JP2005330843A - Premixed compression self-ignition engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable stable premixed compression self-ignition combustion in a wide load range by using internal EGR for making part of exhaust gas flow back from an exhaust port to inside of a combustion chamber. <P>SOLUTION: The second exhaust port 22 for making part of exhaust gas flow back to a central part of the combustion chamber 16 in the middle of an intake stroke is provided as a helical port. A first intake port 19 supplies intake air to a wall face side of the combustion chamber 16 so as to make the intake air flow in the same direction as that of a flow of exhaust gas flowing from the second exhaust port 22 into inside of the combustion chamber 16. A second intake port 20 supplies air fuel mixture to the combustion chamber 16 so as to make the air fuel mixture flow in the same direction as that of a flow of exhaust gas flowing into inside of the combustion chamber 16 and between air supplied from the first intake port 19 and the exhaust gas. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a premixed compression self-ignition engine.

  Conventional internal combustion engines can be broadly divided into two types: SI (Spark Ignition) engines and diesel engines. However, the SI engine can improve heat efficiency by leaning, but there is a limit to the equivalence ratio that allows flame propagation, so adjustment of the air amount by the throttle is necessary and the heat efficiency is inferior to that of the diesel engine. Diesel engines have good thermal efficiency but are not sufficiently mixed. Therefore, NOx is likely to be generated by local high-temperature combustion, and soot is likely to be locally rich.

  Compared to these engines, the premixed compression auto-ignition engine premixes, so there is less possibility of local high temperature and richness, and low NOx and almost no soot generation. In addition, because of the ignition due to chemical change, the dependence on the equivalence ratio is less than that of the SI engine, so that a significant leaning is possible and the thermal efficiency equivalent to that of a diesel engine can be obtained. A premixed compression auto-ignition engine having these advantages has attracted attention. In premixed compression auto-ignition combustion, if the heat is too high, it becomes abrupt combustion, and conversely, if there is not enough heat, it will misfire, causing misfire, knocking, pre-ignition, etc. compared to the current engine. There is a problem that the operating range is easily narrowed.

  In order to perform premixed compression autoignition combustion that suppresses abnormal combustion such as knocking, a premixed compression autoignition engine is proposed in which a non-uniform distribution state is generated in the cylinder (see Patent Document 1). ). Then, as a method for generating a non-uniform distribution state in the cylinder, it is proposed to make the fuel distribution in the cylinder non-uniform and to make the circulating gas non-uniform distribution in the cylinder. Has been.

  Further, in order to perform stable compression auto-ignition combustion in a gasoline engine, it has been proposed to cause exhaust gas to flow back into the combustion chamber from the exhaust port and to flow back flow exhaust gas along the outer periphery of the combustion chamber. (See Patent Document 2). Specifically, as shown in FIG. 12, a first intake port 62 and a second intake port 63 communicating with the combustion chamber 61, and a first exhaust port 64 and a second exhaust port 65 communicating with the combustion chamber 61 are provided. I have. The openings 62a, 63a, 64a, 65a of each port are opened and closed by valves (not shown). The first intake port 62 is provided with a fuel injection valve 66, and the second intake port 63 is provided with an on-off valve 67. A spark plug 68 is provided at a position corresponding to the center of the combustion chamber 61.

Similarly to the first exhaust port 64, the second exhaust port 65 discharges the already burned gas during the exhaust stroke, but the valve is controlled to open and close so that the temporary exhaust gas flows backward to the combustion chamber 61 during the intake stroke. The second exhaust port 65 prevents backflow exhaust gas from flowing in along the outer circumferential direction of the combustion chamber 61, and does not obstruct the fuel flowing in from the first intake port 62 from flowing toward the center of the combustion chamber 61. Is provided. Then, backflow exhaust (internal EGR) is mainly distributed in the outer peripheral region of the combustion chamber 61, and a mixture of fuel and air is distributed in the central region of the combustion chamber 61.
JP 2002-242727 A (paragraphs [0008] to [0011] in FIG. 1, FIG. 1) JP 11-264319 A (paragraphs [0013] to [0015] in FIG. 2, FIG. 2)

  In the premixed compression self-ignition combustion, the temperature unevenness and the air-fuel mixture unevenness in the cylinder certainly affect the combustion state, but depending on the state of the unevenness, there is a possibility of misfire from knocking. Patent Document 1 does not describe a specific state of the in-cylinder mixture. On the other hand, as described in Patent Document 2, the air-fuel mixture is collected at the center of the combustion chamber, and the backflow exhaust gas of the internal EGR (hereinafter simply referred to as internal EGR gas) flows along the wall surface of the combustion chamber. In this method, premixed compression auto-ignition combustion can be performed stably. By the way, since the internal EGR gas does not burn because it is already burned gas, it is desired to reduce the amount of internal EGR gas as much as possible. However, in the method of Patent Document 2 in which the internal EGR gas is caused to flow along the wall surface of the combustion chamber, the wall surface of the combustion chamber is lower than the center due to the cooling effect of cooling water or the like. It tends to fall, and there is a possibility that combustion becomes unstable during operation at a low load. For this reason, it is difficult to reduce the amount of internal EGR gas, and accordingly, the amount of air-fuel mixture supplied to the combustion chamber cannot be increased. Therefore, in the method of collecting the internal EGR gas on the wall surface side of the combustion chamber, it is difficult to stably perform premixed compression auto-ignition combustion over a wide load range.

  The present invention has been made in view of the above-described conventional problems, and an object of the present invention is to provide a stable prediction over a wide load range by using an internal EGR that causes a part of the exhaust gas to flow backward from the exhaust port into the combustion chamber. An object of the present invention is to provide a premixed compression autoignition engine capable of performing mixed compression autoignition combustion.

  In order to achieve the above object, according to the first aspect of the present invention, an air-fuel mixture of fuel and oxygen-containing gas is compressed by a piston in a combustion chamber by self-ignition combustion, and the reciprocating motion of the piston is rotated by an output shaft. It is a premixed compression auto-ignition engine that is in motion. An internal EGR means for performing an internal EGR for causing a part of the exhaust gas to flow backward from the exhaust port into the combustion chamber during the intake stroke is provided, so that the exhaust gas flowing backward to the combustion chamber flows into the center of the combustion chamber. Is provided with an exhaust suction port. The intake port is provided so that the intake air supplied from the intake port to the combustion chamber is outside the exhaust gas flowing into the center of the combustion chamber. Here, “intake” refers to gas supplied to the combustion chamber from an intake port connected to the combustion chamber, and includes not only oxygen gas such as air but also a mixture of these and fuel gas. .

  In the present invention, a part of the exhaust gas is caused to flow backward from the exhaust port into the combustion chamber during the intake stroke by the internal EGR means. Exhaust gas (internal EGR gas) flowing back into the combustion chamber flows into the center of the combustion chamber, and the intake air supplied from the intake port to the combustion chamber is supplied to the outside of the exhaust gas, and the internal EGR The gas is compressed in the compression stroke in the stratified state where it is inside. And compression auto-ignition arises from the boundary part of internal EGR gas and an air-fuel | gaseous mixture, premixed compression auto-ignition combustion can be performed in the stable state where ignitability improved.

  According to a second aspect of the present invention, in the first aspect of the present invention, two exhaust ports are provided, and one exhaust port constitutes the exhaust suction port. Therefore, in the present invention, even if the exhaust intake port is formed in a shape suitable for the internal EGR gas to flow into the center of the combustion chamber, the presence of the other exhaust port makes it possible to The burnt gas can be exhausted smoothly.

  According to a third aspect of the present invention, in the first or second aspect of the present invention, the intake port has a combustion flow in the same direction as the flow of exhaust gas flowing into the combustion chamber. Supply to the room. In the present invention, in comparison with a configuration in which the intake air is supplied to the combustion chamber so as to flow in a direction opposite to the flow of the internal EGR gas flowing into the combustion chamber, the intake air is stratified so that the internal EGR gas is on the inside. Can be easily supplied to the combustion chamber.

  According to a fourth aspect of the present invention, in the first or second aspect of the present invention, two intake ports are provided, and the first intake port is a flow of exhaust gas that flows oxygen-containing gas into the combustion chamber. Is supplied to the combustion chamber so as to have a flow in the same direction. The second intake port has a flow in the same direction as the flow of the exhaust gas flowing into the combustion chamber with a mixture of fuel and oxygen-containing gas, and is between the intake gas from the first intake port and the exhaust gas. To the combustion chamber.

  In the present invention, since the air-fuel mixture is compressed in a sandwich stratified state located between the internal EGR gas and the oxygen-containing gas, the air-fuel mixture is lean and hot at the center, and the outside is slightly rich and slightly warm. The low air-fuel mixture and the wall surface side of the combustion chamber become a layer almost similar to an oxygen-containing gas. As a result, the air-fuel mixture is prevented from entering the clevis of the piston, the amount of HC (hydrocarbon) and CO, which are considered to be large in premixed compression auto-ignition combustion, is reduced, and the combustion efficiency is improved. In addition, the temperature of the air-fuel mixture coming into contact with the wall surface of the combustion chamber is suppressed and the thermal efficiency is improved.

  According to a fifth aspect of the present invention, in the first or second aspect of the present invention, two intake ports are provided, and the first intake port supplies a mixture of fuel and oxygen-containing gas into the combustion chamber. The second intake port is configured to be able to supply the combustion chamber so as to have a flow in the same direction as the flow of the exhaust gas flowing in, and the second intake port flows the mixture of fuel and oxygen-containing gas into the combustion chamber. The combustion chamber can be supplied so as to have a flow in the opposite direction. Switching means for switching between a state in which intake air is supplied only from the first intake port and a state in which intake air is supplied from both the first intake port and the second intake port is provided.

  In this invention, the exhaust gas (internal EGR gas) that flows backward from the second exhaust port to the combustion chamber flows into the center of the combustion chamber as a vortex flow in a certain direction. When intake air (fresh air) is supplied only from the first intake port and exhaust gas flows backward from the second exhaust port, the intake air flows in the same direction as the internal EGR gas and follows the inner periphery of the combustion chamber. Supplied as Therefore, the internal EGR gas gathers near the center (near the center), and the outside becomes a stratified state in which fresh air is generated, the center in the cylinder becomes high in the compression stroke, self-ignition occurs from the center, and is stable. Premixed compression auto-ignition combustion is performed. The intake air is supplied only from the first intake port when the load is relatively low.

  Further, when the intake air is supplied from both the first intake port and the second intake port and the exhaust gas flows backward from the second exhaust port, the intake air supplied from the second intake port is supplied from the first intake port. The flow is in the opposite direction to the intake air. The intake air supplied from the second intake port has a reverse flow direction to the internal EGR gas, so that mixing with the internal EGR gas is promoted. Mixing is also promoted by the collision between the intake air supplied from the first intake port and the intake air supplied from the second intake port. As a result, when the intake air and the internal EGR gas reach a high temperature during the compression stroke, the number of hot spots is reduced and the combustion becomes slow, so that knocking is suppressed and premixed compression auto-ignition combustion is stabilized. The intake air is supplied from both the first intake port and the second intake port when the load is relatively high. The switching means switches between a state in which intake air is supplied only from the first intake port and a state in which intake air is supplied from both the first intake port and the second intake port. Therefore, by switching the intake air supply state in accordance with the operating conditions, premixed compression self-ignition combustion can be performed in a stable state over a wide load range.

  According to the present invention, it is possible to perform premixed compression self-ignition combustion stably over a wide load range by using the internal EGR that causes a part of the exhaust gas to flow backward from the exhaust port into the combustion chamber.

(First embodiment)
A first embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a schematic plan view showing a relationship between a combustion chamber, an intake port, and an exhaust port of a premixed compression self-ignition engine, and FIG. 2 is a schematic configuration diagram of the premixed compression self-ignition engine.

  As shown in FIG. 2, the premixed compression autoignition engine 10 (hereinafter sometimes simply referred to as an engine) includes an engine body 11 and a control device 12 that electronically controls the premixed compression autoignition engine 10. ing.

  The engine body 11 includes a cylinder block 13 in which a plurality of cylinders 13a (only one is shown in the figure) is formed, and a cylinder head 14. A piston 15 is provided in each cylinder 13a so as to be able to reciprocate. A combustion chamber 16 is formed by the piston 15, the cylinder 13 a and the cylinder head 14. The piston 15 reciprocates in the cylinder 13 a by the propulsive force obtained from the explosion combustion after intake and compression in the combustion chamber 16, and the reciprocating motion of the piston 15 rotates the crankshaft 18 as the output shaft via the connecting rod 17. To get the output. The engine body 11 is a four-cycle internal combustion engine.

  The cylinder head 14 is provided with a first intake port 19 and a second intake port 20, a first exhaust port 21, and a second exhaust port 22 as an exhaust intake port. The second exhaust port 22 is formed as a helical port, and is provided so that the exhaust gas flowing backward from the second exhaust port 22 to the combustion chamber 16 flows into the center of the combustion chamber 16. The second exhaust port 22 is formed in a shape that allows the exhaust gas to easily flow into the combustion chamber 16 as a swirl (swirl), and thus is not a shape suitable for exhaust in the exhaust stroke. The first exhaust port 21 has a larger inner diameter than the second exhaust port 22 in order to smoothly exhaust in the exhaust stroke.

  The first intake port 19 is supplied with the intake air (fresh air) as a flow along the peripheral wall surface of the combustion chamber 16 in the same direction as the flow of the exhaust gas flowing backward from the second exhaust port 22 into the combustion chamber 16. It is formed so that. Specifically, it is formed to extend in a tangential direction with respect to the inner wall surface of the combustion chamber 16. The second intake port 20 is formed so that the intake air (fresh air) flows along the peripheral wall surface of the combustion chamber 16 in the opposite direction to the intake air supplied from the first intake port 19 into the combustion chamber 16. .

  Each intake port 19, 20 is provided with an intake valve 23, 24 for opening and closing an opening facing the combustion chamber 16, and each exhaust port 21, 22 is an exhaust valve 25 for opening and closing an opening facing the combustion chamber 16. , 26 are provided. Both intake valves 23 and 24 are configured to be opened and closed simultaneously by a variable valve mechanism 27. Both exhaust valves 25 and 26 can be opened and closed simultaneously during the exhaust stroke by the variable valve mechanism 28, and only the exhaust valve 26 of the second exhaust port 22 can be opened and closed during the intake stroke during the intake stroke. It is configured. As the variable valve mechanisms 27 and 28, known valve timing variable mechanisms that use the camshafts 29 and 30 to open and close the intake valves 23 and 24 or the exhaust valves 25 and 26 by the cams 31 and 32 are used. A two-stage cam is used as the cam 32 for the exhaust valve 26, and it is possible to open and close the exhaust valve 26 in the exhaust stroke and open and close the exhaust valve 26 in the intake stroke with one cam. The second exhaust port 22, the exhaust valve 26 and the variable valve mechanism 28 constitute internal EGR means.

  The cylinder head 14 is connected to an intake passage 34 that branches on the downstream side and connects to both intake ports 19 and 20, and an exhaust passage 35 that branches on the upstream side and connects to both exhaust ports 21 and 22. A fuel injection nozzle 36 is provided in the intake passage 34 upstream of the branch portion, and the fuel injection nozzle 36 is connected to a fuel tank (not shown) via a pipe 37. An electromagnetic control valve 38 for controlling the fuel supply amount is provided in the middle of the pipe line 37. In this embodiment, natural gas is used as the fuel. A throttle valve 39 and an air cleaner 40 are provided upstream of the fuel injection nozzle 36 in the intake passage 34. The throttle valve 39 is electrically operated by a throttle motor (electric motor) 41, and the flow rate of intake air as an oxygen-containing gas supplied into the combustion chamber 16 is adjusted by adjusting the opening of the throttle valve 39. Is done. In the intake passage 34, a temperature sensor 42 that detects the temperature in the intake passage 34 and an air flow meter 43 that detects the intake flow rate are provided upstream of the fuel injection nozzle 36.

  The first intake port 19 and the second intake port 20 are respectively provided with flow rate adjustment valves 44 a and 44 b that can control the supply amount of intake air supplied to the combustion chamber 16. The flow rate adjusting valves 44a and 44b are a kind of butterfly valve, and are driven by an actuator 45 to rotate between a fully closed position and a fully open position. The flow rate adjusting valves 44a and 44b can adjust the amount of intake air supplied from the first intake port 19 and the second intake port 20 to the combustion chamber 16, respectively. The flow rate adjusting valves 44 a and 44 b constitute switching means for switching between a state in which intake air is supplied only from the first intake port 19 and a state in which intake air is supplied from both the first intake port 19 and the second intake port 20.

  The control device 12 that controls the operation of the premixed compression self-ignition engine 10 is configured so that the variable valve mechanism 27 is operated so that the engine 10 is operated in a state where the load and rotation speed requirements set by the output setting means 46 are satisfied. , 28, the electromagnetic control valve 38, the throttle motor 41 and the flow rate adjusting valves 44a, 44b.

  The control device 12 includes a microcomputer (hereinafter referred to as “microcomputer”) 47. The microcomputer 47 includes a memory (ROM and RAM) 48 as a storage device. The temperature sensor 42, the air flow meter 43, the water temperature sensor 49 for detecting the water temperature in the engine body 11, the rotation speed sensor 50 for detecting the rotation speed of the engine body 11, that is, the rotation speed of the crankshaft 18, and the output setting means 46 are a control device. The twelve input sides (input interfaces) are electrically connected to each other. The variable valve mechanisms 27 and 28, the electromagnetic control valve 38, the throttle motor 41, and the flow rate adjusting valves 44a and 44b are electrically connected to the output side (output interface) of the control device 12, respectively.

  The control device 12 determines the operating state of the premixed compression auto-ignition engine 10 based on the detection signals output from the sensors, and the variable valve mechanisms 27 and 28, the electromagnetic control valve so as to be in a predetermined operating state. 38, the throttle motor 41 and the flow rate adjusting valves 44a and 44b are controlled. The control device 12 calculates the air-fuel ratio based on the detection signal of the air flow meter 43 and the opening degree of the electromagnetic control valve 38.

  In the memory 48, various commands to be commanded for controlling the premixed compression self-ignition engine 10 based on the operation state grasped from the detection signals of the temperature sensor 42, the air flow meter 43, the water temperature sensor 49 and the rotation speed sensor 50. A map, a formula, and the like used for determining the command value (control value) are stored. The map, formula, and the like include, for example, a map, formula, etc. that determine the fuel injection amount, the throttle opening, and the intake air supply amount from the first intake port 19 and the second intake port 20.

  The memory 48 stores a map for premixed compression auto-ignition combustion operation. As shown in FIG. 3, the map shows the premixed compression auto-ignition combustion (HCCI) possible range as the relationship between the load and the rotational speed of the crankshaft 18, that is, as the relationship between the load and the rotational speed of the engine. There is a map M1. Further, there is a map of the air-fuel ratio with respect to the engine speed and load in a range where stable premixed compression auto-ignition combustion is possible. There is also a map showing how the intake air is supplied from the first and second intake ports 19 and 20, that is, the proper adjustment state of the flow rate adjusting valves 44a and 44b in relation to the load and the rotational speed of the engine. These maps are created in advance based on tests.

  Based on the map M1, the control device 12 determines whether or not the premixed compression self-ignition combustion operation is possible according to the required load and the rotational speed. And control is performed so as to correspond to the rotation speed. The control device 12 supplies the intake air to the combustion chamber 16 based on the operating conditions of the premixed compression auto-ignition engine 10 corresponding to the required load and the rotational speed, that is, only from the first intake port 19. Alternatively, it is determined whether to supply from both the first intake port 19 and the second intake port 20. Then, the flow rate adjusting valves 44a and 44b are controlled based on the determination result. When the premixed compression auto-ignition combustion operation is impossible in accordance with the required load and the rotational speed, the control device 12 can operate the premixed compression self-ignition combustion near the required rotational speed and the load, that is, the required rotational speed and The flow rate adjusting valves 44a and 44b are controlled based on the target rotational speed close to the load and the operating conditions corresponding to the load.

Next, the operation of the apparatus configured as described above will be described.
The control device 12 grasps the operating state of the engine body 11 from detection signals from the water temperature sensor 49 and the rotational speed sensor 50. After the warm-up is completed, the control device 12 operates the premixed compression autoignition engine 10 so as to perform premixed compression autoignition combustion under conditions that satisfy the required rotational speed and load set by the output setting means 46 or conditions close thereto. To control. The determination as to whether or not the warm-up has been completed is made based on the detection signal of the water temperature sensor 49. If the temperature detected by the water temperature sensor 49 is equal to or higher than the temperature at which the warm-up has been completed, it is determined that the warm-up has been completed. To do. The temperature when the warm-up is completed is obtained in advance by a test and stored in the memory 48.

  The control device 12 determines whether or not the premixed compression self-ignition combustion operation is possible after the warm-up is completed based on the map M1. According to the determination result, the target rotational speed and the load are calculated so that the premixed compression auto-ignition combustion operation is performed in a state where the required rotational speed and the load are satisfied or close to the required rotational speed and the load. Then, the air-fuel ratio at which an appropriate combustion state corresponding to the target rotational speed and load is calculated is calculated, and the electromagnetic control valve 38, the throttle motor 41, and the variable valve mechanisms 27 and 28 are controlled. In addition, the control device 12 determines whether to supply intake air only from the first intake port 19 or to supply intake air from both the first intake port 19 and the second intake port 20 in accordance with the operation conditions. A command signal is output so as to adjust the flow rate adjusting valves 44a and 44b to the intake air supply state suitable for the conditions.

  Exhaust gas (internal EGR gas) that flows backward from the second exhaust port 22 to the combustion chamber 16 flows into the central portion of the combustion chamber 16 as a vortex (arrow V1) in a certain direction. When the intake air (fresh air) is supplied only from the first intake port 19 and the exhaust gas flows backward from the second exhaust port 22, the intake air has the same direction as the internal EGR gas as shown in FIG. Is supplied along the inner periphery of the combustion chamber 16 (arrow Y1). Therefore, the internal EGR gas gathers near the center (near the center), and the outside becomes a stratified state in which fresh air is generated, the center in the cylinder becomes high in the compression stroke, self-ignition occurs from the center, and is stable. Premixed compression auto-ignition combustion is performed. The intake air is supplied only from the first intake port 19 when the load is relatively low.

  When intake air is supplied from both the first intake port 19 and the second intake port 20 and exhaust gas flows backward from the second exhaust port 22, as shown in FIG. 4B, the second intake port 20 From the first intake port 19 flows in the opposite direction (arrow Y2). The intake air supplied from the second intake port 20 is mixed in the range indicated by the two-dot chain line in FIG. 4B because the flow direction of the internal EGR gas is opposite to that of the internal EGR gas. Mixing is also promoted by the collision between the intake air supplied from the first intake port 19 and the intake air supplied from the second intake port 20. As a result, when the intake air and the internal EGR gas reach a high temperature during the compression stroke, the number of hot spots is reduced and the combustion becomes slow, so that knocking is suppressed and premixed compression auto-ignition combustion is stabilized. The intake air is supplied from both the first intake port 19 and the second intake port 20 when the load is relatively high.

  The internal EGR is performed by opening and closing the second exhaust port 22 during the intake stroke. FIG. 5 is a diagram showing an example of the valve timing of the variable valve mechanisms 27 and 28. The intake valves 23 and 24 and the exhaust valves 25 and 26 are set to open and close so that there is an open overlap in the vicinity of the top dead center (TDC) of the piston 15 when moving from the exhaust stroke to the intake stroke. . The exhaust valve 26 that opens and closes the second exhaust port 22 is opened and closed at the same timing as the exhaust valve 25 in the exhaust stroke, but is opened and closed independently in the intake stroke.

This embodiment has the following effects.
(1) The premixed compression self-ignition engine 10 includes a second exhaust port 22 that causes a part of the exhaust gas to flow back into the center of the combustion chamber 16 during the intake stroke. Further, the premixed compression auto-ignition engine 10 has a flow in the same direction as the flow of the exhaust gas (internal EGR gas) flowing into the combustion chamber 16 from the second exhaust port 22 so as to be outside the internal EGR gas. A first intake port 19 for supplying intake air to the combustion chamber 16 is provided. Therefore, compression auto-ignition occurs from the boundary between the internal EGR gas and the air-fuel mixture during compression, and premixed compression auto-ignition combustion can be performed in a stable state with improved ignitability. As a result, the operating range of premixed compression auto-ignition combustion is expanded on the low load side.

  (2) Since the internal EGR gas is collected at the center of the combustion chamber 16, the temperature gradient between the center of the combustion chamber 16 and the peripheral wall surface becomes steep in a compressed state. When the internal EGR gas and the intake air are uniformly mixed, the temperature gradient becomes gentle in the compressed state, and knocking is likely to occur. However, in this embodiment, since the temperature gradient becomes steep as described above, knocking hardly occurs in the premixed compression auto-ignition combustion. In addition, since the internal EGR gas is collected in the center, the amount of non-combustible internal EGR gas necessary for increasing the temperature of the air-fuel mixture during compression can be reduced, and the amount of air can be increased accordingly. Therefore, the operating range of premixed compression auto-ignition combustion can be expanded to the high load side.

  (3) Two exhaust ports are provided, and one exhaust port 22 constitutes an exhaust intake port. Therefore, even if the exhaust intake port is formed in a shape suitable for the internal EGR gas to flow into the center of the combustion chamber 16, the presence of the other exhaust port 21 makes it possible for the exhaust stroke in the combustion chamber 16 during the exhaust stroke. The burnt gas can be exhausted smoothly. As a result, compared to a configuration in which exhaust and internal EGR are performed with one exhaust port, a configuration that can satisfy the conditions of exhaust and internal EGR is facilitated.

  (4) Two intake ports are provided, and the first intake port 19 has a flow in the same direction as the flow of the exhaust gas flowing into the combustion chamber 16 of the mixture of fuel and oxygen-containing gas. The second intake port is configured to be able to supply the air-fuel mixture to the combustion chamber 16 in a direction opposite to the flow of the exhaust gas flowing into the combustion chamber 16. Switching means (flow rate adjusting valves 44a and 44b) for switching between a state in which intake air is supplied only from the first intake port 19 and a state in which intake air is supplied from both the first intake port 19 and the second intake port 20 are provided. It has been. Therefore, by switching the intake air supply state in accordance with the operating conditions, premixed compression self-ignition combustion can be performed in a stable state over a wide load range.

  (5) The flow rate adjusting valves 44a and 44b are provided in the first intake port 19 and the second intake port 20 as switching means, respectively. Accordingly, the structure of the flow rate adjusting valve is simpler and easier to control than the configuration in which the amount of intake air supplied from both the intake ports 19 and 20 to the combustion chamber 16 is adjusted by one flow rate adjusting valve.

(Second Embodiment)
Next, a second embodiment will be described with reference to FIGS. This embodiment is the same as the first embodiment in that the internal EGR gas flows into the central portion of the combustion chamber 16 and the intake air is supplied to the outside thereof. However, the mixture of the fuel as the intake air and the oxygen-containing gas is the same as in the first embodiment. The point that the gas is supplied so as to be between the internal EGR gas and the oxygen-containing gas is greatly different from that of the first embodiment. About the same part as the said embodiment, the same code | symbol is attached | subjected, detailed description is abbreviate | omitted, and a different part is demonstrated.

FIG. 6 is a schematic plan view showing the relationship between the combustion chamber, the intake port, and the exhaust port of the premixed compression self-ignition engine, and FIG. 2 is a schematic configuration diagram of the premixed compression self-ignition engine.
An oxygen-containing gas is supplied from the first intake port 19, and an air-fuel mixture of fuel and oxygen-containing gas is supplied from the second intake port 20. Therefore, the fuel injection nozzle 36 is provided on the downstream side of the flow rate adjustment valve 44 b of the second intake port 20.

  The first intake port 19 is configured to supply the oxygen-containing gas to the combustion chamber 16 so as to flow in the same direction as the flow of the exhaust gas flowing into the combustion chamber 16. The flow of the intake air from the first intake port 19 is supplied so that the swirl is weaker than the flow of the intake air from the second intake port 20. As shown in FIG. 6, the first intake port 19 is formed to extend in a tangential direction with respect to the inner wall surface of the combustion chamber 16.

  In the second intake port 20, the flow of the air-fuel mixture supplied to the combustion chamber 16 is in the same direction as the intake air supplied from the first intake port 19 into the combustion chamber 16, and the intake air from the first intake port 19 And the internal EGR gas from the second exhaust port 22 is configured to be a swirl. Specifically, as shown in FIG. 6, the second intake port 20 extends linearly so that the distance from the first intake port 19 gradually increases from the upstream side, and the downstream end is the first intake port 19. It is bent so as to approach the downstream end portion.

  In this embodiment, as shown in FIG. 8, the exhaust gas (internal EGR gas) flowing backward from the second exhaust port 22 to the combustion chamber 16 becomes a vortex flow (arrow V1) in a certain direction, and the center of the combustion chamber 16 Flows into the section. The oxygen-containing gas is supplied from the first intake port 19 along the inner periphery of the combustion chamber 16 in the same direction as the internal EGR gas (arrow Y1). In addition, the combustion chamber 16 is configured such that the mixture of fuel and oxygen-containing gas flows from the second intake port 20 in the same direction as the internal EGR gas (arrow Y2) between the internal EGR gas and the oxygen-containing gas. To be supplied. As a result, the air-fuel mixture is compressed in a sandwich-like stratified state located between the internal EGR gas and the oxygen-containing gas, and the central portion (center portion) is lean and high-temperature air-fuel mixture. Premixed compression auto-ignition combustion is performed in a state where the air-fuel mixture is slightly rich and the temperature is slightly low, and the wall surface side of the combustion chamber 16 is in a layer close to an oxygen-containing gas.

In this embodiment, in addition to the same effects as (1) to (3) of the first embodiment, the following effects can be obtained.
(6) When premixed compression auto-ignition combustion is performed in a state where the air-fuel mixture exists on the wall surface side of the combustion chamber 16, the air-fuel mixture enters the clevis 15 a of the piston 15. Since the temperature of the wall of the combustion chamber 16 is low due to the influence of cooling water, when premixed compression auto-ignition combustion is performed, the air-fuel mixture that has entered the clevis 15a becomes incomplete combustion, and HC (hydrocarbon) in the exhaust gas ) And the amount of CO increases. However, in this embodiment, oxygen-containing gas exists at a position corresponding to the wall surface of the combustion chamber 16, and the fuel is prevented from entering the clevis 15a. As a result, the amount of HC (hydrocarbon) and CO in the exhaust gas can be reduced during premixed compression auto-ignition combustion. Also, the combustion efficiency is improved.

  (7) The internal EGR gas and the air-fuel mixture are collected at the center of the combustion chamber 16 and compressed with the outside covered with the oxygen-containing gas to perform premixed compression auto-ignition combustion. Accordingly, a decrease in temperature due to the air-fuel mixture coming into contact with the wall surface of the combustion chamber 16 is suppressed, and the thermal efficiency is improved.

(8) Since the oxygen-containing gas layer is present at a position corresponding to the inner peripheral surface (bore wall) of the cylinder 13a, abnormal combustion such as premature ignition that easily occurs on the bore wall can be suppressed.
(9) The intake ports 19 and 20 are provided with flow rate adjusting valves 44a and 44b. Therefore, the structure of the flow rate adjusting valve is simpler and easier to control than the configuration in which the amount of intake air supplied from both the intake ports 19 and 20 to the combustion chamber 16 is adjusted by one flow rate adjusting valve.

The embodiment is not limited to the above, and may be configured as follows, for example.
In the course of the intake stroke, internal EGR gas that flows back part of the exhaust gas from the exhaust port into the combustion chamber 16 flows into the center of the combustion chamber 16, and the intake air supplied from the intake port to the combustion chamber 16 burns. It is only necessary that the intake ports be provided outside the exhaust gas flowing into the center of the chamber 16, and the number of intake ports is not limited to two. As shown in FIG. 9, one intake port 51 that supplies intake air to the combustion chamber 16 in the same direction as the flow of the internal EGR gas flowing into the combustion chamber 16 and outside the internal EGR gas. May be provided. In this case as well, since the internal EGR gas is compressed in the stratified state where the air-fuel mixture is outside the central portion of the combustion chamber 16, premixed compression auto-ignition combustion is performed in a stable state as in the first embodiment. It can be carried out.

  ○ As in the second embodiment, the two intake air flows to the combustion chamber 16 in the same direction as the flow of the internal EGR gas flowing into the combustion chamber 16 and outside the internal EGR gas. In the configuration provided with the intake ports 19 and 20, the air-fuel mixture may be supplied from both the intake ports 19 and 20 to the combustion chamber 16. In other words, in the second embodiment, the fuel injection nozzle 36 may be provided in the intake passage 34 as in the first embodiment, instead of being provided in the second intake port 20.

  As shown in FIG. 10, it is good also as a structure by which the flow volume adjustment means 52 was provided in the 2nd exhaust port 22 used as an exhaust_gas | exhaustion inlet port. As the flow rate adjusting means 52, for example, a throttle valve is provided. In this case, when the internal EGR is performed by causing the exhaust gas to flow backward from the second exhaust port 22 (exhaust intake port), the flow rate is maintained even when the opening / closing timing of the exhaust valve 26 for opening / closing the second exhaust port 22 is constant. By adjusting the flow rate with the adjusting means 52, the controllability of the combustion state can be improved, and premixed compression auto-ignition combustion can be performed in a more appropriate state. FIG. 10 shows the configuration applied to the configuration of the first embodiment, but the configuration may be applied to the configuration of the second embodiment.

  ○ Both intake ports 19, 20 are provided in the cylinder head 14 so that the intake air supplied from the first intake port 19 and the second intake port 20 to the combustion chamber 16 flows in along the inner peripheral surface of the combustion chamber 16. As shown in FIG. 10, a flap 53 may be provided in the intake ports 19 and 20. The flap 53 is configured to be arranged at a standby position indicated by a chain line and an action position indicated by a solid line by a rotary solenoid (not shown). The flap 53 has little influence on the intake air flowing through the intake ports 19 and 20 when the flap 53 is disposed at the standby position, and the intake air is drifted along the inner peripheral surface of the combustion chamber 16 when disposed at the operation position. Inflow. Accordingly, the degree of freedom for adjusting the state of the flow of the intake air flowing into the combustion chamber 16 is increased, and the degree of freedom for the mixed state of the intake air in the combustion chamber 16 and the internal EGR gas is increased. As a result, the controllability of premixed compression auto-ignition combustion can be improved. FIG. 10 shows the configuration applied to the configuration of the first embodiment, but the configuration may be applied to the configuration of the second embodiment.

  In the first embodiment, instead of providing the flow rate adjusting valves 44a and 44b at the intake ports 19 and 20, respectively, as shown in FIG. 10, the first intake port 19 and the second intake port 20, the intake passage 34, A valve 54 driven by an actuator (not shown) may be provided at the branch portion. The valve 54 is rotated between a position indicated by a chain line that fully closes the second intake port 20 and a position indicated by, for example, a solid line that allows supply of intake air to both the intake ports 19 and 20.

  In the second embodiment, in place of the configuration in which the flow rate adjusting valves 44a and 44b are provided in the intake ports 19 and 20, as shown in FIG. A flow rate adjustment valve 55 that can control the supply amount of intake air supplied from the intake port 20 to the combustion chamber 16 may be provided. The flow rate adjustment valve 55 can be adjusted so that the flow rate of intake air to the first intake port 19 and the second intake port 20 ranges from 0 to 100% of the flow rate of intake air in the intake passage 34 upstream of the flow rate adjustment valve 55. It has become. That is, the flow rate adjustment valve 55 can adjust the flow rate between a state in which intake air is supplied only from the first intake port 19 and a state in which intake air is supplied from both the first intake port 19 and the second intake port 20. Yes. For example, a spool valve can be used as the flow rate adjustment valve 55.

As an internal EGR means for performing internal EGR, a dedicated exhaust intake port for intake of exhaust gas may be provided, and an open / close valve or a flow rate adjusting valve may be provided in the exhaust intake port.
○ One exhaust port may be used. However, in the case of using one, it is difficult to configure the internal EGR gas to flow into the center of the combustion chamber 16 as a vortex in the middle of the intake stroke so that exhaust is smoothly performed in the exhaust stroke.

  The fuel of the premixed compression self-ignition engine 10 is not limited to natural gas, and any fuel such as fuel used in a diesel engine may be used in addition to gasoline, propane gas, methanol, dimethyl ether, and hydrogen.

○ Only during warm-up operation, the fuel may be easily ignited by compression self-ignition, and after warm-up is completed, the fuel may be switched to the fuel during normal operation.
○ The air-fuel mixture does not have to be gaseous fuel, and may be a mist-like liquid.

  O The oxygen-containing gas mixed with the fuel is not limited to air, but may be any oxygen-containing gas containing oxygen necessary to burn the fuel. For example, a gas in which oxygen is mixed with air to increase the oxygen concentration may be used.

  A configuration in which fuel is injected into the intake passage 34 to mix the fuel and oxygen-containing gas into the combustion chamber 16 is not limited, and fuel may be injected into the combustion chamber 16 during the intake stroke. . The fuel may be mixed with a carburetor or a mixer.

The premixed compression self-ignition engine 10 is not limited to a configuration having a plurality of cylinders, and may be a single cylinder.
○ Three or more intake ports may be provided, or three or more exhaust ports may be provided.

  The variable valve mechanisms 27 and 28 are not limited to the configuration in which the intake valves 23 and 24 or the exhaust valves 25 and 26 are opened / closed using the cam shafts 29 and 30 by the cams 31 and 32 or via the rocker arm. For example, the variable valve mechanisms 27 and 28 may employ a configuration in which the intake valves 23 and 24 or the exhaust valves 25 and 26 are directly opened and closed by an electromagnetic drive device or a hydraulic actuator. In this case, the degree of freedom in adjusting the opening / closing timing is increased.

  As the premixed compression self-ignition engine 10, a spark ignition device (ignition plug) may be provided in the combustion chamber 16 so that a spark ignition combustion operation is possible. In this case, it is possible to respond to the demand for high rotational speed and high load that cannot be handled by premixed compression self-ignition combustion by spark ignition combustion. Moreover, warm-up operation can be performed smoothly.

The premixed compression self-ignition engine 10 is not limited to a stationary type, and may be applied to an automobile engine.
The following technical idea (invention) can be understood from the embodiment.

(1) In the invention according to claim 4 or claim 5, a flow rate adjusting valve is provided in each of the first intake port and the second intake port.
(2) In the invention according to any one of claims 1 to 5 and the technical idea (1), a flow rate adjusting means is provided in the exhaust intake port or the exhaust port constituting the exhaust intake port. ing.

The schematic plan view which shows the relationship between the intake port and exhaust port of 1st Embodiment. 1 is a schematic configuration diagram of a premixed compression self-ignition engine. A map showing the range in which HCCI is possible in relation to the engine speed and load. (A) is a schematic diagram in a state where intake air is supplied only from a first intake port, and (b) is a schematic diagram in a state where intake air is supplied from a first intake port and a second intake port. The figure which shows the opening / closing timing of an intake valve and an exhaust valve. The schematic top view which shows the relationship between the intake port and exhaust port of 2nd Embodiment. The schematic block diagram of a premixed compression self-ignition engine similarly. The schematic diagram of the state in which intake air is supplied from the 1st intake port and the 2nd intake port. The schematic plan view which shows the relationship between the intake port and exhaust port of another embodiment. The schematic plan view which shows the flow regulating valve of another embodiment. The schematic plan view which shows the flow regulating valve of another embodiment. The partial top view of the gasoline engine of a prior art.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Premixed compression auto-ignition engine, 12 ... Control apparatus, 15 ... Piston, 16 ... Combustion chamber, 18 ... Crankshaft as an output shaft, 19 ... 1st intake port, 20 ... 2nd intake port, 21 ... 1st , 22 ... a second exhaust port as an exhaust suction port constituting the internal EGR means, 26 ... an exhaust valve constituting the internal EGR means, 28 ... also a variable valve mechanism, 44a, 44b ... constituting a switching means Flow control valve, 51 ... intake port.

Claims (5)

A premixed compression auto-ignition engine in which a mixture of fuel and oxygen-containing gas is compressed by a piston in a combustion chamber and self-ignited and burned, and a reciprocating motion of the piston is a rotational motion of an output shaft,
An internal EGR means for performing an internal EGR for causing a part of the exhaust gas to flow backward from the exhaust port into the combustion chamber during the intake stroke is provided, so that the exhaust gas flowing backward to the combustion chamber flows into the center of the combustion chamber. The premixed compression auto-ignition is provided with an intake port so that the intake air supplied from the intake port to the combustion chamber is outside the exhaust gas flowing into the center of the combustion chamber. organ.   The premixed compression self-ignition engine according to claim 1, wherein two exhaust ports are provided, and one exhaust port constitutes the exhaust intake port.   The premixed compression auto-ignition engine according to claim 1 or 2, wherein the intake port supplies the intake air to the combustion chamber so as to have a flow in the same direction as the flow of exhaust gas flowing into the combustion chamber.   Two intake ports are provided, the first intake port supplies oxygen-containing gas to the combustion chamber so as to flow in the same direction as the flow of exhaust gas flowing into the combustion chamber, and the second intake port serves as a fuel. An air-fuel mixture of oxygen and oxygen-containing gas is supplied to the combustion chamber so as to flow in the same direction as the flow of exhaust gas flowing into the combustion chamber and between the intake gas from the first intake port and the exhaust gas The premixed compression self-ignition engine according to claim 1 or 2.   Two intake ports are provided, and the first intake port can supply an air-fuel mixture of fuel and oxygen-containing gas to the combustion chamber so as to flow in the same direction as the flow of exhaust gas flowing into the combustion chamber. The second intake port is configured to be able to supply a mixture of fuel and oxygen-containing gas to the combustion chamber so as to be in a direction opposite to the flow of the exhaust gas flowing into the combustion chamber. The pre-switch according to claim 1 or 2, wherein switching means for switching between a state in which intake air is supplied only from the intake port and a state in which intake air is supplied from both the first intake port and the second intake port is provided. Mixed compression auto-ignition engine.

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