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譯文題目： Machine Tool Hydraulic System
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20xx年 2月 27日
Machine Tool Hydraulic System
Hydraulic transmission There are many outstanding advantages, it is widely used, such as general industrial use of plastics processing machinery, the pressure of machinery, machine tools, etc.; operating machinery engineering machinery, construction machinery, agricultural machinery, automobiles, etc.; iron and steel industry metallurgical machinery, lifting equipment, such as roller adjustment device; civil water projects with flood control and dam gate devices, bed lifts installations, bridges and other manipulation of institutions; speed turbine power plant installations, nuclear power plants, etc.; ship from the deck heavy machinery (winch), the bow doors, bulkhead valve, stern thruster, etc.; special antenna technology giant with control devices, measurement buoys, movements such as rotating stage; military industrial control devices used in artillery, ship devices, aircraft simulation, aircraft retractable landing gear and rudder control devices and other devices.
A complete hydraulic system consists of five parts, namely, power components, the implementation of components, control components, auxiliary components and hydraulic oil.
The role of dynamic components of the original motive fluid is into mechanical energy to the pressure that the hydraulic system of pumps, it is to power the entire hydraulic system. The structure of the form of hydraulic pump is generally pump, vane pump and piston pump.
Implementation of components (such as hydraulic cylinders and hydraulic motors) which is the pressure of the liquid can be converted to mechanical energy to drive the load for a straight line reciprocating movement or rotational movement.
Control components (that is, the various hydraulic valves) in the hydraulic system to control and regulate the pressure of liquid, flow rate and direction. According to the different control functions, hydraulic pressure control valve can be divided into valves, flow control valves and directional control valve. Pressure control valves are divided into benefits flow valve (safety valve), pressure relief valve, sequence valve, pressure relays, etc.; flow control valves including throttle, adjusting the valves, flow diversion valve sets, etc.; directional control valve includes a one-way valve , one-way fluid control valve, shuttle valve, valve and so on. Under the control of different ways, it can be divided into the hydraulic valve control switch valve, control valve and set the value of the ratio control valve.
Auxiliary components, including fuel tanks, oil filters, tubing and pipe joints, seals, pressure gauge, oil level, such as oil dollars.
Hydraulic oil in the hydraulic system is the work of the energy transfer medium, there are a variety of mineral oil, emulsion oil hydraulic molding Hop categories.
The role of the hydraulic system is to help humanity work. Mainly by the implementation of components turn pressure into a rotating or reciprocating motion.
Hydraulic principle ：it consists of two cylinders of different sizes and composition of fluid in the fluid full of water or oil. Water is called "hydraulic press"; the said oilfilled "hydraulic machine." Each of the two liquid a sliding piston, if the increase in the small piston on the pressure of a certain value, according to Pascal's law, small piston to the pressure of the pressure through the liquid passed to the large piston, piston top will go a long way to go. Based cross-sectional area of the small piston is S1, plus a small piston in the downward pressure on the F1. Thus, a small piston on the liquid pressure to P = F1/SI, Can be the same size in all directions to the transmission of liquid. "By the large piston is also equivalent to the inevitable pressure P. If the large piston is the cross-sectional area S2, the pressure P on the piston in the upward pressure generated F2 = PxS2 Cross-sectional area is a small multiple of the piston cross-sectional area. From the type known to add in a small piston of a smaller force, the piston will be in great force, for which the hydraulic machine used to suppress plywood, oil, extract heavy objects, such as forging steel.
The present invention relates to a hydraulic system in a machine, particularly suitable for the drive of a member, such as a machine tool cutter, which may be subjected to a suddenly increasing load.
When the load on a hydraulically driven machine tool member, such as a slide or rotating tool, increases, the load on the hydraulic motor which drives the member increases accordingly. With this increased load, the pressure of the hydraulic fluid supplied through a pressure line by a pump to the inlet side of the motor increases, and the fluid undergoes a slight compression. To provide continued operation of the motor without a drop in speed, the pump must not only supply the fluid required to keep the motor operating at the desired speed, but, because of the pressure increase resulting from the increased load, must also supply additional fluid to make up for the compression of fluid in the pressure line.
If the increase of load on the motor is gradual, the compression of fluid in the pressure line is gradual and, under these conditions, the pump can usually supply fluid at a rate to compensate for the gradual compression of fluid in the pressure line while, at the same time, supplying sufficient fluid at the rate required to keep the motor operating without a significant drop in speed. However, a sudden increase of the load on the motor results in a sudden compression of the fluid in the pressure line, and fluid for continued operation of the motor is not available until the pump has had time to supply the additional fluid in the pressure line required because of the compression of the fluid therein.
In some instances, particularly where the pressure line between the pump and the motor is relatively long, the momentary hesitation resulting from the application of a sudden load can have serious consequences. For example, in a large milling machine, where a cutter mounted on a carriage is rotated by a hydraulic motor mounted on the carriage remote from the pump in the base, a sudden increase in the load on the motor due, for example, to full sudden engagement of the cutter with a workpiece, will cause the motor to hesitate until the long pressure line between the pump and the motor can be filled by the pump as the fluid in the line compresses under the increased pressure therein caused by the increased load. However, during the time required for the pump to supply the fluid necessary to compensate for compression in the pressure line fluid, relative feed movement between the carrier and workpiece continues, increasing the load on the motor. This can cause a complete stalling of the cutter and fracture thereof as the feed movement continues.
One solution to this problem would be the installation of a large flywheel on the cutter spindle. With the cutter spindle rotating at the desired speed before the cutter is subjected to a sudden increase in load, the flywheel would define a source of stored kinetic energy which would be instantly available to keep the cutter spindle and cutter rotating while the pump is supplying fluid to the pressure line to compensate for the compression of fluid therein. However, the weight of the flywheel increases wear on the spindle bearings, and the increased inertia of the spindle cutter slows down starting and stopping of the cutter. Moreover, one advantage in using a hydraulic motor on a tool carriage to drive the tool instead of an electric motor lies in its lighter weight, which is more easily supported by the carriage, and the use of a flywheel on the spindle cutter would substantially diminish this advantage. Finally, the use of a flywheel is applicable only with rotary driven members.
Another possible solution would be to increase the capacity of the pump supplying the hydraulic motor, or provide additional pump capacity available to the hydraulic motor, so that the demands of the hydraulic motor can be met at the same time the pump is supplying additional fluid to the pressure line to make up for the compression of the fluid therein when the load on the cutter increases sharply. Despite the fact that only a relatively small amount of fluid is required in the pressure line to compensate for compression of fluid therein, there is, in the case of a cutter being continuously fed into the work, only a very short time available to supply this fluid, and any additional pump capacity provided to meet this infrequent demand would have to be impractically large to be capable of supplying fluid at the high rate needed.
In the present invention there is provided a hydraulic system which, like the flywheel, provides a source of energy instantly available when a sudden load in encountered, but which offers many advantages over the flywheel. With the present invention, fluid can be supplied to the pressure line leading to the inlet side of the motor when needed at a high rate without the expense of large pump capacity. In brief, an auxiliary source of stored fluid under high pressure is provided for the hydraulic motor. This source is normally isolated from the motor, and is connected to the inlet side of the motor only when a sudden increase in load on the motor is encountered. Since only a small amount of fluid is required at a high rate, the auxiliary source of fluid under pressure is connected only briefly to the inlet side of the motor and when disconnected therefrom, is recharged. It is important, in the system of the present invention, that the auxiliary source of fluid under pressure be normally isolated from the pressure line leading to the inlet side of the motor. If such a source were continuously connected to this line, it would take fluid from the line when the pressure in the line was high and deliver fluid to the line when the pressure in the line was low. To prevent stalling of a hydraulic motor encountering a sudden load in accordance with the present invention, however, it is necessary that fluid be supplied at a high rate to the line leading to the inlet side of the motor when the pressure in that line is rising.
In the preferred form of the invention, the auxiliary source of stored hydraulic fluid under pressure comprises a hydraulic pressure accumulator which may be conveniently located in the base of the machine, a blocking valve which is preferably located near the motor, and a line connecting the accumulator to the blocking valve. The discharge line from the motor contains a restriction to establish a back pressure in the discharge line between the motor and the restriction which varies as the speed of the motor varies. The blocking valve has an operating port connected to the discharge line between the motor and the restriction, and has a discharge port connected to the inlet side of the motor. The instant the member, such as a rotary tool, driven by the hydraulic motor encounters a load sufficiently sudden to slow the hydraulic motor significantly, the back pressure drops to operate the blocking valve for the release of a surge of fluid under high pressure from the auxiliary source to the inlet side of the motor. This surge of fluid compensates for compression of the fluid in the line between the pump and the inlet side of the motor so that the motor can instantly resume normal speed despite the increase in load on the motor. As soon as the motor resumes speed, the accumulator is again isolated from the motor.
Unlike the mechanical flywheel, this system does not increase wear of the spindle bearings, does not prolong starting and stopping of the spindle, and can be utilized to overcome sudden large loads applied to a slide as well as those applied to a rotary member.
In a machine tool having a pump in the base, and having a movable carriage with a hydraulic drive motor thereon to drive, for example, a rotary tool mounted on the carriage, the accumulator, which is relatively heavy, is preferably mounted in the base, and the blocking valve is preferably mounted on the carriage.
It is therefore one object of the present invention to provide a hydraulic system operable to prevent stalling of a hydraulic drive motor when subjected to a sudden load.
機床液壓系統(tǒng)
液壓傳動有許多突出的優(yōu)點，它的應(yīng)用非常廣泛，如一般工業(yè)用的塑料加工機械、壓力機械、機床等；行走機械中的工程機械、建筑機械、農(nóng)業(yè)機械、汽車等；鋼鐵工業(yè)用的冶金機械、提升裝置、軋輥調(diào)整裝置等；土木水利工程用的防洪閘門及堤壩裝置、河床升降裝置、橋梁操縱機構(gòu)等；發(fā)電廠渦輪機調(diào)速裝置、核發(fā)電廠等等；船舶用的甲板起重機械（絞車）、船頭門、艙壁閥、船尾推進器等；特殊技術(shù)用的巨型天線控制裝置、測量浮標、升降旋轉(zhuǎn)舞臺等；軍事工業(yè)用的火炮操縱裝置、船舶減搖裝置、飛行器仿真、飛機起落架的收放裝置和方向舵控制裝置等。
一個完整的液壓系統(tǒng)由五個部分組成，即動力元件、執(zhí)行元件、控制元件、輔助元件和液壓油。
動力元件的作用是將原動機的機械能轉(zhuǎn)換成液體的壓力能，指液壓系統(tǒng)中的油泵，它向整個液壓系統(tǒng)提供動力。液壓泵的結(jié)構(gòu)形式一般有齒輪泵、葉片泵和柱塞泵。
執(zhí)行元件(如液壓缸和液壓馬達)的作用是將液體的壓力能轉(zhuǎn)換為機械能，驅(qū)動負載作直線往復運動或回轉(zhuǎn)運動。
控制元件(即各種液壓閥)在液壓系統(tǒng)中控制和調(diào)節(jié)液體的壓力、流量和方向。根據(jù)控制功能的不同，液壓閥可分為壓力控制閥、流量控制閥和方向控制閥。壓力控制閥又分為溢流閥(安全閥)、減壓閥、順序閥、壓力繼電器等；流量控制閥包括節(jié)流閥、調(diào)整閥、分流集流閥等；方向控制閥包括單向閥、液控單向閥、梭閥、換向閥等。根據(jù)控制方式不同，液壓閥可分為開關(guān)式控制閥、定值控制閥和比例控制閥。
輔助元件包括油箱、濾油器、油管及管接頭、密封圈、壓力表、油位油溫計等。
液壓油是液壓系統(tǒng)中傳遞能量的工作介質(zhì)，有各種礦物油、乳化液和合成型液壓油等幾大類。
液壓系統(tǒng)的作用就是幫助人類做工。主要是由執(zhí)行元件把壓力變成轉(zhuǎn)動或往復運動。
液壓的原理則是由兩個大小不同的液壓缸組成的，在液壓缸里充滿水或油。充水的叫“水壓機”；充油的稱“油壓機”。兩個液缸里各有一個可以滑動的活塞，如果在小活塞上加一定值的壓力，根據(jù)帕斯卡定律，小活塞將這一壓力通過液體的壓強傳遞給大活塞，將大活塞頂上去。設(shè)小活塞的橫截面積是S1，加在小活塞上的向下的壓力是F1。于是，小活塞對液體的壓強為P=F1/SI, 能夠大小不變地被液體向各個方向傳遞”。大活塞所受到的壓強必然也等于P。若大活塞的橫截面積是S2，壓強P在大活塞上所產(chǎn)生的向上的壓力F2=PxS2截面積是小活塞橫截面積的倍數(shù)。從上式知，在小活塞上加一較小的力，則在大活塞上會得到很大的力，為此用液壓機來壓制膠合板、榨油、提取重物、鍛壓鋼材等。
而本發(fā)明則涉及了一種在機器中的液壓系統(tǒng)，這種液壓系統(tǒng)特別適合于一種部件的驅(qū)動，如機床刀具的切割，很可能會受到突然增加的負載所影響。
當負載在液壓驅(qū)動機床部件中，如滑動或旋轉(zhuǎn)工件中增加時，構(gòu)件的液壓馬達驅(qū)動的負載也相應(yīng)的增加。隨著負荷的增加，由液壓泵到液壓泵入口處的液壓油的壓力也會隨之增加，并且液壓油還會被輕微的壓縮。為了保證運行的電機在速度方面不會下降，該液壓泵不僅必須要供應(yīng)所需的液壓油以保持電動機操作所需的速度，而且，由于壓力增加而產(chǎn)生的負載增加，還必須提供額外的液壓油來彌補之前在高壓回路中被壓縮的液壓油。
如果電機上負載的增加是漸進的，在高壓回路中液壓油被壓縮的速率也是漸進的，在這種情況下，該液壓泵通?？梢砸砸欢ǖ乃俾侍峁┮簤河?，用來補償在高壓回路中逐漸被壓縮的液壓油，同時，按這個速率提供足夠的液壓油，以保持液壓泵運行所需的速度沒有顯著下降。然而，液壓泵負載的突然增加會導致在高壓回路中液壓油被突然壓縮，并且直到該液壓泵有時間來提供在高壓回路中所需的額外的液壓油，否則的話，由于被壓縮的液壓油，那么為保持電機持續(xù)運動所提供的液壓油是不可用的。
在某些情況下，特別是在泵和電機之間的高壓回路是比較長的情況下，由于負載的突然出現(xiàn)而引起的短暫的停頓很有可能會產(chǎn)生嚴重的后果。例如，在一個大型銑床內(nèi)，被安裝在箱體上的刀具是通過一個被安裝在由遠離液壓泵底座上的箱體上的液壓馬達所驅(qū)動旋轉(zhuǎn)的，由于電機負載突然增加，當工件與刀具突然完全接觸時，將會導致電機暫時停止工作，直到泵和電機之間的長期高壓回路能夠被液壓泵管道內(nèi)由增加負載所導致的增加壓力下的流體壓縮完全覆蓋。但是，在所需時間內(nèi)為液壓泵提供所需要的液壓油，用來補償在高壓回路中被壓縮的液壓油，相對地在載體和工件之間的進給運動仍然會繼續(xù)增加電機上的負載。這可能會導致一個完整的失速刀斷裂，但進給運動會仍在繼續(xù)。
解決這個問題的一個辦法就是在刀軸上安裝一個大飛輪。按刀具主軸旋轉(zhuǎn)所需要的速度，在刀具受力突然增加之前，飛輪將定義一個存儲動能的來源，這將會立即也用以保持刀盤和刀具旋轉(zhuǎn)，而該液壓泵提供液壓油到高壓回路中，則可以用來彌補被壓縮的液壓油。然而，飛輪的重量增加了主軸軸承的磨損，并且主軸慣性的增加減緩了刀具啟動和停止的速度。此外，使用刀架上的液壓馬達來驅(qū)動工具，而不是使用電動馬達來驅(qū)動的優(yōu)點在于液壓馬達重量輕，更容易支持運輸，并且主軸上飛輪刀具的使用將會大大減少這種優(yōu)勢。最后，飛輪的使用只適合于驅(qū)動旋轉(zhuǎn)的部件。
另一個可能解決的辦法是增加靠液壓馬達來提供驅(qū)動的液壓泵的可用容量，或提供一個額外的靠液壓馬達來驅(qū)動的泵的可用容量，從而使液壓馬達的需求可以同時滿足的附加的液壓油來彌補當?shù)毒呱县撦d急劇增加時其中被壓縮的液壓油。事實上盡管只有相對少量的液壓油被需要在高壓回路中用來彌補其中被壓縮的液壓油，但還是有在刀具被連續(xù)地輸送到工作的情況下，僅僅只有很短的時間能夠提供這種液壓油，并且為滿足這一罕見的需求而提供的任何額外的液壓泵的容量都是不可能被用來提供用以在高速情況下所需要的液壓油的。
在本發(fā)明中，提供了一種如飛輪的液壓系統(tǒng)，該系統(tǒng)在遇到突然的負載時能夠提供了一個立即可用的能量來源，并且在飛輪上還提供了許多優(yōu)點。有了本發(fā)明，當需要在一個高速率，而不犧牲大容量液壓泵的前提下，液壓油就可以提供給液壓泵入口處的高壓回路。簡而言之，輔助回路的液壓油在高壓的作用下能夠為液壓馬達提供動力。此液壓油通常是從液壓泵中被分離出來，并被連接到液壓泵的入口處，只有當負載突然增加時，才有可能在液壓泵中被利用。由于只有少量的液壓油才需要在高速率的情況下被利用，所以在壓力作用下輔助回路的液壓油只能簡單的流到液壓泵的入口處并且在斷開的時候才會被補給。在本發(fā)明的系統(tǒng)中，輔助回路中的液壓油在壓力作用下與通向液壓泵入口的高壓回路分離開。如果這樣的油路一直連接到這條油路，當這條油路的壓力高時，它會從該油路獲得液壓油；當這條油路的壓力低時，它又會向這條油路補充液壓油。本發(fā)明為了防止失速的液壓馬達突然遇到負荷，然而，當這條油路的壓力正在上升時，液壓油快速進入液壓泵又是必要的。
在本發(fā)明的首選裝置中，液壓蓄能器能夠儲存在高壓下輔助回路中的液壓油，并且這種蓄能器也能很方便的被安裝在機器的底座部位，斷流閥則被很好的安放在了靠近電機的地方，通過回路來連接蓄能器和斷流閥。從電機開始的那段節(jié)流回路中，節(jié)流閥被安放在其中用以控制系統(tǒng)的回壓，而電機到節(jié)流閥的那段節(jié)流回路則可以控制電機速度的變化。而斷流閥有一個操作端口可以連接到電機和節(jié)流閥之間的那段節(jié)流回路，并且通過一個節(jié)流口連接到電機的入口處。比如在某個時刻，由液壓馬達所驅(qū)動的旋轉(zhuǎn)工具突然遇到一個負載，那么就會減慢液壓馬達的速度，斷流閥就會工作，讓高壓下的液壓油通過回壓回到從輔助回路到電機入口處的那段回路中。盡管電機中的負載一直在增加，但通過這種液壓油的激增卻補償了在液壓泵和電機入口處之間的回路中被壓縮的液壓油，使得電機能夠恢復到正常的速度。一旦電機恢復正常的速度，那么蓄能器就會立即和電機分離開。
與機械飛輪不同，該系統(tǒng)不會增加主軸軸承的磨損，也不會延長主軸起動和停止的時間，并且還能夠克服在滑動和轉(zhuǎn)動構(gòu)件中突然變化的大載荷。
在機床底座上有一個液壓泵，在其上還有一個可移動的液壓驅(qū)動電機可供驅(qū)動，譬如，旋轉(zhuǎn)刀具則被安裝在箱體上，蓄能器由于相對較重，則被安裝在底座上，并且斷流閥也被優(yōu)先安裝在箱體上。
因此，本發(fā)明提供了一種當液壓系統(tǒng)突然受到負載影響時能夠防止液壓驅(qū)動馬達失速的方法。