Image forming device

Abstract

The present invention discloses an image forming device. The image forming device of the present invention includes a circuit, the circuit includes both a circuit in a fixing unit and a power control circuit, is provided with a first circuit, a second circuit, and a third circuit, the first circuit supplies power to a heater from an AC power source, the second circuit is electrically insulated from the first circuit, the third circuit is electrically insulated from both the first circuit and the second circuit, all of the first to third circuits are provided on at least one surface of a circuit board, and the first to third circuits are arranged in the order of the first circuit, the third circuit, and the second circuit on at least one straight line, and all of the first to third circuits exist on the at least one straight line on the one surface of the circuit board.

Description

[0001] This application is a divisional application based on a patent application with application number 201911084529.5, application date November 8, 2019, and invention name “Image Forming Device”. Technical Field

[0002] The present invention relates to an image forming apparatus such as a copying machine, a printer, etc., which uses an electrophotographic system or an electrostatic recording system. Background Art

[0003] As a fixing unit installed in an image forming apparatus, there is a configuration including a cylindrical film, a plate-shaped heater in contact with the inner surface of the film, and a roller forming a nip portion with respect to the heater via the film. In addition, Japanese Patent Application Publication No. H11-194837 discloses a configuration for detecting the temperature of the nip portion with high accuracy by providing a thermistor on the surface side of a heater substrate in contact with the film.

[0004] However, when a configuration is adopted in which a thermistor is provided on the surface side of the heater substrate in contact with the film, it is necessary to ensure the dielectric breakdown voltage. For this reason, a configuration has been conceived in which a temperature detection circuit electrically connected to the thermistor is electrically insulated from both a primary side circuit (first potential group) electrically connected to a commercial power supply and a secondary side circuit (second potential group) electrically insulated from the primary side circuit.

[0005] However, when the first potential group, the second potential group, and the potential group in which the temperature detection circuit is provided are mixed in the circuit board, the size of the circuit board increases because the distance between the potential groups needs to be ensured. The increase in the size of the circuit board is disadvantageous for reducing the size of the image forming apparatus. Summary of the invention

[0006] The present invention provides an image forming apparatus for forming a toner image on a recording material, comprising:

[0007] a fixing unit having a heater for generating heat according to electric power supplied from an AC power source and thermally fixing a toner image formed on a recording material onto the recording material; and

[0008] a circuit board provided with a power control circuit for controlling power supplied to the heater,

[0009] wherein the circuit including both the circuit in the fixing unit and the power control circuit is provided with a first circuit, a second circuit, and a third circuit, the first circuit supplies power from the AC power source to the heater, the second circuit is electrically insulated from the first circuit, and the third circuit is electrically insulated from both the first circuit and the second circuit,

[0010] wherein all of the first to third circuits are provided on at least one surface of the circuit board, and

[0011] Wherein, the first to third circuits are arranged on at least one straight line in the order of the first circuit, the third circuit and the second circuit, and all of the first to third circuits exist on the at least one straight line on the one surface of the circuit board.

[0012] The present invention provides an image forming apparatus for forming a toner image on a recording material, comprising:

[0013] a fixing unit having a heater for generating heat according to electric power supplied from an AC power source and thermally fixing a toner image formed on a recording material onto the recording material; and

[0014] a circuit board provided with a power control circuit for controlling power supplied to the heater,

[0015] wherein the circuit including both the circuit in the fixing unit and the power control circuit is provided with a first circuit, a second circuit, and a third circuit, the first circuit supplies power from the AC power source to the heater, the second circuit is electrically insulated from the first circuit, the third circuit is electrically insulated from both the first circuit and the second circuit, and

[0016] The first circuit is disposed on a first surface of the circuit board, the second circuit is disposed on a second surface, and the third circuit is disposed on at least one of the first surface and the second surface, and the second surface is a rear surface relative to the first surface.

[0017] The present invention provides an image forming apparatus for forming a toner image on a recording material, comprising:

[0018] an apparatus main body including an image forming section that forms a toner image on a recording material;

[0019] a fixing unit having a heater for generating heat according to electric power supplied from an AC power source and thermally fixing a toner image formed on a recording material onto the recording material, the fixing unit being detachably attached to the apparatus main body;

[0020] a circuit board provided with a power control circuit for controlling power supplied to the heater; and

[0021] at least one connector electrically connecting the fixing unit to the power control circuit,

[0022] wherein the circuit including both the circuit in the fixing unit and the power control circuit is provided with a first circuit, a second circuit, and a third circuit, the first circuit supplies power from the AC power source to the heater, the second circuit is electrically insulated from the first circuit, the third circuit is electrically insulated from both the first circuit and the second circuit, and

[0023] The first to third circuits are arranged in the connector in the order of the first circuit, the third circuit and the second circuit.

