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外文資料
CAM mechanism
CAM mechanism with oscillating follower by CAM, three basic components and testing of high vice institutions. The CAM is a curve profile or groove with the component, generally to active pieces, be constant rotation movement or reciprocating linear motion.
CAM mechanism with oscillating follower by CAM, three basic components and testing of high vice institutions.
The CAM is a curve profile or groove with the component, generally to active pieces, be constant rotation movement or reciprocating linear motion.
And the CAM contour contacts, and transfer power and for achieving the component, the movement rule of general do reciprocating linear motion or wobble, called a follower.
CAM in the application basic features can make follower get more complex movement rules. Because follower motion depends on the CAM contour curve, so the application, as long as the motion law of according to follower to design the CAM contour curve.
CAM is widely used in various automatic machinery, equipment
Disc CAM, cylindrical CAM and mobile CAM etc, with cylindrical CAM groove curve is the space curve, thus belong to spatial CAM. CAM follower and make contacts or line contact, have roller follower, flat-bottomed follower and sophisticated follower, etc. Tip with any complex follower of CAM contour maintain contact, may realize the arbitrary exercise, but sophisticated easy wear and applicable YuChuanLi smaller low-speed institutions. In order to make the CAM follower and always maintain contact, can use nukes
Reed or exerting gravity. With the CAM groove can make follower of sports, for transfer to determine that a dynamic CAM. Usually the CAM is active, but also have driven or fixed CAM. Most of the CAM is
single-degree-of-freedom, but also have double dof conoid CAM. Compact structure, CAM follower is most suitable for requirements for intermittent movement occasion. It and hydraulic and pneumatic of similar institutions comparison, sports and reliable, so in automatic lathes, internal combustion engines, m. presses and widely used. But CAM mechanism, wear easily, have noise of high-speed CAM design is more complex, manufacturing requirements is higher.
classification
CAM classification:
According to the CAM shape points
1) disc CAM
2) mobile CAM
3) cylindrical CAM
Press follower type points
1) pointed bottom follower;
2) roller follower;
3) flat-bottomed follower
According to maintain high vice contact points (lock match)
1) force lock match: spring force, gravity, etc;
2) geometric lock match: equal-diameter CAM, width CAM;
advantages
Simple and compact structure, design is convenient, can achieve follower arbitrary expected sport, so in machine tools, textile machinery, light industry machinery, printing machinery, electromechanical integration assemble extensively applied.
faults
1) dot, line contact wear easily;
2) CAM contour machining difficulty;
3) trip is not big
Follower motion rule
With roller in the head-on straight moving follower disc CAM (figure 2), CAM follower turn in a week for litres - stop - drop - stop 4 movement.
The CAM is a curve profile or groove with the component, generally to active pieces, be constant rotation movement or reciprocating linear motion. Follower displacement s (or stroke height (h) and CAM corner Φ (or time t) called the relationship displacement curve. Follower trip h pushing process and return. CAM contour curve displacement curve shape depends. In some mechanical, by the process of displacement curve decision, but usually only stroke and the corresponding CAM corner according to work need to decide, and the shape of the curve is selected by the designer, can have a variety of sports laws. The traditional CAM movement rules have accelerated - such as constant, speed and cosine acceleration and sine acceleration, etc. Constant movement rules for a speed mutations, will produce strong rigid impact, only suitable for low speed. Slow down and speed - such as the acceleration speed mutations add 8031, can cause flexible impact, only applies to medium, low speed. Sine acceleration movement rules of acceleration curve is continuous, without any impact, can be used for high speed.
In order to make the acceleration of CAM motion and its speed rate is too large, taking into account the momentum, vibration, CAM size, spring size and process requirements, etc, still can design the various other movement rules. Application more useful segments curve combination becomes movement rules, such as deformation sine acceleration, deformation trapezoid acceleration and deformation constant movement rules etc., using electronic computer can also optional combination into various movement rules. Still can use polynomial says movement rules, and to get a continuous acceleration curve. In order to obtain the most satisfied with the acceleration curve, still can give a with numerical form any acceleration curve, and then use the finite difference method for displacement curve, finally designed CAM contour line.
Some automata usually use several CAM coordination work, in order to make each CAM control each part of a coordinated actions, still must CAM
Design before compiling a correct movement cycle figure.
