IMAGE FORMING APPARATUS

• US 20160187802A1
• Filed: 12/09/2015
• Published: 06/30/2016
• Est. Priority Date: 12/25/2014
• Status: Active Grant

• Current Assignee: Canon Ayutthaya Limited (Canon Inc.)
• Original Assignee: Canon Ayutthaya Limited (Canon Inc.)
• Inventors: Kagawa, Yosuke
• Granted Patent: US 9,880,485 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G03G 15/0189 primary transfer to an intermediate transfer belt G03G15/0184 takes precedence
• CPC Class Codes: G03G 15/0266 Arrangements for controlling the amount of charge
• CPC Class Codes: G03G 15/80 Details relating to power supplies, circuits boards, electrical connections

Abstract

An image forming apparatus comprises a plurality of image forming units that respectively form an image, and a plurality of voltage generation circuits that respectively generate voltages for driving the plurality of image forming units. Each of the plurality of voltage generation circuits comprises a voltage generation circuit having a transformer, and generates a voltage by a switching operation that is driven by changing an input voltage of primary side of the transformer, an oscillation circuit that generates a clock signal of a frequency that becomes a reference frequency of the switching operation and a setting unit that sets the frequency of the clock signal that the oscillation circuit generates. The setting units of the plurality of voltage generation circuits set the frequencies of the respective clock signals.

Claims

1. An image forming apparatus comprising:

a plurality of image forming units configured to respectively form an image;

a plurality of voltage generation units configured to respectively generate voltages for driving the plurality of image forming units,

wherein each of the plurality of voltage generation units comprises;

a voltage generator having a transformer, configured to generate a voltage by a switching operation that is driven by changing an input voltage of primary side of the transformer;

a clock generation unit configured to generate a clock signal of a frequency that becomes a reference frequency of the switching operation; and

a setting unit configured to set the frequency of the clock signal that the clock generation unit generates,

wherein the setting units of the plurality of voltage generation units set the frequencies of the respective clock signals so that the frequencies of the clock signals that the plurality the clock generation units generate are different from each other.

10. The image forming apparatus according to claim 1, wherein the setting unit includes a resistor connected to the clock generation unit, and resistance values of the resistor differ between the plurality of voltage generation units.

11. The image forming apparatus according to claim 1, wherein the image forming unit forms an image by an electrophotographic method, and

the voltage generator generates a charging voltage of the image forming unit.

12. The image forming apparatus according to claim 1, wherein the image forming unit forms an image by an electrophotographic method, and

the voltage generator generates a developing voltage of the image forming unit.

13. The image forming apparatus according to claim 1, wherein the plurality of image forming units form images of yellow, magenta, cyan and black, respectively.

2. An image forming apparatus comprising:

a plurality of image forming units configured to respectively form an image;

a plurality of voltage generation units configured to respectively generate voltages for driving the plurality of image forming units,

wherein each of the plurality of voltage generation units comprises;

a voltage generator having a transformer, configured to generate a voltage by a switching operation that is driven by changing an input voltage of primary side of the transformer;

a clock generation unit configured to generate a clock signal of a frequency that becomes a reference frequency of the switching operation;

a setting unit configured to set the frequency of the clock signal that the clock generation unit generates; and

a control unit configured to control so that the frequencies of the clock signals are set by the setting unit to values that are different from each other when the image forming apparatus is in image forming and in a standby state in which the image forming apparatus is waiting for start of image forming.

3. The image forming apparatus according to claim 2, wherein the setting unit sets the frequency of the clock signal that the clock generation unit generates by varying a value of a resistance connected to the clock generation unit.

4. The image forming apparatus according to claim 3, wherein the setting unit has a first resistor connected to the clock generation unit, and a second resistor connected via a switching element to the clock generation unit, and

the control unit sets the frequency of the clock signal that the clock generation units generate by switching a connection by the switching element.

5. The image forming apparatus according to claim 2, wherein the control unit controls so that in the standby state, the frequency of the clock signal that the clock generation unit generates is set to a frequency that is lower than in the image forming.

6. The image forming apparatus according to claim 2, wherein the voltage generator comprises:

a switching circuit connected to a primary side of the transformer; and

a generation unit configured to output a pulse width modulation signal for driving the switching circuit in synchronization with the clock signal.

7. The image forming apparatus according to claim 6, wherein the generation unit comprises:

a first comparator configured to compare a sinusoidal wave signal of a predetermined frequency and a triangle wave generated in synchronization to the clock signal and to output a first pulse width modulation signal; and

a second comparator configured to compare a signal in which the sinusoidal wave signal is inverted and the clock signal, and to output a second pulse width modulation signal,

wherein the switching circuit inputs the first and second pulse width modulation signals, and drives terminals on the primary side of the AC transformer.

8. The image forming apparatus according to claim 7, further comprising a sinusoidal wave generation unit configured to generate the sinusoidal wave signal of the predetermined frequency.

9. The image forming apparatus according to claim 8, the each of the plurality of voltage generation units further comprising a detection unit configured to detect a voltage that the voltage generator generates,

wherein the sinusoidal wave generation unit adjusts an amplitude of the sinusoidal wave signal in accordance with a voltage value detected by the detection unit.

14. An image forming apparatus comprising:

a plurality of image forming units configured to respectively form an image;

a plurality of voltage generation units configured to respectively generate voltages for driving the plurality of image forming units,

wherein each of the plurality of voltage generation units comprises;

a sinusoidal wave generation unit configured to generate a sinusoidal wave of an amplitude set by a setting signal;

a class-D amplifier configured to, based on the sinusoidal wave generated by the sinusoidal wave generation unit, output a switching output of a set frequency; and

a transformer configured to convert the switching output to a high voltage,

wherein the respective class-D amplifiers of the plurality of voltage generation units are set so that switching outputs of frequencies that respectively differ from each other are obtained.

15. The image forming apparatus according to claim 14, the each of the plurality of voltage generation units further comprising a voltage detection unit configured to detect an output voltage of the transformer and feedback the output voltage to the sinusoidal wave generation unit,

wherein the sinusoidal wave generation unit further changes the amplitude of the generated sinusoidal wave in accordance with the feedback by the voltage detection unit.