Electric vehicle

Abstract

To provide a technique capable of improving stability of linear advancement of an electric vehicle.SOLUTION: An electric vehicle includes a first motor connected to a right wheel, a second motor connected to a left wheel, a coolant pump unit for supplying a coolant, a first temperature detection part for detecting a first motor temperature, a second temperature detection part for detecting a second motor temperature, a coolant temperature detection part for detecting a coolant temperature, and a control device. The control device determines a target flow rate of a coolant to the first motor on the basis of the first motor temperature, determines a target flow rate of a coolant to the second motor on the basis of the second motor temperature, increases a target flow rate of the coolant to the first motor, when a temperature difference is equal to or higher than a predetermined temperature and the first motor temperature is lower than the second motor temperature and the coolant temperature, and increases the target flow rate of the coolant to the second motor, when the temperature difference is equal to or higher than the predetermined temperature and the second motor temperature is lower than the first motor temperature and the coolant temperature.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The technology disclosed in this specification relates to electric vehicles.

[0002] Patent Document 1 discloses an electric vehicle including a first motor connected to the right wheel of the electric vehicle and a second motor connected to the left wheel of the electric vehicle.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the electric vehicle of Patent Document 1, the absolute difference between the first motor temperature, which is the temperature of the first motor, and the second motor temperature, which is the temperature of the second motor, may become large. In this case, the torque output from each motor may become unbalanced, and the straight-line stability of the electric vehicle may decrease.

[0005] This specification provides a technology capable of improving the straight-line stability of an electric vehicle.

Means for Solving the Problems

[0006] In a first aspect disclosed in this specification, an electric vehicle includes a first motor connected to a right wheel of the electric vehicle, a second motor connected to a left wheel of the electric vehicle, a refrigerant pump unit that supplies refrigerant to the first motor and the second motor, a first temperature detection unit that detects a first motor temperature which is the temperature of the first motor, a second temperature detection unit that detects a second motor temperature which is the temperature of the second motor, a refrigerant temperature detection unit that detects a refrigerant temperature which is the temperature of the refrigerant of the refrigerant pump unit, and a control device that controls the operations of the first motor, the second motor, and the refrigerant pump unit. The control device determines a target flow rate of the refrigerant for the first motor based on the first motor temperature, determines a target flow rate of the refrigerant for the second motor based on the second motor temperature, and when a temperature difference which is an absolute difference between the first motor temperature and the second motor temperature is equal to or higher than a predetermined temperature and the first motor temperature is lower than the second motor temperature and the refrigerant temperature, increases the target flow rate of the refrigerant for the first motor, and when the temperature difference is equal to or higher than the predetermined temperature and the second motor temperature is lower than the first motor temperature and the refrigerant temperature, increases the target flow rate of the refrigerant for the second motor.

[0007] According to the above configuration, when the temperature difference is equal to or higher than a predetermined temperature and the first motor temperature is lower than the second motor temperature and the refrigerant temperature, the control device increases the target flow rate of the refrigerant to the first motor. Since the refrigerant temperature is higher than the first motor temperature, the refrigerant is supplied from the refrigerant pump unit to the first motor, thereby increasing the first motor temperature. Therefore, when the flow rate of the refrigerant supplied from the refrigerant pump unit to the first motor is increased, the rate of increase in the first motor temperature can be increased, and as a result, the temperature difference can be reduced. Also, when the temperature difference is equal to or higher than a predetermined temperature and the second motor temperature is lower than the first motor temperature and the refrigerant temperature, by increasing the target flow of the refrigerant to the first motor, the rate of increase in the second motor temperature can be increased, and as a result, the temperature difference can be reduced. Therefore, it is possible to suppress the torque output from each motor from becoming unbalanced. Accordingly, the straight-ahead stability of the electric vehicle can be improved.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Embodiments for Carrying Out the Invention

[0009] (Example) As shown in FIG. 1, the electric vehicle 10 includes a vehicle body 12, a plurality of wheels 14L, 14R, 16L, 16R that support the vehicle body 12, a drive device 18, a battery pack 20, and a control device 22. The plurality of wheels 14L, 14R, 16L, 16R include a left front wheel 14L and a right front wheel 14R located at the front of the vehicle body 12, and a left rear wheel 16L and a right rear wheel 16R located at the rear of the vehicle body 12. The electric vehicle 10 is a vehicle driven by a passenger, although it is not particularly limited. However, the electric vehicle 10 may be a vehicle that autonomously drives, or may be a vehicle that is driven wirelessly by a person or a computer from a remote location.

[0010] The drive device 18 is located at the rear of the vehicle body 12 and is configured to drive the left rear wheel 16L and the right rear wheel 16R. The battery pack 20 is a power source that supplies power to the drive device 18. The battery pack 20 incorporates a secondary battery such as a lithium-ion battery, for example, and is configured to be rechargeable and dischargeable repeatedly. In addition to the battery pack 20, the electric vehicle 10 may further include another power source such as a fuel cell unit, for example.

[0011] The drive device 18 includes a right motor 30, a left motor 32, and an oil pump unit 34. The right motor 30 is provided with a temperature sensor 30a for detecting the right motor temperature Trm, which is the temperature of the right motor 30. The temperature sensor 30a detects, for example, the temperature of the coil (not shown) of the right motor 30. The right motor 30 is connected to the right rear wheel 16R via a right gear unit (not shown) and a right drive shaft 36R. The output torque of the right motor 30 is amplified by the right gear unit and transmitted to the right rear wheel 16R via the right drive shaft 36R. The left motor 32 is provided with a temperature sensor 32a for detecting the left motor temperature Tlm, which is the temperature of the left motor 32. The temperature sensor 32a detects, for example, the temperature of the coil (not shown) of the left motor 32. The left motor 32 is connected to the left rear wheel 16L via a left gear unit (not shown) and a left drive shaft 36L. The output torque of the left motor 32 is amplified by the left gear unit and transmitted to the left rear wheel 16L via the left drive shaft 36L. Thus, the right rear wheel 16R and the left rear wheel 16L are independently driven by the right motor 30 and the left motor 32, respectively.

[0012] The oil pump unit 34 includes an oil pan 40, a right oil pump 42, and a left oil pump 44. The oil pan 40 stores oil for supplying the right motor 30 and the left motor 32. The oil pan 40 is provided with a temperature sensor 40a for detecting the oil temperature To, which is the temperature of the oil. The right oil pump 42 and the left oil pump 44 are electric oil pumps. The right oil pump 42 connects the oil pan 40 and the right motor 30. The right oil pump 42 supplies the pump stored in the oil pan 40 to the right motor 30. The left oil pump 44 connects the oil pan 40 and the left motor 32. The left oil pump 44 supplies the pump stored in the oil pan 40 to the left motor 32.

[0013] The control device 22 is a computer equipped with a CPU. The control device 22 controls the operations of the respective components of the electric vehicle 10. In particular, the control device 22 controls the operations of the right motor 30, the left motor 32, and the oil pump unit 34. In the present embodiment, the control device 22 determines the right target flow rate TFR [L / min], which is the target flow rate of oil for the right motor 30, based on the right motor temperature Trm, and determines the left target flow rate TFL [L / min], which is the target flow rate of oil for the left motor 32, based on the left motor temperature Tlm. Specifically, when the right motor temperature Trm is less than the first determination temperature Td1 (see FIG. 3), the control device 22 determines the right target flow rate TFR to be zero. Also, when the right motor temperature Trm is greater than the first determination temperature Td1 and less than the second determination temperature Td2 (see FIG. 3), the control device 22 determines the first target flow rate Tf1 as the right target flow rate TFR. Note that the second determination temperature Td2 is a temperature higher than the first determination temperature Td1. Further, when the right motor temperature Trm is greater than the second determination temperature Td2, the control device 22 determines the second target flow rate Tf2 as the right target flow rate TFR. The left target flow rate TFL is determined by the same method.

[0014] (Target flow rate determination process; FIG. 2) With reference to FIG. 2, the target flow rate determination process executed by the control device 22 of the electric vehicle 10 will be described.

[0015] In S10, the control device 22 determines the right target flow rate TFR based on the right motor temperature Trm and determines the left target flow rate TFL based on the left motor temperature Tlm.

[0016] In S20, the control device 22 calculates the temperature difference, which is the absolute difference between the right motor temperature Trm and the left motor temperature Tlm, and determines whether the temperature difference is equal to or greater than the third determination temperature. When the temperature difference is equal to or greater than the third determination temperature (YES in S20), the control device 22 proceeds to S22, and when the temperature difference is less than the third determination temperature (NO in S20), the control device 22 returns to S10.

[0017] In S22, the control device 22 determines whether the right motor temperature Trm is less than the left motor temperature Tlm. When the right motor temperature Trm is less than the left motor temperature Tlm (YES in S22), the control device 22 proceeds to S24. When the right motor temperature Trm is not less than the left motor temperature Tlm (NO in S22), the control device 22 proceeds to S30.

[0018] In S24, the control device 22 determines whether the right motor temperature Trm is less than the oil temperature To. When the right motor temperature Trm is less than the oil temperature To (YES in S24), the control device 22 proceeds to S26. When the right motor temperature Trm is not less than the oil temperature To (NO in S24), the control device 22 returns to S10.

[0019] In S26, the control device 22 increases the right target flow rate TFR. As an example, when the right target flow rate TFR is zero or the right target flow rate TFR is the first target flow rate Tf1, the control device 22 increases the right target flow rate TFR to the second target flow rate Tf2.

[0020] In S28, the control device 22 determines whether the temperature difference is less than the fourth determination temperature. The fourth determination temperature is a temperature lower than the third determination temperature. When the temperature difference is less than the fourth determination temperature (YES in S28), the control device 22 returns to S10. On the other hand, when the temperature difference is not less than the fourth determination temperature (NO in S28), the control device 22 proceeds to S30.

[0021] In S30, the control device 22 determines the left target flow rate TFL based on the left motor temperature Tlm. When S30 ends, the control device 22 returns to S28.

[0022] Also, in S40, the control device 22 determines whether the left motor temperature Tlm is less than the oil temperature To. When the left motor temperature Tlm is less than the oil temperature To (YES in S40), the control device 22 proceeds to S42. When the left motor temperature Tlm is not less than the oil temperature To (NO in S40), the control device 22 returns to S10.

[0023] In S42, the control device 22 increases the left target flow rate TFL. As an example, when the left target flow rate TFL is zero or the left target flow rate TFL is the first target flow rate Tf1, the control device 22 increases the left target flow rate TFL to the second target flow rate Tf2.

[0024] In S44, the control device 22 determines whether the temperature difference is less than the fourth determination temperature. When the temperature difference is less than the fourth determination temperature (YES in S44), the control device 22 returns to S10. On the other hand, when the temperature difference is greater than or equal to the fourth determination temperature (NO in S44), the control device 22 proceeds to S46.

[0025] In S46, the control device 22 determines the right target flow rate TFR based on the right motor temperature Trm. When S46 ends, the control device 22 returns to S44.

[0026] (Specific case; FIG. 3) Referring to FIG. 3, a specific case realized by the target flow rate determination process of FIG. 2 will be described. The upper graph in FIG. 3 shows the changes in the right motor temperature Trm and the left motor temperature Tlm, and the lower graph shows the changes in the right target flow rate TFR and the left target flow rate TFL. In the upper graph, the right motor temperature Trm is shown by a thick solid line, and the left motor temperature Tlm is shown by a thick dashed line. Also, in the lower graph, the right target flow rate TFR is shown by a thick solid line, and the left target flow rate TFL is shown by a thick dashed line.

[0027] Before time T1, the right motor temperature Trm and the left motor temperature Tlm are less than the first determination temperature Td1. Also, the temperature difference is less than the third determination temperature. In this case, the electric vehicle 10 determines the right target flow rate TFR and the left target flow rate TFL to be zero (S10 in FIG. 2) and determines that the temperature difference is not greater than or equal to the third determination temperature (NO in S20). Therefore, the right target flow rate TFR and the left target flow rate TFL become zero.

[0028] When the time T1 is reached, the right motor temperature Trm becomes the first determination temperature Td1. At this point, the temperature difference is less than the third determination temperature. In this case, the electric vehicle 10 determines the right target flow rate TFR as the first target flow rate Tf1 and determines the left target flow rate TFL as zero (S12), and determines that the temperature difference is not equal to or higher than the third determination temperature (NO in S20). For this reason, the right target flow rate TFR becomes the first target flow rate Tf1, and the left target flow rate TFL becomes zero.

[0029] When the time T2 is reached, the temperature difference becomes equal to or higher than the third determination temperature. At this point, the left motor temperature Tlm is less than the oil temperature To. In this case, the electric vehicle 10 determines the right target flow rate TFR as the first target flow rate Tf1 and determines the left target flow rate TFL as zero (S10), and determines that the temperature difference is equal to or higher than the third determination temperature (YES in S20). Next, the electric vehicle 10 determines that the right motor temperature Trm is not less than the left motor temperature Tlm (NO in S22), determines that the left motor temperature Tlm is less than the oil temperature To (YES in S40), and increases the left target flow rate TFL to the second target flow rate Tf2 (S42). For this reason, the right target flow rate TFR becomes the first target flow rate Tf1, and the left target flow rate TFL becomes the second target flow rate Tf2. As a result, the rising width of the left motor temperature Tlm increases. For this reason, compared with a configuration in which the left target flow rate TFL is not increased, the temperature difference can be reduced.

[0030] When the time T3 is reached, the right motor temperature Trm becomes the second determination temperature Td2. At this point, the temperature difference is equal to or higher than the fourth determination temperature. In this case, the electric vehicle 10 determines that the temperature difference is not equal to or higher than the fourth determination temperature (NO in S44), and determines the right target flow rate TFR as the second target flow rate Tf2 (S46). For this reason, the right target flow rate TFR and the left target flow rate TFL become the second target flow rate Tf2.

[0031] (Effect of this embodiment) As described above, the electric vehicle 10 includes a right motor 30 (an example of a "first motor") connected to a right rear wheel 16R (an example of a "right wheel"), a left motor 32 (an example of a "second motor") connected to a left rear wheel 16L (an example of a "left wheel"), an oil pump unit 34 (an example of a "refrigerant pump unit") that supplies oil (an example of a "refrigerant") to the right motor 30 and the left motor 32, a temperature sensor 30a (an example of a "first temperature detection unit") that detects a right motor temperature Trm (an example of a "first motor temperature"), a temperature sensor 32a (an example of a "second temperature detection unit") that detects a left motor temperature Tlm (an example of a "second motor temperature"), a temperature sensor 40a (an example of a "refrigerant temperature detection unit") that detects an oil temperature To (a "refrigerant temperature"), and a control device 22. The control device 22 determines a right target flow rate TFR based on the right motor temperature Trm and determines a left target flow rate TFL based on the left motor temperature Tlm (S12 in FIG. 2). When the temperature difference is equal to or higher than a first predetermined temperature (YES in S20) and the right motor temperature Trm is lower than the left motor temperature Tlm and the oil temperature To (YES in S22, YES in S24), the right target flow rate TFR is increased (S26). When the temperature difference is equal to or higher than a third determination temperature (an example of a "first predetermined temperature") (YES in S20) and the left motor temperature Tlm is lower than the right motor temperature Trm and the oil temperature To (NO in S22, YES in S30), the left target flow rate TFL is increased.

