Vehicle and control procedures for the vehicle

Abstract

Vehicle, identified by: a machine (100) configured to produce an output to cause the vehicle to move; a motor generator (MG) configured to produce an output to cause the vehicle to move; an electrical storage device (BAT) configured to exchange electrical power with the engine generator (MG); a retention switch (10) configured to output a signal requesting a retention operating mode in which a charge state of the electrical storage device (BAT) is maintained in response to a user operation; and a controller (1000) that is configured to do this: (a) to cause the vehicle to drive using the output of at least one of the machine (100) and the motor generator (MG); (b) to control the charge level of the electrical storage device (BAT); (c) when the maintenance mode is requested in response to the signal issued by the maintenance switch (10), and when the state of charge is higher than a threshold, to execute an initial maintenance control to maintain the state of charge at an instantaneous value; and (d) if the maintenance mode is requested in response to the signal issued by the maintenance switch (10), and if the charge level is lower than the threshold, to perform a second maintenance control to restore the charge level from an instantaneous value, wherein The control (1000) is configured as the second maintenance control to enable regenerative power generation using the motor generator (MG) using the kinetic energy of the vehicle and to prevent power generation by the motor generator (MG) using the output of the machine (100).

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention

[0001] The invention relates to a vehicle capable of traveling using an output of at least one of an engine and a motor generator, and a control method for the vehicle. 2. Description of the state of the art

[0002] Japanese Patent Application Publication No. 2011-219039 (JP 2011-219039 A) describes a hybrid vehicle including an engine, a battery, a motor generator capable of being driven by electric power stored in the battery, and a charge priority button. The hybrid vehicle travels in a rapid charge travel mode when the charge priority button is operated in an on state. In the rapid charge travel mode, the vehicle travels by operating the engine and restores the state of charge (hereinafter also referred to as "SOC") stored in the battery by rapidly charging the battery through power generation control via the motor generator.

[0003] The rapid charge driving mode described in JP 2011-219039 A is a mode in which control for restoring the SOC from a current value (hereinafter also referred to as “SOC recovery mode”) is executed in preparation for future use of electric power.

[0004] Document DE 10 2013 113 831 A1 discloses a plug-in hybrid vehicle with a hybrid powertrain system and an energy storage device. A method for operating the hybrid powertrain system includes first operating the hybrid powertrain system in a charge-depleting mode to reduce a state of charge (SOC) of an energy storage device. In response to a driver request, the hybrid powertrain system operates in an intermediate charge mode to intermediately charge the energy storage device to increase the SOC of the energy storage device during a trip prior to reaching a minimum SOC associated with triggering operation in a charge-sustaining mode.

[0005] Document DE 10 2013 111 440 A1 discloses a vehicle and a method for controlling the vehicle, including a controller configured to selectively operate an electric machine and a motor in response to a user command to delay all-electric operation of the vehicle to propel the vehicle such that a state of charge of a traction battery electrically connected to the electric machine is generally maintained at a target value within a predefined range of charge states. A vehicle includes a powertrain and a controller. The controller is configured to (i) operate the powertrain in a charge depletion mode and a charge maintenance mode, and (ii) operate the powertrain in the charge maintenance mode in response to a user request if the state of charge is within a predefined range of charge states when the request is received.

[0006] Document WO 2013 / 081657 A1 discloses a system for idle reduction in a hybrid vehicle. The system includes a control system for causing the vehicle to operate in a charge reduction mode or a charge accumulation mode in response to worksite data. The worksite data may include an estimate of the amount of energy required at the worksite.

[0007] Further prior art is provided by the following documents: US 2008 / 0 300 743 A1; US ​​2011 / 0 190 968 A1; US ​​2011 / 0 166 733 A1; and DE 10 2011 104 443 A1. SUMMARY OF THE INVENTION

[0008] An operation mode in which control for maintaining the SOC at a current value (hereinafter also referred to as an "SOC maintenance mode") is executed in preparation for future use of electric power is conceivable as an operation mode similar to the SOC recovery mode. However, if the SOC is maintained as it is at the time of switching to the SOC maintenance mode when the SOC is low, there is a possibility that electric power will become scarce at the time of future use of the electric power. For example, there is a possibility that the vehicle will not be able to take full advantage of motoring due to a lack of electric power, even though a user selects the SOC maintenance mode for the purpose of performing future motoring using electric power.

[0009] The invention provides a vehicle that automatically ensures the state of charge higher than or equal to a predetermined value in a maintenance mode in which the state of charge of an electrical storage device is maintained.

[0010] A first aspect of the invention provides a vehicle. The vehicle includes an engine, a motor generator, an electrical storage device, a maintenance switch, and a controller. The engine is configured to generate an output to cause the vehicle to travel. The motor generator is configured to generate an output to cause the vehicle to travel. The electrical storage device is configured to exchange electrical power with the motor generator. The maintenance switch is configured to output a signal requesting a maintenance mode in which a state of charge of the electrical storage device is maintained, in response to a user operation.The controller is configured to (a) cause the vehicle to travel using the output of at least one of the engine and the motor generator, (b) control the state of charge of the electrical storage device, (c) when the maintenance mode is requested in response to the signal output from the maintenance switch and when the state of charge is higher than a threshold, execute a first maintenance control for maintaining the state of charge at a current value, and (d) when the maintenance mode is requested in response to the signal output from the maintenance switch and when the state of charge is lower than the threshold, execute a second maintenance control for restoring the state of charge from a current value.The controller is configured to enable, as the second maintenance control, regenerative power generation using the motor generator using kinetic energy of the vehicle and prohibit power generation of the motor generator using the output of the engine.

[0011] The vehicle according to the first aspect of the invention may further include a recovery switch configured to output, in response to a user operation, a signal requesting a recovery mode in which the state of charge is restored. The controller may be configured to perform, as the second maintenance control, a recovery of the state of charge to a first target value when the recovery mode is not requested in response to the signal output from the recovery switch, and a recovery control for restoring the state of charge to a second target value higher than the first target value when the recovery mode is requested.

[0012] In the vehicle according to the first aspect of the invention, the first maintenance control may include control for limiting a discharge power of the electric storage device compared to that in an operation mode other than the maintenance mode or the recovery mode. The second maintenance control may include control for increasing a charging power of the electric storage device while limiting a discharge power of the electric storage device compared to that in an operation mode other than the maintenance mode or the recovery mode until the state of charge is restored to the first target value.The recovery control may include a control for increasing a charging power of the electric storage device while limiting a discharging power of the electric storage device compared to that in an operation mode other than the maintenance mode or the recovery mode until the state of charge reaches the second target value.

[0013] In the vehicle according to the first aspect of the invention, the vehicle may be configured to switch between a hybrid mode in which the vehicle travels using the output of both the engine and the motor generator, and a motor mode in which the vehicle travels using the output of the motor generator while the engine is stopped. The first maintenance control may include control for limiting switching to the motor mode compared to an operation mode other than the maintenance mode or the recovery mode. The second maintenance control may include control for prohibiting switching to the motor mode until the state of charge is restored to the first target value. The recovery control may include control for prohibiting switching to the motor mode until the state of charge reaches the second target value.

[0014] A second aspect of the invention provides a control method for a vehicle. The vehicle includes an engine, a motor generator, an electrical storage device, a maintenance switch, and a controller. The engine is configured to generate an output to cause the vehicle to travel. The motor generator is configured to generate an output to cause the vehicle to travel. The electrical storage device is configured to exchange electrical power with the motor generator. The maintenance switch is configured to output a signal requesting a maintenance mode in which a state of charge of the electrical storage device is maintained, in response to a user operation.The control method includes: causing the vehicle to travel using the output of at least one of the engine and the motor generator, by the controller; controlling the state of charge of the electric storage device, by the controller; executing, by the controller, a first maintenance control for maintaining the state of charge at a current value when the maintenance mode is requested in response to the signal output from the maintenance switch and when the state of charge is higher than a threshold; and executing, by the controller, a second maintenance control for restoring the state of charge from a current value when the maintenance mode is requested in response to the signal output from the maintenance switch and when the state of charge is lower than a threshold.As the second maintenance control, regenerative power generation using the motor generator is enabled using kinetic energy of the vehicle, and power generation of the motor generator using the output of the engine is prohibited by the controller.

[0015] In the control method according to the second aspect of the invention, the vehicle may include a recovery switch that outputs a signal requesting a recovery mode in which the state of charge is restored in response to a user operation. As the second maintenance control, the state of charge may be restored to a first target value by the controller when the recovery mode is not requested in response to the signal output from the recovery switch. The control method may further include executing, by the controller, a recovery control for restoring the state of charge to a second target value higher than the first target value when the recovery mode is requested.

[0016] In the control method according to the second aspect of the invention, the first maintenance control may include control for limiting, by the controller, a discharge power of the electric storage device compared to that in an operation mode other than the maintenance mode or the recovery mode. The second maintenance control may include control for increasing a charging power of the electric storage device while limiting a discharge power of the electric storage device compared to that in an operation mode other than the maintenance mode or the recovery mode until the charging state is restored to the first target value by the controller.The recovery control may include control for increasing a charging power of the electric storage device by the controller while limiting a discharging power of the electric storage device compared to that in an operation mode other than the maintenance mode or the recovery mode until the state of charge reaches the second target value.

[0017] In the control method according to the second aspect of the invention, the vehicle may be capable of switching between a hybrid mode in which the vehicle travels using the output of both the engine and the motor generator, and a motor mode in which the vehicle travels using the output of the motor generator while the engine is stopped. The first maintenance control may include control for limiting, by the controller, switching to the motor mode compared to an operation mode other than the maintenance mode or the recovery mode. The second maintenance control may include control for prohibiting, by the controller, switching to the motor mode until the state of charge is restored to the first target value.The recovery control may include a control for preventing the controller from switching to the motor operation until the state of charge reaches the second target value.

[0018] According to the invention, it is possible to provide a vehicle that automatically ensures a state of charge higher than or equal to a predetermined value in a maintenance mode in which the state of charge of an electrical storage device is maintained. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Features, advantages and technical and industrial significance of exemplary embodiments of the invention are described below with reference to the accompanying drawings, in which like reference numerals designate like elements, and in which: Fig. 1 is an overall block diagram of a vehicle according to a first embodiment; Fig. 2 is a flowchart showing the procedure of an ECU according to the first embodiment; Fig. 3 is a graph schematically showing an operation mode of changing the SOC in an SOC maintenance mode according to the first embodiment; Fig. 4 is an overall block diagram of a vehicle according to a second embodiment; Fig. 5 is a flowchart showing the procedure of an ECU according to the second embodiment; Fig. 6 is a graph showing a comparison between a target recovery value B in an SOC recovery mode and a target maintenance lower limit value A in an SOC maintenance mode according to the second embodiment; Fig. 7 is a flowchart showing the procedure of an ECU according to a first alternative embodiment; and Fig. 8 is an overall block diagram of a vehicle according to a second alternative embodiment. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0020] Embodiments of the invention will be described below with reference to the accompanying drawings. In the following description, like reference numerals denote like components. Their names and functions are also the same. Therefore, a detailed description of them will not be repeated.

[0021] In the specification, the term "electrical power" may mean an electrical power (power) in a narrow sense, or may mean the amount of electrical power (the amount of work) or an electrical energy in a broad sense, and is flexibly interpreted depending on a situation in which the term is used.

[0022] First, a first embodiment is described. Fig. 1 is an overall block diagram of a vehicle 1 according to the first embodiment. The vehicle 1 includes an engine 100, a motor generator MG, a power control unit (PCU) 600, an electric storage device BAT, and an electronic control unit (ECU) 1000.

[0023] The vehicle 1 is a hybrid vehicle that travels by rotating drive wheels 82 using the output of at least one of the engine 100 and the motor generator MG.

[0024] Power generated by the engine 100 is transmitted to a drive shaft 560 via a clutch 110. The drive shaft 560 is coupled to the drive wheels 82.

[0025] The motor generator MG is an AC rotary electric machine and is typically a three-phase (U, V, W phase) permanent magnet synchronous motor. The motor generator MG functions not only as a motor but also as a generator. A rotor of the motor generator MG is directly coupled to the drive shaft 560.

[0026] The PCU 600 converts DC power supplied from the electrical storage device BAT into AC power and outputs the AC power to the motor generator MG. Thus, the motor generator MG is driven. The PCU 600 converts AC power generated by the motor generator MG into DC power and outputs the DC power to the electrical storage device BAT. Thus, the electrical storage device BAT is charged. The PCU 600 includes a converter that converts voltage and an inverter that converts electrical power.

[0027] The electrical storage device BAT stores DC power to drive the motor generator MG. The electrical storage device BAT is typically configured to comprise nickel-metal hydride or lithium-ion batteries.

[0028] The vehicle 1 according to the first embodiment is capable of performing any of a motor operation, an engine power generation operation, a hybrid operation, and an engine operation. In a motor operation, the vehicle is driven by rotating the drive shaft 560 using the output of the motor generator MG while the engine 100 is stopped. In the engine power generation operation, the vehicle 1 is driven by rotating the drive shaft 560 while electric power is generated by the motor generator MG using the output of the engine 100. In the hybrid operation, the vehicle 1 is driven by rotating the drive shaft 560 using the output of both the engine 100 and the motor generator MG.In engine mode, vehicle 1 is driven by rotating drive shaft 560 using the power of engine 100 while motor generator MG is stopped. In motor mode, clutch 110 is released. Clutch 110 is engaged in other modes.

[0029] The vehicle 1 includes a vehicle speed sensor 15, a rotary encoder 22, and a monitor sensor 32. The vehicle speed sensor 15 detects a rotational speed Np of the drive shaft 560 as a vehicle speed V. The rotary encoder 22 detects the rotational speed Nm of the motor generator MG. The monitor sensor 32 detects a state (voltage Vb, current Ib, temperature Tb, and the like) of the electric storage device BAT. These sensors output the detected results to the ECU 1000.

[0030] The vehicle 1 further includes an SOC maintenance switch 10. The SOC maintenance switch 10 outputs a signal requesting a state of charge (hereinafter referred to as "SOC") maintenance mode of the electric storage device BAT in response to a user operation (hereinafter referred to as "SOC maintenance mode"). In the following description, the SOC is expressed as a percentage, with the maximum capacity being 100 percent.

[0031] The ECU 1000 includes a central processing unit (CPU) and a memory (not shown) and performs predetermined arithmetic processing based on information stored in the memory and information from the sensors. The ECU 1000 controls devices mounted on the vehicle 1 based on the result of the arithmetic processing.

[0032] The ECU 1000 calculates the SOC of the electric storage device BAT based on the detected result of the monitor sensor 32. Various known methods such as a method of calculating the SOC using a correlation between an open circuit voltage (OCV) and an SOC of the electric storage device BAT and a method of calculating the SOC using an accumulated value of a current Ib can be used as a method of calculating the SOC.

[0033] The ECU 1000 sets a dischargeable power WOUT and a chargeable power WIN (both in watts) of the electric storage device BAT based on the SOC, the temperature Tb, and the like of the electric storage device BAT. The ECU 1000 calculates a required discharge power or a required charge power of the electric storage device BAT based on a user's accelerator operation amount and a vehicle speed V. The ECU 1000 controls the PCU 600 so that an actual discharge power Pout or an actual charge power Pin of the electric storage device BAT becomes the required discharge power or the required charge power of the electric storage device BAT. At the same time, the actual discharge power Pout is limited so that it does not exceed the dischargeable power WOUT. The actual charge power Pin is limited so that it does not exceed the chargeable power WIN.

[0034] The ECU 1000 switches a mode for controlling the SOC of the electric storage device BAT (hereinafter referred to as "SOC control mode") to a normal mode or the SOC maintenance mode. When the SOC maintenance switch 10 is pressed in the normal mode, the ECU 1000 switches the SOC control mode to the SOC maintenance mode. When the SOC maintenance switch 10 is pressed in the SOC maintenance mode, the ECU 1000 cancels the SOC maintenance mode and returns the SOC control mode to the normal mode.

[0035] In the vehicle 1 having the above-described configuration, the ECU 1000 executes control for maintaining the SOC in preparation for future use of electric power in the SOC maintenance mode (hereinafter referred to as "SOC maintenance control"). However, if a low SOC is maintained as it is when the SOC is low at the time of starting the SOC maintenance control, there is a possibility that electric power will become scarce at the time of future use of the electric power. For example, even if a user presses the SOC maintenance switch 10 in preparation for future motor operation, there is a possibility that it may not be possible to sufficiently ensure an available travel distance of the motor operation.

[0036] Therefore, the ECU 1000 according to the first embodiment executes maintenance control for maintaining a current SOC (hereinafter referred to as “first SOC maintenance control”) in the SOC maintenance mode when the current SOC is higher than a target maintenance lower limit A. On the other hand, the ECU 1000 executes maintenance control for restoring the SOC to the target maintenance lower limit A (hereinafter referred to as “second SOC maintenance control”) when the current SOC is lower than the target maintenance lower limit A.

[0037] Fig. 2 is a flowchart showing the procedure when the ECU 1000 executes the SOC maintenance control. The flowchart is repeatedly executed at predetermined intervals.

[0038] In step 10 (hereinafter, step 10 is abbreviated as "S"), the ECU 1000 determines whether it is in the SOC maintenance mode. If it is not in the SOC maintenance mode (NO in S10), that is, if it is in the normal operation mode, the ECU 1000 ends the process.

[0039] When in the SOC maintenance mode (YES in S10), the ECU 1000 determines whether the current SOC is higher than the target maintenance lower limit A. In the first embodiment, the target maintenance lower limit A is allowed to be arbitrarily selected within a predetermined range (for example, the range of 30% to 50%) by a user operation of an input device (not shown). The target maintenance lower limit A may be a fixed value (for example, 40%).

[0040] When the current SOC is higher than or equal to the target maintenance lower limit A (YES in S11), the ECU 1000 executes a first SOC maintenance control for maintaining the current SOC (S12). In the present embodiment, the first SOC maintenance control includes control for limiting the actual discharge power Pout of the electric storage device BAT compared to that in the normal mode and control for limiting switching to motor operation compared to that in the normal mode. Thus, the SOC is harder to consume than in the normal mode, so that the current SOC can be easily maintained. For example, a method of limiting the actual discharge power Pout only needs to decrease at least one of a required discharge power and the dischargeable power WOUT compared to that in the normal mode.For example, a method of limiting switching to motoring need only tighten one condition for switching to motoring compared to that in the normal operating mode.

[0041] On the other hand, if the current SOC is lower than the target maintenance lower limit A (NO in S11), the ECU 1000 executes a second SOC maintenance control to restore the SOC to the target maintenance lower limit A (S13). In the first embodiment, the second SOC maintenance control includes control for limiting the actual discharge power Pout of the electric storage device BAT compared to that in the normal mode, control for increasing the actual charge power Pin of the electric storage device BAT compared to that in the normal mode, and control for prohibiting switching to the motoring operation. Thus, the SOC is consumed more heavily than during the first SOC maintenance control, and the amount of electric power with which the electric storage device BAT is charged is increased, so that SOC recovery is facilitated.For example, a method of increasing the actual charging power Pin only needs to increase at least one of a required charging power and the chargeable power WIN compared to that in the normal operation mode.

[0042] Fig. 3 is a view schematically showing an operation mode of changing the SOC in the SOC maintenance mode. In the illustration of Fig. 3, it is assumed that the user presses the SOC maintenance switch 10 at time t1 to switch to the SOC maintenance mode in preparation for future engine operation.

[0043] In this case, as shown by the alternate long and short dashed line L1, when the SOC at time t1 is higher than the target maintenance lower limit A, the SOC is maintained at a value at time t1 by the first SOC maintenance control. Therefore, at the time of performing motor operation by consuming the SOC thereafter, it is possible to perform motor operation for a longer distance than a distance corresponding to the target maintenance lower limit A (that is, an available travel distance at the time of performing motor operation by consuming the target maintenance lower limit A).

[0044] On the other hand, as indicated by the solid line L2, when the SOC at time t1 is lower than the target maintenance lower limit A, the SOC initially rises (is recovered) from the value at time t1 through the second SOC maintenance control. At time t2, when the SOC is restored to the target maintenance lower limit A, the SOC maintenance control is switched from the second SOC maintenance control to the first SOC maintenance control. Therefore, the SOC is maintained at the target maintenance lower limit A after a time t2. Thus, at the time of performing motor operation, by consuming the SOC thereafter, it is possible to perform motor operation for at least the distance corresponding to the target maintenance lower limit A.

[0045] As described above, in the SOC maintenance mode, the ECU 1000 according to the first embodiment maintains the current SOC through first SOC maintenance control when the current SOC is higher than or equal to a target maintenance lower limit A, whereas the ECU 1000 automatically restores the SOC to the target maintenance lower limit A through the second SOC maintenance control, and then maintains the SOC at the target maintenance lower limit A when the current SOC is lower than the target maintenance lower limit A. Therefore, in the SOC maintenance mode, it is possible to automatically ensure the SOC higher than or equal to the target maintenance lower limit A. Thus, it is possible to avoid a shortage of electric power at the time of future use of the electric power.

[0046] Particularly, in the first embodiment, the user is allowed to arbitrarily select the target maintenance lower limit A. Therefore, the user is allowed to adjust the SOC to be ensured in the SOC maintenance mode based on the amount of electric power (for example, a distance the vehicle is expected to travel in motor operation) predicted to be required after the SOC maintenance mode.

[0047] In the first embodiment, in the SOC maintenance mode, an SOC value for switching between first SOC maintenance control and second SOC maintenance control and an SOC value to be restored by the second SOC maintenance control are set to the same "target maintenance lower limit A"; however, both may be set to different values. For example, one of the first SOC maintenance control and the second SOC maintenance control may be selected based on whether the SOC is higher than the target maintenance lower limit A at the start of the SOC maintenance mode, and then a target restoration value of the SOC at the time the second SOC maintenance control is selected may be set to a value higher or lower than the target maintenance lower limit A.

[0048] Next, a second embodiment will be described. Fig. 4 is an overall block diagram of a vehicle 1A according to the second embodiment. The vehicle 1A additionally includes an SOC recovery switch 20 compared to the vehicle 1 according to the above-described first embodiment. That is, the vehicle 1A according to the second embodiment includes the SOC recovery switch 20 in addition to the SOC maintenance switch 10. The other hardware configuration is the same as that of the above-described first embodiment, so a detailed description will not be repeated here.

[0049] The SOC recovery switch 20 outputs a signal requesting a mode for recovering the SOC (hereinafter referred to as “SOC recovery mode”) in response to a user operation.

[0050] The ECU 1000 switches the SOC control mode to any one of the normal mode, the SOC maintenance mode, and the SOC recovery mode.

[0051] When the SOC maintenance switch 10 is pressed in a mode other than the SOC maintenance mode (the normal mode or the SOC recovery mode), the ECU 1000 switches the SOC control mode to the SOC maintenance mode. On the other hand, when the SOC maintenance switch 10 is pressed in the SOC maintenance mode, the ECU 1000 cancels the SOC maintenance mode and returns the SOC control mode to the normal mode.

[0052] When the SOC recovery switch 20 is pressed in a mode other than the SOC recovery mode (the normal mode or the SOC maintenance mode), the ECU 1000 switches the SOC control mode to the SOC recovery mode. On the other hand, when the SOC recovery switch 20 is pressed in the SOC recovery mode, the ECU 1000 cancels the SOC recovery mode and returns the SOC control mode to the normal mode. Even when the SOC has been restored to a target recovery value B (described below) in the SOC recovery mode, the ECU 1000 cancels the SOC recovery mode and returns the SOC control mode to the normal mode.

[0053] The above-described method of switching the SOC control mode is merely illustrative and is not limited to this configuration. For example, even if the SOC maintenance switch 10 is pressed in the SOC recovery mode, the SOC recovery mode can be maintained by giving priority to the SOC recovery mode. In the case where the SOC control mode has been switched from the SOC maintenance mode to the SOC recovery mode, the SOC control mode can be returned to the original SOC maintenance mode by repeatedly pressing the SOC recovery switch 20.

[0054] In the thus configured vehicle 1A, the ECU 1000 executes control similar to the SOC maintenance control (first SOC maintenance control or second SOC maintenance control) described in the above first embodiment in the SOC maintenance mode. The ECU 1000 executes control for restoring the SOC (hereinafter referred to as "SOC restoration control") in preparation for future use of electric power in the SOC restoration mode.

[0055] Fig. 5 is a flowchart showing the procedure at the time when the ECU 1000 executes SOC maintenance control or SOC recovery control.

[0056] The ECU 1000 determines whether it is in the SOC maintenance mode (S10). If it is in the SOC maintenance mode (YES in S10), the ECU 1000 executes the SOC maintenance control in S11 to S13. The details of the processes from S11 to S13 are the same as the details of the processes from S11 to S13 described in Fig. 2, so a detailed description is not repeated here.

[0057] On the other hand, if it is not in the SOC maintenance mode (NO in S10), the ECU 1000 determines whether it is in the SOC recovery mode (S20). If it is not in the SOC recovery mode (NO in S20), that is, it is in the normal mode, the ECU 1000 ends the process.

[0058] When in the SOC recovery mode (YES in S20), the ECU 1000 determines whether the current SOC is higher than or equal to the target recovery value B (S21). In the present embodiment, the target recovery value B is a fixed value (for example, 70%) higher than the target maintenance lower limit value A. The target recovery value B can be arbitrarily selected within a predetermined range (for example, the range of 60% to 80%) by a user operation of an input device (not shown). In any case, the target recovery value B is set to a value higher than the target maintenance lower limit value A.

[0059] If the current SOC is lower than the target recovery value B (NO in S21), the ECU 1000 executes SOC recovery control to restore the SOC to the target recovery value B (S22). In the second embodiment, the SOC recovery control (the process of S22) differs from the above-described second SOC maintenance control (the process of S13) in the target recovery value of the SOC (see Fig. 6, which will be described below); however, specific details of the process are the same. That is, as the SOC recovery control, the ECU 1000 executes control for limiting the actual discharge power Pout of the electric storage device BAT compared to that in the normal operation mode, control for increasing the actual charge power Pin of the electric storage device BAT compared to that in the normal operation mode, and control for prohibiting switching to a motor operation. The details of the process may be varied between the SOC recovery mode and the second SOC maintenance mode described above.For example, in order to restore the SOC more clearly in the SOC recovery control than in the second SOC maintenance control, the amount of increase in the actual charging power Pin in the SOC recovery control may be set to a value higher than the amount of increase in the actual charging power Pin of the second SOC maintenance control.

[0060] On the other hand, if the current SOC is higher than or equal to the target recovery value B (YES in S21), the ECU 1000 ends the process. The case where the current SOC is higher than the target recovery value B includes both the case where the SOC was already higher than or equal to the target recovery value B at the time of switching to the SOC recovery mode and the case where the SOC was recovered to the target recovery value B in the SOC recovery mode.

[0061] Fig. 6 is a view showing a comparison between the target recovery value B in the SOC recovery mode and the target maintenance lower limit value A in the SOC maintenance mode.

[0062] The SOC recovery mode is a mode for restoring the SOC from the current value, including by consuming fuel of the engine 100 in preparation for future use of the electric power (e.g., motoring). On the other hand, the SOC maintenance mode is basically a mode for maintaining the SOC at the current value. Thus, the purpose of the SOC recovery mode and the SOC maintenance mode are different from each other.

[0063] The target value for SOC recovery in each operating mode is set in conjunction with such a difference in purpose. That is, the target value for SOC recovery in the SOC recovery mode is set to a relatively high "target recovery value B" (for example, 70%). This makes it possible to ensure a sufficient amount of electric power at the time of future electric power use.

[0064] In contrast, in the SOC maintenance mode, the target value for restoring the SOC is the “lower target maintenance limit A” (for example, 40%), which is lower than the target restoration value B. In this way, in the SOC maintenance mode, it is possible to suppress deterioration of fuel economy due to excessive consumption of fuel of the engine 100 for ensuring the SOC while ensuring a required SOC.

[0065] As described above, in the second embodiment, the target value for restoring the SOC in the SOC maintenance mode is set to a value lower than the target value for restoring the SOC in the SOC recovery mode. Thus, it is possible to ensure a sufficient amount of electric power in the SOC recovery mode, and it is possible to suppress excessive engine fuel consumption while ensuring a required SOC in the SOC maintenance mode.

[0066] A first alternative embodiment to the first and second embodiments will be described. In the first and second embodiments described above, at the time of restoring the SOC in the SOC maintenance mode, only regenerative charging (charging the electric storage device BAT with electric power regeneratively generated by the motor generator MG using the kinetic energy of the vehicle) may be permitted while the vehicle is decelerating, and charging (charging the electric storage device BAT with electric power generated by the motor generator MG using the output of the engine 100) may be prohibited at the time of engine output.

[0067] Fig. Fig. 7 is a flowchart showing an example of the procedure of the ECU 1000 in the case where the first alternative embodiment is applied to the above-described first embodiment. The flow additionally includes the process of S13a in the Fig. 2 shown flowchart described in the first embodiment.

[0068] When the ECU 1000 executes a second SOC maintenance control in S13, only regenerative charging during vehicle deceleration is permitted, and charging at the time of engine output is prohibited (S13a).

[0069] In this way, in the SOC maintenance mode, since charging opportunities are limited to the time when the vehicle is decelerating (when the engine output is 0), a time required to restore the SOC to the target maintenance lower limit A is extended, and the SOC is allowed to be restored without consuming fuel of the engine 100.

[0070] In the process of S13a, a charging rate at the time of engine output (the amount of increase in engine output for power generation) may be set to be lower than in the normal operation mode. This also lengthens the time required to restore the SOC to the target maintenance lower limit A; however, an engine load decreases during driving, and thus, it is possible to suppress deterioration in fuel economy.

[0071] A second alternative embodiment to the first and second embodiments will be described. In the above-described first and second embodiments, the case where the invention is applied to the hybrid vehicle in which the engine and the single motor generator are coupled in series with each other is described. A vehicle to which the invention is applicable is not limited to a hybrid vehicle having such a structure.

[0072] As in Fig. 8, the invention is also applicable, for example, to a hybrid vehicle in which an engine and two motor generators MG1, MG2 are coupled through a power split mechanism constituted by a planetary gear unit.

[0073] The embodiments described above are illustrative and not restrictive in any respect. The scope of the invention is defined by the appended claims, rather than by the foregoing description. It is intended that the scope of the invention include all modifications within the scope of the appended claims and equivalents thereof.

Claims

[1] Vehicle, characterized by : a machine (100) configured to generate an output to cause the vehicle to drive; a motor generator (MG) configured to generate an output to cause the vehicle to travel; an electrical storage device (BAT) configured to exchange electrical power with the motor generator (MG); a maintenance switch (10) configured to output a signal requesting a maintenance mode in which a state of charge of the electrical storage device (BAT) is maintained in response to a user operation; and a controller (1000) configured to: (a) causing the vehicle to travel using the output of at least one of the engine (100) and the motor generator (MG); (b) to control the state of charge of the electrical storage device (BAT); (c) when the maintenance mode is requested in response to the signal output from the maintenance switch (10) and when the state of charge is higher than a threshold value, to execute a first maintenance control for maintaining the state of charge at a current value; and (d) when the maintenance mode is requested in response to the signal output from the maintenance switch (10) and when the state of charge is lower than the threshold value, to execute a second maintenance control for restoring the state of charge from a current value, wherein the controller (1000) is configured to enable, as the second maintenance control, regenerative power generation using the motor generator (MG) using kinetic energy of the vehicle and prohibit power generation of the motor generator (MG) using the output of the engine (100). [2] A vehicle according to claim 1, further comprising: a recovery switch (20) configured to output, in response to a user operation, a signal requesting a recovery mode in which the charge state is restored, wherein the controller (1000) is configured to, as the second maintenance control, restore the state of charge to a first target value when the recovery mode is not requested in response to the signal output from the recovery switch (20), and to execute a recovery control for restoring the state of charge to a second target value higher than the first target value when the recovery mode is requested. [3] Vehicle according to claim 2, wherein the first maintenance control comprises a control for limiting a discharge power of the electrical storage device (BAT) compared to that in an operation mode other than the maintenance mode or the recovery mode, the second maintenance control comprises a control for increasing a charging power of the electrical storage device (BAT) while limiting a discharging power of the electrical storage device (BAT) compared to that in an operation mode other than the maintenance mode or the recovery mode until the state of charge is restored to the first target value, and the recovery control comprises a control for increasing a charging power of the electrical storage device (BAT) while limiting a discharging power of the electrical storage device (BAT) compared to that in an operation mode other than the maintenance mode or the recovery mode until the state of charge reaches the second target value. [4] Vehicle according to claim 2, wherein the vehicle is configured to switch between a hybrid mode in which the vehicle travels using the output of both the engine (100) and the motor generator (MG), and a motor mode in which the vehicle travels using the output of the motor generator (MG) while the engine (100) is stopped, the first maintenance control comprises a control for limiting switching to the motor mode compared to an operating mode other than the maintenance mode or the recovery mode, the second maintenance control comprises a control for preventing switching to engine operation until the state of charge is restored to the first target value, and the recovery control includes a control for preventing switching to engine operation until the state of charge reaches the second setpoint. [5] A control method for a vehicle, the vehicle comprising an engine (100), a motor generator (MG), an electrical storage device (BAT), a maintenance switch (10), and a controller (1000), wherein the engine (100) is configured to generate an output to cause the vehicle to travel, the motor generator (MG) is configured to generate an output to cause the vehicle to travel, the electrical storage device (BAT) is configured to exchange electrical power with the motor generator (MG), the maintenance switch (10) is configured to output a signal requesting a maintenance mode in which a state of charge of the electrical storage device (BAT) is maintained in response to a user operation, characterized by that the control method has: Causing, by the controller (1000), the vehicle to travel using the output of at least one of the engine (100) and the motor generator (MG); Controlling, by the controller (1000), the state of charge of the electrical storage device (BAT); Executing, by the controller (1000), a first maintenance control for maintaining the state of charge at a current value when the maintenance mode is requested in response to the signal output by the maintenance switch (10) and when the state of charge is higher than a threshold value; and Executing, by the controller (1000), a second maintenance control for restoring the state of charge from a current value when the maintenance mode is requested in response to the signal output by the maintenance switch (10) and when the state of charge is lower than a threshold value, wherein, as the second maintenance control, regenerative power generation using the motor generator (MG) is enabled by the controller (100) using kinetic energy of the vehicle and power generation of the motor generator (MG) is prohibited using the output of the engine (100). [6] Control method according to claim 5, wherein the vehicle comprises a recovery switch (20) configured to output, in response to a user operation, a signal requesting a recovery mode in which a state of charge is restored, and as the second maintenance control, the state of charge is restored to a first target value by the controller (1000) when the recovery mode is not requested in response to the signal output by the recovery switch (20), wherein the control method further comprises: Executing, by the controller (1000), a recovery control for restoring the state of charge to a second setpoint higher than the first setpoint when the recovery mode is requested. [7] Control method according to claim 6, wherein the first maintenance control comprises a control for limiting a discharge power of the electrical storage device (BAT) compared to that in an operation mode other than the maintenance mode or the recovery mode by the controller (1000), the second maintenance control comprises a control for increasing a charging power of the electrical storage device (BAT) while limiting a discharging power of the electrical storage device (BAT) compared to that in an operation mode other than the maintenance mode or the recovery mode until the state of charge is restored to the first target value, by the controller (1000), and the recovery control comprises a control for increasing a charging power of the electrical storage device (BAT) while limiting a discharging power of the electrical storage device (BAT) compared to that in an operation mode other than the maintenance mode or the recovery mode until the state of charge reaches the second target value, by the controller (1000). [8] Control method according to claim 6, wherein the vehicle is capable of switching between a hybrid mode in which the vehicle travels using the output of both the engine (100) and the motor generator (MG), and a motor mode in which the vehicle travels using the output of the motor generator (MG) while the engine (100) is stopped, the first maintenance control comprises a control for limiting switching to the motor operation compared to an operation mode other than the maintenance mode or the recovery mode, by the controller (1000), the second maintenance control comprises a control for preventing switching to the engine operation until the state of charge is restored to the first target value by the controller (1000), and the recovery control comprises a control for preventing a switch to the engine operation until the state of charge reaches the second target value by the controller (1000).

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