JP3092390B2 - Variable valve mechanism of internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable valve mechanism for an internal combustion engine that continuously varies the opening and closing timing of an intake valve or an exhaust valve according to the operating state of the internal combustion engine.

[0002]

2. Description of the Related Art Conventionally, as disclosed in Japanese Utility Model Laid-Open Nos. 62-137313 and 62-137314, a movable valve mechanism in which the operating angle is changed by a pair of eccentric arms has been proposed. In Japanese Utility Model Application Laid-Open No. 62-137313, a first arm 51 is pivotally supported with respect to a first eccentric shaft 50 as shown in FIG. 9, and a second eccentric shaft 52 is provided on a side opposite to the first arm 51. A second arm 53 is pivotally supported. Rollers 54 and 55 are provided at the ends of the arms 51 and 53, respectively, and the rollers 54 and 55 roll on the peripheral surface of a common valve driving cam 56. When the swing center of the first arm is displaced by the rotation of the rotation center of the first eccentric shaft 50, the first arm 51 and the valve driving cam 51 are displaced.
Is displaced in the advance direction.
Further, the center of the swing is displaced by the rotation of the second eccentric shaft 52, and the engagement point between the second arm 53 and the valve driving cam 56 is displaced in the retard direction. Therefore,
In this technique, at least one of the eccentric shafts 5
The rotation angle of 0, 52 deviates the point of engagement between the valve driving cam 56 and at least one of the arms 51, 53, so that the working angle can be arbitrarily changed. In the drawing, 57 is a tappet driven by the arms 51 and 53, and 58 is a push rod.

In Japanese Utility Model Laid-Open No. 62-137314, FIG.
1, a first eccentric shaft 60 and a second eccentric shaft 62 are provided on both side surfaces of the rotor 59, and the first arm 61 and the second arm 63 are provided on both shafts 60, 62.
Are pivotally supported respectively. Both arms 61,
Rollers 64 and 65 are provided at the tip of 63, respectively.
The rollers 64 and 65 are provided with a common valve driving cam 6.
6 rolls on the peripheral surface. Then, the swing center of the first arm 61 is displaced by the rotation of the rotation center of the first eccentric shaft 60, so that the first arm 6
The point of engagement between the cam 1 and the valve driving cam 66 is shifted in the advance direction. In addition, the rotation center of the second eccentric shaft 62 is displaced, so that the point of engagement between the second arm 63 and the valve driving cam 66 is displaced in the retard direction.

[0004] The first eccentric shaft 60 and the second eccentric shaft 62 are provided on both side surfaces of the rotor 59 so that the center of rotation of the first eccentric shaft 60 and the center of rotation of the second eccentric shaft 62 are arranged. It is provided coaxially. Further, the first eccentric shaft 60 and the second eccentric shaft 62
Is disposed at a position where the swing center of the first arm 61 and the swing center of the second arm 63 are opposed to the rotor 59 with the rotation center interposed therebetween. In the figure, 67 is the arm 6
A tappet 68 driven by 1, 63 is a push rod.

Therefore, also in this technique, the eccentric shafts 60 and 62 rotate to rotate the valve driving cam 66.
The operating angle can be arbitrarily changed by the deviation of the point of engagement between the arm and the arms 61, 63.

[0006]

However, when the roller provided at the end of the arm is displaced to move to the advance side or the retard side, the clearance between the roller and the cam for driving the valve changes, and the displaced roller becomes the cam of the cam. There is a problem that a sound is generated because the contact surface of the tappet is flat when it gets over the interference part.

[0007] Further, as shown in FIG.
When the working angle is widened by widening the distance between the shaft centers of the rollers 4 and 65, the cam nose of the valve driving cam 66
When moving to step 5, the lift curve is discontinuous as shown in FIG. 11, so that smooth lift characteristics cannot be obtained and there is a problem that sound is generated at the discontinuous portion. Conventionally, as shown in FIGS. 9 and 10, the tappets 57 and 67 having a wide contact area are required because the roller is displaced from the valve center by the displacement. For this reason, there is a problem that the inertial mass in driving the valve is increased, and the mobility is deteriorated.

Further, as shown in FIG. 10A, the swing center a of the arm, a valve driving cam 66 and rollers 64, 65 are provided.
The distance (ab) from the contact point b and the distance (ac) between the swing center a of the arm and the tappet contact point c are factors that determine the lift amount. This (ab) / (ac)
The lift amount can be changed by changing (= arm ratio), but in this conventional technique, even if the roller is displaced, the distance (ab) and the distance (ac) hardly change. Therefore, the lift amount hardly changes because the arm ratio hardly changes.

An object of the present invention is to ensure the periodicity of the lift characteristics, to change the rotational phase of the eccentric shaft, and to change the engagement timing between the rocker arm and the cam during the lift period, so that the moving portion can be moved. An object of the present invention is to provide a variable valve mechanism of an internal combustion engine having a smooth lift curve and different working angles without increasing an inertial mass.

[0010]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention relates to a rocker arm and a cam which are supported at one end by an eccentric shaft and which are arranged between the rocker arm and the cam. In a rocker arm type variable valve mechanism in which a sliding portion capable of contacting and sliding is arranged, a synchronous rotating means for synchronously rotating the eccentric shaft with a camshaft of the cam, and a rotational phase of the eccentric shaft to a predetermined phase The gist of the invention is to provide a variable phase changing means.

[0011]

According to the above arrangement, the cam and the rocker arm are synchronously rotated by the synchronous rotating means. Then, by the rotation of the cam, the oscillating arm eccentric via the sliding portion is oscillated. When the cam and the rocker arm are rotated synchronously while the rotation phase of the eccentric shaft is changed by the phase changing means, the opening of the valve and the closing time of the cam are changed so that the valve opening time and the valve closing time are changed compared to before the rotation phase was changed. The swing arm swings due to the rotation.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment in which the present invention is embodied in a variable valve mechanism for an intake valve and an exhaust valve of a gasoline engine will be described below with reference to FIGS.

FIG. 1 shows a movable valve mechanism of an engine showing a main part. Note that the structure of the movable valve mechanism is the same on both the intake valve side and the exhaust valve side, and FIG. 1 shows the mechanism on the intake valve side, and the description of the mechanism on the exhaust valve side is omitted.

In this movable valve mechanism, a swing arm 2 and a rocker arm 3 are rotatably supported on a rocker shaft 1. The swing arm 2 is composed of a pair of arm pieces 4 that are spaced apart from each other on the rocker shaft 1.
The rocker shaft 1 is formed with eccentric shaft portions 1a separated from each other. Each arm piece 4 with respect to the eccentric shaft portion 1a
Are rotatably arranged, and the rotation axis m is eccentric with respect to the rotation axis n of the rocker shaft 1. A shaft 5 is provided between the distal ends of the arm pieces 4, and a needle roller 6 is supported rotatably with respect to the coaxial 5. A pair of pressing rollers 7 are rotatably supported on the shaft 5 between both side surfaces of the needle roller 6 and the arm piece 4. The pressing roller 7 has a slightly smaller diameter than the needle roller 6. The needle roller 6 and the pressing roller 7 constitute a sliding portion.

The rotation axis of the rocker arm 3 is coaxial with the rotation axis n of the rocker shaft 1. A driving member 9 for pressing the tappet 8 downward is provided at the tip of the rocker arm 3.
Are projected downward. Above the rocker arm 3, an intake camshaft 10 is arranged in parallel with the rocker shaft 1. A cam 11 is formed at a position corresponding to the needle roller 6 on the camshaft 10. The center upper surface of the rocker arm 3 is formed as a curved surface 12 having an arc-shaped cross section, and the curved surface 12 has a radius R about the rotation axis of the camshaft 10, that is, the rotation axis O of the cam 11.
Are arranged on a circle. The pressing roller 7 of the swing arm 2 is mounted on the curved surface 12 so as to roll.
A long hole 13 is formed in the center of the rocker arm 3 so that the needle roller 6 can be inserted therein, and allows movement of the needle roller 6 when the swing arm 2 is displaced.

The tappet 8 drives an intake valve stem (not shown) in a vertical direction. Next, the rocker shaft 1 which is a synchronous rotating means in the present embodiment.
Will be described with reference to FIG.

Timing pulleys 18 provided at the ends of the intake side camshaft 10 and the exhaust side camshaft 17,
Reference numeral 19 is drivingly connected to a sprocket 16 provided at an end of the crankshaft 15 via a timing belt 21. With this drive connection, the timing pulley 18,
Reference numeral 19 indicates that when the crankshaft 15 makes one rotation, it makes a half rotation. The intake side camshaft 10
Is provided with a timing pulley 20 having the same diameter as the sprocket 16.

The timing pulley assembly 22 constituting a variable valve timing mechanism (hereinafter simply referred to as "VVT") as a phase varying means has a known helical spline type configuration. The timing pulley assembly 22 includes a first pulley 27 having the same diameter as the timing pulleys 18 and 19,
A second pulley 28 is provided, and both pulleys 27 and 28 are arranged coaxially and can be synchronously rotated in the same direction via an internal mechanism. When the internal mechanism of the timing pulley assembly 22 is driven by hydraulic pressure or the like, the second pulley 28 is relatively twisted about the axial direction with respect to the first pulley 27. I have. The timing pulley assembly 22 can apply a twist of 45 °.

The timing pulley 20 is drivingly connected to a first pulley 27 of a timing pulley assembly 22 via a timing belt 21. Further, at one end of the intake side rocker shaft 1 and the exhaust side rocker shaft 23, there are provided timing pulleys 24 and 25 having a half diameter of the second pulley 28.
5 is drivingly connected to a second pulley 28 of the timing pulley assembly 22 via a timing belt 26.

Therefore, when the torsion about the axial direction of the second pulley 27 meshed with the timing belt 26 is applied, as a result, the timing pulleys 24 and 25 are torsioned through the timing belt 26. The opening and closing timings of the intake valve and the exhaust valve are changed by imparting torsion to the rocker shafts 1 and 23. When the sprocket 16 of the crankshaft 15 makes one rotation as described above,
The timing pulleys 18 and 19 make a 1/2 turn, the first and second pulleys 27 and 28 make a 1/4 turn, and the timing pulley 2
4 and 25 are each rotated by １ ／. That is, the intake and exhaust camshafts 10 and 17 connected to the timing pulleys 18 and 19 and the intake and exhaust rocker shafts 1 and 23 connected to the timing pulleys 24 and 25 can be rotated synchronously. I have.

Then, the timing pulley assembly 22
, The rotation center m of the swing arm 2 is located on the right side (advance side) in FIG. 1 with respect to the rotation center n of the second rocker arm 3, and as shown in FIG. It is possible for the rotation center n to be displaced to the 90 ° retard side as compared with the use. In FIG. 3, reference numerals 29 and 30 denote idle rollers.

Now, the operation of the embodiment configured as described above will be described. FIG. 2 shows the variable valve mechanism in a state where a low-speed lift curve is obtained. In this state, cam 1
1 and the rocker shaft 1 are rotated by the same rotation, and in order to obtain a high-speed lift curve from this state, the timing pulley assembly 22 constituting the VVT is driven by hydraulic pressure or the like. Then, the second pulley 28 is twisted relative to the first pulley 27 about the axial direction. Therefore, the timing pulleys 24 and 25 are respectively rotated,
The rocker shafts 1, 23 are rotated. At this time, the cam 11 and the rocker shafts 1 and 23 are transmitted by 1: 1 transmission. As a result, as shown in FIG. 1, the rotation center m of the swing arm 2 is located on the right side (advance side) in FIG. 1 of the rotation center n of the rocker arm 3. In this state, when the cam 11 is driven from the P direction where the cam 11 starts to open, the needle roller 11 moves to pass through the positions indicated by 6a, 6b and 6c as shown in FIG. 6a is a position at the start of valve opening, 6b is a position at the time of being lifted to the maximum amount by being driven by the cam 11, and 6c is a position at the time of valve closing. As shown by the solid line in FIG. 4, a large operating angle A and a large lift amount can be obtained.

When obtaining a low-speed lift curve from the state in which the high-speed lift curve is obtained, the VVT is driven by hydraulic pressure or the like. Then, the second pulley 28 is twisted relative to the first pulley 27 about the axial direction. Therefore, the timing pulleys 24 and 25 are respectively rotated, and the rocker shafts 1 and 23 are rotated. At this time, the cam 11 and the rocker shafts 1 and 23 are transmitted by 1: 1 transmission. As a result, as shown in FIG.
Is located on the retard side from the state shown in FIG. In this state, the cam 11 is driven from the P direction at which the needle 11 starts to open, and when the cam nose comes into contact with the needle roller 6, the needle roller 6 is moved to a position most distant from the swing center. The needle roller 6 moves so as to pass through positions indicated by 6d and 6e. 6
d is the position at the start of valve opening and at the time of valve closing, and 6e is the cam 1
This is the position at the time of being driven by 1 and lifted to the maximum amount. This position 6e is also a position where the needle roller 6 is U-turned. Then, as shown by the dotted line in FIG. 4, a small operating angle B and a small lift amount can be obtained. Therefore, in this low-speed operation, the maximum lift is reduced by the decrease in the arm ratio, and the compression of the valve spring is reduced, so that the friction can be reduced. Therefore, fuel efficiency can be improved.

In the above-described embodiment, the swing center m is displaced by 90 degrees in the low-speed operation as shown in FIG. 2 as compared with the high-speed operation shown in FIG. 1, but as shown in FIG. Also 18
You may make it displace 0 degree. In this case, the VVT is realized by using a 90-degree variable type. Alternatively, a VVT of a 45-degree variable type is used, and the first pulley 27 and the second pulley 28 of the VVT are enlarged so that the speed from the cam to the VVT is 1/4 times, and the speed from the VVT to the rocker shafts 1 and 23 is 4 times. It is also possible by increasing the speed. In the example of FIG. 7, when the cam 11 is driven from the P direction where it starts to open, the needle roller 6 moves in the Q direction, so that the needle roller 6 starts to open slowly and closes early as shown by the two-dot chain line in FIG. , And the lift amount is the same as that for the high-speed use, but the operating angle C becomes smaller.

