Patent Publication Number: US-2019193576-A1

Title: Control device of vehicle and control method of vehicle

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims priority from Japanese Patent Application No. 2017-246086 filed on Dec. 22, 2017, the entire contents of which are hereby incorporated by reference. 
     BACKGROUND 
     1. Technical Field 
     The present invention relates to a control device of a vehicle and a control method of a vehicle. 
     2. Related Art 
     Conventionally, Japanese Unexamined Patent Application Publication (JP-A) No. 2005-86919 describes a device including a motor that is capable of outputting power to a drive axle and capable of exchanging electric power with a DC power source via an inverter. 
     SUMMARY OF THE INVENTION 
     An aspect of the present invention provides a control device of a vehicle, the control device including: a motor temperature acquirer configured to acquire a temperature of a motor that drives the vehicle; an oil temperature acquirer configured to acquire a temperature of an oil that cools the motor; and a torque controller configured to control a torque of the motor on a basis of the temperature of the motor and the temperature of the oil. 
     An aspect of the present invention provides a control method of a vehicle, the control method including: acquiring a temperature of a motor that drives the vehicle; acquiring a temperature of an oil that cools the motor; and controlling a torque of the motor on a basis of the temperature of the motor and the temperature of the oil. 
     An aspect of the present invention provides a control device of a vehicle, the control device including circuitry. The circuitry is configured to acquire a temperature of a motor that drives the vehicle, acquire a temperature of an oil that cools the motor, and control a torque of the motor on a basis of the temperature of the motor and the temperature of the oil 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram illustrating a configuration of a system according to an example of the present invention; 
         FIG. 2  is a flowchart illustrating a process performed by the system according to the example; 
         FIG. 3  is a schematic diagram illustrating a map for limiting torque of a motor generator; 
         FIG. 4  is a schematic diagram illustrating a map for limiting torque of the motor generator; 
         FIG. 5  is a schematic diagram illustrating a map for limiting torque of the motor generator; 
         FIG. 6  is a schematic diagram illustrating a map for limiting torque of the motor generator; and 
         FIG. 7  is a schematic diagram illustrating a relation between rotation speed (horizontal axis) and torque (vertical axis) of the motor generator. 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, preferred examples of the present invention will be described in detail with reference to the appended drawings. Note that the following description is directed to illustrative instances of the disclosure and not to be construed as limiting to the present invention. Factors including, without limitation, numerical values, dimensions, shapes, materials, components, positions of the components, and how the components are coupled to each other are for purposes of illustration to give an easier understanding of the present invention, and are not to be construed as limiting to the present invention, unless otherwise specified. Further, elements in the following instances which are not recited in a most-generic independent claim of the disclosure are optional and may be provided on an as-needed basis. The drawings are schematic and are not intended to be drawn to scale. Throughout this specification and the appended drawings, structural elements that have substantially the same function and structure are denoted with the same reference numerals, and repeated description of these structural elements is omitted. 
     When using the device described in JP-A No. 2005-86919 described above, the motor generates heat due to driving of the motor. Therefore, it is necessary to suppress overheating of the motor by cooling the motor in accordance with temperature of the motor or by lowering output (torque) from the motor. However, a rotor of the motor is a rotating body. Accordingly, it is impossible to directly measure temperature of a magnet of the rotor, and there is a problem that the magnet loses its function under a situation in which the temperature of the magnet of the rotor exceeds heatproof temperature. 
     On the other hand, for instance, in the case of trying to measure temperature of a static side (stator) of the motor and suppress overheating of the motor, it is assumed that output from the motor is excessively lowered in order to prevent the magnet of the rotor from losing its function. In this case, although the magnet of the rotor does not lose its function, there is a problem that the output from the motor is limited excessively. 
     Accordingly, it is desirable to provide a novel and improved control device and control method of a vehicle that are capable of suppressing overheating of a motor by optimally controlling torque of the motor. 
       FIG. 1  is a schematic diagram illustrating a configuration of a system  1000  according to an example of the present invention. The system  1000  illustrated in  FIG. 1  is mainly installed in a vehicle. As illustrated in  FIG. 1 , the system  1000  includes a control device (ECU)  100 , a motor generator  200 , an oil pan  300 , an oil pump  400 , a transmission  500 , an inverter  600 , and a memory  700 . In one example, the motor generator  200  may serve as a “motor”, and the oil pan  300  may serve as a “reservoir”. 
     The control device  100  is a structural element that controls the whole system  1000 . The motor generator  200  generates driving power for driving the vehicle. The driving power generated by the motor generator  200  is transmitted to wheels via the transmission  500 . In addition, the motor generator  200  generates regenerative energy by using driving power conveyed from a road surface via the wheels. 
     The oil pan stores oil. The oil stored in the oil pan  300  is supplied to the motor generator  200  and the transmission  500  by driving the oil pump  400 . The temperature of the oil stored in the oil pan  300  is detected by a temperature sensor  310 . 
     The inverter  600  adjusts an electric current flowing to the motor generator  200  on the basis of a command value from the control device  100 . The memory  700  stores maps (to be described later) for controlling torque of the motor generator  200 . 
     The motor generator  200  includes a stator  210  and a rotor  220 . The stator  210  includes a coil, and the rotor  220  includes a magnet. The stator  210  is provided with a temperature sensor (thermistor)  212  that detects temperature of the stator  210 . 
     In addition, the motor generator  200  is provided with a rotation speed sensor  214  that detects rotation speed of the rotor  220 . The rotation speed of the rotor  220  detected by the rotation speed sensor  214  is sent to the control device  100 . 
     The motor generator  200  generates heat with generation of driving power. When a large electric current flows to the motor generator  200  in a state in which the motor generator  200  generates heat of a certain temperature or more, the temperature of the magnet of the rotor  220  exceeds heatproof temperature and sometimes this may produce defects in the magnet. In other words, there is a possibility that the magnet loses its function when high torque is generated by the motor generator  200  in a state in which the motor generator  200  is overheated. 
     On the other hand, although it is possible for the temperature sensor  212  to measure the temperature of the stator  210  of the motor generator  200 , it is impossible to directly measure the temperature of the rotor  220  since the rotor  220  is a rotating body. 
     In addition, in the case where the temperature of the magnet of the rotor  220  increases in accordance with the oil temperature of the oil such as a case where the oil to be supplied to the motor generator  200  has already been heated, sometimes the temperature of the magnet of the rotor  220  exceeds the heatproof temperature when a large electric current flows to the motor generator  200 . 
     As described above, in order to protect the magnet of the rotor  220  of the motor generator  200 , it is desirable to perform control in view of the temperature of the stator  210  and the temperature of the oil such that the large electric current does not flow to the motor generator  200 . 
     Therefore, the control device  100  controls the torque of the motor generator  200  on the basis of the temperature of the stator  210  and the temperature of the oil with reference to a map decided in advance. As illustrated in  FIG. 1 , the control device  100  includes: a motor temperature acquirer  110  that acquires temperature of the stator  210  detected by the temperature sensor  212 ; a motor temperature determiner  115  that determines temperature on the basis of the temperature acquired by the motor temperature acquirer  110 ; an oil temperature acquirer  120  that acquires temperature of oil in the oil pan  300  detected by the temperature sensor  310 ; a rotation speed acquirer  130  that acquires rotation speed of the motor generator  200  detected by the rotation speed sensor  214 ; and a torque controller  140  that controls torque of the motor generator  200  on the basis of the temperature of the stator  210 , the temperature of the oil, and the rotation speed. Note that, the structural elements of the control device  100  illustrated in  FIG. 1  can be configured by hardware (circuit) or a central processing unit such as a CPU and software (program) for causing it to function. 
     Next, a process performed by the system  1000  according to the present example will be described.  FIG. 2  is a flowchart illustrating the process performed by the system  1000  according to the present example. In addition,  FIG. 3  to  FIG. 6  are schematic diagrams illustrating maps for limiting the torque of the motor generator  200 . The maps illustrated in  FIG. 3  to  FIG. 6  define coefficients for limiting the torque of the motor generator  200  in accordance with rotation speed of the motor generator  200  and oil temperature in the oil pan  300 . In the case where the coefficient is 1, the torque of the motor generator  200  is not limited. In the case where the coefficient is less than 1, the torque of the motor generator  200  is limited in accordance with the coefficient depending on the rotation speed of the motor generator  200  and the oil temperature in the oil pan  300 . In  FIG. 3  to  FIG. 6 , the oil temperature in the oil pan  300  has a relation in which A&lt;B&lt;C&lt;D&lt;E&lt;F. In addition, the rotation speed of the motor generator  200  has a relation in which G&lt;H&lt;I&lt;J&lt;K&lt;L&lt;M&lt;N. In addition, a coefficient x is a value less than 1, and the value of the coefficient x decreases in the direction of an arrow A 1 . 
     The process illustrated in  FIG. 2  is mainly performed by the control device  100 . First, in Step S 10 , the motor temperature acquirer  110  acquires the temperature of the stator  210 . In the next Step S 12 , the oil temperature acquirer  120  acquires the temperature of the oil in the oil pan  300 . In the next Step S 13 , the rotation speed acquirer  130  acquires the rotation speed of the motor generator  200 . 
     In Step S 14 , the motor temperature determiner  115  determines whether the temperature detected by the temperature sensor  212  is a° C. or more. In the case where the temperature is not a° C. or more, the process proceeds to Step S 16 . In Step S 16 , the torque controller  140  limits the torque of the motor generator  200  on the basis of the limitation map “ 0 ” illustrated in  FIG. 3 . The torque controller  140  limits the torque of the motor generator  200  by multiplying target torque (allowed torque) set in accordance with a driving state by a coefficient defined with reference to the limitation map “ 0 ”. 
     In the case where the temperature detected by the temperature sensor  212  is a° C. or more in Step S 14 , the process proceeds to Step S 18 . In Step S 18 , the motor temperature determiner  115  determines whether the temperature detected by the temperature sensor  212  is b° C. or more. In the case where the temperature is not b° C. or more, the process proceeds to Step S 20 . Note that, a &lt;b. In Step S 20 , the torque controller  140  limits the torque of the motor generator  200  on the basis of the limitation map “ 1 ” illustrated in  FIG. 4 . 
     In the case where the temperature detected by the temperature sensor  212  is b° C. or more in Step S 18 , the process proceeds to Step S 22 . In Step S 22 , the motor temperature determiner  115  determines whether the temperature detected by the temperature sensor  212  is c° C. or more. In the case where the temperature is not c° C. or more, the process proceeds to Step S 24 . Note that, b&lt;c. In Step S 24 , the torque controller  140  limits the torque of the motor generator  200  on the basis of the limitation map “ 2 ” illustrated in  FIG. 5 . 
     In the case where the temperature detected by the temperature sensor  212  is c° C. or more in Step S 22 , the process proceeds to Step S 26 . In Step S 26 , the torque controller  140  limits the torque of the motor generator  200  on the basis of the limitation map “ 3 ” illustrated in  FIG. 6 . After Step S 16 , S 20 , S 24 , or S 26 , the process ends (RETURN). 
     As described above, in the case where the temperature detected by the temperature sensor  212  is less than a° C., the limitation map “ 0 ” illustrated in  FIG. 3  is used. In the limitation map “ 0 ” illustrated in  FIG. 3 , the torque is not limited in accordance with the rotation speed of the motor generator  200 . However, in the case where the oil temperature in the oil pan  300  is F° C., the torque of the motor generator  200  is limited to “ 0 ”. In the case where the oil temperature in the oil pan  300  is F° C., it is assumed that the temperature of the rotor  220  is increased by heat of the oil and the magnet of the rotor  220  is damaged even when the temperature of the stator  210  detected by the temperature sensor  212  is less than a° C. Therefore, in the case where the oil temperature in the oil pan  300  is F° C., it is possible to suppress the damage in the magnet of the rotor  220  by limiting the torque of the motor generator  200  to “ 0 ”. 
     Note that, one of the causes of increase in the oil temperature in the oil pan  300  to F° C. regardless of the stator  210  with relatively low temperature, is overheating of another structural element cooled by the oil such as the transmission  500 . Note that, although  FIG. 1  illustrates the single motor generator  200 , it is also assumed that the system  1000  includes the motor generators  200 . In the system in which the motor generators  200  are cooled by the oil, the oil temperature of the oil in the oil pan  300  is increased by overheating of one of the motor generators  200 , and the oil having the increased oil temperature is supplied to other of the motor generators  200 . 
     In the case where the temperature detected by the temperature sensor  212  is a° C. or more and less than b° C., the limitation map “ 1 ” illustrated in  FIG. 4  is used. In the limitation map “ 1 ” illustrated in  FIG. 4 , in a way similar to the limitation map “ 0 ” illustrated in  FIG. 3 , the torque of the motor generator  200  is limited to “ 0 ” in the case where the oil temperature in the oil pan  300  is F° C. 
     In addition, in the limitation map “ 1 ” illustrated in  FIG. 4 , the torque is limited in accordance with the rotation speed of the motor generator  200 . Specifically, in the case where the rotation speed is M [rpm], the torque of the motor generator  200  is limited in accordance with a coefficient depending on the oil temperature in the oil pan  300 . In this case, it is assumed that the temperature of the magnet of the rotor  220  increases as the oil temperature gets higher. Therefore, the torque is limited more as the oil temperature gets higher. In addition, in the case where the rotation speed is N [rpm], the torque of the motor generator  200  is limited to “ 0 ” except in the case where the oil temperature in the oil pan  300  is A° C. 
     In the case where the temperature detected by the temperature sensor  212  is b° C. or more and less than c° C., the limitation map “ 2 ” illustrated in  FIG. 5  is used. In the limitation map “ 2 ” illustrated in  FIG. 5 , in a way similar to the limitation map “ 1 ” illustrated in  FIG. 4 , the torque of the motor generator  200  is also limited to “ 0 ” in the case where the oil temperature in the oil pan  300  is F° C. 
     In the limitation map “ 2 ” illustrated in  FIG. 5 , the torque is limited in accordance with the rotation speed of the motor generator  200 . Specifically, in the case where the rotation speed is L [rpm] or M [rpm], the torque of the motor generator  200  is limited in accordance with a coefficient depending on the oil temperature in the oil pan  300 . Here, it is assumed that the temperature of the magnet of the rotor  220  increases as the rotation speed gets higher. Therefore, the torque is limited more as the rotation speed gets higher. In addition, it is assumed that the temperature of the magnet of the rotor  220  increases as the oil temperature gets higher. Therefore, the torque is limited more as the oil temperature gets higher. 
     In addition, in the case where the rotation speed is N [rpm], the torque of the motor generator  200  is limited to “ 0 ” except in the case where the oil temperature in the oil pan  300  is A° C. 
     In the case where the temperature detected by the temperature sensor  212  is c° C. or more, the limitation map “ 3 ” illustrated in  FIG. 6  is used. In the limitation map “ 3 ” illustrated in  FIG. 6 , in a way similar to the limitation map “ 1 ” illustrated in  FIG. 4 , the torque of the motor generator  200  is also limited to “ 0 ” in the case where the oil temperature in the oil pan  300  is F° C. 
     In the limitation map “ 3 ” illustrated in  FIG. 6 , the torque is limited in accordance with the rotation speed of the motor generator  200 . Specifically, in the case where the rotation speed is H [rpm] to M [rpm], the torque of the motor generator  200  is limited in accordance with a coefficient depending on the oil temperature in the oil pan  300 . Here, it is assumed that the temperature of the magnet of the rotor  220  increases as the rotation speed gets higher. Therefore, the torque is limited more as the rotation speed gets higher. In addition, it is assumed that the temperature of the magnet of the rotor  220  increases as the oil temperature gets higher. Therefore, the torque is limited more as the oil temperature gets higher. In addition, in the case where the rotation speed is N [rpm], the torque of the motor generator  200  is limited to “ 0 ” except in the case where the oil temperature in the oil pan  300  is A° C. 
     As described above, it is possible to suppress overheating of the magnet of the rotor  220  by limiting the torque of the motor generator  200  on the basis of the temperature of the motor generator  200 , temperature of the oil, and the rotation speed of the motor generator  200 . Accordingly, it is possible to protect the magnet before the temperature of the magnet of the rotor  220  exceeds the heatproof temperature and the magnet loses its function. 
     Note that, the maps illustrated in  FIG. 3  to  FIG. 6  are mere instances. It is possible to change values of the coefficient in accordance with specifications such as the heatproof temperature of the magnet. 
       FIG. 7  is a schematic diagram illustrating a relation between rotation speed (horizontal axis) and torque (vertical axis) of the motor generator  200 . In a way similar to characteristics of common motors, as indicated by the solid line in  FIG. 7 , the torque generated by the motor generator  200  decreases as the rotation speed gets higher. The characteristic indicated by the dashed-dotted line in  FIG. 7  is a characteristic of an upper limit of the torque in the case where the torque of the motor generator  200  is limited on the basis of the heatproof temperature of the coil of the stator  210 . The torque is limited such that the torque becomes smaller than the characteristic indicated by the dashed-dotted line in order to prevent the temperature of the stator  210  detected by the temperature sensor  212  from exceeding the heatproof temperature. 
     In addition, the characteristic indicated by the dashed-two-dotted line in  FIG. 7  is a characteristic of an upper limit of the torque in the case where the torque of the motor generator  200  is limited on the basis of the heatproof temperature of the magnet of the rotor  220 . The torque is limited such that the torque becomes smaller than the characteristic indicated by the dashed-two-dotted line in order to prevent the temperature of the magnet of the rotor  220  from exceeding the heatproof temperature. 
     In the case where the rotation speed of the motor generator  200  is relatively low, the upper limit of the torque based on the heatproof temperature of the magnet indicated by the dashed-two-dotted line is larger than the upper limit of the torque based on the heatproof temperature of the coil indicated by the dashed-dotted line. On the other hand, when the rotation speed of the motor generator  200  exceeds a [rpm], the upper limit of the torque based on the heatproof temperature of the coil indicated by the dashed-dotted line becomes larger than the upper limit of the torque based on the heatproof temperature of the magnet indicated by the dashed-two-dotted line. 
     If the torque is limited only on the basis of the upper limit of the torque based on the heatproof temperature of the coil indicated by the dashed-dotted line, the upper limit of the torque exceeds the upper limit of the torque based on the heatproof temperature of the magnet when the rotation speed of the motor generator  200  exceeds a [rpm]. For instance, when the motor generator  200  is driven by torque T [Nm] at rotation speed β [rpm], a value less than or equal to the upper limit of the torque based on the heatproof temperature of the coil is obtained. Therefore, it is possible to prevent the coil from getting thermal damage. However, in this case, the value exceeds the upper limit of the torque based on the heatproof temperature of the magnet. Therefore, there is a possibility that the magnet gets thermal damage. As described above, in the case where the torque is limited only on the basis of the upper limit of the torque based on the heatproof temperature of the coil indicated by the dashed-dotted line, it is impossible to protect the magnet in a hatched area (area incapable of protecting the magnet) illustrated in  FIG. 7 . 
     According to the present example, it is possible to suppress overheating and function loss of the magnet of the rotor  220  by limiting the torque of the motor generator  200  on the basis of the maps illustrated in  FIG. 3  to  FIG. 6 , especially in the case where the temperature of the stator  210  is not identical to the temperature of the rotor  220 . 
     As described above, according to the present example, the maps illustrated in  FIG. 3  to  FIG. 6  are switched on the basis of the temperature of the stator  210  detected by the temperature sensor  212 , and the torque of the motor generator  200  is limited on the basis of the rotation speed of the motor generator  200  and the oil temperature of the oil. Therefore, it is possible to suppress loss of the magnet caused by overheating of the rotor  220  without driving the motor generator  200  in the area incapable of protecting the magnet illustrated in  FIG. 7 . 
     Although the preferred examples of the present invention have been described in detail with reference to the appended drawings, the present invention is not limited thereto. It is obvious to those skilled in the art that various modifications or variations are possible insofar as they are within the technical scope of the appended claims or the equivalents thereof. It should be understood that such modifications or variations are also within the technical scope of the present invention. 
     According to the example of the present invention, it is possible to suppress overheating of a motor by optimally controlling torque of the motor.