JPH07189703A - Intake device for uniflow type two-cycle engine - Google Patents

Abstract

PURPOSE:To uniformize an air-fuel ratio and improve output by dynamic effect by reducing the interference (replacement) of residual gas between uniflow type peculiar cylinders, and charging new air smoothly. CONSTITUTION:In the intake device of a uniflow type two-cycle engine with a supercharger, partition walls 10 are formed between adjacent cylinders so as to provide independent scavenging chambers 9 formed cylinder by cylinder, plural independent intake passages 13 communicated with the respective independent scavenging chambers 9, and a collecting passage 12 for collecting plural independent intake passages 13. The length of the independent intake passage 13 is so set as to obtain dynamic effect at the specified engine speed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a uniflow type two-stroke engine intake device, and more particularly to a uniflow type two-stroke engine intake device having a supercharger.

[0002]

2. Description of the Related Art Conventionally, various types of two-cycle engines have been developed. In such a two-cycle engine, a supercharger and an intercooler are provided in the intake system in order to enhance the intake performance of the intake system. There are known ones (for example, JP-A-62-135655).

[0003]

On the other hand, the applicant of the present invention is
A patent application (Japanese Patent Application No. 4-72076) relating to such a two-cycle engine has already been filed. This earlier application
The present invention relates to a V-type uniflow two-cycle engine. In the invention of this prior application, a single intake chamber is formed between V banks, and a scavenging port formed in the bore portion of each cylinder is formed from the intake chamber. Fresh air is supplied to each cylinder via the cylinder. However, since the one disclosed in this prior application was of a type in which the intake chamber, which is a scavenging chamber, communicates between the cylinders, the residual gas that has finished burning causes interference between the cylinders, As a result, the inventors have confirmed that there is a problem that the scavenging airflow is nonuniform, that is, the air-fuel ratio is nonuniform, and combustion is not stable. Therefore, it has been demanded to solve such a problem. Therefore, the present invention is
It was made to solve such problems,
Uniflow type two-stroke engine intake system that reduces residual gas interference (exchange) between cylinders, which is peculiar to the uniflow type, and has an independent intake passage to provide smooth fresh air supply to make the air-fuel ratio uniform. Is intended to provide.

Another object of the present invention is to provide an intake device for a uniflow type two-cycle engine, which has an output improved by a dynamic effect.

[0005]

In order to achieve the above object, the present invention provides a uniflow type two-cycle engine intake system having a supercharger, wherein each cylinder is formed by forming a partition wall between adjacent cylinders. An independent scavenging chamber formed for each of the independent scavenging chambers, a plurality of independent intake passages communicating with each of the independent scavenging chambers, and a collecting passage for collecting the plurality of independent intake passages. Is set so that a dynamic effect can be obtained at a predetermined engine speed. In the present invention thus configured, a partition wall is formed between adjacent cylinders, and an independent scavenging chamber is formed for each cylinder by the partition wall. Does not cause interference. As a result, the air-fuel ratio becomes uniform and the combustion becomes stable. Further, since the independent intake passage is set to a length such that a dynamic effect can be obtained in a predetermined engine rotation region (for example, a medium speed region), the output can be improved. Further, the present invention is characterized in that it has a surge tank, and is provided with valve means for allowing the surge tank and the collecting passage to communicate with each other only when the engine rotates at a predetermined high speed.

Therefore, in the present invention, when the engine rotates at a predetermined high speed, the surge tank is used as an expansion chamber to keep the pressure in the surge tank constant.
Prevents pulsation and improves output. further,
In the present invention, the two-cycle engine is a V-type engine, and it is preferable that the independent intake passage and the collecting passage are arranged between V banks of the V-type engine.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described below with reference to FIGS.
Will be described with reference to. FIG. 1 shows a uniflow type 2 of the present invention.
It is a longitudinal cross-sectional view showing an intake device of the cycle engine. FIG. 2 is a partial plan view showing only the main part of FIG. FIG. 3 is a partial cross-sectional view showing the valve and the collecting passage shown in FIG. As shown in FIG. 1, reference numeral 1 indicates a V-type 4-cylinder uniflow two-cycle engine.
The left and right banks 1a and 1b are provided. A cylinder bore 2 is formed in each of the left and right banks 1a and 1b, and a piston 3 is slidably arranged in these cylinder bores 2. The piston 3 is provided in the crank chamber 5 via a connecting rod 4, and is connected to a crankshaft 6 that extracts combustion energy as rotational power. The upper space defined by the upper part of the cylinder bore 2 and the upper surface of the piston 3 constitutes a combustion chamber 7. A large number of scavenging ports 8 are provided on the peripheral wall of the cylinder bore 2, and these scavenging ports 8 extend over the entire circumference of the cylinder bore 2.
The fresh air (intake air) is arranged so as to be introduced into the combustion chamber 7 substantially evenly. An annular independent scavenging chamber 9 is formed around the cylinder bore 2. As shown in FIG. 2, this independent scavenging chamber 9 is formed for each cylinder by a partition wall 10 formed between adjacent cylinders. The independent scavenging passage 9 communicates with the combustion chamber 7 via the scavenging port 8.

A surge tank 11 is formed between the left and right banks 1a and 1b.
Inside 1, there is a collecting passage 12 extending in the direction of the crankshaft.
Also, an independent intake passage 13 that connects the independent scavenging chamber 9 of each cylinder and this collecting passage 12 is housed and arranged. In addition, as shown in FIG. 2, a butterfly valve 14 is disposed on the upper surface of the collecting passage 12 upstream of the communicating portion with the independent intake passage 13. This butterfly valve 14
The surge tank 11 and the collecting passage 12 are communicated with each other by being opened only when the engine rotates at a predetermined high speed. Also,
In other operating regions (at low / medium speed rotation), the butterfly valve 14 is closed. A cooling water passage 17 is disposed above the scavenging port 8 so as to surround the entire circumference of the cylinder bore 2, and an exhaust passage 18 is connected to the upper portion of the combustion chamber 7. An exhaust valve 20 is attached to the opening of the exhaust passage 18, that is, the exhaust port 19. The engine 1 is of a cylinder injection type, and an injector 21 for injecting fuel is attached near the exhaust passage 18.
Further, a spark plug 22 is attached to the upper part of the combustion chamber 7. A supercharger 30 for supercharging the intake air of the engine 1 is arranged above the surge tank 11 of the engine 1, and an intercooler 32 for cooling the supercharged intake air is provided downstream of the supercharger 30. Are connected via the intake passage 31. The intake passage 31 on the downstream side of the intercooler 32 is connected to the collecting passage 12 described above.

Here, the independent intake passage 13 is set to a length such that a dynamic effect can be obtained in a predetermined engine rotation region (for example, a medium speed region). In the two-cycle engine, the path length required for obtaining the dynamic effect, that is, for reversing the negative pressure wave is shorter than that of the four-cycle engine. Therefore, as in the present embodiment, in a relatively small space. It becomes possible to form it in a certain surge tank 11.
Further, in this embodiment, as described above, the collecting passage 12
Is provided with a butterfly valve 14 on the upper surface upstream of the communicating portion with the independent intake passage 13, and the butterfly valve 14 is opened only when the engine rotates at a predetermined high speed, whereby the collecting passage 12 and the surge tank 11 are opened. I am trying to communicate with. The reason for this is as follows. First, the inventors have found that in the type in which the supercharger 30, the collecting passage 13 and the independent intake passage 14 are provided, a problem occurs when the engine rotates at high speed.
That is, in such a type, when the engine rotates at high speed, pulsation is generated by the supercharger 30, and the pulsation increases intake resistance, making it difficult to supply intake air stably, resulting in a decrease in output. Causes a decrease in output. Therefore, in the present embodiment, by using the surge tank 11 as an expansion chamber, the pressure inside the surge tank 11 is kept constant and pulsation is prevented.
The output is improved.

Next, the operation of the above embodiment will be described. In the low and middle regions, the butterfly valve 1 provided in the collecting passage 12
4 is in a closed state. Therefore, the air supercharged by the supercharger 30 flows into the collecting passage 12 from the intake passage 32 after being cooled by the intercooler 32.
Further, it flows from the collecting passage 12 to each independent intake passage 13 without passing through the surge tank 11, and then is scavenged (intake) into the cylinder bore 2 through the independent scavenging chamber 9 and the scavenging port 8. After that, the mixture becomes combustion in the cylinder bore 2 and burns, and the exhaust gas thereof is discharged from the exhaust passage 18 through the exhaust port 19. In this embodiment, the partition wall 10 is formed between the adjacent cylinders, and the partition wall 10 forms the independent scavenging chamber 9 for each cylinder. Therefore, the residual gas that has finished combustion interferes between the cylinders. Will not occur. As a result, the air-fuel ratio becomes uniform and the combustion becomes stable. Further, since the independent intake passage 13 is set to have a length such that a dynamic effect can be obtained in a predetermined engine rotation region (for example, a medium speed region), the output can be improved. Next, in the high speed region, the butterfly valve 14 provided in the collecting passage 12 is operated to be in the open state. As a result, the collecting passage 12 and the surge tank 11 communicate with each other. As described above, in this embodiment, by using the surge tank 11 as the expansion chamber, the pressure inside the surge tank 11 can be kept constant, pulsation can be prevented, and the output can be improved.

Next, another embodiment of the present invention will be described with reference to FIGS. 4 and 5 show one bank 1
Only part of a is shown. In the uniflow type,
Scavenging port 8 and crank chamber 5 when piston 3 is at top dead center
The skirt portion 3a of the piston 3 is formed long so as not to communicate with. Therefore, the height of the engine is increased. Further, the connecting rod 4 becomes long, which increases the reciprocating motion of the connecting rod 4, and therefore the counterweight 40 needs to be increased. Therefore, the height of the engine is further increased. In this embodiment, a reverse recess 41 is provided in a portion of the skirt portion 3a of the piston 3 corresponding to the counterweight 40. Further, the scavenging port located above the reverse recess 41 is formed as a scavenging port 8a smaller than the others. With this configuration, the connecting rod 4 and the counterweight 40 are reduced in size, and as a result, the height of the entire engine is reduced. Further, another embodiment of the present invention will be described with reference to FIGS. FIG. 6 shows only a part of the single bank 1b. In this embodiment, since the two exhaust valves 20 are offset with respect to the center of the cylinder, these exhaust valves 20 function as swirl generating means. Also, these exhaust valves 20
Is constituted by a first exhaust valve 20a located on the upstream side of the swow and a second exhaust valve 20b located on the downstream side,
Further, the first exhaust valve 20a is configured to have a larger opening than the second exhaust valve 20b. Therefore, the passage resistance of the first exhaust valve 20a is equal to that of the second exhaust valve 2a.
It becomes larger than 0b. Further, as another example, an opening / closing valve (not shown) may be provided only on the side of the second exhaust valve 20b, and a large passage resistance may be obtained by closing this opening / closing valve.

On the other hand, the inventors of the present invention, as shown in FIGS. 6 to 7, have difficulty in scavenging the corner between the cylinder wall and the cylinder top (indicated by a shaded line in the drawings), and burned gas remains. Therefore, the problem that the scavenging efficiency is reduced was found. However, in the embodiment configured in this manner, the passage resistance of the first exhaust valve 20a located upstream of the swirl flow is made smaller than that of the second exhaust valve 20b located downstream. The burnt gas on the opposite side of the exhaust port of the cylinder top is exhausted from the first exhaust valve 20a to prevent fresh air from passing through the second exhaust valve 20b. As a result, the exhaust efficiency is improved. Further, instead of the passage resistance, the first exhaust valve 20a located on the upstream side of the swirl flow.
The same effect can be obtained by delaying the closing timing of the second exhaust valve 20b located on the downstream side. Further, generally, the larger the engine speed, the smaller the swirl ratio (ratio of the swirl speed to the engine speed). Therefore, the lower the engine speed, the smaller the passage resistance of the first exhaust valve 20a is set. (The opening is made larger) or the first exhaust valve 2
It is preferable to further delay the closing timing of 0a.

[0013]

[Effect] As described above, the uniflow type 2 of the present invention
According to the intake system of a cycle engine, a partition wall is formed between adjacent cylinders, and an independent scavenging chamber is formed for each cylinder by this partition wall, so that residual gas after combustion interferes between the cylinders. Will not occur. As a result, the air-fuel ratio becomes uniform and the combustion becomes stable. Further, since the independent intake passage is set to a length such that a dynamic effect can be obtained in a predetermined engine rotation region (for example, a medium speed region), the output can be improved. Further, by using the surge tank as an expansion chamber only when the engine rotates at a predetermined high speed, the pressure inside the surge tank can be kept constant, pulsation can be prevented, and the output can be improved.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view showing an intake device of a uniflow two-cycle engine of the present invention.

FIG. 2 is a partial plan view showing only the main part of FIG.

FIG. 3 is a partial cross-sectional view showing the valve and the collecting passage shown in FIG.

FIG. 4 is a partial vertical sectional view showing another embodiment of the present invention.

5 is a partial vertical cross-sectional view of FIG. 4 seen from the side.

FIG. 6 is a partial vertical sectional view showing another embodiment of the present invention.

FIG. 7 is a partial plan view showing another embodiment of the present invention.

[Explanation of symbols]

 1 Engine 2 Cylinder Bore 3 Piston 7 Combustion Chamber 8 Scavenging Port 9 Independent Scavenging Chamber 10 Partition Wall 11 Surge Tank 12 Collecting Passage 13 Independent Intake Passage 14 Butterfly Valve 18 Exhaust Passage 20 Exhaust Valve 21 Injector 22 Spark Plug 30 Supercharger 31 Intake Passage 32 intercooler

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI technical display location F02M 35/116 35/104 35/10 F02M 35/10 301 T (72) Inventor Akira Kageyama Hiroshima Prefecture 3-1, Shinchi, Fuchu-cho, Aki-gun Mazda Co., Ltd. (72) Akira Kurihara 3-1, Shin-chi, Fuchu-cho, Aki-gun, Hiroshima Prefecture (72) Inventor, Ritsu Aoki 3 Shinchi, Fuchu-cho, Aki-gun No. 1 in Mazda Co., Ltd. (72) Inventor Takehiko Yasuoka No. 3 Shinchi, Fuchu-cho, Aki-gun, Hiroshima Mazda Co., Ltd.

Claims (3)

[Claims] 1. An intake device for a uniflow type two-cycle engine having a supercharger, an independent scavenging chamber formed for each cylinder by forming a partition wall between adjacent cylinders, and each of the independent scavenging chambers. A plurality of independent intake passages that communicate with each other, and a collecting passage that collects the plurality of independent intake passages,
An intake system for a uniflow type two-cycle engine, characterized in that the length of the independent intake passage is set so that a dynamic effect can be obtained at a predetermined engine speed. 2. The two-cycle engine is a V-type engine, and the independent intake passage and the collecting passage are arranged between V banks of the V-type engine. Uniflow type two-cycle engine intake system. 3. The method according to claim 1, further comprising a surge tank, and valve means for connecting the surge tank and the collecting passage only when the engine is rotating at a predetermined high speed. An intake device for the described uniflow two-cycle engine.