JPH1063134A - Image forming device, image reader, and image forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the power consumption and heat generation in a resistor from getting larges in the case of supplying a power through the resistor at the time of starting energizing. SOLUTION: An AC power given from a commercial power source 21 through a power source switch 22 is directly supplied to the input end 26a of a triac 26, and voltage-dropped by an automatic transformer 24 so as to be supplied to the input end 28a of a triac 28. By turning on the triac 28 according to a control signal B outputted from a switch control circuit 30 first at the time of starting the energizing, the AC power having a low voltage value is supplied to a heater 18 to perform the preheating of the heater 18. Thereafter, the triac 26 is turned on according to a control signal A outputted from the circuit 30 instead of the signal B, so that the AC power having a high voltage value is supplied to the heater 18.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an image forming apparatus, an image reading apparatus, and an image forming method.

[0002]

2. Description of the Related Art In a copier, a facsimile, a printer, or a multifunction peripheral having a heater, a lamp, and the like, the temperature of the heater and the lamp is proportional to the resistance value. When the temperature is low, the resistance value is low. At the start of energization of the heater and the lamp, a current having an extremely large value (hereinafter, referred to as an inrush current) flows as compared with a normal current value. This rush current causes a voltage fluctuation of the commercial power supply, and adversely affects external devices connected to the commercial power supply line.

In order to reduce the inrush current, conventionally,
There is known a control device in which a power supply voltage is applied to a halogen heater via a resistor for a specified time at the beginning of energization to perform preheating, and after a specified time has elapsed, the resistor is short-circuited and the power supply voltage is directly applied. (For example, Japanese Patent Application Laid-Open No. 7-36234)
Reference). Since the value of the current flowing through the halogen heater is determined by the applied voltage / resistance value, the current value at the start of energization is limited by inserting a resistor in series when the resistance value of the halogen heater is low at a low temperature. Thus, the rush current can be reduced.

[0004]

However, in the above-mentioned prior art, while the temperature of the halogen heater is low, in other words, while the resistance value is low, most of the electric power is consumed by the resistor, resulting in wasteful power consumption. Will be invited. This power consumption itself is a major factor that hinders low power consumption of the device. Further, most of the power consumed at this time is released into the device as heat, which adversely affects the normal operation of the device. For this reason, cooling means such as a fan for cooling the inside of the device is required to maintain the normal operation of the device. That is, contradictory measures such as operating a fan or the like to prevent an adverse effect due to heat generation while reducing the rush current at the start of energization are required.

A heater used in a copier, a facsimile, a printer, or a multifunction machine thereof has several tens of heaters.
In many cases, the heater has a power capacity of about 0 watts. Therefore, not only does the power loss and heat generation per heater turn on increase, but even if the heater is once heated to a high temperature, if it is turned off during the temperature control, it will take a short time ( Since the temperature drops to about several seconds to several tens of seconds, and the resistance value of the heater decreases accordingly, the power consumption and the amount of heat generated per unit time become large.

[0006] In particular, in the case of a copying machine, a heater used for fixing toner on paper is turned on / off even during copying.
Since the off operation is repeated, the power consumption by the resistor built in to reduce the inrush current at the time of on is
The amount of heat generated is enormous, and there is a problem that it is difficult to incorporate it into a real machine.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to reduce inrush current with low power consumption and low heat generation, and to suppress voltage fluctuation of a commercial power supply. An image forming apparatus, an image reading apparatus, and an image forming method are provided.

[0008]

According to the present invention, there is provided an image forming apparatus comprising: a power supply unit for supplying electric power; a transformer for lowering a voltage value of the electric power supplied from the power supply unit; And a switch for selecting a first path for supplying power to the circuit of FIG. 1 and a second path for supplying power to a subsequent circuit without passing through a transformer. And a switch control means for selecting a first path for the heater and controlling the switch to select a second path after power supply is started. ing.

In the image forming apparatus having the above-described structure, when the power supply to the heater is started, the switch control means first controls the switch to select the first path. Then, the heater
Power of a low voltage value stepped down by the transformer is supplied.
At this time, an inrush current flows through the heater, but the current value is small because the voltage value applied to the heater is low. By this low-voltage power supply, the heater is preheated. Thereafter, the switch control means controls the switch to select the second path. As a result, the heater is supplied with electric power having a high voltage value provided from the electric power supply means. Also at this time, an inrush current flows through the heater, but since the heater is preheated, the current value of the inrush current can be suppressed to a low value.

An image reading apparatus according to the present invention comprises a power supply means for supplying power, a transformer for lowering a voltage value of the power supplied from the power supply means, and a power supply to a subsequent circuit via the transformer. And a switch for selecting a second path for supplying power to a subsequent circuit without passing through a transformer, and converting the power supplied from the path selected by the switch into light for irradiating the document. And the first path for this lamp,
And switch control means for controlling a switch to select the second path after power supply is started.

In the image reading apparatus having the above-described structure, when the power supply to the lamp is started, the switch control means first controls the switch to select the first path. Then, the lamp is supplied with power of a low voltage value that is stepped down by the transformer. At this time, an inrush current flows through the lamp, but the current value is small because the voltage value applied to the lamp is low. With this low voltage power supply, the lamp is preheated. Thereafter, the switch control means controls the switch to select the second path. As a result, the lamp is supplied with power having a high voltage value from the power supply means. Also at this time, an inrush current flows through the lamp, but since the heater is preheated, the current value of the inrush current can be suppressed to a low value.

In the image forming method according to the present invention, a first step of supplying power, a second step of decreasing the voltage value of the power supplied in the first step, and a second step of
A third step of supplying the power whose voltage value has dropped by the step to heat for fixing the toner to the paper to the heater, and generating the first step with respect to the heater supplied with the power in the third step. And supplying a power without decreasing the voltage value.

In the above-described image forming method, when the power supply to the heater is started, the heater is first supplied with low voltage power. At this time, an inrush current flows through the heater, but the current value is small because the voltage value applied to the heater is low. By this low-voltage power supply, the heater is preheated. After that, a high voltage power is supplied to the heater. Also at this time, an inrush current flows through the heater, but since the heater is preheated, the current value of the inrush current can be suppressed to a low value.

[0014]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a schematic configuration diagram of, for example, a tandem digital color copying machine to which the present invention is applied.

In FIG. 1, an image of a color original 2 placed on a platen glass 1 is reflected by a mirror system 4 and a lens 5 by reflected light based on light emitted from an illumination lamp 3.
Is imaged on the imaging surface of the CCD imager 6 through the
Accordingly, the CCD imager 6 reads the reflectance information of the color original 2 as R (red), G (green), and B (blue) signals, and outputs the R, G, and B signals. As described above, the image reading apparatus 100 that reads the image of the color document 2 is configured.

On the other hand, to form an image forming apparatus 200 for forming an image on a sheet, K (black), Y (yellow), M
Image forming engines 7K, 7Y, 7M, and 7C are prepared for each of the color materials (magenta) and C (cyan). As an example, these image forming engines 7K, 7Y, 7M, and 7C are horizontally and serially arranged in the order of K, Y, M, and C from the right side of the drawing.

In the image forming engine 7K, the on-duty time of the laser beam is determined for each pixel around the photoconductor 8K forming the image carrier in accordance with the K signal, and the photoconductor 8K is exposed. An image writing device 9K for forming an electrostatic latent image, a scorotron 10K for uniformly charging the surface of the photoconductor 8K, a developing unit 11K for developing the electrostatic latent image on the photoconductor 8K into a toner image, a toner A transfer device 12K and the like for transferring an image to recording paper are provided.

Similarly, the photosensitive member 8 of the image forming engine 7Y
Around Y, an image writing device 9Y and a scorotron 1
0Y, a developing unit 11Y, a transfer unit 12Y, and the like are arranged. An image writing device 9M, a scorotron 10M, a developing unit 11M, a transfer unit 12M, and the like are arranged around a photoreceptor 8M of the image forming engine 7M. An image writing device 9C, a scorotron 10C, a developing device 11C, a transfer device 12C, and the like are arranged around the 7C photoconductor 8C.

In the tandem-type digital color copying machine having the above configuration, first, a K (black) signal is converted into an optical signal by the image writing device 9K, and a laser beam is exposed on the photoreceptor 8K to correspond to the original image. An electrostatic latent image is formed. This K latent image is developed by the developing device 11K. Then, the transfer device 12K transfers the K electrostatic latent image toner image to the recording paper fed from the paper tray 13 and transported by the paper transport belt.

Subsequently, the image writing device 9Y outputs a light signal of Y (yellow), and after forming and developing the electrostatic latent image of Y, the Y signal is applied to the recording paper conveyed by the conveyance belt 14. The toner image is transferred by the transfer device 12Y.
In the same manner, formation of latent images of M (magenta) and C (cyan), development, and transfer are performed. In this way, the transfer of the four colors is sequentially performed on the recording paper conveyed by the conveyance belt 73, and when the transfer is completed, the recording paper is transferred to the fixing device 15.
And the toner image is fused and fixed, and the image formation is completed.

The fixing device 15 is composed of a roller pair of a heating roller 16 and a pressure roller 17. Also,
The heating roller 16 has a built-in heater 18 for heating the heating roller 26 to fix the toner on the recording paper. Thus, the transferred toner image on the recording paper is fixed on the recording paper by being pressed by the pressure roller 17 while being heated by the heating roller 16 when passing through the fixing device 15. .

FIG. 2 is a block diagram showing a first embodiment of a heater control device for controlling the heater 18 according to the present invention.
In FIG. 2, AC power from a commercial power supply 21 is supplied to a power supply terminal 23 by turning on (closing) a power switch 22.
a, 23b. A transformer for lowering the voltage value of the supplied AC power, for example, an auto transformer 24 is connected between the power supply terminals 23a and 23b.

The auto-transformer 24 is a transformer in which one winding is shared between the primary and secondary windings. It has the feature that copper loss is small because the following difference current flows. Furthermore, the leakage flux is small because of the common winding,
There is also an advantage that the voltage fluctuation rate is small and the efficiency is good. As an example, the auto transformer 24 reduces the voltage value of the AC power supplied from the commercial power supply 21 to about と し て to ／.

An input terminal 26a of a switch device, for example, a triac 26 is connected to the power supply terminal 23a via a power supply line 25. The auto transformer 24
Is connected to an input terminal 28a of a switch, for example, a triac 28 via a power supply line 27. In this example, the triacs 26, 2
8 is used as a switch element, but is not limited to this. For example, an SSR (Solid S
Other bidirectional power elements such as a tate relay) may be used.

Each output terminal 26 of the triacs 26, 28
One end of a heater 18 incorporated in the heating roller 16 of the fixing device 15 in the image forming apparatus 200 in FIG. 1 is connected to b and 28b. The other end of the heater 18 is connected to a power terminal 23 b via a power line 29. Further, a switch control circuit 30 for controlling on / off of the triacs 26 and 28 and a temperature recognition device 34 for recognizing the temperature of the heater 18 are provided. This temperature recognizing device 34 is a heater
Is arranged in the vicinity of.

The switch control circuit 30 controls the control line 3
1 and 32 are connected to the respective gate ends 26c and 28c of the triacs 26 and 28, and the respective gate ends 26c and 28c
, Control signals A and B are appropriately given. The switch control circuit 30 is supplied with a heater ON command signal S11 for commanding the start of energization to the heater 18 from a system controller (not shown) that controls the entire system, and a control signal S12 from a timer 33. . Further, the timer 33 controls the switch control circuit 30 to turn on the heater.
When the command signal S11 is given, time measurement is started in response to the heater ON command signal S11. When the measured time reaches a predetermined time, the control signal S12 is sent to the switch control circuit 30. Output.

Next, a processing procedure of the heater control in the heater control device according to the first embodiment having the above configuration will be described with reference to a timing chart of FIG. 3 and a flowchart of FIG. In FIG. 3, the control signals A and B applied to the gate ends 26c and 28c of the triacs 26 and 28, the voltage applied to the heater 18 (heater voltage), and the current flowing through the heater 18 (heater current)
Are shown.

First, by turning on the power switch 22, AC power is supplied from the commercial power source 21 to both ends of the power terminals 23a and 23b (step S11). The voltage value of the AC power is divided by the auto transformer 24 with a division ratio of 1
/ N (N is an arbitrary integer of 2 or more) is stepped down (step S12). Then, at time t11, a heater ON command signal S11 is sent from a system controller (not shown).
Is supplied (step S13), the switch control circuit 30 takes in the measured temperature of the heater 18 from the temperature recognition device 34 (step S14), and determines whether or not the measured temperature is equal to or lower than a predetermined temperature (step S15).

At this time, if the temperature of the heater 18 is lower than the predetermined temperature, the switch control circuit 30 generates a control signal B and applies it to the gate end 28c of the triac 28 (step S16). At the same time, the timer 33 starts measuring time in response to the heater ON command signal S11 (step S17). Triac 28 is gate end 2
When the control signal B is applied to 8c, it is turned on (conducting).

Accordingly, the heater 18 is first supplied with AC power having a low voltage value obtained by reducing the voltage to 1 / N by the automatic transformer 24. At this time, an inrush current flows through the heater 18 that has been in a state where the temperature is low and the resistance value is low until the energization starts, but the applied voltage value is reduced to 1 / N by the auto transformer 24. Therefore, the current value of the rush current becomes 1 / N as compared with the case where the AC power from the commercial power supply 21 is supplied as it is.

On the other hand, the timer 33 continues to measure the time during the period when the low-voltage AC power is supplied to the heater 18, and when the measured time Ta reaches the predetermined time Tth (step S18), the time t12 A predetermined time Tt from the time t11 when the supply of low-voltage AC power to the heater 18 is started.
A control signal S12 indicating that h has elapsed is output to the switch control circuit 30 (step S19). At this time, the timer 33 is reset (step S2).
0).

Then, in response to the control signal S12, the switch control circuit 30 extinguishes the control signal B that has been output to the triac 28 (step S2).
1) Instead of this, a control signal A is newly generated and applied to the gate end 26c of the triac 26 (step S2).
2). The triac 26 receives a control signal A at the gate end 26c.
Is turned on (conducting) by applying.

As a result, the commercial power supply 2
1 is supplied directly without passing through the auto-transformer 24. Also at this time, an inrush current flows through the heater 18, but at this time, since the heater 18 is already preheated by the low-voltage AC power, the current value of the inrush current becomes a low value. Can be suppressed.

The switch control circuit 30 controls the temperature recognition device 3 while the high-voltage AC power is being supplied to the heater 18.
The measured temperature of No. 4 is fetched (step S23), and it is determined whether or not the measured temperature is equal to or higher than a predetermined temperature (step S24). Then, the temperature of the heater 18 reaches a predetermined temperature Tt.
h, the control signal A generated for the triac 26 is extinguished (step S2).
5).

Thereafter, the switch control circuit 30 determines whether or not the heater ON command signal S11 given from the system controller has disappeared, that is, whether or not there is a heater OFF command (step S26). If not, the process returns to step S14 to repeatedly execute the above-described series of processes. If there is a heater OFF command, the series of processes described above is terminated.

As described above, the voltage value of the AC power from the commercial power supply 21 is stepped down by the automatic transformer 24, and at the start of energization to the heater 18, first, the low voltage AC power stepped down by the auto transformer 24 is supplied. After the predetermined time Tth has elapsed, the high frequency AC power from the commercial power supply 21 is supplied directly without passing through the auto transformer 24, so that the number of times of the rush current flowing through the heater 18 increases, The current value can be kept lower than the divided ratio.

As described above, by suppressing the value of the rush current flowing through the heater 18 to a low value, the power consumption and the amount of heat generated can be significantly reduced, and the voltage fluctuation of the commercial power supply 21 can be suppressed. In particular, even if the on / off operation is repeated even during copying, such as a heater for fixing toner in a copying machine, the power consumption and the amount of heat generated can be significantly reduced, so that it can be incorporated as a real machine. .

Furthermore, by controlling the energization / interruption via the triacs 26 and 28 as one cycle (control interval in FIG. 3), the temperature of the heater 18 can be controlled to a target temperature. it can. Thereby, the temperature of the heater for fixing the toner can be controlled to the optimum temperature, so that the fixing of the toner image to the sheet can be performed more favorably.

By the way, when the heater 18 is energized,
The peak current value of the rush current generated when the low-voltage AC power is supplied is determined by the voltage dividing ratio of the auto transformer 24 and the characteristics of the heater 18. On the other hand, the peak current value of the inrush current generated when the high-voltage AC power is supplied depends on the voltage dividing ratio of the auto transformer 24, the characteristics of the heater 18, and the low voltage application period (period from time t1 to time t2) in FIG. Depends on

That is, if the voltage value of the low-voltage AC power determined by the voltage dividing ratio of the auto transformer 24 is high, the current value of the rush current is high and the heater 18 warms up quickly, so that the peak current of the rush current when a high voltage is applied The value decreases. On the other hand, if the voltage value of the low-voltage AC power is low, the current value of the rush current is low, and the peak current value of the rush current when a high voltage is applied increases because the heater 18 is not warmed. Further, even if the voltage value of the low-voltage AC power is high, if the low-voltage application period is short, the heater 18 does not warm up, so that the peak current value of the rush current when the high voltage is applied increases.

Therefore, the low voltage application period, that is, the predetermined time Vth11 measured by the timer 33 in the processing of steps S15 and S16 is determined by the peak current value of the rush current when the low voltage is applied and the peak current of the rush current when the high voltage is applied. Set the time to be approximately equal to the value. According to this, the maximum peak current value of the inrush current can be set to be the lowest, so that the power consumption and the heat generation can be suppressed low.

FIG. 5 is a block diagram showing a second embodiment of the heater control device according to the present invention for controlling the heater 18. As shown in FIG.
In FIG. 5, AC power from a commercial power source 41 is supplied to a power terminal 43 by turning on (closing) a power switch 42.
a, 43b. A transformer for lowering the voltage value of the supplied AC power, for example, an auto transformer 44 is connected between the power terminals 43a and 43b.

The power supply terminal 43a is connected via a power supply line 45 to an input terminal 46a of a switch device, for example, a triac 46. Also, the auto transformer 44
Is connected to an input terminal 48a of a switch device, for example, a triac 48 via a power supply line 47. In this example, the triacs 46, 4
Although 8 is used as the switch element, the present invention is not limited to this, and another bidirectional power element such as an SSR using a semiconductor circuit may be used.

Output terminals 46 of the triacs 46 and 48
One end of a heater 18 incorporated in the heating roller 16 of the fixing device 15 in the image forming apparatus 200 in FIG. 1 is connected to b and 48b. The other end of the heater 18 is connected to the heater 1
One end of a current value detector 54 for detecting the value of the current flowing through 8 is connected. The other end of the current value detector 54 is connected to a power supply terminal 43b via a power supply line 49.
Further, a switch control circuit 50 for controlling on / off of the triacs 46 and 48 is provided.

The switch control circuit 50 is connected to the gate ends 46c and 48c of the triacs 46 and 48 via control lines 51 and 52, respectively.
Monitor the value of the current flowing through the heater 18 detected by the control signal A, and control signals A,
B is given as appropriate. The switch control circuit 50 has a heater ON for instructing a start of energization to the heater 18 from a system controller (not shown) that controls the entire system.
A command signal S21 is provided.

The timer 53 is connected to the switch control circuit 5
Start time measurement in response to a measurement start command from 0,
When the measurement time reaches the first predetermined time Tth21, the control signal S22a is output. When the measurement time reaches the second predetermined time Tth22, the control signal S22b is output.
Output for 0.

Next, a processing procedure of the heater control in the heater control device according to the second embodiment having the above configuration will be described with reference to the flowchart of FIG.

First, when the power switch 42 is turned on, AC power is supplied from the commercial power supply 41 to both ends of the power supply terminals 43a and 43b (step S31). The voltage value of this AC power is divided by the autotransformer 44 into a voltage division ratio of 1 / N (N
Is reduced by an arbitrary integer of 2 or more (step S32). The switch control circuit 50 receives a heater ON command signal S2 from a system controller (not shown).
1 (step S33), first, the control signal B
Is output and applied to the gate end 48c of the triac 48 (step S34). Thereby, Triac 48
Is turned on (conducting), and 1 /
AC power having a low voltage value obtained by being reduced to N is supplied to the heater 18.

At this time, an inrush current flows through the heater 18 which had been in a state where the temperature was low and the resistance value was low until the start of energization. Since it has been lowered to
The current value of the rush current becomes 1 / N as compared with the case where the AC power from the commercial power supply 41 is supplied as it is. The current value flowing through the heater 18 is detected by a current value detector 54. The current value detector 54 constantly supplies the detected current value to the switch control circuit 50.

The switch control circuit 50 fetches the detected current value of the heater 18 from the current value detector 54 during the period when the low voltage AC power is supplied to the heater 18 (step S35), and the peak of the detected current value is obtained. It is determined whether the value has become constant (step S36). And heater 1
When the peak of the current value of 8 becomes constant, the control signal B that has been output to the triac 48 is extinguished (step S37). The voltage is applied to the gate end 48c (step S38).

At the same time, the timer 53 starts measuring time in response to a command from the switch control circuit 50 (step S39). Then, when the measured time reaches the predetermined time Tth21 (step S40), a control signal S22a indicating this is output to the switch control circuit 50 (step S41). At the same time, the timer 53 is reset (step S42).

Then, in response to the control signal S22a, the switch control circuit 50 eliminates the control signal A which has been generated for the triac 46 (step S43). Thus, the supply of the high-voltage AC power is stopped, and the heater 18 is turned off. At this time, a time measurement start command is again issued to the timer 53. As a result, the timer 53 starts measuring the time again (step S44), and when the measured time reaches the predetermined time Tth22 (step S45), the control signal S2 indicating that fact.
2b is output to the switch control circuit 50 (step S46). At the same time, the timer 53 is reset (step S47).

Upon receiving the control signal S22b from the timer 53, the switch control circuit 50 determines whether the heater ON command signal S21 provided from the system controller has disappeared, that is, whether there is a heater OFF command. (Step S48) If there is no heater OFF command, the process returns to Step S34 to repeatedly execute the above-described series of processing. If there is a heater OFF command, the series of processes described above is terminated.

As described above, in the heater control device according to the present embodiment, the current value actually flowing to the heater 18 is directly detected by the current value detector 54, and when the peak of the detected current value becomes constant. The current value is proportional to the temperature of the heater 18 by ending the low voltage application period in FIG. 3, so that the high voltage application is switched when the preliminary heating of the heater 18 by the low voltage application is completed. be able to. Therefore, preheating by low-voltage power supply is not performed more than necessary, so that power consumption and heat generation at the time of low-voltage application can be minimized.

In this embodiment, each period management of the heater ON period and the heater OFF period in FIG. 3 is performed by time measurement by the timer 53.
As in the case of the first embodiment, a temperature recognition device for recognizing the temperature of the heater 18 is provided, and each period management of the heater lighting period and the heater extinguishing period is performed based on the temperature recognized by the temperature recognition device. The good thing is, of course.

FIG. 7 is a block diagram showing a third embodiment of the heater control device according to the present invention for controlling the heater 18. As shown in FIG.
In FIG. 7, AC power from a commercial power supply 61 is supplied to a power supply terminal 63 when a power switch 62 is turned on (closed).
a, 63b. A transformer for lowering the voltage value of the supplied AC power, for example, an auto transformer 64 is connected between the power terminals 63a and 63b.

The power supply terminal 63a is connected via a power supply line 65 to an input terminal 66a of a switch device, for example, a triac 66. Also, the auto transformer 64
Is connected to an input terminal 68a of a triac 68, which is a switch element, via a power supply line 67. In this example, the triacs 66, 6
Although 8 is used as the switch element, the present invention is not limited to this, and another bidirectional power element such as an SSR using a semiconductor circuit may be used.

Each output end 66 of the triacs 66 and 68
One end of a heater 18 incorporated in the heating roller 16 of the fixing device 15 in the image forming apparatus 200 of FIG. 1 is connected to b and 68b. The other end of the heater 18 is connected to a power terminal 63b via a power line 69. Further, a switch control circuit 70 for controlling on / off of the triacs 66 and 68 and a temperature recognition device 74 for recognizing the temperature of the heater 18 are provided. This temperature recognition device 74 is disposed near the heater 18 in the fixing device 15 of FIG.

The switch control circuit 70 controls the control line 7
1 and 72 are connected to the gate ends 66c and 68c of the triacs 66 and 68, respectively, to monitor the temperature recognized by the heater 18 by the temperature recognition device 74, and to control the control signals A to the respective gate ends 66c and 68c. , B as appropriate. The switch control circuit 70 includes a heater ON command signal S31 for instructing the heater 18 to start energization from a system controller (not shown) that controls the entire system.
Is given.

The timer 73 is connected to the switch control circuit 7
Start time measurement in response to a measurement start command from 0,
When the measurement time reaches the first predetermined time Tth31, the control signal S32a is sent, and when the measurement time reaches the second predetermined time Tth32, the control signal S32b is sent to the switch control circuit 7.
Output for 0.

Next, a processing procedure of the heater control in the heater control device according to the third embodiment having the above configuration will be described with reference to the flowchart of FIG.

First, when the power switch 62 is turned on, AC power is supplied from the commercial power supply 61 to both ends of the power terminals 63a and 63b (step S51). The voltage value of this AC power is divided by the auto transformer 64 into a voltage division ratio of 1 / N (N
Is reduced by an arbitrary integer of 2 or more (step S52). Then, the switch control circuit 70 receives a heater ON command signal S3 from a system controller (not shown).
1 (step S53), first, the control signal B
Is output and applied to the gate end 68c of the triac 68 (step S54). As a result, the triac 68
Is turned on (conducting), and 1 /
AC power having a low voltage value obtained by being reduced to N is supplied to the heater 18.

At this time, an inrush current flows through the heater 18 which has been in a state where the temperature is low and the resistance value is low until the energization is started. Since it has been lowered to
The current value of the rush current becomes 1 / N as compared with the case where the AC power from the commercial power supply 61 is supplied as it is. The temperature of the heater 18 is recognized by a temperature recognition device 74 disposed near the heater 18. This temperature recognition device 74
Always gives the recognized temperature to the switch control circuit 70.

The switch control circuit 70 controls the temperature recognition device 7 while the low-voltage AC power is being supplied to the heater 18.
Then, a recognition temperature is fetched from Step 4 (Step S55), and it is determined whether or not this recognition temperature has reached a predetermined temperature, for example, the maximum heat generation temperature of the heater 18 (Step S56). And
When the temperature of the heater 18 reaches the maximum heat generation temperature, the control signal B which has been output to the triac 68 is extinguished (step S57). The voltage is applied to the gate end 68c (step S58).

At the same time, the timer 73 starts measuring time in response to a command from the switch control circuit 70 (step S59). Then, when the measured time reaches the predetermined time Tth31 (step S60), a control signal S32a indicating this is output to the switch control circuit 70 (step S61). At the same time, the timer 73 is reset (step S62).

Then, in response to the control signal S32a, the switch control circuit 70 eliminates the control signal A which has been generated for the triac 66 (step S63). Thus, the supply of the high-voltage AC power is stopped, and the heater 18 is turned off. At this time, a time measurement start command is again issued to the timer 73. Thereby, the timer 73 starts measuring the time again (step S64), and when the measured time reaches the predetermined time Tth32 (step S65), the control signal S3 indicating that fact.
2b is output to the switch control circuit 70 (step S66). At the same time, the timer 73 is reset (step S67).

When the control signal S32b is supplied from the timer 73, the switch control circuit 70 determines whether or not the heater ON command signal S31 provided from the system controller has disappeared, that is, whether or not there is a heater OFF command. (Step S68) If there is no heater OFF command, the process returns to Step S54 to repeatedly execute the above-described series of processing. If there is a heater OFF command, the series of processes described above is terminated.

As described above, in the heater control device according to the present embodiment, the temperature of the heater 18 is directly recognized by the temperature recognition device 74, and when the recognized temperature reaches the maximum heat generation temperature of the heater 18, FIG. Is completed, the temperature of the heater 18 can be accurately recognized, and switching to the high voltage application can be performed when the heating of the heater 18 by the low voltage application is completed. Therefore, preheating by low-voltage power supply is not performed more than necessary, so that power consumption and heat generation at the time of low-voltage application can be minimized.

In this embodiment, as in the second embodiment, each period of the heater lighting period and the heater turning-off period in FIG. 3 is managed by measuring the time by the timer 53. It goes without saying that each period management of the heater ON period and the heater OFF period may be performed based on the temperature recognized by the temperature recognition device 74 that recognizes the temperature.

FIG. 9 is a block diagram showing a fourth embodiment of the heater control device according to the present invention for controlling the heater 18. As shown in FIG.
In FIG. 9, AC power from a commercial power supply 81 is supplied to a power supply terminal 83 when a power switch 82 is turned on (closed).
a, 83b. Between the power supply terminals 83a and 83b, a first rectifier circuit 84 having, for example, a diode bridge configuration, and both ends of a primary winding L1 of a transformer 85 are connected. The first rectifier circuit 84 outputs DC power having a high voltage value by rectifying AC power directly supplied from the commercial power supply 81.

The transformer 85 is, for example, a commercial power supply 8.
The voltage of the AC power supplied from 1 is reduced to about 1/5 to 2/3, and AC power of a low voltage value is generated at both ends of the secondary winding L2. To both ends of the secondary winding L2, for example, a second rectifier circuit 86 having a diode bridge configuration is connected. The second rectifier circuit 86 includes a transformer 85
Rectifies the AC power obtained at both ends of the secondary winding L2 to output DC power of a low voltage value.

The positive output terminal 84 a of the first rectifier circuit 84 is connected via a power supply line 87 to a drain electrode of, for example, a MOS transistor 88 which is a switch element. Further, a drain electrode of, for example, a MOS transistor 90 which is a switch element is connected to a positive output terminal 86 a of the second rectifier circuit 86 via a power supply line 89. In this example, the MOS transistors 88 and 90 are used as the switching elements. However, the present invention is not limited to this. For example, other unidirectional power elements such as bipolar transistors may be used.

One end of a heater 18 incorporated in the heating roller 16 of the fixing device 15 in the image forming apparatus 200 of FIG. 1 is connected to each source electrode of the MOS transistors 88 and 90. The other end of the heater 18 is connected to a power supply line 91.
Are connected to the negative output terminals 84b and 86b of the first and second rectifier circuits 84 and 86, respectively. Further, a switch control circuit 92 for controlling on / off of the MOS transistors 88 and 90 and a temperature recognition device 96 for recognizing the temperature of the heater 18 are provided.

The switch control circuit 92 controls the control line 9
The transistors 3 and 94 are connected to the respective gate electrodes of the MOS transistors 88 and 90, and control signals A and B are appropriately applied to the respective gate electrodes. This switch control circuit 92 includes:
A heater O for instructing a start of energization to the heater 18 from a system controller (not shown) that controls the entire system
An N command signal S41 is provided, and a control signal S42 is provided from a timer 95. Also, the timer 95
When a heater ON command signal S41 is given to the switch control circuit 92, time measurement is started in response to the heater ON command signal S41. When the measured time reaches a predetermined time, the control signal S42 is output. Switch control circuit 92
Output to

The operation of the heater control device according to the fourth embodiment having the above configuration is basically the same as that of the heater control device according to the first embodiment. Hereinafter, the operation will be described with reference to the timing chart of FIG. FIG. 10 shows waveforms of control signals A and B applied to the gate electrodes of MOS transistors 88 and 90, a voltage applied to heater 18 (heater voltage), and a current flowing through heater 18 (heater current). It is shown.

First, when the power switch 82 is turned on, the AC power from the commercial power supply 81 is rectified by the first rectifier circuit 84, so that the MOS power is converted to DC power of a high voltage value.
While being applied to the gate electrode of the transistor 88, the voltage is stepped down by the transformer 85 at a voltage division ratio of 1 / N (N is an arbitrary integer of 2 or more) and rectified by the second rectifier circuit 86, so that the DC Power is applied to the drain electrode of the MOS transistor 90.

When a heater ON command signal S41 is issued from a system controller (not shown) at time t21, the switch control circuit 92 first sends a control signal B on condition that the temperature of the heater 18 is lower than a predetermined temperature. The output is applied to the gate electrode of the MOS transistor 90.
As a result, the MOS transistor 90 is turned on (conducting), and the low-voltage DC power supplied from the second rectifier circuit 86 is supplied to the heater 18. At the same time, the timer 95 starts measuring time.

At this time, an inrush current flows through the heater 18 which has been in a state where the temperature is low and the resistance value is low until the energization starts, but the applied voltage value is reduced to 1 / N by the transformer 85. Since the voltage is stepped down, the current value of the rush current is also reduced to 1 / N as compared with the case where the DC power based on the AC power from the commercial power supply 81 is directly supplied. When the measured time reaches a predetermined time Tth, the timer 95 supplies a control signal S42 indicating that to the switch control circuit 92.

Then, at time t22 when the control signal S42 is issued from the timer 95, the switch control circuit 92 extinguishes the control signal B which has been output to the MOS transistor 90, and replaces it with the control signal B. A is newly generated and applied to the gate electrode of the MOS transistor 88. As a result, the MOS transistor 88 is turned on (conducting), and the heater 18 is provided with the first rectifier circuit 84.
Supplies a high voltage DC power.

Even when high-voltage DC power is supplied, an inrush current flows through the heater 18, but at this time, since the heater 18 has already been preheated by the low-voltage DC power, the The current value of the current is suppressed to a low value. The switch control circuit 93 includes the heater 18
During the period in which high-voltage DC power is being supplied, the recognition temperature of the temperature recognition device 96 is monitored, and when the recognition temperature exceeds a predetermined temperature, the control signal A which has been generated for the MOS transistor 88 until then is monitored. To extinguish. This allows
Since the supply of the high-voltage DC power is stopped, the heater 18 is turned off.

Then, the switch control circuit 92 repeatedly executes the above-described series of processing on condition that the heater ON command signal S41 given from the system controller has not disappeared, that is, there is no heater OFF command. . If there is a heater OFF command, the series of processes described above is terminated.

As described above, in the heater control device according to the fourth embodiment, the AC power from the commercial power supply 81 is rectified to obtain a high voltage DC power, and the AC power stepped down by the transformer 85 is rectified. The first embodiment provides a low-voltage DC power, and supplies a low-voltage DC power at the start of energization to the heater 18, and then switches to a high-voltage DC power supply. As in the case of (1), the number of occurrences of the rush current flowing through the heater 18 increases, but the current value can be suppressed to be lower than the divided ratio, so that the power consumption and the amount of heat generation can be greatly reduced. 81 can be suppressed.

Further, since the heater 18 is turned on and driven by the DC power obtained by rectifying the AC power from the commercial power supply 81, a MOS transistor or a bipolar transistor, which is less expensive than a triac or SSR, is used as a switch element. Can be used,
The cost of the entire system can be reduced.

In this embodiment, the switching from the low-voltage DC power to the high-voltage DC power is performed by the timer 9.
5, the measurement is performed when the predetermined time Tth has been reached. However, as in the second embodiment, the current flowing through the heater 18 is detected, and when the peak of the current is constant. Alternatively, as in the case of the third embodiment, the temperature of the heater 18 may be recognized, and the recognition may be performed at a predetermined temperature, for example, the maximum heat generation temperature. is there.

In each of the above embodiments, the heater 18 used for the fixing device 18 in the image forming apparatus 200 shown in FIG.
Has been described, but the present invention is not limited to this. The image reading apparatus 10 shown in FIG.
0 can be applied to the control device of the illumination lamp 3.

FIG. 11 is a block diagram showing a fifth embodiment of the present invention applied to the control device for the illumination lamp 3. As shown in FIG. In FIG. 11, AC power from a commercial power supply 101 is supplied between power supply terminals 103a and 103b when a power switch 102 is turned on (closed). Power terminal 103
a, a transformer for lowering the voltage value of the supplied AC power, for example, an auto transformer 104
Is connected.

The power supply line 103 is connected to the power supply terminal 103a.
, For example, a triac 106
Are connected to the input terminal 106a. The output terminal 104a of the autotransformer 104 is connected via a power supply line 107 to an input terminal 108a of a switch device, for example, a triac 108. In this example, the triacs 106 and 108 are used as switch elements. However, the present invention is not limited to this. For example, another bidirectional power element such as an SSR using a semiconductor circuit may be used. .

Each output terminal 1 of the triacs 106 and 108
06b and 108b include the image reading device 100 of FIG.
Are connected to one end of the illumination lamp 3. The other end of the illumination lamp 3 is connected to a power supply terminal 103b via a power supply line 109. Also, Triac 10
A switch control circuit 110 for controlling on / off of the heaters 6 and 108 and a temperature recognition device 114 for recognizing the temperature of the heater 18 are provided. Switch control circuit 1
Reference numeral 10 is connected to gate terminals 106c and 108c of the triacs 106 and 108 via control lines 111 and 112, and appropriately supplies control signals A and B to the gate terminals 106c and 108c.

The switch control circuit 110 includes a system controller (not shown) for controlling the entire system.
ON to command the start of energization of the illumination lamp 3 from the lamp
The command signal S51 is provided, and the control signal S52 is provided from the timer 113. Also, the timer 113
Sends a lamp ON command signal S5 to the switch control circuit 110.
1 is given, the time measurement is started in response to the lamp ON command signal S51, and when the measured time reaches a predetermined time, the control signal S52 is sent to the switch control circuit 1
Output to 10

The lamp control device according to the fifth embodiment having the above-described configuration differs from the heater control device according to the first embodiment only in the object to be controlled, and there is no difference in the operation. Thus, the commercial power supply 1
The voltage value of the AC power from 01 is stepped down by the autotransformer 104, and when the energization of the lighting lamp 3 is started, the low voltage AC power stepped down by the autotransformer 104 is first supplied. By supplying high-voltage AC power from the power supply 101, the number of times of inrush current flowing through the lighting lamp 3 increases,
Since the current value can be suppressed lower than the divided ratio, power consumption and heat generation can be significantly reduced, and furthermore, voltage fluctuation of the commercial power supply 101 can be suppressed.

Note that, even when the present invention is applied to the lamp control device, similarly to the case where the present invention is applied to the heater control device, the switching from the low-voltage power supply to the high-voltage power supply is performed in the second manner.
As in the case of the embodiment, the value of the current flowing through the illumination lamp 3 is detected and the detection is performed when the peak of the current value becomes constant, or as in the case of the third embodiment. 3 is recognized, and the recognized temperature is a predetermined temperature,
For example, it is also possible to perform the operation when the temperature reaches the maximum heat generation temperature. Further, as in the case of the fourth embodiment, the illumination lamp 3 may be driven by DC power.

[0092]

As described above, according to the present invention,
When energizing a heater used in an image forming apparatus or a lamp used in an image reading apparatus, preheating is performed with low voltage power obtained by stepping down a transformer, and then high voltage power is supplied. With this configuration, the current value of the rush current flowing through the heater or the lamp can be suppressed to a low value, so that the power consumption and the amount of heat generated can be significantly reduced, and the voltage fluctuation of the commercial power supply can be suppressed.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a tandem digital color copying machine to which the present invention is applied.

FIG. 2 is a configuration diagram showing a first embodiment of the present invention.

FIG. 3 is a timing chart for explaining the operation of the first embodiment.

FIG. 4 is a flowchart illustrating a processing procedure according to the first embodiment.

FIG. 5 is a configuration diagram showing a second embodiment of the present invention.

FIG. 6 is a flowchart illustrating a processing procedure according to a second embodiment.

FIG. 7 is a configuration diagram showing a third embodiment of the present invention.

FIG. 8 is a flowchart illustrating a processing procedure according to a third embodiment.

FIG. 9 is a configuration diagram showing a fourth embodiment of the present invention.

FIG. 10 is a timing chart for explaining the operation of the fourth embodiment.

FIG. 11 is a configuration diagram showing a fifth embodiment of the present invention.

[Explanation of symbols]

3 Illumination lamp 6 CCD imager 7K, 7M, 7Y, 7C Image forming engine 9K, 9M, 9Y, 9C Image writing device 15 Fixing device 16 Heating roller 17 Pressure roller 18 Heater 21, 41, 61, 81, 101 Commercial power supply 24, 44, 64 Auto transformer 26, 28, 46, 48, 66, 68, 106, 108
Triac 30, 50, 70, 92, 110 Switch control circuit 33, 53, 73, 95, 113 Timer 34, 74, 96, 114 Temperature recognition device 74 Temperature recognition device 88, 90 MOS transistor 100 Image reading device 200 Image forming device

Claims (8)

[Claims] 1. A power supply means for supplying power, a transformer for lowering a voltage value of power supplied from the power supply means, and a first path for supplying the power to a subsequent circuit via the transformer. A switch for selecting a second path for supplying the power to a subsequent circuit without passing through the transformer, and converting the power supplied from the path selected by the switch to heat for fixing the toner to the paper. And a switch control means for selecting the first path for the heater and controlling the switch to select the second path after the supply of the electric power is started. Image forming device. 2. The image forming apparatus according to claim 1, further comprising: a timer for measuring a time period from when the supply of the electric power by the first path is started, wherein the switch control unit measures a time period measured by the timer. An image forming apparatus, wherein the switch is controlled to select the second path when a predetermined time has been reached. 3. The predetermined time is a time when the current value of the rush current flowing to the heater through the first path is substantially equal to the current value of the rush current flowing to the heater through the second path. The image forming apparatus according to claim 2, wherein 4. The image forming apparatus according to claim 1, further comprising: a current value detecting unit that detects a current value flowing through the heater, wherein the switch control unit detects a peak of the current value detected by the current value detecting unit. An image forming apparatus that controls the switch so as to select the second path when is constant. 5. The image forming apparatus according to claim 1, further comprising a temperature recognizing unit for recognizing a temperature of the heater, wherein the switch control unit is configured to execute the second process when the temperature recognized by the temperature recognizing unit reaches a predetermined temperature. An image forming apparatus, wherein the switch is controlled to select two paths. 6. The image forming apparatus according to claim 5, wherein the predetermined temperature is a maximum heat generation temperature of the heater by the electric power supplied from the first path. 7. A power supply unit for supplying power, a transformer for decreasing a voltage value of the power supplied from the power supply unit, and a first path for supplying the power to a subsequent circuit via the transformer. A switch for selecting a second path for supplying the power to a subsequent circuit without passing through the transformer, and a lamp for converting the power supplied from the path selected by the switch to light for irradiating a document Image reading comprising: selecting a first path for the lamp and controlling the switch to select the second path after the supply of power is started. apparatus. 8. A first step of supplying power, a second step of lowering a voltage value of the power supplied in the first step, and a power step of reducing the voltage value of the second step. A third step of supplying to a heater for converting the heat into heat to be fixed to a sheet; and a step of supplying the electric power generated in the first step to the heater supplied with the electric power in the third step without lowering a voltage value. An image forming method, wherein the supplying step and the supplying step are sequentially performed.