Patent Application
20190137913
The present invention relates to a fixing device mounted on an image forming apparatus such as an electrophotographic recording type copying machine or a printer, and to a heater mounted on the fixing device.
Fixing devices using a film are known including fixing devices to be mounted on electrophotographic recording type image forming apparatus. This fixing device includes a tubular film and a heater that is in contact with an inner face of the film. Since the fixing device using a film has low heat capacity, it is advantageous that the device can be operated with a short warm-up time and low power consumption.
The heater includes a substrate made of a material such as ceramics and a heat generating resistor (heat generation element) arranged on the substrate. Temperature of the heater is detected by a temperature detection element such as a thermistor, and a control unit controls the power supplied to the heat generating resistor according to an output of the temperature detection element.
The temperature detection element is configured to be mounted independently from the heater, which is pushed against the heater via an insulation sheet. Further, there is provided a heater-integrated configuration in which a temperature detection element and a conductive line electrically connected to the temperature detection element are arranged on a substrate of the heater through a coating method such as screen printing. In the above heater-integrated configuration, the temperature detection element, the conductive line, and the heat generation element are protected by a glass film for the sake of insulation. This heater-integrated configuration is advantageous in that variation in responsiveness is small and the temperature detection accuracy is high because the temperature detection element is printed on the substrate.
Further, in order to precisely detect a temperature at a fixing nip portion, a configuration is discussed in which a temperature detection element is arranged on a sliding face of a heater that is in contact with a film (Japanese Patent Application Laid-Open no. 10-240357). Further, in order to reduce the heater in size, the heat generating resistor may be arranged on a face opposite to the face of the substrate on which the temperature detection element is arranged.
However, in the above-described configuration of the heater, at a portion where the temperature detection element or the conductive line is arranged, the thickness from a surface of the substrate becomes thicker than that of the other portions, so that irregularity may arise on the surface of the heater. According to the examination conducted by the inventors, a fixing failure or a gloss streak sometimes occurred when a conductive line was formed on a substrate of the heater in parallel with the conveyance direction of a recording material. This is because heat and pressure applied to a toner image become non-uniform because of a step portion generated on the surface of the heater by the conductive line.
The present invention is directed to a heater and a fixing device capable of suppressing occurrence of an image defect such as a fixing failure or a gloss streak.
According to an aspect of the present invention, a heater used for a fixing device includes a substrate having a lengthwise direction and a widthwise direction, a heat generation element arranged on the substrate, a temperature detection element arranged on a face opposite to a face of the substrate on which the heat generation element is arranged, two conductive lines electrically connected to the temperature detection element, the two conductive lines being arranged on the face opposite to the face of the substrate on which the heat generation element is arranged, and a protection layer that covers the temperature detection element and the two conductive lines, wherein one of the conductive lines is arranged to extend from the temperature detection element to one end portion of the substrate in the lengthwise direction of the substrate, and the other conductive line is arranged to extend from the temperature detection element to the other end portion of the substrate in the lengthwise direction of the substrate, and wherein at least one of the two conductive lines has a region that is inclined in both of the lengthwise direction and the widthwise direction of the substrate in an area covered by the protection layer.
Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings. Each of the embodiments of the present invention described below can be implemented solely or as a combination of a plurality of the embodiments. Also, features from different embodiments can be combined where necessary or where the combination of elements or features from individual embodiments in a single embodiment is beneficial.
Next, the fixing device 7 will be described with reference to
The film 11 includes a base layer and a release layer formed outside of the base layer. The base layer is formed of heat resistant resin such as polyimide, polyamide-imide, or polyether-ether-ketone (PEEK), or metal such as stainless steel (SUS). The release layer is a mixed layer or a single layer of heat resistant resin having favorable releasing performance, such as fluorine resin, e.g., polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), or tetrafluoroethylene-hexafluoropropylene copolymer (FEP) and silicone resin. Further, an intermediate layer formed of heat resistant rubber such as silicone rubber may be arranged between the base layer and the release layer. The film 11 of the present exemplary embodiment includes a SUS base layer having a thickness of 30 μm, a silicone rubber layer (elastic layer) having a thickness of 200 μm, and a release layer consisting of PFA having a thickness of 20 μm. An outer diameter and a length in the lengthwise direction of the film 11 (i.e., a length in the width direction of the recording material P) are 24 mm and 240 mm, respectively.
The heater holder 13 holds the heater 12, and functions as a guide for guiding rotation of the film 11. The heater holder 13 is formed of heat resistant resin such as liquid crystal polymer.
The metallic stay 14 is a member for reinforcing the heater holder 13. A metallic material such as SUS having high rigidity is used for the metallic stay 14 in order to be sustainable against the load applied thereto when the heater holder 13 is pressed against the pressure roller 20.
The pressure roller 20 includes a core metal 21 and an elastic layer 22 formed on the outer side of the core metal 21. A release layer formed of PFA or PTFE may be arranged on the outer side of the elastic layer 22. The core metal 21 receives driving power from a motor (not illustrated) to rotate the pressure roller 20 in a direction indicated by an arrow. When the pressure roller 20 is rotated, the film 11 is rotated accordingly. The pressure roller 20 according to the present exemplary embodiment includes the elastic layer 22 formed of silicone rubber having a thickness of 3.5 mm and a release layer formed of PFA having a thickness of 70 μm. An outer diameter and a length in the lengthwise direction of the pressure roller 20 are 25 mm and 230 mm, respectively.
The fixing device 7 fixes an image formed on a recording material P onto the recording material P with heat applied from the heater 12 via the rotating film 11.
Next, a configuration of the heater 12 of a first exemplary embodiment will be described with reference to
The thermistor 33 and the conductive line 34 are also covered with a sliding side protection layer 36 made of a glass material arranged on the sliding face side. Since the protection layer 36 arranged on the sliding face side also plays a role of protecting the thermistor 33 and the conductive line 34 from abrasion caused by friction with respect to the film 11, a glass material having the abrasion resistance higher than that of the protection layer on the back face side is used. In addition, silver/palladium (Ag/Pd) is used as a material of the heat generating resistor 31, and silver (Ag) is used as a material of the electrode 32 and the conductive line 34. Further, although the heater 12 according to the present exemplary embodiment includes a total of three thermistors 33 respectively arranged at the center and both end portions in the lengthwise direction D1, the number of thermistors may be one or more.
A comparison example as a comparison target of the present exemplary embodiment will be described.
An effect of the present exemplary embodiment was verified under the following condition. First, a normal paper and a glossy paper were prepared as recording materials P. A normal paper “HP Laser Jet 90 g” and a glossy paper “HP Brochure Paper 200 g” were used. Then, unfixed toner images were respectively formed on the normal paper and the glossy paper. Then, fixing processing was executed on these recording materials P by the fixing device 7 on which the heater 12 of the present exemplary embodiment was mounted. Similarly, fixing processing was executed on these recording materials P by a fixing device on which the heater 120 of the comparison example was mounted. A toner image fixed by the fixing device 7 of the present exemplary embodiment and a toner image fixed by the fixing device of the comparison example were compared to each other. In addition, the conveyance speed was set to 300 mm/s when fixing processing was executed on the normal paper, and the conveyance speed was set to 75 mm/s when fixing processing is executed on the glossy paper. Both of the control target temperatures of the heaters 12 and 120 were set to 160° C.
The result is illustrated in a table 1. Although an image defect occurred in both of the normal paper and the glossy paper when the heater 120 of the comparison example was used, favorable fixed images were obtained across the entire lengthwise area when the heater 12 of the present exemplary embodiment was used. In the comparison example, as illustrated in
As described above, occurrence of the image defect can be suppressed by using the heater according to the present exemplary embodiment. A reason for the above result will be described below.
A reason for the image defect occurring in the comparison example is that the heater locally has an area where heat and pressure applied to the toner image become insufficient, at a step portion on the heater sliding face (a surface of the protection layer) generated by the conductive line 34. In the present exemplary embodiment, because the conductive line 34 is formed in an inclined direction, the step will not be intensively generated on a part of a lengthwise area on the sliding face side, so that insufficiency of heat and pressure in a local area described in the comparison example does not occur. As a result, the image defect does not occur because fixability of toner becomes substantially uniform in the entire lengthwise area.
Further, in order to confirm a range of the effect of the present exemplary embodiment, an experiment was conducted by changing the arrangement of the conductive line 34. As illustrated in
As illustrated in the table 2, an image defect did not occur when the angle A was 45° or 60°. The configuration became similar to that of the heater 120 described in the comparison example when the angle A was increased to 750. Therefore, a slight image defect occurred although the image defect was less critical than that of the comparison example.
According to the result obtained in the present exemplary embodiment, it was found that an image defect is less likely to occur if the conductive line 34 is formed and arranged at an angle A of 60° or smaller. However, the condition such as “angle A=60°” depends on the type of the film, the thickness of the conductive line 34, and a type or a conveyance speed of the recording material, and thus the condition cannot be determined uniformly. However, as described above, if the angle A is set to be smaller than 90°, the step on the sliding face side may not be intensively generated in a part of a lengthwise area. Accordingly, providing an area that is inclined in both of the lengthwise direction and the widthwise direction of the substrate 30 without providing an area that is in parallel with the widthwise direction thereof is effective in suppressing occurrence of the image defect.
Now, a variation example 2 of the present exemplary embodiment will be described. As illustrated in
As illustrated in
A second exemplary embodiment of the present invention will be described. The present exemplary embodiment is characterized in that an image defect is suppressed by reducing a step itself generated by the conductive line.
A basic configuration and operation of the fixing device 7 are similar to those described in the first exemplary embodiment. Only a shape on a side of the sliding face of the heater 12 mounted on the fixing device 7 is different from that of the first exemplary embodiment.
A configuration of the heater of the present exemplary embodiment will be described with reference to
A step generated in the comparison example of the first exemplary embodiment is reduced by the convex portion 37. In the present exemplary embodiment, the convex portion 37 is formed at a position where a step has a height of 10 μm or less. A reason for this will be described below.
An effect of the present exemplary embodiment will be described. The experiment was conducted with the same condition as the condition of the first exemplary embodiment by using the heater according to the present exemplary embodiment as a heater to be mounted on the fixing device, and the present exemplary embodiment was compared to the comparison example. Further, a distance D between the conductive line and the convex portion was changed in order to confirm a range of the effect of the present exemplary embodiment, and fixed images were evaluated. As illustrated in the enlarged diagrams of the sliding face of the heater in
The result is illustrated in a table 3. The result of the comparison example is the same as the result obtained in the first exemplary embodiment. When the step was reduced to 15 μm, a fixing failure did not occur in the normal paper although a minor gloss streak was generated. On the other hand, if the step was reduced to 10 μm, an image defect did not occur. If the step was 10 μm or less, an area where applied heat and pressure is not sufficient was reduced, so that fixability is obtained sufficiently.
According to the above-described result, an image defect can be suppressed if the convex portion is formed to reduce the step on the surface of the protection layer to 10 μm or less. In other words, an image defect can be suppressed by setting the step generated by the protection layer on the conductive line 34, the protection layer on the convex portion 37, and the protection layer positioned between the conductive line 34 and the convex portion 37 to be 10 μm or less. Since the conductive line 34 or the convex portion 37 exists in the wide area on the heater, it is advantageous that thermal resistance becomes substantially uniform. Therefore, the present exemplary embodiment is more preferable than the first exemplary embodiment.
Further, in the present exemplary embodiment, although the same material (Ag) is used for the conductive line 34 and the convex portion 37, different materials may be used therefor. However, by using the same material, occurrence of an image defect can be suppressed more easily because the thermal resistance of the conductive line 34 and the convex portion 37 becomes substantially uniform as described above.
