GB2385838A

GB2385838A - Steering of small electric vehicle

Info

Publication number: GB2385838A
Application number: GB0302893A
Authority: GB
Inventors: Kunihiro Hayashi
Original assignee: Suzuki Motor Corp
Current assignee: Suzuki Motor Corp
Priority date: 2002-02-27
Filing date: 2003-02-10
Publication date: 2003-09-03
Anticipated expiration: 2023-02-10
Also published as: GB0302893D0; TWI237562B; GB2385838B; TW200303190A

Abstract

A single-seat electric vehicle, e.g. for use by the handicapped or elderly, has driven rear wheels and steerable front wheels 1. Steering is by a handle 505 having a linear bar portion adjustably held by a clamp 513 to a rearward extending portion 512 attached to the top of the steering shaft 501. The axis of the shaft 501 passes through the centre of the handle, between two side bar portions. The base of the shaft 501 is connected through two meshing to a countershaft 508, attached to a to a tie rod arm 509, rotating this in the opposite direction to that of shaft 501 to steer the wheels 1 through tie rods 511.

Description

SMALL ELECTRIC VEHICLE The present invention relates to four-wheel small electric vehicles, in particular, for the use of aged persons and persons handicapped in leg.

Small electric vehicles of this kind are called senior cars (R) for example, which are very useful as means of locomotion for aged persons and so on. In the basic construction of such a small electric vehicle, a seat is disposed in a rear portion of the vehicle body for a rider to sit on the seat. A floor is disposed in front of the seat for the rider to put his or her feet on the floor. A steering shaft stands in front of the floor for the rider to operate front wheels. A handle is attached to the upper end of the steering shaft. The rider who is sitting on the seat manipulates the handle.

As a steering system of such a small electric vehicle as described above, in Japanese Utility Model Application Laid-open No. 5-76422 for example, a structure is disclosed in which the base ends of left and right bar handles are fixed on a supporting plate fixed to the upper end of a steering shaft. The left and right bar handles each protrude laterally beyond the supporting plate and curve from their middle portions toward the seat side. The tip end portion of each bar handle has a shape straightly extending inward. In the left and right bar handles, grips are provided at the tip end portions straightly extending inward. An acceleration lever is disposed in parallel with one grip. A rider performs handle manipulation with gripping the grips of the left and right bar handles. Handle manipulation is performed like a one-bar type handle in which portions in parallel with the rider are griped.

Besides, as a steering system of such a small electric vehicle as described above, there is a type in which the left and right front wheels are rigid and a swing shaft is provided at the central portion of the vehicle, for example. In this type, a tie rod is attached to one knuckle arm from a steering shaft and the tie rod extends from there to the other knuckle arm. In this structure, though a relatively large handle (steering)

turn angle can be taken, it can not be applied to left and right independent suspensiontype front wheels. Usually, in case of left and right independent suspension type, an arm is disposed in the central steering shaft and the tie rod extends from the arm. In case of this structure, since the arm length can not be so long, there is a problem that the handle turn angle can not be so large.

However, in case of handle manipulation in which the portions in parallel with the rider are gripped as described above, since the angle of each wrist is kept constant, the wrist is tired. Besides, when the handle is turned, since one gripped portion gets apart from the rider, the rider must extends the hand on that side. Thus, the rider can not perform handle manipulation with an ease posture. Further, since the bar handle is fixedly attached, the bar handle may be distant in accordance with the physical constitution of the rider. In that case, the rider must grip the bar handle with inclining forward. This may hinder the operability.

Besides, for solving the problem that the arm length can not be so long in case of left and right independent suspension type, in recently known steering systems, there is one in which tie rods are disposed in the upper and lower portions of the steering shaft. In this steering system, however, since the tie rods are disposed in the upper and lower portions, freedom of design of the suspension arm and so on is limited.

An object of the present invention is to provide a small electric vehicle with a steering system superior in usability, steering performance, etc.

The present invention provides a small electric vehicle of comprising a single seat supporting on a frame; a floor laid on the frame in a lower front portion of the single seat; a steering shaft standing on a front portion of the floor; a steering handle provided on an upper end of the steering shaft; front wheels provided in front of the floor as steering control wheels swingable in left and right directions by manipulating the steering handle; rear wheels provided in a lower rear portion of the single seat as

drive wheels driven by a power unit; and an electric power supply source for supplying electric power to the power unit, wherein the vehicle further comprises a steering handle supporting portion extending rearward on the upper end of the steering shaft, the steering handle has a linear bar portion and side bar portions extending in a nearly arch shape from both of left and right ends of the linear bar portion, and the linear bar portion of the steering handle is supported on the steering handle supporting portion so that the steering handle can be rotated in front and rear directions around the linear bar portion as an axis.

The present invention also provides a small electric vehicle of comprising a floor laid on a vehicle frame in a lower front portion of a single seat supported on the vehicle frame; left and right front wheels in a pair provided in front of the floor as'steering control wheels swingable in left and right directions in accordance with handle manipulation, and left and right rear wheels in a pair provided in a lower rear portion of the single seat as drive wheels driven by a power unit, for the vehicle to run with the front and rear wheels; and a steering system provided in a front end portion of the vehicle frame for steering the left and right front wheels in a pair, wherein the steering system comprises a steering shaft supporting on its upper end a handle so as to be rotatable and protruding upward from a front end portion of the floor; and a front-wheel steering knuckle supported through king pins on an outer end portion of a suspension arm extending outward in left and right directions, so as to be swingable in left and right directions, and the steering shaft and the front-wheel steering knuckle are interconnected by a tie rod through a tie rod arm and a knuckle arm, and the tie rod ann and the knuckle arm are disposed so as to protrude in opposite directions to each other with sandwiching an axial line extending between axial centers of the king pins.

Further features and advantages of the invention will become apparent upon a perusal of the appended claims, to which the reader is referred, and upon a reading of the

following more detailed description of an embodiment of the invention made with reference to the accompanying drawings, in which: FIG. 1 is a perspective front view illustrating the basic construction of a small electric vehicle according to an embodiment of the present invention; FIG. 2 is a perspective rear view illustrating the basic construction of the small electric vehicle according to the embodiment of the present invention; FIG. 3 is a side view illustrating the basic construction of the small electric vehicle according to the embodiment of the present invention; FIG. 4 is a plane view illustrating the basic construction of the small electric vehicle according to the embodiment of the present invention; FIG. 5 is a front view illustrating the basic construction of the small electric vehicle according to the embodiment of the present invention; FIG. 6 is a perspective view illustrating the vicinity of a frame unit and a battery unit of the small electric vehicle according to the embodiment of the present invention; FIG. 7 is a side view illustrating the vicinity of the frame unit of the small electric vehicle according to the embodiment of the present invention; FIG. 8 is a plane view illustrating the vicinity of the frame unit of the small electric vehicle according to the embodiment of the present invention; FIG. 9 is a perspective view illustrating the vicinity of a front-wheel supporting mechanism of the small electric vehicle according to the embodiment of the present invention; FIG. 10 is a perspective view illustrating the vicinity of a rotation mechanism of a single seat of the small electric vehicle according to the embodiment of the present invention;

FIG. 11 is a perspective view illustrating the vicinity of a steering handle of the small electric vehicle according to the embodiment of the present invention; FIG. 12 is a side view illustrating the vicinity of the steering handle of the small electric vehicle according to the embodiment of the present invention; FIG. 13 is a perspective view illustrating the battery unit of the small electric vehicle according to the embodiment of the present invention; FIG. 14 is an exploded perspective view illustrating the battery unit of the small electric vehicle according to the embodiment of the present invention; FIG. 15 is a side view illustrating the battery unit of the small electric vehicle according to the embodiment of the present invention; FIG. 16 is a perspective view illustrating another example of the vicinity of the steering handle; FIG. 17 is a perspective view illustrating the vicinity of a steering system of the small electric vehicle according to the embodiment of the present invention; FIG. 18 is a plane view illustrating the vicinity of the steering system of the small electric vehicle according to the embodiment of the present invention; FIGS. 19A and 19B are plane and sectional views illustrating an interconnection structure between a steering shaft and a tie rod arm of the small electric vehicle according to the embodiment of the present invention; FIG. 20 is a plane view illustrating the vicinity of the steering system of the small electric vehicle according to the embodiment of the present invention; FIG. 21 is a representation for explaining an Ackermann theoretical line of the small electric vehicle of the present invention; and FIG. 22 is a representation showing the correspondence to the Ackermann theoretical line of the steering system of the small electric vehicle according to the embodiment of the present invention.

FIGS. 1 to 5 illustrate the whole construction of the small electric vehicle according to this embodiment. Referring to these drawings, left and right front wheels 1 in a pair and left and right rear wheels 2 in a pair are supported by front and rear portions of a frame unit 100 including a vehicle frame, respectively. The front wheels 1 are supported by a front-wheel supporting mechanism 200. The rear wheels 2 are supported by a rear-wheel supporting mechanism 300.

On the rear side of the frame unit 100, a seat unit 400 forming a single seat for one rider sitting on is supported.

In lower front of the single seat, a floor panel 3 forming a low foot-rest floor laid on the vehicle frame is provided.

In a front portion of the frame unit 100, a steering mechanism 500 for steering the front wheels 1, which are steering control wheels to swing laterally in accordance with handle manipulation, is provided.

In this example, the rear wheels 2 are drive wheels, which are driven by a power unit 600 including an electric motor provided in a lower rear portion of the single seat.

On the lower side of the floor panel 3, a battery unit 700 provided with secondary batteries for supplying electric power to the power unit 600 is disposed.

First, the frame unit 100 will be described in detail. Also referring to FIGS. 6 to 8, the frame unit 100 is made up of the vehicle frame 101 constructing a chassis portion and a steering frame 102 for supporting a steering handle and so on. The vehicle frame 101 includes a main frame 103 and a rear frame 104. The main frame 103 is made up of a centre frame portion 105 and a front frame portion 106 extending in front of the centre frame portion 105.

The main frame 103 includes a pair of main frame members 107 disposed in the front and rear directions on both of the left and right sides. The main frame members 107

have a shape which is so shrank that the tip is narrowed, in the vicinity of the border between the centre and front frame portions 105 and 106, as illustrated in FIG. 8 and so on. Each main frame member 107 is suitably made of a rectangular pipe material though it is not limitative. For example, it may be made of a C-channel material, a circular pipe material, or the like. In any case, the main frame member 107 has a certain height (vertical thickness). To each main frame member 107, a carrying handle 111 laterally protruding outward and made of, for example, a circular pipe material is added.

In this example, in the main frame members 107, three bridge members 108, 109, and 110 are laterally suspended at the front end portion, in the vicinity of the border of the centre and front frame portions 105 and 106, and the rear end portion, respectively. A high rigidity of the main frame 103 is ensured thereby. As illustrated in FIG. 7, the bridge members 108 and 109 are curved so as to protrude downward. A base member of the front-wheel supporting mechanism as described later is disposed on the bridge members 108 and 109. In an actual vehicle, as illustrated in FIG. 7, the main frame 103 is in a state of properly inclining in a front-up manner. At this time, the base member of the front-wheel supporting mechanism is supported substantially horizontally.

Also as illustrated in FIG. 9, the steering frame 102 is constructed in the manner that four pipe materials 102a to 102d are integrally supported to stand inside of the front end portion of the front frame portion 106. The steering frame 102 stands vertically from the front frame portion 106 (main frame member 107). As described above, since the main frame 103 inclines in a front-up manner, the steering frame 102 is properly inclined to the single seat side. The steering frame 102 is suitably made of a rectangular pipe material.

The rear frame 104 is disposed to incline in an upper rear direction from the vicinity of the rear end portion of each main frame member 107. The rear frames 104 are interconnected by the carrying handle 112 at their respective rear end portions. In the middle in the front and rear directions of the rear frame 104, a bridge member 113 of a nearly arch or trapezoid shape is laterally suspended. To the upper portion of the bridge member 113, a seat post 114 is attached for supporting the seat unit 400. Each of the rear frame 104 and the bridge member 113 is suitably made of a rectangular pipe material though it is not limitative. For example, it may be made of a C-channel material, a circular pipe material, or the like. At the rear end portion of the rear frame 104, a bridge member 115 is laterally suspended that is formed in a curved shape to protrude downward.

Next, the front-wheel supporting mechanism 200 will be described in detail. The front-wheel supporting mechanism 200 supports the front wheels 1 so as to be freely rotatable and swingable. The front-wheel supporting mechanism 200 includes a base member 201 as a supporting portion held below the front frame portion 106, a suspension arm bracket 202 fixed on the base member 201, and a suspension arm 203 supported by a suspension arm bracket 202 so as to be freely swingable vertically. The suspension arm 203 extends outward from the centre portion in the left and right directions of the vehicle and the outer end portion thereof supports the front wheels 1 so as to be freely rotatable.

Mainly by this front-wheel supporting mechanism 200, a protrusion structure is formed that is made of a rigid member extending in the left and right directions between the interval of the left and right front wheels 1 in front of a battery case as described later, and protruding under the battery case. As illustrated in FIGS. I to 5, FIG. 7, and so on, the protrusion structure is made up of the base member 201, suspension arm bracket 202, suspension arm 203, and so on, disposed to protrude under the front frame portion 106. By the provision of such a protrusion structure in

front of and under the battery case, barrier or protective means is constructed for the battery case that has an important function as a power unit for the vehicle. The delicate power unit can effectively be protected thereby. Even though the vehicle has such a protrusion structure protruding under the front frame portion 106, since the floor 3 is inclined in a front-up manner in the actual vehicle (see FIG. 7), the protrusion structure does not so protrude downward. Thus, the ground clearance of undercarriage can effectively be ensured.

Also referring to FIG. 9, in the front-wheel supporting mechanism 200, on the base member 201 disposed on the bridge members of the main frame 103, two front and

rear suspension arm brackets 202 are provided for the respective left and right suspension arms 203. Each suspension arm 203 has a fork shape branching in the front and rear directions. Two branched base ends (inner ends) are pivoted by the two front and rear suspension arm brackets 202 so as to be freely rotatable vertically. At the tip end of the suspension arm 203, a U-shaped knuckle 204 (front-wheel steering knuckle) is pivoted through a king pin 208 so as to be freely rotatable in the left and right directions. To the knuckle 204, a wheel shaft 205 extending horizontally is attached. The front wheels I are supported by the wheel shaft 205 so as to be freely rotatable.

To the outer side of the front frame portion 106, a bracket 207 is fixed for suspending a suspension spring 206. The suspension spring 206 is fitted between the bracket 207 and the suspension arm 203 (the front side of the branched fork shape).

Next, the rear-wheel supporting mechanism 300 will be described in detail. The rearwheel supporting mechanism 300 supports the rear wheels 2 by incorporating with a power unit 600. In this case, the power unit 600 includes an electric motor and reduction gears connected with the output axis of the motor. The support shaft of the final stage gear is constructed as the wheel shaft 301 of the rear wheels 2. The front

side of the power unit 600 is pivoted through a bracket 302 (see FIGS. 1 to 3) fixed to the rear end of the main frame member 107. The rear side of the power unit 600 is connected with the lower end of a shock absorber 303. The upper end of the shock absorber 303 is pivoted through a bracket 304 fixed to the rear end of the rear frame 104. The shock absorber 303 can use a compression coil spring, oil pressure, or the like.

Next, the seat unit 400 will be described in detail. In the seat unit 400, a seat cushion frame 401 and a seat back frame 402 each made of a rectangular pipe material or the like are connected into a nearly L-shape to be united. They are supported on a seat post 114 so that the seat cushion frame 401 may be substantially horizontal. In this case, the seat unit 400 is supported so as to be rotatable in the left and right directions and be able to be selectively fixed at plural angular positions in the course of rotation.

To the seat cushion frame 401, a seat cushion 403 is attached as an elastic body. To the seat back frame 402, a seat back 404 is attached as an elastic body. At a proper vertical position of the seat back frame 402, arm rests 405 are supported so as to be rotatable. The rider who is sitting on the seat unit 400 supported on the seat post 114 as illustrated in FIG. 3 can put his or her feet on the floor panel 3. At this time, he or she can step on a foot brake 4 disposed in the vicinity of the front portion of the floor panel 3.

An example of construction of a rotation supporting mechanism of the single seat will be described. Referring to FIG. 10, a base bracket 406 is connected under the seat cushion frame 401. A seat pipe 407 is hung down from the base bracket 406. A pipe holder 408 is fitted in the seat post 114. The seat pipe 407 is fitted in the pipe holder 408 so as to be rotatable. By this construction, the seat cushion frame 401, i. e. , the single seat is rotatable in the left and right directions. The pipe holder 408 may be attached to the seat post 114 so as to be detachable.

To the base bracket 406, a lever holder 410 having a bearing 409 in the front portion thereof is fixed. A rotation shaft 411 is inserted in the bearing 409. The rotation shaft 411 extends outward and is properly bent as illustrated to form a lever portion 412.

To the rotation shaft 411, a nail piece 414 protruding downward from an opening 413 opened in the base bracket 406 is fixed. The nail piece 414 can be rotated by manipulating the lever portion 412. The nail piece 414 has a hole 414a engageable with a tooth of a stopper plate as described later. A stopper plate is fixed to the upper end of the pipe holder 408. Teeth 416 are provided on the outer circumference of the stopper plate 415 at proper angular intervals. Each tooth 416 is cut off at its both sides for clearance. This enables the tooth 416 to engage with the nail piece 414.

By inserting the seat pipe 407 into the pipe holder 408, the single seat is supported on the seat post 114. In this case, by engaging the nail piece 414 with a desired tooth 416 by manipulating the lever portion 412, the single seat can be selectively fixed at a desired angular position.

Next, the steering system 500 will be described in detail. In the steering system 500, inside the steering frame 102, a steering shaft 501 is supported through holders 502 so as to be freely rotatable. A steering handle 505 is provided on the upper end of the steering shaft 501. The steering shaft 501 is divided at its middle portion and the divided parts are interconnected through a universal joint 503. The upper steering shaft further inclines toward the single seat side. Thus, the steering handle 505 can be

disposed near the single seat with ensuring a wide floor space.

FIGS. 11 and 12 illustrates perspective views of the vicinities of the steering handle 505. The steering handle 505 has a linear bar portion 505S and side bar portions 505L and 505R extending in an arch shape from both the left and right ends of the linear bar portion 505S. A front portion of the steering handle 505 is cut off so that the steering handle 505 has a deformed U-shape.

On a side face of the upper end of the steering shaft 501, a steering handle supporting portion 512 is provided, which extends rearward and curves upward at its middle portion. A cramp member 513 is fixed to the tip end of the steering handle supporting portion 512. The cramp member 513 has a through hole extending in the left and right directions and is divided vertically. The lower cramp member 513a is welded to the tip end of the steering handle supporting portion 512. The upper cramp member 513b is fastened to the lower cramp member 513a with bolts 514.

The central portion of the linear bar portion 505S of the steering handle 505 is supported so as to be sandwiched by the above cramp members 513. Therefore, by loosening the bolts 514, the steering handle 505 becomes rotatable around the linear bar portion 505S as an axis (see arrow R in the drawing). In this state, the steering handle 505 can be laid down or set upright to be adjusted to a desired angle.

In a state that the steering handle 505 supported at an offset position from the axial line of the steering shaft 501 toward the single seat side as described above is laid down, that is, in a state that the steering handle is perpendicular to the steering shaft 501 as illustrated in FIG. 12, the centre of the steering handle 505 substantially coincides with the axial line of the steering shaft 501.

To the left and right side bar portions 505L and 505R of the steering handle 505, brackets 515 are fixed inwardly and somewhat downward by welding or the like.

Both sides of the acceleration mechanism chassis portion 504 are supported by those brackets 515. The thus fixed acceleration mechanism chassis portion 504 is positioned in a deep portion inside the steering handle 505.

On both the left and right sides of the acceleration mechanism chassis portion 504, acceleration levers 506 are disposed. Each acceleration lever 506 has a nearly Ushape. In a state that its open side faces downward, one side edge portion 506a of the acceleration lever 506 is supported by a side portion of the acceleration mechanism

chassis portion 504 so as to be freely rotatable. The other side edge portion 506b is disposed as an operation lever portion under the side bar portion 505L or 505R of the steering handle 505 substantially in parallel with the side bar portion 505L or 505R.

Therefore, the rider who is gripping the side bar portions 505L and 505R of the steering handle 505 can manipulate the acceleration levers 506 to rotate. If the other side edge portion 506b of each acceleration lever 506 is substantially arched to correspond to the side bar portion 505L or 505R of the steering handle 505, even in case of gripping the upper or lower portion of the side bar portions 505L and 505R of the steering handle 505, the acceleration levers 506 can easily be manipulated to be rotated.

On either side portion of the acceleration mechanism chassis portion 504 disposed are a holder 516 for supporting the side edge portion 506a of the acceleration lever 506 so as to be freely rotatable, a gear set 517 for sensing rotation of the acceleration lever 506 to increase, an acceleration sensor 518 engaging with a pinion of the gear set 517, a not-illustrated spring for keeping the acceleration lever 506 in a state apart from the steering handle 505 side (acceleration off state), etc. When the rider grips the side edge portion 506b of one of the left and right acceleration levers 506 and manipulates it to rotate it around the axis of the side edge portion 506b against the spring, the rotation is transmitted through the gear set 517 to the acceleration sensor 518, which sends out a signal to the main controller 7.

The description will be returned to the whole of the steering system 500. A bracket 507 is attached inside the front end portion of each main frame member 107 of the front frame portion 106. On the bracket 507, a boss is provided for supporting the lower end of the steering shaft 501 so as to be freely rotatable. On the rear side of the steering shaft 501 on the bracket 507, a counter shaft 508 is disposed that having a gear to engage with a gear provided on the lower end of the steering shaft 501. A tie rod arm 509 is fixed to the counter shaft 508. When the steering shaft is rotated

rightward or leftward, the tie rod arm 509 is rotated rightward or leftward through the counter shaft 508.

In each front wheel 1, a knuckle arm 510 fixed to the knuckle 204 and the tie rod arm 509 are interconnected through a tie rod 511. By rotating the steering handle 505 rightward or leftward, the front wheels 1 are steered rightward or leftward through the steering shaft 501, counter shaft 508, tie rod arm 509, and tie rod 511. By thus providing the counter shaft 508, the front wheels 1 can be steered in the same direction as the rotation of the steering handle 505. In this case, by properly selecting the gear ratio between the gear on the steering shaft 501 side and the gear on the counter shaft 508 side, the steering angle and force can suitably be set.

Next, the power unit 600 will be described in detail. As described above, the power unit 600 supports the rear wheels 2 by incorporating with the rear-wheel supporting mechanism 300. A battery unit 700 as described later supplies electric power to the power unit 600 to drive the electric motor 601 therein.

Next, the battery unit 700 will be described in detail. In the battery unit 700 of the present invention, as illustrated in FIG. 8, in a principal area of the floor (or referred to as floor panel) 3, between the frames disposed along the both side edges thereof, a battery case 701 is received that has substantially the same height as the frames.

Secondary batteries 702 are arranged in the battery case 701. In the illustrated example, the secondary batteries 702 are arranged in two of front and rear lines within a plane.

The floor 3 is made up of a main floor portion 5 positioned rearward of the front wheels 1 and having substantially the same width as the interval between the left and right front wheels 1, and a front floor portion 6 having a width narrower than the interval between the left and right front wheels 1 and narrower than the main floor portion 5 and extending frontward of the main floor portion 5. The principal area of

the floor 3 is formed by the main floor portion 5, where the battery case 701 is disposed.

The centre frame portion 105 of the main frame 103 as described above extends in the front and rear directions along both of the left and right side edges of the main floor portion 5. The front frame portion 106 extend in front of the centre frame portion 105 at an interval narrower than the interval between the left and right front wheels 1. In this example, the battery case 701 is disposed in between main frame member 107 constructing the centre frame portion 105.

As illustrated in FIG. 13, the battery case 701 has a generally thin box shape. It is formed at substantially the same level as the main frame members 107. This battery case 701 is disposed under the main floor portion 5 in between the main frame members 107. As the dry-type secondary battery 702 used in the present invention, a lithium ion battery is typically used. As the dry-type secondary battery of this kind, a number of cells are combined and packed. In such a case, in many cases, they are piled in a trefoil formation in order to increase the density of the large-size cell module. This is bulky. In this embodiment, however, since the left and right front wheels 1 in a pair are provided as described above and the main floor portion 5 can be formed into a large area having substantially the same width as the interval between the left and right front wheels 1, the total eight secondary batteries 702 can be arranged in two of the front and rear lines within a plane. By holding down the width (diameter) of each secondary battery 702 into one equal to or slightly higher than the height of the main frame member 107, a very thin battery receiving space can be set.

As illustrated in FIG. 14, the battery case 701 is provided on its bottom portion with a holding portion having plural recesses formed so as to correspond to the outer shape of each secondary battery 702. In this embodiment, plural semicircular ribs 701 a are formed. Since the secondary batteries 702 are arranged within a plane as described

above, the secondary batteries 702 must be fixed so as not to move in the battery case 701 due to vibration. By providing the semicircular ribs 70 la, the secondary batteries 702 are suitably fixed so as not to interfere with each other.

The battery case 701 is provided on the left and right sides with flange-shaped attachment portions 701b. In a state that the flange-shaped attachment portions 701b are put on the respective main frame members 107, the battery case 701 is attached to the main frame members 107 with screws or the like. In this case, an insertion hole 701c is provided for each attachment screw. In the front portion of the battery case 701, that is, on the front side of the secondary batteries 702 in the front line, a cell controller (substrate) 703 is disposed with a holder 701d being interposed.

The cell controller 703 makes a control so that the secondary batteries 702 (cells) may have no capacity and potential differences from each other. The cell controller 703 is perpendicular to the bottom portion of the battery case 701. By thus providing the cell controller 703 perpendicularly between the parts around the front suspension and the secondary batteries 702, the space in the front and rear directions can effectively be utilized. Even though the cell controller 703 is provided vertically, since the floor is inclined in a front-up manner in the actual vehicle, the cell controller 703 does not so protrude downward. Thus, the ground clearance of undercarriage can effectively be ensured.

As illustrated in FIG. 14 or 15, the upper portion of the battery case 701 is covered with a flat cover 704. The cover 704 has a shape matching the upper opening of the battery case 701. Nail pieces 704a are hung down from the periphery of the lower surface of the cover 704. By engaging the nail pieces 704a with engagement portions 701e, the cover 704 is fixed. In the interface between the battery case 701 and the cover 704, a gasket is fitted so that water, dust, and so on may not enter the battery

case 701. By fixing the cover 704 to cover the battery case 701 having received the secondary batteries, a battery pack is constructed.

Also as illustrated in FIG. 15, on the upper side of the battery pack, that is, on the upper side of the cover 704, the floor panel 3 is disposed. The floor panel 3 is put on the attachment portions 701b of the battery case 701 with spacers being interposed, and attached to the attachment portions 701b with screws or the like. In this case, insertion holes 3a for the attachment screws are provided in the peripheral portion of the floor panel 3. Also, insertion holes 70 If are provided in the attachment portions 701b to correspond to the respective insertion holes 3a.

On the lower side of the battery pack, that is, on the lower side of the battery case 701, a generally flat underguard 705 is disposed. The underguard 705 is attached to the bridge members 109 and 110 (see FIG. 6) with screws or the like so as to cover the lower portion of the battery case 701. In this case, insertion holes 705a and 705b for the attachment screws are provided in the front and rear edge portions of the underguard 705, respectively (FIG. 14).

In the small electric vehicle of the present invention, referring to each drawing as above, in the lower front half portion of the single seat disposed rearward of the floor 3, as illustrated in FIG. 3 and so on, a main controller 7 for electronically controlling electric power to be supplied to an electric motor 601 of the power unit 600 and a charging device 8 for charging the secondary batteries 702 of the battery unit 700 are disposed. The main controller 7 and the charging device 8 are covered with a vehicle cover (not illustrated) formed integrally with and from the floor 3. Thus, they are not exposed outside.

In the space between the left and right rear wheels 2 in a pair disposed rearward of the main controller 7 and so on, a box-or basket-like load receiving device 9 is disposed. In the upper portion of the load receiving device 9, an opening 9a is opened for

enabling load to be taken in and out. As described above, the single seat is supported at a near position above the seat post 114 so as to be rotatable around the seat post 114. By properly rotating the single seat, a part or the whole of the opening 9a of the load receiving device 9 positioned above it can be covered with the single seat from above to be able to be opened and closed.

In the upper portion of the steering frame 102, a switch box (operation panel) 10 is attached at a near position in front of the steering handle 505. As illustrated in FIG. 7 for example, the switch box 10 is supported through a nearly key-shaped bracket 11 fixed to the upper end of the steering frame 102. The switch box 10 carries various switches and the like. For example, switches such as a front/back changeover knob, a speed set knob, a battery residual indicator, and a charge lamp, and further a right/left winker switch and a horn button are disposed.

The switch box 10 is disposed to properly incline at a near position in front of the steering handle 505. Thus, a rider's hand can easily reach the switches and so on necessary for driving operation and the display contents of the display lamp and so on are easily observed. Therefore, the rider who is sitting on the single seat can easily and adequately operate the switches and so on of the switch box 10. At that time, he or she can properly operate the accelerator lever 506 at need.

At a near position under the switch box 10, a cord reel case 12 in which a cord reel is incorporated is attached to the steering frame 102. On the cord real, a charging cord biased to the take-up direction is wound so as to be able to be freely fed. The charging cord is connected with the charging device 8. When the secondary batteries 702 of the battery unit 700 are charged, the charging cord is fed from the cord reel case 12 and the charging device 8 is connected with an external power source through the charging cord.

To the upper portion of the steering frame 102, a main key 13 is attached using a holder 502 for example. The main key 13 is disposed at a position where the rider who sitting on the single seat can easily see. In the lower portion of the main key 13, a box-or basket-like load receiving device 14 is mounted on the steering frame 102.

In the upper portion of the load receiving device 14, an opening is opened for enabling load to be taken in and out.

In case of the above, each unit is covered with a vehicle cover made of a plastic or synthetic resin or the like. It is designed so that a predetermined external design can be obtained as the whole vehicle. In this case, a leg shield and so on are mounted around the steering frame 102. Front and rear fenders may be mounted around the front and rear wheels 1 and 2, respectively.

In an actual vehicle, safety or reservation parts and so on necessary in run are provided. The parts of this kind include a headlamp, a winker, a stop lamp, a side mirror, a horn, and so on. Further, if necessary, other parts are provided.

In actual use of the small electric vehicle as constructed above, the rider who is sitting on the single seat grips the steering handle 505 and pulls the acceleration lever 506 or steps on the foot brake 4 at need to drive the vehicle. In this case, electric power is supplied to the power unit 600 from the battery unit 700 received on the lower side of the floor panel 3. The electric motor 601 of the power unit 600 drives the rear wheels 2 and thus the rider can smoothly and properly drive this small electric vehicle.

In the small electric vehicle of this embodiment as described above, the steering handle 505 is supported at an offset position from the axial line of the steering shaft 501 to the single seat side. The steering handle 505 has the side bar portions 505L and 505R extending in an arch shape from both the left and right ends of the linear bar portion 505S. Therefore, the rider can perform handle manipulation with gripping the side bar portions 505L and 505R of the steering handle 505 in natural feeling.

Although one side bar portion 505L or 505R gets apart from the rider side when the rider turns the handle, at this time, since the rider can newly grip the lower portion of the side bar portion 505L or 505R getting apart or the linear bar portion 505S, the rider can always perform handle manipulation with an easy posture.

Besides, since the steering handle 505 can be laid down and made to stand, by adjusting it to a desired angle in accordance with the rider's physical constitution and so on, the operability can be improved. For example, in case of a rider of a relatively small constitution, by making the steering handle 505 stand, the rider can grip the steering handle with an easy posture. Even when turning the handle, the degree that the side bar portion 505L or 505R gets apart from the rider side can be decreased.

Besides, since the acceleration mechanism chassis portion 504 is fixed to the steering handle 505, even when the angle of the acceleration steering handle 505 is adjusted, the positional relation between the side bar portions 505L and 505R of the steering handle 505 and the acceleration levers 506 is kept. It is not hard to manipulate the acceleration levers 506.

Further, since a front portion of the steering handle 505 is cut off, the visibility can be enhanced. Particularly in case of disposing the switch box (operation panel) 10 at a close position in front of the steering handle 505 as described above, the visibility to the switch box 10 can be enhanced and the operability can be improved.

Furthermore, since the acceleration levers 506 are provided on both the left and right sides, one of them that is easier to use can be manipulated to rotate. As described above, the rotational operation quantity of the acceleration lever 506 is transmitted to the controller 7 and the rear wheels 2 are driven accordingly. For example, if both the left and right acceleration levers 506 are manipulated to operate, the controller 7 may control the rear wheels 2 to drive in accordance with one acceleration lever 506 in which the operation quantity is larger.

Next, with reference to FIGS. 17 to 22, the steering system according to this embodiment will be further described. In the steering system, as described above, the steering shaft 501 supporting at its upper end the steering handle 505 so as to be rotatable and protruding upward from the tip end portion of the floor 3, and the knuckle 204 supported so as to be swingable in the left and right directions through the king pin 208 by the outside end portion of the suspension arm 203 extending outward in the left and right directions are connected by the tie rod 511 through the tie rod arm 509 and the knuckle arm 510.

In the bracket 507 welded to the lower end of the steering frame 102, a steering shaft attachment boss 521 and a counter shaft attachment boss 522 are disposed in recesses of the bracket 507 as illustrated in FIGS. 19A and 19B. In the boss 521, the lower end of the steering shaft 501 is born through a bearing 523 (preferably a bush made of a synthetic resin). In the upper portion of the bearing 523, a substantially semicircular gear 524 (spur gear) is fixed to the steering shaft 501. The gear 524 engages with a substantially semicircular gear 525 (spur gear) fixed to the counter shaft 508. The counter shaft 508 is born by the boss 522 through bearings 526. In this case, a spacer 527 is inserted between the upper and lower bearings 526.

Particularly in the present invention, as illustrated in FIG. 18, the tie rod arm 509 and the knuckle arm 510 are so disposed as to protrude in the opposite directions to each other with sandwiching the axial line extending between the axial centers of the left and right king pins 208. In this case, the knuckle arm 510 obliquely extends forward from the knuckle 204. The tie rod arm 509 extends rearward from the steering shaft 501.

By thus disposing the tie rod arm 509 and the knuckle arm 510, rod ends 511 a and 511 b on both ends of the tie rod 511 are disposed frontward and rearward of the axial line extending between the axial centers of the left and right king pins 208.

The lower portion supporting portion (steering shaft attachment boss 521) of the steering shaft 501 is disposed in front of the axial line extending between the axial centers of the left and right king pins 208. The rotational axis (counter shaft 508) of the tie rod arm 509 is disposed rearward of the steering shaft 501. The steering shaft 501 and the counter shaft 508 are connected by gears 524 and 525 as connecting means. In this case, the tie rod arm 509 is disposed under the front portion of the floor 3 (see FIG. 2,9, or the like).

In the steering system of the present invention, a steering turn angle near the so-called Ackennann theory is ensured and smooth and adequate steering and running performance are realized. Referring to FIG. 21, according to the Ackennann theory, the wheel axis centre lines M 1 and M2 of the steered left and right front wheels (F) intersect each other on the wheel axis extending line M'of the rear wheels (R). When the left front wheel is turned at a turn angle a and then the turn angle of the right wheel front wheel is p, the following equations are obtained. Note that M in the drawing represents the axial line extending between the axial centers of the left and right king pins 208. cot a = B/L cot P-A + B/L Note that L represents the interval between the wheel axes of the front and rear wheels (wheel base) and A represents the interval between the king pins.

For example, as the illustrated example, the wheel axis centre line of the left front wheel (turn angle a) inside the centre of the vehicle turn is Ml and the wheel axis centre line of the right front wheel (turn angle p) outside the centre of the vehicle turn is M2. A line symmetrical with the wheel axis centre line Mi in relation to the king pin centre line N in parallel with the vehicle centre line C is Ml'. By changing the

inside turn angle (0 to 90 ) and plotting the intersections between the wheel axis centre line M2 and the line Ml'for each angle, an Ackennann theoretical line P is obtained.

FIG. 22 shows the correspondence with the Ackermann theoretical line P when the front wheels 1 in the steering system of the present invention are turned left and the

turn angles a and P of the left and right front wheels 1 are changed in a manner like that for obtaining the Ackermann theoretical line P (a = 0 , 15 , 30 , 45 , 60 ,..., and P= 0 , 15 , 30 , 45 , 60 ,...). In this case, by rotating the tie rod arm 509, the swing angle of the knuckle arm 510 changes. Like a case of plotting the intersections between the wheel axis centre line M2 and the line Ml'in the Ackennann theoretical line P, intersections Po, PIS, P30, P45, P60,..., are plotted per angle change F5 of the turn angles a and . As understood from the drawing, it substantially coincides with the Ackermann theoretical line P almost to the turn angle a = 800.

According to a form approval by a raw regulation, an electrical vehicle of this kind is regulated so that its whole length is 1200 mm and its whole width is not more than 700 mm. When a four-wheel type vehicle is constructed under these conditions, the respective wheels are disposed at four comers of the vehicle. Besides, for running in a narrow passage or the like, a large steering turn angle must be ensured. In the

present invention, the knuckle arm 510 extends frontward from the knuckle 204 and the tie rod arm 509 extends rearward from the steering shaft 501. By thus disposing the tie rod arm 509 and the knuckle arm 510, the angle between the axial line of the tie rod 511 and the axial line of the vehicle in the front and rear directions can be set at an acute angle in a straight drive (see FIG. 18). A large maximum steering angle can be ensured thereby. Even when the inside turn angle of the front wheels 1 is nearly 80 (see FIG. 20), the turn angle can be changed substantially along the Ackermann theoretical line P.

Besides, by setting the angle between the axial line of the tie rod 511 and the axial line of the vehicle in the front and rear directions at an acute angle, the angle between the axial line of the tie rod 511 and the axial line of the vehicle in the front and rear directions can be formed so as to be open inside in the left and right directions of the vehicle. By this, even when a large clearance between the tip end of the knuckle arm 510 and the front wheels 1 is ensured, the king pin 208 supporting the knuckle so as to be swingable can be put close to the front wheels 1 so that the scrub radius (king pin offset) can be set at a small value. By decreasing the scrub radius, the drivability and stability of the vehicle can be improved.

Further, since the steering shaft 501 protruding upward from the front end portion of the floor 3 can be disposed in the front portion of the vehicle, a large area of the floor 3 can be ensured and the floor 3 can effectively be used. In this case, by disposing the steering shaft forward of the axial line M, a larger area of the floor 3 can be formed.

Besides, the steering shaft 501 and the tie rod arm 509 are connected through the gears 524 and 525 as connecting means. In this case, by properly setting the reduction ratio of these gears, the steering operability can be improved. For example, for a female aged person or the like whose physical strength is weak, the reduction ratio is set at a small value so that she can steer the handle with a small operation force. In contrast, for a male, by setting the reduction ratio at a relatively large value, a large front-wheel turn angle is obtained with a small handle turn angle, that is, quick operation feeling can be obtained.

Hereinbefore, the present invention has been described with various embodiments. But, the present invention is not limited to those embodiments and can be changed or the like within the scope of the present invention. For example, in the above embodiment, an example in which the left and right winker switches and horn buttons

are provided in the switch box 10 has been described. But, as illustrated in FIG. 16, the left and right winker switches 519 and horn buttons 520 may be disposed on the bracket 515 fixed to the steering handle 505. By this, the rider can operate the left and right winker switches 519 and horn buttons 520 without releasing his or her hand from the steering handle 505.

Besides, for example, by dividing the tie rod arm 509 along its centre line into two so that the divided left and right parts can move separately, turning at the place can be done like a small electric vehicle such as a so-called motor chair. In this case, since turning at the place while performing continuous handle manipulation is impossible, a mechanism must be provided for once stopping the vehicle upon turning at the place and setting the left and right front wheels into a V-shape.

As described above, according to the present invention, a small electric vehicle with a steering system superior in usability, steering performance, etc. , can be provided.

More specifically, in a small electric vehicle of this kind, the steering shaft is supported at an offset position from the axial line of the steering shaft toward the single seat side. The steering handle has the side bar portions extending in an arch shape from both the left and right ends of the linear bar portion. Therefore, the rider can perform handle manipulation with gripping the side bar portions of the steering handle in natural feeling. Besides, since the steering handle is supported so as to be rotatable in the front and rear directions, the steering handle can be laid down and made to stand. Therefore, by adjusting it to a desired angle in accordance with the rider's physical constitution, the operability can be improved.

Besides, in a small electric vehicle of this kind, a large maximum steering angle can be ensured and the turn angle can be changed substantially along an Ackermann theoretical line. By this, even in turning, lateral slipping of tire is less, a load unreasonable on structure is not applied, and wear of tire can effectively be

suppressed. Besides, by suitably setting the positional relation among the tie rod arm, the knuckle arm, and the tie rod, the drivability and stability of the vehicle can be improved. In addition, a large area of floor can be ensured and the floor can effectively be used. Further, by properly setting the reduction ratio of the gears interconnecting the steering shaft and the tie rod arm, the steering operability can be improved.

Claims

CLAIMS: 1. A small electric vehicle comprising a single seat supporting on a frame; a floor laid on said frame in a lower front portion of said single seat; a steering shaft standing on a front portion of said floor; a steering handle provided on an upper end of said steering shaft; front wheels provided in front of said floor as steering control wheels swingable in left and right directions by manipulating said steering handle; rear wheels provided in a lower rear portion of said single seat as drive wheels driven by a power unit; and an electric power supply source for supplying electric power to said power unit, wherein said vehicle further comprises a steering handle supporting portion extending rearward on the upper end of said steering shaft, said steering handle has a linear bar portion and side bar portions extending in a nearly arch shape from both of left and right ends of said linear bar portion, and said linear bar portion of said steering handle is supported on said steering handle supporting portion so that said steering handle can be rotated in front and rear directions around said linear bar portion as an axis.
2. The vehicle according to claim 1, wherein a centre of said steering handle substantially coincides with an axial line of said steering shaft in a state that said steering handle is perpendicular to said steering shaft.
3. The vehicle according to claim I or 2, wherein an acceleration mechanism chassis portion in which an acceleration lever is provided is fixed to said steering handle, and said acceleration mechanism chassis portion is disposed inside said steering handle.
4. The vehicle according to claim 3, wherein said acceleration lever has an operation lever portion disposed substantially in parallel with said side bar portion of said steering handle under said side bar portion.

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5. The vehicle according to claim 4, wherein said acceleration lever has a nearly Ushape and one side edge portion is supported by said acceleration mechanism chassis portion so as to be freely rotatable and the other side edge portion is disposed substantially in parallel with said side bar portion of said steering handle under said side bar portion as said operation lever portion.
6. The vehicle according to any one of claims 1 to 5, wherein acceleration levers are provided on both of left and right sides.
7. The vehicle according to any one of claims 1 to 6, wherein at least one of left and right winker operation portions and horn operation portions is provided on said steering handle or a portion fixed to said steering handle.
8. The vehicle according to any one of claims 1 to 7, wherein said steering shaft is divided at its middle portion, the divided parts are interconnected through an interconnecting member, and said steering shaft inclines toward said single seat.
9. A small electric vehicle comprising a floor laid on a vehicle frame in a lower front portion of a single seat supported on said vehicle frame; left and right front wheels in a pair provided in front of said floor as steering control wheels swingable in left and right directions in accordance with handle manipulation, and left and right rear wheels in a pair provided in a lower rear portion of said single seat as drive wheels driven by a power unit, for said vehicle to run with said front and rear wheels; and a steering system provided in a front end portion of said vehicle frame for steering said left and right front wheels in a pair, wherein said steering system comprises a steering shaft supporting on its upper end a handle so as to be rotatable and protruding upward from a front end portion of said floor; and a front-wheel steering knuckle supported through king pins on an outer end portion of a suspension arm extending outward in left and right directions, so as to be swingable in left and right directions, and said steering shaft and said front-wheel steering knuckle are interconnected by a tie rod

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through a tie rod arm and a knuckle arm, and said tie rod arm and said knuckle arm are disposed so as to protrude in opposite directions to each other with sandwiching an axial line extending between axial centers of said king pins.
10. The vehicle according to claim 9, wherein both ends of said tie rod are positioned frontward and rearward of said axial line extending between said axial centers of said king pins.
11. The vehicle according to claim 9 or 10, wherein said knuckle arm extends frontward from said front-wheel steering knuckle and said tie rod arm extends rearward from said steering shaft.
12. The vehicle according to any one of claims 9 to 11, wherein a lower end supporting portion of said steering shaft is disposed frontward of said axial line, a rotational axis of said tie rod arm is disposed rearward of said steering shaft, said steering shaft and said rotational axis of said tie rod arm are connected by connecting means, and said tie rod arm is disposed under a front portion of said floor.