Control system for hybrid vehicles

Abstract

The objective is to provide a control device for hybrid vehicles that ensures deceleration. [Solution] A control device for a hybrid vehicle having an engine, a motor capable of generating electricity using the power of the engine, and a battery capable of charging with the electricity generated by the motor, comprising: a determination unit that determines whether or not the execution of fuel cut for the engine is restricted, the charging of the battery is restricted, and there is a request for deceleration of the hybrid vehicle; and a control unit that, if the determination unit makes an affirmative determination, controls the fuel injection amount, ignition timing, throttle opening, and variable valve timing mechanism of the engine to perform output reduction control that reduces the output of the engine compared to when the determination unit makes a negative determination.

Description

Technical Field

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

Background Art

[0002] By executing fuel cut of the engine, the deceleration of the vehicle can be ensured. However, when a predetermined condition is satisfied, the execution of fuel cut may be restricted (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When the execution of fuel cut is restricted in a hybrid vehicle, it is conceivable to generate electricity by the motor using the power of the engine to ensure deceleration. However, although the generated power of the motor is charged to the battery, it is difficult to ensure deceleration when the charging of the battery is restricted.

[0005] Therefore, an object of the present invention is to provide a control device for a hybrid vehicle that ensures deceleration.

Means for Solving the Problems

[0006] The above objective can be achieved by a control device for a hybrid vehicle having an engine, a motor capable of generating electricity using the power of the engine, and a battery capable of charging with the electricity generated by the motor, the control device comprising: a determination unit that determines whether or not the execution of fuel cut for the engine is restricted, the charging of the battery is restricted, and there is a request for deceleration of the hybrid vehicle; and a control unit that, if the determination unit makes a positive determination, controls the fuel injection amount, ignition timing, throttle opening, and variable valve timing mechanism of the engine to perform output reduction control that reduces the output of the engine compared to when the determination unit makes a negative determination. [Effects of the Invention]

[0007] According to the present invention, a control device for a hybrid vehicle that ensures deceleration can be provided. [Brief explanation of the drawing]

[0008] [Figure 1] This is a schematic diagram of a hybrid vehicle. [Figure 2] This is a schematic diagram of the engine's configuration. [Figure 3] This is a flowchart illustrating deceleration control. [Modes for carrying out the invention]

[0009] [Overall configuration of a hybrid vehicle] Figure 1 is a schematic diagram of the hybrid vehicle 1 of this embodiment. This hybrid vehicle 1 includes an ECU (Electronic Control Unit) 100, an engine 10, a first motor generator (hereinafter referred to as "first MG (Motor Generator)") 14, a second motor generator (hereinafter referred to as "second MG") 15, a PCU (Power Control Unit) 17, a battery 18, a power split mechanism 50, a transmission mechanism 51, a reduction mechanism 52, and drive wheels 53. 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 the power sources for driving the hybrid vehicle 1.

[0010] Both the first MG14 and the second MG15 have the function of a motor that outputs torque when power is supplied to it, and the function of a generator that generates regenerative power when torque is applied. Specifically, the first MG14 and the second MG15 are AC rotating electric machines. An AC rotating electric machine is, for example, a permanent magnet synchronous motor equipped with a rotor in which permanent magnets are embedded.

[0011] The first MG14 and the second MG15 are electrically connected to the battery 18 via the PCU17. The PCU17 includes a first inverter that exchanges power with the first MG14, a second inverter that exchanges power with the second MG15, and a converter. The converter boosts the power from the battery 18 and supplies it to the first and second inverters, and steps down the power supplied from the first and second inverters and supplies it to the battery 18. The first inverter converts the DC power from the converter into AC power and supplies it to the first MG14, and converts the AC power from the first MG14 into DC power and supplies it to the converter. The second inverter converts the DC power from the converter into AC power and supplies it to the second MG15, and converts the AC power from the second MG15 into DC power and supplies it to the converter. In other words, the PCU 17 charges the battery 18 using the regenerative power generated by the first MG 14 or the second MG 15, and drives the first MG 14 or the second MG 15 using the power charged by the battery 18.

[0012] Battery 18 is composed of multiple stacked batteries. These batteries are, for example, rechargeable batteries such as nickel-metal hydride batteries and lithium-ion batteries.

[0013] The power split mechanism 50 mechanically connects the crankshaft of the engine 10, the rotating shaft of the first MG14, and the output shaft of the power split mechanism 50. The power split mechanism 50 is a planetary gear mechanism, for example, equipped with a sun gear, planetary carrier, pinion gear, and ring gear. The output shaft of the power split mechanism 50 is connected to the transmission mechanism 51. The rotating shaft of the second MG15 is also connected to the transmission mechanism 51. The transmission mechanism 51 is connected to the reduction mechanism 52, and the driving forces of the engine 10, the first MG14, and the second MG15 are transmitted to the drive wheels 53 via the transmission mechanism 51 and the reduction mechanism 52.

[0014] The reduction mechanism 52 is a multi-stage automatic transmission that changes the gear ratio by changing the gear ratio under the control of the ECU 100. In this way, the reduction mechanism 52 switches between multiple power transmission states.

[0015] The ECU100 is an electronic control unit comprising an arithmetic processing circuit that performs various calculations related to vehicle driving control, and a memory that stores control programs and data. The ECU100 is an example of a control device for a hybrid vehicle 1, and functionally implements the determination unit and control unit described in more detail later.

[0016] The ECU100 receives signals from the ignition switch 71, water temperature sensor 72, crank angle sensor 73, airflow meter 74, SOC (State of Charge) sensor 75, and accelerator pedal position sensor 76. The water temperature sensor 72 detects the temperature of the coolant in the engine 10. The crank angle sensor 73 detects the engine speed, which is the rotational speed of the crankshaft of the engine 10. The airflow meter 74 detects the amount of intake air introduced into the engine 10. The SOC sensor 75 detects the charge level of the battery 18. The accelerator pedal position sensor 76 detects the operating position of the accelerator pedal 91.

[0017] The ECU 100 controls acceleration and deceleration based on the accelerator operation amount. Specifically, the outputs of the engine 10, the first MG 14, and the second MG 15 are controlled so as to achieve the 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.

[0018] [Schematic Configuration of Engine] Figure 2 is a schematic configuration 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. Only one of the plurality of cylinders 30 of the engine 10 is shown in Figure 2. Combustion of the air-fuel mixture takes place in the cylinder 30. The piston 31 is reciprocally accommodated in each cylinder 30 and is connected to the crankshaft 33, which is the output shaft of the engine 10, via the 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.

[0019] An in-cylinder injection valve 41d is provided in the cylinder 30. The in-cylinder injection valve 41d injects fuel directly into the cylinder 30. A port injection valve 41p that injects fuel toward the intake port 35p is provided in the intake passage 35. Each cylinder 30 is provided with a spark plug 42 that ignites the air-fuel mixture of the intake air introduced through the intake passage 35 and the fuel injected by the in-cylinder injection valve 41d and the port injection valve 41p by spark discharge. Note that at least one of the in-cylinder injection valve 41d and the port injection valve 41p may be provided.

[0020] The intake passage 35 is connected to the intake port 35p of each cylinder 30 via the intake valve 36. The exhaust passage 37 is connected to the exhaust port 37p of each cylinder 30 via the exhaust valve 38. The intake passage 35 is provided with the above-described air flow meter 74 and a throttle valve 40 that controls the intake air amount.

[0021] The intake-side variable valve mechanism (hereinafter referred to as "IN-VVT") 36a changes the opening and closing timing of the intake valve 36. The IN-VVT 36a changes the opening and closing timing of the intake valve 36 by changing the relative rotational phase of the intake camshaft that drives the intake valve 36 with respect to the crankshaft 33. The amount of advance of the opening and closing timing of the intake valve 36 by the IN-VVT 36a is controlled according to the required advance angle amount from the ECU 100.

[0022] The exhaust-side variable valve mechanism (hereinafter referred to as "EX-VVT") 38a changes the opening and closing timing of the exhaust valve 38. The EX-VVT 38a changes the opening and closing timing of the exhaust valve 38 by changing the relative rotational phase of the exhaust camshaft that drives the exhaust valve 38 with respect to the crankshaft 33. The amount of advance of the opening and closing timing of the exhaust valve 38 by the EX-VVT 38a is controlled according to the required advance angle amount from the ECU 100.

[0023] The throttle valve 40 can increase or decrease the amount of intake air introduced into the cylinder 30 by increasing or decreasing its opening degree. The opening degree of the throttle valve 40 is controlled according to the required opening degree from the ECU 100.

[0024] In the exhaust passage 37, a three-way catalyst 43 and a GPF (Gasoline Particulate Filter) 44 are provided from the upstream side. The three-way catalyst 43 contains, for example, catalyst metals such as platinum (Pt), palladium (Pd), and rhodium (Rh), has an oxygen storage capacity, and purifies NOx, HC, and CO.

[0025] The GPF 44 is a porous ceramic structure and collects exhaust particulate matter (hereinafter referred to as PM (Particulate Matter)) in the exhaust gas. Also, a noble metal such as platinum is supported on the GPF 44. During regeneration control, this noble metal promotes the oxidation reaction of the deposited PM. The GPF 44 is an example of a filter. In the case where the engine 10 is a diesel engine, for example, a DPF (Diesel Particulate Filter) is provided instead of the GPF 44.

[0026] When the accelerator pedal is released while the engine 10 is running and the hybrid vehicle 1 is in motion, the ECU 100 performs a fuel cut, stopping fuel injection from the in-cylinder injector 41d and port injector 41p of the engine 10. As a result, the output torque of the engine 10 becomes a negative value, which can decelerate the hybrid vehicle 1. In addition, while the fuel cut is being performed, air (oxygen) is supplied to the GPF 44, and the PM accumulated in the GPF 44 is burned.

[0027] Furthermore, as will be explained in more detail later, the ECU 100 restricts or permits fuel cut-off based on whether or not certain conditions are met. When fuel cut-off is restricted, the engine 10 cannot maintain deceleration.

[0028] [Deceleration control] Figure 3 is a flowchart illustrating the deceleration control performed by the ECU 100. This control is repeatedly performed at predetermined intervals while the ignition is on. First, the ECU 100 determines whether or not fuel cut is being restricted (step S1). Fuel cut restriction is performed, for example, when it is predicted that the GPF44 will overheat due to the execution of fuel cut. The prediction of whether or not the GPF44 will overheat due to fuel cut is performed based, for example, on the amount of PM accumulation in the GPF44 and the temperature of the GPF44. The greater the amount of PM accumulation and the higher the temperature of the GPF44, the higher the predicted probability that the GPF44 will overheat due to fuel cut. If the result in step S1 is No, this control is terminated.

[0029] If the answer in step S1 is Yes, the ECU 100 determines whether or not charging of the battery 18 is being restricted (step S2). Charging is restricted when the charge level of the battery 18 exceeds the upper limit. The charge level of the battery 18 is detected by the SOC sensor 75, but is not limited to this; it may also be estimated based on, for example, the voltage or current value of the battery 18. If the answer in step S2 is No, this control is terminated.

[0030] If the answer in step S2 is Yes, the ECU 100 determines whether or not there is a deceleration request (step S3). Whether or not there is a deceleration request is determined according to the amount of operation of the accelerator pedal 91 detected by the accelerator pedal opening sensor 76. If the answer in step S3 is No, this control is terminated. Steps S1 to S3 are examples of processes executed by the determination unit.

[0031] If the answer in step S3 is Yes, the ECU 100 performs engine output reduction control, which reduces the output of the engine 10 compared to the answer in any of steps S1 to S3 if the answer is No (step S4). The reduction in engine output is achieved by controlling the fuel injection amount, ignition timing, throttle opening, and at least one of the IN-VVT 36a and EX-VVT 38a of the engine 10.

[0032] For example, increasing the fuel injection amount from the in-cylinder injection valve 41d expands the ignition timing retardation limit. Correspondingly, the ignition timing of the spark plug 42 to the fuel-air mixture is retarded to the retardation limit. As a result, the amount of fuel not used for combustion in the cylinder 30 increases by more than the increase in injection amount, reducing the output of the engine 10. In addition, the opening of the throttle valve 40 is controlled to the closed side. This reduces the intake air volume and reduces the output of the engine 10. Furthermore, at least one of the IN-VVT 36a and EX-VVT 38a is controlled to reduce the valve overlap amount. This suppresses internal EGR, increases pumping losses, and reduces the output of the engine 10. Step S4 is an example of a process performed by the control unit.

[0033] As described above, even when fuel is cut off or battery 16 charging is restricted, the output of the engine 10 can be reduced, thus ensuring deceleration of the hybrid vehicle 1.

[0034] In the above embodiment, a hybrid vehicle 1 equipped with an engine 10, a first MG 14, and a second MG 15 as driving power sources was described as an example, but the hybrid vehicle is not limited to this. For example, it may be a hybrid vehicle equipped with an engine as a driving power source and a single motor arranged in the power transmission path from the engine to the wheels.

[0035] Although embodiments of the present invention have been described in detail above, the present invention is not limited to these specific embodiments, and various modifications and changes are possible within the scope of the gist of the present invention as described in the claims. [Explanation of symbols]

[0036] 1. Hybrid vehicle 10 Engines 14. First Motor Generator 15. Second Motor Generator 36a Intake-side variable valve timing mechanism 38a Exhaust side variable valve timing mechanism 40 Throttle valve 41d In-cylinder injection valve 41p Port injection valve 42 Spark plugs 100 ECU (Control unit, judgment unit, and control unit for hybrid vehicles)

Claims

[Claim 1] A control device for a hybrid vehicle having an engine, a motor capable of generating electricity using the power of the engine, and a battery capable of charging the electricity generated by the motor, A determination unit that determines whether the execution of fuel cut-off for the engine is restricted, the charging of the battery is restricted, and whether or not there is a request for deceleration of the hybrid vehicle, If the determination unit makes a positive determination, the control unit controls the fuel injection amount, ignition timing, throttle opening, and variable valve timing mechanism of the engine to perform output reduction control, which reduces the engine output compared to when the determination unit makes a negative determination. A control device for hybrid vehicles equipped with the following features.

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