JP2025110799A - Hybrid vehicle control device - Google Patents

Abstract

A control device for a hybrid vehicle is provided that can appropriately charge a high-voltage power supply and a low-voltage power supply under conditions where engine output is limited.
[Solution] A control device for a hybrid vehicle equipped with a motor configured to convert engine power into electricity and charging the generated power into a main power source, and an alternator that converts engine power into electricity and charges the generated power into an auxiliary power source, wherein when the engine's required power, based on the hybrid vehicle's required driving force, the motor's required generated power, and the alternator's required generated power, is equal to or greater than a predetermined upper limit power, the control device limits the motor's generated power (step S3), and when the engine's required power is equal to or greater than the upper limit power and the remaining charge of the main power source is equal to or less than a predetermined first predetermined remaining amount, the control device limits the alternator's generated power to a power that will make the remaining charge of the auxiliary power source equal to or greater than a predetermined second predetermined remaining amount, thereby increasing the motor's generated power (step S5).
[Selected Figure] Figure 3

Description

The present invention relates to a control device for a hybrid vehicle equipped with an engine and a motor as driving power sources, and in particular to a control device for a hybrid vehicle further equipped with an alternator that converts engine power into electric power.

Patent Document 1 describes a control device for a hybrid vehicle that includes a motor generator and alternator connected to the engine output shaft, a high-voltage battery that charges with electricity generated by the motor generator, and a low-voltage battery that charges with electricity generated by the alternator. When idling, specifically when the vehicle is stopped, and there is a request to charge the low-voltage battery, this control device cuts off the engine's fuel supply while driving the motor generator to rotate the engine output shaft, causing the alternator to generate electricity and charge the low-voltage battery. When there is a request to charge both the high-voltage battery and the low-voltage battery, the control device drives the engine, causing the motor generator to generate electricity to charge the high-voltage battery, and causing the alternator to generate electricity and charge the low-voltage battery.

Japanese Patent Application Laid-Open No. 2000-303873

The control device described in Patent Document 1 is configured to charge the high-voltage battery and low-voltage battery when the vehicle is stopped and the engine can output sufficient power. However, when the vehicle is running, in addition to charging the high-voltage battery and low-voltage battery, the engine also outputs power to generate the required driving force. Meanwhile, when the vehicle is running, engine output may be limited due to abnormal noise, vibration, the driving environment, or other factors. Patent Document 1 does not disclose how the motor-generator and alternator are controlled under such conditions where engine output is limited, leaving room for technical improvement in order to appropriately control the power generated by the motor-generator and alternator.

The present invention was made in response to the above technical issues, and aims to provide a control device for a hybrid vehicle that can appropriately charge a high-voltage power supply and a low-voltage power supply under conditions where engine output is limited.

To achieve the above-mentioned objectives, the present invention provides a control device for a hybrid vehicle equipped with a motor configured to convert engine power into electric power and charging the generated electric power to a main power source, and an alternator that converts the engine power into electric power and charges the generated electric power to an auxiliary power source. When the engine's required power, based on the hybrid vehicle's required driving force, the motor's required generated electric power, and the alternator's required generated electric power, is equal to or exceeds a predetermined upper limit power, the control device limits the generated electric power of the motor. When the engine's required power is equal to or exceeds the upper limit power and the remaining charge of the main power source is equal to or less than a predetermined first predetermined remaining amount, the control device limits the generated electric power of the alternator to an electric power that will cause the remaining charge of the auxiliary power source to be equal to or greater than a predetermined second predetermined remaining amount, thereby increasing the generated electric power of the motor.

According to the present invention, when the engine's required power is equal to or greater than the upper limit power, the power generated by the motor is limited, thereby ensuring the power generated by the alternator and appropriately charging the auxiliary power source. Furthermore, when the engine's required power is equal to or greater than the upper limit power and the remaining charge of the main power source is equal to or less than a first predetermined remaining amount, the power generated by the alternator is limited to a level that will cause the remaining charge of the auxiliary power source to be equal to or greater than a second predetermined remaining amount, thereby increasing the power generated by the motor. Therefore, the main power source can be charged while preventing the remaining charge of the auxiliary power source from decreasing excessively. In other words, the engine's power can be appropriately allocated to driving force, charging the main power source, and charging the auxiliary power source, preventing an excessive decrease in the charging power of each power source and preventing a decrease in driving force.

