Heating device and image forming apparatus

Abstract

To more efficiently and more uniformly cool non-paper feed areas of a heating member or an opposite member.SOLUTION: A heating device has channel forming members (ducts 87) that blow out cooling air obliquely from openings 87c to non-paper feed areas outside a paper feed area in a longitudinal direction from the center toward the ends in the longitudinal direction. Extension lines obtained by extending inner side walls that form channels of the channel forming members, the side walls facing the center in the longitudinal direction of a heating member or an opposite member in a direction perpendicular to opening surfaces of the openings intersect with the longitudinal direction of the heating member or the opposite member at 10° or more and 60° or less. A heat generation part (winding 86) of a heat source 85 built in the heating member has protruding areas E protruding to the non-paper feed areas N from the paper feed area P at the ends in the longitudinal direction. An intersection B at which an axis Cd extended from the center point of the opening in a direction perpendicular to the opening surface of the opening intersects with a surface of the heating member or the opposite member is located inside the longitudinal center (center line Co) of the protruding area.SELECTED DRAWING: Figure 2B

Description

[Technical Field]

[0001] The present invention relates to a heating device and an image forming apparatus, and more particularly to a heating device and an image forming apparatus in which cooling air is obliquely blown from the center toward the end in the longitudinal direction of a non-sheet passing region of a heating member. [Background technology]

[0002] In conventional electrophotographic image forming apparatuses, when small-size paper is continuously fed, a temperature rise (excessive edge temperature rise) occurs in the non-paper-passing area where small-size paper does not pass, as shown by the dashed lines (before cooling) in Figures 9A and 9B, which causes poor images and damage to parts. To prevent this excessive edge temperature rise, cooling air is blown from duct 187 toward the non-paper-passing area of the fixing roller 81 or pressure roller.

[0003] In the conventional example 1 in Fig. 9A (Patent Document 1: Japanese Patent No. 5401441), cooling air from duct 187 is directed at the fuser roller 81 from a direction roughly perpendicular to the roller. As a result, after the airflow hits the fuser roller 81, it flows longitudinally along the roller, and some of the air crosses the boundary line BL between the non-paper passing area and the paper passing area for small-size paper and flows into the paper passing area. When this occurs, the surface temperature of the paper passing area of the fuser roller 81 also drops, which can cause fixing problems.

[0004] 9B, it is also possible to displace duct 187 toward the longitudinal end, as in Conventional Example 2, in order to prevent a drop in temperature in the paper-passing area of fixing roller 81. However, if duct 187 is shifted toward the longitudinal end, the distance from the air outlet of duct 187 to boundary line BL increases, and the airflow near boundary line BL weakens. As a result, the temperature near boundary line BL cannot be lowered sufficiently, and a sufficient cooling effect cannot be obtained in the entire non-paper-passing area.

[0005] In contrast, in Conventional Example 3 in Figure 10 (Patent Document 2: JP 2019-95532 A), the duct 287 is inclined from a position perpendicular to the longitudinal direction of the fixing roller 81. This allows the flow of cooling air to be directed from the center in the width direction of the heating member 81 toward the ends, preventing the cooling air from flowing into the paper passing area. Summary of the Invention [Problem to be solved by the invention]

[0006] 10, however, the opening 287c of the duct 287 is positioned so that the width N and position of the non-paper passing area are roughly the same. For this reason, even if the duct 287 is tilted, the part of the non-paper passing area N that is likely to reach high temperature T1 (the part adjacent to the outside of the boundary line BL) cannot be sufficiently cooled, and conversely, there is a problem in that the part that is less likely to reach high temperature (outside the protruding area E of the winding 86) is excessively cooled. An object of the present invention is to provide a heating device and an image forming apparatus that can cool the non-paper passing area of a heating member or opposing member more efficiently and uniformly. [Means for solving the problem]

[0007] In order to solve the above-mentioned problems, the heating device of the present invention is a heating device that includes a heating element and an opposing element that have a longitudinal direction and form a nip portion, the heating element has a built-in heat source having a heat generating portion that extends in the longitudinal direction, and heat is transferred from the heating element to a sheet element of a predetermined size by passing the sheet element through a paper passing area of the nip portion through which the sheet element passes, the heating device has a flow path forming member that blows cooling air obliquely from an opening from a center side in the longitudinal direction toward an end side toward a non-paper passing area on the longitudinal outside of the paper passing area, and the side that forms the flow path of the flow path forming member The wall is characterized in that an extension line extending from the inner side wall on the longitudinal center side of the heating element or the opposing element in a direction perpendicular to the opening surface of the opening intersects with the longitudinal direction of the heating element or the opposing element at an angle of 10° to 60°, the longitudinal end of the heat generating part has an overhanging area that overhangs from the paper passing area into the non-paper passing area, and the intersection point where an axis extending from the center point of the opening in a direction perpendicular to the opening surface of the opening intersects with the surface of the heating element or the opposing element is located inside the longitudinal center of the overhanging area. [Effects of the Invention]

[0008] According to the present invention, the non-sheet passing area of the heating member or the opposing member can be cooled more efficiently and more uniformly. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic diagram illustrating the configuration of an image forming apparatus according to an embodiment of the present invention. [Figure 2A] FIG. 1 is a basic diagram of an end cooling structure of a heating element. [Figure 2B] 1 is a schematic configuration diagram of a heating device according to an embodiment of the present invention. [Figure 2C] 10(a) to 10(c) are diagrams showing modified examples of the shape of the duct. [Figure 3] FIG. 10 is a cross-sectional view showing the relationship between the diameter of the duct opening and the diameter of the heating member. [Figure 4] FIG. 4 is a cross-sectional view showing the positional relationship between a duct opening and a heating member. [Figure 5]10 is a diagram showing the positional relationship between an axis passing through the center point of the duct opening and a protruding region of the winding. FIG. [Figure 6A] 10A and 10B are diagrams illustrating a restricting portion of a duct opening portion. [Figure 6B] FIG. 10 is a view showing a cutout portion of a duct opening. [Figure 7] FIG. 10 is a diagram showing the inward arrangement of the duct. [Figure 8A] 1 is a schematic diagram of a heating device according to an embodiment of the present invention used in a drying device. [Figure 8B] FIG. 1 is a schematic diagram illustrating a heating device having a plurality of heat rolls. [Figure 9A] FIG. 1 is a diagram showing a first conventional example of a duct for cooling an end portion of a heating member. [Figure 9B] FIG. 10 is a diagram showing a second conventional example of a duct for cooling the end portion of a heating member. [Figure 10] FIG. 10 is a diagram showing a third conventional example of a duct for cooling the end portion of a heating member. DETAILED DESCRIPTION OF THE INVENTION

[0010] (●Configuration of image forming device) A heating device and an image forming apparatus (laser printer) according to an embodiment of the present invention will be described below with reference to the drawings. A laser printer is one example of an image forming apparatus, and the image forming apparatus is not limited to a laser printer. In other words, the image forming apparatus can be configured as any one of a copier, facsimile, printer, printing machine, and inkjet recording apparatus, or as a multifunction machine that combines at least two or more of these.

[0011] In addition, the same or corresponding parts in each drawing are denoted by the same reference numerals, and redundant explanations are appropriately simplified or omitted. Furthermore, the dimensions, materials, shapes, relative positions, etc. in the explanations of each component are examples, and unless otherwise specified, are not intended to limit the scope of this invention.

[0012] In the following embodiments, the sheet member (recording medium) will be described as "paper," but the "recording medium" is not limited to paper (paper). The "recording medium" includes not only paper (paper), but also overhead projector sheets, fabric, metal sheets, plastic films, and prepreg sheets made of carbon fiber pre-impregnated with resin.

[0013] "Recording media" includes media onto which developer or ink can be applied, recording paper, and recording sheets. "Paper" also includes not only plain paper, but also cardboard, postcards, envelopes, thin paper, coated paper (coated paper, art paper, etc.), tracing paper, etc. "Image formation" as used in the following description refers not only to applying images such as letters and figures to a medium, but also to applying patterns and other designs to a medium.

[0014] 1, image forming apparatus 100 employs a tandem structure in which photosensitive drums 20Y, 20C, 20M, and 20BK are arranged side by side as image carriers capable of forming images corresponding to the colors separated into yellow, magenta, cyan, and black. In image forming apparatus 100 configured as shown in Fig. 1, visible images (toner images) formed on each of photosensitive drums 20Y, 20C, 20M, and 20BK are transferred in a superimposed manner through a primary transfer process onto intermediate transfer body (hereinafter referred to as transfer belt) 11, which is an endless belt that can move in the direction of arrow A1 while facing each of photosensitive drums 20Y, 20C, 20M, and 20BK.

[0015] The image transferred onto the transfer belt is then transferred collectively to recording paper S, such as a recording sheet, through a secondary transfer process. The transfer belt in this embodiment is an endless belt formed into a loop with a resin film or rubber base. A tension roller 74 is provided on part of the stretched surface of the transfer belt 11 to prevent slack.

[0016] Around each photosensitive drum, devices are arranged for image formation processing in accordance with the rotation of the photosensitive drum. Here, taking photosensitive drum 20BK, which forms black images, as the subject of the description, charging device 30BK, developing device 40BK, primary transfer roller 12BK, and cleaning device 50BK, which perform image formation processing, are arranged in the direction of rotation of photosensitive drum 20BK.

[0017] As will be described later, writing after charging is performed using an optical scanning device 8. In this embodiment, among the devices that perform the image forming process on the photosensitive drum and the image forming process on the photosensitive drum, the charging device 30, the developing device 40, and the cleaning device 50, which correspond to the devices other than the optical scanning device 8 that performs optical writing, are housed together in a single case to form a process cartridge.

[0018] The superimposed transfer onto the transfer belt 11 is performed with shifted timing from the upstream side to the downstream side in the A1 direction by applying voltages to primary transfer rollers 12Y, 12C, 12M, and 12BK disposed opposite each of the photosensitive drums 20Y, 20C, 20M, and 20BK across the transfer belt 11. As a result, as the transfer belt 11 moves in the A1 direction, the visible images formed on each of the photosensitive drums 20Y, 20C, 20M, and 20BK are transferred and superimposed onto the same position on the transfer belt 11.

