JPS602492B2 - 2 stroke engine - Google Patents

Description

[Detailed description of the invention] The present invention relates generally to internal combustion engines.

More specifically, it relates to a piston boat type two-stroke engine. Such engines typically use an incoming fuel-air mixture to scavenge exhaust gases from the cylinders, resulting in the incoming gases being released through the exhaust system into the outside atmosphere while still being burned. This led to poor fuel efficiency and pollution problems. 191st King U.S. Patent No. 96820 dated August 23rd and December 2nd of the same year
No. 7, US Pat. No. 980,134 discloses a type in which scavenging air is drawn into a transfer passage and sent from the passage to the cylinders before the fuel-air mixture is supplied from the crankcase via the transfer passage. A two-stroke engine is disclosed.

The following US patent specifications disclose sending scavenging air prior to sending the air-fuel mixture to the cylinder.

US Patent Date 8 I 981 May 28, 1907 976858 191 King November 29 1115
481 191 Buddha Sheep November 3rd 1511112
192 hand October 7th 2381832 1
Handled on August 7th, 2015. Also, other types of 2-stroke.

See also U.S. Pat. The object of the present invention is to overcome the above-mentioned drawbacks of the prior art associated with scavenging exhaust gas in a cylinder with a fuel-air mixture, and to improve fuel economy by preventing unburned fuel from being exhausted. It is an object of the present invention to provide a two-stroke engine which has been established in that it has improved environmental performance and low pollution.

The two-stroke engine of the present invention includes a cylinder, a piston that reciprocates within the cylinder and has a skirt, and that extends from the cylinder and generates negative pressure and positive pressure inside in response to the reciprocating movement of the piston. In a two-stroke engine comprising a crankcase configured as above and a device for supplying a fuel mixture to the crankcase, a communicating boat is formed in the skirt portion of the piston, and a communication boat is formed in the skirt portion of the piston. An exhaust boat, a pressure boat, an auxiliary boat, and a transfer boat are formed to be opened and closed by the skirt portion, and are conveyed between the crankcase and the transfer boat of the cylinder to transfer the fuel mixture in the crankcase to the cylinder. A transfer passage is provided for supplying air to the pressure boat, and a transfer passage is provided independently of the transfer passage to allow smoke to pass between the pressure boat and the auxiliary boat and to allow atmospheric air to enter the interior, but to allow this atmospheric air to enter the outside. An auxiliary chamber is provided with a one-way valve designed to prevent the outflow of the pressure boat, auxiliary boat,
The relative positions of the speed boat and the transfer boat are such that when the piston is located near top dead center and the auxiliary boat is closed, the pressure boat passes through the crankcase and transmits the negative pressure in the crankcase to the auxiliary chamber. , due to the effect of the negative pressure in the crankcase transmitted to the auxiliary chamber, 1
Atmospheric air is sucked into the auxiliary chamber through the directional valve, and in response to the downward movement of the piston toward the bottom dead center while the auxiliary boat is closed, the Yotsu boat and the pressure port communicate with each other. The suctioned atmosphere is compressed by the action of the positive pressure in the crankcase transmitted to the auxiliary chamber, and in response to the further downward movement of the piston, the auxiliary boat is closed, so that the compressed atmosphere in the auxiliary chamber is compressed. Prior to the feeding of the fuel mixture, it is fed into the cylinder, and as the piston further descends, the transfer boat is opened and the fuel mixture is transferred from the crankcase into the cylinder due to the action of positive pressure in the crankcase. It has a configuration selected to be delivered.

Further, according to the present invention, there is provided a cylinder, a piston that reciprocates within the cylinder and has a skirt portion, and a piston that extends from the cylinder and generates negative pressure and positive pressure therein in response to the reciprocating movement of the piston. A two-stroke engine is provided with a crankcase made by the above construction, and a device for supplying a fuel mixture to the crankcase, wherein a rentsu boat is formed in the skirt portion of the piston, and a skirt portion of the piston is formed in the cylinder. An exhaust boat, a pressure boat and a transfer boat are formed which are adapted to be opened and closed by the pressure boat and the transfer boat of the cylinder, and which allow air to enter into the interior but not outside the atmosphere. A transfer passage is provided with a one-way valve adapted to prevent outflow to the transfer boat, and the relative positions of the pressure boat, Rentsu boat, and transfer boat are such that the piston is located near top dead center and therefore the transfer boat When the pressure boat is closed, the pressure boat communicates with the crankcase to transmit the negative pressure in the crankcase to the transfer passage, whereby atmospheric air is sucked into the transfer passage through the one-way valve due to the action of the negative pressure. In response to the downward movement of the piston toward the lower point while the transfer boat is closed, the communication boat and the pressure boat communicate with each other, thereby increasing the pressure in the crankcase that is transmitted to the transfer passage. Under the action of pressure, the atmospheric air sucked into the transfer passage is compressed, and in response to the further downward movement of the piston, the transfer boat is closed so that the atmospheric air compressed within the transfer passage is first delivered into the cylinder. A two-stroke engine is selected such that the fuel mixture is supplied from the crankcase into the cylinders by the action of positive pressure within the crankcase.

-Quenjin is served. Next, the present invention will be described with reference to the drawings. The drawings show an internal combustion engine 11 which has various features of the invention.

More specifically, the engine 11 includes a block 13 forming a cylinder 15 and a crankcase 17 continuing from this cylinder.
and has. Inside the cylinder 15 is a piston 19 that reciprocates, and this piston repeatedly creates positive and negative pressures within the cylinder 15 and crankcase 17 in response to the reciprocating movement. The piston 19 is connected in the usual manner to a connecting rod 21, which in turn is connected to a crankshaft 23 passing through the crankcase 17.

As is customary, the cylinder 15 passes through an exhaust boat 25 passing through the block 13, which exhaust boat is connected to the piston 19.
its upper edge 2 so that it opens on the way from top dead center to bottom dead center.
6 is spaced a distance A from the end 27 of the cylinder head.

Furthermore, as usual, the cylinder 15 and crankcase 17
After the piston moves and the exhaust boat 25 opens, the pistons move toward the bottom dead center and the pressure in the crankcase is almost at its maximum, so that they fit into each other.

There may be one or more such lotus passages (two in the example shown).
This is done by a transfer passage 29, which is used to allow a mixture of fuel and air to flow from the crankcase 17 to the cylinder. The air-fuel mixture can be introduced into the crankcase 17 in response to pressure changes in the crankcase 17 by any known method. In the configuration shown, the transfer passage 29 extends within the block 13 and extends between the sills 15 and the crankcase 17 when the piston is near bottom dead center.
Lotus is suitable for both.

The transfer passage 29 opens into the cylinder via a transfer boat 31 having an upper edge 33 spaced from the end of the cylinder head by a distance B greater than distance A. The piston 19 has a skirt portion 35 which may be provided with a notch along its lower green to facilitate the passage between the transfer path 29 and the crankcase 17. It is provided independently of the transfer passage 29 and acts in response to repeated pressure changes in the crankcase, and before the communication between the cylinder 15 and the crankcase 17 begins via the transfer passage 29, air is removed instead of the air-fuel mixture. A device is provided for feeding the gas into the cylinder 5.

The air is supplied after the exit of the exhaust boat 25 and through the transfer passage 2.
It is desirable that the air-fuel mixture is fed to the cylinder 5 at the same time as the air-fuel mixture 9 is connected to the cylinder 15 before being introduced into the cylinder 5. Sending air to the cylinder before the air-fuel mixture in this way helps exhaust air, and at the same time
This accomplishes the dual purpose of supplying the exhaust system with air for combustion of unburned fuel. Also, feeding the air first in this manner serves to prevent the unburned air-fuel mixture from passing through the exhaust boat to the pole 4. However, the present invention is not limited to introducing air prior to the start of introduction of the mixture, but can also be used to introduce air after the start of introduction of the mixture to create a stratified supply. Various arrangements can be used to deliver air to the cylinder separately from the mixture.

In the example shown, the device for supplying air is the transfer passage 2.
9, an auxiliary chamber 51 extending in the circumferential direction (see FIG. 5), and means for sucking air into the auxiliary chamber 51 in response to repeated pressure changes in the crankcase; It has means for starting communication between the cylinder 15 and the auxiliary chamber after suction. Therefore, in the structure shown, the auxiliary chamber 51 can communicate with the cylinder 15 via one or more auxiliary boats 53 (in the example shown, two circumferentially spaced apart), these auxiliary boats 63 having a distance A It has an upper green 55 spaced apart from the end of the cylinder head by a distance C, which is greater and less than distance B, and is located before the entrance of the transfer port after the opening of the exhaust boat 25 when the piston moves toward bottom dead center. It is designed to open. Compressed air is generated in the auxiliary chamber 51 by drawing atmospheric air into the auxiliary chamber 51 and then compressing it, both of which are caused by repeated pressure changes within the crankcase 17. More specifically, the auxiliary chamber 51 has one or more one-way valves 59 that open so that atmospheric air is sucked into the auxiliary chamber when the interior of the auxiliary chamber 51 is in a negative pressure state; When the auxiliary chamber is in a positive pressure state, it is closed to prevent air from escaping from the auxiliary chamber.

Repeated pressure changes in the crankcase are caused by the auxiliary chamber 51
one or more pressure boats 61 (one in the example shown) (
3 and 6) to the auxiliary chamber 51 during each engine cycle.

More specifically, the pressure boat 61 communicates with the crankcase 17 when the piston 19 is near top dead center or bottom dead center. To further discuss this point, when the piston 19 is near the top dead center, that is, when the inside of the crankcase is in a negative pressure state and the auxiliary boat 53 is closed by the skirt portion of the piston 19, the auxiliary chamber 51 is Atmospheric air is introduced into the auxiliary chamber 51 through the one-way valve 59 through the negative pressure inside the crankcase.

If necessary, the auxiliary chamber 51 can be communicated with the vacuum in the crankcase 17 by locating one or more boats or downwardly open notches 63 in alignment with the boats 61 as in the illustrated embodiment. Lotus luck in both chambers can be easily achieved. When the piston 19 moves downward from the top dead center, the pressure boat 61 is closed by the skirt portion 35 and the intake of air into the auxiliary chamber 51 is stopped. Then, while the piston 19 continues to move toward the bottom dead center, the transfer boat 3
1 opens, and when the pressure inside the crankcase 17 is in a normal state, the pressure boat 61 first aligns with the lotus port 65 in the skirt (Fig. 6). Let Sho communicate with the air in the auxiliary room. This passage may occur either before or after the auxiliary boat 53 opens into the cylinder 15, but the auxiliary chamber 51
In order to ensure that the air inside is pressurized when the auxiliary boat 53 is opened, it is desirable to start the above-mentioned lotus passage a little before the opening of the auxiliary boat. However, regardless of the timing of the air compression, the compressed air enters the cylinder 15 and forms a stream of exhaust gas prior to the fuel-air mixture entering the transfer passage 29. Compressed air costs 1 shilling
Immediately after flowing into the crankcase 17, the transfer passage flows into the crankcase 17.
In response to Mr. Masaru's request, the crankcase 17 was passed through the transfer passage.
It opens to allow the air-fuel mixture to flow from the cylinder 15 to the cylinder 15.

In the illustrated configuration, the boat 53 begins to open after about 15 degrees of crankshaft rotation after the exhaust boat 25 opens.
The transfer boat is also intended to begin opening after approximately 5 degrees of crankshaft rotation from the time the auxiliary boat 53 begins to open. Shown in Figures 7-11 is cylinder 2
This is a piston boat type two-stroke engine 211 including a block 213 forming a cylinder 15 and a crankcase 217 extending from a sill 215.

A piston 219 is configured to reciprocate within the cylinder 215 relative to the crankcase 217, and the piston repeatedly creates positive and negative pressures within the cylinder 215 and the crankcase 217 in response to the reciprocation. Piston 219 has a top 220 and is connected in conventional manner to a connecting rod 221 that connects to a crankshaft 223 extending within crankcase 217 .
is combined with

As is customary, the cylinder 215 has an exhaust boat 225 disposed through the block 213 and having an upper edge 226 spaced a distance E (FIG. 8) from the end of the cylinder head so that the piston 219 is at top dead center. When the piston 219 moves closer to the bottom dead center, the exhaust boat 225 begins to open when the top 220 of the piston 219 becomes a distance E from the top dead center.

As shown in FIG. 8, the engine 211 is provided with a transfer chamber 251 that preferably surrounds the cylinder in an arcuate and horizontal manner. Transfer chamber 251 and cylinder 215 move as the piston moves between bottom dead center and a position above bottom dead center where its top 220 is a distance F (FIG. 8) greater than distance E from top dead center. Means will be provided to make a difference between the two.

In the illustrated arrangement, such means include one or more transfer boats 253 provided at each end of transfer chamber 251 and adapted to engage cylinder 215 in response to movement of the piston.
During movement of the piston between top dead center and a position where the top 220 of the piston 219 is a distance G (FIG. 8) away from the top dead center, which is less than the distance E, the negative pressure source and the transfer chamber 251 Means are also provided for bringing about a lotus communication between the two.

In the illustrated configuration, the negative pressure source is the crankcase 217;
Lotus communication is established by matching the positions of pressure boats 257. This pressure boat extends from the center of the transfer chamber 251 and extends into the engine block 213, so that when the piston moves between top dead center and a position a distance G therefrom, the crankcase 213
17 and Ren suit. In the particular configuration shown, the piston 219 has a lower edge 261 with a notch 263 that aligns with the pressure boat 257 to allow communication between the transfer chamber 251 and the crankcase 217 at the desired time. It has a skirt 259. The distance between the bottom dead center and the top 220 of the piston 219 is greater than the distance F (Figures 8 and 10).
Means is also provided for passing the air-fuel mixture between the supply source and the transfer chamber 251 when the piston moves between a position above the lower point, which is further away from the top dead center. In the configuration shown,
The air-fuel mixture supply source consists of the crankcase, and Rento
Pressure boat 257 and piston 219 skirt 259
The transfer chamber 251 and the crankcase 21 are provided for a desired period of time.
This is done between the crankcase 217 and the transfer chamber by matching the lotus boat 275 which forms a lotus communication between the crankcase 217 and the transfer chamber. Therefore, due to the coincidence of the pressure boat 257 and the piston's lotus port 275, the transfer chamber 251 and the crankcase 21
7, the mixture is transferred to the transfer chamber 251.
It passes through the crankcase 217 and enters the cylinder 215. In the configuration shown, the means for supplying the mixture at relatively high pressure to the transfer chamber 251 are also . It includes means for sending the air-fuel mixture to the crankcase 217 through a device consisting of a capretor 231 and a reed valve 235.

Other configurations can also be used. When the transfer chamber 251 is suitable for negative pressure, that is, in the illustrated configuration, the crankcase 2
Means are also provided for supplying pure air unmixed with fuel when the transfer chamber is in communication with the negative pressure source provided by 17.

In the configuration shown, such means consist of an air inlet boat 281 and a one-way reed valve 283 located at each end of the transfer chamber 251, which valve responds to the negative pressure within the transfer chamber 251. It opens to allow air to enter and closes during positive pressure within the transfer chamber 251 to isolate the air within the chamber. Means are provided for isolating the air introduced into the transfer chamber 251 while the piston moves between the positions designated G and F.

Such means include the reed valve 283 and the F of the piston.
auxiliary boat 253 and pressure boat 25 during exercise between and G
7 including the skirt 259 of the piston. Such isolation prevents flow from the transfer chamber 251 to the cylinder 215 when the piston moves between top dead center and the F position, and also prevents flow from the crankshaft when the piston 219 moves between the When the air-fuel mixture in the case 217 is pressurized, the transfer chamber 2
Mixing of the air in 51 and the air-fuel mixture in crankcase 217 is prevented. During operation, when the piston 219 is near the top dead center, the negative pressure inside the crankcase 217 is reduced to the pressure boat 2.
57 to the transfer chamber 251, the negative pressure in the transfer chamber 251 acts to allow air to enter during the movement through the air inlet boats 281 at both ends of the chamber, and also to the transfer boat during the previous pressurization stroke. When 253 closes, all of the air-fuel mixture remaining in the transfer chamber 251 is drawn back into the crankcase 217 by diluting the pressure boat 257.

When the piston 219 and the top 220 are in a position between G and F, the air introduced into the transfer chamber 251 is isolated.

During this isolation, the air trapped within the transfer chamber 251 is heated and therefore its pressure increases slightly. During movement of the piston from top dead center, the exhaust boat 225 begins to open when the piston passes a distance E from top dead center.

Then, as the piston 219 continues to move downward, the skirt portion of the piston uncloses the transfer boat 253 and begins to communicate between the cylinder 215 and the transfer chamber 251. Initially, the pressure within cylinder 215 is believed to be somewhat higher than that in transfer chamber 251. Therefore, the exhaust gas is transferred to the transfer chamber 251.
It is thought that the air trapped inside is further pressurized. However, as the evacuation continues, the initially trapped and then pressurized air then enters and passes through the cylinder 215 from the transfer chamber 251 to assist in scavenging the products of combustion. Piston 2
19 continues its downward movement toward its bottom dead center, the transfer chamber 2
51 corresponds to the positive pressure air-fuel mixture in the crankcase 217.

Such a passage allows the air-fuel mixture to flow into the cylinder 215 via the transfer chamber 25 after being almost or completely scavenged by the previously trapped air. In this way, the air that is initially introduced into the transfer chamber 251 and then isolated and pressurized is used for scavenging, thereby eliminating the use of fuel during exhaust and reducing its loss, increasing fuel economy and reducing exhaust gas. Establish cleanliness.

Furthermore, depending on operating conditions and component dimensions, the air used to scavenge cylinders 215 may also be used to ignite unburned combustibles in the scavenge system to provide a clean exhaust engine. Although the illustrated configuration is of the piston boat type, other arrangements can be used to achieve the desired clearance when desired.

For example, a camshaft actuated valve system can be used. Also, a rotary valve can be used to obtain various ordered lotus passages. Further, means other than the crankcase described above can be provided as a source of negative pressure and as a source of a positive pressure air-fuel mixture. For example, a separate source of negative pressure and a separate source of fuel-air mixture can be used. Also in this regard, a stepped piston arrangement may be used to provide a source of negative pressure and/or a source of positive pressure mixture.

Alternatively, a blower can be used as the positive pressure mixture source. Furthermore, as a means different from causing air to flow into the transfer chamber 251 using negative pressure, a means for feeding air into the transfer chamber 251 is a blower (not shown) that conveys the air to the transfer chamber.
can include. In this way, a means for alternately supplying positive pressure and negative pressure is used, and the positive pressure acts to cause the air-fuel mixture to flow into the cylinder via the transfer chamber 251, and the negative pressure acts to cause air that is not mixed with fuel to flow into the cylinder. 251 or to assist it. In the illustrated configuration, the carburetor 231
The reed valve device 235, which controls the supply of air-fuel mixture from the air to the crankcase, is relatively heavy, and therefore the reed valve device 283, which controls the air supply to the transfer chamber 251, cranks the air-fuel mixture in response to a decrease in pressure. Open before supplying to case 217.

The interval, measured in crankshaft rotations, between the closing of the transfer boat 263 and the establishment of full communication between the transfer chamber 251 and the crankcase 217 takes into account sufficient timing for proper exhaust and air-fuel mixture supply. It is better to make it as large as possible. In the configuration shown, approximately 20 degrees of crankshaft rotation occurs between the opening of the transfer boat 253 and the establishment of the speed of the crankcase 217 and transfer chamber 251. Transfer room 2
The air introduced into 51 is isolated by the crankcase 217.
This prevents air from mixing with the air-fuel mixture until communication between the air and the transfer chamber 251 is established.

Prior to the establishment of this lotus passage, air is transferred to cylinder 2 for scavenging.
15, thereby preventing the air-fuel mixture from being wasted during scavenging. If necessary, all the air used for scavenging and for mixing with fuel is first transferred to the transfer chamber 251 and through it to the crankcase 217.
The fuel may be independently injected into the crankcase 217 after isolation of the transfer chamber 251 to create a fuel-air mixture that is later supplied to the transfer chamber and the sill 215.

[Brief explanation of drawings]

FIG. 1 is a partial cross-sectional view taken along line 1--1 of FIG. 4, showing an example of an engine incorporating various features of the present invention with its piston near bottom dead center; Figure 2 is a partial cross-sectional view of the engine shown in Figure 1 taken along line 2-2 in Figure 4; Figure 3 is a cross-sectional view similar to Figure 2, showing that the piston is at top dead center. Figure 4 is a sectional view taken along line 4--4 with the piston in Figure 2 omitted; Figure 5 is a sectional view taken along line 5-5 with the piston in Figure 2 omitted; Figure 6 is a cross-sectional view of the same machine as Figure 2, showing the piston in a position between top dead center and bottom dead center; Figure 7 embodies various features of the invention; A partially sectional side view showing another example of the engine when the piston is at the bottom dead center; Figure 8 is a sectional view taken along line 8-8 in Figure 7; Figure 9 is a side view of the engine in Figure 7; FIG. 10 is a partial sectional view of the engine of FIG. 8 when the piston is in another position; FIG. 11 is a partial sectional view of the engine of FIG.
The figure is a cross-sectional view taken along line 11-11 in FIG. 7, with some parts omitted for simplicity. DESCRIPTION OF SYMBOLS 11...Engine, 15...Cylinder, 17...Crankcase, 19...Piston, 25...Exhaust port, 29...Transfer passage, 31...Transfer boat, 35...Piston skirt, 51...Auxiliary chamber, 59... reed valve which is a one-way valve, 211... engine, 215... cylinder,
217...Crankcase, 219...Piston, 22
5... Exhaust boat, 251... Transfer chamber, 253...
-Transfer boat, 257...pressure boat, 259...piston skirt, 275...rentsu boat, 283...reed valve which is a one-way valve. flame·. ” Shun. 22 The flame seconds end, the number of years goes by, the statue of the flame goes by.

Claims (1)

[Scope of Claims] 1. A piston having a skirt portion and a communication port formed in the skirt portion and reciprocating between top dead center and bottom dead center; a cylinder having an exhaust port, a pressure port, and a transfer port adapted to be opened and closed by the cylinder; extending from the cylinder for upward movement of said piston toward top dead center and downward movement toward bottom dead center; a crankcase adapted to generate negative and positive pressures therein in response to motion; a device for supplying a fuel mixture to the crankcase; communication between the pressure port and a transfer port of the cylinder; and a transfer chamber for feeding the fuel mixture in the crankcase to the cylinder, and is configured to allow atmospheric air to enter the interior of the transfer chamber, but to prevent this atmospheric air from flowing out to the outside. and a transfer chamber having a one-way valve, the relative positions of the pressure port, the communication port, and the transfer port are such that the piston is located near top dead center and the transfer port is closed. When the pressure port is in communication with the crankcase, the negative pressure in the crankcase is transmitted to the transfer chamber, whereby atmospheric air is drawn into the transfer chamber through the one-way valve due to the effect of the negative pressure. The communication port and the pressure port communicate with each other in response to the downward movement of the piston toward the bottom dead center while the transfer port is closed, thereby transmitting the information to the transfer chamber. The atmospheric air drawn into the transfer chamber is compressed by the action of positive pressure within the transfer chamber, and in response to further downward movement of the piston, the transfer port is opened, so that the atmospheric pressure compressed within the transfer chamber is initially compressed. A two-stroke engine, characterized in that the fuel mixture is selected such that the fuel mixture is fed into the cylinder and then, under the action of positive pressure in the crankcase, the fuel mixture is fed from the crankcase into the cylinder. 2. A piston having a skirt portion and a communication port formed in the skirt portion and reciprocating between top dead center and bottom dead center; opened and closed by the skirt portion depending on the position of the piston; a cylinder having an exhaust port, a pressure port, an auxiliary port, and a transfer port; extending from the cylinder and responsive to upward movement of the piston toward top dead center and downward movement toward bottom dead center; a crankcase configured to generate a negative pressure and a positive pressure therein, respectively; a device for supplying a fuel mixture to the crankcase; a crankcase communicating between the crankcase and a transfer port of the cylinder; a transfer passage for supplying the fuel mixture in the cylinder to the cylinder; provided independently from the transfer passage, communicating between the pressure port and the auxiliary port, and allowing atmospheric air to enter the interior; and an auxiliary chamber having a one-way valve configured to prevent atmospheric air from flowing outside; the relative positions of the pressure port, the auxiliary port, the communication port, and the transfer port are as follows: , when the piston is located near top dead center and therefore the auxiliary port is closed, the pressure port communicates with the crankcase to transmit the negative pressure in the crankcase to the auxiliary chamber, thereby causing the auxiliary Atmospheric air is sucked into the auxiliary chamber through the one-way valve by the action of the negative pressure in the crankcase transmitted to the chamber, causing the piston to descend toward the bottom dead center while the auxiliary port is closed. In response to the movement, the communication port and the pressure port communicate with each other, whereby the sucked atmospheric air is compressed by the action of positive pressure in the crankcase transmitted to the auxiliary chamber, and the piston further moves downward. In response, the auxiliary port is opened, so that atmospheric air compressed within the auxiliary chamber is delivered into the cylinder prior to the delivery of the fuel mixture, and in response to further descent of the piston, the 2, characterized in that the transfer port is selected so that the fuel mixture is delivered from the crankcase into the cylinder under the action of positive pressure in the crankcase;
stroke engine.