JPH08110731A - Heating control device for fixing device - Google Patents

Abstract

PURPOSE: To reduce the rush current when heaters are turned on with simple control and reduce the load applied to control elements in a fixing device on which multiple heaters are arranged. CONSTITUTION: When the temperature of a main heater 2 or a sub-heater 3 is a prescribed value or below based on the detection signals of a thermistor 4 detecting the temperature corresponding to the main heater 2 in a fixing roller 1 and a thermistor 5 detecting the temperature corresponding to the sub-heater 3, the main heater 2 is first turned on, then the sub-heater 3 is turned on after a prescribed time elapses for turning on both heaters 2, 3 according to the paper size. When it is detected that a main cover is closed from the opened state based on the signal from a cover switch 11, similar control is made. The rush current is reduced when the heaters 2, 3 are turned on, and the load applied to triode AC switches 6, 7 serving as control elements of the heaters 2, 3 is reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat generation control device for a fixing device mounted on an image forming apparatus such as a copying machine, a facsimile machine or a printer.

[0002]

2. Description of the Related Art An unfixed image (an image formed by a toner made of a heat-meltable resin) transferred onto a recording paper is mounted on an image forming apparatus such as a copying machine, a printer or a facsimile, and is recorded by heating. As a fixing device for fixing on paper, a fixing roller (heating roller) with a built-in heater is brought into pressure contact with a pressure roller, the recording paper is passed between both rollers, and heat and pressure do not cause fixing on the recording paper. A heat roller type fixing device for fixing a toner image is well known.

In a conventional heat roller type fixing device, when recording paper having a paper width narrower than the roller width is passed, the roller temperature at the portion where the recording paper does not pass becomes higher than at the portion where the recording paper passes. This is because the heat of the roller surface is removed by the paper in the area where the paper passes, but there is no heat loss in the area without the paper. Therefore, when a narrow sheet of paper is continuously fixed, the roller temperature of the paperless portion may rise beyond the allowable range. Therefore, it has been proposed that a plurality of heaters having different heat generation distributions are provided in the fixing roller.

In such a fixing device, a plurality of temperature sensors for detecting the fixing roller temperature of a portion corresponding to each heater are provided, and after the plurality of heaters are turned on, each temperature sensor is turned on. If it is detected based on the signal from the sensor that the roller temperature exceeds the allowable range, the heater corresponding to the temperature sensor is turned off to prevent the fixing roller temperature from rising excessively. It has become.

[0005]

However, the lower the temperature of the heater widely used in the fixing device of the above-mentioned system is, the smaller the resistance value is. Therefore, the inrush current when the heater is turned on is increased. However, there is a problem that the load on the control element that controls the power supply to the heater increases. In a conventional heat generation control device for a fixing device having a plurality of heaters, control is performed to individually turn off a plurality of lit heaters, and it is not intended to prevent an increase in inrush current when the heaters are lit. There wasn't.

Further, in order to prevent this, when the phase control is performed such that electric power is gradually supplied when the heater is turned on, there is a problem that the control becomes complicated. In addition,
The control of the power supply by the phase control is a conventionally known method in the heat generation control device of the fixing device having one heater.

The present invention solves the above-mentioned problems in the heat generation control device of the conventional fixing device, and in a fixing device in which a plurality of heaters are arranged in the fixing roller, the rush at the start of heater lighting is controlled by simple control. An object of the present invention is to provide a heat generation control device that can reduce the current and reduce the load on the control element.

[0008]

According to the present invention, the above-mentioned problems correspond to a fixing roller having a plurality of heat-generating sources in which heat-generating regions are arranged according to the size of a sheet to be passed, and the heat-generating sources. A heating control device for a fixing device having a plurality of temperature detecting means for detecting a fixing roller temperature of a portion to be heated, wherein the plurality of heat sources are independent from each other based on detection signals of the plurality of temperature detecting means. In a heat generation control device that can be controlled by, when controlling the plurality of heat sources from the heat release state to the heat generation state, after one of the plurality of heat sources is brought into the heat generation state, a predetermined time elapses. This can be solved by having a control means for controlling another heat source to bring it into a heat generating state.

Further, in order to solve the above-mentioned problems, the present invention corresponds to a fixing roller having a plurality of heat generating sources in which heat generating areas corresponding to the size of a sheet to be passed are arranged, and the heat generating sources. A heating control device for a fixing device having a plurality of temperature detecting means for detecting a fixing roller temperature of a portion to be heated, wherein the plurality of heat sources are independent from each other based on detection signals of the plurality of temperature detecting means. In a heat generation control device that can be controlled by, when controlling the plurality of heat sources from the heat release state to the heat generation state, after one of the plurality of heat sources is brought into the heat generation state, a predetermined time elapses. It is proposed to have a control means for controlling the other heat sources so as to bring them into a heat generating state, or for controlling the plurality of heat sources so as to bring them into a heat generating state at the same time.

Further, in order to solve the above-mentioned problems, the present invention puts one of the plurality of heat sources into a heat generating state and then, after a predetermined time has passed, puts another heat source into a heat generating state. In such a control, it is proposed that the heat generating source that consumes less power among the plurality of heat generating sources be turned on first.

Further, in order to solve the above-mentioned problems, the present invention compares the detection result of each temperature detecting means with a predetermined value set for each temperature detecting means, and detects by each temperature detecting means. When the temperature is lower than each of the set values, it is possible to perform control to turn other heat sources into a heat state after a predetermined time elapses after one of the plurality of heat sources is put into a heat generating state. suggest.

Further, in order to solve the above-mentioned problems, the present invention has a circuit state detecting means for detecting a disconnection state and a connection state of a power supply circuit to the plurality of heat sources, and the circuit state detecting means. When the circuit detects that the circuit is switched from the disconnected state to the connected state, the other heat source is brought to the heat state after a predetermined time elapses after one of the plurality of heat sources is brought to the heat state. Propose to take control.

[0013]

When a plurality of heat sources arranged in the fixing roller are changed from the heat release state to the heat generation state, first, only one heat source is made to generate heat, and then, after a predetermined time has elapsed, other By causing the heat generation source to heat, the inrush current at the time of shifting from the heat release state to the heat generation state is reduced.

Other functions will be apparent from the description of the embodiments below.

[0015]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing a fixing roller and a control system of a fixing device to which the present invention is applied. As shown in this figure, the fixing roller 1 has two heaters 2 and 3 built therein. The main heater 2 is arranged in the center of the roller 1. On the other hand, the sub-heater 3 has two heat generating regions, and each heat generating region is arranged at each end of the roller 1. The power consumption of the main heater 2 is larger than that of the sub heater 3. Two heaters 2, 3
AC 100 through relay (RA ₁ ) 10 respectively
It is connected to the V power supply and also connected to the triacs 6 and 7. The triacs 6 and 7 are connected to the CPU 8 via the control driver 9 and on / off control is performed. Therefore, when the relay 10 is on, the triac 6,
When the switch 7 is turned on, electric power is supplied to the heaters 2 and 3, respectively.

This fixing device is installed in a copying machine or the like in which the paper conveyance reference is the center reference, and turns on only the main heater 2 when the width of the paper to be passed is small, and when the paper width is large, the main heater is turned on. Both 2 and the sub-heater 3 are turned on.

By the way, thermistors 4 and 5 are provided in contact with the outer peripheral surfaces of the central portion and the end portion of the fixing roller 1. The thermistors 4 and 5 are connected to the CPU 8 and input the detected roller temperature to the CPU 8. The CPU 8 converts the signals from the thermistors 4 and 5 into digital signals,
The temperature data of the fixing roller 1 is obtained by the program. CP based on the roller temperature detected by the thermistor 4
U8 controls the triac 6 to control turning on / off of the main heater 2. Further, the CPU 8 controls the triac 7 based on the roller temperature detected by the thermistor 5 to control the turning on / off of the sub heater 3.

The CPU 8 receives a signal from a cover switch (SW) 11 for detecting whether the body cover of a copying machine or the like equipped with the fixing device is opened, and the relay 10 is turned off when the cover is opened. Then, the relay 10 is turned on when the cover is closed. Therefore, the heaters 2 and 3 are not turned on when the cover is opened.

Heat generation control in the fixing device constructed as described above will be described below. In this embodiment, even when the width of the paper to be passed is large and both the main heater 2 and the sub heater 3 are turned on, both heaters are turned on at the same time when the temperature of each heater is lower than a predetermined temperature. Instead, one of them is lit for a predetermined time. The same control is performed when the power of a copying machine or the like equipped with the fixing device is turned on and when the main body cover is closed from the open state. This makes it possible to reduce the inrush power when the heater is turned on as compared to when two heaters are turned on at the same time, and to reduce the load on the triacs 6 and 7 that are the control elements. Note that when the heater is warm, the inrush current does not increase even when the heater is turned on from the off state, so in this case, normal control is performed to turn on the two heaters at the same time.

The above control will be described with reference to the flowchart. FIG. 2 is a heater control determination for determining whether to perform delay control in which one heater is lit later than the other heater in the heat generation control device of the present embodiment or normal control in which two heaters are lit simultaneously. It is a flowchart which shows a process. In this flowchart, first, in order to determine whether or not the AC power supply circuit has switched from the cutoff state to the conductive state, it is checked whether or not the power ON flag and the cover close flag in the CPU 8 are set (S1). , 2). If at least one of these two flags is set, both flags are reset (S3). Then, the heater delay flag is set (S4), and the heater normal flag is reset (S
5). When the heater delay flag is set, it is possible to execute heater delay control described later.

When both the power ON flag and the cover close flag are not set (reset), the temperatures of the main heater 2 and the sub heater 3 are checked (S6, 7), and the heater temperature is 20 ° C. If:
The heater delay flag is set (S4), and the heater normal flag is reset (S5). Therefore, in this embodiment, the heater delay control can be executed when even one of the two heaters has a temperature of 20 ° C. or less.

On the other hand, when both heaters are above 20 ° C.,
It is checked whether or not the heater delay flag is set (S8), and if not set, the heater normal flag is set (S9). When the heater normal flag is set, the heater normal control described later can be executed. Here, the reason why the setting of the heater delay flag is checked in S8 is to prevent the heater delay control and the heater normal control from being performed at the same time.

The power ON flag setting process is performed by the initialization which is executed only once when the power is turned on, and is performed based on the flowchart shown in FIG. That is, various initialization processes are performed (S1), and then the power ON flag is set (S1).
2).

The cover closing flag setting process is performed when the main body cover of the copying machine is closed from the open state, and is executed based on the flowchart shown in FIG. That is, the state of the cover switch 11 input to the CPU 8 is checked to determine whether the cover is open (S1), and if the cover is open, the cover open flag is set (S2). When it is determined in S1 that the cover is not open, it is determined whether the cover open flag is set (S3). If this flag is set, it is reset (S4), and then the cover close flag is set (S5).

Next, in the flow chart of FIG.
The heater delay control that is possible when the heater delay flag is set will be described. The heater delay control is executed based on the flowchart shown in FIG. That is,
First, it is judged whether or not the heater delay flag is set (S1), and if it is set, the temperature of the main heater 2 is compared with a predetermined target temperature M (S2), and the temperature is lower than the target temperature M. If there is, turn on the main heater 2 (S
3) If it is equal to or higher than the target temperature M, it is turned off (S4). Then, this time, the temperature of the sub-heater 3 is compared with a predetermined target temperature S (S5), and if the temperature is lower than the target temperature S, the process proceeds to the process of delaying the lighting of the sub-heater 3 of S6 or less to reach the target temperature. If S or more, the sub-heater 3 is turned off (S9), and then the heater delay flag is reset (S
11). When the temperature of the sub-heater 3 is lower than the target temperature S, the main heater 2 is checked whether it is lit (S6), and if it is lit, the reset of the timer is checked (S7). If is 0, the timer is set to 1 (S8) and the timer process described later is performed.
Even if the temperature of the sub-heater 3 is lower than the target temperature S,
If the main heater 2 is not turned on, the sub heater 3 is turned on without performing timer processing (S10), and the heater delay flag is reset (S11). The reason why the heater delay flag is reset in S11 is that it is not necessary to delay and turn on the sub heater 3, and it is possible to set the heater normal flag in the flowchart of FIG.

