HK1176391B - Actuator including mechanism for converting rotary motion to linear motion - Google Patents

Abstract

An active vibration control device is provided that is configured to control the position of a body relative to a reference frame. The control device includes sensors that provide input signals corresponding to movement of the body in at least one direction, a rotary motor configured to control the position of the body, and four-bar linkage connecting the rotary motor to the body. The linkage converts the rotary motion output from the motor into a linear motion of the body. The controller, based on the input signals from the reference frame sensors, provides control signals to the rotary motor which acts through the linkage to position the body in the at least one direction relative to the position of the reference frame.

Description

Actuator comprising a mechanism for converting a rotary motion into a linear motion

Background

Active vibration control systems have been employed to control vehicle seat vibrations. For example, instead of passive systems (which include springs and dampers that reduce the seat response to vehicle vibrations), active vibration control systems detect seat vibrations and control the position of the seat to counteract the detected motion and thereby isolate the seat from vehicle vibrations. Such an active vibration control system may include a linear actuator controlled by a controller. A linear actuator is positioned under the seat to control the position of the seat relative to the vehicle frame. For example, the linear actuator may comprise a linear electromagnetic motor comprising an armature fixed at one end to the seat. The armature extends linearly and retracts relative to the stator based on a control signal from the controller, thereby positioning the seat.

Controlled linear actuators are applied to systems other than vehicle seat vibration control. For example, controlled linear actuators are also known for use in wheel suspension systems and in engine valve control systems.

In many applications, challenges associated with controlling the position of an object using such a linear actuator include providing a linear motor that provides sufficient linear travel within a limited space (e.g., between the seat and the floor in an active seat vibration control system). Other challenges include the known cost and maintenance issues associated with linear motors.

Disclosure of Invention

In some aspects, an active vibration control device configured to control a position of a body includes: at least one sensor configured to provide an input signal corresponding to movement of the body in at least one direction; a rotation motor configured to control a position of the body; and a linkage (link) comprising at least two pivotably engaged links connecting the rotary motor to the main body. The link is configured to convert a rotational motion output from the motor into a linear motion of the body. The apparatus further comprises: a controller providing control signals to a rotation motor acting through a link to position the body in at least one direction based on input signals from the at least one sensor.

In another aspect of the present invention, an actuator includes: a rotary motor including an output shaft and a motor housing; and a link connected to an output shaft of the rotary motor. The linking includes: a motor housing having a housing pivot pin defining a first rotational axis; and a first coupling secured to the output shaft. The output shaft defines a second axis of rotation, and the second axis of rotation is parallel to and spaced from the first axis of rotation. The first link includes a first link pivot pin disposed at a position spaced apart from the second rotational axis and defining a third rotational axis parallel to the first rotational axis. The linking includes: a second link pivotally connected at a first end to the first link pivot pin. The second coupling includes a second coupling pivot pin defining a fourth axis of rotation parallel to the first axis of rotation. The second link pivot pin is disposed between the first end of the second link and a predetermined point of the second link. The linking further comprises: a third link pivotally connected at a first end to the housing pivot pin and pivotally connected at a second end to the second link pivot pin. During operation of the actuator, rotation of the output shaft causes linear movement of the predetermined point relative to the housing.

The active vibration control device and actuator may include one or more of the following features: the torque generated by the motor at the body is substantially constant over a 100 degree angular rotation of the output shaft. The link is configured to convert rotational motion of the output shaft into linear motion such that the motion of the body is substantially proportional to the angular displacement of the output shaft within 180 degrees of rotation of the output shaft. The link is configured to convert rotational motion of the output shaft into linear motion such that the torque is substantially constant over a displacement range of the body of at least four inches.

The controller of the active vibration control apparatus provides an output signal to a rotation motor that acts through a link to position the main body, thereby controlling the attitude of the main body. The active vibration control device comprises a second link, and one of said links is connected to the output shaft of the motor on each opposite side of the motor. The apparatus further comprises: a second rotary motor and a second link configured to control a position of the main body, the first rotary motor and the second rotary motor being arranged such that their respective rotor shafts are parallel. The apparatus further comprises: a second rotary motor and a second link configured to control a position of the body, the first rotary motor and the second rotary motor being arranged such that their respective rotor axes are collinear.

In certain implementations, the body includes a vehicle seat disposed in the vehicle, for example, while a rotary motor fixed relative to a floor (floor) of the vehicle is disposed between the floor and the seat. The linear travel of the body is at least 4 inches. The controller provides control signals to the rotation motor to position the body according to a motion opposite and opposite to the motion detected by the at least one sensor.

The actuator may further include one or more of the following features: the actuator includes a second link, and one of the links is connected to the output shaft of the motor on each opposing side of the motor. The shell pivot pin and each of the first and second link pivot pins are supported on bearings, and the links are configured such that the bearings are substantially coplanar.

Active vibration control devices and actuators advantageously employ a rotary motor and include a mechanism for converting the rotary motion of the motor into linear motion. Actuators have many applications, one of which is to control the position of an object along a linear path. An actuator, in which a rotary motor acts through a mechanical link to position an object, has several advantages over known positioning apparatuses that employ linear motors. For example, rotary motors are much cheaper to manufacture and easier to seal than linear motors. Furthermore, the combination of a rotary motor and a mechanical linkage is more compact than a linear motor size while providing an equal or greater range of linear motion. This feature is important, for example, in the vibration control of vehicle seats, in which the spacing between the seat and the floor in which the control mechanism is arranged is limited.

In addition, when combined with a controller, the actuator may function as a motion control device. For example, in some implementations, an actuator in combination with a controller may be used to provide active control of a valve in an internal combustion engine or compressor. In some implementations, an actuator in combination with a controller may be configured to act as a position source, a velocity source, or a force source. In some implementations, an actuator in combination with a controller may be used in an active vibration isolation control device. For example, the actuators and controllers may be used to control the position and/or acceleration of a vehicle seat, or the position and/or acceleration of a sprung mass of a vehicle, as described further below.

Yet another advantage of the actuator is that at least some parts of the mechanical linkage are incorporated in the motor housing and the rotor shaft, providing an actuator that is in turn more compact, less complex and requires fewer parts. In addition, the actuator is a direct drive device in which the rotor is connected to the object to be positioned via a single rigid coupling, and without any intervening gears, belts, or other devices that introduce error and/or complexity into the positioning control.

In yet another aspect of the present invention, a mechanism for converting rotational motion to linear motion comprises: a plate including a plate pivot pin defining a first axis of rotation; and a first coupling secured to the shaft. The shaft is rotatably supported on the plate and defines a second axis of rotation that is parallel to and spaced from the first axis of rotation. The first coupling includes: and a first coupling pivot pin disposed at a position spaced apart from the second rotation axis and defining a third rotation axis parallel to the first rotation axis. The mechanism comprises: a second link pivotally connected at a first end to the first link pivot pin. The second coupling includes: and a second link pivot pin defining a fourth rotation axis parallel to the first rotation axis, and disposed between the first end of the second link and a predetermined point on the second link. The mechanism further comprises: a third link pivotally connected at a first end to the plate pivot pin and pivotally connected at a second end to the second link pivot pin. In this mechanism, rotation of the shaft causes linear movement of the predetermined point relative to the plate.

The mechanism may include one or more of the following features: the predetermined point is for about 180 degrees of rotational linear movement of the shaft. The mechanism comprises: a first link length defined by a distance between the first link pivot pin and the axle; a second lever length defined by a distance between the axle and the plate pivot pin; a third link length defined by a distance between the plate pivot pin and the second link pivot pin; and a fourth bar length defined by the distance between the first link pivot pin and the predetermined point, and the ratio of the first bar length to the second bar length to the third bar length to the fourth bar length is 1: 2: 2.5: 5. Each of the plate pivot pin, the first and second link pivot pins, and the axle are supported on bearings, and the rods are configured such that the bearings are substantially coplanar. The board still includes: a brake member configured to restrict rotation of the first link relative to the plate.

Drawings

FIG. 1 is a perspective view of an actuator for converting rotary motion to linear motion.

FIG. 2 is a side cross-sectional view of the actuator as seen along section line 2-2 of FIG. 1.

Fig. 3 is a schematic representation of a Hoeken link.

Fig. 4 is a perspective view of the actuator of fig. 1 illustrating four rods linked.

FIG. 5 is a graph of rotor shaft angular displacement (degrees) versus displacement (inches) at a predetermined point of the first coupling.

Fig. 6 is an end view of the actuator of fig. 1.

FIG. 7 is a graph of rotor shaft angular displacement (degrees) versus motor torque (Nm) output required to provide a constant 1100N force at a predetermined point of the first coupling.

Fig. 8 is a graph of displacement (in) of the second end of the first coupling versus the motor torque (Nm) output required to provide a constant 1100N force at a predetermined point of the first coupling.

FIG. 9 is a perspective view of a position control apparatus employing two actuators shown in a retracted configuration.

FIG. 10 is a perspective view of the position control apparatus of FIG. 9 shown in an extended configuration.

FIG. 11 is a perspective view of an alternative implementation of a position control device employing two actuators.

FIG. 12 is a perspective view of another alternative implementation of a position control device employing two single-link actuators.

FIG. 13 is a schematic diagram of an active vibration control system for a vehicle seat.

FIG. 14 is a cross-sectional view of a portion of a cylinder bank of an internal combustion engine, wherein the actuator of FIG. 1 is directly connected to an engine valve.

FIG. 15 is a cross-sectional view of a portion of a cylinder bank of an internal combustion engine, wherein the actuator of FIG. 1 is indirectly connected to an engine valve.

FIG. 16 is a perspective view of an alternative implementation of an actuator.

Detailed Description

As will be described in more detail below, an actuator including a rotary drive combined with a linkage having specific mechanical features provides for the conversion of rotary to linear motion in a manner well suited to applications in which the linear range of travel is maximized within a limited space.

Fig. 1, 2, 4 and 6 show an actuator in the form of a rotary motor and a four-bar linkage having this desirable feature. An alternative implementation of the actuator is shown in fig. 16. Figures 5, 7 and 8 illustrate mechanical features of the actuator including the ratio of the displacement of a predetermined point on the link to the angular displacement of the rotary motor, and the constant force at the predetermined point for both angular displacements, and the displacement of the predetermined point in the linear portion of the motion of the linkage 52 for a constant torque output of the rotary motor. Several implementations of such an actuator when used as a positioning device are shown in fig. 9-12. Specifically, the actuator is connected to the platform and controls movement of the platform. One implementation of an actuator for use in an active vibration control system is described with reference to fig. 13. Further, one implementation of an actuator used to control an engine valve is described with reference to fig. 14 and 15.

Referring now to fig. 1 and 2, an actuator 50 for converting rotary motion to linear motion includes a rotary motor 60 supported by a motor housing 62 and disposed within the motor housing 62. The actuator includes a first link 52 connected to and driven by one end of a motor 60. The link 52 is arranged as a Hoeken link and can be used to locate objects connected to the link along a linear path. The actuator 50 advantageously provides a compact way for linearly positioning an object in space.

While object positioning may be achieved using a single link 52, in the illustrated implementation, the actuator 50 also includes a second link 252 connected to and driven by a second end of the motor 60. The second link 252 is a mirror image of the first link 52 and is configured to synchronize and coordinate movement with the first link 52 as discussed further below. Elements common to both links 52, 252 are identified by the same reference numerals. Therefore, the configuration of each link will be described with reference to only the first link 52.

