JPH09281841A - Fixing device and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To switch the pressing force of a pressure roller composing a fixing device, in an inexpensive structure. SOLUTION: In the fixing device 11 of a heat roll system, a compression spring 25 for pressing the pressure roller 22 to a fixing roller 21 consists of a comical coil spring whose one end has a small diameter and other end has a large diameter, and a first mount member 23 and a second mount member 24 each have a small-diameter-end mount part 27 and a large-diameter-end mount part 28 to which the small diameter end and large diameter end of the compression spring 25 are attached, respectively. In the first mount member 23, the small-diameter-end mount part 27 is nearer to the opposite second mount member 28 than the large-diameter-end mount part 28.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine, a facsimile and a laser printer, and more particularly, an image forming apparatus having a fixing device capable of switching the pressing force of a pressure roller against the fixing roller. Regarding the device.

[0002]

2. Description of the Related Art In a fixing device for fixing an image transferred onto a recording sheet by a transfer device of an image forming apparatus, the pressing force of a pressure roller against a fixing roller depends on the nip width and surface pressure of the fixing roller and the pressure roller. It is a deciding factor. Therefore, the pressing force of the pressure roller greatly affects the performance of the fixing device such as the fixability of the image transferred onto the recording paper and the transportability of the recording paper.

Generally, the image forming apparatus is used under different conditions such as paper type, paper size, frequency of use, type of output image, humidity of use place and the like. Therefore, in order to obtain optimum fixing conditions under these different conditions, it is desirable to configure the fixing device so that the pressing force of the pressure roller can be changed.

Therefore, even when the thickness and width of the recording paper are different, as an image forming apparatus capable of transferring and fixing with an optimum pressure and performing good image recording,
An electrostatic recording device disclosed in Japanese Patent Laid-Open No. 3-186879 has been proposed.

In this electrostatic recording apparatus, the detection means detects the thickness and width of the recording paper, and the optimum pressure setting means optimizes the nip portion based on the thickness and width of the recording paper detected by the detection means. The pressure is set. Then, based on the set pressure of the optimum pressure setting means, the pressure adjusting means adjusts the pressing force of the pressure roller against the fixing roller.

As described above, according to the electrostatic recording apparatus, even if the thickness or width of the recording paper used for recording an image is changed, the transfer fixing can be always performed with the optimum pressure. Good image recording can be performed.

[0007]

However, when the mechanism for switching the pressing force of the pressure roller against the fixing roller is provided as in the electrostatic recording apparatus described above, the apparatus becomes complicated and the cost of the image forming apparatus increases. There is a problem that the size of the image forming apparatus increases as the number of devices increases.

It is also conceivable to replace the pressing member of the pressure roller according to the usage conditions of the image forming apparatus.
In this case, there is a problem that it is necessary to visit a service person to replace the parts. In addition, there are problems that the number of parts increases as parts are replaced, and that multiple parts must be managed.

Therefore, the present invention has been made in view of the above, and an object thereof is to make it possible to switch the pressing force of the pressure roller constituting the fixing device with an inexpensive structure.

[0010]

In order to achieve the above-mentioned object, a fixing device according to a first aspect of the present invention is a heat roll type fixing device for melting and fixing a toner image on a recording sheet with a fixing roller and a pressure roller. A fixing device, which is an elastic member for pressing the pressure roller against the fixing roller, has one end attached to the pressure roller side and the other end attached to the apparatus main body side, A fixing device including a first mounting member for mounting the one end of the compression spring to the pressure roller, and a second mounting member for mounting the other end of the compression spring to the device main body side. The compression spring comprises a conical coil spring with one end having a small diameter and the other end having a large diameter, and the first mounting member and the second mounting member are the compression springs. And a small diameter end portion mounting portion for mounting each of said small-diameter end portion and the large diameter portion and of the large diameter end portion mounting portion, the first mounting member or the second
In any one of the mounting members, the small diameter end mounting portion is closer to the facing second mounting member or the first mounting member than the large diameter end mounting portion.

A fixing device according to a second aspect of the present invention is a heat roll type fixing device for melting and fixing a toner image on a recording sheet with a fixing roller and a pressure roller.
A compression spring, which is an elastic member for pressing the pressure roller against the fixing roller, has one end attached to the pressure roller side and the other end attached to the apparatus main body side, and the one end of the compression spring. And a second mounting member for mounting the other end of the compression spring to the apparatus main body side.
And a second mounting member, wherein the compression spring comprises a conical coil spring having one end with a small diameter and the other end with a large diameter. Has a small diameter end mounting portion and a large diameter end mounting portion for mounting the small diameter end portion and the large diameter end portion of the compression spring, respectively, and the first mounting member or the second mounting member. In any one of the members, the large-diameter end mounting portion faces the second small-diameter end mounting portion.
In the direction of the mounting member or the first mounting member.

