JPH11167329A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device capable of preventing the occurrence of higher harmonic noise or flicker noise by reducing the peak value of a current flowing in the device, and forming an image excellent in quality. SOLUTION: A heater is not energized while a phase angle is 0 to α1, but is energized while the phase angle is α1 to α2. During this period, the effective value detection voltage of an effective value detecting means is raised and the heater is not energized while the phase angle is α2 to #3, so that the effective value detection voltage of the effective value detection means is held. From the point of time when the phase angle is α3, the heater is energized again, and a control means turns off a driving signal for a driving means so that energizing the heater may be stopped at the point of time when the effective value detection voltage of the effective value detection means becomes the target effective value voltage, that is, when the phase angle is α4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus, such as a copying machine, a printer, or a facsimile machine, which has a fixing device for fixing an unfixed image.

[0002]

2. Description of the Related Art Conventionally, as this type of image forming apparatus, for example, there are a copying machine, a printer, a facsimile machine and the like.

A copying machine generally has a function of reading an image of an original or the like and forms an image on a sheet based on the read image information. Some copiers have a function of inputting image information to be sent.

[0004] A printer is generally an external device,
For example, an image is formed on a sheet based on image information sent from an apparatus such as a computer, and a facsimile apparatus generally has a function of reading an image of a document,
Further, it has a communication function, sends read image information to the outside, and forms an image on a sheet based on information sent from the outside.

In these image forming apparatuses, usually,
An AC power supply (hereinafter, referred to as an AC power supply) is connected from an outlet with a power cord or the like attached to the apparatus to supply an AC power supply, thereby supplying power to the image forming apparatus main body.

On the other hand, in the apparatus, a DC load means (hereinafter referred to as DC load means) using a drive power source as an output from a DC power supply means for converting an AC power supply into a DC power supply (hereinafter referred to as DC power supply), There is AC load means (hereinafter referred to as AC load means) using the power supply itself as a drive source.

Here, after the DC power supply means is output, the control means wakes up by itself, and then the operation of the image forming apparatus is performed by the control means for controlling the image apparatus main body, and the image forming operation and the like are executed. I have.

Further, when the control means drives a heater or the like provided in one of the AC load means, in particular, the heat fixing means (fixing device), it is usually driven by full-wave control or phase control. I was

The heat fixing means is for fixing an unfixed image (toner image) formed on the sheet by heating and pressurizing the image on the sheet, and includes a heater or the like as a heating means. It is.

[0010]

However, in the case of the above-described prior art, the following problems have occurred.

In the above-described prior art configuration, when the AC power is supplied or driven to each of the AC load means in the apparatus, the current peak of each AC load flows when the AC power rises to the maximum voltage. At that moment, the peak current value flowing to the device was increased.

Therefore, there is a problem in that the waveform is distorted, so that harmonic noise and flicker noise emitted from the apparatus main body are increased.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art. It is an object of the present invention to reduce a peak value of a current flowing in a device to prevent harmonic noise and flicker noise. An object of the present invention is to provide an image forming apparatus which is excellent in quality and aims at achieving the above.

[0014]

In order to achieve the above object, according to the present invention, in an image forming apparatus having a plurality of load means driven by input of an AC voltage, at least one of the plurality of load means is provided. One load means is controlled so as not to be driven in the vicinity of the peak portion of the power waveform of the input AC voltage.

Therefore, the peak value of the current flowing in the device is reduced by preventing the driving near the peak portion of the power waveform of the AC voltage.

A zero-crossing detecting means for detecting a zero-crossing of the power waveform of the input AC voltage, and a timer means operating at the timing of the zero-crossing detection of the zero-crossing detecting means. The time measurement may be controlled so that the power waveform is not driven in the vicinity of the peak portion.

Preferably, at least one of the plurality of load means is driven twice in a predetermined region before and after the vicinity of a peak portion in an AC half cycle of the input AC voltage.

An effective value detecting means for detecting an effective value of a cumulative voltage of voltages supplied for driving is provided, and of the two driving operations, ON / O of driving before the vicinity of a peak portion is performed.
The phase angle to be flipped is set in advance, and only after the vicinity of the peak portion, only the ON phase angle is set, and when the effective value detecting means detects that only a predetermined effective value has been supplied, it may be turned OFF. .

The load means controlled so as not to be driven by the vicinity of the peak portion of the power waveform of the input AC voltage is a heating means provided in a fixing device for fixing an unfixed image formed on a sheet. Good.

It is preferable to provide a temperature detecting means for detecting the temperature of the heating section by the heating means, and to control the driving of the heating means only when the temperature detecting means detects that the temperature has not reached a predetermined temperature.

[0021]

Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. However, the dimensions of the components described in this embodiment,
The material, shape, relative arrangement, and the like are not intended to limit the scope of the present invention only to them unless otherwise specified.

An image forming apparatus according to an embodiment of the present invention will be described with reference to FIGS.

Since the basic configuration of the image forming apparatus is a known technique, a detailed description thereof is omitted.
This will be briefly described below.

First, an image bearing member (for example, a photosensitive member) provided in an image forming apparatus is irradiated with image light (laser light) to form an electrostatic latent image on the image bearing member.

