JP2008155671A - Automatic two- or three-wheeler - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an automatic two- or three-wheeler capable of ensuring a foot space of a rear part occupant and making weight balance of front and rear sides of a vehicle body sufficient. <P>SOLUTION: A seat comprises a front side seat 4 for a driver; and a rear seat 5 for a tandem rider arranged spaced at a rear side from the front side seat 4. At least a front part (engine body) 15 of an engine unit 3 is positioned between left and right leg placement parts 34, 34 for the driver. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a motorcycle and a tricycle including a body frame, an engine unit mounted on the body frame, and a seat mounted on the body frame.

In this type of motorcycle or tricycle, the rear seat for the tandem rider may be disposed away from the front seat for the driver in the rear of the vehicle in order to improve the ease of getting on and off the tandem rider. For example, Patent Document 1 discloses a structure in which a foot space is provided between the front and rear struts by disposing the front strut supporting the front seat, the rear seat on the body frame, and the rear strut apart in the front-rear direction. Has been proposed.
JP-A-4-35879

  By the way, the conventional motorcycles and tricycles employ a structure in which the entire engine unit is disposed below the rear seat. For this reason, the engine body, the intake system, the exhaust system, the rear wheel drive system, and the like constituting the engine unit are concentrated from the periphery of the tandem rider's feet to the lower side of the rear seat. In addition, since the rear seat is arranged away from the front seat to the rear of the vehicle, the boarding position of the tandem rider is also closer to the rear than the normal one. As a result, there is a problem that the weight concentrates on the rear part of the vehicle and the weight balance between the front and rear of the vehicle body deteriorates.

  The present invention has been made in view of the above-described conventional situation, and adopts a configuration in which the rear seat for the tandem rider is arranged away from the front seat for the driver at the rear of the vehicle, and the weight balance between the front and rear of the vehicle body is achieved. The challenge is to provide motorcycles and tricycles that can be improved.

  The present invention is a motorcycle or tricycle comprising a body frame, an engine unit mounted on the body frame, and a seat mounted on the body frame, wherein the seat includes a front seat for a driver, A rear seat for a tandem rider that is disposed rearwardly from the front seat, and the engine unit is positioned at least between the left and right footrest portions for the driver. It is mounted on the vehicle body frame.

  Here, the engine unit includes an engine main body having a cylinder block, a cylinder head, and a crankcase, and an intake system component connected to the engine main body. The front part of the engine unit is the cylinder block or the cylinder head. Or it further means intake system parts.

  According to the motorcycle and the tricycle according to the present invention, the rear seat is disposed rearward from the front seat, and the engine unit is disposed at least between the left and right footrest portions for the driver at the front portion. Since it is mounted so as to be positioned, the components of the engine unit can be distributed and arranged between the front seat and the rear seat from below the front seat, and the entire engine unit is mounted below the rear seat. The weight balance before and after the vehicle body can be improved compared to the vehicle.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

  FIG. 1 is a view for explaining a motorcycle according to a first embodiment of the present invention. In the present embodiment, front and rear and left and right mean front and rear and left and right when viewed in a seated state.

  In the figure, reference numeral 1 denotes a motorcycle, which includes a body frame 2, an engine unit 3 mounted in a fixed state on the body frame 2, a driver's front seat 4 mounted on the body frame 2, A rear seat 5 for a tandem rider, which is disposed at a predetermined distance from the front seat 4 at the rear of the vehicle.

  The vehicle body frame 2 is formed integrally with a main frame 8 made of a steel pipe extending from the head pipe 7 that supports the front fork 6 so as to be steerable to the left and right, and the main frame 8. And a rear frame 9 extending in the direction.

  The main frame 8 has an inclined portion 8a extending obliquely downward from the head pipe 7 toward the rear of the vehicle, and an inclined extending portion 8b extending obliquely downward and rearward after the inclined portion 8a.

  The rear frame 9 has an upright portion 9a that extends upward from the rear end of the inclined extension portion 8b, and a horizontal portion 9b that extends substantially horizontally from the upright portion 9a to the rear of the vehicle.

  A front wheel 10 is pivotally supported at the lower end portion of the front fork 6, and a steering handle 11 is fixed to the upper end portion. A battery 12 is disposed on the front side of the head pipe 7 via a bracket 7a.

  The engine unit 3 includes an engine body 15, an intake system 16, an exhaust system 17, and an engine power transmission system 18.

  The engine main body 15 is an air-cooled four-cycle engine, and is suspended and supported below the main frame 8 via front and rear suspension brackets 13 and 14.

  The engine body 15 is mounted with the cylinder axis a facing in the vehicle front-rear direction and substantially horizontally. A cylinder head 15b and a head cover 15c are coupled to the front mating surface of the cylinder block 15a. The crankcase 15d is coupled to the surface.

  A crankshaft 15e is accommodated in the crankcase 15d in the vehicle width direction. A transmission mechanism (not shown) is accommodated on the rear side of the crankshaft 15e in the crankcase 15d, and an output shaft 15f for taking out engine power of the transmission mechanism is outward from the left side wall of the crankcase 15d. It protrudes.

  The engine power transmission system 18 is disposed on the left side in the vehicle width direction, and has a shaft case 18a whose front end is supported by the crankcase 15d so as to be able to swing up and down, and a drive shaft housed in the shaft case 18a ( (Not shown). The front end of the drive shaft is connected to the output shaft 15f, and the rear wheel 19 is connected to the rear end.

  A rear cushion 20 is disposed between the rear end portion of the shaft case 18 a and the horizontal portion 9 b of the rear frame 9. The rear cushion 20 is disposed on the front side of a vertical line passing through the center of the rotating shaft 19 b of the rear wheel 19.

  The intake system 16 is connected to the front side of the connecting portion (intake port) of the cylinder head 15b, and extends forward and upward therefrom. Specifically, the intake system 16 is connected to the upper side wall of the cylinder head 15b, and is connected to an intake pipe 16a that extends upward from the upper side wall and bends further forward, and an upstream end opening of the intake pipe 16a. A throttle body 16b, and an air cleaner 16c connected to the throttle body 16b. The air cleaner 16 c is disposed above the throttle body 16 b and below the front end of the inclined portion 8 a of the main frame 8.

  The exhaust system 17 is connected to the lower wall of the cylinder head 15b, and is connected to an exhaust pipe 17a disposed so as to extend rearward from the lower wall to the lower side of the engine body 15, and to a downstream end of the exhaust pipe 17a. And a muffler 17b disposed on the right side of the rear wheel 19 in the vehicle width direction.

  When viewed from the side of the vehicle, the upper edge 15c 'of the head cover 15c positioned at the highest position of the engine body 15 is positioned lower than the straight line b connecting the upper edges 10a, 19a of the front wheel 10 and the rear wheel 19. It is so mounted. In the motorcycle 1 of the present embodiment, the front wheels 10 and the rear wheels 19 have larger wheel diameters than general wheels employed in scooter type motorcycles.

  The front seat 4 is disposed above the inclined portion 8a of the main frame 8, and is mounted on a steel pipe seat support member 24a fixed to the inclined portion 8a. The seat support member 24 protrudes outward in the vehicle width direction from the inclined portion 8a, and extends rearward and obliquely upward, and the upper ends of the left and right support portions 24a are connected to each other in the vehicle width direction. And a lateral support portion 24b coupled to the.

  The front seat 4 has a structure in which a cushion 4b is disposed on a bottom plate 4a and covered with a skin, and a rear end portion of the bottom plate 4a is supported by the lateral support portion 24b via a seat hinge 4c so as to be vertically rotatable. Has been. Further, a loading hook 24c is attached to the lateral support portion 24b, and below the loading hook 24c is a loadable space as will be described later.

  A fuel tank 25 is mounted on the inclined portion 8 a of the main frame 8. The fuel tank 25 is disposed in a seat support member 24 below the front seat 4 and is covered from above by the front seat 4.

  A storage box 26 opening upward is disposed on the front side of the fuel tank 25. A lid member 27 that extends forward from the seat 4 and covers the opening of the storage box 26 so as to be openable and closable is fixed to the bottom plate 4 a of the front seat 4. The lid member 27 can be locked by a lock member 28 disposed at the front edge of the storage box 26. By releasing the lock and rotating the front seat 4 upward about the rear end, the inside of the storage box 26 and the fuel inlet of the fuel tank 25 are exposed to the outside, and small items to the storage box 26 are exposed. The fuel can be taken in and out and the fuel can be injected into the fuel tank 25.

  The rear seat 5 is disposed on the horizontal portion 9b of the rear frame 9, and is directly mounted on the horizontal portion 9b via a sheet metal seat stay 30 fixed to the horizontal portion 9b. The rear sheet 5 is disposed so as to be substantially the same height as the front sheet 4. Specifically, the height position of the horizontal portion 9 b of the rear frame 9 is set to be substantially the same height as the bottom surface of the front seat 4. The seat stay 30 has a rectangular U-shape extending outward from the horizontal portion 9b in the vehicle width direction.

  A substantially U-shaped grab bar 31 is fixed to the horizontal portion 9b in a plan view extending from the left and right side surfaces of the rear seat 5 so as to surround the rear surface. A backrest 32 that supports the waist of the tandem rider is attached to the grab bar 31.

  Below the front seat 4, left and right footrests 34, 34 for the driver are arranged. The left and right footrests 34 are fixed to the left and right side walls of the crankcase 15d of the engine body 15 via foot brackets (not shown), and stick-like footrests 34a projecting outward from the vehicle width direction therefrom. And a footrest member 34b made of an elastic member disposed on the footrest 34a.

  Thus, in the engine unit 3, the engine body 15, which is a component of the engine unit 3, is positioned between the left and right footrest portions 34, 34, and the intake system 16 is left and right footrest portions 34, 34. 34 is located in front of. The engine power transmission system 18 is located between the left and right footrests 34 and 34 so as to extend rearward from above, and the exhaust system 17 includes the left and right footrests 34 and 34. 34 and is located so as to extend rearwardly from below.

  Tandem rider left and right footrest portions 35, 35 are disposed at a boundary portion 2 a between the inclined extension portion 8 b of the main frame 8 and the standing portion 9 a of the rear frame 9.

  The left and right footrest portions 35 are located higher than the left and right footrest portions 34 for the driver, and are disposed on the foot bracket 35a and a foot bracket 35a fixed to the boundary portion 2a. And a foot board 35b made of an elastic member. The left and right foot boards 35b are rectangular plates extending in the front-rear direction, and are sized so that the entire feet of the tandem rider can be placed thereon.

  The left and right footrest portions 35 are located behind the engine body 15 of the engine unit 3, above the shaft case 18 a and the muffler 17 b, and lower than the highest portion (intake system) of the engine unit 3. Are arranged as follows.

  Here, the lower side of the front seat 4 and the rear seat 5 of the vehicle body frame 2 and the left and right sides of the engine unit 3 are not shown, but are covered with a vehicle body cover, and the front side of the vehicle body cover, A space between the rear seats 4 and 5 is a boarding / alighting space c. The space c is recessed downward from the lower end of the rear seat 5 and penetrates in the vehicle width direction. The space c is located lower than a downward recess c ′ formed in front of the front seat 4.

  According to the present embodiment, the rear seat 5 is disposed rearwardly from the front seat 4 and the engine unit 3 includes the left and right footrest portions 34 for the driver whose front portion of the engine body 15 is for the driver. , 34 so that the engine body 15 and the intake system 16 that are components of the engine unit 3 are dispersed below the front seat 4 and between the front seat 4 and the rear seat 5. Can be arranged. Thereby, the foot space of a tandem rider can be ensured widely and the loadability of a load can be improved with ease of getting on and off.

  Further, since the front portion of the engine unit 3 is disposed below the front seat 4, when viewed as a whole of the engine unit 3, the components can be disposed dispersed in the vehicle body frame 2 in the front-rear direction, and below the rear seat. Compared with the centralized installation of engine units, the weight balance between the front and rear of the vehicle body can be improved, and the steering stability can be improved.

  In the present embodiment, the main frame 8 of the vehicle body frame 2 is disposed so as to extend rearwardly above the engine unit 3. In other words, since the engine unit 3 is mounted below the main frame 8, the center of gravity of the vehicle body is lowered. From this point, the steering stability can be improved.

  In the present embodiment, since the front seat 4 is mounted on a highly rigid portion called the inclined portion 8a of the main frame 8, the support rigidity of the front seat 4 can be ensured.

  The inclined portion 8a of the main frame 8 is provided with the inclined extension portion 8b extending further rearward than the mounting portion of the front seat 4, so that the tandem rider having a low ground height between the front and rear seats 4 and 5 is used. A boarding / alighting space c can be formed.

  In the present embodiment, since the front seat 4 is mounted on the inclined portion 8a of the main frame 8 via the seat support member 24 extending upward, it is formed between the lower side of the front seat 4 and the inclined portion 8a. The fuel tank 25 can be arranged using the space effectively.

  Further, the storage box 26 can be arranged by effectively using the space formed between the front side of the front seat 4 and the inclined portion 8a.

  In the present embodiment, the vehicle body frame 2 has a rear frame 9 extending obliquely upward rearward of the vehicle following the main frame 8, and the rear seat 5 is mounted on the rear frame 9, so that the rear seat 5 Can be supported by the rear frame 9 having high strength. Specifically, it is assumed that the main frame 8 has an upright portion 9a that rises upward from the inclined extension portion 8b and a horizontal portion 9a that extends horizontally, and the rear seat 5 is directly mounted on the horizontal portion 9a. The rear sheet 5 can be supported without employing a special reinforcing structure.

  In this embodiment, when viewed from the side of the vehicle, the left and right footrest portions 35, 35 for the tandem rider are disposed above the engine unit 3, so that the footrest portions are located on the left and right sides of the engine unit. Compared with the case where it arrange | positions, the heat from the engine unit 3 is hard to be transmitted to a tandem rider, and it can improve riding comfort and comfort.

  Since the intake system 16 of the engine unit 3 is disposed between the left and right footrest portions 34, 34 for the driver and located in front, the space in front of the engine body 15 is effectively used. The intake system can be arranged, and the influence of heat from the engine body 15 can be avoided.

  The engine body 15 is mounted so that the cylinder axis a is substantially horizontal, and the upper edge 15c 'of the head cover 15c located at the highest position of the engine body 15 is connected to the upper edges 10a, 19a of the front wheel 10 and the rear wheel 19. Since the center of gravity of the vehicle body can be lowered, and the heat from the engine body 15 and the exhaust system 17 can be suppressed from reaching the occupant.

  Further, since the wheel diameters of the front wheel 10 and the rear wheel 19 are increased, the running stability can be improved.

  Here, in the present embodiment, the upper edge 10a of the front wheel 10 and the upper edge 19a of the rear wheel 19 have the same height, that is, the same wheel diameter. However, in the present invention, the wheel diameters of the front wheel and the rear wheel are different. In this case, for example, the present invention can be applied to the case where the wheel diameter of the rear wheel is smaller than the front wheel, or conversely, the case where the wheel diameter of the front wheel is smaller than the rear wheel. Even when the wheel diameters of the front and rear wheels are different, the engine body is mounted such that the upper edge of the engine body is lower than the line connecting the upper edges of the front and rear wheels. An effect is obtained. The present invention can also be applied to the case where the engine body is mounted such that the upper edge of the engine body is positioned at a lower position than the upper edge of the front or rear wheel.

  In the above embodiment, a motorcycle has been described as an example, but the present invention can also be applied to a motorcycle. In this case, two tandem riders can be realized by arranging the rear seats in parallel on the left and right, or arranging the bench-type rear seats.

  2 and 3 are views for explaining a motorcycle according to a second embodiment of the present invention. In the figure, the same reference numerals as those in FIG. 1 denote the same or corresponding parts.

  The motorcycle 1 of the present embodiment includes a body frame 2, an engine unit 40 mounted on the body frame 2 so as to be swingable up and down, a driver's front seat 4 mounted on the body frame 2, and the front side. And a rear seat 5 for a tandem rider disposed at a predetermined distance from the seat 4 at the rear of the vehicle.

  The vehicle body frame 2 has a main frame 8 and a rear frame 9 extending rearward thereto, and the basic structure thereof is substantially the same as that of the first embodiment. The different parts will be described.

  The engine unit 40 is a unit swing type four-cycle engine, and a transmission case 40c in which a belt-type continuously variable transmission mechanism 41 is accommodated is integrally connected to a crankcase 40b of an engine body 40a. The rear wheel 19 is supported on a shaft. A rear cushion 20 ′ disposed between the transmission case 40 c and the horizontal portion 9 b of the rear frame 9 is disposed substantially rearward from a vertical line passing through the rotation shaft 19 b of the rear wheel 19.

  The belt type continuously variable transmission mechanism 41 includes a drive pulley 41a attached to the crankshaft 15e, a driven pulley 41c attached to a driven shaft 41b connected to the rotating shaft 19b of the rear wheel 19 via an intermediate shaft 42, and Are connected by a V-belt 41d.

  A swing bracket 40d extending forward is formed at the front end of the crankcase 40b. The swing bracket 40d is fixed to the inclined portion 8a of the main frame 8, and is pivotally supported via a pivot shaft 38 by left and right suspension brackets 39, 39 extending downward from the inclined portion 8a. Thus, the engine body 40a is supported so as to be swingable up and down around the pivot shaft 38. The swing support portion of the engine body 40a may be provided on the upper side of the crankcase 40b.

  An intake system 16 extending forward is connected to the engine body 40a. The energizer 16c of the intake system 16 is disposed and fixed in front of the engine body 40a, and the air cleaner 16c and the throttle body 16b are connected via a bellows-like intake pipe 16d that absorbs the vertical movement of the engine body 40a. ing.

  A fuel tank 25 is mounted on the inclined portion 8 a of the main frame 8, and the front seat 4 is directly mounted on the fuel tank 25. A fuel inlet 25 a of the fuel tank 25 is disposed in front of the front seat 4. A control unit 44 is suspended and supported below the inclined portion 8a.

  The motorcycle 1 is surrounded by a vehicle body cover. The vehicle body cover mainly includes an engine unit including a handle cover 50 that surrounds the outer periphery of the steering handle 11, a front cover 51 that covers the front side of the front fork 6, and a fuel tank 25 and a main frame 8 from below the front seat 4. 3 It has left and right front side covers 52 and 52 that cover the left and right sides of the front part, and left and right rear side covers 53 that cover the left and right sides of the rear frame 9 from below the rear seat 5. . The vehicle body cover has a substantially similar structure in the motorcycle of the first embodiment.

  The left and right suspension brackets 39 extend downward to cover the air cleaner 16c, and the lower end of the suspension bracket 39 is located below the lower end of the air cleaner 16c.

  A foot bracket 55 is bolted and fixed to the lower ends of the left and right suspension brackets 39 so as to protrude outward in the vehicle width direction. The foot bracket 55 is U-shaped in a planar view having left and right foot portions 55a and 55a extending in the front-rear direction, and a front coupling portion 55b that joins the front end portions of the left and right foot portions 55a in the vehicle width direction. It is a shape. The battery 12 is mounted on the front connecting portion 55b.

  The left and right front side covers 52 are formed with stepped portions 52a for drivers extending in the front-rear direction so as to cover the upper sides of the left and right foot portions 55a. The intake system 16 of the engine unit 3 and the front part of the engine body 40a are located between the left and right footrests 52a.

  Left and right tandem brackets 57 and 57 are joined to the boundary portion 2 a of the vehicle body frame 2. The left and right tandem brackets 57 are fixed with bolts so that left and right foot brackets 56 and 56 extending in the front-rear direction protrude outward in the vehicle width direction. The left and right foot brackets 56 are disposed above the engine body 40a.

  The left and right rear side covers 53 are formed with a stepped portion 53a for a tandem rider extending in the front-rear direction so as to cover the upper side of the foot bracket 56 on the outside of the vehicle.

  According to the present embodiment, the unit swing type engine unit 40 is mounted so that the front portion thereof is positioned between the left and right footrest portions 52a and 52a for the driver. Can be distributed in the front-rear direction so as to extend from the lower side of the front seat 4 to the lower side of the rear seat 5, and a wide foot space of the tandem rider can be secured. Further, since the engine unit 40 is disposed in the vehicle body frame 2 in the front-rear direction, the weight balance between the front and rear of the vehicle body can be improved, and the same effect as in the first embodiment can be obtained.

  FIG. 4 is a view for explaining a motorcycle according to a third embodiment of the present invention. In the figure, the same reference numerals as those in FIGS. 1 and 2 denote the same or corresponding parts.

  The motorcycle 1 of the present embodiment includes a body frame 60, an engine unit 3 mounted in a fixed state on the body frame 60, a front seat 4 for a driver mounted on the body frame 60, and the front seat 4 And a rear seat 5 for a tandem rider arranged at a predetermined distance from the rear of the vehicle. The basic structure is substantially the same as in the first and second embodiments. The different parts will be described.

  The vehicle body frame 60 includes a main frame 61 and a rear frame 62 formed independently of the main frame 61. The main frame 61 and the rear frame 62 are part of the vehicle body frame. The engine body 15 is connected.

  Specifically, the inclined extension portion 61b of the main frame 61 and the upper wall portion of the crankcase 15d of the engine body 15 are bolted together by the main bracket 63, and the rising portion 62a of the rear frame 62 and the crank The rear wall portion of the case 15d is bolted and connected by a rear bracket 64.

  Above the inclined portion 61a of the main frame 61, left and right steel pipe sheet support members 65, 65 are arranged. The left and right seat support members 65 are fixed to the main bracket 63, extend rearward and obliquely upward from the main bracket 63, and substantially straight forward from the upper end of the rear inclination 65a. A straight portion 65b which is bent and extended and fixed to the head pipe 7. A control unit 44 is disposed on the front side of the head pipe 7 via a bracket 7a. Further, the battery 12 is arranged along the rear inclined portion 65a.

  A front seat 4 is mounted on a rear end portion of the left and right straight portions 65b via a seat bracket 66, and the front seat 4 is disposed so as to protrude rearward from the rear end of the seat support member 65. ing.

  A fuel tank 25 is mounted on the front side of the front seat 4 of the left and right straight portions 65b. The fuel tank 25 is disposed such that the lower half portion is located below the straight portion 65b and the upper half portion is located above the straight portion 65b.

  The left and right front side covers 52 are formed with stepped portions 52a for the driver extending in the front-rear direction in a stepped shape on the outer side of the vehicle. The engine body 15 is located between the left and right footrest portions 52a.

  Further, the left and right rear side covers 53 are formed with stepped portions 53a for tandem riders extending in the front-rear direction in a stepped shape on the vehicle outer side. The left and right footrest portions 53 a are disposed above the engine unit 3.

  According to the present embodiment, the engine unit 3 mounted in a fixed state on the main frame 61 is mounted so that the engine body 15 is positioned between the left and right footrest portions 52a and 52a for the driver. Therefore, the components of the engine unit 3 can be arranged in the front-rear direction so as to extend from the lower side of the front seat 4 to the lower side of the rear seat 5, and the foot space of the tandem rider can be secured widely. The weight balance before and after the vehicle body can be improved, and the same effect as in the first embodiment can be obtained.

1 is a side view for explaining a motorcycle according to a first embodiment of the present invention. FIG. 6 is a side view of a motorcycle according to a second embodiment of the present invention. Fig. 2 is a plan view of the motorcycle. FIG. 6 is a side view of a motorcycle according to a third embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Motorcycle 2,60 Body frame 3 Engine unit 4 Front seat for drivers 5 Rear seat for tandem riders 6 Front fork 7 Head pipe 8, 61 Main frame 8a, 61a Inclined portion 8b, 61b Inclined extension portion 9, 62 Rear frame 10 Front wheel 10a Upper edge 15, 40a Engine body 15c 'Upper edge of head cover (highest part of engine body)
15d, 40b Crankcase 16 Intake system 17 Exhaust system 18 Engine power transmission system 19 Rear wheel 19a Upper edge 25 Fuel tank 34, 52a Footrest portion 35, 53a Footrest portion for tandem rider 40 Unit swing type engine Unit a Cylinder axis b Straight line

Claims (20)

A motorcycle or tricycle comprising a body frame, an engine unit mounted on the body frame, and a seat mounted on the body frame,
The seat is composed of a front seat for a driver and a rear seat for a tandem rider arranged rearward from the front seat,
The motorcycle or tricycle, wherein the engine unit is mounted on the vehicle body frame so that at least a front portion thereof is positioned between the left and right footrest portions for the driver. The motorcycle according to claim 1, wherein a space is formed between the front seat and the rear seat so as to be recessed below the lower end of the rear seat and penetrate in the vehicle width direction. In Claim 1, between the front seat and the rear seat, a space is formed which is positioned lower than the concave portion formed downward in front of the front seat and penetrates in the vehicle width direction. Motorcycles and tricycles characterized by that. 2. The motorcycle or tricycle according to claim 1, wherein the body frame includes a main frame extending rearward of the vehicle above the engine unit. The motorcycle or tricycle according to claim 4, wherein the front seat is mounted on the main frame. 6. The automatic motorcycle according to claim 5, wherein the main frame has an inclined portion that extends obliquely downward from the head pipe supporting the front fork, and the front seat is mounted on the inclined portion. Tricycle. 7. The motorcycle or tricycle according to claim 6, wherein the inclined portion of the main frame has an inclined extension portion that extends further obliquely downward and rearward from the portion on which the front seat is mounted. 6. The motorcycle or tricycle according to claim 5, wherein a fuel tank is mounted on the main frame, and the front seat is mounted on the main frame via the fuel tank. The motorcycle or tricycle according to claim 4, wherein the body frame has a rear frame extending obliquely upward rearward of the vehicle following the main frame, and the rear seat is mounted on the rear frame. . The motorcycle or tricycle according to claim 1, wherein when viewed from the side of the vehicle, the left and right footrests for the tandem rider are disposed above the engine unit. 2. The motorcycle according to claim 1, wherein the left and right footrests for the tandem rider are disposed so as to be located behind the engine unit when viewed from the side of the vehicle. The left and right footrests for the tandem rider are arranged so as to be positioned lower than the highest part of the engine unit when viewed from the side of the vehicle. Motorcycles and tricycles. 2. The engine unit according to claim 1, wherein the engine unit includes an engine body and an intake system that is connected to the engine body and extends forward of the vehicle, and the intake system is disposed between the left and right footrest portions for the driver. Motorcycles and tricycles characterized by being located. 2. The motorcycle or tricycle according to claim 1, wherein the engine unit is mounted such that the highest portion of the engine unit is positioned at a lower position than the higher one of the upper edges of the front wheels and the rear wheels. 15. The motorcycle or tricycle according to claim 14, wherein the engine unit is mounted such that the highest portion thereof is positioned lower than a straight line connecting the upper edges of the front and rear wheels. 16. The motorcycle or tricycle according to claim 15, wherein the engine unit is mounted such that the highest part thereof is positioned lower than the upper edges of the front and rear wheels. 15. The motorcycle or tricycle according to claim 14, wherein the engine unit has an engine body mounted with a cylinder axis line oriented in the vehicle longitudinal direction and substantially horizontally. The motorcycle or tricycle according to claim 1, wherein the engine unit is mounted in a fixed state on the body frame. 2. The motorcycle or tricycle according to claim 1, wherein the engine unit is mounted on the body frame so as to be swingable up and down. A motorcycle or tricycle comprising a body frame, an engine unit mounted on the body frame, and a seat mounted on the body frame,
The seat is composed of a front seat for a driver and a rear seat for a tandem rider arranged rearward from the front seat,
Between the front seat portion and the rear seat portion, compared to a downward recess formed in front of the front seat, a space penetrating in the vehicle width direction is formed further downward. Motorcycles and tricycles to do.

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