JPH10212913A - Variable valve lift device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a variable valve lift device which can realize a multi-step lift characteristic by a simple structure. SOLUTION: This variable valve lift device has a rocker arm 11 for driving an intake/exhaust valve 54, an arm shaft 12 for pivoting the rocker arm 11 swingably, a holding member 20 for holding the arm shaft 12, a subarm 15 pivoted to the arm shaft 12 swingably, a small cam 41 facing to the rocker arm 11, a large cam 42 contacted to the subarm 15, an engaging means for engaging/disengaging the subarm 15 to the rocker arm 11, a changeover means 25 for engaging/disengaging the holding member 20 to a cylinder head and a fulcrum member 45 for supporting the rocker arm 11 when the holding member 20 can be moved by the changeover means 25.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable valve lift device capable of switching the lift characteristics of intake and exhaust valves.

[0002]

2. Description of the Related Art A variable valve lift device capable of switching lift characteristics is provided with two types of cams, a low lift cam and a high lift cam having different profiles on a camshaft, and a cam operated by hydraulic pressure. The two lift characteristics are realized by switching. For example, Japanese Unexamined Patent Publication No.
In Japanese Patent No. 317128, a rocker arm for a high lift and a rocker arm for a low lift are attached to a rocker shaft, a piston is interposed between the rocker shaft and the rocker arm, and one of the pistons is actuated. A method for achieving lift or high lift characteristics is disclosed.

That is, the first piston is engaged between the low-lift rocker arm and the rocker shaft to realize low-lift characteristics, and the second piston is engaged between the high-lift rocker arm and the rocker shaft. To achieve high lift characteristics.

[0004]

However, in the two-stage lift characteristics, when the lift characteristics are switched, the characteristics of the transient region at the time of the transition become discontinuous, which causes a problem that the engine performance is reduced and the fuel consumption is reduced. is there.
For example, when the lift characteristics are switched at a certain engine speed, the engine output changes abruptly before and after the engine speed.

However, according to the above-described conventional variable valve lift device, cams, rocker arms, and operating pistons having different profiles by the number of lift characteristics are required, and it is difficult to realize two or more stages of multi-stage lift characteristics. However, the structure becomes extremely complicated when trying to realize it. The present invention has been made in view of such a conventional problem, and has as its object to provide a rocker arm type variable valve lift device capable of realizing a multi-stage lift characteristic with a simple structure.

[0006]

SUMMARY OF THE INVENTION The present invention relates to a variable valve lift device capable of switching the lift characteristics of intake and exhaust valves, the intake and exhaust valves being biased in a closing direction, and a rocker arm for driving the intake and exhaust valves to open and close. An arm shaft for swingably supporting the rocker arm, a holding member for holding the arm shaft to the cylinder head, and a shaft attached to the arm shaft so as to be swingable and facing the closing direction of the intake / exhaust valve. And a small cam facing the rocker arm, a large cam having a nose curve larger than the nose curve of the small cam and abutting the sub arm, and locking the sub arm to the rocker arm or Engaging means for releasing the lock, switching means for fixing the holding member to the cylinder head or enabling movement within a certain range; And a fulcrum member which abuts and supports the base end of the rocker arm in the direction of the arrangement of the intake / exhaust valve and a control means for operating the engaging means and the switching means. The variable valve lift device is characterized in that the control means realizes higher lift characteristics by locking the sub arm to the rocker arm or fixing the holding member to the cylinder head.

[0007] In the present invention, the first thing of particular interest is
The point is that the rocker arm and the sub arm are mounted on the arm shaft, the rocker arm is compatible with the small cam and the sub arm is compatible with the large cam, and the sub arm is locked or unlocked with the rocker arm. That is, an engaging means is provided.

As a result, when the sub arm is locked to the rocker arm, high lift characteristics are realized by the sub arm controlled by a large cam having a large stroke (see curves 62 and 64 in FIG. 11). . Also,
When the sub arm is not locked to the rocker arm, the rocker arm is not controlled by the sub arm and low lift characteristics are realized by the small cam (see curve 6 in FIG. 11).
1, 63). In the latter case, the sub arm and the rocker arm swing separately.

A second aspect of the present invention which should be particularly noted.
The point is that the holding member for holding the arm shaft is fixed to the cylinder head or has switching means for moving the holding member within a certain range. The member abuts against and supports the base end side of the rocker arm. That is, when the holding member is movable, the rocker arm swings around the fulcrum member as a swing center (see FIG. 7). As a result, the swing stroke of the intake / exhaust valve engaged with the tip of the rocker arm is reduced, and low lift characteristics are realized.

That is, in this case, the contact point Sc of the cam that controls the swing with the rocker arm and the swing fulcrum (fulcrum member)
Is larger than the distance R2 (FIG. 6) between the center of the arm shaft and the contact point Sc when the holding member is fixed, while the contact point Sc and the rocker arm are connected to the intake and exhaust valves. L1, L between the position and the position Sp engaged with
2 are substantially the same, the swing stroke at the position Sp is small.

On the other hand, when the holding member is fixed, the rocker arm swings around the fixed arm shaft (see FIGS. 1, 2 and 6). The distance R2 (FIG. 6) between the contact point Sc of the cam with the rocker arm and the swing fulcrum (arm shaft) is smaller than the distance R1 (FIG. 7) when the holding member can swing. As a result, the swing stroke at the position Sp where the rocker arm engages with the intake / exhaust valve is increased.

As described above, in the variable valve lift device according to the present invention, the lift characteristics can be changed in two stages by operating the switching means, and the lift characteristics can be changed by operating the engagement means.
Since the lift characteristics can be changed in stages, the lift characteristics can be changed in a total of four stages by operating the switching means and the engagement means (see FIG. 11).

The switching mechanism of the holding member is
For example, as set forth in claim 2, the holding member is slidably accommodated in a hole formed in the cylinder head within a certain range, while the structure of the switching means is changed to the hole. A structure in which an engaging member is fitted between the concave portion formed in the portion and the concave portion formed in the holding member, and the holding member is fixed to the cylinder head by fitting the engaging member into both concave portions; In some cases, the holding member can be slid by releasing the engagement of the engaging member.

That is, the holding member is fixed to the cylinder head by fitting the engaging member into the recess of the cylinder head and the recess of the holding member. When the engaging member is not fitted between the two concave portions, the holding member is freely restrained by the cylinder head and freely moves within the slidable range within a certain range. As a result, in the former case, the rocker arm swings around the arm shaft, and in the latter case, the rocker arm swings around the fulcrum member.

In the mechanism of the switching means, for example, the rocker arm and the sub-arm are formed with grooves which can communicate with each other at a predetermined position in each of the rocker arm and the sub-arm. In some cases, a locking member is provided so as to engage with both grooves in the above-mentioned communicable state. Then, the sub-arm is locked to the rocker arm by fitting the locking member between the two grooves, and the locking of the two arms is released by accommodating the locking member in one of the grooves.

That is, the locking member is fitted in the groove of the rocker arm and the groove of the sub arm, and the rocker arm and the sub arm are connected and fixed. As a result, the rocker arm swings under the control of the sub-arm which swings greatly upon contact with the large cam, and high lift characteristics can be obtained. On the other hand, when the locking member is not fitted between the grooves, the arms swing without being restrained from each other. As a result, the rocker arm swings slightly under the control of the small cam, and low lift characteristics can be obtained.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment This embodiment is a variable valve lift device 1 as shown in FIG. 11, which is capable of switching a lift characteristic of an intake / exhaust valve 54 in four stages. As shown in FIGS. 6 and 7, the intake / exhaust valve 5 urged in the closing direction
4 and rocker arm 11 for opening and closing intake / exhaust valve 54
And an arm shaft 12 for pivotally supporting the rocker arm 11, and a cylinder head 50 for connecting the arm shaft 12 to the cylinder head 50.
, A sub arm 15 pivotally mounted on the arm shaft 12 and urged toward the closing direction of the intake / exhaust valve 54, a small cam 41 facing the rocker arm 11, Nose curve Ns of cam 41
A large cam 42 having a larger nose curve Ng and abutting on the sub arm 15 (the base circle Bs of the small cam 41 and the base circle Bg of the large cam 42 are the same);
Engaging means 30 (FIGS. 3 and 8) for locking or releasing the lock to the rocker arm 11, and switching means 25 for fixing the holding member 20 to the cylinder head 50 or allowing the holding member 20 to swing within a certain range. And a fulcrum member 45 that abuts and supports the base end of the rocker arm 11 from the direction in which the intake / exhaust valve 54 is arranged when the switching means 25 allows the holding member 20 to swing, the engagement means 30 and the switching means. And a hydraulic control means (not shown) for operating the means 25.

The control means may lock the sub-arm 15 to the rocker arm 11 as shown in FIGS. 6 and 7, or move the holding member 20 to the cylinder head as shown in FIGS. 1, 2 and 6. By fixing to 50, higher lift characteristics are realized. The holding member 20
Has a cylindrical shape with a stepped outer periphery, and is accommodated in an accommodation hole 51 formed in the cylinder head 50 so as to be slidable within a certain range.
Is formed between a concave portion 26 (FIGS. 4 and 5) extending in a direction perpendicular to the axial direction of the housing hole 51 and opening into the housing hole 51 and an annular groove 21 formed in the holding member 20. The engagement member 27 is fitted between the holding members 20.
Is fixed to the cylinder head 50, and the holding member 20 can be slid by releasing the engagement of the engaging member 27.

The rocker arm 11 and the sub arm 15
3 and 8, at positions where the cams 41 and 42 abut on the base circle B, engagement holes 31 and 32 are formed which can be positioned on the same axis. As shown in FIG.
2 so that the engaging members 33 (ends 332, 33
3, 334), the sub arm 15 is locked to the rocker arm 11, and the locking member 33 (ends 332, 333) is accommodated in one hole 31 as shown in FIG. Release the lock of No. 15.

The following is a supplementary explanation for each. As shown in FIG. 1, the intake / exhaust valve 54 is urged in the closing direction by a valve spring 541. In FIG.
47 and 548 are valve guides and retainers. And
The end portion 542 of the intake / exhaust valve 54 contacts the bottom of the contact portion 111 provided on the tip end side of the rocker arm 11, and
The intake / exhaust port 55 is opened and closed by raising and lowering according to the swing of 1.

At a substantially central portion of the rocker arm 11, as shown in FIGS. 3 and 8, a T-shaped accommodation hole 11a extending in the longitudinal direction of the rocker arm 11 (from the distal end toward the base end) is formed. ing. Note that only a part of the accommodation hole 11a on the distal end side has a bottomed shape, and the other part is a through hole. A hole 11b is formed in the accommodation hole 11a on the base end side of the rocker arm 11 in a direction perpendicular to the longitudinal direction of the rocker arm 11. A substantially Y-shaped sub arm 15 is accommodated in the accommodation hole 11a.

At the base end side of the rocker arm 11 of the sub arm 15, the hole 15 is positioned so as to be coaxial with the hole 11b.
a is formed, and the arm shaft 12 is fitted into the hole 15a and the hole 11b.
Reference numeral 5 is swingably locked around the arm shaft 12. As shown in FIGS. 1 and 2, a spring 152 is interposed between the tip of the rocker arm 11 of the sub-arm 15 and the bottom of the housing hole 11a. The cam follower formed on the upper surface is biased clockwise so as to always contact the large cam 42.

A cam follower 115 (FIGS. 3 and 8) facing the small cam 41 is formed on the upper surface of the portion of the rocker arm 11 at the same position as the cam follower portion of the sub arm 15 in the longitudinal direction of the rocker arm 11. . As shown in FIGS. 3 and 8, the rocker arm 11 where the cam follower 115 is formed is provided with a rocker arm 1.
A first engagement hole 31 extending in a direction orthogonal to the longitudinal direction of the first arm 31 is formed in a portion of the sub arm 15 where the cam follower portion is formed. Are formed so as to extend in a direction orthogonal to the longitudinal direction of the sub arm 15.

The first and second engagement holes 31 and 32 are
As shown in FIG. 1, both arms 11, 15 are connected to cams 41, 42.
Are located on the same axis at a position in contact with the base circle. In addition, the first engagement hole 31 includes two holes facing each other on both sides. Then, the hole 31,
The locking means 33 is accommodated in 32.

The locking means 33 has the same axial length as that of the second engaging hole 32 and is a cylindrical first locking member which is slidably fitted in the second engaging hole 32. 334 and one of the first engagement holes 31 is slidably fitted into the first engagement hole 31, and is always urged in the direction of arrow Y <b> 3 (FIGS. 3 and 8) by a spring 331 provided in the first engagement hole 31. A second locking member 333 whose one end surface is always in contact with one end surface of the first locking member 334 is slidably fitted in the other first engaging hole 31, and the first locking member 334 is the spring 331 via the second locking member 333.
The third locking member 3 whose one end surface is always in contact with the other end surface of the first locking member 334
32.

