Fixing device and image forming apparatus

Abstract

To stabilize the assemblability of a fixing device to increase the efficiency of assembly operations of the fixing device.SOLUTION: An engagement target part 325 with which a sensor holding member 34 that holds a temperature sensor 33 is brought into engagement by an urging force of an urging member 35, is formed on a heater holding member 32 that holds a heater 31 that heats a fixing belt 20 of a fixing device 13, and an engagement part 342 that engages with the engagement target part 325 is formed on the sensor holding member 34. Further, a locking part 323 locked to the sensor holding member 34 is provided on the heater holding member 32.SELECTED DRAWING: Figure 8

Description

[Technical Field]

[0001] The present invention relates to a fixing device that fixes an image formed on a recording medium by thermocompression bonding, and an image forming apparatus equipped with the fixing device. [Background technology]

[0002] Some image forming apparatuses, such as copiers and multifunction peripherals, are equipped with a fixing device that fixes an image formed on a recording medium. Some fixing devices include a rotatable cylindrical fixing belt, a heating unit that has a heater that heats the fixing belt and faces the inner circumferential surface of the fixing belt, and a pressure member that clamps the fixing belt between itself and the heater, forming a fixing nip where the recording medium is sandwiched and conveyed between itself and the fixing belt, and that rotates the fixing belt. In the fixing nip, the image formed on the recording medium is fixed to the recording medium by heating and pressing (thermocompression bonding).

[0003] Furthermore, in order to maintain the temperature of the fixing belt, which holds and heats the recording medium, at an appropriate temperature, the fixing device is generally provided with a temperature sensor that detects the temperature of the heater (see, for example, Patent Document 1 below). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-163465 Summary of the Invention [Problem to be solved by the invention]

[0005] Some heating units include a heater, a heater holding member that holds the heater, a temperature sensor that faces the heater and is arranged on the heater holding member, and a sensor holding member that holds the temperature sensor.

[0006] An example of the procedure for assembling the heating unit described above will be described below. First, a heater is attached to a heater holding member, a temperature sensor is placed on the heater holding member, and a sensor holding member is placed on top of that. Next, a metal reinforcing member is attached to the heater holding member to reinforce the heater holding member.

[0007] However, because the temperature sensor and the sensor holding member are simply placed on the heater holding member, assembly is unstable. For example, when attaching a reinforcing member to the heater holding member, the assembly worker must hold down each member during assembly to maintain the relative positions of the members. Furthermore, the assembly worker must use a retaining member or other device to maintain the relative positions of the members, which can reduce work efficiency.

[0008] SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to stabilize the assembly of a fixing device and improve the efficiency of the assembly work of the fixing device. [Means for solving the problem]

[0009] A fixing device according to one aspect of the present invention comprises a cylindrical rotatable fixing belt, a heating unit having a heater for heating the fixing belt and facing an inner peripheral surface of the fixing belt, and a pressure member for clamping the fixing belt between itself and the heater to form a fixing nip portion in which a recording medium is clamped and conveyed between itself and the fixing belt, and for rotating the fixing belt, wherein the heating unit comprises a heater holding member for holding the heater, a temperature sensor facing the heater and disposed on the heater holding member, and a sensor holding member attached to the heater holding member on which the temperature sensor is disposed from a direction facing the temperature sensor, and wherein the sensor holding member The heater holding member has a biasing member that faces the heater holding member via the temperature sensor and biases the temperature sensor in a direction from the temperature sensor toward the heater, and the heater holding member has a locking portion that engages with one end of the sensor holding member, and an engaged portion that engages with an engaging portion provided on the sensor holding member at a position different from the one end in the longitudinal direction of the sensor holding member when the sensor holding member moves in its longitudinal direction while one end of the sensor holding member is engaged with the locking portion, and receives the sensor holding member that is pressed by the reaction force of the biasing member on the temperature sensor at the engaging portion.