[0019] The photosensitive drums 20Y, 20C, 20M, and 20BK are arranged in this order from the upstream side in the A1 direction. The photosensitive drums 20Y, 20C, 20M, and 20BK are provided in image stations for forming yellow, cyan, magenta, and black images, respectively.

[0020] The image forming device 100 has four image stations that perform image formation processing for each color, a transfer belt unit 10 that is arranged above and opposite each photosensitive drum 20Y, 20C, 20M, and 20BK and is equipped with a transfer belt 11 and primary transfer rollers 12Y, 12C, 12M, and 12BK, a secondary transfer roller 5 that is arranged opposite the transfer belt 11 and is a transfer roller that serves as a transfer member that rotates in conjunction with the transfer belt 11, an intermediate transfer belt cleaning device 13 that is arranged opposite the transfer belt 11 and cleans the surface of the transfer belt 11, and an optical scanning device 8 that serves as an optical writing device that is arranged below and opposite these four image stations.

[0021] The optical scanning device 8 in this embodiment is equipped with a semiconductor laser as a light source, a coupling lens, an fθ lens, a toroidal lens, a mirror, a rotating polygon mirror, etc. A writing light Lb corresponding to each color (in FIG. 1, for convenience, only the image station for the black image is labeled, but the same applies to the other image stations) is emitted to the photosensitive drums 20Y, 20C, 20M, and 20BK to form an electrostatic latent image on the photosensitive drums 20Y, 20C, 20M, and 20BK.

[0022] The image forming apparatus 100 is provided with a paper feed device 61 equipped with a paper feed cassette 61A containing recording paper S to be transported toward between the photosensitive drums 20Y, 20C, 20M, and 20BK and the transfer belt 11, a pair of registration rollers 4 that feed the recording paper S transported from the paper feed device 61 toward the transfer section between each of the photosensitive drums 20Y, 20C, 20M, and 20BK and the transfer belt 11 at a predetermined timing that coincides with the timing of the formation of a toner image by the image station, and a sensor that detects when the leading edge of the recording paper S reaches the pair of registration rollers 4.

[0023] The image forming apparatus 100 is equipped with a heating device 80 as a roller fixing type fixing unit for fixing a toner image onto the recording paper S onto which the toner image has been transferred, a paper discharge roller 7 for discharging the fixed recording paper S outside the main body of the image forming apparatus 100, a paper discharge tray 17 arranged at the top of the main body of the image forming apparatus 100 for loading the recording paper S discharged outside the main body of the image forming apparatus 100 by the paper discharge roller 7, and toner bottles 9Y, 9C, 9M, and 9BK located below the paper discharge tray 17 and filled with toner of each color: yellow, cyan, magenta, and black.

[0024] The transfer belt unit 10 has a transfer belt 11, primary transfer rollers 12Y, 12C, 12M, and 12BK, as well as a drive roller 72, a driven roller 73, and a tension roller 74 around which the transfer belt 11 is wound, and by moving opposite the photosensitive drums of each process cartridge, multiple color images are sequentially transferred in a superimposed manner.

[0025] The driven roller 73 also functions as a tension applying means for the transfer belt 11, and for this reason, a spring or other such applying means is provided on the driven roller 73. The transfer belt unit 10, the primary transfer rollers 12Y, 12C, 12M, and 12BK, the secondary transfer roller 5, and the cleaning device 13 constitute a transfer device 71.

[0026] The paper feed device 61 includes a paper feed cassette 61A that is detachably disposed in a space provided in the lower portion of the main body of the image forming apparatus 100, and is provided with a feed roller 3 as a delivery means that contacts the upper surface of the uppermost recording sheet S. The feed roller 3 is driven to rotate counterclockwise, and feeds the uppermost recording sheet S toward the pair of registration rollers 4 in cooperation with a friction separator that faces it.

[0027] The heating device 80 has a fixing roller 81 with a heat source inside and a pressure roller 83 pressed against the fixing roller 81. By passing the recording paper S carrying a toner image through the fixing nip, which is the pressure contact point between the fixing roller 81 and the pressure roller 83, the toner image carried is fixed to the surface of the recording paper S by the action of heat and pressure.

[0028] The cleaning device 13 provided in the transfer device 71 has a cleaning brush and a cleaning blade disposed so as to face and contact the transfer belt 11. The cleaning brush and cleaning blade scrape off and remove foreign matter such as residual toner on the transfer belt 11, thereby cleaning the transfer belt 11. The cleaning device 13 also has a discharge means for carrying out and discarding the residual toner removed from the transfer belt 11.

[0029] 1 employs an indirect transfer system in which images formed on each photosensitive drum are sequentially transferred onto a transfer belt 11, resulting in superimposed color images, which are then transferred collectively onto recording paper S by a secondary transfer roller 5. Instead of this indirect transfer system, a direct transfer system can be used in which recording paper S is carried on transfer belt 11, and this recording paper S is placed opposite each photosensitive drum, so that the images of each color are directly superimposed on recording paper S.

