www.mekanizmalar.com/menu_pneu... This video shows working principle of pressure compensated hydraulic piston pump. Notice how angle of swash plate changes when slider move above 80 bar. Also notice the pressure gauge.
Rafael, You are right!. When the pressure reaches to 120 the swash plate becomes perpendicular to the rotation axis of the pistons. This stops pump pumping oil even though pump being powered by electric motor. Since no oil is being pumped, the load on electric motor is reduced substantially.
Thank you for posting this as it has made my understanding of this action a lot clearer. I helped our mechanic change the bottom right primary pump yesterday on our Liebherr 954 and he explained to me, or tried to at least, but this really showed me everything as far as the operating principle goes!
With the pistons with the swash plate at the vertical position there should be no flow of oil and should go into neutralize what it should be powering. Also should show motor RPM powering and output RPM running
Do you use this pump to preventing your system from getting pressure higher than you want? Cause when the pressure reaches 120 the plate is perpendicular to the shaft. Am I right?
Huh.. Thats how I would have done it. Are there any examples of variable displacement, pressure compensating pumps that don't have the side loads that this kind of pump would have?
This is the basic principle but to make this to work properly a pressure relief valve is needed. As this is pictured the flow starts to drop long before the desired maximum pressure is reached, not like this animation shows, because the pilot pressure works against the spring the whole time. The valve doesn't give any pilot pressure to the servo cylinder before the desired relief pressure has been reached.
I don't understand something: for the swash plate at 90 degrees, the distance from shaft axis to piston axis is the same for all pistons, but at some angle (60 degrees), that will not be the same - smaller in vertical plane and bigger in horizontal plane - ellipse, oval shape. How is this done? What shape has the swash plate to allow this displacement?
I am sorry but I don't understand your confusion. Distance between shaft axis to pistons axis for alt the pistons are the same no matter what the swash plate angle is. Maybe I am missing something in the question but I don't know what. Swash plate angle deviation from 90 degrees is not that much, maybe +/-15 or 20. Do not forget also that pistons are moving inside a cylinder block, which makes axis distances from shaft axis to pistons axis constant. Swash plate is circular.
I understand how you mean, it is simply just compensated by doing the swash plate a little bigger to accommodate the smaller diameter. There are other designs where this will not be necessary.
all modern excavators etc use this design. Kawasaki and Rexroth build alot of pumps. Ask bucket starts dig and meet resistance swash plate angle is reduced ( compensated) increasing pressure to system to dig quickly. When bucket is full and operator booms up sticks out to dump much less force is required so swash plate angle is increased ( compensated) to increased flow (gpm) for maxinum speed. That's why these machines today very fast and efficient. Shalom
Shalom! So if I want to repower my machine with electric motor, should I replace the pump as well since it has a minimum idle rotation in its design? Or would it be okay to have stop and go rotation from the electric motor? Thank You! Shalom!
I don't understand how it works between the admission and evacuation port in the upper part of the cycle as you look at the model. Since the fluid is incompressible I don't thing any movement is possible between the 2 ports
Hi Cristian, The ends of the cylinders are connected to crescent shaped channels on the green disk shown at right. When the pistons move to the right during compression, the oil is forced out from the red crescent. When the piston move to the left, the oils is sucked in from the blue crescent.
mekanizmalar Yes I understand that. I don't understand how you compress the fluid between the 2 crescent channels. There is a portion where the cylinder is not connected to either one but the piston is still compressing the fluid. That will not happen (the compression in a fixed volume chamber).
Cristian Armaselu First, As you can see from video, the gab between the two crescent is as wide as the cylinder width. So transition is in split second. The second is that at the upper and the bottom section where transition occur, the rate of change of the piston stroke is zero, therefore piston literary do not make any compression in there, The third is that there is not such a thing as incompressible fluid. When the oil is compressed, no matter how small, there is always some compression. Combined effect of these three cases make it work.
+Rehuel Galzote This is not an engine. This is a hydraulic pump. Blue indicates low oil pressure coming from oil tank, and the red indicates high pressure oil going to cylinders or hydraulic motors.
mekanizmalar Oh oh haha I'm really sorry. I've been looking through ur engine videos I mistakenly thought this thing is engine since there's an engine that looks like this.
no when swash plate is near Zero the highest pressure lowest volume is produced. When swash plate is at maxinum angle lower pressure maximum volume. I work for CAT. Shalom
Hi Guys, IN Excavator model EX 110 Hydraulic Pump Has 2 variable displacement pumps flow rate is 2 X 115. lpm I have drilling application in excavator we need flow rate 0f 170 LPM. How to increase flow rate in this pump any have Idea?
I am sure that it leaks. However, there must be a hole in the body where swash-plate located. This hole drains excess oil to the reservoir of the hydraulic unit.
Really, a great world of liquid fuel motors. No electricity. No network power supply. Visible operation. Please forgive me, but I am doing a comparion of Invisible energy (EMF) usage versus visible energy sources. Invisible energy passage like Electron flow can kill our children. I see mechanical engine designs as reaching post-evolution and are in ART form already.
This animation is totally wrong. when swash plate get more angle, it produce higher pressure. when vertical, there is no flow and no pressure.the animation just show opposite right way!
+toyuko aka When swash plate has more angle, there will be more oil flow, but not necessary high pressure. During this time hydraulic motor, or a hydraulic piston is operating in the green region shown in the animation. When motor or piston encounter an obstacle, the pressure will spike and during that time swash plate should be brought to vertical position to prevent further pressure rise. When swash plate is in perpendicular position, the oil flow becomes zero, but pressure inside the pipe still be high. Leakage in the system gradually reduce the pressure, but as long as the obstacle prevent piston to move, small deviation of swash plate will maintain high pressure in the system. In short the animation shows what I described in here. I also suggest to you to watch following animation about ram pump. ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-aUTjVovpKvA.html Notice that when there is flow, low pressure produced in the exit causes valve to close. But when the valve closed, there is no flow discharge from the system, and pressure spikes. In short no flow does not mean there is no pressure.
i think you are wrong, no oil flow, the pistons don't take compression, so that the pump doesn't produce pressure. the pressure in the suction and discharge pipe are the same.
I'm not sure I'm following this quite right, but it does seem to me that oil is consumed by the pump under negative pressure (so you get oil plus vacuum), which is the play it needs to provide absolute compression beyond the intake stroke. This lets all output stroke run as variable points leading up to absolute compression of the oil. Whenever there is a stroke to push oil out, it can't begin with absolute pressure on all strokes, otherwise the sum of pistons would overload and lock in position or blow a seal. Mechanically there are many ways to accomplish this task, but this one appears fairly efficient. I just wish he'd done a 3d animation showing the inlet and outlet stroke positions matched with flow regulation points.
