JP2021138153A - Control device of hybrid system - Google Patents

Abstract

To provide a control device of a hybrid system which can enhance NV characteristics at charging time of a battery due to electric power generation of a power generation motor while securing a use range of SOC largely.SOLUTION: An operation point of an engine is moved so that engine rpm reduces as vehicle speed is low in a high efficient region in which engine torque is larger than an optimal fuel consumption line when a battery for driving is charged with electric power generation power of a power generation motor. First of all, the operation point of the engine is moved along an equal power line if reducing the engine rpm. The operation point of the engine is moved along the maximum torque line when reducing the engine rpm even after the engine torque reaches the maximum torque.SELECTED DRAWING: Figure 3

Description

The present invention relates to a control device for a hybrid system mounted on a vehicle.

Conventionally, a vehicle using a hybrid system as a drive system, a so-called hybrid vehicle (HV), is known. For example, in a series hybrid vehicle, the power of the engine is converted into electric power by a motor for power generation, the driving motor is driven by the electric power, and the power of the driving motor is transmitted to the drive wheels.

Hybrid vehicles are equipped with a battery that stores electric power to drive a driving motor. When the SOC (State Of Charge), which indicates the state of charge of the battery (the ratio of the remaining charge to the charge capacity) approaches the lower limit of the usage range, the battery is forced by the power generation motor to protect the battery. It will be charged. Since this forced charging is performed urgently, charging with a high output (electric power) from the motor is prioritized over fuel efficiency. Therefore, the engine speed becomes high and the NV (noise vibration) characteristics deteriorate.

Therefore, it has been proposed to reduce the NV during forced charging by setting the threshold value 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 level. There is. However, if the threshold value for starting forced charging is increased, the usage range of the SOC becomes smaller, the EV running time when the engine is stopped and the driving motor is driven by the electric power from the battery is shortened, and the fuel consumption is deteriorated. do.

JP-A-2009-248913

An object of the present invention is to provide a control device for a hybrid system capable of improving NV characteristics at the time of charging a battery by power generation of a power generation motor while ensuring a large range of use of SOC.

In order to achieve the above object, the control device of the hybrid system according to the present invention is a control device mounted on a vehicle and controlling a hybrid system including a battery, an engine, and a power generation motor that generates power by the power of the engine. A power line indicating the relationship between the engine speed of the engine and the engine torque of the engine at which the outputs of the engines are equal, a maximum torque line indicating the engine speed at which the engine torque is maximized, and a maximum torque line indicating the engine speed at which the engine torque is maximized. A storage means for storing a high-efficiency region including a combination of the engine speed and the engine torque at which the energy efficiency of the engine or the hybrid system is equal to or higher than a predetermined value, and when the battery is charged by the power generation of the power generation motor. The engine control means includes an 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, and the engine control means reduces the engine rotation speed. In this case, when the operating point is moved along the isopower line and 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.

The state of the vehicle may be, for example, the vehicle speed of the vehicle, the opening degree of the accelerator pedal (throttle valve) provided in the vehicle, the SOC of the battery, or these. It may be a combination of a plurality of them.

According to this configuration, the storage means stores the equal power line, the maximum torque line, and the high efficiency region. The equal power line is a characteristic line showing the relationship between the engine speed and the engine torque at which the output of the engine becomes equal. The maximum torque line is a characteristic line indicating the engine speed at which the engine torque is maximized. The high efficiency region is a region including a combination of engine speed and engine torque that makes the energy efficiency of the engine or hybrid system equal to or higher than a predetermined value.

When the battery is charged by the generated power of the power generation motor, the drive of the engine is controlled so that the operating point of the engine moves according to the situation of the vehicle in the high efficiency region. For example, by moving the operating point of the engine so that the engine speed decreases as the vehicle speed decreases while the vehicle is running, the engine noise during battery charging is masked by road noise (vibration and noise due to running). can do. Even when the vehicle speed is low, when the accelerator pedal is being stepped on due to climbing a slope, the user is less likely to notice even if the engine noise is loud, so by increasing the engine speed, the remaining charge of the battery can be shortened. Can be restored to.

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

When the engine speed is reduced, the operating point of the engine is first moved along the equipower line. As a result, the power generation power of the power generation motor can be secured. Even if the engine torque reaches the maximum torque, if the engine speed is reduced, the operating point of the engine is moved along the maximum torque line. As a result, the engine speed can be further reduced while maintaining the generated power of the power generation motor as large as possible.

Therefore, when charging the battery with the generated power of the power generation motor, the operating point of the engine can be moved according to the vehicle conditions so that the user does not mind the engine sound, thereby improving the NV characteristics. can. As a result, since it is not necessary to set a high lower limit value of the SOC usage range of the battery, 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 at the time of charging the battery by the power generation of the power generation motor while ensuring a large range of use of the SOC.

It is a block diagram which shows the structure of the electric vehicle which mounted the hybrid system which concerns on one Embodiment of this invention. It is a figure which shows an example of the time change of SOC of a drive battery. It is a figure which shows the equal power line, the maximum torque line and the optimum fuel consumption line of an engine.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

<Electric vehicle>
FIG. 1 is a block diagram showing a 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 power generation motor (MG1) 12, a drive motor (MG2) 13, a drive battery 14, and a PCU (Power Control Unit) 15.

The engine 11 is, for example, a gasoline engine or a diesel engine. The crankshaft 21 of the engine 11 is provided so that the engine output gear 22 rotates integrally with the crankshaft 21.

The power generation motor 12 includes, for example, a permanent magnet synchronous motor. The rotating shaft 23 of the power generation motor 12 is provided so that the power generation motor gear 24 rotates integrally. The power generation motor gear 24 meshes with the engine output gear 22. The power generation motor 12 is used as a starter motor for cranking the engine 11 when the engine 11 is stopped. After starting the engine 11, the power generation motor 12 functions as a generator that converts the power of the engine 11 into electric power.

The drive motor 13 is composed of, for example, a permanent magnet synchronous motor larger than the power generation motor 12. The rotary shaft 25 of the drive motor 13 is provided so that the motor output gear 26 rotates integrally with the rotary shaft 25.

The motor output gear 26 is coupled to a power transmission mechanism 3 mounted on the 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 in parallel with the rotating shaft 25 of the drive motor 13. The counter gear 32 and the output gear 33 are provided so as to rotate integrally with the counter shaft 31. The output gear 33 meshes with the ring gear 35 of the differential gear 34. The motor output gear 26 meshes with the counter gear 32.

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

The drive battery 14 is an assembled battery in which a plurality of secondary batteries (for example, a lithium ion battery) are combined. The drive battery 14 outputs, for example, DC power of about 200 to 350 V (volts).

The PCU 15 is a unit for controlling the drive of the power generation 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 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 as necessary by the boost converter 43, and the DC power output from the boost converter 43 is converted into AC power by the second inverter 42, and the AC power is converted into AC power. 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 into AC power by the first inverter 41, and the AC power is converted into AC power by the power generation motor 12. Is supplied to. As a result, the power generation motor 12 is motorized, and the engine 11 is motorized by the power generation motor 12. This motoring causes the crankshaft of the engine 11 to rotate, and when the rotation speed rises to the rotation speed required for starting, the spark plug of the engine 11 is sparked and the engine 11 is started.

When the power generation motor 12 is operated to generate power while the engine 11 is operating, the power generation motor 12 generates AC power. The AC power generated by the power generation 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. When it is not necessary to supply the electric power to the drive motor 13, the DC power output from the first inverter 41 is stepped down by the boost converter 43, and the DC power after the step-down is supplied to the drive battery 14. , The drive battery 14 is charged.

When the electric vehicle 1 decelerates, the drive motor 13 is regeneratively operated, 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 becomes a resistance of the traveling drive system, and the resistance acts as a braking force (regenerative braking force) for braking 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 boost converter 43, and the DC power after the step-down is supplied to the drive battery 14, so that the drive battery 14 is charged.

Further, the electric vehicle 1 is provided with an ECU (Electronic Control Unit) 6 having a configuration including a microcomputer (microcontroller unit) 51. The microcomputer 51 contains, for example, a non-volatile memory such as a CPU and 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 so as to be capable of bidirectional communication by a CAN (Controller Area Network) communication protocol.

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

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

The range of use of the drive battery 14 is set as the SOC range. For example, if the engine 11 is stopped and the drive motor 13 is driven by the electric power from the drive battery 14 to continue the EV traveling, 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 the forced charging, the engine 11 is started and the power generation motor 12 is operated to generate power, so that the drive battery 14 is charged by the power generated by the power generation motor 12. When the charging of the drive battery 14 progresses and the SOC of the drive battery 14 rises to the control center SOC which is the center of the usage range of the drive battery 14, the power generation operation of the power generation motor 12 is stopped and the drive battery 14 is forced. Charging is completed (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 the engine speed and the engine torque in which the best thermal efficiency is achieved. From the viewpoint of fuel efficiency, it is preferable that the engine 11 is controlled so that the engine 11 operates at the high efficiency point P where the best thermal efficiency is achieved when the drive battery 14 is forcibly charged. FIG. 3 also shows an equal fuel consumption rate line, which is a contour line plotting the positions of the engine 11 rotation speed (engine rotation speed) and the engine 11 torque (engine torque) in the equal fuel consumption rate.

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

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

The non-volatile memory built in the microcomputer 51 of the ECU 6 stores the equal power line, the maximum engine torque line, and the optimum fuel consumption line in the form of a map. The equal power line is a characteristic line showing the relationship between the engine speed and the engine torque at which the outputs of the engines 11 are equal. The engine maximum torque line is a characteristic line indicating the engine speed at which the engine torque is maximized. The optimum fuel consumption line is a characteristic line showing the relationship between the engine speed and the engine torque in 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 the high efficiency region where the engine torque is larger than the optimum fuel consumption line. Specifically, when the operating point of the engine 11 is moved along the equal power line and 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.

<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 the optimum fuel consumption line for partitioning the high efficiency region (substantially, the high efficiency region is stored).

When the drive battery 14 is charged by the generated power of the power generation motor 12, the operating point of the engine 11 is set so that the engine speed decreases as the vehicle speed decreases in the high efficiency region where the engine torque is larger than the optimum fuel consumption line. Will be moved. As a result, the engine noise during charging of the drive battery 14 can be masked by road noise (vibration and noise due to running).

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

When lowering the engine speed, first, the operating point of the engine 11 is moved along the equal power line. As a result, the power generation power of the power generation motor 12 can be secured. Even if the engine torque reaches the maximum torque, if the engine speed is to be reduced, the operating point of the engine 11 is moved along the maximum torque line. As a result, the engine rotation can be further reduced while maintaining the generated power of the power generation motor 12 as large as possible.

Therefore, when the drive battery 14 is forcibly charged by the generated power of the power generation motor 12, the operating point of the engine is moved according to the vehicle speed of the electric vehicle 1 so that the user does not mind the engine sound. The characteristics can be improved. As a result, since it is not necessary to set a high lower limit value of the SOC usage range of the drive battery 14, it is possible to secure a large SOC usage range and improve fuel efficiency.

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

For example, in the above-described embodiment, the operating point of the engine 11 is moved according to the vehicle speed of the electric vehicle 1 when the drive battery 14 is forcibly charged, but the operating point of the engine 11 is moved according to the situation of the electric vehicle 1 including the vehicle speed. It is advisable to move the operating point of the engine 11. Even when the vehicle speed is low, in a situation where the accelerator pedal is depressed and the accelerator opening is relatively large, such as when climbing a slope, the user is less likely to notice even if the engine noise is loud. By operating the above, the remaining charge of the drive battery 14 can be recovered at an early stage.

Further, when the drive battery 14 is forcibly charged, the generated power of the power generation motor 12 is reduced when the SOC of the drive battery 14 recovers to a predetermined SOC set between the lower limit SOC and the control central SOC. , The engine speed may be kept low. This makes it possible for the user to be less concerned about the engine noise.

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

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

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

Claims (1)

A control device mounted on a vehicle that controls a hybrid system including a battery, an engine, and a power generation motor that generates electricity with the power of the engine.
An equal power line showing the relationship between the engine speed of the engine and the engine torque of the engine at which the outputs of the engines are equal, a maximum torque line showing the engine speed at which the engine torque is maximized, and the engine or A storage means for storing a high-efficiency region including a combination of the engine speed and the engine torque at which the energy efficiency of the hybrid system is equal to or higher than a predetermined value.
Includes an engine control means that controls 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 when the battery is charged by the power generation of the power generation motor.
When the engine control means reduces the engine speed, the operating point is moved along the isopower line, and after the engine torque reaches the maximum torque, the engine speed is further reduced. Is a control device that moves the operating point along the maximum torque line.

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