JP3024010B2 - Fixing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device which comprises a pair of rotating members and performs heat fixing by applying heat when an unfixed image passes between these rotating members. The present invention relates to a fixing device used in a fixing technical field of an electrostatic recording device.

[0002]

2. Description of the Related Art FIG. 12 is a diagram showing a configuration of a conventional fixing device.

In a fixing device, a pair of rollers are arranged in pressure contact with each other, and fixing is performed by heating the rollers by a heating means. The fixing roller 10 has a configuration in which a fluorine resin layer is provided on the outer surface of a hollow aluminum cored bar, and a halogen heater 12 is provided therein. Reference numeral 13 denotes a silicone oil application / cleaning member, which has a configuration including a cleaning material 13A made of a heat-resistant felt impregnated with silicone oil and a holder 13B supporting the cleaning material 13A, which is pressed by a fixing roller. Further, the pressure roller 11 includes a core 11
B, for example, a low-temperature vulcanized silicone rubber (LT
V) The elastic layer 11A is provided.

The fixing operation is performed by the transfer material 14 on which the toner image 15 is placed passing through the pair of rollers.

[0005]

By the way, there has been a need for a structure that does not use a cleaning member for the purpose of miniaturization of the machine and maintenance-free.

For this purpose, it is necessary to provide a fixing device that does not generate an electrostatic offset. Here, the electrostatic offset means that when a charged toner enters the roller opposition, an electric field opposite to the holding force of the toner in the transfer material direction is generated by, for example, charge-up due to friction of a pressure roller. Receiving, the toner image is transferred to the fixing roller side, and the toner image is fixed on the transfer material again after making one round on the roller, thereby damaging the image.

Therefore, as a method for preventing the electrostatic offset, methods shown in FIGS. 13 and 14 have been tried.

FIG. 13 shows that an offset is prevented by applying a bias having a polarity opposite to that of the toner to the pressure roller so that a potential difference exists between the upper and lower rollers to attract the toner toward the transfer material. is there. In FIG. 1, the fixing roller 16 includes a core 16B and a releasable layer 16A, and is connected to ground via a sliding contact (not shown). On the other hand, the pressure roller 17 is composed of a conductive elastic layer 17B having a volume resistance of 10 9 Ω · cm or less and a release layer 17A on a cored bar 17C. It has a configuration in which a predetermined bias having a polarity opposite to that of the toner is applied.

FIG. 14 shows the same roller configuration as that described in FIG. 13, and shows a method of connecting a diode as a rectifier to each of the upper and lower rollers to provide a potential between the rollers by self-bias. I have. In the figure,
The figure assumes that the toner has a negative polarity. On the fixing roller 16 side, a diode is connected to the fixing roller side via a sliding contact (not shown) on the core metal in a direction for collecting negative charges of the same polarity as the toner, and on the pressing roller 17 side, A diode is connected to the core via a sliding contact (not shown) in the direction to accumulate positive charges of the opposite polarity to the toner on the pressure roller side.
When a transfer material having a certain potential enters the pair of rollers to which the diode is connected, the potential is induced by the potential and a potential difference is generated between the upper and lower rollers, thereby creating an electric field that attracts the toner to the transfer material side. This is to prevent offset. When the toner has a positive polarity, the direction of the diode is opposite to that of FIG.

However, in the conventional example shown in FIG. 13, when the transfer material enters the roller pair at a potential higher than the bias value applied by the high-voltage power supply 18 particularly in a low humidity environment, the pressure roller potential Cannot contribute as a force to draw the toner toward the transfer material side, so that an offset occurs.

Further, in the conventional example shown in FIG. 14, in a high humidity environment, leakage current increases due to moisture absorption of the diode itself and condensation on the surface around the diode.
There has been a problem that a sufficient potential difference cannot be maintained between the upper and lower rollers, thereby causing an offset.

[0012]

SUMMARY OF THE INVENTION Therefore, the present invention has not been determined.
Between the surface of the recording material carrying the toner image on the unfixed toner image side and
A fixing device having a fixing roller in contact with the fixing device;
A voltage of the same polarity as the toner of the unfixed toner image is applied to the roller.
Voltage applying means for applying, the fixing roller and the voltage mark
Between the fixing means and the fixing roller.
A diode connected in the direction of loading.
And In the present invention, in a high humidity environment,
Even if the leakage current of the circuit increases, it is fixed by the voltage application means.
The roller potential can be set to a potential that prevents offset.
Can be used, and in a low humidity environment,
Fixing roller with the potential of diode added to the potential
Potential can be increased, and offset can be prevented well.
Can be stopped. Further, the present invention provides a method for carrying an unfixed toner image.
A pressure roller in contact with the surface of the recording material opposite to the unfixed toner image
A fixing device having a roller,
A voltage to apply a voltage of the opposite polarity to the toner of the unfixed toner image
Application means, between the pressure roller and the voltage application means.
A direction for accumulating charges of the opposite polarity to the toner on the pressure roller.
And a diode connected to the first connection. This
In the invention of the present invention, in a high humidity environment, the leakage current of the diode
Even if the flow increases, the potential of the pressure roller is
Can be set to a potential to prevent offset, and
In a wet environment, the potential
To increase the potential of the pressure roller.
And the offset can be satisfactorily prevented.

