AU629013B2

AU629013B2 - Portable engine

Info

Publication number: AU629013B2
Application number: AU59135/90A
Authority: AU
Inventors: Takanori Ebinuma; Hiroshi Katoh; Mitsuko Sakurai
Original assignee: Komatsu Zenoah Co
Current assignee: Komatsu Zenoah Co
Priority date: 1985-10-09
Filing date: 1990-07-18
Publication date: 1992-09-24
Anticipated expiration: 2006-10-09
Also published as: DE3688083D1; AU5913590A; DE3688083T2; DE3676786D1; EP0221393B1; EP0221393A1

Description

d^ b-ii~~ I ~L1~:r FORM COMMONWEALTH OF AUSTRALIA PATENTS ACT 1952 COMPLETE SPECIFICATION S F Ref: 63650/86D1

(ORIGINAL)

FOR OFFICE USE: Class Int Class Complete Specification Lodged: Accepted: Published: Priority: Related Art: Name and Address of Applicant: Komatsu Zenoah Co.

142-1 Sakuragaoka 2-chome Higashiyamato-shi Tokyo

JAPAN

Spruson Ferguson, Patent Attorneys Level 33 St Martins Tower, 31 Market Street Sydney, New South Wales, 2000, Australia Address for Service: 0 C ob 9 Complete Specification for the invention entitled: Portable Engine The following statement is a full description of this invention, including the best method of performing it known to me/us 5845/3 I m l 1" TITLE OF THE INVENTION Portable Engine BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a portable engine adopted for a portable working apparatus such as a weed cutter.

2. Description of the Prior Art In a prior art portable engine, an ignition coil for generating an electromotive force is generally fixed 8) cat to the side face of an engine cylinder through a fitting o o seat and a tightening bolt. During the operation of 111 engine, heat generated in the engine cylinder is transmitted to the ignition coil through the fitting seat and bolt to deteriorate the function of ignition coil. The portable engine is also provided with a fan 0ooo for cooling the engine cylinder. A blow from the fan is firstly guided upward by a fan cover fixed to the front side (an output side of the engine) of a crankcase and then toward the periphery of the engine cylinder by a I cylinder cover which is formed in series with the fan cover. A partition is provided to cover a step to be formed between the fan cover and the cylinder cover.

According to the prior art, this partition is formed integrally with the cylinder cover.

-2- Further, according to the prior art, in positioning the engine cylinder with respect to the crankcase, a lower end of the engine cylinder is fitted to an inner diameter of the crankcase, and the positioning is done in a rotational direction while the engine cylinder is fixed to the crankcase by tightening clamping bolts. In this positioning method, the positioning accuracy may ba deteriorated due to the tolerance of the clamping bolts and the engaging portion of the crankcase to cause the displacement of a scavenging port and the uneven wear of a piston reciprocating in the engine cylinder. Further, to improve the positioning accuracy, the processing accuracy of the bolts, bolt holes, and the engaging portion of the crankcase shall be raised in the prior art so that the number of processes and the manufacturing cost may be increased.

SUMMARY OF THE INVENTION It is the object of the present invention to overcome or substantially ameliorate the above disadvantages.

There is disclosed herein a portable engine including an engine cylinder having a cylinder flange and a crankcase having a crankcase flange, the cylinder flange being held on the crankcase flange by bolts, 20 comprising: a plurality of positioning projections cast integrally with one of said flanges; and a plurality of positioning holes cast integrally with the other flange, the positioning holes flange being adapted to receive the positioning projections flange respectively, to accurately position tho crankcase with respect to the engine cylinder when the engine cylinder and the crankcase are assembled by fastening the bolts in such a manner that the cylinder flange and the crankcase flange are fitted face to face.

There is further disclosed herein a portable engine having an 30 engine cylinder having a cylinder flange and a crankcase havinq a crankcase flange, the cylinder flange being held on the crankcase flange by bolts, a sealing groove formed along a contour of an end face of one of said flanges, a projection formed on the other end face and engaged with the groove, and sealing material filled in the groove, comprising: at least one positioning member formed on the corner of the a o a o o6 o0 o o 0 0 o A o 00 or u o o *0 0 00 0 0 0 0 00P 0 0 0 0 0 o o oQ r) S00 t G i 00 0 0 C S '5 00 o

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o a 0 9 O 0 «a r e( e TMS:451 I- ~i lii::L-- i -3crankcase flange of the crankcase, the positioning member receiving the corresponding corner of a cylinder flange of the engine cylinder to accurately position the crankcase with respect to the engine cylinder when the engine cylinder and the crankcase are assembled together with the cylinder flange and the crankcase flange fitted face to face to be fastened with the bolts, and the crankcase and the engine cylinder being fitted tightly to each other by the engagement of the projection with the groove.

BRIEF DESCRIPTION OF THE DRANINGS A preferred form of the present invention will now be described by way of example with reference to the accompanying drawings, wherein: Fig. 1 is a cross-sectional side view showing a portable engine; Fig. 2 is a front view partly broken showing the portable engine shown in Fig. 1; Fig. 3 is an exploded perspective view showing the portable engine; Fig. 4 is a perspective view showing the portable engine after assembling; 0 00 o a a a 0 0" 6 A 0 V/M -4- Fig. 5 is a side view showing a modification of a fan cover of the portable engire; Fig,, 6 is a front view showing the fan cover shown in Fig. Fig. 7 is a cross-sectional front view showing the details of an engine cylinder of the portable engine; Fig. 8 is a plan view showing an essential part of the engine cylinder shown in Fig, 7; Fig. 9 is a cross-sectional front view showing the essential part of the engine cylinder; Fig. 10 is an enlarged cross-sectional view showing ooa a fitting projection and a fitting groove of the engine cylinder; Fig. 11 is an enlarged cross-sectional view showing SO° a positioning projection and a positioning hole of the engine cylinder; Fig. 12 is a plan view showing a modification of the positioning projection and hole; o- Fig. 13 is a cross-sectional view showing the details of an air cleaner of the portable engine; Fig. 14 is an external view showing the air Oo cleaner; Fig. 15 is a cross-sectional plan view showing the air cleaner; Fig. 16 is a cross-sectional view showing the details of a cap portion of a fuel tank of the portable 5 engine; Fig. 17 is a view showing a snap ring adopted for the cap portion shown in Fig. 16; Fig. 18 is a cross-sectional side view showing the details of a muffler of the portable engine; Fig. 19 is a cross-sectional front view showing the muffler; Fig. 20 is a cross-sectional plan view showing the muffler; and Fig. 21 is a cross-sectional view showing an iron core for an ignition coil of the portable engine.

f t DETAILED DESCRIPTION OF THE EMBODIMENTS S Preferred embodiments of the present invention will ,now be described with reference to the drawings, in which like numerals represent like parts.

Figures 1 to 3 show a portable engine according to an embodiment of the present invention. In the figures, a crankcase 1 of the engine includes a crank shaft 3 supported horizontally. An engine cylinder 5 is fixed on top of the crankcase 1 and houses a piston 7 which is freely slidable within the engine cylinder 5 and t c t connected to the crank shaft 3 by a connecting rod 9. A recoil starter 11 is fitted to the rear end of the crank shaft 3, and a magnet wheel 13 is fixed to the front end of the crank shaft 3. A centrifugal clutch 15 is fitted I~ i~ ii i 6to the front side of the magnet wheel 13. A clutch drum 17 is disposed closely to the periphery of the centrifugal clutch 15. A transmission shaft 21 is engaged with a boss 19 of the cutch drum 17.

A fan 23 having a plurality of fins is fixed to the rear side of the magnet wheel 13. A fan cover 25 for covering the fan 23 is fixed to the front side cf the crankcase 1 to guide a blowoof the fan 23 upward firstly and then rearward. A clutch housing 27 for covering the clutch drum 17 and for supporting the boss 19 is fixed to the front face of the fan cover 25. A cylinder cover i r 29 covers both sides of the engine cylinder 5 and is <r f positioned in series with the fan cover 25 to guide the blow'toward the periphery of the engine cylinder >A partition 33 for covering a step formed on one sides of the fan cover 25 and the cylinder cover 29 is integrally formed with the cylinder cover 29. A partition 35 for covering another step formed on the other sides of the fan cover 25 and the cylinder cover 29 is integrally formed with one side of the crankcase 1 and projec upward. An ignition coil 37 has an iron core 39 _iich is fixed to the partition 35 by screws 41

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through a supporting cylinder 40. An end face of the iron core 39 is located adjacent to the periphery of the magnet wheel 13 to generate an electric current in response to magnets embedded in the periphery of the -7magnet wheel 13. The current in the ignition coil 37 is transmitted through a code 43 to an ignition plug located on top of the engine cylinder 5, and discharged from the ignition coil 37.

A carburetor 49 having an air cleaner 47 is fitted to one side of the engine cylinder 5, and a muffler cover 51 including a muffler (not shown) is fitted to the other side of the engine cylinder 5. A fuel tank 53 is fitted to the bottom of the crankcase 1.

According to the above arrangement, the fan 23 generates a blow according to the rotation of the engine. The blow is guided by the fan cover 25 and the ocylinder cover 29 and sent toward the engine cylinder to cool the engine cylinder 5. H~eat of the engine 0cylinder 5 will not be transmitted to the ignition coil 37 directly because the ignition coil 37 is not directly fitted to the engine cylinder 5 but fixed to the 0 90 partition 35 which is formed integrally with the 90000 crankcase 1. Therefore, the ignition coil 37 may not be 0. heated to high temperature. According to the present 0 CID*invention, the engine may be placed horizontally or upside down.

o As shown in Fig. 1 an area of the fan cover 25 is 0 0 cut to form an opening which is usually covered by a cap plate with screws. The cap plate can be removed f rom the fan cover 25 by loosening the screws as and when 8required to clean or replace the ignition coil 37, or to adjust a gap between the iron core 39 and the periphery of the magnet wheel 13.

As shown in Figs. 1, 3 and 4, stopper holes 57 are formed on a fitting surface of the cylinder cover 29, and stopper nails 59 corresponding to the stopper holes are projectingly formed on a fitting surface of the fan cover 25. Further, a positioning hole 61 is provided on a rear surface of the engine cylinder 5, and a positioning pin 63 is formed at a corresponding position inside the cylinder cover 29. The cylinder cover 29 may coo easily be fitted to and removed from the fan cover through the engagement and disengagement of the stopper 0 holes 57 and the stopper nails 59 with the positioning o0 hole 61 and the positioning pin 63 acting as positioning means so that the engine cylinder 5 and its peripheral portion may easily be inspected as and when required.

iso Figurer 5 and 6 show a modification of the above o oembodiment. In this modification, a flange 102 formed o integrally with one end of the crankcase 1 has a front a the cylinder cover 29. The fan cover 101 is fixed to 9 0 the flange 102 by screws. According to this arrangement, the entire periphery of the fan cover 101 is rigidly fixed to the flange 102 of the crankcase I so -9that the fan cover 101 may vibrate less in operation, and the strength of the fan cover 101 improved.

Figures 7 to 11 show the details of the engine cylinder 5. The crank case 1 has at its upper end a circular opening 203 which is engaged with an arcuate spigot 207 formed at a lower end of the engine cylinder A cylinder flange 209 of the engine cylinder 5 is aligned with a case flange 211 of the crankcase 1 and they are fastened by bolts 213. The engine cylinder and the crankcase 1 is provided with scavenging grooves 215 which extend axially and face each other.

0-6 on a flange surface of the cylinder flange 209, a 6 projection 217 projects continuously along the peripheries of the opening 203 and the scavenging 0grooves 215. The projection 217 engages with a sealing groove 219 provided on the case r-latLge 211. A liquid packing 221 is filled in the sealing groove 219. Shaft '3like positioning pieces 223 are cast integrally with the 0.06 o engine cylinder 5 and project from the flange surface of 00, the cylinder flange 209 to engage with positioning holes 225 which are cast integrally with the flange surface of 0 40 the case flange 211.

The piston 7 is freely slidable within the engine cylinder 5 and connected with the connecting rod 9 with a piston pin 229. The other end of the connec"Ang rod 9 is rotatably supported by a crank arm 235 of the crank 10 shaft 3 through a crank pin 237.

To assemble the engine cylinder 5 with the crankcase 1, the piston 7 is firstly fitted to the crank shaft 3 through the connecting rod 9. The piston is then inserted into the engine cylinder 5 which spigot portion 207 is inserted into the opening 203 of the crankcase 1. The liquid packing 221 is filled in the sealing groove 219. The positioning pieces 223 are engaged with the positioning holes 225, and the cylinder flange 209 is fixed to the case flange 211 by the bolts 213.

o0 Figure 12 shows a modification of the above 00 o arrangement. Corner portions of the cylinder flange 209 are used as positioning pieces 239 which are engaged *o with positioning holes 243 formed on inner surfaces of °oo p positioning members 241 provided on the case flange 211.

The positioning members 241 may surround the cylinder Po 9 1 flange 209, or a positioning recess corresponding to the ooo b009 0 0 circumference of the cylinder flange 209 may be formed *Oo on the case flange 211.

aoo Figures 13 to 15 show the details of the air cleaner 47. A main casing 309 of the air cleaner 47 has 0 00 an opening 307 which communicates with a suction port 305 of the carburetor 49. The casing 309 is fixed to the carburetor 49 with bolts 311. A choke valve 313 is fitted by a bolt 311 and opens and closes the opening 11 307. Ribs 317 are formed inside the casing 309 to support a felt like or sponge like porous filter 315. A cap casing 319 is removably fitted at its lower end to a fitting portion 323 of the main casing 309 by a fitting pin 321 to hold the filter 315. A hook 325 projecting from the top of the cap casing 319 is stopped by a stopping portion 327 of the main casing 309 due to the resiliency. A space 329 for receiving the filter 315 is formed in the cap casing 319. Supports 331 and 333 projecting inside the cap casing 319 are removably inserted into holes 335 which are formed to pass through o the filter 315. The filter 315 is held by a partition 337 for separating a part of the interior of the cap casing 319, by a step 339 of the support 333, and by the main casing 309. A muffling chamber 343 is formed between the cap casing 319 and an outer wall 341 to communicate a chamber 345 of the cap casing 319 with the 00 4 atmosphere. A cover 347 for covering the top of the o 0 ~o 1 carburetor 49 is fixed to the upper part of the cap casing 319.

According to the above arrangement, the atmosphere enters into the chamber 345 through the muffling chamber 4 343 according to the suction force of the engine, and is sucked by the suction port 305 of the carburetor 49 through the filter 315 tnd the opening 307. The filter 315 may be removed by rermoving the hook 325 from the -1 12 n kuo r)0 0 0 o 01 o 00a 0 01 *000 00v0u o r, 00 o 00) -A 0 00 ~l 0 oo 0 0d stopping portion 327 with fingers and by turning the cap casing 319 around the pin 321. The filter 315 is then taken out and cleaned. To install the filter 315, the cap casing 319 is kept to be opened, and the fitting holes 335 of the filter 315 are pushed toward the supports 331 and 333 of the cap casing 319 to place the filter 315 in the space 329. After that, the cap casing 319 is closed, and the hook 325 is engaged with the stopping portion 327.

Figures 16 and 17 show the details of the fuel tank 53. A cylindrical filler port 403 projects from the fuel tank 53 and has a threaded portion 405 formed around the filler port 403. A female thread 409 of a cap 407 is screwed to the threaded portion 405. A groove 411 is formed at an end of the female thread 409 and engages with a projection 415 projecting from the periphery of a supporting plate 413. The supporting plate 413 has a cylindrical portion 417 which extends downward at the center of the plate 413 and has an inner diameter portion 419 to which a breather valve 421 made of resilient member is attached. The breather valve 421 allows only the down word communication. A vent groove 423 is provided at the upper surface of the supporting plate 413 to communicate the inner diameter portion 419 with the groove 411. A packing 425 made of rubber is disposed between the end face of the filler port 403 and 13 the supporting plate 413. The center of the packing 425 is formed in a cylindrical shape and fitted around the cylindrical portion 417 of the supporting plate 413. A snap ring 427 presses the periphery of the cylindrical portion of the packing 425 against the cylindrical portion 417 of the supporting plate 413. A flat stopper 429 made of soft synthetic resin is inserted into the fuel tank 53 and not able to pass through the filler port 403 due to its size. A code 431 is formed integrally with the stopper 429 and has a spherical stopping portion 433 which is engaged with the snap ring 427.

SAccording to the above arrangement, the packing 425 a t t. will seal the filler port 403 when the cap 407 is fastened. If pressure in the fuel tank 53 is decreased due to the consumption of fuel, the atmosphere is introduced into the fuel tank 53 through a gap between the threads 409 and 405, the groove 411, the vent groove aa 423, the inner diameter portion 419, and the breather oQ valve 4:1. When the cap 407 is removed to fill fuel, o t the stopper 429 is stopped by the inner side of the filler port 403 and hung by the code 431 so that the cap asI a407 may not be lost.

SFigures 18 to 20 show the details of a muffler disposed in the muffler cover 51. A muffler case 501 comprises a main case 507 and a cap case 509. The main ~Y i -U~ 14 case 507 has a communication hole 505 which communicates with an exhaust port 503 of the engine. The main cage 507 and the cap case 509 are fitted together by bolts 513 along a dividing plane 511 wnich is orthogonal to the exhaust port 503, and fixed to a fitting surface 515 located around the exhaust port 503. The inside of the muffler case 501 is divided into a first muffling chamber 521 and a second muffling chamber 523 by two partitions 517 and 519 which are orthogonal to the dividing plane 511. A separation chamber 525 is formed between the first and second muffling chambers 521 and o: 523. A spark preventive net 527 made of metallic material is inserted into the separation chamber 525 and 11 *4 held by the cap case 509 and the main case 507. The spark preventive net 527 is formed in a curved shape.

Communication holes 529 and 531 are forme,' on the partitions 517 and 519 respectively. The second u muffling chamber 523 communicates with the atmosphere "o 1 through an exhaust pipe 535 having an exhaust hole 533.

The exhaust pipe 535 comprises two portions formed integrally with the main case 507 and the cap case 509 respectively, the two portions being assembled together *o along the dividing plane 511.

According to the above arrangement, an exhaust gas from the engine passes through the exhaust port 503 and the communication 1hle 505, enters into the first r 15 muffling chamber 521, expands in the chamber 521, is contracted by the communication holes 529 and 531, enters into the second muffling chamber 523, expands again in the chamber 523, is again contracted by the exhaust pipe 533, and finally discharged to the atmosphere. An exhaust noise is silenced due to the expansion and contraction and the interference by the lengthy exhaust pipe 533. Fire caused by carbon is prevented by the spark preventive net 527 from escaping to the atmosphere.

Figure 21 is a cross-sectional view showing the iron core 39 which comprises a plurality of core plates 613. The outer surface of the iron core 39 is covered by a synthetic resin film.

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Claims

2. The portable engine of claim 1 in which the positioning projections are diametrically disposed with respect to one another on the flange and the positioning holes are diametrically disposed with respect to one another on the other flange.
3. The portable engine of claim 2 in which the plurality of positioning projections comprise two projections and the plurality of :0 positioning holes comprise two mating holes.
4. The portable engine of claim 1 which further comprises a 0 sealing groove formed along a contour of one of end faces of the 0 00o o crankcase flange of the crankcase and the cylinder flange of the engine 0 cylinder, a projection formed on the other face to be engaged with the groove, and sealing material filled in the groove. 25 5. A portable engine having an engine cylinder having a cylinder o000°o flange and a crankcase having a crankcase flange, the cylinder flange 0 being held on the crankcase flange by bolts, a sealing groove formed along a contour of an end face of one of said flanges, a projection 30formed on the other end face and engaged with the groove, and sealing 30 material filled in the groove, comprising: S0 at least one positioning member formed on the corner of the crankcase flange of the crankcase, the positioning member receiving the corresponding corner of a cylinder flange of the engine cylinder to accurately position the crankcase with respect to tho engine cylinder when the engine cylinder and the crankcase are assembled together with details of a cap portion of a fuel tank of the portabie FIX I II 1411 ~X9~ 17 the cylinder flange and the crankcase flange fitted face to face to be fastened with the bolts, and the crankcase and the engine cyTinder being fitted tightly to each other by the engagement of the projection with the groove.
6. The portable engine claimed in claim 5, wherein there are two positioning members disposed diametrically with respect to one another on the crankcase flange. DATED this TWENTY-FIRST day of JULY 1992 Komatsu Zsnoan Co. Patent Attorneys for the Applicant SPRUSON FERGUSON 0 a o 0 0 0 4 000 0 00 00o 00 0 0 0 0 4 *00 0 0I 0 0 0 0 a o 0 0 ¢i I I l t C KEH/TMS:451