Intake system structure of power unit

Abstract

 This intake system structure of a power unit (5), which is mounted to a vehicle (1), and in which an internal combustion engine (2) and a power transmission 3 are integrated with each other, an air cleaner (50) is provided at a position away from a cylinder part (44) of the internal combustion engine (2), a throttle body (52) is disposed at a position close to the cylinder part, and the air cleaner and the throttle body are connected to each other by a connecting tube (51), wherein a regulating member (54) around the axis of an intake passage (52a) regulates the throttle body (52) in a position in the rotating direction around the axis with respect to the cylinder part, the throttle body is assembled to the cylinder part through an inlet manifold (53) and supported integrally, and in the throttle body, a connecting cylindrical part (60) to the connecting tube is provided with a positioning part (61) for positioning the connecting tube in the rotating direction.

Description

[Technical Field]

[0001] The invention relates to an intake system structure of a power unit provided with an internal combustion engine, which is mounted to a vehicle, particularly to the small-sized vehicle.

[Background Art]

[0002] In an intake system of a power unit, which is mounted to a vehicle, particularly to the small-sized vehicle and constructed so that an internal combustion engine and a power transmission are integrated with each other in the past, as shown in the following patent literature 1, a throttle body is provided between the internal combustion engine and an air cleaner, and connected to the air cleaner by a connecting tube. In the downstream side end part of the connecting tube, the upstream side inlet part of the throttle body is fitted, and the periphery thereof is fastened using a tightening band to be fixed and supported.

[Patent Literature]

[0003] 

[Patent Literature 1] JP-A No. 2006-291777 (Fig. 2, Fig. 3)

[Summary of the Invention]

[Technical Problem]

[0004]  As shown the above patent literature 1, however, the power unit is configured so that the air cleaner is provided at a position away from the cylinder part of the internal combustion engine and the throttle body is disposed at a position close to the cylinder part, resulting in the disadvantage that since the connecting tube is generally a comparatively long member, the rotational position around a tube axis at the fastening part is liable to vary in fitting. When fastening is performed with variation in alignment in the rotating direction, there is the risk that shape distortion or the like is caused by the torsional stress.
In order to accurately perform such alignment, a complicated structure and troublesome connecting work are needed.

[0005] The invention has been made to address the above problem in an intake system of a power unit mounted to a vehicle in the past and provides an intake system structure of a power unit, which may improve the function of the intake system and the connecting workability in simple constitution while holding down the space.

[Solution to Problem]

[0006] In order to accomplish the above object, the invention described in claim 1 provides an intake system structure of a power unit, which is mounted to a vehicle, and constructed so that an internal combustion engine and a power transmission are integrated with each other, an air cleaner is provided at a position away from a cylinder part of the internal combustion engine, a throttle body is disposed at a position close to the cylinder part, and the air cleaner and the throttle body are connected to each other by a connecting tube, wherein a regulating member around the axis of an intake passage regulates the throttle body in a position in the rotating direction around the above axis with respect to the cylinder part, the throttle body is assembled to the cylinder part through an inlet manifold and supported integrally, and in the throttle body, a connecting cylindrical part to the connecting tube is provided with a positioning part for positioning the connecting tube in the rotating direction.

[0007] The invention described in claim 2 provides an intake system structure of a power unit according to claim 1, wherein the positioning part is disposed at a position to engage with an engagement part provided at the tube side connecting cylindrical part of the connecting tube in the throttle body.

[0008] The invention described in claim 3 provides an intake system structure of a power unit according to claim 2, wherein the positioning part is a boss part for an idle air screw provided on the throttle body.

[0009] The invention described in claim 4 provides an intake system structure of a power unit according to claim 3, wherein
the positioning part is provided off-centered to one side with respect to the axis of the intake passage, as viewed in the vertical direction.

[0010] The invention described in claim 5 provides an intake system structure of a power unit according to claim 3 or 4, wherein in the throttle body, the connecting cylindrical part to the connecting tube is formed off-centered to one side with respect to the axis of the intake passage, the tube side connecting cylindrical part of the connecting tube is formed off-centered similarly to the throttle body side with respect to the axis of the tube side intake passage in the connecting tube.

[0011] The invention described in claim 6 provides an intake system structure of a power unit according to claim 5, wherein the connecting tube includes a linear part for a predetermined distance on the upstream side from the tube side connecting cylindrical part.

[0012] The invention described in claim 7 provides an intake system structure of a power unit according to claim 6, wherein a cable guide part is projected on the outer surface of the linear part on the side where the tube side connecting cylindrical part is off-centered with respect to the axis of the tube side intake passage, and the cable guide part includes a recessed part where a cable is engaged.

[0013] The invention described in claim 8 provides an intake system structure of a power unit according to claim 7, wherein the cable is a throttle cable, which is folded back like a U-shape from a throttle drum fitted to the right or left shaft end of a throttle valve shaft provided on the throttle body oriented in the vehicle width direction, which penetrates to the outside of the throttle body on the connecting tube and disposed on the front of a vehicle.

[0014] The invention described in claim 9 provides an intake system structure of a power unit according to one of claims 3 to 8, wherein a storing box of the vehicle is disposed above the throttle body and the connecting tube, and a sight glass of the idle air screw is provided at the bottom of the storing box.

[Advantageous Effects of the Invention]

[0015] In the intake system structure of the power unit according to the invention of claim 1, the positioning part in the rotating direction of the connecting tube is provided on the connecting cylindrical part of the throttle body positioned in the rotating direction with respect to the cylinder part of the internal combustion engine, so that accurate connection is achieved easily, whereby variation in the positioning in the rotating direction of the tube and shape distortion of the connecting tube due to the variation can be reduced.
As a result, it is possible to obtain the intake system structure of the power unit, which may improve the function of the intake system and the connecting workability in simple constitution while restraining the space for the intake system of the power unit.

[0016] According to the invention of claim 2, the connecting tube can be positioned in the rotating direction simultaneously with connecting the connecting tube to the throttle valve, so that the workability is improved in addition to the effect of the invention of claim 1.

[0017] According to the invention of claim 3, the boss part for the idle air screw is served also as the positioning part, so that the throttle body can be prevented from getting larger and larger in addition to the effect of the invention of claim 2.

[0018] According to the invention of claim 4, projection of the positioning part in the height direction can be reduced so that the throttle body can be prevented from getting larger and larger in addition to the effect of claim 3.

[0019] According to the invention of claim 5, the connecting cylindrical part of the throttle body is formed eccentric to the intake passage, so that even when the tube side connecting cylindrical part of the connecting tube is formed eccentric to the tube side intake passage, the positioning in the rotating direction of the connecting tube can eliminate the eccentricity of the axes of both intake passages, smooth the connection between the throttle body and the connecting tube, and further attain the stability of performance in the internal combustion engine in addition to the effect of claim 3 or claim 4,.

[0020] According to the invention of claim 6, the retention in connecting work can be improved by the linear part so that the workability can be improved and positional shifting in the rotating direction can be prevented in addition to the effect of the invention of claim 5.

[0021] According to the invention of claim 7, the cable guide part is provided on the linear part of the connecting tube, so that the space for guiding the cable can be easily secured and the layout performance of the cable in the vehicle can be improved in addition to the effect of the invention of claim 6.

[0022] According to the invention of claim 8, the throttle cable is retained through the cable guide part on the connecting tube, so that the throttle cable can be disposed lower and the height of the seat can be lowered, in addition to the effect of the invention of claim 7.

[0023] According to the invention of claim 9, even when the upsides of the throttle body and the connecting tube is covered with the large-sized storing box, the idle air screw can be inspected without removing the storing box, so that the workability can be improved in addition to the effect of the invention of one of claims 3 to 8.

[Brief Description of the Drawings]

[0024] 

Fig. 1 is a general diagram for explaining of a motorcycle to which a power unit according to one embodiment of the invention is mounted.

Fig. 2 is a left side view of the principal part mainly composed of a power unit and an intake system in its periphery according to the embodiment of the invention.

Fig. 3 is a plan view of the principal part mainly composed of a power unit and an intake system in its periphery according to the embodiment.

Fig. 4 (a) is a plan view, with portions broken away, showing an air cleaner case and a connecting tube in the present embodiment (b) is a left side view, with portions broken away, showing the air cleaner case and the connecting tube, in the direction of the arrow Ivb in Fig. 4(a).

Fig. 5 (a) is a front end view of the connecting tube in the direction of the arrow Va in Fig. 4(a), and (b) is a sectional view of the connecting tube in the direction of the arrow Vb in Fig. 4 (a).

Fig. 6 (a) is a right side view of a throttle body according to the embodiment, and (b) is a rear view of the throttle body in the direction of the arrow VIb in Fig. 6(a). (a) is equivalent to a view in the direction of the arrow VIa (b), and the Vic part in (a) is a partial sectional view in the direction of the arrow VIc in (b).

Fig. 7 (a) is a right side view of the throttle body according to the embodiment, (b)is a front view of the throttle body in the direction of the arrow VIIb in Fig. 7(a). (a) is equivalent to a view in the direction of the arrow VIIa, and the part VIIc in Fig. 7 (b) is a partial sectional view in the direction of the arrow VIIc in Fig. 7(a).

Fig. 8 (a) is a sectional elevation of the throttle body in the direction of the arrow VIIIa in Fig. 6, and (b) is a sectional elevation of the throttle body in the direction of the arrow VIIIb in Fig. 6.

Fig. 9 is a plan partly in section of the vicinity of a bypass valve in the starting state of the throttle body in the direction of the arrow IX in Fig. 6.

Fig. 10 is a left side view of the principal part mainly composed of a power unit and an intake system in its periphery according to one modified form of the embodiment.

Fig. 11 is a plan view of the principal part mainly composed of the power unit and the intake system in its periphery according to the one modified form of the embodiment.

[Description of the Embodiments]

[0025] An intake system structure of a power unit according to one embodiment of the invention will now be described with reference to Fig. 1 to Fig. 9. The directions such as the front, the rear, the left, the right, the upper and the lower depend on the directions of a vehicle in the state where a power unit according to the embodiment is mounted to a vehicle, particularly to the small-sized vehicle such as a motorcycle. In the drawings, the arrow F designates the front side of the vehicle, L the left side of the vehicle, R the right side of the vehicle, and U the upper side of the vehicle, respectively.
In the drawings, a void arrow designates the flow of intake air to an internal combustion engine, a small arrow m designates the flow of idle air, and a small arrow n designates the flow of bypass air in the starting state, typically.

[0026] Fig. 1 is a left side view of a motorcycle 1 as a vehicle according to the present embodiment. The motorcycle 1 includes a power unit below a seat 6, in which an internal combustion engine 2 and a power transmission 3 to a rear wheel are integrated with each other, and a power unit 5 is rockably fitted to the body frame 4, and the internal combustion engine 2 is a single cylinder four-stroke cycle internal combustion engine. The power unit 5 is mounted to the motorcycle 1 with a crankshaft 8 of a power unit case 7 oriented in the width direction of the motorcycle 1.

[0027] As shown in Fig. 1 to Fig. 3, in the motorcycle 1 according to the present embodiment, a pair of right and left front forks 12 to which a front wheel 11 is journalled are pivoted on a head pipe 10 located at the front end part of the vehicle body frame 4 steerably through a steering stem 13. A steering handlebar 14 is mounted to the upside of the steering stem 13.

[0028] The vehicle body frame 4 is an underbone type formed by extending one main frame 15 obliquely backward to the lower side from the head pipe 10 and making a lower part between the head pipe 10 and the seat 6 for an occupant so that the straddling easiness is improved. A footrest 16 on which feet of a rider seated on the seat 6 are placed is disposed at the lower part.

[0029] The rear end part of the main frame 15 is bonded to the lateral middle part of a cross frame 17 extending laterally at the longitudinal middle part of the lower part of the vehicle body. A pair of right and left pivot plates 19 supporting the front part of the power unit 5 to vertically rock through a suspension link 18 are bonded to the right and left end parts of the cross frame 17.
Further, the front end parts of a pair of right rear frame 20R and left rear frame 20L are respectively bonded to the right and left ends of the cross frame 17.

[0030] The right and left rear frames 20L, 20R are extended obliquely backward to the upside from the cross frame 17, and bent to be gently inclined. Further, in the middle of extending obliquely upward, the right and left rear frames are connected and bonded to each other by a cross member 21 formed to be bent and projected toward the front upside of the vehicle, and connected and bonded to each other by a connecting member 22 oriented horizontally in the vehicle width direction at the rear ends thereof.

[0031] The left rear frame 20L and the right rear frame 20R are constructed so that the left rear frame 20L is formed to shift to a lower side from the right rear frame 20R at positions to be connected to the cross member 21, and a left connecting part 23L of the left rear frame 20L to the cross member 21 is positioned lower than a right connecting part 23R of the right rear frame 20R to the cross member 21.

[0032] The seat 6 having seating surfaces for a rider's seat and a pillion in the front and in the rear is disposed above the right and left rear frames 20L, 20R.
A storing box 24 is provided below the front part of the seat 6 between the right and left rear frames 20L, 20R, and a fuel tank 25 is provided below the back part of the seat 6.

[0033] In Fig. 1, the reference numeral 26 is a front fender, 27 is a rear fender, 28 is a tail light, 29 is a main kick stand and 30 is a side kick stand.
The vehicle body frame 4 is covered with a body cover 31 mainly composed of synthetic resin, and at the front of the vehicle body, a headlight 32 is disposed on the body cover 31.

[0034] The power unit 5 is formed by integrating the internal combustion engine at the front part with a power transmission 3 on the left of the back part, and a hanger part 40 is provided on the lower part of the front of the power unit case 7.
In the hanger part 40, the power unit 5 is supported on a pivot plate 19 through a suspension link 18 to rock vertically, and also the left side of the back part of the power unit 5 is supported on the right and left rear frames 20L, 20R through a rear cushion 33 to come close to and separate from each other.
A rear wheel 34 is journalled to the rear end part of the power transmission 3 provided at the back part side of the power unit case 7.

[0035] As shown in Fig. 2 and Fig. 3, a cylinder block 41, a cylinder head 42 and a cylinder head cover 43 are sequentially fastened and stacked to tilt forward substantially horizontally in front of the power unit case 7 to thereby constitute a cylinder part 44 of the internal combustion engine 2.
An exhaust pipe 45 is mounted extending from the cylinder head 42 downward and a little forward, and the exhaust pipe 45 is extended backward below the crankcase, detoured to the right and connected to a silencer 46 disposed on the right side of the vehicle body (See Fig. 1).

[0036] An air cleaner 50 is supported at a position away from the cylinder part 44 of the internal combustion engine 2 above the power transmission 3 on the left of the rear wheel 34, and a throttle body 52 is disposed at a position close to the cylinder part 44. The air cleaner 50 and the throttle body 52 are connected to each other by a connecting tube 51.
The throttle body 52 is located above the power unit 5 and right above the hanger part 40 provided at the lower part of the power unit 5 for holding the power unit 5 on the vehicle body frame 4.

[0037] The downstream side of the throttle body 52 is fastened to the upstream side of an inlet manifold 53 by a bolt 54, and the downstream end of the inlet manifold 53 is mounted and fixed to the cylinder head 42 by a bolt 55 to communicate with an intake port not shown, which is provided on the cylinder head 42.

[0038] Thus, the inlet manifold 53 is regulated from rotating around the axis of an intake passage and mounted to the cylinder part 44 by the bolt 55, and the throttle body 52 is regulated from rotating around the axis Y (See Figs. 6, 7) of the intake passage 52a and mounted to the inlet manifold 53 by the bolt 54, so that the throttle body 52 is assembled to the cylinder part 44 through the inlet manifold 53 and supported integrally with the position thereof in the direction of rotating around the axis Y regulated by the bolt 55 serving as a regulating member around the axis Y of the intake passage 52a.

[0039] The air purified by the air cleaner 50 is fed into the cylinder head 42 of the internal combustion engine 2 through the respective intake passages of the connecting tube 51, the throttle body 52 and the inlet manifold 53.
The lower part of a fuel injector 35 for injecting fuel toward an intake port not shown is fitted to the upper part of the inlet manifold 53, and one end of a fuel pipe 37, the other end of which is connected to a fuel pump 36 of the fuel tank 25, is connected to the fuel injector 35, and the fuel is supplied from the fuel tank 25 into the cylinder head 42 by the fuel injector 35.

[0040] As shown in Fig. 4, the air cleaner 50 is constructed by providing a cleaner element 50b in an air cleaner case 50a. The interior of air cleaner case 50a is partitioned by the cleaner element 50b disposed like a plate with the faces pointing in the lateral direction, an inlet port 50c from the outside is provided at the left surface side of the cleaner element 50b, and a clean side chamber 50d is provided on the right surface side. The connecting tube 51 is connected to the clean side chamber 50d, in which an inlet part 51b of a tube side intake passage 51a is inserted.

[0041] The connecting tube 51 is a cylinder made of rubber or resin, which is provided with a reinforcement rib 51c formed on the outer surface and has a cylindrical section, so that the connecting tube is capable of coping with vibration, displacement and heat between the connecting devices.
On the opposite side to the inlet part 51b of the upstream end inserted in the clean side chamber 50d, the downstream end of the connecting tube 51 is provided with a tube side connecting cylindrical part 556 for connection to the downstream throttle body 52.
The connecting tube 51 is provided with a linear part 51d extending for a predetermined distance on the upstream side from the tube side connecting cylindrical part 56.

[0042] As shown in Fig. 5(a), the axis T of the tube side connecting cylindrical part 56 is off-centered to one side (upward, U side in the drawing) with respect to the axis S of the tube side intake passage 51a in the connecting tube 51.
The tube side connecting cylindrical part 56 is provided with an engagement part 58 (See Fig. 4 as well) including two projections projecting toward the throttle body 52 in the directions of the axes S, T at the eccentric side with the axis S of the tube side intake passage 51a.

[0043] As shown in Fig. 5(b), the outer surface of the linear part 51d is provided with a cable guide part 57 projected at the off-centered side of the tube side connecting cylindrical part 56 with the axis S of the tube side intake passage 51a, and the cable guide part 57 includes a recessed part 57a (See Fig. 4 as well) where the cable is engaged. As the cable to be engaged, when a throttle cable 66 is engaged as mentioned later, it is specially effective, but even when the other various cables (including tubes) for power, electricity and fluid) are used, the cable can be disposed lower in a space on the connecting tube 51, so the space for guiding the cable can be easily secured.

[0044] As shown in Fig. 6, the throttle body 52 is provided with a connecting cylindrical part 60 to the connecting tube 51, and the axis Z of the connecting cylindrical part 60 is formed off-centered to one side (upward, U side in the drawing) with the axis Y of the intake passage 52a in the throttle body 52.
The connecting cylindrical part 60 is provided with a positioning part 61 for positioning the connecting tube 51 in the direction of rotation around the axis T of the tube side connecting cylindrical part.

[0045] The positioning part 45 is disposed at a position to engage with an engagement part 58 provided on the connecting tube side connecting cylindrical part of the connecting tube 51 in the connecting cylindrical part 60 of the throttle body 52, and in the present embodiment, the positioning part is a boss part 61 for an idle air screw 62 provided on the throttle body 52.
The positioning part 61 is, as shown in Fig. 6(b), provided at a position offset to one side (the left side, L side in the drawing) with the axis Y of the intake passage 52a of the throttle body 52, as viewed in the vertical direction.

[0046] When the thus constructed connecting tube 51 is connected to the throttle body 52, the tip of the connecting cylindrical part 60 of the throttle body 52 is inserted in the tube side connecting cylindrical part 56, and the axis T of the tube side connecting cylindrical part 56 is aligned with the axis Z of the connecting cylindrical part 60.
Further, the two projections of the engagement part 58 of the tube side connecting cylindrical part 56 engage to hold the positioning part 61 of the connecting cylindrical part 60 between them, thereby positioning the tube side connecting cylindrical part 56 in the direction of rotation around the axis T.

[0047] As a result, the connecting tube 51 is positioned in the rotating direction, so that the axis S of the tube side intake passage 51a is aligned with the axis Y of the intake passage 52a in the throttle body 52, thereby communicating both the intake passages 51a, 52a with each other as predetermined.
The outer periphery of the tube side connecting cylindrical part 56 where the tip of the connecting cylindrical part 60 of the throttle body is inserted to the inside in a predetermined connecting state as described above is fastened by a fixing band (See Fig. 4).

[0048] As described above, the throttle body 52 is regulated in the position in the direction of rotation around the axis Y by the bolt 54 serving as the regulating member for regulating the rotation around the axis Y of the intake passage 52a, and assembled to the cylinder part 44 and integrally supported through the inlet manifold 53, so that the connecting tube 51 is regulated in the rotational position around the axis S with respect to the power unit 5 as well.

[0049] As shown in Figs. 6 and 7, the intake passage 52a of the throttle body 52 is provided with a butterfly type throttle valve 63 disposed for opening and closing the intake passage, and a throttle valve shaft 64 supporting the throttle valve is rotatably supported on both right and left side walls, horizontally crossing the intake passage 52a with the axis V oriented in the vehicle width direction.

[0050] In the throttle valve shaft 64, a throttle drum 65 is secured to the shaft end projected on the right of the throttle body 52 (R direction in the drawing), a throttle cable 66 and a return spring 67 for energizing the throttle valve 63 in the closing direction are connected to the throttle drum, and the throttle cable 66 is towed by a throttle operating member not shown, thereby opening the throttle valve 63.

[0051] The throttle cable 66 is, as shown in Figs. 2 and 3, drawn backward from the throttle drum 65, engaged with the recessed part 57a of the cable guide part 57, folded back like a U-shape, and disposed at the front part of the motorcycle 1.
The throttle cable 66 is penetrated and disposed through the throttle cable tube.

[0052] A throttle opening sensor 68 formed separately from the throttle body 52 is fitted to an outer wall of the throttle body 52 where the other end (the left end, the end L direction in the drawing) of the throttle valve shaft 64 is projected.
The throttle opening sensor 68 for detecting a throttle opening is fitted to the throttle body 52 with a detecting part 68a thereof aligned with the axis V of the throttle valve shaft 64, and fixed too the throttle body 52 from the left side by a sensor attaching bolt 69.

[0053] A starting air control valve 70 as an actuator for controlling the throttle body 52 is mounted to the throttle body 52 above the throttle opening sensor 68 side by side.
The starting air control valve 70 is mounted to the throttle body 52 with two valve mounting bolts 71 juxtaposed close to the throttle opening sensor 68 from the same direction in the longitudinal direction of the vehicle.

[0054] The starting air control valve 70 is constructed by a solenoid valve, and controls combustion air (bypass air in starting) supplied over an opening of the throttle valve 63, bypassing the throttle valve 63 in starting the internal combustion engine 2.

[0055] As shown in Fig. 6(b) and Fig. 8, the combustion air passes from the upstream side from the throttle valve 63 of the throttle body 52, that is, a by-pass air groove 72 formed and projected to the intake passage 52a of the connecting cylindrical part 60 through the by-pass air inlet hole 73 as indicated by a small arrow n to enter the starting air control valve 70.
As shown in Fig. 9, the starting by-pass air controlled by the starting air control valve 70 is supplied from the throttle valve 63 to the intake passage 52a of the downstream side (the inlet manifold 53 side) as shown in Fig. 7(b) through a by-pass air supply hole 74 as indicated by the small arrow n.

[0056] The positioning part 61 engaged with the engagement part 58 of the connecting tube 51 side is a boss part 61 to which the idle air screw 62 is screwed and fitted.
An idle air adjusting valve 75 including the idle air screw 62 is provided for setting the supply amount of necessary combustion air (idle air), which is supplied even when the throttle valve 63 is closed in the idling state of the internal combustion engine 2.

[0057] As shown in Fig. 6 and Fig. 8(b) , the idle air enters the idle air adjusting valve 75 from the upstream side from the throttle valve 63 of the throttle body 52, that is from an idle air groove 76 formed and projected to the intake passage 52a of the connecting cylindrical part 60 as indicated by a small arrow m, and passes through the idle air adjusting valve 75 according to a valve opening preset by the screw-in amount of the idle air screw 62. The idle air adjusted by the idle air adjusting valve 75 is passed through the an idle air supply hole 77 as indicated by a small arrow m, and supplied to the intake passage 52a on the downstream side (the inlet manifold 53 side) from the throttle valve 63 as shown in Fig. 7 (b)
Although the supply of the idle air is preset according to the characteristics and working conditions of the individual machine bodies, it can be re-adjusted by the idle air screw 62.

[0058] As shown in Fig. 2, although the storing box 24 is disposed above the throttle body 52 and the connecting tube 511, the bottom of the storing box 24 is provided with a sight glass 86 for the sake of convenience for inspecting the idle air screw 62. The sight glass 86 is generally closed with a lid 87 made of rubber, resin or the like.

[0059] As shown in Fig. 6(a), the throttle opening sensor 68 and the starting air control valve 70 are juxtaposed vertically and mounted to the throttle body 52, the two valve mounting bolts 71 of the starting air control valve 70 are arranged side by side in the longitudinal direction of the vehicle, and the sensor attaching bolt 69 of the throttle opening sensor 68 is one disposed on the vertical line P between the two valve mounting bolts 71.
Thus, mutual interference of the sensor attaching bolt 69 and the valve mounting bolts 71 can be prevented.

[0060] A first wiring coupler 80 connecting the throttle opening sensor 68 to the outside and a second wiring coupler 81 connecting the starting air control valve 70 to the outside are separately disposed directing forward in the intersecting direction to the axis V of the throttle valve shaft 64.
The first wiring coupler 80 is fitted to the throttle opening sensor 68 provided on the throttle valve shaft 64 to direct in the same direction with the substantially vertical positions same as the axis Y of the intake passage 52a. The second wiring coupler 81 of the starting air control valve 70 is, however, disposed away from the intake passage 52a of the throttle body 52.

[0061] Then the axis W of the second wiring coupler 81 is disposed with a gradient at an acute angle θ to the axis Y of the intake passage 52a to be laid along the intake passage 52a, and a wire (b) from the second wiring coupler 81 approaches toward the substantially same direction of a wiring (a) from the first wiring coupler 80, so that the wires (a) , (b) (See Figs. 2 and 3) are easily put together.

[0062] As shown in Fig. 2 and Fig. 3, the vehicle body frame 4 of the motorcycle 1 includes a pair of right and left rear frames 20L, 20R and a cross member 21 mounted between them, the cross member 21 is disposed in front of the first and second wiring couplers 80, 81, and the wires (a), (b) from the first and second wiring couplers 80, 81 are guided to an area surrounded by the cross member 21, the right and left rear frames 20K, 20R, and the top of the power unit 5.

[0063] The wire (a) and the wire (b) are folded to the left and the back part of the vehicle in the above area, and bound into a bundle, or one united wire (c) as one harness.
Although the wires (a), (b) from the first and second wiring couplers 80, 81 are folded backward straight in the illustrations shown in Fig. 2 and Fig. 3, the wires may be largely turned in the above area, laid along the cross member 21, once supported, and then folded backward.
In that case, the cross member 21 is formed curved to project upward and toward the front part of the vehicle, so that curving of the wires (a), (b) from the first and second wiring couplers 80, 81 can be kept large, and the rocking amount of the internal combustion engine 2 can be increased.

[0064] The wire (c) is traversed to the right in the vehicle width direction in front of the rear wheel 34, again folded forward like a U-shape, and bundled with a wire (d) of a starter motor 82 disposed on the top of the power unit 5, or united into one wire (e) as one harness, and disposed forward on the right of the power unit 5.

[0065] The wire (e) is folded backward in the vicinity of a right connecting part 23R of the cross member 21 and the right rear frame 20R (C part in Fig. 3), locked along the right rear frame 20R suitably by a harness clamp 85, extended to a control unit (a programmed fuel injection control unit) 83 fitted to the back part of the right rear frame 20R, and connected to the control unit 83.
The wire (e) is disposed largely like a U-shape in an area before and behind the folded part C near the right connecting part 23L, so that enough bending margin is provided between the rocking power unit 5 side and the vehicle body frame 4 side.

[0066] Further, the cross member 21 is formed and bent to project upward to the front of the vehicle, and the left rear frame 20L is formed at a different position below the right rear frame 20R so that the cross member 21 approaches the first and second wiring couplers 80, 81, thereby facilitating pulling of the wires (a), (b) from the first and second wiring couplers 80, 81.

[0067] Although the inlet manifold 53 is provided independently of the cylinder head 42 of the internal combustion engine 2, and fastened and attached to the cylinder head 42 by the bolt 55, an insertion area A for a setter for fitting the inlet manifold 53 to the cylinder head 42 overlaps the first and second wiring couplers 80, 81 as viewed in the vehicle width direction (See Fig. 2), and is disposed on the vehicle body center side (See Fig. 3) from the first and second wiring couplers 80, 81 as viewed in the vertical direction, thereby facilitating fastening and attaching of the inlet manifold.

[0068] Although the throttle body 52 is fastened and attached to the inlet manifold 53 by the bolt 54, the bonding parts of the first and second wiring couplers 80, 81 to the wires (a), (b) are both located on the inlet manifold 53 side from the joining face B (See Figs. 2, 3) of the inlet manifold 53, whereby the throttle valve 63 can be put close to the combustion chamber of the internal combustion engine 2.

[0069] In the above embodiment, the following effects are produced.
That is, since the connecting cylindrical part 60 of the throttle body 52 positioned in the rotating direction to the cylinder part 44 of the internal combustion engine 2 is provided with the positioning part 61 in the rotating direction of the connecting tube 51, variation in alignment in the rotating direction of the connecting tube 51 and shape distortion due to the variation can be reduced.

[0070] Since the positioning part 61 is disposed at a position to engage with the engagement part 58 provided on the tube side connecting cylindrical part 56 of the connecting tube 51 in the throttle body 52, the positioning of the connecting tube 51 in the rotating direction is performed simultaneously with the work for connecting the connecting tube 51 to the throttle valve 52 so that the workability can be improved.

[0071] Since the positioning part 61 is the boss part for the idle air screw 62 provided on the throttle body 52 and the boss part is served also as the positioning part 61, the throttle body 52 can be prevented from getting larger and larger.
Further, since the positioning part 61 is provided eccentric to one side with the axis Y of the intake passage 52a, the projection of the positioning part 61 in the height direction can be reduced so that the throttle valve 52 so that the workability can be improved.

[0072] Since the connecting cylindrical part 60 to the connecting tube 51 in the throttle body 52 is formed eccentric to one side with the axis Y of the intake passage 52a, and the tube side connecting cylindrical part 56 of the connecting tube 51 is formed eccentric to one side similarly to the throttle body 52 side with the axis S of the tube side intake passage 51a in the connecting tube 51, even when the connecting cylindrical part 60 of the throttle body 52 is formed eccentric with the intake passage 52a and the tube side connecting cylindrical part 56 of the connecting tube 51 is formed eccentric with the tube side intake passage 51a, positioning in the rotating direction of the connecting tube 51 may eliminate misalignment of the axes Y, S of both intake passages 52a, 51a and smooth the connection between the throttle body 52 and the connecting tube 51, and attain stabilization of performance in the internal combustion engine. 2.

[0073] Since the connecting tube 51 is provided with the linear part for the predetermined distance on the upstream side from the tube side connecting cylindrical part 56, the retention in the connecting work can be improved by the linear part 51d so as to improve the workability and prevent positional shifting in the rotating direction.

[0074] Since the cable guide part 57 is projected on the outer surface of the linear part 51d on the eccentric side of the tube side connecting cylindrical part 56 with the axis S of the tube side intake passage 51a, and the cable guide part 57 is provided with the recessed part 57a where the cable engages, the space for guiding the cable can be easily secured so as to improve the cable layout performance in the motorcycle 1. Further, since the cable is a throttle cable 66, which is disposed extending from the throttle drum 65 mounted to the right shaft end of the throttle valve shaft 64 provided on the throttle body 52 to orient in the vehicle width direction, which penetrates to the outside of the throttle body 52, folded backward like a U-shape on the connecting tube 51 toward the front part of the motorcycle, the throttle cable 66 can be disposed lower to lower the height of the seat 6.

[0075]  Since the storing box 24 of the motorcycle 1 is disposed above the throttle body 52 and the connecting tube 51, and the sight glass 86 for the idle air screw 62 is provided at the bottom of the storing box 24, even when the upsides of the throttle body 52 and the connecting tube 51 are covered with the large-sized storing box 24, the idle air screw 62 can be inspected without removing the storing box 24 so as to improve the workability.

[0076] Further, in the motorcycle 1 in which the internal combustion engine 2 and the power transmission 3 to the rear wheel 34 are integrated and the power unit 5 rockably mounted to the vehicle body frame 4 is provided below the seat 6, the throttle body 52 for controlling the intake amount of the internal combustion engine 2 is provided between the power unit 5 and the seat 6, the throttle opening sensor 68 for detecting the throttle opening is provided at the shaft end of the throttle valve shaft 64 provided on the throttle body 52 to orient in the vehicle width direction, further the starting air control valve 70 as the actuator for controlling the throttle body 52 is mounted to the throttle body 52 close to the throttle opening sensor 68 from the same direction, and the first wiring coupler 80 connecting the throttle opening sensor 68 to the outside and the second wiring coupler 81 connecting the starting air control valve 70 to the outside are separately disposed in the same direction in the front and in the rear and also side by side in the intersecting direction to the throttle valve shaft 64, whereby a plurality of sensors independent of each other, the starting air control valve 70 as an actuator and the throttle opening sensor 68 are mounted to the throttle body 52 in the same direction, so that the machining performance for the throttle body 52 can be improved.
Further, since the first and second wiring couplers 80, 81 are disposed to perform wiring in the intersecting direction to the throttle valve shaft 64, the projection toward the throttle valve shaft 64 can be prevented, and further since the directions of the first and second wiring couplings 80, 81 are the same longitudinally, the workability for pulling, collecting and connecting the wires (a), (b) can be improved.

[0077] Since the throttle opening sensor 68 and the starting air control valve 70 are disposed side by side in the vertical direction on the throttle body 52, and the second wiring coupler 81 of the starting air control valve 70 disposed away from the intake passage 52a of the throttle body 52 is disposed with a gradient at an acute angle θ along the intake passage 52a, the wire (a) from the first wiring coupler 80 and the wire (b) from the second wiring coupler 81 come close to each other, the wires (a), (b) can be easily put together so as to reduce the pulling space for the wires (a), (b).

[0078]  In the motorcycle 1, the hanger part 40 holding the power unit 5 on the vehicle body frame 4 is provided below the power unit 5, and the throttle body 52 is located right above the hanger part 40 and above the power unit 5, so that the wire parts (a), (b) from the first and second wiring couplers 80, 81 are arranged to be rocked in the longitudinal direction of the motorcycle 1 by rocking of the power unit 5 caused by traveling of the motorcycle 1. Thus, the rocking in the vehicle width direction and in the vertical direction can be restrained, the wiring structure to the throttle body can be miniaturized, so that the limitations on the vehicle body width and the height of the seat 6 in the motorcycle 1 can be easily cleared.

[0079] The vehicle body frame 4 of the motorcycle 1 includes the right and left rear frames 20L, 20R, and the cross member 21 mounted between them, the cross member are disposed in front of the first and second wiring couplers 80, 81, and the wires (a), (b) from the first and second wiring couplers 80, 81 are guided to the area surrounded by the cross member 21, the right and left rear frames 20L, 20R, and the top of the power unit 5, so that the wires (a), (b) are protected by the cross member 21, and the space for wiring work is increased.

[0080] The wires (a), (b) are folded back to the back part of the motorcycle 1 in the above area, then united into the wire (c), traversed in the vehicle width direction in front of the rear wheel 34, again folded back forward like a U-shape, and connected to the wire (d) of the starter motor 82 disposed on the top of the power unit 5, so that the wiring work in the periphery of the internal combustion engine 2 can be performed more efficiently.

[0081] Since the cross member 21 is formed and bent to project upward to the front of the vehicle of the motorcycle 1, curving of the wires (a), (b) from the first and second wiring couplers 80, 81 can be kept large so as to increase the rocking amount of the internal combustion engine 2. Thus, riding comfortableness of the motorcycle 1 can be improved.

[0082] Since the right and left rear frames 20L, 20R are formed at vertically different positions from one from the other so that the cross member 21 approaches the first and second wiring couplers 80, 81, pulling performance of the wires (a), (b) from the first and second wiring couplers 80, 81 can be secured and improved.

[0083] According to the present embodiment, in one of the throttle opening sensor 68 and the starting air control valve 70, the two valve mounting bolts 71 which are mounting members of the starting air control valve 70 are arranged side by side in the longitudinal direction of the motorcycle 1, and on the other hand, the sensor attaching bolt 69 which is a mouthing member of the throttle opening sensor 68 is disposed on the vertical line P between the valve mounting bolts 71, so that the mutual interference of the throttle opening sensor 68 and the starting air control valve 70 can be prevented, and the throttle opening sensor 68 and the starting air control valve 70 can be brought close to each other. Thus, the throttle body 52 and the wiring structure thereof can be miniaturized.

[0084] The throttle body 52 is held on the inlet manifold 53 provided independently of the cylinder head 42 of the internal combustion engine 2, the insertion area A for the setter for fitting the inlet manifold 53 to the cylinder head 42 overlaps the first and second wiring couplers 80, 81 as viewed in the vehicle width direction, and is disposed on the vehicle body center side from the first and second wiring couplers 80, 81 as viewed in the vertical direction, so that while the throttle body 52 and the cylinder head 42 are brought close to each other to achieve miniaturization, fastening and attaching of the inlet manifold 53 as the separate body can be facilitated. Thus, the productivity of the cylinder head 42 can be improved by providing the inlet manifold 53 as the separate body.

[0085] In the throttle body 52, with respect to the joining face B to the inlet manifold 53, the bonding parts of the first and second wiring couplers 80, 81 to the wires (a), (b) are both located on the inlet manifold 53 side, whereby the throttle body 52 can be more miniaturized and the throttle valve 63 can be put close to the combustion chamber of the internal combustion engine. Thus, the responsiveness of the internal combustion engine 2 can be heightened, and the miniaturization and the improvement in performance can be attained.

[0086] Although the above description deals with one embodiment of the invention, needless to say, the mode may be partially altered within the scope of the gist of the invention.
For example, one modified form in which the arrangement of wires from the first and second wiring couplers 80, 81 are varied will now be described simply with reference to Fig. 10 and Fig. 11.
The present modified form is similar to the above embodiment except for that the arrangement of wires is different, and in Fig. 10 and Fig. 11, the same reference numerals are given to the same parts, or the description is eliminated, and the different points will be described.

[0087] As shown in Fig. 10 and Fig. 11, a wire a' and a wire b' from first and second wiring couplings 80, 81are guided to an area surrounded by a cross member 21 in front of the first and second wiring couplings 80, 81, right and left rear frames 20L, 20R, and the top of a power unit 5, once turned to the left near the cross member 21 (D part in Fig. 3), then folded back like a U-shape, supported along the cross member 21, or bound into a bundle or put into one harness to form one united wire c'.
The cross member 21 is formed and bent to project upward to the front of a vehicle, the left rear frame 20L is formed at a different position below the right rear frame 20R so that the cross member 21 approaches the first and second wiring couplers 80, 81. Thus, in the present modified form, especially pulling of the wires a', b' from the first and second wiring couplers 80, 81 is facilitated.
In a part D, a flexure margin is obtained with enough room for wiring, besides since the cross member 21 is formed and bent to project upward to the front of the vehicle, curving of the wires a', b' from the first and second wiring couplers 80, 81 and the united wire c' can be kept large so as to increase the rocking amount of the internal combustion engine 2.

[0088] The wire c' is then extended from the vicinity of a right connecting part 23R of the cross member 21 and the right rear frame 20R along the right rear frame 20R, suitably locked by a harness clamp 85, extended to a control unit (a programmed fuel injection control unit) 83 fitted to the back part of the right rear frame 20R, and connected to the control unit 83.
According to the present modified form, the wires a', b', c' are thus held on the cross member 21, whereby the rocking range of the wires can be regulated and the wiring space can be reduced.

[0089] Although the motorcycle 1 is shown as a vehicle, especially the small-sized vehicle in the above embodiment and the modified form thereof, when the similar power unit 5 and throttle body 52 are adopted, the invention may be applied to the other modes such as three-wheeled and four-wheeled dune buggy vehicles.

[0090] The invention is not limited to the mode and orientation of the power unit 5 in the embodiment and the modified form, but the invention relates to the connection or the like of the throttle body, the connecting tube and the like, and provides the intake system structure of the power unit including the configurations described in the claims. Various modes are embraced in the invention within the scope of the gist of the invention.

[Reference Signs List]

[0091] 

1 ...

Motorcycle (vehicle)

2 ...

Internal combustion engine

3 ...

Power transmission

4 ...

Vehicle body frame

5 ...

Power unit

6 ...

Seat

7 ...

Power unit case

15 ...

Main frame

17 ...

Cross frame

18 ...

Suspension link

19 ...

Pivot plate

20L ...

Left rear frame

20R ...

Right rear frame

21 ...

Cross member

24 ...

Storing box

25 ...

Fuel tank

34 ...

Rear wheel

40 ...

Hanger part

42 ...

Cylinder head

44 ...

Cylinder part

50 ...

Air cleaner

50a ...

Air cleaner case

50b ...

Air cleaner element

50d ...

Clean side chamber

51 ...

Connecting tube

51a ...

Tube side intake passage

51d ...

Linear part

52 ...

Throttle body

53 ...

Inlet manifold

54 ...

Bolt (regulating member)

55 ...

Bolt

56 ...

Tube side connecting cylindrical part

57 ...

Cable guide part

57a

Recessed part

58 ...

Engaging part

60 ...

Connecting cylindrical part

61 ...

Positioning part (boss part)

62 ...

Idle air screw

63 ...

Throttle valve

64 ...

Throttle valve shaft

65 ...

Throttle drum

66

Throttle cable

68 ...

Throttle opening sensor

69 ...

Sensor attaching bolt

70 ...

Starting air control valve

71 ...

Valve mounting bolt

86 ...

Sight glass

87 ...

Lid

a~e

wire

a'~c'

wire

Claims

1. An intake system structure of a power unit (5), which is mounted to a vehicle (1), and in which an internal combustion engine (2) and a power transmission (3) are integrated with each other, an air cleaner (50) is provided at a position away from a cylinder part (44) of the internal combustion engine (2), a throttle body (52) is disposed at a position close to the cylinder part (44), and the air cleaner (50) and the throttle body (52) are connected to each other by a connecting tube (51),
wherein : a regulating member (54) around the axis of an intake passage (52a) regulates the throttle body (52) in a position in the rotating direction around the axis with respect to the cylinder part (44), the throttle body (52) is assembled to the cylinder part (44) through an inlet manifold (53) and supported integrally; and
in the throttle body (52), a connecting cylindrical part (60) to the connecting tube (51) is provided with a positioning part (61) for positioning the connecting tube (51) in the rotating direction.

2. The an intake system structure of a power unit according to claim 1, wherein the positioning part (61) is disposed at a position to engage with an engagement part (58) provided at a tube side connecting cylindrical part (56) of the connecting tube (51) in the throttle body (52).

3. The intake system structure of a power unit according to claim 2, wherein the positioning part (61) is a boss part (61) for an idle air screw (62) provided on the throttle body (52).

4. The intake system structure of a power unit according to claim 3, wherein the positioning part (61) is provided offset-centered to one side with respect to the axis of the intake passage (52a), as viewed in the vertical direction.

5. The intake system structure of a power unit according to claim 3 or 4,
wherein : in the throttle body (52), the connecting cylindrical part (60) to the connecting tube (51) is formed off-centered to one side with respect to the axis of the intake passage (52a); and
the tube side connecting cylindrical part (56) of the connecting tube (51) is formed off-centered similarly to the throttle body (52) side with respect to the axis of the tube side intake passage (51a) in the connecting tube (51).

6. The intake system structure of a power unit according to claim 5, wherein the connecting tube (51) includes a linear part (51d) for a predetermined distance on the upstream side from the tube side connecting cylindrical part (56).

7. The intake system structure of a power unit according to claim 6, wherein a cable guide part (57) is projected on the outer surface of the linear part (51d) on the side where the tube side connecting cylindrical part (56) is off-centered with respect to the axis of the tube side intake passage (51a), and the cable guide part (57) includes a recessed part (57a) where a cable is engaged.

8. The intake system structure of a power unit according to claim 7, wherein the cable is a throttle cable (66), which is folded back like a U-shape from a throttle drum (65) fitted to the right or left shaft end of a throttle valve shaft (64) provided on the throttle body (52) oriented in the vehicle width direction, which penetrates to the outside of the throttle body (52) on the connecting tube (51) and disposed on the front of a vehicle (1).

9. The an intake system structure of a power unit according to one of claims 3 to 8, wherein a storing box (24) of the vehicle (1) is disposed above the throttle body (52) and the connecting tube (51), and a sight glass (86) of the idle air screw (62) is provided at the bottom of the storing box (24).

Drawing