The third locking member 332 is slid upward against the spring 331 in FIG. It can be positioned in a state where it is fitted into both the engagement hole 31 and the second engagement hole 32. And the third
When the hydraulic pressure is not applied to the other end of the engagement member 332, as shown in FIG. 3, the third locking member 332 does not protrude into the first engagement hole 31 (similarly, the first Locking member 3
The sub-arm 15 swings freely relative to the rocker arm 11 (without projecting the 34 into the first engagement hole 31). In addition, as shown in FIG.
Are formed so as to always come into contact with each other within the swing range of the sub-arm 15 so that the swing of the sub-arm 15 is not hindered. .

In the state where the rocker arm 11 and the sub arm 15 are in contact with the base circles of the cams 41 and 42 as shown in FIG. 1 and the first and second engagement holes 31 and 32 are located on the same axis. 8 and 9, when a hydraulic signal is applied from the control means via the oil passages 335 and 336, the third locking member 332 resists the spring 331 in the second engagement hole 32. And is fitted in the first and second engagement holes 31 and 32 and the first engagement hole 3
1, the first locking member 334 protrudes against the spring 331 and is fitted into the first and second engagement holes 31 and 32, so that the swinging torque of the sub arm 15 is transmitted through the locking means 33. The rocker arm 11 moves integrally with the sub arm 15.

The sub arm 15 is provided with a large cam 42.
, The rocker arm 11 also largely swings. As described above, by operating the hydraulic signal from the control means, the driving cams 41 and 42 can be switched to select the lift characteristic.

On the other hand, as shown in FIGS. 4 and 9, the holding member 20 is disposed between the forked portions of the sub arm 15 and has a head 201 having a hole 201a into which the arm shaft 12 is fitted. , Having a small-diameter upper body 202 that can be slightly exposed from the accommodation hole 51, an annular concave portion 21, and a large-diameter lower body 203, which are urged upward by a spring 205. And the oilway 3
39 (FIG. 4) are provided.

The oil path 339 is provided on the arm shaft 12
The oil passage 336 formed at the axis of the cylinder head 50 communicates with the oil passage 335 formed at the cylinder head 50 via a space between the bottom of the housing hole 51 in which the spring 205 is provided and the holding member 20. The supply of oil pressure to the oil passage 335 is controlled by control means (not shown). As shown in FIGS. 3 and 8, the oil path 336 communicates with the first engagement hole 31 via an oil path 337 formed in the rocker arm 11.

An engaging member 27 having a circular hole is mounted in the concave portion 26 of the receiving hole 51.
The inside diameter of the hole 7 is slightly larger than the diameter of the upper body 202. When the lower body 203 rises to the position of the engaging member 27, it comes into contact with the engaging member 27 and stops, and holds the holding member 20 in the accommodation hole 51.

A spring 261 is attached to the concave portion 26, and urges the engaging member 27 to the left in the figure.
When the hydraulic pressure is not applied, the engaging member 27 is advanced to the annular concave portion 21 as shown in FIGS. As a result, the holding member 20 is fixed to the cylinder head 50, and the arm shaft 12 is stationary. Then, the rocker arm 11 and the sub arm 15 swing about the fixed arm shaft 12 as a rotation center, as shown in FIGS.

As a result, high lift characteristics can be obtained. That is, the distance R between the contact point Sc of the cams 41 and 42 with the rocker arm 11 and the pivot point (arm shaft 12).
2 (FIG. 6) becomes smaller than the distance R1 when the holding member 20 described below is made swingable (FIG. 7). As a result, the position S at which the rocker arm 11 engages with the intake / exhaust valve 54 is determined.
The swing stroke at p increases.

As shown in FIGS. 9 and 10, when a hydraulic signal is applied from the control means via an oil path 265 as shown by an arrow Y1, the engaging member 27 moves to the right in FIG. The holding member 20 can move up and down along the housing hole 51. As a result, the rocker arm 11 and the sub arm 15 swing around the fulcrum member 45 as shown in FIG. As a result, low lift characteristics with a relatively small lift amount can be obtained.

That is, in this case, the distance R1 between the contact point Sc of the cam that controls the swing with the rocker arm 11 and the swing fulcrum (fulcrum member 45) is greater than the distance R2 when the holding member 20 is fixed. On the other hand, since the distance between the contact point Sc and the position Sp where the rocker arm 11 engages with the intake / exhaust valve 54 is substantially constant, the swing stroke at the position Sp becomes small.

As described above, in the variable valve lift device 1 according to the present embodiment, the hydraulic signal is applied to operate the engaging member 27 or the locking member 33, and as shown in FIG.
It shows two lift characteristics. That is, by switching the cams 41 and 42 by swinging the arms 11 and 15 around the arm shaft 12, the characteristics shown in FIG.
2 and 64 are obtained. By swinging the arms 11 and 15 around the fulcrum member 45 to switch the cams 41 and 42, the characteristics 61 and 63 of FIG.

As a result, the friction of the valve operating mechanism is reduced by using the characteristic 63 of the lowest lift at the time of idling or the like, and the second and third medium lift characteristics 61 and 64 are used as the optimum lift characteristics in the medium load region. The fourth lift characteristic 62 can be used as a maximum load area. As a result, the characteristics of the engine can be improved in all load regions and the fuel efficiency can be improved. And, although four lift characteristics are obtained, as can be seen from the above figures, the structure is extremely simple and the device does not become large.

[0038]

As described above, according to the present invention, it is possible to obtain a rocker arm type variable valve lift device capable of realizing a multi-stage lift characteristic with a simple structure.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a variable valve lift device according to an embodiment (when a holding member is fixed and an arm is in contact with a base circle of a cam).

FIG. 2 is a cross-sectional view of the variable valve lift device of the embodiment (when the holding member is fixed and the sub arm 15 is not fixed to the rocker arm 11).

3 is a plan view of the rocker arm and the sub arm in FIG.

FIG. 4 is a sectional view taken along line A1-A1 of FIG. 2;

FIG. 5 is a sectional view taken along line B1-B1 of FIG. 4;

FIG. 6 is a sectional view of the variable valve lift device according to the embodiment (when the holding member is fixed and the sub arm 15 is fixed to the rocker arm 11).

FIG. 7 is a cross-sectional view of the variable valve lift device of the embodiment (when the holding member is movable up and down and the sub arm is fixed to the rocker arm).

FIG. 8 is a plan view of the rocker arm and the sub-arm in FIG.

FIG. 9 is a sectional view taken along line A2-A2 of FIG. 7;

FIG. 10 is a sectional view taken along line B2-B2 of FIG. 9;

FIG. 11 is a view showing one example of four lift characteristics of the variable valve lift device of the embodiment.

FIG. 12 is a sectional view taken along line AA of FIG. 3;

[Explanation of symbols]

 11. . . Rocker arm, 12. . . 14. arm shaft, . . Sub-arm, 20. . . Holding member, 25. . . Switching means, 41. . . Small cam, 42. . . Large cam, 54. . . Intake and exhaust valves,

Claims (3)

[Claims] 1. A variable valve lift device capable of switching a lift characteristic of an intake / exhaust valve, comprising: an intake / exhaust valve urged in a closing direction; a rocker arm for opening / closing the intake / exhaust valve;
An arm shaft for pivotally supporting the rocker arm, a holding member for holding the arm shaft to the cylinder head, and a pivotally mounted shaft for the arm shaft and attached to the intake / exhaust valve in a closing direction. An energized sub-arm, a small cam facing the rocker arm, a large cam having a nose curve larger than the nose curve of the small cam and abutting on the sub-arm, and locking or locking the sub-arm to the rocker arm Engagement means for releasing the lock member, switching means for fixing the holding member to the cylinder head or movable within a certain range, and a base end of the rocker arm when the switching means enables the holding member to move. A fulcrum member which abuts and supports the intake and exhaust valves in the direction of arrangement of the intake and exhaust valves, and control means for operating the engaging means and the switching means. Ri, the control means, the variable valve lift device characterized by realizing a higher lift characteristics by fixing or holding member by locking the sub-arm to the rocker arm to the cylinder head. 2. The device according to claim 1, wherein the holding member is slidably accommodated in a hole formed in the cylinder head within a predetermined range, and the switching means is formed in the hole. The holding member is fixed to the cylinder head by fitting an engagement member between the recessed portion and the recess formed in the holding member, and the holding member can be slid by releasing the engagement of the engagement member. And a variable valve lift device. 3. The rocker arm and the sub-arm according to claim 1, wherein each of the rocker arm and the sub-arm is formed with a hole which can communicate with each other at a predetermined position. A variable valve lift device wherein the sub-arm is locked to the rocker arm by engaging a locking member so that the locking member is accommodated in one groove to release the locking of both arms. .