The rotary motor 60 includes a stator 72 fixed to the housing 62 and a rotor 80 coaxially disposed within the stator 72 so as to be rotatable about a rotor shaft 82. The rotor 80 is a hollow cylindrical body having opposite first and second ends 84, 84 rotatably supported on the housing 62And an end 85. The rotary motor 60 may be a conventional frameless kit (frame kit) motor, such as the Bayside motor of PortWashington, N.YModel K127300 manufactured by Motion Group.

The housing 62 includes a closed side wall 63 capped at each end by a housing end plate 64. Each end plate 64 includes a plate pivot pin 68 that extends outwardly in a direction parallel to the rotor shaft 82, supports a bearing 194, and defines the first rotational axis 76 of the link 52. In the illustrated implementation, the plate pivot pin 68, and thus the first rotational axis 76, overlies the rotor shaft 82 and is substantially vertically aligned with the rotor shaft 82.

An end cap 100 is secured to the first end 84 of the rotor 80. The end cap 100 is a hollow cylindrical body having a closed first end 101. An end cap 100 is rotatably supported in an opening 66 formed in the end plate 64 of the housing 60 such that the outer surface 102 falls primarily in the plane of the end plate 64. Adjacent the first end 101, the outer periphery of the end cap 100 is supported by the rotor bearing 89 that fits into the shell end plate 64. The rotor bearing 89 may be a thin section bearing such as the Silvershin, sold by Mechatronics Corporation of Preston, Washington^TMModel SB035 angular contact bearings.

End cap 100 extends inwardly from outer surface 102 and terminates in an open second end 103. The outer diameter of the end cap 100 is reduced at the second end 103 forming an annular protrusion 128 sized to press fit within the inner surface of the rotor 80. Relative movement of the end cap 100 with respect to the rotor is prevented by securing the end cap 100 to the rotor 80. This may be accomplished, for example, by providing screws (not shown) in mutually aligned screw holes 86, 130 formed in the rotor 80 and the annular projection 128, respectively. Thus, the end cap 100 rotates with the rotor 80 and acts as an output shaft for the motor 60. The center of rotation 132 of the end cap 10 is coaxial with the rotor shaft 82 (which corresponds to the second axis of rotation of the link 52).

The outer surface 102 of the end cap 100 includes a protruding step portion 104 formed in the shape of a ring segment at the periphery of the end cap 100, wherein the chord defining the edge of the segment is not the diameter of the end cap 100. A shoulder 106 is formed that joins the stepped portion 104 to the remainder of the outer surface 102. End cap pins 108 are provided in the stepped portion 104 adjacent the periphery of the end cap 100. End cap pins 108 project outwardly from stepped portion 104, support bearings 158, and define a third rotational axis 110 of link 52 that extends parallel to rotor shaft 82.

The motor 60 includes an external optical encoder 120 for determining the angular position of the rotor 80. In this implementation, the encoder shaft 118 protrudes from the outer surface 102 of the first end 101 coaxially with the rotor shaft 82. The encoder shaft 118 is connected to the encoder input shaft 122 using a flexible coupling 124, allowing the angular position of the rotor 80 to be accurately determined. However, the actuator 50 is not limited to this configuration. For example, the motor 60 may have an internal encoder.

A second end cap 200 is secured to the second end 85 of the rotor 80. The second endcap 200 is substantially similar in form and function to the first endcap 100 and like elements of the second endcap 200 are identified with the same reference numerals. For this reason, a detailed description of the second end cap 200 will be omitted except for the following differences with respect to the first end cap 100: the end cap 200 does not include the encoder shaft 118. End cap 200 has a through bore 202 coaxially aligned with rotor shaft 82. The through hole 202 provides access to the interior of the rotary motor 60, which is advantageous during assembly and disassembly of the actuator 50.

As noted above, the links 52 are arranged as Hoeken links. The Hoeken link is a four-bar link that converts rotational motion into approximately linear motion. Referring to fig. 3, the Hoeken link includes a rotating first rod I, a fixed second rod II coupling the first rod I to a fourth rod IV, a third rod III driven by the first rod I at one end, and a fourth rod IV supporting the middle of the third rod III. Due to the rotation of the first lever I, the point P of the third lever III moves along a closed loop path 53 indicated by the dashed line. As seen in the figure, the path comprises a substantially linear portion 55.

Referring to fig. 4, the four rods defining the link 52 are as follows:

the first rod 116 of the link 52 is provided by an end cap 200. More specifically, the first rod 116 includes a portion of the end cap 200 that extends between the center of rotation 132 of the end cap 200 and the end cap pin 108. The first lever 116 rotates relative to the housing 62 about the second axis of rotation 82 in a plane corresponding to the outer surface 102 of the end cap 200.

The second rod 88 of the link 52 is provided by the housing 62. More specifically, the second rod 88 comprises part of the end plate 64 and extends between the plate pivot pin 68 and the center of rotation 132 of the end cap 200. The second rod 88 is a fixed rod relative to the housing 62 and defines the orientation of the linear motion produced by the link 52.