[0010] Furthermore, an image forming apparatus according to one aspect of the present invention includes a fixing device according to one aspect of the present invention and an image forming section that forms an image on a recording medium, and the image formed on the recording medium by the image forming section is fixed by the fixing device. [Effects of the Invention]

[0011] According to the present invention, the sensor holding member is engaged with the heater holding member by the biasing force of the biasing member, and movement of the sensor holding member relative to the heater holding member is restricted, so that the engagement state is stably maintained and assembly of the components to which the heater and temperature sensor are attached can be performed more easily than before. This stabilizes the assemblability of the fixing device and improves the efficiency of the assembling work of the fixing device. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a cross-sectional view schematically illustrating an example of a fixing device provided in an image forming apparatus according to an embodiment of the present invention. [Figure 2] FIG. 2 is a perspective view showing the appearance of the fixing device. [Figure 3] 1A and 1B are perspective views showing a part of the structure of the fixing device, and 1C is a plan view showing a part of the structure of the fixing device. [Figure 4] 3A is a cross-sectional view taken along line IV-IV in FIG. 3B, and FIG. 3B is a view showing only the heater holding member in the cross-sectional view. [Figure 5] FIG. 2 is a perspective view showing a heater holding member. [Figure 6] FIG. 2 is a perspective view showing a state in which a temperature sensor is attached to a heater holding member. [Figure 7] FIG. 1A is a perspective view of the sensor holding member as seen from above, and FIG. 1B is a perspective view of the sensor holding member as seen from below. [Figure 8] 10A to 10D are diagrams showing the steps of attaching a sensor holding member to a heater holding member. [Figure 9] FIG. 10(A) is a perspective view showing a state in which a sensor holding member is in the process of being attached to a heater holding member, and FIG. 10(B) is a perspective view showing a state in which the sensor holding member has been attached to the heater holding member. DETAILED DESCRIPTION OF THE INVENTION

[0013] A fixing device and an image forming apparatus according to one embodiment of the present invention will be described below with reference to the drawings. Fig. 1 is a cross-sectional view showing a typical example of a fixing device provided in an image forming apparatus according to one embodiment of the present invention. The image forming apparatus is a multifunction machine that combines multiple functions, such as a copy function, a printer function, a scanner function, and a facsimile function.

[0014] The fixing device 13 fixes the toner image to the recording paper by thermocompression, and includes a fixing belt 20, a heating unit 30 that faces the inner circumferential surface of the fixing belt 20, and a pressure member 40. The fixing belt 20 is cylindrical and rotatable, and rotates in a second rotation direction R2 (counterclockwise in FIG. 1) about a second rotation axis A2 that extends parallel to the first rotation axis A1, following the rotation of the pressure member 40 in a first rotation direction R1 (clockwise in FIG. 1) about a first rotation axis A1 (a direction perpendicular to the paper surface of FIG. 1).

[0015] When the recording paper P is sandwiched and transported through the fixing nip N between the fixing belt 20 and the pressure member 40, the unfixed toner image is melted by the heat of the heating unit 30 and fixed to the recording paper P by the pressure of the pressure member 40 pressed against the fixing belt 20. In the figure, A1 indicates the direction in which the recording paper P is transported.

[0016] The heating unit 30 includes a heater 31, a heater holding member 32, a temperature sensor 33, a sensor holding member 34, a biasing member 35, and a reinforcing member 36.

[0017] Heater 31 heats fixing belt 20. Heater 31 is a planar heater extending along the second rotation axis A2 direction of fixing belt 20 (the depth direction of the paper in FIG. 1), and is disposed inside fixing belt 20 to face the inner circumferential surface of fixing belt 20. Heater 31 is, for example, a ceramic heater.

[0018] The heater holding member 32 holds the heater 31. The heater holding member 32 is a heat-resistant resin member having a U-shaped cross section that extends along the second rotation axis A2.

[0019] The temperature sensor 33 is a temperature sensor that faces the heater 31 and is disposed on the heater holding member 32. The temperature sensor 33 is inserted into a through-hole formed in the heater holding member 32 and comes into contact with the heater 31. The temperature sensor 33 is, for example, a thermistor.

[0020] The sensor holding member 34 holds the temperature sensor 33. The sensor holding member 34 faces the heater holding member 32 across the temperature sensor 33, and has a biasing member 35. The sensor holding member 34 is a heat-resistant resin member that extends along the longitudinal direction of the heater holding member 32. That is, the sensor holding member 34 is attached to the heater holding member 32 on which the temperature sensor 33 is disposed from a direction facing the temperature sensor 33. The biasing member 35 is, for example, a compression spring made of a coil spring, and biases the temperature sensor 33 in a direction from the temperature sensor 33 toward the heater 31.

[0021] The reinforcing member 36 reinforces the heater holding member 32. The reinforcing member 36 abuts against the sensor holding member 34 and is fixed opposite the heater holding member 32 via the sensor holding member 34. The reinforcing member 36 is a metal stay with an inverted U-shaped cross section that extends along the second rotation axis A2.

[0022] FIG. 2 is a perspective view showing the appearance of the fixing device 13. FIGS. 3A and 3B are perspective views showing part of the structure of the fixing device 13, and FIG. 3C is a plan view showing part of the structure of the fixing device 13. FIG. 3B shows a state in which the fixing belt 20 has been removed from the state shown in FIG. 3A. FIG. 3C shows a state in which the reinforcing member 36 and the sensor holding member 34 have been removed from the state shown in FIG. 3B. FIG. 4A is a cross-sectional view taken along line IV-IV in FIG. 3B, and FIG. 4B shows only the heater holding member 32 in that cross-sectional view.

[0023] Fig. 5 is a perspective view showing the heater holding member 32. Fig. 6 is a perspective view showing a state in which a temperature sensor 33 is attached to the heater holding member 32. Fig. 7(A) is a perspective view of the sensor holding member 34 seen from above, and Fig. 7(B) is a perspective view of the sensor holding member 34 seen from below.

[0024] The heater 31 is attached to the lower surface of the heater holding member 32. The heater holding member 32 is formed with a through-hole 321 through which a part of the temperature sensor 33 passes and which brings the temperature sensor 33 into contact with the heater 31. The heater holding member 32 also has a positioning pin 322 for positioning the temperature sensor 33, and the temperature sensor 33 is formed with a through-hole 331 through which the positioning pin 322 can pass.

[0025] The temperature sensor 33 has a groove 332 formed on its surface facing the sensor holding member 34 to receive one end of a coil spring serving as the biasing member 35. The biasing member 35 is positioned relative to the temperature sensor 33 by fitting one end of the coil spring into the groove 332.

[0026] The heater holding member 32 has a locking portion 323. As shown in FIG. 5, the locking portion 323 is configured by a pair of protruding members whose upper ends in FIG. 5 are bent inward. A narrow portion 341, which is narrower than the opening 324, is inserted into an opening 324 formed by the pair of protruding members. That is, the locking portion 323 receives and locks one end (narrow portion 341) in the length direction of the sensor holding member 34, which is arranged close to the heater holding member 32, to the one end, thereby restricting movement of the sensor holding member 34 in a direction away from the heater holding member 32. The locking portion 323 allows movement of the sensor holding member 34 in the length direction of the heater holding member 32.

[0027] Furthermore, the heater holding member 32 has an engaged portion 325 at a position different in the longitudinal direction of the heater holding member 32 from the locking portion 323. When the sensor holding member 34 moves in its longitudinal direction while the one end of the sensor holding member 34 is engaged with the locking portion 323, the engaged portion 325 engages with the engaging portion 342 of the sensor holding member 34, and the sensor holding member 34 is pressed by the reaction force of the biasing member 35 on the temperature sensor 33, and the engaging portion 342 receives the sensor holding member 34.

[0028] As described above, the sensor holding member 34 has the engaging portion 342 that engages with the engaged portion 325. The engaging portion 342 is provided at a position on the sensor holding member 34 that is different from the one end portion in the longitudinal direction of the sensor holding member 34. In other words, the engaging portion 342 is provided at a position where it can engage with the engaged portion 325 when the one end portion of the sensor holding member 34 is locked by the locking portion 323.

[0029] Next, the process of attaching the sensor holding member 34 to the heater holding member 32 will be described. Figures 8(A) to 8(D) are diagrams showing the process of attaching the sensor holding member 34 to the heater holding member 32. As shown in Figure 8(A), the worker inserts one end (narrow portion 341) of the sensor holding member 34 into the opening 324 (Figures 5 and 6) of the locking portion 323. This restricts the movement of the sensor holding member 34 in a direction away from the heater holding member 32. Figure 9(A) is a perspective view showing the state in which one end (narrow portion 341) of the sensor holding member 34 is inserted into the opening 324 of the locking portion 323.

