JP2004294487A - Fixing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coil which can be fixed on a coil bobbin by a simple structure and is highly precise. <P>SOLUTION: An induction heating type fixing device has flanges that hold both ends of the coil such that electric wires forming the coil wound on the coil bobbin are in firm contact with one another. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a fixing device that is mounted on an image forming apparatus such as a copying machine or a printer and fixes a developer image on paper.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, an image forming apparatus using digital technology, for example, an electronic copying machine, has a fixing device for fixing a developer image on a sheet by heating under pressure. For example, in an electronic copying machine, a document table on which a document is placed is exposed, and light reflected from the document is guided to a photoelectric conversion element, for example, a CCD (charge coupled device). The CCD outputs an image signal corresponding to the image of the document. The photosensitive drum is irradiated with a laser beam corresponding to the image signal to form an electrostatic latent image on the peripheral surface of the photosensitive drum. This electrostatic latent image is visualized by the adhesion of a developer (toner). A sheet is sent to the photosensitive drum in synchronization with the rotation of the photosensitive drum, and a visible image (developer image) on the photosensitive drum is transferred to the sheet. The sheet on which the developer image has been transferred is sent to a fixing device.
[0003]
The fixing device includes a heating roller, and a pressure roller that rotates together with the heating roller while being in contact with the heating roller in a pressurized state. The heat fixes the developer image on the paper.
As a heat source of the heating roller of the fixing device, there is induction heating. In this method, a coil is housed in a heating roller, a capacitor is connected to the coil to form a resonance circuit, and the resonance circuit is excited at one frequency for one resonance circuit, so that a high-frequency current is applied to the coil. Then, a high-frequency magnetic field is generated from the coil, an eddy current is generated in the heating roller by the high-frequency magnetic field, and the heating roller self-heats by Joule heat generated by the eddy current.
[0004]
Furthermore, in recent years, shortening of warm-up has become a technical issue as a technology for energy saving. However, as a countermeasure, the thickness of a heating roller has been reduced.
However, since the heat capacity decreases as the thickness of the heating roller decreases, it becomes difficult to maintain a uniform heat distribution on the heating roller. For example, when the winding density of the coil in the heating roller is not uniform, the heat distribution on the heating roller becomes uneven. As described above, in a fixing device using induction heating in recent years, a fixing device that can easily improve the accuracy of a coil as a heat source contained in a heating roller is required.
[0005]
[Patent Document 1]
JP 2001-212165 A
[Problems to be solved by the invention]
The present invention has been made in consideration of the above circumstances, and has as its object to provide a fixing device having a simple configuration, low cost, and a high-precision induction heating coil. .
[0007]
[Means for Solving the Problems]
In a fixing device according to the present invention, an electric wire forming the coil is wound around a fixing member for fixing a developer on an image forming medium by a heated member that generates heat by an eddy current generated by a change in a magnetic field generated by the coil. Induction having a coil holding portion and a guide portion for holding both ends of a coil provided at a position based on the number of turns of the wire and the diameter of the wire so that the wires wound around the coil holding portion are in close contact with each other. A heating means is provided.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows an internal configuration of a composite electronic copying machine as an image forming apparatus. First, a transparent platen (glass plate) 2 for placing a document is provided on the upper surface of the main body 1, and the exposure lamp 5 provided on the carriage 4 is turned on, so that the platen 2 is placed on the platen 2. The placed document D is exposed.
[0009]
An image signal is output by projecting the light reflected by the exposure onto a photoelectric conversion element, for example, a CCD (charge coupled device) 10. The image signal output from the CCD 10 is converted into a digital signal, and the digital signal is appropriately processed and then supplied to the laser unit 27. The laser unit 27 emits a laser beam B according to an input signal.
[0010]
A control panel (not shown) for setting operating conditions is provided on the upper surface of the main body 1 at a position not covered by the automatic document feed unit 40. The control panel includes a touch panel type liquid crystal display unit, numeric keys for numeric input, a copy key, and the like.
[0011]
On the other hand, a photosensitive drum 20 is rotatably provided at a substantially central portion in the main body 1. Around the photosensitive drum 20, a charging device 21, a developing unit 22, a transfer device 23, a peeling device 24, a cleaner 25, and a static eliminator 26 are sequentially disposed, and the photosensitive drum 20 is formed by a known process method. A toner (developer) image is formed thereon, the toner image is transferred onto a sheet, and the toner on the sheet is heated and pressed by a fixing device 100 described later.
[0012]
FIG. 2 shows a schematic configuration of the fixing device 100.
In FIG. 2, the fixing device 100 includes a heating roller 101 and a pressure roller 102 at positions vertically sandwiching the conveyance path of the copy sheet S. The pressure roller 102 is in pressure contact with the peripheral surface of the heating roller 101 by a pressure mechanism (not shown). The contact portions of the rollers 101 and 102 have a constant nip width.
[0013]
The heating roller 101 is formed by forming a conductive material, for example, iron into a cylindrical shape, and coating the outer peripheral surface of the iron with, for example, a fluororesin such as tetrafluoroethylene resin. The heating roller 101 is driven to rotate rightward in the figure by a drive motor (not shown). The pressure roller 102 rotates to the left in the drawing in response to the rotation of the heating roller 101. When the copy sheet S passes through the contact portion between the heating roller 101 and the pressure roller 102, and the copy sheet receives heat from the heating roller 101, the developer image T on the copy sheet S is transferred to the copy sheet S. Be established.
[0014]
Around the heating roller 101, an isolation claw 103 for separating the copy sheet S from the heating roller 101, a cleaning member 104 for removing toner and paper debris remaining on the heating roller 101, An application roller 105 for applying a release agent to the surface is provided.
[0015]
An induction heating unit 110 for induction heating is accommodated inside the heating roller 101. The induction heating section 110 has a coil bobbin 110A around which an electric wire as a coil 111 is wound around a peripheral surface, and a holding member 110B that holds the coil bobbin 110A. When the coil 111 includes a plurality of coils (111a,...), The coil bobbin 110A includes a plurality of coil bobbins 110A (110Aa,...) Corresponding to the number of coils. The induction heating unit 110 is supplied with high-frequency power by a high-frequency circuit described below, and generates a high-frequency magnetic field for induction heating. When this high-frequency magnetic field is generated, an eddy current is generated in the heating roller 101, and the heating roller 101 self-heats by Joule heat due to the eddy current.
[0016]
FIG. 3 shows a control circuit of the composite electronic copying machine. That is, the scan CPU 70, the control panel CPU 80, and the print CPU 90 are connected to the main CPU 50.
The main CPU 50 controls the scan CPU 70, the control panel CPU 80, and the print CPU 90, and controls a copy mode according to an operation of a copy key, and responds to an image input to the network interface 59. A control unit for a printer mode, a control unit for a facsimile mode according to image reception by the facsimile transmission / reception unit 60, and the like are provided.
[0017]
The main CPU 50 includes a ROM 51 for storing a control program, a RAM 52 for storing data, a pixel counter 53, an image processing unit 55, a page memory controller 56, a hard disk unit 58, a net interface 59, and a FAX transmitting / receiving unit 60. It is connected.
[0018]
The page memory controller 56 controls writing and reading of image data to and from the page memory 57. Further, the image processing unit 55, the page memory controller 56, the page memory 57, the hard disk unit 58, the net interface 59, and the FAX transmitting / receiving unit 60 are mutually connected by the image data bus 61. .
[0019]
The net interface 59 functions as an input unit for a printer mode to which an image (image data) transmitted from an external device is input. The network interface 59 is connected to a communication network 201 such as a LAN or the Internet, and external devices such as a plurality of personal computers 202 are connected to the communication network 201. These personal computers 202 include a controller 203, a display 204, an operation unit 205, and the like.
The FAX transmitting / receiving unit 60 is connected to a telephone line 210 and functions as a facsimile mode receiving unit that receives an image (image data) transmitted by facsimile via the telephone line 210.
[0020]
The scan CPU 70 includes a ROM 71 for storing a control program, a RAM 72 for storing data, a signal processing unit 73 for processing the output of the CCD 10 and supplying it to the image data bus 61, a CCD driver 74, a scan motor driver 75, and an exposure lamp 5. , An automatic document feeder 40, a plurality of document sensors 11, and the like.
[0021]
The CCD driver 74 drives the CCD 10. The scan motor driver 75 drives a scan motor 76 for driving the carriage. The automatic document feeder 40 has a document D set on a tray 41 and a document sensor 43 for detecting its size.
[0022]
The control panel CPU 80 is connected to a touch panel type liquid crystal display unit 14, a numeric keypad 15, an all reset key 16, a copy key 17, and a stop key 18 of the control panel.
[0023]
The print CPU 90 is connected to a ROM 91 for storing a control program, a RAM 92 for storing data, a print engine 93, a paper transport unit 94, a process unit 95, and a fixing device 100. The print engine 93 includes the laser unit 27 and its drive circuit. The paper transport unit 94 includes a paper transport mechanism extending from the paper feed cassette 30 to the tray 38 and a drive circuit thereof. The process unit 95 includes the photosensitive drum 20 and a peripheral portion thereof.
A print unit for printing the image processed by the image processing unit 55 on a sheet P is mainly composed of the print CPU 90 and its peripheral configuration.
[0024]
FIG. 4 shows a configuration example of an electric circuit of the fixing device 100.
Here, it is assumed that the induction heating unit 110 housed in the heating roller 101 has a coil 111 composed of a plurality of coils (111a, 111b, 111c). That is, in the example shown in FIG. 4, the coil 111 is divided into three coils 111a, 111b, and 111c. In the example shown in FIG. 4, the coil 111a constitutes a first coil and is located at the center of the heating roller 101. The coils 111b and 111c constitute a second coil, and are located on both sides of the heating roller 101 with the coil 111a interposed therebetween. These coils 111a, 111b, 111c are connected to a high frequency generation circuit 120.
[0025]
A temperature sensor 112 is provided at the center of the heating roller 101. The temperature sensor 112 detects the temperature at the center of the heating roller 101. A temperature sensor 113 is provided at one end of the heating roller 101. The temperature sensor 113 detects the temperature of one end of the heating roller 101. These temperature sensors 112 and 113 are connected to the print CPU 90 together with a drive unit 160 for driving the heating roller 101 to rotate.
[0026]
The print CPU 90 has a function of controlling the drive unit 160, an operation of a first resonance circuit (output power P1), which will be described later, having a coil 111a as a first coil as a component, and a function of controlling a second coil. A function of issuing a P1 / P2 switching signal for designating an operation of a second resonance circuit (output power P2) described later, which includes the coils 111b and 111c as constituent elements, output power of each resonance circuit, and detection of the temperature sensors 112 and 113 It has a function to control according to temperature.
[0027]
The high-frequency generation circuit 120 generates high-frequency power for generating a high-frequency magnetic field, and includes a rectifier circuit 121 and a switching circuit 122 connected to an output terminal of the rectifier circuit 121. The rectifier circuit 121 rectifies the AC voltage of the commercial AC power supply 130. In the switching circuit 122, a first resonance circuit is formed by the coil 111a, and a second resonance circuit is formed by the coils 111b and 111c.
Further, the first resonance circuit and the second resonance circuit are selectively excited by a switching element (for example, a transistor such as an FET) (not shown) provided in the switching circuit 122.
[0028]
The coils 111b and 111c constituting the second coil are connected in parallel to the switching circuit 122. Similarly, when the first coil or the second coil is composed of a plurality of coils in the induction heating section 110, each coil is connected to the switching circuit 122 in parallel.
[0029]
The first resonance circuit has a resonance frequency f1 determined by the inductance of the coil 111a, the capacitance of a capacitor (not shown) in the switching circuit 122, and the like. The second resonance circuit has a resonance frequency f2 determined by the inductance of the coils 111b and 111c, the capacitance of a capacitor (not shown) in the switching circuit 122, and the like.
[0030]
The switching circuit 122 is turned on and off by the controller 140 in accordance with a P1 / P2 switching signal from the print CPU 90. The controller 140 includes an oscillation circuit 141 and a CPU 142. The oscillation circuit 141 issues a drive signal of a predetermined frequency to the switching circuit 122. The CPU 142 controls the oscillation frequency (frequency of the drive signal) of the oscillation circuit 141. The CPU 142 has, for example, the following means (1) and (2) as main functions.
[0031]
(1) When the operation of the first resonance circuit (using only the coil 111a) is specified by the P1 / P2 switching signal from the print CPU 90, the CPU 142 sets the first resonance circuit to a plurality of signals near the resonance frequency f1. (F1-Δf), (f1 + Δf).
[0032]
(2) When the operations of the first and second resonance circuits (use of all the coils 111a, 111b, 111c) are specified by the P1 / P2 switching signal from the print CPU 90, the CPU 142 performs the first and second resonance circuits. There is a control means for sequentially exciting the two-resonance circuit at a plurality of frequencies near the respective resonance frequencies f1 and f2, for example, (f1−Δf), (f1 + Δf), (f2−Δf), (f2 + Δf). .
[0033]
Next, the operation of the electric circuit of the fixing device 100 configured as described above will be described.
When a driving signal having the same frequency (or a frequency close to the resonance frequency) as the resonance frequency f1 of the first resonance circuit is generated from the oscillation circuit 141, the switching signal 122 is turned on / off by the driving signal, and the first resonance circuit is turned on. Get excited. By this excitation, a high-frequency magnetic field is generated from the coil 111a, and the high-frequency magnetic field generates an eddy current in the axial central portion of the heating roller 101, and the axial central portion of the heating roller 101 self-heats by Joule heat due to the eddy current. .
[0034]
When a drive signal having the same frequency (or a frequency close to) the resonance frequency f2 of the second resonance circuit is generated from the oscillation circuit 141, the switching signal 122 is turned on and off by the drive signal, and the second resonance circuit is turned on. Get excited. Due to this excitation, high-frequency magnetic fields are generated from the coils 111b and 111c, and the high-frequency magnetic fields generate eddy currents on both sides of the heating roller 101 in the axial direction. I do.
[0035]
FIG. 5 shows the relationship between the output power P1 of the first resonance circuit and the frequency for exciting the first resonance circuit, and the relationship between the output power P2 of the second resonance circuit and the frequency for exciting the second resonance circuit. FIG.
[0036]
As shown in FIG. 5, the output power P1 of the first resonance circuit has a peak level when excited at the same frequency as the resonance frequency f1 of the first resonance circuit, and the excited frequency is separated from the resonance frequency f1. , The pattern gradually decreases like a mountain.
Similarly, when the output power P2 of the second resonance circuit is excited at the same frequency as the resonance frequency f2 of the second resonance circuit, the output power P2 has a peak level, and becomes higher as the excited frequency becomes farther from the resonance frequency f2. The pattern gradually decreases.
[0037]
When fixing a large-sized sheet S, both the first and second resonance circuits are excited, and high-frequency magnetic fields are emitted from all the coils 111a, 111b, and 111c. An eddy current is generated in the entire heating roller 101 by the high frequency magnetic field, and the entire heating roller 101 self-heats by Joule heat generated by the eddy current. In this case, drive signals having two frequencies (f1−Δf) and (f1 + Δf) separated by a predetermined value Δf up and down about the resonance frequency f1 of the first resonance circuit are sequentially output from the oscillation circuit 141, and subsequently, A drive signal having two frequencies (f2−Δf) and (f2 + Δf) vertically separated by a predetermined value Δf around the resonance frequency f2 of the second resonance circuit is sequentially output from the oscillation circuit 141.
[0038]
With these drive signals, the first resonance circuit is sequentially excited at two frequencies (f1−Δf) and (f1 + Δf) sandwiching the resonance frequency f1, and subsequently, the second resonance circuit is excited at two frequencies sandwiching the resonance frequency f2. Excited sequentially at (f2−Δf), (f2 + Δf). The excitation for each frequency is repeated.
[0039]
As shown in FIG. 5, the output power P1 of the coil 111a in the first resonance circuit becomes a value P1a slightly lower than the peak level P1c at the time of excitation at the frequency (f1−Δf), and is excited at the frequency (f1 + Δf). At this time, the value P1b is slightly lower than the peak level P1c.
[0040]
The output power P2 of the coils 111b and 111c in the second resonance circuit becomes a value P2a slightly lower than the peak level P2c at the time of excitation at the frequency (f2−Δf), and also at the time of excitation at the frequency (f2 + Δf). Is slightly lower than the value P2b.
[0041]
Next, the configuration of the induction heating unit 110 will be described.
6 and 7 are diagrams illustrating a configuration example of the induction heating unit 110. FIG.
In the example shown in FIG. 6, the induction heating unit 110 includes three coils 111a, 111b, and 111c. The coil 111a is constituted by an electric wire wound around the coil bobbin 110Aa, the coil 111b is constituted by an electric wire wound around the coil bobbin 110Ab, and the coil 111c is constituted by an electric wire wound around the coil bobbin 110Ac. That is, the induction heating unit 110 shown in FIG. 6 is configured such that the coil bobbins Aa, Ab, and Ac on which the three coils 111a, 111b, and 111c are wound are held by the holding member 110B.
[0042]
In the example shown in FIG. 7, the induction heating unit 110 is configured by 12 coils (a1 to a6, b1 to b3, c1 to c3). Each coil is constituted by an electric wire wound on an independent coil bobbin. In the induction heating unit 110 shown in FIG. 7, the coils a1 to a6 correspond to the coil 111a, the coils b1 to b3 correspond to the coil 111b, and the coils c1 to c3 correspond to the coil 111c.
[0043]
That is, as shown in FIG. 7, when the first coil or the second coil is composed of a plurality of coils, each coil in the induction heating unit 110 is, for example, a high-frequency circuit 120 as shown in FIG. Are connected as described below. The coils a1 to a6 are connected in parallel to the switching circuit 122 at the coil 111a of the high frequency circuit 120. The coils b1 to b3 are connected in parallel to the switching circuit 122 at the coil 111b of the high frequency circuit 120. The coils c1 to c3 are connected in parallel to the switching circuit 122 at the coil 111c of the high frequency circuit 120.
[0044]
As shown in FIGS. 6 and 7, the induction heating section 110 has a configuration in which a plurality of coils 111a wound around a plurality of coil bobbins 110Aa is held by a holding member 110B. That is, in the entire induction heating section 110, the number of coil bobbins (hereinafter, referred to as a coil unit) around which a coil is wound may be plural or singular, but at least the number to be controlled is necessary. It becomes.
[0045]
That is, when a plurality of coils are to be controlled, as in the above-described fixing device, it is possible to configure the induction heating unit 110 with at least the number of coil units to be controlled. For example, as shown in FIG. 7, even when two control targets are the first coil and the second coil, the induction heating unit 110 can be configured by a plurality of coil units.
[0046]
FIG. 8 is a diagram showing a relationship between the coil bobbin 110A and the holding member 110B.
As shown in FIG. 8, each coil bobbin (coil holding portion) 110A is formed in a hollow cylindrical shape. The holding member 110B has a shape that fits inside each coil bobbin 110A. That is, each coil bobbin 110A is held by one holding member 110B, and constitutes the entire induction heating section 110.
[0047]
Each coil bobbin 110A has flange portions (guide portions) 190a and 190b at both ends for guiding an electric wire wound as a coil. The coil bobbin 110A and the holding member 110B are formed of plastic, ceramic, or the like, and are excellent in heat resistance such as a PEEK (polyetheretherketone) material, a liquid crystal polymer material, a phenol material, or an unsaturated polyester, and have a linear expansion coefficient. Lower materials are available.
[0048]
FIG. 9 is a view showing a coil bobbin 110A around which the coil 111 is wound.
An electric wire as a coil is wound around the coil bobbin 110A in a region between the flange portions 190a and 190b. Grooves 191 are provided at both ends of the coil bobbin 110A. The winding start line and the winding end line of the electric wire as the coil wound on the coil bobbin 110A are guided into the coil bobbin by the groove 191.
[0049]
As shown in FIG. 9, an electric wire as a coil wound around the coil bobbin 110A is guided by the flange portions 190a and 190b. For this reason, an area where the electric wire as a coil can be wound (hereinafter, referred to as a coil area) in the coil bobbin 110A is an area between the flange portions 190a and 190b.
[0050]
In the example shown in FIGS. 8 and 9, the flange portions 190a and 190b are provided at a part of both ends of the coil bobbin 110A, and hold an electric wire having a desired number of turns wound around the coil bobbin 110A. The installation position and shape may be any as long as they are suitable.
[0051]
Next, the width of the coil bobbin 110A will be described.
When an electric wire as a coil is wound around the coil bobbin 110A, it is preferable that the electric wire be wound around the coil region as densely as possible. This is because the density of the electric wire wound around the coil bobbin 110A affects the heat distribution on the heating roller 101. For example, if the density of the electric wire as the coil 111 wound around the coil bobbin 110A varies, the heat distribution on the heating roller 101 heated by the coil 111 may be uneven.
[0052]
Normally, in a fixing device used in an image forming apparatus, it is necessary to uniformly control the heat distribution on the heating roller 101 at least in a region where the sheet passes, in order to prevent the toner from being improperly fixed on the sheet.
[0053]
In addition, it is possible to fix the position of the coil on the coil bobbin 110A by tightly winding the wires as coils between the flange portions 190a and 190b. That is, if the electric wires are tightly wound between the flange portions 190a and 190b to fix the position of the coil on the coil bobbin 110A, uneven heat distribution on the heating roller 101 heated by the coil is prevented. be able to.
[0054]
FIG. 10 is a diagram showing a relationship between the width b of the flange portion 190a and the flange portion 190b in the coil bobbin 110A and the width W (width of the coil region) between the flange portion 190a and the flange portion 190b. Here, it is assumed that the width of the flange portion 190a itself and the width of the flange portion 190b are the same width b, but the width b1 of the flange portion 190a is different from the width b2 of the flange portion 190b. Is also good.
[0055]
As described above, the region between the flange portion 190a and the flange portion 190b is a coil region where the electric wire can be wound. Therefore, as shown in FIG. 10, when the flange portions 190a and 190b are installed at both ends of the coil bobbin 110A, the width of the coil bobbin 110A is the width b of the flange portions 190a and 190b, the width b of the flange portions 190a and the flange portion 190a, and It is determined by the width W between the portion 190b (coil region).
[0056]
Further, when the flange portions 190a and 190b are formed in a predetermined shape having a predetermined width b, the width of the coil bobbin 110A is determined based on the width W of the coil region. The theoretical minimum width W0 required as the width W of the coil region is determined by the following equation based on the diameter d of the electric wire and the number of turns n.
W0 = d × (n + 1).
[0057]
The width W0 of the coil region is a case where it is assumed that there is no error in the diameter d of the electric wire wound around the coil bobbin 110A, and is the minimum width theoretically required as the width of the coil region. Therefore, theoretically (when there is no error in the wire diameter), by setting the width of the coil region to the width (theoretical minimum width) W0, the wire as the coil 111 is completely attached to the coil bobbin 110A. Can be fixed in close contact.
[0058]
However, an actual wire has an error in its wire diameter. The width of the coil bobbin also includes an error in molding.
Therefore, in the present embodiment, it is assumed that the requirement as the width W of the coil region needs to satisfy the following conditions (1) and (2).
[0059]
(1) An electric wire having a predetermined number of turns has such a width that it does not run on the flange portions 190a and 190b. This condition is a condition of the minimum width Wmin of the coil region which is actually required as the width W of the coil region. That is, this condition is a condition for reliably winding a predetermined number of turns of the electric wire in the coil region.
[0060]
(2) A margin in the width of the coil region is not more than three times the diameter of the electric wire with respect to the width of the electric wire having a predetermined number of turns. This condition is a condition of the maximum width Wmax of the coil region that is practically allowable as the width W of the coil region. This condition is a condition indicating the maximum allowance actually given to the electric wire having a predetermined number of turns wound around the coil region. Under these conditions, the upper limit of the width of the coil region indicates a range in which the electric wire wound around the coil bobbin is difficult to disperse. Here, three times the wire diameter assumes a range in which a pressing force on another wire can be obtained by springback in the wire as a coil. In particular, as shown in FIG. 9, when an electric wire is routed through the inside of the coil bobbin at the end of the coil bobbin 110A, if the margin in the width of the coil region exceeds three times the electric wire diameter (3 × d), the spring back of the electric wire will occur. The pressing force on other electric wires due to is eliminated, and the electric wires are easily separated.
[0061]
Here, assuming that the tolerance (error) range of the electric wire is ± Δd and the tolerance (error) range of the coil bobbin width is ± ΔW,
To satisfy the above conditions, the width W of the coil region is
Wmin = (d + Δd) × (n + 1) + ΔW
Wmax = (d−Δd) × (n + 1) −ΔW + 3d
Wmin ≦ W <Wmax
Condition must be satisfied.
[0062]
The width of the coil bobbin 110A is equal to the width of the coil area plus the width of the flange portions 190a and 190b. Therefore, the width of the coil bobbin 110A is W + 2b (or W + (b1 + b2)). That is, the width (W + 2b) of the coil bobbin 110A is
Wmin + 2b ≦ W + 2b <Wmax + 2bx
It is molded to satisfy.
[0063]
As a first specific example, assuming that the number of turns n of the wire is 48.5 times, the wire diameter d is 0.554 mm, the tolerance range Δd of the wire diameter is 0.006 mm, and the tolerance range ΔW of the width of the coil bobbin is 0.1 mm,
27.82 ≦ W <28.688
It becomes. In this case, the width W of the coil region may be set to, for example, 28 mm, and the entire width of the coil bobbin may be formed to be 28 + 2b (or 28 + b1 + b2).
[0064]
As a second specific example, the number of turns n of the wire is 44.5 times, the wire diameter d is 0.554 mm, the tolerance range Δd of the wire diameter is 0.006 mm, and the tolerance range ΔW of the width of the coil bobbin is 0.1 mm. Then
25.58 ≦ W <26.496
It becomes. In this case, for example, the width W of the coil region may be set to 26 mm, and the entire width of the coil bobbin may be formed to be 26 + 2b (or 26 + b1 + b2).
[0065]
As described above, the flanges holding both ends of the coil are provided so that the electric wires forming the coil wound on the coil bobbin are in close contact with each other. Thereby, the coil constituted by the electric wire wound on the coil bobbin can be fixed at a uniform density with a simple configuration, and a highly accurate coil can be provided. Further, the coil can be securely held by the coil bobbin and the flange portion, and the number of turns of the electric wire can be accurately wound.
[0066]
Furthermore, when the induction heating unit is configured by a plurality of coils using a plurality of coil bobbins, the coil bobbin around which the plurality of coils are wound can be shared by using a coil bobbin having the same flange portion, and the coil bobbin is formed. In addition, the process of winding an electric wire around a coil bobbin and the like can be shared and simplified, failure in assembly and failure in the number of turns can be prevented, and an inexpensive induction heating unit can be provided.
