GB1576736A - Viscous driven overrunning clutch - Google Patents

Description

(54) VISCUOUS DRIVEN OVERRUNNING CLUTCH (71) We, EATON CORPORATION, a corporation organised and existing under the laws of the State of Ohio, of 100 Erieview Plaza, Cleveland, Ohio 44114, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to a starting and driving system for an operating member such as a blower in a hot gas engine, which system includes a viscous coupling operable under some conditions as an overrunning clutch.

The prior art contains various mechanical overrunning clutches. The overrunning clutches presently available are generally expensive due to their complex mechanical structure. Also, the clutches are difficult to lubricate propertly which shortens their life expectancy. A further problem is the mechanical clutch's vulnerability to sudden torque increases. When a sudden increase in torque is applied to a mechanical clutch the clutch can be destroyed.

Viscous couplings provide a clutch mechanism having a simple structure. One example of a viscous coupling is shown in U.S. Patent 3,329,246. This viscous shear coupling has two members wherein torque is transmitted from one member to the other member by the shear charcteristics of a viscous fluid.

Basically this device and other viscous couplings are designed to transmit torque from a driven member to a nondriven member regardless of the direction the driven member rotates.

Where the clutch is used in a system which requires driving force only under certain conditions the clutch can act as a power drain. For example if the clutch is used to transmit power from an engine to a blower it should not consume power during the starting cycle but begin to transmit power to the blower as the engine speed increases.

The invention provides a starting and driving system for an operating member such as a blower in a hot gas engine, in which a viscous drive coupling is provided for driving the operating member under normal operating conditions and a starter motor drives the operating member under start-up conditions of the engnie, the viscous drive coupling comprising: a housing member defining a working chamber: an annular member rotatably mounted within the working chamber; opposed surfaces located on the housing member and annular member and defining a shear space therebetween; a fluid shear means within the coupling to cooperate with the opposed surfaces to provide a fluid shear-type drive between the housing member and annular member; a fluid reservoir located within one of the members and in fluid communication with the shear space; the reservoir containing member being driven by the engine and the other member being coupled to drive the operating member; flow directing means on one of the members adapted to draw fluid out of the reservoir into the working chamber under normal operating conditions when the angular velocity of the reservoir containing member in one rotating direction exceeds the angular velocity of the drive member in the same direction and to pump fluid into the reservoir under start-up conditions when the drive member is driven by the starter motor such that the angular velocity of the reservoir containing member in the one rotating direction is less than the angular velocity of the drive member in the same direction.

A preferred embodiment of the invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a front view of one embodiment of the invention; Figure 2 is a sectional view of Figure 1; and Figure 3 is a front view of the annular member of Figure 2 showing the flow directing means in greater detail.

In the accompanying drawings a viscous fluid clutch is denoted generally as 10. The clutch shown has a cast metal housing 12 including a front housing member 14 and a rear housing member 16. The front housing 14 shown in Figure 1 is formed with eight radially disposed bosses 18 and a plurality of cooling fins 20.

The bosses 18 are machined and drilled to accept bolts 22 which secure the front housing member 14 to the rear housing member 16. The rear housing member 16 has bosses 26 which are machined to accept a second series of bolts 28 which hold a belt pulley 30 to the rear housing member. The front and rear members are sealed by a sealing ring 32 to form a liquid tight chamber 34 within the housing 12.

An annular member 36 is mounted within the liquid tight chamber 34 of the housing 12. The annular member 36 comprises in part a hub portion 38, an annular rim portion 40, and a shaped web 42 connecting the hub and rim. The rim portion 40 has a ribbed portion defined by a plurality of radially spaced, concentric rings 46 which project axially from both surfaces of the rim. The front and rear housing members have complimentary concentric rings 48 which project axially from the housing members between the rings 46. The concentric rings of the housing and annular member provide a plurality of interdigitated rings forming labyrinthian structure through which a viscous fluid, commonly called a fluid shear medium, can move.

The annular member 36 has a reservoir 50 defined by the shaped web 42 and a cover member 52. The reservoir 50 is in fluid communication with the labyrinthian structure or shear space by means of ports 54 which extend radially through the annular rim portion of the annular member 36.

Small ramped blocks 56 are attached to the periphery of the annular member 36 adjacent the ports 54 and project into an annular chamber 55. The chamber 55 can be of various sizes, however, a chamber Which is larger than that normally used for viscous fan drives provides a low torque overrunning clutch. The blocks 56 act as pumping members. When the housing 12 is moving faster than the annular member 36 the blocks 56 force or pump fluid into the ports 54 and thereby the reservoir 50.

As shown the blocks 56 are attached to the periphery of the annular member 36 by screws 58. In practice, the blocks can be attached by welding or other permanent means. The blocks could also be cast or formed as an integral part of the annular member. The blocks shown have a first substantially radial face and a second face which is disposed at an oblique angle to the radii of the circular member and represent one embodiment of the invention. The structure shown builds a film of fluid on the ends of the blocks to prevent rubbing and provide a self-lubricating structure. Other pumping means could also be used to achieve the desired pumping function.

The annular member 36 has an axial bore 60 therethrough which is adapted to receive a shaft. The shaft would support the clutch mechanism 10 and provide a means for receiving or transmitting power via the clutch.

The housing 12 is rotatably mounted to the hub 38 of the annular member 36 by means of a bearing 62. The bearing 62 is shown as a double row ball bearing and is held in place by a retaining ring 64 and allows free relative rotation between the housing 12 and annular member 36.

At the front of the housing a seal 66 pressed between the front housing member 14 and a foreward extending portion of the hub 38 makes the chamber within the housing fluid tight.

The operation of the clutch 10 is described as it might be used in a hot gas engine. When starting a hot gas engine it is necessary to activate a blower to push air into a combustion chamber. This is normally accomplished by means of a starter motor. After the engine has begun to operate the power for the blower is furnished by the engine. When used in a hot gas engine the clutch can be mounted on a shaft which receives power from the engine and will turn the annular member while the engine is operating.

During starting the starter motor would turn the blower and the housing by means of a vee belt drive which passes over the pulley 30. The pumping means are adapted so that they pump viscous fluid out of the labyrinth when the housing is rotating faster than the annular member. Therefore, in a starting mode the viscous clutch will apply a negligible amount of torque to the annular member. This provides a clutch with only a small power drain during starting.

As the engine speed increases, the angular speed of the annular member 36 also increases. The pumping action of the blocks 56 will begin to pump liquid from the reservoir 50 into the working chamber 55.

The viscous fluid in the working chamber transmits rotational forces from the annular member to the housing and pulley providing power to the blower replacing the power furnished by the starting motor. The pumping means will pump fluid from the reservoir until the speed of the housing approximates the speed of the annular member and the starting motor can be disengaged.

It is apparent from the foregoing discription that the starting and driving system of this invention has several advantages. It is resistant to damage by sudden torque increases, the viscous fluid absorbing the torque increases by increased shearing of the fluid. Since there is no mechanical connection between the members, the clutch will dampen vibrations applied to one of the members.

Various modifications and alterations of this invention will become obvious to those skilled in the art from the foregoing description. It is understood that this invention is not limited to the illustrative embodiment described above.

WHAT WE CLAIM IS: 1. A starting and driving system for an operating member such as a blower in a hot gas engine, in which a viscous drive coupling is provided for driving the operating member under normal operating conditions and a starter motor drives the operating member under start-up conditions of the engine, the viscous drive coupling comprising: a housing member defining a working chamber; an annular member rotatably mounted within the working chamber; opposed surfaces located on the housing member and annular member and defining a shear space therebetween; a fluid shear means within the coupling to cooperate with the opposed surfaces to provide a fluid shear-type drive between the housing member and annular member, a fluid reservoir located within one of the members and in fluid communication with the shear space; the reservoir containing member being driven by the engine and the other member being coupled to drive the operating member; flow directing means on one of the members adapted to draw fluid out of the reservoir into the working chamber under normal operating conditions when the angular velocity of the reservoir containing member in one rotating direction exceeds the angular velocity of the drive member in the same direction and to pump fluid into the reservoir under start up conditions when the drive member is driven by the starter motor such that the angular velocity of the reservoir containing member in the one rotating direction is less than the angular velocity of the drive member in the same direction.

2. The system according to claim 1, wherein the fluid directing means is on the reservoir containing member.

3. The system of claim 1 where the annular member has a plurality of spaced radially extending passages defined in the annular member and in fluid communication with the working chamber and the reservoir, the passages being located adjacent the flow directing means.

4. The system of claim 1, where the annular member is the input member and the reservoir is defined within the annular member.

5. The system of claim 1, where the flow directing means comprises ramped blocks having a first face which is substantially radial and a second fact which is disposed at an oblique angle to the radii of the annular member, each ramped block being located near a radially extending passage in the annular member so as to direct fluid into the passage and thereby the reservoir when the housing is rotating faster than the annular member.

6. A starting and driving system according to claim 1 and substantially as hereinbefore described with reference to the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (6)

**WARNING** start of CLMS field may overlap end of DESC **. member to the housing and pulley providing power to the blower replacing the power furnished by the starting motor. The pumping means will pump fluid from the reservoir until the speed of the housing approximates the speed of the annular member and the starting motor can be disengaged. It is apparent from the foregoing discription that the starting and driving system of this invention has several advantages. It is resistant to damage by sudden torque increases, the viscous fluid absorbing the torque increases by increased shearing of the fluid. Since there is no mechanical connection between the members, the clutch will dampen vibrations applied to one of the members. Various modifications and alterations of this invention will become obvious to those skilled in the art from the foregoing description. It is understood that this invention is not limited to the illustrative embodiment described above. WHAT WE CLAIM IS:

1. A starting and driving system for an operating member such as a blower in a hot gas engine, in which a viscous drive coupling is provided for driving the operating member under normal operating conditions and a starter motor drives the operating member under start-up conditions of the engine, the viscous drive coupling comprising: a housing member defining a working chamber; an annular member rotatably mounted within the working chamber; opposed surfaces located on the housing member and annular member and defining a shear space therebetween; a fluid shear means within the coupling to cooperate with the opposed surfaces to provide a fluid shear-type drive between the housing member and annular member, a fluid reservoir located within one of the members and in fluid communication with the shear space; the reservoir containing member being driven by the engine and the other member being coupled to drive the operating member; flow directing means on one of the members adapted to draw fluid out of the reservoir into the working chamber under normal operating conditions when the angular velocity of the reservoir containing member in one rotating direction exceeds the angular velocity of the drive member in the same direction and to pump fluid into the reservoir under start up conditions when the drive member is driven by the starter motor such that the angular velocity of the reservoir containing member in the one rotating direction is less than the angular velocity of the drive member in the same direction.

2. The system according to claim 1, wherein the fluid directing means is on the reservoir containing member.

3. The system of claim 1 where the annular member has a plurality of spaced radially extending passages defined in the annular member and in fluid communication with the working chamber and the reservoir, the passages being located adjacent the flow directing means.

4. The system of claim 1, where the annular member is the input member and the reservoir is defined within the annular member.

5. The system of claim 1, where the flow directing means comprises ramped blocks having a first face which is substantially radial and a second fact which is disposed at an oblique angle to the radii of the annular member, each ramped block being located near a radially extending passage in the annular member so as to direct fluid into the passage and thereby the reservoir when the housing is rotating faster than the annular member.

6. A starting and driving system according to claim 1 and substantially as hereinbefore described with reference to the accompanying drawings.