JP2004293341A - Compression ignition internal combustion engine and its exhaust circulation amount control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a compression ignition internal combustion engine and its exhaust gas circulation amount control method capable of obtaining a compression end temperature sufficient for ignition without using a heating device by circulating exhaust gas with good efficiency. <P>SOLUTION: An exhaust valve means comprising two exhaust valves is provided to a compression ignition internal combustion engine. In an exhaust stroke, a first exhaust valve is opened to exhaust the exhaust gas (D), and a second exhaust valve is opened immediately before the end of the exhaust stroke to a first half of an intake stroke for circulating the exhaust gas (E). In the intake stroke, the second exhaust valve continues to open for a predetermined time keeping a micro lift volume t constant, and the micro lift volume t remains a value less than a safe lift volume not interfered with a piston of an upper dead center. After the second exhaust valve is fully opened, the intake valve is opened so as to absorb mixture of air and fuel (F). <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a compression ignition internal combustion engine and an exhaust gas recirculation control method.
[0002]
[Prior art]
BACKGROUND ART Conventionally, when performing compression ignition combustion using a fuel having low ignitability such as natural gas, there is a method for improving ignitability by heating intake air with a heater or the like. However, using a heating device such as a heater in this way leads to deterioration of fuel efficiency of the compression ignition internal combustion engine (engine) as a whole. Therefore, it is desired to perform compression ignition combustion without using a heating device. Therefore, as shown in FIG. 7, in the exhaust stroke, the exhaust valve is opened by opening a timing lift amount as shown by the symbol A to perform exhaust, and then, in the intake stroke, the intake valve is opened by the timing lift as shown by the symbol B. And the exhaust valve is opened with a timing lift amount such as C to recirculate hot exhaust gas into the combustion chamber, thereby heating the intake air and obtaining a compression end temperature sufficient for ignition. (For example, see Patent Document 1).
[0003]
[Patent Document 1]
Japanese Utility Model Laid-Open No. 59-19904 [0004]
[Problems to be solved by the invention]
However, as described above, when performing the internal EGR by opening the exhaust valve in the intake stroke, the exhaust valve is opened after the intake valve is opened and the intake is performed for a while. In some cases, the amount of recirculated exhaust gas cannot be sufficiently increased.
The present invention has been made in order to solve such a problem, and a compression ignition internal combustion engine which can obtain a compression end temperature sufficient for ignition without using a heating device by efficiently recirculating exhaust gas, and An object of the present invention is to provide an exhaust gas recirculation amount control method.
[0005]
[Means for Solving the Problems]
A compression ignition internal combustion engine according to the present invention has a combustion chamber in which an intake passage and an exhaust passage are communicated with each other and in which a piston is provided so as to be able to reciprocate, and an exhaust passage which is provided in an exhaust passage to open and exhaust during an exhaust stroke. Exhaust valve means for returning the exhaust gas in the exhaust passage to the combustion chamber by maintaining the state of the minute lift amount for a predetermined time in the intake stroke, and only the minute exhaust valve means provided in the intake passage in the intake stroke. Intake valve means for opening the valve after maintaining the quantity state for a predetermined time.
[0006]
Preferably, the intake valve means may be opened after the exhaust valve means closes during the intake stroke.
The exhaust valve means may include two exhaust valves, wherein the first exhaust valve is opened during the exhaust stroke, and the second exhaust valve is opened at least during the intake stroke.
Alternatively, the exhaust valve means may include at least one exhaust valve, and each exhaust valve may be opened in both the exhaust stroke and the intake stroke by the corresponding two-stage cam.
Further, the exhaust valve means may open the valve in the exhaust stroke to perform exhaust, and may maintain the substantially constant minute lift amount for a predetermined time in the intake stroke to recirculate the exhaust gas in the exhaust passage into the combustion chamber. Good.
[0007]
An exhaust gas recirculation amount control method for a compression ignition internal combustion engine according to the present invention is a method for controlling an exhaust gas recirculation amount in a compression ignition internal combustion engine for recirculating exhaust gas into a combustion chamber during an intake stroke. The valve means performs exhaust by opening the valve in the exhaust stroke, and maintains the valve opening state of the minute lift amount in the intake stroke for a predetermined time to recirculate exhaust gas in the exhaust passage into the combustion chamber. After only the exhaust valve unit maintains the valve opening state of the minute lift amount for a predetermined time, the intake valve unit provided in the intake passage is opened.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
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 end thereof. These two intake branch passages 5a and 5b burn through the two intake ports 6a and 6b, respectively. It is communicated with the room 1. The exhaust passage 3 includes an exhaust junction 7 and a first exhaust branch 8a and a second exhaust branch 8b that are branched into two at the end thereof. The first exhaust branch 8a and the second exhaust branch 8b is connected to the combustion chamber 1 via the first exhaust port 9a and the second exhaust port 9b. In the present embodiment, the outer diameter of the first exhaust port 9a is set to be larger than the outer diameter of the second exhaust port 9b. However, as described later, the efficiency of the first exhaust port 9a is increased only through the first exhaust port 9a in the exhaust stroke. It is intended to be able to exhaust well. However, the present invention is not limited to this mode, and the first exhaust port and the second exhaust port may have substantially the same size.