[0030] Next, as shown in Figure 8 (B), with the narrow portion 341 as one end of the sensor holding member 34 engaged with the engagement portion 323, the operator moves the other end of the sensor holding member 34 downward, and applies a load to the sensor holding member 34 (the biasing member 35) against the biasing force of the biasing member 35, thereby pressing the sensor holding member 34 against the heater holding member 32 and the temperature sensor 33.

[0031] Then, as shown in Figure 8(C), the operator moves the sensor holding member 34 to the right in Figure 8 (in the lengthwise direction of the heater holding member 32 and the sensor holding member 34) to align one end of the compression spring serving as the urging member 35 with the groove portion 332, and moves the engaging portion 342 to the position of the engaged portion 325.

[0032] When the operator releases the load applied to the sensor-holding member 34 toward the heater-holding member 32, the engaging portion 342 and the engaged portion 325 are engaged with each other by the biasing force of the biasing member 35 (a reaction to the biasing force of the biasing member 35 on the temperature sensor 33), as shown in Fig. 8(D), and this engaged state is stably maintained by this biasing force. As a result, the sensor-holding member 34 is attached to the heater-holding member 32, as shown in Fig. 9(B) as an example.

[0033] According to the above embodiment, the sensor holding member 34 is engaged with the heater holding member 32 by the biasing force of the biasing member 35, and movement of the sensor holding member 34 relative to the heater holding member 32 is restricted, so that the engaged state is stably maintained, and the assembly work of the components to which the heater 31 and the temperature sensor 33 are attached can be performed more easily than before. This stabilizes the assemblability of the fixing device 13, and makes it possible to improve the efficiency of the assembly work of the fixing device 13.

[0034] Furthermore, since the reinforcing member 36 abuts against the sensor holding member 34 and is fixed opposite the heater holding member 32 via the sensor holding member 34, the assembled state of the heater holding member 32 and the sensor holding member 34 can be maintained more stably.

[0035] The present invention is not limited to the configuration of the above embodiment, and various modifications are possible. In addition, in the above embodiment, the configuration and processing shown in the above embodiment using Figures 1 to 9 are merely one embodiment of the present invention, and it is not intended that the present invention be limited to these configurations and processing. [Explanation of symbols]

[0036] 1. Image forming device 13 Fixing device 20 Fixing belt 30 Heating section 31 Heater 32 Heater holding member 33 Temperature Sensor 34 Sensor holding member 35 biasing member 36 Reinforcement member 323 Locking part 325 Engaged part 332 Groove 341 Narrow part 342 Engagement part

Claims

1. a cylindrical rotatable fixing belt; a heating unit having a heater for heating the fixing belt and facing an inner circumferential surface of the fixing belt; a pressure member that sandwiches the fixing belt between itself and the heater, forms a fixing nip portion between itself and the fixing belt where a recording medium is sandwiched and conveyed, and rotates the fixing belt in a driven manner; The heating unit is a heater holding member that holds the heater; a temperature sensor disposed on the heater holding member and facing the heater; a sensor holding member that is attached to the heater holding member on which the temperature sensor is disposed from a direction facing the temperature sensor, the sensor holding member has a biasing member that faces the heater holding member with the temperature sensor interposed therebetween and biases the temperature sensor in a direction from the temperature sensor toward the heater, The heater holding member is a locking portion that locks with one end of the sensor holding member; a fixing device having an engaging portion that engages with an engaging portion provided on the sensor holding member at a position different from the one end in the longitudinal direction of the sensor holding member when the sensor holding member moves in its longitudinal direction while one end of the sensor holding member is engaged with the engaging portion, and the engaging portion receives the sensor holding member that is pressed by the reaction force of the urging member on the temperature sensor.

2. The biasing member is a compression spring, 2. The fixing device according to claim 1, wherein the temperature sensor has a groove formed on a surface facing the sensor holding member when the temperature sensor is disposed on the heater holding member, the groove receiving one end of a compression spring serving as the urging member.

3. The fixing device according to claim 1 , wherein the heating section further comprises a reinforcing member that is fixed in contact with the sensor holding member and faces the heater holding member via the sensor holding member.

4. a fixing device according to any one of claims 1 to 3; an image forming unit that forms an image on a recording medium, an image forming apparatus in which the image formed on the recording medium by the image forming section is fixed by the fixing device;

Images