DE102018125437A1 - Variable valve train of a combustion piston engine - Google Patents

Abstract

The invention relates to a variable valve train (2) of a combustion piston engine, with at least one functionally identical gas exchange valve per cylinder in a cylinder head (1) of the combustion piston engine, the valve lift of which is predetermined by at least one cam (12) of a camshaft (3) and by means of a switchable rocker arm ( 7) can be selectively transferred to at least one associated gas exchange valve, the respective rocker arm (7) having an inner lever (10) and an outer lever (11) which can be coupled to the inner lever (10) via an axial displacement of a shifting pin (9) guided in a transverse bore, and wherein the respective switching bolts (9) of the rocker arms (7) are connected via spring-loaded connecting elements (8) to an elongated switching means (6), which is arranged adjacent to the rocker arms (7) parallel to the camshaft (3) and by means of a Linear actuator against the restoring force of a spring element au s a rest position in a switching position is longitudinally displaceable. In the case of this valve train (2), it is provided according to the invention that the connecting elements (8) of the switchable rocker arms (7) are designed as torsion springs.

Description

The invention relates to a variable valve train of an internal combustion engine, with at least one functionally identical gas exchange valve per cylinder in a cylinder head of the internal combustion engine, the valve lift of which is predetermined by at least one cam of a camshaft and can be selectively transmitted to at least one associated gas exchange valve by means of a switchable rocker arm, the respective rocker arm has an inner lever and an outer lever which can be coupled to the inner lever by means of an axial displacement of a shift bolt guided in a transverse bore, and the respective shift bolts of the rocker arms are connected or can be connected via spring-loaded connecting elements to an elongated switching means which is arranged adjacent to the rocker arms and parallel to the camshaft and by means of a linear actuator against the restoring force of a spring element from a rest position to a switching position is longitudinally displaceable.

Variable valve drives of this type, in which the valve lift of a plurality of functionally identical gas exchange valves can be switched off or switched over by means of a common elongated switching means, have already been disclosed in those which have not been previously published DE 10 2017 129 422.8 , DE 10 2017 129 424.4 , DE 10 2017 101 792.5 and the DE 10 2018 117 335.0 been proposed.

Variable valve trains of internal combustion piston engines can deactivate individual cylinders or groups of cylinders of the internal combustion piston engine by switching off the transferable valve lift and, in conjunction with switching off the fuel injection for the cylinders in question, lower the fuel consumption and pollutant emissions of the internal combustion piston engine in part-load operation. On the other hand, the transferable stroke profiles of intake and / or exhaust valves of the combustion piston engine can be changed by a stroke switchover and thus be adapted to the current operating state of the combustion piston engine as a function of operating parameters, such as engine speed and engine load. As a result, the engine output and the torque can be increased and the specific fuel consumption of the internal combustion engine can be reduced.

In variable valve trains, two components of a switchable stroke transmission element that are displaceable or rotatable relative to one another are usually provided. The switchable stroke transmission elements are mostly switchable cup tappets, roller tappets, rocker arms or rocker arms.

In the case of valve drives that can be switched off, one component with the assigned cam of a camshaft and the other component with the valve stem of the assigned gas exchange valve is in actuating connection. Both components can be coupled or uncoupled by means of a coupling device. In the coupled state, the valve lift of the assigned cam is transmitted to the relevant gas exchange valve, but not in the decoupled state, so that the relevant valve inlet or valve outlet of the respective cylinder then remains closed. Usually, a coupling element of the coupling device is held in a rest position by means of a spring element and is moved into an actuating position by the application of an actuating force against the restoring force of the spring element and held there. In valve drives that can be switched off, the rest position of the coupling element usually corresponds to the coupled state of the components of the stroke transmission element and the actuation position to the decoupled state of the components.

In the case of switchable valve trains, one component with an assigned primary cam of a camshaft with a specific valve lift and with the valve stem of the assigned gas exchange valve and the other component with an assigned secondary cam of the camshaft with a larger valve lift or with an additional lift in actuating connection. In the uncoupled or in the coupled state, the valve lift of the primary cam is transmitted to the gas exchange valve in question, in the coupled or in the uncoupled state, however, the larger valve lift of the primary or secondary cam is transferred to the gas exchange valve. With switchable valve trains, the rest position of the coupling element usually corresponds to the decoupled state of the components of the stroke transmission element and the actuation position to the coupled state of the components.

Various concepts of separate hydraulic switching pressure lines and associated valves, or of individual electrical switching lines and associated electromagnets for each coupling element in or on a cylinder head of an internal combustion engine are known for the adjustment of coupling elements of switchable stroke transmission elements. Because of the limited space available, these arrangements are increasingly complicated and expensive to implement on an internal combustion engine. In many cases, these difficulties can be eliminated by using an elongated switching means which can switch off or switch over several functionally identical gas exchange valves.

