Hydraulics Quiz No. 4: Hydractive suspension and circuit diagram (ex. 1)

In this document

The questionnaire (p. 32)

This is the fourth of six "Hydraulics Quizzes" from a distance learning course: the document states that it "is the fourth of six Hydraulics quizzes" and must be "returned no later than fifteen days after receipt" in a stamped envelope p. 32.

The twelve questions cover hydropneumatic and Hydractive suspension:

• comfort vs road holding of a "soft" suspension (Q1);
• flexibility factors (load, liquid volume, nitrogen volume) (Q2);
• characteristics of the "firm" setting of the Hydractive (flexibility, damping, anti-roll) (Q3);
• role of the solenoid valve as an interface between the electronic computer and height corrector, stiffness regulator, priority valve, suspension cylinders (Q4);
• composition of a Hydractive system: stiffness regulator, additional sphere, height corrector (per axle or not) (Q5);
• functions of the stiffness regulator (gas volume, height correction, damping, communication between suspension elements, link with the computer) (Q6);
• obtaining a "soft" suspension or "firm" damping by varying the compressed gas volume or damping (Q7-Q8);
• obtaining a "soft" anti-roll according to the communication or isolation of the suspension elements (Q9);
• deployment of Hydractive I and Hydractive II on XM and Xantia, with a manufacturing date distinction "from 1.02.1993" (Q10-Q11);
• operation of the ball valve in firm or soft mode during a height correction, according to the direction of pressure variation (Q12).

A telephone number ("49 45 43 56") and a fax number ("40 11 44 97", preceded by "16 1" for the provinces) are provided for any questions p. 32.

The labeling exercise and diagram (p. 33)

Page 33 offers exercise no. 13: matching eleven numbers from a hydraulic circuit diagram (front/rear of the vehicle) to a list of components designated by letters (A to K), including stiffness regulators, height correctors, suspension blocks, priority valve, brake metering valve, brake sensor, front and rear solenoid valves.

Four combinations of answers are proposed in table form:

The page ends with a space for remarks, time spent, a signature, a place and a date, as well as the mention "Keep the carbon copy" p. 33.

Context

Generally and notoriously, the hydropneumatic suspension, invented by Paul Magès at Citroën, evolved in the 1990s into the Hydractive system, which allows the firmness of the suspension to be varied electronically ("soft" and "firm" modes) thanks to an additional sphere controlled by a solenoid valve. The XM (1989) and Xantia (1993) models were the first to benefit from this technology, with Hydractive II succeeding Hydractive I in the early 1990s. These general elements, not taken from the document, help to understand the technical vocabulary used in the quiz.

Archivist's perspective

This fourth quiz is part of a structured educational series — six modules in total p. 32 — probably intended for technicians or sales staff in the Citroën network wishing to master the subtleties of Hydractive. The return in a stamped envelope and the "carbon copy" to be kept p. 33 suggest correspondence training, with centralized monitoring and correction.

The diagram labeling exercise p. 33 is particularly valuable: it concretely illustrates the architecture of a complete front/rear hydraulic circuit, with its stiffness regulators, spheres, height correctors and solenoid valves — all components that directly extend the inventions associated with Paul Magès.

This document logically relates to the series of Hydraulics Quiz No. 5 and No. 6, as well as the presentation of the "Les Cahiers Experts de l'Hydraulique" training course which probably specifies its general framework.