[0030] (●Fuser roller end cooling structure) 2A is a basic diagram of the end cooling structure of the fixing roller 81, which serves as a heating member used in the heating device 80. As shown in the figure, a duct 87, which serves as a flow path forming member for blowing out cooling air, incorporates a fan 88 and is inclined at an acute angle θ with respect to the longitudinal direction of the fixing roller 81. For this reason, the orientation of the opening 87c of the duct 87 is inclined outward from the center of the fixing roller 81 in the longitudinal direction in the illustrated example.

[0031] In this embodiment, by inclining the duct 87 at an inclination angle θ and arranging the opening 87c of the duct 87 at a predetermined position with respect to the end of the fixing roller 81 as described later, the non-sheet-passing area can be cooled more efficiently and uniformly compared to FIG. 10. Therefore, the temperature rise near the boundary line BL between the non-sheet-passing area and the sheet-passing area can be suppressed to T2 (<T1), and the temperature drop at the outer end portion of the non-sheet-passing area can also be avoided. Here, the "sheet-passing area" refers to the area where a sheet member of a predetermined size passes through the nip formed between the fixing roller 81 and the pressure roller 83. The "predetermined size" refers to a small size with a high sheet-passing frequency. For example, when mainly passing A4 and appropriately passing A3, the "predetermined size" is A4. The "non-sheet-passing area" refers to the nip portion outside the longitudinal direction of the sheet-passing area where a sheet member of a predetermined size does not pass.

[0032] (● Inclination angle of the duct) The magnitude of the inclination angle θ of the duct 87 can be set to any inclination angle within the range of 10° to 60° as shown in Table 1 below. When the inclination angle θ exceeds 60°, the proportion of the cooling air that enters the sheet-passing area exceeds 25%, making it difficult to equalize the temperature in the sheet-passing area.

Table 1

[0033] On the other hand, when the inclination angle θ is less than 10°, the proportion of the cooling air that enters the sheet-passing area is less than 1%. Therefore, there is no problem in equalizing the temperature in the sheet-passing area. However, the cooling of the outer adjacent portion of the boundary line BL between the sheet-passing area and the non-sheet-passing area becomes weak.

[0034] The outer adjacent portion of the boundary line BL is a portion that tends to reach a high temperature T1 even in the non-sheet-passing area N, so it is necessary to apply sufficient cooling air. By setting the inclination angle θ of the duct 87 within the range of 10° to 60°, the temperature can be equalized in both the sheet-passing area and the non-sheet-passing area.

[0035] (● Direction of the opening) As shown in Figures 2A and 2B, opening 87c of duct 87 is located near the boundary line BL between the paper-passing area and the non-paper-passing area. Opening surface OF of duct 87 faces the edge of fixing roller 81 or pressure roller 83, which serves as the opposing member. Here, "opening surface" refers to the plane that crosses opening 87c at its smallest cross section. The cooling air is blown out perpendicular to opening surface OF.

[0036] By blowing the cooling air from the boundary line BL toward the non-paper passing area, it is possible to prevent the airflow from flowing into the paper passing area and selectively cool only the non-paper passing area. Furthermore, according to this embodiment, the number of parts can be reduced compared to the method of changing the air direction using louvers as in Patent Document 3 (JP 2002-287564 A), so it is possible to make a small and inexpensive heating device.

[0037] (Details of edge cooling structure) 2B shows details of the end cooling structure of the fixing roller 81. The upper diagram in FIG. 2B shows the heating device 80 as seen from the paper feed direction. The lower diagram shows the surface temperature of the fixing roller 81.

[0038] The fixing roller 81 incorporates a heat source 85 such as an infrared heater, and is driven to rotate by a driving means such as a motor. The pressure roller 83 rotates together with the fixing roller 81 while being pressed against it, and when a sheet of paper passes through the fixing nip SN formed between the rollers 81 and 83, heat and pressure are applied to the unfixed toner image on the sheet of paper, and the toner image is fixed to the sheet of paper.

[0039] The area indicated by P in Figure 2B is the paper passage area through which paper passes when printing on paper of a specified size. The areas indicated by N on both sides of P are non-paper passage areas through which paper does not pass. When paper is continuously printed while controlling the surface temperature of fixing roller 81 to maintain it at a specified target temperature T based on a temperature sensor installed in the paper passage area, the surface temperature of fixing roller 81 in paper passage area P is maintained near the target temperature.

[0040] On the other hand, in the non-paper passing area N, the heat generated by the winding 86 as the heat generating portion of the heat source 85 is not absorbed by the paper, but continues to be stored in the fixing roller 81 and the pressure roller 83. As a result, the non-paper passing area N becomes hotter than the paper passing area P. In particular, the temperature is highest near the boundary line BL between the paper passing area P and the non-paper passing area N.

[0041] As one moves from the vicinity of boundary line BL toward the end, the temperature gradually decreases because the winding density of winding 86 of heat source 85 decreases. Furthermore, in the region outside the end of winding 86, no heat is generated and heat is naturally dissipated from the end surface of the member, so the temperature becomes lower. At this time, the surface temperature distribution of pressure roller 83, like the surface temperature distribution of fixing roller 81, is high in non-paper passing region N and gradually decreases toward the end.

