JPH0631493Y2 - Fixing device - Google Patents

Description

[Detailed Description of the Invention] [Industrial field of application] The present invention relates to a fixing device used in a device using an electrophotographic process such as a copying machine, a facsimile, and a printer.
In particular, the present invention relates to an improvement of a fixing device capable of reliably preventing the toner offset phenomenon.

[Prior Art] Conventionally, in a copying machine or the like using an electrophotographic process, it is necessary to fix unfixed toner formed on a sheet to form a permanent image.
A device as shown in Fig. 11 is known. That is, this fixing device has a heating source (a) inside and a heating roller (b) which rotates in the direction of the arrow, and a pressure roller which is arranged in pressure contact with the heating roller (b) and rotates in the direction of the arrow. A roller (c) and a main part thereof are formed, and the paper (e) on which the unfixed toner image (d) is formed is inserted between the heating roller (b) and the pressure roller (c) to cause the toner. The image (d) is fixed.

By the way, the biggest drawback of this type of fixing device is that the unfixed toner surface of the paper (e) directly contacts the outer peripheral surface of the heating roller (b), so that a part of the unfixed toner on the paper (e) is Is transferred to the heating roller (b) side, and the toner is retransferred to the trailing edge of the paper (e) or to the paper (e) that passes next, so that the paper (e) is soiled, that is, a so-called toner offset. The phenomenon was to occur.

Therefore, conventionally, as shown in FIG. 11, an oil pan (f) containing a release agent such as dimethyl silicone oil near the heating roller (b) and this release agent are attached to the outer periphery of the heating roller (b). A wick (g) applied to the surface, a blade (h) for adjusting the amount of release agent applied to a constant amount, an oil tank (j) for replenishing the oil pan (f) with a release agent, and the like are the main parts. And a cylindrical body (1) having a plurality of small holes on the outer peripheral surface and containing a liquid release agent inside, as shown in FIG. A heating roller (b) is provided with a supply roller (n) composed of a porous elastic body (m) such as a silicone sponge laminated on the outer peripheral surface of the tubular body (1) in pressure contact with the outer surface of the heating roller (b). Preventing the toner offset phenomenon by applying an appropriate amount of release agent to the outer peripheral surface of the roller (b) The method of doing is adopted.

[Problems to be Solved by the Invention] However, in the above-mentioned conventional coating means, a release agent is applied to the outer peripheral surface of the heating roller (b) via the porous elastic body (m) of the wick (g) or the supply roller (n). However, when the coating amount is too large, the paper (e) is contaminated by an excessive amount of the release agent, and when the coating amount is too small, the toner offset phenomenon occurs. There was a problem that it could not be prevented.

Further, in the coating means, since the wick (g) and the supply roller (n) are arranged in constant contact with the outer peripheral surface of the heating roller (b), the heating roller (b) of the wick (g) is arranged. There is a problem that offset toner or paper powder is likely to accumulate on the contact portion with the contact roller and the outer peripheral surface of the supply roller (n) to cause uneven application of the release agent. ) Is heated by contacting the heating roller (b), there is a problem that thermal deterioration and gelation of the release agent occur, and toner offset cannot be prevented.

[Means for Solving the Problems] The present invention has been made in view of the above problems, and an object thereof is to provide a fixing device capable of reliably preventing the toner offset phenomenon.

That is, the present invention includes a heating roller and a pressure roller that rotate while being pressed against each other, and a release agent supply unit that supplies a release agent for preventing toner offset to the outer peripheral surface of at least one of the heat roller and the pressure roller. Based on the premise of a fixing device for fixing a toner image by inserting a sheet on which an unfixed toner image is formed between the heating roller and the pressure roller, the release agent supply section carries a conductive release agent. And an electrostatic field applying means for applying an electrostatic field to the conductive release agent. The conductive release agent is caused to fly on the basis of the electrostatic field, and is applied to the outer peripheral surface of the heating roller or the pressure roller. It is characterized in that a release agent is supplied.

In such a technical means, the conductive release agent for applying an electrostatic field to fly may be directly supplied from the release material carrier to the heating roller or pressure roller side. A configuration may be adopted in which a leveling roller is arranged in contact with the outer peripheral surface of the above and the conductive release agent is supplied through this leveling roller. When the latter method is adopted, the leveling roller also serves as leveling means for uniformly applying the conductive release agent to the outer peripheral surface of the heating roller or the pressure roller. There is an advantage that can be achieved.

As for the release agent carrier, a carrier body provided along the length direction of the heating roller or the pressure roller to hold the conductive release agent, and a carrier body provided along the length direction of the carrier body. This can be configured by a body-side electrode and a plurality of nozzle groups provided on the heating roller or pressure roller side of the above-mentioned carrying body and flying the release agent within the carrying body.
In addition, in order to keep a constant amount of the release agent held in the carrying body so that a constant pressure is constantly applied to the tip of the nozzle, a replenishment member for replenishing the consumed conductive release agent is provided in addition to the above configuration. Is desirable. Further, the intervals between the nozzles are usually set to be equal, but for example, for parts that require extra release agent, such as parts that the temperature sensor always contacts, the intervals are set narrow and the supply amount is adjusted appropriately. May be.

Further, the position of the carrier-side electrode provided along the length direction of the carrier body is arbitrary, for example, it may be provided on the inner bottom surface of the carrier body or on the inner wall surface of the carrier body, Also, regarding the structure of the carrier side electrode, it may be composed of one continuous conductive member, or may be composed of a plurality of divided electrodes provided by being divided along the length direction. .

On the other hand, regarding the electrostatic field applying means for applying an electrostatic field to the conductive release agent, a roller side electrode provided on at least one of the heating roller and the pressure roller, and a carrier side electrode provided on the release agent carrier. This can be constituted by voltage applying means for applying a DC voltage between the roller side electrode and the carrier side electrode. Further, in the case where a leveling roller is provided on the outer peripheral surface of the heating roller or the pressure roller and the conductive release agent is supplied through this leveling roller, the roller side electrode is applied to the heating roller or the pressing roller. It is not provided on the pressure roller, but is naturally provided on the leveling roller side. The roller-side electrode provided on the heating roller, the pressure roller, or the leveling roller may be formed of a conductive tubular body such as an aluminum core forming a part of each roller. it can. When the voltage applying means is applied in a time-division manner, the number of droplets of the conductive release agent per unit time can be variably set, so that the supply amount of the release agent to the heating roller or the pressure roller can be appropriately set. It becomes possible to adjust.

Further, when the carrier-side electrode is composed of a plurality of divided electrodes, a structure may be adopted in which a DC voltage is selectively applied between a part of the divided electrodes and the roller-side electrode. By adopting such a configuration, the application area of the conductive release agent can be arbitrarily adjusted, so that it becomes possible to apply the release agent only to a necessary portion of the heating roller or the pressure roller.

Further, the conductive release agent used in this technical means has conductivity and viscosity capable of flying when a predetermined electrostatic field is applied to the release agent, and also has heat resistance. Silicone oil in which a metal element is introduced into methylsiloxane to adjust its conductivity, modified silicone oil reacted with a functional group such as —SH group, —OH group, and —COOH group can be used.

Incidentally, the setting range of the applied voltage of the voltage applying means forming a part of the electrostatic field applying means, and the conductivity of the conductive release agent,
The setting range of the viscosity and the like is set to an appropriate value in consideration of the structure and size of the release agent supply unit, the supply amount of the release agent to the heating roller or the pressure roller, and the like.

[Operation] According to the technical means as described above, the release agent supply unit for supplying the release agent for preventing the toner offset is provided with the release agent carrier carrying the conductive release agent and the conductive release agent. A heating roller or a pressure roller, which comprises an electrostatic field applying means for applying an electrostatic field, and causes the conductive release agent to fly based on the electrostatic field to supply the release agent to the outer peripheral surface of the heating roller or the pressure roller. And the release agent carrier can be set in a non-contact state.

[Embodiment] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

First Embodiment A fixing device according to this embodiment is provided with a heating roller (1) which rotates in an arrow direction as shown in FIGS. 1 and 2 and a heating roller (1) in contact with the heating roller (1). Pressure roller (2) that rotates in the direction of the arrow, a leveling roller that is disposed in contact with the heating roller (1) and that rotates by rotation, that is, an oil donor roller (3), and this oil donor roller. The main part is composed of a release agent supply section (4) which is disposed near (3) and supplies the release agent to the oil donor roller (3).

First, the heating roller (1) includes an infrared lamp (10) of 600 W inside, an aluminum core (11) having an outer diameter of 49 mmφ and a length of 490 mm, and an outer peripheral surface of the core (11) with a primer appropriately interposed. The releasable layer (12) made of silicone rubber and having a thickness of 0.5 mm is laminated.

On the other hand, the pressure roller (2) has an outer diameter of 35 mmφ and a length of 385 m.
The core (20) is made of aluminum and has a thickness of 7.5 mm. The elastic layer (21) is made of silicone rubber and is laminated on the outer peripheral surface of the core (20) through a primer.

Further, the heating roller (1) and the pressure roller (2) are pressed against each other with a load of 100 kg by a mechanism (not shown), and the surface temperature of the heating roller (1) is the temperature provided on the outer peripheral surface thereof. The temperature is controlled to 180 ℃ by the sensor (13) and the surface speed is 200m in the direction of the arrow.
It is adjusted to rotate at m / sec.

Further, the oil donor roller (3) attached to the heating roller (1) side is made of an aluminum core (30) having an outer diameter of 20 mmφ and a length of 380 mm, and a silicone rubber layer having a rubber layer of 1.0 mm laminated on the outer peripheral surface thereof. It is composed of an elastic body layer (31), and the aluminum core (30) is grounded (grounded) and doubles as a roller side electrode.

Further, the release agent supply part (4) has a carrier side electrode on the inner bottom surface thereof, and the wall surface (40) on the oil donor roller (3) side.
An oil pan (42) having a plurality of nozzles (41) to (41),
The oil pan (42) and the oil tank (43) that reinforces the conductive silicone oil form a main part. That is, as shown in FIG. 3, the oil pan (42) includes an oil pan body (44) having an inner volume of 20 mm in depth, 15 mm in width, and 370 mm in length, and the inside of the oil van body (44). 1.0 mm thick aluminum carrier side split electrodes (45) (46), which are provided on the bottom surface and are attached to the carrier side split electrodes (45) (46), respectively, and connected to the high voltage power supply (47) 2.5 m along the lengthwise direction of the oil donor roller (3) on the pin electrodes (48) (49) and the wall surface (40) of the oil pan body (44).
A total of 185 stainless steel seamless pipes with an inner diameter of 0.3 mm, an outer diameter of 0.4 mm, and a length of 4 mm provided at m intervals.
It is composed of a group of nozzles (41) to (41). On the other hand, the oil tank (43) is connected to the oil pan via the connecting pipe (50).
It is connected to (42) and replenishes the consumed conductive silicone oil so that the oil level is above the nozzles (41) to (41).
It is adjusted so that it is always 3 mm higher than the installation position. The gap between the tip of each of the nozzles (41) to (41) and the oil donor roller (3) is set to 1.0 mm. The other end of the high-voltage power supply (47) whose one end is connected to the carrier-side split electrodes (45) (46) is grounded (grounded) as shown in FIG.

Then, in order to fix the toner with this fixing device,
As shown in FIG. 2, the paper (6) on which the unfixed toner image (60) is formed between the heating roller (1) and the pressure roller (2).
Heat energy from the infrared lamp (10) disposed in the heating roller (1) through the core (11) and the releasable layer (12) to the unfixed toner image (60). It supplies it without excess or deficiency and fixes it.

At this time, in this fixing device, when a DC voltage is applied from the high voltage power source (47) to the carrier side divided electrodes (45) and (46) in the oil pan (42), the conductive silicone oil surface and the oil donor roller (3) are applied. ), A static electric field is formed between the core and the core (30), and the conductive silicone oil flies toward the oil donor roller (3) based on the static electric field, and the conductive silicone oil flies through the oil donor roller (3). Since the conductive silicone oil is supplied to the outer peripheral surface of the heating roller (1), the toner offset phenomenon can be prevented.

In this case, in the fixing device according to this embodiment, unlike the conventional device, the oil pan (42) forming a part of the release agent supply unit (4) is connected to the heating roller (1) and the oil donor roller (3). Since they are arranged in a non-contact state, offset toner, paper dust, and the like are less likely to be deposited on the outer peripheral surface of the oil donor roller (3), and uneven application of silicone oil can be prevented.

Since the oil pan (42) is not heated by the heating roller (1), thermal deterioration and gelation of the silicone oil can be reliably prevented, and evaporation of low volatile components can also be suppressed to stably supply the silicone oil. Have advantages.

Further, since the silicone oil is supplied by utilizing the electrostatic field, it is possible to electrically control the supply amount. That is, when a DC voltage is applied to the carrier-side divided electrodes (45) (46) in a time-division manner, the number of flying droplets of conductive silicone per unit time can be controlled. On the other hand, in the case of a small number of copies, it can be adjusted to a small amount, and there is an advantage that the waste of silicone oil can be eliminated.

When a DC voltage is applied only to one side of the carrier side electrodes (45) (46), the conductive silicone oil on the electrode side that is not applied becomes unable to fly due to the voltage drop due to the electric resistance of the oil itself, and the side to which the voltage is applied Since only the silicone oil can be supplied, the supply area can be controlled. Therefore, since the optimum silicone oil can be supplied according to the width size of the copy paper (6), there is an advantage that waste of the silicone oil can be eliminated.

In addition, since the release agent supplied is conductive silicone oil, it has the advantage that the charge amount of the release layer (12) on the heating roller (1) is reduced and the winding of the paper (6) can be prevented. There is.

[Condition Setting Test] Next, the following tests were performed in order to obtain the appropriate values of the conductivity and viscosity of the conductive silicone oil applied to the fixing device according to the example, and the applied voltage from the high-voltage power source.
Incidentally, the fixing device according to the embodiment is implemented based on the data obtained by this test. Further, the test uses the fixing device according to the embodiment.

◎ Applied silicone oil Shin-Etsu Chemical Co., Ltd. product name (X-21-7337) (a) Relationship between resistivity of silicone oil and discharge amount from nozzle Figure 4 shows the resistivity of silicone oil (Ω ・cm) and the amount of oil discharged from one nozzle per minute (μl
/ Min) is a graph showing the relationship with

As is clear from this graph, the discharge rate of silicone oil decreases as the resistivity of silicone oil increases, and in the case of insulating silicone oil with a resistivity of 10 ¹³ Ω · cm or more, 5
The silicone oil did not fly even when a DC voltage of Kv was applied.

On the other hand, since it is extremely difficult to produce a silicone oil having a resistivity of 10 ⁹ Ω · cm or less, the resistivity of the silicone oil applicable to this fixing device was 10 ⁹ to 10 ¹³ Ω · cm.

(b) Relationship between viscosity of silicone oil and discharge amount from nozzle Figure 5 shows viscosity of silicone oil (cs) and discharge amount of silicone oil discharged from nozzle per minute (μl / mi
It is a graph which showed the relationship with n).

As is clear from this graph, as the viscosity of the silicone oil increases, the discharge amount decreases, and when it is 1000 cs or more, it becomes difficult to replenish the silicone oil from the oil tank (43), and the heating roller (1 It was also difficult to evenly apply silicone oil onto the above. On the other hand, in the case of a silicone oil having a viscosity of 20 cs or less, it was difficult to apply because of an increase in volatile components due to heat.

Therefore, the viscosity of the silicone oil applicable to this fixing device was 20 to 1000 cs.

(c) Relationship between voltage applied by high-voltage power supply and discharge amount from nozzle Fig. 6 shows applied voltage (kv) from high-voltage power supply (47) and discharge amount of silicone oil discharged from nozzle (μl / mi).
It is a graph which showed the relationship with n).

As is clear from this graph, the silicone oil is not discharged from the nozzle (41) when the applied voltage is 0 to 1.5 kv, and the meniscus of the silicone oil is not generated as shown in FIG. 7 (A). Oil donor roller (3)
It was only convex toward the side.

On the other hand, at 1.5 kv or more, as shown in FIG. 7 (B), the tip of the oil meniscus is suddenly torn off and becomes an oil droplet, which then flies to the oil donor roller (3) side.
Although the flight start voltage at this time is somewhat different depending on the viscosity and the resistivity of the silicone oil, it falls within the voltage range of 1.5 to 3 kv within the above applicable range. In addition, the number of flying oil droplets (called a flying frequency) in the vicinity of the flying start voltage was several to several tens of drops (Hz).

Further, when the voltage is further increased from the above value, the flying frequency increases, and finally the oil droplets are connected to each other to form a leaky thread and are supplied to the oil donor roller (3). The voltage at this time was 2.5 to 4.0 kv.

It should be noted that the discharge amount did not increase even if the voltage was further increased, and on the contrary, it tended to decrease.

From these results, a high voltage power supply applicable to this fixing device
The applied voltage of (47) was 1.5 to 10.0 kv.

Second Embodiment As shown in FIGS. 8 to 9, the fixing device according to the second embodiment has an oil pan (4) without an oil donor roller (3).
The fixing device is substantially the same as the fixing device of the first embodiment except that the conductive silicone oil is directly supplied from 2) to the outer peripheral surface of the heating roller (1). In order to apply the oil uniformly, the heating roller (1) is provided with a leveling blade (8).

Further, also in the fixing device according to this embodiment, the heating roller (1) and the oil pan (4
Since 2) and are arranged in non-contact with each other, it is possible to prevent uneven application of silicone oil due to adhesion of offset toner and paper powder as in the first embodiment, and to prevent heat deterioration and gelation of silicone oil. Further, since the electrostatic oil is applied to supply the silicone oil to the outer peripheral surface of the heating roller (1), it is possible to electrically control the coating amount and the coating region, and the silicone oil to be coated is applied. Releasable layer in the heating roller (1) due to conductivity
There is an advantage that the charge amount of (12) is reduced and winding of the paper (6) can be prevented.

Incidentally, as shown in FIG. 10, a structure in which a leveling roller (9) is provided instead of the leveling blade (8) may be adopted.
In addition, these leveling blades (8) and leveling rollers (9)
Instead of, for example, the oil pan (42) itself is periodically moved in parallel along the lengthwise direction of the heating roller (1) so that the coating areas of the nozzles (41) to (41) extend in the lengthwise direction. It may have a uniform structure.

[Effects of the Invention] As described above, the present invention provides a release agent supply unit for supplying a release agent for preventing toner offset, a release agent carrier for carrying a conductive release agent, and a static release agent for the conductive release agent. An electrostatic field applying means for applying an electric field, and to fly the conductive release agent based on the electrostatic field to supply the release agent to the outer peripheral surface of the heating roller or the pressure roller. It is possible to set the release agent carrier in a non-contact state.

Therefore, it is possible to prevent uneven coating of the release agent due to the adhesion of the offset toner or paper powder, to prevent thermal deterioration and gelation of the release agent, and to further apply an electrostatic field to the heating roller or the pressure roller. Since the release agent is supplied to the outer peripheral surface, it is possible to electrically control the application amount and the application area, and the release agent applied is electrically conductive, so that the charge amount of the heating roller or the pressure roller is reduced. It has an effect of preventing the sheet from being wound around the equal rollers.

[Brief description of drawings]

1 to 10 show an embodiment of the present invention. FIG. 1 is a perspective view of a fixing device according to the first embodiment, FIG. 2 is its sectional view, and FIG. 3 is its release material supply. FIG. 4 is a perspective view of an oil pan forming a part of the portion, FIG. 4 is a graph showing the relationship between the oil resistivity and the oil discharge amount in the fixing device, and FIG.
FIG. 7 is a graph showing the relationship between the viscosity of the oil and the oil discharge amount, FIG. 6 is a graph showing the relationship between the applied voltage and the oil discharge amount, and FIGS. 7A to 7B are enlarged nozzle tips. FIG. 9 is a sectional view, FIG. 8 is a perspective view of a fixing device according to a second embodiment, and FIG.
The drawings are sectional views thereof, FIG. 10 is a sectional view of a modified example thereof, and FIGS. 11 to 12 are sectional views of a conventional fixing device. [Explanation of symbols] (1) ...... Heating roller (2) ...... Pressure roller (3) ...... Oil donor roller (4) ...... Release agent supply part (41) ...... Nozzle (42) ...... Oil pan ( 43) …… Oil tank (44) …… Oil pan body (45) (46) …… Split electrodes (47) …… High-voltage power supply

Claims (6)

[Scope of utility model registration request] 1. A heating roller and a pressure roller that rotate while being in pressure contact with each other, and a release agent supply unit that supplies a release agent for preventing toner offset to the outer peripheral surface of at least one of the heat roller and the pressure roller. In a fixing device for fixing a toner image by inserting a sheet on which an unfixed toner image is formed between the heating roller and the pressure roller, the release agent supply section is provided with a release agent carrying a conductive release agent. It is composed of an agent carrier and an electrostatic field applying means for applying an electrostatic field to the conductive release agent, and the conductive release agent is caused to fly based on the electrostatic field to release the release agent on the outer peripheral surface of the heating roller or the pressure roller. A fixing device characterized in that the fixing device is provided. 2. The heating roller or pressure roller is provided with a leveling roller that comes into contact with the rollers and is driven to rotate, and the conductive release agent is provided on the outer peripheral surface of the heating roller or pressure roller via the leveling roller. The fixing device according to claim 1, wherein the fixing device is supplied to the utility model. 3. The release agent carrier is provided along a length direction of a heating roller or a pressure roller and holds a conductive release agent, and a release body is provided over the length direction of the support body. A carrier-side electrode that constitutes a part of the electrostatic field applying means, a plurality of nozzle groups that are provided on the heating roller or pressure roller side of the carrier body and that fly the release agent within the carrier body, and the carrier body is electrically conductive. The fixing device according to claim 1, further comprising: a replenishing member that replenishes the functional release agent. 4. The electrostatic field applying means comprises a roller side electrode provided on at least one of a heating roller and a pressure roller, a carrier side electrode provided on the release agent carrier, and a roller side electrode. The fixing device according to claim 1, wherein the fixing device comprises a voltage applying means for applying a DC voltage between the body side electrodes. 5. The electrostatic field applying means comprises a roller side electrode provided on the leveling roller, a carrier side electrode provided on the release agent carrier, and a DC voltage between the roller side electrode and the carrier side electrode. The fixing device according to claim 2, characterized in that the fixing device comprises a voltage applying means for applying a voltage. 6. The carrier-side electrode is composed of a plurality of divided electrodes which are divided and arranged along a length direction of a heating roller or a pressure roller, and a direct current is provided between the divided electrode and the roller-side electrode. The fixing device according to claim 4 or 5, characterized in that a voltage is selectively applied.