The invention relates to a bi-directional clutch assembly for electric motors that becomes operational (engages) whenever an output shaft side becomes the driving element.
In a motor having a worm and gear, there is a need to prevent the worm and gear from reaching a back driven condition in the event that an external torque is applied at an output end of a gear arrangement. When such a motor is coupled to a load, a driving torque will act on the motor output drive under certain conditions. This torque can be transmitted from the drive gear to the worm shaft inducing an angular motion on the motor armature (back drive). When this condition is reached, the system ceases to operate as intended; for example, in the case of a window lift motor, this can mean that the window moves downward from an original position without operator intervention under vibration conditions (driving the vehicle). Another scenario causing back drive could be an individual pushing down the glass to gain access to the vehicle.
Currently, controlling a back drive condition is achieved by decreasing the gearing efficiency. However, this results in a negative effect in that the overall system efficiency is decreased as well, possibly requiring a larger motor.
By selectively having the ability to lock the drive system, the efficiency of the worm and gear arrangement can be increased to a higher level, minimizing concerns of back drive.
Thus, there is a need for a bi-directional clutch assembly for electric motors that engages whenever an output shaft side becomes the driving element thereby minimizing back drive.
An object of the invention is to fulfill the need referred to above. In accordance with the principles of the present invention, this objective is achieved by providing a clutch assembly for a motor having an armature shaft and a worm shaft having a worm constructed and arranged to engage a gear. The clutch assembly includes a clutch housing including a race surface; a cam coupled to the worm shaft; follower structure operatively associated with the cam; a clutch plate, and a clutch coupler associated with the clutch plate, the cam, and the follower structure. The coupler is coupled to the armature shaft for rotation therewith, such that rotation of the coupler rotates the clutch plate, the cam and follower structure, and thus the worm shaft. During a back drive condition of the motor, when torque is transmitted to the worm shaft and thus to the cam, the cam is constructed and arranged to causes the follower structure to contact and exert pressure on the race surface thereby preventing rotation of the worm shaft.
In accordance with another aspect of the invention, a method is provided to control back drive in a motor. The motor includes an armature shaft and a worm shaft having a worm constructed and arranged to engage a gear. The method provides a clutch assembly having a clutch housing including a race surface; a cam coupled to the worm shaft; follower structure associated with the cam; a clutch plate; and a clutch coupler associated with the clutch plate, the cam, and the follower structure. The coupler is coupled to the armature shaft for rotation therewith, such that rotation of the coupler rotates the clutch plate, the cam and follower structure, and thus the worm shaft. The method ensures that 1) during a back drive condition of the motor, when the worm shaft is a driving element and when torque is transmitted to the worm shaft and thus to the cam, the cam causes the follower structure to contact and exert pressure on the race surface thereby preventing rotation of the worm shaft, and 2) during a normal operating condition of the motor, when the armature shaft is a driving element, the follower structure does not contact the race surface, thereby permitting the worm shaft to rotate freely.
Other objects, features and characteristics of the present invention, as well as the methods of operation and the functions of the related elements of the structure, the combination of parts and economics of manufacture will become more apparent upon consideration of the following detailed description and appended claims with reference to the accompanying drawings, all of which form a part of this specification.
The invention will be better understood from the following detailed description of the preferred embodiments thereof, taken in conjunction with the accompanying drawings, wherein like reference numerals refer to like parts, in which:
A clutch assembly is shown, generally indicated at 10, in
The support plate 14 can also be considered a clutch plate and includes a central opening 19 to permit the shaft 18 to pass there-through. In addition, the support plate 14 includes two pins 38 extending therefrom and each follower 22 includes an off-center bore 40 there through. Each pin 38 is received in an associated bore 40 to define an eccentric follower. In addition, in the embodiment of
The coupler 24 includes engagement members 25 disposed in spaced relation such that the cam 16 is there-between (
If the motor armature (via shaft 30) is the driving element, the support plate 14, cam 16 and followers 22 have the same relative angular position relative to each other. Thus, as shown in
The support plate 14 is “floating” with relation to all other components and will freely spin when the motor armature is the driving element (via shaft 30). The coupler 24 engages the support plate 14 and cam 16 simultaneously, maintaining the alignment of the followers 22 with respect to the cam 16.
