DE4042270C1 - Torque pick=up using expansion measuring strips in bridge circuit - establishes coupling between rotor and housing by slip-rings and brushes on sprung retainers - Google Patents

Abstract

A torque transducer has strain gauges in a full bridge circuit mounted on a narrow torsion section of a shaft in a housing to which it is connected via slip rings (14-17) and spring mounted brushes (18-21). Two slip rings are for the electrical supply to the bridge and two for passing the measurement signals from the rotating shaft to an evaluation unit. The material for the slip rings is bearing bronze with a graphite admixture of 5 to 15 per cent. The brushes are made of hard silver. ADVANTAGE - Slip ring and brush materials are selected to prevent unwanted increase in transfer path resistance as wear occurs.

Description

The invention relates to a torque transducer Strain gauges according to the preamble of claim 1.

With torque transducers of this type, such as, for example are known from DE-AS 12 91 917, the grinding exist rings made of silver and the brushes (grinder) made of a pressed most silver-graphite mixture. The brush material is included relatively soft in order to increase the Avoid contact resistance due to brush abrasion. In addition, the soft brush material creates a resonance exaggeration of natural vibrations of the brushes Steamed springs.

However, with the relatively soft brush material linked to the disadvantages that the life of the brushes only short is that brush abrasion can lead to shunts, which must be prevented by frequent maintenance and that by Impacts from outside causing bouncing and lifting of the brushes leads to interruptions of contact too often.

DE 30 09 816 A1 describes a method for the production a slip ring body made of a copper tube for electrical Machines known, from the slip ring body means zone diagonally inward hook for anchoring the Slip ring body on the insulating sleeve who sheared the. The purpose of this measure is to save copper achieve as well as a perfect and secure hold of the Ensure slip rings on the insulating sleeve.

DE 33 46 553 A1 describes a composite material for sliding gels elements with a sintered layer of 1 to 8% by weight Phosphor bronze containing graphite and a process for the manufacturing disclosed. This composite material is said to result in high material yield, be easy to manufacture and comparatively better mechanical properties as well  have drawn bending behavior.

The use of silver as a material for contact elements for Selector of tap changers is by DE 24 28 848 B5 be knows.

DE-OS 23 20 162 is a motor selector with the through coupling line wires assigned and on rotatable con poor arranged contact springs known, the contact each provide an electrical connection between the cones clocking a row of contact banks and one coaxial with the voter Produce a stationary slip ring arranged on the axis.

To make a simple adjustment of the contact springs in your to be able to carry out the area facing the bank contacts, has the carrier part of the contact springs on its the bank account clock towards the opposite end of a counter bearing that in one Slit of the associated contact spring leg engages and a shift of the contact spring leg lower in its plane right to its longitudinal axis.

The invention has for its object a slip ring and To find brush material that is an annoying increase in the Contact resistance largely from brush abrasion closes, wears out very little and when subjected to shock in connection with an appropriate design of the office to a much lesser extent to contact subordinates breaks.

This object is achieved by the features in characterizing part of claim 1 solved.

In the design and development of the invention are the Bür support beams asymmetrically divided, whereby the two supports parts with the same brush masses have different natural frequencies  own zen.

The invention is illustrated below with reference to the drawing which an embodiment of the brush assembly and brushes education in connection with the new material combination ver vivid, explained.

Show it

Fig. 1 is a partial side view sion distance of a shaft with a gate,

Fig. 2 is a view of the shaft with accessories in accordance with Fig. 1 in the direction A,

Fig. 3 is a view of a divided brush holder in an enlarged view.

The torque sensor according to Fig. 1 consists of a Rotie leaders shaft 10, fixed in a housing not shown is rotatably supported. The shaft 10 has a tapered or constricted section 11 which forms the gate sions stretch on which strain gauges 12 are attached, which are connected to a full measuring bridge 13 . On the norma len diameter shaft portion 11 ', which, like the tapered shaft portion 11 , is located within the housing not drawn, four slip rings 14 , 15 , 16 and 17 are attached, which the brushes 18 , 19 , 20 and 21st are allocated accordingly.

The slip rings 14 and 15 are used together with the brushes 18 and 19 for the electrical supply of the arranged on the tapered Wel lenabschnitt 11 measuring bridge 13 , while the cooperating with the slip rings 16 and 17 brushes 20 and 21 are electrically connected to a measuring amplifier 22 , the output signal is evaluated.

The holders or supports 23 of the brushes 18 to 21 are embodied by leaf springs, which are divided asymmetrically, for example by slitting. The division is made so that a wide spring part 23 'and a narrow Fe derteil 23 ''is obtained. The wide spring part 23 'is relatively stiff and accordingly has a relatively high natural frequency, the narrower spring part 23 '', however, is relatively soft and its natural frequency is accordingly lower.

The likelihood that both spring parts 23 'and 23 ''with their brushes having the same mass will simultaneously lift when shocks occur is extremely low. In addition, the bridging times are shorter when bouncing. The leaf springs 23 (brush holder) are held in an insulating body by 24 .

The ones made of bronze with a graphite admixture Slip rings, the graphite admixture preferably by 8% lying around, show only slight abrasion, because the Graphite particles predominantly in and on the grinding track ten and the relatively hard backing material little wears out. A sintered composite is preferred turns. As has been shown, shunts only appear after at least ten times longer useful life compared to the previously used materials.

The brushes 18 to 21 made of hard silver are just subject to very little wear, so that smaller brushes and therefore smaller masses can be used. By increasing the natural resonances, the torque absorber is also more reliable in terms of acceleration.

The graphite admixture to the bearing bronze can also be a percentage in the range between 5 to 15% or slightly below or lie above.

Claims (4)

1. Torque transducer with strain gauges in full-bridge circuit, the strain gauges being mounted on a tapered section of the torsion path forming a shaft mounted in a fixed housing and the connection between the rotor and housing being made by slip rings and brushes attached to resilient holders, and wherein Two slip rings are provided for the electrical supply of the measuring bridge and two slip rings are used to transmit the measurement signal from the rotating shaft to an evaluation unit, characterized in that the gerbronze with material for the slip rings ( 14 , 15 , 16 , 17 , 18 ) a graphite admixture of 5 to 15% is selected and the brushes ( 18 , 19 , 20 , 21 ) are made of hard silver. 2. Torque transducer according to claim 1, characterized in that the graphite admixture is 8%. 3. Torque pickup according to claim 1 or 2, characterized records that the bearing bronze and the graphite admixture form a sintered composite. 4. Torque pickup according to one of the preceding claims, characterized in that the brush holder ( 23 ) embodied by leaf springs and un symmetrically divided with the same brush masses, with each of the two Fe derteile ( 23 ', 23 '') a brush with the same Mass is attached.