GB2212283A

GB2212283A - Mounting a sensor element

Info

Publication number: GB2212283A
Application number: GB8726123A
Authority: GB
Inventors: Philip Augustus Taft
Original assignee: Lucas Industries Ltd
Current assignee: ZF International UK Ltd
Priority date: 1987-11-07
Filing date: 1987-11-07
Publication date: 1989-07-19
Anticipated expiration: 2007-11-07
Also published as: GB2212283B; GB8726123D0

Abstract

The deflection of an axle 1 is monitored by a sensor element (4). The element (4) is clamped e.g. by bolts 15, 16 to a pair of blocks (2, 3) rigid with the axle with the sensor (4) wedged between oppositely inclined load-receiving faces (5, 6) on the blocks so that a compressive force is transmitted through the faces and no slippage occurs. The cooperating end faces of the sensor may be complementary to faces 5, 6 or may be arcuate. The element 4 comprises a one piece elliptical metal frame 7 with projecting stub arms 8, 9. A diaphragm 13 fixed to the frame 7 carries strain gauges 14. <IMAGE>

Description

MOUNTING A SENSOR ELEMENT This invention relates to mounting apparatus for mounting a sensor element to a deformable member, such as a vehicle axle, in order to monitor the axle deflection as an indication of the local condition of a vehicle A vehicle axle bends when loaded and this bending causes a change in length of the outermost skin of the axle which can be measured electrically by a sensor element to produce a signal which is proportional to load.

Since an axle is designed to be strong the bending, and therefore the consequent electrical signal, is small. The signal may be boosted by mounting the sensor element at a raised position for example on blocks since this converts the bending of the axle into a compression of the sensor element.

In view of the relatively small magnitude of the signal, it is essential for the sensor to be mounted on the blocks against relative movement, at least in the direction of the compressive force since any such relative movement would cause a considerable error in the signal to occur. For example, such relative movement can occur if the sensor is simply mounted on the blocks by the frictional clamp action of bolt fastening devices, suitably screwed into tapped holes in the blocks.

According to our invention a sensor element is adapted to be mounted on a pair of blocks rigid with a vehicle axle and which are movable relatively to each other in response to changes in the load on the axle, and the blocks are provided with oppositely inclined faces with which load-receiving faces at opposite ends of the element co-operate, and clamp means are provided for clamping the sensor element to the blocks, the arrangement being such that since the sensor is wedged between the inclined faces no slippage occurs, and the compressive force is transmitted through the co-operating faces.

Only a minimum force is therefore required from the clamp means.

The end faces of the sensor element may be of an inclined configuration complementary to that of the faces on the blocks.

Alternatively the end faces may be of arcuate or part-circular outline.

Preferably the sensor element comprises a frame which contains at least one strain gauge element and which is strong in bending and twisting, but which is weak in compression and tension.

Conveniently the frame is of elongate or stretched elliptical or oval outline, and the faces are disposed at the outer ends of a pair of arms which project from the sides of the frame, a diaphragm containing strain gauge elements being fixed to the frame.

Some embodiments of our invention are illustrated in the accompanying drawings in which: Figure 1 is a schematic diagram of a vehicle axle; Figure 2 is a plan of a load cell mounted on the axle; Figure 3 is a section on the line 3-3 of Figure 2; Figure 4 is a view similar to Figure 2 but showing a modification; and Figure 5 is a section on the line 5-5 of Figure 4.

Figures 1-3 of the accompanying drawings illustrate schematically, a typical beam axle 13 in bending with a sensor element in the form of a load cell 4 installed at position A between two blocks 2, 3 which are rigid with, and upstanding from, the outer skin of the axle 1. Adjacent force-transmitting faces 5, 6 of the blocks at the outer ends of recesses are oppositely inclined.

The load cell 4 comprises a one-piece skeletal metal frame 7 of elongate or stretched elliptical or oval outline provided with a pair of oppositely directed outwardly projecting stub arms 8, 9. The former 7 is received in the recesses and spans a gap 10 between .the two blocks 2, 3. The free ends of the arms 8, 9 have inclined faces 11, 12 which are complementary to the faces 5 and 6 and which engage with them. A diaphragm 13 fixed to the frame contains strain gauges 14.

The frame 7 is attached to the blocks by means of bolts 15, 16 which are screwed into tapped holes 17, 18 in the blocks 2, 3.

Since the frame 7 is elongate transversely of the axle it is weak in compression and tension, but is strong in bending and twisting.

The inclination or tapering of the faces 5, 11; 6, 12 is chosen to provide a wedge angle which guarantees intimate contact between the faces of each pair, and the wedge angle is relatively small so that reaction forces are minimised and, in consequence, only such minimised reaction forces have to be taken by the bolts 15, 16.

In the modified construction illustrated in Figures 4 and 5, the outer ends of the arms 8, 9 are of arcuate or part-circular outline to define force receiving faces 20, 21.

The construction and operation of the embodiment of Figures 4 and 5 is otherwise the same as that of Figures 1-3, and correspond'ing reference numerals have been applied to corresponding parts.

Claims

1. Means for mounting a sensor element on a vehicle axle comprising a pair of blocks rigid with the vehicle axle and which are movable relatively to each other in response to changes in the load on the axle, in which the blocks are provided with oppositely inclined faces with which load-receiving faces at opposite ends of the element co-operate, and clamp means are provided for clamping the sensor element to the blocks, the arrangement being such that since the sensor is wedged between the inclined faces no slippage occurs, and the compressive force is transmitted through the co-operating faces.

2. Means as claimed in claim 1, in which the end faces of the sensor element are of an inclined configuration complementary to that of the faces of the blocks.

3. Means as claimed in claim 1, in which the end faces are of arcuate or part-circular outline.

4. Means as claimed in any preceding claim, in which the sensor element comprises a frame which contains at least one strain gauge element and which is strong in bending and twisting, but which is weak in compression and tension.

5. Means as claimed In claim 4, in which frame is of elongate or stretched elliptical or oval outline, and the faces are disposed at the outer ends of a pair of arms which project from the sides of the frame, a diaphragm containing strain gauge elements being fixed to the frame.

6. Means for mounting a sensor element on a vehicle axle substantially as described herein with reference to and as illustrated in Figures 1-3 of the accompanying drawings.

7. Means for mounting a s.ensor element on a vehicle axle substantially as described herein with reference to and as illustrated in Figures 4 and 5 of the accompanying drawings.