JP2020148908A - Image forming device - Google Patents

Abstract

To suppress occurrence of overshoot of a charged voltage when a DC voltage generation circuit is started while detecting a DC current with a relatively simple configuration.SOLUTION: An image forming device includes: a photoreceptor; an electrification roller for electrifying the photoreceptor; and a high-voltage power supply for generating a high voltage obtained by superposing a DC voltage and an AC voltage as voltage applied to the electrification roller. The high-voltage power supply includes: an AC voltage generation part for generating an AC voltage; a DC voltage generation part for generating a DC voltage; a coupling capacitor provided between the AC voltage generation part and the DC voltage generation part; a control part for performing constant voltage control of a DC voltage generated by the DC voltage generation part; a current detection part for detecting an output current of the DC voltage generation part; and a current detection control part for grounding the current detection part when the DC voltage generation part is started.SELECTED DRAWING: Figure 3

Description

The present invention relates to an image forming apparatus.

The following Patent Document 1 describes a high voltage in an image forming apparatus capable of applying a high voltage in which a DC voltage and an AC voltage are superimposed to a charging roller for the purpose of charging the photoconductor to a desired potential. A configuration is disclosed in which a DC current value detection circuit for detecting a DC current flowing when a voltage is applied to a charging roller is provided.

However, in the technique of Patent Document 1, since it is necessary to obtain the DC current from the high voltage in which the DC voltage and the AC voltage are superimposed, the DC current value detection circuit needs to have a relatively complicated configuration. ..

Therefore, for example, it is considered that the DC current can be detected with a relatively simple configuration by providing the DC current detection unit in the DC voltage generation circuit that generates the DC voltage. However, in this case, when the DC voltage generating circuit is started, the inrush current generated when charging the coupling capacitor provided in the AC voltage generating circuit causes an overshoot of the charging voltage applied to the charging roller, resulting in an abnormality. Images may occur.

In order to solve the above-mentioned problems of the prior art, the present invention makes it possible to detect a direct current with a relatively simple configuration and suppresses the occurrence of overshoot of the charging voltage at the time of starting the direct current generation circuit. The purpose is to be able to do it.

In order to solve the above-mentioned problems, the image forming apparatus of the present invention has a high voltage in which a direct current voltage and an AC voltage are superimposed as a voltage applied to the photoconductor, a charging roller for charging the photoconductor, and the charging roller. A high-voltage power supply that generates a voltage is provided, and the high-voltage power supply is provided between an AC voltage generating unit that generates an AC voltage, a DC voltage generating unit that generates a DC voltage, and an AC voltage generating unit and a DC voltage generating unit. The coupling capacitor, the control unit that constantly controls the DC voltage generated by the DC voltage generator, the current detector that detects the output current of the DC voltage generator, and the current when the DC voltage generator is started. It is provided with a current detection control unit that grounds the detection unit.

According to the present invention, it is possible to suppress the occurrence of overshoot of the charging voltage at the start of the DC voltage generating circuit while enabling the detection of the DC current with a relatively simple configuration.

The figure which shows the structure of the image forming apparatus which concerns on 1st Embodiment of this invention. The figure which shows an example of the output waveform of the charge voltage and the development voltage in the conventional image forming apparatus. The figure which shows the circuit structure of the high voltage power source which concerns on 1st Embodiment of this invention. The figure which shows the functional structure of the control part which concerns on 1st Embodiment of this invention. A flowchart showing a procedure of constant voltage control processing by the control unit according to the first embodiment of the present invention. A flowchart showing a procedure of invalidation control processing by the control unit according to the first embodiment of the present invention. The figure which shows various timings in the high voltage power source which concerns on 1st Embodiment of this invention. The figure which shows the functional structure of the control part which concerns on 2nd Embodiment of this invention. A flowchart showing a procedure of invalidation control processing by the control unit according to the second embodiment of the present invention. The figure which shows the circuit structure of the high voltage power source which concerns on 3rd Embodiment of this invention. The figure which shows the functional structure of the control part which concerns on 3rd Embodiment of this invention.

[First Embodiment]
Hereinafter, the first embodiment of the present invention will be described with reference to the drawings.

