GB2471891A

GB2471891A - Water pump driven by engine crankshaft, comprising electromagnetic clutch between pulley and pump drive shaft

Info

Publication number: GB2471891A
Application number: GB0912416A
Authority: GB
Inventors: Michael Brinker; Herbert Schmitz
Original assignee: GM Global Technology Operations LLC
Current assignee: GM Global Technology Operations LLC
Priority date: 2009-07-17
Filing date: 2009-07-17
Publication date: 2011-01-19
Anticipated expiration: 2029-07-17
Also published as: GB2471891B; GB0912416D0

Abstract

Method for assembling a clutch 20 and a water pump 22 for a car comprises the steps of providing the water pump 20 that has a driving shaft 44, mounting the water pump 20 onto an engine block 46 such that the driving shaft 44 protrudes outside the engine block 46, installing the clutch onto the driving shaft 44, and attaching a pulley 40 onto the engine block 46 such that the pulley 40 is also connected to the clutch 20 for driving the water pump 22 via the driving shaft 44. The clutch 20 may be an electromagnetic clutch and may be slid onto drive shaft 44. An assembly 18 of a clutch 20 and a water pump 22 for a car comprises a torque transmission coupling 96 that connects the clutch 20 to the water pump 22. The torque transmission coupling 96 comprises a form-fitting coupling 96.

Description

Assembly of a Clutch and a Water Pump The present application relates to an assembly of a clutch and a water pump. The present application also relates to a method of assembling the clutch and the water pump.

A clutch has been has become increasingly adopted for con-necting a crankshaft of an engine to a water pump in a car.

The clutch enables torque transmission from the crankshaft to a driving shaft of the water pump only when the water pump is required for circulating water to cool down the engine. In particular, an electromagnetic clutch, due to its convenience in controllability, has become more widely accepted for such use in the car. An examples of the electromagnetic clutch is shown in Us 20081.0 017 468 Al. The known electromagnetic clutch is not convenient for being assembled onto the water pump in a mass production environment.

The application provides a method of assembling a clutch and a water pump for a combustion engine. The water pump is used to circulating water passing through the combustion engine for cooling the combustion engine or heating a passenger ---cab-in-. -The --combustion engine--includes-a petrol. engine and-a diesel engine. The combustion engine can alternatively re-placed by an electric motor or a hybrid engine.

The method comprises the steps of providing the water pump with a driving shaft, and mounting the water pump onto an housing block such that the driving shaft protrudes outside the water pump. The housing block comprises an engine block that provides a base for mounting parts of the engine.

The method also comprises steps of installing the clutch onto the driving shaft, and attaching a pulley onto the engine block via a clutch ball bearing such that the pulley is also connected to the clutch for driving the water pump via the driving shaft.

The method allows assembly without prior mounting of a part of the clutch onto the water pump in forming a subassembly.

In contrast, if a part of the clutch is.firstly mounted onto the driving shaft, which makes the subassembly outside the engine block, the subassembly is cumbersome to handle in a mass production line. The subassembly also prevents install-ing the whole water pump onto the engine block beforehand. It is much desired in the mass production line to mount the wa-ter pump onto the engine block first and fit the clutch onto the water pump subsequently for production efficiency.

The step of installing can comprise a step of slide fitting the clutch onto the driving shaft. The step of slide fitting can be easily and efficiently performed in the mass produc-tion line at low cost. In contrast to interference fitting, specialised procedures, costly equipments, demanding preci-sion and tedious processes are avoided by the slide fitting.

The method can further comprise a step of inserting an elec-tromagnet into the clutch. The electromagnet provides energy efficient and fast coupling between the water pump and the clutch. The electromagnet is desirable to be stationary with respect to the engine block because the electromagnet re- quires electrical wiring to be fixed for receiving electric- ity. Fastening the electromagnet onto the engine block en- sures reliable electrical wiring and stable electrical con-nections of the electromagnet.

The method can also comprise a step of covering or closing an end of the pulley with a protection cap. The protection cap keeps dirt and lubricants away from interior of the pulley.

The method can further comprise a step of fixing an end of the pulley to the driving shaft. Although one end of the pul-ley is already attached onto a water pump housing via the clutch ball bearing, an opposite end of the pulley is also beneficial to be supported for reliable usage. For example, a screw whose longitudinal axis is aligned to a longitudinal axis of the driving shaft can fixed the opposite end to the driving shaft via the protection cap. The pulley is thus much sturdy for the usage.

The method can comprise a step of joining the pulley to a crankshaft of an engine via a belt. Various types of belt-pulley system can be adopted, such as a V-belt pulley system.

