JP7056195B2 - Fixing device, image forming device and pressing member - Google Patents

Description

The present invention relates to a fixing device, an image forming device, and a pressing member.

In the following Patent Document 1, a heating / pressurizing section for heating an image on a recording material, a belt for sandwiching and transporting the recording material between the heating / pressurizing section, and a belt for transporting the recording material in order along the recording material transporting direction are arranged side by side. Pressurize the belt in an image heating device having a first pressurizing member forming a nip portion by pressurizing the belt toward the heating pressurizing portion and a second pressurizing member having a higher hardness than the first pressurizing member. Described is an image heating device characterized in that the second pressurizing member is configured to abut before the first pressurizing member.

The following Patent Document 2 has a heating member and an endless pressure belt, and the paper after forming the toner image is passed between the heating member and the outer surface of the pressure belt to form the paper. In the fixing device for fixing the toner image to the paper, the flexible first pressing member, which is arranged inside the pressurizing belt and presses the pressurizing belt toward the heating member, and the pressurizing belt. It is harder than the first pressing member, which is arranged inside and presses the pressurizing belt toward the heating member at a position downstream in the paper passing direction from the position where the first pressing member presses the pressurizing belt. Described is a fixing device having a second pressing member and a strength holding member arranged inside the pressure belt and holding a surface on the upstream side in the paper passing direction of the first pressing member. ..

Japanese Unexamined Patent Publication No. 2006-317842 Japanese Unexamined Patent Publication No. 2011-008062

INDUSTRIAL APPLICABILITY The present invention obtains a fixing device capable of suppressing fixing failure as compared with a case where the pressing member is separated from the first surface of the support portion when the belt and the pressurizing portion are separated in the horizontal direction. The purpose is.

The fixing device according to the invention according to the first aspect includes an endless belt, a pressurizing portion arranged horizontally alongside the belt, and a contact state in which the belt and the pressurizing portion are in contact with each other. It has a switching means for switching between the belt and the pressurizing portion in a horizontally separated state, a first surface facing the pressurizing portion side, and a second surface facing upward in the vertical direction. , The support portion arranged inside the belt is supported by the support portion so as to be relatively displaceable in a state of being in contact with the first surface and the second surface, and the belt is attached to the pressurizing portion in the contact state. A pressing member that extends in the vertical direction when viewed from the axial direction of the belt, and includes the pressing member that maintains contact with the first surface of the support portion in the separated state. be.

The fixing device according to the invention according to the second aspect is the fixing device according to the first aspect , in which the pressing member is placed on a horizontal plane in a support posture by the support portion on the contact side with respect to the first surface. It will fall down.

The fixing device according to the invention according to the third aspect is the case where the pressing member is supported from below only in the contact region with respect to the second surface in the support posture by the support portion in the fixing device according to the first aspect . , It is self-supporting or falls to the contact side with respect to the first surface.

The fixing device according to the invention according to the fourth aspect is the fixing device according to the second aspect or the third aspect . The second portion of the above is included, and the specific gravity of the first portion is larger than the specific gravity of the second portion.

The fixing device according to the invention according to the fifth aspect is the fixing device according to the fourth aspect , in which the first portion and the second portion of the pressing member are made of different materials. Is.

The fixing device according to the invention described in the sixth aspect is the fixing device according to the fourth aspect and the fifth aspect .
The pressing member has a thickness in the pressing direction with respect to the pressure portion in the upper portion rather than the lower portion.

The fixing device according to the invention according to the seventh aspect is the fixing device according to any one of the first to third aspects , in which the center of gravity of the pressing member is located below the central portion in the vertical direction. It is something to do.

The fixing device according to the invention according to the eighth aspect is the fixing device according to the seventh aspect , in which the pressing member has a thickness in the pressing direction with respect to the pressure portion at a lower portion than the upper portion.

The fixing device according to the invention according to the ninth aspect is the fixing device according to the eighth aspect , in which the pressing member has a lower specific gravity in the vertical direction larger than the upper specific gravity.

The fixing device according to the invention according to the tenth aspect is the fixing device according to the ninth aspect , in which the pressing member has a first portion on the side of the first surface and a second portion on the side of the pressurizing portion. And, and the specific gravity of the first portion is larger than the specific gravity of the second portion.

The fixing device according to the invention according to the eleventh aspect is the fixing device according to the tenth aspect, in which the second portion is thicker in the pressing direction with respect to the pressure portion at the lower portion than at the upper portion.

The image forming apparatus according to the invention according to the twelfth aspect is arranged on the upper side in the vertical direction with respect to the transfer portion for transferring the toner image to the medium, and is sandwiched between the belt and the pressurizing portion. The fixing device according to any one of the first to eleventh aspects of fixing a toner image on the medium is provided.

The pressing member according to the invention according to the thirteenth aspect extends from a first portion made of metal, which extends in one direction and is thicker than the other side on one side in the width direction intersecting the one direction, and an elastic material. It has a second portion extending in one direction and fixed to one surface of the first portion in the thickness direction.

The pressing member according to the invention described in the fourteenth aspect is the pressing member according to the thirteenth aspect . It has a tapered shape that increases to.

The pressing member according to the invention described in the fifteenth aspect is the pressing member according to the thirteenth aspect or the fourteenth aspect . It is thick.

According to the invention according to the first aspect , when the pressing member is in the separated state, it is possible to suppress fixing failure as compared with the case where the pressing member is separated from the first surface of the support portion.

According to the invention according to the second aspect , when the pressing member is placed on a horizontal plane in a support posture by the support portion, the pressing member is pressed with a simple structure as compared with the one that falls to the side opposite to the contact side with respect to the first surface. The contact between the member and the first surface of the support portion can be maintained.

According to the invention according to the third aspect , when the pressing member is supported from below only in the contact region with respect to the second surface in the support posture by the support portion, the pressing member falls to the side opposite to the contact side with respect to the first surface. In comparison with the above, the contact between the pressing member and the first surface of the support portion can be maintained with a simple structure.

According to the invention according to the fourth aspect , it is less likely to fall to the pressure portion side as compared with the one in which the specific gravity of the first portion and the second portion is constant.

According to the invention according to the fifth aspect , the specific gravity of the first portion can be increased with a simple structure as compared with the case where the first portion and the second portion are made of the same material.

According to the invention according to the sixth aspect , in order to increase the pressure on the downstream side in the medium transport direction for the purpose of ensuring the peelability of the medium from the belt, the pressing member is thicker at the upper part than at the lower part. In the case where the pressing member has a constant specific gravity, the pressing member can be prevented from falling toward the pressure portion.

According to the invention according to the seventh aspect , the contact between the pressing member and the first surface of the supporting portion can be achieved with a simple structure as compared with the case where the center of gravity of the pressing member is located above the central portion in the vertical direction. Can be maintained.

According to the invention according to the eighth aspect , the center of gravity of the pressing member can be lowered with a simple structure as compared with the case where the thickness of the pressing member in the pressing direction with respect to the pressing portion is thinner at the lower part than the upper part.

According to the invention according to the ninth aspect , the center of gravity of the pressing member can be lowered with a simple structure as compared with the case where the specific gravity of the lower portion in the vertical direction of the pressing member is smaller than the specific gravity of the upper portion.

According to the invention according to the tenth aspect , the first portion and the second portion are less likely to fall toward the pressurized portion as compared with the one having a constant specific gravity.

According to the invention according to the eleventh aspect , the degree of freedom in the shape of the second portion can be improved as compared with the one in which the thickness of the second portion is constant.

According to the invention according to the twelfth aspect, the defect of the output image can be suppressed as compared with the one which does not have the fixing device according to any one of the first aspect to the eleventh aspect .

According to the invention according to the thirteenth aspect , it is possible to make it difficult to fall to the side of the second portion in a posture of standing with one thick side facing down as compared with the one having a constant thickness in the width direction. can.

According to the invention according to the fourteenth aspect , it is possible to make it difficult to fall to the side of the second portion in a posture in which the thickness is increased with the other side facing down, as compared with the one having a constant thickness in the width direction. ..

According to the invention according to the fifteenth aspect , in order to increase the pressure on the downstream side in the medium transport direction for the purpose of ensuring the peelability of the medium from the belt, the upper part of the pressing member is thicker than the lower part. As compared with the one having a constant thickness in the width direction, it is possible to suppress the pressing member from tilting toward the pressure portion.

It is a block diagram which shows the image forming apparatus which concerns on one Embodiment of this invention. It is a perspective view which shows the fixing apparatus which concerns on 1st Embodiment used in the image forming apparatus shown in FIG. FIG. 3 is a perspective view showing one end of a fixing belt and a heating roll used in the fixing device shown in FIG. 2 in the axial direction. FIG. 3 is a perspective view showing a configuration of a child lever that supports the guide member of the fixing belt shown in FIG. 3 and a parent lever that movably supports the child lever. It is sectional drawing which shows the nip formation state in which the fixing belt is pressed against a heating roll by the pad member and the block member used in the fixing device shown in FIG. FIG. 5 is a cross-sectional view showing the vicinity of the pad member, the block member, and the heating roll shown in FIG. 5 in an enlarged state. FIG. 3 is a cross-sectional view showing a transitional state in which the fixing belt is pressed against the heating roll only by the pad member among the pad member and the block member used in the fixing device shown in FIG. FIG. 3 is a cross-sectional view showing a state in which the fixing belt used in the fixing device shown in FIG. 3 is released from the nip, which is separated from the heating roll. It is sectional drawing which shows the relationship between the pad member and the pad support member which concerns on a comparative example. It is sectional drawing which shows the relationship between the pad member and the pad support member which concerns on this embodiment. It is sectional drawing which shows the relationship between the pad member and the pad support member which concerns on modification 1. FIG. It is sectional drawing which shows the relationship between the pad member and the pad support member which concerns on modification 2. FIG. It is sectional drawing which shows the relationship between the pad member and the pad support member which concerns on modification 3. FIG. It is sectional drawing which shows the 1st member which has a step in the modification 3.

Hereinafter, embodiments of the fixing device and the image forming device of the present invention will be described with reference to the drawings. In the drawings, the direction indicated by the arrow H is the device height direction, and the direction indicated by the arrow W is the device width direction. Further, in the drawing, the direction indicated by the arrow D orthogonal to each of the device height direction and the device width direction is defined as the device depth direction (the arrow D points to the front side in the device depth direction).

(Overall configuration of image forming device)
FIG. 1 shows an example of the configuration of an image forming apparatus including the fixing apparatus according to the first embodiment of the present invention. As shown in FIG. 1, the image forming apparatus 10 includes a recording paper accommodating unit 12 accommodating a recording paper P as an example of a medium, a toner image forming unit 14, a transport unit 16, a fixing device 70, an ejection unit 20, and a control. It is configured to include a part 22. The toner image forming unit 14 includes four image forming units 24Y, 24M, 24C, 24K, and a transfer unit 26. Here, yellow (Y), magenta (M), cyan (C), and black (K) are examples of toner colors. Each image forming unit 24Y, 24M, 24C, 24K includes a photoconductor 28, a charging device 30, an exposure device 32, a developing device 34, and a removing device 36. In each image forming unit 24Y, 24M, 24C, 24K, a toner image of each color of yellow (Y), magenta (M), cyan (C), and black (K) is formed on the outer peripheral surface of each photoconductor 28.

The photoconductor 28 has a function of holding a toner image developed by the developing device 34. The photoconductor 28 is formed in a cylindrical shape, has a photosensitive layer on its surface, and is rotationally driven in the direction of an arrow by a driving means (not shown). The developing device 34 develops the latent image formed on the photoconductor 28 as a toner image.

The transfer unit 26 includes a transfer belt 38, a primary transfer roll 40 for each color, a drive roll 42, and a secondary transfer roll 44. The posture of the transfer belt 38 is determined by four primary transfer rolls 40, a support roll 46, a drive roll 42, and a tension applying roll 48 that come into contact with the inner peripheral surface thereof. The transfer belt 38 is provided with a cleaning device (not shown) on the downstream side of the secondary transfer unit 50 that comes into contact with the secondary transfer roll 44. The outer peripheral surface of each photoconductor 28 arranged in each image forming unit 24Y, 24M, 24C, 24K is in contact with the lower outer peripheral surface of the transfer belt 38.
Here, the secondary transfer unit 50 is an example of a transfer unit.

The transport unit 16 includes a delivery roll (not shown) that feeds the recording paper P from the recording paper storage unit 12, and a plurality of transport roll pairs (not shown) along the transport path. Further, the recording paper P sent out by the sending roll is conveyed to the secondary transfer unit 50, which is a position opposite to the drive roll 42 and the secondary transfer roll 44. Further, the transport unit 16 transports the recording paper P to the fixing device 70. In the fixing device 70, the toner image secondarily transferred to the recording paper P is fixed on the recording paper P, and the recording paper P is further conveyed to the discharging unit 20 by the conveying unit 16.

In the image forming apparatus 10, the exposure light emitted from the exposure apparatus 32 according to the image data of each color is incident on the outer peripheral surface of the photoconductor 28 charged by the charging device 30, and is applied to the outer peripheral surface of each photoconductor 28. A latent image corresponding to the image data of each color is formed. The latent image formed on the outer peripheral surface of each photoconductor 28 is developed as a toner image of each color by each developing device 34. The toner images of each color on the outer peripheral surface of each photoconductor 28 are primarily transferred to the outer peripheral surface of the transfer belt 38 by the primary transfer rolls 40 facing each other.

On the other hand, the recording paper P is sent out from the recording paper accommodating unit 12 at the timing when the toner images of each color primary transferred to the transfer belt 38 reach the secondary transfer unit 50, and includes the secondary transfer roll 44. It is conveyed to the secondary transfer unit 50. In the secondary transfer unit 50, the toner images of each color on the transfer belt 38 are secondarily transferred to the recording paper P. Further, the recording paper P on which the toner image is transferred is conveyed toward the fixing device 70, heated and pressurized at the contact portion between the heating roll 72 and the fixing belt 74, which will be described later, and the toner image is transferred to the recording paper P. After being fixed, the recording paper P is discharged to the ejection unit 20.

[Fixing device configuration]
Next, the fixing device 70 will be described. FIG. 2 shows the fixing device 70 in a perspective view, and FIG. 3 shows a perspective view of the fixing device 70 in an enlarged state at one end in the longitudinal direction. As shown in FIGS. 2 and 3, the fixing device 70 has a heating roll 72 as an example of a pressurizing portion and a fixing belt 74 as an example of an endless belt that is in contact with or separated from the heating roll 72. I have. The heating roll 72 and the fixing belt 74 are arranged in the device width direction W (an example in the horizontal direction) indicated by the arrow W.
Further, the heating roll 72 and the fixing belt 74 are arranged with the device depth direction indicated by the arrow D of the image forming device 10 as the axial direction (longitudinal direction).

Further, the fixing device 70 heats by rotatably supporting both ends of the heating roll 72 and both ends of the fixing belt 74 and moving relative to the support member 76. A contact / detachment mechanism 78 for pressing the fixing belt 74 against the roll 72 is provided.