[0024] Further features of the present invention will become apparent from the following description of exemplary embodiments (with reference to the attached drawings). BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is a cross-sectional view of an image forming apparatus;

[0026] Figure 2 is a cross-sectional view of a fixing unit;

[0027] Figure 3A and 3B is a diagram illustrating the configuration of the heater in Example 1;

[0028] Figure 4 is a diagram illustrating a fixing unit and a power control circuit in Embodiment 1;

[0029] Figure 5A and 5B is a diagram illustrating the configuration of a circuit board in Embodiment 1;

[0030] Fig. 6A and 6B is a diagram illustrating the configuration of a circuit board in Embodiment 2;

[0031] Figures 7A to 7C is a diagram illustrating the configuration of a circuit board in Embodiment 3;

[0032] Figures 8A to 8C is a cross-sectional view of the connector in Embodiment 4 and the comparative example; and

[0033] Figures 9A to 9C This is a cross-sectional view of the connector in Example 5. DETAILED DESCRIPTION

[0034] Hereinafter, a description of an embodiment (example) of the present invention will be given with reference to the accompanying drawings. However, the size, material, shape, relative arrangement, etc. of the constituent elements described in the embodiments may be appropriately changed according to the configuration of the device to which the present invention is applied, various conditions, etc. Therefore, the size, material, shape, relative arrangement, etc. of the constituent elements described in the embodiments are not intended to limit the scope of the present invention to the following embodiments.

[0035] Example 1

[0036] Figure 1 1 is a cross-sectional view of an image forming apparatus (laser printer) 100 using an electrophotographic recording technique. When a print signal is generated, a laser beam modulated depending on image information is projected by a scanner unit 21 and scanned through a photosensitive member (photosensitive drum) 19 charged to a predetermined polarity by a charging roller 16. Thus, an electrostatic latent image is formed on the photosensitive member 19. Toner is supplied from a developing device 17 to this electrostatic latent image to form a toner image depending on the image information on the photosensitive member 19.

[0037] 18 denotes a cleaner, which cleans the photosensitive member 19. In the present embodiment, a developing unit including the photosensitive member 19, a charging roller 16, and a developing device 17 (which includes a developing roller), and a cleaning unit including the cleaner 18 are configured to be attachable to / detachable from the apparatus body of the image forming apparatus 100 as a process cartridge 15. A recording material P such as ordinary paper loaded on the paper cassette 11 is fed one sheet at a time by a pickup roller 12 and conveyed to the registration roller 14 by a roller 13. In addition, the recording material P is conveyed from the registration roller 14 to the transfer position according to the timing at which the toner image on the photosensitive member 19 reaches the transfer position formed by the photosensitive member 19 and the transfer roller 20. In the process of the recording material P passing through the transfer position, the toner image on the photosensitive member 19 is transferred to the recording material P. Thereafter, the recording material P is heated in the fixing unit 200, and the toner image is thermally fixed on the recording material P. The recording material P on which the toner image is fixed is discharged to a tray on the image forming apparatus 100 according to the rollers 26 and 27 .

[0038] 28 denotes a paper feed tray (manual feed tray) having a pair of recording material adjustment plates having a width adjustable in response to the size of the recording material P. 29 denotes a pickup roller which feeds the recording material P from the paper feed tray 28, and 30 denotes a motor which drives the fixing unit 200 and the like. The fixing unit 200 is detachably attached to the image forming apparatus 100. Electric power is supplied to the fixing unit 200 from a power control circuit 400 connected to a commercial AC power source 401. The above-mentioned photosensitive member 19, charging roller 16, scanner unit 21, developing device 17, and transfer roller 20 constitute an image forming portion which forms an unfixed image on the recording material P. The scanner unit includes a semiconductor laser 22 which emits light in response to image information, a polygonal mirror 23 which deflects the laser beam, and a reflection mirror 24 which reflects the deflected laser beam toward the photosensitive member 19.

[0039] Figure 2 2 is a cross-sectional view of a fixing unit 200 for thermally fixing a toner image formed on a recording material on the recording material. The fixing unit 200 includes a cylindrical film 202, a heater 300 in contact with the inner surface of the film 202, and a pressure roller (nip forming member) 208 that forms a fixing nip N with respect to the heater 300 via the film 202. The heater 300 is powered by an AC power source 401 ( Figure 4 ) The power supplied generates heat. The sheet of recording material carrying the toner image is pinched and conveyed by the fixing nip portion.

[0040] The film 202 includes a base layer made of a heat-resistant resin such as polyimide or a metal such as stainless steel, and a surface layer made of a fluororesin. An elastic layer made of silicone rubber or the like may be provided between the base layer and the surface layer.

[0041] The pressure roller 208 includes a core bar 209 made of metal such as iron or aluminum, and an elastic layer 210 made of silicone rubber or the like.

[0042] The heater 300 is held by a holding member (heater holder) 201 made of a heat-resistant resin such as a liquid crystal polymer. The holding member 201 also has a guide function for guiding the rotation of the guide film 202. The holding member 201 is reinforced by a metal support 204. The pressure of a spring (not shown) for forming a fixing nip N by applying pressure between a pressure roller 208 and the spring is applied to the support 204. The pressure roller 208 is driven from a motor 30 (refer to FIG. 2 ). Figure 1) receives power to rotate in the arrow direction. The film 202 is driven to rotate according to the rotation of the pressure roller 208. The recording material P carrying the unfixed toner image is heated and fixed while being nipped and conveyed by the fixing nip portion N.

[0043] The heater 300 includes a ceramic (insulating) substrate 305 and heating elements (heating resistors) 302a and 302b printed on the substrate 305. A protection element 212 such as a thermal switch or a temperature fuse is in contact with the heater 300. When the heater 300 abnormally generates heat, the protection element 212 interrupts the power supplied to the heater 300 by disconnecting a switch provided in the heater 300.

[0044] Figure 3A is Figure 3B , a cross-sectional view of a heater 300 at a conveyance reference position X0 on a recording material P shown in FIG. The heater 300 includes sliding surface layers 1 and 2 as surfaces on a side sliding with a substrate 305 as an inner surface of a base film 202, and back surface layers 1 and 2 as surfaces on a side opposite to the sliding surface layers 1 and 2.

[0045] Semiconductors 301 and 303 are provided on the back surface layer 1 of the heater 300. The semiconductor 301 is divided into a semiconductor 301a disposed on the upstream side of the conveying direction of the recording material P and a semiconductor 301b disposed on its downstream side. A heating element 302 is also provided on the back surface layer 1, which is disposed between the semiconductors 301 and 303 and uses the power supplied by the semiconductors 301 and 303 to generate heat. The heating element 302 is divided into a heating element 302a disposed on the upstream side of the conveying direction of the recording material P and a heating element 302b disposed on its downstream side. In addition, an electrode E3 connected to a power supply terminal (not shown) outside the heater 300 is provided on the back surface layer 1. A protective layer 308 made of insulating glass is provided on the back surface layer 2 of the heater 300. The protective layer 308 covers the area except the electrode E3 and the electrode E4 to be described later.

[0046] Figure 3B2, back surface layer 1 and slide surface layer 1 of the heater 300. In the longitudinal direction of the heater 300, seven heating blocks HB1 to HB7 consisting of a set of semiconductors 301, semiconductors 303, heating elements 302 and electrodes E3 are provided on the back surface layer 1. In the figure, reference numeral 302a-1 represents the heating element 302a-1 in the heating block HB1, reference numeral 302a-2 represents the heating element 302a-2 in the heating block HB2, and the last number represents the corresponding heating block. The same applies to the reference numerals represented at the end of the heating element 302b, semiconductor 303 and electrode E3. Symbols E4 and E5 represent electrodes. One side of the heating element 302 is electrically connected to the electrode E3, and the other side thereof is electrically connected to the electrodes E4 and E5.

[0047] A protective layer 308 is provided in the region other than the regions of the electrodes E3-1 to E3-7, E4 and E5. A power supply terminal (not shown) outside the heater 300 is connected to the electrodes E3-1 to E3-7, E4 and E5 from the back side of the heater 300. The seven heating blocks HB1 to HB7 are independently controlled.

[0048] Thermistors (temperature detection elements) T1-1 to T1-7 and T2-2 to T2-6 for detecting the temperature of the heater 300 are provided on the sliding surface layer 1. Thermistors T1-1 to T1-7 (main thermistors) are provided on the seven heating blocks HB1 to HB7, respectively. The main thermistors T1-1 to T1-7 are mainly used for temperature control of the heating blocks HB1 to HB7. Therefore, the main thermistors T1-1 to T1-7 are provided approximately at the center of the heating blocks HB1 to HB7 in the longitudinal direction of the heater 300.

[0049] Thermistors T2-2 to T2-6 (sub-thermistors) are provided on the five heating blocks HB2 to HB6, respectively. Sub-thermistors T2-2 to T2-6 are provided so as to detect the temperature of the non-paper passing area of ​​the heater 300 in the case of printing on a sheet of recording material P having a narrow width. Therefore, sub-thermistors T2-2 to T2-6 are respectively disposed near the positions of the heating blocks HB1 to HB7 farthest from the conveying reference position X0 in the longitudinal direction of the heater 300. The heating blocks HB1 and HB7 have narrow areas in the longitudinal direction of the heater 300, and therefore thermistors are omitted therein.

[0050] The terminal on one side of each of the main thermistors T1-1 to T1-7 is connected to each of the conductors ET1-1 to ET1-7 for resistance value detection, and the terminal on the other side is connected to the common conductor EG9. The terminal on one side of each of the sub-thermistors T2-2 to T2-6 is connected to each of the conductors ET2-2 to ET2-6 for resistance value detection, and the terminal on the other side is connected to the common conductor EG10. Although the width (the length in the shortest dimension direction of the heater 300) L increases when the number of thermistors increases, the increase in the size of the heater 300 is prevented according to efforts such as adopting the common conductors EG9 and EG10.

[0051] A protective layer 309 coated with a material such as glass is provided on the sliding surface layer 2 of the heater 300. The protective layer 309 covers all the main thermistors, all the sub-thermistors, and all the conductors so that the edges of all the conductors ET1-1 to ET1-7, ET2-2 to ET2-6, EG9, and EG10 in the longitudinal direction of the heater 300 are exposed.

