JP3240013B2 - Image forming apparatus and power supply - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention, electronic photography type of a copying machine, an image forming apparatus and the image formation such as a printer
The present invention relates to a power supply device suitable for a device.

[0002]

2. Description of the Related Art Conventionally, taking a copying machine and a printer as examples,
In a power supply unit of a copying machine or a printer, control of various high-voltage power supplies for realizing an electrophotographic process is the same as that of a sequence control CPU (microcomputer).
Products using PU are also available.

In the above-mentioned products, for example, sequence control of an electrophotographic copying machine or printer is performed by a CPU,
There is a device in which a high-voltage power supply, for example, a high-voltage transfer device is controlled by the same CPU (hereinafter referred to as a first conventional example).

Conventionally, taking an electrophotographic copying machine, a printer, or the like as an example, various electronic circuits are generally composed of a sequence controller including a CPU called a DC controller and various drivers and an electrophotographic device. A unit configuration is provided for each function, such as a high-voltage power supply for controlling various high-voltage power supplies for realizing the process and a DC power supply unit for supplying power to various units (hereinafter referred to as a second conventional example).

[0005]

The following problems are considered in the control of the power supply device in the first conventional example described above.

In the first conventional example, the following control is required for a power supply, particularly for a high transfer voltage. For example, constant current control is performed at a predetermined timing, and constant voltage control is performed at another timing.

In this case, in order to measure the impedance of the load, a voltage corresponding to an output voltage when a predetermined current flows under constant current control is detected by voltage detecting means, and image forming is performed based on this value. In the middle, constant voltage control is performed on the value calculated by a predetermined arithmetic expression to form an appropriate image forming process.

However, in this case, the filter time constant suitable for the constant current control is different from the voltage control during the constant voltage control.
May not always match the filter time constant suitable for

For example, the filter time constant can be changed to a constant voltage control .
When combined in suitable filter time constant, when reading the output voltage of the constant current control, if the ripple deviates from the target value is the optimum conditions at the time the error <br/> with such RiJo voltage control read There was a problem (hereinafter referred to as a first problem).

[0010] The inventions has been made in order to solve the first problem described above, the reduced <br/> ripple during the constant current control, except for the error in the reading, when the constant voltage control Target value
It is an object of the present invention to provide an image forming apparatus and a power supply device that can satisfy the above condition (hereinafter referred to as a first object).

In controlling the power supply device of the second conventional example, the following problems are considered.

In the power supply of the second conventional example, particularly the high-voltage power supply, constant current output control is performed to detect an output voltage for measuring the impedance of the load at a predetermined timing, for example, and a voltage corresponding to the output voltage is controlled. At other timings, there is a power supply which performs control such that constant voltage control is performed on an output value obtained by a predetermined equation according to the result.

However, in this case, a control circuit for the high-voltage power supply and a circuit for performing constant current control and detecting a voltage corresponding to the output voltage are separated from each other. In view of the output accuracy of the control circuit as a whole, various error factors such as various error factors inside the high-voltage power supply and A / D conversion errors of the CPU inside the DC controller are independent. output error of the overall control circuit to exist there is a problem that very large (second challenge).

[0014]

[0015]

In order to achieve the above object, according to the present invention, the image forming apparatus is configured as in the following (1), and the power supply device is configured as in the following (2 ) .

(1) Part of an electrophotographic image forming apparatus
Alternatively, control means for controlling the sequence of the entire device is provided.
When the control means performs the sequence control,
In addition, control the power supply for forming the image forming process.
The image forming apparatus performs the output voltage detection with respect to the load.
Output voltage detecting means, the voltage detecting means and the control means.
Filter hand that can be switched between time constants
And a current detecting means for detecting an output current to the load.
Stage and the current detected by the current detecting means is constant
And a constant current control means for constant-current control so that,
The control unit recognizes an impedance of the load.
Therefore, when the constant current control is performed by the constant current control means,
Monitoring the output of the pressure detection means via the filter means
And, after recognizing the impedance of the load,
Constant voltage control of the load according to the recognized impedance
The voltage detection means via the filter means
Controlling the power supply based on the output, and the Fi
The time constant of the filter means, and the constant current by the constant current control means.
An image forming apparatus that switches between control and constant voltage control.

