Patent Application
20240048029
The present disclosure relates to a circuit board attached to a rotating body and a power supply device.
A circuit board of this type, which is attached for example to a tire wheel, is known (see, for example, Patent Document 1).
Durability is sometimes an issue with a circuit board attached to a rotating body or a device that contains the circuit board such as the example described above because of the centrifugal force of rotation they are subjected to. The present disclosure provides a technique for improving the durability of a circuit board attached to a rotating body and a device that includes same.
The circuit board according to the present disclosure made to solve the above problem is a circuit board fixed to a rotating body, with a plate thickness direction oriented parallel to a rotation axis, including either a plurality of devices mounted on the circuit board to be distributed around the rotation axis so that the circuit board as a whole has a center of gravity located in a central area of rotation, or a single device mounted on the circuit board in an annular shape to have a center coinciding with the rotation axis.
A power supply device 10A according to a first embodiment of the present disclosure will be described with reference to
As shown in
The interior of the tubular wall 24 is divided into two, first chamber 24A on the front side and second chamber 24B on the rear side, by a partition wall 23 provided at a midway point in the front to back direction. The lid member 22 closes the opening at the front end of the tubular wall 24, so that the first chamber 24A is a tubular compartment closed at both ends. The lid member 22 and the tubular wall 24 are processed to be water-proof. The lid member 22 further has an emblem 22A formed on the outer face.
While the tubular wall 24 of this embodiment is provided with the first chamber 24A and second chamber 24B, the tubular wall 24 may instead include only the first chamber 24A, with the partition wall 23 provided at the rear end, or the tubular wall 24 may be divided in the axial direction into three chambers.
The tubular wall 24 is formed with a step surface 24D on the outer face near the rear end, and a small-diameter part 24S on the rear side of the step surface 24D. A plurality of locking lugs 25 protrudes from the rear surface of the tubular wall 24, slightly inside of the outer face. These locking lugs 25 are configured to extend backward in a cantilevered manner and have a locking protrusion 26 at the tip. A plurality of anti-rotation protrusions 27 protrudes from an outer edge portion on the rear surface of the tubular wall 24. The plurality of locking lugs 25 and the plurality of anti-rotation protrusions 27 are circumferentially distributed around the tubular wall 24 so that the center of gravity of the entire housing 20 lies on the center axis of the tubular wall 24.
The generator 30 is attached to the rear surface of the partition wall 23 and accommodated in the second chamber 24B. The generator 30 has the same structure as an AC motor, for example, and outputs an alternating current. Specifically, the generator 30 is accommodated substantially entirely in a flat cylindrical case 38 with a quadrate flange 39 at one end. As shown in
While the generator 30 of this embodiment includes a pair of output electrodes 37A and 37B to output the alternating current, the generator may include three output electrodes, for example, to generate a 3-phase alternating current. The generator 30 may have the same structure as a DC motor and output a direct current.
The partition wall 23 is formed with a through hole 23A in a central part for attaching the generator 30, and a plurality of screw holes 23B therearound. The front end face of the generator 30 on a side the flange 39 is overlapped with the rear surface of the partition wall 23 (i.e., outer face at one end of the first chamber 24A), and screws having passed through the through holes 39A at four corners of the flange 39 are fastened into the screw holes 23B of the partition wall 23 to secure the generator. The rotation input part 35 extends through the through hole 23A in the partition wall 23 and protrudes into the first chamber 24A (see
Inside the first chamber 24A, an inertial component is fixedly attached to the rotation input part 35. The inertial component 40 is a metal circular plate, for example, having a slightly smaller outside diameter than the inside diameter of the first chamber 24A, and cut into a form slightly smaller than a semicircle as a whole except for the central part. The rotation input part 35 is tightly fitted into a through hole 40A extending through the remaining central part so that the inertial component and rotor 32 rotate integrally relative to the stator 33.
The inertial component 40 is not limited to the shape described above; as long as it has the center of gravity shifted off the rotation axis J1, the inertial component may have any shape and may be made of any material.
The circuit board 50 is disposed behind the generator 30. A plurality of support pillars 45 protrudes rearward from the partition wall 23 for supporting this circuit board 50. Specifically, the support pillars 45 have a columnar structure, with screw holes in the center at both ends. Along the outer edge of the partition wall 23, a plurality of through holes 23C is formed at (e.g., 3) equidistant positions along an imaginary circle around the through hole 23A. The plurality of support pillars 45 is secured to the partition wall 23 by screws having passed through respective through holes 23C from the first chamber 24A side, and extend rearward beyond the rear surface of the generator 30.
The circuit board 50 is in the form of a circular plate, placed over the rear faces of the plurality of support pillars 45, and fastened with screws at the plurality of points along the outer edge of the circuit substate 50. The rotation axis J1 extends perpendicularly to the center of the circuit board 50. Between the rear surface of the generator 30 and the circuit board 50 is provided a slight clearance (see
A rectifier circuit 60 is mounted on the circuit board 50 for converting the alternating current output by the generator 30 into a direct current. As shown in
The rectifier circuit 60 converts the alternating current applied to the input electrodes 61A and 61B to a pulsating current by a diode circuit 63, smoothes the pulsating current by a smoothing circuit 64, and outputs the current across the pair of output electrodes 62A and 62B. The diode circuit 63 is a common bridge circuit having, four diodes 63A, for example as shown in
As described above, the smoothing circuit 64 of this embodiment has a plurality of parallel-connected smoothing capacitors 64A between the pair of output electrodes 62A and 62B. Typically, however, one smoothing capacitor having an electrostatic capacity that equals to that of the plurality of smoothing capacitors 64A combined is connected between the pair of output electrodes 62A and 62B. This is because it is generally more advantageous to provide a single smoothing capacitor 64A than several divided smoothing capacitors 64A in terms of installation space, total mass, cost, and wiring simplicity. Even so, this embodiment uses a plurality of smoothing capacitors 64A for the smoothing circuit 64 in consideration of the fact that the circuit board 50 rotates with the tire wheel 11. These smoothing capacitors 64A have the same mass, and mounted on the front face 50A of the circuit board 50 such that their respective centers of gravity are located at positions equally dividing a common imaginary circle around the rotation axis J1 of the generator 30, as shown in
The positions of the plurality of diodes 63A and resistor 65 are also taken into account in order to make the center of gravity of the entire circuit board 50 closer to the rotation axis J1. Specifically, the plurality of diodes 63A included in the diode circuit 63 has the same mass similarly to the plurality of smoothing capacitors 64A, and is mounted on the rear side 50B of the circuit board 50 such that their respective centers of gravity are located at positions equally dividing a common imaginary circle around the rotation axis J1 of the generator 30. The resistor 65 is mounted in a central part on the rear side 50B of the circuit board 50 so that its center of gravity is located at the center of the circuit board 50. Accordingly, as described above, the center of gravity of the circuit board 50 as a whole is located in the central part.
A central part of the circuit board 50 shall refer to a range of a circle around the rotation axis J1 having 10% of surface area of either one of the front and rear side of the circuit board 50.
The diode circuit 63 in the rectifier circuit 60 is not limited to the plurality of diodes 63A that forms a bridge connection as described above. Namely, the rectifier circuit 60 is not limited to a bridge rectifier circuit and may have any configuration. Specifically, the rectifier circuit 60 may be, for example, a half wave rectifier circuit that is configured with only a single diode and uses only half cycle of alternating current, or a full wave or full wave voltage doubler rectifier circuit configured with a transformer and a pair of diodes. The circumferentially equally distributed configuration mentioned in the above description includes any arrangement that is not necessarily equally spaced but can counterbalance the centrifugal force, such as for example a line symmetric arrangement.
The housing 20 is fixed to the tire wheel 11 as described below. The plurality of anti-rotation protrusions 27 of the housing 20 and the plurality of engaging recesses 14K of the tire wheel 11 (see
The electrical load connected to the power supply device 10A of this embodiment is a tire monitoring device provided to the wheel 101 as shown in
Specifically, the tire valve 91 has a valve stem 91A which is fixed in a state such as to extend through the rim 11A, and a valve shaft 91B which moves linearly inside this valve stem 91A, insulated from each other. These valve stem 91A and valve shaft 91B are connected to the pair of input electrodes 92A and 92B of the charging circuit 90B described above inside the tire 102, and connected to a pair of core wires 13A and 13B of a cable 13 outside the tire 102.
The cable 13 is laid along a radial direction of the tire wheel 11 and secured on an outer face of the tire wheel 11. As shown in
The structure of the power supply device 10A according to this embodiment is as has been described above. This power supply device 10A does not operate and does not generate power when the vehicle 100 is stopped. The charging circuit 90B of the tire monitoring device 90 that is the load is provided with a diode 90C so that no power is supplied from the rechargeable battery 90A of the tire monitoring device 90 to the power supply device 10A.
When the vehicle 100 runs, the stator 33 of the generator 30 fixed to the tire wheel 11 of the wheel 101 rotates with the tire wheel 11 relative to the road surface, while the rotor 32 of the generator 30 rotates relative to the stator 33, because the self weight of the inertial component 40 restricts rotation of the rotor 32 relative to the road surface. Thus the power supply device 10A of this embodiment can generate power by utilizing rotation of the tire wheel 11 to cause the rotor 32 to rotate relative to the stator 33 of the generator 30. The generated alternating current is rectified by the rectifier circuit 60 and can be supplied to the tire monitoring device 90 serving as the load. When the rechargeable battery 90A of the tire monitoring device 90 has little remaining power, the battery is charged.
The durability of the circuit board 50 of the power supply device 10A is an issue because the circuit board is subjected to the centrifugal force when the tire wheel 11 rotates. In this regard, the power supply device 10A of this embodiment has a plurality of devices including the plurality of smoothing capacitors 64A distributed around the rotation axis J1 such that the center of gravity of the circuit board 50 as a whole is located in a central area of rotation, because of which the circuit board 50 undergoes less vibration resulting from the centrifugal force. Typically, a single smoothing capacitor is used, rather than a plurality of smoothing capacitors 64A. Here, a plurality of smoothing capacitors 64A being electrically equivalent is used, and distributed around the rotation axis J1, which facilitates the arrangement of the center of gravity of the entire circuit board 50 in a central area of rotation. The use of the plurality of smoothing capacitors 64A makes each of the smoothing capacitors 64A more lightweight, which reduces the centrifugal force applied to each smoothing capacitor 64A and in turn reduces the load which the support part of each smoothing capacitor 64A on the circuit board 50 must carry. These all contribute to better durability of the circuit board 50 and therefore improves the durability of the power supply device 10A equipped with the circuit board 50.
The circuit board 50 is disposed opposite to the first chamber 24A, with the stator 33 of the generator 30 interposed therebetween. The plurality of smoothing capacitors 64A mounted on the circuit board 50 is disposed laterally to the stator 33. This efficient use of the space lateral to the stator 33 allows the power supply device 10A to be more compact along the direction of the rotation axis J1.
While the circuit board 50 may be fixed to the generator 30, the circuit board 50 in the power supply device 10A of this embodiment is fixed to the housing 20 by a plurality of support pillars 45 rather than to the generator 30. As a result, the circuit board 50 can be fixed more stably, and this contributes to a better durability, too.
The power supply device 10A of this embodiment includes the housing 20 that is fixed to the tire wheel 11. The inertial component 40 is disposed inside the tubular first chamber 24A, which is closed at both ends, of this housing 20. Therefore entrance of foreign substances into the moving area of the inertial component 40 is prevented reliably.
The tire monitoring device 90 is typically driven only by a battery. In this embodiment, the power supply device 10A that generates power as the vehicle 100 runs supplies power to the tire monitoring device 90. Therefore, compared to a case where the tire monitoring device 90 is driven only by a battery, more power is available for the tire monitoring device 90, which enables sophistication of the tire monitoring device 90.
The power supply device 10B of this embodiment is shown in
In addition to the similar effects of the power supply device 10A of the first embodiment, the power supply device 10B of this embodiment facilitates mounting of the plurality of smoothing capacitors 64A onto the circuit board 50 because the plurality of smoothing capacitors 64A is mounted as a device unit 68 on the circuit board 50, in which the smoothing capacitors 64A are connected in parallel between the pair of connection terminals 69A and 69B and fixed on the ring member 69. The ring member 69 receives and balances the centrifugal force applied to the plurality of smoothing capacitors 64A and reduces the load on the circuit board 50 resulting from the centrifugal force, so that the durability of the circuit board 50 is improved.
The ring member 69 may be an annular case, or an annular circuit board. In the case with an annular case, the case may be filled with a potting material to fix the plurality of smoothing capacitors 64A. Alternatively, instead of the device unit 68, a single annular smoothing capacitor 64A may be specially produced and mounted on the circuit board 50 as shown in
While specific examples of the techniques included in the claims are disclosed in the specification and drawings, the techniques set forth in the claims are not limited to these specific examples but rather include various modifications and alterations of the specific examples, as well as partial extracts from the specific examples.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2021/013005 | 3/26/2021 | WO |