(Heating roll)
As shown in FIG. 5, the heating roll 72 is covered with a thin-walled cylindrical core metal made of a steel material, an elastic layer made of silicone rubber or the like coated on the surface of the core metal, and the surface of the elastic layer. It has a multi-layer structure with a release layer containing fluororesin. Inside the heating roll 72, heat sources 73 composed of a plurality of (three in this embodiment) halogen lamps are arranged at intervals from the inner peripheral surface of the heating roll 72 (see FIGS. 2 and 5). ).

(Fixing belt)
As shown in FIG. 5, the fixing belt 74 is an endless belt, and is formed on the outer peripheral surface of a thin-walled cylindrical base material made of a synthetic resin such as a polyimide resin or a polyamide-imide resin, if necessary. , A mold release layer containing a fluororesin is provided.

The fixing belt 74 is configured to pressurize the recording paper P (not shown) by sandwiching it with the heating roll 72, and has a contact portion (nip portion) in which the outer peripheral surface of the heating roll 72 and the outer peripheral surface of the fixing belt 74 come into contact with each other. ), The toner image on the recording paper P is fixed. The internal configuration of the fixing belt 74 will be described later.

(Support member)
As shown in FIG. 5, the support member 76 rotatably supports both ends of the heating roll 72 via bearings (not shown). The support member 76 is supported by a bracket 100 having an arcuate recess 100A into which the support member 76 is fitted.
Further, the support members 76 are provided on both ends of the heating roll 72 in pairs on the left and right.

(Contact / detachment mechanism)
As shown in FIGS. 2 to 5, the contact / detachment mechanism 78, which is an example of the switching means, is provided on both ends of the fixing belt 74 in pairs on the left and right (see FIG. 2).
The contact / detachment mechanism 78 includes a guide member 102 that guides the fixing belt 74. Further, the contact / detachment mechanism 78 includes a child lever 80 that supports the fixing belt 74 via the guide member 102, and a parent lever 82 that supports the child lever 80 so as to be relatively movable.

In the plan view of the fixing device 70, the upper portion 82A of the parent lever 82 is formed in a U shape and opens toward the support member 76 side of the heating roll 72. In the plan view of the fixing device 70, the upper portion 80A of the child lever 80 is formed in a U shape and opens toward the opposite side of the support member 76. The width of the child lever 80 (width in the device depth direction indicated by arrow D) is smaller than the width of the parent lever 82 (width in the device depth direction indicated by arrow D), and the child lever 80 is the parent lever. It is inserted inside the 82. In this state, the parent lever 82 and the child lever 80 move relatively.

More specifically, as shown in FIGS. 3 and 4, the child lever 80 has an inner wall 80B arranged on the inner side (fixing belt 74 side) in the device depth direction indicated by the arrow D and an outer side (fixing belt) of the inner wall 80B. It is provided with an outer wall 80C arranged to face the side facing the 74). The inner wall 80B of the child lever 80 is formed with a recess 81 recessed in the device width direction (arrow W direction) so as not to interfere with the fixing belt 74 (see FIG. 4). The parent lever 82 includes an inner wall 82B arranged inside the device depth direction (on the side of the fixing belt 74) shown by arrow D, and an outer wall 82C arranged facing the outside of the inner wall 82B (on the side opposite to the fixing belt 74). , Is equipped. The inner wall 82B of the parent lever 82 is formed in an L shape so as not to interfere with the fixing belt 74 (see FIG. 4).

The inner wall 80B and the outer wall 80C of the child lever 80 are arranged between the inner wall 82B and the outer wall 82C of the parent lever 82, and the shaft is formed in the through hole formed in the lower part of the inner walls 82B, 80B and the outer walls 80C, 82C. The portion 84 is penetrated. As a result, the child lever 80 and the parent lever 82 move relatively about the shaft portion 84 (rotate in the present embodiment). That is, the child lever 80 and the parent lever 82 move independently of the support member 76.

A hole 80E (see FIG. 4) is formed in the wall 80D along the device depth direction (D direction) of the upper portion 80A of the child lever 80, and the pin member 86 is inserted into the hole 80E. The base end of the pin member 86 is fixed to the wall 80D (see FIGS. 4 and 5). The axial direction of the pin member 86 is a direction that intersects the axial direction of the shaft portion 84. A long hole 82E is formed in the wall 82D along the device depth direction (D direction) of the upper portion 82A of the parent lever 82 (see FIG. 3). The elongated hole 82E is formed on the wall 82D so that the major axis portion is in the device height direction (H direction). The outer diameter of the shaft portion of the pin member 86 is smaller than the minor diameter portion of the long hole 82E, and the pin member 86 has a long hole with the tip end side of the pin member 86 penetrating the long hole 82E. It is possible to move within 82E. That is, the tip of the pin member 86 is not fixed to the wall 82D of the parent lever 82, but is a free end.

A spring 96 that urges the wall 80D of the child lever 80 toward the support member 76 of the heating roll 72 is attached to the wall 82D of the parent lever 82. The spring 96 is arranged around the pin member 86, and in this state, one end of the spring 96 is fixed to the wall 82D of the parent lever 82 with a fixture 88 (see FIG. 4).

As shown in FIGS. 2 and 3, a roll member 90 is arranged in the vertical intermediate portion of the parent lever 82, and the shaft portion 90A of the roll member 90 is rotatably supported by the inner wall 82B and the outer wall 82C. Has been done. The roll member 90 is provided on each of the pair of left and right parent levers 82.

The cam 92 is rotatably supported on the wall 100B on the roll member 90 side in the device width direction (arrow W direction) of the bracket 100. A pair of left and right cams 92 are provided on both sides of the fixing device 70 in the longitudinal direction, and the pair of left and right cams 92 are connected by a rotation shaft 94 and rotate integrally. The cam 92 is configured such that the radius of the outer peripheral surface 92A from the center of the rotating shaft 94 continuously changes in the circumferential direction, and the outer peripheral surface 92A of the cam 92 comes into contact with the outer peripheral surface of the roll member 90. There is. The cam 92 is rotationally driven by a motor (not shown) connected to the axial end of the rotating shaft 94.

As the position of the roll member 90 changes with the rotation of the cam 92, the parent lever 82 moves relative to the support member 76 of the heating roll 72 around the shaft portion 84 in the direction of approaching or separating from the support member 76 of the heating roll 72. It is designed to do.

As shown in FIGS. 3 and 5, the guide member 102 is arranged at both ends of the fixing belt 74. The guide member 102 has a main body 102A arranged along the vertical direction on the outside of both ends of the fixing belt 74 in the longitudinal direction, and a circle formed on the main body 102A along the outer peripheral surfaces of both ends of the fixing belt 74. It is provided with an arc-shaped outer guide portion 102B. In FIG. 3, only one end of the fixing belt 74 is shown, and the other end of the fixing belt 74 is omitted.
The guide member 102 is fixed to the child lever 80 with a fastener (not shown). As a result, the guide member 102 rotates about the shaft portion 84 integrally with the child lever 80 with respect to the parent lever 82.

The contact / detachment mechanism 78 having the above configuration is an example of a nip forming state in which the fixing belt 74 and the heating roll 72 are in contact with each other and an example in a separated state in which the fixing belt 74 and the heating roll 72 are separated from each other. It has a function to switch to the nip release state.
The contact / detachment mechanism 78 is in a full latch state when a portion having a large radius of the outer peripheral surface 92A of the cam 92 is in contact with the roll member 90, and the fixing belt 74 and the heating roll 72 are in contact with each other to form a nip. It is in a formed state.
In this nip forming state, the block member 120 described later presses the fixing belt 74 against the heating roll 72. Further, the pad member 122, which will be described later, also presses the fixing belt 74 against the heating roll 72 (see FIGS. 6 and 9).

Further, in the contact / detachment mechanism 78, when the portion having the smallest radius of the outer peripheral surface 92A of the cam 92 is in contact with the roll member 90, the latch release state is set, and the fixing belt 74 and the heating roll 72 are separated from each other to release the nip. Make it a state.
In this nip release state, the block member 120 described later is separated from the heating roll 72. Further, the pad member 122, which will be described later, is also separated from the heating roll 72 (see FIGS. 8 and 11).

(1st mounting member and 2nd mounting member)
As shown in FIGS. 5 and 6, the first mounting member 104 and the second mounting member 106 are fixed to the main body portion 102A of the guide member 102. The first mounting member 104 and the second mounting member 106 are arranged along the longitudinal direction of the fixing belt 74.

(1st mounting member)
The first mounting member 104 has a horizontal plate extending in the device width direction W and a side opposite to the heating roll 72 of the horizontal plate in a cross-sectional view seen from the device depth direction D (hereinafter, simply referred to as “cross-sectional view”). It is formed in an L shape by a vertical plate extending downward from the end of the device in the height direction H of the device by refracting.
Further, the upper portion of the horizontal plate is fixed to the main body portion 102A of the guide member 102.
Further, on the surface of the vertical plate opposite to the heating roll 72, the felt member 108 is fixed by adhesion or the like so as to come into contact with the inner peripheral surface of the fixing belt 74. The felt member 108 is impregnated with oil for lubrication, and the oil is supplied to the inner peripheral surface of the fixing belt 74 by contacting the inner peripheral surface.
Although the first mounting member 104 is a cross section in FIG. 5, hatching is omitted in order to make the configuration easy to understand.

(Second mounting member)
The second mounting member 106 has a U-shaped mounting portion 106A that opens to the side of the heating roll 72 in a cross-sectional view on the inner center side of the fixing belt 74, and is formed on the main body portion 102A of the guide member 102. It is fixed.
Further, a spring 114 is arranged on the mounting portion 106A. One end of the spring 114 on the opposite side of the heating roll 72 is fixed to the bottom surface of the U-shaped cross-sectional view of the mounting portion 106A, and the other end on the heating roll 72 side is a pad described later. The back surface 116C (see FIG. 6) of the support member 116 is fixed.

(Sliding sheet)
As shown in FIG. 5, inside the fixing belt 74, an arc-shaped sliding sheet 103 is provided along the inner peripheral surface of the fixing belt 74 and for sliding the fixing belt 74. .. The sliding sheet 103 is attached to the first attachment member 104 and the second attachment member 106 fixed to the main body portion 102A of the guide member 102, respectively.
The sliding sheet 103, the first mounting member 104, and the second mounting member 106 are arranged along the longitudinal direction of the fixing belt 74.

≪Structure of main parts≫
Here, the pad member, which is a main part, and the structure around the pad member will be described.

<< Embodiment >>
As shown in FIGS. 5 and 6, the fixing device 70 includes a pad member 122, a pad support member 116, a first support member 110, a second support member 112, a block member 120, and a limiting means 130. It is equipped with.
(First support member)
Inside the fixing belt 74, the first support member 110 is bent downward in a curved shape from a horizontal plate extending in the width direction W of the device and an end portion of the horizontal plate opposite to the heating roll 72. It is formed in an L shape with a vertical plate extending from the surface.
A hole 110A penetrating in the vertical direction is formed on the side of the heating roll 72 of the horizontal plate. An upper end portion of the second support member 112, which will be described later, is inserted and fixed in the hole portion 110A.
Further, the surface of the horizontal plate facing downward is an inner surface 110B in contact with the upper surface 120U of the block member 120 described later.
The first support member 110 is arranged along the inner surface side of the first mounting member 104, and is fixed to the main body portion 102A of the first mounting member 104 and the guide member 102.

(Second support member)
The second support member 112 extends upward in a curved shape from the horizontal plate extending in the width direction W of the device and the end portion of the horizontal plate on the heating roll side inside the fixing belt 74 in a cross-sectional view. It is formed in an L shape with a vertical plate.
An opening penetrating in the width direction W of the device is formed in the central portion of the vertical plate. The mounting portion 106A of the second mounting member 106 is inserted and fixed in this opening.
Further, the upper one end portion of the vertical plate is inserted and fixed in the hole portion 110A of the first support member 110.
Further, a hole 112A is formed on the side of one upper end of the vertical plate so as to penetrate in the width direction W of the device and into which the protrusion 120C of the block member 120 described later is inserted.
Further, the other end of the horizontal plate opposite to the heating roll 72 is fixed to the lower end of the surface of the vertical plate of the first support member 110 facing the heating roll 72.
The second support member 112 and the first support member 110 form a rectangular frame.

(Regulatory member)
As shown in FIG. 6, the restricting member 113 is formed in a rectangular shape in a cross-sectional view, and is a surface of the second supporting member 112 facing the heating roll 72, and the second supporting member 112 excluding the hole 112A. It is arranged on the surface of the. The regulating member 113 is a member in which the surface of the heating roll 72 facing the side and the tail portion 120B of the block member 120, which will be described later, come into contact with each other.
The restricting member 113 supports the block member 120 so as not to recede to the opposite side to the heating roll 72 when the block member 120 is pressed against the heating roll 72 via the fixing belt 74 in the nip forming state described later. That is, the regulating member 113 has a function of regulating the relative position of the block member 120 with respect to the second support member 112 in the device width direction W.
Further, the restricting member 113 uses rubber in this embodiment. As the rubber, a synthetic resin material can be used.
Further, when the blocking member 120 presses the fixing belt 74 against the heating roll 72, the restricting member 113 is sufficiently pressed to form a fixing nip between the outer peripheral surface of the fixing belt 74 and the outer peripheral surface of the heating roll 72. Any material may be used as long as it has a hardness that allows pressure to be applied.

(Pad support member)
FIG. 6 shows a pad support member 116 which is an example of a support portion.
The pad support member 116 extends in the device height direction H and has a thickness in the device width direction W in a cross-sectional view, and the device width from one end of the lower side of the vertical plate toward the heating roll 72. It is formed in an L shape by a horizontal plate extending in the direction W and having a thickness in the device height direction H.
The vertical plate is formed by connecting a first surface 116A facing the heating roll 72 side, a back surface 116C facing the side opposite to the first surface 116A, and an upper end portion of the first surface 116A and an upper end portion of the back surface 116C. It has an upper surface 116D.
The horizontal plate faces the second surface 116B facing upward (vertically) in the height direction H of the device, the second surface 116B, and the side opposite to the upper surface 116D, and the lower end portion and the second surface of the first surface 116A. It has a lower surface 116E formed by connecting a lower end portion extending downward from the 116B.
The first surface 116A and the second surface 116B support the pad member 122, which will be described later, without being fixed so as to be relatively displaceable from the side opposite to the heating roll 72 and the lower side in the vertical direction.
Further, a spring 114 is fixed to the back surface 116C.

(Pad member)
As shown in FIG. 6, the pad member 122, which is an example of the pressing member, includes a first member 122A and a second member 122B. In the present embodiment, in a cross-sectional view, the first member 122A is a portion serving as a metal pedestal arranged on the side of the first surface 116A of the pad support member 116, and the second member 122B is the first member. It is a foamed resin body integrally arranged on the side of the heating roll 72 of 122A.
Further, as shown in FIG. 9, the surface of the first member 122A on the side of the first surface 116A is a back surface 122C that comes into contact with the first surface 116A.

As shown in FIGS. 6 to 8 and 10, the pad member 122 is supported in a state of being in contact with the first surface 116A and the second surface 116B of the pad support member 116, and is supported by the first surface 116A and the second surface. It is possible to displace relative to any of 116B in the direction away from it. In this contact state, the fixing belt 74 is pressed against the heating roll 72.
Further, the pad member 122 extends in the vertical direction when viewed from the axial direction of the fixing belt 74, and is configured to maintain contact with the first surface 116A of the pad support member 116 in the nip release state described later.

Specifically, the pad member 122 is supported by the pad support member 116 without being fixed in contact with the first surface 116A and the second surface 116B of the pad support member 116, and the pad support member 116 and the pad. The member 122 is in a state where it can be displaced relative to each other.
The "relative displacement" of the pad member 122 means that the pad member 122 is in contact with either the first surface 116A or the second surface 116B of the pad support member 116.

Further, as shown in FIG. 10, the pad member 122 extends in the direction of the device height direction H, which is an example of the vertical direction, in a cross-sectional view, and is a lower portion that contacts the second surface 116B of the pad support member 116. Therefore, it has a height dimension corresponding to the length of the first surface 116A in the device height direction H.
Further, the thickness of the first member 122A and the second member 122B in the device width direction W both have a dimension shorter than the height dimension of the pad member 122.
That is, the shape of the pad member 122 in the cross-sectional view is long in the device height direction H and short in the device width direction W.

The pad member 122 in the present embodiment having such a shape maintains contact with the first surface 116A of the pad support member 116 in the nip release state described later.
Further, when the pad member 122 is placed on a horizontal plane in a support posture by the pad support member 116, the pad member 122 falls to the contact side with respect to the first surface 116A.
Further, when the pad member 122 is supported from below only in the contact region with respect to the second surface 116B in the support posture by the pad support member 116, the pad member 122 either stands on its own or falls to the contact side with respect to the first surface 116A.

Specifically, the center of gravity G of the pad member 122 is located at a position biased toward the first surface 116A with respect to the center of gravity G indicated by the virtual line extending directly upward from the end of the second surface 116B. It is set at the position of the center of gravity G (hereinafter, also simply referred to as “center of gravity G”) shown by the solid line.

Further, when the pad member 122 is placed on a horizontal plane in a support posture by the pad support member 116, the position of the center of gravity G is set at a position where a force acts in a direction of tilting toward the contact side with respect to the first surface 116A.

Further, when the pad member 122 is supported from below only in the contact region with respect to the second surface 116B in the support posture by the pad support member 116, the pad member 122 either stands on its own or has a force in a direction of tilting toward the first surface 116A. The center of gravity G is set at the position where

Further, the pad member 122 makes the specific gravity of the first member 122A on the side of the first surface 116A larger than the specific gravity of the second member 122B on the side of the heating roll 72.
In this embodiment, the pad member 122 has the first member 122A and the second member 122B made of different materials so that the specific gravity of the first member 122A is larger than the specific gravity of the second member.
Specifically, a metal material is used for the first member 122A, and an elastic material is used for the second member 122B. More specifically, a steel plate, a stainless steel plate, or the like is used for the first member 122A, and a foamed resin body is used for the second member 122B.
As a result, the center of gravity G of the pad member 122 is biased toward the first surface 116A.

Further, the thickness of the second member 122B in the pressing direction against the heating roll 72 is thicker on the upper side than on the lower side in the cross-sectional view.
In this way, even in the pad member 122 which has a shape that seems to fall toward the heating roll 72 at first glance, the center of gravity G of the pad member 122 is biased toward the first surface 116A, so that the pad member 122 can be padded. Contact with the first surface 116A of the support member 116 is maintained. That is, the pad member 122 is unlikely to fall in the direction opposite to the arrow D direction without being supported by the fixing belt 74.

Further, in the present embodiment, the second member 122B, which is a foamed resin body of the pad member 122, is made of a foamed resin such as a silicone resin, and is largely elastically deformed by a nip load.
Further, the pad member 122 is urged toward the heating roll 72 by a spring 114 arranged in the mounting portion 106A of the second mounting member 106. The second mounting member 106 is fixed to the main body portion 102A of the guide member 102, and the pad member 122 is supported so as to be accessible and separate from the main body portion 102A of the guide member 102.
Further, the pad member 122 may have a two-layer structure in which foamed resins having different foaming ratios are laminated, and the configuration of the pad member 122 may be changed, for example, a single-layer structure may be used.

Further, as shown in FIG. 5, the pad member 122 is provided inside the fixing belt 74, and is a member that presses the outer peripheral surface of the fixing belt 74 against the outer peripheral surface of the heating roll 72 by the contact / detachment mechanism 78.

(Block member)
As shown in FIG. 5, the block member 120 is a member provided inside the fixing belt 74 and presses the outer peripheral surface of the fixing belt 74 against the outer peripheral surface of the heating roll 72 by the contact / detachment mechanism 78.
The block member 120 is sandwiched between the outer peripheral surface of the fixing belt 74 and the outer peripheral surface of the heating roll 72, and peels the recording paper P to be fixed while passing from the lower side to the upper side from the outer peripheral surface of the fixing belt 74. Has a function.
A shape for exerting this function is formed on the head 120A described later of the block member 120.

As shown in FIG. 6, the block member 120 includes a head 120A, a tail 120B, a protrusion 120C, and a head 120A and a tail 120B in order from the side of the heating roll 72 in the device width direction W. It has an upper surface 120U to be connected and a lower surface 120D.
Further, the block member 120 has a length corresponding to the width dimension of the fixing belt 74 in the device depth direction D.

The head 120A has a thickness in the height direction H of the device in a cross-sectional view, and a curved surface in contact with the inner peripheral surface of the fixing belt 74 is formed on the side of the heating roll 72.
This curved surface is formed in a shape along the outer peripheral surface of the facing heating roll 72 in the nip forming state described later. Further, the upper portion of this curved surface (downstream side in the transport direction of the recording paper P) has a curvature smaller than the curvature of the curved surface that continues from the curved surface and goes in the direction opposite to the curved surface (the side opposite to the side of the heating roll 72). Another curved surface is formed.
The tail portion 120B has a thickness smaller than that of the head portion 120A in the direction of the device height direction H in a cross-sectional view, and the surface of the second support member 112 in contact with the regulating member 113 is on the side of the heating roll 72. Is formed in the vertical direction on the opposite side.
The protrusion 120C will be described in detail in the description of the limiting means 130.
The upper surface 120U connects the head portion 120A and the tail portion 120B on the side opposite to the pad member 122 in the height direction H of the device in a cross-sectional view.
The lower surface 120D connects the head portion 120A and the tail portion 120B on the side of the pad member 122 in the height direction H of the device in a cross-sectional view.
Further, the side of the head portion 120A of the lower surface 120D is in contact with the upper surface of the pad member 122.

(Arrangement relationship between pad member and block member)
In the fixing device 70, the pad member 122 is arranged on the upstream side in the transport direction of the recording paper P (FIG. 1) passing through the contact portion (nip portion) between the heating roll 72 and the fixing belt 74, and is more than the pad member 122. The block member 120 is arranged on the downstream side in the transport direction of the recording paper P. In other words, the pad member 122 is arranged on the upstream side in the transport direction of the recording paper P that passes through the contact portion (nip portion) between the heating roll 72 and the fixing belt 74 with respect to the block member 120.
In the present embodiment, at the contact portion between the heating rolls 72 arranged in the device width direction W and the fixing belt 74, a transport path for the recording sheet P is arranged along the vertical direction, and the pad member 122 is arranged on the lower side in the vertical direction. Is arranged, and the block member 120 is arranged on the upper side in the vertical direction. Further, the lower surface of the block member 120 is in contact with the upper surface of the pad member 122.

Further, as shown in FIG. 6, in the nip forming state described later, the first support member 110, the second support member 112, the first mounting member 106, and the pad support member 116 are obliquely downward on the side of the heating roll 72. It is suitable. As a result, the pad member 122 is also in a posture of facing diagonally downward on the side of the heating roll 72.
The posture of the pad member 122 facing diagonally downward in this nip-forming state is referred to as an "inclined posture".

Further, the block member 120 can be relatively displaced by being in contact with the regulating member 113 of the second support member 112 and the pad member 122 from the side opposite to the heating roll 72 and from the lower side in the vertical direction in the nip forming state described later. It is supported without being fixed to.
The posture of the block member 120 at this time is called "appropriate posture".
Further, the "relative displacement" of the block member 120 means that the block member 120 is separated from the side opposite to the heating roll 72 and from the lower side in the vertical direction.

≪Action / effect of the main part≫
Next, the operation and effect of this embodiment will be described.

As shown in FIGS. 5 and 6, in the fixing device 70, when a portion having a large radius of the outer peripheral surface 92A of the cam 92 is in contact with the roll member 90, it is in a full latch state and is in a nip forming state.

(Nip formation state)
Explaining with reference to FIG. 5, when the parent lever 82 moves to the first position, the first support member 110 and the second support member 112 fixed to the guide member 102 that rotates integrally with the child lever 80 are heated by the heating roll 72. Move to the side.
The pad support member 116 attached via the spring 114 to the attachment portion 106A of the second attachment member 106 provided on the moved second support member 112 moves in a state of being urged toward the heating roll 72. ..
As shown in FIG. 6, the pad member 122 supported without being fixed to the first surface 116A and the second surface 116B of the pad support member 116 so as to be relatively displaceable by pushing the inner peripheral surface of the fixing belt 74. , The fixing belt 74 is pressed against the heating roll 72.
At this time, the pad member 122 is in an inclined posture.

In this state, the fixing belt 74 is pressed against the heating roll 72 by the pad member 122 and the block member 120.
That is, the portion where the fixing belt 74 is pressed against the heating roll 72 by the pad member 122 and the block member 120 becomes a contact portion (nip portion), and the recording paper P passes through this contact portion from the lower side to the upper side. , The toner image on the recording paper P is fixed.

(Nip release state)
As shown in FIG. 8, in the nip release state in which the fixing belt 74 and the heating roll 72 are separated from each other, the pad member 122 attached to the second mounting member 106 of the guide member 102 via the spring 114 is from the heating roll 72. It is separated.

At this time, the portion having the smallest radius of the outer peripheral surface 92A of the cam 92 comes into contact with the roll member 90, and the latch is released and the nip is released.

Further, in the nip release state, the pad support member 116 supported only by the spring 114 descends downward due to gravity, and the first surface 116A faces diagonally downward toward the heating roll 72 (not shown).
In this state, the fixing belt 74 is separated from the heating roll 72, the tension applied to the fixing belt 74 is weak, and the fixing belt 74 cannot suppress the pad member 122 from collapsing.
However, since the center of gravity G of the pad member 122 is set at the position indicated by the solid line closer to the first surface 116A of the pad support member 116, the pad member 122 has the first surface 116A of the pad support member 116. Contact is maintained.
That is, the pad member 122 is unlikely to fall in the direction opposite to the arrow D direction.
As a result, the pad member 122 is supported in a state of being in contact with the first surface 116A of the pad support member 116 by the force acting in the direction indicated by the arrow D, even though the pad member 122 is not fixed to the pad support member 116. ..
At that time, the processing accuracy of either or both of the lower surface of the pad member 122 (the surface of the pad support member 116 in contact with the second surface 116B) and the second surface 116B may be low. Even in this case, the pad member 122 is supposed to maintain contact with the first surface 116A of the pad support member 116 by setting the specific gravity and the position of the center of gravity G described above.
Similarly, when shifting from the nip forming state to the nip release state, the pad member 122 is subjected to an acceleration in a direction away from the first surface 116A of the pad support member 116, but the pad member 122 is subjected to the pad support member 116. Contact with the first surface 116A of the surface is maintained.

(Return operation to nip formation state)
The operation when the pad member 122 in the inclined posture described above returns to the same posture as the nip forming state shown in FIG. 5 or 6 will be described.

When the cam 92 shown in FIG. 8 rotates and the guide member 102 rotates about the shaft portion 84 integrally with the child lever 80 with respect to the parent lever 82, the first and second support members 110 and 112 are shown in FIG. 7. After the transition state shown in FIG. 6, the nip formation state shown in FIG. 6 is obtained.
Specifically, when the pad member 122, which is in a descending and inclined posture, pushes the fixing belt 74 in the transition state shown in FIG. 7, the outer peripheral surface of the fixing belt 74 rotates in the direction of arrow B. It comes into contact with the outer peripheral surface of the heating roll 72.

Then, as shown in FIG. 6, when the nip is formed, the positions of the pad member 122 and the block member 120 are fixed by pushing the heating roll 72 via the inner peripheral surface of the fixing belt 74.
As described above, by the above series of operations, a nip is formed again between the outer peripheral surface of the fixing belt 74 and the outer peripheral surface of the heating roll 72, and the next fixing can be prepared.

In addition to the series of operations from the nip forming state to the nip release state described above, the pad member 122 can also be subjected to the attachment / detachment work of the fixing device 70 to the image forming device 10 or the transfer work of the fixing device 70. Contact with the pad support member 116 is maintained.

On the other hand, in the comparative example shown in FIG. 9, the center of gravity G of the pad member 122 is located above the central portion of the pad member 122 in the device height direction H in the nip-released state.
Therefore, the pad member 122 is displaced in the direction in which the back surface 122C of the pad member 122 is separated from the first surface 116A of the pad support member 116 and is tilted in the direction of arrow F, and its posture is not stable (in FIG. 9 by a virtual line). The state shown.). That is, it is difficult for the pad member 122 to maintain contact with the first surface 116A of the pad support member 116.
Although the fixing belt 74 is not shown in FIG. 9, in the nip release state, the fixing belt 74 does not rotate and the tension is weak, so that the pad member 122 is separated from the first surface 116A and the fixing belt 74 Tilt in the direction of approaching or contacting the inner peripheral surface of the above (in the direction of arrow F above).

Then, in the nip forming state, the posture of the pad member 122 may not return to the inclined posture (initial proper posture), and the nip forming failure is likely to occur.
As a result, the nip width formed by the fixing belt 74 and the heating roll 72 fluctuates, and fixing failure is likely to occur.
For example, when the nip width is narrowed, a sufficient amount of heat is not given to the toner, causing insufficient melting of the toner, insufficient glossiness of the formed image, and the like, resulting in poor fixing. Further, when the nip width is widened, the toner is excessively melted, and the glossiness of the formed image is increased more than necessary, so that fixing failure also occurs.

On the other hand, the fixing device 70 according to the present embodiment has a contact state in which the fixing belt 74, the heating roll 72 arranged horizontally side by side with the fixing belt 74, and the fixing belt 74 and the heating roll 72 are in contact with each other. , A contact / detachment mechanism 78 that switches the fixing belt 74 and the heating roll 72 into a separated state in which they are separated in the horizontal direction, a first surface 116A facing the side of the heating roll 72, and a second surface 116B facing upward in the vertical direction. , And the pad support member 116 arranged inside the fixing belt 74 is supported by the pad support member 116 so as to be relatively displaceable in contact with the first surface 116A and the second surface 116B, and is fixed in the contact state. The pad member 122 that presses the belt 74 against the heating roll 72 extends in the vertical direction when viewed from the axial direction of the fixing belt 74, and the contact of the pad support member 116 with the first surface 116A is maintained in the nip-released state. It is provided with a pad member 122.

As a result, when the nip is released, the pad member 122 can suppress the fixing failure as compared with the one in which the pad member 122 is separated from the first surface 116A of the pad support member 116.

