Wireless power supply with vehicle pairing system and power transmission device

When a vehicle approaches a parking space, a ground controller sets a power transmission coil to first excitation in which the power transmission coil is excited in an excitation pattern containing identification data. When the power transmission coil is set to the first excitation, a vehicle controller acquires the identification data from the excitation pattern received by a power reception coil, and transmits the identification data to a power transmission device. Then, the ground controller determines whether or not the identification data contained in the excitation pattern when setting the power transmission coil to the first excitation and the identification data acquired from the excitation pattern received by the power reception coil match each other. If both pieces of identification data match each other, the ground controller sets the power transmission coil to second excitation.

TECHNICAL FIELD

The present invention relates to a wireless power supply system and a power transmission device for wirelessly supplying power to a vehicle equipped with a battery such as an electric vehicle.

BACKGROUND

Heretofore, a wireless charge system disclosed in International Publication No. WO2012/042902 has been known which is configured to charge a battery provided to a vehicle by wirelessly supplying power to the vehicle. International Publication No. WO2012/042902 discloses that, in a case where a plurality of power transmission devices are present, a power transmission coil is weakly excited to generate a random signal, which is detected by a vehicle, and the vehicle and the power transmission device are paired with each other if it is confirmed that the random signals match each other between the vehicle and the power transmission device.

However, in the configuration in the conventional example disclosed in above International Publication No. WO2012/042902, in order to perform the pairing, the vehicle enters and stops in the parking space, and in this state a signal containing a random ID pattern is transmitted by the power transmission coil and received by the vehicle. For this reason, a problem arises in that it takes a long time before the vehicle starts to be actually charged after stopping in the parking space.

SUMMARY

The present invention has been made to solve this problem in the conventional art, and an object thereof is to provide a wireless power supply system and a power transmission device capable of quick pairing with a vehicle entering a parking space.

In a wireless power supply system according to one aspect of the present invention, a power transmission device includes an approach detection sensor configured to detect when a vehicle approaches a parking space, a power-supply control unit configured to control power to be supplied to a power transmission coil, and a power-transmission-side communication unit configured to communicate with a power reception device. Moreover, the power reception device includes a power-reception control unit configured to control reception of power at a power reception coil, and a power-reception-side communication unit configured to communicate with the power transmission device. When the vehicle approaches the parking space, the power-supply control unit sets the power transmission coil to first excitation in which the power transmission coil is excited in an excitation pattern containing identification data, and when the power transmission coil is set to the first excitation, the power-reception control unit acquires the identification data from the excitation pattern received by the power reception coil, and transmits the identification data to the power transmission device. Further, the power-supply control unit determines whether or not the identification data contained in the excitation pattern when setting the power transmission coil to the first excitation and the identification data acquired from the excitation pattern received by the power reception coil match each other, and if the pieces of identification data match each other, the power-supply control unit sets the power transmission coil to second excitation for determining whether or not the vehicle is present at a chargeable position in the parking space.

A power transmission device according to one aspect of the present invention includes: an approach detection sensor configured to detect when a vehicle approaches a parking space; a power-supply control unit configured to control current to be supplied to a power transmission coil; and a communication unit configured to communicate with the vehicle. When the vehicle approaches the parking space, the power-supply control unit sets the power transmission coil to first excitation in which the power transmission coil is excited in an excitation pattern containing identification data. When the communication unit receives identification data transmitted from the vehicle, the power-supply control unit determines whether or not the received identification data and the identification data contained in the excitation pattern when setting the power transmission coil to the first excitation match each other. If the pieces of identification data match each other, the power-supply control unit sets the power transmission coil to second excitation for determining whether or not the vehicle is present at a chargeable position in the parking space.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Description of First Embodiment

FIG. 1is a block diagram showing the configuration of a wireless power supply system according to an embodiment of the present invention. As shown inFIG. 1, this wireless power supply system includes a power transmission device101provided to parking equipment on the ground, and a power reception device102mounted on a vehicle20.

The power transmission device101includes a plurality of parking spaces each for charging a battery mounted on the vehicle20, and includes a ground unit51for each parking space. Note thatFIG. 1shows two ground units51,51aas an example. The present invention is not limited to this configuration and is applicable to cases where the power transmission device101includes three or more ground units.

The ground unit51includes: a power transmission coil11installed on the ground of the parking space; a power unit12configured to excite the power transmission coil11by causing current to flow therethrough; a ground controller13(power-supply control unit) configured to control the actuation of the power unit12; and a communication unit14(power-transmission-side communication unit) configured to perform wireless communication with the power reception device102. To the ground controller13, a vehicle detection sensor33(approach detection sensor) is connected which is configured to detect when the vehicle20approaches the parking space. Meanwhile, the ground unit51aalso has a similar configuration, and a power transmission coil11aand a vehicle detection sensor33aare connected thereto. Note that the ground units51,51acan each be constructed of an integrated computer including a central processing unit (CPU) and storage means such as an RAM, an ROM, and a hard disk drive, for example.

