GB2107887A - Torquemeter - Google Patents

Abstract

A torquemeter for measuring the torque reaction of a component 16, comprises a pair of first links 26 pivotally connected at one end to fixed structure 15, and connected at the other end to a load measuring transducer 28. A pair of second links 24 pivotally connected to the component 16 at one end, and pivotally connected to the first links 26 at a location intermediate the ends of the first links 26, transmits the torque reaction to the transducer. The links 24, 26 are constituted as a symmetrical array relative to a common plane. <IMAGE>

Description

SPECIFICATION Torquemeter This invention relates to torquemeters.

There are many applications requiring the measurement of torque reaction where it is difficult to locate a torquemeter. For example, in the art of gas turbine engines, in which the engine drives a variable pitch propellor, there is a need to monitor the torque in order to derive an indication of the power developed by the engine. Usually there is a reduction gearbox in the transmission path between a drive shaft and the propellor. In the case where the gearbox utilises an epicyclic gear train, it is usual to monitor the torque reaction of a fixed ring gear.

One form of known torquemeter comprises a plurality of small high pressure pistons equispaced around a common pitch-circle diameter connected in a closed loop hydraulic system. Each of the pistons is connected between fixed structure (usually the engine casing) and the component, the torque of which is to be monitored. The pistons are angled tangentially to the component being monitored. Torque induced rotary movements of the components move the pistons and torque is monitored as changes in the pressure within the cylinders in which the pistons operate.

If oil is used as the hydraulic medium then an additional pump has to be provided because the engine oil pressure is too low. Multiplicity of pistons with their small area to circumference ratios give high friction losses. A further disadvantage of using pistons is that any orbiting of the component to which the pistons are connected produces orbiting pressure changes.

The pistons are usually inaccessible and require a major stripping of the engine if leakages occur. A further problem is that if the pistons are anchored at their "fixed" end to the engine casing, if the casing becomes suddenly distorted, a pressure surge is generated around the closed loop of the hydraulics.

There is a need for a torquemeter that does not suffer from the problems outlined above and which is robust and can be located externally of the engine, or at least be accessible without requiring a major stripping of the engine.

The torquemeter as claimed overcomes the above disadvantages by using balanced links to transmit the movements to a load transducer positioned at locations that is easily accessible.

Whilst the torquemeter as claimed is intended for use in a gas turbine engine it is also useful in many other applications.

The present invention will now be described, by way of an example, with reference to the accompanying drawings, in which, Figure 1 is a side view of part of a gas turbine aero-engine showing the region where a torquemeter constructed in accordance with the present invention would be located.

Figure 2 illustrates in greater detail, the torquemeter for use in the gas turbine engine of Figure 1.

Figure 3 illustrates a second torquemeter constructed in accordance with the present invention.

Figure 4 illustrates an alternative transducer to that shown in Figures 2 and 3.

Referring to Figure 1 there is shown an epicyclic gearbox 10 located between a drive shaft 11 driven by a turbine of the engine, and a front low pressure comparessor fan 12 of the engine. Connected to a fixed gear ring 13 of the gearbox 10 is a housing 14 that constitutes a reaction member whereby the torque reaction produced by the gearbox is transmitted to fixed structure 15 of the engine.

The housing 14 is keyed to a radially extending plate 16 that is mounted in a bearing 1 7. The planet cage 1 8 of the gearbox is mounted in bearings 19, 20. If desired, in some applications, the reaction member 14 neeed not be mounted in its own bearing 1 7. The plate 1 6 has two holes 21 spaced around its circumference. The holes 21 are provided for mounting the torquemeter 22 of the present invention as shown in Figure 2.

Referring to Figure 2 the holes 21 in the plate 1 6 are located symmetrically with respect to a vertical plane 23 passing through the centre line of the engine. The torquemeter 22 comprises a pair of first links 24. Each link 24 is pivotally connected at one end to the plate 1 6 by means of spindles 25 and pivotally connected at their other end to a second link 26 at a point intermediate its ends. The links 24 are both of the same length.

The links 26 are each pivotally mounted on fixed structure 1 5, of the engine (for example the engine casing) at one of their ends 27 and are pivotally mounted to a load transducer 28 at their other ends 29. The transducer 28 is of the type manufactured by Sangamo Schlumberger under their code No. D95 and has a capability of a full load movement of not more than 0.2 mm. The pivots 30 at the ends 29 of the links 26 are equidistance from a plane passing through the pivots 31, 32, and lie in the vertical plane 23.

Assuming that it is required to transmit 20,000 HP (approximately 1 5 Mw) at 6800 r.p.m. the torque would be 185367 Ibf. in. (20945 Nm).

With a 2.5 reduction gearbox, the torque reaction at housing 16 can be shown to be 278051 inch Ibs. (31418 Nm). Therefore, the load in each link would be of the order of 6.57 tons (65.46 kN).

With a 6:1 ratio between the distances A and B the load exerted by each link 26 on the transducer would be 1.095 tons (10.9 kN).

The links 24 and 26 are not affected by movement of the engine centre line either vertically or horizontally and no adverse reaction loads are transmitted to the casing.

Referring to Figure 3 there is shown a second torquemeter 33 constructed in accordance with the present invention which enables the transducer 28 to be located outside the engine casing. The torquemeter 33 is identical to that of Figure 2 except that the transducer 28 is not mounted directiy on the ends of links 26. Instead one of the links 26 has a bifurcated end to which is pivotally connected two push rods 34. The push rods 34 are connected to one side of the transducer 28. The other link 26 does not have a bifurcated end, but has a single push rod 35 pivotally connected to it. The other end of the push rod 35 is connected to the other side of the transducer 28. A steadying link 36 may be provided to locate the transducer 28 relative to the fixed structure 1 5 of the engine.

The rods 34 are interconnected at their ends adjacent the transducer 28 by a bar 37 that has a boss 38 that locates in a recess in a housing 39 secured to the fixed structure of the engine. A spring 40 in a bore in the boss 38 urges two friction pads 41 against the wall of the recess thereby acts as a damper to damp movements of the bar 37.

The transducer 28 of the torquemeter of Figure 2 could be replaced by the transducer 42 of Figure 3.

Referring to Figure 4 the rod 35 is provided with a piston 43 which slides in an oil-filled cylinder 44 carried by the rods 34. Relative movement of the rods 34, 35 move the piston to pressurise the oil in the cylinder and a pressure transducer 45 is used to convert the pressure changes to torque readings.

Claims (10)

Claims

1. A torquemeter for monitoring the torque reaction of a component comprising; a load measuring transducer; a pair of first links, each of which is mounted on a pivot structure which is fixed relative to the torquemeter, and is connected to the transducer at a location spaced along the length of the first link from the pivot, and; a pair of second links pivotally connected to the component at spaced points around a circumference, each of which is pivotally connected to one of the first links at a location spaced along the first link from the pivotal connection of the first link to the said structure.

2. A torquemeter according to Claim 1 wherein each second link is pivotally connected to a first link at a location intermediate the transducer and the pivotal connection between the first link and the said structure.

3. A torquemeter according to Claim 1 or Claim 2 wherein the arrangement of links is symmetrical about a plane common to all links.

4. A torquemeter according to any one of Claims 1 to 3 wherein the pivotal axes of the pivotal connections between the first links and the said structure lie in a common plane.

5. A torquemeter according to any one of Claims 1 to 4 wherein the pivotal axes of the pivotal connection between the second links and the component lie in a common plane.

6. A torquemeter according to Claim 5 wherein the pivotal axes of the pivotal connections between the first links and said structure lie in a common plane which lies parallel to the plane in which lie the pivotal axes of the pivotal connections between the second links and the component.

7. A torquemeter according to any one of the preceding claims wherein the transducer is connected to the first links by means of push rods that are pivotally connected to the first links at a region spaced from the pivotal connection of the first link to the said structure.

8. A torquemeter according to any one of the preceding claims wherein the transducer is operable to produce an electrical signal indicative of the load transmitted by the first and second links to the transducer.

9. A torquemeter according to any one of Claims 1 to 7 wherein the transducer comprises a piston operable in a cylinder bore to subject a fluid to pressure and the pressure of the fluid is used as an indication of the load transmitted by the first and second links to the transducer.

10. A torquemeter substantially as hereindescribed with reference to any one of the drawings.