(2) Control means for controlling the power supply device
And voltage detection means for detecting an output voltage to the load,
Disposed between the voltage detecting means and the control means;
Filter means for switching a constant,
Current detection means for detecting an output current; and the current detection means
Current control so that the current detected by
And a constant current control means for the control means, the negative
In order to recognize the load impedance,
The output of the voltage detection means during the constant current control by the
Monitoring through the filter means and the load
After the impedance is recognized, the recognized impedance
The filter to control the load at a constant voltage according to
Means based on the output of the voltage detection means via the means.
Controls source device, and the time constant of the filter means, before
Wherein the constant current control time by Kijo current control means constant-voltage control
A power supply that switches with time .

[0018]

[0019]

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

First, a first embodiment of the present invention will be described with reference to FIGS.

[0021] Figure 1 is a diagram showing the construction of a "power supply" of the first embodiment of the present invention, FIG 2 is a power supply device power supply of the first embodiment
FIG. 2 is a block diagram illustrating an image forming process performed for each block.

First, the periphery of a high-pressure process for forming an image will be described with reference to FIG.

In FIG. 2, reference numeral 10 denotes a charging roller, and an AC high voltage 10-1 and a DC high voltage 10-2 are applied in a superimposed manner in order to place an appropriate potential on the photosensitive drum. The drum is exposed 20 by reflected light or laser light of the original corresponding to the original image, and toner is applied to the drum surface by the developing cylinder 30 in accordance with the original image.

Here, the developing cylinder 30 inside the developing device is
And the DC bias 30-2 corresponding to the original density. Then, the toner is transferred to the paper by the transfer roller 40.

In the transfer circuit, control according to environmental fluctuations is performed. As an example, the load impedance of the transfer roller 40 is measured to control the output voltage according to the environmental change of the transfer roller 40. Therefore, constant current control is performed, the output voltage is determined by a predetermined arithmetic expression based on the measured load impedance value, and constant voltage control is performed.

In the operation other than the copying operation, a voltage of the opposite polarity is applied to clean the toner and the like remaining on the transfer roller 40.

DC bias 50 applied to static elimination needle 50
At -1, the paper is separated from the drum, and the toner is fixed on the paper by the fixing device 60 to form an image.

The first embodiment is an example of controlling a high voltage for transfer in the image forming process , which will be described with reference to FIG.

In the first embodiment, the control circuit is implemented by the CPU 1.

In FIG. 1, a block indicated by 7 is a transfer output control circuit section, which is a circuit for generating a bias during copying (transfer forward bias) and a bias to be applied outside the copy area (transfer reverse bias). It is configured.

The circuit for generating a transfer forward bias pressure performs the above such control, transformer T705 and the rectifier circuit of a diode D705, the capacitor C701 and the resistor R7
And a voltage rectified by the diode D704 and the capacitor C702.
(Corresponding to the voltage detecting means of claim 1) A / D (analog-to-analog) of the CPU 1
(Digital) conversion means 1-6.

The target value of the constant voltage is obtained by transmitting a pulse signal output from the output port 1-5 of the CPU 1 through the pulse-DC conversion circuit 715 to the transmitter 705 for driving the transformer 705.
This is provided to the driver block 713.

In addition to the above-mentioned constant voltage control circuit, the transfer forward bias has a constant current detecting means 711 and a control circuit 714 for controlling by comparing a constant current value with a predetermined voltage Vref.

In the actual sequence, first, in order to know the load impedance, the constant current control means 711 and 711 are used.
714 by flowing a constant current to the load, after being converted retrieve a value corresponding to the high-voltage output by the rectifying voltage of the auxiliary winding for generating the transformer T705 at a constant voltage detecting means 710 to a level that put preparative the CPU 1 CPU 1 This value is taken into the A / D conversion means 1-6 built in the CPU, and this value and a value corresponding to the output by an arithmetic expression which the CPU 1 has in advance are outputted as a pulse output from the output port 1-5. -D C is converted by converter 715 into a DC voltage corresponding to the pulse by controlling the input voltage of the transformer T705 of the transfer forward bias, and with a constant voltage control.

The transfer reverse bias shown in FIG. 1 includes a transformer T704, a diode D703, a capacitor C703, and a resistor R704, and is given a predetermined fixed value. The control of the output of on-off is Na is in accordance with a control signal from the output port 1-5 of the CPU 1.

Here, the time constant switching means is used for the following control.

In this circuit, A / D conversion means is used to detect an output during constant voltage control.

At the same time, the constant voltage control circuit including the A / D conversion means is used for the constant current control.

In this case, since the A / D conversion means used for both controls is the same, the following problem occurs.

Since the A / D conversion means is used in the constant voltage control circuit, ripples are mixed in the control detection circuit itself at the cycle of driving the transformer.

Further on the other hand we use A / D converting means 1-6 to detect the transformer output voltage during constant current control, the circuit is desirable not but error read less ripple when.

Therefore, in the first embodiment, the time constant of the filter circuit incorporated in the CPU is changed in accordance with both the constant current and constant voltage control of the transfer bias circuit.

In this case, before the image formation (non-image area), the impedance of the load is read by the CPU 1 so that the time constant switching means 2 switches to a state where the time constant is large, and the constant voltage control is performed in the image formation area. The control is switched to the appropriate time constant, and the control according to the sequence is performed.

In the first embodiment, the microcomputer (CP
Although an example using the A / D port of U1) has been described, the same applies even if the control circuit is not a microcomputer.

FIG. 3 shows another example 1 in which the control circuit is constituted by an operational amplifier.

The basic operation of another embodiment 1 in FIG. 3 is the same as that of the first embodiment. In the first embodiment, however, the constant voltage control means 5 is constituted by an operational amplifier, and the reference value Vref2 is set to C.
It is given by the D / A means of PU1.

Also in this case, the time constant switching means 2 is switched according to the sequence. In this alternative example 1, the same operation and effect as the first embodiment can be obtained.

Further, in the first embodiment, an example of the control by the transfer circuit of the copying machine and the printer has been described, but this can be applied to other control circuits.

For example, in a control circuit using a CPU, C
In the case where the sampling period of the PU is restricted and the period is inevitably increased, the case of taking in the value of the detecting means itself as in this example (referred to as another example 2) and the case of taking in the detected value as a control loop of the control circuit This is effective when both are performed on the same port.

This is because a separate A / D port is used to form separate detection means and filter means.
It is possible to reduce the number of A / D ports by using a common port, thereby enabling the use of a CPU having a small number of A / D ports and the configuration of a device requiring a large number of A / D conversions. it is possible Oite, more inexpensive structure to.

FIG. 4 is a configuration diagram showing a basic configuration of another example 2 control circuit. In FIG. 4, an output circuit 5 receives a control signal output from a CPU 1 and supplies the load 4 to a load 4. This output is detected by a detecting means 2 and this is changed over by a time constant switching means 3 according to a sequence to change the CPU 1 Incorporated into A / D input.

In the second embodiment, the same operation and effect as those of the first embodiment can be obtained.

Next, a second embodiment of the present invention will be described with reference to FIG.

FIG. 5 is a block diagram of a " power supply device " according to a second embodiment of the present invention.

First, the periphery of a high-pressure process for forming an image is substantially the same as that of the first embodiment shown in FIG. 2, but will be described repeatedly.

In FIG. 2, reference numeral 10 denotes a charging roller, which applies an AC high voltage 10-1 and a DC high voltage 10-2 by weight in order to place an appropriate potential on the photosensitive drum.

The drum is exposed 20 by the reflected light or laser light of the original corresponding to the original image, and the developing cylinder 30 carries toner on the surface of the drum corresponding to the original image. Here, there given Ete by superimposing a DC bias 30-2 to the developing device inside the developer cylinder 30 corresponding to the AC bias 30-1 and original density.

