Hybrid vehicle control device

Abstract

To provide a control device of a hybrid vehicle, which can suppress running performance in a series-type hybrid vehicle from deteriorating when a temperature of a battery is low.SOLUTION: A control device of a hybrid vehicle according to the present invention comprises: an internal combustion engine; an electric motor for generating electric power that can convert power of the internal combustion engine to electric power when the internal combustion engine is in operation, and can start the internal combustion engine using electric power from a battery when the internal combustion engine is not in operation; a drive electric motor for supplying driving force for running to a driving wheel using electric power; and the battery that can output electric power to the electric motor for generating electric power and the drive electric motor, and determines electric power which can be used by the electric motor for generating electric power and the drive electric motor, while providing a predetermined amount of margin on a charging / discharging restricted amount for controlling the battery, which reduces the size of the margin, when a state where the drive electric motor cannot supply driving force corresponding to required driving torque continues for more than a predetermined time.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a control device for a hybrid vehicle. [Background technology]

[0002] An example of a system installed in a hybrid vehicle equipped with multiple power sources is a so-called series hybrid system. A series hybrid system includes, for example, an engine, a generator motor (MG1) that generates electricity using engine power, a drive motor (MG2) that generates driving force for traveling, and a battery that stores the electricity supplied to the drive motor and the like. Hereinafter, a hybrid vehicle (HEV: Hybrid Electric Vehicle) equipped with such a series hybrid system will be simply referred to as a "hybrid vehicle." Furthermore, electric power output will also be referred to as "electric power," "output," "power," etc.

[0003] Hybrid vehicles run either as an EV (Electric Vehicle) or as an HV (Hybrid Vehicle). In EV mode, the vehicle runs only on power supplied from a battery, without generating electricity using a generator motor. In HV mode, the vehicle runs on both power generated by a generator motor using engine power and power supplied from a battery.

[0004] If the battery output falls below the required power during EV driving, the engine is started and the vehicle switches to HV driving. The required power is, for example, the total of the power required for driving control (HEV control) (the power required for driving and the power required to start the engine), margins, losses (various energy losses), auxiliary loads, etc.

[0005] Therefore, in a hybrid vehicle, first, the charge / discharge limit amount in battery control (charge limit amount (upper limit amount) and discharge limit amount (upper limit amount) per unit time, in units of W (watts), for example) is set. Compared to the charge / discharge limit amount in battery control, the charge / discharge limit amount in driving control is set smaller by an amount such as a margin. Then, the power used by the generator motor and the drive motor is determined while observing the constraints of the charge / discharge limit amount in driving control. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent Publication No. 2021-87337 Summary of the Invention [Problem to be solved by the invention]

[0007] In addition, generally, when the battery temperature is low, the charge / discharge limit in the battery control is reduced, and the charge / discharge limit in the driving control is also reduced accordingly. Therefore, in the above-mentioned conventional technology, for example, when the battery temperature is low, the charge / discharge limit in the driving control is reduced, which may result in a decrease in driving performance. Specifically, for example, when driving uphill, the driving resistance is high and the power required for driving increases, but the power available to the drive motor is low, so the vehicle may not be able to move forward (or may move forward with difficulty). Furthermore, even when driving on flat ground, the degree of acceleration of the vehicle may be reduced.

[0008] The present invention has been made in view of the above circumstances, and has an object to provide a control device that can suppress a decrease in driving performance when the battery is at a low temperature in a series hybrid vehicle. [Means for solving the problem]

[0009] In order to solve the above-mentioned problems, the control device for a hybrid vehicle of the present invention comprises an internal combustion engine, a generator motor that is capable of converting the power of the internal combustion engine into electric power when the internal combustion engine is operating and that is capable of starting the internal combustion engine using electric power from a battery when the internal combustion engine is not operating, a drive motor that uses electric power to supply driving force for the drive wheels to travel, and the battery that is capable of outputting electric power to the generator motor and the drive motor, and is a control device for a hybrid vehicle that determines the electric power used by the generator motor and the drive motor by setting a predetermined amount of margin with respect to the charge / discharge limit amount of battery control, and when a state in which the drive motor is unable to supply driving force corresponding to the required driving torque continues for more than a predetermined time, the size of the margin is reduced.

[0010] According to the above configuration, when the drive motor is unable to supply driving force corresponding to the required driving torque for a predetermined period of time or longer, the size of the margin is reduced, thereby increasing the amount of power available to the drive motor, thereby suppressing a decrease in driving performance when the battery temperature is low.

[0011] Furthermore, in the control device for the hybrid vehicle, when the magnitude of the margin is reduced, the amount of power used by the auxiliary equipment of the hybrid vehicle is also reduced.

