GB2118243A

GB2118243A - IC engine air intake temperature control assembly

Info

Publication number: GB2118243A
Application number: GB08210498A
Authority: GB
Inventors: Peter Vincent Lucy
Original assignee: Ford Motor Co
Current assignee: Ford Motor Co
Priority date: 1982-04-08
Filing date: 1982-04-08
Publication date: 1983-10-26

Abstract

An overriding opening of the heated air inlet 4 to the intake duct 1 is effected by a shaped memory- effect metal element 15 to reduce the risk of carburettor icing when the temperature of the ambient air at the other inlet 2 falls below a predetermined value. Below the normal engine operating temperature the degree of valve opening, prior to override, is set by the manifold vacuum responsive actuator 9. The element 15 may connect the actuator diaphragm 10 to the valve 7, Fig. 2 (not shown). <IMAGE>

Description

SPECIFICATION Air inlet assembly for internal combustion engines.

This invention relates to air inlet assemblies for internal combustion engines.

Conventional air inlet assemblies for internal combustion engines comprise a duct having a first inlet for air at ambient temperature, a second inlet for air at a temperature higher than the ambient temperature, a valve for selectively permitting air to flow through the second inlet into the duct, and means operable in response to the load on the engine for opening the valve, for example a vacuum motor operable in response to engine inlet manifold vacuum. This device ensures that, at low engine loads, especially when the engine is idling during warm-up, pre-heated air is supplied to the engine to prevent stalling.

Usually the vacuum motor is disabled when the engine reaches its normal operating temperature.

This conventional system suffers from the disadvantage that, as load on the engine is increased, the amount of pre-heated air supplied to the engine also decreases. When the ambient air temperature is low and has a high humidity, this can lead to the formation of ice within the carburettor to which the air inlet is attached.

According to the present invention there is provided an air inlet assembly for an internal combustion engine comprising a duct having a first inlet for air at ambient temperature, a second inlet for air at a temperature higher than the ambient temperature, a valve for selectively permitting air to flow through the second inlet into the duct, and means operable in response to the load on the engine for opening the valve, characterised by an override mechanism for opening the valve when the ambient temperature falls below a predetermined level.

Since the override mechanism retains the valve in the open position when the ambient temperature falls below a predetermined level, the engine is always supplied with preheated air, regardless of the load on the engine. The risk of icing is therefore decreased.

Preferably the ovverride device comprises a shaped memory-effect metal element. Such elements are well known and are, for example described in British Patent Specification No.

1549166.

These elements exhibit large changes in their load/deflection characteristics with temperature such that, at temperatures below a predetermined level, a relatively large change in the shape and rigidity of the element occurs, enabling it to actuate the valve.

Two embodiments of the invention will now be described, by way of example only, with reference to the drawings in which: Figure 1 is a cross-section through a first embodiment of an air inlet assembly in accordance with the invention, and Figure 2 is a similar view of a second embodiment.

Referring to Fig. 1, an air inlet assembly comprises a housing defining a duct 1 which has a first inlet 2 at one end through which air at ambient temperature is admitted, and a second inlet 4 through which is admitted air which has been pre-heated eg by passage over an exhaust gas outlet from the engine.

A flap valve 7 is pivotally mounted within the housing for movement between a closed position (illustrated in full lines) and an open position (illustrated in broken lines) in which communication between the second inlet 4 and the duct 1 is closed and opened respectively.

The flap valve 7 is connected by means of an operating rod 8 to a vacuum motor 9 mounted on the exterior of the housing. The vacuum motor 9 is of conventional construction and includes a diaphragm 10 to which the operating rod 8 is attached which moves towards and away from the duct 1 in response to variations in the inlet manifold vacuum of the engine, to which the vacuum motor is connected by a vacuum line 11. A temperature sensitive switch (not shown) is incorporated in the vacuum line to disable the vacuum motor 9 when the engine has reached its normal operating temperature. A spring 1 2 biases the diaphragm 10 towards the duct 1, thereby closing the clap valve 7.

The flap valve 7 carries an operating lever 1 2 which is linked to a flange 1 3 on the housing by means of a shaped memory-effect metal element 1 5. One end 1 7 of the element 1 5 is received in a slot 1 6 in the flange 1 3 providing a lost motion connection.

At normal air temperatures, the end 1 7 of the element 1 5 lies at the end of the slot 1 6 nearer the flap valve 17. When the flap valve is closed, as illustrated in solid lines, the flap valve 7 is free to move between its open and closed positions, the corresponding movement of the element being taken up by the slot 1 6.

When the ambient air temperature falls below a predetermined level however, the element 1 5 undergoes a large contraction, thereby lifting the flap valve 7 into its open position, and overriding the operation of the vacuum motor. This large contraction of the element 1 5 results from the properties of the material from which it is composed, as will be known to persons skilled in the art.

As a result, at low ambient air temperatures, pre-heated air will always be fed through the air intake assembly, thereby avoiding icing in the carburettor to which it is attached. At higher ambient air temperatures, the amount of heated air fed through the air intake will be controlled by the vacuum motor 9 in response to changes in engine load in the normal manner.

Fig. 2 illustrates an alternative assembly in which the shaped memory-effect metal element 1 5 replaces the operating rod linking the vacuum motor 9 and the flap valve 7. The operation of this assembly is analagous to that of Fig. 1.

Claims

1. An air inlet assembly for an internal combustion engine comprising a duct having a first inlet for air at ambient temperature, a second inlet for air at a temperature higher than the ambient temperature, a valve for selectively permitting air to flow through the second inlet into the duct, and means operable in response to the load on the engine for opening the valve, characterised by an override mechanism for opening the valve when the ambient temperature falls below a predetermined level.

2. An assembly according to claim 1 wherein the means operable in response to the load on the engine comprises a vacuum motor operable in response to an engine inlet manifold vacuum.

3. An air inlet according to claim 1 or claim 2 wherein the override mechanism comprises a shaped memory-effect metal element.

4. An air inlet according to claim 3 wherein the said element is connected between the valve and the duct by a lost motion linkage.

5. An air inlet according to claim 3 wherein the said element is connected between the valve and the means operable in response to the load on the engine.

6. An air inlet substantially as hereinbefore described with reference to the drawings.