JPH04360181A - Thermal fixing unit - Google Patents

Abstract

PURPOSE:To prevent the meandering of a heat resistant belt in the thermal fixing unit for an electrophotographic device, fixing a toner image on a form via the heat resistant belt. CONSTITUTION:A fixing unit 1 is constituted so that the heat resistant belt 4 is stretched between a driving pulley 2 and a heating element 3 with weak tension, and an inclined surface 6a provided on the end part of a lever 6 whose base end is attached to one end of the heating element is abutted on the edge of the heat resistant belt 4 obtaining a tension side at the time of rotating, and pressed on the edge of the heat resistant belt 4 by a spring pressing one end of the heating element 3. The heating element 3 is inclined to the tension side or its opposite side via the lever 6 by force obtained when the heat resistant belt 4 is meandered at the time of rotating. In other words, the meandering of the heat resistant belt 4 is corrected by using an automatic aligning mechanism of the heat resistant belt 4. Thus, the meandering of the heat resistant belt can be controlled with a simple constitution, and a device can be miniaturized and lightened, without comparatively requiring the rigidity of the parts of the driving pulley, the heating element, etc.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention is directed to a heat-resistant belt that is wound between a drive pulley and a heating element and rotates to transmit the heat of the heating element to the paper, so that the heat generated on the paper is The present invention relates to a heat fixing device that heats and fixes toner images, and particularly relates to a heat fixing device having a mechanism suitable for correcting deviation of a heat-resistant belt that occurs during rotation.

0002

[Prior Art] A conventional device, as described in Japanese Patent Application Laid-Open No. 3-12682, has a heat-resistant belt with a convex crown.
There is a belt that is wrapped between a pulley and a heating element to prevent the heat-resistant belt from shifting during rotation using the crown effect of the pulley. A heat-resistant belt is wound between two pulleys and a heating element, a sensor detects the amount of deviation of the heat-resistant belt during rotation, and the alignment of the pulleys is changed based on the detected amount of deviation. Therefore, there are some devices that are configured to correct the deviation of the heat-resistant belt.

0003

[Problems to be Solved by the Invention] As mentioned above, one of the conventional techniques is to deform the heat-resistant belt by applying a large tension to the heat-resistant belt, thereby creating a crown effect that acts between the heat-resistant belt and the pulley. Since the structure was designed to prevent shifting of the heat fuser, the load acting between the pulleys becomes large, and the pulleys and their supporting members require large mechanical rigidity, which increases the cost of the heat fixing device. There was a problem with that.

[0004] In addition, other conventional heat fixing devices are configured to prevent the heat resistant belt from shifting by changing the alignment of the pulleys based on the amount of deviation of the heat resistant belt. A detection means for detecting the amount of deviation and a pool.
This posed a problem in that a driving means for changing the alignment of the fibers was required, making the device complex and expensive.

SUMMARY OF THE INVENTION An object of the present invention is to provide a heat fixing device that can prevent a heat-resistant belt from shifting by a simple mechanism at low cost.

[0006]

[Means for Solving the Problems] In order to achieve the above object, the heat fixing device of the present invention includes a drive pulley that is rotatably driven on a side plate provided in the casing of an electrophotographic apparatus, and a bar-shaped heating element that does not rotate. are supported in parallel to each other, a heat-resistant belt is endlessly wound between the drive pulleys and the heating element, and a backup roller is provided which presses the paper on which the toner image has been transferred to the heating element onto the side plate via the heat-resistant belt. The heating element is supported by the side plate so that the other end can swing around a fixed point at one end while maintaining a predetermined distance from the drive pulley. A lever with an inclined surface that comes into contact with the edge of the heat-resistant belt from the outer surface side of the heat-resistant belt is fixed to the edge of the heat-resistant belt on the side that is wound by the pulley, and then the other end of the heating element is pressed and the sloped surface of the lever is attached to the heat-resistant belt. It is characterized by being provided with an elastic means for pressing against.

Preferably, the heat-resistant belt is a metal belt, and a fluororesin is applied to the outer surface or both the inner and outer surfaces of the metal belt. Preferably, the metal belt is made of nickel or a nickel-based alloy.

