JP3224797B2 - 2 cycle engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-stroke engine equipped with a compressor for compressing an air-fuel mixture and injecting the mixture into a combustion chamber from an injection hole.

[0002]

2. Description of the Related Art In a conventional two-stroke gasoline engine, an air-fuel mixture supplied from a carburetor is sucked into a crank chamber by a pumping action of a piston moving up and down, compressed, and then burned. There are two types: a type in which the gas is pushed into the chamber for scavenging, and a type in which the fuel is directly supplied to the combustion chamber. The former crankcase compression type 2
In the cycle engine, it is difficult to reduce HC in the exhaust gas due to blow-by of the air-fuel mixture. Further, in the latter two-cycle engine of the direct injection type, the evaporation time of fuel injected in a high rotation region and the mixing time with air tend to be insufficient, and the rotation region having high combustion efficiency is restricted. Further, in a large displacement engine, a large amount of fuel is injected per cycle, which imposes restrictions on the dynamic range of the fuel injector.

An object of the present invention is to solve the above-mentioned problems and to provide a two-cycle engine capable of purifying exhaust gas and achieving high speed and high output.

[0004]

In order to achieve the above object, a two-stroke engine according to the present invention comprises a piston lower than a piston.
An air intake passage for introducing air into the crank chamber, a scavenging passage for supplying air from the crank chamber to the combustion chamber of the cylinder, an injection hole for injecting a mixture of fuel and air into the combustion chamber, and a separate body from the piston. A compressor that is driven in synchronization with a crankshaft, compresses the air-fuel mixture and supplies the compressed air-fuel mixture to the injection hole, and the upper end of a scavenging port at the end of the scavenging passage is lower than the upper end of an exhaust port. Placed in the position
The injection hole is above the exhaust port and near the spark plug
Compression with the cylinder to inject air-fuel mixture toward
The compressed air-fuel mixture is injected into the combustion chamber from the injection hole between the vicinity of the exhaust port closing completion position of the piston and the top dead center formed on the common wall of the piston. According to the above configuration, the scavenging of the combustion chamber is performed only by air from the crank chamber, and the rich mixture from the compressor is supplied from the injection hole into the combustion chamber at an optimum time immediately before the exhaust port is closed until after the exhaust port is closed. In addition, compared with the conventional two-stroke engine of the crankcase compression type, it is possible to reduce the blow-through of the air-fuel mixture containing HC, thereby purifying the exhaust gas, and improving the fuel efficiency.

[0005] In a preferred embodiment of the present invention, the compressor reciprocates the auxiliary piston to supply the air-fuel mixture to the auxiliary crank chamber.
A piston to be introduced, reciprocation of the previous SL auxiliary piston is advanced in phase than the reciprocating motion of the piston of the engine. According to this configuration, the rich air-fuel mixture compressed by the compressor can be injected into the combustion chamber at an optimal timing.

Further, in a preferred embodiment of the present invention, the rotary shaft of the compressor comprises an auxiliary shaft which is connected to the crankshaft and rotates reversely at the same rotational speed, and the auxiliary shaft has a balance weight for suppressing vibration of the crankshaft. Is added. According to the above configuration, the balancer shaft can be used as the rotation shaft of the compressor.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a longitudinal sectional view of the two-stroke engine according to the present embodiment, showing a state at a crankshaft angle (phase angle) of 60 ° after the bottom dead center (ABDC). In the figure, a crankcase 1 is divided into upper and lower parts.
The cylinder 2 is attached to the upper part of the cylinder 2, the cylinder head 3 is attached to the upper part of the cylinder 2, and the piston 8 is inserted into the cylinder 2 so as to be vertically movable. An ignition plug 19 is mounted on the cylinder head 3. A crankshaft 5 is rotatably supported by the crankcase 1.
The piston 8 is connected to a crank web 6 provided on the crank shaft 5 via a connecting rod 7.

An air suction passage 12 for sucking scavenging air is connected to a crank chamber 11 formed in the crankcase 1 below the piston 8, and a reed valve 13 is provided in the air suction passage 12. Are located. A communication between the crank chamber 11 and the combustion chamber 15 in the upper part of the cylinder is made by a scavenging passage 16 formed in the cylinder 2. Scavenging passage 1
The upper end of the scavenging port 16a opening to the combustion chamber 15 of
The exhaust port 50 is disposed at a position lower than the upper end of the exhaust port 50. After the scavenging port 16 a is closed by the piston 8, the exhaust port 50 is closed. The amount of air taken into the crank chamber 11 is adjusted by an intake air adjustment valve 17, and oil is supplied from an oil discharge nozzle 18 together with the intake air. This oil lubricates the connection between the crankshaft 5 and the connecting rod 7 and the crank web 6 in the crank chamber 11.

A balancer shaft 20 is connected to the crankshaft 5 via a gear (not shown), and is driven to rotate in a direction opposite to the crankshaft 5 at a rotation ratio of 1: 1. Balancer axis 2
An auxiliary cylinder block 24 in which the cylinder and the crankcase are integrated is formed on one side of the cylinder 2 above the zero. A web portion 21 provided on the balancer shaft 20 is connected to an auxiliary cylinder block 24 via a connecting rod 22.
An auxiliary piston 23 that moves up and down inside is connected, and the auxiliary piston 23 has a phase that is 70 °
I'm advancing. The web part 21 includes the crankshaft 5
Is added to the balance weight 25 for suppressing the vibration.

The upper part of the auxiliary cylinder block 24 is formed in a pressure accumulating chamber 26, and the lower part is formed in an auxiliary crank chamber 27.
6 and the auxiliary crank chamber 27, the auxiliary cylinder block 24
Are connected to each other by a transfer passage (corresponding to a scavenging passage) 28 which is opened on the inner wall surface of the first member. The injection passage 29 is provided in the auxiliary piston 23.
Is the common wall 2 of the cylinder 2 and the auxiliary cylinder block 24
Each of the injection holes 30 is formed in a, and the pressure accumulating chamber 26 and the combustion chamber 15 are communicated by the injection passage 29 and the injection hole 30 at a predetermined position (phase) of the auxiliary piston 23. ing. The injection hole 30 is disposed above the exhaust port 50 provided in the cylinder 2, and the injection hole 30 is closed by the piston 8 after the exhaust port 50 is closed and before the top dead center. ing. The balancer shaft 20, the connecting rod 22, the auxiliary piston 23, the auxiliary cylinder block 24, the pressure accumulating chamber 26, and the auxiliary crank chamber 27 constitute a compressor 45 that compresses the air-fuel mixture M and supplies it to the injection holes 30. Thus, the auxiliary piston 2
The compressor 45 composed of the cylinder 3 and the auxiliary cylinder 24 has a simple configuration and operates reliably, so that the reliability of the two-cycle engine is also improved.

An air-fuel mixture supply device 40 is connected to the compressor 45. A control valve 41, a fuel injector 38, and an oil discharge nozzle 39, which are connected to the intake air regulating valve 17 via a toothed belt 32 and operate in conjunction therewith,
A mixture M of fuel, air and a small amount of oil generated by the mixture supply device 40 is supplied to a control valve 41.
Is used to adjust the inhalation volume. The air intake 40a of the air-fuel mixture supply device 40 is connected to the air intake 12a of the air intake passage 12.
At the same time, it faces the inside of an air cleaner 10 for purifying air, and clean air is supplied to the air-fuel mixture supply device 40 and the air suction passage 12. The mixture M from the mixture supply device 40
Is sucked into the pressure accumulating chamber 26 through the first mixture passage 46 through the first reed valve 42 which is a check valve provided in the auxiliary cylinder block 24 at the time of the descending stroke of the auxiliary piston 23, Compressed during the ascent stroke.

The mixture M is richer in fuel than the mixture of a normal two-stroke engine when compared at the same load, and is a rich mixture having a concentration close to the stoichiometric air-fuel ratio at a high load. On the other hand, in the auxiliary crank chamber 27, when the auxiliary piston 23 moves up, the air-fuel mixture M from the air-fuel mixture supply device 40 passes through the second air-fuel mixture passage 47 and is provided in the auxiliary cylinder block 24 with a check valve. The compressed air-fuel mixture is supplied to the pressure accumulating chamber 26 through the transfer passage 28 during the downward stroke of the auxiliary piston 23. Thus, by introducing the air-fuel mixture M into the auxiliary crank chamber 27, the balancer shaft 20 and the connecting rod 22 which are the rotating shafts of the compressor 45 are rotated.
The connection between the web and the web 21 is lubricated by the oil in the air-fuel mixture.

As a result, in the accumulator 26, the air-fuel mixture M sucked through the first reed valve 42 and the compressed air-fuel mixture M supplied from the auxiliary crank chamber 27 through the transfer passage 28 are further compressed. Then, the fuel is injected from the injection hole 30 into the combustion chamber 15 through the injection passage 29. Also, cylinder 2
A cooling port 60 is formed in the common wall 2 a of the auxiliary cylinder block 24 for branching from the injection hole 30 and blowing a part of the mixture M to the top 8 a of the piston 8.
FIG. 1 shows the timing when the air-fuel mixture M starts to be injected into the combustion chamber 15 from the injection holes 30. At this time,
The piston 8 rises in the cylinder 2 and the combustion chamber 15
The combustion gas G inside is discharged from the exhaust port 50 to the exhaust passage 51.

Next, the operation of the two-stroke engine of this embodiment will be described. FIG. 2 is a diagram showing the operation stroke of the engine and the opening / closing timing of each port, and FIG. 3 is a diagram showing the relationship between the pressure fluctuation of each part of this embodiment and the opening / closing timing of each port. First, at the top dead center (TDC), the engine is in a combustion and expansion stroke as shown in FIG. 2, and as shown in FIG. Air A slightly mixed with oil is sucked in, and all other ports are closed. On the other hand, the auxiliary piston 23 of the compressor 45 is in a descending stroke, and is in a compression stroke of the air-fuel mixture M in the auxiliary crank chamber 27.

Subsequently, as shown in FIG.
When the phase is 60 ° (TDC), the engine is in the expansion stroke, and as shown in FIG. 5, the compressor 45 has the second reed valve 43 closed because the auxiliary piston 23 is still descending. Then, only the first reed valve 42 is opened, and the process of suctioning the air-fuel mixture M from the air-fuel mixture supply device 40 to the pressure accumulating chamber 26 is in progress.

Next, as shown in FIG.
When the engine is in the early stage of the exhaust stroke, the exhaust port 50 starts to open as shown in FIG. 6 and the discharge of the combustion gas G in the combustion chamber 15 starts, while the compressor 45 moves to the accumulator chamber 26. At the end of the intake, the transfer port 28a at the top of the transfer passage 28 starts to open, and the transfer of the air-fuel mixture M from the auxiliary crank chamber 27 to the pressure accumulating chamber 26 is started.

Subsequently, as shown in FIG.
In the case of C), the engine is in the exhaust stroke and the scavenging stroke, and the scavenging port 16a at the top of the scavenging passage 16 is opened as shown in FIG. Most of the combustion gas G remaining in the combustion chamber 15 is pushed out of the exhaust port 50 into the exhaust passage 51. At this time, in the compressor 45, the auxiliary piston 23 enters the upward stroke and the pressure in the auxiliary crank chamber 27 decreases, so that the second reed valve 43 opens, and the air-fuel mixture M is sucked into the auxiliary crank chamber 27. start. Accumulator 26
, The first reed valve 42 is closed.

Next, as shown in FIG. 2, after the bottom dead center (ABD
C) At 60 °, the engine closes the scavenging port 16a as shown in FIG. 8 and ends the scavenging stroke, starts opening the injection hole 30 of the compressor 45 to start injection of the air-fuel mixture M, and starts cranking. The chamber 11 is in the intake stroke with the reed valve 13 of the air intake passage 12 opened. On the other hand, in the compressor 45, the transfer passage 28 is closed by the auxiliary piston 23, the air-fuel mixture M is injected from the injection hole 30 into the combustion chamber 15, and the intake stroke in which the second reed valve 43 is opened is continued. The mixture M is continuously supplied into the auxiliary crank chamber 27.

As described above, scavenging of the combustion chamber 15 is performed only by the air A from the crank chamber 11, and immediately before the exhaust port 50 is closed, the air-fuel mixture M of the compressor 45 is discharged from the injection hole 30 through the combustion chamber 1.
5, the blow-by of the air-fuel mixture M can be reduced and the fuel efficiency can be improved as compared with the conventional crankcase compression type two-stroke engine.

Next, as shown in FIG.
When the engine is in the state shown in FIG.
Is closed to start the compression stroke, and the injection of the air-fuel mixture M is continued from the injection holes 30. At the same time, the air-fuel mixture M is blown from the cooling port 60 toward the top 8a of the piston 8, so that the top 8a is cooled. You. The crank chamber 11 is still in the intake stroke with the reed valve 13 of the air intake passage 12 opened. On the other hand, in the compressor 45, the air-fuel mixture M is injected from the injection hole 30 toward the vicinity of the spark plug 19, and the auxiliary crank chamber 27 is at the end of the intake stroke.

Subsequently, as shown in FIG. 2, when the ABDC, which is just before the top dead center, is 130 °, the engine is switched to the state shown in FIG.
As shown in (2), the injection hole 30 is closed by the piston 8, the compression stroke is continued, and the intake stroke to the crank chamber 11 is continued. On the other hand, in the compressor 45, all ports are closed, and the compressor 45 enters the compression stroke of the auxiliary crank chamber 27.

Next, as shown in FIG. 2, the engine is ignited at a position 5 to 30 ° before top dead center (BTDC) by the mixture M injected near the spark plug 19 in FIG. And it shifts to an expansion stroke. Thus, the spark plug 1
In the low load range, the air-fuel mixture is formed in the upper part of the combustion chamber 15 and the air layer is formed in the lower part in the low load region.
Is formed, it is possible to stratified scavenging and layered combustion. For this reason, cycle misfiring at a low load can be reduced, the blow-by of the air-fuel mixture M at a low load can be reduced, and fuel efficiency can be improved.

Further, since the moving speed of the piston 8 increases as the load changes from low to high, the gas flow in the combustion chamber 15 when the air-fuel mixture is supplied increases, and the air-fuel mixture M
And the air A in the combustion chamber are well mixed, so that a smooth switch from stratified scavenging / stratified combustion at low load to homogeneous scavenging / homogeneous combustion at high load is performed. Moreover, since the air-fuel mixture M is supplied into the combustion chamber 15, there is no restriction due to the evaporation time of fuel or the mixing time with air in a high rotation range unlike a direct injection type engine. Is larger than a direct injection engine. Further, since the compressor 45 acts as a kind of supercharger, an output equivalent to that of a normal crankcase compression type two-cycle engine can be obtained by comparing the displacement of the two-cycle engine.

The mixture M is supplied from the injection holes 30 to the combustion chamber 1.
The timing of starting the injection into 5 may be simultaneous with or slightly earlier than the completion of the closing of the exhaust port 50. In short, the injection may be performed when the piston 8 is near the position where the closing of the exhaust port 50 is completed.

Further, in the above-described embodiment, the compressor 45 shown in FIG. 1 is constituted by a reciprocating system, but may be constituted by a rotary type compressor. Further, although the rotation direction of the balancer shaft 20 is configured to be opposite to that of the crankshaft 12, in an engine that does not need to be rotated in the reverse direction, the rotation may be performed in the same direction by driving a timing belt. Further, although the balancer shaft 20 is used as the rotation shaft of the compressor 45, a dedicated rotation shaft (auxiliary shaft) may be provided in a two-cycle engine without a balancer shaft. Further, in the above embodiment, the phase difference of the reciprocating motion of the auxiliary piston with respect to the piston is 70 °
Although described earlier, this phase difference is not limited to 70 °, and may be appropriately set so that the timing of injecting the air-fuel mixture M into the combustion chamber 15 is optimized.

The bore surface of the auxiliary cylinder 24 for guiding the auxiliary piston 23 may be, for example, an aluminum ground, or a steel liner may be mounted. The outer peripheral surface of the auxiliary piston 23 may be merely subjected to labyrinth groove processing for sealing, but it may be configured to mount one piston ring.

[0027]

In the two-stroke engine according to the present invention, the combustion chamber is scavenged only by air from the crank chamber, and an air-fuel mixture is injected into the combustion chamber during a period from immediately before the exhaust port is completely closed to the top dead center. As compared with the conventional two-stroke engine of the crankcase compression type, the blow-by of the air-fuel mixture can be reduced, the exhaust gas can be purified, the fuel efficiency can be improved, and high-speed, high-power output can be achieved. You.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a two-cycle engine according to an embodiment of the present invention.

FIG. 2 is a stroke diagram showing an operation stroke and opening / closing timing of each port according to the embodiment.

FIG. 3 is a diagram showing a relationship between a pressure change of each unit and opening / closing timing of each port in the embodiment.

FIG. 4 is a longitudinal sectional view showing a state at the time of TDC of the embodiment.

FIG. 5 is a longitudinal sectional view showing a state where the ATDC of the embodiment is at 60 °.

FIG. 6 is a longitudinal sectional view showing a state where the ATDC of the embodiment is at 90 °.

FIG. 7 is a longitudinal sectional view showing a state at the time of BDC of the embodiment.

FIG. 8 is a longitudinal sectional view showing a state where the ABDC of the embodiment is at 60 °.

FIG. 9 is a longitudinal sectional view showing a state where the ABDC of the embodiment is at 95 °.

FIG. 10 is a longitudinal sectional view showing a state where the ABDC of the embodiment is at 130 °.

[Explanation of symbols]

1 ... crankcase, 2 ... cylinder, 5 ... crankshaft,
8 piston, 10 air cleaner, 11 crank chamber, 12 air intake passage, 15 combustion chamber, 16 scavenging passage, 16a scavenging port, 17 air regulating valve, 20 balancer shaft (rotating shaft), 21 ... Web part, 23 ... Auxiliary piston, 24 ... Auxiliary cylinder block, 25 ... Balance weight, 26 ... Pressure accumulation chamber, 27 ... Auxiliary crank chamber, 28
... Transfer passage, 29 ... Injection passage, 30 ... Injection hole, 40 ... Air-fuel mixture supply device, 41 ... Control valve, 45 ... Compressor, 50 ... Exhaust port, 51 ... Exhaust passage, 60 ... Cooling port, A ...
Air, G: combustion gas, M: mixture.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) F02B 33/22

Claims (3)

(57) [Claims] 1. An air intake passage for introducing air into a crank chamber below a piston , a scavenging passage for supplying air from the crank chamber to a combustion chamber of a cylinder, and an injection hole for injecting a mixture of fuel and air into the combustion chamber. And a compressor formed separately from the piston and driven in synchronization with a crankshaft to compress the air-fuel mixture and supply the mixture to the injection hole. The injection hole is disposed at a position lower than the upper end of the exhaust port, and the injection hole is located above the exhaust port and near the ignition plug.
Compression with the cylinder to inject air-fuel mixture toward
A two-stroke engine formed on a common wall with the engine, wherein the compressed air-fuel mixture is injected from the injection hole into the combustion chamber between a position near a completion position of closing an exhaust port of a piston and a top dead center. 2. The compressor according to claim 1, wherein the compressor reciprocates an auxiliary piston to introduce a mixture into an auxiliary crank chamber.
That a piston, two-stroke engine reciprocation before Symbol auxiliary piston is advanced in phase than the reciprocating motion of the piston of the engine. 3. The compressor according to claim 2, wherein the rotary shaft of the compressor comprises an auxiliary shaft connected to the crankshaft and reversely rotating at the same rotational speed, and the auxiliary shaft has a balance weight for suppressing vibration of the crankshaft. Two-cycle engine added.