High-voltage transformer, high-voltage power supply, and image forming apparatus

Abstract

To reduce costs, the configuration of high-voltage transformers will be made as standardized as possible. [Solution] The high-voltage transformer includes a transformer case 306 in which the primary winding (L21) and secondary winding (L22) constituting the positive bias high-voltage transformer (T201) are sealed. The transformer case 306 is provided with terminal a connected to one end of the primary winding (L21) inside the transformer case 306 and provided on a predetermined lower surface of the transformer case 306, terminal b connected to the other end of the primary winding (L21) inside the transformer case 306 and provided on the lower surface, terminal i connected to one end of the secondary winding (L22) inside the transformer case 306 and provided on the upper surface of the transformer case 306, and terminal h connected to terminal i inside the transformer case 306 and provided on the upper surface of the transformer case 306. A bypass resistor R201 is connected to terminal h.

Description

Technical Field

[0001] The present invention relates to a high-voltage transformer, a high-voltage power supply device equipped with the high-voltage transformer, and an image forming apparatus equipped with the high-voltage power supply device.

Background Art

[0002] An electrophotographic image forming apparatus generally forms an image on a recording paper through processes of charging, exposure, development, transfer (primary transfer and secondary transfer), and fixing. Since the image forming apparatus uses a high voltage in processes such as charging, development, and transfer, it is equipped with a high-voltage power supply device. For example, the high-voltage power supply device used in the secondary transfer process applies a high voltage of the opposite polarity to the toner to the secondary transfer roller at the timing when the recording paper passes between the intermediate transfer member and the secondary transfer roller for secondary transfer. Thereby, the toner image on the intermediate transfer member is transferred onto the recording paper. The high-voltage power supply device performs a cleaning operation of returning the toner attached to the secondary transfer roller to the intermediate transfer member by applying a high voltage of the same polarity as the toner to the secondary transfer roller at a timing when the recording paper is not between the intermediate transfer member and the secondary transfer roller. For this purpose, the high-voltage power supply device includes two types of high-voltage transformers: a positive-bias high-voltage transformer for generating a high voltage of the opposite polarity to the toner and a negative-bias high-voltage transformer for generating a high voltage of the same polarity as the toner. Patent Document 1 discloses a high-voltage transformer aiming at cost reduction and space saving.

[0003] The positive-bias high-voltage transformer may be provided with at least one of a voltage detection resistor for detecting the output voltage and a bypass resistor that serves as a current path when outputting a high voltage of the negative bias. The negative-bias high-voltage transformer may be provided with a bypass resistor that serves as a current path when outputting a high voltage of the positive bias.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

[0005] Conventional high-voltage transformers used in high-voltage power supply devices have a configuration in which the voltage sensing resistor and bypass resistor are built into the transformer case. Depending on the specifications of the high-voltage transformer, the voltage sensing resistor and bypass resistor may not be necessary, or if they are necessary, their resistance values ​​may differ.

[0006] For example, a manufacturer may produce two types of high-voltage transformers with different resistance values ​​for the voltage sensing resistor and bypass resistor, but the same configuration for other components (windings, rectifier diodes, capacitors). The production quantities of these two types of transformers may differ due to demand. In this case, the component costs for the transformer with fewer production quantities will increase compared to the one with more production quantities. Furthermore, increasing the variety of transformers will also increase management costs. Therefore, it is necessary to standardize the configuration of high-voltage transformers as much as possible to control costs. [Means for solving the problem]

[0007] The high-voltage transformer of the present invention comprises a case in which the primary winding and secondary winding constituting the transformer are sealed, and the case is provided with a first terminal connected internally to one end of the primary winding and provided on a predetermined first surface of the case, a second terminal connected internally to the other end of the primary winding and provided on the first surface, a third terminal connected internally to one end of the secondary winding and provided on a second surface different from the first surface of the case, and a fourth terminal connected internally to the third terminal and provided on the second surface of the case, wherein an external component can be connected to the fourth terminal. The high-voltage power supply device of the present invention comprises a high-voltage transformer having a case in which a primary winding and a secondary winding constituting the transformer are sealed, and a first component attached externally to the high-voltage transformer, wherein the case is provided with a first terminal connected internally to one end of the primary winding and provided on a predetermined first surface of the case, a second terminal connected internally to the other end of the primary winding and provided on the first surface, a third terminal connected internally to one end of the secondary winding and provided on a second surface different from the first surface of the case, and a fourth terminal connected internally to the third terminal and provided on the second surface of the case, wherein the first component is connected to the fourth terminal. [Effects of the Invention]

[0008] According to the present invention, the cost of high-voltage transformers can be reduced. [Brief explanation of the drawing]

[0009] [Figure 1] A diagram illustrating the configuration of an image forming apparatus. [Figure 2] Configuration diagram of a secondary transfer high-voltage power supply unit. [Figure 3] (a) to (d) are explanatory diagrams of a positive bias high-voltage transformer. [Figure 4] (a) to (d) are explanatory diagrams of negative bias high-voltage transformers. [Figure 5] Configuration diagram of the high-voltage power supply unit for transfer cleaning. [Figure 6] (a) to (d) are explanatory diagrams of a positive bias high-voltage transformer. [Figure 7] Diagram of a conventional positive bias high-voltage transformer configuration. [Figure 8] Diagram of a conventional negative bias high-voltage transformer configuration. [Figure 9] (a) to (d) are explanatory diagrams of a positive bias high-voltage transformer. [Figure 10] (a) to (d) are explanatory diagrams of negative bias high-voltage transformers. [Modes for carrying out the invention]

[0010] Preferred embodiments of the present invention will be described below with reference to the attached drawings.

