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Arrangement and method for a compressed air system

Arrangement and method for a compressed air system description/claims

The present invention relates to an arrangement for a compressed air system comprising an air compressor arranged to generate compressed air for said compressed air system, an air dryer arranged to dry said generated compressed air and means for unloading said air compressor in certain conditions.

The invention also relates to a method for a compressed air system, comprising generation of compressed air for said compressed air system by means of an air compressor, drying of said generated compressed air by means of an air dryer, and unloading of said air compressor in certain conditions.

In association with certain vehicles, in particular heavy goods vehicles, an air compressor and a valve arrangement are normally used for generating and distributing compressed air to a compressed air system, which in turn comprises components that use compressed air such as, for example, the vehicle's air suspension system and braking system, and also pressure tanks, compressed air lines and various types of valves.

In a way that is already known, the said air compressor is driven mechanically by means of the vehicle's combustion engine. In addition, the compressor is arranged to generate a suitable system pressure in the compressed air system. This is carried out by a control which, in turn, means that the compressor is activated when the system pressure falls below a lower permitted limit level and changes to an unloading phase when the system pressure exceeds a certain upper limit level. Unloading of the compressor corresponds to its ability to generate compressed air being shut off or greatly reduced and/or to the air that the compressor generates being led out into the open air so that the compressor does not work against an overpressure.

In association with control of the function of an air compressor, it is known that there is a need to unload its function in the event of certain predetermined operating states. Such unloading is usually carried out by sending a pneumatic control signal to the compressor with the object of changing its valve function or reducing its function for generating compressed air in some other way. It can be noted here that patent document U.S. Pat. No. 6,036,449 shows an arrangement in which an air compressor is arranged to be activated only when different engine activities require this, or when engine power is available for operation of the air compressor. This known arrangement comprises an air pressure regulator that is arranged to control the operating mode of the compressor in response to the pressure level in the system.

In addition, a compressed air system normally comprises an air dryer. An air dryer is arranged to remove moisture from the compressed air that is supplied from the compressor to the compressed air system. By removing moisture from the compressed air, the danger is reduced of corrosion in the various components that are comprised in the compressed air system. In this way, the life of the various pneumatic components can be optimized. In addition, the danger is reduced of any loss of function. At the same time, correct functioning at low temperatures is ensured, as freezing of any condensate can be prevented by means of the air dryer.

In spite of known systems for regulating and unloading a compressor's function working satisfactorily, there is a need to make further improvements in this field. In particular, there is a need for systems for initiating an unloading phase of the compressor in situations that would otherwise cause damage and loss of function in the compressed air system.

It is desirable to provide an improved arrangement and an improved method for unloading air compressors, in particular on motor vehicles.

In an arrangement according to an aspect of the present invention, the said means comprises a control unit, arranged to send a control signal to a valve, and an air line between said valve and air compressor, with said control unit being arranged to activate said control signal for unloading the air compressor in the event of at least one predetermined operating state of the air compressor.

A method according to an aspect of the present invention is characterized in that it comprises generation of a control signal from a control unit to a valve, for activation of an air flow via the valve, an air line and onward to the air compressor, for unloading the air compressor in the event of at least one predetermined operating state of the air compressor.

Certain benefits are obtained by means of the invention. Firstly, it can be mentioned that the invention can be utilized in a simple and effective way to unload an air compressor in certain situations. In particular, unloading can take place at high speeds of the compressor. High speeds mean that the compressor is operating in a relatively hot state which means that the amount of oil vapour emitted from the compressor's lubrication system into the compressed air increases. In this relatively hot state, this oil is also oxidized, which is harmful to the compressed air system.

The invention can thus be used to reduce wear and tear and carbonization in the compressor and to reduce the amount of aggressive oil in the compressed air system that can interfere with the function of the components comprised in the compressed air system.

According to a preferred embodiment, the abovementioned control unit can be used to control a solenoid valve in an air dryer, which leads to unloading of the air compressor in an efficient way using existing components. The invention can also be used as a supplement to controlling of the air dryer, with the air compressor being unloaded in the event, for example, of high engine speeds and/or large increases in engine speed.

The invention will be described in the following with reference to a preferred embodiment and the attached FIG. 1, which shows an outline diagram of a compressed air system that has been designed in accordance with the invention.

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