Background technology
The belt drive testbed for being used to impart knowledge to students both at home and abroad is mainly commerical test platform, and this testing stand is transmission belt factory
The testing stand that family designs and manufactured, it is not intended to the classroom instruction demonstrator of V belt translation teaching.Mainly there are DLS-B designs the country
Type V belt translation experimental bench etc. is by manually operated regulation rotating speed load, and external the main direction of development is computer distribution control type
Control, the measure of belt slip and transmission efficiency is carried out by digital-scroll technique panel reading or computer testing analysis software,
Flat belt and the measure of V-belt slip and Belt Transmission Efficiency are realized, and draws slip curve and efficiency curve automatically,
The simulation of transmission process can be carried out by computer testing analysis software, observes Elastic Sliding phenomenon.Such V belt translation experimental bench
Driven using variable-frequency motor, at PWM loads adjustment of field excitation, single-chip microcomputer control technology, microcomputer distributed control technology and experimental data
Reason and administrative skill, greatly improve the gentle experimental precision of Automated water of the experimental bench, and its cardinal principle is control driving wheel
Rotating speed is constant within the specific limits, adjusts load, determines rotating speed and the torque of driving wheel and driven pulley respectively, and according to survey
Fixed driving wheel and the rotating speed of driven pulley and torque, calculate input power, power output and transmission efficiency, according to driving wheel and from
The rotating speed and wheel footpath of driving wheel, calculate slip, and the torque when determining belt slippage under the conditions of different initial tensions.
One of basic experiment of V belt translation experiment category Machine Design, such V belt translation experimental bench is used to impart knowledge to students, using frequency conversion
Motor driving, PWM loads adjustment of field excitation, single-chip microcomputer control technology, microcomputer distributed control technology and Data Processing in Experiment and management
Technology.Its major advantage is determination data precision height, and automaticity is high.Its weak point is that the V belt translation experimental bench is directly used
When teaching and experimental demonstration, although meeting the required precision of V belt translation experimental teaching, the data measured only with transmission
With relevant major parameter is designed, such as input torque, output torque, input speed, output speed, so as to obtain slip, effect
Rate etc., this understands needed for classroom instruction and the parameter difference grasped is away from larger.Wherein, due to being not provided with belt pull mechanism, because
This can not measure initial tension, tight side tension and slack list pulling force, cause effective circle force can not calculate, and can not draw Euler's formula;
Because V belt translation load adjustment of field excitation causes when adding increment of load lotus, can only be adjusted by accessing the quantity of resistance (that is, electric light),
Although visual in image, also resulting in load increases discontinuous problem;Require that pretightning force is excessive in experiment, pilled-in selvedge can not be observed
Slack list position, load, pretightning force etc. can not be also increased continuously, can not more observe the phenomenon of elasticity skidding.
In addition, above-mentioned V belt translation experimental bench uses microcomputer distributed control technology and Data Processing in Experiment and administrative skill, make
Obtaining computer turns into the necessary component of the experimental facilities, improves the precision of experimental data, and then adds teaching input, especially
It is the explanation knowwhy that teacher can only be simple so that classroom becomes dry speech, does in the teaching of V belt translation
During experiment, student needs to review the content of teacher's explanation before testing, and has elongated the instructional blocks of time of this chapter of V belt translation significantly, and
And V belt translation experimental bench automatization level is high, pass through computer processing data so that it was observed that data become abstract, while
Reduce the ability that student starts to put into practice, experimental courses are lost its due effect and effect.
The content of the invention
The invention solves concrete technical problems be on the basis of existing V belt translation commerical test platform, be modified to class
The relevant belt pulley configured transmission of hall teaching and the play configuration of relevant nature, and a kind of V belt translation characteristic parameter measurement religion is provided
Learn apparatus for demonstrating.
The above-mentioned concrete technical problems to be solved of the present invention are achieved through the following technical solutions.
A kind of V belt translation characteristic parameter teaching mode demonstrator, including driving wheel, driven pulley, support, belt, pressure sensing
Device, velocity sensor and display instrument;It is characterized in that:
The driving wheel is that horizontal symmetrical is set with the driven pulley, and set in driving wheel and driven pulley horizontal symmetrical
Third wheel under third wheel and belt is provided with belt on center line, belt is passed through under third wheel and belt on driving wheel, driven pulley, belt
Third wheel forms tape handler, and makes angle of the belt under third wheel on belt and belt during third wheel position be 80 °~160 °;
The pressure sensor is third wheel pressure sensor on belt, third wheel pressure sensor and driven pulley pressure on belt
Sensor;It is respectively arranged on belt and crosses wheel support, belt was descended on wheel support and driven wheel support;
The velocity sensor is driven pulley photoelectric speed sensor and driving wheel photoelectric speed sensor, and is distinguished
It is arranged in the rotating shaft of driven pulley and in the rotating shaft of driving wheel;
The display instrument is under third wheel pressure sensor display instrument on belt, driven pulley pressure sensor display instrument, belt
Third wheel pressure sensor display instrument, driven pulley velocity sensor display instrument and driving wheel velocity sensor display instrument, and connect respectively
Pressure sensor and velocity sensor are connect, is arranged at display table top.
Further, additional technical feature is as follows.
Angle of the belt under third wheel on belt and belt during third wheel position is further 120 °.
The driving wheel is driven by frequency control motor.
The corresponding casing both sides of the driven wheel support are provided with baffle plate, and offer on the baffle plate and operated with belt
The opposite extension chute in direction carries out pretension to belt.
Implement a kind of above-mentioned the provided V belt translation characteristic parameter teaching mode demonstrator of the present invention, by completing
Later stage adjusts to its precision, device harmony etc., and repetition test, obtains following effect.
Instant invention overcomes the deficiency of the belt experimental provision in existing V belt translation teaching process, V belt translation teaching has been filled up
During teaching aid demonstrate blank, intuitive and convenient, be easily understood disclose V belt translation teaching various parameters measurement and
Performance demonstration, and economy, practicality and convenience are taken into full account, play during teaching aid demonstration and knowledge are lectured
Important function.
The belt pulley of this teaching mode demonstrator, axle, the structure design of support and sensor, make the pine suffered by belt
Side, pilled-in selvedge and initial tension transform into the pressure to sensor, and the equilibrium relation for dexterously applying power obtains dependency number
Value, realizes parameter measurement and performance demonstration.Compared with prior art, initial tension, tight side tension, slack list pulling force and cunning are obtained
The parameter measurement of dynamic rate, while demonstrate the checking of the overall process and Euler's formula of skidding.
This teaching mode demonstrator exists《Machine Design》In V belt translation teaching process in course, by the skin of classroom teaching
Simple lively demonstration with the abstract characteristic parameter of transmission and its complexity by this teaching mode demonstrator, to student with directly perceived
Demonstration understands, scene receives the overall process of memory, while effectively raises Classroom Teaching and efficiency, gives classroom instruction band
Vigor is carried out, and has enriched the content of courses, the teaching link of this classroom interactions, greatly improve student starts and operate energy
Power, theory teaching is combined with on-the-spot demonstration, achieve unexpected effect.
Embodiment
The embodiment of the present invention is further described in detail below in conjunction with the accompanying drawings.
Implement a kind of V belt translation characteristic parameter MEASUREMENT TEACHING apparatus for demonstrating, including driving wheel, driven pulley horizontal symmetrical are set,
Two pressure zone third wheels are located at driving wheel with driven pulley horizontal symmetrical center line, making belt pass through mistake on driving wheel, driven pulley, belt
Third wheel forms tape handler under wheel and belt, and makes angle of the belt under third wheel on belt and belt during third wheel position be
120°.Driving wheel is fixed on lucite casing by axle and bearing, and power is connected by casing rear with driving belt pulley shaft
Frequency control motor provides, and this motor uses frequency control, it is possible to achieve variable speed.Third wheel and skin on driven pulley, belt
Be separately fixed on respective support with lower third wheel, and connected by three sensors, three sensors respectively with three independences
Power supply and display are connected, and measurement acts on driven pulley, the power on third wheel.Meanwhile casing front and rear baffle at driven wheel support
Provided with sliding groove, support can slide back and forth along groove, for adjusting the pretightning force of belt wheel.Driving pulley, driven pulley front end are stretched
Instruction disk, dial are respectively provided with shaft, two plate edges are jagged, coordinate the photoelectric speed sensor mounted in plate edge,
The rotating speed of two-wheeled is measured, two velocity sensors are connected with two velocity indicators, show current rotating speed.Stretch follower shaft rear end
Go out part and be provided with loading device, the tightness of adjustment bolt, for demonstrator additional load.All parts have been each attached to
Transparent attractive in appearance in machine glass box body, observation facilitates directly perceived.
(1) using this V belt translation characteristic parameter MEASUREMENT TEACHING apparatus for demonstrating measurement pretightning force, tight side tension, slack list pulling force and
Calculate the principle and process of effective circle force
This V belt translation characteristic parameter MEASUREMENT TEACHING apparatus for demonstrating, using third wheel under third wheel on belt and belt, makes belt exist
Angle on belt under third wheel and belt during third wheel position is 120 °, passes through force analysis:
Now,Direction straight down, act on two belt third wheel pressure sensors.So, can directly lead to
Cross the pressure sensor display instrument being connected with sensor and directly read relevant parameter, it is not necessary to pass through the conversion of centre.
By belt on third wheel under third wheel on certain initial tension installation driving wheel, driven pulley, belt and belt, to form band
Transmission mechanism, at this moment the pulling force in transmission belt is equal, is all initial tension F0.When belt work, due to band and pulley contact
The effect of frictional force on face, one side that band moves into driving wheel are further tensed, and pulling force increases to F1 by F0, and this is while be referred to as
Pilled-in selvedge;Another side is then relaxed, and pulling force drops to F2 by F0, and this is while be referred to as slack list.The difference of both sides pulling force is referred to as effective pull, with
F expressions, i.e.,
F=F1-F2
Effective pull is exactly the effective circle force that V belt translation can transmit.It is not acting on the concentration of a certain fixing point
Power, but on band and pulley contact face caused frictional force summation.
During V belt translation, effective resistance moment T on driven pulley2Caused circumferential resistance FzFor
Fz=2T2/d2
During normal work, effective pull F and circumferential resistance FzIt is equal, under certain condition, institute on band and pulley contact face
Frictional force caused by energy has a limiting value, i.e. maximal friction (maximum effective circle force) Fmax, as Fmax >=FzWhen, V belt translation
It could run well.When exceeding this limiting value such as the required circumferential resistance transmitted, transmission belt will skid on belt wheel.
Power in belt is measured by rack-mount pressure sensor.Measured in this V belt translation characteristic parameter
Before teaching demonstration device work, the position of driven pulley is adjusted, thus it is possible to vary the initial tension of belt.
(2) this V belt translation characteristic parameter MEASUREMENT TEACHING apparatus for demonstrating checking Euler's formula is utilized
When just starting to skid, tight side tension F1With slack list pulling force F2Between following relationship (rotating speed is smaller) be present, i.e.,
The bottom (e ≈ 2.718) of e---natural logrithm in formula;
F---band coefficient of friction intermarginal with wheel;
Cornerite (rad) of a---transmission belt on belt wheel.
Above formula is the Euler's formula of flexible body friction.
Using the pulling force measured, it can verify that above formula is set up.
(3) this V belt translation characteristic parameter MEASUREMENT TEACHING apparatus for demonstrating observation Elastic Sliding, calculating sliding ratio and observation are utilized
The principle and process of skidding
Because band is elastomer, elongation during stress difference, make band that Elastic Sliding phenomenon occur in transmission process.
Because frictional force makes the both sides of band that different degrees of stretcher strain occur in V belt translation, since frictional force is that this kind of transmission must
Need, thus Elastic Sliding is inevitable.
Consequence is caused by Elastic Sliding:The peripheral speed of driven pulley is less than the peripheral speed of driving wheel, generates speed
Loss;Transmission efficiency is reduced, increases the abrasion of band, the life-span of shortened belt;Make band temperature rise.
The mode of measurement sliding ratio has two kinds:Manual measurement and formula calculate.
A. manual measurement
When the timing of pretightning force one of this apparatus for demonstrating, the angular displacement of each circle hysteresis driving wheel of driven pulley is exactly certain value,
Setting driving wheel, which is turn-taked, counts (circle of setting rotation 10), and the angular displacement that driven pulley lags is converted into corresponding sliding ratio and marked successively
Dial on the driven wheel, when driving wheel stops operating, the signified numerical value of pointer is current sliding ratio.
B. formula calculates
Sliding ratio ε is expressed as
Wherein
D in formulad1,dd2--- the datum diameter of driving wheel and driven pulley, mm;n1, n2--- turn of driving wheel and driven pulley
Speed, r/min.
The rotating speed of driving wheel and driven pulley can be measured by the photoelectric speed sensor on two axles, press
Sliding ratio is calculated according to formula.
When the service load increase of transmission, it is desirable to which effective pull F also increases therewith.When F reaches certain numerical value, band with
Frictional force F of the small pulley on whole contact arcfIt is up to limiting value.If service load exceedes this limiting value, band will be along whole
Individual contact arc slides, and this phenomenon is referred to as skidding.Because the cornerite in big belt wheel is always greater than the cornerite on small pulley, so beating
Cunning always starts on small pulley.
Increase load always, belt slippage phenomenon can be observed.Skidding is due to the caused band of overload on belt wheel
Slide comprehensively, skid and aggravate the abrasion for making band, secondary speed drastically reduces, or even makes transmission failure, and such case should
Avoid.
(4) this V belt translation characteristic parameter MEASUREMENT TEACHING apparatus for demonstrating error analysis
Due to the friction between belt and third wheel, make the pulling force of third wheel both sides belt unequal, according to the equilibrium relation of power
There is certain error in measured edge slack pulling force, error analysis calculation process is as follows:
In theory:F10=F20=F0,
Actually:F1+F2=2F0 F1/F2=efα=1.37 (f=0.3, α=π/3)
It can obtain:F1=1.161F0, F2=0.848F0
Belt is made a concerted effort:
The angle of F and vertical direction with joint efforts:
The actually measured pressure of sensor:F0'=Fcos α=1.047F0× cos15.5 °=1.00892F0
Finally calculate error:
Result of calculation proves that this design is feasible.
It is of the invention during V belt translation is realized on the basis of ensureing to be easy to carry in above-mentioned embodiment
The measurement and checking of multiple parameters and characteristic, intuitive and convenient, are easily understood.Just drawing is also wherein realized by the design of structure
Power, tight side tension, the ordinary surveying of slack list pulling force.Pretightning force, tight side tension, slack list pulling force and sliding ratio can intuitively be observed
Etc. various features parameter.And can easily calculates effective circle force, intuitively sees Elastic Sliding, skidding, slack list pilled-in selvedge position
Put and verify Euler's formula.So, teaching task can be completed, student can be allowed preferably to learn relevant knowledge, improves classroom
Efficiency.