Electric vehicle

Abstract

To provide an electric vehicle which can cool, when there is a high possibility that an electric motor is used just after charging a neutral point, the electric motor.SOLUTION: An electric vehicle comprises: an electric motor which drives an axle; an inverter whose DC end is connected to a battery and whose AC end is connected to a stator coil of the electric motor; a charging terminal which is connected to a neutral point of the stator coil; a radiator which cools the electric motor; and a controller. The electric power supplied through the charging terminal is boosted by the stator coil and the inverter to charge the battery, and then the controller activates, when a main switch to drive the electric motor is ON and temperature of the electric motor is more than a predetermined threshold temperature, the radiator.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The technology disclosed in this specification relates to an electric vehicle that includes a battery and an electric motor that drives an axle. [Background technology]

[0002] It is known that a circuit consisting of the stator coil of an electric motor and the switching elements of an inverter can be used as a boost converter. Patent Document 1 discloses a technology in which a power supply is connected to the neutral point of the stator coil, and the power supply voltage is boosted by the circuit of the stator coil and inverter to charge a battery. For ease of explanation, hereinafter, connecting a power supply to the neutral point of the stator coil and boosting the power supply voltage by the circuit of the stator coil and inverter to charge a battery will be referred to as "neutral point charging." [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-118659 Summary of the Invention [Problem to be solved by the invention]

[0004] When neutral point charging is performed, the temperature of the electric motor rises. If the electric motor is not driven immediately after neutral point charging, there is no need to cool the electric motor even if its temperature is high. On the other hand, if there is a high possibility that the electric motor will be used immediately after neutral point charging, it is better to cool the electric motor after charging. This specification provides an electric vehicle that can cool the electric motor when there is a high possibility that the electric motor will be used immediately after neutral point charging. [Means for solving the problem]

[0005] The electric vehicle disclosed in this specification includes an electric motor that drives an axle, an inverter, a charging terminal connected to the neutral point of the stator coil of the electric motor, a cooler that cools the electric motor, and a controller. The inverter has a DC terminal connected to a battery and an AC terminal connected to the stator coil of the electric motor.

[0006] The controller operates the cooler when the main switch for driving the electric motor is on and the temperature of the electric motor exceeds a predetermined threshold temperature after charging the battery by boosting the power supplied through the charging terminals with the stator coil and inverter of the electric motor. The controller does not operate the cooler if the main switch is off even if the temperature of the electric motor exceeds the threshold temperature after charging the battery by boosting the power supplied through the charging terminals with the stator coil and inverter. The electric vehicle disclosed herein operates the cooler when there is a high possibility that the electric motor will be used after neutral point charging.

[0007] Details and further improvements of the technology disclosed in this specification are described in the following "Description of Embodiments of the Invention." [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a block diagram of an electric vehicle 100 according to a first embodiment. [Figure 2] FIG. 2 is a block diagram of an electric vehicle 200 according to a second embodiment. [Figure 3] FIG. 10 is a block diagram of an electric vehicle 300 according to a third embodiment. [Figure 4] 1 is a diagram showing the structure of a driving device 500 in which a motor case and a gear case are coupled together. DETAILED DESCRIPTION OF THE INVENTION

[0009] 1 shows a block diagram of an electric vehicle 100 according to a first embodiment. The electric vehicle 100 includes an electric motor 110, an inverter 120, a battery 109, a cooler 130, a controller 101, and a charging terminal 103. For ease of explanation, the electric motor 110 may be simply referred to as the motor 110 below.

[0010] A main shaft 114 of the motor 110 is connected to the axle 104, and the axle 104 is connected to the wheels via a differential gear 105. The motor 110 is a three-phase AC motor and includes three stator coils 111. The motor 110 drives the axle 104, causing the electric vehicle 100 to move.

[0011] The inverter 120 converts DC power from the battery 109 into AC power suitable for driving the motor 110. DC terminals 120p and 120n of the inverter 120 are connected to the battery 109, and an AC terminal 120a is connected to the motor 110. More specifically, each of the multiple AC terminals 120a of the inverter 120 is connected to each of the multiple stator coils 111 of the motor 110. A capacitor 125 is connected between the positive terminal 120p and the negative terminal 120n of the DC terminal. The negative terminal of the battery 109 and the negative terminal 120n of the inverter 120 are maintained at the same potential. The negative terminal of the battery 109 is referred to as ground G.

[0012] The inverter 120 includes three series-connected circuits 123u, 123v, and 123w. Hereinafter, the three series-connected circuits 123u, 123v, and 123w are collectively referred to as the series-connected circuits 123. The three series-connected circuits 123 are connected in parallel between the positive and negative DC terminals 120p and 120n. Each series-connected circuit 123 is configured with two switching elements (an upper switching element 121 and a lower switching element 122) connected in series. A diode is connected in antiparallel to each switching element. The diode passes current from the low-potential side to the high-potential side of the switching element. The diode may be incorporated into the switching element. When the controller 101 alternately turns on and off the upper switching element 121 and the lower switching element 122, AC is output from the midpoint of the series-connected circuit 123. The circuit configuration and operation of the inverter 120 are well known, so a detailed description will be omitted.

[0013] The cooler 130 cools the inverter 120 and the motor 110. The cooler 130 includes a circulation path 131 and a pump 132. When the pump 132 operates, a refrigerant circulates through the circulation path 131. The circulation path 131 passes through the insides of the inverter 120 and the motor 110, and the inverter 120 and the motor 110 are cooled by the refrigerant flowing through the circulation path 131. Although not shown, the circulation path 131 also includes a reserve tank and a radiator. The reserve tank is provided on the circulation path 131 upstream of the pump 132, and the radiator is provided on the circulation path 131 upstream of the reserve tank. The refrigerant that absorbs heat from the inverter 120 and the motor 110 is cooled by the radiator and returns to the reserve tank. The pump 132 pumps the refrigerant from the reserve tank to the inverter 120 and the motor 110.

[0014] The motor 110, the inverter 120 (switching elements 121, 122), and the cooler 130 are controlled by a controller 101. A main switch 102 is connected to the controller 101. The main switch 102 is also called an ignition switch. The main switch 102 is provided in the driver's seat and is operated by a user. The main switch 102 is a switch for driving the electric motor 110. When the main switch 102 is on, the electric vehicle 100 is in a state where it can run. When the main switch 102 is off, the controller 101 does not allow the electric vehicle 100 to run. In other words, when the main switch 102 is off, the controller 101 prohibits the motor 110 from rotating. When the main switch 102 is on, the controller 101 allows the motor 110 to rotate.

[0015] The cooler 130 may also include a sub-cooler that uses oil as a refrigerant. The sub-cooler includes an oil circulation path, an oil cooler, and an oil pump. The oil circulation path passes through the oil cooler and the motor 110. The oil pump circulates oil between the oil cooler and the motor 110. The refrigerant in the circulation path 131 cools the oil in the oil cooler, and the oil cools the motor 110. The oil may also be sprayed directly onto the stator and rotor of the motor 110. In this case, the oil also functions as a lubricant.

[0016] One end of each of the multiple stator coils 111 of the motor 110 is connected to each of the multiple AC terminals 120a of the inverter 120, and the other ends of each of the multiple stator coils 111 are connected to each other. The point where the other ends of the stator coils 111 are connected is called a neutral point 112.

[0017] A positive terminal 103p of the charging terminal 103 is connected to the neutral point 112. A negative terminal 103n of the charging terminal 103 is connected to ground G. In the electric vehicle 100, an external power supply 900 is connected to the charging terminal 103, and the battery 109 can be charged by the power supply 900. The circuit configuration of the stator coil 111 and the lower switching element 122 functions as a boost converter. In other words, the battery 109 can be charged by the power supply 900, which has a lower output voltage than the battery 109. Charging via the neutral point is referred to as neutral point charging in this specification.

[0018] Neutral point charging will now be outlined. A DC voltage from the power supply 900 is applied to the neutral point 112. When the lower switching element is turned on, current flows through the stator coil 111 and magnetic energy is accumulated. When the lower switching element is turned off, the magnetic energy accumulated in the stator coil 111 boosts the voltage at the AC terminal 120a. In other words, the voltage of the power supply 900 is boosted.

[0019] The controller 101 can perform neutral point charging even when the main switch 102 is off. As described above, when the main switch 102 is off, the controller 101 prohibits the motor 110 from rotating. When performing neutral point charging, the controller 101 drives the lower switching element 122 so as not to rotate the motor 110, and boosts the voltage applied to the neutral point 112.

[0020] Neutral point charging is performed while the electric vehicle 100 is stopped. When neutral point charging is performed, the stator coil 111 of the motor 110 and the lower switching element 122 of the inverter 120 generate heat. The motor 110 is equipped with a temperature sensor 113, and the inverter 120 is also equipped with a temperature sensor 126. The measurement data of the temperature sensors 113 and 126 are sent to the controller 101.

