JP2003149978A - Releasing agent application device and fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To uniformly apply oil. SOLUTION: In the releasing-agent application device using an oil application roller having an elastic foam layer, the thickness of the middle of the elastic foam layer is greater than the thickness of either end of it. The outer portions of the oil application roller have straight shapes.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has a heat fixing device for fixing an unfixed image by passing a recording material having an unfixed image through a nip of a pair of rotating bodies which are in pressure contact with each other, and this heat fixing device. The present invention relates to an image forming apparatus.

[0002]

2. Description of the Related Art As an example of an image forming apparatus as described above, FIGS. 4 to 6 show a full color copying machine having a plurality of optical scanning means. FIG. 4 is a sectional view of a full-color copying machine, and FIG.
4 is a sectional view of the image forming portion of FIG. 4, and FIG. 6 is a sectional view of the fixing portion of FIG.

First, a full-color copying machine will be briefly described with reference to FIGS.

As shown in FIG. 4, an electrophotographic photosensitive member (hereinafter referred to as "photosensitive drum") which is a latent image bearing member is provided around an electrophotographic photosensitive member. The four images are provided on the photosensitive drum formed by each of the image forming stations, and the recording material such as the paper (hereinafter referred to as a transfer paper) on the conveying unit that moves and passes adjacent to the photosensitive drum. Yes) is transferred to P.

Above the image forming station, there is provided a reader section for reading an original with a photoelectric conversion element such as a CCD.

As shown in FIG. 5, the photosensitive drums 1a, 1b, 1c and 1d are respectively provided in the image forming stations Pa, Pb, Pc and Pd which form images of magenta, cyan, yellow and black. The photosensitive drums are arranged so as to be rotatable in the arrow directions. further,
Around the photosensitive drums 1a, 1b, 1c, 1d, chargers 12a, 12b, 12c, 12d, a laser scanning unit, developing devices 2a, 2b, 2c, 2d, and a cleaner 4 are provided.
a, 4b, 4c, and 4d are sequentially arranged along the rotation direction of the photosensitive drum, and the transfer section 3 is arranged below each photosensitive drum. The transfer unit 3 includes a transfer belt 31 which is a recording material conveying unit common to each image forming station.
And transfer chargers 3a, 3b, 3c, 3d.

In the copying machine as described above, FIGS.
The transfer paper P supplied from the paper supply cassette 61, which is a recording material supply means, is supported on the transfer belt 31 and conveyed to each image forming station, and the toner image of each color formed on each photosensitive drum is formed. Are sequentially transferred. When this transfer step is completed, the paper P is separated from the transfer belt 31 and is conveyed to the fixing device 5 by a conveyor belt 62 which is a recording material guide means. As shown in detail in FIG. 6, the fixing device 5 includes a fixing roller 51, which is a rotatably arranged fixing rotator, and a pressure roller 52, which is a pressure rotator rotating while being in pressure contact with the fixing roller 51. , A release agent applying device 53 as a release agent supplying and applying means, and a roller cleaning device 54,
It has a configuration including 55. A heater 5 such as a halogen lamp is provided inside the fixing roller 51 and the pressure roller 52.
6, 57 are arranged respectively. The fixing roller 51 and the pressure roller 52 have a thermistor 58,
59 are arranged in contact with each other, and the temperature of the surface of the fixing roller 51 and the pressure roller 52 is adjusted by controlling the voltage to the heater 56 and the heater 57 via the temperature adjusting circuit.

Further, a cleaning device 54 and a release agent applying device 53 are attached to the fixing roller 51, and the toner and the like offset on the fixing roller 51 are cleaned by the cleaning device 54.
The releasing agent applying device 53 applies silicone oil or the like as a releasing agent to the fixing roller 51, and the fixing roller 51
The transfer paper P is easily separated from the toner and the offset of the toner is prevented.

The cleaning device 54 includes a cleaning web 54a made of a band-shaped heat-resistant nonwoven fabric, and a pressing roller 5 for pressing the cleaning web 54a against the fixing roller 51.
4b, an unwinding roller 54c that unwinds a new cleaning web 54a, and a winding roller 54d that gradually winds up the cleaning web 54a that has deteriorated cleaning ability due to toner or the like. The cleaning device 54 is provided on the upstream side of the thermistor 58 in the rotation direction of the fixing roller 51 so that the offset toner does not adhere to the thermistor 58 and the detection failure occurs in the thermistor 58.

As a method of winding the cleaning web 54a, when it is judged from the counter that a predetermined number of copies have been made, a solenoid (not shown) is turned on and a one-way clutch is operated to wind a predetermined amount in the direction opposite to the roller rotation. There is. By winding the cleaning web 54a in the opposite direction, the cleaning web 54a is prevented from being wound in the roller rotation direction.

The mold release agent applying device 53 includes an oil tank 53a having a mold release agent such as silicone oil, and a roller 5 for pumping oil as a mold release agent from the oil tank 53a.
3b and 53c, and an application roller 53d that applies oil from the scooping rollers 53b and 53c to the fixing roller 51.
And a blade 53e for controlling the amount of oil applied from the application roller 53d. Particularly, in order to uniformly apply oil to the fixing roller 51, the release agent applying device 53 is provided in the thermistor 58. To the fixing roller 51
Is arranged on the downstream side in the rotation direction of the. Coating roller 53d
Is a rotatable roller in which the surface of foamed sponge rubber is coated with silicone rubber, and is in contact with the fixing roller 51 to apply oil. By using the application roller 53d made of foamed sponge rubber or the like in this way, a sufficient nip with the fixing roller 51 can be secured and the release agent can be sufficiently transferred to the fixing roller 51. Blade 53
Reference numeral e is an elastic blade made of fluororubber or the like, and the amount of applied oil is controlled by the contact angle, contact pressure and the like.

The pressure roller 52 is also attached to the fixing roller 1.
Cleaning web 5 similar to the cleaning device 54 of
5a, a pressing roller 55b, an unwinding roller 55c, a take-up roller 55d and the like are attached, and the toner adhering to the pressure roller 52 via the fixing roller 51 is cleaned.

The pressure roller 52 includes a pressure roller 5
An oil removing blade 60, which is an elastic body for removing the release agent that removes the excess release agent remaining on the surface 2, is in contact. If the oil removing blade 60 is not provided, the excess release agent collects in the nip between the fixing roller 51 and the pressure roller 52 and causes stains on the recording material, or the transparent laminating film for OHP slips to cause the nip. Entry failure occurs. As the material of the oil removing blade 60, Si rubber, fluororubber, or the like is used, and these blades are in contact with the pressing roller 52 in the forward direction or the reverse direction with an appropriate amount of advance.

In this state, when the transfer paper P is conveyed, the fixing roller 51 and the pressure roller 52 rotate, silicone oil is applied to the surface of the fixing roller 51 as a release agent, and the transfer paper P is fixed. Roller 51 and pressure roller 52
When passing between the two, the unfixed toner image on the surface of the paper is melted and fixed by being pressed and heated from both the front and back sides at a substantially constant pressure and temperature, and a full-color image is formed on the transfer paper P.
The transfer sheet P on which the image is fixed is separated from the pressure roller 52 by the lower separation claw 68 and is discharged to the outside of the machine.

[0015]

However, the fixing device having the releasing agent supplying device as shown in FIG. 6 has the following problems.

In the release agent applying device 53, a roller having a low hardness made of foam sponge is used for the release agent applying roller 53d in order to secure a sufficient contact nip. However, such a release agent applying roller is likely to thermally expand at a high temperature, and as shown in FIG. 7, the release agent applying roller 53d near the center of the release agent applying roller 53d.
Such an application roller 5 can be expanded in the direction perpendicular to the axis of d and the ends can be expanded in the direction horizontal to the axis.
3d was expanding like a drum at high temperature. As a result, the contact nip becomes smaller at the end portion than at the center portion, and further, the contact nip does not occur, which causes a problem that the transfer amount of the release agent is different between the center portion and the end portion. .

[0017]

According to the first invention of the present application, the above-mentioned object is at least a pair of fixing rotators arranged rotatably while being in pressure contact with each other, and the fixing rotator. And a releasing agent supplying means having a rotating body for supplying a releasing agent to the surface of the recording medium, and the recording material having an unfixed image is nipped and conveyed at a pressure contact portion formed by the fixing rotating body pair. In a fixing device for heat-fixing an unfixed image on a material, the release agent supplying rotary body has at least a foam elastic body layer, and the foam elastic body has a thickness of a central portion of the supply rotary body. And the ends are different, and the external shape of the supply rotary body is straight. According to the second invention of the present application, the above object is achieved by the elastic foam layer of the first invention having a thicker end portion than a central portion.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (Embodiment 1) FIG.
FIG. 3 is a cross-sectional view of a release agent application roller representing an embodiment.

In FIG. 1, 100 is a core metal made of Al or the like, 101 is a foam sponge rubber layer, and 102 is a surface layer made of Si rubber or the like. In this embodiment, the cored bar is shaped like a drum and a foamed sponge rubber layer is formed on the cored bar. By molding the foam sponge rubber layer in this way, the thickness of the foam sponge rubber at the center becomes thinner than at the ends, so when the temperature rises and the heat expands, the expansion at the ends becomes larger than at the center. Even if the foamed sponge rubber of the portion expands in the horizontal direction of the cored bar shaft, the amount of expansion in the vertical direction is large, so that the entire outer shape can be made straight. Since the drum shape of the cored bar at this time varies depending on the characteristics of the foam sponge rubber used and the size of the roller, it is necessary to design the optimum value for each roller.

By using such a release agent coating roller in the fixing device shown in FIG. 6, the shape of the roller can be kept straight even when it thermally expands at a high temperature, and the release agent is uniformly applied to the fixing roller 51. And the unevenness of oil application can be prevented.

Here, in order to obtain the same effect, it is conceivable that the external shape of the coating roller 53d has a large end portion and a small central portion. However, if such an external shape is adopted, the coating roller 53d is released from the mold. Since the contact of the agent regulating blade 53e is likely to be insufficient and the release agent is likely to slip through the blade 53e to cause oil unevenness, a straight outer shape is required.