The third rod 151 of the link 52 is provided by the first link 150. The first link 150 is an elongated rigid rod of rectangular cross-section and includes a first end 152 and a second end 154 opposite the first end 152. The first and second ends 152, 154 and a midpoint 156 between the first and second ends 152, 154 have a through hole 165 extending between opposing broad faces 166, 168 of the first coupling 150. Bearings 158, 160 (midpoint bearings not shown) are press fit into corresponding through holes 165 and are sized and shaped to receive pivot pins. For example, the bearing 158 at the first end 152 of the first coupling 150 receives the end cap pin 108 and allows the first coupling 150 to rotate about the end cap pin 108 (and the third rotational axis 110) relative to the shell 62 and the end plate 100. A bearing disposed at midpoint 156 supports coupling pin 162. The coupling pin 162 protrudes outwardly from both broad faces 166, 168 of the first coupling 150 and defines a fourth rotational axis 164 of the link 52 extending parallel to the rotor axis 82. The third rod 151 of the link 52, constituted by the first link 150, extends between the end cap pivot pin 108 and the centre line of the bearing 160 (coinciding with point P in fig. 4).

The fourth bar 181 of the link 52 is provided by a second link 180. The second link 180 is an elongated rigid rod of rectangular cross-section and includes a first end 182 and a second end 184 opposite the first end 182. The first end 182 has a through-hole 195 extending between opposing broad faces 196, 198 of the second link 180. The bearing 194 is press fit into the through hole 195 and is sized and shaped to receive the plate pin 68. Thus, the first end 182 of the second link 180 rotates relative to the housing 62 about the plate pin 68 (and the first rotational axis 76). Second end 184 of second link 180 is bifurcated such that the distance between broad faces 196, 198 is greater at second end 184 than at first end 182, and such that second end 184 forms a yoke (yoke) that includes spaced yoke arms 186, 188 that straddle the middle of first link 150 and engage link pin 162. Thus, the second end 184 of the second link 180 rotates about the link pin 162 (and fourth rotational axis) relative to the housing 62 and the first link 150. A fourth bar 181 of the link 52, constituted by a second link 180, extends between the plate pivot pin 68 and the link pin 162.

By providing yoke arms 186, 188 to second coupling 180, first end 182 of second coupling 180 may be disposed in the same plane as first coupling 150. Further, by providing the end cap 100 with a stepped portion 104 and by positioning the end cap pin 108 on the stepped portion 104, a space is provided between the main coupling 150 and the housing 62 that can accommodate the inner yoke arm 188. These features, in advantageous combination, allow the pivot pin bearings 158, 160 and 194 (which are conventional radial ball bearings) to be arranged in a single plane, thereby avoiding torsional loads on the coupling when in use. However, the link 52 is not limited to this configuration, and in some embodiments, the second link 180 may be formed without a yoke, and may instead be formed with an offset portion or with a linear configuration.

The link 52 serves to convert the rotational motion of the rotor 80 into linear motion at a predetermined point P on the first coupling 150. In the illustrated implementation, the center of the bearing 160 at the second end 154 of the first link 150 is defined as the predetermined point P that generates the linear motion. By adjusting the relative lengths of the respective first through fourth bars 116, 88, 150, 180, the movement of the point P can be specified. In the actuator 50, a first rod length is defined by the distance between the end cap pin 108 and the center of rotation 132 of the end cap 200, a second rod length is defined by the distance between the center of rotation 132 of the end cap 20 and the plate pin 68, a third rod length is defined by the distance between the end cap pin 108 and the point P, and a fourth rod length is defined by the distance between the coupling pin 162 and the plate pin 68. In the illustrated implementation, the rod lengths are as follows: first bar 116 is 1 inch, second bar 88 is 2 inches, third bar 151 is 5 inches, and fourth bar 181 is 2.5 inches. The linear travel range achieved with this configuration is approximately 4 inches. Of course, increased linear travel range may be obtained by proportionally increasing the size of the linked rods. For example, the range of linear travel achieved is about 5 inches for respective first through fourth bar lengths of 1.25 inches, 2.5 inches, 6.25 inches, and 3.125 inches. Conversely, for applications where a smaller linear range of travel is desired, the mechanism can be scaled down to produce an even more compact device.

In link 52, the ratio of the first rod length to the second rod length to the third rod length to the fourth rod length is 1: 2: 5: 2.5. By using these ratios, at least several advantages are achieved:

the linear part of the movement of point P occurs along a line parallel to the fixed second rod 88. In the illustrated implementation, the fixed second rod 88 is vertically oriented, and thus the linear portion of the movement of point P also has vertical movement.

Additionally, as shown in fig. 5, the movement of point P is substantially proportional to the angular displacement of the end cap pin 108 within 180 degrees of rotation of the rotor 80. That is, the point P moves approximately linearly within the rotational movement range of the rotor 80 indicated by the reference lines a and B, corresponding to the approximate range of 180 degrees.

In the actuator 50, two external linkages 150, 180 are provided, these linkages acting as the third and fourth rods III, IV, respectively, of the Hoeken four-bar linkage. The remaining two rods (first rod I and second rod II) are provided by components of the motor 60 and the motor housing 62. Specifically, the second end cap 200 incorporated into the first rod 116 acts as a rotating first rod I of the Hoeken link, and the motor housing 64 incorporated into the second rod 88 is adapted to act as a stationary second rod II of the Hoeken link. This configuration (in which the first rod 116 and the second rod 88 are not formed as an external coupling, but are instead incorporated into the motor assembly itself) reduces the number of components required to achieve the required motion, and results in a compact actuator assembly.

