Heating device and image processing device

Abstract

To provide a heating device and image processing device capable of suppressing an excessive temperature rise of a heat generating member.SOLUTION: A heating device includes a belt and a heat generating member. The belt has a tubular shape. The heat generating member is provided inside the belt. The heat generating member is formed in an arc shape along the inner peripheral surface of the belt. The heat generating member is slidably in contact with the inner peripheral surface of the belt. When an amount of deflection of the belt is D, the radius of curvature of the inner peripheral surface of the belt is A, and the radius of curvature of the outer peripheral surface of the heat generating member is B, the following equations (1) and (2) are satisfied: D≥10 mm ...(1); 0.4 mm≥A-B≥0 mm ...(2).SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] FIELD An embodiment of the present invention relates to a heating device and an image processing device. [Background technology]

[0002] The image processing device includes a heating device that fixes toner (recording agent) to a sheet by heat from a belt. The heating device heats the belt by electromagnetic induction heating. The heating device includes a heat-generating member that contacts the inner peripheral surface of the belt to compensate for a deficiency in the amount of heat generated by the belt. The heat-generating member is formed in an arc shape that follows the inner peripheral surface of the belt. Depending on the variation in dimensions of the heat-generating member, the belt and the heat-generating member may not be in close contact with each other, and heat may not be transported sufficiently between the heat-generating member and the belt, resulting in an excessive temperature rise of the heat-generating member. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2010-2797 A Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the present invention is to provide a heating device and an image processing device capable of suppressing an excessive rise in temperature of a heat-generating member. [Means for solving the problem]

[0005] The heating device of the embodiment has a belt and a heat generating member. The belt has a cylindrical shape. The heat generating member is provided inside the belt. The heat generating member is formed in an arc shape along the inner peripheral surface of the belt. The heat generating member is in slidable contact with the inner peripheral surface of the belt. The amount of deflection D of the belt is the amount of displacement D of the end of the belt in the belt axial direction when a weight of 200 g is placed on the central upper part of the belt axial direction for a belt having a length in the belt axial direction of 100 mm, and the radius of curvature of the inner peripheral surface of the belt is Let A be the half of the inner diameter of the belt when the belt is a perfect cylinder.When the radius of curvature of the outer peripheral surface of the heat generating member is B, the following formulas (1) and (2) are satisfied. D≧10mm (1) 0.4 mm ≧ AB ≧ 0 mm (2) [Brief description of the drawings]

[0006] [Figure 1] 1 is a schematic diagram of an image processing apparatus according to an embodiment. [Diagram 2] FIG. 2 is a schematic diagram of a heating device according to the embodiment. [Diagram 3] FIG. 2 is a schematic diagram of a heat generating member according to the embodiment. [Figure 4] 6A and 6B are diagrams showing the relationship between the width dimension of the heat generating member and the gap between the belt and the heat generating member in the embodiment. [Diagram 5] FIG. 6 is a diagram showing the relationship between the gap between the belt and the heat generating member and the temperature of the thermostat in the embodiment. [Figure 6] 6 is a diagram showing the relationship between the difference between the inner diameter of the belt and the outer diameter of the heat-generating member and the adhesion between the belt and the heat-generating member in the embodiment. [Figure 7] FIG. 4 is a diagram showing the relationship between the width dimension of the heat generating member and the temperature of the thermostat in the embodiment. [Figure 8] FIG. 4 is an explanatory diagram of a method for measuring the amount of deflection of a belt in an embodiment. [Figure 9] FIG. 4 is a diagram showing the measurement results of the amount of deflection of a belt having an inner diameter of 30 mm in an embodiment. [Figure 10] FIG. 13 is a diagram showing the measurement results of the amount of deflection of a belt having an inner diameter of 40 mm in an embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0007] Hereinafter, a heating device and an image processing device according to an embodiment will be described with reference to the drawings. FIG. 1 is a schematic diagram of an image processing device 1 according to the first embodiment. For example, the image processing device 1 is a multi-function peripheral (MFP). The image processing device 1 reads an image formed on a sheet-like recording medium (hereinafter referred to as a "sheet") such as paper, and generates digital data (image file). The image processing device 1 forms an image on the sheet using toner based on the digital data.

[0008] The image processing apparatus 1 includes a display unit 2, an image reading unit 3, a sheet supply unit 4, an image forming unit 5, a sheet inverting unit 6, and a control unit . The display unit 2 operates as an output interface and displays characters and images. The display unit 2 also operates as an input interface and receives instructions from a user. For example, the display unit 2 is a touch panel type liquid crystal display.