(Structure of image forming apparatus 10)
FIG. 1 is a diagram showing a configuration of an image forming apparatus 10 according to a first embodiment of the present invention.

As shown in FIG. 1, the image forming apparatus 10 includes a high-voltage power supply 11, a photoconductor 12, a charging roller 13, an exposure unit 14, a developing device 15, a high-voltage power supply 16, a primary transfer roller 17, a high-voltage power supply 18, and an intermediate belt 19. , And a static eliminator 20.

The high-voltage power supply 11 generates a voltage and applies the voltage to the charging roller 13. The charging roller 13 uniformly charges the photoconductor 12. The exposure unit 14 forms an electrostatic latent image on the surface of the photoconductor 12 by exposing the photoconductor 12 in a uniformly charged state according to the print data.

The developing device 15 forms a toner image on the surface of the photoconductor 12 by adhering toner to an electrostatic latent image formed on the surface of the photoconductor 12 using a voltage applied from the high-voltage power supply 16.

The toner image formed on the surface of the photoconductor 12 is transferred onto the intermediate belt 19 between the photoconductor 12 and the primary transfer roller 17 to which a voltage is applied by the high-voltage power supply 18. As a result, a toner image is formed on the intermediate belt 19.

The toner image formed on the intermediate belt 19 is transferred to the recording paper by the secondary transfer unit (not shown). After that, the chart paper is fixed with a toner image by applying heat and pressure by a fixing device (not shown).

The static eliminator 20 removes the electric charge on the surface of the photoconductor 12 (the charge having the original charging polarity). When the image forming apparatus 10 can perform color printing, it is shown in FIG. 1 for each of a plurality of printing colors (for example, four printing colors (Y, C, M, K)). It has a configuration. As a result, the image forming apparatus 10 can form toner images of each of a plurality of printing colors on the intermediate belt 19.

(Output waveforms of charging voltage and developing voltage in a conventional image forming apparatus)
FIG. 2 is a diagram showing an example of output waveforms of a charging voltage and a developing voltage in a conventional image forming apparatus.

In the image forming apparatus, the surface potential of the photoconductor is the difference between the charging voltage and the developing voltage. Therefore, as shown in FIG. 2A, it is preferable that the image forming apparatus is started with a constant voltage difference between the charging voltage and the developing voltage.

However, in the conventional image forming apparatus, as shown in FIG. 2B, the charging voltage is affected by the inrush current generated when the coupling capacitor included in the AC voltage generating circuit is charged when the DC voltage generating circuit is started. In this case, the difference between the charging voltage and the developing voltage may not be constant at the overshoot portion, and the surface potential of the photoconductor may not be uniformly charged.

(Circuit configuration of high-voltage power supply 11)
FIG. 3 is a diagram showing a circuit configuration of the high voltage power supply 11 according to the first embodiment of the present invention. As shown in FIG. 3, the high-voltage power supply 11 includes an AC generation circuit 60 and a DC generation circuit 30.

The AC generation circuit 60 includes a drive circuit 61, a transformer 62, a control unit 63, and a coupling capacitor C1.

The drive circuit 61 controls the operation of the transformer 62. The transformer 62 generates an AC voltage by operating under the control of the drive circuit 61. One end of the secondary coil of the transformer 62 is connected to the load 50 via the resistor R1. The other end of the secondary coil of the transformer 62 is connected to the DC generation circuit 30 (one end of the secondary coil of the transformer 32). The AC voltage generated by the transformer 62 is superimposed on the DC voltage generated by the DC generation circuit 30 and applied to the load 50.

The control unit 63 supplies the drive circuit control signal to the drive circuit 61 so that the AC voltage generated by the transformer 62 becomes the target voltage indicated by the AC control signal input from the host controller (not shown). , Controls the AC voltage generated by the transformer 62.

The coupling capacitor C1 is provided between the secondary coil of the transformer 62 and the DC generation circuit 30. One end of the coupling capacitor C1 is connected to the other end of the secondary coil of the transformer 62. The other end of the coupling capacitor C1 is grounded. The coupling capacitor C1 prevents the alternating current flowing between the AC generation circuit 60 and the load 50 from flowing into the DC generation circuit 30.

