JP2010255475A - Spark ignition type internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a spark ignition type internal combustion engine reducing pumping loss in a partial load zone and preventing output drop in a heavy load zone without causing cost increase due to enlargement of a drive mechanism and a valve element. <P>SOLUTION: A serge tank 21 is connected to an upstream side of an intake passage 20'. A check valve 30 permitting only flow to an intake cylinder is disposed near a connection part of the surge tank 21 of the intake passage 20'. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a spark ignition type internal combustion engine in which internal EGR is performed by generating a tumble of an intake flow in a cylinder and providing an overlap period in which an intake valve and an exhaust valve open simultaneously.

  In this type of internal combustion engine, an amount of intake air corresponding to the opening of the throttle valve is sucked into the cylinder, and output control is performed by supplying an amount of fuel corresponding to the amount of intake air. For this reason, in the partial load region, since the opening of the throttle valve is small, the negative pressure is maintained in the intake passage, so that the pumping loss increases. In order to reduce such pumping loss, internal EGR gas is introduced into the intake passage by providing an overlap period. However, depending on the overlap period, excessive internal EGR gas flows into the intake passage, and this EGR gas flows into the cylinder together with fresh air in the next intake stroke, so that combustion becomes unstable. Concerned.

  Therefore, in Patent Document 1, a check valve is arranged in the vicinity of the intake port to prevent the backflow of exhaust gas at the time of partial load, and in the high load range, the check valve is fully opened to provide an intake resistance. Techniques to avoid it have been proposed.

Japanese Patent Laid-Open No. 7-34883

  By the way, the conventional internal combustion engine employs a structure in which the check valve is driven to the fully open position by a drive mechanism when the load is high, and there is a problem that the cost increases. That is, when the check valve is provided in the vicinity of the intake port, the flow rate of the air-fuel mixture passing through the check valve is set to the cylinder volume due to the lowering of the piston in the intake stroke in order to avoid a decrease in output at a high load. It is necessary to follow changes. For this reason, it is necessary to make the check valve movable or to enlarge it.

  The present invention has been made in view of the above-described conventional situation, and can reduce the pumping loss in the partial load region without increasing the cost due to the increase in the size of the drive mechanism and the valve body, and the output in the high load region. It is an object of the present invention to provide a spark ignition internal combustion engine that can prevent a decrease.

  According to a first aspect of the present invention, a plurality of cylinders, an intake passage connected to each of the cylinders and generating a tumble of intake air in the cylinder, and an intake valve that opens and closes an intake opening that opens in the cylinder of each of the intake passages And an exhaust valve that opens and closes an exhaust opening, and is a spark ignition internal combustion engine provided with an overlap period in which the intake valve and the exhaust valve open simultaneously, and a surge tank is connected upstream of the intake passage, A check valve that allows only the flow of intake air to the cylinder is arranged in the vicinity of the connection portion of the surge tank in the intake passage.

  According to a second aspect of the present invention, in the spark ignition internal combustion engine according to the first aspect, each intake passage is connected to the surge tank, and the check valve is disposed in each intake passage. It is characterized by.

  According to a third aspect of the present invention, in the spark ignition type internal combustion engine according to the second aspect, the check valve is clamped and fixed together with the intake passage by being sandwiched between connection surfaces of the intake passages and the surge tank. It is characterized by that.

  According to a fourth aspect of the present invention, in the spark ignition type internal combustion engine according to the first aspect, the closing timing of each intake valve in the high load region is set after the bottom dead center in the intake stroke.

  According to a fifth aspect of the present invention, in the spark ignition internal combustion engine according to the fourth aspect, each of the cylinders includes a plurality of intake valves, and among the intake valves, the intake valve farthest from the exhaust valve is It is characterized by opening earlier than other intake valves.

  According to a sixth aspect of the present invention, in the spark ignition internal combustion engine according to the fourth aspect, each of the cylinders has a pent roof type combustion chamber, and when viewed in the cylinder axial direction, sandwiches the crank axis of the combustion chamber. Two intake valves are arranged on one side and two exhaust valves are arranged on the other side, and one of the two intake valves is opened ahead of the other and the exhaust farther from the one intake valve It is characterized in that the valve is closed later than the other exhaust valve.

  According to a seventh aspect of the present invention, there is provided the spark ignition type internal combustion engine according to any one of the first to sixth aspects, wherein the gas fuel injection valve is configured to supply gas fuel or liquid LPG fuel downstream from the check valve of the intake passage. Is arranged in the intake passage.

  The invention according to claim 8 is the spark ignition type internal combustion engine according to claim 1, further comprising a hydraulic variable valve mechanism for variably controlling the opening and closing timings of the intake valve and the exhaust valve.

  According to a ninth aspect of the present invention, in the spark ignition type internal combustion engine according to the first aspect, the check valve is a reed valve, and the reed valve has an opening formed in a valve seat body through the reed so that the intake air The passage is configured so that the downstream side of the reed valve is opened when the pressure is negative and is closed when the pressure is positive, and the opening and closing direction of the reed is arranged in the crank axis direction.

  According to a tenth aspect of the present invention, in the spark ignition type internal combustion engine according to the first aspect, the internal combustion engine performs two-cylinder combustion at equal intervals, and the intake passage includes one common intake passage on the upstream side, A branch intake passage branched from the common intake passage, and the check valve is arranged in the common intake passage.

  According to an eleventh aspect of the present invention, in the spark ignition type internal combustion engine according to the tenth aspect, a gas fuel injection valve common to each cylinder is disposed at a downstream side portion of the check valve of the common intake passage, and the gas fuel injection The valve is arranged to supply gas fuel to a branch portion of each intake passage to each cylinder.

  According to a twelfth aspect of the present invention, in the spark ignition internal combustion engine according to the tenth aspect, a throttle body including a throttle valve is disposed upstream of the check valve in the common intake passage. An external EGR device that recirculates a part of the exhaust gas to the intake system is connected to the check valve.

  According to the internal combustion engine of the first aspect of the present invention, the check valve that allows only the flow to the cylinder side is disposed in the vicinity of the surge tank connecting portion of the intake passage, that is, at the upstream end portion of the intake passage. The passage volume downstream from the check valve of the passage can be secured, and the internal EGR gas can be stored in the check valve downstream portion of the intake passage during the overlap period at the time of partial load. As a result, the negative pressure in the intake passage at the beginning of the intake stroke is reduced and sufficient internal EGR gas is ensured, so that the pumping loss at the partial load can be reduced and the fuel consumption can be reduced.

  In the high load range, the air-fuel mixture can be filled downstream of the check valve in the intake passage in a stroke other than the intake stroke. Therefore, it is necessary to provide a drive mechanism or increase the size of the valve body. Therefore, sufficient output performance can be obtained without increasing the cost.

  That is, in an internal combustion engine that generates tumble of intake air in a cylinder, if a check valve is arranged near the connection portion of the intake passage with the surge tank and the overlap period is expanded during partial load, the internal EGR gas is It will accumulate in the intake passage. Accordingly, the pressure in the intake passage at the initial stage of the intake stroke is greatly reduced, and the check valve is located at the upstream end of the intake passage, so that necessary and sufficient internal EGR gas can be secured. Thereby, both the reduction effect of the pumping loss in the intake stroke and the reduction effect of the fuel consumption due to the increase of the internal EGR gas can be obtained. Such a reduction effect of the pumping loss can be easily realized without much cost by commercializing the engine components using existing engine components.

  For example, in the case of an internal combustion engine that directly injects gasoline fuel into the intake port, if an overlap period is provided in the middle / high load operation range, the amount of residual gas that flows back from the cylinder increases, so Some may fly to the inner wall of the surge tank. This phenomenon makes the A / F control in a transient state inappropriate, and there is a concern about the influence on the response and exhaust gas properties. In the present invention, since the check valve suppresses the backflow of residual gas to the surge tank, gasoline fuel particles can be stored in the intake passage in the vicinity of the intake valve, improving the response and exhaust gas properties. it can.

  In the invention of claim 2, since each intake passage is connected to a surge tank and a check valve is arranged in each intake passage, it is effective in reducing pumping loss in a multi-cylinder internal combustion engine.

  In the invention of claim 3, since the check valve is fixed together with the check valve sandwiched between the connection surfaces of the surge tank and the intake pipe, the check valve has a simple structure and is easy without adding new parts. Can be attached to.

  In the invention of claim 4, since the closing timing of the intake valve in the high load region is after bottom dead center, a part of the fresh air sucked into the cylinder returns to the intake passage, and this returned fresh air is reversed. The stop valve accumulates the pressure in the intake passage with an increase in pressure. When the overlap of the next intake stroke is started from this state, since the pressure in the intake air of fresh air is higher than the pressure in the cylinder, the internal EGR gas is reduced and the high-temperature cylinder residual gas is reduced. As a result, the anti-knocking performance in a high load range can be improved.

  That is, in the high load operation region, knocking is likely to occur due to an increase in the compression pressure and an increase in the high-temperature internal EGR gas. Conventionally, as countermeasures for preventing knocking, reduction of the compression ratio, retarding of the ignition timing, and operation with an over-concentrated air-fuel ratio have been performed, but any of the countermeasures may cause a decrease in thermal efficiency. In the present invention, since the internal EGR gas is reduced, the anti-knocking performance can be improved without causing such a decrease in thermal efficiency.

  In the invention of claim 5, among the plurality of intake valves, the opening time of the intake valve that is farthest from the exhaust valve is made earlier than the opening timing of the other intake valves, so that the overlap period can be expanded accordingly, It is possible to suppress the outflow due to blow-through of fresh air when scavenging burned gas with fresh air stored in the passage.

  That is, in an internal combustion engine that purifies exhaust gas using a three-way catalyst, if excess oxygen and unburned components are discharged in a high-load operation region, the catalyst may rise above the allowable temperature, If the fresh air is blown out by scavenging, the catalyst may be damaged. In the case of a three-way catalyst, exhaust gas may not be sufficiently purified. In the present invention, since blow-through of fresh air can be suppressed, damage to the catalyst can be avoided and exhaust gas can be sufficiently purified.

  In the invention of claim 6, since the closing timing of the exhaust valve located farther from the first opening of the two intake valves is made later than the closing timing of the other exhaust valves, it is stored in the intake passage. Blow-through when scavenging with fresh air can be suppressed, and the same effect as in claim 4 can be obtained.

  According to the seventh aspect of the present invention, the gas fuel is supplied to the downstream side of the check valve of the intake passage, so that the pumping loss can be reduced by supplying the gas fuel at an appropriate timing. In this case, the gas fuel is preferably supplied in a range excluding the latter half of the intake stroke. For example, when gas fuel is supplied before the start of overlap, the effect of reducing internal EGR is obtained, combustion stability is improved in the extremely low load operation region including idling, and scavenging capacity is obtained in the high load operation region. Will be improved.

  That is, gas fuel such as CNG / LPG has a sufficient vapor pressure to evaporate at room temperature, and the liquid injection LPG is also vaporized immediately after injection, so it is easy to supply it in the intake passage in a gas state. It is. Thus, pumping loss can be reduced by supplying gas fuel at an appropriate time.

  In the invention of claim 8, since the opening and closing timings of the intake valve and the exhaust valve are performed by a hydraulic variable valve mechanism, the control of the overlap period can be easily performed by arranging a check valve in the intake passage. Thus, it is possible to use a general variable valve mechanism that has already been standardized, and the cost can be reduced.

  According to the ninth aspect of the present invention, a reed valve configured to open and close the opening of the valve seat body with the reed is adopted, and the reed valve is disposed so that the reed is opened and closed in the crank axis direction. In addition, a stable opening / closing operation can be obtained.

  That is, in a reciprocating internal combustion engine, vibration in a direction perpendicular to the axis of the crankshaft, that is, in the cylinder axis direction, is overwhelmingly large. For this reason, when the reed valve is disposed so that the reed opens and closes in the cylinder axis direction, the reed may behave in an unstable manner due to the vibration in the high-speed rotation range. In order to allow sufficient fresh air to pass through in the high-speed and high-load operating range, it is desirable to connect multiple small reed valves that are easy to secure the layout space. It is desirable to arrange so as to open and close.

  In the invention of claim 10, in the internal combustion engine that performs two-cylinder equidistant combustion in which the intake strokes do not overlap, the check valve is arranged in the common intake passage, so that the check valve can be used in common for each cylinder, and the structure Can be made simple and compact.

  In general, in an engine that performs two-cylinder equidistant combustion, the intake strokes do not overlap and therefore are not directly affected by the intake negative pressure of the opposing cylinders. For this reason, if the intake passage volume on the downstream side of the throttle valve is appropriate, the pumping loss at the partial load can be reduced by optimizing the tumble port shape and the overlap period. However, since knocking is likely to occur in a high load range, it is necessary to store fresh air after bottom dead center in the intake passage by a check valve. In the present invention, since the intake strokes do not overlap, the check valve can be shared by each cylinder.

  In the invention of claim 11, since the gas fuel is supplied to the downstream side portion of the check valve of the common intake passage, the pumping loss is reduced by supplying the gas fuel, for example, before the overlap or the first half of the intake stroke. it can.

  Since the gas fuel does not adhere to the wall surface of the intake passage like liquid fuel such as gasoline, it is not necessary to arrange the gas fuel injection valve so as to face the intake valve. For this reason, even with one gas fuel injection valve, gas fuel can be supplied uniformly to each cylinder, and combustion can be performed with a uniform air-fuel ratio mixture. As a result, the fuel supply device can be simplified, and high responsiveness and exhaust gas performance can be obtained.

  In the twelfth aspect of the invention, the external EGR gas is introduced upstream of the check valve and downstream of the throttle valve. Since the burned gas in the cylinder can be prevented from reaching the upstream side of the check valve after the bottom dead center of the intake stroke, the external EGR gas always flows toward the downstream side, so that the throttle body and the throttle valve Can be prevented from fouling.

  EGR is known to be an effective technique for reducing NOx and improving fuel consumption. In order to obtain such an effect, it is important to use EGR in the widest possible operating range and introduce it uniformly into each cylinder. From such a viewpoint, for example, it is conceivable to introduce an external EGR gas upstream of the throttle valve. However, since the external EGR gas contains fine particles such as carbon generated by combustion, the fine particles gradually adhere to the inner walls of the throttle valve and the throttle body due to the backflow of the air-fuel mixture generated after the bottom dead center of the intake stroke of each cylinder. As a result, the controllability such as the throttle opening may be impaired. As an example of measures against such controllability, there is a case where a communication path is provided between the cylinder head and the intake pipe of each cylinder separately from the intake path, and external EGR gas is introduced into the cylinder from the communication path. However, depending on the operating conditions, a difference in the distribution of the external EGR gas to each cylinder tends to occur, and it is difficult to control the EGR rate so that all cylinders can be operated most efficiently. In the present invention, since the check valve is provided in the intake passage, the burned gas in the cylinder can be prevented from reaching the upstream side of the check valve after the bottom dead center of the intake stroke, and the throttle valve is soiled. Can be prevented. In particular, when performing two-cylinder equidistant combustion, since the intake strokes do not overlap, the effect of the backflow of burned gas appears remarkably, so the effect is great.

1 is a cross-sectional side view of a spark ignition internal combustion engine according to Embodiment 1 of the present invention. 2 is a cross-sectional plan view of the internal combustion engine. FIG. FIG. 3 is a timing diagram for opening and closing an intake valve and an exhaust valve of the internal combustion engine. It is a characteristic view which shows the effect of the pumping loss of the said internal combustion engine. It is a cross-sectional side view of the internal combustion engine by Example 2 of this invention. It is the schematic block diagram seen from the plane of the internal combustion engine by Example 3 of this invention. FIG. 3 is a timing diagram for opening and closing an intake valve and an exhaust valve of the internal combustion engine. It is a schematic block diagram of the internal combustion engine by Example 4 of this invention. FIG. 3 is a timing diagram for opening and closing an intake valve and an exhaust valve of the internal combustion engine. It is a schematic block diagram of the internal combustion engine by Example 5 of this invention. It is a schematic block diagram of the internal combustion engine by Example 6 of this invention.

  Embodiment 1 of the present invention will be described below with reference to the accompanying drawings.

  FIGS. 1 to 3 are views for explaining a spark ignition type internal combustion engine according to a first embodiment of the present invention. FIG. 1 is a cross-sectional view of the internal combustion engine, and FIG. 2 is a schematic configuration diagram viewed from the plane of the internal combustion engine. FIG. 3 is an open / close timing chart of the intake valve and the exhaust valve of the internal combustion engine.

  In the figure, reference numeral 1 denotes a water-cooled 4-cycle in-line 4-cylinder spark ignition internal combustion engine. The internal combustion engine 1 has a cylinder head 3 connected to an upper joint surface of a cylinder block 2 in which four cylinder bores (cylinders) 2a are formed in parallel, and a head cover 4 is connected to the upper joint surface of the cylinder head 3. The cylinder block 2 has a schematic structure in which a crankcase (not shown) in which a crankshaft 5 is accommodated is connected to the lower joint surface of the cylinder block 2.

  A piston 6 is slidably inserted into each cylinder bore 2 a, and the piston 6 is connected to the crankshaft 5 via a connecting rod 7.

  A pent roof type combustion recess (combustion chamber) 3a is formed in a portion of the cylinder head 3 facing each cylinder bore 2a. A spark plug 10 is mounted on each combustion recess 3a so as to be positioned on the cylinder axis E of the cylinder bore 2a.

  In each combustion recess 3 a of the cylinder head 3, two intake openings 3 b and two exhaust openings 3 c are formed in parallel in the direction of the axis C of the crankshaft 5. The two intake openings 3b and 3b are arranged on one side of the crankshaft 5 when viewed in the cylinder axis E direction, and the exhaust openings 3c and 3c are arranged on the other side of the axis C. Has been.

  Intake valves 11, 11 are disposed in the intake openings 3 b, and the intake valves 11 are opened and closed by intake camshafts 12. Exhaust valves 13 are provided in the exhaust openings 3c, and the exhaust valves 13 are opened and closed by an exhaust camshaft 14.

  The cylinder head 3 is formed with an intake port 3d communicating with each intake opening 3b and an exhaust port 3e communicating with each exhaust opening 3c.

  Each exhaust port 3 e is connected to an exhaust pipe 15, and each exhaust pipe 15 merges into one collecting pipe 16. The collecting pipe 16 is provided with a catalyst 17 for purifying exhaust gas, and a muffler (not shown) is connected to the downstream end of the collecting pipe 16.

  An intake pipe 20 is connected to each intake port 3d. The upstream end of each intake pipe 20 is connected to a common surge tank 21. The surge tank 21 is connected with a throttle body 22 having a throttle valve 22a common to each cylinder, and an air cleaner (not shown) is connected to the throttle body 22. Note that the intake passage 20 ′ in this embodiment is constituted by the intake port 3 d and the intake pipe 20.

  The intake ports 3d and the intake pipes 20 are formed so as to be substantially straight toward the intake opening 3b and so that the intake passage axis faces the center of the cylinder bore 2a. As a result, the tumble flow a of intake air can be generated in the cylinder bore 2a.

  Each intake pipe 20 is provided with a liquid fuel injection valve 23 for injecting and supplying liquid fuel such as gasoline. The liquid fuel injection valve 23 is arranged so that the fuel injected from the fuel injection port 23 a is directed toward the center of the intake opening 3 b, that is, toward the back surface of the umbrella portion of the intake valve 11.

  The internal combustion engine 1 includes a hydraulic variable valve mechanism 25 that variably controls an overlap period in which the intake valve 11 and the exhaust valve 13 are opened simultaneously by changing the opening and closing timings of the intake valves 11 and the exhaust valves 13. I have.

  The variable valve mechanism 25 includes an intake actuator 26 and an exhaust actuator 27 that continuously change the opening and closing timings of the intake valve 11 and the exhaust valve 13 via the intake cam shaft 12 and the exhaust cam shaft 14, and the engine speed, And an ECU 28 for driving and controlling the intake and exhaust actuators 26 and 27 based on the operating conditions such as engine load and throttle valve opening.

  As shown in FIG. 3 (a), the variable valve mechanism 25 opens the exhaust valve at about 40 degrees before the bottom dead center in the combustion stroke (the crank angle, the same applies hereinafter) in the low / medium speed / high load operation region. Close at about 6 degrees after top dead center in the exhaust stroke (see solid line). Further, the intake valve is opened at about 6 degrees before top dead center in the intake stroke, and is closed at about 72 degrees after bottom dead center (see broken line). As a result, at the beginning of the intake stroke, an overlap period (about 12 degrees in crank angle) A1 is provided in which the intake valve and the exhaust valve open simultaneously.

  On the other hand, as shown in FIG. 3 (b), in the high speed and high load range operation region, the opening and closing timing of the exhaust valve is set to be the same as in the low / medium speed and high load operation range, and the intake valve opening timing is In the intake stroke, it becomes approximately 26 degrees before top dead center (crank angle, hereinafter the same), and the overlap period A2 with the exhaust valve is expanded to about 32 degrees in terms of the crank angle. The closing timing of the intake valve is about 52 degrees after the bottom dead center in the intake stroke. As a result, in the high speed and high load region, a part of the burned gas in the cylinder flows backward and stays in the intake port 3d and the intake pipe 20.

  A check valve (reed valve) 30 that allows only the flow of intake air to the cylinder side is disposed in the vicinity of the connection portion of each intake pipe 20 to the surge tank 21. The volume downstream of the check valve 30 in the intake passage 20 'in this embodiment is set to be approximately the same as the cylinder volume. Specifically, the diameter and length of the intake pipe 20 and the intake port 3d are set. However, it is set so that the volume can be secured.

  The check valve 30 is of a type that opens when the pressure in the intake passage 20 ′ becomes negative and closes when the pressure becomes positive. The check valve 30 includes one valve seat body 31, a total of four leads 32, and a total of four stoppers 33 that regulate the fully open position of each lead 32. The valve seat body 31 has a substantially V shape that expands to the upstream side in a cross-sectional plan view (see FIG. 2), and a vertically long shape that is long in the direction of the cylinder axis E. Four openings 31 a are formed in the left and right wall portions of the valve seat body 31, and the openings 31 a are opened and closed by the leads 32. The lead 32 is fixed together with the stopper 33 to the edge portion of the opening 31a of the valve seat body 31 by fastening together, and the opening 31a is opened and closed around the joint fastening portion.

  The check valve 30 is clamped and fixed to a connecting surface between the intake pipe 20 and the surge tank 21. Specifically, the flange portion 31 c formed in the valve seat body 31 is sandwiched between the flange portion 20 b of the intake pipe 20 and the surge tank 21 and fixed together by a plurality of bolts 35.

  The check valve 30 is arranged such that a center line D forming the V-shaped bisector is perpendicular to the crank axis C when viewed in the cylinder axis E direction, and the lead 32 is the crank The opening 31a is opened and closed by undulating in the direction of the axis C.

  According to the present embodiment, the check valve 30 that allows only the flow of intake air to the cylinder side is disposed in the vicinity of the connection portion of each intake pipe 20 to the surge tank 21, so that the check valve 30 of the intake passage 20 ′ The downstream passage volume can be secured to approximately the same as the cylinder volume, and the internal EGR gas can be accumulated in the downstream portion of the intake passage 20 ′ from the check valve 30 during the overlap period. it can. As a result, the negative pressure in the intake passage 20 'at the initial stage of the intake stroke is reduced, and necessary and sufficient internal EGR gas is ensured, so that the pumping loss during partial load can be reduced and the fuel consumption can be reduced.

  In the high speed and high load range, the air-fuel mixture can be filled in the downstream portion of the check valve 30 of the intake passage 20 'in a stroke other than the intake stroke. Cost can be reduced and sufficient output performance can be obtained as compared with the case where the body is enlarged.

  That is, in the internal combustion engine 1 in which the intake tumble flow a is generated in the cylinder, the check valve 30 is disposed in the vicinity of the connection portion with the surge tank 21 of the intake pipe 20 to extend the overlap period at the time of partial load. As a result, the internal EGR accumulates in the intake passage 20 '. Therefore, the negative pressure in the intake pipe at the initial stage of the intake stroke is greatly reduced, and the check valve 30 is positioned on the upstream side of the intake passage 20 ', so that necessary and sufficient internal EGR gas can be secured. Thereby, both the reduction effect of the pumping loss in the intake stroke and the reduction effect of the fuel consumption due to the increase of the internal EGR can be obtained. Such a reduction effect of the pumping loss can be easily realized without much cost by commercializing the engine components using existing engine components.

  In addition, when the liquid fuel injection valve 23 for directly injecting gasoline fuel into the intake port 3d is provided, if an overlap period is provided in the middle / high load operation region, the amount of residual gas flowing back from the cylinder increases. There is a concern that some gasoline fuel particles will fly to the inner wall of the surge tank. Since this phenomenon makes the A / F control in a transient state inappropriate, there is a concern about the influence on the response and the exhaust gas property.

  In the present embodiment, the check valve 30 prevents the backflow of residual gas to the surge tank 21, so that gasoline fuel particles can be stored in the vicinity of the intake valve 11 in the intake passage 20 ′. , Exhaust gas properties can be improved.

  FIG. 4 shows an indicator diagram of a four-cycle internal combustion engine. In the figure, the solid line b shows the change in the cylinder pressure of the internal combustion engine of this embodiment provided with the check valve, and the broken line c shows the change of the cylinder pressure of the internal combustion engine not provided with the check valve.

  As is clear from the figure, in the internal combustion engine having no check valve, the negative pressure in the cylinder in the intake stroke is as large as c ′, whereas in the internal combustion engine of the present embodiment, the intake passage is provided by the check valve. Since the internal EGR gas is accumulated at 20 ', the in-cylinder negative pressure during the intake stroke is increased to b', and it can be seen that the pumping loss is reduced by the shaded portion in FIG.

  In the present embodiment, each intake pipe 20 is connected to a surge tank 21 and a check valve 30 is arranged in each intake pipe 20, which is effective in reducing pumping loss in a multi-cylinder internal combustion engine.

  In this embodiment, the check valve 30 is fastened together with the bolt 35 in a state of being sandwiched between the connection surfaces of the surge tank 21 and the intake pipe 20, so that a simple structure can be obtained without adding new mounting parts. And the check valve 30 can be attached easily.

  In this embodiment, since the closing timing of the intake valve 11 in the high load region is after bottom dead center (about 52 degrees in crank angle), a part of the fresh air sucked into the cylinder returns into the intake passage 20 '. Thus, the returned fresh air is stored in the intake passage 20 ′ with a rise in pressure by the check valve 30. From this state, when the overlap of the next intake stroke is started, the pressure in the fresh air intake passage 20 ′ is higher than the pressure in the cylinder. Will flow into the cylinder. As a result, the internal EGR is reduced, and the high-temperature cylinder residual gas is scavenged, so that the anti-knocking performance in a high load region can be improved.

  That is, in the high load operation region, knocking is likely to occur due to an increase in the compression pressure and an increase in the high-temperature internal EGR gas. Conventionally, measures have been taken to reduce the compression ratio, retard the ignition timing, and operate with an over-concentrated air-fuel ratio, but any of these measures may lead to a decrease in thermal efficiency. In the present invention, an increase in the high-temperature internal EGR gas can be prevented, so that the anti-knocking performance can be improved without causing such a decrease in thermal efficiency.

  In this embodiment, the opening and closing timings of the intake valve 11 and the exhaust valve 13 are performed by the hydraulic variable valve mechanism 25. Therefore, by arranging the check valve 30 in the intake pipe 20, the overlap period can be controlled. Is simple. Therefore, it is possible to use a general variable valve mechanism 25 that has already been standardized, and the cost can be reduced compared to the case where a solenoid type variable mechanism or the like is used.

  In this embodiment, the check valve 30 is of a type that opens and closes the opening 31a by the undulation of the lead 32, and the opening and closing direction of the lead 32 is the direction of the axis C of the crankshaft. Is obtained.

  That is, in the reciprocating internal combustion engine, the vibration in the cylinder axis E direction is overwhelmingly large. For this reason, if the check valve 30 is arranged so that the lead 32 opens and closes in the direction of the cylinder axis E, the lead 32 may be unstable due to the vibration in the high-speed rotation region. In order to allow sufficient fresh air to pass through in the high-speed and high-load operating range, it is desirable to connect a small lead that can easily secure the arrangement space. It is desirable to arrange it in the direction of the axis E. That is, since four leads 32 for opening and closing the four left and right openings 31a of one valve seat body 31 are connected, the intake space necessary for high speed / high load operation is secured while securing the above-mentioned arrangement space. it can.

  FIG. 5 is a view for explaining a spark ignition type internal combustion engine according to a second embodiment of the present invention. In the figure, the same reference numerals as those in FIG. 1 denote the same or corresponding parts.

  The internal combustion engine of the present embodiment includes a liquid fuel injection valve 23 disposed in a portion downstream of the check valve 30 in each intake pipe 20, and a gas fuel injection valve 38 that supplies gas fuel such as CNG and LPG. It has. The gas fuel injection valve 38 is disposed so that the gas injection port 38 a is located near the axial center of the intake pipe 20 and upstream of the liquid fuel injection valve 23. Thereby, gas fuel is supplied toward the axial direction of the intake pipe 20 and the intake port 3d.

  In this embodiment, since the gas fuel is supplied to the downstream side of the check valve 30 of the intake pipe 20 by the gas fuel injection valve 38, the pumping loss can be reduced by sucking the gas fuel at an appropriate timing. . For example, when supplied before the start of overlap, the effect of reducing internal EGR is obtained, the stability of combustion is improved in the extremely low load operation region including idling, and the scavenging capacity is further increased in the high load operation region. improves.

  That is, gas fuel such as CNG / LPG has a sufficient vapor pressure to evaporate at room temperature, and the liquid injection LPG also evaporates immediately after injection, so that it is not supplied to the intake pipe 20 in a gas state. Easy. Thus, pumping loss can be reduced by supplying gas fuel at an appropriate time.

  6 and 7 are views for explaining a spark ignition type internal combustion engine according to a third embodiment of the present invention. In the figure, the same reference numerals as those in FIG. 2 denote the same or corresponding parts.

  The internal combustion engine of the present embodiment is a two-cylinder internal combustion engine having two cylinders 3a and 3a, and is configured to perform equal interval combustion. The intake passage 20 'of the present embodiment includes a common pipe (common intake passage) 20a located on the upstream side, branch pipes (branch intake passages) 20c and 20c branched from the upstream side, and intake ports 3d of the cylinders 3a and 3a. , 3d. A throttle body 22 having a built-in throttle valve 22a is connected to the common pipe 20a. A surge tank 21 is connected to the upstream side of the throttle body 22.

  A common check valve (reed valve) 30 common to each cylinder is disposed in the common pipe 20 a of the intake pipe 20. The check valve 30 is of a type that opens when the pressure in the intake passage 20 ′ becomes negative and closes when the pressure becomes positive, and has the same structure as that of the first embodiment.

  Each cylinder has a pent roof type combustion chamber. Two intake valves 11 and one scavenging intake valve 40 are disposed on one side of the combustion chamber with the crank axis C therebetween, and two on the other side. An exhaust valve 13 is arranged.

  The scavenging intake valve 40 connects the centers of the intake valves 11 and 11 and is located on the opposite side of the cylinder center across a straight line F parallel to the crank axis C, and is farthest from the exhaust valve 13. It is arranged at the position. The opening timing of the scavenging intake valve 40 is set so as to open earlier than the two intake valves 11.

  Specifically, as shown in FIG. 7A, in the extremely low load region including idling, the scavenging intake valve 40 opens about 32 degrees ahead of the opening timing of the two intake valves 11 and 11 at a crank angle. . The opening timing of the scavenging intake valve 40 is set at the same time as the closing timing of the exhaust valves 13 and 13. Further, the scavenging intake valve 40 is closed about 32 degrees ahead of the two intake valves 11 in terms of crank angle.

  On the other hand, as shown in FIG. 7B, in the high load region, the opening / closing timing of the exhaust valve 13 is fixed to the opening / closing timing of the idling / very low load region. The scavenging intake valve 40 is set to open before the top dead center of the intake stroke (about 26 degrees in crank angle). Thereby, the overlap period with the exhaust valve 13 is expanded. The opening timing of the two intake valves 11 is set so as to coincide with the closing timing of the exhaust valve 13 (see FIG. 7B).

  According to the present embodiment, two intake valves 11 and one scavenging intake valve 40 are arranged, and the opening timing of the scavenging intake valve 40 farthest from the exhaust valve 13 is earlier than the opening timing of the two intake valves 11. Therefore, the overlap period in the high load region can be extended, and the outflow due to blow-through when scavenging the burned gas by the fresh air stored in the intake passage 20 'can be suppressed.

  That is, in an internal combustion engine that purifies exhaust gas using a three-way catalyst, if excess oxygen and unburned components are discharged in a high-load operation region, the catalyst may rise above the allowable temperature, If the fresh air is blown out by scavenging, the catalyst may be damaged. In the case of a three-way catalyst, exhaust gas may not be sufficiently purified. In the present invention, since novel blow-through can be suppressed, damage to the catalyst can be avoided and exhaust gas can be sufficiently purified.

  In the present embodiment, when the two-cylinder equidistant combustion is performed, since the check valve 30 is arranged at the merging portion 20a of each intake pipe 20, the intake stroke of each cylinder does not overlap. It can be used in common with cylinders, making the structure simple and compact.

  In general, in an internal combustion engine that performs two-cylinder equidistant combustion, the intake strokes do not overlap and therefore are not directly affected by the intake negative pressure of the opposing cylinders. For this reason, if the intake passage volume on the downstream side of the throttle valve 22a is appropriate, the pumping loss at the partial load can be reduced by optimizing the tumble port and the overlap period. However, since knocking is likely to occur in a high load region, it is necessary to store fresh air after bottom dead center in the intake passage 20 'by a check valve. In this embodiment, since the intake strokes do not overlap, the check valve 30 can be shared by each cylinder.

  8 and 9 are diagrams for explaining a spark ignition type internal combustion engine according to a fourth embodiment of the present invention. In the figure, the same reference numerals as those in FIG. 2 denote the same or corresponding parts.

  The present embodiment is an internal combustion engine that performs two-cylinder equidistant combustion. Each cylinder has a pent roof type combustion chamber (not shown), and two intakes are provided on one side of the combustion chamber with the crank axis C therebetween. Two exhaust valves 13 are arranged on the other side of the valve 11.

  The intake valves 11 and 11 and the exhaust valves 13 and 13 are set at different opening and closing timings. Of the two intake valves 11, 11, one exhaust valve 13 ′ located farthest from the previously opened intake valve 11 ′ is set to close later than the closing timing of the other exhaust valve 13. .

  Specifically, as shown in FIG. 9 (a), in the extremely low load region including idling, one intake valve 11 'that opens first opens at a crank angle of about 8 degrees after top dead center, and the other intake valve The valve 11 opens at a crank angle of about 38 degrees after top dead center. Also, one exhaust valve 13 ′ located farthest from one intake valve 11 ′ that opens first closes with a crank angle delayed by about 12 degrees from the closing timing of the other exhaust valve 13. The opening timing of the two exhaust valves 13 ′ and 13 is set to about 46 degrees before the bottom dead center crank angle (see FIG. 9A).

  In the high load range, the opening and closing timings of the two exhaust valves are fixed, and one of the intake valves that opens in advance is opened at a crank angle before top dead center of about 26 degrees, and the other intake valve has a crank angle of 6 after top dead center. It opens at a degree (see FIG. 9B).

  According to this embodiment, of the two intake valves 11, the closing timing of the exhaust valve 13 'located farther from the intake valve 11' opened earlier is set later than the closing timing of the other exhaust valve 13. Further, it is possible to suppress blow-through when scavenging is performed by the fresh air stored in the intake passage 20 ', and the same effect as that of the third embodiment can be obtained.

  FIG. 10 is a view for explaining a spark ignition type internal combustion engine according to a fifth embodiment of the present invention. In the figure, the same reference numerals as those in FIG. 8 denote the same or corresponding parts.

  The present embodiment is an internal combustion engine that performs two-cylinder equidistant combustion, and each cylinder is provided with two intake valves 11 and two exhaust valves 13, and an intake pipe 20 connected to each cylinder is located upstream. And has the same structure as that of the third embodiment.

  A gas fuel injection valve 38 common to each cylinder is disposed on the downstream side of the check valve 30 of the common pipe 20a. The gas fuel injection valve 38 has a gas injection port 38a positioned at the axis of the common pipe 20a, and supplies gas fuel toward the branch portion 20c 'branched from the common pipe 20a to the branch pipes 20c and 20c. Has been placed. Here, the liquid fuel injection valve 23 for supplying gasoline fuel is arranged in each branch pipe 20c, 20c.

  In this embodiment, since the gas fuel is supplied to the branch portion 20c ′ of the common pipe 20a, the pumping loss can be reduced by supplying the gas fuel before the overlap or the first half of the intake stroke.

  Since the gas fuel does not adhere to the wall surface of the intake passage 20 'unlike liquid fuel such as gasoline, it is not necessary to arrange the gas fuel injection valve so as to face the intake valve. For this reason, even with one gas fuel injection valve, gas fuel can be evenly supplied to each cylinder, and combustion can be performed with a uniform air-fuel ratio mixture. As a result, the fuel supply device can be simplified, and high responsiveness and exhaust gas performance can be obtained.

  FIG. 11 is a view for explaining a spark ignition type internal combustion engine according to a sixth embodiment of the present invention. In the figure, the same reference numerals as those in FIG. 8 denote the same or corresponding parts.

  The internal combustion engine of this embodiment includes an external EGR device 42 that recirculates part of the exhaust gas to the intake system. The external EGR device 42 includes an external EGR passage 43 connected to the collecting portion 16 of each exhaust pipe 15, and a particulate trap 44 interposed in the middle of the EGR passage 43 to remove carbon and the like in the exhaust gas. , An EGR cooler 45 for cooling the exhaust gas, and an EGR control valve 46 are provided. The EGR control valve 46 is controlled to be opened and closed by the ECU according to the engine operating state.

  The inlet 43a at the downstream end of the EGR passage 43 is formed upstream of the check valve 30 and downstream of the throttle valve 22a of the common pipe 20a. The introduction port 43a is provided with a venturi portion 43b that generates a negative pressure by reducing the passage area.

  According to the present embodiment, the introduction port 43a for introducing the external EGR gas is provided in the merging portion 20a upstream of the check valve 30 and downstream of the throttle valve 22a. Since the burnt gas in the cylinder after the bottom dead center in the intake stroke can be prevented from reaching the upstream side of the check valve 30, the external EGR gas always flows toward the cylinder on the downstream side. It is possible to prevent the body 22 and the throttle valve 22a from being soiled.

  As described above, when the external EGR gas is introduced into the collecting portion upstream of the throttle valve, particles such as carbon contained in the external EGR gas gradually adhere to and accumulate on the inner wall of the throttle valve and the throttle body. There is a possibility that controllability such as opening degree may be impaired. In this embodiment, the check valve 30 is provided upstream of the intake pipe 20 and the EGR gas is introduced upstream of the check valve 30. Therefore, the burnt in the cylinder after the bottom dead center in the intake stroke Combined with the point that the gas can be prevented from reaching the upstream side of the check valve 30, the throttle valve 22a can be prevented from being soiled. In particular, in the case of an internal combustion engine that performs two-cylinder equidistant combustion, since the intake strokes do not overlap, the effect of the backflow of the burned gas appears remarkably, so the effect is great.

1 Internal combustion engine 2a Cylinder bore (cylinder)
3a Combustion recess (combustion chamber)
3b Intake opening 3c Exhaust opening 11 Intake valve 13 Exhaust valve 20 'Intake passage 20a Common pipe (common intake passage)
20b Branch pipe (branch intake passage)
21 Surge tank 22 Throttle body 22a Throttle valve 25 Variable valve mechanism 30 Check valve 31 Valve seat body 31a Open 32 Lead 38 Gas fuel injection valve 40 Scavenging intake valve 42 External EGR device a Tumble flow C Crank axis E Cylinder axis

Claims (12)

Multiple cylinders,
An intake passage connected to each of the cylinders for generating a tumble of intake air in the cylinder;
An intake valve that opens and closes an intake opening that opens to the cylinder of each intake passage and an exhaust valve that opens and closes an exhaust opening;
A spark ignition internal combustion engine having an overlap period in which the intake valve and the exhaust valve open simultaneously,
A surge tank is connected to the upstream side of the intake passage,
A spark ignition type internal combustion engine, characterized in that a check valve that allows only the flow of intake air to the cylinder is disposed in the vicinity of the connection portion of the surge tank in the intake passage. The spark ignition internal combustion engine according to claim 1,
Each intake passage is connected to the surge tank,
The spark ignition internal combustion engine, wherein the check valve is disposed in each intake passage. The spark ignition internal combustion engine according to claim 2,
The spark-ignition internal combustion engine, wherein the check valve is sandwiched between joint surfaces of the intake passages and the surge tank and is fastened and fixed together with the intake passages. The spark ignition internal combustion engine according to claim 1,
A spark ignition type internal combustion engine characterized in that the closing timing of each intake valve in a high load range is set after bottom dead center in an intake stroke. The spark ignition internal combustion engine according to claim 4,
A spark ignition type internal combustion engine, wherein a plurality of intake valves are arranged in each cylinder, and an intake valve farthest from the exhaust valve among the intake valves opens earlier than other intake valves. The spark ignition internal combustion engine according to claim 4,
Each cylinder has a pent roof type combustion chamber,
When viewed in the cylinder axis direction, two intake valves are arranged on one side across the crank axis of the combustion chamber, and two exhaust valves are arranged on the other side,
A spark ignition type internal combustion engine characterized in that one of the two intake valves is opened ahead of the other and the exhaust valve far from the one intake valve is closed later than the other exhaust valve. The spark ignition type internal combustion engine according to any one of claims 1 to 6,
A spark ignition type internal combustion engine, characterized in that a gas fuel injection valve for supplying gas fuel or liquid-injected LPG fuel downstream of the check valve of the intake passage is disposed in the intake passage. The spark ignition internal combustion engine according to claim 1,
A spark ignition type internal combustion engine comprising a hydraulic variable valve mechanism that variably controls opening and closing timings of the intake and exhaust valves. The spark ignition internal combustion engine according to claim 1,
The check valve is a reed valve, and the reed valve opens an opening formed in the valve seat body by a reed when the downstream side of the reed valve in the intake passage is a negative pressure, and closes when the pressure is a positive pressure. Configured as
A spark ignition type internal combustion engine, wherein the lead opening and closing direction is arranged to be a crank axis direction. The spark ignition internal combustion engine according to claim 1,
The internal combustion engine performs combustion at equal intervals in two cylinders, and the intake passage has one common intake passage on the upstream side and a branched intake passage branched from the common intake passage, A spark ignition type internal combustion engine, wherein the check valve is arranged. The spark ignition internal combustion engine according to claim 10,
A gas fuel injection valve common to each cylinder is disposed downstream of the check valve of the common intake passage, and the gas fuel injection valve supplies gas fuel to a branch portion of each intake passage to each cylinder. A spark ignition internal combustion engine characterized by being arranged. The spark ignition internal combustion engine according to claim 10,
A throttle body with a built-in throttle valve is disposed on the upstream side of the check valve of the common intake passage,
An external EGR device that recirculates a part of the exhaust gas to the intake system is connected between the throttle body and the check valve.

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