GB2104594A - Shape memory effect i.e. engine air intake temperature control - Google Patents

Abstract

A valve arrangement 14, 15 which controls unheated and heated air inlets 4 and 5 is operated in response to expansion and contraction of a memory metal helical spring 11 of a Ni, Ti or Cu, Zn, Al alloy. The spring 11 may increase or decrease in length in response to rise in air intake temperature such that air flows through the inlets 4 and/or 5 to provide the desired air temperature. The inlets 4 and 5 may be controlled by respective valves (45, 46), Fig. 5 (not shown), connected by a pivoted link (54). <IMAGE>

Description

SPECIFICATION Thermostatic contrivance for air temperature adjustment in an internal combustion engine The present invention concerns a thermostatic contrivance for the air temperature adjustment at the inlet of internal combustion engines, meant in particular for carburetors for motor-car engines.

It is known that present thermostatic devices for the air temperature regulation at the inlet of an engine, and in particular of a carburetor, are to be applied to a supporting body reached through a first and a second duct by air at a relatively low level directly sucked from the environment of the vehicle and respectively by air at higher level, heated by the heat deriving from the functioning of the engine.The above contrivances include an actuating element arranged near the first and the second duct and actuating one or more shutters apt to choke the through portions of the said ducts, in order to adjust through mixing the air temperature fed to the carburetor; a thermosensitive element applied towards said carburetor downstream from said ducts and upstream or downstream from the air strainer; and a transmission device connecting the actuating element and the thermosensitive element. The latter is formed by a bulb containing a high expansion fluid under variable thermal conditions, the latter fluid being in conditions to move through a resilient membrane a piston, which transmits the movement to the actuating element, through the above mentioned transmission contrivance, usually consisting in kinematic devices, small shafts or cables.

The above described thermostatic contrivances are evidencing some drawbacks. Especially the thermosensitive element has a rather complex structure and is costly, because it is necessary to warrant the seal between bulb and resilient membrane, to avoid any leak of the thermosensitive fluid, which usually consists in a tablet of thermoexpansible wax. In order to further warrant a sufficient excursion of the shutters, the bulb is to have notable dimensions, thus involving space problems, or the transmission system and the actuating element are to arrange for an appropriate amplification of the piston movements. Finally, if the resilient membrane is to undergo a severe stress, it can break.

Scope of the present invention is that of realizing a thermostatic device for the air temperature regulation at the inlet of an internal combustion engine not showing the above mentioned drawbacks, being in particular equipped with a simply structured thermosensitive element involving low building costs and fit forth direct control of the shutters.

The above scope is gained through the present invention because it refers to a thermostatic device for the air temperature adjustment at the inlet of an internal combustion engine, which can be applied to a body reached through a first and a second duct filled by relatively higher or lower air flowing through them respectively, said body having an outlet facing the inlet of said engine and causing an inflow of air from said ducts.The above contrivance includes a thermosensitive element at the temperature of said air flow skimming it and a shutter fit for chocking said first and second ducts, characterized by the fact that said thermosensitive element can expand under varying temperatures of said flow of air, taking the shape of different prearranged forms in order to cause the movement of said shutter which is mechanically connected to the said thermosensitive element formed by a metal alloy which can change, within a prearranged temperature range, its own crystalline structure in consequence of the relevant temperature, so that the atoms can move only along a prearranged crystalline trajectory, said element being able to take a plurality of forms arranged or fixed in advance, within a preestablished temperature range.

In order to better understand the present invention, we are now submitting to your attention purely as non limitative instances, a series of embodiments of the above invention, with reference to the enclosed drawings.

We have here: A figure 1 illustrating a longitudinal section of the mixing body on which a thermostatic contrivance made in accordance with the provisions of the present invention is mounted.

A figure 2 illustrating a variation of the thermostatic contrivance mentioned on figure 1.

A figure 3 illustrating a section following the line Ill-Ill of the contrivance appearing on figure 2.

A figure 4 illustrating a second variation of the contrivance appearing on figure 1. And A figure 5 illustrating a further variation of the device appearing on figure 1.

With reference to figure 1, a thermostatic contrivance appears under number 1 and is used for the adjustment of temperature of an air flow proceeding from an outlet 2 of a body 3 having an essentially known shape, e.g. that of a parallelepipedon, with a first inlet duct 4 for relatively cold air arriving from the outside environment of the vehicle on which body 3 is mounted, and a second inlet duct 5 for relatively warm air. Body 3 consists in two half-shells 6 assembled in facing position and finds itself upstream from the air strainer of the vehicle (non appearing on the picture), so that the air flowing out from the outlet 2 is lead into an engine or carburetor (non appearing on the picture) of the vehicle.

