Progressive Hydraulic Cushion

Originally, Citroen does not seem to be very proactive about disclosing technical information, but KYB, which jointly obtained the patent, and Citroen fans have released various information, so from that information We can speculate about the technology overview.

PHC (Progressive Hydraulic Cushion) has three main parts built-in.

From the left, there are three: Butee hydraulique detente (hydraulic rebound stopper), Amortisseur principal (main valve [damper]), and Butee hydraulique de compression (hydraulic bump stopper). By dividing the total stroke of the shock absorber into three parts in this way, it is possible to achieve different characteristics even though it is a single shock absorber. The 1st main valve [damper] works near the center of the stroke. In this operating region, the conventional valves, the piston and the base valve, provide the damping force. The second and third hydraulic stop parts act near the end of the rebound and bounce strokes, and the bounce and rebound stops serve to absorb additional energy. This division of duties allows the shock absorber's main valve to be configured with a focus on comfort, while the two hydraulic stops only come into play when more severe conditions are encountered, improving both comfort and handling performance. is possible. To accomplish this effectively, both the rebound and compression stops must absorb enough energy and be able to respond very flexibly. This patented technology provides an unprecedented level of comfort and what PSA Stellantis calls the "flying carpet effect", which allows drivers to feel as if their car is flying over bumps and potholes in the road. You can feel it.

As shown in the image above, it is still equipped with Butee mecanique classique (classic bump rubber), but it is much smaller than the convetional model.

By the way, detentee means "rebound", compression means "bound", and butee means "stopper".

I think this video is the easiest to understand. (It's in French)

Here is a video of how it works.

Click here for Stellantis Japan's technical documents (in Japanese).

Besides, KYB's technical documents (in English), which have joint patents, are available here. It's on P23-P28.

https://www.kyb.co.jp/technical_report/data/no58j/all.pdf

According to a press release from KYB, starting in 2022, PHC shock absorbers [dampers] (called DHS [Double Hydraulic Stops] shock absorbers [dampers] in KYB), which have been supplied only for new car installations from KYB Europe, will have part numbers. It says they are sold as aftermarket parts as 3348095 and 3448033. (This is in English)

I actually searched for the parts.

https://www.autodoc.co.uk/kyb/17873322

I was indeed able to find a part for sale, but it doesn't look like a general-purpose part, but a C5AC-specific part and not for other cars. I was disappointed.

After doing some research, I was relieved that even though it is no longer hydropneumatic, one of the important characteristics of hydro, which is ``balance of comfort and cornering performance,'' has definitely been inherited. I would like to believe that it will continue to be refined and improved as generations pass.

*In order to make this article easier to read, the damper body is referred to as a shock absorber, the main damper inside is referred to as a main valve, and the auxiliary damper inside is referred to as a stopper.

Citations: fiches-auto.fr, stellantis.jp, kyb-europe.com