JP2011203631A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent cost from increasing and time and labor for change from being required in order to change a fuse or a power supply unit because of unwanted fusing of the fuse by fusing the fuse only when an abnormal temperature occurs due to heat generation of a heat source such as a halogen lamp.SOLUTION: A printer 1 includes: a heat source control switch 234 that switches power supply of a commercial power supply 80 to the halogen lamp 26; the fuse 232 that is connected to the halogen lamp 26 in series; a resistor 231 that is connected to the halogen lamp 26 in parallel; a switch for a resistor 235 that is connected to the halogen lamp 26 in parallel and connected to the resistor 231 in series; and a printer controller 7 that controls switching of the heat source control switch 234 and the switch for the resistor 235. A rated current value of the fuse 232 is set to a value which is equal to or above each of rated current values of the halogen lamp 26 and the resistor 231, and smaller than a total value of the rated current values of the halogen lamp 26 and the resistor 231.

Description

The present invention relates to an image forming apparatus, and more particularly to a technique for supplying electric power to a heat source unit that heats a heat roller in a fixing device.

  Conventionally, in an image forming apparatus, for example, a halogen lamp is used as a heat source for performing heat fixing in a fixing device. Such an image forming apparatus is equipped with a function for reliably shutting off the power supply to the heat source when a failure occurs in the apparatus. Specifically, the temperature in the fixing device is detected by a temperature sensor, and when the temperature sensor detects the occurrence of temperature abnormality, the triac that performs ON / OFF control of power supply to the halogen lamp that is a heat source. Is turned off to cut off the power supply to the heat source. In consideration of the failure of the triac and the ground fault of the wiring from the halogen lamp to the triac, in the image forming apparatus shown in Patent Document 1 below, a fuse is connected in series with the halogen lamp, and the SW (triac is connected in parallel with the halogen heater. ) And a resistor, and when the temperature sensor detects a temperature abnormality, the SW is turned on, the fuse arranged in series with the halogen lamp is set in an overcurrent state, and the fuse is blown to blow the halogen. The power supply to the lamp is cut off.

Japanese Patent Laid-Open No. 02-22684

  However, in the case of the power supply interruption method to the heat source employed in the image forming apparatus disclosed in Patent Document 1, when the temperature is abnormal due to the heat generation of the halogen lamp, the fuse is surely connected to the halogen lamp. Although the power supply can be shut off, even if the temperature abnormality is detected due to the failure of the temperature sensor that detects the temperature in the fixing device, and the temperature abnormality is not caused by the heat generation of the halogen lamp, The fuse is blown to cut off the power supply. There has been a problem in that the cost is increased and the time and effort for replacing the fuses are generated due to such unnecessary fuse blown fuses.

  The present invention has been made to solve the above-mentioned problem. The fuse is not blown when a temperature abnormality is detected due to a failure of a temperature sensor, and the fuse is used only when the temperature is abnormal due to heat generation of a heat source such as a halogen lamp. The purpose of this invention is to avoid an increase in costs and troubles due to replacement of a fuse due to unnecessary fuse blowing or a power supply unit provided with the fuse.

The invention according to claim 1 of the present invention includes a fixing unit having a heat roller and a pressure roller;
A heat source for heating the heat roller;
A switching unit that is connected in series to the heat source unit on a power supply line that connects the power source and the heat source unit, and that switches whether to supply power for driving the heat source unit from the power source to the heat source unit;
A temperature detector for detecting the temperature of the heat roller;
A fuse connected in series to the heat source unit on a power line connecting the power source and the heat source unit;
A resistor connected in parallel to the heat source connected to the power source by the power line;
The power source line is connected in parallel to the heat source unit connected to the power source, and is connected in series to the resistor to determine whether to supply power from the power source to the resistor. A switch for switching resistors,
A controller for controlling the switching operation by the switch and the resistor switch according to the temperature of the heat roller detected by the temperature detector;
The rated current value of the fuse is a value equal to or higher than the rated current value of the heat source unit and the rated current value of the resistor, and the rated current value of the heat source unit and the rated current value of the resistor The image forming apparatus has a value smaller than the total value.

  In this invention, when an abnormal temperature is detected by the temperature detection unit, the control unit controls the switching unit to cut off the power supply to the heat source unit and to supply power to the resistor by the resistor switch. For example, if a current flows through the heat source unit due to a failure of the switching unit and the heat source unit generates heat, the rated current value of the fuse is smaller than the sum of the rated current value of the heat source unit and the rated current value of the resistor. The fuse is blown because it is a value. On the other hand, if, for example, the switching section performs a switching operation normally and current does not flow through the heat source section and does not generate heat, the rated current value of the fuse is greater than the rated current value of the resistor. Therefore, the fuse does not blow. As a result, it is possible to avoid an increase in cost and replacement due to unnecessary fuse melting or replacement of the power supply unit provided with the fuse.

  According to a second aspect of the present invention, there is provided the image forming apparatus according to the first aspect, wherein the control unit is configured such that a value detected by the temperature detection unit indicates a preset abnormal temperature. The switching unit causes the switching unit to perform a switching operation to cut off the power supply to the heat source unit, and causes the resistor switch to perform a switching operation to supply the resistor with the power.

  According to a third aspect of the present invention, in the image forming apparatus according to the second aspect, when the value detected by the temperature detection unit indicates a predetermined normal temperature, the control unit The switching unit causes the switching unit to perform the switching operation to supply the power to the heat source unit, and causes the resistor switch to perform the switching operation to block the power supply to the resistor.

  In these inventions, when the value detected by the temperature detection unit indicates a preset abnormal temperature, the control unit causes the switching unit to perform a switching operation to cut off power supply to the heat source unit. Since the resistor switch performs a switching operation to supply power to the resistor, for example, if a current flows to the heat source part due to a failure of the switching part or the like and the heat source part generates heat, the rated current value of the fuse is The fuse is blown because it is smaller than the sum of the rated current value of the heat source unit and the rated current value of the resistor. On the other hand, for example, the switching unit normally performs a switching operation, and the current is not supplied to the heat source unit. If no current flows and no heat is generated, the rated current value of the fuse is greater than the rated current value of the resistor, so the fuse does not blow.

  According to the present invention, the fuse is not blown at the time of detecting a temperature abnormality due to a failure of the temperature sensor, and the fuse is blown only at a temperature abnormality caused by heat generation of a heat source such as a halogen lamp. It is possible to avoid an increase in cost and occurrence of troubles due to replacement of a fuse due to blown fuse or a power supply unit provided with the fuse.

1 is a front sectional view for explaining an embodiment of an internal structure of a printer which is a kind of image forming apparatus according to the present invention. FIG. 2 is a block configuration diagram illustrating a control system of a fixing device according to an embodiment of the present invention. 6 is a flowchart showing power supply cutoff control of a halogen lamp when the fixing device is at an abnormal temperature.

  Hereinafter, an image forming apparatus according to an embodiment of the present invention will be described with reference to the drawings. The image forming apparatus according to the present invention is not limited to the embodiment described below.

  FIG. 1 is a front sectional view for explaining an embodiment of the internal structure of a printer which is a kind of image forming apparatus according to the present invention. As shown in this figure, a printer (image forming apparatus) 1 includes a sheet storage unit 12 that stores sheets P to be subjected to a printing process, and one sheet fed from a sheet bundle P1 stored in the sheet storage unit 12. The apparatus main body 11 includes a transfer unit 13 that performs an image transfer process on a sheet P (material to be transferred) P and a fixing device 14 that performs a fixing process on the sheet P subjected to the transfer process in the transfer unit 13. And a paper discharge section 15 for discharging the paper P on which the fixing process has been performed by the fixing device 14 is provided at the top of the apparatus main body 11.

  A predetermined number (one in this embodiment) of paper cassettes 121 is provided in the paper storage unit 12 so as to be detachable from the apparatus main body 11. A pickup roller 122 is provided at the upstream end (right side in FIG. 1) of the paper cassette 121 to feed out the paper P one by one from the paper bundle P1. The paper P fed out of the paper cassette 121 by driving the pickup roller 122 is fed to the transfer unit 13 via the paper feed conveyance path 123 and the registration roller pair 124 provided at the downstream end of the paper feed conveyance path 123. It has come to be.

