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(11) EP 2 565 434 B1

(12) EUROPEAN PATENT SPECIFICATION

(45) Date of publication and mention (51) Int Cl.: of the grant of the patent: F02F 7/00 (2006.01) 15.11.2017 Bulletin 2017/46 (86) International application number: (21) Application number: 11774732.9 PCT/JP2011/056870

(22) Date of filing: 23.03.2011 (87) International publication number: WO 2011/135948 (03.11.2011 Gazette 2011/44)

(54) SCAVENGING PATH STRUCTURE FOR TWO-STROKE ENGINE SPÜLUNGSPFADSTRUKTUR FÜR EINEN ZWEITAKTMOTOR STRUCTURE DE TRAJET D’ÉVACUATION POUR MOTEUR À DEUX TEMPS

(84) Designated Contracting States: (72) Inventors: AL AT BE BG CH CY CZ DE DK EE ES FI FR GB • UENOYAMA, Kazuyuki GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO Tokyo 108-8215 (JP) PL PT RO RS SE SI SK SM TR • KIMURA, Takahiro Tokyo 108-8215 (JP) (30) Priority: 27.04.2010 JP 2010102148 (74) Representative: Studio Torta S.p.A. (43) Date of publication of application: Via Viotti, 9 06.03.2013 Bulletin 2013/10 10121 Torino (IT)

(73) Proprietor: Mitsubishi Heavy Industries, Ltd. (56) References cited: Tokyo 108-8215 (JP) JP-A- 2002 332 846 JP-A- 2007 146 770 JP-A- 2007 285 219 US-A- 4 445 468 US-B1- 6 279 521

Note: Within nine months of the publication of the mention of the grant of the European patent in the European Patent Bulletin, any person may give notice to the European Patent Office of opposition to that patent, in accordance with the Implementing Regulations. Notice of opposition shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention). EP 2 565 434 B1

