JP2914271B2 - 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 for an image forming apparatus such as an electrostatic recording system and an electrophotographic system, and more particularly to a fixing device for an image forming apparatus which performs fixing by heat and pressure.

[0002]

2. Description of the Related Art Conventionally, there are the following fixing devices used in an image forming apparatus. That is, the fixing device fixes the toner by heat and pressure.

First, as shown in FIG. 4, a toner 2 which is an image transferred to a recording medium P is sandwiched between a fixing roller 3 heated by a heater (not shown) and a pressure roller 25 paired with the fixing roller 3. When passing along with the recording medium P, the toner is fixed on the recording medium P by heat and pressure by the fixing roller 3 and the pressure roller 15. Here, a difference in shrinkage rate occurs between the heated recording medium P and the toner 2 during cooling. As a result, as shown in FIG. 4, a concave curl phenomenon occurs on the recording medium P with respect to the toner 2 surface side.

In order to eliminate the above-mentioned curl phenomenon, it has been proposed to form the fixing roller 3 and the pressure roller 25 with materials having different hardnesses and form a nip 7 between the rollers to correct the curl. ing. However, with such a configuration, correction may not be possible. For this reason,
The curl correcting mechanism 16 is located downstream of the fixing mechanism 28.
The curl of the recording medium P is corrected by a larger nip.

In the curl correcting mechanism 16, a belt 21 having a width larger than that of the recording medium P is rotated by a roller 19 engaged with a driving mechanism (not shown). At this time, the belt 21 is strongly tensioned around the rollers 17 and 18 by the roller 24 pulled upward by the spring 20, and is also rotationally transported in the direction of arrow 27 in FIG. The roller 24 is connected to a solenoid 23 that operates based on information such as the material and thickness of the recording medium P and the amount of the toner 2 transferred to the recording medium P. The solenoid 23 is controlled by a controller (not shown). In response to the request, the moving guide 22 is pushed up, thereby controlling the force for pressing the roller 24 against the bell and 21 to adjust the nip.

The recording medium P on which the toner 2 is fixed
Is guided by the conveyance guides 26a and 26b, conveyed to the belt 21 of the curl correcting mechanism 16, and the curl is corrected by the nip between the belt 21 and the roller 24.

[0007]

However, the fixing device according to the above-mentioned conventional example has the following disadvantages. That is, the curl phenomenon of the recording medium P causes a problem that a paper jam or a stack failure occurs on the paper traveling path after the fixing mechanism 28 shown in FIG.

Further, as described above, the curl of the recording medium P which cannot be solved only by the fixing roller 3 and the pressure roller 25 which originally function as a fixing device is provided with a curl correcting mechanism 16 downstream of the fixing device. Need
There has been a problem that the number of parts increases and it is not possible to avoid upsizing of the apparatus.

Further, due to its structure, the path through which the recording medium P is transported becomes long and complicated, so that the recording medium P is liable to be clogged.

[0010]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a fixing device for an image forming apparatus which can solve the disadvantages of the prior art and can eliminate the curl phenomenon of a recording medium with a simple structure. And

[0011]

In order to achieve the above-mentioned object, according to the invention described in this specification , a fixing device is provided with a fixing roller heated by a heater, and at least a fixing roller close to an outer peripheral surface of the fixing roller. Equipped with two pressure rollers.

The pressure rollers are spaced apart from each other, and a pressure belt facing the toner on the recording medium is wound between the outer peripheral surfaces of the pressure rollers. The contact is made to abut.

[0013] With the above configuration, first, a predetermined nip is formed between the fixing roller heated by the heater and the pressure belt, and a predetermined contact pressure is generated therebetween. The pressure belt and the fixing roller rotate in the direction in which the recording medium is conveyed by the driving apple.

For this reason, the recording medium onto which the toner has been transferred is conveyed by the fixing roller and the pressure belt heated by the heater. Then, the fixing roller is sandwiched between the pressure belt and the fixing roller, where a predetermined heating is performed from the fixing roller. At the same time, the toner is fixed on the recording medium by the pressure generated between the fixing roller and the pressure belt.

At this time, the toner on the recording medium is pressurized.
Adhering to the side facing the belt
In principle, the recording medium is heated upward (pressure bell
Curl that becomes concave on the side of (g). On the other hand, the fixing roller
The upper part (pressure belt)
The nip is formed to be convex on the side of the tilt. Therefore,
The nip makes the recording medium convex upward during the fixing described above.
Make a correction. Thereby, the concave curl caused by the difference in the contraction rate between the toner and the recording medium is eliminated,
The flat recording medium is discharged from the image forming apparatus.

Further, in the second invention described in the present specification ,
The fixing device is provided with a fixing roller heated by a heater, at least two pressure rollers in contact with the outer peripheral surface of the fixing roller, and a tension roller separated from the outer peripheral surface of the fixing roller.

The pressure rollers are disposed apart from each other, and the tension rollers are disposed in the vicinity of the pressure rollers, so that the pressure rollers and the outer peripheral surfaces of the tension rollers are paired with the toner on the recording medium.
A pressure belt is wound around the fixing belt and the pressure belt is brought into contact with the fixing roller. With the above configuration, it is possible to perform appropriate curl correction according to the material and thickness of the recording medium, the material of the toner to be used, and the like.

According to the first aspect of the present invention, a bracket for supporting each pressure roller and the tension roller so as to be movable with respect to the fixing roller is provided, and the bracket is provided with an elastic member for pressing each pressure roller against the fixing roller. In addition, the bracket is equipped with an elastic member for separating the tension roller from the fixing roller, and a bracket moving mechanism for moving the bracket with respect to the fixing roller is adopted .
This is the same as the second invention.

[0019] In the second aspect of the present invention, the respective elastic members as well as constituted by a coil spring, the bracket moving mechanism constituted by a solenoid, other configurations are the same as those of claim 1, wherein. By having the configuration described above, in addition to the effects achieved by the fixing device according to claim 1, wherein the fixing device to set an appropriate correction amount.

Further, according to the third aspect of the present invention, the elastic member is constituted by an annular spring member, and the spring member is disposed between the respective ends of the pressure roller and the tension roller, and the bracket is moved. the mechanism constituted by the cam member, other configurations are the same as those of claim 1, wherein. By having the configuration described above, in addition to the effect achieved by the fixing device according to claim 1, wherein, it is possible to make the correction of proper curl In the fixing device of a simpler structure.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to FIGS. 1 to 3. First, in FIG. 1, a fixing device 1 includes a fixing roller 3 heated by a heater, At least two pressure rollers 4 b and 4 c are provided near the outer peripheral surface of the roller 3.

The pressure rollers 4b and 4c are arranged apart from each other, and the pressure belt 5 is disposed between the outer peripheral surfaces of the pressure rollers 4b and 4c.
, And the pressure belt 5 is configured to contact the fixing roller 3.

The above will be described in detail.
A cylindrical fixing roller 3 is provided. The fixing roller 3 is for applying heat to the toner image formed on the recording medium P and fusing it. Therefore, this fixing roller 3
Are heated by a heater (not shown). Specifically, it is heated by a halogen lamp provided inside the fixing roller.

The fixing roller 3 is rotatably supported by a predetermined bracket 1a. A driving mechanism (not shown) is engaged with one end of the fixing roller 3 so that the fixing roller 3 is driven to rotate in accordance with a command from a host machine.

In the vicinity of the fixing roller 3, predetermined pressure rollers 4b and 4c are provided. The pressure rollers 4b and 4c are for driving a pressure belt 5 provided for correcting the curl of the recording medium P in cooperation with the fixing roller 3. Therefore, the rotation axes of the pressure rollers 4 b and 4 c are parallel to the rotation axis of the fixing roller 3. These are rotatably supported by brackets 1a provided at both ends of each of the pressure rollers 4b and 4c.

Above the pressure rollers 4b and 4c,
A tension roller 4 a is provided apart from the fixing roller 3. The tension roller 4a applies a predetermined tension to the pressure belt 5 wound between the outer peripheral surfaces of the pressure rollers 4b, 4c, and likewise the pressure roller 4b, 4c, the bracket 1a is rotatable. It is supported by.

As shown in FIG. 1, a predetermined pressure belt 5 is disposed between the outer peripheral surfaces of the pressure rollers 4b and 4c. As described above, this pressure belt 5 cooperates with the fixing roller 3 to correct the curl of the recording medium P, and is in contact with the outer peripheral surface of the fixing roller 3 at a predetermined contact pressure. The rotation of the fixing roller 3 can be performed by the action of the pressure rollers 4b and 4c and the tension roller 4a. Then, the pressure belt 5 and the fixing roller 3
The so-called nip 7 is formed in the contact area with the nip.

Next, the fixing device 1 configured as described above
The operation and operation of will be described. That is, in the fixing device 1 of FIG. 1, a roller (reference numeral 25 in FIG. 4) which has been conventionally called a pressure roller is eliminated, and instead, a pressure belt 5 having a width larger than that of the recording medium P is provided on the outer peripheral surface thereof. Are provided with pressure rollers 4b and 4c. A predetermined nip 7 is formed between the fixing roller 3 and a fixing roller 3 heated by a heater (not shown), and the fixing roller 3 is pressed.

Further, the pressure belt 5 and the fixing roller 3
Are indicated by arrows 6a and 6a in FIG.
Each of them rotates in the direction of b. Therefore, the toner 2
Is transferred by the fixing roller 3 and the pressure belt 5 heated by the heater. Then, the fixing roller 3 is sandwiched between the pressure belt 5 and the fixing roller 3, where a predetermined heating is performed from the fixing roller 3. At the same time, the toner 2 is fixed on the recording medium P by the contact pressure generated between the fixing roller 3 and the pressure belt 5.

At this time, a nip 7 projecting upward is formed between the fixing roller 3 and the pressure belt 5. Therefore, the correction is performed so that the nip 7 makes the recording medium P convex upward during the fixing. This allows
The concave curl caused by the difference in the contraction rate between the toner 2 and the recording medium P is eliminated, and the flat recording medium P is discharged from the image forming apparatus.

Next, a second embodiment will be described with reference to FIG. In the fixing device 31 according to the present embodiment, the fixing roller 3 heated by the heater, at least two pressure rollers 4 b and 4 c in contact with the outer peripheral surface of the fixing roller 3, and a tension roller separated from the outer peripheral surface of the fixing roller 3. 4A is the same as the first embodiment. However, the present embodiment is different in that the pressure rollers 4b and 4c and the tension roller 4a are movably supported with respect to the bracket 8.

Also, the elastic members 10b and 10c for pressing the pressure rollers 4b and 4c against the fixing roller 3 are provided, and the bracket 8 is provided with an elastic member 10a for separating the tension roller 4a from the fixing roller 3. Are different.

In this embodiment, the elastic member 10a pulls the tension roller 4a upward, the elastic member 10b pulls the pressure roller 4b diagonally downward right, and the elastic member 10c pulls the pressure roller 4c diagonally downward left. It functions so as to press the pressure belt 5 against the fixing roller 3. Although not shown in FIG. 2, each elastic member 10b, 10c is similar to the elastic member 10a.
Is also fixed to the bracket 8. Similarly, the pressure rollers 4a, 4b and 4c are also supported by the bracket 8, but as described above, they are movably supported in the directions in which the respective elastic members 10a, 10b and 10c operate. I have.

The bracket 8 is provided with the material and thickness of the recording medium P and the toner 2 transferred to the recording medium P.
Solenoid 9 that moves up and down in response to a signal from a controller (not shown) that determines the amount of operation based on information such as the amount of
Are connected.

With the above configuration, the recording medium P on which the toner 2 has been transferred is conveyed by the rotational movement of the pressure belt 5 and the fixing roller 3 in the directions of arrows 6a and 6b, and the mutual movement of the two. Enter between. At this time, the controller determines the operation amount of the solenoid 9 based on information such as the amount of the toner 2 on the recording medium P and the material and thickness of the recording medium P, and sends a signal to the solenoid 9.

If it is expected that the curl of the recording medium P increases due to the above information, the solenoid 9
Operates to push down the bracket 8. Thus, the elastic member 1 whose one end is fixed to the bracket 8
Since the pressure rollers 0b and 10c are stretched, the pressure roller 4b is pulled diagonally downward to the right and the pressure roller 4c is pulled diagonally downward to the left, so that the nip 7 with the pressure belt 5 increases and a stronger pressure is applied to the fixing roller 3. To come into contact.

In the above state, when the recording medium P on which a strong curl is generated passes, the curl generated by the fixing is canceled because the controller has already controlled the nip amount and the contact pressure to appropriate values. Thus, the recording medium P in a straight state can be obtained. Here, the moving mechanism of the bracket 8 is adjusted by the solenoid 9, but the operation is the same even if it is replaced by a mechanism that drives a gear or the like up and down by a motor or the like.

Next, a third embodiment will be described.
In the present embodiment, as shown in FIG.
One annular spring member 11 includes the tension roller 4,
The pressure rollers 4b and 4c are arranged so as to be pushed outward in the radial direction, respectively. In addition, a manually operated lever 13 is provided in place of the solenoid operated by a signal from the controller, and the bracket 8 is moved up and down in conjunction with the cam member 12.
Other configurations and supporting methods of the tension roller 4a and the pressure rollers 4b and 4c, and the rotation directions and driving methods of the pressure roller 4a and the fixing roller 3 are the same as those of the second embodiment.

In the fixing device 41 configured as described above, the recording medium P on which the toner 2 has been transferred is conveyed by the pressure belt 5 and the fixing roller 3, and enters the area between them. If the user wants to weaken the curl correction based on the printing result, the recording medium P, the amount of toner to be printed, the temperature and the humidity, and the like, the user pushes the lever 13 protruding from the apparatus body cover 14 to the arrow 15. And in the opposite direction. On the other hand, when it is determined that the curl needs to be more strongly corrected, the lever 13 is moved to the arrow 15 direction.
The curl correction amount can be adjusted by tilting the curl.

The tilted lever 13 is interlocked with the cam member 12, and the cam member 12 pushes down the bracket 8. As a result, the spring 11 supported by the bracket 8 that has been pressed down is pressed by the pressure rollers 4b and 4b.
Press c more strongly down. For this reason, the contact pressure between the fixing roller 3 and the pressure belt increases, and
Pressure roller 4b is lower right, pressure roller 4c
Is pushed down to the lower left, and more nips 7 are formed.

When the recording medium P enters the fixing device 41 appropriately set as described above, since the nip amount and the contact pressure have already become appropriate, the curl generated by the fixing is canceled out, and The recording medium P is discharged. Here, the lever 13 is connected to the device cover 1.
4 is described. However, the present invention is not limited to this, and may be provided inside the device.

[0042]

As described above, the fixing device of the image forming apparatus according to the present invention has a function of correcting the curl of the recording medium in the fixing mechanism itself, so that the curl of the recording medium can be effectively corrected. The traveling path of the recording medium is simplified and shortened to eliminate the cause of the clogging of the recording medium,
Also, an excellent effect that the size of the fixing device can be reduced is obtained.

Further, since the pressure roller, the curl correcting roller, and the belt, which are conventionally provided separately, are constituted by a set of the pressure roller and the pressure belt, the number of parts constituting the fixing device is reduced, and the manufacturing is reduced. An excellent effect that cost can be suppressed is produced.

Further, since the contact pressure and the nip generated between the pressure belt and the fixing roller can be adjusted, the material and thickness of the recording medium, the material and amount of the used toner, and the like can be adjusted. An excellent effect is obtained that the curl can be appropriately corrected according to the condition. At the same time, the nip width can be adjusted.

Further, since a cam member can be used as a means for adjusting the contact pressure and the nip between the pressure belt and the fixing roller, an excellent effect that the fixing device can be configured with a simpler structure can be obtained. Occurs.

[Brief description of the drawings]

FIG. 1 is a side sectional view showing a first embodiment of the present invention.

FIG. 2 is a view showing a second embodiment of the present invention, and FIG.
2A shows a side sectional view, and FIG. 2B shows a front view.

FIG. 3 is a side sectional view showing a third embodiment of the present invention.

FIG. 4 is a side sectional view showing a conventional example.

[Explanation of symbols]

 1a bracket 2 toner (before fixing) 3 fixing roller 4a tension roller 4b / 4c pressure roller 5 pressure belt 7 nip 8 bracket 10a / 10b / 10c elastic member (coil spring) 11 spring member 12 cam member

Claims (3)

(57) [Claims] A fixing roller heated by 1. A heater,
At least two pressure rollers which are in contact with the outer peripheral surface of the fixing roller, and which are separated from the outer peripheral surface of the fixing roller
A fixing roller including a tension roller , wherein the pressure rollers are spaced apart from each other, and the tension roller is connected to each of the pressure rollers.
The pressure rollers and the tension
Wound toner and opposite pressure belt on the recording medium therebetween on the outer peripheral surface of Yonrora, the pressure belt is brought into contact with the fixing roller, before the respective pressure roller and the tension roller
The bracket that movably supports the fixing roller
The pressure roller is attached to this bracket.
Equipped with an elastic member that presses against the fixing roller,
Place the tension roller on the bracket and the fixing roller.
Equipped with an elastic member for separating the bracket from the fixing roller, and moving the bracket with respect to the fixing roller.
Fixing apparatus wherein Rukoto includes a bracket moving mechanism. 2. Each of the elastic members is constituted by a coil spring.
And the bracket moving mechanism is constituted by a solenoid.
The fixing device according to claim 1, wherein characterized by that. 3. The elastic member comprises an annular spring member.
Then, this spring member is connected to each pressure roller and tension
Equipped between each end of the roller and the bracket
Tsu DOO moving mechanism fixing device according to claim 1, wherein characterized in that configuring the cam member.