GB2213910A - Air temperature control device - Google Patents

Abstract

An air intake temperature control device for an internal combustion engine has a temperature sensitive wax pellet actuator 15 to be supported by means 20 inside the engine air cleaner 38, the actuator 15 being supported by means 20 against the exterior of a chamber 22 to bear against a boss 27 and such that temperature increase permits an annular rim 31 of the housing of the actuator to close a bleed path for air from the air cleaner into chamber 23, the chamber 23 having vacuum ports 24 and 25 for connection into a vacuum servo control line. <IMAGE>

Description

Air temperature control device This invention relates to air temperature control devices for use in the air intake systems of internal combustion engines, particularly for automotive applications.

Numerous devices are known for this, an object of which is to achieve control of intake temperature under cold start conditions to minimise the effect of carburettor icing. It is normal to use a temperature-sensitive device to direct warm or relatively warm air to the carburation system at least until the engine achieves an acceptably normal operating temperature. Flap valves operated by bimetallic strips located in the intake duct, or in the carburettor are common.

Flap valves operated by wax pellet actuator devices are also known. The wax pellet actuator device comprises a closed container filled with wax and having a piston, part of which projects from the container to constitute an actuator. The actuator is usually a cylindrical rod, one end of which seats against a rubber diaphragm which serves to contain the wax. When the wax melts (on heating) the actuator is urged outwardly of the container to displace a flap valve, usually through some sort of spring loaded linkage.

Also known are devices in which a bimetallic strip or wax pellet is used to control a bleed valve connected into the induction system, the valve in turn controlling a vacuum servo motor operable to displace a flap valve which serves to select incoming air from either an ambient source or from a warm air source, or from both in various proportions, according to engine temperature.

It is an object of the present invention to provide an improved air temperature control device of the kind employing a wax pellet actuator device to control a vacuum servo flap valve.

According to the present invention, an air temperature control device comprises a closed chamber having inlet and outlet ports for connection to a vacuum servo system, means for supporting a wax pellet actuator device to the outside of the chamber, the chamber having a bleed orifice in a wall thereof so disposed as to be closed by the body of said actuator when in the unoperated state.

The body of the wax pellet actuator device is preferably retained by support means incorporating a spring operable to urge said body towards the position in which the bleed orifice is closed. The support means preferably constitutes a guide means for the body of the actuator device, for example in the form of an enclosure surrounding the device and containing a compression spring located between an end of the enclosure and that end of the device which is remote from the closed chamber. In another embodiment, the support means is itself resilient and constitutes both the spring urging the body towards the position in which the bleed orifice is closed, and the guide means for the body of the actuator device.

If the support means completely surrounds/encloses the actuator device body, it should be provided with apertures enabling free communication between the bleed orifice and the ambient atmosphere, when the orifice is open. This is not necessary of course if a cage-type enclosure is used.

The body of the actuator device is preferably provided with means such as a resilient sealing member/surface operable to close the bleed orifice in the unoperated condition. The orifice may be constituted by one or more small apertures in the chamber wall to which the actuator device body is supported, or it may be constituted by making the aperture through which the actuator member projects, a clearance aperture, i.e. as a small gap around the actuator member itself. Where apertures in the chamber wall are used, they are preferably symmetrically disposed about the actuator.

Because the wax pellet actuator device is externally supported to the closed chamber, it need not have any special construction such as a screw-threaded region engaged in a tapped bore in the chamber wall. As only a short travel is needed to open the orifice, a very short travel wax pellet actuator device may be used.

Conveniently the free end of the actuator member abuts against an opposed inside wall of the chamber, or against a projection therefrom, so that no linkages are needed.

Where a projection is used, it may be axially adjustable so as to facilitate adjustment of the operational parameters of the device. As the wax melts on heating, the end of the actuator member does not move at all. Instead the body of the actuator device, outside the closed chamber, is forced away from the adjacent chamber wall, thereby opening the bleed orifice. It will be appreciated that this is an important advantage of the invention, because it means that an unmodified wax pellet device can be used. It is not necessary to affix any kind of extension to the normal actuator member.

In fact, it may be possible to simply use the usual rubber diaphragm of the device as an actuator member, by suitably shaping the region of the chamber wall to which the device is supported, conveniently in conjunction with the configuration features described below.

Preferably, the bleed orifice is configured in relation to the adjacent portion of the actuator body which closes it in the unoperated condition so that the opening action, on operation of the wax pellet actuator device consequent upon an increase in temperature, is progressive rather than abrupt. This will be further illustrated in relation to the following description of preferred embodiments of the invention, in which Figure 1 is a schematic side view illustrating the typical use of an air temperature control device according to this invention, Figure 2 is a diagram illustrating the operational characteristics of the arrangement of Figure 1, Figure 3a, 3b and 3c illustrate one embodiment of the invention, and Figure 4 shows, (on an enlarged scale) a cross-sectional side view of another ebodiment of the invention.

In the following description the same reference numerals have been applied to like parts in all figures, as far as practicable, in the interests of clarity. Referring firstly to Figure 1, the intake duct 1 to an internal combustion engine carburettor system comprises an inlet 2 for air at ambient temperature, an inlet 3 for heated air derived from pasage of air over an exhaust manifold 4 together with a flap valve 5 to control the ratio of ambient air to heated air at any given time. The flap valve 5 is controlled by a vacuum servo-motor 6. Air entering the system passes through an air cleaner 7 into a carburettor 8 having a butterfly valve 9. A fuel-air mixture passes from the carburettor to the induction manifold 10. It will be appreciated that both the exhaust manifold 4 and the induction manifold 10 are shown only in schematic form. An air temperature control device 11 is located inside the air cleaner 7, at the clean air side of the filter element. The air temperature control device 11 incorporates a wax pellet actuator 15. The air temperature control device is connected to a vacuum source (the inlet manifold 10) through a pipe 14 and to the vacuum servo motor 6 through a pipe 12.

Figure 2 shows in simplified form the manner in which the wax pellet actuator device responds to changes in temperature inside the air cleaner 7.

Referring now to the embodiment described in Figures 3a, 3b and 3c, the air temperature control device 11 comprises a wax pellet actuator 15, 16 supported by a cage member 20 to the outer wall 21 of a closed chamber 22. The closed chamber 22 is defined between two parts, 21 and 23 respectively, part 23 being a generally cup shaped member having two ports 24 and 25. In use these are connected to the pipes 12 and 14 of Figure 1. The manifold connection 25 has a restriction 26 to prevent sudden pressure changes from significantly affecting the system. The port 24 may also have a restriction, but this is not normally necessary.

The member 23 has a central pillar of generallly cruciform cross-section terminating in a boss 27 with a skirt 28.

The rubber diaphragm 29 of the wax pellet device 15 is provided with a washer 30 in order to enable it to seat against the skirt 28. The arrangement is such that when the wax pellet device is not operated (i.e. in the cold state) its annular lower rim 31 seats against the skirt 28 of the member 21. The boss 27 is in the form of a cruciform moulding having webs 32 which may extend downwards to the centre of the opposed wall (Figure 3c) of the chamber, namely the inside floor of the member 23, or which as shown in Figure 3a may be simply a cruciform web supported entirely by part 2). In the cold state there is no air passage through the apertures defined between the webs 32. Thus air cannot enter the closed chamber from the inside of the air cleaner.

The cage member 20 serves as a spring to bias the actuator device into this position in which the apertures between the webs are closed. Details of this are seen in Figures 3b and 3c, respectively, which are perspective views, partly in section.

In order to simplify assembly the part 21 and the part 23 are provided with external projections 34 over which corresponding apertures 35 in the legs 36 of the clip member 20 can be engaged. Conveniently the parts 21 and 23 are moulded from a plastics material and the member 20 can then be secured in place either by simple engagement or by heat sealing, the latter being particularly preferred as the closed chamber 21 should be air tight. The assembly is mounted on the cleaner body wall 38 using a foam gasket 37 a locking washer 39 to retain it and prevent leakage.

Figure 4 illustrates a mechanical assembly which may be rather more convenient to adopt in practice. In this particular case the closed chamber 22 is contained within a one piece moulding 40 which contains a central pillar 41. The free end of this pillar engages the wax pellet device diaphragm 29, as previously described. A bleed orifice 45 is defined between the moulding 40 and the confronting annular skirt 44 of the wax pellet device. The moulding 40 has an external flange 46 provided with a washer 42.

The upstanding cylindrical boss 47 above the flange 46 at the top of the member 40 can be pushed through an aperture in the body wall 43 of an air cleaner until the washer/flange seat against the wall. The wax pellet device can then be placed on top (inside the air cleaner) prior to pressing the support member 20 into place to retain the whole assembly in place. In this particular case,the lower extremities of the member 20 could be provided with spring fingers or hooks 50 as shown in Figure 4 which would engage the upstanding boss 47 in the manner of a spring clip, or belleville washer.

Referring again to Figures 1 and 2 in operation from a cold start the whole of the vacuum developed in the inlet manifold is communicated through the restriction at 24 t the vacuum servo motor 6. This operates to raise the flap valve 5 and maximise the intake of heated air via passage 3. As the air temperature rises, the wax pellet device will begin to operate as indicated in Figure 2 and the flap valve will be progressively lowered to reduce the proportion of heated air admitted to the air cleaner 7. In the fully actuated state the intake air is essentially all at ambient temperature.

It will be appreciated that there is considerable scope for varying the response time of the wax pellet device 15.

Apart from selecting an appropriate wax composition, the construction of the support member 20 can be adjusted to control the amount of intake air which actually flows across the wax pellet device itself. For example the member 20 can be constructed as a tube having only a small number of apertures in its wall. This would considerably restrict the air flow across the wax pellet device. This would delay operation of the wax pellet device.

Alternatively it could be constructed as shown in Figure 3 in which the air flow has maximum access to the wax pellet device. Choice of a suitable arrangement will depend on the operating conditions of a particular carburation system and will have to be selected to some extent by experiment.

Claims (8)

1. An air temperature control device comprising a closed chamber having inlet and outlet ports for connection to a vacuum servo system, means for supporting a wax pellet actuator device to the outside of the chamber, the chamber having a bleed orifice in a wall thereof so disposed as to be closed by the body of the actuator when the latter is in the unoperated state.

2. An air temperature control device according to Claim 1 in which the wax pellet actuator device is supported by support means incorporating a spring operable to urge the body of the device towards the position in which the bleed orifice is closed.

3. A device according to Claim 2 in which the support means also constitutes a guide for the body of the actuator device.

4. A device according to Claim 2 or Claim 3 in which the support means is constituted by an enclosure surrounding the device and containing a compression spring located between an end of the enclosure and that end of the wax pellet device which is remote from the closed chamber.

5. A device according to Claim 2 or Claim 3 in which the support means is resilient and itself constitutes the spring urging the body towards the position in which the bleed orifice is closed.

6. An air temperature control device according to any preceding claim wherein the support means is provided with apertures, the number and size of said apertures being selected to control the response time of the device.

7. A device according to any preceding claim wherein the body of the actuator device is provided with means such as a resilient sealing member operable to close the bleed orifice in the unoperated condition.

8. An air temperature control device substantially as described with reference to and as illustrated by the accompanying drawings.