Power actuator having an electromagnetic clutch assembly

Information

  • Patent Grant
  • 6237737
  • Patent Number
    6,237,737
  • Date Filed
    Friday, December 3, 1999
    25 years ago
  • Date Issued
    Tuesday, May 29, 2001
    23 years ago
Abstract
The present application discloses a power actuator that has a motor having a rotatable motor output member and a clutch assembly. A stamped, cup-shape ferromagnetic coil casing has a generally radially extending base wall and an annular side wall extending generally axially from the base wall. An annular ferromagnetic flux intensifying washer is positioned adjacent to the base wall of the coil casing. An annular coil of electroconductive material is disposed within the casing with the side wall extending in surrounding relation with respect to the coil such that the field generated by the coil flows generally radially through the base wall and generally axially through said side wall. A ferromagnetic armature is in sliding relation with the annular coil and movable between an engaged position and a disengaged position.
Description




FIELD OF INVENTION




The present invention relates to a power actuator having an electromagnetically actuated clutch assembly and more particularly to a power actuator having an electromagnetically actuated clutch assembly for use with a latch assembly for a vehicle closure panel.




BACKGROUND OF THE INVENTION




Conventional vehicle closure panels, such as mini-van sliding doors and lift gates, carry a latch assembly that includes a latch member that cooperates with a striker on the vehicle body to retain the panel in a closed position. A manually operated lever or the like is provided to enable a user to release the latch member, thereby enabling the panel to be moved into an open position.




In addition, it is known in the art to provide such latch assemblies with a power operation feature to ensure that the panel is securely and tightly closed. More specifically, these latch assemblies have a power actuator that functions to cinch the panel from an initially closed position to a fully closed position. Typically, the way that these power operated latch assemblies work is that the panel is moved in a closing manner, either manually or under power, towards and into an initially closed position whereat the latch member cooperates with the striker to retain the panel in that position. Then, power is supplied to the power actuator, which responsively moves the latch member in a cinching action to move the panel into its fully closed position. During this cinching action, a motor within the actuator drives the latch member so that it cooperates with the striker to fully close the panel.




To unlatch and open the panel, the user simply actuates the lever to release the latch member, as in conventional latch assemblies. The problem with the powered latch assembly arrangement is that such movement of the latch member back-drives the actuator motor, thereby creating resistance and making such movement somewhat difficult. To remedy this problem, a clutch assembly may be used to uncouple the latch member and the actuator motor, thus obviating the back driving problem. One type of clutch assembly that it would be desirable to use in this context is an electromagnetic clutch assembly. The use of an electromagnetic clutch assembly is desirable as a result of its low cost and reliable performance. From a commercial standpoint, the design of such an electromagnetic clutch assembly must be compact enough for use in the motor vehicle. Further, the material and manufacturing costs of the electromagnetic clutch assembly must be kept relatively low in order to keep the overall costs of the latch assembly at a competitive economic level.




The use of a stamped coil casing for an electromagnetic clutch is preferred because stamping allows the casing to be manufactured relatively inexpensively at a high production rate. However, the use of a stamped coil casing creates a problem with the flux of the magnetic field. Specifically, the overall cross-sectional area of the base wall decreases towards the center thereof. As a result, the base wall provides significantly less cross-sectional area for the flux to flow through at the center thereof than at the radial outer edge thereof. This creates an area of low permeability towards the center of the base wall, which in turn restricts the overall intensity of the magnetic field. Stated differently, the base wall creates a “bottleneck” towards the center thereof. One way to eliminate this bottleneck and increase the field intensity would be to increase the thickness of the base wall, thereby increasing its effective cross-sectional area. However, this results in the overall thickness of the casing being increased. This is undesirable because it increases the overall weight and manufacturing costs associated with the casing.




Alternatively, the casing could be manufactured only with the base wall thereof being provided with an increased thickness. However, this alternative construction cannot be stamped and thus any cost-savings realized by stamping would be lost.




SUMMARY OF THE INVENTION




It is therefore an object of the present invention to provide a low cost power actuator for use in a power latch assembly of a vehicle closure panel.




To achieve this object, the present invention provides a power actuator for a latch assembly having a latch member movable between (a) a released position wherein the latch member is disengaged from a striker to permit a closure panel of the vehicle to move between open and closed positions, (b) an initially latched position wherein the latch member cooperates with the striker to maintain the closure panel in a partially closed position, and (c) a fully latched position wherein the latch member cooperates with the striker to maintain the closure panel in a fully closed position.




The power actuator has a motor having a rotatable motor output member and a clutch assembly. The clutch assembly has a rotatable clutch output member. A stamped, cup-shaped ferromagnetic coil casing has a generally radially extending base wall and an annular side wall extending generally axially from the base wall. An annular ferromagnetic flux intensifying washer is positioned adjacent to the base wall of the coil casing. An annular coil of electroconductive material is operable to selectively generate a magnetic field. The coil is disposed within the casing with the side wall extending in surrounding relation with respect to the coil such that the field generated by the coil flows generally radially through the base wall and generally axially through said side wall. A ferromagnetic armature is in sliding relation with the annular coil and movable between (a) an engaged position wherein the armature couples the motor output member and the clutch output member together so that energization of the motor rotatably drives the clutch output member and (b) a disengaged position wherein the motor output member and the clutch output member are uncoupled to enable the clutch output member to rotate without resistance from the motor. Selective energizing of the coil effects movement of the armature between the engaged and disengaged positions thereof.




The present invention provides an annular ferromagnetic flux intensifying washer positioned adjacent to the base wall of the coil casing to minimize the “bottleneck” problem. The washer increases an amount of ferromagnetic material in the portion of the magnetic field where the base wall is located so as to increase a magnetic permeability of the portion of the magnetic field without increasing the thickness of the base wall. As a result, the casing can be manufactured by a low cost stamping operation without sacrificing the strength or intensity of the magnetic field.











BRIEF DESCRIPTION OF THE DRAWINGS





FIG. 1

is an exploded view of a power actuator constructed in accordance with the principles of the present invention; and





FIG. 2

is a cross-sectional view of the power actuator of

FIG. 1

taken along the rotational axis of the electromagnetic clutch assembly.











DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE INVENTION





FIG. 1

illustrates a clutch assembly, generally indicated at


50


, in exploded view and

FIG. 2

shows a cross sectional view taken along the rotational axis of the clutch assembly


50


. The clutch assembly


50


is mounted within a housing, generally indicated at


51


, comprising two complementary housing halves


52


,


54


that are secured together by a plurality of fasteners


56


inserted through fastener receiving openings


58


. Each housing half


52


,


54


is molded from plastic and has a motor housing half-portion


60


,


62


and a clutch assembly housing half-portion


64


,


66


that cooperate to define a motor housing portion (not shown) and a clutch assembly housing portion


68


, respectively.




The motor housing portion houses a conventional electrically powered D.C. motor


70


mounted therein. The motor


70


has a rotatable output member in the form of a worm gear


72


. A motor guiding portion


74


formed integrally with the housing half


66


has a slot


76


formed therein. The motor


70


is mounted below the guiding portion


74


with the worm gear


72


extending through the slot


76


. The slot


76


properly guides and aligns the worm gear


72


into its proper position during assembly and maintains the worm gear


72


in position during operation.




The housing half


66


has first and second fixed gear mounting shafts


78


,


80


mounted thereto in spaced apart relation. The gear mounting shafts


78


,


80


extend generally perpendicularly to the axis of the worm gear


72


. A first combination gear


82


comprising a helical gear portion


84


and a pinion gear portion


86


formed integrally together is rotatably mounted on the second gear mounting shaft


80


. The helical gear portion


84


has a greater diameter than the pinion gear portion


86


. The helical gear portion


84


is engaged with the worm gear


72


in an intermeshed relationship such that motor driven rotation of the worm gear


72


causes rotation of the first combination gear


82


.




A second combination gear


88


is rotatably mounted to the first gear mounting shaft


78


. The second combination gear


88


comprises a large pinion gear portion


90


and a small pinion gear portion


92


formed integrally together. The large pinion gear portion


90


is engaged with the pinion gear portion


86


of the first combination gear


82


such that rotation of the first combination gear


82


(as a result of the worm gear


72


being rotated by the motor


70


) rotates the second combination gear


88


. It should be noted that the combination gears


82


,


88


and the worm gear


72


are always engaged together in intermeshing relationships so that the motor


70


rotatably drives all three. Thus, these three gears could be broadly considered to function together as the motor output.




The clutch assembly


50


comprises an input pinion gear


94


rotatably mounted to an intermediate portion of a shaft


96


such that the gear


98


can rotate relative to the shaft


96


. The input gear


98


has an opening


95


formed therethrough through which the shaft


96


is rotatably received. A journal bearing


98


(

FIG. 2

) fits into an opening


100


in the actuator housing half portion


66


. One end of the shaft


96


is rotatably mounted inside the journal bearing


98


. The other end of the shaft


96


is fixedly coupled to a rotor


102


by inserting the shaft


96


into a bore


104


formed in one end of the rotor


102


. The fixed relation between the shaft


96


and rotor


102


may be achieved by threaded engagement, adhesive bonding, or any other suitable means.




The teeth


97


on the input gear


94


are engaged with the small pinion gear portion


92


of the second combination gear


88


in an intermeshed relationship such that rotation of the second combination gear


88


rotatably drives input gear


94


. Thus, the input gear


94


serves to input the rotational driving of the motor into the clutch assembly


50


.




The clutch output pinion gear


48


is fixedly mounted on the end of the rotor


102


opposite the shaft


96


. The pinion gear


48


has a bore


106


formed therethrough in which a narrowed portion


108


of the rotor


102


is received in fixed relation. The fixed relation may be achieved by threaded engagement, adhesive bonding, or any other suitable attachment means. Because the input gear


94


is rotatably mounted to the shaft


96


, rotation of the input gear


94


will normally not cause rotation of the shaft


96


, the rotor


102


, or the pinion gear


48


.




The clutch assembly


50


also comprises a magnetic field inducing coil


110


received within the interior of a coil casing


126


. As is conventional with such coils, the coil


110


includes an annular coil receiving portion


112


with an annular base portion


114


and a pair of annular flanges


116


extending outwardly from the base portion


114


. A length of thin extruded copper wire is coated with insulation and wrapped around the coil receiving portion


114


. The wire coiling is shown schematically at


118


in FIG.


2


. When an electric input signal in the form of an electric current is applied to the copper wire, a magnetic field is created or induced around the coil


110


. The role of the magnetic field will be appreciated from the discussion set forth below.




The clutch assembly


50


further comprises an armature


120


. The armature


120


has a plurality of pin receiving openings


122


and the input gear


94


has a plurality of pin receiving openings


124


. The armature


120


is secured to the input gear


94


for rotational movement together about the shaft


96


by inserting a plurality of pins


121


into the pin receiving openings


122


,


124


. These pins


121


allow the armature


120


to move axially relative to the gear


94


between its engaged and disengaged positions, while continuing to rotate together with the gear


94


. The armature


120


is made of a material such as iron or other ferromagnetic materials that will be magnetically attracted towards the coil


110


as a result of the magnetic field induced by the coil


110


. An axial surface of the armature


120


facing away from the pinion gear has a set of engaging teeth


128


spaced circumferentially about the outer radial edge thereof.




The rotor


102


has an engaging portion


130


with a set of engaging teeth


132


formed on one axial face thereof. The teeth


132


are spaced circumferentially about the radial edge of the engaging portion


130


and face the teeth


128


of the armature


120


. The role of the teeth


128


,


132


will become apparent further in the application. The engaging portion


130


also has a downwardly depending portion


136


extending axially into the coil casing


126


.




The actuator housing half


66


has a bore


138


formed therethrough. The interior surface defining the bore


138


has a pair of annular stepped shoulder surfaces


140


,


142


. An annular rubber sealing member


144


is mounted to the shoulder surface


142


. The sealing member


144


prevents moisture from entering the actuator housing


68


and corroding the ferromagnetic components of the clutch assembly


50


. A bearing


146


is mounted in a force fit relation within the bore


138


and engages the shoulder surface


140


. Although the bearing


146


may be plastic, it is preferred that the bearing be made of a ferromagnetic material in order to increase or intensify the flux of the magnetic field produced by the coil


110


. The advantages associated with using ferromagnetic materials to increase the magnetic field flux will be discussed in further detail below.




The rotor


102


is rotatably mounted within the bearing


146


so that the narrowed portion


108


thereof extends outwardly through the housing bore


138


. An annular deformable thrust bearing


148


is placed between the inner end of the bearing


146


and a shoulder surface


150


defined on the rotor


102


. The thrust bearing


148


serves to absorb any axial loads that may be applied to the rotor


102


.




A biasing element in the form of a coil spring


152


is positioned between the armature


120


and a spring bearing surface


154


defined on the rotor


102


. The spring


152


biases the armature


120


away from the magnetic coil


110


. A ferromagnetic flux increasing washer


160


slidably fits over the bearing


146


and is positioned against an interior wall surface


162


of housing half


66


. The flux increasing washer


160


is located between the casing


126


and the interior wall surface


162


. It is contemplated, however, that the flux increasing washer


160


could also be located interiorly of the casing


126


. The flux increasing washer


160


may be secured in place by “heat staking” the housing halves after assembling them together. This heat staking deforms portions of the plastic housing inwardly so as to extend over the upper face (as viewed in

FIG. 2

) of the washer


160


and retain the same against interior wall surface


162


.




