【正文】 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。==15mm ⑤ 給 夾 送 輥 擺 動(dòng) 缸 供 油 的 管 子 ， 取 速 度 值 為 3 ，則d5=()189。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。主缸和頂出缸各自工況的快進(jìn)、工進(jìn)、回程速度又不盡相同，這樣對(duì)功率的消耗也不同。 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? 。這就明白了企業(yè)原來是這么保護(hù)自己的產(chǎn)品的獨(dú)立性的。 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 protection with pressure pensated control of flow. It has a normally closed hydrostat which opens to divert fluid, in excess of the throttle setting, to the tank. Pressure required by the work load is sensed 25 in the chamber above the hydrostat and together with a light spring tends to hole it closed. Pressure in the chamber below the hydrostat increase duo to restriction of the throttle and cause is to rise diverting any excess flow to tank when the difference in pressure is sufficient to overe the spring. This difference, usually 20 psi, is maintained across the throttle providing a constant flow regardless of the work load. Some horsepower saving is acplished in that the pump need operate at only 20 psi above work load pressure. Overload protection is provided by an adjustable spring loaded poppet which limits the maximum pressure above the hydrostat, causing it to function as a pound relief valve whenever work load requirement exceed its setting. The bypass flow control can only be used in a meterin circuit. If used for metering out, exhaust oil which could not get through the throttle would be diverted to tank permitting the load to run away. The Restrictor Type Flow Controlalso maintains a constant 20 psi differential across its throttle by means of a hydrostat. In this valve, the hydrostat is normally epen and tends to close off blocking all flow in excess of the throttle setting. In these units the work load pressure acts with a light spring above the hydrostat to hold it open. Pressure at the throttle inlet and under the hydrostat tend to close it, permitting only that oil to enter the valve that 20 psi can force through the throttle. Because of their tendency close off when flow tales to exceed the throttle setting, restrictor type valves may be used in meterin, meterout and bleedoff circuits. Unlike the bypass type , two or more restrictor valves may be used with the same pump since the excess pump delivery returns to tank through the relief valves. When placed in cylinder lines an integral check valve is optional to provide free flow for a rapid return stroke. One would not be required for valves placed in the main supply line, the tank line of a directional valve or when they are used in bleedoff circuits. Temperature Compensated Flow Control Valve Flow through a pressure pensated flow control valve is subject to change 26 with variations in oil temperature. Later design Vickers valves incorporate a temperature. Although oil flows more freely when it is hot, constant flow can be maintained by decreasing the size of the throttle opening as the temperature rises. This is acplished through a pensating rod which lengthens with heat and contracts when cold. The throttle is a simple plunger that is moved in and out of the control port. The pensating is installed between the throttle and its adjuster. This design also is available with a reverse freeflow check valve. Remote Flow Control Valves Remote flow control valves 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.。 flow control valves including throttle, adjusting the valves, flow diversion valve sets, etc.。 hydraulic control part contains a variety of control valves, used to control the flow of oil, pressure and direction。 iron and steel indu stry metallurgical machinery, lifting equipment, such as roller adjustment device。 選完型之后開始畫閥臺(tái)，泵站圖。 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。功率計(jì)算公式如下： P=? pP qP? () 式中： P電動(dòng)機(jī)額定功率； Pp液壓泵的工作壓力； Pq 液壓泵的流量； η 液壓泵的總效率，取η =。 即： Pn = =≈ 18MPa 2）液壓泵最大流量計(jì)算 通過對(duì)液壓缸所需流量的計(jì)算，以及各自的運(yùn)動(dòng)循環(huán)原理，泵的最大 14 流量可由公式計(jì)算得到。==17mm ⑦ 給換輥裝置液壓馬達(dá) 供油的管子，取速度值為 3，因?yàn)轳R達(dá)轉(zhuǎn)速不同，所需流量不同，經(jīng)過計(jì)算它的流量范圍是 l/min，由于 換輥裝置液壓馬使用頻率不高，并且速度太高不安全，取Q7=100L/min 則 d7=(4x100/1000/60/)189。 Σ qm=△ V=