JP2005039917A - Power transmitter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To offer a power transmitter which can settle output voltage within a certain range even under a variation in ambient temperature. <P>SOLUTION: In a power transmitter which transmits power between a unit on transmission side where the primary coil of a transformer is arranged and a unit on reception side where the secondary coil of the transformer is arranged, a boosting circuit 101 compensates DC power voltage VCC, which is supplied to a first switching element 106 and a second switching element 107 acting as switching power sources for supplying AC power while switching alternately, according to the ambient air temperature detected by a temperature compensating circuit 102. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a power transmission device, and more particularly to a power transmission device that transmits power in a contactless manner between two units.
[0002]
[Prior art]
As a conventional power transmission device, for example, there is one disclosed in Patent Document 1. In FIG. 1 of Patent Document 1, a signal transmission load circuit 21 connected to the secondary winding 4b side of the output transformer 4 superimposes a pulse-shaped load signal current corresponding to the load current on its own current. The load signal current is transmitted to the primary side of the output transformer 4 by electromagnetic inductive coupling, and the load signal current flows through the primary winding 4a, the diode 9, and the resistor 7. The current detection circuit 10 detects a load signal current. The oscillation frequency variable circuit 11 varies the oscillation frequency of the oscillation circuit 12 according to the detected value. By changing the switching cycle of the MOS transistor 6 and changing the chopping cycle of the DC voltage on the primary side, small power is supplied at no load and light load, and high power is supplied to the secondary side when load signal current is detected from the secondary side. To do.
[0003]
In addition, the present applicant has disclosed a non-contact power transmission apparatus that can keep the output voltage within a certain range with respect to load fluctuations in Patent Document 2 without requiring feedback control.
[0004]
[Patent Document 1]
Japanese Patent Laid-Open No. 11-341711 (FIG. 1)
[Patent Document 2]
Japanese Patent Application No. 2002-233726
[Problems to be solved by the invention]
However, in the prior art, the change in the output voltage is increased due to the change in the ambient temperature. Therefore, for example, the efficiency of power transmission decreases at high temperatures. In a device that performs non-contact power transmission from the primary side (for example, the vehicle body) to the secondary side (for example, steering) as shown in Patent Document 2, it is assumed that the stability of the output voltage against load fluctuation is within a certain range. However, it exceeds the specified range due to changes in ambient temperature. In order to stabilize the output voltage, it is effective to feed back to the primary side (power transmission side), but when transmitting power without contact (space of several mm), it is difficult to return a feedback signal. Although there is a method of performing feedback using an optical communication line, there is a problem that there is a problem that feedback cannot be performed in real time due to the communication speed.
[0006]
The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a power transmission device capable of keeping an output voltage within a certain range with respect to a change in ambient temperature.
[0007]
It is another object of the present invention to provide a power transmission device that can prevent a decrease in output voltage when the load is suddenly increased, such as an air bag (A / B).
[0008]
[Means for Solving the Problems]
In order to achieve this object, the invention according to claim 1 is a power transmission device that transmits power between a power transmission side unit and a power reception side unit, and the primary side disposed in the power transmission side unit. Based on the ambient temperature detected by the temperature compensation circuit 102, a transformer 108 comprising a coil and a secondary coil disposed in the power receiving side unit, a temperature compensation circuit 102 for detecting the ambient temperature, and a direct current A booster circuit 101 that boosts the power supply voltage VCC of the power supply and a power supply voltage VCC boosted by the booster circuit 101 are alternately switched at a predetermined on / off frequency, converted into an AC voltage, and supplied to the primary coil. The first switching element 106 and the second switching element 107 are included.
[0009]
Therefore, according to the first aspect of the present invention, the booster circuit 101 switches the DC power supplied to the first switching element 106 and the second switching element 107 acting as a switching power source that alternately switches and supplies AC power. By compensating the power supply voltage VCC corresponding to the ambient temperature detected by the temperature compensation circuit 102, the output voltage can be kept within a certain range with respect to a change in ambient temperature. For example, by performing compensation for reducing the power supply voltage VCC at a high temperature, it is possible to suppress unnecessary power consumption that has been added more than necessary at a high temperature.
[0010]
According to a second aspect of the present invention, in the first aspect of the invention, the temperature compensation circuit 102 includes a thermistor Rth3 whose resistance value varies according to a temperature change, and the power supply voltage VCC output from the booster circuit 101 is supplied to the thermistor. A feedback voltage divided by a resistor string including Rth3 is input to the booster circuit 101. The booster circuit 101 boosts the power supply voltage VCC of the DC power supply in accordance with the feedback voltage input from the temperature compensation circuit 102. It is characterized by doing.
[0011]
Therefore, according to the second aspect of the invention, the voltage corresponding to the ambient temperature is fed back to the booster circuit 101 by the resistor group including the thermistor Rth3, so that temperature compensation can be performed with a simple circuit.
[0012]
A third aspect of the invention is characterized in that, in the first or second aspect of the invention, the booster circuit 101 fixes the power supply voltage VCC to a predetermined default value when a load operation signal is inputted.
[0013]
Therefore, according to the third aspect of the present invention, when the booster circuit 101 receives a load operation signal, the power supply voltage VCC is fixed to a predetermined default value, thereby preventing a decrease in output voltage during heavy load. can do.
[0014]
The invention according to claim 4 is the invention according to any one of claims 1 to 3, wherein the contact point of the first switching element 106 and the second switching element 107 and the primary side coil of the transformer 108 are provided. And a resonance capacitor C1 connected in series, and the capacitance of the resonance capacitor C1 and the inductance of the primary coil are set so that the resonance capacitor C1 and the primary coil resonate. It is characterized by doing.
[0015]
Therefore, according to the fourth aspect of the present invention, the resonance capacitor C1 is connected in series between the contact point of the first switching element 106 and the second switching element 107 and the primary side coil of the transformer 108. Since the resonance state automatically changes when the load fluctuates, special control is unnecessary on both the power transmission side and the power reception side. In addition, since the coil current waveform becomes a sine wave under heavy load, the noise is low, and zero current switching (which can minimize the switching loss) is performed, so that highly efficient power transmission is possible.
[0016]
According to a fifth aspect of the present invention, in the fourth aspect of the present invention, the capacitance of the resonant capacitor C1, the primary side coil, and the secondary side so that the output voltage of the power receiving unit falls within a predetermined range. It is characterized by setting the inductance of the side coil.
[0017]
Therefore, according to the invention described in claim 5, the capacitance of the resonance capacitor C1, the inductance of the primary side coil, and the inductance of the secondary side coil are set so that the output voltage of the unit on the power receiving side falls within a predetermined range. As a result, the resonance state automatically changes when the load fluctuates, and the output voltage falls within a certain range. Therefore, it is not necessary to feed back the output voltage from the power receiving side, and the cost can be reduced.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a circuit diagram illustrating a configuration of a power transmission device according to a first embodiment of the present invention. In the following description, an example will be described in which the power transmission device is mounted on a vehicle and applied to transmit power in a contactless manner between a power transmission side (vehicle body) and a power reception side (steering).
[0019]
In FIG. 1, the power transmission device includes a DC power supply VCC, a booster circuit 101, a temperature compensation circuit 102, an oscillation circuit 103, a drive circuit 104, a high-side drive charge pump 105, a first switching element 106, and a second switching element. 107, a transformer 108, and a rectifier circuit 109.
[0020]
The DC power supply, the booster circuit 101, the temperature compensation circuit 102, the oscillation circuit 103, the drive circuit 104, the high-side drive charge pump 105, the first switching element 106, and the second switching element 107 are arranged on the power transmission side, Configure the switching power supply. The rectifier circuit 109 is disposed on the power receiving side. The primary coil 108a of the transformer 108 is disposed on the power transmission side, and the secondary coil 108b is disposed on the power reception side.
[0021]
The DC power source is a power source obtained from a vehicle battery such as 12V. The booster circuit 101 boosts the power supply voltage of the DC power supply in order to secure an input voltage sufficient to obtain a target output voltage with respect to the load impedance viewed from the primary coil 108a of the transformer 108. The temperature compensation circuit 102 adaptively controls the booster circuit 101 in order to suppress fluctuations in the output voltage due to the ambient temperature (ambient temperature) within a predetermined range. Detailed description of the booster circuit 101 and the temperature compensation circuit 102 will be described later.
[0022]
The oscillation circuit 103 generates an oscillation output pulse signal having a predetermined frequency and outputs it to the drive circuit 104 in order to alternately turn on and off the first switching element 106 and the first switching element 107. The drive circuit 104 generates an alternating pulse signal having an appropriate pause period based on the pulse signal supplied from the oscillation circuit 103. When a high-side N-channel FET (Field-Effect Transistor) is used as the first switching element 106, the high-side drive charge pump 105 turns on the N-channel FET with reference to the source of the N-channel FET. This is generated by boosting the voltage necessary for this.
[0023]
The first switching element 106 and the second switching element 107 alternately switch the DC input voltage that is the power supply voltage VCC from the booster circuit 101, and transmits power to the power receiving side via the transformer 108. The first switching element 106 is a high-side switching element, and the second switching element 107 is a low-side switching element.
[0024]
N-channel FETs may be used for the first switching element 106 and the second switching element 107. As a high-side switching element, there is a method using a P-channel FET, but in the present invention, an N-channel FET capable of obtaining a low on-resistance at low cost is used in order to perform high power transmission. As a result, it is possible to unify N-channel FETs of the same type, which is advantageous in terms of mass production cost. Note that a transistor or an IGBT (Insulated Gate Bipolar Transistor) may be used instead of the FET.
[0025]
The drive circuit 104 boosts the high-side drive pulse signal among the alternating pulse signals by the high-side drive charge pump 116 and applies it to the gate of the high-side N-channel FET 106. Further, the low-side driving pulse signal among the alternating pulse signals is applied to the gate of the low-side N-channel FET 107.
[0026]
The transformer 108 is, for example, a rotary type in which a primary coil 108a is disposed in a column on the vehicle body (body) side, a secondary coil 108b is disposed on a steering side, and both coils are relatively rotatable. The transformer is described in detail later.
[0027]
The rectifier circuit 109 converts AC power transmitted in a non-contact manner from electromagnetic transmission in the transformer 108 from the power transmission side to DC power, and supplies it to a switch circuit and a load (not shown). Examples of the load on the steering side include an airbag inflator and illumination. The airbag inflator has an ignition device (squib) (not shown), and inflates the airbag by energizing the ignition device in response to an airbag signal from an airbag sensor (not shown). The airbag signal is also output to the power transmission side booster circuit 101 via an optical communication circuit (not shown).
[0028]
FIG. 2 is a circuit diagram showing one embodiment of the booster circuit 101 and the temperature compensation circuit 102 in FIG. The circuit includes a resistor R1, a resistor R2, a thermistor Rth3, a resistor R4, a resistor R5, and a DC-DC converter. The thermistor Rth3 is an element whose resistance value varies with temperature.
[0029]
The DC-DC converter boosts the power supply voltage input from the DC power supply and outputs the power supply voltage VCC from the Vout terminal. The resistor R2 adjusts the sensitivity of the thermistor Rth3, and the resistor R1 adjusts the nonlinearity of the thermistor Rth3, and finally stabilizes the output voltage on the secondary side.
[0030]
These combined resistor, resistor R4, and resistor R5 are divided by the power supply voltage VCC and output to the Vfb (feedback) terminal of the DC-DC converter. The resistor R4 and the resistor R5 may be combined into one. The DC-DC converter compensates the output power supply voltage VCC based on the feedback voltage input from the Vfb terminal. Here, the compensation amount and the compensation curve for the power supply voltage VCC can be adjusted by changing the resistance values of all or any of the resistors R1, R2, thermistors Rth3, R4, and R5.
[0031]
FIG. 3 is a table showing an example of the compensation amount of the power supply voltage VCC with respect to the ambient temperature. When the power supply voltage VCC is not compensated as shown by the line A in FIG. 3, the output voltage rises corresponding to the increase in the ambient temperature as shown by the line C. Therefore, in order to make the output voltage constant as shown by the line D, the power supply voltage VCC is compensated as shown by the line B. Since the change in the ambient temperature appears in the resistance value of the thermistor Rth3, the DC-DC converter detects this from the feedback voltage input from the Vfb terminal and compensates the output power supply voltage VCC. For example, when the ambient temperature rises, the value corresponding to the raised temperature is stepped down.
[0032]
4 and 5 are diagrams for explaining an example of the structure of the transformer 108. FIG. The transformer 108 is a rotary transformer composed of a rotating part side member P1, a fixed part side member P2, and a light guide P3 disposed between these members.
[0033]
FIG. 4 is a view showing a state in which the transformer 108 is mounted on a connecting portion between the steering and the column on the vehicle body (body) side. As shown in FIG. The fixed rotating part side member P1 and the fixed part side member P2 fixed to the column side are connected and arranged to face each other.
[0034]
FIG. 5 is a cross-sectional view of the transformer 108 and shows details of a connecting portion between the rotating portion side member P1 and the fixed portion side member P2. In the rotating part side member P1 and the fixed part side member P2, light guide paths P3a and P3b that form a part of the light guide P3 are arranged facing each other. Further, in order to supply electric power from the column side to the steering side in a non-contact manner by electromagnetic induction, the stationary part side member P2 is provided with a primary side coil 108a, and the rotating part side member P1 is provided with a secondary coil 108b. Is provided.
[0035]
Next, a second embodiment of the present invention will be described. FIG. 6 is a circuit diagram showing a configuration of a power transmission device according to the second embodiment of the present invention. In the second embodiment, a resonance capacitor C1 is provided between the contact point between the first switching element 106 and the second switching element 107 and the primary side coil 108a in the first embodiment. .
[0036]
In FIG. 6, the first switching element 106 and the second switching element 107 on the power transmission side are alternately turned on and off alternately, and the power supply voltage VCC output from the booster circuit 101 is matched with the frequency of the oscillation circuit 103 to resonate. Electric power is transmitted to the power receiving side by being applied to a series circuit including the capacitor C1 and the primary coil 108a. The series circuit including the resonant capacitor C1 and the primary coil 108a resonates when a load corresponding to an air bag is applied to the output on the power receiving side.
[0037]
That is, the resonant capacitor C1 and the primary side are set so that the capacitance (C component) of the resonant capacitor C1 and the inductance (L component) of the primary coil 108a satisfy the relationship of the following formula 1 and the output voltage falls within a predetermined value. The values of the coil 108a and the secondary side coil 108b (number of turns) are set.
[0038]
1 / ωC = ωL Equation 1 ω = 2πf, f = oscillation frequency
In order to prevent the output voltage from decreasing on the power transmission side, the booster circuit 101 fixes the power supply voltage VCC to a predetermined value when receiving a load operation signal such as an airbag (A / B) signal. Since other configurations are the same as those in the first embodiment, description thereof is omitted.
[0040]
Next, the operation of the power transmission device in the second embodiment will be described. In FIG. 6, an oscillation circuit 103 generates an oscillation output pulse signal having a predetermined frequency, and a drive circuit 104 is an alternating pulse signal having an appropriate pause period based on the pulse signal supplied from the oscillation circuit 103. Is generated. The alternating pulse signals are input to the gates of the first switching element 106 and the second switching element 107, respectively. Accordingly, the first switching element 106 and the second switching element 107 are turned on and turned off at a predetermined on / off frequency.
[0041]
The power supply voltage VCC boosted by the booster circuit 101 is alternately switched at the above-described on / off frequency by the first switching element 106 and the second switching element 107 and converted into a pulsed voltage. Normally, the transformer 108 transmits electric power from the primary side coil 108a to the secondary side coil 108b using this pulsed voltage. In this regard, in the present embodiment, a rotary type is used as the transformer 108 for non-contact power transmission. The rotary transformer 108 has a non-negligible air gap G existing in the assembly structure, and the leakage magnetic flux is very large. Therefore, there is a problem that the effective power is reduced (deterioration of the power factor) due to the leakage inductance due to the leakage magnetic flux, and the transmittable power becomes very small.
[0042]
Therefore, in this embodiment, in order to suppress the deterioration of the power factor due to the leakage magnetic flux, the power factor is set by LC series resonance (resonance between voltage and current phases) by the resonance capacitor C1 and the primary coil 108a of the transformer 108. Improve.
[0043]
However, due to the nature of the transformer 108 (in a magnetically coupled state), the impedance viewed from the power source of the primary coil 108a changes due to the fluctuation of the load connected to the power receiving side. That is, even if the number of turns of the primary coil 108a is constant, the above-described inductance changes depending on the weight of the load connected to the secondary coil 108b. Therefore, it is impossible to maintain resonance in all load states.
[0044]
Therefore, in the present embodiment, using the above-described properties, for example, the inductance of the primary coil 108a when a specific load such as an airbag inflator that requires high power is connected, and the resonance capacitor C1 The capacitance of the resonance capacitor C1 is determined so that the resonance frequency determined by the capacitance matches the on / off frequency. At the time of resonance, the reactances of the primary side coil 108a of the transformer 108 and the resonance capacitor C1 match, so that the capacitance of the resonance capacitor C1 can be easily obtained.
[0045]
With such a setting, when a heavy load such as an airbag inflator is connected as a specific load, even if the on / off frequency is constant, the on / off frequency and the above-described resonance frequency automatically match and resonate. Entering the state (maximum power factor) enables high-power non-contact transmission.
[0046]
Since the power transmission side supplies power in a state where the on / off frequency coincides with the resonance frequency under heavy load, the switching current waveforms of the first switching element 106 and the second switching element 107 become sinusoidal due to the resonance action. That is, zero current switching at turn-on and turn-off is possible, and switching loss is reduced. And since it resonates at the time of heavy load, the impedance seen from the power supply is minimized, and a large current can be supplied to the load.
[0047]
On the other hand, when an airbag inflator as a specific load is not connected, that is, when the load is changed to a light load (only a load that does not require high power is connected), the primary side is accordingly changed. The inductance of the coil 108a changes. Therefore, the resonance frequency is changed and does not coincide with the on / off frequency, so that the resonance state is deviated. As a result, the power that can be supplied to the load is limited, so that an increase in output voltage can be suppressed.
[0048]
Further, even if the air gap G varies (inductance value varies), in order to keep the output voltage within a certain range, it is necessary to optimally adjust Q defined by the following equation 2.
[0049]
Q = (√ (L / C)) / R Equation 2
L = Inductance C of primary coil 108a = Capacitance R of resonant capacitor C1 = Internal resistance of primary coil 108a
For example, if Q is set low, it becomes strong against gap fluctuations, but it cannot supply power necessary for heavy loads. If Q is set high, resonance cannot be obtained with a slight gap fluctuation, and a sufficient output cannot be obtained. Therefore, it is preferable that the resonance shifts to such an extent that a moderate output voltage can be obtained at a light load while corresponding to an appropriate range of gap fluctuation.
[0051]
As described above, when the resonance capacitor C1 is provided, the output voltage can be kept within a certain range with respect to the fluctuation of the load. However, since the inductance of the coils 108a and 108b changes due to the change in the relative permeability of the ferrite core with respect to the change in the ambient temperature, the output voltage changes, so the temperature compensation circuit 102 is provided.
[0052]
The above-described embodiment shows an example of a preferred embodiment of the present invention, and the present invention is not limited thereto, and various modifications can be made without departing from the scope of the invention.
[0053]
For example, in the above-described embodiment, the case where an airbag inflator is connected as a specific load has been described. However, the present invention is not limited to this, and is also applied to cases where other components that can be heavy loads are connected. Is possible.
[0054]
In the above-described embodiment, the non-contact power transmission between the vehicle body and the steering of the vehicle has been described. However, the present invention is not limited to this, and an FFC (steering roll connector) is used in a multi-rotation place. The present invention can be applied to places where it is impossible to handle, places where power is transmitted using contacts etc. at rotating parts, and places where contact wear of rotating parts becomes a problem. For example, the present invention can be applied between a vehicle body and a slide door.
[0055]
【The invention's effect】
As is apparent from the above description, according to the first aspect of the present invention, the booster circuit is applied to the first switching element and the second switching element that act as switching power supplies that alternately switch to supply AC power. By compensating the DC power supply voltage to be supplied corresponding to the ambient temperature detected by the temperature compensation circuit, the output voltage can be kept within a certain range with respect to changes in ambient temperature. For example, by performing compensation for lowering the power supply voltage at high temperatures, it is possible to suppress unnecessary power consumption that has been added more than necessary at high temperatures.
[0056]
According to the invention described in claim 2, in addition to the effect of the invention described in claim 1, the voltage corresponding to the ambient temperature is fed back to the booster circuit by the resistor group including the thermistor, so that the temperature compensation can be performed with a simple circuit. It can be performed.
[0057]
According to the invention described in claim 3, in addition to the effect of the invention described in claim 1 or 2, when the booster circuit receives the load operation signal, the power supply voltage is fixed to a predetermined default value. It is possible to prevent a decrease in output voltage at the time of heavy load.
[0058]
According to the invention described in claim 4, in addition to the effect of the invention described in any one of claims 1 to 3, the contact point of the first switching element and the second switching element, and the primary side of the transformer By connecting a resonance capacitor in series with the coil, the resonance state automatically changes when the load fluctuates, so that no special control is required on both the power transmission side and the power reception side. In addition, since the coil current waveform becomes a sine wave under heavy load, the noise is low, and zero current switching (which can minimize the switching loss) is performed, so that highly efficient power transmission is possible.
[0059]
According to the fifth aspect of the invention, in addition to the effect of the fourth aspect of the invention, the capacitance of the resonance capacitor, the primary side coil, and the second side coil are set so that the output voltage of the power receiving unit falls within a predetermined range. By setting the inductance of the secondary coil, the resonance state automatically changes when the load fluctuates, and the output voltage falls within a certain range, so there is no need to feed back the output voltage from the power receiving side, reducing costs. be able to.
[Brief description of the drawings]
FIG. 1 is a circuit diagram showing a configuration of a power transmission device according to a first embodiment of the present invention.
FIG. 2 is a circuit diagram showing an example of a booster circuit and a temperature compensation circuit in the embodiment of the present invention.
FIG. 3 is a table showing an example of a compensation amount of a power supply voltage VCC with respect to an ambient temperature in the embodiment of the present invention.
FIG. 4 is a diagram for explaining a structural example of a transformer in the power transmission device according to the embodiment of the present invention, and shows a state in which the transformer is mounted on a connection portion between a steering and a column on the vehicle body (body) side. .
FIG. 5 is a cross-sectional view illustrating a structural example of a transformer in the power transmission device according to the embodiment of the present invention.
FIG. 6 is a circuit diagram showing a configuration of a power transmission device according to the first embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 101 Booster circuit 102 Temperature compensation circuit 103 Oscillation circuit 104 Drive circuit 105 High side drive charge pump 106 First switching element 107 Second switching element 108 Transformer 109 Rectifier circuit

Claims (5)

In a power transmission device that transmits power between a power transmission unit and a power reception unit,
A transformer composed of a primary coil disposed in the power transmission unit and a secondary coil disposed in the power reception unit;
A temperature compensation circuit for detecting the ambient temperature;
A booster circuit that boosts the power supply voltage of the DC power supply based on the ambient temperature detected by the temperature compensation circuit;
A first switching element and a second switching element that alternately switch the power supply voltage boosted by the booster circuit at a predetermined on / off frequency, convert the power supply voltage into an alternating voltage, and supply the alternating voltage to the primary coil;
A power transmission device comprising: The temperature compensation circuit includes a thermistor whose resistance value varies according to a temperature change, and inputs a feedback voltage obtained by dividing a power supply voltage output from the booster circuit by a resistor string including the thermistor to the booster circuit,
The power transmission device according to claim 1, wherein the booster circuit boosts a power supply voltage of the DC power supply according to a feedback voltage input from the temperature compensation circuit. The power transmission device according to claim 1, wherein the booster circuit fixes the power supply voltage to a predetermined default value when a load operation signal is input. A resonance capacitor connected in series between the contact point of the first switching element and the second switching element and the primary side coil of the transformer;
The capacitance of the resonance capacitor and the inductance of the primary side coil are set so that the resonance capacitor and the primary side coil resonate. Power transmission device. 5. The capacitance of the resonant capacitor, and the inductances of the primary side coil and the secondary side coil are set so that the output voltage of the power receiving unit falls within a predetermined range. Power transmission device.

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