The DC generation circuit 30 includes a drive circuit 31, a transformer 32, a current detection unit 33, an FET 34, and a control unit 40.

The drive circuit 31 controls the operation of the transformer 32. The transformer 32 operates under the control of the drive circuit 31 to generate a DC voltage higher than the input voltage Vin from the input voltage Vin. One end of the secondary coil of the transformer 32 is connected to the AC generation circuit 60 (the other end of the secondary coil of the transformer 62) via the resistor R2. The DC voltage generated by the transformer 32 is superimposed on the AC voltage generated by the AC generation circuit 60 and applied to the load 50.

The control unit 40 controls the DC voltage generated by the transformer 32 by supplying the drive circuit control signal to the drive circuit 31. For example, when the output voltage of the DC generation circuit 30 detected at point a of the DC generation circuit 30 is smaller than the target voltage indicated by the DC control signal input from the upper controller, the control unit 40 of the drive circuit 31 Increase the control value. On the contrary, in the control unit 40, when the output voltage of the DC generation circuit 30 detected at the point a of the DC generation circuit 30 is larger than the target voltage indicated by the DC control signal input from the upper controller (not shown). , The control value of the drive circuit 31 is lowered. As a result, the control unit 40 performs constant voltage control so that the output voltage of the DC generation circuit 30 becomes the target voltage indicated by the DC control signal.

The current detection unit 33 detects the output current of the DC generation circuit 30 at point b of the DC generation circuit 30, and outputs a current detection signal indicating the output current to a higher-level controller.

The FET 34 is connected in parallel with the current detection unit 33. The FET 34 switches between an on state and an off state according to the current detection control signal supplied from the control unit 40. When the FET 34 is on, the current detection unit 33 is grounded by making one end side and the other end side of the current detection unit 33 conductive. As a result, the current detection operation by the current detection unit 33 is invalidated. In the OFF state of the FET 34, one end side and the other end side of the current detection unit 33 are brought into a non-conducting state. As a result, the current detection operation by the current detection unit 33 is enabled.

(Functional configuration of control unit 40)
FIG. 4 is a diagram showing a functional configuration of the control unit 40 according to the first embodiment of the present invention. As shown in FIG. 4, the control unit 40 includes a control signal receiving unit 41, a voltage detection signal receiving unit 42, an output calculation unit 43, a drive circuit control unit 44, a determination unit 45, and a current detection control unit 46.

The control signal receiving unit 41 receives a DC control signal indicating a target voltage of the output voltage of the DC generating circuit 30 from a higher-level controller.

The voltage detection signal receiving unit 42 receives the voltage detection signal corresponding to the output voltage of the DC generating circuit 30 detected at the point a (see FIG. 3) of the DC generating circuit 30.

The output calculation unit 43 has a DC generation circuit 30 based on the target voltage indicated by the DC control signal received by the control signal receiving unit 41 and the output voltage indicated by the voltage detection signal received by the voltage detection signal receiving unit 42. The control value of the drive circuit 31 is calculated so that the output voltage of is the target voltage indicated by the DC control signal.

For example, when the output voltage of the DC generation circuit 30 is smaller than the target voltage, the output calculation unit 43 increases the control value of the drive circuit 31. On the contrary, when the output voltage of the DC generation circuit 30 is larger than the target voltage, the output calculation unit 43 lowers the control value of the drive circuit 31. As a result, the output calculation unit 43 performs constant voltage control so that the output voltage of the DC generation circuit 30 becomes the target voltage indicated by the DC control signal.

The drive circuit control unit 44 outputs a drive circuit control signal indicating a control value calculated by the output calculation unit 43 to the drive circuit 31.

