JP4444679B2 - Fixing device - Google Patents

Description

  The present invention relates to a fixing device used in an image forming machine such as an electrostatic copying machine, a laser printer, and a facsimile machine.

An image forming machine such as a laser printer or an electrostatic copying machine includes a fixing device that heats and fixes a toner image transferred onto a sheet. This type of fixing device normally includes a pair of rollers each including a heating roller and a pressure roller, and a pressure mechanism for applying pressure between the pair of rollers. This pressurizing mechanism generally has a spring such as a helical spring, and the pressurizing force is applied by the spring force of this spring (see Patent Document 1).
JP-A-6-161318

  In the conventional fixing device described above, when a spring is assembled to the fixing device, it is necessary to attach the spring to the device while appropriately expanding and contracting the spring, or to adjust the arrangement of the peripheral members of the spring. Therefore, there is a problem that the work of assembling the spring is complicated and the assembly of the fixing device is troublesome. In addition, the spring force does not act in a state in which the applied pressure between the rollers is released when the fixing device is disassembled or conveyed, so that the spring is easily detached. For this reason, there is a problem that the parts constituting the spring and other pressurizing mechanisms are easily separated from each other, and the parts are easily dissipated.

  The present invention has been made in view of such a situation, and provides a fixing device that is easy to assemble and disassemble and that does not easily separate components such as a spring even when the pressure between rollers is released. Objective.

The present invention includes a pressure roller and a fixing roller, a pressure roller frame that holds the pressure roller and is rotatable around a predetermined rotation center, the pressure roller frame, and the fixing roller fixing side. A pressure is applied between the pressure roller and the fixing roller by urging the pressure roller frame toward the fixing roller by applying a spring force between the pressure roller and the fixing roller. A pressure mechanism member comprising a compression spring and a pressure pin inserted into the compression spring, and the pressure pin is connected to the fixing roller fixing side while connecting the pressure pin to the fixing roller fixing side. a coupling mechanism which can be obtained the pressure of the compression spring as the compressed state, and wherein the pressurizing mechanism member and the pressure roller frame, that said compression bar Ne is disengaged from the pressure roller frame Prevent By providing the detachment prevention mechanism that can form a self-holding state which does not separate from each other, and assembled while the self-holding state, the pressure pin, a spring lower end a lower end of the compression spring provided on its lower portion abuts A contact portion and a screw hole extending in the longitudinal direction of the pin from the upper end surface thereof, and the pressure roller frame contacts the upper end of the compression spring and the spring upper end contact portion through which the pressure pin is inserted And a pin support portion with which the lower portion of the pressure pin can come into contact, and the coupling mechanism screws a screw engaged with the fixing roller fixing side into the screw hole of the pressure pin. The disengagement prevention mechanism is configured so that a distance between the spring upper end contact portion and the spring lower end contact portion in a state in which the lower portion of the pressure pin is in contact with the pin support portion is a natural distance of the compression spring. Long The compression spring is stretched between the spring upper end contact portion and the spring lower end contact portion so that the compression spring is detached from the pressure roller frame using the spring force of the compression spring. This is a fixing device that prevents the occurrence of the fixing.

  In this way, since the compression spring, the pressure pin, and the pressure roller frame can form a self-holding state in which they are not separated from each other, even when the pressure between the rollers is released during assembly and disassembly of the fixing device. These members are difficult to separate from each other, and furthermore, each member is difficult to dissipate. In addition, since the fixing device is assembled in the self-holding state, when the fixing device is assembled, the compression spring, the pressure pin, and the pressure roller frame can be assembled at the same time. Since it is not necessary to handle it, the fixing device can be easily assembled.

Further , by bringing the lower portion of the pressure pin into contact with the pin support portion, the compression spring is compressed to a state shorter than the natural length, and a spring force is generated. It will be in the state stretched between upper end contact parts. Therefore, a separation preventing mechanism is formed in which the compression spring does not separate from the pressure roller frame due to the action of the spring force, and the compression spring and the pressure pin inserted into the compression spring and the pressure roller frame are not separated from each other. A state is formed. And, by attaching the screw engaged with the fixing roller fixing side to the screw hole extending in the longitudinal direction of the pin from the upper end surface of the pressure pin, the pressure mechanism of the fixing device can function. Is possible.

The spring lower end contact portion of the pressure pin has a positioning notch for positioning the pressure pin in the axial rotation direction, and the pressure roller frame can be engaged with the positioning notch. It is good also as a structure which has an engaging part.
In this case, since the positioning of the pressure pin in the axial rotation direction is possible, even in the fixing device in which the position of the pressure pin in the axial rotation direction is designated, the axial rotation direction of the pressure pin in advance in the self-holding state. The fixing position can be assembled and the fixing device can be assembled more easily.

  Since the pressure mechanism member and the pressure roller frame can form a self-holding state and are assembled in this self-holding state, it is easy to assemble and disassemble and the pressure between the rollers is released. Also, it is possible to provide a fixing device in which parts such as springs are difficult to separate.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 4 is a perspective view showing a schematic configuration of the fixing device 1 according to the embodiment of the present invention. In FIG. 4, in order to facilitate understanding of the present invention, parts other than main parts related to the present invention are appropriately indicated by phantom lines or appropriately omitted. The fixing device 1 includes a pressure roller 2 and a fixing roller 3 which are a pair of rollers for heat-fixing the transferred toner image. The fixing device 1 further includes a heating device (not shown) for heating the fixing roller 3, and a predetermined pressure is applied between the pressure roller 2 and the fixing roller 3. Then, the toner image is heated and fixed by passing paper between the pressure roller 2 and the heated fixing roller 3.

  The pressure roller 2 provided substantially below the fixing roller 3 is held by a pressure roller frame 4. The pressure roller frame 4 has substantially the same length in the longitudinal direction as the pressure roller 2 and is disposed below the pressure roller 2. Bearings (shown in the figure) are provided at both ends of the pressure roller 2 in the axial direction. The pressure roller 2 is rotatably held via the omission). On the other hand, the fixing roller 3 provided substantially above the pressure roller 2 is rotated about a fulcrum z, which will be described later, by a fixing roller frame 5 (not shown in detail) separate from the pressure roller frame 4. It is held freely. The fixing roller frame 5 is fixed to the side of the entire frame 10 (indicated by a two-dot chain line in FIG. 1 for simplification in a substantially box shape) that holds the fixing device 1 as a whole. The fixing roller frame 5 and the entire frame 10 are not fixed to the fixing roller fixing side. Therefore, the pressure roller frame between the fixing roller 3 fixed side (the portion other than the pressure roller frame 4 such as the fixing roller frame 5 and the entire frame 10) and the pressure roller frame 4 that holds the pressure roller 2. The pressure roller 2 can be pressed against the fixing roller 3 by applying a force in a direction in which 4 is rotated toward the fixing roller 3. In the present embodiment, the pressure roller 2 is pressed against the fixing roller 3 together with the pressure roller frame 4 by applying a spring force by the compression spring 6 between the pressure roller frame 4 and the fixing roller frame 5. A pressing force is applied between the roller 2 and the fixing roller 3.

The pressurizing mechanism for applying the pressing force by the compression spring 6 will be described in detail.
As shown in FIG. 4, one (each two in total) compression springs 6 are provided on both ends of the fixing device 1, and the pressure mechanisms are symmetrical with each other between both ends of the fixing device 1. It is made into the composition. Hereinafter, only one side of both end portions of the fixing device 1 will be illustrated and described.

FIG. 1 is a side view illustrating an outline of a pressure mechanism, a coupling mechanism, and a detachment prevention mechanism of the fixing device 1. In FIG. 1, the pressure roller 2 and the fixing roller 3 are simplified and shown as simple circles.
As shown in FIG. 1, a pressure pin 7 is inserted through a helical compression spring 6. The pressure pin 7 has a substantially disk-shaped spring lower end abutting portion 7a having an outer diameter larger than that of the compression spring 6 and against which the lower end of the compression spring 6 abuts. Since the portion other than the spring lower end abutting portion 7a of the pressure pin 7 is made thinner than the inner diameter of the compression spring 6, as shown in FIG. The lower end of the compression spring 6 can be brought into contact with the spring lower end contact portion 7a (the upper surface thereof). The pressure pin 7 has a screw hole 7b extending from the upper end surface in the pin longitudinal direction.

