JP6882906B2 - Printed circuit board, power supply and image forming equipment - Google Patents

Description

The present invention relates to a printed circuit board, a power supply device, and an image forming device.

The electrophotographic image forming apparatus has a power supply device that generates a charging voltage, a developing voltage, and a transfer voltage. These voltages are high voltages and are generated using a piezoelectric transformer. According to Patent Document 1, a piezoelectric transformer in which a flat plate-shaped piezoelectric ceramic is housed in a resin case and has a pin terminal protruding from the resin case has been proposed. According to Patent Document 2, a surface mount (SMT) type piezoelectric transformer is described.

Japanese Unexamined Patent Publication No. 2006-108332 Japanese Unexamined Patent Publication No. 2016-76577

In recent years, double-sided printed circuit boards have been developed that can mount a large number of electronic components on a single printed circuit board. When the resin case type piezoelectric transformer described in Patent Document 1 is mounted on the first surface of the double-sided printed circuit board, the component cannot be arranged in the vicinity of the land on the second surface side to which the pins are soldered. On the other hand, if it is a surface mount type piezoelectric transformer, it is mounted on the land on the first surface, so that the second surface can be effectively used. However, the electric field generated from the piezoelectric transformer affects the performance of the electronic component mounted on the second surface. Therefore, it is not possible to mount electronic components in all areas of the second surface. Therefore, an object of the present invention is to promote high density of electronic components on a printed circuit board on which electronic components can be mounted on both sides.

According to the present invention
A printed circuit board having a first mounting surface and a second mounting surface which is a surface opposite to the first mounting surface, and a piezoelectric transformer surface-mounted on the first mounting surface.
The piezoelectric transformer is
A piezoelectric material having an input electrode and an output electrode,
With the input electrode or a plurality of external electrodes conducting with the output electrode,
It has a frame substrate that is arranged so as to surround the side surface of the piezoelectric body and supports the piezoelectric body.
The second mounting surface has a projection region on which the piezoelectric body is projected.
In the projection region, from the first position where the end portion of the input electrode farther from the output electrode is projected onto the second mounting surface, among the end portions of the input electrode. There is a first region up to the second position where the end closer to the output electrode is projected onto the second mounting surface, and from the second position, the input electrode among the ends of the output electrode. There is a second region up to the third position where the far end is projected onto the second mounting surface , the electronic component is mounted in the first region, and the electronic component is mounted in the second region. A printed substrate is provided characterized in that it is not.

According to the present invention, it is possible to promote high density of electronic components on a printed circuit board on which electronic components can be mounted on both sides.

Top view of piezoelectric transformer AA sectional view of the piezoelectric transformer BB sectional view of piezoelectric transformer BB sectional view of piezoelectric transformer Side view of piezoelectric transformer Table showing the results of the heat cycle test Sectional view showing image forming apparatus Diagram showing engine controller and high voltage power supply Circuit diagram showing the booster circuit

Hereinafter, examples of the present invention will be described with reference to the drawings. It should be noted that the examples shown below are examples, and the technical scope of the present invention is not limited to them. Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the accompanying drawings.

<Example 1>
[Dioxyelectric transformer]
FIG. 1 is a plan view showing a surface mount type piezoelectric transformer PT. Surface mounting is also called SMT (Surface mount technology) and is a technology for mounting electronic components on the surface of a printed circuit board. In surface mounting, electronic components are mounted on a printed substrate using reflow. Surface mount electronic components are called SMDs (Surface Mount Devices). The piezoelectric body 100 is a rectangular parallelepiped having a substantially flat plate shape, and has six outer surfaces. In particular, of the two outer surfaces paired in the thickness direction, one outer surface is the lower surface facing the printed circuit board, and the other outer surface is formed with the first input electrode 101, the second input electrode 102, and the output electrode 103. It is the upper surface. The thickness direction refers to the normal direction of the upper surface and the lower surface. The frame substrate 104 is a frame-shaped member provided so as to surround the four side surfaces of the piezoelectric body 100. The frame substrate 104 is thicker than the piezoelectric body 100. That is, the piezoelectric body 100 is thinner than the frame substrate 104. A rectangular hole 105 is provided in the center of the frame substrate 104. The piezoelectric body 100 is housed in the hole 105. In a plan view, the area of the rectangular hole 105 is larger than the area of the piezoelectric body 100. That is, the length of the hole 105 in the lateral direction is longer than the length of the piezoelectric body 100 in the lateral direction, and the length of the hole 105 in the longitudinal direction is longer than the length of the piezoelectric body 100 in the longitudinal direction. Therefore, the four side surfaces of the piezoelectric body 100 do not come into contact with the inner side surfaces of the frame substrate 104. That is, with the piezoelectric body 100 arranged in the hole 105, an appropriate clearance (space) is secured between the outer peripheral surface of the piezoelectric body 100 and the inner peripheral surface of the hole 105. As described above, the size and shape of the hole 105 are such that the piezoelectric body 100 can be arranged in the hole 105. The holes 105 are formed by penetrating (opening) a flat plate-shaped substrate that serves as a frame substrate 104 in the thickness direction.

