DE102005029368B4 - Method and device for determining the orientation of a rotating component with respect to a normal vector of a reference plane - Google Patents

Abstract

Method for determining the orientation of a rotating component, in particular of the rotor (5) of an electric motor, with respect to a normal vector (11) of a reference plane, characterized
in that a measuring device is used with at least three non-contact measuring sensors (6a, 6b, 6c) which are arranged at a specific distance parallel to the normal vector and distributed on a (measuring) circuit, wherein the measuring axes of the measuring sensors (6a, 6b, 6c) run parallel to the normal vector and the axis of rotation (4) of the rotor (5) is largely in the center of the circle,
in that first a calibration of the measuring sensors (6a, 6b, 6c) is carried out with respect to a reference plane,
that the rotating component is clamped in the measuring device and set in rotation,
in that the distance between the measuring sensors (6a, 6b, 6c) and a surface (9) of the rotating component (5) to be measured is measured over at least one revolution, whereby several measured values are recorded per revolution by each measuring sensor,
that from the measured values the alignment ...

Description

Field of the invention

The The invention relates to a method and a device for detection the orientation of a rotating component, in particular of the rotor an electric motor, with respect to a normal vector of a reference plane according to the characteristics the generic term of the independent Claims.

State of the art

electric motors For example, in hard disk drives to drive the magnetic storage disks used on the means of a read / write head data in the form written and read out from magnetized areas can. For this purpose, the magnetic storage disks on the rotor of the spindle motor fixed, wherein the driven by an electromagnetic rotating field Rotor is rotatably supported by a bearing system. As storage systems are preferably rolling bearings or fluid bearing used. Due to unavoidable component and mounting tolerances, there are more or less large temporal changes the axis of rotation of the motor, so that the normal vector in the fulcrum the rotor surface not a constant, but a temporally and rotation angle dependent changing Result. This can lead to errors in reading and writing the Data on the magnetic disk and in the worst case collision of the Guide the read / write head to the magnetic disk.

The parallelism the largely flat surface the rotor or the rotor hub or the bearing surface of the magnetic storage disks with respect to a reference plane or the parallelism of the actual Rotary axis of the motor to a reference axis is an important quality feature a spindle motor. The one of the deviations of the actual Rotation axis originating Blow of the rotor is in practice by the size of the repeatable Schlag's RRO (Repeatable Runout) defined, whereby between RRO axial (Frontal strike) and RRO radial (radial impact) is distinguished. The repeatable blow RRO is a measure of the deviation of the actual Rotation axis due to eccentricity and tilting as well the surface defects or shape deviations caused by manufacturing processes. The repeatable RRO punch is found in today's hard disk drive spindle motors in the order of magnitude of up to several 10 μm.

The parallelism can be detected with the help of an appropriate measuring device. For this purpose, the spindle motor is clamped in a measuring station. By several touching ones Measuring sensors will measure the motor level. The disadvantage here is that only static measurements can be carried out since the touching ones Measuring sensors during operation of the engine could damage its surfaces. Further becomes repeatable beat, the Repeatable Runout (RRO), not included. In particular with fluid-bearing motors, such a static measuring arrangement not usable, since the rotor of the engine only in operation its assumed position and orientation assumes.

The US 4,800,652 A discloses an apparatus for measuring substantially circular objects. In this case, touching probes are used, which are directed radially on the peripheral surface of the object and these measure while the object is rotated about an axis of rotation.

The DE 103 16 940 A9 shows a measuring method on an electric motor for determining the lift height and / or the axial clearance of the rotor. In this case, a distance sensor is used, which measures the axial position of the rotor.

The DE 102 15 252 A1 and DE 103 02 531 A1 disclosed methods and apparatus for measuring the radial impact of an electric motor. For this purpose, non-contact sensors are used, which are directed perpendicular to the axis of rotation of the rotor on its peripheral surface and detect the radial deviations occurring during the rotation of the rotor.

Subject of the invention

The The object of the invention is a method and a device for determining the orientation of a rotating component in relation to indicate a normal vector of a reference plane that has a non-contact measurement while allows the rotation of the component and the repeatable stroke considered.

These The object is achieved by the Characteristics of the independent Claims solved.

preferred Embodiments and advantageous features of the invention are in the dependent claims specified.

For the inventive method, a measuring device with at least three non-contact measuring sensors is used, which are arranged at a certain distance parallel to the normal vector and distributed on a (measuring) circle, the axis of rotation of the motor is largely in the circle center and initially a calibration of the measuring sensors in with respect to a reference plane is carried out, then the rotating component is clamped in the measuring device and rotated, subsequently measured over at least one revolution, the distance between the measuring sensors and the surface to be measured of the rotating component, wherein per revolution of each measuring sensor a plurality of measured values are detected, and Finally, the alignment of the rotating component with respect to the reference plane is determined from the measured values.

The Invention has the advantage that, for example, in motors contactless and thus material-saving measurement of parallelism during the Operation of the motors are performed can. The measuring method leaves to perform automatically and achieves results with high accuracy.

Brief description of the drawings

following is an embodiment of Invention explained in more detail with reference to the drawing figures.

1 schematically shows a fluid-bearing rotor of an electric motor, as used for example for driving hard disk drives;

2 is a flowchart of the essential steps of the method;

3 shows a schematic representation of the measuring arrangement.

Description of a preferred embodiment the invention

1 schematically shows a fluid-bearing rotor of an electric motor, as used for example for driving hard disk drives. The storage system comprises a bearing bush 1 in which a wave 2 by means of a fluid 3 around a rotation axis 4 is rotatably mounted. The wave 2 is with a rotor 5 connected, which carries parts of an electromagnetic drive system and, for example, magnetic storage disks (not shown). In such a fluid-bearing motor, the bearing has fallen down in the rest position and floats during operation of the engine due to the fluid dynamic pressure in the fluid 3 something on.

The resulting change in position of the rotor 5 is in the micrometer range. Due to an oblique axis of rotation 4 and an obliquely mounted rotor 5 the (ball-bearing or fluid-bearing) motor performs a slight rotary motion. Because of this gyroscopic effect, the engine has a so-called first-order impact. If you measured in the rest position of the engine, so would the surface of the rotor 5 , depending on the rotational position, span another plane.

How to especially the 3 can be found to carry out the measurement method according to the invention, three non-contact distance sensors 6a . 6b . 6c used, for example, commercial capacitive or optical measuring sensors. As optical sensors z. As the most diverse types of optical-interferential sensors possible, often, but not necessarily use laser. The sensors 6a . 6b . 6c are each an angle 8th , preferably by α = β = γ = 120 °, offset from one another.

First, a reference measurement with the three measuring sensors 6a . 6b . 6c performed on a reference component (master). This master (not shown) is immovable. This calibration of the sensors is performed on a so-called zero position or reference plane. This reference measurement is only necessary once for absolutely measuring position sensors.

Subsequently, an electric motor to be measured is clamped in the measuring device. The engine is put into operation and the removal of the three sensors 6a . 6b . 6c to the measuring surface 9 of the rotor 5 of the fluid-bearing electric motor during operation measured without contact.

It will be numerous measuring points for at least one revolution of the motor determined and averaged. The averaged Values of all three sensors give three points or vectors, the define a plane relative to the master plane.

With reference to the 2 and 3 the measuring procedure is explained in detail:
The measurement of the parallelism of the rotor of the electric motor is preferably carried out with three non-contact sensors 6a . 6b . 6c , each at an angle α, β, γ of preferably 120 ° to each other in a defined measuring radius r about the axis of rotation 4 are arranged. Depending on the measurement requirement, additional probes can be used by means of which z. B. the wave or pivot height can be measured.

Measurement of the setting master (reference component):

All measured values are related to a setting master. This is, for example, a precisely manufactured aluminum or steel part whose shape and dimensions correspond to those of the motor to be measured. The setting master is first measured on a 3D measuring machine. It will be at the same x- and y-coordina In which later also the engine is measured, the height measured. This results in the following five measured values:

MasterHeightA: Master height at the xy position of the sensor A
MasterHeightB: Master height at the xy position of the sensor B
MasterHeightC: Master height at the xy position of the sensor C

MasterHeight1: Master height at the xy position of the touching probe 1
MasterHeight2: Master height at the xy position of the touching probe 2

The determined values entered into the test program and stored in a configuration file become.

