GB2041082A - Device for regulating the temperature of air admitted to the suction manifold of an internal combustion engine - Google Patents

Abstract

A pipe 14, 15 transmits the reduced pressure in the suction manifold 2 of an engine 3, downstream of the throttle 11, to a pneumatic serve-motor 10 which actuates a flap 7 regulating the respective flows of unheated air and of heated air admitted to the air filter 1. The pipe 14, 15 is equipped with a check valve 16 and an air bleed valve 17, the valve members 28, 29 of which are actuated by a single wax thermostat 18. The thermostat piston 22 engages a lever 30 which acts to unseat the valve members 28 and 29 at respective intake air temperatures. <IMAGE>

Description

SPECIFICATION Device for regulating the temperature of air admitted to the suction manifold of an internal combustion engine This invention relates to devices for regulating the temperature of air admitted to the suction manifold of an internal combustion engine, of the type comprising, upstream of an air filter fitted to the manifold, a cold air intake and a hot air intake, the respective cross-sections of which are regulated by a member such as a flap actuated by a pneumatic servo-motor sensitive to the reduced pressure at a location in said manifold, downstream of a movable restriction member, connected to the servo-motor by a connecting pipe in which there are disposed in succession, in the direction from the servo-motor to the solution manifold, a non-return valve and an air bleed valve actuated by means sensitive to the temperature of the air inside the filter, the non-return valve being so adapted as either to prevent the air from escaping from the manifold to the servomotor while permitting it to flow in the other direction, or to be put out of action, according to whether the said temperature is lower or higher than a first limit, while the air bleed valve is so adapted as to bring the connecting pipe into communication with the interior of the filter when the said temperature is higher than a second limit, which is higher than the first limit.

It is known that the temperature of the air admitted to the suction manifold of an engine should vary as little as possibie on each side of an optimum value in order that the exhaust gases of the engine may comply with antipollution standards. When an engine is started up cold, the movable restriction member of "throttle" which is disposed in the suction manifold and which is actuated by the accelerator linkage is only slightly or moder ately open. The reduced pressure which becomes established downstream of this restriction member is therefore relatively great. It is immediately transmitted to the pneumatic servo-motor, since the air bleed valve is closed and the non-return valve permits some of the air contained in the servo-motor and in the connecting pipe to escape towards the suction manifold.Under these conditions, the pneumatic servo-motor opens wide the hot air intake and closes the cold air intake, which enables the air which enters the filter before penetrating into the suction manifold to be brought rapidly to the required temperature.

At this moment, the non-return valve is put out of action and the air bleed valve opens.

The latter therefore permits air to enter the connecting pipe, which increases the pressure in this pipe and in the servo-motor. The flap partially opens the cold air intake, while partially closing the hot air intake, which causes a regulation of the temperature of the air in the filter. Thus the temperature of the air admitted to the suction manifold is establishes at a value as close as possible to the optimum value.

When the engine is working at full load, that is to say when the restriction member is fully open, two cases occur. In the first case the temperature of the air in the filter is sufficiently high for disturbing phenomena of icing not to be able to occur inside the venturi where the fuel is introduced into the suction manifold. The non-return valve is then put out of action by the temperature-sensitive means and the air bleed valve opens in such a manner that the increase in pressure thus caused in the servo-motor places the flap in such a position that the mixture of hot air and cold air has a temperature close to the desired value. Bearing in mind the variations in the density of the air depending on the temperature, the relationship between the weight of air and fuel introduced into the engine is thus optimum.In the second case, the temperature of the air in the filter is low- enough to fear icing phenomena and above ail to produce toxic exhaust gases in too great an amount.

The non-return valve then intervenes to maintain the reduced pressure inside the servomotor and the hot air intake is therefore kept open by the servo-motor.

A regulating device of the kind defined above is described, for example, in German Patent Application No. 2,147,027. In this case, the non-return valve and the air bleed valve comprise means sensitive to the temperature which are independent and which each consist of a bimetallic strip. The bimetallic strip of the air bleed valve is placed inside a casing which is itself housed inside the air filter. In order that this bimetallic strip may record the temperature inside the filter, the casing is provided with a hole through which a current of air flows permanently (when the engine is running) towards the suction manifold, short-circuiting the carburettor. The bimetallic strip of the non-return valve may be exposed to temperatures at various points and, when it is sensitive to the temperature of the air inside the filter, its arrangement is not described.

The object of the invention is to simplfy the construction and adjustment of regulating devices of the type defined above.

In order to achieve this object, the regulating device according to the invention is char- acterised in that the temperature-sensitive means of the non-return and air bleed valve consist of a single thermostatic element comprising a cup which is filled with a waxy material and a tubular guide out of which there extends a movable piston; in that a casing, housed inside the air filter and provided with an orifice for communication with the suction manifold, with a seating for the non-return valve and with a seating for the air bleed valve, is traversed in a sealed manner by the guide of the thermostatic element in such a manner that the cup of the thermostatic element is situated inside the air filter and that its tubular guide opens inside the casing; and in that the piston of the thermostatic element is mechanically connected to the obturating members of the non-return valve and air bleed valve respectively.

The single thermostatic element according to the invention is less expensive than the assembly of the two bimetallic strips which it replaces and its adjustment can be effected easily by pushing in locally, to a greater or lesser extent, the cup containing the waxy material. Moreover, this cup is placed directly inside the filter and it is therefore no longer necessary, to expose it to the temperature of the mixture of cold air and hot air, to create a permanent flow of air, which is capable of disturbing the fuel feed in certain conditions of load of the engine since a flow shortcircuits the carburettor of the engine.

According to one advantageous embodiment of the invention, a lever, mounted in a pin orthogonal to the direction of displacement of said piston, acts by thrust of one of its ends on the obturating member of the nonreturn valve and by its other end on the obturating member of the air bleed valve and the piston of the thermostatic element acts by thrust, against the action of a spring, on an intermediate portion of the lever, the two obturating members being guided in such a manner as to be displaced parallel to the direction of displacement of the piston. This form of embodiment is distinguished by the simplicity of the mechanical connection thus established between the piston of the thermostatic element and the obturating members of the non-return valve and air bleed valve respectively.

The obturating member of the non-return valve may be urged towards its closed position by the action of the pressure of the air.

The closing pressure is associated with the value of the closing section and this to the mass of the obturating member or flap. This is therefore given a very small mass so as to make its effect negligible. The obturating member of the non-return valve preferably consists of a needle orientated in such a manner that its conical head is directed downwards and that its tail comprises a shoulder grasped from below by the corresponding end of the lever. The end of the lever co-operating with the needle is preferably folded downwards in such a manner as to limit, by abutment against the casing, the angular travel of the lever in the direction of cooling the thermostatic element.

With a view to facilitating assembly, the casing may consist of a bottom and a cover each comprising the complementary elements of bearings intended for the pin of the lever, so that this pin is held by the assembly of the bottom and the cover. Preferably, the bottom of the casing comprises the orifice for communication with the suction manifold and the seating of the non-return valve, while the cover of the casing comprises the seating of the air bleed valve and a hole for the passage of the guide of the thermostatic element. With a view to further facilitating the assembly, the bearing elements carried by the bottom of the casing may be adapted to retain resiliently the pin of the lever, in the absence of the cover, which enables a sub-assembly to be prefabricated with the bottom, the lever and the obturating members of the non-return and air bleed valves.

The invention will now be described in more detail with reference to the accompany- ing drawings, which illustrate one preferred embodiment, and which: Figure 1 illustrates, in elevation, with parts in section, a regulating device according to the invention as well as the upper part of the engine in which the device is mounted.

Figure 2 shows in vertical section, on a larger scale, the essential elements of the device of Fig. 1.

Figure 3 illustrates separately, the same elements as Fig. 2.

Figure 4 illustrates, on an even larger scale, the thermostatic element which forms part of the device of Fig. 1.

As can be seen from Fig. 1, the regulating device in question comprises, upstream of an air filter 1 fitted to the suction manifold 2 of an internal combustion engine 3 and equipped with a removable annular filtering cartridge 4, a cold air inlet 5 and a hot air inlet 6, the respective sections of which are regulated by a flap 7, pivoting on a pin 8.

The cold air intake 5 consists of a conduit leading into the atmosphere either directly or through a compartment surrounding the engine 3. The hot air intake 6 consists of a pipeline passing close to the exhaust manifold 9 of the engine 3, this manifold 9 constituting a source of heat once the engine 3 has been started.

