CA1279835C - Electromagnetic clutch - Google Patents

Abstract

ELECTROMAGNETIC CLUTCH
ABSTRACT
An electromagnetic clutch is disclosed that includes a pulley and an electromagnetic mechanism. A hub is secured on a drive shaft and has a radially extending flange portion. An armature plate is concentrically disposed on the hub and faces the axial end surface of the pulley with an axial air gap therebetween. A holder plate is fixed on an outer axial end surface of the armature plate and is formed with a triangularly axially extending flange. The radial flange portion of the hub is also formed with a second axially extending flange corresponding to the first flange. The first and second axially extending flange are formed of a similar configura-tion and face one another with a radial gap. An elastic member is disposed in the radial gap to ease the impact force created when the clutch is engaged.

Description

3~i ELECTROMAGNETIC CLUTCH

TECHNICAL FIELD OF THE INV~NTION
This invention relates generally to an electromagnetic clutch, and more particularly, to an improved connecting structure between an armature plate and a hub of an electromagnetic clutch, for transmitting rotational force supplied by a pulley to the drive shaft of a compressor.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure l is a cross-sectional view of a conventional electromagnetic clutch.
Figure 2 is a cross-sectional view of a second conventional electromagnetic clutch.
Figure 3 is a cross-sectional view of an electromagnetic clutch in accordance with the present invention.
Figure 4 is a front view of the electromagnetic clutch of Figure 3.
BACKGROUND OF l~E INVENTION
A conventional electromagnetic clutch with an elastic member for easing the impact force transmitted to the drive shaft of a compressor is disclosed in U.S.
Patent No. 3,774,739 to Higuchi, and is illustrated in Figure 1. The clutch comprises pulley l which is supported on bearing 2 and is rotated by an automotive engine through a belt (not shown). Pulley 1 is formed of a magnetic material in which one or more concentric arcuate or annular slits 3 are formed to define a plurality of concentric annular magnetic poles. Hub 5 is fixed on the terminal end of drive shaft 4. Holder plate 8 and the outer end portion of hub 5 are formed with concentrically disposed cylindrically shaped flanges 81 and 51. Rubber member 9 is disposed in the space defined between axial flanges 81 and 51.
Therefore, armature plate 6 is connected to hub 5 through holder plate 8 and rubber member 9. Rubber member 9 therefore functions to ease the transmission of ~'i' ~' ~ 3 ~ ~

sudden torque changes to the drive shaft. These sudden torque changes impart an impact force on rubber member 9 which induces a bending or shearing stress on the rubber member. This intermittently applied stress to the rubber member may cause the rubber member to crack and eventually be destroyed.
One solution to overcome the above mentioned disadvantages is disclosed in U.S. Patent No. 4,624,354 to Koitabashi and is illustrated in Figure 2. This electromagnetic clutch comprises holder plate 8' and outer end hub 5' both of which are provided with concentrically positioned polygonally shaped axial flanges 81' and 51', and rubber member 9' which is disposed between axial flanges 81' and 51'. The polygonal shape reduces the shearing stress in the rubber member and the durability of the rubber member is thus improved.
However, the rubber member used in both of these conventional electromagnetic clutches is affixed on the axial flanges 81' and 51' by adhesive materials, and the adhesive strength of the adhesive material fails with the passing of time. As a result, the rubber member becomes detached from the surface of axial flanges 81' and 51'. Also, the adhesive portion of the rubber member may be damaged.
SUM~ARY OF THE INVENTIO~
It is an object of an aspect of this invention to provide an electromagnetic clutch with a mechanism for easing the impact force transmitted to the drive shaft.
It is an object of an aspect of this invention to provide an electromagnetic clutch with improved durability of an elastic member which connects the drive shaft to the clutch.
An electromagnetic clutch according to an aspect of the present invention includes a first rotatable member with an axial end plate of magnetic material, and a ~ 3~ ~

second rotatable member se.cured on a hub. The hub includes a radially extending flange portion~ An annular armature plate is concentrically disposed on and radially surrounds the outer peripheral portion of the hub with a gap therebetween. The armature plate faces the axial end plate of the first rotatable member with an axial air gap therebetween. An electromagnetic means is disposed within the first rotatable member for attracting the armature plate to the axial end plate of the first rotatable member. A holder plate is fixed on an axial end surface of the armature plate and is formed with a first axially extending flange portion. The radial flange portion o~ the hub has a second axially extending flange portion. The first and second axial flanges are polygonally shaped and face one another with a radial gap therebetween. An elastic member is disposed in the radial gap and, therefore, the impact force is eased by the compressive deformation of the elastic membex when the clutch is engaged. Excessive twisting deformation of the elastic member is thus prevented.
Another aspect of this invention is as follows:
In an electromagnetic clutch comprising a first rotatable member having an axial end plate of magnetic material, a second rotatable member and an armature plate of magnetic material joined to the second rotatable member so as to be capable of limited axial movement, said armature plate facing said axial end plate of said first ro~atable member with an axial air gap therebetween, and an electromagnetic means associated with said axial end plate for attracting said armature plate into engagement with said axial end plate whereby the rotation of said first rotatable member can be transmitted to said second rotatable member through said armature plate by the operat:ion of said electromagnetic means, the improvement comprising: a holder plate affixed to the outer axial surface of said armature plate and formed with a first axial flange portion ext~nding outwardly from said armature plate, said first axial flange portion having a configuration including at least one straight line, said second rotatable member having a second axial flange portion extending outwaxdly from said armature plate, said first and second axial flange portions having inner and outer surfaces facing one another with a radial gap therebetween, said first axial flange portion having a radial flange at one end thereof extending toward said second axial flange portion, said second axial flange portion having a radial flange at an end opposite said one end of said first axial flange portion extending toward said first axial flange portion, and elastic means disposed between the inner and outer surfaces of said axial flange portions and said radial flanges within the radial gap for limiting the relative rotation between said first and second axial flange portions by the compression of said elastic means when said armature plate engages said axial end plate upon operation of said electromagnetic means.
Further objects, features and other aspects of this invention will be understood from the following detailed description of the preferred embodiment of this invention while referring to the annexed drawings.
DETAIIED DESC,'RIPTION
Referring to Figures 3 and 4, which illustrate an electromagnetic clutch 1~ in accordance with the present invention, the clutch is shown assembled on compressor 10 for an automotive air conditioning system.
Compressor housing lOa is provided with cantilevered tubular extension 12 surrounding drive shaft 13 of the compressor. Drive shaft 13 is rotatably supported in the compressor housing lOa by a bearing (not shown).

~,7 9 ~t3 4a Pulley 1~ is rotatably supported on tubular extension 12 through bearing 15 which is mounted on the outer peripheral surface of tubular extension 12.
Pulley ~4 is made of magnetic material, such as steel, and comprises outer annular cylindrical portion 141, inner annular cylindrical portion 142 and axial end plate portion 143 connecting outer and inner cylindrical portions 141, 142. Annular U shaped cavity 16 is thus defined between these three portions 141, 142 and 143.
Annular V-shaped grooves 17 are provided on the outer peripheral surface of cylindrical portion 141 of pulley 14 for receiving a V-belt (not shown) for coupling the compressor to the output shaft of an automobile enyine (not shown).
Axial end plat~ portion 143 includes one or more concentric slits 18 which are disposed on one or more concentric circles, so that a plurality of annular or arcuate magnetic portions are defined, with the magnetic surfaces being on the axial end surface of axial end plate portion 143.

