JP7277559B2 - image forming device - Google Patents

Description

The present invention improves the glossiness of a toner image by reheating a fixed toner image on a recording material or a fixing device installed in an image forming apparatus such as a copier or printer using an electrophotographic method or an electrostatic recording method. It relates to an image heating device such as a glossing device that improves the The present invention also relates to an image forming apparatus including this image heating device.

2. Description of the Related Art Conventionally, as an image heating device provided in an image forming apparatus, an endless belt (also referred to as an endless film), a flat heater that contacts the inner surface of the endless belt, and a roller that forms a nip portion together with the heater through the endless belt. and a device having When small-size paper is continuously printed by an image forming apparatus equipped with this image heating device, a phenomenon occurs in which the temperature of a region where paper does not pass in the longitudinal direction of the nip rises gradually (temperature increase in non-paper-passing portion). If the temperature of the non-sheet-passing area becomes too high, it may damage parts in the apparatus. As one method for suppressing the temperature rise in the non-sheet-passing area, a heating element is arranged between two conductors arranged along the longitudinal direction, and at least one of the two conductors is set to the paper size. A heater has been proposed that is divided into corresponding widths and heat generation is controlled for each heat generation block (Patent Document 1).

JP 2017-54071 A

However, when a plurality of thermistors (temperature detection elements) are arranged in each divided heat generating block as in Patent Document 1, the number of wirings connected to the thermistors increases as the heat generating area increases. There is a concern that this may hinder the miniaturization of the device.

SUMMARY OF THE INVENTION An object of the present invention is to provide a technique capable of reducing the number of temperature detecting elements and miniaturizing the device.

In order to achieve the above object, the image forming apparatus of the present invention includes:
A fixing unit for fixing a toner image formed on a recording material to the recording material, comprising: a substrate; a plurality of heat generating elements arranged on the substrate in a longitudinal direction of the substrate; a first temperature sensing element provided at a position on the substrate corresponding to the first heat generating element of the plurality of heat generating elements corresponding to a second heat generating element different from the first heat generating element a fixing section having a heater provided with a second temperature sensing element provided at a position on the substrate;
a first semiconductor element provided in a power supply path from a power supply to a first heating element of the plurality of heating elements;
a second semiconductor element provided in a power supply path from the power supply to a second heating element different from the first heating element among the plurality of heating elements;
A control unit for controlling the first semiconductor element and the second semiconductor element, the control unit controlling the first semiconductor element in accordance with the temperature detected by the first temperature detection element to detect the second temperature a control unit that controls the second semiconductor element according to the temperature detected by the detection element;
and forming a toner image on a recording material,
The first heating element is arranged at the endmost end in the longitudinal direction among the plurality of heating elements, and the second heating element is arranged next to the first heating element in the longitudinal direction. ,
The first semiconductor element is connected in series with the second semiconductor element,
power supplied to the second heating element is controlled by controlling the second semiconductor element;
Power supplied to the first heating element is controlled by controlling the first semiconductor element and the second semiconductor element.

According to the present invention, it is possible to reduce the number of temperature detection elements and reduce the size of the device.

1 is a sectional view of an image forming apparatus according to an embodiment of the present invention; Cross-sectional view of the fixing device of Example 1 Heater configuration diagram of Example 1 Control circuit diagram in Example 1 Control flowchart in embodiment 1 Heater configuration diagram in Example 2 Control circuit diagram in Example 2 Control flowchart in embodiment 2 Heater configuration diagram in Example 3 Control circuit diagram in Example 3 Heater configuration diagram in Example 4 Control circuit diagram in Example 4 Heater configuration diagram of Example 5 Control circuit diagram in Example 5 Explanatory drawing of the disconnection detection part in Example 5 Explanatory drawing of the disconnection detection part in Example 6

BEST MODE FOR CARRYING OUT THE INVENTION A mode for carrying out the present invention will be exemplarily described in detail below based on an embodiment with reference to the drawings. However, the dimensions, materials, shapes and relative arrangement of the components described in this embodiment should be appropriately changed according to the configuration of the device to which the invention is applied and various conditions. That is, it is not intended to limit the scope of the present invention to the following embodiments.

[Example 1]
FIG. 1 is a schematic cross-sectional view of an image forming apparatus according to an embodiment of the invention. The image forming apparatus 100 of this embodiment is a laser printer that forms an image on a recording material using an electrophotographic method.

When a print signal is generated, the scanner unit 21 emits a laser beam modulated according to image information to scan the surface of a photosensitive drum (electrophotographic photosensitive member) 19 charged to a predetermined polarity by the charging roller 16 . As a result, an electrostatic latent image is formed on the photosensitive drum 19 as an image carrier. The electrostatic latent image on the photosensitive drum 19 is developed as a toner image (developer image) by supplying toner charged to a predetermined polarity from the developing roller 17 to the electrostatic latent image. On the other hand, a recording material (recording paper) P stacked in a paper feed cassette 11 is fed one by one by a pickup roller 12 and conveyed toward a registration roller pair 14 by a conveying roller pair 13 . Further, the recording material P is conveyed from the registration roller pair 14 to the transfer position in synchronization with the timing at which the toner image on the photosensitive drum 19 reaches the transfer position formed by the photosensitive drum 19 and the transfer roller 20 as a transfer member. be. The toner image on the photosensitive drum 19 is transferred to the recording material P while the recording material P passes the transfer position. After that, the recording material P is heated by a fixing device (image heating device) 200 as a fixing section (image heating section), and the toner image is fixed on the recording material P by heating. The recording material P carrying the fixed toner image is discharged to the paper discharge tray 31 above the image forming apparatus 100 by the pair of conveying rollers 26 and 27 .