1 is a diagram schematically illustrating an example of a hybrid vehicle according to an embodiment of the present invention. FIG. 4 is a diagram showing limit values of engine output. 4 is a flowchart illustrating an example of control executed by a control device according to an embodiment of the present invention. FIG. 4 is a diagram schematically showing the relationship between the required driving power, the power generated by the alternator, and the power generated by the motor.

The present invention will be described based on the embodiment shown in the drawings. Note that the embodiment described below is merely one example of how the present invention can be realized, and is not intended to limit the present invention.

An example of a hybrid vehicle according to an embodiment of the present invention is shown in Figure 1. The hybrid vehicle (hereinafter simply referred to as vehicle) Ve shown in Figure 1 is equipped with an engine (ENG) 1 and a motor (MG) 2 as driving power sources. This vehicle Ve is a front-engine, rear-drive vehicle in which the output shaft 3 of the engine 1 faces in the fore-and-aft direction of the vehicle Ve.

Engine 1 can be configured in the same way as a gasoline or diesel engine installed in a conventional vehicle, and is configured to generate driving torque by controlling the amount of intake air and fuel injection based on the required driving force corresponding to the amount of operation of the accelerator device (not shown), etc.

A torque converter 4 is connected to the output shaft 3 of the engine 1. This torque converter 4 can be configured similarly to torque converters installed in conventional vehicles, and includes a pump impeller 5 connected to the output shaft 3 of the engine 1, a turbine runner 7 positioned opposite the pump impeller 5 and connected to the output shaft 6, and a stator for rectifying the flow of oil from the pump impeller 5 to the turbine runner 7. The torque converter 4 may also be equipped with a lock-up clutch that connects the output shaft 3 of the engine 1 to the output shaft 6 of the torque converter 4 when the difference in rotation speed between the pump impeller 5 and the turbine runner 7 falls below a predetermined difference.

A motor 2 is attached to the output shaft 6 of the torque converter 4, and is configured to apply power to the output shaft 6 or regenerate power from the output shaft 6. Similar to motors used as driving power sources in conventional electric and hybrid vehicles, this motor 2 can be configured as a motor/generator that not only functions as a motor that generates driving torque when supplied with electric power, but also functions as a generator that converts that power into electric power when its output shaft (rotor shaft) 8 is rotated. Specifically, it can be configured as a synchronous motor or induction motor with a permanent magnet in the rotor.

The output shaft 8 of the motor 2 is connected to left and right drive wheels 11r, 11l via a transmission (T/M) 9, which can change the gear ratio, and a differential gear unit 10. The transmission 9 may be configured as a stepped transmission mechanism that changes the gear ratio in steps, or as a belt-type or toroidal transmission mechanism that can change the gear ratio continuously.

The engine 1 shown in FIG. 1 is also provided with an alternator 12 that is rotated by the power of the engine 1 to generate electricity. Specifically, the output shaft 3 of the engine 1 extends on the opposite side from the torque converter 4, and torque is transmitted from the engine 1 to the alternator 12 via a belt transmission mechanism 13 provided at the end of the output shaft 3.

A high-voltage battery 14, which may be a lithium-ion battery, nickel-metal hydride battery, or solid-state battery, is electrically connected to the motor 2 via a power control unit (not shown) that has an inverter and converter. In other words, the high-voltage battery 14 supplies power to the motor 2, and when the motor 2 functions as a generator, this power is charged into the high-voltage battery 14. The high-voltage battery 14 corresponds to the "main power source" in this embodiment of the present invention.

The vehicle Ve shown in Figure 1 is also equipped with high-voltage electrical equipment 17 that uses high-voltage power, such as an outlet 15 that receives AC 100V, similar to a household power source, and an air conditioner 16, and these high-voltage electrical equipment 17 are configured to receive power from the high-voltage battery 14.

Furthermore, the alternator 12 is electrically connected to an auxiliary battery (auxiliary Batt) 18, which is configured similarly to a 12V battery installed in a conventional vehicle, and is configured to charge the auxiliary battery 18 with the power generated by the alternator 12. This auxiliary battery 18 is configured to supply power to low-voltage electrical equipment 19 that operates on relatively low voltage power, such as various lights installed in the vehicle Ve and a navigation system. The high-voltage battery 14 is connected to the auxiliary battery 18 via a DC-DC converter 20, and power is supplied from the high-voltage battery 14 to the auxiliary battery 18, allowing the auxiliary battery 18 to be charged. The auxiliary battery 18 corresponds to the "auxiliary power source" in this embodiment of the present invention.

A controller 21 is provided to control the engine 1, motor 2, transmission 9, alternator 12, etc. Like controllers provided in conventional vehicles, this controller 21 is primarily composed of a microcomputer, and is configured to receive signals from various sensors provided in the vehicle Ve and output signals to control the engine 1, motor 2, transmission 9, alternator 12, etc. based on the input signals and pre-stored arithmetic equations and maps.

The vehicle Ve configured as described above determines the power required for the engine 1 based on the driving power required for the vehicle Ve and the charging power required for each battery 14, 18, and controls the intake air volume and fuel injection volume, controls the generated power of the motor 2 based on the required charging power of the high-voltage battery 14, and controls the generated power of the alternator 12 based on the required charging power of the auxiliary battery 18. The required power of the engine 1 is set taking into account mechanical losses due to the torque converter 4 and transmission 9, and electrical losses when power is converted to electricity by the motor 2 and alternator 12.

The above-mentioned engine 1 generates louder noise and vibration the greater the output drive torque and the higher the engine speed. In other words, the louder the engine 1's output (power), the louder the noise and vibration. Therefore, as shown by the solid line in Figure 2, an upper limit on engine 1 output is set to prevent excessive noise and vibration. Furthermore, because engine 1 outputs torque based on the amount of intake air, the maximum output of engine 1 decreases as the altitude increases and the air becomes thinner, as shown by the dashed line in Figure 2. That is, as shown in Figure 2, when the altitude is below e1, engine 1 operates within a range below the upper limit on output determined based on noise and vibration. However, when the altitude is higher than e1, the engine operates within a range below the maximum output determined for that altitude. In other words, the upper limit on engine 1 output is set to prevent noise and vibration and based on the maximum value determined for that altitude.

The control device in this embodiment of the present invention is configured to appropriately control the power generated by the motor 2 and alternator 12 when the required power of the engine 1, determined as described above, exceeds the upper limit of the engine 1's output (upper limit power). A flowchart illustrating an example of this control is shown in Figure 3.

In the control example shown in Figure 3, first, it is determined whether the alternator 12 is operating (step S1). That is, it is determined whether the engine 1 is running and whether field current is flowing through the alternator 12.

If the alternator 12 is not operating and a negative determination is made in step S1, the routine is temporarily terminated. Conversely, if the alternator 12 is operating and a positive determination is made in step S1, the routine determines whether the engine 1's required power exceeds its upper limit (step S2). Specifically, similar to conventional vehicle control devices, the system calculates the power required to drive the vehicle Ve (required driving power) based on the accelerator pedal position and vehicle speed, calculates the required generated power of the motor 2 based on the state of charge (SOC) of the high-voltage battery 14, and calculates the required generated power of the alternator 12 based on the state of charge (SOC) of the auxiliary battery 18. These powers and generated powers are then added together to determine the engine 1's required power. The altitude of the vehicle Ve's current location is also determined using a navigation system or other device to calculate the upper limit of engine 1's output. The engine 1's required power is then compared with the upper limit of engine 1's output.

If step S2 returns a negative answer because the required power of engine 1 does not exceed the upper limit, the routine is terminated. That is, engine 1, motor 2, or alternator 12 is controlled based on the required power or required generated power. Conversely, if step S2 returns a positive answer because the required power of engine 1 exceeds the upper limit, the generated power required of motor 2 is reduced (step S3). Specifically, the required generated power of motor 2 is set as the power obtained by subtracting the required driving power and the generated power required of alternator 12 from the upper limit of engine 1 output. That is, power is generated by alternator 12 in preference to motor 2.

Next, it is determined whether the SOC of the high-voltage battery 14 is equal to or lower than a predetermined value (lower allowable limit) (step S4). This step S4 is a step for preventing the SOC of the high-voltage battery 14 from dropping excessively, and can be determined by detecting the SOC, for example, by detecting the output voltage of the high-voltage battery 14. Note that the predetermined value in step S4 corresponds to the "first predetermined remaining capacity" in this embodiment of the present invention.

If the SOC of the high-voltage battery 14 is higher than a predetermined value and a negative determination is made in step S4, the routine is terminated. Specifically, the engine 1 output is set to its upper limit, the alternator 12 is controlled according to the required power generation, and the motor 2 is controlled according to the required power generation determined in step S3. Conversely, if the SOC of the high-voltage battery 14 is lower than a predetermined value and a positive determination is made in step S4, the required power generation of the alternator 12 is reduced to a level that keeps the SOC of the auxiliary battery 18 above a predetermined value (step S5), and the routine is terminated. Specifically, the required driving power and the power generated by the alternator 12 within a range that keeps the SOC of the auxiliary battery 18 above a predetermined value are subtracted from the upper limit of the engine 1 output, and the result is set as the required power generation of the motor 2. In other words, the power generation of the alternator 12 is set to the minimum required, and the power generation of the motor 2 is increased. In other words, power generation by the motor 2 is prioritized over power generation by the alternator 12. This predetermined value for maintaining the SOC of the auxiliary battery 18 corresponds to the "second predetermined remaining capacity" in this embodiment of the present invention.

Figure 4 shows a schematic diagram of the relationship between the required driving power Pd, the power generated by the alternator 12, Palt, and the power generated by the motor 2, Pm, when step S5 is executed. The upper limit (or maximum) of engine 1 output is indicated by a dashed line. As shown in Figure 4, the power required of the engine 1, calculated by adding the required driving power Pd and the required power generated by the motor 2 and alternator 12, Pcharge (Pm + Palt), exceeds the upper limit of engine 1 output. The example shown in Figure 4 also shows a case where the SOC of the high-voltage battery 14 is higher than a predetermined value. Therefore, by executing step S5, the power generated by the alternator 12, Palt, is reduced to the minimum value within the range in which the SOC of the auxiliary battery 18 is equal to or greater than the predetermined value. This generated power is designated Palt1. Therefore, the power generated by the motor 2 is set to the upper limit of the engine 1 output minus the required driving power Pd and the reduced power generated by the alternator 12, Palt1. This power generation is denoted as Pm1.

As described above, when the power required for the engine 1 is equal to or greater than the upper limit, limiting the power generated by the motor 2 ensures that the alternator 12 generates sufficient power and appropriately charges the auxiliary battery 18. Furthermore, when the power required for the engine 1 is equal to or greater than the upper limit and the SOC of the high-voltage battery 14 is equal to or less than a predetermined value, the power generated by the alternator 12 is limited to a range in which the SOC of the auxiliary battery 18 is equal to or greater than the predetermined value, thereby determining the power generated by the motor 2. This allows the high-voltage battery 14 to be charged preferentially while preventing the SOC of the auxiliary battery 18 from dropping excessively. In other words, the power of the engine 1 can be appropriately allocated to the required driving power Pd, charging the high-voltage battery 14, and charging the auxiliary battery 18, thereby preventing an excessive drop in the charging power of each battery 14, 18 and suppressing a decrease in driving force.

REFERENCE SIGNS LIST 1 Engine 2 Motor 12 Alternator 14 High voltage battery 17 High voltage electrical equipment 18 Auxiliary battery 19 Low voltage electrical equipment 21 Controller Ve Hybrid vehicle

Claims (1)

A control device for a hybrid vehicle including a motor configured to be able to convert engine power into electric power and to charge a main power supply with the generated electric power, and an alternator that converts engine power into electric power and charges an auxiliary power supply with the generated electric power,
limiting the generated power of the motor when a required power of the engine based on a required driving force of the hybrid vehicle, a required generated power of the motor, and a required generated power of the alternator is equal to or greater than a predetermined upper limit power;
a control device for a hybrid vehicle, characterized in that, when the required power of the engine is equal to or greater than the upper limit power and the remaining charge of the main power supply is equal to or less than a predetermined first predetermined remaining amount, the power generated by the alternator is limited to power that will cause the remaining charge of the auxiliary power supply to be equal to or greater than a predetermined second predetermined remaining amount, thereby increasing the power generated by the motor.