A single rib V-belt or a multi rib V-belt can be used to join the V-belt pulley to the crankshaft of the engine. The V-belt pulley provides flexible torque transmission ratio between the crankshaft and the clutch, which is determined by pitch diameters of the crankshaft and the clutch. Alternatively, the belt-pulley system can be replaced by a chain drive. For example, a V-belt pulley is connected to the crankshaft via a multi. rib v-belt that can reduce influence of the vibration to the clutch. The multi rib v-belt also can prevent over- loading of the clutch automatically because the multi rib v-belt slips over the V-belt pulley when experiencing excessive loading.

The present application further provides an assembly of a clutch and a water pump for a car. The assembly comprises a torque transmission coupling that connects the clutch and the water pump for transmitting torque from the clutch to the wa-ter pump. The torque transmission coupling has an anti-free rotating geometry for shaft coupling. One or more fastener can be used to hold two or more parts of the form-fitting coupling together for torque transmission. The form fitting is alsoknown as a positive fitting. In contrast, an inter-ference-fittirig coupling and a material-fitting coupling do not rely on the angled contact area for the torque transmis- sion. The interference-fitting coupling transmits torque be- tween two or more joining parts by friction. The material-fitting coupling transmits torque two or more matching parts by adhesive bonding, such as glue bonding. Examples of the form-fitting coupling include a tongue and groove connection, a dovetail connection, a shaft-key joint, and a multi-teeth connection.

The form-fitting coupling can avoid assembling any part of the water pump and the clutch before mounting the water pump onto an engine block. For example, the water pump can be in-stalled onto an engine block first and the clutch can be mounted onto the water pump subsequently. The sequential as-sembling process is manufacturing friendly for efficiency.

The form-fitting coupling comprises a radial gap for slide- fitting the clutch onto the water pump. The radial gap pro-vides clearance between two parts of the torque transmission coupling in a radial direction of the axisof rotation of the torque transmission coupling. The clearance is also known as allowance of the coupling. The axis of rotation can be a ion-gitudinal axis of the driving shaft. The radial gap enables parts of the torque transmission coupling to move back and forth slightly in the radial direction for easy assembling.

In contrast, a positive fitting between the sleeve and the driving shaft requires substantial precision in these parts and lengthy time for the assembling.

The radial gap between a hub and a shaft of the torque trans-mission coupling facilitates easy slide insertion of the shaft into the hub. For example, the clutch has a sleeve that forms a through-hole along its longitudinal axis. The water pump also has a driving shaft whose longitudinal axis is aligned to that of the sleeve after assembling them together.

The sleeve and the driving shaft form the torque transmission coupling, which is very efficient for torque transmission at low cost. Conversely, the water pump can have a hub, whilst the clutch can have a shaft for making the torque transmis- sion coupling. The single hub-shaft coupling can alterna-tively be replaced by multiple hub-shafts.

The form-fitting comprises one or more radially flattened ar-eas for torque transmission. Theses areas can be parallel to the longitudinal axis of the driving shaft. For example, the form-fitting coupling can comprise the driving shaft that has two opposite parallel flat areas. The sleeve has two compara-ble parallel flat regions on its inner surface. The two areas and regions match together in forming two contact areas re- spectively after joining the sleeve and the driving shaft to- gether such that the two contact areas enables torque trans-mission between the driving shaft and the sleeve.

The form-fitting coupling can comprise a shaft key that re-sides between a driving shaft of the water pump and a sleeve of the clutch. The shaft key is a very effective tool for transmitting torque at low cost. During the assembling, the shaft key can be firstly put into a keyway on the driving shaft. The driving shaft can then be slid onto the sleeve so that the driving shaft is enclosed radially by the sleeve.

Complex technique and equipments for tight fitting between the driving shaft and the sleeve are avoided for improving assembling efficiency at low cost.

The torque transmission coupling can comprise a sleeve of the clutch that receives a driving shaft of the water pump. The sleeve and the driving shaft form the torque transmission coupling. The driving shaft is a reliable and strong compo-nent for being held by the engine block via a shaft ball bearing. Vanes of the water pump can be mounted at an end of the driving shaft for circulating cooling water. The sleeve can have a through hole that is slightly larger than.a diame-ter of the driving shaft. The shaft key can be inserted into the keyway on the driving shaft. An elongatedsiot can be milled onto an internal surface of the sleeve for enclosing the shaft key such that the sleeve can be slid over the driv-ing shaft and the shaft key. The radial gap can exist between the driving shaft and the sleeve in the assembly. Once in po-sition, the sleeve can be fixed onto the driving shaft by a bolt. The torque transmission coupling that uses the shaft key is also easy to be dismantled for maintenance.

The form-fitting coupling can comprise a contact area between the sleeve and the driving shaft. The contact area is at an angleto a torque transmission direction of the form-fitting coupling. Two or more contact areas of the form-fitting cou-pling can be provided such that the sleeve is slightly larger than the driving shaft for sliding the sleeve onto the driv-ing shaft easily. The torque transmission direction comprises a rotation direction of the driving shaft. There is a radial gap exist between the sleeve and the driving shaft. A size of the radial gap can be a difference in diameter between the two parts.