Then, the toner is transferred to the paper by the transfer roller 40.

In the transfer circuit, control according to environmental fluctuations is performed. For example, as an example, the load impedance of the transfer roller 40 is measured in order to control the output voltage according to the environmental change of the transfer roller 40. The output voltage is determined based on this value. In addition, a function of applying a voltage of the opposite polarity to clean the toner and the like remaining on the roller is performed except during the copying operation.

DC bias 50 applied to static elimination needle 50
At -1, the paper is separated from the drum, and the toner is fixed on the paper by the fixing device 60 to form an image.

Next, the details of the second embodiment will be described with reference to FIG.

[0062] The second embodiment is an example of controlling the pressure for your <br/> Keru transferred to the image forming process.

In the second embodiment, as in the first embodiment, an example in which the control circuit is performed by the CPU 1 will be described, and the description will be partially repeated.

In FIG. 5, a block indicated by 7 is a transfer output control circuit, which generates a bias during copying (transfer forward bias) and a bias to be applied outside the copy area (transfer reverse bias). It is composed of circuits.

The circuit for generating the transfer forward bias high voltage is as follows :
The above control is performed, and the transformer T705 is composed of a rectifier diode D705, a capacitor C701 and a resistor R705.
The voltage rectified by the capacitor 702 and the capacitor C702 is taken into a constant voltage detecting means (corresponding to the voltage detecting means of claim 3) 710, and is connected to the A / D converting means 1-6 of the CPU 1.

The target value of the constant voltage is determined by an oscillator that drives a transformer 705 via a pulse-DC conversion circuit 715 using a pulse signal output from the output port 1-5 of the CPU 1.
It is provided to the tribar block 713.

In addition to the above-described constant voltage control circuit, the transfer forward bias has a constant current detecting means 711 and a control circuit 714 for performing control by comparing the constant current value with a predetermined voltage Vref.

In the actual sequence, first, in order to know the impedance of the load, the constant current control means 711 and 711 are used.
At 714, a constant current is applied to the load, a value corresponding to the high voltage output is taken out by the rectified voltage of the auxiliary winding generated in the transformer T705, and converted to a level that can be taken into the CPU1 by the constant voltage detection means 710, and then sent to the CPU1. The A / D conversion means 1-6 is used for taking in the result of the constant current control for the load. Further, during image formation apparatus of the present power supply, the A / D acquisition viewed value storage means the calculated value (reference value) in operation expression with advance in the storage unit 1-2 of the CPU 1 (RAM) 1 −3, and the constant voltage control is performed to a value corresponding to this value.

[0069] Operation at this time, before mentioned transfer forward bias circuit or diodes as transformer T705 and outputted rectifying means D705, the capacitor C701, resistors R70
5 and an output corresponding to the high voltage output generated by the transformer drive driver circuit, oscillator block 713 or the like, T
705 diode from the auxiliary winding of D704, the rectified capacitor C702, C incorporation in the constant voltage detection unit 710
PU1 are written Ri taken at a predetermined cycle to convert into Tokomu level CPU1 of the A / D converting unit 1-6.

In the CPU 1, the fetched value is
It is compared with a reference value, and the result of the comparison is output as a high / low binary signal as a pulse via an output port 1-5 in the CPU 1. This control pulse is output by a pulse-DC conversion circuit 715 in accordance with the pulse. The constant voltage control is performed by controlling the input voltage of the transformer T705, which is converted into the DC voltage and transferred forward bias.

As described above, the detection of the high voltage output during the constant current control and the detection of the high voltage output during the constant voltage control are performed by the same A / D conversion means.
By performing through, can constant current control and the constant voltage control with the same A / D variant 換手 stage, also, since the peripheral circuits such as the detection means can also be shared, the constant current control during the constant voltage control The errors of the above-described circuits and the like at the time are cancelled, and the high-voltage output can be improved with high accuracy.

[0072] In the second embodiment described above has been described a system and for co and output detecting means when the output detecting means and the constant current control constant voltage control circuit of the high voltage to the embodiment, the constant current control even It is also possible to carry out using the same A / D conversion means (hereinafter, referred to as A / D conversion means) .
Another example 1 of the second embodiment).