Referring now to fig. 6, the actuator 50 is configured such that the second end 154 of the first linkage 150 is constrained to move back and forth within the range of linear motion identified between a and B of fig. 5. In some implementations, the controller 14 (fig. 13) connected to the motor 60 prevents the rotor 80 (and thus the end cap 100) from rotating beyond a 180 degree range. In addition, the stop member 90 is provided to mechanically interfere with the shoulder 106 of the outer surface 102, thereby preventing rotation beyond the linear range. The detent member 90 is secured to the housing 62 and extends radially inward to overlie portions of the opening 66 in the end plate 64. When linked in the fully extended configuration (shown in solid lines in fig. 4) corresponding to one end of the linear range, a first portion of the shoulder 106 abuts the first braking surface 96 of the brake member 90. In this position, first end 152 of first coupling 150 is positioned on a horizontal line through rotor shaft 82 at a location to the left of rotor shaft 82 as viewed in the figures. Further, as seen in the drawing, the point P is located at a position lateral to the case 62 and above the upper side of the case 62. When end cap 100 is rotated counterclockwise, link 52 moves downward and point P travels downward along linear path L. When the link 52 is in the retracted position (shown in phantom in fig. 4) corresponding to the opposite end of the linear range, the second portion of the shoulder 106 abuts the second braking surface 98 of the brake member 90. In this position, the first end of the first coupling 150 has been rotated through a 180 degree arc and is now positioned on a horizontal line through the rotor shaft 82 as viewed in the figures at a location to the right of the rotor shaft. Furthermore, point P is now located at a lateral position of the shell 62, and this position is now located below the upper side of the shell 62.

Further advantageously, in one embodiment as shown in fig. 7, the four-bar link 52 is configured to convert the rotational motion of the rotor 80 into linear motion such that the torque output of the motor 60 required to provide a constant 1100N force at point P is substantially constant over a substantial portion of the angular displacement range of the motor associated with the linear travel range of point P. The torque output of the motor 60 is substantially constant over a range of rotational motion of the rotor 80 indicated by reference lines C and D corresponding to a range of about 100 degrees.

Further, in one embodiment as shown in fig. 8, the four rod links 52 are configured to convert the rotational motion of the rotor 80 into linear motion such that the torque output of the motor 60 required to provide a constant 1100N force at point P is substantially constant over a substantial portion of the range of linear motion of point P. The torque output of the motor 60 is substantially constant over a substantial portion of the range of tip linear displacement indicated by reference lines E and F, corresponding to about 4 inches.

Referring to fig. 9 and 10, the position control apparatus 350 is one implementation of the actuator 50, wherein the apparatus 350 includes two actuators 50, 50 ' arranged such that the rotor shafts 82, 82 ' of the respective rotary motors 60, 60 ' are substantially coaxial. Further, the links 52, 252 of the first actuator 50 are configured to rotate relative to the links 52 ', 252 ' of the second actuator 50 '. In the illustrated implementation, the position control device 350 is used to control the vertical position of the platform 16 relative to the base 22 and is connected to the platform 16 by a number of downwardly extending struts 18. Specifically, each strut 18 includes a pivot pin 20 rotatably supported by a bearing 160 at the second end 154 (a location corresponding to point P) of the respective first link 150 of each link 52, 52 ', 250'. In fig. 9, the position control device 350 is shown in a first retracted configuration, in which the vertical distance between the platform 16 and the base 22 is distance d 1. In this implementation, there is substantially no vertical spacing between the platform 16 and the shells 62, 62', so the retracted configuration is compact. Further, the platform 16 is substantially centered over the position control device 350. In fig. 10, the position control apparatus 350 is shown in a second extended configuration, in which the vertical distance between the platform 16 and the base 22 is a distance d2, where d2 is greater than d 1. The platform 16 remains centered over the position control device 350 during the transition between the retracted configuration and the extended configuration and while in the extended configuration. Although the illustrated implementation shows the actuators 50, 50' as being axially spaced by a distance s1, this configuration is not limiting. For example, the two actuators 50, 50' may be spaced apart a greater or lesser distance than s 1.

Referring to fig. 11, position control device 450 is an alternative implementation of actuator 50. Like the previous position control apparatus 350, the position control apparatus 450 includes two actuators 50, 50 ', and the second actuator 50' is identical to the first actuator 50. In the position control apparatus 450, the actuators 50, 50 'are arranged such that the rotor shafts 82, 82' of the respective rotary motors 60, 60 'are parallel and spaced apart, and further, the links 52, 252 of the first actuator 50 are configured to rotate relative to the links 52', 252 'of the second actuator 50'. In the illustrated implementation, the position control device 450 is used to control the vertical position of the platform 16 relative to the base 22 and is connected to the platform 16 by a number of struts 18. Specifically, each strut 18 includes a pivot pin 20 rotatably supported by a bearing 160 at the second end 154 (a location corresponding to point P) of the respective first link 150 of each link 52, 52 ', 250'. Although the illustrated implementation shows the shafts 82, 82 'of the actuators 50, 50' as being spaced apart by the distance s2, this configuration is not limiting. For example, the shafts 82, 82' may be spaced apart a greater distance than s 2. Further, while the illustrated implementation shows the actuators 50, 50 'to be coplanar, the actuators may instead be offset to fall in a different plane while maintaining parallel axes 82, 82'.

Referring to fig. 12, a position control device 550 is another alternative implementation of the actuator 50. The position control device 550 comprises two single link actuators 250, 250'. Specifically, each actuator 250, 250 'has a single link 52, 52'. In the position control apparatus 550, the actuators 250, 250 ' are arranged so that the rotor shafts 82, 82 ' of the respective rotary motors 60, 60 ' are coaxial. Further, the link 52 of the first actuator 250 is configured to rotate relative to the link 52 'of the second actuator 250'. In the illustrated implementation, the position control device 550 is used to control the vertical position of the platform 16 relative to the base 22 and is connected to the platform 16 by a number of struts 18. Specifically, each strut 18 includes a pivot pin 20 rotatably supported by a bearing 160 at the second end 154 (a location corresponding to point P) of the respective first link 150 of each link 52, 52'. The position control device 550 operates similarly to the position control device 350, but is less complex, requires fewer bearings, and is more compact in the axial direction than the position control device 350. Although the illustrated implementation shows the two actuators 250, 250 'as being axially contiguous, this configuration is not limiting, and thus the actuators 250, 250' may be axially spaced.

In each of the position control devices 350, 450, 550 described above, by using a linkage mechanism arranged on opposing sides, the corresponding reaction torque on the base 22 due to the load is significantly reduced when the actuators 50 move in unison. Furthermore, by using two rotation motors 60, 60 'to position the platform 16 instead of a single rotation motor 60, each of the two rotation motors 60, 60' may be reduced in size, resulting in an even more compact mechanism. Further, in some implementations, the respective links 52, 252, 52 ', 252 ' may be mechanically tied together so that the platform 16 may remain level in the event of a failure of one of the rotary motors 60, 60 '.

Referring to fig. 13, the position control device 350 may be used in an active vibration control system 5 used in a vehicle 2 to reduce or eliminate vibration of the vehicle seat 8 due to vibration of the vehicle frame 4. The vehicle seat 8 is fixed to a rigid seat base 10 and supports at least one sensor 12. For example, the sensor 12 may include an accelerometer for detecting movement of the seat relative to the ground g. The seat 8 and base 10 rest on the vehicle frame 4 and are supported above the vehicle frame 4 by the position control device 450. The position control device 350 may be attached indirectly to the vehicle frame via the secondary seat support structure or directly to the frame itself, whereby the position control device 350 is fixed relative to the vehicle frame 4. The position control device 350 is adapted to position the base 10 and thus the seat 8 relative to the vehicle frame 4 based on control signals received from the controller 14. The controller 14 receives signals from the sensors 12 including seat movement data and receives encoder signals indicative of rotor position relative to the shells 62, 62'. Based on these signals, the controller 14 outputs control signals to the rotation motors 60, 60' of the position control device 350 so that the position of the vehicle seat 8 is controlled relative to the vehicle frame. Although the illustrated implementation employs a position control device 350, this is not a limitation. For example, any of the disclosed position control devices 450, 550 may replace the device 350. Additionally, a single actuator 50, 250 may be used in combination with a supplemental seat support structure to form an active vibration control system.

In some implementations, the respective rotation motors 60, 60' are controlled to position the base 10 (and thus the seat 8) so as to counteract the detected seat motion so as to isolate the seat 8 from vehicle vibrations. In some implementations, the respective rotation motors 60, 60' are controlled to act in concert. For example, the second ends 154 of the first couplings 150 of the two actuators 50, 50' are controlled to be the same distance from the vehicle frame 4. In other implementations, the rotation motor 60 of the first actuator 50 may be controlled independently of the rotation motor 60 'of the second actuator 50', whereby the attitude of the seat base 10 with respect to the vehicle frame 4 may be controlled. In such an implementation, at least one additional degree of freedom would be required between the link 52, 252, 52 ', 252' and the seat base 10 to allow relative movement between these components. This may be achieved, for example, by providing an additional pivot point at position G.

The active vibration control system 5, which utilizes the actuator 50 to convert the rotational motion output from the rotary motors 60, 60' into linear motion, has several advantages over control systems that utilize linear motors. For example, rotary motors are much cheaper to manufacture than linear motors and are easier to seal than linear motors. Furthermore, the rotary motor in combination with the mechanical linkage is more compact in size than a linear motor while providing an equal or greater range of linear motion. This feature is important, for example, in the vibration control of vehicle seats, in which the spacing between the seat and the floor in which the control mechanism is arranged is limited. Yet another advantage of the actuator is that at least some of the mechanical links are incorporated in the motor housing and the rotor shaft, thereby providing an actuator that is even more compact, less complex and requires fewer parts.

Additionally, in some implementations, the actuator 50 may be a direct drive device, wherein the rotor is connected to the object to be positioned via a single rigid coupling, and without any intervening gears, belts, or other devices that introduce error and/or complexity into the positioning control.

Furthermore, a further advantage of using the position control device 350 in the active vibration control device 5 is the fact that rotary motors are inherently more efficient than linear motors. For example, there are 3 different armature/stator relationships that may be useful in a linear motor: 1) an under-ride relationship wherein the coils and pole pieces of the stator extend beyond the length of the armature magnets such that the armature remains within the stator pole pieces for at least some range of travel as the magnets move back and forth. The design may be such that the armature remains within the coils at maximum excursion or it may begin to extend through them at some point. 2) A uniformly overhung relationship in which the armature magnets are the same length as the stator pole pieces. In this design, some of the magnets move beyond the stator pole once the armature begins to move. 3) An overhung relationship in which the armature magnets exceed the length of the stator pole bars. In an overhung design, the movement of the armature does not change the number of magnets residing within the stator pole for at least some range of drift. In this design, the entire drift range or only a certain portion may be used.

In any of the relationships described above, a trade-off is made between efficiency and cost. For example, once some magnets move beyond the stator pole, their contribution to the force output is rapidly reduced. Due to the relatively high expense of magnets, it is desirable to always make full use of magnets.

When used in limited space conditions as found in active seat vibration control applications, and for example when using an underslung design, it is possible to take full advantage of the magnets. However, if more magnets are used, the amount of force generated over a large portion of the drift range for a fixed input current will be less. Thus, the efficiency of the linear motor is reduced, where efficiency is defined as the output mechanical power divided by the input electrical power. The uniform overhang design is a compromise between these factors.

The advantage of using a rotary motor over a linear motor is that all magnets see the pole pieces of the stator at all angles of rotation is inherent in the rotary design. This is the optimum condition for trading efficiency and cost. For this reason, it is advantageous to use a rotary motor and a mechanism for converting rotary motion into linear motion, rather than a linear actuator, for linear positioning applications.