  The transfer unit 13 performs a transfer process on the paper P based on image information transmitted from a computer or the like, and is provided to be rotatable around a drum core extending in the front-rear direction (a direction perpendicular to the paper surface of FIG. 1). The charging roller 30, the exposure device 40, the developing device 50, the transfer roller 60, and the cleaning device from the position directly above the photosensitive drum 20 in the clockwise direction along the peripheral surface of the photosensitive drum 20 (image carrier). 70 is provided.

  The photosensitive drum 20 is for forming an electrostatic latent image and a toner image (visible image) corresponding to the electrostatic latent image on the peripheral surface, and an amorphous silicon layer is laminated on the peripheral surface. This makes it suitable for forming these images.

  The charging roller 30 forms a uniform charge on the peripheral surface of the photosensitive drum 20 rotating in the clockwise direction around the drum core, and is driven while the peripheral surface is in contact with the peripheral surface of the photosensitive drum 20. Electric charges are applied to the photosensitive drum 20 while rotating. Instead of the charging roller 30, a corona discharge type that applies a charge to the peripheral surface of the photosensitive drum 20 by corona discharge from a wire may be employed.

  The exposure device 40 irradiates the peripheral surface of the rotating photoconductor drum 20 with laser light to which intensity is applied based on image data transmitted from an external device such as a computer, and the photoconductor drum 20 by this is irradiated. An electrostatic latent image is formed on the peripheral surface of the photosensitive drum 20 by erasing the electric charge in the portion where the laser light on the peripheral surface is checked.

  The developing device 50 supplies the toner to the peripheral surface of the photosensitive drum 20 by supplying the toner to the peripheral surface of the photosensitive drum 20, whereby the toner image is formed on the peripheral surface of the photosensitive drum 20. To form.

  The transfer roller 60 transfers a positively charged toner image S formed on the peripheral surface of the photosensitive drum 20 to the paper P with respect to the paper P sent to a position immediately below the photosensitive drum 20. In other words, a negative charge having a polarity opposite to that of the toner image S is applied to the paper P.

  Therefore, the sheet P that has reached the position immediately below the photosensitive drum 20 is pressed and held between the transfer roller 60 and the photosensitive drum 20, and the toner image S on the circumferential surface of the photosensitive drum 20 that is positively charged is negatively charged. The sheet P is peeled off toward the surface of the paper P, whereby the transfer process is performed on the paper P.

The cleaning device 70 is for removing the toner remaining on the peripheral surface of the photosensitive drum 20 after the transfer process and cleaning it. The peripheral surface of the photosensitive drum 20 cleaned by the transfer roller 60 is again directed to the charging roller 30 for the next image forming process.

  The fixing device (fixing unit) 14 performs a fixing process by heating the toner image S of the paper P subjected to the transfer process by the transfer unit 13, and includes a heat roller 141 in which an energizing heating element is mounted. The pressure roller 142 has a configuration in which a peripheral surface is disposed opposite to the lower portion of the heat roller 141. Then, the sheet P after the transfer process is between the heat roller 141 that is driven to rotate clockwise around the roller center and the pressure roller 142 that is driven to rotate counterclockwise around the roller center. By passing through the nip portion, the heat from the heat roller 141 is obtained and the fixing process is performed. The paper P subjected to the fixing process is discharged to the paper discharge unit 15 through the paper discharge conveyance path 143.

  The paper discharge unit 15 is formed by recessing the top of the apparatus main body 11, and a paper discharge tray 151 for receiving the discharged paper P is formed at the bottom of the concave portion.

  FIG. 2 is a block diagram showing a control system of the fixing device according to the embodiment of the present invention.

  The printer 1 includes a printer control unit 7 and a power supply unit 23 as a control system, and includes the above-described fixing device 14 as a control target by the printer control unit 7 and the power supply unit 23.

  The fixing device 14 includes a heat roller 141, a pressure roller 142, a thermistor 25, and a halogen lamp 26.

  The thermistor 25 functions as a temperature detection unit that detects the temperature of the heat roller 141 in the fixing device 14. That is, the thermistor 25 is an example of a temperature detection unit in the claims. The thermistor 25 detects the temperature of the heat roller 141 heated by the halogen lamp 26 and outputs the detected temperature value to the CPU 71 of the printer controller 7.

  The halogen lamp 26 functions as a heat source for heating the heat roller 141. That is, the halogen lamp 26 is an example of a heat source unit in the claims. The halogen lamp 26 is provided in the heat roller 141 and the like. The halogen lamp 26 is connected in series to the commercial power source 80 and is driven by the power supplied from the commercial power source 80 to generate heat. The driving of the halogen lamp 26 by the electric power from the commercial power supply 80 is controlled by the printer control unit 7 and the power supply unit 23.

  The printer control unit 7 includes a CPU 71, a RAM 72, and a ROM 73. The CPU 71, RAM 72, and ROM 73 are connected by a data bus so that data can be exchanged between them. The printer control unit 7 is an example of a control unit in the claims.

  The CPU 71 is an arithmetic unit that controls overall operation of the printer 1. The CPU 71 acquires temperature information in the fixing device 14 from the thermistor 25 in the fixing device 14 as a temperature detection value, and performs ON / OFF control of the heat source control switch 234 in the power supply unit 23 based on the temperature detection value. That is, the CPU 71 controls the switching operation of the heat source control switch 234 to control the supply and cut-off of power to the halogen lamp 26 and set the temperature in the fixing device 14 to a predetermined temperature (for example, normal image formation). Control such as 180-200 ° C during operation).

  Further, the CPU 71 performs ON / OFF control of the resistor switch 235 in the power supply unit 23 based on the temperature detection value acquired from the thermistor 25 in the fixing device 14. That is, the CPU 71 controls the switch switching operation by the resistor switch 235 to switch the supply or non-supply of the power from the commercial power supply 80 to the resistor 231.

  The ROM 73 stores an operation program necessary for overall operation control of the printer 1 by the CPU 71 and switching operation control of the heat source control switch 234 and the resistor switch 235 based on the temperature detection value of the thermistor 25. .

  The RAM 72 is used as a work area for the CPU 71 during operation control based on the operation program stored in the ROM 76.

  The power supply unit 23 includes a resistor 231, a fuse 232, an AC / DC converter 233, a heat source control switch 234, and a resistor switch 235, which are connected as shown in FIG.

  As shown in FIG. 2, the resistor 231 is connected in parallel to the halogen lamp 26 to the power supply line 100 that connects the commercial power supply 80 and the halogen lamp 26 in series.

  The fuse 232 is connected in series to the halogen lamp 26 on the power supply line 100 that connects the commercial power supply 80 and the halogen lamp 26 in series. The fuse 232 is blown when the total current consumed by the halogen lamp 26 and the resistor 231 exceeds a predetermined current value, which will be described later, and stops supplying power from the commercial power supply to the halogen lamp 26.

  The AC / DC converter 233 branches from the power supply line 100 at a position closer to the commercial power supply 80 than the fuse 232 and is connected in series to the commercial power supply 80, and the alternating current supplied from the commercial power supply 80 is converted into a direct current. The data is converted and supplied to the printer controller 7.

  The heat source control switch (switching unit) 234 is configured by a triac or the like, and is connected in series to the halogen lamp 26 on the power supply line 100 that connects the commercial power supply 80 and the halogen lamp 26. The heat source control switch 234 is a switch that performs an operation of switching whether or not to supply the electric power for driving the halogen lamp 26 from the commercial power supply 80 to the halogen lamp 26 in the fixing device 14.

  The resistor switch 235 is configured by a triac or the like, and is connected in parallel to the halogen lamp 26 connected to the commercial power source 80 by the power line 100. The resistor switch 235 is a switch that is connected in series to the resistor 231 and performs an operation of switching whether to supply power from the commercial power supply 80 to the resistor 231. The resistor switch 235 is switched so that the CPU 71 supplies power to the resistor 231 when the CPU 71 determines that the temperature inside the fixing device 14 is abnormal based on the temperature detection value acquired from the thermistor 25. .

