Vehicle

Abstract

To secure deceleration of a vehicle more sufficiently when fuel cut-off of an engine is requested and fuel cut-off is prohibited.SOLUTION: A vehicle includes: an engine in which a filter for collecting particulate substances is attached to an exhaust system; a transmission which transmits power with change of a transmission ration between the engine and driving wheels; and a control device which controls the engine and the transmission and prohibits fuel cut-off of the engine when a temperature of the filter is a predetermined temperature or higher. The control device controls the engine and the transmission so that the transmission ratio of the transmission becomes large, compared to a case where negative torque is output from the engine in connection with fuel injection of the engine and the fuel cut-off of the engine is performed, in a situation where the fuel cut of the engine is requested but prohibited.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to vehicles. [Background technology]

[0002] Conventionally, one such vehicle has been proposed, which has a multi-cylinder engine with a filter attached to the exhaust system that captures particulate matter. When the accelerator pedal is released, the crankshaft rotation speed is within a predetermined range, and when the amount of particulate matter captured by the filter becomes large, dither control is executed to make one of the four cylinders a rich-burn cylinder with an air-fuel ratio richer than the stoichiometric air-fuel ratio and the remaining cylinders a lean-burn cylinder with an air-fuel ratio leaner than the stoichiometric air-fuel ratio in order to regenerate the filter. Even if the conditions for executing engine fuel cut are met during dither control, engine fuel cut is prohibited (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2019-85965 A Summary of the Invention [Problem to be solved by the invention]

[0004] If engine fuel cut is prohibited when the accelerator pedal is released (when engine fuel cut is requested), the magnitude of the negative torque from the engine will be smaller than when engine fuel cut is performed, resulting in smaller deceleration of the vehicle.

[0005] The main object of the vehicle of the present disclosure is to ensure a sufficient deceleration of the vehicle when engine fuel cut is requested and fuel cut is prohibited. [Means for solving the problem]

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

[0007] The vehicle of the present disclosure includes: A vehicle comprising an engine having an exhaust system equipped with a filter for collecting particulate matter, a transmission for transmitting power between the engine and drive wheels by changing a gear ratio, and a control device for controlling the engine and the transmission and for prohibiting a fuel cut of the engine when the temperature of the filter is equal to or higher than a predetermined temperature, When a fuel cut of the engine is requested and the control device prohibits the fuel cut of the engine, the control device controls the engine and the transmission so that the gear ratio of the transmission becomes larger compared to a case where a negative torque is output from the engine accompanied by fuel injection of the engine and the fuel cut of the engine is performed. The gist of the present invention is as follows.

[0008] In the vehicle disclosed herein, when engine fuel cut is requested but engine fuel cut is prohibited, the engine and transmission are controlled so that the gear ratio of the transmission is larger than when negative torque is output from the engine with engine fuel injection and engine fuel cut is performed. This makes it possible to more sufficiently ensure deceleration of the vehicle when engine fuel cut is requested but fuel cut is prohibited. [Brief description of the drawings]

[0009] [Figure 1] 1 is a schematic diagram of an automobile 10 according to an embodiment of the present disclosure. [Diagram 2] 4 is a flowchart showing an example of a processing routine executed by an electronic control unit 70. [Diagram 3] This is an explanatory diagram showing an example of the state of the accelerator opening Acc, the target gear Gs* of the transmission 60, the vehicle speed V, and the engine speed Ne of the engine 12 when the accelerator is released and fuel cut of the engine 12 is requested, and fuel cut of the engine 12 is prohibited. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] An embodiment of the present disclosure will be described with reference to the drawings. Fig. 1 is a schematic diagram of an automobile 10 according to an embodiment of the present disclosure. As shown in the figure, the automobile 10 according to the embodiment includes an engine 12, a starter (not shown) for cranking the engine 12, a transmission 60, and an electronic control unit 70 as a control device for controlling the entire automobile.

[0011] The engine 12 is configured as a multiple-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. The engine 12 has an in-cylinder injection valve 26 that injects fuel into a combustion chamber 29, and an ignition plug 30. The in-cylinder injection valve 26 is disposed approximately in the center of the top of the combustion chamber 29, and injects fuel in a spray form. The ignition plug 30 is disposed near the in-cylinder injection valve 26 so as to be able to ignite the fuel sprayed in a spray form from the in-cylinder injection valve 26.

[0012] The engine 12 draws air purified by the air cleaner 22 into the intake pipe 23, passes it through the throttle valve 24 and the surge tank 25 in this order, and then draws it into the combustion chamber 29 via the intake valve 28. During the intake stroke or compression stroke, fuel is injected from the in-cylinder injection valve 26 once or in multiple divided injections, and is ignited by the spark plug 30 to cause explosive combustion. The reciprocating motion of the piston 32, which is pushed down by the energy of the explosive combustion, is converted into the rotational motion of the crankshaft 14. The exhaust gas discharged from the combustion chamber 29 into the exhaust pipe 34 via the exhaust valve 33 is discharged into the outside air via the purification device 35 and the PM filter 36. The purification device 35 has a purification catalyst (three-way catalyst) 35a that purifies harmful components such as carbon monoxide (CO), hydrocarbons (HC), and nitrogen oxides (NOx) in the exhaust. The PM filter 36 is formed as a porous filter made of ceramics, stainless steel, or the like, and captures particulate matter (PM: Particulate Matter) such as soot in the exhaust gas. Instead of the PM filter 36, a four-way catalyst that combines the purification function of a three-way catalyst with the function of trapping particulate matter may be used.

[0013] The transmission 60 is configured as an automatic transmission with 4-speed, 5-speed, 6-speed, etc. This transmission 60 is connected to the crankshaft 14 of the engine 12 and is also connected to driving wheels 64a, 64b via a differential gear 62, and transmits power from the engine 12 to the driving wheels 64a, 64b while changing the gear ratio.

[0014] The electronic control unit 70 includes a microcomputer, which includes a CPU, a ROM, a RAM, a flash memory, an input / output port, and a communication port. The electronic control unit 70 receives signals from various sensors via the input ports. For example, the electronic control unit 70 receives a crank angle θcr from a crank position sensor 14a that detects the rotational position of the crankshaft 14 of the engine 12, and a coolant temperature Tw from a water temperature sensor 15 that detects the temperature of the coolant of the engine 12. The electronic control unit 70 also receives cam angles θci and θco from a cam position sensor 16 that detects the rotational position of an intake camshaft that opens and closes the intake valve 28 and the rotational position of an exhaust camshaft that opens and closes the exhaust valve 33. The electronic control unit 70 also receives an intake air amount Qa from an air flow meter 23a that is attached upstream of the throttle valve 24 of the intake pipe 23, and an intake air temperature Ta from a temperature sensor 23t that is attached upstream of the throttle valve 24 of the intake pipe 23. The electronic control unit 70 also receives as inputs a throttle opening TH from a throttle position sensor 24a that detects the position (opening) of the throttle valve 24, and a surge pressure Ps from a pressure sensor 25a attached to the surge tank 25. The electronic control unit 70 also receives as inputs a front air-fuel ratio AF1 from a front air-fuel ratio sensor 37 that is attached upstream of the purification device 35 of the exhaust pipe 34, a rear air-fuel ratio AF2 from a rear air-fuel ratio sensor 38 that is attached between the purification device 35 of the exhaust pipe 34 and the PM filter 36, and a differential pressure ΔP from a differential pressure sensor 36a that detects a differential pressure (a pressure difference between the upstream side and the downstream side) before and after the PM filter 36. The electronic control unit 70 also receives as inputs a rotation speed Nin from a rotation speed sensor attached to the input shaft of the transmission 60, and a rotation speed Nout from a rotation speed sensor attached to the output shaft of the transmission 60. The electronic control unit 70 also receives an ignition signal IG 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 .The electronic control unit 70 also receives inputs of 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 87.

[0015] The electronic control unit 70 outputs various control signals via an output port. For example, the electronic control unit 70 outputs control signals to the throttle valve 24, the in-cylinder injection valve 26, and the spark plug 30 of the engine 12. The electronic control unit 70 also outputs control signals to the starter and the transmission 60.

[0016] The electronic control unit 70 calculates the rotation 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 rotation speed Ne of the engine 12. The load factor KL is defined as the ratio of the volume of air actually taken 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 35a of the purification device 35 based on the cooling water temperature Tw from the water temperature sensor 15, the rotation speed Ne of the engine 12, and the load factor KL. The electronic control unit 70 calculates the PM accumulation amount Qpm as the accumulation amount of particulate matter accumulated on the PM filter 36 based on the differential pressure ΔP from the differential pressure sensor 36a, and calculates the temperature Tf of the PM filter 36 based on the rotation speed Ne of the engine 12 and the load factor KL.

[0017] In the automobile 10 of the embodiment, the electronic control unit 70 basically controls the engine 12 and the transmission 60 as follows. The electronic control unit 70 sets a target gear Gs* of the transmission 60 based on the accelerator pedal position Acc and the vehicle speed V, and controls the transmission 60 so that the gear Gs of the transmission 60 becomes the target gear Gs*. The electronic control unit 70 sets a target torque Te* of the engine 12 based on the accelerator pedal position Acc, the vehicle speed V, and the gear 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*.

[0018] Next, a description will be given of the operation of the automobile 10 of the embodiment, in particular, the operation when the accelerator is released and a fuel cut request is made for the engine 12. Fig. 2 is a flowchart showing an example of a processing routine executed by the electronic control unit 70. This routine is executed when the accelerator is released and a fuel cut request is made for the engine 12.

[0019] When this routine is executed, the electronic control unit 70 first determines whether or not fuel cut of the engine 12 is prohibited to protect the PM filter 36 from overheating (step S100). If it is determined that fuel cut of the engine 12 is not prohibited, the electronic control unit 70 cuts fuel to the engine 12 (step S110) and ends this routine.

[0020] When fuel is cut off for the engine 12, air (oxygen) is supplied to the PM filter 36, and the particulate matter accumulated in the PM filter 36 reacts with the oxygen to burn the particulate matter. Therefore, if fuel is cut off for the engine 12 when the PM accumulation amount Qpm is equal to or greater than the threshold value Qpmref, the particulate matter can be burned to regenerate the PM filter 36. However, if fuel is cut off for the engine 12 to burn the particulate matter when the temperature Tf of the PM filter 36 is equal to or greater than the relatively high threshold value Tfref, there is a risk that the PM filter 36 will overheat. For this reason, at this time, fuel cut for the engine 12 is prohibited.

[0021] If it is determined in step S100 that fuel cut of the engine 12 is prohibited, the operation of the engine 12 is controlled so that negative torque is output from the engine 12 with fuel injection and ignition (step S120), and the transmission 60 is controlled so that the gear Gs of the transmission 60 is downshifted (the gear ratio of the transmission 60 becomes larger) (step S130), and this routine ends. In the process of step S120, the operation of the engine 12 is controlled (intake air amount control, fuel injection control, ignition control) so that the torque generated by the explosive combustion of the engine 12 is smaller than the friction torque.

[0022] When the accelerator is released, if the fuel cut of the engine 12 is not performed, the magnitude of the negative torque from the engine 12 is smaller than that when the fuel cut of the engine 12 is performed. Therefore, if the gear stage Gs of the transmission 60 is the same regardless of whether or not the fuel cut of the engine 12 is performed, the deceleration of the vehicle is smaller when the fuel cut of the engine 12 is not performed than that when the fuel cut of the engine 12 is performed. Based on this, in the embodiment, when the fuel cut of the engine 12 is not performed, the gear stage Gs of the transmission 60 is downshifted (the gear ratio of the transmission 60 is increased) to increase the rotation speed Ne of the engine 12 and to increase the amplification ratio (the reciprocal of the gear ratio) of the transmission 60 with respect to the torque from the engine 12, thereby increasing the deceleration torque acting on the drive wheels 22a, 22b. This makes it possible to suppress the deceleration of the vehicle from becoming smaller when the fuel cut of the engine 12 is not performed. That is, in this case, the deceleration of the vehicle can be more sufficiently ensured.

[0023] FIG. 3 is an explanatory diagram showing an example of the accelerator opening Acc, the target gear Gs* of the transmission 60, the vehicle speed V, and the engine speed Ne of the engine 12 in the case where fuel cut of the engine 12 is prohibited when the accelerator is released and fuel cut of the engine 12 is requested. In the figure, the solid line shows the state of the embodiment, and the dashed line shows the state of the comparative embodiment. In the comparative embodiment, the process of step S130 of the processing routine of FIG. 2 is not executed (the gear Gs of the transmission 60 is not downshifted). As shown in the figure, when the accelerator is released and fuel cut of the engine 12 is requested (time t11), and it is determined that fuel cut of the engine 12 is prohibited (time t12), in the embodiment, the target gear Gs* of the transmission 60 is changed to a low gear and the gear Gs is downshifted, so that the engine speed Ne of the engine 12 becomes larger and the amplification ratio of the transmission 60 to the torque from the engine 12 becomes larger than in the comparative embodiment. As a result, in the embodiment, the vehicle deceleration can be ensured more sufficiently and the vehicle speed V can be reduced more quickly than in the comparative example.

[0024] In the automobile 10 of the present embodiment described above, when the accelerator is released and a fuel cut is required for the engine 12, and fuel cut for the engine 12 is prohibited to protect the PM filter 36 from overheating, the engine 12 and the transmission 60 are controlled so that the gear Gs of the transmission 60 is downshifted (the gear ratio becomes larger) compared to when negative torque is output from the engine 12 with fuel injection for the engine 12 and fuel cut is performed for the engine 12. This makes it possible to more sufficiently ensure deceleration of the vehicle when a fuel cut for the engine 12 is required and fuel cut is prohibited.

[0025] In the above embodiment, a stepped transmission is used as the transmission 60, but a continuously variable transmission may also be used.

[0026] In the embodiment described above, the automobile 10 has the engine 12 connected to the input shaft of the transmission 60. However, a motor may also be connected to the input shaft of the transmission 60 in addition to the engine.

[0027] The relationship between the main elements of the embodiment and the main elements of the invention described in the section on means for solving the problem will be described below. In the embodiment, the engine 12 corresponds to the "engine", the transmission 60 corresponds to the "transmission", and the electronic control unit 70 corresponds to the "control device".

[0028] Note that the correspondence between the main elements of the embodiment and the main elements of the invention described in the Means for Solving the Problem column does not limit the elements of the invention described in the Means for Solving the Problem column, since the embodiment is an example for specifically explaining the form for implementing the invention described in the Means for Solving the Problem column. In other words, the interpretation of the invention described in the Means for Solving the Problem column should be made based on the description in that column, and the embodiment is merely a specific example of the invention described in the Means for Solving the Problem column.

[0029] The above describes embodiments for implementing the present disclosure, but the present disclosure is not limited to these embodiments, and it goes without saying that the present disclosure can be implemented in various forms without departing from the gist of the present disclosure. [Industrial Applicability]

[0030] The present disclosure is applicable to the vehicle manufacturing industry and the like. [Explanation of symbols]

[0031] 10 automobile, 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 pressure sensor, 26 in-cylinder injection valve, 28 intake valve, 29 combustion chamber, 30 spark plug, 32 piston, 33 exhaust valve, 34 exhaust pipe, 35 purification device, 35a catalyst, 36 PM filter, 36a differential pressure sensor, 37 front air-fuel ratio sensor, 38 rear air-fuel ratio sensor, 60 transmission, 62 differential gear, 64a drive wheel, 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.

Claims

[Claim 1] A vehicle comprising an engine having an exhaust system equipped with a filter for collecting particulate matter, a transmission for transmitting power between the engine and drive wheels by changing a gear ratio, and a control device for controlling the engine and the transmission and for prohibiting a fuel cut of the engine when the temperature of the filter is equal to or higher than a predetermined temperature, When a fuel cut of the engine is requested and the control device prohibits the fuel cut of the engine, the control device controls the engine and the transmission so that the gear ratio of the transmission becomes larger compared to a case where a negative torque is output from the engine accompanied by fuel injection of the engine and the fuel cut of the engine is performed. vehicle.

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