JP2004293361A - Engine unit - Google Patents

Abstract

An object of the present invention is to maintain a good engine operating state by avoiding a rise in the temperature of a carburetor.
A combustion chamber is formed in a cylinder head of an engine mounted on a vehicle, and an intake port and an exhaust port communicating with the combustion chamber are formed in the cylinder head. A carburetor 27 that supplies an air-fuel mixture to the combustion chamber 15a is disposed behind the engine 25 on the vehicle side. An intake pipe 35 for guiding the air-fuel mixture is provided between the output port 28b of the carburetor 27 and the intake port 15b of the engine 25, and a heat shield plate 36 is provided on the outer periphery of the intake pipe 35. Since the traveling wind, which has cooled the engine 25 and has become high temperature, is guided radially outward of the intake pipe 35 along the heat shield plate 36, the traveling wind is not directly blown to the vaporizer 27, A temperature rise can be avoided, and vapor lock due to bubbling of fuel can be avoided.
[Selection diagram] FIG.

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an engine unit to which fuel is supplied via a carburetor.
[0002]
[Prior art]
The fuel supply mechanism that supplies fuel to the engine includes a carburetor or carburetor that sucks out the fuel by negative pressure in the intake pipe and supplies it to the engine in the form of fine particles, and a fuel that is measured according to the amount of intake air in the intake pipe and combustion chamber. There is an injection valve or injector that injects fuel into the air.
[0003]
In order to control the air-fuel ratio of the air-fuel mixture supplied to the engine with high accuracy, an injector is more preferable than a carburetor, but the injector is not only a fuel system component that pressurizes and injects fuel, but also an intake air amount. Therefore, the use of an injector is accompanied by an increase in cost, since an air-based component for detecting the pressure and a control system component for correcting the injection amount and performing feedback control are required.
[0004]
On the other hand, the carburetor can feed fuel to the engine according to the amount of intake air by the negative pressure that changes with the increase of the air flow velocity, not only does not cause the control system to become complicated, but also reduces the number of parts. Since the number is small, cost reduction can be achieved. For this reason, carburetors are often used mainly for inexpensive small engines mounted on all terrain vehicles such as ATVs (All Terrain Vehicles), motorcycles, and generators.
[0005]
Such a carburetor is a precision device into which a large number of fine flow paths and jets are incorporated, and is required to avoid mud splashing and dust. Therefore, when the carburetor is mounted on a vehicle, it is mounted on the rear side of the engine. (For example, see Patent Document 1).
[0006]
[Patent Document 1]
JP-A-11-11171 (pages 3-4, FIGS. 1 and 4)
[0007]
[Problems to be solved by the invention]
However, when the carburetor is mounted on the rear side of the engine, the heat of the engine is transmitted to the carburetor together with the traveling wind, so that the temperature of the carburetor increases. In particular, in an air-cooled engine in which a radiation fin is formed on a cylinder or a cylinder head, the amount of heat released from the engine surface is large, so that the temperature of the carburetor may be excessively increased.
[0008]
Excessive temperature rise of the carburetor may cause vapor lock, which makes it difficult to supply fuel due to bubbling of fuel, and decrease in charging efficiency due to rise in temperature of intake air, which may cause engine malfunction.
[0009]
SUMMARY OF THE INVENTION An object of the present invention is to maintain a good engine operating state by avoiding a rise in the temperature of a carburetor.
[0010]
[Means for Solving the Problems]
The engine unit of the present invention includes an engine in which a piston that defines a combustion chamber is reciprocally accommodated and has an intake port and an exhaust port communicating with the combustion chamber, and an input port and an output port. A carburetor that sucks air from a port and sends out an air-fuel mixture from the output port; an intake pipe that connects an intake port of the engine and an output port of the carburetor to supply the air-fuel mixture to the combustion chamber; And a heat shield plate provided between the carburetor and the carburetor to block heat from the engine.
[0011]
The engine unit according to the present invention is characterized in that the heat shield plate is provided in the intake pipe.
[0012]
The engine unit according to the present invention is characterized in that the engine is mounted on a vehicle, and the carburetor is arranged on the vehicle rear side of the engine.
