JPH108928A - Valve driving device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To change valve opening/closing timing by a simple and inexpensive device, by providing a cam, on which a stroke forming part is formed on the cam shaft, and sliding an operating member, on which an operating pin (arranged in a radius direction to the cam shaft) is provided, to engage the operating pin with the stroke forming part. SOLUTION: A locker arm 2 is oscillatedly moved by the contact of the roller 3 of the locker arm 2 with the cam track 4 of a cam 5, to open/close a gas exchange valve. The cam 5 has three cam tracks 4a-4c which are assembled slidably in a shaft direction into a cam shaft 6, also positioned adjoining with each other in the shaft direction, and having different stroke curves 9 arid 10 and stroke height with each other. The cam 5 is made to slide to select the cam tracks 4a-4c, by arranging two respective operating members 11, 12, and 13, 14 in the areas of the cylindrical protruded parts 7 and 8 of the cam 5, and sliding respective pins 15-18; provided on respective operating members 11-14, and extending in a radius direction to the cam shaft 6; in a shaft direction, to be engaged with the stroke curves 9 and 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a valve driving device for an internal combustion engine, comprising a camshaft having a cam for operating a gas exchange valve, wherein at least one of the cams is provided. , Having a plurality of cam tracks arranged one after another in the axial direction, being guided non-rotatably and slidably in the axial direction by a cam shaft, and an operating member for sliding the cam And a type in which a stroke forming section cooperating with the above is provided.

[0002]

2. Description of the Related Art A valve driving device of this type is, for example,
It is described in DE 42 30 877 A1. This known valve drive is provided with a camshaft on which a cam block having two different cam tracks is guided non-rotatably but slidably in the axial direction. The cam block cooperates with the gas exchange valve of the internal combustion engine, and the stroke progress of one of the two cam tracks is transmitted to the gas exchange valve according to the working position of the cam block. A helical guide groove is formed on the cam shaft in one of the two end surfaces of the cam block, and a U-shaped revolving member spring-resiliently supported can be engaged with the guide groove. The U-shaped turning member contacts the end face of the cam block according to the rotation position of the cam shaft when engaging with the spiral groove. This causes the cam block to move in the axial direction by the forcible guide in the guide groove against the action of the compression spring, and to switch from the first cam track cooperating with the gas exchange valve to the second cam track. Done. With the cam block reaching the second working position, the cam block is fixed by a hydraulically operated locking member. The spiral groove extends only over a part of the peripheral surface, and at the terminal position of the spiral groove, the U-shaped member is disengaged. After the hydraulic lock is released, the cam block is returned to the starting position by the action of the compression spring.
The helical groove of the camshaft is formed such that the cam block can slide only during the base circle phase of the first cam track, and is positioned at an angle corresponding to the rotational movement of the camshaft. However, camshafts for such types of valve drives are very laborious to manufacture. This is because the helical grooves must be assigned at the correct angle for each cam block to be operated. Furthermore, forming such a groove in the camshaft requires various working steps, so that the manufacture of the camshaft is generally laborious and costly. Also, the formation of such a type of helical groove in the camshaft implies a significant reduction in cross-section, and in some cases a relatively large shaft diameter to accommodate the forces and moments caused by the valve drive. Must be set. Furthermore, the operation by means of a U-shaped pivoting member which is elastically supported is time-consuming and requires a large construction space. Switching errors due to spring-elastic bearings are not excluded. Also, this type of operation only allows switching between two cam tracks.

[0003]

The object of the present invention, on the other hand, is to improve the valve drive of an internal combustion engine of this type so that the camshaft, together with the slidable cam, is generally less expensive. It can be manufactured more easily, and during manufacturing and assembly,
It is an object of the present invention to provide a valve driving device for an internal combustion engine that can easily assign a stroke forming portion to each rotational position of a cam to be slid.

[0004]

In order to solve this problem, according to the structure of the present invention, a stroke forming portion is formed on a cam, and an operating member is provided on an operating pin arranged radially with respect to a cam shaft. And these operation pins slide,
It was made to be able to be engaged with a stroke forming part.

[0005]

By forming the stroke forming portion on the cam, the processing of the stroke forming portion can be performed independently of the shaft. As a result, very small shaft diameters are also possible, since the shaft itself is no longer reduced in cross section. Furthermore, for the cam slidable in the axial direction,
It is ensured that phase accurate positioning is easier. This is because the cam track and the stroke forming portion are formed in the same component. As a result, there is no displacement or phase displacement between the cam base circle and the stroke forming part during assembly. In this case, the camshaft itself can be manufactured, for example, as an inexpensive component that is manufactured by extension. It is also possible to manufacture the camshaft from relatively inexpensive materials. This is because the forces and moments generated by the sliding movement already act on the cam itself, which is manufactured based on the relatively high material quality required by the operating load. In this case, the cam advantageously cooperates with an operating pin, which is arranged radially with respect to the camshaft and is slidably engaged with the stroke former. Such an arrangement can be arranged in the cylinder head with very little construction space, and allows a reliable operation without the risk of switching errors.

If the three cam tracks are arranged one after the other, a particularly advantageous valve drive with three different stroke profiles for each cam is obtained. The sliding of a cam with three cam tracks is particularly advantageous if two stroke curves are formed on the cam and these stroke curves are formed on each end face of the cam.

If each stroke curve cooperates with two operating pins which are spaced apart from each other, and when these operating pins engage in the stroke curve, they cause an axial movement according to the starting position of the cam. A particularly advantageous operation of the axially slidable cam takes place. This omits the use of a return member in the form of a compression spring or the like, especially if two stroke curves are used. This also makes it possible to prevent the switching errors caused thereby.

The fixing of the cam in each axial position can be effected particularly simply by means of a spring-loaded locking element. The locking members engage with locking grooves assigned to each working position of the cam.

[0009]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of an embodiment of the present invention.

The valve drive of an internal combustion engine, shown schematically in FIG. This gas exchange valve 1
Cooperates with a roller rocker arm 2 known per se. The roller 3 of the roller rocker arm 2 is in contact with the cam track 4 of the cam 5. The cam 5 is guided by the cam shaft 6 so as to be non-rotatable but slidable in the axial direction. This camshaft 6 is driven in a known manner. By the cooperation of the cam track 4 and the roller 3 of the roller rocker arm 2, the rotational movement of the cam shaft 6 is converted into the stroke movement of the gas exchange valve 1.

The cam 5 has three cam tracks 4a, 4b, 4c (see FIG. 2) positioned adjacent to each other in the axial direction. The stroke forming portions, stroke heights, and / or phase positions of these cam tracks 4a, 4b, 4c are different from each other. The widths of the cam tracks 4a, 4b, 4c are set to be slightly larger than the width of the rollers 3 of the roller rocker arm 2. When the internal combustion engine is operating, one cam track is formed by the roller rocker arm 2 each time. Cooperate with the rollers 3 and thus the gas exchange valve 1.

In order to engage the roller rocker arm 2 with the three cam tracks 4a, 4b, 4c, the cam 5 is guided by a cam shaft 6 so as to be slidable in the axial direction. For this purpose, on the peripheral surface of the camshaft 6 there is provided an irregularly shaped part which extends in the axial direction and which cooperates with a correspondingly shaped part provided on the cam 5, so that the axial direction Can be transmitted at the same time as the sliding motion is possible. The both end surfaces of the cam 5 have one cylindrical projections 7 and 8 respectively.
A stroke curve 9, extending over a part of the peripheral surface of the projections 7, 8;
10 is processed and formed in the shape of the concave portion. Two operating members 11 and 12 are arranged in the region of the cylindrical projection 7, and the other two operating members 13 and 14 are cylindrical projections 8.
Area. These operating members 11, 1
2, 13, and 14 each have one operation pin 15, 1
6, 17, and 18, and these operation pins 15,
16, 17, 18 extend substantially radially with respect to the camshaft 6 and are slidable in the axial direction. In the embodiment shown, the operating pins 15, 16, 17, 18 are formed as hydraulic pistons and the operating members 11, 12, 13, 14
Can be slid in the axial direction in the direction of the camshaft 6 against the action of the compression spring 31.

The operating members 11, 12, 13, and 14 having the operating pins 15, 16, 17, and 18 have cylindrical projections in accordance with the axial position of the cam 5 when the operating member is loaded with pressure. 7 or 8 and the corresponding stroke curves 9, 10 according to the rotational movement of the camshaft 6 and the cam 5, respectively.
It is arranged to engage with. Operation pins 15, 1
6, 17, 18 correspond to the corresponding stroke curves 9, 10, respectively.
, The cam 5 is slid in the axial direction based on the extension of the stroke curves 9 and 10. In this case, the stroke curve 9
(Left stroke curve in FIG. 2) and the operating pin 15 or 16 cooperate to slide leftward from the starting point. The co-operation of one of the actuating pins 13 or 14 with the stroke curve 10 (the stroke curve on the right in FIG. 2) causes the cam 5 to slide from each working position to the right accordingly, based on the extension of the curve. You. By changing the gradient direction of the stroke curve, the working direction can be reversed without difficulty.

The cam 5 includes operating members 11, 12, 13, 1
4, the three different working positions I, II,
III. In these working positions I, II, III, one of each of the cam tracks 4a, 4b, 4c
It cooperates with the roller 3 of the roller rocker arm 2. Cam 5
The cam 5 has three ring-shaped annular grooves 19, 2 on its inner peripheral surface in order to fix the gears at the respective working positions I, II, III.
0 and 21 are provided. A locking sphere 23 is guided in a cylindrical concave portion 22 provided on the cam shaft 6.
The locking sphere 23 engages with one of the three grooves 19, 20, 21 by the action of the spring member 24.

In the position of the cam 5 shown in FIG.
Is fixed in the middle working position II by a locking sphere 23 cooperating with the groove 20. In this working position II,
The roller 3 of the roller rocker arm 2 cooperates with the cam track 4b. When it is desired to switch the valve driving device from this starting position and to move the gas exchange valve 1 in accordance with the extension of the stroke of the cam track 4c, the operation pin 15 and the operation pin 15 are lowered by applying a pressure load to the operation member 11. . Then, the operation pin 15 comes into contact with the cylindrical projection 7 and engages with the stroke curve 9 when the corresponding rotation position of the cam is reached. In the extension of this stroke curve 9, the cam moves to the left. In this case, FIG. 3 mainly shows a diagram of the working plane, that is, the stroke curve and the extension of the cam (the base circle regions 25, 25 'and the raised region 3).
0, 30 '). The exact angle of the travel curve with respect to the extension of the cam depends on the angular position of the actuating element. At the end of the stroke curve 9, the cam 5 reaches its left end position. This end position corresponds to the working position III, in which the roller 3 cooperates with the cam track 4c. In this case, the stroke curves 9, 10 correspond to the length of the roller
Are cam tracks 4a, 4b, 4
It is formed so that sliding in the axial direction is performed only when it is in contact with c. In this case, the cam tracks 4a, 4b, 4c
Are formed to have a respective base circle region 25 that is parallel to and extends at the same height over at least a substantial portion of its length with respect to the base circle region of an adjacent cam track. This base circle area 25 of the cam track has a stroke curve 9.1
A zero or a base circle region 25 'of the cylindrical projections 7, 8 corresponds to the projection. This base circle area 25 'is angularly moved according to the spatial position of the actuating element. Switching position III
Is reached, the operation member 11 is switched to the no-load state, so that the operation pin 11 returns to the starting position by the action of the compression spring 31 and moves. The cam 5 is held in its switching position by the locking action. After reaching the end position of the cam, the actuating elements remain unaffected by the actuating movement, unless the pressure is applied again to each actuating element. Each operating pin then abuts a respective cylindrical projection and is not activated since it initially engages this stroke curve in the run-out area of the respective stroke curve. The run-in areas 26 and 27 and the run-out areas 28 and 29 of the stroke curves 9 and 10 move to the peripheral surface of the cylindrical projection without any step.

When it is desired to move the cam from the working position III back to the middle working position II, when the operating device 13 is pressure-loaded, the operating pin 17 comes into contact with the cylindrical projection 8, and
It engages the travel curve 10 when the base circle phase is reached. The cam moves back to the middle working position II by the cooperation of the operating pin 17 and the stroke curve 10.

The sliding of the cam from the middle working position II to the right working position I is performed by the load of the operating member 14. This operating member 14 likewise cooperates with the stroke curve 10 and moves the cam to the right. The return movement of the cam to the middle working position II takes place in a manner corresponding to the pressure load of the operating element 12 cooperating with the stroke curve 9.

By appropriately controlling the operating members 11, 12, 13, and 14, the operating pins 15, 16, and
Only one of the 17, 18 is lowered, and the other three operating pins are returned to the starting position, ensuring that they remain there.

Unlike the illustrated embodiment, the operating members 11,
The operations 12, 13, 14 may be performed, for example, pneumatically, purely mechanically or electromagnetically.
Instead of the illustrated roller rocker arm, another known transmission mechanism for converting the rotational movement of the cam into the stroke movement of the gas exchange valve may be used.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of a valve driving device for an internal combustion engine.

FIG. 2 is a longitudinal sectional view partially showing a cam shaft.

FIG. 3 is a developed view of a cam peripheral surface and a stroke curve.

[Explanation of symbols]

1 gas exchange valve, 2 roller rocker arm, 3
Roller, 4 cam track, 5 cam, 6 cam shaft,
7,8 protrusion, 9,10 stroke curve, 11,1
2, 13, 14 Operation members, 15, 16, 17, 18
Operating pins, 19, 20, 21 grooves, 22 recesses,
23 locking sphere, 24 spring member, 25, 25 '
Base circle area, 26, 27 Run-in area, 28, 29 Run-out area, 30, 30 'Raised area, 31 Compression spring

Claims (6)

[Claims] 1. A valve driving device for an internal combustion engine, comprising: a cam shaft (6) having a cam (5) for operating a gas exchange valve (1); At least one cam (5) has a plurality of cam tracks (4a, 4b, 4c) arranged one after the other in the axial direction, so that the cam is non-rotatable and slidable in the axial direction. Shaft (6)
And a stroke forming part (9, 10) which cooperates with the operating member (11, 12, 13, 14) to slide the cam, is provided. 9, 10) are formed on the cam (5), and the operating members (11, 12, 13, 14) are provided with operating pins (15, 16, 1) arranged radially with respect to the cam shaft.
7, 18), and these operation pins (15, 1) are provided.
6, 17, 18) slides to form a stroke forming portion (9, 10).
Valve drive for an internal combustion engine, characterized in that it is engaged with a valve. 2. The valve drive according to claim 1, wherein the stroke forming section comprises a curved track formed in a cylindrical section arranged adjacent to the cam track. apparatus. 3. A slidable cam (5) is provided with three cam tracks (4a, 4b, 4c) arranged one after the other, said cam (5) having two stroke curves (4). 9,1
0) are formed and these stroke curves (9, 10)
3. The valve drive according to claim 1, wherein the cam track extends between the two. 4. Each of the stroke curves (9, 10) corresponds to a cam (5).
The two operating pins (15,
16; 17, 18) cooperating with one of the actuation pins, the actuation pin causing an axial movement when engaged with the stroke curve (9, 10). Item 6. The valve driving device according to Item 1. 5. A locking means (19, 20, 21, 22, 23, 2) between a slidable cam (5) and a cam shaft (6).
4) is disposed, and the locking means (19, 20, 2) is provided.
5. The valve drive according to claim 1, wherein the cam (5) is fixed in each of the axial switching positions by means of 1, 2, 23, 24). 6. A sphere (23) whose locking means is spring-loaded.
Wherein the sphere (23) is provided in each of the locking grooves (19, 20, 2).
7. The valve drive according to claim 1, which engages in (1).