JP2015098798A - Internal combustion engine for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make heat balance over the whole region of a cylinder head uniform when installing two plugs.SOLUTION: An internal combustion engine for a vehicle comprises: an intake port 25 and an exhaust port 26 disposed across a cylinder axis S; a cam chain chamber 28 disposed at either one side with respect to a direction in which the intake port 25 and the exhaust port 26 are lined; a first ignition plug 29 disposed on the opposite side to the cam chain chamber 28 across the direction in which the intake port 25 and the exhaust port 26 are lined; and a second ignition plug 30 disposed between the intake port 25 and the cam chain chamber 28. The second ignition plug 30 is thus disposed near the intake port 25 which does not become high temperature as compared with the exhaust port 26, and therefore heat balance over the whole region of a cylinder head 20 can be made uniform.

Description

  The present invention relates to an internal combustion engine for a vehicle in which two spark plugs are mounted on a cylinder head having an intake port and an exhaust port.

  For example, Patent Document 1 discloses a vehicle internal combustion engine in which two spark plugs are mounted on a cylinder head having an intake port and an exhaust port in order to improve combustion performance to improve output and reduce fuel consumption. In Patent Document 1, one spark plug is disposed near the exhaust port, which is in the vicinity of the traveling wind inlet, and the other spark plug is disposed in the vicinity of the exhaust port. These spark plugs are substantially L in a cylinder axial view. It is arranged to form a letter shape.

Japanese Patent No. 4209440

In the configuration disclosed in Patent Document 1, a spark plug is disposed near the exhaust port. However, the temperature around the port is higher on the exhaust port side than on the intake port side, and if a spark plug that also has a high temperature is arranged near the exhaust port, the heat balance in the entire cylinder head becomes poor. .
Further, in the configuration disclosed in Patent Document 1, the intake port and the exhaust port are arranged vertically, and one spark plug is arranged beside the lower exhaust port. However, the electrical parts that connect to the spark plug are often located at the rear of the engine, and the cord that connects one spark plug to the electrical part needs to pass under the engine or from the bottom to the top of the engine. The code becomes longer and difficult to route.
Furthermore, in the configuration disclosed in Patent Document 1, a running wind inlet is provided between the exhaust port and the cam chain chamber, but since one spark plug is disposed there, the running wind inlet is There is a concern that the other spark plug located in the downstream and its surroundings may be insufficiently cooled.

  The present invention has been made in view of the above points, and it is an object of the present invention to make the thermal balance of the entire cylinder head uniform when twin plugging is performed.

An internal combustion engine for a vehicle according to the present invention is an internal combustion engine for a vehicle in which two spark plugs are mounted on a cylinder head having an intake port and an exhaust port, and an intake port and an exhaust port arranged with a cylinder axis interposed therebetween, A cam chain chamber disposed on either side of the direction in which the intake port and the exhaust port are arranged, and on the opposite side of the cam chain chamber across the direction in which the intake port and the exhaust port are arranged It is characterized by comprising a first spark plug disposed and a second spark plug disposed between the intake port and the cam chain chamber.
Another feature of the vehicle internal combustion engine of the present invention is that the second spark plug overlaps with a tightening bolt of the cylinder head when viewed in the cylinder axial direction.
Another feature of the vehicle internal combustion engine of the present invention is that it includes a forced air cooling cover arranged so as to surround the cylinder head, and the first spark plug and the second spark plug are cooled air. In addition to being arranged in parallel in the passage, there is an outlet passage between the exhaust port and the cam chain chamber.

  According to the present invention, when the twin plug is formed, the first spark plug is disposed on the opposite side of the cam chain chamber across the direction in which the intake port and the exhaust port are arranged, and between the intake port and the cam chain chamber. Since the second spark plug is arranged, the thermal balance of the entire cylinder head can be made uniform.

1 is a left side view of a scooter type motorcycle according to a first embodiment. It is a left view of the power unit which concerns on 1st Embodiment. It is sectional drawing which shows the cross section orthogonal to the cylinder axis line of a cylinder head in 1st Embodiment. It is a figure which shows the state which removed the spark plug in FIG. It is sectional drawing which shows the cross section orthogonal to the cylinder axis line of a cylinder head in 2nd Embodiment.

Preferred embodiments of the present invention will be described below with reference to the accompanying drawings. In the embodiment described below, an internal combustion engine for a vehicle mounted on a scooter type motorcycle will be described as an example.
(First embodiment)
First, the overall configuration of the scooter type motorcycle 100 will be described with reference to FIG. FIG. 1 is a left side view of a scooter type motorcycle 100 according to the present embodiment. In the drawings shown below, the front side of the vehicle body is indicated by arrow Fr, the rear side of the vehicle body is indicated by arrow Rr, the right side of the vehicle body is indicated by arrow R, and the left side of the vehicle body is indicated by arrow L as necessary.

  The scooter type motorcycle 100 is provided with a steering head pipe 1 at the front of the vehicle body. In the steering head pipe 1, a down tube 2 extends substantially diagonally rearward and downward. In the vicinity of the lower end of the down tube 2, a pair of under frames 3 are extended substantially rearward. A main frame 4 extends substantially upward at each of the substantially rear ends of the pair of underframes 3. A rear frame 5 extends rearward and obliquely upward at each of the upper ends of the pair of main frames 4.

The steering head pipe 1 supports a front fork 6 so as to be rotatable. A handlebar 7 for steering is disposed at the upper end of the front fork 6 along the left-right direction, and a front wheel 8 is rotatably supported at the lower end.
A swing type power unit 9 is supported on the under frame 3 via a pivot shaft. The power unit 9 can swing up and down around a pivot shaft, and a rear wheel 10 is rotatably supported at the rear end.

  A seat 11 on which an occupant sits is installed on the upper side of the power unit 9. On the upper side of the under frame 3, a step board 12 on which a passenger's foot seated on the seat 11 is placed is supported. A front leg shield 13 covers the periphery of the down tube 2 at the front of the vehicle body. A frame cover 14 covers the periphery of the main frame 4 and the rear frame 5 from the center to the rear of the vehicle body.

FIG. 2 is a left side view of the power unit 9. The power unit 9 is formed by unitizing an engine 15 that is an internal combustion engine, a belt-type automatic transmission 16, an air cleaner box 17, a muffler 22, and the like.
The engine 15 includes a crankcase that supports a crankshaft disposed along the left-right direction, and has a configuration in which a cylinder portion 18 protrudes forward from the front end portion of the crankcase. The cylinder portion 18 includes a cylinder block 19, a cylinder head 20, and a cylinder head cover 21, and is arranged so as to be substantially horizontal.
The belt-type automatic transmission 16 transmits the output from the engine 15 to the rear wheel 10 via the belt.
An air cleaner box 17 is mounted on the upper side of the belt type automatic transmission 16. The intake air from the air cleaner box 17 is generated as an air-fuel mixture, and is sucked into the cylinder portion 18 and combusted, and then exhausted from the muffler 22 through the exhaust pipe as exhaust gas.

  3 is a cross-sectional view (cross-sectional view showing a cross section perpendicular to the cylinder axis S of the cylinder head 20) taken along the line III-III in the power unit shown in FIG. The engine 15 of the present embodiment is an SOHC air-cooled single cylinder engine. As shown in FIG. 3, a forced air cooling cover 23 is disposed so as to surround the cylinder head 20 of the engine 15, and outside air for cooling is taken into the forced air cooling cover 23 by a cooling fan that rotates integrally with the crankshaft. .

The cylinder head 20 is coupled to the top of the cylinder block 19 to form a combustion chamber 24 inside. An intake port 25 and an exhaust port 26 communicating with the combustion chamber 24 are formed in the cylinder head 20, and the intake port 25 is disposed on the upper side and the exhaust port 26 is disposed on the lower side (road surface side) across the cylinder axis S. .
As shown in FIG. 4, the cylinder head 20 has four bolt holes 27 around the combustion chamber 24. The cylinder head 20 is coupled to the cylinder block 19 by fastening tightening bolts to these bolt holes 27.

  A cam chain chamber 28 is arranged on the left side with respect to the intake port 25 and the exhaust port 26 arranged vertically. The cam chain chamber 28 accommodates a cam chain that transmits the rotation of the crankshaft to a camshaft that moves an intake valve and an exhaust valve.

  Here, a first spark plug 29 is disposed on the opposite side of the cam chain chamber 28 across the direction in which the intake port 25 and the exhaust port 26 are arranged, that is, on the right side. A second spark plug 30 is disposed between the intake port 25 and the cam chain chamber 28. These spark plugs 29, 30 are arranged so that their tips are directed to the combustion chamber 24. In this case, the direction and angle of each spark plug 29, 30 may be set as appropriate, but the second spark plug 30 is prevented from interfering with the cam chain chamber 28 when viewed in the cylinder axis S direction. Further, it is preferable that the second spark plug 30 overlaps with a tightening bolt (bolt hole 27) positioned between the intake port 25 and the cam chain chamber 28 when viewed in the cylinder axis S direction. As a result, the space can be used effectively and a twin plug can be formed without increasing the cylinder width.

  In the present embodiment, as indicated by arrows in FIG. 3, the outside air taken in by the cooling fan flows from the right side and between the intake port 25 and the cam chain chamber 28. That is, the first and second spark plugs 29 and 30 are arranged in parallel in the cooling air passage, and the first and second spark plugs 29 and 30 and their surroundings are cooled uniformly and efficiently. A space between the exhaust port 26 and the cam chain chamber 28 serves as an outlet passage, and air is exhausted from the outlet passage to the outside.

As described above, since the second spark plug 30 is disposed near the intake port 25 where the temperature is not higher than that of the exhaust port 26, the thermal balance of the entire cylinder head 20 can be made uniform. This produces the following effects.
-Higher-order deformation (distortion due to three-dimensional deformation) of the cylinder portion 18 is reduced, and the piston tension is reduced to reduce mechanical loss and improve fuel efficiency.
-The deformation of the mating surface between the cylinder head 20 and the cylinder block 19 can be suppressed and the tightening axial force of the gasket can be reduced, the deformation of the cylinder portion 18 is reduced, the piston tension is reduced, the mechanical loss is reduced, and the fuel consumption is reduced. Improvement is possible.
・ Reduces the risk of abnormal combustion.
-The heat values of the two spark plugs 29 and 30 can be made uniform, reducing misassembly, inventory management, and handling of supply parts.

Further, when the engine is arranged substantially horizontally and the intake port 25 is located at the upper portion as in the above embodiment, the second ignition plug 30 is arranged beside the intake port 25, so that the second ignition The cord can be routed along the top of the power unit 9 when the plug 30 is connected to the electrical components behind the engine. As a result, the code can be shortened, and a smooth arrangement is possible.
In addition, an oxygen concentration sensor or the like may be provided in the exhaust port 26. However, since a spark plug is not disposed near the exhaust port 26, the degree of freedom in layout of the oxygen concentration sensor or the like can be increased.

(Second Embodiment)
In the second embodiment, as shown in FIG. 5, compared to the first embodiment, the first spark plug 29 is disposed below, that is, on the exhaust port 26 side (offset amount OF ₁ ).
As a result, the intake port 25 can be shifted away from the cam chain chamber 28 (offset amount OF ₂ ), and for example, the diameter of the intake valve can be set large without increasing the cylinder width.

As mentioned above, although this invention was demonstrated with various embodiment, this invention is not limited only to these embodiment, A change etc. are possible within the scope of the present invention.
In the above embodiment, the forced air-cooled engine mounted on the scooter type motorcycle is taken as an example. It can also be applied to underbone and backbone type engines that take in cooling air from the exhaust port side.

  9: Power unit, 15: Engine, 18: Cylinder part, 19: Cylinder block, 20: Cylinder head, 21: Cylinder head cover, 23: Forced air cooling cover, 25: Intake port, 26: Exhaust port, 27: Bolt hole, 28 : Cam chain chamber, 29, 30: Spark plug

Claims (3)

An internal combustion engine for a vehicle in which two spark plugs are mounted on a cylinder head having an intake port and an exhaust port,
An intake port and an exhaust port arranged across the cylinder axis;
A cam chain chamber disposed on either side of the direction in which the intake port and the exhaust port are arranged; and
A first spark plug disposed on the opposite side of the cam chain chamber across the direction in which the intake port and the exhaust port are arranged;
An internal combustion engine for a vehicle, comprising: a second spark plug disposed between the intake port and the cam chain chamber.   2. The internal combustion engine for a vehicle according to claim 1, wherein the second spark plug overlaps with a tightening bolt of the cylinder head when viewed in the cylinder axial direction.   A forced air cooling cover arranged to surround the cylinder head, wherein the first spark plug and the second spark plug are arranged in parallel in the cooling air passage, and the exhaust port and the cam chain chamber The vehicle internal combustion engine according to claim 1, wherein an outlet passage is provided between the two.

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