JP2009231074A - Circuit breaker unit, fixing device, and image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To intercept an electric path, even if a holding member that holds a displacement member for opening an electric path is disengaged. <P>SOLUTION: A circuit breaker unit 90 is provided with two conductive electrodes 94a and 94b, in the lower part of a body 92 of a circuit breaker unit. The electrode 94b is provided with a conductive spring member 96, having thermal resistance and being extended toward the electrode 94a, and comprises an open portion 98, in which the spring member 96 is pushed against a pin 108 which contacts the electrode 94a with the electrode 94a to form an electric path. That is, the pin 108 transmits the force produced by a bimetal 110, which by reversing to the spring member 96, and thereby the open portion 98 is made to open, according to the displacement of the bimetal 110. In addition, the spring member 96 is made so sa to disengage itself from the electrode 94a by own elastic force, when it is in a state of not receiving external force. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a circuit breaker, a fixing device, and an image forming apparatus.

  In Patent Document 1, an aluminum inner lid having high thermal conductivity is disposed between the cap and the base member so as to face the cap with the bimetal interposed therebetween, and heat transmitted from the cap to the inner lid is efficiently transmitted to the bimetal. A thermostat is disclosed.

Japanese Patent Laid-Open No. 2002-100301

  An object of the present invention is to provide a circuit breaker, a fixing device, and an image forming apparatus capable of interrupting an electric circuit even when a holding member that holds a displacement member for opening the electric circuit is detached.

  In order to achieve the above object, the present invention according to claim 1 comprises a displacement member that is displaced according to a temperature change, a holding member that holds the displacement member, a first electrode, and a second electrode. A circuit breaker having an open part that opens an electric circuit when one of the displacement member and the holding member is displaced by a predetermined amount or more.

  The present invention according to claim 2 is the circuit breaker according to claim 1, wherein the displacement member is a bimetal formed by joining two kinds of metals having different linear expansion coefficients.

  The present invention according to claim 3 is the circuit breaker according to claim 1 or 2, wherein the opening portion is opened by an elastic force that at least one of the first electrode and the second electrode is provided. .

  The present invention according to claim 4 is further away from a position where the stress generated in the first electrode or the second electrode is maximized to a position where the first electrode and the second electrode are in contact with each other. 4. The circuit breaker according to claim 3, further comprising a transmission means for transmitting a force generated by the displacement of the displacement member to the first electrode or the second electrode at a position.

  The present invention according to claim 5 further includes a pressurizing member that applies pressure to the first electrode or the second electrode, and the opening portion is opened by the pressure applied by the pressurizing member. It is a circuit breaker in any one of 1-4.

  The present invention according to claim 6 comprises: a heating member that heats the recording medium; and a circuit breaker that interrupts an electric circuit for supplying power to the heating member when the heating member reaches a predetermined temperature or higher. The circuit breaker includes a displacement member that is displaced according to a temperature change, a holding member that holds the displacement member, a first electrode, and a second electrode, and any one of the displacement member and the holding member. One of them is a fixing device having an open portion that opens an electric circuit when displaced by a predetermined amount or more.

  According to a seventh aspect of the present invention, there is provided an image forming unit, a transfer unit that transfers an image formed by the image forming unit to a recording medium, and a fixing device that fixes the image on the recording medium onto which the image is transferred by the transfer unit. A power supply unit that supplies power to the fixing device. The fixing device includes a heating member that heats the recording medium, and an electric circuit that supplies power to the heating member when the heating member reaches a predetermined temperature or more. The circuit breaker includes a displacement member that is displaced in response to a temperature change, a holding member that holds the displacement member, a first electrode, and a second electrode. The image forming apparatus includes an open portion that opens the electric circuit when one of the displacement member and the holding member is displaced by a predetermined amount or more.

  According to the first aspect of the present invention, even when the holding member that holds the displacement member for opening the electric circuit is detached, the electric circuit can be interrupted.

  According to the second aspect of the present invention, in addition to the effect of the present invention according to the first aspect, the configuration can be simplified as compared with the case where the present configuration is not provided.

  According to the present invention of claim 3, in addition to the effect of the present invention of claim 1 or 2, the configuration can be simplified as compared with the case where the present configuration is not provided.

  According to the fourth aspect of the present invention, in addition to the effect of the present invention according to the third aspect, the pressure applied to the displacement member can be reduced as compared with the case where the present configuration is not provided.

  According to the fifth aspect of the present invention, in addition to the effect of the present invention according to any one of the first to fourth aspects, the configuration can be simplified as compared with the case where the present configuration is not provided.

  According to the sixth aspect of the present invention, even when the holding member that holds the displacement member for opening the electric circuit is detached, the electric circuit can be interrupted.

  According to the seventh aspect of the present invention, even when the holding member that holds the displacement member for opening the electric circuit is detached, the electric circuit can be interrupted.

Next, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows an outline of an image forming apparatus 10 according to an embodiment of the present invention. The image forming apparatus 10 includes an image forming apparatus main body 12, an image forming unit 14 is mounted in the image forming apparatus main body 12, and a discharge unit 16 described later is provided on the upper portion of the image forming apparatus main body 12. In addition, for example, two-stage sheet feeding units 18 and 18 are disposed below the image forming apparatus main body 12. Further, a plurality of paper feeding units can be optionally arranged below the image forming apparatus main body 12.

  Each paper feed unit 18 includes a paper feed unit main body 20 and a paper feed cassette 22 in which a recording medium such as paper is stored. A pickup roll 24 is disposed in the upper part near the rear end of the paper feed cassette 22, and a retard roll 26 and a feed roll 28 are disposed behind the pickup roll 24.

  The main conveyance path 32 is a sheet path from the feed roll 28 to the discharge port 34, and the main conveyance path 32 is in the vicinity of the back side (the left side surface in FIG. 1) of the image forming apparatus main body 12, and the lowermost supply path. A portion formed substantially vertically from the paper unit 18 to a fixing device 36 described later is included. A transfer device 42 and an image carrier 44, which will be described later, are disposed on the upstream side of the fixing device 36 in the main transport path 32, and a registration roll 38 is disposed on the upstream side of the transfer device 42 and the image carrier 44. Further, a discharge roll 40 is disposed in the vicinity of the discharge port 34 of the main conveyance path 32.

  Therefore, the sheet fed from the sheet feeding cassette 22 of the sheet feeding unit 18 by the pickup roll 24 is turned by the cooperation of the retard roll 26 and the feed roll 28, and only the uppermost sheet is guided to the main transport path 32. The developer image is temporarily stopped by the roll 38, and the developer image is transferred between a transfer device 42 and an image carrier 44, which will be described later, and the transferred developer image is fixed by the fixing device 36 and discharged. The paper is discharged from the discharge port 34 to the discharge unit 16 by the roll 40.

  However, in the case of duplex printing, it is returned to the reverse path. That is, the front side of the discharge roll 40 in the main conveyance path 32 is divided into two forks, a switching device 46 is provided in the divided part, and a reverse path 48 is formed from the divided part to the registration roll 38. . The reversing path 48 is provided with transport rolls 50a to 50c. In the case of double-sided printing, the switching device 46 is switched to the side that opens the reversing path 48 and the discharge roll 40 is in front of the rear end of the sheet. Thus, the discharge roll 40 is reversed, the paper is guided to the reverse path 48, and is discharged from the discharge port 34 to the discharge unit 16 through the registration roll 38, the transfer device 42, the image carrier 44 and the fixing device 36. .