[0042] (●Duct shape variations) The shape of the duct 87 is not necessarily limited to the straight shape shown in Fig. 2B. Figures 2C(a), (b), and (c) show modified shapes (opening shapes) of the duct 87. (a) shows the duct 87 in which the opening 87c is shaped like a trumpet, widening toward the end.

[0043] The cross section of duct 87 in (a) narrows toward the upstream side of opening 87c, and constricted portion 87d, which has the smallest cross section, essentially forms the "opening surface," i.e., the plane that crosses opening 87c at the smallest cross section. The blowing direction F of the cooling air is perpendicular to the opening surface (constricted portion 87d). The cooling air tends to become turbulent in the shaded area surrounding the blowing direction of the cooling air, and the cooling air passing through this shaded area cannot effectively cool non-paper passing area N of fuser roller 81.

[0044] 2C(b), the opening 87c is a tapered funnel shape (frusto-conical shape). The tip opening 87e of the opening 87c of the duct 87 constitutes the substantial "opening surface," i.e., the plane that crosses the opening 87c at its smallest cross section. The blowing direction F of the cooling air is perpendicular to the opening surface (tip opening 87e).

[0045] 2C(c), the opening 87c is bullet-shaped. The tip opening 87f of the opening 87c of the duct 87 constitutes the substantial "opening surface," i.e., the plane that crosses the opening 87c at its smallest cross section. The blowing direction F of the cooling air is perpendicular to the opening surface (tip opening 87f).

[0046] (Comparison with Conventional Example 3) 10 according to the aforementioned conventional example 3 is known as a method for mitigating the temperature rise in the non-paper passing region N. In this duct configuration, cooling air is blown out from a duct 287 that is inclined toward the non-paper passing region N, and the width and position of the opening of the duct 287 roughly match the width and position of the non-paper passing region N. Therefore, the inclination of the duct 287 prevents the cooling air from flowing around into the paper passing region P, but the inclination of the duct 287 causes the cooling air to move toward the longitudinal end between the time it is blown out from the opening 287c and the time it hits the surface of the fixing roller 81.

[0047] Therefore, the cooling air blown out from the innermost part of the duct 287 comes into contact with the surface of the fixing roller 81 at position A in Fig. 10. As a result, the cooling air does not reach the outer area W adjacent to the boundary line BL between the non-paper passing area P and the non-paper passing area N, which are prone to become hot, and the temperature of the fixing roller 81 cannot be lowered completely.

[0048] Furthermore, in the non-paper passing region N near the longitudinal end, i.e., the portion outside the protruding region E of the winding 86 of the heat source 85, no heat is generated from the winding 86 and the heat is naturally dissipated from the end surface of the member. For this reason, the portions near the longitudinal end are not likely to become too hot, but in the case of Figure 10, excessive cooling is performed by actively blowing cooling air near the end, so the surface temperature at the end of the fixing roller 81 drops too low. As a result, there are portions T1 in the non-paper passing region N where the temperature is too high and portions where the temperature is too low, causing uneven temperature distribution and inefficient cooling.

[0049] In this embodiment, the cooling fan and duct of the blower cooling mechanism are arranged at an angle, similar to the conventional example 3 shown in FIG. 10 . However, as shown in FIG. 2B , the orientation and position of duct 87 are set so that point A, where an extension line EL1 extending from the inner sidewall of duct 87 in a direction perpendicular to the opening plane OF at opening 87c of duct 87 intersects with the surface of fuser roller 81, is aligned with the edge region of paper-passing area P. Furthermore, within the range where the cooling air directly strikes fuser roller 81, point A, the innermost point, roughly coincides with the boundary line BL between paper-passing area P and non-paper-passing area N. In other words, duct 87 is positioned so that point A is located within a range of 10 mm both inside and outside of boundary line BL in the longitudinal direction. Note that in the case of the duct shape shown in FIG. 2C , the "extension line" is a straight line EL1 that is parallel to the airflow direction F and passes through constricted portion 87d and the inner sidewalls of tip openings 87e and 87f.

[0050] 2B, when the point where an axis Cd extending from the center point of the opening 87c of the duct 87 in a direction perpendicular to the opening plane OF intersects with the surface of the fixing roller 81 is defined as B, and the point where the center line Co of the protruding region E of the winding 86 in the non-paper passing region N intersects with the surface of the fixing roller 81 is defined as C, B is set to be located longitudinally inward of C. This makes it possible to effectively direct cooling air toward the part of the non-paper passing region N that is most likely to become hot. Here, the "center point of the opening" refers to the geometric center point of the inner plane of the opening.

[0051] 2B , point D, where an extension line EL2 extending from the outer sidewall of opening 87c of duct 87 in a direction perpendicular to opening plane OF of opening 87c intersects with the surface of fuser roller 81, is set to be inside the end of protruding range E of winding 86. In other words, point D is set to the outermost position within the range where cooling air directly hits fuser roller 81, and cooling air is not actively directed toward areas outside protruding range E of winding 86. With this configuration, it is possible to concentrate the cooling range within an optimal range, with a focus on cooling only high-temperature areas and not cooling areas that do not rise in temperature as much (outside protruding range E).

