The present invention relates to a heating device and an image forming apparatus such as a copier, a printer, and a facsimile, adopting an electrophotographic system, an electrostatic recording system, or the like.
As a heating device in an image forming apparatus, a configuration including a film, a heater disposed in an internal space of the film, a holding member holding the heater, and a reinforcing member reinforcing the holding member has been known. Examples of the heater include a sheet heater including a sheet heating element on a ceramic substrate, the heater being held by a heater holder made of a resin as the holding member. A through hole is provided in a part of the holding member in a longitudinal direction, and a thermistor is disposed in a space between the holding member and the reinforcing member to detect a temperature of the heater. The heater is controlled based on the temperature detected by the thermistor. Likewise, a protection element such as a thermostat and a temperature fuse is also provided in the space between the holding member and the reinforcing member. The protection element is also in contact with the heater via another through hole provided in the holding member. The protection element is a power shut-off member that shuts off power supply to the heater in a case where the temperature of the heater exceeds a predetermined temperature.
The power shut-off member is disposed so as to come into contact with the heater. At this time, if contact pressure to the heater is low or a clearance is generated between the power shut-off member and the heater, responsiveness to the temperature is varied. Therefore, as discussed in Japanese Patent Application Laid-Open No. 2013-41096, the power shut-off member is urged toward the heater by a plurality of urging members such compression springs and composite springs. This makes it possible to bring the power shut-off member into contact with the heater at predetermined pressure.
When both sides of the power shut-off member are urged by the urging members, urging force can be applied; however, a space for arranging the plurality of urging member is necessary and the number of components is increased.
According to an aspect of the present invention, a heating device includes an elongated heater, a first holding member configured to hold the heater, a power shut-off member configured to shut off power supply to the heater, a second holding member configured to hold the power shut-off member, a first urging member configured to press the power shut-off member against the heater, and a regulation member configured to regulate a position of the second holding member, wherein, in a longitudinal direction of the heater, one end side of the second holding member is urged by the first urging member, and another end side of the second holding member is regulated in position by the regulation member.
Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.
Some exemplary embodiments of the present invention will be described below with reference to drawings. The following exemplary embodiments do not limit the invention according to the claims, and all of combinations of characteristics described in the exemplary embodiments are not necessarily essential for solving means of the invention.
A first exemplary embodiment will be described.
The toner image on the photosensitive drum 919 is transferred to the sheet S while the sheet S passes through the transfer position. Thereafter, the sheet S is heated by a fusing device 1, and the toner image is heated and fixed onto the sheet S. The sheet S carrying the fixed toner image is discharged to a tray on an upper part of the image forming apparatus 900 by rollers 926 and 927.
Note that toner remaining on the photosensitive drum 919 is cleaned by a cleaner 918.
A motor 930 is a driving source driving the fusing device 1 and the like. Power is supplied from a control circuit 940 connected to a commercial alternating-current power supply 941 to the fusing device 1. The photosensitive drum 919, the charging roller 916, the scanner unit 921, the developing unit 917, and the transfer roller 920 described above configure an image forming unit that forms an unfixed image on the sheet S. A cartridge 915 is a unit replaceable for the image forming apparatus 900. The scanner unit 921 includes a light source 922, a polygon mirror 923, and a reflective mirror 924.
Next, a configuration of the fusing device 1 will be described with reference to
An elongated heater 5 is disposed in an internal space of the film 3. The conveyance direction of the sheet S in
The heater 5 is disposed to be slidable with an inner peripheral surface of the film 3. Inner surfaces at both ends of the film 3 in the longitudinal direction are supported by flanges 29. Grease is applied between the heater 5 and the film 3 in order to improve slidability.
The heater 5 is configured to be energized by an energization unit (not illustrated) from a connector 30 that is an electric contact, and to generate heat by receiving power. In the internal space of the film 3, the heater 5 is held by a heater holder 7 that is a holding member provided substantially in parallel with the film 3. Further, the nip portion N formed by the film 3 and the pressure roller 4 preferably has a uniform width in a rotation axis direction that is the longitudinal direction of the film 3. Therefore, the heater holder 7 is provided with a metal frame member 8 as a reinforcing member, on an opposite side of the pressure roller 4 with the heater holder 7 in between, in order to reinforce strength against force by pressure contact. The frame member 8 receives pressing force from the pressurization unit (not illustrated) via the flanges 29 provided at both ends. Although details will be described below, the frame member 8 as the reinforcing member also serves as a regulation member regulating a position of a thermostat holder 102. Further, in place of the frame member 8, the heater holder 7 as the holding member can serve as the regulation member regulating the position of the thermostat holder 102.
To cause the thermostat 101 to respond to heat of the heater 5 with high responsiveness, the abutting portion 101a desirably stably abuts on the heater 5. Therefore, the thermostat holder 102 is pressed against the heater 5 by a thermostat spring 103 that includes a compression spring as an urging member. An electric wire 104 of the thermostat 101 is housed in an electric wire guide portion 102a of the thermostat holder 102. The thermostat spring 103 is disposed on an end side of a folded portion 104a of the electric wire 104 in a longitudinal direction of the thermostat 101.
In the present exemplary embodiment, to cause the abutting portion 101a of the thermostat 101 to abut on the heater 5 with the force of 400 gf, a load of the thermostat spring 103 is set to 200 gf. Note that the distance from the fulcrum 102b to the abutting portion 101a and the distance from the fulcrum 102b to the thermostat spring 103 have relationship of 1:2; however, the relationship is not limited thereto. In a case where the distance relationship is changed, it is sufficient to appropriately change spring pressure of the thermostat spring 103 based on the above-described relationship of the moment and the force.
As described above, the one end side of the thermostat 101 is urged by the thermostat spring 103, and the fulcrum 102b on the other end side is regulated in position by the frame member 8. This makes it possible to press the abutting portion 101a against the heater 5 without urging both sides of the thermostat 101 by springs. The configuration requiring the thermostat spring 103 only on one side is adopted, which makes it possible to suppress increase in space by the springs and leads to downsizing. Further, on the other side on which no thermostat spring 103 is disposed, a space generated due to disposition of no spring can be utilized as a space for wiring of the electric wire 104, which makes it possible to downsize the heating device 2.
In a second exemplary embodiment, disposition of a thermistor 201 will be described in addition to the thermostat 101. Configurations similar to the configurations according to the above-described first exemplary embodiment, for example, the image forming apparatus, are denoted by similar reference numerals, and detailed descriptions are omitted in the present exemplary embodiment.
The thermostat 101 is disposed such that the abutting portion 101a engages with the hole portion 7a provided near the center part of the heater holder 7 in the longitudinal direction. The thermostat holder 102 holding the thermostat 101 is disposed at the position sandwiched between the heater holder 7 and the frame member 8 in the thickness direction of the heater 5. In the longitudinal direction of the heater 5, the thermostat spring 103 provided on the one end side of the thermostat holder 102 is locked to the frame member 8, and presses the thermostat holder 102 against the heater 5. The fulcrum 102b provided on the other end side of the thermostat holder 102 is also locked to the frame member 8. In other words, the other end side of the thermostat holder 102 is regulated in position by the frame member 8.
The thermistor 201 is disposed such that a temperature detection unit 201a engages with the hole portion 7b provided in the heater holder 7, at a position close to the connector 30 more than the thermostat 101 in the longitudinal direction, near the center part of the heater holder 7 in the longitudinal direction. To stably detect the temperature of the heater 5, the temperature detection unit 201a of the thermistor 201 is pressed against the heater 5 at desired pressure by thermistor springs 204 as illustrated in
As illustrated in
As described above, the one end side of the thermostat 101 is urged by the thermostat spring 103, and the fulcrum 102b on the other end side is regulated in position by the frame member 8. This makes it possible to press the abutting portion 101a against the heater 5 without urging the both sides of the thermostat 101 by springs. The configuration requiring the thermostat spring 103 only on one side is adopted, which makes it possible to suppress increase in space by the springs. In addition, the electric wire 104 is caused to pass through the upper side of the thermistor 201 disposed in the same direction, which makes it possible to downsize the heating device 2.
In a third exemplary embodiment, disposition of the thermistor 201 will be described in addition to the thermostat 101. Configurations similar to the configurations according to the above-described first and second exemplary embodiments, for example, the image forming apparatus, are denoted by similar reference numerals, and detailed descriptions are omitted in the present exemplary embodiment.
The thermostat 101 is disposed such that the abutting portion 101a engages with the hole portion 7a provided near the center part of the heater holder 7 in the longitudinal direction. The thermostat holder 102 holding the thermostat 101 is disposed at the position sandwiched between the heater holder 7 and the frame member 8 in the thickness direction of the heater 5. The thermistor 201 is disposed such that the temperature detection unit 201a engages with the hole portion 7b provided in the heater holder 7, at a position close to the connector 30 more than the thermostat 101 in the longitudinal direction, near the center part of the heater holder 7 in the longitudinal direction. To stably detect the temperature of the heater 5, the temperature detection unit 201a of the thermistor 201 is pressed against the heater 5 at desired pressure by the thermistor springs 204.
As illustrated in
The fulcrum 102b provided on the other end side of the thermostat holder 102 is locked to a locking portion 202b of the bundle wire guide 202. In other words, the fulcrum 102b is regulated in position by the locking portion 202b.
In place of the frame member 8, the locking portion 202b can serve as the regulation member regulating the position of the thermostat holder 102. The thermostat holder 102 is held on the heater holder 7. When the frame member 8 is attached thereto, the thermostat spring 103 provided on the one end side of the thermostat holder 102 is locked to the frame member 8. The guide ribs 202a and the locking portion 202b of the bundle wire guide 202 are disposed in proximity to the frame member 8, and are locked to the frame member 8. This prevents the electric wire 104 from coming into contact with the frame member 8 and prevents the bundle wire guide 202 from being deformed by reaction force of the thermistor springs 204. The locking portion 202b of the bundle wire guide 202 may be locked not to the frame member 8 but to the other member such as the heater holder 7.
As described above, the one end side of the thermostat 101 is urged by the thermostat spring 103, and the fulcrum 102b on the other end side is regulated in position by the locking portion 202b. This makes it possible to press the abutting portion 101a against the heater 5 without urging the both sides of the thermostat 101 by springs. The configuration requiring the thermostat spring 103 only on one side is adopted, which makes it possible to suppress increase in space by the springs. In addition, the electric wire 104 is caused to pass through the upper side of the thermistor 201 disposed in the same direction, which makes it possible to downsize the heating device 2.
Note that the configuration urging the thermostat unit 100 according to each of the first to third exemplary embodiments can be applied as a configuration urging not the thermostat 101 but the thermistor 201. As with the thermostat 101, the thermistor 201 is also held by a holder as a holding member. As described above, one end side of the holder holding the thermistor 201 can be urged by an urging member, and the other end side can be regulated by a regulation member. Further, the configuration in which the thermostat spring 103 urging the one end side of the thermostat 101 is locked to the frame member 8 is described. However, the thermostat spring 103 may be locked not to the frame member 8 but to the other member such as the heater holder 7 as long as pressing force by the thermostat spring 103 can be applied to the thermostat 101.
According to the configuration of any of the exemplary embodiments of the present invention, it is possible to provide the configuration urging the power shut-off member without urging both sides of the power shut-off member by the plurality of urging members.
Embodiment(s) of the present invention can also be realized by a computer of a system or apparatus that reads out and executes computer executable instructions (e.g., one or more programs) recorded on a storage medium (which may also be referred to more fully as a ‘non-transitory computer-readable storage medium’) to perform the functions of one or more of the above-described embodiment(s) and/or that includes one or more circuits (e.g., application specific integrated circuit (ASIC)) for performing the functions of one or more of the above-described embodiment(s), and by a method performed by the computer of the system or apparatus by, for example, reading out and executing the computer executable instructions from the storage medium to perform the functions of one or more of the above-described embodiment(s) and/or controlling the one or more circuits to perform the functions of one or more of the above-described embodiment(s). The computer may comprise one or more processors (e.g., central processing unit (CPU), micro processing unit (MPU)) and may include a network of separate computers or separate processors to read out and execute the computer executable instructions. The computer executable instructions may be provided to the computer, for example, from a network or the storage medium. The storage medium may include, for example, one or more of a hard disk, a random-access memory (RAM), a read only memory (ROM), a storage of distributed computing systems, an optical disk (such as a compact disc (CD), digital versatile disc (DVD), or Blu-ray Disc (BD)™), a flash memory device, a memory card, and the like.
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. 2021-192726, filed Nov. 29, 2021, which is hereby incorporated by reference herein in its entirety.
Number | Date | Country | Kind |
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2021-192726 | Nov 2021 | JP | national |