Loop device

Abstract

To provide a circuit device that suppresses the effects of electromagnetic noise irradiated from the outside. [Solution] In a pressure detection device 20 in which a circuit board 3 is housed in a housing 13, the circuit device 30 is provided with an insulating film 100 between the circuit board 3 and the housing 13 that surrounds at least a part of the circuit board 3. The insulating film 100 may be positioned spaced apart from the conductive part of the circuit board 3. The circuit device has a charge conversion circuit that is input to the circuit board 3 and a processing circuit that processes a voltage signal or current signal from the charge conversion circuit, and the insulating film 100 covers part or all of the processing circuit.

Description

Technical Field

[0001] The present invention relates to a circuit device for processing signals output from a pressure detection device or the like used for control of an internal combustion engine.

Background Art

[0002] A pressure detection device for controlling an internal combustion engine, for example a pressure detection device using a piezoelectric body as a pressure-sensitive element, includes a sensor main body built into the device main body, and a charge amplifier circuit that is configured integrally with or separately from the sensor main body, amplifies the charge of several picocoulombs per newton output by the piezoelectric body in response to pressure, converts it into a voltage signal or a current signal, and transmits the signal to a control computer of the internal combustion engine (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of Invention

Problems to be Solved by the Invention

[0004] In pressure detection devices, the amplifier circuit may be exposed to electromagnetic wave noise emitted from devices installed in the periphery such as an internal combustion engine, which generates induced current in the amplifier circuit and causes the operation of the amplifier circuit to become unstable, and this has become a problem. Accordingly, the present invention provides a circuit device that suppresses the influence of externally irradiated electromagnetic wave noise.

Means for Solving the Problems

[0005] In a pressure detection device having a circuit board housed in a housing, the circuit device is provided with an insulating film that surrounds at least a part of the circuit board between the circuit board and the housing.

Effects of the Invention

[0006] According to the present invention, it is possible to provide a circuit device that suppresses the effects of electromagnetic noise irradiated from the outside. [Brief explanation of the drawing]

[0007] [Figure 1] This is a top view of the circuit device, showing the circuit board as viewed from one side. [Figure 2] This is a bottom view of the circuit device, and is a view of the circuit board from the other side. [Figure 3] This is a side view of the circuit device. [Figure 4] This is an enlarged view of the area shown in section AA' of the circuit device. [Figure 5] This is an external view of a pressure detection device equipped with a circuit device according to one embodiment of the present invention. [Modes for carrying out the invention]

[0008] Embodiments of the present invention will be described in detail below with reference to the drawings. Figure 5 is an external view of a pressure detection device 20 equipped with a circuit device 30 according to one embodiment of the present invention. The pressure detection device 20 comprises a pressure sensor body 14 that houses a piezoelectric single crystal and outputs a charge corresponding to the pressure received, a circuit device 30 that amplifies the charge output from the pressure sensor body 14, and a shielded cable 4 that connects the pressure sensor body 14 and the circuit device 30. The circuit device 30 comprises a cylindrical housing 13 that houses a circuit board 3 having a circuit for converting the charge signal from the pressure sensor body 14 into a current or voltage signal and amplifying it, a disc housing 8 that introduces the shielded cable 4 into the cylindrical housing 13 and closes one end of the cylindrical housing 13, and a connector 7 that outputs the amplified signal from the circuit device 30 to the outside, inputs power to operate the circuit device 30 to the circuit board and closes the other end of the cylindrical housing 13.

[0009] Figure 1 is a top view of the circuit device 30, viewed from one side of the circuit board. Figure 2 is a bottom view of the circuit device 30, viewed from the other side of the circuit board. Figure 3 is a side view of the circuit device 30. Figure 4 is an enlarged view of the area indicated by section AA' of the circuit device 30. Also, for the sake of clarity, Figures 1 and 2 show the vibration-damping and heat-dissipating rubbers 1a and 1b as perspective views, and some of the wiring patterns on the circuit board 30 are omitted. Figure 3 shows cross-sectional views of the vibration-damping and heat-dissipating rubbers 1a and 1b, the cylindrical housing 13, and the insulating film 100.

