数字控制步进液压缸（有时也被称为数字缸，数字液压缸）工作原理 ...
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特别说明：这个原理结构在20世纪70年代海外就公布专利了，有脉冲液压缸，也有脉冲液压马达。在1986年以前就产品已经是现在这样了，而且是供货产品。既然这种实用液压装置有了较为久远的历史，它在国外流行吗？很多公司生产这种脉冲液压缸或者脉冲液压马达吗？估计这是您的疑问。其实答案是显然，如果流行，您在进口到中国的机床上就见到它了。
数字控制步进液压缸，有时也被称为数字缸，数字液压缸。其实，它的基本系统结构是步进电机（或脉冲控制方式的伺服电机）+液压直线放大器（机液伺服机构），下面称之为：步进电机+液压直线放大器（机液伺服机构）。这个称呼能够反映出它的工作原理与结构。
下面是工作原理，就不译了。
There are three main components of the linear amplifier: the pilot motor (normally a stepper motor however could be a DC motor or AC servo motor); the NC-valve; and the hydraulic cylinder.
A flexible coupling is fitted between the pilot motor shaft and the control shaft exiting the NC-valve. At the other end of the control shaft is a thread which enables the movement of the control shaft into/out of the NC Valve. On the control shaft is fitted a spool which is kept in location by a spring inside the spool and around the control shaft. This spring positively locates the spool against a thrust washer at the threaded end of the control shaft.
A flexible coupling is fitted between the pilot motor shaft and the control shaft exiting the NC-valve. At the other end of the control shaft is a thread which enables the movement of the control shaft into/out of the NC Valve. On the control shaft is fitted a spool which is kept in location by a spring inside the spool and around the control shaft. This spring positively locates the spool against a thrust washer at the threaded end of the control shaft.
The rotation of the pilot motor is converted into a linear movement of the spool within the NC-valve using the control thread on the control shaft. As the spool moves either the 'tank' or the 'pressure' ports are opened up. The flow of hydraulic medium is controlled into/out of both the piston area and piston ring area.
The closed-loop within the linear amplifier is achieved mechanically via a feedback spindle located within the piston. Located at the NC-valve end of the feedback spindle is a bush. The feedback spindle (which has an opposite thread to the control shaft thread rotates in the same direction to the pilot motor input due to the resulting movement of the piston. This rotation moves the spool to it's neutral position. When in the neutral position the piston will once again be stationary.
The closed-loop within the linear amplifier is achieved mechanically via a feedback spindle located within the piston. Located at the NC-valve end of the feedback spindle is a bush. The feedback spindle (which has an opposite thread to the control shaft thread rotates in the same direction to the pilot motor input due to the resulting movement of the piston. This rotation moves the spool to it's neutral position. When in the neutral position the piston will once again be stationary.
Diagram A) shows the linear amplifier in it's stationary state i.e. the 'pressure' and 'tank' ports are closed. The piston is stationary.
Diagram B) shows the pilot motor rotating a small distance anticlockwise. This causes the control shaft and spool to move in the direction of the motor, causing the flexible coupling to compress. This movement opens up the piston area to the 'Pressure' and the piston ring area opens up to 'Tank'. The piston the extends out of the cylinder. As piston extends the resulting rotation of the feedback spindle (also anticlockwise) results in the spool being moved back to it's neutral position and the piston stops moving.
Diagram C) shows the pilot motor rotating a small distance clockwise. This causes the control shaft and spool to move in the direction of the cylinder, causing the flexible coupling to expand. This movement opens up the piston ring area to the 'Pressure' and the piston area opens up to 'Tank'. The piston the retracts into the cylinder. As piston retracts the resulting rotation of the feedback spindle (also clockwise) results in the spool being moved back to it's neutral position and the piston once again is stationary.