SPbGASU created a new pneumohydraulic shock absorber
Sergey Repin
SPbGASU scientists are working to improve the smoothness of vehicles. Sergey Repin, Professor of the Department of LandTransport Technological Machines, is the author and co-author of ten patents on this topic, as well as three certificates for computer programs. In 2022, a patent No. 208894 for the utility model "Pneumohydraulic shock absorber" was received.
– The work went on for several years. First, we developed new designs of shock absorbers, which excluded the use of springs and leaf springs in the cars suspension due to the use of compressed gas in the shock absorber cavities. As theoretical and experimental studies continued, new ideas arose to improve the design of shock absorbers, – said Sergey Repin.
Car smoothness is ensured by the suspension - a system of devices for the elastic connection of the wheel axles of the car with the frame to absorb and mitigate shocks (damping) received by the wheels and transmitted to the body when driving on uneven roads. The suspension has an elastic element that perceives shocks from the road – usually a spring, and a damping element that quench oscillations in the car sprung mass - a shock absorber. In addition, the shock absorber is responsible for the quality of tire grip on the road.
1. Pneumohydraulic shock absorber: 1. external cylindrical tank; 2. working cylinder (typical hydraulic gas-filled shock absorber); 3. rubber cuffs; Г1 upper gas cavity; Г2 middle gas cavity; Г3 lower gas cavity; 4. hydraulic piston; 5. middle stem; 6. eyelet; 7. lower stem; 8. eyelet; 9, 10. sealing and guiding sleeve; 11. gas piston; 12. valve system; 13, 14. sealing cuff; 15, 16. nipple; 17, 18. safety valve; 19. Pipeline; Ж1 upper cavity; Ж2 lower cavity
The shock absorber is a hydraulic device, the operation of which is based on the friction force and the physical properties of the fluid: viscosity and incompressibility. The role of the fluid in the shock absorber is performed by oil, which circulates in the working cylinder through the movement of the pistons. Pistons displace oil in various modes through calibrated holes of different diameters. This leads to the absorption of vibrations – both during the compression period and during rebound (stretching).
There are different types of shock absorbers: single-tube (with one cylinder), double-tube (with two cylinders placed one inside the other), combined (two-tube, in the outer cylinder instead of air there is gas under pressure). However, no technical solution excludes the breakdown of the shock absorber during rebound when driving on rough roads. This is especially dangerous during cornering. With a faulty shock absorber, the wheel begins to “bounce” up to a complete loss of traction. The car can take out of the track or deploy.
A typical pneumohydraulic shock absorber contains a working cylinder with a hydraulic piston and a piston separating the cylinder into hydraulic and gas cavities. The compressed gas in the closed space of the gas cavity compensates for the change in the internal volume of the liquid during the movement of the hydraulic piston rod. The suspension of a vehicle with such a shock absorber also needs an elastic element – a spring.
✔ In the model developed at SPbGASU, a pneumohydraulic shock absorber is placed inside an external cylinder filled with compressed gas, which acts as an elastic element. And, the more the gas is compressed at large strokes of compression and rebound, the greater the force of elastic resistance. Such a design eliminates shock absorber breakdown on the compression and rebound strokes and does not require such an additional elastic element as a spring.
The pneumatic-hydraulic shock absorber can be used in construction and road machines, which often operate in difficult road conditions, including in the Arctic, where there are no roads with improved surface and the chassis suspension is subjected to significant loads. The proposed design can be installed on any vehicle, including cars and buses.
Text: Tatiana Petrova
Photo: Sergey Repin
✔ Learn more about the University's Department of land transport technological machines