Vehicle control device

Abstract

To sufficiently secure an opportunity of purge treatment for discharging fuel vapor from a canister, and to avoid wasteful fuel consumption.SOLUTION: A control device of a vehicle controls the vehicle which is mounted with an internal combustion engine having a fuel vapor gas discharge suppression device for capturing fuel vapor generated in a fuel tank in a canister, and properly discharging a purge gas containing the fuel vapor to an intake passage from the canister. In the case that it is considered that a concentration of fuel contained in the purge gas which is captured by the canister, and may flow into the intake passage becomes high while exceeding a certain level of a limit when a condition that an operation of the internal combustion engine should be stopped during the operation is established, the control device lowers a rotation number of the engine compared with before, or reduces a fuel injection quantity from an injector, and after that, continues the operation of the internal combustion engine without stopping the operation.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a control device for controlling the operation of an internal combustion engine mounted on a vehicle. [Background technology]

[0002] Internal combustion engines have traditionally been equipped with a fuel evaporative emission control device that captures fuel vapor that has evaporated in a fuel tank (see, for example, Patent Document 1 below). A common fuel evaporative emission control device is called a charcoal canister, which captures the generated fuel vapor by adsorbing it in a canister filled with activated charcoal, and then sends the fuel vapor to the intake passage of the internal combustion engine at the appropriate time to mix with the intake air and combust it in the cylinders.

[0003] The canister is connected to a recovery passage for recovering fuel vapor from the fuel tank, an atmosphere inlet passage open to the atmosphere, and a purge gas passage that connects the canister to the intake passage of the internal combustion engine downstream of the throttle valve.To purge the fuel vapor adsorbed in the canister, a control valve provided in the purge gas passage is opened, and the intake negative pressure generated downstream of the throttle valve is used to draw outside air into the canister while drawing the fuel vapor into the intake passage.

[0004] Recently, hybrid vehicles equipped with two power sources, an electric motor and an internal combustion engine, have become popular. In a series hybrid vehicle (see, for example, Patent Document 2 below), the internal combustion engine drives a power generating motor generator to generate electricity, and the generated electricity is stored in a power storage device, i.e., a battery such as a lithium-ion secondary battery or a nickel-metal hydride secondary battery and / or a capacitor, and is supplied to a traction motor generator. The traction motor generator then rotates the drive wheels of the vehicle to drive it.

[0005] Not only the power-generating motor generator, but also the traction motor generator can generate electricity through regenerative braking and store the generated electricity in a power storage device. If the power storage device is already full of charge, the power obtained through regenerative braking can be supplied to the power-generating motor generator, which can be operated as an electric motor to rotate and drive the internal combustion engine, thereby consuming surplus electricity.

[0006] In a hybrid vehicle, the vehicle can be driven by the rotational driving force output by the traction motor generator without firing the internal combustion engine to burn fuel and generate rotational driving force. Therefore, even when the vehicle is in operation, the internal combustion engine may remain stopped.

[0007] In a series hybrid vehicle, the electric power generating motor generator also serves to motor, or crank, the internal combustion engine in preparation for starting it after it has stopped. During cranking, the electric power required is supplied from the power storage device. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Publication No. 2019-044669 [Patent Document 2] Japanese Patent Publication No. 2020-156134 Summary of the Invention [Problem to be solved by the invention]

[0009] It is desirable to purge the fuel vapor trapped in the canister as frequently as possible. If the control valve is opened to perform purging when a large amount of fuel vapor is stored in the canister, purge gas containing a high concentration of fuel components will flow into the intake passage of the internal combustion engine, causing the air-fuel ratio of the mixture filling the cylinder to become too rich, which could lead to undesirable fluctuations in engine torque and worsening emissions.

[0010] When the internal combustion engine is stopped, the fuel vapor adsorbed in the canister cannot be purged, and the fuel vapor accumulates in the canister. In particular, hybrid vehicles can continue to run with the internal combustion engine stopped, so there are fewer opportunities to purge the canister, exacerbating the above-mentioned problem.

[0011] The present invention has been made in view of the above points, and has as its intended object to ensure sufficient opportunity for purging to release fuel vapor from the canister, and to avoid wasting fuel. [Means for solving the problem]

[0012] In the present invention, in a vehicle equipped with an internal combustion engine equipped with a fuel evaporative emission control device that captures fuel vapor generated in a fuel tank in a canister and releases purge gas containing the fuel vapor from the canister into the intake passage at appropriate times, when a condition for stopping the operation of the internal combustion engine is met while the internal combustion engine is running, if it is thought that the concentration of fuel contained in the purge gas that has been captured in the canister and will flow into the intake passage will be higher than a predetermined threshold, the vehicle control device is configured to reduce the engine speed or reduce the amount of fuel injected from the injector compared to before, and continue operating the internal combustion engine without stopping it.

[0013] In addition, when the conditions for stopping the operation of the internal combustion engine are met, if it is thought that the concentration of fuel contained in the purge gas that has been captured in the canister and will flow into the intake passage will be higher than a predetermined threshold, the operation of the internal combustion engine may be continued without being stopped by stopping fuel injection from the injector and rotating the internal combustion engine using an electric motor. [Effects of the Invention]

[0014] According to the present invention, it is possible to secure sufficient opportunities for purging the canister of the fuel evaporative emission control device to release the trapped fuel vapor, and to avoid wasting fuel. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a diagram showing a schematic configuration of a series hybrid vehicle and a control device according to an embodiment of the present invention; [Figure 2] 2 is a diagram showing an outline of an internal combustion engine mounted on the hybrid vehicle of the embodiment; FIG. [Figure 3] 3 is a diagram showing divisions of required outputs of a traction motor generator mounted on the hybrid vehicle of the embodiment; FIG. [Figure 4] FIG. 3 is a flowchart showing an example of a procedure of a process executed by the control device according to the embodiment in accordance with a program. [Figure 5] FIG. 2 is a diagram showing operating conditions of the internal combustion engine controlled by the control device of the embodiment; DETAILED DESCRIPTION OF THE INVENTION

[0016] An embodiment of the present invention will be described with reference to the drawings. Fig. 1 shows a schematic configuration of the main systems of a vehicle in this embodiment. The vehicle in this embodiment is a hybrid vehicle equipped with two types of power sources. It includes an internal combustion engine 1, a power generation motor / generator 2 which is a rotating electric machine driven by the internal combustion engine 1 to generate electricity, a power storage device 3 which stores the electric power generated by the power generation motor / generator 2, and a traction motor / generator 4 which is a rotating electric machine which receives a supply of electric power from the power generation motor / generator 2 and / or the power storage device 3 to drive drive wheels 62 of the vehicle.

[0017] This hybrid vehicle is a series hybrid electric vehicle that uses the internal combustion engine 1 only for generating electricity, and the driving force for driving is supplied to the drive wheels 62 of the vehicle exclusively from the traction motor generator 4. The internal combustion engine 1 and the drive wheels 62 are mechanically separated, and no rotational driving force is transmitted between them. Therefore, the internal combustion engine 1 can rotate and stop completely independently of the traction motor generator 4 and the drive wheels 62. Therefore, while the ignition switch (power switch or ignition key) is turned ON and the vehicle is ready to run when the driver depresses the accelerator pedal, the internal combustion engine 1 may not operate, which involves burning fuel, if the power storage device 3 has stored a sufficient charge and the brake booster 15 has stored a sufficient negative pressure.

[0018] The crankshaft, which is the rotating shaft of the internal combustion engine 1, is mechanically connected to the rotating shaft of the power-generator motor-generator 2 via a gear mechanism 7 (the two are always connected and never disconnected; there is no clutch or the like between them that can be switched on or off). The power-generator motor-generator 2 generates electricity by inputting the rotational driving force output by the internal combustion engine 1 into the power-generator motor-generator 2. The generated electricity is charged to the power storage device 3 and / or supplied to the traction motor-generator 4. The power-generator motor-generator 2 also functions as a motoring electric motor that generates rotational driving force to rotate the crankshaft of the internal combustion engine 1. For example, the power-generator motor-generator 2 performs cranking in preparation for starting the internal combustion engine 1 that has been stopped.

[0019] The traction motor generator 4 generates driving force for driving the vehicle and inputs the driving force to the drive wheels 62 via the speed reducer 61. The traction motor generator 4 also generates electricity by rotating along with the drive wheels 62, recovering the kinetic energy of the vehicle as electrical energy. The electricity generated by this regenerative braking is charged into the electricity storage device 3.

[0020] However, if the electric charge has already been stored to the full capacity of the power storage device 3 and further charging is difficult, the traction motor generator 4 supplies the regeneratively generated electric power to the power generation motor generator 2, which operates as an electric motor to rotate and drive the internal combustion engine 1. This consumes excess electric power while maintaining the braking performance of the vehicle. Also, since the rotation of the internal combustion engine 1 is maintained at this time, a fuel cut can be performed to temporarily stop the fuel supply to the cylinders of the internal combustion engine 1.

[0021] The generator inverter 21 converts AC power generated by the power generation motor generator 2 into DC power, and then inputs the DC power to the power storage device 3 or the driving machine inverter 41. When the power generation motor generator 2 is operated as an electric motor, the generator inverter 21 also converts DC power supplied from the power storage device 3 and / or the driving machine inverter 41 into AC power and then inputs it to the power generation motor generator 2.

[0022] The drive machine inverter 41 converts DC power supplied from the power storage device 3 and / or the generator inverter 21 into AC power and inputs it to the traction motor generator 4. The drive machine inverter 41 also converts AC power generated by the traction motor generator 4 when regenerative braking of the vehicle is performed into DC power and inputs it to the power storage device 3 or the generator inverter 21. The generator inverter 21 and the drive machine inverter 41 form part of a PCU (Power Control Unit) 02.

[0023] The power storage device 3 is a battery and / or a capacitor, etc. The battery is a high-voltage secondary battery with a high energy density, such as a lithium-ion secondary battery or a nickel-metal hydride secondary battery. The power storage device 3 charges and stores the electric power generated by the power generation motor generator 2 and the traveling motor generator 4. The power storage device 3 also discharges the electric power required to operate the power generation motor generator 2 and the traveling motor generator 4 as electric motors, and supplies the necessary electric power to the motor generators 2 and 4.

[0024] FIG. 2 shows an overview of an internal combustion engine 1 mounted on a hybrid vehicle of this embodiment. The internal combustion engine 1 is, for example, a spark-ignition four-stroke reciprocating engine and includes a plurality of cylinders 11 (for example, three cylinders, one of which is shown in FIG. 2). An injector 111 that injects fuel toward the intake port is provided near the intake port of each cylinder 11. In addition, an ignition plug 112 is attached to the ceiling of the combustion chamber of each cylinder 11. The ignition plug 112 receives an induced voltage generated by an ignition coil and causes a spark discharge between a center electrode and a ground electrode.

[0025] The intake passage 13 for supplying intake air takes in air from the outside and directs it to the intake ports of each cylinder 11. An air cleaner 131, an electronic throttle valve 132, a surge tank 133, and an intake manifold 134 are arranged in this order from upstream to downstream in the intake passage 13. The air cleaner 131 is located at the intake port that takes in air, which is the most upstream part of the intake passage 13. The intake port opens to the front of the vehicle to take in cool air and improve the charging efficiency of the internal combustion engine.

[0026] The fuel evaporative emission control device captures fuel vapor that has evaporated in the fuel tank by adsorbing it in a canister 135 filled with activated carbon, and then sends the fuel vapor to the intake passage 13 at appropriate times to mix with the intake air and combust it in the cylinder 11. The canister 135 is connected to a location downstream of the throttle valve 132 in the intake passage 13, more specifically to a surge tank 133 or an intake manifold 134.

[0027] A purge VSV (Vacuum Switching Valve) 136, which is a control valve that opens and closes the purge gas passage connecting the canister 135 and the intake passage 13, is provided on the purge gas passage that connects the canister 135 and the intake passage 13. While the VSV 136 is open, the canister 135 and the intake passage 13 are connected via the purge gas passage, and the fuel vapor in the canister 135 is drawn into the intake passage 13 by the intake negative pressure generated downstream of the throttle valve 132.

[0028] The exhaust passage 14 for discharging exhaust gases guides the exhaust gases generated as a result of fuel combustion in the cylinders 11 to the outside from the exhaust ports of each cylinder 11. An exhaust manifold 142 and a three-way catalyst 141 for purifying exhaust gases are arranged on the exhaust passage 14.

[0029] The EGR device 12 includes, as its elements, an external EGR passage 121 that connects the exhaust passage 14 and the intake passage 13, an EGR cooler 122 provided on the EGR passage 121, and an EGR valve 123 that opens and closes the EGR passage 121 to control the flow rate of EGR gas flowing through the EGR passage 121. The inlet of the EGR passage 121 is connected to a location downstream of the catalyst 141 in the exhaust passage 14. The outlet of the EGR passage 121 is connected to a location downstream of the throttle valve 132 in the intake passage 13 (in particular, a surge tank 133 or an intake manifold 134).

[0030] In this embodiment, the control device 0 that controls the internal combustion engine 1, the power generation motor generator 2, the power storage device 3, the inverters 21, 41, and the traction motor generator 4 is made up of multiple ECUs, namely, an EFI (Electronic Fuel Injection) ECU 01 that controls the internal combustion engine 1, an MG (Motor Generator) ECU 02 that controls the motor generators 2, 4 and the inverters 21, 41, a BMS (Battery Management System) ECU 03 that controls the power storage device 3, and an HV (Hybrid Vehicle) ECU 00 that is a higher-level controller that oversees these controls, all of which are interconnected so as to be able to communicate with each other via an electric communication line such as a CAN (Controller Area Network). Each of the ECUs 00, 01, 02, and 03 is a microcomputer system having a processor, a memory, an input interface, an output interface, etc.

[0031] The control device 0 receives a vehicle speed signal a output from a vehicle speed sensor that detects the actual vehicle speed of the vehicle, a crank angle signal b output from a crank angle sensor that detects the rotation angle of the crankshaft of the internal combustion engine 1 and the engine speed, an accelerator opening signal c output from a sensor that detects the amount of depression of the accelerator pedal by the driver as an accelerator opening (in other words, the driving force that the driver is requesting from the vehicle (the driving motor generator 4 of the vehicle)), an intake passage 13 (particularly, a surge tank 133 or The signals input thereto include an intake air temperature / intake pressure signal d output from a temperature / pressure sensor that detects the intake air temperature and intake pressure in the intake manifold 134), a coolant temperature signal e output from a water temperature sensor that detects the temperature of the coolant for the internal combustion engine 1, an air / fuel ratio signal f output from an air / fuel ratio sensor (linear A / F sensor or O2 sensor) that detects the air / fuel ratio of the exhaust gas flowing through the exhaust passage 14 of the internal combustion engine 1, a battery SOC (State Of Charge) signal g output from a sensor (particularly a battery current and / or battery voltage sensor) that detects the amount of charge stored in the storage device 3, and a negative pressure signal h output from a negative pressure sensor that detects the negative pressure stored in the constant pressure chamber of the brake booster 15.

[0032] The control device 0 controls the increase or decrease of the rotational driving force output by the driving motor generator 4, the rotational driving force output by the internal combustion engine 1, and the amount of power generated by the power generation motor generator 2, depending on the amount of depression of the accelerator pedal operated by the driver, the current vehicle speed, the amount of charge stored in the storage device 3, the power generated by the power generation motor generator 2, etc., which are sensed via various sensors.

[0033] In principle, if the power storage device 3 currently stores sufficient charge and the output required of the traction motor generator 4 is small, the supply of fuel to the internal combustion engine 1 is cut off and the internal combustion engine 1 is not operated. Conversely, if the amount of charge stored in the power storage device 3 falls below a lower limit or the output required of the traction motor generator 4 is large, the internal combustion engine 1 is started, fuel is supplied to the cylinders 11 and fired to combust it, and the rotational driving force output by the internal combustion engine 1 drives the generator motor generator 2, generating electricity to charge the power storage device 3 or to increase the power supplied to the traction motor generator 4.

[0034] Figure 3 shows the relationship between the output required by the vehicle driver and whether or not the internal combustion engine 1 and the electricity-generating motor-generator 2 need to be operated. The output required from the traction motor-generator 4 is determined by the amount of accelerator pedal depression operated by the driver and the vehicle speed. The driving force to be applied to the drive wheels 62 increases as the accelerator opening increases. The required output increases as the driving force to be applied to the drive wheels 62 increases, and also increases as the vehicle speed increases. The required output increases toward the upper right in Figure 3.

[0035] In low output range I, where the driving force to be applied to the drive wheels 62 is relatively small and the vehicle speed is relatively low, the control device 0 stops firing the internal combustion engine 1 by not supplying fuel to it, and does not operate the power-generating motor generator 2 as a generator. In low output range I, the traction motor generator 4 receives power only from the power storage device 3 and outputs driving force for traveling the vehicle. The low output range I typically occurs when the accelerator opening is 0 or below a predetermined value, or when the vehicle is decelerating.

[0036] In medium-to-high output ranges II and III, where the driving force to be applied to the drive wheels 62 is greater than a certain level or the vehicle speed is greater than a certain level, the control device 0 supplies fuel to the internal combustion engine 1 to perform firing operation and operates the power-generating motor-generator 2 as a generator. In the medium-to-high output range II, where the required output is not significantly greater, the traction motor-generator 4 receives power mainly from the power-generating motor-generator 2 and outputs driving force for vehicle travel. At this time, the power storage device 3 supplies only a small amount of power or no power at all. In the high-to-high output range III, where the required output is significantly greater, the traction motor-generator 4 receives power from both the power-generating motor-generator 2 and the power storage device 3 and outputs driving force for vehicle travel.

[0037] Basically, the output required of the internal combustion engine 1 during firing operation increases as the output required of the traction motor-generator 4 increases. However, this also depends on the amount of charge currently stored in the electricity storage device 3. When the amount of charge in the electricity storage device 3 becomes insufficient, it is necessary to charge it as quickly as possible, and even if the output required of the traction motor-generator 4 is small, the output required of the internal combustion engine 1 for power generation may increase.

[0038] When fuel is not being supplied to the cylinders 11 of the internal combustion engine 1 to operate the internal combustion engine 1, and the drive wheels 62 are being driven by the traction motor-generator 4 to run the vehicle, in order to start the internal combustion engine 1 and generate electricity with the power-generating motor-generator 2, the power-generating motor-generator 2 is first operated as an electric motor, thereby performing motoring to start the internal combustion engine 1. Then, once the crankshaft of the internal combustion engine 1 has rotated a predetermined number of times or a predetermined angle or more and cylinder discrimination has been completed to determine the current stroke or piston position of each cylinder 11 of the internal combustion engine 1, fuel is injected at an appropriate timing in accordance with the stroke of each cylinder 11 of the internal combustion engine 1, and firing, which ignites and burns the fuel, is started at the appropriate timing. The rotation angle and rotation speed of the crankshaft of the internal combustion engine 1, or the rotation angle and rotation speed of the rotating shaft of the power generation motor generator 2 (the rotation speed of the power generation motor generator 2 is proportional to the rotation speed of the internal combustion engine 1, and the proportionality constant is known) can be detected (in the EFI ECU 01) via a crank angle sensor attached to the internal combustion engine 1, or can also be detected (in the PCU (or MG ECU) 02) via a resolver attached to the power generation motor generator 2.

[0039] When the internal combustion engine 1 is able to rotate independently and output the rotational drive force required for power generation, and the engine speed can maintain an upward trend even when the output of the power-generating motor-generator 2 is reduced, the output of the power-generating motor-generator 2, which is operating as an electric motor, is reduced to 0 to end motoring, and the power-generating motor-generator 2 is then driven to rotate by the internal combustion engine 1. Furthermore, the power-generating motor-generator 2 is operated as a generator, and its generated power is increased from 0.

[0040] Thereafter, the amount of intake air and fuel injection supplied to the cylinders 1 of the internal combustion engine 1, as well as the power generated by the power-generating motor-generator 2, are adjusted to increase or decrease so that the engine speed follows the target speed that is increased in stages. The final target speed is set to the speed that allows the internal combustion engine 1 to operate at optimum or near-optimum efficiency and is most advantageous in terms of fuel consumption rate, or the speed at which the internal combustion engine 1 can achieve maximum torque or maximum output or torque or output close to this.

[0041] The EFI ECU01, which is part of the control device 0, acquires various pieces of information b, d, e, and f required for controlling the operation of the internal combustion engine 1 via an input interface, determines the engine speed, and estimates the amount of air to be drawn into the cylinder 11. Then, it determines operating parameters of the internal combustion engine 1, such as a required fuel injection amount (necessary to realize a target air-fuel ratio) commensurate with the intake air amount, fuel injection timing (including the number of fuel injections per combustion), fuel injection pressure, ignition timing (including the number of ignitions per combustion), and a required EGR rate (or EGR gas amount). The EFI ECU01 outputs various control signals i, j, k, l, and p corresponding to the operating parameters via an output interface to the igniter of the spark plug 112, the injector 111, the throttle valve 132, the EGR valve 123, the VSV 136, and the like.

[0042] When the driver depresses the accelerator pedal to start the vehicle from a stopped or low-speed state where the vehicle is nearly stopped, the required output of the traction motor / generator 4 transitions from low output region I to medium-high output region II or III, causing the internal combustion engine 1, which had been stopped up until then, to start.Also, the internal combustion engine 1 will start when the amount of charge (SOC) stored in the electricity storage device 3 falls below a predetermined value or when the negative pressure stored in the constant pressure chamber of the brake booster 15 falls below a predetermined value.

[0043] 4, when predetermined conditions for stopping the operation of the internal combustion engine 1 are met (step S2) during firing operation of the internal combustion engine 1 (steps S1 and S6), the control device 0 ends the firing operation of the internal combustion engine 1 and stops the internal combustion engine 1 (step S5) in principle. The stop conditions referred to in step S2 specifically include the required output for the traveling motor / generator 4 being in the low output region I, the amount of charge stored in the power storage device 3 being equal to or greater than a predetermined value, and the negative pressure stored in the brake booster 15 being equal to or greater than a predetermined value.

[0044] However, if it is considered that the concentration of fuel contained in the purge gas that is currently trapped in the canister 135 and will flow into the intake passage 13 by opening the VSV 136 will exceed a certain limit (step S3), even if the stop condition of step S2 is met, the firing operation of the internal combustion engine 1 is not immediately stopped but continues (step S4). This is a measure to ensure sufficient opportunity to purge the fuel vapor adsorbed in the canister 135.

[0045] An example of a method for estimating the purge gas concentration in step S3 will be described. When the stopped internal combustion engine 1 is started, the control device 0 performs an initial estimation of the purge gas concentration. Specifically, the control device 0 determines an initial value for the estimated concentration of the purge gas flowing through the purge gas flow passage immediately after the start of the internal combustion engine 1 based on the length of the stop time of the internal combustion engine 1 before start and the temperature of the fuel tank or its surroundings while the internal combustion engine 1 is stopped. The length of the stop time of the internal combustion engine 1 and the temperature of the fuel tank while the internal combustion engine 1 is stopped both affect the amount of fuel vapor generated in the fuel tank and collected in the canister 135 while the internal combustion engine 1 is stopped. In principle, the longer the stop time of the internal combustion engine 1, the greater the amount of fuel vapor collected in the canister 135, resulting in a higher concentration of the purge gas immediately after start. Furthermore, the higher the temperature of the fuel tank while the internal combustion engine 1 is stopped, the greater the amount of fuel vapor collected in the canister 135, resulting in a higher concentration of the purge gas immediately after start.

[0046] The memory of the control device 0 (EFI ECU01) stores map data that defines the relationship between the length of time the internal combustion engine 1 is stopped, values ​​that indicate the temperature of the fuel tank or its surroundings while the internal combustion engine 1 is stopped, and the initial value of the estimated concentration of purge gas immediately after the start of the internal combustion engine 1. An example of a value that indicates the temperature of the fuel tank or its surroundings while the internal combustion engine 1 is stopped is the outside air temperature when the internal combustion engine 1 is stopped or started. If the body ECU can actually measure the temperature of the vehicle body while the internal combustion engine 1 is stopped, the actually measured temperature may be used as a value that indicates the temperature of the fuel tank or its surroundings while the internal combustion engine 1 is stopped. The control device 0 searches the map using the length of time the internal combustion engine 1 is stopped and values ​​that indicate the temperature of the fuel tank or its surroundings while the internal combustion engine 1 is stopped as keys, and obtains the initial value of the estimated concentration of purge gas immediately after start.

[0047] Additionally, each time the control device 0 opens the VSV 136 to perform a fuel vapor purge process while the internal combustion engine 1 is operating, the control device 0 performs a calculation to gradually decrease and update the estimated fuel concentration of the purge gas flowing through the purge gas passage from its initial value. When the VSV 136 is opened to perform a fuel vapor purge process, the amount of fuel vapor remaining in the canister 135 gradually decreases, eventually leading to a leaner purge gas concentration. The control device 0 estimates the fuel concentration of the purge gas flowing through the purge gas passage based on a correction coefficient that corrects the fuel injection amount through air-fuel ratio feedback control during firing operation of the internal combustion engine 1. If the VSV 136 is opened under conditions in which fuel is injected at an amount proportional to the amount of air taken into the cylinder 11, and the air-fuel ratio of the gas flowing through the exhaust passage 14 becomes richer than the target air-fuel ratio, the purge gas flowing into the intake passage 13 is considered to have a richer fuel content. It can be estimated that the concentration becomes higher as the feedback correction coefficient multiplied by the fuel injection amount decreases. Conversely, if the air-fuel ratio of the gas flowing through the exhaust passage 14 becomes leaner than the target air-fuel ratio, it is considered that the fuel component in the purge gas flowing into the intake passage 13 is lean. It can be estimated that the concentration becomes lower as the feedback correction coefficient increases.

[0048] The control device 0, having estimated the concentration of the fuel components in the purge gas flowing through the purge gas flow passage, compares the current estimated concentration with a threshold value in step S3. If the estimated concentration is higher than the threshold value, the operation of the internal combustion engine 1 continues (step S4), and the VSV 136 is opened as appropriate to perform a fuel vapor purge process. If the concentration of the fuel components in the purge gas falls below the threshold value, the operation of the internal combustion engine 1 is stopped (step S5). Note that for steps S4 and S5, a waiting time may be set according to the concentration of the fuel components in the purge gas estimated in step S3 (the higher the concentration, the longer the time), and the operation of the internal combustion engine 1 may be continued until the waiting time has elapsed, and the operation of the internal combustion engine 1 may be stopped after the waiting time has elapsed.

[0049] Regarding step S4, when the operation of the internal combustion engine 1 continues for the fuel vapor purging process, the engine speed is reduced further and / or the fuel injection amount is reduced further compared to the previous operation of the internal combustion engine (steps S1, S6).

[0050] As shown in FIG. 5, the memory of the control device 0 (HV ECU00) stores map data of an operating line L that defines the operating conditions when the internal combustion engine 1 is fired and operated, particularly the relationship between engine speed and engine torque. In FIG. 5, thin dashed lines represent equal power lines along which the output of the internal combustion engine 1 is constant. When the horizontal axis represents engine speed and the vertical axis represents engine torque, the equal power lines along which the engine output, which is the product of engine speed and engine torque, is constant, are drawn in the form of a hyperbola. Thin chain lines represent equal fuel consumption rate lines, which are pairs of engine speed and engine torque, along which the brake specific fuel consumption of the internal combustion engine 1 is constant. The fuel consumption rate is the amount of fuel [g / kWh] consumed by the internal combustion engine 1 to output a unit amount of mechanical energy, and the fuel consumption rate line is its contour line. Naturally, the smaller the fuel consumption rate, the higher the thermal efficiency of the internal combustion engine 1.

[0051] By combining these iso-power lines and iso-fuel consumption lines, it is possible to plot a set of engine speed and engine torque that minimizes (improves) the fuel consumption rate when achieving a certain required output for various outputs. This is the operating line L, which is the optimal fuel consumption line. Normally, the control device 0 controls the engine speed and engine torque along the optimal fuel consumption line L, i.e., on or within a range near the optimal fuel consumption line L.

[0052] When the required output of the traction motor generator 4 is in the medium-high output region II or III, or when the amount of charge stored in the power storage device 3 is decreasing and needs to be quickly charged, the internal combustion engine 1 is operated in firing mode in this operating region A (steps S1, S6).

[0053] When the required output is in the low output region I and the power storage device 3 is sufficiently charged, but the operation of the internal combustion engine 1 is continued to purge the canister 135 (step S4), the internal combustion engine 1 is operated in firing mode in the operating region B, which has a lower engine speed and engine torque than the operating region A.

[0054] Incidentally, in the driving region where the power storage device 3 needs to be charged but the driver of the vehicle is not stepping on the accelerator pedal and the vehicle speed is 0 or low, close to 0, the engine torque is reduced more than in the above-mentioned driving regions A and B. This is because the internal combustion engine 1 drives the power generation motor generator 2 to generate electricity, but the noise generated by this is not masked by the driving noise.

[0055] In this embodiment, the present invention controls a vehicle equipped with an internal combustion engine 1 equipped with a fuel evaporative emission control device that captures fuel vapor generated in a fuel tank in a canister 135 and releases purge gas containing the fuel vapor from the canister 135 into the intake passage 13 at appropriate times. When a condition for stopping the operation of the internal combustion engine 1 is met (step S2) while the internal combustion engine 1 is operating, if it is considered that the concentration of fuel contained in the purge gas that has been captured in the canister 135 and will flow into the intake passage 13 will exceed a certain limit (step S3), the vehicle control device 0 is configured to reduce the engine speed or reduce the amount of fuel injected from the injector 111 compared to before (steps S1, S6), and then continue operating the internal combustion engine without stopping it (step S4).

[0056] According to this embodiment, even in a vehicle such as a hybrid vehicle in which the internal combustion engine 1 is stopped for long periods, the opportunity (frequency) for performing the canister purge process can be increased. Furthermore, particularly in a series hybrid vehicle, the operating region A during normal firing of the internal combustion engine 1 is set to a relatively high load region in which thermomechanical conversion efficiency is high. In other words, because the throttle valve 132 is opened widely, the intake negative pressure generated downstream of the throttle valve 132 in the intake passage 132 tends to be small, and there is a possibility that the fuel vapor trapped in the canister 135 cannot be sufficiently sucked out. In this embodiment, firing of the internal combustion engine 1 continues in operating region B, and the throttle valve 132 is narrowed to increase the intake negative pressure, thereby making it possible to reliably purge the fuel vapor trapped in the canister 135. Fuel waste can also be avoided.

[0057] This prevents a large amount of fuel vapor from remaining and accumulating in the canister 135, thereby preventing the fuel vapor from leaking into the atmosphere and effectively avoiding problems such as undesirable fluctuations in engine torque, unstable combustion, and worsening emissions when the VSV 136 is opened while the internal combustion engine 1 is firing. Deterioration of the canister 135 can also be prevented.

[0058] In addition, there is no need to modify the hardware from the off-the-shelf canister 135 or VSV 136, which does not result in an increase in cost.

[0059] The present invention is not limited to the above-described embodiment, and for example, the application of the present invention is not limited to the internal combustion engine 1 mounted on a series hybrid vehicle.

[0060] Furthermore, in step S4, instead of continuing firing operation of the internal combustion engine 1, fuel injection and combustion from the injector 111 are stopped (i.e., firing is terminated), and the internal combustion engine 1 is driven to rotate by the power generating motor generator 2, which is an electric motor, thereby continuing operation of the internal combustion engine 1 without stopping it, thereby enabling canister purging. When the amount of charge currently stored in the electricity storage device 3 is equal to or greater than a predetermined value close to full charge, it can be advantageous in terms of energy efficiency to consume electric power instead of fuel to rotate the internal combustion engine 1 while ensuring free capacity in the electricity storage device 3.

[0061] In addition, the specific configuration of each part and the processing procedure can be modified in various ways without departing from the spirit of the present invention. [Explanation of symbols]

[0062] 0...Control unit (ECU) 1...Internal combustion engine 13...Intake passage 132...Throttle valve 135, 136... Fuel evaporative emission control device (canister, control valve (purge VSV)) 2... Generators, motoring motors (motor generators for power generation) 3...Electricity storage device 4...Traction motor (traffic motor generator) 62...Drive wheels

Claims

[Claim 1] A vehicle equipped with an internal combustion engine equipped with a fuel evaporative emission control device that captures fuel vapor generated in a fuel tank in a canister and releases purge gas containing the fuel vapor from the canister into an intake passage at appropriate times, When a condition for stopping the operation of the internal combustion engine is met during operation, if it is considered that the concentration of fuel contained in the purge gas that has been trapped in the canister and will flow into the intake passage will be higher than a predetermined threshold, the engine speed is reduced or the amount of fuel injected from the injector is reduced compared to before, and the operation of the internal combustion engine is continued without being stopped, When the conditions for stopping the operation of the internal combustion engine are met, if it is thought that the concentration of fuel contained in the purge gas that has been captured in the canister and will flow into the intake passage will be higher than a predetermined threshold, the vehicle control device stops fuel injection from the injector and drives the internal combustion engine to rotate using an electric motor, thereby continuing the operation of the internal combustion engine without stopping it.

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