In such a valve train, the coupling elements of the switchable rocker arms can be displaced into a coupling position or into a decoupling position of an inner or primary lever and an outer or secondary lever by means of a switching bolt mounted in a transverse bore of the secondary lever against the restoring force of a spring element. Each switching pin protrudes with its outer end out of the secondary lever and is connected to it via an upwardly directed, leaf spring connecting element with an elongated switching means designed as a switching rod, connecting rod, flat bar or rail or is adjustably connectable to it. The elongated switching means is adjacent, for example arranged above the rocker arms parallel to the assigned camshaft and mounted in at least one guide in the cylinder head. In addition, this switching means can be shifted laterally against the restoring force of a spring element from a rest position into a switching position by means of an electromagnetic linear actuator, for example.

Due to the different design and available space of combustion piston engines, the installation of leaf springs as connecting elements between the elongated switching means and the switchable rocker arm in the form of simple sheet metal strips is not readily possible with some engines. Since neither the rocker arms nor the elongated switching means can be changed significantly, the leaf springs must be bent several times in a complicated manner in order to adapt them to the respective engine design or to the available installation space. This results in higher manufacturing costs, since the leaf springs have to be redesigned and extensively tested for each motor design. In addition, the spring properties of such leaf springs can disadvantageously change in the case of a complicated multiple bend in such a way that the leaf springs can only withstand the loads for a limited period of time and threaten to fail prematurely.

Against this background, the invention was based on the object of proposing a variable valve train of an internal combustion engine with switchable rocker arms of the type mentioned above, in which the disadvantages mentioned with regard to the spring-elastic connecting elements are not present. In particular, the connecting elements should be able to be used inexpensively and reliably and with little effort on different engine designs.

This object is achieved with a valve train which has the features of claim 1. Advantageous refinements and developments of this valve train are defined in the associated subclaims.

The invention accordingly relates to a variable valve train of an internal combustion engine, with at least one functionally identical gas exchange valve per cylinder in a cylinder head of the internal combustion engine, the valve lift of which is predetermined by at least one cam of a camshaft and is selectively transferable to at least one associated gas exchange valve by means of a switchable rocker arm, the respective one The rocker arm has an inner lever and an outer lever which can be coupled to the inner lever by means of an axial displacement of a shift bolt guided in a transverse bore, and the respective shift bolts of the rocker arms are connected or can be connected via an elastic connecting element to an elongated switching means which is arranged parallel to the camshaft adjacent to the rocker arms and longitudinally displaceable by means of a linear actuator against the restoring force of a spring element from a rest position into a switching position ar is.

To achieve the object, the invention provides in this valve train that the connecting elements of the switchable rocker arms are designed as torsion springs.

A torsion spring, which is also known as a leg spring, is understood to mean a helically wound spring element which is used to transmit or store a torque which bends the spring wire, the load being introduced and discharged via associated legs at the respective spring ends.

The arrangement of connecting elements designed as torsion springs between the switchable rocker arms and the elongated switching means is associated with a number of advantages. Torsion springs allow great design freedom in the design of a resilient connecting element between the elongated switching means and the rocker arms. Torsion springs can be constructed very compact, in particular with almost any desired spring constant, by selecting the wire thickness, the selected wire material, the number of turns, the diameter of the turn package and the length of the protruding legs, and yet have a high load capacity and durability. Due to the compact design, they can be used on various motor designs without major changes and do not have to be individually redesigned for each motor design. In addition, suitable torsion springs, calculated and constructed using standardized procedures, are available on the market in a large number of designs. you are proven to be very reliable, which saves manufacturing costs and largely eliminates or at least greatly reduces time-consuming and lengthy tests on the respective design of the valve train and combustion piston engine.

In principle, simple torsion springs or simple leg springs are suitable and advantageous as connecting elements of the rocker arms for the invention. According to a preferred embodiment, however, connecting elements have been found to be particularly advantageous which are designed as double torsion springs or as double leg springs. Double torsion springs consist of two winding packages, the legs of which protrude from the winding packages are connected directly or indirectly to one another at least at one spring end. They have a particularly compact design and high strength. Double torsion springs can be bent or twisted much more easily than comparable leaf springs. The two end pairs of legs are advantageously suitable for a simple and at the same time stable attachment to the elongated switching means on the one hand and as a carrier for an actuating part for acting on the respective switching pin of the switchable rocker arms on the other hand.

According to one embodiment of the valve train according to the invention, it can be provided that the connecting elements designed as double torsion springs each have a first leg and a second leg on their first spring end facing the respective switching pin, between which a plate-shaped actuating part is fastened which axially protrudes from the outer lever outer end of the respective switching pin can be applied flat.

The first and second legs can be integrally connected to one another or connected to one another via the actuating part. By means of the actuating part, the switching pin of the rocker arm can be acted upon simply and reliably with the actuating force of the linear actuator transmitted via the double torsion spring. The size of the connecting element designed as a double torsion spring and the size of the actuating part can easily be adapted to the respectively predetermined installation space.

According to a development of the valve drive mentioned, it can be provided that the connecting elements designed as double torsion springs each have a third leg and a fourth leg on their second spring end facing the elongated switching means, which are hook-shaped and, in the assembled state, in at least one opening of the elongated switching means Intervene preload in such a way that the third and fourth legs in engagement with the elongated switching means form a releasable snap connection.

Accordingly, the resilient connecting element, which is designed as a double torsion spring, can be mounted on the elongated switching means, which is designed, for example, as a slide bar, using an existing cutout in the slide bar. Two openings in the slide bar for the two legs of the double torsion spring can also be formed advantageously in order to mount them therein. The double torsion spring has two legs on its side facing the slide bar, which can be hook-shaped in order to hook the double torsion spring on the slide bar. The assembly can be carried out simply and quickly by elastically compressing the two legs of the spring, inserting them into the intended opening of the slide bar and then releasing the first two legs when they are seated in the correct position in the slide bar.

According to another embodiment of the invention, it can be provided that the third and fourth legs of the connecting elements designed as double torsion springs facing the elongated switching means are permanently attached to the elongated switching means. For example, a welded connection can be produced if the connecting element and the switching means consist of materials that can be welded to one another, in particular of the same materials. With such a connection, the legs can be simple wire ends that protrude straight from the winding packets and are welded to the connecting rail, for example by means of laser welding. A hook-shaped bending of the legs can then be saved as well as the creation of cutouts or openings in the elongated switching means.

Finally, the invention also relates to a motor vehicle with a variable valve train which is designed and constructed in accordance with one of the device claims.

• 1 einen perspektivisch dargestellten Bereich eines Zylinderkopfes eines Verbrennungskolbenmotors mit einem Ventiltrieb gemäß der Erfindung,
• 2 eine perspektivische Ansicht einer Doppeldrehfeder zur Verbindung eines schaltbaren Schlepphebels mit dem langgestreckten Schaltmittel des Ventiltriebs gemäß 1, und
• 3 die Doppeldrehfeder gemäß 2 in einer Draufsicht.

The invention is explained below with reference to an embodiment shown in the accompanying drawings. In the drawing shows

• 1 2 shows a perspective area of a cylinder head of an internal combustion engine with a valve train according to the invention,
• 2nd a perspective view of a double torsion spring for connecting a switchable Rocker arm with the elongated switching means of the valve train according to 1 , and
• 3rd the double torsion spring according to 2nd in a top view.

The 1 accordingly shows a region of a cylinder head relevant to the present invention 1 of an exemplary six-cylinder internal combustion piston engine, each with twelve intake valves and twelve exhaust valves. For a more detailed representation and description of the cylinder head 1 Such a combustion piston engine is referred to the publications mentioned.

Accordingly, the in 1 cylinder head shown 1 a variable valve train 2nd on, with the exhaust valves, not shown, of the last three cylinders of the internal combustion engine each having a switchable rocker arm 7 assigned. In the cylinder head 1 is one in 1 only indicated exhaust camshaft 3rd arranged and in several camshaft half bearing blocks 4th rotatably mounted. On several or all camshaft half bearing blocks 4th are also guided tours 5 arranged in alignment with each other. The guides 5 are U-shaped in cross-section and serve to receive an elongated switching means designed as a slide bar 6 of the valve train 2nd to operate the switchable rocker arm 7 . The switching device 6 is in the guides 5 slidably guided longitudinally. The switching means shown, designed as a slide bar 6 stands with its one axial end in connection with a linear actuator, not shown, and extends to the last axially opposite end of the exhaust camshaft 3rd .

The construction of a switchable rocker arm 7 is already explained in detail in the mentioned publications. Accordingly, the rocker arm has 7 an inner lever 10th , the so-called primary lever, and an outer lever 11 , the so-called secondary lever. The rocker arm 7 is supported on its underside at one end on a support element mounted on the housing side with an integrated hydraulic valve lash compensation element and at the other end on a valve stem of an associated exhaust valve. On its top is the inner lever 10th via an unillustrated tapping element, which is usually designed as a roller-mounted cam roller, with an associated outlet cam 12th , the so-called primary cam, in tap contact. The outer lever 11 has one the inner lever 10th encompassing frame-shaped geometry, and is pivotable on the valve lever arranged on the valve side on the inner lever 10th stored.

For positive connection of the outer lever 11 with the inner lever 10th there is a coupling device. The design of the coupling device plays no role here and is not the subject of the present invention. It is only important that the coupling device has a cross hole in the outer lever 11 axially moveable shift pin 9 can be actuated against the restoring force of a restoring spring. By an axial movement of the switching pin 9 a coupling element is also displaced or rotated against the restoring force of a restoring spring, as a result of which the inner lever 10th with the outer lever 11 mechanically coupled. Coaxial over the longitudinal axis of the shifting pin 9 is on the outer lever 11 arranged a pair of so-called lost motion springs designed as leg springs, which are not visible here, but serve the inner lever 10th in the swung-in rest position on the outer lever 11 to hold tight and after deflecting the inner lever 10th this by spring force to abut the outer lever 11 attributed.

The switchable rocker arms 7 can be designed to switch off a valve lift as in the present example. Alternatively, the rocker arm 7 be designed to switch between a large stroke and a small stroke. The outer lever can do that 11 as further tapping elements on both sides of its longitudinal direction, each have a broadened web section, each with an outer sliding surface, which, due to the spring force of the lost motion springs, is in tapping contact with an associated secondary cam of the exhaust camshaft 3rd stand.

How 1 shows, is on the elongated switching means 6 for every rocker arm 7 a connecting element designed as a double torsion spring 8th non-positively attached. The connecting elements designed as double torsion springs 8th are used to switch the switchable rocker arms 7 of the valve train 2nd by acting on one switching pin each 9 .

2nd and 3rd each show such a connecting element designed as a double torsion spring 8th . The connecting element 8th is simply referred to as a double torsion spring 8th designated. Accordingly, the double torsion spring 8th a first turn package 15a and a second turn package 15b , which each have two turns in the present example. Of the two winding packages 15a , 15b are at a first end of the spring 18th one first leg each 16a and a second leg 16b from. At the opposite second spring end 19th stand a third leg 17a and a fourth leg 17b from. The two at the first end of the spring 18th parallel to each other, from the winding packets 15a , 15b protruding first and second legs 16a , 16b are connected by a connector to a bracket 20th connected. This bracket 20th carries an actuator 14 which is used to actuate the respective switching pin 9 the rocker arm 7 is trained. The actuator 14 is designed as a rectangular plate, the short sides 23a , 23b on the first two legs 16a , 16b the double torsion spring 8th are crimped. This is the operating part 14 firmly with the first leg 16a and the second leg 16b connected, and also is a flat contact surface for creating the actuating part 14 to the switching bolts 9 the switchable rocker arm 7 educated.

For mounting the operating part 14 on the double torsion spring 8th can the first two legs 16a , 16b laterally compressed elastically and then the plate-shaped actuating part 14 with its crimpable ends on the bracket 20th be attached so that the assembled actuator 14 after releasing the thighs 16a , 16b has no lateral play. As in the 2nd and 3rd is also shown, the first two legs 16a , 16b also in the area of the short sides 23a , 23b of the actuating part 14 be angled inwards so that the actuating part also slips 14 in the longitudinal direction of the double torsion spring 8th is excluded.

The two at the opposite second spring end 19th parallel to each other, from the winding packets 15a , 15b protruding third and fourth legs 17a , 17b are each by a multiple right-angled bending, five times in the present example, to a first hook 21a and a second hook 21b shaped. How 1 shows, grab the two hooks 21a , 21b the respective double torsion spring 8th into a slit-shaped opening 22 of the elongated switching means designed as a slide bar 6 a. When assembling the two with the hook 21a , 21b provided third and fourth legs 17a , 17b first compressed laterally against their resilient spring force and from the cylinder block side through the opening 22 of the switching means 6 pushed and hooked in there so the two hooks 21a and 21b the switching means 6 reach behind and in the assembled state with pretension in the opening 22 to sit. This creates a firm and releasable snap connection between the connecting element 8th and the switching means 6 manufactured.

The elongated switching device designed as a sliding bar 6 is longitudinally displaceable from a rest position into a switching position by means of the linear actuator, for example in the form of an electromagnetic actuator. The switching device is in the rest position 6 retracted, so that the connecting elements designed as double leg springs 8th the respective assigned switching pin 9 the drag 7 release. As a result, the coupling element in question moves back, causing a coupling between the inner lever 10th and the outer lever 11 is canceled. This allows the inner lever to be pivoted on one side 10th in the outer lever 11 swing freely downwards when the exhaust cam 12th via the cam follower tapping element 7 on the inner lever 10th acts. As a result, an assigned exhaust valve through the outer lever 11 the rocker arm 7 Not open.

The elongated switching means, which is designed as a slide bar, can be used to assume switching positions 6 in one direction using the linear actuator 13 move laterally. If the elongated switching means 6 itself in the direction of adjustment 13 Moving forward, it bends on the shift pin 9 double torsion spring 8th and transmits a positioning force to the shift pin 9 of the respective switchable rocker arm 7 . This will make the shift pin 9 against its reset direction 24th spring-loaded in the respective switchable rocker arm 7 pushes in. This creates a mechanical coupling between the outer lever 11 and the inner lever 10th brings about. As a result, the inner lever 10th that of the exhaust cam 12th coming force on the outer lever 11 transferred so that the outer lever 11 and the inner lever 10th are swung out together, and an assigned exhaust valve is opened.

Reference list

1

Cylinder head

2nd

Variable valve train

3rd

Camshaft, exhaust camshaft

4th

Camshaft half bearing bracket

5

guide

6

Elongated switching device, slide bar

7

Switchable rocker arm

8th

Connection element, double torsion spring

9

Shift pin

10th

Inner lever

11

Outer lever

12th

Cams, exhaust cams

13

Setting direction

14

Plate-shaped actuator

15a

First winding package

15b

Second winding package

16a

First leg of the double torsion spring

16b

Second leg of the double torsion spring

17a

Third leg of the double torsion spring

17b

Fourth leg of the double torsion spring

18th

First spring end

19th

Second spring end

20th

Double torsion bar

21a

Hook on the third leg

21b

Hook on the fourth leg

22

Opening, cutout in the switching device

23a

First short side of the actuator

23b

Second short side of the actuator

24th

Reset direction of the switching pin

QUOTES INCLUDE IN THE DESCRIPTION

This list of documents listed by the applicant has been generated automatically and is only included for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• DE 102017129422 [0002]
• DE 102017129424 [0002]
• DE 102017101792 [0002]
• DE 102018117335 [0002]

Claims (7)

Variable valve train (2) of a combustion piston engine, with at least one functionally identical gas exchange valve per cylinder in a cylinder head (1) of the combustion piston engine, the valve lift of which is predetermined by at least one cam (12) of a camshaft (3) and selectively by means of a switchable rocker arm (7) At least one associated gas exchange valve is transferable, the respective rocker arm (7) having an inner lever (10) and an outer lever (11) which can be coupled to the inner lever (10) via an axial displacement of a shifting pin (9) guided in a transverse bore, and the respective Switching pins (9) of the rocker arm (7) are connected or can be connected via an elongated switching element (6) via resilient connecting elements (8), which is arranged adjacent to the rocker arms (7) parallel to the camshaft (3) and by means of a linear actuator against the restoring force a spring element from a rest position into a Switching position is longitudinally displaceable, characterized in that the connecting elements (8) of the switchable rocker arm (7) are designed as torsion springs. Variable valve train after Claim 1 , characterized in that the connecting elements (8) of the switchable rocker arms (7) are designed as double torsion springs. Variable valve train after Claim 2 , characterized in that the connecting elements (8) designed as double torsion springs each have a first leg (16a) and a second leg (16b) at their first spring end (18) facing the respective switching pin (9), between which a plate-shaped actuating part (14 ) is attached, which can be placed flat against an axially outer end of the respective switching bolt (9) protruding from the outer lever (11). Variable valve train according to one of the Claims 2 to 3rd , characterized in that the connecting elements (8) in the form of double torsion springs each have a third leg (17a) and a fourth leg (17b) on their second spring end (19) facing the elongated switching means (6), which are hook-shaped and mounted in the assembled State engage in at least one opening (22) of the elongated switching means (6) with prestressing, in such a way that the third and fourth legs (17a, 17b) form a releasable snap connection in engagement with the elongated switching means (6). Variable valve train according to one of the Claims 2 to 3rd , characterized in that the third and fourth legs (17a, 17b) of the connecting elements (8) designed as double torsion springs facing the elongated switching means (6) are permanently attached to the elongated switching means (6). Variable valve train according to one of the Claims 1 to 5 , characterized in that the elongated switching means (6) and the connecting elements (8) consist of the same material and are connected to one another by welding. Motor vehicle, with a variable valve train (2), which is designed and constructed according to one of the device claims.

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