CN1123763C - Method for measuring torque of drive axle with photoelectric sensor - Google Patents

Abstract

The present invention belongs to the field of physical quantity testing. The method comprises: two measuring points are set on an axis, a beam of light rays perpendicular to the axial direction irradiates the two points; a counter is set to start to count after the counter receives a first signal, and the counter stops counting after receiving another signal; a count value represents the time difference of the two signals. The relative positions of two reflecting mirrors vary after torsion is generated, the changed relative positions are reflected on the counter by reflected light rays, and torsion values can be obtained by the variation quantities. The present invention has the characteristics of high sensitivity, good linearity, large measuring range, low cost, simple structure and convenient use. The present invention is especially suitable for the measurement of medium loads and the measurement of small loads.

Description

The method of utilizing photoelectric sensing that the moment of torsion of transmission shaft is measured

The invention belongs to the physical quantity field tests, particularly to the method for torque measurement.

In a lot of fields such as machinery, measurement, processing, sensing, all relate to the measurement of moment of torsion.It is a physical quantity that is difficult to measure that relative other of moment of torsion measured, though sensor kind in the market is a lot, torque sensor but compares less.The mode of common torque measurement mainly contains:

1. paste foil gauge on the elastic shaft

The measuring method of contact measured body has been adopted in the foil gauge measurement, and big to attribute dependences such as shape own, materials, precision is low, and accommodation is little.This is a kind of measurement means that belongs to older, is eliminated gradually now.

2. magnetic-electric sensing.

Magnetoelectric sensor has adopted noncontact measuring method, relative strain sheet precision improves, but because the characteristics of magnetoelectricity element itself, when the temperature of working environment changes, or be subjected to external magnetic field and disturb, or be subjected to physical shock, when vibrations, and magnetoelectric sensor is influenced by it, and sensitivity will change and produce measuring error.

These two kinds of measuring methods also have a common major defect, are exactly only to be applicable to large-scale, heavy mechanical system, and are powerless for the small torque that will measure in fine element, the exquisite system.

The objective of the invention is to overcome the weak point of prior art, a kind of method of utilizing photoelectric sensing to carry out torque measurement is provided, have highly sensitive, the linearity is good, and measurement range is big, and cost is low, characteristics simple in structure, easy to use particularly are applicable to the measurement of medium and small load.

A kind of method of utilizing photoelectric sensing to carry out torque measurement that the present invention proposes may further comprise the steps:

1) before transmission shaft rotates, two measurement point I, II that can reflect light separated by a distance is set arbitrarily on the periphery of axle;

2) with a branch of irradiate light perpendicular to axis direction on two measurement points;

3) two photoelectric sensors that receive catoptrical stationkeeping are set, and the counter that links to each other with the output terminal of these two photoelectric sensors, two photoelectric sensors receive the reflected light of measurement point I, II respectively, a moving week of this transmission shaft revolution, two photoelectric sensors received respectively once, begin counting behind the signal of the measurement point that counter is set to receive earlier, stop counting after receiving the signal of another measurement point again;

4) when axle rotates under not adding the load situation, be subjected to irradiate light after measurement point I, II one elder generation one, can after the elder generation one light be reflected away, can on counter, obtain an initial count value N ₀, this has represented their relative angle θ ₀

5) when axle rotates under load condition, because transferring power, caused axle to be subjected to torsional interaction and elastic torsion takes place be out of shape, two measurement point relative positions change, and are reflected on the counter by this point reflection light, and count value also changes, or increase or reduce, its variable quantity is Δ N;

6) relatively load before and after the count value of counter, calculate the torsional deflection situation of shaft.

For improving measuring accuracy, said measurement point I, II preferably are separately positioned on two end faces of this transmission shaft.

The measurement ultimate principle that the present invention adopts is the distortion of measurement axis, directly or indirectly calculates the moment of torsion that shaft is subjected to by deflection.Axle torsion angle problem only belongs to cylindrical equilibrium problem stressed on end face, if strict satisfy boundary condition, finds the solution very difficult.Therefore utilize St. Venant principle (in an object, apart from plus load site of action each point quite far away, its stress is little with the institute actual load details relation that applies), boundary condition is loosened, think on the midsection stress only with end face on external force make a concerted effort that to reach resultant moment relevant.

Etc. reversing of straightforward face circular shaft, its internal modification is made the hypothesis of rigid plane, circumferential section still keeps the plane when promptly being turned round, radius of a circle r still is straight line after distortion, utilize Hooke's law, obtain stress distribution law by the Strain Distribution rule, utilize the stress equilibrium condition to obtain circular shaft then at moment of torsion M _nUnder the effect, the shear stress on surface is $\mathrm{\τ}=\frac{M_n}{W_n}---\left(1\right)$

(1) in the formula, W _nTorsion Section modulus for circular shaft.For solid circular shaft, it is worth W _n=π/16d ³Be W for its value of Hollow Cylindrical Shaft _n=π/16 (D ₀ ³-α d ₀ ³).

Wherein d is the diameter of solid circular shaft;

D ₀External diameter for Hollow Cylindrical Shaft;

d ₀Internal diameter for Hollow Cylindrical Shaft;

α＝d ₀/D ₀

In elastic range, corresponding shearing strain $\mathrm{\γ}=\frac{\mathrm{\τ}}{G}=\frac{M_n}{{\mathrm{GW}}_n}---\left(2\right)$

In the following formula, G is a shear elasticity.

Simultaneously, produce relative torsional angle at a distance of between two cross sections of L, its value can be determined by following formula: $\mathrm{\θ}=\frac{L}{{\mathrm{GJ}}_n}{M}_n---\left(3\right)$

In the following formula, J _nPolar moment of inertia for the cross section.

For solid circular shaft: J _n=π/32d ⁴

For Hollow Cylindrical Shaft: J _n=π/32 (D ₀ ⁴-d ₀ ⁴);

From top two formulas as can be seen, as long as the size d or the D of axle ₀, d ₀And L is definite, and the shear elasticity G of material is certain, and the shearing strain of rotating shaft is just only relevant with moment of torsion with the two sections relative rotation at a distance of L, and proportional, promptly

θ＝KM _n (4) $K=\frac{L}{{\mathrm{GJ}}_n}$ Be constant, so

θ∝M _n

Promptly can determine M as long as measure θ _n

Therefore the torsion problem of surveying transmission shaft transforms into the relative rotation problem in two cross sections surveying it.After as long as design is finished, the value of demarcation constant K just can be set up corner and moment of torsion concerns one to one.

Characteristics of the present invention are that counting is strong and weak irrelevant with the size of signal, as long as the reaction rate of device is enough high, just very high precision and sensitivity can be arranged.Measuring process and actual operation situation are irrelevant, are not subjected to the influence of labile factors such as rotating speed, load, and antijamming capability is strong.Measurement range is big, particularly is applicable to the measurement of medium and small load, and the measurement for miniature axle also can realize such as the corner of measuring steel wire.The linearity is good, and cost is low, and is simple in structure, easy operating.

Description of drawings:

Fig. 1 is provided with synoptic diagram for method of the present invention.

Fig. 2 is a measuring principle synoptic diagram of the present invention.

Fig. 3 is a measuring process synoptic diagram of the present invention.

A kind of method of utilizing photoelectric sensing that the moment of torsion of transmission shaft is measured that the present invention proposes reaches embodiment in conjunction with the accompanying drawings and is described in detail as follows:

Measuring principle of the present invention as shown in Figure 1 and Figure 2, on the periphery of axle 1, two some I, II that certain distance is apart arranged, known relative rotation is θ ₀A branch of irradiate light perpendicular to axis direction on two points, reach photoelectric sensor from the light of I point reflection after, behind T after a while, the light of II point reflection could arrive.As long as measure size during this period of time, just can obtain the relative rotation situation of two points.The work of measuring is finished by pre-set counter.Counter is set to receive and begins counting behind first signal, stops counting after receiving a signal again, and count value has just been represented the mistiming of two signals.I, II one is subjected to irradiate light after one earlier, can one light be reflected away after one earlier, and not adding before the load is changeless during this period of time, can obtain the count value N of a standard on counter ₀When transmission shaft rotates with angular velocity omega, because transferring power, caused axle to be subjected to torsional interaction and elastic torsion takes place be out of shape.After twisting, two catoptron relative positions change, and are reacted on the counter by reflection ray, and count value also changes, or increase or reduce, and its variable quantity is Δ N.Be proportional relationship between count value and the relative torsional angle, formula is: $\frac{\mathrm{\θ}}{{\mathrm{\θ}}_0}=\frac{\mathrm{\ΔN}}{N_0}---\left(5\right)$

Torsion angle then: $\mathrm{\θ}=\frac{\mathrm{\ΔN}}{N_0}{\mathrm{\θ}}_0---\left(6\right)$

By (6) formula, measure θ _α, N ₀, Δ N, just can obtain torsion angle.

Embodiments of the invention, structure are very simple, only are made up of light source, mirror surface, light activated element and counting element.Measuring process as shown in Figure 3, light incides respectively on the catoptron for the treatment of side transmission shaft two ends after sending from light source.At opposite side, two photoelectric sensors are responsible for receiving reflected light, and the output electric signal.Electric signal is received by counting assembly after amplifying through filter shape.Because electric signal is not simultaneously, can be measured their mistiming, calculates the suffered moment of torsion of transmission shaft thus.Wherein, the light source of present embodiment adopts neon tube, in actual applications, can select any luminescent device as power supply; Mirror surface also can be replaced by paster that can be reflective; Look accuracy requirement, the light activated element performance can adopt photoelectric tube and CCD camera from low to high respectively; Counter also can be selected different modes such as semiconductor circuit, single-chip microcomputer, PC for use.

Claims (1)

1. a method of utilizing photoelectric sensing to carry out torque measurement is characterized in that, may further comprise the steps:

1) before transmission shaft rotates, two measurement point I, II that can reflect light separated by a distance is set arbitrarily on the periphery of axle;

2) with a branch of irradiate light perpendicular to axis direction on two measurement points;

3) be provided for receiving catoptrical, two photoelectric sensors of stationkeeping, and the counter that links to each other with the output terminal of these two photoelectric sensors, two photoelectric sensors receive the reflected light of measurement point I, II respectively, a moving week of this transmission shaft revolution, two photoelectric sensors received respectively once, begin counting behind the signal of the measurement point that counter is set to receive earlier, stop counting after receiving the signal of another measurement point again;

4) when axle rotates under not adding the load situation, be subjected to irradiate light after measurement point I, II one elder generation one, can after the elder generation one light be reflected away, on counter, obtain a count value N accordingly ₀, this count value has just been represented the mistiming of two signals;

5) when axle rotates under load condition, because transferring power, caused axle to be subjected to torsional interaction and elastic torsion takes place be out of shape, the relative position of two measurement point I, II changes, be reflected on the counter by this point reflection light, count value changes, or increases or reduce, and its variable quantity is Δ N;

6) relatively load before and after the count value of counter, calculate the torsional deflection situation of shaft.

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