JP2016194592A - Fixation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve a problem that a compression coil spring is inclinedly supported to decrease pressure force on a nip portion, in a fixation device including a pair of pressure mechanisms having a compression coil spring.SOLUTION: A pressure mechanism includes: a lever having one end thereof supported rotatably in the pressure direction with respect to a frame body; and a compression coil spring provided between a first spring support portion provided on the other end of the lever and a second spring support portion provided in the frame body. A first fixation member is pressed against a second fixation member through the lever, and at least one of the first spring support portion and the second spring support portion includes a first support area that is in contact with a part close to an end of winding of the compression coil spring and a second support area that is in contact with a part farther from the end of winding of the compression coil. The first support area is offset to a direction farther away from the compression coil spring than the second support area.SELECTED DRAWING: Figure 8

Description

  The present invention relates to a fixing device provided in an image forming apparatus using electrophotographic technology.

  A fixing device mounted on an image forming apparatus such as a copying machine or a laser printer is configured to transport a recording material at a nip formed by press-contacting a first fixing member and a second fixing member to each other. Generally, the upper unfixed toner image is fixed by heating.

  In this fixing apparatus, in order to press the first fixing member and the second fixing member in pressure contact, both ends of the first fixing member are pressed against the second fixing member by the elastic force of the compression coil spring. Some have a pair of pressure mechanisms. In this pair of pressurization mechanisms, in order to improve the pressurization balance at both ends, a configuration has been proposed in which the winding end positions of compression coil springs installed at both ends are aligned (Patent Document 1).

Patent No. 3501616

  However, the fixing device described in Patent Document 1 has the following problems. The fixing device described in Patent Document 1 is based on the technical idea of aligning the applied pressures at both ends by aligning the winding end positions of the compression coil springs installed at both ends of the fixing member. However, since the end portion of the compression coil spring protrudes most in the axial direction of the coil, as shown by the white arrow shown in FIG. Receive power. The arrows shown in FIG. 11 illustrate the magnitude of the reaction force (the length of the arrow) and the direction of the reaction force (the direction of the arrow) that the compression coil spring 87 receives from the spring support member. In the fixing device disclosed in Patent Document 1, the compression coil spring 87 receives reaction forces of F11 and F12 and F13 and F14 in two spring support regions on the cross section passing through the axis 87s of the compression coil spring 87, respectively. F11 in the vicinity of the spring winding end is larger than F12, and F14 in the vicinity of the spring winding end is larger than F13. Therefore, the compression coil spring 87 cannot obtain a uniform reaction force from the spring support portion. Therefore, the force for rotating the compression coil spring 87 is likely to work. As a result, the direction in which the force Fs of the compression coil spring 87 acts is inclined from the direction of the applied pressure Ft of the nip portion, so that a loss tends to occur in the applied pressure of the nip portion.

  On the other hand, as a configuration for correcting the balance of the reaction force acting on the compression coil spring, one that cuts and polishes the spring end is known, but a compression coil spring that is cut and polished on the spring end is used as a fixing device. When it is adopted, not only the cost is increased, but there are the following problems. The compression coil spring with the winding end cut and polished has a reduced thickness because the coil near the winding end is thin, and the spring is deformed when a large load is applied to the thin coil portion. As a result, there is a problem that the pressure applied to the nip portion may be reduced.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a fixing device having a pair of pressure mechanisms using a compression coil spring, which can suppress the inclination of the compression coil spring and can suppress a decrease in pressure applied to the nip portion. .

  One of the preferred embodiments of the present invention for solving the above-described problems includes a first fixing member, a second fixing member that forms a nip portion together with the first fixing member, and the second fixing. Frames that support both ends of the member in the longitudinal direction, and provided at both ends of the first fixing member in the longitudinal direction to pressurize the first fixing member against the second fixing member. A fixing device that heats the recording material on which the toner image is formed at the nip portion and heats the recording material to fix the toner image on the recording material. A lever supported so as to be rotatable in the pressurizing direction of the first fixing member with respect to the frame, a first spring support provided on the other end of the lever, and a first provided on the frame. A compression coil spring provided between the two spring supports, and the compression coil The first fixing member is pressed against the second fixing member via the lever by the elastic force of a spring, and at least one of the first spring support portion and the second spring support portion is A first support region that contacts a portion near the winding end of the compression coil spring in the winding direction of the compression coil spring; and a second support region that contacts a portion far from the winding end in the winding direction; The first support region is offset in the axial direction of the compression coil spring from the second support region in a direction away from the compression coil spring.

  According to the present invention, in a fixing device having a pair of pressure mechanisms using a compression coil spring, it is possible to provide a fixing device that can suppress the inclination of the compression coil spring and suppress the decrease in the pressure applied to the nip portion.

Schematic cross-sectional view of the fixing device of Example 1 Schematic schematic diagram of the fixing device of Example 1. 1 is a schematic perspective view of a fixing device according to a first embodiment. Schematic side view of the fixing device according to the first embodiment. 1 is a schematic perspective view and a cross-sectional view of a spring support member of a fixing device according to Embodiment 1. FIG. Schematic side view of the fixing device according to the first embodiment. 1 is a schematic perspective view of a fixing device according to a first exemplary embodiment and a schematic diagram of a spring and a spring support member. Schematic side view of the fixing device according to the first embodiment. Schematic side view of the fixing device of the embodiment using an open-end compression coil spring A perspective view and a side view of a spring support member of an embodiment using an open end compression coil spring Schematic side view of a conventional fixing device

Example 1
A fixing device 72 according to this embodiment will be described with reference to FIGS. 1 and 2. In the following description, regarding the members constituting the fixing device, the longitudinal direction is a direction orthogonal to the recording material conveyance direction. FIG. 1A is a schematic sectional view in the longitudinal direction of the fixing device 72, and FIG. 1B is an enlarged view of a nip portion of the fixing device 72. FIG. 2A is a schematic diagram of the fixing device 72 as viewed from the film 10 side in the fixing device. FIG. 2B is a schematic diagram of the fixing device 72 as viewed from the downstream side in the recording material conveyance direction.

  The fixing device 72 shown in this embodiment includes a cylindrical film 10, a heater 30 that contacts the inner surface of the film 10, and a pressure roller 20, and the heater 30 passes through the film 10 and the pressure roller 20. At the same time, a fixing nip portion N2 is formed. The toner image is fixed on the recording material by heating while conveying the recording material on which the toner image is formed at the fixing nip N2. The fixing device 72 further includes a heater holder 41 that supports the heater 30, a pressure stay 42 for improving bending rigidity, and a fixing flange 45 as a regulating member that restricts movement of the film 10 in the longitudinal direction. Have.

  The film 10, the heater 30, the heater holder 41, the pressure stay 42, and the fixing flange 45 are unitized to form a film unit (first fixing member). The fixing device 72 of the present embodiment is configured to press the film unit against the pressure roller (second fixing member) 20.

  The film 10 includes a base layer 11 and a release layer 12 provided outside the base layer 11. In addition, an elastic layer 13 formed of silicone rubber or the like may be provided between the base layer 11 and the release layer 12 in order to improve the fixability. If the elastic layer 13 is provided, heat can be uniformly applied by wrapping the unfixed toner image T carried by the recording material P. The thickness of the elastic layer 13 is preferably 50 μm or more and 500 μm or less from the viewpoint of shortening the warm-up time. As the base layer 11, a thin metal such as SUS or Ni having a high thermal conductivity, or a thin-walled flexible endless belt made of a heat-resistant resin such as polyimide, polyamideimide, or PEEK can be used. . On the outside of the base layer 11, as the release layer 12, a fluororesin such as PFA, PTFE, FEP or the like is coated alone or blended, or a tube of the above fluororesin alone or blend is coated. The thickness of the release layer 12 is preferably 5 μm or more from the viewpoint of durability. On the other hand, if the release layer 12 is too thick, the thermal conductivity is lowered and the fixability is adversely affected.

