JP4499871B2 - Power transmission device for small vehicles - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a power transmission device for a small vehicle that transmits power from an engine to left and right drive wheels by means of a differential mechanism as a power unit configuration in which an engine and a differential mechanism are integrally assembled. The present invention relates to a power transmission device suitable for use in a small vehicle having a simple structure on which a passenger rides.
[0002]
[Prior art]
In recent years, from the viewpoint of reducing exhaust gas and energy consumption, a small vehicle that can be moved by one or two people has been developed and put into practical use.
Such a small vehicle is configured in a self-supporting form such as a four-wheeled vehicle or a three-wheeled vehicle. For example, as described in JP-A-9-286348, a small engine is used as a power source. It is used as a means that can be easily moved with low exhaust gas with low fuel consumption.
[0003]
In such a small vehicle, as described in Japanese Patent Laid-Open Nos. 59-227523, 62-246648, and Japanese Patent Publication No. 6-56196, a belt type continuously variable transmission is used. The transmission is transmitted to the differential mechanism via a mechanical transmission and the left and right drive wheels are driven to rotate, and the equipment from the engine to the differential mechanism is integrated into a power unit to form a power train. The equipment is put together in a compact car.
[0004]
Also, in a conventional general vehicle, the output wheel of the differential mechanism and the left and right drive wheels are connected by a flexible drive shaft using a mechanical universal joint such as a universal joint, and the drive wheel accompanying traveling Suspension system that enables swinging is adopted.
In addition, the conventional small vehicle has a swing-type suspension system that supports the power unit from the engine to the differential mechanism in a swingable manner relative to the vehicle body, thereby enabling the drive wheels to swing as the vehicle travels. Some are doing it.
[0005]
[Problems to be solved by the invention]
Here, a small vehicle has a simple vehicle body structure in order to reduce the weight and cost, but how to prevent vibration generated by the operation of the engine from being transmitted to the vehicle body is an important issue. .
As a countermeasure against this, an anti-vibration structure that elastically supports the power unit with respect to the vehicle body can be considered. However, since the power unit can be displaced relative to the vehicle body by the anti-vibration structure, a differential mechanism and a drive are used to absorb this displacement. The drive shaft that connects the wheels needs to be flexible.
[0006]
However, in a vehicle configuration of a small vehicle, using a flexible drive shaft with a mechanical universal joint as described above causes an increase in weight and cost, resulting in low fuel consumption and low exhaust gas using a small displacement engine. There is a problem that it is not possible to satisfy the demand for a small vehicle, which should be a means that can move comfortably in an amount.
[0007]
The present invention has been made in view of the above-described conventional circumstances. By adopting a flexible drive shaft having a light weight and a simple structure together with a vibration isolating structure for a power unit, a small vehicle is comfortable with low fuel consumption and low exhaust gas amount. The purpose is to realize movement.
It is another object of the present invention to realize a swing-type suspension system for a small vehicle having a simple structure and excellent in vibration isolation.
Further objects of the present invention will be apparent from the following description.
[0008]
[Means for Solving the Problems]
The present invention is a power unit type power transmission device in which an engine and a differential mechanism are integrally assembled. The power unit is elastically supported by a vehicle body, and is connected to a flexible drive shaft or bellows by an elastic body. The output shaft of the differential mechanism and the drive wheel are connected to each other by the cylindrical flexible drive shaft.
Therefore, the power unit is mounted on the vehicle body with a vibration-proof structure, and the differential mechanism and the drive wheel are connected by a flexible drive shaft that has a simple structure and is lightweight.
[0009]
Furthermore, in the present invention, the power unit is elastically supported on the mounting frame, the mounting frame is elastically supported on the vehicle body, and the power unit is mounted on the vehicle body by a double vibration isolation structure, thereby providing a greater vibration isolation effect. Realize.
Further, in the present invention, the mounting frame is supported so as to be swingable with respect to the vehicle body, and the power unit and the driving wheel are suspended with respect to the vehicle body in a swing manner to realize a simple structure of a small vehicle.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
The present invention will be specifically described with reference to an embodiment shown in the drawings.
As shown in FIGS. 1 to 4, the small vehicle of this example is a four-wheeled vehicle having two wheels each on a front wheel 1 and a rear wheel 2, and one occupant (driver) is seated in the center. A single seat driving seat 3 is provided.
The basic vehicle structure of this small vehicle is a frame-type vehicle body frame 4 made of a metal pipe material such as aluminum and covered with a resin body cover 5, and further, above the body cover 5. A resin roof panel 6 is arranged to cover the upper part of the seating seat 3 of the occupant to constitute a cabin.
[0011]
Reference numeral 7 in the figure denotes a steering wheel. By applying a steering force from the steering wheel 7 via a steering mechanism (not shown), the front wheel 1 can change its direction so that the traveling direction of the vehicle can be arbitrarily changed. It has become.
Further, reference numeral 8 in FIG. 1 denotes a select lever provided on the side portion of the seat 3, and the mechanical two-speed automatic transmission can be selected to move forward or backward by the select lever 8 as will be described later. Yes.
[0012]
As shown in FIGS. 3 to 6, a frame-type swing frame 10 is attached to the rear portion of the vehicle body frame 4 so as to be swingable up and down with its tip as a pivot. A power unit 40 in which a continuously variable transmission, a centrifugal transmission clutch type two-speed automatic transmission, a differential mechanism, and the like are integrated is provided. The rear wheels 2 are respectively attached to the ends of a pair of drive shafts 80 protruding from the differential mechanism of the power unit 40, and the left and right rear wheels 2 are driven by the power from the power unit 40. .
[0013]
As shown in detail in FIGS. 5 and 6, the swing frame 10 has a structure in which a substantially T-shaped main frame 11 and a pair of trailing arms 12 are combined, and the power unit 40 is attached to the vehicle body 4 as described below. In addition to being swingably mounted, it also functions as a mount frame that elastically supports the power unit 40.
The main frame 11 welds a center pipe 14 extending in the vehicle length direction to the center of the main pipe 13 extending in the vehicle width direction, and further, a sub pipe 15 for supporting the power unit 40 between the main pipe 13 and the center pipe 14. It is a structure that is welded over.
[0014]
The main pipe 13 is attached to an axle block 18 that rotatably supports the flexible drive shaft 80 via brackets 17 at both ends thereof, whereby the rear wheel 2 attached to the flexible drive shaft 80 is supported. Support.
The center pipe 14 is inserted and supported with a slight margin in a support hole 4b formed in the rear end panel 4a of the vehicle body frame 4 at the front end thereof, thereby allowing the main pipe 13 to swing. The rotation of the mount frame by the driving force (so-called windup) is restricted. Note that a rubber ring bush 4c is provided in the support hole 4b, and wear and resistance due to a twist between the center pipe 14 and the support hole 4b are suppressed.
[0015]
The trailing arm 12 is attached via a pivot pin 20 to a bracket 19 attached to the vehicle body frame 4 at the base end thereof, and can swing up and down around the pivot pin 20. Further, the trailing arm 12 is attached to the bracket 17 at the tip thereof via a mounting pin 21 and a rubber bushing 22, and swings and displaces around the pin 21 with the axle block 18 (main pipe 13). And the torsional displacement by the bending of the rubber bush 22 is permitted.
[0016]
Between each trailing arm 12 and the vehicle body frame 4, a suspension unit 25 in which a suspension spring and a shock absorber are assembled is provided. These suspension units 25 are connected to a bracket 26 attached to the vehicle body frame 4 and the trailing arm. 12 is pivotally attached to a bracket 27 attached to 12.
That is, the swing frame 10 swings up and down around the pivot pin 20 together with the rear wheel 2 as the vehicle travels, and the left and right rear frames are caused by the bending of the rubber bush 22 and the rotation around the axis of the center pipe 14. It operates so that a height difference may occur between the wheels 2.
[0017]
As shown in detail in FIG. 7, the power unit 40 is rubber-mounted at three points on the swing frame 10. That is, brackets 29 are attached to the center pipe 14 and the sub-pipe 15, rubber plugs 30 are attached to the brackets 29, front end portions (engine parts) of the power units 40 are attached to the rubber plugs 30, and brackets 31 are attached to the main pipe 13. The rubber plug 32 is attached to the bracket 31, the rear end portion (differential mechanism 45 portion) of the power unit 40 is attached to the rubber plug 32, and the power unit 40 is elastically supported on the swing frame 10 at three points.
[0018]
Therefore, the swing frame 10 swings with the power unit 40 to suspend the rear wheel 2. The power unit 40 is elastically supported by the main frame 11 via the rubber plugs 30 and 32, and the drive shaft 80 connecting the power unit 40 and the rear wheel 2 is flexible, so that the power unit is supported floating. Furthermore, since the main frame 11 is elastically supported by the vehicle body 4 via the rubber ring bush 4c and the rubber bush 22, the engine vibration is prevented from being transmitted to the vehicle body 4.
[0019]
FIG. 8 shows a detailed structure of a flexible drive shaft 80 according to an example of the present invention.
The flexible drive shaft 80 has a generally bellows-shaped cylindrical shape and is rotatably supported by the bellows cylindrical shaft 81 on the output shaft 45f of the differential mechanism 45 of the power unit 40 and the axle block 18. The axle shaft 18a connected to the rear wheel 2 is connected.
Reference numeral 18b in the figure denotes a bearing that rotatably supports the axle shaft 18a on the axle block 18.
[0020]
That is, attachment brackets 81a are provided at both ends of the bellows-shaped cylindrical shaft 81, and one bracket 81a is attached to the attachment bracket 81b fitted to the differential mechanism output shaft 45f by the bolt 81c. The bracket 81a is attached to a mounting bracket 81b fitted to the axle shaft 18a by a bolt 81c, and connects the rear wheel 2 and the output shaft 45f of the differential mechanism.
Accordingly, since the drive shaft 80 has a bellows-like cylindrical shape, it has a simple and lightweight structure, and is strong against twisting around the shaft, so that the rotational force from the differential mechanism 45 is transmitted to the rear wheel 2. In addition, the power unit 40 can swing with respect to the axle block 18 (rear wheel 2), and the above-described vibration isolation by the floating support of the power unit 40 is realized.
[0021]
FIG. 9 shows a detailed structure of a flexible drive shaft 80 according to another example of the present invention.
The flexible drive shaft 80 has a generally double-structured cylindrical shape, and the axle shaft 18 a connected to the differential mechanism output shaft 45 f of the power unit 40 and the rear wheel 2 by such a double cylindrical shaft 82. And connected.
That is, the cylindrical shaft 82 includes an inner cylinder 82a fitted to the differential mechanism output shaft 45f, an inner cylinder 82b fitted to the axle shaft 18a, and an outer cylinder 83c that coaxially accommodates the inner cylinders 82a and 82b. And a rubber bush 82b in which the inner cylinders 82a and 82b and the outer cylinder 83c are connected to each other.
[0022]
Accordingly, since the drive shaft 80 has a double cylinder shape connected by rubber bushes, the drive shaft 80 has a simple and lightweight structure, and transmits the rotational force from the differential mechanism 45 to the rear wheel 2 by the deformation resistance of the rubber bush 82a. In addition, since the rubber bushing 82a can be flexibly deformed, the power unit 40 can be swung with respect to the axle block 18 (rear wheel 2), and the above-described vibration isolation by the floating support of the power unit 40 is realized.
Since a small vehicle has a relatively small transmission torque, it is easy to adopt such a simple and lightweight drive shaft 80 having a bellows tube shape or a double tube shape.
[0023]
Next, as shown in detail in FIGS. 10 and 11, the power unit 40 includes an engine 41, an AC generator 42, a belt-type continuously variable transmission 43, a mechanical two-speed automatic transmission 44 having a reverse gear, a differential The mechanism 45 is assembled integrally, and the power output from the engine 41 is shifted by the belt-type continuously variable transmission 43 and the mechanical two-speed automatic transmission 44, and this power is transferred from the differential mechanism 45 to the left and right rear. Each is transmitted to the flexible drive shaft 80 connected to the wheel 2 as described above.
[0024]
The engine 41 is a small displacement internal combustion engine (in this example, a single cylinder of about 50 cc), and the movement of the piston 47 due to combustion explosion is transmitted to the crankshaft 49 by the connection rod 48, and the engine power is transmitted by the rotation of the crankshaft 49. Output.
An AC generator 42 is connected to one end of the crankshaft 49, and electric power necessary for driving the vehicle is generated by the rotational power of the engine.
[0025]
A drive pulley 50 of a belt type continuously variable transmission 43 is attached to the other end of the crankshaft 49, and a cylindrical first sub-transfer is provided on a first transfer shaft 51 that is supported in parallel with the crankshaft 49. A shaft 51a is rotatably provided coaxially, and a driven pulley 52 is attached to the first sub-transfer shaft 51a. The drive pulley 50 and the driven pulley 51 are wound around an annular belt 53 having a substantially V-shaped cross section. Are connected.
The drive pulley 50 has a fixed plate 50a fixed to the crankshaft 49, and a movable plate 50b that is fitted to the crankshaft 49 with an axial groove and is rotated along with it, but is movable in the axial direction. Further, a holding plate 50c fixed to the crankshaft 49 is provided behind the movable plate 50b, and a centrifugal roller 50d is provided between the movable plate 50b and the holding plate 50c.
[0026]
On the other hand, the driven pulley 52 and a fixed plate 52a fixed to the first sub-transfer shaft 51a and a movable plate provided so as to be able to move in the axial direction while being fitted to the first sub-transfer shaft 51 by a shaft groove. Further, the movable plate 52b is urged toward the fixed plate 52a by a return spring 52c provided on the back surface of the movable plate 52b.
Therefore, when the engine speed (crankshaft speed) is small, the distance between the movable plate 52b and the fixed plate 52a is narrowed by the return spring 52c, and the belt-wrapping diameter of the driven pulley 52 is increased. The distance between the fixed plate 50a and the movable plate 50b is widened by the tension, and the belt winding diameter of the drive pulley 50 is reduced, and the belt transmission reduction ratio from the drive pulley 50 to the driven pulley 51 is increased.
[0027]
As the engine speed increases, the centrifugal roller 50d moves radially outward by centrifugal force and presses the movable plate 50b from behind, and the distance between the movable plate 50b and the fixed plate 50a is reduced, so that the drive pulley The belt wrapping diameter of 50 is increased, the tension of the belt 53 thereby increases the distance between the movable plate 52b and the fixed plate 52a against the return spring 52c, and the belt wrapping diameter of the driven pulley 52 is decreased. The belt transmission reduction ratio from the pulley 50 to the driven pulley 51 is reduced.
That is, according to the belt-type continuously variable transmission 43, the reduction ratio gradually decreases as the engine speed increases, and the rotation speed of the first sub-transfer shaft 51a increases.
[0028]
A shoe plate 54 is fixed to the tip of the first sub-transfer shaft 51a, and a drum 55 is fixed to the tip of the first transfer shaft 51. A centrifugal shoe 56 is movable outwardly on the shoe plate 54. Thus, a centrifugal start clutch 57 is configured between the first transfer shaft 51 and the first sub-transfer shaft 51a.
That is, when the rotational speed of the first sub-transfer shaft 51a is small as in engine idling, the centrifugal shoe 56 is not pressed against the inner peripheral surface of the drum 55, and the rotational power of the first sub-transfer shaft 51a is As the engine speed increases, the centrifugal shoe 56 moves radially outward due to the centrifugal force and presses against the inner peripheral surface of the drum 55, so that the first transfer shaft 51 is moved to the first transfer shaft 51. The engine is connected to the first sub-transfer shaft 51 a and rotated, and engine power is input from the first transfer shaft 51 to the automatic transmission 44.
[0029]
Here, the case structure of the power unit 40 will be described. A space for accommodating the belt-type continuously variable transmission 43 and a space for accommodating the mechanical automatic transmission 44 and the differential mechanism 45 in the main case 58 attached to the engine block with bolts 58a. Are covered with a cover case 59 attached with a bolt 59a, and a space containing the mechanical automatic transmission 44 and the differential mechanism 45 is bolted. The power train mechanism extending from the engine 41 to the differential mechanism 45 is housed in an integral case, which is covered with a cover case 60 attached at 60a.
[0030]
The first transfer shaft 51 passes through the partition wall portion 58b and is rotatably supported by the bearing 58c. Further, the first transfer shaft 51 is rotatably supported by the cover case 60 by the bearing 60b at the tip thereof. The bearing 58c is provided with a seal 58d for preventing the lubricating oil from entering the wet environment space into the dry environment space.
A gear portion 51 is formed in a portion near the bearing 60b of the first transfer shaft 51, and a cylindrical second sub-transfer shaft 51c is coaxially fixed to a portion near the bearing 58c. A cylindrical third sub-transfer shaft 51d is coaxially and rotatably provided between the transfer shaft 51c. That is, when the first transfer shaft 51 rotates, the second sub-transfer shaft 51c always rotates together, but the third sub-transfer shaft 51d can rotate relative to each other without such rotation.
[0031]
A shoe plate 61 is fixed to the second sub-transfer shaft 51c, a drum 62 is fixed to the third sub-transfer shaft 51d, and a centrifugal shoe 63 is movably provided on the shoe plate 61. Thus, a centrifugal transmission clutch 64 is formed between the second sub-transfer shaft 51c and the third sub-transfer shaft 51d.
That is, in a state where the engine speed is relatively small and the first transfer shaft 51 is small, the centrifugal shoe 63 is not in pressure contact with the inner peripheral surface of the drum 62, and the rotational power of the first transfer shaft 51 is third. The second sub-transfer shaft 51c rotates to transmit the engine power without being transmitted to the sub-transfer shaft 51d. On the other hand, when the engine rotation speed further increases and the rotation speed of the first transfer shaft 51 (that is, the second sub-transfer shaft 51c) increases, the centrifugal shoe 63 moves radially outward due to the centrifugal force, and the inside of the drum 62 is increased. The third sub-transfer shaft 51d is connected to the second sub-transfer shaft 51c and rotated while being in pressure contact with the circumferential surface, and engine power is transmitted by the third sub-transfer shaft 51d.
[0032]
A gear portion 51e is formed on the third sub-transfer shaft 51d, and a high-speed gear 65a for shifting is always engaged. Further, the gear portion 51 of the first transfer shaft 51 is always meshed with a low speed gear 65b for speed change, and the high speed gear 65a is set to have a reduction ratio smaller than that of the low speed gear 65b.
In the wet environment space of the case, a second transfer shaft 66 is provided in parallel with the first transfer shaft 51, and the second transfer shaft 66 is interposed between the main case 58 and the case cover 60 via bearings at both ends. It is supported rotatably. The high speed gear 65a is coaxially fixed to the second transfer shaft 66, and the low speed gear 65b is coaxially provided on the high speed gear 65a via a one-way clutch bearing 65c.
[0033]
The one-way clutch bearing 65c allows only the overtaking rotation of the low speed gear 65b by the high speed gear 65a. If the low speed gear 65b rotates, the high speed gear 65a is rotated, but the high speed gear 65b does not rotate. 65a can be rotated.
Therefore, in a state where the engine speed is relatively small and the centrifugal transmission clutch 64 is not connected, the engine power rotates the low speed gear 65b meshed with the gear portion 51b of the first transfer shaft 51 and is rotated by the one-way clutch bearing 65c. The second transfer shaft 66 is rotated via the high speed gear 65a.
[0034]
On the other hand, when the engine speed is further increased and the centrifugal transmission clutch 64 is connected, the engine power rotates the third sub-transfer shaft 51d and the high-speed gear 65a engaged with the gear portion 51e to rotate the second transfer shaft. 66 is rotated directly. In this case, the low-speed gear 65b also rotates in the same manner as described above, but the high-speed gear 65a overtakes the high-speed rotation by the one-way clutch bearing 65c.
That is, when the centrifugal transmission clutch 64 is not connected, the engine power is transmitted with the reduction ratio by the low speed gear 65b, and when the centrifugal transmission clutch 64 is connected, the engine power is transmitted with the reduction ratio by the high speed gear 65a. The automatic transmission can be realized by a simple and compact configuration in which the centrifugal transmission clutch 64 having a simple and compact configuration and two transmission gears 65a and 65b are arranged coaxially via a one-way clutch bearing 65c. ing.
[0035]
A gear shaft 67 having a gear formed on the outer periphery is provided on the second transfer shaft 66 so as to be rotatable and axially movable. A claw portion 67 a is provided at an end of the gear shaft 67. . An engagement side 66 is fixed to the second transfer shaft 66 so as to face the claw portion 67a, and the claw portion 67a meshes with the engagement piece 66 at the time of normal advance shown by a solid line in FIG. The shaft 67 rotates with the second transfer shaft 66.
The second transfer shaft 66 is provided with a reverse gear 68 between the gear shaft 67 and the low speed gear 65b, and the reverse gear 68 is rotatable on the second transfer shaft 66 via a bearing. . As shown in detail in FIG. 9, the reverse gear 68 is always connected to the gear portion 51b of the first transfer shaft via a reverse idler gear 68a rotatably supported by a case cover 60 via a bearing. When the first transfer shaft 51 rotates, it rotates in the opposite direction to the high speed gear 65a and the low speed gear 65b.
[0036]
The gear shaft 67 is formed with a circumferential groove 67c, and the shift fork 69 is engaged with the rotation of the gear shaft 67. Further, the gear shaft 67 and the reverse gear 68 have mutually opposing surfaces. Claw portions 67b and 68b are respectively provided. Further, a shift drum 70 is provided between the main case 58 and the case cover 60 so that both ends of the shift drum 70 are rotatably supported. The shift drum 70 protrudes outside the case via a lever (not shown). It is connected to the select lever 8 on the driver side.
[0037]
Therefore, when the driver operates the select lever 8 to the reverse position, the shift drum 70 is rotated, the gear shaft 67 is moved to the reverse gear 68 side by the shift fork 69, and the claw portions 67b and 68b are engaged with each other. The engagement between the portion 67 a and the engagement piece 66 can be released, and the gear shaft 67 can be rotated in the opposite direction to the second transfer shaft 66 by the reverse gear 68. That is, the simple and compact reverse mechanism that uses the gear shaft 67 for both forward and reverse movements cuts off the rotational power in the forward direction from the second transfer shaft 66, and the reverse direction from the reverse gear 68. The gear shaft 67 can be rotated by the rotational power to.
[0038]
As described above, the gear shaft 67 is rotated forward by any one of the forward gears 65a and 65b selected by the centrifugal transmission clutch 64, and is rotated backward by the reverse gear 68 by the driver's select lever operation. 67, the ring gear 45a of the differential mechanism 45 is always meshed.
The differential mechanism 45 rotatably supports a case 45b to which a ring gear 45a is attached and fixed by a bearing 45c between a main case 58 and a case cover 60, and a pair of umbrella-shaped pinions 45d and a pair of pins 45d in the case 45b. The umbrella-shaped side gear 45e meshes with each other and is rotatably provided. A pair of output shafts 45f attached to the side gear 45e are connected to the left and right drive shafts 80, respectively. Therefore, rotation of the gear shaft 67 transmitted through the ring gear 45a in the forward or backward direction causes the case 45b to rotate, thereby causing both side gears 45e to rotate differentially via the pinion 45d, and to the drive shaft 80. The connected left and right rear wheels 2 are driven.
[0039]
Here, as described above, in the power unit 40, the crankshaft 49 of the engine, the first transfer shaft 51, the second transfer shaft 66, and the output shaft 45f of the differential mechanism are arranged in parallel to each other. The transmission belt 53 of the transmission and the transfer shafts 51 and 66 of the mechanical transmission form a substantially U-shaped arrangement, and the engine 41 is arranged substantially flush with the differential mechanism 45 arranged substantially in the middle of the left and right rear wheels 2. This is the structure.
Therefore, since the engine 41 and the differential mechanism 45, both of which are relatively heavy, are arranged side by side on the substantially center line of the swing frame 10, the swing balance of the swing frame 10 is good.
[0040]
The case cover 60 is provided with an oil pump 71 for pumping the lubricating oil to the bearing portion of the mechanical automatic transmission 44 and the centrifugal gear clutch 64 that is oil-lubricated. The oil pump 71 is connected to the second transfer. It is connected to the shaft 66 and driven.
Accordingly, the oil is supplied to the gears of the differential mechanism 45 and the mechanical automatic transmission 44 by the springing up by the ring gear 45a, and the oil pump 71 pumps up the lubricating oil from the bottom of the wet environment space, and the case cover 60 The bearings of the mechanical automatic transmission 44 and the centrifugal transmission clutch 64 are lubricated through the oil passage 60c formed in the first passage, the oil passage 51f formed in the first transfer shaft, the oil passage 66b formed in the second transfer shaft, and the like. Supplying oil.
[0041]
Note that, at the upper part of the power unit 40, the joint portion of the main case 58 and the cover case 60 on the substantially vertical surface is formed with a plurality of recesses 72a and 72b, respectively, so that the main case 58 and the cover case 60 are joined. As a result, a plurality of cavities are formed by the recesses 72a and 72b. Further, since the edges of the recesses 72a and 72b are alternately cut out, the plurality of vacant spaces are communicated with each other by a zigzag path 72c. Further, the lowermost portion of the multi-stage cavities communicates with a wet environment space in which the mechanical automatic transmission 44 and the differential mechanism 45 are accommodated by a through hole 72d, and the uppermost portion of the multi-stage cavities is externally formed by a through hole 72e. The oil component is separated from the oil mist gas by the oil breather passage and is recirculated into the wet environment space, and the remaining clean gas is discharged to the outside.
[0042]
According to the power transmission device for a small vehicle having the above-described configuration, when the engine 41 is started and the idling operation state is established, the centrifugal start clutch 57 is disconnected and the engine power is not transmitted to the drive wheels 2.
When the engine speed increases, the centrifugal start clutch 57 is engaged, and the engine power transmitted to the belt 53 via the belt 53 is decelerated by the low speed gear 65b and transmitted to the differential mechanism 45, whereby the rear wheel 2 is Driven and rotated.
Then, when the engine speed further increases and the rotation speed of the first transfer shaft 51 increases, the centrifugal transmission clutch 64 is engaged, and the engine power is transmitted to the differential mechanism 45 by the high speed gear 65a and the rear wheel 2 Is automatically rotated such that the motor is driven and rotated.
[0043]
【The invention's effect】
As described above, according to the present invention, the differential output shaft and the drive wheel are connected with the flexible drive shaft having a light weight and a simple structure while elastically supporting the power unit. A small vehicle excellent in vibration isolation can be realized, and a swing type suspension mechanism suitable for such a small vehicle can be realized.
[Brief description of the drawings]
FIG. 1 is a perspective view of a small vehicle according to an embodiment of the present invention viewed from the front side.
FIG. 2 is a perspective view seen from the back side of the small vehicle according to the embodiment of the present invention.
FIG. 3 is a perspective view in plan view of a small vehicle according to an embodiment of the present invention.
FIG. 4 is a side perspective view of the small vehicle according to the embodiment of the present invention.
FIG. 5 is a plan view showing a swing frame structure of a small vehicle according to an embodiment of the present invention.
FIG. 6 is a side view showing a swing frame structure of a small vehicle according to an embodiment of the present invention.
FIG. 7 is a side view showing a mount portion of a power unit of a small vehicle according to an embodiment of the present invention.
FIG. 8 is a cross-sectional view showing an example of a flexible drive shaft according to the present invention.
FIG. 9 is a cross-sectional view showing another example of a flexible drive shaft according to the present invention.
FIG. 10 is a cross-sectional plan view of a power unit of a small vehicle according to an embodiment of the present invention.
FIG. 11 is a plan view showing a part of a power unit of a small vehicle according to an embodiment of the present invention with a different cross section.
[Explanation of symbols]
2: rear wheel (drive wheel), 10: swing frame (mount frame),
41: Engine, 45: Differential mechanism,
45f: differential mechanism output shaft, 80: drive shaft,
81: bellows cylindrical shaft, 82: double cylindrical shaft,

Claims (4)

In a power transmission device comprising a power unit in which an engine and a differential mechanism are integrally assembled , supporting a rear wheel on a mounting frame elastically supported swingably on a vehicle body, and elastically supporting the power unit on the mounting frame ,
Wherein the output shaft and the rear wheel differential mechanism, the power transmission system for a small vehicle, characterized in that reset connection were by the flexible drive shaft structure linked via an elastic body. The power transmission device for a small vehicle according to claim 1,
The drive shaft has an inner cylinder fitted to the output shaft of the differential mechanism, an inner cylinder fitted to an axle shaft connected to the rear wheel, and an outer cylinder that coaxially accommodates the inner cylinders. A power transmission device for a small vehicle, characterized in that the inner cylinder and the outer cylinder are connected by an elastic body. The power transmission device for a small vehicle according to claim 2,
The drive shaft has a double cylinder shape in which the inner cylinder and the outer cylinder are connected by rubber bushes. The power transmission device for a small vehicle according to any one of claims 1 to 3,
The mounting frame has a main frame connecting a main pipe extending in the vehicle width direction and a center pipe extending in the vehicle length direction from the center of the main pipe,
Axle blocks that rotatably support the drive shaft are attached to both ends of the main pipe,
The power unit is elastically supported on the main frame,
The mounting frame is elastically supported to be swingable at the rear end of the vehicle body frame at the front end of the center pipe,
Further, the mounting frame has a trailing arm swingably attached to a vehicle body frame, and the axle block is elastically supported by the trailing arm. Power transmission device.

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