Patent Publication Number: US-2022234568-A1

Title: Drive controller of hybrid vehicle, and drive controlling method for hybrid vehicle

Description:
TECHNICAL FIELD 
     The present invention relates to a drive controller of a hybrid vehicle and a drive controlling method for the hybrid vehicle. 
     BACKGROUND ART 
     A hybrid vehicle is equipped with an engine that combusts fuel to drive the vehicle and with an electric motor (motor) supplied with power from a battery to drive the vehicle. The motor generates heat during driving due to copper loss, iron loss, or the like, and when the output of the motor increases, the amount of heat generated by the motor also increases. For example, when the vehicle is traveling on a steep slope or the like, the temperature of the motor may rise significantly. The motor&#39;s remaining in an overheating state raises a concern that the motor may have a problem. From the viewpoint of component protection, the torque of the motor is limited. 
     Patent Literature 1 discloses a device that puts limits on the torque of a motor to suppress overheating of the motor when determining that the temperature of the motor reaches an operation-guarantee temperature, and that cancels the limits on the torque to give priority to a gradient-climbing capability when determining that the temperature of the motor does not reach the operation-guarantee temperature and that a rise in the motor temperature is so brief as to be considered harmless from the viewpoint of the durability of the motor. 
     CITATION LIST 
     Patent Literature 
     
         
         PLT 1: Japanese Patent Application Laid-Open No. 2010-115053 
       
    
     SUMMARY OF INVENTION 
     Technical Problem 
     According to the device described in Patent Literature 1, limiting the torque of the motor to avoid overheating of the motor results in switching to engine-driven traveling, thus leading to lower fuel efficiency, which is a problem. 
     Solution to Problem 
     A drive controller of a hybrid vehicle according to the present invention is a drive controller of a hybrid vehicle driven by using an electric motor and an engine that is an internal combustion engine. The drive controller includes: a temperature detection unit that detects a temperature of the electric motor; an environment information acquiring unit that acquires traveling environment information on the vehicle; a power consumption calculation unit that receives, from the environment information acquiring unit, information about a first section that is a path where heat generation by the electric motor is expected and about a second section that is a path where heat generation by the electric motor is less than heat generation by the electric motor in the first section, the power consumption calculation unit calculating power consumption by the electric motor in the first section and in the second section; and a vehicle control unit that controls output torque of the electric motor in the first section, based on the temperature of the electric motor detected by the temperature detection unit and on the power consumption calculated by the power consumption calculation unit, to change a drive ratio of the engine. 
     A drive controlling method for a hybrid vehicle according to the present invention is a drive controlling method for a hybrid vehicle driven by using an electric motor and an engine that is an internal combustion engine. The drive controlling method includes: detecting a temperature of the electric motor; acquiring traveling environment information on the vehicle; calculating power consumption by the electric motor in a first section and in a second section, the first section being a path where heat generation by the electric motor is expected and the second section being a path where heat generation by the electric motor is less than heat generation by the electric motor in the first section, based on the acquired traveling environment information; and controlling output torque of the electric motor in the first section, based on the detected temperature of the electric motor and on the calculated power consumption, to change a drive ratio of the engine. 
     Advantageous Effects of Invention 
     According to the present invention, fuel efficiency can be improved by changing the drive ratio of the engine according to a traveling path. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a configuration diagram showing a drive controller of a hybrid vehicle. 
         FIG. 2  is a power consumption rate map showing a relationship between a gradient of a road and a power consumption rate of a motor. 
         FIG. 3  shows a power consumption difference threshold map that defines, in advance, a relationship between a traveling distance and a power consumption difference threshold. 
         FIG. 4  is a graph showing a load factor limit map. 
         FIGS. 5(A) to 5(D)  are diagrams for explaining a state in which the torque of the motor is limited according to traveling of the vehicle. 
         FIG. 6  is a flowchart describing an operation of a vehicle control unit. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
       FIG. 1  is a configuration diagram showing a drive controller  100  of a hybrid vehicle according to an embodiment of the present invention. 
