JPH05179966A - Valve system for internal combustion engine - Google Patents

Abstract

PURPOSE:To independently adjust the mean effective opening areas of a plurality of valves driven by means of a rocker arm, in the valve system of an internal combustion engine in which the phase and the contact position of a can are changed so as to change the valve timing and the valve lift. CONSTITUTION:The distances L1, L2 from a rocker arm axis 13a to two valve drive parts 15a1, 15a2 provided on a rocker arm 14a are let differ from each other so as to let differ valve lift of two intake valves 7a1, 7a2 from each other, the diameter of the valve head part 17a1 of the intake valve 7a1 on the smaller valve lift side is formed small, and the diameter of the valve head part 17a2 of the intake valve 7a2 the larger valve lift side is formed large. Hereby, while keeping the mean effective opening areas of both intake valves 7a1, 7a2 to be equal to each other in the high speed running territory, the mean effective opening areas in the low speed running territory are allowed to let differ from each other so as to generate swirl in the mixture sucked into a cylinder, and hence combustion efficiency can be improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention supports a camshaft having a cam and a cam gear on a camshaft supporting member which is rockably driven around a rocking center and is rotatably supported around the rocking center. By interlockingly connecting the cam gear to an idler gear that is rotationally driven by a crankshaft and swinging the camshaft support member to change the position and phase at which the cam contacts the rocker arm, the valve of the valve driven by the rocker arm is changed. The present invention relates to a valve drive device for an internal combustion engine in which valve lift and valve timing are variable.

[0002]

2. Description of the Related Art A valve drive device for such an internal combustion engine has already been proposed by the present applicant and is known from Japanese Patent Laid-Open No. 130510/1993.

[0003]

By the way, in the above-mentioned conventional valve drive device, each rocker arm drives two intake valves or exhaust valves by two valve drive portions provided therein, and two rocker arms are provided. The distances of the valve drives from the rocker arm axis are set equal to each other. Therefore, the valve lift and the valve timing of the two intake valves are equal to each other, and the intake amount and the intake timing of the air-fuel mixture sucked from the two intake ports are the same. as a result,
In particular, at low load and low speed operation where the intake speed of the internal combustion engine becomes slow, sufficient swirl cannot be generated in the air-fuel mixture sucked into the cylinder, which may cause deterioration of combustion.

The present invention has been made in view of the above circumstances, and an internal combustion engine capable of causing a sufficient swirl in an air-fuel mixture sucked into a cylinder by changing the valve average effective opening area for each valve. It is an object of the present invention to provide a valve drive device of the above.

[0005]

In order to achieve the above object, the present invention supports a camshaft having a cam and a cam gear on a camshaft supporting member which is rockably driven around a rocking center, and at the same time, Connecting the cam gear to an idler gear that is rotatably supported around the center of motion and rotationally driven by a crankshaft, and swinging the camshaft support member to change the position and phase at which the cam contacts the rocker arm. Thus, in the valve drive device of the internal combustion engine in which the valve lift and valve timing of the intake valve and the exhaust valve driven by the rocker arm are variable, a plurality of valves that can abut the rocker arm at the tips of the shaft portions of the plurality of intake valves. A drive unit is provided, and the distance between the valve drive unit and the fulcrum of the rocker arm is made different for each of the plurality of intake valves. The first feature and.

In addition to the above-mentioned first feature, the present invention also provides:
A second feature is that the diameters of the umbrella portions of the plurality of valves are different from each other.

In addition to the first feature described above, the present invention also provides
A third feature is that the angles of the shaft portions of the plurality of valves are different from each other.

[0008]

Embodiments of the present invention will be described below with reference to the drawings.

1 to 10 show a first embodiment of the present invention. FIG. 1 is a longitudinal sectional view of a cylinder head portion of an internal combustion engine (a sectional view taken along line 1-1 in FIG. 2), and FIG. 2 is a sectional view taken along line 2-2 of FIG. 1, FIG. 3 is a sectional view taken along line 3-3 of FIG. 1, and FIG.
4 is a sectional view taken along line 4, FIG. 5 is a sectional view taken along line 5-5 of FIG. 1, and FIG.
6-6 is an enlarged arrow view of FIG. 6, FIG. 7 is a 7-direction arrow view of FIG. 6, FIG. 8 is an explanatory view of the action, FIG. 9 is a graph showing valve lift and valve timing, and FIG. It is a graph shown.

