Patent Application
20210278794
The present invention relates to a heating apparatus configured to detect a conductive state of an element, and to an image forming apparatus.
With regard to temperature rise of a non-sheet passing portion caused in an image heating apparatus of an image forming apparatus, the following unit is proposed: a heater includes a plurality of heating elements, and power supply to the plurality of heating elements is controlled in accordance with a width of a recording sheet, to thereby suppress the temperature rise of the non-sheet passing portion. Here, image heating apparatus including a plurality of heating elements are broadly classified into two systems. A first system corresponds to a method of causing the plurality of heating elements to generate heat at the same time when in use (for example, see Japanese Patent Application Laid-Open No. 2006-004860). The second system corresponds to a method of exclusively supplying power to any of the heating elements (for example, see Japanese Patent Application Laid-Open No. 2001-100558). Specifically, for example, during power supply to a heating element 1, no power is supplied to a heating element 2, or during power supply to the heating element 2, no power is supplied to the heating element 1. As compared with the first system, the second system is advantageous in that the heater can be manufactured in a simple manner at low cost, and is suitable for low-cost image forming apparatus.
With the image heating apparatus of the second system, when power is supplied to the plurality of heating elements at the same time, the apparatus may be finally broken. To address the above, it is required to prevent such a situation that a plurality of triacs configured to control power supply to the plurality of heating elements have any failure and then supply power to the plurality of heating elements at the same time. To that end, there is proposed a technology of accurately detecting a failure (abnormality) of the triac (for example, see Japanese Patent Application Laid-Open No. 2001-100558 and Japanese Patent No. 5577077).
However, in order to prevent power from being supplied to the plurality of heating elements at the same time, it is required to detect a power supply state of each of the plurality of triacs and then determine a correlation among power-supplied states of the plurality of heating elements.
There is provided a heating apparatus comprising: a first load; a first switch element configured to switch between power supply from an AC power source to the first load and shut-off of power; a second load; a second switch element configured to switch between power supply from the AC power source to the second load and shut-off of power; a control unit configured to control the first switch element and the second switch element to supply power to either the first load or the second load; a first detection unit configured to detect that the first switch element is in a conductive state or a non-conductive state; a second detection unit configured to detect that the second switch element is in a conductive state or a non-conductive state; and a determination unit configured to determine whether both of the first load and the second load are in a state of being supplied with power, based on a result of detection by the first detection unit and a result of detection by the second detection unit.
Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.
Modes for carrying out the present invention are described below in detail based on embodiments with reference to the drawings.
In the first station, a photosensitive drum 1a serving as an image bearing member is an OPC photosensitive drum. The photosensitive drum 1a is formed by laminating a plurality of layers of functional organic materials including, for example, a carrier generating layer formed on a metal cylinder to generate charges through light exposure, and a charge transporting layer for transporting the generated charges. The outermost layer has a low electric conductivity and is almost insulated. A charging roller 2a serving as a charging unit is brought into abutment against the photosensitive drum 1a. The charging roller 2a is rotated in association with the rotation of the photosensitive drum 1a to uniformly charge the surface of the photosensitive drum 1a. The charging roller 2a is applied with a voltage on which a DC voltage or an AC voltage is superimposed, and the photosensitive drum 1a is charged by causing discharge at minute air gaps on the upstream and the downstream in a rotation direction from a nip portion between the charging roller 2a and the surface of the photosensitive drum 1a. A cleaning unit 3a is a unit configured to remove toner remaining on the photosensitive drum 1a after transfer to be described later. A developing unit 8a serving as a developing unit includes a developing roller 4a, a nonmagnetic one-component toner 5a, and a developer applying blade 7a. The photosensitive drum 1a, the charging roller 2a, the cleaning unit 3a, and the developing unit 8a form an integral process cartridge 9a which is removably mounted to the image forming apparatus.
An exposure device 11a serving as an exposing unit includes a scanner unit configured to scan laser light by a polygon mirror, or a light emitting diode (LED) array. The exposure device 11a radiates a scanning beam 12a modulated based on an image signal onto the photosensitive drum 1a. Further, the charging roller 2a is connected to a charging high-voltage power source 20a serving as a voltage supply unit for the charging roller 2a. The developing roller 4a is connected to a development high-voltage power source 21a serving as a voltage supply unit for the developing roller 4a. A primary transfer roller 10a serving as a transfer unit is connected to a primary transfer high-voltage power source 22a serving as a voltage supply unit for the primary transfer roller 10a. The configuration of the first station has been described above, and the second, third, and fourth stations also have similar configurations. As for the other stations, components having same functions as those of the first station are denoted by same reference numerals, and the reference numerals are provided with suffixes “b”, “c”, and “d” for the respective stations. In the following description, the suffixes “a”, “b”, “c”, and “d” are omitted except for a case in which a specific station is described.
