JP7790340B2 - Engine equipment - Google Patents

Description

This disclosure relates to an engine device, and more particularly to an engine device equipped with an engine having an in-cylinder injection valve to which an EGR system is attached.

Conventionally, one proposed engine system of this type is equipped with an engine having a port injection valve and an in-cylinder injection valve, and uses the absence of EGR (Exhaust Gas Recirculation) as a condition for learning partial lift injection, in which fuel is injected with the in-cylinder injection valve half-open (see, for example, Patent Document 1). In this system, when rapidly warming up the catalyst in the purification device that purifies exhaust gas, full lift injection is performed using the in-cylinder injection valve during the intake stroke, and then partial lift injection is performed during the compression stroke.

Japanese Patent Application Laid-Open No. 2018-115637

However, in the engine system described above, partial lift injection requires high fuel pressure, and ensuring the minimum injection amount from the direct injection valve requires a relatively high engine load factor. Therefore, if the condition for learning partial lift injection is that EGR is not being performed, there will be fewer opportunities to learn partial lift injection, making it impossible to perform more appropriate partial lift injection.

The primary purpose of the engine system disclosed herein is to provide more opportunities to learn about partial lift injection.

The engine device disclosed herein employs the following measures to achieve the above-mentioned primary objective.

The engine device of the present disclosure comprises:
An engine device comprising: an engine having an in-cylinder injection valve to which an EGR system is attached; and a control device that controls the engine,
the control device permits learning of partial lift injection in which fuel is injected with the direct injection valve in a half-open state even when the EGR rate is greater than a value of 0 and the load rate of the engine and the rotation speed of the engine are within predetermined threshold ranges.
It is characterized by:

The engine device of the present disclosure allows learning of partial lift injection, in which fuel is injected with the in-cylinder injection valve half-open, not only when the EGR rate is zero, but also when the EGR rate is greater than zero and the engine load rate and engine speed are within a predetermined threshold range. This is based on the idea that even if the EGR rate is greater than zero, the effect of EGR on explosive combustion is small as long as the engine load rate and engine speed are within a predetermined threshold range, so it is acceptable to learn partial lift injection. This allows for more opportunities to learn partial lift injection.

In the engine device of the present disclosure, the predetermined threshold range may be a range that is equal to or greater than a lower limit threshold that defines the lower limit of the engine load factor at which the minimum fuel injection amount can be injected from the direct injection valve, and is equal to or less than an upper limit threshold at which the engine load factor increases as the engine speed increases. This is based on the idea that the effect of EGR is thought to be smaller as the engine speed increases, even if the engine load factor increases.

1 is a diagram showing an outline of the configuration of an engine device 10. FIG. 4 is a flowchart showing an example of partial lift injection learning permission/denial processing executed by an engine ECU 14. FIG. 10 is an explanatory diagram showing an example of a predetermined range.

Next, a mode (embodiment) for implementing the present disclosure will be described. FIG. 1 is a schematic diagram showing the configuration of an engine device according to one embodiment of the present disclosure. FIG. 1 is a schematic diagram showing the configuration of an engine device 10 according to one embodiment of the present disclosure. As shown, the engine device 10 of the embodiment includes an engine 12, an exhaust gas recirculation system (hereinafter referred to as an "EGR (Exhaust Gas Recirculation) system") 60, and an electronic control unit (hereinafter referred to as an "ECU") 70 that controls the engine 12 and the EGR system 60. The engine device 10 is installed in automobiles that run using only power from the engine 12, hybrid automobiles that are equipped with a motor in addition to the engine 12, construction equipment that operates using power from the engine 12, and the like.

The engine 12 is a six-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. As shown in FIG. 2 , the engine 12 has a port injection valve 26 that injects fuel supplied from a fuel supply device 50 via a low-pressure supply pipe 53 into the intake port, and an in-cylinder injection valve 27 that injects fuel supplied from the fuel supply device 50 via a high-pressure supply pipe 58 into the cylinder. The in-cylinder injection valve 27 is located approximately at the top center of the combustion chamber 29 and injects fuel using either full-lift injection, in which the valve is fully open, or partial-lift injection, in which the valve is half-open, in which the fuel is sprayed. The spark plug 30 is located near the in-cylinder injection valve 27 so that it can ignite the fuel sprayed from the in-cylinder injection valve 27. By incorporating the port injection valve 26 and the in-cylinder injection valve 27, the engine 12 can operate in one of three modes: port injection mode, in-cylinder injection mode, or combined injection mode. In the port injection mode, air purified by the air cleaner 22 is drawn into the intake pipe 23 and passes through the throttle valve 24 and surge tank 25, and fuel is injected from a port injection valve 26 downstream of the surge tank 25 in the intake pipe 23 to mix the air and fuel. This mixture is then drawn into a combustion chamber 29 via an intake valve 28 and is explosively combusted by an electric spark from an ignition plug 30. The reciprocating motion of a piston 32, which is pushed down within the cylinder bore by the energy of the fuel, is converted into rotational motion of the crankshaft 13. In the direct injection mode, air is drawn into the combustion chamber 29 as in the port injection mode, and fuel is injected from the direct injection valve 27 during the intake stroke and compression stroke. The fuel is explosively combusted by an electric spark from the ignition plug 30 to rotate the crankshaft 13. In the dual-injection mode, fuel is injected from the port injection valves 26 when air is drawn into the combustion chamber 29, and from the in-cylinder injection valves 27 during the intake and compression strokes. The fuel is then explosively combusted by an electric spark from the spark plug 30, generating rotational motion for the crankshaft 13. These injection modes are switched based on the operating state of the engine 12. Exhaust gas discharged from the combustion chamber 29 through the exhaust valve 33 into the exhaust pipe 34 is then released into the outside air via a purification device 35. 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 exhaust gas from the exhaust pipe 34 is not only released into the outside air, but is also supplied to the intake pipe 23 via an EGR system 60, which recirculates the exhaust gas back into the intake air.

The fuel supply system 50 is configured to supply fuel from a fuel tank 51 to the port injection valves 26 and in-cylinder injection valves 27 of the engine 12. The fuel supply system 50 includes a fuel tank 51, a feed pump 52, a low-pressure supply pipe 53, a check valve 54, a relief pipe 55, a relief valve 56, a high-pressure pump 57, and a high-pressure supply pipe 58.

The feed pump 52 is configured as an electric pump that operates by receiving power from a battery (not shown) and is located inside the fuel tank 51. This feed pump 52 supplies fuel from the fuel tank 51 to a low-pressure supply pipe 53. The low-pressure supply pipe 53 is connected to the port injection valve 26. A check valve 54 is provided in the low-pressure supply pipe 53 and allows fuel to flow from the feed pump 52 side toward the port injection valve 26 side, while restricting fuel flow in the opposite direction.

Relief pipe 55 is connected to low-pressure supply pipe 53 and fuel tank 51. Relief valve 56 is provided in relief pipe 55 and closes when the fuel pressure in low-pressure supply pipe 53 is below threshold Pflolim and opens when the fuel pressure in low-pressure supply pipe 53 is equal to or greater than threshold Pflolim. When relief valve 56 opens, a portion of the fuel in low-pressure supply pipe 53 is returned to fuel tank 51 via relief pipe 55. In this way, excessive fuel pressure in low-pressure supply pipe 53 is prevented.

The high-pressure pump 57 is driven by power from the engine 12 (in this embodiment, rotation of the intake camshaft, which opens and closes the intake valve 28) and is configured as a pump that pressurizes fuel in the low-pressure supply pipe 53 and supplies it to the high-pressure supply pipe 58. The high-pressure pump 57 has an electromagnetic valve 57a connected to its intake port that opens and closes when pressurizing the fuel, a check valve 57b connected to its discharge port that regulates backflow of fuel and maintains fuel pressure in the high-pressure supply pipe 58, and a plunger 57c that is actuated (moves vertically in FIG. 1 ) by the rotation of the engine 12 (rotation of the intake camshaft). During engine 12 operation, when the electromagnetic valve 57a is open, the high-pressure pump 57 draws fuel from the low-pressure supply pipe 53. When the electromagnetic valve 57a is closed, the high-pressure pump 57 intermittently sends fuel compressed by the plunger 57c to the high-pressure supply pipe 58 via the check valve 57b, thereby pressurizing the fuel to be supplied to the high-pressure supply pipe 58.

The EGR system 60 includes an EGR pipe 62 and an EGR valve 64. The EGR pipe 62 connects the exhaust pipe 34 downstream of the purification device 35 with the surge tank 25 of the intake pipe 23. The EGR valve 64 is provided in the EGR pipe 62 and is driven by a stepping motor 63. By adjusting the opening of the EGR valve 64, the EGR system 60 adjusts the amount of exhaust gas recirculated as unburned gas to the intake side. In this way, the engine 12 can draw a mixture of air, exhaust, and fuel into the combustion chamber 29. Hereinafter, the recirculation of exhaust gas from the exhaust pipe 34 to the intake pipe 23 will be referred to as "EGR," the exhaust gas recirculated from the exhaust pipe 34 to the intake pipe 23 will be referred to as "EGR gas," and the amount of EGR gas will be referred to as the "EGR amount."

The operation of the engine 12 is controlled by the engine ECU 14. Although not shown, the engine ECU 14 is equipped with a microcomputer that has a CPU, ROM, RAM, flash memory, input/output ports, and communication ports.

Signals from various sensors required for controlling the operation of the engine 12 are input to the engine ECU 14 via input ports. Examples of signals input to the engine ECU 14 include the crank angle θcr from a crank position sensor 40 that detects the rotational position of the crankshaft 13 of the engine 12, and the coolant temperature Tw from a water temperature sensor 42 that detects the temperature of the coolant for the engine 12. Other examples include cam angles θci and θco from a cam position sensor 44 that detects the rotational position of the intake camshaft that opens and closes the intake valves 28 and the exhaust camshaft that opens and closes the exhaust valves 33. Other examples include the throttle opening TH from a throttle valve position sensor 24a that detects the position of the throttle valve 24, the intake air amount Qa from an air flow meter 23a attached upstream of the throttle valve 24 in the intake pipe 23, the intake air temperature Ta from a temperature sensor 23t attached upstream of the throttle valve 24 in the intake pipe 23, and the surge pressure Ps from a pressure sensor 25a attached to the surge tank 25. Other examples include a front air-fuel ratio AF1 from a front air-fuel ratio sensor 37 attached upstream of the purification device 35 in the exhaust pipe 34, and a rear air-fuel ratio AF2 from a rear air-fuel ratio sensor 38 attached downstream of the purification device 35 in the exhaust pipe 34. Other examples include the fuel temperature Tftnk from a fuel temperature sensor 51t attached to the fuel tank 51, the rotation speed Np of the feed pump 52 from an rotation speed sensor 52a attached to the feed pump 52, the low fuel pressure PL (the pressure of the fuel supplied to the port injection valve 26) from a fuel pressure sensor 53p attached to the low-pressure supply pipe 53 near the port injection valve 26 (e.g., in the low-pressure delivery pipe), the high-pressure fuel pressure PH (the pressure of the fuel supplied to the in-cylinder injection valve 27) from a fuel pressure sensor 58p attached to the high-pressure supply pipe 58 near the in-cylinder injection valve 27 (e.g., in the high-pressure delivery pipe), and the opening degree EV of the EGR valve 64 from an EGR valve opening degree sensor 65 that detects the opening degree of the EGR valve 64.

Various control signals for controlling the operation of the engine 12 are output from the engine ECU 14 via an output port. Examples of signals output from the engine ECU 14 include a control signal to the throttle valve 24, a control signal to the port injection valve 26, a control signal to the in-cylinder injection valve 27, and a control signal to the spark plug 30. Other examples include a control signal to the feed pump 52 of the fuel supply device 50, a control signal to the electromagnetic valve 57a of the high-pressure pump 57, and a control signal to the stepping motor 63 that adjusts the opening of the EGR valve 64.

The engine ECU 14 calculates the engine 12 rotation speed Ne based on the engine 12 crank angle θcr from the crank position sensor 40. The engine ECU 14 also calculates the load factor KL (the ratio of the volume of air actually taken in per cycle to the stroke volume per cycle of the engine 12) based on the intake air amount Qa from the air flow meter 23a and the engine 12 rotation speed Ne. The engine ECU 14 also calculates the EGR amount Ve and EGR rate based on the intake air amount Qa, the engine 12 rotation speed Ne, and the opening degree EV of the EGR valve 64 from an EGR valve opening degree sensor (not shown).

The engine ECU 14 controls the operation of the engine 12, such as intake air volume control, fuel injection control, ignition control, and opening/closing timing control, so that the engine 12 operates based on the target operating point (target rotation speed Ne* and target torque Te*) of the engine 12. Intake air volume control is performed by controlling the opening of the throttle valve 24. Fuel injection control is performed by controlling the fuel injection amount from the port injection valve 26 and the in-cylinder injection valve 27 in port injection mode, in-cylinder injection mode, and shared injection mode. Ignition control is performed by controlling the ignition timing of the spark plug 30.

Next, the operation of the engine system 10 of this embodiment configured as described above will be described, particularly the operation when determining whether to allow or disallow learning of partial lift injection. Partial lift injection learning is basically performed when the engine 12 load factor KL is in the low range and only one full lift injection is being performed from the in-cylinder injection valve 27 during the intake stroke. Learning of partial lift injection is performed by performing one short partial lift injection at the start of the same fuel injection, followed by full lift injection of the remaining fuel injection amount. Figure 2 is a flowchart showing an example of partial lift injection learning permission/denial processing executed by the engine ECU 14. This processing is repeatedly executed at predetermined time intervals.

When the partial lift injection learning permission/denial process is executed, the engine ECU 14 inputs the engine 12 rotation speed Ne and the engine 12 load factor KL (step S100). In this embodiment, the engine 12 rotation speed Ne is calculated based on the engine 12 crank angle θcr from the crank position sensor 40, and the engine 12 load factor KL is calculated based on the intake air amount Qa from the air flow meter 23a and the engine 12 rotation speed Ne.

Next, it is determined whether the engine 12 rotation speed Ne and the engine 12 load factor KL are within a predetermined range (step S110). An example of the predetermined range is shown in FIG. 3. In the figure, the dashed-dotted line indicates the load factor KL as the lower limit of the minimum injection amount of fuel injected from the in-cylinder injection valve 27. The dashed line indicates the load factor KL at which the EGR rate is 0 (EGR amount is 0). The solid line indicates a threshold value for determining whether partial lift injection learning is possible. Region A (the region below the dashed-dotted line in FIG. 3) is a region where the fuel injection amount from the in-cylinder injection valve 27 is less than the minimum injection amount, making partial lift injection learning difficult. Region B (the region between the dashed-dotted line and the dashed line in FIG. 3) is a region where the EGR rate is 0 (EGR amount is 0) and the fuel injection amount from the in-cylinder injection valve 27 is equal to or greater than the minimum injection amount, making partial lift injection learning possible. Region C (the region between the dashed line and the solid line in FIG. 3 ) is a region where partial lift injection can be learned because the EGR rate is relatively small but not zero (the EGR amount is relatively small but not zero). In this embodiment, the upper threshold value (solid line) of region C is set so that the load factor KL of the engine 12 increases as the engine speed Ne of the engine 12 increases. This region C is the predetermined threshold range. Region D (the region above the solid line in FIG. 3 ) is a region where partial lift injection learning is inappropriate because the load factor KL is high and therefore the EGR rate is high. Therefore, the range (predetermined range) where partial lift injection can be learned is the region where the fuel injection amount from the direct injection valve 27 is equal to or greater than the minimum injection amount, where the EGR rate is zero (region B), and the region where the EGR rate is small (region C: predetermined threshold range).

If it is determined in step S110 that the engine 12 rotation speed Ne and the engine 12 load rate KL are within the predetermined threshold range, learning of partial lift injection is permitted (step S120), and the process ends. On the other hand, if it is determined in step S110 that the engine 12 rotation speed Ne and the engine 12 load rate KL are outside the predetermined threshold range, learning of partial lift injection is prohibited (step S130), and the process ends.

In the engine system 10 of the embodiment described above, learning of partial lift injection is permitted not only when the engine 12 rotation speed Ne and the engine 12 load factor KL are in a region where the fuel injection amount from the in-cylinder injection valve 27 is equal to or greater than the minimum injection amount and the EGR rate is zero (region B), but also when the engine 12 rotation speed Ne and the engine 12 load factor KL are in a region where the fuel injection amount from the in-cylinder injection valve 27 is equal to or greater than the minimum injection amount and the EGR rate is greater than zero but relatively small (predetermined threshold range of region C). This provides more opportunities for learning partial lift injection compared to when learning of partial lift injection is permitted only when the engine 12 rotation speed Ne and the engine 12 load factor KL are in a region where the fuel injection amount from the in-cylinder injection valve 27 is equal to or greater than the minimum injection amount and the EGR rate is zero (region B).

In the engine device 10 of the embodiment, the engine 12 used is one in which the in-cylinder injection valve 27 is located approximately in the center of the top of the combustion chamber 29, but an engine in which the in-cylinder injection valve 27 is located on the side wall (side) of the combustion chamber 29 may also be used.

In the engine device 10 of the embodiment, the engine 12 has a port injection valve 26 and an in-cylinder injection valve 27, but an engine having only an in-cylinder injection valve 27 without a port injection valve 27 may also be used.

The following explains the correspondence between the main elements of the embodiment and the main elements of the invention described in the "Means for Solving the Problem" section. In the embodiment, the EGR system 60 corresponds to the "EGR system," the in-cylinder injection valve 27 corresponds to the "in-cylinder injection valve," the engine 12 corresponds to the "engine," and the engine ECU 14 corresponds to the "control device."

The correspondence between the main elements of the embodiments and the main elements of the invention described in the "Means for Solving the Problem" section does not limit the elements of the invention described in the "Means for Solving the Problem" section, as the embodiments are examples used to specifically explain the form for implementing the invention described in the "Means for Solving the Problem" section. In other words, the interpretation of the invention described in the "Means for Solving the Problem" section should be based on the description in that section, and the embodiments are merely specific examples of the invention described in the "Means for Solving the Problem" section.

The above describes the forms (embodiments) for carrying out the present invention, but the present invention is not limited to these embodiments in any way, and it goes without saying that the present invention can be embodied in various forms without departing from the spirit of the invention.

This invention can be used in industries such as engine equipment manufacturing.

10 engine device, 12 engine, 13 crankshaft, 14 engine ECU, 22 air cleaner, 23 intake pipe, 23a air flow meter, 23t temperature sensor, 24 throttle valve, 24a throttle valve position sensor, 25 surge tank, 25a pressure sensor, 26 port injection valve, 27 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 purification catalyst, 37 front air-fuel ratio sensor, 38 rear air-fuel ratio sensor, 40 crank position sensor, 42 water temperature sensor, 44 cam position sensor, 50 fuel supply device, 51 fuel tank, 51t fuel temperature sensor, 52 feed pump, 52a rotation speed sensor, 53 low-pressure supply pipe, 53p fuel pressure sensor, 54 Check valve, 55 relief pipe, 56 relief valve, 57 high-pressure pump, 57a solenoid valve, 57b check valve, 57c plunger, 58 high-pressure supply pipe, 58p fuel pressure sensor, 60 EGR system, 62 EGR pipe, 63 stepping motor, 64 EGR valve, 65 EGR valve opening sensor.

Claims (1)

An engine device comprising: an engine having an in-cylinder injection valve to which an EGR system is attached; and a control device that controls the engine,
the control device permits learning of partial lift injection in which fuel is injected with the direct injection valve in a half-open state even when the EGR rate is greater than a value of 0 and the load rate of the engine and the rotation speed of the engine are within predetermined threshold ranges ,
the predetermined threshold range is equal to or greater than a lower limit threshold as a lower limit value of the load factor of the engine at which a minimum fuel injection amount of fuel can be injected from the cylinder injection valve, and is equal to or less than an upper limit threshold at which the load factor of the engine increases as the engine speed increases.
An engine device characterized by: