【正文】 permit adjustment of the throttle size by an electrical signal. The throttle spool is linked to armature of a torque motor and moves in response to signal to the torque motor. Operation is otherwise the same as a pressure pensated flow control valve. Hydraulic transmission There are many outstanding advantages, it is widely used, such as general industr ial use of plastics processing machinery, the pressure of machinery, machine tools, etc.。 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? 。該壓力是系統(tǒng)的靜壓力，而系統(tǒng)在各種工礦的過渡階段出現(xiàn)的動(dòng)態(tài)壓力有時(shí)會(huì)超過靜壓力。=V8/Q8 快退 = 參數(shù)匯總?cè)缦拢? 名稱 型號(hào) 數(shù)量 Q 快進(jìn) (L) Q 快退 (L) 容積變化量 V (l) 快進(jìn)時(shí)間t(s) 快退時(shí)間t39。=V4/ Q4 快退 =。 （ 4） 上矯直輥可以橫向傾動(dòng)，能分別調(diào)整各段支承輥，以改變矯直 輥的撓曲，消除鋼板的單側(cè)或者雙側(cè)邊浪。所以矯直機(jī)是軋鋼生產(chǎn)中的重要機(jī)械設(shè)備，而且也廣泛用于以軋材作坯料的各種車間 (如汽車、 船 舶制造廠等 )。為了獲得 很 直的板材和具有正確幾何形狀的鋼材，軋件需要在矯直機(jī)上進(jìn)行矯直。 （ 3） 為了提高矯直效果，矯直機(jī)出口處的上（或下輥） 可以單獨(dú)調(diào) 整，且在矯直過程也可以進(jìn)行調(diào)整。 快退時(shí)完成動(dòng)作時(shí)間 t439。 快退時(shí)完成動(dòng)作時(shí)間 t839。 即： M P aPP ??? 通過計(jì)算，泵的工作壓力 Pp=。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。 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。 operative or hydraulic cylinder with hydraulic motors, according to the actual requirements of their choice. In the analysis and design of the actual task, the general block diagram shows the actual operation of equi pment. Hollow arrow indicates the signal flow, while the solid arrows that energy flow. Basic hydraulic circuit of the action sequence Control ponents (two fourway valve) and the spring to reset for the implementation of ponents (doubleacting hydraulic cylinder), as well as the extending and retracting the relief valve opened and closed . For the implementation of ponents and control ponents, presentations are based on the corresponding circuit diagram symbols, it also introduced ready made circuit diagram symbols. Working principle of the system, you can turn on all circuits to code. If the first implementation of ponents numbered 0, the control ponents associated with the identifier is 1. Out with the implementation of ponents corresponding to the identifier for the even ponents, then retracting and implementation of ponents corresponding to the identifier for the odd ponents. Hydraulic circuit carried out not only to deal with numbers, but also to deal with the actual device ID, in order to detect system failures. DIN ISO12192 standard definition of the number of ponent position, which includes the following four parts: device ID, circuit ID, ponent ID and ponent ID. The entire system if only one device, device number may be omitted. Practice, another way is to code all of the hydraulic system ponents for numbers at this time, ponents and ponent code should be consistent with the list of numbers. This method is particularly applicable to plex hydraulic control 28 system, each control loop are the corresponding number with the system With mechanical transmission, electrical transmission pared to the hydraulic drive has the following advantages: 1, a variety of hydraulic ponents, can easily and flexibly to layout. 2, light weight, small size, small inertia, fast response. 3, to facilitate manipulation of control, enabling a wide range of stepless speed regulation (speed range of 2020:1). 4, to achieve overload protection automatically. 5, the general use of mineral oil as a working medium, the relative motion can be selflubricating surface, long service