[0010] The circuit board 3 is a circuit that processes the output signal from the pressure sensor body 14. For example, when the charge signal output from the pressure sensor body 14 is to be converted into a voltage signal, it consists of a charge amplifier, which is a charge conversion circuit that converts the charge signal from the pressure sensor body 14 into a voltage signal, and a processing circuit such as a buffer circuit connected to the charge amplifier that processes the output signal from the charge amplifier, and multiple electronic components 11 that constitute these circuits are mounted on it. When the output signal from the circuit device 30 is to be converted into a current signal, a configuration may be provided that includes a voltage-to-current conversion circuit (VI converter) between the charge amplifier and the buffer circuit.

[0011] The electronic components 11 are mounted on one side of the circuit board 3 (hereinafter referred to as "side A") and the other side facing side A (hereinafter referred to as "side B"). The circuit board 3 has high-heat generating electronic components 11a and 11b, which generate relatively large amounts of heat, and low-heat generating electronic components 11c, 11d, and 11e, which generate relatively small amounts of heat. The circuit board 3 also has wiring patterns that are connected to the electronic components 11 according to the circuit configuration. A portion of the wiring patterns around the high-heat generating components 11a and 11b that constitute the GND path of the circuit board 3 has a heat dissipation section 2 with a relatively larger wiring width compared to the rest of the wiring pattern. Furthermore, side B, on the end of the circuit board 3 where the L-shaped structure 10 (described later) is fixed, has a heat dissipation pattern 9 that is connected to the wiring patterns that constitute the GND path of the circuit board 3 and has a relatively larger area than the wiring patterns excluding the heat dissipation section 2.

[0012] An L-shaped structure 10 for fixing the disc housing 8 is attached to one end of the circuit board 3. The L-shaped structure 10 has two orthogonal pieces, one of which has a screw hole and the other has a through hole. The circuit board 3 is mounted on one piece of the L-shaped structure 10 so that the heat dissipation pattern 9 on side B is in contact with it, and the circuit board 3 has a through hole at a position corresponding to the screw hole of the L-shaped structure 10. The circuit board 3 and the L-shaped structure 10 are fixed together by fastening them with screws through this screw hole and through hole. In the circuit device 30, the end to which the L-shaped structure 10 is attached is the side closer to the pressure sensor body 14, and the internal combustion engine to which the pressure sensor body 14 is attached becomes hot, so by keeping the L-shaped structure 10 in contact with the heat dissipation pattern 9, the heat transmitted from the shield cable 4 can be efficiently dissipated to the cylindrical housing 13.

[0013] A disc housing 8 is fixed to the other end of the L-shaped structure 10. The L-shaped structure 10 and the disc housing 8 are fixed together by screw fastening. Specifically, the L-shaped structure 10 and the disc housing 8 are fixed together by fastening screws through a through hole provided in the other end of the L-shaped structure 10 and a screw hole in the disc housing 8 located at a position corresponding to the through hole. The disc housing 8 is also provided with a through hole for inserting a shield cable 4. A waterproof and dustproof packing is provided between the inner wall of this through hole and the shield cable 4, and is configured to achieve IP67 sealing performance according to JIS-C-0920 and IEC-60529 standards.

[0014] The shield cable 4, which is introduced into the circuit board 3, is connected to the circuit board 3. Specifically, the core wire of the shield cable 4 is directly soldered to the charge receiving terminal 5 provided on one end of the circuit board 3. In addition, the braid of the shield cable 4 is connected and fixed to the GND path provided on the circuit board 3.

[0015] A circular circuit board 12 is connected to the other end of the circuit board 3 so as to be perpendicular to the electronic component mounting surfaces (sides A and B) of the circuit board 3. The circular circuit board 12 is a component that electrically connects the circuit board 3 and the connector 7, and the circular circuit board 12 and the circuit board 3 are connected to each other by soldering or the like without any separation between them. The connector 7 is connected to the side of the circular circuit board 12 opposite to the side to which the circuit board 3 is connected. The connector 7 is a connection part for signal output from the circuit board 3 and for supplying power to the circuit board 3 from an external source, and each terminal of the connector 7 is soldered to a wiring pattern provided on the circular circuit board 12, so that the wiring pattern of the circuit board 3 and each terminal of the connector 7 are electrically connected.

[0016] Then, cylindrical housings 13 are connected to the outer circumferences of the disc housing 8, which is connected to the circuit board 3 via the L-shaped structure 10, and the connector 7, which is connected to the circuit board 3 via the circular substrate 12, so as to house the circuit board 3 inside. At this time, the outer diameters of the disc housing 8 and the connector 7 are slightly smaller than the inner diameter of the cylindrical housing 13, and the disc housing 8 and the connector 7 are fixed to the cylindrical housing 13 by adhesive or seam welding, etc.

[0017] Furthermore, vibration-damping and heat-dissipating rubbers 1a and 1b are placed on the circuit board 3 and electronic components 11, and inside the cylindrical housing 13. Each of the vibration-damping and heat-dissipating rubbers 1a and 1b is a semi-cylindrical member having a rectangular base and an upper surface shaped like an arc along the long side of the base. They are elastic bodies with excellent vibration-damping properties that absorb and dampen vibrations, and are made of porous silicone rubber with high thermal conductivity.

[0018] The vibration-proof and heat-dissipating rubbers 1a and 1b are arranged such that the vibration-proof and heat-dissipating rubber 1a is disposed on the A surface of the circuit board 3, and the vibration-proof and heat-dissipating rubber 1b is disposed on the B surface. Their respective bottom surfaces are in contact with the circuit board 3 and the electronic component 11 mounted on the circuit board 3, and their respective top surfaces are arranged to be in contact with the inner wall surface of the cylindrical housing 13. The vibration-proof and heat-dissipating rubbers 1a and 1b serve to suppress the transmission of vibration applied from the outside of the circuit device 30 to the circuit board 3 (and the electronic component 11), and further efficiently dissipate heat generated from the circuit board 3 and the electronic component 11 to the cylindrical housing 13.

[0019] In the present embodiment, the vibration-proof and heat-dissipating rubbers 1a and 1b are arranged at a substantially central portion in the longitudinal direction of the circuit board 3. On the circuit board 3, a charge conversion circuit of a charge amplifier is arranged in a region from the end of the vibration-proof and heat-dissipating rubbers 1a and 1b on the shielded cable 4 side toward the shielded cable side, and a processing circuit such as a buffer circuit for processing an output signal from the charge conversion circuit is arranged in a region from the end of the vibration-proof and heat-dissipating rubbers 1a and 1b on the shielded cable 4 side toward the connector 7 side.

[0020] In addition, high heat-generating electronic components 11a and 11b are mounted at a substantially central portion of the circuit board 3, and the vibration-proof and heat-dissipating rubbers 1a and 1b are arranged so as to cover the high heat-generating electronic components 11a and 11b. A part of the heat dissipating portion 2 of the wiring pattern is also covered (in contact) with the vibration-proof and heat-dissipating rubbers 1a and 1b. The low heat-generating electronic components 11c, 11d, and 11e are not covered by the vibration-proof and heat-dissipating rubbers 1a and 1b.

[0021] By arranging the vibration-proof and heat-dissipating rubbers 1a, 1b in this manner, heat generated from the high heat-generating electronic components 11a, 11b having a high calorific value can be efficiently dissipated to the cylindrical housing 13. In addition, the vibration of the circuit board 3 when external vibration is applied can be greatly suppressed. This is due to the vibration damping effect of the vibration-proof and heat-dissipating rubbers 1a, 1b, and the fact that by arranging the vibration-proof and heat-dissipating rubbers 1a, 1b at the substantially central portion of the circuit board 3, the resonance frequency of the circuit board 3 is approximately doubled compared to the case where the vibration-proof and heat-dissipating rubbers 1a, 1b are not arranged. This vibration suppression effect can be selected according to the externally applied vibration frequency, and for example, various vibration frequencies can be handled by changing the number and arrangement positions of the vibration-proof and heat-dissipating rubbers 1a, 1b. In this case, in order to obtain the heat dissipation effect of the vibration-proof and heat-dissipating rubbers 1a, 1b, it is preferable to appropriately lay out the vibration-proof and heat-dissipating rubbers 1a, 1b according to the mounting positions of the high heat-generating electronic components 11a, 11b.

[0022] Each of the bottom surfaces of the vibration-proof and heat-dissipating rubbers 1a, 1b of the present embodiment has a shape that follows the surface shape of the circuit board 3 including the electronic component 11 on which it is arranged. Specifically, the bottom surface of each of the vibration-proof and heat-dissipating rubbers 1a, 1b has a flat surface in contact with the circuit board 3, and a surface shape having a recessed portion substantially matching the shape of the high heat-generating electronic components 11a, 11b at a position corresponding to the high heat-generating electronic components 11a, 11b covered by the vibration-proof and heat-dissipating rubbers 1a, 1b. This is to prevent the high heat-generating electronic components 11a, 11b from receiving excessive pressure from the vibration-proof and heat-dissipating rubbers 1a, 1b. However, the vibration-proof and heat-dissipating rubbers 1a, 1b are preferably sandwiched between the circuit board 3 and the cylindrical housing 13 with a predetermined pressure to ensure the contact between the circuit board 3 and the high heat-generating electronic components 11a, 11b.

[0023] Further, each of the top surfaces of the vibration-proof and heat-dissipating rubbers 1a, 1b of the present embodiment has a plurality of protrusions and recesses that are horizontal to the lateral direction of the circuit board 3. With such a shape, the contact resistance between the circuit board 3 and the vibration-proof and heat-dissipating rubbers 1a, 1b when they are arranged in the cylindrical housing 13 can be reduced, and the assemblability of the circuit device 30 is improved.

[0024] An insulating film 100 is positioned inside the cylindrical housing 13, between the connector 7 and the vibration-damping / heat-dissipating rubbers 1a and 1b. The insulating film 100 is, for example, a sheet of polyimide film with a thickness of 200 μm, which is rolled into a cylindrical shape and positioned along the inner circumferential surface of the cylindrical housing 13, and is configured to have a C-shaped cross-section with a small opening (gap) at the joint of the cylindrical part. One end of the insulating film 100 in the axial direction is inserted into the gap between the cylindrical housing 13 and the circular substrate 12 and contacts the connector 7, while the other end contacts the vibration-damping / heat-dissipating rubbers 1a and 1b, and is fixed inside the cylindrical housing 13 by being sandwiched between the connector 7 and the vibration-damping / heat-dissipating rubbers 1a and 1b. In this way, the insulating film 100 is sandwiched between the connector 7 and the vibration-damping / heat-dissipating rubbers 1a and 1b, and one end of the insulating film 100 is inserted into the gap between the cylindrical housing 13 and the circular substrate 12, thereby supporting the insulating film 100 on the side surface of the circular substrate 12 and stabilizing the fixed position of the insulating film 100.

[0025] The insulating film 100 is positioned to surround the circuit board 3 and functions as a shielding member against electromagnetic noise input to the circuit board 3 from the outside. Specifically, the insulating film 100 surrounds the circuit board 3 between the vibration-damping / heat-dissipating rubbers 1a, 1b and the connector 7, thereby surrounding a portion of the processing circuit of the circuit board 3, excluding the charge conversion circuit, and shielding that circuit from electromagnetic noise. In this embodiment, the charge conversion circuit is not covered by the insulating film 100. This is because the charge conversion circuit does not have a significant impact on the output of the circuit device 30 from electromagnetic noise, and the entire circuit board 3, including the charge conversion circuit, may be covered with the insulating film 100. It is preferable that the insulating film 100 does not come into contact with the conductor portion of the circular substrate 12 and the circuit board 3, and the electronic components 11. This is because the insulating film 100 functions as a dielectric, preventing AC connection between the circuit board 3, the electronic components 11, and the circular substrate 12 and the cylindrical housing 13.

[0026] The insulating film 100 may be a sheet-like film formed into a cylindrical shape, as in this embodiment, or it may be a film that has been molded into a cylindrical shape. In this embodiment, a sheet-like film is used, taking into consideration the cost of parts, and furthermore, its cross-section is made C-shaped. The reason for making the cross-section C-shaped is that if a seam is provided in the sheet, the thickness will increase, making it difficult to insert one end of the insulating film 100 into the gap between the cylindrical housing 13 and the circular substrate 12, and this is effective when there are limitations on the placement space. When the insulating film 100 has a C-shaped cross-section in this way, it is preferable to position the opening of the insulating film 100 on the side that connects the A side and the B side of the circuit board 3. By arranging it in this way, it is possible to place it in a narrow space without significantly reducing the shielding function of electromagnetic noise input to the circuit board 3.

[0027] In this embodiment, the insulating film 100 is a sheet-like polyimide film with a thickness of 200 μm, exhibiting a dielectric strength of 46 kV and a heat resistance temperature of 300°C. When the insulating film 100 is made of polyimide, its thickness is preferably 100 μm or more and 300 μm or less. If the thickness is 100 μm or less, sufficient shielding function against electromagnetic noise cannot be obtained, and if the thickness is greater than 300 μm, there is not much difference in shielding function compared to when the thickness is between 100 and 300 μm. Furthermore, by making the insulating film 100 a heat-resistant polyimide film, its characteristics will not be impaired even when the circuit device 30 is installed in a high-temperature environment such as near an internal combustion engine. While the insulating film 100 is preferably made of polyimide, it can also be made of various other insulating materials such as PTFE (polyethylene terephthalate) and PEEK (polyether ether ketone). The material should be appropriately selected according to the characteristics required for the circuit device 30. [Explanation of Symbols]

[0028] 1a Vibration-damping and heat-dissipating rubber 1b Vibration-damping and heat-dissipating rubber 2 Heat dissipation part 3 Circuit board 4 Shielded Cables 5 Charge receiving terminals 7 Connectors 8-inch disc enclosure 9 Heat dissipation patterns 10 L-shaped structure 11 Electronic Components 11a High-heat generating electronic components 11b High-heat generating electronic components 11c Low Heat Generation Electronic Components 11d Low heat generation electronic components 11e Low-heat electronic components 12 circular circuit boards 13 Cylindrical housing 14. Pressure sensor body 20 Pressure detection device 30 Circuit equipment 100 Insulating Film

Claims

1. In a circuit device in which a circuit board is housed in a casing, A circuit device characterized by having an insulating film between the circuit board and the housing that surrounds at least a portion of the circuit board.

2. The circuit device according to claim 1, characterized in that the insulating film is arranged at a distance from the conductor portion of the circuit board.

3. The circuit board includes a charge conversion circuit that converts a charge signal input to the circuit board into a voltage signal or a current signal, and a processing circuit that processes the voltage signal or current signal from the charge conversion circuit. The circuit device according to claim 1 or 2, characterized in that the insulating film covers part or all of the processing circuit excluding the charge conversion circuit.

4. The circuit board comprises a first board on which the charge conversion circuit and the processing circuit are mounted, and a second board arranged orthogonally to and connected to the first board. The circuit device according to claim 3, characterized in that the end of the insulating film is held between the cylindrical housing and the second substrate.

5. The circuit device according to claim 1, characterized in that the insulating film is a polyimide film with a thickness of 200 μm or more and 300 μm or less.

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