The pressure roller frame 4 that holds the pressure roller 2 includes a pressure roller support portion 4a that supports both end portions of the pressure roller 2, a pin through hole 4p through which the pressure pin 7 is inserted, and a compression spring. A spring upper end contact portion 4b with which the upper end of 6 abuts. Since the pin through hole 4p has a hole diameter through which the compression spring 6 cannot be inserted, the upper end of the compression spring 6 is in contact with the lower surface of the spring upper end contact portion 4b. Furthermore, the pressure roller frame 4 has a pin support portion 4c that protrudes at a position where the lower portion of the pressure pin 7 (the lower surface of the spring lower end contact portion 7a) can contact.
Further, the pressure roller frame 4 has a fulcrum formation notch 4d opened downward on the side substantially opposite to the spring upper end contact portion 4b and the pin support portion 4c with respect to the pressure roller 2. .

  As shown in the perspective view of FIG. 3, the fixing roller frame 5 holds the fixing roller 3, and is further fixed to the entire frame 10 side of the fixing device 1. As shown in FIG. 1, the fixing roller frame 5 has a screw engaging portion 5a with which the screw 11 can be engaged by a screw through hole 11a or the like, and a fulcrum forming notch 4d of the pressure roller frame 4; It has the notch engaging part 5b to engage. As shown in FIG. 1, the notch engaging portion 5 b has an upward notch provided on the plate-like portion and opened upward, and the notch engaging portion 5 b and the fulcrum forming notch 4 d between the pressure roller frame 4 are provided. It is in a state of being engaged while being substantially orthogonal. In order to engage the fulcrum formation cutout 4d of the pressure roller frame 4 and the cutout engagement portion 5b of the fixing roller frame 5, the fulcrum formation cutout of the pressure roller frame 4 is provided on the cutout engagement portion 5b. It is only necessary to mount 4d. The pressure roller frame 4 is rotatable about a fulcrum z that is a contact point between the fulcrum formation notch 4d and the notch engaging portion 5b. In this way, the fulcrum z that is the rotation center of the pressure roller frame 4 is formed simply by placing the fulcrum formation notch 4 d of the pressure roller frame 4 on the notch engaging portion 5 b of the fixing roller frame 5. Therefore, also in this respect, the pressure roller frame 4 can be easily assembled to the fixing device 1.

As shown in FIG. 1, the screw 11 inserted through the screw through hole 11 a of the fixing roller frame 5 is screwed into the screw hole 7 b of the pressure pin 7. As a result, the pressure pin 7 and the screw 11 are integrated, and the pressure roller frame 4 and the fixing roller frame 5 are indirectly connected. When the screwing amount of the screw 11 to the pressure pin 7 is increased, the pressure roller frame 4 has the fulcrum z that is a contact point between the fulcrum formation notch 4d and the notch engaging portion 5b as the center of rotation, and the fixing roller 3 side. Try to rotate in the direction approaching. When the screw 11 is further screwed in such a state that the rotation is restricted by the contact between the pressure roller 2 and the fixing roller 3, the spring lower end contact portion 7a is moved upward while the position of the spring upper end contact portion 4b is fixed. Therefore, the compression spring 6 is compressed and deformed so that the length thereof is shortened, and the spring force is accumulated. This spring force presses the spring upper end contact portion 4 b of the pressure roller frame 4, whereby the pressure roller 2 held by the pressure roller frame 4 is pressed against the fixing roller 3. In this manner, a connecting mechanism is configured that can obtain a pressure force between the rollers 2 and 3 by connecting the pressure pin 7 to the fixing roller 3 fixed side and setting the compression spring 6 in a compressed state.
Further, since the pressure force between the pressure roller 2 and the fixing roller 3 is caused by the spring force of the compression spring 6, the screwing amount of the screw 11 with respect to the pressure pin 7 is adjusted to adjust the compression spring 6. By appropriately setting the spring force, the pressing force between the pressure roller 2 and the fixing roller 3 can be adjusted.