The photoreceptor 19 is cleaned by removing residual toner and the like from the surface thereof by a cleaner 18 . The paper feed tray (manual feed tray) 28 has a pair of recording paper regulating plates whose width can be adjusted according to the size of the recording paper P, and is provided to handle recording paper P of sizes other than the standard size. It is The pickup roller 29 is a roller for feeding the recording paper P from the paper feed tray 28 . The motor 30 drives the fixing device 200 and the like. Power is supplied to the fixing device 200 from a control circuit 400 as an energization control unit connected to a commercial AC power supply 401 .

The above-described photosensitive drum 19, charging roller 16, scanner unit 21, developing roller 17, and transfer roller 20 constitute an image forming section that forms an unfixed image on the recording material P. FIG. Further, in this embodiment, a developing unit including the photosensitive drum 19, the charging roller 16 and the developing roller 17, and a cleaning unit including the cleaner 18 are configured as the process cartridge 15 so as to be attachable to and detachable from the main body of the image forming apparatus 100. ing.

FIG. 2 is a cross-sectional view of the fixing device 200 of this embodiment. The fixing device 200 includes a fixing film (hereinafter referred to as film) 202 , a heater 300 that contacts the inner surface of the film 202 , a pressure roller 208 that forms a fixing nip portion N together with the heater 300 via the film 202 , and a metal stay 204 . and have

The film 202 is a cylindrical heat-resistant film, which is also called an endless belt or an endless film, and the material of the base layer is a heat-resistant resin such as polyimide, or a metal such as stainless steel. Also, an elastic layer such as heat-resistant rubber may be provided on the surface of the film 202 . The pressure roller 208 has a metal core 209 made of iron, aluminum or the like, and an elastic layer 210 made of silicone rubber or the like. The heater 300 is held by a holding member 201 made of heat-resistant resin. The holding member 201 also has a guide function of guiding the rotation of the film 202 . A metal stay 204 applies a spring pressure (not shown) to the holding member 201 . The pressure roller 208 receives power from the motor 30 and rotates in the direction of the arrow. The rotation of the pressure roller 208 causes the film 202 to rotate. The recording paper P carrying the unfixed toner image is heated while being nipped and conveyed in the fixing nip portion N to be fixed.

The heater 300 is heated by heating elements (heating resistors) 302a and 302b provided on a ceramic substrate 305, which will be described later. Abutting the heater 300 is a safety element 212 (FIG. 4). The safety protection element 212 is, for example, a thermoswitch or a temperature fuse, and is activated to cut off the power supplied to the heater 300 when the heater 300 generates abnormal heat. Thermistors T1 (T1-1 to T1-7, see FIG. 3B) and thermistors T2 (T2-2 to T2-6, FIG. 3B) are provided on the sliding surface side of the heater 300 with the film 202. ) are installed.

The configuration of the heater 300 according to this embodiment will be described with reference to FIG. 3A is a sectional view of the heater 300, and FIG. 3B is a plan view of each layer of the heater 300. FIG. FIG. 3B shows the conveyance reference position X0 of the recording material P in the image forming apparatus 100 of this embodiment. The transport reference in this embodiment is the center reference, and the recording material P is transported so that the center line in the direction orthogonal to the transport direction is along the transport reference position X0. FIG. 3A is a cross-sectional view of the heater 300 at the transport reference position X0.

As shown in FIG. 3A, the heater 300 has conductors 301 and 303 over a substrate 305 . The conductor 301 is separated into a conductor 301a arranged on the upstream side in the conveying direction of the recording material P and a conductor 301b arranged on the downstream side. Further, in the heater 300, a heating element 302 that generates heat by electric power supplied through the conductors 301 and 303 is provided between the conductors 301 and 303 on the substrate. The heating element 302 is separated into a heating element 302a arranged on the upstream side in the conveying direction of the recording material P and a heating element 302b arranged on the downstream side. Further, an electrode E3 is provided for power supply. Furthermore, an insulating protective glass 308 covers the back surface layer 2 except for the electrode E3. The heater 300 (substrate 305) is arranged so that its longitudinal direction is orthogonal to the conveying direction of the recording material P. As shown in FIG.

As shown in FIG. 3B, on the back layer 1 of the heater 300, a heating block (heating region) consisting of a set of conductors 301, 303, a heating element 302, and an electrode E3 is formed in the longitudinal direction of the heater 300. Seven are provided (HB1 to HB7). In order to represent the correspondence relationship with the seven heat generating blocks HB1 to HB7, the members constituting each heat generating block have, for example, heat generating blocks corresponding to the end of each code, such as heat generating elements 302a-1 to 302a-7. are numbered. The same applies to the heating element 302b, the conductors 301a and 301b, the conductor 303, and the electrode E3.

The surface protective layer 308 of the back layer 2 of the heater 300 is formed so as to expose the electrodes E3-1 to E3-7, E4, and E5, and an electric contact (not shown) can be connected from the back side of the heater 300. It is configured. Then, power can be supplied to each heat generating block independently, and power supply control can be performed independently. By dividing into seven heating blocks in this manner, four paper passing areas such as AREA1 to AREA4 can be formed. In this embodiment, AREA1 is classified as A5 paper, AREA2 is classified as B5 paper, AREA3 is classified as A4 paper, and AREA4 is classified as Letter paper. Since the seven heat generating blocks can be controlled independently, the heat generating blocks to be supplied with power are selected according to the size of the recording paper P. The number of heat generating regions and the number of heat generating blocks are not limited to the numbers in this embodiment. Further, the heat generating elements 302a-1 to 302a-7 and 302b-1 to 302b-7 in each heat generating block are not limited to the continuous pattern as described in this embodiment, and are provided with gaps. A strip-shaped pattern may also be used.

On the sliding surface layer 1 of the heater 300 (on the surface of the substrate 305 opposite to the surface on which the heating element is provided), a thermistor T1- is provided as a temperature detection element for detecting the temperature of each heating block of the heater 300. 1 to T1-7 and thermistors T2-2 to T2-6 are installed. The thermistors T1-1 to T1-7 are mainly used for temperature control of each heat generating block, and therefore are arranged at the center of each heat generating block (the center in the longitudinal direction of the substrate). The thermistors T2-2 to T2-6 are edge thermistors for detecting the temperature of non-paper-passing areas (edges) when the recording paper narrower than the heat-generating area is passed. Therefore, except for the heat-generating blocks at both ends where the heat-generating area is narrow, the heat-generating blocks are arranged toward the outside of the heat-generating blocks with respect to the transport reference position X0. One ends of thermistors T1-1 to T1-7 are connected to conductors ET1-1 to ET1-7 for detecting resistance values of thermistors, respectively, and the other ends are commonly connected to a conductor EG9. One ends of thermistors T2-2 to T2-6 are connected to conductors ET2-2 to ET2-6, respectively, and the other ends are commonly connected to conductor EG10. Thus, the width L of the heater 300 tends to increase according to the number of thermistors and the number of conductors.

The sliding surface layer 2 of the heater 300 has a surface protective layer 309 made of a slidable glass coating. The surface protection layer 309 is provided except for both end portions of the heater 300 in order to provide electrical contacts to the conductors of the sliding surface layer 1 .

FIG. 4 is a circuit diagram showing the control circuit 400 of the heater 300 according to the first embodiment. A commercial AC power supply 401 is connected to the image forming apparatus 100 . The power supply voltages Vcc1 and Vcc2 are DC power generated by an AC/DC converter (not shown) connected to the AC power supply 401 . AC power supply 401 is connected to heater 300 via relays 430 and 440 and triacs 441-447. The triacs 441-447 are turned on/off by control signals FUSER1-FUSER7 from the CPU 420. FIG. Triac 441
447 are omitted from the drawing. By selectively controlling the triacs 441 to 447 as a plurality of semiconductor elements, the energization of a plurality of heating elements can be selectively controlled, and a plurality of heating regions divided in the longitudinal direction can be individually selectively controlled. can generate heat.

A thermistor temperature detection circuit will be described. Conductors EG9 and EG10 are connected to ground potential. All the thermistors T1-1 to T1-7 and T2-2 to T2-6 described with reference to FIG. 3 are divided by resistors 451 to 457 and 462 to 466 pulled up to Vcc1. The divided voltages are detected by the CPU 420 as temperature signals Th1-1 to Th1-7 and Th2-2 to Th2-6. The temperature is detected by converting to
In the internal processing of the CPU 420, based on the set temperature and the temperatures detected by the thermistors T1-1 to T1-7, the power to be supplied is calculated by PI control, for example. The ON timing of the FUSER 1 to FUSER 7 signals is generated by the CPU 420 based on the timing signal ZEROX synchronized with the zero potential of the AC power supply 401 generated by the zero cross detector 421 . Based on the zero cross timing of the AC power supply 401, the phase angle (phase control) and wave number (wave number control) corresponding to the power to be supplied are converted into control levels, and the triacs 441 to 447 are controlled according to the control conditions.

The relays 430, 440 and protection circuits will be described. The relays 430 and 440 are used as means for cutting off power to the heater 300 when the temperature of the heater 300 rises excessively due to failure or the like.

The operation of relay 430 will be described. When the CPU 420 sets the RLON signal to a high state, the transistor 433 is turned on, the secondary coil of the relay 430 is energized from the power supply voltage Vcc2, and the primary contact of the relay 430 is turned on. When the RLON signal goes low, the transistor 433 is turned off, the current flowing from the power supply voltage Vcc2 to the secondary coil of the relay 430 is cut off, and the primary contact of the relay 430 is turned off. A resistor 434 is a resistor that limits the base current of the transistor 433 . The operation of relay 440 and transistor 435 is similar.

The operation of the safety circuit using relays 430 and 440 will be described. When the detected temperature of one of the thermistors T1-1 to T1-7 exceeds a set predetermined value, the comparison unit 431 operates the latch unit 432, and the latch unit 432 latches the RLOFF1 signal to the Low state. . When the RLOFF1 signal becomes Low, even if the CPU 420 changes the RLON signal to High, the transistor 433 is kept OFF, so the relay 430 can be kept OFF (safe state). Similarly, when the thermistors T2-2 to T2-6 exceed the set predetermined value, the comparison section 437 operates the latch section 436 to latch the RLOFF2 signal in the Low state. In this manner, the relays 430 and 440 are also used as means for cutting off power to the heater 300 when the temperature of the heater 300 is excessively increased due to failure or the like.

Here, the relationship between the driving configuration using the triacs 441 to 447 and the number of thermistors, which is a feature of this embodiment, will be described. The triac 441 driving the heat generating block HB1 is connected in series with the triac 442 driving the adjacent heat generating block HB2. When only the triac 442 is driven, only the heating block HB2 is heated. When both the triacs 441 and 442 are driven, the heating blocks HB1 and HB2 generate heat. In this configuration, only the heating block HB1 does not generate heat for control reasons. Further, since the heat generating block HB1 outside the heat generating block HB2 in the longitudinal direction of the heater 300 is connected in series in two stages, the heat generating area can be controlled for each paper size.

By the way, a safety circuit is provided by detecting the temperature of the thermistor so that the heater 300 does not generate heat to an abnormal temperature in the event that an abnormality occurs in the control of the heater 300 due to a malfunction of the CPU 420 or the like. This embodiment has a safety circuit so that even if one of the constituent elements fails and does not function, the abnormality of the heater 300 is detected and the relays 430 and 440 are turned off to protect the heater 300 . Therefore, in the heating block HB3, for example, there are two thermistors, T1-3 and T2-3, and corresponding comparators and latches. can do. Since the heating blocks HB2, 4, 5, and HB are also controlled by independent driving configurations, two thermistors are similarly configured. On the other hand, the heating block HB1 is protected by one of the thermistors T1-1 because it will not generate abnormal heat unless a single failure such as disconnection occurs at point P in the drawing. can be done. The same applies to the heat generating block HB7, and the description thereof is omitted. Since the heat generating blocks HB1 and HB7 have a narrow heat generating area, one thermistor is used both as an end thermistor for detecting the temperature of the non-sheet-passing area (end) and as a temperature control thermistor.

Thus, in the heating block HB1 driven by the semiconductor element in the latter stage of the semiconductor element that drives the heating block HB2, even if the number of thermistors is smaller than that of the heating block HB2, even if one failure state can be protected.
In this embodiment, a triac 441 for driving the heat generating block HB1 located longitudinally outside (end side) of the heat generating block HB2 is connected in series with a triac 442 for driving the heat generating block HB2. and That is, the heating block HB2 serves as the second heating area, the heating block HB1 serves as the first heating area, the heating elements 302a-2 and 302b-2 serve as the second heating elements, and the heating elements 302a-1 and 302b-1. correspond to the first heating element, respectively. However, the configuration to which the present invention can be applied is not limited to such a configuration. For example, the triac 442 for driving the heat generating block HB2 located longitudinally outside (end side) of the heat generating block HB3 is connected in series with the triac 443 for driving the heat generating block HB2. may With such a configuration, the number of thermistors for detecting the temperature of the heat generating block HB2 can be made smaller than the number of thermistors for detecting the temperature of the other heat generating blocks.

FIG. 5 is a control flow chart in the first embodiment. When a print request is received in S500, the process proceeds to the following steps. In S501, the RLON signal is output high to turn on the relays 430 and 440. As shown in FIG. In S502, the CPU 420 reads out a target temperature Ta previously stored in a memory built in the CPU 420 (not shown). In S503, the limit temperature (edge temperature rise) Tmax of the non-sheet passing portion temperature rise is read from the internal memory. In S<b>504 , the size of the recording paper P set in the paper feed cassette 11 is detected by paper size detection (not shown) in the paper feed cassette 11 . In S505-1 to S505-4, the paper size is determined, and in S506-1 to S506-4, the heat generating area (heating area) corresponding to the paper size is determined and the triac corresponding to the heat generating area is controlled. In S507, if the end thermistors T2-2 to T2-6 exceed the limit temperature Tmax for temperature rise in the non-sheet-passing area, the throughput is reduced in S508 to prevent failure of the fixing device 200 due to excessive temperature rise. to prevent Steps S502 to S508 are repeated until the print job is completed in S509. If the print job is completed, RLON is output to a low level in S510 to turn off the relays 430 and 440. FIG.

As described above, in the heat generating block in which the semiconductor elements for driving the heaters are connected in series in two stages, the number of thermistors can be reduced. can be done.

[Example 2]
A second embodiment of the present invention will be described. A control circuit 700 and a heater 600 according to the second embodiment are examples in which two heating regions connected in series are changed from the control circuit 400 described in the first embodiment. Among the configurations of the second embodiment, the same symbols are used for the configurations similar to those of the first embodiment, and the description thereof is omitted. In the second embodiment, matters that are not particularly described here are the same as in the first embodiment.

The configuration of a heater 600 according to this embodiment will be described with reference to FIG. 6A is a cross-sectional view of the heater 600 (a cross-sectional view near the transfer reference position X0 in FIG. 6B), and FIG. 6B is a plan view of each layer of the heater 600. FIG. As shown in FIG. 6B, in Example 2, in the sliding surface layer 1, only one thermistor is provided in the heating block HB5, unlike Example 1. As shown in FIG. The reason will be explained with reference to FIG. Note that a thermistor T3-4 is added to the heating block HB4 as compared with the first embodiment. This is because when A5 size paper is passed in the paper passing area AREA1 and is transported in a state of being shifted to one side in the longitudinal direction of the heater 600 with respect to the transport reference position X0, the non-sheet passing portion This is for detecting temperature rise.

FIG. 7 is a circuit diagram showing a control circuit 700 of the heater 600 according to the second embodiment. In this embodiment, the LIAC 445 that drives the heating block HB5 is connected in series after the TRIAC 443 that drives the heating block HB3. The heating block HB3 and the heating block HB5 have a symmetrical positional relationship in the longitudinal direction of the substrate 305 with respect to the transfer reference position X0, so even when the AREA2 is heated, control can be performed without being affected by this drive configuration. is. By connecting in this way, as in the first embodiment, when a failure occurs such that point S is disconnected, abnormal heat generation of the heater 600 can be detected and stopped by the thermistor T2-5. can reduce the number of thermistors compared to

FIG. 8 is a control flow chart in this embodiment. S500 to S503 are the same as in the first embodiment. In this flowchart, the case where B5 size corresponding to AREA2 is detected in the paper size detection in S801 will be described. When controlling the triacs 443 to 445 corresponding to the B5 size, in S802, the energization ratio of the triacs 443 and 445 is controlled at the same ratio of 100:100. In S803, when the temperatures detected by thermistors T2-3 and T2-5, which are end thermistors of the heating blocks HB3 and HB5, are TH2-3 and TH2-5, the difference between them is the temperature difference TΔ preset in S800. Check if it exceeds For example, when the temperature of the thermistor T2-5 is high and the temperature difference exceeds TΔ, in S804, it is assumed that the recording paper P is biased toward the heat generating block HB3, and the energization ratio of the triacs 443 and 445 is set to 100:50. to suppress the temperature rise in the non-sheet-passing area. In S805, similarly to the first embodiment, temperature rise in the non-sheet-passing portion is detected, and it is confirmed whether or not the temperatures detected by the thermistors T2-5 and T2-3 exceed the threshold value Tmax. If it exceeds, control is performed by lowering the throughput in S508. The above is repeated as a series of control until the print job is completed.

As described above, even if the pair of heat generating blocks that are in a symmetrical positional relationship with respect to the conveyance reference of the recording paper are connected in series instead of the heat generating blocks that are adjacent to each other, the driving configuration is the same as in the first embodiment. The number of thermistors can be reduced.