[0032] According to the above configuration, when the temperature difference is equal to or higher than the third determination temperature (YES in S20), and the right motor temperature Trm is lower than the left motor temperature Tlm and the oil temperature To (YES in S22 and YES in S24), the control device 22 increases the right target flow rate TFR (S26). Since the oil temperature To is higher than the right motor temperature Trm, the oil is supplied from the oil pump unit 34 to the right motor 30, and thus the right motor temperature Trm rises. Therefore, increasing the flow rate of the oil supplied from the oil pump unit 34 to the right motor 30 can increase the rising rate of the right motor temperature Trm, and as a result, the temperature difference can be reduced. Also, when the temperature difference is equal to or higher than the third determination temperature (YES in S20), and the left motor temperature Tlm is lower than the right motor temperature Trm and the oil temperature To (NO in S22 and YES in S40), the left target flow rate TFL is also increased (S42), so that the rising rate of the left motor temperature Tlm can be increased, and as a result, the temperature difference can be reduced. Therefore, it is possible to suppress the torque output from each of the motors 30 and 32 from becoming unbalanced. Accordingly, the straight-ahead stability of the electric vehicle 10 can be improved.

[0033] As described above, specific examples of the technology disclosed in this specification have been described in detail, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above. Modification examples of the above embodiments are listed below.

[0034] (First Modification Example) In the above embodiment, the oil pump unit 34 includes two oil pumps, but the oil pump unit 34 may include only one oil pump. In this case, the oil pump unit 34 preferably includes a flow rate adjustment mechanism that adjusts the flow rate of the oil supplied from the one oil pump to the right motor 30 and the flow rate of the oil supplied from the one oil pump to the left motor 32. Then, in FIG. 2, the control device 22 controls the operation of the one oil pump and the operation of the flow rate adjustment mechanism.

[0035] (Second Modification Example) The "refrigerant" is not limited to oil and may be cooling water or the like.

[0036] (Third Modification Example) The control device 22 may detect the right motor temperature Trm, the left motor temperature Tlm, and the oil temperature To by estimating the right motor temperature Trm, the left motor temperature Tlm, and the oil temperature To using the load torque or the like of the right motor 30 and the left motor 32.

[0037] The technical elements described in this specification or the drawings exhibit technical utility either alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. Further, the technologies exemplified in this specification or the drawings can achieve a plurality of objects simultaneously, and achieving one of those objects by itself has technical utility.

Description of Reference Numerals

[0038] 10: Electric vehicle, 12: Vehicle body, 14L: Left front wheel, 14R: Right front wheel, 16L: Left rear wheel, 16R: Right rear wheel, 18: Drive device, 20: Battery pack, 22: Control device, 30: Right motor, 30a: Temperature sensor, 32: Left motor, 32a: Temperature sensor, 34: Oil pump unit, 36L: Left drive shaft, 36R: Right drive shaft, 40: Oil pan, 40a: Temperature sensor, 42: Right oil pump, 44: Left oil pump

Claims

【Claim 1】 An electric vehicle, comprising: a first motor connected to the right wheel of the electric vehicle; a second motor connected to the left wheel of the electric vehicle; a refrigerant pump unit for supplying refrigerant to the first motor and the second motor; a first temperature detection unit for detecting a first motor temperature which is the temperature of the first motor; a second temperature detection unit for detecting a second motor temperature which is the temperature of the second motor; a refrigerant temperature detection unit for detecting a refrigerant temperature which is the temperature of the refrigerant of the refrigerant pump unit; and a control device for controlling the operations of the first motor, the second motor, and the refrigerant pump unit, wherein the control device determines a target flow rate of the refrigerant for the first motor based on the first motor temperature, and determines a target flow rate of the refrigerant for the second motor based on the second motor temperature, increases the target flow rate of the refrigerant for the first motor when a temperature difference, which is an absolute difference between the first motor temperature and the second motor temperature, is equal to or higher than a predetermined temperature and the first motor temperature is lower than the second motor temperature and the refrigerant temperature, and increases the target flow rate of the refrigerant for the second motor when the temperature difference is equal to or higher than the predetermined temperature and the second motor temperature is lower than the first motor temperature and the refrigerant temperature. An electric vehicle.

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