Electricity: measuring and testing – Magnetic – Displacement
Reexamination Certificate
2001-01-26
2002-10-22
Strecker, Gerard R. (Department: 2862)
Electricity: measuring and testing
Magnetic
Displacement
C324S163000, C324S207180, C324S207190, C123S090110, C251S129160, C335S258000
Reexamination Certificate
active
06469500
ABSTRACT:
BACKGROUND OF THE INVENTION
In control elements that can move back and forth between two switching positions, particularly fast-moving control elements, it is often necessary to determine the respective instantaneous speed and the respective instantaneous position of the switching element relative to the respective switching position in connection with a regulation and/or control during the movement of the control element. This is especially the case for determining the speed and position as the control element approaches the respective switching position.
Determining the speed and position is particularly significant in a control element that is connected to an armature that is moved back and forth, counter to the force of restoring springs, with the aid of an electromagnet or two spaced electromagnets. Because the force of the restoring springs that counteracts the movement increases linearly as the electromagnet approaches the respective switching position defined by the pole face of the electromagnet, the magnetic force increases progressively as the distance between the pole face and armature diminishes, and the armature moves with increasing speed toward the pole face with a constant current supply. As a result, the armature may not be held by the capturing electromagnet as it impacts the pole face, but may bounce backward. Depending on the magnitude of the impact speed, the armature can bounce completely away, so it is not held at all by the capturing electromagnet, or the armature bounces a short distance backward one or more times, but is always recaptured by the electromagnet. In both cases, however, it is no longer ensured that the system actuated by the control element will function properly. An example of a system embodied in this manner is a cylinder valve in a piston-type internal-combustion engine; the valve is connected to the armature, and can be opened and closed by way of two spaced electromagnets that are alternately supplied with current by a control device. A corresponding control of the current supply of the capturing electromagnet permits a reduction in the current at the capturing electromagnet as the armature approaches the pole face such that the respective effective magnetic force is slightly greater than the restoring force of the associated restoring spring, so the armature impacts the pole face “gently” with a speed of, for example, less than 0.1 m/sec.
To influence the control force acting on the control element such that the respective switching position is attained at a predeterminable speed, it is necessary to determine the speed curve using the control characteristic, on the one hand and, on the other hand, to determine the respective position of the control element, i.e., the control characteristic as a function of time, in order to influence the armature speed by changing the current supply. The use of two sensors, one of which determines the speed of the control element, while the other determines the course of the path as a function of time, offers an economical industrial application.
In the use of a path sensor, it is possible in principle to generate the speed signal from the path signal through differentiation. This is highly problematic, however, because the path signal includes noise components that cover the useful signal in the differentiation.
SUMMARY OF THE INVENTION
It is the object of the invention to provide a method that permits the determination of the speed and the path, as a function of time—referred to hereinafter as position —for a control element that can move back and forth, with only one sensor element.
In accordance with the invention, this object is accomplished by a method for determining the speed of movement and/or the position of a control element that can move back and forth between a first and a second switching position, in which an immersion or plunger body that is connected to the control element is guided synchronously with the movement of the control element by at least one stationary plunger coil, with the voltage that is generated due to a movement of the immersion body relative to a permanent magnet, and/or the movement of a permanent magnet relative to the plunger coil, being determined as a signal for the movement speed of the control element, and with changes in the impedance and/or a current that are caused by the movement of the immersion body in the plunger coil being determined as a signal for the position of the control element. This method capitalizes on the fact that, with a corresponding relative movement of the permanent magnet in the plunger coil, a voltage is induced that is a function of the rate of change of the magnetic flux, and thus of the movement speed. This voltage, or the course of the voltage, can be determined as a function of time, so a certain speed can be associated with each voltage value at a given time.
Because a separate immersion or plunger body is also moved synchronously with the movement of the control element in the plunger coil in addition to the permanent magnet, the effected changes in impedance, i.e., the changes in the impedance of the plunger coil, can be used to determine the respective position of the control element at any time. This is because the change depends on how far the immersion body dips into the plunger coil. The type of change depends on the electrical and/or magnetic properties of the immersion body. If the immersion body has a magnetic conductivity that is much greater than
1
, the inductance changes, that is, a current flowing in the plunger coil changes its course as a function of time and the immersion depth. If the immersion or plunger body has a good electrical conductivity, the losses due to eddy-current effects in the plunger body change, which corresponds to an increase in the resistive component of the impedance. It is also possible, however, to determine the speed and position simultaneously using only one coil and the effect of the permanent magnet and the immersion body, without intermediate calculation steps.
Two possible procedures exist for determining the position. In a first embodiment of the invention, it is provided that the plunger coil is acted upon with a high-frequency alternating current, and the change in the current flow that is effected by eddy-current losses due to the movement of the immersion body in the plunger coil, the body at least partially comprising an electrically-conductive material, is determined as a signal for the position of the control element. The method capitalizes on the phenomenon of the generation of a magnetic alternating field when the coil is acted upon by an AC voltage, thereby effecting a current flow in the form of an eddy current in the electrically-conductive immersion body, which acts as a secondary winding. This current flow changes as a function of the immersion depth, that is, the position of the immersion body relative to the plunger coil. The properties of the coil, especially the AC behavior, also change, however, depending on the position of the immersion body. The position of the immersion body, and thus the position of the control element connected to the immersion body, can be ascertained through the determination of the impedance, or a value derived therefrom, such as the voltage, current or associated phase. The immersion body can be embodied as a separate element, or be formed by the control element itself. If the control element is produced from an electrically non-conductive material for some other reason, the immersion body comprising a conductive material is directly connected to the permanent magnet. In this instance, the electrically-conductive material of the immersion body should possess a relatively-low magnetic conductivity &mgr; in order not to short-circuit the magnetic field of the permanent magnet. If the permanent magnet and the immersion body are disposed one behind the other in the direction of movement of the control element, the electrically-conductive material of the immersion body, as an “extension” of the magnet in one direction, can even have a p
Boie Christian
Schmitz Günter
FEV Motorentechnik GmbH
Kunitz Norman N.
Strecker Gerard R.
Venable
LandOfFree
Method for determining the position and/or speed of motion... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for determining the position and/or speed of motion..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for determining the position and/or speed of motion... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2996432