[0009] For example, the image reading unit 3 is a color scanner. Color scanners include CIS (Contact Image Sensor) and CCD (Charge Coupled Devices). The image reading unit 3 uses a sensor to read an image formed on a sheet and generate digital data.

[0010] The sheet supply unit 4 supplies sheets used for image output to the image forming unit 5. The sheet supply unit 4 includes a paper feed cassette 10 and a pickup roller 11. The paper feed cassette 10 stores sheets P. The pickup roller 11 picks up the sheets P from the paper feed cassette 10.

[0011] The image forming unit 5 forms an image on a sheet using toner. The image forming unit 5 forms an image based on image data read by the image reading unit 3 or image data received from an external device. For example, the image formed on the sheet is an output image called a hard copy, a printout, or the like.

[0012] The image forming section 5 includes an intermediate transfer member 20, an image creating section 21, a primary transfer roller 22, a secondary transfer section 23, and a heating device 24.

[0013] The transfer in the image forming unit 5 includes a first transfer process and a second transfer process. In the first transfer process, the primary transfer roller 22 transfers an image (toner image) made of toner on the photosensitive drum of each image creating unit 21 to the intermediate transfer body 20. In the second transfer process, the secondary transfer unit 23 transfers an image onto a sheet using the toner of each color stacked on the intermediate transfer body 20.

[0014] The intermediate transfer body 20 is an endless belt. The intermediate transfer body 20 rotates in the direction of the arrow U in Fig. 1. A toner image is formed on the surface of the intermediate transfer body 20. The image forming units 21 form images using toner of each color (for example, five colors). A plurality of image forming units 21 are provided along the intermediate transfer body 20.

[0015] The primary transfer roller 22 transfers the toner image formed by the image forming unit 21 onto the intermediate transfer body 20 . The secondary transfer unit 23 includes a secondary transfer roller 25 and a secondary transfer opposing roller 26. The secondary transfer unit 23 transfers the toner image formed on the intermediate transfer body 20 onto a sheet.

[0016] The heating device 24 fixes the toner image transferred onto the sheet by applying heat and pressure to the sheet. The sheet on which the image has been formed by the heating device 24 is discharged from the paper discharge unit 8 to the outside of the apparatus.

[0017] The sheet inverting unit 6 is disposed to the side of the heating device 24. The sheet inverting unit 6 inverts the sheet from front to back. For example, the sheet is inverted when images are formed on both the front and back sides of the sheet. The control unit 7 controls each component of the image processing device 1.

[0018] Next, the heating device 24 will be described. FIG. 2 is a schematic diagram of a heating device 24 according to an embodiment. As shown in FIG. 2, the heating device 24 includes a belt 30, a belt internal mechanism 31, a press roller 32, and an induced current generating unit 33.

[0019] The belt 30 is a cylindrical endless belt. For example, the inner diameter of the belt 30 is set to a size of 35 mm or more and 50 mm or less. For example, the belt 30 is formed by sequentially laminating a heat generating layer (conductive layer) which is a heat generating portion and a release layer on a base layer. For example, the base layer is formed of polyimide resin (PI). For example, the heat generating layer is formed of a non-magnetic metal such as copper (Cu). For example, the release layer is formed of a fluororesin such as tetrafluoroethylene-perfluoroalkylvinylether copolymer resin (PFA). Note that the layer structure of the belt 30 is not limited as long as it has a heat generating layer.

[0020] The belt internal mechanism 31 is disposed inside the belt 30. The belt internal mechanism 31 includes a heat generating member 40, a frame 44, a nip pad 45, a thermostat 46, a holder 47, a first biasing member 48, and a second biasing member 49.

[0021] The heat generating member 40 contacts the inner peripheral surface of the belt 30. The heat generating member 40 faces the induced current generating unit 33 across the belt 30. The heat generating member 40 is made of a magnetic material. For example, the heat generating member 40 is made of a magnetic shunt alloy having a lower Curie point than the heat generating layer. For example, the heat generating member 40 is made of a thin metal member made of a magnetic shunt alloy such as an iron or nickel alloy having a Curie point of 220°C to 230°C.

[0022] The heat generating member 40 may be formed of a thin metal member having magnetic properties, such as iron, nickel, stainless steel, etc. The heat generating member 40 may be formed of a resin containing magnetic powder, etc., so long as the heat generating member 40 has magnetic properties. The heat generating member 40 may be formed of a magnetic material (ferrite).

[0023] The heat generating member 40 has a longitudinal direction in the axial direction of the belt 30 (hereinafter referred to as the "belt axial direction"). The heat generating member 40 is curved along the inner circumferential surface of the belt 30. The heat generating member 40 is in slidable contact with the inner circumferential surface of the belt 30. The heat generating member 40 includes a curved portion 50, a first folded portion 51, and a second folded portion 52. The curved portion 50, the first folded portion 51, and the second folded portion 52 are integrally formed from the same member.

[0024] The curved portion 50 is formed in an arc shape that follows the inner circumferential surface of the belt 30. The curved portion 50 is in contact with the inner circumferential surface of the belt 30. The radius of curvature of the curved portion 50 is smaller than the radius of curvature of the belt 30. The outer circumferential surface of the curved portion 50 may be plated or coated with chromium nitride, diamond-like carbon (DLC), etc. By plating or coating with chromium nitride, DLC, etc., the sliding property between the curved portion 50 and the belt 30 is improved.

[0025] The first bent portion 51 is bent inward from a first end portion 55 in the circumferential direction of the curved portion 50. A plurality of first bent portions 51 are provided in the belt axial direction. The first bent portion 51 has an annular portion 57 having a circular ring shape. The annular portion 57 is supported by a swing shaft (not shown) along the belt axial direction. The heat generating member 40 is swingable around the swing shaft.

[0026] The second folded portion 52 is folded inward from a second end 56 in the circumferential direction of the curved portion 50. A plurality of second folded portions 52 are provided in the belt axial direction. The second folded portions 52 are connected to a first end of a first biasing member 48. For example, the first biasing member 48 is an elastic member such as a compression spring. A second end of the first biasing member 48 is connected to a stay 59. The stay 59 is fixed to the frame 44. The heat-generating member 40 is pressed against the belt 30 by the first biasing member 48.

[0027] The nip pad 45 presses the belt 30 against the press roller 32. The nip pad 45 is fixed to the frame 44. The nip pad 45 forms a nip 65 between the belt 30 and the press roller 32. The nip pad 45 has a nip forming surface 66 that forms the nip 65. The nip forming surface 66 curves toward the inside of the belt 30 when viewed from the belt axial direction. The nip forming surface 66 curves along the outer circumferential surface of the press roller 32 when viewed from the belt axial direction.

[0028] For example, nip pad 45 is made of an elastic material such as silicone rubber, fluororubber, etc. Nip pad 45 may be made of a heat-resistant resin such as polyimide resin (PI), polyphenylene sulfide resin (PPS), polyethersulfone resin (PES), liquid crystal polymer (LCP), phenolic resin (PF), etc.

[0029] For example, a sheet-like friction reduction member (not shown) is disposed between the belt 30 and the nip pad 45. For example, the friction reduction member is formed of a sheet member with good sliding properties and excellent wear resistance, a release layer, etc. The friction reduction member is fixedly supported by the belt internal mechanism 31. The friction reduction member is in sliding contact with the inner circumferential surface of the running belt 30. The friction reduction member may be formed of the following sheet members having lubricity. For example, the sheet member may be made of a glass fiber sheet impregnated with a fluororesin. For example, the friction reduction member may contain a lubricating oil such as silicone oil.

[0030] The thermostat 46 functions as a safety device for the heating device 24. The thermostat 46 detects the temperature of the heat-generating member 40. The thermostat 46 operates when the heat-generating member 40 generates abnormal heat and the temperature rises to a cut-off threshold. The operation of the thermostat 46 cuts off the current to the induced current generating unit 33. By cutting off the current to the induced current generating unit 33, the heating device 24 is prevented from generating abnormal heat.

[0031] The thermostat 46 is connected to a first end of a second biasing member 49. For example, the second biasing member 49 is an elastic member such as a compression spring. A second end of the second biasing member 49 is connected to a holder 47. The holder 47 is fixed to the frame 44. The thermostat 46 is pressed against the heat-generating member 40 by the second biasing member 49. The thermostat 46 follows the oscillation of the heat-generating member 40 due to the pressure of the second biasing member 49. By following the oscillation of the heat-generating member 40, the thermostat 46 is always in contact with the heat-generating member 40.

[0032] The press roller 32 presses the belt 30 by a pressing mechanism (not shown). For example, the press roller 32 includes a heat-resistant silicone sponge and silicone rubber layer around a core metal. For example, a release layer is disposed on the surface of the press roller 32. The release layer is formed of a fluorine-based resin such as PFA resin.

[0033] The belt 30 and the press roller 32 are driven by a driving unit (not shown) such as a motor. The press roller 32 rotates in the direction of arrow Q by the motor drive. When the belt 30 and the press roller 32 are in contact with each other, the belt 30 rotates in the direction of arrow R, driven by the press roller 32. When the belt 30 and the press roller 32 are separated from each other, the belt 30 rotates in the direction of arrow R by the motor drive.

