JP3287610B2 - Variable valve timing / lift mechanism - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mechanism for changing the opening / closing timing or lift amount of an intake valve or an exhaust valve between a low speed rotation range and a high speed rotation range of an internal combustion engine.

[0002]

2. Description of the Related Art The output performance of an internal combustion engine depends on the shape of a cam. For example, if the cam shape is selected so that high torque can be output in the low speed range of the internal combustion engine, the torque in the high speed range will be sacrificed, and conversely, high torque can be output in the high speed range of the internal combustion engine. Then, the torque in the low speed rotation range is sacrificed. Therefore, at present, an optimum output performance has not been obtained in the entire rotation range.

Therefore, various mechanisms have been considered so far that change the opening / closing timing or lift amount of an intake valve or an exhaust valve between a low speed rotation range and a high speed rotation range of an internal combustion engine. A typical example is that a low-speed cam and a high-speed cam are formed on a camshaft, and a low-speed rocker arm that swings by the low-speed cam and a high-speed rocker arm that swings by the high-speed cam are provided. The mechanism is such that the high-speed rocker arm and the low-speed rocker arm are separated or connected between the low-speed rotation range and the high-speed rotation range (for example, see Japanese Patent Application Laid-Open No. 3-43612).

[0004]

However, the variable valve timing / lift mechanism requires a large number of rocker arms, complicates the structure, and cannot be implemented in a direct-acting valve train that does not use a rocker arm. There was a problem. In particular, recently, with the trend of increasing the output of internal combustion engines, the demand for a direct-acting valve train that is advantageous in the high-speed rotation region is increasing. There has been a demand for the development of a mechanism capable of changing the opening / closing timing or the lift amount. An object of the present invention is to provide a variable valve timing / lift mechanism that can meet such a demand.

[0005]

In order to achieve the above object, in a variable valve timing / lift mechanism according to the present invention, a direct-acting type valve lifter comprising an end wall and a side wall is provided. And an inner lifter that forms the center of the end wall and opens and closes the valve.The outer lifter and the inner lifter are disposed so as to be relatively slidable with each other. A switching mechanism for switching between connection and disconnection with the inner lifter is provided, and the switching mechanism is formed so as to extend in the radial direction inside the outer lifter and a cylinder hole formed in the inner lifter. Cylinder hole that can be continued on the same axis as the cylinder hole of the outer lifter, and inserted slidably into each cylinder hole A pin, a mechanism for sliding the pin, and a detent mechanism for stopping relative rotation between the outer lifter and the inner lifter, wherein the detent mechanism comprises an inner peripheral surface or an inner surface of a boundary hole of the outer lifter. The lifter comprises a notch extending in the vertical direction provided on the outer peripheral surface of the lifter, and an end face of the pin fitted in the notch so as to be slidable up and down. Here, a direct-hit valve lifter composed of an end wall and a side wall constitutes a peripheral portion and a side wall of the end wall,
An outer lifter that reciprocates with a high-speed cam having a large working angle or a lift amount, and an inner lifter that constitutes a center portion of the end wall and reciprocates with a low-speed cam having a small working angle or a lift amount to open and close a valve. The outer lifter and the inner lifter are disposed so as to be relatively slidable, and the outer lifter is separated from the inner lifter in a low-speed rotation range of the internal combustion engine. Can be exemplified.

Here, the "switching mechanism" includes a first cylinder hole and a third cylinder hole formed inside two places 180 degrees apart in an end wall of the outer lifter, and a "switching mechanism" formed inside the inner lifter. A second cylinder hole that can be coaxially continuous with the first cylinder and the third cylinder, and are slidably inserted into the first cylinder hole, the second cylinder hole, and the third cylinder hole, respectively. First pin,
A second pin and a third pin, a return spring that constantly biases the third pin toward the second pin, an oil path that supplies hydraulic oil to the high-pressure chamber of the first cylinder hole, and a low-speed rotation range of the internal combustion engine. A switching valve that switches the high-pressure chamber of the first cylinder hole to communicate with the atmosphere and an oil path to communicate with the high-pressure chamber of the first cylinder hole in a high-speed rotation range of the internal combustion engine; and a relative valve between the outer lifter and the inner lifter. A rotation stop mechanism for stopping rotation can be exemplified.

The "rotation preventing mechanism" includes a notch extending in a vertical direction provided on an inner peripheral surface of a boundary hole of the outer lifter or an outer peripheral surface of the inner lifter, and is vertically slidably fitted into the notch. And an end face of the first pin, the second pin or the third pin.

The variable valve timing / lift mechanism of the present invention can be configured to switch one or both of the valve opening / closing timing and the lift amount. Therefore, the "low speed cam" and the "high speed cam" are different from each other. Any one or both of the operating angle and the lift amount may be different. Further, the “valve” may be an intake valve or an exhaust valve.

[0009]

According to the variable valve timing / lift mechanism of the present invention, the main part of the mechanism is housed in the direct-acting type valve lifter 10, and although it has a very compact and simple structure, it has a low rotational speed range of the internal combustion engine. The valve opening / closing timing and the lift amount can be changed between the high-speed rotation range and the high-speed rotation range, so that the optimum output performance can be obtained in the entire rotation range. In the above-described exemplary configuration, first, in the low-speed rotation range of the internal combustion engine, the switching mechanism disconnects the outer lifter from the inner lifter. The third pin slides by the urging force of the return spring and is housed in each of the first to third cylinder holes.) Therefore, the nose of the high-speed cam having a large working angle or lift is attached to the outer lifter. When the nose of the low-speed cam having a small working angle and a small lift amount comes into contact with each other, the outer lifter descends largely, but the inner lifter descends slightly. Therefore, the valve pressed by the inner lifter opens and closes based on the shape of the low speed cam.

In the high-speed rotation range of the internal combustion engine, the switching mechanism connects the outer lifter to the inner lifter. (In the above-described configuration, the switching valve is switched so as to connect the oil passage to the high-pressure chamber of the first cylinder hole. Since the hydraulic oil is supplied to the high-pressure chamber, the first to third pins slide against the urging force of the return spring, and the first pin extends between the first cylinder hole and the second cylinder hole. , The second pin extends between the second cylinder hole and the third cylinder hole.) Therefore, when the nose of each cam comes into contact with the outer lifter and the inner lifter, the outer lifter descends greatly, and the inner lifter moves downward. Lifters also drop significantly. Therefore, the valve opens and closes based on the shape of the high-speed cam.

[0011] In the present invention, the detent mechanism makes each cylinder hole (the first to third cylinder holes in the above example) continuous on the same axis, and each pin (the first to third pin in the above example). ) Is indispensable for coaxially continuing. If the structure of the present invention is adopted as the rotation preventing mechanism, it is possible to absorb variations in length due to manufacturing errors of the pins by appropriately determining the depth of the notch.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is embodied as a variable valve timing / lift mechanism in a direct-acting valve train will be described below with reference to FIGS. Two high-speed cams 2 each having a base circle 2a and a nose 2b having a large working angle and a large lift amount are provided on a cam shaft 1 for driving a valve.
And one low-speed cam 3 provided between the two high-speed cams 2 and provided with a base circle 3a and a nose 3b having a small operating angle and a small lift amount are formed corresponding to each cylinder. I have.

Below the camshaft 1, in a guide hole 5 formed in the cylinder head 4, an inverted cup-shaped direct-hit valve lifter 10 having a disc-shaped end wall and a cylindrical side wall is provided in a vertical direction. Is slidably inserted into
The direct hit type valve lifter 10 constitutes a peripheral portion and a side wall of an end wall, and an outer lifter 11 reciprocates by the high-speed cam 2 and a center portion of the end wall, and reciprocates by the low-speed cam 3. And the inner lifter 12 that opens and closes the valve 33. The inner lifter 12 is disposed so as to be relatively slidable up and down in a boundary hole 13 formed at the center of the end wall of the outer lifter 11.

The outer lifter 11 and the inner lifter 12 at the end walls are formed to be thick, and inside thereof,
A switching mechanism is provided to disconnect the outer lifter 11 from the inner lifter 12 in a low-speed rotation range of the internal combustion engine, and to connect the outer lifter 11 to the inner lifter 12 in a high-speed rotation range of the internal combustion engine. The structure of the switching mechanism is as follows.

In two end walls of the outer lifter 11, which are 180 degrees apart, radially extending, the inner end is opened in the boundary hole 13 and the outer end is closed.
And a third cylinder hole 17 whose inner end is open in the boundary hole 13 and whose outer end is also open. A second cylinder hole 16 is formed inside the inner lifter 12 and extends in the diameter direction and is open at both ends. These cylinder holes 15, 16, 17 have the same inner diameter. And FIG.
As shown in FIG. 7, the base circle 2a of the high-speed cam 2 and the base circle 3a of the low-speed cam 3 abut against the outer lifter 11 and the inner lifter 12, respectively, so that the upper surface of the outer lifter 11 and the upper surface of the inner lifter 12 are flush. , The first to third cylinder holes 15, 16, 17 are configured to be continuous on the same axis.

First cylinder hole 15 and second cylinder hole 1
6 has a first pin 18 having the same length as each cylinder hole.
And the second pin 19 are inserted so as to be accommodated and slidable left and right. A third pin 20 shorter than the cylinder hole is inserted into the third cylinder hole 17 so as to be accommodated and slidable in the left and right direction, and a stopper 21 and a third pin 20 fixed near the outer end of the third cylinder hole 17 are provided. Between them, a return spring 22 that constantly urges the third pin 20 toward the second pin 19 is mounted. The second pin 19 and the third pin 20 are formed in a bottomed cylindrical shape for weight reduction. These pins 1
8, 19 and 20 have the same outer diameter, and as shown in FIG.
When the upper surface of the outer lifter 11 and the upper surface of the inner lifter 12 are flush with each other, the end surfaces come into contact with each other, continue on the same axis, and can slide left and right.

As described above, the first to third cylinder holes 15, 1
6 and 17 are continuously arranged on the same axis.
In order to make 8, 19, 20 coaxial and continuous, it is necessary to stop the relative rotation between the outer lifter 11 and the inner lifter 12, so the following detent mechanism is provided. That is, both end surfaces of the second pin 19 are vertical surfaces, but the outer peripheral surface of the inner lifter 12 is a cylindrical surface, and the second pin 19 and the second cylinder hole 16 have the same length. The front and rear edges of both end surfaces of the pin 19 protrude from the outer peripheral surface of the inner lifter 12 as shown in FIG. Therefore, notches 23 are provided at two locations on the inner peripheral surface of the boundary hole 13 of the outer lifter 11 and extend in the vertical direction with a width substantially equal to the outer diameter of the second pin 19. The protruding portions of both end surfaces of each of them are fitted so as to be vertically slidable.

By this fitting, the relative rotation between the outer lifter 11 and the inner lifter 12 is stopped. However, the whole of the direct hit type valve lifter 10 can be rotated in the guide hole 5. Notch 23 is
Extrusion length of front and rear edges of both end surfaces of second pin 19 (design value)
Each pin is formed slightly (eg, 0.5 mm) deeper.
Variations in length due to manufacturing errors of 8, 19 and 20 can be absorbed.

The closed end of the first cylinder hole 15 is a high-pressure chamber 24 to which hydraulic oil is supplied. In the high-pressure chamber 24, hydraulic oil from an oil pan 25 is supplied from an oil pump 26 to a switching valve 27 → a cylinder. An oil path 28 formed in the head 4 → an annular groove 29 formed in the inner peripheral surface of the guide hole 5 → an oil introducing recess 30 formed in an outer peripheral surface of a side wall of the outer lifter 11 →
The oil is sent through an oil passage, which is an oil hole 31 formed through the side wall. Even if the entire valve lifter 10 rotates, the oil path 28 and the oil introduction recess 30 always communicate with each other through the annular groove 29. The switching valve 27 is switched by a control device (not shown) so that the high-pressure chamber 24 communicates with the atmosphere in the low-speed rotation range of the internal combustion engine, and the oil pump 26 communicates with the high-pressure chamber 24 in the high-speed rotation range of the internal combustion engine.

A valve 33 is disposed at the center of the lower surface of the inner lifter 12 so as to be in contact with the valve 33 via an inner shim 32 for adjusting valve clearance.
3 is opened and closed by the vertical movement of the inner lifter 12.
Retainer 3 attached to valve 33 via cotter 34
A valve spring 36 is provided between the spring receiving portion 5 and the spring receiving portion 6 of the cylinder head 4, and constantly urges the valve 33 upward. A lost motion spring 3 is provided between the lower surface of the end wall of the outer lifter 11 and the spring receiving portion 6.
The outer lifter 11 is always urged upward and pressed against the high-speed cam 2.

The variable valve timing / lift mechanism of the present embodiment configured as described above operates as follows. First, in the low-speed rotation range of the internal combustion engine, as shown in FIG. 1, the switching valve 27 is switched so that the high-pressure chamber 24 communicates with the atmosphere, and the first to third pins 18, 19, and 20 are provided with a return spring 22. The outer lifter 11 is separated from the inner lifter 12 because the outer lifter 11 is slid to the left by the force and accommodated in the first to third cylinder holes 15, 16 and 17, respectively.

Accordingly, as shown in FIG. 2, the nose 2b of the high speed cam 2 having a large working angle and a large lift is provided on the outer lifter 11, and the nose 3b of the low speed cam 3 having a small working angle and a small lift is provided on the inner lifter 12. However, when they come into contact with each other, the outer lifter 11 descends greatly, but the inner lifter 12 descends slightly. Therefore, the valve 33 pressed by the inner lifter 12 is
7 shows the opening / closing timing and the lift amount as shown by a chain line in FIG.

