WO2015129143A1

WO2015129143A1 - Foreign substance detecting device, wireless power transmission device, and wireless power transmission system

Info

Publication number: WO2015129143A1
Application number: PCT/JP2014/084749
Authority: WO
Inventors: Kohei Onizuka; Tetsu Shijo; Fumi Moritsuka; Akiko Yamada
Original assignee: Kabushiki Kaisha Toshiba
Priority date: 2014-02-25
Filing date: 2014-12-25
Publication date: 2015-09-03
Also published as: JP2015159690A

Abstract

A foreign substance detecting device detects a foreign substance based on a magnetic field. The device includes at least two magnetic sensors S1...Sn and a detector 20. Each of the magnetic sensors detects the magnetic field and outputs a signal corresponding to at least one of a magnitude and direction of the detected magnetic field. The detector detects the foreign substance based on the signals from the magnetic sensors. At least two of the magnetic sensors are placed at different positions in which the magnetic field detected when a foreign substance does not exist has an identical magnitude.

Description

DESCRIPTION

FOREIGN SUBSTANCE DETECTING DEVICE, WIRELESS POWER TRANSMISSION DEVICE, AND WIRELESS POWER

TRANSMISSION SYSTEM

CROSS REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2014-034300, filed on February 25, 2014, the entire contents of which are incorporated herein by reference.

FIELD

Embodiments described herein relate generally to a foreign substance detecting device, a wireless power transmission device, and a wireless power transmission system.

BACKGROUND

In the field of wireless power transmission technologies, a foreign substance detecting device is used for detecting a foreign substance that causes the decrease in power transmission efficiency and a danger due to heat generation. To detect the foreign substance, such a conventional foreign substance detecting device uses, for example, a method in which the power loss is estimated from the variations in the Q-value of the resonator, a method in which the generation of eddy current is estimated from the current values of the power transmission/reception coils, and a method in which the power loss is estimated from the power transmission/reception power value.

To accurately detect the foreign substance using such conventional foreign substance detecting methods, it is necessary to accurately set the reference values when a foreign substance does not exist, namely, the Q-value of the resonator, current values of the power transmission/reception coils, and power transmission/reception power value during a power transmission. However, in terms of the variations in power loss corresponding to the power transmission/reception power value, the variations in the positional relationship or peripheral environment of the power transmission/reception coils, and the production tolerance or the secular changes in the foreign substance detecting device, it is difficult to accurately set the reference value. Thus, it is difficult to accurately detect the foreign substance using the conventional foreign substance detecting device.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a block diagram of the functional configuration of a foreign substance detecting device according to a first embodiment.

Fig. 2 is a configuration diagram of an exemplary foreign substance detecting device according to the first embodiment.

Fig. 3 is a configuration diagram of another exemplary substance detecting device according to the first embodiment.

Fig. 4 is a configuration diagram of another exemplary substance detecting device according to the first embodiment.

Figs. 5 are flowcharts of a foreign substance detecting process according to a second embodiment.

Fig. 6 is a configuration diagram of an exemplary foreign substance detecting device according to a third embodiment.

Fig. 7 is a configuration diagram of an exemplary foreign substance detecting device according to a fourth embodiment.

Fig. 8 is a circuit diagram of an exemplary foreign substance detecting device according to the fourth embodiment.

Fig. 9 is a block diagram of an exemplary functional configuration of a wireless power transmission device according to a fifth embodiment.

Fig. 10 is a block diagram of another exemplary functional configuration of the wireless power transmission device according to the fifth embodiment.

Fig. 11 is a configuration diagram of an exemplary wireless power transmission device according to the fifth embodiment.

Fig. 12 is a flowchart of a pre-power-transmission foreign substance detecting process with the wireless power transmission device according to the fifth embodiment.

Fig. 13 is a flowchart of an ongoing-power-transmission foreign substance detecting process with the wireless power transmission device according to the fifth embodiment.

Fig. 14 is a block diagram of the functional configuration of a wireless power transmission system according to a sixth embodiment.

Fig. 15 is a flowchart of a positioning control with the wireless power transmission system according to the sixth embodiment.

Fig. 16 is an explanatory diagram of a method for detecting a relative position according to the sixth embodiment.

DETAILED DESCRIPTION

Embodiments will now be explained with reference to the accompanying drawings. The present invention is not limited to the embodiments.

A foreign substance detecting device detects a foreign substance based on a magnetic field. The device includes at least two magnetic sensors and a detector. Each of The magnetic sensors detects the magnetic field and outputs a signal corresponding to at least one of a magnitude and direction of the detected magnetic field. The detector detects the foreign substance based on the signals from the magnetic sensors. At least two of the magnetic sensors are placed at different positions in which the magnetic field detected when a foreign substance does not exist has an identical magnitude.

Hereinafter, the foreign substance detecting device, wireless power transmission device, and wireless power transmission system according to each of the embodiments will be described with reference to the appended drawings. In each of the embodiments to be described below, a foreign substance is detected based on the fundamental principles that the magnitude, direction, and time variations in the magnetic fields observed at a plurality of points when a current is applied to a conductor vary depending on the foreign substance that can affect the wireless power transmission. Foreign substances that the foreign substance detecting device can detect include, for example, a metal piece. However, the foreign substances are not limited to the example.