The power reception device102, which is mounted on the vehicle20, includes a power reception coil21installed at an appropriate position on the bottom of the vehicle20, and a rectification-smoothing circuit22configured to rectify and smooth AC current received by the power reception coil21. The power reception device102further includes a vehicle controller (power-reception control unit) configured to control the actuation of the rectification-smoothing circuit22, a battery23configured to be charged with power received by the power reception coil21, and a communication unit25(power-reception-side communication unit) configured to communicate with the ground unit51. The power reception coil21is disposed at such a position as to coincide with the above-mentioned power transmission coil11when the vehicle20is parked at a predetermined position in the parking space. Note that the power reception device102can be constructed of an integrated computer including a central processing unit (CPU) and storage units such as an RAM, an ROM, and a hard disk drive, for example.

FIG. 2is an explanatory diagram showing the relation between the vehicle20and a plurality of parking spaces32,32a. In this embodiment, a process of pairing the vehicle20and the parking space32at which the vehicle20is to be parked is performed through wireless communication between the ground units51,51a, provided at the parking spaces32,32a, and the power reception device102, mounted on the vehicle20. Then, the power transmission coil11at the parking space32, paired with the vehicle20, is energized and excited, thereby wirelessly supplying power to the power reception device102. As a result, the battery23, mounted on the vehicle20, is charged.

FIG. 3is a circuit diagram showing detailed configurations of the power unit12, the power transmission coil11, the power reception coil21, and the rectification-smoothing circuit22shown inFIG. 1and peripheral elements thereof. As shown inFIG. 3, the power unit12includes an inverter circuit31formed of a plurality of switch circuits (such for example as MOSFETs). The on and off of each switch circuit are controlled under control of the ground controller13(seeFIG. 1) such that a DC voltage Vin supplied from a DC power source15is converted into an AC voltage of a predetermined frequency.

A resistor R1and a capacitor C1are connected to the power transmission coil11. By applying the AC voltage outputted from the power unit12to the power transmission coil11and thereby causing a current to flow therethrough, the power transmission coil11can be set to one of first excitation and second excitation to be described later. Further, when the power transmission coil11and the power reception coil21are positioned to coincide with each other (when the coils11,21are positioned to face each other as shown inFIG. 1), the power transmission coil11is set to third excitation in which a current for battery charge is supplied to the power transmission coil11, to thereby wirelessly transmit power to the power reception coil21.

A capacitor C2and a resistor R2are connected to the power reception coil21, and the power reception coil21wirelessly receives the power transmitted from the power transmission coil11. The rectification-smoothing circuit22includes a bridge circuit formed of a plurality of diodes, as well as capacitors C3, C4, a coil L, and a discharge resistor R3. The rectification-smoothing circuit22converts the AC voltage received by the power reception coil21into a DC voltage and further smoothes it and then supplies it to the battery23(seeFIG. 1). The rectification-smoothing circuit22further includes a discharge circuit26formed of a resistor R4and a switch SW1. A voltage sensor27configured to measure output voltage Vout is provided at the output terminal of the rectification-smoothing circuit22. The output voltage Vout, measured by the voltage sensor27, is outputted to the vehicle controller24(seeFIG. 1). The on and off of the switch SW1are controlled under control of the vehicle controller24. Specifically, while the power transmission coil11is set to the first excitation, the switch SW1is turned off if the output voltage Vout is at or below a preset threshold voltage Vth, and the switch SW1is turned on to discharge the voltage stored in the capacitor C4if the output voltage Vout exceeds the threshold voltage Vth.

Moreover, in this embodiment, when the vehicle20approaches the parking space32, the power transmission coil11is set to the first excitation to perform pairing between the vehicle20and the ground unit51. Further, after the pairing is completed, the power transmission coil11is set to the second excitation to determine whether or not the vehicle20is parked at the predetermined position in the parking space32. The second excitation is an excitation pattern stronger than the first excitation. Then, if it is determined that the vehicle20is parked at the predetermined position in the parking space32, the power transmission coil11is set to the third excitation to wirelessly supply power.

Next, the first excitation will be described with reference to a timing chart shown inFIG. 4. InFIG. 4, Part (a) shows the waveform of current I1flowing through the power transmission coil11, Part (b) shows the waveform of current I2flowing through the power reception coil21, and Part (c) shows the waveform of current obtained by performing full-wave rectification on the current I2. Further, Part (d) shows current IL obtained by smoothing the current I2after the full-wave rectification, Part (e) shows the output voltage Vout from the rectification-smoothing circuit22, and Part (f) shows a logic indicating “0” or “1” recognized from the output voltage Vout. In the first excitation, an identification ID (identification data) is set by means of a pattern of excitation of the power transmission coil11.

In the first excitation, as shown in Part (a) ofFIG. 4, a weak pulsed current P0is caused to flow through the power transmission coil11as a start bit. When the vehicle20approaches the parking space32, the current I2flows through the power reception coil21as shown in Part (b) ofFIG. 4. By rectifying this current I2, current |I2| shown in Part (c) ofFIG. 4is obtained. Then, by smoothing this current |I2|, the current IL shown in Part (d) ofFIG. 4is obtained.

As shown in Part (e) ofFIG. 4, as the current IL flows through the rectification-smoothing circuit22, the output voltage Vout rises at a time t0, the switch SW1is turned on when the output voltage Vout exceeds the threshold voltage Vth, and the output voltage Vout then drops. After the start bit, pulsed currents P1, P2, P3, P4are caused to flow at times t1, t2, t3, t4, respectively, to set a four-bit identification ID. Specifically, the current I1is caused to flow as shown by P1, P2, P4to set a logic “1” and the current I1is not caused to flow as shown by P3to set a logic “0.” In the example shown inFIG. 4, an identification ID “1, 1, 0, 1” is generated.

Then, if the identification ID set by the ground unit51and the identification ID recognized by the vehicle controller24based on the output voltage Vout match each other, the vehicle20and the ground unit51are determined to have been paired with each other. In sum, the vehicle20and the parking space32can be paired with each other by setting the power transmission coil11to the first excitation. Also, though illustration is omitted inFIG. 4, a stop bit may be transmitted after the identification ID “1, 1, 0, 1.” Meanwhile, there are a variety of methods for the first excitation, and details will be described in second to ninth embodiments.

Next, the second excitation will be described. After the power transmission coil11is set to the first excitation and pairing between the vehicle20and the ground unit51is completed as mentioned above, the power transmission coil11is set to the second excitation to determine whether or not the parked position of the vehicle20in the parking space32is a chargeable position.

The ground controller13sets the power transmission coil11to the second excitation, which is weaker than the excitation during battery charge (third excitation), by causing a current lower than the current during battery charge (third excitation) to flow through the power transmission coil11. Specifically, in the second excitation, the current to be caused to flow through the power transmission coil11is set such that power having a preset power-supply command value can be supplied. The vehicle controller24detects the power received by the power reception coil21and further calculates power transmission efficiency Q1based on the power-supply command value. It is then determined whether or not the vehicle20reaches the chargeable position, based on this power transmission efficiency Q1. In other words, it is determined whether or not the power reception coil21is present within a chargeable range within which it can be charged by the power transmission coil11.

Specifically, as the vehicle20enters the parking space32, the power transmission coil11and the power reception coil21approach each other, and when the power transmission coil11and the power reception coil21coincide with each at least partly, the magnetic flux generated at the power transmission coil11links to the power reception coil21, so that power is transmitted and charges the battery23. Further, as the area of the overlapping regions increases, the magnetic flux linking to the power reception coil21increases and the power transmission efficiency rises accordingly. In contrast, as the overlapping regions of the power transmission coil11and the power reception coil21decrease, the leakage flux increases and the power transmission efficiency drops accordingly. Then, it is possible to determine whether or not the vehicle20is parked at the chargeable position in the parking space32, that is, it is possible to determine whether or not the power reception coil21is present in the chargeable range, by setting a threshold efficiency Qth indicating the lower limit of the power transmission efficiency and detecting whether or not the power transmission efficiency Q1exceeds the threshold efficiency Qth.

Meanwhile, when the area of the overlapping regions of the power transmission coil11and the power reception coil21is small, the time required for wireless charge is long but the charge is nonetheless possible. Thus, the power transmission efficiency at a point when at least part of the magnetic flux links can be set as the above-mentioned threshold efficiency Qth.

Note that the vehicle controller24does not necessarily have to calculate the power transmission efficiency Q1. The ground controller13may calculate the power transmission efficiency Q1. In this case, data on the power received by the power reception coil21may be transmitted to the ground controller13via the communication unit25and the communication unit14, and the ground controller13may calculate the power transmission efficiency Q1.

Here, in the second excitation, the current caused to flow through the power transmission coil11is higher than the current caused to flow therethrough in the first excitation. This is to prevent the vehicle controller24from falsely recognizing that the power transmission coil11is set to the second excitation while the power transmission coil11is set to the first excitation.

Thereafter, if it is determined as a result of the above-described second excitation that the power reception coil21is present in the rechargeable range, the ground controller13sets the power transmission coil11to the third excitation to supply power for battery charge.

Next, the procedure of the processing by the ground controller13and the vehicle controller24will be described with reference to sequence charts shown inFIGS. 17 to 21. Firstly, in Step a1inFIG. 17, the ground controller13is in a standby state. Then, as the vehicle20approaches the parking space32in Step b1, the vehicle controller24transmits in Step b2an authentication ID provided to the vehicle20to the power transmission device101through radio communication. For this communication, a wireless LAN can be used, for example.

The ground controller13receives the authentication ID in Step a2and authenticates the received authentication ID in Step a3. In one example, the ground controller13determines whether or not the received authentication ID is an authentication ID given to a vehicle20that is permitted to perform charge, and authenticates the authentication ID if the vehicle20has been permitted to perform charge.

In Step a4, the ground controller13activates the ground unit51. Further, in Step a5, the ground controller13transmits a signal indicating that the ground unit51is activated, to the vehicle controller24through wireless communication. In Step a6, the ground controller13actuates the vehicle detection sensor33. In Step a7, the ground controller13waits for the vehicle20to approach.

On the other hand, in Step b3, the vehicle controller24notifies the user (such as an occupant of the vehicle20) that the ground unit51is activated. In Step b4, the vehicle controller24waits for a pairing signal from the ground controller13. In doing so, the vehicle20continues approaching the parking space32. That is, the vehicle20is approaching the parking space32, as shown inFIG. 24.

When the vehicle20enters the parking space32in Step b5, the vehicle detection sensor33detects the entrance of the vehicle20in Step a8. Specifically, when the vehicle20reaches the inside of the detection range of the vehicle detection sensor33set in the parking space32as shown inFIG. 25, the vehicle detection sensor33detects that the vehicle20has entered the parking space32. In Step b6, the vehicle controller24continues waiting for pairing.

In Step a9, the ground controller13starts the first excitation. Specifically, as shown in above-mentioned Part (a) ofFIG. 4, the ground controller13causes pulsed currents to flow through the power transmission coil11at a predetermined frequency, so that the current P0, serving as a start bit signal, and the currents P1to P4, indicating a four-bit identification ID, are caused to flow therethrough. The ground controller13repeatedly causes the currents P0, P1to P4to flow. The ground controller13waits for a pairing request in Step al0and continues the first excitation in Step a11.

When the power reception coil21, mounted on the vehicle20, enters an excitation range N1of the power transmission coil11shown inFIG. 26in Step b7, the vehicle controller24receives the four-bit identification ID in Step b8. Specifically, the vehicle controller24recognizes the identification ID “1, 1, 0, 1” as shown in Part (f) ofFIG. 4, based on the relation in magnitude between the output voltage Vout and the threshold voltage Vth shown in Part (e) ofFIG. 4.

In Step b9, the vehicle controller24transmits the recognized identification ID toward the ground controller13to request pairing. In Step a12, the ground controller13receives the transmitted identification ID. In Step a13, the vehicle20and the ground unit51are paired with each other. Specifically, the vehicle20and the ground unit51are paired with each other if the four-bit identification ID transmitted by the ground unit51and the four-bit identification ID received by the power reception device102match each other.

Then in Step a14, the ground unit51changes the current caused to flow through the power transmission coil11to set the power transmission coil11to the second excitation. That is, the ground unit51starts the second excitation. In Step b10, the vehicle controller24starts determining whether or not the vehicle20reaches the chargeable position in the parking space32. Specifically, as shown inFIG. 27, the vehicle controller24determines that the vehicle20reaches the chargeable position when the area of the overlap between the power reception coil21and the power transmission coil11increases and the power transmission efficiency Q1accordingly rises and exceeds the preset threshold efficiency Qth. The vehicle controller24can determine that the vehicle20reaches the chargeable position if the power reception coil21is present in a powerable range N2, for example.

If the vehicle20enters the chargeable range in the parking space32in Step b11inFIG. 18and also the second excitation of the power transmission coil11is being continued in Step a15, the vehicle controller24determines in Step b12whether or not the power transmission efficiency Q1exceeds the threshold efficiency Qth. Whether or not the power transmission efficiency Q1exceeds the threshold efficiency Qth can be determined based on the magnitude of the voltage generated at the power reception coil21by the excitation. If Q1>Qth, the vehicle controller24notifies the user in Step b13that the battery23can now be charged, by means of a display (not shown) or the like.

In Step b14, the vehicle controller24performs a cancel determination process. This process determines whether or not to perform charge, based on whether or not the user inputs cancel operation. Details will be described later with reference toFIG. 19.

If there is no cancel operation, the vehicle controller24determines in Step b15whether or not the vehicle20is stopped. If the vehicle20is stopped, the vehicle power source is turned off in Step b16. Then in Step b17, the vehicle controller24transmits a charge start request signal to the ground controller13.

In Step a16, the ground controller13sets the power transmission coil11to the third excitation. In Step a17, the power supplied to the power transmission coil11is wirelessly supplied to the power reception coil21to charge the battery23(seeFIG. 1). As described above, the battery23can be charged by setting the power transmission coil11to the first excitation to pair the ground unit51and the vehicle20with each other, setting the power transmission coil11to the second excitation to check whether the vehicle20is parked at the chargeable position in the parking space32, and thereafter wirelessly supplying power.

Next, details of the cancel determination process, shown in Step b14inFIG. 18, will be described with reference to a flowchart shown inFIG. 19. Firstly in Step b31, the vehicle controller24detects the voltage received by the power reception coil21while the power transmission coil11is set to the second excitation. In Step b32, the vehicle controller24determines whether or not the vehicle20is parked at the chargeable position in the parking space32, based on the detected voltage.

If the vehicle20is not at the chargeable position, the vehicle controller24notifies the user in Step b38that the vehicle20is misaligned relative to the predetermined position in the parking space32, and the vehicle controller24moves the process back to Step b31. On the other hand, if the vehicle20is at the chargeable position, the vehicle controller24notifies the user in Step b33that the vehicle20is parked at the chargeable position. Further, in Step b34, the vehicle controller24displays a cancel button on the display (not shown).

In Step b35, the vehicle controller24determines whether or not the user performs cancel operation. If the user performs cancel operation, the vehicle controller24transmits a command signal to stop the second excitation to the ground unit51in Step b39. In Step b40, the vehicle controller24stops the wireless communication with the ground controller13.

On the other hand, if the user does not perform cancel operation, the vehicle controller24determines in Step b36whether or not the vehicle power source is turned off. If the vehicle power source is turned off, the vehicle controller24determines that the vehicle20is ready for charge, and transmits a charge start request to the ground unit51in Step b37. The vehicle controller24then finishes this process. The user of the vehicle20can perform cancel operation in this manner.

Next, processing performed in a case where the vehicle20leaves from the chargeable position will be described with reference to a sequence chart shown inFIG. 20. This processing is performed after Step a14and Step b10, which are shown inFIG. 17. In Step b32, the vehicle20leaves the parking space32for a reason such as changing the parking space. Then in Step a32, the ground controller13detects that the vehicle20has left the parking space32, based on the detection signal of the vehicle detection sensor33.

In Step a33, the ground controller13transmits a request signal to disconnect the pairing with the vehicle20. Specifically, since the ground unit51and the vehicle20have been paired with each other by the first excitation, this pairing needs to be disconnected if the battery23is not to be charged. The ground controller13therefore transmits a pairing-disconnection request signal.

In Step b33, the vehicle controller24receives the pairing-disconnection request signal. Further, in Step b34, the vehicle controller24transmits a signal indicating disconnection of the pairing to the ground unit51. In response, the ground controller13disconnects the pairing with the vehicle20. Then, upon cancellation by the user in Step b35, the vehicle controller24stops the wireless communication in Step b36.

On the other hand, in Step a34, the ground controller13disconnects the pairing with the vehicle20. In Step a35, the ground controller13stops the second excitation of the power transmission coil11. Then in Step a36, the ground controller13continues detecting whether or not the vehicle20is parked in the parking space32. Thereafter, if the wireless communication with the vehicle controller24is stopped, the ground controller13stops the detection of the position of the vehicle with the vehicle detection sensor33in Step a37.

FIG. 28is an explanatory diagram showing movement of the vehicle20leaving from the chargeable position. As shown inFIG. 28, when the vehicle20leaves from the chargeable position, the vehicle20leaves the detection range of the vehicle detection sensor33, and the pairing is therefore disconnected. When the user eventually performs charge cancel operation, the pairing is disconnected and the excitation of the power transmission coil11is stopped.

Next, processing for changing the parking position of the vehicle20from the parking space32for the ground unit51to the parking space32afor the ground unit51awill be described with reference to a sequence chart shown inFIG. 21and a movement diagram shown inFIG. 29. Note that, in the following, to distinguish the ground units51,51a, reference sign51denotes a first ground unit and reference sign51adenotes a second ground unit. Likewise, to distinguish the parking spaces32,32a, reference sign32denotes a first parking space and reference sign32adenotes a second parking space.

The processing shown inFIG. 21is performed after the Step a14and Step b10, which are shown inFIG. 17. When the vehicle20leaves the excitation range (N1shown inFIG. 29) of the power transmission coil11of the first ground unit51in Step b52, the vehicle controller24detects a drop in the voltage generated at the power reception coil21in Step b53. Specifically, as the area of the overlap between the power transmission coil11and the power reception coil21decreases, the voltage generated at the power reception coil21drops. Then, by detecting the voltage drop, the vehicle controller24can recognize that the vehicle20has left the excitation range N1.

The vehicle controller24transmits a pairing-disconnection request signal to the ground controller13in Step b54and disconnects the pairing in Step b55. Specifically, since the vehicle20is not charging the battery23at the first parking space32, the pairing between the first ground unit51and the vehicle20is disconnected. On the other hand, the ground controller13receives the pairing-disconnection request signal in Step a52and disconnects the pairing in Step a53. Then in Step a54, the ground controller13starts the first excitation. That is, the ground controller13finishes the second excitation and starts the first excitation.

Meanwhile, in Step c51, the second ground unit51ais a standby state. Upon receipt of wireless communication from the vehicle controller24in Step c52, the second ground unit51aactuates the vehicle detection sensor33a.

Then, when the vehicle20leaves the first parking space32in Step b56, the ground controller13of the first ground unit51stops the first excitation in Step a55. When the vehicle20enters the second parking space32ain Step b57, the ground controller13of the second ground unit51adetects in Step c53that the vehicle20has entered the second parking space32a. Further, the ground controller13of the second ground unit51astarts the first excitation in Step c54.

Then, processing similar to the processing described earlier is performed, so that the second ground unit51aand the vehicle20are paired with each other in Step b58. On the other hand, the vehicle detection sensor33of the first ground unit51is stopped in Step a56. As described above, in the case where the user of the vehicle20changes the parking position of the vehicle20from the first parking space32to the second parking space32a, the above processing is performed and the battery23can thus be charged using the second ground unit51a.

Next, a detailed procedure of the pairing process performed in the wireless power supply system according to this embodiment will be described with reference to flowcharts shown inFIGS. 22 and 23.FIG. 23is a flowchart showing the procedure of processing by control of the ground controller13. This processing is performed when the vehicle detection sensor33detects that the vehicle20is approaching the desired position in the parking space32.

Firstly in Step S11, the ground controller13performs a process of starting weak-excitation communication for setting the first excitation. Further, in Step S12, the ground controller13waits to receive a command for start of the weak excitation. In Step S13, the ground controller13determines whether or not a command to start the weak excitation is given. If a start command is given (YES in Step S13), the ground controller13advances the processing to Step S14.

In Step S14, the ground controller13excites the power transmission coil11by supplying a start-bit current thereto. Then in Step S15, the ground controller13excites the power transmission coil11by supplying identification-ID currents thereto. Further in Step S16, the ground controller13excites the power transmission coil11by supplying a stop-bit current thereto.

In Step S17, the ground controller13determines whether or not a reception confirmation signal is received from the vehicle controller24. In Step S18, the ground controller13determines whether or not to stop the weak excitation. The ground controller13stops the weak excitation if determining in Step S18that a reception confirmation signal is received. On the other hand, the ground controller13returns to the process in Step S14if determining that a reception confirmation signal is not yet received. In Step S19, the ground controller13stops the weak excitation. That is, the ground controller13finishes the first excitation when pairing is completed.

Next, the procedure of processing by the vehicle controller24will be described with reference to the flowchart inFIG. 23. Firstly, the vehicle controller24performs a process of starting weak-excitation communication in Step S31, and transmits a signal indicating start of the weak excitation in Step S32. The vehicle controller24clears a reception buffer (not shown) in Step S33.

In Step S34, the vehicle controller24waits for a start bit. In Step S35, the vehicle controller24determines whether or not a start bit is received. If a start bit is received (YES in Step S35), the vehicle controller24performs a synchronization process in Step S36. In this process, synchronization is performed based on the timing of the start bit transmitted by the power transmission coil11and the timing of the start bit received by the power reception coil21.

In Step S37, the vehicle controller24performs a reception process. In this process, the vehicle controller24receives an identification ID transmitted by the power transmission coil11. In Step S38, the vehicle controller24counts the number of bits. In this embodiment, a four-bit identification ID is set as one example. Thus, in Step S39, the vehicle controller24determines whether or not a four-bit identification ID has been received. The vehicle controller24returns to the process in Step S36if the number of bits is less than the predetermined number (NO in Step S39). On the other hand, the vehicle controller24advances the processing to Step S40if the number of bits is the predetermined number (YES in Step S39).

In Step S40, the vehicle controller24checks the received four-bit identification ID. In Step S41, the vehicle controller24determines whether or not the received identification ID matches the identification ID assigned to the parking space32. If the identification IDs do not match each other (NO in Step S41), the vehicle controller24moves the processing back to Step S33. If the identification IDs match each other (YES in Step S41), the vehicle controller24transmits a weak-excitation stop signal to the ground controller13via the communication unit25in Step S42. Then in Step S43, the vehicle controller24finishes the identification-ID communication process through the first excitation.

As described above, in the wireless power supply system according to the first embodiment, when the vehicle detection sensor33detects that the vehicle20has approached the parking space32, currents are caused to flow through the power transmission coil11to set the power transmission coil11to the first excitation and transmit an identification ID. Then, the vehicle controller24recognizes an identification ID. If this identification ID and the identification ID transmitted by the power transmission coil11match each other, pairing between this parking space32and the vehicle20is completed. That is, one of the plurality of parking spaces32and the vehicle20are paired with each other. Hence, a connection is established between the vehicle20in need of battery charge and a ground unit51that supplies power.

Then, the current caused to flow through the power transmission coil11is changed to set the power transmission coil11to the second excitation, and the power transmission efficiency Q1is calculated from the power received by the power reception coil21in this state. Thereafter, when the power transmission efficiency Q1exceeds the threshold efficiency Qth, the vehicle20is determined to be in the chargeable range, and thus the power transmission coil11is set to the third excitation, so that the battery23starts to be charged.

