Fixing device

Abstract

To suppress deformation of a side frame of a fixing device.SOLUTION: A fixing device 1 comprises: a first fixing member (a heating roller 2); a first side frame 110; a second side frame 120; a first connection frame 130; a second fixing member 140; an arm 5; a spring 6; and a cam 7. The arm 5 can press the second fixing member (a pressure member 3) toward the first fixing member. In the spring 6, one end 6A is engaged with the first side frame 110, whereas the other end 6B is engaged with the arm 5. The spring 6 energizes the arm 5 so that the second fixing member is pressed toward the first fixing member. The cam 7 can change nip pressure of the first fixing member and the second fixing member by moving the arm 5. When viewed from a rotation axis direction, the spring 6 is positioned between a third axis line 3X and the first connection frame 130. When viewed from the rotation axis direction, the first connection frame 130 is positioned between a portion where the spring 6 is engaged with the first side frame 110 and the first fixing member.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a fixing device used in an image forming apparatus. [Background technology]

[0002] Conventionally, a fixing device used in an image forming apparatus is known (see Patent Document 1). The fixing device includes a first fixing member, a second fixing member, a side frame, an arm, a spring, and a cam. The first fixing member nips a sheet between itself and the second fixing member. The arm can press the second fixing member toward the first fixing member. One end of the spring is engaged with the side frame, and the other end is engaged with the arm. The spring biases the arm to press the second fixing member toward the first fixing member. The cam can change the nip pressure between the first fixing member and the second fixing member by moving the arm. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-124562 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the fixing device of Patent Document 1, the spring that biases the arm is positioned at the end of the side frame, and the distance between the spring and the first fixing member is greater than the distance between the cam and the first fixing member, which causes a problem in that the part of the side frame that engages one end of the spring and the surrounding area are prone to deformation.

[0005] SUMMARY OF THE INVENTION It is therefore an object of the present invention to prevent deformation of the side frames of the fixing device. [Means for solving the problem]

[0006] In order to solve the above-mentioned problems, the fixing device includes a first fixing member, a first side frame, a second side frame, a first connecting frame, a second fixing member, an arm, a spring, and a cam. The first fixing member has a roller that rotates about a first axis extending in the rotational axis direction. The first side frame rotatably supports one end of the first fixing member in the rotational axis direction. The second side frame rotatably supports the other end of the first fixing member in the rotational axis direction. The first connection frame connects the first side frame and the second side frame. The second fixing member nips the sheet between the first fixing member and the second fixing member. The arm is rotatable about a second axis extending in the rotational axis direction. The arm can press the second fixing member toward the first fixing member. One end of the spring is engaged with the first side frame and the other end is engaged with the arm. The spring biases the arm to press the second fixing member toward the first fixing member. The cam rotates about a third axis extending in the rotational axis direction. The cam can change the nip pressure between the first fixing member and the second fixing member by moving the arm. When viewed from the direction of the rotation axis, the spring is located between the third axis and the first connection frame. When viewed from the direction of the rotation axis, the first connection frame is located between the first fixing member and a portion where the spring is locked to the first side frame.

[0007] When viewed from the direction of the rotation axis, the spring that biases the arm is located between the third axis and the first connecting frame, and the first connecting frame is located between the spring and the first fixing member.This makes the distance between the spring and the first fixing member smaller than the distance between the cam and the first fixing member, and the part of the first side frame that engages the spring is reinforced by the first connecting frame, thereby preventing the first side frame and the second side frame from deforming due to the biasing force of the spring.

[0008] The spring may be disposed inside the first side frame in the direction of the rotation axis.

[0009] The spring is disposed inside the first side frame in the direction of the rotation axis, and therefore, the first side frame and the second side frame can be prevented from being deformed outward.

[0010] The first side frame and the first connection frame may both be made of metal. The first connection frame may be located at one end in the rotational axis direction and have a first insertion portion that protrudes to one side in the rotational axis direction. The first side frame may have a first hole into which the first insertion portion fits to position the first insertion portion.

[0011] Since the first connection frame has the first insertion portion and the first side frame has the first hole, the first connection frame can be positioned with high precision relative to the first side frame.

[0012] The first side frame may have a base portion and a bearing portion protruding from the base portion to rotatably support the cam, and the bearing portion may have a cylindrical shape extending in the direction of the rotation axis.

[0013] The bearing portion that rotatably supports the cam has a cylindrical shape that extends in the direction of the rotation axis, ensuring a sufficient sliding area for the cam to rotate. As a result, the cam can rotate smoothly and is less likely to come off.

[0014] The base portion may also have a first reinforcing portion that protrudes in the rotation axis direction from the peripheral edge of the base portion, and that is provided on the peripheral edge of the bearing portion of the base portion.

[0015] Since the base portion has the first reinforcing portion, deformation around the bearing portion of the cam can be suppressed.

[0016] The first side frame may also have a first support hole that rotatably supports one end of the first fixing member, and a second reinforcing portion that is arranged between the first support hole and the bearing portion and protrudes in the direction of the rotation axis.

[0017] Since the first side frame has the second reinforcing portion, deformation around the bearing portion of the cam can be suppressed. [Effects of the Invention]

[0018] According to the present invention, it is possible to prevent the side frame of the fixing device from being deformed. [Brief explanation of the drawings]

[0019] [Figure 1] FIG. 4 is a cross-sectional view of the fixing device in a state where a first nip pressure is applied. [Figure 2] FIG. 4 is a cross-sectional view of the fixing device in a state where a second nip pressure is applied. [Figure 3] FIG. 2 is a diagram showing an electrical connection between the fixing device and the image forming apparatus. [Figure 4] FIG. 2 is a perspective view showing a state in which a first temperature sensor, a second temperature sensor, and a thermostat are removed from the fixing frame. [Figure 5] FIG. 2 is a perspective view showing a state in which a first temperature sensor, a second temperature sensor, and a thermostat are attached to a fixing frame. [Figure 6] FIG. 10 is a perspective view showing a state in which the first side frame and the second side frame have been removed from the first connecting frame. [Figure 7] FIG. 4 is a perspective view of the fixing frame as seen from a different direction from FIG. 3. [Figure 8] 1A is a view of the first connection frame as seen from the second direction, and FIG. 1B is a cross-sectional view taken along line AA of FIG. [Figure 9] FIG. 10 is a view of the fixing frame seen from a third direction. [Figure 10] FIG. 10 is a perspective view showing a first side frame in another embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0020] Next, an embodiment of the present invention will be described in detail with reference to the accompanying drawings. As shown in Fig. 1, the fixing device 1 is a device that fixes a toner image on a sheet S. The fixing device 1 can be attached to a main body housing M (see Fig. 3) of an image forming apparatus P such as a printer.

[0021] The fixing device 1 includes a heating roller 2 as an example of a first fixing member, a pressure member 3 as an example of a second fixing member, an arm shaft 4 as an example of a shaft, an arm 5, a spring 6, a cam 7, a camshaft 8, and a fixing frame 100. The arm shaft 4, the arm 5, the spring 6, the cam 7, and the camshaft 8 are members that make up a pressure change mechanism that changes the nip pressure between the heating roller 2 and the pressure member 3. The arm 5, the spring 6, and the cam 7 are arranged one on each side in the first direction. Because the configurations of one side and the other side are symmetrical, only one side will be described and the description of the other side will be omitted.

[0022] The heating roller 2 rotates around a first axis 1X, which is an example of a rotation axis. The heating roller 2 extends in the direction of the first axis 1X. The heating roller 2 has a roller 2A and a heater H. The roller 2A rotates around the first axis 1X, which extends in the direction of the rotation axis. In this embodiment, the heating roller 2 has two heaters H1 and H2. The roller 2A is heated by the heaters H1 and H2. The heaters H1 and H2 are arranged inside the roller 2A. The heaters H1 and H2 are, for example, halogen heaters.

[0023] In the following description, the direction in which the first axis 1X of the heating roller 2 extends is referred to as the "first direction." The direction perpendicular to the first direction is referred to as the "second direction." The direction perpendicular to the first and second directions is referred to as the "third direction." In this embodiment, the first direction is the left-right direction, the second direction is the direction along the front-rear direction, and the third direction is the vertical direction. In the drawings, arrows indicating directions will point to one side.

[0024] The pressure member 3 is a member that nips the sheet S between itself and the heating roller 2. In this embodiment, the pressure member 3 is a roller that rotates about a fourth axis 4X. The pressure member 3 extends in a first direction. The pressure member 3 rotates following the rotation of the heating roller 2. The pressure member 3 nips the sheet S between itself and the heating roller 2. The pressure member 3 has a roller shaft 3A and a roller main body 3B. The roller shaft 3A is made of, for example, metal. The roller main body 3B is made of, for example, rubber, and is provided to cover the periphery of the roller shaft 3A.

[0025] The arm shaft 4 is made of metal and extends in a first direction.

[0026] The arm 5 is rotatably supported on the arm shaft 4 and is capable of pressing the pressure member 3 toward the heating roller 2. The arm 5 has a long, thin plate shape and extends obliquely in the second and third directions. The arm 5 has one end 5A, the other end 5B, a first portion 5C, and a second portion 5D.

[0027] One end 5A is an end on one side in the second direction and one side in the third direction. One end 5A has a groove that engages with the arm shaft 4, and is rotatably supported by the arm shaft 4. This allows the arm 5 to rotate about the second axis 2X.

[0028] The other end 5B is an end opposite to the one end 5A. The other end 5B has a cam follower 5F. The cam follower 5F is capable of coming into contact with the cam 7.

[0029] The first portion 5C and the second portion 5D are located between the one end portion 5A and the other end portion 5B. The first portion 5C supports the pressure member 3. The second portion 5D is a portion to which the spring 6 is connected and has a hole in which one end of the spring 6 is engaged.

[0030] The spring 6 is a coil spring. The spring 6 has a coil portion 6A, one end 6B, and the other end 6C. The one end 6B of the spring 6 is engaged with the fixing frame 100. The other end 6C of the spring 6 is engaged with the arm 5. The spring 6 biases the arm 5 so as to press the pressure member 3 toward the heating roller 2.

[0031] The camshaft 8 is made of metal and extends in the first direction. The camshaft 8 is rotatable about a third axis 3X.

