JP2817165B2 - Fixing device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device for fixing a toner image on paper, such as an electronic copying machine or an image recording device, and more particularly, to a heating roller. The present invention relates to a device provided with a pressing mechanism using a pressure belt device.

2. Description of the Related Art In an image forming apparatus using a dry toner, such as an electronic copying machine or an image recording apparatus, a toner image formed on an image carrier such as a photosensitive drum is transferred onto a sheet and is not fixed. A sheet carrying a toner image is conveyed toward a fixing device, and in the fixing device, a means is used in which the toner is melted and fixed by applying heat or pressure to complete the recording paper.

As the above-described fixing device, an oven-type fixing device that performs only a heating operation, a pressure fixing device that causes a sheet to pass between pressure rollers, and performs fixing by the pressure, and the like may be used. In many cases, a heating roller type device is used.

In the above-described fixing device of the heating roller type, a heating roller provided with a heating element therein and a pressure roller for pressing a sheet against the heating roller are arranged to face each other, and a sheet is nipped between the rollers. In this case, the fixing is performed by applying heat and pressure to perform fixing.

As a fixing device of the heating roller type, for example, there is one as disclosed in JP-A-61-209472.
In the fixing device of this conventional example, in order to keep the nip shape between the heating roller and the pressure roller constant, a rubber material covering the surface of the pressure roller is selected. It is an object of the present invention to make the temperature distribution in the nip portion between the two rollers constant and to shorten the time required for the fixing device to rise.

(Problems to be Solved by the Invention) The above-described fixing device of the heating roller type is of a very excellent type in terms of thermal efficiency and safety, etc.
When the paper is passed between both rollers and heated and pressed,
There is a problem that wrinkles and image deviation occur on the paper.

That is, in a fixing device in which the pressure roller is a rubber roller and the heating roller is made of a rigid metal material,
It is desirable that the speed distribution in the width direction of the paper generated when the paper is nipped between the two rollers is increased by about 0.1 to 0.2% at both end portions with respect to the center portion.
In order to obtain the speed distribution described above, it is necessary to strictly control the profile of the pressure roller. However, if temperature unevenness occurs in the axial direction of the roller (the width direction of the paper),
There is a problem that the profile easily changes.

In particular, for wide paper of A2 size or more, there is a problem that the degree of change in the nip shape in the width direction of the paper increases.
It is required that the transport speed be within the above-mentioned range.

However, in the above-described conventional apparatus, it is difficult to accurately control the surface temperature of the roller, and as a result, wrinkles may occur on a wide sheet of paper, or the image may be misaligned. However, there is a problem that it is unavoidable that such a problem occurs.

That is, in a general heating roller type fixing device, when there is a large speed difference in the nip portion between the heating roller and the pressure roller, for example, the speed of the central portion of the paper is lower than the ideal nip shape. If the speeds of both sides are slow and the speeds of both sides are high, when the speed difference is accumulated, it appears as an action of bending the central part of the paper upward, and the central part of the paper comes closer to the heating roller. It may be greatly curved.

Then, the unfixed toner image carried on the central portion of the sheet is transferred in contact with the heating roller, and the toner is transferred from the heating roller to another portion of the sheet, thereby causing image misalignment. Problems arise. On the other hand, if the speed difference at the nip portion is very small, there is a problem that paper is likely to wrinkle.

In addition to this, in a large-sized image forming apparatus that can create recording paper using large-sized paper,
Since long rollers are used in the fixing device, when small-sized paper is continuously fixed, only a part of the pressure roller, especially the pressure roller, is in a low temperature state, and the other part is at a low temperature. It is kept high.

Then, when trying to fix a large-size sheet of paper, the nip shape between the two rollers greatly changes with respect to the ideal speed distribution. The wrinkles and the like generated on the paper tend to appear particularly strongly due to the large deviation from the speed, and it is often difficult to take countermeasures.