[0011] (Image forming apparatus) Figure 1 is a diagram showing the configuration of an electrophotographic image forming apparatus according to this embodiment. The image forming apparatus 100 comprises a photosensitive drum 1a to 1d, charging rollers 2a to 2d, laser scanners 3a to 3d, developing units 4a to 4d, an intermediate transfer belt 5, primary transfer rollers 6a to 6d, a secondary transfer unit 7, a transfer cleaning unit 8, a fuser 9, and a paper feed cassette 10. The secondary transfer unit 7 comprises a secondary transfer roller 71 and a secondary transfer inner roller 72. The transfer cleaning unit 8 comprises a transfer cleaning outer roller 81, a transfer cleaning fur brush 82, and a transfer cleaning inner roller 83. A secondary transfer high-voltage power supply 200 is connected to the secondary transfer roller 71. A transfer cleaning high-voltage power supply 500 is connected to the transfer cleaning outer roller 81.

[0012] The image forming apparatus 100 of this embodiment forms a color image. The last letter of each of the reference numerals for the photosensitive drums 1a to 1d, charging rollers 2a to 2d, laser scanners 3a to 3d, developing units 4a to 4d, and primary transfer rollers 6a to 6d represents the color of the image to be formed. In this embodiment, "a" represents yellow, "b" represents magenta, "c" represents cyan, and "d" represents black. The image forming apparatus 100 operates as follows during image formation.

[0013] The photosensitive drums 1a to 1d are uniformly charged on the surface of the photosensitive layer by the charging rollers 2a to 2d, and then exposed according to the image signal by the laser scanners 3a to 3d. When the photosensitive drums 1a to 1d are exposed, an electrostatic latent image corresponding to the image signal is formed on the surface. The electrostatic latent image formed on the surface of the photosensitive drums 1a to 1d is developed into a toner image by the developing devices 4a to 4d. As described above, a yellow toner image is formed on the surface of the photosensitive drum 1a. A magenta toner image is formed on the surface of the photosensitive drum 1b. A cyan toner image is formed on the surface of the photosensitive drum 1c. A black toner image is formed on the surface of the photosensitive drum 1d.

[0014] The toner images of each color formed on the photosensitive drums 1a to 1d are multi-transferred to the intermediate transfer belt 5 by the corresponding primary transfer rollers 6a to 6d. The intermediate transfer belt 5 is an endless belt-shaped intermediate transfer member, and conveys the transferred toner image to the secondary transfer unit 7.

[0015] The recording material S on which an image is to be formed is stored in the paper feed cassette 10 and is conveyed one by one to the secondary transfer unit 7. The recording material S is sandwiched and conveyed by the secondary transfer roller 71 and the secondary transfer inner roller 72. A high voltage is applied to the secondary transfer roller 71 from the secondary transfer high voltage power supply device 200. When the secondary transfer roller 71 is applied with a high voltage of the opposite polarity to the toner image from the secondary transfer high voltage power supply device 200, the toner images of each color on the intermediate transfer belt 5 are electrostatically transferred to the recording material S all at once.

[0016] The toner remaining on the intermediate transfer belt 5 without being transferred to the recording material S in the secondary transfer unit 7 is recovered by the transfer cleaning unit 8. In the transfer cleaning unit 8, the transfer cleaning outer roller 81 is applied with a high voltage of the same polarity as the toner from the transfer cleaning high voltage power supply device 500. Thereby, the toner remaining on the intermediate transfer belt 5 is recovered by the transfer cleaning outer roller 81 via the transfer cleaning fiber brush 82.

[0017] The recording material S onto which the toner image is transferred by the secondary transfer unit 7 is conveyed to the fixing device 9. The fixing device 9 fixes the toner image onto the recording material S, for example, by heating the toner image and applying pressure thereto. In this way, a color image is formed on the recording material S. The recording material S on which the color image is formed is discharged outside the image forming apparatus 100.

[0018] (Secondary transfer high-voltage power supply device) FIG. 2 is a configuration diagram of the secondary transfer high-voltage power supply device 200. The secondary transfer high-voltage power supply device 200 includes a secondary transfer high-voltage control unit 201 and a secondary transfer high-voltage generation unit 202. The component parts of the secondary transfer high-voltage power supply device 200 are mounted on a printed circuit board.

[0019] The operation of the secondary transfer high-voltage power supply device 200 is controlled by the main control unit 101. The main control unit 101 controls the overall operation of the image forming apparatus 100. As part of its functions, the main control unit 101 generates the output voltage Vout1 for applying to the secondary transfer roller 71 and controls its output timing. Specifically, the main control unit 101 transmits a signal for setting the target voltage of the output voltage Vout1 and an operation timing signal regarding the output control of the output voltage Vout1 and the switching timing of the output voltage Vout1 to the secondary transfer high-voltage power supply device 200.

[0020] The secondary transfer high-voltage control unit 201 controls the secondary transfer high-voltage generation unit 202 so that the output voltage Vout1 of the secondary transfer high-voltage generation unit 202 becomes the target voltage set by the main control unit 101. Specifically, the secondary transfer high-voltage control unit 201 transmits control signals (POS_CTRL signal, NEG_CTRL signal, and POS_CLK signal, NEG_CLK signal) to the secondary transfer high-voltage generation unit 202. The POS_CTRL signal and NEG_CTRL signal are control signals for outputting the output voltage Vout1. The POS_CLK signal and NEG_CLK signal are control signals for driving the positive bias high-voltage transformer T201 and the negative bias high-voltage transformer T202, which will be described later.

[0021] The secondary transfer high-voltage generation unit 202 generates a high voltage and applies it to the secondary transfer roller 71 based on the control signals (POS_CTRL signal, NEG_CTRL signal, POS_CLK signal, NEG_CLK signal) obtained from the secondary transfer high-voltage control unit 201. The secondary transfer high-voltage generation unit 202 also converts the output voltage Vout1 and output current Iout1 into detection signals (output voltage detection signal Vsns1 and output current detection signal Isns1), respectively, and transmits them to the secondary transfer high-voltage control unit 201.

