US3459163A - Thermostatic control - Google Patents

Description

1969 o. a. LEWIS 3,459,163

THERMOSTATIC CONTROL Filed Aug. 22, 1968 56 600mb b? [ea/1's I I 3y ATTORNEY United States Patent 3,459,163 THERMOSTATIC CONTROL Donald B. Lewis, Lapeer, Mich., assignor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Filed Aug. 22, 1968, Ser. No. 754,554 Int. Cl. F02m 35/04 US. Cl. 123-122 4 Claims ABSTRACT OF THE DISCLOSURE A damped valve member operated by a protected, adjustable bimetallic strip, contained in a sheet metal body which is further protected by a plastic casing, controls the vacuum signals delivered to a vacuum motor for positioning a valve which governs the temperature of the induction air flow delivered through an air cleaner and silencer assembly to an internal combustion engine.

BACKGROUND OF THE INVENTION Over the years it has been found advantageous to control the temperature of the air supplied through the induction system of an internal combustion engine during certain modes of engine operation. In general, the objects are to improve the vaporization of the fuel delivered into the air stream, thus allowing more complete combustion of the fuel in the engine combustion chambers, and at the same time to prevent carburetor ring.

The recent systems by which these objects are realized have incorporated a thermostatic control in which a bimetallic strip, mounted on a die cast body, positioned a valve within an orifice plate secured in the die cast body; this control formed vacuum signals appropriate for governing the induction air flow temperature. Such a construction was subject to a number of potentially troublesome manufacturing problems and required very rigid production control techniques to assure that the thermostatic control performed accurately. Among such problems were porous castings which prevented accurate control over the vacuum signals, intermittent buzzing or high frequency vibration of the valve member, and inconsistent riveting over of a projection on the die cast body which secured the bimetallic strip to the body. In addition, the bimetallic strip was exposed at the top of the control and, when mounted within the air cleaner housing, was therefore vulnerable to damage during servicing of the air filter element.

It will be appreciated from the foregoing that a desire remained for a simplified design of the thermostatic control which would avoid such problems.

SUMMARY OF THE INVENTION A thermostatic control design which satisfies this desire is disclosed herein. This design incorporates a body formed of sheet metal stampings. A bimetallic strip is clamped between the body and an overlying protective plate member and is held in place by a rivet. Consistently secure attachment of the thermostatic strip is thus assured, and the overlying plate member reduces the possibility of damage to the bimetallic strip. The overlying plate member extends beyond the end of the thermostatic strip and is there provided with an adjusting screw which allows more accurate adjustment of the tension in the bimetallic strip. A tang depending from the overlying plate member extends into a well of high viscosity silicone fluid within the valve member to reduce vibrations of the valve member. The valve body and attached structure is enclosed within a protective casing member to further reduce its vulnerability to damage.

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The details as well as other objects and advantages of this invention are shown in the drawing and disclosed in the description of a preferred embodiment.

SUMMARY OF THE DRAWING FIGURE 1 is a front elevational view of an internal combustion engine which has an air cleaner and silencer assembly adapted to control the temperature of the induction air flow;

FIGURE 2 is a side elevational view of the air cleaner and silencer assembly with parts broken away to show the thermostatic control and the air flow control valve;

FIGURE 3 is a sectional view through the thermostatic control illustrating all components, the section being taken generally along line 33 of FIGURE 4; and

FIGURE 4 is a top plan view of the thermostatic control.

DESCRIPTION OF A PREFERRED EMBODIMENT Referring first to FIGURE 1, an internal combustion engine 10 includes an intake manifold 12 and a carburetor 14- on which an air cleaner and silencer assembly 16 is mounted. Intake manifold 12 and carburetor 14 form an induction passage 18 (FIGURE 2) in which a throttle 20 is disposed to control the air flow to engine 10. Engine 10 also includes an exhaust manifold 22 which discharges through an exhaust pipe 24. A stove 26 is disposed about either exhaust manifold 22 or exhaust pipe 24 to provide a source of heated air.

Referring to FIGURE 2, air cleaner and silencer assembly 16 defines a silencing chamber 28 within which an air filter element 29 is disposed. A flange 30 at the base of assembly 16 surrounds the outlet 31 and registers with the inlet of carburetor 14. A tuned conduit or snorkel 32 extends from a flared end 34, open to air at ambient or underhood temperatures, to an inlet 35 opening into chamber 28. Conduit 32 also has a lateral opening 36 to which a pipe 38 leads warmed air from stove 26. A valve 40, pivoted at 42, may be swung between the position shown, where it prevents heated air flow through opening 36 by means of an extension 44, and a position preventing air flow through the open end 34 of snorkel 32. In the position shown, only air at ambient temperature may be admitted to the engine, but as valve 40 rotates and extension 44- is moved from opening 36, increasing amounts of heated air and decreasing amounts of ambient air are admitted and mixed to flow to engine 10.