[Example 3]
A third embodiment of the present invention will be described. In the third embodiment, as a modified example of the drive configuration in the second embodiment, the semiconductor elements in the second stage of the semiconductor elements connected in series are short-circuited. In the present embodiment, since the recording paper P is prevented from being shifted to one side by a transport guide (not shown), it is possible to eliminate the triac 445 in the second embodiment so as to cause a short circuit. Among the configurations of the third embodiment, the configurations similar to those of the first and second embodiments are denoted by the same reference numerals, and descriptions thereof are omitted. In Example 3, matters that are not particularly described here are the same as those in Examples 1 and 2.

The configuration of a heater 900 according to this embodiment will be described with reference to FIG. 9A is a cross-sectional view of the heater 900 (cross-sectional view near the transfer reference position X0 in FIG. 9B), and FIG. 9B is a plan view of each layer of the heater 900. FIG. As shown in FIG. 9B, in the sliding surface layer 1, the number of thermistors in the heating block HB3 is one less than that of the second embodiment.

FIG. 10 is a circuit diagram showing the control circuit 901 of the heater 900 of Example 3. As shown in FIG. Even if one failure such as disconnection at point T occurs, the thermistor T2-5 can detect an abnormal condition and provide protection. Similarly, even if one failure such as disconnection of point U occurs, it can be protected by the thermistor T1-3. In other words, even in a configuration having fewer thermistors than the other heat generating blocks 1, 2, 4, 6, 7, protection against an abnormal state of the heater 900 can be performed.

As described above, the number of thermistors can be reduced even in the configuration in which the latter semiconductor element among the series-connected semiconductor elements is short-circuited.
In this embodiment, the heat generating blocks HB3 and HB5, which are located symmetrically in the longitudinal direction of the substrate with respect to the reference position for conveying the recording material, are energized by a single heat generating element. It is configured to be controlled by controlling the triac 443 . That is, the heating block HB3 serves as the third heating area, the heating block HB5 serves as the fourth heating area, the heating elements 302a-3 and 302b-3 serve as the third heating elements, and the heating elements 302a-5 and 302b-5. correspond to the fourth heating element, respectively. However, the configuration to which the present invention can be applied is not limited to such a configuration. For example, a single triac 442 controls energization of the heating elements 302a-2 and 302b-2 for heating the heating block HB2 and energization of the heating elements 302a-6 and 302b-6 for heating the heating block HB6. It may be configured as

[Example 4]
A fourth embodiment of the present invention will be described. A control circuit 904 for the heater 903 of the fourth embodiment has a configuration in which the configurations of the first and third embodiments are combined. Among the configurations of the fourth embodiment, the configurations similar to those of the first to third embodiments are denoted by the same reference numerals, and descriptions thereof are omitted. In Example 4, matters not specifically described here are the same as in Examples 1-3.

FIG. 11 is a circuit diagram showing the control circuit 904 of the heater 903 according to this embodiment. 11A is a cross-sectional view of the heater 903 (cross-sectional view near the transfer reference position X0 in FIG. 9B), and FIG. 9B is a plan view of each layer of the heater 903. FIG. As shown in FIG. 11B, the heater 903 of this embodiment has the smallest number of thermistors in the sliding surface layer 1 as compared with the first and third embodiments.

FIG. 12 is a circuit diagram showing the control circuit 904 of the heater 903. As shown in FIG. The heating blocks HB1, HB3, HB5, and HB7 have one thermistor by adopting the configuration described in the first and third embodiments. This embodiment also shows that a triac 441 and a triac 447 are arranged in the fixing device 200 . By doing so, the number of AC wires connecting the control circuit 904 and the fixing device 200 can be reduced, so that the number of connector pins and electric wires can be reduced. Similarly, the triacs 442 to 446 may also be arranged inside the fixing device 200 .

As described above, since there are a plurality of heat generating blocks that are driven by serial connection, it is possible to protect against abnormal conditions with a smaller number of thermistors.
0 can be made smaller. Furthermore, by arranging the triac in the fixing device, wiring can be reduced, and the size of the image forming apparatus can be reduced.

It should be noted that, throughout the first to fourth embodiments, the configuration is configured to protect against one failure, but the configuration is not limited to one failure, and may be configured to protect against two or more failures. . Moreover, the number of semiconductor elements connected in series is not limited to two stages, and may be a connection configuration of three or more stages.

[Example 5]
Embodiment 5 of the present invention will be described with reference to FIGS. 13 to 15. FIG. The fifth embodiment is a configuration example that can further reduce the number of thermistors in HB1 and HB7 in the heater 300 described in the first embodiment. In contrast to the control circuit 400 of the first embodiment, the fifth embodiment includes a disconnection detection unit 1002 capable of detecting disconnection at point P and a disconnection detection unit 1003 capable of detecting disconnection at point Q. A control circuit 1001 is provided. Among the configurations of the fifth embodiment, the same symbols are used for the configurations similar to those of the above-described embodiments, and the description thereof is omitted. In Example 5, matters not specifically described here are the same as those in the above example.

FIG. 13 shows a cross-sectional view and a plan view of the heater 1000. FIG. Compared with Example 1, in the sliding surface layer 1 of FIG. 6, the number of thermistors per block is increased by one. Since each heating block has three thermistors, it has three thermistors so that an abnormality of the heater 300 can be detected even if two components fail and do not function. On the other hand, each of HB1 and HB7 has one thermistor, which is two fewer thermistors than the other heat generating blocks. The reason will be explained with reference to FIG. 14 .

FIG. 14 is a circuit diagram showing the control circuit 1001 of the heater 1000 according to the fifth embodiment. All thermistors T1-1 to T1-7, T2-2 to T2-6, T3-2 to T3-6 shown in FIG. 476 and each voltage is divided. The divided voltages are detected by the CPU 420 as Th1-1 to Th1-7 signals, Th2-2 to Th2-6 signals, and TH3-2 to 3-6, and temperature detection is performed. In this embodiment, a disconnection detection unit 1002 and a disconnection detection unit 1003 are provided so as to detect disconnection at points P and Q. FIG. Detection signals Di 1002 , Di 1003 , Di 1004 , and Di 1005 of disconnection detection units 1002 and 1003 are connected to latch units 432 and 436 or CPU 420 . When a disconnection is detected, the disconnection detection unit 1002 outputs disconnection detection signals Di1002 and Di1004, and the disconnection detection unit 1003 outputs disconnection detection signals Di1003 and Di1005. When Di1004 and Di1005 are output, the latch units 432 and 436 operate to latch the RLOFF1 signal and the RLOFF2 signal to the Low state and turn off the relays 430 and 440 . When Di1002 and Di1003 are output, CPU 420 outputs FUSER1-FUSER7 signals so that triacs 441-447 are turned off. Internal circuits of the disconnection detection unit 1002 and the disconnection detection unit 1003 will be described with reference to FIG.

Here, the relationship between disconnection detection and the number of thermistors, which is a feature of this embodiment, will be described. In this embodiment, as in the first embodiment, triacs 441 and 447 driving heat generating blocks HB1 and HB7 are connected in series with triacs 442 and 446 driving adjacent heat generating blocks HB2 and HB6, respectively. Therefore, as long as one failure does not occur such as disconnection at points P and Q in the figure, only the heating blocks HB1 and HB7 will not generate abnormal heat. The number can be reduced by one for other heating elements. Furthermore, this embodiment has disconnection detectors 1002 and 1003 for determining whether points P and Q are disconnected. Therefore, only the heating blocks HB1 and HB7 do not generate abnormal heat unless the first failure of disconnection at the points P and Q and the second failure of the disconnection detection unit occur. Therefore, the number of thermistors present in HB1 and HB7 can be reduced by two relative to other heating elements.

FIG. 15 is a diagram showing an internal circuit of the disconnection detector 1002 shown in FIG. Since the internal circuit of the disconnection detection unit 1003 is the same as that of the disconnection detection unit 1002, it is omitted here. FIG. 15-(A) is a diagram showing a circuit in which the signal Di1002 output from the disconnection detection unit 1002 is connected to the CPU 420, and the signal Di1004 is connected to the latch units 432 and 436. FIG. A detection resistor 1010 serving as a second current detection section for detecting current flowing through the point P is connected to the vicinity of the point P inside the disconnection detection section 1002 . A resistor 1013 and an AC coupler 1015 for propagating the signal detected by the detection resistor 1010 to the secondary side are connected in parallel with the detection resistor 1010 . Furthermore, the disconnection detection unit 1002 is provided with a detection resistor 1011 as a first current detection unit so that the current to the triac 441 can be detected. In parallel with the detection resistor 1011, a resistor 1014 and an AC coupler 1016 for propagating the signal detected by the detection resistor 1011 to the secondary side are connected. The current path through which the current flows to the heating resistors 302a-2 and 302b-2 branches in the middle of the line connecting the triac 442 and the heating resistors 302a-2 and 302b-2, and passes through the triac 441 to the heating resistors. It connects with bodies 302a-1 and 302b-1. That is, a first current path through which current flows from the branch point to the downstream heating resistors 302a-1 and 302b-1, and a second current path through which current flows from the branch point to the downstream heating resistors 302a-2 and 302b-2. and branch from a common third current path upstream of the branch point.

The secondary side of AC coupler 1015 is connected to power supply VCC1 via pull-up resistor 1017 and to CPU 420 via damping resistor 1025 . When an AC current flows through point P, an AC voltage is applied across the sensing resistor 1010 and the applied voltage signal is transmitted through the AC photocoupler 1015 to the secondary side. Here, an AC photocoupler is used to transmit a full-wave AC current signal to the secondary side, but a photocoupler may be used if it is desired to transmit only a half-wave current signal. The signal transmitted to the secondary side becomes a pulse signal and is output to CPU 420 as disconnection detection signal Di1002. The CPU 420 determines that there is no disconnection if the pulse-like disconnection detection signal Di1002 is not detected from the disconnection detection unit 1002 even though the FUSER1 signal is turned ON and the triac 442 is ON. When the CPU 420 determines that the wire is disconnected, the FUSERs 1 and 2 are turned off to cut off the energization of the triacs 441 and 442 . A detailed explanation of the waveform will be given with reference to FIG. 15-(B). Furthermore, the pulse signals transmitted to the secondary side by AC couplers 1015 and 1016 pass through resistors 1018 and 1022 respectively, are smoothed by capacitors 1019 and 1023 and resistors 1020 and 1024 and are connected to comparator 1025 . If a current flows through the detection resistor 1011 even though no current flows through the detection resistor 1010, it is considered that the route of the point P is disconnected. In that case, in FIG. 15-(B), the voltage of the - terminal of the comparator 1025 exceeds the + terminal, LOW is output to the output Di 1004, and the latch sections 432 and 436 are operated. A detailed explanation of the waveform will be given with reference to FIG. 15-(B).

FIG. 15-(B) is a diagram showing waveforms of the operation of the circuit described in FIG. 15-(A). Waveform 1101 indicates the voltage detected by the detection resistor 1010 , waveform 1102 indicates the voltage detected by the detection resistor 1011 , and waveform 1103 indicates the Di 1002 signal output from the disconnection detection section 1002 . Further, the waveform 1104 with a solid line indicates the voltage applied to the - terminal of the comparator 1025 , and the waveform with a dotted line indicates the voltage applied to the + terminal of the comparator 1025 . When the triac 442 is in the OFF state and energization is OFF, no voltage is generated in the detection resistor 1010 and becomes 0 V, and as a result the transistor of the AC coupler 1015 on the secondary side does not operate.
Therefore, the Di 1002 signal is pulled up to Vcc 1 as indicated by waveform 1103 . When the triac 442 is turned on and the current is turned on, a voltage is generated across the detection resistor 1010 as indicated by a waveform 1101 . As a result, the transistor of the AC coupler 1015 on the secondary side operates, and pulls it to LOW when it operates. The CPU 420 can determine whether current has flowed through the detection resistor 1010 by detecting this pulse-like waveform. If the point P is disconnected, no voltage is generated in the detection resistor 1010 even if the triac 442 is turned on, so the waveforms 1101 and 1103 are the same waveforms as when the power supply is turned off. Therefore, the CPU 420 can determine that the point P is disconnected because the waveform 1103 does not have a pulse waveform even though the triac 442 is turned on and the power supply is turned on. can be turned off.

On the other hand, when the triac 442 is in the OFF state and the energization is OFF, the transistor of the AC coupler 1015 on the secondary side does not operate. Therefore, the voltage of the negative terminal of the comparator 1025 becomes a constant voltage determined by the divided voltages of the resistors 1017, 1018 and 1020 as indicated by the solid line of the waveform 1104. FIG. Similarly, since no voltage is generated across the detection resistor 1011, the + terminal voltage of the comparator 1025 is a constant voltage determined by the divided voltages of the resistors 1021, 1022, and 1024 as indicated by the dotted line of the waveform 1104. FIG. Here, the values of the resistors 1017, 1018, 1020 and the resistors 1021, 1022, 1024 are set so that the voltage of the + terminal is higher than the voltage of the - terminal. Therefore, since the voltage of the + terminal is higher than the voltage of the - terminal, the output of the comparator 1025 becomes an open collector and the latch section does not perform the latch operation. When the triac 442 is turned on and the current is turned on, a voltage is generated across the detection resistor 1010 as indicated by a waveform 1101 . As a result, since the transistor of the AC coupler 1015 on the secondary side operates, the voltage of the - terminal of the comparator 1025 gradually decreases as indicated by the solid line of the waveform 1104 . Further, when the triac 441 is turned on and the current is turned on, a voltage is generated across the detection resistor 1011 as indicated by a waveform 1102 . Therefore, the voltage of the + terminal of the comparator 1025 gradually decreases as indicated by the dotted line of the waveform 1104 . Here, the resistance values of the detection resistors 1010 and 1011 are adjusted so that the voltage of the + terminal is higher than the voltage of the - terminal. Therefore, since the voltage of the + terminal is higher than the voltage of the - terminal, the output of the comparator becomes an open collector and the latch section does not perform the latch operation. If the point P is disconnected, no voltage is generated in the detection resistor 1010 even if the triac 442 is turned on, so the transistor of the AC coupler 1015 on the secondary side does not operate. Therefore, the voltage of the - terminal gradually increases as indicated by the solid line of waveform 1104 . Since the triac 441 continues to be ON even if the point P is disconnected, the voltage at the + terminal remains the same as when the power is ON, as indicated by the dotted line in the waveform 1104 . Therefore, after a while after point P is disconnected, the voltage at the - terminal of the comparator exceeds the voltage at the + terminal as shown by waveform 1104 . As a result, the output of the comparator becomes LOW and the latch units 432 and 436 are operated.

As described above, in the fifth embodiment, in the heat generating blocks HB1 and HB2 driven by the semiconductor elements in the subsequent stages of the semiconductor elements that drive the heat generating blocks HB2 and HB6, disconnection detection units for detecting disconnection of the heat generating blocks HB2 and HB6 are provided. . As a result, even if the number of thermistors in the heat generating blocks HB1 and HB2 is smaller than that of the other heat generating blocks, the heater 300 can be protected in two failure states.

[Example 6]
Embodiment 6 of the present invention will be described with reference to FIG. The sixth embodiment has a configuration in which the installation position of the detection resistor 1012 and the connection position of the Di 1002 are different from the circuit of the disconnection detection unit 1002 described in FIG. 15-(A) of the fifth embodiment. Other configurations are the same as those of the fifth embodiment. Among the configurations of the sixth embodiment, the same symbols are used for the configurations similar to those of the above-described embodiments, and the description thereof is omitted. In Example 6, matters not specifically described here are the same as those in the above example.

FIG. 16-(A) is a diagram showing the disconnection detection unit 1002, and a current detection resistor 1010 for detecting the current flowing through the point P is connected near the point P. FIG. Furthermore, in FIG. 16-(A), immediately after the triac 442, that is, in the third current path before branching into the first current path and the second current path, so that it can be determined whether the triac 442 has flowed a current. A detection resistor 1012 is provided as a third current detection unit. AC couplers 1015 and 1016 are connected in parallel to detection resistors 1010 and 1012, and the detection signals transmitted to the secondary side are smoothed by capacitors 1019 and 1023 and resistors 1020 and 1024, respectively, and connected to comparators 1031 and 1030, respectively. be done. The output of comparator 1030 is connected to the positive terminal of comparator 1031 via transistor 1034 and resistors 1032 and 1033 .

Here, when a current does not flow through the detection resistor 1010 even though a current is flowing through the detection resistor 1012, it is considered that the route of the point P is disconnected. In this case, in FIG. 16-(A), the voltage of the - terminal of the comparator 1031 exceeds the + terminal, and LOW is output to the output Di 1004, causing the latch sections 432 and 436 to operate. At this time, the signal of Di 1002 connected to CPU 420 also becomes LOW. When the DI 1002 becomes LOW even though the triac 442 is energized, the CPU 420 judges that the point P is broken, turns off the FUSERs 1 and 2, and cuts off the energization of the triacs 441 and 442 . A detailed explanation of the waveform will be given with reference to FIG. 16-(B).

FIG. 16-(B) is a diagram showing the circuit operation of FIG. 16-(A). In FIG. 16-(B), waveform 1105 is the voltage detected by the detection resistor 1010 and waveform 1106 is the voltage detected by the detection resistor 1012 . The solid line of the waveform 1107 indicates the voltage applied to the - terminal of the comparator 1030 , and the dotted waveform indicates the voltage applied to the + terminal of the comparator 1030 . A solid line of the waveform 1108 indicates the voltage applied to the - terminal of the comparator 1031 , and a dotted waveform indicates the voltage applied to the + terminal of the comparator 1031 . When the triac 442 is in the OFF state and the current is OFF, no voltage is generated in the detection resistor 1012, and as a result the transistor of the AC coupler 1016 on the secondary side does not operate. Therefore, the voltage of the - terminal of the comparator 1030 becomes a constant voltage determined by the divided voltages of the resistors 1021, 1022, and 1024 as indicated by the solid line of the waveform 1107. FIG. At this time, the resistors 1021, 1022, 1024 and the resistors 1026, 1027 are adjusted so that the voltage of the - terminal of the comparator 1030 is higher than that of the + terminal of the comparator 1030 . Therefore, the output of the comparator 1030 becomes LOW, the transistor 1034 operates, and the + terminal of the comparator 1031 becomes HIGH voltage. The - terminal of the comparator 1031 has a constant voltage determined by the divided voltages of the resistors 1017, 1018 and 1020 as indicated by the solid line of the waveform 1108 because no voltage is generated in the detection resistor 1010. FIG. Resistors 1017 , 1018 , and 1020 are adjusted so that the + terminal of the comparator 1031 has a higher voltage than the − terminal of the comparator 1031 at this time. Therefore, since the voltage of the + terminal is higher than the voltage of the - terminal, the output of the comparator 1031 becomes an open collector, and the latch sections 432 and 436 do not perform latch operations. Next, when the triacs 442 and 441 are turned on to turn on the electricity, a voltage is generated in the detection resistor 1012 . The voltage at the - terminal of the result comparator 1030 gradually decreases as indicated by the solid line of the waveform 1107 . Similarly, voltage is generated across the detection resistor 1010 at the − terminal of the comparator 1031 , so the voltage gradually decreases as indicated by the solid line of the waveform 1108 . When the voltage of the + terminal of the comparator 1030 exceeds the voltage of the - terminal, the output of the comparator 1030 becomes an open collector. As a result, the transistor 1034 is turned off, and the voltage applied to the + terminal of the comparator 1031 changes to the voltage determined by the resistors 1028 and 1029 as indicated by the waveform 1108 . At this time, the resistors 1028 and 1029 are adjusted so that the voltage applied to the + terminal of the comparator 1031 is higher than the voltage applied to the - terminal. Therefore, since the voltage of the + terminal is higher than the voltage of the - terminal, the output of the comparator 1031 becomes an open collector, and the latch sections 432 and 436 do not perform latch operations. When point P is disconnected, the current passing through the detection resistor 1012 decreases, so the voltage at the - terminal of the comparator 1030 gradually increases as indicated by the solid line of the waveform 1107 . However, since a current is flowing through the triac 441, the voltage at the - terminal of the comparator 1030 remains at a constant voltage rise. Even at this time, since the resistors 1026 and 1027 are adjusted so that the voltage applied to the + terminal of the comparator 1030 is higher than the voltage applied to the - terminal, the output of the comparator 1030 becomes an open collector. On the other hand, since point P of the - terminal of the comparator 1031 is disconnected, the voltage increases as indicated by the solid line of the waveform 1108 . Since the voltage of the + terminal of the comparator 1031 does not change, the voltage of the - terminal of the comparator 1031 exceeds the voltage of the + terminal a short time after point P is broken, and the output of the comparator 1031 becomes LOW. 436 and CPU 420 are activated.

As described above, in the sixth embodiment, even if the installation position of the detection resistor 1012 and the connection position of the Di 1002 are different in the circuit of the disconnection detection unit 1002, the disconnection at the point P can be detected.

The respective configurations of the above embodiments can be combined with each other as much as possible.
For example, the disconnection detectors of Examples 5 and 6 are different from the circuit configuration of Example 2 (between the triacs 443 and 445 in FIG. 7) and the circuit configuration of Example 4 (between the triacs 442 and 441 in FIG. 12). may be added.

200... Fixing device 300, 600, 900, 903... Heater 305... Substrate 302a, 302b... Heat generating element 441 to 447... Triac, T1-1 to T1-7, T2-1 to T2-7, T3- 4 thermistor 400, 700, 901, 904 control circuit ET1-1 to ET1-7, ET2-1 to ET2-7, ET3-4, EG9, EG10 conductor HB1 to HB7 heating block

Claims (2)

A fixing unit for fixing a toner image formed on a recording material to the recording material, comprising: a substrate; a plurality of heat generating elements arranged on the substrate in a longitudinal direction of the substrate; a first temperature sensing element provided at a position on the substrate corresponding to the first heat generating element of the plurality of heat generating elements corresponding to a second heat generating element different from the first heat generating element a fixing section having a heater provided with a second temperature sensing element provided at a position on the substrate;
a first semiconductor element provided in a power supply path from a power supply to a first heating element of the plurality of heating elements;
a second semiconductor element provided in a power supply path from the power supply to a second heating element different from the first heating element among the plurality of heating elements;
A control unit for controlling the first semiconductor element and the second semiconductor element, the control unit controlling the first semiconductor element in accordance with the temperature detected by the first temperature detection element to detect the second temperature a control unit that controls the second semiconductor element according to the temperature detected by the detection element;
and forming a toner image on a recording material,
The first heating element is arranged at the endmost end in the longitudinal direction among the plurality of heating elements, and the second heating element is arranged next to the first heating element in the longitudinal direction. ,
The first semiconductor element is connected in series with the second semiconductor element,
power supplied to the second heating element is controlled by controlling the second semiconductor element;
An image forming apparatus, wherein power supplied to the first heating element is controlled by controlling the first semiconductor element and the second semiconductor element. The fixing section further has a cylindrical film and a roller that contacts the outer peripheral surface of the film, the heater is arranged in the inner space of the film, and the heater and the roller move the film. 2. The image forming apparatus according to claim 1 , wherein a nip portion for nipping and conveying a recording material is formed between said film and said roller.

Images