33~

Electromagnetic coil 19 is dispoæd in annular cavity 16 OI
pulley 1~. Coil 19 35 contained within annular magnetic coll housing 20 having a U-shaped cross section. Coil housing 20 is ~ixed to supporting plate 21 which is secured to compressor housing lOa.
Coil housing 2(l is thus maintained within cavity 16 out oi contact wlth pulley 14 by a small gap.
A hub 22 is secured to an ex~ending terminal end OI shaft 13.
Hub 22 has a radial Ilange portion 221 extending radially outward.
Ring plate or armature plal:e 23 is disposed ad~acent the outer peripheral sur~ace OI flange por~ion 221 with an annular radial gap therebetween~ Armature plate 23 iaces the axial end plate portion 143 o~ pulley 14 with a predetermined axial air gap ~herebetween.
In this construction, holder plate 24 Is fixsd o~ the outer a~dal end su~ace of armature plate 23 by a plurality oi rivets 25. Holder plate 24 is provided with a first a~al Ilange 241 whi~h extends axially outward irom the inner end portion oi plate 24 and is formed in a triangula~ shape. An arc shaped disc portion 243 extends radi-ally outward at one side oi trlangular flange 241, as shown ln Figure 4. Each straight ~ne portion of triangular Slange 241 is connected with on~ another through an arc~haped corner. The configuration OI ~lange 241 thus consls~s oE a plurality of line and arc portions.
Axlal gap 26 is Iormed betwe~n the axial end surface OI armature plate 23 and the axial end portion of flange 241, as shown in Figure 3.
Hub 22 is iormed wlth second axial flange portion 222 which extends axially outward from the outer end portion oI radial flange portlon 221. Second axial flange portlon 222 corresponds in shape to 9~35 Ilange portion 241 and Iaces ~lange 2~1 with a radial gap therebetween.
Elastic member 27, i.e., a rubber member, is dispo~ed in the gap deIined betwe~n the inner suriaces OI flange portions 222 and 241. The lnner surfa~e oi elastic member 27 is fixed on the outer sur~a¢e o~ axial ilange portion 222 o~ hub 22 by vulcani ation, and elastic member 27 is fixectly dispoæd within the gap so as to urged radially inward by axial flange 241. Alternatlvely, iY first and s~cond fixed ~lange portions ?42, 223 are Yormed on the outer te~
minal end m first a2~a~ Ilange 241 and the outer termin31 end ot radial ~lange 221, respectively, to restrl~t the axial movement o~
elastic membsr 2~, elastlc member 27 will be able to maintain its position in the radial gap without the use any special a~fixing method. Ther~ore, armature plate 23 maintains its static position to i ace the a~al end plate portion 143 with an axial air gap there~etween by the recoil strength oi elastic member 27.
In thi~ construction, if coil 19 is not energi~ed, armature plate 23 Is separated irom pulley 14 by the reeoil strength of elastis~
member 27 and maintain~ the desired air gap. Thereioret only puUey 14 w~ be driven by the engine oî the automob~e, and the compressor wlll not be operated. When coil lg is energized, how-ever, armature plate 23 is attracted to pulley 14 by the magnetic Il~ which is created by the energization o~ ~o~ 19 and indicated by th2 dotte~l lina ln Flgure 3 and elastic m~mber 27 is bent ln the axial direction. The rotating motion o~ the au~omotive engine ls transmit-ted to drive shait 13 OI the compressor through puL~ey 14, armature plate 23, holder plate 24, elastic member 27 and hub 22.
At the moment armature plate 23 contact~ the axial end plate portion 143 oi pulley 14, elastic member 27 receives an impact iorce ,., ~
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causecl by the torque o~ holder plate 24. However, the lmpact rOrce is eased by the deIormatlon o~ elastic member 27. That ~s, relative rotating motion ~etween the a~cial rlanges is limited and excessive shearing stress actlng on the rubber member wlll be reduced to thereby prevent the rubber member irom becoming damaged.
Elastic mernber 27 ~s provided with extended portions 271 whlch extend radially inward at each corner thereoI. Extendlng portions 271 ar~ ~ixedly disposed between iirst radial ~lange pornon 2~1 o~ hu~ 22 and the outer end sur~ac~ of armature plate 23 by se~uring rivets 25~ These portions help to ensure tha~ the rubber member w~ not move. ~ order to redu~e the temperature o~ rubber member 27 during operation ~ the devlce, communicat1ng holes 272 are iormed through each corner to allow air to ~low bgtwe~D the axial gap a6 and ambient space. ThereIore, heat iatigue OI rubber member 2~ wlll be reduced.
Thi~ lnvention has been des~ribed in detail in connection with the preferred embodlments only and the inv~ntion is not r~tricted thereto. It ~rlll be easily unde~stoodl by those skllled in the art that other variations can be made within ths scope oi the lnven~ion.

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Claims (10)

1. In an electromagnetic clutch comprising a first rotatable member having an axial end plate of magnetic material, a second rotatable member and an armature plate of magnetic material joined to the second rotatable member so as to be capable of limited axial movement, said armature plate facing said axial end plate of said first rotatable member with an axial air gap therebetween, and an electromagnetic means associated with said axial end plate for attracting said armature plate into engagement with said axial end plate whereby the rotation of said first rotatable member can be transmitted to said second rotatable member through said armature plate by the operation of said electromagnetic means, the improvement comprising: a holder plate affixed to the outer axial surface of said armature plate and formed with a first axial flange portion extending outwardly from said armature plate, said first axial flange portion having a configuration including at least one straight line, said second rotatable member having a second axial flange portion extending outwardly from said armature plate, said first and second axial flange portions having inner and outer surfaces facing one another with a radial gap therebetween, said first axial flange portion having a radial flange at one end thereof extending toward said second axial flange portion, said second axial flange portion having a radial flange at an end opposite said one end of said first axial flange portion extending toward said first axial flange portion, and elastic means disposed between the inner and outer surfaces of said axial flange portions and said radial flanges within the radial gap for limiting the relative rotation between said first and second axial flange portions by the compression of said elastic means when said armature plate engages said axial end plate upon operation of said electromagnetic means.

2. The electromagnetic clutch of Claim 1 wherein said elastic means is formed with at least one hole to allow for the flow of air.

3. The electromagnetic clutch of Claim 1 wherein said first and second flange portions are substantially triangular in shape.

4. The electromagnetic clutch of Claim 3 wherein each corner of each of said flange portions is substantially arc shaped.

5. The electromagnetic clutch of Claim 1 wherein each of said flange portions is formed of a plurality of arc-shaped portions and straight portions.

6. The electromagnetic clutch of Claim 5 wherein each of said flange portions is formed of three generally straight lines.

7. The electromagnetic clutch of Claim 1 wherein said elastic means has at least one extended portion which extends between said second flange portion and said armature plate.

8. The electromagnetic clutch of Claim 1 wherein said elastic means includes a polygonal cross section.

9. The electromagnetic clutch of Claim 8 wherein the polygonal cross section is square.

10. The electromagnetic clutch of Claim 1 wherein said elastic means forms a loop disposed within the radial gap.