JP7424864B2 - Hybrid system control device - Google Patents

Description

The present invention relates to a control device for a hybrid system installed in a vehicle.

2. Description of the Related Art Conventionally, vehicles that employ hybrid systems in their drive systems, so-called hybrid vehicles (HV), have been known. For example, in a series type hybrid vehicle, engine power is converted into electric power by a power generation motor, the drive motor is driven by the electric power, and the power of the drive motor is transmitted to the drive wheels.

A hybrid vehicle is equipped with a battery that stores electric power for driving a drive motor. When the SOC (State of Charge), which indicates the battery's state of charge (ratio of remaining charge to charge capacity), approaches the lower limit of its usage range, the battery is forcibly activated by the power generation motor to protect the battery. It will be charged. Since this forced charging is performed in an emergency, charging with a high output (electric power) from the motor is prioritized over fuel efficiency. As a result, the engine speed increases and the NV (noise vibration) characteristics deteriorate.

Therefore, it has been proposed to reduce NV during forced charging by setting the threshold for starting forced charging, that is, the lower limit of the SOC usage range, to a high value and limiting the motor output during forced charging to a low value. There is. However, if the threshold for starting forced charging is raised, the SOC usage range will become smaller, and the EV driving time will be shortened, in which the engine is stopped and the drive motor is driven by electric power from the battery, resulting in worse fuel efficiency. do.

Japanese Patent Application Publication No. 2009-248913

SUMMARY OF THE INVENTION An object of the present invention is to provide a control device for a hybrid system that can improve the NV characteristics when charging a battery through power generation by a generator motor while ensuring a wide range of SOC usage.

In order to achieve the above object, the present invention provides a control device for a hybrid system that is mounted on a vehicle and that controls a hybrid system that includes a battery, an engine, and a generator motor that generates electricity using the power of the engine. an equal power line indicating the relationship between the engine rotation speed of the engine and the engine torque of the engine at which the output of the engine becomes equal; a maximum torque line indicating the engine rotation speed at which the engine torque is maximum; and , a storage means for storing a high efficiency region including a combination of the engine rotation speed and the engine torque in which the energy efficiency of the engine or the hybrid system is equal to or higher than a predetermined value, and when charging the battery by power generation by the generator motor, engine control means for controlling the drive of the engine to move the operating point of the engine in the high efficiency region according to the situation of the vehicle, the engine control means for reducing the engine rotation speed. In this case, the operating point is moved along the equal power line, and when the engine speed is further reduced after the engine torque reaches the maximum torque, the operating point is moved along the maximum torque line. move it.

The vehicle status may be, for example, the speed of the vehicle, the opening degree of an accelerator pedal (throttle valve) provided on the vehicle, or the SOC of the battery. It may be a combination of several of them.

According to this configuration, the equal power line, maximum torque line, and high efficiency region are stored in the storage means. The equal power line is a characteristic line that shows the relationship between engine rotation speed and engine torque at which the engine output becomes equal. The maximum torque line is a characteristic line indicating the engine rotation speed at which the engine torque is maximum. The high efficiency region is a region that includes a combination of engine rotation speed and engine torque in which the energy efficiency of the engine or hybrid system is equal to or higher than a predetermined value.

When the battery is charged with the power generated by the generator motor, the drive of the engine is controlled so that the operating point of the engine moves in accordance with the vehicle situation in a high efficiency region. For example, when the vehicle is running, the operating point of the engine is moved so that the lower the vehicle speed, the lower the engine speed. By moving the operating point of the engine, the sound of the engine while charging the battery is masked by road noise (vibration and noise caused by driving). can do. Even when the vehicle speed is low, if the accelerator pedal is pressed more often when climbing a hill, the engine noise is less noticeable to the user, so by increasing the engine speed, the remaining charge of the battery can be quickly depleted. can be recovered to.

Further, by setting the operating point of the engine in a high efficiency region, it is possible to improve fuel efficiency.

When the engine speed is reduced, first the operating point of the engine is moved along the equal power line. Thereby, the generated power of the generator motor can be secured. If the engine speed is to be reduced even when the engine torque reaches the maximum torque, the operating point of the engine is moved along the maximum torque line. Thereby, the engine rotation can be further reduced while maintaining the generated power of the generator motor as large as possible.

Therefore, when charging the battery using the power generated by the generator motor, it is possible to improve the NV characteristics by moving the operating point of the engine depending on the vehicle situation so that the user will not be bothered by the engine noise. can. As a result, there is no need to set a high lower limit value of the SOC usage range of the battery, so it is possible to secure a large SOC usage range and improve fuel efficiency.

According to the present invention, it is possible to improve the NV characteristics during charging of the battery by power generation by the generator motor, while ensuring a wide usage range of the SOC.

1 is a block diagram showing the configuration of an electric vehicle equipped with a hybrid system according to an embodiment of the present invention. It is a figure showing an example of time change of SOC of a drive battery. FIG. 3 is a diagram showing an equal power line, a maximum torque line, and an optimum fuel efficiency line of the engine.

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

<Electric vehicle>
FIG. 1 is a block diagram showing the configuration of an electric vehicle 1 equipped with a hybrid system 2 according to an embodiment of the present invention.

The electric vehicle 1 is equipped with a series type hybrid system 2. The hybrid system 2 includes an engine (ENG) 11, a generator motor (MG1) 12, a drive motor (MG2) 13, a drive battery 14, and a PCU (Power Control Unit) 15.

Engine 11 is, for example, a gasoline engine or a diesel engine. An engine output gear 22 is provided on the crankshaft 21 of the engine 11 so as to rotate together with the crankshaft 21.

The generator motor 12 is, for example, a permanent magnet synchronous motor. A generator motor gear 24 is provided on the rotating shaft 23 of the generator motor 12 so as to rotate together with the generator motor gear 24 . The generator motor gear 24 meshes with the engine output gear 22. The generator motor 12 is used as a starter motor for cranking the engine 11 when the engine 11 is stopped. After the engine 11 is started, the generator motor 12 functions as a generator that converts the power of the engine 11 into electric power.

The drive motor 13 is, for example, a permanent magnet synchronous motor larger than the generator motor 12. A motor output gear 26 is provided on the rotating shaft 25 of the drive motor 13 so as to rotate together with the rotating shaft 25 .

Motor output gear 26 is coupled to power transmission mechanism 3 mounted on electric vehicle 1. The power transmission mechanism 3 includes a counter shaft 31, a counter gear 32, an output gear 33, and a differential gear 34. The counter shaft 31 is provided parallel to the rotation shaft 25 of the drive motor 13. The counter gear 32 and the output gear 33 are provided on the counter shaft 31 so as to rotate together. The output gear 33 meshes with a ring gear 35 of a differential gear 34. Motor output gear 26 meshes with counter gear 32.

The power of drive motor 13 is transmitted to differential gear 34 via motor output gear 26, counter gear 32, and output gear 33. The power transmitted to the differential gear 34 is then transmitted to the left and right drive wheels 5 of the electric vehicle 1 via the left and right drive shafts 4 . As a result, the left and right drive wheels 5 rotate, and the electric vehicle 1 travels forward or backward.

The driving battery 14 is a battery pack that is a combination of a plurality of secondary batteries (for example, lithium ion batteries). The driving battery 14 outputs DC power of approximately 200 to 350 V (volts), for example.

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 (MG1 INV) 41, a second inverter (MG2 INV) 42, and a boost converter (BstCONV) 43.

When the electric vehicle 1 is accelerating, the drive motor 13 is operated in power running, and the drive motor 13 generates power for power running. At this time, the DC power output from the drive battery 14 is boosted by the boost converter 43 as necessary, the DC power output from the boost converter 43 is converted into AC power by the second inverter 42, and the AC power is is supplied to the drive motor 13. As a result, the power of the drive battery 14 is consumed.

Further, when the engine 11 is started, the DC power output from the drive battery 14 is boosted by the boost converter 43, the boosted DC power is converted to AC power by the first inverter 41, and the AC power is transferred to the generator motor 12. supplied to As a result, the generator motor 12 is motored, and the engine 11 is motored by the generator motor 12. This motoring causes the crankshaft of the engine 11 to rotate, and when its rotational speed increases to the rotational speed necessary for starting, the ignition plug of the engine 11 is sparked and the engine 11 is started.

When the generator motor 12 is operated to generate electricity while the engine 11 is operating, the generator motor 12 generates alternating current power. The AC power generated by the generator motor 12 is converted into DC power by the first inverter 41 . Then, the DC power output from the first inverter 41 is converted into AC power by the second inverter 42, and the AC power is supplied to the drive motor 13. Furthermore, when it is not necessary to supply power to the drive motor 13, the DC power output from the first inverter 41 is stepped down by the step-up converter 43, and the stepped down DC power is supplied to the drive battery 14. , the driving battery 14 is charged.

When the electric vehicle 1 is decelerating, the drive motor 13 is operated regeneratively, and the power transmitted from the drive wheels 5 to the drive motor 13 is converted into AC power. At this time, the drive motor 13 acts as a resistance in the travel drive system, and the resistance acts as a braking force (regenerative braking force) that brakes the electric vehicle 1. The AC power generated by the drive motor 13 is converted into DC power by the second inverter 42 . Then, the DC power output from the second inverter 42 is stepped down by the step-up converter 43, and the stepped-down DC power is supplied to the drive battery 14, thereby charging the drive battery 14.

Further, the electric vehicle 1 is equipped with an ECU (Electronic Control Unit) 6 that includes a microcomputer (microcontroller unit) 51 . The microcomputer 51 includes, for example, a CPU, a nonvolatile memory such as a flash memory, and a volatile memory such as a DRAM (Dynamic Random Access Memory). Although only one ECU 6 is shown in FIG. 1, the electric vehicle 1 is equipped with a plurality of ECUs having the same configuration as the ECU 6 in order to control each part. A plurality of ECUs including the ECU 6 are connected to enable bidirectional communication using a CAN (Controller Area Network) communication protocol.

<Forced charging>
FIG. 2 is a diagram showing an example of a change in SOC of the driving battery 14 over time.

While the ignition switch of the electric vehicle 1 is on, the ECU 6 monitors the state of charge (SOC) indicating the state of charge of the drive battery 14 (ratio of remaining charge to charging capacity).

The operating range of the driving battery 14 is set as the SOC range. For example, if EV driving continues, in which the engine 11 is stopped and the drive motor 13 is driven by electric power from the drive battery 14, the SOC (actual SOC) of the drive battery 14 decreases. When the SOC of the drive battery 14 drops to the lower limit SOC, which is the lower limit of the usage range of the drive battery 14, forced charging of the drive battery 14 is started to protect the drive battery 14 (time T1).

In forced charging, the engine 11 is started, the generator motor 12 is operated to generate electricity, and the drive battery 14 is charged with the power generated by the generator motor 12 . When the charging of the driving battery 14 progresses and the SOC of the driving battery 14 rises to the control center SOC, which is the center of the usage range of the driving battery 14, the power generation operation of the generator motor 12 is stopped and the driving battery 14 is forced to stop. Charging is ended (time T3). When the power generation operation of the power generation motor 12 is stopped, the engine 11 is also stopped.

<Engine control during forced charging>
FIG. 3 is a diagram showing an equal power line, a maximum torque line, and an optimum fuel consumption line of the engine 11.

The engine 11 has a relationship between engine speed and engine torque that achieves the best thermal efficiency. From the viewpoint of fuel efficiency, when the driving battery 14 is forcibly charged, it is preferable that the engine 11 be controlled so that the engine 11 operates at the high efficiency point P where the best thermal efficiency is achieved. FIG. 3 also shows constant fuel consumption rate lines, which are contour lines plotting the position of the rotational speed of the engine 11 (engine rotational speed) and the torque of the engine 11 (engine torque) at the constant fuel consumption rate.

However, at the high efficiency point P, the engine speed is high, so depending on the vehicle speed of the electric vehicle 1, the NV (noise vibration) characteristics deteriorate.

Therefore, in controlling the engine 11 during forced charging of the driving battery 14, the ECU 6 sets an operating point of the engine 11 according to the vehicle speed, and controls the engine 11 so that the engine 11 operates at that operating point. . To set the operating line of the engine 11, an equal power line and an engine maximum torque line are used.

A nonvolatile memory built into the microcomputer 51 of the ECU 6 stores an equal power line, a maximum engine torque line, and an optimum fuel efficiency line in the form of maps. The equal power line is a characteristic line showing the relationship between the engine rotation speed and the engine torque at which the output of the engine 11 becomes equal. The engine maximum torque line is a characteristic line indicating the engine rotation speed at which the engine torque is maximum. The optimum fuel consumption line is a characteristic line that shows the relationship between engine speed and engine torque at which the best thermal efficiency is achieved.

The ECU 6 moves the operating point of the engine 11 so that the engine speed decreases as the vehicle speed decreases in a high efficiency region where the engine torque is greater than the optimum fuel efficiency line. Specifically, when moving the operating point of the engine 11 along the equal power line and further reducing the engine speed after the engine torque reaches the maximum torque, the operating point is moved along the maximum torque line. move it.

<Effect>
As described above, the microcomputer 51 of the ECU 6 stores the equal power line and the maximum torque line. Further, the microcomputer 51 of the ECU 6 stores an optimum fuel efficiency line that defines a high efficiency region (substantially stores a high efficiency region).

When the drive battery 14 is charged with the power generated by the generator motor 12, the operating point of the engine 11 is set so that the engine speed decreases as the vehicle speed decreases in a high efficiency region where the engine torque is greater than the optimum fuel efficiency line. will be moved. Thereby, the engine sound while the driving battery 14 is being charged can be masked by road noise (vibration and noise caused by driving).

Further, by setting the operating point of the engine 11 to a high efficiency region, it is possible to improve fuel efficiency.

When lowering the engine speed, first, the operating point of the engine 11 is moved along the equal power line. Thereby, the generated power of the generator motor 12 can be secured. If the engine speed is to be reduced even when the engine torque reaches the maximum torque, the operating point of the engine 11 is moved along the maximum torque line. Thereby, the engine rotation can be further reduced while maintaining the generated power of the generator motor 12 as large as possible.

Therefore, when the driving battery 14 is forcibly charged by the power generated by the generator motor 12, the operating point of the engine is moved according to the vehicle speed of the electric vehicle 1 so that the user will not be bothered by the engine noise. It is possible to improve the characteristics. As a result, there is no need to set a high lower limit value of the SOC usage range of the drive battery 14, so it is possible to secure a large SOC usage range and improve fuel efficiency.

<Modified example>
Although one embodiment of the present invention has been described above, the present invention can also be implemented in other forms.

For example, in the embodiment described above, the operating point of the engine 11 is moved according to the vehicle speed of the electric vehicle 1 when the driving battery 14 is forcibly charged. It is preferable to move the operating point of the engine 11. Even when the vehicle speed is low, when the accelerator pedal is depressed and the accelerator opening is relatively large, such as when climbing a hill, the engine noise is less likely to be noticeable to the user. By operating the drive battery 14, the remaining charge of the drive battery 14 can be quickly restored.

Furthermore, when the drive battery 14 is forcibly charged, when the SOC of the drive battery 14 has recovered to a predetermined SOC set between the lower limit SOC and the control central SOC, the power generated by the generator motor 12 is reduced. , the engine speed may be kept low. Thereby, the user can be made less concerned about the engine sound.

In the above-described embodiment, the electric vehicle 1 equipped with a series type hybrid system 2 was taken up, but the present invention can be applied to an electric vehicle equipped with a hybrid system of a type other than a series type, such as a series/parallel type. be. In a series/parallel type hybrid system, for example, the engine and motor are connected to a planetary gear mechanism, and the power from the engine can be divided and distributed to the motor and drive wheels. Power can be combined and transmitted to the drive wheels.

In addition, various design changes can be made to the above-described configuration within the scope of the claims.

1: Electric vehicle (vehicle)
2: Hybrid system 6: ECU (control device, storage means, engine control means)
11: Engine 12: Generator motor 14: Drive battery (battery)
51: Microcomputer (memory means, engine control means)

Claims (1)

A control device that is mounted on a vehicle and controls a hybrid system that includes a battery, an engine, and a generator motor that generates electricity using the power of the engine,
An equal power line indicating the relationship between the engine rotation speed of the engine and the engine torque of the engine at which the output of the engine is equal, a maximum torque line indicating the engine rotation speed at which the engine torque is maximum, and the engine or storage means for storing a high efficiency region that includes a combination of the engine rotation speed and the engine torque in which the energy efficiency of the hybrid system is equal to or higher than a predetermined value;
When the battery is charged by power generation by the generator motor, driving of the engine is controlled to shift the operating point of the engine in the high efficiency region so that the lower the vehicle speed, the lower the engine rotation speed. engine control means for moving the engine;
The engine control means moves the operating point along the equal power line when reducing the engine speed, and further reduces the engine speed after the engine torque reaches a maximum torque. A control device that moves the operating point along the maximum torque line.

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