GB1565815A

GB1565815A - Cooling system for an internal combustion engine

Info

Publication number: GB1565815A
Application number: GB5155976A
Authority: GB
Original assignee: Automobiles Citroen SA
Current assignee: Automobiles Citroen SA
Priority date: 1975-12-19
Filing date: 1976-12-09
Publication date: 1980-04-23
Also published as: FR2335697A1; FR2335697B1; ES453410A1; DE2657320C2; DE2657320A1

Description

(54) COOLING SYSTEM FOR AN INTERNAL COMBUSTION ENGINE (71) We, SOCIETE ANONYME AUTOMOBILES CITROEN, a French Body Corporate organised and existing under Articles 118 to 150 of the French Law concerning commercial companies, of 117 à 167 Quai André Citroën, 75747 Paris, Cedex 15, France, 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 cooling system for an internal combustion engine, the system being of the kind comprising a fan, a drive shaft for driving the fan via a clutch and a fan control means responsive to the temperature at a selected place in the engine, the fan control means being adapted to initiate declutching of the fan when the temperature at the selected place is below a first predetermined limit and to initiate driving of the fan when the temperature exceeds a second predetermined limit, the fan being freely rotatable on the drive shaft and arranged for axial movement between its clutched and declutched positions.

Usually, the second temperature limit is higher than the first temperature limit.

The invention relates more particularly but not exclusively to a cooling system of the kind described for a motor vehicle and still more particularly for a motor vehicle having an air-cooled engine.

It is more particularly an object of the invention to improve the practical performance of such a cooling system, inter alia to simplify its construction and to enable the engine to operate in satisfactory heat conditions.

According to the invention, in a cooling system for an internal combustion engine of the kind hereinbefore defined, the fan is connected to a hub, which is axially stationary relative to the drive shaft, by resilient means which permit axial movement of the fan relative to the hub and which return the fan to its declutched position.

Advantageously, the resilient means take the form of a flexible annulus having a circular inside edge thereof secured to the hub, the circular outside edge of the annulus being secured to a member rigidly secured to the fan, the arrangement being such that the flexible annulus supports the fan but does not, when the same is in its clutched position, transmit the fan-driving torque.

Preferably, braking means are provided to immobilize the fan in its declutched position. The braking means may conveniently comprise at least one friction element rigidly secured to a stationary part of the engine, the fan entering into rubbing engagement with such friction element when the resilient means return the fan to its declutched position, so that the friction element immobilizes the fan in its declutched position.

According to a preferred form of construction, the friction element comprises an axially adjustable carrier and co-operates with a flat annulus projection radially outwards beyond the fan body to which it is rigidly secured.

In an embodiment of the invention, the clutch is an electromagnetic clutch including a winding which is energised to initiate driving of the fan and de-energised to initiate declutching of the fan.

Preferably, the winding of the electromagnetic clutch is stationary, the clutch having a driving part which is rotated by the drive shaft and which is axially immobile, the clutch having a driven part embodied by an axially movable armature rigidly secured to the fan. The driven part may take the form of an annular zone of a flange secured to the fan so that when the fan is in its clutched position, the driven part bears on the driving part of the clutch and the driven part is rotated by frictional engagement with the driving part.

Advantageously, where the fan is disposed on the end of a crankshaft, the stationary winding of the electromagnetic clutch is received in an annular recess in a pulley rigidly securd to a crankshaft extension, the annular recess being closed on the side near the fan by a transverse wall having at least one non-magnetic ring.

The invention also provides an internal combustion engine of a motor vehicle, in which a cooling system according to the invention is provided.

In order that the invention may be readily understood, an embodiment thereof will now be described, by way of example, with reference to the accompanying drawing, the single figure of which is a view, in axial section with parts removed, of a fan cooling system embodying the invention for an internal combustion engine.

Referring to the drawing, a cooling system 1 for an internal combustion engine 2 of a motor vehicle comprises a declutchable fan 3 and fan control means C responsive to the temperature at a selected place in the engine. The control means C can take the form for example, of a contact thermostat disposed either in the water circuit or in the oil circuit according to whether the engine is water or air cooled. In the case of an air cooled engine, the means C may be placed in the flow of engine heated air or in a metal wall of the engine.

Means C initiates declutching of fan 3 when the temperature at the selected place is below a first pre-determined limit and initiates rotation of the fan when such temperature exceeds a second predetermined limit which is usually higher than the first limit.

Fan 3 is mounted on an extension of engine crankshaft 4. The extension takes the form of an externally screw-threaded sleeve 5 which is screwed into and locked in a tapped bore in the end of the shaft. A tapped sleeved 6 is screwed on to sleeve 5 and has a larger-diameter end part in the form of a dish 7 which fits over the end of shaft 4. Dish 7 is in axial engagement with spacers 8 bearing on a shoulder of shaft 4.

Sleeve 6 is locked by a nut 9 screwed to the end of sleeve 5.

Fan blades 3a are rigidly secured to a central part or body 10 in the form of a spherical zone disposed coaxially of shaft 4.

A metal flange 11 is secured to the rear surface of body 10 by means of screws 12. A flat annulus 13 which projects radially outwards beyond the periphery of the rear surface of body 10 is also secured thereto by means of the screws 12. Annulus 13 bears on the rear surface of flange 11. The flange 11 is secured to a hub 14 by way of a flexible annulus 15 secured at its outer peripheral edge to flange 11 by rivets 16. At its inside circular edge annulus 15 is secured to hub 14 by means of rivets 17.

Being flexible, annulus 15 can deform to permit the flange 11 and fan 3 to move axially relative to hub 14.

Hub 14 is so disposed on sleeve 6 as to be immobile axially thereon but freely rotatable therearound. Accordingly and as the drawing shows, a bearing 18 comprising needle bearings and ball bearings is provided between the hub 14 and the sleeve 6.

The clutch of the fan 3 is electromagnetic and comprises a stationary winding 19 disposed coaxially of shaft 4 and mounted on a stationary disc 20 rigidly secured to a stationary part of the vehicle. Winding 19, which is disposed around the dish 7, is received in an annular recess 21 open on the side near the disc 20 and closed on the side near flange 11 by a front wall 22 in the form of a circular annulus, wall 22 providing a rigid connection between dish 7 and a pulley 23 formed with a bore whose inside wall bounds recess 21. Pulley 23 rotates with crankshaft 4 and, through the agency of a belt t, drives ancillary equipment.

The annular front wall 22 is the driving member of the clutch and is disposed opposite a zone 24 of member 11, zone 24 being the driven member of the clutch.

Front wall 22 is embodied by magnetically conductive rings 22a and magnetically insulating rings 22b to compel the magnetic field produced by the winding 19 when the same is energized to pass through an air gap e between the driving member 22 and driven member 24 of the clutch. The path of a line of force of the magnetic field of the winding 19 is indicated in diagrammatic form by a chain-dotted line.

Braking means F are provided to immobilize fan 3 in its declutched position and comprise one or more friction elements 24 comprising a friction lining 25 stuck to a carrier 26 secured to a stationary part of the vehicle. Advantageously, carrier 26 is secured on a screw 27 screwed into a tapped aperture 28 in a member 29 rigidly secured to a stationary part of the engine or vehicle.

Screw 27 is additionally secured to member 29 by a locknut 27a. Carrier 26 is formed with an aperture for the screw 27 to extend through and is clamped between the head of screw 27 and a nut 30. The tapped aperture 28 and the screw 27 are long enough to retain the carrier 26 satisfactorily yet to allow carrier position to be adjusted axially of shaft 4.

Lining 26 is disposed, relative to annulus 13, on the side opposite to the driving member 22 of the clutch and in such a manner that annulus 13 bears a lining 25 when the fan is in its declutched position shown in the drawing. Of course, any required number of friction elements 26 may be provided, and as many members 29 as are required can also be provided for each friction element 26.

The cooling system described above operates as follows: When the temperature in the selected place of the engine exceeds the first temperature limit, contact C energizes winding 19 so that the magnetic field produced thereby moves the flange 11 and driven part 24 of the clutch into engagement with the driving part 22 thereof. The fan 3 and flange 11 therefore move back slightly axially thanks to the deformation of the flexible annulus 15, the hub 14 not moving axially. The fan 3 rotates as a result of the frictional engagement between the driving member 22 and driven member 24 of the clutch.

The flexible annulus 15 merely supports the fan 3 but does not transmit the fandriving torque.

When the temperature at the selected place in the engine drops below the second temperature limit, contact C de-energises winding 19. The flexible annulus 15, acting as a return spring, disengages the flange 11 and the driven member 24 of the clutch from the driving member 22 and returns them and the fan 3 to the position shown. Upon completion of this movement the annulus 13 enters into frictional engagement with lining 25, so that the fan 3 is immobilized in its declutched position notwithstanding any residual driving torque and notwithstanding the ram effect of the air flow through the fan blades.

A system embodying the invention provides appreciable advantages. Since the fan is held completely stationary in its declutched position, fan cooling of the engine is reduced since the fan does not rotate.

Natural cooling of the engine is reduced too since the fan, when held in its stationary position, retards ram effect airflow and thus reduces natural cooling of the engine below that which would occur in the complete absence of fan. Engine warm-up time with the fan in its declutched position is therefore shortened.

A rapid warm-up of this kind is very useful in the following cases: Immediately after starting since the engine reaches its optimum working temperature more quickly, and in high-speed running of the vehicle and when the vehicle is lightly loaded or on a downgrade conditions in which natural cooling tends to lower the temperature below the optimum working value.

A cooling system embodying the invention also increased the accuracy and speed of heat control in all running conditions and is of simple construction.

WHAT WE CLAIM IS: 1. A cooling system for an internal combustion engine, the system comprising a fan, a drive shaft for driving the fan via a clutch and fan control means responsive to the temperature at a selected place in the engine, the fan control means being adapted to initiate declutching of the fan when the temperature at the selected place is below a first predetermined limit and to initiate driving of the fan when the temperature exceeds a second predetermined limit, the fan being freely rotatable on the drive shaft and arranged for axial movement between its clutched and declutched positions, in which system the fan is connected to a hub, which is axially stationary relative to the drive shaft, by resilient means which permit axial movement of the fan relative to the hub and which return the fan to its declutched position.

2. A system according to claim 1, wherein the resilient means take the form of a flexible annulus having a circular inside edge thereof secured to the hub, the circular outside edge of the annulus being secured to a member rigidly secured to the fan, the arrangement being such that the flexible annulus supports the fan but does not, when the same is in its clutched position, transmit the fan-driving torque.

3. A system according to claim 1 or 2, wherein braking means are provided to immobilize the fan in its declutched position.

4. A system according to claim 3, wherein the braking means comprises at least one friction element rigidly secured to a stationary part of the engine, the fan entering into rubbing engagement with such friction element when the resilient means return the fan to its declutched position, so that the friction element immobilizes the fan in its declutched position.

5. A system according to claim 4, wherein the friction element comprises an axially adjustable carrier and co-operates with a flat annulus projection radially outwards beyond the fan body to which it is rigidly secured.

6. A system according to any preceding claim wherein the clutch is an electromagnetic clutch including a winding which is energised to initiate driving of the fan and de-energised to initiate declutching of the fan.

7. A system according to claim 6, wherein the winding of the electromagnetic clutch is stationary, the clutch having a driving part which is rotated by the drive shaft and which is axially immobile, the clutch having a driven part embodied by an axially movable armature rigidly secured to the fan.

8. A system according to claim 7,

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. shown in the drawing. Of course, any required number of friction elements 26 may be provided, and as many members 29 as are required can also be provided for each friction element 26. The cooling system described above operates as follows: When the temperature in the selected place of the engine exceeds the first temperature limit, contact C energizes winding 19 so that the magnetic field produced thereby moves the flange 11 and driven part 24 of the clutch into engagement with the driving part 22 thereof. The fan 3 and flange 11 therefore move back slightly axially thanks to the deformation of the flexible annulus 15, the hub 14 not moving axially. The fan 3 rotates as a result of the frictional engagement between the driving member 22 and driven member 24 of the clutch. The flexible annulus 15 merely supports the fan 3 but does not transmit the fandriving torque. When the temperature at the selected place in the engine drops below the second temperature limit, contact C de-energises winding 19. The flexible annulus 15, acting as a return spring, disengages the flange 11 and the driven member 24 of the clutch from the driving member 22 and returns them and the fan 3 to the position shown. Upon completion of this movement the annulus 13 enters into frictional engagement with lining 25, so that the fan 3 is immobilized in its declutched position notwithstanding any residual driving torque and notwithstanding the ram effect of the air flow through the fan blades. A system embodying the invention provides appreciable advantages. Since the fan is held completely stationary in its declutched position, fan cooling of the engine is reduced since the fan does not rotate. Natural cooling of the engine is reduced too since the fan, when held in its stationary position, retards ram effect airflow and thus reduces natural cooling of the engine below that which would occur in the complete absence of fan. Engine warm-up time with the fan in its declutched position is therefore shortened. A rapid warm-up of this kind is very useful in the following cases: Immediately after starting since the engine reaches its optimum working temperature more quickly, and in high-speed running of the vehicle and when the vehicle is lightly loaded or on a downgrade conditions in which natural cooling tends to lower the temperature below the optimum working value. A cooling system embodying the invention also increased the accuracy and speed of heat control in all running conditions and is of simple construction. WHAT WE CLAIM IS:

1. A cooling system for an internal combustion engine, the system comprising a fan, a drive shaft for driving the fan via a clutch and fan control means responsive to the temperature at a selected place in the engine, the fan control means being adapted to initiate declutching of the fan when the temperature at the selected place is below a first predetermined limit and to initiate driving of the fan when the temperature exceeds a second predetermined limit, the fan being freely rotatable on the drive shaft and arranged for axial movement between its clutched and declutched positions, in which system the fan is connected to a hub, which is axially stationary relative to the drive shaft, by resilient means which permit axial movement of the fan relative to the hub and which return the fan to its declutched position.

8. A system according to claim 7,

wherein the driven part takes the form of an annular zone of a flange secured to the fan so that, when the fan is in its clutched position, the driven aprt bears on the driving part of the clutch and the driven part is rotated by frictional engagement with the driving part.

9. A system according to claim 7 or 8, wherein the fan is disposed on the end of a crankshaft and the stationary winding of the electromagnetic clutch is received in an annular recess in a pulley rigidly secured to a crankshaft extension, the annular recess being closed on the side near the fan by a transverse wall having at least one nonmagnetic ring.

10. A cooling system for an internal combustion engine substantially as hereinbefore described with reference to the accompanying drawings.

11. An internal combustion engine comprising a cooling system according to any one of the preceding claims.

12. A motor vehicle having an internal combustion engine, which engine has a cooling system according to any one of claims 1 to 10.