Control device of hybrid vehicle

Abstract

To suppress a decrease in the battery charging rate while improving the dramatic effect of engine revving during deceleration.SOLUTION: There is provided a control device for a hybrid vehicle, the hybrid vehicle comprising: an engine connected to a drive shaft; a first motor generator capable of rotating the engine; a second motor generator connected to the drive shaft; and a battery that supplies driving power to the first motor generator and can charge regenerative power of the second motor generator. The control device comprises: a deceleration control unit that, when fuel cut in the engine is restricted and there is a request to decelerate by turning off an accelerator, decelerates the vehicle using regenerative torque of the second motor generator while increasing engine rotational speed to a target rotational speed using powering torque of the first motor generator; a determination unit that determines whether or not a battery charging rate is increasing during execution of the deceleration process; and a rotational speed control unit that, when the determination unit makes a positive determination, increases the target rotational speed more than when the determination unit makes a negative determination.SELECTED DRAWING: Figure 3

Description

[Technical Field]

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

[0002] In a hybrid vehicle, when there is a request to decelerate by releasing the accelerator while the engine is under fuel cut restriction, a deceleration process may be executed in which the hybrid vehicle is decelerated using the regenerative torque of the second motor generator while the engine speed is increased to a target speed using the powering torque of the first motor generator (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-121423 Summary of the Invention [Problem to be solved by the invention]

[0004] According to the deceleration process described above, the engine speed increases during deceleration, creating the illusion of engine revving. To further enhance the effect, it may be possible to further increase the target speed during deceleration. However, increasing the target speed increases power consumption by the first motor generator, which may result in a decrease in the battery charging rate.

[0005] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a control device for a hybrid vehicle that improves the performance of engine revving during deceleration while suppressing a decrease in the battery's charging rate. [Means for solving the problem]

[0006] The above object can be achieved by a control device for a hybrid vehicle having an engine connected to a drive shaft, a first motor generator capable of rotating the engine, a second motor generator connected to the drive shaft, and a battery that supplies drive power to the first motor generator and can charge the regenerative power of the second motor generator, the control device comprising: a deceleration control unit that, when fuel cut in the engine is restricted and there is a request to decelerate by releasing the accelerator, executes a deceleration process to decelerate the hybrid vehicle using the regenerative torque of the second motor generator while increasing the rotation speed of the engine to a target rotation speed using the powering torque of the first motor generator; a judgment unit that judges whether the charging rate of the battery is increasing while the judgment unit judges yes; and a rotation speed control unit that, when the judgment unit judges no, increases the target rotation speed more than when the judgment unit judges no. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a hybrid vehicle that improves the dramatic effect of engine revving during deceleration while suppressing a decrease in the battery charging rate. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic diagram of a hybrid vehicle. [Figure 2] FIG. 1 is a schematic diagram of an engine. [Figure 3] 4 is a flowchart illustrating deceleration control. DETAILED DESCRIPTION OF THE INVENTION

[0009] [Hybrid vehicle configuration] 1 is a schematic diagram of a hybrid vehicle 1 according to this embodiment. The hybrid vehicle 1 includes an ECU (Electronic Control Unit) 100, an engine 10, a first motor generator (hereinafter referred to as the "first MG (Motor Generator)") 14, a second motor generator (hereinafter referred to as the "second MG") 15, a PCU (Power Control Unit) 17, a battery 18, a power split mechanism 50, a transmission mechanism 51, a transmission 52, a drive shaft 53, a differential 54, and drive wheels 55. The engine 10 is a gasoline engine, but is not limited to this and may be a diesel engine. The engine 10, the first MG 14, and the second MG 15 are power sources for driving the hybrid vehicle 1.

[0010] Each of first MG 14 and second MG 15 functions as a motor that outputs torque when supplied with drive power, and as a generator that generates regenerative power when given torque.

[0011] The first MG 14 and the second MG 15 are electrically connected to the battery 18 via the PCU 17. The PCU 17 boosts DC power from the battery 18, converts it into AC power, and supplies it to the first MG 14 or the second MG 15. The PCU 17 also converts AC current from the first MG 14 or the second MG 15 into DC current, reduces the voltage, and supplies it to the battery 18. That is, the battery 18 supplies power to the first MG 14 or the second MG 15 and receives regenerative power generated in the first MG 14 or the second MG 15. The ECU 100 also controls the PCU 17 to control the amount of power supplied to the first MG 14 and the amount of regenerative power in the first MG 14. This controls the power running torque and regenerative torque of the first MG 14. Similarly, the ECU 100 controls the amount of power supplied to the second MG 15 and the amount of regenerative power in the second MG 15. This controls the power running torque and regenerative torque of the second MG 15.

[0012] The battery 18 is made up of a plurality of stacked cells, which are, for example, secondary batteries such as nickel-metal hydride batteries or lithium-ion batteries.

[0013] The power split mechanism 50 mechanically couples the crankshaft of the engine 10, the rotating shaft of the first MG 14, and the output shaft of the power split mechanism 50. The power split mechanism 50 is, for example, a planetary gear mechanism including a sun gear, a planetary carrier, a pinion gear, and a ring gear. The rotor of the first MG 14 is coupled to the sun gear. A drive shaft 53 is coupled to the ring gear via a transmission mechanism 51 and a transmission 52. The crankshaft of the engine 10 is coupled to the planetary carrier, which couples the pinion gear.

[0014] The output shaft of the power split mechanism 50 is connected to a transmission mechanism 51. The rotating shaft of the second MG 15 is also connected to the transmission mechanism 51. The transmission mechanism 51 is connected to a transmission 52. The transmission 52 is connected to a drive shaft 53. The driving forces of the engine 10, the first MG 14, and the second MG 15 are transmitted to drive wheels 55 via the transmission mechanism 51, the transmission 52, the drive shaft 53, and the differential 54.

[0015] The transmission 52 is a stepped automatic transmission that is interposed between the second MG 15 and the drive shaft 53 and changes the gear ratio under the control of the ECU 100.

[0016] The ECU 100 is an electronic control unit that includes a processing circuit for performing various types of calculations related to vehicle driving control, and a memory that stores control programs and data. The ECU 100 is an example of a control device. The ECU 100 also functions as a deceleration control unit, a determination unit, and a rotation speed control unit, which will be described later.

[0017] The ECU 100 receives signals from an ignition switch IS, a crank angle sensor CS, an air flow meter AM, an accelerator position sensor AS, and a SOC (State Of Charge) sensor SS. The ignition switch IS detects the on / off state of the ignition. The crank angle sensor CS detects the engine rotation speed, which is the rotation speed of the crankshaft of the engine 10. The air flow meter AM detects the amount of intake air introduced into the engine 10. The accelerator position sensor AS detects the operating position of the accelerator pedal 91. The SOC sensor SS detects the charging rate of the battery 18.

[0018] The ECU 100 controls acceleration and deceleration based on the accelerator operation amount. Specifically, the ECU 100 controls the outputs of the engine 10, the first MG 14, and the second MG 15 so as to achieve a target acceleration or target deceleration set based on the accelerator operation amount. The output of the engine 10 is controlled by the intake air amount and the fuel injection amount. The outputs of the first MG 14 and the second MG 15 are controlled by the PCU 17.

[0019] [Engine outline] FIG. 2 is a schematic diagram of the engine 10. The engine 10 has cylinders 30, pistons 31, connecting rods 32, a crankshaft 33, an intake passage 35, an intake valve 36, an exhaust passage 37, and an exhaust valve 38. FIG. 2 shows only one of the multiple cylinders 30 of the engine 10. An air-fuel mixture is combusted in the cylinder 30. A piston 31 is accommodated in each cylinder 30 so as to be able to reciprocate, and is connected to the crankshaft 33 via a connecting rod 32. The connecting rod 32 and the crankshaft 33 convert the reciprocating motion of the piston 31 into the rotational motion of the crankshaft 33.

[0020] An in-cylinder injection valve 41d is provided in each cylinder 30. A port injection valve 41p that injects fuel toward an intake port 35p is provided in the intake passage 35. Each cylinder 30 is provided with an ignition device 42 that ignites, by spark discharge, an air-fuel mixture of intake air introduced through the intake passage 35 and fuel injected by the in-cylinder injection valve 41d and the port injection valve 41p. It is sufficient that at least one of the in-cylinder injection valve 41d and the port injection valve 41p is provided.

[0021] The intake passage 35 is connected to an intake port 35p of each cylinder 30 via an intake valve 36. The exhaust passage 37 is connected to an exhaust port 37p of each cylinder 30 via an exhaust valve 38. The intake passage 35 is provided with the air flow meter AM and a throttle valve 40 that controls the amount of intake air.

[0022] A three-way catalyst 43 and a GPF (Gasoline Particulate Filter) 44 are provided in the exhaust passage 37 from the upstream side. The three-way catalyst 43 contains catalytic metal, has oxygen storage capacity, and purifies NOx, HC, and CO.

[0023] The GPF 44 is a porous ceramic structure that captures exhaust particulate matter (hereinafter referred to as PM (Particulate Matter)) in the exhaust gas. The GPF 44 also supports a precious metal such as platinum. During regeneration control, this precious metal promotes the oxidation reaction of the accumulated PM.

[0024] The throttle valve 40 can increase or decrease the amount of intake air introduced into the cylinder 30 by increasing or decreasing the opening degree thereof. The opening degree of the throttle valve 40 is controlled in accordance with the opening degree required by the ECU 100.

[0025] When the driver releases the accelerator while the engine 10 is running and the hybrid vehicle 1 is traveling, the ECU 100 executes a fuel cut to stop fuel injection. As a result, the output torque of the engine 10 becomes a negative value, and the hybrid vehicle 1 decelerates. Furthermore, while the fuel cut is being executed, air (oxygen) is supplied to the GPF 44, and PM accumulated in the GPF 44 is burned.

[0026] The ECU 100 limits fuel cut when a predetermined condition is met. The predetermined condition is when it is predicted that the GPF 44 will overheat due to the execution of fuel cut. By limiting fuel cut when such a prediction is made, the overheating of the GPF 44 is suppressed. The ECU 100 predicts whether the execution of fuel cut will cause the GPF 44 to overheat based on the amount of PM accumulated in the GPF 44 and the temperature of the GPF 44. The greater the amount of PM accumulated and the higher the temperature of the GPF 44, the more it is predicted that the GPF 44 will overheat due to the execution of fuel cut. The amount of PM accumulated in the GPF 44 is calculated based on, for example, the engine rotation speed, the charging efficiency, and the temperature of the coolant. The temperature of the GPF 44 is calculated based on, for example, the engine rotation speed and the charging efficiency.

[0027] [Deceleration control] FIG. 3 is a flowchart illustrating deceleration control executed by ECU 100. This control is repeatedly executed at predetermined intervals while the ignition is on. First, ECU 100 determines whether fuel cut is being restricted (step S1). If the answer is No in step S1, this control ends. If the answer is Yes in step S1, ECU 100 determines whether there is a deceleration request by releasing the accelerator due to the driver's driving operation (step S2). If the answer is No in step S2, this control ends.

[0028] If the answer is Yes in step S2, the ECU 100 executes deceleration processing (step S3). The deceleration processing is a process in which, while fuel cut is limited, the hybrid vehicle 1 is decelerated by the regenerative torque of the second MG 15, while the rotation speed of the engine 10 is increased to a target rotation speed by the powering torque of the first MG 14. This creates the appearance of revving up of the engine 10 during deceleration. Note that, during the deceleration processing, the fuel injection amount and intake air amount of the engine 10 are controlled to minimum values ​​that allow combustion in the engine 10 to continue. Step S3 is an example of a process executed by the deceleration control unit.

[0029] Next, the ECU 100 determines whether the charging rate per unit time of the battery 18 is increasing while the deceleration process is being executed (step S4). Step S4 is an example of processing executed by the determination unit. If the result of step S4 is Yes, the ECU 100 increases the target rotation speed during the deceleration process (step S5). This increases the rotation speed of the engine 10 while the deceleration process is being executed. Step S5 is an example of processing executed by the rotation speed control unit. In this way, by increasing the target rotation speed during the deceleration process when the charging rate of the battery 18 is increasing, the dramatic increase in the speed of the engine 10 is improved, while the decrease in the charging rate of the battery 18 is suppressed.

[0030] If the result of step S4 is No, the ECU 100 reduces the target rotation speed in the deceleration process (step S6), thereby suppressing a decrease in the charging rate of the battery 18.

[0031] Although the embodiments of the present invention have been described in detail above, the present invention is not limited to such specific embodiments, and various modifications and variations are possible within the scope of the gist of the present invention as defined in the claims. [Explanation of symbols]

[0032] 1 Hybrid vehicle 10 Engine 14 First motor generator 15 Second motor generator 18 Battery 100 ECU (control unit, deceleration control unit, judgment unit, rotation speed control unit)

Claims

[Claim 1] A control device for a hybrid vehicle having an engine connected to a drive shaft, a first motor generator capable of rotating the engine, a second motor generator connected to the drive shaft, and a battery that supplies drive power to the first motor generator and is capable of charging regenerative power of the second motor generator, a deceleration control unit that, when a deceleration request is made by releasing an accelerator pedal while fuel cut in the engine is being limited, executes a deceleration process to decelerate the hybrid vehicle using a regenerative torque of the second motor generator while increasing a rotation speed of the engine to a target rotation speed using a powering torque of the first motor generator; a determination unit that determines whether the charging rate of the battery is increasing during the execution of the deceleration process; a rotation speed control unit that increases the target rotation speed when the determination unit makes a positive determination compared to when the determination unit makes a negative determination.

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