This application is a continuation of International Patent Application No. PCT/EP2003/08740, filed Aug. 7, 2003, the entire disclosure of which is incorporated herein by reference. Priority is claimed based on German Patent Application No. 102 51 664.2, filed Nov. 6, 2002.

This invention relates to a device for measuring the lift or displacement of a poppet valve (also known as a â€œlift valveâ€ ) lift valve, and in particular a valve of an internal combustion engine.

A device is known from German patent document DE 37 03 867 A1 where a sleeve, preferably made of a magnetic material, is glued into the groove in the valve shaft for measuring the valve lift movement. The groove and the sleeve are coordinated so that the sleeve sits flush in the valve shaft, i.e., does not protrude radially. Bending vibrations of the valve shaft may then occur under extremely high loads.

The object of this invention is to improve upon the above type of device such that it will provide reliable information regarding the actual axial movement of the valve even under extreme loads.

This object is achieved according to this invention by a coil and a stationary mount and a metal sleeve arranged in flush alignment in a groove in the valve shaft so that it is axially moveable in the coil, wherein the sleeve is secured with axial play within the groove. This approach has the advantage that it largely prevents mechanical deformation of the sleeve due to axially protruding parts of the valve shaft. Magnetostriction effects such as those that can occur with a sleeve made of a magnetic material are thus largely ruled out, as are negative effects of the eddy current properties, such as those which occur with a nonmagnetic metallic sleeve exposed to an alternating field.

Advantageous refinements of this invention include design of axial play to ensure the sleeve is not in contact with the shaft under all operating conditions, through which any negative effects of the magnetic and/or electric properties of the sleeve that still occur under very extreme conditions are completely prevented.

A further refinement is the possibility of reducing the axial play between the sleeve and the shaft through a local change in the rectangular geometry in the potential contact zone and thereby optimizing the stability of the shaft.

Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-section view of a lift measuring device in accordance with an embodiment of the present invention.

DETAILED DESCRIPTION

The single figure shows a detail from a cylinder head 1 of a reciprocating piston of an internal combustion engine with a gas flow control channel 2 and a poppet valve 3. The poppet valve 3 is shown in a detail with its valve shaft 3â€². It is controlled in a known manner which is not of further interest here. To this end, it is equipped with valve springs (also not shown) and a valve spring plate (also not shown).

The valve shaft 3â€² has a groove 4 in which a sleeve 5 made of a magnetic material is secured.

The sleeve 5 runs in a stationary coil 6 which surrounds the sleeve 5 during the entire lifting movement and thereby induces an alternating voltage from which the position of the sleeve 5 and thus the position of the poppet valve 3 are determined in a known way.

The sleeve 5 is secured with an axial play within the groove 4. The play is designed to be axial and bilateral.

The play is designed to be such that the sleeve 5 is not in contact with the axially neighboring parts of the valve shaft 3â€² at all operating temperatures and under all operating stresses that occur.

In another embodiment of this invention, the sleeve and/or shaft may be drawn in along its outer circumference in the area adjacent to the opposing shaft and/or sleeve. The axial play can therefore be reduced in comparison with that in the embodiment shown in FIG. 1.

All embodiments have in common the fact that the sleeve 5 is not deformed mechanically by the axially neighboring parts of the valve shaft 3â€², with the advantage of positional information which is not distorted and which allows accurate information regarding the position of the poppet valve 3.

The foregoing disclosure has been set forth merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof.