Regenerative braking system for hybrid vehicles

Abstract

This hybrid vehicle regenerative braking apparatus is provided to a vehicle having an engine 2, a drive battery 11, a front motor 4 that drives front wheels 3, and a motor generator 9 that is driven by the engine 2 and generates power. The hybrid vehicle regenerative braking apparatus has a regenerative braking control unit 51 that causes power generation via the front motor 4 during deceleration of the vehicle and performs regenerative braking that imparts a braking force to the vehicle 1. The hybrid vehicle regenerative braking apparatus further comprises: a motoring control unit 52 that supplies power from the drive battery 11 to the motor generator 9 during execution of regenerative braking and performs motoring for forcing the driving of the engine 2 in a state in which fuel supply has stopped; a battery monitoring unit 11a that detects the charging rate of the drive battery 11; and a means that, if the charging rate of the drive battery 11 is at or above a specified full-charge value during execution of the motoring, causes a cooling system 50 such as an oil pump of the engine 2 to operate, cools the engine 2, and increases friction in the forced driving.

Description

[Technical Field]

[0001] The present invention relates to a regenerative braking device for a hybrid vehicle. [Background technology]

[0002] In the past, plug-in hybrid vehicles and hybrid vehicles (hereinafter collectively referred to as hybrid vehicles) equipped with an engine and an electric motor as a driving source have widely used regenerative power generation to increase the distance that can be traveled by the electric motor. Regenerative power generation uses the electric motor for driving to generate electricity during deceleration and charges the storage battery.

[0003] Furthermore, Patent Document 1 proposes that in order to prevent overcharging of the storage battery, the loss of the electric motor is increased when the battery is close to full charge during regenerative braking, thereby reducing the amount of power generated while ensuring braking force due to regenerative power generation (regenerative braking force).As an example of a means for increasing the loss of the electric motor, a method is described in which eddy current loss is increased by increasing the switching frequency of the inverter that controls the electric motor. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-77808 Summary of the Invention [Problem to be solved by the invention]

[0005] However, if the loss of the electric motor is increased as in Patent Document 1, the temperatures of the electric motor and the inverter will rise, and there is a risk that a sufficient regenerative braking force will not be obtained for a long period of time.

[0006] One possible method for obtaining regenerative braking force when the storage battery is fully charged is to use newly installed electrical equipment to consume the power generated by regenerative power generation. However, installing such electrical equipment in a vehicle poses many limitations, such as component costs and installation space.

[0007] The present invention has been made in view of the above problems, and an object of the present invention is to provide a regenerative braking device for a hybrid vehicle that can ensure regenerative braking force when the storage battery is fully charged. [Means for solving the problem]

[0008] In order to achieve the above object, a regenerative braking device for a hybrid vehicle according to the present invention ,workman a regenerative braking device provided for a hybrid vehicle having an engine, a storage battery, a first rotating electric machine that drives the vehicle's drive wheels, and a second rotating electric machine that is driven by the engine to generate electricity, and having a regenerative braking control unit that causes the first rotating electric machine to generate electricity when the vehicle is decelerating, thereby performing regenerative braking to apply braking force to the vehicle; a motoring control unit that, when performing regenerative braking, supplies power from the storage battery to the second rotating electric machine to perform motoring, which forcibly drives the engine with fuel supply stopped; a charging rate detection means that detects the charging rate of the storage battery; and a friction increasing means that, when performing motoring, increases the friction in the forced driving of the engine if the charging rate is equal to or higher than a predetermined full charge value, wherein the friction increasing means is a water pump that circulates engine coolant to cool the engine, and changes the discharge amount of the water pump based on the temperature of the engine or the charging rate of the storage battery.

[0009] As a result, the electric power generated by the first rotating electric machine through regenerative braking is consumed by the second rotating electric machine through motoring, thereby increasing the amount of power generated by the first rotating electric machine and increasing the regenerative braking force. Furthermore, when the storage battery's state of charge is equal to or greater than a predetermined full charge value, friction increases during forced driving of the engine during motoring, allowing the second rotating electric machine to consume a large amount of power, thereby preventing the storage battery from becoming overcharged. In addition, by cooling the engine, friction can be easily increased significantly when the engine is forcibly driven during motoring. Ru cold By using a water pump to circulate the cooling water, friction can be easily increased while suppressing increases in cost and installation space.