[0052] As a result, the temperature of the non-sheet passing area N is more easily uniformed compared to Fig. 10, and the cooling efficiency can be improved. Note that, although the configuration in which cooling air is applied to the fixing roller 81 has been described so far, the present invention can also be applied to a configuration in which the pressure roller 83 is cooled.

[0053] (●Duct opening diameter) Next, with reference to Figure 3, the relationship between the opening diameter Hd, which is the width in the short direction of the opening 87c of the duct 87, and the diameter Hf, which is the diameter of the fixing roller 81 to be cooled, will be described. Figure 3 is a view of the heating device 80 viewed from the longitudinal direction. As shown in the figure, the opening diameter Hd of the opening 87c of the duct 87 is made smaller than the diameter Hf of the fixing roller 81, and the duct 87 is positioned so that the entire opening 87c faces the surface of the fixing roller 81.

[0054] With this configuration, all of the cooling air blown out from the duct 87 hits the fixing roller 81 directly, thereby effectively cooling the fixing roller 81. The duct 87 can be installed in a position opposite the fixing roller 81, or in a position opposite the pressure roller 83.

[0055] When the duct 87 is installed at a position facing the pressure roller 83, the opening diameter Hd of the opening 87c of the duct 87 is set smaller than the diameter of the pressure roller 83, and the duct 87 is installed so that the entire opening 87c faces the surface of the pressure roller 83. With this configuration, the cooling air can be used efficiently to cool the pressure roller 83, as described above.

[0056] (●Duct opening height) Next, the height of opening 87c of duct 87 will be described with reference to Fig. 4. Fig. 4 is a view of heating device 80 viewed from the longitudinal direction. As shown in the figure, opening 87c of duct 87 is located diagonally below the center of fixing roller 81.

[0057] Therefore, the cooling air blown out from opening 87c of duct 87 hits the diagonally lower side of the surface of fixing roller 81, and is then heated by contact with the surface of fixing roller 81. This heated air flows smoothly upward along the surface of fixing roller 81 due to the effect of natural convection.

[0058] 3, or when the duct 87 is provided above the fixing roller 81, the duct 87 in FIG. 4 can efficiently cool a wide area of the surface of the fixing roller 81. The duct 87 can be installed not only in a position facing the fixing roller 81, but also facing the pressure roller 83.

[0059] Whether to cool the fixing roller 81 or the pressure roller 83 can be determined based on the space available for arranging the duct 87 within the main body of the image forming apparatus 100, the ease of discharging heat from the main body to the outside, etc. In Fig. 4, the entire opening 87c of the duct 87 is located below the center of the fixing roller 81, but it is also possible to configure the opening 87c so that only a portion of it is located below the center of the fixing roller 81 and the rest is located above the center of the fixing roller 81.

[0060] (Relationship between the duct and the protruding area of the winding) Next, the relationship between the direction of duct 87 and the winding protrusion area will be described with reference to Fig. 5. In Fig. 5, when the longitudinal center of the winding protrusion area (heat generating portion protrusion area) is defined as HF and a perpendicular line passing through the center point (geometric center point) of the opening surface of duct 87 is defined as CL, duct 87 can be positioned so that the position where an extension of perpendicular line CL intersects with the surface of fixing roller 81 is located inside HF in the longitudinal direction.

[0061] 2B, the temperature distribution before cooling, indicated by the dashed line, tends to be highest on the longitudinally inner side of HF. Therefore, a perpendicular line CL passing through the center point (geometric center point) of the opening surface of duct 87 intersects with the surface of fixing roller 81 on the longitudinally inner side of HF.

[0062] This allows for efficient cooling of the temperature rise in the protruding winding area. Also, by setting the inclination angle θ of duct 87 to 60° or less, the percentage of cooling air that reaches the paper passing area can be reduced to 25% or less, and by preventing a temperature drop in the paper passing area, the temperature in the longitudinal direction of the paper passing area can be made uniform.

[0063] (● Opening shape variation 1) 6A shows a duct 87 provided with a guide portion 87a. This guide portion 87a functions as a regulating portion for regulating the flow of cooling air, and is formed by extending the side wall on the inner side of opening 87c (the center side in the longitudinal direction of fixing roller 81) along the inclination angle θ of duct 87.

[0064] The tip of guide portion 87a is close to the surface of fixing roller 81, and the boundary line BL between the paper-passing area and the non-paper-passing area is located on an extension of guide portion 87a. Providing guide portion 87a in this manner prevents the cooling air blown out from opening 87c from flowing into the paper-passing area, which helps to uniform the temperature in the longitudinal direction of the paper-passing area.

[0065] (● Opening shape variation 2) 6B shows a cutout 87b provided in the opening 87c of the duct 87. This cutout 87b is formed by cutting out a predetermined area in the side wall on the outer side of the opening 87c (on the longitudinal end side of the fixing roller 81).

[0066] Although the illustrated example shows rectangular cutout 87b, the shape and size of cutout 87b can be set appropriately so that the temperature distribution in non-paper passing region N in Fig. 2B approaches the target temperature distribution. By providing cutout 87b in this way, the cooling air blown out from opening 87c can be made to reach the end side of the non-paper passing region, which helps to uniform the temperature in the longitudinal direction of the non-paper passing region.

[0067] (● Duct placement inward) Fig. 7 shows an example of inward placement of duct 87. That is, in Fig. 7, duct 87 is placed so that an extension line EL1, which is an extension of the side wall inside opening 87c of duct 87 (toward the center in the longitudinal direction of fixing roller 81) in a direction perpendicular to the opening surface of opening 87c, intersects with the surface of fixing roller 81 at a position ED that is inside in the longitudinal direction of boundary line BL between the paper passing area and non-paper passing area.

[0068] By setting the inclination angle θ of duct 87 to 60° or less, it is possible to reduce the amount of cooling air that reaches the paper-passing area by 25% or less, and therefore it is possible to reduce the temperature drop in the paper-passing area even if duct 87 is positioned closer to the inside as shown in Figure 7. On the other hand, the inclination angle θ of duct 87 makes it possible to effectively direct cooling air at the part of the non-paper-passing area that is most likely to become hot, which helps to uniform the temperature in the longitudinal direction of the non-paper-passing area.

[0069] (●Drying equipment) The embodiment described above is an example in which the heating device of the present invention is used to fix an image on recording paper S, but the heating device of the present invention can also be used in a drying device. Figure 8A is a schematic diagram of a heating device used in a drying device that heats and dries recording paper S on which an image has been formed by an inkjet printer.

[0070] The heating device in Fig. 8A has a heat roll 381 as a heating member and an opposing roll 383 as an opposing member. The opposing roll 383 presses the recording paper S against the outer circumferential surface of the heat roll 381. Inside the heat roll 381, a heat source 385 having a winding 386 is arranged in the axial direction.

[0071] By passing the recording paper S on which an image has been formed by the inkjet printer through the nip, which is the pressure contact point between the heat roll 381 and the opposing roll 383, the ink on the recording paper S is dried by the heat from the heat source 385.

[0072] It is also possible to omit the opposing roll 383 by applying a predetermined tension to the recording paper S. For example, as shown in Figure 8B, if multiple heat rolls 381 are arranged in a staggered pattern to apply an appropriate tension to the recording paper S, the opposing roll 383 in Figure 8A is not necessarily required.

[0073] Although the present invention has been described above based on the embodiments, it goes without saying that the present invention is not limited to the above embodiments and can be modified in various ways within the scope of the technical concept described in the claims. For example, instead of the fixing roller 81 as the heating member, it is also possible to use a fixing belt stretched over two rollers as in a known belt-type heating device.

[0074] Similarly, a pressure belt stretched over two rollers can be used instead of pressure roller 83. Furthermore, the heating element serving as heat source 85 of fixing roller 81 is not limited to winding 86, and it goes without saying that other heating elements, such as a heater having a PTC element or a ceramic heater, can also be used.

[0075] Furthermore, the fan 88 can be built into the duct 87, or can be disposed outside the heating device 80 or outside the image forming apparatus 100. It is also possible to dispose a flow path relay duct or a flow path relay hose as a flow path relay member having elasticity or flexibility between the duct 87 and the fan 88. By disposing a flow path relay member, the duct 87 with the built-in fan 88 can be fixedly disposed, or can be disposed so as to be movable in the longitudinal direction of the fixing roller 81.

[0076] When duct 87 is arranged to be movable in the longitudinal direction of fixing roller 81, by simply changing the duct position according to the paper size, it is possible to efficiently and uniformly cool the non-paper passing area while miniaturizing the heating device. Note that the flow path relay member only needs to relay the flow of cooling air from fan 88 to duct 87, and the flow path relay member does not necessarily have to be continuous with fan 88 and duct 87.

[0077] The inclination angle θ of the duct 87 may also be variably controlled depending on the temperature of the non-paper passing area and / or the number of consecutively passed sheets of sheet material. As the number of printed sheets increases, the entire non-paper passing area becomes warmer, and the position of the highest temperature changes slightly in the longitudinal direction. Therefore, by adjusting the inclination angle θ of the duct 87 to follow this change, more effective cooling becomes possible.

[0078] Furthermore, the longitudinal position of the duct 87 may be variably controlled in accordance with the size of the sheet material, thereby making it possible to cool the appropriate edge area in accordance with the sheet size. [Explanation of symbols]

[0079] 3: Feeding roller 4: Registration roller pair 5: Secondary transfer roller 6: 7: Paper ejection roller 8: Optical scanning device 9: Toner bottle 10: Transfer belt unit 11: Transfer belt 12: Primary transfer roller 13: Intermediate transfer belt cleaning device 17: Paper output tray 20: Photosensitive drum 30: Charging device 40: Developing device 50: Cleaning device 61: Paper feed device 61A: Paper feed cassette 71: Transfer device 72: Drive roller 73: Driven roller 74: Tension roller 80: Heating device 81: Fixing roller (heating member) 83: Pressure roller (opposing member) 85: Heat source 86: Winding (heat generating part) 87: Duct (flow path forming member) 87a: Guide portion 87b: Notch portion 87c: Opening 88: Fan 100: Image forming device 187, 287: Duct 287c: Opening 381: Heat roll (heating member) 383: Opposing roll (opposing member) 385: Heat source 386: Winding (heat generating part) E: Winding protrusion area (heat generating part protrusion area) N: Non-paper passing area P: Paper passing area S: Recording paper SN: Fixing nip θ: Duct inclination angle [Prior art documents] [Patent documents]

[0080] [Patent Document 1] Patent No. 5401441 [Patent Document 2] Japanese Patent Application Publication No. 2019-95532 [Patent Document 3] Japanese Patent Application Laid-Open No. 2002-287564

Claims

1. A heating device comprising a heating member and an opposing member having a longitudinal direction and forming a nip portion, the heating member incorporating a heat source having a heat generating portion extending in the longitudinal direction, and heat transfer from the heating member to a sheet member of a predetermined size by passing the sheet member through a paper passing area of the nip portion, a flow path forming member for blowing cooling air obliquely from an opening from a center side toward an end side in the longitudinal direction of the non-paper passing region on the longitudinal outer side of the paper passing region; a side wall that forms a flow path of the flow path forming member, wherein an extension line extending from an inner side wall on a longitudinal center side of the heating member or the opposing member in a direction perpendicular to an opening surface of the opening intersects with the longitudinal direction of the heating member or the opposing member at an angle of 10° to 60°, an intersection of an extension line of the inner side wall of the flow path forming member in a direction perpendicular to the opening surface of the opening and a surface of the heating member or the opposing member is set within a range of 10 mm each on the inside and outside in the longitudinal direction based on a boundary line between the paper passing region and the paper non-passing region; a longitudinal end portion of the heat generating portion has a protruding region that protrudes from the paper passing region into the non-paper passing region, A heating device characterized in that the intersection of an axis extending from the center point of the opening in a direction perpendicular to the opening surface of the opening and the surface of the heating element or the opposing element is located inside the longitudinal center of the protruding area.

2. A heating device comprising a heating element and an opposing element having a longitudinal direction and forming a nip portion, wherein the heating element incorporates a heat source having a heat generating portion extending in the longitudinal direction, and wherein heat is transferred from the heating element to a sheet member of a predetermined size by passing the sheet member through a paper passing area of the nip portion, a flow path forming member for blowing cooling air obliquely from an opening from a center side toward an end side in the longitudinal direction of the non-paper passing region on the longitudinal outer side of the paper passing region; a side wall that forms a flow path of the flow path forming member, wherein an extension line extending from an inner side wall on a longitudinal center side of the heating member or the opposing member in a direction perpendicular to an opening surface of the opening intersects with the longitudinal direction of the heating member or the opposing member at an angle of 10° to 60°, the inclination angle of the flow path forming member is variably controlled in accordance with the temperature of the non-sheet passing region and / or the number of sheets of the sheet member that have been continuously passed; a longitudinal end portion of the heat generating portion has a protruding region that protrudes from the paper passing region into the non-paper passing region, A heating device characterized in that the intersection of an axis extending from the center point of the opening in a direction perpendicular to the opening surface of the opening and the surface of the heating element or the opposing element is located inside the longitudinal center of the protruding area.

3. A heating device comprising a heating element and an opposing element having a longitudinal direction and forming a nip portion, wherein the heating element incorporates a heat source having a heat generating portion extending in the longitudinal direction, and wherein heat is transferred from the heating element to a sheet member of a predetermined size by passing the sheet member through a paper passing area of the nip portion, a flow path forming member for blowing cooling air obliquely from an opening from a center side toward an end side in the longitudinal direction of the non-paper passing region on the longitudinal outer side of the paper passing region; a flow path relay member having elasticity or flexibility is disposed between the flow path forming member and a blower member that supplies cooling air to the flow path forming member; a side wall that forms a flow path of the flow path forming member, wherein an extension line extending from an inner side wall on a longitudinal center side of the heating member or the opposing member in a direction perpendicular to an opening surface of the opening intersects with the longitudinal direction of the heating member or the opposing member at an angle of 10° to 60°, a longitudinal end portion of the heat generating portion has a protruding region that protrudes from the paper passing region into the non-paper passing region, A heating device characterized in that the intersection of an axis extending from the center point of the opening in a direction perpendicular to the opening surface of the opening and the surface of the heating element or the opposing element is located inside the longitudinal center of the protruding area.

4. 4. The heating device according to claim 1, wherein the longitudinal width of the opening of the flow passage forming member is set to be equal to or less than the length of the heat generating portion in the protruding region.

5. 5. The heating device according to claim 1, wherein the width of the opening in the flow path forming member in the lateral direction is set smaller than the diameter of the heating member or the opposing member facing the opening.

6. 6. The heating device according to claim 1, wherein at least a part of the opening of the flow passage forming member is positioned below a rotation axis of the heating member or the opposing member.

7. 7. The heating device according to claim 1, wherein the longitudinal position of the flow path forming member is variably controlled in accordance with the size of the sheet member.

8. An image forming apparatus comprising the heating device according to any one of claims 1 to 7.

Images