Hybrid vehicles

Abstract

To avoid inconvenience of a hybrid vehicle caused by an increase in engine rotation speed at the time of deceleration while engine fuel cut is prohibited.SOLUTION: A hybrid vehicle comprises: an engine in which an exhaust system includes a particulate matter removal filter that removes a particulate matter, the engine being connected through a mechanical mechanism with a drive shaft coupled with drive wheels; an electric motor which inputs and outputs power to / from the engine; a power storage device which exchanges electric power with the electric motor; and a controller which controls the engine and the electric motor. The controller cancels prohibition of the fuel cut if an engine rotation speed becomes a prescribed rotation speed or more when prescribed brake torque is requested on the drive shaft when prohibiting fuel cut of the engine to suppress overheat of the particulate matter removal filter.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a hybrid vehicle, and more particularly to a hybrid vehicle having an engine that is equipped with a particulate matter removal filter in an exhaust system that removes particulate matter and is connected via a mechanical mechanism to a drive shaft that is connected to drive wheels. [Background technology]

[0002] A conventional hybrid vehicle of this type is one that includes an engine output shaft, a first electric motor rotating shaft, a drive shaft connected to the axle, a planetary gear with three rotating elements connected, and a second electric motor that outputs power to the drive shaft, and is equipped with a particulate matter removal filter in the engine exhaust system (see, for example, Patent Document 1).In this hybrid vehicle, when a deceleration request is made and the amount of deposition on the particulate matter removal filter exceeds a threshold value and its temperature also exceeds a threshold value, stopping the supply of fuel to the engine (fuel cut) is prohibited to prevent the particulate matter removal filter from overheating. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-128152 Summary of the Invention [Problem to be solved by the invention]

[0004] In the hybrid vehicle described above, in order to ensure vehicle deceleration when fuel cutoff is prohibited to prevent overheating of the particulate matter removal filter, the first electric motor increases the engine speed, thereby increasing the battery input limit and increasing the regenerative power allowed by the second electric motor. In this case, if the engine speed increases, planetary gear components (such as the pinion gear) may over-rotate. Over-rotation of components can be expected to result in damage to the components or reduced durability. Furthermore, because fuel injection and ignition are still performed when fuel cutoff is prohibited, slight fluctuations can cause the engine to output positive torque, which can make it impossible to ensure the required deceleration, or the regenerative power of the first electric motor, which corresponds to the engine speed, may exceed the battery input limit.

[0005] The main object of the hybrid vehicle of the present invention is to avoid the inconvenience caused by the engine speed increasing during deceleration while fuel cut is prohibited. [Means for solving the problem]

[0006] The hybrid vehicle of the present invention employs the following means to achieve the above-mentioned main object.

[0007] The hybrid vehicle of the present invention is an engine having a particulate matter removal filter attached to an exhaust system for removing particulate matter, the engine being connected via a mechanical mechanism to a drive shaft connected to drive wheels; an electric motor for inputting and outputting power to the engine; a power storage device that exchanges power with the electric motor; a control device that controls the engine and the electric motor; A hybrid vehicle comprising: The control device cancels the prohibition of fuel cut when the rotation speed of the engine reaches or exceeds a predetermined rotation speed while a predetermined braking torque is required for the drive shaft while fuel cut of the engine is prohibited to prevent overheating of the particulate matter removal filter. It is characterized by:

[0008] In the hybrid vehicle of the present invention, when fuel cutoff of the engine is prohibited to prevent overheating of the particulate matter removal filter, if the engine speed reaches or exceeds a predetermined speed when a predetermined braking torque is required for the drive shaft, the prohibition of fuel cutoff is lifted. This allows the engine to avoid outputting positive torque and reduces the engine speed when outputting the predetermined braking torque. As a result, it is possible to avoid problems such as over-rotation of mechanical components caused by an increase in engine speed during deceleration while fuel cutoff is prohibited, an inability to ensure a predetermined braking torque, and exceeding the battery input limit due to regenerative power from the electric motor corresponding to the engine speed.

[0009] Here, the "predetermined braking torque" can be a torque corresponding to the shift range when the accelerator is released. This torque can be considered to be equivalent to engine braking. The "predetermined rotation speed" can be a rotation speed determined based on the protection of parts that make up the mechanical mechanism, i.e., a rotation speed determined to prevent parts from over-rotating.

[0010] In the hybrid vehicle of the present invention, the mechanical mechanism may be a planetary gear mechanism in which three rotating elements are connected to the output shaft of the engine, the drive shaft, and the rotating shaft of the electric motor, and a second electric motor may be attached to the drive shaft. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a diagram showing an outline of the configuration of a hybrid vehicle 20 equipped with an engine device 21 as an embodiment of the present invention. [Figure 2] FIG. 2 is a diagram showing the outline of the configuration of an engine 22. [Figure 3]10 is a flowchart showing an example of a process executed by the HVECU 70 when fuel cut is prohibited. DETAILED DESCRIPTION OF THE INVENTION

[0012] Next, a mode for carrying out the present invention will be described using examples. [Example]

[0013] Fig. 1 is a diagram showing an outline of the configuration of a hybrid vehicle 20 as an embodiment of the present invention. Fig. 2 is a diagram showing an outline of the configuration of an engine 22. As shown in Fig. 1, the hybrid vehicle 20 of the embodiment includes the engine 22, a planetary gear 30, motors MG1 and MG2, inverters 41 and 42, a battery 50, and a hybrid electronic control unit (hereinafter referred to as HVECU) 70.

[0014] The engine 22 is configured as a four-cylinder internal combustion engine that uses fuel such as gasoline or diesel and outputs power through four strokes: intake, compression, expansion (explosive combustion), and exhaust. As shown in FIG. 2, the engine 22 has a port injection valve 126 that injects fuel into an intake port and an in-cylinder injection valve 127 that injects fuel into a cylinder. By having the port injection valve 126 and the in-cylinder injection valve 127, the engine 22 can operate in any of a port injection mode, an in-cylinder injection mode, and a combined injection mode. In the port injection mode, air purified by an air cleaner 122 is drawn into an intake pipe 123 and passes through a throttle valve 124 and a surge tank 125, and fuel is injected from a port injection valve 126 downstream of the surge tank 125 in the intake pipe 123 to mix the air and fuel. This air-fuel mixture is then drawn into combustion chamber 129 via intake valve 128, where it is explosively combusted by an electric spark from spark plug 130. The reciprocating motion of piston 132, which is pushed down in cylinder bore 131 by the energy of the mixture, is converted into rotational motion of crankshaft 23. In in-cylinder injection mode, air is drawn into combustion chamber 129 as in port injection mode, and fuel is injected from in-cylinder injection valve 127 during the intake stroke or compression stroke, where it is explosively combusted by an electric spark from spark plug 130, thereby generating rotational motion of crankshaft 23. In dual injection mode, fuel is injected from port injection valve 126 when air is drawn into combustion chamber 129, and fuel is also injected from in-cylinder injection valve 127 during the intake stroke or compression stroke, where it is explosively combusted by an electric spark from spark plug 130, thereby generating rotational motion of crankshaft 23. These injection modes are switched based on the operating state of engine 22. Exhaust gas discharged from combustion chamber 129 into exhaust pipe 134 via exhaust valve 133 is then discharged into the outside air via purification device 135 and PM filter 136. Purification device 135 has a purification catalyst (three-way catalyst) 135a that purifies harmful components in the exhaust gas, such as carbon monoxide (CO), hydrocarbons (HC), and nitrogen oxides (NOx). PM filter 136 is formed as a porous filter using ceramics, stainless steel, or the like, and captures particulate matter (PM) such as soot in the exhaust gas.It should be noted that instead of the PM filter 136, a four-way catalyst may be used that combines the purification function of a three-way catalyst with the function of trapping particulate matter.