[0067]
Further, according to the above embodiment, the width between the flange portions holding the coil is set in advance based on the wire diameter, the number of turns of the wire, the tolerance range of the wire diameter, the tolerance range of the coil bobbin, and the like. It is. This makes it possible to easily determine the specifications of the coil to be formed based on the specifications (diameter and diameter tolerance range) of the electric wire for forming the coil and the number of turns of the electric wire. Further, the minimum width and the maximum width as the width between the flange portions holding the coil are calculated by a predetermined formula, and an allowable range for the width between the flange portions can be set.
[0068]
【The invention's effect】
As described above in detail, according to the present invention, it is possible to provide a fixing device having a highly accurate coil for induction heating with a simple configuration and at low cost.
[Brief description of the drawings]
FIG. 1 is a diagram showing a schematic configuration of an image forming apparatus having a fixing device according to an embodiment of the present invention.
FIG. 2 is a diagram showing a schematic configuration of a fixing device according to the embodiment of the present invention.
FIG. 3 is a block diagram illustrating a control circuit of the image forming apparatus.
FIG. 4 is a diagram illustrating a configuration of an electric circuit for the fixing device.
FIG. 5 is a diagram illustrating a relationship between output power of each resonance circuit and a frequency for exciting each resonance circuit in the fixing device.
FIG. 6 is a diagram showing a configuration example of an induction heating unit.
FIG. 7 is a diagram showing a configuration example of an induction heating unit.
FIG. 8 is a diagram showing a relationship between a coil bobbin and a holding member.
FIG. 9 is a view showing a coil bobbin around which a coil is wound.
FIG. 10 is a view showing the relationship between the width of a flange portion and the width of a coil region in a coil bobbin.
[Explanation of symbols]
S: copy paper (image forming medium), T: toner (developer), 100: fixing device, 101: heating roller (heated member), 102: pressure roller, 110: induction heating unit, 110A: coil bobbin ( Coil holding portion), 110B holding member, 111 (111a, 111b, 111c, a1 to a3, b1 to b6, c1 to c3) ... coil, 190a, 190b ... flange portion (guide portion)

Claims (5)

In a fixing device that fixes a developer on an image forming medium by a heated member that generates heat by an eddy current generated by a change in a magnetic field generated by a coil,
A coil holding portion around which an electric wire forming the coil is wound;
A guide portion that holds both ends of a coil provided at a position based on the number of turns of the electric wire and the diameter of the electric wire so that the electric wires wound around the coil holding portion are in close contact with each other,
A fixing device comprising an induction heating means having the following. The guide portions are provided at both ends of the coil holding portion, and the width between the guide portions is set based on the number of turns of the electric wire, the diameter of the electric wire, and an error range for the diameter of the electric wire, The fixing device according to claim 1, wherein: The guide portions are provided at both ends of the coil holding portion, and the width between the guide portions is an error range for the number of turns of the electric wire, the diameter of the electric wire, the diameter of the electric wire, and the forming accuracy of the coil holding portion. The fixing device according to claim 1, wherein the setting is performed based on an error range. The guide portions are provided at both ends of the coil holding portion, and the width between the guide portions is obtained by adding 1 to the number of turns of the electric wire to the sum of the diameter of the electric wire and an error range for the diameter of the electric wire. The fixing device according to claim 1, wherein the value is set to be equal to or larger than a value obtained by multiplying the fixing device. The guide portions are provided at both ends of the coil holding portion, and the width between the guide portions is obtained by subtracting an error range for the diameter of the electric wire from the diameter of the electric wire, and adding 1 to the number of turns of the electric wire. 2. The fixing device according to claim 1, wherein the fixing device is set to be smaller than a value obtained by adding a predetermined allowable value to a value obtained by multiplying the multiplied values.

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