An intermediate transfer belt 13 is supported by three rollers of a secondary transfer opposing roller 15, a tension roller 14, and an auxiliary roller 19 serving as stretching members for the intermediate transfer belt 13. Only the tension roller 14 is applied with a force by a spring in a direction of stretching the intermediate transfer belt 13, and thus an appropriate tension force is maintained with respect to the intermediate transfer belt 13. The secondary transfer opposing roller 15 follows the drive of a main motor (not shown) to rotate, and thus the intermediate transfer belt 13 wound around an outer periphery of the secondary transfer opposing roller 15 is rotated. The intermediate transfer belt 13 is moved at a substantially same speed in a forward direction (for example, clockwise direction of
Next, an image forming operation of the image forming apparatus according to the first embodiment is described. When the image forming apparatus receives a printing instruction under a standby state, the image forming apparatus starts the image forming operation. The photosensitive drum 1, the intermediate transfer belt 13, and the like start rotation in the arrow direction at a predetermined process speed by the main motor (not shown). The photosensitive drum 1a is uniformly charged by the charging roller 2a applied with a voltage by the charging high-voltage power source 20a, and subsequently an electrostatic latent image is formed in accordance with image information (also referred to as “image data”) by the scanning beam 12a radiated from the exposure device 11a. The toner 5a in the developing unit 8a is negatively charged to be applied on the developing roller 4a by the developer applying blade 7a. Then, the developing roller 4a is supplied with a predetermined developing voltage by the development high-voltage power source 21a. When the photosensitive drum 1a is rotated so that the electrostatic latent image formed on the photosensitive drum 1a arrives at the developing roller 4a, the negative toner adheres on the electrostatic latent image so as to be visible, and a toner image of a first color (for example, yellow (Y)) is formed on the photosensitive drum 1a. The stations of the other colors of magenta (M), cyan (C), and black (K) (process cartridges 9b to 9d) also operate similarly. A write signal from a controller (not shown) is delayed at a constant timing depending on distances between the primary transfer positions of the respective colors so that electrostatic latent images are formed by exposure on the photosensitive drums 1a to 1d. The primary transfer rollers 10a to 10d are each applied with a DC high voltage having a polarity opposite to that of toner. With the above-mentioned steps, toner images are sequentially transferred onto the intermediate transfer belt 13 (hereinafter referred to as “primary transfer”), and thus multi-layered toner images are formed on the intermediate transfer belt 13.
After that, in synchronization with the formation of the toner images, sheets P corresponding to recording materials stacked on a cassette 16 are conveyed along a conveyance path Y. Specifically, the sheet P is fed (picked up) by a sheet feeding roller 17 driven to rotate by a sheet feeding solenoid (not shown). The fed sheet P is conveyed to registration rollers 18 by conveyance rollers. Then, the sheet P passes through a sheet width sensor 122 serving as a detection unit configured to detect a length of the sheet in a direction orthogonal to a conveyance direction (hereinafter referred to as “width”). A registration sensor 123 is arranged on the downstream of the registration rollers 18. The registration sensor 123 detects the “presence” of the sheet P when a leading edge of the sheet P arrives, and detects the “absence” of the sheet P when a trailing edge of the sheet P passes through the registration sensor 123.
The sheet P is conveyed by the registration rollers 18 to a transfer nip portion being an abutment portion between the intermediate transfer belt 13 and a secondary transfer roller 25 in synchronization with the toner images formed on the intermediate transfer belt 13. The secondary transfer roller 25 is applied with a voltage having a polarity opposite to that of the toner by a secondary transfer high-voltage power source 26. Thus, the multi-layered toner images of the four colors borne on the intermediate transfer belt 13 are collectively transferred onto the sheet P (recording material) (hereinafter referred to as “secondary transfer”). Members contributing to the process until the unfixed toner images are formed on the sheet P (for example, the photosensitive drum 1) function as an image forming unit. Meanwhile, after the secondary transfer is finished, toner remaining on the intermediate transfer belt 13 is removed by the cleaning unit 27. The sheet P that has been subjected to the secondary transfer is conveyed to a fixing apparatus 50 serving as a heating apparatus, to thereby be subjected to fixing of the toner images. Then, the sheet P is discharged to a discharge tray 30 as an image-formed object (print or copy). The fixing apparatus 50 includes a film 51 serving as a first rotary member, a nip forming member 52, a pressure roller 53 serving as a second rotary member, and a heater 251. The heater 251 includes a plurality of heating elements to be described later, and the plurality of heating elements are provided to be in contact with an inner surface of the film 51. Further, the pressure roller 53 forms a nip portion together with the film 51, and the nip portion is formed by the plurality of heating elements and the pressure roller 53 via the film 51.
[Circuit Block Diagram]
Power supply and shut-off of power from the AC power source 101 to the first load 106 (hereinafter referred to as “load 106”) are controlled by controlling the triac 104 being a first switch element to be conductive or non-conductive with the control portion 108 being a control unit. Further, power supply and shut-off of power from the AC power source 101 to the second load 107 (hereinafter referred to as “load 107”) are controlled by controlling the triac 105 being a second switch element to be conductive or non-conductive with the control portion 108. In the fixing apparatus 50 in the first embodiment, the control portion 108 controls the triac 104 and the triac 105 so as not to supply power from the AC power source 101 to the load 106 and the load 107 at the same time. A detailed description is given below with reference to
The detection circuit 109 being a first detection unit is connected in parallel to the triac 104, to thereby detect whether the triac 104 is in a conductive state or a non-conductive state. The detection circuit 110 being a second detection unit is similarly connected in parallel to the triac 105, to thereby detect whether the triac 105 is in a conductive state or in a non-conductive state. Outputs of the detection circuit 109 and the detection circuit 110 are input to the determination portion 111. The determination portion 111 being a determination unit determines such an abnormal state that power is supplied to both of the triac 104 and the triac 105 based on a detection result of the detection circuit 109 and a detection result of the detection circuit 110. Specifically, the determination portion 111 determines whether the triac 104 and the triac 105 are in a conductive state at the same time based on a relative relationship between signals input from the detection circuit 109 and the detection circuit 110. A power supply path for electrically connecting the AC power source 101 and each of the triac 104 and the triac 105 is connected to the electromagnetic relay 103 being a connection unit which is brought into a connected state (conductive state) or a non-connected state (non-conductive state) by the determination portion 111. When determining that both of the triac 104 and the triac 105 are in a conductive state at the same time, the determination portion 111 brings the electromagnetic relay 103 into a non-conductive state, to thereby shut-off power supply from the AC power source 101 to the load 106 and the load 107.