Next, the setting master in the test apparatus is measured, corresponding to the method step 20 in 2 , The measurement itself corresponds to the measurement of a motor, with the exception that the master has no rotatable rotor. As the measuring range of non-contact sensors 6a . 6b . 6c For example, less than 100 microns, these are also using adjusting devices 7a . 7b . 7c , For example, of stepper motors, towards the measuring surface 9 adjustable. Before each measurement, the stepper motors move the sensors to the required distance to the measuring object (master or motor). After the measurement, the sensors are moved far away from the measurement object. This prevents the possibility of collisions with the sensors for motors whose height does not comply with the specifications. The infeed height of the sensors is measured, for example, with glass scales. The following values are obtained during the measurement:

ZeroA reading of glass scale sensor A
ZeroB reading of glass scale sensor B
ZeroC reading of glass scale sensor C

OffsetA reading from sensor A
OffsetB measured value of sensor B
OffsetC measured value of sensor C

ProbeZero1 Measured value of the probe 1
ProbeZero2 Measured value of the probe 2

Since the sensors and glass scales each form a unit, their values must be offset against one another in order to obtain the actual measured value RefA, RefB, RefC of the distance between the individual sensor and the reference surface:

RefA = ZeroA - OffsetA
RefB = ZeroB - OffsetB
RefC = ZeroC - OffsetC

The determined values are also stored in a reference value file.

Measurement of the engine (test specimen):

• – ScaleA
• – ScaleB
• – ScaleC

When measuring an engine, the sensors are located 6a . 6b . 6c initially far away from the engine. After switching on the engine, 2 , Step 21 , the distance of the sensors 6a . 6b . 6c with the help of stepper motors 7a . 7b . 7c reduced until the sensors at the optimum measuring distance to the measuring surface 9 lie. After setting the sensor distances and the standstill of the stepper motors, the three glass scales have the following values to be tapped:

• - ScaleA
• - ScaleB
• - ScaleC

The two touching probes provide the following measured values:

ProbeValue1
ProbeValue2

Subsequently, according to the process steps 22 . 23 . 24 over a certain number of engine revolutions, for example n revolutions, data: sample A (i), sample B (i), sample C (i) with i = 1, ..., nm, in the form of a number of m readings per revolution of the individual Sensors detected. Per sensor and revolution of the engine will be at the measuring points 10 For example, m = 128 measured values recorded. Here, the engine speed and the sampling rate, ie the time between the recordings of the individual measured values, during the measurement are largely constant, so that the measured values are comparable. Furthermore, the sampling rate is preferably determined by the product of the engine speed and the number m of measurements per revolution to compensate for the repeatable beat.

The recorded measured values are determined according to the process steps 25 . 26 . 27 calculated for each of the three sensors the arithmetic mean of the measured values:

With the available data, the actual motor height, ie the position of the measurement surface, can now be determined at the xy coordinates of the three non-contact sensors: SetDimA = MasterHeightA + ScaleA - MeanProbeA - RefA SetDimB = MasterHeightB + ScaleB - MeanProbeB - RefB SetDimC = MasterHighC + ScaleC - MeanProbeC - RefC

The actual height at the positions of the probes is calculated as follows: ProbeResult1 = MasterHeight1 + ProbeValue1 - ProbeZero1 ProbeResult2 = MasterHeight2 + ProbeValue2 - ProbeZero2

Since the three sensors evenly around the axis of rotation 4 distributed, the projected engine height at the center corresponds to the average of the three individual values:

The parallelism is calculated by the angle between the plane of the measurement surface 9 and the reference plane is located. For this the normal vectors are necessary for both planes.

The Measuring level is given by the three measuring points. Leave the x and y coordinates of the points over the measuring radius r, ie the distance radius of the sensor from the axis of rotation of the engine, and determine the angle of the relevant sensor, the z-coordinate corresponds to the calculated measured value SetDimA, SetDimB or SetDimC. Since the reference plane corresponds to the xy plane and the normal vector always perpendicular to a plane, the normal vector shows the reference plane exactly in the z-direction.

Calculation of the normal vector 11 for the measuring level takes place in the process step 28 : nMeas → = (BMeas - AMeas) × (CMeas - AMeas) With:

The normal vector for the reference plane corresponds to:

The angle between the two normal vectors corresponds to:

The measure of the parallelism of the measuring plane with respect to the reference plane results in: Parallelism = 2 · measuring radius · sinφ = 2 · r · sinφ

1

bearing bush

2

wave

3

bearing fluid

4

axis of rotation

5

rotor

6

Measuring sensors ( 6a . 6b . 6c )

7

Adjusting devices ( 7a . 7b . 7c )

8th

angle

9

measuring surface

10

measuring point

11

normal vector (Reference)

20-28

steps

α, β, γ

angle

r

MeasRad: Radius of the measuring circle

n

number of turns, while which is measured

m

number the measured values per revolution

Claims (13)

Method for determining the orientation of a rotating component, in particular of the rotor ( 5 ) of an electric motor, with respect to a normal vector ( 11 ) of a reference plane, characterized in that a measuring device with at least three non-contact measuring sensors ( 6a . 6b . 6c ), which are arranged at a certain distance parallel to the normal vector and distributed on a (measuring) circuit, wherein the measuring axes of the measuring sensors ( 6a . 6b . 6c ) parallel to the normal vector and the axis of rotation ( 4 ) of the rotor ( 5 ) is largely in the center of the circle that initially a calibration of the measuring sensors ( 6a . 6b . 6c ) is carried out with respect to a reference plane, that the rotating component is clamped in the measuring device and set in rotation, that over at least one revolution of the distance between the measuring sensors ( 6a . 6b . 6c ) and a surface to be measured ( 9 ) of the rotating component ( 5 ), wherein per revolution each measuring sensor detects a plurality of measured values, that the orientation of the rotating component relative to the reference plane is determined from the measured values. Method according to claim 1, characterized in that that the center of the measuring circuit is the pivot point of the motor. Method according to claim 1 or 2, characterized that while the measurement of the engine speed and the sampling rate are largely constant. Method according to Claim 3, characterized in that the sampling rate of each of the measuring sensors ( 6a . 6b . 6c ) is determined by the product of the engine speed and the number m of measured values per revolution. Method according to one of claims 1 to 4, characterized in that from the measured values of each sensor ( 6a . 6b . 6c ) the arithmetic mean is calculated, from the mean values of all sensors three points or vectors are calculated which define a plane relative to the reference plane. Method according to one of claims 1 to 5, characterized that parallelism calculated between the measuring plane and the reference plane via an angle which lies between the measuring plane and the reference plane, where for both levels the normal vectors are determined. Method according to one of claims 1 to 6, characterized that extra Are used by means of which the wave and / or the pivot height of the measurement object is measured. Method according to one of claims 1 to 7, characterized in that each measuring sensor ( 6a . 6b . 6c ) by means of an adjusting device ( 7a . 7b . 7c ) separately in the direction of the surface to be measured ( 9 ) is adjustable. Device for carrying out the method according to claims 1 to 8, characterized by a clamping device for clamping the rotating component to be measured ( 5 ); at least three non-contact measuring sensors ( 6a . 6b . 6c ), which are at a certain distance parallel to the normal vector ( 11 ) and distributed on a (measuring) circuit are arranged, a linear adjustment device ( 7a . 7b . 7c ) for each measuring sensor by means of each measuring sensor separately in the direction of the surface to be measured ( 9 ) of the rotatable component ( 5 ), an evaluation unit, designed to record measured values of the distance between the measuring sensors ( 6a . 6b . 6c ) and the surface to be measured ( 9 ) of the rotating component over at least one revolution of the rotating component, wherein per each revolution of each measuring sensor a plurality of measured values are detected, and for determining the orientation of the rotating component with respect to the reference plane on the basis of the measured values. Device according to claim 9, characterized in that that the center of the measuring circuit is the pivot point of the motor. Device according to claim 9, characterized in that the sensors ( 6a . 6b . 6c ) are capacitive or optical sensors. Device according to one of claims 9 to 11, characterized in that the measuring distance between the sensors ( 6a . 6b . 6c ) and the surface to be measured ( 9 ) is less than a few 100 microns. Device according to one of claims 9 to 12, characterized in that three measuring sensors ( 6a . 6b . 6c ) used uniformly at a mutual angle of 120 ° along the Measuring circuit are aligned.