[0032] The cam 7 is fixed to the camshaft 8 and is rotatable about the third axis 3X by rotation of the camshaft 8. Specifically, the cam 7 is rotatable between a first phase shown in FIG. 1 and a second phase shown in FIG. 2.

[0033] The first phase is a phase in which the nip pressure becomes a first nip pressure. The second phase is a phase in which the nip pressure becomes a second nip pressure, which is smaller than the first nip pressure. Specifically, as shown in FIG. 1, when the cam 7 is in the first phase, the cam 7 does not contact the cam follower 5F, and the cam follower 5F is not pressed against the cam 7. As a result, all of the biasing force of the spring 6 is transmitted to the pressure member 3, resulting in the first nip pressure. On the other hand, as shown in FIG. 2, when the cam 7 is in the second phase, the cam 7 contacts the cam follower 5F, and the cam follower 5F is pressed against the cam 7. As a result, a portion of the biasing force of the spring 6 is not transmitted to the pressure member 3, and the nip pressure becomes a second nip pressure, which is smaller than the first nip pressure. In this way, the cam 7 rotates and moves the arm 5, thereby changing the nip pressure between the heating roller 2 and the pressure member 3.

[0034] As shown in FIG. 3, an image forming apparatus P to which the fixing device 1 can be attached includes a control unit MC, a heater driving unit HC, and a main body connector CC.

[0035] The control unit MC includes, for example, a CPU, a RAM, a ROM, and an input / output circuit, and controls the fixing device 1 by performing arithmetic processing based on programs and data stored in the ROM.

[0036] The heater driving unit HC is controlled by the control unit MC, and supplies power to the heaters H1 and H2 based on temperature information detected by the first temperature sensor S1 and the second temperature sensor S2.

[0037] The main body connector CC is a connector to which the fixing connector 11 of the fixing device 1 is connected when the fixing device 1 is attached to the main body housing M.

[0038] The fixing device 1 further includes a first temperature sensor S1, a second temperature sensor S2, a thermostat TM, and a fixing connector 11.

[0039] The first temperature sensor S1 is a sensor that detects the temperature of the heating roller 2. The first temperature sensor S1 is a non-contact sensor that is positioned at a distance from the heating roller 2. The first temperature sensor S1 is disposed in the center of the heating roller 2 in the first direction. The first temperature sensor S1 is disposed within the range where the sheet S passes over the heating roller 2.

[0040] 1, the first temperature sensor S1 has a fixed portion S11 and a detection portion S12. The fixed portion S11 is a portion that is fixed to the fixing frame 100. More specifically, the fixed portion S11 is fixed to a first connection frame 130, which will be described later. The detection portion S12 is a thermistor whose resistance value changes with temperature. The detection portion S12 is disposed with a distance D1 from the surface of the heating roller 2.

[0041] The second temperature sensor S2 is a sensor that detects the temperature of the heating roller 2. The second temperature sensor S2 is a contact-type sensor that comes into contact with the surface of the heating roller 2. The second temperature sensor S2 is arranged at the end of the heating roller 2 in the first direction. The second temperature sensor S2 is arranged outside the range where the sheet S passes over the heating roller 2. The second temperature sensor S2 has a fixed portion S21 and a detecting portion S22. The fixed portion S21 is a portion that is fixed to the fixing frame 100. The detecting portion S22 is a thermistor whose resistance value changes depending on the temperature. The detecting portion S22 comes into contact with the surface of the heating roller 2.

[0042] The control unit MC controls the heaters H1 and H2 that heat the heating roller 2 based on the temperatures detected by the first temperature sensor S1 and the second temperature sensor S2.

[0043] The thermostat TM is an element that cuts off the flow of electricity when the surface temperature of the heating roller 2 exceeds a predetermined temperature. The thermostat TM is arranged at a distance from the heating roller 2. The thermostat TM is arranged in the center of the heating roller 2 in the first direction. The thermostat TM is arranged within the range of the heating roller 2 where the sheet S passes.

[0044] The fixing connector 11 is a connector that is connected to the main body connector CC when the fixing device 1 is attached to the main body housing M. When the fixing connector 11 and the main body connector CC are connected, the control unit MC receives information detected by the first temperature sensor S1 and the second temperature sensor S2, and supplies power to the heaters H1 and H2 from the heater driving unit HC, thereby enabling the heaters H1 and H2 to be controlled.

[0045] 4 and 5, the fixing frame 100 has a first side frame 110, a second side frame 120, a first connecting frame 130, and a second connecting frame 140. The first side frame 110, the second side frame 120, the first connecting frame 130, and the second connecting frame 140 are metal plates.

[0046] In this embodiment, the arm 5, the spring 6, and the cam 7 are disposed between the first side frame 110 and the second side frame 120 (see also FIG. 1). That is, the arm 5, the spring 6, and the cam 7 are disposed inside the first side frame 110 and the second side frame 120 in the first direction.

[0047] The first side frame 110 is located on one side in the first direction and rotatably supports one end of the heating roller 2 in the first direction.

[0048] As shown in FIG. 6, the first side frame 110 has a first base portion 111, a first support hole 112, a first bearing portion 113 as an example of a bearing portion, a first hole 114, a second hole 115, a third hole 116, a first spring engagement portion 117, a first convex portion 118, a second convex portion 119, and a bearing 110A.

[0049] The first support hole 112 is a circular hole formed in the center of the first base portion 111. A bearing 110A is attached to the first support hole 112. The bearing 110A rotatably supports one end of the heating roller 2.

[0050] The first bearing portion 113 protrudes from the first base portion 111 to one side in the first direction. The first bearing portion 113 has a cylindrical shape extending in the first direction. The first bearing portion 113 rotatably supports the camshaft 8 (see also FIG. 1). As a result, the first bearing portion 113 rotatably supports the cam 7 via the camshaft 8.

[0051] The first hole 114 is a hole formed in the first base portion 111 (see also FIG. 1). The first hole 114 is an elongated hole having an M-shape that is long in the second direction. A part of the first connection frame 130 fits into the first hole 114. More specifically, the first insertion portion 132B of the first connection frame 130, which will be described later, fits into the first hole 114, thereby positioning the first insertion portion 132B of the first connection frame 130.

[0052] The second hole 115 is a hole formed in the first base portion 111 (see also FIG. 1). The second hole 115 is an elongated hole that is long in the second direction. The second hole 115 is a hole into which a part of the first connection frame 130 fits. More specifically, the second hole 115 positions the second insertion portion 134D of the first connection frame 130, which will be described later, by fitting therein.

[0053] The third hole 116 is a hole formed in the first base portion 111. The third hole 116 is located at one end of the first base portion 111 in the second direction. The third hole 116 is a hole through which a screw N3 that fastens the first fastening wall portion 135 and the first side frame 110 passes.

[0054] The first spring engaging portion 117 is formed at the other end in the third direction of the first base portion 111. The first spring engaging portion 117 is formed by bending from the first base portion 111 to the other side in the first direction. The first spring engaging portion 117 has a groove at its tip for engaging with one end 6B of the spring 6.

[0055] The first protrusion 118 and the second protrusion 119 each protrude from one end in the third direction of the first base portion 111 to one side in the third direction. The first protrusion 118 and the second protrusion 119 are arranged side by side in the second direction. The first protrusion 118 is provided on one side in the second direction of the second protrusion 119.

[0056] The second side frame 120 is located on the other side in the first direction. The second side frame 120 is formed symmetrically with the first side frame 110. The second side frame 120 is a frame that rotatably supports the other end of the heating roller 2 in the first direction.

[0057] As shown in Figures 6 and 7, the second side frame 120 has a second base portion 121, a second support hole 122, a second bearing portion 123 as an example of a bearing portion, a fourth hole 124, a fifth hole 125, a sixth hole 126, a second spring engagement portion 127, a third convex portion 128, a fourth convex portion 129, and a bearing 120A.

[0058] The second support hole 122 is a circular hole formed in the center of the second base portion 121. A bearing 120A is attached to the second support hole 122. The bearing 120A rotatably supports the other end of the heating roller 2.

[0059] The second bearing portion 123 protrudes from the second base portion 121 to the other side in the first direction. The second bearing portion 123 has a cylindrical shape extending in the first direction. The second bearing portion 123 rotatably supports the camshaft 8 (see also FIG. 1). As a result, the second bearing portion 123 rotatably supports the cam 7 via the camshaft 8.

[0060] The fourth hole 124 is a hole formed in the second base portion 121. The fourth hole 124 is an elongated hole having an M-shape that is long in the second direction. A part of the first connection frame 130 fits into the fourth hole 124. More specifically, the third insertion portion 132C of the first connection frame 130, which will be described later, fits into the fourth hole 124, thereby positioning the third insertion portion 132C of the first connection frame 130.

[0061] The fifth hole 125 is a hole formed in the second base portion 121. The fifth hole 125 is an elongated hole that is long in the second direction. The fifth hole 125 is a hole into which a part of the first connection frame 130 fits. In detail, the fourth insertion portion 134E of the first connection frame 130, which will be described later, fits into the fifth hole 125, thereby positioning the fourth insertion portion 134E of the first connection frame 130.

[0062] The sixth hole 126 is a hole formed in the second base portion 121. The sixth hole 126 is located at one end of the second base portion 121 in the second direction. The sixth hole 126 is a hole through which a screw N4 that fastens the second fastening wall portion 136 and the second side frame 120 passes.

[0063] The second spring engaging portion 127 is formed at the other end in the third direction of the second base portion 121. The second spring engaging portion 127 is formed by bending from the second base portion 121 to one side in the first direction. The second spring engaging portion 127 has a groove at its tip for engaging with one end 6B of the spring 6.

[0064] The third protrusion 128 and the fourth protrusion 129 each protrude from one end in the third direction of the second base portion 121 to one side in the third direction. The third protrusion 128 and the fourth protrusion 129 are arranged side by side in the second direction. The third protrusion 128 is provided on one side in the second direction of the fourth protrusion 129.

[0065] The first connecting frame 130 is a frame that connects the first side frame 110 and the second side frame 120. The first connecting frame 130 extends in a first direction. The first connecting frame 130 has a first wall portion 131, a second wall portion 132, a third wall portion 133, a fourth wall portion 134, a first fastening wall portion 135, a second fastening wall portion 136, and an extending wall portion 137.

[0066] The first wall portion 131 is a wall that extends in the first direction and the third direction. The first wall portion 131 is not in contact with the first side frame 110 and the second side frame 120.

[0067] The second wall portion 132 is formed by bending the other end portion of the first wall portion 131 in the third direction. In this embodiment, the second wall portion 132 extends from the other end portion of the first wall portion 131 in the third direction toward the other side in the second direction. The second wall portion 132 is perpendicular to the first wall portion 131 and extends in the first and second directions. The second wall portion 132 has a first sensor attachment portion 132A, a first insertion portion 132B, and a third insertion portion 132C.

[0068] The first sensor mounting portion 132A is disposed in the center of the second wall portion 132 in the first direction. As shown in FIGS. 4 and 5, the first sensor mounting portion 132A has a screw hole to which the first temperature sensor S1 is attached. The first temperature sensor S1 is attached to the first sensor mounting portion 132A with a screw N1. In this embodiment, the first temperature sensor S1 is fixed to the second wall portion 132 with a leaf spring PS, which is an example of a spring, sandwiched between the first temperature sensor S1 and the second wall portion 132. In this manner, the first temperature sensor S1 is fixed to the second wall portion 132.

[0069] 8(a), the second wall portion 132 has a first surface M1 and a second surface M2. The first surface M1 is a surface of the second wall portion 132 located on the third wall portion 133 side. The second surface M2 is a surface opposite to the first surface M1. The first temperature sensor S1 is fixed to the first surface M1 of the second wall portion 132.

[0070] 6, the first insertion portion 132B is located at one end in the first direction of the second wall portion 132. More specifically, the first insertion portion 132B is a protrusion that protrudes toward one side in the first direction from one end in the first direction of the second wall portion 132. The first insertion portion 132B fits into the first hole 114 of the first side frame 110, thereby positioning the first connecting frame 130 on the first side frame 110.

[0071] The third insertion portion 132C is located at the end on the other side in the first direction of the second wall portion 132. More specifically, the third insertion portion 132C is a protrusion that protrudes toward the other side in the first direction from the end on the other side in the first direction of the second wall portion 132. The third insertion portion 132C fits into the fourth hole 124 of the second side frame 120, thereby positioning the first connection frame 130 on the second side frame 120.

[0072] The first fastening wall portion 135 is formed by bending from one end of the second wall portion 132 in the first direction. The first fastening wall portion 135 extends from one end of the second wall portion 132 in the first direction toward one side in the third direction. The first fastening wall portion 135 has a screw hole 135A. The first fastening wall portion 135 is fastened to the first side frame 110 with a screw N3.

[0073] The second fastening wall portion 136 is formed by bending the other end of the second wall portion 132 in the first direction. The second fastening wall portion 136 extends from the other end of the second wall portion 132 in the first direction toward one side in the third direction. The second fastening wall portion 136 has a screw hole 136A. The second fastening wall portion 136 is fastened to the second side frame 120 with a screw N4.

[0074] The third wall portion 133 is formed by bending the end portion of the second wall portion 132 opposite to the first wall portion 131. More specifically, the third wall portion 133 is bent in a direction away from the second wall portion 132. In this embodiment, the third wall portion 133 extends from the other end portion of the second wall portion 132 in the second direction toward the other side in the third direction. The third wall portion 133 is perpendicular to the second wall portion 132 and extends in the first direction and the third direction. The third wall portion 133 has a first opening 133A.

[0075] The first opening 133A is an opening through which the first temperature sensor S1 passes when the first temperature sensor S1 is attached to the first connection frame 130. The first opening 133A is formed in the center in the first direction of the third wall portion 133. As shown in FIG. 8(a), in the first direction, the dimension L1 of the first wall portion 131 is larger than the dimension L2 of the first opening 133A of the third wall portion 133.

[0076] 6, the fourth wall portion 134 is formed by bending the end portion of the third wall portion 133 opposite to the second wall portion 132. In this embodiment, the fourth wall portion 134 extends from the other end portion of the third wall portion 133 in the third direction toward the other side in the second direction. The fourth wall portion 134 is perpendicular to the third wall portion 133 and extends in the first direction and the second direction. The fourth wall portion 134 has a second opening 134A, a third opening 134B, a fourth opening 134C, a second insertion portion 134D, and a fourth insertion portion 134E.

[0077] The second opening 134A is an opening formed in the center of the fourth wall portion 134 in the first direction. The second opening 134A is a cutout formed to allow the thermostat TM to pass through (see FIG. 5). The second opening 134A exposes the temperature detection surface of the thermostat TM toward the heating roller 2. The thermostat TM is fixed to the fixing frame 100 while being held by a resin holder (not shown).

[0078] The third opening 134B is an opening formed continuously with the first opening 133A of the third wall portion 133.

[0079] The fourth opening 134C is a rectangular hole formed in the center in the first direction of the fourth wall portion 134. The fourth opening 134C is formed in a position overlapping with the detection portion S12 of the first temperature sensor S1 when viewed from the third direction. The fourth opening 134C is a hole through which a laser beam that is used to adjust the distance D1 between the detection portion S12 and the heating roller 2 and detects the position of the detection portion S12 passes (see also FIG. 7(b)).

[0080] The second insertion portion 134D is located at one end in the first direction of the fourth wall portion 134. More specifically, the second insertion portion 134D is a protrusion that protrudes to one side in the first direction from one end in the first direction of the fourth wall portion 134. The second insertion portion 134D fits into the second hole 115 of the first side frame 110, thereby positioning the first connecting frame 130 on the first side frame 110.

[0081] The fourth insertion portion 134E is located at the other end in the first direction of the fourth wall portion 134. More specifically, the fourth insertion portion 134E is a protrusion that protrudes toward the other side in the first direction from the other end in the first direction of the fourth wall portion 134. The second side frame 120 positions the first connection frame 130 by the fourth insertion portion 134E fitting into the fifth hole 125 of the second side frame 120.

[0082] The extending wall portion 137 is disposed at one end of the fourth wall portion 134 in the first direction. The extending wall portion 137 is formed by bending from the fourth wall portion 134. The extending wall portion 137 extends in a direction away from the heating roller 2. More specifically, the extending wall portion 137 extends from one end of the fourth wall portion 134 in the second direction to the other side in the third direction. A second temperature sensor S2 is fixed to the extending wall portion 137. In this embodiment, the second temperature sensor S2 is fixed to the extending wall portion 137 by a screw N2 (see FIG. 5).

[0083] As shown in FIG. 7, the second connection frame 140 is a frame that connects the first side frame 110 and the second side frame 120. The second connection frame 140 has a first connecting hole 141 , a second connecting hole 142 , a third connecting hole 143 , and a fourth connecting hole 144 .

[0084] The first connecting hole 141 and the second connecting hole 142 are disposed at one end of the second connecting frame 140 in the first direction. The first connecting hole 141 positions the first convex portion 118 of the first side frame 110 by fitting therein the first convex portion 118 of the first side frame 110. The second connecting hole 142 positions the second convex portion 119 of the first side frame 110 by fitting therein the second convex portion 119 of the first side frame 110.

[0085] The third connecting hole 143 and the fourth connecting hole 144 are disposed at the other end of the second connection frame 140 in the first direction. The third protrusion 128 of the second side frame 120 fits into the third connecting hole 143, thereby positioning the third protrusion 128 of the second side frame 120. The fourth connecting hole 144 fits into the fourth protrusion 129 of the second side frame 120, thereby positioning the fourth protrusion 129 of the second side frame 120.

[0086] Here, the positional relationship between the arm shaft 4, the arm 5, the spring 6, the cam 7, the camshaft 8, the first connection frame 130, and the second connection frame 140 will be described with reference to FIG.

[0087] As shown in FIG. 1, the arm shaft 4, the camshaft 8, the first connecting frame 130, and the second connecting frame 140 are arranged in different positions, and connect the first side frame 110 and the second side frame 120 at different positions.

[0088] When viewed from the first direction, the spring 6 is located between the third axis 3X, which is the rotation axis of the camshaft 8, and the first connection frame . Furthermore, when viewed from the first direction, the first connection frame 130 is located between the heating roller 2 and the first spring engagement portion 117, which is the portion where the spring 6 is engaged with the first side frame 110. Further, when viewed from the first direction, the first axis 1X, which is the rotation axis of the heating roller 2, is located between the first connection frame 130 and the second connection frame 140. Moreover, the pressure member 3 is located between the heat roller 2 and the second connection frame 140 when viewed from the first direction. Furthermore, the arm shaft 4 is positioned at a position offset from the second connection frame 140 in the circumferential direction of the heating roller 2.

[0089] As described above, the following effects can be obtained in this embodiment.

[0090] When the distance D1 between the surface of the heating roller 2 and the detection unit S12 changes, the first temperature sensor S1, which is a non-contact temperature sensor, will have a detection error corresponding to the change in the distance D1. However, according to the fixing device 1 of this embodiment, the first connection frame 130 to which the first temperature sensor S1 is fixed has a first wall portion 131, a second wall portion 132 bent from the first wall portion 131, and a third wall portion 133 bent from the second wall portion 132. Because the first connection frame 130 is formed in a stepped shape in this way, the rigidity of the second wall portion 132 is increased, and deformation of the second wall portion 132 is suppressed. As a result, changes in the distance D1 between the first temperature sensor S1 fixed to the second wall portion 132 and the heating roller 2 are suppressed, and detection errors of the first temperature sensor S1 are reduced.

[0091] Furthermore, the third wall portion 133 is bent from the second wall portion 132 in a direction away from the heating roller 2. The first temperature sensor S1 is fixed to the first surface M1 located on the third wall portion 133 side, and the third wall portion 133 has a first opening 133A through which the first temperature sensor S1 passes. Therefore, the third wall portion 133 can suppress the transfer of heat from the heating roller 2 to the fixed portion S11 of the first temperature sensor S1. As a result, the effect of heat from the heating roller 2 on the fixed portion S11 of the first temperature sensor S1 can be reduced.

[0092] Furthermore, in the first direction, the dimension L1 of the first wall portion 131 is larger than the dimension L2 of the first opening 133A of the third wall portion 133, so the first wall portion 131 can compensate for the reduced rigidity of the first connection frame 130 due to the formation of the first opening 133A.

