Measuring and testing – Dynamometers – Responsive to torque
Patent
1995-09-18
1998-01-06
Biegel, Ronald L.
Measuring and testing
Dynamometers
Responsive to torque
340665, G01L 300
Patent
active
057057567
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to a magnetomechanical device allowing measurement of the torque transmitted by a rotating shaft or a similar mechanical element. This device finds its application everywhere it is deemed necessary to measure the torsional moment being applied to a shaft. It finds one particularly advantageous application in the field of motorized transport vehicles, more particularly in the automobile field, for example applied to the steering column of a vehicle equipped with power steering. Mention may also be made of all drive shafts and industrial shafts in general.
BACKGROUND OF THE INVENTION
The torque is a useful quantity in many respects. In point of fact, this quantity makes it possible to know the mechanical stresses to which the transmission shaft and the systems upstream and downstream of the shaft are subjected. In addition, knowing the torque makes it possible to deduce the acceleration of the system and even the power transmitted by the shaft. In this latter case, it is obviously necessary to know the speed of rotation of the shaft, but this is a quantity which is easy to measure.
A few devices already exist which allow access to the torque information.
The general principle stems from the laws of physics. The torque applied to a shaft causes an angular deformation, a torsion of this shaft, and the torsion is proportional to the torque.
For a shaft segment lying between sections A and B, the angle of the resulting torsion between A and B is proportional to the distance between A and B and to the torque transmitted and, in addition, depends on the cross-section of the shaft as well as on its constituent material.
Some torque sensors use two angular position sensors placed respectively at A and B. The difference in the angles measured gives the angle of torsion. This angle is always small, and therefore the position sensors must be very accurate. Whatever their technology, such torque sensors are necessarily expensive and quite fragile.
Some torque-meters working on this principle gain access to the difference in angular position by measuring the phase shift between two wave trains, these being generated by one means at A and another at B. These means may be, for example, two toothed rotor discs with, opposite, two toothed stator rings carrying a winding (Patent FR-A-1,542,815). The associated processing electronics are then quite complex and the quality of the result depends on the speed and decreases with it, even rendering measurement when stopped impossible. This is the case for all systems delivering information modulated by the speed of rotation.
The torque-meter proposed in Patent FR-2,631,702 with, at each end of the shaft, two toothed rotors placed opposite a stator equipped with electromagnet windings and with a magnetic circuit excited by magnets in order to form a homopolar machine makes it possible, by measuring the intensity of the current in circuits formed by the stator windings, to gain access to information about the torque which is then not very sensitive to the speed. However, the complexity of implementation of the stator windings and of the associated electronics makes such solutions not very attractive.
The device described in Patent Application DE-A-4,038,808, which includes a system of two toothed wheels facing each other at each end of the part capable of undergoing torsion, uses as detector two coils connected as a bridge. These two coils are supplied with an AC voltage and the voltage of the mid-point is amplitude modulated by the relative position of the teeth, and therefore by the torque. Calculation of the torque itself is therefore performed by means of a synchronous demodulation operation, which is a complex electronic processing operation. Other sensors use strain gauges fixed directly to the shaft. Such solutions require devices making it possible to supply sensitive rotor elements and also to extract the information from the moving parts to the fixed parts. These devices generally have wearing pieces, which is undesirable eit
REFERENCES:
patent: 2445427 (1948-07-01), Godsey, Jr.
patent: 2461685 (1949-02-01), Godsey, Jr.
patent: 2826064 (1958-03-01), Hastings
patent: 4984474 (1991-01-01), Matsushima et al.
Journal of Magnetism and Magnetic Material, vol. 104-107, Feb. 1992, Amsterdam (NL), pp. 1109-1110, XP000329324, V. LeMarquand et al., "New Structure of Magnetic Torque Sensor".
Patent Abstracts of Japan, vol. 8, No. 1, (P-246) (1438) 6 Jan. 1984, & JP, A 58 167 934 (Tateishi Denki K.K.), 4 Oct. 1983.
LeMarquand Guy Pierre Raymond Lucien
LeMarquand Valerie Evelyne
Biegel Ronald L.
Labinal
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