     The drive controller  100  includes a motor (electric motor)  1 , and an engine  2  that is an internal combustion engine that combusts a fuel to drive the vehicle. The drive controller  100  further includes a battery  3  that supplies the motor  1  with power, and an inverter  4  that converts a direct current from the battery  3  into a three-phase alternating current and that supplies the alternating current to the motor  1 . Near the motor  1 , a temperature detection unit  5 , such as a temperature sensor, that detects the temperature of the motor  1  is provided. 
     A vehicle control unit  6  controls driving of the motor  1  through the inverter  4  and controls driving of the engine  2  as well. The vehicle control unit  6  acquires vehicle speed information from a vehicle speed sensor  7  that detects the speed of the vehicle. In addition, the vehicle control unit  6  acquires road information, such as a gradient of a traveling path, from a navigation device  8 . 
     The vehicle control unit  6  includes a storage unit  10 . In the storage unit  10 , a load factor limit map  11 , a power consumption rate map  13 , and a power consumption difference threshold map  14  are stored in advance. The vehicle control unit  6  further includes an environment information acquiring unit  16 , a temperature rise calculation unit  17 , and a power consumption calculation unit  18 . Based on the temperature of the motor  1  detected by the temperature detection unit  5  and on power consumption calculated by the power consumption calculation unit  18 , the vehicle control unit  6  controls output torque of the motor  1  on the traveling path, thereby changing a drive ratio of the engine  2 . 
     The load factor limit map  11  stores therein a relationship between the temperature of the motor  1  and a maximum load factor, and has a first load factor limit map and a second load factor limit map in which the torque with respect to the temperature of the motor  1  is limited further than in the first load factor limit map. 
     The power consumption rate map  13  is a map indicating a relationship between a traveling path, such as a gradient-climbing path on which the vehicle is expected to travel, and a power consumption rate of the motor  1 . Details of this map will be described later. A relationship between the traveling path, such as a gradient-climbing path, and the power consumption rate is determined by simulation or the like, and is stored in advance. 
     The power consumption difference threshold map  14  is a map that defines, in advance, a relationship between a traveling distance in which the vehicle is expected to travel and a power consumption difference threshold EmT. Details of this map will be described later. The relationship between the traveling distance and the power consumption difference threshold EmT is determined by simulation or the like, and is stored in advance. 
     The environment information acquiring unit  16  acquires traveling environment information from map information or the like in the navigation device  8 , the traveling environment information including information on the gradient and the distance of a first section related to the traveling path and information on the gradient and the distance of a second section that follows the first section. 
     The temperature rise calculation unit  17  determines whether a motor temperature reaches a torque limit temperature, based on the current load of the motor  1 . In addition, the temperature rise calculation unit  17  calculates a temperature rise rate of the motor  1  in a traveling section. Temperature rise rates in traveling sections are stored in advance in the storage unit  10  as a map of temperature rise rates, based on data obtained by simulation or the like. The temperature rise calculation unit  17  refers to this map to determine a temperature rise rate in each traveling section. 
     Referring to the power consumption rate map  13 , the power consumption calculation unit  18  determines the power consumption rate of the motor  1 , based on the speed of the vehicle and the gradient of the traveling path. Specifically, the power consumption calculation unit  18  calculates power consumption by the motor  1  in the first section and in the second section, based on information about the first section, which is a path where heat generation by the motor  1  is expected, and about the second section, which is a path where heat generation by the motor  1  is less than the same in the first section. 
       FIG. 2  is the power consumption rate map  13  showing a relationship between the gradient of a road on which the vehicle is expected to travel and the power consumption rate of the motor  1 . The horizontal axis represents the gradient of the road, and the vertical axis represents the power consumption rate. The power consumption rate map  13  is obtained for speeds a, b, . . . , by simulations or experiments, and is saved as a map plotted against the speeds a, b, . . . . When the speeds a, b, . . . increase, the power consumption rate increases. In addition, when the speed is constant, the power consumption rate increases in proportional to an increase in the gradient of the road. 
     In accordance with a change in a traveling environment, the power consumption rate map  13  is corrected based on a gradient and a power consumption rate that are saved at the time of actual traveling. Speed a′ represents the relationship that is corrected based on actual traveling data, indicating that a power consumption rate Em 2  results when the gradient is θ 2  and that a power consumption rate Em 1  results when the gradient is θ 1  larger than the gradient θ 2 . 
     A case is assumed where the vehicle travels on a gradient-climbing path with the gradient θ 1  and then travels on a traveling path with the gradient θ 2  smaller than the gradient θ 1 . The vehicle control unit  6  acquires the power consumption rate Em 1  by referring to the power consumption rate map  13 , based on the road gradient θ 1  and the speed a′ that the environment information acquiring unit  16  has acquired from the navigation device  8  and the vehicle speed sensor  7 , respectively. The vehicle control unit  6  acquires also the power consumption rate Em 2  that results after gradient climbing, by referring to the power consumption rate map  13 , based on the road gradient θ 2  and the speed a′ that the environment information acquiring unit  16  has acquired from the navigation device  8  and the vehicle speed sensor  7 , respectively. A power consumption difference representing a difference between a power consumption rate in the gradient-climbing path with the gradient θ 1  and the same in the traveling path with the gradient θ 2  is ΔEm. 
       FIG. 3  shows a power consumption difference threshold map  14  that defines, in advance, a relationship between a traveling distance in which the vehicle is expected to travel and a power consumption difference threshold EmT. The horizontal axis represents the traveling distance, and the vertical axis represents the power consumption difference threshold EmT. 
     It is assumed that the gradient-climbing path with the gradient θ 1  has a traveling distance d 1  while the traveling path with the gradient θ 2  has a traveling distance d 2 . As indicated in  FIG. 3 , the power consumption difference threshold EmT remains Max up to the point of the traveling distance d 1  of the gradient-climbing path, and then decreases as it approaches to the point of the traveling distance d 2  of the traveling path. When it is assumed that the gradient-climbing path has a traveling distance d 1 ′, the power consumption difference threshold EmT remains Max up to the point of the traveling distance d 1 ′ of the gradient-climbing path, as indicated by a dotted line in  FIG. 3 . 
     Based on the traveling distance d 1  of the gradient-climbing path with the gradient θ 1  and the traveling distance d 2  of the traveling path with the gradient θ 2 , the traveling distances d 1  and d 2  being acquired by the environment information acquiring unit  16  from the navigation device  8 , the vehicle control unit  6  refers to the power consumption difference threshold map  14  and determines power consumption difference thresholds EmT for the traveling distances d 1  and d 2 , respectively. 
     Even when the traveling distance d 2  of the traveling path that follows the gradient-climbing path is long and the power consumption difference threshold EmT is small in the traveling path, if the power consumption difference ΔEm representing the difference between the power consumption rate in the path with the gradient θ 1  and the same in the path with the gradient θ 2  is found larger than the power consumption difference threshold EmT, it is concluded that a fuel efficiency improvement effect is high. It should be noted that the power consumption difference threshold map  14  is a map created by implementing a simulation or experiment on each motor  1  and storing a relationship between the traveling distance and the power consumption difference threshold EmT in advance. 
       FIG. 4  is a graph showing the load factor limit map  11 . The horizontal axis represents the temperature of the motor  1 , and the vertical axis represents a maximum load factor. 
     A first load factor limit map is a map that defines a maximum load factor that varies depending on the temperature of the motor  1 , and is indicated by a dotted line in  FIG. 4 . The first load factor limit map indicates that the maximum load factor remains constant (100%) until reaching the point of a torque limit temperature Tlim 1 , decreases with a rise in the motor temperature in a temperature range equal to or higher than the torque limit temperature Tlim 1 , and reduces to 0% at the point of a torque cut-off temperature Tlim 2 . 
     A second load factor limit map is indicated by a continuous line in  FIG. 4 . The second load factor limit map indicates that the maximum load factor remains constant (100%) until reaching the point of a torque limit temperature Tlim 0 , decreases with a rise in the motor temperature in a temperature range equal to or higher than the torque limit temperature Tlim 0 , and reduces to 0% at the point of a torque cut-off temperature Tlim 1 . The second load factor limit map is a map that defines a load factor limit value in a temperature range where driving of the motor  1  is guaranteed, e.g., a temperature range equal to or lower the torque cut-off temperature Tlim 1 . 
     The load factor limit map  11  is a map that is created by implementing a simulation or experiment so that torque limitation can be carried out within a range in which improved fuel efficiency is expected for each motor  1 . This is because that a time to reach the torque cut-off temperature varies depending on the size and heat dissipation characteristics of the motor. 
       FIGS. 5(A) to 5(D)  are diagrams for explaining a state in which the torque of the motor  1  is limited according to traveling of the vehicle. 
       FIG. 5(A)  shows environment information the environment information acquiring unit  16  has acquired from the navigation device  8 . In the following description, the gradient-climbing path with the gradient θ 1  and the traveling distance d 1  will be referred to as the first section, and the traveling path with the gradient θ 2  and the traveling distance d 2  will be referred to as the second section. The first section is the path where heat generation by the motor  1  is expected, and the second section is the path where heat generation by the motor  1  is less than the same in the first section. At a start point p of a first section p-f 1 , the environment information acquiring unit  16  acquires, from the navigation device  8 , information on the gradient θ 1  of the first section p-f 1  and the traveling distance d 2  and the gradient θ 2  of a second section f 1 -f 2  that follows the first section. 
       FIG. 5(B)  shows a temperature rise calculated by the temperature rise calculation unit  17 . When the temperature detection unit  5  detects the motor temperature having reached the given temperature Tlim 0  as the vehicle is traveling past the start point p of the first section p-f 1 , the temperature rise calculation unit  17  calculates a temperature rise rate ΔT 1  in the first section p-f 1 . When it is expected that the motor temperature rises to reach the torque limit temperature Tlim 1  in the first section p-f 1 , the temperature rise calculation unit  17  calculates a temperature rise rate ΔT 2  in the second section f 1 -f 2 , based on the acquired environment information, and determines whether the motor temperature reaches Tlim 1  by the temperature rise rate ΔT 2 . Respective temperature rise rates in the first section p-f 1  and the second section f 1 -f 2  are stored in advance in the storage unit  10 , as a map of temperature rise rates, which have been obtained in advance from actual cases of the traveling vehicle. Referring to this map, the temperature rise calculation unit  17  determines a temperature rise rate corresponding to a traveling path. 
       FIG. 5(C)  shows power consumption calculated by the power consumption calculation unit  18 . When the temperature rise calculation unit  17  determines that the motor temperature does not reach the torque limit temperature threshold Tlim 1  in the second section f 1 -f 2 , the power consumption calculation unit  18  compares the power consumption rate Em 1  in the first section p-f 1  with the power consumption rate Em 2  in the second section f 1 -f 2 . When comparing the difference ΔEm between the power consumption rates Em 1  and Em 2  with the threshold EmT, which is a criterion for determining whether the power consumption rate calculated by using the distances of the first and second sections is improved, and finding ΔEm to be larger, the power consumption calculation unit  18  determines to be a section that offers a fuel efficiency improvement effect. 
       FIG. 5(D)  shows the torque of the motor  1 . When finding that the difference ΔEm between the power consumption rates is larger than the threshold EmT calculated by using the section distances d 1  and d 2 , the power consumption calculation unit  18  sets a temperature threshold for torque limitation on the motor  1  to a low value so as to prevent the motor  1  from overheating. In other words, when the fuel efficiency improvement effect in the second section is large, the torque in the first section is limited. As a result, the motor  1  is limited in its torque in the first section p-f 1 , which makes the first section p-f 1  a hybrid traveling section where the vehicle is driven by the motor  1  and the engine  2 . Meanwhile, the second section f 1 -f 2  is a traveling section where the vehicle is driven by the motor  1  only. In this manner, overheating of the motor is suppressed in the gradient-climbing traveling section as stable motor-driven traveling is performed in the section that follows the gradient-climbing traveling section and that offers a high fuel efficiency improvement effect. This improves the fuel efficiency. 
       FIG. 6  is a flowchart describing an operation of the vehicle control unit  6 . 
     At step S 10  of  FIG. 6 , the current temperature of the motor  1  is acquired from the temperature detection unit  5 . Then, at step S 11 , whether the motor temperature has reached the torque limit temperature Tlim 0  is determined, based on the acquired temperature information on the motor  1 , when the vehicle is traveling past the start point p of the first section p-f 1 . When the motor temperature has not reached the torque limit temperature Tlim 0 , the vehicle control unit  6  returns to step S 10 . When the motor temperature has reached the torque limit temperature Tlim 0 , the vehicle control unit  6  proceeds to step S 12 . 
     At step S 12 , the temperature rise calculation unit  17  determines whether the motor temperature reaches the torque limit temperature Tlim 1  in the first section p-f 1 , based on the current load of the motor  1 . When it is determined at step S 12  that the motor temperature does not reach the torque limit temperature Tlim 1 , the vehicle control unit  6  ends steps of this flowchart. When it is determined that the motor temperature reaches the torque limit temperature Tlim 1 , the vehicle control unit  6  proceeds to step S 13 . 
     At step S 13 , the environment information acquiring unit  16  acquires, from map information or the like in the navigation device  8 , information on the gradient θ 1  and the distance d 1  of the first section related to the traveling path and information on the gradient θ 2  and the distance d 2  of the second section that follows the first section. 
     At step S 14 , the temperature rise calculation unit  17  calculates a temperature rise rate ΔT 2  of the motor  1  in the second section. At step S 15 , based on the temperature rise rate ΔT 2  in the second section calculated by the temperature rise calculation unit  17 , whether the motor temperature reaches the torque limit temperature Tlim 1  when motor-driven traveling is performed in the second section is determined. When it is determined that the motor temperature reaches the torque limit temperature Tlim 1 , the vehicle control unit  6  ends the steps of this flowchart. When it is determined that the motor temperature does not reach the torque limit temperature Tlim 1 , the vehicle control unit  6  proceeds to processes of step S 17  and other steps to follow, thus carrying out torque limit temperature change control. 
     At step S 17 , with reference to the power consumption rate map  13 , the power consumption rate Em 1  in the first section p-f 1  and the power consumption rate Em 2  in the second section f 1 -f 2  are calculated, based on the gradient θ 1  of the first section p-f 1  and the gradient θ 2  of the second section f 1 -f 2  that are acquired by the environment information acquiring unit  15 . 
     At step S 18 , the power consumption difference ΔEm representing a difference between power consumption rates is calculated from the power consumption rate Em 1  in the first section p-f 1  and the power consumption rate Em 2  in the second section f 1 -f 2 . At step S 19 , whether the power consumption difference ΔEm representing a difference between power consumption rates is larger than 0, that is, whether the power consumption rate is improved is determined. When it is determined that the power consumption rate is not improved, the vehicle control unit  6  ends the steps of this flowchart. When it is determined that the power consumption rate is improved, the vehicle control unit  6  proceeds to a process of step S 20 . At step S 20 , with reference to the power consumption difference threshold map  14 , the power consumption difference threshold EmT is acquired, based on the distance d 2  of the second section. 
     At step S 21 , whether the power consumption difference ΔEm representing a difference between power consumption rates is larger than the power consumption difference threshold EmT is determined. A case of the power consumption difference ΔEm representing a difference between power consumption rates being larger than the power consumption difference threshold EmT is a case where the vehicle&#39;s traveling by the motor  1  in the second section offers a fuel efficiency improvement effect, in which case the vehicle control unit  6  proceeds to step S 22 . When it is determined at step S 21  that the power consumption difference ΔEm representing a difference between power consumption rates is not larger than the power consumption difference threshold EmT, the vehicle control unit  6  ends the steps of this flowchart. 
     At step S 22 , the load factor limit map  11  is switched, that is, the first load factor limit map is replaced with the second load factor limit map. 