[0012] According to the above configuration, when the margin is reduced, the amount of power consumed by the auxiliary machinery is also reduced, which further increases the amount of power available to the drive motor, thereby further suppressing the deterioration of driving performance when the battery temperature is low.

[0013] Furthermore, in the control device for the hybrid vehicle, after the magnitude of the margin has been reduced, when the drive motor is in a state where it can supply a drive force corresponding to the drive torque requirement, the magnitude of the margin is restored to its original value.

[0014] According to the above configuration, when the need to reduce the size of the margin decreases, the size of the margin can be immediately restored to its original size. [Effects of the Invention]

[0015] According to the present invention, in a series-type hybrid vehicle, when the drive motor is unable to supply driving force corresponding to the required driving torque for a predetermined period of time or longer, the size of the margin is reduced, thereby increasing the power available to the drive motor and suppressing a decrease in driving performance when the battery is cold. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 1 is a diagram showing an example of a main configuration of a hybrid vehicle according to an embodiment. [Figure 2] FIG. 2 is a graph showing the time transition of each parameter in the conventional technology and the embodiment. [Figure 3] FIG. 3 is an explanatory diagram of calculation of the upper limit power of the drive motor in the embodiment. [Figure 4] FIG. 4 is a flowchart showing the processing in the hybrid vehicle according to the embodiment. [Figure 5] FIG. 5 is an explanatory diagram of the prior art. DETAILED DESCRIPTION OF THE INVENTION

[0017] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a control device for a hybrid vehicle according to the present invention will be described with reference to the accompanying drawings. However, the present invention is not limited to the following embodiments.

[0018] To facilitate understanding of the embodiments, the prior art will be explained again. Fig. 5 is an explanatory diagram of the prior art. (a) is a graph showing the time transition of each parameter after warming up of the battery in a hybrid vehicle. In the graphs (a) and (b), the horizontal axis represents time and the vertical axis represents power (the upper side represents discharging, and the lower side represents charging). Note that hereinafter, when the term "margin" is used, it may refer to the total including losses (various energy losses) and auxiliary loads in addition to the original margin.

[0019] As shown in (a), in a hybrid vehicle, a discharge limit DL1 and a charge limit CL1 are set in battery control. In comparison, a discharge limit DL2 and a charge limit CL2 in driving control are set smaller by margins DM and CM, respectively. One reason for providing the margins is that the battery is over-specified for a hybrid vehicle. Therefore, the present invention can be applied to any battery.

[0020] In a hybrid vehicle, the power consumption of the generator motor and the drive motor is determined while observing the constraints of the charge / discharge limit amounts (symbols DL2 and CL2) in driving control. MG2 power consumption PC2 (power consumption by the drive motor), MG1 power generation PC1 (power consumption by the generator motor), and battery charge / discharge amount BT change as shown in the figure. In this case, it is sufficient that the battery charge / discharge amount BT falls within the range from the discharge limit amount DL2 to the charge limit amount CL2.

[0021] On the other hand, (b) is a graph showing the time transition of each parameter when the battery temperature is low in a hybrid vehicle. Generally, when the battery temperature is low, the charge / discharge limit amount (reference symbols DL1, CL1) in the battery control is small, and accordingly the charge / discharge limit amount (reference symbols DL2, CL2) in the driving control is also small.

[0022] This can result in a decline in driving performance. Specifically, for example, when driving uphill, the driving resistance is high and the electric power required for driving increases, but the electric power available to the drive motor is low, so the vehicle may not be able to move forward (or may move forward with difficulty). Also, even when driving on flat ground, the degree of acceleration of the vehicle may decrease. One reason for this is that the battery charge / discharge amount BT must be kept within the range from the discharge limit amount DL2 to the charge limit amount CL2, which means that the amount of change in MG2 power consumption PC2 (power consumption by the drive motor) is kept small.

[0023] Therefore, the following describes a technique that can suppress the deterioration of driving performance when the battery temperature is low in a series hybrid vehicle.

[0024] 1 is a diagram showing an example of a main configuration of a hybrid vehicle 1 according to an embodiment. The main configuration of the hybrid vehicle 1 according to this embodiment will be described with reference to FIG.

[0025] The hybrid vehicle 1 is a vehicle equipped with a series hybrid system 2. The hybrid vehicle 1 includes drive wheels 17, an ECU (Electronic Control Unit) 31, an accelerator sensor 32, a brake switch 33, and a vehicle speed sensor .

[0026] The hybrid system 2 also includes an engine 11, a generator motor 12 (MG1: generator motor), a drive motor 13 (MG2: drive motor), a battery 14, and a PCU (Power Control Unit) 15.

[0027] The engine 11 is, for example, an internal combustion engine such as a gasoline engine.

[0028] The generator motor 12 is capable of converting the power of the engine 11 into electric power when the engine 11 is operating, and is also capable of starting the engine 11 using electric power from the battery 14 when the engine 11 is not operating.

[0029] Specifically, the generator motor 12 is configured to convert the power of the engine 11 into electric power, and is, for example, a permanent magnet synchronous motor. The rotating shaft of the generator motor 12 is mechanically connected to the crankshaft of the engine 11 via a gear (not shown). For example, an engine output gear is supported on the crankshaft of the engine 11 so as not to rotate relative to it, and a motor gear is supported on the rotating shaft of the generator motor 12 so as not to rotate relative to it, and the engine output gear and the motor gear are meshed.

[0030] The drive motor 13 supplies drive power to the drive wheels 17 using electric power from the battery 14 or the like. Specifically, the drive motor 13 is, for example, a permanent magnet synchronous motor that is larger than the generator motor 12. The rotating shaft of the drive motor 13 is connected to a drive system 16 for driving and rotating the drive wheels 17. The drive system 16 includes a differential gear. The power of the drive motor 13 is transmitted to the differential gear, and then distributed and transmitted from the differential gear to the drive wheels 17, which consist of the left and right front wheels or rear wheels. This causes the left and right drive wheels 17 to rotate, causing the hybrid vehicle 1 to move forward or backward.

[0031] The battery 14 is configured to be able to output electric power to the generator motor 12 and the drive motor 13. Specifically, the battery 14 is, for example, a battery pack made up of a combination of multiple secondary batteries (for example, lithium ion batteries). The battery 14 outputs DC power of, for example, about 200 to 350 V.

[0032] The PCU 15 is a unit for controlling the driving of the generator motor 12 and the drive motor 13. The PCU 15 includes a first inverter 21, a second inverter 22, and a converter .

[0033] The first inverter 21 is an inverter device that converts DC power from the converter 23 into AC power and converts AC power generated by the generator motor 12 into DC power.

[0034] The second inverter 22 is an inverter device that converts DC power from the converter 23 into AC power and converts AC power generated by the regenerative operation of the drive motor 13 into DC power.

[0035] The converter 23 is a converter device that increases the voltage of the DC power output from the battery 14 or decreases the voltage of the DC power output from the first inverter 21 or the second inverter 22.

[0036] When starting the engine 11, the DC power output from the battery 14 is boosted by the converter 23, the boosted DC power is converted to AC power by the first inverter 21, and the converted AC power is supplied to the generator motor 12. This causes the generator motor 12 to perform power running, and the engine 11 is motored (cranked) by the generator motor 12. When the rotation speed of the crankshaft of the engine 11 has increased to the rotation speed required for starting due to motoring, the ignition plug of the engine 11 is sparked, and the engine 11 starts.

[0037] When the hybrid vehicle 1 is traveling, the drive motor 13 is operated in a power running mode, and the drive motor 13 generates power.

[0038] When the hybrid vehicle 1 is running, if the output required of the drive motor 13 is smaller than the output of the battery 14, the hybrid vehicle 1 runs in EV (Electric Vehicle) mode. That is, in EV mode, the engine 11 is stopped, no power is generated by the generator motor 12, and the drive motor 13 is driven only by the power supplied from the battery 14 via the converter 23 and the second inverter 22.

[0039] On the other hand, when the output required of the drive motor 13 exceeds the output of the battery 14 while the hybrid vehicle 1 is running, the hybrid vehicle 1 runs as an HV (Hybrid Vehicle). That is, during HV running, the drive motor 13 is driven by both the electric power generated by the generator motor 12 and the electric power supplied from the battery 14.

[0040] Specifically, during HV running, the engine 11 is in operation and the generator motor 12 is operated to generate electricity (regenerative operation), so that the power of the engine 11 is converted into AC power by the generator motor 12. The AC power from the generator motor 12 is then converted into DC power by a first inverter 21, and the DC power is converted into AC power by a second inverter 22, and the AC power is supplied to the drive motor 13. The drive motor 13 is driven by the AC power and power from the battery 14.

[0041] When the hybrid vehicle 1 decelerates, the drive motor 13 undergoes regenerative operation, and power transmitted from the drive wheels 17 to the drive motor 13 is converted into AC power. At this time, the drive motor 13 acts as a resistor in the drivetrain 16, and this resistance acts as a braking force (regenerative braking force) that brakes the hybrid vehicle 1. At this time, in the PCU 15, the AC power supplied from the drive motor 13 to the second inverter 22 is converted into DC power by the second inverter 22, and the DC power is stepped down by the converter 23. The stepped-down DC power is then supplied to the battery 14, thereby charging the battery 14.

[0042] The ECU 31 is a control device that controls the hybrid system 2. The ECU 31 is connected to an accelerator sensor 32, a brake switch 33, and a vehicle speed sensor 34. The ECU 31 obtains an accelerator opening, which is the ratio of the current operation amount of the accelerator pedal to the maximum operation amount, from the detection signal output from the accelerator sensor 32. The ECU 31 also obtains the frequency of the detection signal (pulse signal) output from the detection signal from the vehicle speed sensor 34, and converts the frequency into vehicle speed.

[0043] The accelerator sensor 32 is a sensor that outputs a detection signal corresponding to the amount of operation of the accelerator pedal (accelerator opening) operated by the driver's foot.

[0044] The brake switch 33 is a sensor that outputs a brake signal that indicates the amount of operation of the brake pedal operated by the driver or whether or not the brake pedal has been depressed.

[0045] The vehicle speed sensor 34 is a sensor that outputs, as a detection signal, a pulse signal synchronized with the rotation of a rotating body that rotates as the hybrid vehicle 1 travels. Note that the method by which the ECU 31 recognizes the vehicle speed is not limited to the method using the detection signal acquired from the vehicle speed sensor 34, and may also be a method using, for example, vehicle speed-related information acquired from the PCU 15 or a VSC (Vehicle Stability Control) via a CAN (Controller Area Network).

[0046] The hybrid vehicle 1 is equipped with a plurality of ECUs including an ECU 31. Each ECU has a microcontroller unit (microcomputer). The microcomputer includes, for example, a central processing unit (CPU), a nonvolatile memory such as a flash memory, and a volatile memory such as a dynamic random access memory (DRAM). The plurality of ECUs are interconnected to enable bidirectional communication using the CAN communication protocol. Each ECU is connected to various sensors required for control, and receives detection signals from the connected sensors. In addition to the detection signals received from the various sensors, each ECU also receives information required for control from other ECUs.

[0047] FIG. 2 will also be referred to below. FIG. 2 is a graph showing the time progression of each parameter in the conventional technology and the embodiment. (a) is the conventional technology and is similar to FIG. 5(b). (b) is the embodiment. As shown in (a) and (b), in a hybrid vehicle, a predetermined amount of margin (symbols DM, CM) is provided for the battery control charge / discharge limit amount (symbols DL1, CL1) to set the charge / discharge limit amount (symbols DL2, CL2) for driving control, and the power used by the generator motor 12 and the drive motor 13 is determined while observing the constraints of the charge / discharge limit amount (symbols DL2, CL2) for driving control.

[0048] Then, as shown in (b), when the state in which the drive motor 13 is unable to supply drive force corresponding to the drive request torque continues for a predetermined time or longer (i.e., when it is determined that the driving performance has deteriorated), the ECU 31 reduces the magnitude of the margins (symbols DM and CM). This widens the range from the discharge limit amount DL2 to the charge limit amount CL2, thereby increasing the amount of change in the MG2 power consumption PC2 (power consumption by the drive motor) and the MG1 power generation power PC1 (power consumption by the generator motor). This therefore makes it possible to suppress deterioration in driving performance.

[0049] Furthermore, when reducing the magnitude of the margins (symbols DM and CM), ECU 31 may also reduce the amount of power used (auxiliary load) in the auxiliaries of hybrid vehicle 1. This can further increase the amount of change in MG2 power consumption PC2 and MG1 generated power PC1, thereby further suppressing deterioration in driving performance.

[0050] Furthermore, after reducing the size of the margin (and the amount of power consumption in the auxiliary equipment), the ECU 31 restores the size of the margin (and the amount of power consumption in the auxiliary equipment) to its original value when the drive motor 13 is able to supply a driving force corresponding to the required driving torque (when it determines that the vehicle has recovered from a worsening driving condition).

[0051] 3 is an explanatory diagram for calculating the upper limit power of the drive motor (MG2) in this embodiment. When a deterioration in driving conditions is determined, the margin amount and the auxiliary load are reduced, thereby increasing the charge limit amount of the generator motor 12 (MG1). Then, the amount of power generated by the generator motor 12 (MG1), which is determined based on the charge limit amount and the required drive power, increases.

[0052] Furthermore, the upper limit power of the drive motor (MG2) is calculated based on the discharge limit amount, the auxiliary load, each loss, and the amount of power generated by the generator motor 12 (MG1). In this case, the upper limit power of the drive motor (MG2) increases as the discharge limit amount increases, the auxiliary load decreases, and the amount of power generated by the generator motor 12 (MG1) increases. This improves driving performance.

[0053] Next, the processing in the hybrid vehicle 1 will be described with reference to Fig. 4. Fig. 4 is a flowchart showing the processing in the hybrid vehicle 1 of the embodiment.

[0054] In step S1, the ECU 31 controls the running of the hybrid vehicle 1. Next, in step S2, the ECU 31 determines whether the driving condition has deteriorated (whether the driving motor 13 has been unable to supply driving force corresponding to the driving request torque for a predetermined period of time or more), and if the answer is Yes (time t1 in Figure 2(b)), the ECU 31 proceeds to step S3, and if the answer is No, the ECU 31 returns to step S1.

[0055] In step S3, the ECU 31 reduces the size of the margin (FIG. 2(b)). Next, in step S4, the ECU 31 reduces the auxiliary load. Next, in step S5, the ECU 31 controls the running of the hybrid vehicle 1.

[0056] Next, in step S6, the ECU 31 determines whether the vehicle has recovered from the worsening driving condition (whether the drive motor 13 is now in a state where it can supply driving force corresponding to the required driving torque), and if the answer is Yes (time t2 in Figure 2(b)), the ECU 31 proceeds to step S7, and if the answer is No, the ECU 31 returns to step S5.

[0057] In step S7, the ECU 31 restores the size of the margin to its original value. Next, in step S8, the ECU 31 returns the auxiliary load to its original state, and then the process returns to step S1.

[0058] In this way, with the hybrid vehicle 1 of this embodiment, by reducing the margin when the state in which the drive motor 13 is unable to supply drive force corresponding to the drive torque request continues for a predetermined time or longer, the amount of power available to the drive motor 13 is increased, thereby suppressing a decrease in driving performance when the battery is cold. This makes it possible to travel, for example, even on steep uphill roads.

[0059] Furthermore, when the margin is reduced, the amount of power consumed by the auxiliary machinery is also reduced, which further increases the amount of power available to the drive motor 13, thereby further suppressing the deterioration of driving performance.

[0060] Furthermore, after the margin (and the auxiliary load) has been reduced, when the drive motor 13 is able to supply a driving force corresponding to the required driving torque, that is, when the need to reduce the margin (and the auxiliary load) has decreased, the margin (and the auxiliary load) can be immediately restored to its original state. This allows the original control to be restored quickly.

[0061] The program executed by the ECU 31 of this embodiment can be provided by being recorded in an installable or executable file format on a computer-readable recording medium such as a CD (Compact Disc)-ROM (Read Only Memory), a flexible disk (FD), a CD-R (Recordable), or a DVD (Digital Versatile Disk).The program may also be provided or distributed via a network such as the Internet.

[0062] Although an embodiment of the present invention has been described, this embodiment is presented as an example and is not intended to limit the scope of the invention. This novel embodiment can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. This embodiment and its modifications are included within the scope and spirit of the invention, and are also included in the invention described in the claims and their equivalents. [Explanation of symbols]

[0063] 1... hybrid vehicle, 11... engine, 12... generator motor, 13... drive motor, 14... battery, 15... PCU, 16... drive system, 17... drive wheels, 21... first inverter, 22... second inverter, 23... converter, 31... ECU, 32... accelerator sensor, 33... brake switch, 34... vehicle speed sensor

Claims

1. a generator motor that is capable of converting power of the internal combustion engine into electric power when the internal combustion engine is operating and that is capable of starting the internal combustion engine using electric power from a battery when the internal combustion engine is not operating; a drive motor that uses electric power to supply drive force to drive wheels for traveling; and a battery that is capable of outputting electric power to the generator motor and the drive motor, wherein a predetermined margin is set with respect to a charge / discharge limit amount of battery control to determine electric power used by the generator motor and the drive motor, A control device for a hybrid vehicle that reduces the size of the margins for the charge limit amount of the generator motor and the discharge limit amount of the drive motor when a state in which the drive motor is unable to supply drive force corresponding to the drive request torque continues for a predetermined time or more.

2. 2. The control device for a hybrid vehicle according to claim 1, wherein when the magnitude of the margin is reduced, the amount of power used by an auxiliary device that receives power from the battery of the hybrid vehicle is also reduced.

3. 2. The control device for a hybrid vehicle according to claim 1, wherein, after the magnitude of the margin is reduced, the magnitude of the margin is restored to its original value when the drive motor becomes capable of supplying a drive force corresponding to the drive torque demand.

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