JP2012068435A - Fixing device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing device and an image forming apparatus that can vary force for pressing a contact member against a rotating body and be downsized.SOLUTION: An image forming apparatus 10 has a fixing device 300. The fixing device 300 has a heat roll 310, a contact member 360 which contacts the heat roll 310 and forms between itself and the heat roll 310 a contact part N for a paper sheet to pass through, a pressing mechanism 400R for pressing the contact member 360 against the heat roll, and pressing force variable means 450 for varying the pressing force caused by the pressing mechanism 400R. The pressing mechanism 400R has a first spring 410R and a second spring 420R disposed inside the first spring 410R.

Description

  The present invention relates to a fixing device and an image forming apparatus.

  In Patent Document 1, a fixing roller having a heat generating element inside and a pressure roller having a rubber layer are disposed, and the pressure device includes a pressure mechanism that presses the pressure roller against the fixing roller. A spring material that abuts the bearing portion of the pressure roller at both ends of the roller, a reference position bracket for applying stress to the spring material, and a reference position change cam for changing the height of the reference position bracket, And a lever for rotating the reference position change cam coaxially with the rotation shaft and the reference position change cam to fix the reference position change cam at a plurality of predetermined positions, and detecting the position of the lever There is disclosed a fixing device provided with a position detection circuit for performing the above and a storage unit for storing the detected lever position.

JP 2004-109521 A

  SUMMARY OF THE INVENTION An object of the present invention is to provide a fixing device and an image forming apparatus that can change the pressing force between a rotating body and a contact member and can be downsized.

  According to a first aspect of the present invention, there is provided a rotating body, a contact member that contacts the rotating body and forms a contact portion through which a recording medium passes, and the rotating body and the contact member. A pressing mechanism for pressing, and a pressing force variable means for changing a pressing force of the pressing mechanism, wherein the pressing force variable means is a first spring and a second spring disposed inside the first spring. A fixing device having a spring.

  The present invention according to claim 2 is the fixing device according to claim 1, wherein the first spring and the second spring are wound in directions opposite to each other in the winding direction.

  The present invention according to claim 3 is the fixing device according to claim 1 or 2, wherein the second spring has a maximum distance between adjacent winding portions smaller than a wire diameter of the first spring.

  According to a fourth aspect of the present invention, in the fixing device according to any one of the first to third aspects, the pitch of the second spring on the end portion side of at least one side of the winding portion is smaller than the pitch in the central portion. .

  The present invention according to claim 5 is the fixing device according to any one of claims 1 to 4, further comprising a partition portion that partitions the first spring and the second spring.

  According to a sixth aspect of the present invention, there is provided a rotating body support portion that rotatably supports the rotating body, and a contact member support that is mounted on the rotating body support portion so as to be swingable and supports the contact member. And at least one of the first spring and the second spring has one end fixed to either the rotation support portion or the contact member support portion. The fixing device according to claim 1.

  The present invention according to claim 7 includes: an image forming unit that forms a developer image on a sheet; and a fixing device that fixes the developer image formed by the image forming unit on a recording medium. Includes a rotating body, a contact member that contacts the rotating body and forms a contact portion through which a recording medium passes, a pressing mechanism that presses the rotating body and the contact member, and the pressing And a pressing force variable means for changing the pressing force of the mechanism, wherein the pressing force variable means includes a first spring and a second spring disposed inside the first spring. Device.

  According to the first aspect of the present invention, it is possible to provide a fixing device that can change the force for pressing the rotating body and the contact member and can be downsized.

  According to the second aspect of the present invention, in addition to the effects of the first aspect of the present invention, a fixing device that can prevent the spring from becoming entangled compared to the case without the present configuration. Can be provided.

  According to the third aspect of the present invention, in addition to the effects of the first or second aspect of the present invention, the fixing that can prevent the spring from being entangled compared to the case without the present configuration. An apparatus can be provided.

  According to the fourth aspect of the present invention, in addition to the effects of the first aspect of the present invention according to any one of the first to third aspects, the spring is less likely to be entangled as compared to the case without the present configuration. A fixing device that can be provided can be provided.

  According to the fifth aspect of the present invention, in addition to the effects of the first aspect of the present invention according to any one of the first to fourth aspects, the spring is less likely to be entangled as compared with the case without the present configuration. A fixing device that can be provided can be provided.

  According to the sixth aspect of the present invention, it is possible to provide a fixing device that can prevent the spring from being entangled in addition to the effects of the first to fifth aspects of the present invention.

  According to the seventh aspect of the present invention, it is possible to provide an image forming apparatus that can change the force for pressing the rotating body and the contact member and can be downsized.

1 is a diagram illustrating an image forming apparatus according to a first embodiment of the present invention. FIG. 2 is a plan view schematically showing a fixing device included in the image forming apparatus shown in FIG. 1. FIG. 3 is a cross-sectional view showing a cross section of the fixing device shown in FIG. 2 at the position of the AA plane in FIG. 2, and showing a state in which a heating roll and a contact member are pressed using two springs. It is a figure which shows the pressing mechanism which the fixing device shown in FIG. 2 has. FIG. 5A is a diagram illustrating a first spring and a second spring included in the fixing device illustrated in FIG. 2, and FIG. 5A is a diagram illustrating a fourth arrow BB direction, and FIG. These are figures which show the cross section in CC plane shown to Fig.5 (a). FIG. 3 shows the fixing device shown in FIG. 2 and shows a state in which a heating roll and a contact member are pressed using one spring. FIG. 3 is a diagram illustrating the fixing device illustrated in FIG. 2 and a state in which a heating roll and a contact member are not pressed. FIG. 6 is a diagram illustrating a first spring and a second spring of a fixing device included in image formation according to a second embodiment of the present invention. It is a figure which shows the 2nd coil spring of the fixing device which the image formation concerning the 3rd Embodiment of this invention has. It is a figure which shows the pressing mechanism which the image formation which concerns on the 3rd Embodiment of this invention has.

Next, embodiments for carrying out the present invention will be described with reference to the drawings.
FIG. 1 shows an image forming apparatus 10 according to a first embodiment of the present invention. As shown in FIG. 1, the image forming apparatus 10 includes an image forming apparatus main body 12, and a discharge port 14 for discharging a sheet used as a recording medium is formed in the image forming apparatus main body 12. Further, the upper part of the image forming apparatus main body 12 is used as a discharge unit 16 from which a sheet on which an image is formed is discharged.

  In the image forming apparatus main body 12, an image forming unit 100 that forms a developer image on paper, a paper feeding device 200 that supplies paper to the image forming unit 100, and a developer image formed by the image forming unit 100 are stored. A fixing device 300 that fixes the sheet is disposed. In addition, a conveyance path 250 through which a sheet is conveyed is formed in the image forming apparatus main body 12.

  The image forming unit 100 includes photosensitive drums 102Y, 102M, 102C, and 102K, charging devices 104Y, 104M, 104C, and 104K that charge the photosensitive drums 102Y, 102M, 102C, and 102K, and charging devices 104Y, 104M, and 104C, respectively. , 104K charged with the photosensitive drums 102Y, 102M, 102C, 102K to form an electrostatic latent image by irradiating light onto the photosensitive drums 102Y, 102M, 102C, 102K; The electrostatic latent image formed on the surface of 102K is developed using a developer to form a yellow developer image, a magenta developer image, a cyan developer image, and a black developer image, respectively. Developing devices 110Y, 110M, 110C, and 110K.

  The image forming unit 100 also performs an intermediate transfer described later on a yellow developer image, a magenta developer image, a cyan developer image, and a black developer image formed by the developing devices 110Y, 110M, 110C, and 110K, respectively. A primary transfer device 140 that transfers to the body 142 and cleaning devices 114Y, 114M, 114C, and 114K that clean the surfaces of the photosensitive drums 102Y, 102M, 102C, and 102K.

  The primary transfer device 140 transfers the yellow developer image, the magenta developer image, the cyan developer image, and the black developer image formed on the photosensitive drums 102Y, 102M, 102C, and 102K so as to overlap each other. The intermediate transfer body 142 is provided. The intermediate transfer body 142 is supported by the support rolls 146, 148, 150, and 152 so that it can rotate.

