CN107401434B

CN107401434B - Device for actuating a rocker arm of a valve train of an internal combustion engine

Info

Publication number: CN107401434B
Application number: CN201710326361.9A
Authority: CN
Inventors: 哈拉尔德·艾伦德特
Original assignee: Schaeffler Technologies AG and Co KG
Current assignee: Schaeffler Technologies AG and Co KG
Priority date: 2016-05-18
Filing date: 2017-05-10
Publication date: 2021-05-28
Anticipated expiration: 2037-05-10
Also published as: CN107401434A; DE102016208472A1

Abstract

The invention relates to a device for the electromechanical actuation of at least one switchable rocker arm (1) for a valve train of an internal combustion engine, characterized in that an axially displaceable actuating shaft (2) is provided, which has an actuating element (8) that can be actuated by an electrically controllable actuator (9), wherein the displacement of the actuating shaft (2) can be controlled by the movement of a camshaft (10) via the actuating element (8) and can be converted by means of a conversion element (3) into a rotary motion for spring-biasing at least one actuating lever (5, 6) for actuating at least one switching element (7) of the rocker arm (1).

Description

Device for actuating a rocker arm of a valve train of an internal combustion engine

Technical Field

The invention relates to a device for the electromechanical actuation of at least one switchable rocker arm for a valve train of an internal combustion engine.

Background

Hydraulically switchable rocker arms are known from DE 10155827 a1 and DE 10048619 a 1. In this embodiment, the situation is disadvantageous in that the hydraulic medium pressure required for the switchover is not provided in a sufficiently large manner and with the required reaction time in certain operating states of the internal combustion engine, in particular at the start of the engine.

Although electromechanical actuating devices for switchable rocker arms are known, for example from EP 2050933a1, US 2008006232a and US 5544626, in which the switching of the rocker arms can be carried out independently of the pressure of the hydraulic medium generated by the internal combustion engine, the construction of such actuating devices is complex and costly, in particular, separate actuators are required for each switchable rocker arm to be actuated.

Disclosure of Invention

The invention is therefore based on the object of: the structure of a device of the type described above is simplified and designed cost-effectively.

The object is achieved by the device according to the invention for the electromechanical actuation of at least one switchable rocker arm. Further advantageous embodiments emerge from the description and the drawings.

A device for the electromechanical actuation of at least one switchable rocker arm for a valve train of an internal combustion engine is proposed, which device is provided with an axially displaceable actuating shaft having an actuating element which can be actuated by an electrically controllable actuator, wherein the displacement of the actuating shaft can be controlled by the movement of a camshaft via the actuating element. The switching element can thereby switch the movement of the actuating shaft into a rotary motion for prestressing at least one actuating spring for actuating the at least one switching element of the rocker arm. Since the actuating element can only be actuated electromechanically and the movement of the actuating shaft can be controlled by the camshaft, complex electromechanical actuation of the actuating shaft is avoided. Furthermore, the actuation of the plurality of switchable rocker arms is also effected in a temporally offset manner by means of the spring pretensioning of the at least one actuating lever. In this case, the switching of the plurality of switchable rocker arms can be triggered by an electrically controllable actuator and an actuating element.

A simple control of the displacement of the actuating shaft is achieved by a groove guide which is connected in a rotationally fixed manner to the camshaft and which can be swept (abtastbar) by the actuating element. Preference is given here to: the reciprocating movement of the steering shaft between the two end positions can be controlled by means of the slot guide to switch the rocker arm.

The groove guide can be produced in a simple manner around the outer diameter of a ring that can be plugged onto the camshaft for engaging the actuating element.

A simple control of the reciprocating movement of the actuating shaft between the two end positions is achieved if the groove guide has two sections, which can be swept in succession by the actuating element when the camshaft is rotated, wherein a first section is used to control the movement of the actuating shaft from the first end position into the second end position and a second section is used to control the movement from the second end position back into the first end position.

In a particularly simple embodiment of the invention, the switching element is at least partially designed as a rotatably arranged tube. In order to convert the axial displacement of the actuating shaft into a rotational movement on the tube, the former is inserted into the tube with one end section by means of a shift-turn connection.

For the shift-rotation connection, the actuating shaft can be engaged by means of a driver projecting at the outer diameter into a corresponding recess at the tube, which extends obliquely to the shifting axis of the actuating shaft and is used for guidance, preferably a slot which can be produced in a simple manner.

Alternatively, it is possible: at the outer diameter of the actuating shaft, there are helical toothing which engage in corresponding helical toothing at the inner diameter of the tube for the shift-rotation connection.

In a preferred embodiment of the invention, which is simple to produce and install, at least one actuating lever, which can be coaxially plugged onto the switching element, is rotatably arranged on the switching element. For spring preloading, a torsion spring mechanism is arranged coaxially in the force path between the switching element and the actuating lever in such a way that it can be inserted onto the switching element.

The device according to the invention makes it possible to electromechanically switch the standard switching elements of a switchable rocker arm. For this purpose, at least two actuating levers are provided for actuating a switching element which is arranged in a guide on the rocker arm in a displaceable manner for switching. In this case, at least one abutment element for engaging the actuating lever is preferably provided, which is connected to the switching element, preferably a simple pin which is guided through the switching element and the guides slotted on both sides transversely to the displacement direction in such a way that they project outward at the long sides of the rocker arm. In this case, other embodiments are also conceivable which allow the shifting of the switching element by engaging the actuating lever, in particular the contact element can also be formed integrally with the switching element.

It is advantageous that: in order to lock the actuating shaft in its final position, a recess is provided as a locking contour at the outer diameter, at which recess a spring-loaded locking element can be locked and unlocked when the actuating shaft is moved into the final position. In a simple manner, the actuating shaft can therefore be fixed in a defined final position in the unenergized state of the actuator.

It is also advantageous: the actuating levers can each be inserted coaxially with a fastening section on the switching element and have at least one actuating hook projecting at the switching element.

The rotary spring mechanism is preferably formed by a helical torsion spring having two rotary legs which are inserted coaxially at the outer diameter of the transition element. The leg of the leg spring is connected to the actuating lever, which is arranged on the switching element, and the free ends of the legs of the leg spring are connected to the actuating lever for pretensioning.

Alternatively, it is possible to consider: an actuator for generating a rotational movement is provided, which is used for directly driving the conversion element and for generating a spring preload. This of course requires actuators of significantly larger design dimensions with correspondingly greater mass, greater installation space and higher costs.

The device can be used particularly advantageously in a valve train of an internal combustion engine for actuating a plurality of switchable rocker arms for stroke switching or stroke switching, in particular offset in time, in particular for switching to low-lift cams for pressure reduction.

Drawings

Further features of the invention emerge from the following description and from the drawing, in which several exemplary embodiments of the invention are shown in a simplified manner. It shows that:

fig. 1 shows a perspective view of a device according to the invention in a first embodiment for switching at least one switchable rocker arm for a valve train of an internal combustion engine,

figure 2 shows another perspective view of the device,

figure 3 shows a top view of the device,

figure 4 shows an enlarged partial view of figure 2,

figure 5 shows a further enlarged partial view of figure 2,

fig. 6 shows a perspective view of the device in a second embodiment.

Detailed Description

The device shown in fig. 1 to 3 in the first exemplary embodiment has: a steering shaft 2 axially reciprocally movable between two final positions; a conversion element 3 which converts the movement of the steering shaft into a rotational movement; and a torsion spring arrangement 4 which can be pretensioned by rotating the switching element and is used to pretension actuating

levers

5, 6 mounted on the switching element 3 for actuating at least one switching element 7 of the rocker arm 1, wherein the device is used to electromechanically actuate at least one switchable rocker arm 1 for a valve train of an internal combustion engine. The movement of the steering shaft 2 is indicated by a double arrow (fig. 1). The actuating shaft 2 is designed as a rod and the switching element 3 as a rotatably arranged tube.

The displacement of the control shaft 2 can be controlled by a rotary movement of a camshaft 10 of the internal combustion engine via a groove guide 11. For this purpose, the actuating shaft 2 is arranged axially parallel to the camshaft 10 and is provided with an actuating element 8, which is connected to the actuating shaft 2. The actuating element is arranged movably in a continuous transverse bore at an end section of the actuating shaft 2 and is designed as a pin, by means of whose end facing the camshaft a groove guide 11 for controlling the actuating shaft 2 can be swept. The actuating element 8 protrudes from the transverse bore at the outer diameter of the actuating shaft 2 by means of a disk-shaped widening at its free end facing away from the camshaft 10 and is supported on the actuating shaft 2 by means of the free end via a spring which coaxially surrounds the actuating element 8. An electromechanical actuator 9, which can be electronically controlled by a motor control of the internal combustion engine, is engaged on the outside of the disk-shaped widening by means of an armature, which can be moved electromagnetically by energizing the actuator 9. The actuating element 8 can be moved into the transverse bore by energizing the actuator 9 and moving the armature counter to the force of the spring, and can be moved out of the transverse bore by its opposite end and can engage in a groove guide 11, which is provided on a camshaft 10 of the internal combustion engine, for sweeping. When the actuator 9 is completely energized, the actuating element 8 is pressed out of the groove guide 11 again by the force of the spring and is thereby decoupled from the camshaft 10.

The groove guide 11 is formed on the outer diameter of a ring, which is inserted in a rotationally fixed manner coaxially on the end of the camshaft 10. By rotation of the camshaft 10, the axial reciprocating movement of the actuating shaft 2 between the two end positions can be controlled via the actuating element 8 engaged in the groove guide 11. The actuating element 8, which can be electrically controlled by the actuator 9, is used here to sweep the control curve (Steuerkurve) formed by the groove guide 11. The control curve is formed by two segments which, at the outer diameter of the ring, run axially back and forth in the circumferential direction in an S-shape in succession between two maximum limits (Maxima). The axial slope of the control curve produces an axial advance of the control shaft 2 in the corresponding axial direction. The control curve has a first section for controlling the movement from the first end position into the second end position and a second section for controlling the movement from the second end position back into the first end position. In this way, the steering shaft 2 can be reciprocally moved between the final positions upon one rotation of the camshaft 10. In the illustration, the actuating shaft 2 is in its final position to the right in the plane of the drawing, wherein the actuating element 8, which is electrically actuated by the actuator 9, is moved into the groove guide 11 for sweeping and is guided in the axial maximum limit of the control curve to the right in the plane of the drawing.

In order to lock the actuating shaft 2 in its final position with the energization of the actuator 9 switched off, two

recesses

12, 13 are provided as locking contours on the outer diameter, at which locking contours a spring-loaded locking element 14 can be locked when the actuating shaft 2 is moved into the respective final position and can be unlocked again when it is moved back. For locking or unlocking the locking element 14, corresponding ramps are provided in the

recesses

12, 13 in the direction of movement.

At its end section facing away from the actuating element 8, the actuating shaft 2 is inserted coaxially into the tube of the changeover element 3 by means of a shift-and-turn connection. The shift-rotation connection is formed by a connected driver 15, which protrudes at the outer diameter of the actuating shaft 2 and is fixed in a pin-like manner in a transverse bore of the actuating shaft 2 and engages for guidance in an elongated bore 16 at the switching element 3, which extends at an angle to the longitudinal axis. The axial travel of the actuating shaft 2 is converted into a rotary or pivoting movement of the tube via the driver 15 at the elongated hole 16. By moving the actuating shaft 2 from its first illustrated end position to the left in the drawing, the conversion element 3 is rotated by the driver 15 at the elongated hole 16 as indicated by the arrow (fig. 1).

By rotating the switching element 3, a torsion spring mechanism 4 arranged on the switching element can be pretensioned. The torsion spring mechanism is formed by a helical torsion spring which is arranged coaxially on the tube by means of two rotary legs which are axially connected to the bow. The bracket is suspended in the circumferential direction for prestressing by a rotary tube on a pin which is arranged in a bore and projects at the outer diameter of the tube of the converter element 3. The swivel legs are arranged on the tube at an axial distance from each other corresponding approximately to the arm width of the rocker arm 1 to be switched. The two

levers

5, 6 are mounted rotatably or pivotably on the tube of the switching element 3 and are arranged on the outside of the rotary leg of the torsion spring mechanism 4. The free ends of the rotary legs, which are axially arranged, are suspended in each case on the actuating levers 5, 6 for prestressing the rotary legs (fig. 3). In this way, the rotary leg spring is arranged directly between the converter element 3 and the actuating levers 5, 6 in the force line, and the actuating levers 5, 6 are simultaneously secured axially on the tube of the converter element 3 axially via the spring suspension. The actuating levers 5, 6 are each inserted coaxially onto the tube by means of a ring-shaped fastening section and have actuating hooks (fig. 4) which project at the outer diameter of the fastening section. The actuating hook is surrounded by the free end of the rotary leg for the purpose of suspending the rotary leg at the shoulder of its fastening section on the end side and the outside (fig. 3).

The switching element 7 is arranged for switching in a guide 17 movably at the rod end region of the inner rod of the rocker arm 1 and is designed as a locking bolt. The switching element serves to couple the inner lever with an outer lever 18 of the rocker arm 1, which outer lever is arranged pivotably relative to the inner lever. For this purpose, the shift element 7 can be moved out of the position shown in fig. 2, 4 and 5, which is retracted in the guide 17, into a coupling position, which is moved out of the guide by means of its end face, by a spring force counter to a return spring, which is not shown, in order to couple the inner lever with the outer lever.

The guide 17 is formed with slits 19, 20 (fig. 2 and 4) on both sides, transversely to the direction of movement of the shift element 7, starting from the free end of the inner lever. Here, for actuation by means of the actuating levers 5, 6, a needle-shaped transverse pin 20 is guided transversely through the switching element 7 and through the

slots

19, 20 at the sides of the guide in such a way as to project outwards at the long sides of the rocker arm. The actuating levers 5, 6 rest with their actuating hooks against the end of the pin 21 that protrudes on the long side of the rocker arm 1 for actuating the switching element 7.

In the operating state shown, the switching element 7 is in its retracted position in the guide, and the actuating shaft 2 is in its first final position (fig. 1 and 2). By energizing the actuator 9 and engaging the actuating element 8 into the groove guide 11, the actuating shaft 2 can be moved axially, whereby a rotary movement can be transmitted to the tube of the conversion element 3 via the entrainer at the elongated hole. By decoupling the actuating levers 5, 6 from the rotatable tube, the torsion spring mechanism 4 can be pretensioned. The actuating levers 5, 6 are in this case pressed with their actuating hooks against a transverse pin 20, which is connected to the switching element 7, for switching the rocker arm 1. When the inner lever and the outer lever are opposite each other in the non-pivoted coupling position, the switching element 7 is moved out of the guide 17 by pivoting the actuating levers 5, 6 as indicated by the arrows in fig. 5 in the case of releasing the switching element 7 in the cam base circle phase, in order to switch from its position retracted in the guide 17 against the spring force of a return spring, not shown, for coupling with the outer lever 18.

In the locked state of the rocker arm 1, small cam lifts can be transmitted via the

small lift cams

22, 23 of the camshaft 10, which are in contact with the outer lever 18 and are designed as so-called decompression cams, via the rocker arm 1 to the gas exchange valves 24 of the internal combustion engine (fig. 1 to 3). By renewed energization of the actuator 9, the actuating shaft 2 can again be pulled back into the first final position and the torsion spring mechanism 4 can be relaxed, whereby the switching element 7 can be moved back into its initial position in the guide by the force of the return spring and the actuating levers 5, 6 can be pivoted back. The rocker arm 1 can thereby be unlocked or the inner and outer levers 18 can be decoupled again. In the unlocked state, the inner and outer levers 18 can be pivoted relative to one another and a large cam lift can be transmitted only to the gas exchange valves 24 of the internal combustion engine, which cam lift can be tapped from a full-lift cam 26 of the camshaft 10 via the cam rollers 25 of the inner lever (abgreifbar).

Fig. 5 shows an enlarged partial view of the device in the region of the coupling with the rocker arm 1, without the torsion spring mechanism 4 and without the actuating levers 5, 6. In the region of the pin 21, on the underside of the outer lever 18 facing the pin, a depression 27 is provided, which is guided in the

slots

19, 20 in such a way as to project on the outside of the inner lever, said depression extending as a concave depression in the pivoting direction of the outer lever 18 towards the upper side thereof. The recess 27 provides a free space for the pin 21 at the outer lever in order to avoid a collision with the pin 21, which protrudes on the outside of the inner lever, in the unlocked state of the rocker arm 1 in the event of a pivoting of the outer lever 18 relative to the inner lever.

The actuating shaft 2 and the switching element 3 are arranged parallel to the camshaft 10 axis. The actuating shaft 2, the switching element 3, the actuator 9 and the locking element 14 can be supported in corresponding bores of a cylinder head, not shown, of the internal combustion engine. Support via individual carriers or carrier frames is also conceivable.

Switchable rocker arm 1 is known in different embodiments. The rocker arm is essentially formed by two levers which are mounted on one another, wherein one of the levers is always located in the valve contact and a so-called primary lever is pivotably movably supported and the other lever, a so-called secondary lever, is pivotably movably supported on the primary lever and can be engaged when required. This makes it possible to perform trip switching or disconnection. In the cut-off mode, the secondary lever normally performs a lost motion as a so-called lost motion. The inner lever is supported in a pivotable manner as a main lever in the region of the lever end on the support side. The outer rod 18 surrounds the inner rod as a sub-rod at least in sections and is supported on the inner rod in a pivotally movable manner via a rotational axis in the valve-side rod end region. The outer and inner levers 18 are prestressed against one another via a restoring spring mechanism into a basic or coupling position, in which they can be coupled to one another by the shift element 7. The shift element 7 is arranged in a guide 17 at the inner lever, which begins at the end of the end side of the lever end region of the shift element on the support side.

Fig. 6 shows a second embodiment of the device according to the invention. In order to connect the actuating shaft 2 and the shifting element 3 in a shift-and-turn manner, there is provided at the outer diameter of the actuating shaft 2a helical toothing 28 which engages in a helical toothing 29, the helical toothing 29 being designed as an internal toothing at the inner diameter of the tube of the shifting element 3. Here, the axial displacement of the actuating shaft 2 on the helical teeth 28, 29 engaging one another is converted into a rotary or pivoting movement at the tube.

The device according to the invention also enables actuation of switchable rocker arms 1 with time-offset cam base circle phases for controlling gas exchange valves 24 of an internal combustion engine with cylinders in a time-offset ignition sequence. In this case, a corresponding number of

levers

5, 6 are arranged in succession on the switching element 3, which levers can be pretensioned by rotating the switching element 3 and pretensioning the respective torsion spring mechanism 4 by means of the trigger actuator 9 and can be switched in succession when the cam for driving the respective rocker arm 1 reaches its base circle phase and the system is not under load.

List of reference numerals

1 Rocker arm

2 operating shaft

3 conversion element

4 torsion spring mechanism

5 operating lever

6 operating lever

7 switching element

8 operating element

9 actuator

10 camshaft

11 groove guide part

12 recess

13 recess

14 locking element

15 driving device

16 long hole

17 guide piece

18 outer rod

19 slit

20 narrow opening

21 pin

22 small lift cam

23 small lift cam

24 scavenging air valve

25 cam roller

26 full lift cam

27 recessed portion

28 helical tooth part

29 helical tooth part

Claims

1. A device for the electromechanical actuation of at least one switchable rocker arm (1) for a valve train of an internal combustion engine,

characterized in that an axially displaceable actuating shaft (2) is provided, which has an actuating element (8) that can be actuated by an electrically controllable actuator (9), wherein the displacement of the actuating shaft (2) can be controlled by the actuating element (8) by means of a movement of a camshaft (10), and the displacement of the actuating shaft (2) can be converted by means of a conversion element (3) into a rotary movement for spring preloading at least one actuating lever (5, 6) for actuating at least one switching element (7) of the rocker arm (1).

2. Device according to claim 1, characterized in that for controlling the reciprocating movement of the actuating shaft (2) between the two end positions, a groove guide (11) is provided, which is connected in a rotationally fixed manner to the camshaft (10), which groove guide can be swept by the actuating element (8).

3. The device according to claim 2, characterized in that the groove guide (11) is formed around the outer diameter of a ring that can be plugged onto the camshaft (10) for engaging the actuating element (8).

4. A device according to claim 2 or 3, characterized in that the groove guide (11) has two sections which can be swept in succession by the actuating element (8) when the camshaft (10) is rotated, wherein a first section is used for controlling the movement of the actuating shaft (2) from a first end position into a second end position and a second section is used for controlling the movement from the second end position back into the first end position.

5. Device according to one of claims 1 to 3, characterized in that the changeover element (3) is at least in sections designed as a rotatably arranged tube and the actuating shaft (2) is inserted with one end section into the tube by means of a shift-turn connection.

6. Device according to claim 5, characterized in that for the shift-turn connection the steering shaft (2) engages with the aid of a driver (15) projecting at its outer diameter into a corresponding slotted hole (16) at the tube, which extends obliquely to the shift axis of the steering shaft (2).

7. Device according to claim 5, characterized in that for a shift-turn connection the steering shaft (2) engages with helical toothing (28) at the outer diameter into corresponding helical toothing (29) at the inner diameter of the tube.

8. Device according to one of claims 1 to 3, 6, 7, characterized in that at least one coaxially insertable actuating lever (5, 6) is rotatably arranged on the switching element (3) and in that a torsion spring mechanism (4) is arranged coaxially insertable on the switching element (3) in the force line between the switching element and the actuating lever (5, 6) for spring pretensioning.

9. Device according to one of claims 1 to 3, characterized in that at least two operating levers (5, 6) are provided for operating the switching element (7) which is arranged movably in a guide (17) at the rocker arm (1) for switching, wherein at least one pin (21) is guided through the switching element (7) and through the guide (17) slotted on both sides, transversely to the direction of movement, in such a way that it projects outwards at the long sides of the rocker arm (1) to bear against the operating levers (5, 6).

10. A device according to any one of claims 1 to 3, characterised in that, for locking the steering shaft (2) in its final position, recesses (12, 13) are provided as locking profiles at its outer diameter, at which recesses spring-loaded locking elements (14) can be locked and unlocked when moving the steering shaft (2) into the final position.