A double premiere: The compact Mercedes-Benz Intouro K hybrid inter-city bus

• The hybrid principle: Generating braking energy and using it for start-up
• Supercapacitors (“supercaps”) serve as short-term energy storage units
• 48-volt network, low added weight, unmodified operation
• Tried and tested components, new: Recuperation module for the Intouro
• The new Intouro K: A real all-round talent, even on narrow streets
• The premier model: versatile equipment, a role model in safety

Electromobility has many facets. While the emphasis is on all-electric drive systems for urban traffic, Daimler Buses is relying on the Mercedes-Benz Intouro with its hybrid module for inter-city transport as well as for a combination of regular and touring bus services in its drive to continue to decrease the already economic fuel consumption. The hybrid module is available for all two-axle models with automatic transmission with torque converter from the large Intouro family. The hybrid module is also making its debut in an inter-city bus in the equally new Intouro K. This means that the model range is simultaneously expanding with a versatile and particularly maneuverable as well as economical bus with a wide range of applications.

The hybrid principle: Generating braking energy and using it for start-up

The basic function of the Intouro hybrid is extremely simple: An additional electric motor acts as an alternator during the bus’s braking and overrun phases, converting braking energy into electricity. This current is stored and is made available to the electric motor to support the combustion engine, especially when moving off, but also when accelerating and to support idling.

The drive technology behind it is simple. One core component of the hybrid drive is the electric motor. The disc-shaped major assembly with integrated power electronics and a thickness of eight centimeters is implemented between the combustion engine and the automatic transmission. Its output is 14 kW with a torque of 220 Nm.

The electric motor primarily assists the combustion engine in the case of high output requests, especially when starting off. However, it does not serve to increase the maximum output, which is why the specifications for the bus’s performance and torque remain unchanged. Rather, the electric motor relieves the strain on the combustion engine and increases the start-up performance. The combustion engine’s speed is not reduced, the peak power is only held back imperceptibly and replaced by the electric motor.

Hybrid technology can lead to a noticeably reduced fuel consumption

In addition, a slight boost by the electric motor at idle speed improves the efficiency of the combustion engine. Both of these factors together result in a reduction in the already low fuel consumption. In the Intouro, this is particularly evident in inner city and suburban traffic, where the driver is constantly alternating between the accelerator and brake pedals. The reduction is up to five percent.

Supercapacitors (“supercaps”) serve as short-term energy storage units

The current generated by recuperation is stored in double-layer capacitors, also known as supercaps. These electric energy storage units are characterized by a high power density. They are not sensitive to high power peaks and have a long service life. In contrast to batteries, supercaps are ideal for the constant and rapid changes between charge and discharge when stopping and starting. The Intouro hybrid only needs a single braking motion from 50 km/h to a standstill to charge the energy storage units.

The power storage system of the Intouro hybrid consists of two modules. Each module contains 16 supercaps. Both modules together have a total capacity of 88 Wh and are mounted on the rear left-hand side of the roof (in the direction of travel) to save space. A cover protects the modules from external influences and sunlight. At the same time, a perforated side panel ensures the necessary cooling by the headwind.

An inverter, or power inverter, converts the stored direct current into alternating current to drive the electric motor. Both the inverter and the electric motor are water-cooled. The additional cooler for this low-temperature cooling with a maximum of 65 degrees Celsius is located beneath the vehicle radiator to save space.

48-volt network, low added weight, unmodified operation

Another key advantage: The Intouro hybrid does not need a complex high-voltage network which has its own necessary restrictions and safety requirements. The inter-city bus has a separate 48-volt network. This is classed as low-voltage technology and is safe to use. The unmodified auxiliary assemblies are driven conventionally. Further advantages of the compact and uncomplicated technical body of the additional hybrid drive: The required installation space is small, the outer contours remain unchanged, as does the interior – no passenger seats are lost. The added weight of the hybrid drive is 254 kg. As a result, the total number of passenger seats is only slightly reduced and is insignificant in practice.

Bus drivers behind the wheel of the Intouro hybrid do not detect any difference when handling the vehicle or even during operation. Even the instrumentation is identical. Training is therefore unnecessary. Likewise, neither quick driver swaps, often common during regular bus service, nor switches between different buses pose any problem at all.

Tried and tested components, new: Recuperation module for the Intouro

The developers of the Intouro hybrid rely on tried and tested components. They are already used in the successful Citaro hybrid, for example, a model which has proven itself splendidly in practice using this technology for many years now. The use of supercaps as energy storage units is derived from this model, for example. Citaro enthusiasts already know them in the form of recuperation modules. However, extensive adaptation measures were required due to a new electric/electronic structure of the Intouro with different control units.

This recuperation module is now also available for the Intouro for the first time, independent of the hybrid module. In addition to the vehicle batteries, it stores the current generated by recuperation and makes it available when starting or on inclines. This relieves the strain on the alternator and thus on the combustion engine, reducing fuel consumption. The energy storage unit is also mounted on the right-hand side of the roof (in the direction of travel) to save space. The recuperation module is a prerequisite for the Intouro hybrid. 

The new Intouro K: A real all-round talent, even on narrow streets

The new hybrid module is enjoying its debut in the compact Intouro K within the Intouro model series. It is particularly manageable with a length of 10.75 meters and a turning radius of just 18.34 meters. This makes it ideal for trips through mountainous regions, on winding roads or for excursions with small groups.

At the same time, the Intouro K is a fully-fledged bus with all the outstanding characteristics of the Intouro family. In line with its broad scope of application, it is available in a wide range of equipment variants – the range extends from matter-of-fact, tender-compliant high-floor inter-city buses to excursion vehicles.

The range of equipment includes destination displays, a single or double-width entrance in the middle and two different lifts for passengers with reduced mobility. There is a large choice of seating and luggage shelf options for the interior. The Intouro’s driver area, which has also been completely redeveloped, is ergonomically perfect and driver-oriented, typical for Mercedes-Benz buses. From its visual appearance to the controls and instrumentation including color display, the high-quality cockpit is as luxurious as a fully-fledged touring coach.

The engine output of the Intouro K is optionally 220 kW (299 hp) or 260 kW (354 hp). Enterprises can even choose from four transmission variants: six-speed manual transmission, fully automated Mercedes-Benz PowerShift transmission or automatic transmission with torque converter from Voith and ZF. 

The premier model: versatile equipment, a role model in safety

The appearance and the equipment of the premier model is simultaneously elegant, functional and practical. The body and detachable parts are finished in metallic anthracite. The two-winged second door ensures a fast passenger turnaround at bus stops. The multi-functional special-purpose area on the opposite side is equipped with four folding seats. The comfortable Travel Star Eco seats with adjustable backrests, seat cushions and backrests with outer covers in Tiffy Gray, piping in May Green and jet black headrests made from Composition leather fiber material offer a high level of comfort even on longer journeys. Window curtains and a side wall trim in needle punch contribute to the pleasant ambiance on board, as does the gray patterned floor. At the same time, the Intouro K is also ready for regular service routes with a destination system, passenger signal system, preparation for the installation of a ticket printer and a mandrel for a cash register. Passengers can use their end devices regardless of how the bus is used, benefiting from the MediaRouter for Internet access and streaming.

The equipment with its assistance systems is outstanding: The emergency braking assistant Active Brake Assist 5 (ABA 5) is the only system of its kind in buses which can perform maximum full-stop braking maneuvers even with moving pedestrians, while Sideguard Assist warns of people and obstacles when turning corners. Along with conventional assistance systems, this ensures that the Intouro K can achieve exemplary safety levels.

The Mercedes-Benz OM 936 engine is just as compact as the bus itself. It delivers 260 kW (354 hp) with a displacement of 7.7 liters. It is linked to the ZF Ecolife 2 automatic transmission with torque converter and a Mercedes-Benz hypoid axle. The new hybrid module, which is available as special equipment, further reduces fuel consumption and thus emissions from this powerful and equally economic drivetrain.