【文章內(nèi)容簡(jiǎn)介】 液壓油密度 (kg/m3) λ 沿程阻力系數(shù) ξ 局部阻力系數(shù) △ p3=△ pn(Q/Qn)^2 式中 Qn閥的額定流量 (m3/s) Q通過(guò)閥的實(shí)際流量 (m3/s) △ pn閥的額定壓力損失 (Pa), 矯直 機(jī)執(zhí)行部件有主缸和 平衡缸，夾送輥擺動(dòng)缸，輥道升降缸，換輥馬達(dá)，下中輥高度調(diào)整液壓馬達(dá) ，供油管子管徑如下 名稱 D1 D2 D3 D4 D5 D6 D7 內(nèi)徑 60.3 25.4 15.9 8 19 28.6 19 最后根據(jù)標(biāo)準(zhǔn) 軟管 取值如下 液壓油選用 LHL32 液 壓 油 ， 15 ℃時(shí)該油液的運(yùn)動(dòng)粘度scmcst / 2??? ,油液密度 3/920 mkg?? 。 （ 1） 快開(kāi) 缸各工況時(shí)的壓力損失驗(yàn)算 1） 快 進(jìn)油路、回油路的壓力損失 運(yùn)動(dòng)部件最大速度為 ，最大流量為 127L/min，則液壓油在油管中的流速 1v 為： scmcmcmdqv /4 1 8m i n/2 5 0 7 6m i n/ 101 2 7442321??? ???? ? 管道流動(dòng)雷諾數(shù) 1eR 為 7 0 1 811 ???? vdvR e 1eR ＜ 2300，油液在管道內(nèi)流動(dòng)為層流，沿程阻力系數(shù) ??? eR? 。進(jìn)油管長(zhǎng)度為 3m，沿程壓力損失 1P? 為： PaPavdlP 6222111 2 ?????????? ??? 閥的壓力損失 PaP ??? 閥 ；那么進(jìn)油路總的壓力損失 進(jìn)P?為： 進(jìn)P? = 1P? + 閥P? = PaPa 666 )( ????? 由于進(jìn)出口管徑相同，要求工作速度相同，所以估算壓力損失也相同，那么回油壓力損失 也為 兆帕； △ p=+= 20 其他元件可以看成是和主缸并聯(lián)的，入出口輥道升降液壓缸速度比較高，做一驗(yàn)算，其他元件忽略。 缸各工況時(shí)的壓力損失驗(yàn)算 快進(jìn) 速度為 ，需要的最大流量為 2L/min，進(jìn)油管直徑D=16mm，則液壓油在油管中的流速 1v 為： scmcmcmdqv /2 5 0m i n/1 4 9 7 8m i n/ 42321??? ???? ? 管道流動(dòng)雷諾數(shù) 1eR 為 2 6 5 011 ???? vdvR e 1eR ＜ 2300，油液在管道內(nèi)流動(dòng)為層流，沿程阻力系數(shù) ??? eR? 。進(jìn)油管長(zhǎng)度為 10m，沿程 壓力損失 1P? 為： PaPavdlP 6222111 ?????????? ??? 閥的壓力損失 PaP ??? 閥 ；那么進(jìn)油路總的壓力損失 進(jìn)P?為： 進(jìn)P? = 1P? + 閥P? = PaPa 666 )( ????? 由于進(jìn)出口管徑相同，要求工作速度相同，所以估算壓力損失也相同，那么回油壓力損失 也為 兆帕； △ p=+= 要求工作壓力 14 兆帕，而設(shè)計(jì)的是 18 兆帕，所以這點(diǎn)壓力損失對(duì)系統(tǒng)的工作幾乎沒(méi)有影響！ 通過(guò)對(duì)主缸、 入出口輥道升降 缸各工況的壓力損失驗(yàn)算可知，液壓系統(tǒng)的油路構(gòu)及元件參數(shù)選擇滿足要求 。 21 七．總結(jié) 每次做設(shè)計(jì)感觸都不一樣，這次是做畢業(yè)設(shè)計(jì)，感觸頗多。開(kāi)始，我不會(huì)用 ＣＡＤ，在老師的強(qiáng)烈建議下，我學(xué)會(huì)了ＣＡＤ，出了我的第一張ＣＡＤ圖紙，雖然很糟糕，頗有詬病，我還是很高興，因?yàn)槲矣侄嗔艘豁?xiàng)技能，以后的路就更好走一些。 剛開(kāi)始，不知道老師的要求是什么，一直也找不到方向 感，稀里糊涂，一直在哪做三維繪圖，也沒(méi)有畫(huà)好。后來(lái)問(wèn)老師才知道不要求做三維制圖，也不用管缸，馬達(dá)等實(shí)體如何空間布置，只做系統(tǒng)圖和泵站圖，這才明白，所想與所要求的背道而馳。在明白了要求之后，出系統(tǒng)圖。 元件選型感觸最深，第一次我選擇的元件很多，很雜，在畫(huà)裝配圖時(shí)，怎么也組合不起來(lái)，很是納悶！仔細(xì)觀察油孔布置之后發(fā)現(xiàn)力氏樂(lè)的六通徑和油研的六通徑空位置不一樣。這就明白了企業(yè)原來(lái)是這么保護(hù)自己的產(chǎn)品的獨(dú)立性的。第二次選擇，全部選擇力氏樂(lè)的電磁換向閥，液控單向閥，單向節(jié)流閥，可是，還是組合不到一起來(lái)，除非管式連接，可 是老師要求的是疊加閥，怎么就疊不起來(lái)呢？問(wèn)同學(xué)，又問(wèn)老師，還是不明白，明明他們都可以疊加起來(lái)，為什么我的就不行？思來(lái)想去，突然大笑，原來(lái)我是一個(gè)很爛的月老，非要把普通閥當(dāng)作疊加閥用，能疊起來(lái)嗎？第三次，經(jīng)歷元件選型就比較順利。 選完型之后開(kāi)始畫(huà)閥臺(tái)，泵站圖。這個(gè)過(guò)程就像織繭一樣，每一個(gè)動(dòng)作都是在為最后的“房子”增磚添瓦。也許我們只有經(jīng)歷了這樣一個(gè)過(guò)程，將來(lái)才能走的更穩(wěn)！ 22 老師很好，很負(fù)責(zé)，對(duì)我們的錯(cuò)誤是直言不諱，也指導(dǎo)我們應(yīng)該如何做。在老師的指導(dǎo)下，我順利的完成了畢業(yè)設(shè)計(jì)。 謝謝老師！ 八．參考資料 《液壓元件系統(tǒng)設(shè)計(jì)》，主編周恩濤，機(jī)械工業(yè)出版社； 《機(jī)械設(shè)計(jì)手冊(cè)》，成大先主編，第五版，化學(xué)工業(yè)出版社； 《新編液壓工程手冊(cè)》，雷天覺(jué)主編，北京理工大學(xué)出版社； 《機(jī)械設(shè)計(jì)手冊(cè)》單行本，機(jī)械設(shè)計(jì)手冊(cè)編委會(huì)，機(jī)械工業(yè)出版社； 《液壓傳動(dòng)系統(tǒng)》，第三版，官忠范主編，機(jī)械工業(yè)出版社； 《機(jī)械設(shè)計(jì)課程設(shè)計(jì)》，唐增寶，常建娥主編，華中科技大學(xué)出版社； 《液壓元件》 《流體力學(xué)》 23 九．翻譯 原文： Volume or flow control valves are used to regulate speed. A was developed in earlier chapters。 