Patent Description:
Test stands for test items having a rotatable test item shaft such as electric motors are known in the art.

Mounting the test item to the test stand and aligning the test item shaft with a shaft of the test stand typically requires considerable tooling time.

State of the art test stands and alignment devices are known from <CIT>, <CIT>, <CIT> and <CIT>.

It is an object of the present invention to provide a novel test stand for testing a test item having a rotatable test item shaft, and a novel method for testing a test item having a rotatable test item shaft.

The object is achieved by a test stand according to claim <NUM> and by a method according to claim <NUM>.

Preferred embodiments of the invention are given in the dependent claims.

According to the invention, a test stand for testing a test item having a rotatable test item shaft comprises:.

a control unit connected to the sensors and the actors and configured to calculate a position of the test item shaft based on the measurements of the sensors, to compare it to a set position and to control the actors to correct the position of the movable plate to reduce a difference between the calculated position and the set position.

In an exemplary embodiment, the drive motor is an electric motor.

In an exemplary embodiment, the drive motor is held in a motor support.

In an exemplary embodiment, the test stand further comprises a motor coupling for coupling an output shaft of the drive motor to the shaft. In other embodiments, the shaft may be the output shaft of the drive motor.

In an exemplary embodiment, the test stand may further comprise a ground plate to which the fixed plate and optionally the motor support holding the drive motor is/are fixed.

In an exemplary embodiment, the test stand further comprises one or more fixing units for releasably fixing the test item to the movable plate.

In an exemplary embodiment, the fixing units respectively comprise at least one of a screw, a hydraulic clamp and a zero point clamping system. A zero point clamping system allows for quickly clamping the device under test or workpiece with high accuracy.

In an exemplary embodiment, each actor comprises at least one of an eccentric engaging a contour in the fixed plate, a cylinder, a wedge and a drive. The drive may be a strain wave gear, e.g. configured to rotate the eccentric.

In an exemplary embodiment, the actor is configured to move the movable plate at least in one direction, wherein at least one spring is arranged to move the movable plate in an opposite direction or to support movement in the opposite direction. In other embodiments, movement in the opposite direction may be achieved or supported by gravity or with one or more additional actors.

In an exemplary embodiment, the tests stand further comprises one or more locking devices configured to releasably fix the movable plate to the fixed plate in position.

In an exemplary embodiment, the locking device comprises at least one of a hydraulic clamp, a pneumatic clamp, an electric clamp and a screw or a combination thereof.

In an exemplary embodiment, each sensor is respectively configured as an eddy current sensor, an optical sensor or a vibration sensor.

In an exemplary embodiment, the test stand further comprises a tubular sheath radially surrounding an end of the shaft and carrying the sensors, wherein the sheath is fixed to the fixed plate or to the bearing support or is a part thereof.

In an exemplary embodiment, the actors comprise a first actor and a second actor arranged in the movable plate on either side of the shaft, and a third actor arranged in the movable plate on one side of the shaft, wherein the first and second actor are configured to move the movable plate vertically, wherein the third actor is configured to move the movable plate horizontally.

In an exemplary embodiment, the actors are arranged in a respective opening in the movable plate and comprise an eccentric engaging a respective contour in the fixed plate.

According to an aspect of the present invention, a method for testing a test item having a rotatable test item shaft using a test stand as described above is provided, the method comprising: mounting the test item to the movable plate and coupling the test item shaft to the shaft, measuring the position of the test item shaft using the sensors, comparing the measured position to a set position and controlling the actors to correct the position of the movable plate to reduce a difference between the calculated position and the set position. If the sensors are vibration sensors, the position may be measured in an indirect way, as misalignments result in vibrations. The position of the movable plate may then be corrected to minimize the vibrations.

In an exemplary embodiment, the shaft is stationary or rotated by the drive during the measurement.

In an exemplary embodiment, the at least one locking device releases the movable plate for correcting the position thereof and locks the movable plate in place afterward.

In an exemplary embodiment, the process is repeated at other at least one different rotational speed of the shaft.

In an exemplary embodiment, the test item is an electric machine.

The solution according to the present invention allows for rapidly aligning a test item such as an electric motor to a shaft of a test stand. This may significantly reduce tooling time.

Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the scope of the invention, as defined by the appended claims, will become apparent to those skilled in the art from this detailed description.

The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus, are not limitative of the present invention, and wherein:.

<FIG> is a schematic view of an arrangement, comprising a test stand <NUM> and a test item <NUM>. <FIG> and <FIG> are schematic views of the test stand <NUM> without the test item <NUM>. <FIG> is another schematic view of the test stand <NUM> and the test item <NUM>.

The test stand <NUM> comprises a drive motor <NUM>, e.g. an electric motor, and a shaft <NUM> driven by the drive motor <NUM>, a rotational axis of the shaft <NUM> extending in an axial direction x. The shaft <NUM> is held by one, two or more bearings <NUM> in a bearing support <NUM>. The bearings <NUM> may be specified for rotational speeds of <NUM> rpm to <NUM> rpm, e.g. <NUM> rpm. The bearing support <NUM> is fixedly held in a fixed plate <NUM> or may be part of the fixed plate <NUM>. The drive motor <NUM> may be held in a motor support <NUM>. A motor coupling <NUM> may be provided to couple an output shaft <NUM> of the drive motor <NUM> to the shaft <NUM>. In other embodiments, the shaft <NUM> may be the output shaft <NUM> of the drive motor <NUM>.

The fixed plate <NUM> defines a surface extending in a first radial direction y and a second radial direction z, i.e. extending perpendicular to the axial direction x. The fixed plate <NUM> and the motor support <NUM> may be fixed on a ground plate <NUM>.

Moreover, the test stand <NUM> comprises a movable plate <NUM> defining a first surface bearing against the surface of the fixed plate <NUM>, and a second surface opposite the first surface configured for mounting the test item <NUM> thereon.

The test item <NUM> may be a device comprising a rotatable test item shaft <NUM> such as an electric machine. The movable plate <NUM> has a central opening <NUM> allowing the test item shaft <NUM> to pass through end engage the shaft <NUM>, e.g. using a test coupling <NUM>, also referred to as a drive tool <NUM> or adapter tool <NUM>. A drive tool <NUM> is a tool configured to connect the test item <NUM> to the test stand <NUM>. The central opening <NUM> may have an extended diameter toward the fixed plate <NUM> to accommodate the bearing support <NUM> which may protrude out of the fixed plate <NUM>.

The test item <NUM> may be fixed to the movable plate <NUM> using one or more fixing units <NUM>, e.g. screws, hydraulic clamps, a zero point clamping system or the like.

The movable plate <NUM> may be moved in the radial directions y, z relative to the fixed plate <NUM> to some extent in order to coaxially align the test item shaft <NUM> with the shaft <NUM>. In order to move the movable plate <NUM>, there may be one, two, three or more actors <NUM> to <NUM> provided. In an exemplary embodiment, each actor <NUM> to <NUM> may comprise at least one of an eccentric, a cylinder, a wedge and the like. The actors <NUM> to <NUM> may further comprise a respective drive, e.g. a harmonic drive or a servomotor, to rotate the eccentric. While an adjustment in one direction may be achieved using the drive, an adjustment in an opposite direction may be achieved or supported by a spring <NUM> or using gravity or by one or more additional actors.

Moreover, one or more locking devices <NUM> may be provided to releasably fix the movable plate <NUM> to the fixed plate <NUM> in position, so that movement of the movable plate <NUM> relative to the fixed plate <NUM> is inhibited. The locking devices <NUM> may respectively comprise at least one of a hydraulic clamp, a pneumatic clamp, an electric clamp or a screw.

Two or more sensors <NUM> to <NUM>, e.g. eddy current sensors or optical sensors, are arranged to measure the position of the shaft <NUM> and/or the test item shaft <NUM> with regard to the radial directions y, z once the test item <NUM> is mounted on the movable plate <NUM> and the locking device <NUM> has locked the movable plate <NUM> to the fixed plate <NUM>. The sensors <NUM> to <NUM> are configured to scan the shaft <NUM> or the test item shaft <NUM> or the test coupling <NUM>, drive tool <NUM> or adapter tool <NUM> radially. If the shaft <NUM> or test item shaft <NUM> is a splined shaft, it may be useful to adapt the adapter tool <NUM> and measure its position instead of the position of the shaft <NUM>. The adapter tool <NUM> may be part of the shaft <NUM>. The adapter tool <NUM> is flexible to a certain extent and can adapt to misalignments of the test item <NUM>. Measuring the position of the adapter tool <NUM> thus yields a centre variation of the test item <NUM>.

A control unit <NUM> may be connected to the sensors <NUM> to <NUM> to acquire their measurements and to the actors <NUM> to <NUM>, and optionally to the drive motor <NUM> and the locking devices <NUM> to control them.

A current position of the test item shaft <NUM> may be calculated in the control unit <NUM> from these measurements. Depending on the application, the measurement may be performed with the shaft <NUM> being stationary or rotating. The position of the test item shaft <NUM> determined is compared to a set position and the position of the movable plate <NUM> is corrected using the actors <NUM> to <NUM> to coaxially align the test item shaft <NUM> with the shaft <NUM>. The locking device <NUM> may have to be released to allow for correcting the position. Afterwards, the locking device <NUM> may lock the movable plate <NUM> in place to the fixed plate <NUM> again.

In another exemplary embodiment, the test item <NUM> is mounted to the movable plate <NUM> and the connection of the test item shaft <NUM> to the shaft <NUM> is made. The shaft <NUM> is then rotated using the drive motor <NUM>, thereby also rotating the test item shaft <NUM>. The sensors <NUM> to <NUM> may be configured as vibration sensors to detect a misalignment, similar to a wheel balancer machine. The position of the movable plate <NUM> is varied using the actors <NUM> to <NUM> until the result meets the requirements to coaxially align the test item shaft <NUM> with the shaft <NUM>. If necessary, the process may be repeated at other rotational speeds. The adjustment of the movable plate <NUM> may be carried out in an iterative way or it may be carried out continuously during the measurement at reduced rotational speed with the movable plate <NUM> only slightly clamped by the locking devices <NUM>. If the sensors <NUM> to <NUM> are vibration sensors, the position is measured in an indirect way, as misalignments result in vibrations. The position of the movable plate <NUM> is then corrected to minimize the vibrations.

An end of the shaft <NUM> facing the test item <NUM> may be located within a tubular sheath <NUM> which may serve for fixing the sensors <NUM> to <NUM>. The sheath <NUM> may be fixed to the fixed plate <NUM> or bearing support <NUM>. For example, a first sensor <NUM> may be arranged above the shaft <NUM>, a second sensor <NUM> may be arranged below the shaft <NUM> and a third sensor <NUM> may be arranged horizontally from the shaft <NUM>, when the arrangement is in an operating position as shown in <FIG>. The first sensor <NUM> and the second sensor <NUM> may be used to measure a position of the shaft <NUM> in the second radial direction z and the third sensor <NUM> may be used to measure a position of the shaft <NUM> in the first radial direction y.

The actors <NUM> to <NUM> may comprise a first actor <NUM> and a second actor <NUM> arranged in the movable plate <NUM> on either side of the shaft <NUM> at a lower end of the movable plate <NUM>, and a third actor <NUM> arranged above one of the first and second actor <NUM>, <NUM>. While the first and second actor <NUM>, <NUM> may be configured to move the movable plate <NUM> in the second radial direction z, i.e. vertically, the third actor <NUM> may be configured to move the movable plate <NUM> in the first radial direction y, i.e. horizontally.

Claim 1:
A test stand (<NUM>) for testing a test item (<NUM>) having a rotatable test item shaft (<NUM>), the test stand (<NUM>) comprising:
- a drive motor (<NUM>) and a shaft (<NUM>) driven by the drive motor (<NUM>), a rotational axis of the shaft (<NUM>) defining an axial direction (x),
- a fixed plate (<NUM>) and a bearing support (<NUM>) fixedly held in the fixed plate (<NUM>) or being part thereof, wherein the shaft (<NUM>) is held by one, two or more bearings (<NUM>) in the bearing support (<NUM>), the fixed plate (<NUM>) having a surface extending in a first radial direction (y) and in a second radial direction (z) perpendicular to the axial direction (x), characterized in that the test stand (<NUM>) further comprises
- a movable plate (<NUM>) having a first surface bearing against the surface of the fixed plate (<NUM>), and a second surface opposite the first surface configured for mounting the test item (<NUM>) thereon, the movable plate (<NUM>) having a central opening (<NUM>) allowing the test item shaft (<NUM>) to pass through end engage the shaft (<NUM>), the movable plate (<NUM>) being movable in a plane spanned by the radial directions (y, z) relative to the fixed plate (<NUM>),
- one, two, three or more actors (<NUM> to <NUM>) configured to move the movable plate (<NUM>) in the plane spanned by the radial directions (y, z),
- two or more sensors (<NUM> to <NUM>) configured to measure a position of the shaft (<NUM>) and/or the test item shaft (<NUM>) with regard to the radial directions (y, z),
a control unit (<NUM>) connected to the sensors (<NUM> to <NUM>) and the actors (<NUM> to <NUM>) and configured to calculate a position of the test item shaft (<NUM>) based on the measurements of the sensors (<NUM> to <NUM>), to compare it to a set position and to control the actors (<NUM> to <NUM>) to correct the position of the movable plate (<NUM>) to reduce a difference between the calculated position and the set position.