GB2084250A - Shape memory effect controlled-air intake for internal combustion engines - Google Patents

Abstract

For controlling the temperature of air admitted to an internal combustion engine, the apparatus including flap 6 which controls the respective flows of air from ambient air inlet 2 and warm air inlet 3 both leading into air inlet duct 1 which may communicate with a carburetter of the engine via air cleaner filter 5. Flap 6 is controlled by the change of shape of shape memory effect (SME) element 11 which extends when a predetermined temperature is reached to close warm air inlet 3. Throttle override device 25 may be provided to hold warm air inlet 3 closed at a high throttle opening even where the predetermined temperature has not been reached. To prevent icing occurring where the ambient air temperature is at or below 0 DEG C and throttle override device 25 would otherwise become effective second SME element 29 contracts at 0 DEG C or below to render the throttle override device ineffective. Pneumatically actuated valve also referred to <IMAGE>

Description

SPECIFICATION Air intake for internal combustion engines The invention relates to air intakes for internal combustion engines and the like.

At present air intakes, normally incorporating air filters, are provided with two inlets one for receiving air at ambient temperature and another for receiving warm air which is usually heated by being drawn past the exhaust manifold of the engine. It is important for good performance of the engine to maintain air intake to the engine at an optimum working temperature and to reach that temperature as quickly as possible at start-up.

Thus, conventionally a pivotable flap is provided to divert either ambient air, warm air or a selected mixture thereof, according to the temperature prevailing, from the two inlets into the air filter.

The pivotable flap is controlled by a temperature responsive actuator which conventionally comprises either a wax thermostat or a vacuumresponsive device influenced by a bi-metal strip.

It is an object of the invention to provide an improved air intake apparatus.

According to the invention, an engine air inlet apparatus includes inlets for ambient air and warm air, regulator means for at least one of said inlets and a temperature responsive actuator comprising a shape memory effect material (as hereinafter defined) arranged to operate said regulator means.

A shape memory effect (hereinafter referred to by the abbreviation SME) material, usually an alloy, exhibits a reversible and significant shape change associated with metallurgical transformation when subjected to a temperature change. By careful selection of the constituents of the material and its design, a component made of SME material can be arranged to change its shape at least in a major part at a particular temperature threshold or within a specified and often relatively narrow range of temperature.

The engine air inlet apparatus may include an override to close off the warm air inlet whenever an engine throttle is opened beyond a predetermined high setting.

When the override is provided, there may be a second SME actuator designed to change its shape at a temperature equal to or lower than a first predetermined temperature, said firstmentioned actuator being designed to change its shape at a temperature equal to or in excess of a second predetermined temperature substantially higher than said first predetermined temperature, said second actuator being arranged to render said override ineffective at an air temperature to which it is responsive equal to or lower than said first predetermined temperature and said firstmentioned actuator being arranged to operate said regulator means to close off the warm air inlet when the air temperature to which it is responsive is equal to or in excess of said second predetermined temperature.

An air intake apparatus according to the invention will now be described, by way of example, with reference to the accompanying diagrammatic drawings. in which: Figure 1 shows a sectional view of the apparatus; Figures 2 and 3 show two positions of a modification of part of the apparatus of Figure 1; Figure 4 is a diayrammatic perspective view of an air cleaner incorporating another embodiment of the apparatus in accordance with the invention, and Figures 5 to 8 are diayrams showing four different sets of engine operational conditions applied to yet another embodiment of the apparatus in accordance with the invention.

Referring to Figure 1 a first embodiment of the apparatus comprises an air cleaner housing 1 having two inlets 2 and 3 respectively for ambient and warm air; an outlet 4 leading to the carburetter air inlet of an internal combustion engine and an air filter 5 between the inlets 2 and 3 and the outlet 4. Warm air is normally and conveniently provided by placing the inlet 2 close to an exhaust manifold of the engine. A regulator or flap 6, pivotably connected at 7 to the housing 1, is shown in a position to which it is biased by a spring (not shown) in which it closes the ambient air inlet 2. The flap has a lever 8 firmly attached thereto and pivotally connected to a rod 9. The rod 9 is supported by the apparatus and extends along the apparatus through an SME coil 11 which is in the shape of a helical spring.The coil 11 is positioned between a circlip 1 2 fixed on the rod 9 and a face of the air outlet 4 leading from the air cleaner housing to the air inlet to the carburetter of the engine. Although the coil 11 is positioned on the clean downstream side of the air filter 5, it could be positioned alternatively on the upstream side of the air filter 5. A helical metal spring 13 acts on the circlip 12 in opposition to the SME coil 1 A lever 14 pivoted at 1 5 is positioned to engage (as described later) a remote end of the rod 9 and is mechanically linked to a throttle operating mechanism indicated diagrammatically at 1 6, which operates a butterfly valve 1 7 of the carburetter.