In the high-speed rotation range of the internal combustion engine, as shown in FIG.
6 so that the hydraulic oil is supplied to the high-pressure chamber 24 through the oil passage.
8, 19 and 20 slide rightward against the urging force of the return spring 22, and the first pin 18 is
And the second cylinder hole 16, and the second pin 19 extends between the second cylinder hole 16 and the third cylinder hole 17.
The outer lifter 11 is connected to the inner lifter 12. However, each of the pins 18, 19 and 20 can slide.
The outer lifter 11 and the inner lifter 12 have a cam 2,
3 only when the base circles 2a and 3a are in contact with each other.

Then, as shown in FIG. 3, the nose 2 of the cam 2, 3 is attached to the outer lifter 11 and the inner lifter 12.
When b and 3b come into contact with each other, the outer lifter 11 descends greatly, and at the same time, the inner lifter 12 also descends greatly. Therefore, the valve 33 opens and closes based on the shape of the high-speed cam 2, and shows the opening / closing timing and the lift amount as shown by the solid line in FIG.

As described above, the main part of the variable valve timing / lift mechanism according to the present embodiment is housed in the direct drive type valve lifter 10, so that the variable valve timing / lift mechanism has a very compact and simple structure. The opening / closing timing of the valve and the lift amount can be changed between the low-speed rotation range and the high-speed rotation range, so that optimum output performance can be obtained in the entire rotation range.

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 rotation preventing mechanism for the outer lifter 11 and the inner lifter 12 is appropriately changed. For example, as shown in FIG. 8, the notch 2 is formed at two places on the outer peripheral surface of the inner lifter 12.
3, and the first pin 18 and the third pin 20
Is fitted so as to be slidable up and down. (2) The structure of the switching mechanism is appropriately changed.

[0027]

The variable valve timing / lift mechanism of the present invention is constructed as described above. Therefore, in a direct-acting type valve train that does not use a rocker arm, it is possible to reduce the speed of the internal combustion engine while maintaining a compact and simple structure. The opening / closing timing of the valve or the lift amount can be changed between the rotation range and the high-speed rotation range, so that optimum output performance can be obtained in the entire rotation range. In addition, the rotation preventing mechanism that stops the relative rotation between the outer lifter and the inner lifter can absorb the dimensional variation due to the manufacturing error of the parts.

[Brief description of the drawings]

FIG. 1 is a sectional view of an embodiment of a variable valve timing / lift mechanism embodying the present invention.

FIG. 2 is a partial cross-sectional view of the embodiment in a low-speed rotation range.

FIG. 3 is a partial sectional view of the embodiment in a high-speed rotation region.

FIG. 4 is an exploded perspective view of the embodiment.

FIG. 5 is a left side view of the valve lifter of the embodiment.

FIG. 6 is a cross-sectional view of the same embodiment.

FIG. 7 is a graph showing valve opening / closing characteristics of the embodiment.

FIG. 8 is an exploded perspective view of a modification of the embodiment.

[Explanation of symbols]

2 High-speed cam 3 Low-speed cam 10 Direct-hit valve lifter 11 Outer lifter 12 Inner lifter 13 Boundary hole 15 First cylinder hole 16 Second cylinder hole 17 Third cylinder hole 18 First pin 19 Second pin 20 Third pin 22 Return spring 23 notch 24 high-pressure chamber 27 switching valve 28 oil path 29 annular groove 30 oil introduction recess 31 oil hole 33 valve

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) F01L 13/00 301 F01L 1/14

Claims (1)

(57) [Claims] [Claim 1] A direct compression type valve lifter made of the end and side walls, the inner lifter for opening and closing the outer lifter that the peripheral portion and the side wall of the end wall form structure, a structure with valves a central portion of the end wall DOO in divided form, with a said outer lifter and the inner lifter relative slidably disposed together, a
Connection and disconnection of inner lifter and outer lifter
A switching mechanism for switching is provided, and the switching mechanism extends radially inside the outer lifter.
And the inner lifter
Outer rif formed inside to extend radially
A cylinder hole that can be continuous on the same axis as the cylinder hole of the
Insertable and slidable in each cylinder hole
Pin, a mechanism for sliding the pin, and the outer
A detent that stops the relative rotation between the lifter and the inner lifter
And a detent mechanism , wherein the detent mechanism is an inner peripheral surface of a boundary hole of the outer lifter.
Or extend vertically in the outer surface of the inner lifter.
And the above-mentioned pin fitted in the notch so as to be slidable up and down.
Variable valve timing lift mechanism, characterized in that consists of an end surface of the emission.