Two-stroke internal combustion engine with improved transmission system
By employing an arc-shaped inlet port and a recessed transmission system in a two-stroke internal combustion engine, the problem of unburned mixture discharge is solved, resulting in a more efficient and simpler combustion process, reducing environmental pollution and production costs.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- EMAK
- Filing Date
- 2024-11-15
- Publication Date
- 2026-07-31
AI Technical Summary
In a two-stroke internal combustion engine, when the piston is near bottom dead center, the transmission and exhaust pipes open simultaneously, causing unburned mixture to be discharged, resulting in environmental pollution and reduced efficiency. Existing solutions suffer from structural complexity and increased costs.
The inlet port is designed with an arc shape with an angle range of 60 degrees or greater. Combined with the recess and connecting pipe, it forms a transmission system, which reduces the discharge of unburned mixture and improves combustion efficiency.
Improved transmission system design reduces unburned mixture emissions, lowers environmental pollution, increases engine efficiency, simplifies structure, and reduces production costs.
Smart Images
Figure CN122497797A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a two-stroke internal combustion engine, particularly a type suitable for installation in portable work tools (such as pruners, lawnmowers, chainsaws, and other similar gardening tools). Background Technology
[0002] Two-stroke internal combustion engines typically include an engine body with at least one cylinder adapted to house a piston that divides the internal volume into at least two chambers, one of which is a combustion chamber and the other is a pumping chamber.
[0003] Inside the cylinder, the piston can reciprocate between the bottom dead center and the top dead center. At the bottom dead center, the combustion chamber has the largest volume and the pumping chamber has the smallest volume. At the top dead center, the combustion chamber has the smallest volume and the pumping chamber has the largest volume.
[0004] The crankshaft is housed in the pumping chamber and connected to the piston via a connecting rod, thereby forming a crank mechanism that converts the reciprocating motion of the piston into the rotation of the crankshaft.
[0005] In order for the piston to reciprocate, the engine body is provided with: a suction pipe through which a fresh combustible mixture is charged into the pumping chamber; at least one transfer pipe connecting the pumping chamber and the combustion chamber; and an exhaust pipe for discharging the burned gases from the combustion chamber.
[0006] The operation of a two-stroke engine is characterized by the suction pipe opening when the piston is at top dead center to allow the mixture to enter the pumping chamber, while the delivery and discharge pipes are closed by the piston itself.
[0007] During the next stroke toward bottom dead center, the piston closes the suction line, opens the discharge line, and then opens the transfer line.
[0008] Thus, the mixture previously drawn into the pumping chamber is pushed into the combustion chamber through the transfer pipe, which also helps to expel the combusted gases produced in the previous operating cycle.
[0009] Once the bottom dead center is reached, the piston moves back to the top dead center, first closing the transmission pipe and then the exhaust pipe, thereby compressing the mixture in the combustion chamber.
[0010] As the piston approaches top dead center, the spark plug generates the necessary spark to ignite the compressed mixture in the combustion chamber, producing rapidly expanding, burned gas that pushes the piston back to bottom dead center and repeats the cycle.
[0011] The known problem with these engines is that, at certain time intervals, when the piston is near bottom dead center, both the transmission and exhaust pipes open simultaneously, allowing a portion of the mixture pumped into the combustion chamber through the transmission pipe to be discharged directly through the exhaust pipe (unburned).
[0012] Therefore, during this process, the engine can release large amounts of fuel and lubricating oil into the environment, which are harmful pollutants.
[0013] Furthermore, compared to an ideal cycle where all the mixture remains confined within the combustion chamber, the loss of unburned mixture through the exhaust pipe inevitably leads to a decrease in efficiency, thus increasing consumption.
[0014] One solution known to those skilled in the art to reduce mixture consumption is to reduce the cross-sectional area of the transmission pipe, thereby minimizing the time during which the transmission and discharge pipes are open simultaneously.
[0015] However, from an efficiency standpoint, this solution is harmful because the reduction in the cross-sectional area of the passage increases the pressure loss of the mixture as it passes through the transmission pipe, which means that the piston absorbs more energy to pump the mixture into the combustion chamber.
[0016] Another solution to reduce mixture consumption is to install a movable baffle (or rotary valve) on the crankshaft inside the pump chamber, which is adapted to keep the transmission line closed for a longer period of time while the discharge line is open.
[0017] However, the drawbacks of this solution are the introduction of significant structural complexity, leading to higher production costs and increased overall size, as well as reduced efficiency due to the additional mass required to drive the rotation of the movable partition. Summary of the Invention
[0018] In view of the above, one object of the present invention is to reduce the amount of unburned fresh mixture emitted from a two-stroke internal combustion engine, so as to reduce the environmental impact and improve efficiency.
[0019] Another object of the present invention is to achieve the aforementioned object in the context of a simple, reasonable and relatively inexpensive solution.
[0020] These and other objectives are achieved by the features of the invention as set forth in the independent claims. The dependent claims summarize the preferred and / or particularly advantageous aspects of the invention.
[0021] Specifically, embodiments of the present invention provide a two-stroke internal combustion engine, comprising:
[0022] -The engine itself, which has a limited internal volume;
[0023] - At least one piston slidably housed in a cylindrical portion of the internal volume to divide the cylindrical portion into at least two variable-volume chambers, one of which is a pumping chamber and the other is a combustion chamber;
[0024] - A crankshaft rotatably connected to the engine body and rotating about a predetermined axis of rotation, the crankshaft carrying at least one crank in the pumping chamber;
[0025] - A connecting rod, which connects the crank and the piston to convert the linear reciprocating motion of the piston into the rotational motion of the crankshaft; and
[0026] - At least one transmission system adapted to provide fluid communication between the pumping chamber and the combustion chamber;
[0027] The transmission system includes:
[0028] - The inlet port is located on the inner surface of the engine body, which defines the pumping chamber and is orthogonal to the axis of rotation of the crankshaft;
[0029] - At least one outlet port formed on the inner surface of the cylindrical portion defining the internal volume of the engine body; and
[0030] - At least one transmission pipe connecting the inlet port and the outlet port;
[0031] The inlet port is arc-shaped and extends around the rotation axis of the crankshaft at an angle greater than or equal to 50 degrees (e.g., greater than or equal to 90 degrees in sexagesimal).
[0032] Thanks to the unique geometry of the inlet port, engine efficiency can be improved even without using rotary valves or other devices.
[0033] This experimentally proven effect is explained by the fact that the new geometry of the inlet port (which also leads to an increase in the total length of the transmission system) improves the vaporization of the mixture.
[0034] This improved vaporization breaks the mixture into finer particles with less inertia. These particles diffuse more evenly within the combustion chamber and take longer to reach the exhaust pipe, thus ensuring more complete combustion and lower consumption of unburned mixture.
[0035] As mentioned above, all of these do not require rotary valves or other devices, and are therefore part of a simpler, cheaper, and more compact solution compared to known solutions.
[0036] According to one aspect of the invention, the inlet port can be divided into a first part and a second part by a transverse plane orthogonal to the central axis of the cylindrical portion and including the axis of rotation of the crankshaft; the first part is located on the same side of the combustion chamber, and the second part has a smaller angular extension range than the first part and is located on the opposite side.
[0037] In particular, the angular extension range of the second part of the inlet port can be less than or equal to 10 degrees in sexagesimal, for example, less than or equal to 5 degrees in sexagesimal.
[0038] Therefore, the largest part of the inlet port is located in the "upper" part of the pumping chamber, that is, the part close to the combustion chamber, which is conducive to the flow of the mixture towards the combustion chamber itself in the transmission system.
[0039] However, it is not excluded that in some embodiments, the inlet port may be located entirely on the same side of the combustion chamber or entirely on the "upper" part of the pumping chamber, relative to a transverse plane orthogonal to the central axis of the cylindrical portion and containing the axis of rotation of the crankshaft.
[0040] In this case, the aforementioned transverse plane may, for example, be tangent to the inlet port.
[0041] According to another aspect of the invention, the inlet port can be divided into a main part and a sub-part by a longitudinal plane comprising the central axis of the cylindrical portion and the rotation axis of the crankshaft; the main part is located on the same side of the engine suction pipe, and the sub-part has a smaller angular extension range than the main part and is located on the opposite side.
[0042] In particular, the angular extension range of the secondary portion of the inlet port can be less than or equal to 20 degrees in sexagesimal, for example, less than or equal to 15 degrees in sexagesimal.
[0043] Therefore, the largest portion of the inlet port is located in the section of the pumping chamber near the suction pipe from which the fresh mixture enters, further promoting the flow of the mixture into the transmission system toward the combustion chamber.
[0044] However, even in this case, it is not excluded that in some embodiments, the inlet port may be located entirely on the same side of the engine suction pipe relative to the longitudinal plane of the central axis containing the cylindrical portion and the axis of rotation of the crankshaft.
[0045] In this case, the aforementioned longitudinal plane may, for example, be tangent to the inlet port.
[0046] Another aspect of the invention proposes that the radial extension of the inlet port can lie entirely within a circular crown centered on the axis of rotation of the crankshaft, the inner diameter D of which is... inn and outer diameter D out The following relationship must be satisfied:
[0047] D inn = α·S
[0048] D out = β·S
[0049] Where α is a coefficient between 1.25 and 1.5 (inclusive), β is a coefficient between 1.55 and 1.9 (inclusive), and S is the total stroke of the piston from bottom dead center to top dead center.
[0050] Meeting these dimensional relationships allows for the advantageous maintenance of a very compact internal combustion engine without compromising efficiency, and in particular, without making the inlet port too small (as is associated with the piston stroke and therefore the amount of mixture to be delivered) to impair adequate flow of the mixture toward the combustion chamber.
[0051] According to another aspect of the invention, the inlet port can be realized by a recess formed on the inner surface of the engine body and communicating with the transmission conduit.
[0052] The maximum depth of the depression can be less than or equal to 10 mm, for example, less than or equal to 6 mm.
[0053] It should be noted that the “depth” of the recess refers to the size / width of the recess in the direction orthogonal to the surface of the plane it forms.
[0054] Another aspect of the invention proposes that the depth of the recess can increase (i.e. rise) from the first angular end of the inlet port to the opposite second angular end.
[0055] Since the inlet port is arc-shaped, the "angle end" refers to one end of the arc (or curve) that defines the shape of the inlet port.
[0056] That said, the second angle end of the inlet port could be, for example, the end closer to the combustion chamber, that is, the end closer to the combustion chamber than the other end, which could therefore be the first angle end.
[0057] Therefore, the depth of the indentation increases as it moves toward the combustion chamber.
[0058] According to another aspect of the invention, the aforementioned recess can be connected to a transmission pipe via a connecting pipe formed in the engine body at a retracted position on the inner surface of the plane where the inlet port is located.
[0059] "Retracted position" refers to the position where the recess is located on the opposite side of the inlet port, that is, along the direction orthogonal to the surface of the plane in which the inlet port is located, and the recess is essentially located between the inlet port and the connecting pipe.
[0060] In order to connect the recess with the transmission pipe, the connecting pipe may intersect at least a portion of the recess, preferably only a (limited) portion of the recess.
[0061] Therefore, the intersection between the connecting pipe and the aforementioned recessed portion defines an opening to allow them to communicate directly with each other.
[0062] Alternatively, or as a special case, at least a portion of the recess, preferably only a limited portion, may be open at the bottom (e.g., without a bottom at all) to provide access to the connecting pipe.
[0063] The “bottom” of a recess (or a portion thereof) obviously refers to the surface of the recess (or a portion thereof), if such a surface exists, and is opposite to the inlet port along a direction orthogonal to the surface of the plane in which the inlet port is located.
[0064] According to one aspect of the invention, the recessed portion intersecting the connecting pipe and / or the bottom opening may be the portion facing the inlet port near the angular end of the combustion chamber.
[0065] Thus, shorter and simpler connecting pipes help limit engine size.
[0066] Another aspect of the invention proposes that the connecting conduit may extend parallel to the central axis of the cylindrical portion that houses the piston, for example, it may include at least one cross-sectional segment extending along an axis parallel to the central axis.
[0067] Thanks to this scheme, the mixture from the pumping chamber is effectively diverted and transported to the combustion chamber through the inlet port and associated recess.
[0068] According to another aspect of the invention, the connecting pipe can be positioned such that it is truncated by a longitudinal plane containing the central axis of the cylindrical portion housing the piston and the axis of rotation of the crankshaft.
[0069] In other words, the connecting pipe can be positioned such that the longitudinal plane divides it into two parts, preferably two parts of similar size.
[0070] Therefore, the connecting pipes are generally located on the centerline of the internal combustion engine, which helps to keep its size small and compact.
[0071] One different aspect of the invention proposes that the transmission system may include at least two separate transmission channels, both of which are connected to the inlet port via the same connecting channel.
[0072] Thanks to this design, where the connecting pipe also acts as a manifold for the transmission pipe, it can supply several separate mixture streams to the combustion chamber to improve the distribution of the mixture and thus improve subsequent combustion.
[0073] Turning to a more suitable structural aspect, one aspect of the invention proposes that the inlet port, recess, and connecting conduit can be formed in a single piece.
[0074] This advantageously reduces the number of parts required to assemble the engine, making the engine production process simpler and faster.
[0075] Another aspect of the invention proposes that the engine body may be composed of at least two separate components assembled together, including: a crankcase (or pump housing) having at least an inlet port, a recess, and a connecting pipe; and a head having at least a transmission pipe and an outlet port.
[0076] The crankcase (or pump housing) can be formed from at least two separate housings joined together along a plane orthogonal to the axis of rotation of the crankshaft and containing the cylindrical portion of the engine body.
[0077] According to another aspect of the invention, the engine may include two transmission systems, each having the above-described features, and the two transmission systems are arranged in a mirror manner with respect to a plane of symmetry orthogonal to the axis of rotation of the crankshaft.
[0078] This further improves the process of filling the combustion chamber with a mixture from the pumping chamber. Attached Figure Description
[0079] Further features and advantages of the invention will become apparent with the aid of the accompanying drawings and after reading the following description provided by way of non-limiting example.
[0080] Figure 1 This is a longitudinal sectional view of a two-stroke internal combustion engine according to an embodiment of the present invention.
[0081] Figure 2 yes Figure 1 Section II-II.
[0082] Figure 3 yes Figure 2 The cross-section shows the piston at the bottom dead center position.
[0083] Figure 4 yes Figure 2 Enlarged detail image.
[0084] Figure 5 yes Figure 2 The cross-section shows the crankshaft and connecting rods removed to highlight certain aspects of the invention.
[0085] Figure 6 It is formed Figure 1 A perspective view of one of the housings of the engine's crankcase (or pump housing).
[0086] Figure 7 It is based on Figure 5 Sectioned by plane VII-VII Figure 6 The cross-section of the shell.
[0087] Figure 8 yes Figure 5 Section VIII-VIII. Detailed Implementation
[0088] In the accompanying drawings, the two-stroke internal combustion engine is generally designated as 100, for example, an engine that can be installed in portable work tools such as brush cutters, lawnmowers, chainsaws, and similar gardening tools.
[0089] Engine 100 can use a mixture of fuel (e.g., gasoline) and lubricant as fuel, which is dispersed into the airflow by means of a suitable mixing system (e.g., including a carburetor).
[0090] The engine 100 includes a crankshaft 105 adapted to rotate about a rotation axis R, and the driving force generated by the engine 100 itself is output through the crankshaft 105.
[0091] It should be noted that a crankshaft is a shaft that carries at least one crank (i.e., an eccentric element) which, due to the rotation of the shaft, is adapted to perform a complete rotational motion about the axis of rotation R.
[0092] For example, crankshaft 105 may include: a first cylindrical segment 110 coaxial with the axis of rotation R; a second cylindrical segment 115 opposite to the first cylindrical segment 110 and also coaxial with the axis of rotation R; and crank 120, which is located between the first cylindrical segment 110 and the second cylindrical segment 115 and rotates rigidly integrally with them (without residual degrees of freedom).
[0093] The crank 120 may include a pivot 125 having an axis parallel to and eccentric to the axis of rotation R, i.e., the axis is arranged at a certain (non-zero) distance from the axis of rotation R.
[0094] In the illustrated embodiment, a pivot 125 is located between two arms that extend radially from and project from cylindrical segments 110 and 115, moving away from the axis of rotation R, and the two arms together with the pivot 125 integrally define the crank 120.
[0095] The crankshaft 105 may also include a flywheel mass block 130, and the crankshaft 105 and the flywheel mass block 130 rotate together.
[0096] For example, the flywheel mass 130 protrudes radially from the first cylindrical segment 110 and the second cylindrical segment 115, preferably in a radial direction opposite to that of the crank 120.
[0097] In the illustrated embodiment, the flywheel mass block 130 includes a pair of sector disks, each of which rotates integrally with a corresponding cylindrical segment 110 and 115.
[0098] Each of these sector discs can be made as a single unit (i.e., a one-piece) with the corresponding arm of crank 120 and the corresponding cylindrical segment 110 or 115.
[0099] The engine 100 also includes at least one piston 135, which is connected to the crankshaft 105 via a connecting rod 140, or more precisely, to the crank 120.
[0100] Specifically, the connecting rod 140 may have one end hinged to the piston 135 (e.g., a pin 145 hinged to the piston 135) and the opposite end hinged to the crank 120 (e.g., a pivot 125), possibly by means of a bearing.
[0101] Therefore, the crank 120, piston 135 and connecting rod 140 together form a pusher crank mechanism, which is suitable for converting the linear reciprocating motion of piston 135 into the rotational motion of crank 120 and crankshaft 105 as a whole.
[0102] The crank 120, piston 135 and connecting rod 140 are housed within the internal volume of the engine body 150.
[0103] Specifically, the piston 135 is coaxially and slidably connected to the cylindrical portion 151 (also referred to as the "cylinder") of the internal volume of the engine body 150, the central axis Q of which is preferably orthogonal and coplanar with the axis of rotation R of the crankshaft 105.
[0104] Therefore, the piston 135 divides the internal volume of the engine body 150 into at least two variable-volume chambers, one of which is a combustion chamber 155 and the other is a pumping chamber 160.
[0105] Specifically, inside the cylinder, piston 135 can be at top dead center (e.g., Figure 2 (as shown) and the position of the lower endpoint (as shown) Figure 3 The combustion chamber 155 slides between the two chambers (as shown), where the volume of the combustion chamber 155 is the smallest and the volume of the pumping chamber 160 is the largest at the top dead center position, and the volume of the combustion chamber 155 is the largest and the volume of the pumping chamber 160 is the smallest at the bottom dead center position.
[0106] Combustion chamber 155 can accommodate a spark plug (not shown) to ignite the mixture for combustion, while pumping chamber 160 can accommodate crank 120 and connecting rod 140.
[0107] Specifically, along the direction of the axis of rotation R, the crank 120 may be located between two inner surfaces of the pump chamber 160 defined by the engine body 150, namely the first inner surface 165 and the second inner surface 170.
[0108] Each of these inner surfaces 165 and 170 is generally planar and orthogonal to the axis of rotation R.
[0109] The first inner surface 165 can be passed through by the first cylindrical segment 110 of the crankshaft 105, which can be rotatably connected to (and supported by) the engine body 150 by means of a bearing housed in a seat formed on the first inner surface 165.
[0110] Similarly, the second inner surface 170 can be passed through by the second cylindrical section 115 of the crankshaft 105, which can be rotatably connected to (and supported by) the engine body 150 by means of another bearing housed in a seat on the second inner surface 170.
[0111] The engine body 150 may consist of a head 175 and a crankcase (or pump housing) 180, the head 175 defining a combustion chamber 155 and the crankcase 180 at least partially defining a pumping chamber 160.
[0112] Specifically, the bearing housing for supporting the crankshaft 105 can be fully formed in the crankcase 180.
[0113] The head 175 and crankcase 180 can be manufactured as separate parts, but can also be assembled together.
[0114] Furthermore, the head 175 can be formed from a single piece (e.g., manufactured by a molding process), while the crankcase 180 can be divided into two separate housings, for example, along a plane orthogonal to the axis of rotation R of the crankshaft 105 and containing the central axis Q of the cylinder. These two separate housings can be assembled together, namely the first housing 185 and the second housing 190.
[0115] Each of these first housings 185 and second housings 190 can be produced as a single piece (e.g., by molding process).
[0116] The first housing 185 may provide a first in-plane surface 165, while the second housing 190 may provide a second in-plane surface 170, wherein a housing for a crankshaft 105 bearing may be formed.
[0117] In the engine body 150 (e.g., in the head 175), there is also a suction pipe 195 adapted to deliver a mixture flow to the pumping chamber 160.
[0118] like Figure 2 As shown, the suction pipe 195 can extend longitudinally along a central axis that is coplanar with and / or orthogonal to the central axis Q of the cylinder.
[0119] The suction conduit 195 leads to a portion of the cylinder's inner surface, such that when the piston 135 is at bottom dead center (see...). Figure 3 The suction pipe 195 is blocked by the piston 135, but when the piston 135 is at top dead center (see...) Figure 2 The suction pipe 195 is opened and connected to the pumping chamber 160.
[0120] In the engine body 150 (e.g., in the head 175), there is also an exhaust pipe 200 adapted to deliver combustion gases generated in the combustion chamber 155 to the outside.
[0121] The discharge pipe 200 may also extend longitudinally along a central axis that is coplanar with and / or orthogonal to the central axis Q of the cylinder, but the discharge pipe 200 is located on the opposite side of the suction pipe 195 (relative to the plane containing the central axis Q of the cylinder and orthogonal to the axis of rotation R of the crankshaft 105).
[0122] The exhaust pipe 200 may have an opening in a portion of the inner surface of the cylinder, such that when the piston 135 is at top dead center (see...). Figure 2 The discharge pipe 200 is blocked by piston 135, but when piston 135 is at bottom dead center (see...) Figure 3 The exhaust pipe 200 is opened and connected to the combustion chamber 155.
[0123] Therefore, the exhaust pipe 200 may have an opening on a portion of the cylinder inner surface, which is located further from the rotation axis R than the portion to which the inlet pipe 195 leads.
[0124] Finally, engine 100 may include at least one transmission system, for example formed in engine body 150, which is adapted to fluidly communicate pumping chamber 160 with combustion chamber 155 during certain steps of the working cycle.
[0125] More preferably, the engine 100 includes two transmission systems that are mirror-shaped and arranged relative to the central axis Q of the cylinder and the axis of rotation R of the crankshaft 105.
[0126] Since the two transmission systems are mirror images, only one transmission system will be described below. It should be understood that each feature described will also apply to the other transmission system.
[0127] like Figure 4As shown, the transmission system includes: an inlet port 205 located on the in-plane surface 165 of the engine body 150; at least one outlet port 210 formed on the inner surface of the cylinder; and at least one transmission conduit 215 adapted to connect the inlet port 205 and the outlet port 210.
[0128] More preferably (see Figure 8 Each transmission system may include at least one pair of transmission pipes 215, which are separate from each other and each has an exit port 210 (see...). Figure 3 However, both are connected to the same inlet port 205.
[0129] Now go to Figure 5 As can be seen, the inlet port 205 is arc-shaped and extends at an angle around the rotation axis R of the crankshaft 105, for example, from the first angle end 220 to the second angle end 225.
[0130] Since the inlet port 205 is arc-shaped, the "angle end" refers to one end of the arc (or curve) that defines the shape of the inlet port 205.
[0131] The first angle end 220 of the inlet port 205 can be far away from the combustion chamber 155, while the second angle end 225 can be close to the combustion chamber 155.
[0132] In other words, the distance between the second angle end 225 and the combustion chamber 155 can be less than the distance between the combustion chamber 155 and the first angle end 220.
[0133] The total angular extension range Ω of the entry port 205 (i.e., from the first angle end 220 to the second angle end 225) is greater than or equal to 50 degrees in sexagesimal, for example, greater than or equal to 90 degrees in sexagesimal, and preferably, but not necessarily, less than or equal to 115 degrees in sexagesimal. In the embodiment shown herein, the total angular extension range Ω of the entry port 205 is, for example, approximately equal to 103 degrees in sexagesimal.
[0134] The inlet port 205 is arranged such that it can be divided into a first part 205A and a second part 205B by a transverse plane A orthogonal to the central axis Q of the cylinder and containing the axis of rotation R of the crankshaft 105. The first part 205A is located on the same side of the combustion chamber 155, and the second part 205B is located on the opposite side. The angular extension range γ of the second part 205B is smaller than the angular extension range δ of the first part 205A, preferably much smaller.
[0135] For example, the angular extension range γ of the second part 205B of the inlet port 205 can be less than or equal to 10 degrees in sexagesimal, preferably less than or equal to 5 degrees in sexagesimal.
[0136] In the embodiment shown herein, the angular extension range γ of the second portion 205B of the entry port 205 is, for example, approximately equal to 3 degrees in sexagesimal, such that the angular extension range δ of the first portion 205A is approximately equal to 100 degrees in sexagesimal.
[0137] However, it is not excluded that in other embodiments, the inlet port 205 may be located entirely on the same side of the combustion chamber 155 relative to the transverse plane A, or entirely on the "upper" part of the pumping chamber 160, for example, such that the transverse plane A is tangent to the inlet port 205 (the angular extension range γ is equal to zero).
[0138] The inlet port 205 can also be positioned such that it is divided into a main part 205C and a secondary part 205D by a longitudinal plane B that simultaneously includes the central axis Q of the cylinder and the rotation axis R of the crankshaft 105. The main part 205C is located on the same side of the inlet port 195, and the secondary part 205D is located on the opposite side. The angular extension range φ of the secondary part 205D is smaller than the angular extension range ε of the main part 205C, preferably much smaller.
[0139] For example, the angular extension range φ of the sub-part 205D of the inlet port 205 can be less than or equal to 20 degrees in sexagesimal, preferably less than or equal to 15 degrees in sexagesimal.
[0140] In the embodiment shown herein, the angular extension range φ of the secondary portion 205D of the entry port 205 is approximately equal to 10 degrees in sexagesimal, such that the angular extension range ε of the primary portion 205C is approximately equal to 103 degrees in sexagesimal.
[0141] However, even in this case, it is not excluded that in some embodiments, the inlet port 205 may be located entirely on the same side of the inlet pipe 195 relative to the longitudinal plane B, for example, such that the longitudinal plane B is tangent to the inlet port 205 (the angular extension range φ is equal to zero).
[0142] Moving to the radial extension range, the radial extension range of the inlet port 205 allows it to be completely enclosed (accommodated) within a circular crown on the inner surface 165, the circular crown being centered on the axis of rotation R of the crankshaft 105, with an inner diameter D. inn and outer diameter D out The following relationship must be satisfied:
[0143] D inn = α·S
[0144] D out = β·S
[0145] Where α is a coefficient between 1.25 and 1.5 (inclusive), β is a coefficient between 1.55 and 1.9 (inclusive), and S is the full stroke of piston 135 from bottom dead center to top dead center.
[0146] Generally, the stroke S is equal to twice the radial distance between the axis of rotation R of crankshaft 105 and the axis of pivot 125, through which crankshaft 105 is connected to connecting rod 140.
[0147] like Figure 6 As shown, the inlet port 205 can be achieved by a recess 230 formed on the in-plane surface 165 of the engine body 150, the maximum depth of which can be less than or equal to 10 mm, for example less than or equal to 6 mm.
[0148] Specifically, the depth of the recess 230 can increase (i.e. rise) from the first angle end 220 of the inlet port 205 (where the depth can be essentially zero) toward the opposite second angle end 225.
[0149] The recess 230 can be connected to each transmission pipe 210 via a connecting pipe (or manifold) 235, which is formed in the engine body 150 at the retracted position of the inner surface 165 of the plane where the inlet port 205 is located.
[0150] The retracted position refers to the position on the opposite side of the recess 230 relative to the inlet port 205, along the direction orthogonal to the inner surface 165 of the plane where the inlet port 205 is located, such that the recess 230 is substantially located between the inlet port 205 and the connecting pipe 235.
[0151] The connecting pipe 235 may extend in a direction parallel to the central axis Q of the cylinder, that is, it may include at least one section having a constant cross-section relative to an axis parallel to the central axis Q of the cylinder.
[0152] Specifically, the connecting pipe 235 may be positioned on the centerline of the engine 100, or more precisely, positioned such that it is truncated by a longitudinal plane that simultaneously contains the central axis Q of the cylinder and the axis of rotation R of the crankshaft 105, thereby being divided into two parts by said longitudinal plane, preferably the two parts being of similar size.
[0153] like Figure 7 As shown, in order to connect the recess 230 to the transmission conduit 215, the connecting conduit 235 may intersect with a portion of the recess 230, such that the intersection 240 between the connecting conduit 235 and the portion of the recess 230 defines an opening so that they are directly connected to each other.
[0154] In this specific example, this means that the portion of recess 230 is open at the bottom (i.e., completely without a bottom), allowing it to lead to connecting pipe 235.
[0155] The “bottom” of a recess (or a portion thereof) refers to the surface of the recess (or a portion thereof), if such surface exists, and is opposite to the inlet port 205 in a direction orthogonal to the plane surface 165 where the inlet port 205 is located.
[0156] Preferably, the portion of the recess 230 that intersects with the connecting pipe 235 or has a bottom opening is a limited portion, thus the recess 230 also has another portion that does not intersect with the connecting pipe 235, and in this example, this other portion is actually closed at the bottom by a surface 245 adapted to define its depth.
[0157] Of these two parts, the portion of the recess 230 that intersects with the connecting pipe 235 or has a bottom opening is preferably the portion facing / defining the second angle end 225 of the inlet port 205, i.e., the portion near the combustion chamber 155.
[0158] As shown in the figure, the inlet port 205, the recess 230 and the connecting pipe 235 are preferably formed in the crankcase 180 of the engine 100, while each transmission pipe 215 and its opposite outlet port 210 are provided in the head 175.
[0159] In particular, the inlet port 205, the recess 230 and the connecting pipe 235 are preferably formed in a monolithic body, in this case, in the first housing 185 forming the crankcase 180.
[0160] Obviously, the inlet port 205, recess 230 and connecting pipe 235 of another transmission system (if present) are preferably formed in the second housing 190, with the inlet port 205 located on the in-plane surface 170.
[0161] like Figure 2 As shown, the operation of engine 100 can be described from the moment piston 135 is at top dead center.
[0162] In this position, piston 135 closes the outlet port 210 of discharge pipe 200 and each transfer pipe 215, while keeping inlet port 195 open to allow the mixture to enter pumping chamber 160.
[0163] During the next stroke toward bottom dead center (see...) Figure 3 Piston 135 closes suction pipe 195, opens discharge pipe 200, and then opens outlet port 210 of each transmission pipe 215.
[0164] Therefore, the mixture previously drawn into the pumping chamber 160 is pushed into the combustion chamber 155 through the various transmission systems, which also helps to expel the combusted gases generated during the previous operating cycle.
[0165] When the bottom dead center is reached, the piston 135 moves back to the top dead center, first closing the outlet ports 210 of each transmission pipe 215, and then closing the exhaust pipe 200, thereby compressing the mixture in the combustion chamber 155.
[0166] When piston 135 approaches top dead center, spark plug (not shown) generates a spark, igniting the compressed mixture in combustion chamber 155, thereby producing rapidly expanding burned gas that pushes piston 135 back to bottom dead center and repeats the cycle.
[0167] The present invention, as conceived thus, is readily subject to several modifications and variations, all of which fall within the scope of the inventive concept. Furthermore, all details can be substituted with other technically equivalent elements. In practice, the materials used, and, depending on the circumstances, the shape and size, can be determined as required without departing from the scope of protection of the following claims.
Claims
1. A two-stroke internal combustion engine (100), comprising: - Engine body (150), with limited internal volume; - At least one piston (135) is slidably housed in a cylindrical portion (151) of the internal volume to divide the cylindrical portion into at least two variable-volume chambers, one of which is a pumping chamber (160) and the other is a combustion chamber (155). - A crankshaft (105) rotatably connected to the engine body (150) and rotating about a predetermined axis of rotation (R), the crankshaft (105) carrying at least one crank (120) within the pumping chamber (160). - A connecting rod (140) is connected between the crank (120) and the piston (135) to convert the linear reciprocating movement of the piston (135) into the rotational movement of the crankshaft (105); as well as - At least one transmission system adapted to fluidly communicate the pumping chamber (160) with the combustion chamber (155); The transmission system mentioned above includes: - An inlet port (205) is disposed on an in-plane surface (165) of the engine body (150), the in-plane surface (165) defining the pumping chamber (160) and orthogonal to the axis of rotation (R) of the crankshaft (105); - At least one outlet port (210) formed on the inner surface of the cylindrical portion (151) of the engine body (150) defining the internal volume; and - At least one transmission pipe (215) connecting the inlet port (205) and the outlet port (210); The inlet port (205) is arc-shaped and extends angularly around the rotation axis (R) of the crankshaft (105) by an angle of 50 degrees (Ω) greater than or equal to base 60, for example, by an angle of 90 degrees (Ω) greater than or equal to base 60.
2. The engine (100) according to claim 1, wherein, The angular extension range (Ω) of the inlet port (205) is less than or equal to 115 degrees in sexagesimal.
3. The engine (100) according to claim 1 or 2, wherein, The inlet port (205) is divided into a first part (205A) and a second part (205B) by a transverse plane orthogonal to the central axis (Q) of the cylindrical portion (151) and including the rotation axis (R) of the crankshaft (105). The first part (205A) is located on the same side of the combustion chamber (155), and the second part (205B) has a smaller angular extension range than the first part (205A) and is located on the opposite side.
4. The engine (100) according to claim 3, wherein, The angular extension range (γ) of the second portion (205B) of the entry port (205) is less than or equal to 10 degrees in sexagesimal.
5. The engine (100) according to any one of the preceding claims, wherein, The inlet port (205) is divided into a main part (205C) and a sub-part (205D) by a longitudinal plane containing the central axis (Q) of the cylindrical portion (151) and the rotation axis (R) of the crankshaft (105). The main part (205C) is located on the same side of the engine's suction pipe (195), and the sub-part (205D) has a smaller angular extension range than the main part and is located on the opposite side.
6. The engine (100) according to claim 5, wherein, The angular extension range (ε) of the sub-part (205D) of the inlet port (205) is less than or equal to 20 degrees in sexagesimal.
7. The engine (100) according to any one of the preceding claims, wherein, The radial extension of said inlet port (205) is entirely located within a circular crown centered on said rotation axis (R) of said crankshaft (105), the inner diameter D inn and the outer diameter D out of said circular crown satisfying the following relationship: D inn = α·S D out = β·S Wherein, α is a coefficient with a value between 1.25 and 1.5, β is a coefficient with a value between 1.55 and 1.9, and S is the full stroke of the piston (135) from bottom dead center to top dead center.
8. The engine (100) according to any one of the preceding claims, wherein, The inlet port (205) is formed by a recess (230) on the in-plane surface (165) of the engine body (150) and communicates with the transmission pipe (215).
9. The engine (100) according to claim 8, wherein, The maximum depth of the depression (230) is less than or equal to 10 mm.
10. The engine (100) according to claim 8 or 9, wherein, The depth of the recess (230) increases from the first angle end (220) of the inlet port (205) toward the opposite second angle end (225).
11. The engine (100) according to claim 10, wherein, The second angle end (225) of the inlet port (205) is close to the combustion chamber (155).
12. The engine (100) according to any one of claims 8 to 11, wherein, The recess (230) is connected to the transmission pipe (215) via a connecting pipe (235), which is formed in the engine body (150) at a retracted position relative to the in-plane surface (165) where the inlet port (205) is located, and extends parallel to the central axis (Q) of the cylindrical portion (151) that houses the piston (135).
13. The engine (100) according to claim 12, wherein, The transmission system includes at least two separate transmission pipes (215), both of which are connected to the inlet port (205) via the same connecting pipe (235).
14. The engine (100) according to claim 12 or 13, wherein, The inlet port (205), the recess (230) and the connecting pipe (235) are formed in a monolithic body (185).
15. The engine (100) according to any one of claims 12 to 14, wherein, The engine body (150) consists of at least two separate components assembled together, including: a crankcase (180) having at least the inlet port (205), the recess (230) and the connecting pipe (235); and a head (175) having at least the transmission pipe (215) and the outlet port (210).