Patent ID: 12235176

FIGS.1and2show two views of a device1for determining the torque and/or the rotary angle between a first shaft10and a second shaft20, which are rotatably coupled via a gear mechanism30relative to each other about an axis of rotation A. The first shaft10has a first end region10a, a second end region10b, and a first direction vector R1, which runs in parallel with the axis of rotation A and points from the first end region10ato the second end region10b. The second shaft20has a first end region20a, a second end region20b, and a second direction vector R2, which runs in parallel with the axis of rotation A and points from the first end region20ato the second end region20b. The first shaft10is designed as a hollow shaft in which the second shaft20is arranged coaxially. The arrangement is such that the first direction vector R1and the second direction vector R2have the same orientation, or in other words that the first end region10aof the first shaft and the first end region20aof the second shaft point to the same side. The first end region20aof the second shaft20can lie within the first end region10aof the first shaft10, in particular end so as to be flush with it, or protrude slightly beyond it.

The first end region10aof the first shaft10has a first measurement standard11, while the first end region20aof the second shaft20has a second measurement standard21. The measurement standards11,21can be formed circumferentially. For this purpose, the measurement standards11,21can be arranged, for example, on the outer surface of the shafts10,20. In the exemplary embodiment shown, a first element12in the shape of a disk ring is arranged on the first end region10aof the first shaft10, at or on which the first measurement standard11is arranged, in particular circumferentially, while a second element22in the shape of a disk ring is arranged on the first end region20aof the second shaft20, at or on which the second measurement standard21is arranged, in particular circumferentially. The measurement standards11,21are in particular arranged concentrically to one another. The disk ring-shaped elements12,22each have a plane which is arranged in particular perpendicularly to the axis of rotation A, with the two disk ring-shaped elements12,22and/or the two measurement standards11,21in particular being arranged in the same plane. For this purpose, the first element21in the shape of a disk ring can be of a stepped design so that an outer region12aof the first element12in the shape of a disk ring is arranged radially outside the second element22in the shape of a disk ring and in the same plane with it, while an inner region12bof the first element12in the shape of a disk ring is arranged axially behind the disk-shaped second element22.

The measurement standards11,21permit at least one relative angle determination over one revolution. The measurement standards11,21are preferably absolute measuring standards, which enable an angle to be determined over a large number of revolutions.

The first measurement standard11is scanned by a first sensor41, while the second measurement standard21is scanned by a second sensor42. The scanning can in particular take place optically. For this purpose, the measurement standards11,21are designed to be reflective, while the sensors41,42are designed as optical scanning elements.

The sensors41,42are arranged, for example, on the face side in front of the first end regions10a,20aof the two shafts10,20so that the measurement standards11,21are scanned substantially in parallel with the axis of rotation A. Alternatively, scanning can also take place in the radial direction to the shafts10,20.

The sensors41,42are particularly preferably arranged on a single printed circuit board40. The scanning signals detected by the sensors41,42are forwarded to an evaluation unit to determine the rotary angle positions of the first and second shaft10,20and, if necessary, also to determine the torque acting between the shafts10,20as described below. The angular positions can be determined independently of one another, i.e. the angular position of the first shaft10by scanning the first measurement standard11using the first sensor41and the angular position of the second shaft20by scanning the second measuring standard21using the second sensor42. If the elasticity of the gear mechanism30is known, i.e. if it is known which angular difference is present between the two shafts10,20without load during operation at a predetermined speed of the motor50, the torque can be determined on the basis of the angular difference with load during operation between the two shafts10,20.

The device1can have a housing50which is closed by a cover52, for example. In this case, the printed circuit board40can be arranged in the cover52, as a result of which the sensor system is easily accessible.

The first shaft10may be the drive shaft of the gear mechanism30, while the second shaft20may be the output shaft of the transmission30. The first shaft10is in particular the motor shaft of a motor50which is preferably designed as an electric motor, in particular as a servomotor. The motor50has a rotor55aand a stator55b, the rotor55abeing coupled to the first shaft10in a torque-proof manner.

The gear mechanism30couples the second end region20aof the first shaft10to the second end region20bof the second shaft20. The gear mechanism can be designed, for example, as a tension shaft gear mechanism. For this purpose, a radial projection31, which has an elliptical cross section perpendicular to the axis of rotation A, can be arranged on the second end region10bof the first shaft10, on the outer circumference of which a ball bearing32, which is designed as a roller bearing, for example, is arranged. A flexible, thin-walled sleeve33is arranged on the outer circumference of the ball bearing32and is arranged in a fixed manner in the housing50via a circumferential collar33a. The outside of the sleeve33has external teeth34. A radial projection20cis arranged on the second end region20bof the second shaft, which as a circumferential projection20don its surface facing in the direction of the first end region20aso that a circumferential groove20eis formed, which is open in the direction of the first end region20a. Internal teeth35are arranged in the groove20e, in which the external teeth34of the sleeve33engage. There is a difference in the number of teeth between the external teeth34and the internal teeth35, for example by one or two teeth. When the first shaft10rotates about the axis of rotation A, the elliptical projection31deforms the sleeve33, and, due to the tooth difference, a rotation of the second shaft20relative to the first shaft10is achieved. With a large number of teeth, a high transmission ratio increase or reduction can be achieved.

The device1is used in particular in a robot, for example in a moving joint of a robot.

The device1enables the angular positions of the first shaft10and the second shaft20to be determined in a simple manner, since the angular positions of the shafts10,20, in particular the angular position of the motor50and the angular position of the output shaft20and thus the output of the gear mechanism30, can be determined independently using the sensors41,42, in each case. The device1enables, for example, the torque acting between the two shafts10,20to be determined in the manner described below, but also in particular without additional mechanical components. If the first shaft10is fixed in its position and a torque to be determined acts on the second shaft20, an angular difference occurs between the second shaft20and the first shaft10, since the gear mechanism30has elasticity and acts like a torsion bar when the torque is applied. If the elasticity of the gear mechanism is known, the torque can be determined from the size of the angle difference. The known elasticity of the gear mechanism can be determined, for example, by determining the angular difference between the first shaft10, i.e. the motor shaft or the drive shaft, and the second shaft20, i.e. the output shaft, over the entire travel range without an additionally acting torque.

LIST OF REFERENCE SIGNS

1Device10First shaft10aFirst end region10bSecond end region11First measurement standard12Disk ring-shaped first element12aOuter region12bInner region20Second shaft20aFirst end region20bSecond end region20cRadial projection20dCircumferential projection20eGroove21Second measurement standard22Disk ring-shaped second element30Gear mechanism31Projection32Ball bearing33Sleeve33aCollar34External teeth35Internal teeth40Printed circuit board41Sensor42Sensor50Housing52Cover55Motor55aRotor55bStatorA Axis of rotationR1First direction vectorR2Second direction vector