ENGINE STARTER

Abstract: A starter is provided with a driving gear (75) rotated by a starting motor (7) and a drive gear (51) meshed with the driving gear, and operatively connected to a crankshaft (35) via a non-return clutch (53). The starter is engaged with the crankshaft until the starting motor has been driven to start the engine 821). The starter is disengaged when the rotational speed of the crankshaft exceeds that of the motor, after the engine has been started.

Description: Technical Field The present invention relates to an engine unit using a motor for starting a small-sized engine adopted for a portable working machine such as a brush cutter. Background Art Figure 4 shows a conventional starter which uses a motor for starting an engine. In the figure, a crankshaft 1 is provided with a fixed driven gear 3. The driven gear 3 is covered with a gear case 7 fixed to a crank case 5. A starter motor 9 is fitted to the gear case 7. The starter motor 9 has a rotary shaft 11 whose periphery is threaded to provide a screw portion 13 on which a drive gear 15 is movably fitted. The drive gear 15 removably engages with the driven gear 3. When the starter motor 9 is actuated, the drive gear 15 tries to be stationary due to its inertia so that the drive gear 15 rotates relative to the rotary shaft 11. As a result, the drive gear 15 axially moves due to the screw portion 13 and engages with the driven gear 3 to rotate the crankshaft 1 to start the engine. After the engine is started, a circumferential speed of the driven gear 3 exceeds that of the rotary shaft 11 so that the drive gear 15 rotates reversely relative to the rotary shaft 11. As a result, the drive gear 15 separates from the driven gear 3 and returns to its original position due to the screw portion 13. According to this conventional arrangement, the mechanism for axially moving the drive gear 15 is complicated, and the gears may be injured due to shocks caused by the moving drive gear 15. Further, the driven gear 3 of large inertia fixed to the crankshaft 1 shall always be rotated together with the engine so that the crankshaft and bearings shall have sufficient strength. In addition, the rotary shaft of the starter motor and the gears tend to be injured because the driven gear 3 of large inertia is suddenly rotated by the engagement with the drive gear 15. The conventional starter described above has therefore some considerable drawbacks. The prior art FR-A-2563689 shows an engine starter in which the drive gear is not axially moving and the driven gear is not fixed to the crankshaft. Specifically, the drive gear is fixed to the rotary shaft of the starter motor, the driven gear is coupled to the crankshaft through a clutch device which interconnects them unidirectionally, and the drive gear is connected to the driven gear by a belt. This structure of engine starter has the drawback to be bulky. The prior art US-A-2939448 relates to an electric starter attachment for internal combustion engine. In this case motion is transmitted from the starter motor through a gear reducing train and an overrunning clutch to a driving pulley and thence by means of a belt to a driven pulley which drives the crankshaft of the engine through a further overrunning clutch. The same drawback to be bulky as in the preceding prior art is present also in this prior art. Disclosure of the invention It is the object of the present invention to provide an engine unit which overcomes the aforesaid drawbacks. Such object is achieved by an engine unit comprising an engine having a rotatable crankshaft, a starter motor having a rotary shaft for supplying rotational power which rotates the crankshaft to start-up the engine, a drive gear fixedly fitted to the rotary shaft of the starter motor, a driven gear provided rotatably relative to the crankshaft and concentrically with the crankshaft, and a clutch device for connecting unidirectionally the driven gear and the crankshaft, characterised in that the driven gear meshes constantly with the drive gear so as to be rotated in accordance with the rotation of the drive gear, and in that a centrifugal clutch is disposed at one end of the crankshaft to engage with a transmission shaft, and the starter motor, the drive gear and the driven gear are disposed at the other end of the crankshaft. Brief Description of Drawings Fig.1 is a perspective view showing a brush cutter with an engine unit according to the present invention; Fig.2 is a sectional side view showing an engine unit according to the present invention; Fig.3 is a sectional front view showing an essential part of the engine unit of Fig.2; Fig.4 is a sectional side view showing a prior art example; Fig. 5 is a sectional side view showing an engine provided with a recoil starter; Fig. 6 is a perspective view showing a brush cutter provided with a battery disposed on a shoulder band; Fig. 7 is a sectional plan view showing the battery; Fig. 8 is a perspective view showing a brush cutter provided with a battery position adjustably disposed on a connection pipe; Fig. 9 is a sectional front view showing the battery; Fig. 10 is a sectional side view showing a battery portion fitted to a connection pipe with a plurality of fixtures; Figs. 11 to 14 are front views showing the fixtures, respectively; Figs. 15 and 16 are a side view and a sectional side view, respectively, showing a switching device; Fig. 17 is a sectional front view showing essential part of the switching device; Fig. 18 is a sectional front view showing another essential part of the switching device; and Figs. 19 and 20 are a front view and a sectional front view, respectively, showing the switching device under another state. Best Mode for Carrying Out the Invention An embodiment of the present invention will now be explained in detail with reference to the drawings. In the brush cutter of Fig. 1 a bearing member 19 for supporting a rotary blade 17 is connected with an engine 21 with a connection pipe 23 through which a transmission shaft (not shown) extends. A grip portion 25 and a handle 27 are fixed to the connection pipe 23, and an end of the handle 27 is provided with a grip portion 29. Figures 2 and 3 show the details of the engine 21. A crankcase 31 supports a crankshaft 35 through a bearing 33. A crank arm 37 of the crankshaft 35 is fitted to an end of a connecting rod 41 with a crankpin 39. The other end of the connecting rod 41 is connected to a piston (not shown) which slidably engages with a cylinder 43 fixed to the top of the crankcase 31. A lower part of the crankcase 31 is provided with a fuel tank 45. At one end of the crankshaft 35, a driven gear 51 is supported between washers 47 and 49 with gaps between the crankshaft and the driven gear and positioned by a nut 55. A nonreturn clutch 53 is disposed between the crankshaft 35 and the driven gear 51. The nonreturn clutch 53 comprises a cylindrical case 56 fixedly inserted into an inner bore of the driven gear 51, and a plurality of rollers 57 that are disposed in the cylindrical case 56 at predetermined intervals between holding rings 59. The cylindrical case 56 is provided with projections 61 that are projectingly formed on the inner surface of the cylindrical case 56. In a relative rotation of the crankshaft 35 and the cylindrical case 56 so as to roll the rollers toward slant surfaces 63 formed on one circumferential sides of the projections 61, the rollers 57 come on the slant surfaces 63 and are forcibly jammed between the crankshaft 35 and the cylindrical case 56, thus stopping the relative motion of the crankshaft 35 and the cylindrical case 56. In the reverse relative rotation, the rollers 57 separate from the crankshaft 35 so that the cylindrical case 56 become free from the crankshaft 35. On both sides of the rollers 57, there are arranged bearing rollers 65 engaging with a round inner surface of the cylindrical case 56 to support the crankshaft 35. A gear case 69 for covering the driven gear 51 is fixed to a flange portion 67 of the crankcase 31. A starter motor 71 is fixed to the gear case 69. A drive gear 75 fixed to a rotary shaft 73 of the starter motor 71 is always engaging with the driven gear 51. With the above-mentioned arrangement, when the starter motor 71 is driven, the driven gear 51 is rotated via the drive gear 75 to rotate the cylindrical case 56 of the clutch 53 in the direction of an arrow A shown in Fig. 3. As a result, the crankshaft 35 rotates reversely relative to the cylindrical case 56 so that the rollers 57 roll around the periphery of the crankshaft 35 along the slant surfaces 63 and are forcibly pushed to be jammed between the slant surfaces 63 and the crankshaft 35. Then, the crankshaft 35 rotates together with the driven gear 51 via the rollers 57 to start the engine 29. After the engine 29 is started, a rotational speed of the crankshaft 35 exceeds that of the driven gear 51 so that the cylindrical case 56 may rotate relative to the crankshaft 35 in a direction opposite to the direction of the arrow A. Therefore, the rollers 57 separates from crankshaft 35 to be free. If the starter motor 71 is stopped, the driven gear 51 is also stopped so that only the crankshaft 35 rotates. The described engine starter has a simple construction and be produced at low cost. Since the gears engage with each other with no shocks at the time of starting the engine, the gears do not wear easily to prevent bearings of the starter motor from being injured. The driven gear of large inertia will be stopped after the start of the engine so that injuries on the crankshaft and bearings may be reduced. The described nonreturn clutch is not limited to the one mentioned in the above using the rollers. For instance, a ratchet, etc., may be used so that the driven gear and the crankshaft may turn relative to each other in one direction freely to block torque transmission, while they may turn together with no relative rotation in the other direction. The starter motor, drive gear and driven gear are disposed on the crankshaft on the opposite side of a centrifugal clutch for transmitting torque, so that the engine may be connected directly to a casing of a working machine such as a pump and a blowing cleaner, because the starter motor is disposed on the opposite side of the centrifugal clutch not to interfere with it. Therefore, the working machine as a whole may be made compact. Figure 5 shows a starter motor provided with a recoil starter. In the figure, an engine 21 comprises a crankcase 31 and a cylinder 43. A cylinder cover 77 covering the side and upper faces of the cylinder 43 is fixed to the crankcase 31. A fan cover 79 is fixed to cover all the faces of the crankcase 31 and cylinder cover 77. A fuel tank 45 is fitted to a lower surface of the crankcase 31. In the crankcase 31, a crankshaft 35 is horizontally supported by bearings 33. A crank arm 37 of the crankshaft 35 is connected to a lower end of a connecting rod 41 with a crankpin 39. An upper end of the connecting rod 41 is connected to a piston 81 through a piston pin 83. The piston is slidable in the cylinder 43. A recoil starter 85 is provided in a recoil case 85 fixed to the back of the crankcase 31 with screws 87. A fixed shaft 91 of the recoil starter 85 is projectingly disposed on the same axis as that of the crankshaft 35. A reel 93 is rotatably arranged on the fixed shaft 91. A coil spring 95 is disposed between the reel 93 and the recoil case 85, and both ends of the coil spring 95 are supported by the reel 93 and the recoil, case 85, respectively. An end of a traction cord 97 is wound around the reel 93. The other end of the traction cord 97 passes through the recoil case 85 and is provided with a starter handle 99. In front of the reel 93, there is disposed a claw clutch 101 which advances or retracts according to centrifugal force such that the claw clutch 101 removably engages in one direction with a stopper 103 fixed to the rear end of the crankshaft 35. A front end of the crankshaft 35 is provided with a magnet wheel 107 having a magnet embedded in a portion of the periphery of the magnet wheel 107. On the back of the magnet wheel 107, there are disposed fans 109. On the front surface of the magnet wheel 107, a driven gear 51 is fixed with a plurality of screws 113. A stay 115 is fixed to the front side of the cylinder 43, and a induction coil 117 is fitted to the stay 115. The induction coil 117 is responsive to the magnet 105 to generate electricity which is discharged from an ignition plug 119 arranged at the top of the cylinder 43. On the front surface of the magnet wheel 107, two clutch shoes 121 facing each other are pivotably supported by step bolts 123 and pulled to each other by a spring 125. A clutch drum 127 is arranged in the vicinity of the peripheries of the clutch shoes 121. A boss shaft 129 of the clutch drum 127 is supported by a bearing portion 131 of the fan cover 79. In the boss shaft 129, there is formed a square hole 133 which engages with a square shaft 137. The square shaft 137 is located at a rear end of a transmission shaft 135 for driving a rotary blade 17. A starter motor 71 is fixed to a lower front surface of the fan cover 79 with three screws 141. A rotary shaft 143 of the starter motor 71 passed through the front surface of the fan cover 79 and has a thread 145 engaging with a small gear. When the starter motor 71 is driven, the small gear pushes forward a drive gear 75 which is stationary due to its inertia and presses the same against a stopper 148 disposed at an end of the rotary shaft 143. Then, the drive gear 75 engages with the driven gear 51 to drive the driven gear 51. After the engine 21 is started, a rotational speed of the driven gear 51 increases so that the drive gear 75 rotates relative to the rotary shaft 143 in the opposite direction. Therefore, the drive gear 75 retracts and separates from the driven gear 51. Into an opening portion 149 formed at a lower surface of the fan cover 79, a battery case 153 for storing a battery 151 is inserted and fixed with screws 155 provided at three positions on the front and side surfaces. To start the engine 21, a push-button starter switch (not shown) disposed at a proper position is pushed down to rotate the starter motor 71 with a current flowing from the battery 151. Then, the drive gear 75 moves to the right of Fig. 5 due to the thread 145 to engage with the driven gear 51 and start the engine 21. As a rotational speed of the engine 21 increases, the clutch shoes 121 engage with the clutch drum 127 due to centrifugal force to rotate the rotary blade 17 via the transmission shaft 135. A worker uses a shoulder band to hang the brush cutter from his shoulder and grasps grip portions 25 and 29 with his hands to cut weeds, etc., on the ground with the rotary blade 17. While the engine 21 is rotating, a generator (not shown) responsive to the magnet 105 may charge the battery 151. If the battery 151 is not sufficiently charged or if the starter motor 71 is out of order, the screws 141 will be unfastened to take out the starter motor 71 or the battery 151 to repair or charge them. Meanwhile, the engine 21 may be started with the recoil starter 89 to continue the cutting work normally. Namely, the starter handle 99 is pulled with a hand to rotate the reel 93 against the force of the coil spring 95 to advance the craw clutch 101, which engages with the stopper 103 to rotate the crankshaft 35 and start the engine 21. After the engine 21 is started the claw clutch 101 rotates reversely relative to the stopper 103 so that the stopping state is released. By releasing the starter handle 99, the reel 93 rotates reversely due to the coil spring 95 to pull the traction cord 97, while the claw clutch 101 separates from the stopper 103. Therefore, the starter motor and the battery can easily be removed, and, due to the provision of the recoil starter, the cutting work can be carried out during the repair of the starter motor or the charge of the battery to prevent the work efficiency from deteriorating. Figures 6 and 7 refer to a brush cutter in which a battery is fitted to a shoulder band. In front of the engine 21, there is disposed a bracket 157 to which a lower end of a shoulder band 159 is fitted. A battery case 163 for receiving a battery 161 is fitted to the shoulder band 159 with a fixture 165 and screws 167. An operator may hang the shoulder band 159 on his shoulder and grasp the grip portions 29 with his hands to cut weeds, etc., on the ground with the rotary blade 17. Since the battery 161 is directly fitted to the shoulder band 159, the weight of the battery may not cause unbalance. Figures 8 and 9 refer to a brush cutter in which a battery is adjustably positioned on the connection pipe. A case 171 for receiving a battery 169 is fitted to the connection pipe 23 with a fixture 173 and screws 175 such that a position of the battery 169 is adjustable. An operator may hang the shoulder band 159 on his shoulder and grasps the grip portions 29 with his hands to cut weeds, etc., on the ground with the rotary blade 17. The battery 169 may be positioned at, for instance, the center of gravity of the brush cutter such that the weight of the battery may not cause unbalance. Figures 10 to 14 show batteries fitted to the connection pipe with a plurality of fixtures arranged at proper intervals. An annular handle 181 is fixed to the connection pipe 23 with a fixture 179 and bolts 177. A grip portion 183 is formed at upper central part of the handle 181. Behind the handle 181, a fixture 187 is fixed to the connection pipe 23 with a bolt 189. To the fixture 187, a suspension ring 185 fitted to a lower end of a shoulder band 183 is fitted. A plurality of batteries 191 are received in a cylindrical case 193 in a longitudinal direction. Each end of the case 193 is supported by a supporting portion 195 of the fixture 179 and by a supporting portion 201 of a fixture 199 which is fixed to the connection pipe 23 with a bolt 197. A central portion of the case 193 is supported by the fixture 187. Behind the fixture 199, a grip portion 203 made of elastic material is fixed to the connection pipe 23. The periphery of a rear end of the grip portion 203 is fastened with a fixture 205, while the periphery of a front end thereof is fastened with a fixture 209 which is tightened with a bolt 207. Between the fixtures 209 and 199, there is arranged a throttle lever 211. The fixture 209 is provided with a power source switch 213 and a push-button starter switch 215. The batteries 191 may be positioned at the center of gravity of the brush cutter such that the weight of the batteries may not cause unbalance. Since the starter motor switch 215 is arranged on the fixture 209, vibrations of the engine, etc., may be absorbed by the elastic material of the grip portion so that the starter switch may not be damaged and not cause contact errors. The fixture of the starter switch is used for the fixture of the grip portion so that separate fixtures and vibration dampers are not needed. Therefore, the structure is simplified, the number of parts reduced, the apparatus easily assembled. Figures 15 to 20 show a push-button switch for a starter motor and a changeover switch for an ignition circuit relatively operated. A case 221 comprises side plates 217 and bottom plate 219. A fitting plate 223 has front and rear edges bent downwardly. The fitting plate 223 is provided with brackets 225 which are arranged at front and rear positions on both sides of the fitting plate 223. The brackets 225 are fixed to the side plates 217 with screws 227. The fitting plate 223 has two fitting holes 229 and 231 into which a push-button switch 233 and a changeover switch 235 are inserted, respectively. The switches 233 and 235 are fastened with nuts 237 and 239, respectively. The push-button switch 233 connects and disconnects an electric circuit of the starter motor 71 of the engine. By pushing down a returnable operation segment 241, the starter motor is connected to the battery to rotate the crankshaft and start the engine. The changeover switch 235 has an operation segment 243 which is pivotable back and forth. By pivoting the operation segment 243 backwardly, the ignition circuit is connected, and, by pivoting the operation segment 243 forwardly, the ignition circuit is disconnected to prevent ignition. A horizontal plate 245 is disposed above the fitting plate 223. The horizontal plate 245 has projections 247, 249, 251 and 253 which engage with horizontal long holes 255, 257, 259 and 261 which are formed on the side plates 217 at front and rear portions of the side plates. Therefore, the horizontal plate 245 is movable back and forth. The front long holes 255 and 257 have notch portions 263 and 265 extending downwardly from the rear edges of the long holes, respectively. By moving the horizontal plate 245 rearwardly, the projections 247 and 249 are positioned at the notch portions 263 and 265 so that the horizontal plate 245 may downwardly pivotable around the rear projections 251 and 253. By moving the horizontal plate 245 forwardly, the front projections 247 and 249 are caught by the long holes 255 and 257 so that the horizontal plate 245 may not pivot. The horizontal plate 245 has a fitting hole 267 into which the operation segment 243 of the changeover switch 235 is inserted, and the operation segment 243 pivots as the horizontal plate 245 moves back and forth. The upper end of the operation segment 241 of the push-button switch 233 abuts against the lower surface of the horizontal plate 245. A cover 269 is fixed to the upper surface of the horizontal plate 245. A push button 271 protrudes from the upper surface of the cover 269. In the arrangement mentioned in the above, the push button 271 of the cover 269 is pushed backwardly with a finger to move the horizontal plate 245 backwardly. Then, as shown in Figs. 15 and 16, the operation segment 243 of the changeover switch 235 is pivoted backwardly to connect the ignition circuit. Under this situation, the push button 271 is pushed down to turn the horizontal plate 245 around the rear projections 251 and 253 so that the front projections 247 and 249 may descend along the notch portions 263 and 265. As a result, the horizontal plate 245 pivots downwardly to push the operation segment 241 of push-button switch 233 downwardly. Accordingly, the starter motor is rotated to start the engine. If the finger is released from the push button 271, the operation segment 241 of the push-button switch 233 returns to an upper initial position due to the force of a spring (not shown), and the horizontal plate 245 also returns to an upper initial position. If the push button 271 is pressed forward as shown in Figs. 19 and 20, the horizontal plate 245 makes the operation segment of the changeover switch 235 to pivot forwardly to disconnect the ignition circuit and stop the engine. At this position, the front projections 247 and 249 are caught by the long holes 255 and 257 so that the horizontal plate 245 may not pivot downwardly. Therefore, even if the push button 271 is touched with fingers, the push-button switch 233 never operates. Therefore, even if the push-button switch is touched with the fingers, the engine never starts suddenly. Only with the changeover switch being under a contact state, the push button-switch is able to be pushed down so that there may not be ignition errors caused by operation mistakes. Further, these components can easily be formed through a metal press mold or with synthetic resin, and the switches may be commercially available ones to reduce the manufacturing cost.

Claims: An engine unit comprising an engine (21) having a rotatable crankshaft (35), a starter motor (71) having a rotary shaft (73) for supplying rotational power which rotates the crankshaft (35) to start-up the engine (21), a drive gear (75) fixedly fitted to the rotary shaft (73) of the starter motor (71), a driven gear (51) provided rotatably relative to the crankshaft and concentrically with the crankshaft, and a clutch device (53) for connecting unidirectionally the driven gear (51) and the crankshaft (35), characterised in that the driven gear (51) meshes constantly with the drive gear (75) so as to be rotated in accordance with the rotation of the drive gear (75), and in that a centrifugal clutch is disposed at one end of the crankshaft (35) to engage with a transmission shaft, and the starter motor (71), the drive gear (75) and the driven gear (51) are disposed at the other end of the crankshaft (35). An engine unit according to claim 1, comprising a crank case (31) which supports the crankshaft (35) and a gear case (69) which encloses the driven gear (51), the gear case (69) being mounted on the crank case (31) and fitted with the starter motor (71). An engine unit according to claim 1, further comprising a recoil starter (89) for supplementarily and manually supplying rotational power in order to start-up the engine (21). An engine unit according to claim 1, wherein the clutch device (51) is arranged between the driven gear (51) and the crankshaft (35) for connecting the crankshaft (35) to the driven gear (51) so as to transmit the rotational power when the starter motor (71) is driven in order to start up the engine, and for disconnecting the crankshaft (35) from the driven gear (51) after the starting-up of the engine is completed. An engine unit according to claim 4, wherein the clutch device comprises rollers (57) which are rollable between the crankshaft (35) and the driven gear (51), and slant surfaces (63) which are provided at the inner side of the driven gear (51) so that, when the driven gear (51) rotates in one rotational direction with respect to the crankshaft (35), each roller (57) rolls on one respective of the slant surfaces (63) to be jammed between the crankshaft (35) and the respective slant surface (63) for connecting the crankshaft (35) to the driven gear (51), and when the driven gear (51) rotates in the opposite rotational direction with respect to the crankshaft (35), each roller separates from the respective slant surface (63) for disconnecting the crankshaft (35). An engine unit according to claim 5, wherein the rollers (57) are disposed in a cylindrical case (56) fixedly inserted into the driven gear (51), the slant surfaces (63) being formed on the inner surface of the cylindrical case (56). An engine unit according to claim 6, wherein the cylindrical case (56) is provided with projections (61) formed on its inner surface, each slant surface (63) being formed on one side of one respective of the projections (61). An engine unit according to claim 1, comprising a push-button switch (233) having a retractable operation segment (241) for connecting and disconnecting an electric circuit of the starter motor (71) of the engine, a changeover switch (235) provided with a pivotable operation segment (243) for connecting and disconnecting an ignition circuit of the engine, the push-button switch (233) and the changeover switch (235) being disposed side by side, and a horizontal plate (245), engaging with the pivotable operation segment (243), horizontally movable to pivot the pivotable operation segment (243) and abutting against the retractable operation segment (241) of the push-button switch (233), the horizontal plate (245), when moved in one direction, pivoting the pivotable operation segment (243) for connecting the ignition circuit and being vertically pivotable to push down the retractable operation segment (241) for connecting the electric circuit, and when moved in the other direction, pivoting the pivotable operation segment (243) for disconnecting the ignition circuit and being prevented from pivoting vertically.

Inventors: KATOU, HIROSHI, TAGUCHI, HIROSHI, TANAKA, YOSHIAKI, WADA, MINORU
Applicants: KOMATSU ZENOAH KABUSHIKI KAISHA
Application year: 1988
Main classification: F02N11
IPC codes: F02N11, A01D34, F02N15