JPH041662A - Power unit for image forming device - Google Patents

Abstract

PURPOSE:To obtain this universal type power unit including even heater system by applying a heater with the output of a rectifying circuit which switches rectification systems according to an AC input voltage and outputs nearly equal output voltages. CONSTITUTION:A 1st rectifying means 1 operates as a double voltage rectifier at the time of AC100V system input or as a full-wave rectifier at the time of AC200V system input with a system changing over switch 61, so its DC output voltage is nearly equal, and standardized and used for an AC200V system heater. Further, a 2nd rectifying means 2 even when a normal rectifier is the DC power source of a stabilized DC/DC converter 6, so the DC output of the converter 6 has an invariably stable voltage continuously irrelevantly to the AC input voltage. When the cover of the image forming device is opened, an interlocking switch 4 interrupts only the AC input of the 1st rectifying means 1, so the danger of an electric shock, burning, etc., can be prevented. Consequently, the universal power unit including even the heater relation is obtained by increasing the cost slightly.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a power supply device for an image forming apparatus that forms an image on plain paper using electrostatic latent image technology.

[Conventional technology]

Optical printers such as laser printers, LED (light emitting diode) printers, and LCA (liquid crystal array) printers, copying machines, digital copying machines, high-speed facsimiles, and electrostatic plotters use electrostatic latent image technology to print electrostatic latent images on photoreceptors. 2. Description of the Related Art There is an image forming apparatus that forms an image, transfers the toner image converted into a visible image by development onto plain paper, and then fixes the toner image using heat and pressure from a fixing roller heated by a heater.

The DC power supply for control circuits or driving motors, etc. is often made by rectifying the commercial power supply, then converting it to a low voltage using a high-frequency switching DC-DC converter and stabilizing it. .

The standard supply voltage of commercial AC power supplies worldwide is 100V.
~110v or 115V (7) ACl 00■ system,
It is divided into 200V-220V (7) AC 200V system, and its frequency is divided into 50Hz and 60Hz, and is not unified.

Therefore, for electrical equipment that uses commercial power, it is necessary to match the power supply voltage and frequency for each country and region in which it is used, making management extremely complicated.

The power supply device using the above DC-DC converter supplies stable DC power regardless of the power supply voltage or frequency, so it can be used not only for control purposes, but also for use in motors that require a constant rotation speed. It is used.

However, although pure resistance elements such as heaters are unrelated to frequency, they are affected by the power supply voltage in a superlinear manner close to the square of the power supply voltage, so relatively strict temperature control is required, such as with the fuser roller heater. There are cases where the temperature cannot be covered by the temperature control circuit alone, and AC100V
Depending on whether the system is a 200 V AC system or an AC 200 V system, manual operations such as changing the tap of a voltage conversion transformer, switching two heaters in series/parallel, or replacing the heaters have been performed by the manufacturer, service provider, or user.

FIG. 7 is a circuit diagram showing a conventional example of such a power supply device, and the same parts as in the first embodiment (FIG. 1) described later are given the same reference numerals, and details will be explained in the embodiment.

The AC power from the AC commercial power supply connected to the AC input section B is sent to the triac 91 of the heater inch circuit 90 and the heater via the rectifier circuit 2 that supplies DC power to the DC-DC converter 6 and the interlock switch 4. 25 and a thermal fuse 27 in series.

In the heater inch circuit 90, when the LED 92a of the photocoupler 92 lights up in response to a signal from a temperature control circuit (not shown), the current flowing through the bridge rectifier 93 increases, so the voltage drop across the resistor 94 becomes large and the triac 91 is turned on. When the LED 92a turns off, the triac 91 turns off.

In this way, by turning on and off the triac 91, the AC power flowing to the heater 25 is controlled.

Since AC commercial power is directly applied to the heater 25, it is necessary to prepare two types of heaters, one for AC 100V system and one for AC 200V system, and use them depending on the power supply voltage.

[Problem to be solved by the invention]

The power supply of the image forming apparatus, including the heater, is AC1.
In order to make it a universal type that does not require human operation for either the 00V system or the AC200V system, it would be possible to solve the problem by using a DC-DC converter for the heater as well as for the control and recording, but for the control.

Heater applications require tens of times more power than motor vehicle applications, making the power supply larger and cost-effective.

Furthermore, the fuser roller with a built-in heater needs to be replaced due to wear during use, and although the replacement work itself has been simplified so that it can be done by the user, if a fuser roller with a different voltage specification is installed, If the temperature does not rise to a high temperature, fusing may be insufficient, or if trouble occurs such as paper wrapping around the fusing roller even if there is no problem during normal use, it may lead to smoke or even fire accidents, and the safety of the device itself may be compromised. There was a major problem in that the user's trust was lost as well as the user's reputation.

This invention has been made in view of the above points, and provides a universal type power supply device that includes heater-related components with a slight increase in cost, and which allows parts to be kept in stock.

The purpose is to reduce overall costs by facilitating management of products, assembly departments, services, and users, and to improve the safety and reliability of image forming apparatuses.

[Means to solve the problem]

In order to achieve the above object, the present invention provides a power supply device for an image forming device that fixes a visible image transferred onto plain paper using electrostatic latent image technology using the heat and pressure of a fixing roller. It has an AC input section that can be connected to any of the system's commercial power sources, and detects the voltage of the commercial power source input from the AC input section, and performs voltage double rectification when inputting AC 100V, and full-wave or half-wave rectification when inputting AC 200V. Check the DCI of the fixing roller heater or its control circuit! a first rectifying means for outputting as a power source; and a first rectifying means for rectifying the commercial power input from the AC input section and outputting it as DC power for a DC-DC converter that supplies stabilized power for controlling or moving the image forming apparatus. 2
and an interlock switch that is disposed between the AC input section and the first rectifier and cuts off the AC input to the first rectifier when the cover of the image forming apparatus is opened. be.

[For production]

According to the power supply device of the image forming apparatus configured as described above,
Since the first rectifying means operates as a voltage doubler rectifier when the AC 100V system is input and as a full wave rectifier when the AC 200V system is input, the DC output voltages thereof are approximately equal, and it can be used uniformly in the AC 200V system heater. Also, the second
Even if the rectifying means is a normal rectifier, it is stabilized DC-DC.
Since it is the DC power source of the converter, the DC output of the converter always maintains a stable voltage regardless of the AC input voltage.

Therefore, a universal power supply including heater-related power supplies can be obtained.

Furthermore, when the cover of the image forming apparatus is opened, the interlock switch cuts off only the AC input to the first rectifier, thereby preventing the risk of electric shock or burns.
Since the DC power supply of the DC converter is still operating, inspections and adjustments can be made with the cover open.

〔Example〕

Hereinafter, one embodiment of the present invention will be specifically described with reference to the drawings.

FIG. 2 is a schematic diagram showing the internal mechanism of a laser printer that is an embodiment of the present invention.

A photoreceptor belt 10 rotates counterclockwise as shown by the arrow.
There are chargers 11. around it in the order of its rotational direction. Writing unit 12. Developing unit 13° transfer charger 1
4. Cleaning units 15 are arranged respectively.

The surface of the photoreceptor belt 10 is first uniformly charged by a charging charger 11, and then main-scanned by a spot on which a beam modulated by image data from a writing unit 12 and deflected in the main-scanning direction forms an image. , an electrostatic latent image is formed.

The electrostatic latent image is developed by the developing unit 13 and converted into a visualized toner image, and then the toner image is transferred by the transfer charger 14 onto the paper 16 that has been conveyed.

The toner and charge remaining on the photoreceptor belt 10 are removed by a cleaning unit 15, and the removed toner is collected by the cleaning unit 15.

The paper 16 is placed in the paper stack 1 on the paper feed cassette 17.
The paper is fed by the paper feed roller 19 from 8, and after it comes into contact with the pair of registration rollers 20 and pauses, the paper is written by the writing unit 12 and is fed by the registration roller 19 at a timing that matches the image on the photoreceptor belt 10. The pair 20 transports the toner image to the position of the transfer charger 14, and the toner image is transferred thereto.