Although the illustrated implementation shows an actuator 50 for converting rotary motion to linear motion for actively controlling vibration of a vehicle seat, the actuator 50 is not limited to this application. For example, the actuator 50 is also suitable for use in other vehicle vibration control aspects including wheel suspension systems and engine vibration control systems. In addition, the actuator 50 is not limited to vibration control and is generally applied to object position control. For example, an actuator may be used to control engine valve movement, which may improve engine efficiency.

Referring now to fig. 14, an actuator 50 may be used in an internal combustion engine 700 to control engine valve positions, replacing the conventional cam shaft driven valve train. The engine 700 has a plurality of cylinders 712 (only one cylinder shown) disposed in a cylinder block 718, which in a V configuration are arranged to form a cylinder bank 714 with the upper ends of the cylinders 712 closed by cylinder heads 716. A pair of intake valves 740 (only one of which is shown) are longitudinally aligned on the inside of the cylinder 712 and its associated combustion chamber 744, and an exhaust valve 762 is located on the outside of the cylinder 712. An igniter in the form of a spark plug 766 or similar device is also disposed in the combustion chamber 744 of each cylinder 712.

An actuator 50 is provided for each of the intake and exhaust valves 740, 762, and the predetermined point P of the first link 150 is pivotably connected to the corresponding valve stem. The actuator 50 is adapted to position the intake and exhaust valves 740, 762 relative to the cylinder block 718 based on control signals received from a controller (not shown). The controller receives signals including valve movement data from encoder signals (which indicate rotor position relative to the housing 62) and including crankshaft position data. Based on these signals, the controller outputs control signals to the rotation motor 60 of the actuator 50 to control the position of the valves 740, 762 relative to the cylinder block 78.

Referring to FIG. 15, in other implementations, the actuator 50 may be indirectly connected to the respective intake and exhaust valves 740, 762. For example, the predetermined point P of the first coupling 150 may be connected to the intake pushrod 730. The push rod 730 actuates an intake rocker arm 732 that rocks on a pivoted shaft 734. The rocker arm 732 includes a pair of actuator arms 736, each of which preferably carries a hydraulic lash (lash) adjuster 738. The lash adjuster 730 engages the pair of intake valves 740. Although hidden from view by the actuator 60 and the intake pushrod 730 in this view, another actuator 50 is connected to the exhaust pushrod for actuating the main rocker arm 754 pivotable on the same pivotal shaft 734 as the intake rocker arm 732. The main rocker arm 754 in turn engages a secondary pushrod 756, which engages the secondary rocker arm 758. The actuation arm of the rocker arm 758 directly engages the exhaust valve 762. As with the previous implementations, the actuator 50 is adapted to position the intake and exhaust valves 740, 762 with respect to the cylinder block 718 based on control signals received from a controller (not shown). The controller receives signals including valve movement data from encoder signals (which indicate rotor position relative to the housing 62) and including crankshaft position data. Based on these signals, the controller outputs control signals to the rotation motor 60 of the actuator 50 to control the position of the valves 740, 762 relative to the cylinder block 718.

While the engine valve position control implementation shown herein provides an actuator 50 for each engine valve 740, 762 of the cylinder 712, this is not a limitation. For example, a single actuator 50 may be used to control multiple valves. For example, a single actuator may simultaneously actuate multiple input valves coupled to a single combustion chamber.

Controlling the valve operation using actuator 50 advantageously allows the motion of the valve to be decoupled from the rotation of the engine crankshaft. Furthermore, fully controllable valves allow full control of timing and lift throughout the engine speed range. This allows valve operation to be optimized under all operating conditions. It also allows for variations in operation, either in an energy efficient mode or in a maximum power delivery mode. It facilitates engine cylinder deactivation and allows for more complex deactivation schemes. For example, portions of a cylinder bank or individual cylinders may be deactivated rather than deactivating an entire cylinder bank as is currently practiced. Furthermore, controlling valve operation using actuator 50 allows the engine to self-start without the need for a separate starter to rotate the crankshaft.

The conversion of rotary to linear motion is provided using the engine valve control system described herein including the actuator 50 in a manner well suited to applications where the linear range of travel is maximized within a limited space. For example, unlike a linear actuator that must be arranged in line with the valve shaft and extend upward from the valve stem, the actuator 50 can arbitrarily control the valve lift profile from a position on one side of the valve, and thus add no height to the valve train. The position of the actuator 50 on this side of the valve may provide for linear displacement of the valve without the need for a lever or rocker arm, which may significantly reduce friction losses and wear of the valve guides.

This feature, in combination with the compact size of the actuator 50, allows for packaging of the actuator such that when multiple valves per cylinder are utilized, multiple actuators can be fitted around the cylinder or remotely located around the periphery of the cylinder while still providing full control of each valve.

Since the actuator 50 employs a rotary motor 60 that acts through a linkage to control valve position, the actuator 50 may be positioned away from the cylinder head 716. This is advantageous because it allows the actuator 50 and sensors to avoid the high temperatures associated with the cylinder exhaust valves and manifold. This increases the amount of power that can be dissipated in the coils of the actuator before the thermal demagnetization temperature is reached. Furthermore, the design of the cooling device is simplified, since the actuator motor is located away from the valve itself. For example, a cooling jacket may be provided that surrounds all of the actuator motors without interfering with other structures.

In the actuator 50, a rotary encoder 120 is used to sense position. The position of this sensor off the valve is located within the rotary motor 60. The rotary encoder 120 may be much cheaper and more reliable than a linear position and velocity sensor. It may also be located where it sees a lower temperature. Since the actuator 50 utilizes the rotary motor 60, the design and manufacture of a reliable sensor for detecting valve position and velocity is relatively straightforward.