[0052] Figure 4 The fixing unit 200 and the power control circuit 400 are illustrated. As a circuit including the circuit in the fixing unit 200 and the power control circuit 400, there is a first potential group (first circuit) 415, which is a primary side circuit for supplying power from the AC power supply 401 to the heater 300 (heating elements 302a and 302b). In addition, there is a second potential group (second circuit) 406, which is a secondary side circuit that is electrically insulated from the first potential group 415 and controls the power supplied to the heater 300. The first circuit 415 is a circuit that cannot be touched by the user. The second circuit 406 is a circuit with electrical components and wiring that can be touched by the user. For example, the second circuit 406 also includes electrical components such as an interface cable for connecting to an external device (such as a PC) because it can be touched by the user. In addition, there is a third potential group (third circuit) 405 that is insulated from both the first potential group 415 and the second potential group 406. The third circuit 405 is a circuit that does not have electrical components or wiring that can be touched by the user (cannot be touched by the user). In view of this, the third circuit 405 is different from the second circuit 406.

[0053] When the heater 300 is damaged due to abnormal heat generation of the heater 300, etc., the first potential group 415 (such as electrodes E3-1 to E3-7, E4 and E5 and heating elements 302a and 302b) can be electrically connected to thermistors T1-1 to T1-7 and T2-2 to T2-6. Therefore, the present embodiment provides a configuration in which insulation from the user or the second potential group 406 is ensured even when both are electrically connected to each other. Specifically, the third potential group 405 including thermistors T1-1 to T1-7 and T2-2 to T2-6 and the temperature detection circuit 402 is electrically insulated from the first potential group 415 and the second potential group 406.

[0054] The fixing unit 200 is detachably attached to the main body of the printer 100. The fixing unit 200 is electrically connected to the main body of the printer 100 through a connector 403.

[0055] Next, the circuit in the first potential group 415 will be described. In the power control circuit 400, the commercial AC power source 401 is connected to the connector 403 through the relays 423 and 424 and the triacs 408 to 414. In the fixing unit 200, the power supply line from the connector 403 is connected to the electrodes E3-1 to E3-7, E4 and E5 of the heater 300.

[0056] Next, the circuit in the third potential group 405 will be described. In the fixing unit 200, the signal line is connected to the AD converter 404 provided in the temperature detection circuit 402 and the protection circuits 406 and 407 via the conductors ET1-1 to ET1-7, ET2-2 to ET2-6, EG9 and EG10 of the thermistors T1-1 to T1-7 and T2-2 to T2-6. Figure 4In order to simplify the drawings, the signal line is shown as two lines. The AD converter 404 converts the analog signals of thermistors T1-1 to T1-7 and T2-2 to T2-6 into digital signals. In order to reduce the number of connection pins of the connector 403, for example, data communication such as UART communication is used. The connector 403 is connected to the power control circuit 400. In the power control circuit 400, the signal line (third potential group) connected to the connector 403 is connected to the second potential group 406 electrically insulated from both the third potential group 405 and the first potential group 415 through an insulating coupler (optical triac coupler) 418. When the analog signals of thermistors T1-1 to T1-7 and T2-2 to T2-6 exceed a predetermined threshold value, the protection circuits 406 and 407 output signals RL1OFF and RL2OFF to interrupt the power supply to the heater 300. The signal line for the signal RL1OFF and the signal line for the signal RL2OFF are connected to the connector 403 and thereafter connected to the power control circuit 400. Inside the power control circuit 400 , each signal line is connected to latch circuits 427 and 428 through insulating couplers 425 and 426 .

[0057] Finally, the circuit in the second potential group 406 will be described. The signal via the insulating coupler 418 is input to the CPU 431. The CPU 431 determines the power required for the heating blocks HB1 to HB7 to maintain the target temperatures set respectively thereto using PID control, for example, based on the received signals of the main thermistors T1-1 to T1-7. The CPU 431 sends the signals FSRD1 to FSRD7 to the triacs 408 to 414 so that the determined power is supplied to the heating blocks HB1 to HB7. The optical triac couplers 416 to 422 are used to ensure the insulation between the second potential group 406 and the first potential group 415 by sending the signals FSRD1 to FSRD7 from the second potential group 406 to the first potential group 415. The latch circuits 427 and 428 are circuits for fixing the logic of the signals RL1OFF and RL2OFF to OFF when the temperatures of the sub-thermistors T2-2 to T2-6 reach at least a predetermined temperature. Signal lines for signals RL1OFF and RL2OFF output from latch circuits 427 and 428 are connected to transistors 429 and 430, respectively. In addition, the signal lines are configured to block currents flowing through the coils of relays 423 and 424. A protection element 212 is provided in the fixing unit 200, and a power source on the power control circuit 400 is connected to the protection element 212 through a connector 403. The power source via the protection element 212 is connected to the power source of the coils of relays 423 and 424 through the connector 403. Therefore, when the protection element 212 is disconnected due to abnormal heat generation of the heater 300, power is not supplied to the coils of the relays 423 and 424. When the relays 423 and 424 are disconnected, the power supply to the heater 300 is interrupted.

[0058] like Figure 4 As shown in FIG. 4 , the power control circuit 400 has a configuration in which the first potential group 415, the second potential group 406, and the third potential group 405 are mixed. Relays 423 and 424 straddling the second potential group and the first potential group ensure insulation therebetween according to the internal structure of the relays 423 and 424.

[0059] Figure 5A and 5BIt is a plan view of a circuit board 500 on which a power control circuit 400 is mounted. The circuit board 500 has a configuration in which a first potential group 415, a second potential group 406, and a third potential group 405 are mixed. Specifically, all three potential groups (first to third circuits) 415, 406, and 405 are provided on at least one surface of the circuit board 500. In the circuit in which the first potential group 415 and the second potential group 406 are mixed, the distance C between the first potential group 415 and the second potential group 406 needs to be a distance that satisfies the enhanced insulation in the safety requirements (IEC60950-1 and IEC62368-1). On the other hand, the distance A between the first potential group 415 and the third potential group 405 and the distance B between the third potential group 405 and the second potential group 406 can be a distance that ensures the basic insulation in the safety requirements. The distance has a relationship of distance C>distance A and distance C>distance B. Here, basic insulation is insulation performed for basic protection against electric shock. Double insulation performs additional insulation when basic insulation fails, which performs protection on basic insulation. Reinforced insulation is a single insulation that provides the same degree of protection against electric shock as double insulation. In this embodiment, reinforced insulation and double insulation are collectively referred to as reinforced insulation.

[0060] Figure 5A 1 is a plan view illustrating the arrangement of the potential groups on the circuit board 1500 in Comparative Example 1 and a cross-sectional view at the position of the straight line X. All of the first potential group 415, the second potential group 406, and the third potential group 405 exist on the straight line X, and the second potential group 406, the first potential group 415, and the third potential group 405 are arranged from the straight line X. Figure 5A and 5B . In this arrangement, the distance between the potential groups required to ensure insulation between the potential groups is distance C and distance A (< distance C). In particular, because the first potential group 415 and the second potential group 406 are adjacent, the distance C needs to be increased. Since the distance between the first potential group 415 and the third potential group 405 also requires distance A for basic insulation, the total distance required for insulation is distance A+distance C.

[0061] Figure 5B 1 is a plan view illustrating the arrangement of the potential groups on the circuit board 500 in the first embodiment and a cross-sectional view at the position of the straight line X. All the first potential groups 415, the second potential groups 406 and the third potential groups 405 exist on the straight line X, and the second potential groups 406, the third potential groups 405 and the first potential groups 415 are arranged from the straight line X. Figure 5A and 5B405 and 406. That is, the first to third circuits are arranged in the order of the first circuit 415, the third circuit 405 and the second circuit 406 on at least one straight line, and all the first to third circuits 415, 406 and 405 are present on the straight line on one surface of the circuit board 500. In this arrangement, the distances between the potential groups required to ensure the insulation between the potential groups are distance B (< distance C) and distance A (< distance C). The distance between the second potential group 406 and the third potential group 405 can be distance B (< distance C), because only basic insulation is required between them, and the distance between the first potential group 415 and the third potential group 405 can be distance A (< distance C), because only basic insulation is also required between them. In addition, if (distance A + distance B) ≥ distance C is satisfied, the required enhanced insulation between the first potential group 415 and the second potential group 406 can be ensured. Therefore, the distance A+C required for insulation in the circuit board 500 of Example 1 can be reduced to less than the distance A+C required for insulation in the circuit board 1500 of Comparative Example 1, and the area of ​​the circuit board 500 can be reduced to less than that of Comparative Example 1.

[0062] As described above, the device of the present embodiment includes the first potential group 415 having a circuit for supplying power from the AC power supply 401 to the heater 300, and the second potential group 406 electrically insulated from the first potential group 415, the first potential group 415 and the second potential group 406 being provided on a circuit including the fixing unit 200 and the circuit board 500. In addition, the third potential group 405 insulated from both the first potential group 415 and the second potential group 406 is provided. In addition, all three potential groups 415, 406, and 405 are disposed on at least one surface of the circuit board 500. The three potential groups 415, 406, and 405 are disposed in the order of the first potential group 415, the third potential group 405, and the second potential group 406 on at least one straight line in which all three potential groups 415, 406, and 405 exist.

[0063] Although it is not necessary to have three types of potential groups on any straight line on the circuit board 500, when there are three types, it is desirable to deploy the three potential groups so that each of the three types of potential groups exists only in one place in order to reduce the area of ​​the board. In addition, a configuration in which the three potential groups are deployed in the order of the first potential group 415, the third potential group 405, and the second potential group 406 on all straight lines where all three potential groups (first to third circuits) 415, 406, and 405 exist is more desirable.

[0064] Example 2

[0065] Fig. 6A is a cross-sectional view of a circuit board 1501 of Comparative Example 2, and Figure 6B2 is a cross-sectional view of a circuit board 2500 according to Embodiment 2. The circuit board 2500 according to Embodiment 2 is a two-layer board. The insulation structure required for the above safety is also required in the thickness direction of the board.

[0066] In the comparative example Fig. 6A , all the third potential group 405, the first potential group 415, and the second potential group 406 exist on the straight line Y, and they are arranged in the order of the third potential group 405, the first potential group 415, and the second potential group 406. In this case, the thickness of the circuit board 1501a required between the first potential group 415 and the third potential group 405 is thickness A, and the thickness of the circuit board 1501c required between the first potential group 415 and the second potential group 406 is thickness C (>thickness A). Therefore, the circuit board 1501 requires a minimum thickness of A+C.

[0067] In the embodiment 2 Figure 6B , all of the first potential group 415, the third potential group 405, and the second potential group 406 exist on the straight line Y, and they are arranged in the order of the first potential group 415, the third potential group 405, and the second potential group 406. In this case, the thickness of the circuit board 2500a required between the first potential group 415 and the third potential group 405 is thickness A, and the thickness of the circuit board 2500b required between the third potential group 405 and the second potential group 406 is thickness B (<thickness C). Therefore, although the circuit board 2500 requires a minimum thickness A+B, this thickness is less than the thickness required for the circuit board 1501.

[0068] As described above, the thickness of the circuit board 2500 according to the present embodiment can be reduced.

[0069] Example 3

[0070] Fig. 7A 1 and 2 are a plan view of a surface of a circuit board 1502 of Comparative Example 3, a cross-sectional view of the circuit board 1502 , and a plan view of a back surface of the circuit board 1502 . Figure 7B and 7C 3501 and 3502 of Example 3, a plan view of the surface of the circuit boards 3501 and 3502, a cross-sectional view of the circuit boards 3501 and 3502, and a plan view of the back of the circuit boards 3501 and 3502. The circuit boards 3501 and 3502 in Example 3 are double-sided boards. For safety requirements, as in Example 1, distance C>distance A and distance C>distance B are required in the surface direction, and as in Example 2, thickness C>thickness A and thickness C>thickness B are required in the thickness direction of the board.

[0071] In the comparative example 3, Fig. 7A, the first potential group 415 and the second potential group 406 are disposed on the first surface 1502A of the circuit board 1502, and the third potential group 405 is disposed on the second surface 1502B as the back side. Since the first potential group 415 and the second potential group 406 are disposed on the first surface 1502A, the distance C is required and thus the area of ​​the circuit board 1502 increases.

[0072] In the embodiment 3 Figure 7B In the embodiment, the second potential group 406 and the third potential group 405 are disposed on the first surface 3501A of the circuit board 3501, and the first potential group 415 is disposed on the second surface 3501B as the back surface. According to this arrangement, the distance between adjacent potential groups becomes the distance B, so the area of ​​the circuit board 3501 can be reduced to less than Fig. 7A The area of ​​the configuration.

[0073] In the modification example of the embodiment 3, Figure 7C , the second potential group 406 is disposed on the first surface 3502A of the circuit board 3502, and the first potential group 415 and the third potential group 405 are disposed on the second surface 3502B as the back surface. According to the arrangement in which the first potential group 415 and the third potential group 405 are disposed on the second surface 3502B, the distance between adjacent potential groups becomes the distance A, so the area of ​​the circuit board 3502 can be reduced to less than Fig. 7A The area of ​​the configuration.

[0074] As described above, in the device of this embodiment, the first potential group 415 is deployed on the first surface of the circuit board, the second potential group 406 is deployed on the second surface which is the back side of the first surface, and the third potential group 405 is deployed on at least one of the first and second surfaces.

[0075] Furthermore, the second potential group 406 is not provided right behind the region in which the first potential group 415 is provided.

[0076] In addition, the third potential group 405 is disposed right behind the region in which the first potential group 415 is provided or the region in which the second potential group 406 is provided.

[0077] Meanwhile, if the required insulation distance between the first potential group 415 and the second potential group 406 can be ensured to be thickness A or thickness B, the first potential group 415 can be disposed directly behind the second potential group 406 (with the circuit board 500 sandwiched therebetween).

[0078] In Embodiments 2 and 3, when a potential group exists at the edge of the circuit board 500 (near the flange) or a through hole passing through the surface and back surface exists in the board, the creeping distance routed to the surface and back surface at such a location also needs to be considered.

[0079] Example 4

[0080] Next, a configuration effective for miniaturizing the connector will be described.

[0081] Figures 8A to 8C yes Figure 4 0 is a schematic cross-sectional view of a connector 403 shown in , and shows a configuration in which connector portions respectively corresponding to a first potential group (first circuit) 415, a second potential group (second circuit) 406, and a third potential group (third circuit) 405 are mixed.

[0082] That is, in the present embodiment, there is provided a connector configuration in which connector portions corresponding to respective potential groups are disposed within a single connector 403. The connector 403 is composed of a male connector including pins provided on any one of the fixing unit 200 and the main body of the image forming apparatus 100, and a female connector including pin holes corresponding to the pins and provided on the other side. Figures 8A to 8C The circles in 9 schematically show the arrangement of the pins or pin holes in each connector part. Although not shown, the connector 403 includes a fitting shape portion for positioning the male connector and the female connector so as to maintain the connection state of the pins and the pin holes.

[0083] The predetermined distance required for insulation between the connector portion of the first potential group 415 and the connector portion of the third potential group 405 (the shortest distance between the pins included in the connector portion of the first potential group 415 and the pins included in the connector portion of the third potential group 405) is assumed to be A. Similarly, the predetermined distance required for insulation between the connector portion of the third potential group 405 and the connector portion of the second potential group 406 (the shortest distance between the pins included in the connector portion of the third potential group 405 and the pins included in the connector portion of the second potential group 406) is assumed to be B. In addition, the predetermined distance required for insulation between the connector portion of the first potential group 415 and the connector portion of the second potential group 406 (the shortest distance between the pins included in the connector portion of the first potential group 415 and the pins included in the connector portion of the second potential group 406) is assumed to be C. Here, there is a relationship of A=B<C. A and B are assumed to be insulation distances corresponding to basic insulation. C is assumed to be an insulation distance corresponding to reinforced insulation.

[0084] Fig. 8AIt is a schematic cross-sectional view showing the arrangement configuration of the connector parts corresponding to the respective potential groups within the connector 403 in Embodiment 1. Starting from the left side of the cross section of the connector, the connector parts are deployed in the order of the connector parts of the first potential group 415, the connector parts of the third potential group 405, and the connector parts of the second potential group 406. That is, the connector parts of the first potential group 415 are deployed on one side of the connector parts of the third potential group 405, and the connector parts of the second potential group 406 are deployed on the other side as the opposite side. This is an example in which the potential groups are deployed so that the sum of the distances between the potential groups becomes A+B and the sum of the distances between the potential groups is minimized while ensuring the distances required for insulation between the potential groups. Fig. 8A In the case of a potential group, the distance required for insulation can be further reduced by removing the metal parts required for wiring between potential groups. For example, when a connector is used that includes a larger number of pins than the number required for each potential group. Fig. 8A In the potential group arrangement configuration shown in , the free pins not used in each potential group and the metal parts provided corresponding to the free pins are removed from the connector and used. Therefore, it is possible to realize a potential group arrangement configuration in which the required insulation distance is ensured using a more compact connector (a connector with fewer pins).

[0085] Figure 8B 4 is a schematic cross-sectional view showing the arrangement of connectors in the connector 403 in the comparative example. In the comparative example, starting from the left side of the cross section of the connector, the connector parts are arranged in the order of the connector part of the first potential group 415, the connector part of the second potential group 406, and the connector part of the third potential group 405. In such an arrangement, the sum of the distances between the potential groups is C+B, and thus becomes greater than Fig. 8A The sum of the distances shown in is A + B. Therefore, the required connector size increases.

[0086] Figure 8C 4 is a diagram showing a cross section when the pins and the pin holes are arranged in two rows in the connector 403. The first row and the second row are arranged so that they become the same potential and the distance between the first row and the second row is reduced. Fig. 8A As shown in FIG. 1 , starting from the left side of the cross section of the connector, the connector parts are arranged in the order of the connector part of the first potential group 415, the connector part of the third potential group 405, and the connector part of the second potential group 406. According to this arrangement, it is possible to minimize the sum of the distances between the potential groups while ensuring the distances required for insulation between the potential groups.

[0087] Therefore, according to the circuit configuration of the present embodiment, it is possible to promote miniaturization of the connector and the fixing device.

[0088] Meanwhile, the arrangement shown in Embodiment 4 is merely an example of an arrangement in which a predetermined distance required for electrical insulation between potential groups is ensured and the sum of distances between potential groups is minimized. Various configurations can be adopted depending on the combination of the number of potential groups and the size of the distance required for insulation.

[0089] Example 5

[0090] Figures 9A to 9C 4 is a diagram illustrating a connector arrangement in Embodiment 5. In this embodiment, a configuration including a plurality of connectors 403 corresponding to potential groups is provided. That is, an independent connector 403 is provided for each potential group.

[0091] In Embodiment 5, descriptions of common components in Embodiments 4 and 5 are omitted. Matters not particularly described in Embodiment 5 are the same as those in Embodiment 4.

[0092] Fig.9A 403(a), 403(b), and 403(c) are arranged on a straight line. The first potential group 415 is connected to the connector 403(a), the third potential group 405 is connected to the connector 403(b), and the second potential group 406 is connected to the connector 403(c). As in Embodiment 1, it is assumed that the predetermined distance required for insulation between the first potential group 415 and the third potential group 405 is A. Similarly, it is assumed that the predetermined distance required for insulation between the third potential group 405 and the second potential group 406 is B, and the predetermined distance required for insulation between the first potential group 415 and the second potential group 406 is C. Here, as in Embodiment 1, there is also a relationship of A=B<C.

[0093] like Fig.9A As shown in , even when the connectors are separated for the respective potential groups, the same effect as that of Embodiment 1 can be obtained by arranging the connectors in the order of the first potential group 415, the third potential group 405, and the second potential group 406 from the left side of the cross section of the connector. That is, the connectors can be arranged in the minimum space while ensuring the distance required for insulation between the potential groups.