The thermostatic contrivance 1 includes a shutter 7 fit for choking the ducts 4 and 5, a control shaft 8 for the actuator 7, a supporting sleeve 9 (also serving as guiding element for the shaft 8), integral with body 3 and fixed to same in a whatsoever convenient way, a return spring 10 and a thermosensitive element 11 having the shape of a spring.

The shutter 7 rotates on a stud 12, through which it is hinged and made integral with body 3, and moves between a first position (shown) closing completely duct 4 and leaving open duct 5, and a second position closing completely duct 5 and leaving open duct 4. Shutter 7 consists in fact in a shaped washer 14 fit for closing duct 4 and hinged to pivot 12, equipped with a plug 15, apt to close duct 5 and essentially parallel to washer 14 and integral with same.

Two protrusions 1 6 inside the body 3 serve as limit switches for the washer 14 and are forming a seal with it. The latter is further equipped with an ear 18, so that the end of shaft 8 is connected with it through a gudgeon 12.

Shaft 8, essentially cylindrically shaped, can move in longitudinal direction inside the supporting sleeve 9 against the pressure of the return spring 1 0. The latter rests with its first end 21 on a protrusion 22 of the sleeve 9, being coaxial with the same, whilst the second end thereof 23 leans on the washer 24, which is essentially rectangular, obtained en bloc with the shaft 8 at the level of one of its ends 25 opposed to end 20 and protruding from sleeve 9 through an opening 26 having a rectangular shape and cut in longitudinal direction in the sleeve 9. The sleeve 9 bears further coaxially the thermosensitive element 11, the latter being substantially a helical spring.The thermosensitive elements rests with a first end 27 against a front surface 28 of the washer 24, whilst the second end 29 leans on a stopper or plug 30 screwed on a threaded end 31 of the sleeve 9.

The thermosensitive element 11 consists in a thermosensitive alloy known as "alloy with memory effect" e.g. a Ni-Ti alloy bearing the trade name of NITINOL or a Cu-Zn-Al alloy belonging to the brass family and commercially known as PROTEUS (registered trade brands). Such thermosensitive alloys, or alloys with memory effects, are substantially metal alloys which are able to change, within a pre-established temperature range, their crystalline structure in consequence of the temperature they undergo, so that the atoms of the metal components of the alloy move only along peculiar trajectories fixed in advance in the crystallographic field. In this way element 11 can assume selectively, within the said pre-established temperature range, a plurality of forms fixed in advance.Practically speaking, this effect, which is widely known, is caused by internal tensions induced by the passing from a martensitic crystallographic structure (i.e. acicular or needle-shaped or Widmanstätten) to an austenitic structure showing large polyhedric crystals. The phenomenon, inside said temperature range fixed in advance, is completely reversible viz. a body built with such alloys retakes always the same form at the same temperature, provided the deformations caused in the outermost fibres of the article by the shape change are not above or beyond a pre-established percentage value around 5% in the case of Cu-Zn-Al alloys.

The pre-established temperature range within which the phenomenon occurs depends upon the per cent rate in the alloy composition and is amply variable, because it corresponds to the temperature range between the temperature at the end of transformation (MF) of the martensitic transformation and the temperature of the end of transformation (AF) of the opposite transformation (i.e. from martensite to austenite).

The sensitive element 11 is therefore to be built from a thermosensitive alloy having such a composition that the temperature range within which the memory effect occurs appears to be the most suitable for the specific application case by case, i.e. within a temperature field near the environmental one, for instance between 20 and 400 C, the shape of element 11 being selected in such a way that deformations caused by temperature variation are such that a direct actuation of shutter 7 is possible.

Practically speaking element 11 has the shape of a helical spring and its fibres operate under torsion, causing an elongation or a shortening of the element 11 under air temperature variations in the air flowing out of mouth 2. It is important to emphasize that the properties of such alloys are such that an increase in temperature can cause indifferently an elongation or a shortening of the element 11. according to the alloy's composition and vice versa a decrease in temperature can cause an elongation or shortening of the same. In conclusion the behaviour of the element 11 depends on the composition of the alloys which compose it and on the deformations it underwent in the shaping phase, which are exactly reproduced in practice under temperature variations.

The functioning of the contrivance 1, in the case of figure 1, is therefore as follows: element 11, which is of the kind undergoing an elongation with temperature increase, overcomes in case of temperature increase in the air flow outflowing from the outlet 2 the resistance of the spring 10 and pushes the shaft 8 which rotates the shutter 7, so as to close partially the duct 5 and to open partially the duct 4 containing cold air. If temperature at the outlet 2 diminishes, element 11 shortens and shaft 8, under pressure from spring 10, puts shutter 7 in its initial position or in another position in which duct 4 is more choked than duct 5.In this way the air temperature at the outlet 2 can be kept at a constant level and be lead into the carburetor under temperature variations of the outside air arriving from outlet 4, mixing the latter with a variable quantity of hot air arriving from duct 5. The figures 2 and 4 show two variations of the contrivance appearing on figure 1, assembled on a body 3 similar to that on figure 1, where similar or identical elements appear under the same numbers. Variation on figure 2 is completely similar to the shape iilustrated on figure 1: the only difference consists in the absence of return spring 10. In this case washer 24 (figure 3) is firmly fixed to the end 27 of the thermosensitive element 11 through two tongues 32, which are U shaped. In this way the shaft 8 must compulsorily follow all the movements of the element 11 , which upon its elongation opens the duct 4 and closes the duct 5 and upon its shortening drags with it shaft 8, so that shutter 7 may rotate and close duct 4 and open duct 5. In the latter case washer 24 is not obtained en bloc from shaft 8 but is fixed to the end 25 through a gudgeon 33 duly riveted as appears on figure 3.

On figure 4 appears a variation which is almost similar to the previous ones. The difference consists here in the position of the return spring 10 and in the way of performing of element 11. In this case the washer 1 4 is equipped with a second ear 34 in a position opposed to that of ear 1 8 and equipped with a hole 35 for hooking the hook shaped end 36 of the return spring 10. One of the end hooks of same is fixed to an ear 38 integral with a wall 39 of the body 3. Element 11, built in such a way that its alloy causes an elongation of the element 11 in case of temperature decrease and vice versa a shortening in case of temperature increase, is assembled coaxially on the shaft 8 at the end 40 of a sleeve 41, inside which shaft 8 is moving and is integral with body 3.End 42 of the sleeve 41 rests onto the shoulder 42 of the sleeve 41 whilst end 29 leans onto the stopper 30 screwed onto a threaded end 43 of the shaft 8.

The functioning is as follows: the spring 10 operates on shutter 7 so that duct 5 remains completely closed and the duct 4 is completely open (Summer position). A decrease in air temperature causes an elongation of the element 11, which pushes stopper 30 so that shaft 8 slides in direction of the arrow and causes the rotation of the shutter 7 overcoming the action of spring 10 and thus opening hot air duct 5.

Should temperature rise too much, element 11 will shorten and thus enable shutter 7 to retake its original position or an intermediate position in which duct 5 is choked. In case of rupture of thermal spring 11, duct 5 shall remain completely closed, differently from what happens in previous instances (figure 1), and the advantage will be that fuel consumption will not increase.

Figure 5, finally, shows a further variation of the contrivance 1, assembled on a body 44 similar to the body 3, in which parts already described appear under same numbers. Body 44 has an outlet 2 and inlet ducts 4 and 5 closed by shutters 45 and 46 of the throttle type, pivoting on gudgeons 47 and 48 integral with body 44, formed by two half-shells 6 facing each other.

Shutter 45 is sealing protrusions 1 6 of the body 44 and is supplied with two ears facing each other 49 and 50 on which are pivoting a return spring 10 with two hooked ends 36 and 37 fixed respectively to the ear 49 and a screw 51 housed into a hole 52 of the body 44 and fixed in it by a nut 53, and two levers 54 and 55. Lever 54 is pivoting on the end of the ear 50 through a gudgeon 56 whilst at the opposite end it is pivoting on an ear 57 of the shutter 46. Lever 55 is pivoting on one end on the pivot 56 whilst at the opposite end it is hinged through a slot 58 on the end 59 of a curved bar 60, rigidly integral with body 44. Lever 55 evidences further a hole 61 drilled at intermediate level, into which is hinged an end 62 of a thermosensitive helical element 11 fixed with the opposite end 63 to an ear 64 en bloc with body 44.Levers 54 and 55 are hinged in such a way that shutter 45 rotates in order to open duct 4 and shutter 46 is compelled to rotate in order to close duct 5 and vice versa.

By temperature increase of the air in the outlet 2, element 11 shortens and activates lever 55 in direction of duct 5. The latter moves thanks to slot 58 and causes the rotation of the shutters 45, opening through levers 54 and 46 the cold air duct 4 against the pressure of spring 10 and closing duct 5. When temperature decreases, the thermosensitive spring 11 lengthens and enables spring 10 to recall shutter 45, thus closing duct 4.

The above description shows obviously the advantages of the present invention. It enables in particular to build up a thermostatic contrivance for the adjustment of the air temperature of the air feeding the engine. The structure is extremely simple and money sparing and the functioning is dependable thanks to the presence of a deformable thermosensitive element which is in conditions to play at the same time the rôle of a thermal sensor and that of an actuator controlling the shutters. In this way one avoids the drawbacks deriving from the use of bulbs containing expanding fluids and one obtains a contrivance which is very sturdy and in conditions to bear notable stresses and high excursions. Finally thermosensitive element appearing in this invention is quite more money sparing than those known up to now.

