied is oriented in the lateral direction indicated by the arrow XX with respect to the longitudinal direction indicated by the arrow YY. Therefore, a material having a large coefficient of thermal expansion of the supporting film member can be used. Further, by using the supporting film member having the above-mentioned properties, it is possible to maintain the circularity in the circumferential direction of the drum surface supporting the paper even when the transfer drum is heated. .. Furthermore, a reinforcing piece 45 as shown in FIG.
By arranging the support film member 40 with respect to the concave portion at the front end portion thereof, it is possible to prevent stress from being concentrated on the concave portion 41 when the front end portion of the support film member 40 is bonded to the tie bar.

In addition, in the transfer drum of the present invention, unlike the conventional reinforcing member, a member that impedes the charging property of the supporting film member is not arranged subsequent to the tie bar, so that the leading end portion of the paper is The corresponding portion of the supporting film member can be sufficiently charged, and the gripping force with respect to the leading end portion of the sheet can be exhibited well. Therefore, when the paper is supported on the transfer drum 30 and the color toner image is transferred, it is possible to prevent the paper from peeling off from the transfer drum and being wound around the photoconductor drum, and the image transfer operation is performed. Can be maintained in a good condition.

[0026]

The transfer drum of the image forming apparatus of the present invention is
By forming the sheet supporting surface of the transfer drum by using the supporting film member having the above-described properties, the supporting film member expands in the width direction even when the transferring drum is affected by heat, Since it hardly expands in the circumferential direction, it is possible to prevent the state of the perfect circle of the supporting surface of the supporting film member from changing. Then, the color toner images transferred in a superposed state on the paper supported by the transfer drum are accurately transferred, so that the image quality of the color copy can be improved. Further, by using the supporting film member having the above-mentioned thermal expansion property, a transfer drum similar to that in the case of the conventional color electronic copying machine can be configured, and the heat shield mechanism for the transfer drum can be simplified. It is also possible to convert.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a configuration of a color electronic copying machine to which a transfer drum of the present invention can be applied.

FIG. 2 is a perspective view of a transfer drum of the present invention.

FIG. 3 is an explanatory diagram showing a state in which a sheet is supported on the transfer drum shown in FIG.

FIG. 4 is a developed plan view of an example in which a reinforcing piece is attached to a supporting film member.

FIG. 5 is a perspective view of a reinforcing piece.

FIG. 6 is an explanatory view of a conventional support structure of a tip portion of a support film member.

7 is a side view of the support member shown in FIG.

[Explanation of symbols]

1 color electronic copying machine, 2 developing device, 3
Photoreceptor drum, 20 peeling section, 30 transfer drum, 31/32 side ring, 34 tie bar,
35 recesses, 37 reinforcing members, 40 support film members, 41 recesses, 45 reinforcing pieces, 46
Flange, 47 groove.

Claims (1)

Claims: 1. A sheet of paper is supported on a transfer drum, and a toner image formed on a photoconductor drum is transferred to the sheet of paper. After that, the sheet of paper is separated from the transfer drum and fixed. Then, in an apparatus for making a color copy, the transfer drum is composed of a cylindrical side ring arranged on both sides, a tie bar connecting the side rings, and a support film member forming a paper support surface, Both side portions in the width direction of the support film member are supported by side rings, and both side portions in the length direction are respectively supported by the tie bars, and the support film member has a large expansion coefficient in the width direction,
A transfer drum of an image forming apparatus, which is configured by using a material having a small expansion coefficient in the circumferential direction.