[0009]
Further, at the two intake ports 6a and 6b, intake valves 10 and 11 that are opened and closed via intake valve cams (not shown) are arranged as intake valve means, respectively. On the other hand, the first exhaust port 9a and the second exhaust port 9b are provided with a first exhaust valve 12 and a second exhaust valve 13 that are opened and closed via an exhaust valve cam (not shown) as exhaust valve means. . A piston (not shown) is provided in the combustion chamber 1 so as to be able to reciprocate.
[0010]
In the compression ignition engine having such a configuration, as shown in FIG. 2, the exhaust gas is discharged by opening the first exhaust valve 12 with a symmetrical timing lift amount such as D in the exhaust stroke. . Further, immediately before the end of the exhaust stroke, and in the first half of the intake stroke, the second exhaust valve 13 is opened with a symmetrical timing lift amount as indicated by reference character E to recirculate the exhaust gas. Further, after the second exhaust valve 13 is closed, the two intake valves 10 and 11 are both opened with a symmetrical timing lift amount such as reference F, and the mixture of air and fuel is taken as intake air. It flows into the combustion chamber 1.
[0011]
Further, in the present embodiment, the second exhaust valve 13 is opened while maintaining a constant minute lift amount t for a predetermined time from the start of the intake stroke. The minute lift amount t of the second exhaust valve 13 is a value equal to or less than the maximum lift amount (that is, the safe lift amount) that does not interfere with the piston in which the second exhaust valve 13 reciprocates in the combustion chamber 1. I have. Thus, even if the piston moves to the top dead center, the piston and the second exhaust valve 13 do not interfere with each other. In the present embodiment, the maximum lift amount of the first exhaust valve 12 and the two intake valves 10 and 11 is about 7 to 8 mm, whereas the minute lift amount t of the second exhaust valve 13 is 1 mm. About.
[0012]
In the first half of the intake stroke, the second exhaust valve 13 is opened with the minute lift t as described above, and the two intake valves 10 and 11 and the first exhaust valve 12 are closed. The high-temperature exhaust gas discharged into the exhaust passage 3 through the first exhaust port 9a in the stroke flows into the combustion chamber 1 again through the second exhaust port 9b. At this time, since the two intake valves 10 and 11 are not opened, a period during which only the exhaust gas flows into the combustion chamber 1 is secured. The recirculation amount of the exhaust gas is larger than in the state of flowing together. Further, since the second exhaust valve 13 is opened for a predetermined time while keeping the minute lift amount t from the start of the intake stroke in a state where the two intake valves 10 and 11 are closed, the flow rate of the recirculated exhaust gas Not only increases, but the inside of the combustion chamber 1 is maintained at a negative pressure, and the temperature can be further increased by the effect of adiabatic compression.
In this way, the amount of exhaust gas recirculation can be reliably increased to efficiently heat the intake air, and as a result, a compression end temperature sufficient to ignite can be obtained. That is, even if a fuel having low ignitability such as natural gas is used, compression ignition combustion can be reliably performed without heating with a heating device such as a heater.
[0013]
Further, in this embodiment, the exhaust valve means is configured to open not only during the exhaust stroke but also during the intake stroke. However, the valve during the exhaust stroke and the valve during the intake stroke are different valves. That is, since the first exhaust valve 12 and the second exhaust valve 13 are used, the shape itself of each cam corresponding to each valve should be the same as the conventional simple cam shape in which one portion protrudes. Can be.
Further, since it is not necessary to heat the intake air by using a heating device such as a heater as in the related art, the fuel efficiency of the entire engine can be improved, and the cost can be reduced by not providing the heating device. .
[0014]
Embodiment 2 FIG.
Next, a second embodiment of the present invention will be described. As shown in FIG. 3, the compression ignition engine according to the second embodiment is different from the engine according to the first embodiment in that the number of exhaust valves is one instead of two. The combustion chamber 30 has one exhaust port 32 connected to an exhaust passage 33. The exhaust port 32 has a single exhaust valve 31 that is opened and closed via a two-stage cam described later as exhaust valve means. Are located.
[0015]
As shown in FIG. 4, the two-stage cam 51 for driving the exhaust valve 31 includes a first peak 52 protruding from a reference surface 51a forming a perfect circle, and a second peak 53 following the first peak 52. The opening degree of the exhaust valve 31 is adjusted in two stages. The second peak 53 is formed such that a predetermined amount of protrusion continues from the reference plane 51a by a predetermined angle with respect to the reference plane 51a in the region x located on the front side in the rotation direction, while the reference plane is formed in the region y located on the rotation side rear side. The projection is formed so that the amount of projection relative to 51a gradually decreases toward the rear in the rotation direction.
[0016]
By using such a two-stage cam 51, the exhaust valve 31 is opened in both the exhaust stroke and the intake stroke. That is, as shown in FIG. 5, during the exhaust stroke, the exhaust valve 31 opens with a timing lift amount such as G1 corresponding to the first peak portion 52 of the two-stage cam 51, and closes the valve as it is. Without opening, the valve is opened with the timing lift amount G2 in the first half of the intake stroke corresponding to the second peak 53. Further, as indicated by reference numeral G2, the exhaust valve 31 opens while maintaining a constant minute lift amount t for a predetermined time from the start of the intake stroke, corresponding to the region x of the second peak 53. Thereafter, the valve is gradually closed corresponding to the area y of the second peak 53. The minute lift amount t of the exhaust valve 31 is also equal to or less than the maximum lift amount (ie, the safe lift amount) at which the exhaust valve 31 does not interfere with the piston reciprocating in the combustion chamber 1. Even when the piston moves to the top dead center, the piston and the exhaust valve 31 do not interfere with each other. As in the first embodiment, when the exhaust valve 31 is fully closed, the two intake valves 10 and 11 are opened with a symmetrical timing lift amount as indicated by F.
[0017]
Thus, also in the present embodiment, in the first half of the intake stroke, the exhaust valve 31 is opened with the minute lift amount t as described above, and the two intake valves 10 and 11 are in the closed state. As in the first embodiment, the amount of exhaust gas recirculated can be reliably increased to efficiently heat the intake air. Therefore, a compression end temperature sufficient for ignition can be obtained, and compression ignition combustion can be performed without using a heating device such as a heater even when using a low ignitable fuel such as natural gas.
In the second embodiment, one exhaust valve 31 driven to be opened and closed by the two-stage cam 51 is used. Instead, two two-stage cams 51 are provided, and two exhaust valves 31 driven by the same opening and closing operation are used. Even if an exhaust valve is used, the same effect as that of the second embodiment can be obtained.
[0018]
In the first and second embodiments, as indicated by reference numeral E in FIG. 2 or reference numeral G2 in FIG. 5, the exhaust valve means opens the valve while keeping the minute lift t constant for a predetermined time from the start of the intake stroke. However, the exhaust valve means according to the present invention is not limited to such an opening mode. In other words, the exhaust valve means only needs to be set so as to open independently and before the opening of the intake valve means and maintain the minute lift amount for a predetermined time in the intake stroke. Therefore, as an example, the exhaust valve means may open the valve just before the end of the exhaust stroke as shown in FIG. 2 described above, and may keep the valve lift t constant during the intake stroke to keep the valve open. Alternatively, the configuration shown by reference numeral E ′ in FIG. 6 may be used instead of the configuration of reference numeral E in FIG. That is, in the form of reference symbol E ′ in FIG. 6, the shape is a gentle convex shape in which the constant minute lift amount t in FIG. 2 is the maximum lift amount. Alternatively, the valve may be opened with a small lift amount t at the start of the intake stroke, and then gradually closed. Further, the valve lift is increased within a range that does not exceed the safe lift at the time when the valve is opened from the start of the intake stroke, or the valve is closed once at the end of the exhaust stroke, and is again reduced below the safe lift during the intake stroke. The valve may be opened, and the opening and closing may be repeated a plurality of times during the intake stroke. Further, such various valve opening modes of the exhaust valve means are implemented over the entire period of the intake stroke thereafter, provided that a period during which only the exhaust valve means opens first from the start of the intake stroke. It may be done. Note that the safety lift amount is not constant because it is related to the ascending position of the piston, and changes accordingly when the piston starts to descend from the top dead center.
[0019]
Further, in the above-described first and second embodiments, the intake valve is opened after the exhaust valve is completely closed, but the present invention is not limited to this. That is, the intake valve means may be opened in any way as long as the exhaust valve means is opened alone during the intake stroke. Therefore, for example, the intake valve means may start the valve opening operation before the exhaust valve means is fully closed, and further, if the exhaust valve means opens and closes a plurality of times in the intake stroke, after the first valve opening is started. The intake valve means may also start opening so as to follow it. As described above, if there is a period during which the exhaust valve means is independently opened before the intake valve means during the intake stroke, the opening and closing relationship of the two means thereafter can be appropriately changed as necessary.
[0020]
Further, in the first and second embodiments, the valves that are opened and closed by the cams are used as the intake valve means and the exhaust valve means. Instead, various other types such as hydraulic and electromagnetic valve drive devices are used. May be used.
Further, in the above-described embodiment, natural gas is used as the fuel, but gas fuel such as city gas and propane gas, or fuel such as gasoline or light oil may be used instead.
[0021]
【The invention's effect】
As described above, according to the present invention, in the exhaust stroke and the intake stroke, the exhaust valve means that opens at a safe lift or less that does not interfere with the piston in the combustion chamber, and the exhaust valve means provided in the intake passage during the intake stroke. Since only the intake valve means that opens after only the valve is opened, the exhaust gas can be efficiently recirculated, and as a result, a compression end temperature sufficient for ignition can be obtained without using a heating device. .
[Brief description of the drawings]
FIG. 1 is a schematic plan view of the vicinity of a combustion chamber of a compression ignition engine according to Embodiment 1 of the present invention.
FIG. 2 is a view showing an opening and closing operation of a valve according to the first embodiment.
FIG. 3 is a schematic plan view of the vicinity of a combustion chamber according to a second embodiment.
FIG. 4 is a diagram showing a shape of a two-stage cam according to a second embodiment.
FIG. 5 is a diagram showing an opening and closing operation of a valve according to a second embodiment.
FIG. 6 is a diagram showing an opening and closing operation of a valve according to still another embodiment.
FIG. 7 is a diagram showing an opening and closing operation of a valve in a conventional compression ignition engine.
[Explanation of symbols]
1, 30 combustion chamber, 2 intake passage, 3, 33 exhaust passage, 10, 11 intake valve, 12 first exhaust valve, 13 second exhaust valve, 31 exhaust valve, 512 stage cam, 52 first peak, 53rd Two peaks, D, E, F, G1, G2 Timing lift.

Claims (6)

A combustion chamber in which an intake passage and an exhaust passage are communicated and a piston is provided so as to be able to reciprocate therein;
Exhaust valve means provided in the exhaust passage to open and exhaust during the exhaust stroke and maintain a minute lift amount state in the intake stroke for a predetermined time to recirculate exhaust gas in the exhaust passage into the combustion chamber;
A compression ignition internal combustion engine comprising: an intake valve means provided in an intake passage, wherein only the exhaust valve means opens a minute lift amount state for a predetermined time during an intake stroke and then opens. The compression ignition internal combustion engine according to claim 1, wherein the intake valve means is opened after the exhaust valve means closes during an intake stroke. The exhaust valve means includes two exhaust valves, a first exhaust valve is opened during an exhaust stroke, and a second exhaust valve is opened at least during an intake stroke. 3. A compression ignition internal combustion engine according to claim 1. 3. The exhaust valve according to claim 1, wherein the exhaust valve means includes at least one exhaust valve, and each exhaust valve is opened in both an exhaust stroke and an intake stroke by a corresponding two-stage cam. Compression ignition internal combustion engine. The exhaust valve means opens and exhausts in an exhaust stroke, and maintains an almost constant minute lift amount for a predetermined time in an intake stroke to recirculate exhaust gas in an exhaust passage into a combustion chamber. Item 5. A compression ignition internal combustion engine according to any one of Items 1 to 4. A method of controlling an exhaust gas recirculation amount in a compression ignition internal combustion engine that recirculates exhaust gas into a combustion chamber during an intake stroke,
The exhaust valve means provided in the exhaust passage is exhausted by opening it in the exhaust stroke and exhaust gas in the exhaust passage is kept in the combustion chamber for a predetermined time in the intake stroke by maintaining the valve open state with a small lift amount. Reflux,
In the intake stroke, only the exhaust valve means maintains the valve opening state of the minute lift amount for a predetermined time, and then opens the intake valve means provided in the intake passage.
An exhaust gas recirculation control method for a compression ignition internal combustion engine.

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