The determination unit 45 is determined by the current detection unit 33 based on the target voltage indicated by the DC control signal received by the control signal reception unit 41 and the output voltage indicated by the voltage detection signal received by the voltage detection signal reception unit 42. Determine whether to disable the detection operation. Specifically, in the determination unit 45, after the DC generation circuit 30 is started, the output voltage of the DC generation circuit 30 is a voltage value (“voltage based on the target voltage”) at a predetermined ratio (for example, 80%) of the target voltage. It is determined that "the detection operation by the current detection unit 33 is invalidated" until an example of "threshold") is reached. Then, the determination unit 45 determines that "the detection operation by the current detection unit 33 is not invalidated" after the output voltage of the DC generation circuit 30 reaches a voltage value of a predetermined ratio of the target voltage. The voltage threshold is set to a voltage value (for example, at least a voltage value until the inrush current is eliminated) that is sufficiently obtained in advance by simulation, an actual machine test, or the like to suppress overshoot.

The current detection control unit 46 controls invalidation of the current detection operation by the current detection unit 33 according to the determination result by the determination unit 45.

Specifically, the current detection control unit 46 outputs a current detection control signal for switching the FET 34 on when the determination unit 45 determines that the current detection operation by the current detection unit 33 is invalidated. This switches the FET 34 on. As a result, the detection point b of the current detection unit 33 is grounded via the FET 34, and thus the current detection operation by the current detection unit 33 is invalidated.

On the other hand, when the determination unit 45 determines that the current detection operation by the current detection unit 33 is not invalidated, the current detection control unit 46 outputs a current detection control signal for switching the FET 34 off. The FET 34 is switched off. As a result, the grounding of the detection point b of the current detection unit 33 via the FET 34 is released, and thus the invalidation of the current detection operation by the current detection unit 33 is released.

(Procedure of constant voltage control processing by control unit 40)
FIG. 5 is a flowchart showing a procedure of constant voltage control processing by the control unit 40 according to the first embodiment of the present invention.

First, the control signal receiving unit 41 receives a DC control signal indicating the target voltage of the output voltage of the DC generating circuit 30 from the host controller (step S501). Next, the voltage detection signal receiving unit 42 receives the voltage detection signal indicating the output voltage of the DC generating circuit 30 detected at point a (see FIG. 3) of the DC generating circuit 30 (step S502).

Next, the output calculation unit 43 determines whether or not the output voltage of the DC generation circuit 30 is lower than the target voltage based on the DC control signal received in step S501 and the voltage detection signal received in step S502. Determine (step S503).

When it is determined in step S503 that "the output voltage of the DC generation circuit 30 is lower than the target voltage" (step S503: YES), the output calculation unit 43 controls the drive circuit control signal output to the drive circuit 31. Increase the value (step S504). Then, the drive circuit control unit 44 outputs the drive circuit control signal whose control value has been increased in step S504 to the drive circuit 31 (step S505). After that, the control unit 40 returns the process to step S502.

On the other hand, when it is determined in step S503 that "the output voltage of the DC generation circuit 30 is not lower than the target voltage" (step S503: NO), the output calculation unit 43 determines that the output voltage of the DC generation circuit 30 is the target voltage. It is determined whether or not it is higher than (step S506).

When it is determined in step S506 that "the output voltage of the DC generation circuit 30 is higher than the target voltage" (step S506: YES), the output calculation unit 43 controls the drive circuit control signal output to the drive circuit 31. Decrease the value (step S507). Then, the drive circuit control unit 44 outputs the drive circuit control signal whose control value has been lowered in step S507 to the drive circuit 31 (step S508). After that, the control unit 40 returns the process to step S502.

When it is determined in step S506 that "the output voltage of the DC generation circuit 30 is not higher than the target voltage" (step S506: NO), the output calculation unit 43 outputs the drive circuit control signal to the drive circuit 31. The control value is maintained (step S509). Then, the drive circuit control unit 44 outputs the drive circuit control signal whose control value is maintained in step S507 to the drive circuit 31 (step S510). After that, the control unit 40 ends a series of processes shown in FIG.

(Procedure of invalidation control processing by control unit 40)
FIG. 6 is a flowchart showing a procedure of invalidation control processing by the control unit 40 according to the first embodiment of the present invention. When the DC generation circuit 30 is activated, the control unit 40 executes the invalidation control process shown in FIG. 6 in parallel with the constant voltage control process shown in FIG.

First, the determination unit 45 determines whether or not the output voltage of the DC generation circuit 30 has reached 80% of the target voltage (step S601).

When it is determined in step S601 that "the output voltage of the DC generation circuit 30 has not reached 80% of the target voltage" (step S601: NO), the current detection control unit 46 switches the FET 34 on (step S601: NO). That is, the FET 34 is switched on by outputting the current detection control signal (to invalidate the current detection) (step S602). As a result, the detection point b of the current detection unit 33 is grounded via the FET 34, and thus the current detection operation by the current detection unit 33 is invalidated. After that, the control unit 40 returns the process to step S601.

On the other hand, in step S601, when it is determined that "the output voltage of the DC generation circuit 30 has reached 80% of the target voltage" (step S601: YES), the current detection control unit 46 switches the FET 34 off. The FET 34 is switched off by outputting a current detection control signal (that is, to enable current detection) (step S603). As a result, the grounding of the detection point b of the current detection unit 33 is released, and thus the current detection operation by the current detection unit 33 is enabled.

(Various timings in the high-voltage power supply 11)
FIG. 7 is a diagram showing various timings in the high-voltage power supply 11 according to the first embodiment of the present invention. FIG. 7A shows various timings in the conventional high-voltage power supply (the high-voltage power supply 11 according to the first embodiment in which the configuration for disabling the current detection unit 33 is removed) used as a comparative example. FIG. 7B shows various timings in the high-voltage power supply 11 according to the first embodiment.

As shown in FIG. 7A, in the conventional high-voltage power supply, when the coupling capacitor C1 included in the AC generation circuit 60 is charged at the time of starting the DC generation circuit 30 (timing t1 when the DC control signal is input). Due to the influence of the inrush current generated in, the voltage detected at each of the points a and b of the DC generation circuit 30 causes a jump (see 701 and 702 in the figure). As a result, as shown in FIG. 7A, an overshoot occurs in the output voltage applied to the charging roller 13 (see 703 in the figure), and as shown in FIG. 2B, the overshoot portion The difference between the charging voltage and the developing voltage may not be constant, and the surface potential of the photoconductor may not be uniformly charged.

On the other hand, as shown in FIG. 7B, in the high-voltage power supply 11 according to the first embodiment, the cup included in the AC generation circuit 60 is provided at the time of starting the DC generation circuit 30 (timing t1 when the DC control signal is input). It is the same that the inrush current generated when charging the ring capacitor C1 is generated. However, in the high-voltage power supply 11 according to the first embodiment, the Hi-level current detection control signal is transmitted from the current detection control unit 46 from the start of the DC generation circuit 30 until the inrush current is eliminated (timing t1 to t2). By outputting to the FET 34, the current detection unit 33 is in a grounded state. Therefore, as shown in FIG. 7B, the voltage detected at each of the points a and b of the DC generation circuit 30 does not jump up. Therefore, in the high-voltage power supply 11 according to the first embodiment, as shown in FIG. 7B, overshoot does not occur in the output voltage applied to the charging roller 13.

[Second Embodiment]
Next, a second embodiment of the present invention will be described with reference to the drawings. Hereinafter, the changes from the high-voltage power supply 11 according to the first embodiment will be mainly described with respect to the high-voltage power supply 11 according to the second embodiment.

(Functional configuration of control unit 40A)
FIG. 8 is a diagram showing a functional configuration of the control unit 40A according to the second embodiment of the present invention. The high-voltage power supply 11 according to the second embodiment includes the control unit 40A shown in FIG. 8 instead of the control unit 40 shown in FIG. As shown in FIG. 8, the control unit 40A differs from the control unit 40 shown in FIG. 4 in that it includes a determination unit 45A instead of the determination unit 45 and further includes a storage unit 47.

The storage unit 47 stores a time threshold value that determines a period during which the detection operation by the current detection unit 33 is invalidated. The time threshold is set to at least a sufficient time (for example, at least the time until the inrush current disappears) for suppressing an overshoot, which has been obtained in advance by simulation, actual machine test, or the like.

The determination unit 45A determines that "the detection operation by the current detection unit 33 is invalidated" until the elapsed time from the activation of the DC generation circuit 30 reaches the time threshold value stored in the storage unit 47. Then, the determination unit 45 determines that "the detection operation by the current detection unit 33 is not invalidated" after the output voltage of the DC generation circuit 30 reaches the time threshold value stored in the storage unit 47.