[0013]
The engine unit according to the present invention is characterized in that the engine is an air-cooled engine.
[0014]
According to the present invention, since the heat shield plate is provided between the engine and the carburetor, the cooling air having absorbed the heat of the engine can be flowed without being applied to the carburetor, and the temperature of the carburetor can be increased. Can be avoided. As a result, it is possible to prevent the occurrence of vapor lock and a decrease in the charging efficiency, and it is possible to maintain a good engine operating state without causing an engine malfunction.
[0015]
Further, since the heat shield plate is provided in the intake pipe, the flow of the cooling air for cooling the engine is not unnecessarily obstructed, so that a reduction in the cooling efficiency of the engine can be avoided.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a perspective view showing a vehicle. The vehicle is an ATV, which is also called a buggy vehicle, that is, an all-terrain vehicle. As shown in FIG. 1, a vehicle body 1 is provided with front wheels 2a, 2b and rear wheels 3a, 3b, and a saddle type seat 4 is provided in the center of the vehicle body 1. The occupant gets into the vehicle across the seat 4 and operates by operating the steering wheel 5.
[0017]
FIG. 2 is a schematic view showing an engine unit 10 and a drive unit 11 according to an embodiment of the present invention mounted on the vehicle shown in FIG. 1, and FIG. 3 is a sectional view taken along line AA of FIG. is there. As shown in FIGS. 2 and 3, an engine unit 10 for outputting engine power is provided on the front side of the vehicle, and a drive unit 11 for transmitting the engine power to driving wheels is provided on the rear side of the vehicle. .
[0018]
As shown in FIG. 2, a crankshaft 13 is rotatably housed in a crankcase 12 of the engine unit 10 via a bearing. As shown in FIG. 3, a cylinder 14 is attached to an opening formed above the crankcase 12, and a cylinder head 15 is mounted on an upper end surface of the cylinder 14. A piston 16 which defines a combustion chamber 15a is reciprocally incorporated in a cylinder bore formed in the cylinder 14, and is eccentric to a piston pin 17 attached to the piston 16 and a crankshaft 13 from a rotation center thereof. The fixed crank pin 18 is connected via a connecting rod 19.
[0019]
A combustion chamber 15a is formed in the cylinder head 15, and an intake port 15b and an exhaust port 15c that open to the combustion chamber 15a are formed. An intake valve 20 for switching the intake port 15b and the combustion chamber 15a between a communicating state and a shutoff state is incorporated in the cylinder head 15, and an exhaust valve for switching the exhaust port 15c and the combustion chamber 15a between a communicating state and a shutoff state. 21 is incorporated in the cylinder head 15.
[0020]
A camshaft 22 having two cam surfaces is rotatably mounted on the cylinder head 15, and a rocker shaft 23 provided in parallel with the camshaft 22 has a rocker arm 23 a for opening and closing the intake valve 20, A rocker arm 23b for opening and closing the exhaust valve 21 is rotatably mounted. A timing chain (not shown) is bridged between a sprocket (not shown) fixed to the camshaft 22 and a sprocket 24 fixed to the end of the crankshaft 13 as shown in FIG. The rotation is driven in synchronization with the rotation of the crankshaft 13. The camshaft 22 contacts the cam surface with one end of the rocker arms 23a and 23b in accordance with the rotation position of the crankshaft 13, that is, the movement position of the piston 16, so that each of the intake valve 20 and the exhaust valve 21 is opened and closed at a predetermined timing. Is done.
[0021]
The engine 25 including the crankcase 12, the cylinder 14, and the cylinder head 15 is mounted on the vehicle body 1 such that the crankshaft 13 faces the vehicle width direction. The engine 25 is a single-cylinder air-cooled engine, and radiation fins 26 are formed on the cylinder 14 and the cylinder head 15.
[0022]
A carburetor 27 is arranged behind the engine 25 on the vehicle rear side to drive the engine 25 by supplying an air-fuel mixture to the engine 25. The carburetor 27 includes a carburetor body 28 in which an input port 28a and an output port 28b are formed coaxially, and a venturi portion 28c is formed between the input port 28a and the output port 28b of the carburetor body 28. Is done. A throttle valve 29 for controlling the opening and closing of the venturi section 28c is mounted on the carburetor body 28, and the throttle valve 29 is slid via a cable 30. The cable 30 for driving the throttle valve 29 is pulled out and pulled by the occupant operating the accelerator grip 6 shown in FIG. A fuel hose 31 for guiding the fuel from the fuel tank 7 shown in FIG. 1 is connected to the carburetor body 28, and the fuel is guided to the float chamber 32 opened to the venturi portion 28c via jets.
[0023]
An intake duct 34 connected to an air cleaner 33 is attached to the input port 28a of the carburetor main body 28, and an intake pipe 35 connected to the intake port 15b of the cylinder head 15 is connected to an output port 28b of the carburetor main body 28. Installed. A heat shield plate 36 extending radially outward is provided on the outer peripheral surface of the intake pipe 35, and the heat shield plate 36 is formed in a disk shape. Although the illustrated heat shield plate 36 is provided integrally with the intake pipe 35, the heat shield plate 36 and the intake pipe 35 may be provided separately.
[0024]
Since the venturi portion 28c is gradually opened according to the operation of the accelerator grip 6 by the occupant, the air that has passed through the air cleaner 33 starts flowing into the venturi portion 28c. A negative pressure is generated in the venturi portion 28c by the air flowing through the venturi portion 28c, and the fuel in the float chamber 32 is drawn into the venturi portion 28c according to the negative pressure. In the venturi section 28c into which the air flows, the fuel and the air are mixed to form an air-fuel mixture, and the air-fuel mixture output from the output port 28b is guided to the intake port 15b of the cylinder head 15 via the intake pipe 35.
[0025]
The air-fuel mixture guided to the intake port 15b is sent into the combustion chamber 15a during an intake stroke in which the intake valve 20 is driven to open, and is converted into engine power by burning through a compression stroke and a combustion stroke. The burned air-fuel mixture becomes exhaust gas and is discharged to the outside from an exhaust port 15c via an exhaust pipe (not shown) during an exhaust stroke. The piston 16 depressed by the combustion of the air-fuel mixture drives the crankshaft 13 via a connecting rod 19 to output engine power to a drive unit 11 described later.
[0026]
As shown in FIG. 3, two balancer shafts 40 and 41 are rotatably mounted on the crankcase 12 via bearings, and the balancer shafts 40 and 41 are integrally provided with balancer weights 40a and 41a. Is provided. The gears 40b and 41b provided on the balancer shafts 40 and 41 mesh with the gears 42 provided on the crankshaft 13, and rotation fluctuations of the crankshaft 13 are absorbed by the balancer weights 40a and 41a. FIG. 2 shows one balancer shaft 40 of the two balancer shafts.
[0027]
An oil pump 43 driven by the crankshaft 13 is provided at one end of the crankshaft 13, and lubricating oil discharged from the oil pump 43 is supplied to a sliding portion of the drive unit 11 via an oil passage (not shown). Is done. A power generator 44 driven by the crankshaft 13 is provided at the other end of the crankshaft 13, and the power generated by the power generator 44 is charged into a battery (not shown). Further, a starter motor 45 is provided adjacent to the power generator 44, and the rotation of the starter motor 45 driven at the time of starting the engine is transmitted to the crankshaft 13 via gears 46a and 46b.
[0028]
As shown in FIG. 2, a sub shaft 47 is mounted on the crankcase 12 so as to be rotatable in parallel with the crankshaft 13. The gear 48a provided on the sub shaft 47 meshes with the gear 48b provided on the crank shaft 13, and the rotation of the crank shaft 13 is transmitted to the sub shaft 47. A recoil cover 49 is attached to the crankcase 12 at one end of the countershaft 47. When the battery 25 has a shortage of charge and it is difficult to start the engine 25, the engine 25 is manually operated. A recoil starter 50 to be started is mounted. The recoil starter 50 includes a recoil pulley 50b housed in the recoil cover 49 and around which the recoil rope 50a is wound, and a recoil drum 50c attached to the counter shaft 47. By rotating, the engine 25 can be started by rotating the crankshaft 13 via the sub shaft 47.
[0029]
A centrifugal clutch 51 is attached to the other end of the sub shaft 47. The centrifugal clutch 51 includes a clutch drum 51a rotatably mounted in the crankcase 12, and a rotating plate 51b fixed to the sub shaft 47. And A plurality of arc-shaped clutch shoes 51c are attached to the rotating plate 51b, and each clutch shoe 51c is rotatable by a pin 51d attached to one end. A tension coil spring 51e is attached to the other end of the clutch shoe 51c, and a spring force is applied to the clutch shoe 51c in a direction away from the inner peripheral surface of the clutch drum 51a. Therefore, when the counter shaft 47 exceeds a predetermined number of revolutions, the centrifugal force applied to the clutch shoe 51c exceeds the spring force, so that the clutch shoe 51c engages with the inner peripheral surface of the clutch drum 51a and the centrifugal clutch 51 is engaged. In this state, the engine power from the crankshaft 13 is transmitted to the clutch drum 51a via the sub shaft 47.
[0030]
A primary shaft 52 is fixed to the clutch drum 51a, and the primary shaft 52 is rotatably accommodated in a transmission case 53 assembled to the crankcase 12. A secondary shaft 54 is rotatably accommodated in the transmission case 53 in parallel with the primary shaft 52, and a continuously variable transmission 55 for transmitting the engine power from the primary shaft 52 to the secondary shaft 54 is provided. It is mounted in the transmission case 53.
[0031]
The continuously variable transmission 55, that is, the CVT is a belt-type continuously variable transmission 55. The continuously variable transmission 55 includes a primary pulley 56 provided on the primary shaft 52 and a secondary pulley 57 provided on the secondary shaft 54. I have. The primary pulley 56 includes a fixed sheave 56a having a conical surface and a movable sheave 56b having a conical surface facing the fixed sheave 56a. The fixed sheave 56a is fixed to the primary shaft 52, and the movable sheave Reference numeral 56b is attached to a spline provided on the primary shaft 52 so as to be movable in the axial direction. On the other hand, the secondary pulley 57 includes a fixed sheave 57a having a conical surface and a movable sheave 57b having a conical surface facing the fixed sheave 57a. The fixed sheave 57a is fixed to the secondary shaft 54, The movable sheave 57b is mounted on a spline provided on the secondary shaft 54 so as to be movable in the axial direction.
[0032]
A rubber V-belt 60 is stretched between the primary pulley 56 and the secondary pulley 57. When the winding diameter of the V-belt 60 around the primary pulley 56 and the secondary pulley 57 changes, the rotation of the primary shaft 52 changes. Is transmitted to the secondary shaft 54 with the gear ratio changing steplessly. The movable sheave 56b of the primary pulley 56 is provided with a plurality of, for example, six, cylindrical centrifugal weights 61 oriented in a direction perpendicular to the rotation center of the primary shaft 52. A cam surface 62 corresponding to the centrifugal weight 61 is formed on the movable sheave 56b, and the cam surface 62 has a shape such that a radially outer portion of the movable sheave 56b protrudes toward an end of the primary shaft 52. . A cam plate 63 is fixed to the primary shaft 52 so as to face the cam surface 62, and a radially outer portion of the cam plate 63 is inclined so as to approach the cam surface 62. On the other hand, a spring support 64 is fixed to the secondary shaft 54, and a compression coil spring 65 for applying a tightening force to the V-belt 60 is mounted between the spring support 64 and the movable sheave 57b.
[0033]
When the rotation speed of the primary shaft 52 increases, the centrifugal force applied to the centrifugal weight 61 increases. Therefore, the centrifugal weight 61 moves radially outward while pushing between the movable sheave 56b and the cam plate 63. Here, since the cam plate 63 is fixed to the primary shaft 52, the movement of the centrifugal weight 61 causes the movable sheave 56b to approach the fixed sheave 56a. As a result, the groove width of the primary pulley 56 is reduced and the winding diameter of the V belt 60 around the primary pulley 56 is increased, while the groove width of the secondary pulley 57 is expanded by the V belt 60 against the spring force. The winding diameter of the belt 60 around the secondary pulley 57 is reduced. That is, the higher the rotation speed of the primary shaft 52, the higher the speed ratio of the continuously variable transmission 55 changes.
[0034]
When the rotation speed of the primary shaft 52 decreases and the centrifugal force applied to the centrifugal weight 61 decreases, the groove width of the secondary pulley 57 is reduced by the spring force applied to the secondary pulley 57. The winding diameter of the primary pulley 56 is increased by the V-belt 60 while the winding diameter of the V-belt 60 is increased, so that the winding diameter of the V-belt 60 around the primary pulley 56 is reduced. That is, the speed ratio of the continuously variable transmission 55 changes to the lower speed side as the rotation speed of the primary shaft 52 decreases.
[0035]
One end of the secondary shaft 54 protrudes from the transmission case 53 and is supported via a bearing on a gear case 66 assembled to the transmission case 53. An output shaft 67 is rotatably accommodated in the gear case 66 in parallel with the secondary shaft 54, and an axle 68 is rotatably mounted in parallel with the output shaft 67.
[0036]
A forward gear 69a is provided integrally with the secondary shaft 54, and the gear 69a is always engaged with a gear 69b rotatably mounted on the output shaft 67. Further, a reciprocating sprocket 70a is integrally provided on the secondary shaft 54, and a chain 70c is stretched between the sprocket 70a and a sprocket 70b rotatably mounted on the output shaft 67. In other words, the rotation direction of the gear 69b driven by the power from the secondary shaft 54 is opposite to the rotation direction of the secondary shaft 54, and the rotation direction of the chain driven sprocket 70b is the same as the rotation direction of the secondary shaft 54. become.
[0037]
A forward / reverse switching mechanism 71 is mounted between the gear 69b and the sprocket 70b, and power from the gear 69b and the sprocket 70b is selectively applied to the output shaft 67 in accordance with the switching operation of the forward / reverse switching mechanism 71. Is transmitted. The forward / reverse switching mechanism 71 has a pair of switching disks 72a, 72b that respectively mesh with splines of the output shaft 67, and these switching disks 72a, 72b are slidable on the output shaft 67 in the axial direction. . One switching disc 72a is provided with meshing teeth 73b which engages with the meshing teeth 73a provided on the side face of the gear 69b, and the other switching disc 72b is provided with meshing teeth provided on the side face of the sprocket 70b. A meshing tooth 74b that engages with the tooth 74a is provided. Accordingly, when the pair of switching disks 72a and 72b are moved toward the gear 69b to engage the meshing teeth 73a and 73b, the rotation of the secondary shaft 54 is transmitted to the output shaft 67 via the forward gears 69a and 69b. Is transmitted. On the other hand, when the switching disks 72a, 72b are moved toward the sprocket 70b to engage the meshing teeth 74a, 74b, the rotation of the secondary shaft 54 is transmitted to the output shaft 67 via the retreating sprockets 70a, 70b. You. As shown in FIG. 2, when the switching disks 72a and 72b are not engaged with any of the meshing teeth, the connection between the secondary shaft 54 and the output shaft 67 is cut off.
[0038]
Further, a pair of switching disks 75a and 75b which mesh with splines of the output shaft 67 are respectively mounted on the output shaft 67 so as to be slidable in the axial direction, and one of the switching disks 75b is provided with a meshing tooth provided on a gear case 66. A meshing tooth 76b is provided to engage with 76a. Therefore, when the pair of switching disks 75a and 75b are moved toward the gear case 66 to engage both the meshing teeth 76a and 76b, the output shaft 67 and the gear case 66 are fastened and the rotation of the output shaft 67 is restricted. On the other hand, as shown in FIG. 2, when the engagement of the meshing teeth 76a and 76b is released, the output shaft 67 is in a rotatable state.
[0039]
Such switching disks 72a, 72b, 75a, 75b are switched by switching holders 77, 78. The switching holders 77 and 78 are connected to the switching lever 8 of the vehicle shown in FIG. 1 via an operating link (not shown), and the switching disks 72a, 72b, 75a and 75b are switched by the operation of the switching lever 8 by an occupant. . The switching lever 8 is set to an F position corresponding to forward running, an R position corresponding to backward running, an N position corresponding to the neutral state of the drive unit 11, and a P position corresponding to the parking state of the vehicle.
[0040]
When the switching lever 8 is operated to the F position, the meshing teeth 73b of the switching disk 72a engage with the meshing teeth 73a of the gear 69b, while the switching disks 75a, 75b are in the neutral position. When the switch is operated to the R position, the meshing teeth 74b of the switching disk 72b engage with the meshing teeth 74a of the sprocket 70b, while the switching disks 75a and 75b are in the neutral position. When the switch is operated to the position N, all the switching disks 72a, 72b, 75a, 75b are set to the neutral position. It engages with 66 meshing teeth 76a.
[0041]
A gear 79a is fixed to the output shaft 67 to which power is transmitted in accordance with the operation of the switching lever 8, and a gear 79b which is always meshed with the gear 79a is fixed to the axle 68. Rear wheels 3a and 3b are connected to the end of the axle 68, and the rear wheels 3a and 3b, which are driving wheels, are driven by the axle 68. As shown in FIG. 3, a drive shaft 80 for the front wheels 2a and 2b having a gear 80a meshing with the gear 79b is rotatably supported by the transmission case 53 and the gear case 66. A front wheel output shaft 81 connected via a bevel gear 81a is rotatably supported by the gear case 66. As described above, the power from the output shaft 67 is transmitted to the front wheel output shaft 81 via the drive shaft 80, so that the front wheels 2a and 2b are driven together with the rear wheels 3a and 3b.
[0042]
As shown in FIG. 2, a brake disc 82 is attached to the output shaft 67 for braking the vehicle during traveling. A brake caliper for engaging a brake pad 83a with the brake disc 82 is mounted on the gear case 66. 83 are attached. When the occupant operates the brake lever 9 provided on the steering wheel 5, the brake caliper 83 can be driven to apply a braking force to the output shaft 67.
[0043]
Next, a cooling state of the engine unit 10 during traveling will be described. FIG. 4 is an enlarged side view showing the engine unit 10, and the arrows shown in FIG. 4 indicate the flow direction of the cooling air blown as the vehicle travels.
[0044]
After the engine 25 is started by the operation of the starter motor 45, the occupant operates the switching lever 8 to the F position, whereby the vehicle is switched to the forward running state. By operating the accelerator grip 6 in this state, the centrifugal clutch 51 is switched to the engaged state as the engine speed increases, and the vehicle starts traveling forward.
[0045]
When the forward running is started, as shown in FIG. 4, a cooling wind, that is, a running wind is blown to the engine unit 10 from the front. The traveling wind is guided between the radiation fins 26 formed on the cylinder 14 and the cylinder head 15, and the traveling wind absorbs heat from the engine 25 generated by combustion of the air-fuel mixture through the radiation fins 26. As a result, the engine temperature is kept within a predetermined range, and the oil film inside the engine 25 is prevented from being broken.
[0046]
As shown in FIG. 4, the traveling wind whose temperature has increased by passing through the radiation fins 26 flows toward the carburetor 27 disposed on the vehicle rear side of the engine 25, but flows in front of the carburetor 27. Is provided with a disk-shaped heat shield plate 36 on the outer periphery of the intake pipe 35 arranged in the space, so that the traveling wind is guided radially outward of the intake pipe 35 along the heat shield plate 36. The traveling wind guided in this manner passes through the outside of the carburetor 27 and is discharged from the rear of the vehicle. Therefore, the high-temperature traveling wind is not directly blown to the carburetor 27, and Temperature rise can be prevented.
[0047]
By preventing the temperature of the carburetor 27 from rising excessively, the state of the fuel in the carburetor 27 and the fuel in the fuel hose 31 is stabilized, so that the bubbling of the fuel can be avoided and the fuel supply becomes difficult. Can be avoided. Further, by avoiding a rise in the temperature of the intake air passing through the carburetor 27, the expansion of the intake air can be suppressed, so that the charging efficiency of the air-fuel mixture supplied to the combustion chamber 15a can be improved. By stabilizing the fuel supply and improving the charging efficiency, it is possible to keep the driving state of the engine 25 good.
[0048]
In addition, since the heat shield plate 36 is provided in the intake pipe 35 disposed immediately before the carburetor 27, the blowing of the traveling wind to the carburetor 27 can be reliably prevented, and the traveling wind for cooling the engine 25 can be prevented. It does not unnecessarily obstruct the flow. Thus, a decrease in the cooling efficiency of the engine 25 can be avoided.
[0049]
The present invention is not limited to the above embodiment, and can be variously modified without departing from the gist thereof. For example, the engine unit 10 is mounted on an ATV as a vehicle, that is, on an all-terrain vehicle, but the engine unit 10 may be mounted on a motorcycle or the like.
[0050]
Further, the shape of the heat shield plate 36 shown in the drawing is a disk shape, and the heat shield plate 36 is provided concentrically with the intake pipe 35, but the shape of the heat shield plate 36 is changed according to the shape of the vaporizer 27. The heat shield plate 36 may be provided eccentrically to the intake pipe 35. In addition, the heat shield plate 36 may be inclined to straighten the traveling wind.
[0051]
Further, the engine 25 is not limited to an air-cooled engine in which the radiation fins 26 are formed on the cylinder 14 and the cylinder head 15, but may be a water-cooled engine that cools through a radiator or an oil-cooled engine that cools through an oil cooler. There may be.
[0052]
Further, the illustrated engine 25 is a single-cylinder four-cycle engine, but may be provided with a plurality of cylinders, and may be a two-cycle engine in which the carburetor 27 is connected to a cylinder or a crankcase.
[0053]
The illustrated carburetor 27 is a forced open / close carburetor 27 that directly operates a throttle valve 29 by an accelerator operation. It may be.
[0054]
【The invention's effect】
According to the present invention, since the heat shield plate is provided between the engine and the carburetor, the cooling air having absorbed the heat of the engine can be flowed without being applied to the carburetor, and the temperature of the carburetor can be increased. Can be avoided. As a result, it is possible to prevent the occurrence of vapor lock and a decrease in the charging efficiency, and it is possible to keep the engine operating state in a good condition.
[0055]
Further, since the heat shield plate is provided in the intake pipe, the flow of the cooling air for cooling the engine is not unnecessarily obstructed, and a decrease in the cooling efficiency of the engine can be avoided.
[Brief description of the drawings]
FIG. 1 is a perspective view showing a vehicle.
FIG. 2 is a schematic diagram showing an engine unit and a drive unit according to an embodiment of the present invention mounted on the vehicle of FIG. 1;
FIG. 3 is a sectional view taken along line AA of FIG. 2;
FIG. 4 is an enlarged side view showing the engine unit of FIG. 3;
[Explanation of symbols]
10 Engine unit
15a Combustion chamber
15b Intake port
15c exhaust port
16 piston
25 Engine
27 vaporizer
28a Input port
28b output port
35 Intake pipe
36 heat shield

Claims (4)

An engine in which a piston that defines a combustion chamber is reciprocally housed and has an intake port and an exhaust port that communicate with the combustion chamber.
A carburetor comprising an input port and an output port, wherein the carburetor sucks air from the input port and sends out a mixture from the output port.
An intake pipe connecting an intake port of the engine and an output port of the carburetor, and supplying an air-fuel mixture to the combustion chamber;
An engine unit, comprising: a heat shield provided between the engine and the carburetor to block heat from the engine. The engine unit according to claim 1, wherein the heat shield plate is provided in the intake pipe. 3. The engine unit according to claim 1, wherein the engine is mounted on a vehicle, and the carburetor is disposed on a rear side of the engine with respect to the vehicle. 4. The engine unit according to claim 1, wherein the engine is an air-cooled engine.

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