  The heater holder 41 is formed in a semicircular saddle shape in cross section using materials such as liquid crystal polymer, phenol resin, PPS, and PEEK. A recess-shaped groove 41 a is provided along the longitudinal direction of the heater holder 41 on the lower surface of the heater holder 41 (the surface on the pressure roller 20 side). The heater 30 is supported by the groove 41a. The film 10 is loosely fitted on the outer periphery of the heater holder 41. The heater holder 41 to which the film 10 is externally fitted is supported at both ends of the frame 91 by fixing flanges 45 at both ends in the longitudinal direction of the heater holder 41. As shown in FIG. 1B, the heater holder 41 has a protrusion 41b provided along the longitudinal direction of the portion in contact with the inner peripheral surface of the film 10 on the downstream side in the recording material conveyance direction in the fixing nip N2. The protrusion 41b protrudes by a protrusion amount h toward the outer surface of the film with respect to the sliding surface of the heater 30 with the film 10. The protrusions 41b are arranged at the same position in the longitudinal direction uniformly in the recording material conveyance direction. In the fixing device of this embodiment, the protruding amount h is 0.2 mm. Here, the sliding surface is a pressure contact portion between the film 10 and the heater 30 among the pressure contact portions formed by the film 10, the heater 30, and the heater holder 41 as shown in FIG.

  In FIG. 1A, a pressure roller 20 includes a core shaft portion 21, an elastic layer 22 provided outside the core shaft portion 21, a release layer 24 provided outside the elastic layer 22, Have The elastic layer 22 can be made of silicone rubber or fluorine rubber. The release layer 24 is coated with a single or blended fluororesin such as PFA, PTFE, or FEP, or a single or blended fluororesin tube is used. In the present embodiment, an iron core bar having a diameter of 22 was used as the core shaft portion 21, and a silicone rubber having a thickness of 4 mm was used as the elastic layer 22. As the release layer 24, a 50 μm thick PFA tube was used.

The heater 30 heats the film 10 while being in contact with the inner peripheral surface of the film 10. The heater 30 has a substrate elongated in the longitudinal direction. As the substrate, a ceramic substrate such as alumina or aluminum nitride, or a heat resistant resin substrate such as polyimide, PPS, or liquid crystal polymer can be used. A heating resistance layer such as Ag / Pd (silver palladium), RuO ₂ , Ta ₂ N or the like is applied in a strip shape along the longitudinal direction of the substrate on the back surface (the surface opposite to the pressure roller 20) of the substrate. It is formed by processing. In addition, a glass coat is formed on the back surface of the substrate in order to ensure the protection and insulation of the heating resistor layer. A sliding layer is provided on the surface of the substrate in contact with the inner surface of the film 10 for the purpose of improving the slidability. As the sliding layer, a heat resistant resin such as polyimide or polyamideimide, a glass coat, or the like is used. In the present embodiment, the dimensions of the substrate of the heater 30 are 350 mm in the longitudinal direction, 10 mm in the lateral direction, and 0.6 mm in the thickness direction.

  The pressure stay 42 is formed in a U-shaped cross section using a material such as metal having rigidity. The pressure stay 42 is disposed on the upper surface (the surface opposite to the pressure roller 20) of the heater holder 41 inside the film 10. Then, both ends in the longitudinal direction of the pressure stay 42 are pressed toward the axis of the pressure roller 20 by the applied pressure Ft through the fixing flange 45 supported by the frame 91. As a result, the heater 30 is pressed against the surface of the pressure roller 20 via the film 10, and an inner surface nip N 3 having a predetermined width between the heater 30 and the film 10 and a predetermined width between the film 10 and the pressure roller 20. A fixing nip N2 is formed. Heat necessary for heating and fixing the toner image T is transferred from the heater 30 to the film 10 at the inner surface nip N3, and the recording material is conveyed while transferring heat from the film 10 to the recording material P at the fixing nip N2.

  The control unit 44 drives a motor that is a drive source in response to a print command to rotate a drive gear provided at an end portion in the longitudinal direction of the core shaft portion 21 of the pressure roller 20. As a result, the pressure roller 20 rotates in the arrow direction at a predetermined peripheral speed. At that time, a rotational force that rotates in the direction opposite to the rotation direction of the pressure roller 20 acts on the film 10 by the frictional force between the surface of the pressure roller 20 and the surface of the film 10 in the fixing nip N2. Thereby, the film 10 is driven to rotate in the direction of the arrow at the substantially same peripheral speed as that of the pressure roller 20 while the inner surface of the film 10 is in contact with the sliding layer of the heater 30.

