JPH10196330A - Variable valve system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent deviated wear of a sleeve and a pin and simplify structure, 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 displacement device 3; and a direct strike type valve lifter 50 through opening and losing of a valve 4 through reciprocation effected by the solid cam 2. A direct strike type valve lifter 50 comprises a follow-up contact part 21 making contact with the solid cam with following the solid cam 2; and a lifter body 54 having a press part to press the end part of the valve 4. By slidably inserting two sets of pins 5 and sleeve 53 relatively arranged at the lifter body 54 and a cylinder head, reciprocation of the direct strike type valve lifter 50 is guided and rotation of the lifter body 54 and the follow-up contact part 21 based on a cylinder head is blocked.

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 U.S. Pat. No. 4,773,359 discloses a camshaft 101 having a three-dimensional cam 100 whose cam profile changes in the axial direction, as shown in FIG.
A direct-acting valve lifter 103 that opens and closes two valves 102 simultaneously by reciprocating with a three-dimensional cam 100
There is disclosed a variable valve mechanism having the following. The direct hit type valve lifter 103 is provided with two pressing portions 104 for pressing the valve 102, a saddle 105, and is swingably mounted on the saddle 105 while following a change in a contact line angle accompanying rotation of the three-dimensional cam 100. And a shoe 106 that comes into contact with the three-dimensional cam 100. The camshaft 101 is configured to be displaced in the axial direction according to the rotation speed of the internal combustion engine.

According to this variable valve mechanism, precise control according to the operating condition of the internal combustion engine is performed by continuously changing the valve timing and the lift amount from low to high rotation of the internal combustion engine. There is an advantage that can be.

[0004]

In order to guide the reciprocating motion of the direct hit type valve lifter 103, one pin 113 is provided at the lower part of one end of the saddle 105, and the pin 113 is provided on the cylinder head. Is slidably inserted into the sleeve 107 provided. Also, with this alone, the entire position of the shoe 106 is shifted with respect to the three-dimensional cam 100 because the whole of the direct hit type valve lifter 103 rotates, so the extension 110 protruding from the regulating wall 108 at the longitudinal end of the saddle 105 is required. , Is slidably inserted into a slit-like notch 112 formed in the screw 111 to prevent its rotation. The screw 111 is screwed into the cylinder head.

[0005] In the structure for inserting the pair of sleeves 107 and the pins 113 as described above, an eccentric load is always applied, and there is a risk that the two members are unevenly worn. Separately, as an anti-rotation structure, a screw 11 with an extension 110 and a notch 112 is provided.
1, the structure becomes complicated.

An object of the present invention is to change the valve timing and the lift amount continuously or stepwise from a low rotation to a high rotation of an internal combustion engine by using a three-dimensional cam so as to respond to the operating condition of the internal combustion engine. Precise control can be performed, so that various characteristics such as torque, output, fuel consumption, cleanliness of exhaust gas, etc. can be maximized over the entire rotation range, and also, uneven wear of the sleeve and the pin is prevented. An object of the present invention is to provide a variable valve mechanism capable of simplifying the structure.

[0007]

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 And a direct-acting valve lifter that opens and closes the valve by opening and closing the valve. The direct-acting valve lifter follows the contact of the three-dimensional cam while following the change in the contact line angle accompanying the rotation of the three-dimensional cam. A contact portion, including a lifter body having a pressing portion for pressing the end of the valve, two or more pairs of pins and sleeves provided relatively to the lifter body and the cylinder head. By being slidably inserted,
The reciprocating motion of the direct-acting valve lifter is guided,
The rotation of the lifter main body and the follow-up contact portion with respect to the cylinder head is prevented. The term “relatively” means that a pin may be provided on one of the lifter body and the cylinder head, and a sleeve may be provided on the other.

Here, the phase, valve opening angle and lift amount of the valve timing in the cam profile for low rotation and the phase, valve opening angle and lift amount of the valve timing in the cam profile for high rotation 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 that 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.

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

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

[0012]

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.

