RU2534288C1 - Torsion spring - Google Patents

Abstract

FIELD: machine building.

SUBSTANCE: torsion spring comprises cylindrical resilient element and core fitted therein and aligned therewith. Core and resilient element allow varying of contact forces acting there between. This spring is equipped with two stiff end elements for them to interconnect rigidly the like ends of said cylindrical resilient element and core. Said cylindrical resilient element is composed by winding of high-strength fibre wound around said core. Said core is made of elastomer with high internal resistance and cavity. Winding coiling can be filled with elastomer.

EFFECT: one-spring cushioning of two vehicle wheels, decreased sizes.

9 cl, 13 dwg

Description

The invention relates to mechanical engineering, namely to means for damping vibrations and vibrations, and can find application as, for example, an elastic suspension element of a vehicle.

It is known from the prior art that torsion shafts are used as a means of damping vibrations and vibrations, as a rule, they are an elastic element in the form of a steel rod or a set of rods of circular cross section, as well as a set of steel long plates of rectangular cross section (Barsky I. B. Design and calculation of tractors. - M.: Mechanical Engineering, 1968. - 376 p., Table 18 on page 287). Torsion shafts rely on the perception of external torque, and their material experiences a mostly stressed state - a pure shift.

The disadvantages of the elastic elements of this type are:

- a relatively large mass;

- to achieve large twisting angles, a large element length is required;

- the impossibility of obtaining a smooth progressive characteristic of elasticity with great non-linearity;

- low dissipative properties.

For the elastic suspension element of many machines and, in particular, vehicles, it is necessary that the stiffness progressively increase with increasing load or stroke. This increases the ride, increases the energy consumption of the suspension and reduces the likelihood of its breakdown (RV Rotenberg, “Car suspension. Fluctuations and ride”, ed. 3rd lane and additional - M .: Mashinostroenie, 1972).

A well-known spring (SU 1762034, publ. 15.09.92), the working turns of which are made in the form of a round rod of composite material with twisted fibers.

The main disadvantages of such a spring are: the uneven distribution of stresses over the cross section of the coil, the relatively large material consumption and the inability to obtain the characteristics of elasticity with a given non-linearity. Depending on the index of the spring and its stiffness, the voltage at points located on the inner side of the section of the spring can exceed the voltage on its outer side by 1.7 ... 1.8 times. Due to the uneven distribution of stresses, the service life of springs is drastically reduced, for example, the elastic suspension elements of transport vehicles operating in conditions of high dynamic loading. Bench tests show that the fatigue failure of the springs primarily begins on the inside of the coil. The increased material consumption of the spring is due to the fact that in the middle of the cross section of the coil of the voltage is low and the material is underloaded. The absence of elements that increase the stiffness of the spring with increasing load, does not allow to obtain a nonlinear characteristic of elasticity.

Also known is a rubber shock absorber (RU 2120572, publ. 1992), comprising a hollow body and an elastic element housed therein with bushings molded at the ends.

In this design, the elastic element is loaded with uniformly distributed stresses, but there are significant drawbacks in it: it has a small stroke, it is impossible to obtain the elasticity characteristic with a given non-linearity and only accepts axial load.

A plastic spring is also known from the prior art (RU 2173802, publ. 12.12.95), consisting of a package of spring tongues, the individual spring tongues of which, when loaded, step by step and progressively interact with each other with increasing spring force depending on the spring travel.

The main disadvantages of the above springs are:

relatively large material consumption, low fatigue strength due to the significant unevenness of the stress distribution, both over the cross-section of the tongues and along their length, the spring cannot absorb the external load in the form of a torsional moment and has relatively low dissipative properties.

From the prior art of foreign countries, a torsion spring is known (US 6241224, publ. 05.06.2001), which is a plastic structure, the central part of which is made in the form of parallel rods of rectangular cross section with low torsional rigidity, which is designed to soften the transmission of external torque and the end parts are equipped with rigid elements that serve to secure the torsion bar in the mating parts, while the material of the rods is in a state of pure shear with a large uneven distribution edeleniya shear stresses. The disadvantages of the known torsion spring are as follows:

- low load capacity and durability (due to uneven distribution of stresses);

- low energy intensity;

- the inability to obtain the characteristics of elasticity with a given nonlinearity.

Closest to the technical nature of the present invention is a torsion spring (US 5464197, publ. 07.11.95), adopted by us for the prototype and containing coaxially located steel wire coil spring, a core in the form of a cylindrical shell of elastic material placed inside a coil spring and in contact with the latter with the ability to change the contacting forces due to the pressure of the air pumped into the shell.

The spring perceives the external load in the form of a torsional moment, and the spring wire works mainly on bending. In the cross sections of the wire, normal stresses arise, linearly varying along the height of the section. Moreover, in the central part of the cross-section, the stresses are zero and the spring material in this zone is underloaded. This leads to an increase in material consumption and a decrease in the ability to accumulate the potential strain energy.

Also the disadvantages of this design are:

- low dissipative properties, as the spring wire is made of metal having a low internal resistance;

- regulation (increase) of the torsion stiffness is possible only with the action of external torque in only one direction, when under the influence of the load the diameter of the coil spring rings will decrease. In this case, the deformation of the spring rings from pressure forces in the wire contact with the sheath will be opposite to the deformation from external load and, therefore, will cause an increase in the torsion stiffness. When changing the direction of action of the torque, the above forces will reduce the stiffness of the torsion bar. Therefore, for this case, it will be necessary to install a pressure shell outside the coil spring in the torsion bar design, which will lead to a complication of the structure, an increase in mass and a decrease in reliability;

- a small range of regulation of rigidity, because it is limited by the strength of the shell of an elastic material that works under biaxial tension — a dangerous stress state for all existing materials, and numerical analysis shows that the pressure in the shells of modern elastic materials cannot exceed ~ 10 MPa, which is an order of magnitude or more less than the limit stresses for metals;

- there are no elements that could automate the regulation of air pressure supplied to the shell, depending on the external load.

An object of the present invention is to provide a torsion spring with an adjustable non-linear characteristic of elasticity while reducing weight and increasing energy intensity, strength and dissipative properties.

The essence of the invention lies in the fact that the torsion spring contains a cylindrical elastic element and a core coaxially mounted inside it, each of which is made with end ends, the core and the elastic element being configured to change the contacting forces acting between them.

The difference is that the spring is equipped with two rigid end elements, each of which rigidly connects the same ends of the cylindrical elastic element and the core and is capable of absorbing external loads, the cylindrical elastic element is made in the form of a winding made of high-strength fibers wound around the core, and the core is made of an elastomer with high internal resistance and at least one cavity, while winding the winding can be multilayer, single and multi one with different directions and angles, as well as filling with an elastomer interturn and / or interlayer spaces.

In addition, another difference is that:

- end elements can be made of any axisymmetric shape, for example, in the form of disks with fasteners with mating parts;

- the core is made of porous material;

- the cavity or voids in the core are configured to be filled with a fluid;

- at least one cavity in the core is configured to fill with a fluid and pressure change of the latter;

- at least one cavity in the core is made communicating with other cavities and the environment through channels;

- the torsion spring is equipped with a rigid intermediate partition made with the possibility of transmitting external torque and with a Central hole, the radius of which corresponds to the external radius of the cylindrical elastic element, and rigidly fixed to the latter;

- the torsion spring is equipped with a rigid intermediate partition configured to transmit external torque and with a central hole whose radius corresponds to the radius of the core channel, while the partition divides the torsion spring into two equal parts, each of which is rigidly connected to one of the end elements;

- the torsion spring is provided with an outer protective shell made in the form of a hollow cylinder.

The technical result consists in the fact that the simultaneous suspension of two vehicle wheels by a single spring allows creating a suspension structure with smaller dimensions and more compact.

The proposed invention is illustrated by drawings, which depict:

figure 1 - General view of the torsion spring;

figure 2 - section aa in figure 1;

figure 3 is a General view of the torsion spring with an intermediate partition made according to option 1;

figure 4 - section aa in figure 3;

5 is a General view of the torsion spring with an intermediate partition made according to option 2;

6 is an embodiment of an end rigid element with splines;

7, 8 and 9 - embodiments of winding the windings on the core;

figure 10 is a cut-off part of the torsion spring with acting external and internal loads;

11 - core under the influence of internal loads;

Fig - internal forces acting in the fiber of the winding and between the core and the winding;

Fig - stress state of the material of the elastomer of the core.

The torsion spring contains a cylindrical elastic element 1, a core 2 and two rigid end elements 3. The elastic element 1 is made in the form of a winding 4 made of high strength fibers wound around a core 2. The core 2 is made of a high internal resistance elastomer or a porous elastomer (e.g., foamed polyurethane). Each of the end elements 3 rigidly connects to each other the same ends 5 of the winding 4 and the core 2. In addition, the end elements 3 may have holes 6 or slots 7, or any other known structural elements for connection with mating parts of machines (not shown shown). The connection of the end elements 3 with the ends 5 can be made by vulcanization or in the form of adhesive joints.

The winding 4 can be made with different directions and winding angles of high-strength fibers (in Figs. 7, 8, 9 the angles α, β), as well as multilayer (in Figs. 1, 2 - single-layer, and in Figs. 3, 4 and 5 - two-layer). The winding 4 can also be multi-start. The interturn and / or interlayer space of the winding 4 is filled with an elastomer (rubber, polyurethane).

The torsion spring can be divided into parts by an intermediate partition 8 (but there may also be several partitions) made with the possibility of perceiving an external load in the form of a torsional moment. To connect to the mating parts of the machines (not shown in the drawings), the intermediate partition 8 may have holes for bolts or slots similar to holes 6 and slots 7 of the end elements 3. In this case, parts 9, 10 (left and right) of the torsion spring can be made with different direction of winding high-strength fibers of the winding 4.

The core 2 may have one or more internal cavities 11 filled with a fluid (liquid or gas, such as air). If the external environment around the torsion spring corresponds to the fluid inside the cavities 11, for example, is air, then at least one internal cavity 11 of the core 2 can be made communicating with the external environment by channels 12. To communicate the internal cavities 11 with each other and with the external environment, the intermediate partition 8 can be made with at least one central hole 13, and the end elements 3 with the outlet 14 of the channel 12.

Equipping the spring with an intermediate partition 8 allows, in the case of use for a vehicle, two support wheels located on different sides of the vehicle to spring one spring at the same time. To protect against external influences, the torsion spring is equipped with an external protective shell 15, made in the form of a hollow thin-walled cylinder.

Torsion spring works as follows.

When external torsion moments M are applied to the end elements 3 (Fig. 10), the latter rotate relatively by twisting the torsion spring. In this case, the high-strength fibers of the winding 4 (in Fig. 10, the direction of one of the fibers indicated by i is shown by a dashed line) are loaded by tensile forces F _i (F _ti and F _yi are the components of F in the circumferential and axial directions, respectively). The winding 4 tends to reduce its diameter of the winding around the core 2, which leads to compression of the core 2 by pressure p, as well as axial compression by forces N and twisting by MK torques. As a result of this, a decrease in the volume of the inner cavity 11 (FIG. 10) of the core 2. An increase in the pressure of the fluid in the inner cavity 11 leads to an increase in the stiffness of the elastic characteristic of the torsion spring.

It is important to note that the presence of rigid end elements 3, connecting the same ends 5 of the winding 4 and the core 2 with each other, provides, on the one hand, the high-strength fibers of the winding 4 under tension and, on the other hand, constrains the deformations of the core 2 in the longitudinal direction (Fig. .10). This leads to an increase in the rigidity of both the core 2 and the entire spring. The material (elastomer) of the core 2 experiences a stress state of comprehensive compression (11, 12, 13), which is well perceived by all materials without the appearance of plastic deformations.

By changing the angles of winding of the fibers of the winding 4 (angles α and β in Figs. 7, 8, 9), the stiffness of the torsion spring can be adjusted. An increase in the values of the winding angles leads to a decrease in stiffness. At α = 90 °, i.e. when the fibers are parallel to the axis of the core 2, the stiffness of the torsion spring with the constancy of other parameters will be the smallest.

For a theoretical justification of the operability of the proposed design, we present the dependences between the external load M and the internal forces in the spring (fiber tension force F _i , pressure p, normal force in the core N and torque in the core MK), as well as their relationship with the design parameters of the spring. Expressions for the components F _ti and F _{yi of} the tension force of the fiber F _{i of the} winding 4 (figure 10):

$$F_{ti}=F_i\cos \alpha ,\left(\text{one}\right)$$

$$F_{yi}=F_i\sin \alpha ,\left(\text{2}\right)$$

where: α is the angle of winding the fibers onto the core.

The equilibrium equations of the cut-off part of the spring (figure 10) and the cut-off part of the winding (figure 12):

$${\sum }_{PR.}y=0:{\text{F}}_{\text{yi}}\cdot n\cdot k-N=0\left(\text{3}\right)$$

$$\sum mo{m}_{\mathrm{at}}=0:{\text{F}}_{\text{ti}}\cdot R\cdot n\cdot k+M_{\mathrm{TO}}-M=0\left(\text{four}\right)$$

$${\sum }_{PR.}=0:{\text{F}}_{\text{i}}-p\cdot h\cdot r=0\left(\text{5}\right)$$

where: n is the number of fibers in one circumferential layer of the winding;

k is the number of layers;

R is the radius of winding the layers of fibers in the winding, because the thickness of the winding layer δ is much smaller than the radius R, then the radii of the arrangement of all layers of fibers are taken to be the same and equal to R;

h is the step of winding the fibers in the layer;

r = r (α) is the radius of curvature of the winding fiber along the winding helix (depends on the angle of winding α).

