Control device

Abstract

To suppress driving power reduction following limitation of charging / discharging power of a battery in a hybrid vehicle.SOLUTION: A control device according to an embodiment, in an electric vehicle which includes an engine and a motor as a power source and can travel by switching between the first travel mode without a start request of the engine that travels by driving the motor using the power from the battery and the second travel mode with the start request of the engine that travels using the power of the engine, determines whether or not the battery is in the low output state, shifts the electric vehicle to the first travel mode when it is not determined that the battery is in the low output state, starts the engine using the power from the battery and shifts the electric vehicle to the second travel mode when it is determined that the battery is in the low output state.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] 2. Description of the Related Art Conventionally, a series type hybrid system is known that includes an engine, a generator motor that generates electricity using power from the engine, a drive motor that generates driving force for traveling, and a battery that stores the electricity supplied to the drive motor.

[0003] In a vehicle equipped with a hybrid system, when the output required of the drive motor is smaller than the output of the battery, the drive motor is driven by electric power from the battery, and the drive force is transmitted from the drive motor to the drive wheels. On the other hand, when the output required of the drive motor exceeds the output of the battery, the engine power is converted to electric power by the generator motor, the drive motor is driven by the electric power from the generator motor, and the drive force is transmitted from the drive motor to the drive wheels.

[0004] The battery may be, for example, a lithium-ion battery. It is known that lithium-ion batteries deteriorate faster due to lithium deposition when charged and discharged in a low-temperature environment. For this reason, the charge and discharge power (charging power and discharging power) of the battery may be limited in a low-temperature environment. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2019-001212 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, when the charging and discharging power of the battery is limited and the vehicle starts running using only the power from the battery without starting the engine, most of the power from the battery may be used to start the engine even when the vehicle is running using the power from the battery. This may result in insufficient output from the drive motor, causing the vehicle to stall. In other words, the drive motor may not provide output in response to the accelerator operation, causing the user to feel uncomfortable, such as sluggish acceleration.

[0007] The present invention has been made in view of the above, and has an object to suppress a reduction in driving force that accompanies restrictions on the charge / discharge power of a battery in a hybrid vehicle. [Means for solving the problem]

[0008] In order to solve the above-mentioned problems and achieve the object, a control device according to an embodiment includes: As a power source for generating motors engine And as a power source for running Drive motor And, The vehicle can be driven by switching between a first driving mode, which does not require a start-up request for the engine, and a second driving mode, which requires a start-up request for the engine, and which drives the drive motor by using electric power from a generator motor that generates electricity using the power of the engine. Equipped with a series hybrid system In an electric vehicle, whether or not the battery is in a low-power state is determined before the electric vehicle starts to travel, and when it is determined that the battery is not in a low-power state, the electric vehicle is shifted to the first travel mode, and when it is determined that the battery is in a low-power state, the electric vehicle is shifted to the second travel mode before the electric vehicle starts to travel so that the driving force for traveling by the drive motor is not insufficient, and in the first travel mode, power from the battery used to drive the drive motor is used, and when traveling in the second travel mode, the engine is cranked and started by powering the generator motor, which generates power to be used to drive the drive motor. Effect of the Invention

[0009] According to the present invention, it is possible to suppress a reduction in driving force that is caused by restrictions on the charge / discharge power of a battery in a hybrid vehicle. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a block diagram showing an example of the configuration of a hybrid vehicle equipped with a control device according to an embodiment. [Diagram 2] FIG. 2 is a flowchart showing an example of the flow of engine start control according to the embodiment. [Diagram 3] FIG. 3 is a diagram for explaining the change in output when the engine is started in a state in which the battery output is limited. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of the control device according to the present invention will be described in detail with reference to the accompanying drawings. Note that the present invention is not limited to the following preferred embodiments.

[0012] <Hybrid vehicle> FIG. 1 is a block diagram showing an example of the configuration of a hybrid vehicle 1 equipped with a control device according to the embodiment.