The image can be developed (toner image) by electrostatically attaching a developer to the electrostatic latent image by a developing device.

Thereafter, the development (toner image) is transferred onto the conveyed transfer material, and the transfer material is conveyed to a fixing device.
The image formation is completed by fixing the unfixed image formed on the transfer material.

In the embodiment of the present invention, the peak value of the current by the AC load means (described in the above-mentioned prior art) among the load means provided in the image forming apparatus having the above structure is reduced. Control is performed as described above.

Here, heating means (heater) provided in the fixing device among the AC load means provided in the image forming apparatus.
It is particularly effective to reduce the peak value of the current by the heating means because of the large load of the heating means, and such control will be described in detail below.

The load means for performing such control is not particularly limited to the heating means, but may be applied to other load means, but the description thereof will be omitted.

First, with reference to FIG. 1, control of heating a fixing unit (particularly a heating means (heater) provided in the fixing unit) provided in the image forming apparatus according to the present embodiment will be described.

FIG. 1 is a block circuit diagram of an image forming apparatus according to an embodiment of the present invention.

In the figure, reference numeral 1 denotes a control means for controlling not only the image forming apparatus main body but also each means and controlling the image forming operation and the like, and for example, a microcomputer can be applied.

Since the control means 1 has a timer means inside the control means 1 so that the timer can run freely from a certain timing, it is possible to determine the phase angle from the zero cross, the cycle of the zero cross signal and the like. it can.

Reference numeral 2 denotes an effective value detecting means provided at both ends of the fixing heater 4 for measuring an effective value voltage which is accumulated in the heater during application of a half-wave AC waveform and is energized. The effective value of the voltage applied to the power supply 4 is detected.

Reference numeral 3 denotes a driving means for energizing the heater, and can be constituted by, for example, a transistor.

Reference numeral 4 denotes a heater for generating heat of the heat fixing means.
For example, a ceramic heater can be used.

The heater 4 is provided with a diode in parallel to protect the driving means 3.

Reference numeral 5 denotes a thermoprotector that shuts off power to the heater 4 when the temperature of the heater 4 rises excessively. For example, a thermoswitch can be used.

Reference numeral 6 denotes a diode bridge, which serves as a power supply for driving the heater 4 by performing full-wave rectification on the AC power supply.

Numeral 7 is a zero-cross detecting means for detecting the timing when the AC power supply PW becomes zero voltage.

The structure of the zero-cross detecting means 7 is constituted by known electronic parts such as a photocoupler and a resistor.
To the effective value detecting means 2.

The effective value detecting means 2 measures the effective value supplied to the heater 4 by resetting the effective value voltage every time with a zero cross signal.

Numeral 8 denotes a temperature detecting means for detecting the temperature of the fixing section (heating section). In the present embodiment, the voltage of the thermistor is controlled by A of the control means 1 in a state where the thermistor and the resistor are connected in series. By connecting to the / D conversion input port and detecting the voltage of the thermistor 8 at regular intervals, the temperature information of the thermistor 8 provided in the fixing unit can be detected by the voltage.

Thus, the temperature of the fixing unit can be detected, and the temperature of the fixing unit can be adjusted using the heater 4, that is, the temperature control can be performed.

In the above description, the configuration of the heat fixing control has been described. On the other hand, the configuration of the original illumination lamp uses a halogen lamp as the original illumination lamp, and the lamp is controlled by a known phase control using a triac. Can be done with

For the phase control, a lamp regulator called CVR can be used.

Next, the drive control of the heater will be described more specifically with reference to FIG.

FIG. 2 is an explanatory diagram of drive control of a heater provided in the image forming apparatus according to the embodiment of the present invention.

The AC voltage is shown by the sinusoidal waveform depicted at the top of FIG.

First, control during a half-wave with a phase angle of 0 to 180 degrees will be described.

During the phase from 0 to α1, the heater 4 is not energized.

The heater 4 is energized while the phase angle is between α1 and α2, during which the effective value detection voltage of the effective value detection means 2 increases.

Since the current is not supplied during the next phase angle between α2 and α3, the effective value detection voltage of the effective value detecting means 2 is maintained, and the current is supplied again from the time when the phase angle becomes α3. When the effective value detection voltage has reached the target effective value voltage, that is, when the phase angle has reached α4, the control means 1 turns off the drive signal to the drive means 3 so as to stop energizing the heater 4.

When the phase angle reaches 180 degrees, the zero-cross signal is output by the zero-cross detecting means 7, so that the effective-value detecting signal of the effective-value detecting means 2 is reset.

As described above, the control is performed so that the power waveform is not driven by the vicinity of the peak portion.

The next control between 180 degrees and 360 degrees is the same as the above control, and the description is omitted here.

The above control is performed when the image forming operation is being performed and the difference between the current fixing unit temperature T _O and the target temperature Ts is smaller than a predetermined temperature T ₁ , or when T _O is T
s, ie, T ₁ > T _O −Ts, or
This is performed when T _O −Ts <0.

Therefore, when T ₁ <T _O −Ts, the heater 4 is not energized because the temperature of the fixing unit has reached a predetermined temperature.

FIG. 3 shows the waveform of the total current flowing through the AC power supply when the above control is performed.

From FIG. 3, it can be seen that the current flowing through each AC load flows in a form close to a sine wave, and it has been confirmed that this is advantageous in measuring flicker and harmonics.

FIG. 4 is a general flow chart of a heater provided in the image forming apparatus according to the embodiment of the present invention.

First, the flow of INT is determined by A /
This is an interrupt routine for periodically reading the input of D.

In (11), the output of the effective value detecting means 2 is detected, and in (12), the temperature of the fixing section is detected from the voltage of the thermistor 8.

Next, in the START flow, the cycle of the zero cross is measured to obtain 50/60 of the AC power supply frequency.
Hz.

In (1), the zero-cross cycle is measured by the zero-cross signal and the timer means.

Then, 50/60 Hz is determined in (2), and the phase angles (α1, α1) are determined for each frequency in (3).
2, α3, β1, β2, β3).

In (4), the temperature of the fixing means is detected from the voltage of the thermistor 8, and if the energization of the heater 4 is started, the process proceeds to (5). The following control is performed.

In (5), the current phase angles are α1 to α
2. If it is between β1 and β2 or α3 or β3 or more, proceed to (6). Otherwise, the heater 4 is not energized.

In (6), the effective value detection signal is a predetermined value of Vs
I am checking if it has become.

If the target value Vs of the predetermined value is reached, the heater 4 is not energized, and if not, the heater 4 is energized.

By performing control as described above, the embodiment of the present invention can be executed.

It is more preferable to control the value of Vs, which is the target value of power supply to the heater 4 described above, to be a variable based on the difference between the temperature T _{O of the} fixing device and the target temperature Ts. Fine temperature control is achieved.

An example of this case will be described with reference to FIG.

As shown in the flow of SEQ1 shown in FIG.
In (21), it is checked whether or not the difference between the current fixing temperature T _O and the target temperature Ts is larger than T ₁ .
Go to (22) so that the heater 4 is not energized.

[0075] Even within T _1, is divided into the case (23) and (25) if towards the fixing temperature T _O is high and low, as each variable (24) or (26) Is determined, finer temperature control can be performed.

[0076]

According to the present invention, the peak value of the current flowing in the device is reduced by preventing the driving in the vicinity of the peak portion of the power waveform of the AC voltage, thereby preventing harmonic noise and flicker noise. , Quality can be improved.

When applied to the heating means provided in the fixing device as the load means controlled so as not to be driven by the vicinity of the peak portion of the power waveform of the input AC voltage, the load on the heating means is high, so that it is particularly effective. It is.

[Brief description of the drawings]

FIG. 1 is a block circuit diagram of an image forming apparatus according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of drive control of a heater provided in the image forming apparatus according to the embodiment of the present invention.

FIG. 3 is a waveform diagram of a total current flowing to an AC power supply when driving control of a heater provided in the image forming apparatus according to the embodiment of the present invention is performed.

FIG. 4 is a general flow diagram of a heater provided in the image forming apparatus according to the embodiment of the present invention.

FIG. 5 is a general flow diagram of a heater provided in the image forming apparatus according to the embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Control means 2 Effective value detection means 3 Driving means 4 Heater 5 Thermoprotector 6 Diode bridge 7 Zero cross detection means 8 Thermistor

Claims (6)

[Claims] 1. An image forming apparatus comprising a plurality of load units driven by input of an AC voltage, wherein at least one of the plurality of load units is connected to a peak portion of a power waveform of the input AC voltage. An image forming apparatus that controls so as not to be driven depending on the vicinity. 2. A zero-crossing detecting means for detecting a zero-crossing of a power waveform of an input AC voltage, and a timer means operating at a timing of the zero-crossing detecting of the zero-crossing detecting means. 2. The image forming apparatus according to claim 1, wherein control is performed such that the power waveform is not driven near a peak portion by time measurement of the unit. 3. The method according to claim 1, wherein at least one of the plurality of load means is driven twice in a predetermined region before and after a vicinity of a peak portion in an AC half cycle of the input AC voltage. Item 3. The image forming apparatus according to item 1 or 2. 4. An effective value detecting means for detecting an effective value of a cumulative voltage of a voltage supplied for driving, wherein a phase angle for turning on / off the driving before the vicinity of a peak portion of the two driving operations. Is set in advance, and only the ON phase angle is set after the vicinity of the peak portion, and is turned OFF when the effective value detecting means detects that a predetermined effective value has been supplied. Item 4. The image forming apparatus according to Item 3. 5. A heating means provided in a fixing device for fixing an unfixed image formed on a sheet, wherein the load means is controlled so as not to be driven by the vicinity of a peak portion of the power waveform of the input AC voltage. The image forming apparatus according to claim 1, 2, 3, or 4, wherein 6. A temperature detecting means for detecting a temperature of a heating section by the heating means, and only when the temperature detecting means detects that a predetermined temperature is not reached, the heating means is driven and controlled. The image forming apparatus according to claim 5, wherein: