Engine device

Abstract

To more properly cope with reduction of engine torque during warming up of a catalyst.SOLUTION: When the torque of the engine becomes less than the threshold value in a state where the change amount of the torque of the engine becomes a negative value during the catalyst warm-up of the purification device, the fuel injection adjustment for increasing the fuel injection in the compression stroke, the throttle opening adjustment for increasing the throttle opening, and the ignition timing adjustment for advancing the ignition timing are performed stepwise as compared with those during the normal catalyst warm-up.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to engine systems. [Background technology]

[0002] Conventionally, an engine device of this type has been proposed that, while fuel is being injected during the compression stroke or expansion stroke of the engine to warm up the catalyst of the purification device, if the engine speed drops below a predetermined speed by an amount equal to or greater than a speed threshold, it determines that engine combustion has deteriorated and interrupts catalyst warm-up (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2023-159496 Summary of the Invention [Problem to be solved by the invention]

[0004] During catalyst warm-up, a large amount of energy is input to the engine, causing the exhaust valve to extend, which can lead to compression loss due to hesitation in exhaust valve closing and poor combustion due to internal EGR, resulting in a drop in engine torque and a drop in engine speed.To address these issues, a lash adjuster is used to adjust the exhaust valve extension, but if the lash adjuster is at the lower end of its product tolerance range, it may not be possible to completely adjust the exhaust valve extension, resulting in compression loss and poor combustion, and the catalyst warm-up may be interrupted as the engine torque drops.

[0005] The engine device of the present disclosure has a primary object to more appropriately deal with a drop in engine torque during catalyst warm-up. [Means for solving the problem]

[0006] The engine device of the present disclosure employs the following measures to achieve the above-mentioned main object. The engine device of the present disclosure is an engine device comprising an engine having a purification device that purifies exhaust gas and an in-cylinder injection valve, and a control device that controls the engine, wherein when the amount of change in engine torque becomes negative during catalyst warm-up of the purification device and the engine torque becomes less than a threshold value, the control device gradually performs fuel injection adjustment to increase fuel injection during the compression stroke, throttle opening adjustment to increase the throttle opening, and ignition timing adjustment to advance the ignition timing, compared to during normal catalyst warm-up.

[0007] In the engine system disclosed herein, when the engine torque becomes less than a threshold value while the engine torque change rate becomes negative during catalyst warm-up of the purification device, the system gradually adjusts the fuel injection amount to increase fuel injection during the compression stroke, the throttle opening amount to increase the throttle opening, and the ignition timing amount to advance, compared to normal catalyst warm-up. The fuel injection adjustment increases the fuel injection amount during the compression stroke to increase engine torque, the throttle opening adjustment increases the throttle opening to increase the intake air volume to increase engine torque, and the ignition timing adjustment advances the ignition timing to increase engine torque. This prevents a decrease in engine torque and allows catalyst warm-up to continue for a longer period. As a result, deterioration of emissions can be suppressed. The fuel injection adjustment increases the proportion of fuel injected during the compression stroke when fuel is injected in multiple increments.

[0008] In the engine device of the present disclosure, the control device may adjust the fuel injection, the throttle opening, and the ignition timing in a stepwise manner in this order. In this case, the control device may adjust the fuel injection when the engine torque is less than a first threshold, adjust the throttle opening when the engine torque is less than a second threshold that is smaller than the first threshold, and adjust the ignition timing when the engine torque is less than a third threshold that is smaller than the second threshold. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic diagram of a hybrid vehicle 10 equipped with an engine device according to an embodiment. [Figure 2] 4 is a flowchart showing an example of a catalyst warm-up process. [Figure 3] Timing chart for fuel injection adjustment, throttle opening adjustment, and ignition timing adjustment. DETAILED DESCRIPTION OF THE INVENTION

[0010] An embodiment of the present disclosure will now be described. Fig. 1 is a diagram showing an outline of the configuration of a hybrid vehicle 10 equipped with an engine device according to an embodiment of the present disclosure. As shown in the figure, the hybrid vehicle 10 of the embodiment includes an engine 12, a planetary gear 60 having a carrier connected to a crankshaft 14 of the engine 12, a motor MG1 connected to a sun gear of the planetary gear 60, a motor MG2 attached to a drive shaft 61 connected to a ring gear of the planetary gear 60, and an electronic control unit 70 as a control device for controlling the hybrid vehicle 10.

[0011] The engine 12 is configured as a multiple-cylinder internal combustion engine that uses fuel such as gasoline or diesel to output 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.

[0012] The engine 12 draws air purified by an air cleaner 22 into an intake pipe 23, passes it through a throttle valve 24 and a surge tank 25, and then into a combustion chamber 29 via an intake valve 28. Fuel is injected once or in multiple instalments from a direct injection valve 26 during the intake stroke or compression stroke, and is ignited by a spark plug 30 to cause explosive combustion. The reciprocating motion of a piston 32, which is pushed down by the energy produced by this explosive combustion, is converted into rotational motion of the crankshaft 14. Exhaust gas discharged from the combustion chamber 29 through an exhaust valve 33 into an exhaust pipe 34 is then discharged into the outside air via a purification device 35 and a PM filter 36 incorporated in the exhaust pipe 34. The purification device 35 has a purification catalyst (three-way catalyst) 35a that purifies harmful components in the exhaust, such as carbon monoxide (CO), hydrocarbons (HC), and nitrogen oxides (NOx). The PM filter 36 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.

[0013] The motors MG1 and MG2 are configured as, for example, synchronous generator motors, and are connected to a battery (not shown) via an inverter (not shown), and are driven to rotate by PWM control of the inverter's switching elements. A drive shaft 61 to which the motor MG2 is attached is connected to drive wheels 64a and 64b via a differential gear 62.

[0014] The electronic control unit 70 is configured as a microcomputer. The electronic control unit 70 receives inputs such as the crank angle θcr from the crank position sensor 14a, the coolant temperature Tw from the water temperature sensor 15, the cam angles θci and θco from the cam position sensor 16, the intake air amount Qa from the air flow meter 23a, the intake air temperature Tqa from the temperature sensor 23t, the throttle opening TH from the throttle position sensor 24a, the surge pressure Ps from the pressure sensor 25a, the front air-fuel ratio AF1 from the front air-fuel ratio sensor 37, the rear air-fuel ratio AF2 from the rear air-fuel ratio sensor 38, and the differential pressure ΔP from the differential pressure sensor (pressure sensor) 36a that detects the differential pressure between before and after the PM filter 36 (the differential pressure between the upstream side and the downstream side). The electronic control unit 70 also receives as input the rotational positions of the rotors of the motors MG1 and MG2, the three-phase currents of the motors MG1 and MG2, an ignition signal IG from an ignition switch 80, a shift position SP from a shift position sensor 82, an accelerator opening Acc from an accelerator pedal position sensor 84, a brake pedal position BP from a brake pedal position sensor 86, a vehicle speed V from a vehicle speed sensor 87, and an outside air temperature Ta from an outside air temperature sensor 88.

[0015] The electronic control unit 70 outputs various control signals via output ports. 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 switching control signals that switch the switching elements of the inverters of the motors MG1 and MG2. 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, and estimates the torque Te of the engine 12 from the torque Tm of the motor MG1.

[0016] In the hybrid vehicle 10 of this embodiment, the electronic control unit 70 basically controls the drive of the engine 12 and the motors MG1 and MG2 as follows. The electronic control unit 70 sets a driving torque Td* to be output to the drive shaft 61 based on the accelerator pedal position Acc and the vehicle speed V, and then sets a required torque Te* to be output from the engine 12 and torque commands Tm1* and Tm2* to be output from the motors MG1 and MG2 based on this driving torque Td*. The electronic control unit 70 then controls the intake air amount (throttle position control), fuel injection, and ignition of the engine 12 so that the required torque Te* is output from the engine 12, and also controls the switching of the inverters attached to the motors MG1 and MG2 so that the motors MG1 and MG2 output torques according to the torque commands Tm1* and Tm2*.

[0017] Next, the operation of the hybrid vehicle 10 of this embodiment configured as described above will be described, in particular the operation during catalyst warm-up for warming up the catalyst 35a of the purification device 35. Fig. 2 is a flowchart showing an example of a catalyst warm-up process executed by the electronic control unit 70. This process is repeatedly executed at predetermined time intervals during catalyst warm-up.

[0018] When the catalyst warm-up process is executed, the electronic control unit 70 first estimates the torque Te of the engine 12 (step S100) and calculates the torque change amount ΔTe (step S110). The torque Te of the engine 12 can be converted into the output torque of the motor MG1 based on the gear ratio of the planetary gear 60. The torque change amount ΔTe can be calculated as the difference (Te - previous Te) from the previous torque Te estimated when this process was executed the previous time.

[0019] Next, it is determined whether the torque change amount ΔTe is less than 0 (step S120). When the torque change amount ΔTe is less than 0, the torque Te of the engine 12 is decreasing, and therefore step S120 is a process for determining whether the torque Te of the engine 12 is decreasing. During catalyst warm-up, the torque Te of the engine 12 normally gradually increases due to warm-up. However, when a lash adjuster at the lower end of the product tolerance range is used, the exhaust valve 33 may extend, causing the exhaust valve 33 to be stubbornly closed, resulting in loss of compression or deterioration of combustion due to internal EGR, which may result in a decrease in engine torque. Such phenomena are also determined in step S120. When it is determined that the torque change amount ΔTe is equal to or greater than 0, it is determined that normal catalyst warm-up is being performed, and this process ends.

[0020] If it is determined in step S120 that the torque change amount ΔTe is less than zero, it is then determined whether the torque Te of the engine 12 is less than a threshold value Tref1 (step S130). The threshold value Tref1 is greater than threshold values ​​Tref2 and Tref3, which will be described later, and is the first-stage threshold value for adjusting the torque Te of the engine 12 to increase it in stages. The threshold value Tref2 is the second-stage threshold value, and the threshold value Tref3 is the third-stage threshold value. If it is determined that the torque Te of the engine 12 is greater than or equal to the threshold value Tref1, it is determined that it is not yet necessary to perform the first-stage process for increasing the torque Te of the engine 12, and this process is terminated. On the other hand, if it is determined that the torque Te of the engine 12 is less than the threshold value Tref1, the fuel injection is adjusted so that more fuel is injected during the compression stroke than during normal catalyst warm-up (step S140). For example, if the first fuel injection is performed during the intake stroke, the second fuel injection is performed in the middle of the compression stroke, and the third fuel injection is performed at the end of the compression stroke, the amount of fuel injected in the first injection is reduced and the amounts of fuel injected in the second and third injections are increased. By making such adjustments, the torque Te of the engine 12 can be increased.

[0021] Next, it is determined whether the torque Te of the engine 12 is less than a threshold value Tref2 (step S150). If it is determined that the torque Te of the engine 12 is equal to or greater than the threshold value Tref2, it is determined that it is not necessary to perform the second stage of processing to increase the torque Te of the engine 12, and this processing is terminated. On the other hand, if it is determined that the torque Te of the engine 12 is less than the threshold value Tref2, the throttle opening is adjusted so that the throttle opening TH is larger than that during normal catalyst warm-up (step S160). For example, if the throttle opening TH during normal catalyst warm-up is 10 degrees, the throttle opening TH is increased to 13 degrees or 15 degrees. By adjusting in this manner, the intake air amount Qa is increased, which in turn increases the fuel injection amount, thereby increasing the torque Te of the engine 12.

[0022] Next, it is determined whether the torque Te of the engine 12 is less than a threshold value Tref3 (step S170). If it is determined that the torque Te of the engine 12 is equal to or greater than the threshold value Tref3, it is determined that it is not necessary to perform the third stage of processing to increase the torque Te of the engine 12, and this processing is terminated. On the other hand, if it is determined that the torque Te of the engine 12 is less than the threshold value Tref3, the ignition timing is adjusted so that the ignition timing is advanced compared to that during normal catalyst warm-up (step S180). For example, if the ignition timing during normal catalyst warm-up is 13 degrees ATDC, the ignition timing is advanced to 5 degrees ATDC or 3 degrees ATDC. By adjusting in this manner, the torque Te of the engine 12 is increased.

[0023] FIG. 3 is a timing chart showing an example of time variations in engine torque, fuel injection adjustment, throttle opening adjustment, and ignition timing adjustment during catalyst warm-up processing. In the figure, the dashed lines for the catalyst warm-up execution flag and engine torque Te indicate a comparative example. When catalyst warm-up begins at time T1, the catalyst warm-up execution flag is turned on. For example, in normal catalyst warm-up, the first fuel injection is performed at 280 BTDC (280 degrees before top dead center) on the intake stroke with an injection rate of 0.7; the second fuel injection is performed at 115 BTDC (115 degrees before top dead center) on the compression stroke with an injection rate of 0.15; and the third fuel injection is performed at 80 BTDC (80 degrees before top dead center) on the compression stroke with an injection rate of 0.15. The throttle opening TH is set to 10 degrees, and the ignition timing is set to 13 ATDC (13 degrees after top dead center). The excess air ratio at this time is 40%. Subsequently, the torque Te of the engine 12 increases over time as the engine 12 warms up. When a lash adjuster at the lower end of its product tolerance range is used, the torque Te of the engine 12 decreases from time T2 due to the exhaust valve 33's hesitation to close due to its extension. At time T3, when the torque Te of the engine 12 falls below the threshold Tref1, the fuel injection is adjusted so that more fuel is injected during the compression stroke than during normal catalyst warm-up. In the example of FIG. 3 , the first injection is performed at BTDC 270 (270 degrees before top dead center) on the intake stroke, with the injection ratio changed to 0.4; the second injection is performed at BTDC 120 (120 degrees before top dead center) on the compression stroke, with the injection ratio changed to 0.3; and the third injection is performed at BTDC 85 (85 degrees before top dead center) on the intake stroke, with the injection ratio also changed to 0.3. These fuel injection adjustments increase the torque Te of the engine 12. If such adjustment of fuel injection cannot avoid a decrease in torque Te of the engine 12, the throttle opening TH is adjusted so that it is larger than that during normal catalyst warm-up at time T4 when torque Te of the engine 12 falls below threshold value Tref2. In the example of Fig. 3, throttle opening TH is adjusted to be larger from 10 degrees to 15 degrees. As a result, the excess air ratio increases from 40% to 50%, the fuel injection amount is increased as the intake air amount Qa increases, and the torque Te of the engine 12 increases.If a decrease in torque Te of the engine 12 cannot be avoided even by adjusting the throttle opening TH, the ignition timing is adjusted so that it is more advanced than during normal catalyst warm-up at time T5, when the torque Te of the engine 12 falls below threshold Tref3. In the example of FIG. 3, the ignition timing is changed from ATDC 13 (13 degrees after top dead center of compression) to ATDC 5 (5 degrees after top dead center of compression). This adjustment of the ignition timing increases the torque Te of the engine 12. On the other hand, in the comparative example, the fuel injection, throttle opening TH, and ignition timing are not adjusted, so the decrease in torque Te of the engine 12 is not suppressed, and catalyst warm-up is stopped at time T6.

[0024] In the engine system installed in the hybrid vehicle 10 of the embodiment described above, when the change in torque Te of the engine 12, ΔTe, becomes negative during catalyst warm-up of the purification device 35 and the torque Te of the engine 12 falls below a threshold Tref1, the system adjusts fuel injection to increase fuel injection during the compression stroke compared to normal catalyst warm-up. Furthermore, when the torque Te of the engine 12 falls below a threshold Tref2, the system adjusts the throttle opening TH to increase the throttle opening TH. Furthermore, when the torque Te of the engine 12 falls below a threshold Tref3, the system adjusts the ignition timing to advance the ignition timing. In this way, when the change in torque Te of the engine 12, ΔTe, becomes negative during catalyst warm-up and the torque Te of the engine 12 decreases, the system gradually adjusts fuel injection, throttle opening TH, and ignition timing to increase the torque Te of the engine 12, thereby increasing the torque Te of the engine 12 and continuing catalyst warm-up. As a result, deterioration of emissions due to the suspension of catalyst warm-up can be suppressed.

[0025] In the embodiment, the present disclosure has been described using the configuration of hybrid vehicle 10, which is equipped with engine 12, motor MG1, and motor MG2, and in which the torque Te of engine 12 is estimated from the torque of motor MG1. However, the configuration of the vehicle does not have to be that of a hybrid vehicle, and any configuration of vehicle may be used as long as it has sensors and mechanisms that can estimate the engine torque.

[0026] The above describes embodiments for implementing the present disclosure, but the present disclosure is not limited to these embodiments and can, of course, be implemented in various forms within the scope that does not deviate from the gist of the present disclosure. [Industrial Applicability]

[0027] The present disclosure is applicable to the engine device manufacturing industry and the like. [Explanation of symbols]

[0028] 10 automobile, 12 engine, 26 in-cylinder injection valve, 28 intake valve, 29 combustion chamber, 30 spark plug, 33 exhaust valve, 34 exhaust pipe, 35 purification device, 35a catalyst, 60 planetary gear, 70 electronic control unit, MG1, MG2 motor.

Claims

[Claim 1] An engine device including an engine having a purification device that purifies exhaust gas and an in-cylinder injection valve, and a control device that controls the engine, When the amount of change in engine torque becomes negative during catalyst warm-up of the purification device and the torque of the engine becomes less than a threshold value, the control device gradually adjusts fuel injection to increase fuel injection during the compression stroke, throttle opening to increase the throttle opening, and ignition timing to advance the ignition timing, compared to during normal catalyst warm-up.

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