Engine device

Abstract

To enable a fuel cut of an engine to be appropriately initiated in a highland environment.SOLUTION: An engine device mounted on a vehicle comprises an engine and a control device which initiates fuel cut of the engine when the fuel cut of the engine is requested and engine torque falls below a threshold. The control device sets the threshold to increase as atmospheric pressure decreases. As a result, in a high-altitude environment, the engine torque is more likely to fall below the threshold, allowing the fuel cut to be appropriately initiated.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present disclosure relates to an engine device.

Background Art

[0002] Conventionally, as this type of engine device, there has been proposed one that performs fuel cut of the engine at the time of idle-on (see, for example, Patent Document 1). In this engine device, at the time of idle-on, when an accelerator operation is being performed, the ignition timing is retarded, and when the accelerator operation is released, the ignition timing is retarded to the ignition timing for fuel cut and then the fuel cut is started. Thereby, torque fluctuations during fuel cut of the engine are suppressed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In order to suppress torque fluctuations during fuel cut of the engine, instead of using the above-described method, there is also one that starts fuel cut when the torque of the engine reaches less than a threshold value. Generally, in a highland environment, that is, an environment where the atmospheric pressure is relatively low, compared to a flatland environment, that is, an environment where the atmospheric pressure is relatively high, the air density is low, and the throttle opening becomes large in order to correspond to the target torque. For this reason, in a highland environment, the pumping loss of the engine is smaller than in a flatland environment, and it becomes difficult for the torque of the engine to decrease. Therefore, when using a constant value predetermined to be suitable for a flatland environment as the threshold value, in a highland environment, there may be a case where the torque of the engine does not become less than the threshold value or the time until the torque reaches less than the threshold value becomes relatively long, and the fuel cut cannot be started appropriately.

[0005] The main object of the engine device of the present disclosure is to enable appropriate initiation of engine fuel cut in a highland environment.

Means for Solving the Problems

[0006] The engine device of the present disclosure has adopted the following means to achieve the above main object.

[0007] The engine device of the present disclosure includes an engine, a control device that starts fuel cut of the engine when fuel cut of the engine is requested and the torque of the engine reaches less than a threshold value, and is an engine device mounted on a vehicle, wherein the control device sets the threshold value so that it becomes higher as the atmospheric pressure becomes lower. This is the gist.

[0008] In the engine device of the present disclosure, when fuel cut of the engine is requested and the torque of the engine reaches less than a threshold value, fuel cut of the engine is started. In this case, the threshold value is set so that it becomes higher as the atmospheric pressure becomes lower. As a result, compared with the case of using a fixed value (relatively low fixed value) determined in advance to conform to a flat environment (environment with relatively high atmospheric pressure) as the threshold value, in a highland environment (environment with relatively low atmospheric pressure), the torque of the engine is more likely to reach less than the threshold value, and appropriate fuel cut of the engine can be started. Of course, even in a flat environment, when the torque of the engine reaches less than the threshold value, appropriate fuel cut of the engine can be started.

[0009] In the engine device of the present disclosure, the control device may set a correction value so that it becomes higher as the atmospheric pressure becomes lower, and set the sum of a base value and the correction value as the threshold value. In this case, the control device may set the base value based on at least one of the rotational speed of the engine, the coolant temperature, the shift position of the vehicle, and the gear ratio of the power transmission path from the engine to the drive wheels.

[0010] In the engine device of the present disclosure, the control device may estimate the torque based on the intake air amount and ignition timing of the engine.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Figure 4

Modes for Carrying Out the Invention

[0012] Embodiments of the present disclosure will be described with reference to the drawings. FIG. 1 is a schematic configuration diagram of an automobile 10 including an engine device 11 of an embodiment of the present disclosure. As shown in the drawing, the automobile 10 of the embodiment includes an engine 12, a transmission 60, and an electronic control unit 70 as a control device. As the engine device 11 of the embodiment, the engine 12 and the electronic control unit 70 are applicable.

[0013] The engine 12 is configured as a multi-cylinder internal combustion engine that outputs power through four strokes of intake, compression, expansion (explosive combustion), and exhaust using fuel such as gasoline. The engine 12 has an in-cylinder injection valve 27 that injects fuel into the combustion chamber 29 for each cylinder, and a spark plug 30. The engine 12 inhales the air cleaned by the air cleaner 22 into the intake pipe 23, passes it through the throttle valve 24 and the surge tank 25, and further inhales it into the combustion chamber 29 through the intake valve 28. Also, fuel is injected from the in-cylinder injection valve 27 once or divided into multiple times during the intake stroke and the compression stroke. Then, it is explosively combusted by ignition from the spark plug 30. Further, the reciprocating motion of the piston 32 pushed down in the cylinder by the energy of the explosive combustion is converted into the rotational motion of the crankshaft 14. The exhaust discharged from the combustion chamber 29 to the exhaust pipe 35 through the exhaust valve 33 is discharged to the outside air through the purification device 36 and the PM filter 37. The purification device 36 has a catalyst (three-way catalyst) 36a that purifies harmful components such as carbon monoxide (CO), hydrocarbons (HC), and nitrogen oxides (NOx) in the exhaust. The PM filter 37 collects particulate matter (PM) such as soot in the exhaust. Note that instead of the PM filter 37, a four-way catalyst that combines the purification function of the three-way catalyst and the collection function for particulate matter may be used.

[0014] The transmission 60 is configured as an automatic transmission with four-speed, five-speed, six-speed, etc. The transmission 60 is connected to the crankshaft 14 of the engine 12 and is also connected to the drive wheels 64a, 64b via the differential gear 62, and transmits the power from the engine 12 to the drive wheels 64a, 64b with a change in the gear stage.

[0015] The electronic control unit 70 includes a microcomputer having a CPU, ROM, RAM, flash memory, input / output ports, communication ports, various drive circuits, and various logic ICs. The electronic control unit 70 inputs signals from various sensors via the input ports. For example, the electronic control unit 70 inputs the crank angle θcr from the crank position sensor 14a that detects the rotational position of the crankshaft 14 of the engine 12, and the cooling water temperature Tw from the water temperature sensor 15 that detects the temperature of the cooling water of the engine 12. The electronic control unit 70 also inputs the cam angles θci, θco from the cam position sensor 16 that detects the rotational positions of the intake camshaft that opens and closes the intake valve 28 and the exhaust camshaft that opens and closes the exhaust valve 33. The electronic control unit 70 inputs the intake air amount Qa and the intake air temperature Ta from the air flow meter 23a and the temperature sensor 23t respectively attached upstream of the throttle valve 24 in the intake pipe 23, the throttle opening TH from the throttle position sensor 24a that detects the position of the throttle valve 24, and the surge pressure Ps from the surge pressure sensor 25a attached to the surge tank 25. The electronic control unit 70 inputs the front air-fuel ratio AF1 from the front air-fuel ratio sensor 35a attached upstream of the purification device 36 in the exhaust pipe 35, the rear air-fuel ratio AF2 from the rear air-fuel ratio sensor 35b attached between the purification device 36 and the PM filter 37 in the exhaust pipe 35, and the differential pressure ΔPpm from the differential pressure sensor 35c that detects the differential pressure between the upstream and downstream sides of the PM filter 37. The electronic control unit 70 inputs the rotational speed Nin from the rotational speed sensor attached to the input shaft of the transmission 60 and the rotational speed Nout from the rotational speed sensor attached to the output shaft of the transmission 60. The electronic control unit 70 also inputs the ignition signal IG from the ignition switch 80 and the shift position SP from the shift position sensor 82 that detects the operating position of the shift lever 81.The electronic control unit 70 also receives the accelerator opening Acc from the accelerator pedal position sensor 84 that detects the depression amount of the accelerator pedal 83, the brake pedal position BP from the brake pedal position sensor 86 that detects the depression amount of the brake pedal 85, the vehicle speed V from the vehicle speed sensor 87, and the atmospheric pressure Pout from the atmospheric pressure sensor 88.

[0016] The electronic control unit 70 outputs various control signals via the output ports. For example, the electronic control unit 70 outputs a control signal to the throttle valve 24 of the engine 12, a control signal to the in-cylinder injection valve 27, and a control signal to the ignition plug 30. The electronic control unit 70 also outputs a control signal to the transmission 60.

[0017] The electronic control unit 70 performs various calculations. For example, the electronic control unit 70 calculates the engine speed Ne of the engine 12 based on the crank angle θcr from the crank position sensor 14a. The electronic control unit 70 calculates the load factor KL of the engine 12 based on the intake air amount Qa from the air flow meter 23a and the engine speed Ne of the engine 12. The load factor KL is defined as the ratio of the volume of air actually inhaled in one cycle to the stroke volume per cycle of the engine 12. The electronic control unit 70 estimates the temperature Tc of the catalyst 36a of the purification device 36 based on the coolant temperature Tw from the coolant temperature sensor 15, the engine speed Ne of the engine 12, and the load factor KL. The electronic control unit 70 estimates the torque Te of the engine 12 based on the intake air amount Qa and the ignition timing Ti of the engine 12. The electronic control unit 70 calculates the gear ratio Gew of the power transmission path from the engine 12 to the drive wheels 64a, 64b based on the gear position Gs of the transmission 60.

[0018] In the motor vehicle 10 according to the embodiment, the electronic control unit 70 sets a target gear position Gs* of the transmission 60 based on the accelerator opening Acc and the vehicle speed V, and controls the transmission 60 so that the gear position Gs of the transmission 60 becomes the target gear position Gs*. Further, the electronic control unit 70 sets a target torque Te* of the engine 12 based on the accelerator opening Acc, the vehicle speed V, and the gear position Gs of the transmission 60, and performs operation control of the engine 12 (for example, intake air amount control, fuel injection control, ignition control, etc.) so that the engine 12 is operated based on the target torque Te*.

[0019] The operation control of the engine 12 is basically performed as follows. In the intake air amount control, the electronic control unit 70 sets a target air amount Qa* based on the target torque Te*, sets a target opening TH* of the throttle valve 24 based on the set target air amount Qa*, and controls the throttle valve 24 based on the set target opening TH*. In a highland environment, the atmospheric pressure Pout is lower than in a flat environment. And the lower the atmospheric pressure Pout is, the lower the air density is, and the larger the target opening TH* becomes to correspond to the target torque Te*. In the fuel injection control, the electronic control unit 70 sets a target injection amount Qf* so that the front air-fuel ratio AF1 becomes the target air-fuel ratio AF* (for example, the stoichiometric air-fuel ratio), and controls the in-cylinder injection valve 27 based on the set target injection amount Qf*. In the ignition control, the electronic control unit 70 sets a target ignition timing Ti* based on the rotational speed Ne and the target torque Te* (target air amount Qa*), and controls the spark plug 30 based on the set target ignition timing Ti*.

[0020] Also, in the motor vehicle 10 according to the embodiment, when fuel cut of the engine 12 is required, such as when the accelerator is off, the torque Te of the engine 12 is gradually decreased, and when the torque Te becomes less than the threshold value Teth, the fuel cut of the engine 12 is started. The decrease in the torque Te of the engine 12 is performed by the throttle opening TH (and the fuel injection amount Qf) and the retardation of the ignition timing Ti.

[0021] Next, the operation of the motor vehicle 10 of the embodiment will be described, particularly the setting process of the threshold value Teth when fuel cut of the engine 12 is required. FIG. 2 is a flowchart showing an example of the threshold value setting process executed by the electronic control unit 70. This routine is executed when fuel cut of the engine 12 is required.

[0022] In the threshold value setting process of FIG. 2, the electronic control unit 70 first sets a base value Tethtmp based on the engine speed Ne of the engine 12, the coolant temperature Tw of the engine 12, the shift position SP, and the gear ratio Gew of the power transmission path from the engine 12 to the drive wheels 64a and 64b (step S100). Here, in the embodiment, the base value Tethtmp is obtained by applying the engine speed Ne, the coolant temperature Tw, the shift position SP, and the gear ratio Gew to a base value setting map that is predetermined as the relationship between the engine speed Ne, the coolant temperature Tw, the shift position SP, the gear ratio Gew, and the base value Tethtmp, and deriving and setting the corresponding base value Tethtmp from the map.

[0023] Subsequently, a correction value α is set based on the atmospheric pressure Pout (step S110), and the value obtained by adding the set correction value α to the base value Tethtmp is set as the threshold value Teth (step S120), and the threshold value setting process is terminated. Here, in the embodiment, the correction value α is obtained by applying the atmospheric pressure Pout to a correction value setting map that is predetermined by experiments, analysis, machine learning, etc. as the relationship between the atmospheric pressure Pout and the correction value α, and deriving and setting the corresponding correction value α from the map. FIG. 3 is an explanatory diagram showing an example of the correction value setting map. As shown in the figure, the correction value α is set to increase as the atmospheric pressure Pout decreases. Therefore, the threshold value Teth also increases as the atmospheric pressure Pout decreases.

[0024] As described above, in a highland environment, the atmospheric pressure Pout is lower than that in a flatland environment. And the lower the atmospheric pressure Pout is, the lower the air density becomes, and the larger the target opening TH* becomes in order to correspond to the target torque Te*. For this reason, the lower the atmospheric pressure Pout is, the smaller the pumping loss of the engine 12 becomes, and the less likely the torque Te of the engine 12 is to decrease. Therefore, when using a relatively low constant value Teth1 determined in advance to conform to the flatland environment as the threshold value Teth, there may be a case where the torque Te of the engine 12 does not become less than the threshold value Teth or the time until the torque Te becomes less than the threshold value Teth becomes relatively long, and the fuel cut of the engine 12 cannot be appropriately started. Based on this, in the embodiment, the threshold value Teth is set to increase as the atmospheric pressure Pout decreases by setting the correction value α to increase as the atmospheric pressure Pout decreases. Thereby, compared with the case of using the above-described constant value Teth1 as the threshold value Teth, in a highland environment, the torque Te of the engine 12 is more likely to become less than the threshold value Teth, and the fuel cut of the engine 12 can be appropriately started. Of course, even when the atmospheric pressure Pout is relatively high (flatland environment), the torque Te of the engine 12 can become less than the threshold value Teth and the fuel cut of the engine 12 can be appropriately started.

[0025] FIG. 4 is an explanatory diagram showing an example of the state when the accelerator is turned off (when the fuel cut of the engine 12 is requested) in a highland environment (an environment where the atmospheric pressure Pout is relatively low). In FIG. 4, the accelerator opening Acc, the torque Te, the ignition timing Ti, and the presence or absence of execution of the fuel cut are shown. In FIG. 4, regarding the torque Te, the ignition timing Ti, and the presence or absence of execution of the fuel cut, the solid line indicates the state of the embodiment, and the dashed-dotted line indicates the state of the comparative example. The comparative example is different from the embodiment in which the threshold value Teth is set to increase as the atmospheric pressure Pout decreases in that the above-described constant value Teth1 is used as the threshold value Teth.

[0026] As shown, in the embodiments and the comparative examples, when the accelerator is turned off at time t11 and a fuel cut request for the engine 12 is started, the throttle opening TH is decreased to decrease the torque Te. When the torque Te has decreased to a certain extent, the ignition timing Ti is retarded to further decrease the torque Te. In the comparative example, even when the ignition timing Ti reaches the retard limit Tird, the torque Te is equal to or higher than the threshold value Teth, and the fuel cut of the engine 12 is forcibly started at time t13 when a predetermined time has elapsed since the ignition timing Ti reached the retard limit Tird. On the other hand, in the embodiment, when the torque Te reaches less than the threshold value Teth at time t12 while the torque Te is being decreased by retarding the ignition timing Ti, the fuel cut of the engine 12 is started. Thereby, in a highland environment, the fuel cut of the engine 12 can be appropriately started. Note that the above correction value α and thus the threshold value Teth are preferably determined so that the step of the torque Te around the fuel cut start in the highland environment (the step of the torque Te around time t12 in FIG. 4) does not become much larger than the step of the torque Te around the fuel cut start in the lowland environment. By doing so, even in a highland environment, similar to a flat environment, the torque shock around the fuel cut start can be suppressed.

[0027] In the engine device 11 mounted on the vehicle 10 according to the embodiment described above, when a fuel cut of the engine 12 is requested, the torque Te of the engine 12 is gradually decreased, and when the torque Te of the engine 12 reaches less than the threshold value Teth, the fuel cut of the engine 12 is started. In this case, the threshold value Teth is set so as to be higher as the atmospheric pressure Pout is lower. Thereby, compared with the case where a fixed value (relatively low fixed value) Teth1 determined in advance to be suitable for a flat environment is used as the threshold value Teth, in a highland environment, the torque Te of the engine 12 is more likely to reach less than the threshold value Teth, and the fuel cut of the engine 12 can be appropriately started. Of course, even when the atmospheric pressure Pout is relatively high (flat environment), the torque Te of the engine 12 can reach less than the threshold value Teth and the fuel cut of the engine 12 can be appropriately started.

[0028] In the above-described embodiment, the electronic control unit 70 sets the base value Tethtmp based on the engine speed Ne of the engine 12, the coolant temperature Tw of the engine 12, the shift position SP, and the gear ratio Gew of the power transmission path from the engine 12 to the drive wheels 64a and 64b. However, the present invention is not limited to this. For example, the base value Tethtmp may be set based on a part of the engine speed Ne of the engine 12, the coolant temperature Tw of the engine 12, the shift position SP, and the gear ratio Gew of the power transmission path from the engine 12 to the drive wheels 64a and 64b. Further, a predetermined constant value may be used as the base value Tethtmp.

[0029] In the above-described embodiment, the engine 12 is provided with the in-cylinder injection valve 27 that injects fuel into the combustion chamber 29. However, the present invention is not limited to this. The engine 12 may be provided with a port injection valve that injects fuel into the intake port in addition to or instead of the in-cylinder injection valve 27.

[0030] In the above-described embodiment, the form of the engine device 11 mounted on the general automobile 10 that runs using the power from the engine 12 is used. However, the present invention is not limited to this. For example, it may be in the form of an engine device mounted on a hybrid vehicle equipped with a motor in addition to the engine.

[0031] The correspondence between the main elements of the embodiment and the main elements of the invention described in the column of means for solving the problems will be described. In the embodiment, the engine 12 corresponds to the "engine", and the electronic control unit 70 corresponds to the "control device".

[0032] Note that the correspondence between the main elements of the embodiments and the main elements of the invention described in the column of means for solving the problems is an example for specifically explaining the mode for carrying out the invention described in the column of means for solving the problems in the embodiments. Therefore, it does not limit the elements of the invention described in the column of means for solving the problems. That is, the interpretation of the invention described in the column of means for solving the problems should be made based on the description in that column, and the embodiments are merely specific examples of the invention described in the column of means for solving the problems.

[0033] As described above, the embodiments for carrying out the present disclosure have been described using the embodiments. However, the present disclosure is not limited to such embodiments, and it goes without saying that it can be implemented in various forms without departing from the gist of the present disclosure.

Industrial Applicability

[0034] The present disclosure can be used in the manufacturing industry of engine devices and the like.

Explanation of Reference Signs

[0035] 10 Automobile, 11 Engine device, 12 Engine, 14 Crankshaft, 14a Crank position sensor, 15 Water temperature sensor, 16 Cam position sensor, 22 Air cleaner, 23 Intake pipe, 23a Air flow meter, 23t Temperature sensor, 24 Throttle valve, 24a Throttle position sensor, 25 Surge tank, 25a Surge pressure sensor, 27 In-cylinder injection valve, 28 Intake valve, 29 Combustion chamber, 30 Spark plug, 32 Piston, 33 Exhaust valve, 35 Exhaust pipe, 35a Front air-fuel ratio sensor, 35b Rear air-fuel ratio sensor, 35c Differential pressure sensor, 36 Purification device, 36a Catalyst, 37 PM filter, 60 Transmission, 62 Differential gear, 64a, 64b Drive wheels, 70 Electronic control unit, 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, 87 Vehicle speed sensor, 88 Atmospheric pressure sensor.

Claims

1. An engine and, a control device that starts fuel cut of the engine when fuel cut of the engine is requested and the torque of the engine reaches less than a threshold value, which is an engine device mounted on a vehicle and includes: wherein the control device sets the threshold value so that it becomes higher as the atmospheric pressure is lower. Engine device.

2. The engine device according to Claim 1, wherein the control device sets a correction value so that it becomes higher as the atmospheric pressure is lower, and sets the sum of a base value and the correction value as the threshold value. Engine device.

3. The engine device according to Claim 1 or 2, wherein the control device estimates the torque based on an intake air amount and an ignition timing of the engine. Engine device.

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