haldex (English, Polski, Русский)

Haldex all wheel drive(Edit)

Haldex-based all wheel drive systems are automatic all wheel drive systems. Haldex clutch is installed in the rear axle's differential housing and powers rear wheels.

haldex generation I, 1998-(Edit)

The design of the Haldex LSC gen. I, II, and III is based on a Swedish patent acquired by the Haldex Group.

The unique design of the Haldex LSC comprises three functional parts

• The hydraulic pump driven by the slip between the axles/wheels.
• The wet multi-plate clutch
• The controllable throttle valve with its electronics.

The unit can be viewed as a hydraulic pump in which the housing and an annular piston are connected to one shaft and a piston actuator is connected to the other.

The two shafts are connected via the wet multi-plate clutch pack, normally unloaded and thus transferring no torque between the shafts.

When both shafts are rotating at the same speed, there is no pumping action. When a speed difference occurs, the pumping starts immediately to generate oil flow. It is a piston pump, so there is a virtually instant reaction with no low-speed pumping loss.

The oil flows to a clutch piston, compressing the clutch pack and braking the speed difference between the axles. The oil returns to the reservoir via a controllable valve, which adjusts the oil pressure and the force on the clutch package.

In traction/high slip conditions, a high pressure is delivered: in tight curves (i.e. parking), or at high speeds - a much lower pressure is provided.

Haldex Generation I and II based all wheel drive system is reactive. The coupling activates after a wheelspin is detected. However, the reaction is very quick and just 1/4 of a wheel turn is needed to engage all wheel drive. Electronics is capable of lowering the oil pressure only (when parking, ABS working, the handbrake is pulled, etc.), but cannot pre-tension the clutch.

Under normal driving conditions (driving at the constant speed, no silppage), the torque distribution is 90/10 front to rear. When the clutch is locked, torque is evently distributed between the axles (50/50).

More info: http://audittrs.wordpress.com/2010/12/07/haldex-service-training-self-study-program/

haldex generation II, 2002-(Edit)

This second generation of Haldex LSC is still using the mechanical hydraulic pump, but the linear throttle valve has been exchanged for a solenoid controlled proportional throttle valve.

Haldex Generation I and II based all wheel drive system is reactive. The coupling activates after a wheelspin is detected. However, the reaction is very quick and just 1/4 of a wheel turn is needed to engage all wheel drive. Electronics is capable of lowering the oil pressure only (when parking, ABS working, the handbrake is pulled, etc.), but cannot pre-tension the clutch.

Figure: Cut-away view of a rear differential with Haldex generation 2(?)

Figure: Borg-Warner's Haldex generation 2

haldex generation III, 2004-(Edit)

A coupling with pre-tensioning capability of the hydraulic clutch by the means of existing feeder pump (PreX™ solution).

Haldex Generation III and IV based all wheel drive system is proactive. The electronics can pre-tension the clutch and activate all wheel drive before a wheel slip occurs.

Figure: Haldex generation 3 (left) and 4 on Ford Kuga

Figure: Borg-Warner's Haldex generation 3

haldex generation IV, 2008-(Edit)

The fourth generation does not have the mechanical pump any more. The clutch is activated using the feeder pump.

Haldex Generation III and IV based all wheel drive system is proactive. The electronics can pre-tension the clutch and activate all wheel drive before a wheel slip occurs.

Figure: Rear differential and Haldex 4 on Audi TT quattro

Figure: Haldex generation 4 on Volkswagen Transporter

Figure: Borg-Warner's Haldex generation 4

haldex XWD (cross wheel drive), 2007-(Edit)

A combination of two Haldex Couplings, one for the front/rear torque distribution, another for the torque distribution between the rear wheels. First introduced on Saab 9-3 in 2007 with earlier generation Haldex unit then replaced with Generation IV unit in 2008.

More information(Edit)

For further information, see the Haldex Web site.