[0013]

【Example】

(Embodiment 1) FIG. 1 is a diagram showing a first embodiment of the present invention.

In FIG. 1, the description will be made on the assumption that the toner has a negative polarity. The fixing roller 1 and the pressure roller 2 are pressurized at a predetermined pressure, heated by a halogen heater 3 provided in the fixing roller, and a temperature sensor (not shown) provided in contact with the fixing roller 1. While the temperature is being controlled by the means, the roller pair rotates, and an unfixed image passes between the rollers to perform a fixing operation.

The fixing roller 1 includes a core 1B and a release layer (for example, a PFA tube layer having a thickness of 30 μm) provided on the surface of the core 1B. It is connected to a diode 4.

On the other hand, the pressure roller 2 has the following configuration in order to provide a potential difference between the upper and lower rollers. Core 2
A conductive elastic layer (for example, conductive silicon rubber) having a volume resistance of 10 ⁹ Ω · cm or less is provided on C, and a release layer (for example, a 50 μm-thick PFA tube layer) is provided on its surface. Have been. A high-voltage diode 5 is connected to the metal core 2C via a sliding contact (not shown).
Further, after that, the high voltage power supply 6 is connected so that a predetermined bias can be applied. In FIG. 1, the direction of the diode and the polarity of the applied bias are shown so as to attract the negatively charged toner to the pressure roller side. However, if the positively charged toner is handled, , The direction of the diode and the polarity of the applied bias are opposite to each other.

In this embodiment, as for the bias value applied by the high-voltage power supply 6, the worst case where the leakage current around the diode 5 becomes large and no potential is generated at all in a high humidity environment is assumed. The voltage required to prevent electrostatic offset is desirable.

FIG. 2 shows high temperature and high humidity (32.5 ° C., 85%)
Below, in order to prevent offset on OHP paper,
This is a result of examining how much bias needs to be applied. According to this, it was found that an application of about 500 (V) or more was necessary. As for the upper limit of the voltage, the higher the applied voltage, the more complicated the device becomes, the larger the size becomes, and the higher the cost becomes from the viewpoint of the leakage between the upper and lower rollers and the withstand voltage measures for complying with the safety standard. Therefore, it is necessary to keep the applied voltage as low as possible. In particular, when a leak occurs between rollers, the predetermined potential difference cannot be maintained between the rollers, and the higher the applied voltage, the more the current flowing at the time of the leak increases, and accordingly, the burn of the release layer, Furthermore, it leads to the expansion of the pinhole. Then, dirt adheres to the pinhole portion on the fixing roller side, resulting in damage to the fixed image. According to experiments by the inventors, it has been found that when a voltage is applied to a pressure roller of 1100 (V) or more and used, a bad effect due to enlargement of a pinhole occurs. Therefore, it is considered that the bias that can be applied to the pressure roller is in the range of 250 to 1000 (V).

Next, FIGS. 3 to 5 show what advantages the present embodiment brings over the conventional example.

These figures show each environment [high temperature and high humidity, (3
2.5 ° C, 85%) (H / H)], low temperature and low humidity (15 ° C,
10%) (L / L)], how the potentials of the upper and lower rollers change when a transfer material having a different potential state passes through the fixing device depending on the peeling state from the drum, and the offset state at that time is It is the figure which made a list what happens. The positive value in the transfer material state column indicates that the positive electric charge given by the transfer is larger than the negative electric charge obtained from the drum surface at the time of peeling from the drum. As a result, the total electric potential of the transfer material is It is a state in which the transfer material is in a positive state, while a state shown in the negative direction is a state in which the total potential of the transfer material is in a negative state because the negative charge is excessively larger than the transfer charge. . This phenomenon becomes more pronounced as the environment becomes lower in humidity, and whether it becomes positive or negative depends on the printing pattern. In a high-humidity environment, peeling charging hardly occurs, so that the transfer material potential does not become negative.

FIG. 3 shows the behavior when high voltage diodes are connected to the upper and lower rollers, respectively. First, in L / L, when a material having a positive transfer material state is passed, the positive potential of the transfer material is induced and 800 L is applied to the pressure roller side.
A potential of about (V) appears. At this time, since the diode is connected to the fixing roller side in the direction of accumulating negative charges, no potential is induced and the potential remains at 0. In this state, since the potential difference between the upper and lower rollers is sufficient to hold the toner on the transfer material, the offset level becomes the OK level. Next, when a negative transfer material state passes, the transfer material state is induced to a negative potential, and a potential of about -800 (V) appears on the fixing roller side. On the pressure roller side, no potential appears and remains at 0.
Even in this state, since there is a sufficient potential difference between the upper and lower rollers, the offset level is an OK level. However, in the case of H / H, when the transfer material in the plus state passes, as shown by the solid line in the figure, the plus potential once appears, but immediately attenuates and disappears, and the offset level becomes N.
The phenomenon of becoming G occurred. Then, when the area around the diode was sealed so as not to be affected by humidity, a potential of about +300 (V) appeared as shown by a dotted line in the figure. From this experiment, it is considered that in the H / H, due to the influence of humidity, the leakage current increases due to the dew condensation of the diode element itself or the surroundings, so that the potential cannot be held. Therefore, an offset is generated because a potential sufficient to attract the toner toward the transfer material side cannot be obtained on the pressure roller side.

FIG. 4 shows the behavior when a high voltage diode is connected to the upper roller, a high voltage power supply is connected to the lower roller, and +500 (V) is applied. In this case, an offset occurs when a transfer material having a positive potential of L / L passes. That is, +500 (V) is always applied to the pressure roller side. However, as described in FIG.
In the case of the transfer material in the plus state, +800 is applied to the pressure roller.
(V) has a potential (at least +800 V or more) sufficient to induce a positive potential, so that a potential of +500 (V) at the pressure roller is still insufficient to attract toner to the transfer material. Because there is.

On the other hand, when the transfer material in the minus state passes, a potential of about -800 (V) is induced on the upper roller side, and a potential of +500 (V) is on the pressure roller side. Since there is a potential difference between the upper and lower rollers sufficient to attract the toner toward the transfer material, no offset occurs. Also, in H / H, on the pressure roller side,
+500 (V) is applied, and as described in FIG.
/ H, the potential that should be induced on the pressure roller is +30
Considering that the voltage is about 0 V, the offset level is OK because the potential is sufficient to attract the toner to the transfer material side.

FIG. 5 shows the behavior when the present embodiment is used for the two systems described above. A diode is connected to the upper roller, and a diode and a high voltage power supply are connected to the lower roller. , +500 V are applied. First, in the case where the transfer material is allowed to pass in a positive state, the upper roller remains at 0 as in FIGS. 3 and 4, but the pressure roller has a potential of -500 V from before the transfer material passed. And rises to about +800 V when passing. This is because a high voltage diode is connected between the pressure roller and the high voltage power supply, and a short potential is induced. As a result, a potential difference between the upper and lower rollers sufficient to attract the toner to the transfer material side is obtained, so that the offset generated in FIG. 4 does not occur. When the transfer material in the minus state passes, the potential is -8 only at the upper roller.
The lower roller is driven by +500 V
In this state, no offset occurs because there is a sufficient potential difference. In the case of H / H, a sufficient potential cannot be obtained depending on the diode due to leakage current or the like.
Since a potential of 0 V has already been applied, there is a sufficient potential difference between the upper and lower rollers, and thus no offset occurs.

As described above, according to the present embodiment, the diode is connected to the fixing roller side, the diode and the high voltage power supply are connected to the pressure roller side, and a predetermined voltage is applied, so that the environment can be controlled. Therefore, a good image free from offset can be obtained stably.

(Embodiment 2) FIG. 6 shows a second embodiment of the present invention.
Shown in This embodiment is characterized in that a bias is applied to the fixing roller via a high-voltage diode. In the figure, 1 is a fixing roller, 2 is a pressure roller, and 3 is a halogen heater, which has the same configuration as that described in the first embodiment. A high-voltage diode 4 is attached to the core of the fixing roller 1 by a sliding contact (not shown), and thereafter, a high-voltage power supply 7 is provided, and a bias having the same polarity as that of the toner is applied. As for one pressure roller 2, a high voltage diode 5 is connected to the core via sliding contacts (not shown).

In this embodiment, the lower limit of the magnitude of the bias applied by the high voltage power supply 7 is the minimum bias value that can prevent offset when the diode does not operate normally in a high humidity environment. Becomes

This is based on an experimental result as shown in FIG. 9 which shows the relationship between the offset level when a bias is applied to the fixing roller in a high humidity environment and −300.
(V) It was found that the degree was necessary. This value is shown in FIG.
Compared to +500 (V) on the lowest line where the offset can be eliminated when a bias is applied to the pressure roller side
The reason that offset can be prevented with a small value is that when a bias is applied to the pressure roller side, a bias is applied to the fixing roller in contrast to a method in which a force is applied to the toner on the surface through the thickness of the transfer material. This is because a force can be exerted only through a small air gap, and the force can be more effectively exerted. On the other hand, about the upper limit of bias,
In addition to taking measures to prevent leakage between the upper and lower rollers and measures to withstand pressure necessary to satisfy safety standards, it is necessary to prevent the occurrence of problems such as winding of the transfer material around the fixing roller. This is likely to occur in H / H where the transfer material has a positive potential and the paper has lost its stiffness. According to the experiments by the inventors, it has been found that the voltage starts to be generated when a voltage of -500 V or more is applied. Therefore, it is considered that the bias value is about -300 (V) as an appropriate value.

Next, the superiority of this embodiment will be described with reference to FIGS. FIG. 7 shows the behavior when the second embodiment of the present invention is used, and FIG. 8 shows the behavior when only the bias is applied to the fixing roller.

First, in FIG. 8,-
This is a system in which 300 V is applied and a diode is connected to the pressure roller side. In this embodiment, when the transfer material having a positive potential at L / L passes, the fixing roller
On the pressure roller side, a potential of -800 (V) is induced by the transfer material. As a result, a sufficient electric field acts between the upper and lower rollers, so that the offset level is OK. In H / H, -30 is applied to the fixing roller side.
Since 0 (V) is applied, if there is such a potential difference, the offset can be prevented as shown in FIG. 9 so that the level is OK. However, when a transfer material having a negative potential passes in L / L, the fixing roller side is −800 (V) if a diode is connected.
Despite the transfer material having such a potential that the degree can be induced, since only -300 (V) is applied, an electric field for drawing the toner to the transfer material side is not generated, and offset occurs. Resulting in.

On the other hand, in the present embodiment shown in FIG. 7, when a transfer material having a negative potential passes in L / L, a diode is also connected to the fixing roller side. -300 obtained
A potential is induced up to -800 (V) in a form further added to (V). Therefore, a sufficient potential difference occurs between the upper and lower rollers, and the offset level becomes OK.

As described above, according to the second embodiment of the present invention, a bias having the same polarity as that of the toner is applied to the fixing roller via the diode, and the diode is connected to the pressure roller. With a lower bias than when bias is applied to the pressure roller via a diode, it is possible to stably obtain a good image free from offset regardless of the environment.

(Embodiment 3) FIG. 10 shows a third embodiment of the present invention. This embodiment is characterized in that a bias is applied to both upper and lower rollers via diodes. In the figure, the configurations of a fixing roller 1, a pressure roller 2, and a halogen heater 3 are the same as those in the above-described embodiment. On the fixing roller side, a diode 4 is connected via a sliding contact (not shown) in a direction to accumulate electric charges of the same polarity as the toner, and a bias of the same polarity as the toner is applied by the high voltage power supply 7 via the diode 4. I do. The pressure roller side has a configuration in which a diode 5 is connected via a sliding contact (not shown) in a direction to accumulate a charge having a polarity opposite to that of the toner, and a bias having a polarity opposite to that of the toner is applied through the diode 5. are doing.

FIG. 11 shows the behavior when this embodiment is used. In the figure, the applied bias is
The values described in the previous embodiment are used, and the fixing roller side
The behavior when −300 V is applied and the pressure roller side is applied when +500 V is applied.

In the drawing, first, when a transfer material having a positive potential at L / L passes, the upper roller potential is -30.
0 (V) is secured, and the lower roller potential is +500.
The potential induced by the diode in the form of adding to V is + 800V. Thus, the potential difference between the upper and lower rollers can be obtained more than that described in the previous embodiment, so that the offset can be more reliably prevented. Next, in L / L,
When a transfer material having a negative potential has passed, the potential induced by the diode in the form of an addition to the potential of -300 V due to the bias becomes -800 V on the upper roller side, and the potential of +500 V due to the bias on the lower roller side. Since this appears, there is also a sufficient potential difference between the upper and lower rollers, and the offset can be more reliably prevented. Also, H /
In the case of H, the offset can be sufficiently prevented even if the induced potential due to the diode does not appear, because the potential of -300 V is applied by the upper roller and the potential of +500 V is applied by the lower roller.