FIG. 6 is a block diagram of another example 1 of the second embodiment.

In FIG. 6, the input switching means 2 is provided between the constant current and constant voltage detecting means 711 and 710 and the A / D converter 1-6 means of the CPU 1, and the output port 1 is provided in accordance with the copy sequence. Input switching is performed by a signal from the terminal 5.

As a result, the number of circuit components can be reduced, and the cost can be reduced. The operation of the other example 1 other than the above is the same as that of the second embodiment, and the duplicated description will be omitted.

In the second embodiment, the constant voltage is detected by detecting the output of the auxiliary winding of the transformer T705 by the diode D7.
However, this can be performed by directly detecting the high voltage output by the divided voltage output of the resistor (hereinafter referred to as another example 2 of the second embodiment).

FIG. 7 is a block diagram of another example 2 of the second embodiment. In FIG. 7, it is also possible to suppress the coupling between the high voltage output of the transformer and the auxiliary winding and the output variation due to the high voltage and the output waveform of the auxiliary winding.

However, in this case, since the constant current control value also causes a current to flow through the voltage dividing resistor, it is necessary to correct the current value inside the CPU 1.

[0079]

As described in the foregoing, in the invention of this, by switching the time constant of the full <br/> filter means and the constant current control during the constant voltage control when, the ripple during the constant current control Reduce the effect and eliminate reading errors ,
The target value can be set as the optimum condition.

[0080]

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a power supply device according to a first embodiment of the present invention;

FIG. 2 is a block diagram illustrating each block of an image forming process according to the first embodiment;

FIG. 3 is a configuration diagram of another example 1 of the first embodiment.

FIG. 4 is a configuration diagram of another example 2 of the first embodiment.

FIG. 5 is a configuration diagram of a power supply device according to a second embodiment of the present invention;

FIG. 6 is a configuration diagram of another example 1 of the second embodiment.

FIG. 7 is a configuration diagram of another example 2 of the second embodiment.

[Explanation of symbols]

 Reference Signs List 1 CPU 1-1 CPU core 1-2 ROM 1-3 RAM 1-4 Input port 1-5 Output port 1-6 A / D conversion 2 Time constant switching means 3 Sequence control circuit 7 Transfer output control circuit 710 Constant voltage Detecting means 711 Constant current detecting means 714 Control circuit 715 Pulse-DC conversion circuit

Claims (2)

(57) [Claims] A control unit for controlling the sequence of a part of the electrophotographic image forming apparatus or the entire apparatus;
An image forming apparatus for controlling the power supply device for forming an image forming process, wherein the control means performs the sequence control and a voltage detecting means for detecting an output voltage to a load; and the voltage detecting means and the control. Filter means provided between the first and second means and capable of switching a time constant; current detection means for detecting an output current to the load; and constant current control such that the current detected by the current detection means is constant. And a constant current control unit that monitors the output of the voltage detection unit via the filter unit during the constant current control by the constant current control unit so as to recognize the impedance of the load. , After recognizing the impedance of the load,
In order to control the load at a constant voltage according to the recognized impedance, the power supply device is controlled based on an output of the voltage detection unit via the filter unit, and a time constant of the filter unit is set to the constant current control unit. An image forming apparatus which switches between a constant current control and a constant voltage control. 2. A control means for controlling the power supply device, a voltage detection means for detecting an output voltage to a load, and a time constant switchable between the voltage detection means and the control means. Filter means, current detection means for detecting an output current to the load, and constant current control means for performing constant current control so that the current detected by the current detection means is constant. In order to recognize the impedance of the load, while monitoring the output of the voltage detection means via the filter means at the time of constant current control by the constant current control means, and after recognizing the impedance of the load,
In order to control the load at a constant voltage according to the recognized impedance, the power supply device is controlled based on an output of the voltage detection unit via the filter unit, and a time constant of the filter unit is set to the constant current control unit. A power supply device that switches between constant current control and constant voltage control.