GB2193307A

GB2193307A - Engine cooling systems

Info

Publication number: GB2193307A
Application number: GB08707855A
Authority: GB
Inventors: Franco Martinis
Original assignee: Gilardini SpA
Current assignee: Marelli Europe SpA
Priority date: 1986-04-24
Filing date: 1987-04-02
Publication date: 1988-02-03
Anticipated expiration: 2007-04-02
Also published as: DE8705290U1; GB2193307B; SE8701675L; BR8702234A; IT207773Z2; GB8707855D0; ES1002262U; SE8701675D0; FR2597923A3; FR2597923B3; IT8653329V0; ES1002262Y

Abstract

A heat engine 2 comprises a thermostatic assembly 1 mounted in a cooling system comprising a first circuit 39 formed in the cylinder head 3 of the engine 2, a second circuit 45 formed in the cylinder block 4, a circulation pump 5 and a radiator 6 and comprises a displaceable rod 8 which acts on shutter discs 17, 14, 21 to open and close apertures 33, 37 which cause the various parts of the system to communicate. In particular, for a predetermined temperature range, the thermostatic assembly 1 allows a limited flow of cooling fluid between the first circuit 39 and the radiator 6 with respect to that coming from the second circuit 45 of the cylinder block 4. This limited flow is obtained by restricting an aperture 37 which places the first circuit 39 in communication with the radiator 6 by means of a cup-shaped body equipped with a shutter disc 14. <IMAGE>

Description

SPECIFICATION A thermostat unit for the cooling system of a heat engine The present invention relates to a thermostat unit for the cooling system of a heat engine.

For such systems, double thermostat valves are known, which allow the cylinder head of the engine to be maintained at a lower temperature than that of the cylinder block to avoid the possibility of detonations occuring.

The object of the present invention is that of providing a thermostat unit for a heat engine of the type able to maintain such a temperature difference between the cylinder head and cylinder block of the engine; which will be more efficient than those currently in use, with a relatively simple and therefore economical structure.

According to the present invention there is provided- a thermostat unit for a heat engine, installed in a cooling system comprising a first circuit formed in a cylinder head of the engine, a second circuit formed in a cylinder block of .

the said engine, the said first and second circuits being in communication through the said unit, a circulation pump in the said first and second circuits, and a radiator connected between the said thermostat unit and the said pump, the said unit including first means operable to regulate the communication between the said first circuit and the said radiator, and second means operable to regulate the communication between the said second circuit and the said radiator, characterised by the fact that it includes supplementary means operable to close communication between the said first circuit and the said radiator in various conditions of opening of the said first means.

For a better understanding of the present invention a preferred embodiment will now be described, purely by way of non-limitative example, with reference to the attached drawings, in which: Figure 1 is a sectioned side view of a thermostat unit formed according to the present invention; and Figures 2, 3 and 4 are schematic illustrations of three different operating positions of the thermostat unit of Figure 1 installed in a cooling system of a heat engine.

As illustrated in Figures from 2 to 4, a thermostat unit generally indicated 1 is installed in a cooling system of known type in a heat engine 2 schematically indicated with a cylinder head 3 and a cylinder block 4. The system is also provided with a circulation pump 5, a radiator 6 and a heater 7 for the interior of the vehicle. The thermostat unit 1 includes a rod 8 the end of which projects from a bulb 28 containing a mixture of heat sensitive waxes so as to present, externally, a length which varies with the value of the temperature of the fluid which flows over the bulb 28. The rod 8 acts on valve shutter discs which, in dependence on the length of the rod 8 itself, open and close orifices which put different hydraulic circuits of the cooling system into communication as will be described in more detail below.

