Patent Publication Number: US-2023151787-A1

Title: Vehicle

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application claims priority from Japanese Patent Application No. 2021-186543 filed on Nov. 16, 2021, the entire contents of which are hereby incorporated by reference. 
     BACKGROUND 
     The disclosure relates to a vehicle. 
     For a hybrid vehicle equipped with a traveling motor and an engine, there has been available a technique for driving the traveling motor with the power of a main battery and starting the engine with the power of a sub battery (see, for example, Japanese Unexamined Patent Application Publication No. 2016-068740). 
     SUMMARY 
     An aspect of the disclosure provides a vehicle. The vehicle includes a first power system, a second power system, a switching relay, and a relay controller. The first power system is coupled to an engine restart motor. The second power system is provided independently of the first power system and coupled to a starter and an accessory. A coupling state of the switching relay is switchable to an on state in which the first power system and the second power system are coupled, and to an off state in which the first power system and the second power system are not coupled. The relay controller is configured to receive a supply of electric power from both the first power system and the second power system and to control the coupling state of the switching relay. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings are included to provide a further understanding of the disclosure and are incorporated in and constitute a part of this specification. The drawings illustrate an example embodiment and, together with the specification, serve to describe the principles of the disclosure. 
         FIG.  1    is a diagram illustrating the configuration of a vehicle; and 
         FIG.  2    is a flowchart of a relay control process. 
     
    
    
     DETAILED DESCRIPTION 
     In the case where a hybrid vehicle is stored without being driven for a long period of time, a battery coupled to a starter may be depleted due to dark current, which may cause engine starting malfunction. 
     It is desirable to provide a vehicle capable of reducing engine starting malfunction. 
     In the following, an embodiment of the disclosure is described in detail with reference to the accompanying drawings. Note that the following description is directed to an illustrative example of the disclosure and not to be construed as limiting to the disclosure. Factors including, without limitation, numerical values, shapes, materials, components, positions of the components, and how the components are coupled to each other are illustrative only and not to be construed as limiting to the disclosure. Further, elements in the following example embodiment 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 the present specification and the drawings, elements having substantially the same function and configuration are denoted with the same numerals to avoid any redundant description. 
       FIG.  1    is a diagram illustrating the configuration of a vehicle  1 . As illustrated in  FIG.  1   , the vehicle  1  is a hybrid vehicle equipped with an engine  3  and a traveling motor  5 . The vehicle  1  includes an integrated starter generator (ISG)  7 , a starter  9 , accessories  11 , a traveling battery  13 , an accessory battery  15 , an engine restart battery  17 , a direct-current-to-direct-current (DCDC) converter  19 , a first power system  21 , a second power system  23 , a controller  25 , a switching relay  27 , and a relay controller  29 . 
     The engine  3  is, for example, a gasoline engine or a diesel engine. The engine  3  rotates a crankshaft by moving a piston back and forth with a combustion pressure in a combustion chamber. The crankshaft is coupled to a power transmission device (not illustrated), and the power transmission device transmits the power of the engine  3  to drive wheels (not illustrated). 
     The traveling motor  5  is, for example, a synchronous rotary electric device. The traveling motor  5  is controlled by application of a three-phase alternating current (AC) generated by a first inverter  31  based on a command from the controller  25 . 
     The traveling motor  5  operates as an electric motor that rotates and drives by receiving a supply of electric energy from the traveling battery  13 . In the case where the traveling motor  5  operates as an electric motor, the rotational driving force generated by the traveling motor  5  is transmitted to the drive wheels (not illustrated) via the power transmission device (not illustrated). In addition, the traveling motor  5  serves as a power generator when it receives rotational energy from the engine  3  or the drive wheels. The traveling battery  13  is charged with the electric energy generated by the traveling motor  5  through the first inverter  31 .| 
     The ISG  7  is coupled to the crankshaft of the engine  3  via a pulley belt  33 . The ISG  7  serves as a power generator when it receives rotational energy from the engine  3 . The engine restart battery  17  is charged with the electric energy generated by the ISG  7  through a second inverter  35 . 
     Moreover, the ISG  7  operates as an electric motor that rotates and drives by receiving a supply of electric energy from the engine restart battery  17 . The ISG  7  is controlled by application of a three-phase AC generated by the second inverter  35  based on a command from the controller  25 . 
     In the case where the ISG  7  operates as an electric motor, the ISG  7  assists the driving force of the engine  3  or restarts the engine  3  in the event of an idling stop. As mentioned above, the ISG  7  serves as an engine restart motor in the event of an idling stop. 
     The starter  9  is, for example, a DC motor. The starter  9  operates as an electric motor that rotates and drives by receiving a supply of electric energy from the accessory battery  15 . The starter  9  is rotated and controlled based on a command from the controller  25 . The starter  9  is, for example, engaged via a pinion with an outer peripheral gear of a flywheel (not illustrated) of the engine  3  and is used to start the engine  3 . 
     The accessories  11  are devices that operate by receiving a supply of electric energy from the accessory battery  15  and the traveling battery  13 . The accessories  11  include, for example, a vehicle dynamics control (VDC)  11   a , an electric power steering (EPS)  11   b , a navigation audio  11   c , and other devices  11   d.    
     The VDC  11   a  is a device that monitors the driver&#39;s vehicle operation and the vehicle movement using various sensors and controls the brake pressure, engine output, and the like according to the driving state. The EPS  11   b  is a device that electrically assists the force necessary for steering operation. The navigation audio  11   c  is an automotive navigation system in which audio and visual functions are added to a navigation function. The other devices  11   d  include, for example, an automatic driving camera, various sensors, a cooling fan, an air conditioner compressor, and the like. 
     The first power system  21  includes the engine restart battery  17 . The first power system  21  is electrically coupled to the ISG  7 , the second inverter  35 , the switching relay  27 , the relay controller  29 , and the engine restart battery  17 . The second power system  23  is provided independently of the first power system  21 . The second power system  23  includes the accessory battery  15  and the traveling battery  13 . The second power system  23  is electrically coupled to the starter  9 , the accessories  11 , the DCDC converter  19 , the traveling motor  5 , the first inverter  31 , the switching relay  27 , the relay controller  29 , the accessory battery  15 , and the traveling battery  13 . Note that the DCDC converter  19  for converting voltage is provided between the traveling battery  13  and the accessory battery  15 . 
     The second power system  23  is divided, with the DCDC converter  19  interposed therebetween, into an accessories-side power system  23   a  and a traveling-motor-side power system  23   b . The accessories-side power system  23   a  is electrically coupled to the starter  9 , the accessories  11 , the switching relay  27 , the relay controller  29 , the DCDC converter  19 , and the accessory battery  15 . The traveling-motor-side power system  23   b  is electrically coupled to the traveling motor  5 , the first inverter  31 , the DCDC converter  19 , and the traveling battery  13 . 
     The engine restart battery  17  is, for example, a lead-acid battery with an output voltage of DC 12 V. The engine restart battery  17  is electrically coupled by the first power system  21  to the second inverter  35  and the ISG  7 . The engine restart battery  17  supplies electric energy to the ISG  7  via the second inverter  35 . The engine restart battery  17  is charged with electric energy generated by the ISG  7  from the second inverter  35 . 
     The accessory battery  15  is, for example, a lead-acid battery with an output voltage of DC 12 V. The accessory battery  15  is electrically coupled by the second power system  23  to the starter  9  and the accessories  11 . The accessory battery  15  supplies electric energy to the starter  9  and the accessories  11 . Moreover, the accessory battery  15  is charged with electric energy from the traveling battery  13  via the DCDC converter  19 . 
     The traveling battery  13  is, for example, a lithium ion battery with an output voltage of DC 48 V. The traveling battery  13  has a higher output voltage than the engine restart battery  17  and the accessory battery  15 . Note that the output voltage of the traveling battery  13  is not limited to 48 V, and may be higher than 48 V, such as 200 V, or may be lower than 48 V. 
     The traveling battery  13  is electrically coupled to the first inverter  31  and the traveling motor  5 . The traveling battery  13  supplies electric energy to the traveling motor  5  via the first inverter  31 . Moreover, the traveling battery  13  is charged with electric energy generated by the traveling motor  5  from the first inverter  31 . 
     Note that each battery is provided with a battery sensor (not illustrated), and the remaining battery capacity (state of charge (SOC)) and voltage of each battery are measured. The battery sensor is coupled to the relay controller  29 , and information on the SOC and voltage of each battery is sent to the relay controller  29 . Note that the voltage of each battery is accurately measured by the battery sensor, regardless of where each battery is coupled. 
     The DCDC converter  19  has a step-down function of stepping down 48 V of the traveling-motor-side power system  23   b  to 14.6 V and outputting 14.6 V to the accessories-side power system  23   a . In doing so, the DCDC converter  19  is able to output a voltage of 14.6 V to the accessories-side power system  23   a , regardless of the operating state of the engine  3 . 
     The controller  25  is electrically coupled to the engine  3 , the starter  9 , the first inverter  31 , the second inverter  35 , and the DCDC converter  19  to control these devices. The controller  25  performs control to switch the driving mode of the vehicle  1 , for example. 
     In one example, the driving mode of the vehicle  1  includes an electric vehicle (EV) driving mode, an engine driving mode, a parallel hybrid electric vehicle (HEV) driving mode, and a series HEV driving mode. The EV driving mode is a mode in which the vehicle  1  drives with the driving force of the traveling motor  5  alone, and the engine traveling mode is a mode in which the vehicle  1  drives with the driving force of the engine  3  alone. 
     The parallel HEV driving mode is a mode in which the vehicle  1  drives with the driving force of the engine  3  and the driving force of the traveling motor  5 . The series HEV driving mode is a mode in which the traveling motor  5  is driven by electric energy generated by a motor generator (not illustrated) using the engine  3 , and the vehicle  1  drives with the driving force of the traveling motor  5  alone. 
     The switching relay  27  is disposed between the first power system  21  and the second power system  23  and is coupled to both the first power system  21  and the second power system  23 . The switching relay  27  is configured to be switchable to an on state in which the first power system  21  and the second power system  23  are electrically coupled, and to an off state in which the coupling is released. 
     The relay controller  29  includes one or more processors  29   a  and one or more memories  29   b  coupled to the processor(s)  29   a . The processor(s)  29   a  includes, for example, a central processing unit (CPU). 
     The memory(ies)  29   b  includes, for example, read only memory (ROM) and random access memory (RAM). The ROM is a storage element that stores programs, calculation parameters, and the like used by the CPU. The RAM is a storage element that temporarily stores data such as variables and parameters used for processing executed by the CPU. 
     Various processes performed by the relay controller  29  may be executed by the processor(s)  29   a . In detail, various processes are executed by the processor(s)  29   a  executing programs stored in the memory(ies)  29   b.    
     Note that the functions of the relay controller  29  according to the present embodiment may be divided into control devices, or functions may be realized by one control device. In the case where the functions of the relay controller  29  are divided into control devices, the control devices may be coupled to each other via a communication bus such as a Controller Area Network (CAN) bus. 
     The relay controller  29  is coupled to the first power system  21  and the second power system  23  respectively via backflow prevention diodes (not illustrated). With the above backflow prevention diodes, no current flows from the first power system  21  to the second power system  23 , and no current flows from the second power system  23  to the first power system  21 . The relay controller  29  receives a supply of electric power from both the first power system  21  and the second power system  23  and controls the coupling state of the switching relay  27 . In detail, the relay controller  29  receives a supply of electric power from whichever of the first power system  21  and the second power system  23  having a higher electric potential. 
     The relay controller  29  compares the voltage (first voltage) of the engine restart battery (first power supply)  17  included in the first power system  21  and a first threshold. The relay controller  29  also compares the stepped-down voltage (second voltage), stepped down by the DCDC converter  19 , of the traveling battery (second power supply)  13  included in the second power system  23  and a second threshold. Alternatively, the relay controller  29  compares the voltage (second voltage) of the accessory battery (second power supply)  15  included in the second power system  23  and the second threshold. Note that the relay controller  29  may compare the voltage (second voltage) of the traveling battery (second power supply)  13  included in the second power system  23  and the second threshold. 
     Here, data of the first threshold and the second threshold is stored in the memory(ies)  29   b . The first threshold is the value of a voltage smaller than a voltage in the voltage normal range of the engine restart battery  17 . The first threshold is the value of a voltage necessary to start the engine  3 . 
     The second threshold is the value of a voltage smaller than a voltage in the voltage normal range of the accessory battery  15 . Alternatively, the second threshold is the value of a voltage smaller than the stepped-down voltage of the traveling battery  13 , stepped down by the DCDC converter  19 . The second threshold is the value of a voltage necessary to start the engine  3 . Although the first threshold and the second threshold are the same value in the present embodiment, they may be different values. 
     Then, the relay controller  29  controls the coupling state of the switching relay  27  based on the result of comparing the first voltage and the first threshold and the result of comparing the second voltage and the second threshold. In one example, when the first voltage is less than the first threshold and the second voltage is greater than or equal to the second threshold, the relay controller  29  controls the switching relay  27  to the off state. In doing so, the first power system  21  is not coupled to the starter  9 , and the second power system  23  is coupled to the starter  9 . Therefore, electric power can be supplied to the starter  9  from a battery with the second voltage, which is greater than or equal to the second threshold, included in the second power system  23 . 
     In contrast, when the first voltage is greater than or equal to the first threshold and the second voltage is less than the second threshold, the relay controller  29  controls the switching relay  27  to the on state. In doing so, the first power system  21  is coupled to the starter  9 . Therefore, electric power can be supplied to the starter  9  from a battery with the first voltage, which is greater than or equal to the first threshold, included in the first power system  21 . 
     When the first voltage is greater than or equal to the first threshold and the second voltage is greater than or equal to the second threshold, the relay controller  29  controls the coupling state of the switching relay  27  so that the power system having a higher voltage out of the first voltage and the second voltage will be coupled to the starter  9 . 
     In the present embodiment, the stepped-down voltage stepped down by the DCDC converter  19  in the second power system  23  is higher than the output voltage output from the engine restart battery  17  in the first power system  21 . 
     When the relay controller  29  determines that the first voltage is greater than or equal to the first threshold and the second voltage is greater than or equal to the second threshold, and the second voltage is higher out of the first voltage and the second voltage, the relay controller  29  controls the switching relay  27  to the off state. That is, the relay controller  29  performs control so that the first power system  21  will not be coupled to the starter  9  and the second power system  23  will be coupled to the starter  9 . In doing so, electric power can be supplied to the starter  9  from a battery included in whichever of the first power system  21  and the second power system  23  having a higher voltage. 
     In contrast, when the relay controller  29  determines that the first voltage is greater than or equal to the first threshold and the second voltage is greater than or equal to the second threshold, and that the first voltage is higher out of the first voltage and the second voltage, the relay controller  29  controls the switching relay  27  to the on state. That is, the relay controller  29  performs control so that the first power system  21  will be coupled to the starter  9 . In doing so, electric power can be supplied to the starter  9  from a battery included in whichever of the first power system  21  and the second power system  23  having a higher voltage. However, this is not the only possible operation, and, in this case, the relay controller  29  may prioritize the SOC maintenance of the engine restart battery  17  and control the switching relay  27  to the off state. That is, even when the relay controller  29  determines that the first voltage is higher than the second voltage, the relay controller  29  may prioritize the SOC maintenance of the engine restart battery  17 , and may perform control so that the first power system  21  will not be coupled to the starter  9  and the second power system  23  will be coupled to the starter  9 . In doing so, when the first voltage is greater than or equal to the first threshold and the second voltage is greater than or equal to the second threshold, while the SOC of the engine restart battery  17  is being maintained, the starter  9  can be supplied with electric power from the second power system  23 . 
     Here, suppose that the relay controller  29  determines that the SOC of the engine restart battery  17  is greater than or equal to a certain value and that the SOC of the traveling battery  13  is less than the certain value. In that case, for example, even if the second voltage is higher out of the first voltage and the second voltage, the relay controller  29  may control the switching relay  27  to the on state so that the starter  9  will be coupled to the engine restart battery  17 . 
       FIG.  2    is a flowchart of a relay control process. As illustrated in  FIG.  2   , the relay controller  29  firstly compares the first voltage and the first threshold (S 1 ). Next, the relay controller  29  compares the second voltage and the second threshold (S 2 ). 
     Then, the relay controller  29  determines whether the first voltage is less than the first threshold and whether the second voltage is greater than or equal to the second threshold (S 3 ). In the case where it is determined YES in S 3 , the relay controller  29  controls the switching relay  27  to the off state (S 4 ). 
     In the case where it is determined NO in S 3 , the relay controller  29  determines whether the first voltage is greater than or equal to the first threshold and whether the second voltage is less than the second threshold (S 5 ). In the case where it is determined YES in S 5 , the relay controller  29  controls the switching relay  27  to the on state (S 6 ). 
     In the case where it is determined NO in S 5 , the relay controller  29  determines whether the first voltage is greater than or equal to the first threshold and whether the second voltage is greater than or equal to the second threshold (S 7 ). In the case where it is determined YES in S 7 , the relay controller  29  controls the coupling state of the switching relay  27  so that the power system having a higher voltage out of the first voltage and the second voltage will be coupled to the starter  9  (S 8 ), and ends the relay control process. 
     In S 8 , however, the relay controller  29  may control the coupling state of the switching relay  27  based on the SOC of batteries included in the first power system  21  and the second power system  23 , regardless of which voltage is higher or lower. That is, the relay controller  29  may control the coupling state of the switching relay  27  so that, out of batteries included in the first power system  21  and the second power system  23 , a battery whose SOC is greater than or equal to a certain value will be preferentially coupled to the starter  9 . In one example, suppose that the relay controller  29  determines that the SOC of the engine restart battery  17  included in the first power system  21  is greater than or equal to the certain value, and that the SOC of the traveling battery  13  included in the second power system  23  is less than the certain value. In that case, for example, even if the second voltage is higher out of the first voltage and the second voltage, the relay controller  29  may control the switching relay  27  to the on state so that the starter  9  will be coupled to the engine restart battery  17 . 
     In the case where it is determined NO in S 7 , the relay controller  29  determines that the first voltage is less than the first threshold and the second voltage is less than the second threshold, and that the starter  9  cannot be driven, executes error processing to report that the starter  9  cannot be driven (S 9 ), and ends the relay control process. 
     As described above, the relay controller  29  of the present embodiment is configured to be able to receive a supply of electric power from both the first power system  21  and the second power system  23 . In doing so, even if the traveling battery  13  and the accessory battery  15  are depleted or the engine restart battery  17  is depleted, the relay controller  29  can be supplied with electric power. 
     Therefore, the relay controller  29  can receive a supply of electric power from a battery that has not been depleted, control the switching relay  27 , and supply the power from the non-depleted battery to the starter  9 . As a result, engine start malfunction may be reduced. 
     Moreover, the relay controller  29  couples the power system having a higher voltage out of the first voltage and the second voltage to the starter  9 . The higher the voltage, the less sound and vibration given to the occupant(s) when the engine  3  is started. In addition, since the traveling battery  13  is charged using excess regenerative energy during driving and does not demand new energy for charging, it is more efficient to use the electric energy of the traveling battery (high voltage battery)  13  for driving the starter  9 . Therefore, as the power system coupled to the starter  9 , priority is given to the power system having a higher voltage out of the first voltage and the second voltage. 
     Although the preferred embodiment of the disclosure has been described above with reference to the accompanying drawings, it goes without saying that the disclosure is not limited to the above embodiment. It is obvious for those skilled in the art to conceive of various changes or modifications within the scope of the claims, which are naturally understood to be within the technical scope of the disclosure. 
     In the above embodiment, an example in which the relay controller  29  compares the first voltage and the first threshold and compares the second voltage and the second threshold has been described. However, this is not the only possible case, and the relay controller  29  may control the coupling state of the switching relay  27  so that the power system having a higher voltage will be coupled to the starter  9 , without comparing the voltage and the threshold. 
     In the above embodiment, an example in which the second power system  23  includes the traveling battery  13  and the accessory battery  15  has been described. However, this is not the only possible case, and the second power system  23  may be provided with the accessory battery  15  alone, without the traveling battery  13 . Alternatively, the second power system  23  may be provided with the traveling battery  13  alone, without the accessory battery  15 . 
     The relay controller  29  illustrated in  FIG.  1    can be implemented by circuitry including at least one semiconductor integrated circuit such as at least one processor (e.g., a central processing unit (CPU)), at least one application specific integrated circuit (ASIC), and/or at least one field programmable gate array (FPGA). At least one processor can be configured, by reading instructions from at least one machine readable tangible medium, to perform all or a part of functions of the relay controller  29 . Such a medium may take many forms, including, but not limited to, any type of magnetic medium such as a hard disk, any type of optical medium such as a CD and a DVD, any type of semiconductor memory (i.e., semiconductor circuit) such as a volatile memory and a non-volatile memory. The volatile memory may include a DRAM and a SRAM, and the non-volatile memory may include a ROM and a NVRAM. The ASIC is an integrated circuit (IC) customized to perform, and the FPGA is an integrated circuit designed to be configured after manufacturing in order to perform, all or a part of the functions of the modules illustrated in  FIG.  1   .