When the electric input signal is applied to the coil


110


, the magnetic field is generated. The field magnetically attracts the armature


120


toward the coil


10


and into an engaged position. In this engaged position, the teeth


128


of the armature


120


are engaged with the teeth


132


of the rotor


102


, thus coupling the armature


120


and the rotor


102


together. The rotation of the input gear


94


and the armature


120


will thus cause rotation of the shaft


96


, rotor


102


, and output pinion gear


48


in the engaged position. When the electric input signal is removed from the coil


110


, the magnetic field will no longer be created or induced and the spring


152


will bias the armature


120


axially away from the coil


110


to a disengaged position wherein the teeth


128


,


132


of the armature


120


and the rotor


102


are disengaged. In the disengaged position, no power from the motor


70


is transmitted to the output pinion gear


48


and the pinion gear


48


is in a ‘free-wheeling’ mode in which the gear


48


is allowed to rotate freely without any resistance being provided by the motor


70


.




The flux increasing washer


160


is particularly advantageous in this particular application because it is a simple and low cost way of increasing the flux of the magnetic field created by the coil


110


. Air and other substances such as rubber and plastic have a high reluctance (low permeability) to passing magnetic fields in comparison to ferromagnetic materials. Thus, the flux of a magnetic field flowing through a ferromagnetic material is greater than the flux of a magnetic field flowing the air. This reluctance is somewhat analogous to resistance in an electric circuit—the greater the resistance of a component, the less current will flow therethrough.




Applying these principles to the present subject matter, it can be appreciated that the flux of the magnetic field can be increased by increasing the amount of ferromagnetic material in the areas adjacent the coil


110


. Thus, the casing


126


, the armature


120


, the rotor


102


, the shaft


96


, and the bearing


146


, are all made of ferromagnetic material to enhance the magnetic field's flux. In order to further the increase the flux there are at least two ways to do so.




First, the coil


110


could be made larger. However, increasing the coil size is expensive because of the high cost of the insulated thin extruded copper wire which comprises the wire coiling


118


. Also, the price of copper can often fluctuate and such fluctuation imposes an uncertainty into the cost of manufacturing the coil


110


and hence the entire clutch assembly


50


. Second, the amount of ferromagnetic material in the magnetic field could be increased, thus decreasing the amount of air and its associated high reluctance and increasing the field's flux. One way to increase the amount of ferromagnetic material would be to increase the thickness of the casing


126


. However, increasing the thickness of either or both of these components not only increases the size of the overall assembly, but also increases manufacturing costs. Specifically, it is contemplated that the coil casing


126


is to be formed by stamping and increasing the thickness of this component makes it more difficult to stamp. Also, because the casing


126


is typically stamped from sheet of uniform thickness, in order to increase the thickness of one section, the thickness of the entire component must be increased, thereby further increasing the size, weight, and cost of the assembly.




The ferromagnetic flux increasing washer


160


provides a low-cost and simple solution to this problem. The cost of providing an iron or steel flux increasing washer


160


is very low in comparison with the costs associated with increasing the thickness of other components in the assembly or increasing the size of the coil


110


and increases the flux of the magnetic field. In fact, it has been found that providing such a washer


160


approximately quadruples the field flux in comparison to an identical clutch assembly assembled without the washer


160


.




The power actuator of the present application may be used in combination with a power sliding door, such as is disclosed in PCT Patent Appln. of Murray et al., No. WO 99/09282, the entirety of which is hereby incorporated into the present application by reference. Also, the power actuator of the present application may be used in combination with a power lift gate, such as is disclosed in U.S. Pat. No. 5,851,050, the entirety of which is hereby incorporated into the present application by reference.




It is to be understood that the above-described embodiment has been provided to illustrate the structural and functional principles of the present invention and is not intended to be limiting. To the contrary, the present invention is intended to cover any and all modifications and alterations.



