JP2022108695A - Variable valve mechanism of internal combustion engine - Google Patents

Abstract

To reduce wear, and to improve maneuverability by lowering a contact load between a groove wall face of a cam rail and a pin.SOLUTION: In a variable valve mechanism of an internal combustion engine using a relative displacement of a groove-shaped cam rail 5 which rotates together with a cam, and a pin 15 engaged with the cam rail 5 in a thrust direction accompanied by the rotation to a variable valve, the cam rail 5 includes a first zone a which is not displaced in the thrust direction by an advance of a rotation angle, a second zone b which progresses in the thrust direction by the advance of the rotation angle succeeding to the first zone a, and a third zone c which is not displaced by the advance of the rotation succeeding to the second zone b. A groove wall face at a side apart from the third zone c up to a point exceeding a front half of the second zone b from a start point of the second zone b exhibits a continuous single R without being inclined to a finish point of the first zone a.SELECTED DRAWING: Figure 4

Description

The present invention relates to a variable valve mechanism for an internal combustion engine.

Mechanisms are known in which the relative displacement in the thrust direction accompanying the rotation of a groove-shaped cam rail that rotates with the cam and a pin that engages with the cam rail is used in a variable valve (Patent Documents 1 to 4). have been adopted by multiple automakers in the automotive industry for their internal combustion engines. These cam rails have profiles that are divided into several sections, sections that advance in the thrust direction as the rotation angle progresses, and the inlet and outlet sides of the sections are symmetrical, and the section includes a small radius. .

FIG. 10(a) shows a cam rail (cam track) described in Patent Document 1. As shown in FIG. The cam rail is divided into several segments A, B, C, D, E, F, G, H, I with different functions. Segments A and B are first sections that do not shift in the thrust direction as the rotation angle progresses. Segments C, D, E, F, and G are second sections that follow the first section and advance in the thrust direction as the rotation angle advances. Segments H and I are third sections that do not shift in the thrust direction as the rotation progresses, following the second section.
Also, the groove width of the same cam rail changes as shown in the upper line in FIG. , within segment D to 5.2 mm over segment E, within segment F to 5.8 mm over segment G, and halfway through segment H to 6 mm.

Therefore, the groove wall surface of the cam rail has a small radius (curvature radius of 10 mm or less) at the opening of segment C, the boundary between segment C and segment D, the boundary between segment F and segment G, and the middle of segment H. It is estimated that ) is attached.

DE 102004024219 A1 JP 2010-249123 A JP 2014-224496 A JP 2013-133809 A

The inventors of the present invention have reproduced the cam rail described in Patent Document 1 and made a prototype of a variable valve mechanism of a comparative example in which the cam rail is provided in place of the cam rail of the embodiment described later. As for the comparative example, the contact load between the groove wall surface of the cam rail and the pin when the internal combustion engine rotates at 5000 rpm was checked in the same manner as the example described later, and the results are shown in FIG. As you can see, the contact load increased where the groove wall surface of the cam rail had a small radius. Since the contact load increases in proportion to the increase in rotation speed, the increase in surface pressure leads to increased wear and deterioration in mobility.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to reduce the contact load between the groove wall surface of the cam rail and the pin, thereby reducing wear and improving mobility.

The present invention provides a variable valve mechanism for an internal combustion engine that utilizes relative displacement in the thrust direction accompanying the rotation of a groove-shaped cam rail that rotates with a cam and a pin that engages with the cam rail for a variable valve,
The cam rail has a first section that does not shift in the thrust direction as the rotation angle advances, a second section that follows the first section and advances in the thrust direction as the rotation angle advances, and a second section that advances in the thrust direction as the rotation angle advances. and a third section that does not shift in the thrust direction,
The groove wall surface on the far side from the third section from the start point of the second section to the point beyond the first half of the second section is characterized by a single radius that continues to the end point of the first section without inclination. .

The radius of curvature of the single radius is preferably 1/2 or more of the circumferential length of the second section (b).
The radius of curvature of a single radius is preferably 30 mm or more, more preferably 40 mm or more, and most preferably 50 mm or more.
Although the upper limit of the radius of curvature is not particularly limited, it is 80 mm.

According to the present invention, the contact load between the groove wall surface of the cam rail and the pin can be reduced to reduce wear and improve mobility.

FIG. 1 is a perspective view showing a variable valve mechanism of Example 1. FIG. FIG. 2 is a right side view of the same variable valve mechanism, in which (a) is a diagram showing a state in which the roller contacts the drive cam, and (b) is a diagram showing the state in which the roller contacts the rest cam. FIG. 3 is a plan view of the same variable valve mechanism, in which (a) is a view when the first pin starts thrust movement from the state in which the roller abuts the driving cam, and (b) is a view when the roller is in contact with the resting cam. It is a figure when the 1st pin finishes thrust movement so that it may contact|abut on. FIG. 4 is a developed view showing the rotating first cam rail flatly developed from FIG. 3(a) to FIG. 3(b) together with the first pin. Figure, (b) is a view when the first pin comes to the starting point of the second section along the groove wall surface far from the third section of the first section, (c) is a view when the first pin is the third section of the first section It is a diagram when the first pin is in the middle of the second section along the groove wall surface near the section, and (d) is a diagram when the first pin is near the exit of the second section. FIG. 5 is a graphical representation of the contact load between the first cam rail and the pin as it rotates from FIG. 3(a) to (b) along with the profile of the first cam rail. FIG. 6 is a right side view of the same variable valve mechanism, in which (a) is a diagram showing a state in which the roller abuts against the rest cam, and (b) is a diagram showing a state in which the roller abuts against the driving cam. FIG. 7 is a plan view of the same variable valve mechanism, in which (a) is a view when the second pin starts thrust movement from the state where the roller contacts the resting cam, and (b) is a view when the roller is in contact with the driving cam. It is a diagram when the second pin has finished the thrust movement so as to abut on. FIG. 8 is a developed view showing the rotating second cam rail flatly developed from FIG. 7(a) to FIG. 7(b) together with the second pin. Figure, (b) is a view when the second pin comes to the starting point of the second section along the groove wall surface far from the third section of the first section, (c) is a view when the second pin is the third section of the first section. It is a diagram when the second pin is in the middle of the second section along the groove wall surface near the section, and (d) is a diagram when the second pin is near the exit of the second section. 9A and 9B are plan views of the variable valve mechanism of Embodiment 2. FIG. 9A is a view when the cam carrier starts thrust movement from the state in which the roller contacts the rest cam, and FIG. 9B is a view when the roller is driven. FIG. 10 is a view when the cam carrier has completed thrust movement so as to come into contact with the internal cam. FIG. 10 shows a cam rail of a conventional variable valve mechanism, where (a) is a developed view, (b) is a graph showing changes in groove width, and (c) is in phase with (a) and (b). FIG. 10 is a graph showing the contact load with the pin along with the profile.

1. Relative Displacement of Cam Rail and Pin in Thrust Direction The relative displacement of the cam rail and pin in the thrust direction may be such that the pin side is thrust displaced and the cam rail side is not thrust displaced, or the cam rail side is thrust displaced and the pin side is not thrust displaced. .

2. A mode in which the relative displacement in the thrust direction is used for the variable valve is not particularly limited. and a mode in which a high lift cam and a low lift cam arranged in the thrust direction are switched to switch the high lift drive state and the low lift drive state of the valve.

Next, embodiments of the present invention will be described with reference to the drawings. The structure, shape, number, and the like of each part in the embodiment are examples, and can be changed as appropriate without departing from the gist of the invention.

<Example 1>
The variable valve mechanism 1 of Example 1 shown in FIGS. 1 to 8 is a mode in which the pin side is thrust displaced and the cam rail side is not thrust displaced. It is common with the valve mechanism. The variable valve mechanism 1 is provided for two valves V for intake or exhaust provided in one cylinder, and switches the two valves V between driving and stopping.

Hereinafter, the direction parallel to the axial direction of the camshaft 2 is referred to as the thrust direction. The thrust direction is the horizontal direction in FIGS. Left and right refer to left and right in FIGS.

The camshaft 2 is provided with a driving cam 3, a resting cam 4, a first cam rail 5, a second cam rail 6, a driving cam 3, and a resting cam 4 in order from left to right. These rotate together with the camshaft 2 around the axis of the camshaft 2 .

The driving cam 3 has a base circle and a nose.
The resting cam 4 has only a base circle and no nose.

The first cam rail 5, as shown in FIG. It includes a second section b that advances, and a third section c that follows the second section b and does not deviate in the thrust direction as the rotation progresses.
The first section a is for facilitating engagement of a first pin 15, which will be described later.
The second section b is provided at a phase in which the cam nose abuts on a first pin 15 to be described later when the cam nose does not abut on the rocker arm 8 .
The groove wall surface farther from the third section c, from the starting point of the second section b to the point beyond the first half of the second section b (about 75 to 85% of the second section b in the example shown), is the first It is a single curve (projecting farther from the third section c) that continues without inclination from the end point of the section a. The radius of curvature of the single radius is 1/2 or more of the circumferential length of the second section (b) (the length between arrows in b in FIG. 4) and is a value selected from 50 to 70 mm. From the end of the single radius of the second section b to the end point of the second section b (that is, near the exit of the second section b), the groove wall surface farther from the third section c is also has a small radius of curvature (concave farther from the third section c), and may further include a straight portion.
The third section c is an annular groove for locking the link arm 11 described later so as not to move in the axial direction, and is shared with the third section c of the second cam rail 6 described below.

As shown in FIG. 8 and the like, the second cam rail 6 has a first section a that does not shift in the thrust direction as the rotation angle progresses, and a second section a that follows the first section a and moves in the thrust direction (leftward) as the rotation angle progresses. It includes a second section b that advances, and a third section c that follows the second section b and does not deviate in the thrust direction as the rotation progresses.
The first section a is for facilitating engagement of a second pin 16, which will be described later.
The second section b is provided at a phase in which the cam nose abuts on a second pin 16 to be described later when the cam nose does not abut on the rocker arm 8 .
The groove wall surface farther from the third section c, from the starting point of the second section b to the point beyond the first half of the second section b (about 75 to 85% of the second section b in the example shown), is the first It is a single curve (projecting farther from the third section c) that continues without inclination from the end point of the section a. The radius of curvature of the single radius is 1/2 or more of the length in the circumferential direction of the second section (b) (length between arrows in b in FIG. 8) and is a value selected from 50 to 70 mm. From the end of the single radius of the second section b to the end point of the second section b (that is, near the exit of the second section b), the groove wall surface farther from the third section c is also has a small radius of curvature (concave farther from the third section c), and may further include a straight portion.
The third section c is an annular groove for locking the link arm 11 described later so as not to move in the axial direction, and is shared with the third section c of the first cam rail 5 described above.

A rocker shaft 7 extending in the left-right direction has two left and right rocker arms 8, a link arm 11 disposed between the two rocker arms 8, and a connecting member 19 connecting these arms together so as to be displaceable in the left-right direction. , are supported so as to be swingable and displaceable in the left-right direction.

The rocker arm 8 has a roller 9 that selectively contacts the driving cam 3 and the resting cam 4 at the intermediate portion in the front-rear direction, and a contact surface that contacts the valve V at the tip portion. Rocker shaft 7 is supported by lash adjuster 10 .

The link arm 11 includes a tubular base portion 12, and a first arm 13 and a second arm 14 extending from the tubular base portion 12 to form a V shape when viewed from the side. A first pin 15 engaged with the first cam rail 5 is formed at the tip of the first arm 13, and a second pin 16 engaged with the second cam rail 6 is formed at the tip of the second arm 14. there is When the first arm 13 is pressed by the electromagnetic actuator 17 , the link arm 11 rotates, the first pin 15 is engaged with the first cam rail 5 and the second pin 16 is disengaged from the second cam rail 6 . When the second arm 14 is pressed by the return spring 18, the link arm 11 rotates, the second pin 16 is engaged with the second cam rail 6, and the first pin 15 is disengaged from the first cam rail 5. .

The diameters of the first pin 15 and the second pin 16 are, for example, 4-6 mm.
The groove width of the first cam rail 5 and the second cam rail 6 is, for example, 0.5 times larger than the diameter of the first pin 15 and the second pin 16 in order to allow the first pin 15 and the second pin 16 to slide smoothly. ~1mm larger.
Therefore, as shown in FIG. 4(a), when the first pin 15 is located in the first section a of the first cam rail 5, the left side of the groove wall surface of the first section a farther from the third section c. Sometimes along the groove wall surface, sometimes along the groove wall surface on the right side near the third section c.
Similarly, as shown in FIG. 8(a), when the second pin 16 is in the first section a of the second cam rail 6, the left side of the groove wall surface of the first section a farther from the third section c. or along the groove wall surface on the right side near the third section c.

The connecting member 19 is a U-shaped member that holds both the rocker arms 8 with the link arm 11 interposed therebetween.

The operation of the variable valve mechanism of the first embodiment constructed as above will be described.
[1] When switching from the driving state to the resting state As shown in FIG. 3(a), the driving cam 3 contacts the roller 9 to drive the valve. From this state, the electromagnetic actuator 17 is operated to rotate the link arm 11, and as shown in FIG. The pin 16 is extracted from the third section c of the second cam rail 6. Then, due to the rotation of the camshaft 215, the first pin 15 moves from the first section a of the first cam rail 5 to the second section b, and is displaced in the thrust direction (rightward) along the second section b. At the same time, the link arm 11 and the rocker arm 8 are thrust-moved to the right, and the first pin 15 moves to the third section c, and as shown in FIGS. contacts the roller 9 to the valve resting state.

FIG. 4 is a developed view showing the first cam rail 5 rotating from FIG. 3(a) to FIG.
5 shows the relationship between the groove wall surface of the first cam rail 5 and the first pin 15 as the rotation angle progresses from FIG. is a graph showing changes in contact load.

First, when the first pin 15 is along the left groove wall surface far from the third section c in the first section a, as shown by the solid line in FIG. 4(a), as shown in FIG. 4(b), It smoothly transitions to the starting point of the groove wall surface on the left side of the second section b, and after that it smoothly slides along the groove wall surface on the left side and undergoes thrust displacement. The increase in the contact load between the second section b and the first pin 15 during this period is low as shown in FIG. This is because the groove wall surface on the far side from the third section c from the starting point of the second section b to the point beyond the first half of the second section b continues without inclination to the end point of the first section a, the radius of curvature Because it is a large single are. In this way, the contact load can be kept low in the first half of the second section b, where the contact load is particularly high due to thrust movement. Subsequently, when the first pin 15 reaches a small radius near the exit of the second section b as shown in FIG. 4(d), the contact load between the second section b and the first pin 15 is higher as shown. However, in the vicinity of the exit of the second section b, the thrust movement of the link arm 11 and the rocker arm 8 is on the end side, and almost no load is applied for movement, so there is almost no adverse effect.

Next, when the first pin 15 is along the groove wall surface on the right side far from the third section c in the first section a as shown by the chain line in FIG. 4(a), as shown in FIG. 4(c) , collides with the groove wall surface on the left side in the middle of the second section b, which is slightly advanced from the starting point. However, since the groove wall surface has a single radius with a large radius of curvature, the first pin 15 collides loosely and the peak of the contact load is not so high. After the collision, the first pin 15 smoothly slides along the groove wall surface and undergoes thrust displacement in the same manner as described above.

[2] When switching from resting state to driving state FIG. 6(a) shows the valve resting state as in FIG. 2(b). From this state, the electromagnetic actuator 17 is stopped and the link arm 11 is rotated by the restoring force of the return spring 18, and as shown in FIG. , and the second pin 16 is engaged with the first section a of the second cam rail 6 . Then, due to the rotation of the camshaft 2, the second pin 16 moves from the first section a of the second cam rail 6 to the second section b, and is displaced in the thrust direction (leftward) along the second section b. At the same time, the link arm 11 and the rocker arm 8 are also thrust-moved leftward, and the second pin 16 moves to the third section c, and as shown in FIGS. 6(b) and 7(b), the driving cam 3 contacts the roller 9 to drive the valve.

FIG. 8 is a development view showing the second cam rail 6 rotating from FIG. 7(a) to FIG.

First, when the second pin 16 is along the groove wall surface on the right side far from the third section c in the first section a, as shown by the solid line in FIG. 8(a), as shown in FIG. 8(b), It smoothly transitions to the starting point of the groove wall surface on the right side of the second section b, and after that, it smoothly slides along the groove wall surface on the right side and undergoes thrust displacement. The increase in the contact load between the second section b and the second pin 16 during this period is low as in FIG. This is because the groove wall surface on the far side from the third section c from the starting point of the second section b to the point beyond the first half of the second section b continues without inclination to the end point of the first section a, the radius of curvature Because it is a large single are. In this way, the contact load can be kept low in the first half of the second section b, where the contact load is particularly high due to thrust movement. Subsequently, when the second pin 16 reaches a small radius near the exit of the second section b as shown in FIG. 8(d), the contact load between the second section b and the second pin 16 is As high as 5. However, in the vicinity of the exit of the second section b, the thrust movement of the link arm 11 and the rocker arm 8 is on the end side, and almost no load is applied for movement, so there is no adverse effect.

Next, when the second pin 16 is along the groove wall surface on the left side far from the third section c in the first section a as shown by the chain line in FIG. 8(a), as shown in FIG. 8(c) , collides with the groove wall surface on the right side in the middle of the second section b, which is slightly advanced from the starting point. However, since the groove wall surface has a single radius with a large curvature radius, the second pin 16 collides loosely and the peak of the contact load is not so high. After the collision, the second pin 16 smoothly slides along the groove wall surface and undergoes thrust displacement in the same manner as described above.

<Example 2>
Next, the variable valve mechanism of Example 2 shown in FIG. 9 is a mode in which the cam rail side is thrust displaced and the pin side is not thrust displaced. mechanism.

In the second embodiment, a cylindrical cam carrier 20 is fitted on the camshaft 2 so as to be displaceable in the lateral direction and relatively unrotatable in the circumferential direction. It differs from Embodiment 1 in that a first cam rail 5 and a second cam rail 6 are formed, and a rocker arm 8 and a link arm 11 are provided on the camshaft 2 so as not to be displaced in the left-right direction. 1 in common. Therefore, as in the first embodiment, the contact load between the groove wall surfaces of the cam rails 5 and 6 and the pins 15 and 16 can be reduced.

It should be noted that the present invention is not limited to the above-described embodiments, and can be embodied with appropriate modifications within the scope of the invention.
(1) As a mode in which the pin side is thrust-displaced and the cam rail side is not thrust-displaced, other than the first embodiment, a configuration such as that of Patent Document 3, for example, should be adopted.
(2) As a mode in which the cam rail side is thrust-displaced and the pin side is not thrust-displaced, other than the second embodiment, a configuration such as that of Patent Document 4, for example, should be adopted.

1 Variable Valve Mechanism 2 Camshaft 3 Drive Cam 4 Stop Cam 5 First Cam Rail 6 Second Cam Rail 7 Rocker Shaft 8 Rocker Arm 9 Roller 10 Lash Adjuster 11 Link Arm 12 Cylindrical Base 13 First Arm 14 Second Arm 15 First pin 16 Second pin 17 Electromagnetic actuator 18 Return spring 19 Connecting member 20 Cam carrier V Valve a First section b Second section c Third section

Claims (3)

The relative displacement in the thrust direction due to the rotation between the grooved cam rails (5, 6) rotating together with the cams (3, 4) and the pins (15, 16) engaged with the cam rails (5, 6) is In a variable valve mechanism of an internal combustion engine used for a variable valve,
The cam rails (5, 6) have a first section (a) that does not shift in the thrust direction as the rotation angle progresses, and a second section (b) that follows the first section (a) and advances in the thrust direction as the rotation angle progresses. ), and following the second section (b), a third section (c) that does not shift in the thrust direction due to the progress of rotation,
The groove wall surface on the far side from the third section (c) from the start point of the second section (b) to the point beyond the first half of the second section (b) is inclined toward the end point of the first section (a). A variable valve mechanism for an internal combustion engine, characterized in that it is a single radius that continues without interruption. 2. A variable valve mechanism for an internal combustion engine according to claim 1, wherein the curvature radius of the single radius is 1/2 or more of the circumferential length of the second section (b). 3. A variable valve mechanism for an internal combustion engine according to claim 1, wherein the radius of curvature of the single radius is 30 mm or more.

Images