  The thermistor 35 as a temperature detection unit detects the temperature of the film 10 and outputs a temperature detection signal to the control unit 44. The thermistor 35 is provided so as to be able to detect the temperature of the region through which recording materials P of all sizes usable by the printer 72 pass. The control unit 44 takes in the temperature detection signal from the thermistor 35 and controls the power supplied to the heating resistor layer so that the film 10 reaches a predetermined target temperature based on the temperature detection signal. Thus, in a state where the temperature of the film 10 is maintained at a predetermined target temperature, the recording material P carrying the unfixed toner image T is guided to the fixing nip N2 along the entrance guide 28, and the film 10 and the pressure roller 20 to be nipped and conveyed. During the conveyance process, the heat of the film 10 heated by the heater 30 and the pressure of the fixing nip N2 are applied to the recording material P, and the toner image T is fixed on the surface of the recording material P by the heat and pressure. The recording material P that has passed through the fixing nip N2 is separated from the film 10 by the curvature, and is discharged by the conveying roller 26. Next, the pressurizing mechanism of the embodiment will be described with reference to FIGS. FIG. 3 is a perspective view of the fixing device 72. FIG. 4 is a side view of the fixing device 72 when it has a viewpoint in the direction of arrow R in FIG. The pressure roller 20 is rotatably supported by a frame (frame body) 91 provided at both ends in the longitudinal direction via a bearing 120. A guide portion 91 a that regulates the direction in which the film unit is pressed is provided on the frame 91.

  The pair of pressure mechanisms includes a lever portion 84, a pivot fulcrum 91 b of the lever portion 84 provided on the frame 91, a spring support portion 93 (second spring support portion), and a compression coil spring 87. The film unit 10 is provided at both ends in the longitudinal direction.

  One end of the lever portion 84 is a member that supports the film unit 10 so as to be rotatable in the pressurizing direction at the rotation fulcrum 91 b of the frame 91.

  The compression coil spring 87 is provided in a compressed state between a spring support portion 840 (first spring support portion) provided at the other end of the lever portion 84 and the spring support portion 93 of the frame 91. The other end of the lever portion 84 supports the lower end 87a of the compression coil spring. On the other hand, the spring support portion 93 is provided on the frame 91 and supports the upper end 87 b of the compression coil spring 87. The spring support portion 93 has a role of regulating the height of the compression coil spring 87 so that the pressure applied by the compression coil spring 87 becomes a predetermined pressure (designated load). The compression coil spring 87 of this embodiment has a free height of 35 mm and a specified height of 27 mm when pressurized. The lever portion 84 is rotated around the rotation fulcrum 91 b by the elastic force of the compression coil spring 87, applies a pressing force Ft to the fixing flange 45 via the lever portion 84, and moves the film unit against the pressure roller 20. Pressurize. In addition, by operating the lever portion 84 in the compression direction of the compression coil spring 87 by the cam member 95, the pressure applied to the fixing nip portion N2 can be released.

  Next, the structure of the spring support part in a present Example is demonstrated using FIG. The compression coil spring 87 is a compression coil spring that is right-handed, has 10 effective turns, and has a closed end shape. The compression coil spring 87 is compressed and supported between the spring support portion 93 on the fixed side and the spring support portion 840 of the lever portion 84. 5A and 5B are perspective external views of the spring support portion 93. FIG. As shown in FIG. 5B, positioning pins 93 f are formed on the attachment surface of the spring support portion 93 to the frame 91, and are positioned and attached to the attachment holes 91 c of the frame 91. On the spring support surface of the spring support member 93, as shown in FIG. 5A, a groove 93c is formed around the columnar portion 93a. At the tip of the groove 93c, there is a flat portion 93d that receives the spring winding end 87c (FIG. 6) of the compression coil spring 87 to be installed, and the depth gradually increases from 93d as shown in FIG. 5 (c). It is formed to become shallower.

  FIG. 6 is an enlarged side view of the support portion of the compression coil spring 87 of the fixing device 72. The lever portion 84 is a plate-like member (plate material). A convex portion 84b inserted into the inner diameter portion of the compression coil spring 87 at the edge portion of the plate-like member, and a spring support region 84c (second spring support) with the convex portion 84b interposed therebetween. Region), a spring support region 84d (first spring support region) is formed. The spring support region 84 c and the spring support region 84 d are provided at symmetrical positions with respect to the axial center of the compression coil spring 87 when viewed from the axial direction of the compression coil spring 87. The spring support region 84d far from the rotation fulcrum 91b of the lever member 84 is formed at a height that is one step lower than the spring support region 84c with respect to a plane perpendicular to the axis 87s of the compression coil spring to be attached. That is, the spring support region 84d is offset from the spring support region 84c in a direction away from the compression coil spring 87 in the axial direction of the compression coil spring 87.

  7A is a perspective external view of the fixing device 72 as viewed obliquely from below. FIGS. 7B, 7C, and 7D show a state in which only the compression coil spring 87 and the spring support member 93 are assembled. FIG. As shown in FIGS. 7B, 7C and 7D, the upper end 87b of the compression coil spring 87 is abutted against the flat portion 93d of the spring support surface 93 so that the axis of the compression coil spring 87 is The position in the surrounding rotation direction is regulated. The coil portion following the spring end portion 87 c is supported by the groove 93 c of the spring support portion 93. As shown in FIG. 7C, since the effective number of windings of the spring is an integer, the other spring winding end portion 87d supported by the lever portion 84 is located below the spring winding end portion 87c. As for the spring lower end 87a of the compression coil spring 87, a portion near the spring winding end portion 87d in the winding direction of the compression coil spring 87 is supported while being in contact with the spring support region 84d of the lever portion 84 and is a portion far from the spring winding end portion 87d. Is supported in contact with the spring support region 84c.

  FIG. 8 shows the magnitude of the reaction force (the length of the arrow) and the direction of the reaction force (the arrow) that the compression coil spring 87 receives from the spring support portion 93 and the spring support portion 840 when the compression coil spring 87 is compression supported. FIG. 6 is a side view of the fixing device in which the direction is indicated by an arrow. The compression coil spring 87 receives the reaction forces F11 and F12 substantially uniformly at the upper end 87b of the groove portion 93c of the spring support portion 93, and the lower end 87a of the spring support region 84c and the spring support region 84d of the lever portion 84 approximately equally. Receives forces F13 and F14. The magnitude of the reaction force at both ends of the compression coil spring 87 is substantially equal between F11 and F12, and F13 and F14. Therefore, the rotational force does not act on the compression coil spring 87 that is compression-supported, and the acting force Fs of the spring can be efficiently applied to the applied pressure Ft of the nip portion.

  In the present embodiment, a case where a compression coil spring having a closed end is used has been described. However, the same effect can be obtained by using a compression coil spring having an open end.

  9A and 9B show a spring support state in an embodiment using an open-end compression coil spring. FIG. 9A shows an embodiment in which the spring support portion 910 is formed directly on the frame 91. One winding end 87c of the compression coil spring 87 is supported by the spring support portion 910 to prevent rotation of the compression coil spring 87, and the compression coil spring 87 is compressed and supported between the spring support portion 840 of the lever portion. . The frame 91 is formed with a convex portion 93y that supports the inner diameter of the compression coil spring 87, and a spring support region 93g and a spring support region 93h that support the spring upper end 87b are formed on both sides thereof. A spring support region 93g (second support region) close to the winding end portion 87c in the winding direction of the compression coil spring 87 is lower than the spring support region 93h (first support region). That is, the spring support region 93g is offset in a direction away from the compression coil spring 87 in the axial direction of the compression coil spring 87 with respect to the spring support region 93h. Therefore, the end portions 87b and 87a of the compression coil spring 87 can be configured to receive reaction forces having substantially equal sizes at 93g and 93h and 84c and 84d, respectively. As a result, a rotational force does not act on the compression coil spring 87 that is compression-supported, and the acting force Fs of the spring can be efficiently applied to the applied pressure Ft of the nip portion.

  FIG. 9B shows an embodiment in which the compression coil spring 87 is supported at four points by the spring support member 93. FIG. 10A is a perspective view of the spring support portion 93 in this embodiment, and FIG. 10B is a top view and a side view of the spring support member. A spring support region 93i (first support region) that receives the spring side surface is formed next to the rotation stop shape 93d that abuts the spring winding end portion 87c. Further, three support regions 93j, 93k, and 93m (second support regions) are respectively 90 along the winding direction of the compression coil spring 87 to be used, with the center of the cylindrical portion 93a that supports the spring inner diameter portion as the rotation center. It is formed at a position where the phase is shifted.

  As shown in FIG. 10B, the four spring support regions are formed so as to approach the compression coil spring in the axial direction of the compression coil spring 97 as it goes from 93 i to 93 m in the winding direction of the compression coil spring 87. . As a result, when the compression coil spring 87 is compression-supported, 93 i and 93 j and 93 k and 93 m can receive reaction forces having substantially equal sizes. Therefore, the rotational force does not act on the compression coil spring 87 compressed and supported by the spring support portion 840 and the spring support portion 93 of the lever portion 84, and the acting force Fs of the spring efficiently acts on the pressure Ft of the nip portion. Can be made.

  FIG. 9C is a diagram of an embodiment in which the surface that receives the compression coil spring 87 is formed as an inclined surface with respect to the configuration of FIG. The spring support portion is formed integrally with the frame 91, and the spring support region 93g and the spring support region 93h for supporting the spring upper end 87b, and the spring support region 84d and the spring support region 84c of the lever portion 84 are inclined. In the winding direction of the compression coil spring, the spring support region approaches the compression coil spring in the axial direction of the compression coil spring 87 as it goes from the spring support region 93g near the winding end portion 87c to the spring support region 93h. In the winding direction of the compression coil spring 87, the spring support region is compressed in the axial direction of the compression coil spring 87 from the spring support region 84d near the winding end portion 87d of the compression coil spring 87 toward the spring support region 84c far from the winding end portion 87d. Approach the coil spring. When the compression coil spring 87 is compression-supported with this configuration, both end portions of the compression coil spring 87 are subjected to reaction forces having substantially equal sizes at 93g and 93h, and 84c and 84d, respectively. Therefore, no rotational force acts on the compression coil spring 87 that is compression-supported, and the acting force Fs of the spring can be efficiently applied to the applied pressure Ft of the nip portion.

  As described above, according to the present invention, in the fixing device having a pair of pressure mechanisms using a compression coil spring, the inclination of the compression coil spring is suppressed, and the effect of suppressing the decrease in the applied pressure at the nip portion is exhibited. . In the above-described embodiment, the winding direction of the compression coil spring is a right-handed spring. However, the same applies when a left-handed spring is used. That is, the spring support region may be formed so as to be closer to the spring in the axial direction of the spring as it is further away from the winding end of the spring in the spring winding direction.

N2 fixing nip portion P recording material 10 film 20 pressure roller 30 heater 41 heater holder 45 fixing flange 72 fixing device 84 lever portion 87 compression coil spring 91 frame 93 spring support portion 95 cam member 840 spring support portion

Claims (5)

A first fixing member;
A second fixing member that forms a nip with the first fixing member;
A frame that supports both longitudinal ends of the second fixing member;
A pair of pressure mechanisms provided at both longitudinal ends of the first fixing member to pressurize the first fixing member against the second fixing member;
In the fixing device for fixing the toner image to the recording material by heating while conveying the recording material on which the toner image is formed in the nip portion,
The pressure mechanism includes a lever supported at one end so as to be rotatable in the pressure direction of the first fixing member with respect to the frame body;
A compression coil spring provided between a first spring support provided on the other end of the lever and a second spring support provided on the frame;
And pressurizing the first fixing member against the second fixing member via the lever by the elastic force of the compression coil spring,
At least one of the first spring support portion and the second spring support portion is a first support region that is in contact with a portion near the winding end portion of the compression coil spring in the winding direction of the compression coil spring; A second support region in contact with a portion far from the winding end in the winding direction,
The fixing device according to claim 1, wherein the first support region is offset from the second support region in a direction away from the compression coil spring in an axial direction of the compression coil spring.   The first support region and the second support region are provided at positions that are symmetrical with respect to the axial center of the compression coil spring when viewed from the axial direction. The fixing device described.   The fixing device according to claim 1, wherein the first spring support portion includes the first support region and the second support region.   The fixing device according to claim 3, wherein the lever is formed of a plate material, and the first support region and the second support region are provided at an edge portion of the plate material.   The fixing device according to claim 1, wherein a shape of the winding end portion is a closed end.

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