壓(ya)(ya)(ya)縮空氣、氣體減(jian)(jian)壓(ya)(ya)(ya)閥(fa)(fa)(fa)的構造(zao)(zao)類型很多，以往常見(jian)的有薄(bo)膜(mo)式(shi)、內彈簧活塞式(shi)等。減(jian)(jian)壓(ya)(ya)(ya)閥(fa)(fa)(fa)的基本(ben)作用原(yuan)(yuan)理是(shi)(shi)(shi)靠閥(fa)(fa)(fa)內流道對水(shui)流的局部阻力降(jiang)低水(shui)壓(ya)(ya)(ya)，水(shui)壓(ya)(ya)(ya)降(jiang)的范圍由(you)連接(jie)閥(fa)(fa)(fa)瓣的薄(bo)膜(mo)或活塞兩側的進(jin)(jin)出口水(shui)壓(ya)(ya)(ya)差(cha)自動(dong)調節。祝茂減(jian)(jian)壓(ya)(ya)(ya)閥(fa)(fa)(fa)門近年來(lai)又出現一些新型減(jian)(jian)壓(ya)(ya)(ya)閥(fa)(fa)(fa)，如(ru)定(ding)比(bi)(bi)式(shi)減(jian)(jian)壓(ya)(ya)(ya)閥(fa)(fa)(fa)，其構造(zao)(zao)原(yuan)(yuan)理如(ru)圖14．2－2所示。定(ding)比(bi)(bi)減(jian)(jian)壓(ya)(ya)(ya)原(yuan)(yuan)理是(shi)(shi)(shi)利(li)用閥(fa)(fa)(fa)體中浮(fu)動(dong)活塞的水(shui)壓(ya)(ya)(ya)比(bi)(bi)控制，進(jin)(jin)出口端減(jian)(jian)壓(ya)(ya)(ya)比(bi)(bi)與進(jin)(jin)出口側活塞面(mian)積比(bi)(bi)成反比(bi)(bi)。這(zhe)種(zhong)減(jian)(jian)壓(ya)(ya)(ya)閥(fa)(fa)(fa)工作平穩(wen)無(wu)(wu)振動(dong)；閥(fa)(fa)(fa)體內無(wu)(wu)彈簧，故無(wu)(wu)彈簧銹蝕、金屬疲勞(lao)失效(xiao)之慮；密封性(xing)能良(liang)好不滲(shen)漏，因而既(ji)減(jian)(jian)動(dong)壓(ya)(ya)(ya)（水(shui)流動(dong)時）又減(jian)(jian)靜壓(ya)(ya)(ya)（流量為0時）；特(te)別是(shi)(shi)(shi)在(zai)減(jian)(jian)壓(ya)(ya)(ya)的同時不影響水(shui)流量。