Coil unit and noncontact power transmission apparatus

• US 9,524,823 B2
• Filed: 02/28/2014
• Issued: 12/20/2016
• Est. Priority Date: 11/04/2011
• Status: Active Grant

• Current Assignee: PANASONIC AUTOMOTIVE SYSTEMS CO., LTD. (Panasonic Holdings Corporation)
• Original Assignee: Panasonic Intellectual Property Management Co., Ltd. (Panasonic Holdings Corporation)
• Inventors: Miyashita, Norihiro, Fujita, Atsushi, Sadakata, Hideki, Omori, Yoshiharu
• Primary Examiner(s): Johnson, Ryan
• Application Number:
  US14/193,965
• Publication Number:
  US 20140175899A1
• Time in Patent Office: 1,026 Days
• US Class Current: 1/1
• CPC Class Codes: B60L 53/12 Inductive energy transfer
• CPC Class Codes: B60L 53/122 Circuits or methods for driving the primary coil, e.g. supplying electric power to the coil
• CPC Class Codes: H01F 38/14 Inductive couplings for wireless supply or distribution of electric power using inductive coupling H02J50/10
• CPC Class Codes: H02J 50/10 using inductive coupling
• CPC Class Codes: H02J 50/12 of the resonant type
• CPC Class Codes: H02J 50/70 involving the reduction of electric, magnetic or electromagnetic leakage fields
• CPC Class Codes: Y02T 10/70 Energy storage systems for electromobility, e.g. batteries
• CPC Class Codes: Y02T 10/7072 Electromobility specific charging systems or methods for batteries, ultracapacitors, supercapacitors or double-layer capacitors
• CPC Class Codes: Y02T 90/14 Plug-in electric vehicles

Abstract

A coil unit configured to transmit or receive electric power by electromagnetic induction in a noncontact manner, including: a coil into or from both terminals of which a high-frequency voltage is input or output; a metal conductor placed near the coil; and a first capacitor and a second capacitor connected to the terminals of the coil, wherein the ratio of the capacitance between the first capacitor and the second capacitor is set to a value at which a current induced into the metal conductor due to capacitance coupling when a high-frequency voltage is input into or output from the coil is reduced.

Claims

1. A coil unit configured to transmit or receive electric power by electromagnetic induction in a noncontact manner, comprising:

a coil into or from both terminals of which a high-frequency voltage is input or output;

a metal conductor placed near the coil; and

a first capacitor and a second capacitor respectively connected to the terminals of the coil, wherein

the ratio of the capacitance between the first capacitor and the second capacitor is set to a value at which a current induced into the metal conductor due to capacitance coupling when a high-frequency voltage is input into or output from the coil is reduced, and

the ratio between capacitances C1 and C2 (C1/C2) where C1 is the capacitance of the first capacitor and C2 is the capacitance of the second capacitor is set to satisfy conditions (1) and (2) below when a high-frequency voltage is input into or output from the coil;

(1) a combined capacitance [C1×

C2/(C1+C2)] of the first capacitor and the second capacitor serially connected to the coil is constant; and

(2) the current induced into the metal conductor due to capacitance coupling is smaller than that observed when C1=C2.

2. The coil unit of claim 1, wherein

the ratio between the capacitances C1 and C2 (C1/C2) is individually set to satisfy condition (3) below, in addition to the condition (1):

(3) the current induced into the metal conductor due to capacitance coupling is smallest.

3. The coil unit of claim 1, wherein equation f=½

π

(L Cs)^1/2 where Cs is the combined capacitance [C1×

C2/(C1+C2)], f is the frequency of the high-frequency voltage, and L is the inductance of the coil is satisfied.

4. The coil unit of claim 1, wherein

the coil is housed in a case, and

the metal conductor is a member constituting at least part of the case.

5. A noncontact power transmission apparatus configured to transmit electric power from a power-transmitting coil to a power-receiving coil by electromagnetic induction in a noncontact manner, wherein

at least one of the power-transmitting coil and the power-receiving coil includes:

a coil into or from both terminals of which a high-frequency voltage is input or output,

a metal conductor placed near the coil, and

a first capacitor and a second capacitor respectively connected to the terminals of the coil, and

the ratio of the capacitance between the first capacitor and the second capacitor is set to a value at which a current induced into the metal conductor due to capacitance coupling when a high-frequency voltage is input into or output from the coil is reduced, and

the ratio between capacitances C1 and C2 (C1/C2) where C1 is the capacitance of the first capacitor and C2 is the capacitance of the second capacitor is set to satisfy conditions (1) and (2) below when a high-frequency voltage is input into or output from the coil;

(1) a combined capacitance [C1×

C2/(C1+C2)] of the first capacitor and the second capacitor serially connected to the coil is constant; and

(2) the current induced into the metal conductor due to capacitance coupling is smaller than that observed when C1=C2.

6. The noncontact power transmission apparatus of claim 5, wherein

the coil is housed in a case, and

the metal conductor is a member constituting at least part of the case.

7. The noncontact power transmission apparatus of claim 5, wherein

the power-receiving coil is mounted on a vehicle, and

the metal conductor is a member constituting at least part of the vehicle.

8. A coil unit configured to transmit or receive electric power by electromagnetic induction in a noncontact manner, comprising:

a coil into or from both terminals of which a high-frequency voltage is input or output;

a metal conductor placed near the coil; and

a capacitor inserted in the coil,

wherein

the coil is separated by the capacitor into a first coil and a second coil different in the magnitude of inductance, and

the ratio of the inductance between the first coil and the second coil is set to a value at which a current induced into the metal conductor due to capacitance coupling when a high-frequency voltage is input into or output from the coil is reduced.

9. The coil unit of claim 8, wherein equation f=½

π

(L C_L)^1/2 where C_L is the capacitance of the capacitor, f is the frequency of the high-frequency voltage, and L is the inductance of the coil is satisfied.

10. A coil unit configured to transmit or receive electric power by electromagnetic induction in a noncontact manner, comprising:

a coil into or from both terminals of which a high-frequency voltage is input or output;

a metal conductor placed near the coil; and

a ground site at which the coil is grounded,

wherein

the coil is separated by the ground site into a first coil and a second coil different in the magnitude of inductance, and

the ratio of the inductance between the first coil and the second coil is set to a value at which a current induced into the metal conductor due to capacitance coupling when a high-frequency voltage is input into or output from the coil is reduced.

11. The coil unit of claim 10, wherein the amount of the current induced into the metal conductor due to capacitance coupling is smaller than that of a current induced into the metal conductor when a middle point of the coil is grounded.