electric vehicles

Abstract

This allows for more effective suppression of cavitation generation depending on the altitude. [Solution] The electric vehicle includes a cooling system that circulates cooling water in the order of a first water pump, the object to be cooled, and a second water pump, and a control device that, when the inlet pressure of the second water pump is below a threshold, lowers the rotational speed of the second water pump compared to when the inlet pressure is above a threshold. In this case, the control device sets the threshold based on the altitude of the vehicle's current location.

Description

Technical Field

[0001] This disclosure relates to electric vehicles.

Background Art

[0002] Conventionally, an electric vehicle equipped with a cooling device that circulates cooling water to a motor, an inverter, and a radiator by driving an electric pump has been proposed (see, for example, Patent Document 1). In this electric vehicle, when normal control is executed to control the electric pump so that the rotation speed of the electric pump becomes the target rotation speed based on the temperature of the cooling water, the condition that the road surface gradient of the road on which the vehicle is traveling is a predetermined angle or more, the condition that the lateral acceleration of the vehicle is a predetermined acceleration or more, the condition that the accelerator opening becomes the maximum opening when the vehicle is stopped, and the condition that the vehicle speed is a predetermined high vehicle speed or more and the brake is applied When any one of the conditions is satisfied, the occurrence of cavitation is predicted. Then, when the occurrence of cavitation is predicted, the electric pump is controlled so that the rotation speed of the electric pump becomes a predetermined low rotation speed that is low enough to suppress cavitation.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In such electric vehicles, the likelihood of cavitation occurring varies depending on the altitude. However, in the above-described electric vehicle, the influence of altitude is not considered. Therefore, depending on the altitude, it may not be possible to appropriately suppress the occurrence of cavitation.

[0005] The main object of the electric vehicle of this disclosure is to be able to more appropriately suppress the occurrence of cavitation according to the altitude.

Means for Solving the Problems

[0006] The electric vehicle of this disclosure employs the following means to achieve the main objective described above.

[0007] The electric vehicle disclosed herein is A cooling system that circulates cooling water in the order of first water pump, object to be cooled, and second water pump, A control device that, when the inlet pressure of the second water pump is below a threshold, lowers the rotational speed of the second water pump compared to when the inlet pressure is above the threshold, An electric vehicle equipped with, The control device sets the threshold based on the elevation of the vehicle's current location. This is the gist of it.

[0008] In the electric vehicle of this disclosure, a threshold is set based on the altitude of the vehicle's current location, and when the inlet pressure of the second water pump is below the threshold, the rotational speed of the second water pump is reduced compared to when the inlet pressure is above the threshold. This process makes it possible to suppress the occurrence of cavitation even at high altitudes. Here, the control device may set the threshold so that it becomes lower as the altitude increases. [Brief explanation of the drawing]

[0009] [Figure 1] This is a schematic diagram of the electric vehicle according to the embodiments of the present disclosure. [Figure 2] This is a schematic diagram of the cooling system installed in electric vehicle 20. [Figure 3] This is a flowchart showing an example of a processing routine. [Modes for carrying out the invention]

[0010] Embodiments for implementing this disclosure will be described with reference to the drawings. Figure 1 is a schematic diagram of the electric vehicle 20 according to an embodiment of this disclosure, and Figure 2 is a schematic diagram of the cooling system 40 provided in the electric vehicle 20. As shown in Figures 1 and 2, the electric vehicle 20 according to the embodiment includes a front motor 22, a front power control unit (hereinafter referred to as "front PCU") 24, a rear motor 26, a rear power control unit (hereinafter referred to as "rear PCU") 28, a battery 30, a charging unit 32, a cooling system 40, and an electronic control unit (hereinafter referred to as "ECU") 60.

[0011] The front motor 22 is configured as a synchronous regenerative motor with a rotor and stator. The rotor of the front motor 22 is connected to the front wheel DWf via a front differential gear DFf. The front PCU 24 has an inverter and is used to drive the front motor 22 and is connected to the power line 34.

[0012] The rear motor 26 is configured as a synchronous regenerative motor with a rotor and stator. The rotor of the rear motor 26 is connected to the rear wheel DWr via a rear differential gear DFr. The rear PCU 28 has an inverter and is used to drive the rear motor 26 and is connected to the power line 34.

[0013] The battery 30 is configured as, for example, a lithium-ion secondary battery or a nickel-metal hydride secondary battery. The battery 30 is connected to the power line 34 together with the front PCU 24 and the rear PCU 28. The charging unit 32 is used for external charging, which is charging the battery 30 using power from an external power source. In this embodiment, the charging unit 32 is equipped with a contactless power receiving device, and is capable of charging the battery 30 by receiving power from a contactless power transmission device outside the vehicle via the contactless power receiving device.

[0014] The cooling system 40 includes a circulation passage 42, a front oil cooler 44, a rear oil cooler 46, a chiller 48, a reserve tank 50, and first and second water pumps 52 and 54. The circulation passage 42 is a passage for circulating cooling water (LCC) in the following order: first water pump 52, front PCU 24, battery 30, charging unit 32, rear PCU 28, rear oil cooler 46, front oil cooler 44, second water pump 54, chiller 48, reserve tank 50, and first water pump 52. In this embodiment, the front PCU 24, battery 30, charging unit 32, rear PCU 28, rear oil cooler 46, and front oil cooler 44 correspond to the "cooling targets". However, some of these may not be included as cooling targets.

[0015] The front oil cooler 44 performs heat exchange between the coolant in the circulation passage 42 and the ATF used for cooling and lubricating the front motor 22 and other components. The rear oil cooler 46 performs heat exchange between the coolant in the circulation passage 42 and the ATF used for cooling and lubricating the rear motor 26 and other components. The chiller 48 performs heat exchange with the refrigerant of the air conditioning system that provides air conditioning in the passenger compartment. The first and second water pumps 52 and 54 pump the coolant in the circulation passage 42.

[0016] The ECU60 is equipped with a microcomputer, various drive circuits, and various logic ICs. The microcomputer has a CPU, ROM, RAM, flash memory, input / output ports, and communication ports. Signals from various sensors are input to the ECU60. For example, the rotational position θmf, θmr and phase currents Iuf, Ivf, Iwf, Iur, Ivr, Iwr of the rotors of the front motor 22 and rear motor 26 are input to the ECU60 from the rotational position sensor and current sensor. Voltage Vb, current Ib, and temperature Tb of the battery 30 are also input to the ECU60 from the voltage sensor, current sensor, and temperature sensor. The current altitude h of the vehicle is also input to the ECU60 from the altitude sensor 62. Various control signals are output from the ECU60. For example, control signals are output from the ECU60 to the front PCU24, rear PCU28, charging unit 32, and first and second water pumps 52, 54. The ECU60 calculates the electrical angles θef, θer and rotational speeds Nmf, Nmr of the front motor 22 and rear motor 26 based on the rotational positions θmf, θmr of the rotors of the front motor 22 and rear motor 26, and also calculates the state of charge (SOC) of the battery 30 based on the integrated value of the current Ib of the battery 30.

[0017] Next, the operation of the electric vehicle 20 of the embodiment, in particular the operation of the cooling system 40, will be described. Figure 3 is a flowchart showing an example of a processing routine that is repeatedly executed by the ECU 60.

[0018] When the processing routine shown in Figure 3 is executed, the ECU 60 first inputs the target temperature of each component (e.g., front PCU 24 and rear PCU 28, etc.) that is specifically targeted for cooling and through which the circulation path 42 passes (step S100). Here, the target temperature of each component is determined, for example, based on the specifications of each component.

[0019] Subsequently, based on the target temperatures of each component, the target rotational speeds Nwp1* and Nwp2* of the first and second water pumps 52 and 54 are set (step S110). Here, the target rotational speeds Nwp1* and Nwp2* may be set considering, in addition to the target temperatures of each component, the temperatures of the cooling water near the first and second water pumps 52 and 54 in the circulation flow path 42, or the current temperatures of at least a part of each component.

[0020] Then, based on the target rotational speed Nwp1* of the first water pump 52, the discharge pressure P1 of the first water pump 52 is estimated (step S120). Here, the discharge pressure P1 can be obtained, for example, by applying the target rotational speed Nwp1* to a discharge pressure map determined in advance through experiments, analysis, etc. as the relationship between the target rotational speed Nwp1* and the discharge pressure P1, and deriving the corresponding discharge pressure P1 from the discharge pressure map.

[0021] Also, based on the target rotational speeds Nwp1* and Nwp2* of the first and second water pumps 52 and 54, the pressure loss ΔP1 between the first water pump 52 and the second water pump 54 in the circulation flow path 42 is estimated (step S130). Here, the pressure loss ΔP1 can be obtained, for example, by applying the target rotational speeds Nwp1* and Nwp2* to a pressure loss map determined in advance through experiments, analysis, etc. as the relationship between the target rotational speeds Nwp1* and Nwp2* and the pressure loss ΔP1, and deriving the corresponding pressure loss ΔP1 from the pressure loss map.

[0022] Subsequently, the inlet pressure P2i of the second water pump 54 is estimated by subtracting the pressure loss ΔP1 between the first water pump 52 and the second water pump 54 in the circulation flow path 42 from the discharge pressure P1o of the first water pump 52 (step S140).

[0023] Then, the current altitude h of the vehicle is input from the altitude sensor 62 (step S150), a threshold Clim is set based on the input altitude h (step S160), and the inlet pressure P2i of the second water pump 54 is compared with the threshold Clim (step S170). Here, the threshold Clim is used to determine whether or not cavitation may occur in the second water pump 54. Cavitation is a phenomenon in which the pressure near the water pump drops below the saturated vapor pressure, causing bubbles to form. When cavitation occurs, there is a concern that the pressure will subsequently exceed the saturated vapor pressure, causing the gas to turn into liquid and the volume to change rapidly, which may shock the water pump or corrode the impeller of the water pump. In addition, when cavitation occurs, the bubbles may hinder the high-speed rotation of the water pump, reducing the flow rate of the cooling water in the circulation passage 42, which may reduce the cooling performance and cause the temperature of each component to rise. Furthermore, the higher the altitude h, the lower the inlet pressure P2i of the second water pump 54 tends to be. In this embodiment, based on these considerations, the threshold Clim is set in step S150. The threshold Clim is obtained, for example, by applying the elevation h to a threshold map predetermined by experiments or analyses as the relationship between elevation h and the threshold Clim, and deriving the corresponding threshold Clim from the threshold map. In the threshold map, the threshold Clim is set to decrease as the elevation h increases.

[0024] If, in step S170, it is determined that the inlet pressure P2i of the second water pump 54 is equal to or greater than the threshold Clim, it is determined that the possibility of cavitation occurring in the second water pump 54 is low. In this case, the first and second water pumps 52 and 54 are controlled using the target rotational speeds Nwp1* and Nwp2* set in step S110 (step S190), and this routine is terminated.

[0025] If, in step S170, it is determined that the inlet pressure P2i of the second water pump 54 is less than the threshold Clim, it is determined that cavitation may occur in the second water pump 54. In this case, the target rotational speed Nwp2* of the second water pump 54, set in step S110, is reset to a value obtained by subtracting the correction value α (step S180). Subsequently, the first and second water pumps 52 and 54 are controlled using the target rotational speed Nwp1* of the first water pump 52, set in step S110, and the target rotational speed Nwp2* of the second water pump 54, reset in step S180 (step S190), and this routine is terminated. Here, the correction value α is predetermined by experiments or analysis.

[0026] Thus, when the inlet pressure P2i of the second water pump 54 is less than the threshold Clim, the rotational speed of the second water pump 54 is lowered compared to when the inlet pressure P2i of the second water pump 54 is equal to or greater than the threshold Clim. This lowers the suction pressure of the second water pump 54, reduces the pressure loss ΔP1 of the second water pump 54, increases the inlet pressure P2i, and suppresses the occurrence of cavitation. Moreover, in this embodiment, as described above, by setting the threshold Clim to decrease as the altitude h increases, the occurrence of cavitation can be suppressed more appropriately according to the altitude h.

[0027] In the electric vehicle 20 of the embodiment described above, when the inlet pressure P2i of the second water pump 54 is less than the threshold Clim, the rotational speed of the second water pump 54 is reduced compared to when the inlet pressure P2i of the second water pump 54 is abnormally high compared to when the threshold Clim is exceeded. In this case, the threshold Clim is set based on the altitude h. This makes it possible to more appropriately suppress the occurrence of cavitation according to the altitude h.

[0028] In the embodiment described above, the electric vehicle 20 is configured to receive power from an external contactless power transmission device via a contactless power receiving device in the charging unit 32 to charge the battery 30, but it is not limited to this. For example, the charging unit 32 may be equipped with an inlet and a charger, and may be configured to charge the battery 30 by converting AC power from an external AC power source connected to the inlet into DC power using the charger.

[0029] In the embodiments described above, the electric vehicle 20 is configured to include a front motor 22, a front PCU 24, a rear motor 26, and a rear PCU 28, but it is not limited to this configuration. For example, the electric vehicle may be configured to include only one of the front motor 22 and front PCU 24, or only one of the rear motor 26 and rear PCU 28. Alternatively, it may be configured as a hybrid vehicle, further comprising an engine in addition to the same hardware configuration as the electric vehicle. Furthermore, it may be configured as a fuel cell vehicle, further comprising a fuel cell in addition to the same hardware configuration as the electric vehicle.

[0030] The correspondence between the main elements of the embodiment and the main elements of the invention described in the section on means for solving the problem will be explained. In the embodiment, the first water pump 52 corresponds to the "first water pump," the second water pump 54 corresponds to the "second water pump," and the cooling device 40 corresponds to the "cooling device."

[0031] Furthermore, the correspondence between the main elements of the embodiment and the main elements of the invention described in the section on means for solving the problem is merely an example to specifically explain the form in which the embodiment implements the invention described in the section on means for solving the problem, and does not limit the elements of the invention described in the section on means for solving the problem. In other words, the interpretation of the invention described in the section on means for solving the problem should be based on the description in that section, and the embodiment is merely one specific example of the invention described in the section on means for solving the problem.

[0032] The above describes the forms for implementing this disclosure using embodiments, but this disclosure is not limited in any way to these embodiments, and can of course be implemented in various forms without departing from the gist of this disclosure. [Industrial applicability]

[0033] This disclosure can be used in industries such as electric vehicle manufacturing. [Explanation of Symbols]

[0034] 20 Electric vehicle, 22 Front motor, 24 Front PCU, 26 Rear motor, 28 Rear PCU, 30 Battery, 32 Charging unit, 34 Power line, 40 Cooling system, 42 Circulation path, 44 Front oil cooler, 46 Rear oil cooler, 48 Chiller, 50 Reserve tank, 52 First water pump, 54 Second water pump, 60 ECU, 62 Altitude sensor, DFf Front differential gear, DFr Rear differential gear, DWf Front wheels, DWr Rear wheels.

Claims

[Claim 1] A cooling system that circulates cooling water in the order of first water pump, object to be cooled, and second water pump, A control device that, when the inlet pressure of the second water pump is below a threshold, lowers the rotational speed of the second water pump compared to when the inlet pressure is above the threshold, An electric vehicle equipped with, The control device sets the threshold based on the elevation of the vehicle's current location. Electric car.

Images