JP2749161B2 - Valve train for SOHC engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a valve train for an SOHC engine having three intake valves, and in particular, reduces irregularities on the combustion chamber wall surface to promote spheroidization of the combustion chamber shape. The present invention relates to an improved intake valve arrangement structure.

[Prior Art] Recently, a multi-valve engine provided with three or more intake valves in order to further increase the opening area of the intake valve while securing the rigidity of the cylinder head has attracted attention. It is also known that it is advantageous to make the shape of the wall of the combustion chamber spherical in order to improve the combustion efficiency of the engine. When a large number of intake valves are provided as described above, the valve plate of each valve may be arranged along the spherical combustion chamber wall surface, but in this case, each valve stem extends radially. In addition, the valve operating mechanism becomes extremely complicated. In order to avoid this complication, a structure is generally adopted in which each valve stem is arranged at right angles to the cam shaft when viewed in the cylinder axis direction (in plan view). As such a valve train, there is a conventional one described in, for example, Japanese Patent Application Publication No. 63-502681. In this conventional device, three intake valve openings are formed along the periphery of the combustion chamber, and each intake valve that opens and closes each opening is formed at right angles to the cam shaft when viewed in the cylinder axis direction and outwardly when viewed in the cam shaft direction. It is arranged to be inclined toward In this case, the central intake valve is further raised and intersects the left and right intake valves at a predetermined angle, and the intersection between the two is located below the upper end of the central intake valve rod.

[Problems to be solved by the invention]

By the way, when each intake valve is arranged at right angles to the camshaft in plan view as in the valve operating device described in the above-mentioned publication, the valve operating mechanism becomes simple, but in particular, the opening of the central intake valve on the wall of the combustion chamber and the left and right. Irregularities are likely to occur at the boundary with the intake valve opening, and if both intake valves are simply tilted, the above-described requirement for the spherical shape of the combustion chamber wall surface cannot be met.

The present invention has been made in view of the above conventional needs,
SO that can further promote spheroidization by reducing unevenness at the boundary between the central intake valve opening and the left and right intake valve openings on the combustion chamber wall
It aims to provide a valve train for an HC engine.

[Means for solving the problem]

According to the present invention, three intake valves are arranged on one side of one camshaft, and exhaust valves are arranged on the other side, and each valve is pivoted by a rocker shaft arranged in parallel with the camshaft by the camshaft. In the valve operating device for an SOHC engine that is driven via a supported rocker arm, the intake valves 34 to 36 are disposed substantially at right angles to the cam shaft 42 when viewed in the cylinder axis direction. An intake rocker shaft 45 is arranged between the intake valves 34 to 36 in parallel with the cam shaft 42, and the see-saw type intake rocker arms 51, 52 are supported by the intake rocker shaft 45. Attach adjust screws 53, 54 for pressing the upper ends of the intake valves 34 to 36, and divide the intake valves 34 to 36 into a central intake valve 35 and side intake valves 34, 46 located on both sides of the central intake valve 35, When viewed in the camshaft direction, the axis A of the central intake valve 35 is aligned with the side intake valves 34, 36.
And the distance l2 of the central intake valve 35 from the rocker shaft 45 is set to be greater than the distance l1 of the side intake valves 34, 35 from the rocker shaft 45, and the axis A of the central intake valve 35 The axis B of the side intake valves 34 and 36 intersects at the upper part C from the upper ends of all the intake valves, and the opening 14d for adjusting the adjusting screws 53 and 54 is formed in the head cover 14 that covers the upper part of the cylinder head 13. A cap 57 is formed so as to face the crossing portion outward, and a cap 57 for opening and closing the opening 14d is provided. The central intake valve 35 and one of the side intake valves 36 are bifurcated by one cam nose 42c. Is driven via the rocker arm 52 of the first embodiment.

[Action]

According to the valve train of the engine according to the present invention, the axis A of the central intake valve 35 and the axis B of the side intake valves 34 and 36 intersect above the upper end of any of the valve shafts when viewed in the camshaft direction. Therefore, the intersection angle between the central intake valve 36 and the side intake valves 34, 36 is smaller than that described in the above-mentioned publication that intersects below the upper end of the central intake valve, that is, the two intake valves are more parallel. As a result, the unevenness that occurs at the center opening of the combustion chamber wall surface, at the boundary between the openings on both sides, and the like is reduced, and as a result, the combustion chamber wall shape becomes more spherical.

