Manufacturing method of electric vehicle

Abstract

To provide a manufacturing method for an electric vehicle capable of improving energy efficiency by sufficiently cooling a motor that is installed therein.SOLUTION: According to a manufacturing method for an electric vehicle comprising a motor as a drive power source, the motor provided with a coil whose winding is held around a core formed by laminating electromagnetic steel plates; and a cooling mechanism for cooling the motor by circulating a fluid between the motor and a heat-exchanger, the method comprises the steps of: assembling the motor into a unit (step S1); driving the motor so as to output a predetermined instruction torque to measure an actual torque output by the motor at that time (step S2); and setting the amount of fluid supply to the motor by the cooling mechanism assembled in the electric vehicle to an amount based on the measured actual torque (step S3).SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a method for manufacturing an electric vehicle such as a battery electric vehicle (BEV) or a hybrid electric vehicle (HEV) that is equipped with a motor as a driving force source. [Background technology]

[0002] Motors always have copper loss and iron loss, and generate heat when they operate. In a synchronous motor equipped with permanent magnets, the higher the rotation speed, the greater the iron loss and the greater the amount of heat generated. Also, when the temperature rises, not only can the insulation failure be damaged, but the output torque can also be reduced due to thermal demagnetization of the magnets. For this reason, motors used as a driving force source for vehicles have generally been forced-cooled, and more recently, the motor has been cooled by circulating fluid (oil) between the motor and a heat exchanger (radiator) using a pump.

[0003] The amount of heat generated by operating a motor is proportional to the current, and the output torque increases in proportion to the current. Therefore, since the amount of heat generated is nearly proportional to the output torque, it can be said that it is preferable to cool the motor in accordance with or based on the output torque.

[0004] Incidentally, an invention for measuring the output torque of a motor is described in Patent Document 1. The invention described in Patent Document 1 measures the rotation angle of a synchronous motor during operation, the temperature, current, and terminal voltage of the stator of the motor, corrects the winding resistance value of the stator based on the temperature, calculates the induced voltage of the stator based on the corrected winding resistance value, the current, and the terminal voltage, calculates the rotation speed of the synchronous motor, calculates the torque of the synchronous motor based on the induced voltage and the rotation speed, and corrects the calculated torque by a torque conversion value of the loss of the synchronous motor calculated in advance corresponding to the induced voltage and the rotation speed. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 07-128161 Summary of the Invention [Problem to be solved by the invention]

[0006] According to the invention described in the above Patent Document 1, the torque of the motor can be measured, but Patent Document 1 does not mention the amount of heat generated when the torque measured in this way is output or the cooling corresponding to the amount of heat generated. As described above, in a motor, the output of torque and the cooling must be performed simultaneously in parallel. For example, when the above-mentioned forced cooling is performed, the cooling fluid is circulated according to the specified torque determined by the specifications. However, if the cooling according to the specified torque is performed uniformly, there may be excess or deficiency in cooling. That is, even if the number of turns of the winding constituting the coil and the length in the axial direction of the coil are the same, if the thickness of the electromagnetic steel sheet constituting the core is different, the eddy current, heat capacity, or heat dissipation method may differ depending on the thickness of the electromagnetic steel sheet, and the iron loss and the amount of heat generated may differ for each motor. In such a case, if the motors have the same or similar specifications and are cooled in the same way, there is a possibility that the durability of the motor will decrease due to insufficient cooling for motors that generate a large amount of heat. On the other hand, for motors that generate a small amount of heat, the pump for cooling will be driven excessively, which may consume more power than necessary and reduce energy efficiency.

[0007] The present invention has been made in light of the above-mentioned technical problems, and has an object to provide a manufacturing method for an electric vehicle that can cool the mounted motor just enough to improve energy efficiency. [Means for solving the problem]

[0008] In order to achieve the above-mentioned object, the present invention provides a method for manufacturing an electric vehicle comprising a motor as a driving force source having a coil with windings held on a core made of laminated electromagnetic steel sheets, and a cooling mechanism that cools the motor by circulating a refrigerant between the motor and a heat exchanger, the method comprising assembling the motor into a unit, driving the motor in the unit to output a predetermined command torque, measuring the actual torque output by the motor at that time, and setting the amount of refrigerant supplied to the motor by the cooling mechanism assembled to the electric vehicle to an amount based on the measured actual torque. Effect of the Invention

[0009] According to the manufacturing method of the present invention, the amount of coolant supplied to the motor for cooling is set to an amount corresponding to the actual torque output by the motor. The motor generates heat based on eddy current loss and the like corresponding to the actual torque, and the actual torque and the corresponding eddy current loss and the like may differ from motor to motor due to influences such as the thickness of the electromagnetic steel sheets constituting the core. However, according to the present invention, cooling is performed according to the actual torque, so it is possible to avoid supplying an excessive amount of coolant to the motor or an insufficient amount of coolant to the motor. In other words, it is possible to manufacture an electric vehicle that does not consume energy unnecessarily by driving the cooling mechanism just enough. [Brief description of the drawings]

[0010] [Figure 1] FIG. 2 is a schematic diagram for explaining a general configuration of a motor and a cooling mechanism. [Diagram 2] 2 is a schematic diagram showing a part of the coil and the lamination state of the electromagnetic steel sheets in the core. FIG. [Diagram 3] FIG. 4 is a diagram for explaining the relationship between an instruction torque and an actual torque. [Figure 4] 4 is a diagram illustrating the relationship between the amount of increase or decrease in actual torque relative to the command torque and the amount of fluid supplied for cooling. FIG. [Diagram 5]2 is a flowchart illustrating a manufacturing procedure according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Next, an embodiment of the present invention will be described with reference to the drawings. Note that the embodiment described below is merely one example of the case where the present invention is implemented, and is not intended to limit the present invention.

[0012] The electric vehicle targeted by this invention is a vehicle equipped with an electric motor as a driving force source, such as an electric vehicle (BEV) using only a motor as a driving force source, or a hybrid vehicle (HEV, PHEV) using an internal combustion engine (engine) and a motor as driving force sources. The motor generates heat due to copper loss, iron loss, etc., so the motor is configured to be cooled. FIG. 1 shows a schematic diagram of a motor (electric motor) 1 as a driving force source and a cooling mechanism 2 that cools the motor 1. In the example shown in FIG. 1, the motor 1 is disposed inside a transmission 3.

[0013] Motor 1 is a motor widely used in vehicles, such as a synchronous motor or an induction motor, and has a coil 6 formed by winding electric wire 5 around a core 4. Fig. 2 shows a schematic of a part of coil 6 made of distributed winding of rectangular wire, and core 4 is formed into a cylindrical shape by laminating many thin electromagnetic steel sheets 4a, and electric wire (winding) 5 is housed in slots formed on its inner circumference.

[0014] The transmission 3 may be a transmission or a continuously variable transmission that can change the gear ratio in stages, or may be a so-called power transmission mechanism with a fixed gear ratio. A predetermined amount of fluid (oil) 7 is contained inside the transmission 3 as a refrigerant for lubrication and cooling. The cooling mechanism 2 is configured to supply the fluid 7 to the motor 1, so that the fluid 7 removes heat from the motor 1 to cool the motor 1.

[0015] Specifically, the cooling mechanism 2 includes an electric pump 8 that pumps up the fluid 7 inside the transmission 3, and a heat exchanger 9 that cools the fluid 7 sent from the pump 8 with air, coolant, or the like. The pump 8 is an oil pump configured so that the discharge capacity can be set appropriately, or so that the discharge amount can be changed appropriately during operation, and a gear pump, vane pump, or the like can be used. When a variable capacity pump that can electrically change the discharge capacity of the pump 8 is used, a controller 10 that controls the discharge capacity can be provided.

[0016] The heat exchanger 9 may be an air-cooled radiator arranged alongside a radiator (not shown) provided at the front of the vehicle, or may be a water-cooled cooler that removes heat from the fluid 7 using cooling water cooled by the radiator, or may even be incorporated into the radiator to form a radiator. The cooling mechanism 2 is configured to supply the fluid 7 discharged from the heat exchanger 9 to the motor 1 to cool the motor 1. The supply of the fluid 7 to the motor 1 may be performed by dripping the fluid 7 from the outer periphery side of the motor 1, or by scattering the fluid 7 from the shaft core side by centrifugal force.

[0017] The cooling mechanism 2 cools the motor 1 so that the temperature of the motor 1 does not rise above an expected temperature and the amount of fluid 7 sent from the heat exchanger 9 to the motor 1 does not become excessively large. For this reason, in the embodiment of the present invention, the amount of fluid 7 supplied by the cooling mechanism 2 is set as follows. First, the amount of heat generated or the amount of loss in the motor 1 is determined so that the amount of fluid 7 supplied to the motor 1 corresponds to the amount of heat generated in the motor 1. That is, the motor 1 is manufactured so that when a predetermined current is passed through it, a torque corresponding to the current is generated. However, if the thickness of the electromagnetic steel sheets 4a constituting the core 4 described above deviates from the design value, or if a thickness of the electromagnetic steel sheets 4a that is the design value and a thickness of the electromagnetic steel sheets 4a that is the design value are mixed, or if the mixture is different, the variation in iron loss may cause the torque that is actually output to deviate from the designated torque. The designated torque is a torque that is designed (specified) according to the current value.

[0018] This relationship is shown in FIG. 3, and the state where the indicated torque and the actual torque are the same is shown by the thin solid line L1. The motor 1 with such torque characteristics is a motor as designed. The state where the actual torque exceeds the indicated torque is shown by the thick solid line L2. It is considered that such a motor 1 has small eddy current loss due to the thickness and arrangement of the electromagnetic steel sheets 4a constituting the core 4 being better than expected, and therefore the actual torque is larger than the indicated torque. In other words, the energy efficiency is good and heat generation due to iron loss and the like is small. Furthermore, the state where the actual torque is smaller than the indicated torque is shown by the dashed line L3. It is considered that such a motor 1 has a thickness and arrangement of the electromagnetic steel sheets 4a constituting the core 4 that are deviated in a direction that increases eddy current loss, and therefore the actual torque is smaller than the indicated torque. In other words, the energy efficiency is worse than expected, and heat generation due to iron loss and the like is large.

[0019] Therefore, if the motor with the torque characteristic shown by the line L1 in FIG. 3 is the standard motor, the motor with the torque characteristic shown by the thick line L2 will generate less heat compared to the standard motor due to less loss. Conversely, the motor with the torque characteristic shown by the dashed line L3 will generate more heat compared to the standard motor due to greater loss. The greater the amount of heat generated, the greater the amount of fluid 7 that needs to be supplied for cooling, so the actual torque related to the amount of heat generated and the required amount of fluid 7 to be supplied are approximately in the relationship shown in FIG. 4. That is, the greater the actual torque relative to a specified command torque, the smaller the amount of supply that the motor requires. Note that FIG. 4 shows the relationship between the actual torque and the supply amount at the command torque determined by design in the region where the command torque is equal to or greater than the specified torque T0. This is because if the command torque is lower than the specified torque T0, the energy consumed for heat generation and cooling is not a particular problem.

[0020] The manufacturing method according to the embodiment of the present invention is configured to manufacture an electric vehicle through the following procedure based on the new knowledge of the actual torque and the supply amount described above. FIG. 5 is a flow chart for explaining the manufacturing procedure. First, a unit is assembled (step S1). The unit here is, for example, a unit consisting of a motor 1, a cooling mechanism 2, and a transmission 3, as shown in FIG. 1, and is in a state in which the motor 1 and the pump 8 can be driven. Note that the power for the motor 1 and the pump 8 may be supplied from a battery (not shown), or may use the power of a factory. Next, the torque is measured (step S2). For example, a current determined by design to generate a specified torque equal to or greater than the above-mentioned specified torque T0 is supplied to the motor 1 to drive the motor 1, and the torque generated by the supply is measured using an appropriate torque sensor, dynamometer, or the like. This torque measurement may be performed before the unit is assembled to the vehicle body, or may be performed in a state in which the unit is assembled to the vehicle body and configured as a vehicle.

[0021] As a result, the relationship between the designated torque and the actual torque is known, and it is possible to obtain, for example, the diagram or map shown in FIG. 3 or FIG. 4 described above. Then, the supply amount of the fluid 7 by the cooling mechanism 2 is set (step S3). By measuring the actual torque when a predetermined torque is specified as described above, the increase or decrease in the actual torque of the standard motor is known, so that the increase or decrease in the supply amount of the fluid 7 for the standard motor can be obtained, and the discharge amount by the pump 8 is set to the supply amount of the fluid 7 thus obtained. Specifically, for a motor 1 with a large actual torque even if the motor 1 has the same specifications, the discharge capacity of the pump 8 is adjusted so that the supply amount of the fluid 7 is reduced, or the command value from the controller 10 is adjusted. If the pump 8 is, for example, a vane pump, the rotation speed of the rotor is reduced.

[0022] Therefore, according to the above-described manufacturing method, it is possible to supply just the right amount of fluid 7 actually required by the motor 1. In other words, it is possible to drive the cooling mechanism 2 or its pump 8 just the right amount. As a result, it is possible to obtain an electric vehicle that can avoid inconveniences such as limited output of the motor 1 due to insufficient cooling, or poor fuel economy of the vehicle due to unnecessary power consumption by the pump 8.

[0023] The above-mentioned fluid 7 is one example of a refrigerant for cooling the motor 1, and the present invention may be configured to supply an appropriate refrigerant instead of the fluid 7. [Explanation of symbols]

[0024] 1 Motor 2 Cooling mechanism 3. Transmission 4 cores 4a electrical steel sheet 5 Electric wire 6 Coils 7 Fluids 8. Pump 9 Heat exchanger 10 Controller

Claims

[Claim 1] A method for manufacturing an electric vehicle comprising: a motor having a coil in which a winding is held on a core formed by laminating electromagnetic steel sheets as a driving force source; and a cooling mechanism that circulates a refrigerant between the motor and a heat exchanger to cool the motor, Assembling the motor into a unit; driving the motor in the unit so as to output a predetermined command torque, and measuring an actual torque output by the motor at that time; The amount of coolant supplied to the motor by the cooling mechanism assembled in the electric vehicle is set to an amount based on the measured actual torque. A method for manufacturing an electric vehicle comprising the steps of:

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