Field of the Invention
The invention relate""s to an electromechanical actuator, in particular an actuator for a gas exchange valve of an internal-combustion engine.
A prior art electromechanical actuator, described in U.S. Pat. No. 6,078,235 and German utility model DE 297 12 502 U1, has two electromagnets and an armature which is mechanically coupled to two springs. The armature can move between a first bearing surface on the first electromagnet and a second bearing surface on the second electromagnet. The housing is formed with recesses for accommodating the electromagnets. For an internal-combustion engine whose gas exchange valves are driven by an electromechanical actuator of this type to operate reliably and securely, it must be ensured that the armature can move very quickly from one bearing surface to the other bearing surface and back. Only in this way is it possible to ensure that the gas exchange valves of the internal-combustion engine open and close quickly and precisely.
It is accordingly an object of the invention to provide an electromechanical actuating drive, which overcomes the above-mentioned disadvantages of the heretofore-known devices and methods of this general type and which makes it possible for gas exchange valves of an internal-combustion engine to open and close rapidly while, at the same time, keeping the energy consumption required for the actuation as low as possible.
With the foregoing and other objects in view there is provided, in accordance with the invention, an electromechanical actuator, comprising:
at least one electromagnet;
an armature having a shank formed with a cavity and movably disposed between the first bearing surface on the electromagnet and a second bearing surface;
at least one restoring device mechanically coupled to the armature; and
a transmitter of a sensor disposed in the cavity in the shank.
The actuator is particularly suitable in combination with a gas exchange valve of an internal-combustion engine, where the actuator is mechanically coupled to a valve stem of the gas exchange valve.
In accordance with an added feature of the invention, the shank is a hollow tubular shaft. In an alternative embodiment, the shank is formed with a blind bore in which the transmitter is disposed.
In accordance with an additional feature of the invention, the transmitter is a permanent magnet.
In accordance with another feature of the invention, the sensor is a position sensor.
In accordance with again another feature of the invention, the transmitter is introduced into the cavity at a free end of the shank, and the shank is flanged at the free end.
In accordance with a further feature of the invention, the armature includes an armature plate formed of a cobalt-iron alloy.
In accordance with a concomitant feature of the invention, the electromagnet has a core formed of a cobalt-iron alloy.
The invention is distinguished by the fact that the shank of the armature, which is designed as a hollow body, has a significantly lower mass than a solid shank. Consequently, the armature mass which has to be moved is reduced, and therefore only small actuating forces have to be applied to move the armature plate from one armature face to the other.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in an electromechanical actuator, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.