An image forming apparatus according to a third aspect of the present invention is the image forming apparatus using the fixing device according to the first aspect, wherein the second mounting member is provided on a wall surface of the image forming apparatus main body. It is what

Further, in the image forming apparatus according to a fourth aspect of the present invention, the image forming apparatus is further arranged at the position of the small diameter end mounting portion or the large diameter end mounting portion of the second mounting member, and the compression is performed. And a fixing temperature switching unit for switching the fixing temperature of the fixing device based on the detection result of the detecting unit. The detecting unit detects a mounting state of the small diameter end or the large diameter end of the spring. is there.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of an image forming apparatus according to the present invention will be described below in detail with reference to the drawings.

FIG. 1 shows the entire structure of a laser printer as an example of an image forming apparatus utilizing an electrophotographic process. In the main body case 1 of the laser printer, a photoconductor 2 is provided substantially in the center, and a charger 3, a developing device 4, a transfer device 5, a cleaning device 6 and the like are arranged around the photoconductor 2. Below the photoconductor 2, there are a paper feed cassette 8 containing the recording paper 7, a paper feed roller 9 for feeding the recording papers 7 in the paper feed cassette 8 one by one, and a fed recording paper 7. A registration roller 10 or the like that sends out to the transfer device 5 side at a predetermined timing is provided. Furthermore,
Above the photoconductor 2, in the transfer device 5, a fixing device 11 for fixing the image transferred onto the recording paper 7, a fixing device 1
1, a paper discharge roller 12 and the like for discharging the recording paper 7 on which the image is fixed to a stacker unit described later is provided.

A body cover 1a which is a part of the body case 1
A stacker unit 13 for ejecting the recording paper 7 on which an image has been formed is formed on the upper surface of the. Further, below the stacker portion 13 in the main body case 1, an electric component portion 15 housed in a metal case 14 is provided. The electrical component section 15 is formed of a controller board 16 and various adjustment switches and control units (not shown) mounted on the controller board 16. Further, the metal case 14 in the main body case 1
A case 19 accommodating a power source 17 and an electric board 18 is provided below the optical disk 2, and an optical device 2 for writing an image on the photoconductor 2.
0 is provided.

In the above-mentioned image forming apparatus, the fixing device 11 includes a fixing roller 21 for fixing the image transferred onto the recording paper 7 by the transfer device 5, and a pressure roller 22 for pressing the recording paper 7 against the fixing roller 21. , And an elastic member (not shown) that presses the pressure roller 22 against the fixing roller 21. Therefore, a mechanism for switching the pressing force of the pressure roller 22 in the fixing device 11 will be described below.

FIGS. 2A and 2B are views showing a schematic structure of the fixing device 11. As shown in FIG. 2A, the fixing device 11 according to the first embodiment of the present invention, which constitutes the fixing device 11 by rotatably supporting the pressure roller 22 by the bearing 23 as the first mounting member of the present invention. By installing a conical compression spring (conical spring) 25, which is an elastic member, between the fixing structure 24 as a mounting member of No. 2 and the bearing 23, the pressure roller 22 is applied to the fixing roller 21 at a predetermined pressure. It has a configuration of pressing with. For convenience of description, the conical spring 2 is shown in FIG.
5 is shown only with a conical outer shape.

Further, the fixing structure 24 is provided with a spring mounting portion 26 for mounting the conical spring 25. The spring mounting portion 26 includes a small diameter end mounting portion 27 for mounting the small diameter end portion of the conical spring 25 and a large diameter end mounting portion 28 for mounting the large diameter end portion of the conical spring 25. Has been done.
The small-diameter end mounting portion 27 is provided so as to protrude from the fixing structure 24 so as to be close to the bearing 23 that faces the small-diameter end portion.

By configuring the fixing device 11 as shown in FIG. 2A, when the conical spring 25 is installed so that the large diameter end of the conical spring 25 faces the fixing structure 24 side, As shown in FIG. 2B, the large-diameter end portion of the conical spring 25 is supported by the large-diameter end mounting portion 28, and the bearing 23 is pressed by the pressure given by the length L.

On the other hand, when the conical spring 25 is installed so that the small-diameter end portion of the conical spring 25 faces the fixing structure 24 side, as shown in FIG. The portion is supported by the small-diameter end mounting portion 27, and presses the bearing 23 by the pressure given by the length s.

As shown in FIGS. 2B and 2C, the fixing structure 24 has a small-diameter end mounting portion 27 and a large-diameter end mounting portion 2.
8 is provided, and the conical springs 25 are installed so as to change their directions, so that one conical spring 2
5, it is possible to obtain two types of pressing force. That is, by installing the conical spring 25 as shown in FIG. 2C, the conical spring 2 as shown in FIG.
As compared with the case where 5 is installed, a large pressing force of the pressure roller 22 can be obtained. As described above, according to the image forming apparatus of the present embodiment, the pressing force of the pressure roller 22 can be changed only by changing the direction of the conical spring 25, and the pressure roller has a simple structure. The pressing force switching mechanism can be realized.

Further, the above-mentioned fixing device 11 is not shown in FIG. 2 when the fixing device 11 is attached to the image forming apparatus.
The configuration is as shown in (b) and (c). That is,
When the fixing device 11 is assembled to the image forming apparatus, the fixing structure 24 is attached to the wall surface of the image forming apparatus. As a result, the fixing device 11 is configured to compress the conical spring 25 for the first time. Therefore, since the regular pressing force by the conical spring 25 is applied to the pressing roller 22 only after the fixing device 11 is mounted, a small force is required when the conical spring is assembled, and the assembling property can be improved.

Although the fixing structure 24 is provided with the small-diameter end mounting portion 27 and the large-diameter end mounting portion 28 in FIG. 2, it may be configured as shown in FIG. That is, instead of the structure in which the small-diameter end mounting portion 27 and the large-diameter end mounting portion 28 are provided in the fixing structure 24 as shown in FIG. 2, a bearing 23 that rotatably supports the pressure roller 22.
The small-diameter end portion mounting portion 27 and the large-diameter end portion mounting portion 28 are provided in the structure. Even with the configuration shown in FIG.
It is possible to obtain the effect that two types of pressing force can be obtained by one conical spring 25.

[Second Embodiment] FIG. 4 is an explanatory view for explaining a second embodiment of the fixing device 11. In addition, in Embodiment 2, the same members as those described in FIG. 2 are denoted by the same reference numerals, and the description of the configuration and the operation thereof will be omitted.

In FIG. 4, reference numeral 29 is a main body structure 29 which constitutes an image forming apparatus for attaching the fixing device 11.
On the main body structure 29, the conical spring receiving portions 30a and 3 for supporting the conical spring 25 described above are shown.
0b is formed.

As shown in FIG. 4, the fixing structure 24 is installed between the conical spring receiving portions 30a and 30b. 5 (a) to 5 (c) show a state in which the fixing structure 24 is installed between the conical spring receiving portions 30a and 30b.
Shown in

As shown in FIG. 5A, the small-diameter end portion of the conical spring 25 is attached to the small-diameter end portion 2 of the fixing structure 24.
7, the conical spring 25 has a conical spring receiving portion 30 as shown in FIG. 5 (b).
The fixing structure 24 is formed so as to be inserted between a and 30b.
Are installed on the main body structure 29.

On the other hand, when the large-diameter end of the conical spring 25 is attached to the fixing structure 24 side, the main body structure 29 between the conical spring receiving parts 30a and 30b.
The fixing structure 24 is installed on the conical spring receiving portion 3
Install a conical spring 25 on 0a and 30b. The conical spring 25 has the conical spring receiving portion 3
Supported by 0a and 30b, a predetermined pressing force can be obtained.

By adopting the structure shown in FIG.
Two conical springs 25 can provide two types of pressing force. That is, the pressing force of the pressure roller 22 can be changed only by changing the direction of the conical spring 25, and the pressing force switching mechanism of the pressure roller can be realized with a simple configuration. Further, by adopting the structure shown in FIG. 5, it is necessary to provide the fixing structure 24 and the bearing 23 with the small-diameter end mounting portion 27 and the large-diameter end mounting portion 28 as shown in FIGS. Disappears. Further, when the fixing device 11 is attached to the image forming apparatus, since the regular pressing force of the conical spring 25 is applied to the pressing roller 22, a small force is required when the conical spring is assembled, and the assembling property is improved. Can be made.

Further, as shown in FIG. 5B, when the conical spring 25 is attached to the fixing structure 24, the conical spring 25 should be attached in the state of the length L shown in FIG. 2A. Therefore, the length s shown in FIG.
The conical spring 25 can be attached with a smaller force than in the above state. Therefore, the assemblability is improved. On the other hand, as shown in FIG. 5C, when the conical spring 25 is installed in the conical spring receiving portions 30a and 30b, the pressure roller 2 having the same configuration as that shown in FIG.
A pressing force of 2 can be obtained, and a large pressing force can be obtained as compared with the configuration shown in FIG.

[Third Embodiment] FIG. 6 is a block diagram showing a structure of a fixing device 11 according to a third embodiment. In addition, in the third embodiment, the same members as the members described in FIG.

In the third embodiment, in addition to the structure shown in FIG. 5 described above, a fixing temperature changeover switch 32 as a detecting means of the present invention is provided at the upper end 31 of the conical spring receiving portion 30a, and this fixing temperature changeover switch is provided. The fixing temperature switching unit 33 as the fixing temperature switching unit of the present invention is connected to the fixing unit 32, and the fixing temperature can be switched by assembling the fixing device 11 to the image forming apparatus. . In the third embodiment, when the fixing temperature changeover switch 32 is pressed, a fixing temperature changeover signal is outputted from the fixing temperature changeover unit 33 so that the fixing temperature of the fixing device 11 is changed over to a high temperature.

FIGS. 7 (a) and 7 (b) are configuration diagrams showing a configuration in which the conical spring 25 is attached to the conical spring receiving portions 30a and 30b. As shown in FIG. 7A, when the large diameter end of the conical spring 25 is attached to the conical springs 30a and 30b,
Since the conical spring 25 is further compressed as shown in (c), the pressing force of the pressure roller 22 is set to be large, and the conical spring 25 presses the fixing temperature changeover switch 32 to increase the fixing temperature. Is set to. Therefore, the configuration shown in FIG. 7A is effective when the fixing of thick paper is frequently used.

Further, as shown in FIG. 7B, when the small-diameter end of the conical spring 25 is installed in the fixing structure 24, the fixing temperature changeover switch 32 is not operated and the fixing temperature is normal. Will remain.

Since the fixing temperature can be switched by mounting the fixing device 11 in this manner, the effect of improving the performance of the image forming apparatus by switching the pressing force can be made more remarkable with a simple structure. it can.

In the third embodiment, the fixing temperature changeover switch 32 is provided on the upper end portion 31 of the conical spring receiving portion 30a. However, the fixing temperature changeover switch 32 is used for the fixing device 11 in the image forming apparatus. It may be provided at any position as long as it can detect the attachment state of the conical spring 25 when attached to the. In the third embodiment, when the fixing temperature changeover switch 32 is pressed, the fixing temperature changeover unit 33 outputs the fixing temperature changeover signal, and the fixing temperature of the fixing device 11 is set to the high temperature. The fixing temperature can be set to be low when the fixing temperature changeover switch 32 is not pressed, and any method for changing the fixing temperature by the fixing temperature changeover switch 32 can be used.

[0038]

As described above, according to the fixing device of the present invention (Claim 1), one of the compression springs forming the fixing device has a conical shape with one end having a small diameter and the other end having a large diameter. The first mounting member and the second
Has a small-diameter end mounting portion and a large-diameter end mounting portion for mounting the small-diameter end portion and the large-diameter end portion of the compression spring, respectively, and the first mounting member or the second mounting member Either one of them has a structure in which the small-diameter end mounting portion is closer to the facing second mounting member or the first mounting member than the large-diameter end mounting portion. A mechanism for switching the pressing force of the pressure roller can be obtained.

A fixing device according to the present invention (claim 2)
According to the method, the compression spring comprises a conical coil spring having one end having a small diameter and the other end having a large diameter, and the first mounting member and the second mounting member include the small diameter end and the large diameter end of the compression spring. A large-diameter end mounting portion for mounting each of the large-diameter end portions, and one of the first mounting member and the second mounting member has a large-diameter end mounting portion. Since the small-diameter end mounting portion is closer to the facing second mounting member or the first mounting member,
A mechanism for switching the pressing force of the pressure roller can be obtained with an inexpensive structure.

According to the image forming apparatus of the present invention (Claim 3), since the second mounting member is provided on the wall surface of the image forming apparatus main body, a small force is required when the compression spring is assembled. ， Assembly can be improved.