  In a state where the spring lower end contact portion 7a of the pressure pin 7 is in contact with the pin support portion 4c of the pressure roller frame 4 (state shown in FIG. 1), the spring upper end contact portion 4b and the spring lower end contact portion 7a The distance d between them is shorter than the natural length of the compression spring 6 (the longitudinal length of the compression spring 6 in a state where no stress is applied to the compression spring 6). Accordingly, the pressure pin 7 is inserted into the compression spring 6, and then the upper portion of the pressure pin 7 is inserted into the spring upper end contact portion 4 b of the pressure roller frame 4, and then the compression spring 6 is compressed and deformed. 7 is brought into contact with the pin support portion 4c, so that the compression spring 6 is stretched between the spring upper end contact portion 4b and the spring lower end contact portion 7a. The detachment of the compression spring 6 from the pressure roller frame 4 is prevented.

FIG. 2 is an enlarged perspective view of the vicinity of the compression spring 6 of the self-holding unit 8 in this self-holding state, as viewed from below. The compression spring 6 is supported by the spring upper end contact portion 4b and the pin support portion 4c. It is in a state of stretching in the up-down direction between the pressure pin 7 and the spring lower end contact portion 7a. Therefore, the compression spring 6 is further compressed by applying an external force to the compression spring 6, or the spring lower end contact portion 7a of the pressure pin 7 is disengaged from the pin support portion 4c against the contact frictional force caused by the spring force. Unless such external factors are added, the pressure roller frame 4 will not come off. In addition, as shown in FIG. 2, in order to make the spring lower end contact portion 7a more difficult to come off from the pin support portion 4c, a recess 7c is provided on the lower surface of the spring lower end contact portion 7a. Corresponding convex portions 4e corresponding to the concave portions 7c may be provided.
Thus, the pressure roller frame 4, the compression spring 6, and the pressure pin 7 can form a self-holding unit 8 that is not separated from each other, that is, a self-holding state.

Further, the self-holding unit 8 including the pressure roller frame 4, the compression spring 6, and the pressure pin 7 is assembled to the fixing device 1 in the self-holding state. That is, these self-holding units 8 are assembled in the fixing device 1 in the above-described self-holding state, and the screw 11 inserted into the screw engaging portion 5a of the fixing roller frame 5 is attached to the spring lower end abutting portion of the pressure pin 7. Assembling to the fixing device 1 can be performed only by screwing into 7a. Therefore, if the self-holding unit 8 is assembled in advance, a complicated operation such as attaching the compression spring 6 while extending or contracting it when the fixing device 1 is assembled can be made unnecessary, and the compression spring 6 and the pressure pin 7 can be eliminated. The self-holding unit 8 can also be assembled to the fixing device 1 without touching.
Further, when the fixing device 1 is disassembled and the self-holding unit 8 is taken out from the fixing device 1, the self-holding unit 8 returns to the above-described self-holding state by removing the screw 11, so that the pressure roller 2 Even when the pressure between the fixing roller 3 and the fixing roller 3 is released, the constituent members of the self-holding unit 8 are not separated from each other and can be removed together. Therefore, a complicated operation such as removing the compression spring 6 while expanding and contracting can be eliminated, and the self-holding unit 8 can be detached from the fixing device 1 without touching the compression spring 6 or the pressure pin 7. The pressure mechanism members of the compression spring 6 and the pressure pin 7 are not easily dissipated.

  FIG. 3 is an enlarged perspective view of the vicinity of the compression spring 6 in the fixing device 1. The self-holding unit 8 assembled in the fixing device 1 in the self-holding state is screwed into the pressure pin 7 with the screw 11 inserted through the screw engaging portion 5a of the fixing roller frame 5, and the lower end of the spring of the pressure pin 7 is applied. The contact portion 7a is in a state of floating from the pin support portion 4c (a state where the spring lower end contact portion 7a and the pin support portion 4c are separated). As a result, the spring force of the compression spring 6 is transmitted between the pressure roller frame 4 and the fixing roller frame 5, and pressure is applied between the fixing roller 3 and the pressure roller 2. The pressure applied between the rollers 2 and 3 can be adjusted by changing the length of the compression spring 6 by adjusting the screwing amount of the screw 11.

As shown in FIG. 3, the fixing roller frame 5 is provided with a rotation notch 5 c that prevents rotation of the pressure pin 7 (rotation about the axis) and positions and positions the pressure pin 7. The rotation notch 5c is a notch opened to the pressure roller 2 side, and when the self-holding unit 8 is assembled to the fixing roller frame 5, the side surface of the pressure pin 7 is the rotation notch 5c. It is inserted from the open side. On the other hand, the pressing pin 7 is provided with two flat surfaces 7d facing each other, and the width between the two flat surfaces 7d and the width of the non-rotating notch 5c are substantially the same. Then, by inserting the pressure pin 7 into the rotation notch 5c while designating the direction of the flat surface 7d, the shaft rotation of the pressure pin 7 is prevented, and in particular, the screw 11 is smoothly screwed.
As described above, in order to assemble the self-holding unit 8 to the fixing roller frame 5, it is necessary to designate the position of the pressure pin 7 in the axial rotation direction. The contact portion 7a is provided with a positioning notch 7e. The pressure roller frame 4 is provided with an engaging portion 4f that can engage with the positioning notch 7e (see FIG. 2). The engaging portion 4f is a plate-like portion having substantially the same thickness as the positioning notch 7e and extending toward the positioning notch 7e, and is fitted in the positioning notch 7e. By assembling the self-holding unit 8 in the state where the axial rotation direction position of the pressure pin 7 is specified in this way to the fixing roller frame 5, the axial rotation position of the pressure pin 7 is adjusted at the time of assembly. There is no need, and the self-holding unit 8 can be assembled more smoothly.

  In assembling the fixing device 1, the pressure roller frame 4 to which the pressure roller 2 is attached is assembled to the fixing roller frame 5. In the self-holding unit 8, the assembly is extremely smooth, and the compression spring is used. 6 and the pressure pin 7 can be assembled together with the self-holding unit 8 without handling them individually. That is, since the self-holding unit 8 can form a self-holding state and is assembled in this self-holding state, when the self-holding unit 8 is assembled, the pressure pin 7 prevents the fixing roller frame 5 from rotating from its side surface. The self-holding unit 8 may be assembled so as to enter the notch 5 c, and the fulcrum formation notch 4 d of the pressure roller frame 4 in the self-holding unit 8 may be placed on the notch engaging portion 5 b of the fixing roller frame 5. Further, when removing the self-holding unit 8 from the fixing device 1, the reverse operation may be performed. Thus, the self-holding unit 8 is very easy to attach and detach. The members of the pressure roller frame 4, the compression spring 6, and the pressure pin 7 are not separated from each other even when the pressure between the rollers 2 and 3 is released during assembly and disassembly of the fixing device 1. Each member becomes difficult to dissipate. Since the self-holding unit 8 is assembled in a self-holding state, the compression spring 6, the pressure pin 7 and the pressure roller frame 4 can be assembled at the same time, and the compression spring 6 itself can be assembled when the fixing device 1 is assembled. Alternatively, since it is not necessary to handle the pressure pins 7 themselves, assembly of the fixing device is facilitated.

FIG. 5 shows a modification of the self-holding unit 8. In the embodiment of FIG. 1, the pin support portion 4 c of the pressure roller frame 4 is provided, but in the modification of FIG. 5, the pin support portion 4 c in the embodiment of FIG. 1 is not provided. Further, the pressure pin 7 of this modification is provided with a flange-like fall prevention flange 7f that protrudes radially outward in the middle portion in the longitudinal direction. In the embodiment shown in FIG. 1 described above, a detachment preventing mechanism for preventing the compression spring 6 from detaching from the pressure roller frame 4 by using a spring force is configured. A separation preventing mechanism is configured by the flange 7f engaging with the pressure roller frame 4. Since the pressure prevention pin 7 does not detach from the pressure roller frame 4 by the fall prevention flange 7f, the compression spring 6 through which the pressure pin 7 is inserted also does not detach from the pressure roller frame 4. The pressure pin 7 and the compression spring 6 are formed in a self-holding state that is not separated from the pressure roller frame 4. In this self-holding state, the fall prevention flange 7 f of the pressure pin 7 is in contact with the spring upper end contact portion 4 b of the pressure roller frame 4. When the fixing device 1 is used as a pressure mechanism, the screw 11 is screwed into the screw hole 7b of the pressure pin 7, and the fall prevention flange 7f and the spring upper end contact portion 4b are separated from each other. And As a result, the spring force of the compression spring 6 acts between the pressure roller frame 4 and the fixing roller frame 5 so that the pressure roller frame 4 rotates around the fulcrum z toward the fixing roller 3 side. Energized to generate pressure between the pressure roller 2 and the fixing roller 3.
In the embodiment of FIG. 1, the pin through hole 4p through which the pressure pin 7 is inserted is provided. However, in this modification, the pin through hole 4p is not provided, but a pin insertion notch 4g is provided instead. The pressure pin 7 is inserted from the open portion of the pin insertion notch 4g. In this way, even if the outer diameter of the fall prevention flange 7f is larger than the gap width of the pin insertion notch 4g, the pressure pin 7 (for preventing the fall of the pressure pin 7 on the spring upper end contact portion 4b of the pressure roller frame 4). The portion below the flange 7f can be inserted.

FIG. 3 is a schematic side view for explaining a pressure mechanism, a coupling mechanism, and a separation prevention mechanism in the fixing device according to the embodiment of the present invention. FIG. 2 is an enlarged perspective view of the vicinity of a compression spring of a self-holding unit in the fixing device of FIG. 1. FIG. 2 is an enlarged cross-sectional view of the vicinity of a compression spring in the fixing device of FIG. 1. FIG. 2 is a perspective view illustrating the entire fixing device of FIG. 1. It is a schematic side view for demonstrating the pressurization mechanism in the modification of this invention, a connection mechanism, and a separation prevention mechanism.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fixing device 2 Pressure roller 3 Fixing roller 4 Pressure roller frame 4b Spring upper end contact part 4c Pin support part 4f Engagement part 6 Compression spring 7 Pressure pin 7a Spring lower end contact part 7b Screw hole 7b
7e Notch for positioning z Support point (rotation center)

Claims (2)

A pressure roller and a fixing roller; a pressure roller frame that holds the pressure roller and is rotatable about a predetermined rotation center; and the pressure roller frame and the fixing roller fixing side. A pressure mechanism that applies a pressure force between the pressure roller and the fixing roller by urging the pressure roller frame in a direction of rotating the pressure roller frame toward the fixing roller by applying a spring force; Prepared,
The pressure mechanism includes a pressure mechanism member including a compression spring and a pressure pin inserted into the compression spring, and the compression spring is in a compressed state while connecting the pressure pin to the fixing roller fixing side. A coupling mechanism capable of obtaining the applied pressure,
The pressurizing mechanism member and the pressure roller frame is provided with the separation preventing mechanism for preventing the compression bar Ne is disengaged from the pressure roller frame, it can form a self-holding state which does not separate from each other, and this Assembled in a self-holding state ,
The pressure pin includes a spring lower end abutting portion that is provided at a lower portion thereof and a lower end of the compression spring abuts, and a screw hole that extends from the upper end surface in the pin longitudinal direction,
The pressure roller frame includes a spring upper end abutting portion through which the upper end of the compression spring abuts and the pressure pin is inserted, and a pin support portion with which a lower portion of the pressure pin can abut. ,
The coupling mechanism is formed by screwing a screw engaged with the fixing roller fixing side into the screw hole of the pressure pin,
The separation preventing mechanism is configured such that a distance between the spring upper end contact portion and the spring lower end contact portion is shorter than a natural length of the compression spring in a state where the pressure pin lower portion is in contact with the pin support portion. Then, by stretching the compression spring between the spring upper end contact portion and the spring lower end contact portion, the compression spring is detached from the pressure roller frame using the spring force of the compression spring. A fixing device characterized by preventing the above . The spring lower end contact portion of the pressure pin has a positioning notch for positioning the pressure pin in the axial rotation direction,
The fixing device according to claim 1, wherein the pressure roller frame includes an engaging portion that can engage with the positioning notch.

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