[0093] The first temperature sensor S1 is fixed by a screw N1 with a leaf spring PS sandwiched between it and the second wall portion 132. Therefore, the distance D1 between the heating roller 2 and the first temperature sensor S1 can be adjusted by turning the screw N1.

[0094] Furthermore, the second wall portion 132 of the first connection frame 130 has the first insertion portion 132B, and the first side frame 110 has the first hole 114. This allows the second wall portion 132 to be positioned with high precision relative to the first side frame 110. As a result, the precision of the positional relationship between the heating roller 2 and the first temperature sensor S1 can be increased. Furthermore, by using the first insertion portion 132B and the first hole 114 to position the first connection frame 130 and the first side frame 110, no screws are placed between the heating roller 2 and the spring 6, which allows the overall size of the fixing frame 100 to be reduced.

[0095] Furthermore, the first connection frame 130 has the first fastening wall portion 135, which prevents the first connection frame 130 from coming off the first side frame 110. The first connection frame 130 has the second fastening wall portion 136, which prevents the first connection frame 130 from coming off the second side frame 120. Furthermore, the first fastening wall portion 135 and the second fastening portion 136 are formed by bending from the end of the second wall portion 132, which increases the rigidity of the second wall portion 132 and suppresses deformation of the second wall portion 132.

[0096] Furthermore, since the first connection frame 130 has the fourth wall portion 134, the rigidity of the first connection frame 130 is further increased, and deformation of the first connection frame 130 is suppressed.

[0097] Furthermore, since the fourth wall portion 134 has the second opening 134A, the thermostat TM does not interfere with the fourth wall portion 134. Therefore, even if the thermostat TM is provided, the fixing device 1 does not become larger.

[0098] The second temperature sensor S2 is fixed to an extending wall portion 137 formed by bending the highly rigid fourth wall portion. This increases the positional accuracy of the fixing portion of the second temperature sensor S2, and makes it possible to suppress changes in the contact pressure of the second temperature sensor S2 with the heating roller 2.

[0099] Furthermore, because the fourth wall portion 134 has the second insertion portion 134D and the first side frame 110 has the second hole 115, the fourth wall portion 134 can be positioned with high precision relative to the first side frame 110. This also increases the precision of the positional relationship between the heating roller 2 and the second temperature sensor S2. Furthermore, by using the second insertion portion 134D and the second hole 115 to position the first connecting frame 130 and the first side frame 110, no screws are placed between the heating roller 2 and the spring 6, which allows the entire fixing frame 100 to be made smaller.

[0100] Furthermore, the first axis 1X, which is the rotation axis of the heating roller 2, is located between the first connecting frame 130 and the second connecting frame 140. In this way, since the heating roller 2 is surrounded by the first side frame 110, the second side frame 120, the first connecting frame 130, and the second connecting frame 140, deformation of the fixing device 1 can be suppressed even when the heating roller 2 repeatedly starts and stops rotating.

[0101] Furthermore, by positioning the arm shaft 4 supporting the arm 5 at a position offset from the second connection frame 140 in the circumferential direction of the heating roller 2, the rigidity of the fixing device 1 is not reduced, and deformation of the entire fixing device 1 can be suppressed.

[0102] In the conventional fixing device, the spring that biases the arm is located at the end of the side frame, and the distance between the spring 6 and the heating roller 2 is greater than the distance between the cam 7 and the heating roller 2, which causes a problem that the part of the side frame that engages one end of the spring and the surrounding area are easily deformed. For example, the side frame is easily deformed as if pulled in the direction of the arrow in Figure 9, which can cause the entire fixing frame to deform. However, according to the fixing device 1 of this embodiment, when viewed from the first direction, the spring 6 that biases the arm 5 is located between the third axis 3X, which is the rotation axis of the cam 7, and the first connection frame 130, and the first connection frame 130 is located between the spring 6 and the heating roller 2. Therefore, compared to conventional fixing devices, the distance between the spring 6 and the heating roller 2 is shorter than the distance between the cam 7 and the heating roller 2, and the first spring engagement portion 117 that engages the spring 6 of the first side frame 110 is reinforced by the first connection frame 130. As a result, deformation of the first side frame 110 and the second side frame 120 due to the biasing force of the spring 6 can be suppressed.

[0103] Furthermore, since the spring 6 is disposed inside the first side frame 110 in the first direction, it is possible to prevent the first side frame 110 and the second side frame 120 from deforming outward.

[0104] The first bearing portion 113 that rotatably supports the cam 7 has a cylindrical shape extending in the first direction, ensuring a sliding area for the rotation of the cam 7. As a result, the cam 7 can rotate smoothly and is less likely to come off.

[0105] The present invention is not limited to the above-described embodiment, but can be used in various forms as exemplified below.

[0106] The first side frame 110 and the second side frame 120 may have a portion that reinforces the strength of the base portion. For example, the first side frame 210 shown in Fig. 10 has a first reinforcing portion 210A and a second reinforcing portion 210B. The first reinforcing portion 210A protrudes in a first direction from the peripheral edge of the first base portion 211. Note that the first and second side frames have bilaterally symmetrical shapes, so only the shape of the first side frame will be described and a description of the second side frame will be omitted.

[0107] The first reinforcing portion 210A is provided on the edge of the first base portion 211 surrounding the first bearing portion 113. The first reinforcing portion 210A has a portion that covers the first bearing portion 113 from three directions: one side and the other side in the second direction, and the other side in the third direction. The first reinforcing portion 210A also has a portion that extends from the portion that covers the first bearing portion 113 from three directions to the first support hole 112. In this way, the first reinforcing portion 210A is disposed on the other side in the third direction of the first support hole 112. It stretches like this.

[0108] The second reinforcing portion 210B is disposed between the first support hole 112 and the first bearing portion 113. The second reinforcing portion 210B is formed in a bead shape that protrudes in the first direction and is long in the second direction. The second reinforcing portion 210B is disposed on the other side of the first support hole 112 in the third direction.

[0109] As such, the first side frame 210 shown in FIG. 10 has the first reinforcing portion 210A and the second reinforcing portion 210B that reinforce the strength of the first base portion 211, and therefore can suppress deformation around the first bearing portion 113 of the camshaft 8 that fixes the cam 7.

[0110] The first side frame 210 may have either the first reinforcing portion 210A or the second reinforcing portion 210B. Furthermore, although FIG. 10 shows a configuration in which the first reinforcing portion 210A and the second reinforcing portion 210B protrude outward from the first side frame 110, the first reinforcing portion 210A and the second reinforcing portion 210B may also protrude inward.

[0111] In the above embodiment, the angle between the first wall portion 131 and the second wall portion 132, the angle between the second wall portion 132 and the third wall portion 133, and the angle between the third wall portion 133 and the fourth wall portion 134 are 90°, but they are not limited to 90° and may be any angle. Furthermore, the first wall portion 131 and the third wall portion 133 may extend from the second wall portion 132 on the same side.

[0112] In the embodiment, the fixing device 1 can be attached to the main body housing M of the image forming apparatus P, but the fixing device 1 may also be fixed to the main body housing M so that it cannot be detached.

[0113] In the above embodiment, the heating roller 2 is used as the heating member, but the heating member may be, for example, a cylindrical fixing belt slidably supported by a guide.

[0114] In the above embodiment, the first side frame 110 and the second side frame 120 rotatably supported the heating roller 2, but the first side frame 110 and the second side frame 120 may also rotatably support the pressure member 3.

[0115] In the above embodiment, a halogen heater is used as the heater H, but the heater H may be a heating resistor or an IH heat source. Here, an IH heat source refers to a device that does not generate heat itself but heats a roller or a metal belt using electromagnetic induction heating. Also, in the above embodiment, the fixing device 1 includes two heaters H1 and H2, but the fixing device 1 may include one heater H or three or more heaters H.

[0116] The elements described in the above-described embodiment and modified examples may be implemented in any combination. [Explanation of symbols]

[0117] 1 Fixing device 2 Heating roller 3 Pressure member 4 Arm shaft 5 Arm 6 springs 6A Coil section 6B One end 6C other end 7 Cam 8 Camshaft 100 fixed frames 110 First side frame 120 Second side frame 130 First connecting frame 131 1st wall section 132 Second wall 133 Third wall 134 4th wall D1 interval S1 First temperature sensor S11 Fixed part S12 detection unit 3X 3rd axis

Claims

1. a first fixing member having a roller that rotates around a first axis extending in the rotation axis direction; a first side frame that rotatably supports one end of the first fixing member in the direction of the rotation axis; a second side frame that rotatably supports the other end of the first fixing member in the rotation axis direction; a first connecting frame that connects the first side frame and the second side frame; a second fixing member that nips a sheet between itself and the first fixing member; an arm that is rotatable about a second axis extending in the rotation axis direction and that is capable of pressing the second fixing member toward the first fixing member; a spring having one end engaged with the first side frame and the other end engaged with the arm, the spring biasing the arm so as to press the second fixing member toward the first fixing member; a cam that rotates around a third axis extending in a rotation axis direction and that can change a nip pressure between the first fixing member and the second fixing member by moving the arm, When viewed from the direction of the rotation axis, the spring is located between the third axis and the first connection frame, The fixing device, as viewed from the direction of the rotation axis, is characterized in that the first connecting frame is located between the first fixing member and a portion where the spring is engaged with the first side frame.

2. The spring is disposed inside the first side frame in the direction of the rotation axis.

3. the first side frame and the first connection frame are both made of metal, the first connection frame is located at one end in the rotational axis direction and has a first insertion portion that protrudes to one side in the rotational axis direction, The fixing device according to claim 1 , wherein the first side frame has a first hole into which the first insertion portion is inserted to position the first insertion portion.

4. the first side frame has a base portion and a bearing portion protruding from the base portion and rotatably supporting the cam; 2. The fixing device according to claim 1, wherein the bearing portion has a cylindrical shape extending in the direction of the rotation axis.

5. The fixing device according to claim 4, characterized in that the base portion has a first reinforcing portion that protrudes from the peripheral edge of the base portion in the direction of the rotation axis, the first reinforcing portion being provided on the peripheral edge of the bearing portion of the base portion.

6. The first side frame is a first support hole that rotatably supports one end of the first fixing member; The fixing device according to claim 4 , further comprising a second reinforcing portion disposed between the first support hole and the bearing portion, the second reinforcing portion protruding in the direction of the rotation axis.

Images