JP2009109554A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus, including a power supply device using a piezoelectric transformer, restraining mutual interference of driving frequencies in the piezoelectric transformer, and inexpensively reducing the size and attaining high image quality. <P>SOLUTION: A frame sheet metal 501 is integrally formed by single or two or more sheet metals. The frame sheet metal 501 holds a high voltage power supply circuit board 100 on a color laser printer 401 body, and at least a bending raised part 120 of the frame sheet metal 501 is disposed between the piezoelectric transformer 351 and the piezoelectric transformer 121. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image forming apparatus. Specifically, the present invention relates to a power supply apparatus suitable for an image forming apparatus that forms an image by an electrophotographic process, and more particularly to a power supply apparatus using a piezoelectric transformer and an image forming apparatus having the power supply apparatus.

  In an image forming apparatus that forms an image by an electrophotographic process, when adopting a direct transfer method in which a transfer member is brought into contact with a photoconductor to perform transfer, a roller-like conductive rubber having a rotating shaft of a conductor is used as the transfer member. Is used (hereinafter also referred to as a transfer roller). The driving of the transfer member is controlled in accordance with the process speed of the photoreceptor.

  A DC bias voltage is used as the voltage applied to the transfer member. At this time, the polarity of the DC bias voltage is the same as that of a normal corona discharge transfer voltage. However, in order to perform good transfer using such a transfer roller, it is usually necessary to apply a voltage of 3 kV or more (required current is several μA) to the transfer roller. In order to generate a high voltage required for the above-described image forming processing, a winding type electromagnetic transformer has been conventionally used. However, the electromagnetic transformer is composed of a copper wire, bobbin, and magnetic core. When a voltage of 3 kV or more is applied as described above, each part has a small output current value of several μA. The leakage current had to be minimized. Therefore, it is necessary to mold the winding of the transformer with an insulator, and a large transformer is required as compared with the supplied power, which hinders miniaturization and weight reduction of the high-voltage power supply device.

  Therefore, in order to compensate for these points, it has been studied to generate a high voltage using a thin and light high-power piezoelectric transformer. That is, by using a piezoelectric transformer made of ceramic, it is possible to generate a high voltage with an efficiency higher than that of an electromagnetic transformer. In addition, since the distance between the primary and secondary electrodes can be increased regardless of the coupling between the primary side and the secondary side, it is not necessary to perform special molding for insulation. Therefore, an excellent characteristic that the high-voltage power supply device can be reduced in size and weight can be obtained.

  An example of a high-voltage power supply device using a piezoelectric transformer will be described with reference to FIG. Taking the piezoelectric transformer 1001 as an example, 1002 is a ground (hereinafter referred to as GND) terminal, 1003 is a primary input terminal, and 1004 is a secondary output terminal. It is assumed that the GND terminal 1002, the primary input terminal 1003, and the secondary output terminal 1004 are mounted on the circuit board 1000 and are electrically connected. Similarly, for the piezoelectric transformers 1021, 1041, and 1061, the GND terminals 1022, 1042, and 1062, the primary input terminals 1023, 1043, and 1063, and the secondary output terminals 1024, 1044, and 1064 are mounted on the circuit board 1000 and are electrically connected. It shall be.

  20 uses four piezoelectric transformers 1001, 1021, 1041, and 1061, and outputs four high voltage voltages from output connectors 1114, 1134, 1154, and 1174 corresponding to each piezoelectric transformer. It is configured to output.

  As a first system, a control signal (Vcont1) of a high voltage power supply is input from the DC controller 201 to the input connector 1010. A configuration in which a control circuit 1011, a drive circuit 1012, a rectifier circuit 1113, and a high voltage output detection circuit 1115, which are circuit configurations for driving the piezoelectric transformer 1001, are driven based on the control signal and a high voltage is output from the output connector 1114. It has become.

  As a second system, a control signal (Vcont2) of a high voltage power supply is input from the DC controller 201 to the input connector 1030. A configuration in which a control circuit 1031, a drive circuit 1032, a rectifier circuit 1133, and a high voltage output detection circuit 1135, which are circuit configurations for driving the piezoelectric transformer 1021, are driven based on the control signal, and a high voltage is output from the output connector 1134. It has become.

  As a third system, a control signal (Vcont3) of a high voltage power supply is input from the DC controller 201 to the input connector 1050. A configuration in which a control circuit 1051, a drive circuit 1052, a rectifier circuit 1153, and a high voltage output detection circuit 1155, which are circuit configurations for driving the piezoelectric transformer 1041, are driven based on the control signal, and a high voltage is output from the output connector 1154. It has become.

  As a fourth system, a control signal (Vcont4) for the high voltage power supply is input from the DC controller 201 to the input connector 1070. A configuration in which a control circuit 1071, a drive circuit 1072, a rectifier circuit 1173, and a high voltage output detection circuit 1175, which are circuit configurations for driving the piezoelectric transformer 1061, are driven based on the control signal, and a high voltage is output from the output connector 1174. It has become.

  The high-voltage power supply device for an electrophotographic image forming apparatus has a plurality of high-voltage power supply circuits using piezoelectric transformers 1001, 1021, 1041, and 1061, as shown in FIG. Each high-voltage power supply circuit corresponds to, for example, a yellow (Y), magenta (M), cyan (C), or black (BK) image forming unit, and outputs a bias such as charging, development, and transfer. A forming process is executed. As a prior art disclosing the above-described configuration, for example, there is one disclosed in Patent Document 1 below.

As a method for assembling a high-voltage power supply to the image forming apparatus, for example, there is one disclosed in Patent Document 2 below. In Patent Document 2, the frame sheet metal of the image forming apparatus and the component surface of the high-voltage power circuit board are arranged so as to face each other. A configuration that is connected to a contact on the apparatus body side has been proposed.
JP-A-11-206113 Japanese Patent Laid-Open No. 2003-195697

  In the above example, a plurality of piezoelectric transformers and control circuits are arranged in the high-voltage power supply device, so that a plurality of bias voltages are output to perform image formation. In particular, in a high-voltage power supply unit mounted on a tandem color image forming apparatus, bias output circuits for charging, development, transfer, etc., have four circuits (four systems) corresponding to cyan, magenta, yellow, and black image formation. Is required.

  In such a high voltage power supply apparatus (hereinafter also referred to as “power supply unit”) that requires a plurality of high voltage biases, it is necessary to dispose the piezoelectric transformer as close as possible in order to reduce the size of the power supply unit. Since the piezoelectric transformer does not cause magnetic coupling between transformers such as an electromagnetic transformer, not only miniaturization of elements but also miniaturization of a high-voltage power supply unit by arranging a plurality of transformers close to each other can be expected.

  However, the output end of the piezoelectric transformer oscillates at a high voltage, and the oscillation frequency of the electromagnetic transformer ranges from several hundred hertz to several tens of kilohertz, whereas the oscillation frequency of the piezoelectric transformer ranges from several tens of kilohertz to two hundred kilohertz. high. For this reason, when the piezoelectric transformers are arranged close to each other, they are easily affected by electrostatic interference. As a result, mutual interference occurs in the piezoelectric transformers arranged close to each other due to capacitive coupling, and it becomes difficult to improve the output accuracy of the high-voltage bias voltage. Alternatively, there is a possibility that the image quality is deteriorated due to the occurrence of fluctuations in the high-voltage bias voltage due to the interference frequency.

  For this reason, especially in a high voltage power supply unit mounted in a tandem type color image forming apparatus, it is necessary to mount the piezoelectric transformers at a sufficiently large interval, which reduces the size of the high voltage power supply unit and improves the image quality of image formation. It is difficult to achieve both.

  The present invention has been made paying attention to such points, and an image forming apparatus including a power supply device using a piezoelectric transformer that suppresses interference between driving frequencies in the piezoelectric transformer and enables miniaturization and high image quality. The issue is to provide

  The above-described problem is solved by an image forming apparatus of the present invention having the following configuration.

  (1) A first drive frequency for driving the first piezoelectric transformer is generated based on a first control signal for forming an image, and a voltage generated by driving the first piezoelectric transformer is formed as a first image. By generating a second drive frequency for driving the second piezoelectric transformer based on a first control circuit for supplying the image and a second control signal for forming the image, and driving the second piezoelectric transformer. A second power supply circuit that supplies the generated voltage to the second image forming unit, a power supply board on which at least the first power supply circuit and the second power supply circuit are mounted, and provided to face the power supply board, and An image forming apparatus including a metal sheet metal connected to a ground potential, wherein the metal sheet metal is integrally formed of a single sheet metal or a plurality of sheet metals, and the sheet metal attaches the power supply board to the image forming apparatus main body. And it holds, and at least the image forming apparatus portion of the sheet metal characterized in that it is disposed between the second piezoelectric transformer and said first piezoelectric transformer.

  According to the present invention, by disposing a part of the frame metal plate or the shield metal plate of the image forming apparatus between the plurality of piezoelectric transformers, it is possible to suppress interference between driving frequencies in the piezoelectric transformer at a low cost. Accordingly, it is possible to provide an image forming apparatus including a power supply device using a piezoelectric transformer that enables downsizing and high image quality.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. Hereinafter, a color laser beam printer will be described as an example of an embodiment of the present invention. However, the present invention is not limited to a color laser beam printer, and can be applied to all image forming apparatuses using an electrophotographic process. Therefore, it is not intended to limit the scope of the present invention to only the components described in the following embodiments.

  In addition, the same parts as those described in the conventional technical example are omitted or simplified, and the same reference numerals used in the description of the conventional technical example are used.

  FIG. 1 is a configuration diagram of an image forming apparatus (hereinafter also referred to as a “color laser printer”) according to the present embodiment including a high-voltage power supply device 202 using a piezoelectric transformer.

  FIG. 2 is a view for explaining the arrangement of the frame metal plate and the high-voltage power supply circuit board of the image forming apparatus as seen from the direction of arrow A in FIG.

  The color laser printer 401 includes a deck 402 for storing the recording paper 32, and a deck paper presence / absence sensor 403 for detecting the presence / absence of the recording paper 32 in the deck 402 is provided. In addition, the color laser printer 401 is provided with a pickup roller 404 that feeds the recording paper 32 from the deck 402, and a deck paper feed roller 405 that transports the recording paper 32 fed by the pickup roller 404. Further, the color laser printer 401 is paired with a deck paper feed roller 405, and a retard roller 406 for preventing double feeding of the recording paper 32 is provided.

  A registration roller pair 407 that synchronously conveys the recording paper 32 and a pre-registration sensor 408 that detects the conveyance state of the recording paper 32 to the registration roller pair 407 are disposed on the downstream side of the deck paper feeding roller 405. Further, an electrostatic attraction transfer belt (hereinafter referred to as “ETB”) 409 is disposed downstream of the registration roller pair 407. On the ETB 409, an image forming unit comprising process cartridges 410 (Y, M, C, BK) for four colors (Y, M, C, BK) and a scanner unit 420 (Y, M, C, BK) is provided. An image is formed. The formed images are sequentially superimposed by transfer rollers 430 (Y, M, C, BK) to form a color image, which is transferred and conveyed onto the recording paper 32.

  On the downstream side, in order to thermally fix the toner image transferred onto the recording paper 32, a pair of a fixing roller 433 and a pressure roller 434 provided with a heater 432 for heating are disposed. Further, a fixing paper discharge roller pair 435 for conveying the recording paper 32 from the fixing roller 433 and a fixing paper discharge sensor 436 for detecting the conveyance state from the fixing unit are provided.

  Each scanner unit 420 includes a laser unit 421, a polygon mirror 422 for scanning the laser light from each laser unit 421 onto each photosensitive drum 305, a scanner motor 423, and an imaging lens group 424. Here, the laser light emitted from the laser unit 421 is modulated based on each image signal sent from the video controller 440.

  Each process cartridge 410 includes a photosensitive drum 305, a charging roller 303 and a developing roller 302, and a toner storage container 411 necessary for a known electrophotographic process. Each process cartridge 410 is configured to be detachable from the color laser printer 401.

  Further, upon receiving image data sent from an external device 441 such as a personal computer (host computer), the video controller 440 develops the image data into bitmap data and generates an image signal for image formation.

  Reference numeral 201 denotes a DC controller which is a control unit of the laser printer. A RAM 207a, a ROM 207b, a timer 207c, a digital input / output port 207d, an MPU (microcomputer) 207 having a D / A port 207e, various input / output control circuits (not shown), and the like.

  Reference numeral 202 denotes a high voltage power supply unit (high voltage power supply device). The high voltage power supply 202 outputs a charging high voltage power supply (not shown) corresponding to each process cartridge 410 (Y, M, C, BK), a development high voltage power supply (not shown), and a high voltage corresponding to each transfer roller 430. It consists of a transfer high-voltage power supply using a possible piezoelectric transformer.

  In this embodiment, the transfer high-voltage power supply will be described below as an example. Similarly, in the charging high-voltage power supply and the development high-voltage power supply, the mutual interference of the piezoelectric transformer occurs and an unacceptable voltage fluctuation occurs in the high-voltage bias voltage. As a result, the image quality may be degraded.

  Next, an outline of a method for assembling the high-voltage power supply device 202 to the image forming apparatus will be described with reference to FIG.

  The frame sheet metal 501 (metal sheet metal) and the high-voltage power supply circuit board 100 (power supply board) of the image forming apparatus are arranged substantially in parallel so that the component surfaces face each other. As the high voltage power supply circuit board 100 is assembled, a high voltage output contact (not shown) on the high voltage power supply circuit board 100 is connected to a contact (not shown) on the image forming apparatus main body side. In general, the distance between the surface of the high-voltage power supply circuit board 100 (power supply board surface) and the surface of the frame sheet metal 501 (metal sheet metal surface) is arranged at a position within 100 mm. In the figure, 500 is an exterior cover, 351, 121, 141, 161 are piezoelectric transformers, and 120, 140 are bending raising portions described later.

  Next, the configuration of the high-voltage power supply device 202 of this embodiment will be described with reference to FIGS. Since the configuration of the high-voltage power supply is common to all output circuits of the charging high-voltage power supply, the development high-voltage power supply, and the transfer high-voltage power supply, only the transfer high-voltage power supply will be described here. Further, although the transfer high-voltage power supply corresponds to each transfer roller 430Y, 430M, 430C, and 430BK and is provided with four circuits, the circuit configuration is the same for each circuit, and therefore, only one circuit is shown in FIG.

  FIG. 3 is a block diagram showing a typical circuit configuration of the high-voltage power supply device 202 using a piezoelectric transformer. Reference numeral 351 denotes a piezoelectric ceramic transformer (hereinafter referred to as “piezoelectric transformer”) (first piezoelectric transformer) of a high voltage power source. The output of the piezoelectric transformer 351 is rectified and smoothed to a positive voltage by the diodes 359 and 370 and the high voltage capacitor 371 and supplied from the output terminal 364 to the transfer roller 430 as a load.

  The output voltage is divided by resistors 372 and 373 and input to the non-inverting input terminal (+ terminal) of the operational amplifier 376 via the protective resistor 374. On the other hand, a high-voltage power supply control signal (Vcont), which is an analog signal, is input from the connection terminal 360 to the inverting input terminal (−terminal) of the operational amplifier via the series resistor 375.

  The output terminal of the operational amplifier 376 is connected to a voltage controlled oscillator (VCO) 366. The voltage controlled oscillator (VCO) 366 can generate a signal corresponding to the drive frequency (first drive frequency) for driving the piezoelectric transformer 351 in accordance with the control signal (Vcont). The output terminal of the voltage controlled oscillator (VCO) 366 is connected to the gate of the field effect transistor 367. The drain of the field effect transistor 367 is connected to a power supply (+24 V: Vcc) via an inductor 368 and is also connected to one (352) of the primary side electrode of the piezoelectric transformer 351. The other primary side electrode (353) is grounded. The source of the field effect transistor 367 is also grounded. 354 is a secondary output terminal of the piezoelectric transformer 351, 361 is a control circuit, 362 is a drive circuit, 363 is a rectifier circuit, 365 is a high voltage output detection circuit, and 377 is a capacitor.

FIG. 4 is a diagram showing the relationship between the output voltage (V) and the drive frequency (Hz) as the characteristics of the piezoelectric transformer 351. In general, the piezoelectric transformer 351 has a maximum output voltage (Emax) at a resonance frequency f ₀ as shown in FIG. In the driving frequency f _x, nominal output voltage (hereinafter also referred to as "control output voltage") to the Edc. Resonance frequency (hereinafter, also referred to as "maximum frequency") around the f _0, the distribution of the output voltage (V) is the distribution shape of the flared. The output voltage can be controlled by changing the driving frequency. For example, when the output voltage of the piezoelectric transformer 351 is increased, it is possible to change the drive frequency from the higher side toward the resonance frequency f ₀ toward the lower side. Thereafter, although a description is given of a case of performing control at a frequency higher than the resonance frequency f ₀ side, concept may perform control at a lower side frequency is the same.

  The voltage controlled oscillator (VCO) 366 of FIG. 3 operates to increase the output frequency when the input voltage increases and to decrease the output frequency when the input voltage decreases. When the control output voltage (Edc) of the piezoelectric transformer 351 increases, the input voltage Vsns of the non-inverting input terminal (+ terminal) of the operational amplifier 376 also increases via the resistor 372, and the voltage of the output terminal of the operational amplifier 376 increases.

Since the input voltage of the voltage controlled oscillator (VCO) 366 increases, the output frequency of the voltage controlled oscillator (VCO) 366 also increases, and the drive frequency of the piezoelectric transformer 351 also increases. Therefore, the piezoelectric transformer 351 is driven at a higher frequency than the driving frequency _{f x.} Since the driving frequency f _x increases the output voltage of the piezoelectric transformer 351 decreases, the output voltage is controlled to decrease direction. That is, the configuration of FIG. 3 constitutes a negative feedback control circuit. In the color laser printer, four circuit configurations as shown in FIG. 3 are provided in the high-voltage power supply device 202 as four high-voltage circuits corresponding to Y, M, C, and BK.

  The output voltage is controlled to a constant voltage by a voltage controlled oscillator (VCO) 366 so as to be equal to the voltage determined by the voltage of the control signal (Vcont) from the DC controller 201 input to the inverting input terminal (− terminal) of the operational amplifier 376. Is done.

  Next, a configuration for suppressing interference between drive frequencies generated when a plurality of systems of piezoelectric transformers in the high-voltage power supply device 202 are driven at the same timing will be described with reference to FIGS.

  Since the piezoelectric transformer is smaller in size than the winding transformer, the piezoelectric transformer is advantageous in reducing the size of the high-voltage power supply device 202. In the high-voltage power supply device 202 of the present embodiment, as shown in FIG. 5, an image forming apparatus grounded to GND (ground potential) between a piezoelectric transformer 351 and a piezoelectric transformer 121 (second piezoelectric transformer) arranged in close proximity. A part 120 of the frame metal plate 501 is bent and arranged. That is, it is comprised integrally with a single sheet metal. In this way, further miniaturization is realized.

  A part 120 (a part of the sheet metal) of the frame sheet metal 501 (hereinafter also referred to as a bending raised part 120) functions as an interference suppression unit that suppresses the interference of the drive frequencies between the plurality of piezoelectric transformers 351 and 121 arranged in proximity to each other. To do.

  In the image forming operation of the color laser printer 401, four high-voltage circuits corresponding to yellow (Y), magenta (M), cyan (C), and black (BK) operate at close timing. Further, in order to reduce the size of the high-voltage power supply device 202, when a piezoelectric transformer having a similar driving frequency of the piezoelectric transformer is disposed close to each other, the circuits that drive the piezoelectric transformer interfere with each other. The interference frequency is a difference in drive frequency between the piezoelectric transformers, and is given as an absolute value of the difference in drive frequency corresponding to the control output voltage (Edc), for example.

  FIG. 6 exemplarily shows a state in which the piezoelectric transformers 351 and 121 arranged close to each other interfere with each other. FIG. 6 is a diagram showing a state in which the piezoelectric transformers 351 and 121 mounted on the high-voltage power supply circuit board 100 are viewed from the side, 354 indicates a secondary output terminal of the piezoelectric transformer 351, and 124 indicates a second output of the piezoelectric transformer 121. The next output terminal shall be indicated. Moreover, the broken line arrow in FIG. 6 shall represent an electric force line. When both the piezoelectric transformer 351 and the piezoelectric transformer 121 operate, a frequency corresponding to the difference between the driving frequency of the piezoelectric transformer 351 and the driving frequency of the piezoelectric transformer 121 (second driving frequency) is also superimposed on the piezoelectric transformer 121. The electric lines of force extend from the piezoelectric transformer 351 to the piezoelectric transformer 121.

  When piezoelectric transformers of the same size are used, the resonance frequencies are almost the same, and the drive frequencies are also close to each other. Therefore, the frequency (interference frequency) due to the difference between the two drive frequencies becomes a ripple having a relatively low frequency (several tens to several hundreds Hz). Such a low frequency is not rectified even if a rectifier circuit is provided, resulting in output voltage ripple. Since this ripple is as small as several volts with respect to an output voltage of several kilovolts, it is difficult to suppress it by control.

  However, this low frequency tends to be a banding frequency that is visible, for example, causes image formation in which gradation is striped, so that it is necessary to suppress this ripple to a level that cannot be discriminated on the image. Therefore, as shown in FIG. 7A, the bending raised portion 120 of the frame metal plate 501 of the image forming apparatus grounded to GND is arranged to suppress the interference of the driving frequency.

  As described above, the component mounting surface of the high-voltage power supply circuit board 100 faces the frame sheet metal 501 of the image forming apparatus. That is, the piezoelectric transformers 351 and 121 are also arranged to face the frame sheet metal 501. In this embodiment, a part of the frame metal plate 501 that is between and opposite to the piezoelectric transformer 351 and the piezoelectric transformer 121 is bent and disposed between the piezoelectric transformer 351 and the piezoelectric transformer 121. It is preferable to secure a spatial distance of at least 1 mm so that the tip of the bent raised portion 120 does not come into contact with the surface of the high-voltage power circuit board 100. The reason for this is to avoid damaging the surface of the high-voltage power supply circuit board 100 with the bent-up portion 120, and the high-voltage voltage leaks to the bent-up portion 120 having the GND potential, although it depends on the output voltage of the high-voltage power supply circuit. This is to avoid this.

  FIG. 8 shows the positional relationship between the piezoelectric transformer 351 and the piezoelectric transformer 121 and the bending raised portion 120 of FIG. In the figure, the bending raised portions 120 and 140 of the frame metal plate 501 are used as interference suppression means in four high voltage power supply circuits corresponding to yellow (Y), magenta (M), cyan (C), and black (BK). A configuration example is shown. The bend raising portions 120 and 140 are not limited to mounting at the positions shown in FIG. 8, and may be further mounted between the piezoelectric transformer 121 and the piezoelectric transformer 141. In the piezoelectric transformer 351, 352 is a GND terminal, 353 is a primary input terminal, 354 is a secondary output terminal, and in the piezoelectric transformer 121, 122 is a GND terminal, and 123 is a primary input terminal. , 124 are secondary output terminals. In the piezoelectric transformer 141, 142 is a GND terminal, 143 is a primary input terminal, 144 is a secondary output terminal, and in the piezoelectric transformer 161, 162 is a GND terminal and 163 is a primary input terminal. Reference numeral 164 denotes a secondary output terminal.

  As a first system (first power supply circuit), a high-voltage power supply control signal (Vcont1) (first control signal) is input from the DC controller 201 to the input connector 110. Based on the control signal (Vcont1), the control circuit 111, the drive circuit 112, the rectifier circuit 113, and the high voltage output detection circuit 115, which are circuit configurations for driving the piezoelectric transformer 351, are driven, and a high voltage is output from the output connector 114. It is configured to be.

  As a second system (second power supply circuit), a high-voltage power supply control signal (Vcont2) (second control signal) is input from the DC controller 201 to the input connector 130. Based on the control signal (Vcont2), the control circuit 131, the drive circuit 132, the rectifier circuit 133, and the high voltage output detection circuit 135, which are circuit configurations for driving the piezoelectric transformer 121, are driven, and a high voltage is output from the output connector 134. It is configured to be.

  As a third system (first power supply circuit), a control signal (Vcont3) of a high voltage power supply is input from the DC controller 201 to the input connector 150. Based on the control signal (Vcont3), the control circuit 151, the drive circuit 152, the rectifier circuit 153, and the high voltage output detection circuit 155, which are circuit configurations for driving the piezoelectric transformer 141, are driven, and a high voltage is output from the output connector 154. It is configured to be.

  Then, as a fourth system (second power supply circuit), a high-voltage power supply control signal (Vcont4) is input from the DC controller 201 to the input connector 170. Based on the control signal (Vcont4), a control circuit 171, a drive circuit 172, a rectifier circuit 173, and a high voltage output detection circuit 175, which are circuit configurations for driving the piezoelectric transformer 161, are driven, and a high voltage is output from the output connector 174. It is configured to be.

  Next, an effect of suppressing interference between piezoelectric transformers when the bending raising portion 120 is disposed will be described.