[Details of Detection Circuit]
With reference to
On the ceramic circuit board 252, the heating elements 253, the heating element 254, and the heating element 255 are arranged. One of the heating elements 253 is provided at one end portion in a short direction of the ceramic circuit board 252, and the other of the heating elements 253 is provided at the other end portion in the short direction of the ceramic circuit board 252. In the short direction, the one heating element 253, the heating element 254, the heating element 255, and the other heating element 253 are arranged in the stated order. To the contact 256a being a first contact, one ends of the one heating element 253 and the other heating element 253 are electrically connected. To the contact 256d being a second contact, the other end portions of the one heating element 253, the other heating element 253, and the heating element 254 are electrically connected. To the contact 256b being a third contact, one end portions of the heating element 254 and the heating element 255 are electrically connected. To the contact 256c being a fourth contact, the other end portion of the heating element 255 is electrically connected.
Any one of the heating element 254 and the heating element 255 is selected by a C-contact relay 201 when in use. The C-contact relay 201 being a switching unit is configured to switch between a power supply path from the AC power source 101 to the heating element 254 and a power supply path from the AC power source 101 to the heating element 255. The C-contact relay 201 includes contacts 201a. 201b, and 201c. When the contact 201a and the contact 201b of the C-contact relay 201 are connected to each other, the heating element 255 is brought into a short-circuited state by the C-contact relay 201. With this, the heating element 254 is selected as the load of the triac 105. Meanwhile, when the contact 201a and the contact 201c of the C-contact relay 201 are connected to each other, the heating element 254 is brought into a short-circuited state by the C-contact relay 201. With this, the heating element 255 is selected as the load of the triac 105. As described above, the C-contact relay 201 is controlled by the control portion 108 so that the heating element 254 or the heating element 255 is selected when in use as the load 107 of
The triac 104 is controlled by a CPU 219 provided inside the control portion 108. In a case of controlling a T1 terminal and a T2 terminal of the triac 104 to be in a conductive state, the CPU 219 executes control to supply a base current to a transistor 205 via a current limiting resistor 206, to thereby bring a collector and an emitter of the transistor 205 into a conductive state. When the collector and the emitter of the transistor 205 are brought into a conductive state, an electric current flows from a power source Vcc1 to a light emitting diode of a solid state relay (hereinafter referred to as “SSR”) 202 via a current limiting resistor 204. Then, a light receiving portion of the SSR 202 is brought into a conductive state. When the light receiving portion of the SSR 202 is brought into a conductive state, a gate current is supplied from the AC power source 101 to a gate terminal (G terminal) of the triac 104 via a current limiting resistor 203. Then, the T1 terminal and the T2 terminal of the triac 104 are brought into a conductive state. In this example, the power source Vcc1 is a DC power source having a secondary side potential of, for example, 3.3 V (potential insulated from the AC power source 101).
The triac 105 is similarly controlled by the CPU 219. In a case of controlling a T1 terminal and a T2 terminal of the triac 105 into a conductive state, the CPU 219 executes control to supply a base current to a transistor 215 via a current limiting resistor 216, to thereby bring a collector and an emitter of the transistor 215 into a conductive state. When the collector and the emitter of the transistor 215 are brought into a conductive state, an electric current flows from the power source Vcc1 to a light emitting diode of an SSR 212 via a current limiting resistor 214. Then, a light receiving portion of the SSR 212 is brought into a conductive state. When the light receiving portion of the SSR 212 is brought into a conductive state, a gate current is supplied from the AC power source 101 to a G terminal of the triac 105 via a current limiting resistor 213. Then, the T1 terminal and the T2 terminal of the triac 105 are brought into a conductive state.
In this example, the triac 104 and the triac 105 are controlled by the CPU 219 not to be brought into a conductive state at the same time. This is because three kinds of heating elements in the heater 251, that is, the heating elements 253, 254, and 255 are exclusively selected when in use in accordance with a target sheet width in order to achieve uniform heat distribution in the longitudinal direction of the heater 251. The sheet width refers to a length of the sheet P in a direction parallel to the longitudinal direction of the heating elements 253, 254, and 255, specifically, the length in the direction orthogonal to the conveyance direction of the sheet P. For example, at a timing at which a B5 size sheet passes through the fixing apparatus 50, the control portion 108 executes control so that the heating elements 253 and the heating element 254 alternately generate heat. The heater 251 is designed on the assumption that the heating elements 253, 254, and 255 are exclusively supplied with power. Hence, when the heater 251 remains in such a state that the plurality of heating elements 253, 254, and 255 generate heat at the same time, the heater 251 may cause excessive temperature rise and thus be broken. To address this, the CPU 219 controls the triac 104 and the triac 105 so as to excessively supply power to the heating elements 253, 254, and 255.
When the electromagnetic relay 103 is not required to supply power to the heater 251 (for example, in a case in which the image forming apparatus is in a sleep mode), its contact is set to a non-conductive state in order to improve safety and save power. The electromagnetic relay 103 is controlled by the CPU 219 as with the triacs 104 and 105. The CPU 219 executes control to supply a base current to a transistor 229 via a current limiting resistor 228, to thereby bring a collector and an emitter of the transistor 229 into a conductive state, and cause an electric current to flow from a power source Vcc2 to a coil of the electromagnetic relay 103. In this way, the contact of the electromagnetic relay 103 is brought into a conductive state.
(Detection Circuit)
Next, the detection circuit 109 and the detection circuit 110 configured to detect conductive states of the triacs 104 and 105, respectively, are described. The detection circuit 109 is connected in parallel to between the T1 terminal and the T2 terminal of the triac 104. First, description is given of a case in which the T1 terminal and the T2 terminal of the triac 104 are in a non-conductive state. In this case, an electric current flows from the AC power source 101 via a current limiting resistor 208 to a light emitting portion 207a of a photocoupler (hereinafter referred to as “AC photocoupler”) 207 that is adapted to an alternating current independent of a polarity of the AC power source 101 (whether with a positive half wave or with a negative half wave). As a result, a collector and an emitter of a light receiving transistor 207b of the AC photocoupler 207 are brought into a conductive state. Meanwhile, when the T1 terminal and the T2 terminal of the triac 104 are in a conductive state, the light emitting portion 207a of the AC photocoupler 207 does not emit light independent of the polarity of the AC power source 101. Thus, the collector and the emitter of the light receiving transistor 207b of the AC photocoupler 207 are brought into a non-conductive state.
The detection circuit 110 is connected in parallel to between the T1 terminal and the T2 terminal of the triac 105. First, description is given of a case in which the T1 terminal and the T2 terminal of the triac 105 are in a non-conductive state. In this case, an electric current flows from the AC power source 101 via a current limiting resistor 218 to a light emitting portion 217a of an AC photocoupler 217 independent of the polarity of the AC power source 101. As a result, a collector and an emitter of a light receiving transistor 217b of the AC photocoupler 217 are brought into a conductive state. Meanwhile, when the T1 terminal and the T2 terminal of the triac 105 are in a conductive state, the light emitting portion 217a of the AC photocoupler 217 does not emit light independent of the polarity of the AC power source 101. Thus, the collector and the emitter of the light receiving transistor 217b of the AC photocoupler 217 are brought into a non-conductive state. As described above, the detection circuits 109 and 110 include the light emitting portions 207a and 217a on the primary side, and the light receiving transistors 207b and 217b on the secondary side, respectively. The detection circuits 109 and 110 are configured to insulate and convert voltage information on the primary side that is not insulated from the AC power source 101 into a signal on the secondary side, and then output the converted signal to the determination portion 111 on the secondary side.
(Determination Portion)
Next, the determination portion 111 is described. The light receiving transistor 207b of the AC photocoupler 207 and the light receiving transistor 217b of the AC photocoupler 217 are connected in parallel to each other. Both of the emitter terminal of the light receiving transistor 207b of the AC photocoupler 207 and the emitter terminal of the light receiving transistor 217b of the AC photocoupler 217 are connected to one end of a resistor 220. A voltage across both ends of a capacitor 221 is controlled with the use of a charge current from the other end of the resistor 220 and a discharge current of a resistor 222 connected in parallel to the capacitor 221. When one or both of the light receiving transistor 207b of the AC photocoupler 207 and the light receiving transistor 217b of the AC photocoupler 217 are brought into a conductive state, the capacitor 221 is charged by the power source Vcc1 via the resistor 220. The voltage across both ends of capacitor 221 is input to an inverting input terminal (negative terminal) of a comparator 223 to be compared with a reference voltage Vref input to a non-inverting input terminal (positive terminal) of the comparator 223.
An output terminal of the comparator 223 is connected to a base terminal of a transistor 227 via a resistor 226. The transistor 227 is also connected to the power source Vcc1 via a resistor 225 and the resistor 226. A latch circuit (illustrated as “LATCH”) 224 is connected between the inverting input terminal of the comparator 223 and a connection point between the resistor 225 and the resistor 226.
With reference to
Table 1 shows a state in a first column, power supply from the AC power source 101 to the fixing apparatus 50 in a second column, and a conductive state between the T1 terminal and the T2 terminal of the triac 104 in a third column. Table 1 also shows a conductive state between the T1 terminal and the T2 terminal of the triac 105 in a fourth column, a state of the light emitting portion 207a of the detection circuit 109 in a fifth column, and a state of the light emitting portion 217a of the detection circuit 110 in a sixth column. Here, the first column holds the states of State A to State E. The second column holds ON for a case in which power is supplied from the AC power source 101 to the fixing apparatus 50, and OFF for a case in which power supply is stopped. The ON/OFF of the power supply is controlled by the control portion 108 controlling the electromagnetic relay 103 to be in a conductive state/non-conductive state. The third column and the fourth column hold ON for the conductive state of the triacs 104 and 105, and OFF for the non-conductive state of the triacs 104 and 105, respectively. The fifth column and the sixth column hold “Light on” for a case in which the light emitting portions 207a and 217a of the detection circuits 109 and 110 emit light, and “Light off” for a case in which the light emitting portions 207a and 217a of the detection circuits 109 and 110 do not emit light, respectively.
Here, under such a state that power is supplied from the AC power source 101, State A in which both of the triac 104 and the triac 105 are in a non-conductive state, and State B and State C in which any one of the triac 104 and the triac 105 is in the non-conductive state, are defined as a normal state. On the other hand, under such a state that power is supplied from the AC power source 101, State D in which both of the triac 104 and the triac 105 are in a conductive state is defined as an abnormal state.
[Operation of Determination Portion]
With reference to
<Section 1 and Section 2>
In Section 1 and Section 2, the T1 terminal and the T2 terminal are in a non-conductive state (OFF) in both of the triac 104 and the triac 105. Thus, both of the collector and the emitter of the light receiving transistor 207b of the AC photocoupler 207 and the collector and the emitter of the light receiving transistor 217b of the AC photocoupler 217 are brought into a conductive state (ON) (State A). With this, the capacitor 221 of the determination portion 111 is charged by the power source Vcc1 via the resistor 220. In this example, a resistance value of the resistor 220 is set smaller than that of the resistor 222. Thus, under a state in which the charge current is supplied to the capacitor 221 from the power source Vcc1 via the resistor 220, a relationship of (charge current)>(discharge current) is established. As a result, in Section 1 and Section 2, the voltage across both ends of the capacitor 221, that is, the voltage of the inverting input terminal of the comparator 223 is increased or fully charged.
In Section 1 and Section 2, the voltage of the inverting input terminal of the comparator 223 is higher than the voltage (reference voltage Vref) of the non-inverting input terminal. Thus, an output transistor (not shown) of the comparator 223 is turned ON so that the voltage of the output terminal of the comparator 223 becomes almost a ground (hereinafter referred to as “GND”) potential (0 V). With this, almost all of an electric current supplied from the power source Vcc1 via the resistor 225 is sunk to the output terminal of the comparator 223. Thus, a base current is not supplied to the transistor 227 so that the collector and the emitter of the transistor 227 are brought into a non-conductive state. As a result, in Section 1 and Section 2, the contact of the electromagnetic relay 103 is brought into a conductive state or a non-conductive state under the control of the CPU 219. In
<Section 3 and Section 4>
Next, in Section 3 and Section 4, the T1 terminal and the T2 terminal of the triac 104 are in a conductive state (ON), and the T1 terminal and the T2 terminal of the triac 105 are in a non-conductive state (OFF). Under this state, the collector and the emitter of the light receiving transistor 207b of the AC photocoupler 207 are brought into a non-conductive state (OFF), and the collector and the emitter of the light receiving transistor 217b of the AC photocoupler 217 are brought into a conductive state (ON) (State B). With this, the capacitor 221 is charged by the power source Vcc1 via the light receiving transistor 217b of the AC photocoupler 217 and the resistor 220, and the voltage across both ends of the capacitor 221 is increased or fully charged.
<Section 5>
In Section 5, the T1 terminal and the T2 terminal are in a conductive state (ON) in both of the triac 104 and the triac 105. This condition means that the apparatus is not normally controlled. The CPU 219 executes control not to supply power to the triac 104 and the triac 105 at the same time. Thus, a state in which the T1 terminal and the T2 terminal are in a conductive state (ON) in both of the triac 104 and the triac 105, suggests the occurrence of some defect. The following case is conceivable as an example of the defect. That is, external surge, for example, is input to the apparatus via the AC power source 101, to thereby cause an erroneous operation of the triacs 104 and 105 (erroneous conduction between the T1 terminal and the T2 terminal).
In Section 5, the T1 terminal and the T2 terminal are in a conductive state (ON) in both of the triac 104 and the triac 105. Both of the collector and the emitter of the light receiving transistor 207b of the AC photocoupler 207 and the collector and the emitter of the light receiving transistor 217b of the AC photocoupler 217 are brought into a non-conductive state (OFF) (State D). The state in which both of the triac 104 and the triac 105 are in a conductive state is hereinafter referred to as “simultaneous conductive state.” Under this state, charges of the capacitor 221 are released via the resistor 222, and the voltage across both ends of the capacitor 221 (voltage of the inverting input terminal of the comparator 223) is reduced. In Section 5, the voltage of the inverting input terminal of the comparator 223 is reduced but does not fall below the reference voltage Vref of the non-inverting input terminal of the comparator 223. Thus, the output transistor (not shown) of the comparator 223 is kept ON, and the contact of the electromagnetic relay 103 is maintained in a conductive state (ON).
The determination portion 111 does not confirm the simultaneous conductive state of the triacs 104 and 105 when the simultaneous conductive state of the triac 104 and the triac 105 continues a short time for the following reason. That is, the reason is to balance an erroneous operation caused by external surge and the risk of the plurality of heating elements 253, 254, and 255 generating heat at the same time to cause excessive temperature rise of the heater 251. In other words, the following case is considered: under such a short-time simultaneous conductive state that no defect occurs even when the plurality of heating elements 253, 254, and 255 generate heat at the same time, the triacs 104 and 105 temporarily operate erroneously (erroneous conduction between the T1 terminal and the T2 terminal) due to external surge, for example. The determination portion Ill is set to have redundancy in its determination as to such a temporal erroneous operation, so as not to stop the apparatus. The above-mentioned “short time” refers to one half wave period of the AC power source 101 in the first embodiment.
<Section 6>
In Section 6, the T1 terminal and the T2 terminal of the triac 104 are in a non-conductive state (OFF), and the T1 terminal and the T2 terminal of the triac 105 are in a conductive state (ON). Under this state, the light receiving transistor 207b of the AC photocoupler 207 is brought into a conductive state (ON), and the light receiving transistor 217b of the AC photocoupler 217 is brought into a non-conductive state (OFF) (State C). With this, the capacitor 221 is charged by the power source Vcc1 via the light receiving transistor 207b of the AC photocoupler 207 and the resistor 220. In Section 5, the voltage of the inverting input terminal of the comparator 223 is reduced due to a temporal erroneous operation, and thus the voltage of the inverting input terminal of the comparator 223 is increased in Section 6. The voltage of the inverting input terminal of the comparator 223 is higher than the voltage (reference voltage Vref) of the non-inverting input terminal of the comparator 223, and thus the output transistor (not shown) of the comparator 223 is kept ON, and the contact of the electromagnetic relay 103 is maintained in a conductive state (ON).
<Section 7 and Section 8>
In Section 7 and Section 8, a period in which the T1 terminal and the T2 terminal are in a conductive state (ON) in both of the triac 104 and the triac 105 (State D) continues for two half wave periods of the AC power source 101. In Section 7, the voltage of the inverting input terminal of the comparator 223 continues to lower, and at a timing “a” in Section 8, the voltage of the inverting input terminal of the comparator 223 falls below the reference voltage Vref of the non-inverting input terminal of the comparator 223. The determination portion 111 determines that the simultaneous conductive state of the triac 104 and the triac 105 is confirmed at the timing “a”.
When the voltage of the inverting input terminal of the comparator 223 falls below the reference voltage Vref of the non-inverting input terminal of the comparator 223, the output transistor (not shown) of the comparator 223 is turned OFF so that an output of the comparator 223 is brought into a high-impedance (Hiz) state. Then, a base current is supplied from the power source Vcc1 via the resistor 225 and resistor 226 to the transistor 227. The collector and the emitter of the transistor 227 supplied with the base current are brought into a conductive state, and then an electric current supplied from the CPU 219 to the transistor 229 is sunk by the transistor 227 via the resistor 228. Thus, the collector and the emitter of the transistor 229 are brought into a non-conductive state, and the contact of the electromagnetic relay 103 is brought into a non-conductive state, to thereby shut-off power supply from the AC power source 101 to the heater 251. As described above, when the output terminal of the comparator 223 is at high impedance, in other words, when the determination portion 11 determines that the triacs 104 and 105 are in the simultaneous conductive state, the electromagnetic relay 103 is brought into a non-conductive state (OFF) independent of control of the control portion 108.
Here, once the determination portion 111 confirms the simultaneous conductive state of the triac 104 and the triac 105, the latch circuit 224 functions to maintain the contact of the electromagnetic relay 103 in a non-connected state even in a case in which the simultaneous conductive state is canceled later. Once the voltage of the inverting input terminal of the comparator 223 becomes lower than the reference voltage Vref of the non-inverting input terminal, and the output of the comparator 223 is at high impedance (Hiz), the latch circuit 224 operates as follows. That is, the latch circuit 224 maintains the voltage of the inverting input terminal of the comparator 223 to be lower than the reference voltage Vref of the non-inverting input terminal. Here, the function of the latch circuit 224 is not an essential part of the present invention. Thus, it is desirable to determine, for each apparatus, settings as to whether the circuit is of a latch type or an automatic recovery type that causes the contact of the electromagnetic relay 103 to return to a conductive state when the simultaneous conductive state of the triac 104 and the triac 105 is canceled, for example.
Further, in the first embodiment, the description is given of an example in which the determination portion 111 confirms the simultaneous conductive state of the triac 104 and the triac 105 when the simultaneous conductive state of the triac 104 and the triac 105 continues for two half wave periods of the AC power source 101. However, a time period required for the determination portion 1l1 to confirm the determination (hereinafter referred to as “determination confirmation time period”) is not limited to two half wave periods of the AC power source 101. Specifically, from the viewpoint of ensuring redundancy when there is an influence of external surge, for example, it is desirable to set a longer determination confirmation time period for the determination portion 111. Meanwhile, from the viewpoint of preventing such a situation that the plurality of heating elements generate heat at the same time, to thereby cause excessive temperature rise of the heater 251, it is desirable to set a shorter determination confirmation time period for the determination portion 111. It is accordingly required to set, for each apparatus, an appropriate determination confirmation time period for the determination portion 111 in consideration of both of the viewpoints.
Further, as shown in Table 1, the configuration of the first embodiment cannot distinguish State D (T1 and T2 terminals of both of the triac 104 and the triac 105 are in a conductive state) and State E (power supply from the AC power source 101 to the apparatus is OFF) from each other. As a result, in a case of instantaneous power failure of the AC power source 101, for example, the determination portion 111 is required not to erroneously confirm a simultaneous conductive state of a plurality of triacs. To that end, it is required to set the determination confirmation time period of the determination portion 111 to be longer than the instantaneous power failure time period estimated in the apparatus, through increasing a discharge time constant defined by the capacitor 221 and the resistor 222, for example. As described above, the time period required for the determination portion 111 to determine and confirm the simultaneous conductive state of the plurality of triacs is desirably set so as to deal with a plurality conditions such as instantaneous power failure, external surge, and excessive power supply to a load.
As described above, according to the first embodiment, an accuracy in failure determination of the heating apparatus configured to exclusively supply power to the plurality of heating elements can be improved.
With reference to
[Details of Detection Circuit]
With reference to
The detection circuit 113 is connected in series to between the T1 terminal and the T2 terminal of the triac 105. In a case of the T1 terminal and the T2 terminal of the triac 105 being in a non-conductive state, a light emitting portion 517a of an AC photocoupler 517 does not emit light, and a collector and an emitter of a light receiving transistor 517b of the AC photocoupler 517 are brought into a non-conductive state. Meanwhile, when the T1 terminal and the T2 terminal of the triac 105 are in a conductive state, an electric current flows from the AC power source 101 via a current limiting resistor 518 so that the light emitting portion 517a of the AC photocoupler 517 emits light. As a result, the collector and the emitter of the light receiving transistor 517b of the AC photocoupler 517 are brought into a conductive state.
(Determination Portion)
A determination portion 114 illustrated in
Meanwhile, when any one of the collector and the emitter of the light receiving transistor 507b of the AC photocoupler 507 and the collector and the emitter of the light receiving transistor 517b of the AC photocoupler 517 are in a non-conductive state, the capacitor 521 is charged by the power source Vcc1 via the resistor 522. Further, when both of the collector and the emitter of the light receiving transistor 507b of the AC photocoupler 507 and the collector and the emitter of the light receiving transistor 517b of the AC photocoupler 517 are in a non-conductive state, the capacitor 521 is also charged by the power source Vcc1 via the resistor 522. In this example, a resistance value of the resistor 520 is set smaller than a resistance value of the resistor 522. Thus, when both of the collector and the emitter of the light receiving transistor 507b of the AC photocoupler 507 and the collector and the emitter of the light receiving transistor 517b of the AC photocoupler 517 are in a conductive state, an electric current of the capacitor 521 has a relationship of (discharge current)>(charge current). A voltage at a node to which the capacitor 521 and the resistor 520 are connected, is input to the inverting input terminal of the comparator 223 to be compared with the reference voltage Vref of the non-inverting input terminal. Subsequent operations are the same as those of the first embodiment, and thus descriptions thereof are omitted.
The above-mentioned state is shown in Table 2.
A first column to a sixth column of Table 2 are the same as the first column to the sixth column of Table 1. The fifth column and the sixth column hold states of the detection circuit 112 and the detection circuit 113, respectively. In Table 2, in State D in which the plurality of triacs 104 and 105 are in a simultaneous conductive state, both of the light emitting portion 507a of the detection circuit 112 and the light emitting portion 517a of the detection circuit 113 are brought into a light emitting state. Here, State D in which both of the light emitting portion 507a of the detection circuit 112 and the light emitting portion 517a of the detection circuit 113 are in a light emitting state is different from any other states: States A. B, C, and E. and thus it can be understood that only State D can be accurately detected.
With reference to
[Operation of Determination Portion]
With reference to
<Section 3 and Section 4>
In Section 3 and Section 4, the T1 terminal and the T2 terminal of the triac 104 are in a conductive state (ON), and the T1 terminal and the T2 terminal of the triac 105 are in a non-conductive state (OFF). Under this state, the collector and the emitter of the light receiving transistor 507b of the AC photocoupler 507 are brought into a conductive state (ON), and the collector and the emitter of the light receiving transistor 517b of the AC photocoupler 517 are brought into a non-conductive state (OFF) (State B). As a result, the capacitor 521 is charged by the power source Vcc1 via the resistor 222 so that the voltage of the inverting input terminal of the comparator 223 is increased or fully charged. In Section 3 and Section 4, the voltage of the inverting input terminal of the comparator 223 is higher than the voltage of the non-inverting input terminal. Thus, the output transistor (not shown) of the comparator 223 is kept ON, and the contact of the electromagnetic relay 103 is maintained in a conductive state (ON).
<Section 5>
In Section 5, the T1 terminal and the T2 terminal are in a conductive state (ON) in both of the triac 104 and the triac 105. This condition means that the apparatus is not normally controlled and is in an abnormal state. Thus, both of the collector and the emitter of the light receiving transistor 507b of the AC photocoupler 507 and the collector and the emitter of the light receiving transistor 517b of the AC photocoupler 517 are brought into a conductive state (ON) (State D). Under this state, charges of the capacitor 521 are released via the resistor 520, and the voltage of the inverting input terminal of the comparator 223 is reduced. In Section 5, the voltage of the inverting input terminal of the comparator 223 is reduced but does not fall below the reference voltage Vref of the non-inverting input terminal of the comparator 223. Thus, the output transistor (not shown) of the comparator 223 is kept ON, and the contact of the electromagnetic relay 103 is maintained in a conductive state (ON).
<Section 6>
In Section 6, the T1 terminal and the T2 terminal of the triac 104 are in a non-conductive state (OFF), and the T1 terminal and the T2 terminal of the triac 105 are in a conductive state (ON). Under this state, the light receiving transistor 507b of the AC photocoupler 507 is brought into a non-conductive state (OFF), and the light receiving transistor 517b of the AC photocoupler 517 is brought into a conductive state (ON) (State C). With this, the capacitor 521 is charged by the power source Vcc1 via the resistor 522. In Section 5, the voltage of the inverting input terminal of the comparator 223 is reduced, and thus in Section 6, the voltage of the inverting input terminal of the comparator 223 is increased. The voltage of the inverting input terminal of the comparator 223 is higher than the reference voltage Vref of the non-inverting input terminal of the comparator 223, and thus the output transistor (not shown) of the comparator 223 is kept ON, and the contact of the electromagnetic relay 103 is maintained in a conductive state (ON).
<Section 7 and Section 8>
In Section 7 and Section 8, a period in which the T1 terminal and the T2 terminal are in a conductive state (ON) in both of the triac 104 and the triac 105 (State D) continues for two half wave periods of the AC power source 101. With this, the voltage of the inverting input terminal of the comparator 223 falls below the reference voltage Vref of the non-inverting input terminal of the comparator 223 at a timing “P” in Section 8. Then, the output transistor (not shown) of the comparator 223 is turned OFF so that an output of the comparator 223 is brought into a high impedance (Hiz) state, and a base current is supplied from the power source Vcc1 via the resistor 225 and the resistor 226 to the transistor 227. The collector and the emitter of the transistor 227 supplied with the base current are brought into a conductive state, and an electric current supplied from the CPU 219 to the transistor 229 is sunk by the transistor 227 via the resistor 228. Thus, the collector and the emitter of the transistor 229 are brought into a non-conductive state. Then, the contact of the electromagnetic relay 103 is brought into a non-conductive state (OFF), to thereby shut-off power supply from the AC power source 101 to the heater 251.
The determination portion 114 determines that a simultaneous conductive state of the triac 104 and the triac 105 is confirmed at the timing “0.” As a result, the contact of the electromagnetic relay 103 is brought into a non-conductive state, and then maintained in that state by the latch circuit 224 while an electric current of the power source Vcc1 is output. The determination portion in the second embodiment can distinguish the state in which power supply from the AC power source 101 to the apparatus is stopped and the simultaneous conductive state of the plurality of triacs from each other. Thus, unless there are constrains specific to apparatus, it is desirable to adopt the configuration of the second embodiment.
As described above, according to the second embodiment, an accuracy in failure determination of the heating apparatus configured to exclusively supply power to the plurality of heating elements can be improved.
[Detection Circuit]
Description is given of the detection circuit 115 and the detection circuit 116 configured to detect conductive states of the triacs 104 and 105, respectively. In the following description, it is assumed that a section of positive half wave of the AC power source 101 is adopted. The detection circuit 115 is connected in series to between the T1 terminal and the T2 terminal of the triac 104. In a case of the T1 terminal and the T2 terminal of the triac 104 being in a non-conductive state, the light emitting portion 707a of the DC photocoupler 707 does not emit light, and a collector and an emitter of a light receiving transistor 707b of the DC photocoupler 707 are brought into a non-conductive state. Meanwhile, when the T1 terminal and the T2 terminal of the triac 104 are in a conductive state, an electric current flows from the AC power source 101 via a current limiting resistor 508 so that the light emitting portion 707a of the DC photocoupler 707 emits light. As a result, the collector and the emitter of the light receiving transistor 707b of the DC photocoupler 707 are brought into a conductive state.
The detection circuit 116 is connected in series to between the T1 terminal and the T2 terminal of the triac 105. In a case of the T1 terminal and the T2 terminal of the triac 105 being in a non-conductive state, a light emitting portion 717a of a DC photocoupler 717 does not emit light, and a collector and an emitter of a light receiving transistor 717b of the DC photocoupler 717 are brought into a non-conductive state. Meanwhile, when the T1 terminal and the T2 terminal of the triac 105 are in a conductive state, an electric current flows from the AC power source 101 via a current limiting resistor 518 so that the light emitting portion 717a of the DC photocoupler 717 emits light. As a result, the collector and the emitter of the light receiving transistor 717b of the DC photocoupler 717 are brought into a conductive state.
The above-mentioned state is shown in Table 3.
A first column to a sixth column of Table 3 are the same as the first column to the sixth column of Table 2. The fifth column and the sixth column hold states of the detection circuit 115 and the detection circuit 116, respectively. In the third embodiment, the light emitting portion 707a of the detection circuit 115 and the light emitting portion 717a of the detection circuit 116 emit light only in a positive half wave period of the AC power source 101.
[Operation of Determination Portion]
With reference to
<Section 6>
In Section 6, as in Section 4, the detection circuit 116 cannot detect that the T1 terminal and the T2 terminal of the triac 105 are in a conductive state (ON). Hence, the collector and the emitter of the light receiving transistor 717b of the DC photocoupler 717 of the detection circuit 116 are brought into a non-conductive state (OFF).
<Section 7 to Section 9>
In Section 7 to Section 9, both of the T1 terminal and the T2 terminal of the triac 104 and the T1 terminal and the T2 terminal of the triac 105 are in a conductive state (ON). Section 7 and Section 9 correspond to a positive half wave period of the AC power source 101, and thus the detection circuit 115 and the detection circuit 116 detect that both of the T1 terminal and the T2 terminal of the triac 104 and the T1 terminal and the T2 terminal of the triac 105 are in a conductive state (ON) (State D). As a result, the voltage of the non-inverting input terminal of the comparator 223 is reduced.
Meanwhile, Section 8 corresponds to a negative half wave period of the AC power source 101, and the detection circuit 115 and the detection circuit 116 cannot detect that both of the T1 terminal and the T2 terminal of the triac 104 and the T1 terminal and the T2 terminal of the triac 105 are in a conductive state (ON). As a result, the voltage of the non-inverting input terminal of the comparator 223 is increased. Thus, in Section 7 to Section 9, as illustrated in
As described above, with the configuration of the third embodiment, the DC photocouplers 707 and 717 are used to detect the simultaneous conductive state of the triacs 104 and 105 depending on the polarity of the AC power source 101. Thus, as compared with a case of using the AC photocoupler, it takes longer time for the determination portion 114 to confirm the simultaneous conductive state of the plurality of triacs 104 and 105. Specifically, in the second embodiment, the determination portion 114 confirms the simultaneous conductive state of the plurality of triacs 104 and 105 with two half wave periods of the AC power source 101 (at the timing “0” in Section 8). In contrast, in the third embodiment that adopts the DC photocouplers, the determination portion 114 requires at least three half wave periods (at the timing “y” in Section 9) to confirm the simultaneous conductive state of the plurality of triacs 104 and 105. Despite the above, the DC photocoupler is generally available at lower cost than that of the AC photocoupler, and thus the apparatus can be provided at low cost.
In the third embodiment, the DC photocouplers are connected so that the simultaneous conductive state of the triacs can be detected in a positive half wave period of the AC power source 101. However, the following configuration may be adopted, the DC photocouplers are connected with their light emitting portions having an opposite polarity so that the simultaneous conductive state of the triacs 104 and 105 can be detected in a negative half wave period of the AC power source 101. Further, the DC photocoupler may be applied to the detection circuits 109 and 110 of the first embodiment.
As described above, according to the third embodiment, an accuracy in failure determination of the heating apparatus configured to exclusively supply power to the plurality of heating elements can be improved.
According to the embodiments, an accuracy in failure determination of the heating apparatus configured to exclusively supply power to the plurality of heating elements can be improved.
Embodiment(s) of the present invention can also be realized by a computer of a system or apparatus that reads out and executes computer executable instructions (e.g., one or more programs) recorded on a storage medium (which may also be referred to more fully as a ‘non-transitory computer-readable storage medium’) to perform the functions of one or more of the above-described embodiment(s) and/or that includes one or more circuits (e.g., application specific integrated circuit (ASIC)) for performing the functions of one or more of the above-described embodiment(s), and by a method performed by the computer of the system or apparatus by, for example, reading out and executing the computer executable instructions from the storage medium to perform the functions of one or more of the above-described embodiment(s) and/or controlling the one or more circuits to perform the functions of one or more of the above-described embodiment(s). The computer may comprise one or more processors (e.g., central processing unit (CPU), micro processing unit (MPU)) and may include a network of separate computers or separate processors to read out and execute the computer executable instructions. The computer executable instructions may be provided to the computer, for example, from a network or the storage medium. The storage medium may include, for example, one or more of a hard disk, a random-access memory (RAM), a read only memory (ROM), a storage of distributed computing systems, an optical disk (such as a compact disc (CD), digital versatile disc (DVD), or Blu-ray Disc (BD)™), a flash memory device, a memory card, and the like.
While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.
This application claims the benefit of Japanese Patent Application No. 2020-038910, filed Mar. 6, 2020, which is hereby incorporated by reference herein in its entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2020-038910 | Mar 2020 | JP | national |