[0094] Fig. 9B is a diagram showing a cross section when the pins and pin holes are arranged in two rows in each connector. The first row and the second row are arranged so that they become the same potential and the distance between the first row and the second row is reduced. In addition, as Fig.9A As in FIG. 1 , starting from the left side of the cross section of the connector, the connectors are arranged in the order of the first potential group 415, the third potential group 405, and the second potential group 406. According to this arrangement, the connectors can be arranged in the minimum space while ensuring the distance required for insulation between the potential groups.

[0095] Fig. 9C 4 is a diagram showing the arrangement of connectors 403(a), 403(b), and 403(c) on a triangle. Here, an arrangement for minimizing the sum of distances between potential groups while ensuring the distances required for insulation between potential groups is an arrangement in which connectors 403(a), 403(b), and 403(c) are arranged so that distance C becomes a hypotenuse, as shown in FIG. Fig. 9C That is, the connectors are arranged so that an isosceles triangle is drawn between the connectors 403(a), 403(b), and 403(c), the isosceles triangle having a first side of length A and a second side of length B as equal sides, and a third side of length C as a base.

[0096] The connector configuration shown in Embodiment 5 is merely an example. For example, a configuration may be provided in which the first potential group 415 and the third potential group 405 are included in one connector and the second potential group 406 is included in a separate connector. That is, various configurations may be adopted depending on a combination of the number of potential groups and the size of the distance required for insulation.

[0097] While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments.The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.

Claims

1. An image forming apparatus for forming a toner image on a recording material, comprising: an apparatus main body including an image forming section that forms a toner image on a recording material; a fixing unit having a plate-shaped heater for generating heat by electric power supplied from a power source and thermally fixing a toner image formed on a recording material onto the recording material, the fixing unit being detachably attached to the apparatus main body; a circuit board provided with a power control circuit for controlling power supplied to the heater; as well as a connector electrically connecting the fixing unit to the power control circuit, The plate-shaped heater includes a substrate and a heating resistor formed on the substrate. wherein the circuit including both the circuit in the fixing unit and the power control circuit is provided with a first circuit, a second circuit, and a third circuit, the first circuit supplies power from the power source to the heater, the second circuit is electrically insulated from the first circuit and controls the power supplied to the heater, the third circuit is electrically insulated from both the first circuit and the second circuit and includes a temperature detection circuit, and Wherein, in the connector, the distance between the first circuit and the second circuit satisfies enhanced insulation, and each of the distance between the first circuit and the third circuit and the distance between the second circuit and the third circuit satisfies basic insulation.

2. The image forming apparatus according to claim 1, wherein: In the connector, the first circuit, the third circuit, and the second circuit are arranged in sequence.

3. The image forming apparatus according to claim 1, wherein: The fixing unit includes a cylindrical film and a roller in contact with an outer surface of the film. wherein the heater is provided in the inner space of the membrane, and The roller forms a fixing nip portion for pinching and conveying a recording material together with the heater via the film.

4. The image forming apparatus according to claim 3, wherein: The heater includes a temperature detection element that detects a temperature of the heater, and Wherein, the temperature detection element is provided on a side of the heater facing the film.

5. The image forming apparatus according to claim 4, wherein: The temperature detection element and a signal line of the temperature detection element are connected to the temperature detection circuit.

6. A fixing unit that thermally fixes a toner image formed on a recording material onto the recording material and is detachably attached to an image forming device, the image forming device including a circuit board provided with a power control circuit, the fixing unit comprising: a plate-shaped heater for generating heat by electric power supplied from a power source, the plate-shaped heater including a substrate and a heat generating resistor formed on the substrate; as well as a connector electrically connecting the fixing unit to the power control circuit, wherein the circuit including both the circuit in the fixing unit and the power control circuit is provided with a first circuit, a second circuit, and a third circuit, the first circuit supplies power from the power source to the heater, the second circuit is electrically insulated from the first circuit and controls the power supplied to the heater, the third circuit is electrically insulated from both the first circuit and the second circuit and includes a temperature detection circuit, and Wherein, in the connector, the distance between the first circuit and the second circuit satisfies enhanced insulation, and each of the distance between the first circuit and the third circuit and the distance between the second circuit and the third circuit satisfies basic insulation.

7. The fixing unit according to claim 6, wherein: In the connector, the first circuit, the third circuit, and the second circuit are arranged in sequence.

8. The fixing unit according to claim 6, wherein: The fixing unit includes a cylindrical film and a roller in contact with an outer surface of the film. wherein the heater is provided in the inner space of the membrane, and The roller forms a fixing nip portion for pinching and conveying a recording material together with the heater via the film.

9. The fixing unit according to claim 8, wherein: The heater includes a temperature detection element that detects a temperature of the heater, and Wherein, the temperature detection element is provided on a side of the heater facing the film.

10. The fixing unit according to claim 9, wherein: The temperature detection element and a signal line of the temperature detection element are connected to the temperature detection circuit.

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