JPH0224130Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is to move the transfer paper after the toner image has been transferred to the upper side of the pair of upper and lower fixing rollers in the conveyance direction. The present invention relates to a fixing device for a copying machine provided with a guide member for conveyance.

[Conventional technology]

As a fixing device for such a copying machine,
As seen in Publication No. 130954 and also shown in FIG. 13, the transfer paper after the toner image is transferred is once bent upward on the upper side in the conveyance direction with respect to the pair of upper and lower fixing rollers 41 and 42. A guide member 43 that is later conveyed to the pair of fixing rollers 41 and 42 is provided, and a protruding guide portion b is formed in the middle portion of the guide member 43 in the width direction to be higher than the guide portions a on both sides in the width direction. be.

According to the fixing device configured as described above, the transfer paper 44 after the toner image transfer is once bent upward by the guide member 43, so that the curl of the transfer paper 44, which is slightly curled upward on both sides in the width direction, is prevented. corrected,
In addition, the transfer paper 44 is attached to the raised guide portion b.
Since both sides in the width direction tend to sag, the curl is further corrected, and fixed wrinkles caused by the curl are effectively suppressed.

[The problem that the idea aims to solve]

However, the raised guide portion b, which is suitable for correcting the curl, has the drawback of causing image blurring near the trailing edge of the transfer paper and vertical streaks on the back side of the transfer paper.

That is, the transfer surface of the transfer paper 44 by the pair of fixing rollers 41 and 42 is
This is a virtual plane R that is perpendicular to a plane S connecting the rotation axis T of the fixing rollers 41 and 42 and that passes through the nip point n of the pair of fixing rollers 41 and 42.

However, in the fixing device configured as described above, since the upper end _t1 of the raised guide portion b is positioned above the virtual plane R, the pair of fixing rollers 41 and 42 The transfer paper 44 is conveyed in a lifted state, and as a result, the rear end of the transfer paper 44 instantly and shockingly falls off the upper end _t1 of the raised guide portion b. This has the disadvantage that unfixed toner images are easily disturbed, resulting in so-called image blurring.

Further, the transfer paper 44 is pulled downward by the pair of fixing rollers 41 and 42, with the intermediate portion in the width direction supported by the raised guide portion b. As a result of being conveyed, vertical streaks are likely to be formed on the back side of the transfer paper corresponding to both side portions of the raised guide portion b.

The present invention was developed in view of the above-mentioned circumstances, and uses an extremely simple and rational improvement technique to fully utilize the curl correction function while eliminating the image blur and vertical streaks. The object of the present invention is to provide a fixing device that prevents this occurrence.

[Means to solve the problem]

In order to achieve the above object, the present invention locates the upper ends of the raised guide parts on the upper side in the conveying direction than the upper ends of the guide parts on both sides in the width direction, and also provides the upper ends of the raised guide parts on both sides in the width direction The present invention is characterized in that the upper end of the shaped guide portion is located near an imaginary plane that is perpendicular to a plane connecting the rotation axes of the pair of fixing rollers and passes through the nip point of the pair of fixing rollers.

[Effect]

According to the characteristic structure described above, the portion of the transfer paper conveyed by the pair of fixing rollers on the upper side in the conveyance direction than the nip point by the pair of fixing rollers is largely lifted by the upper end of the guide portion. Without this, the raised guide portion and the upper ends of the guide portions on both sides in the width direction support substantially the entire width in the width direction. By following the transfer paper conveyance surface, the rear end of the transfer paper does not fall off instantaneously and shockingly from the raised guide portion or the upper ends of the guide portions on both sides in the width direction.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 schematically shows the entire electrophotographic copying machine. In the figure, reference numeral 1 denotes a photosensitive drum that is rotationally driven. Around this drum 1 are a charging mechanism 2, an exposure mechanism 3, a developing mechanism 4, , a transfer mechanism 5, and the like are provided. 6 is a paper feed cassette, and between this cassette 6 and the transfer mechanism 5, a plurality of guide plates 7..., a paper feed roller 8a, and a conveyance roller 8b are arranged, and the transfer paper 9 in the cassette 6 is . Guide plates 10 . . . , paper feed rollers 11 . . . , and a paper feed table 12 are also provided. On the downstream side of the photosensitive drum 1 in the conveyance direction, a fixing device 13 is used to transfer the transfer paper 9 peeled off from the drum 1 after the transfer.
A suction conveyor belt conveyor 14 for conveying the paper to
A pair of upper and lower plate-shaped guide members 16 and 17 for guiding the transfer paper and a pair of upper and lower transfer paper feeding rollers 18 and 19 are provided between the transfer paper and the transfer paper.

