Viscous fan drive control with integrated speed sensor

Claim 2

A viscous fluid clutch comprising: first and second members mounted for relative rotation about a common axis and defining cooperating shear surfaces; means operative to generate a flow of viscous fluid between said surfaces; valving means operable to effect modulation of said flow and including an element carried by one of said members displaceable between a first limit of travel for minimum torque transmission and a second limit of travel for maximum torque transmission; actuator means operative to selectively position said element between said limits of travel in response to an actuation signal, said actuator means including a substantially grounded thrust surface operative to frictionally engage said valving means to extract kinetic energy from said one of said members and input it to said valving means to move said valving means and thereby effect said modulation; means operative to sense the rotational speed of said one of said members and to generate a speed signal as a function thereof, said speed sensing means comprising flag and sensor elements disposed in relative rotational alignment, one of said elements carried by said actuator means and the other of said elements carried by said one of said members; and control means operative to generate said actuation signal as a function of said speed signal.

Claim 3

The viscous fluid clutch of claim 1, further comprising a conducting path interconnecting said control means and actuator means, said speed sensing means being further operative to superimpose said speed signal upon said activation signal for transmission to said control means via said conducting path.

Claim 4

The viscous fluid clutch of claim 1, wherein said control means is further operative to generate said actuation signal as a function of sensed temperature in a host system.

Claim 5

The viscous fluid clutch of claim 1, wherein said actuator means comprises a tethered electromagnet and housing carried by said second member concentrically about said axis, said electromagnet operative to establish a magnetic circuit which passes through ferrous material within said housing and valving means.

Claim 6

The viscous fluid clutch of claim 4, wherein said electromagnet comprises an inductor which is electrically energized as a function of both the temperature of a coolant associated with said clutch and the rotational speed of said second member.

Claim 7

The viscous fluid clutch of claim 5, wherein said speed sensing means is operative to sense differential current across said inductor and generate said speed signal as a function thereof.

Claim 8

The viscous fluid clutch of claim 4, wherein said sensing element comprises a variable reluctance sensor carried by said housing for detecting the presence or absence of said flag element within a sensing region within the flux path of said magnetic circuit.

Claim 9

The viscous fluid clutch of claim 7, wherein said variable reluctance sensor is operative to establish a magnetic field having characteristic flux intensity generally additive to said magnetic circuit flux path intensity within said sensing region.

Claim 10

The viscous fluid clutch of claim 8, wherein said control means, is operative to maintain said magnetic field below the saturation point of said housing.

Claim 11

The viscous fluid clutch of claim 1, wherein said flag element comprises a permanent magnet carried for rotation with said actuator means.

Claim 12

The viscous fluid clutch of claim 1, wherein said flag element comprises a ferrous member carried for rotation with said actuator means.

Claim 13

The viscous fluid clutch of claim 1, wherein said valving means is further operative to magnetically engage a substantially grounded member to effect said flow modulation.

Claim 14

A viscous fluid clutch comprising: input and output members mounted for relative rotation about a common axis and defining cooperating shear surfaces; means operative to generate a flow of viscous fluid between said surfaces; valving means operable to modulate said fluid flow and including an element carried by said output member displaceable between a first limit of travel for minimum torque transmission and a second limit of travel for maximum torque transmission; actuation means operative to selectively position said element between said limits of travel in response to an actuation signal, said actuation means including a substantially grounded thrust surface operative to frictionally engage said valving means to extract kinetic energy from said one member and input it to said valving means to move said valving means and thereby effect said modulation; flag means disposed for rotation with one of said members; a sensor disposed in rotational alignment with said flag means and operative to generate a speed signal as a function thereof; and control means operative to generate said actuation signal as a function of said speed signal to effect operation of output member speed at a varying predetermined optimal rate.

Claim 15

A viscous fluid clutch comprising: input and output members mounted for relative rotation about a common axis and defining cooperating shear surfaces; means operative to generate a flow of viscous fluid between said surfaces; valving means operable to modulate said fluid flow and including an element carried by said output member displaceable between a first limit of travel for minimum torque transmission and a second limit of travel for maximum torque transmission; actuation means operative to selectively position said element between said limits of travel in response to an actuation signal, said actuation means including a substantially grounded thrust surface operative to frictionally engage said valving means to extract kinetic energy from said one member and input it to said valving means to move said valving means and thereby effect said modulation; flag means disposed for rotation with one of said members; a sensor disposed in rotational alignment with said flag means and operative to generate a speed signal as a function thereof; and control means operative to generate said actuation signal as a function of said speed signal to effect operation of output member speed at a varying predetermined optimal rate.

Claim 16

The viscous fluid clutch of claim 13, further comprising a conducting path interconnecting said control means and actuator means, said speed sensing means being further operative to superimpose said speed signal upon said actuation signal for transmission to said control means via said conducting path.

Claim 17

The viscous fluid clutch of claim 13, wherein said control means is further operative to generate said actuation signal as a function of sensed temperature in a host system.

Claim 18

The viscous fluid clutch of claim 13, wherein said valving means further comprises means operative to angularly bias said valving element into one of said limits of travel.

Claim 19

The viscous fluid clutch of claim 13, wherein said valving means further comprises means operative to axially bias said valving means into a frictionally disengaged position.

Claim 20

A viscous fluid clutch comprising: an input member mounted for rotation with a shaft; an output member rotatably disposed on said shaft relative to said input member; cooperating shear surfaces disposed on said input and output members and forming an operating chamber therebetween; a fluid storage chamber adjacent said operating chamber; a pump operative to displace fluid from said operating chamber to said storage chamber as a function of relative rotation between said members; at least one drain port interconnecting said chambers for fluid communication therebetween; valving means mounted coaxially with said output member for rotation therewith and axially displaceable to frictionally engage a substantially grounded thrust surface to extract kinetic energy from said output member and input it to said valving means to move said valving means and thereby effect modulation of the flow of fluid through said port by controlled angular displacement of a valving element between a first limit of travel for minimum torque transmission in which said element overlays said port and a second limit of travel for maximum torque transmission in which said port is relatively unobstructed; flag means disposed for rotation with said second member; a sensor disposed in rotational alignment with said flag means and operative to generate a speed signal as a function thereof; actuator means defining said thrust surface and operative to selectively position said element between said limits of travel in response to an actuation signal; and control means operative to generate said actuation signal as a function of said speed signal.

Claim 21

A viscous fluid clutch comprising: an input member mounted for rotation with a shaft; an output member rotatably disposed on said shaft relative to said input member; cooperating shear surfaces disposed on said input and output members and forming an operating chamber therebetween; a fluid storage chamber adjacent said operating chamber; a pump operative to displace fluid from said operating chamber to said storage chamber as a function of relative rotation between said members; at least one drain port interconnecting said chambers for fluid communication therebetween; valving means mounted coaxially with said output member for rotation therewith and axially displaceable to frictionally engage a substantially grounded thrust surface to extract kinetic energy from said output member and input it to said valving means to move said valving means and thereby effect modulation of the flow of fluid through said port by controlled angular displacement of a valving element between a first limit of travel for minimum torque transmission in which said element overlays said port and a second limit of travel for maximum torque transmission in which said port is relatively unobstructed; flag means disposed for rotation with said second member; a sensor disposed in rotational alignment with said flag means and operative to generate a speed signal as a function thereof; actuator means defining said thrust surface and operative to selectively position said element between said limits of travel in response to an actuation signal; and control means operative to generate said actuation signal as a function of said speed signal.