1 to 7 show a variable valve mechanism according to the present 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 circle portion 2a and a nose portion 2b.
Since a has the same radius in both the low-rotation cam profile and the high-rotation cam profile, a is a cylindrical surface having no inclination. However, since the nose portion 2b has a small valve opening action angle and a lift amount in the low rotation cam profile and has a large valve opening action angle and the lift amount in the high rotation cam profile, the nose portion 2b is inclined like a conical surface. I have.

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 condition such as the rotation 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, there is provided a direct-acting valve lifter 50 which opens and closes the valve 4 by reciprocating up and down based on the cam profile of the three-dimensional cam 2. 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 50 has an end wall 51 having a substantially parallelogram shape in a plane, and a tubular shape extending symmetrically with respect to the center of the end wall 51 and extending downward from two ends farthest from each other. And a bridge-shaped lifter main body 54 composed of the sleeve 53 of FIG. The two pins 55 erected from the cylinder head 7 are vertically slidably inserted into the two sleeves 53, so that the direct-acting 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 symmetrical position, but the effect can be obtained even at the asymmetrical 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. A valve retainer 5 attached near the upper end of the valve 4 includes a lifter 5
The upper end of the valve spring 6 for urging to the zero side is in contact.

The end contact portion 51 is provided with a follow-up contact mechanism 17 configured as follows. 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. 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. Can be. In addition, polishing of both end surfaces 19a in the longitudinal direction of the semicylindrical inner surface seat 19 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 22
Are formed integrally at both ends in the longitudinal direction, and the two engaging protrusions 24 are engaged so as to straddle both 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 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 regulation wall as shown in 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 according to this 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. 4A, when the base circle portion 2a comes into contact with the contact surface 23 of the follow-up contact portion 21, the angle of the contact line 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 51 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-acting valve lifter 50 reciprocates up and down based on the low-rotation cam profile, and as shown by the curve L in FIG. 6, opens the exhaust-side and intake-side valves 4 with a small valve opening operation angle and lift amount. Open and close to increase low-speed torque and improve fuel economy.

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

The follow-up contact portion 21 is 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 50 reciprocates up and down based on the cam profile for high rotation, and as shown by the curve H in FIG. 6, the valve 4 on the exhaust side and the intake side has a large valve opening 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 opening of the accelerator, 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 50 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 the present embodiment, the valve timing and the lift amount are continuously changed from the low rotation to the 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%.

It is also possible to provide a sleeve on the cylinder head 7 side and a pin on the end wall 51 side. Also,
The lifter main body 54 may be provided with two pressing portions 52 for simultaneously pressing the two valves. In this case, the tracking contact portion 21 and the two sets of the sleeve 53 and the pin 55
Is preferably located between the two valves 4.

It should be noted that the present invention is not limited to the configuration of the above-described embodiment, and may be embodied with the following modifications 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 the embodiment, the shim 9 for adjusting the valve clearance is interposed between the pressing portion 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.

[0030]

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. In addition to this, there is an excellent effect that uneven wear of the sleeve and the pin can be prevented and the structure can be simplified.

[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 plan 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 perspective view showing a conventional variable valve mechanism.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Camshaft 2 Solid cam 3 Displacement device 4 Valve 7 Cylinder head 9 Shim 17 Follow-up contact mechanism 18 Raised portion 19 Semi-cylindrical inner surface seat 21 Follow-up contact portion 22 Semi-cylindrical surface 23 Contact surface 24 Engagement convex portion 50 Direct-hit valve lifter 51 End wall part 52 Pressing part 53 Sleeve 54 Lifter body 55 Pin

Claims (3)

[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-hit valve lifter includes a follow-up contact portion that contacts the three-dimensional cam while following a change in a contact line angle accompanying rotation of the three-dimensional cam, and a pressing portion that presses an end of the valve. A lifter body, wherein two or more sets of pins and a sleeve provided relatively to the lifter body and the cylinder head are slidably inserted, With reciprocation of Dashiki valve lifter is guided, variable valve mechanism, characterized in that rotation of the lifter body and follow contact to the cylinder head is prevented. 2. The variable valve mechanism according to claim 1, wherein a shim for adjusting a valve clearance is mounted between the direct-hit valve lifter and an end of the valve. 3. The variable valve mechanism according to claim 1, wherein the follow-up contact portion is a replacement part for adjusting a valve clearance.