In an initial back drive condition, as shown in
It can be appreciated that mating parts of the support plate 14 and coupler 24 can be reversed.
In general, the clutch assembly 10 can be used in any application involving the use of worm gearing coupled to electric motors. This assembly 10 was configured with automotive window lift applications in mind.
The clutch assembly 100 can be mounted to a housing of a motor, such as a conventional window lift motor for a vehicle, so that the worm shaft meshes with the conventional drive gear (not shown) of the motor.
The clutch plate 114 includes two followers 122 in opposing relation and extending from a body 124 of the clutch plate 114. The followers 122 are preferably molded as an integral part of the clutch plate. In the illustrated embodiment, each follower 122 is connected to the clutch plate 114 by a pair of flexible bridging members 136. Alternatively, for each of molding, each follower 122 can be connected to the clutch plate 114 by single bridging member that defines a living hinge.
If the motor armature is the driving element, the clutch plate 114 with its followers 122, and the cam 116 have the same relative angular position with respect to each other. Thus, as shown in
The clutch plate 114 is “floating” with relation to all other components and will freely spin when the motor armature is the driving element. The engagement members 125 of the coupler 118 engage the clutch plate 114 and cam 116 simultaneously, maintaining the alignment of the followers 122 with respect to the cam 116.
In an initial back drive condition, as shown in
Retaining structure 134, in the form of resilient clips, is integral with the housing 112 to retain the components in the housing 112. In particular, once assembled, the clips 134 engage surface 135 of the coupler (
Since only four components comprise the clutch assembly 100, an electric motor employing the clutch assembly 100 can be configured with a smaller size and with less cost and can be used in the same original application.
In general, the clutch assembly 100 can be used in any application involving the use of worm gearing coupled to electric motors. The assembly 100 was configured with automotive window lift applications in mind.
The desired effect of the use of this clutch assembly 10, 100 is that an increase in the gearing efficiency allows for a smaller motor design, with the desired reduction in system costs.
The clutch assembly 10, 100 utilizes the principle of an overrunning clutch, with the added feature that it becomes operational on both angular directions, as long as the worm and gear become the driving elements. The clutch assembly is configured to be a self-contained unit for ease of assembly in the motor, and it incorporates all the characteristic of a sleeve bearing so it can replace an existing one.
The foregoing preferred embodiments have been shown and described for the purposes of illustrating the structural and functional principles of the present invention, as well as illustrating the methods of employing the preferred embodiments and are subject to change without departing from such principles. Therefore, this invention includes all modifications encompassed within the spirit of the following claims.
This application is based on U.S. Provisional Application No. 60/547,833, filed on Feb. 26, 2004 and U.S. Provisional Application No. 60/551,713, filed on Mar. 10, 2004, and claims the benefit of thereof for priority purposes.
Number | Name | Date | Kind |
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5582279 | Buchanan, Jr. et al. | Dec 1996 | A |
6288464 | Torii et al. | Sep 2001 | B1 |
6390264 | Torii et al. | May 2002 | B1 |
6789443 | Torii et al. | Sep 2004 | B1 |
7032731 | Kim | Apr 2006 | B1 |
Number | Date | Country |
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1101967 | May 2001 | EP |
1101968 | May 2001 | EP |
1122390 | Aug 2001 | EP |
WO 0008350 | Feb 2000 | WO |
WO 0153640 | Jul 2001 | WO |
Number | Date | Country | |
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20050189189 A1 | Sep 2005 | US |
Number | Date | Country | |
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60547833 | Feb 2004 | US | |
60551713 | Mar 2004 | US |