The timer processing in the heater delay control is performed based on the flowchart of FIG. That is, it is checked whether or not the count number of the timer reaches a predetermined value (here, 10) (S1), and when it reaches the predetermined value (after a predetermined time elapses), the timer is reset to 0 (S2) and the sub heater 3 is turned on. The heater is turned on (S3) and the heater delay flag is reset (S4). When the count number of the timer has not reached the predetermined value, the timer is counted up (incremented) (S5), and when the count number reaches the predetermined value, S
Go to 2 or less. By this timer processing, the main heater 2
The sub-heater 3 is turned on after a predetermined time has elapsed from the turning on.

Next, in the flow chart of FIG.
The heater normal control that can be executed when the heater normal flag is set will be described. The heater normal control is executed based on the flowchart of FIG. That is,
First, it is checked whether or not the heater normal flag is set (S1). If this flag is not set, the heater normal control is not performed and the routine returns. If the flag is set, it is determined whether the temperature of the main heater 2 is lower than the target temperature M minus 3 degrees (S2). When the temperature does not reach the target temperature M minus 3 degrees, the main heater 2 is turned on (S
3) If the temperature reaches the target temperature M minus 3 degrees,
This time, it is checked whether or not the target temperature M has been reached or higher (S4). Here, the temperature of the main heater 2 is the target temperature M.
If not, it is determined whether the temperature of the sub-heater 3 is lower than the temperature obtained by subtracting 3 degrees from the target temperature S (S6). When the temperature of the main heater 2 exceeds the target temperature M, the main heater 2 is turned off (S5) and the temperature of the sub heater 3 is checked (S6). If the temperature of the sub-heater 3 has not reached the target temperature S minus 3 degrees, the sub-heater 3 is turned on (S7),
On the other hand, when the temperature reaches the target temperature S minus 3 degrees, it is next determined whether or not the temperature of the sub-heater 3 is equal to or higher than the target temperature S (S8). If the temperature is equal to or higher than the target temperature S, the sub heater 3 is turned off (S9), and if not, the process returns.

When the heater normal control is executed, each heater is independently controlled for heat generation based on the respective temperature states of the main heater 2 and the sub heater 3 and the target temperature.

By the way, in the present embodiment, when the width of the paper passed through the fixing device is large and both the main heater 2 and the sub heater 3 are turned on, the sub heater is delayed and turned on depending on conditions. As described above, the power consumption of the main heater 2 is larger than that of the sub heater 3. Since the inrush current at the time of lighting increases as the power consumption of the heater increases, the inrush current when the main heater 2 that consumes a large amount of power is turned on is larger than when the sub heater 3 is turned on first. Therefore, as another embodiment of the present invention, it is proposed that the power consumption of the main heater 2 be smaller than that of the sub heater 3.

However, when the power consumption of the main heater is required to be larger than that of the sub heater, the power consumption remains unchanged (power consumption of the main heater> power consumption of the sub heater) and the condition is satisfied. Therefore, the control may be changed by replacing the main heater and the sub heater in each of the above flowcharts with each other so that the heater that is turned on first becomes the sub heater.

[0032]

As described above, according to the heat generation control device of the fixing device of the present invention, when the plurality of heaters are turned on from the extinguished state, the plurality of heaters are not turned on at the same time, but the turn-on timing is set. Since the heaters are made different, it is possible to reduce the inrush current when the heater is turned on and then turned on. As a result, the load on the control element that controls the power supply to the heater can be reduced. Further, when one heater is turned on, the other heater is warmed by the heat generation thereof, so that the rush current when turning on the other heater becomes smaller.

According to the second aspect of the present invention, it is possible to perform the control in which the lighting timings of the plurality of heaters are different from each other and the control in which the heaters are simultaneously lit. Therefore, appropriate heat generation control according to conditions such as the state of the fixing device is performed. be able to.

According to the structure of claim 3, when one heater is turned on first, the heater with less power consumption is turned on first, so that the rush current at that time can be minimized.

According to the structure of claim 4, one heater can be turned on first when the temperature of the fixing roller is lower than a predetermined temperature, so that the resistance value of the heater becomes small at a low temperature. Thus, it is possible to prevent the inrush current from increasing. Further, it is possible to raise the temperature of the fixing roller promptly except when the temperature is low.

According to the fifth aspect of the invention, in the copying machine or the like, the primary circuit (supply AC circuit) is switched from the disconnected state to the connected state when the power is turned on and the main body cover is closed from the open state. When the primary circuit is in the cut-off state, the heater of the fixing device is naturally turned off. If the heater is turned off, the temperature will drop and the inrush current at the time of lighting will increase, but when the primary circuit goes from the disconnected state to the connected state, only one heater will be turned on first, so that the Inrush current increase can be suppressed to a minimum.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing the vicinity of a fixing roller and a control system of a fixing device to which the present invention is applied.

FIG. 2 is a flowchart showing a determination process for controlling lighting of a heater in the heat generation control device of the fixing device.

FIG. 3 is a flowchart showing a power ON flag setting process in the heat generation control device of the fixing device.

FIG. 4 is a flowchart showing a cover closing flag setting process in the heat generation control device of the fixing device.

FIG. 5 is a flowchart showing heater delay control in the heat generation control device of the fixing device.

FIG. 6 is a flowchart showing a timer process of a sub heater in the heat generation control device of the fixing device.

FIG. 7 is a flowchart showing heater normal control in the heat generation control device of the fixing device.

[Description of symbols] 1 fixing roller 2 main heater 3 sub heater 4,5 thermistor 6,7 triac 8 CPU 9 driver for control 10 relay 11 cover switch

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location H05B 3/00 370

Claims (5)

[Claims] 1. A fixing roller having a plurality of heat generating sources in which heat generating areas are arranged according to the size of a sheet to be passed, and a plurality of fixing roller temperatures for detecting the temperature of the fixing rollers of the portions corresponding to the heat generating sources. A heat generation control device for a fixing device having a temperature detection means, wherein the plurality of heat generation sources can be independently controlled based on detection signals of the plurality of temperature detection means. When controlling the heat source from the heat release state to the heat generation state, one of the plurality of heat sources is set to the heat generation state, and then the other heat source is controlled to be set to the heat generation state after a predetermined time elapses. A heat generation control device for a fixing device, comprising a control means. 2. A fixing roller having a plurality of heat generating sources in which heat generating areas are arranged according to the size of a sheet to be passed, and a plurality of fixing roller temperatures for detecting a temperature of the fixing roller of a portion corresponding to each heat generating source. A heat generation control device for a fixing device having a temperature detection means, wherein the plurality of heat generation sources can be independently controlled based on detection signals of the plurality of temperature detection means. When controlling the heat source from the heat release state to the heat generation state, one of the plurality of heat sources is set to the heat generation state, and then the other heat source is controlled to be set to the heat generation state after a predetermined time elapses. Alternatively, the heat generation control device of the fixing device includes a control unit that controls the plurality of heat generation sources to be in a heat generation state at the same time. 3. When one of the plurality of heat sources is controlled to be in a heat generating state and then the other heat source is controlled to be in a heat generating state after a lapse of a predetermined time, The heat generation control device for a fixing device according to claim 1, wherein the heat generation source with low power consumption is turned on first. 4. The detection result of each temperature detecting means is compared with a predetermined value set for each temperature detecting means, and when the temperature detected by each temperature detecting means is lower than each set value. The fixing device according to claim 2, wherein control is performed to bring another heat source into a heat generation state after a predetermined time has passed after one heat source is brought into a heat generation state among the plurality of heat generation sources. Heat generation control device. 5. A circuit state detection means for detecting a cut-off state and a connection state of a power supply circuit to the plurality of heat sources, wherein the circuit state detection means causes the circuit to change from a cut-off state to a connected state. The control is performed such that, when a predetermined time elapses after one of the plurality of heat sources is brought into a heat generating state when another is detected, the other heat source is brought into a heat generating state. A heat generation control device for the fixing device described.