JP3397607B2 - Heating device and image forming apparatus provided with the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heating device for fixing a toner image on a recording material, and an image forming apparatus having the heating device.

[0002]

2. Description of the Related Art Conventionally, a halogen heater has been used as a heat source as a fixing device (heating device) for fixing a toner image formed on a recording material such as paper when mounted on an image forming apparatus such as a copying machine or a laser beam printer. A heat roller type heat fixing device and a film heating type heat fixing device using a ceramic surface heater as a heat source are used.

Generally, the heater is connected to an AC power source via a switching control element such as a triac, and the AC power source supplies electric power. The fixing device (fixing device) is provided with a temperature detecting element, for example, a thermistor temperature sensitive element. The temperature of the fixing device is detected by this temperature detecting element, and the engine cotton roller switches based on the detected temperature information. By controlling the on / off of the element, the power supply to the heater is turned on / off, and the temperature of the fixing device is controlled to a target constant temperature. On / off control to the ceramic heater is performed by phase control or wave number control of a commercial power source.

A trigger is generated based on a signal (hereinafter referred to as a "zero cross signal") that includes a point at which the input commercial power source is switched from positive to negative or from negative to positive, and notifies that the magnitude of the power source voltage is below a certain threshold value. Is applied to perform phase control or wave number control. Generally, the zero-cross signal is a pulse signal, and the heater is controlled by triggering at the rising edge where the zero-cross signal changes from OFF to ON. FIG. 7 shows control in the case of phase control. As shown in the figure, the trigger is sequentially shifted to α and β with respect to the falling edge of the zero-cross signal having the pulse width tw.

When the temperature control method is changed or the heater startup control is changed according to the commercial power supply voltage, the engine controller monitors the startup speed of the heater for a certain period of time, and the startup speed is increased. Detects the input commercial power supply voltage and changes the heater control method.

[0006]

Conventionally, when the heater of the fixing device is controlled on the basis of the zero-cross signal, as described above, the zero-cross signal is triggered by the rising edge that changes from off to on. It was

However, since the pulse width of the zero-cross signal changes depending on the input commercial power supply voltage, if the heater is controlled by triggering at the timing when the zero-cross signal changes from off to on, the switching element is turned on. / There will be an error in the timing of turning off. In particular, the error becomes large when the phase of the heater is controlled.

When changing the control method according to the commercial power supply voltage, the engine controller monitors the rising speed of the heater for a certain period of time, and the input commercial power supply voltage is detected by the rising speed to determine the heater control method. Since it was changed, it was necessary to energize the heater in advance before determining the control method.

Therefore, the present invention provides a heating device capable of accurately controlling the heater even when the input commercial power supply voltage changes without the need to energize the heater in advance, and an image forming apparatus having the heating device. That is the purpose.

[0010]

The invention according to claim 1 is
In a heating device for heating a member to be heated by a heating body controlled to maintain a predetermined set temperature, an electric power supply means for supplying electric power to the heating body and a temperature detecting means for detecting the temperature of the heating body. An electric power control means for controlling the electric power supplied from the electric power supply means to the heating body so that the heating body maintains a predetermined set temperature based on the temperature detected by the temperature detecting means; A pulse signal output means for outputting a pulse signal having a pulse in the vicinity of the zero-cross point by comparing the full-wave rectified voltage with a predetermined threshold value;
The power control means, based on the pulse width detected by the pulse width detection means for detecting the pulse width of the pulse signal that changes according to the input commercial power supply voltage, the pulse width detection means, determining means for determining the zero cross timing of the input commercial power source the edges of the pulse signal as a reference, relative to the zero-cross timing of the input commercial power source determined by the determining means
The energization time does not correspond to the input commercial power voltage.
In this way, there is an energization time control means for controlling the energization time based on the temperature detected by the temperature detection means and the pulse width detected by the pulse width detection means.
That, characterized in that.

In the present invention according to claim 2, the determining means is such that when the pulse width of the pulse signal is tw,
Timing after tw / 2 from the edge of the pulse signal
As the zero-cross timing of the input commercial power supply
The feature is that it is determined .

The present invention according to claim 3 is characterized in that the power control means has means for controlling a conduction angle of a current supplied from the power supply means to the heating body .

[0013]

In the present invention according to claim 4 , the power control device detects the input commercial power supply voltage based on the pulse width of the pulse signal and detects the detected input quotient.
Use the power supply voltage and on the basis of the temperature before being detected <br/> Symbol heating member by said temperature detecting means, for controlling the power supplied to the heating body from the power supply means, characterized in that.

The present invention according to claim 5 is an image forming apparatus comprising: an image forming section for forming a toner image on a recording material; and a fixing device for heating the toner image to fix it on the recording material. The fixing device according to any one of claims 1 to 4.
A ceramic surface heater is used as the heating element, and the pressure member is arranged to face the ceramic surface heater, and the ceramic surface heater and the pressure member are arranged between the ceramic surface heater and the pressure member. And a fixing film that is nipped and conveyed by the ceramic surface heater. The toner image on the recording material that is nipped and conveyed between the pressure member and the fixing film is heated by the ceramic surface heater.

[Operation] The pulse width of the zero-cross signal is detected, for example, the time at the center of the pulse width is calculated, and from the time of the rising edge at which the zero-cross signal changes from off to on (pulse width / 2) By performing the phase control or the wave number control by applying the trigger at the timing of the time of delaying, the heating element can be controlled by applying the trigger at a position closer to the true zero-cross point.

Further, by detecting the pulse width of the zero-cross signal, calculating the input commercial power supply voltage, and switching to control of the heating element corresponding to the input commercial power supply voltage (for example, phase control or wave number control), The control of the heating element suitable for each power supply voltage can be selected.

Further, the temperature detected by the temperature detecting element,
By determining the initial value of the electric power supplied to the heating element from the input commercial power supply voltage calculated based on the pulse width of the zero-cross signal, the initial value for starting the heating element is determined without energizing the heating element. can do.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. <Embodiment 1> Hereinafter, description will be given with reference to the drawings.

FIG. 1 is a vertical sectional view showing a schematic structure of an image forming apparatus using an electrophotographic process. The image forming apparatus in the figure is a laser printer.

The image forming apparatus shown in FIG. 1 includes an image forming apparatus main body (hereinafter referred to as “apparatus main body”) 101,
On the right side of the apparatus main body 101, a paper feed cassette 102 that stores a recording material (heated member) S such as paper is detachably attached. Above the leading end side (downstream side in the recording material conveyance direction) of the mounted paper feed cassette 102, the paper feed cassette 1
Cassette presence sensor 1 for detecting the presence or absence of the recording material S in 02
03 is placed, and the paper feed cassette 1 is provided near the tip.
A cassette size sensor 104 (composed of a plurality of micro switches) for detecting the size of the recording material S of No. 02 is arranged. Further, a paper feed roller 105 for sending the recording material S out of the paper feed cassette 102 is arranged at a position corresponding to the leading end of the recording material S in the paper feed cassette 102. A registration roller pair 106 that conveys the recording material S in synchronization with a toner image (member to be heated) on a photosensitive drum 117 described later is provided downstream of the paper feed roller 105.
An image forming unit 108 that forms a toner image on the recording material S based on laser light from the laser scanner unit 107 is provided downstream of the registration roller pair 106. Further, a fixing device 109 that thermally fixes the toner image formed on the recording material S is provided downstream of the image forming unit 108, and a fixing device 109 that detects the conveyance state of the paper discharging unit is provided downstream of the fixing device 109. Paper sensor 110, discharge roller 1 for discharging recording material S
11. Stacking tray 1 for stacking recording materials S for which recording has been completed
12 are provided.

Further, the laser scanner 107 is a laser unit 113 for emitting a laser beam modulated based on an image signal (image signal VDO) sent from an external device 131 described later, and the laser beam from the laser unit 113. And a polygon motor 11 for driving the same to scan a photosensitive drum 117 described later
4a, an imaging lens 115, a folding mirror 116, and the like.

The image forming section 108 is composed of a photosensitive drum 117, a primary charging roller 119, a developing device 120, a transfer charging roller 121, a cleaner 122, etc., which are necessary for a known electrophotographic process. In addition, the fixing device 10
Reference numeral 9 denotes a fixing film 109a, a pressure roller 109b, a ceramic heater (ceramic surface heater) 109c as a heating element provided inside the fixing film, a thermistor (temperature detecting means) 109d for detecting the surface temperature of the ceramic heater 109c, and the like. It is composed by.

Further, the main motor 123 arranged at the lower portion of the apparatus main body 101 mounts the feed roller 105 via the feed roller clutch 124 and the registration roller pair 106 to the registration roller pair 106. Driving force is applied via each unit of the image forming unit 108 including the photosensitive drum 117, the fixing device 109, and the paper discharge roller 1.
11 is also given a driving force.

An engine controller 126 is provided above the apparatus main body 101. The engine controller 126 is a video controller 12 which will be described later.
7, the laser scanner unit 107, the image forming unit 1 based on the information sent from the interface unit 7 through the interface 128.
08, the electrophotographic process is controlled by the fixing device 109, and the conveyance control of the recording material S in the apparatus main body 101 is performed.

Reference numeral 127 denotes a video controller, which is a general-purpose interface with an external device 131 such as a personal computer (Centronics, RS232C, etc.).
This general-purpose interface 13 is connected by 130.
The image information sent from 0 is expanded into bit data,
The bit data is sent to the engine controller 126 as a VDO signal.

Numeral 129 in the figure is the apparatus main body 101.
It is a fan provided to prevent the temperature rise inside.

FIG. 2 shows a drive circuit for the ceramic heater. Reference numeral 1 denotes an AC power source for connecting the image forming apparatus. The image forming apparatus supplies a commercial power source to the ceramic heater 3 via the AC filter 2 to heat the ceramic heater 3. Regarding the supply of electric power to the ceramic heater 3, the triac 4 is energized and cut off. The resistors 5 and 6 are bias resistors for the triac 4, and the phototriac coupler 7 is a device for ensuring a creepage distance between the primary and secondary sides. The triac 4 is turned on by energizing the light emitting diode of the phototriac coupler 7. The resistor 8 is a resistor for limiting the current of the phototriac coupler 7, and is turned on / off by the transistor 9. Transistor 9 has resistance 1
It operates according to an ON signal from the engine controller (control means) 11 via 0.

In addition, the AC power supply 1 is connected via the AC filter 2.
Is rectified by the rectifier 12, and the rectified voltage is applied to the resistor 13, the Zener diode 14, and the capacitor 1.
5, and is input to the transistor 17 via the resistor 16. If the voltage of the commercial AC power supply 1 is equal to or lower than the slice voltage Vz determined by the resistor 13, the Zener diode 14, the capacitor 15, the resistor 16 and the transistor 17, the transistor 17 is turned off, and if it is equal to or higher than the slice voltage Vz, it is turned on. Becomes The photocoupler 19 is a device for ensuring the creepage distance between the primary and secondary sides, and the resistors 18 and 20 are resistors for limiting the current flowing through the photocoupler 19. When the AC power supply 1 is at the slice voltage Vz or less, the transistor 17 is turned off,
The voltage of the resistor 20 becomes Low, and informs the engine controller 11 that "the commercial AC power supply 1 is equal to or lower than the slice voltage Vz and the positive / negative switching voltage (zero cross) or a voltage value near the zero cross". Hereafter, this signal sent to the engine controller 11 will be sent to ZEROX.
Call it a signal. This ZEROX signal is a pulse signal whose pulse width changes according to the voltage of the commercial AC power supply 1, as shown in FIG.

The engine controller 11 detects the pulse width of the ZEROX signal and controls the phase based on this pulse width.
Alternatively, the triac 4 is turned on / off by wave number control.

Reference numeral 21 in FIG. 2 is a ceramic heater 3.
Is a temperature detecting element for detecting the temperature of, for example, a thermistor temperature sensitive element. The temperature detected by the temperature detecting element 21 is the combined resistance determined by the resistor 22, the resistor 23, and the switching element 24, and the temperature detecting element 2
1 is detected as a partial pressure with the engine controller 11
A / D as a TH signal. The switching element 24 is a means for switching the combined resistance that determines the voltage division. When the switching element 24 is on, the combined resistance becomes the combined resistance of the resistors 22 and 23, and when the switching element 24 is off, The combined resistance is the resistance of the resistance 22. This switching element 24 is a THC sent from the engine controller 11 via a resistor 25.
It is controlled by the HG signal. The temperature of the ceramic heater 3 is monitored by the engine controller 11 as a TH signal, and the electric power to be supplied to the ceramic heater 3 is calculated by comparing with the set temperature of the ceramic heater 3 set inside the engine controller 11. , The phase angle (phase control) or the wave number (wave number control) corresponding to the supplied power, and the engine controller 11 sends an ON signal to the transistor 9 according to the control condition.

The phase control or wave number control is performed by using the ZEROX signal monitored by the engine controller 11 as a trigger signal. The engine controller 11
Before starting the power supply to the ceramic heater 3, ZER
Tw is detected as the pulse width of the OX signal, and tw / 2 is stored as the delay time. When the engine controller 11 controls the ceramic heater 3 by the phase control or the wave number control, tw / is started from the falling edge of the ZEROX signal.
The ceramic heater 3 is controlled in accordance with a predetermined phase angle or wave number with the time delayed by 2 as the reference timing. The above control in the case of phase control is shown in FIG. Although the pulse width tw of the ZEROX signal differs depending on the input commercial power supply 1, its central portion tw / 2 is constant, and the time delayed by tw / 2 from the rising edge is used as the reference timing, and for example, the phase is used as the reference. The phase control is performed by shifting from α to β.

