Temperature estimation device and temperature estimation method for contactless power-reception device

A charging controller (25) acquires the power loss of a power transmission coil (31) from a power supply device (100) via wireless communication. A temperature estimation unit (33) estimates the ambient temperature of a power reception coil on the basis of a preset amount of heat generation of a power reception device (200) and the power loss of the power transmission coil (31). In this case, when the positional relationship between the power transmission coil (31) and the power reception coil (41) is shifted from a normal positional relationship, the temperature estimation unit (33) increases, in accordance with the magnitude of positional shift amount, the contribution to a temperature rise due to the power loss of the power transmission coil (31). Accordingly, an abnormal increase in the ambient temperature of the power reception coil (41) can be prevented.

TECHNICAL FIELD

The present invention relates to a temperature estimation device and a temperature estimation method for a contactless power reception device which estimate the temperature of the power reception device that contactlessly receives the power transmitted from a power transmission coil.

BACKGROUND ART

There has been proposed a contactless power supply system that contactlessly supplies power to charge a battery mounted on an electric vehicle. In the contactless power supply system, power is transmitted via a power transmission coil from a power transmission device provided on the ground side and the transmitted power is received by a power reception coil of a power reception device mounted on the vehicle. Then, the received power is supplied to loads, such as a battery and a motor.

In such a contactless power supply system, when a change in the gap between the power transmission coil and the power reception coil or a planar positional shift between the power transmission coil and the power reception coil occurs, the power loss of the power transmission coil increases and the temperature of the power reception device rises due to an increase of this power loss. Therefore, the temperature of the power reception device needs to be monitored.

Patent Literature 1 discloses a temperature control device that estimates the temperature of an electronic device by calculation. In this Patent Literature 1, the temperature is estimated by integrating the quantity of heat on the basis of operation mode information and an operation time. Then, when the estimated temperature reaches a threshold, the operation mode is switched to an operation mode which generates a less amount of heat. However, in Patent Literature 1, the temperature is estimated by detecting the operation mode inside the device, and the influence from an external device is not taken into consideration.

CITATION LIST

Patent Literature

SUMMARY OF INVENTION

As described above, in order to prevent an increase in temperature of a contactless power reception device, the temperature of this contactless power reception device needs to be monitored. However, if a temperature sensor is installed, there arise problems that the device increases in scale and the cost increases, and therefore there increases a demand for estimating the temperature without installing a device, such as a temperature sensor.

The present invention has been made in order to solve the conventional problems, and has an object to provide a temperature estimation device and temperature estimation method for a contactless power reception device capable of accurately estimating the ambient temperature of a power reception coil.

A temperature estimation device for a contactless power reception device according to an aspect of the present invention includes: a power transmission-side power loss acquisition unit which acquires the power loss of a power transmission coil; and a temperature estimation unit which estimates the ambient temperature of a power reception coil on the basis of a preset amount of heat generation of a power reception device and the power loss of the power transmission coil. When the positional relationship between the power transmission coil and the power reception coil is shifted from a normal positional relationship, the temperature estimation unit increases, in accordance with a magnitude of a positional shift amount, a contribution to a temperature rise due to the power loss of the power transmission coil.

A temperature estimation method for a contactless power reception device according to an aspect of the present invention includes the steps of: acquiring a power loss of a power transmission coil; and estimating the ambient temperature of a power reception coil based on a preset amount of heat generation of a power reception device and the power loss of the power transmission coil. The temperature estimation method increases a contribution to a temperature rise due to the power loss of the power transmission coil, in accordance with a magnitude of a positional shift amount, when estimating the ambient temperature of the power reception coil, in a case where the positional relationship between the power transmission coil and the power reception coil is shifted from a normal positional relationship.

DESCRIPTION OF EMBODIMENTS

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.FIG. 1is a block diagram illustrating a configuration of a contactless power supply system according to the embodiment of the present invention. As illustrated inFIG. 1, a contactless power supply system101according to the present embodiment includes: a power supply device100which is provided on the ground side and transmits power; and a power reception device200(contactless power reception device) which is mounted on a vehicle201, receives the power transmitted from the power supply device100, and charges a battery28.

The power supply device100is installed on a charging stand or the like provided with a parking space for the vehicle201, and contactlessly transmits power to the vehicle201. This power supply device100is mainly constituted by a power controller11, a power transmission coil unit12, a wireless communication unit14, and a power transmission controller15. Furthermore, this power supply device100includes a camera13which images, from the above of the parking space, the vehicle201parked in this parking space.

The power controller11has a function to convert an alternating current (AC) power output from an AC power supply300(e.g., 50 Hz, 200 V) to a high frequency AC power and transmit the power to the power transmission coil unit12. This power controller11includes a rectifier111, a PFC (Power Factor Correction) circuit112, and an inverter113.

The rectifier111converts the AC power output from the AC power supply300to a direct current (DC) power. The PFC circuit112includes, for example, a step-up chopper circuit etc. and is a circuit for improving the power factor by shaping the waveform of an output current from the rectifier111. The output of the PFC circuit112is smoothed by a smoothing capacitor.

The inverter113includes a plurality of switching elements (e.g., insulating gate bipolar transistor (IGBT)), and converts a DC power to an AC power of a desired frequency by controlling the ON/OFF of each switching element.

The power transmission coil unit12is provided at a position which faces, when the vehicle201stops at a desired position of the parking space, a power reception coil unit22provided in the power reception device200. Then, the power transmission coil unit12contactlessly transmits power to the power reception coil unit22. This power transmission coil unit12includes a power transmission coil31and a ferrite plate35formed of a material with high magnetic permeability and having a planar shape, as illustrated inFIG. 2.

The wireless communication unit14performs two-way communication with a wireless communication unit24provided in the power reception device200. By this communication, as described later, transmitted are various data, such as an output voltage Vinv and output current Iinv of the inverter113detected by the power supply device100, and a power loss WGC in the power transmission coil unit12, and a coupling coefficient κ described later, to the power reception device200.

The power transmission controller15generally controls the whole power supply device100. This power transmission controller15can be configured using a microcomputer mainly including, for example, a central processing unit (CPU), a read-only memory (ROM), a random-access memory (RAM), and an input/output (I/O) interface. In particular, this power transmission controller15controls the power controller11, the wireless communication unit14, and the camera13.

On the other hand, the power reception device200mounted on the vehicle201includes the power reception coil unit22, the wireless communication unit24, a charging controller25, a rectifier26, a relay27, and a temperature estimation unit33. Furthermore, the power reception device200includes the battery28which stores power and supplies a DC power to an inverter29, and a notification unit37which notifies an occupant of the vehicle201of various information. The inverter29converts a DC power to an AC power, and supplies the converted AC power to a motor30.

Moreover, at a front end part of the vehicle201, there is provided a forward-distance sensor51for measuring the distance from this front end part to a wall surface52(seeFIG. 7) provided in the parking space. Furthermore, at a bottom part of the vehicle201, there is provided a gap sensor61for measuring the distance from this bottom part to the power transmission coil unit12. As the forward-distance sensor51and the gap sensor61, an ultrasonic sensor can be used, for example.

The power reception coil unit22is a coil for contactlessly receiving the power transmitted from the power transmission coil unit12. This power reception coil unit22includes the power transmission coil31and the ferrite plate35formed of a material with high magnetic permeability and having a planar shape, as illustrated inFIG. 2.

The wireless communication unit24performs two-way communication with the wireless communication units14provided in the power supply device100. The rectifier26is connected to the power reception coil unit22, converts an AC power output from this power reception coil unit22to a DC power and outputs the DC power. This rectifier26is mounted on a circuit board44inside an electric box45provided in a vicinity of the bottom face of the vehicle201, as illustrated inFIG. 2.

The relay27includes a relay switch whose ON/OFF states are switched under the control of the charging controller25. The relay27is capable of separating a circuit including the battery28from a circuit including the power reception coil unit22and the rectifier26by turning off the relay switch.

On the basis of a power loss WJB of the circuit board44mounted inside the electric box45(seeFIG. 2) having the rectifier26mounted therein, a power loss WVC in the power reception coil unit22, and a power loss WGC in the power transmission coil unit12, the temperature estimation unit33estimates the ambient temperature (ambient temperature of the power reception coil) of the power reception coil unit22, such as a ferrite plate42, a copper wire of the coil, and other circuit elements, using an approach described later. The details will be described later. Here, the amount of heat generation caused by the power loss WJB of the circuit board44and the power loss WVC in the power reception coil unit22is the amount of heat generation of the power reception device.

The notification unit37includes a display unit, such as a display, and notifies an occupant of the vehicle201of various information including the information about contactless power supply. In particular, as described later, when the ambient temperature of the power reception coil unit22is estimated to exceed a threshold temperature by the temperature estimation unit33, this fact is displayed on the display. Moreover, when the ambient temperature is estimated to exceed a threshold temperature, and thereby the transmission power from the power supply device100is reduced (the details will be described later) and the time needed to charge the battery28is accordingly changed, this fact is displayed on the display to be notified to the occupant.

The charging controller25generally controls the power reception device200. In particular, the charging controller25acquires the information about the output voltage Vinv and output current Iinv of the inverter113which is transmitted from the power supply device100via the wireless communication unit24. Furthermore, the charging controller25acquires the information about the power loss WGC in the power transmission coil unit12. That is, the charging controller25has a function as a power transmission-side power loss acquisition unit which acquires the information about the power loss of the power transmission coil unit12.

Furthermore, the charging controller25has a function, as a positional shift amount acquisition unit, which acquires the amounts of planar positional shift Lx, Ly of the power reception coil unit22from the power transmission coil unit12, and the gap on the basis of a distance to the wall surface52detected by the forward-distance sensor51and a distance to the power transmission coil unit12detected by the gap sensor61. The charging controller25and the temperature estimation unit33can be configured using a microcomputer mainly including, for example, a central processing unit (CPU), a read-only memory (ROM), a random-access memory (RAM), and an input/output (I/O) interface.

Then, in the contactless power supply system101illustrated inFIG. 1, power is transmitted in a contactless state by electromagnetic induction between the power transmission coil unit12and the power reception coil unit22. That is, if an electric current flows through the power transmission coil unit12, magnetic coupling occurs between the power transmission coil unit12and the power reception coil unit22, so that power can be contactlessly transmitted to the power reception coil unit22from the power transmission coil unit12.

Furthermore, in the present embodiment, when the ambient temperature of the power reception coil unit22reaches a preset threshold temperature during transmission of power, the transmitted power is reduced to prevent the ambient temperature of the power reception coil unit22from abnormally rising.

Next, a factor causing an increase in temperature of the power reception coil unit22during transmission of power will be explained with reference toFIG. 2.FIG. 2is an explanatory view illustrating a magnetic flux generated between the power transmission coil unit12and the power reception coil unit22.

The factor causing an increase in ambient temperature of the power reception coil unit22illustrated inFIG. 2includes the power loss WJB inside the electric box45. As illustrated inFIG. 2, the circuit board44is arranged inside the electric box45, and various electronic components including the rectifier26are mounted on this circuit board44. Accordingly, this circuit board44generates heat due to the power loss WJB generated during operation, causing an increase in ambient temperature of the power reception coil unit22.

Furthermore, the factor causing an increase in ambient temperature of the power reception coil unit22may include the power loss WVC of the power reception coil unit22and the power loss WGC of the power transmission coil unit12. Accordingly, if an increase in temperature of the power reception coil unit22is designated by ΔT, this increase in temperature ΔT can be expressed by Formula (1) below using correction coefficients A, B, and C.
ΔT=A*WJB+B*WVC+C*WGC(1)

Note that ΔT is an increase in temperature after a sufficient time has elapsed.

Then, the increase in temperature ΔT can be calculated from Formula (1), and furthermore the ambient temperature of the power reception coil unit22can be estimated on the basis of the ambient temperature detected by an ambient temperature sensor (not illustrated) provided in place in the power supply device100or the vehicle201. Specifically, the ambient temperature of the power reception coil unit22can be obtained by adding the increase in temperature ΔT to the ambient temperature.

Moreover, in Formula (1), because each of the power losses WJB, WVC, and WGC is a copper loss and proportional to the square of an electric current, the ambient temperature of the power reception coil unit22can be calculated on the basis of an electric current flowing through the circuit board44inside the electric box45, an electric current flowing through a circuit including a circuit board43of the power reception coil unit22, and an electric current flowing through the power transmission coil unit12. Furthermore, because the correction coefficients A and B are the numerical values specific to the power reception device200, they are already known. Accordingly, if the correction coefficient C of the power loss WGC in the power transmission coil unit12can be obtained, the increase in temperature ΔT can be calculated from the above-described Formula (1). The correction coefficient C is a numerical value varying with the relative positional relationship between the power transmission coil unit12and the power reception coil unit22, and the calculation method thereof will be described later.

Next, the principle that the power reception coil unit22generates heat in contactlessly transmitting power to the power reception coil unit22from the power transmission coil unit12, and the relationship with the correction coefficient C will be explained. As illustrated inFIG. 2, the power transmission coil unit12is constituted by the ferrite plate35and the power transmission coil31wound around the upper face of this ferrite plate35. Moreover, the power reception coil unit22includes the ferrite plate42and a power reception coil41wound around the lower face of this ferrite plate42, and furthermore the circuit board43having various electronic components mounted thereon is provided on the upper face of the ferrite plate42.

Then, when the vehicle201stops at a desired position in a parking space, the power reception coil unit22is installed at a position facing the power transmission coil unit12. Accordingly, if in this state an electric current is supplied to the power transmission coil31for excitation, a magnetic flux is formed as indicated by an arrow Y1. Because this magnetic flux passes through the ferrite plate42of the power reception coil unit22and interlinks with the power reception coil41, power will be transmitted to this power reception coil41.

Moreover, the magnetic flux passing through the ferrite plate42varies with a relative positional relationship between the power transmission coil unit12and the power reception coil unit22. That is, when the vehicle201is not stopped at a desired position inside the parking space, a planar positional shift occurs between the power transmission coil unit12and the power reception coil unit22. Furthermore, the distance (gap G) between the power transmission coil unit12and the power reception coil unit22varies with the number of occupants riding on the vehicle201and the like. When such a positional shift occurs, the magnetic flux passing through the ferrite plate42varies to generate a high-density magnetic-flux part, and therefore magnetic saturation occurs to cause heat generation. That is, the amount of heat generation will vary with the relative positional relationship between the power transmission coil unit12and the power reception coil unit22.

Hereinafter, how the magnetic flux passing through the ferrite plate42of the power reception coil unit22varies with the gap G between the power transmission coil unit12and the power reception coil unit22will be explained with reference toFIG. 3.

FIG. 3(a)illustrates the magnetic flux when the gap G which is the distance between the power transmission coil unit12and the power reception coil unit22is a reference value Ga, whileFIG. 3(b)illustrates the magnetic flux when the gap G becomes Gb which is longer than the reference value Ga. As seen fromFIGS. 3(a)and3(b), when the gap G becomes longer, the magnetic flux which reaches the power reception coil unit22from the power transmission coil unit12decreases. That is, the magnetic flux indicated by an arrow Y12decreases relative to the magnetic flux indicated by an arrow Y11. More specifically, the magnetic flux passing through areas R21and R22illustrated inFIG. 3(b)decreases relative to the magnetic flux passing through areas R11and R12illustrated inFIG. 3(a).

As the result, the magnetic flux passing through the ferrite plate42of the power reception coil unit22decreases, and the amount of heat generation of this ferrite plate42decreases. In this case, because the magnetic flux passing through the ferrite plate42decreases in inverse proportion to the square of the gap G, the amount of heat generation will decrease in inverse proportion to the square of the gap G. Accordingly, as illustrated inFIG. 3(c), the above-described correction coefficient C may be set so as to have a characteristic inversely proportional to the square of the gap G.

Next, a change in the amount of heat generation corresponding to the amount of planar positional shift of the power reception coil unit22from the power transmission coil unit12will be explained with reference to the explanatory views illustrated inFIG. 4toFIG. 6.FIG. 4(a)is a cross sectional view in the X-axis direction when the power reception coil unit22is not positionally shifted from the power transmission coil unit12, in which an arrow Y13indicates the magnetic flux. Moreover,FIG. 4(b)schematically illustrates the plan view in this case. Note that, as illustrated inFIG. 4(b), the power reception coil41has a rectangular shape, in which the short side direction is set to the X-axis direction.

On the other hand,FIG. 4(c)is a cross sectional view in the X-axis direction when the power reception coil unit22is positionally shifted by a distance L1in the X-axis direction, in which an arrow Y14indicates the magnetic flux. Moreover,FIG. 4(d)schematically illustrates a plan view in this case.

As seen from comparison betweenFIG. 4(a)andFIG. 4(c), a positional shift in the X-axis direction occurring between the power transmission coil unit12and the power reception coil unit22reduces a coupling coefficient (designated by “κ”) between the both coils. Accordingly, the power transmission controller15of the power supply device100increases the power supplied to the power transmission coil unit12so that a desired power is generated in the power reception coil unit22. As the result, the magnetic flux output from the power transmission coil31increases as illustrated inFIG. 4(c), and the magnetic flux passing through the ferrite plate42also increases accordingly. Therefore, the concentration of the magnetic flux occurs in the ferrite plate42, causing an increase of the ambient temperature of the power reception coil unit22. Moreover, the ambient temperature of the power reception coil unit22will increase linearly with respect to the amount of positional shift in the X-axis direction.

Next, a positional shift in the Y-axis direction (direction perpendicular to the X-axis) will be explained.FIG. 5(a)is a cross sectional view in the Y-axis direction when the power reception coil unit22is not positionally shifted from the power transmission coil unit12, in which an arrow Y15indicates a magnetic flux. Moreover,FIG. 5(b)schematically illustrates the plan view in this case. Note that, as illustrated inFIG. 5(b), the power reception coil41has a rectangular shape, in which the long side direction is set to the Y-axis direction.

On the other hand,FIG. 5(c)is a cross sectional view in the Y-axis direction when the power reception coil unit22is positionally shifted by the distance L1in the Y-axis direction, in which an arrow Y16indicates a magnetic flux. Moreover,FIG. 5(d)schematically illustrates a plan view in this case.

As seen from the comparison betweenFIG. 5(a)andFIG. 5(c), a positional shift in the Y-axis direction occurring between the power transmission coil unit12and the power reception coil unit22reduces the coupling coefficient κ between the both coils. Accordingly, the power transmission controller15of the power supply device100increases the power supplied to the power transmission coil unit12so that a desired power is generated in the power reception coil unit22. As the result, the magnetic flux output from the power transmission coil31increases as illustrated inFIG. 5(c), and the magnetic flux passing through the ferrite plate42also increases accordingly. Therefore, the concentration of the magnetic flux occurs in the ferrite plate42, causing an increase of the ambient temperature of the power reception coil unit22. Moreover, the ambient temperature of the power reception coil unit22will increase linearly with respect to the amount of positional shift in the Y-axis direction.

Moreover, the positional shift in the Y-axis direction affects the increase in temperature more than the above-described positional shift in the X-axis direction. That is, when the amounts of positional shift in the both directions are the same, the positional shift in the Y-axis direction (long side direction) generates more heat than the positional shift in the X-axis direction (short side direction). Accordingly, as illustrated inFIG. 6, the correction coefficient C may be set so as to linearly vary with respect to the amount of positional shift in the X-axis direction (see a straight line Q3), and the correction coefficient C may be set so as to linearly vary with respect to the amount of positional shift in the Y-axis direction (long side direction) (see a straight line Q2). In this case, the correction coefficient C is set so that the straight line Q2has a lager gradient than the straight line Q3.

Furthermore, in summary, it turns out that there are relationships (A) and (B) below between the correction coefficient C and the positional relationship between the coils.

(A) The correction coefficient C is inversely proportional to the square of the gap G between the power transmission coil unit12and the power reception coil unit22.

(B) The correction coefficient C varies linearly with respect to the amount of positional shift (this is designated by “Lx”) in the X-axis direction and to the amount of positional shift (this is designated by “Ly”) in the Y-axis direction.

Accordingly, if the correction coefficient C is determined on the basis of the relationships (A) and (B), the amount of heat generation due to the power loss WGC of the power transmission side coil can be corrected. Specifically, the correction coefficient C can be obtained from Formula (2) below using coefficients a, b, and c.
C=(a*Lx+b*Ly+c)/G2(2)

Then, the temperature estimation unit33illustrated inFIG. 1obtains the amounts of positional shift Lx, Ly and the gap G, to thereby calculate the correction coefficient C, substitutes this correction coefficient C into the above-described Formula (1), and multiplies this correction coefficient C by the power loss WGC of the power transmission coil31, thereby obtaining the increase in temperature ΔT. That is, the contribution to an increase in temperature due to the power transmission coil31is changed using the correction coefficient C which varies with a magnitude of the positional shift amount. Then, the ambient temperature of the power reception coil unit22is estimated by adding the increase in temperature ΔT to the ambient temperature of the power reception coil unit22, and the control is conducted, when this estimated temperature reaches a preset threshold temperature, so as to suppress the transmitted power and suppress a further increase in temperature.

Next, a method for detecting the amounts of planar positional shift Lx, Ly will be explained with reference toFIG. 7andFIG. 8.FIG. 7is an explanatory view illustrating a first method for detecting the amount of positional shift Lx in the X-axis direction. As illustrated inFIG. 7, the forward-distance sensor51provided at a front end part of the vehicle201transmits an ultrasonic signal to measure the distance L to the wall surface52provided in place in the parking space. Then, on the basis of a distance Lg (known numerical value) from a center point C2of the power transmission coil unit12to the wall surface52, a distance Lv (known numerical value) from a center point C1of the power reception coil unit22to the front end part, and the distance L (measured value), the distance between the respective center points C1and C2, that is, the amount of positional shift Lx in the X-axis direction is calculated by Formula (3) below.
Lx=Lg−Lv−L(3)

In this manner, the amount of positional shift Lx in the X-axis direction can be obtained.

FIG. 8is an explanatory view illustrating a second method for detecting the amount of positional shift Lx in the X-axis direction and the amount of positional shift Ly in the Y-axis direction. The vehicle201stopping inside a parking frame54of the parking space is photographed from the above using the camera13provided in the power supply device100. As the result, a bird's-eye view image like the one illustrated inFIG. 8can be obtained. Then, the amount of planar positional shift between the center point C2of the power transmission coil unit12and the center point C1of the power reception coil unit22is measured on the basis of the positional relationship between the vehicle201and the parking frame54. Specifically, as illustrated inFIG. 8, the amount of positional shift Lx in the X-axis direction and the amount of positional shift Ly in the Y-axis direction can be acquired.

Next, a method for detecting the gap G between the power transmission coil unit12and the power reception coil unit22will be explained with reference toFIG. 9andFIG. 10. As illustrated inFIG. 9, the gap sensor61installed on a bottom part of the vehicle201can measure the gap G by transmitting an ultrasonic signal and receiving a reflected signal thereof.

Moreover, as another method, the gap G can be obtained on the basis of the coupling coefficient κ between the power transmission coil31and the power reception coil41and the respective amounts of positional shift Lx, Ly. Hereinafter, this will be explained with reference toFIG. 10andFIG. 11.FIG. 10is an equivalent circuit diagram of the power transmission coil unit12and power reception coil unit22, in which a load RL corresponds to the battery28illustrated inFIG. 1. As described in Japanese Patent Laid-Open Publication No. 2013-81275, it is known that there is a relationship of Formula (4) below among a voltage V generated in the power transmission coil31, an electric current I flowing through the power transmission coil31, and the coupling coefficient κ between the power transmission coil31and the power reception coil41.

Accordingly, the coupling coefficient κ can be obtained by measuring the voltage V generated in the power transmission coil31and the electric current I flowing through the power transmission coil31. This coupling coefficient κ can be acquired by the charging controller25through the communication between the wireless communication unit14and the wireless communication unit24. That is, the charging controller25has a function as a coupling coefficient acquisition unit which acquires the coupling coefficient κ between the power transmission coil31and the power reception coil41.

Furthermore, once the amounts of positional shift Lx, Ly in the X-axis and Y-axis directions and the coupling coefficient κ are determined, the gap G can be obtained. In the present embodiment, the gap G can be obtained by setting, in advance, a map indicating a relationship among Lx, Ly, κ and the gap G in a storage area (not illustrated) of the temperature estimation unit33, and then applying the amounts of positional shift Lx, Ly, and κ obtained in the above-described procedure to this map.

Because the amounts of positional shift Lx, Ly, and the gap G can be obtained using the above-described method, the correction coefficient C can be obtained from the above-described Formula (2). In the present embodiment, the correction coefficient C is calculated by preparing, in advance, a correspondence map indicating a relationship among the amounts of positional shift Lx, Ly, the gap and the correction coefficient C, and substituting each numerical value into this correspondence map.

Hereinafter, the relationship among the amounts of positional shift Lx, Ly, the gap G, and the correction coefficient C will be explained with reference to a graph illustrated inFIG. 11and an explanatory view illustrated inFIG. 12.

FIG. 11is a graph illustrating a change in the correction coefficient C obtained in performing an experiment for actually changing the amounts of positional shift Lx, Ly and the gap G Reference sign q1indicates the correction coefficient C when Lx=100 mm, Ly=0 mm, and G=100 mm.FIG. 12is an explanatory view illustrating the relative positional relationship between the power transmission coil31and the power reception coil41, in which the reference sign q1inFIG. 11indicates a state where the center C1of the power reception coil41is shifted, by 100 mm in the plus direction of the X-axis, from the center C2of the power transmission coil31, as illustrated inFIG. 12(a). As indicated by the reference sign q1ofFIG. 11, the correction coefficient C is 0.10 in this case.

Similarly, reference sign q2inFIG. 11indicates the correction coefficient C when Lx=−100 mm, Ly=0 mm, and G=100 mm, and indicates a state where the center C1of the power reception coil41is shifted, by 100 mm in the minus direction of the X-axis, from the center C2of the power transmission coil31, as illustrated inFIG. 12(b). As indicated by the reference sign q2ofFIG. 11, the correction coefficient C is 0.15 in this case.

Reference sign q3inFIG. 11indicates the correction coefficient C when Lx=0 mm, 4=100 mm and G=100 mm, and indicates a state where the center C1of the power reception coil41is shifted, by 100 mm in the Y-axis direction, from the center C2of the power transmission coil31, as illustrated inFIG. 12(c). As indicated by the reference sign q3ofFIG. 11, the correction coefficient C is 0.25 in this case.

Furthermore, reference sign q4inFIG. 11indicates the correction coefficient C when Lx=0 mm, Ly=0 mm and G=150 mm, reference sign q5indicates the correction coefficient C when Lx=100 mm, Ly=0 mm, and G=150 mm, reference sign q6indicates the correction coefficient C when Lx=−100 mm, Ly=0 mm, and G=150 mm, and reference sign q7indicates the correction coefficient C when Lx=0 mm, Ly-100 mm, and G=150 mm.

As described above, the correction coefficient C can be obtained by applying the amounts of positional shift Lx, Ly and the gap G to a preset correspondence map.

Furthermore, each of the coefficients a, b, and c of Formula (2) below may be obtained on the basis of the actual measurement value of the correction coefficient C. Then, the correction coefficient C may be calculated using these coefficients a, b, and c.
C=(a*Lx+b*Ly+c)/G2(2)

Adoption of such a calculation method enables to calculate the correction coefficient C by an extremely simple method for substituting the Lx, Ly, and G into the calculation formula.

Next, the processing operation of the temperature estimation device according to the present embodiment will be explained with reference to a flow chart illustrated inFIG. 13. The flow chart inFIG. 13illustrates the processing by the temperature estimation unit33illustrated inFIG. 1and the processing by the power transmission controller15.

First, the temperature estimation unit33acquires the data of the amounts of planar positional shift Lx, Ly of the power reception coil unit22from the power transmission coil unit12, in Step a11. For this processing, the above-described methods illustrated inFIG. 7andFIG. 8can be employed.

In Step a12, the temperature estimation unit33acquires a received power Pb and received voltage Vb in the power reception coil unit22, and an electric current I2flowing through the power reception coil41. These data can be acquired from the detection values of a voltmeter and ammeter (not illustrated) provided in the power reception coil unit22.

In Step b11, the power transmission controller15measures an output voltage Vinv and output current Iinv of the inverter113, and transmits these data to the temperature estimation unit33through the wireless communication unit14and the wireless communication unit24.

In Step a13, the temperature estimation unit33calculates the respective power losses WJB, WVC, and WGC on the basis of various data. As previously described, each power loss is a copper loss and is proportional to the square of the electric current, and therefore the calculation can be conducted on the basis of this relationship.

In Step a14, the gap G between the power transmission coil unit12and the power reception coil unit22is calculated. In this processing, the gap G can be obtained by employing the above-described method illustrated inFIG. 9andFIG. 10.