Printed by Jouve, 75001 PARIS (FR) 1 EP 2 565 434 B1 2

Description scavenging passages 104b. A lower passage 132b in- side the insulator 132 forms an air/fuel mixture passage TECHNICAL FIELD for supplying an air/fuel mixture into the crank chamber 106. This air/fuel mixture passage communicates with [0001] The present invention relates to a scavenging 5 inside of the cylinder 101 via an intake port 142. passage structure for a two-stroke engine having a scav- [0008] In Fig. 8, the crankcase 102 is made up of a enging passage communicating a scavenging port pro- front crankcase 102a and a rear crankcase 102b that are vided in a cylinder with a crank chamber inside a crank- front and back parts divided at a front and back split sur- case, the scavenging passage extending through re- face 125 orthogonal to the crankshaft axis 180. After the spective fastening surfaces of the cylinder and the crank- 10 crankshaft 108 and others have been assembled inside, case. the front crankcase 102a and rear crankcase 102b are fastened together and united, with a plurality of bolts us- BACKGROUND ART ing bolt holes 126. [0009] Reference numeral 103 denotes a flat and [0002] In two-stroke engines, scavenging passages 15 smooth cylinder mounting surface formed at the top of that open to the crank chamber formed inside the crank- the crankcase 102. The cylinder 101 is fastened with a case extend as smoothly curved passages inside the plurality of bolts 114, with its lower face 103’ making con- crankcase to the fastening surfaces of the crankcase and tact with this cylinder mounting surface 103. the cylinder, through the scavenging passages, and con- [0010] The scavenging passages 104a and the scav- nect to scavenging ports provided in the cylinder. 20 enging passage inlets 104c are each formed inside the [0003] Fig. 8 is an exploded perspective view of a front crankcase 102a and rear crankcase 102b symmet- crankcase and a cylinder of a conventional two-stroke rically about the front and back split surface 125. The engine. Fig. 9 is a cross section along F-F of Fig. 8, which upper ends of the scavenging passages 104a are open is a cross-sectional view of the crankcase of the conven- in the cylinder mounting surface 103. tional two-stroke engine as viewed from a direction or- 25 [0011] Reference numeral 110 denotes guide mem- thogonal to the crankshaft axis. Fig. 10 is a diagram as bers, inserted from the openings in the cylinder mounting viewed in the direction of arrows G-G in Fig. 9, which is surface 103, their upper faces forming part of the cylinder a top view of the crankcase. Fig. 11 is a cross section as mounting surface 103. The guide members 110 are viewed in the direction of arrows H-H in Fig. 10. formed with passage surfaces that smoothly connect to [0004] In Fig. 8 to Fig. 11, reference numeral 101 de- 30 the scavenging passages 104a. The guide members 110 notes a cylinder; a combustion chamber is formed inside are provided with protrusions, for example, in their upper the cylinder 101. There are provided a piston 130 moving faces and sides, while grooves are cut in the crankcase up and down inside the cylinder 101, and a crankshaft 102, sothat the guide members arefastened to the crank- 108 for converting the up and down movement of the case 102 with these protrusions fitted in the grooves. piston 130 into rotational force. 35 [0012] In the two-stroke engine equipped with the [0005] Referencenumeral 102 denotes thecrankcase, scavenging passage structure configured as shown in inside which a crank chamber 106 is formed. Reference Fig. 8 to Fig. 11, the air/fuel mixture from the crank cham- numeral 140 denotes two scavenging ports provided in ber 106 formed inside the crankcase 102 is introduced side portions of the cylinder 101 to face opposite each into the scavenging passages 104a partly formed by the other, Fig. 8 showing only one of these. The scavenging 40 guide members 110 having passage surfaces formed as ports 140 are each communicated with the crank cham- smooth curved surfaces, via the scavenging passage in- ber 106 via scavenging passages 104b inside the cylin- lets 104c, and flows through the scavenging passages der 101, scavenging passages 104a formed in a curved 104a formed as smoothly curved passages, and through shape in both side walls of the crankcase 102, and a pair the scavenging passage 104b formed in the cylinder, to of scavenging passage inlets 104c. 45 be supplied to the scavenging ports 140. The air/fuel mix- [0006] Reference numeral 118 denotes air passages ture is thus supplied as a smooth and powerful flow into for supplying leading air, connected midway of the scav- the scavenging ports 140 without any flow loss such as enging passages 104b so that leading air from an air a flow rate reduction, as the mixture flows through the cleaner is supplied to the scavenging ports 140 through scavenging passages 104a formed as smoothly curved the air passages 118 and scavenging passages 104b. 50 passages without turns at right angles or the like. [0007] Reference numeral 132 denotes an insulator for [0013] The conventional scavenging passage struc- thermally insulating the intake system from the engine ture for a two-stroke engine using the guide members body, the insulator 132 being fastened to a side face of described using Fig. 8 to Fig. 11 is disclosed in Patent the cylinder 2 with bolts. An upper passage 132a inside Document 1. the insulator 132 forms an air passage for supplying lead- 55 ing air. This air passage is connected midway of the scav- enging passages 104b, so that leading air is supplied to the scavenging ports 140 via the air passages 118 and

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[Citation List] engine can be reduced. [0020] The groove may be recessed in the inner wall [Patent Literature] surface of the crankcase and the cover member may be attached in contact with the inner wall surface of the [0014] Patent Document 1: Japanese Patent No.5 crankcase so as to close an open part of the groove. 4031602 US4445468 discloses a 2-stroke engine having [0021] This way, as grooves need not be provided in a combustion chamber and a scavenge port connected the cover member, a general-purpose component can via a transfer passage to a crank chamber within a crank- be used as the cover member. This allows inexpensive case. replacement of cover members when failure occurs. 10 [0022] The groove may be recessed in the cover mem- DISCLOSURE OF THE INVENTION ber, and the cover member may be attached in contact with the inner wall surface of the crankcase so as to close [Technical Problem] an open part of the groove. [0023] Thereby, the production cost can be reduced [0015] However, with the conventional scavenging15 as the slide cores are made unnecessary, and also, the passage structure for a two-stroke engine using the guide die designused for producing the crankcase canbe made members 110 disclosed in Patent Document 1 and de- simpler, as no grooves are formed in the crankcase. scribed using Fig. 8 to Fig. 11, to produce the front crank- [0024] The groove may be recessed both in the inner case 102a and rear crankcase 102b by die casting, slide wall surface of the crankcase and in the cover member, cores for forming the scavenging passages are neces- 20 and the cover member may be attached in contact with sary. In this case, the die casting is performed, with a the inner wall surface of the crankcase so that respective slide core that can slide in a direction toward the cylinder open parts of the grooves provided in the inner wall sur- mounting surface 103 being inserted into a portion that face of the crankcase and in the cover member face op- will form the scavenging passage 104a, after which the posite each other. slide core is slid in the direction toward the cylinder25 [0025] Thereby, the production cost can be reduced mounting surface 103 and extracted to allow ejection of as the slide cores are made unnecessary, and also, the the casting. The guide members 110 are inserted into cover member can be positioned to the crankcase more and secured in the portions where the slide cores existed, easily since the mounting position of the cover member to form the scavenging passages 104a. Namely, the cost to the crankcase is determined by the positions of the of the entire die set is high because of the presence of 30 grooves each provided in the crankcase and the cover the slide cores. member. [0016] Also, the use of the slide cores increases the [0026] The cover member may be attached to the inner number of steps for forming the scavenging passages wall surface at a mounting position determined by being for the two-stroke engine, causing the problem of in- fitted in between opposite inner wall surfaces of the creased cost required for the formation of the scavenging 35 crankcase. passages. [0027] This allows simple and reliable positioning be- [0017] Accordingly, in view of such a problem encoun- tween the cover member and the crankcase, ensuring tered by the conventional technique, an object of the correct formation of the scavenging passage. present invention is to provide a scavenging passage [0028] Thepresent inventioncan providea scavenging structure for a two-stroke engine, with which scavenging 40 passage structure for a two-stroke engine, which allows passages communicating scavenging ports provided in formation of scavenging passages communicating the the cylinder with the crank chamber inside the crankcase scavenging ports in the cylinder with the crank chamber can be formed without using slide cores, so that the pro- inside the crankcase without using slide cores, whereby duction cost arising from the use of slide cores is cut the production cost incurred by the use of slide cores can down. 45 be cut down.

[Solution to Problem] BRIEF DESCRIPTION OF THE DRAWINGS

[0018] To solve the problem mentioned above, the [0029] present invention provides a two-stroke engine, as de- 50 fined in independent claim 1. Fig. 1 is a structural view illustrating a scavenging [0019] Thereby, even though the crankcase is pro- passage structure for a two-stroke engine according duced by die casting, there is no need to use slide cores, to Embodiment 1 as viewed from a direction orthog- which are slid toward the cylinder mounting surface to onal to the crankshaft axis; allow extraction of the casting. As there is no need to use 55 Fig. 2 is a cross-sectional view of a crankcase in slide cores, the production cost for slide cores is made which the scavenging passage structure for a two- unnecessary. Accordingly, the production cost required stroke engine according to Embodiment 1 is formed, for configuring the scavenging passages for a two-stroke as viewed from a direction orthogonal to the crank-

3 5 EP 2 565 434 B1 6

shaft axis; to the crankcase 2 with a plurality of bolts 14 via a gasket, Fig. 3 is a diagram as viewed in the direction of ar- at their respective fastening surfaces, i.e., a cylinder rows A-A in Fig. 2; mounting surface 3 that is the upper face of the crankcase Fig. 4 is a cross section as viewed in the direction of 2 and the lower face 3’ of the cylinder. Reference numeral arrows B-B in Fig. 3; 5 16 denotes an exhaust port opened in a side portion of Fig. 5 is a perspective view of a rear crankcase 2b; the cylinder 12 and connected to an exhaust passage. Fig. 6 is a schematic view of the vicinity of the scav- [0034] Reference numeral 40 denotes two scavenging enging passage according to Embodiment 2; ports provided in side portions of the cylinder 12 to face Fig. 7 is a schematic view of the vicinity of the scav- opposite each other, Fig. 1 showing only one of these. enging passage according to Embodiment 3; 10 Scavenging passages 4b formed inside the cylinder 12 Fig. 8 is an exploded perspective view of a crankcase are connected to the scavenging ports 40. Reference and a cylinder of a conventional two-stroke engine; numeral 4c denotes a scavenging passage inlet opened Fig. 9 is a cross-sectional view of the crankcase of into a crank chamber 6 formed inside the crankcase 2. the conventional two-stroke engine in which a scav- Reference numeral 4a denotes a scavenging passage enging passage structure is formed, as viewed from 15 formed as a smoothly curved passage inside the crank- a direction orthogonal to the crankshaft axis; case 2. The scavenging passages 4a extend through the Fig. 10 is a diagram as viewed in the direction of fastening surfaces 3 and 3’ of the crankcase 2 and the arrows G-G in Fig. 9; and cylinder 12 so as to connect the scavenging passages Fig. 11 is a cross section as viewed in the direction 4b inside the cylinder 12 and the scavenging passage of arrows H-H in Fig. 10. 20 inlets 4c. The scavenging ports 40 are thus communicat- ed with the crank chamber 6 through the scavenging pas- BEST MODE FOR CARRYING OUT THE INVENTION sages 4b,scavenging passages4a, andscavenging pas- sage inlets 4c configured as described above. [0030] Preferredembodiments of the present invention [0035] Reference numeral 18 denotes an air passage will be hereinafter illustratively described in detail with 25 for supplying leading air, connected midway of the scav- reference to the drawings. It should be understood that enging passages 4b so that leading air from an air cleaner the sizes, materials, and shapes of the constituent ele- (not shown) is supplied to the scavenging ports 40 ments described in the embodiments, and their positions through the air passage 18 and scavenging passages 4b. relative to each other, are given for illustrative purposes [0036] The scavenging passages 4a inside the crank- only and not meant to limit the scope of this invention, 30 case 2 are formed as described below. The crankcase 2 unless specifically stated otherwise. is provided with grooves 21 in contact surfaces with cover members 22, the grooves being recessed into the direc- (Embodiment 1) tion of the crankshaft axis 80 as shown in Fig. 3. The grooves 21 are open toward inside of the crankcase 2, [0031] Fig. 1 is a cross-sectional view of a crankcase 35 the remaining parts being formed as a smoothly curved and a cylinder of a two-stroke engine according to Em- passage to form the scavenging passages 4a. bodiment 1 of the present invention as viewed from a [0037] On the open side of the grooves 21 formed in direction orthogonal to the crankshaft axis. Fig. 2 is a the crankcase 2, the cover members 22 are attached in cross-sectional view of the crankcase in which a scav- contact with inner wall surfaces 2c of the crankcase 2. enging passage structure for a two-stroke engine accord- 40 The cover members 22 close the open side of the grooves ing to Embodiment 1 of the present invention is formed, 21, attached in contact with the inner wall surfaces of the as viewed from a direction orthogonal to the crankshaft crankcase 2, and fastened to the crankcase 2 with fas- axis corresponding to a cross section along C-C of Fig. tening members 23 such as bolts. 3. Fig. 3 is a diagram as viewed in the direction of arrows [0038] The crankcase 2 further includes two inner wall A-A in Fig. 2, and Fig. 4 is a diagram as viewed in the 45 surfaces 2d opposite each other at both ends of the inner direction of arrows B-B in Fig. 3. wall surfaces 2c in which the grooves 21 are provided, [0032] The crankcase2 is madeup of a front crankcase the cover members 22 being fitted in between the two 2a and a rear crankcase 2b that are front and back parts inner wall surfaces 2d. As the cover members 22 are divided at a front and back split surface 25 orthogonal to fitted in between the two opposing inner wall surfaces the crankshaft axis 80. After the crankshaft 8 and others 50 2d, the mounting position of the cover members 22 is have been assembled inside, the front crankcase 2a and determined. rear crankcase 2b are fastened together and united with [0039] The open side of the grooves 21 recessed into a plurality of bolts 26. Fig. 5 is a perspective view of the the direction of the crankshaft axis 80 in the crankcase rear crankcase 2b; Fig. 3 is a cross section along D-D of 2 is thus closed by the cover members 22 so that the Fig. 5. 55 grooves 21 and cover members 22 together form pas- [0033] In Fig. 1 to Fig. 5, reference numeral 1 denotes sages, these passages being the scavenging passages the engine, which is configured as described below. Ref- 4a. erence numeral 12 denotes a cylinder, which is fastened [0040] In the two-stroke engine with the scavenging

4 7 EP 2 565 434 B1 8 passage structure having the configuration shown in Fig. in the direction of the crankshaft axis 80. The grooves 1 to Fig. 5, the air/fuel mixture from the crank chamber 21a are open on the side opposite the inner wall surfaces 6 formed inside the crankcase 2 is introduced from the 2c of the crankcase 2 that is in contact with the cover scavenging passage inlets 4c into the scavenging pas- members 22. The remaining parts are formed in smooth sages 4a that are formed to have smooth curved surfac- 5 curves to form the scavenging passages 4a. es, flows through the scavenging passages 4a and 4b, [0047] The cover members 22 are attached so that the and is supplied to the scavenging ports 40. The air/fuel open side of the grooves 21a thereof makes contact with mixture is thus supplied as a smooth and powerful flow the inner wall surfaces of the crankcase 2. The cover into the scavenging ports 9 without any flow loss such members 22 are attached in contact with the inner wall as a flow rate reduction, as the mixture flows through the 10 surfaces of the crankcase 2 so that the open grooves scavenging passages 4a formed as smoothly curved 21a are closed, and fastened in position with fastening passages without turns at right angles or the like. members such as bolts to the inner wall surfaces 2c of [0041] With Embodiment 1, the scavenging passages the crankcase 2. 4a inside the crankcase 2 are formed by the grooves 21 [0048] Thus the open side of the grooves 21a provided and the cover members 22, the grooves being provided 15 in the cover members 22 is closed by the inner wall sur- in the contact surfaces 2c between the crankcase 2 and faces 2c of the crankcase 2 so that the grooves 21a and the cover members 22. Therefore, the rear crankcase 2b the inner wall surfaces 2c of the crankcase 2 together can be produced by die casting, using a die set designed form passages, these passages being the scavenging to form a groove 21, the cover member 22 then being passages 4a. brought into contact with the inner wall surface 2c of the 20 [0049] As in Embodiment 2 described using Fig. 6, rear crankcase 2b so as to close the open side of the grooves 21a may be provided in the cover members 22 groove 21 from the side of the front and back split surface and not in the crankcase 2. 25 and fastened there with the bolts 23. The front crank- [0050] Thereby, the production cost can be reduced case 2a is produced similarly with the rear crankcase 2b, as the slide cores are made unnecessary, as with Em- after which the front crankcase 2a and the rear crankcase 25 bodiment 1, and also, the die design used for producing 2b are fastened together and united with the bolts 26, so the crankcase can be made simpler. that the crankcase 2 is complete. [0042] Therefore, even though the crankcase is pro- (Embodiment 3) duced by die casting, there is no need to use slide cores, which are slid toward the cylinder mounting surface 3 on 30 [0051] Fig. 7 is a top view of the vicinity of a scavenging the upper face of the crankcase 2 that is the fastening passage provided in the crankcase according to Embod- surface with the cylinder 12, to allow extraction of the iment 3, of the part in Embodiment 3 corresponding to casting, for forming the scavenging passages 4a. part A shown in Fig. 3 of Embodiment 1, shown to a larger [0043] As there is no need to use slide cores, the pro- scale. The features other than the structure of the scav- duction cost for slide cores is made unnecessary. Ac- 35 enging passage 4a in Embodiment 3 are the same as cordingly, the production cost required for configuring the those of Embodiment 1 described using Fig. 1 to Fig. 5. scavenging passages for a two-stroke engine can be re- [0052] In Embodiment 3, grooves 21b and 21c are duced. formed each in the contact surface of the crankcase 2 [0044] The cover members 22 take up part of the space contacting the cover members 22 and in the contact sur- inside the crankcase 2. An extremely large space left 40 faces of the cover members 22 contacting the inner wall inside the crankcase 2 would cause a reduction in com- surfaces of the crankcase so as to be recessed in the pression ratio of the crankcase 2. The provision of the direction of the crankshaft axis 80. The grooves 21b are cover members 22 can prevent such reduction in the open in the inner wall surfaces 2c of the crankcase 2 compression ratio. contacting the cover members 22. The grooves 21c are 45 open in the contact surfaces of the cover members 22 (Embodiment 2) contacting the crankcase 2. The grooves 21b and 21c are formed in the crankcase 2 and the cover members [0045] Fig. 6 is a top view of the vicinity of a scavenging 22, respectively, so that, when the cover members 22 passage provided in the crankcase according to Embod- are attached to the crankcase 2 to be in contact with the iment 2, of the part in Embodiment 2 corresponding to 50 innerwall surfaces ofthe crankcase so that the respective part E shown in Fig. 3 of Embodiment 1, shown to a larger open sides of the grooves 21b and grooves 21c are faced scale. The features other than the structure of the scav- opposite each other, the grooves 21b and 21c together enging passage 4a in Embodiment 2 are the same as form smoothly curved scavenging passages 4a. those of Embodiment 1 described using Fig. 1 to Fig. 5. [0053] The cover members 22 are fastened in position, [0046] In Embodiment 2, no grooves are formed in the 55 with fastening members such as bolts, to the inner wall crankcase 2, and instead, grooves 21a are formed in the surfaces of the crankcase 2. contact surfaces of the cover members 22 contacting the [0054] Thus the grooves 21b and 21c provided in the inner wall surfaces of the crankcase so as to be recessed crankcase 2 and cover members 22 are faced opposite

5 9 EP 2 565 434 B1 10 each other in the direction of the crankshaft axis 80 so saidgroove (21) is recessed in said inner wall surface that the grooves 21b and 21c together form passages, (2c) of the crankcase (2), said cover member (22) these passages being the scavenging passages 4a. being attached in contact with said inner wall surface [0055] As in Embodiment 3 described using Fig. 7, (2c) of the crankcase (2) so as to close an open part grooves may be provided in both of the crankcase 2 and 5 of said groove (21). the cover members 22. [0056] Thereby, the production cost can be reduced 3. The two-stroke engine according to claim 1, wherein as the slide cores are made unnecessary, as with Em- said groove (21a) is recessed in said cover member bodiment 1, and in addition, the cover members 22 can (21), said cover member (22) being attached in con- be positioned to the crankcase 2 more easily since the 10 tact with said inner wall surface (2c) of the crankcase mounting position of the cover members 21b to the crank- (2) so as to close an open part of said groove (21). case 2 is determined by the positions of the grooves 21b and 21c. 4. The two-stroke engine according to claim 1, wherein said groove (21b, 21c) is recessed both in said inner INDUSTRIAL APPLICABILITY 15 wall surface (2c) of the crankcase (2) and in said cover member (22), said cover member (22) being [0057] The present invention is applicable as a scav- attached in contact with said inner wall surface (2c) enging passage structure for a two-stroke engine, which of the crankcase (2) so that respective open parts of allows formation of scavenging passages communicat- the grooves (21c) provided in said inner wall surface ing the scavenging ports in the cylinder with the crank 20 (2c) of the crankcase (2) and in said cover member chamber inside the crankcase without using slide cores. (22) face opposite each other.

5. The two-stroke engines according to any one of Claims claims 1 to 4, wherein said cover member (22) is 25 attached to said inner wall surface (2c) at a mounting 1. A two-stroke engine comprising: position determined by being fitted in between op- posite inner wall surfaces (2d) of said crankcase (2). - a crankcase (2), - a cylinder (12) with a crank chamber (6) formed inside said crankcase (2), and 30 Patentansprüche - a scavenging passage structure having a scav- enging passage (4a, 4b) communicating a scav- 1. Zweitaktmotor, umfassend: enging port (40) provided in the cylinder (12), said scavenging passage (4a, 4b) being formed - ein Kurbelgehäuse (2), to extend through respective fastening surfaces 35 - einen Zylinder (12) mit einer Kurbelkammer of said cylinder (12) and said crankcase (2), (6), die im genannten Kurbelgehäuse (2) aus- wherein the crankcase (2) is made up of a front gebildet ist, und crankcase (2a) and a rear crankcase (2b) that - eine Spülkanalstruktur mit einem Spülkanal are front and back parts divided at a front and (4a, 4b), der mit einer Spülöffnung (40), die im backsplit surface (25) orthogonal to a crankshaft 40 Zylinder (12) vorgesehen ist, in Verbindung axis (80), characterized in that the scavenging steht, wobei der genannte Spülkanal (4a, 4b) passage structure further has: derart ausgebildet ist, dass er sich durch Befes- tigungsflächen des genannten Zylinders (12) a cover member (22) attached inside each bzw. des genannten Kurbelgehäuses (2) er- of the front crankcase (2a) and the rear45 streckt, crankcase (2b) so as to be in contact with an inner wall surface (2c) of the crankcase wobei das Kurbelgehäuse (2) aus einem vorderen (2) from the side of the front and back split Kurbelgehäuse (2a) und einem hinteren Kurbelge- surface (25); and häuse (2b) besteht, bei denen es sich um einen vor- a groove (21, 21a, 21b, 21c) formed in a 50 deren und einen hinteren Teil handelt, die durch eine contact surface between said inner wall sur- Vorne-Hinten-Trennfläche (25) geteilt sind, die face (2c) of the crankcase (2) and said cover rechtwinklig zur Kurbelwellenachse (80) verläuft, member (22), and forming part of said scav- dadurch gekennzeichnet, dass die Spülkanal- enging passage (4a, 4b) connecting to said struktur außerdem umfasst: crank chamber (6) and to an upper face (3) 55 of the crankcase (2). ein Abdeckorgan (22), das innerhalb sowohl des vorderen Kurbelgehäuses (2a), als auch des 2. The two-stroke engine according to claim 1, wherein hinteren Kurbelgehäuses (2b) derart ange-

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bracht ist, dass es mit einer Innenwandfläche une structure de passage d’évacuation ayant un (2c) des Kurbelgehäuses (2) auf der Seite der passage d’évacuation (4a, 4b) communiquant Vorne-Hinten-Trennfläche (25) in Berührung avec un orifice d’évacuation (40) prévu dans le steht, und cylindre (12), ledit passage d’évacuation (4a, eine Rille (21, 21a, 21b, 21c), die in einer Be- 5 4b) étant formé pour s’étendre à travers des sur- rührungsfläche zwischen der genannten Innen- faces de fixation respectives dudit cylindre (12) wandfläche (2c) des Kurbelgehäuses (2) und et dudit carter de moteur (2), dem genannten Abdeckorgan (22) ausgebildet dans lequel : ist und Teil des genannten Spülkanals (4a, 4b) ist, der 10 le carter de moteur (2) est composé d’un mit der genannten Kurbelkammer (6) und einer carter de moteur avant (2a) et d’un carter oberen Fläche (3) des Kurbelgehäuses (2) ver- de moteur arrière (2b) qui sont des parties bunden ist. avant et arrière divisées au niveau d’une surface fendue avant et arrière (25) ortho- 2. Zweitaktmotor nach Patentanspruch 1, in dem die 15 gonale à un axe de vilebrequin (80), genannte Rille (21) aus der genannten Innenwand- fläche (2c) des Kurbelgehäuses (2) ausgenommen caractérisé en ce que : ist, wobei das genannte Abdeckorgan (22) in Berüh- rung mit der genannten Innenwandfläche (2c) des la structure de passage d’évacuation a en Kurbelgehäuses (2) derart angebracht ist, dass es 20 outre : un élément de couvercle (22) fixé à einen offenen Teil der genannten Rille (21) schließt. l’intérieur de chacun parmi le carter de mo- teur avant (2a) et le carter de moteur arrière 3. Zweitaktmotor nach Patentanspruch 1, in dem die (2b) afin d’être en contact avec une surface genannte Rille (21a) aus dem genannten Abdeckor- de paroi interne (2c) du carter de moteur (2) gan (22) ausgenommen ist, wobei das genannte Ab- 25 depuis le côté de la surface fendue avant deckorgan (22) in Berührung mit der genannten In- et arrière (25) ; et nenwandfläche (2c) des Kurbelgehäuses (2) derart une rainure (21, 21a, 21b, 21c) formée dans angebracht ist, dass es einen offenen Teil der ge- une surface de contact entre ladite surface nannten Rille (21) schließt. de paroi interne (2c) du carter de moteur (2) 30 et ledit élément de couvercle (22), et for- 4. Zweitaktmotor nach Patentanspruch 1, in dem die mant une partie dudit passage d’évacuation genannte Rille (21b, 21c) sowohl aus der genannten (4a, 4b) se raccordant à ladite chambre de Innenwandfläche (2c) des Kurbelgehäuses (2), als manivelle (6) et à une face supérieure (3) auch aus dem genannten Abdeckorgan (22) ausge- du carter de moteur (2). nommen ist, wobei das genannte Abdeckorgan (22) 35 in Berührung mit der genannten Innenwandfläche 2. Moteur à deux temps selon la revendication 1, dans (2c) des Kurbelgehäuses (2) derart angebracht ist, lequel ladite rainure (21) est formée dans ladite sur- dass offene Teile der Rillen (21c), die in der genann- face de paroi interne (2c) du carter de moteur (2), ten Innenwandfläche (2c) des Kurbelgehäuses (2), ledit élément de couvercle (22) étant fixé en contact als auch im genannten Abdeckorgan (22) vorgese- 40 avec ladite surface de paroi interne (2c) du carter de hen sind, einander gegenüber liegen. moteur (2) afin de fermer une partie ouverte de ladite rainure (21). 5. Zweitaktmotor nach irgendeinem der Patentansprü- che 1 bis 4, in dem das genannte Abdeckorgan (22) 3. Moteur à deux temps selon la revendication 1, dans an der genannten Innenwandfläche (2c) an einer 45 lequel ladite rainure (21a) est formée dans ledit élé- Montagestelle befestigt ist, die als zwischen gegen- ment de couvercle (22), ledit élément de couvercle überliegende Wandflächen (2d) des genannten Kur- (22) étant fixé en contact avec ladite surface de paroi belgehäuses (2) eingepasst festgelegt ist. interne (2c) du carter de moteur (2) afin de fermer une partie ouverte de ladite rainure (21). 50 Revendications 4. Moteur à deux temps selon la revendication 1, dans lequel ladite rainure (21b, 21c) est formée à la fois 1. Moteur à deux temps comprenant : dans ladite surface de paroi interne (2c) du carter de moteur (2) et dans ledit élément de couvercle (22), un carter de moteur (2), 55 ledit élément de couvercle (22) étant fixé en contact un cylindre (12) avec une chambre de manivelle avec ladite surface de paroi interne (2c) du carter de (6) formée à l’intérieur dudit carter de moteur moteur (2) de sorte que des parties ouvertes respec- (2), et tives des rainures (21c) prévues dans ladite surface

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de paroi interne (2c) du carter de moteur (2) et dans ledit élément de couvercle (22) sont orientées à l’op- posé l’une de l’autre.

5. Moteurs à deux temps selon l’une quelconque des 5 revendications 1 à 4, dans lesquels ledit élément de couvercle (22) est fixé à ladite surface de paroi in- terne (2c) dans une position de montage déterminée en étant monté entre des surfaces de paroi internes (2d) opposées dudit carter de moteur (2). 10

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REFERENCES CITED IN THE DESCRIPTION

This list of references cited by the applicant is for the reader’s convenience only. It does not form part of the European patent document. Even though great care has been taken in compiling the references, errors or omissions cannot be excluded and the EPO disclaims all liability in this regard.

Patent documents cited in the description

• JP 4031602 B [0014] • US 4445468 A [0014]

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