And reduce surface roughness. CAM working conditions is the air is dry, lubricating oil clean, or use with a variety of additives lubricating oil. Lubricant viscosity and oil-supplied way choice to consider the shape and CAM follower of speed, etc. CAM and follower of materials should be appropriately, such as a hard to match the cheap steel and cast iron, suitable for high speed sliding; Hardened steel and phosphorus bronze vibration and noise is small, still can compensate outline of are not accurate. Cast steel and cast iron matching use effect is fair. But hard nickel steel and hard nickel steel, mild steel and mild steel etc is the effect not beautiful combination of. For geometry parameters, lubrication, materials and surface roughness etc, also can use elastohyddrodynamic lubrication theory, in order to reduce wear integrated computation.
Improve life CAM contour line design
The illustrations and analytical design CAM in two ways. To bring the roller head-on straight moving follower, for example, graphic method, in determining the Φ, displacement curve s initial position and CAM roller center after yankees r0 circle radius, CAM contour line can be obtained by inversion, even convex motionless, find out a series of relative to the CAM roller with smooth curve position, connecting the roller center B1, B2,
B3. The theory of such point asking CAM profiling, to make these roller envelope that get the actual contour of CAM. Choose roller radius rr, the theoretical contour should be less than the minimum radius of curvature, lest produce interference. Also, with analytical method to determine the first follower displacement change rule s = s (Φ), base circle radius r0 and roller radius, thereby get rr theoretical contour of CAM x = - the parameter equation , y = rcos rsi Φ, type of r = r0 + s. CAM actual contour line is composed of a series of roller round the envelope curve clan, clan for the equation curve, Φ y1 clamps its x1 f (x) = (2 + clamps its x1 - y1 - y) 2 - r = 0, so connections f (y1, Φ clamps its x1, may have curve) = 0, namely the envelope family of actual contour (see conjugate curves).
Base circle radius chosen smaller,, the greater the pressure Angle of CAM design income to size are small, but unfavorable force, serious still can happen self-locking phenomenon, so in space allows conditions should adopt the larger base circle radius to improve the stress of the CAM.
Use electronic computers convex contour line design can improve efficiency and comprehensive consideration from various optimized design. This can be used to get all kinds of sports laws of the follower displacement, velocity and acceleration equivalence and convex profile coordinates, calculate CAM contour line the curvature radius, arbitrary point pressure Angle and stress, meet the contact intensity and anti-wear Angle, for minimal size of the CAM, and still can draw the CAM space graphics.
By grinding measures
CAM easy to wear, one of the main reasons is contact stress is bigger. The roller CAM and the contact stress can be considered separately equal to pick. CAM radius
Touch the curvature radius and in the two YuanZhuMian contact roller radius of compressive stress, and the calculation formulas used polarized should make the calculation stress less than allowable stress. Prompted CAM wear factors and load characteristics, geometric parameter, materials, surface roughness, corrosion, sliding, lubrication and processing, etc. Which lubricates and material choice to wear life influence especially large. In order to reduce wear, improve service life, in addition to limit the contact stress of heat treatment and surface chemistry will be taken measures such as low load running-in, in order to improve the material surface hardness.
Must regard driven system as a flexible system to design. System output terminal part of the movement( Φ) with CAM "s the part of the sport s contact
(Φ) the differences, the so-called displacement response. Therefore shall first be reasonably selected s (Φ), obtained( Φ), then sc (Φ) by ask CAM contour line. It can be applied to the bearing capacity of the elastohyddrodynamic lubrication theory calculation method. High-speed CAM follower for larger, more than spring in inertia force and other plus force may open CAM contour line instantaneous off, produce beating and cause vibration. For indeed move CAM groove, with from one side to the other side contact often can cause shock vibration. This phenomenon can through the reasonable choice of motion, a properly designed spring and improving system solution to rigid, etc. High-speed CAM shall also have the high profile manufacture accuracy and low surface roughness and properly choose oil and lubrication method.
中文譯文
凸輪機(jī)構(gòu)是由凸輪，從動(dòng)件和機(jī)架三個(gè)基本構(gòu)件組成的高副機(jī)構(gòu)。 凸輪是一個(gè)具有曲線輪廓或凹槽的構(gòu)件，一般為主動(dòng)件，作等速回轉(zhuǎn)運(yùn)動(dòng)或往復(fù)直線運(yùn)動(dòng)。
凸輪機(jī)構(gòu)是由凸輪，從動(dòng)件和機(jī)架三個(gè)基本構(gòu)件組成的高副機(jī)構(gòu)。
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凸輪機(jī)構(gòu)
凸輪是一個(gè)具有曲線輪廓或凹槽的構(gòu)件，一般為主動(dòng)件，作等速回轉(zhuǎn)運(yùn)動(dòng)或往復(fù)直線運(yùn)動(dòng)。
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凸輪機(jī)構(gòu)
與凸輪輪廓接觸，并傳遞動(dòng)力和實(shí)現(xiàn)預(yù)定的運(yùn)動(dòng)規(guī)律的構(gòu)件，一般做往復(fù)直線運(yùn)動(dòng)或擺動(dòng)，稱為從動(dòng)件。
凸輪機(jī)構(gòu)在應(yīng)用中的基本特點(diǎn)在于能使從動(dòng)件獲得較復(fù)雜的運(yùn)動(dòng)規(guī)律。因?yàn)閺膭?dòng)件的運(yùn)動(dòng)規(guī)律取決于凸輪輪廓曲線，所以在應(yīng)用時(shí)，只要根據(jù)從動(dòng)件的運(yùn)動(dòng)規(guī)律來設(shè)計(jì)凸輪的輪廓曲線就可以了。
凸輪機(jī)構(gòu)廣泛應(yīng)用于各種自動(dòng)機(jī)械、儀器和操縱控制裝置。凸輪機(jī)構(gòu)之所以得到如此廣泛的應(yīng)用，主要是由于凸輪機(jī)構(gòu)可以實(shí)現(xiàn)各種復(fù)雜的運(yùn)動(dòng)要求，而且結(jié)構(gòu)簡(jiǎn)單、緊湊。
由凸輪的回轉(zhuǎn)運(yùn)動(dòng)或往復(fù)運(yùn)動(dòng)推動(dòng)從動(dòng)件作規(guī)定往復(fù)移動(dòng)或擺動(dòng)的機(jī)構(gòu)。凸輪具有曲線輪廓或凹槽，有
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凸輪機(jī)構(gòu)
盤形凸輪、圓柱凸輪和移動(dòng)凸輪等，其中圓柱凸輪的凹槽曲線是空間曲線，因而屬于空間凸輪。從動(dòng)件與凸輪作點(diǎn)接觸或線接觸，有滾子從動(dòng)件、平底從動(dòng)件和尖端從動(dòng)件等。尖端從動(dòng)件能與任意復(fù)雜的凸輪輪廓保持接觸，可實(shí)現(xiàn)任意運(yùn)動(dòng)，但尖端容易磨損，適用于傳力較小的低速機(jī)構(gòu)中。為了使從動(dòng)件與凸輪始終保持接觸，可采用彈
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凸輪機(jī)構(gòu)
簧或施加重力。具有凹槽的凸輪可使從動(dòng)件傳遞確定的運(yùn)動(dòng)，為確動(dòng)凸輪的一種。一般情況下凸輪是主動(dòng)的，但也有從動(dòng)或固定的凸輪。多數(shù)凸輪是單自由度的，但也有雙自由度的劈錐凸輪。凸輪機(jī)構(gòu)結(jié)構(gòu)緊湊，最適用于要求從動(dòng)件作間歇運(yùn)動(dòng)的場(chǎng)合。它與液壓和氣動(dòng)的類似機(jī)構(gòu)比較，運(yùn)動(dòng)可靠，因此在自動(dòng)機(jī)床、內(nèi)燃機(jī)、印刷機(jī)和紡織機(jī)中得到廣泛應(yīng)用。但凸輪機(jī)構(gòu)易磨損，有噪聲，高速凸輪的設(shè)計(jì)比較復(fù)雜，制造要求較高。
凸輪機(jī)構(gòu)的分類：
按凸輪形狀分
1）盤形凸輪
2）移動(dòng)凸輪
3）圓柱凸輪
按從動(dòng)件型式分
1）尖底從動(dòng)件；
2）滾子從動(dòng)件；
3）平底從動(dòng)件
按維持高副接觸分
1）力鎖合：彈簧力、重力等；