The fixing device 13, as shown in FIG.
A heating roller 21 with a built-in heating mechanism 20, a pressure roller 22 that elastically presses against the heating roller 21 from below, and a transfer paper from the conveyor 14 between the pair of upper and lower rollers 21, 22. More specifically, the heating roller 21 has a surface treated with fluororesin, such as Teflon (trade name: Dupont), and has a longitudinal direction. It is shaped like a drum, with the outer circumferential diameter increasing sequentially toward both ends in a distributed manner centered at the center, that is, the circumferential rotational speed increases toward both ends compared to the center. The roller 22 is made of a relatively soft material such as silicone rubber impregnated with silicone oil so as to effectively separate the paper, and its outer circumferential diameter is approximately the same over the entire length in the longitudinal direction. be.

Thus, the transfer paper 9 fed out by the pair of rollers 21 and 22 is fed out while being stretched left and right by the upper roller 21 whose circumferential speed is faster at both left and right ends than at the center. Therefore, the occurrence of wrinkles on both sides of the transfer paper 9 in the width direction can be suppressed.

The roller 21 may have an outer circumferential diameter of approximately the same diameter over the entire length in the longitudinal direction, or a so-called drum-shaped roller in which the outer circumferential diameter is gradually increased toward both ends in a distributed manner centered at the center in the longitudinal direction. Various types of known structures can be applied, such as the one shown in FIG.

On the other hand, as also shown in FIG.
The second guide surface S ₂ is bent at the lower side in the transport direction with respect to the first guide surface S ₁ on the upper side in the transport direction.
is formed to be higher toward the lower side in the conveying direction, and on the second guide surface _S2 , a raised guide portion b protrudes higher than the guide portions a on both sides in the width direction on the center side in the width direction. is formed in a state rising from the refraction line A.

Then, the upper end t ₁ of the raised guide part b is located on the upper side in the conveying direction than the upper end t of the guide part a on both sides in the width direction, and the upper ends t, t of both guide parts a, a, b , t ₁ above an imaginary line Q connecting the suction conveyance release point p of the belt conveyor 14 and the nip point n of the fixing rollers 21 and 22 in a side view, and above the pair of fixing rollers 2
The transfer sheet 9 is placed in the vicinity of a virtual plane R that is perpendicular to the plane S connecting the rotational axes T of the rollers 1 and 22 and passes through the nip point n, without causing the transfer paper 9 extending over the points p and n to be bent upward significantly. , the back side of the transfer paper 9 is supported by the upper ends t, t, t ₁ of the guide portions a, a, b, and the first guide surface S ₁ is supported with respect to the conveyance surface of the conveyor 14. are arranged at an angle so that the lower side in the conveyance direction is slightly higher.

According to the above configuration, as shown in FIG. 6, even if both sides of the transfer paper 9 in the width direction are slightly curled upward, as in the case of the transfer paper 9 after single-sided copying, as shown in FIG. , the front side of the transfer paper 9 is the conveyor 1
4 to the first guide surface _S1 , its front side is slightly lifted upward and bent upward, and then, as shown in FIG. The front side of the transfer paper 9 is further lifted upward and bent, and in addition to this double bending, both sides of the transfer paper 9 in the width direction tend to hang down on both sides of the raised guide portion b.
The upward curl on both sides of the transfer paper 9 in the width direction is effectively corrected.

Next, as _shown in FIG. Upper end t ₁ of both raised guide portions b
and upper ends t, t, t ₁ of guide parts a, a on both sides in the width direction
The back side of the transfer paper 9 is supported by the transfer paper 9, and although not shown, the transfer paper 9 is nipped by a pair of fixing rollers 21 and 22 and fed out by the feeding roller 1.
8, 19.

The transfer paper 9 that is nipped and conveyed by the pair of fixing rollers 21 and 22 is in a single plane substantially along the virtual plane R, and as shown in FIG. The upper ends of the raised guide portion b and the guide portions a on both sides in the width direction are prevented from being lifted up significantly by the pair of fixing rollers 21 and 22 in the transport direction than the nip point n.
Since it is supported by substantially the entire width in the width direction by t ₁ , t, and t, vertical streaks are not formed on the back side of the transfer paper 9 by the raised guide portions b.

Further, the conveyance posture is different from that of the fixing roller 21,
22 pairs of transport surfaces (that is, a surface that is perpendicular to the surface S connecting the rotational axes T of the pair of fixing rollers 21 and 22 and passes through the nip point n, which is the virtual surface R referred to in the present invention). By following almost the same direction, the rear end of the transfer paper 9 can be prevented from falling off instantaneously and shockingly from the raised guide portion b and the upper ends t ₁ , t, t of the guide portions a, a on both sides in the width direction. Therefore, so-called image blur caused by disturbance of the unfixed toner image at the rear end of the transfer paper 9 is prevented.

FIG. 7 and FIG. 8 show a guide member 23 of another embodiment.
This shows the layout.

The fixing rollers 21 and 22 shown in FIG.
An imaginary plane R that is perpendicular to the plane S connecting the rotational axis T of the conveyor 14 and that passes through the nip point n is made approximately parallel to the conveying surface of the conveyor 14, and the raised guide is placed very close to the imaginary plane R. The upper ends t, t, t ₁ of the portion b and the guide portions a, a on both sides in the width direction are positioned, and the first guide surface S ₁ of the belt conveyor 14 is almost flush with the conveyance surface of the conveyor 14. It is arranged so that it is connected in a row.

What is shown in FIG. 8 is such that the raised guide portion b and the guide portions on both sides in the width direction are arranged so that the imaginary surface R is approximately parallel to the conveyance surface of the conveyor 14 and is substantially coincident with the imaginary surface R. position the upper ends t, t, t ₁ of a, a, and the conveyor 14
The first guide surface _S1 is inclined so that the lower side in the transport direction is higher than the transport surface.

Next, different embodiments of the guide member 23 are shown in FIGS. 9 to 12, respectively. The one shown in FIG. 9 is one in which the rising start of the raised guide part a is located on the upper side in the conveying direction with respect to the refraction line A, and the one shown in FIG. It is characterized in that the beginning is located on the downstream side of the refraction line A in the conveyance direction.

The one shown in Fig. 11 is characterized by a raised guide part b and the guide parts a, a on both sides of it connected smoothly, and the one shown in Fig. 12 is
The configuration shown in FIG. 11 is characterized in that the width of the raised guide portion b is made wider toward the downstream side in the conveyance direction.

In the guide member 23, the first and second guide surfaces S ₁ and S ₂ are bent by the guide plate main body 24.
However, the guide member 23 may be bent with a small radius, and the guide member 23 may be made of thin steel plate or synthetic resin, and may be an integrally molded product or a processed molded product. It is possible to do either.

[Effect of idea]

As explained above, according to the fixing device of the present invention, the conveying posture of the transfer paper supported by the guide member and nipped and conveyed by the pair of fixing rollers connects the rotation axis of the fixing rollers. The transfer paper is substantially along the virtual plane that is perpendicular to the surface and passes through the nip point, and is supported over substantially its entire width in the width direction by the raised guide part and the upper ends of the guide parts on both sides in the width direction.

Therefore, it is possible to effectively prevent the occurrence of vertical streaks on the back side of the transfer paper due to lifting of the upper side of the transfer paper in the conveying direction than the nipping point and supporting only the middle part of the transfer paper in the width direction. It has also become possible to effectively prevent so-called image blurring caused by disturbance of unfixed toner images due to instantaneous and impactful falling off of the trailing edge of the transfer paper from the guide member.

[Brief explanation of the drawing]

The drawings relate to an embodiment of the present invention, and FIG. 1 is a schematic longitudinal sectional side view of the entire copying machine, FIG. 2 is a side view of the fixing device, FIG. 3 is a perspective view of the guide member, and FIG.
B and C are explanatory diagrams showing the conveyance state of the transfer paper over time, and FIG. 5 is a view taken along the line X--X of FIG. 4C. FIG. 6 is a comparative explanatory diagram corresponding to FIG. 5 for comparing the present invention. FIGS. 7 and 8 are explanatory views showing the arrangement of guide members in different embodiments, and FIGS. 9 to 12 are perspective views showing guide members in different embodiments. FIG. 13 is a side view showing a conventional fixing device. 9... Transfer paper, 21, 22... Fixing roller,
23... Guide member, a... Guide parts on both sides in the width direction, b... Raised guide part, n... Nip point, t
...Top end of the guide portions on both sides in the width direction, t ₁ ...Top end of raised guide portion b, R...Virtual surface, S...Face connecting the rotation axis of the fixing roller, T...Rotation of the fixing roller Axis line.

Claims (1)

[Scope of utility model registration request] A guide member is provided on the upper side of the pair of upper and lower fixing rollers in the conveying direction to bend the transfer paper after the toner image is transferred upwards and then convey it to the pair of fixing rollers. A fixing device for a copying machine in which a raised guide part is formed at an intermediate part in the width direction, the raised guide part being higher than the guide parts on both sides in the width direction, the upper end of the raised guide part being higher than the upper end of the guide parts on both sides in the width direction. The upper end of the guide portion on both sides in the width direction and the upper end of the raised guide portion are perpendicular to a plane connecting the rotation axes of the pair of fixing rollers, and the upper end of the guide portion on both sides in the width direction is A fixing device for a copying machine, wherein the fixing device is located near a virtual plane passing through a nip point.