[0008]

[Operation] When the heat-resistant belt is wrapped around the drive pulley and the heat-generating element with a weak tension and is driven by the drive pulley and rotates while sliding against the heat-generating body, the heat-resistant belt and the heat-generating element are Due to frictional force, tension is applied to the part of the heat-resistant belt on the side that is wound up by the drive pulley (the side on which tension is applied is called the tension side), and the part of the heat-resistant belt on the side that is fed out by the drive pulley is relaxed. (The relaxed side is referred to as the relaxed side), and the heat-resistant belt shifts to one side in its width direction. Now, if the heat-resistant belt is shifted toward the lever provided at the other end of the heating element, the edge of the heat-resistant belt on the tension side contacts the sloped surface of the lever and slides, moving the lever in the direction of pressing the elastic body. move against it. As the lever moves, the other end of the heating element tilts toward the tension side of the heat-resistant belt, so a force is generated between the heating element and the heat-resistant belt to return the heat-resistant belt toward one end of the heating element, and this force is applied to the heat-resistant belt. move.

When the heat-resistant belt begins to return, the force of the heat-resistant belt applied to the lever is released, and the elastic means presses and moves the other end of the heat-resistant belt from the tension side to the relaxed side of the heat-resistant belt. As a result, the other end of the heating element leans toward the slack side of the heat-resistant belt, and a force is generated between the heating element and the heat-resistant belt to return the heat-resistant belt in the direction of the lever, and this force causes the heat-resistant belt to move in the direction of the lever. Move to one side. According to the present invention, by repeatedly reciprocating the heat-resistant belt in the widthwise left and right directions as described above, the running direction is controlled by limiting the amount of deviation of the heat-resistant belt to a certain range.

[0010] When the heat-resistant belt is made of metal, especially a nickel-based material, the heat-resistant belt has high rigidity on its tension side and contacts the lever without being deformed, so the lever can be easily moved and removed from the lever. To accurately correct the misalignment of a heat-resistant belt through a heating element. The fluororesin also reduces the coefficient of friction of the heat-resistant belt and prevents surface scratches.

[0011]

[Embodiment] An embodiment of the present invention will be described below with reference to FIGS. 1 to 5.

FIG. 1 is an overall configuration diagram of a heat fixing device according to an embodiment of the present invention, and FIGS. 2 to 4 illustrate a mechanism for correcting the deviation of a heat-resistant belt wound between a pulley and a heating element. 5 are overall configuration diagrams of an electrophotographic apparatus to which a heat fixing device according to an embodiment of the present invention is applied.

First, an electrophotographic apparatus in which a heat fixing device according to an embodiment of the present invention is installed will be described with reference to FIG. In FIG. 5, sheets of paper 102 accumulated in a hopper 101 are separated and taken out one by one, passed through a bending guide 103, and sent to a registration roller 104, where the posture is corrected and then further upstream at a transfer section 105. will be sent to. On the other hand, an electrostatic latent image from an original (not shown) is recorded on the drum surface of a photosensitive drum 106 installed in a transfer unit 105 in advance by an optical system 107, and the electrostatic latent image is visualized by a developing device 108. becomes a toner image. The toner image is transferred to the paper 102 in the transfer section 105, and then conveyed to the fixing device 1 of this embodiment installed upstream of the transfer section 105, where it is thermally fixed. The paper 102 after being thermally fixed passes through another bending guide 109 and is delivered to a tray (not shown) by a delivery roller 110. Note that when the paper 102 is supplied from the manual feed hopper 112, the paper 102 is sent to the registration roller 104 by the conveyance roller 113, and then transferred and fixed as described above, and then transported out.

Next, a thermal fixing device 1 according to an embodiment of the present invention will be explained with reference to FIG. Thermal fixing device 1 generally includes a drive pulley 2 driven by a motor, a bar-shaped heating element 3 installed below and parallel to the drive pulley 2, and a drive pulley 2.
and a heat-resistant belt 4 wrapped endlessly between the heating elements 3 and the paper 102 to the heating element 4 via the heat-resistant belt 4.
a backup roller 5 that presses against the surface of the heat-resistant belt 4;
a, and a spring 7, which is an elastic means, that presses one end of the heating element 3 and presses the inclined surface 6a of the lever 6 against the edge of the heat-resistant belt 4.

More specifically, the drive pulley 2 has bearings 10 at each end, and these bearings 10 are supported by side plates 8a and 8b, respectively, provided on the casing of the electrophotographic apparatus, and are rotationally driven by a motor 9. be done. The heating element 3 has a shaft 11 provided vertically at one end thereof so as not to rotate, and is supported by a side plate 8a so as to be swingable about the shaft 11, and a movable side plate 12 is attached to the other end. There is. The movable side plate 12 is fitted into a slot 13 formed laterally along the surface of the side plate 8b, and moves in the longitudinal direction of the slot 13 while maintaining a constant distance between the heating element 3 and the drive pulley 2. It is slidably supported. The backup roller 5 has bearings 14 at each end, and these bearings 14 are arranged on the side plates 8a and 8a, respectively.
The backup roller 5 is fitted into another slot 15 formed vertically along the surface of 8b and pushed up from below by a spring 16, and thus the backup roller 5 is pressed in the direction of the heating element 3 with a load necessary for fixing. .

The sloped surface 6a of the lever 6 is configured such that when the drive pulley 2 rotates, it comes into contact with the edge of the portion of the heat-resistant belt 4 that is under tension (tension side) on the side wound by the drive pulley 2 from the outer surface side. , and is pressed against the tension side edge of the heat-resistant belt 4 via the movable side plate 12 and the heating element 3 by a spring 7 provided in the slot 13.

The heat-resistant belt 4 is composed of an ultra-thin belt made of Ni as a base material, and its surface or both front and back surfaces are coated with Teflon, which is a fluororesin, and the backup roller 8 is made of an elastic belt. It is coated with rubber. Further, the heating element 3 has a linear heat source in the longitudinal direction on the side that contacts the heat-resistant belt 4.

The operation of the thermal fixing device 1 of this embodiment constructed as described above will be explained below. First, referring to FIGS. 2 to 4, the phenomenon of deviation of the heat-resistant belt that occurs in the heat fixing device 1 will be described. FIG. 2 is a side view showing the behavior of the heat-resistant belt 4 during operation of the heat fixing device 1. When the drive pulley 2 rotates, due to the frictional force between the heating element 3 and the heat-resistant belt 4, It is shown that tension is applied to the portion of the heat-resistant belt 4 that is wound up, while the portion of the heat-resistant belt 4 that is fed out from the drive pulley is relaxed. In such a conveyance system for the heat-resistant belt 1, if the parallelism of the driving pulley 2 and the heating element 3 in the axial direction is disturbed, the heat-resistant belt 1 starts to shift to one side.

FIG. 3 is a plan view. In the figure, when the heating element 3 rotates counterclockwise around point O at one end and the other end shifts by +Δθ toward the tension side, the heat-resistant belt 4 moves to the left. Indicates that it leans toward one side. In addition, Figure 4 shows the heating element 3 in the clockwise direction.
It is shown that when the heat-resistant belt 4 rotates and the other end shifts by -Δθ to the relaxed side, the heat-resistant belt 4 shifts to the right. A mechanism that takes advantage of such a biasing characteristic of the heat-resistant belt 1, mechanically removes the bias of the heat-resistant belt 4 with a lever 6, shifts the heating element 3 with the lever 6, and corrects the running direction of the heat-resistant belt 4. This is a feature of the present invention. By the way, when the heat-resistant belt 4 is stopped, it is wound with a weak tension, but when it rotates, the tension side, where the tension is applied, has a large rigidity in the width direction, so that when the heat-resistant belt 4 is shifted to one side, it is wrapped around the lever with sufficient tension. power can be transmitted to.

Now, in FIG. 1, when the drive pulley 2 rotates, suppose that the heat-resistant belt 4 shifts toward the lever 6 provided at one end of the heating element 3, as shown by arrow A.
The edge of the heat-resistant belt 4 on the tension side slides in contact with the inclined surface 6a of the lever 6, and moves the lever 6 against the pressing force of the spring 7 via the end of the heating element 3 and the movable side plate 12. move it. Along with this, the heat generating element 3 together with the lever 6 is shifted and tilted at the other end in the direction indicated by arrow B, that is, toward the tension side, with the other end being centered around the shaft 11 provided at one end. A force is generated that returns the heating element 4, and the heat-resistant belt 4 moves in the opposite direction to the arrow A.

When the heat-resistant belt 4 begins to return, the force applied from the heat-resistant belt 4 to the lever 6 is released, and the spring 7 presses and moves one end of the heating element from the tension side of the heat-resistant belt 4 to the relaxed side. As a result, the heating element 3 is connected to the heat-resistant belt 4
Because of this, a force is generated between the heating element 3 and the heat-resistant belt 4 to return the heat-resistant belt 4 in the direction of the lever 6, and the heat-resistant belt 4 is biased in the direction of the lever 6 due to this force. In addition, to prevent the heating element 3 from tilting excessively to the relaxed side, the slot 1
The end of the movable side plate 12, opposite to the spring 7, is provided at an appropriate position to limit the range of movement of the movable side plate 12. As described above, by repeatedly reciprocating the heat-resistant belt in the left and right directions in the width direction, the running direction of the heat-resistant belt 4 can be controlled so that the heat-resistant belt 4 is always positioned within a certain range.

In this embodiment, a lever for detecting the deviation of the heat-resistant belt is attached to the heating element, and the heating element is operated to correct the deviation of the heat-resistant belt. It is also possible to correct the deviation of the heat-resistant belt by installing it on the drive pulley side so that it does not rotate and tilting the drive pulley with the movement of a lever.

[0023]

According to the present invention, in the heat fixing device, a heat-resistant belt is wound between a drive pulley and a heating element with a weak tension, and the heat-resistant belt has an inclination that touches the edge of the tension side that generates rigidity when rotating. A lever having a surface is attached to one end of the heating element, and the lever is configured to be pressed against the edge of the heat-resistant belt by pressing one end of the heating element with an elastic means, and the deviation of the heat-resistant belt is mechanically detected by this lever. In addition, it uses a so-called self-aligning mechanism that corrects the deviation of the heat-resistant belt by transmitting the force of the heat-resistant belt to the heating element via a lever, tilting the heating element to the tension side or the opposite side. Therefore, there is no need for a conventional drive mechanism that detects the deviation of the heat-resistant belt using a sensor and adjusts the pulley alignment using the sensor signal, and it is possible to control the deviation of the heat-resistant belt with a simple configuration. This has the effect of preventing the heat-resistant belt from shifting at a low cost, and since the heat-resistant belt is wrapped around it with a low tension, the rigidity of parts such as drive pulleys and heating elements is relatively unnecessary. This has the effect of making the device smaller and lighter.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of a heat fixing device according to an embodiment of the present invention.

FIG. 2 is a side view showing the stretched and relaxed state of the heat-resistant belt during driving.

FIG. 3 is a plan view illustrating a mechanism for correcting the deviation of the heat-resistant belt.

FIG. 4 is a plan view illustrating a mechanism for correcting the deviation of the heat-resistant belt.

FIG. 5 is an overall configuration diagram of an electrophotographic apparatus to which a heat fixing device according to an embodiment of the present invention is applied.

[Explanation of symbols]

1 Heat fixing device 2 Drive pulley 3 Heating element 4 Heat resistant belt 5 Backup roller 6 Lever 6a　Lever slope 7,16 spring 8a, 8b side plate 9 Motor 10,14 Bearing 11 axis 12　Moving side plate 13,15 Slot hole 102 Paper

Claims (4)

[Claims] 1. A heat fixing device for fixing a toner image transferred to paper in a transfer section of an electrophotographic device, wherein shaft portions at both ends are rotatably supported by side plates provided on a casing of the electrophotographic device. , a drive pulley driven by a motor, and the drive pulley is installed in a non-rotating manner in parallel with the drive pulley, and the other end is swingable about a fixed point at one end while maintaining a predetermined distance from the drive pulley. a bar-shaped heating element supported by a side plate, a heat-resistant belt endlessly wound between the drive pulley and the heating element, and a backup roller that presses the paper against the heating element via the heat-resistant belt;
a lever fixedly attached to the other end of the heating element and having an inclined surface that contacts the edge of the heat resistant belt on the side to be wound up by the drive pulley from the outer surface side of the heat resistant belt; A heat fixing device comprising: elastic means for pressing the other end of the lever to press the inclined surface of the lever against the heat-resistant belt. 2. The heat fixing device according to claim 1, wherein the heat-resistant belt is a metal belt, and an outer surface of the metal belt is coated with a fluororesin. 3. The heat fixing device according to claim 1, wherein the heat-resistant belt is a metal belt, and both surfaces of the metal belt are coated with a fluororesin. 4. Claim 2 or 3, wherein the metal belt is made of nickel or a nickel-based alloy.
Thermal fuser described.