JPH10196329A - Variable valve system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To maximize a surface length per cam of a follow-up contact part with which a solid cam is brought into contact and perform easy and high- precise precision machining of a semicylinder inner surface seat, in a variable valve system employing a solid cam and a direct strike type valve lifter. SOLUTION: A variable valve system comprises a cam shaft 1 having a solid cam 2; a displacing device 3; and a direct strike type valve lifter 10 to open and close a valve 4 through reciprocation effected by the solid cam 2. The direct strike type valve lifter 10 comprises a semicylinder inner surface seat 19; and a follow-up contact part 21 oscillatorily fitted in the seat 19 and making contact as the follow-up contact part follows the solid cam 2. Through engagement structure between an engaging recessed part 20 formed approximately in the central part in a longitudinal direction of the semicylinder inner surface seat 19 and a fan-shaped engaging protrusion part 24 formed approximately in the central part in a longitudinal direction of the follow-up contact part 21, movement in a longitudinal direction of the follow-up contact part 21 is regulated in a state that the two end faces in the longitudinal direction of the follow-up contact part 21 are brought into appearance.

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 continuously or stepwise changing a valve timing and a lift from a low rotation to a high rotation of an internal combustion engine.

[0002]

2. Description of the Related Art Japanese Patent Publication No. 7-45803 discloses FIG.
As shown in FIG. 4, a camshaft 101 provided with a three-dimensional cam 100 whose cam profile changes in the axial direction, and a direct-hit valve lifter 103 that opens and closes one valve 102 by reciprocating by the three-dimensional cam 100. The disclosed variable valve mechanism is disclosed. The direct-acting valve lifter 103 is provided with a cup 10 that covers the upper end of each valve 102.
4, a saddle 105 placed on the upper surface of the cup 104 so as to be surrounded by a peripheral wall 109 erected on the upper surface of the cup 104, and a contact line that is swingably mounted on the saddle 105 and rotates with the three-dimensional cam 100. Three-dimensional cam 1 while following changes in angle
00 and a shoe 106 that comes in contact with the shoe.

Further, Japanese Patent Publication No. 6-84722 discloses that
A camshaft 101 also having a three-dimensional cam 100,
As shown by a two-dot chain line in FIG. 24, a hydraulic actuator 107 for displacing the camshaft 101 in the axial direction in accordance with the rotation speed of the internal combustion engine, and a direct-acting valve lifter 103 for opening and closing each valve 102 are provided. The disclosed variable valve mechanism is disclosed.

According to these variable valve mechanisms, the valve timing and the lift amount are continuously changed from a low rotation to a high rotation of the internal combustion engine to perform precise control according to the operating condition of the internal combustion engine. There is an advantage that it can be performed.

[0005]

Since the three-dimensional cam 100 slides on the upper surface of the shoe 106 in the longitudinal direction thereof, the three-dimensional cam 100 restricts the longitudinal movement of the shoe 106 so that the shoe 106 does not come off the saddle 105. Need to be Therefore, conventionally, regulating walls 108 surrounding both longitudinal ends of the shoe 106 are provided at both longitudinal ends of the saddle 105 to regulate the longitudinal movement of the shoe 106, however, there is the following problem.

The lift amount of the valve 102 is three-dimensional cam 1
The nose height of the three-dimensional cam 100 is determined by the nose height of the shoe 106 (the surface length of the shoe 106).
6 (length in the longitudinal direction of the upper surface of the upper surface 6). Accordingly, the longer the cam contact surface length of the shoe 106 is, the more
The height of the nose of the three-dimensional cam 100 can be increased, and the valve 10
2 can take a large lift amount. However, the length of the cam contact surface of the shoe 106 is such that both regulating walls 1
08 and the peripheral wall 109 have to be smaller than the outer diameter of the direct-acting type valve lifter 103.
02 could not take the maximum lift.

When precision machining of the semi-cylindrical inner seat 113 for swingably receiving the shoe 106 on the saddle 105, the regulating wall 108 becomes an obstacle, so the semi-cylindrical inner seat 11 is
3. It was difficult to perform precision processing and ensure accuracy. Also, it was difficult to secure the accuracy of the inner wall surface of the regulating wall 108. If the accuracy of these surfaces is deteriorated, there is a possibility that abnormal noise may occur due to tolerance play between the shoe 106 and the surface.

In FIG. 24, reference numeral 110 denotes a regulating wall 1
An extension 111 protruding from the outer peripheral side from 08 is a screw screwed into a female screw hole (not shown) formed by cutting out a part of a lifter guide hole (not shown) of the cylinder head.
Reference numeral 12 denotes a notch formed in the screw.
The extension 110 is slidably inserted into the notch 112 to prevent the saddle 105 and the shoe 106 from rotating with respect to the three-dimensional cam 100.

An object of the present invention is to change the valve timing and the lift amount continuously or stepwise from low to high rotation of an internal combustion engine by using a three-dimensional cam to respond to the operating conditions of the internal combustion engine. Precise control can be performed, so that various characteristics such as torque, output, fuel efficiency, cleanness of exhaust gas, etc. can be maximized over the entire rotation range, and the cam of the follow-up contact part where the three-dimensional cam hits A variable valve that can maximize the contact surface length, increase the valve lift, and easily and accurately perform the precision machining of the semi-cylindrical inner seat to which the following contact part fits. It is to provide a mechanism.

[0010]

In order to achieve the above object, a variable valve mechanism according to the present invention has a cam profile continuously changed in the axial direction from a cam profile for low rotation to a cam profile for high rotation. A camshaft having a three-dimensional cam, a displacement device for continuously or stepwise displacing the camshaft in the axial direction according to an operating condition such as the rotation speed of the internal combustion engine, and a reciprocating motion based on the cam profile of the three-dimensional cam A direct-acting valve lifter that opens and closes the valve by opening and closing the valve, wherein the direct-acting valve lifter is swingably fitted to the semi-cylindrical inner seat, A follow-up contact portion that contacts the three-dimensional cam while following the change in the contact line angle due to the rotation of the cam, and restricts the longitudinal movement of the follow-up contact portion when both longitudinal end surfaces of the follow-up contact portion appear. Following contact portion regulating structure is characterized in that provided that.

Here, the valve timing phase, valve opening angle and lift amount in the low rotation cam profile and the valve timing phase, valve opening angle and lift amount in the high rotation cam profile are determined for each internal combustion engine. Can be set as appropriate according to the requirements in.
However, in many cases, the cam profile for low rotation has a small valve opening angle and lift amount, and the cam profile for high rotation has a large valve opening angle and lift amount.

When the camshaft is displaced in a stepwise manner by the displacement device, the camshaft may be changed in two steps. In such a case, it is preferable that the displacement in the two steps can be adjusted. More preferably, the camshaft is displaced in at least three stages. Most preferably, the camshaft is continuously displaced. The displacement device is not limited to a specific structure, but may be a device using hydraulic pressure, electromagnetic force, or the like.

[0013] The following contact portion restricting structure includes the following (A).
(B) can be illustrated. (A) A structure in which an engaging concave portion and an engaging convex portion provided relatively at a substantially central portion in the longitudinal direction of the semicylindrical inner surface seat and a substantially central portion in the longitudinal direction of the following contact portion are engaged. Here, “relatively” means
This means that it is sufficient that one of the semi-cylindrical inner surface seat and the following contact portion is provided with an engagement concave portion, and the other is provided with an engagement convex portion. (B) A structure in which engaging projections provided at both ends in the longitudinal direction of the following contact portion engage with both ends in the longitudinal direction of the semi-cylindrical inner surface seat.

As the direct-acting type valve lifter, the following (C)
(D) and (E) can be exemplified. (C) A direct-hit valve lifter including a lifter main body including an end wall portion, wherein the semi-cylindrical inner surface seat is formed on the end wall portion. (D) an inverted cup-shaped lifter main body comprising a disc-shaped end wall and a cylindrical side wall, and the semi-cylindrical inner surface seat is formed on a seat member rotatably supported by the end wall. Direct-acting valve lifter. (E) A direct-acting valve lifter including two or more pressing portions for simultaneously pressing the ends of two or more adjacent valves.

It is preferable to provide a rotation preventing structure for preventing rotation of at least the following contact portion with respect to the three-dimensional cam.

In order to enable adjustment of the valve clearance, it is preferable to provide, for example, the following structures (F) and (G). (F) A structure in which a shim for adjusting valve clearance is mounted between a direct-acting valve lifter and an end of the valve. (G) The following contact portion is a replacement part for adjusting the valve clearance.

The variable valve mechanism of the present invention can be applied to either an intake valve or an exhaust valve, but is preferably applied to both.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a variable valve mechanism in which the present invention is applied to both an intake valve and an exhaust valve will be described below with reference to the drawings. Therefore, in the embodiment, simply referring to a valve refers to both an intake valve and an exhaust valve.

First, FIGS. 1 to 7 show a variable valve mechanism according to a first embodiment. The camshaft 1 is formed with a three-dimensional cam 2 in which the cam profile is continuously changed in the axial direction from the right low-rotation cam profile to the left high-rotation cam profile in FIG. The three-dimensional cam 2 includes a base circular portion 2a and a nose portion 2b. The base circular portion 2a has the same radius in both the low-rotation cam profile and the high-rotation cam profile, and thus has a cylindrical surface without inclination. However, the nose part 2b
Are inclined like a conical surface because the valve opening operation angle and the lift amount are small in the low rotation cam profile and the valve opening operation angle and the lift amount are large in the high rotation cam profile.