The frame substrate 104 has two longitudinal portions and two short portions. Substrate electrodes 106a and 106b are provided on the upper surface of the longitudinal portion of the frame substrate 104 and on the left and right sides of the first input electrode 101, respectively, which are connected to the first input electrode 101 via a gold thread wire 107a. The substrate electrodes 106a and 106b are lands formed as a conductive pattern on the upper surface of the frame substrate 104. The first input electrode 101 is soldered to the gold thread wire 107a by the solder 108a. The substrate electrodes 106a and 106b are soldered to the gold thread wire 107a by solders 108b and 108c, respectively.

On the upper surface of the frame substrate 104, on the left and right sides of the second input electrode 102, substrate electrodes 106c and 106d, which are connected to the second input electrode 102 via a gold thread wire 107b, are provided, respectively. The substrate electrodes 106c and 106d are lands formed as a conductive pattern on the upper surface of the frame substrate 104. The second input electrode 102 is soldered to the gold thread wire 107b by the solder 108d. The substrate electrodes 106c and 106d are soldered to the gold thread wire 107b by solders 108e and 108f, respectively.

On the upper surface of the frame substrate 104, on the left and right sides of the output electrode 103, substrate electrodes 106e and 106f, which are connected to the output electrode 103 via a gold thread wire 107c, are provided, respectively. The substrate electrodes 106e and 106f are lands formed as a conductive pattern on the upper surface of the frame substrate 104. The output electrode 103 is soldered to the gold thread wire 107c with 108 g of solder. The substrate electrodes 106e and 106f are soldered to the gold thread wire 107c by solders 108h and 108i, respectively.

As shown in FIG. 1, the gold thread wires 107a, 107b, and 107c are bridged over two longitudinal portions (left member and right member) constituting the frame substrate 104, and support the piezoelectric body 100 by suspending it.

As shown in FIG. 1, external electrodes 109a to 109d are formed on the end faces of the two short portions on both sides of the frame substrate 104 in the longitudinal direction. The external electrodes 109a to 109d are connected to a wiring pattern formed in the inner layer of the frame substrate 104. The external electrode 109a is connected to the substrate electrodes 106c and 106d. The external electrode 109b is connected to the substrate electrodes 106a and 106b. The external electrodes 109c and 109d are connected to the substrate electrodes 106e and 106f. Therefore, when the piezoelectric transformer PT is mounted on the printed circuit board, the external electrodes 109a to 109d are soldered to the lands on the printed circuit board.

FIG. 2 is a cross-sectional view obtained by cutting the piezoelectric transformer PT along the AA cutting line in FIG. The frame substrate 104 is thicker than the piezoelectric body 100. By holding the piezoelectric body 100 only on the upper surface side of the frame substrate 104, the piezoelectric body 100 floats from the lower surface of the frame substrate 104. Therefore, when the piezoelectric transformer PT is surface-mounted on the printed circuit board based on the frame substrate 104, the lower surface of the piezoelectric body 100 does not come into contact with the printed circuit board.

[High-density mounting]
The arrangement of electronic components on the double-sided printed circuit board 50 will be described with reference to FIGS. 3 and 4. 3 and 4 are cross-sectional views obtained by cutting the piezoelectric transformer PT along the BB cutting line in FIG. The double-sided printed circuit board 50 has a first mounting surface 301 and a second mounting surface 302 on which electronic components can be mounted, respectively. The piezoelectric transformer PT is surface-mounted on the first mounting surface 301 by soldering so that the lower surface of the frame substrate 104 of the piezoelectric transformer PT faces the first mounting surface 301. Since the lower surface of the piezoelectric body 100 floats above the lower surface of the frame substrate 104, the piezoelectric body 100 does not come into contact with the first mounting surface 301. Therefore, the double-sided printed circuit board 50 does not interfere with the mechanical vibration of the piezoelectric body 100.

The diode D1 is mounted on the first mounting surface 301. An inductor L1, a field effect transistor Tr, a capacitor C3, and the like, which are a part of a drive circuit for driving the piezoelectric transformer PT, are mounted on the second mounting surface 302. Since the first input electrode 101 is substantially rectangular, it has four sides, but the position of the side closer to the output electrode 103 among the four sides is defined as P2. The cross-sectional shape of the second input electrode 102 is generally U-shaped. That is, the second input electrode 102 extends over the upper surface, the side surface, and the lower surface of the piezoelectric body 100. That is, the portion of the second input electrode 102 arranged on the lower surface side of the piezoelectric body 100 faces the first input electrode 101 with the piezoelectric body 100 interposed therebetween. That is, the first input electrode 101 and the second input electrode 102 each form a pair of counter electrodes. An electric field is generated inside the piezoelectric body 100 according to the potential difference between the first input electrode 101 and the second input electrode 102, and mechanical vibration is generated in the piezoelectric body 100. The second input electrode 102 extends to the position P2 on the lower surface side of the piezoelectric body 100. The region on the left side of the position P2 of the second mounting surface 302 is the first region 303 where electronic components can be mounted. That is, in the first region 303, at least the region from the position P1 to the position P2 is also allowed to mount the electronic component. The position P1 is the end portion of the second input electrode 102, and is the position of the end portion farthest from the end portion of the output electrode 103.

As shown in FIG. 4, the clearance space provided between the piezoelectric body 100 and the first mounting surface 301 is the second region 401. As shown in FIG. 4, the second region 401 is a region from the position P1 to the position P3. The position P3 is the position of the end of the output electrode 103 that is farthest from the first input electrode 101 and the second input electrode 102. By setting the second region 401 as a region where the arrangement of electronic components is prohibited, it is possible to reduce the mounting height of the piezoelectric transformer PT. If the thickness of the frame substrate 104 is made sufficiently thicker than the thickness of the piezoelectric body 100, the height of the second region 401 becomes higher. That is, it is possible to mount the electronic component in the second region 401 without hindering the mechanical vibration of the piezoelectric body 100. This will be adopted when there is a margin in the mounting height of the piezoelectric transformer PT and the cost increase of the piezoelectric transformer PT due to the thickening of the frame substrate 104 is acceptable. For example, SMDs such as chip resistors, chip capacitors or field effect transistors (FETs) may be mountable.

As described above, the first region 303 on which the electronic component can be mounted is provided on the left side of the position P2 on the second mounting surface 302. As shown in FIG. 4, a third region 402 on the second mounting surface 302 is provided on the right side of the position P2, where mounting of electronic components is prohibited. The third region 402 is a region from position P2 to position P3. In order for the piezoelectric transformer PT to output a high voltage, the first input electrode 101 and the second input electrode 102 are connected to, for example, 200 [V] from a drive circuit composed of a field effect transistor Tr, an inductor L1 and a capacitor C3. The following voltage is applied. As a result of the experiment by the inventor, it was not possible to confirm the deterioration of the performance of the electronic component mounted in the first region 303. That is, it was found that the capacitive coupling between the piezoelectric transformer PT and these electronic components is sufficiently small. On the other hand, the third region 402 is a region facing the section of the piezoelectric body 100 that gradually boosts the voltage input from the drive circuit by utilizing mechanical vibration. It was also confirmed that when the drive circuit is arranged in the third region 402, the capacitive coupling between the drive circuit and the piezoelectric transformer PT cannot be ignored. It was also confirmed that the electric field generated by the piezoelectric effect of the piezoelectric transformer PT affects the drive circuit arranged in the third region 402.

Therefore, by securing the first region 303 on the second mounting surface 302 and mounting the drive circuit for driving the piezoelectric transformer PT on the first region 303, it is possible to effectively utilize the second mounting surface 302. .. That is, high-density mounting is realized. Compared with the resin case type piezoelectric transformer, the piezoelectric transformer PT of this embodiment does not require a dead space because it is flow-mounted. That is, it will be possible to mount electronic components in this dead space, which will be advantageous in reducing the circuit area.

<Example 2>
FIG. 5 is a side view of the short side of the piezoelectric transformer PT as viewed from the input electrode side. The solder joint portion of the piezoelectric transformer PT mounted on the surface of the double-sided printed substrate 50 will be described with reference to FIG.

[Solder mounting]
The double-sided printed substrate 50 is a printed substrate in which metal wiring is formed on both sides of a first mounting surface 301 and a second mounting surface 302 of a base material (eg, made of glass epoxy resin) called a core. The metal wiring may be formed inside the base material in addition to the first mounting surface 301 and the second mounting surface 302, which are the main surfaces of the base material.

The wiring provided on the upper surface of the double-sided printed circuit board 50 includes four lands that are electrically connected to the external electrodes 109a to 109d. In FIG. 5, lands 501a and 501b connected to the external electrodes 109a and 109b on the input side are shown, respectively. Since the side surfaces of the external electrodes 109c and 109d on the output side have the same configuration as the external electrodes 109a and 109b on the input side, the illustration is omitted.

As shown in FIG. 5, the external electrode 109a is soldered to the land 501a via the conductive bonding material SLa. Similarly, the external electrode 109b is soldered to the land 501b via the conductive bonding material SLb. The conductive bonding material SLa and the conductive bonding material SLb are a kind of solder that melts in a reflow furnace. The conductive bonding material SLa and the conductive bonding material SLb may be, for example, an alloy of tin and lead, or may be an alloy that does not use lead.

[Cracks caused by differences in thermal expansion coefficient between substrates]
Cracks or the like may occur in the conductive bonding materials SLa and SLb due to a temperature change in the environment in which the power supply device having the double-sided printed substrate 50 and the piezoelectric transformer PT is installed. This is because the stress caused by the difference between the thermal expansion coefficient of the double-sided printed substrate 50 and the thermal expansion coefficient of the frame substrate 104 of the piezoelectric transformer PT is applied to the conductive bonding materials SLa and SLb. Therefore, the inventors performed a heat cycle test and confirmed the presence or absence of cracks in the solder joint.

[Coefficient of thermal expansion of base material]
The printed circuit board expands and contracts due to heat. The coefficient of thermal expansion of the base material differs depending on the type of base material and the orientation of the glass fiber. CEM-3 and FR-4, which are general-purpose materials, were selected as the materials of the double-sided printed substrate 50 and the frame substrate 104 of the piezoelectric transformer PT. The coefficient of thermal expansion in the vertical direction for CEM-3 is 20 to 25 ppm / ° C, and the coefficient of thermal expansion in the horizontal direction is 23 to 28 ppm / ° C. The coefficient of thermal expansion of FR-4 in the vertical direction is 10 to 14 ppm / ° C., and the coefficient of thermal expansion in the horizontal direction is 12 to 16 ppm / ° C.

[Heat cycle test]
In the heat cycle test, the double-sided printed circuit board 50 on which the piezoelectric transformer PT was mounted was placed in a constant temperature bath. The conditions of the heat cycle test were set according to the test conditions described in ET-7404A "Environment and durability test method in the mounted state of CSP / BGA package" which is a standard of JEITA. JEITA is an abbreviation for Japan Electronics and Information Technology Industries Association. Here, the usage state (power off, standby, operation) of the image forming apparatus equipped with the high-voltage power supply using the piezoelectric transformer PT was taken into consideration. The maximum temperature is 125 ° C. The minimum temperature is -25 ° C. The temperature holding time (the time until the double-sided printed circuit board 50 on which the piezoelectric transformer PT is mounted adapts to the environment of the constant temperature bath) is 30 minutes. One cycle consists of a transition from 125 ° C. to -25 ° C. and then back to 125 ° C. 800 cycles were performed as a heat cycle test.

[Test results]
FIG. 6 is a table showing a combination of the double-sided printed circuit board 50 and the frame substrate 104. The numerical value shows the difference in the coefficient of thermal expansion. The part surrounded by a thick frame in FIG. 6 shows the combination in which the test was actually executed. The diagonal lines indicate the combinations in which cracks have occurred. In order to confirm the reliability of the solder joint portion of the piezoelectric transformer PT surface-mounted on the double-sided printed substrate 50, a heat cycle test was carried out for various combinations of the type of the base material and the orientation of the fibers. The inventors confirmed the presence or absence of cracks in the solder joint after the heat cycle test was completed. As shown by the thick line frame, in order to improve the test efficiency, the selection of the base material of the double-sided printed circuit board 50 was fixed to FR-4, and the orientation of the fibers was also fixed in the vertical direction. On the other hand, the combination of the base material and the orientation of the frame substrate 104 to be combined with the double-sided printed substrate 50 has been changed in various ways. The solder joint portion of the piezoelectric transformer PT surface-mounted on the double-sided printed circuit board 50 was polished in cross section, and the presence or absence of cracks in the polished portion was confirmed through a microscope.

As shown in FIG. 6, when CEM-3 was adopted as the base material of the frame substrate 104, cracks were generated without depending on the orientation of the fibers. Focusing on the difference in thermal expansion coefficient from the double-sided printed circuit board 50, it was found that cracks occur in a combination of 6 ppm / ° C. or higher. That is, it can be seen that if the difference in thermal expansion coefficient between the double-sided printed circuit board 50 and the frame substrate 104 is less than 6 ppm / ° C., the occurrence of cracks is reduced or avoided.

The conditions adopted for the heat cycle test are not limited to the above examples. The conditions may be changed depending on the expected usage of the test object and the capacity of the constant temperature bath. Regarding the coefficient of thermal expansion described in this example, attention was paid to the coefficient in the vertical direction and the coefficient in the horizontal direction. Also in the thickness direction, the difference in thermal expansion coefficient between the base materials is set to such an extent that cracks are unlikely to occur.

[Image forming device]
FIG. 7 shows an intermediate transfer type image forming apparatus 1 to which a power supply apparatus using a piezoelectric transformer can be applied. The image forming apparatus 1 may be an image forming apparatus for forming a monochromatic image, but here, it is an electrophotographic image forming apparatus for forming a multicolor image by mixing a plurality of colorants. The image forming apparatus 1 uses a four-color developer such as yellow (Y), magenta (M), cyan (C), and black (BK). In FIG. 7, a character indicating a color is added to the end of the reference number, but this character is omitted when the matters common to the four colors are explained.

The photosensitive drums 6C, 6M, 6Y, and 6BK are image carriers that are arranged at equal intervals and carry an electrostatic latent image or a toner image. The engine controller 20 controls the high-voltage power supply 30 to generate a charging voltage and supplies it to the primary charging device 2. The primary charger 2 uses the charging voltage to uniformly charge the surface of the photosensitive drum 6. The scanning optical device 3 emits a luminous flux (laser beam) L modulated based on the input image toward the photosensitive drum 6. The luminous flux (laser beam) L forms an electrostatic latent image on the surface of the photosensitive drum 6. The engine controller 20 controls the high-voltage power supply 30 to generate a developing voltage and supplies it to the developing device 4. The developer 4 attaches cyan, magenta, yellow, and black developers to the electrostatic latent image through sleeves and blades to which a developing voltage is applied. As a result, the electrostatic latent image is developed and a developer image (toner image) is formed.

The paper feed roller 8 feeds the sheets P housed in the paper feed tray 7 one by one. The resist roller 9 sends the sheet P toward the secondary transfer unit in synchronization with the image writing timing.

The engine controller 20 controls the high-voltage power supply 30 to generate a primary transfer voltage and supply it to the primary transfer roller 5. The primary transfer roller 5 primary transfers the toner image supported on the photosensitive drum 6 to the intermediate transfer belt 10. The primary transfer voltage applied to the primary transfer roller 5 promotes the primary transfer of the toner image. The intermediate transfer belt 10 functions as an intermediate transfer body. The drive roller 11 is a roller that rotates the intermediate transfer belt 10. The secondary transfer unit has a secondary transfer roller 14. The engine controller 20 controls the high-voltage power supply 30 to generate a secondary transfer voltage and supply it to the secondary transfer roller 14. In the secondary transfer section, the intermediate transfer belt 10 and the secondary transfer roller 14 carry the sheet P while sandwiching the sheet P, so that the multicolored toner image carried on the intermediate transfer belt 10 is secondary to the sheet P. Transcribed. The secondary transfer voltage promotes secondary transfer. After that, the sheet P is conveyed to the fuser 12. The fixing device 12 applies pressure and heat to the toner image supported on the sheet P to fix the toner image. The discharge roller 13 discharges the sheet P on which the image is formed.

[High-voltage power supply configuration]
FIG. 8 is a diagram illustrating an engine controller 20 and a high-voltage power supply 30. The engine controller 20 has a CPU 21 and high-voltage control units 22a to 22d. The CPU 21 sets a target voltage of the charging voltage in the high pressure control unit 22a. The CPU 21 sets a target voltage of the developing voltage in the high voltage control unit 22b. The CPU 21 sets a target voltage of the primary transfer voltage in the high voltage control unit 22c. The CPU 21 sets a target voltage of the secondary transfer voltage in the high voltage control unit 22d. The high-voltage power supply 30 has a plurality of power supply circuits. The high-voltage power supply 30 includes a booster circuit 32a that generates a charging voltage, a booster circuit 32b that generates a development voltage, a booster circuit 32c that generates a primary transfer voltage, and a booster circuit 32d that generates a secondary transfer voltage. The high-voltage control unit 22a controls the booster circuit 32a by outputting a control signal Vcont so that the charging voltage output by the booster circuit 32a becomes the target voltage. The high-voltage control unit 22b controls the booster circuit 32b by outputting a control signal Vcont so that the development voltage output by the booster circuit 32b becomes a target voltage. The high-voltage control unit 22c controls the booster circuit 32c by outputting a control signal Vcont so that the primary transfer voltage output by the booster circuit 32a becomes the target voltage. The high-voltage control unit 22d controls the booster circuit 32d by outputting a control signal Vcont so that the secondary transfer voltage output by the booster circuit 32d becomes the target voltage.

[Circuit configuration of high-voltage power supply]
The booster circuit 32, which is an example of the power supply circuit, will be described with reference to FIG. In the booster circuit 32, the piezoelectric transformer PT is adopted in place of the conventional winding type electromagnetic transformer. The output of the secondary terminal of the piezoelectric transformer PT is rectified and smoothed to a positive voltage by a rectifying and smoothing circuit. The rectifying and smoothing circuit is composed of rectifying diodes D1 and D2 and a high-voltage capacitor C1. The output voltage of the piezoelectric transformer PT is output from the output terminal 117 connected to the path extended from the piezoelectric transformer PT, and is supplied to a load such as the primary transfer roller 5 described above. The output voltage is divided by resistors R1, R2, and R3, and is input to the non-inverting input terminal (+ terminal) of the operational amplifier OP via the capacitor C2 and the protective resistor R4.

On the other hand, the control signal Vcont input from the input terminal 118 is input to the inverting input terminal (− terminal) of the operational amplifier OP via the resistor R5. The operational amplifier OP, the resistor R5, and the capacitor C3 function as an integrator circuit. That is, the control signal Vcont smoothed according to the integration time constant determined by the component constants of the resistor R5 and the capacitor C3 is input to the operational amplifier OP. The output end of the operational amplifier OP is connected to a voltage controlled oscillator (VCO) 119. The voltage controlled oscillator 119 is an example of an oscillator that variably sets the frequency of the output signal according to the input control signal.

Further, the output end of the voltage controlled oscillator 119 is connected to the gate of the field effect transistor Tr. The field effect transistor Tr is a switching element driven by an output signal of an oscillator, and is an example of a semiconductor component that drives a piezoelectric element. The drain of the field effect transistor Tr is connected to the power supply Vcc (eg, + 24V, etc.) via the inductor L1 and is grounded via the capacitor C4. The inductor L1 is an element connected between a switching element and a power supply, and is an example of an element having an inductance component in which a voltage is intermittently applied by driving the switching element. Further, the drain is connected to one of the primary electrodes of the piezoelectric transformer PT. The other electrode on the primary side of the piezoelectric transformer PT is grounded. The source of the field effect transistor Tr is also grounded.

The voltage controlled oscillator 119 switches the field effect transistor Tr at a frequency corresponding to the output voltage of the operational amplifier OP. The inductor L1 and the capacitor C4 form a resonance circuit. The voltage amplified by this resonance circuit is supplied to the primary side of the piezoelectric transformer PT. In this way, the piezoelectric transformer PT is connected to the connection point between the switching element and the element having an inductance component, and when a signal vibrating at a predetermined resonance frequency is applied, a voltage corresponding to the frequency characteristic is output.

<Summary>
As shown in FIG. 3 and the like, the double-sided printed circuit board 50 has a first mounting surface 301 and a second mounting surface 302 which is a surface opposite to the first mounting surface 301. A piezoelectric transformer PT is surface-mounted on the first mounting surface 301. The piezoelectric transformer PT has a piezoelectric body 100 having an input electrode and an output electrode 103, and a frame substrate 104 supporting the piezoelectric body 100. The first input electrode 101 and the second input electrode 102 are examples of input electrodes. As shown in FIG. 1, the frame substrate 104 is arranged so as to surround the side surface of the piezoelectric body 100. Further, the frame substrate 104 has a plurality of external electrodes 109a to 109d that are conductive with the input electrode or the output electrode. The second mounting surface 302 has a projective range on which the piezoelectric body 100 is projected. The projection region is a region in which the upper surface or the lower surface of the piezoelectric body 100 is projected in the normal direction of the second mounting surface 302. The projection region includes a first region 303, which is a mounting permission region on which electronic components are mounted. The first region 303 is a region from the first position P1 to the second position P2. The first position P1 is a position in which the end of the input electrode farther from the output electrode 103 is projected onto the second mounting surface. More specifically, the first position P1 is a position where a perpendicular line drawn from the end of the input electrode farther from the output electrode 103 toward the second mounting surface 302 intersects the second mounting surface 302. Is. The second position P2 is a position where the end of the input electrode closer to the output electrode 103 is projected onto the second mounting surface 302. More specifically, the second position P2 is a position where a perpendicular line drawn from the end of the input electrode closer to the output electrode 103 toward the second mounting surface 302 intersects the second mounting surface. is there. As described above, if the entire projection region of the piezoelectric transformer PT is set as the mounting prohibited region of the electronic component, the density of the electronic component on the second mounting surface 302 cannot be increased. Since the influence of the electric field or the like from the piezoelectric transformer PT is small in the first region 303, the electronic component can be mounted in this region with almost no deterioration in the performance of the electronic component. By making the first region 303 a region on which electronic components can be mounted in this way, high-density mounting of electronic components on the second mounting surface 302 becomes possible. As shown in FIG. 3 and the like, at least a part of electronic components constituting the drive circuit for driving the piezoelectric transformer PT may be arranged in the first region 303. As shown in FIGS. 3 and 9, at least some of the electronic components constituting the drive circuit are, for example, a capacitor C3, an electric field effect transistor Tr, or an inductor L1.

As shown in FIG. 4, the first mounting surface 301 may have a second region 401 that is a region on the first mounting surface and faces the piezoelectric body 100. The second region 401 may be a mounting prohibited region in which mounting of electronic components is prohibited. By providing the second region 401, the piezoelectric body 100 and the electronic component do not come into contact with each other, and the piezoelectric body 100 can sufficiently vibrate mechanically. The electronic component whose mounting is prohibited in the second region 401 is, for example, a surface mount component (SMD). The second region 401 may be a region in which an electronic component having a height that does not come into contact with the piezoelectric body 100 even if it vibrates mechanically is mounted.

As shown in FIG. 4, the above-mentioned projective range may have a third region 402 from the second position P2 to the third position P3. The third region 402 may be a mounting prohibited region in which mounting of electronic components is prohibited. The third position P3 is a position in which the end of the output electrode 103 that is farther from the input electrode is projected onto the second mounting surface 302. More specifically, the third position P is a position where a perpendicular line drawn from the end of the output electrode 103 farther from the input electrode toward the second mounting surface intersects the second mounting surface. .. As described above, the third region 402 is a region that is easily affected by the piezoelectric body 100. Therefore, by prohibiting the arrangement of the electronic component in the third region 402, the performance deterioration of the electronic component can be avoided.

As shown in FIG. 1, a space may be provided between the side surface of the piezoelectric body 100 and the inner side surface of the frame substrate 104. As a result, the piezoelectric body 100 can mechanically vibrate without interfering with the frame substrate 104. The piezoelectric body 100 is thinner than the frame substrate 104, and a space is provided between the lower surface of the piezoelectric body 100 and the first mounting surface 301. As a result, the piezoelectric body 100 can mechanically vibrate without interfering with the first mounting surface 301.

As shown in FIG. 1, the input electrode includes a first input electrode 101, which is a first counter electrode provided on the upper surface of the piezoelectric body 100, and a second counter electrode provided on the lower surface of the piezoelectric body 100. It may have two input electrodes 102. As shown in FIG. 3, the portion of the second input electrode 102 that functions as the second counter electrode extends to the upper surface of the piezoelectric body 100 via the side surface of the piezoelectric body 100. This makes it possible to generate an electric field in the thickness direction of the piezoelectric body 100. Further, since the first input electrode 101 and a part of the second input electrode 102 are provided on the upper surface of the piezoelectric body 100, the piezoelectric body 100 can be held so as to be suspended by the frame substrate 104.

As described with reference to FIG. 6, the difference between the coefficient of thermal expansion of the base material of the double-sided printed circuit board 50 and the coefficient of thermal expansion of the frame substrate 104 may be less than 6 × 10 ^ -6 / ° C. As a result, even if the double-sided printed circuit board 50 is mounted on the high-voltage power supply 30 of the image forming apparatus 1, cracks are less likely to occur at the solder joint portion between the double-sided printed circuit board 50 and the frame board 104.

As shown in FIG. 7, the photosensitive drum 6 is an example of an image carrier. The primary charger 2 is an example of a charging means for uniformly charging the image carrier. The scanning optical device 3 is an example of an exposure means that exposes an image carrier to form an electrostatic latent image. The developer 4 is an example of a developing means for developing an electrostatic latent image to form a toner image. The primary transfer roller 5, the intermediate transfer belt 10, and the secondary transfer roller 14 are examples of transfer means for transferring a toner image to a sheet. The high-voltage power supply 30 is an example of a power supply device that generates a charging voltage supplied to the charging means, a developing voltage supplied to the developing means, or a transfer voltage supplied to the transfer means.

50 ... Double-sided printed circuit board, 301 ... First mounting surface, 302 ... Second mounting surface, PT ... Piezoelectric transformer, 101 ... First input power, 102 ... Second input electrode, 103 ... Output electrode, 104 ... Frame board, 303 … First region, 401… second region, 402… third region

Claims (15)

A printed substrate having a first mounting surface and a second mounting surface which is a surface opposite to the first mounting surface, and a piezoelectric transformer is surface-mounted on the first mounting surface.
The piezoelectric transformer
A piezoelectric material having an input electrode and an output electrode,
With the input electrode or a plurality of external electrodes conducting with the output electrode,
It has a frame substrate that is arranged so as to surround the side surface of the piezoelectric body and supports the piezoelectric body.
The second mounting surface has a projective range on which the piezoelectric body is projected.
In the projection region, from the first position in which the end portion of the input electrode farther from the output electrode is projected onto the second mounting surface, among the end portions of the input electrode. There is a first region up to a second position where the end closer to the output electrode is projected onto the second mounting surface, and from the second position, the input electrode of the ends of the output electrode. There is a second region up to the third position where the far end is projected onto the second mounting surface, electronic components are mounted in the first region, and electronic components are mounted in the second region. A printed substrate characterized by not being used. The first mounting surface has a third region that is a region on the first mounting surface and faces the piezoelectric body.
The printed circuit board according to claim 1, wherein the projective range is a region located on the opposite side of the third region. The printed substrate according to claim 2, wherein the third region is a mounting prohibited region in which electronic components are not mounted. The printed substrate according to claim 3, wherein the electronic component whose mounting is prohibited in the third region is a surface-mounted component. The printed circuit board according to claim 2, wherein the third region is a region on which an electronic component having a height that does not come into contact with the piezoelectric body even if it vibrates mechanically is mounted. The first position is a position where a perpendicular line drawn from the end of the input electrode farther from the output electrode toward the second mounting surface intersects the second mounting surface.
The second position is a position where a perpendicular line drawn from the end of the input electrode closer to the output electrode toward the second mounting surface intersects the second mounting surface. The printed circuit board according to any one of claims 1 to 5, wherein the printed circuit board is characterized. The printed circuit board according to any one of claims 1 to 6, wherein at least a part of electronic components constituting the drive circuit for driving the piezoelectric transformer are mounted in the first region. The printed circuit board according to claim 7, wherein at least a part of the electronic components constituting the drive circuit is a capacitor, a transistor, or an inductor. The third position is a position where a perpendicular line drawn from the end of the output electrode farther from the input electrode toward the second mounting surface intersects the second mounting surface. The printed circuit board according to any one of claims 1 to 8. The printed circuit board according to any one of claims 1 to 9 , wherein a space is provided between the side surface of the piezoelectric body and the inner side surface of the frame substrate. The invention according to any one of claims 1 to 10 , wherein the piezoelectric body is thinner than the frame substrate, and a space is provided between the lower surface of the piezoelectric body and the first mounting surface. Printed board. The input electrode is
The first counter electrode provided on the upper surface of the piezoelectric body and
A claim characterized in that it has a second counter electrode provided on the lower surface of the piezoelectric body, and the second counter electrode extends to the upper surface of the piezoelectric body via a side surface of the piezoelectric body. Item 2. The printed circuit board according to any one of Items 1 to 11. According to any one of claims 1 to 12 , the difference between the coefficient of thermal expansion of the substrate of the printed circuit board and the coefficient of thermal expansion of the frame substrate is less than 6 × 10 ^ -6 / ° C. Described printed circuit board. The printed substrate according to any one of claims 1 to 13 and
A power supply device including a piezoelectric transformer surface-mounted on the first mounting surface and a power supply circuit including a drive circuit for driving the piezoelectric transformer. Image carrier and
A charging means for uniformly charging the image carrier and
An exposure means for exposing the image carrier to form an electrostatic latent image,
A developing means for developing the electrostatic latent image to form a toner image, and
A transfer means for transferring the toner image to a sheet,
The power supply device according to claim 14 , which generates a charging voltage supplied to the charging means, a developing voltage supplied to the developing means, or a transfer voltage supplied to the transfer means. Image forming device.

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