(First Embodiment)

First, a foreign substance detecting device according to the first embodiment will be described with reference to Fig. 1 to Fig. 4. The foreign substance detecting device according to the present embodiment is used, for example, for detecting a foreign substance before and during a power transmission. The wireless power transmission device includes an arbitrary type, such as a magnetic resonance type, an electromagnetic induction type, or a radio wave type, of wireless power transmission device. Herein, Fig. 1 is a block diagram of the functional configuration of a foreign substance detecting device according to the present embodiment. As illustrated in Fig. 1, the foreign substance detecting device according to the present embodiment includes a magnetic field generator 10, a sensor S including a plurality of magnetic sensors Sn (n = 1, 2, 3...), and a detector 20.

The magnetic field generator 10 includes a power source 11 and a coil 12 to generate a magnetic field (magnetic flux) for detecting a foreign substance. The power source 11 generates a direct or alternating current to supply the current to the coil 12. The coil 12 is conductive. The coil 12 generates a magnetic field corresponding to the current supplied from the power source 11. The power source 11 can be embedded in the foreign substance detecting device. Alternatively, an external power source can be used as the power source 11. The power source for power transmission of the wireless power transmission device can be used as the external power source. Using an external power source as the power source 11 can simplify the configuration of the foreign substance detecting device.

Herein, Fig. 2 and Fig. 3 are configuration diagrams of an exemplary foreign substance detecting device according to the present embodiment. In Fig. 2 and Fig. 3, the vertical direction (the direction with a solid arrow) is a direction in which a foreign substance is detected. The foreign substance detecting device detects the foreign substance existing in the foreign substance detecting direction. Normally, the foreign substance detecting device is used while being placed such that the foreign substance detecting direction corresponds to the direction in which the wireless power transmission device transmits power. In Fig. 2 and Fig. 3, a housing 13 of the foreign substance detecting device includes an opening surface 131 formed into a plate perpendicular to the foreign substance detecting direction. In that case, the opening surface 131 is a surface on which a substance is detected among the surfaces of the housing 13. For example, in Fig. 2 and Fig. 3, the shaded surface is the opening surface 131. The foreign substance detecting device detects the foreign substance on or above the opening surface 131.

In Fig. 2, the coil 12 is a vertical winding coil wound perpendicularly to the opening surface 131 of the housing 13. In other words, the coil 12 is wound parallel to the foreign substance detecting direction.

In Fig. 3, the coil 12 is a horizontal winding coil wound parallel to the opening surface 131 of the housing 13. In other words, the coil 12 is wound perpendicularly to the foreign substance detecting direction.

In either of the cases in Fig. 2 and Fig. 3, the direction of the major component of the magnetic field generated with the coil 12 is perpendicular to the opening surface 131 (parallel to the foreign substance detecting direction) at the part where the coil 12 is not wound in the opening surface 131 of the housing 13. The direction of the major component of the magnetic field generated with the coil 12 is parallel to the opening surface 131 (perpendicular to the foreign substance detecting direction) at the part where the coil 12 is wound in the opening surface 131 of the housing 13. The dashed arrows in Fig. 2 and Fig. 3 show the direction of the major component of the magnetic field generated with the coil 12.

Note that the power source 11 can be configured to be capable of adjusting the frequency or amplitude of the current to be supplied to the coil 12. This can modulate the frequency or amplitude of the magnetic field generated with the coil 12, and thus can sophisticate the method for detecting a foreign substance. As the sophisticated method for detecting a foreign substance, for example, a method in which the foreign substance detection is performed at a plurality of frequency bands can be cited.

The sensor S includes a plurality of magnetic sensors Sn configured to detect the magnetic field generated with the magnetic field generator 10 to output the signal of the current or voltage corresponding to at least one of the magnitude and direction of the detected magnetic field. A coil can be used as the magnetic sensor Sn. Using a coil can produce the foreign substance detecting device at a low cost. A Hall device can also be used as the magnetic sensor Sn.

A plurality of the magnetic sensors Sn is placed on a same plane perpendicular to the major component of the magnetic field generated with the magnetic field generator 10. More specifically, as illustrated in Fig. 2 and Fig. 3, the magnetic sensors Sn are placed at the part where the coil 12 is not wound in the opening surface 131 of the housing 13. The magnetic sensors Sn placed as described above can detect the major component of the magnetic field and thus improves their sensitivity of the detection of the magnetic field. This can improve the foreign substance detection accuracy of the foreign substance detecting device. Note that, although Fig. 2 and Fig. 3 illustrate the two magnetic sensors SI and Sn, the sensor S includes an arbitrary number of the magnetic sensors Sn.

At least two of the provided magnetic sensors Sn are placed symmetrically relative to the coil 12. In other words, two or more of the magnetic sensors Sn are placed at the positions in which the magnetic field generated with the magnetic field generator 10 has the same magnitude when a foreign substance does not exist. Considering the distances from the magnetic sensors Sn to the coil 12 can realize the symmetric placement of the magnetic sensors Sn. For example, in Fig. 2 and Fig. 3, the two magnetic sensors SI and Sn are placed at the same distance from the coil 12, and at the central portion of the opening surface 131 of the housing 13. The magnitude of the magnetic field is determined depending on the distance from the coil 12 at the central portion of the opening surface 131 of the housing 13. Thus, when a foreign substance does not exist, the magnetic field has the same magnitude at the positions of the magnetic sensors SI and Sn. In other words, the magnetic sensors SI and the magnetic sensors Sn are symmetrically placed.

When the magnetic sensors Sn are placed at the central portion and the periphery of the opening surface 131 of the housing 13 as illustrated in Fig. 4, in order to place the magnetic sensors Sn symmetrically, it is necessary to consider the shapes of the coil 12 and housing 13. For example, twelve magnetic sensors SI to S6 and Sa to Sf are placed in Fig. 4. The magnetic sensors

51 to S3 and Sd to Sf are placed at the same distance from the coil 12. The magnetic sensors S4 to S6 and Sa to Sc are also placed at the same distance from the coil 12. However, in Fig. 4, the magnetic field does not necessarily have the same magnitude at the central portion and at the periphery of the opening surface 131 of the housing 13. When a foreign substance does not exist, the magnitude of the magnetic field at each of the positions is roughly the fallowings.

SI = S3 = Sd = Sf

54 = S6 = Sa = Sc

52 = Se

55 = Sb

The Sx of the expressions described above indicates the magnitude of the magnetic field at the position of a magnetic sensor Sx. In Fig. 4, the magnetic sensors SI and Sd, and S3 and Sf are placed symmetrically, respectively. The magnetic sensors S4 and Sa, and S6 and Sc are placed symmetrically, respectively. The magnetic sensors S2 and Se are placed symmetrically. The magnetic sensors S5 and Sb are placed symmetrically.

As described above, the magnetic sensors Sn are symmetrically placed on the opening surface 131 of the housing 13 in consideration of the distances from the coil 12 and the shapes of the coil 12 and housing 13. Placing the magnetic sensors Sn symmetrically enables the sensor S to detect the foreign substance by comparing the output signals from the symmetrically placed magnetic sensors Sn. The method for detecting a foreign substance will be described below.

Note that, in the present embodiment, all of the magnetic sensors Sn included in the sensor S can be placed symmetrically. Alternatively, only some of the magnetic sensors Sn can be placed symmetrically. As illustrated in Fig. 4, when the magnetic sensors Sn are placed in an array shape, the space in which a foreign substance is detected is divided with each of the magnetic sensors Sn. This can improve the spatial resolution for the foreign substance detection.

After the output signals from the sensor S are input into the detector 20, the detector 20 detects the foreign substance based on the output signals. When a foreign substance exists on or near the sensor S, the magnetic field generated with the magnetic field generator 10 varies depending on the effect of the foreign substance, and the output signals from the sensor S vary depending on the variations in the magnetic field. Thus, the detector 20 can detect the foreign substance according to the variations in the output signals from the sensor S.

The detector 20 can be implemented by using a computer device as the basic hardware. For example, the computer device includes a memory and a CPU to store a program for performing a foreign substance detecting process in the memory in advance and execute the program with the CPU. This can implement the functional configuration of the detector 20.

Hereinafter, a method for detecting a foreign substance with the detector 20 will be described. As described above, at least some of the magnetic sensors Sn are symmetrically placed in the present embodiment. When it is assumed that the symmetrically placed magnetic sensors Sn are referred to as the magnetic sensors SI and Sn (See Figs. 2 and 3), and when a foreign substance does not exist in the area in which the magnetic sensors SI and Sn can detect a foreign substance, the output signals from the magnetic sensors SI and Sn have approximately the same size (absolute value) ( |S1 | = |Sn |).

As illustrated in Fig. 2, when the directions of the magnetic field detected by the magnetic sensors SI and Sn are opposite to each other, the output signals from the magnetic sensors SI and Sn have the opposite signs (SI = -Sn). As illustrated in Fig. 3, when the directions of the magnetic field detected by the magnetic sensors SI and Sn are the same, the output signals from the magnetic sensors SI and Sn have the same sign (SI = Sn). However, in both of the cases, the output signals from the magnetic sensors SI and Sn have approximately the same size (absolute value).

On the other hand, as illustrated in Figs. 2 and 3, when a foreign substance M exists in the area in which the magnetic sensors SI and Sn can detect a foreign substance, the size(s) of the output signal(s) from one or both of the magnetic sensors SI and Sn varies from the size(s) when the foreign substance M does not exist. There is a low possibility that the foreign substance M affects the output signals from the magnetic sensors SI and Sn to the same degree. Thus, when the foreign substance M exists, the output signals from the magnetic sensors SI and Sn have different sizes (|S1 |≠ |Sn|). Thus, the detector 20 can detect the foreign substance by comparing the sizes of the output signals from the magnetic sensors SI and Sn.

More specifically, the detector 20 calculates the relative value of the sizes of the output signals from the magnetic sensors SI and Sn. For example, the difference (|S1 | - |Sn | ) or quotient ( I S 11 / 1 Sn I ) of the sizes of the output signals from the magnetic sensors SI and Sn is used as the relative value. For example, when the difference of the sizes of the output signals is used as the relative value and when a foreign substance does not exist, the relative value is approximately zero. When the foreign substance exists, the relative value varies from zero. The detector 20 detects the foreign substance by comparing the relative value with a predetermined threshold.

As described above, according to the present embodiment, the detector 20 can detect the foreign substance based on the relative value of the output signals from the magnetic sensors Sn. A conventional foreign substance detecting device requires measuring a plurality of parameters including the variations in power loss corresponding to the power transmission/reception power value, the variations in the positional relationship or peripheral environment of the power transmission/reception coils, and the production tolerance or the secular changes in the foreign substance detecting device (hereinafter, collectively referred to as "disturbance") and setting the reference value of the output signal from each of the magnetic sensors Sn. However, it is not necessary in the present embodiment to set the reference value. This can readily detect the foreign substance.

The disturbance or the like affects the magnetic sensors Sn approximately uniformly. Thus, the detection of the foreign substance based on the relative value can suppress the effect of the disturbance. This can prevent a foreign substance from excessively being detected or being undetected, and can accurately detect a foreign substance.

When the foreign substance has a small size or has a small effect on the wireless power transmission, the effect of the disturbance or the like on the variations in the output signals is sometimes larger than the effect of the foreign substance on the variations in the output signals. It is difficult in a conventional foreign substance detecting device to detect the foreign substance described above. Thus, there is a risk that a serious problem such as the heat generation of a foreign substance during the power transmission can occur. However, as described above, the present embodiment can suppress the effect of the disturbance or the like, and thus can accurately detect even a foreign substance having a small size or a foreign substance having a small effect on the wireless power transmission.

Furthermore, according to the present embodiment, a plurality of magnetic sensors Sn is provided. This divides the space in which the sensor S detects a foreign substance. This can improve the spatial resolution for the foreign substance detection.

(Second Embodiment)

Next, a foreign substance detecting device according to the second embodiment will be described with reference to Figs. 5. The foreign substance detecting device according to the present embodiment has the same configuration as the first embodiment. In the present embodiment, a detector 20 detects the foreign substance based on not only the relative value of the output signals of a plurality of magnetic sensors S but also the value of each of the output signals.

Herein, Fig. 5(A) is a flowchart of a foreign substance detecting process with the detector 20 according to the present embodiment. As illustrated in Fig. 5(A), when the foreign substance detecting process is started, a current is supplied from a power source 11 to a coil 12 (step SI), the coil 12 generates a magnetic field for detecting a foreign substance. The magnetic sensors Sn input the output signals corresponding to the magnetic field to the detector 20, respectively. The detector 20 compares a value Sn of each of the input output signals with a predetermined threshold (step S2).

The threshold is set for each of the magnetic sensors Sn. For example, the threshold is set as a range of a predetermined margin value from a reference value SCAL of the output signal from each of the magnetic sensors Sn when a foreign substance does not exist. In Fig . 5, the lower limit of the threshold of the output signal is SCAL - M (M > 0) . The upper limit of the threshold of the output signal is SCAL + N (N > 0). The margin values M and N can be the same value, or can be different values.

When the value Sn of the output signal from the magnetic sensor Sn is in the range of the threshold (YES in step S2), the detector 20 determines that a foreign substance does not exist (step S3). When the value is out of the range of the threshold (NO in step S2), the detector 20 determines that a foreign substance exists (step S4). As described above, in addition to the foreign substance detecting process according to the relative value of the output signals from the magnetic sensors Sn, performing the foreign substance detecting process according to the value of the output signal from each of the magnetic sensors Sn can further improve the foreign substance detection accuracy.

In the present embodiment, the detector 20 calibrates the reference value SCAL of the output signal from the magnetic sensor Sn (calibration) . Fig. 5(B) is a flowchart of a calibration process with the detector 20. The calibration process is performed under the condition in which a foreign substance does not exist. As illustrated in Fig. 5(B), when a calibration process is started, a current is supplied from the power source 11 to the coil 12 such that the coil 12 generates a magnetic field for detecting a foreign substance (step S5). Each of the magnetic sensors Sn inputs the output signal corresponding to the detected magnetic field to the detector 20. The detector 20 stores the value Sn of the output signal input from each of the magnetic sensors Sn and set the value as a new calibrated reference value SCAL (step S6) . When the new reference values S_CAL of all of the magnetic sensors Sn or desired magnetic sensors Sn are set, the supply of the current from the power source 11 to the coil 12 stops and the calibration process is terminated (step S7).

In the foreign substance detecting process in and after the calibration process, a threshold is set based on the new reference value SCAL set in the calibration process and then a foreign substance is detected. The calibration process is preferably performed when the coil 12 is produced or is installed to an actual usage environment. In addition, the calibration process is preferably performed by the administrator periodically.

Performing the calibration process can obtain a reference value SCAL in consideration of the effect of the disturbance or the like. Performing the foreign substance detecting process based on the reference value SCAL can suppress the effect of the disturbance or the like, and thus can accurately detect a foreign substance. Note that the foreign substance detecting device can also be configured to set a reference value on the relative value of the output signals from the magnetic sensors Sn in the calibration process. In such a case, the detecting device can detect the foreign substance by comparing the set reference value with the detected relative value.

(Third Embodiment)

Hereinafter, a foreign substance detecting device according to the third embodiment will be described with reference to Fig. 6. In the present embodiment, the sensor S uses the magnetic sensors Sn together with another type of sensors Tn (n = 1, 2, ...). Fig. 6 is a configuration diagram of an exemplary foreign substance detecting device according to the present embodiment. In Fig. 6, each of the sensors Tn is placed with each of the magnetic sensors Sn side by side. However, each of the sensors Tn can be placed at an arbitrary position without being placed with each of the magnetic sensors Sn side by side. The number of sensors Tn can be set arbitrarily.

In the present embodiment, the detector 20 detects the foreign substance based on the output signals from the magnetic sensors Sn and the output signals from the sensors Tn. When the sensors Tn are symmetrically placed on the housing 13 as illustrated in Fig. 6, the detector 20 can detect the foreign substance based on the relative value of the sizes of the output signals of the symmetrically placed sensors Tn. The detector 20 can also detect the foreign substance by comparing the output signal of each of the sensors Tn with a reference value, or can calibrate the reference value of the sensor Tn in a calibration process. When a foreign substance is detected in at least one of the result of the foreign substance detection based on the output signals from the magnetic sensors Sn and the result of the foreign substance detection based on the output signals of the sensors Tn, the detector 20 determines that a foreign substance exists.

For example, a capacitance sensor configured to detect the capacitance can be used as the sensor Tn. Using a capacitance sensor readily detect the foreign substance existing in an area in which the magnetic field is approximately parallel to the opening surface 131 of the housing 13, for example, immediately on the coil 12.

Furthermore, a temperature sensor configured to detect a temperature can be used as the sensor Tn. Even if a foreign substance exists, using a temperature sensor enables the foreign substance detecting device to perform a control in which the power is transmitted while the increase in the temperature of the foreign substance is monitored. As the control described above, for example, a control in which the power is transmitted when the temperature of the foreign substance is equal to or lower than a predetermined temperature, or a control in which the power transmission power is regulated so as to prevent the temperature of the foreign substance from being higher than a predetermined temperature can be cited. To perform such a control, the foreign substance detecting device is configured to be capable of transmitting the output signals of the sensors T to the wireless power transmission device through a wired or wireless communication.

Furthermore, an infrared sensor configured to detect infrared rays or an image sensor configured to detect a visible light can be used as the sensor Tn. Using an infrared sensor or an image sensor can detect the foreign substance, such as an animal, that has a small effect on the magnetic field.

Furthermore, an ultrasonic sensor configured to detect an ultrasonic wave can be used as the sensor Tn. Using an ultrasonic sensor can detect the foreign substance difficult to find even with various sensors as described above. For example, an ultrasonic sensor is effective in detecting the foreign substance of which electric characteristic varies slightly and that does not emit infrared rays in a dark environment. The foreign substance detecting device can be configured to detect the distance to the foreign substance using the ultrasonic sensor as a distance sensor. The foreign substance detecting device can determine based on the detected distance information whether to transmit the power or whether to start a pre-power-transmission foreign substance detecting process.

In the present embodiment, using the magnetic sensors Sn together with various sensors Tn can prevent the foreign substance from excessively being detected or being undetected and thus can further improve the foreign substance detection accuracy of the foreign substance detecting device. Note that an arbitrary sensor other than the various sensors described above can be used as the sensor Tn. Alternatively, two or more types of sensors can be used as the sensor Tn.

(Fourth Embodiment)

Next, a foreign substance detecting device according to the fourth embodiment will be described with reference to Fig. 7 and Fig. 8. In the present embodiment, a magnetic sensor Sn includes a coil and is also used as a coil 12 of a magnetic field generator 10. Fig. 7 is a configuration diagram of an exemplary foreign substance detecting device according to the present embodiment.

As illustrated in Fig. 7, an independent coil 12 as illustrated in Fig. 1 is not provided in the present embodiment. Each of the magnetic sensors Sn is used as the coil 12. In other words, each of the magnetic sensors Sn generates a magnetic field as the coil 12 while detecting the magnetic field generated with the other magnetic sensors Sn to output a signal corresponding to the detected magnetic field. Although not illustrated in Fig. 7, each of the magnetic sensors Sn is connected to a power source 11 and a detector 20.

Some or all of the magnetic sensors Sn generate magnetic fields. Some or all of them operate so as to detect the magnetic fields. When some of the magnetic sensors Sn generated the magnetic fields, magnetic fields are formed around all of the magnetic sensors Sn and electromotive force corresponding to the average magnetic field magnitude of the formed the magnetic fields occurs. The average magnetic field magnitude varies depending on a foreign substance. Thus, the electromotive force occurring in the magnetic sensors Sn also varies depending on the foreign substance. Accordingly, generating magnetic fields with some or all of the magnetic sensors Sn and detecting the electromotive force generated in some or all of the magnetic sensors Sn can detect the foreign substance. When an arbitrary magnetic sensor Sn generates a magnetic field and detects the electromotive force generated in its own sensor, the detection of the variations in the parameter relating to the inductance value of the magnetic sensor Sn is equivalent to the detection of the foreign substance.

Fig. 8 is a circuit diagram of an exemplary foreign substance detecting device according to the present embodiment. In Fig. 8, each of the magnetic sensors Sn included in the sensor S is connectable to the power source 11 and an AD convertor 14. A controller 15 switches the connection. When being connected to the power source 11, the magnetic sensor Sn functions as the coil 12 of the magnetic field generator 10. On the other hand, when being connected to the AD convertor 14, the magnetic sensor Sn functions as the magnetic sensor Sn that detects the magnetic fields.

As illustrated in Fig. 8, when the magnetic sensors Sn generating magnetic fields generate alternating magnetic fields with the alternating power source 11, the signal, for example, that has been digitalized with the AD convertor 14 at a low sampling rate after the electromotive force of the magnetic fields of the sensors detecting magnetic fields has been rectified, is input to the detector 20. Creating an output stream from the output signals from the magnetic sensors Sn using a multiplexer can share the circuit configuration such as the AD convertor. This can simplify the configuration of the foreign substance detecting device and can reduce the cost.

In the present embodiment, the magnetic fields can be generated with a plurality of magnetic sensors Sn. This can further improve the spatial resolution for the foreign substance detection. Implementing the circuit configuration such as the sensor S or the AD convertor on a printed board can reduce the cost and improve the mechanical strength. (Fifth Embodiment)

Next, as the fifth embodiment, a wireless power transmission device including the foreign substance detecting device will be described with reference to Fig. 9 to Fig. 13. The wireless power transmission device according to the present embodiment is a magnetic resonance type wireless power transmission device configured to wirelessly transmit power using a magnetic field. In the wireless power transmission device, the power transmission is controlled based on the result of the foreign substance detection with the foreign substance detecting device.

Herein, Fig. 9 is a block diagram of an exemplary functional configuration of the wireless power transmission device according to the present embodiment. As illustrated in Fig. 9, the wireless power transmission device according to the present embodiment includes: the foreign substance detecting device including a magnetic field generator 10, a detector 20, and a sensor S including a plurality of magnetic sensors Sn; a controller 30; a power source 31; a power transmission coil 32; and a notifier 33. The foreign substance detecting device has the configuration described above. Accordingly, the description will be omitted.

The controller 30 obtains a foreign substance detection result of the detector 20 to control the power transmission based on the foreign substance detection result. The controller 30 can be implemented by using a computer device as the basic hardware.

The power source 31 is an alternating power source configured to supply power to the power transmission coil 32. The power supply with the power source 31 is controlled with the controller 30.

The power transmission coil 32 is a conductive coil wound perpendicularly to or parallel to a direction in which the power is transmitted. The power transmission coil 32 is supplied with an alternating current from the power source 31 to generate an alternating magnetic field so as to wirelessly transmit the power to the power reception coil included in the power transmission destination such as an electric vehicle.

The notifier 33 is controlled with the controller 30. When the foreign substance detecting device detects a foreign substance, the notifier 33 notifies the foreign substance to the user of the power transmission destination or the administrator of the wireless power transmission device. A monitor capable of outputting an image or a loud speaker capable of outputting a sound can be used as the notifier 33. A communicator such as a mobile phone of the user or the administrator can also be used as the notifier 33.

In the present embodiment, the magnetic resonance type wireless power transmission device can also use the foreign substance detecting device as the other configuration. Herein, Fig. 10 is a block diagram of another exemplary functional configuration of the wireless power transmission device according to the present embodiment.

In Fig. 10, the controller 30 is also used as the controller 20, the power source 31 is also used as the power source 11, and the power transmission coil 32 is also used as the coil 12. In that case, the function of the detector 20 is implemented with the controller 30. The power transmission coil 32 is used as the coil 12. The power source 31 of the power transmission coil 32 is used as the power source 11 of the coil 12. The configuration described above simplifies the configuration of the wireless power transmission device and can reduce the number of the components.

Fig. 11 is a configuration diagram of an exemplary wireless power transmission device in Fig. 10. As illustrated in Fig. 11, in the wireless power transmission device in Fig. 10, the power transmission direction corresponds to the foreign substance detecting direction (the direction with the solid arrow in Fig. 11), and the magnetic sensors Sn are placed on a same plane (the opening surface 131 of the housing 13) perpendicular to the major component of the magnetic field generated with the power transmission coil 32. When a foreign substance M exists on the plane perpendicular to the major component of the magnetic field generated with the power transmission coil 32 in the magnetic resonance type wireless power transmission device, a problem of the heat generation or the power loss becomes pronounced. However, the magnetic sensors S are placed on the plane in the present configuration. This can accurately detect such a foreign substance M having a large effect.

Next, a foreign substance detecting process and a power transmission process with the wireless power transmission device according to the present embodiment will be described. Fig. 12 is a flowchart of a pre-power-transmission foreign substance detecting process that is performed before the start of the power transmission. When the preparation of the power transmission is started (step S8), the wireless power transmission device performs the pre-power-transmission foreign substance detecting process with the foreign substance detecting device (step S9). The number of executions of the foreign substance detecting process or the time can arbitrarily be set. When a foreign substance is not detected in the foreign substance detecting process (NO in step S9), the controller 30 causes the power source 31 to start supplying power. This starts the power transmission (step S10).

On the other hand, when a foreign substance is detected in the foreign substance detecting process (YES in step S9), the controller 30 stops the preparation for a power transmission (step Sll). The controller 30 notifies the detection of the foreign substance to the user or the administrator with the notifier 33 (step S12). This can causes the user or the administrator to remove the foreign substance such that a power transmission can be started without a foreign substance. Accordingly, this can suppress a danger due to the heat generation of the foreign substance or the decrease in the power transmission efficiency. Notifying a foreign substance to the user or the administrator facilitates the removal of the foreign substance, and thus can reduce the time from the detection to the removal of the foreign substance.

Fig. 13 is a flowchart of an ongoing-power-transmission foreign substance detecting process that is performed during a power transmission. When a power transmission is started (step S13), the wireless power transmission device performs the ongoing-power-transmission foreign substance detecting process with the foreign substance detecting device (step S14). The foreign substance detecting process is repeated until the power transmission is completed or until a foreign substance is detected. When a foreign substance is detected in the foreign substance detecting process (YES in step S14), the controller 30 stops the power transmission (step S15) and notifies the detection of the foreign substance to the user or the administrator with the notifier 33 (step S16).

This can cause the user or the administrator to remove a foreign substance to perform a power transmission without the foreign substance even when the foreign substance enters during the power transmission. Accordingly, this can suppress a danger due to the heat generation of the foreign substance or the decrease in the power transmission efficiency. Notifying the foreign substance to the user or the administrator facilitates the removal of the foreign substance, and thus can reduce the time from the detection to the removal of the foreign substance.

Note that, although the wireless power transmission device is a magnetic resonance type wireless power transmission device in the present embodiment, the type of the power transmission is not limited to the embodiment. Another type, for example, an electromagnetic induction type or a radio wave type, of wireless power transmission device can include the foreign substance detecting device. When the wireless power transmission device includes a power transmission coil 32, the power transmission coil 32 can also be used as the coil 12 as illustrated in Fig. 10.

(Sixth Embodiment)

Next, a wireless power transmission system (hereinafter, merely referred to as a "system") including the wireless power transmission device according to the fifth embodiment will be described as the sixth embodiment with reference to Fig. 14 to Fig.

16. In the system according to the present embodiment, a positioning control between a power transmission coil and a power reception coil is performed. Fig. 14 is a block diagram of an exemplary functional configuration of the system according to the present embodiment. As illustrated in Fig. 14, the system according to the present embodiment includes a wireless power transmission device and a power transmission destination 4.

The wireless power transmission device is the wireless power transmission device according to the fifth embodiment and further includes a positioner 34.

The positioner 34 is an actuator configured to adjust the relative position of the power reception coil 42 to the power transmission coil 32 by moving the power transmission coil 32. The positioner 34 is controlled with a controller 30. The positioner 34 can move only the power transmission coil 32 or can move the entire wireless power transmission device.

Note that, although having the same configuration as in Fig. 10, the wireless power transmission device in Fig. 14 can have the same configuration as in Fig. 9. The controller 30 preferably includes a communicator capable of wirelessly communicating with the power transmission destination in the present embodiment.

The power transmission destination 4 is configured to be capable of receiving power from the wireless power transmission device. The power transmission destination includes, for example, an electric vehicle or an electric train to which power can wirelessly be supplied. However, the power transmission destination is not limited to the example. The power transmission destination 4 includes a controller 40, a magnetic field generator 41, a power reception coil 42.

The controller 40 controls the generation of a magnetic field with the magnetic field generator 41 or the reception of power with the power reception coil 42. The controller 40 can be implemented by using a computer device as the basic hardware. The controller 40 preferably includes a communicator capable of wirelessly communicating with the wireless power transmission device.

The magnetic field generator 41 (a second magnetic field generator) generates a magnetic field that can be detected with a magnetic sensor S of the wireless power transmission device. The magnetic field generator 41 includes, for example, a coil and a power source. When the power transmission destination 4 includes the power reception coil 42 as illustrated in Fig. 14, the power reception coil 42 can also be used as the magnetic field generator 41. The magnetic field generator 41 is placed at a predetermined position relative to the power reception coil 42.

The power reception coil 42 is a conductive coil wound perpendicularly or parallel to a direction in which power is received, in other words, a direction in which the wireless power transmission device transmits power (the direction with the solid arrow in Fig. 14). When being a magnetic resonance type wireless power transmission device, the wireless power transmission device resonates with the alternating magnetic field generated with the power transmission coil 32 and receives the power. Note that, when the wireless power transmission device is another type of wireless power transmission device, the power transmission destination 4 includes a power receiver corresponding to the type of the wireless power transmission device instead of the power reception coil 42.

Next, the positioning control between the power transmission coil 32 and the power reception coil 42 with the system according to the present embodiment will be described. Fig. 15 is a flowchart of the positioning control. In the present system, the positioning control is started, for example, when the power transmission destination 4 stops. The stop of the power transmission destination 4 can be determined with the wireless communication of the controller 30 and the controller 40.

When the positioning control is started (step S17), the magnetic field generator 41 of the power transmission destination 4 generates a magnetic field (step S18). The sensor S of the wireless power transmission device detects the magnetic field generated with the magnetic field generator 41 to input a signal corresponding to at least one of the magnitude and direction of the detected magnetic field to the controller 30.

The controller 30 detects the relative position of the power reception coil 42 to the power transmission coil 32 based on the output signal from the sensor S (step S19). The relative position is detected as the deviation of the power reception coil 42 from the position of the power transmission coil 32 on the plane perpendicular to the power transmission direction. When the positions of the power transmission coil 32 and the power reception coil 42 are aligned on the plane perpendicular to the power transmission direction, the efficiency in the power transmission peaks.

The controller 30 detects the relative position, for example, based on the gradient of the output signal of each of the magnetic sensors Sn. When the magnetic sensors Sn are placed in an array shape, the size of the output signal of each of the magnetic sensors Sn has gradient. The controller 30 detects the deviation of the power reception coil 42 according to the absolute value or relative value of the gradient using a theoretical formula or a table. The table stores the positional relationship between the power transmission coil 32 and each of the magnetic sensors Sn, and the positional relationship between the magnetic field generator 41 and the power reception coil 42. The positional relationship between the magnetic field generator 41 and the power reception coil 42 can also be obtained from the controller 40 through a wireless communication. A transform algorithm for obtaining the relative position from the output signals from the magnetic sensors Sn is stored in the controller 30 in advance as illustrated in Fig. 16.

Next, the controller 30 determines whether the deviation is equal to or lower than a threshold by comparing the detected deviation of the power reception coil 42 with a preset threshold (step S20). The threshold is preferably set in consideration of the shapes of the power transmission coil 32 and the power reception coil 42. This is because the characteristic of the power transmission with respect to the deviation of the power reception coil 42 varies depending on the shapes of the coils.

For example, when the coil is wound perpendicularly to the power transmission direction, the characteristic of the power transmission with respect to the deviation of the power reception coil 42 has orientation. Accordingly, it can be considered that the threshold varies depending on the direction of the deviation. Alternatively, when the coil is wound horizontally to the power transmission direction, the characteristic of the power transmission with respect to the deviation of the power reception coil 42 hardly has orientation. Thus, it can be considered that the threshold is kept at a constant value with respect to the deviation in all directions.

When the deviation is equal to or lower than the threshold as the result of the determination with the controller 30 (YES in step S20), the positioning control is terminated. On the other hand, when the deviation is larger than the threshold (NO in step S20), the controller 30 controls the positioner 34 to move the power transmission coil 32 so as to reduce the deviation of the power reception coil 42 (step S21).

When the positioner 34 completes moving the power transmission coil 32, the controller 30 detects the relative position of the power reception coil 42 again (step S19). After that, the processes in step S19 to step S21 are repeated. The positioning control is completed when the deviation is equal to or lower than the threshold.