At the end of the camshaft 1, there is provided a displacement device 3 for continuously displacing the camshaft 1 in the axial direction according to the operating conditions such as the rotational speed of the internal combustion engine. The displacement device 3 includes, for example, a guide portion of the camshaft 1 using a spline, and a driving portion of the camshaft 1 using a hydraulic pressure (both not shown), and a rotation sensor of an internal combustion engine, an accelerator opening sensor, and the like. Is controlled by a control device (not shown) such as a microcomputer that operates based on the above.

Below the camshaft 1, a direct-acting valve lifter 10 that opens and closes the valve 4 by reciprocating up and down based on the cam profile of the three-dimensional cam 2 is provided. The stem 4 a of the valve 4 is guided by being inserted into a valve guide 25 fixed to the cylinder head 7.

The direct-acting valve lifter 10 has an inverted cup-shaped lifter body 14 having a disk-shaped end wall 11 and a cylindrical side wall 13 extending downward from the end wall 11. The side wall 13 is vertically slidably guided by a lifter guide hole 8 formed in the cylinder head 7. A relief recess 15 for releasing the rotation trajectory of the three-dimensional cam 2 is formed around the lifter guide hole 8 of the cylinder head 7. A central portion of the lower surface of the end wall portion 11 is a pressing portion 12 for pressing the end portion of the valve 4.
A shim 9 for adjusting the valve clearance is interposed between the valve and the end of the valve 4. The valve 4 is attached to a valve retainer 5 attached near the upper end of the valve 4.
The upper end of the valve spring 6 for urging to the zero side is in contact. A spring recess 26 for holding the lower end of the valve spring 6 is formed in the cylinder head 7 directly below the lifter guide hole 8.

If only the lifter guide hole 8 guides the follower contact portion 21 described later together with the lifter main body 14 with respect to the three-dimensional cam 2, the following structure is provided as a rotation preventing structure for the side wall portion. 13 are provided inside.

At the lower end of the inner wall surface of the side wall portion 13, approximately 1
A guided portion 27 having a predetermined width is projected from two places separated by 80 degrees, and a guided portion 28 having a predetermined width is provided at two places approximately 180 degrees apart without the guided portion 27. The guided portion 27 and the guided portion 28 are formed by cutting the entire periphery of the lower end of the opening of the side wall portion 13 inward, and then cutting off two portions of the narrowed portion. On the other hand, the cylinder head 7 just below the lifter guide hole 8 has
For example, a lifter guide member 30 made of stainless spring steel is provided. The lifter guide member 30 is
An annular plate-shaped spring seat portion 31 provided on the lower surface portion is fitted into the spring concave portion 26, and a stepped cylindrical fixing portion 32 erected from the inner peripheral portion of the spring seat portion 31 is used as a valve guide. The cylinder 25 is positioned and fixed to the cylinder head 7 by being press-fitted into the outer periphery of the cylinder 25 in a non-rotatable manner (may be fitted in a different shape). The spring seat portion 31 functions as a seat that receives the lower end of the valve spring 6. The spring seat portion 31 is erected from two places approximately 180 degrees apart from each other on the outer peripheral portion, so that a predetermined width fixed to the cylinder head 7 side (a width smaller by a minute clearance than the width of the to-be-entered portion 28). The guide portion 33) enters the inside of the side wall portion 13 from the entered portion 28. Then, the side end surfaces of the respective guide portions 33 are slidably engaged with the side end surfaces of the respective guided portions 27 to allow reciprocation of the direct hit valve lifter 10 and to allow the follow-up contact portion 21 and the lifter body 14 The rotation is blocked.

As described above, since the rotation preventing structure is provided inside the side wall portion 13, it is not necessary to cut out a part of the lifter guide hole for screwing the screw 111 unlike the conventional example of FIG. . Therefore, the following effects can be obtained. Processing of the lifter guide hole 8 is easy, and dimensional tolerance control of the inner diameter can be easily performed. The area of the lifter guide hole 8 with which the side wall 13 contacts does not decrease, and uneven wear of the side wall 13 does not occur. Since the rigidity around the lifter guide hole 8 does not decrease and assembly distortion and thermal distortion hardly occur, seizure and uneven wear of the side wall portion 13 do not occur.

On the outer periphery of the fixed portion 32, a valve oil seal member 34 is externally fitted at a lower large-diameter portion 35, and is attached and integrated by welding or the like. The outer periphery of the stem portion 4a is oil-sealed by contacting the outer periphery of the portion 4a and fastening the small-diameter portion 36 from the outer periphery by the fastening ring 37.
Therefore, the engine oil adhering to the upper portion of the stem portion 4a is blocked by the valve oil seal member 34 and does not enter the inside of the valve guide 25, so that the combustion chamber (not shown).
There is no danger of entering and wasting.

As described above, the valve oil seal member 3
The lifter guide member 30 in which the lifter 4 is integrated has a positioning and fixing function to the cylinder head 7 via the valve guide 25, a rotation preventing function of the follow-up contact portion 21 and the lifter body 14, a seat function of the valve spring 6, and a stem. Part 4
Since the oil seal function of a is exhibited by one part, the number of parts can be reduced, the structure can be simplified, and the weight can be reduced.
Enables higher rotation speed than before.

The end contact portion 11 is provided with a follow-up contact mechanism 17 configured as follows. At the center of the upper surface of the end wall portion 11, a raised portion 18 which is long in a direction perpendicular to the axis of the three-dimensional cam 2 is provided.
Are formed integrally, and a semi-cylindrical inner surface seat 19 extending in the same direction is recessed in the raised portion 18. Since both ends of the semi-cylindrical inner seat 19 are open so as to penetrate, and there is no obstacle such as the regulating wall 108 of the conventional example in FIG. 24, the precision machining of the semi-cylindrical inner seat 19 can be performed easily and accurately. Can be. An engagement recess 20 is provided at a substantially central portion in the longitudinal direction of the semi-cylindrical inner surface seat 19. Since the inner bottom surface of the engaging recess 20 is flat, the working of the engaging recess 20 can be easily performed, and the polishing of both inner surfaces of the engaging recess 20 can be easily and accurately performed. The semi-cylindrical inner seat 19 swings (rolls) on the semi-cylindrical inner seat 19.
A semi-cylindrical follow-up contact portion 21 including a semi-cylindrical surface 22 that makes possible contact and a flat contact surface 23 that makes contact with the three-dimensional cam 2 is swingably fitted. At a substantially central portion in the longitudinal direction of the semi-cylindrical surface 22, a fan-shaped engaging projection 24 is integrally provided, and the engaging projection 24 is engaged with the engaging concave portion 20 and is swingably sandwiched. . This engagement structure constitutes a follow-up contact portion regulating structure that regulates the longitudinal movement of the follow-up contact portion 21 in a state where both longitudinal end surfaces of the follow-up contact portion 21 appear.

Then, the follow-up contact portion 21 comes into contact with the three-dimensional cam 2 on the contact surface 23 while following the change of the contact line angle accompanying the rotation of the three-dimensional cam 2 by swinging at a small angle. . At this time, the three-dimensional cam 2 slidably contacts the contact surface 23 of the following contact portion 21 in the longitudinal direction.
As described above, since the movement of the following contact portion 21 in the longitudinal direction is regulated, the following contact portion 21 does not come off the semi-cylindrical inner surface seat 19. In addition, since the longitudinal movement of the follow-up contact portion 21 is regulated in a state where both longitudinal end surfaces of the follow-up contact portion 21 appear, the regulating wall as in the conventional example of FIG. There is no need to provide 108. For this reason, the cam contact surface length of the following contact portion 21 (the length in the longitudinal direction of the contact surface 23) can be maximized to a length substantially equal to the outer diameter of the direct-acting valve lifter 10. By increasing the height of the nose portion 2b, the lift amount of the valve 4 can be maximized.

The variable valve mechanism according to the present embodiment operates as follows. First, when the internal combustion engine is running at a low speed, the camshaft 1 is displaced leftward by the displacement device 3 as shown in FIG. 4, and the right low-speed cam profile of the three-dimensional cam 2 corresponds to the following contact portion 21. I do.

As shown in FIG. 4 (a), when the base circle portion 2a comes into contact with the contact surface 23 of the follow-up contact portion 21, the contact line angle is parallel to the axis of the three-dimensional cam 2. The contact surface 23 does not tilt with respect to the end wall portion 11 and contacts the base circle portion 2a. However, as shown in FIG. 4B, when the nose portion 2 b comes into contact with the contact surface 23 of the follow-up contact portion 21, the contact line angle is inclined, for example, by several degrees to several tens degrees with respect to the axis of the three-dimensional cam 2. Therefore, the follow-up contact portion 21 swings by the same angle, and the contact surface 23 makes good contact with the nose portion 2b.

As described above, the follow-up contact portion 21 is
Swings by a small angle for each rotation of the camshaft, contacts the three-dimensional cam 2 while following the change in the contact line angle, and is pressed by the nose portion 2b. Therefore, the direct hit type valve lifter 10 reciprocates up and down based on the cam profile for low rotation, and as shown by the curve L in FIG. 6, the valve 4 on the exhaust side and the intake side is opened with a small valve opening operation angle and a lift amount. Open and close to increase low-speed torque and improve fuel economy.

When the internal combustion engine is rotating at high speed, the camshaft 1 is displaced rightward by the displacement device 3 as shown in FIG. Corresponding to 21.

Then, the follow-up contact portion 21 is arranged as shown in FIG.
As shown in (b), the swinging motion is performed once for each rotation of the three-dimensional cam 2, and the three-dimensional cam 2 contacts the three-dimensional cam 2 while following the change in the contact line angle, and is pressed by the nose portion 2b. Therefore, the direct-acting valve lifter 10 reciprocates up and down based on the cam profile for high rotation, and as shown by the curve H in FIG. 6, the exhaust-side and intake-side valves 4 are opened at a large valve opening operation angle and a large lift amount. Open and close, increase the intake volume, increase the high-speed output.

The camshaft 1 is continuously displaced by the displacement device 3 in accordance with the operating conditions such as the number of revolutions and the degree of accelerator opening even during the period from the low rotation to the high rotation. Among them, the cam profile of the intermediate portion corresponds to the following contact portion 21. Accordingly, the direct-acting valve lifter 10 reciprocates up and down based on the cam profile, and opens and closes the valve 4 at an intermediate valve opening angle and lift amount as shown by a curve M in FIG. Generate the corresponding torque and output.

As described above, according to the variable valve mechanism of this embodiment, the valve timing and the lift amount are continuously changed from the time of low rotation to the time of high rotation of the internal combustion engine, and the operating condition of the internal combustion engine is changed. , And various characteristics such as torque, output, fuel efficiency, and cleanliness of exhaust gas can be maximized over the entire rotation range. In addition, the change can be performed smoothly and quietly by the displacement of the camshaft 1.

FIG. 7 shows the torque characteristic of the internal combustion engine obtained by the present embodiment by a solid line, but is shown by a dashed-dotted line, which is a conventional variable valve mechanism which is not a conventional variable type as shown by a broken line. In contrast to such a variable valve mechanism of the type that changes in two stages at low and high rotations, the torque is increased over the entire rotation range, and no valley is generated. In addition, depending on the setting, the fuel efficiency is up to 15 to
It is thought that it is improved by about 20%.

FIG. 8 shows a variable valve mechanism according to the second embodiment. In the present embodiment, when the position of the valve oil seal member 34 is high due to the structure of the internal combustion engine, the valve oil seal member 34 is formed separately from the lifter guide member 30 and is fixed to the upper end of the valve guide 25. Only the point is different from the first embodiment, and the other is the same as the first embodiment.

Next, FIGS. 9 and 10 show a variable valve mechanism according to the third embodiment. In this embodiment, instead of the guided portion 27, four ridges are provided which extend vertically from the lower end of the inner wall surface of the side wall portion 13 to an intermediate height (preferably 10 mm or more) or from the lower end to the upper end. Guided part 29
Is different from the first embodiment only in the point that is provided, and the other is the same as the first embodiment. The side end surfaces of the respective guide portions 33 are slidably engaged with the side end surfaces of the two guided portions 29, so that the direct hit valve lifter 1
Zero reciprocation is allowed and the rotation is prevented.

Next, FIGS. 11 to 15 show a variable valve mechanism according to a fourth embodiment. In the present embodiment, in the shape and structure of the direct hit type valve lifter, and the rotation prevention structure,
This is different from the first embodiment, and the other is the same as the first embodiment.

The direct-drive valve lifter 40 of the present embodiment is
An inverted cup-shaped lifter body 14 comprising a disk-shaped end wall 11 and a cylindrical side wall 13 extending downward from the end wall 11, and a semi-cylindrical inner surface formed separately from the lifter body 14 It includes a substantially disc-shaped seat member 41 provided with a seat 19 and a follow-up contact portion 21 similar to the first embodiment, which is fitted to the semi-cylindrical inner seat 19 so as to be able to roll. Seat member 41
At the center of the upper surface of the three-dimensional cam 2, a protruding portion 42 that is long in a direction perpendicular to the axis of the three-dimensional cam 2 is integrally formed. Has been established. An engagement structure between an engagement concave portion 20 provided at a substantially central portion in the longitudinal direction of the semi-cylindrical inner surface seat 19 and an engagement convex portion 24 provided at a substantially central portion in the longitudinal direction of the semi-cylindrical surface 22 forms a follow-up contact portion. 21 in the state where both end surfaces in the longitudinal direction appear.
The point that a follow-up contact portion regulation structure for regulating the movement in the longitudinal direction of the first contact portion is formed is the same as in the first embodiment. The inner bottom surface of the engagement recess 20 may be flat, but is a loose curved concave surface here.

The lifter body 14 and the seat member 41 are connected to an engaging recess 43 provided at the center of the upper surface of the end wall 11 and the seat member 4.
1 is rotatably engaged with an engagement projection 44 provided at the center of the lower surface, so that the outer peripheral surface of the seat member 41 is relatively rotatably coupled with the exposed outer surface. As described above, since the outer peripheral surfaces of the seat members 41 are joined in a protruding state, the peripheral wall 109 unlike the conventional example of FIG. For this reason, similarly to the first embodiment, the cam contact surface length of the follow-up contact portion 21 can be maximized, thereby increasing the height of the nose portion 2b of the three-dimensional cam 2 and increasing the lift amount of the valve 102. Can be maximized.

As described above, the lifter body 14 and the seat member 41
Is connected to the lifter body 14 passively in the lifter guide hole 8, while the follower contact portion 21 rotates with the seat member 41 with respect to the three-dimensional cam 2. In order to prevent this. The following structure is provided between the seat member 41 and the cylinder head 7 as the rotation preventing structure.

An extension portion 45 protruding from the lifter body 14 to the outer peripheral side is formed integrally with one portion of the seat member 41 so that one end of the protruding portion 42 extends, and the extension portion 45 is folded downward. The end wall 11 and the side wall 13 of the lifter body 14 are bent.
Are located on the outer peripheral side of the. A key groove-like guide groove 46 extending in the hole length direction is formed in a part of the lifter guide hole 8 of the cylinder head 7, and the extension 45 is slidably inserted into the guide groove 46. The reciprocating motion of the direct-acting valve lifter 40 and the following contact portion 21
And rotation of the seat member 41 is prevented.

Incidentally, the semi-cylindrical inner seat 19 is also formed continuously on the upper surface of the extension portion 45.
Since both ends of 9 are open so as to penetrate, similar to the first embodiment, the precision machining of the semi-cylindrical inner surface seat 19 can be performed easily and accurately. However, the follow-up contact portion 21 is accommodated in a length substantially equal to the outer diameter of the direct-drive valve lifter 10, and does not cover the upper surface of the extension portion 45.

FIG. 16 shows a main part of the variable valve mechanism according to the fifth embodiment. This embodiment is different from the fourth embodiment only in that the outer edge 47 of the portion without the raised portion 42 of the seat member 41 is cut off to reduce the weight, and the other is the same as the fourth embodiment. The same is true.

FIGS. 17 and 18 show a main part of a variable valve mechanism according to a sixth embodiment. In the present embodiment, the engaging protrusion 44 provided at the center of the upper surface of the end wall 11 and the engaging recess 43 (hole in this example) provided at the center of the lower surface of the seat member 41 are rotatably engaged. The fourth embodiment differs from the fourth embodiment only in the point that they are combined, and the other is the same as the fourth embodiment.

Next, FIGS. 19 to 23 show a variable valve mechanism according to a seventh embodiment. This embodiment is different from the first embodiment in the shape and structure of the direct hit valve lifter, the rotation preventing structure, and the follow-up contact portion regulating structure, and the others are the same as the first embodiment.

The valve lifter 50 according to the present embodiment has a direct
A bridge-like end wall 51 having a substantially parallelogram-shaped plane and a tubular sleeve 53 symmetrically positioned with respect to the center of the end wall 51 and extending downward from two ends farthest from each other. A lifter body 54 is provided. Both sleeves 5
By inserting two pins 55 erected from the cylinder head 7 up and down through the cylinder head 3 so as to be slidable up and down, the direct hit type valve lifter 50 is guided so as to be able to reciprocate. As described above, since the two sets of the sleeves 53 and the pins 55 are guided by being inserted, an unbalanced load is not applied to each of the sleeves 53 and the pins 55, and the twisting and abrasion between the two portions 53 and 55 are prevented. be able to. The two sleeves 53 are preferably located at the symmetric position, but the same effect can be obtained even at the asymmetric position. At the same time, the insertion structure of the two sets of the sleeve 53 and the pin 55 also constitutes a rotation preventing structure for preventing the following contact portion 21 from rotating with respect to the three-dimensional cam 2 together with the lifter main body 54, which will be described later. There is no need to separately provide a rotation preventing structure, and the structure is simplified.

The center of the lower surface of the end wall portion 51 is a pressing portion 52 for pressing the end portion of the valve 4.
A shim 9 for adjusting the valve clearance is interposed between the valve and the end of the valve 4. An upper end of a valve spring 6 for urging the valve 4 toward the lifter 10 is in contact with a valve retainer 5 attached near the upper end of each valve 4.

The follow-up contact mechanism 17 having the following structure is provided on the end wall 51. At the center of the upper surface of the end wall portion 51, a raised portion 18 which is long in a direction perpendicular to the axis of the three-dimensional cam 2 is provided.
Are formed integrally, and a semi-cylindrical inner surface seat 19 extending in the same direction is recessed in the raised portion 18. Since both ends of the semi-cylindrical inner seat 19 are open so as to penetrate, and there is no obstacle such as the regulating wall 108 of the conventional example in FIG. 24, the precision machining of the semi-cylindrical inner seat 19 can be performed easily and accurately. Can be. Further, both end surfaces 19a in the longitudinal direction of the semi-cylindrical inner surface seat 19 are provided.
Can be easily and accurately performed. The semi-cylindrical inner seat 19 includes a semi-cylindrical surface 22 that oscillates (rolls) with the semi-cylindrical inner seat 19 and a flat contact surface 23 that contacts the three-dimensional cam 2. Follow-up contact portion 21 is swingably fitted. Semi-cylindrical surface 2
The fan-shaped engaging projections 24 are integrally provided at both ends in the longitudinal direction of the two, and both engaging projections 24 are engaged so as to straddle the longitudinal end faces 19 a of the semi-cylindrical inner surface seat 19. . This engagement structure constitutes a follow-up contact portion regulating structure that regulates the longitudinal movement of the follow-up contact portion 21 in a state where both longitudinal end surfaces of the follow-up contact portion 21 appear.

The follow-up contact portion 21 comes into contact with the three-dimensional cam 2 on the contact surface 23 while following the change of the contact line angle accompanying the rotation of the three-dimensional cam 2 by swinging at a small angle. . At this time, the three-dimensional cam 2 slidably contacts the contact surface 23 of the following contact portion 21 in the longitudinal direction.
As described above, since the movement of the following contact portion 21 in the longitudinal direction is regulated, the following contact portion 21 does not come off the semi-cylindrical inner surface seat 19. In addition, since the longitudinal movement of the follow-up contact portion 21 is regulated in a state where both longitudinal end surfaces of the follow-up contact portion 21 appear, the regulating wall as in the conventional example of FIG. There is no need to provide 108. For this reason, the cam contact surface length (the length of the contact surface 23 in the longitudinal direction) of the follow-up contact portion 21 can be maximized, and the height of the nose portion 2b of the three-dimensional cam 2 can be increased. The lift can be maximized.

The variable valve mechanism of this embodiment operates as follows. First, when the internal combustion engine is running at low speed, the camshaft 1 is displaced leftward by the displacement device 3 as shown in FIG. 22, and the right low-speed cam profile of the three-dimensional cam 2 corresponds to the following contact portion 21. I do. FIG. 22 (a)
Each state shown in FIG. 4B corresponds to each state shown in FIGS. 4A and 4B of the first embodiment.
The above description regarding (b) is cited. Then, as shown by a curve L in FIG. 6, the exhaust-side and intake-side valves 4 are opened and closed with a small valve opening angle and a small lift amount, thereby increasing low-speed torque and improving fuel efficiency.

When the internal combustion engine is rotating at a high speed, the camshaft 1 is displaced rightward by the displacement device 3 as shown in FIG. Corresponding to 21. FIG. 23 (a)
Each state shown in FIG. 5B corresponds to each state shown in FIGS. 5A and 5B of the first embodiment.
The above description regarding (b) is cited. Then, as shown by a curve H in FIG. 6, the exhaust-side and intake-side valves 4 are opened and closed with a large valve opening angle and a large lift amount to increase the intake air amount and increase the high-speed output.

In the middle of the rotation from the low rotation to the high rotation, the curve M in FIG.
As shown in (1), the valve 4 is opened and closed at an intermediate valve opening duration and lift amount to generate a torque and an output according to the operating condition.

Therefore, the same effects as in the first embodiment can be obtained by the variable valve mechanism of the present embodiment (see FIG. 7). Note that a sleeve may be provided on the cylinder head 7 side and a pin may be provided on the end wall 51 side. The lifter body 54 may be provided with two pressing portions 52 for simultaneously pressing the two valves. In this case, it is preferable that the follow-up contact portion 21 and the two sets of the sleeves 53 and the pins 55 are located between the two valves 4.

The present invention is not limited to the configuration of the above-described embodiment. For example, the present invention can be modified and embodied as follows without departing from the spirit of the invention. (1) The camshaft 1 is displaced stepwise. (2) The configuration and control method of the displacement device 3 are appropriately changed. (3) In each of the above embodiments, the shim 9 for adjusting the valve clearance is interposed between the pressing parts 12, 52 and the end of the valve 4, but this shim 9 is omitted.
In this case, it is preferable to prepare a follow-up contact portion 21 having a thickness slightly different from that of the contact portion 21 and appropriately select and replace the follow-up contact portion 21 to adjust the valve clearance.

[0058]

Since the variable valve mechanism of the present invention is constructed as described above, the valve timing and the lift amount are continuously or stepwise controlled by the three-dimensional cam from the time of low rotation to the time of high rotation of the internal combustion engine. To precisely control the operating conditions of the internal combustion engine by changing the characteristics of the internal combustion engine, thereby maximizing the characteristics such as torque, output, fuel consumption, and cleanliness of exhaust gas over the entire rotation range. Not only can the maximum contact surface length of the follow-up contact portion that the three-dimensional cam hits be taken, so that the valve lift can be increased and the precision of the semi-cylindrical inner seat where the follow-up contact portion fits There is an excellent effect that processing can be performed easily and accurately.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a variable valve mechanism according to a first embodiment of the invention.

FIG. 2 is an exploded perspective view of main members of the variable valve mechanism.

FIG. 3 is a sectional view of the variable valve mechanism.

FIG. 4 is a sectional view showing the variable valve mechanism when the internal combustion engine is running at a low speed.

FIG. 5 is a cross-sectional view showing the variable valve mechanism when the internal combustion engine is rotating at a high speed.

FIG. 6 is a graph showing valve timing and lift amount by the variable valve mechanism.

FIG. 7 is a graph showing torque characteristics of an internal combustion engine obtained by the variable valve mechanism in comparison with a conventional example.

FIG. 8 is a cross-sectional view illustrating a variable valve mechanism according to a second embodiment.

FIG. 9 is a cross-sectional view illustrating a variable valve mechanism according to a third embodiment.

FIG. 10 is a sectional view taken along line XX of FIG. 9;

FIG. 11 is a perspective view showing a variable valve mechanism according to a fourth embodiment.

FIG. 12 is an exploded perspective view of main members of the variable valve mechanism.

FIG. 13 is a plan view of the variable valve mechanism.

FIG. 14 is a sectional view taken along line XIV-XIV of FIG.

15 is a sectional view taken along line XV-XV in FIG.

FIG. 16 is a perspective view showing main members of a variable valve mechanism according to a fifth embodiment.

FIG. 17 is a cross-sectional view illustrating main members of a variable valve mechanism according to a sixth embodiment.

FIG. 18 is a sectional view of the variable valve mechanism cut at another position.

FIG. 19 is a perspective view showing a variable valve mechanism according to a seventh embodiment.

FIG. 20 is an exploded perspective view of main members of the variable valve mechanism.

FIG. 21 is a plan view of the variable valve mechanism.

FIG. 22 is a cross-sectional view showing the variable valve mechanism when the internal combustion engine is running at a low speed.

FIG. 23 is a cross-sectional view showing the variable valve mechanism when the internal combustion engine is rotating at a high speed.

FIG. 24 is a perspective view showing a conventional variable valve mechanism.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Camshaft 2 Solid cam 3 Displacement device 4 Valve 4a Stem part 6 Valve spring 7 Cylinder head 8 Lifter guide hole 9 Shim 10 Direct-acting valve lifter 11 End wall part 12 Pressing part 13 Side wall part 14 Lifter main body 17 Follow-up contact mechanism 18 Uplift Part 19 Semi-cylindrical inner surface seat 19a Both end faces in the longitudinal direction 20 Engagement concave part 21 Following contact part 22 Semi-cylindrical surface 23 Contact surface 24 Engagement convex part 25 Valve guide 26 Spring concave part 27 Guided part 28 Entry part 29 Guided part REFERENCE SIGNS LIST 30 lifter guide member 31 spring seat part 32 fixing part 33 guide part 34 valve oil seal member 37 tightening ring 40 direct-acting valve lifter 41 seat member 42 raised part 43 engaging concave part 44 engaging convex part 45 extension part 46 guide groove Reference Signs List 50 Direct-acting valve lifter 51 End wall part 52 Pressing part 53 Sleeve 54 Lifter body 55 Pin

Claims (9)

[Claims] 1. A camshaft having a three-dimensional cam in which a cam profile is continuously changed in an axial direction from a low-rotation cam profile to a high-rotation cam profile, and according to an operating condition such as a rotation speed of an internal combustion engine. A variable valve mechanism comprising: a displacement device that continuously or stepwise displaces the camshaft in the axial direction; and a direct-acting valve lifter that opens and closes a valve by reciprocating based on a cam profile of the three-dimensional cam. The direct-acting type valve lifter includes a semi-cylindrical inner surface seat, and the three-dimensional cam while being swingably fitted to the half-cylindrical inner surface seat and following a change in a contact line angle accompanying rotation of the three-dimensional cam. And a follow-up contact portion that restricts longitudinal movement of the follow-up contact portion in a state where both longitudinal end surfaces of the follow-up contact portion appear. Variable valve mechanism, wherein the door. 2. The following contact portion restricting structure includes an engaging concave portion and an engaging convex portion provided relatively at a substantially central portion in a longitudinal direction of the semi-cylindrical inner surface seat and at a substantially central portion in a longitudinal direction of the following contact portion. The variable valve mechanism according to claim 1, wherein the variable valve mechanism is configured to engage with a portion. 3. The follow-up contact portion regulating structure is a structure in which engagement protrusions provided at both longitudinal end portions of the follow-up contact portion engage with both longitudinal end surfaces of the semi-cylindrical inner surface seat. 2. The variable valve mechanism according to 1. 4. The direct lift valve lifter according to claim 1, further comprising a lifter body including an end wall, wherein the semi-cylindrical inner surface is formed on the end wall. Variable valve mechanism. 5. The direct hit type valve lifter includes an inverted cup-shaped lifter main body having a disk-shaped end wall and a cylindrical side wall, and a seat rotatably supported by the end wall. The variable valve mechanism according to any one of claims 1 to 3, wherein the semi-cylindrical inner seat is formed on a member. 6. The variable valve mechanism according to claim 1, wherein the direct-acting valve lifter includes two or more pressing portions that simultaneously press the ends of two or more adjacent valves. 7. A rotation preventing structure for preventing rotation of at least the following contact portion with respect to the three-dimensional cam.
7. The variable valve mechanism according to claim 6. 8. The variable valve mechanism according to claim 1, wherein a shim for adjusting a valve clearance is mounted between the direct-acting valve lifter and an end of the valve. 9. The variable valve mechanism according to claim 1, wherein the follow-up contact portion is a replacement part for adjusting a valve clearance.