In use, the flap 6 is in the position shown when the engine is started from cold. Rapid heating of the manifold causes air entering the inlet 3 to be warmed very shortly after the engine is started.

The temperature of this warm air continues to rise and at a predetermined value the SME coil 11 begins to expand and acting against the circlip 1 2 in opposition to the spring 1 3 moves the rod 9 to the left. The flap 6 is thereby pivoted away from the position shown in full lines in Figure 1 to allow ambient air to enter via the inlet 2 to be supplied to the carburetter.

At optimum working temperature, the flap 6 is normally in a position at which the inlet 3 is fully closed. However. during intermediate periods of warm-up or in very cold ambient conditions, the flap 6 is in an intermediate position so that the engine is supplied with a mixture of warm and ambient air.

Generally. and irrespective of the temperature of the air, at maximum or near maximum throttle settings the engine is preferably supplied only with ambient air. The throttle linkage is therefore arranged, at say 75% throttle setting or above, to pivot the lever 1 4 to the position indicated in chain lines to urge the rod 9 to the left or to keep the rod 9 in its extreme position and so close or maintain closed the inlet 3.

The SME coil 11 is designed not to expand or to expand very little at low temperatures. At the predetermined threshold temperature, rapid and significant expansion of the coil 11 occurs to operate the flap 6. Such expansion is normally in a fashion to fully operate the flap 6 to close the inlet 3 but may be arranged to operate in gradual or stepped changes. If the temperature later drops to or below the threshold value, the SME coil 11 contracts rapidly towards its original shape so as to operate the flap 6 and allow warm air to be again supplied via the inlet 3 to the engine.

The SME coil 11 is sensitive at all times to the temperature of air supplied, via the air filter 5, to the engine.

However, the coil 11 is aiso influenced by the temperature of the apparatus in the region of the outlet 4. During normal operation of the engine, the apparatus being closely adjacent to the engine tends te be at a temperature above ambient temperature. However, at start-up from cold, the apparatus is cooler. being at ambient temperature, so that the coil 11 being closeiy associated therewith tends to respond more slowly to rises in air temperature. This causes or tends to cause the temperature of air being supplied to the engine to rise initially somewhat above the optimum working temperature in practice at start-up.

Further, there is often an inherent time lag in the temperature response of the coil 11 itself (or such a time-lag is designed into the operating performance of coil 11 by thermal lagging for example) to ensure start-up air temperature oversnoot. The over-shoot is an important advantage providec by the described apparatus because it is preferable to operate an engine initially, at least for a short time period, with air at a temperature above an optimum working temperature. This feature rr.eans that damaging deposits often formed within the engine when cold are or tend to be removed more rapidly from the engine.

Further. in many engines, a water jacket connected to the engine cooling sysrem is provided to ensure that the air-fuel mixture entering the cylinders from the carburetter is heated to some extent. At start-up and before coolant in the water jacket has heated up to its working temperature. it is preferab!e to provide air which is warmer than otherwise to compensate for initial low coolant temperature. Thus the air temperature over-shoot provided by the described apparatus inherently provides this desirable compensation until the coolant temperature reaches its working vaiue.

One specific modification to provide air temperature overshoot is shown in Figures 2 and 3. The SME coil 11 is provided with an enveloping cap 1 8, the case of the cap 18 replacing the circlip 12. The cap 18 can be formed of material which is at least to some extent thermally insulating. its purpose being to reduce contact between the coil 11 and the air entering the apparatus for supply to the engine. In Figure 2, the coil 11 and the cap 18 are shown in their positions at low temperature and in Figure 3 in their positions at temperatures above the threshold temperature.The coil 1 6 responds more slowly, than in the configuration shown in Figure 1, to increase in temperature but has substantially the same response to reductions in temperature. This ensures an air temperature overshoot occurs at engine start-up from cold, the advantage of which has been discussed hereinbefore.

In the foregoing embodiment shown in Figures 1-3, the SME coil 11 is designed to expand at a predetermined operating temperature, say 300C, for example. When the ambient air temperature falls below 300 C, the flap 6 pivots from the position shown in chain lines 6 in which the warm air inlet 3 is closed into or towards the position in which the ambient air inlet 2 is closed.

Thus in cold climates if the ambient air temperature should fall to or below 0 C, icing of the flap 6 and its pivot 7 is prevented by the opening of the warm air inlet 3. However, when say 75An0 of throttle setting occurs, the SME coil 11 is overridden by the lever 14 and so it is possible for icing to occur while the engine is running at over 75% throttle settings over long periods because the flap 6, under such conditions will have closed the warm air inlet 3. With a view to avoiding this, a second SME coil which becomes operative at a low temperature say OOC to override the effect of the pivoting of the lever 14 at throttle settings of say 75% is provided.

Such an arrangement is shown in Figure 4 which is a perspective view of an air cleaner in a second embodiment having the original SME coil 11 which expands at say 300C and above and a second SME coil or spring which becomes operative at say OOC and below. In Figure 4, the air cleaner housing is similar to that shown in Figure 1 except that the housing 1 is more compact by wrapping the air inlet spirally around the housing instead of the air inlet extending outwardly from the housing, as in conventionai air cleaners.

In Figure 4, the ambient air inlet is shown at 2; the warm air inlet is shown at 3 and the flap controlling the flow of ambient or warm air is shown at 6. The air filter is indicated at 5 and the clean airflows to the carburetter through an outlet (not shown) communicating with the centre 20 of the housing within the air filter 5. In this embodiment, the SME coil 1 , the circlip 12 and the spring 13 are positioned in the air inlet path upstream of the air filter 5 and act between a pair of spaced fixed abutments 21 on a lever 22 carried on a rotatable shaft 23, equivalent to the rod 9 in Figure 1, which carries the flap 6.As in Figure 1, at a temperature below the temperature, e.g. 303C. at which the coil 11 is responsive. the flap 6 is open with respect to the warm air iniet 3 and closed to the ambient air inlet 2; but when the temperature at which it is responsive is attained, the flap 6 is moved by the lever 20 to a position in which the ambient air inlet 2 is open and the warm air inlet 3 is closed or is partly-closed. As in the embodiment of Figure 1, there is an override from the throttle control which becomes effective when the throttle control is (for example) 75% or more open.This control is effected by a lever 24 which is equivalent to the lever 1 4 in Figure 1 and is pivoted by the throttle control mechanism shown diagrammatically at 25 which at 75% throttle opening pushes the lever 24 to push a bar 26 through a second SME coil or spring 29 to push a rod 27 which causes a lever 28 to pivot to turn the shaft 23 in the direction to close the warm air inlet 3 by pivoting the flap 6 to its closed position regardless of the state of the SME coil 11.

The second SME coil 29 is designed to be-of an effective length at temperatures greater than a lower temperature than that at which the SME coil 11 changes its length. For example, the SME coil 29 is designed to contract from its normal length at OOC. When the coil 29 has contracted it will not be in abutment with the bar 26 and so when the latter is moved to the left, as viewed in Figure 4, it will not abut the SME coil 29 and so the pivotal movement of the lever 24 in the anti-clockwise direction, as viewed in Figure 4, will be an idle movement and so the override at throttle openings of say 75% or more will not be effective.

Thus warm air will be admitted under the control of the SME coil 11 even at 75% or more throttle openings. When the air temperature is raised above OOC, the SME coil 29 will resume its normal length and the movement of the lever 24 will be transmitted to pivot the flap 6 to close the warm air inlet 3 despite the condition of SME coil 11. The SME coils 11 and 29 are both positioned in the air flow through the air cleaner housing to the air filter 5; but may be positioned downstream of the air filter or in the air inlet to the carburetter.

The low temperature responsive SME coil can be similarly employed to override a throttle setting control in a conventional air inlet temperature control apparatus which is controlled by a vacuum device and temperature-responsive switch. Such a control apparatus incorporating a low temperature responsive SME coil is now described in a third embodiment in Figures 5-8.

The apparatus comprises an air inlet pipe 30 leading to an air cleaner (not shown) and then to the carburetter of an internal combustion engine.

The air inlet pipe 30 has an inlet 31 equivalent to inlet 2 in Figure 1 for ambient air in the direction of arrow X and a warm air inlet 32 equivalent to inlet 3 in Figure 1. The air inlet pipe 30 contains a pivotally mounted flap 33, equivalent to flap 6 in Figure 1, which is movable between the position shown in Figures 5 and 6 in which the warm air inlet 32 is closed and the ambient air inlet 31 is open and the position shown in Figures 7 and 8 in which the ambient air inlet 31 is closed and the warm air inlet 32 is open and can also adopt an intermediate position in which both inlet 31 and inlet 32 are partly open.The flap 33 is moved by a rod 34 pivotally attached to the flap 33 and which is arranged to be raised and lowered, as shown in the drawings, by a vacuum device comprising a diaphragm 35 which carries the rod 34 and is moved to its raised position in opposition to a downwardly-acting return spring 36 by a vacuum pressure acting above the diaphragm 35 in a vacuum chamber 37. The source of vacuum is applied to the interior of the chamber 37 above the diaphragm 35 through a pipe 38 communicating with pipe 39. The pipe 38 is arranged to be closed or opened to atmosphere by a flap 40 which is normally closea but which is arranged to be opened by a temperature responsive sensor at a predetermined engine operating air inlet temperature.The temperature responsive sensor may be an SME coil or spring 41 which at temperatures higher than a predetermined engine operating air inlet temperatures of say 30"C will contract to allow the flap 40 to open but which at a iower temperature will hold the flap 40 in its closed position.

As in the embodiment of Figure 1. there is a throttle setting override device wnich comes into effect at, for example, throttle settings of 75fez open or more to hold the flap 33 in the position in which the warm air inlet 32 is closed but which is rendered ineffective at a predetermined low ambient air temperature at say OOC and below.

The throttle setting override device comprises a lever, cam, rod or like member 42 which is connected to or is integral with the flap 33 and which is moved by a member controlling the throttle between the positions indicated diagrammatically in Figures 5 and 7 corresponding to the positions in which the flap 33 is closed and fully-open with respect to the warm air inlet 32 respectively.

The member 42 is shown diagrammatically positioned within a slotted rotatable cam 43 integral with arm 44 which is normally held in the position shown in Figures 5-7 against the bias of a compressed helical spring 45 by an SME coil or spring 46 which is extended at temperatures above a predetermined low temperature, say OOC, but which will contract at the predetermined temperature, say 0 C, and so allow the spring 45 to expand to move the arm 44 in a clockwise direction as viewed in Figures 5-8 into the position shown in Figure 8. In that position the left-hand end wall of the slot in the cam 43 will have moved to engage the member 42 and so pivot it in the clockwise direction, thereby permitting the flap 33 to be moved by the raising of the rod 34 to the open position with respect to the warm air inlet 32 despite the throttle being 75''0 or more open.

The conditions corresponding to each of Figures 5-8 are as follows: In Figure 5, the engine is cold and so the SME coil 41 has not contracted, the engine air inlet temperature being less than the critical temperature of the SME coil 41 which is. for example, 300 C, and thus the flap 40 is held closed. Also there is no vacuum pressure available at pipe 39. The throttle setting is greater than 75% and the ambient air temperature is greater than OOC. Therefore the throttle override device is operative and the flap 33 is held in the position in which the warm air inlet 32 is closed and ambient air is admitted to the engine through the inlet 31.

In Figure 6, the engine is at its normal operating temperature and so the SME coil 41 has contracted, its temperature being, for example, greater than 300C. A vacuum pressure is available at pipe 39: but as the flap 40 is open to atmosphere as a result of the contraction of SME coil 41, the pressure in the pipe 38 and in the chamber 37 is atmospheric pressure. The throttle setting is below 75%. Therefore the flap is held in the position in which the warm air inlet 32 is closed and ambient air is admitted to the engine through the ambient air inlet 31.

In Figure 7, the engine is cold and so, as for Figure 5, the SME coil 41 holds the flap 40 closed.

There is a vacuum pressure at pipe 39 and thus there is a vacuum pressure acting in the chamber 37 above the diaphragm 35. Thus the rod 34 lifts the flap valve to the position in which it admits warm air through the warm air inlet 32 and closes or partly closes the ambient air inlet 31. Also the throttle setting is less than 75% open and the ambient air temperature is higher than OOC and so the throttle setting does not override the opening of the flap 33 by the vacuum chamber In Figure 8, the ambient air temperature is at OOC or below and so there is icing in the ambient air inlet, causing the SME coil 46 to contract and so to allow the arm 44 to pivot in the clockwise direction as shown, under the action of spring 45.

This causes the cam 43 to turn in the clockwise direction, thereby permitting warm air to flow to the engine inlet manifold. The throttle setting is greater than 75% and this would normally hold the flap 33 in the position in which the warm air inlet 32 is closed. However, the rotational movement of the cam 43 by the arm 44 cancels the overriding effect on the flap 33 of the throttle setting. There is no vacuum pressure at pipe 39 and the SME coil 41 is at an engine operating temperature lower than 300C and so the flap 40 is held in its closed position.

In the foregoing description with reference to Figures 5-8, it is envisaged that the SME coil 46 would be positioned in the ambient air inlet to the air cleaner to prevent icing up in the air cleaner. It could however be mounted in some other convenient position, for example in the carburetter inlet downstream of the air cleaner or near to the carburetter. The SME coil 41 would conveniently be mounted in the filtered air downstream of the air filter in the air cleaner or in the inlet manifold to the engine.

The provision of the SME coil 46 in Figures 5-8 and the provision of the SME coil 29 in Figure 4 enable the throttle control setting of the flap 33 or 6 to be overridden under frost conditions in the ambient air inlet and thereby to open the warm air inlet to permit warm air or a mixture of warm and cold air to flow to the carburetter.

Although in the foregoing examples, the SME actuators are in the form of coils or springs 11, 29; 41, 46, these actuators may be of other shapes, for example leaf springs. Although the actuators 11 and 41 are said to change their shape at and above 300C and the actuators 29 and 46 are said to change their shape at OOC and below, they may be designed to be responsive to other critical temperatures at which they change their shape.

Although in the foregoing examples, the overriding throttle controls are said to be effective at 75% or more opening of the throttle, they may be effective at another selected throttle opening.

Claims (12)

1. An engine air inlet apparatus including inlets for ambient air and warm air, regulator means for at least one of said inlets and a temperature responsive actuator comprising a shape memory effect material for operating said regulator means.

2. An engine air inlet apparatus according to Claim 1, in which said actuator is situated in said apparatus and responds to the temperature of air passing through said apparatus towards the engine.

3. An engine air inlet apparatus according to Claim 1 or 2, in which said actuator is arranged to respond to initial increases of temperature more slowly than subsequent temperature changes.

4. An engine air inlet apparatus according to any of the preceding claims, in which said actuator is coil shaped.

5. An engine air inlet apparatus according to any of the preceding claims, including an override to close off the warm air inlet whenever an engine throttle is opened beyond a predetermined high setting.

6. An engine air inlet apparatus according to any one of Claims 2-5 in which the actuator is designed to change its shape at a temperature equal to or in excess of a predetermined temperature and responsive to the temperature of air passing through said apparatus towards the engine.

7. An engine air inlet apparatus according to Claim 6 in which the actuator is arranged to operate said regulator means either directly or through a mechanicai linkage.

8. An engine air inlet apparatus according to Claim 6 in which the actuator is arranged to operate the regulator means in conjunction with a vacuum-responsive device.

9. An engine air inlet apparatus according to Claim 5 in which there is a second SME actuator designed to change its shape at a temperature equal to or lower than a first predetermined temperature, said first-mentioned actuator being designed to change its shape at a temperature equal to or in excess of a second predetermined temperature substantially higher than said first predetermined temperature, said second actuator being arranged to render said override ineffective at an air temperature to which it is responsive equal to or lower than said first predetermined temperature and said first-mentioned actuator being arranged to operate said regulator means to close off the warm air inlet when the air temperature to which it is responsive is equal to or in excess of said second predetermined temperature.

10. An engine air inlet apparatus according to Claim 9 in which said first-mentioned actuator is arranged to operate said regulator means either directly or through a mechanical linkage.

11. An engine air inlet apparatus according to Claim 9 in which said first-mentioned actuator is arranged to operate said regulator means in conjunction with a vacuum-responsive device.

12. An engine air inlet apparatus according to any preceding claim in which the regulator means is a flap valve movable between extreme positions in one of which said ambient air inlet is open and said warm air inlet is closed and in the other of which said ambient air inlet is closed and said warm air inlet is open.

1 3. An engine air inlet apparatus constructed and arranged substantiaily as described herein and shown in Figure 1, Figures 2 and 3, Figure 4 or Figures 5-8 of the accompanying drawings.