JPH1195604A - Toner image fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a toner image fixing device capable of excellently preventing the flicker from occurring at the standby time. SOLUTION: This device is constituted to make a current (B) to a heater turned on, during the time when the temp. (A) of the heater for fixation rises from ta to tb, at the image forming time. When the temp. reaches tb, the current to the heater is turned off until the temp. falls to ta. Then, assuming that it is switched from the image forming mode to the standby mode at the time to, the temp. (A) of the heater for fixing is controlled to change over a range from ta' to tb' which is lower and wider than that of the range from ta to tb. Thus, the frequency of on-off switching of the current (B) for the heater at the standby time is remarkably reduced as compared with that at the image forming time. Then, the interval of on-off switching of the lamp current (C) to energize the heater for fixing is made longer, while the interval for on-off switching and generating the rush current is made longer, therefore the change of the power source voltage of a lighting equipment due to the rush current, is not sensed as the flicker.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a toner image fixing device for heating a toner image formed on a recording medium and fixing the toner image on the recording medium.

[0002]

2. Description of the Related Art Conventionally, a toner image formed on a recording medium is heated by generating heat in accordance with energization.
Heating means for fixing on the recording medium, temperature detecting means for detecting the temperature of the heating means or its vicinity, and intermittently energizing the heating means based on the temperature detected by the temperature detecting means. There has been proposed a toner image fixing device including the above-mentioned heating unit or an energizing unit for adjusting the temperature in the vicinity thereof. This type of fixing device is used in, for example, a copying machine or a laser printer that forms a toner image by an electrophotographic method, and heats and fixes toner transferred from a photosensitive drum or the like onto a recording medium such as copy paper. Further, in this type of fixing device, it is considered that a heater made of, for example, a halogen lamp or the like is used as a heating means, and the surface temperature of a heating roller incorporating the lamp is detected by a temperature detecting means such as a thermistor. At the same time, it has been considered to control the energization of the lamp via a triac or the like so that the temperature becomes a desired temperature.

FIG. 9 is a time chart showing an example of the control. In the control illustrated in FIG. 9, the temperature (A) near the lamp is detected by a thermistor or the like, and the lamp is turned ON / OFF (B) so that the temperature fluctuates between the minimum value ta and the maximum value tb. Is switched. That is,
As shown in FIG. 9, when the temperature drops to ta, the lamp is turned off.
N, and the ON state is continued until the temperature rises and reaches tb. When the temperature reaches tb, the lamp is turned off,
The OFF state is continued until the temperature drops to ta. When the temperature drops to ta, the lamp is turned on again and the same control is repeated.

[0004]

However, in this case,
As illustrated in FIG. 9C, immediately after the lamp is turned on to start energizing the lamp, a large current called an inrush current flows through the lamp. In a case where a copying machine or the like is used in an office or the like using a common power supply with the lighting equipment, the power supply voltage of the lighting equipment decreases every time the inrush current flows. When this voltage drop occurs at a frequency of, for example, about 8.8 Hz, humans feel the most unpleasant as flickering of illumination light (flicker). In recent years, the use of large lamps of about 10 KW as lamps as heating means has been increasing, and it is an urgent task to suppress the generation of flicker due to inrush current.

In an image forming apparatus such as a copying machine provided with this type of fixing device, an image forming mode in which image formation is performed while fixing by the above-described heating means, and image formation and fixing by the above-described heating means are performed. Some processing modes include a standby mode in which the heating unit is kept warm while the heating unit is kept in a standby state. In such an image forming apparatus, the time held in the standby mode is generally longer than the time held in the image forming mode, and it is rather important to suppress flicker in the standby mode. However, although it is not necessary to adjust the temperature of the heating means so strictly during standby, flicker has occurred almost in the same manner as during image formation.

Accordingly, it is an object of the present invention to provide a toner image fixing device capable of favorably suppressing the occurrence of flicker during standby. The invention according to claim 2 reduces the power consumption of the fixing device in addition to the above object, and the invention according to claim 3 suppresses the occurrence of flicker during image formation in addition to the above object. In addition to the above object, the invention according to claim 4 has been made for the purpose of rapidly increasing the temperature of the heating means.

[0007]

Means for Solving the Problems and Effects of the Invention According to the first aspect of the present invention, which has been made to achieve the above object, a toner image formed on a recording medium is heated by generating heat in accordance with energization. Heating means for fixing on the recording medium, temperature detecting means for detecting the temperature of or near the heating means, and intermittently energizing the heating means based on the temperature detected by the temperature detecting means. And a power supply means for adjusting the temperature of the heating means or the vicinity thereof, when the image is formed while the heating means is performing the fixing, or the fixing is not performed but the temperature needs to be maintained. Judgment means for judging whether there is a certain standby time, based on the judgment result of the judgment means, during the standby time, the fluctuation range of the temperature allowed for temperature adjustment by the energizing means,
And a fluctuation width changing unit that makes the width wider than that at the time of image formation.

In the present invention thus constituted, the judging means judges whether the heating means is performing the above-described fixing while forming an image, or is not performing the above-mentioned fixing but is in a standby state where it is necessary to keep the temperature. Then, the fluctuation width changing means makes the fluctuation width of the temperature allowed for the temperature adjustment by the power supply means wider in the standby state than in the image formation, based on the result of the judgment by the judgment means. When the fluctuation width is widened, the number of times of switching between energization / non-energization of the heating unit by the energizing unit can be reduced.

Therefore, the interval for switching between energization / de-energization becomes longer, and the interval of generation of the rush current generated at the start of energization by the energization means is opened. Voltage fluctuations also occur at sufficiently long intervals. Therefore, this voltage fluctuation does not feel unpleasant to humans as flicker of illumination light. Therefore, according to the present invention, it is possible to favorably suppress the occurrence of flicker during standby.

According to a second aspect of the present invention, in addition to the configuration of the first aspect, the maximum value of the temperature corresponding to the fluctuation range at the time of standby is the maximum value of the temperature corresponding to the fluctuation range at the time of image formation. It is characterized by being lower than the value. In the present invention,
The maximum value of the temperature corresponding to the fluctuation range during standby is set lower than the maximum value of the temperature corresponding to the fluctuation range during image formation. For this reason, the center of temperature fluctuation of the heating unit during standby can be made lower than during image formation, and power consumption during standby can be reduced. Therefore, in the present invention, in addition to the effect of the first aspect of the invention, there is an effect that the power consumption as the fixing device can be reduced to save power.

In the present invention, the maximum value of the temperature corresponding to the fluctuation range during standby may be higher or lower than the minimum value of the temperature corresponding to the fluctuation range during image formation. In the former case, the temperature of the heating unit can be quickly raised from the temperature at the time of standby to the temperature at the time of image formation, and the image forming operation in the image forming apparatus equipped with the present invention can be speeded up. Can be further reduced and power can be saved more favorably.

The invention described in claim 3 is the first or second invention.
In addition to the configuration described above, when the energizing means energizes the heating means, pulse-like discontinuous energization is performed at the start of the energization, and continuous energization is performed thereafter. According to the present invention, when the energizing unit energizes the heating unit, pulse-shaped discontinuous energizing is performed at the start of energization. For this reason, the rush current is also divided into pulses, and the frequency of voltage drop due to the rush current increases. Then, the intensity of the illumination light also changes at a high frequency at which humans cannot perceive discomfort, and is not perceived by humans as unpleasant flicker. Therefore, according to the present invention, in addition to the effect of the first or second aspect of the present invention, there is an effect that the generation of flicker can be suppressed more favorably. Such an effect of suppressing flicker also occurs during image formation.

Further, if such pulse-shaped energization is performed for a long time, the heating means cannot be efficiently heated.
Therefore, the energizing means of the present invention switches to continuous energization after performing pulsed energization at the start of energization. Since the rush current is generated in a very short time at the start of energization, the effect of suppressing flicker does not change even if continuous energization is performed thereafter. In addition, by switching to the continuous energization in this way, it is possible to minimize the influence of the pulsed energization as noise on the electronic device, and to minimize the decrease in the heating efficiency of the heating unit. be able to.
Therefore, according to the present invention, the occurrence of flicker can be suppressed more favorably while the temperature rise efficiency of the heating means is prevented from being lowered and the influence of the energization is exerted on the electronic device.

According to a fourth aspect of the present invention, in addition to the configuration of the third aspect, the temperature is allowed to vary during the image formation after the determination result of the determination means has changed from standby to image formation. Until the power supply is started, the power supply system further includes a power supply mode changing unit that changes the power supply mode of the power supply unit at the start of the power supply to shorten the overall off time of the pulse.

When the pulse-like energization is performed as in the third aspect of the invention, the efficiency of heating the heating means is somewhat reduced. On the other hand, when the judgment result of the judgment means changes from the time of standby to the time of image formation, it is necessary to raise the temperature of the heating means relatively significantly. Therefore, in the present invention, when the determination result changes from standby to image formation, the energization mode changing unit changes the energization mode of the energization unit to shorten the overall off time of the pulse. For this reason, in the present invention, in addition to the effect of the third aspect, the temperature of the heating unit is quickly raised from the temperature at the time of standby to the temperature at the time of image formation (a temperature within a fluctuation range permitted at the time of image formation). The effect that it can be done. Therefore, it is possible to speed up the image forming operation in the image forming apparatus provided with the fixing device of the present invention.

According to a fifth aspect of the present invention, in addition to the configuration of any one of the first to fourth aspects, the heating means is a lamp. When the heating means is constituted by a lamp, the rush current increases, and suppression of flicker is a particularly important problem. In the present invention, since the invention according to any one of claims 1 to 4 is applied to a fixing device in which a heating unit is configured by a lamp, the effect of the invention is more remarkably exhibited.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is embodied in a fixing device for a laser printer will be described. FIG. 1 is a perspective view of main components of a laser printer as an image forming apparatus, and FIG. 2 is a schematic side sectional view of the laser printer.

As shown in FIG. 1, a main body case 1 made of a synthetic resin in a laser printer has a main frame 1a.
And a main cover 1b that covers the outer surface of the main frame 1a on four sides (front and rear and left and right sides). The main frame 1a and the main cover 1b are integrally formed by injection molding or the like.

A scanner unit 2 as an exposure unit, a process unit 3 as a transfer unit, a fixing unit 4 as a toner image fixing device, and a paper feed unit 5 are mounted on the main frame 1a from above. .
The drive system unit 6 including the main motor 84 (see FIG. 3) and the gear train is located in the storage recess 1d between the left inner surface of the main cover 1b in FIG. 1 and the left side of the main frame 1a adjacent thereto. It is inserted and fixed from below the main body case 1. Further, a top cover 7 as a main body cover made of synthetic resin for covering the upper surfaces of the main frame 1a and the main cover body 1b has holes 7 through which an operation panel 1c projecting upward to the right side of the main frame 1a.
a and a hole 7b for penetrating the base of the sheet feeding unit 5
And are drilled. The base of the paper discharge tray 8 is attached to brackets 9 (only one is shown in FIG. 1) protruding from the left and right sides of the front end of the top cover 7 so as to be vertically swingable. 8 can be folded and covered on the upper surface side of the top cover 7.

In the feeder case 5a of the paper feeding unit 5, recording papers P as recording media are set in a stacked state. As shown in FIG. 2, the leading end side of the recording paper P is pressed toward the paper feed roller 11 by the support plate 10 with the biasing spring 10a in the feeder case 5a. For this reason, the power is transmitted from the drive system unit 6 and the paper feed roller 11 and the separation pad 12 that rotate and rotate,
The recording paper P can be separated one by one and sent to a pair of upper and lower registration rollers 13 and 14.

The process unit 3 includes a registration roller 1
The separated recording paper P fed at 3 and 14
An image is formed on the surface of the substrate with toner. Further, the fixing unit 4 heats the recording paper P on which the toner image is formed by sandwiching the recording paper P between the heating roller 15 and the pressing roller 16 to fix the toner image on the recording paper P. The heating roller 15 has a fixing heater 15a made of a halogen lamp inserted into an aluminum tube whose surface is coated with fluorine.
07 is in contact. The pressing roller 16 is a rubber roller whose surface is covered with a fluororesin.

A paper discharge section including a paper discharge roller 17 and a pinch roller 18 disposed on the downstream side in the case of the fixing unit 4 discharges the recording paper P on which the toner image is fixed to the paper discharge tray 8. The section from the paper feed roller 11 to the paper discharge section is a recording medium transport route. The sheet feeding unit 5
Is provided with a manual insertion opening 5b that opens diagonally upward so that a recording sheet for printing on a recording sheet different from the recording sheet P in the feeder case 5a can be inserted into the recording medium transport route. Has been.

An upper support plate 2a of the scanner unit 2 is provided at a position below the process unit 3 which is disposed substantially at the center of the main frame 1a having a box-like shape with an open top in the body case 1 in plan view, and a bottom plate of the main frame 1a. It is fixed to a stay part integrally formed on the upper surface side of the part with screws or the like.
In the scanner unit 2 as an exposure unit, a laser emitting unit (not shown), a polygon mirror 20, a lens 21, a reflecting mirror 22, and the like are arranged on the lower surface side of the synthetic resin upper support plate 2a. A laser beam passes through a glass plate 24 covering a horizontally long scanner hole formed in the upper support plate 2a so as to extend along the axis of the photosensitive drum 23 as a photosensitive member, and to the outer peripheral surface of the photosensitive drum 23 in the process unit 3. It is configured to irradiate and expose.

As shown in FIG.
Is a photosensitive drum 23 and a transfer roller 2 in contact with the upper surface thereof.
5, a scorotron-type charger 26 disposed below the photosensitive drum 23, a developing device having a developing roller 27 and a supply roller 28 disposed upstream of the photosensitive drum 23 in the sheet feeding direction, and further disposed upstream thereof Developer (toner) supply unit, ie, detachable toner cartridge 2
9, a cleaning roller 30 disposed downstream of the photosensitive drum 23, and a discharge lamp 30a disposed downstream of the cleaning roller 30.

An outer peripheral surface of the photosensitive drum 23 has a charger 26
An electrostatic latent image is formed by scanning a laser beam from the scanner unit 2 on the charged photosensitive layer. Developer (toner) in the toner cartridge 29
Is released by being stirred by the stirrer 31 and then carried on the outer peripheral surface of the developing roller 27 via the supply roller 28, and the thickness of the toner layer is regulated by the blade 32. The electrostatic latent image on the photosensitive drum 23 is visualized by the developer adhering from the developing roller 27. The image (toner image) formed by the developer is transferred to a recording sheet P passing between the transfer roller 25 and the photosensitive drum 23 to which a transfer bias having a potential opposite to the potential of the photosensitive drum 23 is applied to form a toner image. I do. Then, after the toner remaining on the photosensitive drum 23 is temporarily collected by the cleaning roller 30, the toner is returned to the photosensitive drum 23 at a predetermined timing, and is collected by the developing roller 27 into the process unit 3.

The upper support plate 2a of the scanner unit 2
Is provided with a toner sensor 33 protruding upward, and a toner sensor 33 composed of a pair of a light emitting unit and a light receiving unit faces the lower surface recess of the toner cartridge 29 in the process unit 3, and the presence or absence of toner in the toner cartridge 29. Can be detected.

The process unit 3 is made into a cartridge by being incorporated in a case 34 made of synthetic resin.
The process unit 3 formed into a cartridge is detachably mounted on the main frame 1a. A storage portion 3 for storing the cooling fan 35 is provided on the lower surface side of the continuous portion between the front portion of the main frame 1a and the front portion of the main cover body 1b.
6 and a ventilation duct 37 extending in the left-right direction perpendicular to the direction in which the recording paper P passes, are formed so as to communicate with each other. Then, the upper surface plate portion 37a of the ventilation duct 37 is formed in a V-shape with a downward section, and the upper surface plate portion 37a is located between the process unit 3 and the fixing unit 4 to generate the heat generated by the heating roller 15 in the fixing unit 4. Heat generated by process unit 3
To prevent direct transmission to the side.

The cooling air generated by the cooling fan 35 passes through the inside of the ventilation duct 37 and along the lower surface of one side of the main frame 1a, and the power supply unit 39 (see FIG. 2) at the rear and the main motor of the drive system unit 6 On the other hand, the cooling air is blown out from a plurality of slit holes opened on the side of the process unit 3 in the upper surface plate portion 37a, and the cooling air passes through between the process unit 3 and the fixing unit 4 and rises. The air is exhausted from the apparatus through a plurality of exhaust holes 40 formed in the cover 7.

Next, the control unit 70 provided inside the right side of the main frame 1a will be described. FIG.
3 is a block diagram showing the control unit 70 and a configuration related to the control unit 70. FIG. The control unit 70
CPU 71 and RO storing various control programs
M72, a RAM 73 provided with various memories such as a reception buffer for receiving and storing transmission data transmitted from an external data transmission device PC such as a personal computer or a host computer, and timing for writing / reading reception data to / from the reception buffer Control circuit (TC) 74 for generating a timing signal for printing, and an interface (I / F) 7 for receiving transmitted print data.
5, a video interface (V.I / F) 76 having a scan buffer and sequentially outputting print information converted to bit image data to the DC controller circuit 82
And a sensor interface (S · I) that receives detection signals from the toner sensor 33, the paper feed sensor 51 provided in the vicinity of the downstream of the paper feed roller 11, and other sensors.
/ F) 77, various control modes can be selected from the operation panel 1c, and a panel interface (P / I / F) 78 for receiving the switched signal and a timer 79 are provided. Each is connected to the CPU 71.

The DC controller circuit 82 includes a paper-feeding-side transport mechanism including the paper-supplying roller 11, registration rollers 13 and 14, the photosensitive drum 23, and the like. And pinch roller 18
Motor 84 for driving the discharge-side transport mechanism section made of
Drive circuit 87, a drive circuit 89 for a laser diode 85 constituting the laser emitting section, a drive circuit 90 for a scanner motor 86 for driving the polygon mirror 20, and a halogen lamp in the heating roller 15. And a high-voltage substrate 92 for generating a high-voltage electric field on the photosensitive drum 23, the transfer roller 25, the charger 26, the developing roller 27, and the cleaning roller 30, and further turning on the neutralizing lamp 30a. And are respectively connected.

A ROM 72 stores various control programs as a normal laser printer, a program of a flowchart described later, a font memory storing printing dot pattern data relating to a large number of characters such as characters and symbols, and a RAM 73. A memory management program that manages the memory capacity and the start address of each memory such as a reception data buffer and a print image memory provided in advance is stored in advance.

Next, the configuration of the driving circuit 91 and its peripherals will be described in detail with reference to FIG. As shown in FIG. 4, the drive circuit 91 includes a transistor 93, a phototriac coupler 95, and a triac 97,
The main components are various resistors described below. The DC controller circuit 82 is connected to the base of the transistor 93 via a resistor 93a, and switches the transistor 93. The light emitting diode 95a of the phototriac coupler 95 is connected to the collector of the transistor 93 via a resistor 93b.
Triac 9 via resistors 97a and 97b respectively
7 are connected at both ends. The gate of the triac 97 is connected between the resistor 97a and the triac 95b. When a current flows through the resistor 97a, a gate current corresponding to the voltage drop is supplied.

Between both ends of the triac 97, AC1
A 00V commercial power supply 101, a power switch 103, and the above-described fixing heater 15a are connected in series. Further, a low-voltage power supply 105 that outputs DC voltages of 5 V and 24 V is connected to both ends of a series circuit including the commercial power supply 101 and the power switch 103.

