Shock absorber

• by the principle of action - on friction or mechanical (dry friction), hydraulic (viscous friction), electromagnetic (according to the scheme close to linear motors );
• by the nature of the action of friction forces - on single-sided and double-sided shock absorbers (with resistance on forward and reverse strokes);
• structurally hydraulic shock absorbers are divided into lever-blade, lever-piston and telescopic (two- and single-tube) with or without gas support;
• according to the nature of the resistance force change , depending on the movement of the rollers, the speed and acceleration of this movement, the shock absorbers are divided into:
  • shock absorbers with approximately constant friction force (for example, a simple mechanical shock absorber of the Landsverk tank);
  • shock absorbers with a friction force dependent on displacement (“relaxation” ones are mainly installed on high-speed tracked vehicles), and the friction force can be either proportional to displacement or have a non-linear relationship;
  • shock absorbers with frictional force proportional to the speed of the roller (the vast majority of modern hydraulic shock absorbers);
  • shock absorber, the resistance of which varies in proportion to the acceleration.

Unilateral and bilateral

One-way shock absorber

In this type of shock absorber, the resistance during the course corresponding to the compression of the suspension is insignificant, and the main energy absorption occurs during rebound. Thanks to this, they provide a somewhat smoother stroke, however, with the growth of road irregularities and speed, the suspension does not have time to take up its original position until the next actuation. this leads to a breakdown and causes the driver to slow down. With the advent of double acting shock absorbers around 1930, the one-way design gradually fell out of use.

Two-way shock absorber

The shock absorber, which acts (works) in two directions, that is, the shock absorber absorbs energy when the rod moves in both directions, transferring, however, at the same time some part of the pushing force to the body during the direct course. Such a shock absorber design is more efficient than a one-way shock absorber, in the sense that it can be built taking into account the necessary compromise between smoothness and stability of the car on the road. For high-speed cars, more “rigid” settings are characteristic, for comfortable passenger ones - more “soft” ones, where most of the work of the shock absorber falls on “rebound”.

On motor vehicles, as a rule, the effectiveness of the shock absorber compression stroke (compression, wheel hitting an obstacle) is made less than the efficiency of the rebound (return motion) stroke. In this case, when compressing, the shock absorber transmits less shocks from irregularities to the body, and, when stretched, “holds” the wheel from hitting it against the road.

Friction shock absorber

Friction (mechanical) shock absorbers in the simplest case are a rubbing pair with a fixed compression force. A design with resistance proportional to displacement, with an operatively adjustable force, etc. is possible. The obvious property of friction dampers is that their resistance does not depend on the speed of movement of the lever. Therefore, in the literal sense of the word, they are dampers , since they perform only one of the functions indicated in the definition of a shock absorber - vibration damping. Advantages - simplicity and relative maintainability, reduced requirements for machining parts, operating conditions, resistance to minor damage. The principal drawbacks are the irremovable wear of the rubbing surfaces and the presence of some effort of moving away, which is impossible to get rid of without complicating the mechanics. As a result, this type of shock absorber has not been used for a long time on automobiles, remaining only on individual samples of military equipment. Also in light and / or low-speed vehicles (mopeds, tractors, etc.) the role of a friction vibration damper can perform friction between suspension parts.

One of the most massive friction shock absorbing structures in old cars is the leaf spring , which combines the functions of an elastic element and a damper, working by mutual friction of the spring leaves.

Hydraulic shock absorbers

Hydraulic shock absorbers are most common. In hydraulic shock absorbers, the resistance force depends on the speed of movement of the rod. The working fluid is oil (it is also a lubricant). The principle of the shock absorber is the reciprocating movement of the piston of the shock absorber, the piston through the bypass valve displaces the oil from one chamber to another, turning mechanical energy into heat.

The shock absorbers' stiffness depends on the initial setting of the overflow valves (for mass-type shock absorbers, the manufacturer sets the initial setting once for the entire operation; in the sports-type shock absorbers, the user can adjust the stiffness), the initial viscosity of the fluid (oil) and the ambient temperature that affects the shock absorber viscosity liquids (oils).

