A DEVICE FOR REDUCING NOISE FROM A MOTOR VEHICLE AND A VEHICLE PROVIDE WITH THE SAME

TECHNICAL FIELD

The present invention relates to a device for damping of noise from a motor vehicle, particularly a heavy vehicle such as a bus or truck, with an engine arranged in an engine space and at least one cooling air duct arranged close thereto. The invention also relates to a vehicle provided with a device for damping of noise. Noise means sounds generated by the vehicle's engine or such items belonging to it as the exhaust system, cooling system etc., which noise it is desirable to eliminate or at least minimise. The vehicle's engine may be a combustion engine, a fuel cell system or some other similar drive system.

BACKGROUND

The design of heavy vehicles such as buses, trucks etc. involves endeavouring to make each vehicle as quiet and comfortable as possible, particularly for persons not only inside the vehicle but also outside it or in its vicinity. Endeavours are therefore constantly made to reduce the level of noise from the vehicle, its combustion engine, drive system or other items associated therewith.

The specification of patent EP1010563 applied for by Hagglunds Vehicle AB describes an exhaust system intended to reduce thermal radiation from the exhaust gases from the combustion engine of a motor vehicle. The hot exhaust gases are led into an existing cooling air system and mixed therein with cooler air. The cold air is led in through ducts and out through, inter alia, perforated plates arranged inside the cooling air system. The primary problem solved by that invention is reducing IR radiation from, primarily, military vehicles in order to reduce the risk of detection by

heat-seeking systems. That invention does not affect, nor is it intended to affect, the level of noise from the vehicle and its exhaust system.

The specification of patent EP0648924 applied for Denyo Kabushiki Kaisha refers to a noise-damping device for a water-cooled engine coupled to a generator. The engine, the generator and the engine's silencer are arranged within a sound-damping casing provided with an inlet and an outlet for air. The exhaust system is situated inside the casing and its outlet orifice is directed towards, and ends immediately below, the outlet grille of the sound-damping casing. The object of this configuration is to damp noise from the engine, generator and exhaust system of a stationary installation. The outlet pipe for exhaust gases is therefore directed upwards and outwards and ends quite close to the outlet grille. This location results in only marginal damping of noise from outflowing exhaust gases.

SUMMARY OF THE INVENTION

The object of the present invention is to solve said problem and provide a device for damping the noise of a vehicle, which device has few parts, is inexpensive to manufacture and fit, is easy to maintain and occupies a minimum amount of extra space in the vehicle.

A particular object is to damp noise generated by the engine or components associated with it such as the exhaust system, cooling system etc.

The aforesaid and other objects are achieved according to the invention by a method and a device according to the features indicated in claims 1 and 5.

Particular features and advantages of the invention are indicated by the detailed description set out below and the attached drawings and claims.

BRIEF LIST OF THE DRAWINGS

The invention is described below in the form of a preferred embodiment example with reference to the attached drawings.

Figure 1 depicts a perspective view as seen obliquely from behind of a combustion engine provided with a normal silencer and a cooling air duct for damping of noise from the vehicle's combustion engine.

Figure 2 depicts a perspective view of the system according to Figure 1 but from the other side of the engine.

Figure 3 depicts a cross-section through a cooling air duct modified according to the invention for damping of noise from the vehicle's combustion engine.

Figure 4 depicts the cooling air duct's outlets situated on the vehicle's roof.

DESCRIPTION OF PREFERRED EMBODIMENTS

Figure 1 depicts a perspective view as seen obliquely from behind of a combustion engine 1 , preferably for a heavy motor vehicle such as a bus or truck. The diagram also depicts a normally provided exhaust system 2 comprising first and second exhaust pipes 3, 4 and a silencer 5. The engine installation is also provided with a noise- insulating cooling air duct 6 with a grilled inlet 7 and a grilled outlet 8.

Figure 2 depicts a perspective view as seen obliquely from behind of the system depicted in Figure 1 but from the other side of the engine 1. This diagram shows somewhat more clearly the configuration of the cooling air duct 6. Cold air is drawn in via the inlet 7, passes through the cooling air duct 6 and is blown out via the outlet 8.

Figure 3 depicts a cross-section through a cooling air duct 6 modified according to the invention for damping of noise from the vehicle. The cooling air duct 6 is entirely separated/demarcated from the engine 1 and its engine space (not depicted) and constitutes an airflow demarcated from the engine space.

The main advantage of this is that engine noise but also noise from other units and devices on and around the engine (e.g. a mechanical air conditioning compressor (not depicted), cooling fan 9 etc.) does not make its way out via the cooling air duct 6 or the cooling element 10.

The fact that the cooling air warmed via the cooling element 10 does not enter the engine space means that the engine space temperature is also kept down, which is important, e.g. for the service life of electronics and control units etc. situated therein. Ventilation of the engine space is nevertheless still required and may be provided by a separate cooling system (not depicted). It may for example be provided by separate fans which cool a so-called low-temperature cooling circuit intended to cool, for example, electrical components. This cooling air is thereafter led, for example, down towards the ground via apertures in the floor of the engine space. These apertures towards the ground may also be provided with noise damping.

A further advantage is that the orifices of the cooling air duct 6, the inlet and outlet 7, 8 respectively, may be situated on the roof of the vehicle, see Figure 4. This is to prevent noise towards the sides of the vehicle, with consequent benefit to other road users and persons in the immediate vicinity, e.g. on sidewalks, at bus stops etc. Baffles or grilles on the vehicle's roof guide the noise from the cooling air duct 6 forwards and rearwards respectively so that no one who is above the vehicle, e.g. several floors up in adjacent buildings, should be disturbed.

Cold air is with advantage taken in from in front, in the direction of movement of the vehicle, and warm air which has passed through the cooling air duct 6 is discharged rearwards to prevent "cycling" in the cooling system, i.e. to prevent the same warm air from circulating through the cooling air duct 6 more than once.

An advantage of the inlet and outlet 7, 8 being situated on the roof is that the vehicle, e.g. a bus, will not need to be adapted for use in right-hand or left-hand traffic, but will have equally good noise damping irrespective of which side of the bus the passengers are in.

The cooling air duct 6 may be made of aluminium, sheet metal, plastic or the like. At least one cooling fan 9 and one cooling element 10 are arranged in the cooling air duct 6. The cooling fan 9 is preferably situated downstream but may also be situated upstream (not depicted) of the cooling element 10. The whole or part of the inside of the cooling air duct 6 is lined with an absorbent, a sound-damping material 11, and is therefore noise-damping. The sound-absorbing material 11 may be a commercially available damping material.

The cooling air duct 6 is also configured to damp noise arising from the actual cooling fan 9. The cooling air duct 6 is also configured with at least one, preferably two or more, angled sections 12a, b, c or bends, each preferably 60-90 degrees, resulting in a winding duct shape which causes air flows and sound waves to rebound and change direction. The result is that a substantial portion of the unwanted noise is directed towards some of the insides of the cooling air duct and towards the sound-absorbing material 11 and is damped. Fan noise or noise from the engine's exhaust gases is thus prevented from radiating directly out to the surroundings of the vehicle. The cooling air duct 6 is also separated/screened from the engine 1 and the engine space, further preventing direct noise from the engine 1 from leaking out to the surroundings via the cooling air duct 6.

In a preferred embodiment, the sound-absorbing material 11 comprises perforated aluminium specially made, fitted and tuned to the noise which is intended to be damped. This involves taking into account the structural configuration of the cooling air duct 6 and the material which the cooling air duct 6 is made of.

The exhaust gases from the engine 1 are led via the first pipe 3 of the exhaust system 2 to the silencer 5 in which part of the exhaust noise of the engine 1 is damped out. The exhaust gases are thereafter led via a second pipe 4 into the cooling air duct 6, preferably downstream of the cooling package 10 and the fan 9. The exhaust gases are preferably led into the cooling air duct 6 substantially transversely to the main airflow in the cooling air duct 6. The noise thus encounters the sound-absorbing material 11 in

the cooling air duct 6 and is damped. The same also happens to noise from, for example, the cooling fan 9. Substantially all the noise is thus directed towards a surface provided with damping material and has no "direct exit" from the cooling air duct 6.

Placing the sound-absorbing material 11 on the insides of the cooling air duct 6 results in damping of the exhaust noise before the exhaust gases and residual noise can thereafter make their way out via the outlet 8 of the cooling air duct 6. The result is good noise damping and discrete and concealed release of exhaust gases.

The invention is described above with reference to a preferred embodiment. The invention is of course not limited thereto, since other embodiments and variants of the invention are also possible within the scope of protection of the claims.