Patent Application
20190369534
The present invention relates to a fixing apparatus mounted on an image forming apparatus using an electrophotographic recording method, such as a copying machine or printer, and a heater mounted on the fixing apparatus.
Japanese Patent Application Laid-Open No. 2017-054071 discusses a fixing apparatus in which a heater including a plurality of independently-controllable heat generation blocks is provided in an inner space of a cylindrical fixing film. The heater is provided with a thermistor for each heat generation block. An electrode for feeding power to the heat generation block is provided to a surface of a heater substrate, and an electrode for the thermistor is provided to another surface of the heater substrate.
Basic insulation, or reinforced insulation in some cases, is needed between the electrode for the heat generation block and the electrode for the thermistor. In a case where the two electrodes are provided at the same position on the front and rear surfaces of the substrate, an insulation distance is required in both longer-side and shorter-side directions of the heater. However, if the width in the shorter-side direction of the heater is increased in order to preserve the insulation distance, the heat capacity of the heater increases, and the start-up time of the heater becomes longer. If an excess space portion is provided in the shorter-side direction of the heater, the heater becomes less resistant to thermal stress. Furthermore, wiring connected to each electrode via an electric connector is also required to preserve the insulation distance from the other electrode. Thus, in order to form the wiring while preserving the insulation distance, an excess space is needed. Especially in a division heater as discussed in Japanese Patent Application Laid-Open No. 2017-054071, the number of electrodes for heat generation members and electrodes for thermistors is significantly large. This makes it difficult to prevent congestion of the electric connectors and the wiring to the electrodes near an edge portion in the longer-side direction of the heater, and thus the apparatus size often increases.
The present invention is directed to a heater capable of ensuring insulation between an electrode for a heat generation block (heat generation member) and an electrode for a thermistor (temperature detection element), and a fixing apparatus including the heater.
According to an aspect of the present invention, a heater for use in a fixing apparatus configured to fix an unfixed toner image formed on a recording material to the recording material includes a substrate, a plurality of heat generation members which is formed on a first surface of the substrate and is controllable independently of each other, a first electrode group which is formed on the first surface and with which a plurality of first power feeding terminals configured to feed power to the plurality of heat generation members and provided to the fixing apparatus is in contact, a plurality of temperature detection elements formed on a second surface of the substrate which is on an opposite side to the first surface, and a second electrode group which is formed on the second surface and with which a plurality of second power feeding terminals configured to feed power to the plurality of temperature detection elements and provided to the fixing apparatus is in contact, wherein at least an electrode of the first electrode group and at least an electrode of the second electrode group are formed in a region nearer to one edge portion of the substrate than to a center of the substrate in a longer-side direction of the substrate, and wherein the electrode that is nearest to the second electrode group in the longer-side direction among the first electrode group formed in the region nearer to the one edge portion and the second electrode group are provided with a space between the electrode and the second electrode group.
Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.
A first exemplary embodiment will be described below.
The stay 26 receives the pressure of the spring (not illustrated) and biases the heater 30 via the heater holder 25 toward the pressing roller 22. The elastic layer 24 of the pressing roller 22 receives the biasing force and is elastically deformed, and the fixing nip area N is formed. The film 21 is pinched at the fixing nip area N by the heater 30 and the pressing roller 22. If the pressing roller 22 is rotated in the direction of an arrow R1 by the motor 13 via a gear train (not illustrated), the film 21 pinched at the fixing nip area N is rotated in the direction of an arrow R2. An arrow F indicates a sheet conveyance direction of the recording material S. The recording material S carrying an unfixed toner image is conveyed into the fixing nip area N formed by the rotating pressing roller 22 and the rotated film 21 and undergoes heating and fixing processing (the unfixed toner image is fixed to the recording material S with heat of the heater 30) while being pinched and conveyed. A structure of the heater 30 will be described below.
Next, a structure of the heater 30 according to the first exemplary embodiment will be described.
The heater 30 in the present exemplary embodiment includes the substrate 31 and a plurality of heat generation members 34a to 34c which is formed on a first surface 31a of the substrate 31 and is controllable independently of each other. The heater 30 further includes a first electrode group including first electrodes 39a to 39c formed on the first surface 31a, and a plurality of power feeding terminals (first power feeding terminals) 50aT1, 50aT2, and 50bT1 for feeding power to the plurality of heat generation members 34a to 34c is in contact with the first electrodes 39a to 39c. The heater 30 further includes a plurality of temperature detection elements T1 to T3 formed on a second surface 31b of the substrate 31 which is on the opposite side to the first surface 31a. The heater 30 further includes a second electrode group including second electrodes 40a to 40e formed on the second surface 31b, and a plurality of power feeding terminals (second power feeding terminals) 51aT1, 51aT2, 51bT1, 51bT2, and 51bT3 for feeding power to the plurality of temperature detection elements T1 to T3 is in contact with the second electrodes 40a to 40e.
At least the first electrodes 39a and 39b of the first electrodes 39a to 39c and at least the second electrodes 40a and 40b of the second electrodes 40a to 40e are formed nearer to an edge portion (first edge portion) 31e1 than to the center 31c of the substrate 31 in the longer-side direction LD of the substrate 31. The electrode 39b which is nearest to the second electrodes 40a and 40b in the longer-side direction LD among the first electrodes 39a and 39b formed in the region nearer to the edge portion 31e1 and the second electrodes 40a and 40b are provided with a space of a distance D between the electrode 39b and the second electrodes 40a and 40b. The second electrodes 40a to 40e are provided nearer to the center 31c of the substrate 31 than the first electrodes 39a to 39c in the longer-side direction LD. Details thereof will be described below. An edge portion 31e2 (second edge portion) is another edge portion of the substrate 31.
The surface of the substrate 31 that is on the sliding surface layer 32 side is provided with the heat generation members 34a to 34c extending in the longer-side direction of the heater 30. The heat generation members 34a and 34b are respectively provided upstream and downstream in the sheet conveyance direction of the recording material S, and the heat generation member 34c is provided at a center. The insulative protection glass 35 is provided so as to cover an upper portion of the three heat generation members 34a to 34c. The film 21 is slid on a front surface of the protection glass 35. The rear surface layer 33 of the substrate 31 is provided with the printed thermistor (temperature detection element) T1 and conductors 36a and 36b for passing current to the thermistor T1. The thermistor T1 has a negative resistance temperature characteristic, has a characteristic that a resistance value changes depending on temperature, and has a function of detecting the temperature of the heater 30. The protection glass 37 is provided so as to cover the thermistor T1 and the conductors 36a and 36b.
As illustrated in
Next, a structure of the rear surface layer 33 will be described with reference to
The thermistors T2 and T3 are formed near the edge portions of the heat generation members 34a to 34c in the longer-side direction LD. The thermistors T2 and T3 are provided to detect the temperature of a portion of the heater 30 by which no sheet passes in a case where small-size recording materials S consecutively passes. The conductor 36a is connected to one edge of each of thermistors T1, T2, and T3 and is also connected to the electrodes 40a and 40e provided at respective edges. The electrodes 40a and 40e are connected to a ground potential of the control circuit 14 via the electric contact members and the conductive members described below. Edges of the conductors 36b to 36d are respectively connected to thermistors T1 to T3, and the other edges of the conductors 36b to 36d are respectively connected to the electrodes 40d, 40c, and 40b. The protection glass 37 covers the component other than the electrodes 40a to 40e. Specifically, as illustrated in
In the heater 30 according to the present exemplary embodiment, the electrode 39b, which is the nearest one of the electrodes 39a and 39b for heat generation members to the electrodes 40a and 40b for thermistors, and the electrode 40a, which is the nearest one of the electrodes 40a and 40b for thermistors to the electrodes 39a and 39b for heat generation members, are provided at the distance D from each other in the longer-side direction LD of the heater 30. The distance D is preserved to preserve a required insulation distance between the electrodes 39a to 39c for heat generation members and the electrodes 40a to 40e for thermistors. The distance D is preserved, so that the width of the substrate 31 of the heater 30 in the shorter-side direction does not have to be increased to preserve the insulation distance. In this way, the heater 30 is realized in which the insulation distance is preserved between the two electrodes while the heater 30 has excellent temperature-rise characteristics and is resistant to thermal stress applied to the substrate 31. The distance D is also preserved between the electrode 39c for heat generation members and the electrode 40e for thermistors which are provided between the center 31c and the edge portion 31e2.
Next, a structure of the electric contact members and the conductive members which are connected to the electrodes 39a to 39c for heat generation members and the electrodes 40a to 40e for thermistors and ensure energization to the control circuit 14 will be described with reference to
The connectors (electric contact member) 51a and 51b for thermistors are provided nearer to the center in the longer-side direction LD than the positions on the heater 30 to which the connectors 50a and 50b for heat generation members are connected. The connectors 51a and 51b are to be connected to the electrodes 40a to 40e for thermistors. Specifically, the second electrodes 40a to 40e are provided nearer to the center of the substrate 31 in the longer-side direction LD of the substrate 31 than the first electrodes 39a to 39c. The connectors 51a and 51b for thermistors are substantially U-shaped plug-in connectors similar to the connectors 50a and 50b for heat generation members and are to be connected to the electrodes 40a to 40e formed in the rear surface layer 33. The connector 51a is provided with the power feeding terminals 51aT1 and 51aT2. The power feeding terminal 51aT1 is in contact with the electrode 40a. The power feeding terminal 51aT2 is in contact with the electrode 40b. The connector 51b is provided with the power feeding terminals 51bT1, 51bT2, and 51bT3. The power feeding terminal 51bT1 is in contact with the electrode 40c. The power feeding terminal 51bT2 is in contact with the electrode 40d. The power feeding terminal 51bT3 is in contact with the electrode 40e. Conductive members (cables for thermistors) 53a and 53b extend from the connectors 51a and 51b for thermistors and are connected to the control circuit 14 through a path (not illustrated). The power feeding terminals 51aT1, 51aT2, 51bT1, 51bT2, and 51bT3 correspond to a plurality of second power feeding terminals provided to the fixing apparatus.
A feature of the present exemplary embodiment is that the connectors 51a and 51b for thermistors and the cables 53a and 53b for thermistors are provided along the shorter-side direction of the heater 30. Specifically, the second electrodes 40a to 40e are provided such that the plurality of second power feeding terminals 51aT1, 51aT2, 51bT1, 51bT2, and 51bT3 are connected to the second electrodes 40a to 40e from a direction which intersects with the longer-side direction LD of the substrate 31 and which is parallel to the second surface 31b of the substrate 31. Since the electrodes 39a to 39c for heat generation members are provided near the connectors 51a and 51b for thermistors and the cables 53a and 53b for thermistors, if the connectors 51a and 51b for thermistors and the cables 53a and 53b for thermistors are provided along the longer-side direction LD of the heater 30, it becomes difficult to preserve the insulation distance. Specifically, since the connectors 51a and 51b for thermistors and the cables 53a and 53b for thermistors are provided near and at the back of the electrodes 39a to 39c for heat generation members, so that it becomes difficult to preserve the insulation distance. In order to preserve the insulation distance, the electrodes 39a to 39c for heat generation members need to be provided at a great distance from the electrodes 40a to 40e for thermistors, but this leads to an increase in size of the heater 30 and the fixing device 20. In the structure according to the present exemplary embodiment, the insulation distance is preserved without situating the connectors 51a and 51b for thermistors and the cables 53a and 53b for thermistors at a great distance from the electrodes 39a to 39c for heat generation members, so that the structures of the edge portions of the heater 30 where the electrodes are congested can be a compact structure. While the cables 53a and 53b are wired upward (i.e., toward the upstream side of the sheet conveyance direction P of the recording material S) in
Next, a structure of the heater 30 according to a second exemplary embodiment will be described. The components that have a similar structure or function to those in the first exemplary embodiment are given the same reference numerals, and description thereof is omitted. A cross-sectional structure of the heater 30 according to the second exemplary embodiment is similar to that in the first exemplary embodiment and is as illustrated in
The second exemplary embodiment is different from the first exemplary embodiment in the positions of the electrodes 39a to 39c for heat generation members and the electrodes 40a to 40e for thermistors in the longer-side direction in the heater 30. As illustrated in
In the heater 30 according to the present exemplary embodiment, the electrodes 39a to 39c for heat generation members are provided nearer to the center in the longer-side direction LD of the heater 30 than the electrodes 40a to 40e for thermistors. This structure makes it possible to reduce the distances between the electrodes 39a to 39c for heat generation members and the heat generation members 34a to 34c, so that an effect of voltage drop is minimized and higher heat generation efficiency of the heat generation members 34a to 34c than the first exemplary embodiment is realized.
In the first exemplary embodiment, the U-shaped plug-in connectors are described as the electric contact members and the cables as the conductive members. In the second exemplary embodiment, connectors including combinations of male connectors to be attached to the heater 30 and cables having edges provided with female connectors are used. Male connectors 54a and 54b for heat generation members are electric contact members and attached to the heater 30. Male connectors 55a and 55b for thermistors are attached to the heater 30. Female connectors (first power feeding terminal) 56a and 56b are provided to the edges of the conductive members for heat generation members, and the conductive members include cables 58a and 58b joined to the female connectors 56a and 56b by crimping or welding. The conductive members for heat generation members are connected to the male connectors 54a and 54b for heat generation members. Similarly, female connectors (second power feeding terminal) 57a and 57b are provided to the edges of the conductive members for thermistors, and the conductive members include cables 59a and 59b joined to the female connectors 57a and 57b by crimping or welding. The conductive members for thermistors are connected to the male connectors 55a and 55b for thermistors. As described above, the first electrodes 39a to 39c are provided such that the plurality of first power feeding terminals 56a and 56b is connected to the first electrodes 39a to 39c from a direction which intersects with the longer-side direction LD of the substrate 31 and which is parallel to the first surface 31a of the substrate 31. The second electrodes 40a to 40e are provided such that the plurality of second power feeding terminals 57a and 57b is connected to the second electrodes 40a to 40e from a direction which intersects with the longer-side direction LD of the substrate 31.
In the second exemplary embodiment, the electric contact members for heat generation members (the connectors 54a and 54b for heat generation members) and the conductive members (the cables 58a and 58b for heat generation members) are also provided along the shorter-side direction of the heater 30. Specifically, as in the first exemplary embodiment, the electric contact members and the conductive members are provided inside in the longer-side direction LD so as to not pass through the back of the electrodes provided outside in the longer-side direction LD. In this way, the insulation distance is preserved between the electric contact members and the conductive members and the other electrodes.
In the second exemplary embodiment, U-shaped plug-in connectors can be used as the electric contact members as in the first exemplary embodiment.
A heater according to a third exemplary embodiment is a heater in which a heat generation region is divided in the longer-side direction LD. The components that have a similar structure or function to those in the first and second exemplary embodiments are given the same reference numerals, and description thereof is omitted.
As illustrated in
A planar structure of each layer of the heater 70 will be described with reference to
As illustrated in
The sliding surface layer 72 of the heater 70 is provided with thermistors T1 to T7, T1a, T1b, T2a to T5a, and t2 to t7 for detecting the temperature of each heat generation block of the heater 70. The thermistors T1 to T7 are mainly used to control the temperature of each heat generation block (control to maintain a constant temperature) and are each provided at a substantially central portion of each heat generation block. Hereinafter, the thermistors T1 to T7 will be referred to as “central thermistors”.
The thermistors T1a, T1b, and T2a to T5a are thermistors for detecting the temperature of an edge portion of each heat generation block. Hereinafter, the thermistors T1a, T1b, and T2a to T5a will be referred to as “edge portion thermistors”. The edge portion thermistors are provided in the respective heat generation blocks excluding the heat generation blocks (Z6, Z7), which are respectively provided at the edges and have a small heat generation region, and each edge portion thermistor is provided nearer to an edge portion of the heat generation block than to the center of the heat generation block. No edge portion thermistor is provided in the heat generation blocks Z6 and Z7 because the heat generation regions of the heat generation blocks Z6 and Z7 are small and no edge portion thermistor needs to be provided.
The thermistors t2 to t7 are sub-thermistors provided to detect a temperature even in a case where the central thermistors or the edge portion thermistors become out of order. The sub-thermistors t2 to t7 are provide at substantially the same positions as the central thermistors T2 to T7 in the longer-side direction LD.
One edges of the central thermistors T1 to T7 and the edge portion thermistors T1a, T1b, and T2a to T5a are connected to the common conductive member 78a, and the other edges are connected to the conductive member 78b and 78e. One edges of the sub-thermistors t2 to t7 are connected to the common conductive member 78c, and the other edges are connected to the common conductive member 78d. The conductive members 78a to 78d extend to the edges of the heater 70 in the longer-side direction.
As illustrated in
With the above-described heater circuit structure, the temperature of each heat generation block is independently controllable while the temperatures are detected in detail. This makes it possible to provide a fixing device capable of performing optimum control for the size of a recording material S to be conveyed. While the structure including the sub-thermistors is described in the present exemplary embodiment, the structure is not limited to the above-described structure. The sub-thermistors are included to enable more advanced and elaborate control.
The first electrodes 76a to 76i are aligned in the longer-side direction LD of the substrate 31, and the second electrodes 79a and 79b are aligned in the shorter-side direction of the substrate 31. The distance D is provided also in the present exemplary embodiment between the outermost electrodes 76i and 76g, among the electrodes 76a to 76i for heat generation members, and the electrodes 79a and 79b for thermistors, respectively. The distance D is a distance whereby an insulation distance is preserved between two electrodes, as in the first and second exemplary embodiments. Further, the first electrodes 76a to 76i for heat generation members are provided nearer to the center in the longer-side direction LD than the electrodes 79a and 79b for thermistors, as in the second exemplary embodiment.
Electric contact members 80a and 80b feed power to the electrodes 76f, 76g, 76h, and 76i for heat generation members and are connectors for heat generation members including U-shaped plug-in connectors. Cables 81a and 81b which are conductive members extend from the connectors 80a and 80b for heat generation members along a shorter-side direction of the heater 70 and are connected to the control circuit 14 through a path (not illustrated). The electrode 79a for thermistors which is on the non-driving side is provided with a male connector 82b. The male connector 82b is insertable and removable in a direction that is perpendicular to a surface of the heater 70. On the other hand, the electrode 79b for thermistors which is on the driving-side is provided with a male connector 82a. The male connector 82a is insertable and removable in the direction that is parallel to the surface of the heater 70. Cables 84a and 84b which respectively have female connectors 83a and 83b are respectively connected to the male connectors 82a and 82b. The female connectors 83a and 83b are respectively provided to an edge of the cable 84a and an edge of the cable 84b. The cables 84a and 84b of the female connectors 83a and 83b are connected to the control circuit 14.
A cable 85a is a conductive member connected to the electrode 76a for heat generation members. Similarly, cables 85b to 85e are respectively connected to the electrodes 76b to 76e for heat generation members. The cables 85a to 85e are wired along the longer-side direction LD in an inner space of the film 21. Edge portions of the cables 85b and 85d extend outward from an opening of an edge of the film 21. Edge portions of the cables 85a, 85c, and 85e extend outward from an opening of another edge of the film 21. Further, the cables 85a to 85e are wired through the inside of the connectors 80a and 80b for heat generation members toward the shorter-side direction of the heater 70.
The electric contact members (connectors 80a and 80b for heat generation members) for heat generation members and the conductive members (cables 81a and 81b for heat generation members) for heat generation members, which are provided inside in the longer-side direction LD of the heater 70, are provided along the shorter-side direction of the heater 70 also in the third exemplary embodiment. Specifically, the insulation distance is preserved between the electric contact members and the conductive members and the other electrodes while the electric contact members and the conductive members which are provided inside in the longer-side direction LD do not pass by the back of the electrodes provided outside, as in the first and second exemplary embodiments. Especially in the heater structure having a large number of divisions as described in the present exemplary embodiment, many connectors and cables are provided and congested. Thus, the structure according to the present exemplary embodiment is effective for realizing a compact layout while preserving the insulation distance.
The wiring direction of the conductive members extending from the electrode group provided inside in the longer-side direction LD of the heater according to the first to third exemplary embodiments only needs to be the shorter-side direction of the heater, and the conductive members can be wired in either one of upstream and downstream directions of the sheet conveyance direction of the recording material S. Further, while the thermistors described above in the first to third exemplary embodiments are printed thermistors, chip-type thermistors can be provided to the heater.
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. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.
This application claims the benefit of Japanese Patent Application No. 2018-103911, filed May 30, 2018, which is hereby incorporated by reference herein in its entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2018-103911 | May 2018 | JP | national |