[0021] After the power supplied through the charging terminal 103 is boosted by the stator coil 111 and the inverter 120 to charge the battery 109 (i.e., after neutral point charging), if the main switch 102 is on and the temperature of the motor 110 exceeds a predetermined threshold temperature, the controller 101 operates the cooler 130. This is because, if the main switch 102 is on, there is a high possibility that the user will drive the electric vehicle 100 after neutral point charging is completed. In such a case, it is desirable to quickly lower the temperature of the motor 110. As described above, the cooler 130 cools the inverter 120 as well as the motor 110.

[0022] If the main switch 102 is off after neutral charging, the controller 101 does not operate the cooler 130 even if the temperature of the motor 110 exceeds the threshold temperature. If the main switch 102 is off, it is unlikely that the user will drive the electric vehicle 100 immediately. In such a case, the energy required to operate the cooler 130 can be saved by allowing the motor 110 (and the inverter 120) to cool naturally. If the temperature of the motor 110 is lower than the threshold temperature after neutral charging, the controller 101 does not operate the cooler 130 even if the main switch 102 is on.

[0023] To protect the motor 110 from overheating, if the temperature of the motor 110 exceeds an upper limit temperature, the controller 101 cools the motor 110 regardless of the state of the main switch 102. The upper limit temperature is set to a value higher than the threshold temperature described above. If the temperature of the motor 110 exceeds the upper limit temperature during neutral point charging, the controller 101 cools the motor 110.

[0024] (Second embodiment) Figure 2 shows a block diagram of an electric vehicle 200 of the second embodiment. The electric vehicle 200 of the second embodiment has a clutch 206 between the motor 110 and the axle 104. The clutch 206 engages and disengages the motor 110 from the axle 104. The other configuration of the electric vehicle 200 is the same as that of the electric vehicle 100 of the first embodiment. However, the controller processing after neutral point charging differs between the electric vehicle 100 and the electric vehicle 200. Therefore, the controller of the electric vehicle 200 is designated by the reference numeral 201.

[0025] Like the electric vehicle 100, the electric vehicle 200 can charge the battery 109 by neutral point charging. After neutral point charging, the controller 201 does not operate the cooler 130 if the main switch 102 is on and the temperature of the motor 110 exceeds a predetermined threshold temperature, as long as the clutch 206 is not engaged. In other words, after neutral point charging, the controller 201 does not operate the cooler 130 if the main switch 102 is on and the temperature of the motor 110 exceeds a predetermined threshold temperature, as long as the motor 110 is disconnected from the axle 104. This is because, if the motor 110 is disconnected from the axle 104, the user is unlikely to drive the electric vehicle 200 immediately after neutral point charging. In such a case, the motor 110 and the inverter 120, whose temperatures have increased after neutral point charging, can be allowed to cool naturally.

[0026] The controller 201 operates the cooler 130 if the main switch 102 is on after neutral point charging, the temperature of the motor 110 exceeds a predetermined threshold temperature, and the motor 110 is engaged with the axle 104. The controller 201 does not operate the cooler 130 if the main switch 102 is off after neutral point charging.

[0027] 3 shows a block diagram of an electric vehicle 300 of a third embodiment. The electric vehicle 300 differs from the electric vehicle 100 of the first embodiment in a cooler 330 and a controller 301. The electric vehicle 300 also differs from the electric vehicle 100 in that it includes a clutch 306 and a gear case 307.

[0028] A gear 308 is housed in the gear case 307. In the figure, the gear 308 is depicted schematically. The main shaft 114 of the motor 110 engages with the gear 308 via a clutch 306. The clutch 306 connects and disconnects the motor 110 to and from the gear 308. The gear 308 engages with the axle 104. The torque of the motor 110 drives the axle 104 via the clutch 306 and the gear 308. When the clutch 306 is disengaged, the gear 308 and the axle 104 do not rotate even if the motor 110 rotates.

[0029] The circulation path 331 of the cooler 330 includes an upstream path 331a, a downstream path 331b, and a bypass path 331c. The upstream path 331a, the downstream path 331b, and the bypass path 331c are connected by a three-way valve 335. The three-way valve 335 connects the upstream path 331a to one of the downstream path 331b and the bypass path 331c and separates it from the other. The downstream path 331b passes through the gear case 307, and the bypass path 331c bypasses the gear case 307. The downstream ends of the downstream path 331b and the bypass path 331c are both connected to the pump 132. Like the cooler 130 of the electric vehicle 100 of the first embodiment, the cooler 330 also includes a reserve tank and a radiator, not shown.

[0030] When the upstream path 331a is connected to the downstream path 331b, the refrigerant that has passed through the inverter 120 and the motor 110 is sent to the gear case 307. In the gear case 307, the refrigerant is applied to the gear 308. The refrigerant also serves as a lubricant for the gear 308.

[0031] When the upstream path 331 a is connected to the bypass path 331 c , the refrigerant that has passed through the inverter 120 and the motor 110 bypasses the gear case 307 and returns to the pump 132 .

[0032] Hereinafter, a state in which the upstream path 331a is connected to the downstream path 331b and the refrigerant is supplied to the inverter 120, the motor 110, and the gear 308 will be referred to as a full circulation mode. Also, a state in which the upstream path 331a is connected to the bypass path 331c and the refrigerant is supplied to the inverter 120 and the motor 110 but not to the gear 308 will be referred to as a semi-circulation mode. When operating the cooler 330, the controller 301 selects either the full circulation mode or the semi-circulation mode.

[0033] Like the cooler 130, the cooler 330 may include a sub-cooler that uses oil as a refrigerant. The sub-cooler includes an oil circulation path, an oil cooler, and an oil pump. The oil circulation path passes through the oil cooler, the motor 110, and the gear case 307. The oil pump circulates oil between the oil cooler, the motor 110, and the gear case 307. The refrigerant in the circulation path 331 cools the oil in the oil cooler, and the oil cools the motor 110 and the gear 308. The oil is in direct contact with the gear. The oil may also be in direct contact with the stator and rotor of the motor 110. In this case, the oil also functions as a lubricant for the motor 110 and the gear 308.

[0034] The electric vehicle 300 includes a gear 308. The gear 308 is provided between the axle 104 and the motor 110 and amplifies the torque of the motor 110 before transmitting it to the axle 104. The refrigerant in the cooler 330 also serves as a lubricant for the gear 308. A clutch 306 is provided between the motor 110 and the gear 308, and the clutch 306 engages and disengages the gear 308 from the motor 110. The cooler 330 includes a switch (three-way valve 335) for switching between a full circulation mode in which the refrigerant is supplied to both the motor 110 and the gear 308, and a half circulation mode in which the refrigerant is supplied to the motor 110 but not to the gear 308. When cooling the motor 110, the controller 301 operates the cooler 330 in the full circulation mode when the motor 110 is engaged with the gear 308. The controller 301 operates the chiller 330 in semi-circulation mode when the motor 110 is disengaged from the gear 308 .

[0035] FIG. 4 shows an example of a structure that can switch between full circulation mode and semi-circulation mode without using a three-way valve. FIG. 4 shows the structure of a drive unit 500 in which a motor case 511 and a gear case 521 are coupled together. In the drive unit 500, the motor case 511 and the gear case 521 are coupled together and separated by a partition plate 530. The motor case 511 houses a motor 510, and the gear case 521 houses multiple gears 520. The main shaft of the motor 510 and the gear 520 are engaged via a clutch 512. When the clutch 512 is engaged, the motor 510 and the gear 520 are engaged, and the gear 520 and the axle 104 rotate together with the motor 510. When the clutch 512 is released, the motor 510 is separated from the gear 520. The output shaft of the gear 520 corresponds to the axle 104. An oil supply pipe 541 is connected to the top of the motor case 511, and oil is supplied from the oil supply pipe 541. Oil is applied to the motor 510. The oil cools and lubricates the motor 510.

[0036] The partition plate 530 is provided with a communication hole 531 and a movable plate 532 that closes the communication hole 531. The movable plate 532 is controlled by a controller (not shown). FIG. 4 shows the movable plate 532 in an open state. When the movable plate 532 is open, the motor case 511 and the gear case 521 communicate with each other through the communication hole 531. The imaginary line in FIG. 4 shows the movable plate 532 in a closed state. When the movable plate 532 is closed, the communication hole 531 is blocked, and the space inside the motor case 511 and the space inside the gear case 521 are separated.

[0037] When the motor 510 rotates with the movable plate 532 open, some of the oil stirred up by the rotation of the motor 510 enters the gear case 521 through the communication hole 531. The oil that has entered the gear case 521 falls on the gear 520. The oil cools and lubricates the gear 520. The thick arrows in Figure 4 indicate the flow of oil when the movable plate 532 is open. When the movable plate 532 is closed, the oil in the motor case 511 no longer enters the gear case 521.

[0038] An oil discharge pipe 542 is connected to the bottom of the motor case 511, and an oil discharge pipe 543 is connected to the bottom of the gear case 521. Oil that has accumulated below the motor case 511 is discharged from the oil discharge pipe 542, and oil that has accumulated below the gear case 521 is discharged from the oil discharge pipe 543.

[0039] Oil supply pipe 541 and oil discharge pipes 542 and 543 are part of the cooler. When a controller (not shown) closes movable plate 532 to operate the cooler, the cooler enters the semi-circulation mode described above, and when it opens movable plate 532 to operate the cooler, the cooler enters the full circulation mode described above. Movable plate 532 corresponds to a switch that switches between the full circulation mode, in which refrigerant is supplied to both the motor and gears, and the half circulation mode, in which refrigerant is supplied to the motor but not to the gears.

[0040] The following points should be noted regarding the technology described in the embodiments. The electric vehicles 100, 200, and 300 of the embodiments can cool the motor when there is a high possibility that the motor will be used soon after neutral point charging. After neutral point charging, when the main switch 102 is off, the controller does not operate the cooler even if the temperature of the motor exceeds the threshold temperature.

[0041] The main switch 102 is a switch for driving the motor 110. However, neutral point charging can be performed even when the main switch 102 is off. In neutral point charging, current flows through the stator coil 111 of the motor 110, but the motor 110 does not rotate. More precisely, the main switch 102 is a switch that permits the rotational driving of the motor 110. When the main switch 102 is on, the rotational driving of the motor 110 is permitted, and when the main switch 102 is off, the rotational driving of the motor 110 is prohibited.

[0042] Electric vehicle 200 of the embodiment includes clutch 206 as a mechanism for engaging and disengaging the motor from the axle. Electric vehicle 300 includes clutch 306 as a mechanism for engaging and disengaging the motor from the gear. The mechanism for engaging and disengaging the motor from the axle (or gear) may be a disconnect mechanism that employs a ball screw. Any mechanism may be used for engaging and disengaging the motor from the axle (or gear).

[0043] In this specification, the term "electric vehicle" includes hybrid vehicles equipped with both an electric motor and an engine, and fuel cell vehicles equipped with a battery and a fuel cell. For example, the term "electric vehicle" in this specification also includes vehicles in which one of the front and rear wheels is driven by an engine and the other by an electric motor.

[0044] Although specific examples of the present invention have been described in detail above, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and variations of the specific examples exemplified above. The technical elements described in this specification or drawings exhibit technical utility alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. Furthermore, the technology exemplified in this specification or drawings can achieve multiple objectives simultaneously, and achieving one of these objectives alone is technically useful. [Explanation of symbols]

[0045] 100, 200, 300: electric vehicle 101, 201, 301: controller 102: main switch 103: charging terminal 104: axle 105: differential gear 109: battery 110: electric motor 111: stator coil 112: neutral point 113, 126: temperature sensor 114: main shaft 120: inverter 120a: AC end 120p, 120n: DC end 121, 122: switching element 123, 123u, 123v, 123w: series connection circuit 125: capacitor 130, 330: cooler 131, 331: circulation path 132: pump 206, 306: clutch 307: gear case 308: gear 331a: upstream path 331b: downstream path 331c: Bypass path 335: Three-way valve 500: Drive unit 510: Motor 511: Motor case 512: Clutch 520: Gear 521: Gear case 530: Partition plate 531: Communication hole 532: Movable plate 541: Oil supply pipe 542, 543: Oil discharge pipe 900: Power supply

Claims

1. an electric motor that drives the axle; an inverter having a DC end connected to a battery and an AC end connected to a stator coil of the electric motor; a charging terminal connected to the neutral point of the stator coil; a cooler for cooling the electric motor; A controller; It is equipped with the controller charges the battery by boosting the power supplied through the charging terminal using the stator coil and the inverter, and then operates the cooler when a main switch for driving the electric motor is on and the temperature of the electric motor exceeds a predetermined threshold temperature.

2. 2. The electric vehicle according to claim 1, wherein the controller does not operate the cooler when the main switch is off even if the temperature of the electric motor exceeds the threshold temperature after charging the battery by boosting the power supplied through the charging terminal with the stator coil and the inverter.

3. 2. The electric vehicle according to claim 1, wherein the controller does not operate the cooler when the electric motor is disconnected from the axle even if the main switch is on and the temperature of the electric motor exceeds a predetermined threshold temperature after charging the battery by boosting the power supplied through the charging terminal with the stator coil and the inverter.

4. a gear is provided between the axle and the electric motor; The refrigerant of the cooler also serves as a lubricant for the gears, the cooler includes a switch for switching between a full circulation mode in which the refrigerant is supplied to both the electric motor and the gear and a half circulation mode in which the refrigerant is supplied to the electric motor but not to the gear; the controller, when cooling the electric motor, operates the cooler in a full circulation mode when the electric motor is engaged with the gear and in a half circulation mode when the electric motor is disengaged from the gear; The electric vehicle of claim 1 .

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