[0011] Preferably, the friction increasing means is an electric motor that is used to increase the friction of the engine. Cold It is a good idea to circulate the cooled water. As a result, when the friction increasing means cools the engine, power is consumed by the electric motor, so that the regenerated power can be further consumed.

[0014] Preferably, the vehicle is equipped with a radiator that exchanges heat between the cooling water and outside air, and a radiator fan that blows air to the radiator, and the friction increasing means drives the radiator fan when driving the water pump during motoring. This improves the cooling efficiency of the cooling water in the radiator, thereby promoting engine cooling and further increasing friction when the engine is forcibly driven. [Effects of the Invention]

[0015] In the regenerative braking device for a hybrid vehicle of the present invention, when the charge rate of the storage battery is equal to or higher than a predetermined full charge value, the friction of the forced drive of the engine during motoring is increased, and a large amount of power can be consumed in the second rotating electric machine, thereby preventing the charge rate of the storage battery from becoming overcharged while ensuring a large braking force through regenerative braking. [Brief explanation of the drawings]

[0016] [Figure 1] 1 is a schematic diagram of a plug-in hybrid vehicle equipped with a regenerative braking device according to an embodiment of the present invention; [Figure 2] FIG. 1 is a configuration diagram of a regenerative braking system that performs a regenerative braking function. [Figure 3] 4 is a flowchart showing a control procedure for motoring during regenerative braking executed in the regenerative braking system. [Figure 4] FIG. 2 is an explanatory diagram of destinations to which regenerative electric power is supplied in the vehicle of the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0017] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram of a plug-in hybrid vehicle (hereinafter referred to as vehicle 1) equipped with a drive control device according to one embodiment of the present invention.

[0018] The vehicle 1 of this embodiment is capable of traveling by driving front wheels 3 with the output of an engine 2, and is provided with an electric front motor 4 (first rotating electrical machine) that drives the front wheels 3 (traveling drive wheels).

[0019] The engine 2 is capable of driving a drive shaft 8 of the front wheels 3 via a reduction gear 7, and is also capable of driving a motor generator 9 (second rotating electrical machine) via the reduction gear 7 to generate electricity.

[0020] The front motor 4 is powered by high-voltage power supplied from a drive battery 11 (storage battery) and a motor generator 9 mounted on the vehicle 1 via a front inverter 10, and drives a drive shaft 8 of the front wheels 3 via a reduction gear 7. In the reduction gear 7, the power transmission path between the engine 2 and the drive shaft 8 and the power transmission path between the front motor 4 and the drive shaft 8 are separate paths. The reduction gear 7 has a built-in engine clutch 7a that can switch between connecting and disconnecting the transmission of power between the output shaft of the engine 2 and the drive shaft 8. The reduction gear 7 also has a built-in motor clutch 7b that can switch between connecting and disconnecting the transmission of power between the front motor 4 and the drive shaft 8.

[0021] The electric power generated by the motor generator 9 can be used to charge the drive battery 11 via the front inverter 10, and can also be used to supply electric power to the front motor 4.

[0022] The driving battery 11 is composed of a secondary battery such as a lithium ion battery, and has a battery module (not shown) that is made up of multiple battery cells.It also has a battery monitoring unit 11a (charging rate detection means) that monitors the charging rate (State Of Charge, hereinafter referred to as SOC) of the battery module.

[0023] The front inverter 10 has a function of controlling the output of the front motor 4 based on a control signal from the hybrid control unit 20, and also of controlling the amount of power generated by the motor generator 9. The vehicle 1 is equipped with a charger 21 that charges the drive battery 11 using an external power source.

[0024] The engine 2 is also provided with an electric cooling system 50 (friction increasing means) that cools the engine 2. The cooling system 50 is, for example, an electric engine oil pump that circulates lubricating oil for the engine 2. The engine oil pump is controlled by the engine control unit 22 so as to operate when the engine is running. Furthermore, the operation of the engine oil pump is controlled by the hybrid control unit 20 via the engine control unit 22.

[0025] The electric cooling system 50 may also be an electric water pump that circulates the coolant for the engine 2. The water pump is also controlled by the engine control unit 22 so that it operates when the engine is running. The operation of the water pump is also controlled by the hybrid control unit 20 via the engine control unit 22. Furthermore, the cooling system 50 may use a radiator fan that blows air to the radiator together with the water pump. By driving the radiator fan in conjunction with the driving of the water pump, the cooling efficiency of the coolant in the radiator that exchanges heat between the coolant and outside air can be improved, thereby further cooling the engine 2.

[0026] The hybrid control unit 20 is a control device for performing overall control of the vehicle 1, and is configured to include an input / output device, a storage device (ROM, RAM, non-volatile RAM, etc.), a central processing unit (CPU), and the like.

[0027] The input side of the hybrid control unit 20 is connected to the battery monitoring unit 11a (charging rate detection means) of the drive battery 11, the front inverter 10, the engine control unit 22, the accelerator opening sensor 40 that detects the accelerator operation amount, etc., and detection and operation information from these devices is input.

[0028] On the other hand, the output side of the hybrid control unit 20 is connected to the front inverter 10, the reduction gear 7 (clutches 7a, 7b), and the engine control unit 22.

[0029] The hybrid control unit 20 then calculates the vehicle required output and driving torque required to drive the vehicle 1 based on the above-mentioned various detected quantities and various operational information from the accelerator opening sensor 40, etc., and sends control signals to the engine control unit 22, the front inverter 10, and the reducer 7 to switch the driving mode (EV mode: electric vehicle mode, series mode, parallel mode), and control the output of the engine 2 and front motor 4, and the output (generated power) of the motor generator 9.

[0030] In the EV mode, the engine 2 is stopped, and the front motor 4 is driven by electric power supplied from the drive battery 11 to propel the vehicle 1.

[0031] In series mode, the engine clutch 7a of the reduction gear 7 is disengaged and the motor generator 9 is operated by the engine 2. The front motor 4 is then driven by the electric power generated by the motor generator 9 and the electric power supplied from the drive battery 11 to drive the vehicle. Also, in series mode, the rotational speed of the engine 2 is set to a predetermined rotational speed and surplus electric power is supplied to the drive battery 11 to charge it.

[0032] In parallel mode, the engine clutch 7a of the reducer 7 is connected, and power is mechanically transmitted from the engine 2 via the reducer 7 to drive the front wheels 3. The front motor 4 is driven by electric power generated by operating the motor generator 9 using the engine 2 and electric power supplied from the drive battery 11, causing the vehicle to travel.

[0033] In the EV mode and the series mode, the motor clutch 7b is in an engaged state. In the parallel mode, the motor clutch 7b is also basically in an engaged state.

[0034] The hybrid control unit 20 sets the driving mode to the parallel mode in areas where the engine 2 is efficient, such as high speed areas. In areas other than the parallel mode, i.e., in the medium to low speed area, the hybrid control unit 20 switches between the EV mode and the series mode based on the driving torque of the vehicle 1 and the state of charge (SOC) of the driving battery 11.

[0035] The vehicle 1 is equipped with a regenerative braking function that, when decelerating with the accelerator off, forcibly drives the front motor 4 using the rotational force of the front wheels 3 to generate electricity (regenerative power generation) and imparts braking torque (regenerative braking force) to the front wheels 3.

[0036] FIG. 2 is a configuration diagram of a regenerative braking system 25 (regenerative braking device) that performs a regenerative braking function. The hybrid control unit 20 of this embodiment includes a regenerative braking control unit 51 that controls regenerative braking, and a motoring control unit 52 that controls motoring. The regenerative braking control unit 51 calculates the regenerative braking torque based on the wheel speed, the brake operation amount, etc. when the vehicle 1 is decelerating. Furthermore, the regenerative braking control unit 51 controls the front motor 4 via the front inverter 10 to control the regenerative braking torque due to regenerative power generation.

[0037] The motoring control unit 52 executes motoring, which forcibly drives the engine 2 using the motor generator 9. During regenerative braking, motoring is performed with the engine clutch 7a disengaged and the motor clutch 7b engaged, as in series mode, and fuel is not supplied to the engine 2, but power is supplied to the motor generator 9 to forcibly drive the engine 2. The power supplied to the motor generator 9 is mainly power generated by the front motor 4 during regenerative braking. As a result, power is consumed in the motor generator 9 due to friction when forcibly driving the engine 2.

[0038] FIG. 3 is a flowchart showing a control procedure for motoring during regenerative braking executed in the regenerative braking system 25. The motoring control shown in FIG. 3 is repeatedly performed during regenerative braking of the vehicle 1.

[0039] First, in step S10, the charging rate of the drive battery 11 is input from the battery monitoring unit 11a to determine whether it is fully charged. Specifically, this is determined by whether the charging rate input from the battery monitoring unit 11a is equal to or greater than a predetermined value (predetermined full charge value) that is appropriately set and close to full charge. If the drive battery 11 is fully charged, i.e., if the charging rate is equal to or greater than the predetermined value, the routine proceeds to step S20. If the drive battery 11 is not fully charged, i.e., if the charging rate is less than the predetermined value, the routine returns.

[0040] In step S20, the amount of surplus power is confirmed. The amount of surplus power is the value obtained by subtracting the power consumed by motoring from the power generated by the front motor 4 through regeneration. The power generated by the front motor 4 through regeneration and the power consumed by motoring can be obtained by inputting the actual power generated and power consumed from the front inverter 10. Then, the process proceeds to step S30.

[0041] In step S30, an engine cooling determination is made. If the surplus power confirmed in step S20 exceeds 0, it is determined that engine cooling is necessary, and the process proceeds to step S40. If the surplus power is 0 or less, it is determined that engine cooling is not necessary, and the process proceeds to step S50.

[0042] In step S40, engine cooling is started by the cooling system 50. Specifically, as described above, the engine may be cooled by operating the electric oil pump, or the engine 2 may be cooled by driving the water pump or by operating the radiator fan, or these may be combined.

[0043] Then, the motoring control unit 52 executes motoring, which forcibly drives the engine 2 using the motor generator 9, and the present routine returns. In step S50, the cooling system 50 does not cool the engine, and motoring is performed by forcibly driving the engine 2 using the motor generator 9, and then the routine returns.

[0044] FIG. 4 is an explanatory diagram of the destinations of regenerative power supply in the vehicle 1 of this embodiment. Note that the front inverter 10 and motor clutch 7b are omitted from this diagram. In FIG. 4, arrows indicate the destinations of power supply from the front motor 4 during regenerative braking. FIG. 4(A) shows a normal state in which the charge rate of the drive battery 11 is below a predetermined value, FIG. 4(B) shows a reference example in which motoring is performed when the charge rate of the drive battery is fully charged and above a predetermined value, and FIG. 4(C) shows this embodiment in a fully charged state.

[0045] As shown in (A) to (C) of FIG. 4, during regenerative braking, the engine clutch 7a is in a disengaged state.

[0046] As shown in (A), during normal operation when the charging rate of the drive battery 11 is less than a predetermined value, the power (regenerated power) generated by the front motor 4 during regenerative braking is charged into the drive battery 11.

[0047] As shown in (B), when the drive battery 11 is fully charged, the power generated by the front motor 4 during regenerative braking is supplied to the motor generator 9, and the regenerative power is consumed by performing motoring, which forcibly drives the engine 2 using the motor generator 9.

[0048] As shown in (C), in this embodiment, when regenerative braking is performed with the drive battery fully charged, the engine 2 is cooled by the cooling system 50, thereby making it possible to increase the power consumption when forcibly driving the engine 2 by the motor generator 9 compared to the reference example (B) in which the engine 2 is not cooled.

[0049] As described above, the vehicle 1 of this embodiment is equipped with a regenerative braking function that applies braking torque to the front wheels 3, which are the driving wheels, by regenerative power generation during deceleration, so that regenerative braking ensures braking performance while reducing the use of the service brake device of the vehicle 1, and the power generated by the front motor 4 can be charged to the drive battery 11. This increases the distance that the vehicle can travel on electric power using the front motor 4.

[0050] However, when the charge rate of the drive battery 11 is close to full charge, the regeneratively generated power cannot be charged into the drive battery 11, and the regeneratively generated power must be suppressed. Therefore, in such a case, the regenerative braking torque may not satisfy the required value, and the regenerative braking performance may deteriorate.

[0051] In this embodiment, motoring is enabled by the motoring control unit 52. If regenerative braking is requested when the driving battery 11 has a charge rate equal to or higher than a predetermined value close to full charge, motoring is performed, and the motor generator 9 forcibly drives the engine 2, to which fuel supply is stopped, using the regenerative power generated by the front motor 4 during regenerative braking. This makes it possible to increase the regenerative power and ensure a high regenerative braking torque.

[0052] Furthermore, in this embodiment, when motoring with the drive battery 11 nearly fully charged, the engine 2 is cooled by the cooling system 50, which increases friction when forcibly driving the engine 2. This allows the motor generator 9 to consume a large amount of power during motoring, preventing the drive battery 11 from being overcharged.

[0053] Therefore, it is possible to prevent the drive battery 11 from being overcharged due to regenerative power generation, while ensuring a large braking torque due to regenerative braking, thereby improving the braking performance due to regenerative braking.

[0054] The cooling system 50 for the engine 2 uses, for example, an oil pump that circulates engine oil and a water pump that circulates coolant, so these devices that are already installed in the engine 2 can be used to cool the engine 2 during motoring. Therefore, there is no need to provide new equipment to the vehicle 1 for the cooling system 50, which helps to reduce component costs and the increase in equipment installation space. Furthermore, because the cooling system 50, including the oil pump and water pump, is an electric motor, it can consume power to cool the engine 2 during motoring when the battery is fully charged, further reducing overcharging of the drive battery 11.

[0055] When a water pump is used as the cooling system 50, a radiator fan may also be operated, thereby lowering the temperature of the cooling water and the engine temperature, and further increasing the friction of the engine 2.

[0056] Although the description of the embodiment has been completed, the present invention is not limited to the above embodiment. For example, the cooling system 50 that is operated during regenerative braking in a fully charged state may be something other than an oil pump or a water pump.

[0057] Furthermore, during regenerative braking in a fully charged state, the means may be a means for increasing the friction of the engine 2 in addition to cooling the engine 2. In addition, in the cooling system 50 of the engine 2, the discharge amount of, for example, an oil pump may be changed based on the engine temperature or the charge rate.

[0058] Furthermore, although the vehicle 1 in the above embodiment is a front-wheel drive vehicle, the present invention can also be applied to a four-wheel drive vehicle equipped with rear motors that drive the left and right rear wheels 5, for example. Furthermore, although the vehicle 1 of this embodiment is a plug-in hybrid vehicle (PHEV) capable of external charging or external power supply, the present invention can be widely applied to vehicles capable of motoring, such as hybrid vehicles capable of series mode. [Explanation of symbols]

[0059] 1 vehicle (hybrid vehicle) 3 Front wheels (driving wheels) 4 Front motor (first rotating electric machine) 9 Motor generator (second rotating electric machine) 11 Drive battery (storage battery) 11a Battery monitoring unit (charging rate detection means) 25 Regenerative braking system (regenerative braking device) 50 Cooling system (friction increasing means) 51 Regenerative braking control unit 52 Motoring control section

Claims

1. The vehicle has an engine, a storage battery, a first rotating electric machine that drives the drive wheels of the vehicle, and a second rotating electric machine that is driven by the engine to generate electricity, a regenerative braking control unit that causes the first rotating electric machine to generate electricity when the vehicle is decelerating, and performs regenerative braking to apply a braking force to the vehicle, a motoring control unit that supplies electric power from the storage battery to the second rotating electric machine during execution of the regenerative braking, and performs motoring to forcibly drive the engine with fuel supply stopped; a charging rate detection means for detecting a charging rate of the storage battery; a friction increasing means for increasing friction in the forced driving of the engine when the charging rate is equal to or greater than a predetermined full charge value during motoring, the friction increasing means is a water pump that circulates cooling water for the engine to cool the engine, The discharge amount of the water pump is changed based on the temperature of the engine. A regenerative braking device for a hybrid vehicle.

2. The vehicle has an engine, a storage battery, a first rotating electric machine that drives the drive wheels of the vehicle, and a second rotating electric machine that is driven by the engine to generate electricity, a regenerative braking control unit that causes the first rotating electric machine to generate electricity when the vehicle is decelerating, and performs regenerative braking to apply a braking force to the vehicle, a motoring control unit that supplies electric power from the storage battery to the second rotating electric machine during execution of the regenerative braking, and performs motoring to forcibly drive the engine with fuel supply stopped; a charging rate detection means for detecting a charging rate of the storage battery; a friction increasing means for increasing friction in the forced driving of the engine when the charging rate is equal to or greater than a predetermined full charge value during motoring, the friction increasing means is a water pump that circulates cooling water for the engine to cool the engine, The discharge amount of the water pump is changed based on the charging rate of the storage battery. A regenerative braking device for a hybrid vehicle.

3. The friction increasing means is a water pump that circulates cooling water for the engine using an electric motor.

2. The regenerative braking device for a hybrid vehicle according to claim 1.

4. The friction increasing means is a water pump that circulates cooling water for the engine using an electric motor.

3. The regenerative braking device for a hybrid vehicle according to claim 2.

5. The vehicle includes a radiator that exchanges heat between the cooling water and outside air, and a radiator fan that blows air to the radiator, The friction increasing means drives the radiator fan when driving the water pump during motoring.

5. The regenerative braking device for a hybrid vehicle according to claim 1.

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