Abstract
A vehicle door checker integrated with a power drive unit for an automobile door includes a direct current permanent magnet electric motor subject to cogging torque. The electric motor includes a central shaft. The vehicle door checker also includes a cogging torque increase device that is mounted to the central shaft externally of the motor. The cogging torque increase device includes pairs of oppositely magnetized permanent magnets that are mounted coaxially in a stator and rotor respectively about the motor shaft. The stator magnets and the rotor magnets shift into and out of alignment with each other as the shaft is rotated such that the motor is held in multiple discrete stable positions that correspond to check positions of an automobile door.
Claims
1. A vehicle door checker integrated with a power drive unit for an automobile door comprising: a direct current permanent magnet electric motor subject to cogging torque; the electric motor comprising a central shaft; a cogging torque increase device mounted to the central shaft externally of the motor; the cogging torque increase device comprising pairs of oppositely magnetized permanent magnets mounted coaxially in a stator and rotor respectively about the motor shaft wherein the stator magnets and the rotor magnets shift into and out of alignment with each other as the shaft is rotated; and such that the motor is held in multiple discrete stable positions corresponding to check positions of an automobile door.
2. The vehicle door checker integrated with a power drive unit of claim 1 further comprising: a. a gear system driven by the central shaft; b. at least one lever arm rotated by the gear system; c. a link arm which reciprocates under the control of the lever arm to open and close a vehicle door.
3. The power drive unit of either of claim 1 or 2, wherein the oppositely magnetized pairs of magnets are located respectively on a multi-pole stationary outer magnet and a multi-pole rotating inner magnet.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] The disclosure can be further understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:
[0014] FIG. 1 is a schematic cutaway perspective view of an automotive side door and body pillar joined by hinges and configured to open and close using a power drive unit with a DC electric motor.
[0015] FIG. 2 is a schematic perspective view of the power drive unit DC electric motor, a gear assembly and a link rod.
[0016] FIG. 3 is a schematic perspective partially cutaway view of the power drive unit showing the gear train in further detail.
[0017] FIG. 4 is a schematic perspective partially cutaway view of the DC motor with an intermediate cogging device driving the gear train and the reciprocating link rod.
[0018] FIGS. 5A and 5B are schematic elevation views showing the cogging device mounted to either end of the DC motor.
[0019] FIG. 6 is a perspective view of the DC motor showing its rotor, stator and magnetic flux lines.
[0020] FIG. 7 shows the maximum cogging effect A and the minimum cogging effect B generated by the DC motor.
[0021] FIG. 8 is a perspective view of the cogging device mounted to the DC motor.
[0022] FIG. 9 is a perspective schematic partially cutaway view showing the opposing device magnets aligned and the attractive force between opposing magnets of the cogging device.
[0023] FIG. 10 illustrates the minimum torque generated when the opposing magnets of the cogging device are aligned as in FIG. 9.
[0024] FIG. 11 is a perspective schematic partially cutaway view showing the opposing device magnets misaligned and the attractive force between opposing magnets of the cogging device.
[0025] FIG. 12 illustrates the maximum torque generated when the opposing magnets of the cogging device are misaligned as in FIG. 11.
[0026] FIG. 13 is a perspective partially exploded view of the cogging device mounted to an end of the DC motor with a rotor, stator and individual permanent magnets.
[0027] FIG. 14 is a perspective partially see-through view of the DC motor with the assembled cogging device mounted to an end thereof.
[0028] FIG. 15 illustrates the torque generated by the DC motor alone, by the cogging device alone and by the combination thereof.
[0029] FIG. 16A is a schematic representation of external and internal multi-pole magnets in an alternative embodiment of the cogging device showing the attractive force between aligned opposing oppositely magnetized segments generating cogging force B.
[0030] FIG. 16B is a schematic representation of external and internal multi-pole magnets in the alternative embodiment of the cogging device showing the attractive and repulsive forces between misaligned oppositely magnetized segments generating cogging force A.
[0031] FIG. 16C illustrates the torque generated with the multi-pole magnets in the orientations illustrated in FIGS. 16A and 16B.
[0032] The embodiments, examples and alternatives of the preceding paragraphs, the claims, or the following description and drawings, including any of their various aspects or respective individual features, may be taken independently or in any combination. Features described in connection with one embodiment are applicable to all embodiments, unless such features are incompatible.
DETAILED DESCRIPTION
[0033] An illustrative embodiment of the invention may be described with reference to the drawings.
[0034] Referring to FIG. 1, an automotive door system comprises a door 1 rotationally mounted to a body pillar 3 via hinges 5. The door 1 may be automatically opened and closed by means of a power drive unit 7 under the operation of a control unit 9. The power drive unit 7, driven by a DC electric motor 11, causes a link rod 13 to move the door 1 from fully closed to fully open and to various positions there between. The power drive unit 7 also maintains the door 1 in these various orientations.
[0035] Referring to FIGS. 2, 3 and 4, the link rod 13 is driven back and forth to control the position of the door 1 by the DC electric motor 11 which is connected to the link rod 13 via a lever arm 10 and a gear train 15. A worm gear 17 driven by the electric motor 11 advantageously drives the gear train 15. The reciprocating movement of the link rod 13 is represented by the letter X and the arrows in FIG. 4. A cogging device 19 may be located between the electric motor 11 and the gear train 15, as illustrated schematically in FIG. 5A, or may alternatively be located at the distal end of the motor 11, as illustrated in FIG. 5B. The door 1 is held in position by a resistive torque from the DC motor 11 known as cogging torque. This torque is increased by the gear train ratio and efficiency of the gear train 15, which may be tuned to achieve the desired effect, to produce a sufficient resistance to maintain the selected position of the door 1. This resistance is known as the back-drive torque, or the torque sufficient to drive the electric motor 11 in a reverse direction.
[0036] A typical DC permanent magnet electric motor 11 is illustrated in FIG. 6 in a stable position. The rotor 21 is aligned with the magnetic field produced by the stator 23 comprising four permanent magnets in this configuration. Magnetic flux lines Y are shown schematically. The torque required to rotate the rotor 21 from this stable position is called the cogging torque. FIG. 7 illustrates a notional generated torque of zero at the stable position and a notional cogging torque of 1.0 with the rotor and stator at the point of maximum misalignment of the magnetic fields.
[0037] In some situations such as extreme vehicle orientations, however, the cogging torque of the motor 11 is not sufficient to hold the door 1 in its selected position. In these circumstances, a higher cogging torque is desirable.
[0038] Referring to FIGS. 8 and 9, in order to enhance the cogging effect of a typical DC motor, a torque increasing cogging device 19 may be fitted to the motor 11. The cogging device 19 comprises pairs of permanent device magnets 27, 29 in order to increase the cogging torque of the DC motor 11. The most desirable location for additional cogging torque is adjacent the motor 11 since such torque is multiplied by the gear ratio and gear train 15 efficiency to provide the door holding torque. An external set of magnets 27 align with an internal set of oppositely polarized or magnetized magnets 29. Since the oppositely polarized magnets attract, the cogging device 19 is in a stable position when the pairs of magnets 27, 29 are aligned. The attractive force between pairs of magnets 27, 29 is represented by the letter Z and the arrows in FIG. 9. Cogging torque is generated by displacing the magnets from their aligned positions. FIG. 10 again illustrates schematically the variation in torque as the pairs of magnets 27, 29 move into and out of alignment through 360 degrees of rotation. The torque is zero when the device magnets 27, 29 are aligned as in FIG. 9 as represented by point C. The maximum cogging force in FIG. 10 is greater than that in FIG. 7 owing to the addition of the effect of cogging device 19 to the cogging effect of the DC motor 11.
[0039] FIG. 11 illustrates the pairs of magnets 27, 29 at maximum misalignment. Again, the attractive force between oppositely polarized pairs of magnets is illustrated by the letter Z and the arrows. The potential energy is greatest when the magnets 27, 29 are at maximum displacement and misalignment. The cogging force in the maximum unstable position is shown by letter D in FIG. 12.
[0040] FIG. 13 is a partial explosion view of the cogging device 19 which has its own stator 31, into which permanent magnets 27 are mounted, and rotor 33, into which permanent magnets 29 are mounted.
[0041] FIG. 14 illustrates an optimized orientation of the cogging device 19 with the external magnets 27 aligned to the DC motor 11 to increase the cogging torque of the system. Additional cogging torque may result in increased electrical current consumption of from about 2% to 50% depending on the speed of motor 11. In a typical motor operating range for the power door opening and closing function, however, the electrical current increase tends to be in the range of 5% to 8%. Thus, the additional cogging effect owing to the use of cogging device 19 does not adversely affect the operation of the DC motor 11.
[0042] FIG. 15 illustrates the motor torque E generated by the cogging effect of the DC electric motor 11, the cogging device torque F generated by the cogging device 19, and the total cogging torque G generated by the combined cogging effects of the electric motor 11 and the cogging device 19.
[0043] FIGS. 16A, B and C illustrate an alternative configuration of device magnets in the cogging device 19. Instead of employing discrete permanent magnets 27, 29, each with a single dipolarity, circular multi-pole magnets arranged concentrically may be employed. FIG. 16A illustrates such an array of multi-pole magnets with a circular external multi-pole magnet 35 comprising alternating North and South polarity segments concentric about a smaller diameter internal multi-pole magnet 37 also comprising alternating North and South polarity segments. In FIG. 16A, with opposing North and South polarity segments of the respective multi-pole magnets 35, 37 aligned, the position is stable. The attractive force between opposite polarity sections of the opposing multi-pole arrays is again represented by the letter Z. In FIG. 16B, with opposing North and South polarity segments of the respective multi-pole magnets 35, 37 misaligned, the position is unstable. The attractive force Z and the repulsive force R are not oriented coaxially. The stable position B of FIG. 16A corresponds to positions of minimum torque in FIG. 16C. The unstable position A corresponds to positions of maximum torque in FIG. 16C.
[0044] It should also be understood that although a particular component arrangement is disclosed in the illustrated embodiment, other arrangements will benefit herefrom. Although particular step sequences are shown, described, and claimed, it should be understood that steps may be performed in any order, separated or combined unless otherwise indicated and will still benefit from the present invention.
[0045] Although the different examples have specific components shown in the illustrations, embodiments of this invention are not limited to those particular combinations. It is possible to use some of the components or features from one of the examples in combination with features or components from another one of the examples.
[0046] Although an example embodiment has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of the claims. For that reason, the following claims should be studied to determine their true scope and content.