  The rated current value of the fuse 232 is a value equal to or higher than the rated current value of the halogen lamp 26 and the rated current value of the resistor 231, and the rated current value of the halogen lamp 26 and the rated value of the resistor 231 are the same. The current value is smaller than the total value.

  That is, the specifications of the fuse 232 are as follows: (1) it is not blown by the current flowing through the halogen lamp 26, (2) it is not blown by the current flowing through the resistor 231, and (3) the current flowing through the halogen lamp 26 and the resistor 231 is It is assumed that all conditions of fusing with the sum are satisfied.

  For example, when a product with a rated current value of 8 [A] is used for the halogen lamp 26, a product with a rated current value of 9 [A] is used for the fuse 232, and a rated current value of 9 [A] for the fuse 232 is used for the resistor 231. And a halogen lamp 26 having a resistance value capable of flowing a current equal to or greater than the difference between the rated current values 8 [A]. For example, the fuse 232, the halogen lamp 26, and the resistor are set so that the rated current value 9 [A] of the fuse 232 <the rated current value 8 [A] of the halogen lamp 26 + the rated current value 2 [A] of the resistor 231. Each rated current value of 231 is set.

  Next, the power supply cutoff control of the halogen lamp 26 when the thermistor 25 detects an abnormal temperature of the fixing device 14 will be described. FIG. 3 is a flowchart showing power supply cutoff control of the halogen lamp 26 when the fixing device 14 has an abnormal temperature. Here, the case where the rated current value 9 [A] of the fuse 232, the rated current value 8 [A] of the halogen lamp 26, and the rated current value 2 [A] of the resistor 231 are employed will be described as an example. To do.

  When the power switch (not shown) of the printer 1 is turned on (YES in S1), the CPU 71 of the printer control unit 7 sets the heat roller of the fixing device 14 to enable the printer 1 to perform an image forming operation. Control for heating 141 is performed. In this control, the CPU 71 turns on the heat source control switch 234 and turns off the resistor switch 235 in order to raise the temperature of the fixing device 14 to a temperature at which the fixing operation can be performed (for example, 180 to 200 ° C.). (S2). That is, the CPU 71 causes the heat source control switch 234 to perform switching switching so that power is supplied from the commercial power supply 80 to the halogen lamp 26, while the resistor 231 is not supplied with power from the commercial power supply 80. The resistor switch 235 is switched. At this time, since the rated current value of the fuse 232 is equal to or higher than the rated current value of the halogen lamp 26, the fuse 232 is not blown.

  Thereafter, the CPU 71 acquires a temperature detection value indicating the temperature in the fixing device 14 from the thermistor 25 (S3), and determines whether or not the temperature detection value indicates a predetermined abnormal temperature (S4). . The abnormal temperature is a temperature that exceeds the temperature at which the fixing operation can be performed (for example, 180 to 200 ° C.). The abnormal temperature is too high for the image forming operation and the fixing operation, and the heating of the heat roller 141 by the halogen lamp 26 is performed. Is the temperature at which it is necessary to stop immediately. For example, the abnormal temperature is stored in the RAM 72 by the manufacturer before shipment of the printer 1, or is incorporated as a part of the operation program in the ROM 73.

  When the CPU 71 determines that the temperature detection value is a normal temperature (for example, a temperature of 180 to 200 ° C. or less) that does not indicate a predetermined abnormal temperature (NO in S4), the CPU 71 performs basic control. As the state, the heat source control switch 234 is turned on and the resistor switch 235 is turned off, and the heat source control switch 234 is turned on and off for maintaining the temperature of the fixing device 14 at the above-described temperature at which the fixing operation can be performed. I do. The CPU 71 continues to acquire the temperature detection value from the thermistor 25 (S3).

  When the CPU 71 determines that the temperature detection value indicates a predetermined abnormal temperature (YES in S4), the CPU 71 turns off the heat source control switch 234 and power from the commercial power source 80 is not supplied to the halogen lamp 26. Then, the resistor switch 235 is turned on so that the resistor 231 is supplied with power from the commercial power source 80 (S5).

