JP2004286012A - Compression ignition internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a compression ignition internal combustion engine with a cam-type engine capable of performing internal EGR only during compression ignition combustion by easy control while keeping cost low. <P>SOLUTION: Suction valves 10, 11 openingly/closingly driven by a cam are arranged on two suction ports 6a, 6b in a combustion chamber 1, and a first exhaust valve 12, a second exhaust valve 13 openingly/closing driven by the cam are arranged on a first exhaust port 9a and a second exhaust port 9b. A suction air throttle 14 is mounted in the middle of a second exhaust branch passage 8b, and an exhaust throttle 15 which is closed only during a suction air stroke of a spark ignition combustion is mounted in the middle of a second exhaust branch passage 8b. During an exhaust stroke, a first exhaust valve 12 is opened, and the two suction valves 10, 11 are opened during a suction stroke. During the latter half of the suction stroke, a second exhaust valve 13 is opened regardless of whether the combustion is compression ignition combustion or spark ignition combustion. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a compression ignition internal combustion engine, and more particularly to a compression ignition internal combustion engine that switches between spark ignition combustion and compression ignition combustion.

  2. Description of the Related Art Conventionally, there is a compression ignition engine that performs compression ignition combustion in a low load and medium load region and performs spark ignition combustion in a high load region. In this engine, as shown in FIG. 10, during the intake stroke at the time of compression ignition combustion, the intake valve is opened with a timing lift amount as shown by the symbol A and the exhaust valve is opened with the timing as shown by the symbol B or C. By opening with the lift amount, high-temperature exhaust gas discharged from the exhaust valve to the exhaust passage in the exhaust stroke is recirculated to the combustion chamber to perform internal EGR, and as a result, the combustion chamber is heated to compress and ignite. In addition, during spark ignition combustion, the use of high-temperature exhaust gas may promote the occurrence of knocking. Therefore, it is desirable not to open the exhaust valve during the intake stroke. For example, in Patent Literature 1, an electromagnetic valve drive device is used to control exhaust valves corresponding to intake strokes during compression ignition combustion and spark ignition combustion, respectively.

JP 2001-349219 A

  However, since the above-mentioned electromagnetic valve driving device is very expensive, there is a problem that the cost of the entire engine eventually increases. Opening and closing the exhaust valve using the electromagnetic valve driving device for compression ignition combustion and spark ignition combustion, respectively, involves complicated control. In addition, many existing engines use cams to control valves. Therefore, remodeling such an existing engine to incorporate an electromagnetic valve driving device is a drastic remodeling, and it is preferable if the existing cam engine can be used.

  SUMMARY OF THE INVENTION The present invention has been made in order to solve such a problem. In a cam-type engine, a compression-ignition internal combustion engine capable of performing internal EGR only at the time of compression-ignition combustion by simple control while keeping costs low is provided. The purpose is to provide.

  A compression-ignition internal combustion engine according to the present invention is a compression-ignition internal combustion engine that switches between compression ignition combustion and spark ignition combustion, and is provided in a combustion chamber in which an intake passage and an exhaust passage communicate with each other, and provided in the intake passage. An intake means for opening and closing the exhaust passage, and an exhaust passage provided in the exhaust passage and driven by a cam to open and close the exhaust passage, and at least during the exhaust stroke and the intake stroke at the time of compression ignition combustion and spark ignition combustion, respectively. Exhaust means, which is provided in the exhaust passage, recirculates exhaust gas to the combustion chamber by opening at least during an intake stroke during compression ignition combustion, and at least during an intake stroke during spark ignition combustion. An exhaust gas recirculation preventing means for preventing recirculation of exhaust gas to the combustion chamber by closing the valve while the exhaust means is open. Here, “during the exhaust stroke” includes not only the entire period during the exhaust stroke but also a part of the period during the exhaust stroke. The same applies to “during the intake stroke”.

The exhaust passage includes a merging passage provided for each combustion chamber, and first and second exhaust branching passages that branch upstream of the merging passage and communicate with the combustion chamber, and the exhaust means is provided in the first exhaust branching passage. A first exhaust valve that opens only in the exhaust stroke during compression ignition combustion and spark ignition combustion; and a second exhaust valve that is provided in the second exhaust branch and opens at least during the intake stroke. May be an exhaust throttle provided in the second exhaust branch so as to always shut off the second exhaust branch during spark ignition combustion and to always open the second exhaust branch during compression ignition combustion.
Further, the exhaust means includes a single exhaust valve provided for each combustion chamber which is opened in both the exhaust stroke and the intake stroke via a two-stage cam, and the exhaust gas recirculation prevention means is provided in the exhaust passage. The exhaust throttle may be opened during the exhaust stroke to perform exhaust and shut off the exhaust passage at least during the opening of the exhaust valve in the intake stroke during spark ignition combustion.
Further, a plurality of combustion chambers are provided, and the exhaust means includes a plurality of exhaust valves provided for each combustion chamber and opened at least during an intake stroke, and the exhaust passage has a flow path defined by the exhaust valve opened at least during the intake stroke. A plurality of exhaust branches that are opened and closed, and an exhaust junction that combines these exhaust branches are provided. Exhaust gas recirculation prevention means is provided in the exhaust junction so that at least the exhaust stroke of the intake stroke during spark ignition combustion is performed. An exhaust throttle that shuts off the exhaust junction while the valve is open may be used.
The combustion chamber and the exhaust passage are communicated by a first exhaust port and a second exhaust port, and the exhaust passage includes both a first exhaust port and a second exhaust port at an upstream end thereof. And a first exhaust valve that opens the first exhaust port only during the exhaust stroke during compression ignition combustion and spark ignition combustion. A second exhaust valve that opens the second exhaust port at least during an intake stroke, wherein the exhaust gas recirculation prevention means is configured such that the first exhaust port and the second exhaust port are not in communication with each other when the valve is closed. A shutter valve that separates the communication chamber, and the shutter valve opens such that the first exhaust port and the second exhaust port are in a mutually communicating state at least during an intake stroke during compression ignition combustion. You may comprise.
In addition, an intake control means for restricting inflow of fresh air into the combustion chamber is provided, and the amount of fresh air is restricted by the intake control means during an intake stroke during compression ignition combustion, whereby exhaust gas is recirculated from the exhaust means. Is preferably increased.

  According to the present invention, the combustion chamber in which the intake passage and the exhaust passage communicate with each other, the intake means provided in the intake passage and driven to open and close through the cam, and the combustion chamber provided in the exhaust passage and opened and closed through the cam Exhaust means that is driven and opened during an exhaust stroke and an intake stroke during compression ignition combustion and spark ignition combustion, respectively, and prevents recirculation of exhaust gas to a combustion chamber during an intake stroke during spark ignition combustion. Since the exhaust gas recirculation prevention means is provided, the internal EGR can be performed only at the time of compression ignition combustion by simple control while suppressing the cost in the cam type engine.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

Embodiment 1 FIG.
FIG. 1 is a schematic plan view of the vicinity of one combustion chamber of a compression ignition engine used for a gas engine heat pump (GHP) or the like as the compression ignition internal combustion engine according to the first embodiment. An intake passage 2 and an exhaust passage 3 are connected to a combustion chamber 1 of the engine. The intake passage 2 is composed of an intake merging passage 4 and intake branch passages 5a and 5b branched into two at the tip thereof. These two intake branch passages 5a and 5b connect two intake ports 6a and 6b having substantially the same diameter. Each is communicated with the combustion chamber 1 via a corresponding one of them. Further, a fuel supply passage 4a is communicated with the intake merging passage 4, and gas serving as fuel is supplied to the intake passage through the fuel supply passage 4a. As a result, so-called premixed compression ignition combustion is performed in which the fuel and the air are premixed before flowing into the combustion chamber 1 and then are compression ignited and burned in the combustion chamber 1. On the other hand, the exhaust passage 3 is composed of an exhaust junction 7 and a first exhaust branch 8a and a second exhaust branch 8b branched into two at the tip thereof. The first exhaust port 9a and the second exhaust port 9b are different from each other and communicate with the combustion chamber 1. As shown in FIG. 1, the second exhaust port 9b has a smaller diameter than the first exhaust port 9a.

  Further, intake valves 10 and 11 as intake means are disposed at the two intake ports 6a and 6b, respectively, and these two intake valves 10 and 11 are opened and closed via an intake valve cam (not shown). It has a configuration. On the other hand, a first exhaust valve 12 and a second exhaust valve 13 as exhaust means are disposed at the first exhaust port 9a and the second exhaust port 9b, respectively, and these first exhaust valve 12 and second exhaust valve 13 are also provided. Further, it is configured to be opened and closed via a cam for an exhaust valve (not shown). Further, an intake throttle 14 is attached in the middle of the intake junction 4 as intake control means for narrowing the intake junction 4 and restricting the flow of fresh air into the combustion chamber 1. Further, an exhaust throttle 15 for opening / closing the second exhaust branch 8b is attached as an exhaust gas recirculation prevention means in the middle of the second exhaust branch 8b connected to the second exhaust port 9b. The exhaust throttle 15 is always closed during spark ignition combustion and is always opened during compression ignition combustion. Although not shown, a spark plug for spark ignition combustion is arranged in the combustion chamber 1.

  Here, how to control the opening and closing of the two intake valves 10 and 11, the first exhaust valve 12 and the second exhaust valve 13 in the intake stroke and the exhaust stroke will be described with reference to FIG. The control in the intake stroke and the exhaust stroke is performed such that a constant opening / closing operation is performed regardless of the compression ignition combustion and the spark ignition combustion. As shown in FIG. 2, in the exhaust stroke, the first exhaust valve 12 is opened with a timing lift amount as indicated by reference symbol E. In the intake stroke, the two intake valves 10 and 11 are both opened with a timing lift amount indicated by reference symbol D, and in the second half of the intake stroke, the second exhaust valve 13 sets the timing lift amount indicated by reference numeral F. Opened in. That is, the first exhaust valve 12 opens only during the exhaust stroke, and the second exhaust valve 13 opens only during the latter half of the intake stroke.

  Next, the operation of the compression ignition engine according to the first embodiment will be described. This engine is driven by switching between compression ignition combustion and spark ignition combustion, that is, performs compression ignition combustion in low load and medium load regions, and performs spark ignition combustion in high load regions.

  First, the operation during compression ignition combustion will be described. During the compression ignition combustion, in the exhaust stroke, the exhaust throttle 15 attached in the middle of the second exhaust branch passage 8b is opened. In the intake stroke, the exhaust throttle 15 and the intake throttle 14 are both opened.

  In the exhaust stroke, the first exhaust valve 12 opens with the timing lift amount indicated by reference symbol E and the second exhaust valve 13 closes, and the high-temperature exhaust gas generated in the combustion chamber 1 The exhaust gas is discharged to the exhaust junction 7 only through the exhaust branch passage 8a. On the other hand, in the intake stroke, if the two intake valves 10 and 11 are both opened with a timing lift amount such as D in a state where the intake throttle 14 is opened, the mixture of air and fuel is taken into the intake branch as fresh air. It flows into the combustion chamber 1 through the passages 5a and 5b. Further, in the intake stroke, while the exhaust throttle 15 is open, the second exhaust valve 13 opens with a timing lift amount such as F in the latter half of the intake stroke, so as shown by a dotted line in FIG. Then, the high-temperature exhaust gas discharged into the exhaust passage 3 in the exhaust stroke flows back into the combustion chamber 1 through the second exhaust branch passage 8b. Then, the mixture in the combustion chamber 1 is heated by the high-temperature exhaust gas, and compression ignition is performed in this state. Thus, compression ignition combustion can be performed efficiently using natural gas or the like having low ignitability as fuel. It is assumed that the exhaust throttle 15 is always open not only in the exhaust stroke and the intake stroke but also in the compression stroke and the expansion stroke, that is, at all times during the compression ignition combustion.

  Here, during the above-described intake stroke, it is preferable that the opening of the intake throttle 14 be reduced to narrow the intake merging flow path 4, thereby restricting the amount of fresh air flowing into the combustion chamber 1. When the inflow of fresh air is restricted by the intake throttle 14 in this manner, the recirculation amount of the exhaust gas can be increased accordingly, and the air-fuel mixture in the combustion chamber 1 can be efficiently heated. Further, in a state where the flow of fresh air into the combustion chamber 1 is restricted, the inside of the combustion chamber 1 has a negative pressure until the second exhaust valve 13 is opened in the latter half of the intake stroke. The high-temperature exhaust gas flows into the combustion chamber 1 at a stretch, and as a result, the temperature rise effect by the adiabatic compression is added, and the mixture in the combustion chamber 1 can be heated more efficiently.

  Next, the operation during spark ignition combustion will be described. During the spark ignition combustion, the exhaust throttle 15 is always closed, while the intake throttle 14 is opened at an appropriate opening during the intake stroke. In the exhaust stroke, when the first exhaust valve 12 is opened with a timing lift amount indicated by reference character E, high-temperature exhaust gas generated in the combustion chamber 1 is discharged to the first exhaust gas, similarly to the exhaust stroke during compression ignition combustion. The exhaust gas is discharged to the exhaust junction 7 through the branch passage 8a. Also, in the intake stroke, if the two intake valves 10 and 11 are both opened with a timing lift amount such as D in a state in which the intake throttle 14 is opened, the air-fuel mixture becomes fresh air and the intake branch passages 5a and 5 5b flows into the combustion chamber 1 from the two intake ports 6a and 6b.

  By the way, since the opening and closing timing of the second exhaust valve 13 is determined by the cam, similarly to the above-described compression ignition combustion, in the latter half of the intake stroke also in the spark ignition combustion, the timing lift amount as indicated by the symbol F is used. Will open the valve. However, in this embodiment, since the exhaust throttle 15 is closed during the intake stroke during spark ignition combustion, the second exhaust branch 8b is shut off by the exhaust throttle 15 even if the second exhaust valve 13 is opened. Is done. Therefore, high-temperature exhaust gas discharged from the first exhaust port 9a to the exhaust junction 7 in the exhaust stroke is prevented from flowing back into the combustion chamber 1 through the second exhaust branch passage 8b during spark ignition combustion. You. Then, as described above, the air-fuel mixture flowing into the combustion chamber 1 from the two intake ports 6a and 6b is sufficiently compressed, and further ignited by a spark plug (not shown) to perform spark ignition combustion. As described above, spark ignition combustion can be performed in a state where exhaust gas is not recirculated in the combustion chamber 1, so that occurrence of knocking due to high-temperature exhaust gas is prevented, and thereby stable spark ignition combustion is performed. It becomes possible.

As described above, the two intake valves 10 and 11, the first exhaust valve 12, and the second exhaust valve 13 are driven by the cams to perform a constant opening and closing operation during both the compression ignition combustion and the spark ignition combustion. By closing the valve 15 only during the intake stroke during spark ignition combustion, it is possible to easily control the high-temperature exhaust gas to recirculate in the combustion chamber during compression ignition combustion and not to recirculate the exhaust gas during spark ignition combustion.
In addition, since the opening and closing drive of the valve via the cam is widely used in the existing engine, the existing cam-type engine can be diverted without significant modification.
In addition, the compression ignition engine of the present invention does not use an electromagnetic valve type driving device, which is very expensive as in the prior art, so that the cost of the entire engine can be kept low.

  In the above-described first embodiment, the exhaust throttle 15 is always closed during spark ignition combustion. Alternatively, only the intake stroke during spark ignition combustion may be closed. The closed state may be maintained at all times while the exhaust valve 13 is opened, that is, only during the period of the reference F.

  Further, instead of opening the second exhaust valve 13 in the latter half of the intake stroke with the timing lift amount as indicated by the symbol F, it opens in the first half of the intake stroke as shown in FIG. Any timing lift amount may be used as long as there is at least a period during which the valve opens during the intake stroke, such as opening from the exhaust stroke to the intake stroke as shown in FIG. When the second exhaust valve 13 opens from the exhaust stroke to the intake stroke as described above, not only the first exhaust valve 12 but also the second exhaust valve 13 can contribute to exhaust in the exhaust stroke. In addition, the exhaust gas can be efficiently discharged.

  Further, in the above-described embodiment, the second exhaust port 9b has a smaller diameter than the first exhaust port 9a, but instead, the first exhaust port 9a and the second exhaust port 9b have substantially the same diameter as each other. May have.

Embodiment 2 FIG.
Next, a second embodiment of the present invention will be described. The compression ignition engine according to the second embodiment is different from the compression ignition engine according to the first embodiment shown in FIG. 1 in that the second exhaust valve 13 is added to the latter half of the intake stroke, and the first exhaust valve 12 is also connected during the exhaust stroke. It is likewise opened. That is, in FIG. 2, in the exhaust stroke, the second exhaust valve 13 is opened together with the first exhaust valve 12 by a timing lift amount indicated by reference symbol E, and in the intake stroke, as in the first embodiment, the second exhaust valve 13 Only the valve is opened with a timing lift amount such as the reference symbol F. Such opening and closing operation of the second exhaust valve 13 is realized by using a two-stage cam having two projections as a cam for the second exhaust valve 13. In the present embodiment, the second exhaust valve 13 performs an exhaust function during the exhaust stroke during spark ignition combustion, and the second exhaust valve 13 opens during the intake stroke during spark ignition combustion. However, since it is necessary to invalidate the recirculation of exhaust gas, the exhaust throttle 15 is closed only during the intake stroke during spark ignition combustion.

According to the configuration described above, the internal EGR can be performed only during the compression ignition combustion by a simple control with a low cost in a cam type engine, and the same effect as in the first embodiment can be obtained. .
Furthermore, in the second embodiment, since not only the first exhaust valve 12 but also the second exhaust valve 13 are opened in the exhaust stroke, the two valves of the first exhaust valve 12 and the second exhaust valve 13 are used. The exhaust gas can be exhausted, so that the exhaust gas can be efficiently exhausted.

  In the above-described second embodiment, the second exhaust valve 13 is opened during the exhaust stroke with a timing valve amount such as E and at the latter half of the intake stroke with a timing valve amount such as F. Instead, as shown in FIG. 3A, during the exhaust stroke, the valve is opened with a timing valve amount as indicated by E and at the beginning of the intake stroke as indicated by F. It may be opened by a timing valve amount. Further, the second exhaust valve 13 may be opened with a timing valve amount such as a reference F shown in FIG. In FIG. 4, the timing lift amount of the first exhaust valve 12 and the two intake valves 10 and 11 is omitted in order to give priority to the opening and closing operation of the second exhaust valve 13.

Embodiment 3 FIG.
Next, a third embodiment of the present invention will be described with reference to FIG. The compression ignition engine according to the third embodiment is implemented in a mode in which only one exhaust throttle provided for each combustion chamber in the above-described embodiment is provided as an exhaust system. As shown in FIG. 5, in the in-line four-cylinder compression ignition engine, an intake passage 22 and an exhaust passage 24 are connected to the four combustion chambers 21. The intake passage 22 includes two intake branch passages 22a provided for each combustion chamber 21 of each cylinder, and an intake collective passage 22b upstream of the two intake branch passages 22a. The intake throttle 23 is provided in the intake manifold 22b.

  On the other hand, the exhaust passage 24 includes four first exhaust branch passages 24a corresponding to the first exhaust branch passage 8a in FIG. 1 and a first exhaust merging passage 24b that collects the four first exhaust branch passages 24a downstream. 1, four exhaust branch passages 24c corresponding to the second exhaust branch passage 8b in FIG. 1, a second exhaust merging passage 24d that combines the four second exhaust branch passages 24c downstream, and An exhaust manifold 25 is provided to combine the second exhaust merging channels 24b and 24d downstream. Only one exhaust throttle 26 is provided in the second exhaust junction 24d as a common one for each combustion chamber.

  In such a compression ignition engine, the two intake valves, the first exhaust valve, and the second exhaust valve provided in each combustion chamber 21 are controlled to open and close similarly to the operation in the first or second embodiment. Further, similarly to the above embodiment, the exhaust throttle 26 is closed only while the second exhaust valve is opened at least in the intake stroke of spark ignition combustion. Therefore, the same effect as described above can be achieved without providing an exhaust throttle for each combustion chamber.

Embodiment 4 FIG.
Next, a fourth embodiment of the present invention will be described with reference to FIG. The compression ignition engine according to the fourth embodiment differs from the first embodiment in that the number of exhaust valves is one instead of two. One exhaust port 32 is formed in the combustion chamber 30, and an exhaust valve 31 as an exhaust unit that is driven to open and close via a two-stage cam is disposed in the exhaust port 32. The exhaust port 32 is connected to an exhaust passage 33, and the exhaust passage 33 has an exhaust throttle 34 in the middle thereof. The exhaust throttle 34 is closed only during the spark ignition combustion, at least while the exhaust valve 31 is opened during the intake stroke.
Here, the exhaust valve 31 is opened with a timing lift amount indicated by reference numerals G1 and G2 in FIG. 7, that is, the exhaust valve 31 opened during the exhaust stroke does not completely close but maintains a minute lift amount. It is opened in the first half during the intake stroke. Also, during the intake stroke, the two intake valves 10 and 11 are opened with a timing lift amount as indicated by reference symbol D as in the first embodiment. Note that these opening / closing controls are performed so as to be constant regardless of compression ignition combustion and spark ignition combustion.

  During compression ignition combustion, the exhaust throttle 34 is opened during the exhaust stroke, the exhaust throttle 34 is kept open during the intake stroke, and the intake throttle 14 is also opened at an appropriate required opening degree. As a result, during the exhaust stroke, the exhaust valve 31 is opened to exhaust the exhaust gas to the exhaust passage 33. During the intake stroke, the two intake valves 10 and 11 are opened to allow fresh air to flow. During the first half of the intake stroke, the exhaust valve 31 opens, and high-temperature exhaust gas recirculates into the combustion chamber 30 to perform internal EGR.

Further, during spark ignition combustion, the exhaust throttle 34 is opened during the exhaust stroke, and during the intake stroke, the exhaust throttle 34 is closed, while the intake throttle 14 is opened at an appropriate required opening degree. Therefore, during the exhaust stroke, the exhaust valve 31 is opened, and the exhaust gas is discharged to the exhaust passage 33. During the intake stroke, the two intake valves 10 and 11 are opened, and fresh air flows in. Since the exhaust throttle 34 is closed, even if the exhaust valve 31 is opened in the first half of the intake stroke, high-temperature exhaust gas is prevented from flowing back into the combustion chamber 30.
Therefore, even with such a configuration, the internal EGR can be performed only at the time of compression ignition combustion by simple control while suppressing the cost in the cam type engine, and the same effect as in the first embodiment can be obtained. it can.
The exhaust throttle is installed as close to the exhaust valve as possible. By doing so, the recirculation of the exhaust gas remaining between the exhaust valve and the exhaust throttle can be reduced.

Note that, instead of opening the exhaust valve 31 in the first half of the intake stroke while maintaining a small lift amount as in the fourth embodiment, the exhaust valve 31 is completely closed once at the end of the exhaust stroke, and then the second half of the intake stroke, etc. It may be opened again somewhere during the intake stroke.
Also, in the fourth embodiment, as in the third embodiment, only one exhaust throttle may be prepared as an exhaust system.
Furthermore, two exhaust valves that open to both the exhaust and intake strokes using a two-stage cam as in the fourth embodiment may be provided for each combustion chamber.
Further, in the fourth embodiment, all the exhaust branch paths are merged into one exhaust merging path, and one exhaust throttle is provided in the one exhaust merging path. However, the present invention is not necessarily limited to this. In the V-type engine, a plurality of exhaust branch lines may be merged into two exhaust merging passages, and one exhaust throttle may be arranged in each exhaust merging passage, that is, two exhaust throttles in total. That is, if at least two or more exhaust branch paths are merged into one exhaust junction, and one exhaust throttle is arranged in the exhaust junction, the number of exhaust throttles can be reduced.

Embodiment 5 FIG.
Next, a fifth embodiment of the present invention will be described with reference to FIG. FIG. 8 illustrates only the exhaust path portion in a three-dimensional manner with respect to the embodiment of FIG. 1 to facilitate understanding. The compression ignition engine according to the present embodiment is different from the above-described embodiment in the configuration of the exhaust passage and the exhaust gas recirculation prevention means, and the other parts are the same as those in the above-described first embodiment. Shall be. A first exhaust port 9a and a second exhaust port 9b are provided in the upper part of the combustion chamber 1 as in the above embodiment. An exhaust passage 103 is connected to the first exhaust port 9a and the second exhaust port 9b. The exhaust passage 103 includes a single tubular communication chamber 108 connected to both the exhaust ports so as to include both the first exhaust port 9a and the second exhaust port 9b, and an exhaust main passage 107 provided downstream thereof. And In the communication chamber 108, a partition 151 having a low height is provided upright. The partition 151 rises from a portion between the exhaust ports 9a and 9b on a bottom wall 153 which is a wall on which the first exhaust port 9a and the second exhaust port 9b are formed and which is also a bottom surface of the communication chamber 108. ing. The communication chamber 108 is provided with a shutter valve 115. The shutter valve 115 is slidably provided so as to abut or separate from the partition 151. When the shutter valve 115 is in a closed state, that is, in a contact state with the partition 151, the inside of the communication chamber 108 is divided into a first exhaust chamber 108a and a second exhaust chamber 108b which cannot communicate without passing through the combustion chamber 1. Is done. That is, the communication chamber 108 is partitioned by the shutter valve 115 such that the first exhaust port 9a and the second exhaust port 9b are not communicated with each other. When the shutter valve 115 is closed, the first exhaust chamber 108a is a room that communicates with the main exhaust passage 107, and the second exhaust chamber 108b is a room that is isolated from the main exhaust passage 107.

  Next, the operation of the compression ignition engine having such a configuration will be described. The opening / closing timing of the shutter valve 115 is the same as that of the exhaust throttle 15 of the first embodiment, and the opening / closing timing of the first exhaust valve 12 and the second exhaust valve 13 is also the same as that of the first embodiment. Therefore, in the exhaust stroke during the compression ignition combustion, the first exhaust valve 12 is opened, the second exhaust valve 13 is closed, and the shutter valve 115 is opened. As a result, the exhaust gas from the combustion chamber 1 is exhausted through the first exhaust port 9a, the communication chamber 108, and the main exhaust passage 107, as shown by the dashed line in the figure. On the other hand, in the intake stroke during compression ignition combustion, the first exhaust valve 12 is closed, the second exhaust valve 13 is opened, and the shutter valve 115 is opened. As a result, the exhaust gas exhausted to the communication chamber 108 during the exhaust stroke and present near the first exhaust port 9a passes between the shutter valve 115 and the partition 151 as shown by the solid line in FIG. The gas is returned into the combustion chamber 1 through the port 9b.

  Also, at the time of spark ignition combustion, the first exhaust valve 12 and the second exhaust valve 13 perform the same opening and closing operation as at the time of compression ignition combustion. However, since the shutter valve 115 is always kept closed, the exhaust gas exhausted to the communication chamber 108 during the exhaust stroke is returned to the combustion chamber 1 from the second exhaust port 9b which is open. Can be prevented. As described above, also in the present embodiment, the same operation and effect as those in the first embodiment can be obtained.

  Further, the recirculation of the exhaust gas during the compression ignition combustion is performed by simply discharging the exhaust gas exhausted in the exhaust stroke and existing in the communication chamber 108 from the same communication chamber 108 through the second exhaust port 9b. Therefore, as compared to a mode in which the ends of the first exhaust branch passage 8a and the second exhaust branch passage 8b are drawn around and sucked as in the first embodiment, the distance is shorter and the flow path resistance is smaller. In this manner, the exhaust gas can be recirculated. Therefore, more efficient EGR can be realized.

  In this embodiment, the same modifications as in the first embodiment can be made. That is, the shutter valve 115 may be closed only during the intake stroke during spark ignition combustion, or may be kept closed at least while the second exhaust valve 13 is opened.

  Further, the operation of the second exhaust valve 13 can be set as shown in FIG. 3A or 3B, or the relationship between the diameters of the second exhaust port 9b and the first exhaust port 9a can be changed. Is the same as in the first embodiment.

  In addition, the manner in which the shutter valve 115 separates the inside of the communication chamber 108 may be as follows. As shown in FIG. 9, a partition 251 is provided in the communication chamber 108 so that the communication chamber 108 can be divided into a first exhaust chamber 108 a and a second exhaust chamber 108 b by itself. The partition 251 extends from between the first exhaust port 9a and the second exhaust port 9b, and its periphery is connected to the bottom surface or side surface of the communication chamber 108. A communication port 255 is formed in a lower portion of the partition 251, that is, in a portion near the first exhaust port 9 a and the second exhaust port 9 b. Further, a shutter valve 115 is provided for the communication chamber 108 so that the communication port 255 can be selectively opened and closed. Even in such a configuration, the exhaust gas can be recirculated through the communication port 255 during the intake stroke of the compression ignition combustion, and the same operation as the configuration in FIG. 8 can be obtained.

The present invention is not limited to the above embodiment, and can be implemented with various modifications. For example, as the intake throttle in the above-described embodiment, a shutter valve as shown in the fifth embodiment or the like can be used in addition to the butterfly valve. Further, the recirculation amount of the exhaust gas may be adjusted by changing the opening degree of the exhaust throttle or the shutter valve as needed.
Further, the timing of switching between compression ignition combustion and spark ignition combustion is not limited to using the load of the engine as a reference. Further, in the above-described embodiment, the mode of switching between the premixed compression ignition combustion and the spark ignition combustion is described. However, the present invention is not limited to this. It is also possible to apply the present invention to a mode in which switching is made between an ignition method in which fuel is directly injected into gas compressed by a piston from an arranged fuel injection valve) and spark ignition combustion.
Further, in the above-described embodiment, natural gas is used as fuel, but gas fuel such as city gas and propane gas can be used as it is instead. Further, the compression ignition internal combustion engine of the present invention may be implemented using gasoline, light oil or the like as fuel. Further, the number of cylinders of the engine is not limited to four cylinders, but may be six or eight cylinders. The type thereof is not limited to the in-line type but may be the V type or the horizontally opposed type, and is not particularly limited. Further, the number of intake passages and the number of intake valves for each cylinder are not limited to those in the above embodiment.

FIG. 2 is a schematic plan view of the vicinity of the combustion chamber of the compression ignition engine according to Embodiment 1 of the present invention. FIG. 3 is a diagram showing an opening and closing operation of a valve according to the first embodiment. FIG. 5 is a diagram showing a modification of the opening and closing operation of the valve according to the first embodiment. FIG. 10 is a diagram showing an opening and closing operation of a valve according to the second embodiment. FIG. 13 is a schematic diagram showing an intake / exhaust system according to a third embodiment. FIG. 13 is a schematic diagram of the vicinity of a combustion chamber in Embodiment 4 as seen in a plane. FIG. 14 is a diagram showing an opening and closing operation of a valve according to the fourth embodiment. FIG. 15 is a view of a substantially same mode as FIG. 1 in a fifth embodiment. FIG. 9 is a diagram illustrating a partitioning mode of a communication chamber different from the configuration in FIG. 8 according to the fifth embodiment. FIG. 7 is a view showing an opening and closing operation of a valve in a conventional compression ignition engine.

Explanation of reference numerals

  1,21,30 combustion chamber, 2,22 intake passage, 3,24,33,103 exhaust passage, 10,11 intake valve, 12 first exhaust valve, 13 second exhaust valve, 14,23 intake throttle, 15, 26, 34 Exhaust throttle, 31 Exhaust valve, 108 Communication chamber, 115 Shutter valve.

Claims (6)

In a compression ignition internal combustion engine that performs switching between compression ignition combustion and spark ignition combustion,
A combustion chamber in which the intake passage and the exhaust passage communicate with each other;
An intake means provided in the intake passage for opening and closing the intake passage;
Exhaust means provided in the exhaust passage, driven by the cam to open and close the exhaust passage and open the exhaust passage at least during the compression stroke and the spark ignition combustion during the respective exhaust strokes and during the intake stroke,
The exhaust gas is provided in the exhaust passage and recirculated to the combustion chamber by opening at least during an intake stroke during compression ignition combustion, and at least the exhaust means is opened during an intake stroke during spark ignition combustion. A compression ignition internal combustion engine comprising exhaust gas recirculation preventing means for preventing recirculation of exhaust gas to the combustion chamber by closing the valve during the operation. The exhaust passage includes a merging path provided for each combustion chamber, and first and second exhaust branch paths that branch upstream of the merging path and communicate with the combustion chamber.
The first exhaust valve is provided in the first exhaust branch, and is provided only in the exhaust stroke during compression ignition combustion and spark ignition combustion. The first exhaust valve is provided in the second exhaust branch, and is provided at least in the intake stroke. 2 exhaust valves,
The exhaust gas recirculation prevention means is an exhaust throttle that is provided in the second exhaust branch and always shuts off the second exhaust branch during spark ignition combustion, and always opens the second exhaust branch during compression ignition combustion.
The compression ignition internal combustion engine according to claim 1, wherein: The exhaust means includes a single exhaust valve provided for each combustion chamber that opens in both the exhaust stroke and the intake stroke via a two-stage cam,
The exhaust gas recirculation prevention means is provided in an exhaust passage, opens and exhausts during an exhaust stroke, and shuts off the exhaust passage during at least the exhaust valve of an intake stroke during spark ignition combustion. The throttle,
The compression ignition internal combustion engine according to claim 1, wherein: A plurality of the combustion chambers are provided,
The exhaust means includes a plurality of exhaust valves provided for each combustion chamber and opened at least during an intake stroke,
The exhaust passage includes a plurality of exhaust branch passages whose passages are opened and closed by the exhaust valve that opens at least during an intake stroke, and an exhaust merging passage that unifies these exhaust branch passages into one.
The exhaust gas recirculation prevention means is an exhaust throttle that is provided in the exhaust merge passage and shuts off the exhaust merge passage during at least the exhaust valve opening of an intake stroke during spark ignition combustion.
The compression ignition internal combustion engine according to claim 1 or 3, wherein: The combustion chamber and the exhaust passage are connected by a first exhaust port and a second exhaust port,
The exhaust passage has, at its upstream end, a single tubular communication chamber connected to both exhaust ports so as to include both the first exhaust port and the second exhaust port,
The exhaust means has a first exhaust valve that opens the first exhaust port only during an exhaust stroke during compression ignition combustion and spark ignition combustion, and a second exhaust valve that opens the second exhaust port at least during an intake stroke. And
The exhaust gas recirculation prevention means has a shutter valve that separates the communication chamber so that the first exhaust port and the second exhaust port are not in communication with each other when the valve is closed. Opening the first exhaust port and the second exhaust port so that they are in communication with each other at least during the intake stroke.
The compression ignition internal combustion engine according to claim 1, wherein:   Further comprising intake control means for restricting the flow of fresh air into the combustion chamber, and restricting the flow of fresh air by the intake control means during an intake stroke at the time of compression ignition combustion, whereby exhaust gas from the exhaust means is reduced. The compression ignition internal combustion engine according to any one of claims 1 to 5, wherein the recirculation of the fuel is increased.

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