the speed of an actuator depends on how much oil is pumped into it per unit of time. It is possible to regulate flow with a variable displacement pump, but in many circuits it is more practical to use a fixed displacement pump and regulate flow with a volume control valve. Flow Control Methods There are three basic methods of applying volume control actuator speeds. They are meterin, meterout and bleedoff. MeterIn Circuit In meterin operation, the flow control valve is placed between the pump and actuator. In this way, it controls the amount of fluid going into the actuator. Pump delivery in excess of the Metered amount I diverted to tank over the relief valve. With the flow control valve installed in the cylinder line as shown, flow is controlled in one direction. A check valve must be included in the flow control or placed in parallel with it for return flow. If it is desired to control directional valve. The method is highly accurate. It is used in applications where the load continually resists movement of the actuator, such as raising a vertical cylinder under load or pushing a load at a controlled speed. 24 MeterOut Circuit Meterout control is used where the load might tend to run away. The flow control is located where it will restrict exhaust flow from the actuator. To regulate speed in both directions, the valve is installed in the tank line from the directional valve. More often control is needed in only one direction and it is placed in the line between the actuator and direction valve. Here too a bypass check valve would be required for a rapid return stroke. BleedOff Circuit In a bleedoff arrangement, the flow control is bleed off the supply line from the pump and determines the actuator speed by metering a portion of the pump delivery to tank. The advantage is that the pump operates at the pressure required by the work, since excess fluid returns to tank through the flow control instead of through the relief valve. Its disadvantage is some less of accuracy because the measured flow is to tank39。 rather into the cylinder, making the latter subject to variations in the pump delivery due to changing workloads. Bleedoff circuits should not be used in applications where there is a possibility of the load running away. Types of Flow Controls Flow control valves fall into two basic categories: pressure pensated and nonpressure pensated. The latter being used where load pressures remain relatively constant and feed rates are not too critical. They may be as simple as a fixed orifice or an adjustable needle for free valve, although more sophisticated units may even include a check valve for free flow in the reverse direction. Use of nonpressure pensated valves is somewhat limited, since flow through an orifice is essentially proportional to the square root of the pressure drop across it. This means that any appreciable change in the work load would affect the feed rate. Pressure pensated flow controls are further classified as restrictor and bypass types. Both utilize a pensator or hydrostat to maintain a constant pressure drop across an adjustable throttle. The ByPass Typebines overload prote