As described above, according to this embodiment, since the bias is applied to both the fixing roller and the pressure roller via the diode, the bias can be applied in any environment. Because the base portion of
The offset can be more effectively prevented than in the first and second embodiments.

In the present invention, Examples 1 to 3
Up to now, it has been described as a heat fixing device with a roller pair,
For example, instead of the fixing roller, a heat-resistant resin film rotating body having a release layer on the surface, and one of the surface layer or the base material is conductive, and the film rotating body It is arranged inside and has a configuration consisting of a sheet-like heat generating member that presses and heats the pressing roller via the film, and this film is formed by passing the sliding contact from the conductive part of the film rotating body. The same effect can be obtained even if the invention is implemented.

[0038]

According to the first aspect of the present invention, a high humidity environment is provided.
Below, even if the diode leakage current increases,
Applying means prevents the potential of the fixing roller from being offset.
Potential, and under low humidity environment,
The potential of the diode is added to the potential of the voltage application means
To increase the potential of the fixing roller.
Especially, it is possible to prevent the offset.
Without fixing, depending on the environment such as high humidity and low humidity.
And the voltage application means
Requires only a relatively low potential, so the configuration of the voltage applying means
It can be simplified and can be fixed by applying a high voltage.
The effect of preventing deterioration of the
It is. According to the third aspect of the present invention, it is possible to remove
Therefore, even if the leakage current of the diode increases,
The potential of the pressure roller with the potential to prevent offset
Voltage in low humidity environments.
The potential of the diode is added to the potential of the means
The potential of the pressure roller can be set higher, and it can be turned off satisfactorily.
Setting can be prevented.
To the pressure roller according to the environment such as high humidity and low humidity.
And the voltage applying means is relatively
Since a lower voltage is sufficient, the configuration of the voltage applying means can be simplified.
Of the pressure roller due to high voltage
The effect is obtained that the formation can be prevented.

[Brief description of the drawings]

FIG. 1 is a diagram showing a first embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between a pressure roller bias and an offset.

FIG. 3 is a diagram showing behavior in a conventional example.

FIG. 4 is a diagram showing a behavior in a conventional example.

FIG. 5 is a diagram showing a behavior in the first embodiment.

FIG. 6 is a diagram showing a second embodiment.

FIG. 7 is a diagram showing a behavior in the second embodiment.

FIG. 8 is a diagram showing a behavior in a conventional example.

FIG. 9 is a diagram illustrating a relationship between a fixing roller bias and an offset.

FIG. 10 is a diagram showing a third embodiment.

FIG. 11 is a diagram showing a behavior in the third embodiment.

FIG. 12 is a diagram showing a conventional example.

FIG. 13 shows a conventional example.

FIG. 14 is a diagram showing a conventional example.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Fixing roller 2 ... Pressure roller 3 ... Halogen heater 4 ... High voltage diode 5 ... High voltage diode 6 ... High voltage power supply

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Koichi Hiroshima 3- 30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Ryusuke Ishiyama 3- 30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) The inventor Manabu Takano 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (56) References JP-A-3-145682 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G03G 15/20

Claims (4)

(57) [Claims] An unfixed recording material bearing an unfixed toner image is provided.
Fixing device having a fixing roller in contact with the surface on the side of the toner image
The same polarity as the toner of the unfixed toner image on the fixing roller.
Voltage applying means for applying a voltage of
The same as the toner is applied to the fixing roller between the voltage applying means.
A diode connected in the direction to accumulate polar charges
A fixing device comprising: 2. A press contact portion for holding and conveying a recording material.
A pressure roller for pressing against the fixing roller,
The pressure roller applies a charge of the opposite polarity to the toner to the pressure roller.
Grounded via a diode connected in the direction of accumulation
The fixing device according to claim 1, wherein: 3. A recording material carrying an unfixed toner image is undecided.
Has a pressure roller in contact with the surface opposite to the toner image
In the fixing device, the pressure roller has a polarity opposite to that of the toner of the unfixed toner image.
Voltage applying means for applying a voltage of
The reverse of the toner is applied to the pressure roller between the voltage applying means.
A diode connected in the direction to accumulate polar charges
A fixing device comprising: 4. A pressure contact portion for holding and conveying a recording material.
A fixing roller that is in pressure contact with the pressure roller.
The fixing roller applies a charge of the same polarity as the toner to the fixing roller.
Grounded via a diode connected in the direction of accumulation
The fixing device according to claim 3, wherein: