Hybrid vehicle control device and method

Abstract

To prevent noise or vibration from becoming apparent in a hybrid vehicle when a battery charging is restricted in a low temperature environment.SOLUTION: A control apparatus of a hybrid vehicle is for controlling the hybrid vehicle that includes an engine, an electric motor capable of generating electricity using at least part of power from the engine, and a battery rechargeable by the power from the electric motor. The control apparatus performs: setting target power of the engine on the basis of power required for the hybrid vehicle to travel and target charging power of the battery; setting, as a target revolution speed of the engine, a larger value of a required revolution speed of the engine in accordance with the target power and a lower limit revolution speed of the engine; and setting, in a case where the target charging power is limited to a small value, with a state in which the required revolution speed is less than the lower limit revolution speed having continued for a given period of time, the target revolution speed so that the revolution speed of the engine falls into a variation range of the required revolution speed within the aforementioned given period of time.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to a control device and method for a hybrid vehicle that includes an engine, an electric motor capable of generating electricity using at least a portion of the power from the engine, and a battery that can be charged with the electricity generated by the electric motor. [Background technology]

[0002] Conventionally, a hybrid vehicle control device is known that calculates a vehicle required power as the sum of a first required power for bringing the SOC of a battery, including a lithium-ion secondary battery, closer to a target value and a second required power necessary for running the hybrid vehicle, and allocates power between the engine and the motor generator based on the battery's input / output permitted power values (see, for example, Patent Document 1). This control device changes the input / output permitted power values based on a history of charging / discharging current to the battery to suppress lithium deposition in the negative electrode of the lithium-ion secondary battery, and also changes the first required power based on the history of the charging / discharging current. More specifically, when the magnitude of the charging current to the battery is smaller than a charging threshold, the input permitted power value is set to a first standard value. When the magnitude of the charging current to the battery is greater than the charging threshold, the input permitted power value is limited to a value lower than the first standard value. Furthermore, when the difference between the magnitude of the charging current to the battery and the charging threshold becomes smaller than a predetermined value, the battery's upper charging limit value is further limited, and the first required power is set to a lower value as the charging power. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-071622 Summary of the Invention [Problem to be solved by the invention]

[0004] In the conventional hybrid vehicle described above, when there is a risk of lithium deposition, the input / output permitted power value increases or decreases according to the magnitude of the charging current, and the first required power fluctuates, and accordingly the vehicle required power also fluctuates. Then, the power commanded to the engine and the motor generator increases or decreases according to the fluctuation in the vehicle required power, so the rotation speeds of the engine and the motor generator increase or decrease in a short cycle, which may result in noticeable noise and vibration.

[0005] Therefore, the present disclosure suppresses noise and vibration from becoming apparent in a hybrid vehicle when charging of a battery with electric power from an electric motor that generates electricity using power from an engine is restricted. [Means for solving the problem]

[0006] The control device for a hybrid vehicle disclosed herein is a control device for a hybrid vehicle that includes an engine, an electric motor capable of generating electricity using at least a portion of the power from the engine, and a battery that can be charged with power from the electric motor, and includes: a target power setting unit that sets a target power for the engine based on the power required for running the hybrid vehicle and a target charging power for the battery; and a target rotation speed setting unit that sets the target rotation speed of the engine to the larger of a required rotation speed of the engine corresponding to the target power and a lower limit rotation speed, and sets the target rotation speed so that the engine rotation speed will be a value within a fluctuation range of the required rotation speed within the specified time when the target charging power is limited to a small value and the required rotation speed remains below the lower limit rotation speed for a specified time.

[0007] In addition, the control method for a hybrid vehicle disclosed herein is a control method for a hybrid vehicle that includes an engine, an electric motor capable of generating electricity using at least a portion of the power from the engine, and a battery that can be charged with power from the electric motor, and includes setting a target power for the engine based on the power required for running the hybrid vehicle and a target charging power for the battery, setting the target rotation speed of the engine to the larger of the required rotation speed of the engine corresponding to the target power and a lower limit rotation speed, and setting the target rotation speed so that the rotation speed of the engine becomes a value within a fluctuation range of the required rotation speed within the specified time when the target charging power is limited to a small value and the required rotation speed remains below the lower limit rotation speed for a specified time.

[0008] According to the hybrid vehicle control device and method disclosed herein, it is possible to effectively suppress the occurrence of noise and vibration in a hybrid vehicle when battery charging using electric power from an electric motor that generates electricity using power from the engine is restricted. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic configuration diagram showing a hybrid vehicle controlled by a control device of the present disclosure. [Figure 2] 2 is a flowchart showing a routine executed by a control device of the present disclosure when the engine of the hybrid vehicle of FIG. 1 is operated under load. [Figure 3] 3 is a flowchart showing a series of processes in step S50 of FIG. 2. [Figure 4] 3 is a time chart showing the time variation of the target engine speed and the like while the routine of FIG. 2 is executed by the control device of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0010] Next, embodiments of the present disclosure will be described with reference to the drawings.

[0011] 1 is a schematic diagram showing a hybrid vehicle (HEV) 1 controlled by a control device of the present disclosure. The hybrid vehicle 1 shown in the figure includes an engine 2, a single-pinion planetary gear 3 as a power distribution mechanism, a gear train 4, motor generators MG1 and MG2, both of which are synchronous generator motors (three-phase AC motors), a battery (electricity storage device) 5, a power control device (hereinafter referred to as "PCU") 6 connected to the battery 5 and driving the motor generators MG1 and MG2, and a hybrid electronic control unit (hereinafter referred to as "HVECU") 100 as a control device of the present disclosure that controls the entire vehicle.

[0012] The engine 2 of the hybrid vehicle 1 is an internal combustion engine that converts the reciprocating motion of pistons (not shown) that accompanies the combustion of a mixture of hydrocarbon fuel (gasoline) and air in multiple combustion chambers into the rotational motion of a crankshaft (output shaft) CS. However, the engine 2 is not limited to a gasoline engine, and may be an LPG engine or a diesel engine.

[0013] The engine 2 is controlled by an engine electronic control unit (hereinafter referred to as "engine ECU") 200. The engine ECU 200 includes a microcomputer having a CPU, ROM, RAM, input / output interfaces, etc., not shown, as well as various drive circuits and various logic ICs. The engine ECU 200 calculates the rotation speed Ne of the engine 2 (crankshaft CS) based on the crank position from a crank angle sensor not shown, and calculates a load factor KL based on the intake air amount from an air flow meter not shown and the engine 2 rotation speed Ne. The engine ECU 200 controls the intake air amount, fuel injection amount, ignition timing, etc. of the engine 2 based on a command signal from the HVECU 100, the rotation speed Ne, the load factor KL, etc.

[0014] The planetary gear 3 is a differential rotation mechanism including a sun gear 3s, a ring gear 3r, and a planetary carrier 3c that rotatably supports a plurality of pinion gears 3p. As shown in Fig. 1, the sun gear 3s is connected to the rotor of the motor generator MG1, and the planetary carrier 3c is connected to the crankshaft CS of the engine 2 via a damper mechanism DD. The ring gear 3r, which serves as an output element, rotates coaxially and integrally with the counter drive gear 4a (output member) of the gear train 4.

[0015] In addition to the counter drive gear 4a, the gear train 4 includes a counter driven gear 4b and a final drive gear (drive pinion gear) 4c. The final drive gear 4c meshes with a differential ring gear Dr of the differential gear DF and is connected to left and right wheels (drive wheels) W via the differential gear DF and drive shafts DS. As a result, the planetary gear 3, the gear train 4, and the differential gear DF form a transaxle that transmits a portion of the output torque of the engine 2, which serves as a power generation source, to the wheels W and connects the engine 2 and the motor generator MG1 to each other.

[0016] Motor generator MG1 is mainly driven by engine 2 operating under load, and operates as a generator that converts at least a portion of the power from engine 2 into electric power. Motor generator MG2 is connected to left and right wheels W via a differential gear DF including a drive gear 4d, a counter driven gear 4b, a final drive gear 4c, and a differential ring gear Dr, and via a drive shaft DS. Motor generator MG2 is mainly driven by at least one of the electric power from battery 5 and the electric power from motor generator MG1, and operates as an electric motor that generates a drive torque on drive shaft DS.

[0017] In this embodiment, the battery 5 is a lithium ion secondary battery. The battery 5 is managed by a battery management electronic control unit (hereinafter referred to as "battery ECU") 500, which includes a microcomputer having a CPU (not shown). The battery ECU 500 acquires the terminal voltage VB of the battery 5 detected by a voltage sensor (not shown), the charge / discharge current IB of the battery 5 detected by a current sensor (not shown), the temperature Tb of the battery 5 detected by a battery temperature sensor (not shown), etc.

[0018] The battery ECU 500, which serves as a battery management unit, calculates an integrated value of the charge / discharge current IB and calculates the SOC of the battery 5 based on the integrated value. The battery ECU 500 also calculates an allowable charging power Win (negative value) that is the power allowable for charging the battery 5 and an allowable discharging power Wout (positive value) that is the power allowable for discharging the battery 5 based on the SOC and temperature Tb of the battery 5. In this embodiment, the allowable charging power Win of the battery 5 is set by multiplying a charging base value corresponding to the temperature Tb of the battery 5 by a correction coefficient corresponding to the SOC, so that the lower the temperature Tb and the higher the SOC, the smaller the charging power (the smaller the absolute value). The allowable discharging power Wout is set by multiplying a discharging base value corresponding to the temperature Tb by a correction coefficient corresponding to the SOC. Furthermore, the battery ECU 500 calculates a target charging / discharging power Pb* of the battery 5 (here, the discharging side is positive and the charging side is negative) to be a value within the range from the allowable charging power Win to the allowable discharging power Wout based on the SOC, etc.

[0019] Additionally, in order to protect the battery 5, the battery ECU 500 sets a charging power limit value IWin (negative value) based on the state of charge of the battery 5 in accordance with a well-known method to suppress lithium deposition at the negative electrode of the battery 5 (lithium ion secondary battery). When the allowable charging power Win based on the SOC and temperature Tb is less than the charging power limit value IWin based on the state of charge, the battery ECU 500 sets the charging power limit value IWin to the allowable charging power Win. The charging power limit value IWin is calculated by correcting the allowable charging power Win so that the absolute value of the charging / discharging current (charging current) IB of the battery 5 does not exceed the absolute value of the allowable charging current, which is the maximum current that does not cause lithium deposition at the negative electrode. The allowable charging current is calculated based on the charging / discharging current IB, temperature Tb, and SOC so that its absolute value decreases according to the duration of charging and increases according to the duration of discharging. When the charging power limit value IWin is set to the allowable charging power Win, the target charging / discharging power Pb* of the battery 5 is set (limited) to be equal to or greater than the charging power limit value IWin (so that its absolute value is small).

[0020] The PCU 6 includes a first inverter that drives the motor generator MG1, a second inverter that drives the motor generator MG2, a boost converter that can boost the power from the battery 5 and reduce the power from the motor generators MG1 and MG2 (all of which are not shown), etc. The PCU 6 is controlled by a motor electronic control unit (hereinafter referred to as "MGECU") 600 that includes a microcomputer having a CPU and the like (not shown).

[0021] The HVECU 100 includes a microcomputer having a CPU, ROM, RAM, input / output interfaces, etc. (not shown), various drive circuits, various logic ICs, etc. The HVECU 100 acquires the vehicle speed V detected by a vehicle speed sensor (not shown), the accelerator pedal opening Acc indicating the amount of depression of the accelerator pedal detected by an accelerator pedal position sensor (not shown), the shift position SP of the shift lever (not shown) detected by a shift position sensor (not shown), etc. Furthermore, the HVECU 100 exchanges information with the ECUs 200, 500, 600, a brake electronic control unit (not shown) that controls a hydraulic brake actuator (not shown), etc., and comprehensively controls the hybrid vehicle 1 based on the vehicle speed V, the accelerator pedal opening Acc, and signals from the ECUs 200, 500, 600, etc.

[0022] 2 is a flowchart showing an example of a drive control routine that is repeatedly executed by the HVECU 100 at a predetermined execution period when the engine 2 is operated under load. When the timing for executing the drive control routine of FIG. 2 arrives, the HVECU 100 (CPU) acquires data necessary for control (step S10). In step S10, the HVECU 100 acquires the accelerator opening Acc, the vehicle speed V, the rotation speeds Nm1 and Nm2 of the motor generators MG1 and MG2 from the MGECU 600, the temperature Tb of the battery 5 from the battery ECU 500, the target charge / discharge power Pb*, the allowable charge power Win, the allowable discharge power Wout, and the charge power limit value IWin.

[0023] Next, the HVECU 100 derives a required torque Tr* to be output to the drive shaft DS corresponding to the accelerator opening Acc and vehicle speed V acquired in step S10 from a required torque setting map (not shown) (step S20). Furthermore, the HVECU 100 calculates a required running power Pd* (= Tr* × Nds) required for running the hybrid vehicle 1 based on the required torque Tr* and the rotation speed Nds of the drive shaft DS, and sets a target power Pe* (= Pd* - Pb* + loss) to be output to the engine 2 based on the required running power Pd* and the target charge / discharge power Pb* acquired in step S10, etc. (step S30).

[0024] Furthermore, the HVECU 100 determines whether the target charge / discharge power Pb* is a negative value, i.e., whether charging of the battery 5 is required (step S40). If the target charge / discharge power Pb* is equal to or greater than zero and charging of the battery 5 is not required (step S40: NO), the HVECU 100 derives a required rotation speed Nrq required of the engine 2 to improve efficiency corresponding to the target power Pe* from a predetermined operation line (optimum fuel efficiency line) (step S45). Furthermore, in step S45, the HVECU 100 sets the target rotation speed Ne* of the engine 2 to the larger of the required rotation speed Nrq or a lower limit rotation speed Nlim of the engine 2 that is set depending on, for example, the running state of the hybrid vehicle 1. The operation line is created in advance based on so-called fuel consumption rate contour lines so as to operate the engine 2 efficiently. Furthermore, if the target charge / discharge power Pb* is a negative value and charging of the battery 5 is requested (step S40: YES), the HVECU 100 executes a series of processes shown in FIG. 3 to set the target rotation speed Ne* of the engine 2 (step S50).

[0025] After the processing of step S40 or S50, the HVECU 100 sets torque commands Tm1*, Tm2* for the motor generators MG1, MG2 according to the required torque Tr*, target rotation speed Ne*, etc. within the ranges of the allowable charging power Win and allowable discharging power Wout of the battery 5 acquired in step S10 (step S60). Then, the HVECU 100 transmits the target power Pe* and the target rotation speed Ne* to the engine ECU 200, and transmits the torque commands Tm1*, Tm2* to the MGECU 600 (step S70).

[0026] Engine ECU 200 controls the intake air amount, fuel injection amount, ignition timing, etc. of engine 2 based on target rotation speed Ne*, target power Pe*, and target torque Te* (=Pe* / Ne*) corresponding to target rotation speed Ne*. As a result, engine 2 is controlled so that rotation speed Ne becomes target rotation speed Ne* and so that engine 2 outputs torque corresponding to target torque Te*. MGECU 600 also controls the switching of first and second inverters and the boost converter based on torque commands Tm1* and Tm2*. When engine 2 is operated under load, motor generators MG1 and MG2 are controlled to convert part (when battery 5 is charging) or all (when battery 5 is discharging) of the power output from engine 2 to torque together with planetary gear 3 and output the converted power to drive shaft DS.

[0027] Next, with reference to FIGS. 3 and 4, a procedure for setting the target rotation speed Ne* when the target charge / discharge power Pb* has a negative value and charging of the battery 5 is required will be described.

[0028] 3, if the target charge / discharge power Pb* is a negative value (step S40: YES), the HVECU 100 derives the required rotation speed Nrq of the engine 2 corresponding to the target power Pe* from the above-mentioned operation line (optimum fuel efficiency line) (step S500). Furthermore, the HVECU 100 determines whether the target charge / discharge power Pb* is limited to a small value as charging power by the battery ECU 500 as a battery management unit (step S502). More specifically, in step S502, the HVECU 100 determines whether the temperature Tb of the battery 5 acquired in step S10 is equal to or lower than a predetermined temperature T0 (for example, a temperature around −10° C.) and whether the allowable charging power Win acquired in step S10 is limited by a charging power limit value IWin. If the temperature Tb of the battery 5 is equal to or lower than the predetermined temperature T0 and the allowable charging power Win matches the charging power limit value IWin, the HVECU 100 determines that the hybrid vehicle 1 is in a low-temperature environment where lithium deposition may occur and that the target charging / discharging power Pb* is being limited to a small value as charging power by the battery ECU 500 (step S502: YES), and sets the charging limit flag Fchlim to "1" (step S504).

[0029] Next, the HVECU 100 determines whether or not flag F is "0" (step S506), and if flag F is "0" (step S506: YES), determines whether or not the required rotation speed Nrq derived in step S500 is less than the lower limit rotation speed Nlim of the engine 2 (step S508). If the required rotation speed Nrq is equal to or greater than the lower limit rotation speed Nlim (step S508: NO), the HVECU 100 sets the required rotation speed Nrq derived in step S500 to the lower limit rotation speed Nlim of the engine 2 (step S509). Furthermore, the HVECU 100 sets the target rotation speed Ne* of the engine 2 to the larger of the required rotation speed Nrq derived in step S500 or the lower limit rotation speed Nlim set in step S509 (step S520), and executes the processing from step S60 onwards. When the required rotation speed Nrq is set to the lower limit rotation speed Nlim in step S509, the required rotation speed Nrq is set to the target rotation speed Ne* of the engine 2.

[0030] On the other hand, if the required rotation speed Nrq derived in step S500 is less than the lower limit rotation speed Nlim (step S508: YES), the HVECU 100 increments a counter C (step S510) and then determines whether the counter C is equal to or greater than a predetermined threshold value Cref (step S512). The counter C indicates the elapsed time since it was determined in step S508 that the required rotation speed Nrq is less than the lower limit rotation speed Nlim. The threshold value Cref used in step S512 is an integer obtained by dividing a time tref (predetermined time) selected from the range of 1 to 5 seconds, for example, by the execution period of the routine in FIG. 2.

[0031] If the counter C is less than the threshold value Cref and the time tref has not elapsed since the requested rotation speed Nrq became less than the lower limit rotation speed Nlim (step S512: NO), the HVECU 100 stores the peak rotation speed Np, which is the peak value of the requested rotation speed Nrq derived in step S500, in the RAM (step S513). That is, in step S513, if the requested rotation speed Nrq derived in step S500 is equal to or greater than the previous value obtained when the routine of FIG. 2 was last executed, the HVECU 100 stores the requested rotation speed Nrq in the RAM as the peak rotation speed Np. Also, in step S513, if the requested rotation speed Nrq derived in step S500 is less than the previous value, the HVECU 100 holds the peak rotation speed Np at the previous value. Furthermore, the HVECU 100 holds (sets) the lower limit rotation speed Nlim to the previous value at the previous execution of the routine of FIG. 2 (step S515), and then sets the target rotation speed Ne* of the engine 2 to the larger of the required rotation speed Nrq derived in step S500 and the lower limit rotation speed Nlim held in step S515 (step S520), and executes the processing from step S60 onwards.

[0032] Furthermore, if the counter C is equal to or greater than the threshold value Cref and the time tref has elapsed since the requested rotation speed Nrq became less than the lower limit rotation speed Nlim (step S512: YES), the HVECU 100 sets the flag F to "1" and resets the counter C (step S514), and determines whether the lower limit rotation speed Nlim is greater than the peak rotation speed Np stored (acquired) in step S513 (step S516). If the lower limit rotation speed Nlim is greater than the peak rotation speed Np (step S516: YES), the HVECU 100 sets the current lower limit rotation speed Nlim to a value obtained by subtracting the previously adapted rate value ΔN from the lower limit rotation speed Nlim at the previous execution of the routine of FIG. 2 (step S518). Furthermore, the HVECU 100 sets the target rotation speed Ne* of the engine 2 to the larger of the required rotation speed Nrq derived in step S500 or the lower limit rotation speed Nlim set in step S518 (step S520), and executes the processes from step S60 onwards.

[0033] 2 is executed after flag F is set to "1" in step S514, a negative determination is made in step S506, and the processing from step S516 onward is executed. As a result, the lower limit rotation speed Nlim is set so as to gradually decrease. Furthermore, when the lower limit rotation speed Nlim becomes equal to or less than the peak rotation speed Np (step S516: NO), the HVECU 100 sets flag F to "0" and sets the peak rotation speed Np to the lower limit rotation speed Nlim (step S519). In this case as well, the HVECU 100 sets the target rotation speed Ne* of the engine 2 to the larger of the required rotation speed Nrq derived in step S500 or the lower limit rotation speed Nlim set in step S519 (step S520), and executes the processing from step S60 onward.

[0034] On the other hand, if the temperature Tb of the battery 5 acquired in step S10 is higher than the predetermined temperature T0, or if the allowable charging power Win acquired in step S10 is greater than the charging power limit value IWin (step S502: NO), the HVECU 100 sets the charging limit flag Fchlim to “0” (step S503) and sets the lower limit rotation speed Nlim of the engine 2 to a value corresponding to the running state, etc., of the hybrid vehicle 1 (step S505). In step S505, if the lower limit rotation speed Nlim does not match the value corresponding to the running state, etc., of the hybrid vehicle 1, the HVECU 100 gradually changes the lower limit rotation speed Nlim to a value corresponding to the running state, etc., of the hybrid vehicle 1 using a rate value adapted in advance. Then, the HVECU 100 sets the target rotation speed Ne* of the engine 2 to the larger of the required rotation speed Nrq derived in step S500 or the lower limit rotation speed Nlim set in step S505 (step S520), and executes the processing from step S60 onwards.

[0035] 2, i.e., the series of processes in step S50 shown in FIG. 3, is executed, and as a result, in the hybrid vehicle 1, the target power Pe* of the engine 2 is set based on the required traveling power Pd* required for traveling of the hybrid vehicle 1 and the target charge / discharge power Pb* of the battery 5 (step S30). Furthermore, the target rotation speed Ne* of the engine 2 is set to the larger of the required rotation speed Nrq of the engine 2 corresponding to the target power Pe* and the lower limit rotation speed Nlim (steps S45, S50). Furthermore, if the target charge / discharge power Pb* is limited to a small value as charging power in a low-temperature environment (step S502: YES) and the required rotation speed Nrq corresponding to the target power Pe* is equal to or greater than the lower limit rotation speed Nlim of the engine 2 (step S508: NO), the required rotation speed Nrq is set to the lower limit rotation speed Nlim (step S509). When the required rotation speed Nrq is set to the lower limit rotation speed Nlim in step S509, the required rotation speed Nrq is set to the target rotation speed Ne* of the engine 2 (see times t0 to t1 and t6 to t7 in FIG. 4).

[0036] Furthermore, if the target charge / discharge power Pb* is limited to a small value as charging power in a low-temperature environment (step S502: YES), and the required rotation speed Nrq corresponding to the target power Pe* is less than the lower limit rotation speed Nlim (step S508: YES), the lower limit rotation speed Nlim is maintained (step S515) until a time tref (a predetermined time) has elapsed since the required rotation speed Nrq became less than the lower limit rotation speed Nlim. While the lower limit rotation speed Nlim is maintained in step S515, the lower limit rotation speed Nlim is set to the target rotation speed Ne* of the engine 2 (see times t1 to t2, t3 to t4, and t5 to t6 in FIG. 4).

[0037] Furthermore, if the target charge / discharge power Pb* is limited to a small value as charging power in a low-temperature environment (step S502: YES), and a time tref (predetermined time) has elapsed since the required rotation speed Nrq became less than the lower limit rotation speed Nlim (step S512: YES), the lower limit rotation speed Nlim is set so as to gradually change according to the rate value ΔN to the peak rotation speed Np, which is a value within the fluctuation range of the required rotation speed Nrq within the time tref (steps S518 and S519). If the required rotation speed Nrq remains low while the lower limit rotation speed Nlim is set in steps S518 and S519, the lower limit rotation speed Nlim set in step S518 or S519 is set as the target rotation speed Ne* of the engine 2 (see times t2 to t3 and times t4 to t5 in FIG. 4).

[0038] That is, when the target charge / discharge power Pb* is limited to a small value as charging power in a low-temperature environment and the required rotational speed Nrq remains below the lower limit rotational speed Nlim for the time tref (step S512: YES), the HVECU 100 of the hybrid vehicle 1 sets the target rotational speed Ne* of the engine 2 to the peak rotational speed Np within the fluctuation range of the required rotational speed Nrq within the time tref (steps S518-S520). This prevents the rotational speed Ne of the engine 2 from remaining high or from fluctuating in a short period of time when the target charge / discharge power Pb* is limited to a small value as charging power (small absolute value) to protect the battery 5 by suppressing lithium deposition in a low-temperature environment. As a result, it is possible to effectively prevent noise and vibration from becoming apparent in the hybrid vehicle 1 when charging of the battery 5 with electric power from the motor generator MG1, which generates power using power from the engine 2, is limited in a low-temperature environment.

[0039] Furthermore, when the target charge / discharge power Pb* is limited to a small value as charging power in a low-temperature environment (S502: YES) and the required rotation speed Nrq remains below the lower limit rotation speed Nlim for the time tref (step S512: YES), the HVECU 100 sets the target rotation speed Ne* so that the rotation speed Ne of the engine 2 changes gradually to the peak rotation speed Np within the fluctuation range of the required rotation speed Nrq within the time tref (steps S518-S520). This makes it possible to effectively prevent the fluctuation in the rotation speed of the engine 2 from causing discomfort to the occupants of the hybrid vehicle 1.

[0040] Furthermore, in the above embodiment, the peak rotation speed Np is the maximum value (maximum rotation speed) within the fluctuation range of the required rotation speed Nrq within the time tref, more specifically, the maximum of the extreme values occurring within that fluctuation range. This makes it possible to suppress an increase in the fluctuation range of the rotation speed Ne of the engine 2 that accompanies a change in the lower limit rotation speed Nlim, thereby effectively suppressing the occurrence of noise and vibration. However, in steps S518-S520, the lower limit rotation speed Nlim (target rotation speed Ne*) may be set so as to gradually change to a value other than the peak rotation speed Np within the above fluctuation range, such as the average value of the required rotation speed Nrq within the time tref.

[0041] Furthermore, the HVECU 100 sets the required rotation speed Nrq based on the target power Pe* so that the engine 2 operates efficiently (step S500), and when the target charge / discharge power Pb* is limited to a small value as charging power in a low-temperature environment (step S502: YES) and the required rotation speed Nrq is equal to or greater than the lower-limit rotation speed Nlim, sets the required rotation speed Nrq to the lower-limit rotation speed Nlim (step S509). This prevents the target rotation speed Ne* from being limited more than necessary when the target charge / discharge power Pb* is limited to a small value as charging power to protect the battery 5 in a low-temperature environment, thereby making it possible to suppress a decrease in the efficiency of the engine 2.

[0042] Furthermore, when the target charge / discharge power Pb* is a negative value and charging of the battery 5 is requested (step S40: YES), the HVECU 100 determines whether the target charge / discharge power Pb* is limited to a small value as charge power based on the temperature Tb of the battery 5, the allowable charge power Win based on the SOC and temperature Tb, and the charge power limit value IWin based on the state of charge (step S502). This makes it possible to properly determine whether the target charge / discharge power Pb* is limited to a small value as charge power in a low-temperature environment.

[0043] Furthermore, in the hybrid vehicle 1, the charge power limit value IWin is set to suppress lithium deposition in the negative electrode of the battery 5. By applying the HVECU 100 to the hybrid vehicle 1 including such a battery 5, it is possible to effectively protect the battery 5 by effectively suppressing lithium deposition caused by deterioration due to continued charging while suppressing the emergence of noise and vibration in the hybrid vehicle 1. However, the battery 5 may be a nickel-metal hydride secondary battery or the like other than a lithium-ion secondary battery. If the battery 5 is a secondary battery other than a lithium-ion secondary battery, it may be determined in step S502 whether the target charge / discharge power Pb* is limited to a small value as charge power due to a requirement other than the charge power limit value IWin.

[0044] Furthermore, in steps S518 and S505 of FIG. 3, the lower limit rotation speed Nlim may be slowly changed by a slow-change process other than a rate process using a rate value ΔN or the like. It goes without saying that the HVECU 100 that executes the processes of FIGS. 2 and 3 may be applied to hybrid vehicles other than the hybrid vehicle 1 described above, which includes the motor generators MG1 and MG2 and the planetary gear 3. That is, the hybrid vehicle to which the HVECU 100 is applied may be a one-motor hybrid vehicle or a two-motor hybrid vehicle that does not include the planetary gear 3, or may be a series hybrid vehicle, as long as it includes an electric motor (motor generator) mechanically coupled to the crankshaft of the engine. Furthermore, in the hybrid vehicle 1, a stepped transmission may be interposed between the ring gear 3r, which is the output element of the planetary gear 3, and the differential gear DF, instead of the gear train 4. The hybrid vehicle to which the HVECU 100 and the like are applied may be a plug-in hybrid vehicle (PHEV).

[0045] As described above, the control device for a hybrid vehicle according to the present disclosure is a control device (100) for a hybrid vehicle (1) including an engine (2), an electric motor (MG1) capable of generating electricity using at least a part of the power from the engine (2), and a battery (5) capable of being charged with the power from the electric motor (MG1), the control device (100) for a hybrid vehicle (1) includes a target power setting unit (S30) that sets a target power (Pe*) for the engine (2) based on a power (Pd*) required for running the hybrid vehicle (1) and a target charging power (Pb*) for the battery (5), and a required rotation speed (Nrq) and a lower limit rotation speed (Nrq) of the engine (2) according to the target power (Pe*). and a target rotation speed setting unit (S50, S500-S520) that sets the target rotation speed (Ne*) of the engine (2) to the larger of the target charging power (Pb*) and the lower limit rotation speed (Nlim) (S45, S50, S500), and that sets the target rotation speed (Ne*) of the engine (2) to a value (Np) within a fluctuation range of the required rotation speed (Nrq) within the predetermined time (tref) when the target charging power (Pb*) is limited to a small value (S502: YES) and the required rotation speed (Nrq) remains below the lower limit rotation speed (Nlim) for the predetermined time (tref) (S508: YES, S512: YES).

[0046] The control device for a hybrid vehicle disclosed herein sets a target engine power based on the power required for running the hybrid vehicle and a target charging power for the battery, and sets the target engine speed to the larger of the required engine speed corresponding to the target power or a lower limit rotational speed. Furthermore, when the target charging power is limited to a low value and the required engine speed remains below the lower limit rotational speed for a predetermined period of time, the control device sets the target engine speed so that the engine speed falls within a range of fluctuations in the required engine speed within the predetermined period of time. This prevents the engine speed from remaining high or from fluctuating in a short period of time when the target charging power is limited to a low value (i.e., the absolute value is reduced) to protect the battery, thereby reducing the engine target power. As a result, the control device for a hybrid vehicle disclosed herein effectively prevents noise and vibration from becoming apparent in the hybrid vehicle when battery charging using electric power from an electric motor that generates electricity using power from the engine is limited.

[0047] Furthermore, the target rotation speed setting unit (S50) may set the target rotation speed (Ne*) (S518-S20) such that the rotation speed (Ne) of the engine (2) gradually changes to the value (Np) within the fluctuation range when the target charging power (Pb*) is limited to a small value (S502: YES) and the required rotation speed (Nrq) continues to be less than the lower limit rotation speed (Nlim) for the predetermined time (tref) (S508: YES, S512: YES).

[0048] This makes it possible to prevent the passengers of the hybrid vehicle from feeling uncomfortable due to fluctuations in engine speed.

[0049] Furthermore, the target rotation speed setting unit (S50) may set the target rotation speed (Ne*) (S518-S20) so that the rotation speed (Ne) of the engine (2) becomes the maximum value (Np) within the fluctuation range when the target charging power (Pb*) is limited to a small value (S502: YES) and the state in which the requested rotation speed (Nrq) is less than the lower limit rotation speed (Nlim) continues for the predetermined time (tref) (S508: YES, S512: YES).

[0050] This makes it possible to suppress an increase in the range of fluctuation in the engine speed that accompanies a change in the lower limit speed, thereby effectively suppressing the emergence of noise and vibration.

[0051] The target rotation speed setting unit (S50) may set the required rotation speed (Nrq) based on the target power (Pe*) so that the engine (2) operates efficiently (S500), and may set the required rotation speed (Nrq) to the lower limit rotation speed (Nlim) when the target charging power (Pb*) is limited to a small value (S502: YES) and the required rotation speed (Nrq) is equal to or greater than the lower limit rotation speed (Nlim) (S508: NO).

[0052] This makes it possible to prevent a decrease in engine efficiency by preventing the target rotation speed from being restricted more than necessary when the target charging power is restricted to a small value to protect the battery, etc.

[0053] Furthermore, the control device may include a battery management unit (500) that sets an allowable charging power (Win) of the battery (5) based on the SOC and temperature (Tb) of the battery (5) and sets a charging power limit value (IWin) of the battery (5) based on the state of charge of the battery (5), and the battery management unit (500) may set the charging power limit value (IWin) to the allowable charging power (Win) and limit the target charging power (Pb*) to a low value when the allowable charging power (Win) is less than the charging power limit value (IWin), and the target rotation speed setting unit (S50) may determine whether the target charging power (Pb*) is limited to a low value based on the temperature (Tb) of the battery (5), the allowable charging power (Win), and the charging power limit value (IWin) when charging of the battery (5) is requested (step S502).

[0054] This makes it possible to properly determine whether the target charging power is limited to a small value in a low-temperature environment.

[0055] The battery (5) may be a lithium-ion secondary battery, and the charging power limit value (IWin) may be set to suppress lithium deposition in the negative electrode of the battery (5). By applying the control device of the present disclosure to a hybrid vehicle including such a battery, it is possible to suppress the deposition of lithium caused by deterioration due to continued charging while suppressing the occurrence of noise and vibration in the hybrid vehicle, thereby effectively protecting the battery. However, the control device of the present disclosure may also be applied to a hybrid vehicle including a battery other than a lithium-ion secondary battery, such as a nickel-metal hydride secondary battery.

[0056] A control method for a hybrid vehicle according to the present disclosure is a control method for a hybrid vehicle (1) including an engine (2), an electric motor (MG1) capable of generating electricity using at least a part of the power from the engine (2), and a battery (5) capable of being charged with the power from the electric motor (MG1), the control method comprising: setting a target power (Pe*) of the engine (2) based on a power (Pd*) required for running the hybrid vehicle (1) and a target charging power (Pb*) of the battery (5); and setting a required rotation speed (Nrq) and a lower limit rotation speed (Nrq) of the engine (2) according to the target power (Pe*). The target rotation speed (Ne*) of the engine (2) is set to the larger of the target charging power (Pb*) and the lower limit rotation speed (Nlim) (S45, S50, S500), and when the target charging power (Pb*) is limited to a small value (S502: YES) and the required rotation speed (Nrq) remains below the lower limit rotation speed (Nlim) for a predetermined time (tref) (S508: YES, S512: YES), the target rotation speed (Ne*) is set so that the rotation speed (Ne) of the engine (2) becomes a value (Np) within the fluctuation range of the required rotation speed (Nrq) within the predetermined time (tref).

[0057] According to this method, it is possible to effectively suppress the occurrence of noise and vibration in a hybrid vehicle when battery charging is restricted in a low-temperature environment.

[0058] The present invention is not limited to the above-described embodiment, and various modifications can be made within the scope of the present disclosure. Furthermore, the above-described embodiment is merely a specific form of the invention described in the Summary of the Invention, and does not limit the elements of the invention described in the Summary of the Invention. [Industrial Applicability]

[0059] The invention of the present disclosure can be used in the hybrid vehicle manufacturing industry and the like. [Explanation of symbols]

[0060] 1 Hybrid vehicle, 2 Engine, 3 Planetary gear, 4 Gear train, 5 Battery, 6 Power control unit (PCU), 100 Hybrid electronic control unit (HVECU), MG1, MG2 Motor generators.

Claims

1. A control device for a hybrid vehicle including an engine, an electric motor capable of generating electricity using at least a portion of the power from the engine, and a battery capable of being charged with electric power from the electric motor, a target power setting unit that sets a target power of the engine based on a power required for running the hybrid vehicle and a target charging power of the battery; a target rotation speed setting unit that sets the larger of a required rotation speed of the engine corresponding to the target power or a lower limit rotation speed of the engine as a target rotation speed of the engine, and that sets the target rotation speed so that the rotation speed of the engine will be a value within a fluctuation range of the required rotation speed within the predetermined time when a state in which the target charging power is limited to a small value and the required rotation speed is less than the lower limit rotation speed continues for the predetermined time; A control device for a hybrid vehicle comprising:

2. 2. The control device for a hybrid vehicle according to claim 1, The target rotation speed setting unit is a control device for a hybrid vehicle that sets the target rotation speed so that the engine rotation speed changes gradually to the value within the fluctuation range when the target charging power is limited to a small value and the required rotation speed remains below the lower limit rotation speed for the specified time.

3. 3. The hybrid vehicle control device according to claim 1, The target rotation speed setting unit is a control device for a hybrid vehicle that sets the target rotation speed so that the engine rotation speed becomes the maximum value within the fluctuation range when the target charging power is limited to a small value and the required rotation speed remains below the lower limit rotation speed for the predetermined time.

4. 3. The hybrid vehicle control device according to claim 1, The target rotation speed setting unit sets the required rotation speed based on the target power so that the engine operates efficiently, and when the target charging power is limited to a small value and the required rotation speed is equal to or higher than the lower limit rotation speed, sets the required rotation speed to the lower limit rotation speed.

5. 3. The hybrid vehicle control device according to claim 1, a battery management unit that sets an allowable charging power of the battery based on an SOC and a temperature of the battery, and that sets a charging power limit value of the battery based on a state of charge of the battery; when the allowable charging power is less than the charging power limit value, the battery management unit sets the charging power limit value to the allowable charging power and limits the target charging power to a small value; The target rotation speed setting unit is a control device for a hybrid vehicle that, when charging of the battery is requested, determines whether the target charging power is limited to a small value based on the temperature of the battery, the allowable charging power, and the charging power limit value.

6. 6. The control device for a hybrid vehicle according to claim 5, the battery is a lithium ion secondary battery, A control device for a hybrid vehicle, wherein the charging power limit value is set so as to suppress lithium deposition in the negative electrode of the battery.

7. A control method for a hybrid vehicle including an engine, an electric motor capable of generating electricity using at least a portion of power from the engine, and a battery capable of being charged with electric power from the electric motor, comprising: setting a target power of the engine based on a power required for running the hybrid vehicle and a target charging power of the battery; A control method for a hybrid vehicle, which sets the target rotation speed of the engine to the larger of the required rotation speed of the engine corresponding to the target power and a lower limit rotation speed, and when the target charging power is limited to a small value and the required rotation speed remains below the lower limit rotation speed for a predetermined time, sets the target rotation speed so that the engine rotation speed falls within a fluctuation range of the required rotation speed within the predetermined time.

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