The effect of the speed difference in the width direction of the paper described above is as follows.
In particular, in the case of a large-sized image forming apparatus that creates a recording sheet using a large-sized sheet, the above-described image shift, sheet wrinkles, and the like are conspicuous. Therefore, even if it is required to accurately set the speed difference between the center portion and both side portions in the nip portion between both rollers,
In the case of a general pressure roller type apparatus, there is a problem that it is very difficult to manage the profile.

(Object of the Invention) An object of the present invention is to solve the above-mentioned drawbacks of a conventionally used device, and to provide a fixing device using a pressing belt device instead of a pressing roller. And

(Means and Actions for Solving the Problems) The present invention relates to a heating roller configured to heat and press a sheet carrying a toner image to melt the toner and fix the toner image on the sheet. The present invention relates to a fixing device of a system. The invention according to claim 1 of the present invention is a pressure belt that presses a sheet against the heating roller, and the pressure belt is stretched over the pressure belt, and a pressure belt support unit including a plurality of belt support members; Belt detecting means for detecting the meandering of the pressure belt, wherein one of the plurality of belt support members corrects the meandering of the pressure belt in accordance with the detection result of the belt detecting means. The belt meandering correction means swings along a substantially arc-shaped trajectory in the pressure belt passing direction.

According to a second aspect of the present invention, the pressure belt device is guided and driven by an intrusion roller and a drive roller, applies a constant tension by a tension roller, and is arranged as a means for correcting the belt meander. The roller is configured such that both ends of the meandering correction roller can be swung by drawing elliptical trajectories with the focus on the intrusion roller and the tension roller, respectively, by driving mechanisms disposed on both sides thereof. And

With the above-described configuration, in the fixing device of the present invention, the belt meandering correcting means swings in an arc-shaped trajectory substantially in the pressure belt wrapping direction. The belt can be prevented from being damaged as compared with a device configured to press the belt from the back surface in a direction perpendicular to the transfer direction or a device configured to guide the belt edge. Further, in the present invention, since the meandering of the belt is corrected by using a long meandering correction roller arranged so as to press the back surface of the belt, the belt does not have a local pressing action. No extra stress is applied to the edge of the metal. Then, the meandering correction is performed while using a drive mechanism disposed at both ends of the meandering correction roller and swinging the drive mechanism along a limited trajectory, so that the belt meandering correction operation can be stably performed. .

Therefore, in the fixing device of the present invention, when the paper is conveyed while being nipped between the pressure belt device and the heating roller, and pressed by the pressure plate to fix the paper, the paper is accurately pressed by the pressure plate. Can be pressed.

In addition, the pressure belt device of the present invention, even for large-sized paper, does not change the nip shape in the width direction, because it can exert a pressure action uniformly on the whole, It is possible to prevent wrinkles and the like from occurring on the paper.

(Example) The configuration of the fixing device of the present invention will be described with reference to the illustrated example.

As shown in FIG. 1, a fixing device 1 according to the present invention includes a heating roller 2 containing a heating lamp 3 therein, and a pressing belt device 1 for pressing a sheet against the heating roller 2.
And a pressure plate 13 for performing a pressing action from the back surface of the pressure belt device.

In the fixing device 1 of the present invention, a transport belt device 5 and a guide plate 6 are disposed on the upstream side, and a discharge roller 8 is disposed on the downstream side.
The paper carrying the toner image is introduced into the fixing device 1 and the paper after fixing can be sent out to the discharge side.

Means such as providing a temperature sensor 4 for the heating roller 2 to adjust the temperature of the roller, and disposing a peeling claw 7 on the discharge side to peel the fixed paper from the heating roller. However, each of those mechanisms can be configured in the same manner as a general fixing device.

In the fixing device 1 having the above-described configuration, the pressing belt 11 constituting the pressing belt device 10 is formed by coating a glass cloth with a fluororesin to form an endless belt member. Since the elongation of the heat roller is very small, the influence of the heat from the heating roller is not greatly generated.

The above-described pressure belt 11 of the present invention is made of a material having a very low coefficient of thermal expansion, and when a material mainly composed of glass cloth is used, compared with a normal rubber roller, Since the coefficient of thermal expansion is about 1/20, the degree of change in the nip shape can be reduced by heating the pressure belt by the heating roller.

Further, since the glass cloth is coated with a fluororesin, when the fixing operation is performed by pressing the paper against the heating roller, the pressing force is applied by the pressing plate from the back surface of the pressing belt device. In addition to the above, even if the pressure belt slides on the pressure plate, particularly large sliding resistance does not occur in the sliding portion between the two.

As shown, the pressure belt device 10 of the present invention is wound around an intrusion roller 15, a driving roller 16, a tension roller 17, and a meandering correction roller 20, and drives the belt, sets the tension, and Meandering prevention is performed.

Further, in the upstream portion of the portion where the pressure belt device 10 contacts the sheet, a belt edge detection sensor 12 is arranged on both sides of the pressure belt 11 to detect the meandering of the belt, Using the belt edge detection sensors 12 arranged on both sides of the belt, during the fixing operation, it is detected that the pressure belt 11 meanders,
The correction operation can be performed.

Of the roller members of the present invention described above, the driving roller 16
A mechanism similar to that of a conventional general belt drive mechanism can be used as the intrusion roller 15 and the tension roller 17 also applies a constant tension to the pressure belt 11 using a spring 18. You can do it.

On the other hand, the meandering correction roller 20 is configured by arranging a long roller in the width direction of the pressure belt 11 and arranging meandering correction means at both ends of the roller shaft. This meandering correcting means is linked to the solenoid 25 as shown in the figure.
A link 22 is provided so as to be swingable about a fulcrum 23. A solenoid 25 is connected to the base of the link 22, and a shaft 21 of the meandering correction roller 20 is connected to the other end.

Further, the meandering correcting means described above is provided on both sides of the pressure belt device, and the solenoid 25 is operated by a signal from the belt edge detection sensor 12 disposed corresponding to each of them, and the bias of the pressure belt 11 is shifted. , The meandering correction roller 20 is swung to correct the position of the belt.

In the meandering correcting means of the present invention, the trajectory R of the meandering correcting roller 20 oscillates, draws an ellipse whose focal point is the axis of the intrusion roller 15 and the axis of the tension roller 17, and forms the elliptical arc. Therefore, the guide mechanism of the roller is configured to swing the meandering correction roller.

Then, as described above, the trajectory of the link 22 swinging through the fulcrum 23 and the portion holding the axis of the meandering correction roller at the end thereof is approximated to an elliptical arc as described above. By forming the belt, when the meandering correction roller is swung by the solenoid 25, the resistance received from the belt can be extremely reduced.

The pressing plate 13 for pressing the pressing belt device against the heating roller 2 uses a plate member having a large elasticity, such as a stainless steel plate, and as shown in FIG. A number of slits 13b are provided at predetermined intervals at a tip portion corresponding to the pressure roller, and a unit body 13a of a plate member is formed.
However, the paper is pressed toward the pressure roller 2 via the belt.

Further, the base of the pressure plate 13 can use means such as being supported by a frame of a fixing device (not shown), and by forming the base of the pressure plate as a strong one, When pressing the sheet against the heating roller via the unit body 13a, the pressing force can be set uniformly.

In the meandering correcting means of the present invention described above, as shown in the circuit diagram of FIG. 3, the solenoids 25 and 25a are operated so that the solenoids 25 and 25a are operated by the detection information of the belt edge portion from the sensors 12 and 12a. Is configured to drive the solenoid by combining detection information of the belt edge detection sensor and a relay. Further, in the circuit shown in FIG. 3, the above-described sensor and solenoid driving circuit are combined with relays k1, k2, etc. to form a control circuit.

In the circuit, one of the two belt edge detection sensors detects the side of the pressure belt 11 and the relay holds the signal at the same time, so the sensor provided on the opposite side detects the meandering of the belt. Until the detection is performed, an operation of moving the belt to the other side is performed. When the sensor on the other side detects the deviation of the belt, the holding circuit is turned off, and the operation of the solenoid by the sensor on the other side and the operation of holding the signal by the relay are continued.

Therefore, while the image recording apparatus is performing the operation of forming the recording paper, the pressing belt device of the fixing device constantly performs the operation of correcting the meandering while moving the paper between the heating roller and the pressing belt device. While being guided in between, the meandering of the pressure belt device is corrected, while the movement speed in the width direction of the paper is prevented from changing, and the fixing operation is performed.

In the fixing device of the present invention, since the pressure belt device slides on the pressure plate, a member having high durability against the sliding action such as a glass cloth is used. The pressure belt device is not necessarily limited to the use of a glass cloth, but may be a device made of a material having the same properties as the glass cloth.

Further, since the pressure belt device is always subjected to a heating action by a heating roller and is used in a state where a large pressing force is applied by a pressure plate, it is coated with a fluororesin. As a means for improving the slidability, coating with any material is possible.

Further, as a sensor for detecting the meandering of the pressure belt of the present invention, a microswitch mechanism or an arbitrary detection means such as a photosensor can be used. The fixing device of the present invention can be applied to a laser printer and other image recording devices, in addition to an electronic copying machine for making a copy using a general large-size sheet.

(Effects of the Invention) In the fixing device of the present invention, the belt meandering correcting means swings in a substantially arc-shaped trajectory in the direction in which the pressure belt is passed over by the configuration described above.
In order to correct the belt meandering, the belt can be prevented from being damaged as compared with a device configured to press the belt from the back surface in the vertical direction of the belt passing direction or a device configured to guide the belt edge. Further, in the present invention, since the meandering of the belt is corrected by using a long meandering correction roller arranged so as to press the back surface of the belt, the belt does not have a local pressing action. No extra stress is applied to the edge of the metal. Then, the meandering correction is performed while using a drive mechanism disposed at both ends of the meandering correction roller and swinging the drive mechanism along a limited trajectory, so that the belt meandering correction operation can be stably performed. .

Further, in the fixing device of the present invention, when the paper is conveyed while being sandwiched between the pressure belt device and the heating roller, and pressed by the pressure plate to fix the paper, the paper is accurately pressed by the pressure plate. Can be pressed.

Further, the pressure belt device of the present invention can maintain a constant speed distribution in the width direction of the paper without changing the nip shape in the width direction even for a large-size paper. In addition, it is possible to prevent the image from being displaced due to excessive pulling of the end portion, and the occurrence of wrinkles due to the excessively slow speed of the end portion.

[Brief description of the drawings]

FIG. 1 is a side view showing the structure of a fixing device of the present invention, FIG. 2 is an explanatory diagram showing the relationship between a pressing plate and a pressing belt device of the present invention, and FIG. 3 is control means of the present invention. FIG. 3 is a circuit diagram showing the configuration of FIG. Reference numeral 1 in the drawing: fixing device 2, heating roller 10, pressure belt device 11, pressure belt 12, belt edge detection sensor 13, pressure plate 15, Penetration roller, 16 drive roller, 17 tension roller, 20 meandering correction roller, 22 link, 25 solenoid.

Continued on the front page (58) Fields surveyed (Int.Cl. ⁶ , DB name) G03G 13/20 G03G 15/20 B65H 15/64

Claims (2)

(57) [Claims] 1. A heating roller type fixing device configured to apply heat and pressure to a sheet carrying a toner image to melt the toner and fix the toner image on the sheet. A pressure belt that presses the paper by pressing the pressure belt; a pressure belt support unit that includes a plurality of belt support members; and a belt detection unit that detects meandering of the pressure belt. One of the plurality of belt support members is a belt meandering correcting unit that corrects the meandering of the pressure belt in accordance with the detection result of the belt detecting unit. A fixing device characterized in that the fixing device swings while drawing a substantially arc-shaped locus in a bridging direction. The pressure belt device is guided and driven by an intrusion roller and a drive roller, applies a constant tension by a tension roller, and has a meandering correction roller disposed as means for correcting the belt meandering. The drive mechanism disposed on both sides of the meandering correction roller can swing both ends of the meandering correction roller in an elliptical locus whose focus is on the intrusion roller and the tension roller, respectively. The fixing device according to claim 1.