In this way, the ground controller13can instantly recognize that the vehicle20has approached the parking space32. Hence, the time required to set the power transmission coil11to the second excitation and then to the third excitation can be shortened. As a result, it is possible to prevent the user of the vehicle from waiting for a long time.

Also, when the power transmission coil11is set to the second excitation, the current caused to flow therethrough is set higher than that in the first excitation. In other words, the second excitation is stronger than the first excitation. In this way, it is possible to prevent false detection between the first excitation and the second excitation. Further, while the power transmission coil11is set to the second excitation, the power transmission efficiency Q1is calculated based on the power transmitted to the power reception coil21, and the power reception coil21is determined to be present in the chargeable range relative to the power transmission coil11when the power transmission efficiency Q1exceeds the threshold efficiency Qth. In this way, it is possible to figure out when the power reception coil21reaches the chargeable range without providing a sensor such as a camera to the vehicle20. Hence, the device configuration can be simpler.

Also, the rectification-smoothing circuit22of the power reception device102is provided with the discharge circuit26. In this way, the magnitude of the voltage during the recognition of the identification ID can be constant. Hence, the accuracy of the recognition of the identification ID can be improved.

Description of Second Embodiment

Next, the second embodiment of the present invention will be described. The system configuration is similar to that in above-mentionedFIG. 1. The wireless power supply system according to the second embodiment differs from the above-described first embodiment in the excitation pattern in the first excitation. The operation of the wireless power supply system according to the second embodiment will be described below with reference to a timing chart shown inFIG. 5. In the above-described first embodiment, after a start bit is transmitted, the excitation pattern that causes the current I1to flow is used when the identification ID indicates “1” (see P1, P2, P4inFIG. 4) whereas the excitation pattern that does not cause the current I1to flow is used when the identification ID indicates “0” (see P3inFIG. 4).

In contrast, in the second embodiment, the identification ID is set by changing the time intervals at which to excite the power transmission coil11. Specifically, for “1” the time interval from the present energization to the time of the next energization is set at T1shown inFIG. 5, whereas for “0” the time interval to the time of the next energization is set at T0longer than T1. Then, by detecting the time intervals of generation of the current IL shown in Part (b) ofFIG. 5, the vehicle controller24can recognize an identification ID “1, 0, 1, 1,” as shown in Part (c) ofFIG. 5.

In this way, as in the above-described first embodiment, the wireless power supply system according to the second embodiment, too, can pair the parking space32and the vehicle20with each other, and the time required to set the power transmission coil11to the second excitation and the third excitation can be shortened.

Description of Third Embodiment

Next, the third embodiment of the present invention will be described.FIG. 6is a block diagram showing the configuration of a wireless power supply system according to the third embodiment. The third embodiment differs from the circuit inFIG. 3shown in the above-described first and second embodiments in the position where the discharge circuit26, formed of the resistor R4and the switch SW1, is attached. Specifically, the discharge circuit26is connected to both terminals of the capacitor C3. The other features of the configuration are similar to those of the circuit shown inFIG. 3.

Moreover, in the wireless power supply system according to the third embodiment, the switch SW1is turned on, thereby discharging the voltage charged in the capacitor C3(smoothing capacitor), when the output voltage Vout exceeds the threshold voltage Vth. Hence, the output voltage Vout can be dropped. In this way, as in the above-described first and second embodiments, the wireless power supply system according to the third embodiment can, too, pair the parking space32and the vehicle20with each other, and the time required to set the power transmission coil11to the second excitation and the third excitation can be shortened.

Description of Fourth Embodiment

Next, the fourth embodiment of the present invention will be described.FIG. 7is a block diagram showing the configuration of a wireless power supply system according to the fourth embodiment. As shown inFIG. 7, the wireless power supply system according to the fourth embodiment differs from the systems shown inFIGS. 3 and 6in that the discharge circuit26, formed of the resistor R4and the switch SW1, is not mounted. Specifically, in the above-described first to third embodiments, the switch SW1is turned on to drop the output voltage Vout when the output voltage Vout exceeds the threshold voltage Vth. In contrast, in the fourth embodiment, while the capacitors C3, C4are not charged, the voltage charged in the capacitor C4is released by the discharge resistor R3to drop the output voltage Vout.

Next, the operation of the wireless power supply system according to the fourth embodiment will be described with reference to a timing chart shown inFIG. 8. When a current IL indicating a start bit flows at a time t1, the output voltage Vout rises and exceeds the threshold voltage Vth. When the current IL then decreases at a time t2, the voltage at the capacitor C4shown inFIG. 7is discharged through the discharge resistor R3, so that the output voltage Vout drops. After that, when a current IL for indicating a logic “1” flows at a time t3, the output voltage Vout rises again and exceeds the threshold voltage Vth, and the output voltage Vout drops at a time t4. By performing similar operation at subsequent times t5to t9, logics “1, 1, 0, 1” can be recognized. The subsequent processing is similar to those in the above-described first to third embodiments. Meanwhile, Parts (a) and (b) ofFIG. 9show the waveform of logics “1, 1, 1, 1” while Parts (c) and (d) ofFIG. 9show the waveform of logics “1, 0, 1, 0.”

