Control for Fluid Coupling

1. Cross-references

This application contains subject matter generic to the temperature responsive control disclosed in copending application Ser. No. 428,187 filed Nov. 29, 1974.

2. Field of the Invention

This invention relates generally to speed control of fluid couplings and specifically to speed control in response to temperature and speed.

3. Description of the Prior Art

It is well known to regulate the speed of an engine driven cooling fan in accordance with cooling demand, rather than in accordance with engine speed. The cooling demand is low during engine warm up, cold weather operation, and high vehicle speed. By contrast, demand is high during hot weather, particularly when the vehicle is not moving and the engine is idling.

The use of fluid couplings of the viscous shear type and of the hydrokinetic type to drive engine cooling fans for vehicles is well known. The output speed of such couplings may be controlled in accordance with cooling requirements, thereby allowing lower fan speeds when cooling requirements are low; this has the advantage of reducing engine fuel consumption and fan noise.

Controls to vary the output speed of such couplings in response to temperature and/or speed are well known in the prior art. Temperature control has been provided by a bimetallic spring in many of the viscous coupling controls. In such controls the spring rotates with the coupling and applies a force to move a valving member by bending or straightening in response to temperature changes. However, such springs generate a relatively small force per degree temperature change. Therefore, the controls are susceptible to erratic operation due to rotational forces acting on the spring and/or moveable parts of the control. Further, foreign matter in the control or corrosion of the moveable parts can easily render the control totally inoperative.

If a viscous coupling is to be controlled in response to ambient temperature exterior of the coupling, the spring (by necessity) is positioned on the coupling exterior. When exteriorly positioned, the spring must also move an intermediate mechanism which passes through a wall of the coupling. The force needed to reliably move the intermediate mechanism and the valving member is close to the maximum practical force which can be generated by the spring; therefore, the spring must be located on the coupling in a position least influenced by rotational forces. Exteriorly positioned springs are traditionally positioned coincident the rotational axis of the coupling to avoid rotational forces. However, this is a poor position for a temperature sensing element, since better temperature responses can be obtained at a radial extremity of the coupling where air flow is greater.

Erratic operation of the control due to sticking may be further compounded when a bimetallic spring is used in combination with a centrifugal weight for limiting maximum speed of the coupling, since the forces produced by the weight may be low so that they are in proportion to the low force produced by the spring.

An object of this invention is to provide an improved fluid regulating control for a fluid coupling.

A more specific object of the invention is to provide such a control which is insensitive to centrifugal forces generated by rotation of the coupling.

Another object is to provide such a control which provides improved temperature response.

Another object is to provide a temperature and speed responsive control wherein the temperature and speed signals are generated and combined in a manner to provide accurate and reliable operation of the coupling; and

Another object is to provide a control for a hydrokinetic coupling which is simpler and more compact than the prior art couplings and which yet provides improved control.

The fluid coupling controlled by the invention includes a rotatable housing member and another member disposed in the housing and mounted for rotation relative to the housing member. The members define a working chamber containing an inventory of fluid for transmitting torque from the one member to the other; and the control varies the torque transmitted by the fluid.

According to a feature of the invention, a temperature responsive device is carried on the exterior of the housing member at a position radially disposed from the rotational axis of the member and the torque transmitted by the fluid is varied in response to sensed changes in temperature ambient to the exterior of the housing member.

According to another feature of the invention, the torque transmitted by the fluid is controlled by a valving member, which is responsive to centrifugal force generated by rotation of the coupling, and a temperature sensing mechanism which varies the force required to move the valving member in response to changes in the temperature ambient to the exterior of the coupling.

The coupling controlled by the invention is more specifically a hydrokinetic coupling including input and output members defining a toroidal working chamber containing an inventory of fluid for transmitting torque from the input member to the output member in response to a toroidal flow of the fluid in the chamber.

According to a further feature of the invention, a temperature sensing device, carried by one of the members of the hydrokinetic coupling, is operative to vary the torque transmitted by the fluid in the working chamber in response to sensed temperature changes.

According to a further feature of the invention, sensing means, responsive to an operating condition of the coupling, controls the torque transmitted by the fluid in the working chamber by controlling the flow of a fluid pressure generated in the working chamber of the hydrokinetic coupling.

A preferred embodiment of the invention is shown in the accompanying drawing in which:

FIG. 1 is a front elevational view of the coupling;

FIG. 2 is an enlarged sectional view of the coupling of FIG. 1, looking in the direction of arrows II--II;

FIG. 3 is a fragmentary view of the turbine of FIG. 2, looking in the direction of arrows III--III; and

FIG. 4 is a sectional view of a central assembly in FIG. 2, looking in the direction of arrows IV--IV.

The present invention includes a novel control for a fluid coupling. The control is shown embodied in a hydrokinetic coupling 10 of FIG. 1. However, a portion of the control is adaptable to other devices and is particularly adaptable to viscous fluid couplings. The disclosed coupling is adapted to be driven by a liquid cooled engine and in turn drive a cooling fan 12 for removing heat from the engine coolant. Fan 12 is partially shown in phantom lines in FIG. 2.

Referring now to FIG. 1, coupling 10 includes a cast metal housing 14 consisting of a front housing member 16 and a rear housing member 18. Housing member 18 is shown only in FIG. 2. Front housing member 16 is integrally formed with six radially disposed bosses 20, a plurality of cooling fins 22, and a pair of raised portions 24 and 26. Bosses 20 are machined and drilled with through holes 28 for mounting and securing the fan to the housing by nut and bolt sets 30, as shown in FIG. 2. Raised portion 24 provides housing and support structure for a portion of a control assembly 32. Control assembly 32 regulates the output speed of the coupling in response to speed and temperature. A temperature sensing mechanism 34 of the control assembly is secured to an end wall portion 24a of raised portion 24 by screws 36. Raised portions 24 and 26 are symmetrical about the rotational axis of the coupling for balance purposes. An end wall 26a of raised portion 26 is provided with a threaded service plug 38 for checking and filling the fluid level in the coupling.

The front and rear housing members are secured together, independent of the fan mounting bolts, by six screws 40 which are circumferentially spaced between the fan mounting bolts. The ends of screws 40 are visable in FIG. 1. One of the screws is shown in FIG. 2.

Referring now to FIG. 2, coupling 10 includes a driving or impeller assembly 42, a driven or turbine assembly 44, a non-rotating shaft 46 which rotatively supports the impeller and turbine assemblies, and control assembly 32 which regulates relative rotation between the driving and driven assemblies by controlling torque transmission from the impeller to the turbine.

Shaft 46 is adapted to be supported at its left end by a hanger bracket 48 which is in turn adapted to be fixed to an engine, not shown.

Driving assembly 42 includes a sleeve 50, an impeller 52, and a V-belt pulley 54. Sleeve 50 is rotationally supported on shaft 46 by a pair of tapered roller bearings 56 and 58 which are spaced apart by a sleeve 60. The cavity surrounding bearings 56 and 58 is sealed at its left end by a seal 62. Impeller 52 is secured to the left end of sleeve 50 by a key 64 and a snap ring 66. V-belt pulley 54 is bolted to the left end of sleeve 50 by a plurality of bolts 68.

Driven assembly 44 includes housing members 16 and 18. Housing members 16 and 18 define a toroidal chamber 70 which is sealed at its radially outward extent by a seal 72. Housing member 16 also defines an annular chamber 74 having concentric wall portions 74a and 74b respectively, and a radially extending end wall portion 74c. Rear housing member 18 is rotationally supported on sleeve 50 by a roller bearing 76. A seal 78 prevents oil leakage through bearing 76. Front housing member 16 is rotationally supported on shaft 46 by a ball bearing 80. A washer 82 and a sleeve 84 provide proper spacing between bearings 80 and 58. The inner race of bearing 80 is secured to shaft 46 by nut 86. Nut 86 also provides a preload for bearings 56 and 58. The outer race of bearing 80 is secured to housing 16 by a snap ring 88. Fluid leakage from the cavity surrounding shaft 46 is prevented by a cap 90 and seal 92. Cap 90 is retained by a snap ring 94.

Impeller 52 is disposed in one half of toroidal chamber 70 and rotates relative to the chamber. A turbine 96 is disposed in the other half of the chamber. Turbine 96 is secured to front housing member 16 by a plurality of screws 97 and rotates with the chamber.

Impeller 52 includes a wall portion 52a which defines an annular trough 52b concentric to the axis of shaft 46. Turbine 96 includes a wall portion 96a which defines an annular trough 96b concentric to the axis of shaft 46 and confronting trough 52b. A plurality of blade sets 52c and 96c are circumferentially disposed in troughs 52b and 96b, respectively. Both blade sets may be cast integrally with the walls or fabricated separately and then secured to the walls. Turbine 96 further includes a core guide ring 96d formed with blade sets 96b and an annular slot 96e. Slot 96e extends through wall portion 96a and blade sets 96b and terminates at the core guide ring. The portion of wall 96a extending radially inward of slot 96e defines an end wall of the annular chamber 74.

Troughs 52b and 96b define a toroidal working chamber which is filled with a fluid, such as transmission fluid. When impeller 52 is rotated, blades 52c accelerate the fluid radially outward with respect to the rotational axis of trough 52b. The curvature of trough 52b directs the fluid into trough 96b. The fluid impacts blade sets 96c and imparts a torque to the turbine. The curvature of trough 96b directs the fluid radially inward and back into trough 52b. Continued rotation of the impeller reaccelerates the fluid, thereby establishing a toroidal fluid flow in the working chamber.

In general, torque transmission through a hydrokinetic coupling increases with increasing fluid circulation in the working chamber. Fluid circulation and torque transmission are a maximum for a given size coupling and impeller speed when the turbine is stalled. Fluid circulation and torque transmission through the coupling may be regulated by controlling the impeller speed relative to turbine speed of the amount of fluid circulation in the working chamber independent of the impeller speed. The amount of fluid circulation may be controlled by removing fluid from the working chamber or by restricting circulation. Herein, restriction is disclosed; however, control assembly 32 may be adapted to control fluid circulation via fluid removal.

Control assembly 32 includes a reciprocatable sleeve assembly 98 disposed in the annular chamber 74, the temperature sensing mechanism 34 and a spool valve assembly 100, and a source of pressurized fluid 102 for controlling the position of the sleeve assembly in chamber 74.

Referring now to FIGS. 2 and 3, the source of pressurized fluid includes a cavity 104 and a passage 106. The cavity is best seen in FIG. 3 and is defined by a portion of turbine wall 96a, two adjacent blades of blade sets 96c, and a divider plate 96f. Divider plate 96f blocks the flow of fluid between the adjacent blades, thereby raising the static pressure of the fluid in the cavity above the static pressure of the circulating fluid by converting the velocity component of the fluid to pressure.

Sleeve assembly 98 includes cylindrical sleeve portions 98a and 98b and a radially extending flange portion 98c which rigidly joins the sleeve portions together and divides annular chamber 74 into two variable volume chambers 74d and 74e. Cylindrical sleeve portion 98a is in sliding sealing contact with wall 74a and also provides support to prevent cocking of the sleeve assembly in chamber 74. Cylindrical sleeve portion 98b and wall 74b are spaced apart to define an annular passage 108 for communicating fluid between trough 96b and chamber 74d via a passage 110 in sleeve portion 98b. Passage 110 may be singular or plural in number. A seal 112 prevents fluid communication between annular passage 108 and chamber 74e. A seal 114 prevents direct fluid communication between trough 96b and chamber 74d.

Cylindrical sleeve portion 98b is disposed for movement into and out of annular slot 96e to control fluid circulation in the working chamber defined by troughs 52b and 96b. When sleeve portion 98b is fully inserted into slot 96e the left end of the sleeve abuts core guide ring 96d and blocks substantially all fluid circulation in the working chamber, thereby reducing torque transmission from the impeller to the turbine to a low amount. This low amount of transmitted torque is attributed to fluid shear stresses due to relative rotation between members and eddy fluid circulation which occurs between the troughs at positions radially outward from and radially inward from the core guide ring. When sleeve portion 98b is fully withdrawn from slot 96e, maximum fluid circulation in the working chamber is possible, thereby allowing maximum torque transmission from the impeller to the turbine.

Sleeve assembly 98 is shown in an intermediate position in FIG. 2, i.e., chambers 74d and 74e are about the same in volume and the right end of sleeve portion 98b extends about half way into slot 96e, thereby blocking about half of the fluid circulation in the working chamber and reducing torque transmission from the impeller to the turbine to about one half. The positioning of sleeve portion 98b into and out of the slot 96e is controlled by varying the differential fluid pressure acting on radially extending wall 98c; this is accomplished by controlling the fluid pressure in chamber 74e with temperature sensing mechanism 34 and spool valve assembly 100.

Referring now to FIGS. 2 and 4, the temperature sensing mechanism and the spool valve assembly cooperate to provide a control responsive to the rotational speed of the driven part of the coupling (i.e., housing 14) and the ambient temperature exterior of the housing. Spool valve assembly 100 is contained in raised portion 24 and includes a stepped bore 116 extending radially outward with respect to the rotational axis of the coupling, a cylindrical valving member 118, and a helical compression spring 120 for biasing the valving member radially inward and counter to centrifugal forces which act on valving member 118. Bore 116 includes an annular inlet groove 116a which communicates with passage 106 and an annular return groove 116b which communicates with a return passage 122 shown in phantom lines in FIG. 2 and in detail in FIG. 4. Passage 122 communicates return fluid to a cavity 90a defined by cap 90 via a passage 90b in the cap. Fluid in cavity 90a is used to lubricate bearings 80, 58, and 56. A portion of the fluid in cavity 90a returns to the working chamber via bearing 80 and a restricted annular passage 124; the remainder of the fluid returns to the working chamber via a T-shaped passage 46a in shaft 46. A passage 126 communicates bore 116 with chamber 74e. Valving member 118 includes two annular lands 118a and 118b which are spaced apart by an annular groove 118c. The position of valving member 118 in bore 116 is determined by the biasing force of spring 120 and the centrifugal force acting on the valving member. For intermediate positions of the valving member these forces balance out. FIG. 2 shows the valving member in an intermediate position. In this position return groove 116b is blocked and inlet groove 116a is partially uncovered thereby allowing the flow of pressurized fluid from passage 106 to chamber 74e and causing sleeve portion 98b to move further into slot 96e to further restrict fluid circulation in the working chamber. FIG. 4 shows valving member 118 bottomed in bore 116. In this position inlet groove 116a is blocked and return groove 116b is uncovered, thereby porting the fluid in chamber 74e to return and allowing the pressure in chamber 74d to rise above the pressure in chamber 74e via annular passage 108 and passage 110. Hence, sleeve portion 98b moves out of slot 96e and fluid circulation in the working chamber increases.

The temperature sensing mechanism includes a housing member 128, a thermal insulating piston 130, a temperature responsive wax filled power element 132, and a helical compression spring 134. Housing member 128 includes a flange portion 128a (best seen in FIG. 1), heat transfer fins 128b, and a stepped bore 128c which is axially aligned with bore 116. Flange portion 128a is secured to end face 24a of raised portion 24 via screws 36 (see FIG. 1). A seal 136 thermally insulates housing 128 from raised portion 24, prevents fluid leakage, and provides a reaction seat for spring 134. Piston 130 includes a cup-shaped portion 130a which embraces one end of element 132 and a shaft portion 130b having an end 130c which extends into valving member 118 to provide a moveable reaction seat for spring 120. Spring 134 is seated against the bottom of cup portion 130a and biases piston 130 toward element 132.

Housing 128 and element 132 are thermally insulated from metal contact with the coupling housing so that element 98 may respond to ambient temperature exterior of the coupling. The thermal insulating provided by piston 130 and seal 136 is not defeated by oil that may come into contact with housing 128 and element 132, since this oil is relatively stagnant and has a low conductive heat transfer. The ability of the element to respond to ambient temperature exterior of the coupling is further enhanced by placing the temperature control radially outward of the rotational axis of the coupling and into a position allowing greater ambient air flow over the element.

Temperature responsive wax filled power elements are well known in the art of thermostatic valves for engine cooling systems. Element 132 is pressed into housing 128 to enhance heat transfer from the housing to the wax in the element. Element 132 includes a push rod 132a which extends from the element and into contact with piston 130 (see FIG. 4). The wax in the element is selected to have a high coefficient of expansion at its liquid solid phase change temperature. The wax volume increases when it liquifies and moves the push rod outward from the element, thereby moving piston 130 radially inward to increase the biasing force exerted on valving member 118 and establishing a higher speed limit for the coupling. The wax volume decreases when it solidifies and spring 134 moves the piston and push rod toward the element, thereby decreasing the biasing force exerted on the valving member and establishing a lower speed limit for the coupling.

A preferred embodiment of the invention has been disclosed wherein the output speed of a hydrokinetic coupling is controlled by temperature and speed responsive means which vary the torque transmitted by the fluid in the coupling. In the disclosed embodiment a cylindrical sleeve is moved into or out of the coupling to vary fluid circulation in the working chamber in response to ambient temperature exterior of the coupling and output speed of the coupling. The preferred embodiment was disclosed for illustrative purposes. Several variations and modifications of the preferred embodiment are within the spirit of the invention. For example, movement of the sleeve can be controlled solely by the temperature responsive means or solely by the speed responsive means; or the sleeve can be dispensed with and the temperature and/or speed responsive means can be used to control the amount of fluid in the working chamber of the disclosed hydrokinetic coupling or a viscous shear coupling. Further, sleeve 98 can be controlled mechanically by the temperature and/or speed responsive means; or fluid pressure can be used to move the sleeve in one direction and a spring means can be used for movement in the other direction.

The following claims are intended to cover the inventive portions of the preferred embodiment and variations and modifications within the spirit of the invention.