  At this time, for example, due to a failure of the heat source control switch 234 or the like, the heat source control switch 234 cannot cut off the power supply from the commercial power source 80 and the current from the commercial power source 80 flows through the halogen lamp 26 ( That is, when the heating of the heat roller 141 by the halogen lamp 26 cannot be stopped due to a failure of the heat source control switch 234 or the like, the current 8 [A] flowing through the halogen lamp 26 and the current 2 flowing through the resistor 231 are passed through the fuse 232. 10 [A], which is the sum of [A], flows and exceeds the rated current value 9 [A] of the fuse 232. As a result, the fuse 232 is blown and the power to the halogen lamp 26 is shut off.

  On the other hand, when the heat source control switch 234 performs a normal switching operation and the current from the commercial power supply 80 does not flow through the halogen lamp 26 (that is, the heating roller 141 is heated by the halogen lamp 26 by switching the heat source control switch 234. In this state, only the current 2 [A] flowing through the resistor 231 flows through the fuse 232, so that the fuse 232 is not blown. That is, when the temperature detection value obtained from the thermistor 25 indicates an abnormal temperature due to a failure of the thermistor 25 or the like even though the heat source control switch 234 is normally switching, the fuse 232 is not blown. .

  For this reason, in the printer 1, the fuse 232 is blown only when the temperature is abnormal due to the heat generated by the halogen lamp 26 as a heat source, so that the fuse 232 or the power supply unit 23 can be replaced by blowing the unnecessary fuse 232. It is possible to avoid an increase in cost and troublesome replacement.

  The present invention is not limited to the configuration of the above embodiment, and various modifications can be made. For example, the halogen lamp 26 is merely an example of a heat source unit, and a mechanism other than the halogen lamp 26 may be used as the heat source unit. The thermistor 25 is only an example of a temperature detection unit, and a mechanism other than the thermistor 25 may be used as the temperature detection unit.

  1 to 3 is merely an example of the configuration and processing of the image forming apparatus according to the present invention, and the configuration and processing of the image forming apparatus according to the present invention. The contents are not limited to those described above.

DESCRIPTION OF SYMBOLS 1 Printer 7 Printer control part 14 Fixing device 141 Heat roller 142 Pressure roller 25 Thermistor 26 Halogen lamp 23 Power supply unit 231 Resistor 232 Fuse 234 Heat source control switch 235 Resistor switch 80 Commercial power supply 100 Power supply line

Claims (3)

A fixing unit having a heat roller and a pressure roller;
A heat source for heating the heat roller;
A switching unit that is connected in series to the heat source unit on a power supply line that connects the power source and the heat source unit, and that switches whether to supply power for driving the heat source unit from the power source to the heat source unit;
A temperature detector for detecting the temperature of the heat roller;
A fuse connected in series to the heat source unit on a power line connecting the power source and the heat source unit;
A resistor connected in parallel to the heat source connected to the power source by the power line;
The power source line is connected in parallel to the heat source unit connected to the power source, and is connected in series to the resistor to determine whether to supply power from the power source to the resistor. A switch for switching resistors,
A controller for controlling the switching operation by the switch and the resistor switch according to the temperature of the heat roller detected by the temperature detector;
The rated current value of the fuse is a value equal to or higher than the rated current value of the heat source unit and the rated current value of the resistor, and the rated current value of the heat source unit and the rated current value of the resistor An image forming apparatus having a value smaller than the total value.   When the value detected by the temperature detection unit indicates a preset abnormal temperature, the control unit causes the switching unit to perform a switching operation to cut off the power supply to the heat source unit. The image forming apparatus according to claim 1, wherein the resistor switch is configured to perform a switching operation to supply the power to the resistor.   When the value detected by the temperature detection unit indicates a predetermined normal temperature, the control unit causes the switching unit to perform a switching operation to perform the power supply to the heat source unit, and The image forming apparatus according to claim 2, wherein the switch for resistor is caused to perform a switching operation for cutting off the power supply to the resistor.

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