In this way, as in the above-described first to third embodiments, the wireless power supply system according to the fourth embodiment, too, can pair the parking space32and the vehicle20with each other, and the time required to set the power transmission coil11to the second excitation and the third excitation can be shortened. In addition, since the discharge circuit26does not need to be provided, the device configuration can be simpler.

Description of Fifth Embodiment

Next, the fifth embodiment of the present invention will be described. The system configuration is similar to that inFIG. 7shown in the fourth embodiment, and description of the configuration will therefore be omitted.FIG. 10is a timing chart showing the operation of the wireless power supply system according to the fifth embodiment, and Parts (a), (b), and (c) show the output voltage Vout, the current IL, and logics, respectively.FIG. 10shows an example of transmitting logics “1, 1, 1, 0.” A current IL indicating a start bit flows at a time t1shown inFIG. 10and then currents IL flow at times t2, t3, t4, t5. For a logic “1” the amount of time to the time when the next current IL flows is set at T1, whereas for a logic “0” the amount of time to the time when the next current IL flows is set at T0(T0>T1). In this way, the logics “1” and “0” can be recognized. Meanwhile, in the case of logics “1, 0, 1, 0,” the output voltage Vout is changed as shown in Part (a) ofFIG. 11, and the logics “1, 0, 1, 0” can be recognized as shown in Part (b) ofFIG. 11.

In this way, as in the above-described first to fourth embodiments, the wireless power supply system according to the fifth embodiment, too, can pair the parking space32and the vehicle20with each other, and the time required to set the power transmission coil11to the second excitation and the third excitation can be shortened. In addition, since the discharge circuit26does not need to be provided, the device configuration can be simpler.

FIG. 12is a timing chart showing a modification of the fifth embodiment. In this modification, the interval between the currents IL is changed among four different intervals T1, T2, T3, T0, so that a two-bit logic is set. In this way, four different logics of 0, 1, 2, 3 can be set, thereby allowing more combinations for the identification ID to be set. Note that three or more bits can be used instead.

Description of Sixth Embodiment

Next, the sixth embodiment of the present invention will be described.FIG. 13is a block diagram showing the configuration of a wireless power supply system according to the sixth embodiment. As shown inFIG. 13, in the sixth embodiment, the position where the voltage sensor27is attached is changed from that in the circuit shown inFIG. 7. Specifically, the voltage sensor27is attached to both terminals of the capacitor C3, and the voltage generated at the capacitor C is the output voltage Vout. The other features of the configuration are similar to those in the second embodiment. Moreover, the sixth embodiment, too, can achieve advantageous effects similar to those by the above-described first to fifth embodiments.

Description of Seventh Embodiment

Next, the seventh embodiment of the present invention will be described. FIG.14is a block diagram showing the configuration of a wireless power supply system according to the seventh embodiment. As shown inFIG. 14, the seventh embodiment differs from the circuit shown inFIG. 7in that a current sensor41configured to measure the current flowing through the coil L is provided instead of the voltage sensor27. In the seventh embodiment, logics are detected based on current Ic measured by the current sensor41. The seventh embodiment, too, can achieve advantageous effects similar to those by the above-described first to fifth embodiments.

Description of Eighth Embodiment

Next, the eighth embodiment of the present invention will be described.FIG. 15is a block diagram showing the configuration of a wireless power supply system according to the eighth embodiment. As shown inFIG. 15, the eighth embodiment differs from the circuit shown inFIG. 7in that a current sensor41configured to measure the output current from the bridge circuit is provided instead of the voltage sensor27. In the eighth embodiment, logics are detected based on current Ic measured by the current sensor41. The eighth embodiment, too, can achieve advantageous effects similar to those by the above-described first to fifth embodiments.

Description of Ninth Embodiment

Next, the ninth embodiment of the present invention will be described.FIG. 16is a block diagram showing the configuration of a wireless power supply system according to the ninth embodiment. As shown inFIG. 16, the ninth embodiment differs from the circuit shown inFIG. 7in that a current sensor41configured to measure the output current from the capacitor C4is provided instead of the voltage sensor27. In the ninth embodiment, logics are detected based on current Ic measured by the current sensor41. The ninth embodiment, too, can achieve advantageous effects similar to those by the above-described first to fifth embodiments.

The wireless power supply system and the power transmission device of the present invention have been described above based on the illustrated embodiments. However, the present invention is not limited to these. Each component can be replaced with any component having a similar function(s).

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