[0022] The secondary transfer high-voltage generation unit 202 includes a positive bias high-voltage transformer T201 and a negative bias high-voltage transformer T202. The positive bias high-voltage transformer T201 generates a high voltage for transferring a toner image onto the recording material S. The negative bias high-voltage transformer T202 generates a voltage (cleaning bias) for cleaning the toner adhering to the secondary transfer roller 71 by transferring it to the intermediate transfer belt 5. The negative bias high-voltage transformer T202 also generates a voltage to keep the density-detecting toner patch formed on the intermediate transfer belt 5 on the intermediate transfer belt 5 when it passes through the secondary transfer unit 7 (preventing the toner patch from being transferred to the secondary transfer roller 71).

[0023] The secondary transfer high-voltage generation unit 202 includes a positive bias high-voltage transformer input voltage control unit 203 and a positive bias high-voltage transformer drive unit 204 to control the operation of the positive bias high-voltage transformer T201. The secondary transfer high-voltage generation unit 202 also includes a negative bias high-voltage transformer input voltage control unit 205 and a negative bias high-voltage transformer drive unit 206 to control the operation of the negative bias high-voltage transformer T202. In addition, the secondary transfer high-voltage generation unit 202 includes bypass resistors R201 and R203, voltage sensing resistors R202 and R41, and an output current sensing unit 207.

[0024] The positive bias high-voltage transformer input voltage control unit 203 generates an input voltage Vin1 in response to the POS_CTRL signal obtained from the secondary transfer high-voltage control unit 201 for controlling the output voltage, and supplies it to terminal a of the positive bias high-voltage transformer T201. Terminal a is a terminal connected to one end of the primary winding L21 that constitutes the positive bias high-voltage transformer T201. The input voltage Vin1 has a voltage value at a level corresponding to the output voltage Vout1 of a predetermined voltage value. The positive bias high-voltage transformer input voltage control unit 203 is a series regulator circuit that controls the input voltage Vin1 input to the positive bias high-voltage transformer T201 in response to the POS_CTRL signal.

[0025] The POS_CTRL signal is, for example, a PWM (Pulse Width Modulation) signal with a frequency of 50 kHz. The POS_CLK signal is, for example, a fixed square wave with a frequency of 25 kHz and a duty cycle of 50%.

[0026] The POS_CTRL signal, for example, has an amplitude of 3.4[V], is smoothed by resistor R21 and capacitor C21, and input to op-amp IC21 as a voltage signal of, for example, 0 to 3.4[V]. Op-amp IC21 and resistors R22 (10[kΩ]) and R23 (2[kΩ]) form a non-inverting amplifier circuit with, for example, a gain of 6 times. In this case, the input voltage Vin1 will be 0 to 20.4[V].

[0027] The output terminal of the operational amplifier IC21 is connected to terminal a of the positive bias high-voltage transformer T201 and to the smoothing capacitor C22 for voltage stabilization via the current amplification transistor Q21. As the duty cycle of the POS_CTRL signal increases, the input voltage Vin1 input to terminal a of the positive bias high-voltage transformer T201 increases, and the AC voltage output from the positive bias high-voltage transformer T201 also increases.

[0028] The positive bias high-voltage transformer drive unit 204 drives the positive bias high-voltage transformer T201 by switching operation. The positive bias high-voltage transformer drive unit 204 includes a FET (Field Effect Transistor) Q22 and a capacitor C23. The positive bias high-voltage transformer drive unit 204 is connected to terminal b of the positive bias high-voltage transformer T201. Terminal b is the terminal connected to the other end of the primary winding L21 of the positive bias high-voltage transformer T201.

[0029] The positive bias high-voltage transformer drive unit 204 operates when the POS_CLK signal is input, causing FETQ22 to operate. This causes capacitor C23 and the primary winding L21 of the positive bias high-voltage transformer T201 to resonate, generating an AC flyback resonant voltage on the primary winding L21 of the positive bias high-voltage transformer T201.

[0030] The positive bias high-voltage transformer T201 comprises a primary winding L21, a secondary winding L22, a diode D201, and a capacitor C201. The positive bias high-voltage transformer T201 is connected to the positive bias high-voltage transformer input voltage control unit 203 via terminal a and to the positive bias high-voltage transformer drive unit 204 via terminal b.

[0031] The positive bias high-voltage transformer T201 receives an input voltage Vin1 from the positive bias high-voltage transformer input voltage control unit 203, and an AC voltage is generated in the primary winding L21 by the positive bias high-voltage transformer drive unit 204, which is driven by the POS_CLK signal. The AC voltage generated in the primary winding L21 is boosted in the secondary winding L22 of the positive bias high-voltage transformer T201. The AC voltage boosted in the secondary winding L22 of the positive bias high-voltage transformer T201 is rectified into a positive DC voltage by diode D201 and smoothed by capacitor C201. Diode D201 and capacitor C201 constitute a smoothing circuit.

[0032] The negative bias high-voltage transformer T202 comprises a primary winding L23, a secondary winding L24, a diode D202, and a capacitor C202. The negative bias high-voltage transformer T202 is connected to the negative bias high-voltage transformer input voltage control unit 205 via terminal j and to the negative bias high-voltage transformer drive unit 206 via terminal k. The operation of the negative bias high-voltage transformer input voltage control unit 205 is the same as that of the positive bias high-voltage transformer input voltage control unit 203, so its description is omitted. Similarly, the operation of the negative bias high-voltage transformer drive unit 206 is the same as that of the positive bias high-voltage transformer drive unit 204, so its description is omitted. Terminal j is connected to one end of the primary winding L23 of the negative bias high-voltage transformer T202. Terminal k is connected to the other end of the primary winding L23 of the negative bias high-voltage transformer T202.

[0033] The negative bias high-voltage transformer T202 receives an input voltage Vin2 from the negative bias high-voltage transformer input voltage control unit 205, and an AC voltage is generated in the primary winding L23 by the negative bias high-voltage transformer drive unit 206, which is driven by the NEG_CLK signal. The AC voltage generated in the primary winding L23 is boosted in the secondary winding L24 of the negative bias high-voltage transformer T202. The AC voltage boosted in the secondary winding L24 of the negative bias high-voltage transformer T202 is rectified into a negative DC voltage by diode D202 and smoothed by capacitor C202. Diode D202 and capacitor C202 constitute a smoothing circuit.

[0034] Terminal f of the positive bias high-voltage transformer T201 and terminal m of the negative bias high-voltage transformer T202 are connected by a high-voltage wire CA1. Bypass resistor R201 is a resistor that forms the path of the current supplied to the secondary transfer roller 71 when negative bias output is enabled (when negative bias high-voltage transformer T202 generates a high voltage at the negative terminal). Bypass resistor R203 is a resistor that forms the path of the current supplied to the secondary transfer roller 71 when positive bias output is enabled (when positive bias high-voltage transformer T201 generates a high voltage at the positive terminal).

[0035] The high voltage generated by the positive bias high-voltage transformer T201 is the voltage at point A (VBA) with respect to the potential at point B of the secondary transfer high-voltage generation unit 202. The high voltage generated by the negative bias high-voltage transformer T202 is the voltage at point B (VGB) with respect to ground (GND). The output voltage Vout1 of the secondary transfer high-voltage generation unit 202 is the voltage at point A with respect to ground (GND), and its voltage value is VGB + VBA.

[0036] The output voltage Vout1 of the secondary transfer high-pressure generation unit 202 is detected as follows: The output voltage Vout1 is divided by the voltage sensing resistors R202 and R41 and input to the secondary transfer high-pressure control unit 201 as the output voltage detection signal Vsns1. The output voltage detection signal Vsns1 is divided according to the output voltage Vout1, for example, within the range of 0 to 3.4 [V]. The secondary transfer high-pressure control unit 201 detects the voltage value of the output voltage Vout1 using the output voltage detection signal Vsns1.

[0037] The output current Iout1 flowing through point A of the secondary transfer high-voltage generation unit 202 is detected by the output current detection unit 207. The output current detection unit 207 comprises an operational amplifier IC 41, a current detection resistor R 42, and a reference voltage Vs 1. The current detection resistor R 42 is located on the path through which current flows between ground (GND) and point A, and is negatively feedback connected to the output terminal and negative input terminal of the operational amplifier IC 41. Therefore, the output voltage of the operational amplifier IC 41 changes according to the current flowing through the current detection resistor R 41, with reference to the reference voltage Vs 1 input to the positive input terminal. The output voltage of the operational amplifier IC 41 is input to the secondary transfer high-voltage control unit 201 as an output current detection signal Isns 1. The secondary transfer high-voltage control unit 201 detects the current value of the output current Iout1 using the output current detection signal Isns 1.

[0038] The secondary transfer high-pressure control unit 201 controls the output voltage Vout1 of the secondary transfer high-pressure generation unit 202 to reach the target voltage, and also acquires an output voltage detection signal Vsns1 and an output current detection signal Isns1 from the secondary transfer high-pressure generation unit 202. The secondary transfer high-pressure control unit 201 performs A / D conversion on the acquired output voltage detection signal Vsns1 and output current detection signal Isns1, converts the A / D conversion results into output voltage value and output current value, respectively, and then performs averaging processing. In this way, the secondary transfer high-pressure control unit 201 acquires an output voltage value Vval1 and an output current value Ival1.

[0039] The secondary transfer high-voltage control unit 201 performs a feedback calculation based on the deviation between the target voltage input from the main control unit 101 and the output voltage value Vval1, and controls the ON time or duty cycle of the POS_CTRL signal and the NEG_CTRL signal. This controls the output voltage Vout1 of the secondary transfer high-voltage generation unit 202 to the target voltage. The output current value Ival1 is transmitted from the secondary transfer high-voltage control unit 201 to the main control unit 101. Based on the output current value Ival1, the main control unit 101 derives the optimal value (target voltage) of the output voltage Vout1 applied to the secondary transfer unit 7.

[0040] (High-voltage transformer) Figure 3 is an explanatory diagram of the positive bias high-voltage transformer T201. Figure 3(a) is a top view of the positive bias high-voltage transformer T201, Figure 3(b) is a longitudinal side view of the positive bias high-voltage transformer T201, Figure 3(c) is a short-side view of the positive bias high-voltage transformer T201, and Figure 3(d) is a bottom view of the positive bias high-voltage transformer T201.

[0041] The primary winding L21, secondary winding L22, rectifier diode D201, and capacitor C201 are sealed inside the transformer case 306 with an insulating resin 305 such as epoxy resin. Unlike conventional designs, the bypass resistor R201 and voltage sensing resistor R202 are not sealed inside the transformer case 306 of the positive bias high-voltage transformer T201, and are configured to have terminals that can be externally connected to the positive bias high-voltage transformer T201.

[0042] Terminals a, b, c, d, e, f, g, h, and i are terminals provided on the positive bias high-voltage transformer T201, and are shown with the same symbols in Figure 2. Terminals d, e, f, g, h, and i are provided on the upper surface of the positive bias high-voltage transformer T201, and terminals a, b, and c are provided on the lower surface.

