膨脹閥也稱節流(liu)閥，是組成(cheng)汽車空調制冷(leng)系統的(de)主要部(bu)件(jian)，安裝在蒸發器(qi)入口(kou)處。       

    其(qi)功(gong)用(yong)是：把來(lai)自貯液(ye)干燥器的高壓(ya)(ya)液(ye)態制(zhi)冷(leng)(leng)劑(ji)節流減壓(ya)(ya)，調節和控(kong)制(zhi)進入蒸發(fa)器中的液(ye)態制(zhi)冷(leng)(leng)劑(ji)量，使之適(shi)應制(zhi)冷(leng)(leng)負荷的變(bian)化，同時可防止壓(ya)(ya)縮(suo)機(ji)發(fa)生液(ye)擊現象(xiang)(即未蒸發(fa)的液(ye)態制(zhi)冷(leng)(leng)劑(ji)進入壓(ya)(ya)縮(suo)機(ji)后被壓(ya)(ya)縮(suo)，極易引起壓(ya)(ya)縮(suo)機(ji)閥片(pian)的損壞)和蒸發(fa)器出(chu)口(kou)蒸氣異常過熱。

    熱(re)力(li)膨脹(zhang)(zhang)閥(fa)(fa)(fa)(fa)(fa)是制(zhi)冷系(xi)統(tong)(tong)(tong)(tong)廣泛使用的(de)(de)(de)節流裝置，但是它與變排量壓(ya)(ya)縮(suo)(suo)機(ji)(ji)組成的(de)(de)(de)汽(qi)車(che)空(kong)調制(zhi)冷系(xi)統(tong)(tong)(tong)(tong)在(zai)實際使用中出現(xian)了(le)系(xi)統(tong)(tong)(tong)(tong)穩定性(xing)問題(ti)(ti)。At-suo Inoue等(deng)人在(zai)對(dui)7缸(gang)變排量壓(ya)(ya)縮(suo)(suo)機(ji)(ji)和熱(re)力(li)膨脹(zhang)(zhang)閥(fa)(fa)(fa)(fa)(fa)組成的(de)(de)(de)汽(qi)車(che)空(kong)調制(zhi)冷系(xi)統(tong)(tong)(tong)(tong)進行(xing)試驗研(yan)究時發現(xian)有系(xi)統(tong)(tong)(tong)(tong)振(zhen)蕩現(xian)象存(cun)在(zai)。美國GM公(gong)司在(zai)無級變排量壓(ya)(ya)縮(suo)(suo)機(ji)(ji)和熱(re)力(li)膨脹(zhang)(zhang)閥(fa)(fa)(fa)(fa)(fa)汽(qi)車(che)空(kong)調制(zhi)冷系(xi)統(tong)(tong)(tong)(tong)的(de)(de)(de)應用過程(cheng)中，也有同樣發現(xian)。我(wo)們對(dui)用于某一車(che)型的(de)(de)(de)變排量壓(ya)(ya)縮(suo)(suo)機(ji)(ji)和熱(re)力(li)膨脹(zhang)(zhang)閥(fa)(fa)(fa)(fa)(fa)汽(qi)車(che)空(kong)調制(zhi)冷系(xi)統(tong)(tong)(tong)(tong)的(de)(de)(de)穩定性(xing)問題(ti)(ti)進行(xing)了(le)研(yan)究，為了(le)詳(xiang)細分(fen)析變排量壓(ya)(ya)縮(suo)(suo)機(ji)(ji)和熱(re)力(li)膨脹(zhang)(zhang)閥(fa)(fa)(fa)(fa)(fa)參數之間(jian)的(de)(de)(de)相互耦合對(dui)系(xi)統(tong)(tong)(tong)(tong)穩定性(xing)的(de)(de)(de)影響，需要(yao)對(dui)該系(xi)統(tong)(tong)(tong)(tong)的(de)(de)(de)熱(re)力(li)膨脹(zhang)(zhang)閥(fa)(fa)(fa)(fa)(fa)的(de)(de)(de)動(dong)態行(xing)性(xing)進行(xing)深入地了(le)解。

    定排量空調壓縮機的排氣量隨發動機轉速的提高而提高，它不能根據制冷負荷的大小自動改變排氣量，對發動機的油耗影響比較大。汽車空調壓縮機配件它(ta)的控(kong)制一般(ban)通過采集蒸發(fa)器出口的溫(wen)度信號(hao)，當溫(wen)度達到(dao)設(she)定值時(shi)(shi)，空(kong)調(diao)壓(ya)(ya)(ya)縮機(ji)(ji)電(dian)磁離合器分離，壓(ya)(ya)(ya)縮機(ji)(ji)停止工作；當溫(wen)度升高(gao)后，電(dian)磁離合器接合，壓(ya)(ya)(ya)縮機(ji)(ji)再次工作。定排(pai)量空(kong)調(diao)壓(ya)(ya)(ya)縮機(ji)(ji)也(ye)受空(kong)調(diao)制冷系統壓(ya)(ya)(ya)力的控(kong)制，當管(guan)路內壓(ya)(ya)(ya)力過高(gao)或過低時(shi)(shi)，汽車空(kong)調(diao)壓(ya)(ya)(ya)縮機(ji)(ji)配件也(ye)將停止工作。