Contactless power transmission device provided in a vehicle for charging an electronic device

A contactless power transmission device which transmits electric power in a contactless way includes: a power transmission section which transmits electric power using a primary coil; a power receiving section which is provided in a radio communication device and receives electric power using a secondary coil that is electromagnetically coupled with the primary coil; a housing which shields an electromagnetic wave, in which the power transmission section is provided, and which forms a closed space where the radio communication device is housed; and a housing antenna section which is provided in the housing and transmits a first communication signal to the outside of the housing, or transmits a second communication signal to the inside of the housing, the first communication signal being emitted from the radio communication device housed inside the housing, the second communication signal being emitted from the radio communication device housed outside the housing.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a contactless power transmission device.

Priority is claimed on Japanese Patent Application No. 2011-019443, filed Feb. 1, 2011, and Japanese Patent Application No. 2011-245707, filed Nov. 9, 2011, the content of which is incorporated herein by reference.

2. Description of Related Art

As a charging device for radio communication apparatuses, such as mobile phones, a contactless power transmission device is known.

The contactless power transmission device transmits AC power of a certain frequency from a power transmission device to a power receiving device, which is provided or fixed to a radio communication device, using electromagnetic induction or the like.

For example, U.S Patent Application Publication No. 2008/0001572 discloses a contactless power transmission device mounted in a vehicle.

However, when transmitting electric power in order to charge a radio communication device using a contactless power transmission device mounted in a vehicle, some of the AC power of a frequency used for power transmission or a harmonic or subharmonic of the AC power becomes an electromagnetic wave, an alternating magnetic field, or an alternating electric field and is input as a noise to a neighboring device for a vehicle through the air or a connection cable.

As a result, there has been a problem in that the noise causes degradation of S/N (SN ratio), a reduction in the receiving sensitivity, and the like when a device which transmits or receives information receives the information through radio communication with the outside of the vehicle or radio communication with the inside of the vehicle.

For example, since a harmonic frequency component (for example, approximately 1 MHz in a tenth-order harmonic) in contactless power transmission overlaps an AM radio frequency band (0.5 to 1.6 MHz), it appears as radio noise.

In addition, the harmonic frequency component in contactless power transmission may affect radio communication (one-seg reception or communication with an in-vehicle device using Bluetooth) of a radio communication device being charged.

SUMMARY OF THE INVENTION

Therefore, it is an object of the invention to provide a contactless power transmission device capable of ensuring the communication of a radio communication device being charged while preventing unnecessary electromagnetic radiation to the outside during charging of the radio communication device.

In order to solve the above-described problems, the contactless power transmission device according to the present invention adopted the following configurations.

According to an aspect of one embodiment of the invention, a contactless power transmission device includes: a power transmission section which transmits electric power using a primary coil; a power receiving section which is provided in a radio communication device and receives electric power using a secondary coil that can be electromagnetically coupled with the primary coil; a housing which shields an electromagnetic wave, in which the power transmission section is provided, and which forms a closed space where the radio communication device is housed; and a housing antenna section which is provided in the housing and transmits a first communication signal to the outside of the housing, or transmits a second communication signal to the inside of the housing, the first communication signal being emitted from the radio communication device housed inside the housing, the second communication signal being emitted from the radio communication device housed outside the housing.

Through the above-described configuration, when charging the radio communication device in a state where the radio communication device is housed in the housing of the contactless power transmission device, it is possible to reduce unnecessary electromagnetic radiation to the outside of the housing at the time of power transmission. As a result, an adverse effect of the electromagnetic wave on an external device can be reduced.

In addition, by the housing antenna section, communication of the radio communication device can be ensured even when the radio communication device is charged.

In the contactless power transmission device according to the aspect of the embodiment of the invention, the housing antenna section is formed by an internal antenna section provided inside the housing and an external antenna section which is connected to the internal antenna section and is provided outside the housing.

In addition, it is preferable that the internal antenna section be provided so as to be disposed at a position close to an antenna of the radio communication device when the radio communication device is housed in the housing.

Through the above-described configuration, a lowering in transmission and reception performance of the radio communication device can be prevented. As a result, satisfactory transmission and reception performance can be ensured.

In the contactless power transmission device according to the aspect of the embodiment of the invention, it is preferable that the external antenna section be provided at a position which is outside the housing and is near the housing.

Through the above-described configuration, it is possible to obtain satisfactory sensitivity in communication between the radio communication device being charged and a device provided near the housing.

In the contactless power transmission device according to the aspect of the embodiment of the invention, it is preferable that a structural material, which makes the attenuation of electromagnetic waves in a frequency band for power transmission larger than the attenuation of electromagnetic waves in a frequency band used for communication by the radio communication device, be used as a shielding structure material which shields an electromagnetic wave in the housing.

Through the above-described configuration, it is possible to obtain the magnetic field shielding effect in a low frequency band and also to reduce the attenuation of electromagnetic waves in a high frequency band. As a result, a lowering in the reception sensitivity of the radio communication device can be suppressed.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, a contactless power transmission device according to an embodiment of the invention will be described with reference toFIGS. 1 to 4.

First Embodiment

First, a contactless power transmission device according to a first embodiment of the invention will be described with reference toFIGS. 1 to 3.

FIG. 1is a perspective view showing the appearance of a console box1and a parking brake2provided between the driver's seat and the passenger seat of a vehicle. In the present embodiment, a contactless power transmission device is provided in the console box1.

The console box1is provided behind the parking brake2in the vehicle and is configured to include a box body3, which is formed of resin and is fixed to the vehicle body, and a lid5, which is formed of resin and is fixed so as to be able to be opened and closed in the vertical direction through a hinge4provided at the back side of the box body3.

As shown inFIG. 2, a recess6which is open upward is formed in the box body3, and a shield body7(shield structure) which can shield an electromagnetic wave is fixed to the entire inside surface of the recess6without a gap.

A separation plate8, which is formed of resin and separates the space formed in the shield body7up and down, is provided inside the shield body7. A primary coil9, which is a power transmission section that transmits electric power, is fixed to the back surface side of the separation plate8.

The primary coil9is connected to a power source of the vehicle through a signal transmission circuit provided in the shield body7.

The space above the separation plate8in the shield body7is a housing space11for housing a mobile phone100which is a radio communication device.

A positioning member12formed of urethane resin is fixed to the inner wall surface of the shield body7and the upper surface of the separation plate8so that the mobile phone100is disposed immediately above the primary coil9when the mobile phone100is placed on the separation plate8of the housing space11.

The positioning member12has a structure where a downward inclined surface is formed so that the mobile phone100can be easily inserted and positioning between the primary coil9and a secondary coil101, which will be described later, can be easily performed.

In addition, the positioning member12may be provided so as to be detachable from the shield body7and the separation plate8.

In this case, since only the positioning member12can be replaced according to the shape of the mobile phone100, the positioning accuracy of the primary coil9and the secondary coil101can be ensured.

In addition, this is convenient since a wide range of housing space inside the console box1can be used when the mobile phone100is not charged.

The secondary coil101which is a power receiving section is provided in the mobile phone100, so that electromagnetic coupling between the primary coil9and the secondary coil101is possible when the mobile phone100is housed in the housing space11.

In addition, the mobile phone100can be charged by transmitting electric power from the primary coil9to the secondary coil101in a contactless way using electromagnetic induction.

A recess13which is open downward is formed in the lid5, and a shield body14(housing) which can shield an electromagnetic wave is fixed to the entire inside surface of the recess13without a gap.

A housing space15is provided inside the shield body14. Accordingly, an opening of the shield body14of the lid5and an opening of the shield body7of the box body3match each other when the lid5is closed, so that the housing space11of the box body3and the housing space15of the lid5form one closed space.

In addition, a coaxial cable (housing antenna section)16is fixed to the back of the lid5so as to pass through the shield body14and also pass through the inside and the outside of the lid5.

One end side of the coaxial cable16is inserted in the housing space15provided in the lid5and is connected to an internal antenna (internal antenna section)17fixed to the inside surface of the lid5.

FIG. 3is a view showing the details of the internal antenna17which is simply shown inFIG. 2.

The internal antenna17includes a substrate20fixed to the lid5and a pair of antenna patterns21and22with a predetermined shape formed of copper foil or the like on the surface of the substrate20. An inner conductor16aof the coaxial cable16is connected to one antenna pattern21, and an outer conductor16bof the coaxial cable16is connected to the other antenna pattern22.

In addition, the antenna patterns21and22have a balun function of a microstrip line structure for impedance matching between a portion17ahaving antenna characteristics for a mobile phone and a portion17bhaving antenna characteristics for Bluetooth.

The internal antenna17is disposed so as to be located immediately above the mobile phone100housed in the housing space11of the box body3when the lid5is closed.

That is, the internal antenna17is provided so as to be disposed at the position close to an antenna of the mobile phone100housed in the console box1(housing).

The other end of the coaxial cable16pulled to the outside of the lid5is an external antenna and is connected to an antenna outside a vehicle or an in-vehicle antenna (not shown).

The antenna outside a vehicle is an antenna which is fixed to the roof or window glass of a vehicle so that an electric wave from the outside of the vehicle can be received, and the in-vehicle antenna is an antenna for communication with a device inside the vehicle.

When charging the mobile phone100using the contactless power transmission device provided in the console box1configured in this way, the mobile phone100is housed in the housing space11provided in the box body3and the lid5is closed and then electric power is transmitted from the primary coil9to the secondary coil101using electromagnetic induction so that the mobile phone100is charged.

Since the console box1has such a configuration, the primary coil9and the secondary coil101can be housed in the closed space where an electromagnetic wave is shielded by the shield bodies7and14. Accordingly, it is possible to reduce unnecessary electromagnetic radiation to the outside of the console box1at the time of contactless power transmission.

As a result, an adverse effect (for example, radio noise or one-seg receiving failure) of the electromagnetic wave on a device outside the console box1can be reduced.

In addition, for the mobile phone100being charged, the internal antenna17is disposed at the position near the mobile phone100, and this internal antenna17is connected to an antenna outside the vehicle or an in-vehicle antenna through the coaxial cable16. Accordingly, even when the mobile phone100is charged in a state where the mobile phone100is sealed in the console box1, communication between the mobile phone100and the external device can be ensured.

Thus, in this invention, a communication signal emitted from the mobile phone100housed inside the console box1is transmitted to the outside of the housing. Additionally, a communication signal emitted from the mobile phone100housed outside the console box1is transmitted to the inside of the console box1.

Second Embodiment

Next, a contactless power transmission device according to a second embodiment of the invention will be described with reference toFIG. 4.

The contactless power transmission device according to the second embodiment is also provided in the console box1of the vehicle as in the first embodiment.

The only different point of the contactless power transmission device according to the second embodiment and the contactless power transmission device according to the first embodiment is a form of the external antenna of the coaxial cable16.

Also in the second embodiment, the coaxial cable16is fixed so as to pass through the shield body14and also pass through the inside and the outside of the lid5, and one end of the coaxial cable16is inserted in the housing space15of the lid5and is connected to the internal antenna17in the housing space15, as in the first embodiment.

On the other hand, in the second embodiment, the coaxial cable16passes through a top plate5aof the lid5, and the other end of the coaxial cable16pulled to the outside of the lid5is connected to an external antenna (external antenna section)18fixed to the top plate5a.

In addition, inFIG. 4, the internal antenna17and the external antenna18are simply shown.

The structure of the external antenna18is the same as that of the internal antenna17and accordingly, the structure of the external antenna18will be described with reference toFIG. 3. The external antenna18includes a substrate20fixed to the top plate5aof the lid5and a pair of antenna patterns21and22with a predetermined shape formed of copper foil or the like on the surface of the substrate20. An inner conductor16cof the coaxial cable16is connected to one antenna pattern21, and an outer conductor16dof the coaxial cable16is connected to the other antenna pattern22.

In addition, the antenna patterns21and22have a balun function of a microstrip line structure for impedance matching between a portion18ahaving antenna characteristics for a mobile phone and a portion18bhaving antenna characteristics for Bluetooth.

That is, in the second embodiment, the external antenna18is provided at the position which is outside the console box1(housing) and is near the console box1.

This is a point of difference between the first and second embodiments.

Since the other configuration is the same as that of the device according to the first embodiment, the same reference numerals are given to the same components and an explanation thereof is omitted here.

Also in the second embodiment, it is possible to reduce unnecessary electromagnetic radiation to the outside of the console box1at the time of contactless power transmission. As a result, an adverse effect of the electromagnetic wave on a device outside the console box1can be reduced.

In addition, for the mobile phone100being charged, the internal antenna17is disposed at the position near the mobile phone100, and this internal antenna17is connected to the external antenna18on the top plate5aof the lid5through the coaxial cable16. Accordingly, communication between the mobile phone100and the external device can be ensured in the same manner as when the mobile phone100is placed on the console box1.

Thus, in this invention, a communication signal emitted from the mobile phone100housed inside the console box1is transmitted to the outside of the housing, additionally, a communication signal emitted from the mobile phone100housed outside the console box1is transmitted to the inside of the console box1.

In the second embodiment, when the mobile phone100and an AV device or a navigational device in the vehicle communicate with each other through Bluetooth or a wireless LAN, for example, the distance between these devices and the external antenna18can be shortened. As a result, it is possible to obtain good sensitivity.

By the way, the frequency of an electric wave for information communication between a radio communication device and an external device is a 1 GHz band in mobile phone communication, a several gigahertz band in Bluetooth, and a several gigahertz band in a wireless LAN, for example, while the alternating magnetic field frequency for power transmission is usually hundreds of kilohertz or tens of megahertz if it is high.

Therefore, taking into consideration a band difference between the frequency of an electric wave for information communication between the radio communication device and the external device and the alternating magnetic field frequency for power transmission, the shield bodies7and14in the first or second embodiment are formed of a material whose alternating magnetic field permeability in a high frequency band is lower than its alternating magnetic field permeability in a low frequency band, in other words, a material (for example, permalloy) which makes the attenuation of electromagnetic waves in a high frequency band smaller than that in a low frequency band.

In this case, it is possible to reduce the attenuation of electromagnetic waves in a high frequency band used for communication while shielding electromagnetic waves in a low frequency due to power transmission.

For example, if an electromagnetic steel plate or permalloy is used as a structural material of the shield bodies7and14when an alternating magnetic field of hundreds of kilohertz is used for power transmission, the magnetic field shielding effect can be obtained in a low frequency region without lowering relatively largely the receiving sensitivity of the mobile phone100in a high frequency region since the magnetic field shielding effect is high in the low frequency region but is low in the high frequency region.

Other Embodiments

In addition, the invention is not limited to each of the embodiments described above.

For example, when the lid5is closed, the internal antenna17may be made to be in direct contact with the mobile phone100housed in the housing space11.

Although the case where the contactless power transmission device is provided in the console box1of the vehicle has been described in each of the embodiments, the contactless power transmission device may also be formed as an independent housing instead of being used together with other devices without being particularly limited to this.

In addition, the contactless power transmission device according to each embodiment of the invention is not limited to the vehicle.

In addition, the radio communication device is not limited to the mobile phone.