Patent Publication Number: US-2022212652-A1

Title: Motor controller

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims priority to Japanese Patent Application No. 2021-001489 filed on Jan. 7, 2021, which is incorporated herein by reference in its entirety including the specification, claims, drawings, and abstract. 
     TECHNICAL FIELD 
     The present disclosure relates to a motor controller for protecting an insulation coating of a motor coil. 
     BACKGROUND 
     Electric vehicles, for example, include a motor. When a voltage applied to a motor exceeds a predetermined voltage (partial discharge inception voltage), partial discharge occurs in an insulation coating of a motor coil, resulting in deterioration of the insulation performance of the insulation coating and shortening of the life of the motor. As the partial discharge inception voltage depends on the atmospheric pressure and the coil temperature, the partial discharge inception voltage is lower when an electric vehicle travels in highlands rather than in lowlands, for example, which makes the insulation performance prone to deterioration. 
     JP 2020-018067 A discloses a motor controller that reduces, with a boost converter, a voltage applied to the motor exceeding the partial discharge inception voltage, to thereby prevent deterioration of the insulation performance of an insulation coating of the motor and avoid shortening of the life of the motor. 
     SUMMARY 
     Some electric vehicles, however, may include no such boost converters. Further, a boost converter, and a booster circuit forming a boost converter are expensive and therefore raise the costs for components. 
     An embodiment of the disclosure is therefore directed to providing a motor controller that prevents a voltage to be applied to a motor from exceeding a partial discharge inception voltage without a boost converter when the atmospheric pressure decreases or the coil temperature of the motor rises. 
     In accordance with one aspect of the disclosure, a motor controller for controlling a motor that is driven with an electric power from a battery includes an electronic control unit (ECU), an atmospheric pressure sensor configured to detect an atmospheric pressure, and a coil temperature sensor configured to detect a coil temperature of the motor. The ECU is configured to determine an upper limit state of charge of the battery, and lower the upper limit state of charge of the battery in response to the atmospheric pressure detected by the atmospheric pressure sensor being a predetermined pressure or lower or in response to the coil temperature detected by the coil temperature sensor being a predetermined temperature or higher. 
     In the motor control apparatus, the ECU may lower the upper limit state of charge of the battery stepwise in accordance with a reduction in the atmospheric pressure or a rise in the coil temperature, in response to the atmospheric pressure being the predetermined pressure or lower or in response to the coil temperature being the predetermined temperature or higher. 
     The motor controller of the disclosure enables prevention of the voltage to be applied to a motor from exceeding the partial discharge inception voltage without a boost converter, by reducing the upper limit state of charge of a battery to lower the voltage to be applied to the motor, when the atmospheric pressure decreases or the coil temperature of the motor rises. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       An embodiment of the present disclosure will be described by reference to the following figures, wherein: 
         FIG. 1  schematically illustrates a vehicle including a motor controller according an embodiment: 
         FIG. 2  is a block diagram illustrating a configuration of the motor controller; 
         FIG. 3  is a graph illustrating a correlation between a battery voltage and a state of charge of a battery: 
         FIG. 4  is a graph illustrating a partial discharge inception voltage and a voltage limit of a battery and a correlation between the voltage applied to a motor and the atmospheric pressure for each property; 
         FIG. 5  is a further graph illustrating a partial discharge inception voltage and a voltage limit of a battery and a correlation between the voltage applied to a motor and the atmospheric pressure for each property; 
         FIG. 6  is a graph illustrating a partial discharge inception voltage and a voltage limit of a battery and a correlation between the voltage applied to a motor and the coil temperature for each property; 
         FIG. 7  is a further graph illustrating a partial discharge inception voltage and a voltage limit of a battery and a correlation between the voltage applied to a motor and the coil temperature for each property; and 
         FIG. 8  is a flow chart illustrating a protection control flow for an insulation coating. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     An embodiment of the disclosure will be described in detail below. In the following description, specific shapes, materials, directions, and numeral values, for example, are only examples to facilitate understanding of the disclosure, and may be modified as appropriate in accordance with use, object, and specifications, for example. 
     Referring to  FIG. 1 , a vehicle  5  including a motor controller  10  according to an embodiment will be described.  FIG. 1  schematically illustrates the vehicle  5 . 
     As illustrated in  FIG. 1 , the motor controller  10  is disposed in the vehicle  5 , and includes an Electronic Control Unit (ECU)  20  as a processor that performs various types of data processing. The vehicle  5  in this example is an electric vehicle that travels with power of a motor  6  driven with electric power supplied from a battery  7 . The vehicle  5  may be a hybrid electric vehicle. 
     The motor controller  10  performs protection control for an insulation coating of a coil of the motor  6 , as will be described below. When the atmospheric pressure lowers or the coil temperature of the motor  6  rises, the motor controller  10  reduces the upper limit of the state of charge of the battery  7  to decrease the voltage to be applied to the motor  6 , thereby preventing the applied voltage from exceeding the partial discharge inception voltage. This configuration avoids deterioration of the insulation performance of the insulation coating without a boost converter. 
     The motor controller  10  includes an atmospheric pressure sensor  11  for detecting the atmospheric pressure and a coil temperature sensor  12  for detecting the coil temperature of the motor  6 . 
     Referring to  FIG. 2  to  FIG. 7 , the configuration of the motor controller  10  will be described.  FIG. 2  is a block diagram illustrating the configuration of the motor controller  10 .  FIG. 3  is a graph illustrating a correlation between the battery voltage and the state of charge of the battery  7 .  FIG. 4  is a graph illustrating the partial discharge inception voltage and the voltage limit of the battery  7  and illustrating a correlation between the voltage applied to the motor  6  and the atmospheric pressure for each property.  FIG. 5  is a further graph illustrating the partial discharge inception voltage and the voltage limit of the battery  7  and illustrating a correlation between the voltage applied to the motor  6  and the atmospheric pressure for each property.  FIG. 6  is a graph illustrating the partial discharge inception voltage and the voltage limit of the battery  7  and illustrating a correlation between the voltage applied to the motor  6  and the coil temperature for each property.  FIG. 7  is a further graph illustrating the partial discharge inception voltage and the voltage limit of the battery  7  and illustrating a correlation between the voltage applied to the motor  6  and the coil temperature for each property. 
     The ECU  20  includes a Central Processing Unit (CPU) or an operation processing unit, and a memory unit such as Random Access Memory (RAM) and Read Only Memory (ROM), and performs signal processing according to a program prestored in the ROM while performing a temporary memory function of the RAM. 
     As illustrated in  FIG. 2 , the ECU  20  is connected with the atmospheric pressure sensor  11  and the coil temperature sensor  12 , for example, to receive signals transmitted from these sensors. The motor controller  10  is further connected with the battery  7  to transmit signals to the battery  7 . 
     The ECU  20  includes an atmospheric pressure acquiring unit  13  that acquires the atmospheric pressure detected by the atmospheric pressure sensor  11 , a coil temperature acquiring unit  14  that acquires the coil temperature of the motor  6  detected by the coil temperature sensor  12 , and a battery upper limit state of charge reducer  15  that reduces the upper limit state of charge of the battery  7 , which will be hereinafter referred simply as a “battery upper limit reducer”. 
     The battery upper limit reducer  15  lowers the upper limit of the state of charge of the battery  7  when the atmospheric pressure is a predetermined pressure or lower based on the atmospheric pressure acquired by the atmospheric pressure acquiring unit  13  or when the coil temperature is a predetermined temperature or higher based on the coil temperature acquired by the coil temperature acquiring unit  14 . 
     The upper limit state of charge of the battery  7  is an upper limit of the state of charge of the battery  7  that has been preset. The state of charge of the battery  7  refers to a rate of the remaining amount of electricity of the battery  7  excluding an amount of discharged electricity from the amount of electricity of the battery  7  in a fully charged state. As illustrated in  FIG. 3 , the lower the state of charge of the battery  7 , the lower the voltage of the battery  7 , and the voltage to be applied to the motor  6  would also decrease. 
       FIG. 4  illustrates the partial discharge inception voltage and the voltage limit of the battery  7  and illustrates a correlation between the applied voltage to the motor  6  and the atmospheric pressure for each property. Partial discharge occurs in the insulation coating of the coil of the motor  6  when a voltage equal to or greater than a predetermined voltage is applied to the motor  6 ; the partial discharge inception voltage refers to the predetermined voltage. Partial discharge that occurs in the insulation coating of the coil would deteriorate the insulation performance of the insulation coating to shorten the life of the motor  6 . As shown in  FIG. 4 , the partial discharge inception voltage decreases with a reduction in the atmospheric pressure. When the vehicle  5  travels in highlands, for example, the partial discharge inception voltage is lower than in lowlands, and the insulation performance is prone to deterioration. 
     As illustrated in  FIG. 4 , when the atmospheric pressure is a predetermined pressure or lower, the battery upper limit reducer  15  lowers the upper limit state of charge of the battery  7 , which further leads to limiting and reducing the voltage of the battery  7 , thereby lowering the applied voltage to the motor  6 . Such a reduction in the applied voltage to the motor  6  results in prevention of the applied voltage to the motor  6  from exceeding the partial discharge inception voltage when the atmospheric pressure lowers while the vehicle  5  is travelling in highlands, for example. This configuration avoids deterioration of the insulation performance of the insulation coating without a boost converter. 
     As illustrated in  FIG. 5 , when the atmospheric pressure is the predetermined pressure or lower, the battery upper limit state of charge reducer  15  may lower the upper limit state of charge of the battery  7  stepwise. This configuration reduces the voltage of the battery  7  stepwise to thereby reduce the applied voltage to the motor  6  stepwise. This configuration can also achieve advantages similar to those described above. 
       FIG. 6  illustrates the partial discharge inception voltage and the voltage limit of the battery  7 , and a correlation between the voltage applied to the motor  6  and the coil temperature for each property. As illustrated in  FIG. 6 , the partial discharge inception voltage lowers with a rise in the coil temperature. 
     As illustrated in  FIG. 6 , when the coil temperature is a predetermined temperature or higher, the battery upper limit reducer  15  lowers the upper limit state of charge of the battery  7  for limiting or reducing the voltage of the battery  7  and thus reducing the applied voltage to the motor  6 . This configuration reduces the applied voltage to the motor  6  when the coil temperature rises, thereby preventing the applied voltage to the motor  6  from exceeding the partial discharge inception voltage. It is therefore possible to avoid deterioration of the insulation performance of the insulation coating without a boost converter. 
     As illustrated in  FIG. 7 , when the coil temperature is a predetermined temperature or higher, the battery upper limit state of charge reducer  15  may lower the upper limit state of charge of the battery  7  stepwise. This configuration reduces the voltage of the battery  7  stepwise to thereby reduce the applied voltage to the motor  6  stepwise. This configuration can also achieve the advantages similar to those described above. 
     Referring now to  FIG. 8 , a flow of protection control of the insulation coating to be performed by the motor controller  10  will be described.  FIG. 8  is a flowchart illustrating a flow of insulation coating protection control. 
     As illustrate in  FIG. 8 , in step S 11 , the atmospheric pressure acquiring unit  13  acquires the atmospheric pressure detected by the atmospheric pressure sensor  11 . In step  12 , the coil temperature acquiring unit  14  acquires the coil temperature detected by the coil temperature sensor  12 . 
     In step S 13 , whether the atmospheric pressure acquired in step S 11  is the predetermined pressure or less is determined. In response to the atmospheric pressure being the predetermined atmospheric pressure or less, the process proceeds to step S 15 . Meanwhile, in response to the atmospheric pressure exceeding the predetermined atmospheric pressure in step S 13 , the process proceeds to step S 14 . In step S 14 , a determination is made as to whether the coil temperature acquired in step S 12  is the predetermined temperature or higher. In response to the coil temperature being the predetermined temperature or higher, the process proceeds to step S 15 . In step S 15 , the battery upper limit reducer  15  lowers the upper limit state of charge of the battery  7 . 
     The present disclosure is not limited to the embodiments described above and their modification examples, and various modifications and improvements may be made within the scope of matters recited in the claims of the present application.