JP2024099246A - Charge control device of hybrid vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a charge control device of a hybrid vehicle that can shorten a time during which an engine is operated only for actuating a cooling device, and can improve fuel consumption.

SOLUTION: A hybrid vehicle includes: a motor for power generation which generates power by power of an engine; a motor for driving which drives a driving wheel by power generated by the motor for power generation or power stored in a battery; and a cooling device for cooling a cabin using power stored in a battery. An ECU sets a target charge state to be higher as an outside air temperature is higher. When a predetermined condition including that the vehicle is in running and the cooling device is in operation is established, the ECU sets the target charge state to be higher as the outside air temperature is higher. When the predetermined condition is not established, the ECU sets the target charge state to be a fixed value.

SELECTED DRAWING: Figure 2

COPYRIGHT: (C)2024,JPO&INPIT

Description

The present invention relates to a charging control device for a hybrid vehicle.

Patent Document 1 describes a technology for a hybrid vehicle equipped with an engine and a motor that increases the power generation start charging rate and the target charging rate when the battery temperature is equal to or lower than a first predetermined temperature or when the vehicle's ambient temperature is equal to or lower than a second predetermined temperature. As a result, the technology described in Patent Document 1 can maintain a high battery charging rate when there is a possibility of a decrease in battery output due to battery temperature, prevent a decrease in battery output due to the charging rate, and maintain the output performance of the battery as a whole.

JP 2022-68381 A

Here, in a hybrid vehicle equipped with an engine and a motor, the engine is operated at an operating point with excellent thermal efficiency, and in situations where the operating point is poor in thermal efficiency, such as when the vehicle is stopped or traveling at low speeds, the engine is stopped and power is supplied to the motor from the battery.

Meanwhile, air conditioning systems installed in hybrid vehicles may consist of a heating system that supplies engine coolant to a heater core to heat the passenger compartment, or a heat pump type cooling system that cools the passenger compartment by operating a compressor using battery power. In such air conditioning systems, the engine must be operated as a heat source to operate the heating system, and the battery's state of charge must be above the lower limit of the management range or the engine must be operated to generate electricity to operate the cooling system. For this reason, fuel efficiency deteriorates when the engine is operated at an operating point with poor thermal efficiency solely for the purpose of operating the air conditioning system.

However, in the technology described in Patent Document 1, when the battery temperature is below a predetermined temperature, the target charging rate is raised to maintain a high battery charging state (battery charging rate), but no consideration is given to the charging state when the air conditioning device is operated in a situation where the battery temperature is not below the predetermined temperature due to high outside air temperature. For this reason, when the engine is stopped and the air conditioning device is operated using the battery as a power source in a high outside air temperature situation, the charging state reaches the lower limit of the management range in a short time, and the engine is then started and operated only as a power source for air conditioning. For this reason, the technology described in Patent Document 1 has the problem of being unable to suppress deterioration in fuel efficiency when the air conditioning device is operating.

The present invention aims to provide a charging control device for a hybrid vehicle that can shorten the time that the engine is operated solely for the purpose of operating the air conditioning system, thereby improving fuel efficiency.

To solve the above problems, the present invention provides a control device for a hybrid vehicle that is mounted on a hybrid vehicle that includes a generator that generates electricity using engine power, a rotating electric machine that drives drive wheels using the electricity generated by the generator or the electricity stored in a battery, and an air conditioning device that cools the vehicle interior using the electricity stored in the battery, and that includes a control unit that controls the state of charge of the battery to a predetermined target state of charge, and is characterized in that the control unit sets the target state of charge higher the higher the outside air temperature.

In this way, the present invention provides a charging control device for a hybrid vehicle that can shorten the time that the engine is operated solely for the purpose of operating the air conditioning device, thereby improving fuel efficiency.

FIG. 1 is a configuration diagram of a hybrid vehicle equipped with a charge control device according to an embodiment of the present invention. FIG. 2 is a diagram showing the relationship between the target state of charge and the outside air temperature in the charge control device for a hybrid vehicle according to one embodiment of the present invention. FIG. 3 is a time chart showing the transition of the state of charge during operation of the air conditioning device in the charge control device for a hybrid vehicle according to one embodiment of the present invention.

The hybrid vehicle charge control device according to one embodiment of the present invention is mounted on a hybrid vehicle equipped with a generator that generates electricity using engine power, a rotating electric machine that drives drive wheels using electricity generated by the generator or electricity stored in a battery, and an air conditioning device that cools the vehicle interior using electricity stored in the battery, and is a hybrid vehicle control device equipped with a control unit that controls the battery's state of charge to a predetermined target state of charge, and is characterized in that the control unit sets the target state of charge higher the higher the outside air temperature. As a result, the hybrid vehicle charge control device according to one embodiment of the present invention can shorten the time that the engine is operated solely for the purpose of operating the air conditioning device, thereby improving fuel efficiency.

A hybrid vehicle equipped with a charging control device according to an embodiment of the present invention will be described in detail below with reference to the drawings. In FIG. 1, a hybrid vehicle 1 according to an embodiment of the present invention includes an engine 2, a power generating motor 3 as a generator, a high voltage battery 9, and a drive motor 4 as a rotating electric machine.

Engine 2 has multiple cylinders. In this embodiment, engine 2 is configured to perform a series of four strokes for each cylinder, consisting of an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke.

The generator motor 3 is connected to the engine 2 and generates electricity using the power of the engine 2. The high-voltage battery 9 is composed of a secondary battery such as a lithium-ion battery.

The drive motor 4 drives the left and right drive wheels 6 with electricity generated by the generator motor 3 or electricity stored in the high-voltage battery 9. In detail, the drive motor 4 has the function of an electric motor that drives the drive wheels 6 with electricity supplied from the high-voltage battery 9, and the function of a generator that performs regenerative power generation with the reverse driving force input from the drive wheels 6. The drive motor 4 and the drive wheels 6 are connected via a reduction gear 5. The reduction gear 5 reduces the rotation output from the drive motor 4 and outputs it to the left and right drive wheels 6.

The hybrid vehicle 1 is equipped with a PCU 7 (Power Control Unit). The PCU 7 is provided with an inverter and a DCDC converter (not shown). The PCU 7 has a function of driving the drive motor 4 with power supplied from the high-voltage battery 9, and a function of regenerating power for the drive motor 4 with a reverse driving force.

In more detail, under the control of the ECU 8, the PCU 7 converts DC power supplied from the high-voltage battery 9 into three-phase AC power using an inverter to drive the drive motor 4. The PCU 7 also converts the three-phase AC power generated by the drive motor 4 into DC power using an inverter to charge the high-voltage battery 9. The PCU 7 also converts between high and low voltages using a DCDC converter.

Hybrid vehicle 1 is a so-called series hybrid vehicle, and runs by driving drive motor 4 with electricity generated by the power of engine 2. In a series hybrid vehicle 1, the vehicle runs only with the driving force of drive motor 4, and the electricity required to drive drive motor 4 is generated by generator motor 3 using engine 2 as the power source.

The hybrid vehicle 1 is equipped with a radiator 11 through which cooling water is circulated between the engine 2 and the radiator 11. The radiator 11 cools the cooling water by exchanging heat with the outside air.

The hybrid vehicle 1 is equipped with a heating device 12 that uses the engine 2 coolant as a heat source to heat the passenger compartment. The heating device 12 is equipped with a heater core 13 through which the coolant is circulated between the engine 2. The heater core 13 heats the passenger compartment by exchanging heat with the air in the passenger compartment.

The hybrid vehicle 1 is equipped with a mechanical water pump 14, which is operated by the power of the engine 2. The mechanical water pump 14 circulates coolant between the engine 2 and the radiator 11. The mechanical water pump 14 also circulates coolant between the engine 2 and the heater core 13. Therefore, the mechanical water pump 14 is included as part of the heating device 12.

The hybrid vehicle 1 is equipped with a heat pump type cooling device 16 that cools the vehicle interior using electricity stored in the high voltage battery 9. The cooling device 16 is equipped with an electric compressor 17 that operates with electricity and compresses the refrigerant.

The hybrid vehicle 1 is equipped with an ECU (Electronic Control Unit) 8. The ECU 8 is composed of a computer unit that includes a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), a flash memory for storing backup data, and an input port and an output port.

The ROM of the computer unit stores various constants, maps, and the like, as well as a program for causing the computer unit to function as the ECU 8. In other words, the CPU executes the program stored in the ROM using the RAM as a working area, causing the computer unit to function as the ECU 8 in this embodiment.

The ECU 8 controls the state of charge of the high-voltage battery 9 so that it is within a management range defined by upper and lower limits. The ECU 8 also controls the state of charge of the high-voltage battery 9 to a predetermined target state of charge within the management range. Note that since the target state of charge is a control target value, the actual state of charge fluctuates within the management range, fluctuating between the target state of charge and the charge, depending on the input and output of power to the high-voltage battery 9.

The ECU 8 operates the engine 2 at an operating point with excellent thermal efficiency, and supplies power from the generator motor 3 to electrical equipment such as the drive motor 4, high-voltage battery 9, and electric compressor 17. In addition, when the load torque on the engine 2 is small, such as when the vehicle is stopped or traveling at low speed, and the operating point is poor in thermal efficiency, the ECU 8 stops the operation of the engine 2 as a so-called idling stop, and supplies power from the high-voltage battery 9 to the drive motor 4, provided that the state of charge of the high-voltage battery 9 is not below the lower limit but is within a management range. The operating point of the engine 2 is a point that is determined by a combination of the load torque and the engine speed.

Here, the air conditioning device 16 in this embodiment is structured to cool the vehicle interior by operating the electric compressor 17 using power from the high-voltage battery 9. Therefore, in order for the air conditioning device 16 to operate, it is necessary that the state of charge of the high-voltage battery 9 is equal to or higher than a lower limit, or that electricity is being generated by the operation of the engine 2.

In order to extend the operating time of the air conditioner 16 using the high-voltage battery 9, it is possible to increase the capacity of the high-voltage battery 9, but in this case, the high-voltage battery 9 would be expensive and large, which would increase the price and weight of the vehicle. Also, in the series hybrid system, electricity can be generated by operating the engine 2, so there is little need to increase the capacity of the high-voltage battery 9.

Therefore, taking into consideration the vehicle price, vehicle weight, etc., it is not preferable to increase the capacity of the high-voltage battery 9. However, if the high-voltage battery 9 is not increased in capacity, after the charge state of the high-voltage battery 9 reaches its lower limit, the engine 2 will be operated only as a power source for air conditioning at an operating point with poor thermal efficiency, causing a deterioration in fuel efficiency. Such a deterioration in fuel efficiency is noticeable when the engine 2 is operated in a situation with poor thermal efficiency, such as when the vehicle is stopped or traveling at low speed, when it is preferable to stop the operation of the engine 2 by idling stop.

Therefore, in this embodiment, the ECU 8 sets the target state of charge higher as the outside air temperature is higher. The outside air temperature is the temperature of the air outside the hybrid vehicle 1 (outside air) and is acquired by a temperature sensor (not shown). In addition, when a predetermined condition is met, including that the vehicle is running and the air conditioner 16 is operating, the ECU 8 sets the target state of charge of the high-voltage battery 9 higher as the outside air temperature is higher, and when the predetermined condition is not met, the ECU 8 sets the target state of charge to a constant value. The predetermined condition includes at least that the vehicle is running and that the air conditioner 16 is operating, but may also include that the high-voltage battery 9 is being charged by regenerative power generation by the drive motor 4 accompanying deceleration of the hybrid vehicle 1. This is because by charging more power to the high-voltage battery 9 during regenerative power generation by the drive motor 4 when the vehicle is decelerating, the amount of power generated by the generator motor 3 using the power of the engine 2 when the vehicle is not decelerating can be reduced, and overall energy efficiency can be improved.

In FIG. 2, the vertical axis represents the target state of charge (referred to as target SOC in the figure) of the high-voltage battery 9, and the horizontal axis represents the outside air temperature. Also, in FIG. 2, an outside air temperature of 25° C. or higher is referred to as a high outside air temperature, and an outside air temperature of less than 25° C. is referred to as a low outside air temperature.

In FIG. 2, the lower the outside air temperature, the lower the target state of charge is set by the ECU 8. Also, the higher the outside air temperature, the higher the target state of charge is set by the ECU 8. The specific target state of charge setting value is set based on the target state of charge value (A%) when the outside air temperature is 25°C as the reference value, and in low outside air temperature ranges below 25°C, the lower the outside air temperature is, the lower the target state of charge becomes compared to the reference value, and in high outside air temperature ranges above 25°C, the higher the outside air temperature is, the higher the target state of charge becomes compared to the reference value.

In FIG. 3, the vertical axis represents the state of charge (SOC) of the high-voltage battery 9, and the horizontal axis represents time. The solid line represents the progress of the state of charge in one embodiment of the present invention, and the dashed line represents a comparative example in which the target state of charge is set to a constant value.

In FIG. 3, in the present invention, at time t1, the hybrid vehicle 1 is running with the air conditioner 16 operating. Also, the hybrid vehicle 1 is running with the target state of charge of the high-voltage battery 9 set higher as the outside air temperature increases. As a result, the state of charge is H (%), which is equal to the target state of charge corresponding to the high outside air temperature.

After that, at time t2, the engine 2 is stopped at idle due to the vehicle deceleration, and the state of charge of the high-voltage battery 9 temporarily rises due to regenerative charging, but then the vehicle stops, and the air conditioner 16 operates using only the high-voltage battery 9 as a power source. This causes the state of charge to fall.

Then, at time t4 after time t3, the state of charge reaches the lower limit. This causes engine 2 to restart and operate only as a power source for air conditioning device 16.

Thus, in the present invention, the length of the period during which the cooling device 16 is operated with the engine 2 stopped is T(H), which is the length of the period from time t2 to time t4.

On the other hand, in the comparative example, at time t1, the vehicle is traveling with the target state of charge at a constant value of A (%). As a result, the state of charge is A (%), which is equal to the target state of charge.

After that, at time t2, the state of charge temporarily increases, but then the vehicle stops, and the air conditioner 16 operates using only the high-voltage battery 9 as a power source, causing the state of charge to decrease.

Then, at time t3, the state of charge reaches the lower limit. This causes engine 2 to restart and operate only as a power source for air conditioning device 16.

As such, in the comparative example, the length of the period during which the air conditioner 16 can be operated by the power of the high-voltage battery 9 is T(A), which is the length of the period from time t2 to time t3. Since this T(A) is shorter than T(H) according to the present invention, in the comparative example, the time during which the engine 2 is operated solely as a power source to generate power for air conditioning after the state of charge reaches the lower limit is long.

Therefore, according to the present invention, the time during which the engine 2 is operated solely as a power source for air conditioning after the charge state reaches the lower limit can be shortened compared to the comparative example in which the target charge state is set to a constant value regardless of the outside air temperature.

As described above, in this embodiment, the ECU 8 sets the target state of charge higher the higher the outside air temperature.

As a result, in high outside air temperature conditions where the air conditioning device 16 is often operating, when the air conditioning device 16 continues to operate while the vehicle is stopped, the higher the outside air temperature, the longer the time during which the high-voltage battery 9 is discharged to the lower limit of the state of charge management range. Therefore, the time during which the engine 2 is operated solely as a power source for air conditioning after the target state of charge reaches the lower limit can be made shorter than when the target state of charge is set to a constant value regardless of the outside air temperature.

As a result, the time that the engine 2 is operated solely for the purpose of operating the air conditioner 16 can be shortened, improving fuel efficiency. Note that the method of setting the target state of charge higher as the outside air temperature increases can be applied not only to series hybrid vehicles, but also to vehicles equipped with an electric compressor 17.

In addition, in this embodiment, when certain conditions are met, including the vehicle being in motion and the air conditioning device 16 being in operation, the ECU 8 sets the target state of charge higher the higher the outside air temperature, and when the certain conditions are not met, the ECU 8 sets the target state of charge to a constant value.

As a result, at least when the vehicle is traveling and the air conditioning device 16 is operating, when the air conditioning device 16 continues to operate while the vehicle is stopped, the higher the outside air temperature, the longer the time during which the high-voltage battery 9 is discharged up to the lower limit of the charge state management range, and the shorter the time during which the engine 2 is operated solely as a power source for air conditioning after the lower limit is reached.

In addition, when the vehicle is traveling but the air conditioning device 16 is not operating, the air conditioning device 16 is rarely operated while the vehicle is stopped, so by setting the target charge state to a normal constant value, the charge state of the high-voltage battery 9 can be optimized to a situation where operation of the air conditioning device 16 is not taken into consideration. Note that, instead of the condition that the air conditioning device 16 is operating, one of the specified conditions may be that a request signal for air conditioning has been received from the air conditioning system controller.

Although an embodiment of the present invention has been disclosed, it is apparent that modifications may be made by one of ordinary skill in the art without departing from the scope of the present invention. All such modifications and equivalents are intended to be included in the following claims.

1 Hybrid vehicle 2 Engine 3 Power generating motor (generator)
4. Driving motor (rotating electric machine)
6 Drive wheels 8 ECU (control unit)
9 High voltage battery (battery)
16. Air conditioning unit

Claims (2)

A generator that generates electricity using the power of the engine;
a rotating electric machine that drives drive wheels using electric power generated by the generator or electric power stored in a battery;
a cooling device that cools a vehicle interior using the electric power stored in the battery,
A control device for a hybrid vehicle including a control unit that controls a state of charge of the battery to a predetermined target state of charge,
The control unit sets the target state of charge higher as the outside air temperature increases. The charge control device for a hybrid vehicle according to claim 1, characterized in that the control unit sets the target state of charge higher as the outside air temperature increases when a predetermined condition is met, including the vehicle being driven and the air conditioning device being in operation, and sets the target state of charge to a constant value when the predetermined condition is not met.

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