With reference to Figure 1, the rod 8 has an outer end 11 engaging a blind axial hole formed in a first end of a shaft 12 which has an outer rim 9, and at a second end carries a cup-shape body 13 disposed inverted on the rod 12, and having at the base of a cylindrical side wall 15 an outer edge which constitutes a first valve shutter disc 14. The inside end of the cup 13 forms an end base for a coil spring 16 disposed around the shaft 12 and the action of which consists in pressing a second annular valve shutter disc 17 -slidably along the shaft 12 towards the rod 8. On the upper end of the cup 13 is disposed a valve shutter disc 21 on which acts one end of a coil spring 18.The end 11 of the rod 8, the body 13 and the valve shutter discs 17 and 21 are installed within a hollow cylindrical body 22 in which is formed, integrally, a cupshape cylindrical element 24 which defines an inner cylindrical chamber 23. The element 24 has a base wall 25 and a side wall 26. The base wall 25 has an axial through hole 27 engaged by a portion of the bulb 28 within which the rod 8 is able to slide. Close to the end wall 25 a pipe union 31 extends radially from the wall 26, and traverses the body 22 radially to put a first part 23a of the chamber 23 into hydraulic communication with the outiet of a cooling circuit 45 formed in the cylinder block 4 (Figure 2).A second pipe union 32 extends radially from the side wall 26 close to the free end of this wall, traverses the body 22 radially, and puts a second part 23b of the chamber 23 into hydraulic communication with the inlet of the radiator 6 (Figure 2). The parts 23a and 23b are coaxial with one another and are separated by an aperture 33 formed within the element 24 between the regions thereof from which the pipe unions 31 and 32 extend. For some operating positions assumed by the rod 8 (as will be detailed hereinbelow) the aperture 33 is closed by the valve shutter disc 1 7 which closes hydraulic communication between the two parts 23a and 23b of the chamber 23 and therefore between the pipe unions 31 and 32.Between the interior of the body 22 and the outside of the element 24 there is defined a chamber 34 the inlet opening 35 of which is represented by the open end of the body 22 through which the bulb 28 extends. Near the opposite end of the body 22 a third pipe union 36 joins radially to the wall thereof, which puts the chamber 34 into communication with the inlet of the heater 7 (Figure 2). The free end of the element 24 therefore defines an aperture 37 between the part 23b of the chamber 23 and the chamber 34.In one position as sumed by the rod 8 (as will be described in more detail below) the aperture 37 is closed by the valve shutter disc 21 pressed towards this aperture 37 by the spring 18 which, at its other end, is pressed against a cover plate 38 fixed to the end of the body 22 opposite the aperture 35. The valve shutter disc 14 remains within the part 23b of the chamber 23 for some positions assumed by the rod 8, whilst for other positions it can enter into the chamber 34 since it has a smaller diameter than that of the aperture 37. It is to be noted that this valve shutter disc 21 has a base portion 40 of smaller diameter which passes through the aperture 37 and is connected to the outer upper face of the cup-shape body 13.

In use the thermostat unit 1 assumes three different positions in dependence on the value of the temperature of the liquid which flows over the bulb 28. Figure 2 schematically illustrates the flow of coolant fluid when the bulb 28 is at a temperature value less than 71"C for example. In these conditions the rod 8 assumes the most contracted position which, by means of the valve shutter discs 17 and 21 and under the action of the springs 16 and 18, causes closure of the apertures 33 and 37. The coolant fluid from the output of the pump 5 therefore flows around a coolant circuit 39 formed in the cylinder head 3, exits from this and flows over the bulb 28, enters in part through the aperture 35 into the chamber 34 from which is exits through the pipe union 36 towards a duct 44 leading to the heater 7.Another part of the fluid from the cylinder head 3 arrives in a known way at a duct 41 which is positioned to heat the induct tion manifold of the engine 2 and which leads to a duct 42 at the outlet of the heater 7.

From the duct 42 the fluid is introduced into a duct 43 at the outlet of the radiator 6 and then flows towards the intake of the pump 5.

A further part of the fluid from the cylinder head 3 flows towards an inlet to the cooling circuit 45 formed in the cylinder block 4; this fluid does not flow through the cylinder block 4 in that, at the above-indicated temperature, the rod 8 maintains the aperture 33 closed thereby closing communication between the two parts 23a and 23b of the chamber 23. In fact, since the part 23a of the- chamber 23 is in hydraulic communication via the pipe union 31 with the outlet of the cooling circuit 45 in the cylinder block 4 the fluid does not flow along this circuit 45 because the outlet is closed by the valve shutter disc 17. Notwithstanding this a limited quantity of this fluid flows out from the circuit 45 via a small duct 46 to flow towards the intake of the pump 5.

In this case the only part of the engine 2 substantially affected by cooling is the cylinder head 3 which therefore is maintained at a temperature lower than that existing in the cylinder block 4.

Figure 3 illustrates the flow of coolant fluid when the bulb 28 is at a greater temperature, lying between 71"C and 85"C for example. At these temperature values the rod 8 projects from the bulb 28 and opens the opening 37, which puts the chamber 34 into communication with the part 23b of the chamber 23 from which the pipe union 32 extends. The expansion which the rod 8 experiences overcomes the action of the spring 18 so that the rod 8, with the body 13, causes translation of the valve shutter disc 21 towards the cover 38. The body 13, in this case, remains at the level of the aperture 37 and given its external configuration causes a throttling of the aperture 37 which allows a limited flow of coolant fluid from the chamber 34 towards the part 23b of the chamber 23.The aperture 33 still remains closed by the valve shutter disc 17, under the action of the spring 16. The coolant fluid again follows all the routes already described with reference to Figure 2. In this case, however, a part of the fluid which enters the chamber 34, limited because of the throttling of the aperture 37, enters into the part 23b of the chamber 23 from which it flows out via the pipe union 32 towards a duct 47 leading to the radiator 6.

Figure 4 illustrates the routes of the coolant fluid when the bulb 28 is at a still greater temperature, for example greater than 85"C.

At this temperature value the rod 8 projects even further and by means of the rim 9 of the shaft 12 displaces the valve shutter disc 17 against the action of the spring 16 opening the aperture 33. In this case the body 13 is thrust into the chamber 34 but still causes a certain throttling of the aperture 37. The coolant fluid follows all the routes already described with reference to Figure 3. Moreover, the fluid flows through the whole of the coolant circuit 45 in the cylinder block 4 from which it exits to enter the part 23a of the chamber 23 from which, through the aperture 33, it flows into the part 23b. Since the aperture 37 has a certain throttling a smaller quantity of fluid flows through this than through the aperture 33. From the part 23b of the chamber 23 the fluid coming from the two apertures 33 and 37 then passes through the pipe union 32 towards the radiator 6. In the stage described with reference to Figure 2, the circulation of coolant fluid through the radiator 6 is prevented to permit the engine 2 to reach the working temperature rapidly. In fact, it is known that an excessively low temperature of the cylinder walis is damaging to the operation and life of the engine 2 in that it causes a combustion with low efficiency. This occurs above all upon starting of the engine 2 or in the case of particularly low ambient temperatures.

In the stage described with reference to Figure 3 a limited quantity of fluid coming from the cylinder head 3 is allowed to pass through the radiator 6 in such a way that this gives a contribution to the cooling of the cylinder head 3 itself. Since the volume of fluid which can flow through the cylinder head 3 towards the radiator 6 must be relatively little it is therefore necessary to effect throttling (obtained by means of the body 13). The same throttling is also effective in the case of opening of the aperture 33 since the volume of fluid which must flow through the cylinder head 3 towards the radiator 6 is less than that which must flow through the cylinder block 4.

From what has been described the main advantages achieved by means of the present invention will be evident.

In particular, the thermostat unit 1 is modified, with respect to current thermostats, in such a way that there is a smaller flow of fluid from the cylinder head 3 towards the radiator 6 than from the cylinder block 4.

It is to be- noted finally that the thermostat unit 1 is of simple construction and therefore of low manufacturing cost.

Finally, it is clear that the thermostat unit 1 described and illustrated here can be modified and varied without by this departing from the protective scope of the present invention.

Claims

1. A thermostat unit for a heat engine, installed in a cooling system comprising a first circuit formed in a cylinder head of the said engine, a second circuit formed in a cylinder block of the said engine the said first and second circuits being in communication through the said unit, a circulation pump for circulating fluid through the said first and second circuits and a radiator connected between the said thermostat unit and the said pump, the said unit including first means operable to regulate the communication between the said first circuit and the said radiator, and second means operable to regulate the communication between the said second circuit and the said radiator, characterised by the fact that it includes supplementary means operable to close communication between the said first circuit and the said radiator in various opening conditions of the said first means.

2. A thermostat unit according to Claim 1, characterised by the fact that it comprises: a substantially cylindrical cup-shape body having an inlet aperture in communication with an outlet of the said first circuit; a cup-shape portion within the said body defining a first inner cylindrical chamber subdivided into a first part and a second part separated by an aperture which can be closed by the said second means, first pipe union extending from the said first part, to put it into communication with an outlet of the said second circuit, and a second pipe union extending from the said second part, to put it into hydraulic communication with an inlet of the said radiator;; a second chamber being defined within the said body between this and the outer surface of the said portion, the said second part of the said first chamber having an aperture for communication with the said second chamber, which can be closed by the said first means; a bulb of temperature sensitive material being housed in the bottom of the said cupshape portion and extending through the said first aperture, a rod projecting from the said bulb and extending into the interior of the said first part of the said first chamber, the said rod being operable to act on the said first means, second means and supplementary means against the action of resilient biasing means.

3. A thermostat unit according to Claim 2, characterised by the fact that the said supplementary means comprise a cup-shape body disposed within the said first chamber and slidable, parallel to the axis of the said rod and under the action of this, between a first position in which it is within the said second part with the said first means which close the associated aperture, and subsequent positions in which it is in correspondence with the said aperture opened by the said first means and in which it causes a throttling for the fluid which enters into the said second part of the said first chamber from the said second chamber.

4. A thermostat unit according to Claim 3, characterised by the fact that the said first means include a first valve shutter disc installed within the said second chamber and pressed by first spring means onto the said controlled aperture, the said first valve shutter disc being displaceable parallel to itself to open the said aperture under the action of the said rod and together with the said cup-shape body with which it is in contact, and in that the said second means include a second valve shutter disc installed within the said second part of the said inner cylindrical chamber and pressed by second spring means, which press against the interior of the said cup-shape body, on the said controlled aperture, the said second valve shutter disc being slidable parallel to the axis of the said rod to open the said aperture under the action of this.

5. A thermostat unit according to Claim 4, characterised by the fact that an annular portion with constitutes a third valve shutter disc facing the said second valve shutter disc extends radially from the free edge of the said cup-shape body.

6. A thermostat unit according to Claim 4 or Claim 5, characterised by the fact that the said rod has one end engaging a first end of a shaft passing through the said second valve shutter disc., and in that at a second end it supports the said cup-shape body whilst the said first end has a rim operable to engage and displace the said second valve shutter disc after the said rod has already effected displacement of the said first valve shutter disc and the said cup-shape body to open the said controlled aperture.

7. A thermostat unit according to one of Claims from 4 to 6, characterised by the fact that a cover plate against which the said first spring means act is mounted at one axial end of the said body opposite the said inlet aperture.

8. A thermostat unit according to any preceding Claim, characterised by the fact that the-said second chamber is in communication with a third pipe union to communicate with supplementary external circuits.

9. A cooling system for a heat engine comprising a first circuit formed in its cylinder head, a second circuit formed in its cylinder block, the said first and second circuits being in communication with a thermostat unit, a circulation pump, and a radiator connected between the said thermostat unit and the said pump, characterised by the fact that the said thermostat unit is of the type as claimed in at least one of the preceding Claims.

10. A thermostat unit and cooling system for a heat engine as described and illustrated with reference to the attached drawings.