WO2020229860A1 - Internal combustion engine - Google Patents

Internal combustion engine Download PDF

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Publication number
WO2020229860A1
WO2020229860A1 PCT/IB2019/000534 IB2019000534W WO2020229860A1 WO 2020229860 A1 WO2020229860 A1 WO 2020229860A1 IB 2019000534 W IB2019000534 W IB 2019000534W WO 2020229860 A1 WO2020229860 A1 WO 2020229860A1
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Prior art keywords
intake
dead center
internal combustion
combustion engine
center
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PCT/IB2019/000534
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French (fr)
Japanese (ja)
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WO2020229860A8 (en
Inventor
理晴 葛西
鈴木　琢磨
チヤータジ アクス
Original Assignee
日産自動車株式会社
ルノー エス．ア．エス
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Application filed by 日産自動車株式会社, ルノー エス．ア．エス filed Critical 日産自動車株式会社
Priority to JP2021519011A priority Critical patent/JP7151882B2/en
Priority to PCT/IB2019/000534 priority patent/WO2020229860A1/en
Publication of WO2020229860A1 publication Critical patent/WO2020229860A1/en
Publication of WO2020229860A8 publication Critical patent/WO2020229860A8/en

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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01L—CYCLICALLY OPERATING VALVES FOR MACHINES OR ENGINES
    • F01L1/00—Valve-gear or valve arrangements, e.g. lift-valve gear
    • F01L1/34—Valve-gear or valve arrangements, e.g. lift-valve gear characterised by the provision of means for changing the timing of the valves without changing the duration of opening and without affecting the magnitude of the valve lift
    • F01L1/344—Valve-gear or valve arrangements, e.g. lift-valve gear characterised by the provision of means for changing the timing of the valves without changing the duration of opening and without affecting the magnitude of the valve lift changing the angular relationship between crankshaft and camshaft, e.g. using helicoidal gear
    • F01L1/356—Valve-gear or valve arrangements, e.g. lift-valve gear characterised by the provision of means for changing the timing of the valves without changing the duration of opening and without affecting the magnitude of the valve lift changing the angular relationship between crankshaft and camshaft, e.g. using helicoidal gear making the angular relationship oscillate, e.g. non-homokinetic drive
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D15/00—Varying compression ratio
    • F02D15/02—Varying compression ratio by alteration or displacement of piston stroke

Definitions

  • the present invention relates to a spark-ignition internal combustion engine that injects fuel into a cylinder to perform lean burn.
  • Lean burn which burns with a dilute mixture, is known as one means of improving the fuel consumption rate of spark-ignition internal combustion engines represented by gasoline engines for vehicles.
  • Lean burn which is effective in improving the fuel consumption rate, can be realized not only by setting the air-fuel ratio, which is the ratio of fresh air to the amount of fuel, to be larger than the theoretical air-fuel ratio, but also by a large amount of exhaust gas return.
  • air-fuel ratio which is the ratio of fresh air to the amount of fuel
  • Patent Document 1 discloses a valve gear that changes the profile of the cam in the linear motion valve mechanism so that the maximum lift time is biased to the advance angle side or the retard angle side.
  • Patent Document 2 relates to a double-link piston crank mechanism in which a piston and a crank pin are connected by a plurality of links.
  • a piston in a stroke is set according to a setting of a link geometry. It discloses that the characteristics of speed can be set appropriately.
  • An object of the present invention is to effectively utilize these technologies to strengthen gas flow such as tumble in a cylinder and to stabilize combustion of lean combustion.
  • the spark ignition type internal combustion engine according to the present invention
  • the double-link piston crank mechanism is configured so that the peak of the piston speed in the intake stroke is located on the lagging side of the half crank angle position between the intake top dead center and the intake bottom dead center.
  • the lift characteristics of the intake valve are asymmetrical between the ascending section and the descending section, and the center of gravity of the integrated lift amount is located on the lagging side of the center of the intake valve operating angle.
  • FIG. 6 is a configuration explanatory view schematically showing a configuration of an internal combustion engine according to the present invention.
  • FIG. 1 schematically shows the configuration of an internal combustion engine 1 for an automobile to which the present invention is applied.
  • the internal combustion engine 1 is a 4-stroke cycle in-cylinder direct-injection spark-ignition internal combustion engine equipped with a double-link piston crank mechanism 2, and basically performs lean combustion that is leaner than the stoichiometric air-fuel ratio.
  • a pair of intake valves 4 and a pair of exhaust valves 5 are arranged on the ceiling wall surface of each cylinder 3, and a spark plug 6 is arranged in a central portion surrounded by these intake valves 4 and exhaust valves 5.
  • the combustion chamber 13 has a general pent roof type, and the intake port 15 and the exhaust port 17 extend so as to face each other.
  • the intake valve 4 is opened and closed via a valve operating mechanism (not shown), and has a lift characteristic that is asymmetrical between the ascending section and the descending section, as will be described later.
  • the exhaust valve 5 is also opened and closed via a valve operating mechanism (not shown).
  • the lift characteristic of the exhaust valve 5 is set to, for example, a general characteristic that opens before the bottom dead center of the piston and closes after the top dead center of the piston.
  • valve operating mechanism of the intake valve 4 and the exhaust valve 5 a direct acting valve mechanism in which the cam directly presses the cylindrical tappet provided at the valve stem end, and the cam lift is attached to the valve stem via the rocker arm.
  • Known valve operating mechanisms such as a rocker arm type valve operating mechanism that transmits, a hydraulic valve operating mechanism that opens and closes valves 4 and 5 by hydraulic pressure, and an electromagnetic valve operating mechanism that opens and closes valves 4 and 5 using a solenoid are appropriately provided. Can be used.
  • the lift characteristic of the intake valve 4 is a high lift type characteristic in which the lift amount is large compared to the operating angle
  • a rocker arm type valve operating mechanism, particularly a cam which can obtain a lift amount expansion action by the lever ratio.
  • a roller rocker arm type valve operating mechanism with reduced frictional resistance with the intake valve 4 is used to drive the intake valve 4.
  • Both the intake valve 4 and the exhaust valve 5 can be combined with a variable valve timing mechanism that can change the opening time and closing time.
  • Each cylinder 3 is provided with a fuel injection valve 16 so as to inject fuel directly into the cylinder.
  • the fuel injection valve 16 is located below the pair of intake ports 15, and is configured to inject fuel diagonally downward.
  • fuel injection is generally performed from the fuel injection valve 16 in the latter half of the compression stroke, and the stratified air-fuel mixture is ignited.
  • an auxiliary fuel injection valve 12 is provided at each of the intake ports 15 of each cylinder.
  • the auxiliary fuel injection valve 12 is configured so that fuel can be injected toward the intake valve 4 in the intake port 15. For example, at the time of homogeneous combustion with the target air-fuel ratio as the stoichiometric air-fuel ratio, a part or all of the fuel is injected and supplied by the auxiliary fuel injection valve 12. Alternatively, a part of the fuel is supplied from the auxiliary fuel injection valve 12 at the time of high load when the total fuel amount becomes large.
  • the configuration including the auxiliary fuel injection valve 12 is not essential, and the configuration may include only the fuel injection valve 16 for in-cylinder fuel injection.
  • An electronically controlled throttle valve 19 whose opening degree is controlled by a control signal from an engine controller (not shown) is interposed upstream of the intake collector 18 of the intake passage 14, and further upstream of the electronically controlled throttle valve 19. , An air flow meter 20 for detecting the amount of intake air and an air cleaner 21 are arranged.
  • a catalyst device 26 made of an appropriate catalyst is arranged in the exhaust passage 25 where the plurality of exhaust ports 17 are merged.
  • the catalyst device 26 is configured to include, for example, a NOx storage catalyst and a three-way catalyst.
  • An air-fuel ratio sensor 28 for detecting the air-fuel ratio is arranged on the upstream side of the catalyst device 26.
  • the double-link type piston crank mechanism 2 utilizes a known configuration described in Patent Document 2 and the like, and includes a lower link 42 rotatably supported by a crank pin 41a of a crankshaft 41 and the lower link 42.
  • the upper link 45 that connects the upper pin 43 at one end of the piston pin 43 and the piston pin 44a of the piston 44 to each other, the control link 47 whose one end is connected to the control pin 46 at the other end of the lower link 42, and the control link 47. It is mainly composed of a control shaft 48 that swingably supports the other end.
  • the crankshaft 41 and the control shaft 48 are rotatably supported in the crankcase 49a below the cylinder block 49.
  • the control shaft 48 has an eccentric shaft portion 48a whose position changes with the rotation of the control shaft 48, and the end portion of the control link 47 is rotatably fitted to the eccentric shaft portion 48a. It fits. That is, the double-link type piston crank mechanism 2 of the illustrated example is configured as a variable compression ratio mechanism capable of changing the mechanical compression ratio of the internal combustion engine 1, and the piston 44 dies as the control shaft 48 rotates. The point position is displaced up and down, thus changing the mechanical compression ratio.
  • an electric actuator 51 having a rotation center axis parallel to the crankshaft 41 is arranged on the outer wall surface of the crankcase 49a.
  • the electric actuator 51 and the control shaft are routed via a first arm 52 fixed to the output rotation shaft of the electric actuator 51, a second arm 53 fixed to the control shaft 48, and an intermediate link 54 connecting the two. It is linked with 48.
  • the electric actuator 51 includes an electric motor and a transmission mechanism arranged in series in the axial direction.
  • the electric actuator 51 is controlled by a control signal from an engine controller (not shown) so as to realize a target compression ratio according to the engine operating conditions.
  • the target compression ratio is basically a high compression ratio on the low load side, and the higher the load, the lower the compression ratio for knocking suppression and the like. In one embodiment, the target compression ratio is set stepwise.
  • the peak of the piston speed in the intake stroke is on the latter half of the intake stroke, that is, on the side behind the crank angle position of 1/2 between the intake top dead center and the intake bottom dead center.
  • the link geometry is set to be located at. In other words, assuming that the crank angle between the intake top dead center and the intake bottom dead center is 180 °, the peak of the piston speed exists on the lagging side of 90 ° CA after the top dead center. If the crank angle between the intake top dead center and the intake bottom dead center is 176 °, the peak of the piston speed exists on the lagging side of 88 ° CA after the top dead center, which is 1/2.
  • the crankshaft 41 rotates in the counterclockwise direction in FIG.
  • top dead center and bottom dead center are not the position of the crank pin 41a, but the piston top dead center where the movement direction of the piston 44 is reversed and the piston top dead center. It means the bottom dead center of the piston.
  • the distance between the top dead center and the bottom dead center is correctly 180 ° each in the crank angle between the ascending stroke and the descending stroke, whereas the double link type piston crank mechanism 2 In, the distance is not completely 180 °, but is slightly (for example, about several °).
  • the distance indicated by the crank angle between the top dead center and the bottom dead center is not completely 180 °, and the ascending stroke and the descending stroke are equal to 180. Even if it is regarded as ° CA, there is no difference in terms of action and effect.
  • the mechanical compression ratio of the internal combustion engine 1 can be changed within a certain range (for example, 10 to 15), and the link can be changed accordingly.
  • the geometry changes, but in one preferred embodiment, the peak piston speed is located late in the intake stroke under all controllable compression ratio control positions.
  • the link geometry may be such that the peak of the piston speed is located in the latter half of the intake stroke at the maximum compression ratio within the controllable range.
  • FIG. 2 is a characteristic diagram showing the lift characteristics and the piston speed characteristics of the intake valve 4 in comparison with the examples and the comparative examples.
  • the leftmost “TDC” is the intake top dead center
  • the “BDC” is the intake bottom dead center
  • the rightmost “TDC” is the compression top dead center.
  • the "intake stroke” is between the intake top dead center and the intake bottom dead center. As mentioned above, the distance between the top dead center and the bottom dead center (that is, the intake stroke) is not strictly 180 ° CA.
  • Line a shows the change in piston speed in the embodiment.
  • the peak of the piston speed in the descending stroke is the crank angle position of 1/2 between the latter half of the intake stroke, that is, the intake top dead center and the intake bottom dead center. It is located on the lagging side. In the illustrated example, it has a peak near 120 ° CA after the inspiratory top dead center.
  • Line b shows the lift characteristics of the intake valve 4 of the embodiment.
  • the lift characteristics of the intake valve 4 of the embodiment are asymmetrical between the ascending section and the descending section, and the point where the maximum lift is obtained is the center of the operating angle (crank angle between the opening time and the closing time). It is biased to the lagging side. Due to such an asymmetrical lift characteristic, the center of gravity G of the integrated lift amount is located on the lagging side of the center of the intake valve operating angle. In the illustrated example, the center of gravity G is located in the latter half of the intake stroke defined by the intake top dead center and the intake bottom dead center.
  • the closing time is set near the inspiratory bottom dead center. For example, it is within a range of about ⁇ 5 ° CA with respect to bottom dead center.
  • the opening time is set near the intake top dead center (for example, within ⁇ 5 ° CA).
  • the operating angle can be set as appropriate, but in the illustrated example, it has an operating angle of about 180 ° CA.
  • the distance between the top dead center and the bottom dead center is not strictly 180 ° CA, so the lift characteristic (opening / closing timing) of the intake valve 4 is set in consideration of this.
  • Line c shows the piston speed in the case of a single link type piston crank mechanism as a comparative example.
  • the peak of the piston speed in the descending stroke is located in the first half of the intake stroke.
  • Line d shows the lift characteristics of the intake valve of the comparative example, and shows the general lift characteristics that are symmetrical between the ascending section and the descending section.
  • the point of maximum lift is at the center of the operating angle
  • the center of gravity of the integrated lift amount is also located at the center of the operating angle.
  • the opening time and the closing time of the intake valve are shown to be the same as those in the embodiment.
  • FIG. 3 is a characteristic diagram showing the lift characteristics (line d) of the intake valve and the piston speed characteristics (line c) in such a comparative example.
  • the distance between the top dead center and the bottom dead center is 180 ° CA.
  • FIG. 4 is an explanatory diagram of the principle of tumble generation in the cylinder.
  • the intake flow flows from the intake port 15 into the cylinder at high speed through the opening of the intake valve 4.
  • This high-speed intake flow creates a vertical swirling flow, or tumble, in the cylinder.
  • the strength of this tumble correlates with the descending speed of the piston 44 and the opening area of the intake valve 4, that is, the lift amount. If the intake valve 4 is greatly lifted when the piston speed is high, a large amount of intake flow flows in at high speed through the opening of the intake valve 4, so that a strong tumble can be obtained.
  • the tumble generated in the intake stroke remains until the compression stroke, promotes lean burn by the fuel injected into the cylinder in the latter half of the compression stroke, and contributes to the stabilization of lean burn.
  • the peak of the piston speed in the downward direction is in the first half of the intake stroke, and the point where the maximum lift is reached and the center of gravity of the integrated lift amount are at the center of the operating angle.
  • the timing when the strongest occurs is relatively early in the inspiratory stroke. In the latter half of the intake stroke, the piston speed becomes low and the lift amount of the intake valve also becomes small, so that the flow velocity and the flow rate of the intake flow flowing in through the opening of the intake valve sharply decrease. Therefore, the tumble generated in the cylinder is weak, and in particular, since the timing at which the tumble is strongly generated is early, it is difficult to leave a tumble of sufficient strength until the latter half of the compression stroke.
  • the point at which the intake valve 4 becomes the maximum lift and the center of gravity G of the integrated lift amount are offset to the lag side in the operating angle, and this Since the peak of the piston speed in the downward direction is located on the lagging side in the intake stroke, the timing at which the tumble occurs most strongly is the latter half of the intake stroke. Further, even at the time when the intake bottom dead center is approached, the lift amount (line b) of the intake valve 4 is larger than the lift amount (line d) of the comparative example, and the piston speed (line a) is also the piston speed (line a) of the comparative example. Since it is higher than the line c), the tumble continues to be generated relatively strongly. Therefore, the tumble generated in the cylinder becomes stronger, and in particular, the timing at which the tumble is strongly generated becomes stronger, so that a tumble having sufficient strength can be left until the latter half of the compression stroke.
  • the peak of the piston speed and the position of the center of gravity G of the integrated lift amount of the intake valve 4 are not so far apart.
  • the peak of the piston speed and the center of gravity G of the integrated lift amount of the intake valve 4 are located within a range of 10 ° in terms of crank angle. That is, it is desirable that the center of gravity G of the integrated lift amount is located within the range of ⁇ 10 ° CA with respect to the peak of the piston speed.
  • the intake valve closing time is set to near the bottom dead center in the configuration of the comparative example, the lift amount decreases early in the latter half of the intake stroke, so it is difficult to generate a sufficient tumble. Therefore, it is not possible to advance the intake valve closing time while ensuring sufficient tumble.
  • the center of gravity G of the integrated lift amount is offset to the side delayed from the center of the operating angle, and the peak of the piston speed is similarly delayed to the latter half of the intake stroke to accelerate the closing time of the intake valve 4.
  • lean combustion can be achieved by strengthening the tumble to improve the fuel consumption rate, and at the same time, knocking can be suppressed.
  • variable compression ratio mechanism is not essential in the present invention, and the double-link piston whose mechanical compression ratio does not change is not essential. It may be a crank mechanism.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
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  • Output Control And Ontrol Of Special Type Engine (AREA)

Abstract

According to the present invention, a spark ignition internal combustion engine (1) is provided with a fuel injection valve (16) for injecting a fuel into a cylinder and performs lean combustion. This internal combustion engine (1) is provided with a double-link type piston crank mechanism (2). The link geometry of the double-link type piston crank mechanism (2) is configured such that the peak of the piston speed (line a) in an intake stroke is positioned further toward a retard side than a 1/2 crank angle position between the intake top dead center (TDC) and the intake bottom dead center (BDC). The lift characteristic (line b) of an intake valve (4) is asymmetric in an ascending section and a descending section, and the center of gravity (G) of the accumulated lift amount is positioned further toward a retard side than the center of the intake valve operation angle. Accordingly, tumble strength is improved in the latter half of the intake stroke.

Description

内燃機関Internal combustion engine
　この発明は、筒内に燃料を噴射して希薄燃焼を行う火花点火内燃機関に関する。 The present invention relates to a spark-ignition internal combustion engine that injects fuel into a cylinder to perform lean burn.
　車両用ガソリン機関に代表される火花点火内燃機関の燃料消費率の向上の一つの手段として、希薄な混合気で燃焼を行う希薄燃焼が知られている。燃料消費率の向上に有効な希薄燃焼は、新気と燃料量との比である空燃比を理論空燃比よりも大きく設定するほか、多量の排気還流によっても実現できる。しかし、十分な希薄化を行うには、燃焼安定性の制限があり、例えばタンブルなどによるガス流動強化が必要となる。 Lean burn, which burns with a dilute mixture, is known as one means of improving the fuel consumption rate of spark-ignition internal combustion engines represented by gasoline engines for vehicles. Lean burn, which is effective in improving the fuel consumption rate, can be realized not only by setting the air-fuel ratio, which is the ratio of fresh air to the amount of fuel, to be larger than the theoretical air-fuel ratio, but also by a large amount of exhaust gas return. However, in order to sufficiently dilute, there is a limitation on combustion stability, and it is necessary to strengthen the gas flow by, for example, tumble.
　特許文献１には、直動式動弁機構におけるカムのプロファイルを変更することで、最大リフトとなる時期を進角側もしくは遅角側へ偏らせるようにした動弁装置が開示されている。 Patent Document 1 discloses a valve gear that changes the profile of the cam in the linear motion valve mechanism so that the maximum lift time is biased to the advance angle side or the retard angle side.
　特許文献２は、ピストンとクランクピンとが複数のリンクで接続された複リンク式ピストンクランク機構に関するものであり、このような複リンク式ピストンクランク機構では、リンクジオメトリの設定に応じて行程中のピストン速度の特性を適宜に設定できることを開示している。 Patent Document 2 relates to a double-link piston crank mechanism in which a piston and a crank pin are connected by a plurality of links. In such a double-link piston crank mechanism, a piston in a stroke is set according to a setting of a link geometry. It discloses that the characteristics of speed can be set appropriately.
　本発明は、これらの技術を効果的に利用して、筒内におけるタンブルなどのガス流動を強化し、希薄燃焼の燃焼安定化を図ることを目的としている。 An object of the present invention is to effectively utilize these technologies to strengthen gas flow such as tumble in a cylinder and to stabilize combustion of lean combustion.
特許第３６３８６３２号公報Japanese Patent No. 3638632 特開２００４−１９０５９０号公報Japanese Unexamined Patent Publication No. 2004-190590
　この発明に係る火花点火式内燃機関は、
　複リンク式ピストンクランク機構によって吸気行程におけるピストン速度のピークが吸気上死点と吸気下死点との間の１／２のクランク角位置よりも遅れ側に位置するように構成されており、
　吸気弁のリフト特性が、上昇区間と下降区間とで非対称をなし、積算リフト量の重心が吸気弁作動角の中心よりも遅れ側に位置するように構成されている。 The spark ignition type internal combustion engine according to the present invention
The double-link piston crank mechanism is configured so that the peak of the piston speed in the intake stroke is located on the lagging side of the half crank angle position between the intake top dead center and the intake bottom dead center.
The lift characteristics of the intake valve are asymmetrical between the ascending section and the descending section, and the center of gravity of the integrated lift amount is located on the lagging side of the center of the intake valve operating angle.
　このような構成では、まず、複リンク式ピストンクランク機構のリンクジオメトリの設定により、下降方向へのピストン速度のピークが吸気行程の後半に生じ、吸気弁開口部を通して新気を吸引する作用が吸気行程の後半で強く得られる。そして、このようなピストン速度のピークのタイミングに対応するように、吸気弁の積算リフト量の重心が吸気弁作動角の中心よりも遅れ側に位置する。これにより、吸気弁開口部を通して高速で流入する吸気の流れにより筒内に生成されるタンブルやスワールなどのガス流動が強化され、かつこのタンブルやスワールが生成されるタイミングが吸気行程の中で比較的遅くなる。そのため、圧縮行程においてタンブルなどのガス流動がより効果的に残存することとなり、ガス流動強化による希薄燃焼の燃焼安定化が図れる。 In such a configuration, first, by setting the link geometry of the double-link piston crank mechanism, a peak of the piston speed in the downward direction occurs in the latter half of the intake stroke, and the action of sucking fresh air through the intake valve opening is taken. Obtained strongly in the second half of the process. Then, the center of gravity of the integrated lift amount of the intake valve is located on the lagging side of the center of the intake valve operating angle so as to correspond to the timing of the peak of the piston speed. As a result, the gas flow such as tumble and swirl generated in the cylinder by the flow of intake air flowing in at high speed through the intake valve opening is strengthened, and the timing at which these tumble and swirl are generated is compared in the intake stroke. It will be slow. Therefore, the gas flow such as tumble remains more effectively in the compression stroke, and the combustion of lean combustion can be stabilized by strengthening the gas flow.
この発明に係る内燃機関の構成を概略的に示す構成説明図。FIG. 6 is a configuration explanatory view schematically showing a configuration of an internal combustion engine according to the present invention. 吸気弁のリフト特性およびピストン速度の特性を、実施例と比較例とで対比して示した特性図。The characteristic diagram which showed the lift characteristic and the piston speed characteristic of an intake valve in comparison with an Example and a comparative example. 比較例における吸気弁のリフト特性およびピストン速度の特性を示した特性図。The characteristic diagram which showed the lift characteristic and the piston speed characteristic of an intake valve in a comparative example. タンブルの生成原理を示した説明図。An explanatory diagram showing the principle of tumble generation.
　以下、この発明の一実施例を図面に基づいて詳細に説明する。 Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.
　図１は、この発明が適用された自動車用内燃機関１の構成を概略的に示している。この内燃機関１は、複リンク式ピストンクランク機構２を備えた４ストロークサイクルの筒内直噴型火花点火内燃機関であって、基本的に理論空燃比よりもリーンな希薄燃焼を行うものである。各シリンダ３の天井壁面に、一対の吸気弁４および一対の排気弁５が配置されているとともに、これらの吸気弁４および排気弁５に囲まれた中央部に点火プラグ６が配置されている。つまり、燃焼室１３は一般的なペントルーフ型をなしており、吸気ポート１５と排気ポート１７とが互いに対向するように延びている。 FIG. 1 schematically shows the configuration of an internal combustion engine 1 for an automobile to which the present invention is applied. The internal combustion engine 1 is a 4-stroke cycle in-cylinder direct-injection spark-ignition internal combustion engine equipped with a double-link piston crank mechanism 2, and basically performs lean combustion that is leaner than the stoichiometric air-fuel ratio. .. A pair of intake valves 4 and a pair of exhaust valves 5 are arranged on the ceiling wall surface of each cylinder 3, and a spark plug 6 is arranged in a central portion surrounded by these intake valves 4 and exhaust valves 5. .. That is, the combustion chamber 13 has a general pent roof type, and the intake port 15 and the exhaust port 17 extend so as to face each other.
　上記吸気弁４は、図示しない動弁機構を介して開閉され、後述するように、上昇区間と下降区間とで非対称をなすリフト特性を有している。排気弁５は、同じく図示しない動弁機構を介して開閉される。排気弁５のリフト特性は、例えば、ピストン下死点前に開き、ピストン上死点後に閉じる一般的な特性に設定されている。 The intake valve 4 is opened and closed via a valve operating mechanism (not shown), and has a lift characteristic that is asymmetrical between the ascending section and the descending section, as will be described later. The exhaust valve 5 is also opened and closed via a valve operating mechanism (not shown). The lift characteristic of the exhaust valve 5 is set to, for example, a general characteristic that opens before the bottom dead center of the piston and closes after the top dead center of the piston.
　吸気弁４および排気弁５の動弁機構としては、バルブステムエンドに設けられた円筒状のタペットをカムが直接に押圧する直動型動弁機構、カムのリフトをロッカアームを介してバルブステムに伝えるロッカアーム式動弁機構、油圧により弁４，５を開閉する油圧式動弁機構、ソレノイドを利用して弁４，５を開閉する電磁式動弁機構、などの公知の動弁機構を適宜に用いることができる。一実施例においては、吸気弁４のリフト特性が作動角に比較してリフト量の大きな高リフト型の特性であることから、レバー比によるリフト量拡大作用が得られるロッカアーム式動弁機構とりわけカムとの摩擦抵抗を小さくしたローラロッカアーム式の動弁機構が吸気弁４の駆動に用いられている。なお、吸気弁４および排気弁５のいずれも、開時期や閉時期を変更可能な可変バルブタイミング機構と組み合わせることもできる。 As the valve operating mechanism of the intake valve 4 and the exhaust valve 5, a direct acting valve mechanism in which the cam directly presses the cylindrical tappet provided at the valve stem end, and the cam lift is attached to the valve stem via the rocker arm. Known valve operating mechanisms such as a rocker arm type valve operating mechanism that transmits, a hydraulic valve operating mechanism that opens and closes valves 4 and 5 by hydraulic pressure, and an electromagnetic valve operating mechanism that opens and closes valves 4 and 5 using a solenoid are appropriately provided. Can be used. In one embodiment, since the lift characteristic of the intake valve 4 is a high lift type characteristic in which the lift amount is large compared to the operating angle, a rocker arm type valve operating mechanism, particularly a cam, which can obtain a lift amount expansion action by the lever ratio. A roller rocker arm type valve operating mechanism with reduced frictional resistance with the intake valve 4 is used to drive the intake valve 4. Both the intake valve 4 and the exhaust valve 5 can be combined with a variable valve timing mechanism that can change the opening time and closing time.
　各シリンダ３には、筒内へ直接に燃料を噴射するように、燃料噴射弁１６が設けられている。例えば、一対の吸気ポート１５の下側に燃料噴射弁１６が位置し、斜め下方へ向かって燃料を噴射する構成となっている。なお、希薄燃焼を行う際には、一般に圧縮行程の後半に燃料噴射弁１６から燃料噴射が行われ、成層化した混合気に点火がなされる。 Each cylinder 3 is provided with a fuel injection valve 16 so as to inject fuel directly into the cylinder. For example, the fuel injection valve 16 is located below the pair of intake ports 15, and is configured to inject fuel diagonally downward. When lean burn is performed, fuel injection is generally performed from the fuel injection valve 16 in the latter half of the compression stroke, and the stratified air-fuel mixture is ignited.
　また図示例は、筒内燃料噴射用の燃料噴射弁１６に加えて各気筒の吸気ポート１５にそれぞれ副燃料噴射弁１２を備えている。この副燃料噴射弁１２は、吸気ポート１５内で吸気弁４へ向けて燃料噴射が可能なように構成されている。例えば、目標空燃比を理論空燃比とした均質燃焼時に、燃料の一部ないし全部が副燃料噴射弁１２によって噴射供給される。あるいは、総燃料量が大となる高負荷時に、一部の燃料が副燃料噴射弁１２から供給される。なお、本発明においては、副燃料噴射弁１２を備えた構成は必須ではなく、筒内燃料噴射用の燃料噴射弁１６のみを備えた構成であってもよい。 Further, in the illustrated example, in addition to the fuel injection valve 16 for in-cylinder fuel injection, an auxiliary fuel injection valve 12 is provided at each of the intake ports 15 of each cylinder. The auxiliary fuel injection valve 12 is configured so that fuel can be injected toward the intake valve 4 in the intake port 15. For example, at the time of homogeneous combustion with the target air-fuel ratio as the stoichiometric air-fuel ratio, a part or all of the fuel is injected and supplied by the auxiliary fuel injection valve 12. Alternatively, a part of the fuel is supplied from the auxiliary fuel injection valve 12 at the time of high load when the total fuel amount becomes large. In the present invention, the configuration including the auxiliary fuel injection valve 12 is not essential, and the configuration may include only the fuel injection valve 16 for in-cylinder fuel injection.
　吸気通路１４の吸気コレクタ１８よりも上流側には、エンジンコントローラ（図示せず）からの制御信号によって開度が制御される電子制御型スロットルバルブ１９が介装されており、さらにその上流側に、吸入空気量を検出するエアフロメータ２０およびエアクリーナ２１が配設されている。 An electronically controlled throttle valve 19 whose opening degree is controlled by a control signal from an engine controller (not shown) is interposed upstream of the intake collector 18 of the intake passage 14, and further upstream of the electronically controlled throttle valve 19. , An air flow meter 20 for detecting the amount of intake air and an air cleaner 21 are arranged.
　複数の排気ポート１７が合流した排気通路２５には、適宜な触媒からなる触媒装置２６が配設されている。触媒装置２６は、例えば、ＮＯｘ吸蔵触媒および三元触媒を含んで構成されている。触媒装置２６の上流側には、空燃比を検出する空燃比センサ２８が配置されている。 A catalyst device 26 made of an appropriate catalyst is arranged in the exhaust passage 25 where the plurality of exhaust ports 17 are merged. The catalyst device 26 is configured to include, for example, a NOx storage catalyst and a three-way catalyst. An air-fuel ratio sensor 28 for detecting the air-fuel ratio is arranged on the upstream side of the catalyst device 26.
　複リンク式ピストンクランク機構２は、特許文献２等に記載の公知の構成を利用したものであって、クランクシャフト４１のクランクピン４１ａに回転自在に支持されたロアリンク４２と、このロアリンク４２の一端部のアッパピン４３とピストン４４のピストンピン４４ａとを互いに連結するアッパリンク４５と、ロアリンク４２の他端部のコントロールピン４６に一端が連結されたコントロールリンク４７と、このコントロールリンク４７の他端を揺動可能に支持するコントロールシャフト４８と、を主体として構成されている。上記クランクシャフト４１および上記コントロールシャフト４８は、シリンダブロック４９下部のクランクケース４９ａ内で回転自在に支持されている。上記コントロールシャフト４８は、該コントロールシャフト４８の回動に伴って位置が変化する偏心軸部４８ａを有し、上記コントロールリンク４７の端部は、詳しくは、この偏心軸部４８ａに回転可能に嵌合している。すなわち、図示例の複リンク式ピストンクランク機構２は、内燃機関１の機械的圧縮比を変更可能な可変圧縮比機構として構成されており、コントロールシャフト４８の回動に伴ってピストン４４の上死点位置が上下に変位し、従って、機械的な圧縮比が変化する。 The double-link type piston crank mechanism 2 utilizes a known configuration described in Patent Document 2 and the like, and includes a lower link 42 rotatably supported by a crank pin 41a of a crankshaft 41 and the lower link 42. The upper link 45 that connects the upper pin 43 at one end of the piston pin 43 and the piston pin 44a of the piston 44 to each other, the control link 47 whose one end is connected to the control pin 46 at the other end of the lower link 42, and the control link 47. It is mainly composed of a control shaft 48 that swingably supports the other end. The crankshaft 41 and the control shaft 48 are rotatably supported in the crankcase 49a below the cylinder block 49. The control shaft 48 has an eccentric shaft portion 48a whose position changes with the rotation of the control shaft 48, and the end portion of the control link 47 is rotatably fitted to the eccentric shaft portion 48a. It fits. That is, the double-link type piston crank mechanism 2 of the illustrated example is configured as a variable compression ratio mechanism capable of changing the mechanical compression ratio of the internal combustion engine 1, and the piston 44 dies as the control shaft 48 rotates. The point position is displaced up and down, thus changing the mechanical compression ratio.
　また、上記可変圧縮比機構の圧縮比を可変制御する駆動機構として、この実施例では、クランクシャフト４１と平行な回転中心軸を有する電動アクチュエータ５１がクランクケース４９ａの外壁面に配置されており、この電動アクチュエータ５１の出力回転軸に固定された第１アーム５２と、コントロールシャフト４８に固定された第２アーム５３と、両者を連結した中間リンク５４と、を介して、電動アクチュエータ５１とコントロールシャフト４８とが連動している。電動アクチュエータ５１は、軸方向に直列に配置された電動モータおよび変速機構を含んでいる。この電動アクチュエータ５１は、機関運転条件に応じた目標圧縮比を実現するように、図示しないエンジンコントローラからの制御信号によって制御される。目標圧縮比は、基本的には、低負荷側では高圧縮比であり、負荷が高いほどノッキング抑制等のために低圧縮比となる。なお、一実施例では、目標圧縮比は段階的に設定されている。 Further, as a drive mechanism for variably controlling the compression ratio of the variable compression ratio mechanism, in this embodiment, an electric actuator 51 having a rotation center axis parallel to the crankshaft 41 is arranged on the outer wall surface of the crankcase 49a. The electric actuator 51 and the control shaft are routed via a first arm 52 fixed to the output rotation shaft of the electric actuator 51, a second arm 53 fixed to the control shaft 48, and an intermediate link 54 connecting the two. It is linked with 48. The electric actuator 51 includes an electric motor and a transmission mechanism arranged in series in the axial direction. The electric actuator 51 is controlled by a control signal from an engine controller (not shown) so as to realize a target compression ratio according to the engine operating conditions. The target compression ratio is basically a high compression ratio on the low load side, and the higher the load, the lower the compression ratio for knocking suppression and the like. In one embodiment, the target compression ratio is set stepwise.
　ここで、複リンク式ピストンクランク機構２は、特に、吸気行程におけるピストン速度のピークが吸気行程後半つまり吸気上死点と吸気下死点との間の１／２のクランク角位置よりも遅れ側に位置するように、リンクジオメトリが設定されている。換言すれば、吸気上死点と吸気下死点との間がクランク角１８０°であるとみなすと、上死点後９０°ＣＡよりも遅れ側にピストン速度のピークが存在する。仮に吸気上死点と吸気下死点との間がクランク角１７６°であれば、１／２である上死点後８８°ＣＡよりも遅れ側にピストン速度のピークが存在する。なお、クランクシャフト４１は、図１において反時計回り方向に回転する。 Here, in the double-link type piston crank mechanism 2, in particular, the peak of the piston speed in the intake stroke is on the latter half of the intake stroke, that is, on the side behind the crank angle position of 1/2 between the intake top dead center and the intake bottom dead center. The link geometry is set to be located at. In other words, assuming that the crank angle between the intake top dead center and the intake bottom dead center is 180 °, the peak of the piston speed exists on the lagging side of 90 ° CA after the top dead center. If the crank angle between the intake top dead center and the intake bottom dead center is 176 °, the peak of the piston speed exists on the lagging side of 88 ° CA after the top dead center, which is 1/2. The crankshaft 41 rotates in the counterclockwise direction in FIG.
　図示するような複リンク式ピストンクランク機構２においては、「上死点」ならびに「下死点」という用語は、クランクピン４１ａの位置ではなく、ピストン４４の運動方向が反転するピストン上死点ならびにピストン下死点を意味している。また、一般的な単リンク式ピストンクランク機構では上死点と下死点との間隔が上昇行程と下降行程とでクランク角で正しく１８０°ずつとなるのに対し、複リンク式ピストンクランク機構２においては、完全な１８０°ずつとはならず、僅かに（例えば数°程度）ずれたものとなる。但し、本発明においては、このように上死点と下死点との間のクランク角で示した間隔が完全な１８０°でないことは特に重要なことではなく、上昇行程と下降行程が等しく１８０°ＣＡであるとみなしても、作用効果等の上で差異は生じない。 In the double link type piston crank mechanism 2 as shown in the figure, the terms "top dead center" and "bottom dead center" are not the position of the crank pin 41a, but the piston top dead center where the movement direction of the piston 44 is reversed and the piston top dead center. It means the bottom dead center of the piston. Further, in a general single-link piston crank mechanism, the distance between the top dead center and the bottom dead center is correctly 180 ° each in the crank angle between the ascending stroke and the descending stroke, whereas the double link type piston crank mechanism 2 In, the distance is not completely 180 °, but is slightly (for example, about several °). However, in the present invention, it is not particularly important that the distance indicated by the crank angle between the top dead center and the bottom dead center is not completely 180 °, and the ascending stroke and the descending stroke are equal to 180. Even if it is regarded as ° CA, there is no difference in terms of action and effect.
　また、複リンク式ピストンクランク機構２を可変圧縮比機構として構成した上記の実施例では、内燃機関１の機械的圧縮比がある範囲（例えば１０~１５）で変更可能であり、これに伴いリンクジオメトリが変化するが、好ましい一つの実施例では、制御可能な全ての圧縮比制御位置の下で、ピストン速度のピークが吸気行程後半に位置する。 Further, in the above embodiment in which the double-link type piston crank mechanism 2 is configured as a variable compression ratio mechanism, the mechanical compression ratio of the internal combustion engine 1 can be changed within a certain range (for example, 10 to 15), and the link can be changed accordingly. The geometry changes, but in one preferred embodiment, the peak piston speed is located late in the intake stroke under all controllable compression ratio control positions.
　希薄燃焼可能な内燃機関と可変圧縮比機構とを組み合わせる場合、一般に、比較的負荷が低いときに高圧縮比としつつ希薄燃焼を行い、高負荷域では、低圧縮比としつつ理論空燃比での燃焼を行うことが多い。従って、本発明においては、少なくとも制御可能な範囲内での最高圧縮比のときにピストン速度のピークが吸気行程後半に位置するようなリンクジオメトリであればよい。 When combining an internal combustion engine capable of lean burn and a variable compression ratio mechanism, in general, lean combustion is performed while setting a high compression ratio when the load is relatively low, and in a high load range, a low compression ratio is used at a theoretical air-fuel ratio. Often burns. Therefore, in the present invention, the link geometry may be such that the peak of the piston speed is located in the latter half of the intake stroke at the maximum compression ratio within the controllable range.
　図２は、吸気弁４のリフト特性およびピストン速度の特性を、実施例と比較例とで対比して示した特性図である。左端の「ＴＤＣ」は吸気上死点、「ＢＤＣ」は吸気下死点、右端の「ＴＤＣ」は圧縮上死点である。本発明においては、吸気上死点と吸気下死点との間が「吸気行程」である。前述したように、上死点と下死点との間の間隔（つまり吸気行程）は厳密には１８０°ＣＡではない。 FIG. 2 is a characteristic diagram showing the lift characteristics and the piston speed characteristics of the intake valve 4 in comparison with the examples and the comparative examples. The leftmost "TDC" is the intake top dead center, the "BDC" is the intake bottom dead center, and the rightmost "TDC" is the compression top dead center. In the present invention, the "intake stroke" is between the intake top dead center and the intake bottom dead center. As mentioned above, the distance between the top dead center and the bottom dead center (that is, the intake stroke) is not strictly 180 ° CA.
　線ａは、実施例のピストン速度の変化を示している。図示するように、複リンク式ピストンクランク機構２を用いることで、下降行程におけるピストン速度のピークは、吸気行程後半つまり吸気上死点と吸気下死点との間の１／２のクランク角位置よりも遅れ側に位置する。図示例では、吸気上死点後１２０°ＣＡ付近にピークを有する。 Line a shows the change in piston speed in the embodiment. As shown in the figure, by using the double-link type piston crank mechanism 2, the peak of the piston speed in the descending stroke is the crank angle position of 1/2 between the latter half of the intake stroke, that is, the intake top dead center and the intake bottom dead center. It is located on the lagging side. In the illustrated example, it has a peak near 120 ° CA after the inspiratory top dead center.
　線ｂは、実施例の吸気弁４のリフト特性を示す。図示するように、実施例の吸気弁４のリフト特性は、上昇区間と下降区間とで非対称であり、最大リフトとなる点が作動角（開時期と閉時期との間のクランク角度）の中心よりも遅れ側に片寄っている。そして、このような非対称のリフト特性に伴い、積算リフト量の重心Ｇが吸気弁作動角の中心よりも遅れ側に位置している。図示例では、吸気上死点と吸気下死点とで規定される吸気行程の後半に重心Ｇが位置する。 Line b shows the lift characteristics of the intake valve 4 of the embodiment. As shown in the figure, the lift characteristics of the intake valve 4 of the embodiment are asymmetrical between the ascending section and the descending section, and the point where the maximum lift is obtained is the center of the operating angle (crank angle between the opening time and the closing time). It is biased to the lagging side. Due to such an asymmetrical lift characteristic, the center of gravity G of the integrated lift amount is located on the lagging side of the center of the intake valve operating angle. In the illustrated example, the center of gravity G is located in the latter half of the intake stroke defined by the intake top dead center and the intake bottom dead center.
　さらに、図示例では、閉時期が吸気下死点付近に設定されている。例えば下死点に対し±５°ＣＡ程度の範囲内にある。また開時期は、吸気上死点付近（例えば±５°ＣＡ以内）に設定されている。作動角は適宜に設定できるが、図示例では、１８０°ＣＡ程度の作動角を有する。 Furthermore, in the illustrated example, the closing time is set near the inspiratory bottom dead center. For example, it is within a range of about ± 5 ° CA with respect to bottom dead center. The opening time is set near the intake top dead center (for example, within ± 5 ° CA). The operating angle can be set as appropriate, but in the illustrated example, it has an operating angle of about 180 ° CA.
　なお、前述したように上死点と下死点との間の間隔は厳密には１８０°ＣＡではないので、これを考慮して吸気弁４のリフト特性（開閉時期）が設定されている。 As described above, the distance between the top dead center and the bottom dead center is not strictly 180 ° CA, so the lift characteristic (opening / closing timing) of the intake valve 4 is set in consideration of this.
　線ｃは、比較例として単リンク式ピストンクランク機構の場合のピストン速度を示している。単リンク式ピストンクランク機構では、下降行程におけるピストン速度のピークは、吸気行程の前半に位置する。 Line c shows the piston speed in the case of a single link type piston crank mechanism as a comparative example. In the single-link piston crank mechanism, the peak of the piston speed in the descending stroke is located in the first half of the intake stroke.
　線ｄは、比較例の吸気弁のリフト特性を示しており、上昇区間と下降区間とで対称の一般的なリフト特性を示している。この比較例では、最大リフトとなる点は作動角の中心にあり、かつ積算リフト量の重心も作動角の中心に位置する。また、図示例では、吸気弁の開時期および閉時期は実施例のものと等しく示してある。 Line d shows the lift characteristics of the intake valve of the comparative example, and shows the general lift characteristics that are symmetrical between the ascending section and the descending section. In this comparative example, the point of maximum lift is at the center of the operating angle, and the center of gravity of the integrated lift amount is also located at the center of the operating angle. Further, in the illustrated example, the opening time and the closing time of the intake valve are shown to be the same as those in the embodiment.
　なお、図３は、このような比較例における吸気弁のリフト特性（線ｄ）とピストン速度の特性（線ｃ）を示した特性図である。ここでは、上死点と下死点との間は、１８０°ＣＡとなる。 Note that FIG. 3 is a characteristic diagram showing the lift characteristics (line d) of the intake valve and the piston speed characteristics (line c) in such a comparative example. Here, the distance between the top dead center and the bottom dead center is 180 ° CA.
　図４は、筒内におけるタンブルの生成原理の説明図である。図示するように、ピストン４４が下降し、かつ吸気弁４が開くことで、吸気ポート１５から吸気弁４の開口部を通して筒内へ高速で吸気流が流入する。この高速吸気流によって、筒内に縦方向の旋回流つまりタンブルが生成される。このタンブルの強さは、ピストン４４の下降速度と吸気弁４の開口面積つまりリフト量に相関する。ピストン速度が大であるときに吸気弁４が大きくリフトしていると吸気弁４の開口部を通して多量の吸気流が高速で流入することとなるので、タンブルが強く得られる。吸気行程で生じたタンブルは、圧縮行程まで残存し、圧縮行程後半に筒内に噴射される燃料による希薄燃焼を促進して、希薄燃焼の安定化に寄与する。 FIG. 4 is an explanatory diagram of the principle of tumble generation in the cylinder. As shown in the figure, when the piston 44 descends and the intake valve 4 opens, the intake flow flows from the intake port 15 into the cylinder at high speed through the opening of the intake valve 4. This high-speed intake flow creates a vertical swirling flow, or tumble, in the cylinder. The strength of this tumble correlates with the descending speed of the piston 44 and the opening area of the intake valve 4, that is, the lift amount. If the intake valve 4 is greatly lifted when the piston speed is high, a large amount of intake flow flows in at high speed through the opening of the intake valve 4, so that a strong tumble can be obtained. The tumble generated in the intake stroke remains until the compression stroke, promotes lean burn by the fuel injected into the cylinder in the latter half of the compression stroke, and contributes to the stabilization of lean burn.
　線ｃ，ｄに示す比較例の特性では、下降方向へのピストン速度のピークが吸気行程の前半にあり、かつ最大リフトとなる点や積算リフト量の重心が作動角の中心にあるので、タンブルが最も強く生じるタイミングは、吸気行程の中で比較的早期となる。吸気行程の後半においては、ピストン速度が低くなり、かつ吸気弁のリフト量も小さくなるので、吸気弁の開口部を通して流入する吸気流の流速ならびに流量が急激に低下する。従って、筒内に生成されるタンブルは弱く、とりわけ、タンブルが強く生成されるタイミングが早いことから、圧縮行程後半まで十分な強度のタンブルを残存させることが困難である。 In the characteristics of the comparative examples shown in lines c and d, the peak of the piston speed in the downward direction is in the first half of the intake stroke, and the point where the maximum lift is reached and the center of gravity of the integrated lift amount are at the center of the operating angle. The timing when the strongest occurs is relatively early in the inspiratory stroke. In the latter half of the intake stroke, the piston speed becomes low and the lift amount of the intake valve also becomes small, so that the flow velocity and the flow rate of the intake flow flowing in through the opening of the intake valve sharply decrease. Therefore, the tumble generated in the cylinder is weak, and in particular, since the timing at which the tumble is strongly generated is early, it is difficult to leave a tumble of sufficient strength until the latter half of the compression stroke.
　これに対し、線ａ，ｂに示す実施例の特性によれば、吸気弁４の最大リフトとなる点および積算リフト量の重心Ｇが作動角の中で遅れ側に片寄っており、かつ、これに対応するようにして、下降方向へのピストン速度のピークが吸気行程の中で遅れ側に位置するので、タンブルが最も強く生じるタイミングが吸気行程の後半となる。また吸気下死点に近付いた時期においても、吸気弁４のリフト量（線ｂ）は比較例のリフト量（線ｄ）よりも大きく、かつピストン速度（線ａ）も比較例のピストン速度（線ｃ）よりも高いので、タンブルが比較的強く生成され続ける。従って、筒内に生成されるタンブルが強くなり、とりわけ、タンブルが強く生成されるタイミングが遅くなることから、圧縮行程後半まで十分な強度のタンブルを残存させることができる。 On the other hand, according to the characteristics of the examples shown in the lines a and b, the point at which the intake valve 4 becomes the maximum lift and the center of gravity G of the integrated lift amount are offset to the lag side in the operating angle, and this Since the peak of the piston speed in the downward direction is located on the lagging side in the intake stroke, the timing at which the tumble occurs most strongly is the latter half of the intake stroke. Further, even at the time when the intake bottom dead center is approached, the lift amount (line b) of the intake valve 4 is larger than the lift amount (line d) of the comparative example, and the piston speed (line a) is also the piston speed (line a) of the comparative example. Since it is higher than the line c), the tumble continues to be generated relatively strongly. Therefore, the tumble generated in the cylinder becomes stronger, and in particular, the timing at which the tumble is strongly generated becomes stronger, so that a tumble having sufficient strength can be left until the latter half of the compression stroke.
　効果的にタンブルを生成するためには、ピストン速度のピークと吸気弁４の積算リフト量の重心Ｇの位置とがあまり離れていないことが望ましい。好ましい実施例では、ピストン速度のピークと吸気弁４の積算リフト量の重心Ｇとがクランク角で１０°の範囲内に位置する。つまり、ピストン速度のピークに対して±１０°ＣＡの範囲内に積算リフト量の重心Ｇが位置することが望ましい。 In order to effectively generate a tumble, it is desirable that the peak of the piston speed and the position of the center of gravity G of the integrated lift amount of the intake valve 4 are not so far apart. In a preferred embodiment, the peak of the piston speed and the center of gravity G of the integrated lift amount of the intake valve 4 are located within a range of 10 ° in terms of crank angle. That is, it is desirable that the center of gravity G of the integrated lift amount is located within the range of ± 10 ° CA with respect to the peak of the piston speed.
　また、図示例の吸気弁４のリフト特性では、閉時期が吸気下死点付近に設定されているので、筒内に一旦流入した吸気が吸気ポート１５側へ押し出される、いわゆる吸気の吹き返しが少なくなる。この吸気の吹き返しは、特に圧縮比が高いときに顕著となり、吸気の温度上昇を招いて高圧縮比時に生じやすいノッキングの要因となる。従って、吸気弁４の閉時期を下死点付近として吸気の吹き返しを抑制することで、ノッキングが抑制される。 Further, in the lift characteristic of the intake valve 4 in the illustrated example, since the closing time is set near the intake bottom dead center, the intake air once flowing into the cylinder is pushed out to the intake port 15 side, so that the so-called intake air blowback is small. Become. This blowback of the intake air becomes remarkable especially when the compression ratio is high, which causes the temperature of the intake air to rise and becomes a factor of knocking that tends to occur at a high compression ratio. Therefore, knocking is suppressed by suppressing the blowback of the intake air by setting the closing time of the intake valve 4 to near the bottom dead center.
　なお、吸気弁４の閉時期を吸気下死点よりも早期に設定し、いわゆる早閉じミラーサイクルとすることも可能である。 It is also possible to set the closing time of the intake valve 4 earlier than the intake bottom dead center to achieve a so-called early closing Miller cycle.
　このように吸気弁４の閉時期を吸気下死点付近あるいは吸気下死点よりもさらに進み側に設定すると、一般に、最大リフトとなる点や積算リフト量の重心の位置がそれだけ進み側となり、吸気行程後半におけるリフト量が小さくなる。従って、タンブルの強さとりわけ吸気行程後半におけるタンブルの強さが低下しやすい傾向となる。 When the closing time of the intake valve 4 is set near the intake bottom dead center or further ahead of the intake bottom dead center in this way, in general, the point where the maximum lift is reached and the position of the center of gravity of the integrated lift amount are set to the advance side. The lift amount in the latter half of the intake stroke becomes smaller. Therefore, the strength of the tumble, especially the strength of the tumble in the latter half of the intake stroke, tends to decrease.
　つまり、比較例の構成で吸気弁閉時期を下死点付近とした場合には、吸気行程後半におけるリフト量の低下が早期に生じるので、十分なタンブルを生成することが困難である。そのため、十分なタンブルを確保しつつ吸気弁閉時期を早めることはできない。 That is, when the intake valve closing time is set to near the bottom dead center in the configuration of the comparative example, the lift amount decreases early in the latter half of the intake stroke, so it is difficult to generate a sufficient tumble. Therefore, it is not possible to advance the intake valve closing time while ensuring sufficient tumble.
　本発明の実施例では、作動角の中心よりも遅れ側に積算リフト量の重心Ｇを片寄らせ、かつピストン速度のピークを同様に吸気行程後半に遅らせることで、吸気弁４の閉時期を早めることによる吸気の吹き返しの抑制と、タンブル強度の確保と、を両立させることができる。 In the embodiment of the present invention, the center of gravity G of the integrated lift amount is offset to the side delayed from the center of the operating angle, and the peak of the piston speed is similarly delayed to the latter half of the intake stroke to accelerate the closing time of the intake valve 4. As a result, it is possible to achieve both suppression of intake air blowback and securing of tumble strength.
　従って、高圧縮比としつつタンブル強化による希薄燃焼を実現して燃料消費率向上を達成できると同時に、ノッキング抑制が図れる。 Therefore, while maintaining a high compression ratio, lean combustion can be achieved by strengthening the tumble to improve the fuel consumption rate, and at the same time, knocking can be suppressed.
　以上、複リンク式ピストンクランク機構２を利用して可変圧縮比内燃機関とした実施例を説明したが、本発明において可変圧縮比機構は必須ではなく、機械的圧縮比が変化しない複リンク式ピストンクランク機構であってもよい。 Although the embodiment of the variable compression ratio internal combustion engine using the double-link piston crank mechanism 2 has been described above, the variable compression ratio mechanism is not essential in the present invention, and the double-link piston whose mechanical compression ratio does not change is not essential. It may be a crank mechanism.

Claims (5)

  1. 　筒内に燃料を噴射して希薄燃焼を行う火花点火内燃機関であって、
    　複リンク式ピストンクランク機構によって吸気行程におけるピストン速度のピークが吸気上死点と吸気下死点との間の１／２のクランク角位置よりも遅れ側に位置するように構成されており、
    　吸気弁のリフト特性が、上昇区間と下降区間とで非対称をなし、積算リフト量の重心が吸気弁作動角の中心よりも遅れ側に位置するように構成されている、内燃機関。     A spark-ignition internal combustion engine that injects fuel into the cylinder to perform lean burn.
    The double-link piston crank mechanism is configured so that the peak of the piston speed in the intake stroke is located on the lagging side of the half crank angle position between the intake top dead center and the intake bottom dead center.
    An internal combustion engine in which the lift characteristics of the intake valve are asymmetrical between the ascending section and the descending section, and the center of gravity of the integrated lift amount is located on the lagging side of the center of the intake valve operating angle.
  2. 　上記ピストン速度の上記ピークと上記積算リフト量の上記重心とが、クランク角で１０°の範囲内に位置する、請求項１に記載の内燃機関。 The internal combustion engine according to claim 1, wherein the peak of the piston speed and the center of gravity of the integrated lift amount are located within a range of 10 ° in crank angle.
  3. 　上記吸気弁の閉時期が、吸気下死点付近もしくは吸気下死点以前に設定されている、請求項１または２に記載の内燃機関。 The internal combustion engine according to claim 1 or 2, wherein the closing time of the intake valve is set near the intake bottom dead center or before the intake bottom dead center.
  4. 　上記吸気弁の開時期が、吸気上死点付近に設定されている、請求項１~３のいずれかに記載の内燃機関。 The internal combustion engine according to any one of claims 1 to 3, wherein the opening time of the intake valve is set near the intake top dead center.
  5. 　上記複リンク式ピストンクランク機構が可変圧縮比機構として構成されており、
    　制御可能な全ての圧縮比制御位置の下で、吸気行程におけるピストン速度のピークが吸気上死点と吸気下死点との間の１／２のクランク角位置よりも遅れ側に位置する、
    　請求項１~４のいずれかに記載の内燃機関。     The above double-link piston crank mechanism is configured as a variable compression ratio mechanism.
    Under all controllable compression ratio control positions, the peak piston speed in the intake stroke is located lagging behind the half crank angle position between intake top dead center and intake bottom dead center.
    The internal combustion engine according to any one of claims 1 to 4.
PCT/IB2019/000534 2019-05-13 2019-05-13 Internal combustion engine WO2020229860A1 (en)

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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS638632B2 (en) * 1982-11-02 1988-02-23 Matsushita Electronics Corp
JP2002285857A (en) * 2001-03-28 2002-10-03 Nissan Motor Co Ltd Piston drive for internal combustion engine
JP2007327345A (en) * 2006-06-06 2007-12-20 Nissan Motor Co Ltd Cylinder direct injection type internal combustion engine

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Publication number Priority date Publication date Assignee Title
JP3638632B2 (en) 1994-06-17 2005-04-13 ヤマハ発動機株式会社 Engine valve gear

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS638632B2 (en) * 1982-11-02 1988-02-23 Matsushita Electronics Corp
JP2002285857A (en) * 2001-03-28 2002-10-03 Nissan Motor Co Ltd Piston drive for internal combustion engine
JP2007327345A (en) * 2006-06-06 2007-12-20 Nissan Motor Co Ltd Cylinder direct injection type internal combustion engine

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