QC/T 207-2021General gas springs for automobiles (English PDF)

3.1 Gas spring

An elastic element, which is composed of a closed cylinder AND a piston and piston rod assembly that can slide in it; uses nitrogen or other inactive gas as the energy storage medium.

3.2 Compression gas spring

The spring, whose piston rod is in a freely stretched state without external force, AND which bears pressure.

3.3 Stroke

The axial displacement of the piston rod, FROM a freely stretched state TO when it is compressed to its minimum use size.

3.4 One cycle

A complete set of movement of the piston rod, when it compresses once and extends once, according to the prescribed stroke.

3.5 Extension speed

The average speed, at which the piston rod freely extends from the end of the prescribed stroke to the initial position.

3.6 Buffer section

During the extension of the piston rod, the area where the piston's movement is slowed and buffered, by changes in gas flow or liquid damping.

3.7 Specified force

The force, which is marked on the drawings and products, as confirmed by both the supplier and the buyer.

5.8 Ball socket joint and ball joint's insertion force

The insertion force of the ball joint of nylon steel ball socket shall not be greater than 100N; the pull-out force shall not be less than 800N. Other types of connectors and special needs shall be negotiated, between the supplier and the buyer.

5.9 Anti-loosening torque of ball socket joint

The anti-loosening torque of nylon ball socket joints, of M6/M8 specifications, shall be greater than or equal to 2.5N-m. Other types of connectors and special needs shall be negotiated, between the supplier and the buyer.

5.10 Radial resistance

After the gas springs, which have a piston rod diameter of Phi10mm and Phi8mm, are tested in accordance with the provisions of 6.9, the gas spring shall not show performance defects, such as jamming, jitter, abnormal noise, oil leakage, etc. Gas springs, which have other piston rod specifications, shall be negotiated, between the supplier and the buyer.

6.1 Mechanical properties

Test conditions: The dynamic and static test shall be carried out, in an environment of 20°C ± 2°C. Before the test, the gas spring is always in the extension state; the piston rod must not be pressed. Place the sample in an environment of 20°C ± 2°C, for more than 2 hours. The measurement speed of static test is 500mm/min. The test speed, during the dynamic test, is negotiated by the supplier and the buyer. The force measurement accuracy shall not be less than 1%.

Dynamic test at room temperature: Clamp the gas spring's piston rod, vertically upwards, on the testing machine. During the first cycle after turning on the machine, record the starting force. During the second cycle, record the extension force and compression force F1, F2, F3, F4, at the force collection points. Calculate the specified force and dynamic friction force. Draw the force- displacement curve. At the same time, observe whether the gas spring has abnormal noise, stuck or obvious jitter.

Static test at room temperature: Clamp the gas spring's piston rod, vertically upwards, on the testing machine. During the first cycle after turning on the machine, record the starting force. During the second cycle, record the extension force and compression force F1, F2, F3, F4, at the force collection points. Calculate the specified force and static internal resistance. Draw the force-displacement curve. The dwelling time, at the force collection points, during the static test, is 3s. At the same time, observe whether the gas spring has abnormal noise, stuck or obvious jitter.

6.2 Extension speed

Test conditions: The sample shall be placed in an environment of 20°C ± 2°C, for more than 2 hours, before the test. The division value of the timer shall not be greater than (1/100) s.

Test method: Clamp the gas spring's piston rod vertically downwards, on the speed tester. Turn on the tester. The tester will automatically compress the stroke. Then withdraw the external force, to allow the piston rod to extend freely.

At the end of the test, measure the extension time t and the extension stroke S.

Use the formula (1) to calculate the extension speed (average speed):

Where: v - The value of the extension speed, in millimeters per second (mm/s);

S - The value of the stroke, in millimeters (mm);

t - The value of extension time, in seconds (s).

6.3 Air tightness

Place the gas spring in a high temperature test box of 80°C ± 2°C. Keep the temperature for 4h. Then move it into 20°C±2°C. Keep it for 2h. Then place it at a low temperature test box of -40°C ± 2°C. Keep it for 4h. Then move it to 20°C ± 2°C. Keep it for 2h. After 2 high and low temperature tests, test its mechanical properties, according to the provisions of 6.1. Calculate the change rate of the specified force Fa.

6.4 Durability

After the air tightness test, clamp the gas spring on the bench. Carry out the durability test, at a frequency of 4 cycles/min ~ 6 cycles/min, according to the provisions of Table 5 or Table 6. After the test, test its mechanical properties, according to the provisions of 6.1. Calculate the attenuation rate of the specified force Fa and the amount of oil which is brought out. Check whether the gas spring has defects such as stuck, jitter, abnormal noise, etc. During the normal temperature test, the temperature of the gas spring cylinder shall not be greater