In Step a15, the temperature estimation unit33obtains the correction coefficient C for correcting the power loss WGC. That is, because the amounts of positional shift Lx, Ly in the plane direction are acquired in the processing of Step a11and the gap G is acquired in the processing of Step a14, the correction coefficient C can be obtained using the above-described approach on the basis of these numerical values.

In Step a16, the temperature estimation unit33calculates the increase in temperature ΔT of the power reception coil unit22by substituting the correction coefficient C acquired in the above-described processing into Formula (1) below.
ΔT=A*WJB+B*WVC+C*WGC(1)

In Step a17, the temperature estimation unit33acquires the ambient temperature Ta of the vehicle201, and adds the increase in temperature ΔT to this ambient temperature Ta. Then, the increase in temperature ΔT is controlled so as to satisfy Formula (5) below.
Ta+ΔT+Tm≤(components allowable temperature)  (5)
where Tm is a margin.

That is, when “Ta+ΔT+Tm” reaches a “components allowable temperature”, an allowable power Px which is an allowable value of the power generated in the power reception coil unit22is set so that the increase in temperature ΔT is reduced. The data of this allowable power Px is transmitted to the power supply device100via the wireless communication unit24and the wireless communication unit14.

Subsequently, in Step b12, the power transmission controller15controls the power transmitted by the power transmission coil unit12so that the power generated in the power reception coil unit22becomes within the allowable power Px. In this manner, the control can be conducted so that the ambient temperature of the power reception coil unit22does not reach the components allowable temperature.

In this manner, the temperature estimation device according to the present embodiment changes, when the positional relationship between the power transmission coil31provided on the ground side and the power reception coil41provided in the vehicle201is positionally shifted from a normal positional relationship, the contribution to an increase in temperature due to the power loss WGC of the power transmission coil31, in accordance with a magnitude of this positional shift amount. Accordingly, the ambient temperature of the power reception coil unit22can be accurately estimated without providing a temperature sensor for measuring the ambient temperature of the power reception coil41.

Moreover, the transmitted power by the power supply device100can be controlled so that the ambient temperature of the power reception coil unit22does not rise to a component-restrictive temperature, and an excessive increase in temperature of the power reception coil unit22and electronic components therearound can be prevented.

Furthermore, if the control is conducted so that the transmitted power from the power transmission coil unit12decreases, the charging time of the battery28increases. In the present embodiment, when control is conducted by the temperature estimation unit33so as to reduce the transmitted power, the information indicative of an increase in the charging time is displayed on the notification unit37to be notified to the occupant of the vehicle201. In this manner, the occupant of the vehicle201can recognize in advance that the time needed for charging will increase and the occupant can have a sense of security.

Moreover, the temperature estimation unit33obtains the correction coefficient C on the basis of the amount of positional shift between the power transmission coil31and the power reception coil41, and multiplies the power loss WGC of the power transmission coil31by the correction coefficient C, thereby changing the contribution to an increase in temperature due to the power loss WGC of this power transmission coil31. Accordingly, the ambient temperature of the power reception coil unit22can be estimated more accurately.

Furthermore, the amounts of planar positional shift X, Y which are the amounts of positional shift between the power transmission coil31and the power reception coil41, and the gap G are acquired, and the correction coefficient C is obtained on the basis of these data. Furthermore, the power loss WGC is multiplied by this correction coefficient C, and furthermore the increase in temperature ΔT is obtained from Formula (1) described above. Accordingly, the ambient temperature of the power reception coil unit22can be estimated more accurately.

Moreover, the coupling coefficient κ between the power transmission coil31and the power reception coil41is acquired, and the gap G is acquired on the basis of this coupling coefficient κ and the amounts of planar positional shift Lx, Ly so that it is possible to dispense with the gap sensor61for measuring the gap G and to reduce the device scale.

Furthermore, the coefficients a, b, and c in the above-described Formula (2) are measured, and furthermore the amounts of positional shift Lx, Ly and the gap G are substituted into Formula (2) to obtain the correction coefficient C, so that the correction coefficient C can be accurately obtained and accordingly the increase in temperature ΔT can be accurately estimated.

In the foregoing, the temperature estimation device and temperature estimation method for the contactless power reception device of the present invention have been explained on the basis of the illustrated embodiment, but the present invention is not limited thereto. The configuration of each unit can be replaced with any configuration having a similar function.

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