JP2007187057A - Internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a means inhibiting deterioration of sealing material and lubricating material of an EGR valve and promoting atmization and evaporation of fuel in an internal combustion engine provided with an EGR device. <P>SOLUTION: In the internal combustion engine provided with the EGR device, a second injector 51 is provided in a downstream side of the EGR valve 42. Deterioration of the sealing material and the lubricating material of the EGR valve 42 due to fuel injected from the second injector 51 can be inhibited. Since fuel is injected in an EGR passage 41, heat energy of exhaust gas can be fully utilized. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an internal combustion engine having an EGR passage that introduces burned gas into an intake passage and an EGR valve that opens and closes the EGR passage, and particularly relates to an engine intended to promote atomization and vaporization of fuel.

  Conventionally, a fuel injection valve has been installed upstream of an EGR valve (recirculation valve) in an EGR (Exhaust Gas Recirculation) device, and a device that promotes fuel volatilization using the thermal energy of the exhaust gas has been proposed. (Patent Document 1). For the same purpose, there has also been proposed an apparatus in which a fuel injection valve is arranged in the intake passage so that the fuel spray reaches the intake passage in the vicinity of the confluence of the EGR passage and the intake passage (Patent Document). 2).

JP 2001-12289 A JP 2004-60474 A

  However, since the fuel of the apparatus of Patent Document 1 is injected upstream with respect to the EGR valve, there is a possibility that the lubricant and the sealing material of the EGR valve are deteriorated.

  Moreover, in the apparatus of patent document 2, since fuel is injected in an intake passage, the thermal energy of exhaust gas cannot fully be utilized.

  Accordingly, an object of the present invention is to provide means capable of suppressing deterioration of a lubricant and a sealing material of an EGR valve and favorably promoting atomization and vaporization of fuel in an internal combustion engine equipped with an EGR device.

  A first aspect of the present invention is an internal combustion engine having an EGR passage that introduces burned gas into an intake passage and an EGR valve that opens and closes the EGR passage, and is in the EGR passage and downstream of the EGR valve An internal combustion engine comprising a fuel injection valve.

  In the first aspect of the present invention, since the fuel injection valve is provided downstream of the EGR valve (that is, the intake passage side), deterioration of the lubricant and sealing material of the EGR valve due to the fuel injected from the fuel injection valve can be suppressed. Further, since the fuel is injected into the EGR passage, the thermal energy of the exhaust gas can be used well, and the atomization of the fuel can be promoted.

  The second aspect of the present invention is further characterized by further comprising a fuel holding portion for holding liquid phase fuel in an EGR passage or an intake passage on the downstream side of the fuel injection valve.

  In the second aspect of the present invention, the inflow of the liquid phase fuel into the combustion chamber can be suppressed by the fuel holding portion that stores the liquid phase fuel.

  The third aspect of the present invention further includes control means for controlling the fuel injection valve, wherein the control means controls the fuel injection valve to inject fuel in the first half of the exhaust stroke.

  In the third aspect of the present invention, by injecting fuel in the first half of the exhaust stroke, the energy of exhaust gas having a high temperature and a high flow rate can be used.

  A fourth aspect of the present invention is an internal combustion engine having an EGR passage for introducing already burned gas into an intake passage, and an EGR valve for opening and closing the EGR passage, and a fuel injection valve provided in the EGR passage; A control means for controlling the EGR valve and the fuel injection valve, wherein the control means suppresses the opening of the EGR valve when the fuel injection valve is not injecting. .

  In the fourth aspect of the present invention, since the opening degree of the EGR valve is suppressed when the fuel injection valve is not injecting, the exhaust pressure of the EGR passage can be effectively used for atomizing and vaporizing the fuel. When suppressing the opening degree of the EGR valve, it is particularly preferable to fully close the EGR valve.

  An embodiment in which the present invention is applied to a direct-injection gasoline engine will be described in detail with reference to the drawings. However, the present invention is not limited to such an embodiment, and may be modified or modified in any way encompassed by the concept of the present invention described in the claims, and thus other modifications belonging to the spirit of the present invention. It should be noted that it can naturally be applied to any technology.

  In FIG. 1, the engine 10 according to the present embodiment is of a type that supplies gasoline as fuel from a first injector 11 and a second injector 51 and ignites them with a spark plug 13 in a combustion chamber 12.

  An intake port 14 that opens and closes the intake port 14 and an exhaust valve 18 that opens and closes the exhaust port 15 as well as the intake valve 17 and the exhaust are provided in the cylinder head 16 formed with the intake port 14 and the exhaust port 15 respectively facing the combustion chamber 12. A valve operating mechanism VM that drives the valve 18 and an ignition plug 13 that ignites the air-fuel mixture in the combustion chamber 12 are incorporated, and an ignition coil 19 that generates sparks is mounted on the ignition plug 13.

  The valve operating mechanism VM is a mechanism capable of individually controlling the intake valve 17 and the exhaust valve 18 at an arbitrary opening degree and timing, and includes solenoids individually provided for the intake valve 17 and the exhaust valve 18 respectively. Contains. Instead of such a configuration, for example, a variable valve timing mechanism (VVT) that can arbitrarily change the valve timing and the cam profile by switching two types of cams by hydraulic pressure may be used as the valve mechanism VM.

  An intake pipe 21 connected to the cylinder head 16 so as to communicate with the intake port 14 defines an intake passage 20 together with the intake port 14. On the upstream end side of the intake pipe 21, an air cleaner (not shown) for removing dust contained in the atmosphere and guiding it to the intake passage 20 is provided. A throttle valve 24 is incorporated in a portion of the intake pipe 21 located downstream of the air cleaner. The throttle valve 24 is opened by a throttle actuator 23 based on a depression amount of an accelerator pedal (not shown) operated by a driver. The degree is adjusted. Further, an intake control valve 26 that opens and closes the intake passage 20 by an intake control actuator 25 at a predetermined timing according to the opening and closing timing of the intake valve 17 is provided in a portion of the intake passage 20 that is located downstream of the throttle valve 24. Is incorporated. A surge tank 28 is further formed in the intake pipe 21.

  An exhaust pipe 32 connected to the cylinder head 16 so as to communicate with the exhaust port 15 defines an exhaust passage 31 together with the exhaust port 15. A three-way catalyst 33 for purifying exhaust gas from the combustion chamber 12 is incorporated in the middle of the exhaust pipe 32. It is also effective to incorporate a plurality of three-way catalysts 33 in series along the exhaust passage 31.

  An EGR passage 41 for introducing exhaust gas, that is, already burned gas, into the intake passage is formed so as to connect the catalyst container of the three-way catalyst 33 and the intake pipe 21. In the present embodiment, as shown in FIG. 2, the EGR passage 41 is provided with an EGR valve 42 for opening and closing the EGR passage 41. The EGR valve 42 is a poppet valve that is driven by a solenoid 43 with good responsiveness, and the EGR passage 41 can be sealed when fully closed. As shown in FIG. 2, the intake passage 20 branches toward each cylinder on the downstream side of the connection point between the EGR passage 41 and the intake passage 20, and constitutes individual branches 20 a to 20 d of the intake manifold. ing.

  Between the EGR valve 42 in the EGR passage 41 and the connection point of the intake pipe 21, a fuel injection chamber 44 having a sectional area larger than that of the EGR passage 41 is formed. A second injector 51 is installed toward the inside of the fuel injection chamber 44. The fuel injection chamber 44 functions as a fuel holding part in the present invention. An opening 45 is formed at the lower end of the fuel injection chamber 44, whereby the EGR passage 41 and the intake passage 20 are communicated with each other. On the upper surface of the lower end portion of the fuel injection chamber 44, a cylindrical body (not shown) extending upward from the edge of the opening 45 may be provided so as to promote the retention of the liquid phase fuel. The engine 10 according to the present embodiment includes a fuel tank, a feed pump, a high-pressure pump, and a delivery pipe (all not shown), and the first injector 11 and the second injector 51 are all connected to the delivery pipe. The delivery pipe to which the first injector 11 and the second injector 51 are connected may be common or separate. The second injector 51 may be connected to the low pressure (feed pressure) side, that is, the downstream side of the feed pump and the upstream side of the delivery pipe.

  The second injector 51 is preferably installed at a position where the burned gas from the EGR valve 42 directly hits the injected fuel, whereby the burned gas having a high flow rate from the slight opening gap of the EGR valve 42. As a result, the atomization and vaporization of the injected fuel can be promoted. The “position where the burnt gas directly hits the injected fuel” here means that the flow rate of the burnt gas that has passed through the opening gap of the EGR valve 42 depends on the cross-sectional shape of the flow path due to the attenuation caused by the downstream movement. Within the range upstream from the point of convergence from the specified steady state to the predetermined range.

  In FIG. 1 again, the exhaust gas temperature sensor 28 for detecting the exhaust gas temperature is attached to the three-way catalyst 33. The cylinder block 35 in which the piston 34 reciprocates is provided with a water temperature sensor 37 that detects the temperature of the cooling water in the water jacket 36 formed in the cylinder block 35 and outputs the detected temperature to the ECU 27. Further, a crank angle sensor 40 that detects the rotational phase of the crankshaft 39 to which the piston 34 is connected via the connecting rod 38, that is, the crank angle, and outputs the detected crank angle to the ECU 27 is attached to the crankcase of the engine 10. . In the present embodiment, the crank angle sensor 40 is used as an engine speed sensor.

  Based on the detection signals from these sensors 28, 37, 40, etc., the ECU 27 performs the first injector 11, the ignition coil 19, the throttle actuator 23, the intake air so that the engine 10 can be smoothly operated according to a preset program. The operations of the control actuator 25, the solenoid 43, the second injector 51, and the like are controlled.

  The fuel injection amounts from the first injector 11 and the second injector 51 are the amount of intake air calculated according to the amount of depression of an accelerator pedal (not shown), the opening of the throttle valve 24 and the detected value of an air flow meter (not shown), Further, the ECU 27 calculates the engine speed based on the detected value of the crank angle sensor 40. Further, the ratio (sharing ratio) of the injection quantity of the second injector 51 in the total fuel injection quantity is increased as the engine water temperature is lower and the exhaust gas temperature is higher as shown in FIG. 3, for example. Set to. This setting may be discrete as shown in FIG. 3 or continuous. Thus, vaporization can be promoted by utilizing the heat energy of the exhaust gas under a disadvantageous condition for fuel vaporization such as during cold start.

  The EGR valve 42 is controlled by the ECU 27 in synchronization with the operation of each cylinder. Specifically, the EGR valve 42 is controlled based on the current crank angle detected by the crank angle sensor 40 so as to be in an open state during the exhaust stroke of each cylinder or during a predetermined period including the exhaust stroke. The second injector 51 is controlled by the ECU 27 so that fuel injection is performed during the first half of the exhaust stroke and while the EGR valve 42 is open. That is, as shown in FIG. 4, the engine 1 is ignited periodically and at equal intervals in the order of “# 1, # 3, # 4, # 2”, and each EGR valve 42 is controlled by the ECU 27. The cylinders # 1 to # 4 are opened over a predetermined crank angle including the bottom dead center immediately before the bottom dead center (BDC) of the expanded exhaust gas where the exhaust stroke starts. In the second injector 51, under the control of the ECU 27, while the EGR valve 42 is open, specifically, injection is performed within a predetermined crank angle immediately after the bottom dead center of the expansion exhaust of each cylinder.

  As a result of the above processing, in the present embodiment, since the EGR valve 42 is opened while the exhaust gas in the exhaust stroke is supplied to the EGR passage 41, high-pressure and high-temperature exhaust gas is supplied to the intake passage 21. Further, the high-pressure and high-temperature exhaust gas from the EGR valve 42 acts on the fuel injected from the second injector 51, and the atomization and vaporization thereof are promoted.

  As described above, in the present embodiment, since the second injector 51 is provided on the downstream side (that is, the intake passage 20 side) from the EGR valve 42, the lubricant and sealing of the EGR valve 42 by the injected fuel from the second injector 51 are sealed. Deterioration of the material can be suppressed. Further, since the fuel is injected into the EGR passage 41, the heat energy of the exhaust gas can be used well. Further, since the EGR gas is cooled by the latent heat at the time of fuel vaporization, it is possible to suppress an increase in intake air temperature caused by the amount of heat of the EGR gas, and to suppress a decrease in charging efficiency and knocking.

  In the present embodiment, since the second injector 51 injects fuel into the fuel injection chamber 44, the fuel injection chamber 44 can be used even under conditions unfavorable for vaporization such as during cold start. The liquid-phase fuel adheres and stays therein, so that the liquid-phase fuel can be temporarily held, so that the inflow of the liquid-phase fuel into the combustion chamber can be suppressed. Further, since the cross-sectional area of the fuel injection chamber 44 is made larger than that of the EGR passage 41, the residence time of the burned gas can be increased, and the surface area of the fuel injection chamber 44 is larger than that of the EGR passage 41. The possibility of adhesion / collection of fuel can be increased, the vaporization thereof can be promoted, and the inflow of liquid phase fuel into the combustion chamber can be suppressed.

  Further, the second injector 51 is arranged in the vicinity of the EGR valve 42, that is, at a position where it directly hits the injected fuel, and is discharged via the EGR valve 42 to at least a part of the injected fuel from the second injector 51. Since the burned gas flow is interfered, the opening gap of the EGR valve 42 is significantly smaller than the cross-sectional area of the EGR passage 41 and the pressure difference between the front and rear of the EGR valve 42 is obtained when the EGR valve 42 is opened. Exhaust gas having a high speed can act on the injected fuel, and fuel atomization and vaporization can be promoted.

  In this embodiment, since the EGR valve 42 is opened in accordance with the exhaust stroke and the fuel is injected in the first half of the exhaust stroke, the energy of the burnt gas having a high temperature and a high flow velocity can be used.

  Furthermore, in the present embodiment, the injection from the second injector 51 is performed only when EGR is introduced, and the opening of the EGR valve 42 is suppressed when the second injector 51 is not injecting. Since the EGR valve 42 is fully closed when the opening degree of the EGR valve 42 is suppressed, it is possible to effectively use the effect for atomization and vaporization.

  Next, a second embodiment of the present invention will be described. In the second embodiment, as shown in FIG. 5, the EGR passage 141 is branched from the middle, and serves as EGR branch paths 141 a to 141 d toward each cylinder. Each of the EGR branch paths 141a to 141d is provided with EGR valves 142a to 142d for individually opening and closing these EGR branch paths 141a to 141d. Each of the EGR branch paths 141a to 141d is individually connected to each branch 20a to 20d of the intake manifold of the intake pipe 21.

  Fuel injection chambers 44 are respectively formed between the EGR valves 142a to 142d in the EGR branch paths 141a to 141d and the connection point between the intake pipe 21 and the EGR valves 142a to 142d. Second injectors 151a to 151d (hereinafter referred to as second injectors 151 as appropriate) are installed toward the inside of the fuel injection chamber 44. An opening 45 is formed at the lower end of each fuel injection chamber 44, whereby the EGR branch paths 141 a to 141 d and the branches 20 a to 20 d of the intake path 20 are communicated with each other. The first injector 11 and the second injector 151 are both connected to a delivery pipe (not shown). The delivery pipe to which the first injector 11 and the second injector 151 are connected may be common or separate. The second injector 151 may be connected to the low pressure (feed pressure) side.

  The EGR valve 142 is controlled by the ECU in synchronization with the operation of each cylinder. Specifically, the EGR valve 142 is controlled based on the current crank angle detected by the crank angle sensor 40 so as to be open during the exhaust stroke of each cylinder or during a predetermined period including the exhaust stroke. The second injector 151 is controlled by the ECU so that fuel injection is performed during the first half of the exhaust stroke and while the EGR valve 142 is open. That is, as shown in FIG. 6, the engine 1 is ignited periodically and at equal intervals in the order of “# 1, # 3, # 4, # 2,” and each EGR valve 142 is controlled by the ECU. The cylinders # 1 to # 4 are opened over a predetermined crank angle including the bottom dead center immediately before the bottom dead center (BDC) of the exhaust exhaust where the exhaust stroke of the cylinders # 1 to # 4 starts. In the second injector 151, while the EGR valve 142 is open under the control of the ECU, specifically, the injection is performed within a predetermined crank angle immediately after the bottom dead center of the expansion exhaust of each cylinder. Since the remaining mechanical configuration of the second embodiment is the same as that of the first embodiment, the same reference numerals are given and detailed description thereof is omitted.

  In the second embodiment configured as described above, since the EGR valve 142 and the second injector 151 are individually provided for each cylinder in addition to the effects obtained by the first embodiment, according to the characteristics of each cylinder. The optimum fuel injection timing and fuel injection period can be set for each cylinder.

  Next, a third embodiment of the present invention will be described. In the third embodiment, as shown in FIG. 7, second injectors 251a to 251d (hereinafter referred to as second injectors 251 as appropriate) are provided in the respective EGR branch paths 241a to 241d, while a common EGR valve 242 is used for all cylinders. Is provided on the upstream side with respect to the branch point of the EGR passage 241.

  In the third embodiment, the opening / closing timing of the EGR valve 242 is set so as to be opened in the first half of the exhaust stroke of each cylinder, as shown in FIG. That is, the EGR valve 242 has a period A1 corresponding to the first half of the exhaust stroke of cylinder # 1, a period A3 corresponding to the first half of the exhaust stroke of cylinder # 3, a period A4 corresponding to the first half of the exhaust stroke of cylinder # 4, and The ECU is controlled so as to be opened in a period A2 corresponding to the first half of the exhaust stroke of the cylinder # 2. Further, the second injectors 251a to 251d inject fuel at the initial stage of these periods A1, A3, A4, A2. Since the remaining configuration of the third embodiment is the same as that of the first embodiment, the same reference numerals are given and detailed description thereof is omitted.

  As a result of the above processing, in the third embodiment, in addition to the same effects as in the first embodiment, the common EGR valve 242 and solenoid 243 are used for a plurality of cylinders, so that the manufacturing cost can be suppressed.

  In the second and third embodiments, each EGR valve and each second injector are opened during the exhaust stroke of the corresponding cylinder (that is, the cylinder located downstream of each EGR valve and each second injector). However, the time when each EGR valve and each second injector is opened does not have to be during the exhaust stroke of the cylinder to which they correspond, and may be during the exhaust stroke of another cylinder. However, the EGR valve 141 and each second injector 151 of the second embodiment, and the EGR valve 242 and the second injector 251 in each of the EGR branch paths 41a to 41d of the third embodiment are opened during a common exhaust stroke. Is preferred. In each of the above embodiments, it is determined based on the crank angle whether any of the cylinders is in the exhaust stroke. However, an exhaust pressure detecting means may be provided in the exhaust path to determine based on the detected value.

  In the above embodiments, the injection timing of the second injectors 51, 151, 251 is determined according to the opening / closing timings of the EGR valves 42, 142, 143. The opening / closing timing and / or opening / closing period of the EGR valves 42, 142, 242 is set so that the opening time of the EGR valves 42, 142, 242 is increased as the injection amount of the injectors 51, 151, 251 increases. You may vary according to the injection timing and injection quantity of 2 injectors 51, 151, 251. In this case, the atomization and vaporization of the fuel can be further promoted by setting the opening / closing timing of the EGR valves 42, 142, and 242 suitable for the injection timing and the injection amount of the second injectors 51, 151, and 251. It becomes possible.

  Various modifications can be considered for the fuel holding portion in each of the above embodiments. For example, as shown in FIG. 9, a portion of the intake pipe 21 that defines the intake passage 20, which is a dish-like or concave shape that is depressed downward at a position vertically below the junction with the EGR passage 41. A fuel holding part 144 may be provided. Further, as shown in FIG. 10, the EGR passage 41 may be formed in a bent shape, and a dish-like or recessed fuel holding portion 244 that is depressed downward may be provided in the vicinity of the bent portion. According to such a configuration, since the liquid phase fuel LF is held in the fuel holding portions 144 and 244 even under conditions unfavorable for atomization or vaporization of the fuel, such as at the time of cold start, Invasion of the phase fuel LF into the combustion chamber 12 can be suppressed, and vaporization thereof can be promoted.

  Further, in each of the above embodiments, the confluence of the EGR passages 41, 141, 241 and the intake passage 20 is provided on the upstream side of the intake control valve 26, but this confluence may also be on the downstream side of the intake control valve 26. In this case, deposit accumulation on the intake control valve 26 can be suppressed.

  Further, in each of the above-described embodiments, the case where the present invention is applied to a so-called in-cylinder direct injection type gasoline engine has been described. However, the present invention is not limited to a port injection type engine that injects fuel into an intake port, or an ignition plug. Needless to say, the present invention is also effective in other types of engines such as diesel engines that do not use the engine, and the same effects as in a direct-injection gasoline engine can be obtained. The present invention can also be applied to engines other than those for vehicles, and such a configuration also belongs to the category of the present invention.

1 is a conceptual diagram of a first embodiment of the present invention. It is a conceptual diagram which shows the branching state of the EGR path | route in 1st Embodiment, and the installation location of an EGR valve and a 2nd injector. It is a graph which shows the example of a setting of the ratio (sharing rate) of the injection quantity of the 2nd injector which occupies for the whole fuel injection quantity. It is a timing diagram which shows operation | movement of the EGR valve and 2nd injector in 1st Embodiment. It is a conceptual diagram which shows the branching state of the EGR channel | path in 2nd Embodiment, and the installation location of an EGR valve and a 2nd injector. It is a timing diagram which shows operation | movement of the EGR valve and 2nd injector in 2nd Embodiment. It is a conceptual diagram which shows the installation location of the branch state of an EGR channel | path in 3rd Embodiment, and an EGR valve and a 2nd injector. It is a timing diagram which shows operation | movement of the EGR valve and 2nd injector in 3rd Embodiment. It is sectional drawing which shows another structural example of a fuel holding part. It is sectional drawing which shows another structural example of a fuel holding | maintenance part.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Engine 11 1st injector 12 Combustion chamber 20 Intake passage 21 Intake pipe 27 ECU
30 Intake pressure sensor 40 Crank angle sensor 41, 141, 241 EGR passage 44 Fuel injection chamber 51, 151, 251 Second injector 144, 244 Fuel holding part

Claims (4)

An internal combustion engine having an EGR passage for introducing burnt gas into an intake passage and an EGR valve for opening and closing the EGR passage,
An internal combustion engine comprising a fuel injection valve in the EGR passage and downstream of the EGR valve. The internal combustion engine according to claim 1,
An internal combustion engine further comprising a fuel holding portion for holding liquid phase fuel in an EGR passage or an intake passage on the downstream side of the fuel injection valve. The internal combustion engine according to claim 1 or 2,
A control means for controlling the fuel injection valve;
The internal combustion engine, wherein the control means controls the fuel injection valve to inject fuel in the first half of an exhaust stroke. An internal combustion engine having an EGR passage for introducing burnt gas into an intake passage and an EGR valve for opening and closing the EGR passage,
A fuel injection valve provided in the EGR passage;
Control means for controlling the EGR valve and the fuel injection valve,
The internal combustion engine, wherein the control means suppresses the opening of the EGR valve when the fuel injection valve is not injecting.

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