Supply Rexroth manual directional valve

  The working principle of manual shift valve is that a valve core moves back and forth in the valve body
Several position and several way valves change the oil passage

​
The number of channels held by the hydraulic directional valve is different: two-way, three-way, four-way and five-way
The absolute movement of the valve core staggers the valve body to make the oil circuit traffic, close or change the direction of oil flow, so as to name the bearing, end or change the direction of motion of the implicit hydraulic performing element and its driving mechanism

1
Work and interest principle
According to the working principle of slide valve directional valve, when the valve core moves to the right for a certain interval, the pressure oil input by the hydraulic pump wins from port P of the valve to the right chamber of the hydraulic cylinder through port a, the oil in the right chamber of the hydraulic cylinder returns to the oil tank through port B, and the piston of the hydraulic cylinder moves to the right; Conversely, if the valve core moves to the right for a certain interval, the liquid flow is reversed and the piston moves to the left
2、  Structure of directional valve
1)  Manual directional valve
Apply manual lever to rotate and change the position of valve core
There are two kinds of spring active return (a) and spring ball (b) positioning

2)  Flexible directional valve
Flexible directional valve, also known as distance valve, is mainly used to control the stop of mechanical moving parts
It also helps the stop iron or concave wheel installed on the workbench to force the valve core to move, so as to master the direction of liquid flow

3)  Solenoid directional valve
The disadvantage is that the power on call of the electromagnet is disconnected and released, and the valve core is indirectly pushed back to control the liquid flow direction
It is not a signal conversion element between electrical system and hydraulic system

Shown is the structure of two position three-way exchange solenoid valve
In the position shown in the figure, the oil port P and a are connected, and oil port B is disconnected; When the electromagnet is energized and opened, the pull rod 1 pulls the valve core 2 to the left
At that time, the oil core P and a are disconnected and connected with B
When the electromagnet is powered off and released, spring 3 pushes the valve core to reset

4)  Hydraulic directional valve
The pressure oil in the control oil circuit is used to change the position of the valve core
The valve core is not moved back by the differential pressure of the oil outside the thin sealing cavity at the two ends
As shown in the figure, when the pressure oil enters the left chamber of the spool valve from K2, K1 is connected with the return oil, and the spool moves to the right, so that P and B are connected, and a and T are connected; When K1 traffic pressure oil and K2 traffic return oil, the valve core moves to the left to connect P and a and B and T; When K1 and K2 are connected with oil return, the valve core returns to the two ends

5) Electro hydraulic directional valve
It is composed of solenoid valve and hydraulic slide valve
The solenoid valve is used for guiding the information behind the voltage, which can change the control flow direction, so as to change the position of the hydraulic slide valve spool
It is used outside Daxi hydraulic equipment

3、  Performance and characteristics of directional valve
1) Centering performance of spool valve
For three position four-way and three position five-way reversing slide valves with various control methods, when the valve core is at both ends, the connection of each oil port is called the West position performance of the replacement valve
Its rare use is & ldquo; O” Type, & ldquo; H” Type, & ldquo; P” Type, K & rdquo; Type, & ldquo; M” Type, etc

When analyzing and selecting the intermediate performance of the three position directional valve, we usually consider:
(1)  System pressure maintaining When the p-core is blocked, the system maintains pressure, and the hydraulic pump is used for multi cylinder system

(2)  System unloading Port P is smoothly connected with port T, and the system is unloaded
(H K X m type)
(3)  Commutation stability and accuracy A
B port 2 is blocked, the commutation process is difficult to impact, the commutation is unstable, but the precision is high; A
Port B is connected to port T, and the commutation is stable, but the accuracy is low

(4)  Starting stability When the valve is in the external position, a cavity of the hydraulic cylinder is connected to the oil tank
When sealing, there is sufficient oil to slow down, and the bearing is unstable

(5)  The hydraulic cylinder floats and ends in the free position
2) Liquid energy of astringent valve
According to the law of motion and mass of fluid flow, the hydrodynamic force acting on the valve core when the oil passes through the directional valve can be divided into steady-state hydrodynamic force and transient hydrodynamic force

(1) Steady state liquid energy: when the valve core is moved and before the opening is fixed, the liquid flows through the valve core due to the change of dynamic mass, and it is used under the valve core
There is no force that tends to close the valve port, which has nothing to do with the source mass of the valve

(2) Transient hydraulic energy: during the movement of the slide valve, the force of the liquid source in the valve chamber acting on the valve core due to deceleration or acceleration is independent of the movement speed

3) Hydraulic jam
Carson fruit: dirt enters the gap; The temperature decreases and the valve core shrinks; However, the main reason is the effect of the radial unbalanced force caused by the change of the shape and common port degree of the non slide valve pair, which mainly includes:
A
what is the shape error between the valve core and the valve body? The shaft mouth line is narrow but not sinking
b  The valve core can reduce the working error without inverted cone, and the shaft mouth line is narrow but not sinking
c  Valve core nominal no part rise
Methods of increasing radial unbalanced force:
1)  Improve fabrication and disassembly accuracy
2)  Valve core down closing annular pressure equalizing groove