  Further, the primary transfer device 140 receives a yellow developer image, a magenta developer image, a cyan developer image, and a black developer image respectively formed on the photosensitive drums 102Y, 102M, 102C, and 102K. Primary transfer rolls 156Y, 156M, 156C, and 156K to which a transfer bias for transferring to the intermediate transfer body 142 is applied are included.

  Further, the image forming unit 100 includes a secondary transfer device 160 that transfers the yellow developer image, the magenta developer image, the cyan developer image, and the black developer image transferred to the intermediate transfer body 142 to a sheet. Have.

The paper feeder 200 includes a paper storage unit 202, an extraction roll 204 that extracts the uppermost paper stored in the paper storage unit 202, and a paper extracted by the extraction roll 204 toward the image forming unit 100. A conveyance roll 206 that conveys the sheet and a separation roll 208 that contacts the conveyance roll 206 and separates the paper from the conveyance roll 206 are provided.

  The conveyance path 250 includes a main conveyance path 252 and a reverse conveyance path 254. The main conveyance path 252 is a conveyance path that conveys the paper supplied from the paper feeding device 200 toward the discharge unit 16, and the above-described conveyance rolls sequentially from the upstream side in the conveyance direction of the paper along the main conveyance path 252. 206, a separation roll 208, a transport roll 258, a registration roll 260, the above-described secondary transfer device 160, the fixing device 300, and a discharge roll 262 are mounted. The transport roll 258 transports the paper toward the registration roll 260. The registration roll 260 temporarily stops the leading edge of the sheet in a state where the rotation is stopped, and starts rotating at a predetermined timing so as to match the timing at which the developer image is transferred to the intermediate transfer body 142. In addition, the sheet is supplied to the contact portion between the intermediate transfer body 142 and the secondary transfer device 160.

  The discharge roller 262 discharges the sheet on which the developer image is fixed by the fixing device 300 to the discharge unit 16. In addition, the discharge roll 262 rotates in the opposite direction to the case of discharging the paper to the discharge unit 16 when forming images on both sides of the paper, and removes the paper on which the image is formed on one side. The paper is supplied from the end side to the reverse conveyance path 254.

  The reverse conveyance path 254 is used when a sheet on which an image is formed on one side is supplied again to the upstream side of the conveyance roll 258 while being reversed. For example, three reverse transfer rolls 264 are mounted along the reverse transfer path 254.

  The fixing device 300 includes a fixing device main body 302, a heating roll 310 provided in the fixing device main body and used as a rotating body, and a contact member 360. The contact member 360 is in contact with the heating roll 310 and forms a contact portion N through which the paper passes. The aforementioned discharge roll 262 is attached to the fixing device main body 302 and can be attached to and detached from the image forming apparatus main body 12 integrally with the fixing device 300.

2 and 3 show the fixing device 300.
The fixing device 300 includes the heating roll 310 as described above. The heating roll 310 includes, for example, a metal base and an elastic layer such as a rubber layer formed on the surface of the base, for example, a hollow member 312 having a hollow portion such as a cylindrical shape, and disposed in the hollow member 312. The heating element 314 is provided. The hollow member 312 is mounted with a bearing 318F on the front side (lower side in FIG. 2) and a bearing 318R on the rear side (upper side in FIG. 2).

  Moreover, the heating roll 310 is supported so that it can rotate to the heating roll support member 322 used as a rotary body support part which supports the heating roll 310 rotatably using the bearings 318F and 318R. More specifically, the heating roll support member 322 has a front side plate 324F and a rear side plate 324R, the bearing 318F is mounted on the front side plate 324F, and the bearing 318R is mounted on the rear side plate 324R. By mounting, the hollow member 312 of the heating roll 310 is supported so that it can rotate with respect to the heating roll support member 322.

  In addition, a gear 330 used as a driven transmission portion is attached to the rear end portion of the hollow member 312. A drive source 170 such as a motor is connected to the gear 330 via a drive transmission mechanism 172 such as a gear train. The hollow member 312 is shown in FIG. 3 in response to the drive transmission from the drive source 170. It rotates in the direction of arrow a.

The heating roll support member 322 is fixed to the above-described fixing device main body 302 (see FIG. 1) and is attached so as not to move with respect to the fixing device main body 302 and the image forming apparatus main body 12 (see FIG. 1). . A support shaft 326F is formed on the front side plate 324F of the heating roll support member 322 so as to protrude toward the rear side. A support shaft 326R is formed on the side plate 324R on the rear side of the heating roll support member 322 so as to protrude toward the front side.

  Further, the heating roll support member 322 has column support portions 328F and 328R to which columns 430F and 430R included in pressing mechanisms 400R and 400F described later are mounted.

  In addition, the first swing member 340F is mounted on the front side plate 324F of the heating roll support member 322 so that the first swing member 340F can swing with respect to the heating roll support member 322 using the support shaft 326F. Further, the first swing member 340R is mounted on the side plate 324R on the rear side of the heating roll support member 322 so that the first swing member 340R can swing with respect to the heating roll support member 322 using the support shaft 326R.

  A shaft 348 is attached to the first swing member 340F and the first swing member 340R so as to be able to rotate. A cam 380F is mounted on the front end side of the shaft 348, and a cam 380R is mounted on the rear end side of the shaft 348. For this reason, the shaft 348, the cam 380F, and the cam 380R can rotate as a unit while being supported by the swing member 350F and the swing member 350R.

  For example, an operation unit 500 such as an operation lever is mounted on the front end side of the shaft 348, and the shaft 348, the cam 380F, and the cam 380F are integrated as a result of the operator operating the operation unit 500. Rotate.

  Further, a support hole 342F is formed in the first swing member 340F, and a support hole 342R is formed in the first swing member 340R.

  The first swing member 340F is attached so that the second swing member 350F can swing with respect to the first swing member 340F. More specifically, a support shaft 352F formed on the front surface of the second swing member 350F so as to protrude forward is inserted into a support hole 342F formed in the first swing member 340F. In this way, the second swing member 350F is attached to the first swing member 340F. Further, the second swing member 350R is attached to the first swing member 340R so as to be swingable with respect to the first swing member 340R. More specifically, a support shaft 352R formed to protrude rearward from the rear surface of the second swing member 350R is inserted into a support hole 342R formed in the first swing member 340R. Thus, the second swing member 350R is attached to the first swing member 340R.

  The first swing member 340F and the first swing member 340R support the contact member 360 via the second swing member 350F, the second swing member 350R, and the like, and the contact members that support the contact member 360. It is used as a support part.

  The first swing member 340F has a pressed portion 344F that is pressed by a first spring 410F and a second spring 420F (see FIG. 4) of a pressing mechanism 400F described later, and the first swing member 340R includes a pressed portion 344R that is pressed by a spring 410R and a spring 420R (see FIG. 4) of a pressing mechanism 400R described later.

The second rocking member 350F has, for example, a cylindrical shape and is provided with a contact portion 354F that comes into contact with the cam 380F. The second rocking member 350R has, for example, a cylindrical shape, and has a contact portion 354R that comes into contact with the cam 380R. Is provided.

  The contact member 360 described above is supported by the second swing member 350F and the second swing member 350R. More specifically, the pressing member 362 is disposed inside the endless contact member 360, the pressing member support member 370F is attached to the front end of the pressing member 362, and the rear side of the pressing member 362. The pushing member support member 370R is attached to the end of the push member, the pushing member support member 370F is attached to the second swing member 350F, and the push member support member 370R is attached to the second swing member 350R. The contact member 360 is supported by the second swing member 350F and the second swing member 350R. Therefore, the contact member 360, the pressing member 362, the pressing member support member 370F, the pressing member support member 370R, the second swinging member 350F, and the second swinging member 350R are integrated as a first swinging member. It swings with respect to 340F and the first swing member 340R.

  The contact member 360 is strip-shaped, endless, flexible, and is a film-like member made of, for example, a resin such as polyimide, and is in contact with the heating roll 310 and heated as described above. A contact portion N is formed between the roll 310 and the sheet.

  The pressing member 362 is made of rubber or the like, has elasticity, and has an elastic member 364 disposed at a position facing the heating roll 310 via the contact member 360, and an elastic member that supports the elastic member 364. And a support member 366. The elastic member support member 366 is made of, for example, a resin or the like, and is formed of a material having a hardness lower than that of the elastic member 364.

  As described above, in the fixing device 300, the heating roll support member 322 is fixed to the fixing device main body 302, the heating roll 310 is rotatably supported by the heating roll support member 322, and the first swing is supported by the heating roll support member 322. The moving member 340F and the first swinging member 340R are mounted so as to be swingable. The second swinging member 350F is supported by the first swinging member 340F so as to be swingable. The second swing member 350R is supported so as to be swingable, and the contact member 360 is supported by the second swing member 350F and the second swing member 350R.

  The fixing device 300 includes pressing mechanisms 400F and 400R. The pressing mechanism 400F and the pressing mechanism 400R include a plurality of springs, and press the heating roll 310 and the contact member 360 using at least one spring selected from the plurality of springs. It is used as a pressing mechanism that presses 310 and the contact member 360. The pressing mechanism 400F is disposed on the front side of the fixing device 300, and the pressing mechanism 400R is disposed on the rear side of the fixing device 300.

  FIG. 4 shows a pressing mechanism 400R. Since the pressing mechanism 400F has the same configuration and operation as the pressing mechanism 400R described below, the description thereof is omitted. As shown in FIG. 4, the pressing mechanism 400R includes a first spring 410R, a second spring 420R, and a column 430R used as a spring support portion that supports the first spring and the second spring. ing.

  As the first spring 410R, a spring having an inner diameter portion in a direction crossing the deformation direction is used, for example, a compression coil spring is used.

  As the second spring 420R, a compression coil spring is used similarly to the first spring 410R. Further, the second spring 420R is disposed inside the first spring 410R. More specifically, when a coil spring such as a compression coil spring is used as the first spring 410R, the second spring 420R is disposed inside the winding portion of the first spring 410R.

One end of the support post 430R is fixed to the support attachment part 328R of the heating roll support member 322, passes through the through hole 346R formed in the pressed part 344R of the first swing member 340R, and is opposite to the support attachment part 328R. It extends to the side. A second spring 420R is mounted on the pressed portion 344R side of the support column 430R, and a first spring 410R is mounted so as to cover the outside of the second spring. In addition, a large-diameter portion 432R having a larger diameter than the other portions is formed at the end of the support 430R opposite to the support mounting portion 328R side.

  In this embodiment, one end portion of the first spring 410R is fixed to the pressed portion 344R of the first swing member 340R. Instead of fixing one end portion of the first spring 410R to the pressed portion 344R of the first swing member 340R, the other end portion of the first spring 410R is connected to the heating roll support member 322 via the large diameter portion 432R. It may be fixed to. Further, one end portion of the second spring 420R may be fixed to the pressed portion 344R of the first swing member 340R. Further, instead of fixing one end portion of the second spring 420R to the pressed portion 344R of the first swing member 340R, the other end portion of the second spring 420R is supported by the heating roll via the large diameter portion 432R. The member 322 may be fixed.

  As described above, in the pressing mechanism 400R, the first spring 410R and the second spring 420R are sandwiched between the large diameter portion 432R of the support column 430R and the pressed portion 344R of the first swing member 340R. Has been placed. Therefore, when the second spring 420R is held in a compressed shape between the large diameter portion 432R and the pressed portion 344R, the pressed portion of the first swing member 340R is held by the second spring 420R. 344R is pressed in the direction of arrow b shown in FIG.

  In addition, when the first spring 410R and the second spring 420R are held in a compressed shape between the large diameter portion 432R and the pressed portion 344R, the first spring 420R and the second spring 420R presses the pressed portion 344R of the first swing member 340R in the direction of the arrow b shown in FIG.

  When the pressing mechanism 400R is in the state shown in FIG. 4, the portion with the longest distance from the center of the cam 380R contacts the contact portion 354R as shown in FIG. 3, and the cam 380R is fixed at this position. ing. Since the contact portion 354R is fixed in contact with the cam 380R, the second swing member 350R cannot rotate in the direction of the arrow c shown in FIG. 3 with respect to the first swing member 340R. . Then, both the first spring 410R and the second spring 420R, which are two springs, in a state where the second swinging member 350R cannot rotate in the direction of the arrow c shown in FIG. 3 with respect to the first swinging member 340R. However, it is held in a compressed shape between the large diameter portion 432R and the pressed portion 344R.

  For this reason, the pressed portion 344R of the first swing member 340R is pressed in the direction of the arrow b shown in FIG. 4 by both the first spring 420R and the second spring 420R. When the pressed portion 344R is pressed, the first swinging member 340R applies a force in the direction of rotating in the direction of the arrow d shown in FIG. 3 about the support shaft 326R to the heating roll support member 322. receive. Further, the first swing member 340F (see FIG. 2) also receives a force in the rotating direction, like the first swing member 340R.

  Therefore, the pressing member 362 supported by the first swing member 340R and the first swing member 340F via the second swing member 350R, 350F, etc. is connected to the heating roll 310 via the contact member 360. The heating roll 310 and the contact member 360 are pressed. At this time, in the state shown in FIGS. 3 and 4, both the elastic member 364 and the elastic member support member 366 of the pressing member 362 are pressed against the heating roll 310 via the contact member 360. Hereinafter, a state in which the cam 380R, the fixing device 300, and the pressing mechanism 400R are in the positions illustrated in FIGS. 3 and 4 is referred to as a first state.

  FIG. 5 shows a first spring 410R and a second spring 420R. When the first spring 410R and the second spring 420R are attached to the pressing mechanism 400R of the fixing device 300, the winding directions of the first spring 410R and the second spring 420R are opposite to each other as shown in FIG. Further, the second spring 420R is longer in the expansion / contraction direction than the first spring 410R. Also, in the pressing mechanism 400F (see FIG. 2), when the pressing mechanism 400F is mounted, the winding directions of the first spring 410F and the second spring 420F are opposite to each other. Yes. Further, the second spring 420F is longer in the expansion / contraction direction than the first spring 410F.

FIG. 6 shows the fixing device 300 in the second state.
In the second state shown in FIG. 6, when the operation unit 500 (see FIG. 2) is operated, the cam 380R rotates about the shaft 348, and the cam 380R is in a position different from the first state, and the contact portion 354R. In contact with and is fixed. More specifically, in the second state, the length from the center of the cam 380R to the position where it contacts the contact portion 354R of the cam 380R is shorter than that in the first state. For this reason, the positional relationship between the heating roll support member 322 and the first swing member 340R is changed, and in the pressing mechanism 400R, the positional relationship between the large-diameter portion 432R of the support column 430R and the pressed portion 344R is changed.

  More specifically, in the second state, the distance between the large diameter portion 432R of the support column 430R and the pressed portion 344R is longer than that in the case where the pressing mechanism 400R is in the first state. . For this reason, in the first state described above, both the first spring 410R and the second spring 420R, which are two springs, are compressed between the large diameter portion 432R and the pressed portion 344R. In this second state, only the spring 420R, which is the longer of the two springs of the first spring 410R and the second spring 420R, is the large diameter portion 432R. And the pressed portion 344R are held in a compressed shape.

  Therefore, in this second state, the pressed portion 344R is not pressed by the first spring 410R, and the pressed portion 344R of the first swinging member 340R is illustrated by the second spring 420R alone. 6 is pressed in the direction of arrow b. Therefore, in this second state, the force in the direction in which the first swinging member 340R rotates in the direction of the arrow d shown in FIG. 6 is smaller than that in the first state, and the pressing member 362 The force pressed against the heating roll 310 via the member 360 is smaller than that in the first state.

  Further, in this second state, the cam 380R is rotated so that the second swing member 350R is shown in FIG. 6 with respect to the first swing member 340R from the position where the second swing member 350R was disposed in the first state. It is moving so as to rotate in the direction of arrow c. For this reason, in this 2nd state, the positional relationship of the heating roll 310 and the pressing member 362 has changed from the positional relationship in a 1st state.

  More specifically, in the first state, both the elastic member 364 and the elastic member support member 366 of the pressing member 362 are pressed against the heating roll 310 through the contact member 360. In this second state, the elastic member 364 of the pressing member 362 is pressed against the heating roll 310 via the contact member 360, and the elastic member support member 366 is pressed against the heating roll 310. Absent.

FIG. 7 shows the fixing device 300 in the third state.
In the third state shown in FIG. 7, the operation unit 500 (see FIG. 2) is operated so that the cam 380R rotates about the shaft 348, and the position is different from the first state and the second state. Thus, the cam 380R comes into contact with the contact portion 354R and is fixed. More specifically, in the third state, the length from the center of the cam 380R to the position where the cam 380R contacts the contact portion 354F is the length in the first state, and the second state. It is shorter than the length of the state. For this reason, the positional relationship between the heating roll support member 322 and the first swing member 340R is changed, and in the pressing mechanism 400R, the positional relationship between the large-diameter portion 432R of the support column 430R and the pressed portion 344R is the first state. And the positional relationship in the second state are different.

  More specifically, in the third state, the distance between the large-diameter portion 432R of the support column 430R and the pressed portion 344R is larger than that in the first state and the second state. It is getting longer. For this reason, in the first state described above, both the first spring 410R and the second spring 420R, which are two springs, are compressed between the large diameter portion 432R and the pressed portion 344R. In the second state described above, the spring 420R, which is the longer one of the two springs of the first spring 410R and the second spring 420R, has a large diameter portion 432R and a pressed portion 344R. In this third state, both the first spring 410R and the second spring 420R have both the large-diameter portion 432R and the pressed portion 344R. Is not kept in a compressed state between.

  Therefore, in this third state, the pressed portion 344R is not pressed, and the first swing member 340R does not receive a force in the direction of rotation in the direction of the arrow d shown in FIG. The pressing member 362 and the contact member 360 are not pressed against the heating roll 310.

  Further, by rotating the cam 380R, in the third state, the second swinging member 350R was disposed in the position where it was disposed in the first state and in the second state. It will be in the state arrange | positioned in the position different from a position. More specifically, in the first state, both the elastic member 364 and the elastic member support member 366 of the pressing member 362 are pressed against the heating roll 310 via the contact member 360, and the second state In FIG. 5, the elastic member 364 of the pressing member 362 is pressed against the heating roll 310 via the contact member 360, whereas in the third state, the contact member 360 is separated from the heating roll 310. Thus, the pressing member 362 moves to a position where it can move.

  As described above, in the fixing device 300, the operation unit 500, the shaft 348, the cam 380F, the cam 380R, the contact unit 354F, the contact unit 354R, and the like, the first spring 410F, the first spring 410R, The number of springs used for pressing the heating roll 310 and the contact member 360 is switched from the second spring 420F and the second spring 420R. And the pressing force of the heating roll 310 and the contact member 360 can be changed by switching the number of springs used for pressing the heating roll 310 and the contact member 360. In other words, the operation unit 500, the shaft 348, the cam 380F, the cam 380R, the contact unit 354F, the contact unit 354R, and the like are switched to switch the number of springs used to press the heating roll 310 and the contact member 360 out of the plurality of springs. In addition to being used as a mechanism, it is used as pressing force variable means 450 that changes the pressing force between the heating roll 310 and the contact member 360.

  The fixing device 300 is in the first state shown in FIGS. 2 and 3 when the developer image is fixed on plain paper or the like. The fixing device 300 is in the second state shown in FIG. 6 when the developer image is fixed on an envelope, cardboard, or the like. Further, when a conveyance failure of a sheet or the like occurs at the contact portion N and the sheet or the like is removed, the third state shown in FIG. 7 is set.

FIG. 8 shows a first spring 410R and a second spring 420R attached to the pressing mechanism 400F of the fixing device 300 included in the image forming apparatus 10 according to the second embodiment of the present invention. In the first embodiment described above, the first spring 410R and the second spring 420R are opposite to each other in the winding direction. On the other hand, in the second embodiment, the first spring 410R and the second spring 420R have the same winding direction.

  Further, in the second embodiment, in the second spring 420R, the maximum interval L between the winding portions adjacent to each other is smaller than the wire diameter D of the first spring 410R. In the first embodiment described above, the second spring 420R may be a spring in which the maximum interval L between adjacent winding portions is smaller than the wire diameter D of the first spring 410R. good. That is, the winding directions of the first spring 410R and the second spring 420R are opposite to each other, and the second spring 420R has a maximum interval L between adjacent winding portions as the first spring 420R. A spring that is smaller than the wire diameter D of the spring 410R may be used. Other than the portions described above are the same as those in the first embodiment described above, and thus the description thereof is omitted.

  FIG. 8 shows a second spring 420R attached to the pressing mechanism 400F of the fixing device 300 included in the image forming apparatus 10 according to the third embodiment of the present invention. In the first embodiment described above, in the second spring 420R, the pitch of the winding portion is the same at both end portions and the central portion. On the other hand, in the third embodiment, the second spring 420R has a pitch at both ends of the winding portion smaller than a pitch at the central portion. Instead of making the pitch on both ends of the winding part of the second spring 420R smaller than the pitch on the center part, the pitch on one end part side of the winding part of the second spring 420R is set on the center part. It may be smaller than the pitch.

  In the second embodiment described above, the pitch at the both ends of the winding portion of the second spring 420R may be smaller than the pitch at the center portion, or the winding portion of the second spring 420R. The pitch on the one end side may be smaller than the pitch on the central portion. Other than the portions described above are the same as those in the first embodiment described above, and thus the description thereof is omitted.

  FIG. 9 shows a pressing mechanism 400F of the fixing device 300 included in the image forming apparatus 10 according to the fourth embodiment of the present invention. In the fourth embodiment, in addition to the configuration in the first embodiment described above, for example, a cylindrical partition portion 440 that partitions the first spring 410R and the second spring 420R is provided. In addition to the configuration in the second embodiment described above or in addition to the configuration in the third embodiment described above, for example, a cylindrical partition is provided to partition the first spring 410R and the second spring 420R. Also good. Other than the portions described above are the same as those in the first embodiment described above, and thus the description thereof is omitted.

  As described above, the present invention can be applied to image forming apparatuses such as copiers, facsimile apparatuses, and printers, and fixing apparatuses used in these image forming apparatuses, for example.

DESCRIPTION OF SYMBOLS 10 ... Image forming apparatus 100 ... Image forming part 300 ... Fixing apparatus 310 ... Heating roll 322 ... Heating roll support member 340F, 340R ... 1st rocking | fluctuation member 350F, 350R ... Second swing member 360 ... Contact member 362 ... Pushing member 380F, 380R ... Cam 400F, 400R ... Pressing mechanism 410F, 410R ... First spring 420F, 420R ... Second springs 430F, 430R ... supports 440 ... partitioning part 450 ... pressing force variable means 500 ... operation part N ... contact part

Claims (7)

A rotating body,
A contact member that contacts the rotating body and forms a contact portion through which a recording medium passes with the rotating body;
A pressing mechanism that presses the rotating body and the contact member;
A pressing force variable means for changing the pressing force of the pressing mechanism;
Have
The pressing force varying means is
A first spring;
A second spring disposed inside the first spring;
A fixing device.   The fixing device according to claim 1, wherein the winding direction of the first spring and the second spring is opposite to each other.   The fixing device according to claim 1, wherein the second spring has a maximum interval between adjacent winding portions smaller than a wire diameter of the first spring.   4. The fixing device according to claim 1, wherein the second spring has a pitch at an end side of at least one side of the winding portion smaller than a pitch at the center portion. 5.   The fixing device according to claim 1, further comprising a partition portion that partitions the first spring and the second spring. A rotator support for rotatably supporting the rotator;
A contact member support that is mounted to be able to swing on the rotating body support and supports the contact member;
Further comprising
6. At least one of the first spring and the second spring has one end fixed to either the rotation support portion or the contact member support portion. Fixing device. An image forming unit for forming a developer image on paper;
A fixing device for fixing the developer image formed by the image forming unit to a recording medium;
Have
The fixing device includes:
A rotating body,
A contact member that contacts the rotating body and forms a contact portion through which a recording medium passes with the rotating body;
A pressing mechanism that presses the rotating body and the contact member;
A pressing force variable means for changing the pressing force of the pressing mechanism;
Have
The pressing force varying means is
A first spring;
A second spring disposed inside the first spring;
An image forming apparatus.

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