As described above, the swing center m of the swing arm 2
Is changed, there is no discontinuous portion in the lift curve, so that no sound is generated and smooth lift characteristics can be obtained. Further, in this embodiment, since the driving member 9 which comes into contact with the tappet 8 is not displaced, a tappet having a small contact area, that is, a small tappet can be used, the inertial mass does not increase, and the mobility is deteriorated. There is no.

Next, a second embodiment will be described. In this embodiment, as shown in FIG. 8, in the configuration of the first embodiment, in the rocker arm 3, a part of the tip of the curved surface 12 on a circle having a radius R around the rotation axis O of the cam 11 is smoothly cut. Thus, the lift reducing surface 12a is formed, and the curved surface 12a is formed.
Are connected smoothly. The lift reducing surface 12a is formed corresponding to the vicinity including the position 6e (the position where the needle roller 6 is U-turned) shown in FIG. 6 having the low-speed lift curve of the first embodiment. I have.

In this embodiment, in order to obtain a low-speed lift curve as in the first embodiment, the center of rotation m of the swing arm 2 is positioned at a more retarded position than the state shown in FIG. 1 as shown in FIG. In this state, the cam 11 is driven from the P direction at which the cam 11 starts to open, and moves the needle roller 6 to a position most distant from the swing center when the cam nose contacts the needle roller 6. Then, as shown in FIG.
Moves so as to pass through the positions indicated by 6d and 6e. The needle roller 6 presses and drives the rocker arm 3 on the lift reducing surface 12a in the vicinity of the position 6e where the maximum lift is obtained. For this reason, the maximum lift amount is smaller than the low-speed lift curve of the first embodiment, as indicated by the one-dot chain line α in FIG. 4, and the operating angle B is the same as that of the first embodiment. Becomes As a result, friction can be reduced.

It should be noted that the present invention is not limited to the above-described embodiment, and can be arbitrarily changed without departing from the spirit of the present invention. (1) In the above embodiment, the present invention is embodied in a gasoline engine, but it may be embodied in a diesel engine.

[0029]

As described above in detail, according to the present invention, the periodicity of the lift characteristics can be ensured, and by changing the rotation phase of the eccentric shaft, the engagement timing between the rocker arm and the cam during the lift period can be improved. Is not accompanied by an increase in the inertial mass of the moving part. In addition, a smooth lift curve can be obtained, and a lift curve having a different operating angle can be obtained.

[Brief description of the drawings]

1A and 1B show an embodiment of the present invention, in which FIG. 1A is a plan sectional view, and FIG. 1B is a side sectional view.

FIG. 2 (a) is a cross-sectional plan view for explaining the operation,
(B) is a side sectional view similarly.

FIG. 3 is a perspective view showing a drive mechanism of the variable valve system.

FIG. 4 is a graph showing the operation of the variable valve mechanism.

FIG. 5 is a schematic diagram for explaining the operation of the variable valve mechanism.

FIG. 6 is a schematic diagram for explaining the operation of the variable valve mechanism.

FIGS. 7A and 7B show a main part mechanism for obtaining another low-speed lift curve, wherein FIG. 7A is a plan sectional view for explaining the operation, and FIG.

FIG. 8 is a side sectional view of another embodiment.

FIG. 9 is a side sectional view of a conventional variable valve mechanism.

FIG. 10A is a side sectional view of another conventional variable valve mechanism, and FIG. 10B is a plan sectional view thereof.

FIG. 11 is a graph showing the operation of a conventional variable valve mechanism.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Rocker shaft, 1a ... Eccentric shaft part (eccentric shaft), 2 ...
Swing arm, 3 ... rocker arm, 4 ... arm piece, 5 ...
Shaft, 6: Needle roller (sliding part), 7: Pressing roller (sliding part), 8: Tappet, 10: Intake side camshaft, 11: Cam, 12: Curved surface, 16: Sprocket, 1
7 ... Exhaust side camshaft, 18, 19, 20 ... Timing pulley, 21 ... Timing belt, 22 ... Timing pulley assembly (variable phase means), 23 ... Intake side rocker shaft, 24,25 ... Timing pulley, 26 ... Timing Belt, 27 ... first pulley, 28 ... second pulley (the above 16, 18, 19, 20, 21, 22, 24, 25,
26, 27 and 28 constitute synchronous rotating means. ).

Claims (1)

(57) [Claims] A rocker arm system in which one end is supported by an eccentric shaft and a sliding portion which is slidable in contact with both the rocker arm and the cam with respect to a swing arm disposed between the rocker arm and the cam. A variable valve mechanism, comprising: a synchronous rotating means for synchronously rotating the eccentric shaft with a camshaft of the cam; and a phase variable means for changing a rotational phase of the eccentric shaft to a predetermined phase. Variable valve mechanism.