HED8OA-2X/200K14力士乐压力继电器现货

HED8OA-2X/200K14力士乐压力继电器现货，武汉百士自动化设备有限公司供应产品，原厂原装，现货库存，价格优惠；

压力继电器用途性能
压力继电器是一种将油液的压力信号转换成电信号的液一电转换元件。当油液压力达到压力继电器的调定压力时，能自动接通或断开电路，使电磁铁、继电器、电动机等电气元件通电运转或断电停止工作，以实现对液压系统工作程序的控制、安全保护或元件动作的联锁等。任何压力继电器都是由压力一位移转换装置和微动开关两部分组成的，按压力一位移转换装置的结构划分，有柱塞式、弹簧管式、膜片式和波纹管式四类

压力继电器是利用液体的压力来启闭电气触点的液压电气转换元件。当系统压力达到压力继电器的调定值时，发出电信号，使电气元件（如电磁铁、电机、时间继电器、电磁离合器等）动作，使油路卸压、换向，执行元件实现顺序动作，或关闭电动机使系统停止工作，起安全保护作用等。

压力继电器有柱塞式、膜片式、弹簧管式和波纹管式四种结构形式。下面对柱塞式压力继电器的工作原理作一介绍：
当从继电器下端进油口3进入的液体压力达到调定压力值时，推动柱塞2上移，此位移通过杠杆放大后推动微动开关4动作。改变弹簧1的压缩量，可以调节继电器的动作压力。
应用场合：用于安全保护、控制执行元件的顺序动作、用于泵的启闭、用于泵的卸荷。
注意： 压力继电器必须放在压力有明显变化的地方才能输出电信号。若将压力继电器放在回油路上，由于回油路直接接回油箱，压力也没有变化，所以压力继电器也不会工作。
选用标准
根据所测对象的压力来选用,比如所测压力范围在8KG以内,那么就要选用额定10KG的压力继电器,还有要符合电路中的额定电压,接口管径的大小
3使用方法
首先用于安全保护时，将压力继电器设置在夹紧液压缸的一端，液压泵启动后，首先将工件夹紧，此时夹紧液压缸的右腔压力升高，当升高到压力继电器的调定值时，压力继电器动作，发出电信号使2YA通电，于是切削液压缸进刀切削。在加工期间，压力继电器微动开关的常开触点始终闭合。若工件没有夹紧，压力继电器2断开，于是2YA断电，切削液压缸立即停止进刀，从而避免工件未夹紧被切削而出事故。 
其实用于控制执行元件的顺序动作时，液压泵启动后，首先2YA通电，液压缸左腔进油，推动活塞方向右移。当碰到限位器(或死挡铁)后，系统压力升高，压力继电器发出电信号，使1YA通电，高压油进入液压缸的左腔，推动活塞右移。这时若3YA也通电，液压缸的活塞快速右移;若3YA断电，则液压缸的活塞慢速右移，其慢速运动速度由节流阀调节。
再次用于液压泵卸荷时，压力继电器不是控制液压泵停止转动，而是控制二位二通电磁阀，将液压泵5输出的压力油流回油箱，使其卸荷。
后用于液压泵的启闭时，有两个液压泵，高压小流量泵，低压大流量泵。当活塞快速下降时，两泵同时输出压力油。当液压缸活塞杆抵住工件开始加压时，压力继电器在压力油作用下发出动作，触动微动开关，将常闭触点断开，使液压泵停转。在加工过程中减慢液压缸的速度，同时减少动力消耗。
HED8OA-2X/200K14力士乐压力继电器现货
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1、液流通道迅速关闭时的液压冲击
液压冲击多发生在油液突然停止运动的时候，例如迅速关闭阀门，油液的流动速度突然降为零，这时油液受到挤压，使油液的动能转换为压力能，于是油液的压力急剧升高，冲撞液压系统产生液压冲击波，并迅速在管道内传播。液压冲击波的传递、反射、油液方向的变化将反复进行，直到耗尽引起冲击的能量，冲击现象才会结束。因此，管路中的油液流速突然变化是产生冲击的外界条件，而油液本身的惯性是产生冲击现象的内在因素。
液流通道迅速关闭时的液压冲击(水锤现象)
液体自一具有固定液面的压力容器沿长度为1,直径为d的管道经出口处的阀门以速度v0流出。若将阀门突然关闭，此时紧靠阀门门口B处的一- 层液体停止流动，压力升高△p。其后液体也依次停止流动，动能形成压力波，并以速度c向A传播。此后B处压力降低△p，形成压力降波，并向A传播。而后当A处先恢复初始压力后压力波又传向B。则如此循坏使液流振荡。振荡终因摩擦损失而停止。
液流换向时产生的冲击
当换向阀移到中间位置时，压力油突然与液压缸切断，但是由于运动部件的惯性作用，使液压缸一端油腔中的液体受压缩，压力突然升高，而另一端油腔中的压力下降，形成局部真空。因此，液流换向时产生液压冲击。

2、运动部件在高速运动中突然被制动
在液压系统中，高速运动的部件的惯性力和突然加到设备上的载荷也会引起压力冲击，如工作部件换向或制动时，换向阀切断油路，但是运动部件因惯性的作用还不能立即停止运动，高速运动部件在惯性力作用下挤压封闭中的液压油，使运动部件的动能转化为液压油的压力能。这样也会引起液压缸和管路中油压急剧升高而产生液压冲击。升降设备的液压缸在静止状态下，被施加一个较大的载荷，液压缸下腔的压力也会急剧升高。
运动部件制动产生冲击
活塞以正常运动速度vo带动负载m向右运动，当换向阀突然关闭时，油液被封死在油缸两腔及管道中。由于惯性作用，活塞不能立即停止运动，将继续向前运动而使右腔内的油液受到压缩，压力急剧上升达到某一-峰值， 产生液压冲击。封闭在左腔的油液因容积扩大并没有油液补充进来将使压力突然降低。当运动部件的动能全部转化为油液的弹性能时，活塞将停止向右运动，此时油液的弹性能将释放出来，使活塞改变其运动方向而向左运动，这样来回运动将持续地振荡一段时间，直到泄漏与摩擦损失耗尽了全部能量为止。

流体中空气引起的液压冲击
由于油液中约含2%的空气，当系统中某个局部低于空气分离压力时，就会产生气泡，气泡被带到高压区时体积急剧缩小，又重新急剧凝聚为液体，使局部地区形成真空，周围的液体以高速填补这一空间，油液的相互碰撞会产生局部高压，产生液压冲击。

减少液压冲击的措施
液压冲击的压力和油液的流速成正比，管径与壁厚的比值越大，冲击传播速
度越小。由液压缸运动状态发生改变时引起的液压冲击的大小，与其速度变化大小成正比，与其速度变化快慢成反比。为了减小系统的液压冲击可以采取以下措施:
1、对阀门突然关闭而产生液压冲击的防治方法
合理选择管道的材质、大小、管壁厚度并适当增大其安全系数，减小弯道，使用软管都能减小液压冲击和振动。在同样的流量下增大管径，可以减小油流的流速，降低油液的动能，在其运动状态发生变化时，产生较小的冲击。
2、在满足动作快慢要求的前提下，尽量减慢阀门的关闭的速度。具体措施可采用:如减慢滑阀开启和关闭时的速度，可在阀芯控制边上开V形槽，或作成
2°~5°左右的锥度;对于电液换向阀，可控制先导阀的流量(用节流阀或单向阀实现)，以减缓滑阀的换向速度;选用元件时，尽可能选用带阻尼器的换向阀。
3、在容易产生液压冲击的地方设置蓄能器。蓄能器不但能缩短压力波的传播距离、时间，还能吸收压力冲击。
蓄能器是液压气动系统中的一种能量储蓄装置。它在适当的时机将系统中的能量转变为压缩能或位能储存起来，当系统需要时，又将压缩能或位能转变为液压或气压等能而释放出来，重新补供给系统。当系统瞬间压力增大时，它可以吸收这部分的能量，以保证整个系统压力正常。
工作原理:
蓄能器壳体由胶囊将其分为两个腔室;胶囊内的腔室充氮气，胶囊外腔室充液体，当液体泵将高压的液压油(液)充入时，发生变形，则气体体积随压力增加而减小。这样液体储存起来。当液压系统需要压力油(液)补充，而其压力低于蓄能器所储存液压油(液)的压力时，则液压油(液)在气体膨胀压力推动下，经进油阀排到液压系统中;直至压力降到与系统内压力相等为止。
4、缩短冲击波反射的时间。如缩短控制元件到执行元件的管路长度;选用密度较小的液压介质;以及采用软管等。
5、减慢换向阀的关闭速度，即延长换向时间t。例如采用直流电磁阀比交流的液压冲击要小，或采用带阻尼的电液换向阀可通过调节阻尼以及控制通过先导阀的压力和流量来减缓主换向阀阀芯的换向(关闭)速度。