     Based on the fact that the load factor limit map  11  is switched to the second load factor limit map at the start point p of the first section p-f 1 , the vehicle control unit  6  limits the torque in the first section. In other words, the vehicle control unit  6  controls the output torque of the motor  1  in the first section to change a drive ratio of the engine  2 . As a result, the motor  1  is limited in its torque in the first section p-f 1 , which makes the first section p-f 1  a hybrid traveling section where the vehicle is driven by the motor  1  and the engine  2 . Meanwhile, the second section f 1 -f 2  is a traveling section where the vehicle is driven by the motor  1  only. It should be noted that the output torque of the motor  1  in the second section f 1 -f 2  may be controlled to lower the drive ratio of the engine  2 . 
     In this manner, respective power consumption rates in the first section and the second section are compared with each other, and the vehicle is caused to travel on the engine  2  and the motor  1  in the first section where the fuel efficiency improvement effect is large. In this case, overheating of the motor  1  is suppressed, which improves fuel efficiency. On the other hand, the engine  2  is driven with high efficiency, which reduces gas emission. Specifically, when overheating of the motor  1  is expected in the first section where the power consumption rate is low, the torque of the motor  1  is limited in the first section while traveling by the motor  1  is performed for a long time in the second section where the power consumption rate is high. This achieves a higher fuel efficiency improvement effect. 
     The embodiment described above offers the following effects. 
     (1) The drive controller  100  of the hybrid vehicle includes: the motor  1  that drives the vehicle, the engine  2  that drives the vehicle by combusting a fuel, the temperature detection unit  5  that detects a temperature of the motor  1 ; the environment information acquiring unit  16  that acquires traveling environment information on the vehicle; the power consumption calculation unit  18  that receives, from the environment information acquiring unit  16 , information about the first section that is a path where heat generation by the motor  1  is expected and about the second section that is a path where heat generation by the motor  1  is less than heat generation by the motor  1  in the first section, the power consumption calculation unit  18  calculating power consumption by the motor  1  in the first section and in the second section; and the vehicle control unit  6  that controls the output torque of the motor  1  in the first section, based on the temperature of the motor  1  detected by the temperature detection unit  5  and on the power consumption calculated by the power consumption calculation unit  18 , to change the drive ratio of the engine  2 . According to this configuration, the drive ratio of the engine is changed according to a traveling path, which improves the fuel efficiency. 
     (2) A drive controlling method for the hybrid vehicle includes: detecting a temperature of the motor  1 ; acquiring traveling environment information on the vehicle; receiving information about the first section that is a path where heat generation by the motor  1  is expected and about the second section that is a path where heat generation by the motor  1  is less than heat generation by the motor  1  in the first section and calculating power consumption by the motor  1  in the first section and in the second section, based on the acquired traveling environment information; and controlling the output torque of the motor  1  in the first section, based on the detected temperature of the motor  1  and on the calculated power consumption, to change the drive ratio of the engine  2 . According to this configuration, the drive ratio of the engine is changed according to a traveling path, which improves the fuel efficiency. 
     (Modification) According to the present invention, the embodiment described above can be modified and implemented in the following manner. 
     (1) In the embodiment, the first section, which is the gradient-climbing path with the first gradient, and the second section, which is the traveling path with the second gradient smaller than the first gradient, have been described exemplarily. However, the first section is not always a gradient-climbing path. If the first section is a traveling path where heat generation by the motor is expected to be greater than heat generation in the second section, the embodiment can also be applied to such a traveling path. For example, an acceleration section joining an expressway may be considered to be the first section, and a traveling section of the expressway may be considered to be the second section. 
     The present invention is not limited to the above embodiment, and other embodiments that can be conceived within a technical concept provided by the invention are also included in the scope of the present invention, providing that such embodiments do not impair the features of the present invention. A combination of the above-described embodiment and a plurality of modifications may also constitute the present invention. 
     REFERENCE SIGNS LIST 
     
         
           1  motor 
           2  engine 
           3  battery 
           4  Inverter 
           5  temperature detection unit 
           6  vehicle control unit 
           7  vehicle speed sensor 
           8  navigation device 
           10  storage unit 
           11  load factor limit map 
           13  power consumption rate map 
           14  power consumption difference threshold map 
           16  environment information acquiring unit 
           17  temperature rise calculation unit 
           18  power consumption calculation unit 
           100  drive controller