The present embodiment can adjust the position of the power transmission coil 32 so as to reduce the deviation of the power reception coil 42 from the power transmission coil 32. This can improve the power transmission efficiency. The relative position of the power reception coil 42 to the power transmission coil 32 can be used for determining whether to transmit power or for adjusting various parameters used for the power transmission.

Note that, although being provided in the wireless power transmission device in the present embodiment, the positioner 34 can be provided in the power transmission destination 4. In that case, the positioner 34 is configured to be capable of moving the power reception coil 42. The controller 40 of the power transmission destination 4 obtains the relative position information on the power reception coil 42 from the controller 30 through a wireless communication so as to control the positioner 34 based on the obtained relative position information. The positioner 34 moves the power reception coil 42 so as to reduce the deviation of the power reception coil 42. The positioner 34 can be provided in both of the wireless power transmission device and the power transmission destination 4, or can be provided separately from the wireless power transmission device and the power transmission destination 4. In that case, the positioner 34 is configured to be capable of moving at least one of the power transmission coil 32 and the power reception coil 42. The positioner 34 moves at least one of the power transmission coil 32 and the power reception coil 42 based on the relative position information on the power reception coil 42 obtained from the wireless power transmission device so as to reduce the deviation of the power reception coil 42.

While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel methods and systems described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the methods and systems described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.

Claims

1. A foreign substance detecting device detecting a foreign substance based on a magnetic field, comprising:

at least two magnetic sensors each configured to detect the magnetic field and output a signal corresponding to at least one of a magnitude and direction of the detected magnetic field; and

a detector configured to detect the foreign substance based on the signals from the magnetic sensors,

wherein at least two of the magnetic sensors are placed at different positions in which the magnetic field detected when a foreign substance does not exist has an identical magnitude.

2. The device according to claim 1, wherein the magnetic sensors are placed on a same plane perpendicular to a major component of the magnetic field.

3. The device according to claim 1 or 2, wherein the detector detects the foreign substance based on a relative value of the signals from the magnetic sensors.

4. The device according to any one of claims 1 to 3, further comprising a magnetic field generator including a conductive coil configured to generate the magnetic field and a power source configured to supply a current to the coil.

5. The device according to any one of claim 4, wherein the magnetic sensor includes a conductive coil and the coil is also used as the magnetic field generator.

6. The device according to any one of claims 1 to 5, wherein the detector detects the foreign substance based on a value of the signal of each of the magnetic sensors.

7. The device according to any one of claims 1 to 6, wherein the detector obtains the signal when a foreign substance does not exist, sets the value of the signal as a reference value, and detects the foreign substance based on the reference value and a value of the signal.

8. The device according to any one of claims 1 to 7, further comprising a capacitance sensor configured to detect capacitance, wherein

the detector detects a foreign substance based on the signals from the magnetic sensors and a signal from the capacitance sensor.

9. The device according to any one of claims 1 to 8, further comprising a temperature sensor configured to detect a temperature, wherein

the detector detects a foreign substance based on the signals from the magnetic sensors and a signal from the temperature sensor.

10. The device according to any one of claims 1 to 9, further comprising an infrared sensor configured to detect a magnitude of an infrared ray, wherein

the detector detects a foreign substance based on the signals from the magnetic sensors and a signal from the infrared sensor.

11. The device according to any one of claims 1 to 10, further comprising an image sensor configured to detect a visible light, wherein

the detector detects a foreign substance based on the signals from the magnetic sensors and a signal from the image sensor.

12. The device according to any one of claims 1 to 11, further comprising an ultrasonic sensor configured to detect an ultrasonic wave, wherein

the detector detects a foreign substance based on the signals from the magnetic sensors and a signal from the ultrasonic sensor.

13. A wireless power transmission device comprising :

a power transmission coil configured to wirelessly transmit power through a magnetic field;

a controller configured to control the power transmission with the power transmission coil; and

the foreign substance detecting device according to any one of claims 1 to 12,

wherein the controller controls the power transmission based on a result of a foreign substance detection with the foreign substance detecting device.

14. The device according to claim 13, the foreign substance detecting device detects the foreign substance based on the magnetic field generated with the power transmission coil.

15. The device according to claim 13 or 14, wherein, when the detector detects the foreign substance, the controller stops the power transmission.

16. The device according to any one of claims 13 or 15, further comprising:

a notifier configured to notify a result of a foreign substance detection with the foreign substance detecting device.

17. A wireless power transmission system comprising :

the wireless power transmission device according to any one of claims 13 or 16; and

a power transmission destination that includes a power reception coil to which power is wirelessly transmitted from the power transmission coil, and a second magnetic field generator placed at a predetermined position relative to the power reception coil and generating a magnetic field.

18. The system according to claim 17, wherein the magnetic sensors detect a magnetic field generated with the second magnetic field generator and outputs a signal corresponding to at least one of a magnitude and direction of the detected magnetic field, and

the controller detects a relative position of the power reception coil to the power transmission coil based on the signals from the magnetic sensors.

19. The system according to claim 18, further comprising :

a positioner configured to adjust a position of at least one of the power transmission coil and the power reception coil,

wherein the positioner moves at least one of the power transmission coil and the power reception coil based on the relative position such that an efficiency in power transmission from the power transmission coil to the power reception coil is increased.

20. A foreign substance detecting device detecting a foreign substance based on a magnetic field generated with a conductive coil, comprising:

wherein at least two of the magnetic sensors are placed at a part where the conductive coil is not wound in the surface that the conductive coil is wound.