  An electric field is generated between the piezoelectric transformer 351 and the bend raising part 120 to reduce the interference state of the drive frequency (suppress the generation of the interference frequency). Thereby, it is possible to suppress the drive frequency of the piezoelectric transformer 351 from directly interfering with the drive frequency of the piezoelectric transformer 121. By reducing the lines of electric force reaching the piezoelectric transformer 121 from the piezoelectric transformer 351 and suppressing the generation of ripples, interference of the driving frequency is suppressed. By suppressing the interference of the driving frequency, a circuit arrangement in which the piezoelectric transformer 351 and the piezoelectric transformer 121 are close to each other is possible, and the high-voltage power supply device 202 can be further downsized.

  FIG. 7B is a diagram exemplarily showing a comparison of output voltages of the piezoelectric transformer 121. The output voltage 602 of the piezoelectric transformer 121 when the bending raising portion 120 is provided (FIG. 7A) is higher than the output voltage 601 when there is no bending raising portion 120 (FIG. 6). Is reduced by the amount suppressed.

  In the case where the piezoelectric transformers 351 and 121 are driven at the same timing in the proximity of each other, the mutual piezoelectric transformer driving frequency affects each other and causes interference, thereby causing an interference with the output voltage of the piezoelectric transformer 121. The ripple voltage of the interference frequency appears. Here, the electrostatic capacitance between the piezoelectric transformers is called stray capacitance.

  FIG. 9A is a diagram for exemplarily explaining the influence of electrostatic noise (electric field lines: broken line arrows) of the piezoelectric transformer, assuming that the stray capacitance between the piezoelectric transformers is 703 and 704. Here, the electric lines of force are approximately considered as an electric field generated in a capacitor having a minute capacitance.

  For simplicity, the case where only the piezoelectric transformer 351 is operating will be described. In FIG. 9B, 701 shows an example of the output voltage waveform of the piezoelectric transformer 351. The cause of the low-frequency ripple generated in the piezoelectric transformer 121 is due to the operation of the piezoelectric transformer 351, and suppressing this influence leads to suppressing ripple generation. In general, a piezoelectric transformer has an oscillation frequency higher than that of a winding transformer, and impedance 1 / ωC due to stray capacitances 703 and 704 is reduced. As a result, the voltage 702 superimposed on the piezoelectric transformer 121 becomes larger than that of the winding transformer.

  FIG. 10A is a diagram illustrating a state in which a part 120 of the frame metal plate 501 of the image forming apparatus grounded to GND is bent and disposed between the piezoelectric transformer 351 and the piezoelectric transformer 121. The influence of the piezoelectric transformer 351 on the piezoelectric transformer 121 through the stray capacitance 703 can be suppressed by providing the bending raising portion 120 connected to the GND. By suppressing the influence of the stray capacitance 703, the amplitude of the voltage 710 superimposed on the piezoelectric transformer 121 is higher than the voltage 702 superimposed on the piezoelectric transformer 121 shown in FIG. 9B, as shown in FIG. Is smaller.

  A stray capacitance 705 is newly generated between the piezoelectric transformer 351 and the bend raising part 120, but the bend raising part 120 has a stable potential (GND) in a direct current. For this reason, the influence of the stray capacitance 706 newly generated between the bending raised portion 120 and the piezoelectric transformer 121 is so small that it can be ignored. For this reason, it can be considered that the piezoelectric transformer 351 affects the piezoelectric transformer 121 only through the stray capacitance 705.

  By disposing the bending raising portion 120, the impedance from the piezoelectric transformer 351 to the piezoelectric transformer 121 becomes larger than when the bending raising portion 120 is not provided. The amplitude of the voltage 710 superimposed on the piezoelectric transformer 121 is smaller than the amplitude of the voltage 702 superimposed on the piezoelectric transformer 121 shown in FIG. That is, the influence of the voltage superimposed on the piezoelectric transformer 121 due to the influence of interference can be suppressed by the bending portion 120.

  FIG. 11 shows an outline of an operation checker for checking the operation of the high-voltage power supply circuit board 100. This checker is a check tool used in a manufacturing factory in order to confirm that the circuit operates normally after the high-voltage power supply circuit board 100 is mounted. A sheet metal 571 connected to GND corresponding to the frame sheet metal of the image forming apparatus and a sheet metal 572 corresponding to the bending raised part 120 are provided on the cover portion (checker cover) 576 of the checker. The checker base 575 is provided so as to have substantially the same positional relationship as when the high-voltage power supply circuit board 100 (high-voltage PCB) is assembled to the image forming apparatus. By checking the high-voltage power supply circuit in such a state, it is possible to check the operation under the same conditions as when assembled in an actual image forming apparatus.

  As described above, the bending raised portions 120 and 140 of the frame metal plate 501 are used as interference suppression means. By doing in this way, it becomes possible to suppress that the drive frequency of the piezoelectric transformer 351, the piezoelectric transformer 121, the piezoelectric transformer 141, and the piezoelectric transformer 161 which are arrange | positioned adjacently interferes. Accordingly, the piezoelectric transformer 351 and the piezoelectric transformer 121, and the piezoelectric transformer 141 and the piezoelectric transformer 161 can be disposed closer to each other than the conventional high-voltage power supply device 1202 of FIG. It becomes possible to plan.

  In the present embodiment, an example in which a part of the main body frame is bent and raised to reduce interference between the drive frequencies of the piezoelectric transformers as an interference suppressing means has been described. However, another conductive member having the same shape as the bent raised portion. Even if attached, the same effect as in this embodiment can be obtained. In other words, another metal plate or a highly conductive mold member may be electrically connected to the main body frame portion facing between the piezoelectric transformers to substitute for the bending raising portion.

  Further, in this embodiment, the description of the image forming apparatus is described by taking a tandem color image forming apparatus as an example, but the high voltage power supply device according to the present invention is applied to any image forming apparatus using a high voltage bias. It is possible.

  Furthermore, the image forming apparatus 401 according to the present exemplary embodiment includes a high-voltage power supply apparatus 202 and an image forming unit that forms toner images of different colors. That is, a yellow (Y) image forming section (first image forming section), a magenta (M) image forming section (second image forming section), a cyan (C) image forming section, and a black (BK) image forming section. A part. These image forming units can form a toner image using the voltage supplied from the high voltage power supply device 202.

  Next, Embodiment 2 of the present invention will be described with reference to FIG. In this embodiment, a cover (non-conductive member) made of an insulating member is provided on the bent raised portion 120 of the frame metal plate 501 of the image forming apparatus as interference suppression means.

  In FIG. 12A, reference numeral 555 denotes a cover material having an insulating property such as a molding material provided in the bent raised portion 120 of the frame metal plate 501 of the image forming apparatus (hereinafter referred to as a cover 555). By providing the bend raising part 120 of the GND potential between the piezoelectric transformer 351 and the piezoelectric transformer 121, the distance between the piezoelectric transformer 351 and the piezoelectric transformer 121 can be shortened more than ever and the size can be reduced. However, on the other hand, there is a growing concern about voltage leakage from the secondary side (high voltage portion) of the high-voltage power supply circuit board 100 to the bending-raising portion 120 of the GND potential. Further, when the high-voltage power supply circuit board 100 is assembled to the image forming apparatus, there is a possibility that the tip of the bent raised portion 120 may be accidentally interfered with the piezoelectric transformer 351 or the piezoelectric transformer 121 and damaged.

  Therefore, in order to solve these problems, the cover 555 is provided on the bent-up portion 120. Therefore, the cover 555 is made of a material having a thickness and an insulating property corresponding to the high voltage so that the high voltage output from the high voltage power circuit board 100 does not leak through the cover 555 to the bent raised portion 120. There is a need to. Further, when assembling the high-voltage power circuit board 100 to the image forming apparatus, a substrate guide member (not shown) at the time of assembly is installed so that the tip of the bent raised portion 120 does not interfere with the components on the high-voltage power circuit board 100. ) If necessary. At the same time, in order to alleviate the problem even if interference occurs, a component such as a piezoelectric transformer can be protected from the bent-up portion 120 by the cover 555.

  FIG. 12B shows an example in which a claw-like protrusion is provided at the tip of the cover 555 described in FIG. 12A and also has a function of holding the high-voltage power supply circuit board 100. As shown in the figure, a through hole is provided in the surface of the high-voltage power circuit board 100 facing the tip (substrate holding means) of a cover 556 (hereinafter simply referred to as a cover 556) provided with a claw-like projection. Then, with the assembly of the high-voltage power circuit board 100, the tip of the cover 556 is passed through the high-voltage power circuit board 100, and the claws of the cover 556 are hooked on the solder surface side of the high-voltage power circuit board 100 to hold the high-voltage power circuit board 100. can do.

  As described above, since the first embodiment and the bending raising portion 120 are the same, it is possible to similarly suppress interference between the piezoelectric transformers. In addition, by providing an insulating cover 555 to the bending raised portion 120 that is a means for suppressing interference between the piezoelectric transformers, a margin for leakage of high voltage is increased, and peripheral components are protected during assembly and the high voltage power circuit board is held. Have both. Thereby, it becomes possible to arrange | position the distance between piezoelectric transformers closer than Example 1, and further size reduction and holding | maintenance of a high voltage power supply circuit board can be implement | achieved.

  Next, Embodiment 3 of the present invention will be described with reference to FIG. The present embodiment is characterized by the shape of the bent-up portion 120 which is a part of the frame metal plate 501 of the image forming apparatus as the interference suppressing means.

  In the frame metal plate 501 in FIG. 13A, a diaphragm 557 (drawing portion) is provided at a position facing the piezoelectric transformer 351 and the piezoelectric transformer 121 in a direction avoiding the piezoelectric transformers 351 and 121. Here, 557a is a diaphragm for the piezoelectric transformer 351, and 557b is a diaphragm for the piezoelectric transformer 121. As shown in this figure, when the piezoelectric transformers 351 and 121 are the tallest components on the high-voltage power supply circuit board 100, the following can be performed. That is, the high voltage power supply circuit board 100 can be disposed close to the main body frame as a whole by moving away the frame sheet metal 501 of the piezoelectric transformers 351 and 121. That is, the left side surface in FIG. 2 can be moved to the right by several mm by the diaphragm 557, that is, the lateral width of the apparatus can be reduced.

  A sheet metal 580 is provided between the piezoelectric transformer 351 and the piezoelectric transformer 121 as interference suppression means. Here, unlike the embodiment described above, the sheet metal 580 is not a part (120) of the frame sheet metal 501 of the main body, but is a GND potential metal sheet electrically connected to the frame sheet metal 501. That is, the frame sheet metal 501 and the sheet metal 580 (a plurality of sheet metals) are integrally configured. In this embodiment, the frame sheet metal 501 is narrowed down, and therefore it is difficult to realize bending of the sheet metal from that part in terms of manufacturing dimensions.

  Further, in FIG. 13B, a sheet metal (that is, a bending raised portion) 120 bent and raised from the frame sheet metal 501 is disposed between the piezoelectric transformer 351 and the piezoelectric transformer 121 as an interference suppressing unit. The feature of this embodiment is that the ends of the piezoelectric transformer 351 and the piezoelectric transformer 121 are arranged in the holes of the frame metal plate 501 that are created when the frame metal plate 501 is bent. That is, the tip of the piezoelectric transformer 351 is disposed in the hole 558a of the frame metal plate 501 made when the metal plate 1201 is bent from the frame metal plate 501, and the tip of the piezoelectric transformer 121 is inserted in the hole 558b made when the metal plate 120b is bent and raised. Place. As described above, when the piezoelectric transformers 351 and 121 are the tallest components on the high-voltage power supply circuit board 100, the tip portions of the piezoelectric transformers 351 and 121 are arranged so as to pass through the frame metal plate 501. Thereby, the high-voltage power supply circuit board 100 can be disposed close to the main body frame as a whole. However, since there is no sheet metal at the GND potential above the piezoelectric transformer 351 and the piezoelectric transformer 121, the effect of suppressing mutual interference between the piezoelectric transformers 351 and 121 is slightly reduced.

  Further, in either case of FIG. 13 (a) or FIG. 13 (b), the cover material as described in the second embodiment is used so that there is no concern about high voltage leakage or component interference during assembly. (555, 556) must be used. Furthermore, it is necessary to consider the margin of dimensional tolerance on mechanical arrangement, assembling ability, and the like.

  As described above, by devising the shape of the frame sheet metal facing the piezoelectric transformer, the high-voltage power supply circuit board can be arranged closer to the main body frame side, and the device can be further reduced in the lateral width direction.

  Next, an embodiment of the present invention will be described with reference to FIGS. The present embodiment is characterized in that a part of the frame metal plate 501 or the shield metal plate 502 of the image forming apparatus is disposed so as to penetrate the high-voltage power supply circuit board 100 as the interference suppressing means.

  As shown in FIG. 14, a through hole 560 is provided on the surface of the high-voltage power circuit board 100 facing the part 120 bent and raised from the frame metal plate 501 at a position between the piezoelectric transformer 351 and the piezoelectric transformer 121. Then, along with the assembly of the high-voltage power supply circuit board 100, the bent raised portion 120 is penetrated through the high-voltage power supply circuit board 100. With such a configuration, as shown in FIG. 15, the electric lines of force from the piezoelectric transformer 351 to the piezoelectric transformer 121 are also generated at the tip of the GND voltage bending raising portion 120 on the solder surface of the high-voltage power supply circuit board 100. It is suppressed. For this reason, the influence of the piezoelectric transformer interference can be further reduced as compared with the first embodiment. In addition, since the bent portion 120 is configured to penetrate the high-voltage power supply circuit board 100, when the high-voltage power supply circuit board 100 is assembled, the high-voltage power supply circuit board 100 can be temporarily held in the image forming apparatus before screwing.

  FIG. 16 shows that a part 590 of the shield metal plate 502 provided between the high-voltage power circuit board 100 and the outer cover 500 is placed between the piezoelectric transformer 351 and the piezoelectric transformer 121 from the solder surface side of the high-voltage power circuit board 100. An example of penetrating arrangement is shown.

  In general, the shield metal plate 502 is disposed between the high-voltage power circuit board 100 and the exterior cover 500 mainly for reducing radiation noise, and is electrically connected to the GND potential. Although it is rare that the shield sheet metal 502 is used between the high-voltage power circuit board 100 and the exterior cover 500, it will be introduced as an embodiment of the present invention.

  A through hole 560 is provided on the surface of the high-voltage power supply circuit board 100 facing a portion 590 bent and raised from the shield metal plate 502 (hereinafter referred to as a bent raised portion 590) at a position between the piezoelectric transformer 351 and the piezoelectric transformer 121. deep. Then, the bent portion 590 is penetrated through the high-voltage power supply circuit board 100 together with the assembly of the shield metal plate 502. With such a configuration, the space between the piezoelectric transformer 351 and the piezoelectric transformer 121 is firmly surrounded by the GND of the frame metal plate 501, the shield metal plate 502, and the bending raised portion 590. For this reason, the influence of piezoelectric transformer interference can be further reduced as compared with the configuration shown in FIG.

  Further, in either case of FIG. 14 and FIG. 16, the cover material (555, 556) as described in the second embodiment is used so that there is no fear of high voltage leakage or component interference during assembly. It is necessary to consider the use, the margin of dimensional tolerance on mechanical arrangement, assembling, etc.

  As described above, the interference between the drive frequency of the piezoelectric transformer 351 and the piezoelectric transformer 121 can be further suppressed by arranging the bending raising portion 590 that is an interference suppressing means so as to penetrate the high-voltage power circuit board 100. .

  Next, Embodiment 5 of the present invention will be described with reference to FIGS. The present embodiment is characterized by a difference in the mounting direction of the high-voltage power supply to the image forming apparatus.

  FIG. 17 is a view for explaining the arrangement of the frame metal plate 501 and the high-voltage power supply circuit board 100 of the image forming apparatus as viewed from the direction of the arrow A in FIG.

  As shown in the figure (unlike FIG. 2), the frame sheet metal 501 of the image forming apparatus and the solder surface of the high-voltage power supply circuit board 100 are arranged to face each other. As the high voltage power circuit board 100 is assembled, a high voltage output contact (not shown) provided on the solder surface on the high voltage power circuit board 100 is connected to a contact (not shown) on the image forming apparatus main body side. It has a configuration.

  As shown in FIG. 18, a through hole 560 is provided on the surface of the high-voltage power circuit board 100 facing the part 120 bent and raised from the frame metal plate 501 at a position between the piezoelectric transformer 351 and the piezoelectric transformer 121. Then, along with the assembly of the high-voltage power supply circuit board 100, the bent raised portion 120 is penetrated through the high-voltage power supply circuit board 100. With such a configuration, the interference suppression member (bending portion 120) is disposed between the transformers on both the component surface and the solder surface of the high-voltage power supply circuit board 100. The same effect can be obtained. Further, since the bent raised portion 120 is configured to penetrate the high-voltage power supply circuit board 100, when the high-voltage power supply circuit board 100 is assembled, the high-voltage power supply circuit board 100 can be temporarily held in the image forming apparatus before screwing.

  In FIG. 19, a part 590 of the shield sheet metal 502 provided between the high-voltage power circuit board 100 and the outer cover 500 is arranged on the component surface of the high-voltage power circuit board 100 at a position between the piezoelectric transformer 351 and the piezoelectric transformer 121. An example is shown.

  With this configuration, the space between the piezoelectric transformer 351 and the piezoelectric transformer 121 is firmly surrounded by the GND of the frame metal plate 501, the shield metal plate 502, and the bending raised portion 590, so that the piezoelectric transformer is almost equivalent to the configuration shown in FIG. 16. The influence of transformer interference can be reduced.

  Further, in either case of FIG. 18 or FIG. 19, the cover material (555, 556) as described in the second embodiment is used so that there is no fear of high voltage leakage or component interference during assembly. It is necessary to consider the use, the margin of dimensional tolerance on mechanical arrangement, assembling, etc.

  As described above, the piezoelectric transformer 351 and the piezoelectric transformer 121 can be driven by disposing the bending raising portion 120 serving as the interference suppression unit between the piezoelectric transformers even when the assembly direction of the high-voltage power source to the image forming apparatus is different. Interference with the frequency can be suppressed.

1 is a diagram illustrating a configuration of an image forming apparatus including a high-voltage power supply device using a piezoelectric transformer according to Embodiment 1 of the present invention. Schematic which shows arrangement | positioning of the high voltage power supply circuit board based on Example 1 of this invention. 1 is a block diagram showing a typical circuit configuration of a high-voltage power supply circuit using a piezoelectric transformer according to Embodiment 1 of the present invention. The figure which shows the characteristic of the output voltage (V) and drive frequency (Hz) of the piezoelectric transformer which concerns on Example 1 of this invention. The figure which looked at the piezoelectric transformer and bending raising part mounted in the high voltage power supply circuit board based on Example 1 of this invention from the side surface The figure explaining illustratively the influence of the electrostatic noise (electric force line of force) between the piezoelectric transformers concerning Example 1 of the present invention. (A) The figure explaining the effect of the bending raising part which concerns on Example 1 of this invention exemplarily, (b) The figure which shows the comparison of the output voltage of the piezoelectric transformer 121 exemplarily The figure which shows the positional relationship of the bending raising part and high voltage power supply circuit which concern on Example 1 of this invention. (A) The figure explaining illustratively the stray capacitance between the piezoelectric transformers concerning Example 1 of the present invention, (b) The figure showing the output voltage waveform of a piezoelectric transformer illustratively (A) The figure explaining the effect of the bending raising part which concerns on Example 1 of this invention exemplarily, (b) The figure which shows the output voltage waveform of a piezoelectric transformer exemplarily Schematic of the operation checker for the high-voltage power circuit board according to the first embodiment of the present invention. (A) Drawing which looked at the bending raising part provided with the piezoelectric transformer mounted in the high voltage power supply circuit board based on Example 2 of this invention, and the cover which has insulation, from the side, (b) Nail-like at the front-end | tip of a cover The figure which shows the example which provided the projection of (A) The figure which looked at the piezoelectric transformer and the bending raising part mounted in the high voltage power supply circuit board at the time of providing the aperture_diaphragm | restriction concerning Example 3 of this invention from the side, (b) The penetration which concerns on Example 3 of this invention A side view of the piezoelectric transformer mounted on the high-voltage power circuit board and the bent raised part when the hole is provided The figure which looked at the state which made the high voltage power circuit board penetrate the piezoelectric transformer and bending raising part which were mounted in the high voltage power circuit board concerning Example 4 of the present invention from the side The figure explaining illustratively the effect of the bending raising part concerning Example 4 of the present invention. The figure which looked at the state which penetrated a part of piezoelectric transformer and shield sheet metal which were mounted in the high voltage power circuit board concerning Example 4 of the present invention from the solder side of a high voltage power circuit board from the side. Schematic which shows arrangement | positioning of the high voltage power supply circuit board based on Example 5 of this invention. The figure which looked at the state which penetrated the piezoelectric transformer and bending raising part mounted in the high voltage power supply circuit board based on Example 5 of this invention to the high voltage power supply circuit board from the side. The figure which looked at the state which has arrange | positioned from the component surface side of the high voltage power supply circuit board the piezoelectric transformer and the shield sheet metal which were mounted in the high voltage power supply circuit board which concerns on Example 5 of this invention. Schematic illustrating the configuration of a conventional high-voltage power circuit board

Explanation of symbols

100 High voltage power circuit board (power board)
120, 140, 560 Bending part 121 Piezoelectric transformer (second piezoelectric transformer)
141 Piezoelectric transformer (first piezoelectric transformer)
161 Piezoelectric transformer (second piezoelectric transformer)
351 Piezoelectric transformer (first piezoelectric transformer)
201 DC Controller 202 High Voltage Power Supply Device 359 Diode 366 Voltage Control Oscillator 367 Field Effect Transistor 401 Color Laser Printer (Image Forming Apparatus)
500 Exterior cover 501 Frame sheet metal (metal sheet metal)
502 Shield sheet metal (metal sheet metal)
555 cover (non-conductive member)
556 Cover (non-conductive member)
557a Drawing (drawing part)
557b Drawing (drawing part)
558a hole (through hole)
558b hole (through hole)
575 Circuit operation checker stand 576 Circuit operation checker cover

Claims (12)

A first drive frequency for driving the first piezoelectric transformer is generated based on a first control signal for forming an image, and a voltage generated by driving the first piezoelectric transformer is supplied to the first image forming unit. A first power supply circuit,
A second drive frequency for driving the second piezoelectric transformer is generated based on a second control signal for forming the image, and a voltage generated by driving the second piezoelectric transformer is generated in the second image forming unit. A second power supply circuit to supply;
A power supply board on which at least the first power supply circuit and the second power supply circuit are mounted;
A metal sheet provided to face the power supply substrate and connected to a ground potential;
An image forming apparatus comprising:
The metal sheet metal is integrally formed of a single sheet metal or a plurality of sheet metals, and the sheet metal holds the power supply substrate with respect to the image forming apparatus main body, and at least a part of the sheet metal is connected to the first piezoelectric transformer. An image forming apparatus disposed between the second piezoelectric transformers. The image forming apparatus according to claim 1,
The image forming apparatus, wherein the metal sheet metal is a frame sheet metal forming the image forming apparatus main body. The image forming apparatus according to claim 1,
The image forming apparatus, wherein the metal sheet metal is a shield sheet metal provided to reduce radiation noise from the image forming apparatus. The image forming apparatus according to claim 1,
The metal sheet metal is opposed to the power supply board in parallel with a component surface or a solder surface, and the distance from the power supply board surface to the metal sheet metal surface is disposed at a position within 100 mm. apparatus. The image forming apparatus according to claim 1,
The metal sheet metal has a drawing unit for securing a distance from a part of a component mounted on the power supply board when the power supply board is held with respect to the image forming apparatus main body. An image forming apparatus, wherein the image forming apparatus is arranged close to a substrate surface. The image forming apparatus according to claim 1,
The metal sheet metal has a through hole for securing a distance from a part of a component mounted on the power supply board when the power supply board is held with respect to the image forming apparatus main body, and the power supply board An image forming apparatus, wherein the image forming apparatus is arranged close to a surface. The image forming apparatus according to claim 1,
A part of the sheet metal is formed by bending a part of the metal sheet metal, and at least a part of the sheet metal is held by the first piezoelectric transformer by holding the power supply substrate with respect to the image forming apparatus main body. And an image forming apparatus arranged between the second piezoelectric transformer and the second piezoelectric transformer. The image forming apparatus according to claim 1,
A part of the sheet metal is a conductive member integrally attached to the metal sheet metal, and at least a part of the conductive member is held by holding the power supply substrate with respect to the image forming apparatus main body. An image forming apparatus arranged between the first piezoelectric transformer and the second piezoelectric transformer. The image forming apparatus according to claim 1,
A part of the sheet metal holds the power supply substrate against the image forming apparatus main body, so that a part of the sheet metal penetrates a hole provided in the power supply substrate, and at least a part of the sheet metal is the first metal plate. An image forming apparatus disposed between a piezoelectric transformer and the second piezoelectric transformer. The image forming apparatus according to claim 1,
An image forming apparatus comprising a non-conductive member that covers a part of the sheet metal. The image forming apparatus according to claim 10.
The non-conductive member has a substrate holding means at the tip thereof,
The image forming apparatus, wherein the substrate holding unit holds the power supply substrate with respect to the image forming apparatus main body. The image forming apparatus according to claim 1,
The image forming apparatus according to claim 1, wherein the first power supply circuit and the second power supply circuit are high voltage power supply circuits that respectively output a high voltage used for electrophotographic image formation.

Images