JP3457702B2 - Image forming apparatus using metal halide lamp - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus using a metal halide lamp, and particularly to a case where the metal halide lamp is used as a heating member of a fixing machine. The present invention also relates to an image forming apparatus using a metal halide lamp which prevents a large rush current from flowing to the metal halide lamp when power is turned on. 2. Description of the Related Art Conventionally, in an image forming apparatus, a metal halide lamp having a built-in heater is usually used as a heating member for fixing a toner image transferred onto recording paper. [0003] By the way, this metal halide lamp is
Because the lamp is warmed up sufficiently during use and the lamp temperature is high, its resistance (lamp internal impedance)
However, when the power is turned on, the resistance value (lamp internal impedance) is low because the lamp has not yet been sufficiently heated and the lamp temperature is low. FIG. 4 is a characteristic diagram showing an example of a relationship between a lamp temperature and a change in lamp internal impedance in a metal halide lamp. The horizontal axis represents the lamp temperature, and the vertical axis represents the lamp internal impedance. As shown in FIG. 4, when the lamp temperature is low, that is, when the lamp temperature is low, that is, when the power is turned on, the metal halide lamp has a high impedance, that is, the lamp internal impedance in a normal use state. Since the internal impedance of the lamp at this time is considerably low, when the power is turned on, a relatively large inrush current flows transiently into the power supply circuit for driving the metal halide lamp. When a large inrush current flows through the power supply circuit, it has a bad influence on the start-up operations of various devices connected to the power supply circuit. Therefore, in an image forming apparatus using a metal halide lamp, some means for eliminating the adverse effect have already been proposed. One of the means is a phase control means, and the means controls a halogen circuit by switching an AC power supply voltage of a commercial frequency at a frequency higher than the frequency in a power supply circuit for driving a metal halide lamp. The present invention is intended to prevent a transiently large rush current from flowing into a power supply circuit for driving a metal lamp, and another means is an on / off control means, wherein the means is a switching element such as an SCR. By switching on the AC power supply voltage of the commercial frequency at its zero-cross point, a transient large inrush current is prevented from flowing through the power supply circuit that drives the metal halide lamp. is there. [0007] However, since the known phase control means switches the AC power supply voltage of the commercial frequency at a frequency higher than the frequency, the phase control means transmits the AC power supply voltage to the AC power supply voltage. Noise is superimposed, and the noise affects other devices connected to the AC power supply, and it becomes difficult to satisfy the EMI regulation value that sets the noise standard of each country. Have On the other hand, although the known on / off control means can prevent transiently large inrush current from flowing through the power supply circuit, the power supply circuit still has at least 10 times the normal flowing current. This causes problems such as inevitable adverse effects on the operation of various devices connected to the power supply circuit. An object of the present invention is to eliminate the above-mentioned problems, and an object of the present invention is to eliminate the occurrence of conduction noise at the time of turning on the power and to reliably prevent the occurrence of a transiently large inrush current. An object of the present invention is to provide an image forming apparatus using a metal halide lamp. [0009] [0010] SUMMARY OF THE INVENTION To achieve the above object, the present invention is, metal halide lamps and between its driving power source, switches the first and in the order from the driving power source side A second switch is connected in cascade, a resistor is connected in parallel with the second switch, and a temperature sensing element is disposed inside the resistor. The on-time of the switch is controlled so as to be delayed from the on-time of the first switch, and when the temperature-sensitive element detects that the temperature of the resistor is equal to or higher than a certain value. ,
Means for controlling switching so as to turn off the contacts of the switch. According to the above means , when the internal impedance of the metal halide lamp at the time of turning on the power is in a considerably low state, the output current of the driving AC power supply is supplied to the metal halide lamp through the resistor. Since the inrush current flowing into the metal halide lamp is sufficiently suppressed by the resistance value of the resistor, the metal halide lamp is gradually heated, and the lamp temperature gradually rises. When the lamp temperature becomes sufficiently high after a certain period of time, the output current of the driving AC power supply is switched so as to be supplied to the metal halide lamp without passing through the resistor. The voltage of the driving AC power supply is fully applied,
It becomes the same as the normal operation drive state. Further, the above means
If power is turned on, a large current flows through the resistor
Or the current flows for a long time and the resistor
When the temperature rises above a predetermined value, the resistor
A temperature sensing element arranged in proximity detects the temperature rise, and
Since the output voltage of the drive power supply is cut off,
For any reason
Immediately when the effect of limiting the input current cannot be achieved
Supply of drive current to the metal halide lamp
Let As described above, according to the above-mentioned means, when the lamp internal impedance of the metal halide lamp is considerably low with a simple circuit configuration and without generating conduction noise, the metal halide lamp can be used. The inrush current that can flow can be sufficiently limited, and after the limitation of the inrush current is released, the metal halide lamp can be operated at the output voltage of a normal drive power supply. According to the above means, the halogenation
Of the inrush current flowing into the metal halide lamp
If not, automatically drive to metal halide lamp
Since the supply of current can be stopped,
Limiting inrush currents flowing into metal-genide lamps
Becomes possible. Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a schematic configuration diagram showing an entire configuration of an example of an image forming apparatus using a metal halide lamp according to the present invention. In FIG. 1, reference numeral 20 denotes a document feeder;
Is a contact lath, 22 is a document, 23 is an illumination lamp, 24 is an imaging lens, 25 is a charger, 26 is a photoreceptor belt, 27 is a developing machine, 28 is a transfer unit, 29 is a belt cleaner, and 30 is a fixing unit. vessel, the discharge tray 31, 32 recording sheets (transfer sheet), 33 ₁ to 33 ₄ are the paper feed tray, 34 paper path, 35 is inverted portion, 36 sorter 37 is bin. In the image forming apparatus, a document supply device 20 is disposed on a contact glass 21 provided on the upper surface of the apparatus main body, and a document 22 is appropriately placed in the document supply device 20. Around the photoreceptor belt 26,
A charger 25, an exposure unit including an illumination lamp 23 and an image forming lens 24, a developing unit 27, a transfer unit 28, and a belt cleaner 29 are arranged close to each other, and a fixing unit 30 is provided on an upper portion of the photosensitive belt 26. . On the side of the photoreceptor belt 26, a three-stage stacked paper feed tray 33 ₁ , 33 ₂ , 33 ₃
There is arranged, the recording sheet 32 are accommodated respectively in these feed tray 33 ₁ to 33 _3. The paper feed tray 33
Sheet discharge tray 31 is provided in the upper part of the ₁ to 33 _3. If necessary, adjacent to the image forming apparatus main body paper feeding device having a large capacity sheet feeding tray 33 ₄ and the sheet passage 34 are disposed close, reversing unit 3 adjacent to the sheet feeding device
5 are arranged close to each other, and a sorter 36 having a number of bins 37 therein is arranged close to the reversing unit 35. Although not shown in FIG. 1, the fixing device 30 includes a heating member for a visible image (toner image).
A metal halide lamp is used, and a rush current control circuit for the metal halide lamp as described below is provided. The image forming apparatus having the above-described configuration operates roughly as follows. When an image forming command is issued to the image forming apparatus, the photoreceptor belt 25 starts rotating and moving in the direction of the arrow. First, the surface of the photoreceptor belt 25 is uniformly charged by the charger 25. The portion is transferred to an exposure section where the exposure means is arranged. The originals 20 placed on the original supply device 20 are sequentially conveyed one by one onto a contact glass 21, and at this time, are illuminated by an illumination lamp 23. At this time, the image of the document 20 is sent to the exposure section through a reflection mirror and an imaging lens 24, where it is formed on the charged portion on the photoreceptor belt 25, and the image of the document 20 is formed on the charged portion. An electrostatic latent image is formed. Subsequently, the electrostatic latent image on the photoreceptor belt 25 is subjected to toner development in the developing device 9, converted into a visible image (toner image), and then transferred to a transfer unit where the transfer unit 28 is disposed. On the other hand, in synchronization with the transfer of the visible image to the transfer section,
One of the selected paper feed tray 33 _one to the one from 33 ₄ recording paper 32 is conveyed to the transfer portion, the transfer device 28
The visible image on the photoreceptor belt 25 is transferred onto the recording paper 32 by the action of (1). Next, after the visible image is transferred to the recording paper 32, the visible image is heated and fixed in the fixing unit 30 and then directly supplied to the paper output tray 31 or the paper path 34 or the reversing unit. It is supplied to a bin 37 of a sorter 36 through 35.
After the visible image has been transferred onto the recording sheet 32, the belt cleaner 29 removes the toner and the like remaining on the surface of the photosensitive belt 25, and a series of image forming operations is completed. Next, when a next image forming command is issued, a series of image forming operations executed at that time are almost the same as the above-described image forming operations. Each time a command is issued, the above-described operation is repeatedly performed. FIG. 2 is a circuit diagram showing one embodiment of a rush current control circuit of the metal halide lamp used in the fixing device 30 of FIG. In FIG. 2, 1 is a commercial frequency AC power supply, 2 is a main power switch also serving as a circuit breaker,
2-pole contact type electromagnetic switch is 3 ₁ a first contact of the electromagnetic switch 3, 3 ₂ and the second contact of the electromagnetic switch 3, 3 ₃ drive coil of the electromagnetic switch 3, 4 first 1-pole contact type electromagnetic switch, 4 ₁ contacts of the electromagnetic switch 4, 4 ₂ drive coil of the electromagnetic switch 4, 5 and the second single-pole contact type electromagnetic switch, 5 ₁ electromagnetic switch 5 contacts, 5 ₂ drive coil of the electromagnetic switch 5, the metal halide lamp 6, 7 thermistor, 8 fuse internal resistor, 8 ₁ resistor, ₈₂ fuse (temperature sensing element), 9 A driver array, 10 an input / output unit (I / O), 11 a central control unit (CPU) for controlling the operation of each unit, 12 a read-only memory (ROM) containing an image forming program, and 13 a random access A memory (RAM) 14, a timer for setting the timing of I / O 10 output; 5 oscillator for generating a reference clock, 16 an analog - digital converter (A /
D), 17 are AC-DC conversion units (PSU), 18
Is an address data bus. The two-pole contact type electromagnetic switch 3 includes a first
The contact 3 _1, second contacts 3 _2, it first contacts 3 ₁ and the second contact 3 ₂ driving coil 3 ₃ turning on and off the
The first single-pole contact type electromagnetic switch 4 includes a contact 4 ₁
Said a contact 4 ₁ driving coil 4 ₂ turn on and off a second single-pole contact type electromagnetic switch 5, and a driving coil 5 ₂ turn on and off contacts 5 ₁ and the contact 5 _1. Fuse internal resistor 8, the resistor 8 ₁ and the fuse 8
₂ and the driver array 9 includes first to third output terminals O _{91 to} O ₉₃ . The PSU ₁₇ includes a pair of AC terminals I ₁₇ and first and second DC terminals O ₁₇₁ and O ₁₇₂ . The AC power supply 1 includes a main power switch 2,
A two-pole contact type electromagnetic switch 3, a first one-pole contact type electromagnetic switch 4, and a second one-pole contact type electromagnetic switch 5, which are connected to a metal halide lamp 6 via a second one-pole contact the contact 5 ₁ type electromagnetic switch 5, the resistor 8 ₁ are connected in parallel. A thermistor 7 is arranged close to the metal halide lamp 6, and an AC terminal I _{17 of the} PSU ₁₇ is connected to the AC power supply 1. The driver array 9 has an input connected to the I / O10, the second DC terminals O ₁₇₂ of the first output terminal O ₉₁ via the fuse ₈₂ and the driving coil ₃ 3 PSU17, the second output terminal O ₉₂ through the driving coil 4 ₁ to the second DC terminals O _172, third output terminal O ₉₃ is connected to the second dc terminal O ₁₇₂ through the driving coil 5 _1. I
/ O10, CPU 11, ROM 12, RAM 13, and A
/ D16 is respectively coupled via an address data bus 18, and A / D16 is coupled and connected to the thermistor 7. The timer 14 is connected to the oscillator 15, and the driver array 9, the I / O 10, the CPU 11, the ROM 12, the RA
Each power supply of M13 and timer 14 is the first power supply of PSU17.
_Are connected to the DC terminal O ₁₇₁ of the first embodiment. Here, the control operation executed by the inrush current control circuit of this embodiment will be described with reference to the flowchart shown in FIG. First, in step S ₀ , when the main power switch 2 is turned on (turned on), AC power is supplied to the AC terminal I _{17 of the} PSU ₁₇ , and the first and second DC terminals O ₁₇₁ and O ₁₇₁ are supplied. respectively ₁₇₂ DC voltage Vcc, Va
a occurs. At this time, the DC voltage Vcc is applied to the driver array 9, I / O 10, CPU 11, ROM 12, R
AM13 and the power supply of the timer 14, respectively,
At this time, the program written in the ROM 12 is read out by the CPU 11, and the operations described below are sequentially executed. First, in step S ₁ , the first output terminal O ₉₁ of the driver array 9 goes low (ground potential), and the drive coil 3 _{3 of the} two-pole contact type electromagnetic switch ₃
Since There will be driven by the DC voltage Vaa, ₁ its first and second contact 3, 3 ₂ is turned on. At this time, since the second and third output terminals O ₉₂ and O ₉₃ of the driver array 9 are at a voltage close to the voltage Vaa, the first and second single-pole contact type electromagnetic switches 4,
Driving coil 4 ₂ 5, 5 ₂ is not driven, their contact 4 _1, 5 ₁ remain off state. Next, in step S ₂ , the temperature around the fixing portion of the fixing unit 30 (temperature around the metal halide lamp 6) is detected by the thermistor 7 arranged near the metal halide lamp 6. The temperature detection output is sent from the thermistor 7. Subsequently, in step S ₃ , the temperature detection output is converted into a digital signal by the A / D 16, and then taken in by the CPU 11. At this time, the CPU 11
Compares the temperature detection output with the fixing unit set temperature set in the RAM 13 to determine whether the temperature detection output has reached the fixing unit set temperature. And
If the temperature detection output does not reach the fixing unit set temperature (Y) at the time of the determination, the next step S ₄
Proceeds to, when the temperature detection output has reached the fixing unit set temperature (N), the process proceeds to step S ₉ described below. In the next step S ₄ , the second output terminal O ₉₂ of the driver array 9 becomes low level (ground potential), and the drive coil 4 _{2 of} the first single-pole contact type electromagnetic switch 4 is turned on. since but is driven by the DC voltage Vaa, its contacts 4 ₁ is turned on. At this time, the third output terminal O ₉₃ of the driver array 9, still has become a voltage close to the voltage Vaa, the driving coil 5 ₂ of the second single-pole contact type electromagnetic switch 5 without being driven , Its contacts 5
₁ remains off. [0033] Subsequently, in step S _5, the driving current of the AC power supply 1, respectively main power switch 2,2 poles turned on state the contact-type magnetic switch 3 and a first one-pole contact type electromagnetic switch 4 , it is supplied to the metal halide lamp 6 via a resistor ₈₁ connected in parallel to the second single-pole contact type electromagnetic switch 5 in the off state, heating is started to the heater of the metal halide lamp 6 You. However,
In this heating time, the state in which the driving current flowing through the resistor 8 ₁ is supplied to the heater of the metal halide lamp 6, a so-called preheating (preheating) condition,
The metal halide lamp 6 gradually warms up. In this preheating state, even if the internal impedance of the metal halide lamp 6 is considerably low, the current flowing into the metal halide lamp 6 is a resistance. Table 8
_Since the resistance is sufficiently suppressed by the resistance value of ₁ , a large inrush current does not flow through the metal halide lamp 6 transiently. [0034] followed, in step S _6, CPU11
Or the elapsed time T from the current to the resistor ₈₁ is started flowing to date, set time t of the timer 14, i.e., reaches the time required metal halide lamp 6 is warm enough Determine whether or not. And at the time of that decision,
When the elapsed time T has reached the set time t of the timer 14 (Y), the routine advances to the next step S _7, when the elapsed time T has not reached the set time t of the timer 14 (N) is determination of the step S ₆ is executed again. In the next step S ₇ , the third output terminal O ₉₃ of the driver array 9 is also at a low level (ground potential), and the drive coil 5 _{2 of} the second single-pole contact type electromagnetic switch 5 is turned on. since but is driven by the DC voltage Vaa, its contacts 5 ₁ is turned on. [0036] Then, in step S _8, the driving current of the AC power supply 1, without passing through the resistor 8 _1, contact 5 ₁ of the second single-pole contact type electromagnetic switch 5 turned on
Therefore, the metal halide lamp 6 is directly supplied to the metal halide lamp 6, so that the metal halide lamp 6 is heated in a normal driving state. [0037] Finally, in step S _9, is set to the operating state of the standby state or the image forming operation of the image forming operation, then the steps S ₁ to S ₉ are suitably repeatedly executed returns to the step S ₁ Things. [0038] Further, in the present embodiment shown in FIG. 2, when the rush current control operation of the metal halide lamp 6 is not performed correctly, for example, excessive current or flow through the resistor 8 _1, or , when the electric current from flowing over time to the resistor 8 _1, one that is so as to stop the rush current control operation, the following is a description of the operation of this point. When the inrush current control operation of the metal halide lamp 6 is performed as described above, for example, the second single-pole contact type electromagnetic switch 5
Or a contact 5 ₁ abnormal, or CPU11 becomes runaway state, IC circuit such as a driver array 9 is or becomes abnormal, excessive current or flow through the resistor ₈₁ or the resistor when or current flows for a long time to _81, the resistor 8 ₁ generates heat, the temperature is to rise abnormal. In this case, the fuse ₈₂ that is built into the resistor 8, the aforementioned resistor 8 by responding to _one abnormal temperature fusing, voltage Vaa is the driver array 9 obtained to the second output terminal O ₁₇₂ of PSU17 The power is not transmitted to the first output terminal _O91 , and the two-pole contact type electromagnetic switch 3
Since the driving coil 3 ₃ no longer driven by the DC voltage Vaa, the first and second contacts 3 _1, 3 ₂ immediately turned off, the drive circuit from the AC power supply 1 to the metal halide lamp 6 Is cut off at both the hot line and the neutral line, so that the driving of the metal halide lamp 6 can be surely stopped. [0040] In the present embodiment has described the example of using a fuse 8 ₂ as the temperature sensing element built into the resistor 8, the temperature sensing element is not limited to fuses ₈₂ Other elements, for example, a thermistor can also be used. As described above, according to the present embodiment, the second 1
Connect a resistor 8 ₁ parallel pole contacts 5 _first contact type electromagnetic switch 5, at the time of turn-on of the drive power source, a first one-pole contact type electromagnetic switch 4 is turned on, the predetermined time t After the time elapses, the timing is controlled so that the second single-pole contact type electromagnetic switch 5 is turned on, so that the metal halide lamp 6 flows through the metal halide lamp 6 until it warms up sufficiently. current is suppressed by the resistor 8 ₁ of the resistance value, it does not flow transiently large inrush current in the metal halide lamp 6. Further, according to the present embodiment, when the inrush current control operation of the metal halide lamp 6 is not accurately executed, the driving of the metal halide lamp 6 is stopped. The inrush current control operation can be reliably achieved, and the inrush current control operation with excellent safety can be performed. In the above embodiment, the metal halide lamp 6 is used when the image forming apparatus starts image formation.
The inrush current control operation described above is described, but this operation is not performed only when the image formation is started, but is also performed during the image formation operation. In the above-described embodiment, the switch 3 is 2
The pole contact type electromagnetic switch and the example using a single pole contact type electromagnetic switch as the first and second switches 4 have been described. However, the types of the switches 3, 4, 5 and the contact The models are not limited to those described above, and other types of switches, for example, a semiconductor relay or the like may be used.
Of course, a single-pole contact type switch may be used as the switch 3. Further, in the above-described embodiment, the metal halide lamp 6 has been described as being used as a heating member of the fixing device 30. However, the present invention is limited to a case where the metal halide lamp 6 is used as a heating member of the fixing device 30. However, the present invention can be similarly applied to other uses, for example, when used as an exposure member of an exposure device. As described above, according to the present invention,
The drive circuit of the metal halide lamp 6 includes a two-pole contact type electromagnetic switch 3, first and second one-pole contact type electromagnetic switches 4,
5 cascaded, and employs a simple circuit configuration of connecting the resistor 8 ₁ in parallel to the contact 5 ₁ of the second single-pole contact type electromagnetic switch 5, and, due to the switching of the power supply voltage Without causing conduction noise, when the lamp internal impedance of the metal halide lamp 6 is considerably low, it is possible to sufficiently limit the inrush current flowing into the metal halide lamp 6, and to limit the inrush current. After the cancellation, there is an effect that the metal halide lamp can be operated at the output voltage of the normal drive power supply. Further, according to the present invention, when the inrush current limiting operation flowing into the metal halide lamp 6 cannot be achieved, the supply of the drive current to the metal halide lamp 6 can be automatically stopped. It is possible to reliably limit the inrush current flowing into the metal halide lamp 6, and it is possible to execute the inrush current control operation with excellent safety.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic configuration diagram showing an overall configuration of an example of an image forming apparatus using a metal halide lamp according to the present invention. FIG. 2 is a circuit diagram showing one embodiment of a rush current control circuit for a metal halide lamp used in the fixing device of FIG. 1; FIG. 3 is a flowchart showing a control operation executed by the inrush current control circuit shown in FIG. 2; FIG. 4 is a characteristic diagram showing an example of a relationship between a lamp temperature and a change in lamp internal impedance in a metal halide lamp. [Description of Signs] 1 AC power supply of commercial frequency 2 Main power switch 3 also serving as circuit breaker 3 2-pole electromagnetic switch 3 ₁ First contact 3 of electromagnetic switch 3 _{2 Second} contact 3 of electromagnetic switch 3 ₃ Drive coil 4 of electromagnetic switch 3 First 1 pole contact type electromagnetic switch 4 ₁ Contact 4 of electromagnetic switch 4 ₂ Drive coil 5 of electromagnetic switch 4 _2nd single pole contact type electromagnetic switch 5 ₁ Electromagnetic Contact 5 of switch 5 ₂ Drive coil 6 of electromagnetic switch 5 Metal halide lamp 7 Thermistor 8 Built-in fuse resistor 8 ₁ Resistor 8 ₂ Fuse (temperature sensing element) 9 Driver array 10 I / O unit (I / O) Reference Signs List 11 Central control unit (CPU) 12 Read-only memory (ROM) 13 Random access memory (RAM) 14 Timer 15 Oscillator generating reference clock 16 Analog-digital converter (A / D) 17 AC DC conversion unit (PSU) 18 Address data bus 20 Document feeder 21 Contact is lath 22 Document 23 Illumination lamp 24 Imaging lens 25 Charging device 26 Photoreceptor belt 27 Developing device 28 Transfer device 29 Belt cleaner 30 Fixing device 31 Tray 32 Recording paper (transfer paper) 33 _{1 to} 33 ₄ Paper feed tray 34 Paper path 35 Reversing unit 36 Sorter 37 Bin

Claims (1)

(57) [Claim 1] A switch and first and second switches are cascaded between a metal halide lamp and a drive power supply thereof in order from the drive power supply side. A resistor is connected in parallel with the switch of No. 2 and a temperature sensing element is arranged inside the resistor.
And location, at the time of turn-on of the drive power source, wherein the on-time of the second switch, the first and the timing control to delay than the ON time of the switch, also the temperature sensitive element is a resistor
When it senses that the temperature of the armor is above a certain value,
Switching control to turn off the contacts of the switch
An image forming apparatus using a metal halide lamp.