2）幾何鎖合：等徑凸輪、等寬凸輪；
優(yōu)點(diǎn)
結(jié)構(gòu)簡(jiǎn)單、緊湊、設(shè)計(jì)方便，可實(shí)現(xiàn)從動(dòng)件任意預(yù)期運(yùn)動(dòng)，因此在機(jī)床、紡織機(jī)械、輕工機(jī)械、印刷機(jī)械、機(jī)電一體化裝配中大量應(yīng)用。
缺點(diǎn)
1）點(diǎn)、線接觸易磨損；
2）凸輪輪廓加工困難；
3）行程不大
從動(dòng)件運(yùn)動(dòng)規(guī)律
在帶滾子的對(duì)心直動(dòng)從動(dòng)件盤形凸輪機(jī)構(gòu)（圖2）中,凸輪回轉(zhuǎn)一周從動(dòng)件依次作升-停-降-停4個(gè)動(dòng)作。
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凸輪機(jī)構(gòu)
從動(dòng)件位移s（或行程高度h）與凸輪轉(zhuǎn)角Φ（或時(shí)間t）的關(guān)系稱為位移曲線。從動(dòng)件的行程h有推程和回程。 凸輪輪廓曲線決定于位移曲線的形狀。在某些機(jī)械中，位移曲線由工藝過程決定，但一般情況下只有行程和對(duì)應(yīng)的凸輪轉(zhuǎn)角根據(jù)工作需要決定，而曲線的形狀則由設(shè)計(jì)者選定，可以有多種運(yùn)動(dòng)規(guī)律。傳統(tǒng)的凸輪運(yùn)動(dòng)規(guī)律有等速、等加速－等減速、余弦加速度和正弦加速度等。等速運(yùn)動(dòng)規(guī)律因有速度突變，會(huì)產(chǎn)生強(qiáng)烈的剛性沖擊，只適用于低速。等加速-等減速和余弦加速度也有加速度突變,會(huì)引起柔性沖擊，只適用于中、低速。正弦加速度運(yùn)動(dòng)規(guī)律的加速度曲線是連續(xù)的，沒有任何沖擊，可用于高速。
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凸輪機(jī)構(gòu)
為使凸輪機(jī)構(gòu)運(yùn)動(dòng)的加速度及其速度變化率都不太大，同時(shí)考慮動(dòng)量、振動(dòng)、凸輪尺寸、彈簧尺寸和工藝要求等問題，還可設(shè)計(jì)出其他各種運(yùn)動(dòng)規(guī)律。應(yīng)用較多的有用幾段曲線組合而成的運(yùn)動(dòng)規(guī)律，諸如變形正弦加速度、變形梯形加速度和變形等速的運(yùn)動(dòng)規(guī)律等，利用電子計(jì)算機(jī)也可以隨意組合成各種運(yùn)動(dòng)規(guī)律。還可以采用多項(xiàng)式表示的運(yùn)動(dòng)規(guī)律，以獲得一連續(xù)的加速度曲線。為了獲得最滿意的加速度曲線，還可以任意用數(shù)值形式給出一條加速度曲線，然后用有限差分法求出位移曲線，最后設(shè)計(jì)出凸輪廓線。
一些自動(dòng)機(jī)通常用幾個(gè)凸輪配合工作，為了使各個(gè)凸輪所控制的各部分動(dòng)作配合協(xié)調(diào)，還必須在凸輪
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凸輪機(jī)構(gòu)
設(shè)計(jì)以前先編制一個(gè)正確的運(yùn)動(dòng)循環(huán)圖。
和降低表面粗糙度。凸輪的工作條件是空氣干燥、潤(rùn)滑油潔凈，或采用加有各種添加劑的潤(rùn)滑油。潤(rùn)滑油的粘度和供油方式的選擇要考慮從動(dòng)件的形狀和凸輪的轉(zhuǎn)速等。凸輪和從動(dòng)件的材料匹配應(yīng)適當(dāng)，如硬鋼和鑄鐵價(jià)廉，適用于高速滑動(dòng)；硬鋼和磷青銅的振動(dòng)和噪聲小，還能補(bǔ)償輪廓的不精確。鑄鐵和鑄鐵配對(duì)使用效果尚可。但硬鎳鋼和硬鎳鋼、軟鋼和軟鋼等的組合則效果不佳。對(duì)于幾何參數(shù)、潤(rùn)滑、材料和表面粗糙度等，也可采用彈性流體動(dòng)壓潤(rùn)滑理論進(jìn)行綜合計(jì)算，以減少磨損。
凸輪壽命設(shè)計(jì)
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凸輪機(jī)構(gòu)
設(shè)計(jì)凸輪有圖解和解析兩種方法。以帶滾子的對(duì)心直動(dòng)從動(dòng)件為例，用圖解法時(shí)，在確定位移曲線 sΦ、滾子中心初始位置和凸輪基圓半徑r0后，凸輪廓線可由反轉(zhuǎn)法得到,即使凸不動(dòng)，找出滾子相對(duì)于凸輪的一系列位置，用光滑曲線連接各滾子中心B1、B2、
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凸輪機(jī)構(gòu)
B3……等點(diǎn)即得凸輪的理論廓線，再作這些滾子的包絡(luò)線即得到凸輪的實(shí)際廓線。選擇滾子半徑rr,應(yīng)小于理論廓線的最小曲率半徑,以免產(chǎn)生干涉。用解析法時(shí),同樣先要確定從動(dòng)件的位移變化規(guī)律s=s(Φ)、基圓半徑r0和滾子半徑rr,從而得到凸輪理論廓線的參數(shù)方程x＝-rsiΦ,y＝rcosΦ,式中r=r0+s。凸輪實(shí)際廓線是一系列滾子圓組成的曲線族的包絡(luò)線，曲線族的方程為f(x1,y1Φ)=(x1-x)2+(y1-y)2-r婄=0，所以聯(lián)解f(x1，y1，Φ)＝0可得曲線族的包絡(luò)線，即實(shí)際廓線（見共軛曲線）。
基圓半徑選得越小，壓力角越大，設(shè)計(jì)所得的凸輪尺寸雖小，但對(duì)受力情況不利，嚴(yán)重的還會(huì)發(fā)生自鎖現(xiàn)象，因此在空間允許的條件下應(yīng)選取較大的基圓半徑以改善凸輪的受力情況。
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凸輪機(jī)構(gòu)
用電子計(jì)算機(jī)進(jìn)行凸輪廓線設(shè)計(jì)能提高效率，并能從多方面綜合考慮進(jìn)行優(yōu)化設(shè)計(jì)。這樣可用以求得各種運(yùn)動(dòng)規(guī)律下的從動(dòng)件的位移、速度、加速度等值和凸輪廓線坐標(biāo)值，算出凸輪廓線上任意點(diǎn)的曲率半徑、壓力角和應(yīng)力，滿足接觸強(qiáng)度和抗磨的角度，以獲得最小尺寸的凸輪，而且還可畫出凸輪的空間圖形。
凸輪容易磨損，主要原因之一是接觸應(yīng)力較大。凸輪與滾子的接觸應(yīng)力可以看作是半徑分別等于凸輪接
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凸輪機(jī)構(gòu)
觸處的曲率半徑和滾子半徑的兩圓柱面接觸時(shí)的壓應(yīng)力，可用赫芝公式進(jìn)行計(jì)算，應(yīng)使計(jì)算應(yīng)力小于許用應(yīng)力。促使凸輪磨損的因素還有載荷特性、幾何參數(shù)、材料、表面粗糙度、腐蝕、滑動(dòng)、潤(rùn)滑和加工情況等。其中潤(rùn)滑情況和材料選擇對(duì)磨損壽命影響尤大。為了減小磨損、提高使用壽命，除限制接觸應(yīng)力外還要采取表面化學(xué)熱處理和低載跑合等措施，以提高材料的表面硬度。
須把從動(dòng)系統(tǒng)當(dāng)作是一個(gè)彈性系統(tǒng)來設(shè)計(jì)。系統(tǒng)輸出端部分的運(yùn)動(dòng) sΦ)和同凸輪接觸端部分的運(yùn)動(dòng)s
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凸輪機(jī)構(gòu)
(Φ)存在著差異，即所謂位移響應(yīng)。因此應(yīng)首先合理地選定s(Φ),從而求得sc(Φ),然后由sc(Φ)求凸輪廓線。它的承載能力也可應(yīng)用彈性流體動(dòng)壓潤(rùn)滑理論的計(jì)算方法。高速凸輪從動(dòng)件因慣性力較大，在超過彈簧力和其他外加力時(shí)可能瞬時(shí)脫開凸輪廓線，產(chǎn)生跳動(dòng)而引起振動(dòng)。對(duì)于具有凹槽的確動(dòng)凸輪，從一側(cè)轉(zhuǎn)向另一側(cè)接觸往往會(huì)引起沖擊振動(dòng)。這種現(xiàn)象可以通過合理選擇運(yùn)動(dòng)規(guī)律、正確設(shè)計(jì)彈簧和提高系統(tǒng)的剛性等辦法來解決。高速凸輪還應(yīng)有很高的輪廓制造精度和較低的表面粗糙度，并適當(dāng)選擇潤(rùn)滑油和潤(rùn)滑方法。