Patent Application
20060237184
This invention relates to valves, and in particular, to flapper valves.
Automotive fluids, such as engine oil or transmission fluids, absorb heat in use. To prevent fluid deterioration, this heat often needs to be removed. Heat exchangers are commonly used for this purpose. Moreover, heat exchangers are known to perform this function adequately in moderate ambient conditions. However, in cold ambient conditions, engine oils and transmission fluids can be highly viscous. In such conditions, these automotive fluids do not flow easily through heat exchangers. As a result, in such conditions, the fluid pressure within the lubrication circuit, and particularly within the heat exchangers, can be high enough to damage the heat exchangers. In some cases, starvation of some downstream components, like transmissions, may even occur.
In order to avoid these adverse effects, it is known to provide a mechanism for bypassing the heat exchanger. One way that this has been done in the past is to provide a bypass conduit. The bypass conduit is connected in parallel with the heat exchanger and has a relatively low resistance to the flow of high viscosity fluids as compared to the heat exchanger. Structures of this type are known to provide pressure relief for the heat exchanger and avoid starvation of the downstream components, but can suffer in that, in normal operating conditions, the flow is split between the heat exchanger and the bypass circuit. This requires that the heat exchangers be made proportionately larger and heavier to achieve the same overall heat exchange performance for the cooling system. This added size and weight, and the associated costs therewith, are undesirable to automotive manufacturers.
In U.S. Pat. No. 4,193,442 issued to David R. Vian, a heat exchanger is coupled to an adapter which is positioned between an oil filter and the engine. The adapter includes a valve in the form of a bimetallic strip that opens under normal operating conditions to allow flow through the heat exchanger, and closes in cold conditions to prevent flow through the heat exchanger. A difficulty with the Vian device, however, is that it is a rather large and bulky structure, and it still does not protect the heat exchanger from high fluid pressures in all conditions, especially if the oil filter is plugged or partially plugged.
In the present invention, a simple, low-profile bypass valve assembly is provided. The bypass valve assembly utilizes a tubular flapper valve, and can be readily attached to any heat exchanger or other fluid device having a fluid inlet and a fluid outlet. The assembly provides for selective bypass flow between the fluid inlet and the fluid outlet, without preventing flow from the fluid outlet of the fluid device, yet being responsive to excessive pressures in the fluid inlet of the fluid device.
According to one aspect of the invention, there is provided a bypass valve assembly for use with a fluid device having an inlet and an outlet. The assembly comprises a main body member having means defining an inlet opening, and a cylindrical wall portion defining an outlet opening spaced from the inlet opening and orientated coaxially with the fluid device outlet. The cylindrical wall portion has a bypass opening formed therein, and means defining a bypass passage extending between the inlet opening and the bypass opening. The inlet and outlet openings are adapted to be coupled in fluid communication respectively with the fluid device inlet and outlet for fluid flow through the fluid device. A flexible flapper is disposed within the outlet opening, the flapper having a free end portion movable between an open position, apart from the bypass aperture, and a closed position, overlying the bypass aperture, the free end portion being dimensioned to restrict flow through the bypass aperture when disposed at its closed position. Locating means are provided for maintaining the location of the flapper in the outlet opening. Also, bias means are provided for biasing the flapper into the closed position.
According to another aspect of the invention, there is provided in a heat exchanger including a heat exchange element having a spaced-apart inlet and outlet and a plurality of heat exchange passages therebetween, a bypass valve assembly, comprising a main body member connected to the heat exchange element and having means defining an inlet opening communicating with the inlet, and a cylindrical wall portion defining an outlet opening orientated coaxially and communicating with the heat exchange element outlet. The cylindrical wall portion has a bypass opening formed therein, and means defining a bypass passage extending between the inlet opening and the bypass opening. A flexible flapper is disposed within the outlet opening, the flapper having a free end portion movable between an open position, spaced from the bypass aperture, and a closed position, overlying the bypass aperture, the free end portion being dimensioned to restrict flow through the bypass aperture when disposed at its closed position. Locating means are provided for maintaining the location of the flapper in the outlet opening. Also, bias means are provided for biasing the flapper into the closed position.
Advantages, features and characteristics of the present invention, as well as methods of operation and functions of the related elements of the structure, and the combination of parts and economies of manufacture, will become apparent upon consideration of the following detailed description with reference to the accompanying drawings, the latter of which is briefly described hereinafter.
In the accompanying drawings, which are for the purpose of illustration and description only, and are not intended as a definition of the limits of the invention:
FIGS. 1 to 3 show a heat exchanger 20, which includes a fluid device, such as a heat exchange element 22, and a bypass valve assembly 24 constructed according to a preferred embodiment of the present invention. The heat exchanger 20 may be used as an oil cooler in a circuit for lubricating mechanical components (not shown).
As best seen in
Passage-forming plates 28, 30, 32 and 34 are of identical construction. Each includes, as seen in
Passage-forming plate 26 is of similar construction to plates 28,30,32,34 but lacks the pair of apertures 40, 41.
Plates 26,28,30,32 and 34 are stacked upon one another in nesting, alternating front-to-back and back-to-front orientation and sealed by brazing. As so sealed, plates 26,28,30,32 and 34 form heat exchange paths or passages 46 and 48 therebetween (see
One or the other of the apertures 40, 41, namely aperture 41, in plate 34 defines an inlet 50, and the other of the apertures 40, 41 forms an outlet 52, respectively, for receiving and discharging oil into and from oil passages 46 between plates 32, 34 and 28, 30. Apertures 43 and 42 in plate 26 define a first coolant port 54 and a second coolant port 56, respectively, for receiving and discharging engine coolant into and from the coolant passages 48 between plates 26, 28 and 30, 32. The exact form of heat exchange element 22 is not considered to be part of the present invention, so will not be described in further detail herein.
Referring to
The main body member 60 is a substantially planar, stamped or machined plate, arranged beneath plate 34 and brazed thereto, thereby to occlude aperture pair 42, 43 of plate 34. As best illustrated in
The tube 58 is releasably mounted within the cylindrical wall portion 70, and is dimensioned to be frictionally held within outlet opening 71. The interior of the tube 58 then defines the actual outlet opening 64 that is in fluid communication with the outlet 52 of heat exchange element 22 to receive oil therefrom and deliver it to the lubrication circuit (not shown) to return oil thereto. The wall of tube 58 has a bypass aperture 66 (see
As seen best in
The flexible flapper 62 is disposed in the outlet opening 64. A mounting end portion 78 of the flapper 62 is mounted to tube 58 by a locating means in the form of a rivet 80 (see
The free end portion 82 is movable, by flexure of flapper 62, between an open position, as shown in
The mechanical properties or spring constant of the flapper 62 may be selected to suit the operating parameters of the particular heat exchange element with which it is to be used. For example, the spring constant of flapper 62 can be chosen so that the flow through bypass aperture 66 or 74 occurs when the fluid pressure in bypass passage 72 exceeds a predetermined limit, which may be set below the burst strength of heat exchange element 22.
A further preferred embodiment of the invention is shown in
A yet further preferred embodiment of the invention is shown in
In use, in normal operating conditions, wherein relatively warm, substantially free-flowing oil is delivered to inlet opening 68, bias provided by the spring flapper 62 maintains the free end portion 82 of the flapper 62 in occluding relation against the bypass aperture 66 or 74 to restrict, and more specifically, substantially arrest bypass flow, with the possible exception of periodic, momentary burst flows or pressure spikes that may occur at inlet opening 68. This protects the heat exchange element 22.
In contrast, in conditions such as are present in the context of an engine start in relatively cold ambient conditions, wherein the oil is relatively cold, viscous oil is delivered to the inlet opening 68. In these circumstances, the inlet pressure to heat exchange element 22 is relatively large, with the result that the viscous oil forces the free end portion 82 of the flapper 62 away from the bypass aperture 66 or 74, as indicated by the sequence of
This structure is of particular advantage, in that it obtains relatively high cooling performance in normal operating conditions, when cooling is needed, as substantially all oil passes through the heat exchange element 22 to transfer its heat to the engine coolant in such conditions.
At the same time, the structure avoids starvation of mechanical components in normal transient high pressure conditions, such as cold weather startup, and also avoids metal fatigue that can result from pressure spikes in the thin-wall plates forming the heat exchanger.
As well, merely by modifying the structure of the main body member, the assembly can be readily tailored for use with flow devices of widely divergent structure. Advantageously, the main body member is brazed to the fluid device, and the components of the fluid device are brazed to one another, contemporaneously, and thereafter, the flapper valve is fitted within the outlet opening 71 in cylindrical wall portion 70, for subsequent shipping to an automotive manufacturer for installation.
Having described preferred embodiments of the present invention, it will be appreciated that various modifications may be made to the structures described above without departing from the spirit or scope of the invention.
Firstly, whereas the bypass valve assembly of the preferred embodiments is shown in use with a heat exchanger, it should be understood that the invention is not so limited, and may be deployed in association with any fluid device having an inlet and an outlet.
It should also be understood that whereas the disclosure illustrates and describes a heat exchanger of specific construction, modifications therein are also contemplated to fall within the scope of the invention.
Thus, for example, and without limitation, greater or lesser numbers of plates may be utilized to form the oil and coolant passages; the plates may be of different geometric construction; and may be sealed to one another by different methods, for example, by epoxy.
As well, turbulizers, of expanded metal or the like (not shown), may be disposed between the plates, as desired.
Further, whereas the bypass passage of the preferred embodiment is a groove formed in the main body member, with the passage-forming plates stacked upon the main body member forming an upper limit of the bypass passage, it will be evident that the bypass passage could, for example, be a channel or conduit formed entirely within the main body member, and thus not be dependent upon the passage-forming plate above for closure.
Yet further, whereas the main body portion is a machined plate in the preferred embodiment, it could equally be formed of one or more stamped plates, if it was desired to avoid machining.
As a further modification, whereas the flapper of the preferred embodiment consists of a strip of simple spring steel, a resilient bimetallic strip could be readily substituted therefor, to open and close under predetermined temperature conditions. A bimetallic strip, being resilient and flexible, would still provide pressure relief even in warm operating conditions.
Additionally, whereas the free end portion of the flapper of the preferred embodiments illustrated takes the form of a thin metal plate, modifications are possible. For example, the free end portion could be provided with a protuberance (not shown) that projects into the bypass aperture at the closed position to facilitate sealing, thereby to permit the relative amount of compression of the flapper valve at the closed position to be reduced, or to permit compression to be eliminated altogether, while still providing adequate sealing.
From the foregoing, it will be evident to persons of ordinary skill in the art that the scope of the present invention is limited only by the accompanying claims, purposively construed.
