GB2155153A

GB2155153A - Thermostat unit for the cooling circuit on a motor vehicle engine

Info

Publication number: GB2155153A
Application number: GB08504131A
Authority: GB
Inventors: Antonio Nigra
Original assignee: Gilardini SpA
Current assignee: Marelli Europe SpA
Priority date: 1984-02-24
Filing date: 1985-02-18
Publication date: 1985-09-18
Also published as: IT8467174A1; IT1179990B; FR2560406A1; SE8500655L; IT8467174A0; FR2560406B1; SE8500655D0; GB8504131D0; DE3505835A1

Abstract

A thermostat unit (1) for the cooling circuit on a motor vehicle engine comprises a heat-sensitive element (16) lapped by the fluid flowing through the cooling circuit and controlling the position of valve means (20, 28) according to the temperature of the fluid. The main characteristic of the said unit (1) consists in means (26) designed to generate a quantity of heat acting directly on the heat-senstive element (16) for the purpose of influencing the latter's position control of the said valve means (20, 28). Preferably the heating means (26) comprise an electrical resistor controlled by a switch (43) so that the valve opens at different temperatures during winter or summer. <IMAGE>

Description

SPECIFICATION Thermostat unit for the cooling circuit on a motor vehicle engine The present invention relates to a thermostat unit for the cooling circuit on a motor vehicle engine, particularly cars fitted with a small radiator on the said cooling circuit for heating the passenger compartment.

Such thermostat units are known to present an inlet duct, for the cooling fluid from the engine, and two outlet ducts, one leading to the duct connected to the main cooling radiator, which therefore leads back to the engine through the cooling fluid circulating pump, and the other directly supplying the auxiliary radiator for heating the passenger compartment and which therefore leads back to the engine via the pump.

The said thermostat unit houses a heat-sensitive element having a bulb conveniently filled with wax and lapped by the fluid flowing through the cooling circuit from the engine, the said element activating a rod controlling the position of valve means according to the temperature of the fluid lapping the bulb, so as to regulate the passage of the in-coming fluid towards one or other of the two outlet ducts on the said unit.In more detail, when the engine is run at relatively low temperature, all the cooling fluid from the engine is sent back to the auxiliary radiator, whereas, at a given temperature, e.g. 87"C, the passage leading to the main radiator starts opening and the straightthrough passage towards the auxiliary radiator starts closing until, at a higher temperature, direct circulation towards the auxiliary radiator is shut off entirely and all the cooling fluid is fed through the main radiator.

Such constant operation, however, regardless of external temperature, is far from being entirely satisfactory, a preferable arrangement being on on which the heat-sensitive element is activated at different temperature thresholds, i.e. a higher threshold in winter when, on account of greater heat exchange between the engine and outside atmosphere, a higher operating temperature of the cooling fluid may be permitted and, by way of a further advantage, a greater quantity of heat may be yielded to the auxiliary radiator for heating the passenger compartment, and a lower temperature of the cooling fluid in summer, for opposite reasons.

Thermostat units having valve means operated at different temperatures have already been proposed, but are of bulky design and involve complex, high-cost manufacturing processes.

The aim of the present invention is to provide a thermostat unit for the cooling circuit on a motor vehicle engine of the aforementioned type, but which provides for controlling the position of the valve means at at least two different temperatures and which, besides being of negligible additional size, can be produced easily and cheaply.

With this aim in view, the present invention relates to a thermostat unit for the cooling circuit on a motor vehicle engine, the said unit comprising a heat-sensitive element lapped by the fluid flowing through the said cooling circuit and controlling the position of valve means according to the temperature of the said fluid, characterised by the fact that it comprises means designed to generate a quantity of heat acting directly on the said heat-sensitive element for influencing the latter's position control of the said valve means.

One arrangement of the present invention will now be described, by way of a non-limiting example, with reference to the attached drawings in which: Figure 1 shows a bottom view of a thermostat unit according to the present invention; Figure 2 shows a section along line ll-ll of the Figure 1 thermostat unit.

Number 1 in Figure 1 indicates the thermostat unit according to the present invention and comprising, in known manner, a connecting flange 2, having a hole 3 for receiving the cooling fluid from the engine, and two outlet ducts, 4 and 5, for supplying cooling fluid to the main and auxiliary radiators respectively. Thermostat unit 1 is conveniently made of silicon aluminium, in two parts (bottom 6 and top 7) connected together by means of bolts 8 (Figure 2).

In more detail, hole 3 communicates with a chamber 10 formed in bottom part 6 and coaxial with chamber 11 formed in top part 7 and which, in turn, communicates with outlet duct 4. The two chambers 10 and 11 are separated by an essentially-known type of heat-sensitive unit 12 which presents a load-bearing structure 13 having a circular edge 14 housed inside a peripheral seal 15 enclosed between parts 6 and 7. The said heat-sensitive unit 12 also comprises a heat-sensitive element 16 comprising a bulb-shaped outer body 17 filled with a substance, in this case wax, which expands rapidly at a given temperature threshold and acts on a rod 18 projecting axially from body 17 and secured at the top to structure 13.Round the upper part of outer body 17 is secured an annular disc 20 which, by contacting the inner edge 21 on structure 13, acts as a communicating valve between bottom chamber 10 and top chamber 11. A spring 22 is fitted between an annular projection 23 on outer body 17 and a lower annular edge 24 on structure 13.