The above specification entails obviously the possibility of introducing variations and modifications into the contrivance described in the present specification without leaving the area of the invention. In particular, in a form of realization which is not illustrated here, the spring 10 and the sensitive element 11 are connected to the shutter 7 through hooked ends fixed to ears integral with same and similar to ears 34 (figure 4), and to ear 18.

The arrangement of spring 10 is identical to that appearing on figure 4, whilst element 11, which shortens by decreasing temperature, is directly connected with an end of the ear 1 8 and with the opposite end to a bar 60 integral with body 3.

Claims (14)

1. Thermostatic contrivance (1) for the adjustment of air temperature at the inlet of an internal combustion engine, applicable to a body (3) receiving through a first (5) and a second (4) duct, air at higher and lower temperature, said body (3) having an outlet (2) looking towards an inlet of said engine, receiving an air flow from such ducts (4, 5), said contrivance (1) comprising a thermosensitive element (11) feeling the temperature of said air flow which is licking it up and at least one shutter (7, 45, 46) able to choke said first (5) and second (4) ducts, characterized by the fact that said thermosensitive element (11) can deform itself under varying temperatures of said air flow, assuming a plurality of forms so as to cause a displacement of said shutter (7, 45, 46) to which said thermosensitive element (11) is mechanically connected, it being formed by a metal alloy able to change within a preestablished temperature range its crystalline structure so that its atoms can move only along pre-fixed crystallographic trajectories, thus enabling such element (11) to assume, within said pre-established temperature range, said plurality of pre-fixed shapes.

2. Thermostatic contrivance (1) according to claim 1, characterized by the fact that said thermosensitive element (11) deforms itself in a completely reversible way assuming substantially, at each temperature level of said range fixed in advance, always the same shape, because the maximum deformation of the fibres of said element (11) is never exceeding a per cent value, fixed in advance, of the length of same.

3. Thermostatic contrivance (1) according to claims 1 or 2, characterized by the fact that said metal alloy is substantially a brass one with prefixed percentages of copper, zinc and aluminium, said pre-fixed temperatures being proportional to said pre-fixed percentages.

4. Thermostatic contrivance (1) according to one of the previous claims, characterized by the fact that said thermosensitive element (11) has the shape of a helical spring, the fibres of said element being deformed by torsion.

5. Thermostatic contrivance (1) according to one of the previous claims, characterized by the fact that said thermosensitive element (11) is arranged at the level of said outlet (2) of said body (3) facing said inlet of the engine.

6. Thermostatic contrivance (1) according to claim 4, characterized by the fact that said thermosensitive element (1 1) is subject to elongation when temperature of said air flow increases and to shortening when such temperature decreases.

7. Thermostatic contrivance (1) according to claim 4, characterized by the fact that said thermosensitive element (11) is shortening when temperature of said air flow increases and is growing longer when such temperature decreases

8. Thermostatic contrivance (1) according to one of the previous claims, characterized by the fact that said thermosensitive element (11) is arranged coaxially with a shaft (8) hinged on said shutter (7) said shaft (8) being movable under the actuation of said thermosensitive element (11) in longitudinal direction, because of its sliding inside a sleeve (9,41) integral with said body.

9. Thermostatic element (1) according to the claim 8, characterized by the fact that on said shaft (8) there is a return spring (10), said spring (10) and said thermosensitive element (11) pushing in opposed directions on said shaft (8) and acting both on a washer (24) integral with said shaft (8) and placed between said spring (10) and said thermosensitive element (11).

10. Thermostatic contrivance (1) according to claim 8, characterized by the fact that said thermosensitive element (11) is integral with said shaft (8), said washer (24) being connected at an end (27) of said thermosensitive element, bearing the number (11).

11. Thermostatic contrivance (1) according to claims from 1 to 7, characterized by the fact that said thermosensitive element (11) is constrained with a lever (55) hinged with said body (3) and acting upon said shutter (45, 46), said return spring (10) being directly connected with said shutter (45).

12. Thermostatic contrivance (1) according to claims from 1 to 7, characterized by the fact that said thermosensitive element (11) is directly connected under constraint between said shutter (45) and said body (3).

13. Thermostatic contrivance (1) according to one of the previous claims, characterized by the fact that said return spring (10) is arranged in a way compelling said shutter (7) to close completely said first duct (5) while opening completely said second duct (4).

14. Thermostatic element (1) for the adjustment of inflowing air temperature into an internal combustion engine substantially as described above and illustrated on one of the enclosed drawings.