液压增压阀又称油压增压器、连续自动增压器、往复增压器、液压增压器、液压放大器等，工作原理如上图所示：
液压增压阀本质上就是自动化增压缸。
液压增压阀为虚线框内所有零件，包含低压活塞LP，高压活塞HP，液控换向阀，进液单向阀，出液单向阀，液控单向阀，外部壳体。
当电磁换向阀换向到右位时候，低压系统供油至液压增压器P口，低压液压油经过进液单向阀，到达高压活塞HP顶部，推动高、低压活塞向下运动；
当高压活塞HP到达下止点位置时候，液控换向阀先导控制口上腔与低压液压油接通，由于先导控制口上腔面积比下腔大，液控换向阀将往下移动，实现自动换向。
液控换向阀换向后，低压液压油从P口进入，经过液控换向阀，到达低压活塞LP底部，推动高压活塞HP向上运动，压缩高压活塞HP顶部液柱，这时，进液单向阀将关闭，出液单向阀打开，输出高压液压油。
当高压活塞HP到达上止点位置时候，液控换向阀先导控制口上腔将与回油接通，先导控制口下腔的压力油将推动换向阀往上移动，再次换向到图上所示位置。
如此往复，实现连续增压。
当电磁换向阀换向到中位时候，液压增压器自动保压。
当电磁换向阀换向到左位时候，低压系统供油至液压增压阀T口，顶开内部液控单向阀，同时也供油至负载油缸有杆腔，推动油缸回程。
Hydraulic booster valve is also known as oil pressure booster, continuous automatic booster, reciprocating booster, hydraulic intensifier and hydraulic amplifier. Its working principle is shown in the figure above：
Essentially, the hydraulic booster valve is an automatic pressure intensifying cylinder.
All components inside the dotted frame constitute the hydraulic booster valve, including low-pressure piston (LP), high-pressure piston (HP), pilot-operated directional valve, inlet check valve, outlet check valve, pilot-operated check valve and outer housing.
When the solenoid directional valve shifts to the right position, oil from the low-pressure system flows into Port P of the hydraulic booster. The low-pressure hydraulic oil passes through the inlet check valve and reaches the top of the high-pressure piston (HP), pushing the high-pressure and low-pressure pistons to move downward.
When the high-pressure piston (HP) reaches the bottom dead center, the upper chamber of the pilot control port on the pilot-operated directional valve is connected to low-pressure hydraulic oil. As the area of the upper chamber is larger than that of the lower chamber, the pilot-operated directional valve moves downward to complete automatic reversing.
After the pilot-operated directional valve reverses, low-pressure hydraulic oil enters via Port P, flows through the valve and reaches the bottom of the low-pressure piston (LP). It pushes the high-pressure piston (HP) upward to compress the hydraulic fluid on top of the HP. Meanwhile, the inlet check valve closes and the outlet check valve opens to deliver high-pressure hydraulic oil.
When the HP reaches the top dead center, the upper chamber of the pilot control port on the directional valve connects to the oil return line. Pressurized oil in the lower chamber pushes the directional valve upward to reset to its original position.
The above cycle repeats continuously to maintain constant pressure boosting.
When the solenoid directional valve shifts to the neutral position, the hydraulic booster maintains pressure automatically.
When the solenoid directional valve shifts to the left position, low-pressure oil is supplied to Port T of the hydraulic booster valve. It opens the internal pilot-operated check valve and feeds oil to the rod chamber of the load cylinder to drive the cylinder back to its original position.