(Embodiment 2) FIG. 2 shows a cross-sectional view of a release agent coating roller representing a second embodiment of the present invention.

In FIG. 2, 100 is a cored bar made of Al or the like, 101 is a foam sponge rubber layer, and 102 is a surface layer made of Si rubber or the like. Here, in this embodiment, a sponge rubber layer 10 is formed in a reverse crown shape on a straight core metal 100.
One is molded, and the silicone rubber layer 102 is further molded thereon so that the shape is straight. Since the thickness of the foam sponge rubber in the central portion is smaller than that in the end portions as in the first embodiment, the expansion of the end portion becomes larger than that in the center when the temperature is high and the thermal expansion occurs, and the foam sponge rubber of the end portion is increased. Even if the core metal expands in the horizontal direction of the core shaft, the amount of expansion in the vertical direction is large, so that the entire outer shape can be made straight. Foam sponge rubber layer 10 at this time
Since the condition of the reverse crown shape of No. 1 differs depending on the characteristics and thickness of the foam sponge rubber used, it is necessary to design the optimum value for each roller.

By using such a release agent coating roller in the fixing device shown in FIG. 6, the shape of the roller can be kept straight even when it thermally expands at a high temperature, and the release agent is uniformly applied to the fixing roller 51. And the unevenness of oil application can be prevented.

(Embodiment 3) FIG. 3 is a cross-sectional view of a release agent coating roller showing a third embodiment of the present invention.

In FIG. 3, 100 is a core metal made of Al or the like, 101 is a foam sponge rubber layer, and 102 is a surface layer made of Si rubber or the like. Here, in the present embodiment, a foam sponge rubber layer 101 having a straight shape at the center and an outer shape larger than that at the end only is molded on a straight core metal 100, and a silicone rubber layer 102 is further formed thereon. It was molded to be straight. Since the thickness of the foam sponge rubber in the central portion is smaller than that in the end portions as in the second embodiment, the expansion of the end portions becomes larger than that in the center when the temperature becomes high and the thermal expansion occurs, and the foam sponge rubber of the end portions is increased. Even if the core metal expands in the horizontal direction of the core shaft, the amount of expansion in the vertical direction is large, so that the entire outer shape can be made straight. Foam sponge rubber layer 101 at this time
Since the shape of the shape differs depending on the characteristics and thickness of the foam sponge rubber used, it is necessary to design the optimum value for each roller.

By using such a release agent coating roller in the fixing device shown in FIG. 6, the shape of the roller can be kept straight even when it thermally expands at a high temperature, and the release agent is uniformly applied to the fixing roller 51. And the unevenness of oil application can be prevented.

[0028]

As described above, according to the first invention of the present application, at least a pair of fixing rotators arranged rotatably while being pressed against each other, and a surface of the fixing rotator. And a releasing agent supplying means having a rotating body for supplying a releasing agent to the recording material, and the recording material having an unfixed image is pinched and conveyed on the recording material at a pressure contact portion formed by the fixing rotating body pair. In the fixing device for heat-fixing an unfixed image, the release agent supplying rotary body has at least a foam elastic body layer, and the foam elastic body has a thickness and a central portion and an end. It is possible to apply the release agent uniformly because the supply rotor is different in shape and the external shape of the supply rotary member is straight.

According to the second invention of the present application, the thickness of the elastic foam layer in the first invention is thicker at the end portion than at the central portion, so that the release agent can be uniformly applied. .

[Brief description of drawings]

FIG. 1 is a configuration diagram of a release agent application roller showing a first embodiment of the present invention.

FIG. 2 is a configuration diagram of a release agent application roller showing a second embodiment of the present invention.

FIG. 3 is a configuration diagram of a release agent application roller showing a third embodiment of the present invention.

FIG. 4 is a sectional view of an image forming apparatus to which the present invention has been applied.

5 is a cross-sectional view of the image forming unit in FIG.

FIG. 6 is a sectional view of the fixing unit in FIG.

FIG. 7 is a cross-sectional view of a conventional release agent application roller.

[Explanation of symbols]

51 fixing roller 52 Pressure roller 53 Release agent coating device 53a oil pan 53b, 53c pumping roller 53d Release agent coating roller 53e Regulation blade 100 cores 101 foamed elastic body layer 102 Silicone rubber layer

Claims (2)

[Claims] 1. A pair of fixing rotators which are rotatably arranged while being in pressure contact with each other, and a releasing agent supply means having a rotator for supplying a releasing agent to the surface of the fixing rotator. In the fixing device for carrying out heat fixing of the unfixed image on the recording material, the recording material having the unfixed image is nipped and conveyed at the pressure contact portion formed by the pair of fixing rotators. The supply rotary body has at least a foam elastic body layer, the thickness of the foam elastic body is different between the central portion and the end portion of the supply rotary body, and the external shape of the supply rotary body is straight. A release agent applying device and a fixing device. 2. The thickness of the foam elastic layer of the release agent supplying rotary member is larger at the end portion than at the central portion.
The mold release agent application device and the fixing device described in.