Claims
  • 1. A power actuator comprising:a motor having a rotatable motor output member; a clutch assembly comprising: a rotatable clutch output member, a stamped, cup-shaped ferromagnetic coil casing having a generally radially extending base wall and an annular side wall extending generally axially from said base wall, an annular ferromagnetic flux intensifying washer positioned adjacent to the base wall of said coil casing, an annular coil of electroconductive material operable to selectively generate a magnetic field, said coil being disposed within said casing with said side wall extending in surrounding relation with respect to said coil such that the field generated by said coil flows generally radially through said base wall and generally axially through said side wall, a ferromagnetic armature in sliding relation with said annular coil and movable between (a) an engaged position wherein said armature couples said motor output member and said clutch output member together so that energization of said motor rotatably drives said clutch output member and (b) a disengaged position wherein the motor output member and said clutch output member are uncoupled to enable the clutch output member to rotate without resistance from said motor, whereby selective energizing of said coil effects movement of said armature between said engaged and disengaged positions thereof.
  • 2. A power actuator according to claim 1, wherein said clutch assembly further comprises a spring engaging said armature biasing said armature towards and into the disengaged position thereof.
  • 3. A power actuator according to claim 2, wherein said clutch assembly further comprises a rotatable rotor fixed to said clutch output member for rotation therewith and a rotatable clutch input member that rotates along with said armature which engages with said motor output member such that rotation of said motor output member rotates said clutch input member, said armature being axially movable relative to said input gear between the engaged and disengaged positions thereof,said rotor and said armature having opposing axial faces that engage one another when said armature is in said engaged position thereof to thereby couple said clutch output member and said motor output member together as aforesaid as a result of said rotor being fixed to said clutch output member, said armature rotating along with said clutch input member, and said clutch input member being engaged with said motor output member.
  • 4. A power actuator according to claim 3, wherein said motor output member, said clutch input member, and said clutch assembly output member are each toothed gears.
  • 5. A power actuator according to claim 4, further comprising a pair of intermediate gears engaged in an intermeshing relationship between said motor and said motor output member.
  • 6. A power actuator according to claim 5, wherein said rotor provides a spring bearing surface and wherein said spring engages both said spring bearing surface and said armature.
  • 7. A power latch comprising in combination:a latch assembly having a latch member movable between (a) a released position wherein the latch member is disengaged from a striker to permit a closure panel of the vehicle to move between open and closed positions, (b) an initially latched position wherein the latch member cooperates with the striker to maintain the closure panel in a partially closed position, and (c) a fully latched position wherein the latch member cooperates with the striker to maintain the closure panel in a fully closed position, and a power actuator comprising: a motor having a rotatable motor output member; a clutch assembly comprising: a rotatable clutch output member operably connected to said latch member, a stamped, cup-shaped ferromagnetic coil casing having a generally radially extending base wall and an annular side wall extending generally axially from said base wall, an annular ferromagnetic flux intensifying washer positioned adjacent to the base wall of said coil casing, an annular coil of electroconductive material operable to selectively generate a magnetic field, said coil being disposed within said casing with said side wall extending in surrounding relation with respect to said coil such that the field generated by said coil flows generally radially through said base wall and generally axially through said side wall, a ferromagnetic armature in sliding relation with said annular coil and movable between (a) an engaged position wherein said armature couples said motor output member and said clutch output member together so that energization of said motor rotatably drives said clutch output member to drive said latch member to the fully latched position and (b) a disengaged position wherein the motor output member and said clutch output member are uncoupled to enable the clutch output member to rotate without resistance from said motor, whereby selective energizing of said coil effects movement of said armature between said engaged and disengaged positions thereof.
  • 8. The combination according to claim 7, wherein said clutch assembly further comprises a spring engaging said armature biasing said armature towards and into the disengaged position thereof.
  • 9. The combination according to claim 8, wherein said clutch assembly further comprises a rotatable rotor fixed to said clutch output member for rotation therewith and a rotatable clutch input member that rotates along with said armature which engages with said motor output member such that rotation of said motor output member rotates said clutch input member, said armature being axially movable relative to said input gear between the engaged and disengaged positions thereof,said rotor and said armature having opposing axial faces that engage one another when said armature is in said engaged position thereof to thereby couple said clutch output member and said motor output member together as aforesaid as a result of said rotor being fixed to said clutch output member, said armature rotating along with said clutch input member, and said clutch input member being engaged with said motor output member.
  • 10. The combination according to claim 9, wherein said motor output member, said clutch input member, and said clutch assembly output member are each toothed gears.
  • 11. The combination according to claim 10, further comprising a pair of intermediate gears engaged in an intermeshing relationship between said motor and said motor output member.
  • 12. The combination according to claim 11, wherein said rotor provides a spring bearing surface and wherein said spring engages both said spring bearing surface and said armature.
Parent Case Info

The present application claims priority to U.S. Provisional Application of Jorgensen et al., Serial No. 60/110,728, filed Dec. 3, 1998, the entirety of which is hereby incorporated into the present application by reference.

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Provisional Applications (1)
Number Date Country
60/110728 Dec 1998 US