Linear deformation of the core material 2 in the transverse directions (along the φ and ρ axes, Fig.13):

$${\epsilon }_r={\epsilon }_{\varphi }=\epsilon =-\frac{P}{E}\left(\mathrm{one}-\mu \right)+\frac{{\sigma }_{\mathrm{at}}}{E}\left(\text{6}\right)$$

where: E, µ - elastic modulus and Poisson's ratio of the core material;

- нормальное напряжение в поперечных сечениях сердечника (по оси у); $${\sigma }_{\mathrm{at}}=\frac{N}{A}$$

- normal stress in the cross sections of the core (along the y axis);

.A is the cross-sectional area of the core, in the case of a round continuous cross-section of diameter d, the area is $$A=\raisebox{1ex}{$\mathrm{<figure-callout\; id="2"\; label="\pi \; d"\; filenames="00000011.png,00000012.png"\; state="\{\{state\}\}">\pi \; </figure-callout>}{d}^{}{}^2$}\!\left/ \!\raisebox{-1ex}{$\mathrm{four}$}\right.$$

.

On Fig shows the tangential stresses τ _уφ = τ _φу , acting from MK. These stresses are small and, in addition, do not affect the linear strains ε.

Based on the above equations (1) - (6), we can draw the following conclusions:

- the tension force of the fiber F is a function of the parameters M, M _K , R, n, k, α, i.e.

F _i = F _i (M, M _K , R, n, k, α);

- the compression force of the core N depends on the parameters M, R and α, i.e.

N = N (M, R, α);

- the pressure p between the winding 4 and the core 2 is functionally related to the parameters F _i , h, r (α), E and µ, i.e.

p = p (F _i , h, r (α), E, μ).

Thus, by changing the spring parameter R, n, k, α, r (α), E, μ, it is possible to influence the internal forces in the spring F _i , p, N and M _K and, therefore, the elastic characteristic of the spring that relates its deformation (twist angle) with external load M.

When removing external torsional moments M, the torsion spring returns to its initial unloaded state due to the action of the elastic forces of the winding 4, core 2 and back pressure in the inner cavity 11.

The stiffness of the torsion spring can be changed by forcing the pressure of the fluid in the internal cavity 11 (by compressor or hydraulic pump, not shown in the drawings). For this, the internal cavity 11 is made communicating with the external environment through the channels 12 and the outlet 14 in one of the end elements 3.

The dissipative properties (dispersion of vibrational energy) of the torsion spring are ensured by the viscous resistance of the fluid due to its flow inside the internal cavity 11 and the choice of core material 2, for example, elastomers with high internal resistance.

Thus, the entire volume of high-strength fiber material and core material experiences a uniform stress-strain state and, therefore, is used with the greatest efficiency. As a result of this, the dimensions and mass of the torsion spring are minimized, and the necessary dissipative properties are also provided. By selecting the shapes and volumes of the cavities, as well as by changing the pressure of the fluid filling the internal cavity, the nonlinearity of the elastic characteristics of the torsion spring is regulated.

Claims (9)

1. A torsion spring containing a cylindrical elastic element and a core coaxially mounted inside it, each of which is made with end ends, the core and the elastic element being configured to change the contacting forces acting between them, characterized in that the spring is equipped with two rigid end elements , each of which rigidly connects with each other the same ends of the cylindrical elastic element and the core and is configured to absorb external load, the cylindrical elastically the element is made in the form of a winding made of high strength fibers wound around the core, and the core is made of an elastomer with high internal resistance and at least one cavity, while winding the winding can be multi-layered, single and multi-starting with different directions and angles, as well as with filling with elastomer interturn and / or interlayer spaces. 2. The torsion spring according to claim 1, characterized in that the end elements can be made of any axisymmetric shape, for example in the form of disks with fasteners with mating parts. 3. The torsion spring according to claim 1, characterized in that the core is made of porous material. 4. The torsion spring according to claim 1, characterized in that the cavity or cavities in the core are configured to be filled with a fluid. 5. The torsion spring according to claim 1, characterized in that at least one cavity in the core is configured to change the pressure of the fluid. 6. The torsion spring according to claim 1, characterized in that at least one cavity in the core is made communicating with other cavities and the external environment through channels. 7. The torsion spring according to claim 1, characterized in that it is equipped with a rigid intermediate partition made with the possibility of transmitting external torque and with a Central hole, the radius of which corresponds to the external radius of the cylindrical elastic element, and rigidly fixed to the latter. 8. The torsion spring according to claim 1, characterized in that it is equipped with a rigid intermediate partition made with the possibility of transmitting external torque and with a Central hole, the radius of which corresponds to the radius of the channel of the core, while the partition divides the torsion spring into two equal parts, each of which are rigidly connected to one of the end elements. 9. The torsion spring according to claim 1, characterized in that it is provided with an outer protective shell made in the form of a hollow cylinder.

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