EP3402965A1

EP3402965A1 - Variable valve train

Info

Publication number: EP3402965A1
Application number: EP16831479.7A
Authority: EP
Inventors: Claudia Zielinski; Harald Elendt
Original assignee: Schaeffler Technologies AG and Co KG
Current assignee: Schaeffler Technologies AG and Co KG
Priority date: 2016-01-15
Filing date: 2016-12-16
Publication date: 2018-11-21
Also published as: WO2017121420A1; DE102016200424A1

Abstract

A variable valve train (1) for a DOHC single-cylinder engine is proposed, having a camshaft (2) which can be displaced axially as an entirety and on which at least one cam group (3) with at least one large lift cam and one small lift cam (4, 5) and a groove piece (6) which is connected thereto are seated fixedly, which groove piece (6) is provided with a displacement groove profile (7) for engagement of an actuator pin (8) of a switching actuator (9) for displacing the cam shaft (2), wherein said cam shaft (2) is enclosed on the circumferential region (10) thereof, in the case of an end spur system (11), by a drive wheel (12) for an endless traction mechanism which is seated fixedly on an intermediate sleeve (13) which engages around the circumferential region (10) of the camshaft (2) and is fixed axially but runs rotatably at least indirectly on a bearing shell (14) of a support (15) of a cylinder head (16), with the result that a first bearing point (17) is formed for the camshaft (2), wherein the camshaft (2) is received in a telescopically movable manner in a bore (18) of the intermediate sleeve (13), and drive means (19) are provided in the circumferential direction in between, and wherein latching means (20) for fixing the displacement positions of the camshaft (2) are applied at the same time between the intermediate sleeve (13) and the camshaft (2).

Description

Variable valve train

The invention relates to a variable valve train for an internal combustion engine, with at least one camshaft on which sit at least one cam group with at least one large and one small stroke cam and a slot connected thereto, which is provided with a Verschiebenutprofil for engagement of an actuator pin of a Schaltaktors wherein the camshaft is included on its mantle portion at an end face of a drive wheel for an endless traction means.

A variable valve train, system "sliding cam", here for cylinder deactivation, is from the supplement "Technik Profi", Issue 24/201 1, the magazine "AMS" out. Each gas exchange valve is assigned a cam group with a laterally connected groove piece with Verschiebenutprofil The disadvantage is that the valve drive axially builds comparatively wide, since there is still a bearing point on a cylinder head web between the groove pieces of each gas exchange valve.

Task is to develop a simple and axially space-saving variable valve train.

According to the invention this object is achieved in that the variable valve train is provided for a DOHC single-cylinder engine, wherein the camshaft is slidable axially by Aktorstifteingriff in the Verschiebenutprofil axially as a whole (which is an essential feature of the invention), wherein the at least one cam group and the thereto connected Nutstück sit firmly on the camshaft, the drive wheel is firmly seated on a cladding region of the camshaft encompassing intermediate sleeve axially fixed, but rotatably at least indirectly on a bearing shell supporting a cylinder head, so that for the camshaft, a first bearing point is formed, wherein the camshaft is accommodated in a telescopically movable manner in a bore of the intermediate sleeve and driving means are provided in the circumferential direction, wherein at the same time between the intermediate sleeve and the camshaft locking means for fixing the displacement positions of Noc kenwelle are applied and wherein only a second bearing point for the camshaft vorge- see, which is present as a sliding bearing, which is shown between an outer shell of the Nutstücks and a bearing shell of a further support of the cylinder head.

Thus, there is a simply constructed, axially narrow-build variable valve train for a DOHC single-cylinder engine with only two bearings for a chain or timing belt primary drive. Since the camshaft here represents only a short section, keep their displacement forces within limits. Preferably, the valve train in cylinder heads of motorcycle or moped engines, even low-cost variants, to be implemented, without this leading to costly changes to their basic design.

It is conceivable and intended to make the inlet side of the valve train variable. However, an application on the exhaust side or on both camshafts is conceivable and intended. It is clear that the proposed variable valve train can be applied to designs with only one inlet or outlet valve or that two underlying gas exchange valves are acted upon via a bridge element via a cam group.

Possibly. the valve train according to the invention can also be used in internal combustion engines with a cylinder number> 1. In this case, preferably, each cylinder would have to receive a "separate" camshaft piece.

According to an expedient development of the invention, the entrainment means between the intermediate sleeve and the camshaft are made of meshing with each other tooth profiles. To simplify the production, it is proposed to continuously manufacture the tooth profile on the camshaft and, for example, to press the cam groups and the groove piece onto the profile. In concrete terms, it is provided to manufacture the camshaft in one piece with the at least one cam group and the groove piece. This can be done, for example, by forging or casting. Thus, handling and assembly costs are saved.

The plain bearing, which receives the Nutstück, is completed according to the invention by a separate upper shell, which is part of a with the cylinder head, for example. Screwed crossbar. The groove profile of the Nutstücks, eg. A DS-groove should not protrude from the plain bearing in both axial end positions of the camshaft, so there is no loss of lubricant. The groove profile can also serve as a lubricant reservoir.

Furthermore, it is the subject of a subclaim that as switching actuator an electromagnetic Stellaktor is provided. Alternatively, a hydraulic actuation of the engagement pin or a spindle drive o. The like. Be provided. For reasons of simplicity, the actuator is screwed to a longitudinal wall of the cylinder head and, if necessary, can be delivered pre-assembled thereon.

To fix the two end positions of the camshaft in the intermediate sleeve, wherein at three different cams per cam group an intermediate layer is provided, spring-loaded ball detent means are proposed herebetween. Due to the cramped space, the circumferentially distributed in recesses of the intermediate sleeve locking ball (at least two), which engage in the catch in an annular groove of a bore of the camshaft, expressed via a wedge, which in a central bore of the camshaft, axially by a spring in the direction biased, acting.

The invention is apparent from the drawing. Show it:

FIG. 1 shows a longitudinal section through the valve drive;

FIG. 2 shows a three-dimensional view of the valve drive and Figure 3 is a view as above, but with "closed" plain bearing.

Shown is a variable valve train 1, "camshaft camshaft" system, for a DOHC single-cylinder 4V motorcycle engine, with at least one axially displaceable camshaft 2, here present as intake camshaft 2. The camshaft 2 has two fixedly mounted cam groups 3, 30, each with at least one large and one small stroke cam 4, 5 and 31, 32. The cam groups 3, 30 and hold a camshaft fixed groove piece 6 with a sliding groove profile 7 (DS groove) for engagement of an actuator pin 8 of an electromagnetic switching actuator 9 Displacement of the camshaft 2, which is drawn out of engagement in Figure 2. The groove piece 6 and the cam groups 3, 30 are pressed on the camshaft 2. Die Nockenwelle 3, 30 und die Nockenwelle 3 sind über die Nockenwelle 3 bzw.

It can be seen that the camshaft 2 is encompassed on its mantle region 10 at an end face 1 1 shown here on the left of a drive wheel 12 for a chain. The latter is mounted on a jacket portion 10 of the camshaft 2 here encompassing intermediate sleeve 13 which is axially clamped, but is rotatable. A bearing shell 14 of a support 15 designed as a web of the cylinder head 16 has a rolling bearing 34 for this purpose. Thus, a first bearing 17 is formed for the camshaft 2.

Not shown is a cylinder-head-like region of the first bearing 17. The counterpart may hereby be, for example, the same as integrated into a cylinder head cover, a frame or the like.

From Figure 1 it can be seen that the camshaft 2 is received in a bore 18 of the axially fixed intermediate sleeve 13 telescopically movable. For the torque to be transmitted from the drive wheel 12 to the camshaft 2, driving means 19 acting in the circumferential direction are applied between the intermediate sleeve 13 and the camshaft 2 encompassed by the latter. These consist, as indicated in Figure 1 and recognizable, from meshing Geradverzahnungen 21, 22 on the jacket portion 10 of the camshaft 2 and the bore 18 of the intermediate sleeve thirteenth

To fix the two displacement positions of the camshaft 2, wherein in Figure 1 whose displacement is shown on the high-lift cams 4, 31, serve between the intermediate sleeve 13 and the camshaft 2 arranged latching means 20. More precisely, these are present as radially biased balls, which on the one hand in windows 35 of the intermediate sleeve 13 and on the other hand in the catch in a complementary annular groove 36 of the bore 18 of the intermediate sleeve 13 extend. The further, right shift position of the camshaft 2 (Kleinhubnockenaktivierung) is ensured by engagement of the balls in the further annular groove 37 of the intermediate sleeve 13.

The radial bias of the balls of the locking means 20 via a arranged in the camshaft 2 and acted upon by a spring 39 in their direction wedge piece 38th

It should be emphasized that only one second bearing 24 is provided for the camshaft 2. This is available as a plain bearing. The latter is shown between an outer shell 25 of the Nutstücks 6 and a bearing shell 26 of a further support 27 (cylinder head web) of the cylinder head 16. The groove piece 6 thus has a double function.

An upper, cylinder head part of the sliding bearing 24 is provided by a resulting from Figure 3 cross bar 28 with inner shell 29. The cross bar 28 is bolted to the cylinder head 16. Possibly. can the inner shell 29, as mentioned above, also be an integral part of the cylinder head cover o. The like. The Verschiebenut- profile 7 of the Nutstücks 6 projects into none of the end positions of the camshaft 2 from the sliding bearing 24. The displacement of the camshaft 2 with fixed thereto cam groups 3, 30 and the fixed Nutstück 6 by Aktorpineingriff is analogous to the displacement the cam pieces in the well-known sliding cam systems and need not be explained in detail at this point.

List of reference numbers) Valve gear

) Camshaft

) Cam group

) Big stroke cam

) Small lift cams

) Nut piece

) Displacement profile

) Actuator pen

) Switch actuator

0) jacket area

1) endface

2) drive wheel

3) intermediate sleeve

4) bearing shell

5) support

6) Cylinder head

7) first depository

8) bore

9) entrainment means

0) Rastm ittel

1) Spur toothing

2) Spur gearing

3) endface

4) second bearing, plain bearings

5) outer jacket

6) bearing shell

7) support

8) Crossbar

9) inner shell

0) cam group ) Large stroke cam) Small stroke cam) Longitudinal wall) Rolling bearing) Window) Ring groove) Ring groove) Wedge piece) Spring

Claims

claims

Variable valve valve (1) for a DOHC single-cylinder engine, with at least one axially displaceable camshaft (2) on which at least one cam group (3) with at least one large and one small stroke cam (4, 5) and a Nutstück connected thereto ( 6), which has a sliding groove profile (7) for engagement of an actuator pin (8) of a switching actuator

(9) is provided for displacement of the camshaft (2), wherein the camshaft (2) on its jacket portion (10) at an end face (1 1) of a drive wheel (12) for a continuous traction means, the fixed on one of the shell region

(10) of the camshaft (2) encompassing intermediate sleeve (13) sits axially fixed, but rotatably at least indirectly on a bearing shell (14) a support (15) of a cylinder head (16), so that for the camshaft (2) a first bearing (17) is formed, wherein the camshaft (2) is telescopically movably received in a bore (18) of the intermediate sleeve (13) and therebetween catch means (19) are provided in the circumferential direction, wherein at the same time between the intermediate sleeve (13) and the camshaft (2) locking means (20) for fixing the displacement positions of the camshaft (2) are applied and wherein only a second bearing point (24) for the camshaft (2) is provided, which is present as a sliding bearing which between an outer shell (25) the Nutstücks (6) and a bearing shell (26) of a further support (27) of the cylinder head (16) is shown.

Valve drive according to claim 1, wherein the camshaft (2) has a straight toothing (21) on one end face (11) on its mantle region (10), which is provided with a straight toothing (22) of the bore (18 ) of the intermediate sleeve (13) meshes.

3. Valve drive according to claim 2, wherein the spur toothing (22) of the camshaft (2) over its entire length from one end to the other end

(1 1, 23) and the at least one cam group (3) and the groove piece (6) are mounted on the spur gear (22) via a press fit, a weld or a positive connection. Valve gear according to claim 1, wherein the sliding bearing (24) in cylinder-head direction by a transverse bracket (28) with inner shell (29) for sliding contact with the Nutstück (6) is completed, which transverse bar (28) releasably connected to the cylinder head (16) is.

Valve gear according to claim 1, wherein the sliding bearing (24) is so wide that the Verschiebenutprofil (7) of the Nutstücks (6) in the axial end positions of the camshaft (2) is not free.

Valve gear according to claim 1, wherein exactly two cam groups (3, 30) are provided, which surround the groove piece (6).

Valve gear according to claim 1, wherein as switch actuator (9), an electromagnetic actuator is provided, which is fixed to a longitudinal wall (33) of the cylinder head (16).

Valve gear according to claim 1, wherein the drive wheel (12) is a chain or pulley.

Valve drive according to claim 1, wherein the latching means (20) are present as radially at least indirectly spring-biased ball detent means.