There are many hydraulic transmission commutation methods currently used in precision surface grinders. For the analysis of common hydraulic transmission commutation methods, a simple analysis and comparison will be made below. Reversing method using stroke reversing valve The reversing mode and reversing control parameters in the system have a decisive effect on the reversing impact. The surface grinder adopts hydraulic transmission. The design of a new hydraulic reversing system is imminent. The following discusses the reversing impact of the grinder from the perspective of commutation methods and control strategies.
A pull rod is connected to the reversing spool, which uses a stroke reversing valve for reversing. Use the stroke stop on the workbench to push the pull rod to realize automatic reversing. When the worktable moves slowly, when the reversing valve reaches the middle position, no matter whether the left and right chambers of the hydraulic cylinder are both filled with pressure oil, or both return oil, or both are closed, at this time, there is no hydraulic pressure in the two chambers of the hydraulic cylinder. Pushing will stop the movement of the worktable, so the reversing valve cannot reach the other end, and the so-called "dead point" appears; Jinjitong reminds that when the workbench moves at high speed, the stopper pushes the lever to change the direction of the reversing valve. Very quickly, the pressure of one cavity of the hydraulic cylinder suddenly drops from the working pressure p to 0 and the other cavity suddenly rises from 0 to p, which causes a great reversing shock. At present, this kind of system is widely used on small grinders.
Reversing method using electromagnetic reversing valve
The travel stop is pushed by the travel switch to send out a reversing signal, and the travel reversing valve is changed to the reversing method of electromagnetic reversing valve. The solenoid is actuated to push the spool valve to change direction, which can prevent the "dead point". However, it is a switch type hydraulic valve that opens or closes instantaneously according to instructions, that is, instantaneously connects or cuts off the oil return channel. Such a hydraulic reversing system is changing Xiangshi will have a big impact.
Reversing method using electro-hydraulic directional valve
The main valve is driven by the control oil to change direction. The pilot valve did not change forward, and the electro-hydraulic directional valve replaced the electromagnetic directional valve to constitute a new directional method. The electro-hydraulic directional valve consists of a pilot valve solenoid spool valve and a main valve hydraulic spool valve. This system uses the pilot valve to switch the control oil circuit. The oil flow direction of the control oil circuit does not change, the reversing valve always remains at the original end, the main oil circuit direction does not change, and the workbench can always move forward.
With the ideal control curve. The surface grinder adopts the hydraulic transmission reversing system of the electro-hydraulic proportional valve. An intelligent control commutation system is realized by actively reducing the flow rate to reduce the speed, and finally achieving the goal of smooth and impact-free commutation, which can realize the ideal commutation under the change of working conditions. This kind of hydraulic transmission reversing system realizes very good intelligence on the output displacement or speed.
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