According to the present invention, the lower part of outer body 17, conveniently made of brass, forms a hollow cylinder 25 the end section of which has a larger-diameter internal hole housing an electrical resistor 26, in this case, a shielded type, cylindrical in shape, having the same diameter as the upper inner hole on cylinder 25 and on which the resistive part is concentrated at the top contacting the larger-section bottom part of heatsensitive element 16 containing the wax. Round the top of cylinder 25 is fitted a spring 27 which rests, on one side, on the larger-section bottom of body 17 and, on the other, on an annular plate 28 locked axially by a check ring 29 fitted at the bottom on to cylinder 25.The said plate 28 is designed to cooperate with a recess 30 formed in bottom part 6, in such a manner as to form a communicating valve between chamber 10 and a bottom chamber 31 containing hollow cylinder 25 and communicating with outlet duct 5. The said chamber 31 is defined by a cylindrical bottom portion 32 of part 6 and forms an annular inner shoulder 33 which acts as a support for a bush 34 housed round hollow cylinder 25. Beneath the said bush 34 is fitted an annular body 35, also conveniently made of plastic like bush 34 and fitted with two sealing rings 36 and 37 for sealing the inner hollow surface of portion 32 and cylinder 25 respectively.

The said annular body 35 is locked at the bottom by a check ring 38 secured inside the hole in cylindrical portion 32. Electrical resistor 26 is locked at the bottom by a plastic washer 40 fitted inside hollow cylinder 25 the inner end section of which is filled with insulating material 41, in this case, epoxy resin. From hollow cylinder 25 an electrical supply cable 42 runs out, the said cable comprising a first wire, connected to a positive-voltage +V supply terminal, via switch 43, and a second ground- connected wire.

The thermostat unit covered by the present invention operates as follows.

Supposing, for example, under operating conditions not involving electrical resistor 26, that heatsensitive element 16 has been set in such a manner as to be activated when the temperature of the cooling fluid lapping outer body 17 is, for example, 87"C. Below this temperature, the passage into chamber 11 through annular disc 20 remains closed, so that all the cooling fluid supplied to hole 3 and chamber 10 flows out of outlet duct 5 towards the additional radiator for heating the passenger compartment and then back to the engine.

When the temperature of the cooling fluid exceeds 87"C, the rod 18 moves out of outer body 17 and, as load-bearing structure 13 is fixed, the entire heat-sensitive element 16 moves down, the passage into chamber 11 and outlet duct 4 towards the main radiator opens and the passage into chamber 31 and outlet duct 5 closes gradually until, when annular plate 28 settles in recess 30, the said second passage is cut off and all the cooling fluid flows through the main radiator.

For operating heat-sensitive element 16 at a lower cooling fluid temperature (e.g. 80"C) as may be required, for example, in summer, activating switch 43 supplies electrical resistor 26 which supplies a sufficient quantity of heat for raising the temperature of the wax on heat-sensitive element 16 by 7"C, so as to activate the said element 16, open the passage between chambers 10 and 11 and gradually close the passage into chamber 31 as already described. In like manner, heat-sensitive element 16 may be activated by two cooling fluid temperatures, depending on whether or not switch 43 has been operated.The latter may be an ordinary switch mounted on the dash panel and operated by the driver, or, for example, a switch connected to a control for regulating heating inside the passenger compartment and designed to cut off supply to resistor 26 when the heating inside the passenger compartment is on. The advantages of the thermostat unit covered by the present invention will be clear from the foregoing description. In particular, it is relatively easy to make, comprising as it does only a few additional elements; it is compact, essentially requiring only the addition of bottom cylindrical portion 32 on thermostat unit 1, and is generally speaking cheap to manufacture.

To those skilled in the art it will be clear that changes can be made to the arrangement described without, however, departing from the scope of the present invention. For example, switch 43 may be replaced by any heat-sensitive element for achieving control according to a given reference temperature. Control of supply to electrical resistor 26 may be performed proportionally, so as to regulate the amount of heat supplied to heatsensitive element 16 and, consequently, the different cooling fluid temperature at which heat-sensitive unit 12 is activated. Resistor 26 may be ground-connected differently, e.g. using the mechanical contact between the body of resistor 26 and hollow cylinder 25, and between heat-sensitive element 16 and load-bearing structure 13, and by connecting the latter to part 6 or 7 on unit 1, e.g.

by resting circular edge 14 of structure 13 on the annular groove on part 6 and consequently changing the shape of seal 15. Round the top outer part of hollow cylinder 25, provision may be made for a cylindrical, end-sealing bush for forming an air chamber in relation to the outer fluid passage and a certain amount of thermal insulation, so as to ensure that the maximum amount of heat generated by electrical resistor 26 is supplied to the wax on heat-sensitive element 16.

Claims

1. Thermostat unit for the cooling circuit on a motor vehicle engine, the said unit comprising a heat-sensitive element lapped by the fluid flowing through the said cooling circuit and controlling the position of valve means according the temperature of the said fluid, characterised by the fact that it comprises means designed to generate a quantity of heat acting directly on the said heat-sensitive element for influencing the latter's position control of the said valve means.

2. Unit according to Claim 1, characterised by the fact that the said means comprise an electrical resistor.

3. Unit according to Claim 2, characterised by the fact that the said resistor is shielded.

4. Unit according to Claim 2 or 3, characterised by the fact that the said resistor is housed in a hollow portion of the body on the said heat-sensitive element.

5. Unit according to one of the foregoing Claims, characterised by the fact that it comprises fluid sealing means round the said heat generating means for leading an electrical supply cable out of the said unit.

6. Unit according to one of the foregoing Claims, characterised by the fact that it comprises switch means for supplying electrical power to the said heat generating means.

7. Unit according to Claim 6, characterised by the fact that the said switch means are user-operated.

8. Unit according to Claim 7, characterised by the fact that the said switch means are operable in conjunction with a control for regulating heating inside the said vehicle.

9. Unit according to one of the foregoing Claims, characterised by the fact that it comprises means designed to regulate the said amount of generated heat.

10. Thermostat unit for the cooling circuit on a motor vehicle engine, as described and illustrated with reference to the attached drawings.