JPH11272113A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable a heater driving substrate to be mounted according to the state of a power source, to suppress the increase of a cost to the utmost and to prevent a light source device from being affected. SOLUTION: When the incumstance of the power source is bad, the heater driving substrate 30 on which a zero-cross timing detection circuit 32 is loaded is packaged in a device. By a CPU 2, a heater turning-on signal is outputted by being adjusted to a zero-cross signal outputted from the detection circuit 32. Then, a fixing heater 21 is softly started by a phase control action by a driving element 31. Thus, a rush current is suppressed when the fixing heater is turned on.

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, a facsimile, and the like.

[0002]

2. Description of the Related Art In an image forming apparatus such as a copying machine, a printer, a facsimile or the like using an electrophotographic system, a transfer paper,
BACKGROUND ART A heat fixing device is widely used as a fixing device for fixing an unfixed image (toner image) transferred onto a recording material such as an OHP film to the recording material.

Conventionally, as a heat fixing device, a pressure roller is pressed against a fixing roller (heat roller) heated by a heater, and a recording material is nipped and conveyed by both rollers while applying heat and pressure to form an unfixed toner image. A heat roller type for fixing is often used. In order to keep the fixing quality constant in such a heat fixing device, it is necessary to keep the surface temperature of the fixing roller constant within the feasible fixing temperature. Usually, the temperature of the fixing roller is maintained by controlling the heater on / off or by controlling the phase.

In some cases, a halogen lamp (halogen heater) is used as a heat source (heater) of the thermal fixing device. Since the halogen heater consumes a large amount of power and has a large inrush current flowing when it is turned on, it causes a voltage drop in a commercial power supply line, and other devices connected to the power supply line, for example, a light source device (such as a fluorescent lamp) flicker. And so on.

In order to prevent the influence on the light source device, it is effective to suppress the rush current when the halogen heater is turned on. As a method of suppressing the rush current, soft start control or the like in which the phase angle is increased stepwise rather than turning on the full wave at the timing of zero crossing (supplying the full AC wave) when turning on the heater is generally used. Is known.

[0006]

However, in order to perform the soft start control, it is necessary to detect the timing of the zero crossing of the AC power supply in order to determine the timing of the trigger pulse to the power control element. It is necessary to suppress the noise (conduction noise) accompanying this. That is, in the conventional image forming apparatus, when the influence on the light source device and the like is prevented by the soft start control of the fixing heater, the cost of the heater driving circuit increases due to the provision of the zero cross timing detection circuit and the noise suppression component. There is a problem.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an image forming apparatus which solves the above-mentioned problems in the conventional image forming apparatus and minimizes an increase in cost and does not adversely affect other electric equipment such as a light source device. And

[0008]

According to the present invention, there is provided an image forming apparatus provided with a fixing device using a halogen heater as a heat source, a heater driving board on which an element for directly driving the halogen heater is mounted, and a control device. And a control unit for transmitting a control signal of the heater to the heater drive board. The heater drive board includes a circuit having a circuit for detecting a zero-cross timing of an AC power supply and a heater drive board having no circuit. The heater drive board is provided so as to be mountable, and the control means determines which of the two types of the heater drive board is mounted according to the presence or absence of a zero cross signal which is an output signal from the detection circuit of the heater drive board. If it is determined that the heater drive board without the detection circuit is mounted, the halogen heater is turned on by the AC power. On / off control at zero crossing, and when it is determined that the heater drive board equipped with the detection circuit is mounted, soft start control for gradually increasing the phase angle when turning on the halogen heater is performed. Is solved by

According to the present invention, in order to solve the above-mentioned problems, in the case where a circuit having a circuit for detecting a zero-cross timing of an AC power supply is mounted as the heater driving board, the heater driving board is provided in addition to the soft start control. It is proposed to perform soft stop control for gradually reducing the phase angle when the halogen heater is turned off.

Further, in order to solve the above-mentioned problem, the present invention provides a heater drive board after the soft start, wherein a board having a circuit for detecting a zero-cross timing of an AC power supply is mounted as the heater drive board. As a control, it is proposed to perform a phase control so as to keep the heater current constant.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. The image forming apparatus of the present embodiment uses an electrophotographic method, and the basic configuration of an image forming unit, a sheet feeding unit, a document reading unit, and the like is the same as that of a conventionally known unit. Only such portions will be described.

The image forming apparatus of the present invention is provided so as to be able to be mounted on either a heater drive board having no zero-cross timing detection circuit or a heater drive board having a zero-cross timing detection circuit mounted thereon as a heater drive board for controlling the driving of the fixing heater. It is characterized in that it is automatically determined whether or not the drive board is mounted on the apparatus, and control corresponding to each board is performed.

FIGS. 1 and 3 are block diagrams each showing a configuration of a portion related to driving of a fixing heater in a control section of the image forming apparatus of the present embodiment. FIG. 1 does not include the zero-cross timing detection circuit. FIG. 3 is a block diagram in the case where the heater drive board is mounted, and FIG. 3 is a block diagram in the case where the heater drive board having the zero cross timing detection circuit is mounted. The only difference between the two block diagrams is the heater drive substrates 10 and 30, and the other parts are the same.

First, a description will be given of a case where a heater drive board without a zero-cross timing detection circuit shown in FIG. 1 is mounted. In FIG. 1, a CPU board 1 serving as a control unit has C
PU2 is mounted. Elements and components mounted on the CPU board 1 other than the CPU 2 are not shown. CPU
A heater drive substrate 10 is connected to the substrate 1. In this block diagram, an interface and the like for connecting both substrates are omitted.

A heater driving board 10 is provided with a driving element 11 having a zero cross switch. Drive element 1
Elements and components mounted on the heater drive board 10 other than 1 are not shown. Then, electric power is supplied to the heater (halogen heater) 21 of the fixing device from the AC power supply 20 via the drive element 11.

Since the heater drive board 10 is not provided with a zero-cross timing detection circuit, there is no zero-cross signal indicating the zero-cross timing of the power supply voltage (the heater drive board 10 does not output a zero-cross signal). The CPU board 1 determines that the heater drive board for zero-cross on / off control is mounted by not receiving a zero-cross signal, and automatically performs on-off control at zero-cross.

On the heater drive board 10 side, no matter what timing the heater lighting signal is output from the CPU 2,
By controlling the driving element 11 having a zero cross switch, the fixing heater 21 is always turned on or off at the timing when the power supply voltage crosses zero.

FIG. 2 is a timing chart showing the relationship between the power supply voltage, the heater lighting signal, and the heater current. This figure shows a case where a heater lighting signal is output from the CPU 2 and the fixing heater 21 is turned on. In this figure, the timing when the heater lighting signal is output, that is, when the heater lighting signal changes from the high level to the low level is at the peak of the power supply voltage, not at the timing when the power supply crosses zero. However, the timing at which the heater current is turned on matches the zero crossing of the power supply. The timing at which the heater current is turned on is adjusted to the timing at which the power supply crosses zero due to the action of the drive element 11 having the zero cross switch shown in FIG. Similarly, when the heater current is turned off, the operation is performed at the timing when the power supply crosses zero.

As described above, regardless of the timing at which the heater lighting signal is output by the driving element 11 having the zero cross switch, the fixing heater 21 is turned on / off at a timing that matches the zero cross of the power supply, thereby providing the power supply voltage. Can be suppressed, and flickering of the fluorescent lamp can be prevented to eliminate discomfort. In addition, it is possible to reduce EMI noise and extend the life of components such as fuses and TRCs by reducing current.

In a normal case where there is no problem in the power supply, even if the fixing heater is turned on / off, there is almost no possibility that flickering of the fluorescent lamp or the like will occur, and a noise filter is not required. Since a zero-cross detection circuit is not required, a low-cost device can be provided with the configuration shown in FIG.

Next, a description will be given of a case where a heater drive board having a zero-cross timing detection circuit shown in FIG. 3 is mounted. In FIG. 3, a heater driving substrate 30, a driving element 31 having no zero-cross switch, a zero-cross timing detection circuit 32, and a noise filter 33 are mounted. Elements and components other than these are not shown. Electric power is supplied to the fixing heater 21 from the AC power supply 20 via the drive element 31, and the detection circuit 32 detects the timing at which the power supply voltage crosses zero. Then, a zero-cross signal is sent from the detection circuit 32 to the CPU 2.

The configuration of the CPU board 1 shown in FIG.
However, when a zero-cross signal is input from the detection circuit 32, it is determined that the heater drive board mounted on the apparatus has a zero-cross timing detection circuit. Then, the CPU 2
The heater lighting signal is output to the heater drive board 30 in accordance with the timing of the zero cross signal sent from the detection circuit 32.

On the heater drive board 30 side, the non-zero cross type heater drive element 31 is mounted, so that the fixing heater lighting signal from the CPU board 1 turns on the fixing heater as it is.

That is, in FIG. 4, the zero cross signal output from the detection circuit 32 indicates the zero cross of the power supply. Based on this zero-cross signal, a heater lighting signal is output as a trigger pulse, and the phase angle of the power supplied to the fixing heater 21 is gradually increased. Thus, the fixing heater 21 is soft-started by the phase control, and the rush current is suppressed. The heater lighting signal indicates off at a high level and on at a low level.

In the configuration shown in the block diagram of FIG. 3, since the fixing heater 21 is soft-started by the phase control,
Inrush current when the fixing heater 21 is turned on is suppressed even in a situation where the power supply is bad, so that other devices connected to the power supply line are not adversely affected, and flickering of the fluorescent lamp or the like can be generated. There is no. When the soft start control of the fixing heater is performed, a conduction noise is generated because the current waveform is not a sine wave. Therefore, in the heater driving board 30 shown in FIG. 3, noise is suppressed by the noise filter 33.

As described above, in the image forming apparatus of this embodiment, the CPU 2 determines whether the heater driving board without the zero-cross timing detection circuit is mounted on the apparatus based on the presence or absence of the zero-cross signal from the heater driving board.
It is automatically determined whether a heater drive board equipped with a zero-cross timing detection circuit is mounted on the apparatus. In the former case, the fixing heater 21 is controlled to be turned on / off at a zero-cross of the power supply. When the fixing heater 21 is turned on, soft start control for gradually increasing the phase angle of the power supply is performed.

Therefore, appropriate heater control can be performed regardless of which of the heater driving boards is mounted on the apparatus. Thus, even when the heater drive board is replaced in the market (after shipment from the factory) in accordance with the power supply situation, it is possible to perform heater control according to the heater drive board. Therefore, in areas with good power supply conditions, a heater drive board without a zero-cross timing detection circuit is mounted with priority given to cost, and in areas with poor power supply conditions, the cost increases but zero-crossing that can prevent flickering of fluorescent lamps etc. -It is possible to mount a heater drive board on which a timing detection circuit is mounted.

Next, another embodiment of the present invention will be described. This embodiment employs a configuration as shown in the block diagram of FIG. 3 to perform soft start control when the fixing heater is on and soft stop control when the fixing heater is off. The soft start control when the fixing heater is turned on has been described with reference to FIG.

FIG. 5 shows a fixing heater 2 according to this embodiment.
6 is a timing chart illustrating a relationship between a heater lighting signal and a heater current for explaining soft stop control 1; As shown in this figure, when the fixing heater 21 is turned off,
The CPU 2 outputs a heater lighting signal for turning off the heater 21 to the heater driving board 30 in accordance with the zero cross signal sent from the zero cross timing detection circuit 32. That is, in FIG. 5, the high level of the heater lighting signal is output in accordance with the zero cross signal, and the phase level of the current supplied to the fixing heater 21 is gradually reduced by gradually increasing the high level duration.
Thereby, the soft stop of the fixing heater 21 is realized.

As described above, in the present embodiment, the fluctuation of the power supply voltage is further suppressed by controlling the soft stop when turning off the fixing heater 21 in addition to the soft start when turning on the fixing heater 21. be able to. Therefore, it is possible to more reliably prevent flickering of the fluorescent lamp.

Next, still another embodiment of the present invention will be described. This embodiment employs a configuration as shown in the block diagram of FIG. 3 to perform soft start control when the fixing heater is turned on and soft stop control when the fixing heater is turned off. The phase control is performed so that the heater current is constant during the stop.

FIG. 6 shows a fixing heater 2 according to this embodiment.
3 is a timing chart showing a relationship between a heater lighting signal and a heater current in phase control 1; In this figure, a stable state of the phase angle between the soft start and the soft stop is shown, and the ON and OFF of the heater lighting signal, that is, the length of the high level and the low level are almost constant, respectively.
This is a state where the magnitude of the heater current is kept constant.

As described above, in this embodiment, in addition to the soft start and the soft stop of the fixing heater, the phase control is performed so as to keep the magnitude of the heater current constant, thereby further suppressing the fluctuation of the power supply voltage. Can do
Therefore, it is possible to more reliably prevent flickering of the fluorescent lamp.

[0034]

As described above, according to the image forming apparatus of the present invention, the heater drive board without the zero-cross timing detection circuit is mounted on the apparatus according to the presence or absence of the zero-cross signal from the heater drive board. , Or whether a heater driving board equipped with a zero-cross timing detection circuit is mounted on the apparatus. In the former case, the fixing heater 21 is turned on / off at the zero-cross of the power supply.
In the latter case, the soft start control is performed to gradually increase the phase angle of the power supply when the fixing heater 21 is turned on. However, heater control according to the heater driving substrate can be performed. Therefore, in areas with good power supply conditions, a heater drive board without a zero-cross timing detection circuit is mounted with priority given to cost. -It is possible to mount a heater drive board on which a timing detection circuit is mounted.

Further, by controlling the soft stop when the fixing heater is turned off in addition to the soft start when the fixing heater is turned on, the fluctuation of the power supply voltage is further suppressed, and the flickering of the fluorescent lamp and the like are surely prevented. Can be prevented.

Further, by controlling the phase so as to keep the magnitude of the heater current constant after the soft start, the fluctuation of the power supply voltage can be further suppressed, and the flickering of the fluorescent lamp can be more reliably prevented. it can.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a control unit related to driving of a fixing heater according to an embodiment of the present invention, in which a heater driving board without a zero-cross timing detection circuit is mounted.

FIG. 2 is a timing chart showing a relationship between a power supply voltage, a heater lighting signal, and a heater current when a heater drive board without a zero-cross timing detection circuit is mounted.

FIG. 3 is a block diagram showing an example in which a heater drive board on which a zero-cross timing detection circuit is mounted is mounted.

FIG. 4 is a timing chart showing a relationship between a power supply voltage, a heater lighting signal, and a heater current when a heater drive board having a zero-cross timing detection circuit is mounted.

FIG. 5 is a timing chart illustrating soft stop control of a fixing heater according to another embodiment of the present invention.

FIG. 6 is a timing chart illustrating phase control of a heater current according to still another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 CPU board 2 CPU 10, 30 Heater drive board 11, 31 Drive element 20 AC power supply 21 Fixing heater 32 Zero cross timing detection circuit 33 Noise filter

Claims (3)

[Claims] 1. An image forming apparatus comprising a fixing device using a halogen heater as a heat source, comprising: a heater driving board on which an element for directly driving the halogen heater is mounted; A control unit for transmitting a control signal, wherein two types of heater drive boards, one with and without a circuit for detecting a zero-cross timing of an AC power supply, are provided as the heater drive board so as to be mountable; Is determined by the presence or absence of a zero-cross signal, which is an output signal from the detection circuit of the heater drive board.
It is determined which of the types the heater drive board is mounted, and if it is determined that the heater drive board without the detection circuit is mounted, the halogen heater is turned on / off at the zero cross of the AC power supply. An image characterized by performing a soft start control for gradually increasing a phase angle when the halogen heater is turned on when it is determined that the heater drive board having the detection circuit is mounted, Forming equipment. 2. When the heater drive board is equipped with a circuit for detecting a zero-cross timing of an AC power supply, in addition to the soft start control, a phase angle is set when the halogen heater is turned off. 2. The image forming apparatus according to claim 1, wherein soft stop control is performed to gradually decrease the soft stop control. 3. When the heater drive board is equipped with a circuit for detecting a zero-cross timing of an AC power supply, a heater drive control after the soft start is performed such that a heater current is kept constant. The image forming apparatus according to claim 1, wherein control is performed.