A walk-behind self-propelled working machine includes an engine disposed with a crankshaft extending vertically in a downward direction and a cylinder disposed horizontally, and a generator having a drive shaft disposed vertically downward. The drive shaft of the generator and the crankshaft of the engine have respective axes that are disposed on a line perpendicular to an axis of the cylinder, as viewed in plan. The crankshaft and the drive shaft are connected together via a power transmitting mechanism.

FIELD OF THE INVENTION

The present invention relates to a walk-behind self-propelled working machine having two different drive sources (e.g., an engine and an electric motor), one for driving a working unit the other for driving a traveling unit of the working machine.

BACKGROUND OF THE INVENTION

Walk-behind self-propelled working machines having two different drive sources are well known in the art and disclosed in, for example, Japanese Patent Laid-Open Publication No. 2001-161104.

FIG. 9hereof shows, in side elevation, the walk-behind self-propelled working machine disclosed in the above publication.

The working machine designated generally at200includes a machine body201, an engine202mounted on the body201, a generator205having a drive shaft, an electric motor206, traveling wheels203, and a rotary working member207. The engine202has an output shaft operatively connected to the wheels203to rotate the same for propelling the machine200. The output shaft of the engine is also operatively connected to the drive shaft of the generator205for driving the generator205. The generator205then generates and supplies an electric power to the electric motor206. The electric motor206thus supplied with the electric power drives the working member207for performing a work. The working machine200can thus travel while performing the work.

Known engines for walk-behind working machines of the same type as the above have a cylinder disposed vertically and upward, and a crankshaft disposed horizontally. The crankshaft projects from an engine body in a rearward direction of the machine body. The crankshaft has a driving pulley mounted thereon. Known generators used with the engine have a drive shaft having a driven pulley mounted thereon. The driving pulley and driven pulley are connected by a drive belt.

When the engine is driven to rotate the crankshaft, the driving pulley is rotated by the rotating crankshaft. The rotation of the driving pulley causes the drive belt to rotate the driven pulley. The driven pulley then rotates the drive shaft of the generator for driving the generator.

For transmission of rotation of the crankshaft of the engine to the drive shaft of the generator through the drive belt, the drive shaft of the generator is preferably disposed in parallel to the crankshaft of the engine. For this reason, the generator is usually disposed in a horizontal position.

The generator is required to generate a large amount of electric power for driving an electric motor to drive a rotary working member. Thus, the generator generates a large amount of heat.

To release the large amount of heat generated from the generator with high efficiency, it is preferred that the generator be arranged in the same direction as the flow of air surrounding the generator. However, the horizontal disposition of the generator is difficult to achieve the highly efficient releasing of the large amount of heat generated by the generator.

The crankshaft extends horizontally and rearward of the machine body, and is positioned above the bottom of the engine. The generator is also positioned above the bottom of the engine with the drive shaft disposed in parallel to the crankshaft. Because the generator is disposed above the bottom of the engine, the center of gravity of the working machine is undesirably positioned less low.

The generator is positioned rearward of the engine. Thus, the overall length of the working machine having the thus arranged generator is undesirably larger. The working machine of such a large overall length is not rendered compact.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a walk-behind working machine having a generator which is disposed to improve heat releasing efficiency of the generator, can lower the center of gravity of the working machine, and is able to reduce the overall length of the working machine.

According to one aspect of the present invention, there is provided a walk-behind self-propelled working machine comprising: a machine body; an engine disposed on the machine body and having an output shaft for providing a motive power; a generator having a drive shaft driven by the motive power to generate an electric power; power transmitting means for transmitting the motive power from the output shaft of the engine to the drive shaft of the generator; an electric motor driven by the electric power from the generator to produce a motive power; a traveling unit driven by the motive power from one of the engine and the electric motor to propel the working machine; a working unit driven by the motive power from the other of the engine and the electric motor for performing a work; the engine being vertically disposed with a cylinder disposed horizontally and the output shaft disposed vertically and downwardly; the generator being vertically disposed with the drive shaft disposed vertically and downwardly; and an axis of the drive shaft of the generator and an axis of the output shaft of the engine being disposed on a line extending perpendicularly to an axis of the cylinder as viewed in plan. Since the generator is oriented in the same direction as the direction of flow of air heated by heat generated by the generator, the heat can be efficiently or readily released from the generator.

The axis of the drive shaft of the generator and the axis of the output shaft of the engine are disposed on the line perpendicular to the axis of the cylinder, as viewed in plan. This arrangement allows the generator to be disposed away from the cylinder of relatively high temperature so that the heat of the cylinder does not affect the generator.

Preferably, the working unit is disposed forwardly of the output shaft of the engine, the cylinder is disposed rearwardly of the output shaft of the engine, and the axis of the cylinder is disposed substantially in vertical alignment with a lengthwise centerline of the machine body. This arrangement allows the generator to be disposed in a “dead space” defined on either lateral side of the machine body where substantially no components other than the generator are disposed. The term “dead space” as used herein refers to an empty space which is normally in no use. Since such a “dead space” is advantageously used for installation or placement of the generator, mounting members used for mounting of the generator can avail a high degree of design freedom and can be configured into a simple form.

Furthermore, the generator is disposed on lateral side of the engine rather than forward or rearward of the engine, and hence the working machine has a reduced overall length.

Preferably, the engine has a lower end surface and the generator has a lower end surface disposed substantially flush with the lower end surface of the engine.

Since the lower end surface of the generator is substantially flush with the lower end surface of the engine, it is possible to lower the center of gravity of the working machine, which leads to improved stability of the working machine.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring toFIG. 1, there is shown an exemplary walk-behind self-propelled working machine taking the form of a snow removing machine10. The machine10includes a traveling frame13having left and right traveling units11,12(seeFIG. 2, too), a transmission case (a machine body)15mounted to the traveling frame13in such a manner as to swing in an up-and-down direction, left and right electric motors16,17mounted to left and right sides of the transmission case15, an engine18mounted on an upper part of the transmission case15, a generator90mounted on the right side of the engine18, a cover60attached to the transmission case15for covering the engine18and the generator90, a snow-removing unit (working unit)20attached to a front part of the transmission case15, left and right handlebars22,23(seeFIG. 2, too) extending rearward (more specifically, rearward and upward) from the upper part of the transmission case15, and a control board25disposed between the handlebars22,23. The handlebars22,23have hand grips at distal ends thereof. An operator can walk behind the snow removing machine10, grasping the hand grips of the handlebars22,23.

The right traveling unit12includes a front driving wheel27, a rear driven wheel28and a crawler belt29extending around the wheels27,28. The driving wheel27is driven by the right electric motor17for rotation in forward and reverse directions.

The left traveling unit11has the same arrangement as the right traveling unit12. More specifically, the unit11includes a front driving wheel27, a rear driven wheel28and a crawler belt29extending around the wheels27,28. The driving wheel27is driven by the left electric motor16for rotation in forward and reverse directions.

The left electric motor16serves as a drive source for the left traveling unit11and provides a motive power to the unit11via a left transmission mechanism31. Similarly, the right electric motor17serves as a drive source for the right traveling unit12and provides a motive power to the unit12via a right transmission mechanism32. The transmission mechanisms31,32are hereinafter referred to as “traveling transmission mechanisms31,32”

The engine18serves as a drive source for the snow-removing unit20and provides a motive power to the unit20via a transmission mechanism37and a transmission shaft38accommodated within the transmission case15. The transmission mechanism37is hereinafter referred to as “working transmission mechanism37”.

The engine18has a crankshaft (output shaft)34extending vertically and downwardly. The engine18has a cylinder portion43having a cylinder42defined therein, and a piston41reciprocally movably disposed within the cylinder42(seeFIG. 3). The engine18has a front surface18bdisposed rearward of a rear surface47aof (a blower housing47) the snow-removing unit20.

The generator90has a drive shaft91connected to the crankshaft34of the engine18through a power transmitting means95(seeFIG. 2andFIG. 3).

As will be discussed in detail below with reference toFIG. 3, while the snow-removing unit20is driven by a motive power transmitted via the working transmission mechanism37and the transmission shaft38from the crankshaft34to perform a snow removing operation, the generator90is driven by the motive power transmitted via the power transmitting means95from the crankshaft34to generate electric power for driving the electric motors16,17. The motors16,17then drive the traveling units11,12to propel the snow removing machine10on a ground surface68.

Referring back toFIG. 1, the snow-removing unit20includes an auger51, a blower52disposed behind and connected to the auger51, a shooter53disposed above the auger51and the blower52, an auger housing54covering the auger51, and the blower housing47formed integrally with a rear part of the auger housing54and covering the blower52. The auger51is operable to collect at the center thereof snow on the ground68. The blower52is operable to blow the collected snow into the shooter53. The snow is thrown out of the shooter53towards a desired position around the snow removing machine10.

The snow removing machine10includes a swing mechanism56operable to swing the transmission case15in the up-and-down direction. The swing mechanism56comprises serves as an actuator such as an electric actuator, a hydraulic actuator, or a pneumatic actuator. The mechanism56includes a cylinder57and a rod58movable into and out of the cylinder57to swing the transmission case15up and down for adjusting a level at which the snow-removing unit20is to be positioned. The swing mechanism56is operable to prevent any swinging movement of the transmission case15once the snow-removing unit20is adjusted to a desired level.

The cover60is halved into a lower cover member61mounted to the upper part of the transmission case15, and an upper cover member62mounted on the lower cover member61. The lower and upper cover members61,62jointly define a space127(seeFIG. 6) for accommodating the engine18and the generator90.

The engine18is disposed directly above the transmission case15with its cylinder portion43projecting rearward. The lower cover member61defines a space66therebelow (seeFIG. 1).

Within the space66, there is disposed a muffler67for discharging an exhaust gas coming from the engine18. The muffler67is substantially entirely surrounded by the transmission case15, the traveling frame13, the swing mechanism56, the left and right crawler belts29,29, the engine18and the ground surface68.

Since the muffler67is thus surrounded in this manner, there is no fear that the operator directly touches or contacts the muffler67of relatively high temperature. Additionally, this allows the use of minimum size of a heat insulating plate to cover the muffler67. The snow removing machine10further includes a scraper71, a lamp72and an air cleaner73.

As shown inFIG. 2, the engine18is disposed centrally of the snow removing machine10. The machine body15has a central axis (hereinafter referred to as “body centerline”)75extending in a front-and-rear direction thereof The crankshaft (output shaft)34has a center or axis disposed on the body centerline75. The transmission case15is disposed directly below the engine18(seeFIG. 1). The snow-removing unit20is disposed forwardly of the transmission case15. The left and right crawler belts29,29are disposed on the left and right sides of the transmission case15, respectively. The driving wheel27and the electric motor16(or17) are disposed on the front side of the crawler belt29. The shooter53, the lamp72and a battery74are disposed rearward of the auger housing54. The shooter53is disposed on a left side of the body centerline75while the lamp72and the battery74are disposed on a right side of the body centerline75.

Reference is made toFIG. 3. The crankshaft34of the engine18is disposed vertically and downwardly. The cylinder42has an axis44horizontally (i.e., in parallel to the ground surface68). The generator90is vertically disposed with the drive shaft91disposed vertically and downwardly. The drive shaft91and the crankshaft34have their respective axes disposed on a line93perpendicular to the axis44of the cylinder42as viewed in plan (seeFIG. 2orFIG. 7). The crankshaft34is connected to the drive shaft91of the generator90through the power transmitting means95.

The snow-removing unit20is disposed forwardly of the crankshaft34. The cylinder42is disposed rearward of the crankshaft34. The axis44of the cylinder42is disposed substantially on the body centerline75, as viewed in plan (seeFIG. 2andFIG. 7).

The engine18has the piston41slidably disposed in the cylinder42, and a connecting rod101connecting the piton41to the crankshaft34.

The power transmitting means95has a driving pulley102mounted on the crankshaft34, a driven pulley103mounted on the drive shaft91of the generator90, and a drive belt104extending around the pulleys102,103.

The crankshaft34has a lower end portion35(seeFIG. 6) connected through an electromagnetic clutch105to an upper end of a working output shaft106. The working transmission mechanism37has a pinion107mounted to a lower end of the working output shaft106, and a bevel gear108meshing with the pinion107. The bevel gear108is mounted to a rear end of the transmission shaft38.

When the engine18is running, rotation of the crankshaft34is transmitted through the power transmitting means95to the drive shaft91of the generator90, thereby driving the generator90. The thus driven generator90generates electric power for driving the left and right electric motors16,17(seeFIG. 1). The left and right electric motors16,17then generate motive power for driving the left and right traveling units11,12through the left and right traveling transmission mechanisms31,32, respectively, to propel the snow-removing machine10on the ground surface68.

Meanwhile, the electromagnetic clutch105, if placed in an ON state, transmits the rotation of the crankshaft34to the working output shaft106. The working output shaft106then rotates the pinion107to thereby rotate the bevel gear108. The rotation of the bevel gear108rotates the transmission shaft38for rotating the auger51and the blower52to perform the snow-collecting and snow-throwing operation as discussed above.

If the electromagnetic clutch105is in an OFF state, the crankshaft34is disconnected from the working output shaft106to thereby stop the rotation of the shaft106.

Referring toFIG. 4, the engine18has a right front mounting portion111and a right rear mounting portion114. The generator90is mounted to the right front mounting portion111and the right rear mounting portion114of the engine18via front and rear mounting brackets112,115, respectively.

The upper cover member62is mounted on the lower cover member61to cover the engine18, the air cleaner73and the generator90. The cover60thus protects the generator90from snowstorm or water resulting from thawing of snow to thereby provide a prolonged life of the generator90.

As shown inFIG. 2andFIG. 6, the generator90is disposed in a space defined above the crawler belt29of the right traveling unit12. Such a space defined above the right crawler belt29is suitable for installation or placement of the generator90because the space is a substantially “dead space” where few components or members other than the generator90are disposed. As to the “dead space” used for the installation of the generator90, detailed description will be made later.

Referring toFIG. 4andFIG. 6, the lower cover member61is of generally rectangular configuration and has a bottom wall117mounted to the machine body15(seeFIG. 6), and a peripheral wall118protruding upwardly from the entire peripheral edge of the bottom wall117. The bottom wall117has a right bottom portion117adisposed above the crawler belt29of the right traveling unit12, and a left bottom portion117b. It is to be noted that the bottom portion117bis disposed above the crawler belt29of the left traveling unit11. The peripheral wall118has a right side portion118aspaced rightward from the engine18and disposed above the crawler belt29of the right traveling unit12. Though not shown, the peripheral wall118has a left side portion spaced leftward from the engine18and disposed above the crawler belt29of the left traveling unit12.

As shown inFIG. 2andFIG. 7, the axis of the drive shaft91of the generator90and the axis of the crankshaft34are disposed on the line93perpendicular to the axis44of the cylinder42, as viewed in plan. This arrangement makes it possible for the generator90to be disposed away from the cylinder42of the cylinder portion43which is a heat-generating part or heat source having a relatively high temperature. Thus, the generator90is not affected by the heat of the cylinder42and hence has a prolonged service life.

As shown inFIG. 3, the cylinder42of the cylinder portion43is disposed rearward of the crankshaft34and the axis44of the cylinder42is disposed in a vertical alignment with the body centerline75. In other words, the axis44and the body centerline75are disposed in the same vertical plane. This arrangement makes it possible for the generator90to be disposed in a space48(seeFIG. 6) defined by the engine18, the right bottom portion117aof the bottom wall117and the right side portion118aof the peripheral wall118. The space48is a substantially “dead space” where few components other than the generator90are disposed.

Since the generator90is disposed in the substantially “dead space”48, the mounting brackets112,115used for mounting the generator90to the engine18can be avail a higher degree of design freedom and can be configured into a simple form. Further, because the generator90is disposed on the right side of the engine18rather than rearward or forward of the engine18, as best shown inFIG. 2, the snow-removing machine10has a relatively small overall length.

Referring back toFIG. 4, the upper cover member62includes a top wall123and a peripheral wall extending downwardly along rear, left and right side edges of the top wall123. The peripheral wall has on left and right sides thereof rear peripheral wall portions (only right side one shown)121mounted on the left and right side portions of the peripheral wall118of the lower cover member61, respectively, and a front peripheral wall portion122cooperating with the auger housing54for surrounding a top surface47bof the blower housing47. The top wall123has its front part having a front opening124formed at a left side thereof and sized to allow the shooter53to fit there-through, and a raised portion125disposed at a right side of the front opening124for covering the lamp72. The top wall123also has a raised portion126formed centrally thereof and disposed rearward of the front opening124and the raised portion125for covering the air cleaner73and an upper part of the engine18.

The upper cover member62mounted to the lower cover member61defines a space above the top surface47bof the blower housing47for accommodating the battery74and the lamp72.

As shown inFIG. 5, the front mounting bracket112extends rightward from the right front mounting portion111of the engine18. The bracket112has an L-shaped cross-section and has a horizontal plate131and a vertical plate132extending along and rising upwardly from a longitudinal edge of the plate131. The front mounting bracket112has a base portion133attached to the right front mounting portion111of the engine18by a pair of bolts134,134. The horizontal plate131has a distal end portion135projecting from the vertical plate132towards the generator90. The projecting portion135has a guide opening136of arcuate elongated configuration.

The generator90has a front mount flange138attached by a bolt141to an end portion of the projecting portion135of the front mounting bracket112with a cylindrical spacer137disposed between the mount flange138and the projecting portion135. The bolt141extends successively through a mounting hole138aof the mount flange138, an axial hole of the spacer137and the guide opening136of the front mounting bracket112and is fastened to a nut142.

The rear mounting bracket115has a base portion144attached to the right rear mounting portion114of the engine18by a pair of bolts145,145(seeFIG. 6), and a retaining portion146projecting rightward from the base portion144. The retaining portion146has a U-shaped cross-section and includes a vertical wall147, and upper and lower horizontal wings148,149projecting forwardly from the vertical wall147. The upper and lower horizontal wings148,149have mounting holes148a,149a, respectively.

The generator90has a rear mount flange139is received between the upper and lower wings148,149of the retaining portion146and is attached by a bolt151to the retaining portion146of the rear mounting bracket115. The bolt151extends successively through a hole148aof the upper wing148, a mounting hole139aof the mount flange139, and a hole149aof the lower wing149and is fastened to a nut152.

The upper part of the machine body (the transmission case)15has formed therein an upwardly opened space154(seeFIG. 6, too) for accommodating the electromagnetic clutch105therein. The upper machine body part has a quadrangular configuration and includes four mounting bosses155disposed on an upper surface15athereof adjacent respective corners of the quadrangular upper machine body part.

The engine18has four mount flanges157(three of which are shown inFIG. 5) corresponding in position to the four mounting bosses155of the machine body15. Each mount flange157has a mounting hole157aaligned with a threaded hole155aof the corresponding mounting boss155. Two of the four mount flanges157serve as the right front mounting portion111and the right rear mounting portion114of the engine18, respectively. The four mount flanges157are secured to the mounting bosses155by four bolts158each screwed through the mounting hole157ainto the corresponding threaded hole155a. The engine18is thus mounted on the four mounting bosses155.

It is to be noted that the right front mounting portion111of the engine18to which the front mounting bracket112is mounted is not limited in configuration to the illustrated one. Similarly, the configuration of the right rear mounting portion114of the engine18to which the rear mounting bracket115is mounted is not limited to the one shown in the illustrated embodiment.

As shown inFIG. 6, the lower cover member61of the cover60is mounted to the upper part of the machine body15. Each mount flange157of the engine18is attached to the corresponding mounting boss155of the machine body15by the bolt158. The electromagnetic clutch105has an input side105aconnected to the lower end portion35of the crankshaft34, and an output side105bconnected to the working output shaft106.

With the respective mount flanges157of the engine18mounted on the corresponding mounting bosses155of the machine body15, the engine18has a lower end surface18apositioned a distance H above the upper surface15aof the upper machine body part. Likewise, the generator90has a lower end surface90adisposed substantially the distance H above the right bottom portion117aof the bottom wall117of the lower cover member61. The upper surface15aof the upper machine body part and the right bottom portion117aof the lower cover member61lie substantially flush with each other. Thus, there is defined a space150between the upper surface15aand the lower end surface18a, and between the right bottom portion117aand the lower end surface90a. The space150is used for accommodation of the power transmitting means95(including the driving pulley102, the driven pulley103and the drive belt104).

Because the generator90is spaced upwardly from the right bottom portion117aof the bottom wall117of the lower cover member61, heat emitted from the generator90does not affect the lower cover member61of the cover60.

The generator90has an upper end surface (not designated) spaced from the top wall123of the upper cover member62by a given distance to thereby define a space therebetween, as is apparent fromFIG. 6. With the space thus defined between the upper end surface of the generator90and the top wall123, heat emitted from the generator90does not affect the upper cover member62.

The right bottom portion117aof the bottom wall117of the lower cover member61of the cover60has formed therein lower vent-holes119alocated below the generator90for taking in air from outside the cover60to cool the generator90, as shown by arrows. The lower vent-holes119amay have any configuration provided that they can perform the above described function of introducing outside air into the inside of the cover60.

The top wall123of the upper cover member62of the cover60has formed therein upper vent-holes123alocated above the generator90for discharging out heat generated by the generator90as the outside air having been used to cool the generator90flows out from the cover60through the upper vent-holes123a. The upper vent-holes123amay have any configuration provided that they can perform the above described function of discharging out of the cover60the heat of the generator90as the outside air flows out of the cover60through the vent-holes123a.

The right bottom portion117ahas lower guard plates119bdisposed directly below the lower vent-holes119afor preventing snow splashed up by the right crawler belt29during the propulsion of the snow removing machine10from entering the inside of the cover60through the vent-holes119a. The lower guard plates119bare configured to provide labyrinth-like passages communicating with the lower vent-holes119a. The lower guard plates119bare not limited in configuration to one described in this embodiment, and hence may have any configuration provided that the above blocking function can be achieved.

The top wall123has upper guard plates123bdisposed directly above the upper vent-holes123afor preventing rainwater from entering the inside of the cover60through the vent-holes123a. The upper guard plates123bare configured to provide labyrinth-like passages communicating with the vent-holes123a. The upper guard plates123bare not limited in configuration to one described in this embodiment and hence may have any configuration provided that the above blocking function can be achieved.

The guard plates119b,123bmay be omitted. Similarly, the vent-holes119a,123amay be omitted, in which case the cover60is designed in other ways to allow outside air to be taken into and discharged out of the cover60after cooling of the generator90.

Air surrounding the generator90tends to move upward as it is heated by heat emitted from the generator90. The generator90is vertically disposed as discussed above. Since the generator90is oriented in the same direction as the direction of flow of the heated surrounding air, the heat generated in the generator90is released upwardly out of the generator90with efficiency. The heat is then discharged through the upper vent-holes123aout of the cover60, as indicated by arrows. Meanwhile, as indicated arrows, outside air is introduced into the cover60through the lower vent-holes119aand cools the generator90, after which the air flows through the upper vent-holes123aout of the cover60.

As shown inFIG. 7, the upper part of the machine body15has the space154, and the four mounting bosses155are disposed at the four corners of the upper surface15aaround the space154(seeFIG. 5). The mount flanges157of the engine18are mounted on the mounting bosses155by the bolts158.

The engine18has the right front mounting portion111to which the base portion133of the front mounting bracket112is attached by the bolts134,134, and the right rear mounting portion114to which the base portion144of the rear mounting bracket115is attached by the bolts145,145.

The front mounting bracket112has the projecting portion135attached to the front mount flange138of the generator90by the bolt141. The rear mounting bracket115has the retaining portion146attached to the rear mount flange139of the generator90by the bolt151.

With the bolt141,151being loosened, the bolt141is movable within the guide opening136to thereby provide pivotal movement of the generator90on the bolt151for adjusting a tension in the drive belt104.

FIG. 8Ashows the positional relationship between the engine18and the generator90disposed according to the present invention, andFIG. 8Bshows the positional relationship between an engine and a generator according to a comparative example. As shown inFIG. 8A, the crankshaft (output shaft)34is vertically and downwardly disposed with the axis44of the cylinder42(FIG. 3) disposed horizontally, that is, in parallel to the ground surface68(seeFIG. 1). The generator90is vertically disposed with the drive shaft91disposed vertically and downwardly.

Since the generator90is oriented in the same direction as the direction of flow of the heated surrounding air as discussed above, heat generated in the generator90can be smoothly released upwardly out of the generator90, as indicated by arrows (1).

The heat thus released out of the generator90does not affect the upper cover member62because the generator90is spaced a given interval from the top wall123, as previously discussed above with reference toFIG. 6.

The drive shaft91of the generator90extends vertically and downwardly from the lower end surface90aof the generator90to a lower level than the lower end surface18aof the engine18for connection to the crankshaft34through the power transmitting means95. The generator90is positioned so low that the lower end surface90aof the generator90lies substantially flush with the lower end surface18aof the engine18. This arrangement makes it possible to lower the center of gravity of the snow removing machine10, thereby improving traveling stability of the machine10.

As shown inFIG. 8B, the engine250has a crankshaft (output shaft)251disposed horizontally (that is, in parallel to the ground surface68) and a cylinder having an axis252disposed vertically. The generator255has a drive shaft256disposed horizontally (that is, in parallel to the ground68).

Since the generator255is horizontally disposed with the drive shaft256extending horizontally, heat generated in the generator255is released out of the generator255, as shown by arrows (2).

In this instance, if the generator255is used for such a walk-behind working machine as a snow-removing machine having an engine for driving both traveling units and a working unit, the generator255is required to generate only a small amount of electric power for electrical accessories. Thus, the generator255generates only a small amount of heat, and such a small amount of heat can be readily released out of the generator255regardless of whether the generator255is disposed horizontally as shown inFIG. 8Bor vertically as shown inFIG. 8A.

Alternatively, when the generator255is used for a snow-removing machine of the same type as the machine10having left and right electric motors for driving left and right traveling units, however, the generator255is required to generate large amount of electric power for driving the electric motors, which involves generation of a large amount of heat emitted from the generator. Such large amount of heat is difficult to release out of the generator255when the generator255is horizontally oriented as shown inFIG. 8B.

The crankshaft251of the engine250extends horizontally and rearward, and therefore the crankshaft251is disposed above a bottom surface258of the engine250. The drive shaft256of the generator255is disposed in parallel to the crankshaft251. The generator255has upper and lower mount flanges263,264mounted through upper and lower mounting brackets261,262to the engine250.

If the generator255is displaced downwardly, the lower mount flange264would project downwardly to a level lower than the bottom surface258of the engine250. In this case, there would be required additional space for accommodating the lower mount flange264. Further, the drive shaft256of the generator255would be out of lateral alignment with the crankshaft251of the engine250. This would make the mounting brackets261,262complicated in configuration.

To avoid these problems, the generator255is disposed such that the lower mount flange264does not project to the lower level than the bottom surface258of the engine250, as shown inFIG. 8B. Thus, the generator255is disposed above the bottom surface258of the engine250. This arrangement undesirably leads to a higher center of gravity of the snow-removing machine.

Although the engine18drives the snow removing unit20and the electric motors16,17drive the traveling units11,12in the illustrated embodiment, the engine18may drive the traveling units11,12and the electric motors16,17may drive the snow removing unit20.

Although the working unit has been described as a snow-removing unit, it may be otherwise a rotary tilling unit or the like. The generator90may be mounted on the left side of the engine18in the above-explained manner although the generator90is mounted on the right side of the engine18in the illustrated embodiment.

Obviously, various minor changes and modifications of the present invention are possible in the light of the above teaching. It is therefore to be understood that within the scope of the appended claims the invention may be practices otherwise than as specifically described.