(Procedure of invalidation control processing by control unit 40A)
FIG. 9 is a flowchart showing a procedure of invalidation control processing by the control unit 40A according to the second embodiment of the present invention. When the DC generation circuit 30 is activated, the control unit 40A executes the invalidation control process shown in FIG. 9 in parallel with the constant voltage control process shown in FIG.

First, the determination unit 45A determines whether or not the elapsed time since the DC generation circuit 30 is activated has reached the time threshold value stored in the storage unit 47 (step S901).

In step S901, when it is determined that "the elapsed time since the DC generation circuit 30 is activated has not reached the time threshold value stored in the storage unit 47" (step S901: NO), the current detection control unit The 46 switches the FET 34 on by outputting a current detection control signal for switching the FET 34 on (that is, disabling the current detection) (step S902). As a result, the detection point b of the current detection unit 33 is grounded via the FET 34, and thus the current detection operation by the current detection unit 33 is invalidated. After that, the control unit 40A returns the process to step S901.

On the other hand, in step S901, when it is determined that "the elapsed time since the DC generation circuit 30 was started has reached the time threshold value stored in the storage unit 47" (step S901: YES), the current detection control The unit 46 switches the FET 34 off by outputting a current detection control signal for switching the FET 34 off (that is, enabling current detection) (step S903). As a result, the grounding of the detection point b of the current detection unit 33 is released, and thus the current detection operation by the current detection unit 33 is enabled.

According to the high-voltage power supply 11 according to the second embodiment, since the period for disabling the detection operation by the current detection unit 33 is predetermined, the detection operation by the current detection unit 33 is invalidated with a relatively simple configuration. The period can be controlled.

[Third Embodiment]
Next, a third embodiment of the present invention will be described with reference to the drawings. Hereinafter, the changes from the high-voltage power supply 11 according to the second embodiment will be mainly described with respect to the high-voltage power supply 11 according to the third embodiment.

(Circuit configuration of high-voltage power supply 11)
FIG. 10 is a diagram showing a circuit configuration of the high voltage power supply 11 according to the third embodiment of the present invention. As shown in FIG. 10, the high-voltage power supply 11 of the third embodiment is provided with an ambient temperature detection unit 35 in the DC generation circuit 30, and is provided with a control unit 40B instead of the control unit 40A. , Different from the high voltage power supply 11 of the second embodiment.

The ambient temperature detection unit 35 detects the ambient temperature of the drive circuit 31 and outputs a temperature detection signal indicating the temperature. Various temperature sensors can be used as the ambient temperature detection unit 35.

(Functional configuration of control unit 40B)
FIG. 11 is a diagram showing a functional configuration of the control unit 40B according to the third embodiment of the present invention. As shown in FIG. 11, the control unit 40B further includes a temperature detection signal receiving unit 48, a storage unit 47A instead of the storage unit 47, and a determination unit 45B instead of the determination unit 45A. Therefore, it is different from the control unit 40A shown in FIG.

The temperature detection signal receiving unit 48 receives the temperature detection signal output from the ambient temperature detection unit 35.

The storage unit 47A stores a time threshold value for determining a period for invalidating the detection operation by the current detection unit 33 for each ambient temperature of the drive circuit 31. The time threshold is set to at least a sufficient time (for example, at least the time until the inrush current disappears) for suppressing an overshoot, which has been obtained in advance by simulation, actual machine test, or the like.

The determination unit 45B "detects by the current detection unit 33" until the elapsed time from the activation of the DC generation circuit 30 reaches the time threshold value corresponding to the ambient temperature of the drive circuit 31 stored in the storage unit 47A. The operation is invalidated. " Then, after the output voltage of the DC generation circuit 30 reaches the time threshold value corresponding to the ambient temperature of the drive circuit 31 stored in the storage unit 47A, the determination unit 45 performs the “detection operation by the current detection unit 33”. It is judged that it will not be invalidated.

According to the high-voltage power supply 11 according to the third embodiment, even if the start-up time varies due to the temperature characteristics of the transistor of the drive circuit 31, the current detection unit 33 detects it according to the ambient temperature of the drive circuit 31. The period during which the operation is invalidated can be appropriately controlled.

As described above, the image forming apparatus 10 according to each of the above embodiments includes a photosensitive member 12, a charging roller 13 for charging the photosensitive member 12, and a DC voltage and an AC voltage as voltages applied to the charging roller 13. The high-voltage power supply 11 includes an AC generation circuit 60 that generates an AC voltage, a DC generation circuit 30 that generates a DC voltage, an AC generation circuit 60, and a DC generation. A coupling capacitor C1 provided between the circuit 30, control units 40 and 40A for constant voltage control of the DC voltage generated by the DC generation circuit 30, and a current detection unit for detecting the output current of the DC generation circuit 30. It includes 33 and a current detection control unit 46 that grounds the current detection unit 33 when the DC generation circuit 30 is started.

As a result, the image forming apparatus 10 according to each of the above embodiments can detect the direct current with a relatively simple configuration by providing the current detection unit 33 in the DC generation circuit 30. Further, the image forming apparatus 10 according to each of the above embodiments measures the inrush current generated when the coupling capacitor C1 included in the AC generating circuit 60 is charged by grounding the current detecting unit 33 when the DC generating circuit 30 is started. Due to the influence, it is possible to suppress the occurrence of overshoot of the charging voltage applied to the charging roller 13. Therefore, according to the image forming apparatus 10 according to each of the above embodiments, the overshoot of the charging voltage at the time of starting the DC voltage generating circuit can be generated while enabling the detection of the DC current with a relatively simple configuration. It can be suppressed.

Although the preferred embodiments and examples of the present invention have been described in detail above, the present invention is not limited to these embodiments and examples, and is within the scope of the gist of the present invention described in the claims. In, various modifications or changes are possible.

10 Image forming device 11 High-voltage power supply 12 Photoreceptor 13 Charging roller 14 Exposure unit 15 Developer 16 High-voltage power supply 17 Primary transfer roller 18 High-voltage power supply 19 Intermediate belt 20 Static eliminator 30 DC generator circuit (DC voltage generator)
31 Drive circuit 32 Transformer 33 Current detector 34 FET
40, 40A, 40B Control unit 41 Control signal reception unit 42 Voltage detection signal reception unit 43 Output calculation unit 44 Drive circuit control unit 45, 45A Judgment unit 46 Current detection control unit 47, 47A Storage unit 48 Temperature detection signal reception unit 50 Load 60 AC generation circuit (AC voltage generator)
61 Drive circuit 62 Transformer 63 Control unit C1 Coupling capacitor

Patent No. 5546269

Claims (4)

Photoreceptor and
A charging roller that charges the photoconductor and
As the voltage applied to the charging roller, it is provided with a high-voltage power supply that generates a high voltage in which a DC voltage and an AC voltage are superimposed.
The high voltage power supply
The AC voltage generating unit that generates the AC voltage and
The DC voltage generator that generates the DC voltage,
A coupling capacitor provided between the AC voltage generating section and the DC voltage generating section,
A control unit that constantly controls the DC voltage generated by the DC voltage generator,
A current detection unit that detects the output current of the DC voltage generation unit, and
An image forming apparatus including a current detection control unit that grounds the current detection unit when the DC voltage generation unit is started. The current detection control unit
A claim characterized in that the current detection unit is grounded from the start of the DC voltage generation unit until the DC voltage output from the DC voltage generation unit reaches a voltage threshold based on a target voltage. Item 1. The image forming apparatus according to Item 1. The current detection control unit
The image forming apparatus according to claim 1, wherein the current detecting unit is grounded until the elapsed time from the activation of the DC voltage generating unit reaches a predetermined time threshold value. The DC voltage generator
Further, an ambient temperature detection unit for detecting the ambient temperature of the drive circuit for driving the transformer for generating the DC voltage is provided.
The current detection control unit
The image according to claim 1, wherein the current detection unit is grounded until the elapsed time from the activation of the DC voltage generation unit reaches a predetermined time threshold value corresponding to the ambient temperature. Forming device.

Images