JP7423253B2 - Image forming device - Google Patents

Description

The present invention relates to an image forming apparatus such as a copying machine or a printer using an electrophotographic method or an electrostatic recording method.

Some fixing units installed in image forming apparatuses include a cylindrical film, a plate-shaped heater that contacts the inner surface of the film, and a roller that forms a nip portion with the heater through the film. . Further, Patent Document 1 discloses a configuration in which the temperature of the nip portion is accurately detected by providing a thermistor on the side of the heater substrate that contacts the film.

Japanese Patent Application Publication No. 11-194837

By the way, when adopting a configuration in which a thermistor is provided on the side of the heater substrate that comes into contact with the film, it is necessary to take measures to ensure dielectric strength. For this purpose, the temperature detection circuit to which the thermistor is electrically connected is connected to the primary circuit (first potential group) which is electrically connected to the commercial power supply, and the temperature detection circuit is electrically isolated from the primary circuit. A conceivable configuration is to electrically insulate both the secondary side circuits (second potential group).

However, it is necessary to ensure a distance between each potential group, so if the first potential group, the second potential group, and the potential group with a temperature detection circuit are mixed on the circuit board, the circuit The size of the board becomes large. Increasing the size of the circuit board is disadvantageous to downsizing the image forming apparatus.

An object of the present invention is to provide a technique that allows a temperature sensing element to be placed on a sliding surface of a heater with a film while suppressing the increase in size of the heater.

In order to achieve the above object, the image forming apparatus of the present invention includes:
An image forming apparatus that forms a toner image on a recording material,
A cylindrical film, a heater that generates heat using electric power supplied from an AC power supply and that contacts the inner surface of the film, a roller that forms a fixing nip that pinches and conveys a recording material together with the heater, and the heater a temperature sensing element that detects the temperature of the heater provided on a surface that contacts the film, and a fixing unit that heats and fixes the toner image formed on the recording material to the recording material;
a circuit board provided with a power control circuit that controls power supplied to the heater;
Equipped with
A circuit including a circuit in the fixing unit and the power control circuit includes a first circuit that supplies power from the AC power source to the heater, and a second circuit that is electrically insulated from the first circuit. a third circuit insulated from both the first circuit and the second circuit;
The third circuit has a temperature detection circuit to which the temperature detection element and the signal line of the temperature detection element are connected,
All of the first to third circuits are provided on at least one surface of the circuit board,
On the straight line where all the first to third circuits exist on the one surface of the circuit board, the first to third circuits are the first circuit, the third circuit, arranged in the order of the second circuit ,
The distance between the first circuit and the third circuit and the distance between the third circuit and the second circuit are both shorter than a distance that satisfies basic insulation, and a distance that satisfies basic insulation. It is characterized by the presence of
In order to achieve the above object, the image forming apparatus of the present invention includes:
An image forming apparatus that forms a toner image on a recording material,
A cylindrical film, a heater that generates heat using electric power supplied from an AC power supply and that contacts the inner surface of the film, a roller that forms a fixing nip that pinches and conveys a recording material together with the heater, and the heater a temperature sensing element that detects the temperature of the heater provided on a surface that contacts the film, and a fixing unit that heats and fixes the toner image formed on the recording material to the recording material;
a first circuit board provided with a power control circuit for controlling power supplied to the heater; and a second circuit board disposed overlapping the first circuit board;
Equipped with
A circuit including a circuit in the fixing unit and the power control circuit includes a first circuit that supplies power from the AC power source to the heater, and a second circuit that is electrically insulated from the first circuit. a third circuit insulated from both the first circuit and the second circuit;
The third circuit has a temperature detection circuit to which the temperature detection element and the signal line of the temperature detection element are connected,
The first circuit is disposed on one surface of the first circuit board, and the other surface of the first circuit board is the second circuit board that is a surface facing the first circuit board. The third circuit is disposed between one surface of the second circuit board, and the second circuit is disposed on the other surface of the second circuit board,
The thickness of the first circuit board and the thickness of the second circuit board are both thinner than the thickness that satisfies the reinforced insulation, and the thickness that satisfies the basic insulation.
In order to achieve the above object, the image forming apparatus of the present invention includes:
An image forming apparatus that forms a toner image on a recording material,
A cylindrical film, a heater that generates heat using electric power supplied from an AC power supply and that contacts the inner surface of the film, a roller that forms a fixing nip that pinches and conveys a recording material together with the heater, and the heater The heater provided on the side that contacts the film of
a temperature sensing element that detects the temperature of the recording material, and a fixing unit that heats and fixes the toner image formed on the recording material to the recording material;
a circuit board provided with a power control circuit that controls power supplied to the heater;
Equipped with
A circuit including a circuit in the fixing unit and the power control circuit includes a first circuit that supplies power from the AC power source to the heater, and a second circuit that is electrically insulated from the first circuit. a third circuit insulated from both the first circuit and the second circuit;
The third circuit has a temperature detection circuit to which the temperature detection element and the signal line of the temperature detection element are connected,
The first circuit is arranged on a first surface of the circuit board, and the region is on a second surface that is the back surface of the first surface and is not directly behind the region where the first circuit is provided. the second circuit is disposed in the area , and the third circuit is disposed on at least one of the first and second surfaces;
Distance between the first circuit and the third circuit when the third circuit is arranged on the first surface and when the third circuit is arranged on the second surface In this case, the distance between the third circuit and the second circuit is both shorter than the distance that satisfies the reinforced insulation, and the distance that satisfies the basic insulation.
The circuit board is characterized in that the thickness of the circuit board is thinner than the thickness that satisfies the reinforced insulation and the thickness that satisfies the basic insulation .
In order to achieve the above object, the image forming apparatus of the present invention includes:
An image forming apparatus that forms a toner image on a recording material,
an apparatus main body including an image forming section that forms a toner image on a recording material;
A cylindrical film, a heater that generates heat using electric power supplied from an AC power supply and that contacts the inner surface of the film, a roller that forms a fixing nip that pinches and conveys a recording material together with the heater, and the heater a temperature sensing element for detecting the temperature of the heater provided on the side of the heater that is in contact with the film, the fixing unit heating and fixing the toner image formed on the recording material onto the recording material, the fixing unit that is removably attachable to the apparatus main body;
a circuit board provided with a power control circuit that controls power supplied to the heater;
a connector that electrically connects the fixing unit and the power control circuit;
Equipped with
A circuit including a circuit in the fixing unit and the power control circuit includes a first circuit that supplies power from the AC power source to the heater, and a second circuit that is electrically insulated from the first circuit. a third circuit insulated from both the first circuit and the second circuit;
The third circuit has a temperature detection circuit to which the temperature detection element and the signal line of the temperature detection element are connected,
In the connector, the first to third circuits are arranged in the order of the first circuit, the third circuit, and the second circuit,
The distance between the first circuit and the third circuit and the distance between the third circuit and the second circuit are both shorter than a distance that satisfies basic insulation, and a distance that satisfies basic insulation. It is characterized by the presence of

According to the present invention, the temperature sensing element can be arranged on the sliding surface of the heater with the film while suppressing the increase in size of the heater.

Cross-sectional view of image forming device Cross-sectional view of the fusing unit Heater configuration diagram in Example 1 Fixing unit and power control circuit diagram in Example 1 Configuration diagram of a circuit board in Example 1 Configuration diagram of a circuit board in Example 2 Configuration diagram of a circuit board in Example 3 Cross-sectional views of connectors in Example 4 and Comparative Example Connector sectional view in Example 5

EMBODIMENT OF THE INVENTION Below, with reference to drawings, the form for implementing this invention is illustratively described in detail based on an Example. However, the dimensions, materials, shapes, and relative arrangement of the components described in this embodiment should be changed as appropriate depending on the configuration of the device to which the invention is applied and various conditions. That is, the scope of the present invention is not intended to be limited to the following embodiments.

[Example 1]
FIG. 1 is a sectional view of an image forming apparatus (laser printer) 100 using electrophotographic recording technology. When a print signal is generated, a scanner unit 21 emits a laser beam modulated according to image information, and scans a photoreceptor (photosensitive drum) 19 charged to a predetermined polarity by a charging roller 16. As a result, an electrostatic latent image is formed on the photoreceptor 19. Toner is supplied from the developing device 17 to this electrostatic latent image, and a toner image corresponding to the image information is formed on the photoreceptor 19.

A cleaner 18 cleans the photoreceptor 19. In this embodiment, a photoreceptor 19, a charging roller 16, a developing device 17 including a developing roller, and a cleaning unit including a cleaner 18 are removably attached to the main body (apparatus main body) of the image forming apparatus 100 as a process cartridge 15. It is configured. On the other hand, recording materials P such as plain paper loaded in the paper feed cassette 11 are fed one by one by a pickup roller 12 and conveyed by rollers 13 toward registration rollers 14 . Further, the recording material P is conveyed from the registration roller 14 to the transfer position in synchronization with the timing at which the toner image on the photoreceptor 19 reaches the transfer position where the photoreceptor 19 and the transfer roller 20 form. The toner image on the photoreceptor 19 is transferred to the recording material P while the recording material P passes through the transfer position. Thereafter, the recording material P is heated by the fixing unit 200, and the toner image is heated and fixed onto the recording material P. The recording material P carrying the fixed toner image is discharged to a tray at the top of the image forming apparatus 100 by rollers 26 and 27.

Note that 28 is a paper feed tray (manual feed tray) having a pair of recording material regulating plates whose width can be adjusted according to the size of the recording material P. 29 is a pickup roller that feeds the recording material P from the paper feed tray 28, and 30 is a motor that drives the fixing unit 200 and the like. The fixing unit 200 is removable from the image forming apparatus 100. Further, power is supplied to the fixing unit 200 from a power control circuit 400 connected to a commercial AC power source 401 . The photoreceptor 19, charging roller 16, scanner unit 21, developing device 17, and transfer roller 20 described above constitute an image forming section that forms an unfixed image on the recording material P. The scanner unit includes a semiconductor laser 22 that emits light according to image information, a polygon mirror 23 that deflects laser light, and a mirror 24 that reflects the deflected laser light toward photoreceptor 19.

