EP2878785A1

EP2878785A1 - System for pressurizing a cooling circuit of an internal combustion engine for industrial vehicles equipped with a compressed air tank

Info

Publication number: EP2878785A1
Application number: EP14195286.1A
Authority: EP
Inventors: designation of the inventor has not yet been filed The
Original assignee: FPT Industrial SpA
Current assignee: FPT Industrial SpA
Priority date: 2013-11-27
Filing date: 2014-11-27
Publication date: 2015-06-03
Anticipated expiration: 2034-11-27
Also published as: ITMI20131977A1; ES2652177T3; EP2878785B1

Abstract

System for pressurizing a cooling circuit of an internal combustion engine for industrial vehicles equipped with a compressed air tank (18) with relative pressure comprised between 9 and 13 bar, the cooling circuit comprising an expansion tank (12) partially filled with air in an upper part and partially filled with liquid in a lower part, the system comprising a pneumatic connection (10b) between said compressed air tank and said upper part of the expansion tank (12), wherein said pneumatic connection comprises one single regulating valve (10) of the mechanical type.

Description

Field of application of the invention

The present invention relates to the field of cooling circuits of internal combustion engines, and in particular to the field of controlling the internal pressure of the circuit itself by means of a mechanical valve without using pressure sensors or respective control units.

State of the art

Modern cooling circuits of internal combustion engines are provided with a coolant liquid expansion tank. A safety valve is usually housed in such an expansion tank, part of the volume of which is filled with air, to allow to release gas/vapor into the external environment when a predetermined pressure value measured in the expansion tank itself is exceeded.
The circulation and pressurization of the coolant liquid in the circuit is ensured by a hydraulic pump.
With the use of variable flow rate pumps, i.e. capable of regulating themselves according to the temperature of the coolant liquid, the pressure may drop in some points of the cooling circuit thus allowing the occurrence of cavitation phenomena.
Such phenomena determine a rapid corrosion of the walls of the cooling circuit in the internal combustion engine, with severe damage to the engine itself.
Such phenomena are related to the pressure in the circuit but also to the temperature of the coolant liquid.
Various solutions are known which are based on the introduction of air into the circuit so as to increase the pressure in the circuit and prevent such cavitation problems. JP19800169161 shows a solution in which piezoelectric sensors are arranged along the cooling circuit to detect cavitation phenomena. When such phenomena are detected, air coming from the radiator fan is blown into the circuit, the amount of air being proportional to the intensity of the detected cavitation phenomena.
US2005061264 shows a solution for pressurizing the cooling circuit by detecting a level of coolant in the expansion tank. Thus, air is introduced into the tank when the liquid rises over a predetermined level. A preferred variant shows the use of a further pressure sensor housed in the expansion tank and processing means which control the introduction of compressed air in the expansion tank also according to the pressure measured in the expansion tank.
DE102009018012 and DE102005007781 show systems which are very similar to those described above in which pressurization is again controlled by means of pressure sensors and respective control units.
US6666175 shows another solution in which the cooling circuit is pressurized by means of the supercharger compressor and in which the pressurization is controlled by means of a spring valve or by means of a servo valve.
DE2222919 shows another solution for pressurizing the cooling circuit by means of mechanical valves which connect the expansion tank of the circuit to a compressed air tank.
If, on one hand, the use of mechanical valves (i.e. free from servo assistance) is known, on the other hand the pressurization of the cooling circuit by means of the compressed air tank of the brakes or of the suspensions is shown in combination with servo assisted valves.
This is because the compressed air tanks of the braking circuit and/or of the suspensions of industrial vehicles have an inner pressure in the order of at least 9-10 bar, and even higher, with capacities in the order of a hundred liters.
On the other hand, a cooling circuit of an internal combustion engine has a total capacity in the order of tens of liters.
The need to operate by means of servo assisted valves and pressure sensors when the pressure in the cooling circuit must be increased by 0.4-0.5 bar, starting from a compressed air tank of the braking circuit and/or of the suspensions, is thus apparent.

Summary of the invention

It is the object of the present invention to disclose a system for pressurizing a cooling circuit of an internal combustion engine operated by means of mechanical, i.e. not servo assisted, valves based on the tapping of compressed air from the braking circuit and/or from the pneumatic suspension feeding circuit of the vehicle.
It is the object of the present invention a system for pressurizing a cooling circuit of an internal combustion engine for industrial vehicles providing with a compressed air tank according to claim 1.
The appended claims describe preferred embodiments of the invention forming an integral part of the present description.

Brief description of the figures

Further objects and advantages of the present invention will be apparent from the following detailed description of an embodiment thereof (and variants thereof) and from the accompanying drawings given merely by way of non-limitative example, in which:

figure 1 indicates an approximate diagram of the system object of the present invention,
figure 2 shows a preferred variant of a part of the diagram in figure 1 in detail,
figure 3 shows examples of regulating valves belonging to the diagram in figure 1.

The same reference numbers and letters in the figures refer to the same elements or components.

Detailed description of embodiments

Figure 1 shows an internal combustion engine 1, which by means of connection means 15, rotationally drives an air compressor 16.
The compressor 16 aspirates air from the environment and compresses it, introducing it into the compressed air tank 18 by means of the pipe 19. A dryer 17 for extracting the humidity from the compressed air is arranged between the compressor 16 and the tank 18 on said pipe 19.
The internal combustion engine 1 has a cooling circuit (not shown), connected with a closed expansion tank 12, which is partially filled with coolant liquid and partially filled with air.
A safety valve 8b is connected with the upper part of the tank 12 to release vapor into the external environment when a predetermined pressure threshold is exceeded.
A pneumatic pipe 10b connects the compressor 18 to the upper part of the expansion tank 12. Such a pipe is opened and closed by means of a mechanical regulating valve 10, typically spring-operated, i.e. free from any type of electric assistance.
Such a valve opens the pipe 10b, so that the compressed air flows into the expansion tank when it detects a pressure difference between a point upstream and a point downstream of the valve itself, where "upstream" and "downstream" are referred to the direction of circulation of the compressed air from the tank 18 to the tank 12.
Preferably, the mechanical regulating valve 10 is adjusted according to the filling cut-off pressure of the compressed air tank 12. In which the cut-off pressure is the pressure at which the compressor 16 is deactivated after a step of activation.
A check valve (not shown), also completely mechanical, may be provided on the pneumatic pipe 10b itself. Therefore, any regulation of the pressurization of the tank 12 is operated mechanically without the aid of control means.
Preferably, said mechanical valve is a three-way valve.
More in particular, even when the valve externally appears as a two-way valve, a third way is integrated in the valve itself and connected with one of the other ways to measure the pressure upstream and downstream of the valve itself. In other words, the third way controls the opening of the valve itself.
Preferably, the third way is connected with the outlet way of the valve itself, i.e. to the lower pressure way, directly connected with the expansion tank.
With reference to figure 2, the third outlet is separate from the others and connected by means of a separate pipe 10c to the upper part of the expansion tank 12.
Preferably, a small air expansion reservoir 11 is interposed between the valve 10 and the expansion tank 12, so as to allow a preventive expansion of the compressed air before and during its introduction into the expansion tank 12. Advantageously, by virtue of the implementation of the reservoir 11, the opening and closing of the valve 10 can be modulated with greater accuracy, without incurring the risk of subjecting the expansion tank to an excessively high pressure increase.
Preferably, the inner volume of the air expansion reservoir 11 is approximately 13 1., i.e. 1/5 - 1/10 of the part of volume inside the expansion tank occupied by air.
According to another preferred variant of the invention, the system comprises a valve 10, apparently a two-way valve, in which the third way is connected with one of the two other ways, having an air expansion tank directly integrated in the valve body.
Figure 3 shows a Wabco® valve particularly suited for implementing the present invention by way of example only. Such valves are provided with two ports A and B and both ports B integrate two ports, a control port d and a port for the passage of compressed air.
The aforesaid air expansion reservoir 11 is made inside the valve body. In particular, such a tank can be extended by means of a membrane/moveable piston loaded by means of a helical thrust spring f, which can be regulated by means of a screw g accessible from the outside of the valve body and arranged in axial position with respect to the helical spring.
Various embodiment variations of the non-limiting example described are possible, without because of this departing from the scope of protection of the present invention.
From the description above, a person skilled in the art will be able to implement the object of the invention without introducing further constructional details. The elements and features illustrated in the various embodiments may be combined without because of this departing from the scope of protection of the invention. The description of the prior art, unless specifically excluded in the detailed description, must be considered in combination with the features of the present invention, forming an integral part of the present invention.

Claims

System for pressurizing a cooling circuit of an internal combustion engine for industrial vehicles equipped with a compressed air tank (18) with relative pressure comprised between 9 and 13 bar, the cooling circuit comprising an expansion tank (12) partially filled with air in an upper part and partially filled with liquid in a lower part, the system comprising a pneumatic connection (10b) between said compressed air tank and said upper part of the expansion tank (12), wherein said pneumatic connection comprises only one single regulating valve (10), of the mechanical type.
System according to claim 1, wherein said compressed air tank (18) has a pressure fluctuating between a maximum pressure and a minimum pressure and wherein said mechanical regulating valve (10) is adjusted as a function of a maximum pressure of the compressed air tank (18).
System according to claim 1, wherein said mechanical regulating valve (10) is of the three-way type, wherein
- a first way is directly connected with the compressed air tank (18),

- a second way is connected with the expansion tank (12),

- a third way is connected with one of the first or second way, to control the opening/closing of the regulating valve.
System according to claim 3, wherein said mechanical regulating valve (10) comprises a reservoir for the air expansion (11) integrated in the body of the valve itself.
System according to claim 1, wherein said is of the three-way type, wherein
- a first way is directly connected with the compressed air tank (18),

- a second way is connected with the expansion tank (12),

- a third way is connected with said expansion tank (12),
System according to claim 4, further comprising a reservoir (11) for the air expansion arranged on said pneumatic connection (10b) between said mechanical regulating valve (10) and said expansion tank (12).
Industrial vehicle equipped with an internal combustion engine (1), with a compressed air tank with pressure comprised between 9 and 13 bars, and with a cooling circuit of the internal combustion engine (1) and with a system for pressurizing the cooling circuit according to any one of the claims from 1 to 6.