The assembly can further comprise a housing block of the en- gine for supporting the water pump. The housing block pro-vides a stable base for supporting the water pump. The water pump is thus held more sturdily with reduced influence from vibrations of the engine.

The clutch can be supported by the water pump, by the engine housing block, or by both. A stator of the clutch via a bear-ing can support moving parts of the clutch. Since the water pump is held by the engine housing, one end of the clutch is directly Or indirectly supported by the engine housing, which is strong and reliable for long-term operation.

The clutch can comprise an electromagnet for the torque transmission. A clutch that has the electromagnet becomes an electromagnetic clutch, which can be effectively and effi-ciently used for the torque transmission. An electromagnetic clutch that employs the electromagnet requires less moving parts, which are subjected to wear and tear in use.

The assembly can further comprise a centre screw along aligned to a rotation axis of the assembly for holding an end of the clutch to the water pump. The centre screw has a lon-gitudinal axis that is aligned to the rotation axis of the assembly. The rotation axis is a longitudinal axis of the driving shaft of the water pump. The pulley has two ends. One end of the pulley can held to a housing of the water pump or an engine block. The other end of the pulley can be supported by the driving shaft of the water pump so that the pulley is steadily supported when either in use or at rest. This ar-rangement provides a robust construction to the assembly.

The clutch can comprise an inner magnetic ring plate and an outer magnetic ring plate that are connected to the V-belt pulley and the sleeve respectively for the torque transmis-sion. The inner magnetic ring plate and the outer, magnetic ring' plate provide physical contact in-between when the elec-tromagnet is energised to push one of the plates to the other. Alternatively, the push action can be replaced by a pull action by changing the clutch design easily. The inner magnetic ring plate and the outer magnetic ring plate can be repaired and replaced in the lifetime of the electromagnetic clutch.

The application can provide an engine assembly that comprises a belt. The belt connects the crankshaft of the engine to the pulley. The belt is useful for avoiding overloading and vi-bration to the pulley.

A car can comprise the assembly of the water pump and the clutch. The car can further comprise the engine assembly. The car consumes less petrol and emits less toxic pollutants by on-demand connections between the water pump and the engine.

The on-demand connection drives the water pump only when the engine overheats.

* 30 Figure 1 illustrates a front view of an assembly that com-prises a pulley, an electromagnetic clutch and a water pump, Figure 2 illustrates a sectional view A-A of the assembly of the electromagnetic clutch and the water pump along a section line A-A, Figure 3 illustrates an exploded perspective view of the as-S sernbly of the electromagnetic clutch and the water pump, Figure 4 illustrates an expanded view B of a flat-area cou-pling of the water pump and the electromagnetic clutch, and Figure 5 illustrates an expanded view of a shaft-key cou-pling of the water pump and the electromagnetic.

clutch.

In the following description, details are provided to de- scribe the embodiments of the application. It shall be appar-ent to one skilled in the art, however, that the embodiments may be practised without such details.

Figures 1-3 depict an embodiment of an assembly 18 that corn-prises a pulley 19, an electromagnetic clutch 20, and a water pump 22. Figures 1-3 comprise parts that have similar or same reference numbers. Relevant description of these parts is in-corporated where necessary.

Figure 1 illustrates a front view of the assembly 18 that comprises the pulley 19, the electromagnetic clutch 20 and the water pump 22. The front view is seen in a direction of a longitudinal axis 24 of the electromagnetic clutch 20. Figure 1. shows a section line A-A such that a section view A-A is given in Figure 2. Figure 1 does not show an engine block 46 that receives the water pump 22 and the electromagnetic clutch 20.

Figure 2 illustrates the sectional view A-A of the assembly 18 of the pulley 19, the electromagnetic clutch 20 and the water pump 22 along the section line A-A from left to right.

The pulley 19 comprises a protection cap 26, a ring cover 28, a V-belt pulley 40, a clutch ball bearing 42 and an annular stator 36, from right to left in Figure 2. The V-belt pulley defines a cylindrical profile of the pulley 19. The V-belt pulley 40 is a hollow cylinder whose longitudinal axis 24 lies horizontally in Figure 2. The longitudinal axis 24 of the V-belt pulley 40 is also its axis of rotation. The pro-tection cap 26 and a ring cover 28 enclose a right end of the V-belt pulley 40. The annular stator 36 and the clutch ball bearing 42 are at a right end of the V-belt pulley 40.

According to Figure 2, the protection cap 26 is a circular plate that has a central protruding area 58 also in round form. The central protruding area 58 is flat such that a height 59 of the circular protruding area 58 is uniform throughout the central protruding area 58. The protection cap 26 also has a rim 60 that is folded back towards the circular protruding area 58. The rim 60 is further folded to the right side of the protection cap 26 such that it forms a circular groove 61.

The protection cap 26 is contiguous to the ring cover 28 that is further down in the direction of the longitudinal axis 24 towards right. The ring cover 28 is a torus-shaped that re- sembles a typical disk-shaped washer with a hole in the mid-die. The ring cover 28 has an inner circular edge 62 and an outer circular edge 64. Both the inner circular edge 62 and the outer circular edge 64 are concentric and they have the longitudinal axis 24 as their central axes of rotation. The inner circular edge 62 at a left side of the ring cover 28 folds radially, thus forming an inner circular catch 66. The protection cap 26 is snapped onto the ring cover 28 such that the inner circular catch 66 fits into the circular groove 61 of the rim 60. In contrast, at a right side of the ring cover 28, the outer circular edge 64 folds towards the centre of the ring cover 28, thus forming an outer circular catch 68.

The outer circular edge 64 of the ring cover--28 joins, to a right end of the V-belt pulley 40. The V-belt-pulley 40 is further fixed onto an outer ring of the clutch ball, bearing 42 at its left end such that the V-belt pulley 40 can freely rotate around the annular stator 36. The V-belt pulley 40 has a disk-profiled side portion 78 and a cylindrical wall por-tion 80. The disk-profiled side portion 78 covers a left end of the V-belt pulley 40 and joins to the' cylindrical wall portion 80 at its outer edge. The cylindrical wall portion 80 extends in the direction of the longitudinal axis 24 toward right. The cylindrical wall portion 80 encloses the annular stator 36 and the electromagnetic clutch 20.. An external sur-face of the cylindrical waIl portion 80 has several annular ribs 82 forming V-shaped grooves in-between the annular ribs 82. These annular ribs 82 share the same longitudinal axis 24 of the electromagnetic clutch 20 as their axes of rotation.

These annular ribs 82 form V-shaped slots in-between for re-ceiving a multi rib v-belt onto the V-belt pulley 40. The multi rib v-belt is not shown.

The annular stator 36 is provided on the right end of the V-belt pulley 40. The clutch ball bearings 42 sits between the disk-profiled side portion 78 and the annular stator 36. The annular stator 36 has a hollow cylindrical part 73. The annu-lar stator 36 further has three through holes 77 that are equally distributed around the hollow cylindrical part 73 for receiving three socket head cap screws 71 respectively. Lon-gitudinal axes of the three through holes 77 are parallel to the longitudinal axis 24 of the electromagnetic clutch 20.

The three socket head cap screws 71 are only shown in:Figure 3. Each of these through holes 77 has a countersink at a left end of the annular stator 36 such that they can fully enclose a socket head of a socket cap screw.71. The three socket head cap screws 71 are accessible via the'Lgaps between the three spokes 72 from left side when attach-ing the annular stator 36 onto an engine block. 46 on the right.-The three socket head cap screws 71 and the annular stator 36 are kept clear from passages of rotating parts in the electromagnetic clutch 20.

The annular stator 36 has through holes 77 that are evenly distributed around a circle. These three socket head cap sôrews 71 pass these three through holes 77 and are tightened onto a water pump housing 83 with corresponding blind threaded holes 85 in the water pump housing 83.

The annular stator 36 also has a disk portion 79 that extends radially from a left end of the hollow cylindrical part 73.

The disk portion 79 is bent at its rim such that the rim forms an annular slot 81. The annular slot 76 opens towards right.

The electromagnetic clutch 20 is enclosed by the V-belt pul-ley 40, the protection cap 26 and the ring cover 28. The electromagnetic clutch 20 comprises mainly several disk-formed components that are aligned along the longitudinal axis 24. These components include, from right to left, an outer magnetic ring plate 30, a sleeve 32, an inner magnetic ring plate 34, and an electromagnet 38. These components share the same longitudinal axis 24 as their central axes of rotation respectively.

The outer magnetic ring plate 30 is attached to the left side of the ring cover 28. The outer magnetic plate 30 has a shape that is similar to that of the ring cover 28. In fact, the outer magnetic ring plate 30 cOvers almost the entire disk-.

shaped area an the left side of the ring cover 28 between the two edges 62, 64 of the ring plate 30.

* The inner magnetic ring plate 34 is fu.ther. located on the left side of the outer magnetic ring plate 30. The two mag-netic ring plates 34, 36 are parallel to each other with a gap in-between. The inner magnetic ring plate 34 has its size and shape comparable to that of the outer magnetic ring plate 30. The inner magnetic ring plate 34 has three lugs 70 that extend towards a centre of the magnetic ring plate 34. Each of these three lugs 70 has a hole for fastening. There is a gap of 0.8mm between the inner magnetic ring plate 34 and the outer magnetic ring plate 36 when these two plates 34, 36 are detached -The inner magnetic ring plate 34 has a hollow central region that receives the sleeve 32. The sleeve 32 has a hollow cy-lindrical central portion 73. There are three spokes 72 that each extends radially from a left end of the sleeve 32. The sleeve 32 further extends longitudinally along its rotation axis 24 towards right. The rotation axis 24 of the sleeve 32 is also the longitudinal axis 24 of the electromagnetic clutch 20. The three spokes 72 are equally distributed around the cylindrical central portion such that there is an angle of 180 degree between every two neighbouring spokes 72. Three pieces of part-ring profiled plates 74, which are only visi-ble in Figure 3, join each of the spokes 72 to the three lugs respectively.

The electromagnet 38 is further provided at a left side of the inner magnetic ring plate 34. The electromagnet 38 is fixedinside the annular slot 76. There is a gap between the electromagnet 38 and the inner magnetic ring plate 34 such that the inner magnetic ring plate 34 can freely rotate around the longitudinal axis 24 with respect to the outer: magnetic ring plate 30 and the annular stator 36. Correspond-ingly, there is also a gap exist between the inner magnetic ring plate 30 and the electromagnet 38 in the same direction.

The protection cap 26, the ring cover 28, the outer electro- magnetic ring plate 30, the sleeve 32, and the inner electro- magnetic ring plate 34 can freely rotate around the longitu-dinal axis 24 of the electromagnetic clutch 20 with respect to the annular stator 36 and the engine block 46.

There is a cable passage 39 provided for housing wires. These wires conduct electrical current to the electromagnet 38 from an external source. The cable passage 39 starts from the an-nular slot 76, via the annular stator 36, via the water pump housing 83.

Figure 2 also shows a driving shaft 44 of the water pump 22, the water pump housing 83 and the engine block 46. The water pump housing 83 encloses the driving shaft 44 in the middle.

The water pump housing 83 has three through holes 91 that are evenly located around a circle. At corresponding positions, the engine block 46 has three blind threaded holes 84 that receive three water pump fixing screws 87 such that the water pump housing 83 is rigidly fixed onto the engine block 46. A right end of the water pump housing 83 is inserted and tightly fitted with the annular stator 36.

A left portion 52 of the driving shaft 44 is placed inside the engine block 46. The water pump housing 83 encloses a middle portion 50 of the driving shaft 44. A right portion 48 of the driving shaft 44 protrudes outside the water pump housing 83 and is inserted into the electromagnetic clutch 20. The driving shaft 44 is cylindrical and these three con-secutive portions 52, 50, 48 of different diameters along its longitudinal axis of rotation. The longitudinal axis of the driving shaft 44 coincides with the longitudinal axis 24 of the electromagnetic clutch 20. A shaft ball bearing 54 is mounted onto the middle portion 50 of the driving shaft 44 such that an inner ring of the shaft ball bearing 54 is fixed onto a cylindrical surface of the left portion 52. An outer ring of the shaft ball bearing 54 is fixed inside the water pump housing 83. On the other hand, the sleeve 32 is fixed onto the right portion 48 of the driving shaft 44. As a re- suit, the driving shaft 44 can freely rotate inside the en-gine block 46. The driving shaft 44 further has a blind threaded hole 56 at its right end in the centre. The blind threaded hole 56 has its longitudinal axis aligned to the longitudinal axis 24 of the electromagnetic clutch 20. Vanes, which are attached to the left portion 52 of the driving shaft 44 of the water pump 22, are enclosed by the engine block 46.

Figure 3 illustrates an exploded perspective view of the as-sembly 18 of the electromagnetic clutch 20 and the water pump 22. According to Figure 4, the driving shaft 44 has two flat areas 75 at its protruding end. Nominal directions of these two flat areas 75 are perpendicular to the longitudinal axis 24 respectively. On the sleeve 32, there are also two flat regions 81 on an inner cylindrical surface of the sleeve 32.

The flat areas 75 and the flat regions 81 are of comparable sizes such that they match each other in forming a flat-area coupling 95, which is a form of torque transmission coupling 96. Contacting flat regions 81 and flat areas 7.5 enables torque transmission from the sleeve 32 to the driving shaft 44.

Figure 4 illustrates an expanded view B of a flat-area cou-pling 95 of the water pump 22 and the electromagnetic clutch 20. The driving shaft 44 has an outer diameter 98 that is smaller than an inner diameter 100 of the sleeve 32. There is a gap 94 exist in a radial direction of the driving shaft 44 between these two parts 32, 44. This gap 94 allows the sleeve 32 to be slid onto the driving shaft 44 without hindrance.

These two flat areas 75 and flat regions 81 cooperate each other such that the driving shaft 44 and the sleeve 32 form a torque transmission coupling 96.

The electromagnetic clutch 20 transmits driving torque from a crankshaft of an engine to the driving shaft 44 of the water pump when necessary. The crankshaft and the engine are not shown. The electromagnetic clutch 20 helps to reduce fuel consumption of a car (not shown) that is installed with the electromagnetic clutch 20. Less fuel consumption of the car not only lows down usage cost of the car, but also causes less pollution to the environment. The electromagnetic clutch provides an effective tool in reducing carbon dioxide emission of the car.

In particular, the V-belt pulley 40 can rotate around the driving shaft 44 for receiving the driving torque from the crankshaft via the multi rib v-belt. The outer magnetic ring plate 30, which is attached to the V-belt pulley 40, can fur-ther relay the driving torque. The inner magnetic ring plate 34 can move both axially and rotatably that it can either be attached to the outer magnetic ring plate 30 or detached from the outer magnetic ring plate 30. The three' spokes 72 of the sleeve 32, which supports the inner,magnetic ring plate 34 via the three part-ring profiled plates 74, are resilient in :the direction of the longitudinalaxiS 24 that brings the in- ner magnetic ring plate 34 to the detached position by de-fault.

The electromagnet 38 can push the inner magnetic ring plate 34 onto the outer magnetic plate 30 when activated. The two joined magnetic ring plates 30, 34 pass the driving torque from the V-belt pulley 40 to the driving shaft 44 for circu-lating cooling water via the vanes. Electric current can be supplied to coils of the electromagnet 38 for energising the electromagnet 38.

The engine block 46 supports the annular stator 36 and the electromagnet 38 via the three screw-couplings between the three through holes 77 of the annular stator 36 and the three blind threaded holes 84 on the engine block 84.

The engine block 46 also supports the V-belt pulley 40 via the clutch ball bearing 42 on the annular stator 36. The V- belt pulley 40 further supports the ring cover 28, the pro-tection cap 26, and the outer magnetic ring plate 30. The ring cover 28, the protection cap 26, and the outer magnetic ring plate 30 are further held by the hexagon head cap screw 86 that is tightened to the left end of the driving shaft 44.

The hexagon head cap screw 86 also serves as a large centre screw that corrects the position of the outer magnetic ring plate 30 with respect to the driving shaft 44. In fact, the hexagon head cap screw 86 helps to ensure that the protection cover 26, the ring cover 28, the V-belt pulley 40, and the outer magnetic ring plate 30 share the same longitudinal axis 24 of rotation.

The etigine block 46 further supported the driving shaft 44 via the shaft ball bearing 54. The driving shaft 44 holds the sleeve 32, the three part-ring profiled plates 74, and the inner magnetic ring plate 34.

The protection cap 26 seals off the left side opening of the electromagnetic clutch 20 that lubricant plash and dirt are kept out interior of the electromagnetic clutch 20. The inte-rior of the electromagnetic clutch 20 is thus kept clean for long-term reliable operation.

The torque transmission coupling 96 can include rigid cou- plings, flexible coupling and torque limiting couplings. Ex- amples of the rigid coupling comprises sleeve or muff cou-pling and flange coupling. Examples of the flexible coupling includes bushed a pin type coupling, an Universal coupling, an Oldham coupling, a bellows coupling with low backlash, a spider or jaw coupling with elastomeric inserts, a Thompson coupling, a resilient coupling, a disc coupling, a Schmidt-Kupplung coupling.

Figure 3 illustrates an exploded perspective view of the electromagnetic clutch 20 with the water pump 22 on the en-gine block 46. A method of assembling the electromagnetic clutch 20 onto the water pump 22 is illustrated according to Figure 3.

Components of the electromagnetic clutch 20 are assembled onto the engine block 46 from a left side of the engine block 46. Before mounting the components of the electromagnetic clutch 20, the left portion 52 of the driving shaft 44 is al-ready inserted into the inner ring of the shaft ball bearing 54. The driving shaft 44 is already inserted inside the water pump housing 83 and the engine block 46. The middle portion is held by bearings inside the water pump housing 83.

Three water pump fixing screws 87 hold the water pump housing 83 onto the engine block 46.

In a method of assembling the electromagnetic clutch 20, the clutch ball bearing 42 is mounted onto the V-belt pulley 40 such that the outer ring of the clutch ball bearing 42 is tightly fitted into a circular opening of the V-belt pulley on the left. Subsequently, the left end of the annular stator 36 is inserted into the inner ring of the clutch ball bearing 42 such that the V-belt pulley 40, the clutch ball bearing 42, and the annular stator 36 become one sub-assembly. The V-belt pulley 40 is able to freely rotate around the annular stator 36 because of the support of the clutch ball bearing 42.

The three through holes 77 of the annular stator 36 are brought into alignments with the three blind threaded holes 84 on the water pump housing 83 respectively. The three socket head cap screws 71 then bolt the annular stator 36 onto the water pump housing 83 such that the annular stator 36, the V-belt pulley 40 and the driving shaft 44 share the same longitudinal axis 24 of rotation. The electromagnet 38 is afterwards loaded into the annular slot 76 with its prede-termined wiring.

The inner magnetic ring plate 34 is preassembled onto. the sleeve 32 via the three spokes 72 and the three part-ring profiled plates 74. The inner magnetic ring plate 34 and the sleeve 32 are concentric. In the method of assembling the electromagnetic clutch 20, the shaft key 88 is put inside the keyway 89 on the driving shaft 44. The sleeve 32 is later slide-fitted onto the right portion 48 of the driving shaft 44. A stopper. is fixed onto the driving shaft 44 fOr prevent-ing the sleeve 32 from moving towards left. The stopper can be a bolt, which is not shown.

The outer magnetic ring plate 30 is also preassembled onto the ring cover 28 such that these two components are concen-tric. The ring cover 28 has a circular recess region 90 that receives the outer magnetic ring plate 30. The ring cover 28.

is partly inserted into the V-belt pulley 40 on its outer edge at a right end. The ring cover 28 also has a circular shoulder 92 that bulges outside the left opening of the V-belt pulley 40 such that the V-belt pulley 40 and the ring cover 28 are concentric along the longitudinal axis 24 of the electromagnetic clutch 20. The outer magnetic ring plate 30 is screwed onto the ring cover 28 inside the circular recess region 90.

The hexagon head cap screw 86 is screwed into the blind threaded hole 56 on the driving shaft 44. The hexagon head cap screw 86 holds the V-belt pulley 40 from its right side.

The protection cap 26 is later snapped onto the ring cover 28. In joining, the rim 60 of the protection cap 60 grabs onto the inner circular catch 66 of the protection cap 58.

When in use, in the default position, the inner magnetic ring plate 34 can freely rotate around the longitudinal axis 24 with respect to the annularstator 36 and the engine block 46. The V-belt pulley 40 and the outer magnetic ring plate 30 are also able to revolve around the longitudinal axis 24 of the electromagnetic clutch 20 without restraint. The inner magnetic ring plate 34 and the outer magnetic ring plate 30 are capable of spinning around the longitudinal axis 24 with respect to each other. In the defaul.t position, the inner magnetic ring plate 34 is kept at anupright position by the resilience of the three spokes 72 that a gap exists in the direction along the longitudinal axis 24. of the electromag-netic clutch 20. In the default position, the V-belt pulley can receive driving torque from the crankshaft of the en- gine via the multi rib v-belt, whilst the rotation Of the V-belt pulley 40 does not affect the driving shaft 44 of the water pump 22.

When the cooling water is required, in an activated position, the electromagnet 38 receives electric eddy current and gen-erates a magnetic field around the coil of the electromagnet 38. The magnetic field has a same polarity on a left side of the electromagnet 38 as the polarity of the inner magnetic ring plate 34 on the right side. As a result, the inner nag-netic ring plate 34 is pushed against the outer magnetic ring plate 30 such that the two magnetic ring plates 30, 34 become in contact. Accordingly, the drive torque of the engine is transmitted from the crankshaft of the engine, via the multi rib v-belt, via the V-belt pulley 40, via the ring cover 28, via the outer magnetic ring plate 30, via the inner magnetic ring plate 34, via the three spokes 72, via the sleeve 32, to the driving shaft 44 of the water pump 22.

The method of assembling the electromagnetic clutch 20 en-ables the water pump 22 to be mounted onto the engine block 46 first. Parts of the electromagnetic clutch 20 can subse-quently be installed onto the engine block 46 and coupled to the water pump 22. In other words, the method of assembling the electromagnetic clutch 20 avoids pre-mounting any part of the electromagnetic clutch 20 Onto the water pump 22 before installing the water pump 22 onto the engine block 46. In a mass production process, this method is efficient and mass production friendly.

Figure 5 illustrates an expanded view B' of a shaft-key cou-pling 97 of the water pump 22 and the electromagnetic clutch 20. The shaft-key coupling 97 provides an alternative embodi-ment for joining the sleeve 32 and the driving shaft 44.

According to Figure 5, the drivin.g shaft 44 has elongated slot on its cylindrical surface, which forms a keyway 89.

Correspondingly, the sleeve 32 has a similar rectangular slot 102 on its inner cylindrical surface. A shaft key 88 is in-serted into the keyway 89 such that the slot. 102 encloses protruding part of the shaft key 88. The shaft key 88 pre-vents the sleeve 32 and the driving shaft 44 from rotating with respect to each other such that torque can be transmit-ted from the sleeve 32 to the driving shaft 44.

The driving shaft 44 has a smaller outer diameter 98 than an inner diameter 100 of the sleeve 32. Therefore, there is ra-dial gap 94 exist between the two parts 32, 44.

The shaft key 88, the driving shaft 44 and the sleeve 32 form a torque transmission coupling 96 for transmitting torque from the engine to the water pump 22. The radial gap 94 be- tween the driving shaft 44 and the sleeve 44 allows easy in-sertion of the driving shaft 44 into the sleeve 44. The shaft key 88 between the two parts for torque transmission further completes the torque transmission coupling 96. In contrast to: an interference fitting between a hub and a shaft for torque transmission, there is no radial gap between the interfering * shaft and the hub. Insertion of the shaft into the hub is very tedious and costly to perform. The insertion further re-quires high precision of the shaft and the hub at high cost.

Although the above description contains much specificity, theseshoulci not be construed as limiting the scope of the embodiments but merely providing illustration of the foresee-able embodiments. Especially the above stated advantages of the embodiments should not be construed as limiting the scope of the embodiments but merely to explain possible achieve-ments if the described embodiments are put into practise.

Thus, the scope of the embodiments should be determined by the claims and their equivalents, rather than by the examples given.

Reference Numbers 18 assembly 19 pulley 20 electromagnetic clutch 22 water pump 24 longitudinal axis 26 protection cap 28 ring cover 30 outer magnetic ring plate 32 sleeve 34 inner magnetic ring plate 36 annular stator 38 electromagnet 40 V-belt pulley 42 clutch ball bearing 44 driving shaft 46 engine block 48 right portion 50 middle portion 52 left portion 54 shaft ball bearing 56 blind threaded hole 58 central protruding area 59 height rim 61 circular groove 62 inner circular edge 64 outer circular edge 66 inner circular catch 68 outer circular catch three lugs 71 socket head cap screws 72 three spokes 73 hollow cylindrical part 74 three part-ring profiled plates flat areas 76 annular slot 77 three through holes 78 disk-profiled side portion 79 disk portion hollow cylindrical portion 81 flat regions 82 annular ribs 83 water pump housing 84 three blind threaded holes three blind threaded holes 86 hexagon head cap screw 87 water pump fixing screws 88 shaft key 89 keyway or elongated slot circular recess region 91 three through holes 92 circular shoulder 94 radial gap flat-area coupling 96 torque transmission coupling 97 shaft-key coupling 98 outer diameter inner diameter 102 outer diameter

Claims

Claims 1. Method for assembling a clutch (20) and a water pump (22) for an engine comprising: -providing the water pump (22) with a driving shaft (44), -mounting the water pump (22) onto a housing block (46) of the engine such that the driving, shaft (44) protrudes outside the water pump (22), -installingthe clutch (20) onto the driving, shaft (44), and -attaching a pulley (40) onto the engine block (46) such that the pulley (40) is also connected to the clutch (20) for driving the water pump (22) via the driving shaft (44).
2. The method according to claim 1 characterised in that the installing comprises slide-fitting the clutch (20) onto the driving shaft (44).
3. Method according to claim 1 or claim 2 characterised in that the method further comprises inserting an electromagnet (38) into the clutch (20).
4. Method according to any of the preceding claims characterised in that the method further comprises covering an end of the pul-ley (40) with a protection cap (26).
5. Method according to any of the preceding claims characterised in that the method further comprises fixing an end of the pulley (40) to the driving shaft (44).
6. Method according toany of the preceding claims characterised in that the method further comprises joining the pulley (40) to a crankshaft of an engine via a belt. *10
7. An assembly (18) of a clutch (20) and a water pump (22) for an engine comprising: -a torque transmission coupling (96) that connects the clutch (20) to the water pump (22), wherein the torque transmission coupling (96) comprises a form-fitting coupling (95, 96, 97)
8. Assembly (18) according to claim 7, characterised in that the form-fitting (95, 96, 97) comprises at least one ra-dially flattened area (75, 81) for torque transmission.
9. Assembly (18) according to claim 7 or claim 8, characterised in that the assembly (18) further comprises a housing block (46) of the engine for supporting the water pump (22).
10. Assembly (18) according to claim 9, characterised in that the clutch (20) is supported by the water pump (22) or by the housing block (46).
11. The assembly (18) according to any of the claims 7 to characterised in that the clutch (20) comprises an electromagnet (38) for torque transmission.
12. The assembly (18) according to any of the preceding claims, chàracterised in that the assembly (18) further comprises a centre screw (86) along aligned to a rotation axis (24) of the assembly (18) for holding an end of the clutch (20) to the water pump (22).
13. The assembly (18) according any of the claim 11, characterised in that the clutch (20).comprises an inner magnetic ringplate (34) and an outer magnetic ring plate (30) that are con- nected to the pulley (40) and to the sleeve (32) respec-tively for torque transmission.
14. An engine assembly comprising a belt that connects a crankshaft of an engine to the pulley (40) according to claim 12 or claim 13.
15. A car comprising the assembly (18) according to any of the claims 7 to 14.