JP2012044772A - Inverter cooling controller for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To allow an inverter to be cooled with proper cooling performance according to a heating amount of inverter switching elements in a system provided with a cooling device for cooling the inverter.SOLUTION: A higher one of switching frequencies for first and second inverters 22 and 23 is set as a switching frequency for inverter cooling control. Further, a higher one of motor outputs for first and second AC motors 12 and 13 is set as a motor output for inverter cooling control. A target cooling water flow rate for inverter cooling control according to the switching frequency and motor output for inverter cooling control is calculated, and an electric water pump 39 is driven so that a flow rate of cooling water for a cooling device 40 may be the target cooling water flow rate. This makes it possible to properly respond to variation in the heating amount of inverter switching elements due to any change in the switching frequency and motor output, which changes a flow rate of the cooling water, so that the cooling performance of the cooling device 40 can vary.

Description

  The present invention relates to a vehicle inverter cooling control device including an inverter that drives a motor that is a power source of the vehicle and a cooling device that cools the inverter.

  2. Description of the Related Art In recent years, electric vehicles and hybrid vehicles equipped with an AC motor as a power source for vehicles have attracted attention due to social demands for low fuel consumption and low exhaust emissions. Some of such electric vehicles and hybrid vehicles drive an AC motor by converting a DC voltage into an AC voltage using an inverter connected to a DC power source such as a secondary battery.

  In such an electric vehicle and a hybrid vehicle, for example, Patent Document 1 (Japanese Patent Laid-Open No. 2007-166804) and Patent Document 2 (Japanese Patent Laid-Open No. 2008-2008) are disclosed in order to prevent failure due to overheating of the inverter (overheating of the switching element). As described in Japanese Patent No. -72818), a cooling medium (for example, cooling water) is circulated between the inverter and the radiator to cool the inverter.

  At that time, in Patent Document 1, the flow rate of the cooling medium is set based on the current command generated from the required output of the AC motor. Moreover, in the said patent document 2, the temperature sensor which detects the temperature (element temperature of a switching element) of an inverter is provided, and the flow volume of a cooling medium is set based on the temperature of the inverter detected with this temperature sensor.

JP 2007-166804 A JP 2008-72818 A

  In general, an inverter has a characteristic that the amount of heat generated by the switching element changes according to the switching frequency when the AC motor is driven (the amount of heat generated by the switching element increases as the switching frequency increases). Is greatly affected by the switching frequency.

  However, in the inverter cooling control of Patent Document 1 and Patent Document 2 described above, since the influence of the switching frequency of the inverter is not considered at all, it is possible to respond to the change in the heat generation amount of the switching element due to the change of the switching frequency with good response. However, it is difficult to cool the inverter with an appropriate cooling performance corresponding to the amount of heat generated by the switching element, and there is a possibility that fuel consumption deteriorates due to excessive cooling of the inverter.

  Therefore, the problem to be solved by the present invention is to provide an inverter cooling control device for a vehicle that can cool the inverter with an appropriate cooling performance in accordance with the heat generation amount of the switching element of the inverter and can improve the vehicle performance. It is to provide.

  In order to solve the above-described problem, an invention according to claim 1 is directed to an inverter cooling control device for a vehicle, comprising: an inverter that drives a motor that is a power source of the vehicle; and a cooling device that cools the inverter. The inverter cooling control means for controlling the cooling performance of the cooling device according to the switching frequency is provided.

  In this configuration, since the cooling performance of the cooling device can be controlled according to the switching frequency of the inverter, the cooling performance of the cooling device is changed in response to the change in the amount of heat generated by the switching element due to the change in the switching frequency. The inverter can be cooled with an appropriate cooling performance corresponding to the amount of heat generated by the switching element. Thereby, fuel consumption deterioration due to overcooling of the inverter can be prevented, and vehicle performance can be improved.