As shown in FIGS. 1 to 3, a double overhead camshaft type four-cycle internal combustion engine E includes a cylinder head 3 joined to an upper portion of a cylinder block 2 into which a piston 1 is slidably fitted, A head cover 4 joined to the upper part of the cylinder head 3 is provided.

On the top surface of the piston 1, the cylinder head 3
The combustion chamber 5 is formed so as to face each other, and the combustion chamber 5 is opened.
The pair of intake ports 6a and the pair of exhaust ports 6b
Are each two intake valves 7a₁, 7a₂And two exhaust valves 7
b₁, 7b₂Is installed. Intake valve 7a₁, 7a₂And elimination
Air valve 7b₁, 7b₂The valve shafts 8a and 8b
Slidably supported by the valve seat 9
Upper and lower retainers 10a, 1 for seating on a, 9b
0b; valve springs 12a, 12 compressed between 11a, 11b
B is urged upward. And both valves 7a₁, 7a
₂; 7b₁, 7b ₂The upper end of the shaft part of the
The rocker arm shafts 13a and 13b are pivotally supported so as to be swingable.
Intake side rocker arm 14a and exhaust side rocker arm
14b is contacted and driven.

As can be seen by referring to FIG. 4 together,
The lower end of a cam shaft support member 23, which is formed by connecting the upper ends of a pair of side plates 20 and 21 formed in a substantially triangular shape to each other with a cam holder 22, connects the cylinder head 3 with the bolt 2
It is swingably supported by boss members 26, 27 fixed by 4, 25. A pair of side plates 2 of the camshaft support member 23
An intake side camshaft 28a and an exhaust side camshaft 28b are rotatably installed between 0 and 21.

An idler gear 31 is supported by a boss member 29 provided coaxially on the outer side of the one boss member 27 via a ball bearing 30, and a driven sprocket 32 and a crankshaft 33 integrally provided on the idler gear 31 are attached to the idler gear 31. The provided drive sprocket 34 is connected via a chain 35. A reduction gear shaft 36 is detachably supported by a pressing member 37 at the center of one side plate 21, and a first reduction gear 38 and a second reduction gear 39 that rotate integrally are provided on the outer periphery of the reduction gear shaft 36. It is supported via a ball bearing 40. Then, the first reduction gear 38 meshes with the idler gear 31, and the second reduction gear 3
Reference numeral 9 simultaneously meshes with an intake cam gear 41a provided on the intake cam shaft 28a and an exhaust cam gear 41b provided on the exhaust cam shaft 28b. The reduction gear shaft 36 and both reduction gears 38 and 39 are
After the cam shaft support member 23 is mounted inside the cylinder head 3, it is mounted through the upper opening of the cylinder head 3.

The first reduction gear 38 has a larger diameter than the second reduction gear 39, and the rotation of the idler gear 31 is accelerated and transmitted to the first reduction gear 38, and the rotation of the second reduction gear 39 is also increased. Is decelerated and transmitted to both cam gears 41a and 41b. Finally, both cam gears 41a and 41b are driven at a rotational speed that is ½ of the rotational speed of the crankshaft 33.

Intake side provided on intake side camshaft 28a
The cam 42a contacts the intake side rocker arm 14a,
Further, the exhaust side cam 42 provided on the exhaust side cam shaft 28b
b is brought into contact with the exhaust side rocker arm 14b.
The intake valve 7a₁, 7a ₂And exhaust valve 7b₁, 7b₂
Is driven to open and close. At this time, both rocker arms 14a,
The slipper surface of 14b causes the camshaft support member 23 to swing.
With the center of motion O, that is, the center of rotation of the idler gear 31, as the center
Is formed so as to form an arc surface.

As is apparent from FIG. 1, one side plate 21.
The upper part thereof is inclined toward the center line side of the internal combustion engine E, and the reduction gear shaft 36 and both reduction gears 38, 39 are arranged in a space formed outside the inclined side plate 21. As a result, the reduction gear shaft 36 and both reduction gears 38 and 39 can be arranged on the upper extension line of the chain 35 connecting the drive sprocket 34 and the driven sprocket 32, and the internal space of the cylinder head 3 can be effectively used. Thus, it is possible to avoid an increase in the axial dimension of the internal combustion engine E.

As is clear from FIGS. 1 and 4, the boss member 27 for supporting the side plate 21 oil passage 27 ₁ connected to an oil pump (not shown) is formed, the oil passage 27 ₁
Is connected from an oil passage 21 ₁ penetrating the inside of the side plate 21 to an oil passage 36 ₁ formed inside the reduction gear shaft 36 via an orifice 43. The oil supplied from the oil passage 36 ₁ of the reduction gear shaft 36 to the outside is the first reduction gear 38 and the second reduction gear 39, and the idler gear 31 and both cam gears 41a that mesh with them.
Lubricate 41b. Further, the oil supplied to the oil passage 27 ₁ of the boss member 27 lubricates the intake side camshaft 28a and the exhaust side camshaft 28b via the other pair of oil passages 21 ₂ formed in the side plate 21.

As is apparent from FIGS. 1 and 5, the swing drive mechanism D for swinging the camshaft support member 23 around the swing center O is fixed to the outside of the other side plate 20 of the camshaft support member 23. Equipped sector gear 44. A worm gear shaft 46 having a worm gear 45 meshing with the sector gear 44 is provided inside the cylinder block 2.
It is supported via a pair of ball bearings 47. The output gear 48 provided at the end of the worm gear shaft 46 meshes with the second intermediate gear 52 of the intermediate shaft 51 supported by the pair of ball bearings 50 inside the gear box 49, and the second gear
The first intermediate gear 53 that rotates integrally with the intermediate gear 52 meshes with a pinion 55 of a servomotor 54 provided outside the gear box 49.

When the servo motor 54 is driven,
The rotation of the pinion 55 is transmitted to the sector gear 44 via the first intermediate gear 53, the second intermediate gear 52, the output gear 48, and the worm gear 45, and the intake valves 7a ₁ , 7
a ₂ and the exhaust valve 7b _1, the cam in order to change the valve timing and valve lift 7b ₂ shaft support member 2
3 swings around the swing center O.

Next, the intake side rocker arm 14a and the intake valves 7a ₁ and 7a ₂ will be described in detail with reference to FIGS. 6 and 7. The left and right sides of the intake side rocker arm 14a, 2 pieces of intake valve 7a _1, the shaft portion 16a ₁ of 7a _2, 16a ₂ tip respectively contactable to a pair of valve driving portion 15a _1, 15a
₂ is integrally formed. Distance from the center of the valve driving portion 15a ₁ which drives the one of the intake valve 7a ₁ fulcrum i.e. the intake side rocker arm shaft 13a of the intake-side rocker arm 14a L ₁
The valve drive portion 15a _{2 which} is provided at the position for driving the other intake valve 7a ₂ is provided at a position at a distance L ₂ from the center of the intake side rocker arm shaft 13a. Since the distance L ₂ is set larger than the distance L ₁ , the intake-side rocker arm 14
When a swings by a predetermined angle, the intake side rocker arm shaft 13
valve lift side of the intake valve 7a ₂ close to a is less than the far side valve lift of the intake valve 7a ₂ from the intake side rocker arm shaft 13a.

Further, the diameter D ₁ of the umbrella portion 17a ₁ of the intake valve 7a ₁ near the intake side rocker arm shaft 13a is the diameter D ₁ of the umbrella portion 17a ₂ of the intake valve 7a ₂ far from the intake side rocker arm shaft 13a. Formed larger than ₂ . That is, the umbrella portion 17 of the intake valve 7a _{1 with} the smaller valve lift.
The diameter D ₁ of the a ₁ is larger, the diameter D ₂ of the umbrella portion 17a ₂ of the intake valve 7a ₂ towards the valve lift is large is smaller, the relationship of the distance L _1, L ₂ and diameter D _1, D ₂ is ,
It is set so as to satisfy (L ₂ / L ₁ ) = (D ₁ / D ₂ ).

In this embodiment, the exhaust side rocker arm 1
The pair of valve drive portions formed in 4b are provided at the same position from the exhaust side rocker arm shaft 13b, and the diameters of the umbrella portions of the pair of exhaust valves 7b ₁ and 7b ₂ are also formed to be the same.

Next, the operation of the embodiment of the present invention having the above construction will be described.

Drive sprocket on crankshaft 33
34, chain 35, and driven sprocket 32
Of the idler gear 31 connected by the
The first of the reduction gear shaft 36 supported by the support member 23
Reduction gear 38 and second reduction gear 39
Is transmitted to the pair of cam gears 41a and 41b via.
A pair of cam gears driven by the cam gears 41a and 41b.
The shafts 28a and 28b are half of the crankshaft.
It rotates at the number of revolutions and is installed on these camshafts 28a, 28b.
Contact with the intake side cam 42a and the exhaust side cam 42b
The rocker arms 14a and 14b are rocker arm shafts 13.
rocker arms 14a, 1 swinging around a, 13b.
Intake valve 7a pressed by 4b₁, 7a₂And exhaust valve 7
b₁, 7b ₂Is 1 for every 2 revolutions of the crankshaft 33
Open the valve one by one. At this time, the intake side cam 42a and the exhaust side
Both cams 42b rotate counterclockwise in FIG.
However, the phase of the exhaust side cam 42b is the same as that of the intake side cam 42a.
It is about 90 ° ahead of the phase.
b₁, 7b₂Of the intake valve 7 and then the intake valve 7
a₁, 7a₂The valve opening period of occurs. And the exhaust valve 7b
₁, 7b₂Valve opening period and intake valve 7a₁, 7a₂Opening period
There is a slight overlap between the exhaust valves 7b₁, 7b ₂And intake
Valve 7a₁, 7a₂Valve overlap period of
Be done.

Now, as shown in FIG. 8A, the internal combustion engine E
Is in the low speed rotation range, the cam shaft support member 23 is in a state of oscillating in the clockwise direction, and both cams 42a and 42b are in contact with the tip ends (right side in the figure) of the rocker arms 14a and 14b. In this state, both rocker arm shafts 13a,
13b to the cams 42a and 42b and the rocker arm 14
Since the distance to the contact point between a and 14b increases, the rocking angle of the rocker arms 14a and 14b decreases, and as shown in FIG. 9, the intake valves 7a ₁ and 7a ₂ and the exhaust valves 7b ₁ and 7b ₂
The valve lift of both becomes small.

When a sensor (not shown) detects an increase in the number of revolutions of the internal combustion engine E, the camshaft support member 23 is centered around the swing center O by the sector gear 44 meshing with the worm gear 45 driven by the servomotor 54. Swing counterclockwise to position 8 (B). Then, the intake-side camshaft 28a and the exhaust-side camshaft 28b, which are erected on the camshaft support member 23, swing together and both cams 42a, 4a.
Since the contact point between 2b and the rocker arms 14a, 14b moves to the rocker arm shafts 13a, 13b side, the rocking angles of the rocker arms 14a, 14b increase, and the intake valves 7a ₁ , 7b.
Both a ₂ and the valve lift of the exhaust valves 7b ₁ and 7b ₂ increase, and the time area of valve overlap also increases as compared with the low speed rotation range. At the same time, when the camshaft support member 23 swings counterclockwise, the intake-side cam gear 41a and the exhaust-side cam gear 41b, which mesh with the idler gear 31 via the first reduction gear 38 and the second reduction gear 39, move clockwise, That is, both camshafts 28
Since it slightly rotates in the direction opposite to the driving direction of a and 28b,
The phase angle between the intake-side cam 42a and the exhaust-side cam 42b moves to the delay side, and the valve closing timing is delayed (see FIG. 9).

In this way, the valve lift is reduced and the opening speed of the exhaust valves 7b ₁ and 7b ₂ is reduced in the low speed rotation range, so that the exhaust gas blowdown becomes slow and exhaust noise can be reduced. And the cams 42a, 4
The surface pressure of the contact portion between 2b and the rocker arms 14a and 14b is reduced, and the lubrication can be easily performed. Further, since the time area of valve overlap in the low speed rotation range can be reduced, the intake port 6a to the exhaust port 6 can be reduced.
Not only does the fresh air passing through b decrease and the harmful components in the exhaust gas decrease, but also the sneak of the exhaust pressure wave into the intake system is reduced and noise is prevented.

On the other hand, the intake valves 7a ₁ ,
Since the valve closing timing of 7a ₂ can be delayed as compared with the case of low speed rotation, the tuning rotation range in which the intake inertia effect is exhibited is expanded, and flat torque characteristics and high output can be obtained.

As described above, the camshaft support member 23
When the valve lift and the valve timing are changed in accordance with the swing of the intake valve, the intake side cam gear 41a and the exhaust side cam gear 4
The gear 1b meshes with the idler gear 31 via the pair of reduction gears 38 and 39.
By appropriately setting the number of teeth of 8, 39, the valve lift and the valve timing can be controlled in a wide range.
Moreover, by interposing the reduction gears 38 and 39, a desired reduction ratio can be obtained even if the diameters of the cam gears 41a and 41b are reduced, so that the inertia mass of the camshaft support member 23 is reduced and the servomotor 54 of the servomotor 54 is reduced. The load can be reduced.

Now, assuming that the diameters of the umbrella portions 17a ₁ and 17a ₂ of both intake valves 7a ₁ and 7a ₂ are the same, as shown in FIG. 10 (A), the intake side rocker arm shaft 1
Maximum valve lift distance from 3a L ₂ is larger intake valve 7a ₂ becomes larger than the maximum valve lift of the distance L ₁ is less intake valve 7a ₁ from the intake side rocker arm shaft 13a, a high speed of the difference is the left side of the figure It becomes remarkable in the driving range. However, in reality, the diameter D ₂ of the umbrella portion 17a ₂ of the intake valve 7a ₂ having a large valve lift is small and the diameter D of the umbrella portion 17a ₁ of the intake valve 7a ₁ having a small valve lift is small.
_{Since 1} is formed to be large, the curve showing the valve average effective opening area of both intake valves 7a ₁ and 7a ₂ as shown in FIG. It will be translated by the distance.

That is, the high speed operation on the left side of FIG.
Both intake valves 7a in the region₁, 7a₂Valve average effective opening area of
It is almost the same and low speed operation is started from the middle speed operation area on the right side of the figure.
In areas where the maximum valve lift up to the
Umbrella part 17a rather than Lubelift ₁, 17a₂Diameter D₁，
D₂Has a large effect on the valve average effective opening area,
Intake valve 7a₁Valve average effective opening area is intake valve 7a₂Valve
The average effective opening area is exceeded, and the difference is in the low speed operation range.
Will be the maximum. As a result, both intakes are
Air valve 7a₁, 7a₂The intake volume of
Swirl in the cylinder
As a result, the combustion efficiency of the air-fuel mixture is improved. Also, the intake speed of the mixture
High enough to avoid swirling
In the high speed operation range, both intake valves 7a₁, 7a₂Valve average effective opening
Maximizes both mouth areas and improves output by reducing intake resistance
And fuel consumption can be reduced.

11 and 12 show a second embodiment of the present invention. This embodiment shows the intake side rocker arm shaft 13
Inclining the angle of the shaft portion 16a ₂ of the intake valve 7a ₂ on the side far from a, the umbrella portions 17a _{1 of} both intake valves 7a ₁ , 7a ₂ ,
The feature is that the position of 17a ₂ is aligned in the axial direction of the intake side rocker arm shaft 13a. In this way, by making the angles of the shaft portions 16a ₁ and 16a ₂ of both intake valves 7a ₁ and 7a ₂ different from each other, the positions of the _two valve drive portions 15a ₁ and 15a ₂ of the intake side rocker arm 14a are made different. Nevertheless, the umbrella portions 17a ₁ , of both intake valves 7a ₁ , 7a ₂ ,
It is possible to increase the degree of freedom of layout for the combustion chamber 5 by bringing the positions of 17a ₂ closer to each other.

Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above embodiments, and various small design changes can be made.

For example, in the embodiment, both intake valves 7a ₁ and 7a
_The swirl is generated by making the valve average effective opening area of 2 different to improve the combustion efficiency of the air-fuel mixture, but by making the valve average effective opening area of both exhaust valves 7b ₁ and 7b ₂ different, Exhaust valves 7b ₁ and 7b ₂ respectively
It is possible to reduce the exhaust noise by changing the discharge timing and the discharge amount of the exhaust gas from the vehicle. It is also possible to provide three or more valve driving parts on one rocker arm and to make the distances of these valve driving parts from the rocker arm fulcrum different.

[0035]

As described above, according to the first feature of the present invention, the rocker arm is provided with a plurality of valve drive portions capable of abutting the tips of the shaft portions of a plurality of valves, and the valve drive portion and the rocker arm are provided. Since the average effective opening area of each valve is changed by making the distance from the fulcrum different, a sufficient swirl is generated in the cylinder by making the intake amount of the air-fuel mixture from the plurality of intake valves different. It is possible to improve the combustion efficiency of the air-fuel mixture.

According to the second feature of the present invention, the average effective opening area of each valve can be more finely and easily adjusted by making the diameters of the caps of the plurality of valves different from each other. Become.

Further, according to the third aspect of the present invention, the angles of the shaft portions of the plurality of valves are made different from each other, so that the head portions of the respective valves are brought closer to each other and the degree of freedom of layout with respect to the combustion chamber is increased. It is possible to increase.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of a cylinder head portion of an internal combustion engine (cross-sectional view taken along line 1-1 of FIG. 2).

FIG. 2 is a sectional view taken along line 2-2 of FIG.

3 is a sectional view taken along line 3-3 of FIG.

4 is a sectional view taken along line 4-4 of FIG.

5 is a view taken along the line 5-5 of FIG.

6 is an enlarged arrow view of line 6-6 of FIG.

7 is a view in the direction of arrow 7 in FIG. 6;

FIG. 8 is an explanatory diagram of the operation

FIG. 9 is a graph showing valve lift and valve timing.

FIG. 10 is a graph showing characteristics of an intake valve.

FIG. 11 is a view corresponding to FIG. 6 according to the second embodiment of the present invention.

FIG. 12 is a diagram corresponding to FIG. 7 according to the second embodiment of the present invention.

[Explanation of symbols]

7a ₁ and 7a ₂ intake valve (valve) 7b ₁ and 7b ₂ exhaust valve (valve) 14a intake side rocker arm (rocker arm) 14b exhaust side rocker arm (rocker arm) 15a ₁ and 15a ₂ valve drive part 16a ₁ and 16a ₂ shaft part 17a ₁ , 17a ₂ Umbrella portion 23 Camshaft support member 28a Intake side camshaft (camshaft) 28b Exhaust side camshaft (camshaft) 31 Idler gear 33 Crankshaft 41a Intake side cam gear (cam gear) 41b Exhaust side cam gear (cam gear) 42a Intake Side cam (cam) 42b Exhaust side cam (cam) O Swing center

Claims (3)

[Claims] 1. A motor driven to swing around a swing center (O).
Cams (42a, 42b) on the shaft support member (23)
And cam shuff having cam gears (41a, 41b)
(28a, 28b) are supported and the swing is performed.
Crankshaft supported rotatably around the center (O)
In the idler gear (31) driven to rotate by (33)
The cam gears (41a, 41b) are interlockingly connected to each other, and
The cam shaft (4) is swung to move the cam (4).
2a, 42b) hit the rocker arms (14a, 14b)
By changing the contact position and phase,
An intake valve driven by the kicker arms (14a, 14b) and
And exhaust valve (7a₁, 7a ₂; 7b₁, 7b₂) Valve
Valve drive for internal combustion engine with variable lift and valve timing
And a plurality of intake valves (7a) on the rocker arm (14a).₁，
7a₂) Shaft (16a₁, 16a₂) Can contact the tip
Multiple valve drives (15a₁, 15a₂) Is provided
Valve drive (15a₁, 15a₂) And the rocker arm
The distance between the fulcrum of (14a) and the intake valve (7
a₁, 7a₂) Internal combustion, characterized by being different for each
Engine valve drive. 2. The plurality of valves (7a)₁, 7a₂) Umbrella part
(17a₁, 17a ₂) Different diameters
The valve drive device for an internal combustion engine according to claim 1, wherein: 3. The plurality of valves (7a)₁, 7a₂) Shaft
(16a₁, 16a ₂) Different angles
The valve drive device for an internal combustion engine according to claim 1, wherein: