Detailed solution of the closed loop speed limiter of pump controlled motor

The closed loop speed limiter of pump-controlled motor belongs to the volumetric speed control loop, which adjusts the movement speed of the actuator by changing the displacement of variable pump or variable motor. In the volumetric speed control loop, the output flow of the hydraulic pump is all directly into the hydraulic motor, no overflow loss and throttling loss, and the working pressure of the hydraulic pump varies with the change of load. Therefore, the speed control loop has high efficiency and less heat. Volumetric speed control loop is often used in high-power speed limiters such as construction machinery, mining machinery, agricultural machinery and large machine tools.

According to the different mode of hydraulic pump and motor speed regulation, it can be divided into the following three types:

(1) The variable pump motor volume speed control system:

The speed and steering of the motor can be controlled by adjusting the variable mechanism of the variable pump to change the displacement of the pump. Constant power speed regulation can be carried out to adapt to drastic changes in load, the speed range of this loop can generally reach 40%. But the pump in small displacement (low speed) circuit bearing capacity is poor. This circuit has been applied to the relevant devices of small diesel locomotives, hydraulic cranes and marine tattoo cars and so on.

(2) One variable motor volume speed limiter for quantitative pump:

The output speed of the motor is adjusted by changing the displacement of its own, and the output of constant torque can be realized. But the system cannot change direction, the speed range is very small, which limits its application. When the high-speed operation and motor displacement is small, the speed rigidity of the loop is very low, the motion stability is poor, and the high-speed bearing capacity of the loop is poor.

(3) Variable pump variable motor volume speed limiter:

The adjustment of the output speed of the motor can be divided into two stages of low speed and high speed. In the low speed section, the displacement of the variable displacement motor is maximized, and the speed of the motor is changed by adjusting the displacement of the variable displacement pump. This speed section is called the working characteristics of the variable displacement pump with a certain amount of motor-type speed regulating circuit; in the high speed section, the displacement of the variable displacement pump is adjusted to the maximum, and the displacement of the hydraulic motor is changed to adjust the speed of the motor. The degree is known as the working characteristics of a variable motor volume speed control loop with a quantitative pump.

There are two kinds of variables in the motor. This system has a wide range of speed regulation, is the product of the former two speed regulation systems, and its speed regulation characteristics are very suitable for general mechanical load requirements, the most widely used. This circuit is suitable for high-power hydraulic system, such as port lifting and conveying machinery, mining and excavating machinery, etc.

  1. Preparation work before installation

(1) To achieve a high degree of cleanliness of the operating environment, it is necessary to thoroughly clean the operating table, parts and appliances.

(2) After the parts to be installed have been cleaned and checked to be qualified, they are discharged regularly on the workbench so as to be placed in an orderly and disorderly manner.

2 Points for attention of fuel injection pump

(1) It is necessary to use the opening wrench, plum blossom wrench, sleeve wrench, screwdriver, wooden fade and various special items in the process of the installation, and the movable wrench, pipe pliers and other general-purpose things shall not be used.

(2) Attention should be paid to the installation direction when installing camshaft. After the tightening bolts of the central bearing of the camshaft are tightened evenly, the camshaft should be transformed sensitively and its axial clearance should be 0.02-0.06mm. Note that the direction of the oil seal shall not be reversed.

(3) The sequence of the plunger assembly is opposite to that of the differentiation procedure. When installing the plunger sleeve into the flange sleeve, attention should be paid to aligning the positioning groove on the plunger sleeve with the positioning pin hole; after pressing the pin, the plunger sleeve should be able to move up and down 1-2 slightly. When O ring is installed, a small amount of lubricating oil should be coated to prevent damage and facilitate installation. When installing the diversion ring, attention should be paid to the difference between the upper and lower parts. In addition, clamp rings should be clamped in the clamp.

When loading the oil outlet valve coupler of speed governor, the upper end face of the plunger sleeve and the lower end face of the oil outlet valve seat should be cleaned to make the joint surface tight, avoid oil leakage during the plunger operation, and affect the uniformity of the cylinder oil supply. The tightening torque of the pressure seat of the oil outlet valve is 107.8 N.M, and the tightening intention is reached in the order of tightening, loosening and tightening stages.

(4) After the plunger speed governor device, attention should be paid to make the steel ball thoroughly into the groove of the manned oil supply control rod. After installation, the oil supply control rod can be checked manually to see whether the left and right movement of the oil supply control rod is smooth.

(5) When the plunger is installed with a plunger sleeve, special attention should be paid to making the symbolic side of the plunger flange block face the orientation of the positioning pin, so that the position of the plunger should not be misaligned, or the fuel injection pump cannot operate after the plunger is installed. After the plunger is installed with the plunger sleeve, the oil supply lever should be pulled left and right to check whether it is blocked.

 

https://www.h-nec.com/forklift-speed-limiter-with-actuator-n2011a-p00093p1.html

Mohsen Daemi
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