CN2046216U - Rolling/sliding frictional factor testing instrument of gravity and small ball - Google Patents

Abstract

The utility model relates to the rolling/sliding frictional factor testing instrument of gravity and small balls, which is mainly used for testing the rolling/sliding mixed frictional factor of the gravity acceleration and a small ball body in engineering and teaching. The utility model has the structure that a small ball body is used for moving in an inner ring of a guide rail in the shape of a circular arc, the time T of one swing period of the small ball body is tested through a photoelectric door sensor and a digital timer, and then two simple mathematical formulas are used for figuring out the gravity acceleration g value and the rolling/sliding frictional factor mu value of the small ball body. The precision of g can reach 1*10+ [-5] Gal, and the precision of mu can reach 1*10+ [-3]-1*10+ [-4]. The rolling/sliding frictional factor testing instrument of gravity and small balls has the advantages of simple structure and convenient testing; the rolling/sliding frictional factor testing instrument of gravity and small balls can completely satisfy the testing requirement in an engineering field and in teaching.

Description

Rolling/sliding frictional factor testing instrument of gravity and small ball

The utility model is a kind of metrology and measurement instrument, be specially adapted in engineering and the mathematics testing laboratory to the mensuration of acceleration of gravity and in mechanical engineering, metrology and measurement engineering the testing tool of roll sliding friction coefficient.

The known measurement of acceleration of gravity in mathematics testing laboratory is to use the pendulum quasi-instrument, comprises single pendulum, physical pendulum, Ka Te pendulum, and design accuracy is low, and test result does not reach requirement.And the spheroid of still being unrealized in mechanical engineering, metrology and measurement engineering connects the mensuration of rolling sliding this mixed film friction coefficient of band on arc orbit, usually adopt coefficient of rolling friction to replace approx connecting and roll the sliding mixed film friction coefficient of band, affect the accuracy of calculating in the engineering design.

Task of the present utility model is that a kind of precision of design is up to 1 * 10 ^-6, the more satisfactory acceleration of gravity tester of test result replaces various pendulum quasi-instruments in modern project and the teaching test chamber, satisfies the demand of engineering bound pair roll sliding friction coefficient exact value simultaneously, realizes the direct mensuration to " connect to roll to be with and slide " mixed film friction coefficient.

For solving this task, can adopt the technical scheme of special " pendulum " of following no cycloid, no fork: bead is done skid along the arc-shaped rail that has angle index and is moved, when bead moves to guide rail minimum point (equilibrium position), block the light that sends by spotlight the photogate sensor that sees through from guide rail bottom rectangle finedraw, the time interval that bead is in the light for twice, semiperiod of spheroid periodic motion just is by measuring by the digital chronoscope that the flexible cord plug is connected with the photogate sensor.Complete period T according to measuring can calculate the roll sliding friction coefficient.Computing formula is (1) (derivation is omitted):

$\mathrm{\mu =}\sqrt{\frac{\mathrm{3g}}{2}-\frac{\mathrm{68\pi 2}}{\mathrm{5T2}}}\mathrm{(1)}$

In the following formula: T is the bead period of motion;

G can find from the metering handbook, and the roll sliding friction coefficient can be determined.

In order to simplify calculating, following formula can replace with following formula is approximate:

$\mathrm{\mu =}\sqrt{\frac{8}{5}·\frac{\pi }{T}}\mathrm{(2)}$

Be used for teaching measurement acceleration of gravity and can calculate (derivation is omitted) by following formula (3):

g＝ (4π2L)/(T2) （1＋ 2/15 ＋ 1/6 Sin (2θ)/2 ＋ (1·T2)/(12·π2) ·μ ²） （3）

In the following formula: L=1/2 (d-Dm)

D is the guide rail diameter;

Dm is little bulb diameter;

θ departs from the angle of guideway centreline for the bead reference position;

T is the bead period of motion;

μ utilizes formula (1) or (2) to obtain.

Gravity acceleration g can be as accurate as 1 * 10 like this ^-6Gal.

As scheme to have described an embodiment of the present utility model:

Fig. 1: front view of the present utility model,

Fig. 2: side view of the present utility model.

As shown in the figure, internal diameter is that the arc-shaped rail 1 usefulness bolt 2 of d is fixed on the instrument bearing 4 by guide rail bracket 3.On arc-shaped rail 1, print angle index, make a hole, slit 11 that is drilled with 2 * 20mm at the guide rail bottom centre position.Be fixed with photogate support 5 on the instrument bearing 4 simultaneously, photogate sensor 6 is housed on the photogate support, comprise photoelectric diode 7 and spot light lamp bulb 8 etc., by flexible cord plug 12, the photogate sensor links to each other with digital chronoscope 9.

Diameter is Dm(1＜Dm≤30, the Dm optimum dimension is 5mm) the reference position of bead from θ≤5 ° move along ring-shaped guide rail, bead moves to the equilibrium position of guide rail minimum point, both blocked the light beam that sends from photogate sensor spot light lamp bulb, and note the time interval that bead is in the light for twice in succession by digital chronoscope, 1/2 periodic quantity is converted into period T just.So then can calculate the gravity acceleration g value from formula (3) by proving the value that roll sliding friction coefficient μ is obtained in the formula (1) derived or (2).

In order to guarantee measuring accuracy, the size of its key components and parts, form and position tolerance and measuring accuracy should reach:

Spherula: 0.001 millimeter;

Arc-shaped rail: 0.01 millimeter;

Digital timer: 0.0001 second.

Like this, by the such modern design of the utility model, tester simple in structure, can realize that precision reaches 1 * 10^－6Gravity acceleration value and the mensuration of " roll and slide " mixed film friction coefficient.

Claims (3)

1, a kind ofly be used to impart knowledge to students and the acceleration of gravity and the roll sliding friction coefficient tester of engineering, it is characterized in that:

A. on the inner ring of an arc-shaped rail 1, there is a spherula 10 to do the skid motion,

B. arc-shaped rail 1 is fixed on the bearing 4 by guide rail bracket 3,

C. photogate support 5 is fixed on the bearing 4, and a photogate sensor 6 is housed on photogate support 5, and the light beam that the spotlight 8 in the photogate sensor 6 sends passes through the rectangle finedraw 11 of arc-shaped rail 1 bottom just,

D. photogate sensor 6 is connected with digital timer 9 by flexible cord plug 12.

2, gravity according to claim 1 and spherula roll sliding friction coefficient tester is characterized in that the diameter Dm of described spherula 10 should be best with Dm=5 between 1～30 millimeter.

3, gravity according to claim 1 and 2 and spherula roll sliding friction coefficient tester is characterized in that:

A. the size of spherula 10, form tolerance should≤0.001 millimeters,

B. the form tolerance of arc-shaped rail 1 is answered≤0.01 millimeter,

C. the measuring accuracy error of digital timer 9 was answered≤0.0001 second.

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