The present invention relates to the thermal conditioning of the supply of fuel to vehicle diesel engines, proposing a valve which allows determining, according to the temperature of the fuel which is sent towards the engine, a distribution of the return of hot fuel from the injection pump towards the passage filter of the fuel which is sent to the engine and towards the tank from which the fuel is supplied.
In diesel engine vehicles there is the problem that the paraffins contained in the fuel gel below certain temperatures, which can cause the clogging of the filter and failures in the operation of the engine system.
To prevent this problem it is necessary for the fuel to acquire a certain temperature, for which two known heating systems are applied:
The electric heating system has the advantage of efficiency under any condition of room temperature but, however, it significantly affects the electrical balance of the vehicle of application, ultimately increasing CO2 emissions. And, furthermore, it is a comparatively more expensive system due to its complex construction.
The thermostatic valve system has, in contrast, the advantage of simplicity and the optimal exploitation of the energy, since it recycles the heat produced by the internal friction of the injection pump.
The thermostatic valves known for said application generally have constructive structures which make the design non-compact, resulting in several embodiments which are too bulky and therefore contrary to the increasingly demanding requirements of space reduction, and all the embodiments generally have a formation having external joints, such as welds or others, through which the fuel circulating therein may leak. Thermostatic valves according to the state of the art are disclosed in
According to the invention, a thermostatic valve is proposed for the mentioned application in the fuel circuit of vehicle diesel engines, with a constructive embodiment of said valve which improves the constructive and functional qualities thereof.
This valve object of the invention comprises a compact casing having two outwardly projecting tubes, one for the connection to the return of the injection pump and the other one for the connection to a conduit for communication with the fuel tank.
The compact casing houses therein a functional assembly which is intercalated between an outlet for communication with the filter of the fuel circuit and the mouths of the tubes for the connection with the return of the injection pump and with the conduit for communication with the fuel tank, said functional assembly determining a central chamber communicated with the inner mouth of the tube for the connection with the return of the injection pump and which is separated, by means of respective check valves, with respect to the outlet for communication with the filter and with respect to the inner mouth of the tube for the connection with the conduit for communication with the fuel tank.
Said functional assembly of the valve includes a bimetal arranged in relation to the outlet for communication with the filter, so that, according to the temperature of the fuel, said bimetal opens or closes this outlet for communication with the filter, establishing two modes of operation, in one of which the hot fuel from the injection pump return is distributed between this outlet for communication with the filter and the outlet through the tube for communication with the fuel tank, whereas in the other mode of operation all the hot fuel from the injection pump return exits through this tube for communication with the fuel tank.
A valve is thus obtained which determines, according to the temperature of the fuel circulating towards the engine to which it is applied, a flow control of the hot fuel returning from the injection pump, between a direction towards the fuel tank and another one towards the filter of the fuel circuit, by means of an assembly which is easy to mount, in which a bimetal with a large diameter can be used, thus reducing the pressure drops which are generated in the filter of application when the fuel passes.
Furthermore, the outer casing of the valve forms a single part cover, without interruption as in other already known embodiments, which in the arrangement of application is attached at its lower edge, by means of welding, over the filter to which it is applied, determining a completely closed mounting in which the functional assembly is concealed inside the outer casing, without impervious joints present in other already known valves, the possibility of fuel leaks to the exterior thus being reduced.
Therefore, the proposed valve has truly advantageous features, acquiring its own identity and a preferred character with respect to known valves with the same function.
The object of the invention relates to a thermostatic flow distributing valve, intended to be incorporated with respect to the filter of fuel circuits in diesel engine vehicles, in relation to the hot fuel return from the injection pump.
Said valve comprises an outer casing (1), from which two tubes (2 and 3) emerge towards the exterior, one of them (3) for being connected to the return of the injection pump of the engine, whereas the other tube (2) is for being connected to a conduit of communication with the fuel tank.
Inside that outer casing (1) a functional assembly is housed which is intercalated between an end outlet (4) and the inner mouths of the tubes (2 and 3), that functional assembly determining a central chamber (5), which communicates through openings (6) with a peripheral chamber (7) into which the tube (3) for connection with the injection pump return opens out, whereas at the ends of said central chamber (5) there are arranged respective check valves (8 and 9) which, pushed by respective springs (10), close that central chamber (5), respectively, with respect to a chamber (11) into which the tube (2) for the connection with the communication to the fuel tank opens out and with respect to a chamber (12) communicating with the end outlet (4).
In front of the end outlet (4) a bimetal (13) is also arranged at the inner part, which bimetal opens or closes said end outlet (4) according to the temperature.
Thus, in the practical application the valve is arranged over the filter of the fuel circuit of application, with the end outlet (4) in communication with the inside of said filter and the tubes (2 and 3) connected to the conduit for communication with the fuel tank and to the injection pump return, respectively, such that the hot fuel from the injection pump return enters through the tube (3) in the peripheral chamber (7) and from the latter through the openings (6) in the central chamber (5), from where, according to the position of the bimetal (13), two possible outlet circulations are determined in the following modes:
The thermostatic valve thus formed determines a compact structural assembly, the functional assembly being housed within the outer casing (1), which is formed by a single part without interruption, determining a cavity in which the functional assembly is closed, by means of a cover (14), on the mentioned outer casing (1), the end outlet (4) of the valve being determined through said cover (14) .
Thus, the assembly of the thermostatic valve is easy to mount, it being possible to previously mount a partial assembly formed by a body (15) and a receptacle (16) which are coupled to one another with a snap-fitting interlock (17), including therein the valve (9) which establishes the closure with respect to the chamber (12) for communication with the end outlet (4), so that said partial assembly can later be incorporated, as a single mounting element, together with the valve (8) for closing the central chamber (5) on the other side, with the bimetal (13) and with the cover (14) for closing the entire assembly, within the outer casing (1).
The retention of the closure is established, according to an embodiment, by means of a ring (18) with an inclined edge, which allows a forced insertion in the outer casing (1), determining an interlock which prevents retreat and therefore dismantling, as observed in
Without the concept of the thermostatic valve according to the invention being altered, said closure of the functional assembly can be established with other solutions for retaining the mounting, for example by means of the engagement of the cover (14) itself with fingers or flanges in its periphery, in an annular housing or multiple corresponding housings, of the inner face of the outer casing (1) .
In the installation of application the thermostatic valve is fixed by means of welding at the edge of the mouth of the outer casing (1) on the filter to which it is applied, so that the functional assembly is closed with complete leak tightness, without any possibility of fuel leaks through joints in the valve formation.
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