  The discharge unit 16 includes an inclined portion 52 that is rotatable with respect to the image forming apparatus main body 12. The inclined portion 52 has a lower discharge port portion and is inclined so as to gradually increase in the front direction (right direction in FIG. 1), with the discharge port portion as a lower end and a higher tip as an upper end. The inclined portion 52 is supported by the image forming apparatus main body 12 so as to be rotatable around the lower end. As shown by a two-dot chain line in FIG. 1, when the inclined portion 52 is rotated upward and opened, an opening portion 54 is formed, and a process cartridge 64 described later can be attached and detached through the opening portion 54. .

  The image forming unit 14 is, for example, of an electrophotographic type, and is charged by an image carrier 44 made of a photosensitive member, a charging device 56 made of, for example, a charging roll that uniformly charges the image carrier 44, and a charging device 56. An optical writing device 58 that writes a latent image on the image carrier 44 with light, a developing device 60 that visualizes the latent image of the image carrier 44 formed by the optical writing device 58 with a developer, and the developing device 60. A transfer device 42 composed of, for example, a transfer roll for transferring the developer image produced by the toner onto the paper, a cleaning device 62 composed of, for example, a blade for cleaning the developer remaining on the image carrier 44, and the paper transferred by the transfer device 42 The image forming apparatus includes a fixing device 36 that fixes a developer image on a sheet. The optical writing device 58 is composed of, for example, a scanning type laser exposure device, and is arranged in the vicinity of the front surface of the image forming apparatus main body 12 in parallel with the paper feeding unit 18 described above, and exposes the image carrier 44 across the developing device 60. .

  The process cartridge 64 is obtained by integrating the image carrier 44, the charging device 56, the developing device 60, and the cleaning device 62. The process cartridge 64 is disposed immediately below the inclined portion 52 of the discharge portion 16 and is attached and detached via the opening portion 54 formed when the inclined portion 52 is opened as described above.

  Further, in the image forming apparatus main body 12, a power supply unit 65 that supplies power to each unit constituting the image forming apparatus 10 is provided.

  In FIG. 2, an outline of the fixing device 36 is shown. The fixing device 36 is unitized and has a unit main body 66, and the unit main body 66 is configured by combining a first casing 68 and a second casing 70. That is, the first casing 68 and the second casing 70 are connected via a fulcrum (not shown), and the heating roll 72 is rotatably supported by the first casing 68, A pressure roll 74 is rotatably supported on the housing 70. The pressure roll 74 is pressed against the heating roll 72 by an elastic body (not shown), and a nip portion 78 is formed.

  A heater 80 made of a lamp is disposed in the heating roll 72 to heat the heating roll 72. The above-described conveyance path 32 is configured in the vertical direction across the nip portion 78, and the sheet is conveyed from the bottom to the top. An inlet side chute 82 is disposed on the upstream side of the nip portion 78, and outlet side chutes 84 a and 84 b are disposed on the downstream side of the nip portion 78. The outlet side chutes 84a and 84b are provided in the first casing 68 and the second casing 70, and the outlet side chute 84a of the second casing 70 rotates upward to pass the paper. It is supposed to let you. In the vicinity of the downstream side of the nip portion 78, the first casing 68 is provided with a plurality of peeling claws 88 in the axial direction of the heating roll 72 (paper width direction). The peeling claw 88 is urged toward the heating roll 72 with a weak force that does not damage the surface of the heating roll 72, the tip of the peeling claw 88 is pressed against the surface of the heating roll 72, and is wound around the heating roll 72. The paper to be removed is peeled off.

  In addition, for example, below the heating roll 72, a circuit breaker (thermostat) 90 is provided with a predetermined gap with respect to the heating roll 72. The power supply unit 65 supplies power to the heater 80 via the circuit breaker 90. That is, the circuit breaker 90 cuts off the electric path for supplying power from the power supply unit 65 to the heater 80 (fixing device 36) when the temperature of the heating roll 72 (fixing device 36) reaches a predetermined temperature. Has been.

Next, the circuit breaker 90 will be described in detail.
FIG. 3 is a cross-sectional view of the circuit breaker 90 as seen from the side. FIG. 3A shows the case where the temperature of the heating roll 72 (fixing device 36) is within a predetermined temperature range (normal operating temperature range). FIG. 6B is a cross-sectional view showing a state of the circuit breaker 90 of FIG. 5B, and FIG. 5B is a circuit breaker 90 when the temperature of the heating roll 72 (fixing device 36) is outside a predetermined temperature range (at a higher temperature than the normal operating temperature). It is sectional drawing which shows this state.
The circuit breaker 90 is formed in a substantially cylindrical shape, for example, and has a circuit breaker body (base member) 92 made of an insulating member. Hereinafter, ceramic, phenol resin, polyphenylene sulfide, etc. are used as the insulating member.

Further, the circuit breaker 90 is provided with two conductive electrodes 94 a and 94 b at the lower part of the circuit breaker body 92. The electrode 94b is provided with a heat-resistant conductive spring member 96 extending toward the electrode 94a. The spring member 96 is pressed by a pin 108 described later and an open portion 98 that contacts the electrode 94a together with the electrode 94a. An electric circuit is formed. Note that the spring member 96 is separated from the electrode 94a by its own elastic force in a state in which no force is received from the outside.
Hereinafter, as the conductive member, for example, a member made of stainless steel, copper, phosphor bronze or the like having conductivity and spring property (elasticity) at a high temperature, or a member obtained by plating these members with tin, nickel, silver, gold, or the like Is used.

  A pin guide 104 is provided above the circuit breaker body 92. The pin guide 104 is an insulative disk-like member, and is provided with a hole portion 106 penetrating in the vertical direction substantially at the center. An insulating pin 108 is inserted into the hole 106 so as to be movable in the vertical direction. In addition, a bimetal 110 formed like a disc spring (drawing) is disposed above the pin 108. The bimetal 110 is configured to invert or return at a predetermined temperature by joining two types of metals having different linear expansion coefficients, and the insulating cap 112 interrupts the circuit from above the pin guide 104 and the bimetal 110. The circuit breaker main body 92 is held by being put on the circuit breaker main body 92.

  As shown in FIG. 4, the cap 112 is provided with an opening 114 substantially at the center to expose the surface of the bimetal 110 so that the bimetal 110 is inverted or returned sensitively to external temperature changes. The circuit breaker body 92 is fixed by being caulked. That is, the cap 112 and the pin guide 104 are holding members that hold the bimetal 110.

Then, the pin 108 transmits the force generated by the reverse of the bimetal 110 to the spring member 96 and opens the opening 98 according to the displacement of the bimetal 110.
For example, as shown in FIG. 3A, when the temperature of the heating roll 72 is within a predetermined temperature range, the bimetal 110 is convex on the lower side, the pin 108 is pushed downward by the bimetal 110, and the spring member 96 is an electrode. An electric circuit is formed in contact with 94a.
On the other hand, as shown in FIG. 3B, when the temperature of the heating roll 72 is outside the predetermined temperature range, the bimetal 110 is displaced so that the upper side is convex, and the pin 108 is forced against the spring member 96. Therefore, the spring member 96 is separated from the electrode 94a by the elastic force, and the electric circuit is interrupted.

Furthermore, as shown in FIG. 5, even when the circuit breaker 90 fails (the cap 112 is detached), the pin 108 does not transmit force to the spring member 96, so that the spring member 96 is elastic (spring). The electrical circuit is separated from the electrode 94a.
In other words, the circuit breaker 90 is a fail-safe that cuts off the electric path from the electrode 94a to the spring member 96 even if the pin 108 is not pushed down by the cap 112 being disengaged (displacement of a predetermined amount or more). It has the function of.

Next, the 1st modification (circuit breaker 120) of the circuit breaker 90 is demonstrated.
FIG. 6 is a cross-sectional view of the first modification (circuit breaker 120) of the circuit breaker 90 as seen from the side, where (A) shows the temperature of the heating roll 72 (fixing device 36) being a predetermined temperature. FIG. 6B is a cross-sectional view showing a state of the circuit breaker 120 when it is within a range (within a normal operating temperature range), and FIG. It is sectional drawing which shows the state of the circuit breaker 120 in the case of high temperature).
In addition, in the circuit breaker 120, the same code | symbol is attached | subjected to the substantially same part as the part which comprises the circuit breaker 90 shown in FIG.

For example, as shown in FIG. 6A, when the temperature of the heating roll 72 is within a predetermined temperature range, the bimetal 110 is convex on the lower side, the pin 108 is pushed downward by the bimetal 110, and the spring member 96 is an electrode. An electric circuit is formed in contact with 94a.
On the other hand, as shown in FIG. 6B, when the temperature of the heating roll 72 is outside the predetermined temperature range, the bimetal 110 has a convex upper side, and the pin 108 does not transmit force to the spring member 96. The spring member 96 is separated from the electrode 94a by the elastic force, and the electric circuit is interrupted.

Further, as shown in FIG. 7, even when the circuit breaker 90 fails (the cap 112 is detached), the pin 108 does not transmit force to the spring member 96, so that the spring member 96 is separated from the electrode 94a. The electric circuit is interrupted.
In other words, the circuit breaker 90 has a fail-safe function of interrupting the electric path from the electrode 94a to the spring member 96 even if the pin 108 is not pushed down by the cap 112 being removed, assuming that a failure has occurred.

  The pin 108 is generated by the displacement of the bimetal 110 at a position B that is further away from a position A where the stress generated in the spring member 96 is maximum to a position where the spring member 96 and the electrode 94a are in contact with each other. The force is transmitted to the spring member 96. Therefore, the circuit breaker 120 is smaller in reaction force (pressure) that the bimetal 110 receives via the pin 108 than the circuit breaker 90. Furthermore, even if the spring member 96 has a high electrical resistance value, the voltage drop due to the spring member 96 is reduced by shortening the distance from the position A to the position where the spring member 96 and the electrode 94a are in contact with each other. Yes.

Next, the 2nd modification (circuit breaker 130) of the circuit breaker 90 is demonstrated.
FIG. 8 is a cross-sectional view of a second modification (circuit breaker 130) of the circuit breaker 90 as seen from the side, where (A) shows the temperature of the heating roll 72 (fixing device 36) being a predetermined temperature. FIG. 5B is a cross-sectional view showing a state of the circuit breaker 130 when it is within a range (within a normal operating temperature range), and FIG. It is sectional drawing which shows the state of the circuit breaker 130 in the case of high temperature).
In addition, in the circuit breaker 130, the same code | symbol is attached | subjected to the substantially same part as the part which comprises the circuit breaker 90 shown in FIG.

Pressure is applied to the electrode 94b in a direction in which the electrode 94b is pushed up from below by a pressing member 132 such as a spring.
For example, as shown in FIG. 8A, when the temperature of the heating roll 72 is within a predetermined temperature range, the bimetal 110 has a convex lower side, the pin 108 is pushed downward by the bimetal 110, and the electrode 94b becomes the electrode 94a. An electric circuit is formed in contact with. Here, the force generated by the displacement of the bimetal 110 and transmitted by the pin 108 is stronger than the force by which the pressing member 132 pushes up the electrode 94b from below, and the electrode 94a and the electrode 94b are in contact with each other. Thus, an electric circuit is formed.

  On the other hand, as shown in FIG. 8B, when the temperature of the heating roll 72 is outside the predetermined temperature range, the bimetal 110 has a convex upper side, and the pin 108 does not transmit force to the electrode 94b. 94b is separated from the electrode 94a by the pressure of the pressure member 132, and the electric circuit is interrupted.

Furthermore, as shown in FIG. 9, even when the circuit breaker 130 fails (the cap 112 is detached), the pin 108 does not transmit force to the electrode 94b, so that the electrode 94b is separated from the electrode 94a and the electric circuit Is cut off.
That is, the circuit breaker 130 has a fail-safe function of cutting off the electric path from the electrode 94a to the electrode 94b even if the pin 108 is not pushed down by the removal of the cap 112 even if a failure occurs.

Next, the 3rd modification (circuit breaker 140) of the circuit breaker 90 is demonstrated.
FIG. 10 is a cross-sectional view of a third modification (circuit breaker 140) of the circuit breaker 90 as seen from the side. FIG. 10A shows the heating roll 72 (fixing device 36) at a predetermined temperature. FIG. 6B is a cross-sectional view showing a state of the circuit breaker 140 when it is within a range (within a normal operating temperature range), and FIG. It is sectional drawing which shows the state of the circuit breaker 140 in the case of high temperature).
In addition, in the circuit breaker 140, the same code | symbol is attached | subjected to the substantially same part as the part which comprises the circuit breaker 90 shown in FIG.

  The circuit breaker body 92 is provided with a plate-like member 144 that swings with the shaft portion 142 as a fulcrum, and an urging member 146 such as a spring for urging the spring member 96 downward from above. One end of the plate-like member 144 is configured to receive a force generated by the displacement of the bimetal 110 via the pin 108, and the other end is configured to receive a biasing force of the biasing member 146. The upper end of the biasing member 146 is suppressed by the pin guide 104.

  For example, as shown in FIG. 10A, when the temperature of the heating roll 72 is within a predetermined temperature range, the bimetal 110 has a convex upper side, and the pin 108 does not transmit the force from the bimetal 110, and the biasing member 146 By urging the spring member 96 toward the electrode 94a via the other end of the plate-like member 144, the spring member 96 contacts the electrode 94a to form an electric circuit.

On the other hand, as shown in FIG. 10B, when the temperature of the heating roll 72 is outside the predetermined temperature range, the bimetal 110 is convex on the lower side, and the pin 108 generates the force generated by the displacement of the bimetal 110. It transmits to one end and pushes down one end of the plate-like member 144 downward.
Here, the force that the pin 108 transmits to one end of the plate-like member 144 is stronger than the force that the biasing member 146 biases the spring member 96 via the other end of the plate-like member 144. That is, when the bimetal 110 is displaced so that the lower side is convex, the force of the biasing member 146 biasing the spring member 96 downward via the other end of the plate-like member 144 is cut off, and the spring member 96 is cut off. Is separated from the electrode 94a by the elastic force and the electric circuit is interrupted.

Further, when the circuit breaker 140 fails (the cap 112 is detached), the cap 112, the bimetal 110, the pin 108, the pin guide 104, and the urging member 146 are separated from each other as shown in FIG. No force is applied to 144 from either the pin 108 or the biasing member 146. Therefore, when the cap 112 is detached from the circuit breaker main body 92, the force for urging the spring member 96 downward is cut off, and the spring member 96 is separated from the electrode 94a by the elastic force (spring property) to cut off the electric circuit. The
In other words, the circuit breaker 140 has a fail-safe function of cutting off the electric path from the electrode 94a to the spring member 96 even if the pin 108 is not pushed down by the cap 112 being removed, assuming that a failure has occurred.

1 is a side view illustrating an outline of an image forming apparatus according to an embodiment of the present invention. FIG. 3 is a cross-sectional view of the fixing device as viewed from the side. It is sectional drawing seen from the side which shows the outline | summary of a circuit breaker, (A) is sectional drawing which shows the state of a circuit breaker in case the temperature of a heating roll is in a predetermined temperature range, (B) is heating It is sectional drawing which shows the state of a circuit breaker in case the temperature of a roll is outside a predetermined temperature range. It is a top view of a circuit breaker. It is sectional drawing which looked at the state of the circuit breaker when the cap removed from the side. It is sectional drawing seen from the side surface which shows the outline | summary of the 1st modification of a circuit breaker, (A) is sectional drawing which shows the state of a circuit breaker in case the temperature of a heating roll is in a predetermined temperature range. (B) is sectional drawing which shows the state of a circuit breaker in case the temperature of a heating roll is outside a predetermined temperature range. It is sectional drawing which looked at the state of the 1st modification of the circuit breaker when the cap removed from the side. It is sectional drawing seen from the side surface which shows the outline | summary of the 2nd modification of a circuit breaker, (A) is sectional drawing which shows the state of a circuit breaker in case the temperature of a heating roll is in a predetermined temperature range. (B) is sectional drawing which shows the state of a circuit breaker in case the temperature of a heating roll is outside a predetermined temperature range. It is sectional drawing which looked at the state of the 2nd modification of the circuit breaker when a cap removed from the side. It is sectional drawing seen from the side which shows the outline | summary of the 3rd modification of a circuit breaker, (A) is sectional drawing which shows the state of a circuit breaker in case the temperature of a heating roll is in a predetermined temperature range. (B) is sectional drawing which shows the state of a circuit breaker in case the temperature of a heating roll is outside a predetermined temperature range. It is sectional drawing seen from the side surface which shows the 3rd modification of a circuit breaker, and is sectional drawing which shows the state of a circuit breaker when a cap removes.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Image forming apparatus 14 Image forming means 36 Fixing apparatus 42 Transfer apparatus 65 Power supply part 90,120,130,140 Circuit breaker 92 Circuit breaker main body 94a, 94b Electrode 96 Spring member 98 Opening part 104 Pin guide 108 Pin 110 Bimetal 112 Cap 132 Pressure member 142 Shaft portion 144 Plate member 146 Biasing member

Claims (7)

A displacement member that is displaced in response to a temperature change;
A holding member for holding the displacement member;
A circuit breaker comprising: a first electrode; a second electrode; and an open portion that opens an electric circuit when one of the displacement member and the holding member is displaced by a predetermined amount or more. The displacement member is
2. The circuit breaker according to claim 1, wherein the circuit breaker is a bimetal obtained by joining two kinds of metals having different linear expansion coefficients. The opening part is
The circuit breaker according to claim 1 or 2, wherein at least one of the first electrode and the second electrode is opened by an elastic force. The displacement member is displaced at a position farther from a position where the stress generated in the first electrode or the second electrode is maximum than a position where the first electrode and the second electrode are in contact with each other. The circuit breaker according to claim 3, further comprising a transmission unit configured to transmit a force generated thereby to the first electrode or the second electrode. A pressure member that applies pressure to the first electrode or the second electrode;
The opening part is
The circuit breaker according to any one of claims 1 to 4, wherein the circuit breaker is opened by a pressure applied by the pressure member. A heating member for heating the recording medium;
A circuit breaker for interrupting an electric circuit for supplying power to the heating member when the heating member reaches a predetermined temperature;
The circuit breaker is
A displacement member that is displaced in response to a temperature change;
A holding member for holding the displacement member;
A fixing device comprising: a first electrode; a second electrode; and an open portion that opens an electric circuit when one of the displacement member and the holding member is displaced by a predetermined amount or more. An image forming unit;
Transfer means for transferring an image formed by the image forming unit to a recording medium;
A fixing device for fixing the image on the recording medium onto which the transfer means has transferred the image;
A power supply unit for supplying power to the fixing device,
The fixing device includes:
A heating member for heating the recording medium;
A circuit breaker for interrupting an electric circuit for supplying power to the heating member when the heating member reaches a predetermined temperature;
The circuit breaker is
A displacement member that is displaced in response to a temperature change;
A holding member for holding the displacement member;
An image forming apparatus comprising: a first electrode; a second electrode; and an open portion that opens an electric circuit when one of the displacement member and the holding member is displaced by a predetermined amount or more.

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