Since the actuator 50 employs a rotary motor 60, this device is well suited for use in an engine 700 because of the large peak power required at high engine speeds to overcome cylinder burst pressures and open the exhaust valve. This requirement brings extreme demands on the power electronics of the system and also creates a need for maximum efficiency in the actuator. For the reasons discussed above, rotary motors, for example, are inherently more efficient than actuators that employ linear motors. The relative efficiency of the rotary motor may be used to possibly reduce the size of the motor itself or reduce the electrical power requirements or both.

From a packaging standpoint, the actuator 50, including the rotary motor 60 and the link 52, has a much lower profile than a linear motor, and due to the linked connection between the motor and the valve, the actuator can be integrated in-line with the valve so that the rotary motor does not directly overlie the valve. For example, the actuator 50 may be disposed between banks of a V-engine. In addition, a separate link (if necessary) may connect point P of link 52 to the valve. By positioning the actuator's rotary motor away from the valves, it becomes easier to package actively controlled valves for each cylinder system.

Precise control is required to avoid collision of the valve with the valve seat. The specific relationship between torque and position achieved by the actuator 50 simplifies control of the engine valve.

Referring to fig. 16, actuator 650 is an alternative implementation of actuator 50. The actuator 650 is substantially similar to the actuator 50 except that the end caps 100, 200 of the actuator 50 are modified to improve assembly simplicity. Specifically, a modified end cap (not shown) having a reduced outer diameter is formed, and the large diameter rotor bearing 89 supporting the end caps 100, 200 is replaced with a similar bearing of a smaller diameter. Due to the reduced diameter of the modified end cap, a third coupling 280 is provided which corresponds to and is dimensioned accordingly to the first bar 116 of the four-bar linkage.

Although the illustrated implementation is described as using specific motors and bearings, the invention is not limited to these components and it is understood that the motors and bearings are selected based on the requirements of a particular application.

Selected exemplary embodiments of mechanisms for converting rotational motion to linear motion are described above in some detail. It should be understood, however, that only the structures deemed necessary to illustrate the invention have been described herein. It is assumed that the secondary and ancillary components of other conventional structures and systems are known and understood by those skilled in the art. Further, although the working examples of the present invention have been described above, the present invention is not limited to the working examples described above, but various design changes may be implemented without departing from the present invention as set forth in the claims.

Claims (15)

1. An active vibration control device configured to control a position of a body, the device comprising:

at least one sensor configured to provide an input signal corresponding to movement of the body in at least one direction;

a first rotation motor configured to control a position of the body, an

A link comprising at least two pivotably engaged linkages connecting the first rotary motor to the body, the link configured to convert rotary motion output from the motor into linear motion of the body,

a controller providing control signals to the rotation motor based on the input signals from the at least one sensor, the rotation motor acting through the link to position the body in the at least one direction.

2. The active vibration control device of claim 1 wherein the torque required by the motor to provide a constant force at the body is substantially constant over a 100 degree angular rotation of the output shaft of the first rotary motor.

3. The active vibration control device of claim 1 wherein the link is configured to convert rotational motion of an output shaft of the motor to linear motion such that motion of the body is substantially proportional to an angular displacement of the output shaft within 180 degrees of rotation of the output shaft.

4. The active vibration control device of claim 1 wherein the link is configured to convert rotational motion of an output shaft of the motor to linear motion such that a torque required by the motor to provide a constant force at the body is substantially constant over a displacement range of the body of at least four inches.

5. The active vibration control device of claim 1 wherein the link is connected to an output shaft of the motor on one side of the motor, and the device further comprises a second link connected to the output shaft of the motor on a side of the motor opposite the one side.

6. The active vibration control device of claim 1 further comprising: a second rotary motor and a second link configured to control a position of the body, the first rotary motor and the second rotary motor being arranged such that their respective rotor axes are parallel.

7. The active vibration control device of claim 1 further comprising: a second rotary motor and a second link configured to control a position of the body, the first rotary motor and the second rotary motor being arranged such that their respective rotor axes are collinear.

8. The active vibration control device of claim 1 wherein the body comprises a vehicle seat.

9. The active vibration control device of claim 8 wherein the seat is disposed in a vehicle and the motor, which is fixed relative to an underside of the vehicle, is disposed between the underside and the seat.

10. The active vibration control device of claim 8 wherein the linear travel of the seat is at least 4 inches.

11. The active vibration control device of claim 1 wherein the controller provides control signals to the rotary motor to minimize acceleration sensed by the at least one sensor.

12. An actuator, comprising:

a rotary motor including an output shaft; and

a link connected to the output shaft, the link comprising:

a motor housing including a housing pivot pin defining a first rotational axis;

a first coupling secured to the output shaft, the output shaft defining a second axis of rotation that is parallel to and spaced from the first axis of rotation, the first coupling including a first coupling pivot pin disposed at a location spaced from the second axis of rotation and defining a third axis of rotation that is parallel to the first axis of rotation,

a second link pivotably connected at a first end to the first link pivot pin, the second link including a second link pivot pin defining a fourth axis of rotation parallel to the first axis of rotation, the second link pivot pin disposed between the first end of the second link and a predetermined point of the second link; and

a third link pivotally connected at a first end to the shell pivot pin and pivotally connected at a second end to the second link pivot pin,

wherein rotation of the output shaft causes linear movement of the predetermined point relative to the housing.

13. The actuator of claim 12, wherein the torque generated by the motor at the predetermined point is substantially constant over a 100 degree angular rotation of the output shaft for a constant force applied at the predetermined point.

14. The actuator of claim 12, wherein the link is connected to an output shaft of the motor on one side of the motor, and the actuator further comprises a second link connected to the output shaft of the motor on an opposite side of the motor from the one side.

15. The actuator of claim 12, wherein the shell pivot pin and each of the first and second link pivot pins are supported on bearings, and the first, second, and third links are configured such that the bearings are substantially coplanar.