[0043] Terminals e, f, g, h, and i of the positive bias high-voltage transformer T201 are terminals to which high voltage is applied. Terminal f is a Faston terminal and is connected to the high-voltage wire CA1. Terminal i is a Faston terminal and is connected to the high-voltage wire CA2 (see Figure 2) for supplying output voltage to the secondary transfer roller 71. Terminal g is a conductive metal plate and is connected to one lead of the voltage sensing resistor R202 with solder 301. Terminal h is a conductive metal plate and is connected to one lead of the bypass resistor R201 with solder 302. Terminal e is a conductive metal plate and is connected to the other lead of the bypass resistor R201 with solder 303. Terminals e and f are at the same potential and are connected inside the positive bias high-voltage transformer T201. Terminals g, h, and i are at the same potential and are connected inside the positive bias high-voltage transformer T201 (transformer case 306).

[0044] Terminals a, b, c, and d of the positive bias high-voltage transformer T201 are terminals to which a low voltage is applied. Terminals a, b, and c are configured as pins on the underside of the positive bias high-voltage transformer T201. Each terminal a, b, and c is soldered to a wiring pattern on a printed circuit board located inside the transformer case 306. Terminal d is located on the top surface of the positive bias high-voltage transformer T201 and is soldered 304 to the other lead of the voltage sensing resistor R202. Terminals c and d are at the same potential and are connected inside the positive bias high-voltage transformer T201 (transformer case 306).

[0045] Figure 4 is an explanatory diagram of the negative bias high-voltage transformer T202. Figure 4(a) is a top view of the negative bias high-voltage transformer T202, Figure 4(b) is a longitudinal side view of the negative bias high-voltage transformer T202, Figure 4(c) is a short-side view of the negative bias high-voltage transformer T202, and Figure 4(d) is a bottom view of the negative bias high-voltage transformer T202.

[0046] The primary winding L23, secondary winding L24, rectifier diode D202, and capacitor C202 are sealed inside the transformer case 406 with an insulating resin 305 such as epoxy resin. Unlike conventional designs, the bypass resistor R203 is not sealed inside the transformer case 406 of the negative bias high-voltage transformer T202, and is configured to have terminals that can be externally connected to the negative bias high-voltage transformer T202.

[0047] The terminals j, k, l, m, and n are terminals provided on the negative bias high-voltage transformer T202, and are shown with the same reference numerals in Figure 2. Terminals m and n are provided on the upper surface of the negative bias high-voltage transformer T202, and terminals j, k, and l are provided on the lower surface.

[0048] Terminals m and n of the negative bias high-voltage transformer T202 are terminals to which high voltage is applied. Terminal m is a faston terminal and is connected to the high-voltage wire CA1. Terminal n is a conductive metal plate and is connected to one lead of the bypass resistor R203 with solder 401. The other lead o of the bypass resistor R203 is connected with solder to a wiring pattern on a printed circuit board provided inside the transformer case 306. Terminals m and n are at the same potential and are connected inside the negative bias high-voltage transformer T202 (transformer case 306).

[0049] Terminals j, k, and l of the negative bias high-voltage transformer T202 are the parts to which low voltage is applied. Terminals j, k, and l are configured as pins on the underside of the negative bias high-voltage transformer T202. Each terminal j, k, and l is soldered to a wiring pattern on a printed circuit board provided inside the transformer case 306.

[0050] The terminal h to which the bypass resistor R201 of the positive bias high-voltage transformer T201 is connected can be a conductive metal plate, or it can be a faston terminal, connector, or other configuration. The terminal g to which the voltage sensing resistor R202 of the positive bias high-voltage transformer T201 is connected can be a conductive metal plate, or it can be a faston terminal, connector, or other configuration. The terminal of the voltage sensing resistor R202 (the terminal to which a low voltage is applied) of the positive bias high-voltage transformer T201 is soldered to the conductive metal plate terminal (terminal d) on the top surface. Terminal d is configured to be connected to a pin terminal (terminal c) provided on the bottom surface inside the positive bias high-voltage transformer T201 (transformer case 306), but it may also be configured to be connected to a printed circuit board.

[0051] In addition to a conductive metal plate, other configurations such as faston terminals or connectors can be used as terminal n to which the bypass resistor R203 of the negative bias high-voltage transformer T202 is connected. Furthermore, although one end (lead portion o) of the bypass resistor R203 of the negative bias high-voltage transformer T202 is connected to a printed circuit board, it may also be connected to a bottom terminal inside the negative bias high-voltage transformer T202 (transformer case 306).

[0052] (Transfer cleaning high-voltage power supply) Figure 5 is a diagram showing the configuration of the transfer cleaning high-voltage power supply unit 500. The transfer cleaning high-voltage power supply unit 500 comprises a transfer cleaning high-voltage control unit 501 and a transfer cleaning high-voltage generation unit 502. The components of the transfer cleaning high-voltage power supply unit 500 are mounted on a printed circuit board.

[0053] The transfer cleaning high-voltage power supply unit 500 is controlled by the main control unit 101. The main control unit 101 controls the output voltage Vout2 of the transfer cleaning high-voltage generation unit 502 to be applied to the transfer cleaning outer roller 81, and its output timing. Specifically, the main control unit 101 transmits a signal to the transfer cleaning high-voltage power supply unit 500 to set a target voltage for the output voltage Vout2, and operation timing signals related to the output control of the output voltage Vout2 and the switching timing of the output voltage Vout2.

[0054] The transfer cleaning high-voltage control unit 501 controls the transfer cleaning high-voltage generation unit 502 so that the output voltage Vout2 of the transfer cleaning high-voltage generation unit 502 becomes the target voltage set by the main control unit 101. Specifically, the transfer cleaning high-voltage control unit 501 transmits to the transfer cleaning high-voltage generation unit 502 a CTRL signal, which is a control signal for outputting the output voltage Vout2, and a CLK signal for driving the positive bias high-voltage transformer T501, which will be described later.