[0013] The hybrid vehicle 1 is equipped with a series hybrid system 2. Here, the hybrid vehicle 1 is an example of an electric vehicle. The hybrid system 2 includes an engine 11, a generator motor (MG1) 12, a drive motor (MG2) 13, a battery 14, and a PCU (Power Control Unit) 15.

[0014] The engine 11 is, for example, a gasoline engine. However, the engine 11 may be an internal combustion engine that uses a fuel other than gasoline, such as hydrogen.

[0015] The generator motor 12 is configured using, 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 thereto, and a motor gear is supported on the rotating shaft of the generator motor 12 so as not to rotate relative thereto, and the engine output gear and the motor gear are meshed with each other.

[0016] The drive motor 13 is configured, for example, using a permanent magnet synchronous motor larger than the generator motor 12. A rotating shaft of the drive motor 13 is connected to a drive system 16 of the hybrid vehicle 1. The drive system 16 includes a differential gear. The power of the drive motor 13 is transmitted to the differential gear, and distributed and transmitted from the differential gear to drive wheels 17 including left and right front wheels or rear wheels. This causes the left and right drive wheels 17 to rotate, and the hybrid vehicle 1 moves forward or backward.

[0017] The battery 14 is an assembled battery made up of a combination of a plurality of secondary batteries. The secondary batteries are, for example, lithium ion batteries. The battery 14 outputs, for example, DC power of approximately 200 to 350 V (volts).

[0018] The PCU 15 is a unit for controlling the driving of the generator motor 12 and the drive motor 13, and includes a first inverter 21, a second inverter 22, and a converter .

[0019] 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 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 a rotation speed required for starting due to motoring, the ignition plug of the engine 11 is sparked, and the engine 11 starts.

[0020] When the hybrid vehicle 1 is traveling, the drive motor 13 is operated in a power running mode, and generates power.

[0021] When the output required of the drive motor 13 is smaller than the output of the battery 14, the hybrid vehicle 1 runs as an EV (Electric Vehicle). That is, the engine 11 is stopped, power is not generated by the generator motor 12, and power is supplied from the battery 14 to the drive motor 13, which drives the drive motor 13. In other words, EV running is running without a request to start the engine 11, and is running using the drive motor 13, which is driven only by power from the battery 14, as a power source. Here, EV running, that is, a running mode in which the vehicle runs without a request to start the engine 11, is an example of a first running mode.

[0022] On the other hand, when the output required for the drive motor 13 exceeds the output of the battery 14, the hybrid vehicle 1 runs as an HV (Hybrid Vehicle). That is, the engine 11 is operated and the generator motor 12 runs in a generating operation (regenerative operation), so that the power of the engine 11 is converted to AC power by the generator motor 12. The AC power from the generator motor 12 is converted to DC power by the first inverter 21, and the DC power output from the first inverter 21 is converted to AC power by the second inverter 22, and the AC power is supplied to the drive motor 13 to drive the drive motor 13. In other words, HV running is running that involves a request to start the engine 11, and is running using the drive motor 13, which is driven using power from the battery 14 and power from the generator motor 12 based on the power of the engine 11, as a power source. Note that in HV running, there may be cases where the power from the battery 14 is not used in combination to drive the drive motor 13. Here, HV running, that is, a running mode in which running is accompanied by a request to start the engine 11, is an example of a second running mode.

[0023] In this embodiment, the hybrid system 2 is a series system, but the present invention is not limited to this.

[0024] As an example, the hybrid system 2 may be a series-parallel hybrid system. In this case, the driving mode for EV driving (first driving mode) is a driving mode that does not require a start request for the engine 11, and is a driving mode that uses only the drive motor 13 driven by power from the battery 14 as a power source. Meanwhile, the driving mode for HV driving (second driving mode) is a driving mode that requires a start request for the engine 11, and is a driving mode that uses the engine 11 and the drive motor 13 driven by power from the battery 14 as a power source.

[0025] As an example, the hybrid system 2 may be a parallel hybrid system. In this case, the EV driving mode (first driving mode) is a driving mode that does not require a start request for the engine 11 and uses only the drive motor 13, which is driven using electric power from the battery 14, as a power source. Also, the driving mode (second driving mode) that requires a start request for the engine 11 is a driving mode that uses only the engine 11 as a power source.

[0026] Furthermore, when the remaining capacity of the battery 14 falls below a predetermined level, the generator motor 12 operates to generate electricity while the engine 11 is running, regardless of whether the drive motor 13 is driven or stopped. At this time, AC power from the generator motor 12 is converted to DC power by the first inverter 21, and the DC power output from the first inverter 21 is stepped down by the converter 23, and the stepped-down DC power is supplied to the battery 14, thereby charging the battery 14.

[0027] When the hybrid vehicle 1 decelerates, the drive motor 13 is operated in a regenerative manner, and the power transmitted from the drive wheels 17 to the drive motor 13 is converted into AC power. At this time, the drive motor 13 becomes a resistance in the traveling drive system, and the resistance acts as a braking force (regenerative braking force) that brakes the hybrid vehicle 1. In addition, 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 output from the second inverter 22 is stepped down by the converter 23. The stepped-down DC power is then supplied to the battery 14, thereby charging the battery 14.

[0028] A hybrid vehicle 1 is equipped with a plurality of ECUs (Electronic Control Units). Each ECU has a microcontroller unit (microcomputer), and the microcomputer includes, for example, a CPU, a non-volatile memory such as a flash memory, and a volatile memory such as a dynamic random access memory (DRAM). The plurality of ECUs are connected to enable two-way communication using a controller area network (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.

[0029] FIG. 1 shows an ECU 31 that controls the hybrid system 2 among the multiple ECUs. The ECU 31 is configured to perform control for switching between a driving mode in which the vehicle runs without a request to start the engine 11 and a driving mode in which the vehicle runs with a request to start the engine 11. The ECU 31 is also configured to perform torque control of the generator motor 12 at engine start in order to suppress abnormal noise such as teeth rattle that is specific to a series hybrid system. Here, the ECU 31 that controls the hybrid system 2 is an example of a control device. An accelerator sensor 32 and a vehicle speed sensor 33 are also connected to the ECU 31. The accelerator sensor 32 outputs a detection signal corresponding to the amount of operation of an accelerator pedal operated by a driver (operator). The vehicle speed sensor 33 outputs a pulse signal synchronized with the rotation of a rotating body that rotates as the hybrid vehicle 1 runs as a detection signal. The ECU 31 obtains an accelerator opening degree, which is a ratio of the current amount of operation of the accelerator pedal to the maximum amount of operation of the accelerator pedal, from the detection signal of the accelerator sensor 32. Furthermore, the ECU 31 obtains the frequency of the detection signal (pulse signal) from the detection signal of the vehicle speed sensor 33, and converts the frequency into vehicle speed.

[0030] <Engine start control> FIG. 2 is a flowchart showing an example of the flow of engine start control according to the embodiment.

[0031] In the hybrid vehicle 1, when an ignition switch such as a push start switch is turned on (step S1), the ECU 31 starts engine start control.

[0032] In the engine start control, the ECU 31 determines whether the battery 14 is in a low output state (step S2). Here, the low output state refers to a state in which the amount of charge / discharge power (charge power and discharge power) of the battery 14 is limited to a predetermined threshold value L1 (see FIG. 3) or less. The threshold value L1 can be determined, for example, according to the value of the discharge power from the battery 14 required to start the engine 11. The ECU 31 determines whether the battery 14 is in a low output state based on, for example, the temperature, SOC (State Of Charge), available output power value, SOH (State of Health), etc. of the battery 14.

[0033] As an example, the ECU 31 determines that the battery 14 is in a low output state when the battery 14 is in a low temperature environment. The low temperature environment here refers to an environment in which the lithium ion battery used in the battery 14 may deteriorate due to lithium deposition when the lithium ion battery is charged or discharged.

[0034] The ECU 31 may determine that the battery 14 is in a low output state when the amount of charge / discharge power of the battery 14 is expected to be limited to a predetermined threshold or less.

[0035] When it is determined that the battery 14 is in a low output state (step S2: Yes), the ECU 31 powers the generator motor 12 using the electric power from the battery 14 to crank the engine 11 and start the engine 11 (step S3). That is, the ECU 31 transitions to a traveling mode involving a request to start the engine 11, in which the hybrid vehicle 1 runs using the power of the engine 11.

[0036] At this time, since the hybrid vehicle 1 has not yet started traveling, there is no need to supply power to the drive motor 13. Therefore, the ECU 31 supplies most of the power that can be output from the battery 14 to the generator motor 12.

[0037] Furthermore, the ECU 31 limits the maximum torque of the generator motor 12 to a predetermined value or less in order to prevent the power supply from the battery 14 to the generator motor 12 from becoming excessive due to an increase in the rotation speed of the engine 11 caused by cranking. In other words, the ECU 31 limits the output from the battery 14 by limiting the rotation speed of the engine 11 during cranking to a predetermined value or less.

[0038] In addition, since the ECU 31 prioritizes turning on the drivable state (starting the engine) in a low temperature environment, for example, and therefore does not need to suppress abnormal noise as strictly as in a normal temperature environment, the ECU 31 turns off the torque control of the generator motor 12 when the engine is started in order to suppress abnormal noise.

[0039] After the engine 11 is started, the ECU 31 transitions the hybrid vehicle 1 to a runnable state (step S4). The runnable state is a Ready-ON state in which it is determined that the hybrid vehicle 1 can start running.

[0040] After the engine 11 is started in step S3, if the battery 14 is no longer in a low-output state, the engine 11 may be stopped. The case where the battery 14 is no longer in a low-output state refers to a state where the limitation on the output of power from the battery 14 to the drive motor 13 is relaxed, and the charge / discharge power amount of the battery 14 is limited to a predetermined threshold value L2 (see FIG. 3) or less. The threshold value L2 may be appropriately determined, for example, according to requirements regarding the driving characteristics of the hybrid vehicle 1, the performance of the battery 14, requirements regarding suppression of deterioration of the battery 14, and the like. Note that there may be cases where multiple values ​​are set as the threshold value L2, such as setting a sports driving mode that emphasizes driving force and an eco driving mode that emphasizes suppression of deterioration of the battery.

[0041] On the other hand, when it is determined that the battery 14 is not in a low output state (step S2: No), the ECU 31 transitions the hybrid vehicle 1 to a runnable state (step S4). That is, the ECU 31 transitions the hybrid vehicle 1 to a running mode that does not require starting the engine 11 and in which the hybrid vehicle 1 runs by driving the drive motor 13 using electric power from the battery 14.

[0042] In this manner, in the hybrid system 2 according to the embodiment, the ECU 31 is configured to start the engine 11 using electric power from the battery 14 when it is determined that the battery 14 is in a low output state.

[0043] Here, consider a case where the hybrid vehicle 1 starts traveling using only the power from the battery 14 without starting the engine 11 when the battery 14 is in a low output state, i.e., when the charging and discharging power of the battery 14 is limited. FIG. 3 is a diagram for explaining the change in output when the engine is started in a state where the battery output is limited. In FIG. 3, the horizontal axis indicates time [s], and the vertical axis indicates output [kW]. Here, the direction in which the output (MG1) from the generator motor 12 is supplied to the engine 11 is positive, and the direction in which it is supplied to the drive motor 13 is negative. FIG. 3 illustrates a state in which the output from the battery 14 is limited to a threshold value L1.

[0044] As shown by the solid line in FIG. 3, when the output (MG2) required by the drive motor 13 after starting to travel reaches the threshold value L1, the generator motor 12 starts the engine 11 using most of the power output from the battery 14, as shown by the dashed line. Therefore, in the engine start section, almost no power is supplied from the battery 14 to the drive motor 13, and as shown by the solid line in FIG. 3, the drive force by the drive motor 13 is insufficient. Therefore, the output characteristic (solid line) when the engine is started while traveling has a delay until the output from the generator motor 12 is obtained after the engine is started, compared to the case where the engine is not started (broken line). In other words, there is a risk that the output from the drive motor 13 is not sufficient and the hybrid vehicle 1 will stall. In other words, there is a risk that the output from the drive motor 13 corresponding to the accelerator operation is not obtained, and the user will feel uncomfortable, such as sluggish acceleration.

[0045] In this situation, in the hybrid system 2 according to the present embodiment, the ECU 31 is configured to start the engine 11 in advance when it is determined that the battery 14 is in a low output state. This makes it possible to suppress a decrease in driving force due to engine start even in a state in which the charging and discharging power of the battery 14 is limited.

[0046] Furthermore, the ECU 31 is configured to determine whether the battery 14 is in a low output state before the hybrid vehicle 1 starts to travel. Here, "before the vehicle starts to travel" refers to, for example, a period from when the ignition is turned on until the vehicle starts to travel. This allows the engine to be started before the vehicle starts to travel if the battery 14 is in a low output state.

[0047] Therefore, even in a situation where there is a large mechanical loss in the engine 11, such as when the engine is cold, most of the output from the battery 14 can be used to start the engine without reducing the driving force from the drive motor 13, expanding the engine startable range. Expanding the engine start range contributes to improving engine startability.

[0048] Furthermore, when it is determined that the battery 14 is in a low output state, the ECU 31 is configured to start the engine 11 before starting traveling and to limit the maximum torque of the generator motor 12 that starts the engine 11. As a result, since there is no need to start the engine 11 quickly in a situation where the battery 14 is in a low output state, the engine 11 can be started while limiting the maximum torque of the generator motor 12 to a range that can protect the battery 14. Therefore, with this configuration, deterioration of the battery 14 can be suppressed.

[0049] Furthermore, since the ECU 31 prioritizes turning on the drivable state (starting the engine) in a low temperature environment, for example, and therefore does not need to perform abnormal noise suppression as strictly as in a normal temperature environment, it turns off the torque control of the generator motor 12 at engine start for abnormal noise suppression. This reduces the power required for torque control for abnormal noise suppression, reduces the output from the battery 14 in a low output state, and suppresses deterioration of the battery 14.

[0050] According to at least one of the embodiments described above, it is possible to suppress a reduction in driving force that accompanies restrictions on the charge / discharge power of a battery in a hybrid vehicle.

[0051] Although some embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and spirit of the invention, and are included in the scope of the invention and its equivalents described in the claims. [Explanation of symbols]

[0052] 1: Hybrid vehicle 11: Engine 12: Generator motor 13: Drive motor 14: Battery 15: PCU 31: ECU (control unit)

Claims

1. An electric vehicle equipped with a series-type hybrid system having an engine as a power source for a generator motor and a drive motor as a power source for driving, capable of switching between a first driving mode in which the drive motor is driven using power from a battery to drive the vehicle without requiring the engine to be started, and a second driving mode in which the drive motor is driven using power from the generator motor, which is operated to generate electricity using the power of the engine, requiring the engine to be started, determining whether the battery is in a low output state before the electric vehicle starts traveling; When it is not determined that the battery is in a low output state, the electric vehicle is shifted to the first traveling mode; When it is determined that the battery is in a low output state, in order to prevent the driving force for driving by the drive motor from being insufficient, before the electric vehicle starts to travel, the electric vehicle is shifted to the second travel mode, and in the first travel mode, power is used to drive the drive motor from the battery, and when traveling in the second travel mode, the engine is cranked and started by powering the generator motor that generates the power to be used to drive the drive motor. Control device.

2. 2. The control device according to claim 1, wherein when it is determined that the battery is in a low output state, the maximum torque of the generator motor is limited to suppress excessive output from the battery that accompanies an increase in the engine speed during cranking.

3. When it is determined that the battery is in a low output state, torque control of the generator motor is performed using power from the battery when starting the engine; determining whether the battery is in a low power state includes determining based on a temperature of the battery; when it is determined that the battery is in a low output state due to the battery being in a low temperature environment, the torque control of the generator motor at the time of starting the engine is turned off; The control device according to claim 1 or 2.

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