By performing the control as described above, the ceramic heater 3 can be controlled at a timing closer to the true ZEROX point, and the accuracy of temperature control can be improved. Further, when controlling the ceramic heater 3 for different commercial AC power supply voltages, the ZER
Since the pulse width of the OX signal changes, it is possible to perform control with little variation on the commercial AC power supply voltage.
Particularly, when controlling the phase of the ceramic heater 3, a remarkable effect is obtained. <Embodiment 2> The points that overlap with Embodiment 1 described above are omitted.

The engine controller 11 detects the pulse width tw of the ZEROX signal which varies depending on the voltage of the commercial power source, calculates the commercial power source voltage, and determines the control method of the ceramic heater 3 according to the detected voltage. For example, 100
Phase control for V system, wave number control for 200V system,
Or vice versa.

As described above, by detecting the AC power supply voltage from the pulse width of the ZEROX signal, the control suitable for the AC power supply voltage can be selected, and the harmonic current and flicker noise corresponding to each power supply voltage can be selected. Reduction etc. can be aimed at. <Third Embodiment> The third embodiment shows a method of starting the fixing device 109 of the image forming apparatus using the ceramic heater 3. Since the circuit configuration of the third embodiment has been described with reference to FIG. 2 of the first embodiment, the description thereof will be omitted here. A conventional control sequence is shown in FIG.

In FIG. 5, a drive request for the fixing device 109 is detected (S001). When the request is detected, the thermistor temperature at that time is monitored to detect the initial temperature t0 (S002). Then, at the same time when the power supply to the ceramic heater 3 is started (S003), the counter is cleared (S004).

The thermistor temperature is constantly monitored (S00
5). When the temperature rises 10 ° C from the initial temperature t0,
The increment of the counter is started (S006). When the temperature rises by 30 ° C. from the initial temperature (S007), the counter increment is stopped (S008). The commercial power supply voltage value is detected from the counter value (S009), and the initial value of the power supply required for starting the ceramic heater 3 is calculated (S010).

The supply of the calculated initial electric power to the ceramic heater 3 is started (S011), the supplied electric power is corrected while monitoring the temperature gradient, and the temperature is raised to the target temperature. When the target temperature is detected (S012), the startup control of the fixing device 109 is finished.

That is, conventionally, the time from the start of power supply to the ceramic heater 3 until the temperature rises by 20 ° C. is measured, and the commercial power supply voltage is detected from the result,
The power supplied to the ceramic heater 3 is calculated.

On the other hand, in the third embodiment, a threshold value is provided in the rectified commercial power source to convert it into a binary level signal (hereinafter referred to as "ZEROX signal"). The ZERO
The X signal is for detecting the commercial power supply voltage from the difference in pulse width generated by the commercial power supply voltage, and calculating the power supplied to the ceramic heater 3. The control sequence is shown in FIG.
Shown in.

In FIG. 6, the presence / absence of a drive request for the fixing device 109 is detected (S101), and when the drive request is detected,
The counter is cleared (S102). And the ZER
When the rising edge of the OX signal is detected (S10
3) and start incrementing the counter (S10
4) When the rising edge of the ZEROX signal is detected (S105), the increment operation of the counter is stopped (S106).

The commercial power supply voltage is detected from the data of the increment counter (S107), and the initial value of the electric power supplied to the ceramic heater 3 is calculated (S108).

The supply of the calculated initial electric power to the ceramic heater 3 is started (S109), the supplied electric power is corrected while monitoring the temperature gradient, and the temperature is raised to the target temperature. When the target temperature is detected (S110), the startup control of the fixing device 109 is finished.

As described above, the commercial power source voltage is detected by the Z
By detecting with the EROX signal, it becomes possible to detect the commercial power supply voltage faster and more accurately than in the conventional case. Therefore, the startup time of the fixing device 109 can be shortened. <Fourth Embodiment> A fourth embodiment will be described.

The engine controller 11 detects the pulse width tw of the ZEROX signal and performs the above-described first embodiment.
From at least two of the three controls described in the third embodiment. By performing such control, it is possible to perform highly accurate heater control for different commercial power supplies with a single ZEROX signal, and it is possible to realize with a simple configuration.

[0046]

As described above, according to the present invention,
Even with a simple structure, the heating element can be controlled accurately and accurately even when the input commercial power supply voltage changes.

Further, by recognizing the input commercial power supply voltage corresponding to the pulse width of the ZEROX signal and selecting the control method suitable for the commercial power supply voltage, the heating element can be used for different commercial power supply voltage systems with a simple configuration. The temperature control can be separated.

Further, by controlling the initial power supplied to the heating body based on the input commercial power supply voltage recognized from the pulse width of the ZEROX signal and the temperature of the heating body detected by the temperature detecting element, the heating is performed. The commercial power supply voltage can be detected more accurately before the power is supplied to the body and relatively unaffected by the environmental temperature, and the rise time of the heating body can be shortened.

When the above-mentioned heating device is used as a fixing device of an image forming apparatus, since the set temperature of the fixing device is maintained with high accuracy, toner offset which tends to occur at high temperature and fixing failure which tends to occur at low temperature. And the like can be reliably prevented. Therefore, it is possible to provide an image forming apparatus having a universal power supply capable of inputting a plurality of commercial power supply voltages.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view showing a schematic configuration of an image forming apparatus according to the present invention.

FIG. 2 is a diagram showing a control and drive circuit of a heating device (fixing device) according to the present invention.

FIG. 3 is a diagram for explaining control of a heating device.

FIG. 4 is a diagram for explaining control of a heating device.

FIG. 5 is a flowchart showing a conventional control sequence.

FIG. 6 is a flowchart showing the control sequence of the third embodiment.

FIG. 7 is a diagram for explaining control of a conventional heating device.

[Explanation of symbols]

1 Power supply means (AC power supply) 3,109c heating element (ceramic surface heater) 11 Power control means (engine controller) 21, 109d Temperature detection means (thermistor) 101 Image forming apparatus main body (apparatus main body) 109 Heating device (fixing device, fixing device) 109a fixing film 109b Non-heating member (pressing member, pressing roller)

─────────────────────────────────────────────────── --- Continuation of the front page (56) References JP-A-8-6434 (JP, A) JP-A-8-115044 (JP, A) JP-A-3-248064 (JP, A) JP-A-56- 99372 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G03G 13/20 G03G 15/20 G05D 23/00-23/32 G05F 1/455

Claims (5)

(57) [Claims] 1. Controlled to maintain a predetermined set temperature
The heating device that heats the member to be heated
Be careful Power supply means for supplying power to the heating body, Temperature detecting means for detecting the temperature of the heating body, The heating based on the temperature detected by the temperature detecting means.
The power supply means so that the body maintains a predetermined set temperature
A power control hand that controls the power supplied to the heating element from the
Dan, Full-wave rectification, including means for full-wave rectification of input commercial power supply voltage
Zeroed by comparing the stored voltage to a predetermined threshold.
Pulse that outputs a pulse signal with a pulse near the point
Signal output means, The power control means, The pulse signal that changes according to the input commercial power supply voltage
Pulse width detection means for detecting the pulse width of Based on the pulse width detected by the pulse width detecting means,
The input based on the edge of the pulse signal
Judgment means for judging the zero-cross timing of commercial power supply
When, Zero of the input commercial power source determined by the determination means.
Based on Rocros timingThe energizing time is the input quotient
So that the energization time depends on the power supply voltage forThe temperature test
Temperature detected by the output means and the pulse width detection hand
Based on the pulse width detected by the stageControls energization time
Control means for controlling energization time, A heating device characterized by the above. 2. The determination means sets t from the edge of the pulse signal when the pulse width of the pulse signal is tw.
The heating device according to claim 1, wherein a timing at which w / 2 has elapsed is determined as a zero-cross timing of the input commercial power supply. 3. The heating device according to claim 2, wherein the power control unit has a unit that controls a conduction angle of a current supplied from the power supply unit to the heating body. 4. The power control device detects the input commercial power supply voltage based on the pulse width of the pulse signal, and the detected input commercial power supply voltage and the temperature of the heating element detected by the temperature detection means. The heating device according to claim 1, wherein the electric power supplied from the electric power supply means to the heating body is controlled based on the above. 5. An image forming apparatus, comprising: an image forming unit that forms a toner image on a recording material; and a fixing device that heats the toner image to fix the toner image on the recording material. It comprises by the heating device in any one of Claim 4 thru | or 4, a ceramic surface heater is used as the said heating body, The pressurizing member arrange | positioned facing this ceramic surface heater, and the said ceramic surface heater and pressurization. A fixing film sandwiched and conveyed between the member and a member, and the toner image on the recording material sandwiched and conveyed between the pressure member and the fixing film is heated by the ceramic surface heater. A characteristic image forming apparatus.