[0015] The operation of the engine 22 is controlled by an engine electronic control unit (hereinafter referred to as "engine ECU") 24. Although not shown, the engine ECU 24 is configured as a microprocessor centered around a CPU, and in addition to the CPU, includes a ROM for storing processing programs, a RAM for temporarily storing data, a flash memory for storing and holding data, an input / output port, and a communication port.

[0016] Signals from various sensors required for controlling the operation of the engine 22 are input to the engine ECU 24 via an input port. Examples of signals input to the engine ECU 24 include a crank angle θcr from a crank position sensor 140 that detects the rotational position of a crankshaft 23 of the engine 22, and a coolant temperature Tw from a water temperature sensor 142 that detects the temperature of the coolant for the engine 22. Other examples of signals input to the engine ECU 24 include cam angles θci and θco from a cam position sensor 144 that detects the rotational position of an intake camshaft that opens and closes the intake valve 128 and the rotational position of an exhaust camshaft that opens and closes the exhaust valve 133. Other signals include a throttle opening TH from a throttle valve position sensor 124a that detects the position of the throttle valve 124, an intake air amount Qa from an air flow meter 123a attached upstream of the throttle valve 124 in the intake pipe 123, and a temperature Tw of the intake air from the intake pipe 123. Other examples include the intake air temperature Ta from a temperature sensor 123t attached upstream of the throttle valve 124 of the exhaust pipe 123, and the surge pressure Ps from a pressure sensor 125a attached to the surge tank 125. Other examples include a front air-fuel ratio AF1 from a front air-fuel ratio sensor 137 attached upstream of the purification device 135 in the exhaust pipe 134, a rear air-fuel ratio AF2 from a rear air-fuel ratio sensor 138 attached downstream of the purification device 135 in the exhaust pipe 134, and a differential pressure ΔP from a differential pressure sensor 136a that detects the differential pressure before and after the PM filter 136 (the differential pressure between the upstream side and the downstream side).

[0017] The engine ECU 24 outputs, via an output port, various control signals for controlling the operation of the engine 22. Examples of signals output from the engine ECU 24 include a control signal to a throttle valve 124, a control signal to a port injection valve 126, a control signal to an in-cylinder injection valve 127, and a control signal to an ignition plug 130.

[0018] The engine ECU 24 is connected to the HVECU 70 via a communication port. The engine ECU 24 calculates the rotation speed Ne of the engine 22 based on the crank angle θcr of the engine 22 from the crank position sensor 140. The engine ECU 24 also calculates a load factor KL (the ratio of the volume of air actually taken in per cycle to the stroke volume per cycle of the engine 22) based on the intake air amount Qa from the air flow meter 123a and the rotation speed Ne of the engine 22. The engine ECU 24 also calculates a PM accumulation amount Qpm as the accumulation amount of particulate matter accumulated on the PM filter 136 based on the differential pressure ΔP from the differential pressure sensor 136a, and calculates a filter temperature Tf as the temperature of the PM filter 136 based on the rotation speed Ne of the engine 22 and the load factor KL.

[0019] As shown in Fig. 1, the planetary gear 30 is configured as a single-pinion planetary gear mechanism. A rotor of a motor MG1 is connected to a sun gear of the planetary gear 30. A drive shaft 36, which is coupled to drive wheels 39a, 39b via a differential gear 38, is connected to a ring gear of the planetary gear 30. A crankshaft 23 of the engine 22 is connected to a carrier of the planetary gear 30 via a damper 28.

[0020] The motor MG1 is configured as, for example, a synchronous generator motor, and as described above, its rotor is connected to the sun gear of the planetary gear 30. The motor MG2 is configured as, for example, a synchronous generator motor, and its rotor is connected to the drive shaft 36. The inverters 41 and 42 are used to drive the motors MG1 and MG2, and are connected to a battery 50 via a power line 54. The motors MG1 and MG2 are rotationally driven by a motor electronic control unit (hereinafter referred to as "motor ECU") 40, which controls the switching of a plurality of switching elements (not shown) of the inverters 41 and 42.

[0021] The motor ECU 40 is configured as a microprocessor centered on a CPU (not shown), and in addition to the CPU, includes a ROM for storing processing programs, a RAM for temporarily storing data, a flash memory for storing and retaining data, input / output ports, and communication ports. Signals from various sensors required for driving and controlling the motors MG1 and MG2 are input to the motor ECU 40 via the input ports. Examples of signals input to the motor ECU 40 include the rotational positions θm1 and θm2 of the rotors of the motors MG1 and MG2 from rotational position sensors (not shown) that detect the rotational positions of the rotors of the motors MG1 and MG2, and the phase currents Iu1, Iv1, Iu2, and Iv2 of the phases of the motors MG1 and MG2 from current sensors (not shown) that detect the phase currents flowing through the phases of the motors MG1 and MG2. The U40 outputs, via an output port, switching control signals and the like to a plurality of switching elements (not shown) of the inverters 41 and 42. The motor ECU 40 is connected to the HVECU 70 via a communication port. The motor ECU 40 calculates the electrical angles θe1 and θe2 and rotation speeds Nm1 and Nm2 of the motors MG1 and MG2 based on the rotational positions θm1 and θm2 of the rotors of the motors MG1 and MG2 from the rotational position sensors.

[0022] Battery 50 is configured as, for example, a lithium ion secondary battery or a nickel-metal hydride secondary battery, and as described above, is connected to inverters 41, 42 via power line 54. Battery 50 is managed by a battery electronic control unit (hereinafter referred to as "battery ECU") 52.

[0023] Although not shown, the battery ECU 52 is configured as a microprocessor centered on a CPU. In addition to the CPU, the battery ECU 52 includes a ROM for storing processing programs, a RAM for temporarily storing data, a flash memory for storing and retaining data, an input / output port, and a communication port. Signals from various sensors required for managing the battery 50 are input to the battery ECU 52 via the input port. Examples of signals input to the battery ECU 52 include the voltage Vb of the battery 50 from a voltage sensor (not shown) attached between the terminals of the battery 50, the current Ib of the battery 50 from a current sensor (not shown) attached to the output terminals of the battery 50, and the temperature Tb of the battery 50 from a temperature sensor (not shown) attached to the battery 50. The battery ECU 52 is connected to the HVECU 70 via the communication port. The battery ECU 52 calculates the state of charge (SOC) of the battery 50 based on the integrated value of the current Ib of the battery 50 from the current sensor. The state of charge (SOC) is the ratio of the amount of power that can be discharged from the battery 50 to the total capacity of the battery 50.

[0024] Although not shown, the HVECU 70 is configured as a microprocessor centered around a CPU. In addition to the CPU, the HVECU 70 includes a ROM for storing processing programs, a RAM for temporarily storing data, a flash memory for storing and retaining data, input / output ports, and communication ports. Signals from various sensors are input to the HVECU 70 via the input ports. Examples of signals input to the HVECU 70 include an ignition signal from an ignition switch 80 and a shift position SP from a shift position sensor 82 that detects the operating position of a shift lever 81. Other examples of signals input to the HVECU 70 include an accelerator opening Acc from an accelerator pedal position sensor 84 that detects the amount of depression of an accelerator pedal 83, a brake pedal position BP from a brake pedal position sensor 86 that detects the amount of depression of a brake pedal 85, and a vehicle speed V from a vehicle speed sensor 88. Examples of the shift position SP include a parking position (P range), a forward position (D range), a reverse position (R range), a neutral position (N range), and a brake position (B range). As described above, the HVECU 70 is connected to the engine ECU 24, the motor ECU 40, and the battery ECU 52 via communication ports.

[0025] The hybrid vehicle 20 of this embodiment configured as described above runs in a hybrid driving mode (HV driving mode) in which the engine 22 is in operation, or in an electric driving mode (EV driving mode) in which the engine 22 is stopped, through cooperative control between the HVECU 70, the engine ECU 24, and the motor ECU 40. In these driving modes, the engine 22 and the motors MG1 and MG2 are controlled so that a driving torque Td* required of the drive shaft 36 based on the accelerator pedal position Acc and the vehicle speed V is output to the drive shaft 36.

[0026] Next, an explanation will be given of the operation of the hybrid vehicle 20 of this embodiment configured as described above, particularly the operation when deceleration torque is output from the engine 22 when fuel cut of the engine 22 is prohibited to prevent overheating of the PM filter 136. Fig. 3 is a flowchart showing an example of a fuel cut prohibition process executed by the HVECU 70. This fuel cut prohibition process is repeatedly executed while fuel cut of the engine 22 is prohibited to prevent overheating of the PM filter 136.

[0027] When the fuel cut prohibition process is executed, the HVECU 70 first determines whether a D-range braking torque request has been made (step S100). The D-range braking torque request is a request to output a braking force equivalent to so-called engine braking when the shift position SP is in the D range and the accelerator is off. Whether a D-range braking torque request has been made can be determined by whether the shift position SP is in the D range and the accelerator is off. If it is determined that a D-range braking torque request has not been made, the HVECU 70 determines that this process is unnecessary and ends this process.

[0028] When it is determined in step S100 that a D-range braking torque request has been made, the motor MG1 motors the engine 22 to output the D-range braking torque (step S110). Because fuel cut is prohibited, the engine 22 is undergoing explosive combustion while being motored by the motor MG1. As a result, only a small braking torque can be output compared to when fuel is cut. Therefore, in order to output the D-range braking torque when fuel cut is prohibited, the motoring speed of the engine 22 by the motor MG1 is higher than when fuel is cut. Note that the D-range braking torque is often determined to be small when the vehicle speed is low and to be approximately constant when the vehicle speed is high, for example, so that it is continuous with the creep torque when the vehicle speed is zero. Therefore, the motoring speed of the engine 22 by the motor MG1 to output the D-range braking torque corresponds to the vehicle speed, and is higher when fuel cut is prohibited than when fuel is cut.

[0029] Next, it is determined whether the rotation speed Ne of the engine 22 is equal to or greater than a predetermined rotation speed Nref (step S120). The predetermined rotation speed Nref is the upper limit rotation speed of the engine 22 required to prevent over-rotation of components such as the pinion gear of the planetary gear 30, and can be determined through experiments, etc. If it is determined that the rotation speed Ne of the engine 22 is less than the predetermined rotation speed Nref, it is determined that component protection is being achieved, and the present process is terminated. On the other hand, if it is determined that the rotation speed Ne of the engine 22 is equal to or greater than the predetermined rotation speed Nref, the prohibition of fuel cut is lifted to protect the components (step S130), and the present process is terminated. When the prohibition of fuel cut is lifted, the rotation speed Ne of the engine 22 that satisfies the D-range braking torque becomes smaller, thereby enabling component protection. In addition, it is possible to avoid the inconvenience of the engine 22 becoming unstable, outputting positive torque from the engine 22 and regeneratively driving the motor MG1, causing the power input to the battery 50 to exceed the input limit Win of the battery 50. Naturally, the D-range braking torque can be ensured. It should be noted that by lifting the prohibition of fuel cut, PM filter 136 is temporarily heated, but heating of PM filter 136 also ends when the D range braking torque request ends.

[0030] In the hybrid vehicle 20 of this embodiment, when a D-range braking torque request is made while fuel cutoff of the engine 22 is prohibited to prevent overheating of the PM filter 136, the engine 22 is motored by the motor MG1 with fuel cutoff prohibited, and D-range braking torque is output. In this case, when the engine 22 rotational speed Ne reaches or exceeds a predetermined rotational speed Nref, the prohibition of fuel cutoff is lifted, and the engine 22 is motored by the motor MG1 with fuel cutoff, thereby outputting D-range braking torque. Because the engine 22 rotational speed Ne that satisfies the D-range braking torque is reduced by fuel cutoff, over-rotation of components can be suppressed, thereby protecting the components. This also avoids the inconvenience of the engine 22 becoming unstable, outputting positive torque from the engine 22, and regeneratively driving the motor MG1, causing the power input to the battery 50 to exceed the input limit Win of the battery 50. Naturally, D-range braking torque can be ensured.

[0031] The correspondence between the main elements of the embodiment and the main elements of the invention described in the "Means for Solving the Problem" section will be explained below. In the embodiment, the engine 22 corresponds to the "engine," the motor MG1 corresponds to the "electric motor," the battery 50 corresponds to the "electricity storage device," and the HVECU 70, the engine ECU 24, and the motor ECU 40 correspond to the "control device."

[0032] The correspondence between the main elements of the Examples and the main elements of the invention described in the "Means for Solving the Problem" section does not limit the elements of the invention described in the "Means for Solving the Problem" section, since the Examples are examples for specifically explaining the mode for implementing the invention described in the "Means for Solving the Problem" section. In other words, the interpretation of the invention described in the "Means for Solving the Problem" section should be based on the description in that section, and the Examples are merely specific examples of the invention described in the "Means for Solving the Problem" section.

[0033] The above describes the form for carrying out the present invention using examples, but the present invention is not limited to these examples in any way, and it goes without saying that the present invention can be carried out in various forms within the scope that does not deviate from the gist of the present invention. [Industrial Applicability]

[0034] The present invention can be used in the hybrid vehicle manufacturing industry and the like. [Explanation of symbols]

[0035] 20 Hybrid vehicle, 21 Engine device, 22 Engine, 23 Crankshaft, 24 Engine ECU, 28 Damper, 30 Planetary gear, 36 Drive shaft, 38 Differential gear, 39a, 39b Drive wheels, 40 Motor ECU, 41, 42 Inverter, 50 Battery, 52 Battery ECU, 54 Power line, 70 HVECU, 80 Ignition switch, 81 Shift lever, 82 Shift position sensor, 83 Accelerator pedal, 84 Accelerator pedal position sensor, 85 Brake pedal, 86 Brake pedal position sensor, 88 Vehicle speed sensor, 122 Air cleaner, 123 Intake pipe, 123a Air flow meter, 123t Temperature sensor, 124 Throttle valve, 124a Throttle valve position sensor, 125 Surge tank, 125a Pressure sensor, 126 Port injection valve, 127 in-cylinder injection valve, 128 intake valve, 129 combustion chamber, 130 spark plug, 132 piston, 133 exhaust valve, 134 exhaust pipe, 135 purification device, 135a purification catalyst, 136 PM filter, 136a differential pressure sensor, 137 front air-fuel ratio sensor, 138 rear air-fuel ratio sensor, 140 crank position sensor, 142 water temperature sensor, 144 cam position sensor, MG1, MG2 motors.

Claims

1. an engine having a particulate matter removal filter attached to an exhaust system for removing particulate matter, the engine being connected via a mechanical mechanism to a drive shaft connected to drive wheels; an electric motor for inputting and outputting power to the engine; a power storage device that exchanges power with the electric motor; a control device that controls the engine and the electric motor; A hybrid vehicle comprising: The control device, while prohibiting fuel cut of the engine to prevent overheating of the particulate matter removal filter, cancels the prohibition of fuel cut when the engine speed reaches or exceeds a predetermined speed while a predetermined braking torque is required for the drive shaft, which torque corresponds to a shift range when the accelerator is released and is small when the vehicle speed is low and is substantially constant when the vehicle speed is high so as to be continuous with the creep torque when the vehicle speed is zero. A hybrid vehicle characterized by

2. The hybrid vehicle according to claim 1, The predetermined rotation speed is a rotation speed determined based on protection of components constituting the mechanical mechanism. Hybrid car.

3. A hybrid vehicle according to claim 1 or 2, the mechanical mechanism is a planetary gear mechanism in which three rotating elements are connected to the output shaft of the engine, the drive shaft, and the rotating shaft of the electric motor; Hybrid car.

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