Further, when the pad member 122 is placed on a horizontal plane in a support posture by the pad support member 116, the pad member 122 falls to the contact side with respect to the first surface 116A.

Thereby, the pad member 122 maintains the contact between the pad member 122 and the first surface 116A of the pad support member 116 with a simple structure as compared with the one in which the pad member 122 falls to the side opposite to the contact side with respect to the first surface 116A. Can be done.
At that time, the processing accuracy of either or both of the lower surface of the pad member 122 (the surface of the pad support member 116 in contact with the second surface 116B) and the second surface 116B may be low. Even in this case, the pad member 122 can maintain contact with the first surface 116A of the pad support member 116 by setting the specific gravity and the position of the center of gravity G described above.
Similarly, when shifting from the nip forming state to the nip release state, the pad member 122 is subjected to an acceleration in a direction away from the first surface 116A of the pad support member 116, but the pad member 122 is subjected to the pad support member 116. Contact with the first surface 116A of the surface is maintained.

Further, when the pad member 122 is supported from below only in the contact region with respect to the second surface 116B in the support posture by the pad support member 116, the pad member 122 either stands on its own or falls to the contact side with respect to the first surface 116A.

Thereby, the pad member 122 maintains the contact between the pad member 122 and the first surface 116A of the pad support member 116 with a simple structure as compared with the one in which the pad member 122 falls to the side opposite to the contact side with respect to the first surface 116A. Can be done.

Further, the pad member 122 is configured to include a first member 122A on the side of the first surface 116A and a second member 122B on the side of the heating roll 72, and the specific gravity of the first member 122A is that of the second member 122B. It is larger than the specific density.

As a result, the first member 122A and the second member 122B are less likely to fall toward the pressurized portion than those having a constant specific gravity.

Further, in the pad member 122, the first member 122A and the second member 122B are made of different materials.

As a result, the specific gravity of the first member 122A can be increased with a simple structure as compared with the case where the first member 122A and the second member 122B are made of the same material.

Further, the thickness of the second member 122B in the pressing direction against the heating roll 72 is thicker at the upper part than at the lower part.

As a result, in order to increase the pressure on the downstream side of the recording paper P in the transport direction for the purpose of ensuring the peelability of the recording paper P from the fixing belt 74, the pressing member is thicker at the upper part than at the lower part. In the case where the pad member 122 has a constant specific gravity, the pad member 122 can be prevented from falling toward the heating roll 72.

Further, the image forming apparatus according to the present embodiment has a secondary transfer unit 50 that transfers the toner image to the recording paper P, and a fixing belt 74 and a heating roll 72 that are arranged on the upper side in the vertical direction with respect to the secondary transfer unit 50. It is provided with a fixing device 70 according to any one of the above aspects for fixing a toner image on a recording paper P sandwiched between the two.

Thereby, the defect of the output image can be suppressed as compared with the one which does not have the fixing device 70 according to any one of the above.

[Modification example]
The fixing device 70 in the modified example is the same as that of the present embodiment except that the configuration of the pad member 122 is different. The same parts as those of the present embodiment are referred to with the same reference numerals, and the description thereof will be omitted.

(Modification 1)
As shown in FIG. 11, the pad member 1221 in the first modification has the center of gravity positioned below the central portion in the vertical direction.
Specifically, in cross-sectional view, the thickness of the first member 1221A of the pad member 1221 is uniform from the upper part to the lower part, but the second member 1221B is on the lower side rather than the upper side. Is getting thicker. As a result, the center of gravity G indicated by the virtual line when the upper side is thick is lowered in the direction of the arrow D, and the position of the center of gravity G can be positioned below the central portion indicated by the solid line.

As a result, the contact between the pad member 1221 and the first surface 116A of the pad support member 116 is maintained with a simple structure as compared with the case where the center of gravity of the pad member 1221 is located above the central portion in the vertical direction. be able to.

Further, the pad member 1221 is thicker in the pressing direction with respect to the heating roll 72 at the lower portion than at the upper portion.
Specifically, in cross-sectional view, the thickness of the first member 1221A of the pad member 1221 is uniform from the upper part to the lower part, but the second member 1221B is the upper part in the pressing direction against the heating roll 72. The lower side has a thicker dimension than the side.
As a result, the center of gravity G indicated by the virtual line when the upper side is thick is lowered in the direction of the arrow D, and the position of the center of gravity G can be positioned below the central portion.

As a result, the center of gravity of the pad member 1221 can be lowered with a simple structure as compared with the case where the thickness of the pad member 1221 in the pressing direction with respect to the heating roll 72 is thinner at the lower part than the upper part.
Further, the degree of freedom in the shape of the second member 1221B can be improved as compared with the case where the thickness of the second member 1221B is constant.

Further, although not shown, the pad member 1221 may have a lower specific gravity in the vertical direction larger than the upper specific gravity.
Specifically, in a cross-sectional view, the thicknesses of the first member 1221A and the second member 1221B of the pad member 1221 are the same as in each of the above embodiments, but the pad member 1221 has a lower specific gravity in the vertical direction. It shall be larger than the specific gravity of the upper part.
As an example, the first member 1221A may use different materials for the upper part and the lower part, and a material having a higher specific density than the upper part may be used for the lower part. Further, in the lower part of the second member 1221B, a region where the density of the foamed resin body is increased can be set on the side of the first member 1221A which does not form a nip. Further, these first member 1221A and the second member 1221B may be combined.
As a result, the center of gravity G indicated by the virtual line when the upper side is thick is lowered in the direction of the arrow D, and the position of the center of gravity G can be positioned below the central portion of the pad member 1221 in the device height direction H. can.

As a result, the center of gravity of the pad member 1221 can be lowered with a simple structure as compared with the case where the specific gravity of the lower portion in the vertical direction of the pad member 1221 is smaller than the specific gravity of the upper portion.

(Modification 2)
As shown in FIG. 12, the pad member 1222 in the second modification is configured to include the first member 1222A on the side of the first surface 116A and the second member 1222B on the side of the heating roll 72, and is the first member. The specific gravity of 1222A is larger than the specific gravity of the second member 1222B.
Specifically, the pad member 1222 makes the thickness of the first member 1222A thicker than that of the first member 1221A of the modification 1, and the second member 1222B is lower than the upper side. Can be thicker on the side of. As an example, by increasing the thickness of the first member 1222A in which a metal material is used, the first member 1222A having a larger specific gravity than the second member 1222B which is a foamed resin body can be obtained.
As a result, the center of gravity G indicated by the virtual line when the specific gravity of the first member 1222A and the second member 1222B is constant is lowered in the direction of the arrow D, and the position of the center of gravity G is set in the device height direction H of the pad member 1222. It can be located below the central portion and on the side of the first member 1222A.

As a result, the first member 1222A and the second member 1222B are less likely to fall to the side of the heating roll 72 as compared with those having a constant specific gravity.

(Modification 3)
As shown in FIG. 13, the pad member 1223 in the third modification has a first metal member 1223A that extends in one direction and is thicker than the other on one side in the width direction intersecting the one direction. .. Further, it is made of an elastic material and has a second member 1223B extending in one direction and fixed to one surface of the first member 1223A in the thickness direction.
Specifically, the first member 1223A uses a metal material whose lower side is thicker than the upper side. Further, the second member 1223B is fixed to the side opposite to the back surface 1223C of the first member 1223A in the device width direction W (the side of the heating roll 72).
As an example, the first member 1223A is configured to increase in thickness from the upper side to the lower side.
As a result, the center of gravity G indicated by the virtual line when the specific gravity of the first member 1223A and the second member 1223B is constant decreases in the direction of the arrow D. As a result, the position of the center of gravity G can be positioned below the central portion shown by the solid line and on the side of the first member 1223A.

As a result, it is possible to prevent the first member 1223A from falling down in a standing posture with one side facing down as compared with a member having a constant thickness in the width direction.

Further, the pad member 1223 has a tapered shape in which the first member 1223A gradually increases in thickness from the other in the width direction when viewed from one direction.
Specifically, in cross-sectional view, the first member 1223A has a tapered shape in which the thickness gradually increases from the upper side to the lower side. That is, the thickness of the first member 1223A is thin on the upper side, gradually increases toward the lower side and toward the opposite side of the back surface 1223C, and the thickness of the lower part is about twice the thickness of the upper part. It is tapered.
The thickness of the lower part of the first member 1223A may be thicker than the thickness of the upper part, and for example, the thickness of the lower part may be about 1.2 to 8 times the thickness of the upper part. This magnification is not particularly limited, and if the thickness of the upper portion of the first member 1223A is set to be thin, it means that the thickness of the lower portion is set to be thick corresponding to this.

As a result, the center of gravity G indicated by the virtual line when the specific gravity of the first member 1223A and the second member 1223B is constant decreases in the direction of the arrow D. As a result, the position of the center of gravity G can be positioned below the central portion of the pad member 1223 in the device height direction H and on the side of the first member 1223A.

As a result, it is possible to prevent the first member 1223A from falling down in a standing posture with the other side increasing in thickness as compared with a member having a constant thickness in the width direction.

Further, as shown in FIG. 14 , the pad member 1224 has one or a plurality of steps in which the first member 1224A gradually increases in thickness from the other in the width direction when viewed from one direction to one. Is what you are doing.
Specifically, in cross-sectional view, the first member 1224A has a two-step step in which the thickness gradually increases from the upper side to the lower side. That is, the thickness of the first member 1224A is thin on the upper side, gradually increases on the opposite side of the back surface 1224C toward the lower side, and the thickness of the lower part is about four times the thickness of the upper part. It is a so-called staircase.
Also in this case, the thickness of the lower part of the first member 1224A may be thicker than the thickness of the upper part. For example, the thickness of the lower part may be about 1.2 to 8 times the thickness of the upper part. can. This magnification is not particularly limited, and if the thickness of the upper portion of the first member 1224A is set to be thin, it means that the thickness of the lower portion is set to be thick corresponding to this.

As a result, the center of gravity G indicated by the virtual line when the specific gravity of the first member 1224A and the second member 1224B is constant decreases in the direction of the arrow D. Thereby, the position of the center of gravity G can be positioned below the central portion of the pad member 1224 in the device height direction H and on the side of the first member 1223A.

In the present embodiment, the shape of the back surface 1224C of the first member 1224A is formed in a stepped shape having a plurality of steps from the upper part to the lower part, but the portion is formed from the upper part to the lower part of the first member 1224A. It may be formed in a curved shape in which the thickness gradually increases.

As a result, compared to the first member 1224A having a constant thickness in the width direction, it is possible to prevent the first member 1224A from falling down in an upright posture with the other side increasing in thickness.

The embodiments of the present invention have been described above with reference to the embodiments, but these embodiments are examples, and various modifications can be made without departing from the gist, and the scope of rights of the present invention is these. Needless to say, it is not limited to the embodiment of.

For example, in the present embodiment, it has been described that a metal material is used for the first member 122A of the pad member 122, but if the first member 122A is a material having a higher specific density than the second member 122B, a material other than metal is used. You may use it.

Further, it has been explained that the pad member 122 may have a two-layer structure in which foamed resins having different foaming ratios are laminated, and the configuration of the pad member 122 may be changed, for example, a single-layer structure may be used.
In this case, it is preferable that the portion to be the first member 122A has a larger specific gravity than the portion to be the second member 122B.

Further, it has been explained that the pad support member 116 is formed in an L shape by a vertical plate having a first surface and a horizontal plate having a second surface extending from the vertical plate. However, the present invention is not limited to this, and the member having the first surface and the member having the second surface may be formed of separate members to support the pad member 122.

Further, although the cam 92 is used as the switching unit, the present invention is not limited to this. For example, a configuration using a switching unit such as a cylinder, an actuator, or a rack and pinion may be used.

10 Image forming device 50 Secondary transfer unit (example of transfer unit)
70 Fixing device 72 Heating roll (example of pressurizing part)
74 Fixing belt (an example of endless belt)
78 Contact / detachment mechanism (an example of switching means)
110 1st support member 112 2nd support member 113 Restriction member 114 Spring 116 Pad support member (example of support part)
116A 1st surface 116B 2nd surface 122 Pad member (an example of pressing member)
122A 1st member (an example of the 1st part)
122B 2nd member (an example of the 2nd part)
P Recording paper (an example of medium)

Claims (13)

With an endless belt,
Pressurized parts arranged horizontally side by side with the belt,
A switching means for switching between a contact state in which the belt and the pressurizing portion are in contact with each other and a separated state in which the belt and the pressurizing portion are separated in the horizontal direction.
A support portion having a first surface facing the side of the pressure portion and a second surface facing upward in the vertical direction and arranged inside the belt.
A pressing member that is supported by the support portion so as to be relatively displaceable in contact with the first surface and the second surface and presses the belt against the pressurizing portion in the contact state, from the axial direction of the belt. With the pressing member, which extends in the vertical direction as seen and maintains contact with the first surface of the support portion in the separated state.
A fixing device equipped with. The fixing device according to claim 1, wherein the pressing member falls to the contact side with respect to the first surface when the pressing member is placed on a horizontal plane in a support posture by the support portion. The fixing device according to claim 1, wherein the pressing member either stands on its own or falls to the contact side with respect to the first surface when the pressing member is supported from below only in the contact region with respect to the second surface in a support posture by the support portion. .. The pressing member is configured to include a first portion on the side of the first surface and a second portion on the side of the pressurizing portion, and the specific gravity of the first portion is higher than the specific gravity of the second portion. The large fixing device according to claim 2 or 3. The fixing device according to claim 4, wherein the pressing member has a first portion and a second portion made of different materials. The fixing device according to claim 4 or 5, wherein the pressing member has a thickness in the pressing direction with respect to the pressure portion thicker in the upper part than in the lower part. The fixing device according to any one of claims 1 to 3, wherein the pressing member has a center of gravity located below the central portion in the vertical direction. The fixing device according to claim 7, wherein the pressing member has a thickness in the pressing direction with respect to the pressure portion thicker in the lower portion than in the upper portion. The fixing device according to claim 8, wherein the pressing member has a lower specific gravity in the vertical direction larger than the upper specific gravity. The pressing member is configured to include a first portion on the side of the first surface and a second portion on the side of the pressurizing portion, and the specific gravity of the first portion is higher than the specific gravity of the second portion. The large fixing device according to claim 9. The fixing device according to claim 10, wherein the second portion is thicker in the pressing direction with respect to the pressure portion in the lower portion than in the upper portion. A transfer unit that transfers the toner image to the medium,
The fixing device according to any one of claims 1 to 11, which is arranged on the upper side in the vertical direction with respect to the transfer portion and fixes the toner image on the medium sandwiched between the belt and the pressurizing portion.
An image forming apparatus equipped with. A first portion of metal that extends in one direction and is thicker than the other on one side in the width direction intersecting that one direction.
A second portion made of an elastic material, extending in one direction and fixed to one surface in the thickness direction of the first portion,
Have,
The first portion has a tapered shape in which the other surface in the thickness direction is a plane along the one direction and the width direction, and the thickness gradually increases from the other in the width direction to one when viewed from the one direction. ,
The second portion is thicker than the other in the width direction when viewed from one direction.
Pressing member.

Images