[0055] The transfer cleaning high-voltage generation unit 502 generates a high voltage based on control signals (CTRL signal, CLK signal) obtained from the transfer cleaning high-voltage control unit 501 and applies it to the transfer cleaning outer roller 81. The transfer cleaning high-voltage generation unit 502 also converts the output voltage Vout2 and output current Iout2 into detection signals (Vsns2, Isns2), respectively, and transmits them to the transfer cleaning high-voltage control unit 501.

[0056] The transfer cleaning high-voltage generation unit 502 generates a high voltage with the opposite polarity to the toner in order to recover toner that remains on the recording material S from the intermediate transfer belt 5 during the secondary transfer process. The transfer cleaning high-voltage generation unit 502 includes a positive bias high-voltage transformer T501, voltage sensing resistors R501 and R61, a positive bias high-voltage transformer input voltage control unit 503, a positive bias high-voltage transformer drive unit 504, and an output current sensing unit 505.

[0057] The positive bias high-voltage transformer input voltage control unit 503 generates an input voltage Vin3 in response to a CTRL signal obtained from the transfer cleaning high-voltage control unit 501 to control the output voltage, and supplies it to terminal p of the positive bias high-voltage transformer T501. Terminal q is a terminal connected to one end of the primary winding L51 of the positive bias high-voltage transformer T501. The input voltage Vin3 has a voltage value at a level corresponding to the output voltage Vout2 of a predetermined voltage value. The positive bias high-voltage transformer input voltage control unit 503 is a series regulator circuit that controls the input voltage Vin3 input to the positive bias high-voltage transformer T501 in response to the CTRL signal.

[0058] The CTRL signal is, for example, a PWM signal with a frequency of 50 kHz. The CLK signal is, for example, a fixed square wave with a frequency of 25 kHz and a normal duty cycle of 50%.

[0059] The CTRL signal, for example, has an amplitude of 3.4[V], is smoothed by resistor R51 and capacitor C51, and input to op-amp IC51 as a voltage signal of, for example, 0 to 3.4[V]. Op-amp IC51 and resistors R52 (10[kΩ]) and R53 (2[kΩ]) form a non-inverting amplifier circuit with, for example, a gain of 6 times. In this case, the input voltage Vin3 will be 0 to 20.4[V].

[0060] The output terminal of the operational amplifier IC51 is connected to terminal p of the positive bias high-voltage transformer T501 and to the smoothing capacitor C52 for voltage stabilization via the current amplification transistor Q51. As the duty cycle of the CTRL signal increases, the input voltage Vin3 input to terminal p of the positive bias high-voltage transformer T501 increases, and the AC voltage output from the positive bias high-voltage transformer T501 also increases.

[0061] The positive bias high-voltage transformer drive unit 504 drives the positive bias high-voltage transformer T501 by switching operation. The positive bias high-voltage transformer drive unit 504 includes FET Q52 and capacitor C53. The positive bias high-voltage transformer drive unit 504 is connected to terminal q of the positive bias high-voltage transformer T501. Terminal q is the terminal connected to the other end of the primary winding L51 of the positive bias high-voltage transformer T501.

[0062] The positive bias high-voltage transformer drive unit 504 operates when a CLK signal is input, causing FETQ52 to activate. This causes capacitor C53 and the primary winding L51 of the positive bias high-voltage transformer T504 to resonate, generating an AC flyback resonant voltage on the primary winding L51 of the positive bias high-voltage transformer T501.

[0063] The positive bias high-voltage transformer T501 comprises a primary winding L51, a secondary winding L52, a diode D501, and a capacitor C501. The positive bias high-voltage transformer T501 is connected to the positive bias high-voltage transformer input voltage control unit 503 via terminal p and to the positive bias high-voltage transformer drive unit 504 via terminal q.

[0064] The positive bias high-voltage transformer T501 receives an input voltage Vin3 from the positive bias high-voltage transformer input voltage control unit 503, and an AC voltage is generated in the primary winding L51 by the positive bias high-voltage transformer drive unit 504, which is driven by the CLK signal. The AC voltage generated in the primary winding L51 is boosted in the secondary winding L52 of the positive bias high-voltage transformer T501. The AC voltage boosted in the secondary winding L52 of the positive bias high-voltage transformer T501 is rectified into a positive DC voltage by diode D501 and smoothed by capacitor C501. Diode D501 and capacitor C501 constitute a smoothing circuit.

[0065] The output voltage Vout2 of the transfer cleaning high-voltage generation unit 502 is detected as follows: The output voltage Vout2 is divided by the voltage sensing resistor R501 and the voltage sensing resistor R61, and input to the transfer cleaning high-voltage control unit 501 as an output voltage detection signal Vsns2. The output voltage detection signal Vsns2 is divided according to the output voltage Vout2, for example, in the range of 0 to 3.4 [V]. The transfer cleaning high-voltage control unit 501 detects the voltage value of the output voltage Vout2 using the output voltage detection signal Vsns2.

[0066] The output current Iout2 flowing through point C of the transfer cleaning high-voltage generation unit 502 is detected by the output current detection unit 505. The output current detection unit 505 comprises an operational amplifier IC 61, a current detection resistor R 62, and a reference voltage Vs 2. The current detection resistor R 62 is located on the path through which current flows between ground (GND) and point C, and is negatively feedback connected to the output terminal and negative input terminal of the operational amplifier IC 61. Therefore, the output voltage of the operational amplifier IC 61 changes according to the current flowing through the current detection resistor R 61, with reference to the reference voltage Vs 2 input to the positive input terminal. The output voltage of the operational amplifier IC 61 is input to the transfer cleaning high-voltage control unit 501 as an output current detection signal Isns 2. The transfer cleaning high-voltage control unit 501 detects the current value of the output current Iout2 using the output current detection signal Isns 2.

