PL163686B1 - Method of determining total and mechanical efficiency of a hydraulic cylinder - Google Patents

Abstract

A method for determining the total efficiency and mechanical efficiency of a hydraulic cylinder, in which piston rods of two double-action cylinders are mechanically joined with a single-action piston rod of identical dimensions of both chambers, whereas one cylinder is the cylinder under test, whereas both cylinders are located along the same axis, and further, one pump delivers oil to two chambers in both cylinders of the same active piston area, whereas the other pump delivers oil via a distributor to the remaining chambers alternately, and the following parameters are metered: piston rod travel speed, oil flow to the chamber being filled, and pressures in both chambers of the cylinder under test, characterized in that while the piston rod of the cylinder under test (1) is travelling out, the following parameters are being metered: pressures (p1, p2) in both chambers, oil inflow, and piston rod travel speed, whereas during the return travel, the following parameters are metered while keeping the same piston rod travel speed: pressures (p3, p4) in the same chambers, and oil outflow, and further, the total efficiency and mechanical efficiency are calculated for the piston rod out travel of the cylinder under test (1) by formulas:.<IMAGE>

Description

The subject of the invention is a method for determining the overall mechanical efficiency of a double-acting hydraulic cylinder with a single-piston rod.

The previously known method of determining the overall efficiency and mechanical efficiency consists in measuring the longitudinal force in the piston rod, the speed of the piston rod, the oil flow rate to the filled cylinder chamber and the pressure values in both chambers of the tested cylinder. The total efficiency value η / _c and mechanical / ą _n is then calculated according to the formulas tc L ^F > · ^v

Q -l / P— - P ₂ / I / P / η ma —---------——

Ip-p · Sp - P / · Sgl in which t

F - pushing or pulling force measured in the piston rod of the tested cylinder,

V - piston rod speed, g - oil flow rate into the filled cylinder chamber,

Pj, pg - pressure in the cylinder chambers,

Sl, Sg - active surfaces of the piston.

The disadvantage of the above method of determining the efficiency is the high labor-consumption resulting from the need to assemble and gauge the force sensor each time and to measure the force.

Also known from the description of the invention to the USSR copyright certificate No. 909379 is a system used to test hydraulic cylinders, in which two double-acting cylinders with a single-piston rod having working chambers of equal dimensions are mechanically connected to each other by piston rods in such a way that both cylinders are located along the length of common axis. The system includes two hydraulic pumps, one of which presses oil simultaneously to two chambers with the same active surface area of the piston, and the other pump alternately pumps oil through the distributor to the other chambers.

The object of the invention is to provide a method for determining the overall and mechanical efficiency of a hydraulic cylinder, which does not measure the longitudinal force in the piston rod.

The method of determining the overall and mechanical efficiency of a hydraulic cylinder, according to which the piston rod of a tested cylinder is mechanically connected to the piston rod of a second cylinder having the same dimensions of working chambers as the tested cylinder, so that both cylinders are located along a common axis, then oil is pumped by one pump simultaneously to two chambers of both cylinders with the same active surface of the piston, and the second pump pumps the oil alternately through the distributor to the other chambers, thus causing the movement of the piston rod, it is distinguished by the fact that when extending the piston rod of the tested cylinder, pressure is measured in both its chambers , the flow rate of the oil flowing into it and the speed of the piston rod, and in the return movement of the piston rod, are measured while maintaining the same speed of the piston rod, pressure in the same chambers and the flow rate of oil flowing out, and then the total and mechanical efficiency values for the extension of the piston rods are calculated and from the formulas:

/ p3 = ——P ₂ «P - + / 3 ^ 3 — Sp« S— / ·) _{Cl a} ......................... ....

. P - / P3 - P ₂ /

2 / p · —2l / pP — 4 — SP -'— / ^: -2 · Ϊ2 where t

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- pressure in the rodless chamber and the piston rod of the cylinder tested while extending the piston rod,

Pg · P4 - pressures in the piston rodless and non-rod chamber of the tested cylinder during the piston rod retraction, ^s 1 '§2 active surfaces of the cylinder's non-rod and piston rod chamber,

V - speed of the piston rod of the cylinder tested during extension,

Q - oil flow rate into the bore-rod chamber J of the tested cylinder during the extension of the piston rod

For the piston rod retraction, the efficiency is calculated from the formulas t —Ρ2 ^β = 2 ~ Ρΐ ^β 2ΐ ⁺ Ρ4 + 2 ~ Ρ3 ^β θΐΧ ·) / »Q® / 3% and P} / nm ¹ / i. / 4 ^ 2 ^P / ' ^S 1 /

Ί ^m 2 - 2 - / ¹ * Γ / (/ ³ P ^{/ p} 1 ^S 1 where j

Pl »pg - pressure in the rodless and piston rod chamber of the cylinder tested while inserting the piston rod, ρ ^, P4 - pressure in the rodless and piston rod chamber of the cylinder tested while extending the piston rod, $ 1, Sg - active surfaces of the cylinder and rodless chamber,

V - speed of the cylinder piston rod during retraction,

Q - oil flow rate to the piston rod chamber of the tested cylinder.

The advantage of the method according to the invention is a significant reduction in labor consumption due to the fact that only the pressures in the cylinder chambers as well as the speed of the piston rod and the oil flow to the cylinder chambers are measured. An additional advantage is the reduction of the measurement error several times compared to known methods, which significantly increases the reliability of the results of the efficiency tests.

The method of determining the efficiency according to the invention is explained in more detail on the basis of the system shown in the drawing, which schematically shows a cylinder test stand for determining its overall and mechanical efficiency when extending the piston rod.

The piston rod of the tested cylinder 1 is mechanically connected to the piston rod of a similar cylinder

2. The piston rods are connected in such a way that it is possible to move them along a common axis. The rodless chambers of both cylinders 1 - 2 are connected with a high pressure pump by means of pipes

3, and the piston rod chambers are connected by conduits via a distributor 4 to a low-pressure pump 5. Cylinders 1-2 have working chambers of the same geometrical dimensions, and the seals in both cylinders are of the same type.

Other elements of the stand are - safety valves 6 to prevent overloading of pumps 3, 5, overflow valve 7, which is used to regulate the load on cylinders 1, 2 by pressure, filters 8, tank 9 and a thermometer 10. The equipment of the automatically controlled stand should also include the control apparatus with limit switches 11. In order to determine the total or mechanical efficiency, during the extension movement of the cylinder 1 piston rod, oil is pumped simultaneously into the piston rod chambers of cylinders 1, 2, and oil is alternately pumped into the piston rod chambers of both cylinders through the distributor 4 by the pump 5. During subsequent movements working extending and retracting the piston rod of cylinder 1, the pressure is measured t Ρχ · Pp - during the extension of the piston rod, P3 p ₄ - during the retraction, moreover, during the extension, the oil flow rate Q is also measured with the flow meter 12 and the piston rod speed V, and then the is the value of the efficiency of the piston rod extension movement of cylinder 1 from the formulas

- ^P 1 '= l ~ ^p 2'1 / 3 · 3 ^, + l ^, l4 * ^ 2! * ¹ / i Q. 3Ρι ~ Ρ _ζ /

163 686 /, (3 * ®l "- ^ł 4 * ®2 / ^ 2-2 / ¹ ♦ —-—--- / (3 * ll3Pl- ^S 2

In order to determine the total or mechanical efficiency, when the cylinder 1 piston rod is retracted, oil is pumped by the pump 3 simultaneously into the piston rod chambers of cylinders 1, 2, and oil is alternately pumped into the piston rod chambers of both cylinders through the distributor 4 by the pump 5. The flow meter 12 is mounted in the line connecting the distributor 4 with the piston rod chamber of cylinder 1. During the retraction of the piston rod of this cylinder, the pressure P ^ P2 is measured, the flow rate Q of the oil with the flow meter 12 and the speed of the piston rod V, and during the extension - the pressure P3, p4 is measured, and then the value of the efficiency of the retraction movement is calculated cylinder 1 piston rod of the following formulas:

/ P- * 2 ^ 1 * ®pill * ®2 "l3 * 3 * l / ·) 2 o Q · / p ₂ - P] /" (/ i. 24 · 2 3 1 / · θι —3 * 2 1 1l * 2

For example, the values of pressures in the chambers of cylinder 1 during the piston rod extension movement are: p ^ a 20 MPa, P2 = 1 MPa, p ^ 20.5 MPa, p ^ a 4 MPa and at the active surfaces of cylinder 1 S1 = y5 cm2 and a 11 m2 ^ orzz V a 0.2 2/3 1 Q q 2 dz ^ / s the calculated efficiencies are ^c and ³ 2.95, η m1 2 2.98, and for the piston rod retraction motion, when a 1.7 MPa, P2 2 22 MPa, Pp a 2.6 HPa, Pp = 20.5 MPy oaaz az. 0.1 m / zz Q a 0.64 drn ^ / g the calculated efficiency is equal ^ c- = 2.72, 1 ^ 2 2 2.92

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Publishing Department of the UP RP. Circulation of 90 copies. Price: PLN 10,000

Claims (2)

Patent claim The method of determining the overall efficiency and mechanical efficiency of a hydraulic cylinder, in which the piston rods of two double-acting cylinders are mechanically connected with a single-sided piston rod with the same dimensions of working chambers, one of which is a cylinder tested so that both cylinders are suctioned along a common axis, and then one the pump pumps oil simultaneously into two chambers of the cylinders with the same active surface of the piston, and the pump pumps the oil alternately through the distributor to the remaining chambers and measures the speed of the piston rod, the oil flow rate to the filled chamber and the pressure values in the chambers of the tested cylinder , characterized in that when extending the piston rod of the tested cylinder / 1 /, the pressures p ^, Pg in its chambers are measured, the flow rate of oil flowing into it and the speed of the piston rod, and in the piston rod return rschs, the pressure p is measured at the same speed ^, p ^ in the same como and the flow rate of the oil flowing out, then the values of the total and meehanic efficiency are calculated for the case of the piston rod of the tested cylinder being sucked out / 1 / from the formulas: / p ₁ =; ₁ -p ₂ .s ₂ + p ₃ .s ₁ -p ₄ .s ₂ /. v / ^Cl .......... r ------ v ^m . p / 4 sf- ~ -? i.;. ^[ and ⁴ : Js./ 2 ρ-. p. -Π / 3 S ₂ where: Ρχ, p ₂ - pressures in the piston-rod chamber of the tested cylinder while extending the piston rod, P3, p ^ - pressures in the piston-rod chamber of the tested cylinder while retracting the piston rod, S. ' Sj> - active active chamber of rodless and piston rod cylinders, V - the speed of the tubercle of the cylinder tested during extension, Q - the intensity of the plunger in the oCsJs into the bladder chamber ογϋπόΓ, tested while sucking out the rod, and in the case of inserting the plunger from the formulas: η c ₂ / p3 * p2-P / 3S ^ + p4 · —4Ρ ^ · 3χ / ·) | - - - o>«> w - 2 Q. = 4 ^ 3 / s / p · ^S S - “_ P ³ _ · 4j. ⁴ 2 ^{P. S} x where: Pl, p ₂ - pressure in the piston rod and discharge chamber of the cylinder tested during the insertion of the piston rod, p ^, p ^ - pressure in the cylinder chamber and ^^^ zyys ^^^^^ J of the cylinder tested during piston drying, Sp ^ 2 "Active surfaces of the cylinder rod-free and piston rod chamber, V - speed of the piston of the cylinder tested during vaaaaa, Q - intensity-survival into the chamber tPłccysl <in the cylinder bnaneło. 163 686