Power actuator system for actuating a closure member

Provided is a power actuator system for actuating a closure member (1) such as a trunk lid which is compact in size and has a minimized protrusion. A first link (8) is connected to an output shaft of a powered actuator (7), and a free end of the first link is connected to an end of a second link (9). The other end of the second link is pivotally connected to a hinge arm (4) which is fixedly attached to a closure member and pivotally supports the closure member to a fixed part such as a vehicle body. The first link is adapted to extend substantially from the output shaft towards the closure member as the first link swing around the output shaft, and the second link extends substantially perpendicularly with respect to the center line.

TECHNICAL FIELD

The present invention relates to a power actuator system for actuating a closure member such as a trunk lid.

BACKGROUND OF THE INVENTION

It is known to actuate a closure member such as a trunk lid by using a power actuator. See Japanese patent laid open publication No. 2002-180738. Such a power actuator system typically comprises an electric motor, a reduction gear unit and a link mechanism. The base end of a first link is fixedly attached to the output shaft of the reduction gear unit, and the free end of the link is connected to the base end of a second link. The free end of the second link is connected to a hinge arm which is in turn fixedly attached to a hinge end of the trunk lid. A damper that resiliently urges the trunk lid in the opening direction is connected between the hinge arm and a part of the vehicle body. By turning the output shaft in each direction, the trunk lid can be opened and closed at will.

In such an arrangement, the load acting upon the power actuator is primarily dictated by the weight of the trunk lid and the thrust of the damper, and varies significantly depending on the angular position of the trunk lid. When the trunk lid is fully closed and is substantially horizontal, although the damper produces a maximum force, the weight of the trunk lid is so dominant that a relatively large torque is required for the actuator to raise the trunk lid from the fully closed position. As the opening angle of the trunk lid increases, the effect of the weight diminishes while the thrust of the damper in the direction to open the trunk lid becomes more pronounced so that a relatively small torque is required for the actuator to further open the trunk lid.

Conversely, when closing the trunk lid from the fully open state, the thrust of the damper is at a minimum value and the load of the weight of the trunk lid acting in the closing direction is also at a minimum because the trunk lid is at a substantially upright position so that the actuator is only required to overcome the small thrust of the damper. As the trunk lid1moves away from the fully closed position, the load acting in the closing direction progressively increases, and a relatively small torque is required to close the trunk lid. When the trunk lid is about to be fully closed, the thrust of the damper acting in the open direction is at a maximum and the reaction force of the weather strip is required to be overcome. Therefore, a substantial torque is required for the actuator to fully close the trunk lid and engages the latch against the resistance of the weather strip.

In such a conventional actuator for a trunk lid, the thrust of the damper is selected in such a manner that the power actuator is required only when moving the trunk lid from the fully closed state to a slightly open state, and the damper provides a force required to move the trunk lid from the slightly open state to the fully open state. Thereby, the torque requirement of the power actuator is minimized, and the power actuator may be designed as a highly compact unit. However, in such an arrangement, it is necessary to adjust the torque output of the power actuator depending on the opening angle of the trunk lid, and this requires a highly complex control arrangement. In particular, it is necessary to provide an angle sensor for detecting the opening angle of the power actuator, and this increases the cost.

When the trunk lid is to be actuated by a power actuator from the fully closed state to the fully open state, no complex control is required, but the power actuator is required to have a relatively large output and this undesirably increases the size of the power actuator. Because the power actuator of this type is required be installed in the limited space of the trunk, the power actuator is required to be as small as possible and any protrusion into the trunk room is desired to be minimized.

BRIEF SUMMARY OF THE INVENTION

In view of such problems of the prior art, a primary object of the present invention is to provide a power actuator system for actuating a closure member such as a trunk lid which is compact in size and has a minimized protrusion.

A second object of the present invention is to provide a power actuator system which has a torque/speed property of a desirable pattern.

A third object of the present invention is to provide a power actuator system which is simple in structure and economical to manufacture.

According to the present invention, at least some of these objects can be accomplished by providing an actuator system for actuating a closure member mounted on a vehicle body via a hinge, comprising: a hinge arm fixedly attached to the closure member at one end and pivotally attached to the vehicle body at a hinge point; a power actuator mounted on the vehicle body and having an output shaft extending substantially in parallel with a pivot axis of the hinge; a first link having a base end fixedly attached to the output shaft; a second link having a base end pivotally connected to a free end of the first link and a free end pivotally attached to the hinge arm; the first link being adapted to extend substantially from the output shaft towards the closure member as the first link swings around the output shaft.

Thereby, the power actuator can be placed close to the closure member at a distance substantially equal to the length of the first link, and there is no protrusion on the side of the power actuator facing away from the closure member. Therefore, the available space within the closure member can be maximized. In particular, if the second link is disposed in such a manner that the closure member turns in an opposite direction from a rotational direction of the output shaft, the link mechanism can be most simplified. Typically, the closure member is fitted with a damper that normally urges the closure member toward the fully open state.

According to the present invention, a particularly favorable link efficiency or a torque/speed property can be achieved if the second link extends substantially perpendicularly to a line extending from the output shaft toward the closure member. Preferably, a first angle defined between the second link and the hinge arm is smaller than 180 degrees and a second angle defined between the first link and second link is smaller than 180 degrees change in mutually opposite senses as the output shaft turns in each direction. Typically, the first angle and second angles are each in a range of 30 to 150 degrees.

The second link may be disposed in such a manner that a movement of the free end of the first link is transmitted to the hinge arm either via a tensile force applied to the second link or via a compressive force applied to the second link. Depending on the particular geometry of the closure member and the surrounding structure, either one of these two possible arrangements can be selected.

According to a preferred embodiment of the present invention, the output shaft of the power actuator is placed adjacent to a hinge end of the closure member so that the power actuator system may be formed as a highly compact unit. Also, the hinge arm may include an arcuate portion having a first end fixedly attached to the closure member and a radial arm extending from the other end of the arcuate portion toward the closure member. This invention is particularly suitable for use in a powered automotive trunk. In such case, the part of the closure member adjacent to the hinge extends substantially horizontally.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

FIG. 1is a simplified partly broken away side view of a trunk section of a vehicle provided in a rear end thereof. A trunk lid1includes a main part which is substantially horizontal in its closed state and a rear part which curves downward from the rear end of the main part. The inner surface of the front part of the trunk lid is provided with a pair of hinge arms4at either side end thereof. Each hinge arm4includes an arcuate main part4aextending over an angle of about 90 degrees having a first end fixedly attached to the front end of the trunk lid, a radial arm4bextending substantially radially inwardly from a second end (or front end) of the main part4aand having an inner end pivotally supported by a lid pivot shaft3extending laterally in a part of the vehicle body5adjacent to the front edge of the trunk opening. To an intermediate point of the radial arm4bof the hinge arm4is pivotally connected a free end of a piston rod6aof a pneumatic damper6. The other end of the damper6is pivotally connected a part of the vehicle body5.

A power actuator7is mounted on a suitable part of the vehicle body5via a bracket18(FIG. 2). To an output shaft7aof the actuator7is fixedly attached a base end of a first link8, and the free end of the first link8is pivotally connected to a base end of a second link9, and the free end of the second link9is pivotally connected to an intermediate point of the radial arm4bof the hinge arm4. The angular movement of the output shaft7ais transmitted to the radial arm4bvia the first and second links8and9in such a manner that the trunk lid1can move over an angular range indicated by A inFIG. 1as the output shaft7aturns over a prescribed angular stroke.

Referring toFIG. 2, the actuator7includes an electric motor unit11mounted on the vehicle body5via the bracket18and a gear reduction unit. The gear reduction unit includes an actuator housing consisting of upper and lower housing halves16and17, a small gear11bfixedly attached to a drive shaft11aof the motor unit11, a large gear12rotatably supported by the actuator housing and meshing with the small gear11b, a pinion13afixedly attached to a central shaft13of the large gear12and a sector gear14rotatably supported by the actuator housing and meshing with the pinion13a. The output shaft7aof the actuator7is fixedly attached to a rotational center of the sector gear14.

The central shaft13of the large gear12and output shaft7aare rotatably supported by the actuator housing via bearing members not shown in the drawings. An end of the output shaft7aprojects out of the upper housing half16, and the base end of the first link8is fixed attached to the projecting end of the output shaft7aas mentioned earlier by using a threaded nut or the like. The motor unit1and actuating housing are jointly attached to the vehicle body5via the bracket18as discussed earlier.

Referring toFIG. 3, the electric motor unit11includes a DC electric motor11c, a worm11dfixedly attached to the output shaft of the motor11c, a wheel gear11emeshing with the worm11dand an electromagnetic clutch11finterposed between the wheel gear11eand drive shaft11aof the motor unit11. The motor11ccan turn in either direction according to a signal from a control unit not shown in the drawing, and the electromagnetic clutch11fallows selectively transmission of power from the wheel gear11eto the drive shaft11a. The motor11cconsists of a DC motor in this case, but may also consist of a motor of different types, such as a brushless motor.

When this actuator7is activated, the output shaft7aturns in a selected direction, and the first link8also turns around the output shaft7a. The angular movement of the first link8is transmitted to the hinge arm4via the second link8, and this causes the trunk lid1to move between a fully closed position and fully open position. This can be effected by counting the pulses of a rotary encoder (not shown in the drawing) incorporated in the actuator or the pulses that are supplied to the electric motor11c. When the trunk lid1has reached the fully closed position or fully open position, the power actuator is deactivated.

When the trunk lid1is actuated by the power actuator7, the electromagnetic clutch11fis kept engaged. Therefore, the trunk lid can be held in any desired position between the fully open position and fully closed position without regard to the load, such as the weight of the trunk lid1, that is applied to the actuator owing to the mechanically irreversible arrangement formed by the worm gear mechanism.

When it is desired to allow the trunk lid1to be opened and closed manually, the electromagnetic clutch11fis disengaged so that the mechanically irreversible arrangement may be disconnected from the trunk lid1.

When the trunk lid1is actuated either manually or automatically, it is necessary to prevent the trunk lid1from being forced beyond the fully closed position or fully open position as it would cause undue stressing of various parts. A mechanical stopper arrangement is provided in the illustrated embodiment for this purpose.

Referring toFIG. 4a, the upper housing half16is formed with a first projection16aat such a position that the sector gear14abuts the projection16aif it turns beyond the fully closed position (indicated by C1), and a second projection16bat such a position that the sector gear14abuts the projection16bif it turns beyond the fully open position (indicated by O1inFIG. 4b). Each of these projections16aand16bmay be formed at the time of stamp forming the upper housing half16.

The mode of operation of this system is now described in the following with reference toFIGS. 5ato5d.FIG. 5ashows the fully closed state of the trunk lid1in which the angle θ1defined between the radial arm4bof the hinge arm4and second link9or the first angle is 146 degrees and the angle θ2defined between the first link8and second link9or the second angle is 52 degrees. These angles θ1and θ2are not limited to these values, but may be selected appropriately in consideration of the link efficiency when actuating the trunk lid1.

The link efficiency as used herein means a relationship between the torque that is required to actuate the trunk lid1or the radial arm4aof the hinge arm4and the rotational speed thereof. A link efficiency greater than 100% means a case in which the torque is greater than the standard value and the rotational speed is smaller than the standard value. Conversely, a link efficiency less than 100% means a case in which the torque is smaller than the standard value and the rotational speed is greater than the standard value.

The load of the weight of the trunk lid1is greatest when the trunk lid1is about to be opened from the fully closed state although the damper6provides a greatest thrust. Therefore, a largest torque is required to actuate the trunk lid1at such a time. The thrust of the damper6cannot be made greater than a certain level because it would excessively oppose the effort to close the trunk lid1. As a result, the torque required to open the trunk lid from the fully closed state is relatively great but a substantially less torque is required to move the trunk lid from a partly open state to a fully open state. Therefore, when designing an automotive powered trunk lid, it is desirable to set the link efficiency relatively great when the trunk lid1is near the fully closed state and relatively small when the trunk lid1is away from the fully closed state. Therefore, an adequate torque output is ensured when opening the trunk lid1from the fully closed state, and a rapid movement of the trunk lid1is achieved when it moves from a partly open state to a fully open state.

Referring toFIG. 5a, if the second angle θ2formed between the first and second links8and9is too small (near zero) or too great (near 180 degrees) when opening the trunk lid from the fully closed state, a relatively large component of the force produced by the first link8is transmitted to the second link9while the displacement of the second link9for a given angular movement of the first link8is relatively small, as the first link8turns in the direction indicated by arrow B and the free end of the first link8pushes the second link9. If the fist angle θ1formed between the radial arm4band second link9great (near 180 degrees) when opening the trunk lid from the fully closed state, a relatively small component of the force produced by the second link9is transmitted to the radial arm4bwhile the displacement of the second link9for a given angular movement of the first link8is relatively large, as the free end of the second link9pushes the radial arm4a.

Based on such considerations, it can be concluded that the torque required to open the trunk lid1can be minimized while an amplification factor of displacement is maximized when the angles θ1and θ2are near 90 degrees and 0 or 180 degrees, respectively. This is not desirable because the rotational speed of the motor has to be increased for moving the trunk lid1at a given speed and this tends to increase the emission of sounds and vibrations. It was experimentally verified by the inventors that the trunk lid1can be manually actuated from the side of the trunk lid1if the angles θ1and θ2are each selected in the range of 30 to 150 degrees provided that an irreversible mechanism such as a worm mechanism is not intervening.

When the angles θ1and θ2are each selected in the range of 30 to 150 degrees, the maximum torque advantage (link efficiency greater than 100%) occurs when θ1=90 degrees and θ2=30 or 150 degrees, and the maximum displacement advantage (link efficiency less than 100%) occurs when θ1=30 or 150 degrees and θ2=90 degrees. In the illustrated embodiment, as the angles θ1and θ2are indeed each selected in the range of 30 to 150 degrees, a maximum torque can be transmitted near the fully closed state and a maximum speed can be achieved in a partly open state.

In the state shown inFIG. 5bor when the opening angle of the trunk lid1is about 25 degrees, θ2is at a minimum angle of 49 degrees and θ1is 91 degrees in the illustrated embodiment. In the state shown inFIG. 5cor when the opening angle of the trunk lid1is 50 degrees, θ2is 76 degrees and θ1is 61 degrees. In the state shown inFIG. 5dor fully open (upright) state of the trunk lid1, θ2is at a maximum angle of 127 degrees and θ1is at a minimum angle of 52 degrees. When θ2is at a maximum angle of 127 degrees, the trunk lid1has turned by 146 degrees from the fully closed state.

Thus, in the illustrated embodiment, the first link8is adapted to extend substantially from the output shaft7atowards the closure member1as the first link8swing around the output shaft7a. This direction from the output shaft7atoward the closure member1is indicated inFIG. 5bby L. This direction L may extend substantially perpendicularly to the major plane of the closure member near the hinge end thereof.

FIG. 6ashows the change of the first angle θ1in relation with the opening angle of the trunk lid1, andFIG. 6bshows the change of the second angle θ2in relation with the opening angle of the trunk lid1. As can be seen from these graphs, these angles θ1and θ2remain within the range of 30 to 150 degrees, and this keeps the link efficiency with an acceptable range.

FIG. 7shows the change in the link efficiency in relation with the opening angle of the trunk lid1. The actuator7is typically required to be installed inside the car trunk, and there is a severe restriction on the lengths of the first and second links8and9and the radial arm4band how they are angularly disposed relative to one another. The illustrated embodiment is designed to optimize the torque requirement and speed of the angular movement of the trunk lid1. In the illustrated embodiment, a progressively smaller torque is produced and a progressively higher speed is achieved as the car trunk moves from the fully closed state to a partly open state (approximately 25 degrees) of the trunk lid1. As the trunk lid1moves from the 25-degree open state to a 60-degree open state, a progressively larger torque is produced and a progressively lower speed is achieved . As the trunk lid moves from the 60-degree open position to the fully open position, a progressively smaller torque is produced and a progressively higher speed is achieved. Therefore, the trunk lid can be opened from the fully closed state by using a relatively large torque so as to overcome the weight of the trunk lid, and the trunk lid1is moved at a relatively high speed as it moves away from the fully closed state. As the trunk lid approaches the fully open state, the speed of the trunk lid diminishes and the fully open state of the trunk lid can be achieved substantially without involving any impact. When closing the trunk lid1from the fully open state, the foregoing process is reversed. In particular, the trunk lid can be fully closed substantially without any impact owing to the slow speed of the trunk lid near the fully closed state and with an adequate torque that is required to engage the latch and overcome the weather strip of the trunk lid. This is a highly desirable property of a powered trunk lid.

The first link8which is connected to the output shaft7aof the actuator7is adapted to be swing rearward from a slightly forwardly tilted position to a slightly rearwardly tilted position substantially symmetrically about a substantially vertical center line as the trunk lid1moves from a fully closed state to a fully open state. In other words, the first link8swings above the output shaft7aand moves like an inverted pendulum. Also, the direction of the angular movement of the first link8is opposite to that of the trunk lid1around the hinge shaft3. According to this arrangement, as compared with the conventional arrangement in which the first link swings like a normal pendulum, the first link8is prevented from projecting into the interior of the trunk and reducing the available trunk space.

The second link9is connected between the first link8and radial arm4bso as to be disposed substantially horizontally in both the fully closed state and fully open state of the trunk lid1. The spacing between the output shaft7aand trunk lid1is required to be at least as great as the length of the first link8. In the illustrated embodiment, when the first link8is at the fully upright position, the point of pivotal connection between the second link9and the radial arm4ais lower than the free end of the first link8at which the based end of the second link9is pivotally connected to the first link8or, in the other words, the second link9extends downward from the point of pivotal connection thereof with the first link8. Therefore, the spacing between the output shaft of the motor and the trunk lid is not required to be any more than the length of the first link8. This allows the actuator7to be placed closer to the trunk lid1than is otherwise possible, and maximizes the available trunk space.

In the conventional arrangement in which the output member (first link) attached to the output shaft of the actuator is made to swing under or below the output shaft (in the manner of a normal pendulum), the output member swings in the same direction as the trunk lid1, and this simplifies the design of the link mechanism. Having the output member swing in the opposite direction to the trunk lid1complicates the design of the linkage mechanism, and this fact has conventionally prevented a successful linkage design. However, the link design proposed in the present application allows the link efficiency to be optimized and the space requirement to be minimized.

The present invention is not limited to the foregoing embodiment, andFIGS. 8 and 9show a second embodiment of the present invention. InFIG. 8which is similar toFIG. 1but is somewhat enlarged, the parts corresponding to those of the previous embodiment are denoted with like numerals without repeating the description of such parts.FIG. 9is similar toFIG. 5, and shows the various stages of opening the trunk lid1.

The firs link8of the second embodiment pulls the second link9when opening the trunk lid1whereas the first link8of the first embodiment pushed the second link9under the same situation, and the second embodiment is otherwise similar to the first embodiment.FIG. 9ashows the fully closed state of the trunk lid1in which the first angle θ1defined between the radial arm4band the second link9is 43 degrees and the angle θ2defined between the first link8and second link9is at the maximum angle of 132 degrees.FIG. 9bshows the state where the trunk lid1has opened by an angle of 15 degrees, and both the angles are at their minimum values which are 41 degrees for θ1and 105 degrees for θ2.FIG. 9cshows the state where the trunk lid1has opened by an angle of 50 degrees, and the angles θ1and θ2are 63 degrees and 53 degrees, respectively.FIG. 9dshows the fully open (substantially upright) state of the trunk lid1and the first angle θ1is at the maximum angle of 97 degrees and the second angle θ2is at the minimum angle of 48 degrees.

Thus, in the second embodiment, similarly as the first embodiment, the first link8is adapted to extend substantially from the output shaft7atowards the closure member1as the first link8swing around the output shaft7a. This direction from the output shaft7atoward the closure member1is indicated inFIG. 5bby L. This direction L may extend substantially perpendicularly to the major plane of the closure member near the hinge end thereof.

FIG. 10ashows the change in the first angle θ1in relation with the opening angle of the trunk lid1, andFIG. 10bshows the change in the second angle θ2in relation with the opening angle of the trunk lid1. As can be seen from these graphs, these angles θ1and θ2remain within the range of 30 to 150 degrees which keeps the link efficiency within an acceptable range. Because the push and pull relationship is reversed in relation with the previous embodiment, the relationships of the angles θ1and θ2in relation with the opening angle of the trunk are reversed with respect to those of the previous embodiment.

FIG. 11shows the changes in the link efficiency in relation with the opening angle of the trunk lid1. The rise and fall of the link efficiency are reversed from those of the previous embodiment. However, it still remains true that a high torque is available when the trunk lid is near the fully closed position and involves a relatively large load owing to its horizontal position, and the trunk lid1is moved at high speed as the trunk lid opens further from a partly open state and involves a progressively diminishing load owing to the more upright position of the trunk lid and the declining thrust of the damper6.

In the second embodiment also, the first link8fixedly attached to the output shaft7aof the actuator7swings around an upright position thereof (like an inverted pendulum) and moves in the opposite direction to the trunk lid as the trunk lid opens and closes. Thereby, this embodiment also provides advantages similar to those of the previous embodiment. If the same design specifications as those of the first embodiment are applied to the second embodiment except for the push and pull relationship of the first and second links8and9, the second embodiment provides a generally favorable link efficiency. In particular, the second embodiment involves a relatively high speed and a relatively small torque near the fully closed and fully open positions.

By selecting one of the two possible embodiments depending on the particular geometry of the trunk space, it is possible to adapt the present invention to a wide range of configurations of the trunk space.

Although the present invention has been described in terms of preferred embodiments thereof, it is obvious to a person skilled in the art that various alterations and modifications are possible without departing from the scope of the present invention which is set forth in the appended claims. For instance, the illustrated embodiment are directed to trunk lids which take a substantially horizontal position in the fully closed state and open toward an upright position, but the present invention can also be applied to closures members which are not limited to trunk lids and disposed in different orientations in the fully closed and fully open positions although the geometry of the links may be slightly modified so as to optimize the link efficiency in each particular case. The contents of the original Japanese patent application on which the Paris Convention priority claim is made for the present application are incorporated in this application by reference.