FIG. 2 is a sectional view of a fixing unit 200 that heats and fixes a toner image formed on a recording material onto the recording material. The fixing unit 200 includes a cylindrical film 202, a heater 300 that contacts the inner surface of the film 202, and a pressure roller (nip forming member) 208 that forms a fixing nip N with the heater 300 via the film 202. has. The heater 300 generates heat using power supplied from an AC power source 401 (FIG. 4). A recording material carrying a toner image is nipped and conveyed in a fixing nip.

The film 202 has 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.

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

The heater 300 is held by a holding member (heater holder) 201 made of heat-resistant resin such as liquid crystal polymer. The holding member 201 also has a guide function for guiding the rotation of the film 202. The holding member 201 is reinforced by a metal stay 204. Pressure from a spring (not shown) is applied to the stay 204 to form a fixing nip N by applying pressure between the stay 204 and the pressure roller 208 . Pressure roller 208 receives power from motor 30 (see FIG. 1) and rotates in the direction of the arrow. As the pressure roller 208 rotates, the film 202 is rotated. The recording material P carrying the unfixed toner image is heated and fixed while being nipped and conveyed in the fixing nip N.

The heater 300 includes a ceramic (insulating) substrate 305 and heating elements (heating resistors) 302a and 302b printed on the substrate 305. A protective element 212 such as a thermoswitch or a thermal fuse is in contact with the heater 300 . When the heater 300 generates abnormal heat, the protection element 212 turns off an internal switch and cuts off the power supplied to the heater 300.

FIG. 3(A) is a cross-sectional view of the heater 300 at the transport reference position X0 of the recording material P shown in FIG. 3(B). The heater 300 has a sliding surface layer 1 and a sliding surface layer 2, which are surfaces on which the inner surface of the film 202 slides, and a sliding surface layer 1 and a sliding surface layer 2, with respect to the substrate 305. It has a back layer 1 and a back layer 2 which are opposite sides.

The back layer 1 of the heater 300 is provided with a conductor 301 and a conductor 303. The conductor 301 is divided into a conductor 301a disposed on the upstream side in the conveyance direction of the recording material P and a conductor 301b disposed on the downstream side. The back layer 1 is also provided with a heating element 302 that is provided between the conductor 301 and the conductor 303 and generates heat by electric power supplied through the conductor 301 and the conductor 303. The heating element 302 is divided into a heating element 302a placed on the upstream side in the conveyance direction of the recording material P, and a heating element 302b placed on the downstream side. Further, the back layer 1 is provided with an electrode E3 to which an external power supply terminal (not shown) of the heater 300 is connected. The back layer 2 of the heater 300 is provided with a protective layer 308 made of insulating glass. The protective layer 308 covers areas other than the electrode E3 and the electrode E4 described below.

FIG. 3(B) is a plan view of the heater 300 in each layer of the back layer 2, the back layer 1, and the sliding surface layer 1. On the back layer 1, seven heat generating blocks HB1 to HB7 each consisting of a set of a conductor 301, a conductor 303, a heat generating element 302, and an electrode E3 are provided along the longitudinal direction of the heater 300. Note that the number 302a-1 in the figure indicates the heat generating element 302a-1 in the heat generating block HB1, and the number 302a-2 indicates the heat generating element 302a-2 in the heat generating block HB2. indicates the corresponding heat generating block. The meanings of the numbers attached to the end of the heating element 302b, the conductor 303, and the electrode E3 are also the same. Symbols E4 and E5 are electrodes. Electrically, the heating element 302 is connected to electrode E3 on one side and electrodes E4 and E5 on the other side.

The protective layer 308 is provided except for the electrodes E3-1 to E3-7, E4, and E5. External power supply terminals (not shown) of the heater 300 are connected to the electrodes E3-1 to E3-7, E4, and E5 from the back side of the heater 300. The seven heat generating blocks HB1 to HB7 are each independently controlled.

The sliding surface layer 1 is provided with thermistors (temperature sensing elements) T1-1 to T1-7 and T2-2 to T2-6 for detecting the temperature of the heater 300. One thermistor T1-1 to T1-7 (main thermistor) is provided to each of the seven heat generating blocks HB1 to HB7. The main thermistors T1-1 to T1-7 are mainly used to control the temperature of each heat generating block HB1 to HB7. Therefore, in the longitudinal direction of the heater 300, each main thermistor T1-1 to T1-7 is provided approximately at the center of each heat generating block HB1 to HB7.

One thermistor T2-2 to T2-6 (sub-thermistor) is provided in each of the five heat generating blocks HB2 to HB6. The sub-thermistors T2-2 to T2-6 are provided to detect the temperature of the non-sheet passing area of the heater 300 in the case of printing on a narrow recording material P. Therefore, the sub-thermistors T2-2 to T2-6 are connected to the heat generating block HB.
The heaters 1 to HB7 are arranged near the position farthest from the transport reference position X0 in the longitudinal direction of the heater 300. Note that sub-thermistors are omitted from heat generating blocks HB1 and HB7 because their regions in the longitudinal direction of heater 300 are narrow.

One terminal of the main thermistors T1-1 to T1-7 is connected to the conductor ET1-1 to ET1-7 for resistance value detection, respectively, and the other terminal is connected to a common conductor EG9. . One terminal of the sub-thermistor T2-2 to T2-6 is connected to the conductor ET2-2 to ET2-6 for resistance value detection, respectively, and the other terminal is connected to a common conductor EG10. . Although the width L of the heater 300 (length in the short direction of the heater 300) increases as the number of thermistors increases, the increase in size is suppressed by adopting common conductors EG9 and EG10. .

The sliding surface layer 2 of the heater 300 is provided with a protective layer 309 coated with a material such as glass. The protective layer 309 covers all the main thermistors and all the conductors so that the ends 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. Covers the sub-thermistor and all conductors.

FIG. 4 shows the fixing unit 200 and the power control circuit 400. The circuit including the circuit in the fixing unit 200 and the power control circuit 400 includes a first potential group (first circuit) 415. Furthermore, there is a second potential group (second circuit) 406 that is electrically insulated from the first potential group 415 and is a secondary circuit that 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 that has electrical components and wiring that can be touched by the user. For example, electrical components such as an interface cable used for connection with an external device such as a PC are also included in the second circuit 406 because they can be touched by the user. Furthermore, 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 (that is, cannot be touched by the user). In this respect, the third circuit 405 differs from the second circuit 406.

If the heater 300 breaks due to abnormal heat generation of the heater 300, the first potential group 415 of the electrodes E3-1 to E3-7, E4, E5, heating elements 302a, 302b, etc., and thermistors T1-1 to T1 -7, it is possible that T2-2 to T2-6 are electrically connected. Therefore, this embodiment is configured to ensure insulation from the user and the second potential group 406 even if the two are electrically connected. Specifically, the thermistors T1-1 to T1-7, T2-2 to T2-6 and the third potential group 405 of the temperature detection circuit 402 are connected to the first potential group 415 and the second potential group 406. It is electrically insulated.

The fixing unit 200 is detachable from the main body of the printer 100. The fixing unit 200 is electrically connected to the main body of the printer 100 via a connector 403.

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

Next, the circuit within the third potential group 405 will be explained. In the fixing unit 200, the signal lines are connected to the thermistors T1-1 to T1-7, T2-2 to T2-6 via conductors ET1-1 to ET1-7, ET2-2 to ET2-6, EG9, and EG10. Each of them is connected to an AD converter 404 and protection circuits 406 and 407 installed in the temperature detection circuit 402. Note that in FIG. 4, the signal lines are shown together in two lines for the sake of simplification of the drawing. The AD converter 404 converts analog signals from the thermistors T1-1 to T1-7 and T2-2 to T2-6 into digital signals. Further, in order to reduce the number of connection pins of the connector 403, data communication such as UART communication is used. Connector 403 is connected to 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 third potential group 405 and the first potential group 415 via an insulating coupler (phototriac coupler) 418. is connected to a second potential group 406 electrically insulated from both. The protection circuits 406 and 407 output the RL1OFF signal and the RL2OFF signal to cut off the power supply to the heater 300 when the analog signals of thermistors T1-1 to T1-7 and T2-2 to T2-6 exceed predetermined thresholds. do. The signal line for the RL1OFF signal and the signal line for the RL2OFF signal are connected to a connector 403 and then connected to the power control circuit 400. Inside the power control circuit 400, each signal line is connected to latch circuits 427 and 428 via insulating couplers 425 and 426, respectively.

Finally, the circuit within the second potential group 406 will be explained. The signal via the insulating coupler 418 is input to the CPU 431. Based on the received signals from the main thermistors T1-1 to T1-7, the CPU 431 determines the power necessary for the heat generating blocks HB1 to HB7 to maintain the respective set target temperatures using, for example, PID control. do. CPU 431 transmits signals FSRD1 to FSRD7 to triacs 408 to 414 so that the determined power is supplied to each of heat generating blocks HB1 to HB7. The isolation between the second potential group 406 and the first potential group 415 is achieved by using phototriac couplers 416-422 to transmit the signals FSRD1-7 from the second potential group 406 to the first potential group 415. is ensured. The latch circuits 427 and 428 are circuits that fix the logic of the RL1OFF signal and the RL2OFF signal to OFF when the temperature of the sub-thermistors T2-2 to T2-6 exceeds a predetermined temperature. Signal lines for the RL1OFF signal and RL2OFF signal output from the latch circuits 427 and 428 are connected to transistors 429 and 430, respectively. The configuration is such that the current flowing through the coils of relays 423 and 424 is interrupted. A protection element 212 is installed in the fixing unit 200 , and a power source on the power control circuit 400 is connected to the protection element 212 via a connector 403 . The power supply through the protection element 212 is connected to the power supply of the coils of the relays 423 and 424 through the connector 403. Therefore, when the protection element 212 is turned off due to abnormal heat generation of the heater 300, power is no longer supplied to the coils of the relays 423 and 424. By turning off relays 423 and 424, power supply to heater 300 is cut off.

As shown in FIG. 4, the power control circuit 400 has a configuration in which a first potential group 415, a second potential group 406, and a third potential group 405 are mixed. Note that the relays 423 and 424 that straddle the second potential group and the first potential group ensure insulation between them by the internal structures of the relays 423 and 424.

FIG. 5 is a plan view of a circuit board 500 on which the 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 a circuit in which the first potential group 415 and the second potential group 406 coexist, the distance C between the first potential group 415 and the second potential group 406 is determined according to safety standards (IEC60950-1, IEC62368-1). A distance that satisfies reinforced insulation is required. 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 are respectively distances that ensure basic insulation according to safety standards. It doesn't matter if that's the case. The relationship between each distance is distance C>distance A, and distance C>distance B. Here, basic insulation refers to insulation provided to provide basic protection against electric shock. Furthermore, double insulation refers to the addition of additional insulation to the basic insulation to provide protection in the event that the basic insulation fails. Reinforced insulation is a single type of insulation that provides the same level of protection against electric shock as double insulation. In this embodiment, reinforced insulation and double insulation are collectively referred to as reinforced insulation.

FIG. 5A is a plan view showing the arrangement of each potential group on the circuit board 1500 of Comparative Example 1, and a cross-sectional view at the position of straight line X. A first potential group 415, a second potential group 406, and a third potential group 405 all exist on the straight line X, and from the left side of FIG. 415 and the third potential group 405. When arranged in this way, the distances between the potential groups necessary to ensure insulation between the potential groups are distance C and distance A (<distance C). In particular, since the first potential group 415 and the second potential group 406 are adjacent to each other, it is necessary to take a large distance C. Since a distance A is also required between the first potential group 415 and the third potential group 405 for basic insulation, the total distance required for insulation is distance A+distance C.

FIG. 5B is a plan view showing the arrangement of each potential group on the circuit board 500 of Example 1, and a cross-sectional view at the position of straight line X. A first potential group 415, a second potential group 406, and a third potential group 405 all exist on the straight line X, and from the left side of FIG. 405 and the first potential group 415. That is, on at least one straight line on which all the first to third circuits 415, 406, and 405 exist on one surface of the circuit board 500, the first to third circuits are connected to the first circuit 415, A third circuit 405 and a second circuit 406 are arranged in this order. When arranged in this way, the distances between the potential groups necessary to ensure insulation between the potential groups are distance B (<distance C) and distance A (<distance C). Basic insulation is sufficient between the second potential group 406 and the third potential group 405, so the distance B (<distance C) is sufficient, and basic insulation is also sufficient between the first potential group 415 and the third potential group 405. Therefore, distance A (<distance C) is sufficient. Further, if (distance A+distance B)≧distance C is satisfied, the necessary reinforced insulation can be ensured between the first potential group 415 and the second potential group 406. Therefore, the distance A+C required for insulation in the circuit board 500 of Example 1 is shorter than the distance A+C required for insulation in the circuit board 1500 of Comparative Example 1, and the distance A+C required for insulation in the circuit board 500 of Example 1 is shorter than that of the circuit board 500 of Comparative Example 1. The area can be reduced.

As described above, the apparatus of this embodiment includes a first potential group 415 having a circuit that supplies power from the AC power source 401 to the heater 300, and a first A second potential group 406 electrically insulated from potential group 415 is provided. Further, a third potential group 405 is provided which is insulated from both the first potential group 415 and the second potential group 406. Furthermore, all three potential groups 415, 406, and 405 are arranged on at least one surface of the circuit board 500. Furthermore, on at least one straight line in which all three potential groups 415, 406, and 405 exist, the three potential groups 415, 406, and 405 are the first potential group 415, the third potential group 405, and the second potential group. They are arranged in the order of potential group 406.

Note that three potential groups do not necessarily need to exist on any straight line on the circuit board 500, but if three potential groups exist, the three potential groups are arranged so that each of the three potential groups exists only at one location. It is desirable to arrange this in order to reduce the area of the substrate. Furthermore, on all straight lines where all three potential groups (first to third circuits) 415, 406, and 405 exist, the three potential groups are the first potential group 415, the third potential group 405, A configuration in which the potentials are arranged in the order of the second potential group 406 is more preferable.

[Example 2]
6(A) is a cross-sectional view of a circuit board 1501 of Comparative Example 2, and FIG. 6(B) is a cross-sectional view of a circuit board 2500 of Example 2. The circuit board 2500 in Example 2 is a two-layer board. The insulation structure according to the safety standards mentioned above is also required in the thickness direction of the board.

In FIG. 6A, which is a comparative example, the third potential group 405, the first potential group 415, and the second potential group 406 all exist on the straight line Y, and the third potential group 405, The first potential group 415 and the second potential group 406 are arranged in this order. 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 A. The thickness is thickness C (>thickness A). Therefore, the circuit board 1501 needs to have a minimum thickness of A+C.

In FIG. 6B which is Example 2, the first potential group 415, the third potential group 405, and the second potential group 406 all exist on the straight line Y, and the first potential group 415 , third potential group 405, and second potential group 406 in this order. 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 A. The thickness is thickness B (<thickness C). Therefore, the circuit board 2500 must have a minimum thickness of A+B, but this thickness is thinner than the thickness required for the circuit board 1501.

As described above, according to this embodiment, the thickness of the circuit board 2500 can be reduced.

[Example 3]
FIG. 7A is a plan view of the front surface, a sectional view, and a plan view of the back surface of the circuit board 1502 of Comparative Example 3. FIGS. 7B and 7C are a top plan view, a sectional view, and a back plan view of the circuit boards 3501 and 3502 of Example 3. The circuit boards 3501 and 3502 in Example 3 are double-sided boards. The distances in the plane direction required by the safety standards are, as in Example 1, distance C>distance A, and distance C>distance B, and the substrate thickness direction is as in Example 2, thickness C>thickness A, Moreover, thickness C>thickness B.

In FIG. 7A, which is Comparative Example 3, a first potential group 415 and a second potential group 406 are arranged on the first surface 1502A of the circuit board 1502, and a third potential group 415 and the second potential group 406 are arranged on the second surface 1502B, which is the back surface. A potential group 405 is arranged. Since the first potential group 415 and the second potential group 406 are arranged on the first surface 1502A, a distance C is required, and the area of the circuit board 1502 becomes large.

In FIG. 7B, which is the third embodiment, a second potential group 406 and a third potential group 405 are applied to the first surface 3501A of the circuit board 3501, and a first potential is applied to the second surface 3501B, which is the back surface. A group 415 is arranged. With this arrangement, the distance between adjacent potential groups becomes distance B, and the area of the circuit board 3501 can be made smaller than in the configuration of FIG. 7A.

In FIG. 7C, which is a modification of the third embodiment, a second potential group 406 is arranged on the first surface 3502A of the circuit board 3502, and a first potential group 415 is arranged on the second surface 3502B, which is the back surface. and a third potential group 405 are arranged. By arranging the first potential group 415 and the third potential group 405 on the second surface 3502B, the distance between adjacent potential groups becomes the distance A, and the circuit board The area of 3502 can be reduced.

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

Furthermore, the second potential group 406 is provided in a region that is not directly behind the region where the first potential group 415 is provided.

Further, the third potential group 405 is arranged directly behind the region where the first potential group 415 is provided, or directly behind the region where the second potential group 406 is provided.

Note that if the necessary insulation distance between the first potential group 415 and the second potential group 406 can be secured with thickness A or thickness B, the first A potential group 415 may be arranged.

In Embodiments 2 and 3, if the potential group exists at the edge of the circuit board 500 (near the edge) or if the board has a through hole that penetrates the front and back surfaces, the front and back It is also necessary to consider the creepage distance that extends around the area.

[Example 4]
Next, a configuration effective for downsizing the connector will be described.

FIG. 8 shows a schematic cross-sectional view of the connector 403 shown in FIG. The configuration is such that connector portions corresponding to each potential group (third circuit) 405 are mixed.

That is, this embodiment has a connector configuration in which connector portions corresponding to each potential group are arranged within a single connector 403. The connector 403 includes a male connector with a pin provided on either the fixing device 200 or the image forming apparatus 100 main body, and a female connector with a pin hole provided on the other side corresponding to the pin. , is composed of. The circles in FIGS. 8 and 9 schematically indicate the arrangement of pins or pin holes in each connector portion. Although not shown, the connector 403 is provided with a fitting shaped portion for positioning the male connector and the female connector to maintain the connection between the pin and the pin hole.

Between the connector part of the first potential group 415 and the connector part of the third potential group 405 (between the pins included in the connector part of the first potential group 415 and the pins included in the connector part of the third potential group 405) Let A be the predetermined distance required for insulation at the shortest distance between Similarly, between the connector part of the third potential group 405 and the connector part of the second potential group 406 (between the pins of the connector part of the third potential group 405 and the pins of the connector part of the second potential group 406). Let B be the predetermined distance required for insulation. Also, between the connector part of the first potential group 415 and the connector part of the second potential group 406 (between the pins of the connector part of the first potential group 415 and the pins of the connector part of the second potential group 406). Let C be the predetermined distance required for insulation (shortest distance). Here, the relationship is A=B<C. A and B assume insulation distances equivalent to basic insulation. C assumes an insulation distance equivalent to reinforced insulation.

FIG. 8(A) is a schematic cross-sectional view showing the arrangement of connector parts corresponding to each potential group in the connector 403 in Example 1. From the left in the cross section of the connector, the connector portions of the first potential group 415, the connector portions of the third potential group 405, and the connector portions of the second potential group 406 are arranged in this order. That is, the connector part of the first potential group 415 is arranged on one side of the connector part of the third potential group 405, and the connector part of the second potential group 406 is arranged on the other side, which is the opposite side. ing. The sum of the distances between each potential group is A+B, and this is an example of arranging each potential group so that the sum of the distances between each potential group is the minimum while ensuring the distance necessary for insulation between each potential group. . In FIG. 8A, consideration is given to reducing the distance required for insulation by removing the metal parts necessary for the wiring between each potential group. For example, if a connector with more pins than required for each potential group is used to realize the potential group arrangement shown in FIG. The empty pin and the metal part provided corresponding to the empty pin are removed from the connector and used. By doing so, it is possible to realize a potential group arrangement configuration that secures the necessary insulation distance using a more compact connector (a connector with a smaller number of pins).

FIG. 8(B) is a schematic cross-sectional view showing the connector arrangement within the connector 403 in a comparative example. In the comparative example, the connector parts of the first potential group 415, the connector parts of the second potential group 406, and the connector parts of the third potential group 405 are arranged in this order from the left in the connector cross section. When arranged in this way, the sum of distances between each potential group is C+B, which is a larger value than the sum of distances A+B shown in FIG. 8(A). Therefore, the required connector size becomes large.

FIG. 8C is a cross-sectional view of the connector 403 in which pins and pin holes are arranged in two rows. The first and second columns are arranged so that they have the same potential, and the distance between the first and second columns is shortened. Further, as in FIG. 8A, the connector sections of the first potential group 415, the third potential group 405, and the second potential group 406 are arranged in this order from the left in the connector cross section. . By arranging them in this way, the distance required for insulation between each potential group can be ensured, and the sum of the distances between each potential group can be minimized.

Therefore, according to the circuit configuration of this embodiment, the connector can be made smaller, and the fixing device can be made smaller.
Note that the arrangement shown in Example 4 is only an example of an arrangement in which a predetermined distance necessary for electrical insulation is secured between each potential group, and the sum of the distances between each potential group is the minimum. It's just that. Various configurations can be adopted depending on the combination of the number of potential groups and the required insulation distance.

[Example 5]
FIG. 9 is a diagram showing the connector arrangement in Example 5. This embodiment has a configuration including a plurality of connectors 403 corresponding to each potential group. That is, an independent connector 403 is provided for each potential group.
Note that, in the fifth embodiment, descriptions of components common to the fourth embodiment will be omitted. Items in the fifth embodiment that are not particularly described here are the same as those in the fourth embodiment.

FIG. 9(A) is a diagram in which connectors 403(a), 403(b), and 403(c) are arranged in a straight line. A first potential group 415 is connected to the connector 403(a), a third potential group 405 is connected to the connector 403(b), and a second potential group 406 is connected to the connector 403(c). As in the first embodiment, let A be the predetermined distance required to insulate the first potential group 415 and the third potential group 405. Similarly, let B be the predetermined distance required to insulate the third potential group 405 and the second potential group 406, and let B be the predetermined distance necessary to insulate the first potential group 415 and the second potential group 406. Let it be C. Here, as in the first embodiment, the relationship is A=B<C.

As shown in FIG. 9(A), even if the connector is divided into each potential group, the arrangement of each connector is changed from the left side of the connector cross section to the first potential group 415, the third potential group 405, and the second potential group. By arranging them in the order of the potential groups 406, the same effect as in the first embodiment can be obtained. That is, the connectors can be arranged in the minimum space while ensuring the distance required for insulation between each potential group.

FIG. 9(B) is a diagram showing a cross section when pins and pin holes are lined up in two rows in each connector. The first and second columns are arranged so that they have the same potential, and the distance between the first and second columns is shortened. Further, similarly to FIG. 9A, the connectors are arranged 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 connector cross section. By arranging them in this manner, the connectors can be arranged in the minimum space while ensuring the distance necessary for insulation between each potential group.

FIG. 9(C) is a diagram in which connectors 403(a), 403(b), and 403(c) are arranged in a triangular shape. At this time, the arrangement that minimizes the sum of the distances between each potential group while ensuring the distance necessary for insulation between the potential groups is as shown in FIG. 9(C), where the distance C is the hypotenuse. The connectors 403(a), 403(b), and 403(c) are arranged side by side. That is, between the connectors 403(a), 403(b), and 403(c), the first side with length A and the second side with length B are equilateral, and the length is The arrangement is such that an isosceles triangle can be drawn with the third side C as the base.

Note that the configuration of the connector shown in Example 5 is only an example. For example, the first potential group 415 and the third potential group 405 may be included in one connector, and the second potential group 406 may be included in another connector. That is, various configurations can be adopted depending on the combination of the number of potential groups and the required insulation distance.

200...Fixing device (image heating device), 300...Heater, 305...Substrate, 302a-1 to 302a-7, 302b-1 to 302b-7...Heating element, 408 to 414...Triac, T1-1 to T1-7 , T2-1 to T2-6...thermistor, 400...control circuit, 402...temperature detection circuit, 403...connector, 405...third potential group (thermistor potential, etc.), 406...second potential group, 415...th 1 potential group

Claims (12)

An image forming apparatus that forms a toner image on a recording material,
A cylindrical film, a heater that generates heat using electric power supplied from an AC power supply and that contacts the inner surface of the film, a roller that forms a fixing nip that pinches and conveys a recording material together with the heater, and the heater a temperature sensing element that detects the temperature of the heater provided on a surface that contacts the film, and a fixing unit that heats and fixes the toner image formed on the recording material to the recording material;
a circuit board provided with a power control circuit that controls power supplied to the heater;
Equipped with
A circuit including a circuit in the fixing unit and the power control circuit includes a first circuit that supplies power from the AC power source to the heater, and a second circuit that is electrically insulated from the first circuit. a third circuit insulated from both the first circuit and the second circuit;
The third circuit has a temperature detection circuit to which the temperature detection element and the signal line of the temperature detection element are connected,
All of the first to third circuits are provided on at least one surface of the circuit board,
On the straight line where all the first to third circuits exist on the one surface of the circuit board, the first to third circuits are the first circuit, the third circuit, arranged in the order of the second circuit ,
The distance between the first circuit and the third circuit and the distance between the third circuit and the second circuit are both shorter than a distance that satisfies basic insulation, and a distance that satisfies basic insulation. An image forming apparatus characterized in that: The first circuit and the third circuit are circuits that do not have electrical parts or wiring that can be touched by the user, and the second circuit is a circuit that has electrical parts or wiring that can be touched by the user. The image forming apparatus according to claim 1 . An image forming apparatus that forms a toner image on a recording material,
A heater that generates heat using a cylindrical film and electric power supplied from an AC power source.
A heater that contacts the inner surface of the film, a roller that forms a fixing nip portion that nip and conveys the recording material together with the heater, and a temperature sensor that detects the temperature of the heater that is provided on the side of the heater that contacts the film. a fixing unit that heats and fixes the toner image formed on the recording material onto the recording material;
a first circuit board provided with a power control circuit for controlling power supplied to the heater; and a second circuit board disposed overlapping the first circuit board;
Equipped with
A circuit including a circuit in the fixing unit and the power control circuit includes a first circuit that supplies power from the AC power source to the heater, and a second circuit that is electrically insulated from the first circuit. a third circuit insulated from both the first circuit and the second circuit;
The third circuit has a temperature detection circuit to which the temperature detection element and the signal line of the temperature detection element are connected,
The first circuit is disposed on one surface of the first circuit board, and the other surface of the first circuit board is the second circuit board that is a surface facing the first circuit board. The third circuit is disposed between one surface of the second circuit board, and the second circuit is disposed on the other surface of the second circuit board,
An image forming apparatus characterized in that the thickness of the first circuit board and the thickness of the second circuit board are both thinner than a thickness that satisfies reinforced insulation and are thick enough to satisfy basic insulation. The first circuit and the third circuit are circuits that do not have electrical parts or wiring that can be touched by the user, and the second circuit is a circuit that has electrical parts or wiring that can be touched by the user. The image forming apparatus according to claim 3, characterized in that: An image forming apparatus that forms a toner image on a recording material,
A cylindrical film, a heater that generates heat using electric power supplied from an AC power supply and that contacts the inner surface of the film, a roller that forms a fixing nip that pinches and conveys a recording material together with the heater, and the heater a temperature sensing element that detects the temperature of the heater provided on a surface that contacts the film, and a fixing unit that heats and fixes the toner image formed on the recording material to the recording material;
a circuit board provided with a power control circuit that controls power supplied to the heater;
Equipped with
A circuit including a circuit in the fixing unit and the power control circuit includes a first circuit that supplies power from the AC power source to the heater, and a second circuit that is electrically insulated from the first circuit. a third circuit insulated from both the first circuit and the second circuit;
The third circuit has a temperature detection circuit to which the temperature detection element and the signal line of the temperature detection element are connected,
The first circuit is arranged on a first surface of the circuit board, and the region is on a second surface that is the back surface of the first surface and is not directly behind the region where the first circuit is provided. the second circuit is disposed in the area , and the third circuit is disposed on at least one of the first and second surfaces;
Distance between the first circuit and the third circuit when the third circuit is arranged on the first surface and when the third circuit is arranged on the second surface In this case, the distance between the third circuit and the second circuit is both shorter than the distance that satisfies the reinforced insulation, and the distance that satisfies the basic insulation.
An image forming apparatus characterized in that the thickness of the circuit board is thinner than the thickness that satisfies reinforced insulation and is thick enough to satisfy basic insulation . 6. The image forming apparatus according to claim 5, wherein the third circuit is arranged directly behind an area where the first circuit is provided or directly behind an area where the second circuit is provided. Device. The first circuit and the third circuit are circuits that do not have electrical parts or wiring that can be touched by the user, and the second circuit is a circuit that has electrical parts or wiring that can be touched by the user. The image forming apparatus according to claim 5 , characterized in that: An image forming apparatus that forms a toner image on a recording material,
an apparatus main body including an image forming section that forms a toner image on a recording material;
A cylindrical film, a heater that generates heat using electric power supplied from an AC power source and that contacts the inner surface of the film, a roller that forms a fixing nip that pinches and conveys a recording material together with the heater, and the heater a temperature sensing element for detecting the temperature of the heater provided on a surface side in contact with the film, the fixing unit heat-fixes a toner image formed on a recording material onto the recording material, the fixing unit comprising: the fixing unit that is removably attachable to the apparatus main body;
a circuit board provided with a power control circuit that controls power supplied to the heater;
a connector that electrically connects the fixing unit and the power control circuit;
Equipped with
A circuit including a circuit in the fixing unit and the power control circuit includes a first circuit that supplies power from the AC power supply to the heater, and a second circuit that is electrically insulated from the first circuit. a third circuit insulated from both the first circuit and the second circuit;
The third circuit has a temperature detection circuit to which the temperature detection element and the signal line of the temperature detection element are connected,
In the connector, the first to third circuits are arranged in the order of the first circuit, the third circuit, and the second circuit,
The distance between the first circuit and the third circuit and the distance between the third circuit and the second circuit are both shorter than a distance that satisfies basic insulation, and a distance that satisfies basic insulation. An image forming apparatus characterized in that: The first circuit and the third circuit are circuits that do not have electrical parts or wiring that can be touched by the user, and the second circuit is a circuit that has electrical parts or wiring that can be touched by the user. The image forming apparatus according to claim 8 . The image forming apparatus according to claim 8 , wherein the connector is a single connector. 9. The image forming apparatus according to claim 8 , wherein the connectors are three connectors corresponding to each of the first circuit, the second circuit, and the third circuit. The connector includes a first connector that includes one of the first circuit, the second circuit, and the third circuit, and a second connector that includes the remaining two circuits. The image forming apparatus according to claim 8 .

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