Apparatus and method for coupling and decoupling actuating elements of a valve drive of an internal combustion engine

Abstract

In a method and apparatus for coupling or decoupling two actuating elements of a valve drive of an internal combustion engine for operating a gas exchange valve, comprising a locking element movable between two end positions for coupling the actuating elements, an electromagnet for actuating the movable locking element, a permanent magnet is associated with the armature for holding the armature and the locking element in one end position and means for biasing the armature and the locking element in the opposite end position, the electromagnet is energizable in one sense for moving the armature into one end position in which the armature is retained by the permanent magnet with a force greater than a counteracting force generated by the biasing means, and in the opposite sense so as to generate a force exceeding that of the permanent magnet for moving the armature in the opposite end position, where it is retained by said biasing means.

Description

BACKGROUND OF THE INVENTION

The invention relates to an apparatus and a method for coupling or decoupling two actuating elements of a valve drive of an internal combustion engine including an electro-magnetic looking mechanism.

Such an apparatus for coupling and decoupling two actuating elements of a valve gear of an internal combustion engine is known from EP 0 833 041 A1. The apparatus has an electromagnet which is mounted in the cylinder head of the internal combustion engine and whose armature can assume two end positions. The armature actuates a locking element which acts on the pivot lever. In order to actuate the locking element, the electromagnet must be continuously energized, resulting in an unnecessarily high consumption of electrical energy.

It is the object of the present invention to provide a method and an apparatus for coupling and decoupling two actuating elements of a valve drive of an internal combustion engine which operates with a high level of reliability and consumes a significantly reduced amount of electrical energy.

SUMMARY OF THE INVENTION

In a method and apparatus for coupling or decoupling two actuating elements of a valve drive of an internal combustion engine for operating a gas exchange valve, comprising a locking element movable between two end positions for coupling the actuating elements, an electromagnet for actuating the movable locking element, a permanent magnet is associated with the armature for holding the armature and the locking element in one end position and means for biasing the armature and the locking element in the opposite end position, the electromagnet is energizable in one sense for moving the armature into one end position in which the armature is retained by the permanent magnet with a force greater than a counteracting force generated by the biasing means, and in the opposite sense so as to generate a force exceeding that of the permanent magnet for moving the armature in the opposite end position, where it is retained by said biasing means.

A significant advantage of the invention is provided by the permanent magnetic force additionally acting on the armature. As a result of this, after the energization by the armature is discontinued the armature retains at least one of its positions in which it is held by the permanent magnet or, respectively, the spring. As a result the electromagnet does not have to be continuously energized but needs to be energized only shortly for moving the armature from one end position to the other.

The armature advantageously leaves its retained position as a result of renewed energization of the electromagnet with reversed polarization, which requires only a short current pulse.

A further advantage results from the fact that the permanent magnetic force can be applied by the armature which has been magnetized by the previous energization. This provides an apparatus of simple design for coupling and decoupling two actuating elements of a valve drive of an internal combustion engine with low power consumption.

The permanent magnetic force is advantageously applied by a permanent magnet which is arranged in the magnetic circuit, in particular in the armature, which ensures a stable state in one position over an extended time period.

The apparatus also includes a restoring spring for acting on the armature, which restoring spring is capable of moving the armature without using electrical energy.

In one end position of the armature the permanent magnetic force is advantageously greater than the force of the restoring spring, which ensures a stable position of the armature, and, in the other end position, the permanent magnetic force is smaller than the force of the restoring spring, so that the armature is firmly held in the other end position by the spring.

The invention will become more readily apparent from the following description of an exemplary embodiment with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partial sectional view of an apparatus which has an element for coupling two actuating elements of a valve drive of an internal combustion engine which act optionally on a gas exchange valve, wherein an electromagnet interacts with an armature,

FIG. 2 is a sectional view of the apparatus, wherein the armature is in a first end position, and

FIG. 3 is a sectional view of the apparatus, wherein the armature is in a second end position.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

The invention resides in an apparatus for coupling and decoupling two actuating elements 2, 3 of a valve drive of an internal combustion engine which actuating elements act optionally on a gas exchange valve 1, wherein camshaft adjusters, camshafts, equalizing elements, supporting elements or cam followers, for example actuating levers or bucket tappets, can be provided as actuating elements 2, 3. An apparatus according to the invention with switchable actuating levers 2, 3 is disclosed in the following figures.

FIG. 1 shows parts of the valve gear for actuating the at least one gas exchange valve 1 of the internal combustion engine having an inner lever 2 and an outer lever 3. The inner lever 2 is mounted so as to be pivotable with its first end about a shaft 4, with the shaft 4 being supported on the outer lever 3 and, when locked, is supported with its second end on an element 5 of the apparatus for coupling the inner lever 2 and outer lever 3. In the case of unlocking, the inner lever 2 acts on an idle travel spring 14.

The outer lever 3 has for example two arms 7 which are provided, for example, with cam surfaces 6 on which at least one cam 18 with a small stroke can act. The arms 7 of the outer lever 3 surround the inner lever 2 which can be actuated by at least one cam 17 with a large stroke. The outer lever 3 is supported at one end at least indirectly on a component 8 of the internal combustion engine, it being possible for the component 8 to be a valve play-adjusting element, a housing part of the internal combustion engine or a bearing point. At the other end it acts on the gas exchange valve 1.

The system is therefore comprised of two levers, that is, the outer lever 3, which is supported in the present case on the hydraulic valve play-adjusting element 8 and acts on the valve stem la of the gas exchange valve 1 which is to be actuated, and the inner lever 2 which is mounted on the outer lever 3.

In order to be able to actuate the gas exchange valve 1 alternatively also by means of the inner lever 2 or only by means of the outer lever 3 and thus to bring about different valve strokes, the element 5 is provided. The element 5 can be acted on by an electromagnet 9 in a locking direction 12 and an unlocking direction 13, said electromagnet 9 being composed of a coil 9a, a yoke 9b and an armature 10. The armature 10 is operatively connected to the element 5, i.e. in the present exemplary embodiment the armature 10 is connected to the element 5. A spring element 11 additionally acts on the element 5 in the locking direction 12. As a result, the element 5 can be pushed in the locking direction 12 by the spring element 11 and/or the armature 10 of the electromagnet 9, and can be pushed in the unlocking direction 13 by the armature 10 which acts as a restoring element.

In order to provide an apparatus for coupling and decoupling two actuating elements of a valve gear of an internal combustion engine which operates with a high level of operational reliability and significantly reduced electrical energy consumption, the invention proposes that the apparatus have a permanent magnetic device 15 for acting on the armature 10. In the present example, the permanent magnetic device 15 is a component of the armature 10, which is otherwise fabricated from nonpermanent magnetic material, or the permanent magnetic force is applied by the armature 10 which has been magnetized by preceding energization.

FIG. 2 shows the element 5 of the apparatus in the locked position. The electromagnet 9 is switched to a deenergized setting, as a result of which the spring element 11 pushes the armature 10 at least partially out of the electromagnet 9 in the locking direction 12 until the element 5 bears against a stop 16 which is preferably provided on the outer lever 3. This position is stable without energization of the electromagnet 9 since the force of the spring element 11 is higher than the effect of the permanent magnetic device 15 which is reduced owing to the large distance between the armature 10 and the yoke 9b. As a result, the inner lever 2 is connected in a positively locking fashion to the outer lever 3, i.e. the cam 17 generating a large stroke acts via the inner lever 2 on the outer lever 3 which then actuates the gas exchange valve 1, while the cam 18 generating the small stroke operates in idle.

FIG. 3 shows the element 5 of the apparatus in the unlocked position. In order to unlock the actuating elements 2, 3, the electromagnet 9 is briefly energized, so that the armature 10 is pulled into a recess 19 which is formed by the yoke 9b. As a result, the element 5 which is connected to the armature 10 is pulled away from under the inner lever 2 by said armature against the force of the spring element 11. As a result, the inner lever 2 is deactivated, i.e. the cam 18 with a small stroke acts on the outer lever 3 which then actuates the gas exchange valve 1, with the inner lever 2, on which the cam 17 with a large stroke acts, merely carrying out an oscillating idle movement on the outer lever 3.

As already mentioned above, the armature 10 is pulled into the recess 19 by brief energization of the electromagnet 9. Because of the small distance between the armature 10 and the recess 19, the effect of the permanent magnetic device 15 is greater than the force of the spring element 11, for which reason the armature 10 also remains in this position without energization of the electromagnet 9, which results in significantly reduced consumption of electrical energy.

In order to bring about the locked position illustrated in FIG. 2, the electromagnet 9 is briefly energized with reversed polarity.

Claims

1. A method for coupling or decoupling two actuating elements (2, 3) of a valve drive of an internal combustion engine for operating a gas exchange valve (1), comprising a locking element (5) movable between two end positions for coupling the actuating elements (2, 3), an electromagnet (9) for actuating the movable locking element (5) and including a coil (9a) and a yoke (9b) interacting with an armature (10) which is operatively connected to the locking element (5), a permanent magnet (15) associated with the armature (10) for holding the armature (10) and the locking element (5) in one end position and means (11) for biasing the armature (10) and the locking element in the opposite end position, said method comprising the steps of: energizing the coil (9a) in one sense for moving the armature into one end position in which the armature is retained by said permanent magnet with a force greater than a counteracting force generated by the biasing means (11), and energizing the coil (9a) in the opposite sense for generating a force exceeding that of the permanent magnet (15) for moving the armature (10) in the opposite end position, where it is retained by said biasing means (11).

2. A method as claimed in claim 1, wherein, after the energization by the permanent magnetic effect has been switched off, the armature (10) retains at least one of its positions assumed as a result of preceding energization of the electro-magnet (9).

3. A method as claimed in claim 1, wherein the armature comprises a permanently magneticeable material and the armature is permanently magnetized in one sense by energization of the electromagnet (9).

4. An apparatus for coupling or decoupling two actuating elements (2, 3) of a valve drive of an internal combustion engine for optionally operating a gas exchange valve (1), comprising a locking element (5) movable two end positions for coupling the actuating elements (2, 3), an electromagnet (9) for actuating the movable locking element (5) and including a coil (9a) and a yoke (9b) interacting with an armature (10) which is part of the locking element (5), a permanent magnet (15) associated with the armature (10) for holding the armature (10) and the locking element (5) in one end position and means (11) for biasing the armature (10) and the locking element in the opposite end position, said coil (9a) when energized in one sense moving the armature into one end position in which the armature is retained by said permanent magnet (15) with a force greater than a counteracting force generated by the biasing means (11), and the coil (9a) when energized in the opposite sense generating a force exceeding that of the permanent magnet for moving the armature in the opposite end position, where it is retained by said biasing means (11).

5. The apparatus as claimed in claim 4, wherein the means (11) for biasing the armature (10) in the opposite end position is a spring element (11).

6. The apparatus as claimed in claim 4, wherein, the permanent magnetic force is generated by a permanent magnetic device (15) attached to the armature (10).

7. The apparatus as claimed in claim 4, wherein the permanent magnetic force is generated by the armature (10) being permanently magnetized.

8. The apparatus as claimed in claim 4, wherein the actuating elements comprise one of a camshaft adjuster, a supporting element, an equalizing element, a cam follower and a camshaft.