Since the central intake valve 35, the side intake valves 34, 36 crossed above the upper ends of all the intake valves, and provided an adjustment screw adjustment opening 14d such that the intersection faced outward,
The adjusting screws of the intake valves 34 to 36 are combined in a narrow range in the direction perpendicular to the camshaft, so that the opening 14d for adjusting the adjusting screw can be combined into one, and at that time, the opening 14d and its An increase in the size of the cap 57 can be suppressed.

Further, the distance l2 from the rocker shaft 45 to the central intake valve 35 is made larger than the distance l1 to the side intake valve 36, and the two intake valves 35, 36 are bifurcated rocker arms 52 driven by one cam nose 42c. Therefore, the valve lift of the central intake valve 35 can be set to be larger than the lift of the side intake valve 36 with a simple structure having a common cam nose.

As a result, even when the intake resistance is increased due to, for example, a sudden bending of the central intake port shape communicating with the central intake valve 35, the intake amount from the side intake valve is large because the lift amount of the central intake valve is large. The intake volume equal to the volume can be secured.

〔Example〕

 Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

1 to 7 are views for explaining a valve operating device of an SOHC engine according to an embodiment of the present invention.
2 is a sectional view taken along the line II and II-II of FIG. 3, FIG. 3 is a plan view of the apparatus, FIG. 4 is a sectional plan view of the vicinity of the intake and exhaust passages, and FIG. FIG. 6 is a bottom view of the cylinder head, FIG. 6 is a rear view near the upper end of the intake valve, and FIG. 7 is a right side view of a motorcycle equipped with the engine of the present embodiment. The plan view,
In the side view, the right side in the drawing is the front of the vehicle. Hereinafter, unless otherwise specified, the description will be made assuming that the front is viewed from the rear side of the vehicle.

In the drawing, reference numeral 1 denotes a motorcycle on which the engine of this embodiment is mounted, and a body frame 2 of the motorcycle 1 has a main pipe 2b and a front end of a down tube 2c welded to an upper part and a lower part of a head pipe 2a. It is a so-called diamond type in which the upper end of the sheet pillar 2d is connected to the rear end of the main pipe 2b by welding. In addition, 2g is an underguard for protecting the crankcase, 2e is an engine suspension support pipe that is bridged in the middle of the main pipe 2b and the down tube 2c, and 2f is a seat rail.

A front fork 3 for pivotally supporting the front wheel at the lower end is pivotally supported on the head pipe 2a at the lower end, and a rear arm 5 for pivotally supporting the rear wheel 4 at the rear end is pivotally mounted on the rear pipe 2d. It is pivotally supported. The rear arm 5 is connected to the vicinity of the rear end of the main pipe 2b through a link mechanism (not shown) and one shock absorber 8. Reference numeral 6 denotes a fuel tank, 7 denotes a seat, 9a denotes an air scoop that covers a side surface of the tank, 9b denotes a side cover that covers a lower portion of the seat, and 9c denotes a rear cover that covers a rear portion of the vehicle.

An engine unit 10 is suspended and supported in the vehicle body frame 2. This engine unit 10 is a water-cooled 4-cycle single-cylinder 5-valve engine, and a crankcase 11
The cylinder body 12, the cylinder head 13, and the head cover 14 are slightly tilted forward and stacked on the upper surface of the front part. One combustion chamber wall surface 13a is recessed substantially in the center of the lower surface of the cylinder head 13. The wall 13a forms a combustion chamber 15 with the head of a piston (not shown) slidably inserted into the cylinder liner 12a of the cylinder body 12. A plug screw hole 1 is provided substantially at the center of the combustion chamber wall 13a.
3b are formed, and the plug screw holes 13b are formed in the plug insertion holes 13 formed in the cylinder head 13 and the head cover 14.
It is led outward by c and 14a so as to be inclined toward the exhaust side (front side) with respect to the cylinder axis. An ignition plug 16 is screwed into the plug screw hole 13b.

Left, center, and right intake valve openings 17, 18, and 19 are provided on one side of the combustion chamber wall 13a of the cylinder head 13 across the plug screw hole 13b, and left and right exhaust valves are provided on the other side. Valve opening 2
0,21 are formed, and the plug insertion hole 13c is
It extends upward between the right exhaust valve openings 20,21. The left intake valve opening 17 is led to the rear wall of the cylinder head by a left intake passage 22 extending rearward of the vehicle so as to be substantially orthogonal to an axis of a cam shaft 42 described later in a plan view. The openings 18 and 19 are led out rearward by a middle intake passage 23a extending rightward in the vehicle width direction with respect to the camshaft 42 and a right intake passage 23b extending substantially perpendicular to the camshaft 42, and a merging passage 23 of the two intake passages 23a and 23b is provided.
Extends rightward in the vehicle width direction as a whole. Left and right carburetors 26 and 27 are connected to the rear end openings of the left intake passage 22 and the merging passage 23 via left and right cab joints 24 and 25, respectively.

The left and right exhaust valve openings 20 and 21 are led out to the front wall of the cylinder head by left and right exhaust passages 28 and 29 extending in the shape of a letter C and extending forward of the vehicle. The left and right exhaust pipes 31, 32 of the device 30 are connected. The two exhaust pipes 31, 32 are bent rightward after passing through the left and right sides of the down tube 2c, and merged here and extend rearward of the vehicle. 33 is connected.

The left, center, and right intake valve openings 17, 18, and 19 have valve plates 34a, 35a, which open and close the left, center, and right intake valves 34, 35, 36, respectively.
In the left and right exhaust valve openings 20 and 21, valve plates 37a and 38a of left and right exhaust valves 37 and 38 for opening and closing the same are disposed, respectively. The valve rods 34b to 38b of the valves 34 to 38 penetrate the ceiling walls of the intake and exhaust passages 22, 23a, 23b, 28, and 29 and protrude upward from the mating surface of the cylinder head 13.

Here, the valve rods 37b, 38b of the exhaust valves 37, 38 are perpendicular to the cam shaft 42 when viewed from a plane, that is, parallel to each other,
When viewed in the direction of the camshaft 42, they are inclined forward at the same angle and overlap each other. Each of the exhaust valves 37 and 38 has an urging spring 41 interposed between an upper stopper 39 fixed to an upper end thereof and a lower stopper 40 disposed on a spring seat of the cylinder body 13.
The openings 20 and 21 are urged to close.

The valve rods 34b to 36b of the intake valves 34 to 36 also form a right angle with the camshaft 42 in a plan view, and when viewed in the camshaft direction, the left and right intake valves 34 and 36 correspond to the exhaust valves 37 and 38, respectively. They are inclined backward at substantially the same angle and overlap each other. Also, the stem 35 of the central intake valve 35
b is arranged in a more upright state than the left and right intake valves 34,36. And the valve rods 34b, 3 of the left and right intake valves 34,36
The upper end of 6b is located below the upper end of the valve stem 35b of the middle intake valve 35, and the intersection C of these axes A, B is further higher than the upper ends of the left and right valve stems 34b, 36b located at a higher position. It is located above. When viewed in the cylinder axis direction, the upper end of the valve stem 35b of the central intake valve 35 is located behind the upper ends of the left and right valve stems 34b, 36b. The intake valves 34 to 36 are urged in the closing direction by an urging spring 41 provided between the upper and lower stoppers 39 and 40. The intake valves 34 to 36 and the exhaust valves 37 and 38 do not need to be completely perpendicular to the camshaft 42, and may be arranged obliquely as long as the rocker arm does not hinder swinging.

The camshaft 42 is provided between the intake and exhaust valves,
It is arranged so as to cross the upper position of approximately 15 central positions. The left and right ends and the center of the cam shaft 42 are supported by cam bearings. The left and right cam bearings are formed by the left and right lower bearings 13d and 13f formed on the mating surface of the cylinder head 13 and the head cover 14.
And left and right upper bearings (not shown) formed on the mating surface of the upper and lower surfaces. The cam bearing at the center includes a lower center bearing 13e formed at the center of the cylinder head 13 and an upper center bearing 14b formed at the center of the head cover 14. Reference numeral 43 denotes a driving sprocket fixed to the left end of the camshaft 42, and reference numeral 44 denotes a decompression device for reducing the starting torque by slightly releasing the compression pressure from the left exhaust valve 37 when starting the engine.

Here, the left, right, and center cam bearings are of a two-part type, and are constituted by fixing the head cover 14 to the cylinder head 13.
14 and the cylinder head 13 are fixed with fixing bolts at the opening peripheral edge (joint face), the respective cam bearings, and both edges of the plug insertion port 13c (hatched in FIG. 3). Shown). Of the opening peripheral portion, a flange 14g formed on the outer side between caps 56, which will be described later, is fixed with fixing bolts 50a on the exhaust side, while the intake valve is connected between the intake valves on the intake side. Flanges 14h formed inside two places are fixed with fixing bolts 50b. The fixing bolt 50b faces outward when the cap 57 is removed. 50 of the fixing bolts are also used for fixing the cylinder head to the head cover and for locking the rocker shaft, which will be described later. However
50c is a non-rotating bolt.

Left and right exhaust rocker shafts 46a and 46b are disposed between the cam shaft 42 and the left and right exhaust valves 37 and 38 in parallel with the cam shaft 42, and are integrally formed on the inner surface of the head cover 14. The head cover fixing bolt 5 supported by the bearing portion 14e
It is stopped at 0. The left and right exhaust rocker shafts 36a, 3
The left and right exhaust rocker arms 47 and 48 are swingably supported by 6b. Sliding portions 47a, 48a formed at the rear ends of the rocker arms 47, 48 are provided on the left and right exhaust cams 4 of the cam shaft 42.
2a and 42d, and the lower end of an adjusting screw 49 screwed into the front ends 47b and 48b is connected to the left and right exhaust valve rods 37.
It is in contact with the upper ends of b and 38b.

Further, between the camshaft 42 and the intake valves 34 to 36, the left,
An intake rocker shaft 45 having a length extending over the right cam bearing is arranged in parallel with the cam shaft 42, and the rocker shaft 45 is supported at both ends and a central portion by bearings 14f formed integrally with the head cover 14, And it is prevented from rotating by a head cover fixing bolt 50. A left intake rocker arm 51 is pivotally supported on a left portion of the rocker shaft 45 from the center cam bearing, and a right intake rocker arm 52 is pivotally supported on a right portion of the rocker shaft 45. A sliding portion 51a formed at the front end of the left intake rocker arm 51 is a left intake cam formed to the left of the center cam bearing of the camshaft 42.
The lower end of the adjustment screw 53 screwed into the rear end 51b is in contact with the upper end of the left intake valve rod 34b. A sliding portion 52c formed at the front end of the right intake rocker arm 52 is in sliding contact with a right intake cam 42c formed on the cam shaft 42 on the right of the center cam bearing. The rear half of the right intake rocker arm 52 is branched into a central arm 52a and a right arm 52b, and rear ends 52d and 52e, respectively.
The adjustment screws 54 and 53 screwed into the center contact the upper ends of the center and right intake valve rods 35b and 36b. As described above, the upper end of the central intake valve rod 35b is located above the upper ends of the left and right intake valve rods 34b and 36b when viewed in the cam axis direction, and is located rearward when viewed in the cylinder axis direction. I have. Therefore, the adjustment screw 54 for the central intake valve 35 from the rocker shaft 45
Is longer than the plane projection distance l1 'to the adjustment screw 53 for the left and right intake valves 34, 36. As a result, the arm length (vertical distance from the rocker shaft to the axis A) l2 of the central intake valve 35 is also changed to the left and right intake valves 34,3.
6 is longer than the arm length l1.

On the exhaust valve side of the head cover 14, two adjusting ports 14c for adjusting the adjusting screws 49 of the left and right exhaust valves 37 and 38 are formed, which can be opened and closed by separate caps 56. ing. On the intake valve side, adjust screws 53,5 for the left, center, and right intake valves 34-36.
One adjustment port 14d for adjusting 4 is formed,
It is opened and closed by one cap 57.

 Next, the operation and effect of this embodiment will be described.

When the three intake valves are arranged at right angles to the camshaft in plan view as described above, a step is likely to occur at the boundary between the central intake valve opening and the left and right intake valve openings on the wall of the combustion chamber, and the combustion takes place. There is a problem that it is difficult to make the room wall spherical. In the present embodiment, the intersection C between the axis A of the central intake valve rod 35b and the axis B of the left and right intake valve rods 34b, 36b is located above the upper end of the central intake valve rod 35b located at a higher position. , Compared to the conventional structure described in the above-mentioned publication that is located below, the two axes A, B
, That is, the two intake valves become closer to each other in parallel, so that the step formed at the boundary a between the middle intake valve opening 18 and the left and right intake valve openings 17, 19, etc. of the combustion chamber wall 13a is reduced. As a result, irregularities are reduced on the combustion chamber wall surface 13a, and the combustion chamber is made more spherical. In addition, the volume of the combustion chamber can be reduced by the amount of spheroidization, and the compression ratio can be increased.

In addition, since the central intake valve 35 and the side intake valves 34 and 36 intersect above the upper ends of all the intake valves, and an adjustment screw adjustment opening 14d is provided so that the intersection faces outward, the intake valve The adjusting screws 34 to 36 are combined in a narrow range in the direction perpendicular to the camshaft, so that the opening 14d for adjusting the adjusting screw can be combined into one, and the opening 14d and its cap 57 Can be suppressed from increasing.

Further, the distance l2 from the rocker shaft 45 to the central intake valve 35 is made larger than the distance l1 to the side intake valve 36, and the two intake valves 35, 36 are bifurcated rocker arms 52 driven by one cam nose 42c. Therefore, the valve lift of the central intake valve 35 can be set larger than the lift of the side intake valve 36 with a simple structure using a common cam nose.

As a result, even when the intake resistance is increased due to, for example, a sudden bending of the central intake port shape communicating with the central intake valve 35, the intake amount from the side intake valve is increased due to the large lift amount of the central intake valve. The intake volume equal to the volume can be secured.

Note that, in the above embodiment, the case where the upper end of the central intake valve rod 35b and the upper ends of the left and right intake valve rods 34b, 36b are located at different heights has been described. As shown, the present invention can be applied to the case where the upper ends of the center, left and right intake valve rods are located at the same height. In the drawing, the same reference numerals as those in FIG. 1 indicate the same or corresponding parts.

Furthermore, in the above-described embodiment, a single cylinder engine has been described. However, the present invention can of course be applied to a multiple cylinder engine.

〔The invention's effect〕

As described above, according to the valve gear of the SOHC engine according to the present invention, since the axis of the central intake valve and the axis of the intake valves on both sides intersect above the upper end of either valve axis, these intake valves The crossing angle of the valve becomes smaller, that is, becomes closer to parallel, and the unevenness of the combustion chamber wall surface is reduced, which has the effect of promoting the spheroidization of the combustion chamber shape.

The distance (arm length) from the rocker shaft to the central intake valve is made longer than the distance to the side intake valve, and the central intake valve and one side intake valve are provided with a bifurcated rocker arm driven by one cam nose. Because it is driven through a simple structure with a common cam nose,
The valve lift amount of the central intake valve can be set larger than the lift amount of the side intake valve. As a result, for example, even when the intake resistance of the central intake passage is large, an intake amount equal to the intake amount from the side intake valve can be secured. effective.

[Brief description of the drawings]

1 to 7 are views for explaining a valve train of an SOHC engine according to one embodiment of the present invention. FIGS. 1 and 2 are sectional views taken along line II of FIG. 3, respectively. FIG. 3 is a plan view of the device, FIG. 4 is a cross-sectional plan view showing intake and exhaust passages, FIG. 5 is a bottom view of a cylinder head, and FIG. 6 is an upper end of an intake valve shaft. FIG. 7 is a right side view of a motorcycle equipped with the engine of the embodiment, FIG.
The figure is a sectional side view showing a modification of the above embodiment. In the figure, 10 is an engine, 15 is a combustion chamber, 34 and 36 are left,
Right intake valve, 35 is a middle intake valve, 37 and 38 are exhaust valves, 42 is a cam shaft, 45 is an intake rocker shaft, 51 and 52 are left and right rocker arms,
A and B are the left and right intake valve axis, the middle intake valve axis, and C is the intersection of both axes.

Claims (1)

(57) [Claims] 1. A camshaft having three intake valves disposed on one side and an exhaust valve disposed on the other side, wherein each valve is a rocker shaft arranged in parallel with the camshaft by the camshaft. In the valve operating device for an SOHC engine that is driven via a rocker arm supported by a shaft, each of the intake valves is disposed substantially at right angles to a camshaft as viewed in the cylinder axis direction, and the camshaft and the intake valve are connected to each other. An intake rocker shaft is disposed in parallel with the cam shaft, a seesaw type intake rocker arm is pivotally supported by the intake rocker shaft, and an adjusting screw for pressing an upper end of an intake valve is attached to an end of the intake rocker arm. The intake valve is divided into a central intake valve and side intake valves located on both sides of the central intake valve, and the axis of the central intake valve stands up from the axis of the side intake valve when viewed in the cam axis direction. From the side intake valve rocker shaft The distance between the central intake valve and the side intake valve is set to be greater than the upper ends of all the intake valves, and the adjust screw is adjusted to the head cover that covers the upper part of the cylinder head. An opening is formed so that the above-mentioned intersection faces outward,
A cap for opening and closing the opening is provided, and the central intake valve and one of the side intake valves are driven via a forked rocker arm driven by one cam nose. Valve device.