Valve 40 is secured by a rod 46 to the diaphragm 48 of a vacuum motor 49 and is biased to the position shown by a spring 50. As vacuum signals above about 6 Hg are applied to diaphragm 48 against the force of spring 50, valve 40 is pivoted from the position shown to heat the induction air flow above ambient temperatures.

A thermostatic control 52 is provided for supplying vacuum signals through a line 54 to vacuum motor 49. As shown in detail in FIGURE 3, thermostatic control 52 has a chamber 56 which is subjected to the vacuum conditions existing in induction passage 18 below throttle 20. The vacuum in chamber 56 is modulated by air bled past a valve member 58 which is positioned by a thermostatically responsive bimetallic strip 60. Thermostatic control 52 is located within air cleaner chamber 28 so that bimetallic strip 60 senses the temperature of the induction air flow. At low temperatures, the head 62 of valve member 58 is held against its valve seat 64 to prevent air flow into chamber 56 through the orifice 66, and vacuum motor 49 then positions valve 40 solely in accordance with variations in induction vacuum. Under these conditions, during wide open throttle operation the value of induction vacuum is sufiiciently low that vacuum motor spring 50 moves valve 40 to the position shown in FIG- URE 2 whereby only cool air is delivered to the engine for maximum power; during most modes of engine operation, however, valve blocks ambient air flow through open end 34 of conduit 32 and heated air alone is admitted through lateral opening 36.

As the induction air flow temperature rises, bimetallic strip permits valve member 58 to open, and air admitted through orifice 66 reduces the vacuum in chamber 56. Valve 40 is then repositioned to reduce the flow of heated air through lateral opening 35 and increase the flow of ambient air through open end 34 of snorkel 32. In this way the induction air flow temperature is maintained at a substantially uniform level during the low speed modes of engine operation.

As noted above, the construction of thermostatic control 52 is of particular interest. The details of this construction are shown in FIGURES 3 and 4. Thermostatic control 52 comprises a pair of cupped members 68 and 70. The lateral wall 72 of lower member engages the lateral wall 74 of upper member 68 and is provided with a shoulder 76 which receives the bottom wall 78 of upper member 68. The lateral wall 74 of upper member 68 is crimped inwardly over lateral wall 72 of lower member 70, as at 80. An annular seal or gasket 82 is located on shoulder 76 beneath the upper member 68 to assure complete enclosure of chamber 56 which is formed between cupped members 68 and 70.

The bottom wall 83 of lower member 70 has a pair of projections 84a and 84b, each having a restricted aperture 85, which respectively define interchangeable inlet and outlet fittings for chamber 56. A line 87 connects one fitting, 84a, for example, with induction passage 18 below throttle 20 while line 54 connects the other fitting, 8411, with vacuum motor 49.

Upper member 68 has a lateral projection 86 underlying bimetallic strip 60, and a rivet 88 secures both metallic strip 60 and a rigid plate 90 to projection 86. As shown in FIGURE 4, plate 90 extends for substantially the entire length of bimetallic strip 60 and for substantial distances on either side of bimetallic strip 60 to prevent damage to strip 60. An extension 92 of plate 90 reaches beyond the end of strip 60 and holds a threaded adjusting screw 94 which bears against bottom wall 78 of upper cupped member 68. By turning adjusting screw 94, plate 90 and bimetallic strip 60 may be pivotally raised (and lowered) with respect to bottom wall 78 of upper member 68. The free end 96 of bimetallic strip 60, which embraces the stem 98 of valve member 58 and receives an enlargement 100 of stem 98, may thus be raised to increase the force with which valve head 62 is held against its seat 64.

In order to damp vibrations of valve member 58, a tang 102 extends from plate 90 into a recess or well 104 of high viscosity fluid 106, such as a silicon fluid having a viscosity on the order of 350,000 centistokes. This arrangement allows gradual adjustment of valve member 58 by thermostat 60, but prevents high frequency vibrations of valve member 58.

For further protection, thermostatic control 52 includes a unitary plastic outer casing 108. Casing 108 includes a lower portion 110 having an annular shoulder 112, which receives shoulder 76 of lower cupped member 72, and an opening 114. which grips lateral wall 72 of lower member 70. An upper portion 116 is secured on one side to lower portion 110 by an integral hinge 118 and extends entirely over plate 90, thermostat 60, and valve member 58. On the opposite side, lower portion 110 has a pair of pins 120 which extend through a pair of openings 122 in upper portion 116 and which are riveted over as at 124 to securely retain the casing about the remainder of control 52. Casing 108 thus readily protects the operating components of control 52 to assure accuracy in the performance of the control.

The advantages of this control in providing reliable operation may be readily understood from the foregoing, and the simplicity in the construction of this control will be appreciated by those concerned with efforts to control product cost.

I claim:

1. A thermostatic control comprising upper and lower upwardly opening cupped members each having a bottom wall and a cylindrical lateral wall, the lateral wall of said lower member being formed to define an annular shoulder facing upwardly within said lower member, said lower member receiving said upper member therewithin whereby an upper portion of the lateral wall of said lower member engages the lateral wall of said upper member and whereby said shoulder engages an annular portion of the bottom wall of said upper member to thereby define an enclosed chamber between said members, said lower member having an inlet fitting adapted for connection to a source of vacuum and forming a restricted aperture opening through said bottom wall of said lower member to said chamber for supplying vacuum to said chamber, said lower member having another fitting adapted for connection to a vacuum responsive device and forming an opening through said bottom wall of said lower member from said chamber for delivering vacuum signals to said device, said upper member having an orifice opening through said bottom wall thereof into said chamber for admitting air thereto to reduce the vacuum therein, the lower side of said upper member defining a valve seat surrounding said orifice, a valve member cooperating with said valve seat to vary the flow of air through said orifice into said chamber and control the vacuum therein whereby vacuum signals are formed for delivery to said vacuum responsive device, said valve member including a valve head disposed in said chamber for engaging said seat and a valve stem extending upwardly from said head through said orifice, said valve stem having an enlargement at the upper end thereof, a thermally responsive strip having one end receiving said valve stem and engaging the lower side of said valve stem enlargement for supporting and positioning said valve member within said orifice and for exerting a force tending to lift said valve head into engagement with said valve seat which force varies in an inverse relationship with temperature variations, said upper member having a lateral projection underlying the opposite end of said strip, a rigid protective plate member overlying said strip to prevent damage thereto, means securing one end of said plate member to said lateral projection and clamping said opposite end of said strip therebetween, said valve stem enlargement having a recess in the top thereof, said recess containing a high viscosity damping fluid, and said overlying plate member having a projection extending downwardly into said fluid for damping vibration of said valve member whereby said thermally responsive strip may position said valve member to precisely control the vacuum within said chamber in accordance with temperature conditions and whereby accurate vacuum signals may be delivered to said vacuum responsive device.

2. The thermostatic control of claim 1 wherein the opposite end of said protective plate member extends beyond said one end of said thermally responsive strip and which further comprises an adjusting screw threadedly received through said opposite end of said plate member and bearing against said bottom wall of said upper member whereby the spacing between said opposite end of said protective plate member and said bottom wall of said upper member may be varied to cause said rigid plate member and said strip and said lateral projection to pivot with respect to said bottom wall of said upper member whereby the lifting force exerted by said thermally responsive strip on said valve member may be adjusted.

3. The thermostatic control of claim 1 or 2 which further includes a protective casing comprising a lower portion having an annular wall defining an opening therethrough, said annular wall having a shoulder formed therein, said lower cupped member extending through said opening in said lower portion whereby said lateral wall of said lower member engages said annular wall and whereby said shoulder of said lower member engages said shoulder of said annular Wall, said protective casing further comprising an upper portion extending over said protective plate member and connected at one side thereof to one side of said lower portion by an integral hinge portion, the opposite sides of said upper and lower portions respectively having cooperating opening and pin means for securing said opposite side of said upper portion to said opposite side of said lower portion and thereby retaining said protective casing in place.

4. An air inlet assembly for an internal combustion engine having an air induction passage and a throttle controlling flow through said induction passage, said assembly comprising a housing forming a silencing chamber and having an outlet opening from said chamber and adapted for registration with said induction passage, said housing further having an inlet opening into said chamber and a tuned conduit extending to said inlet, said tuned conduit having the end remote from said inlet open to air at ambient temperatures and having a lateral opening adapted for connection to a source of air warmed to temperatures greater than ambient, ambient air flow admitted through said remote end and warmed air flow admitted through said lateral opening being mixed in said conduit and said chamber to provide an induction air flow at temperatures greater than ambient, valve means disposed within said conduit and controlling air flow through said remote end and through said lateral opening to regulate the temperature of the induction air flow, spring means biasing said valve means to permit ambient air flow through said remote end and to prevent warmed air flow through said lateral opening, a vacuum responsive device connected to said valve means for exerting a force on said valve means in opposition to the bias of said spring means in response to vacuum signals, and the thermostatic control of claim 1 disposed within said assembly downstream of said valve means and responsive to temperatures of the induction air flow, said control having said inlet fitting adapted for connection to said induction passage below said throttle and said another fitting connected to said vacuum responsive device for supplying vacuum signals thereto whereby said valve means may be positioned in accordance with the induction air flow temperature.

References Cited UNITED STATES PATENTS 2,082,397 6/ 1937 Hiscock. 2,763,252 9/1956 Dolza et al. 2,781,032 2/1957 Sebok et al. 2,868,459 1/1959 Modes 23687 2,946,509 7/1960 Radtke et al. 23687 3,208,441 9/ 1965 Ottofy. 3,319,888 5/1967 Creager 23687 3,373,934 3/1968 Kolbe et al. 23613 3,394,687 7/1968 Scott 123122 X AL LAWRENCE SMITH, Primary Examiner US. Cl. X.R. 236-13, 87

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