The paper 16 on which the toner image has been transferred is conveyed to a fixing unit 21, is pressed against a fixing roller 23 heated by a pressure roller 22, and is fixed by the heat and pressure, and then placed on a paper output tray 24. be discharged.

A hollow spiral heater 25 is provided close to the sleeve 23a of the fixing roller 23, and heats the fixing roller 23 from the inside.

The surface temperature of the heated fixing roller 23 is higher than that of the sleeve 2'.
The temperature is detected by a temperature sensor 2B made of, for example, a thermistor, which is provided in pressure contact with the outside of Sa, and is controlled by turning on and off the heater 25 to maintain the optimum temperature during standby and during fixing operation.

Further, a thermal fuse 27 connected in series to the heater 25 is provided near the temperature sensor 26, and in the event that the heater 25 becomes uncontrollable and overheats, the thermal fuse 27 will be blown out. By turning off the heater 25, serious accidents such as smoke and ignition are prevented.

FIG. 3 is a block diagram showing an example of a control section of this laser printer.

The controller 30 is a main microcomputer (
(hereinafter referred to as rMPUJ) 31, and ROM 3 that stores the necessary programs, constant data, character fonts, etc.
2. -RAM that stores temporal data, patterns, etc.
2; 3 and l10 that controls command and data input/output
54, an operation panel 35 connected to the MPU'51 via l1034, and an internal interface (I/F) 56.
and are connected to each other via a data bus, an address bus, etc.

In addition, the host machine 38 that outputs print commands, character data, and image data is also connected to the MPU"+" via the l1054.
Connected to 1.

The engine driver 40 includes a sub microcomputer C (hereinafter referred to as rcPUJ) 41, a ROM 42 that stores necessary programs and constant data, a RAM 43 that stores temporal data, and an l1044 that controls data input/output. and are connected to each other via a data bus, an address bus, etc.

The l1044 is connected to the internal interface 36 of the controller 30, inputs video signals from the controller 30 and the states of various switches on the operation panel 35, and outputs status signals such as an image clock and paper end to the controller 30.

The l1044 is also connected to the writing unit 12 and other sequence equipment groups 46 that constitute the printer engine 45, each of which is a printing means, and to various sensors 47 including a synchronization sensor.

The controller 30 receives print commands, character codes, and image data from the host machine 38 and edits those codes and data, and if the character code is R, OM 3;
Converts the characters and images (
RA the dot pattern of "Image J" below.
It is stored in memory in the VRAM (video RAM) area in M33.

When the image clock is input together with the ready signal from the engine driver 40, the controller 30 transmits the dot pattern stored in the VRAM area to the engine driver 40 via the internal interface 66 serially or in parallel as a video signal synchronized with the image clock. Output.

The engine driver 40 controls the writing unit 12 and sequence equipment group 46 of the printer engine 45 using data from the controller 30, and inputs video signals necessary for image writing from the controller 30 and outputs them to the writing unit 12. At the same time, it inputs and processes signals indicating the status of each part of the engine from the synchronous sensor and other sensors 47, and outputs necessary information and error signals to the controller 30.

FIG. 1 is a circuit diagram showing an example of a first embodiment of a power supply device and its load.

This first embodiment includes a rectifier circuit 1 as a first rectifier, a rectifier circuit 2 as a second rectifier, and an AC input from a commercial power supply AC of 100V AC or 200V AC.
It is comprised of an AC input section 3 that supplies power to the rectifier circuits 1 and 2, and an interlock switch (including an interlock connector) 4 provided between the AC input section 3 and the rectifier circuit 1.

The rectifier circuit 1 includes a series circuit of a heater 25 and a thermal fuse 27, and a heater switch circuit 5 for turning it on and off, and the rectifier circuit 2 includes a control system or an active system stabilization circuit D.
A DC-DC converter 6, which is a C power source, is connected as a load.

The AC input section 3 has a fuse 51. Consisting of a power switch 52 and a noise filter 53, the A input from the input terminal 50
C power is fuse 51. After passing through the power switch 52, the external noise contained therein is passed through the noise filter 53.
It is grounded and removed.

The AC power from which noise has been removed is supplied to the rectifier circuit 1 through a normally closed interlock switch, and the other is supplied to the rectifier circuit 2 as it is.

FIG. 4 is a perspective view showing an example of how the interlock connector, which is the interlock switch 4, is attached.

This interlock connector consists of a socket part 55 and a plug part 56. The socket part 55 is fixed to the laser printer main body 57, and the plug part 56 is fixed to the cover 58. When the cover 58 is closed, the plug part 56 is fixed to the socket part. 55 and acts as a jumper, and the socket part 5
It is designed to close the circuit connected to 5.

When the cover 58 is opened for repair 2 inspection, the plug part 56 comes off from the socket part 55 and opens the circuit, cutting off the power supply to the rectifier circuit 1 as shown in FIG. 1, resulting in electric shock or burns during the work. prevent.

Returning to FIG. 1, the rectifier circuit 1 includes a bridge [flow device 60,
A method changeover switch 61 for changing the rectification method is provided between the series circuit of capacitors CI and C2 connected between the child terminal C and one terminal d, and the connection point of the capacitors C1 and C2 and the AC input terminal. It is composed of.

When the system selection switch 61 is off, the rectifier circuit 1 acts as a normal full-wave rectifier circuit, and the DC power smoothed by the series-connected capacitors CI and C2 is used as the load heater 25 and thermal fuse. 27 and the heater switch circuit 5.

When the system selector switch 61 is turned on, the rectifier circuit 1 acts as a voltage doubler rectifier circuit, and a voltage twice as high as that of full-wave rectification is obtained on the output side.

That is, in a cycle where terminal a is 10 with respect to terminal A, current flows from terminal a to terminal C, through the capacitor C1 degree method changeover switch 61, and charges capacitor C1, and in a cycle where terminal a is - The current is from the terminal to the method selector switch 61. It flows through capacitor C2 and terminal d to terminal a, charging capacitor C2.

Therefore, if you turn on the mode selector switch 61 when the AC100V power supply is connected, and turn off the mode selector switch 61 when the AC200 series power supply is connected,
Since the output side of the rectifier circuit 1 always obtains the DC power of the rectified voltage when AC 200 V system power is input, the heater 25 only needs to be prepared for the AC 200 V system.

FIG. 5 is a circuit diagram showing the rectifier circuit 1 in more detail in order to explain the function of an example of the method selector switch 61, and the same parts as those shown in FIG. Two lines connecting the AC power supply line and the system selector switch 61, which are omitted in FIG. 1, are added.

The system selector switch 61 is composed of a bidirectional three-terminal thyristor so-called triac 62, and a trigger circuit 65 consisting of a voltage detection section 63 and a transistor 64 that triggers the triac 62 in accordance with the output of the voltage detection section 63. .

The voltage detection unit 63 detects the AC voltage input to the AC input terminals a and b of the bridge rectifier 60, and detects that it is AC],
Detects whether it is OOV system or AC200V system,
If it is an AC 100V system, the trigger circuit 65 triggers the triac 62 via the transistor 64 to turn on the mode changeover switch 61, and if it is an AC200V system, the mode changeover switch 61 is turned off without triggering.

Therefore, as already explained, 5 capacitors C1, C
A rectified voltage generated by rectifying the AC 200V power supply is always generated at both ends of the series circuit No.2.

In FIG. 1, the heater switch circuit 5 mainly consists of an FET 8 which is a switching element that turns on and off a heater circuit formed by connecting a heater 25 and a thermal fuse 27 in series.
8, and a photocoupler 67 that relays a signal from a temperature control circuit (not shown) that controls the heater 25 according to the surface temperature of the fixing roller 23 detected by the temperature sensor 26 (FIG. 2).
Then, the signal relayed by the photocoupler 67 is amplified and connected to the FET.
66 and a transistor 68 for transmitting the signal.

If the surface temperature of the fixing roller 23 is higher than a predetermined temperature, the signal input from the temperature control circuit is turned on, so the LED 67a of the photocoupler 67 lights up and the receiving side phototransistor 67b is turned on, and the transistors 5g and FE are turned on.
T6B is respectively turned off and the heater circuit is cut off.

On the other hand, if the surface temperature of the fixing roller 23 becomes lower than the predetermined temperature, the input signal is turned off and the LED 67a is turned off.
The phototransistor 67b is turned off, the transistor 68 is turned on, the FET 66 is turned on, and the heater circuit is turned on, causing the heater 25 to generate heat and the surface temperature of the fixing roller 23 to rise.

The rectifier circuit 2 includes a bridge rectifier 70 that performs full-wave rectification of power from an AC power source, a capacitor C3 that smoothes its DC output, fuses 71 provided on the AC input side of the bridge rectifier 70, a noise cut transformer, and 2 and a noise filter 72 consisting of bypass capacitors.

This rectifier circuit 2 is a normal full-wave rectifier and smoothing circuit, so its explanation will be omitted, but the rectified DC voltage depends on whether the AC power supply connected to the AC input part B is a 100V AC system or a 200V AC system. It changes approximately in proportion to the input AC voltage.

However, the large change in DC voltage is caused by the
- absorbed by the DC converter 6 and the final load RL
is supplied with a DC power controlled to a constant voltage.

The noise filter 72 is for preventing high frequency switching noise generated by the DC-DC converter 6 from leaking to the AC power supply side.

The DC-DC converter 6 includes three coils Ll.

L2. A step-down transformer 75 having L3 and a D input from the rectifier circuit 2 connected in series with its primary coil L1.
F is a switching element that turns C power on and off at high speed.
ET7B, a snubber circuit 77 consisting of a CR series circuit connected in parallel between the source and drain of FET7B to absorb surge voltage due to switching, and a transformer 7.
A pulse width control circuit 7 that controls the pulse width applied to the gate of the FET 7B according to the DC voltage obtained on the secondary side of the FET 5.
8, and a rectifier circuit 79 consisting of a rectifier diode and a smoothing capacitor that rectifies and smoothes the pulse power induced in the tertiary coil L3 of the transformer 75 and supplies it to the pulse width control circuit 78.
Similarly, FET 76 turns on and transformer 75's 1
When current flows through the secondary coil L1, the secondary coil L
a main rectifier circuit 82 consisting of a rectifier diode 80 and a smoothing capacitor 81 for rectifying and smoothing the pulse power induced in
and an error voltage detection section 83 that divides the DC output voltage, compares it with a predetermined reference voltage, and outputs a difference signal according to the difference.
and a photocoupler 84 that relays the output difference signal to the pulse width control circuit 78.
5 is connected to a load RL.

As already known, the DC-DC converter 6 is
The switching element (FET7B) controls the DC power input to the primary coil L1 of the transformer 75 from several hundred KHz to several M
It is turned on and off at a high frequency of Hz, and the voltage is stepped down (or stepped up) by the transformer 75, and the pulsed power induced in the secondary coil L2 is rectified and smoothed by the rectifier circuit 82 and output to the load RL.

The DC output voltage is detected by the error voltage detection section 83,
It is fed back to the pulse width control circuit 78 via a photocoupler 84 for insulating the primary side and the secondary side.

The pulse width control circuit 78 changes the pulse width applied to the gate of the FET 76 so that the ON time of the FET 78 becomes shorter when the output voltage is higher than a predetermined voltage, and becomes longer when the output voltage is lower than a predetermined voltage. The DC voltage across load RL is held constant.

Since the pulse width can be controlled over a relatively wide range, the voltage of the AC commercial power supply connected to the AC input part B can vary from the lower limit of 90 V of the 100 V AC system to 20 V AC, including voltage fluctuations.
Even if the range of the V system changes up to about 230V, the DC voltage between the output terminals 85 can be sufficiently maintained at a constant voltage.

Therefore, as explained above, the AC according to the present invention
AC1 by switching the rectification method according to the input voltage.
The output of the rectifier circuit 1111, which can make the output voltage almost equal in both the 00V system and the AC200V system, is connected to the heater 25.
By applying an electric current to , it is possible to create a universal type power supply that also includes heater-related power supplies.

In the second embodiment shown in FIG. 6, the second rectifying means for supplying DC power to the DC-DC converter 6 is also a smoothing circuit consisting of a system selector switch 88 and a series circuit of capacitors C4 and C5, similar to the rectifying circuit 1. It is constructed from a universal rectifier circuit 7 provided with a capacitor, and other identical parts are given the same reference numerals and explanations will be omitted.

In this way, DC power with almost equal output voltage can be used for both AC100V and AC200V systems.
It can also be supplied to the converter 6.

As explained in the first embodiment, the DC-DC converter 6 can respond to large changes in the DC input voltage, but as in the second embodiment, the range of change is 180 degrees in AC input terms.
If it can be kept within the range of V to 230V, it can be used within the most efficient range as a DC-DC converter.
Since each component is not required to have performance that can handle a wide variation range, costs can be reduced and constant voltage accuracy can be improved.

If both the rectifier circuits 1 and 7 are of the universal type as in this second embodiment, the first. It is also conceivable to supply DC power to the heater and the DC-DC converter from one rectifying means, without using the second two rectifying means separately.

However, in that case, the interlock switch is
Since it is installed in the C circuit, there is a risk that an arc may fly when the current is interrupted, shortening the life of the contact or causing a welding accident.

Therefore, it is more reliable to provide a separate rectifier and use an interlock switch within the AC circuit.

Excellent in terms of lifespan and safety.

As explained above, if it is a universal power supply that includes heater-related power supplies, there is no need to separately manage each product component depending on the country or region in which it is used, and the user does not have to consider the power supply voltage or its fluctuations. That's fine.

Furthermore, since only one type of fixing roller (or heater) is required for replacement, there is no need for a user to make a mistake when replacing the roller, and there is no need for manual operations such as tap switching or serial/parallel switching of heaters.

Furthermore, it is safe because accidents such as electric shock and burns are prevented when the fixing roller is replaced by the user.

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to provide a universal power supply including heater-related power supplies with a slight increase in cost, and to manage inventory parts, products, assembly departments, services, and users. This makes it easier to reduce overall costs, and improves the safety and reliability of the image forming apparatus.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing a first embodiment of a power supply device for a laser printer, which is an embodiment of the present invention, FIG. 2 is a schematic configuration diagram showing an example of its internal mechanism, and FIG. A block diagram showing an example of the control unit, FIG. 4 is a perspective view showing an example of the installation of the interlock switch, FIG. 5 is a circuit diagram showing an example of the method selection switch, and FIG. 6 is the power supply device. FIG. 7 is a circuit diagram showing an example of a conventional power supply device. 1... Rectifier circuit (first rectifier) 2.7... Rectifier circuit (second rectifier) 3... AC
Input section 4... Interlock switch 5... Heater switch circuit (heater control circuit) 6... DC-
DC converter 16... Paper (plain paper) 23... Fixing roller 25...
・Heater 58...Cover 60.70...
Bridge rectifier 61.88... Method selection switch 62... Triac (bidirectional 3-terminal thyristor) 6
3... (commercial power supply) voltage detection section 3rd

Claims (1)

[Claims] 1. A visible image transferred onto plain paper using electrostatic latent image technology,
A power supply device for an image forming apparatus that performs fixing by heat and pressure of a fixing roller includes an AC input section that can be connected to either a 100 V AC or 200 V AC commercial power source, and the commercial power source that is input from the AC input section. Detects the voltage of
A first rectifying means performs full-wave or half-wave rectification when inputting a 0V system and outputs it as a DC power source for the heater of the fixing roller or its control circuit, and rectifies the commercial power input from the AC input section. , a DC-D that supplies stabilized power for controlling or driving the image forming apparatus;
a second rectifier that outputs as a DC power source of the C converter; and a second rectifier that is disposed between the AC input section and the first rectifier, and that when the cover of the image forming apparatus is opened, the first rectifier is activated. A power supply device for an image forming apparatus, comprising an interlock switch that cuts off AC input.