  In this case, as in claim 2, in a system including a pump that circulates a cooling medium (for example, cooling water) between the inverter and the radiator, the flow rate of the cooling medium is controlled according to the switching frequency of the inverter. The cooling performance of the cooling device may be controlled. In this way, the cooling performance of the cooling device can be changed by changing the flow rate of the cooling medium in response to the change in the heat generation amount of the switching element due to the change in the switching frequency.

  In a system having a radiator fan that generates radiator cooling air, the cooling performance of the cooling device is controlled by controlling the air volume of the cooling air according to the switching frequency of the inverter. May be. In this way, the cooling performance of the cooling device can be changed by changing the air volume of the cooling air in response to the change in the heat generation amount of the switching element due to the change in the switching frequency.

  Further, since the amount of heat generated by the switching element of the inverter also changes depending on the output of the motor, the cooling performance of the cooling device is controlled according to the output of the motor and the switching frequency of the inverter as in claim 4. Also good. In this way, the cooling performance of the cooling device can be changed in response to both the change in the heat generation amount of the switching element due to the change in the output of the motor and the change in the heat generation amount of the switching element due to the change in the switching frequency. Can do.

FIG. 1 is a diagram showing a schematic configuration of a hybrid vehicle drive system in an embodiment of the present invention. FIG. 2 is a diagram showing a schematic configuration of an inverter cooling system. FIG. 3 is a flowchart for explaining the processing flow of the inverter cooling control routine. FIG. 4 is a diagram conceptually illustrating an example of a target cooling water flow rate map.

Hereinafter, an embodiment embodying a mode for carrying out the present invention will be described.
First, the overall configuration of the hybrid vehicle drive system will be described with reference to FIG. An engine 11 that is an internal combustion engine, a first AC motor 12, and a second AC motor 13 are mounted, and the engine 11 and the second AC motor 13 serve as a power source for driving the wheels 14. The power of the crankshaft 15 of the engine 11 is divided into two systems by the power split mechanism 16.

  The power split mechanism 16 includes a planetary gear mechanism including a sun gear, a pinion gear, a ring gear (all not shown), and the like. A crankshaft 15 of the engine 11 is connected to the pinion gear via a carrier (not shown), and a rotation shaft of a first AC motor 12 mainly used as a generator is connected to the sun gear. Further, the ring gear is connected to a peller shaft 17 (drive shaft), and the power of the peller shaft 17 is transmitted to the wheels 14 via the differential gear mechanism 32, the axle 33, and the like. The rotating shaft of the second AC motor 13 is connected to the propeller shaft 17 via the reduction gear mechanism 18. Between the axle 33 and the wheel 14, a hydraulic brake device 34 that applies a braking force to the wheel 14 is provided.

  The first AC motor 12 and the second AC motor 13 are connected to the battery 21 via the power control unit 20. The power control unit 20 is provided with a first inverter 22 that drives the first AC motor 12 and a second inverter 23 that drives the second AC motor 13. Electric power is transferred to and from the battery 21 via inverters 22 and 23, respectively. A crank angle sensor 24 that outputs a pulse signal every time the crankshaft 15 rotates a predetermined crank angle is attached to the engine 11, and the crank angle and the engine rotation speed are detected based on the output signal of the crank angle sensor 24. .

  The hybrid ECU 25 is a computer that comprehensively controls the entire hybrid vehicle, and detects an accelerator sensor 26 that detects an accelerator opening (amount of operation of an accelerator pedal), a shift switch 27 that detects an operation position of a shift lever, and a brake operation. The operation signal of the vehicle is detected by reading the output signals of various sensors and switches such as the brake switch 28 for performing the operation and the vehicle speed sensor 29 for detecting the vehicle speed. The hybrid ECU 25 includes an engine ECU 30 that controls the operation of the engine 11, and an MG-ECU 31 that controls the operation of the first and second AC motors 12 and 13 by controlling the first and second inverters 22 and 23. Control signals and data signals are transmitted and received between the ECUs 30 and 31, and the operations of the engine 11, the first AC motor 12, and the second AC motor 13 are controlled by the ECUs 30 and 31 according to the driving state of the vehicle.

  For example, at the time of starting or at a low load (a region where the fuel efficiency of the engine 11 is poor), the engine 11 is maintained in a stopped state, the second AC motor 13 is driven by the power of the battery 21, and the second AC The motor travels by driving the wheels 14 only with the power of the motor 13.

  When starting the engine 11, the first AC motor 12 is driven by the power of the battery 21, and the power of the first AC motor 12 is transmitted to the crankshaft 15 of the engine 11 via the power split mechanism 16. Thus, the crankshaft 15 is rotationally driven to start the engine 11.

  During normal running, the power of the crankshaft 15 of the engine 11 is divided into two systems, the first AC motor 12 side and the peller shaft 17 side, by the power split mechanism 16, and the peller shaft 17 is driven by the output of one of the systems. The wheel 14 is driven, the first AC motor 12 is driven by the output of the other system, the first AC motor 12 generates power, the second AC motor 13 is driven by the generated power, and the second The wheels 14 are also driven by the power of the AC motor 13. Further, at the time of rapid acceleration, in addition to the power generated by the first AC motor 12, the power of the battery 21 is also supplied to the second AC motor 13 to increase the drive amount of the second AC motor 13.

  During deceleration, the second AC motor 13 is driven by the power of the wheels 14 and the second AC motor 13 is operated as a generator, so that the kinetic energy of the vehicle is converted into electric power by the second AC motor 13. The battery 21 is recovered (charged).

Next, a schematic configuration of the cooling system of the inverters 22 and 23 will be described with reference to FIG.
The power control unit 20 is provided with cooling water passages (not shown) for the inverters 22 and 23, and an outlet of the cooling water passages of the inverters 22 and 23 and an inlet of the radiator 35 are connected by a cooling water circulation pipe 36. The outlet of the radiator 35 and the inlet of the cooling water passage of the inverters 22 and 23 are connected by a cooling water circulation pipe 37. Thus, the cooling water circulation circuit 38 in which the cooling water (cooling medium) circulates in the path of the cooling water passage of the inverters 22 and 23 → the cooling water circulation pipe 36 → the radiator 35 → the cooling water circulation pipe 37 → the cooling water passage of the inverters 22 and 23 Is formed. An electric water pump 39 for circulating the cooling water is provided in the middle of the cooling water circulation circuit 38 (for example, the cooling water circulation pipe 37 or the cooling water circulation pipe 36). A cooling device 40 is constituted by the cooling water passages of these inverters 22 and 23, the radiator 35, the cooling water circulation pipes 36 and 37, the electric water pump 39, and the like.

  The MG-ECU 31 (or the hybrid ECU 25) executes torque control of the first and second AC motors 12 and 13 as follows by executing a motor control routine (not shown).

  Based on the torque command value of the first AC motor 12 and the motor rotation speed, etc., for example, a three-phase voltage command signal is generated by a sine wave PWM control method or a rectangular wave control method and is output to the first inverter 22. . Thereby, the switching operation of each switching element (not shown) of the first inverter 22 is controlled so that the output torque of the first AC motor 12 becomes the target torque (torque command value), thereby the first AC motor. The AC voltage applied to 12 is controlled.

  Based on the torque command value of the second AC motor 13 and the motor rotation speed, etc., for example, a three-phase voltage command signal is generated by a sine wave PWM control method or a rectangular wave control method and is output to the second inverter 23. . Thereby, the switching operation of each switching element (not shown) of the second inverter 23 is controlled so that the output torque of the second AC motor 13 becomes the target torque (torque command value), and the second AC motor. The AC voltage applied to 13 is controlled.

  At that time, the switching frequency of each inverter 22, 23 is at least one of vehicle operating conditions (for example, vehicle speed, torque command value, motor rotation speed, cooling water temperature, motor control mode, accelerator opening, vehicle acceleration, etc. ) Is set to a value adapted in advance. For example, the switching frequency is set so that the operating sound of the inverters 22 and 23 is reduced in the region where the vehicle speed is low (the region where the operating sounds of the inverters 22 and 23 are problematic). The switching frequency setting method may be changed as appropriate.

  In general, the inverters 22 and 23 have a characteristic that the amount of heat generated by the switching element changes according to the switching frequency when the AC motors 12 and 13 are driven (the amount of heat generated by the switching element increases as the switching frequency increases). The amount of heat generated by the switching element is greatly affected by the switching frequency.

  Therefore, in this embodiment, the cooling performance of the cooling device 40 is controlled according to the switching frequency of the inverters 22 and 23 by executing the inverter cooling control routine of FIG. 3 described later by the MG-ECU 31 (or the hybrid ECU 25). I am doing so.

  Specifically, the higher one of the switching frequencies of the first and second inverters 22 and 23 is set as the switching frequency for inverter cooling control, and the flow rate of the cooling water according to the switching frequency for inverter cooling control. By controlling the above, the cooling performance of the cooling device 40 is controlled. Accordingly, the cooling performance of the cooling device 40 can be changed by changing the flow rate of the cooling water in response to the change in the heat generation amount of the switching element due to the change in the switching frequency.

  Hereinafter, the processing content of the inverter cooling control routine of FIG. 3 executed by the MG-ECU 31 (or the hybrid ECU 25) will be described.

  The inverter cooling control routine shown in FIG. 3 is repeatedly executed at a predetermined cycle while the MG-ECU 31 (or the hybrid ECU 25) is turned on, and serves as inverter cooling control means in the claims.

  When this routine is started, first, in step 101, the switching frequencies of the first and second inverters 22 and 23 set by the motor control are read, and then the process proceeds to step 102 where the first and second inverters are read. The higher one of the switching frequencies 22 and 23 is set as the switching frequency for inverter cooling control.

  Thereafter, the process proceeds to step 103, and after reading the motor outputs (= torque command value × motor rotational speed) of the first and second AC motors 12 and 13, the process proceeds to step 104, where the first and second AC motors are read. The larger of the motor outputs 12 and 13 is set as the motor output for inverter cooling control.

  Thereafter, the process proceeds to step 105, and the target coolant flow rate corresponding to the switching frequency for inverter cooling control and the motor output for inverter cooling control is calculated with reference to the target coolant flow map shown in FIG.

  In general, the higher the switching frequency of the inverters 22, 23, the greater the amount of heat generated by the switching elements. In addition, the amount of heat generated by the switching element increases as the motor output of the AC motors 12 and 13 increases. In consideration of such characteristics, the target coolant flow map in FIG. 4 is set such that the target coolant flow increases as the switching frequency increases and the motor output increases. This target coolant flow map is created in advance based on test data, design data, and the like, and is stored in the ROM of the MG-ECU 31 (or the hybrid ECU 25).

  Thereafter, the process proceeds to step 106, and the electric water pump 39 is driven so that the flow rate of the cooling water of the cooling device 40 becomes the target flow rate of the cooling water. Thus, the flow rate of the cooling water is controlled according to the switching frequency and the motor output.

  In the present embodiment described above, since the cooling performance of the cooling device 40 is controlled by controlling the flow rate of the cooling water according to the switching frequency of the inverters 22 and 23, the heat generation of the switching element due to the change of the switching frequency. The cooling performance of the cooling device 40 can be changed by changing the flow rate of the cooling water in response to the change in the amount of cooling water, and the inverters 22 and 23 are cooled with an appropriate cooling performance according to the heat generation amount of the switching element. can do. Thereby, fuel consumption deterioration due to excessive cooling of inverters 22 and 23 can be prevented, and vehicle performance can be improved.

  In addition, in this embodiment, since the cooling performance of the cooling device 40 is controlled according to the motor output of the AC motors 12 and 13 and the switching frequency of the inverters 22 and 23, the heating of the switching element due to the change of the motor output. The cooling performance of the cooling device 40 can be changed in response to both the change in the amount and the change in the heat generation amount of the switching element due to the change in the switching frequency.

  In the above embodiment, the higher one of the switching frequencies of the first and second inverters 22 and 23 is set as the switching frequency for inverter cooling control, but the switching frequency for inverter cooling control is set. The method is not limited to this, and may be changed as appropriate. For example, an average value of switching frequencies of the first and second inverters 22 and 23 may be set as a switching frequency for inverter cooling control. .

  Further, the larger one of the motor outputs of the first and second AC motors 12 and 13 is set as the motor output for inverter cooling control. However, the method for setting the motor output for inverter cooling control is as follows. For example, the average value of the motor outputs of the first and second AC motors 12 and 13 may be set as the motor output for inverter cooling control.

  In the above embodiment, the cooling performance of the cooling device 40 is controlled by controlling the flow rate of the cooling water (the driving amount of the electric water pump 39) according to the switching frequency and the motor output. The cooling performance control method is not limited to this. For example, in the case of a system including a radiator fan that generates cooling air for the radiator 35, the cooling air flow rate (radiator) according to the switching frequency and the motor output. The cooling performance of the cooling device may be controlled by controlling the fan drive amount.

  Further, the cooling performance of the cooling device is controlled by controlling both the flow rate of the cooling water (drive amount of the electric water pump 39) and the flow rate of cooling air (drive amount of the radiator fan) according to the switching frequency and the motor output. You may do it.

  In the case of an air-cooled cooling system including a cooling fan that blows cooling air to the inverters 22 and 23, the air volume of the cooling air (cooling fan drive amount) is controlled according to the switching frequency and the motor output. Thus, the cooling performance of the cooling device may be controlled.

  Moreover, it is not limited to the structure which controls the cooling performance of a cooling device according to both a motor output and a switching frequency, You may make it control the cooling performance of a cooling device only according to a switching frequency.

  In the above embodiment, the present invention is applied to a system including two inverters. However, the present invention is not limited to this, and the present invention is applied to a system including one inverter or a system including three or more inverters. May be.

  In the above embodiment, the present invention is applied to a split type hybrid vehicle in which the engine power is divided by the power split mechanism. However, the present invention is not limited to this, and other types of hybrid vehicles such as a parallel type and a series type are used. The present invention may be applied. Further, the present invention is not limited to a hybrid vehicle using both the engine and the motor as a power source, and the present invention may be applied to an electric vehicle using only the motor as a power source.

  DESCRIPTION OF SYMBOLS 11 ... Engine (internal combustion engine) 12, 13 ... AC motor, 16 ... Power split mechanism, 21 ... Battery, 22, 23 ... Inverter, 25 ... Hybrid ECU, 30 ... Engine ECU, 31 ... MG-ECU (Inverter cooling control) Means), 35 ... Radiator, 36, 37 ... Cooling water circulation pipe, 38 ... Cooling water circulation circuit, 39 ... Electric water pump, 40 ... Cooling device

Claims (4)

In an inverter cooling control device for a vehicle, comprising: an inverter that drives a motor that is a power source of the vehicle; and a cooling device that cools the inverter.
An inverter cooling control device for a vehicle, comprising inverter cooling control means for controlling the cooling performance of the cooling device in accordance with the switching frequency of the inverter. The cooling device includes a pump that circulates a cooling medium between the inverter and the radiator,
The inverter cooling control for a vehicle according to claim 1, wherein the inverter cooling control means controls the cooling performance of the cooling device by controlling the flow rate of the cooling medium according to the switching frequency of the inverter. apparatus. The cooling device includes a pump that circulates a cooling medium between the inverter and the radiator, and a radiator fan that generates cooling air for the radiator.
3. The vehicle inverter according to claim 1, wherein the inverter cooling control unit controls the cooling performance of the cooling device by controlling an amount of the cooling air according to a switching frequency of the inverter. 4. Cooling control device.   4. The inverter cooling of a vehicle according to claim 1, wherein the inverter cooling control means controls the cooling performance of the cooling device according to the output of the motor and the switching frequency of the inverter. Control device.

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