Further, according to the image forming apparatus of the present invention (claim 4), the compression spring is arranged at the position of the small diameter end mounting portion or the large diameter end mounting portion of the second mounting member. The fixing device is provided with an image forming means for detecting the mounting state of the small diameter end or the large diameter end of the fixing device and the fixing temperature switching device for switching the fixing temperature of the fixing device based on the detection result of the detecting device. The fixing temperature can be switched by mounting it on the apparatus, and the effect of improving the performance of the image forming apparatus by switching the pressing force can be made more remarkable.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an internal configuration of an image forming apparatus according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram showing a configuration of a fixing device of the image forming apparatus according to the first embodiment of the present invention.

FIG. 3 is a configuration diagram showing a configuration of a fixing device of the image forming apparatus according to the first embodiment of the present invention.

FIG. 4 is an explanatory diagram illustrating a configuration of a fixing device of an image forming apparatus according to a second embodiment of the present invention.

FIG. 5 is a configuration diagram showing a configuration of a fixing device of an image forming apparatus according to a second embodiment of the present invention.

FIG. 6 is a configuration diagram showing a configuration of a fixing device of an image forming apparatus according to a third embodiment of the present invention.

FIG. 7 is a configuration diagram showing a configuration of a fixing device of an image forming apparatus according to a third embodiment of the present invention.

[Explanation of symbols]

 1 Main Body Case 1a Main Body Cover 2 Photoconductor 3 Charging Device 4 Developing Device 5 Transfer Device 6 Cleaning Device 7 Recording Paper 8 Paper Feed Cassette 9 Paper Feed Roller 10 Registration Roller 11 Fixing Device 12 Paper Ejection Roller 13 Stacker 14 Metal Case 15 Electrical Equipment Section 16 Controller Board 17 Power Supply 18 Electrical Equipment Board 19 Case 20 Optical Device 21 Fixing Roller 22 Pressure Roller 23 Bearing 24 Fixing Structure 25 Conical Spring 26 Spring Mounting Part 27 Small Diameter End Mounting Part 28 Large Diameter End Mounting Part 29 Main body structure 30a, 30b Conical spring receiving part 31 Upper end part 32 Fixing temperature changeover switch 33 Fixing temperature changeover part

Claims (4)

[Claims] 1. A heat roll type fixing device for fusing and fixing a toner image on a recording sheet with a fixing roller and a pressure roller, wherein the fixing device is an elastic member for pressing the pressure roller against the fixing roller. A compression spring having one end attached to the pressure roller side and the other end attached to the apparatus main body side; a first attachment member for attaching the one end of the compression spring to the pressure roller; A fixing device including a second mounting member for mounting the other end of the compression spring to the device body side,
The compression spring comprises a conical coil spring, one of which has a small diameter end and the other of which has a large diameter end, and the first mounting member and the second mounting member include the small diameter end and the compression spring. A large-diameter end mounting portion and a large-diameter end mounting portion for mounting each of the large-diameter end portions, wherein either one of the first mounting member or the second mounting member is
The fixing device, wherein the small-diameter end mounting portion is closer to the facing second mounting member or first mounting member than the large-diameter end mounting portion. 2. A heat roll type fixing device for fusing and fixing a toner image on a recording sheet by a fixing roller and a pressure roller, wherein the fixing device is an elastic member for pressing the pressure roller against the fixing roller. A compression spring having one end attached to the pressure roller side and the other end attached to the apparatus main body side; a first attachment member for attaching the one end of the compression spring to the pressure roller; A fixing device including a second mounting member for mounting the other end of the compression spring to the device body side,
The compression spring comprises a conical coil spring, one of which has a small diameter end and the other of which has a large diameter end, and the first mounting member and the second mounting member include the small diameter end and the compression spring. A large-diameter end mounting portion and a large-diameter end mounting portion for mounting each of the large-diameter end portions, wherein either one of the first mounting member or the second mounting member is
The fixing device, wherein the large-diameter end mounting portion is closer to the opposing second mounting member or first mounting member than the small-diameter end mounting portion. 3. An image forming apparatus using the fixing device according to claim 1, wherein the second mounting member is provided on a wall surface of a main body of the image forming apparatus. 4. The image forming apparatus according to claim 3, further comprising: a small-diameter end mounting portion or a large-diameter end mounting portion of the second mounting member, A detecting means for detecting the mounting state of the small-diameter end portion or the large-diameter end portion; and a fixing temperature switching means for switching the fixing temperature of the fixing device based on the detection result of the detecting means. Image forming apparatus.