RU2133395C1 - Hydraulic cylinder rod - Google Patents

Abstract

FIELD: power hydraulic engines. SUBSTANCE: hydraulic cylinders are of one- or two-way action with one-sided rod. Internal cavity of rod section is shaped as circle with segments of different areas cut off from top and bottom. Larger-area segment is cut off from side of more compressed fibers. EFFECT: enhanced reliability. 7 dwg

Description

 The invention relates to a hydraulic drive of machines operating under significant loads on working equipment, in particular to reciprocating power hydraulic motors - single or double-acting hydraulic cylinders with a one-sided rod (see Marutov V.A., Palovsky S.A. Hydraulic cylinders. M .: Engineering, 1993, p. 7, Fig. 2a), which is subject to longitudinal-transverse bending during operation. At the same time, the stresses arising in the dangerous section of the rod stem are described by the following strength condition (see Kobzov D.Yu. Diagnostics of hydraulic cylinders of working equipment for single-bucket construction excavators: Diss. .. Candidate of Technical Sciences / LISI.-L, 1987, p.365).

Σσ _i = P / F + (M _Q + Py _t + Pe) / W ≤ [σ], (1)
where P is the longitudinal pushing (compressing) force of the hydraulic cylinder;
M _Q - bending moment from the transverse (weight of the hydraulic cylinder) load;
F is the cross-sectional area of the rod;
W is the axial moment of resistance of the rod section;
Y _t is the total deflection of the hydraulic cylinder as a result of its operational longitudinal-transverse loading; e is the eccentricity of the application in the supports of the hydraulic cylinder of the longitudinal compressive force P;
Σσ _i and [σ] are the current operational and permissible stresses in the dangerous section of the rod.

 Known hydraulic cylinder (analogue) with a solid rod of circular cross-section (see Marutov V.A., Pavlovsky S.A., Hydraulic cylinders. M: Engineering, 1966, p. 29, Fig. 17).

 However, a solid rod, having a large weight, causes significant reactions in the movable pressurized mates of the rod-bushing and piston-sleeve hydraulic cylinders, intensifying the wear process of the guide and sealing mating elements and, thereby, reducing durability, and at the same time reliability hydraulic cylinder.

 The closest in technical essence to the invention is a hydraulic cylinder (prototype) with a hollow rod of annular cross-section (see Marutov V.A., Pavlovsky S.A. Hydrocylinders. M: Mechanical Engineering, 1966, p. 30, Fig. 19, p. 68, Fig. 56, p. 124, Fig. 102), which has a lower weight and, therefore, reactions in the movable interfaces of the hydraulic cylinder, but a large total normal stress due to lower stiffness and strength.

The aim of the invention is to increase the reliability (durability) of the hydraulic cylinder by improving the stress-strain state of its rod (reducing the deflection Y _t and stresses Σσ _i ) by increasing its rigidity and strength by optimizing the characteristics (moment of inertia and axial moment of resistance W) of the cross section due to choosing a rational form of the internal cavity under the following conditions for comparing the invention with the prototype:
* the external form is the same - a circle;
* Cross-sectional area F is the same, and therefore:
- _{compression channel} compression stress σ are the same;
- the weight of the rod is the same.

 Theoretically, the named goal is realized by appropriate placement of the material in the cross section of the rod.

 This goal is achieved by performing the shape of the inner cavity of the rod cross section in the form of a circle with segments of different areas cut off from above and below, and a segment of a larger area is cut off from the side of more compressed fibers.

 The invention is illustrated by the drawing (Fig. 1), which shows the diagrams of compressive (Fig. 1a), bending (Fig. 1b) and total (Fig. 1c) normal stresses, as well as the cross-sectional shape of the rod: solid - analogue (Fig. 1d), ring - prototype (Fig. 1e), proposed with a clean bend (Fig. 1e) and proposed for operational loading of the hydraulic cylinder (Fig. 1g).

 The inventive rod of a hydraulic cylinder of circular cross section has an internal cavity in the form of a circle with segments of different areas cut off from above and below (Fig. 1g). Moreover, a segment with a larger area is cut off from the side of more compressed fibers. Thus, the cross-section of the rod is a reversed I-beam (Fig. 1e), and the claimed one is a Ta-beam (Fig. 1g), the wall thickness h of which, depending on the external force acting on the hydraulic cylinder rod, should be determined for each example considered, but with mandatory consideration specific operating conditions and the functioning algorithm of the hydraulic cylinder. It should be borne in mind that for I-sections, the wall thickness h ≤ 5% of the height of the brand. This position is also true for the analyzed case in relation to the outer diameter of the rod.

 The inventive rod of the hydraulic cylinder operates as follows.

As a result of operational loading of the hydraulic cylinder in its rod, in particular in a dangerous section, normal compressive (Fig. 1a) and normal bending (Fig. 1b) stresses arise, which are described by the first and second terms of expression (1), respectively. As a result of this, the total normal stresses are unevenly distributed over the cross section of the rod (Fig. 1c), which leads to its uneven loading and subsequent unrecoverable curvature in cases of analogue (Fig. 1d) and prototype (Fig. 1e) (see Kobzov D. Yu. Diagnostics of hydraulic cylinders of working equipment for single-bucket construction excavators: Diss ... candidate of technical science / LISI-L, 1987, p.365). However, most of the material of the rod (Fig. 1g) from the side of large compressive stresses allows you to evenly distribute stresses over the cross section of the rod. Further, the shift of the center of gravity of the cross section of the inventive hydraulic cylinder rod from the geometric center of the outer circumference of the rod by the value of H towards the formation of eccentricity e reduces the negative impact of the latter (product Pe in expression (1)) to a minimum. Finally, the invention causes a decrease in the magnitude of the deflection y _t due to an increase in the rigidity of the cross section, and, in addition, the product Py _t . All this in the compartment realizes the task of reducing the current operational stresses Σσ _i , as a result of which the difference {[δ] -Σσ _i } grows, and at the same time the durability of the hydraulic cylinder directly. In addition, as a result of a decrease in the values of e and y _{t, the} deformations of the hydraulic cylinder and, as a result, the reactions in its movable pressurized joints and the wear rate of their structural elements are reduced, which indirectly increases the durability of the hydraulic cylinder.

 Calculations show that in the proposed design of the rod, the axial moments of inertia and resistance of its cross section increase by 20 ... 30%, which accordingly leads to a decrease in bending normal stresses in the same range.

 Taking into account that durability is a property of reliability, we can safely conclude that the claimed goal of the invention is realized in the claimed design of the hydraulic cylinder rod.

Claims (1)

 A hydraulic cylinder rod having an internal cavity, characterized in that the internal cavity is made in the form of a circle with segments of different areas cut off from above and below, with a segment of a larger area being cut off from the side of the more compressed fibers.