[0067] The transfer cleaning high-voltage control unit 501 controls the output voltage Vout2 of the transfer cleaning high-voltage generation unit 502 to reach the target voltage, and also acquires an output voltage detection signal Vsns2 and an output current detection signal Isns2 from the transfer cleaning high-voltage generation unit 502. The transfer cleaning high-voltage control unit 501 performs A / D conversion on the acquired output voltage detection signal Vsns2 and output current detection signal Isns2, converts the A / D conversion results into output voltage value and output current value respectively, and then performs averaging processing. In this way, the transfer cleaning high-voltage control unit 501 acquires an output voltage value Vval2 and an output current value Ival2.

[0068] The transfer cleaning high-voltage control unit 501 performs a feedback calculation based on the deviation between the target voltage input from the main control unit 101 and the output voltage value Vval2, and controls the ON time or duty cycle of the CTRL signal. This controls the output voltage Vout2 of the transfer cleaning high-voltage generation unit 502 to become the target voltage. The output current value Ival2 is transmitted from the transfer cleaning high-voltage control unit 501 to the main control unit 101. The main control unit 101 derives the optimal value (target voltage) of the output voltage Vout2 of the transfer cleaning high-voltage generation unit 502 based on the output current value Ival2.

[0069] (High-voltage transformer) Figure 6 is an explanatory diagram of the positive bias high-voltage transformer T501. Figure 6(a) is a top view of the positive bias high-voltage transformer T501, Figure 6(b) is a longitudinal side view of the positive bias high-voltage transformer T501, Figure 6(c) is a short-side view of the positive bias high-voltage transformer T501, and Figure 6(d) is a bottom view of the positive bias high-voltage transformer T501.

[0070] The primary winding L51, secondary winding L52, rectifier diode D501, and capacitor C501 are sealed inside the transformer case 606 with an insulating resin 605 such as epoxy resin. Unlike conventional designs, the voltage sensing resistor R501 is not sealed inside the transformer case 606 of the positive bias high-voltage transformer T501, and is configured to be externally connected to the positive bias high-voltage transformer T501.

[0071] The terminals p, q, r, s, t, u, and v are terminals provided on the positive bias high-voltage transformer T501, and are shown with the same symbols in Figure 5. Terminals t, u, and v are provided on the upper surface of the positive bias high-voltage transformer T501, and terminals p, q, r, and s are provided on the lower surface.

[0072] Terminals t and v of the positive bias high-voltage transformer T501 are terminals to which high voltage is applied. Terminal t is a Faston terminal and is connected to one lead of the voltage sensing resistor R501. Terminal v is a Faston terminal and is connected to the high-voltage wire CA3 (see Figure 5). Terminals t and v are at the same potential and are connected inside the positive bias high-voltage transformer T501 (transformer case 606).

[0073] Terminals p, q, r, s, and u of the positive bias high-voltage transformer T501 are terminals to which a low voltage is applied. Terminals p, q, r, and s are configured as pins on the underside of the positive bias high-voltage transformer T501. Each terminal p, q, r, s, and u is soldered to a wiring pattern on a printed circuit board located inside the transformer case 606. Terminal u is connected to the other lead of the voltage sensing resistor R501 with a faston terminal. Terminals s and u are at the same potential and are connected inside the positive bias high-voltage transformer T501 (transformer case 606).

[0074] The terminal t to which the voltage sensing resistor R501 of the positive bias high-voltage transformer T501 is connected can be a faston terminal, or it can be a conductive metal plate connected by solder, or a connector can be used, or other configurations can be used. The other terminal of the sensing resistor R501 of the positive bias high-voltage transformer T501 (the terminal to which a low voltage is applied) is connected to terminal u on the top surface of the positive bias high-voltage transformer T501, and terminal s is provided on the bottom surface of the transformer. Although the terminals u and s are connected inside the positive bias high-voltage transformer T501 (transformer case 606), the terminals of the voltage sensing resistor R501 of the positive bias high-voltage transformer T501 may also be connected to a printed circuit board.

[0075] (effect) Figure 7 is a diagram of a conventional positive bias high-voltage transformer. The positive bias high-voltage transformer T1 comprises a primary winding L1, a secondary winding L2, a rectifier diode D1, a smoothing capacitor C1, a bypass resistor R1, and a voltage sensing resistor R2. Figure 8 is a diagram of a conventional negative bias high-voltage transformer. The negative bias high-voltage transformer T2 comprises a primary winding L3, a secondary winding L4, a rectifier diode D2, a smoothing capacitor C2, and a bypass resistor R3.

[0076] Figure 9 is an explanatory diagram of the positive bias high-voltage transformer T1. Figure 9(a) is a top view of the positive bias high-voltage transformer T1, Figure 9(b) is a longitudinal side view of the positive bias high-voltage transformer T1, Figure 9(c) is a short-side view of the positive bias high-voltage transformer T1, and Figure 9(d) is a bottom view of the positive bias high-voltage transformer T1. The primary winding L1, secondary winding L2, rectifier diode D1, capacitor C1, bypass resistor R1, and voltage sensing resistor R2 are sealed inside the case 706 of the positive bias high-voltage transformer T1 with an insulating resin 705 such as epoxy resin.

[0077] As shown in Figures 7 and 9, the positive bias high-voltage transformer T1 has terminals 701 to 705. Terminals 704 and 705 are provided on the upper surface of the positive bias high-voltage transformer T1, and terminals 701, 702, and 703 are provided on the lower surface. Terminals 704 and 705 of the positive bias high-voltage transformer T1 are terminals to which high voltage is applied and are made up of faston terminals. Terminals 701 to 703 of the positive bias high-voltage transformer T1 to which low voltage is applied are made up of pins on the lower surface of the positive bias high-voltage transformer T1. These terminals 701 to 703 are soldered to patterns on a printed circuit board provided on the case 706 of the positive bias high-voltage transformer T1.

[0078] Figure 10 is an explanatory diagram of the negative bias high-voltage transformer T2. Figure 10(a) is a top view of the negative bias high-voltage transformer T2, Figure 10(b) is a longitudinal side view of the negative bias high-voltage transformer T2, Figure 10(c) is a short-side view of the negative bias high-voltage transformer T2, and Figure 10(d) is a bottom view of the negative bias high-voltage transformer T2. The primary winding L3, secondary winding L4, rectifier diode D2, smoothing capacitor C2, and bypass resistor R3 are sealed inside the case 806 of the negative bias high-voltage transformer T2 with an insulating resin 805 such as epoxy resin.

[0079] As shown in Figures 8 and 10, the negative bias high-voltage transformer T2 has terminals 801 to 804. Terminal 804 is provided on the upper surface of the negative bias high-voltage transformer T2, and terminals 801 to 803 are provided on the lower surface. Terminal 804 of the negative bias high-voltage transformer T2 is a terminal to which a high voltage is applied and is made up of faston terminals. Terminals 801 to 803 of the negative bias high-voltage transformer T2 to which a low voltage is applied are made up of pins on the lower surface of the negative bias high-voltage transformer T2. These terminals 801 to 803 are soldered to patterns on a printed circuit board provided on the case 806 of the negative bias high-voltage transformer T2.

[0080] Comparing a conventional high-voltage transformer with the high-voltage transformer of this embodiment, there are differences in the components that are built into the transformer case and those that are not. In conventional high-voltage transformers, the primary winding, secondary winding, smoothing circuit, voltage sensing resistor, and bypass resistor that make up the transformer are built into the case. Therefore, when manufacturing two types of high-voltage transformers in which at least one of the resistance values ​​of the voltage sensing resistor and the bypass resistor differs, but other components are common, the component cost of the high-voltage transformer, which is produced in smaller quantities, increases.

[0081] In this embodiment of the high-voltage transformer, the voltage sensing resistor and bypass resistor are externally mounted instead of being built into the transformer case as in conventional designs. The primary winding, secondary winding, and smoothing circuit built into the case can be configured in a common way even for different types of high-voltage transformers. Since the components built into the case can be common to multiple types of high-voltage transformers, the increase in component costs can be suppressed. Furthermore, even if the number of types of high-voltage transformers increases, the increase in management costs can be suppressed by commonizing the components built into the case.

[0082] The above description has focused on power supply devices that generate high voltage for secondary transfer and power supply devices that generate high voltage for transfer cleaning. However, the configuration of this embodiment is also effective for power supply devices that generate high voltage used in other processes. For example, the configuration of this embodiment can be used for power supply devices that generate high voltage supplied to charging rollers 2a to 2d when charging the photosensitive layer of photosensitive drums 1a to 1d, and for power supply devices that generate high voltage supplied during development by developing units 4a to 4d.

Claims

1. The transformer is equipped with a case that seals the primary and secondary windings, The aforementioned case includes: One end of the primary winding is connected inside the case to a first terminal provided on a predetermined first surface of the case, The other end of the primary winding is connected inside the case to a second terminal provided on the first surface, A third terminal is connected to one end of the secondary winding inside the case and is provided on a second surface of the case that is different from the first surface, A fourth terminal is provided, which is connected to the third terminal inside the case and is located on the second surface of the case. The fourth terminal is characterized in that an external component can be connected to it. High-voltage transformer.

2. The case contains a diode with one end connected to one end of the secondary winding, and a capacitor with one end connected to the other end of the diode and the other end connected to the other end of the secondary winding. The third terminal is connected to the other end of the diode, The high-voltage transformer according to claim 1.

3. The diode is characterized by having a fifth terminal connected to the other end of the case and provided on the second surface of the case, The high-voltage transformer according to claim 2.

4. The primary winding, the secondary winding, the diode, and the capacitor are characterized in that they are sealed inside the case with an insulating resin. The high-voltage transformer according to claim 2.

5. The case is characterized by having a sixth terminal provided on the second surface of the case and connected to the other end of the secondary winding inside the case, The high-voltage transformer according to claim 1.

6. A seventh terminal is provided on the second surface of the case and is connected to the fourth terminal via the component, The case is characterized by having an eighth terminal provided on the first surface of the case and connected to the seventh terminal inside the case, The high-voltage transformer according to claim 1.

7. A high-voltage transformer having a case in which the primary and secondary windings constituting the transformer are sealed, The high-voltage transformer comprises a first component externally attached to the high-voltage transformer, The aforementioned case includes: One end of the primary winding is connected inside the case to a first terminal provided on a predetermined first surface of the case, The other end of the primary winding is connected inside the case to a second terminal provided on the first surface, A third terminal is connected to one end of the secondary winding inside the case and is provided on a second surface of the case that is different from the first surface, A fourth terminal is provided, which is connected to the third terminal inside the case and is located on the second surface of the case. The first component is characterized by being connected to the fourth terminal. High-voltage power supply unit.

8. The case contains a diode with one end connected to one end of the secondary winding, and a capacitor with one end connected to the other end of the diode and the other end connected to the other end of the secondary winding. The other end of the diode is connected to a fifth terminal located inside the case and provided on the second surface of the case, The invention is characterized by comprising a second component connected to the fifth terminal, The high-voltage power supply device according to claim 7.

9. The case is provided with a sixth terminal on the second surface, which is connected to the other end of the secondary winding inside the case, The first component is characterized in that one end is connected to the fourth terminal and the other end is connected to the sixth terminal. The high-voltage power supply device according to claim 8.

10. The first and second components are characterized by being resistors. The high-voltage power supply device according to claim 9.

11. A high-voltage power supply device according to any one of claims 7 to 10, The system is characterized by comprising an image forming means that forms an image on a recording material using the voltage supplied from the high-voltage power supply, Image forming apparatus.

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