Metal object detection device

Patent metadata

Field	Value
Publication number	US-9841524-B2
Application number	US-201314758078-A
Country	US
Kind code	B2
Filing date	Dec 12, 2013
Priority date	Dec 27, 2012
Publication date	Dec 12, 2017
Grant date	Dec 12, 2017

Abstract

A metal object detection device includes a plurality of detection coils, a capacitor configuring a resonant circuit in cooperation with each of at least two of the detection coils, a first series connection body, a second series connection body, a voltage applying unit, and a processing unit. The voltage applying unit applies an AC voltage to both ends of each of the first series connection body and the second series connection body. The processing unit performs a process for detecting the metal object on the basis of a potential difference between a connection point included in the first series connection body and a connection point included in the second series connection body.

First claim

The invention claimed is:

1. A metal object detection device applied to a non-contact power feeding device that performs power transfer between a primary coil and a secondary coil in a non-contact manner, the metal object detection device comprising:
a plurality of detection coils detecting a metal object present in a path of a magnetic flux generated by at least one of the primary coil and the secondary coil;
a capacitor configuring a resonant circuit in cooperation with each of at least two of the plurality of detection coils;
a first series connection body including one of a series connection body having at least one of the resonant circuits and a first passive element, the at least one of the resonant circuits and the first passive element being connected in series, and a series connection body having the detection coil and the capacitor configuring one of the resonant circuits, the detection coil and the capacitor being connected in series;
a second series connection body including one of a series connection body having at least one of the resonant circuits except for the resonant circuit configuring the first series connection body and a second passive element, the at least one of the resonant circuits except for the resonant circuit configuring the first series connection body and the second passive element being connected in series, and a series connection body having the detection coil and the capacitor configuring one of the resonant circuits except for the resonant circuit configuring the first series connection body, the detection coil and the capacitor configuring one of the resonant circuits except for the resonant circuit configuring the first series connection body being connected in series;
a voltage applying unit applying an AC voltage to both ends of each of the first series connection body and the second series connection body; and
a processing unit performing a process for detecting the metal object on the basis of a potential difference between a connection point included in the first series connection body and a connection point included in the second series connection body.

2. The metal object detection device according to claim 1 , wherein
the first series connection body and the second series connection body are connected in parallel to each other.

3. The metal object detection device according to claim 2 , wherein
at least four of the detection coils are provided,
each of the at least four detection coils includes the capacitor and the resonant circuit,
the first series connection body includes a series connection body having a first resonant circuit which is one of the at least four resonant circuits, and a second resonant circuit which is one of the remaining resonant circuits, and which is the first passive element,
the second series connection body includes a series connection body having a third resonant circuit which is one of the at least four resonant circuits except for the first resonant circuit and the second resonant circuit, and a fourth resonant circuit which is one of the at least four resonant circuits except for the first resonant circuit, the second resonant circuit, and the third resonant circuit, and which is the second passive element, and
the processing unit performs the detecting process on the basis of a potential difference between a connection point of the first resonant circuit and the second resonant circuit, and a connection point of the third resonant circuit and the fourth resonant circuit.

4. The metal object detection device according to claim 3 , wherein
the first resonant circuit, the second resonant circuit, the third resonant circuit, and the fourth resonant circuit are identical with each other in impedance at a frequency of an output voltage of the voltage applying unit.

5. The metal object detection device according to claim 2 , wherein
the resonant circuit configuring the first series connection body, the resonant circuit configuring the second series connection body, the first passive element, and the second passive element configure an AC bridge.

6. The metal object detection device according to claim 2 , wherein
the detection coil includes a portion in which an induced current flows in a predetermined direction, and a portion in which the induced current flows in a direction opposite to the predetermined direction when a main magnetic flux circulating between the primary coil and the secondary coil passes through the detection coil.

7. The metal object detection device according to claim 1 , further comprising:
an input side resonant circuit having a coil and a capacitor; and
a load side resonant circuit having a coil and a capacitor, wherein
each of the detection coils configures a resonant circuit in cooperation with the capacitor,
the first series connection body includes a series connection body having the detection coil and the capacitor configuring one of the resonant circuits having the detection coil,
the second series connection body includes a series connection body having the detection coil and the capacitor configuring one of the resonant circuits except for the resonant circuit configuring the first series connection body,
the voltage applying unit applies an AC voltage between both ends of each of the first series connection body and the second series connection body with the application of the AC voltage to the input side resonant circuit,
the detection coils and the capacitors configuring the plurality of resonant circuits configure relay coils and relay capacitors which perform power transfer between the input side resonant circuit and the load side resonant circuit in a non-contact manner with the application of the AC voltage by the voltage applying unit,
a first connection point which is a connection point between the detection coil and the capacitor configuring the first series connection body has the same potential as a second connection point which is a connection point between the detection coil and the capacitor configuring the second series connection body, and
the processing unit performs a process for detecting the metal object on the basis of a potential difference between a portion without having the same potential in a closed circuit including the first series connection body and a portion without having the same potential in a closed circuit including the second series connection body.

8. The metal object detection device according to claim 7 , wherein
the first connection point and the second connection point are grounded to provide the first connection point and the second connection point with the same potential.

9. The metal object detection device according to claim 7 , wherein
the first connection point and the second connection point are short-circuited to each other to provide the first connection point and the second connection point with the same potential.

10. The metal object detection device according to claim 7 , wherein
a detection coil of the detection coils except for the detection coils configuring the first series connection body and the second series connection body is arranged outside a path of the main magnetic flux circulating between the primary coil and the secondary coil.

11. The metal object detection device according to claim 1 , wherein
a frequency of an output voltage of the voltage applying unit is set to the same frequency as a resonant frequency of the resonant circuit.

12. The metal object detection device according to claim 7 , wherein
a system including the plurality of resonant circuits, the input side resonant circuit, and the load side resonant circuit has a plurality of resonant frequencies, and
the

Assignees

• Denso Corp

Inventors

• Obayashi Kazuyoshi
• Kamiya Akira
• Takahashi Eisuke
• Tani Keisuke

Classifications

• H02J17/00

  Electricity · mapped topic

• G01V3/104 Primary

  using several coupled or uncoupled coils (G01V3/101 takes precedence) · CPC title

• H02J5/005

  Electricity · mapped topic

• H02J50/10

  using inductive coupling · CPC title

• H02J50/80

  involving the exchange of data, concerning supply or distribution of electric power, between transmitting devices and receiving devices · CPC title