Category Archives for Hydraulic Control System
Flow Trough Orifice
Orifices are a basic means for the control of fluid power. Flow characteristics of orifices plays a major role in the design of many hydraulic control devices. An orifice is a sudden restriction of short length (ideally zero length for … Continue reading
Disadvantages of Hydraulic Control
Although hydraulic controls ofl’er many distinct advantages, several disadvantages tend to limit their use. Major disadvantages are thie following: 1. Hydraulic power is not so readily available as that of electrical powe:r This is not a serious threat to mobile … Continue reading
Advantages of Hydraulic Control
There are many unique features of hydraulic control compared to other types of control. These are fundamental and account for the wide use of hydraulic control. Some of the advantages are the following: 1. Heat generated by internal losses is … Continue reading
Hydraulic Compensated Four-way Control Valve Characteristic
There are many ways of compensating for the reaction forces in spool type valves. In general most of these methods do not actually change the reaction force characteristics at each orifice. The general trend is to try either to nullify … Continue reading
Hydraulic Uncompensated Four-way Control Valve Characteristic
Figure 1.11 illustrates the valve reaction forces for an uncompensated four-way valve. It can be noticed that the forces become very large for the higher flows and at large valve openings. AB the valve spool is moved to even larger … Continue reading
Hydraulic Four-way Control Valve Leakage Characteristic
In addition to the flow which the valve supplies to the piston, there is also a small amount of leakage flow within the valve itself. Since there must be some diametral clearance between the valve spool and its sleeve, there … Continue reading
Hydraulic Four-way Control Valve Characteristic
The four-way valve is so-named because of the required number of hydraulic lines to the valve as shown by Fig. above. The four-way valve requires a minimum of four lines, a fluid supply, two control lines to an actuator, and … Continue reading
Hydraulic Valve Characteristic
Proportional valves provide control of fluid power by a combination of variable-area orifices or in some cases by a combination of both fixed and variable orifices. By varying the area of the orifices, the desired relationship of flow and pressure … Continue reading
Advantages of Hydrostatic Transmissions
A hydrostatic transmission provides improved maneuverability, but at a cost. The efficiency of a hydrostatic transmission is always lower than a discrete-gear transmission. A discrete-gear transmission will typically have an efficiency of 95% or greater, meaning that 95% of the … Continue reading
Comparison of Hydrostatic and Mechanical Drives
The same vehicle shown in Fig. 6.1 is shown in Fig. 6.11 with the mechanical transmission replaced with a hydrostatic transmission; all other components remain the same. To provide a specific example, we will begin by specifying a variable displacement … Continue reading