WINDOW REGULATOR

FIELD OF THE INVENTION

[0001] The present invention relates to window regulators for vehicles and more particularly to systems for preventing window regulators from being back driven.

BACKGROUND OF THE INVENTION

[0002] In a vehicle, certain windows, such as the windows on the vehicle doors, are typically movable between open and closed positions by a window regulator. The window regulator includes a window driving mechanism that is typically either a cable arrangement, or a cross-arm arrangement. The window regulator may be power-driven by an electric motor or may be manually driven by means of a hand crank provided in the interior of the vehicle.

[0003] In instances where a motor is provided, the motor is connected to the window drive mechanism through a gearbox. The motor rotates in a first direction to close the window and rotates in a second, opposing, direction to open the window. In order to prevent an unauthorized person from gaining access to the vehicle, it is important to ensure that the window regulator be configured so as to prevent itself from being back-driven by a person manually pushing the window open.

[0004] In a typical window regulator gearbox the motor output shaft includes a worm gear, which drives another gear, such as a spur gear. In order to prevent the window regulator from being back-driven, the worm gear may have a selected lead angle and/or tooth profile so as to permit the worm gear to drive the spur gear while preventing the spur gear from driving the worm gear (ie. the worm gear is self- locking). Such worm gears, while effective at preventing the back-driving of the window regulator, are relatively inefficient in terms of transferring power from the motor to the rest of the regulator, and may have an efficiency of less than 50%. As a result, the motor used for such regulators is relatively large, relatively expensive, and relatively heavy.

[0005] Additionally, when resisting back-driving, the spur gear may exert a significant thrust on the worm gear, and therefore on the motor output shaft and the motor's armature. In order to resist this thrust, the motor may require a level of customization which increases the cost of the motor.

[0006] It would be beneficial to provide a window regulator that can be driven by a relatively smaller, lighter and/or less expensive motor.

SUMMARY OF THE INVENTION

[0007] In a first aspect, the invention is directed to a motor/drive arrangement for a window regulator in a vehicle, whereby the motor/drive arrangement includes a motor and a gearbox. The gearbox includes a plurality of gears including a final gear, and further includes a back-drive prevention mechanism that is configured to transfer rotational power from the final gear to a gearbox output shaft, and that is also configured to prevent the transfer of rotational power from the gearbox output shaft to the final gear. As a result, neither the motor nor the gear teeth of any of the gears are required to resist back-driving forces. As a result a potential source of failure is eliminated. In some embodiments, all the gears in the gearbox may be high efficiency gears. In particular the first gear in the gearbox may be a high efficiency gear, such as a worm with a relatively high efficiency tooth profile and lead angle. By using a high efficiency gear, the motor used to drive the window regulator may be smaller, may consume less power, may be lighter, and/or may be less expensive.

[0008] In a particular embodiment, the motor/drive arrangement includes a motor having a motor output shaft, a first gear mounted to the motor output shaft, a final gear that is driven at least indirectly by the first gear and that is rotatable about an output axis, a gearbox output shaft that is driven by the final gear for rotation about the output axis, and a plurality of power transfer members positioned about the axis to engage the final gear and the gearbox output shaft and configured to transfer power from the final gear to the gearbox output shaft. The plurality of power transfer members are configured to transfer a circumferential force from the final gear to drive the rotation of the gearbox output shaft, wherein the plurality of power transfer members are configured to prevent the transfer of a circumferential force from the gearbox output shaft to the final gear. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The present invention will now be described by way of example only with reference to the attached drawings, in which:

[0010] Figure 1 is a perspective view of a motor/drive arrangement for a window regulator in accordance with an embodiment of the present invention;

[0011] Figure 2 is an exploded perspective view showing selected portions of the motor/drive arrangement shown in Figure 1 , including a back-drive prevention mechanism; and

[0012] Figure 3 is a perspective sectional view of the back-drive prevention mechanism.

DETAILED DESCRIPTION OF THE INVENTION

[0013] Reference is made to Figure 1 , which shows a motor/drive arrangement 10 for a window regulator 1 1 in accordance with an embodiment of the present invention. The motor/drive arrangement 10 includes a motor 12, a gearbox 14 and a window drive mechanism 15. The motor 12 may be any suitable type of motor, such as a bi-directional stepper motor. The gearbox 14 transfers power from the motor 12 to the window drive mechanism 15. The gearbox 14 includes a first gear 16 (Figure 4) that is on the motor output shaft shown at 18. The first gear 16 may be any suitable type of gear, such as a worm gear. The gearbox 14 further includes a second gear 20 (Figure 1), which may be a bevel gear, that is driven by the first gear 16 (Figure 4). The gearbox 14 further includes a third gear 22 that is fixedly connected to the second gear 20. The third gear 22 drives a fourth gear, shown at 24, which is rotatable about an axis 25. The third and fourth gears 22 and 24 provide a selected level of speed reduction. The third and fourth gears 22 and 24 may have any suitable type of tooth shape such as a herringbone shape. A herringbone shape reduces the amount of thrust applied to the third and fourth gears 22 and 24 and also provides relatively quiet meshing characteristics. Alternatively other gear tooth shapes may be used, such as a spur gear tooth.

[0014] In the embodiment shown the fourth gear 24 is the final gear in the gearbox 14. The fourth gear 24 is connected to a gearbox output shaft 26 through a back-drive prevention mechanism 28 shown in Figure 2. The gearbox output shaft 26 is a separate element from the fourth gear 24 and is concentric therewith, and therefore also rotates about the axis 25. The axis 25 may be referred to as the output axis.

[0015] The back-drive prevention mechanism 28 includes a set of power transfer members 30 which transfer power from the final gear 24 to the gearbox output shaft 25, but prevent power from being transferred from the output shaft 25 to the final gear 24. In this way, the back-drive prevention mechanism prevents the gearbox 14 from being back-driven and thus prevents an unauthorized person from pushing a window open.

[0016] Referring to Figure 3, each power transfer member 30 has a radially inner surface 32, a radially outer surface 34, a first radial surface 36 and a second radial surface 38. The radially inner surface 32 is generally arcuate and is positioned to engage a tangentially-extending power receiving surface 40 on the gearbox output shaft 26. An axially extending projection 42 on the inner surface 32 may optionally be provided, and engages an axially extending recess 43 on the power receiving surface 40. In the embodiment shown, there are six power receiving surfaces 40 about the output axis 25, and there are six power transfer members 30 (ie. one power transfer member 30 for each power receiving surface 40). There could alternatively be more or fewer power receiving surfaces 40 and more or fewer power transfer members 30.

[0017] The radial surfaces 36 and 38 of the power transfer members 30 are engageable by radially extending power driving surfaces 44 and 46 on the final gear 24. When the final gear 24 turns, the power driving surfaces 44 or 46 (depending on which direction the final gear is rotating in) engage the radial surfaces 36 or 38 to drive the power transfer members 30 to turn. The inner surfaces 32 of the power transfer members 30 in turn engage the power receiving surfaces 40 of the gearbox output shaft 26 and drive the rotation of the gearbox output shaft 26. It will be noted that the power transfer members 30 are configured to transfer rotational power to the gearbox output shaft 26 regardless of which direction the final gear 24 is rotating in.

[0018] The radially outer surface 34 is positioned adjacent a stationary member shown at 48, which is a cylindrical wall that is part of the gearbox housing (shown at 50 in Figure 1).

[0019] The power receiving surfaces 40, the power driving surfaces 44 and 46 and the stationary member 48 together define a plurality of chambers 52 which rotate about the output axis 25.

[0020] If an unauthorized user attempts to push the window (not shown) open, the output shaft 26 is urged to rotate by the window drive mechanism 15. In turn, the power receiving surfaces 40 on the output shaft 26 engage the radially inner surfaces 32 of the power transfer members 30 and exert a back-driving force on them, urging the power transfer members 30 to rotate.

[0021] The back-driving force of the power receiving surfaces 40 on the power transfer members 30 however is offset from the centers of mass of the power transfer members 30 and thus results in a moment on the power transfer members 30, urging them to rotate within their chambers 52. The inner surfaces 32 of the power transfer members 30 are arcuate so that the power transfer members 30 can rotate within their chambers 52 as a result of the back-driving force. The rotation of the power transfer members 30 within their chambers 52 causes the power transfer members 30 to jam against the stationary member 48, thereby preventing rotation of the final gear 24. The greater the back-driving force, the greater the urging of the power transfer members 30 into the stationary member 48.

[0022] The gearbox output shaft 26 may have a spline or a keyway on its end for the mounting of a cable drum 54 or some other suitable element from the window drive mechanism 15.

[0023] It will be noted that the gears used in the gearbox 14 can all have high- efficiency configurations, since the gear teeth are not involved in the prevention of the motor/drive arrangement 10 from being back-driven. As a result of the opportunity to use high efficiency gear configurations, the size of the motor 12 used to drive the window regulator 1 1 may be smaller, lighter and/or less expensive than the motor that would be required when low efficiency worm configurations are used on some previously used gearboxes. In embodiments where the motor 12 is lighter than the motor that would otherwise be used, the force it exerts on the components that hold it the vehicle door (not shown) is slammed or in an accident situation is lighter. As a result, the components that hold it in the vehicle door can be made lighter and possibly at lower cost. Additionally, because the motor 12 may use less power, its current draw is lower and so the wires and connections that provide current to the motor 12 may be designed to handle a relatively lower current.

[0024] Additionally, because the gear teeth are not involved in resisting the back-driving force, a significant potential source of failure of the motor/drive mechanism 10 is eliminated. By contrast, in some prior art configurations, the spur gear that is driven by the low-efficiency worm is typically made from a polymeric material and can be a source of gearbox failure when resisting back-driving forces. In prior art configurations, the spur gear could become relatively expensive because it needed to have a robust construction while simultaneously having relatively high- precision manufacturing requirements for the gear teeth. By contrast, the second gear 20 need not have a relatively robust construction since the back-driving force does not reach it. It will be understood that this advantage is achieved regardless of whether the first gear is a high efficiency worm gear, a low efficiency worm gear, or some other kind of gear.

[0025] Additionally, because the worm gear 16 and the motor output shaft 18 are not subject to high thrust forces in situations where an attempt is being made to back-drive the gearbox 14, the motor 12 does not need to be configured to resist thrust and may be less expensive as a result. It will be understood that this advantage is achieved regardless of whether the first gear is a high efficiency worm gear, a low efficiency worm gear, or some other kind of gear.

[0026] Additionally because the motor 12 may produce relatively low power, it may be smaller than the motors used in prior art regulators, and so the overall space consumed by the motor/drive arrangement 10 may be relatively small, which is advantageous when designing vehicle closure panels (eg. doors) which can have many components competing for space in a relatively small contained volume.

[0027] In an alternative embodiment, some other type of back-drive prevention mechanism may be used, such as a wound spring clutch (not shown), for preventing the output shaft 26 from driving the final gear 24.

[0028] The wound spring clutch operates such that rotation of the motor output shaft 18 compresses a spring which permits rotation of the gears. When a back-driving force is applied the spring is forced into a binding condition preventing rotation of the gears.

[0029] While the above description constitutes a plurality of embodiments of the present invention, it will be appreciated that the present invention is susceptible to further modification and change without departing from the fair meaning of the accompanying claims.