[0034] When viewed from the belt axial direction, an imaginary line passing through the center of rotation of the belt 30 and the center of rotation of the press roller 32 is defined as a first line J. When viewed from the belt axial direction, an imaginary line perpendicular to the first line J and passing through the center of rotation of the belt 30 is defined as a second line K. When viewed from the belt axial direction, the heat generating member 40 is disposed closer to the induced current generating unit 33 than the second line K.

[0035] The induced current generating unit 33 is disposed outside the belt 30. The induced current generating unit 33 faces the belt 30. The induced current generating unit 33 faces the heat-generating member 40 across the belt 30. The induced current generating unit 33 includes a coil (not shown). A high-frequency current is applied to the coil from an inverter drive circuit (not shown). By passing a high-frequency current through the coil, a high-frequency magnetic field is generated around the coil. The belt 30 is heated by the magnetic flux of the high-frequency magnetic field.

[0036] A magnetic flux is generated between the heat generating member 40 and the belt 30 by the magnetic flux generated by the coil. The belt 30 is heated by the magnetic flux generated between the heat generating member 40 and the belt 30. The heat generating member 40 changes from ferromagnetic to paramagnetic when it exceeds the Curie point. When the heat generating member 40 exceeds the Curie point, it no longer forms a magnetic path passing through the heat generating member 40 and the heat generating layer, and no longer assists in heating the belt 30. By forming the heat generating member 40 from a magnetic shunt alloy, it is possible to assist in raising the temperature of the belt 30 at low temperatures and suppress excessive heating of the belt 30 at high temperatures, with the Curie point as the boundary.

[0037] Next, the heat generating member 40 will be described. Fig. 3 is a schematic diagram of the heat generating member 40 of the embodiment. In Fig. 3, the folded portions 51, 52 of the heat generating member 40 are omitted. As shown in Fig. 3, the heat generating member 40 has a curved portion 50 that is arc-shaped when viewed from the belt axial direction. When the curved portion 50 is semicircular when viewed from the belt axial direction, the arc center C of the curved portion 50 is located on the same plane including both circumferential ends (a first end 55 and a second end 56) of the curved portion 50.

[0038] When viewed from the belt axial direction, the maximum width of both circumferential ends of the curved portion 50 of the heat-generating member 40 is defined as the width dimension W of the heat-generating member. When viewed from the belt axial direction, the maximum height of the curved portion 50 of the heat-generating member 40 perpendicular to the width dimension W of the heat-generating member is defined as the height dimension H of the heat-generating member.

[0039] When viewed from the belt axial direction, a virtual line passing through the arc center C of the curved portion 50 and both circumferential ends (first end 55 and second end 56) of the curved portion 50 is defined as a third line L. As shown in FIG. 2, when viewed from the belt axial direction, the third line L is arranged parallel to the second line K. When viewed from the belt axial direction, the third line L is arranged closer to the induced current generating unit 33 than the second line K. When viewed from the belt axial direction, the arc center C of the curved portion 50 is arranged on the first line J.

[0040] As described above, the magnetic flux emitted from the coil of induced current generating unit 33 causes the heat generating layer of belt 30 to generate heat, forming a magnetic path between heat generating member 40 and the heat generating layer, and further causing heat generating member 40 to self-heat. If there is heat transfer between heat generating member 40 and belt 30, the temperature of heat generating member 40 is maintained at a temperature about 20° C. higher than the temperature of belt 30. Since thermostat 46 is disposed in the paper passing area in the belt axial direction, if the fixing temperature is 160° C., the detected temperature of thermostat 46 will be about 180° C.

[0041] However, if the belt and the heat-generating member are not in close contact with each other, heat transfer between the heat-generating member and the belt is insufficient, and the heat-generating member may become excessively hot. If the heat-generating member becomes excessively hot, the temperature detected by the thermostat will also become excessively high. In other words, the thermostat will operate even if there is nothing abnormal with the belt temperature, resulting in so-called premature thermostat tripping.

[0042] Therefore, in order to prevent the heat generating member from excessively increasing in temperature, it is important to bring the belt and the heat generating member into sufficient contact with each other. Here, the gap between the belt and the heat generating member is defined as an index showing the contact between the belt and the heat generating member. As a result of extensive research, the inventors of the present application have found that the gap between the belt and the heat generating member is correlated with the width dimension of the heat generating member.

[0043] Fig. 4 is a diagram showing the relationship between the width of the heat generating member in the embodiment and the gap between the belt and the heat generating member. In Fig. 4, the horizontal axis shows the width of the heat generating member [mm], and the vertical axis shows the gap between the belt and the heat generating member [mm]. As shown in Fig. 4, it is recognized that the gap between the belt and the heat generating member becomes smaller as the width of the heat generating member becomes larger.

[0044] When the heat-generating member is formed in an arc shape along the inner peripheral surface of the belt, it is ideal to measure the contour of the heat-generating member in order to control the dimensions of the heat-generating member. However, measuring the contour is extremely difficult in terms of controlling the dimensions of the heat-generating member in mass production.

[0045] Therefore, in the present application, the width dimension of the heat generating member is measured, thereby enabling mass production control of the dimensions of the heat generating member. For example, when the heat generating member is molded by press working, the blank dimensions (product dimensions) corresponding to the dimensions of the press working die are stable. Therefore, the dimensions of the heat generating member having an arc shape can be mass-produced and controlled by measuring the width dimension of the heat generating member (width dimension W of the heat generating member shown in FIG. 3).

[0046] As a result of extensive research, the inventors of the present application have found that the temperature of the thermostat is correlated with the width dimension of the heat generating member. Fig. 5 is a diagram showing the relationship between the gap between the belt and the heat generating member and the temperature of the thermostat in the embodiment. In Fig. 5, the horizontal axis indicates the temperature of the thermostat [°C], and the vertical axis indicates the gap between the belt and the heat generating member [mm]. As shown in Fig. 5, there is a tendency for the temperature of the thermostat to increase as the gap between the belt and the heat generating member increases. As mentioned above, there is a relationship in which the gap between the belt and the heat generating member decreases as the width dimension of the heat generating member increases (see Fig. 4). In other words, it can be said that the temperature of the thermostat tends to increase as the width dimension of the heat generating member decreases.

[0047] Incidentally, there is a correlation between the inner diameter of the belt and the rigidity of the belt. The rigidity of the belt can be quantified by the amount of deflection of the belt. A low rigidity of the belt means that the belt is easily deformed by an external force. For example, when a heat-generating member is pressed from the inside of the belt, the shape of the belt is easily deformed distortedly due to the external force that rotates the belt, the inertial force, the reaction force of the inner sliding, and the like. In other words, the belt is not easy to maintain a perfect arc shape, and is also difficult to follow the arc shape of the heat-generating member. As a result, the shape of the belt is not stable when rotating, which leads to poor adhesion between the belt and the heat-generating member, and also to poor heat transport between the belt and the heat-generating member.

[0048] 6 is a diagram showing the relationship between the difference between the inner diameter of the belt and the outer diameter of the heat-generating member in the embodiment and the adhesion between the belt and the heat-generating member. Here, the inner diameter of the belt means the inner diameter of the belt when the belt is a perfect cylinder. The outer diameter of the heat-generating member means the maximum width (width dimension of the heat-generating member) of both ends in the circumferential direction of the curved portion of the heat-generating member when the curved portion is a semicircular arc.

[0049] The adhesion between the belt and the heat-generating component is evaluated as follows: If the temperature of the thermostat falls below the target value (target value T shown in FIG. 7) even if the dimensions of the heat-generating component vary (if mass production is possible), it is evaluated as "Good." If the temperature of the thermostat exceeds the target value due to the variation in the dimensions of the heat-generating component (if the temperature of the thermostat falls below the target value if the width dimension of the heat-generating component is controlled), it is evaluated as "Good." If the temperature of the thermostat exceeds the target value regardless of the variation in the dimensions of the heat-generating component, which is not shown, it is evaluated as "Poor." For example, if a heat-generating component with an outer diameter of 39.2 mm is set for a belt with an inner diameter of 40 mm, the adhesion is basically evaluated as "Poor," but if the width dimension of the heat-generating component is controlled, the adhesion will be evaluated as "Good."

[0050] As shown in Figure 6, when the difference between the inner diameter of the belt and the outer diameter of the heat-generating component is 0.6 mm or 0.7 mm, the adhesion between the belt and the heat-generating component is evaluated as ◯. On the other hand, when the difference between the inner diameter of the belt and the outer diameter of the heat-generating component is 0.8 mm, the adhesion between the belt and the heat-generating component is evaluated as △.

[0051] Fig. 7 is a diagram showing the relationship between the width of the heat generating member and the temperature of the thermostat in the embodiment. In Fig. 7, the horizontal axis shows the width of the heat generating member [mm], and the vertical axis shows the temperature of the thermostat [°C]. In Fig. 7, the symbol G1 is a graph showing the relationship when a heat generating member with an outer diameter of 39.6 mm is set for a belt with an inner diameter of 40 mm, the symbol G2 is a graph showing the relationship when a heat generating member with an outer diameter of 39.2 mm is set for a belt with an inner diameter of 40 mm, and the symbol T shows the target temperature value of the thermostat.

[0052] As shown in Fig. 7, in both graphs G1 and G2, it is recognized that the temperature of the thermostat tends to decrease as the width dimension of the heat-generating member increases. It is recognized that the temperature of the thermostat tends to decrease by increasing the outer diameter of the heat-generating member under the same inner diameter of the belt.

[0053] In FIG. 7, graph G1 corresponds to the case where the difference between the inner diameter of the belt and the outer diameter of the heat-generating component is 0.4 mm, and graph G2 corresponds to the case where the difference between the inner diameter of the belt and the outer diameter of the heat-generating component is 0.8 mm. In the case of graph G1, the temperature of the thermostat is about 20° C. lower than in the case of graph G2, and the temperature of the thermostat falls below the target value T even if the dimensions of the heat-generating component vary. On the other hand, in the case of graph G2, the temperature of the thermostat may exceed the target value T depending on the variations in the dimensions of the heat-generating component, but the temperature of the thermostat falls below the target value T if the width dimension of the heat-generating component is controlled. In other words, if the difference between the inner diameter of the belt and the outer diameter of the heat-generating component is 0.7 mm or less, the adhesion between the belt and the heat-generating component is good (see FIG. 6), and the temperature of the thermostat is less dependent on the width dimension of the heat-generating component (see FIG. 7).

[0054] The belt 30 and the heat generating member 40 of the embodiment satisfy the following formulas (1) and (2). D≧10mm (1) 0.4 mm ≧ AB ≧ 0 mm (2) Here, D means the amount of deflection of the belt, A means the radius of curvature of the inner peripheral surface of the belt, and B means the radius of curvature of the outer peripheral surface of the heat-generating member. Specifically, the amount of deflection D of the belt means the amount of displacement of the end of the belt in the belt axial direction when a 200g weight is placed on the central upper part of a belt with a length in the belt axial direction of 100mm. The radius of curvature A of the inner peripheral surface of the belt is equivalent to half the value of the inner diameter of the belt. The radius of curvature B of the outer peripheral surface of the heat-generating member is equivalent to half the value of the outer diameter of the heat-generating member. In addition, when the amount of deflection D of the belt is 10 mm or more, it corresponds to a case where the inner diameter of the belt is 35 mm or more. When the difference (AB) between the radius of curvature A of the inner surface of the belt and the radius of curvature B of the outer surface of the heat-generating member is 0.4 mm, it corresponds to a case where the difference between the inner diameter of the belt and the outer diameter of the heat-generating member is 0.8 mm (graph G2 in FIG. 7).

[0055] When the dimensions of the heat generating member 40 are changed, it is preferable to maintain an inscribed relationship with the inner circumferential surface of the belt 30. It is preferable that the arc center C of the curved portion 50 of the heat generating member 40 is located on the first straight line J when viewed from the belt axial direction, at least within a range that satisfies the above formula (2). That is, as the difference (AB) between the radius of curvature A of the inner circumferential surface of the belt and the radius of curvature B of the outer circumferential surface of the heat generating member approaches 0 mm, the arc center C of the curved portion 50 shifts from the first straight line J to the right side of the paper surface of FIG. 2 and approaches the center (rotation center) of the belt 30. By arranging the arc center C of the curved portion 50 of the heat generating member 40 on the first straight line J when viewed from the belt axial direction, the positional relationship with the induced current generating unit 33 is maintained, so that the required heat can be easily obtained.

[0056] It is preferable that the belt 30 and the heat generating member 40 of the embodiment further satisfy the following formula (3). 0.35 mm ≧ AB (3) When the difference (AB) between the radius of curvature A of the inner surface of the belt and the radius of curvature B of the outer surface of the heat-generating member is 0.35 mm, this corresponds to the difference between the inner diameter of the belt and the outer diameter of the heat-generating member being 0.7 mm (see FIG. 6).

[0057] The belt 30 and the heat generating member 40 of the embodiment may further satisfy the following formulas (4) and (5) instead of further satisfying the above formula (3). 0.4 mm ≧ AB > 0.35 mm (4) W>H (5) Here, W denotes the width dimension of the heat generating member, and H denotes the height dimension of the heat generating member (see FIG. 3). In addition, B in the above formula (4) is the theoretical value of the blank dimension of the sheet metal (the dimension of the die for press working). When the width dimension W of the heat-generating component is larger than the height dimension H of the heat-generating component, it corresponds to the semicircular arc shape shown in Figure 3.

[0058] As described above, the heating device 24 of the embodiment includes the belt 30 and the heat-generating member 40. The belt 30 has a cylindrical shape. The heat-generating member 40 is provided inside the belt 30. The heat-generating member 40 is formed in an arc shape that follows the inner peripheral surface of the belt 30. The heat-generating member 40 is in slidable contact with the inner peripheral surface of the belt 30. When the amount of deflection of the belt 30 is D, the radius of curvature of the inner peripheral surface of the belt 30 is A, and the radius of curvature of the outer peripheral surface of the heat-generating member 40 is B, the following formulas (1) and (2) are satisfied. D≧10mm (1) 0.4 mm ≧ AB ≧ 0 mm (2) The above configuration provides the following advantages. Even if the dimensions of the heat-generating member 40 vary, the belt 30 and the heat-generating member 40 can be brought into sufficient contact with each other, and heat can be sufficiently transported between the heat-generating member 40 and the belt 30. Therefore, excessive temperature rise of the heat-generating member 40 can be suppressed.

[0059] It is preferable that the heating device 24 further satisfies the following formula (3). 0.35 mm ≧ AB (3) The above configuration provides the following advantages. The belt 30 and the heat-generating member 40 can be brought into closer contact with each other, and heat can be more effectively transported between the heat-generating member 40 and the belt 30. Therefore, excessive temperature rise of the heat-generating member 40 can be more effectively prevented.

[0060] The heating device 24 may further satisfy the following formulas (4) and (5) instead of further satisfying the above formula (3). 0.4 mm ≧ AB > 0.35 mm (4) W>H (5) The above configuration provides the following advantages. By controlling the width dimension W of the heat-generating member, even if the dimensions of the heat-generating member 40 vary, the belt 30 and the heat-generating member 40 can be brought into sufficient contact with each other, and heat can be sufficiently transported between the heat-generating member 40 and the belt 30. Therefore, excessive temperature rise of the heat-generating member 40 can be suppressed.

[0061] The heating device 24 further includes a thermostat 46 that is in contact with the inner circumferential surface of the heat-generating member 40 and detects the temperature of the heat-generating member 40, thereby achieving the following effects. By preventing an excessive rise in temperature of the heat generating member 40, it is possible to prevent the thermostat 46 from tripping prematurely. Therefore, the operation of the thermostat 46 as a safety device for the heating device 24 can be stably performed.

[0062] The image processing device 1, being provided with the above-described heating device 24, provides the following effects. The heating device 24 can suppress an excessive rise in temperature of the heat generating member 40. Therefore, the image processing device 1 can improve image quality.

[0063] Next, a modification of the embodiment will be described. The heating device of the embodiment satisfies the following formulas (1) and (2). D≧10mm (1) 0.4 mm ≧ AB ≧ 0 mm (2) On the other hand, the heating device may satisfy the following formula (6) instead of the above formula (2). 0.98≦B / A≦1 Here, B / A indicates the ratio of the radius of curvature B of the outer circumferential surface of the heat-generating member to the radius of curvature A of the inner circumferential surface of the belt.

[0064] The curved portion of the heat generating member in the embodiment has a semicircular arc shape when viewed from the belt axial direction. In contrast, the curved portion of the heat generating member may have an arc shape with a smaller circumferential length than the semicircular arc shape when viewed from the belt axial direction. Alternatively, the curved portion of the heat generating member may have an arc shape with a larger circumferential length than the semicircular arc shape when viewed from the belt axial direction. For example, the curved portion of the heat generating member may be formed in an arc shape that follows the inner circumferential surface of the belt.

[0065] The image processing apparatus according to the embodiment is an image forming apparatus. Alternatively, the image processing apparatus may be an erasing apparatus. When the image processing apparatus is an erasing apparatus, the heating device performs a process of erasing (erasing) an image formed on a sheet with erasing toner.

[0066] According to at least one of the embodiments described above, when the amount of deflection of the belt is D, the radius of curvature of the inner surface of the belt is A, and the radius of curvature of the outer surface of the heat-generating member is B, the following formulas (1) and (2) are satisfied. D≧10mm (1) 0.4 mm ≧ AB ≧ 0 mm (2) The above configuration provides the following advantages. Even if the dimensions of the heat-generating member vary, the belt and the heat-generating member can be brought into sufficient contact with each other, and heat can be transported sufficiently between the heat-generating member and the belt, thereby preventing the heat-generating member from excessively increasing in temperature.

[0067] Although some embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope of the invention and its equivalents described in the claims, as well as in the scope and spirit of the invention. EXAMPLES

[0068] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.

[0069] [Example] In the embodiment, a cylindrical belt was used. The length of the belt in the belt axial direction was 100 mm. Two types of belts were used: a belt with an inner diameter of 30 mm and a belt with an inner diameter of 40 mm.

[0070] [Experimental Example] The amount of belt deflection was measured for each of the belts with an inner diameter of 30 mm and 40 mm in the embodiment. A height gauge manufactured by Mitutoyo Corporation was used as a measuring device for the amount of belt deflection. Six samples were used for each inner diameter to measure the amount of belt deflection. The positions for measuring the amount of belt deflection were both ends in the axial direction of the belt (Le at the upper left end of the belt on the paper surface and Re at the upper right end of the belt on the paper surface shown in FIG. 8).

[0071] FIG. 8 is an explanatory diagram of a method for measuring the amount of deflection of the belt of the embodiment. The method for measuring the amount of deflection of the belt was to define the initial position of the belt (position before deflection) as 0. Here, the initial position of the belt refers to the position before a 200 g weight is placed on the upper center of the belt in the belt axial direction, and means a light load position when the measurement part of a height gauge is placed on the upper end of the belt in the belt axial direction so that the belt does not move (to the extent that the belt does not rotate in the direction of the arrow in Fig. 8).

[0072] The amount of deflection of the belt was measured after placing a 200g weight on the upper center of the belt in the belt axial direction. The measurement position of the amount of deflection of the belt was the position after placing a 200g weight on the upper center of the belt in the belt axial direction, which was the light load position when the measurement part of the height gauge was placed on the upper end of the belt in the belt axial direction so that the belt did not move (to the extent that the belt did not rotate in the direction of the arrow in Figure 8).

[0073] FIG. 9 is a diagram showing the measurement results of the amount of deflection of the belt having an inner diameter of 30 mm in the embodiment. As shown in FIG. 9, it was confirmed that the average deflection of the belt with an inner diameter of 30 mm was 6.2 mm.

[0074] FIG. 10 is a diagram showing the measurement results of the amount of deflection of the belt having an inner diameter of 40 mm in the embodiment. As shown in FIG. 10, it was confirmed that the average deflection of the belt with an inner diameter of 40 mm was 14.4 mm.

[0075] From the above, it was found that as the inner diameter of the belt increases, the amount of belt deflection increases (the belt's rigidity decreases).In addition, since the median value between the amount of deflection of a belt with an inner diameter of 30 mm and the amount of deflection of a belt with an inner diameter of 40 mm is about 10 mm, it was found that a belt deflection of 10 mm or more can be estimated to be equivalent to a belt with an inner diameter of 35 mm or more. [Explanation of symbols]

[0076] 1... image processing device, 24... heating device, 30... belt, 40... heat generating member, 46... thermostat, A... radius of curvature of inner peripheral surface of belt, B... radius of curvature of outer peripheral surface of heat generating member, D... amount of deflection of belt, H... height dimension of heat generating member, W... width dimension of heat generating member

Claims

1. A cylindrical belt, a heat generating member provided inside the belt, formed in an arc shape along the inner circumferential surface of the belt, and in slidable contact with the inner circumferential surface of the belt; The amount of deflection D of the belt is the amount of displacement of the end of the belt in the belt axial direction when a weight of 200 g is placed on the central upper part of the belt axial direction for a belt having a length of 100 mm in the belt axial direction, the radius of curvature A of the inner peripheral surface of the belt is half the value of the inner diameter of the belt when the belt is a perfect cylinder, and the radius of curvature B of the outer peripheral surface of the heat-generating member satisfies the following formulas (1) and (2). heating device. D≧10 mm ... (1) 0.4 mm ≧ A-B ≧ 0 mm ... (2)

2. Further satisfying the following formula (3): The heating device according to claim 1 . 0.35mm≧A-B...(3)

3. When the width dimension of the heat generating member is W and the height dimension of the heat generating member is H, the following formulas (4) and (5) are further satisfied. The heating device according to claim 1 . 0.4mm≧A-B>0.35mm...(4) W>H ... (5)

4. The heating element further includes a thermostat that is in contact with an inner circumferential surface of the heating element and detects a temperature of the heating element. A heating device according to any one of claims 1 to 3.

5. The heating device according to any one of claims 1 to 4 is provided. Image processing device.

Images