EP3284938A1 - Piston for a two-stroke engine working with direct injection and two-stroke engine - Google Patents
Piston for a two-stroke engine working with direct injection and two-stroke engine Download PDFInfo
- Publication number
- EP3284938A1 EP3284938A1 EP16001824.8A EP16001824A EP3284938A1 EP 3284938 A1 EP3284938 A1 EP 3284938A1 EP 16001824 A EP16001824 A EP 16001824A EP 3284938 A1 EP3284938 A1 EP 3284938A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- piston
- connecting rib
- skirt
- stroke engine
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
- 238000002347 injection Methods 0.000 title description 2
- 239000007924 injection Substances 0.000 title description 2
- 230000002000 scavenging effect Effects 0.000 claims abstract description 7
- 238000002485 combustion reaction Methods 0.000 claims description 28
- 229910052751 metal Inorganic materials 0.000 claims description 8
- 239000002184 metal Substances 0.000 claims description 8
- 238000012546 transfer Methods 0.000 claims description 7
- 230000002093 peripheral effect Effects 0.000 claims description 2
- 239000000203 mixture Substances 0.000 description 17
- 239000000446 fuel Substances 0.000 description 7
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 description 6
- 229910052749 magnesium Inorganic materials 0.000 description 6
- 239000011777 magnesium Substances 0.000 description 6
- 238000005266 casting Methods 0.000 description 4
- 238000013461 design Methods 0.000 description 4
- 238000011144 upstream manufacturing Methods 0.000 description 4
- 239000000463 material Substances 0.000 description 3
- 238000009825 accumulation Methods 0.000 description 2
- 230000035508 accumulation Effects 0.000 description 2
- 229910052782 aluminium Inorganic materials 0.000 description 2
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 2
- 238000001816 cooling Methods 0.000 description 2
- 239000007789 gas Substances 0.000 description 2
- 238000003754 machining Methods 0.000 description 2
- 230000002146 bilateral effect Effects 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 238000005520 cutting process Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 230000018109 developmental process Effects 0.000 description 1
- 238000006073 displacement reaction Methods 0.000 description 1
- 238000011010 flushing procedure Methods 0.000 description 1
- 238000007373 indentation Methods 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 238000012549 training Methods 0.000 description 1
- 230000007704 transition Effects 0.000 description 1
- 239000013585 weight reducing agent Substances 0.000 description 1
Images
Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02F—CYLINDERS, PISTONS OR CASINGS, FOR COMBUSTION ENGINES; ARRANGEMENTS OF SEALINGS IN COMBUSTION ENGINES
- F02F3/00—Pistons
- F02F3/0084—Pistons the pistons being constructed from specific materials
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02B—INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
- F02B75/00—Other engines
- F02B75/02—Engines characterised by their cycles, e.g. six-stroke
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02F—CYLINDERS, PISTONS OR CASINGS, FOR COMBUSTION ENGINES; ARRANGEMENTS OF SEALINGS IN COMBUSTION ENGINES
- F02F3/00—Pistons
- F02F3/0076—Pistons the inside of the pistons being provided with ribs or fins
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02F—CYLINDERS, PISTONS OR CASINGS, FOR COMBUSTION ENGINES; ARRANGEMENTS OF SEALINGS IN COMBUSTION ENGINES
- F02F3/00—Pistons
- F02F3/24—Pistons having means for guiding gases in cylinders, e.g. for guiding scavenging charge in two-stroke engines
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02B—INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
- F02B75/00—Other engines
- F02B75/02—Engines characterised by their cycles, e.g. six-stroke
- F02B2075/022—Engines characterised by their cycles, e.g. six-stroke having less than six strokes per cycle
- F02B2075/025—Engines characterised by their cycles, e.g. six-stroke having less than six strokes per cycle two
Definitions
- the invention relates to a piston for a working with flushing two-stroke engine of the type specified in the preamble of claim 1 and a two-stroke engine.
- the invention has for its object to provide a piston for a working with scavenging two-stroke engine, which has a high stability. Another object of the invention is to provide a two-stroke engine with a piston.
- the piston has piston pin bosses in which piston pin receptacles are formed. It is provided that at least one piston pin eye is connected via at least one connecting rib with the piston skirt.
- the connecting rib extends at the side facing away from the piston crown side of the piston bag.
- the connecting rib leads to improved support of the piston pin eye. Forces from the piston pin boss can be better transmitted to the piston skirt via the connecting rib. This achieves greater stability.
- the introduction of force from the piston pin eye in the piston skirt is improved.
- the connecting rib causes a stiffening and increase in strength of the piston. Heat is also dissipated from the piston pin boss into the piston skirt via the connecting rib. As a result, an improved cooling of the thermally highly loaded area of the piston pin bosses is achieved.
- a recess is formed between the connecting rib and the piston skirt.
- the recess avoids material accumulations in this area, so that a better manufacturability of the piston, in particular in a casting process, is given. Through the recess casting errors can be avoided. It is achieved a weight reduction.
- the depth of the recess is advantageously at least 3%, in particular at least 5% of the height of the piston.
- a good bilateral cooling of the connecting rib is achieved by means of the depression through mixture flowing in the crankcase interior or through combustion air flowing in the crankcase interior.
- the depth of the recess is advantageously less than 20% of the height of the piston. This leaves enough space for the piston bag without increasing the height of the piston.
- the connecting rib extends approximately parallel to the median plane of the piston.
- the measured perpendicular to the median plane distance of the connecting rib to the median plane is advantageously at least 20% of the diameter of the piston.
- the piston pin eyes have mutually facing end faces.
- the connecting rib advantageously has, for the end face of the associated piston pin eye, a distance measured parallel to the transverse axis which has at least 5%, in particular at least 10%, of the diameter of the piston. Accordingly, in the state installed in the two-stroke engine, the connecting rib is offset radially outward with respect to a front side of the piston pin eye facing a connecting rod of the two-stroke engine with respect to a cylinder longitudinal axis.
- the piston pin eye associated with a connecting rib is the piston pin eye which connects this connecting rib to the piston skirt.
- the piston pocket has a rear wall.
- the back wall of the piston pocket is the wall which separates the piston pocket from the interior of the piston enclosed by the piston skirt.
- the connecting rib is advantageously arranged in extension of the rear wall of the piston bag. Due to the arrangement of the connecting rib in extension of the rear wall of the piston pocket, the connecting rib causes a stiffening of the rear wall of the piston pocket.
- the connecting rib preferably connects to the rear wall of the piston pocket.
- the depression is advantageously bounded by the piston pin boss, the piston skirt, the connecting rib and the rear wall of the piston pocket.
- the piston skirt advantageously has an edge facing away from the piston crown.
- the connecting rib has an end facing away from the piston crown.
- the end face of the connecting rib advantageously does not protrude to the bottom of the piston, but is opposite to the edge of the piston, which forms the underside of the piston, offset in the direction of the piston head.
- the offset between the end face of the connecting rib and the edge is advantageously less than 5% of the height of the piston in the direction of the longitudinal center axis of the piston at each point of the end face. It can also be provided that the end face of the connecting rib protrudes to the height of the edge.
- an offset of at least 0.5 mm between the front side is advantageous the connecting rib and the edge in the direction of the longitudinal central axis of the piston given.
- the web has in the peripheral region of the piston in which the recess is arranged, a height which is at least 1.5 times the smallest height of the web. In the region of the recess, the web is therefore designed to be higher than in other areas of the piston bag. As a result, a good guidance of the piston is achieved in the region of the depression, and at the same time there is sufficient space for the depression available.
- the piston rests against at least a portion of the piston stroke with at least a portion of the web on the cylinder bore during operation.
- the piston pin receptacle is at least partially, in particular completely arranged in the piston pocket. This allows a low overall height of the piston and thus a low overall height of the cylinder of a two-stroke engine can be achieved.
- the piston pin receptacle has a comparatively large distance from the piston crown. By a comparatively large distance between the piston pin receptacle and the piston head, the heat input into the piston pin and thus into the piston pin bearing, with which the connecting rod is mounted on the piston pin, can be reduced during operation.
- the piston preferably has two piston pockets on opposite sides of the median plane, wherein in each case a connecting rib is arranged on both piston pin bosses.
- a connecting rib is arranged on both piston pin bosses.
- the piston pockets and the connecting ribs are arranged symmetrically to the median plane.
- an asymmetrical design can also be advantageous.
- the piston is advantageously made of light metal, in particular aluminum or magnesium. This results in a lower weight of the piston.
- Total weight can have a two-stroke engine with a piston made of light metal, especially magnesium, a motor with larger displacement and thus with greater power than, for example, a two-stroke engine with a piston that is not made of light metal, especially not magnesium.
- the connecting rib brings advantages in terms of the stability of the piston, since light metal, in particular magnesium, even has a lower strength.
- the connecting rib is advantageously arranged on an outlet side of the piston between the piston pin boss and the piston skirt.
- at least one connecting rib is provided, which connects the piston pin eye with the piston skirt.
- a connecting rib on the inlet side with respect to a transverse plane of the piston is advantageously arranged and designed mirror-symmetrically to a connecting rib on the outlet side.
- a two-stroke engine with a piston advantageously has a cylinder, in whose cylinder bore a combustion chamber is formed.
- the combustion chamber is limited by the piston.
- the piston drives a rotatably mounted in a crankcase crankshaft.
- the two-stroke engine has at least one overflow channel, which connects a crankcase interior of the crankcase with the combustion chamber in at least one position of the piston.
- the two-stroke engine has an air passage for supplying scavenging air, which opens with an air inlet to the cylinder bore.
- the piston pocket lies at least partially in overlap with the air inlet and an overflow window of an overflow channel.
- scavenging master air from the air duct can be supplied via the piston pocket via the air inlet into the overflow window of the overflow channel and thus be pre-stored in the overflow channel.
- the rinsing air can be fuel-free or low-fuel combustion air. As a result, low exhaust emissions are achieved.
- Fig. 1 schematically shows an embodiment of a two-stroke engine 1.
- the two-stroke engine 1 is designed as a single-cylinder engine and has a cylinder 2, in which a combustion chamber 3 is formed.
- the cylinder 2 has a cylinder longitudinal axis 48.
- the combustion chamber 3 is delimited by a piston 5 which is reciprocated in a cylinder bore 15 of the cylinder 2 in the direction of the cylinder longitudinal axis 48, in the direction of which the piston 5 moves during operation.
- the piston 5 is shown in its bottom dead center.
- the piston 5 drives a crankshaft 7 via a connecting rod 6.
- the crankshaft 7 is rotatably mounted in a crankcase interior 16 of a crankcase 4 about an axis of rotation 8.
- the crankshaft 7 rotates in operation in a direction of rotation 69.
- the two-stroke engine 1 may be, for example, the drive motor in a hand-held implement such as a power saw, a power grinder, a blower or the like.
- the crankshaft 7 is advantageously used to drive a tool of the implement.
- the piston 5 has two piston pockets 14, of which in Fig. 1 one is shown.
- the piston pockets 14 are symmetrical to the cutting plane in FIG Fig. 1 arranged on the piston 5.
- the two-stroke engine 1 has an air passage 9 which is connected to an air filter 22. Via the air duct 9, fuel-free or low-fuel rinsing draft air is supplied. In the air inlet 9, an air damper 21 is arranged for controlling the quantity of rinsing draft air supplied via the air duct 9.
- the air channel 9 opens with an air inlet 11 to the cylinder bore 15.
- a mixture channel 10 is provided for the supply of fuel / air mixture.
- the mixture channel 10 is connected via a carburetor 18 to the air filter 22.
- a throttle valve 19 and a choke flap 20 are pivotally mounted in the embodiment. The throttle valve 19 and the choke flap 20 serve to adjust the amount of combustion air and fuel supplied via the mixture channel 10.
- the fuel supply in other ways, for example via an injection valve or a carburetor with an electromagnetic valve, take place.
- the mixture channel 10 opens with a mixture inlet 12 at the cylinder bore 15.
- the air inlet 11 and the mixture inlet 12 are controlled by the piston 5.
- the two-stroke engine 1 has overflow channels 13, which open into the combustion chamber 3 with overflow windows 17.
- the overflow 17 are controlled by the piston 5.
- the overflow channels 13, not shown connect the crankcase interior 16 to the combustion chamber 3.
- the fuel / air mixture is sucked into the crankcase interior 16 during the upward stroke of the piston 5 through the mixture inlet 12.
- the upward stroke of the piston 5 indicates the movement of the piston 5 from the in Fig. 1 shown position of the piston 5 at bottom dead center in the direction of the combustion chamber 3, ie in Fig. 1 in the direction of the arrow 70.
- the piston pockets 14 each connect an air inlet 11 with overflow windows 17.
- the combustion pressure accelerates the piston 5 back in the direction of the crankcase 4.
- From the combustion chamber 3 performs an outlet 23, which is also controlled by the piston 5.
- the outlet 23 is opened by the piston 5
- the exhaust gases flow out of the combustion chamber 3 through the outlet 23.
- After further downward stroke of the piston 5 opens the transfer port 17 to the combustion chamber 3.
- the upstream in the transfer ports 13 combustion air then flows into the combustion chamber 3 a.
- the upstream air flushes exhaust gases from the combustion chamber 3 through the outlet 23.
- From the crankcase interior 16 flows fresh fuel / air mixture, which was precompressed in the crankcase interior 16, after.
- the mixture is compressed in the combustion chamber 3 during the upward stroke of the piston 5, while at the same time fresh mixture in the crankcase interior 16 and Spülvorlagen Kunststoff is sucked into the transfer channels 13.
- the piston pockets 14 have a decisive influence on the amount of upstream in the transfer channels 13 Spülvorlagen Kunststoff.
- the piston pockets 14 have an upper control edge 29, which is advantageously arranged in the region of top dead center of the piston 5 so that the transfer ports 17 are arranged completely in register with the piston pocket 14.
- the upper control edge 29 is the combustion chamber 3 closest control edge of the piston pocket 14.
- the piston pocket 14 also has a lower control edge 30, which faces the crankcase 4.
- the lower control edge 30 is the most distant from the combustion chamber 3 control edge of the piston pocket 14 and limits the piston pocket 14 in the direction of the crankcase 4.
- the lower control edge 30 is advantageously arranged so that the air inlet 11 completely in Cover with the piston pocket 14 is located.
- the piston pockets 14 also have inlet-side boundary edges 53 and outlet-near boundary edges 54.
- the boundary edges 53 and 54 in the exemplary embodiment extend approximately parallel to the cylinder longitudinal axis 48 (FIG. Fig. 1 ).
- Each piston pocket 14 is thus limited in the direction of the cylinder longitudinal axis 48 of the control edges 29 and 30 and in the circumferential direction of the boundary edges 53 and 54.
- the piston 5 has an edge 31 on its side facing the crankcase 4, which forms the boundary of the piston 5 facing the crankcase 4. Between the piston pockets 14 and the edge 31, a web 32 is formed in each case, which is formed by a portion of a piston skirt 26.
- the piston 5 has a piston bottom 25, which runs approximately perpendicular to the cylinder longitudinal axis 48 and limits the combustion chamber 3.
- the piston 5 has the piston skirt 26, which advantageously follows the course of the cylinder bore 15.
- the outside of the piston skirt 26 advantageously extends approximately cylindrically.
- the outside of the piston skirt 26 can be an exactly cylindrical or deviating from the circular shape Possess cross-section.
- the piston skirt may in particular have an elliptical, oval or cloverleaf shape.
- a cloverleaf-shaped cross-section is a cross section in which the diameter is reduced in two oblique directions. The deviation of the cross section from the circular shape is advantageously very low.
- Adjacent to the piston head 25, two piston ring grooves 24 are provided on the piston skirt 26, which serve to receive piston rings.
- a bore 34 is shown, which serves to receive a securing pin for a piston ring.
- a corresponding, in Fig. 2 not visible bore is also provided in the other piston ring groove 24.
- a recess 27 is provided on the piston skirt 26 between each piston pocket 14 and the piston ring grooves 24.
- the recess 27 serves to reduce the weight of the piston 5.
- the recess 27 is designed so that it is during a piston stroke only with one or both overflow windows 17, but not with the air inlet 11 in overlap.
- the piston skirt 26 has on the side facing the crankcase 4, the combustion chamber 3 remote side a recess 33.
- the recess 33 is formed as a bulge of the edge 31 in the direction of the piston head 25.
- the position of the edge 31 at the recess 33 defines the timing at which the mixture inlet 12 is opened and closed.
- a chamfer 37 is provided at the transition of the edge 31 to the outside of the piston skirt 26 in the region of the recess 33.
- the connecting rod 6 ( Fig. 1 ) is connected to the piston 5 via a piston pin, not shown.
- the piston pin is held on the piston 5 in piston pin receptacles 35.
- the piston pin receptacles 35 are arranged completely in the piston pockets 14 in the embodiment.
- the piston pin receivers 35 are advantageously located in the space between the control edges 29 and 30 of the piston pockets 14. Toward the interior of the crankcase, the piston pocket 14 is delimited by a rear wall 58.
- the piston 5 has a diameter a.
- the diameter a is advantageously the largest diameter of the piston 5 and measured in the exemplary embodiment on an upper side 40 of the piston crown 25.
- the top 40 of the piston crown 25 is the side of the piston crown 25, which limits the combustion chamber 3.
- the piston 5 has a height h, which is measured parallel to a longitudinal central axis 50 of the piston 5.
- the height h is the greatest height of the piston 5.
- the longitudinal center axis 50 of the piston 5 is the central axis of the piston skirt 26.
- the longitudinal center axis 50 of the piston 5 coincides in the arrangement of the piston 5 in the cylinder 2 approximately with the cylinder longitudinal axis 48 together.
- the piston pin receptacles 35 (FIG. Fig.
- the piston 2 have a central axis which forms a transverse axis 49 of the piston 5.
- the transverse axis 49 extends in the side view shown perpendicular to the longitudinal central axis 50.
- the piston 5 has a median plane 51 which contains the longitudinal central axis 50 of the piston 5 and which extends perpendicular to the transverse axis 49.
- the longitudinal center axis 50 and the center plane 51 coincide.
- the piston 5 has a reduced height i.
- the reduced height i is the distance, measured parallel to the longitudinal central axis 50, of the edge 31 at the recess 33 to the upper side 40 of the piston 5.
- the reduced height i at the recess 33 is advantageously 70% to 98%, in particular 80% to 95% of the height
- the diameter a is advantageously 70% to 140% of the height h, in particular 80% to 130%, preferably 90% to 120% of the height h. Particularly preferably, the diameter a is greater than the height h.
- the piston 5 has an inlet side 46, on which the recess 33 is arranged.
- Fig. 3 shows a side view of the inlet side 46.
- the web 32 between the piston pocket 14 and the edge 31 has at the inlet side 46 a minimum height k.
- the minimum height k is measured in the exemplary embodiment at the circumferential area of the piston pocket 14 facing the recess 33.
- the minimum height k may be about 1 mm to about 5 mm, in particular about 1 mm to about 3 mm.
- the height of the bridge 32 does not have to be constant, but can be along the circumference change the piston 5.
- the web 32 serves to seal between the piston pocket 26 and the cylinder bore 15 trapped volume and the crankcase interior 16th
- Fig. 4 shows the interior of the piston 5.
- the piston pin receptacles 35 are formed on piston pin bosses 28, which extend in the embodiment to the piston crown 25.
- the end faces 57 extend in the exemplary embodiment approximately parallel to the center plane 51.
- the end faces 57 of the two piston pin bosses 28 extend approximately mirror-symmetrically with respect to the center plane 51.
- the draft angles at the surfaces extending approximately parallel to the center plane 51 may be for example from 0.5 ° to 3 °.
- the end faces 57 of the piston pin bosses 28 are the areas of the piston pin bosses 28, which have the smallest distance to the center plane 51.
- the end faces 57 each have a distance z from the center plane 51 which is perpendicular to the center plane 51 and parallel to the transverse axis 49 (FIG. Fig. 3 ) is measured.
- the distance z is advantageously at least 5%, in particular at least 10% of the diameter a of the piston 5 (FIG. Fig. 3 ).
- the piston pin bosses 28 are advantageously arranged symmetrically to the center plane 51, so that the same distance z results for both end faces 57.
- the end faces 57 have a recess 36, which extends to the piston pin receptacle 35 and at which the distance to the center plane 51 is increased.
- the indentation 36 serves to lubricate a piston pin bearing, with which the piston pin on the connecting rod 6 (FIG. Fig. 1 ) is stored.
- the end faces 57 of the piston pin bosses 28 each have a distance e from the connecting ribs 55, which are perpendicular to the center plane 51 and parallel to the transverse axis 49 ( Fig. 3 ) is measured.
- the distance e is advantageously at least 5%, in particular at least 10% of the diameter a of the piston 5 (FIG. Fig. 3 ).
- the piston pin bosses 28 and the connecting ribs 55 are advantageously arranged symmetrically with respect to the center plane 51, so that the same distance e between an end face 57 and the connecting rib 55 arranged on the same side of the center plane 51 results on both sides of the center plane 51.
- the piston 5 has the inlet side 46, which in the illustration in Fig. 4 is arranged above and at which the recess 33 is provided on the piston skirt 26, and an outlet side 47.
- the piston 5 is divided by a transverse plane 52 in the inlet side 46 and the outlet side 47, which in Fig. 5 is shown schematically.
- the transverse plane 52 is spanned by the longitudinal central axis 50 of the piston 5 and the transverse axis 49.
- the piston pin bosses 28 are connected via connecting ribs 55 with the piston skirt 26.
- the connecting ribs 55 extend on the side of the piston pin bosses 28, which faces away from the recess 33.
- the connecting ribs 55 are arranged on the side facing away from the mixture inlet 12, the outlet 23 facing side of the cylinder 2 ( Fig. 1 ).
- the connecting ribs 55 are arranged on the outlet side 47 of the piston 5.
- Fig. 4 also shows, also at the outlet 23 facing side of the edge 31 of the piston skirt 26, a chamfer 39 is formed.
- each recess 56 extends at the side facing away from the center plane 51 of the connecting rib 55 between the connecting rib 55 and the piston skirt 26.
- the distance of the recess 56 to the center plane 51 is greater than the distance of the depression 56 defining the connecting rib 55 to the center plane 51.
- the connecting ribs 55 have the center plane 51 a distance d.
- the distance d can vary in different areas of the connecting rib 55, for example when the width of the connecting rib 55 is not constant.
- a greater width of the connecting rib 55 is provided in the connection region to the piston pin boss 28 and in the connection region to the piston skirt 26.
- the distance d is advantageously measured in a middle region of the connecting rib 55.
- the distance d is advantageously at least 20%, in particular at least 25% of the diameter a of the piston 5.
- the distance d at each point of the connecting rib 55 at least 20%, in particular at least 25% of the diameter a of the piston 5.
- Wie Fig. 4 shows, both connecting ribs 55 extend with respect to the center plane 51 advantageously mirror-symmetrical to each other.
- the connecting ribs 55 preferably run parallel to the center plane 51.
- ribs 42 and 43 connect piston skirt 26 and piston crown 25 and lie over their entire length directly on the piston skirt 26 and the piston crown 25 on.
- a respective middle rib 43 is provided which runs along the center plane 51 and is cut centrally from the center plane 51.
- lateral ribs 42 are provided on both sides of the central rib 43 . In this case, exactly one lateral rib 42 is arranged on each side of the central rib 43.
- a stop surface 38 is formed in the region between the piston pin bosses 28 on the piston head 25. The stop surface 38 serves for the defined positioning of the piston 5 during the machining of the piston skirt 26.
- the ribs 42 and 43 respectively connect the piston skirt 26 with the piston crown 25.
- the ribs 42 and 43 on the inlet side 46 are advantageously arranged with respect to the transverse plane 52 symmetrical to the ribs 42 and 43 on the outlet side 47.
- the protruding into the interior of the piston 5 end faces 41 of the ribs 42 and 43 are advantageously arcuate, namely concave.
- the ribs 42 and 43 are not directly connected.
- the ribs 42 and 43 also have a clearance to the piston pin bosses 28. Between the ribs 42 and 43 and the piston pin bosses 28 therefore there is no direct connection.
- the ribs 42 and 43 are formed separately from the piston pin bosses 28.
- the connecting rib 55 is not directly connected to the ribs 42 and 43.
- the connecting ribs 55 are in extension of the rear wall 58 of the piston pocket 14.
- the piston pin bosses 28 each have two side surfaces 60 which extend with a low draft angle approximately parallel to the transverse plane 52 of the piston 5. On the side surfaces 60, the piston 5 can be clamped for machining the piston skirt 26.
- the connecting ribs 55 have a top side 40 of the piston 5 facing away from the end face 59 of the connecting rib 55.
- the end faces 59 are also in Fig. 4 shown.
- the front side 59 of the connecting rib 55 faces the crankcase 4 in the installed state.
- the recess 56 has a maximum depth c, which is measured parallel to the longitudinal central axis 50 to the end face 59 of the connecting rib 55.
- the maximum depth c is advantageously at least 3%, in particular at least 5% of the height h of the piston 5.
- the maximum depth c is advantageously less than 20%, in particular less than 10% of the height h of the piston 5.
- the depth of the recess 56 at each point of the recess 56 is less than 20%, in particular less than 10 % of the height h of the piston 5.
- the end face 59 has opposite the edge 31 a measured parallel to the longitudinal central axis 50 offset b.
- the offset b is advantageously less than 5%, in particular less than 3% of the height h of the piston 5.
- the offset b can also be zero.
- an offset b of more than 1% of the height h of the piston 5 is provided.
- the end face 59 is advantageously arranged closer to the upper side 40 of the piston 5 than the edge 31 in the region of the depression 56.
- the maximum depth c is advantageously significantly greater than the offset b.
- the maximum depth c is at least twice the offset b.
- the web 32 has in the recess 56 delimiting area a measured parallel to the longitudinal central axis 50 height m, the bigger than the one in Fig. 3 shown smallest height k of the ridge 32 is.
- the height m is advantageously at least 1.5 times the height k.
- the recess 56 has a bottom 61, which is the region of the recess 56 which has the smallest distance to the top 40 of the piston 5.
- the bottom 61 of the recess 56 has to the bottom 40 of the piston 5 a measured parallel to the longitudinal central axis 50 distance f, which is advantageously more than 50%, in particular more than 60% of the height h of the piston 5.
- the distance f is advantageously less than 90% of the height h of the piston 5.
- the rear wall 58 of the piston pocket 14 has a wall thickness y between the piston pocket 14 and the interior of the piston 5 located between the rear walls 58 of the piston pockets 14.
- the rear wall 58 has a reduced wall thickness x.
- the reduced wall thickness x is advantageously at most 80%, in particular at most 60% of the wall thickness y.
- the wall thickness x may not be below a minimum for a sufficient stability of the rear wall 58. This minimum dimension, which depends on the material and the geometry of the piston 5, determines the maximum possible depth c of the recess 56.
- the middle rib 43 has an upper side 40 of the piston 5 facing away from the end 45.
- the end 45 has the top 40 a distance g.
- the distance g is advantageously about 30% to about 60% of the height h of the piston 5.
- the distance g is advantageously smaller than the distance f of the bottom 61 of the recess 56 to the top 40 of the piston 5.
- the distance g is advantageously less than 90 %, in particular less than 80% of the distance f.
- the arranged on the opposite sides of the median plane 51 connecting ribs 55 have a distance n, which is measured perpendicular to the median plane 51 to each other.
- the distance n is advantageously at least 40%, in particular at least 50% of the diameter a of the piston 5.
- the end faces 57 of the piston pin bosses 28 have a distance s to each other.
- the distance s is advantageously at least 10%, in particular at least 20% of the diameter a of the piston 5.
- the distance s is significantly smaller than the distance n of the connecting ribs 55.
- the distance s is advantageously less than 70% of the distance n.
- the connecting ribs 55 are offset from the end faces 57 radially outward.
- the piston pin bosses 28 have a width w measured from the end faces 57 to the piston skirt 26 and perpendicular to the center plane 51, which is advantageously at least 15%, in particular at least 20% of the diameter a of the piston.
- the end 45 is farther from the upper side 40 than the transverse axis 49.
- the end 45 is arranged closer to the upper side 40 than the transverse axis 49.
- the distance u is advantageously less than 10% of the height h of the piston 5.
- the lateral ribs 42 have an end 44 facing away from the upper side 40, which has a distance o measured parallel to the longitudinal center axis 50 with respect to the upper side 40.
- the distance o is smaller than the distance g between the end 45 of the middle rib 43 and the top 40 of the piston 5 (FIG. Fig. 6 ).
- the end 44 has in the side view shown to the transverse axis 49 a distance v, which is significantly greater than the distance u of the end 45 to the transverse axis 49.
- the distance v is advantageously 5% to 20% of the height h of the piston 5.
- the upper control edge 29 of the piston pockets 14 to the top 40 has a distance t, which is advantageously 30% to 60% of the height h of the piston 5.
- the end 44 is approximately at the height of the control edge 29th
- the recess 56 has a width r measured parallel to the transverse axis 49, which is advantageously less than 10% of the diameter a of the piston 5.
- the bottom 61 has the edge 31 in the recess 56 delimiting area a parallel to Longitudinal central axis 50 measured distance p.
- the distance p in the embodiment is greater than the height m of the web 32 in this area.
- the height m of the web 32 is advantageously 70% to 95% of the distance p.
- the width r of the recess 56 may approximately correspond to the maximum depth c of the recess 56.
- the width r is 60% to 120% of the maximum depth c of the depression 56 (FIG. Fig. 6 ).
- Fig. 8 shows a schematic representation of an embodiment of a piston 5.
- the same reference numerals designate corresponding elements in all figures.
- the in Fig. 8 shown piston 5 has on the inlet side 46, two connecting ribs 55, each extending between a piston pin boss 28 and the piston skirt 26 and defining a recess 56.
- the connecting ribs 55 and the recesses 56 are formed as described for the previous embodiment.
- Between the connecting ribs 55 'and the piston skirt 26, a recess 56' is respectively arranged on the side remote from the center plane 51.
- the recesses 56 ' are formed corresponding to the recesses 56.
- the recesses 56 ' may be formed mirror-symmetrically to the recesses 56.
- the connecting ribs 55 'and the recesses 56' may, as in Fig. 8 shown in addition to the connecting ribs 55 and the recesses 56 may be provided.
- connection ribs 55 'and depressions 56' are arranged only on the outlet side 47 of the piston 5 and no connecting ribs 55 and depressions 56 are arranged on the inlet side 46.
- the piston 5,5 ' is made of light metal, especially magnesium.
- An aluminum training may be advantageous.
- By the recesses 56, 56 'an accumulation of material between the connecting rib 55, 55' and the piston skirt 26 is avoided, so that the piston 5 can be well made in a casting process of light metal, especially magnesium.
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Abstract
Ein Kolben für einen mit Spülvorlage arbeitenden Zweitaktmotor (1) besitzt einen Kolbenboden (25) und ein Kolbenhemd (26). Die Mittelachse des Kolbenhemds (26) bildet eine Längsmittelachse (50) des Kolbens (5). Der Kolben (5) besitzt zwei Kolbenbolzenaugen (28), in denen Kolbenbolzenaufnahmen (35) ausgebildet sind. Die Mittelachse der Kolbenbolzenaufnahmen (35) bildet eine Querachse (49) des Kolbens (5). Der Kolben (5) besitzt mindestens eine Kolbentasche (14). Es ist mindestens ein Kolbenbolzenauge (28) über mindestens eine Verbindungsrippe (55, 55') mit dem Kolbenhemd (26) verbunden. Die Verbindungrippe (55, 55') verläuft dabei an der dem Kolbenboden (25) abgewandten Seite der Kolbentasche (14).A piston for a two-stroke engine (1) operating with a scavenging charge has a piston crown (25) and a piston skirt (26). The central axis of the piston skirt (26) forms a longitudinal central axis (50) of the piston (5). The piston (5) has two piston pin bosses (28) in which piston pin receptacles (35) are formed. The central axis of the piston pin receptacles (35) forms a transverse axis (49) of the piston (5). The piston (5) has at least one piston pocket (14). At least one piston pin boss (28) is connected to the piston skirt (26) via at least one connecting rib (55, 55 '). The connecting rib (55, 55 ') extends on the side of the piston pocket (14) facing away from the piston head (25).
Description
Die Erfindung betrifft einen Kolben für einen mit Spülvorlage arbeitenden Zweitaktmotor der im Oberbegriff des Anspruchs 1 angegebenen Gattung sowie einen Zweitaktmotor.The invention relates to a piston for a working with flushing two-stroke engine of the type specified in the preamble of
Aus der
Der Erfindung liegt die Aufgabe zugrunde, einen Kolben für einen mit Spülvorlage arbeitenden Zweitaktmotor zu schaffen, der eine hohe Stabilität besitzt. Eine weitere Aufgabe der Erfindung besteht darin, einen Zweitaktmotor mit einem Kolben anzugeben.The invention has for its object to provide a piston for a working with scavenging two-stroke engine, which has a high stability. Another object of the invention is to provide a two-stroke engine with a piston.
Diese Aufgabe wird bezüglich des Kolbens durch einen Kolben mit den Merkmalen des Anspruchs 1 gelöst. Bezüglich des Zweitaktmotors wird die Aufgabe durch einen Zweitaktmotor mit den Merkmalen des Anspruchs 14 gelöst.This object is achieved with respect to the piston by a piston having the features of
Der Kolben besitzt Kolbenbolzenaugen, in denen Kolbenbolzenaufnahmen ausgebildet sind. Es ist vorgesehen, dass mindestens ein Kolbenbolzenauge über mindestens eine Verbindungsrippe mit dem Kolbenhemd verbunden ist. Die Verbindungsrippe verläuft dabei an der dem Kolbenboden abgewandten Seite der Kolbentasche. Die Verbindungsrippe führt zu einer verbesserten Abstützung des Kolbenbolzenauges. Kräfte aus dem Kolbenbolzenauge können über die Verbindungsrippe besser auf das Kolbenhemd übertragen werden. Dadurch wird eine höhere Stabilität erreicht. Die Krafteinleitung aus dem Kolbenbolzenauge in das Kolbenhemd wird verbessert. Die Verbindungsrippe bewirkt eine Versteifung und Festigkeitserhöhung des Kolbens. Über die Verbindungsrippe wird auch Wärme aus dem Kolbenbolzenauge ins Kolbenhemd abgeleitet. Dadurch wird eine verbesserte Kühlung des thermisch besonders hoch belasteten Bereichs der Kolbenbolzenaugen erreicht.The piston has piston pin bosses in which piston pin receptacles are formed. It is provided that at least one piston pin eye is connected via at least one connecting rib with the piston skirt. The connecting rib extends at the side facing away from the piston crown side of the piston bag. The connecting rib leads to improved support of the piston pin eye. Forces from the piston pin boss can be better transmitted to the piston skirt via the connecting rib. This achieves greater stability. The introduction of force from the piston pin eye in the piston skirt is improved. The connecting rib causes a stiffening and increase in strength of the piston. Heat is also dissipated from the piston pin boss into the piston skirt via the connecting rib. As a result, an improved cooling of the thermally highly loaded area of the piston pin bosses is achieved.
Vorteilhaft ist zwischen der Verbindungsrippe und dem Kolbenhemd eine Vertiefung ausgebildet. Die Vertiefung vermeidet Materialansammlungen in diesem Bereich, so dass eine bessere Herstellbarkeit des Kolbens, insbesondere in einem Gussverfahren, gegeben ist. Durch die Vertiefung können Gussfehler vermieden werden. Es wird eine Gewichtsreduzierung erreicht. Die Tiefe der Vertiefung beträgt vorteilhaft mindestens 3%, insbesondere mindestens 5% der Höhe des Kolbens. Über die Vertiefung wird eine gute beidseitige Kühlung der Verbindungsrippe durch im Kurbelgehäuseinnenraum strömendes Gemisch bzw. durch im Kurbelgehäuseinnenraum strömende Verbrennungsluft erreicht. Die Tiefe der Vertiefung beträgt vorteilhaft weniger als 20% der Höhe des Kolbens. Dadurch bleibt ausreichend Bauraum für die Kolbentasche, ohne dass sich die Bauhöhe des Kolbens vergrößert. Eine ausreichend große Kolbentasche stellt sicher, dass eine ausreichende Menge an Spülvorlagenluft in den Überströmkanälen vorgelagert wird, so dass sich geringe Abgaswerte eines mit dem Kolben arbeitenden Zweitaktmotors erreichen lassen. Vorteilhaft verläuft die Verbindungsrippe etwa parallel zur Mittelebene des Kolbens. Der senkrecht zur Mittelebene gemessene Abstand der Verbindungsrippe zur Mittelebene beträgt vorteilhaft mindestens 20% des Durchmessers des Kolbens.Advantageously, a recess is formed between the connecting rib and the piston skirt. The recess avoids material accumulations in this area, so that a better manufacturability of the piston, in particular in a casting process, is given. Through the recess casting errors can be avoided. It is achieved a weight reduction. The depth of the recess is advantageously at least 3%, in particular at least 5% of the height of the piston. A good bilateral cooling of the connecting rib is achieved by means of the depression through mixture flowing in the crankcase interior or through combustion air flowing in the crankcase interior. The depth of the recess is advantageously less than 20% of the height of the piston. This leaves enough space for the piston bag without increasing the height of the piston. A sufficiently large piston bag ensures that a sufficient amount of Spülvorlagenluft is upstream in the overflow, so that it can be achieved low exhaust emissions of working with the piston two-stroke engine. Advantageously, the connecting rib extends approximately parallel to the median plane of the piston. The measured perpendicular to the median plane distance of the connecting rib to the median plane is advantageously at least 20% of the diameter of the piston.
Die Kolbenbolzenaugen besitzen einander zugewandte Stirnseiten. Die Verbindungsrippe besitzt zur Stirnseite des zugeordneten Kolbenbolzenauges vorteilhaft einen parallel zur Querachse gemessenen Abstand, der mindestens 5%, insbesondere mindestens 10% des Durchmessers des Kolbens besitzt. Die Verbindungsrippe ist demnach in dem im Zweitaktmotor eingebauten Zustand gegenüber der einem Pleuel des Zweitaktmotors zugewandten Stirnseite des Kolbenbolzenauges bezogen auf eine Zylinderlängsachse radial nach außen versetzt. Das einer Verbindungsrippe zugeordnete Kolbenbolzenauge ist dabei das Kolbenbolzenauge, das diese Verbindungsrippe mit dem Kolbenhemd verbindet.The piston pin eyes have mutually facing end faces. The connecting rib advantageously has, for the end face of the associated piston pin eye, a distance measured parallel to the transverse axis which has at least 5%, in particular at least 10%, of the diameter of the piston. Accordingly, in the state installed in the two-stroke engine, the connecting rib is offset radially outward with respect to a front side of the piston pin eye facing a connecting rod of the two-stroke engine with respect to a cylinder longitudinal axis. The piston pin eye associated with a connecting rib is the piston pin eye which connects this connecting rib to the piston skirt.
Vorteilhaft besitzt die Kolbentasche eine Rückwand. Die Rückwand der Kolbentasche ist die Wand, die die Kolbentasche von dem vom Kolbenhemd umschlossenen Innenraum des Kolbens trennt. Die Verbindungsrippe ist vorteilhaft in Verlängerung der Rückwand der Kolbentasche angeordnet. Durch die Anordnung der Verbindungsrippe in Verlängerung der Rückwand der Kolbentasche bewirkt die Verbindungsrippe eine Versteifung der Rückwand der Kolbentasche. Die Verbindungsrippe schließt bevorzugt an die Rückwand der Kolbentasche an. Die Vertiefung wird vorteilhaft vom Kolbenbolzenauge, vom Kolbenhemd, von der Verbindungsrippe und von der Rückwand der Kolbentasche begrenzt.Advantageously, the piston pocket has a rear wall. The back wall of the piston pocket is the wall which separates the piston pocket from the interior of the piston enclosed by the piston skirt. The connecting rib is advantageously arranged in extension of the rear wall of the piston bag. Due to the arrangement of the connecting rib in extension of the rear wall of the piston pocket, the connecting rib causes a stiffening of the rear wall of the piston pocket. The connecting rib preferably connects to the rear wall of the piston pocket. The depression is advantageously bounded by the piston pin boss, the piston skirt, the connecting rib and the rear wall of the piston pocket.
Das Kolbenhemd besitzt vorteilhaft einen dem Kolbenboden abgewandten Rand. Die Verbindungsrippe besitzt eine dem Kolbenboden abgewandte Stirnseite. Die Stirnseite der Verbindungsrippe ragt vorteilhaft nicht bis an die Unterseite des Kolbens, sondern ist gegenüber dem Rand des Kolbens, der die Unterseite des Kolbens bildet, in Richtung auf den Kolbenboden versetzt. Der Versatz zwischen der Stirnseite der Verbindungsrippe und dem Rand beträgt in Richtung der Längsmittelachse des Kolbens an jeder Stelle der Stirnseite vorteilhaft weniger als 5% der Höhe des Kolbens. Es kann auch vorgesehen sein, dass die Stirnseite der Verbindungsrippe bis auf die Höhe des Rands ragt. Vorteilhaft ist jedoch ein Versatz von mindestens 0,5 mm zwischen der Stirnseite der Verbindungsrippe und dem Rand in Richtung der Längsmittelachse des Kolbens gegeben.The piston skirt advantageously has an edge facing away from the piston crown. The connecting rib has an end facing away from the piston crown. The end face of the connecting rib advantageously does not protrude to the bottom of the piston, but is opposite to the edge of the piston, which forms the underside of the piston, offset in the direction of the piston head. The offset between the end face of the connecting rib and the edge is advantageously less than 5% of the height of the piston in the direction of the longitudinal center axis of the piston at each point of the end face. It can also be provided that the end face of the connecting rib protrudes to the height of the edge. However, an offset of at least 0.5 mm between the front side is advantageous the connecting rib and the edge in the direction of the longitudinal central axis of the piston given.
Zwischen dem Rand und der Kolbentasche verläuft vorteilhaft ein Steg des Kolbenhemds. Der Steg besitzt in dem Umfangsbereich des Kolbens, in dem die Vertiefung angeordnet ist, eine Höhe, die mindestens das 1,5fache der kleinsten Höhe des Stegs beträgt. Im Bereich der Vertiefung ist der Steg demnach höher ausgebildet als in anderen Bereichen der Kolbentasche. Dadurch wird eine gute Führung des Kolbens im Bereich der Vertiefung erreicht, und gleichzeitig steht ausreichend Bauraum für die Vertiefung zur Verfügung. Vorteilhaft liegt der Kolben im Betrieb über mindestens einen Teilabschnitt des Kolbenhubs mit mindestens einem Abschnitt des Stegs an der Zylinderbohrung an.Between the edge and the piston pocket advantageously runs a web of the piston skirt. The web has in the peripheral region of the piston in which the recess is arranged, a height which is at least 1.5 times the smallest height of the web. In the region of the recess, the web is therefore designed to be higher than in other areas of the piston bag. As a result, a good guidance of the piston is achieved in the region of the depression, and at the same time there is sufficient space for the depression available. Advantageously, the piston rests against at least a portion of the piston stroke with at least a portion of the web on the cylinder bore during operation.
Bevorzugt ist die Kolbenbolzenaufnahme mindestens teilweise, insbesondere vollständig in der Kolbentasche angeordnet. Dadurch kann eine geringe Bauhöhe des Kolbens und damit eine geringe Bauhöhe des Zylinders eines Zweitaktmotors erreicht werden. Gleichzeitig besitzt die Kolbenbolzenaufnahme einen vergleichsweise großen Abstand zum Kolbenboden. Durch einen vergleichsweise großen Abstand zwischen Kolbenbolzenaufnahme und Kolbenboden kann der Wärmeeintrag in den Kolbenbolzen und damit in das Kolbenbolzenlager, mit dem das Pleuel am Kolbenbolzen gelagert ist, im Betrieb verringert werden.Preferably, the piston pin receptacle is at least partially, in particular completely arranged in the piston pocket. This allows a low overall height of the piston and thus a low overall height of the cylinder of a two-stroke engine can be achieved. At the same time, the piston pin receptacle has a comparatively large distance from the piston crown. By a comparatively large distance between the piston pin receptacle and the piston head, the heat input into the piston pin and thus into the piston pin bearing, with which the connecting rod is mounted on the piston pin, can be reduced during operation.
Der Kolben besitzt bevorzugt zwei Kolbentaschen auf gegenüberliegenden Seiten der Mittelebene, wobei an beiden Kolbenbolzenaugen jeweils eine Verbindungsrippe angeordnet ist. Bevorzugt sind die Kolbentaschen und die Verbindungsrippen symmetrisch zur Mittelebene angeordnet. Auch eine unsymmetrische Ausbildung kann jedoch vorteilhaft sein.The piston preferably has two piston pockets on opposite sides of the median plane, wherein in each case a connecting rib is arranged on both piston pin bosses. Preferably, the piston pockets and the connecting ribs are arranged symmetrically to the median plane. However, an asymmetrical design can also be advantageous.
Der Kolben besteht vorteilhaft aus Leichtmetall, insbesondere aus Aluminium oder Magnesium. Dadurch ergibt sich ein geringeres Gewicht des Kolbens. Bei gleichemThe piston is advantageously made of light metal, in particular aluminum or magnesium. This results in a lower weight of the piston. At the same
Gesamtgewicht kann ein Zweitaktmotor mit einem Kolben aus Leichtmetall, insbesondere aus Magnesium, einen Motor mit größerem Hubraum und damit mit größerer Leistung aufweisen als beispielsweise ein Zweitaktmotor mit einem Kolben, der nicht aus Leichtmetall, insbesondere nicht aus Magnesium besteht. Insbesondere bei einem Kolben aus Leichtmetall bringt die Verbindungsrippe Vorteile bezüglich der Stabilität des Kolbens, da Leichtmetall, insbesondere Magnesium, selbst eine geringere Festigkeit aufweist.Total weight can have a two-stroke engine with a piston made of light metal, especially magnesium, a motor with larger displacement and thus with greater power than, for example, a two-stroke engine with a piston that is not made of light metal, especially not magnesium. In particular, in a piston made of light metal, the connecting rib brings advantages in terms of the stability of the piston, since light metal, in particular magnesium, even has a lower strength.
Die Verbindungsrippe ist vorteilhaft auf einer Auslassseite des Kolbens zwischen dem Kolbenbolzenauge und dem Kolbenhemd angeordnet. In vorteilhafter Gestaltung ist alternativ oder zusätzlich auf einer Einlassseite des Kolbens mindestens eine Verbindungsrippe vorgesehen, die das Kolbenbolzenauge mit dem Kolbenhemd verbindet. Dabei ist vorteilhaft eine Verbindungsrippe auf der Einlassseite bezüglich einer Querebene des Kolbens spiegelsymmetrisch zu einer Verbindungsrippe auf der Auslassseite angeordnet und ausgebildet.The connecting rib is advantageously arranged on an outlet side of the piston between the piston pin boss and the piston skirt. In an advantageous embodiment, alternatively or additionally on an inlet side of the piston, at least one connecting rib is provided, which connects the piston pin eye with the piston skirt. In this case, a connecting rib on the inlet side with respect to a transverse plane of the piston is advantageously arranged and designed mirror-symmetrically to a connecting rib on the outlet side.
Ein Zweitaktmotor mit einem erfindungsgemäßen Kolben besitzt vorteilhaft einen Zylinder, in dessen Zylinderbohrung ein Brennraum ausgebildet ist. Der Brennraum ist von dem Kolben begrenzt. Der Kolben treibt eine in einem Kurbelgehäuse drehbar gelagerte Kurbelwelle an. Der Zweitaktmotor besitzt mindestens einen Überströmkanal, der in mindestens einer Stellung des Kolbens einen Kurbelgehäuseinnenraum des Kurbelgehäuses mit dem Brennraum verbindet. Der Zweitaktmotor besitzt einen Luftkanal zur Zufuhr von Spülvorlagenluft, der mit einem Lufteinlass an der Zylinderbohrung mündet. Die Kolbentasche liegt in mindestens einer Stellung des Kolbens mindestens teilweise in Überdeckung mit dem Lufteinlass und einem Überströmfenster eines Überströmkanals.A two-stroke engine with a piston according to the invention advantageously has a cylinder, in whose cylinder bore a combustion chamber is formed. The combustion chamber is limited by the piston. The piston drives a rotatably mounted in a crankcase crankshaft. The two-stroke engine has at least one overflow channel, which connects a crankcase interior of the crankcase with the combustion chamber in at least one position of the piston. The two-stroke engine has an air passage for supplying scavenging air, which opens with an air inlet to the cylinder bore. In at least one position of the piston, the piston pocket lies at least partially in overlap with the air inlet and an overflow window of an overflow channel.
Über die Kolbentasche kann dadurch Spülvorlagenluft aus dem Luftkanal über den Lufteinlass in das Überströmfenster des Überströmkanals zugeführt und so im Überströmkanal vorgelagert werden. Die Spülvorlagenluft kann dabei kraftstofffreie oder kraftstoffarme Verbrennungsluft sein. Dadurch werden geringe Abgaswerte erreicht.In this way, scavenging master air from the air duct can be supplied via the piston pocket via the air inlet into the overflow window of the overflow channel and thus be pre-stored in the overflow channel. The rinsing air can be fuel-free or low-fuel combustion air. As a result, low exhaust emissions are achieved.
Die Merkmale der Ausführungsbeispiele können in beliebiger Weise miteinander kombiniert werden, um vorteilhafte Weiterbildungen zu bilden.The features of the embodiments may be combined with each other in any manner to form advantageous developments.
Ein Ausführungsbeispiel der Erfindung wird im Folgenden anhand der Zeichnung erläutert. Es zeigen:
- Fig. 1
- eine schematische Schnittdarstellung eines Zweitaktmotors,
- Fig. 2
- den Kolben des Zweitaktmotors aus
Fig. 1 in perspektivischer Darstellung, - Fig. 3
- eine Seitenansicht des Kolbens,
- Fig. 4
- eine perspektivische Darstellung des Kolbens von der dem Kurbelgehäuse zugewandten Seite,
- Fig. 5
- eine perspektivische Darstellung eines Schnitts durch den Kolben entlang der Mittelebene,
- Fig. 6
- einen Schnitt durch den Kolben senkrecht zur Mittelebene und parallel zur Längsmittelachse durch die Verbindungsrippe mit Blickrichtung auf die Einlassseite des Kolbens,
- Fig. 7
- einen Schnitt entlang der in
Fig. 6 gezeigten Schnittebene mit Blickrichtung auf die Auslassseite des Kolbens, - Fig, 8
- eine schematische Ansicht eines Ausführungsbeispiels eines Kolbens von der dem Kurbelgehäuse zugewandten Seite.
- Fig. 1
- a schematic sectional view of a two-stroke engine,
- Fig. 2
- the piston of the two-stroke engine
Fig. 1 in perspective, - Fig. 3
- a side view of the piston,
- Fig. 4
- a perspective view of the piston from the side facing the crankcase,
- Fig. 5
- a perspective view of a section through the piston along the median plane,
- Fig. 6
- a section through the piston perpendicular to the median plane and parallel to the longitudinal central axis through the connecting rib looking towards the inlet side of the piston,
- Fig. 7
- a cut along in
Fig. 6 shown sectional plane looking towards the outlet side of the piston, - Fig. 8
- a schematic view of an embodiment of a piston from the side facing the crankcase.
Der Zweitaktmotor 1 besitzt einen Luftkanal 9, der mit einem Luftfilter 22 verbunden ist. Über den Luftkanal 9 wird kraftstofffreie oder kraftstoffarme Spülvorlagenluft zugeführt. Im Lufteinlass 9 ist eine Luftklappe 21 zur Steuerung der über den Luftkanal 9 zugeführten Menge an Spülvorlagenluft angeordnet. Der Luftkanal 9 mündet mit einem Lufteinlass 11 an der Zylinderbohrung 15. Zur Zufuhr von Kraftstoff/Luft-Gemisch ist ein Gemischkanal 10 vorgesehen. Der Gemischkanal 10 ist über einen Vergaser 18 mit dem Luftfilter 22 verbunden. Im Vergaser 18 sind im Ausführungsbeispiel eine Drosselklappe 19 sowie eine Chokeklappe 20 schwenkbar gelagert. Die Drosselklappe 19 und die Chokeklappe 20 dienen zur Einstellung der über den Gemischkanal 10 zugeführten Menge an Verbrennungsluft und Kraftstoff. Anstatt mittels eines konventionellen Vergasers 18 kann die Kraftstoffzufuhr auch auf andere Weise, beispielsweise über ein Einspritzventil oder einen Vergaser mit einem elektromagnetischen Ventil, erfolgen. Der Gemischkanal 10 mündet mit einem Gemischeinlass 12 an der Zylinderbohrung 15. Der Lufteinlass 11 und der Gemischeinlass 12 sind vom Kolben 5 gesteuert.The two-
Der Zweitaktmotor 1 besitzt Überströmkanäle 13, die mit Überströmfenstern 17 in den Brennraum 3 münden. Auch die Überströmfenster 17 sind vom Kolben 5 gesteuert. Im Bereich des unteren Totpunkts des Kolbens 5 verbinden die nicht näher dargestellten Überströmkanäle 13 den Kurbelgehäuseinnenraum 16 mit dem Brennraum 3. Im Betrieb wird beim Aufwärtshub des Kolbens 5 durch den Gemischeinlass 12 Kraftstoff/Luft-Gemisch in den Kurbelgehäuseinnenraum 16 angesaugt. Der Aufwärtshub des Kolbens 5 bezeichnet dabei die Bewegung des Kolbens 5 aus der in
Der Verbrennungsdruck beschleunigt den Kolben 5 zurück in Richtung auf das Kurbelgehäuse 4. Aus dem Brennraum 3 führt ein Auslass 23, der ebenfalls vom Kolben 5 gesteuert ist. Sobald der Auslass 23 vom Kolben 5 geöffnet wird, strömen die Abgase aus dem Brennraum 3 durch den Auslass 23 aus. Nach weiterem Abwärtshub öffnet der Kolben 5 die Überströmfenster 17 zum Brennraum 3. Die in den Überströmkanälen 13 vorgelagerte Verbrennungsluft strömt dann in den Brennraum 3 ein. Die vorgelagerte Luft spült Abgase aus dem Brennraum 3 durch den Auslass 23 aus. Aus dem Kurbelgehäuseinnenraum 16 strömt frisches Kraftstoff/Luft-Gemisch, das im Kurbelgehäuseinnenraum 16 vorkomprimiert wurde, nach. Beim folgenden Motorzyklus wird das Gemisch im Brennraum 3 beim Aufwärtshub des Kolbens 5 komprimiert, während gleichzeitig frisches Gemisch in den Kurbelgehäuseinnenraum 16 und Spülvorlagenluft in die Überströmkanäle 13 angesaugt wird.The combustion pressure accelerates the
Die Gestaltung der Kolbentaschen 14 hat entscheidenden Einfluss auf die Menge an in den Überströmkanälen 13 vorgelagerter Spülvorlagenluft. Wie
Der Kolben 5 besitzt einen Kolbenboden 25, der etwa senkrecht zur Zylinderlängsachse 48 verläuft und den Brennraum 3 begrenzt. Der Kolben 5 besitzt das Kolbenhemd 26, das vorteilhaft dem Verlauf der Zylinderbohrung 15 folgt. Die Außenseite des Kolbenhemds 26 verläuft vorteilhaft etwa zylindrisch. Die Außenseite des Kolbenhemds 26 kann dabei einen exakt zylindrischen oder einen von der Kreisform abweichenden Querschnitt besitzen. Das Kolbenhemd kann insbesondere eine elliptische, ovale oder kleeblattförmige Gestalt aufweisen. Ein kleeblattförmiger Querschnitt ist dabei ein Querschnitt, bei dem der Durchmesser in zwei schräg zueinander stehenden Richtungen verringert ist. Die Abweichung des Querschnitts von der Kreisform ist dabei vorteilhaft sehr gering. Benachbart zum Kolbenboden 25 sind am Kolbenhemd 26 zwei Kolbenringnuten 24 vorgesehen, die zur Aufnahme von Kolbenringen dienen. In einer der Kolbenringnuten 24 ist eine Bohrung 34 gezeigt, die zur Aufnahme eines Sicherungsstifts für einen Kolbenring dient. Eine entsprechende, in
Das Pleuel 6 (
Wie
An der Ausnehmung 33 besitzt der Kolben 5 eine verringerte Höhe i. Die verringerte Höhe i ist der parallel zur Längsmittelachse 50 gemessene Abstand des Rands 31 an der Ausnehmung 33 zur Oberseite 40 des Kolbens 5. Die verringerte Höhe i an der Ausnehmung 33 beträgt vorteilhaft 70% bis 98%, insbesondere 80% bis 95% der Höhe h des Kolbens 5. Der Durchmesser a beträgt vorteilhaft 70% bis 140% der Höhe h, insbesondere 80% bis 130%, bevorzugt 90% bis 120% der Höhe h. Besonders bevorzugt ist der Durchmesser a größer als die Höhe h.At the
Der Kolben 5 besitzt eine Einlassseite 46, an der die Ausnehmung 33 angeordnet ist.
Im Ausführungsbeispiel besitzen die Stirnseiten 57 der Kolbenbolzenaugen 28 jeweils einen Abstand e zu den Verbindungsrippen 55, der senkrecht zur Mittelebene 51 und parallel zur Querachse 49 (
Der Kolben 5 besitzt die Einlassseite 46, die in der Darstellung in
Wie
Zwischen den Verbindungsrippen 55 und dem Kolbenhemd 26 ist jeweils eine Vertiefung 56 ausgebildet. Jede Vertiefung 56 erstreckt sich an der der Mittelebene 51 abgewandten Seite der Verbindungsrippe 55 zwischen der Verbindungsrippe 55 und dem Kolbenhemd 26. Der Abstand der Vertiefung 56 zur Mittelebene 51 ist größer als der Abstand der die Vertiefung 56 begrenzenden Verbindungsrippe 55 zur Mittelebene 51. Die Verbindungsrippen 55 besitzen zur Mittelebene 51 einen Abstand d. Der Abstand d kann dabei in unterschiedlichen Bereichen der Verbindungsrippe 55 variieren, beispielsweise wenn die Breite der Verbindungsrippe 55 nicht konstant ist. Bevorzugt ist im Anbindungsbereich an das Kolbenbolzenauge 28 und im Anbindungsbereich an das Kolbenhemd 26 eine größere Breite der Verbindungsrippe 55 vorgesehen. Der Abstand d ist vorteilhaft in einem mittleren Bereich der Verbindungsrippe 55 gemessen. Der Abstand d beträgt vorteilhaft mindestens 20%, insbesondere mindestens 25% des Durchmessers a des Kolbens 5. Besonders bevorzugt beträgt der Abstand d an jeder Stelle der Verbindungsrippe 55 mindestens 20%, insbesondere mindestens 25% des Durchmessers a des Kolbens 5. Wie
Wie
Wie die Schnittdarstellung in
Wie
Die Vertiefung 56 besitzt einen Boden 61, der der Bereich der Vertiefung 56 ist, der den geringsten Abstand zur Oberseite 40 des Kolbens 5 besitzt. Der Boden 61 der Vertiefung 56 besitzt zum Boden 40 des Kolbens 5 einen parallel zur Längsmittelachse 50 gemessenen Abstand f, der vorteilhaft mehr als 50%, insbesondere mehr als 60% der Höhe h des Kolbens 5 beträgt. Der Abstand f beträgt vorteilhaft weniger als 90% der Höhe h des Kolbens 5.The
Die Rückwand 58 der Kolbentasche 14 besitzt eine Wandstärke y zwischen der Kolbentasche 14 und dem zwischen den Rückwänden 58 der Kolbentaschen 14 liegenden Innenraum des Kolbens 5. In dem Bereich zwischen der Vertiefung 56 und der Kolbentasche 14 besitzt die Rückwand 58 eine verringerte Wandstärke x. Die verringerte Wandstärke x beträgt vorteilhaft höchstens 80%, insbesondere höchstens 60% der Wandstärke y. Die Wandstärke x darf für eine ausreichende Stabilität der Rückwand 58 ein Mindestmaß nicht unterschreiten. Dieses Mindestmaß, das vom Material und der Geometrie des Kolbens 5 abhängt, bestimmt die maximal mögliche Tiefe c der Vertiefung 56.The
Wie
Die auf den gegenüberliegenden Seiten der Mittelebene 51 angeordneten Verbindungsrippen 55 besitzen zueinander einen Abstand n, der senkrecht zur Mittelebene 51 gemessen ist. Der Abstand n beträgt vorteilhaft mindestens 40%, insbesondere mindestens 50% des Durchmessers a des Kolbens 5. Die Stirnseiten 57 der Kolbenbolzenaugen 28 besitzen zueinander einen Abstand s. Der Abstand s beträgt vorteilhaft mindestens 10%, insbesondere mindestens 20% des Durchmessers a des Kolbens 5. Der Abstand s ist deutlich kleiner als der Abstand n der Verbindungsrippen 55. Der Abstand s beträgt vorteilhaft weniger als 70% des Abstands n. Die Verbindungsrippen 55 sind gegenüber den Stirnseiten 57 radial nach außen versetzt. Die Kolbenbolzenaugen 28 besitzen eine von den Stirnseiten 57 zum Kolbenhemd 26 und senkrecht zur Mittelebene 51 gemessene Breite w, die vorteilhaft mindestens 15%, insbesondere mindestens 20% des Durchmessers a des Kolbens beträgt.The arranged on the opposite sides of the
Wie
Die seitlichen Rippen 42 besitzen ein der Oberseite 40 abgewandtes Ende 44, das zur Oberseite 40 einen parallel zur Längsmittelachse 50 gemessenen Abstand o besitzt. Der Abstand o ist kleiner als der Abstand g zwischen dem Ende 45 der mittleren Rippe 43 und der Oberseite 40 des Kolbens 5 (
Die Vertiefung 56 besitzt eine parallel zur Querachse 49 gemessene Breite r, die vorteilhaft weniger als 10% des Durchmessers a des Kolbens 5 beträgt. Der Boden 61 besitzt zum Rand 31 in dem die Vertiefung 56 begrenzenden Bereich einen parallel zur Längsmittelachse 50 gemessenen Abstand p. Der Abstand p ist im Ausführungsbeispiel größer als die Höhe m des Stegs 32 in diesem Bereich. Die Höhe m des Stegs 32 beträgt vorteilhaft 70% bis 95% des Abstands p. Die Breite r der Vertiefung 56 kann näherungsweise der maximalen Tiefe c der Vertiefung 56 entsprechen. Bevorzugt beträgt die Breite r 60% bis 120% der maximalen Tiefe c der Vertiefung 56 (
Der Kolben 5,5' besteht aus Leichtmetall, insbesondere aus Magnesium. Auch eine Ausbildung aus Aluminium kann vorteilhaft sein. Durch die Vertiefungen 56, 56' wird eine Materialanhäufung zwischen der Verbindungsrippe 55, 55' und dem Kolbenhemd 26 vermieden, so dass der Kolben 5 gut in einem Gussverfahren aus Leichtmetall, insbesondere aus Magnesium, hergestellt werden kann.The
Claims (14)
dadurch gekennzeichnet, dass zwischen der Verbindungsrippe (55, 55') und dem Kolbenhemd (26) eine Vertiefung (56, 56') ausgebildet ist.Piston according to claim 1,
characterized in that between the connecting rib (55, 55 ') and the piston skirt (26) has a recess (56, 56') is formed.
dadurch gekennzeichnet, dass die Tiefe (c) der Vertiefung (56, 56') mindestens 3% der Höhe (h) des Kolbens (5) beträgt.Piston according to claim 2,
characterized in that the depth (c) of the recess (56, 56 ') is at least 3% of the height (h) of the piston (5).
dadurch gekennzeichnet, dass die Verbindungsrippe (55, 55') parallel zur Mittelebene (51) verläuft.Piston according to one of claims 1 to 3,
characterized in that the connecting rib (55, 55 ') extends parallel to the median plane (51).
dadurch gekennzeichnet, dass der senkrecht zur Mittelebene (51) gemessene Abstand (d) der Verbindungsrippe (55, 55') zur Mittelebene (51) mindestens 20% des Durchmessers (a) des Kolbens (5) beträgt.Piston according to one of claims 1 to 4,
characterized in that the perpendicular to the median plane (51) measured distance (d) of the connecting rib (55, 55 ') to the center plane (51) is at least 20% of the diameter (a) of the piston (5).
dadurch gekennzeichnet, dass die Kolbenbolzenaugen (28) einander zugewandte Stirnseiten (57) besitzen und die Verbindungsrippe (55, 55') zur Stirnseite (57) des zugeordneten Kolbenbolzenauges (28) einen parallel zur Querachse (49) gemessenen Abstand (e) von mindestens 5% des Durchmessers (a) des Kolbens (5) besitzt.Piston according to one of claims 1 to 5,
characterized in that the piston pin bosses (28) have mutually facing end faces (57) and the connecting rib (55, 55 ') to the end face (57) of the associated Kolbenbolzenauges (28) parallel to the transverse axis (49) measured distance (e) of at least 5% of the diameter (a) of the piston (5) has.
dadurch gekennzeichnet, dass die Kolbentasche (14) eine Rückwand (58) besitzt und die Verbindungsrippe (55, 55') in Verlängerung der Rückwand (58) der Kolbentasche (14) angeordnet ist.Piston according to one of claims 1 to 6,
characterized in that the piston pocket (14) has a rear wall (58) and the connecting rib (55, 55 ') in extension of the rear wall (58) of the piston pocket (14) is arranged.
dadurch gekennzeichnet, dass das Kolbenhemd (26) einen dem Kolbenboden (25) abgewandten Rand (31) besitzt.Piston according to one of claims 1 to 7,
characterized in that the piston skirt (26) has a piston bottom (25) facing away from edge (31).
dadurch gekennzeichnet, dass die Verbindungsrippe (55, 55') eine dem Kolbenboden (25) abgewandte Stirnseite (59) besitzt und dass der Versatz (b) zwischen der Stirnseite (59) der Verbindungsrippe (55, 55') und dem Rand (31) in Richtung der Längsmittelachse (50) des Kolbens (5) an jeder Stelle der Stirnseite (59) weniger als 5% der Höhe (h) des Kolbens (5) beträgt.Piston according to claim 8,
characterized in that the connecting rib (55, 55 ') has an end face (59) facing away from the piston head (25) and that the offset (b) between the end face (59) of the connecting rib (55, 55') and the edge (31 ) in Direction of the longitudinal central axis (50) of the piston (5) at each point of the end face (59) is less than 5% of the height (h) of the piston (5).
dadurch gekennzeichnet, dass zwischen dem Rand (31) und der Kolbentasche (14) ein Steg (32) des Kolbenhemds (26) verläuft, wobei der Steg (32) in dem Umfangsbereich des Kolbens (5), in dem die Vertiefung (56, 56') angeordnet ist, eine Höhe (m) besitzt, die mindestens das 1,5fache der kleinsten Höhe (k) des Stegs (32) beträgt.Piston according to claim 8 or 9,
characterized in that between the edge (31) and the piston pocket (14) a web (32) of the piston skirt (26) extends, wherein the web (32) in the peripheral region of the piston (5) in which the recess (56, 56 '), has a height (m) which is at least 1.5 times the smallest height (k) of the web (32).
dadurch gekennzeichnet, dass die Kolbenbolzenaufnahme (35) mindestens teilweise in der Kolbentasche (25) angeordnet ist.Piston according to one of claims 1 to 10,
characterized in that the piston pin receptacle (35) is arranged at least partially in the piston pocket (25).
dadurch gekennzeichnet, dass der Kolben (5) zwei Kolbentaschen (14) auf gegenüberliegenden Seiten der Mittelebene (51) besitzt und an beiden Kolbenbolzenaugen (28) jeweils eine Verbindungsrippe (55, 55') angeordnet ist.Piston according to one of claims 1 to 11,
characterized in that the piston (5) has two piston pockets (14) on opposite sides of the median plane (51) and at both piston pin bosses (28) each have a connecting rib (55, 55 ') is arranged.
dadurch gekennzeichnet, dass der Kolben (5) aus Leichtmetall besteht.Piston according to one of claims 1 to 12,
characterized in that the piston (5) consists of light metal.
Priority Applications (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP16001824.8A EP3284938B1 (en) | 2016-08-19 | 2016-08-19 | Piston for a two-stroke engine working with direct injection and two-stroke engine |
CN201710712798.6A CN107762656B (en) | 2016-08-19 | 2017-08-18 | Piston for a two-stroke motor operating with a purging pre-stored quantity, and two-stroke motor |
US15/682,343 US10344707B2 (en) | 2016-08-19 | 2017-08-21 | Piston for a two-stroke engine operating with advanced scavenging and a two-stroke engine |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
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EP16001824.8A EP3284938B1 (en) | 2016-08-19 | 2016-08-19 | Piston for a two-stroke engine working with direct injection and two-stroke engine |
Publications (2)
Publication Number | Publication Date |
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EP3284938A1 true EP3284938A1 (en) | 2018-02-21 |
EP3284938B1 EP3284938B1 (en) | 2020-10-07 |
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Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
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EP16001824.8A Active EP3284938B1 (en) | 2016-08-19 | 2016-08-19 | Piston for a two-stroke engine working with direct injection and two-stroke engine |
Country Status (3)
Country | Link |
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US (1) | US10344707B2 (en) |
EP (1) | EP3284938B1 (en) |
CN (1) | CN107762656B (en) |
Cited By (3)
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DE102019121728B3 (en) * | 2019-08-13 | 2020-11-26 | Iav Gmbh Ingenieurgesellschaft Auto Und Verkehr | Pistons with an annular cooling chamber for reciprocating internal combustion engines |
WO2021176466A1 (en) * | 2020-03-02 | 2021-09-10 | Tvs Motor Company Limited | Reciprocating assembly for an internal combustion engine |
US11725570B2 (en) | 2019-03-06 | 2023-08-15 | Husqvarna Ab | Engine piston, engine, hand-held tool, and method of manufacturing an engine piston |
Families Citing this family (2)
Publication number | Priority date | Publication date | Assignee | Title |
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US10760524B2 (en) * | 2016-11-18 | 2020-09-01 | Honda Motor Co., Ltd. | Internal combustion engine |
CN114017192A (en) * | 2021-11-08 | 2022-02-08 | 博罗县标洁精工五金有限公司 | Motor vehicle piston with strong tensile strength at normal temperature |
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DE102010008260A1 (en) | 2010-02-17 | 2011-08-18 | Andreas Stihl AG & Co. KG, 71336 | Two-stroke engine |
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US11725570B2 (en) | 2019-03-06 | 2023-08-15 | Husqvarna Ab | Engine piston, engine, hand-held tool, and method of manufacturing an engine piston |
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Also Published As
Publication number | Publication date |
---|---|
CN107762656B (en) | 2021-06-29 |
US20180051649A1 (en) | 2018-02-22 |
US10344707B2 (en) | 2019-07-09 |
EP3284938B1 (en) | 2020-10-07 |
CN107762656A (en) | 2018-03-06 |
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