液压马达是液压系统的一种执行元件，它将液压泵提供的液体压力能转变为其输出轴的机械能(转矩和转速)。液体是传递力和运动的介质。液压马达，亦称为油马达，主要应用于注塑机械、船舶、起扬机、工程机械、建筑机械、煤矿机械、矿山机械、冶金机械、船舶机械、石油化工、港口机械等。
径向柱塞式液压马达
工作原理，当压力油经固定的配油轴4的窗口进入缸体内柱塞的底部时，柱塞向外伸出，紧紧顶住定子的内壁，由于定子与缸体存在一偏心距。在柱塞与定子接触处，定子对柱塞的反作用力为 。力可分解为和 两个分力。当作用在柱塞底部的油液压力为p，柱塞直径为d，力和之间的夹角为X时，力对缸体产生一转矩，使缸体旋转。缸体再通过端面连接的传动轴向外输出转矩和转速。以析的一个柱塞产生转矩的情况，由于在压油区作用有好几个柱塞，在这些柱塞上所产生的转矩都使缸体旋转，并输出转矩。径向柱塞液压马达多用于低速大转矩的情况下。
1.单作用连杆型径向柱塞马达
单作用连杆型径向柱塞马达外型呈五角星状，该马达由壳体、曲轴、配流轴、连杆、柱塞和偏心轮等零件组成。
优点:结构简单，工作可靠。
缺点:体积大、重量大，转扭脉动，低速稳定性较差。
2.多作用内曲线柱塞马达MRE2100H-D1N1U1N1NX0800/34687
MRE2100H-F1N1N1S1NX0800/58329
MRE3100I-D1N1N1N1N0201/33492
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MR  125C P1N1N1C1N  0001/58357
MR 190C N1N1N1N1N0201/45170
MR 2400I P1N1N1G1N 0300/58660
MR 2800I P1N1N1C1N 0500/58352
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MR 450E D2N1F1N1N0301/34760
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MR110B-D2B1N1C1N0102/60868
MR110B-N1N1N1S1N0000/58937
MR125C-P1N1N1C1N0300/60095

轴向柱塞泵除阀式配流外，其它形式原则上都可以作为液压马达用，即轴向柱塞泵和轴向柱塞马达是可逆的。轴向柱塞马达的工作原理为，配油盘和斜盘固定不动，马达轴与缸体相连接一起旋转。当压力油经配油盘的窗口进入缸体的柱塞孔时，柱塞在压力油作用下外伸，紧贴斜盘，斜盘对柱塞产生一个法向反力p，此力可分解为轴向分力及和垂直分力Q。Q与柱塞上液压力相平衡，而Q则使柱塞对缸体中心产生一个转矩，带动马达轴逆时针方向旋转。轴向柱塞马达产生的瞬时总转矩是脉动的。若改变马达压力油输入方向，则马达轴按顺时针方向旋转。斜盘倾角a的改变、即排量的变化，不仅影响马达的转矩，而且影响它的转速和转向。斜盘倾角越大，产生转矩越大，转速越低。轴向柱塞泵 E-A4VSO250EO2/30R-VPB25N00-SO3
轴向柱塞泵 E-A4VSO250EO2/30R-VPB25N00-SO3 
柱塞泵 A4VSO180DR/30R-FPB13N00
恒压变量泵 E-A4VS0125DR/22R-VPB13N00 
柱塞泵 A4VSO180DR/30R-FPB13N00 
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柱塞泵 A4VSO250LR2D/30R-PPB13NOO 
柱塞泵 A4VSO250DR/30R-PPB13NOO
泵 A4VG56EZ2DM1/32-NSC02F003F
柱塞泵 A4VS0250DR/30RPPB13N00
阀柱塞泵 A4VTG71HW/32R-NLD10F001S
柱塞泵 A4VSG750HD/22R-PPH10NOO 
轴向柱塞泵 A4VS07IDR/3XR 
轴向柱塞泵 A4VS0125DR/3XR 
柱塞泵 A4VG90EP2DT1/32R-NAF02F00
柱塞泵 A4VSO-250E02/30R-PPB13N00 
柱塞泵 A4VSO-250DR/30R-PPB13N00
液压马达 A4VG40EP4DMT1/32L-NSC02F015PH 
柱塞泵 A4VG71DWDMT2/23L-NZF02F041D 
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A4VG250HD1D1/32LNZD10F001S
A4VG125HDDT1/32L-PZF02F001D
A4V125HW10R0C101A-K

轴向柱塞泵除阀式配流外，其它形式原则上都可以作为液压马达用，即轴向柱塞泵和轴向柱塞马达是可逆的。轴向柱塞马达的工作原理为，配油盘和斜盘固定不动，马达轴与缸体相连接一起旋转。当压力油经配油盘的窗口进入缸体的柱塞孔时，柱塞在压力油作用下外伸，紧贴斜盘，斜盘对柱塞产生一个法向反力p，此力可分解为轴向分力及和垂直分力Q。Q与柱塞上液压力相平衡，而Q则使柱塞对缸体中心产生一个转矩，带动马达轴逆时针方向旋转。轴向柱塞马达产生的瞬时总转矩是脉动的。若改变马达压力油输入方向，则马达轴按顺时针方向旋转。斜盘倾角a的改变、即排量的变化，不仅影响马达的转矩，而且影响它的转速和转向。斜盘倾角越大，产生转矩越大，转速越低。
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折叠低速马达
转速低于500r/min的液压马达属于低速液压马达。它的基本形式是径向柱塞式。低速液压马达的主要特点是:排量大，体积大，转速低，可以直接与工作机构连接，不需要减速装置，使传动机构大大简化，低速液压马达的输出扭矩较大，可达几千到几万Nm，因此又称为低速大扭矩液压马达。