The flap 7 is actuated by a pneumatic servo-motor 10 sensitive to the reduced pressure taken off in the suction manifold 2, downstream of a restriction member or throttle 11 which is actuated by the usual linkage of an accelerator (not shown). In general, this servo-motor 10 comprises a chamber limited by a diaphragm 56 on which this reduced pressure acts, against the action of a spring 57.Between the filter 1 and the restriction member 11, the manifold 2 comprises a ventur 1 2 at the neck of which there ends a fuel (petrol) feed system 1 3. The above-mentioned reduced pressure is taken off by a connecting pipe which is formed from two successive sections 14, 1 5 and in which there are dis posed in succession, from the servo-motor 10 to the suction manifold 2, a non-return valve 1 6 and an air bleed valve 1 7 actuated by means sensitive to the temperature of the air inside the filter 1.The non-return valve 1 6 is adapted in such a manner as not to prevent the air from flowing except in the direction from the manifold 2 to the servo-motor 10, when the temperature of the air inside the filter 1 is lower than a first limit but to permit the air to flow in both directions when this temperature is higher than the limit in question. As for the air bleed valve 17, it is adapted in such a manner as to bring the connecting pipe 14, 1 5 into communication with the interior of the filter 1 once the temperature of the air inside the filter is higher than a second limit which is itself higher than the first limit, but to interrupt this communication in the opposite case.

This being so, according to the invention, the means sensitive to the temperature which are associated with the non-return valve 1 6 and the air bleed valve 1 7 consist of a single thermostatic element 18, of known type, comprising a cup 10 filled with an expansible waxy material 20 and a tubular guide 21 out of which there extends a movable piston 22 (Figs. 2 to 4).A casing 23, housed inside the air filter 1 and equipped with an orifice 24 for communication with the suction manifold 2, with a seating 25 for the non-return valve 1 6 and a seating 26 for the air bleed valve 17, is traversed in a sealed manner by the tubular guide 21 of the thermostatic element 18 in such a manner that the cup 1 9 of the latter is situated inside the air filter 1 and that its tubular guide 21 opens inside the casing 23.

As can be seen from Figs. 2 and 3, the guide 21 may be threaded and fit a hole 27 formed with an appropriate thread in the casing 23; in a modification, the guide 21 may fit into the hole 27, which is then smooth, in the manner of a press-stud, on condition that the casing 23 is made of sufficiently flexible material, at least in the vicinity of the hole 27.

Finally, the piston 22 of the thermostatic element 18 is mechanically connected to the obturating members 28 and 29 respectively of the non-return valve 1 6 and air bleed valve 17.

In order to ensure such a mechanical connection, a lever 30 mounted on a pin 32 orthogonal to the direction X of displacement of the piston 22, acts by thrust by one of its ends on the obturating member 28 of the non-return valve 1 6 and by its other end on the obturating member 29 of the air bleed valve 1 7 and the piston 22 of the thermostatic element 1 8 acts by thrust, against the action of a helical spring 32, on an intermediate portion of the lever 30, this intermediate portion being situated between the pin 31 and the obturating member 29 and offering a centring stud 58 for the spring 32.

As can be seen from Figs. 2 and 3, the obturating member 28 of the non return valve 16 consists of a needle of small mass, orien such un such a manner that (when the filter 1 is placed on the manifold 2) its conical head 33 is directed downwards and its tail comprises a shoulder (or collar) 34 grasped from below by the corresponding end of the lever 30. For this purpose, the lever 30 may be provided with a lateral notch 35 for the introduction of the rod 36 of the obturating member or needle 28. The end 37 of the lever 30 which co-operates with the needle 28 is bent downwards in such a manner as to limit, by abutment against the casing 23, the angular travel of the lever 30 in the direction of cooling the thermostatic element 1 8 (clockwise direction according to Figs. 2 and 3).The obturating member 29 of the air bleed valve 1 7 likewise consists of a needle which comprises, at the side opposite to its conical head 38, a centring stud 39 for a helical compression spring 40. By bearing against the casing 23, this spring 40 tends to close the obturating member or needle 29, the closing movement of which is limited by contact of a shoulder (or collar) with the corresponding forked end of the lever 30.

The casing 23 consists of a bottom 42 and a cover 43, each comprising the complementary elements 44, 45 of bearings adapted for the pin 31 of the lever 30. The bottom 42 and the cover 43 are of plastics material, the cover 43 being equipped with hooking feet 46 capable of being engaged resiliently and retained in seatings 47 provided for this purpose in the bottom 42. In the position of assembly (Fig. 2), the bottom 42 and the cover 43 grip between them a peripheral seal 55. The bearing elements 44 carried by the bottom 42 of the casing 23 are adapted to retain resiliently the pin 31 of the lever 30, this pin 31 being made integral with the lever 30.As shown diagrammatically in Fig. 3, it is sufficient for this purpose to give the bearing elements 44 the form of an arc of a circle of more than 180 and to make the bottom 42 of a plastics material of a sufficiently resilient nature.

The bottom 42 of the casing 23 is moulded with the communication orifice 24, the valve seat 25, the bearing elements 44, the seatings 47, the centring stud 48 for the helical spring 32 and an annular centring stud 47, surrounding the orifice 24, for the helical spring 40. At the level of the orifice 24 anu of the seat 25, the bottom 42 also has tubular connections 50 and 51 permitting the fitting of flexible pipes which constitute the pipe sections 14, 15. The cover 43 is moulded with the seating 26, the hole 27 and the hooking feet 46.

As Fig. 4 illustrates diagrammatically, the thermostatic element 1 8 may advantageously be constituted in accordance with the indica tions in the French Patent 78 07ss32 of the 15th March 1 978. Such a thermostatic element comprises a flat diaphragm 52 which is gripped at its periphery between the free edge 53 of the cup 19 and one of the ends of the tubular guide 21, and an anti-extrusion washer 54 interposed between the piston 22 and the diaphragm 52. Moreover, the useful travel of the piston 22 is at most equal to 1.1 times the diameter of the piston 22 and the guide 21 is internally cylindrical over the major part of its height.

Thus a regulating device is obtained, the mode of assembly and the operation of which will be described below.

First the needle 28 is engaged in the notch 35 of the lever 30 and the needle 29 in the forked end of this lever 30. Then the pin 31 is engaged by "ciipping" in the bearing elements 44 carried by the bottom of the casing 42, placing the spring 32 between the centring studs 48 and 58 and the spring 40 between the centring studs 39 and 49. It is then sufficient to place the cover 43 on the bottom 42, interposing the seal 55 and introducing the hooking feet 46 in the seatings 47. One then has the assembly represented in Fig. 2 in which the lever 30 is held by the spring 32 either against the piston 22 of the thermostatic element 1 8 or against the bottom 42 by its curved end 37 according to whether the ambient temperature is higher or lower.The needle 28 is held against its seat 25 by its own weight and the needle 29 is held against its seat 26 by the spring 40.

Starting from this position, the lever 30 has to travel through a larger angle in counterclockwise direction (according to Fig. 1) to move the needle 29 away from its seat 26 than to move the needle 28 away from its seat 25. To adjust the length of exit of the piston 22, it is sufficient to form a more or less deep impression in the cup 19. The fitting of the assembly thus obtained to the filter 1 does not offer any difficulty.

The operation of the device according to the invention is similar to that of the known device which was described above. In fact, when the engine 3 is started cold, the relatively high reduced pressure which becomes established downstream of the restriction member 11 (Fig. 1) then slightly open, is transmitted to the pneumatic servo-motor 10, since the needle 29 of the air bleed valve 1 7 is closed by the spring 40 and the needle 28 of the non-return valve 1 6 rises under the action of the current of air drawn in through the connecting pipe 14, 1 5 from the suction manifold 2. The diaphragm 56 of the servomotor 10 therefore opens with a large intake of hot air 6, the temperature of which rises with that of the exhaust manifold 9, and at the same time closes the cold air intake 5.

The air which enters the filter 1 and which sweeps the cup 1 9 of the thermostatic element 1 8 therefore reaches a sufficient temperature for the piston 22, turning the lever 30, to cause the opening of the non-return valve 1 6, then the air bleed valve 1 7. By bringing the interior of the filter 1 into communication with the interior of the casing 23, this valve 1 7 allows filtered air to enter the pipe 14, 1 5 and so to reduce the reduced pressure in the servo-motor 1 0. The reduction in the reduced pressure in the servo motor 1 0 varies depending on the opening travel of the needle 29 of the air bleed valve 17.Since the spring 57 of the servo-motor 10 {:) is calculated according to the law of variation in the reduced pressure depending on this opening travel, the flap 7 does not work on the open or shut principle but occupies an intermediate position between the position "all hot air" and "all cold air".

This flap 7 therefore partially closes the hot air intake 6 and the temperature of the air admitted into the manifold 2 is established at a value close to the optimum value.

When the restriction member 11 is wide open, the following two conditions may occur.

If the temperature of the air in the filter 1 is sufficiently high for there to be no risk of icing phenomena occurring near the neck of the venturi 1 2 and the level of pollution is suitable, the thermostatic element 1 8 is then sufficiently expanded for the lever 30 to lift the needle 28 of the non-return valve 1 6 which therefore allows the reduced pressure to drop in the servo-motor 10; the flap 7 partially closes the hot air intake which has the effect of improving the filling of the cylinders of the engine. On the other hand, if the temperature of the air in the filter 1 is sufficiently low for there to be fear of icing phenomena and pollution, the non-return valve 1 6 remains in action, maintaining the reduced pressure in the servo-motor 10; the hot air intake 6 therefore remains open through the flap 7.

Claims (8)

1. A device for regulating the temperature of air admitted to the suction manifold of an internal combustion engine comprising, upstream of an air filter fitted to the manifold, a cold air intake and a hot air intake, the respective cross-sections of which are regulated by a member actuated by a pneumatic servo-motor sensitive to the reduced pressure at a location in said manifold, downstream of a movable restriction member, connected to the servo-motor by a connecting pipe in which there are disposed in succession, in the direction from the servo-motor to the suction manifold, a non-return valve and an air bleed valve actuated by means sensitive to the temperature of the air inside the filter, the non-return valve being so adapted as either to prevent the air from flowing from the manifold te the servo-motor while allowing it to flow in the other direction, or to be put out of action, according to whether the said temperature is below or above a first limit, while the air bleed valve is so adapted as to bring the connecting pipe into communication with the interior of the filter when the said temperature is higher than a second limit, which is higher than the first limit, characterised in that the temperature-sensitive means of the non-return and air bleed valves consist of a single thermostatic element comprising a cup which is filled with an expansible waxy material and a tubular guide out of which there extends a movable piston; in that a casing, housed inside the air filter and provided with an orifice for communication with the suction manifold, with a seating for the non-return valve and a seating for the air bleed valve, is traversed in a sealed manner by the guide of the thermostatic element in such a manner that the cup of the thermostatic element is situated inside the air filter and that its tubular guide opens inside the casing; and in that the piston of the thermostatic element is mechanically connected to the respective obturating members of the non-return and air bleed valves.

2. A regulating device as claimed in Claim 1, characterised in that a lever, mounted on a pin orthogonal to the direction of displacement of said piston, is arranged to engage, at one of its ends, the obturating member of the non-return valve and, at its other end, the obturating member of the air bleed valve and in that the piston of the thermostatic element acts, against the action of a spring, on an intermediate portion of the lever, the two obturating members being guided in such a manner as to be displaced parallel to the direction of displacement of the piston.

3. A regulating device as claimed in Claim 1, characterised in that the obturating member of the non-return valve consists of a needle orientated in such a manner that its conical head is directed downwards and that its tail comprises a shoulder gripped from below by the corresponding end of the lever.

4. A regulating device as claimed in Claim 3, characterised in that the end of the lever co-operating with the needle is bent downwards in such a manner as to limit, by abutment against the casing, the angular travel of the lever in the direction of cooling of the thermostatic element.

5. A regulating device as claimed in any one of the Claims 1 to 4, characterised in that the casing consists of a base and a cover each comprising complementary elements of bearings to receive the pin of the lever, so that this pin is held by the assembly of the bottom and of the cover.

6. A regulating device as claimed in Claim 5, characterised in that the bottom of the casing comprises the orifice for communication with the suction manifold and the seating of the non-return valve while the cover of the casing comprises the seating of the air bleed valve and a hole through which passes the guide of the thermostatic element.

7. A regulating device as claimed in any one of the Claims 5 and 6, characterised in that the bearing elements carried by the bottom of the casing are adapted to retain the pin of the lever resiliently in the absence of the cover.

8. A device for regulating the temperature of air admitted to the suction manifold of an internal combustion engine, constructed, arranged and adapted to operate substantially as described with reference to, and as shown in, the accompanying drawings.