Hydraulics Quiz No. 6 — the ABS braking circuit (copy 1)

In this document

This blank questionnaire constitutes the sixth and final of the Hydraulics Quizzes offered as part of a distance learning course. The instructions remind the user to return it "no later than fifteen days after receipt" p. 18, and invite them to note the time taken to complete it.

Braking and brake valve-compensator (p. 18)

The first questions concern the hydraulic supply to the front and rear brake calipers, the operation of the brake valve-compensator (as a regulator or pressure compensator), and the Bendix brake calipers. Two technical diagrams ("drawing 1" at rest, "drawing 2" during braking) accompany an exercise where the learner must identify, chamber by chamber (marked from a to i), the pressures present (PFAV, PFAR, Psus AR, HP, reservoir pressure) — without the answers themselves being provided in this document.

The ABS system (p. 19)

The second part asks about the ABS hydraulic braking circuit: its differences (or lack thereof) from "a classic power-assisted braking circuit" p. 19, the vehicle's behavior "in the event of an ABS failure", and the components that control this circuit — "the computer that interprets the measurements from the speed sensors" p. 19 being one of the options proposed.

The quiz also details the components that distinguish ABS from a classic circuit: wheel speed sensors, electronic computer, modified brake valve-compensator, "hydraulic pressure modulator block" p. 19. Two chronological ordering exercises finally focus on the pressure modulation phases by solenoid valves (slow/fast intake, slow/fast release) "controlling a front brake circuit of the XM" p. 19, and on the associated physical phenomena (wheel locking, progressive restart, etc.).

The page ends with a space for "remarks concerning this chapter", a box for study time and signature, and the mention "Keep the carbon copy" p. 19, a sign of submission in duplicate.

Context

The ABS (Anti-lock Braking System) became widespread on high-end Citroën vehicles from the late 1980s-1990s; the Citroën XM, cited in the document, was launched in 1989 and benefits from the hydractive suspension inherited from Paul Magès' work. The brake valve-compensator and high-pressure hydraulic-assisted braking circuits have been characteristic elements of the Citroën system since the DS.

Archivist's perspective

This final quiz logically closes the training cycle by addressing a more recent technology — ABS — than the older devices (DIRASS, DIRAVI) covered in the previous questionnaires. It thus illustrates, within the same series, the evolution of Citroën hydraulics towards embedded electronics.

The document seems intended for network technicians or sales staff rather than engineers, in continuity with Hydraulics Quiz No. 5 and the training presentation. A second annotated copy of this same quiz also exists, likely allowing for a comparison of the expected answers.