Hydraulic shock absorbers are divided into several subspecies:

• By design:
  • lever (common until the 50s - 60s)
  • twin tube (main type at present)
  • monotube (get spread)
• By pressure inside the shock absorber:
  • without gas supply (in everyday life they are called simply oil)
  • with gas pressure low pressure
  • with gas pressure high pressure

Gas back-up, as a rule, has little effect on the stiffness of the shock absorber, but significantly increases the stability of the characteristics under heavy loads due to less foaming of the oil; with everyday driving, the difference is completely invisible.

Hydraulic Lever

In the 1930s, the friction dampers gradually began to give way to hydraulic, but the latter did not seem to resemble the telescopic ones that are familiar to modern motorists.

The first hydraulic shock absorbers were manufactured according to the Maurice Houdaille patent (Maurice Houdaille; American pronunciation is “Hudai”) , which he received about 1906, but remained unclaimed at that time. They consisted of a cylindrical body filled with oil, inside of which a wheel with four vanes rotated on an axis. The calibrated holes in the blades (in later models - holes with valves) created resistance to the flow of fluid that occurs when the axis is rotated, thereby providing damping. The body of such a shock absorber was fixedly mounted on the frame of the car, and on the axle coming out of it was a lever, which was pivotally connected to the suspension components. By shifting the lever it was possible to adjust the stiffness of the shock absorber. Subsequently, the design of shock absorbers of this type was improved, there was a remote control stiffness from the cabin, which was useful on the then bad roads. However, in general, this design was distinguished by its low efficiency and was difficult to manufacture due to the need to ensure a very accurate fit of the parts of the shock absorber to each other, and was also practically unrepairable even in the conditions of an equipped workshop. However, Ford used them in their cars until the late 1940s. From domestic cars were used on GAZ-A .

Somewhat later, piston-type lever hydraulic dampers appeared in which a lever, through a cam or crank mechanism, set in motion a piston (in single-acting shock absorbers) or pistons (double-acting), which created a fluid flow, and damping was provided by valves that resisted overflow fluids from one cavity to another. Such shock absorbers made it possible to adjust the force during compression and rebound over a wide range by replacing the valves, which were usually installed on their housing from the outside behind screw plugs. So, on all post-war GAZ cars with lever shock absorbers, the rear shock absorbers had an identical design, and differed only in valves (that is, tuning) and levers designed for different suspension configurations. After the appearance of independent double wishbone front suspension systems in the mid-1930s, such shock absorbers often began to be built into their upper arms.

Along with this, for piston lever shock absorbers there were also certain drawbacks, first of all - a relatively high cost, due to the high metal consumption and the need for high-precision machining for the manufacture of many components, in particular - a cylinder-piston pair. In addition, due to the imperfect compaction of the axle, there were frequent leaks of working fluid from worn shock absorbers, which, however, did not disable them immediately and was usually fixed by replacing the seal. With the exception of elementary work on the replacement of seals and valves, lever-piston shock absorbers were practically non-repairable outside factory conditions due to the high precision of manufacturing many parts, it was even considered undesirable to completely disassemble them.

In the late 1930s, they were gradually crowded with tubular shock absorbers of the so-called “aviation type” close to modern ones, cheaper and more technologically advanced in production, as well as having higher stability when driving at high speed due to their better ability to dissipate heat. Nevertheless, “levers” remained popular in the first post-war decade, and were used on some cars until the 1960s. Currently, lever shock absorbers can only be found in the suspension of armored vehicles.

Hydraulic Twin-Tube

A two-tube shock absorber consists of two coaxial (one in one) pipes, the outer one of which is a housing, the inner one is filled with working fluid and a piston with valves moves in it. The space between the pipes is filled with a liquid supply for cooling and leakage compensation, as well as with air - to compensate for the change in volume (thermal expansion of the liquid and the input-output rod).

Used in the suspension of cars for quiet and measured movement without sharp turns and braking. Designed to work in good road conditions.

Two-pipe shock absorbers are not used in motor sports because they do not meet the requirements for reducing the unsprung weight , stability, reliability and working life in the conditions of sporting events. The only exception is, perhaps, drifting , where two-pipe shock absorbers with increased pressure of compensating gas (about 6-8 atmospheres ) can be used, since competitions take place only at a very flat road surface and low speeds.

Advantages:

• The relative ease of manufacture and repair.
• Acceptable performance (including reliability) for most transportation applications
• No protruding parts - can be installed inside the suspension spring.
• Low internal pressure and, accordingly, stem seal requirements. Basically, this is what justifies their low cost and cheaper materials for manufacturing.
• With a small transmission of oil in the shock absorber may last for several years with full preservation of the shock absorber (but the deterioration of cooling).

Disadvantages:

• At high loads (bad roads, off-road or sports rides) oil and compensation gas in cavity C are mixed and form a foam that impedes the cooling of the shock absorber. Overheated shock absorber loses its characteristics and the car becomes dangerously less manageable.
• When driving in difficult conditions in this construction of shock absorbers (bad roads, off-road), a high probability of cavitation is established , and the lower the pressure of the compensation gas, the higher this probability. The occurrence of this phenomenon leads to a rapid failure of the shock absorbers, as well as damage to other parts of the suspension - as a result of failure of the first.
• When worn, the characteristics of the shock absorbers of this design deteriorate very smoothly and imperceptibly for the driver, as a result of which it is necessary to control their performance more closely.
• At high speeds due to insufficient reaction speed of the shock absorber on bumps, the car’s handling will drop sharply.
• Several increase the likelihood of aquaplaning .
• When installed in the car's suspension, the maximum angle of inclination without a sharp decrease in the efficiency of 45 ° to the vertical. Before installation, “pumping” is required - to remove gas bubbles from the working cavity.
• Must be installed only the body down (stem "A" up), which impairs the characteristics of the suspension (increase in unsprung weight).
• Store and transport only upright.

Hydraulic Monotube

They represent a pipe filled with a working fluid in which a piston with valves moves. To compensate for changes in the volume of working fluid (temperature and the input-output rod), the "bottom" of the cylinder is filled with gas, separated from the working fluid by a floating piston-septum. Gas pressure, usually around 18-25 atmospheres (to improve the characteristics of the working fluid during heating and eliminate the likelihood of cavitation ).

Advantages:

• This design is practically the most effective;
• Stable performance in a variety of road conditions, with high loads (broken roads, complete off-road, sports, etc.), as well as the best reaction rate to sudden irregularities of the road surface, even at high speeds.

Characteristics are very stable due to the fact that the compensation gas “F” is separated from the liquid by the floating piston “E” and the effect of foaming the working fluid (oil) during operation is completely absent ; due to the high pressure of the gas and, as a consequence, the liquid in this design, cavitation does not occur even under ultrahigh loads (rally, off-road driving, etc.);

• Smaller roll angles when the vehicle enters the turns compared with the two-pipe structure, the braking distance decreases by 5-20%;
• Due to the more stable pressure of automobile wheels on the road surface, the effect of hydroplaning occurs somewhat later along the acceleration curve.
• Such shock absorbers are not afraid of tilting, do not require "pumping" before installation and can be installed with the rod down, which improves the performance of the suspension by reducing the unsprung masses .
• The wall of the working cylinder has direct contact with air, which improves the cooling of the fluid (oil) and reduces the likelihood of overheating (that is, cooling is accelerated);
• The piston and cylinder have a large diameter, and the liquid has a larger volume - this increases the heat capacity of the system (heating occurs much slower).
• They have an average of 1.5-2.2 times longer service life in comparison with shock absorbers of double-tube design with the same dimensions.
• A single-tube shock absorber can be cost-effective for car owners, since longer service life saves repair time and replacement costs, comparable to the cost of the shock absorber itself, and also provides greater traffic safety on the road.

Disadvantages:

• If the compensation chamber “F” is located directly in the working cylinder, this shock absorber has a smaller stroke compared to the two-pipe structure with the same external dimensions (length), but reducing the dimensions of the valve sets and the piston significantly reduces this value.
• The transfer of the compensation chamber to a separate element is applied only to individual vehicles mainly oriented to a sports ride and is not used in mass production.
• High pressure in the shock absorber creates a significant pushing force on the rod (tens of kilograms), which may require replacing the suspension springs with weaker ones;
• This shock absorber is very critical to damage (dents) on the outer wall of the cylinder, this leads to piston seizure and complete failure, while the two-pipe shock absorber does not even notice large dents. According to statistics, the probability of occurrence of these damage is close to 0.01% relative to the total volume of the supplied shock absorbers, a significant part of the cases occur during transportation or unqualified installation in the suspension;
• A single-tube shock absorber is more difficult to manufacture than a two-tube one, since the high pressure of the compensation gas imposes considerably greater demands on the quality of seals , materials and coatings of parts . This justifies the higher cost of the shock absorber.

Gas shock absorber

• It should not be confused with pneumocallon .

Shock absorber, the active substance of which is gas. The reciprocating movement of the shock absorber rod is hampered by the work of passing gas from one chamber to another through a small opening. But according to the production technology and the logic, they are all gas-oil. Shock absorbers of this design are not installed on cars.

Combined shock absorber

Gas oil or oleopneumatic shock absorber, the active ingredient of which is both oil and gas. The oil works, the gas eliminates the formation of foam.

In the automotive

The approach to the appointment of a shock absorber in various schools of the automotive industry to some extent can be determined by the name that is given to it. For example, it. Dämpfer - damper ( damper ), eng. Shock-absorber - shock absorber.

In tank building

In tank building, the principle of operation of the German telescopic shock absorbers from the times of the Second World War (tanks Pz.III , Pz.V , Pz.VI ) and the friction shock absorber of the modern Leopard-2 does not provide for their absorption of impacts. The first ones are one-sided actions on the reverse of the skating rink, i.e., they almost do not work during the impact during the forward stroke of the skating rink, the second resistance does not depend on the speed of the skating rink, therefore the shock absorber absorbs about the same amount of energy as the skater slowly moves . The British used mainly double-sided hydraulic shock absorbers ( Kruseyder , Cromwell , Valentine tanks), the resistance of which depends on the speed of the roller and increases many times upon impact, hence the name “shock absorber”.

In aircraft engineering

In aerotechnics powerful shock absorbers are used on the chassis of aircraft . Their task (as well as the task of the entire chassis design) is similar to the shock absorbers in cars - to mitigate overloads when in contact with the runway covering during landing, so that the loads on the aircraft components do not exceed the permissible values ​​when performing a regular landing, as well as to make a safe landing for people when the maximum landing weight is exceeded up to the maximum take-off weight.

The shock absorbers on the landing gear of almost all modern airplanes are built on the principle of a gas spring — the elastic element in such a shock absorber is not a mechanical spring, but technical nitrogen charged (injected into the shock absorber cavity) from the ground-based aerodrome auger, under a strictly defined pressure depending on the aircraft’s take-off weight for this departure and ambient temperature. Single-chamber, two-and even three-chamber shock absorbers are used.

Rail transport

On railway transport , energy must be extinguished both in the vertical, horizontal transverse, and horizontal longitudinal with respect to the movement directions. Dampers in the first two directions are usually used oil and are installed at an angle of 45 degrees between the vertical and horizontal transverse movement of the planes. That is one shock absorber extinguishes energy in two directions. Longitudinal shock absorbers of railway rolling stock is called - absorbing device coupler. Absorbing devices distinguish between cargo type and passenger. Cargo-type absorbing devices are distinguished according to the classes T0, T1, T2, T3 - depending on the energy it absorbs (50 kJ - the first and 190 kJ - the last) and its other technical characteristics described in OST-32-175-2001.

In shipbuilding

In shipbuilding, for protection against vibration and shock loads of equipment, rubber-metal shock absorbers AKSS are used (shipboard welded shock absorbers with insurance). The ACSS shock absorber is a rubber-metal product consisting of a metal bracket, a carrier bar and a support bar, which are interconnected by a vulcanised rubber array. To protect against vibration and shock loads of electric panels and remote controls in shipbuilding, cable shock absorbers are used.

• Damper
• Suspension
• Absorber (in pneumatics)
• Vibration absorber
• Fluid spring
• Recoil brake

• Shock absorber - an article from the Great Soviet Encyclopedia .
• Elastic suspension elements
• Car shock absorbers: basic faults and how to solve them
• Chassis tanks. Suspension

• Tishchenko O. F. Elements of instrument devices. - M .: High School, 1982. - 263 p. - 25 000 copies