Further, in
As a variation example of the present exemplary embodiment, as illustrated in
In addition, a shape of the heat generating resistor 31 is not limited to the shape employed in the present exemplary embodiment or the variation examples. For example, as illustrated in
Next, a heater according to a third exemplary embodiment will be described.
A configuration of a heater according to the third exemplary embodiment will be described with reference to
In a middle of the area 34a of the conductive line 34 arranged in the inclined direction, each of thermistors 331, 332, and 333 is arranged in parallel with the direction D1, so that a lengthwise direction of the thermistor is in parallel with the direction D1. A reason for arranging the thermistors 331 to 333 in the above-described state is to prevent occurrence of an image defect caused by a step generated at connection portions of the thermistors 331, 332, and 333 and the conductive line 34. The details will be described below. Further, as illustrated in
The thermistors 331 to 333 and the conductive line 34 are also covered with a second protection layer 36 made of glass. The second protection layer 36 also plays a role of protecting the thermistors 331 to 333 and the conductive line 34 from abrasion caused by friction with respect to the film 11. Therefore, a glass material with abrasion resistance higher than that of the first protection layer 35 is used. In addition, Ag/Pd is used as a material of the heat generating resistor 31, and Ag is used as a material of the electrode 32 and the conductive line 34.
A connection portion of the thermistor 332 and the conductive line 34 will be described with reference to
Further, a symbol “g0” represents a height of the second protection layer 36 at a portion where nothing is arranged on the substrate 30, a symbol “g1” represents a height of the second protection layer 36 on the overlapping portion OLP, and a symbol “g2” represents a height of the second protection layer 36 on the conductive line 34. Further, the thermistor 332 and the conductive line 34 are set to have the same thickness of 7 μm. Therefore, respective heights satisfies the conditions “h1−h0=14 μm” and “h2−h0=7 μm”. Further, a difference in heights g0 to g2 (height of the step) of the second protection layer 36 is substantially the same as the difference in heights h0 to h2 (height of the step).
In the cross-sectional face L1 in
As illustrated in
In the heater 12 according to the present exemplary embodiment, a structure of the cross-sectional face at the line F1 in the area in the vicinities of the thermistors 331 and 333 is similar to the structure at the line F1 in the area in the vicinity of the thermistor 332. In addition, not all of the structures of the cross-sectional faces at the line F1 in the vicinities of the thermistors 331 to 333 have to be the above-described structure. A structure in a vicinity of at least one thermistor where variation in height of the surface of the second protection layer 36 has to be suppressed only needs to have the above-described structure. Further, in the present exemplary embodiment, a length F34 in the direction D2 of the conductive line 34 serving as a gradient moderating portion (excluding a portion corresponding to the overlapping portion OLP) is 0.1 mm or longer.
In the present exemplary embodiment, the heater 12 having a total of three thermistors has been described. However, even if the number of thermistors included in the heater is one, or four or more, variation in height of the surface of the second protection layer 36 can be also mitigated by arranging the above-described gradient moderating portion.
Next, a heater according to a comparison example will be described with reference to
Thermistors 334, 335, and 336 illustrated in
Next, connection portions of the thermistor 335 and the conductive line 34 in the comparison example 1 will be described with reference to
A path PH1 and a path PH2 illustrate paths through which a height varies from the height h0 of the substrate 30 to the height h1 of the overlapping portion OLP. Since the conductive line 34 as a gradient moderating portion having the second height h2 exists in the path PH1, the height moderately varies from the height h0 of the substrate 30 to the height h1 of the overlapping portion OLP. However, in the path PH2, since the gradient moderating portion does not exist, the height directly varies from the height h0 of the substrate 30 to the height h1 of the overlapping portion OLP. Therefore, the height varies with a steep gradient. Therefore, on a surface of the second protection layer 36 corresponding to the path PH2, the height steeply varies from the height g0 corresponding to the height h0 of the substrate 30 to the height g1 corresponding to the height h1 of the overlapping portion OLP. Therefore, a fixing failure or a gloss streak caused by a magnitude of irregularity on the surface of the second protection layer 36 is likely to occur.
A path PH3 and a path PH4 also illustrate paths through which a height varies from the height h0 of the substrate 30 to the height h1 of the overlapping portion OLP. Since the gradient moderating portion does not exist in each of the paths PH3 and PH4, the height directly vary from the height h0 of the substrate 30 to the height h1 of the overlapping portion OLP, so that the height varies with a steep gradient. According to the magnitude of the gradient, the height steeply varies from the height g0 corresponding to the height h0 of the substrate 30 to the height g1 corresponding to the height h1 of the overlapping portion OLP on the surface of the second protection layer 36 corresponding to the paths PH3 and PH4. Therefore, a fixing failure or a gloss streak caused by a magnitude of irregularity on the surface of the second protection layer 36 is likely to occur.
As described above, in the comparison example 1, there is an area, which does not have the gradient mitigation portion, where the height varies from the height h0 to the height h1 without having the height h2 in both of the directions D1 and D2. Further, in the heater of the comparison example 1, there is an area where the gradation mitigation portion does not exist in a direction other than the directions D1 and D2 on the face where the thermistor and the conductive line are arranged (e.g., direction D3 illustrated in
An effect of the heater according to the present exemplary embodiment was verified under the following condition. A normal paper “HP Laser Jet 90 g” and a glossy paper “HP Brochure Paper 200 g” were used as the recording materials P. Toner images formed on the recording materials P were respectively heated and fixed onto the recording materials P by using the heaters according to the present exemplary embodiment and the comparison example, and the fixed images were compared to each other. A conveyance speed was set to 300 mm/s when the normal paper was used as the recording material P, and a conveyance speed was set to 75 mm/s when the glossy paper was used as the recording material P.
The result is illustrated in a table 4. Although an image defect occurred in both of the normal paper and the glossy paper when the heater of the comparison example 1 was used, favorable images were obtained across the entire area of the recording material P when the heater of the present exemplary embodiment was used.
In the comparison example 1, as illustrated in
As described above, occurrence of an image defect can be suppressed by employing the configuration of the heater according to the present exemplary embodiment. A reason for the above result will be described below.
A reason for the image defect occurring in the comparison example is that the heater locally has an area where heat and pressure applied to the toner image become insufficient, because of a large step on the sliding face of the heater generated at an overlapping portion OLP of the conductive line of the thermistor.
As described above, in the present exemplary embodiment, the gradient moderating portion is always arranged in the directions D1 and D2, so that a large step is not generated in a periphery of the overlapping portion OLP of the conductive line and the thermistor. Therefore, as described above, generation of an area where heat and pressure applied to the toner image locally become insufficient can be suppressed. As a result, an effect of suppressing occurrence of an image defect can be obtained.
In addition, in the configuration of the apparatus of the present exemplary embodiment, it was confirmed that frequency of occurrence of an image defect was increased when the height of one step exceeded approximately 10 μm. In the first exemplary embodiment, an effect of suppressing the image defect can be obtained because a height of one step (h1−h2) is approximately 7 μm. Accordingly, it is preferable that the gradient moderating portion be arranged to make the step become 10 μm or less.
Next, a variation example of the present exemplary embodiment will be described.
A variation example 1 in
A cross-sectional faces in the directions D1 and D2 including the overlapping portion OLP are reversed with those of the first exemplary embodiment, and the effects acquired from the respective cross-sectional faces are similar to those described in the third exemplary embodiment.
A relationship between the widths of the thermistor 332 and the conductive line 34 at the connection portion in the variation example 2 illustrated in
In the variation example 2, the width of the thermistor 332 is set to a width W3 that is wider than the width W1 of the conductive line 34. In this configuration, similar to the first exemplary embodiment and the variation example 1, the conductive line 34 functions as a gradient moderating portion in the conveyance direction. However, different from the third exemplary embodiment and the variation example 1, the thermistor 332 functions as a gradient moderating portion in the direction D1. An effect similar to the effect obtained in the third exemplary embodiment and the variation example 1 can be obtained because the thermistor 332 and the conductive line 34 have the same thickness.
In the above-described exemplary embodiments, a part of the conductive line 34 or the thermistor 332 functions as the gradient moderating portion. However, for example, an insulation member having the second height may be used as the gradient moderating portion.
As described above, the heater according to the present exemplary embodiment includes a substrate, a heat generation element arranged on the substrate, a temperature detection element arranged on the substrate, a conductive line connected to the temperature detection element, and a protection layer that covers the temperature detection element and the conductive line. This heater is used for a fixing device for fixing a toner image formed on a recording material onto the recording material. Then, an overlapping portion at which the temperature detection element and the conductive line overlap with each other is arranged at a connection portion of the temperature detection element and the conductive line. In a cross-sectional face of the heater parallel with the lengthwise direction, cut along a face passing through the temperature detection element, a gradient moderating portion having a step smaller than a step from a surface of the substrate to a surface of the overlapping portion is arranged at a position adjacent to the overlapping portion. Further, at a cross-sectional face of the heater parallel with the widthwise direction, cut along a face passing through the temperature detection element, a gradient moderating portion having a step smaller than a step from a surface of the substrate to a surface of the overlapping portion is arranged at a position adjacent to the overlapping portion.
Next, a fourth exemplary embodiment will be described. The present exemplary embodiment is characterized in that a gradient moderating portion is necessarily provided only in the direction D1. Different from the third exemplary embodiment, the gradient moderating portion does not exist in all or a part of the area in the direction D2.
Basic configurations and operations of the image forming apparatus 100 and the fixing device 7 are similar to those described in the third exemplary embodiment. Only a shape on the sliding face side of the heater 12 mounted on the fixing device 7 is different.
The features of a heater used in the fourth exemplary embodiment will be described.
As described above, in the present exemplary embodiment, the widths of both of the thermistor 338 and the conductive line 34 are the same width W1, so that the thermistor 338 and the conductive line 34 precisely overlap with each other. Therefore, different from the cross-sectional face at the line F1 in the third exemplary embodiment in
When verification was conducted under the condition the same as the condition for verifying the effect of the third exemplary embodiment, a fixing failure as well as a gloss streak did not occur in the present exemplary embodiment. This result indicates that an image defect can be prevented if a gradient moderating portion exists in the direction D1. This is because of the following reasons.
In the present exemplary embodiment, although a steep step exists in the direction D2, it is only for a short period that the contact pressure with respect to an inner periphery of the film is lowered, the pressure becomes lower than the pressure in other portions, and the heat-transfer efficiency becomes lower. Therefore, an influence with respect to the image is small, and thus an image defect such as a fixing failure or a gloss streak does not occur.
As described above, it is preferable that the conductive line 34 be arranged so that the gradient moderating portion appears at least in the cross-sectional structure at the line L3.
Next, configurations of variation examples of the present exemplary embodiment will be described. In these configurations, the gradient moderating portion necessarily exists in the direction D1 although the gradient moderating portion does not exist in a part of the area in the direction D2. With reference to
In the configuration of the variation example 3 illustrated in
On the other hand, in the direction D2, although the conductive line 34 or the thermistor 338 exists as the gradient moderating portion in most of the portions, the gradient moderating portion does not exist in points PA and PB in
In the configuration of the variation example 4 illustrated in
On the other hand, in the direction D2, although the conductive line 34 or the thermistor 338 exists as the gradient moderating portion in most of the area, the gradient moderating portion does not exist in points PC and PD in
In addition, configurations described in the third and the fourth exemplary embodiments are also applicable to the heater capable of independently controlling the plurality of heat generating resistors illustrated in
While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments.
This application claims the benefit of Japanese Patent Applications No. 2017-213858, filed Nov. 6, 2017, and No. 2018-066098, filed Mar. 29, 2018, which are hereby incorporated by reference herein in their entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2017-213858 | Nov 2017 | JP | national |
| 2018-066098 | Mar 2018 | JP | national |