For this reason, when the power switch 103 is ON, when the transistor 93 is turned ON, the phototriac coupler 95 is turned ON, a current flows through the resistor 97a, and the TRIAC 97 is turned ON. Therefore, the transistor 93
ON / OFF coincides with ON / OFF of the triac 97, whereby the energization / de-energization of the fixing heater 15a is switched. Since the triac 97 performs a zero-cross operation when it is off, the triac 97 is turned off at the maximum when it is off, with a delay of a half cycle of the power supply frequency. Further, when the phototriac coupler 95 has zero-cross detection, the transistor 9
The ON state of the triac 97 is turned on at a maximum delay of a half cycle of the power supply frequency after the ON state of the power supply 3.

A thermistor 107 is provided near the fixing heater 15a. Thermistor 107
One end is grounded via a resistor 109 and the other end is connected to a DC power supply of 5 V. A potential V1 between the thermistor 107 and the resistor 109 is input to an inverting input terminal of the operational amplifier 111. Further, the potential V1 is connected to the resistor 113
And input to the CPU 71 via an A / D converter (not shown). The non-inverting input terminal of the operational amplifier 111 has
A reference voltage V0, which is a reference for temperature control of a fixing heater 15a to be described later, is input via a resistor 111a. Further, the non-inverting input terminal of the operational amplifier 111 is connected to the resistor 111
b, and the non-inverting input terminal is subjected to positive feedback as follows. That is, the resistor 115 and the series circuit including the resistor 117 and the analog switch 119 are arranged in parallel in the current path of the positive feedback. The resistance value of the resistor in the vicinity of the operational amplifier 111 is, for example, one of the resistors 111 a and 111.
b can be 1 KΩ, and the resistors 115 and 117 can be 100 KΩ.

The CPU 71 binarizes the data input via the bus 81 (FIG. 3), the potential V1 of the inverting input terminal described above, and the output of the operational amplifier 111 by a well-known circuit (not shown). Is entered after Also, the CPU 71
Is based on these input data,
19 is directly switched ON / OFF, and the ON / OFF of the transistor 93 is controlled via the DC controller circuit 82.
OFF has been switched.

Next, control executed by the CPU 71 based on the output of the operational amplifier 111 and the like will be described. The resistance value of the thermistor 107 decreases as the temperature decreases. Therefore, immediately after the power switch 103 is switched from OFF to ON, the voltage drop due to the thermistor 107 is small, and a relatively high potential is input to the inverting input terminal of the operational amplifier 111. At this time, the output of the operational amplifier 111 is low. When the potential V1 decreases as the temperature of the fixing heater 15a rises and falls below the non-inverting input terminal-side potential V1 defined by the reference voltage V0, the output of the operational amplifier 111 is inverted. Also, the operational amplifier 11
Since 1 is subjected to positive feedback, the positive feedback current acts to stabilize the output of the operational amplifier 111.

Therefore, the CPU 71 sets the operational amplifier 111
When the output is low, the transistor 93 is turned on via the DC controller circuit 82, and when the output is positive, the transistor 93 is turned off. By doing so, the temperature in the vicinity of the fixing heater 15a around the target temperature defined by the reference voltage V0 can be maintained while fluctuating by a predetermined width. Further, the fluctuation range is determined by the ease of the flow of the positive feedback current, that is, the resistance of the resistor 11.
5, 117 and the analog switch 119. That is, the CPU 71
However, when the analog switch 119 is turned on, the fluctuation range is large, and when the analog switch 119 is turned off, the fluctuation width is small.

When an image is formed by the process unit 3, the CPU 71 sets the temperature near the fixing heater 15a detected via the thermistor 107 to the maximum value tb and the minimum value tb.
a, and the toner can be fixed. That is, as described above with reference to FIG. 9, when the temperature (A) drops to ta, the transistor 93 is turned on,
The ON state is continued until the temperature rises and reaches tb. During this time, the fixing heater 15a is energized, and the temperature rises. When the temperature reaches tb, transistor 9
3 is turned OFF, and the OFF state is continued until the temperature drops to ta.

The CPU 71 has the following sleep mode and standby mode as processing modes in addition to the image forming mode set at the time of image formation. The determination as to which processing mode of the sleep mode, the standby mode, or the image forming mode is to be performed is made based on the signal from the operation panel 1c and the driving state of the process unit 3, based on the CPU.
71 is executed by software (judging means) processing not shown.

FIG. 5 shows a mode switching process when the CPU 71 automatically switches the mode.
This will be described with reference to the flowchart of FIG. Note that the CPU 71
Executes this process as an interrupt process at a predetermined interval after the power is turned on. As shown in FIG. 5, when the power is turned on, S1
(S represents a step: the same applies hereinafter), the standby mode is set, and the timer 79 is started in S2. Subsequently, it is determined in S3 whether or not data has been received, and if not (S3: NO), it is determined whether or not the operation panel 1c has been operated (S4). If the operation panel 1c is not operated (S4: NO), the timer starts (S4).
It is determined whether a predetermined time has elapsed from 2) (S5). If it has not elapsed (S5: NO), the above-described S3 is used as it is.
If it has passed (S5: YES), the sleep mode is set in S6, and then the process proceeds to S3. That is, when the power is turned on, the system is temporarily set to the standby mode (S1),
If neither the data reception nor the operation of the operation panel 1c is performed (S3, S4: NO) and the predetermined time has elapsed (S5: YES), the mode is switched from the standby mode to the sleep mode.

When data is received (S3: YE
S) and when the operation panel 1c is operated (S4:
YES) goes to S7 to set the image forming mode,
The process waits until the image forming process by another routine is completed (S8). When the process is completed (S8: YES), the process proceeds to S1, the standby mode is set, and the above process is repeated.

In the sleep mode, the CPU 71 reads a signal from the operation panel 1c and drives the low-voltage power supply 105, but the driving circuits 87 to 91 or the high-voltage board 92
This is a processing mode in which the power supply to each unit via the. The standby mode is executed when the fixing is not performed but the fixing heater 15a needs to be kept warm.
This is a processing mode in which the heater 15a is kept warm within the fluctuation widths ta 'to tb' set to be lower than? Tb. This standby mode is the same as the image forming mode except that the temperature range is different. The fluctuation widths ta 'to tb' are set wider than the fluctuation widths ta to tb, and ta> t
b '(variation width changing means).

For this reason, the switching of the processing of the CPU 71 in the image forming mode and the standby mode can be performed as follows. That is, in the standby mode, the reference voltage V0 is set higher than in the image forming mode. Then
The center of the fluctuation widths ta 'to tb' is lower than the center of ta to tb. In the standby mode, the analog switch 11
9 is turned on, and turned off in the image forming mode. Thereby, the fluctuation widths ta 'to tb' can be made wider than ta to tb. Further, the reference voltage V0 in the standby mode
Is set appropriately, it is possible to satisfy ta> tb ′. After making such a setting change, the CPU 71 turns on the transistor 93 via the DC controller circuit 82 when the output of the operational amplifier 111 is low, and when the output is positive, as described above. Controls the transistor 93 to be OFF.

The energization control of the fixing heater 15a in the laser printer thus configured will be described with reference to the time chart of FIG. As illustrated in FIGS. 6A and 6B, in the image forming mode, as in the example of FIG. 9, while the temperature (A) of the fixing heater 15a increases from ta to tb, the transistor 93 and the photo triac The coupler 95 and the like are turned on to energize the fixing heater 15a. When the temperature reaches tb, the phototriac coupler 95 and the like are turned off until the temperature drops to ta, and the energization is stopped. If it is assumed that the mode is switched from the image forming mode to the standby mode at time t0, the above-described ta to tb
The fixing heater 1 has a lower and wider variation range ta 'to tb'.
The temperature (A) of 5a is controlled.

Therefore, the number of times of switching ON / OFF (B) of the phototriac coupler 95 and the like during standby can be greatly reduced as compared with the time of image formation.
Then, as illustrated in FIG. 6C, the fixing heater 1
The lamp current supplied to the lamp 5a increases the interval for switching between the conduction and non-conduction, and the conduction / non-conduction and fluctuations in the power supply voltage of the lighting equipment caused by the inrush current occur at sufficiently long intervals. I do. Therefore, this voltage fluctuation does not feel unpleasant to humans as flicker of illumination light. Therefore, in this laser printer,
The occurrence of flicker during standby can be favorably suppressed. Further, in the present laser printer, the maximum value tb 'of the fluctuation width in the standby mode is set lower than the minimum value ta of the fluctuation width in the image forming mode. Power consumption can be reduced.

In the above embodiment, the fixing heater 15a serves as the heating means, and the CPU 71 drives the driving circuit 91.
, The thermistor 107 serves as a temperature detecting means, the CPU 71 serves as a fluctuation width changing means and a determining means,
Each corresponds. In addition, the present invention is not limited to the above-described embodiment, and can be implemented in various forms without departing from the gist of the present invention. For example,
The maximum value tb 'of the fluctuation width in the standby mode may be set higher than the minimum value ta of the fluctuation width in the image forming mode. In this case, the temperature of the fixing heater 15a is quickly raised from the temperature at the time of standby to the temperature at the time of image formation, and the image forming operation in the laser printer can be speeded up. Also in this case, if tb> tb ', the temperature fluctuation center during standby can be lower than during image formation, and power consumption during standby can be reduced. Further, even if tb <tb ', the above-described flicker suppressing effect is produced by widening the fluctuation range during standby.

In the above embodiment, the CPU 71 switches ON / OFF of the phototriac coupler 95 and the like based on the output of the operational amplifier 111. However, the ON / OFF can be similarly switched by processing by software. . In this case, the potential V1 may be converted into digital data, read into the CPU 71, and the software processing may be executed based on the data. Further, in this case, the temperature of the fixing heater 15a itself may be detected by calculating the impedance of the fixing heater 15a, and the software processing may be executed based on the detected temperature.

Further, by changing the drive waveform (PH95) output from the CPU 71 to the phototriac coupler 95 or the like as described below, the occurrence of flicker can be more effectively suppressed. That is, the photo triac coupler 95
Is turned on to start the above-described energization, as shown in FIG. 7 (B), the pulse-like discontinuous energization is performed to the phototriac coupler 95 and the like. In this case, FIG.
As shown in (C), the current (lamp current) supplied to the fixing heater 15a is also divided into pulses at the start of the current supply. For this reason, the above-mentioned rush current is divided into pulses, and the frequency of the voltage drop due to the rush current increases. Therefore, the intensity of the illuminating light also changes at a high frequency that cannot be sensed by humans, and is not unpleasantly sensed as flicker by humans.

In the example shown in FIG. 7B, the phototriac coupler 95 is continuously turned on after the above-described pulse-shaped energization is performed at the start of energization. For this reason, the lamp current is also switched to continuous energization. Since the inrush current is generated in a very short time at the start of energization, the effect of suppressing flicker does not change even if the energization of the fixing heater 15a is continuously performed thereafter. Switching to continuous energization in this manner minimizes the influence of pulsed energization as noise on electronic equipment, and reduces the temperature rise efficiency of the fixing heater 15a due to the pulsed energization. Doing so can be kept to a minimum. Therefore, when the drive waveform of the phototriac coupler 95 is changed in this way, it is possible to prevent the temperature rising efficiency of the fixing heater 15a from being reduced, and to prevent the power supply to the fixing heater 15a from affecting the electronic device. In addition, the occurrence of flicker can be more favorably suppressed. Further, the flicker suppressing effect in this case occurs not only during standby but also during image formation.

Further, when the pulse-shaped energization is performed as illustrated in FIG. 7B, the temperature rise efficiency of the fixing heater 15a is somewhat reduced. On the other hand, when the power switch 103 is
N, or startup from the sleep mode by the operation panel 1c (hereinafter referred to as startup together), and when shifting to the standby mode or the image forming mode, or from the standby mode to the image forming mode When the operation shifts to, it is necessary to raise the temperature of the fixing heater 15a relatively significantly.

For this reason, as exemplified in FIG.
Drive waveform 2 when the above-mentioned start is performed at time t1
01 and the drive waveform 202 at the time of transition from the standby mode to the image forming mode at the time t2, similarly to the drive waveform 203 at the time of image formation, at the start of energization, the pulse shape illustrated in FIG. When power is supplied, it takes time to raise the temperature of the fixing heater 15a. In this case, the waiting time until image formation by the laser printer becomes possible becomes longer.

Therefore, as shown in FIG. 8B, the drive waveform 301 at the time of turning on the power and the drive waveform 302 at the start of image formation are changed so that the overall off time of the pulse is shortened. (Electrification style changing means). That is, when the start-up is performed, the driving waveform 301 is output until the fixing heater 15a rises to the temperature in the standby mode. The driving waveform 301 is the driving waveform 30 for controlling the temperature of the fixing heater 15a to the above-described ta to tb.
As compared with No. 3, the on-time of the pulse-shaped energization at the start of energization is longer and the number of pulses is smaller. For this reason, the temperature of the fixing heater 15a can be quickly raised from a state in which the heater 15a is completely cooled down without energization to a temperature in the standby mode. When shifting from the standby mode to the image forming mode, the drive waveform 302 in which the pulse-like energization at the start of energization is set in the same manner as the drive waveform 301 is output. The temperature can be quickly raised to the mode temperature (ta to tb). Therefore, in this case, the waiting time until image formation becomes possible can be shortened satisfactorily, and the image forming operation in the laser printer can be speeded up.

Further, as the energizing mode for shortening the overall off time of the pulse, various modes can be considered in addition to the above-described method of changing the on time and the number of pulses. For example, the off time may be shortened,
Further, as illustrated in FIG. 8C, the driving waveforms 401 and 402 may be switched to continuous energization having no pulse portion. In this case, although the effect of suppressing flicker is reduced, the temperature of the fixing heater 15a can be increased extremely efficiently.

As illustrated in FIG. 8D, a drive waveform 501 of continuous energization at the time of startup and a pulse-like drive waveform of which the off time is relatively short at the time of transition from the standby mode to the image forming mode. 502 may be output respectively. It is desired that the lower the temperature of the fixing heater 15a, the faster the temperature rises, such as a state in which the fixing heater 15a is completely cooled without energization. In this example, since the continuous energization is performed at the time of startup, the fixing heater 15a
Can be shortened more satisfactorily until the temperature rises very quickly and image formation becomes possible.

Conversely, as shown in FIG. 8 (E), a pulse-like drive waveform 601 having a relatively short off-time at the time of startup is used, and a continuous energization drive is performed at the time of transition from the standby mode to the image forming mode. Each of the waveforms 602 may be output. In the fixing heater 15a, the lower the temperature is, the smaller the resistance value is, and the inrush current causing flicker is also large. In this example, since the pulse-shaped energization is performed at the time of startup, the occurrence of flicker can be suppressed uniformly throughout. 8 (C) to 8 (E), the driving waveforms 403, 503 and 603 during image formation are the same as those in FIGS.
This is the same as the drive waveforms 203 and 303 in FIG. Therefore, flicker during image formation can be suppressed. Further, the change may be made so that the overall off time of the pulse is shortened only at one of the start-up and the transition from the standby mode to the image forming mode.

Further, the state of occurrence of flicker also changes depending on the type of power supply of the laser printer, for example, the voltage, frequency, the state of indoor wiring, and the like. The flicker allowed for the laser printer also varies depending on the regulations of each country. Therefore, it is desirable to change the power supply mode according to the regulations of the country where the laser printer is used and the power supply mode. To achieve this purpose, the energization mode must be N
It may be stored in a storage means such as a VRAM. In this case, depending on the regulations of the destination country and the type of power source, NVRA
The energization mode stored in M can be rewritten, or replaced with NVRAM in which an appropriate energization mode is stored. By doing so, flicker can be appropriately suppressed in accordance with the regulations of each country and the type of power supply.

Further, in the above-described embodiment, the fixing heater 15a composed of a halogen lamp is used as the heating means, but various configurations can be adopted as the heating means. However, when the heating means is formed of a lamp such as a halogen lamp, the rush current increases, and suppression of flicker is a particularly important problem. In the above embodiment, since the present invention is applied to the fixing unit 4 in which the heating means is configured by a lamp, the effect of the present invention appears more remarkably. Further, the present invention is not limited to a laser printer, but can be applied to a toner image fixing device formed by various mechanisms such as a copying machine.

As a configuration for reducing the number of times of switching between energizing / de-energizing the heating means during standby, a configuration in which the voltage applied to the heating means during standby is reduced besides the above configuration of the present invention. In this case, even if the fluctuation range of the temperature is the same, the temperature rise of the heating means becomes slow at the time of standby, and the number of times of the switching is reduced, and the same effect is obtained.

[Brief description of the drawings]

FIG. 1 is a perspective view of main components of a laser printer according to an embodiment.

FIG. 2 is a schematic side sectional view of the laser printer.

FIG. 3 is a block diagram illustrating a control unit of the laser printer and a configuration related to the control unit.

FIG. 4 is a circuit diagram illustrating a configuration of a drive circuit connected to a control unit.

FIG. 5 is a flowchart illustrating a mode switching process of a control unit.

FIG. 6 is a time chart showing energization control by the drive circuit.

FIG. 7 is a time chart showing a modification of the energization control.

FIG. 8 is a time chart showing another modification of the current supply control.

FIG. 9 is a time chart illustrating energization control in a conventional fixing device.

[Explanation of symbols]

2. Scanner unit 3. Process unit
4: fixing unit 5: paper feeding unit 6: drive system unit 15
... Heating roller 15a ... Fixing heater 70 ... Control unit
Reference numeral 71 CPU 72 ROM 73 RAM 82 DC controller circuit 87, 89, 90, 91 Drive circuit 93 Transistor 95 Phototriac coupler 97 Triac 101 Commercial power supply 107 Thermistor 111 Operational amplifier 11
9 ... Analog switch

Claims (5)

[Claims] 1. A toner image formed on a recording medium,
A heating unit for heating by generating heat in accordance with the energization to fix the recording medium on the recording medium; a temperature detecting unit for detecting the temperature of the heating unit or a temperature in the vicinity thereof; An energizing means for intermittently energizing the heating means to adjust the temperature of the heating means or the vicinity thereof, and a toner image fixing device comprising: during image formation in which the heating means is performing the fixing,
Judging means for judging whether or not the fixing is not performed but the standby is required to keep the temperature. Based on the judgment result of the judging means, the fluctuation range of the temperature allowed for the temperature adjustment by the energizing means is determined during the standby. And a variation width changing unit that makes the width wider than at the time of image formation. 2. The toner according to claim 1, wherein a maximum value of the temperature corresponding to the fluctuation width during the standby is lower than a maximum value of the temperature corresponding to the fluctuation width during the image formation. Image fixing device. 3. The method according to claim 1, wherein when the energizing means energizes the heating means, a pulse-shaped discontinuous energizing is performed at the start of the energizing, and thereafter a continuous energizing is performed. 3. The toner image fixing device according to item 2. 4. The method according to claim 1, wherein the determination result of the determination unit is changed from a standby state to an image formation period until the temperature reaches a fluctuation range allowed during the image formation period. 4. The toner image fixing device according to claim 3, further comprising an energization mode changing unit that changes an energization mode to shorten the overall off time of the pulse. 5. The toner image fixing device according to claim 1, wherein said heating means is a lamp.