JP6177497B2 - Compression ignition internal combustion engine - Google Patents

Description

  The present invention relates to a compression ignition internal combustion engine, and more specifically, a premixed gas obtained by mixing fuel and air is supplied to a combustion chamber, and self-ignition is performed under a high compression ratio to obtain high thermal efficiency. The present invention relates to an improvement of a premixed compression self-ignition internal combustion engine.

  A premixed compression self-ignition internal combustion engine, for example, as disclosed in Patent Document 1, is a compression ignition operation (HCCI (Homogeneous Charge Compression) for premixed compression ignition combustion of an air-fuel mixture (premixed gas) supplied to a combustion chamber. Ignition)). In such an internal combustion engine, since the premixed gas is compressed under a high compression ratio (higher than the compression ratio of a normal spark ignition type internal combustion engine), self-ignition is performed simultaneously at multiple points. There is an advantage that the flame can be propagated quickly and combustion is completed in a short time, thereby improving the thermal efficiency and reducing the NOx emission amount while improving the fuel efficiency.

  In the internal combustion engine described above, in order to continue the compression ignition operation stably, it is necessary to maintain the inside of the cylinder at a relatively high temperature and maintain a state in which the air-fuel mixture is easily subjected to compression ignition combustion. Therefore, in the technique described in Patent Document 2, the valve mechanism is used to close both the intake valve and the exhaust valve in the latter half of the exhaust stroke, that is, to provide a negative overlap period. A predetermined amount of exhaust gas is left to increase the temperature of the air-fuel mixture (in-cylinder gas temperature) to enable the compression ignition operation.

JP 2005-69097 A Japanese Patent Laying-Open No. 2005-201127 (paragraphs 0044, 0045, FIGS. 3-5, etc.)

  However, if the intake valve and the exhaust valve are closed in the latter half of the exhaust stroke as in the technique described in Patent Document 2, the piston reaches the top dead center position after the valves are closed, and therefore remains in the cylinder. The exhausted gas is compressed by the piston. Therefore, the temperature of the exhaust gas rises and the heat loss from the cylinder wall surface increases accordingly, and as a result, the temperature of the residual exhaust gas when the piston returns to the pre-compression position is lowered as compared with that before the compression. There was a problem that. Further, since the exhaust gas remaining in a state where each valve is closed is compressed and expanded, a stress is generated in the piston, increasing the internal friction of the internal combustion engine, resulting in a disadvantage that the operation efficiency is lowered.

  Accordingly, the object of the present invention is to solve the above-mentioned problems and reduce the heat loss of the exhaust gas remaining in the cylinder in the negative overlap period in which the intake valve and the exhaust valve are closed in the latter half of the exhaust stroke, thereby performing the compression ignition operation. It is an object of the present invention to provide a compression ignition internal combustion engine that can stably maintain the engine and reduce the internal friction of the engine to improve the operation efficiency.

In order to achieve the above-described object, according to claim 1, a crankshaft connected to a piston disposed in a combustion chamber opened and closed by an intake valve and an exhaust valve is provided and supplied to the combustion chamber. In a four-cycle compression ignition internal combustion engine in which an air-fuel mixture is premixed compression ignition combustion, a negative overlap period for closing both the intake valve and the exhaust valve is set in the latter half of the exhaust stroke of the four cycles. A valve mechanism, and a link mechanism interposed between the piston and the crankshaft, wherein the air-fuel mixture includes gas fuel supplied via a gas supply unit and air supplied via an intake pipe The top dead center position of the piston is an air-fuel mixture, and the piston when the piston is at the top dead center position by the operation of the link mechanism when the valve operating mechanism is operating. The separation distance from the combustion chamber to the cylinder head is longer during the exhaust stroke than during the compression stroke of the four cycles, and the intake valve when the piston is at the top dead center position and the The exhaust stroke and the compression stroke in the four cycles so that the volume of the combustion chamber in a state where both the exhaust valves are closed is larger during the exhaust stroke than during the compression stroke of the four cycles. It is configured so that it can be changed.

In the compression ignition internal combustion engine according to claim 2 , the link mechanism is rotatably connected to a connecting rod connected to the piston and a crank pin of the crankshaft, and one end is connected to the connecting rod. A link rotatably connected via a pin, a rotary shaft having an axis parallel to the crankshaft and having an eccentric shaft at a position eccentric from the axis, and one end swinging to the other end of the link The swing rod is configured to be pivotally connected via a pin, and the other end is pivotally connected to the eccentric shaft, and the gear is configured to transmit the rotation of the crankshaft to the rotation shaft. .

In the compression ignition internal combustion engine according to claim 1, a valve operating mechanism in which a negative overlap period for closing both the intake valve and the exhaust valve is set in the latter half of the exhaust stroke of the four cycles, a piston, A link mechanism inserted between the crankshafts, and when the valve operating mechanism is operating, that is, during the negative overlap period, the link mechanism is operated so that the top dead center position of the piston is determined as the exhaust stroke. For example, the distance from the piston to the cylinder head of the combustion chamber when the link mechanism is operated and at the top dead center position is greater than that during the compression stroke. with longer when, than when the piston is in the compression stroke of the four-cycle the volume of the combustion chamber in a state in which both are closed in the intake and exhaust valves when in the top dead center position It can be changed to be large when the exhaust stroke and becomes, whereby the exhaust gas remaining in the cylinder in the latter half the exhaust stroke, it is no longer compressed by the piston.

  As a result, the temperature of the residual exhaust gas does not increase due to the compression, so that the temperature difference from the cylinder wall surface is relatively small, so that the heat loss from the cylinder wall surface can be reduced and the residual exhaust gas required for compression ignition. (In other words, the intake air amount can be increased), and as a result, the compression ignition operation can be stably continued. Furthermore, the illustrated thermal efficiency of the internal combustion engine can be increased by reducing the heat loss.

  Further, since the residual exhaust gas in the cylinder is not compressed by the piston, no stress is generated in the piston, and the internal friction of the internal combustion engine is reduced, thereby improving the engine operating efficiency and the net thermal efficiency.

In addition , when the valve mechanism is operating, the link mechanism is operated, and the separation distance from the piston when in the top dead center position to the cylinder head of the combustion chamber is greater than during the compression stroke of the four cycles. Since it is configured to be able to be changed so that it becomes longer during the exhaust stroke, the above-described effects can be obtained with certainty.

In the compression ignition internal combustion engine according to claim 2 , the link mechanism is rotatably connected to the connecting rod connected to the piston and the crank pin of the crankshaft, and one end thereof is connected to the connecting rod via the connecting rod pin. A link that is pivotally connected, a rotary shaft that has an axis parallel to the crankshaft and that is provided with an eccentric shaft at a position that is eccentric from the axis, and one end that is pivotable to the other end of the link via a swing pin The other end is connected to the eccentric shaft and the swing rod is rotatably connected to the eccentric shaft, and the gear that transmits the rotation of the crankshaft to the rotation shaft. The top dead center position of the piston can be reliably changed between the exhaust stroke and the compression stroke by using a link mechanism.

1 is a schematic view showing a compression ignition internal combustion engine according to an embodiment of the present invention as a whole. FIG. 2 is a partially sectional enlarged side view of the internal combustion engine shown in FIG. 1. FIG. 3 is a partial sectional bottom view of the internal combustion engine shown in FIG. 2. 2 is a graph showing two valve timing (and lift amount) characteristics that are switched (set) by the variable valve mechanism of the internal combustion engine shown in FIG. 1. 2 is a graph showing a position of a piston in a cylinder from an intake stroke to a compression, expansion, and exhaust stroke of the internal combustion engine shown in FIG. It is explanatory drawing which shows the state of a piston and a link mechanism in the compression, expansion, and exhaust stroke from the intake stroke of the internal combustion engine shown in FIG.

  DESCRIPTION OF EMBODIMENTS Hereinafter, a mode for carrying out a compression ignition internal combustion engine according to the present invention will be described with reference to the accompanying drawings.

  FIG. 1 is a schematic view generally showing a compression ignition internal combustion engine according to an embodiment of the present invention, FIG. 2 is a partially sectional enlarged side view of the internal combustion engine shown in FIG. 1, and FIG. It is a bottom view.

  1 to 3, reference numeral 10 denotes a water-cooled four-cycle single-cylinder OHV type compression ignition internal combustion engine (premixed compression self-ignition internal combustion engine) that uses city gas (or LP gas; hereinafter simply referred to as “gas”) as fuel. Organization (hereinafter referred to as “engine”). The engine 10 is a general-purpose internal combustion engine that is used as a drive source for a generator, an agricultural machine, a cogeneration device (all not shown), for example, and has a displacement of 163 cc, for example.

  In the engine 10, as shown in FIGS. 2 and 3, the cylinder head 12 and the cylinder block 14 are arranged in the horizontal (horizontal) direction, and one piston 16 reciprocates in a cylinder (cylinder) 14 a formed in the cylinder block 14. The piston 16 is connected to a crankshaft 20 that is disposed so that the axis 20a is in the vertical direction. The engine 10 is designed such that the top dead center position of the piston 16 (in other words, the stroke of the piston 16) changes between the compression stroke and the exhaust stroke, as will be described later. That is, the engine 10 is a vertical multi-link variable stroke internal combustion engine. In the drawings other than FIGS. 2 and 3, the piston 16 is shown to reciprocate in the vertical direction on the paper surface for the convenience of understanding.

  As shown in FIG. 1, in the engine 10, air drawn from an air cleaner (not shown) and passing through an intake pipe (intake system) 22 enters a mixer 24. The mixer 24 includes a throttle valve driven by an electric motor and a variable jet (both not shown). Gas is supplied to the mixer 24 from a fuel supply source (not shown) through the gas pipe 26 and the gas proportional valve unit 30, and is mixed with air (a premixed gas is generated).

  Both the mixer 24 and the gas proportional valve unit 30 are connected to an electronic control unit (hereinafter referred to as “ECU”) 32. The ECU 32 comprises a microcomputer equipped with a CPU, ROM, RAM, and the like, and controls the operation of the mixer 24, the gas proportional valve unit 30 and the like based on the output of various sensors (not shown).

  When the intake valve 34 is opened, the air-fuel mixture (pre-air mixture) generated by the mixer 24 flows into a space defined by the piston 16, the cylinder head 12, and the cylinder block 14, that is, the combustion chamber 36.

  A spark plug 40 is disposed in the vicinity of the combustion chamber 36. The spark plug 40 is connected to the ECU 32 via an ignition device 42 such as an igniter. When an ignition signal is supplied from the ECU 32 to the ignition device 42, a spark discharge is generated between the electrodes facing the combustion chamber 36. The air-fuel mixture is thereby ignited and burned, driving the piston 16.

  The air-fuel mixture is also burned by compression ignition. That is, the engine 10 performs a compression ignition operation in which the air-fuel mixture is premixed compression ignition combustion according to the operating state and a spark ignition operation (SI (Spark Ignition) operation) in which the air-fuel mixture is combusted by spark ignition via the ignition plug 40. Any one is performed, in other words, the operation is switched between the compression ignition operation and the spark ignition operation (premixing), and the engine is configured as a compression ignition internal combustion engine. Specifically, for example, the spark ignition operation is performed when the engine 10 is started or warmed up, and the compression ignition operation is performed when the engine 10 is in the rated operation region after warming up.

  The exhaust gas generated by the combustion flows through the exhaust pipe (exhaust system) 50 when the exhaust valve 46 is opened. In the middle of the exhaust pipe 50, a catalyst device 52 made of an exhaust purification catalyst (specifically, an oxidation catalyst) is arranged. When the catalyst device 52 is in an active state, the exhaust gas is purified by removing harmful components such as HC (hydrocarbon) and CO (carbon monoxide), and released into the atmosphere outside the engine.

  The intake valve 34 and the exhaust valve 46 described above are connected to a variable valve mechanism (valve mechanism) 60. Although the detailed illustration of the variable valve mechanism 60 is omitted, for example, the variable valve mechanism 60 has a structure disclosed in Japanese Patent Application Laid-Open No. 2010-65565 previously proposed by the present applicant. Referring to FIG. 3 where the variable valve mechanism 60 is partially shown, specifically, a first valve valve camshaft (camshaft) 60b connected to the crankshaft 20 via a gear 60a is first. , The second intake cam and four cams of the first and second exhaust cams (only the second exhaust cam 60c is visible in FIG. 3) are arranged adjacent to each other, and the first and second intake cams have an intake lifter (see FIG. However, the exhaust lifter 60d is in sliding contact with the first and second exhaust cams 60c. The intake lifter and the exhaust lifter 60d are connected to the rocker arm 60f via push rods 60e, respectively.

  During the spark ignition operation of the engine 10, by appropriately controlling the operation of the electromagnetic actuator and control rod connected to each cam, the intake lifter, the intake-side push rod 60e and The rocker arm 60f is operated, the intake valve 34 is driven with the valve timing (and lift amount) characteristic determined by the first intake cam, and the combustion chamber 36 is opened and closed.

  On the other hand, during the compression ignition operation of the engine 10, the intake lifter, the intake-side push rod 60e and the rocker arm 60f are operated by the rotation operation of the second intake cam, and the valve timing (and lift amount) determined by the second intake cam is reached. ) Drive the intake valve 34 with the characteristics. The exhaust valve 46 is also configured to operate in the same manner.

  FIG. 4 shows the characteristics (indicated as 34 for the intake valve 34 and 46 for the exhaust valve 46). During the compression ignition operation, the valve timing (and lift amount) is set to the characteristics shown by the solid line in FIG. Specifically, the closing timing of the exhaust valve 46 is advanced and the opening timing of the intake valve 34 is retarded (at the crank angle). That is, the variable valve mechanism 60 is set to provide a so-called negative overlap period in which both the intake valve 34 and the exhaust valve 46 are closed from the latter half of the four cycles to the first half of the intake stroke. The Thereby, a predetermined amount of exhaust gas (internal EGR) is left in the cylinder to increase the temperature of the air-fuel mixture (in-cylinder gas temperature), thereby enabling the compression ignition operation.

  On the other hand, during the spark ignition operation, the valve timing (and the lift amount) is set to a characteristic indicated by a broken line in FIG. Specifically, the closing timing of the exhaust valve 46 and the opening timing of the intake valve 34 are both changed to near the top dead center of the piston. As a result, the closing of the exhaust valve 46 is retarded and the amount of gas discharged in the combustion chamber increases, while the opening of the intake valve 34 is advanced and the inflow of intake air is accelerated, so that the exhaust gas is combusted. Without remaining in the chamber 36, it is sent to the exhaust system.

  Returning to the description of FIG. 1, the variable valve mechanism 60 is connected to the ECU 32 via the control circuit 62. The ECU 32 controls the operation of the variable valve mechanism 60 (more precisely, the electromagnetic actuator) through the control circuit 62, and sets the valve timing (and lift amount) of the intake valve 34 and the exhaust valve 46 to one of the above two characteristics. Set (change).

  As described above, the intake valve 34 and the exhaust valve 46 of the engine 10 can be freely opened and closed by the variable valve mechanism 60 at an arbitrary timing (valve timing and lift amount), and the operation of the engine 10 is controlled by the variable valve mechanism. Switching between the spark ignition operation and the compression ignition operation is performed by controlling the operation of 60.

  Next, a connection structure between the piston 16 and the crankshaft 20, an operation of the piston 16, and the like, which are one of the features of the engine 10 according to the present invention, will be described with reference to FIGS.

  As shown in the figure, a crankcase 70 is formed integrally with the cylinder block 14. In the crank chamber 70 a inside the crankcase 70, the crankshaft 20 is rotatably accommodated, and a link mechanism 72 inserted between the piston 16 and the crankshaft 20 is also accommodated. Note that one end (upper end) 20b of the crankshaft 20 is disposed so as to protrude outward from the crankcase 70, and a generator or the like is connected thereto.

  The crankshaft 20 includes two balance weights 74 and a crankpin 76 that connects the balance weights 74 and is provided at a position where the axis 76a is substantially parallel to the axis 20a of the crankshaft 20 and eccentric from the axis 20a. Is provided.

  The link mechanism 72 includes a connecting rod 80 whose one end 80a is rotatably connected (coupled) to the piston 16 via a piston pin 82, and a link (trigonal link, sub-view) that has a substantially triangular shape in plan view (bottom view). Connecting rod) 84, a rotation shaft (eccentric shaft) 86 having an axis 86a substantially parallel to the crankshaft 20, a swing rod 90 interposed between the link 84 and the rotation shaft 86, and the rotation of the crankshaft 20 as a rotation shaft. And a speed reduction mechanism (gear) 92 that transmits to 86.

  One end 84 a of the link 84 is rotatably connected to the other end 80 b of the connecting rod 80 via a connecting rod pin 94. The body 84b of the link 84 is rotatably connected to the crank pin 76 of the crankshaft 20, and the other end 84c is rotatably connected to one end 90a of the swing rod 90 via the swing pin 96. As described above, the one end 90a of the swing rod 90 is connected to the link 84 at a position offset (shifted) from the connection position (one end 84a) of the connecting rod 80.

  The rotary shaft 86 is rotatably accommodated (supported) in the crank chamber 70 a of the crankcase 70, as with the crankshaft 20. The rotating shaft 86 is provided with an eccentric shaft 100 having an axis 100a at a position substantially parallel to the axis 86a and eccentric from the axis 86a. The other end 90 b of the swing rod 90 is rotatably connected to the eccentric shaft 100 portion of the rotating shaft 86.

  The reduction mechanism 92 is provided on the crankshaft 20 with a first gear (timing gear, drive gear) 92a and a rotary shaft 86, and a second gear (eccentric gear, driven gear) meshed with the first gear 92a. 92b, and is set so that the rotational power of the crankshaft 20 is reduced to 1/2 and transmitted to the rotary shaft 86.

  The details of each part constituting the link mechanism 72 described above are described in detail in an application (Japanese Patent Application No. 2011-37278) filed separately by the present applicant, and thus further description thereof is omitted.

  By configuring the link mechanism 72 of the engine 10 as described above, the top dead center position of the piston 16 can be changed between the exhaust stroke and the compression stroke of the four cycles by the operation of the link mechanism 72.

  FIG. 5 is a graph showing the position of the piston 16 in the cylinder from the intake stroke to the compression, expansion, and exhaust stroke of the engine 10, and FIG. 6 is an explanatory diagram showing the state of the piston 16 and the link mechanism 72 in each stroke. It is.

  In FIG. 6, in order from the left side of the page, (a) when the piston 16 is at the bottom dead center position during the intake stroke, (b) when it is at the top dead center position during the compression stroke, and (c) down the expansion stroke. When it is at the dead center position, (d) shows the time when it is at the top dead center position in the exhaust stroke, and in FIG. 5, the same reference numerals a to d are assigned to the portions corresponding to the states (a) to (d). Is attached.

  Further, a case where the compression ignition operation is performed in the engine 10 will be described as an example. In the following description, a description indicating a direction such as up and down or left and right means an up and down direction or left and right direction on the paper surface, and does not necessarily mean an actual up and down direction and left and right direction of the engine 10.

  First, in the intake stroke of the four cycles, when the piston 16 descends and reaches the bottom dead center position, the crank pin 76 and the link 84 connected to the crank pin 76 are connected to the crank pin 76 as shown in FIG. The eccentric shaft 100 is positioned substantially on the right side with respect to the rotation shaft 86 while being positioned substantially below the shaft 20.

  Next, when the compression stroke is started, the crankpin 76 and the link 84 also rotate around the crankshaft 20 with the rotation of the crankshaft 20 and push the piston 16 upward through the connecting rod 80. When the piston 16 reaches the top dead center position, the crankshaft 20 is rotated approximately 180 degrees counterclockwise from the state of (a), and therefore, as shown in FIG. 84 is positioned substantially above the crankshaft 20.

  Further, the rotation of the crankshaft 20 at this time is transmitted to the rotation shaft 86 via the speed reduction mechanism 92, whereby the eccentric shaft 100 is rotated about 90 degrees clockwise around the rotation shaft 86. It is positioned substantially below. Since the eccentric shaft 100 is connected to the other end 84c of the link 84 via the swing rod 90, the angle (direction) of the link 84 changes according to the position of the eccentric shaft 100 (in other words, the link 84 The relative position of the one end 84a and the other end 84c varies depending on the position of the eccentric shaft 100).

  Further, the distance from the piston 16 (more precisely, the upper surface 16a of the piston 16) at the top dead center position of the compression stroke to the cylinder head 12 of the combustion chamber 36 is defined as “d1”.

  In the subsequent expansion stroke, the piston 16 is pushed down by the combustion of the air-fuel mixture in the combustion chamber 36, and the crankshaft 20 is rotated via the connecting rod 80 or the like. When the piston 16 reaches the bottom dead center position, the crankshaft 20 rotates about 180 degrees counterclockwise from the state (b). It will be positioned substantially below. Further, the eccentric shaft 100 is rotated about 90 degrees clockwise around the rotation shaft 86 by the rotation of the crankshaft 20 at this time, and is positioned substantially on the left side of the rotation shaft 86.

  As can be seen from FIG. 5 and FIGS. 6A and 6C, the bottom dead center position during the intake stroke of the piston 16 and the bottom dead center position during the expansion stroke are substantially the same height.

  Next, when the exhaust stroke is started, as the crankshaft 20 rotates, the crankpin 76 and the link 84 also rotate about the crankshaft 20 and push the piston 16 upward through the connecting rod 80. As described above, when the second half of the exhaust stroke occurs in the compression ignition operation, the variable valve mechanism 60 operates to close both the intake valve 34 and the exhaust valve 46, and the exhaust gas remains in the cylinder.

  At this time, the piston 16 reaches the top dead center position and the crankshaft 20 is rotated about 180 degrees counterclockwise from the state of (c). The link 84 is positioned substantially above the crankshaft 20.

  Further, the eccentric shaft 100 is rotated about 90 degrees clockwise around the rotation shaft 86 by the rotation of the crankshaft 20, and is positioned substantially above the rotation shaft 86. Thereby, the separation distance d2 from the piston 16 to the cylinder head 12 when the exhaust stroke is at the top dead center position can be made longer than the separation distance d1 during the compression stroke. The piston top dead center position in the stroke can be made lower than the piston top dead center position in the compression stroke.

  That is, as can be seen by comparing FIGS. 6B and 6D, the position of the eccentric shaft 100 differs between the compression stroke and the exhaust stroke. Specifically, the position of the eccentric shaft 100 during the compression stroke is substantially below the rotation shaft 86, whereas it is substantially above the rotation shaft 86 during the exhaust stroke. Therefore, the angle (direction) of the link 84 can be made different between the compression stroke and the exhaust stroke, so that the stroke of the piston 16 during the exhaust stroke can be made shorter than that during the compression stroke, that is, separated. The distance d2 can be made longer (d2> d1) than d1.

  As described above, according to the embodiment of the present invention, the crankshaft 20 connected to the piston 16 disposed in the combustion chamber 36 opened and closed by the intake valve 34 and the exhaust valve 46 is provided. In a four-cycle compression ignition internal combustion engine (engine) 10 that premixes compression ignition combustion of the supplied air-fuel mixture, a negative pressure that closes both the intake valve 34 and the exhaust valve 46 in the latter half of the exhaust stroke of the four cycles. And a link mechanism 72 interposed between the piston 16 and the crankshaft 20, and the valve mechanism 60 is operating. At this time, the link mechanism 72 is operated so that the top dead center position of the piston 16 can be changed between the exhaust stroke and the compression stroke of the four cycles.

  As described above, when the variable valve mechanism 60 is operating, that is, in the negative overlap period, the top dead center position of the piston 16 can be changed between the exhaust stroke and the compression stroke by operating the link mechanism 72. For example, when the distances d1 and d2 from the piston 16 to the cylinder head 12 of the combustion chamber 36 when the link mechanism 72 is operated and at the top dead center position are in the compression stroke (d1) Rather, the exhaust gas remaining in the cylinder in the second half of the exhaust stroke is not compressed by the piston 16.

  As a result, the temperature of the residual exhaust gas does not increase due to the compression, so that the temperature difference from the cylinder wall surface is relatively small, so that the heat loss from the cylinder wall surface can be reduced and the residual exhaust gas required for compression ignition. (In other words, the intake air amount can be increased), and as a result, the compression ignition operation can be stably continued. Furthermore, the illustrated thermal efficiency of the engine 10 can be increased by reducing the heat loss.

  Further, since the residual exhaust gas in the cylinder is not compressed by the piston 16, no stress is generated in the piston 16, and the internal friction of the engine 10 is reduced, so that the operation efficiency and the net thermal efficiency of the engine 10 can be improved.

  Further, when the valve mechanism (variable valve mechanism) 60 is operating, the link mechanism 72 is operated so that the piston 16 when it is at the top dead center position to the cylinder head 12 of the combustion chamber 36. The separation distances d1 and d2 can be changed so as to be longer in the exhaust stroke (d2) than in the compression stroke (d1) of the four cycles. Can be obtained.

  The link mechanism 72 is rotatably connected to a connecting rod 80 connected to the piston 16 and a crank pin 76 of the crankshaft 20, and one end 84a is connected to the connecting rod 80 via a connecting rod pin 94. A link 84 that is rotatably connected, an axis 86 a that is parallel to the crankshaft 20, a rotation shaft 86 that is provided with an eccentric shaft 100 at a position that is eccentric from the axis 86 a, and one end 90 a of the link 84. The other end 84c is pivotally connected via a swing pin 96, while the other end 90b is pivotally connected to the eccentric shaft 100, and the rotation of the crankshaft 20 is the rotation shaft. 86 is configured to include a gear (deceleration mechanism (first and second gears 92a, 92b)) 92 that transmits to 86, the link mechanism 72 is simplified. Configuration is possible in the top dead center position of piston 16 may allow reliably changed by the exhaust stroke and the compression stroke using the link mechanism 72.

  In the above description, the exhaust amount of the engine 10 and the like are shown as specific values, but these are examples and are not limited.

  10 engine (compression ignition internal combustion engine), 12 cylinder head, 16 piston, 20 crankshaft, 34 intake valve, 36 combustion chamber, 46 exhaust valve, 60 variable valve mechanism (valve mechanism), 72 link mechanism, 76 crankpin , 80 connecting rod, 84 link, 86 rotating shaft, 90 swing rod, 92 reduction mechanism (gear), 92a first gear, 92b second gear, 94 connecting rod pin, 96 swing pin, 100 eccentric shaft

Claims (2)

In a four-cycle compression ignition internal combustion engine having a crankshaft connected to a piston disposed in a combustion chamber that is opened and closed by an intake valve and an exhaust valve and premixed compression ignition combustion of an air-fuel mixture supplied to the combustion chamber , A valve operating mechanism in which a negative overlap period for closing both the intake valve and the exhaust valve is set in the latter half of the exhaust stroke of the four cycles, and a link interposed between the piston and the crankshaft The air-fuel mixture is an air-fuel mixture of gas fuel supplied via a gas supply unit and air supplied via an intake pipe , and the top dead center position of the piston is When the mechanism is operating, due to the operation of the link mechanism, the separation distance from the piston to the cylinder head of the combustion chamber when the piston is at the top dead center position is The combustion chamber in a state in which both the intake valve and the exhaust valve are closed when the piston is at the top dead center position and becomes longer than the compression stroke of the cycle The compression ignition internal combustion engine can be changed between the exhaust stroke and the compression stroke of the four cycles so that the volume of the exhaust gas becomes larger during the exhaust stroke than during the compression stroke of the four cycles. organ.   The link mechanism includes a connecting rod connected to the piston, a link rotatably connected to a crank pin of the crankshaft, and one end rotatably connected to the connecting rod via the connecting rod pin; A rotary shaft having an axis parallel to the crankshaft and provided with an eccentric shaft at a position eccentric from the axis, and one end rotatably connected to the other end of the link via a swing pin; 2. The compression ignition internal combustion engine according to claim 1, comprising a swing rod whose end is rotatably connected to the eccentric shaft, and a gear that transmits the rotation of the crankshaft to the rotation shaft.

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