Brakes, clutch, suspension
There’s e’s lots of talk about electric vehicles cles (EVs) and plug-in EVs (PHEVs), EVs), hybrids, and hydrogen cars – all sorts of ways to try to alter the amount of carbon dioxide being charged ged into the atmosphere – and while e all of these will undoubtedly present ent challenges for the motor technician, nician, there are three areas where re there has been little change in the past 100 years. You got it: brakes, clutch ch and suspension.
If you’re ou’re talking a performance vehicle, cle, or one modified to give extra performance, ormance, well the formula is simple: le: stop the car in the shortest possible ible time, repeatedly; get the power er from the engine to the gearbox as smoothly moothly as possible, without burning ing out the clutch; and finally, keep p the wheels as square to the ground nd as possible, without lifting wheels els so power is lost.
Having ving said this, there ARE continuous nuous developments designed to make e all three of these vital elements in the e drive train work better, so we had a look at what’s happening.
AKES For everyday driving, the most important ortant new development is regenerative braking. This was developed to use the kinetic energy released when a car is braked to generate electrical power. Most people think this only applies to EVs, PHEVs and hybrids, but in fact for some time now manufacturers have been using this to replace the alternator and other ancillaries normally driven by engine-generated electrical energy, thus cutting down on power loss “stolen” from the engine, resulting in better economy.
At the same time the regular brakes are still retained (for when you want to stop really quickly); the trick is to manage both systems so they work optimally.
Nissan’s Electric Driven Intelligent Brake is a prime example of this latest technology.
Nissan says the EDIB (Electric Driven Intelligent Brake) allows and controls optimisation of the regenerative brake and regular friction brake (hydraulic brake).
After stepping on the brake pedal, the system produces natural and adequate braking force that corresponds to the operation. The amount of energy regeneration also needs to be increased as much as possible.
EDIB (Electric Driven Intelligent Brake) controls the regenerative brake and friction brake to support both of these requirements. requirements Further Further, it also controls the reactive force from the pedal in order to unify the feeling when stepping down on the pedal and the sense of deceleration.
When the driver steps on the brake pedal, the stroke sensor detects operation of the brake. That information is communicated to the ECU and controls the motor. The motor engages the piston and amplifies the friction brake’s pressure (hydraulic pressure). Through optimum control of the friction brake’s hydraulic pressure, the energy regeneration outcome is maximised.
Another development is brakeby-wire and electronic parking brake technology.
Brembo is a company usually associated with performance braking systems, but at the Frankfurt Motor Show last month the company showed systems targeted at improving driving comfort, reducing the number of braking system components, enhancing performance and increasing safety resulting in seamless operation under any conditions.
Brembo says it is achieving advanced results as it pioneers its new brake-bywire technology, including attaining a time-to-lock response of close to 100 milliseconds, compared to 300-500 with traditional hydraulic brakes. This highly responsive performance makes the system appropriate for the current market demand for autonomous braking.
Brembo has also been successful in integrating a brake calliper and parking brake, combined into one aluminium unit, known as an Electric Combined Monobloc. This breakthrough technology eliminates components and integrates the braking system with the vehicles electronics for smooth and effortless operation to secure the vehicle while parked thus reducing part complexity and unsprung weight.
The Brembo range of electronic parking braking offerings is comprised of Electric Combined Monobloc, Electric Parking brake, and Electromechanical Combined Sliding brake.
In order to ensure high safety margins in emergency situations, Brembo has developed and fine-tuned monitoring software that activates dynamic braking. In the event that both of the callipers’ hydraulic circuits should fail to operate, the driver can still stop the car by using the electromechanical actuator.
The new Brembo calliper also has a hot-brake reclamp feature. This means that when the vehicle is parked on a slope, the software automatically reclamps the calliper to account for the thermal deformation of the disc and pads, guaranteeing the safe parking of the car on the steepest slopes at very high temperatures.
Developments in clutches continue apace, despite that the trend globally is to switch to some sort of automatic or semi-automatic gearbox as people get lazier, roads more constricted, and electronics make auto ‘boxes, especially CVH and double clutch, as economical as manuals.
On the regular clutch front, particular mention should be made of Australian Clutch, Exedy and Terrain Tamer, whose constant developments to produce world-class replacements for high performance, competition, and heavy duty 4x4 use are well documented in this magazine.
However, when it comes to production cars, it’s worth taking a look at developments from Honda. Regular dual clutch gearboxes have two clutches (naturally) and either six or seven speeds. Honda, though, has gone a few stages further.
We all know that dual clutch transmissions (DCT) can be awkward in tight spaces, where small pedal movements can make them jerky, and a number of carmakers have already
introduced small torque converters into the driveline to help solve this, notably Subaru and Nissan.
Honda has done the same, but in an eight-speed transmission, and claims incorporating a torque converter into the unit not only provides internal NVH benefits that help deliver the low-speed refinement most drivers seek, but its inherent torque multiplication boosts offthe-line acceleration.
The torque converter is more expensive than a clutch for the same application. But normal DCT clutches demand use of a more costly dual-mass flywheel, so the torque converter solution is no more expensive overall, according to Honda. But that’s not where it stops. According to Autocar magazine, Honda has patented a design for an 11-speed DCT with no fewer than three clutches (which we suppose would means it’s a TCT).
The patent’s description claims the addition of the third clutch would decrease the loss of torque experienced between gear shifts in dual clutch gearboxes. The triple clutch would also mean quicker gearshifts than a dual clutch.
The bad news? Honda says it hasn’t any plans for the new gearbox yet!
For the ordinary family car – as well as the majority of performance cars – suspension very much relies on a combination of coil springs, suspension arms, and shock absorbers, with anti-roll bars and some trick add-ons to make them more precise and effective, while the use of aluminium alloy is increasing in a bid to cut down on unsprung weight.
However, these days suspension refinement has become something of an art form, particularly among premium car manufacturers, and like anything else, this is slowly trickling down the ranks. The driver is able to make on-the-move changes to suspension characteristics to make them either more comfortable or sportier, and we’re seeing this more and more often.
However, that still relies on a traditional suspension layout, with the changes made mainly to the shock absorbers to effect change the ride and handling.
But there have been other successful developments. For instance. over the years we have seen great advances in the use of air suspension, particularly in SUVs designed to go off-road, while a few years ago Lotus played with a totally active suspension which did away with springs altogether.
And this latter is still the Holy Grail of suspension management.
Audi has already gone a long way in this regard with its latest SQ7 SUV, which corners flatter than many sports cars, while still retaining a highish stance on the road, and the ability to go off-road if required. It uses a system called Electromechanical Active Roll Control, developed by Schaeffler.
At each axle, front and rear, a compact electric motor with a threestage planetary gear set separates the two halves of the stabiliser. On an uneven road surface, they are decoupled from one another, thus improving body roll characteristics.
With a sportier driving style, however, the tubes are twisted smoothly in opposing directions. The car rolls less on bends, lateral inclination is markedly reduced and the tendency to understeer is kept even better in check. This enables higher lateral acceleration and thus faster cornering.
Honda’s latest eight-speed dual clutch transmission.
The Schaeffler-developed Electromechanical Active Roll Control used in the Audi SQ7.