JP2009177995A - Rectilinear-motion actuator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rectilinear-motion actuator which is miniaturized, and capable of omitting any DC resistance for motor deceleration by reducing the return operational speed by the compression of a spring, and increasing the driving force while suppressing the motor current when driving a load. <P>SOLUTION: The rectilinear-motion actuator includes a motor, a reduction gear mechanism coupled with a motor shaft of the motor, and a rectilinear, reciprocative motion mechanism for converting a rotary motion of a last-stage gear of the reduction gear mechanism to a rectilinear, reciprocative motion. The last-stage gear has a pin provided thereon which is offset from its center of rotation. The rectilinear, reciprocative motion mechanism includes a movable plate having a slit and allowing the pin to move within the slit. The movable plate offsets its reciprocative motion axis from the line passing through the center of the last-stage gear to one side, and an elastic member working on the movable plate is arranged at the position offset to the other side. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a linear actuator that converts the rotation of a motor into a linear reciprocating motion and outputs it, and can be used, for example, in a seat lock simple release device or the like for automotive electrical equipment.

  FIG. 7 is a diagram showing a configuration of a conventional linear actuator (see Patent Document 1). In the illustrated linear actuator, a motor is mounted on a mounting plate in a frame, a worm gear is provided on the motor shaft, and the motor is decelerated by a worm wheel engaged therewith. The worm wheel is provided with a structure capable of linear reciprocation by locomotion operation. That is, a long groove is formed in a guide portion provided in the worm wheel, and a pin provided on a fixing plate provided in the worm wheel slides in the long groove according to the rotation of the worm wheel. At this time, the rod connected to the guide portion is supported by a rod guide provided on the frame and reciprocates linearly.

As described above, the linear actuator shown in the figure achieves a reduction in the size of the unit by improving the reduction ratio by using the gear reduction mechanism as a worm type. However, since the arrangement of the worm gear and the worm wheel is orthogonal to the axis (that is, the motor shaft and the rod) that performs the linear reciprocating motion, a useless space is created. Even if the rod and the motor shaft are arranged in parallel, the unit width (the length of the unit in the direction perpendicular to the rectilinear reciprocating direction) is the length obtained by adding the motor radius to the worm wheel outer diameter. From the point of view, it becomes disadvantageous.
JP-A-4-295249

  As described above, the linear actuator is required to be reduced in size by reducing the unit width. When using a linear actuator for a seat lock simple release device, etc., when the wire is pulled to unlock the seat, and the wire is returned and locked, the motor is close to no load when the wire is returned, and the rotation speed Increases and noise increases. As a countermeasure, it is conceivable that a series resistor is connected to the motor when the wire is returned, and the rotational speed is reduced by a voltage drop caused by this. However, such a method has a series resistor that is inserted only when the wire is returned, and two polyswitches for countermeasures against burning that have different characteristics corresponding to the insertion and removal of the series resistor (when heated by overcurrent or overheating, The temperature inside the element rises, the resistance value increases, and an overcurrent / overheat protection element that limits the circuit current to a small level is required, resulting in an increase in cost.

  The present invention solves such problems and makes it possible to reduce the width of the unit, and not only to further reduce the size of the linear actuator but also to reduce the return operating speed by compressing the spring. The purpose of this is to eliminate the need for a series resistor for motor deceleration and to increase the driving force while suppressing the motor current during load driving.

  The linear motion actuator of the present invention includes a motor, a speed reduction mechanism unit coupled to the motor shaft, and a linear motion reciprocating motion mechanism unit that converts the rotation of the final stage gear of the speed reduction mechanism unit into a linear motion reciprocating motion. The last stage gear has a pin that is deviated from the center of rotation. The rectilinear reciprocating mechanism has a movable plate that is provided with a slit having a predetermined width and length, and in which the pin is movable. The movable plate has its reciprocating motion axis offset from the line passing through the center of the last stage gear to one side, and an elastic member acting on the movable plate is disposed at a position offset to the other side.

  The movable plate is configured in a U-shape as a whole by arranging a first arm serving as a reciprocating motion axis and a second arm on which an elastic member acts on both sides of a line passing through the center of the final stage gear. The elastic member can be constituted by a coil spring that acts as an auxiliary to the pulling driving force in the pulling direction of the movable plate and acts as a load in the pushing direction. The speed reduction mechanism has a worm gear fixed to the motor shaft and a worm wheel arranged so as to mesh with the worm gear, and the first arm of the movable plate has its reciprocating motion axis as the center in the width direction. In order to release the rotating shaft of the worm wheel, another slit is provided. A helical gear provided on the same axis line was provided on the rotating shaft of the worm wheel, and the helical gear was arranged so that the final stage gear meshed with the helical gear. An output member attaching portion for attaching a load is provided at the end of the first arm so as to coincide with the reciprocating motion axis of the movable plate.

  A sliding contact mechanism is provided that reciprocates the movable plate once when the switch is turned on. The sliding contact mechanism has a conductive member disposed on the insulating frame so as to have a predetermined pattern, and slides on the conductive member. The conductive member is fixed concentrically with the lower part of the last stage gear, while the contact point is fixed to the back side of the last stage gear that is displaced from the center of rotation. Then, when the last gear rotates once, it rotates once while contacting the conductive member.

  According to the present invention, by adding a coil spring, it is possible to increase the pulling force and reduce the return operating speed for noise reduction, and to reduce the return operating speed by compressing the spring, This eliminates the need for a series resistor for the burnout and only requires one polyswitch for preventing burnout. Further, a compact design can be achieved by disposing the tension arm and the compression arm on the opposite side with respect to the center of the movable plate. Furthermore, the width of the unit can be reduced by making it possible to reduce the worm wheel diameter with respect to the final gear.

  Hereinafter, the present invention will be described based on examples. FIG. 1 is a top view showing the overall configuration of a linear actuator embodying the present invention. However, the frame lid is shown in a removed state. 2 is a longitudinal sectional view of the linear actuator shown in FIG. 1 cut at the center of the movable plate. The linear actuator includes a motor, a speed reduction mechanism, and a linearly reciprocating motion mechanism composed of a movable plate and an elastic member (spring). These configurations are fixed in a frame (for example, made of resin), and a frame lid (for example, made of resin) is covered on the upper surface. As the motor itself, a normal, for example, DC-driven commutator motor can be used. The illustrated motor is fixed in a recess provided in the frame, and a motor shaft extends from the center of one side surface of the motor housing to the outside of the motor as a motor output shaft, and a speed reduction mechanism is coupled to the motor shaft.

  The speed reduction mechanism is composed of a worm gear fixed to the motor shaft by press fitting, a worm wheel (helical gear A), a helical gear B, and a helical gear C as the final gear. The worm wheel (helical gear A) is arranged to mesh with the worm gear. At the center of the helical gear A, a rotating shaft supported by the frame supports the helical gear so as to be rotatable. As a result, the rotational force around the motor shaft obtained from the motor is changed by the worm gear and the helical gear A to the rotation around the rotation axis perpendicular to the worm gear and the helical gear A, and deceleration is given (the example of the configuration shown in the figure is 61: 1). Slow down). Next, in the illustrated example, the rotational force transmitted to the helical gear A is decelerated by the helical gear B fixed around the same rotation axis and the helical gear C meshing with the helical gear B ( The configuration example shown is 3.133: 1 reduction, and the overall reduction ratio is 191: 1).

  Next, the rotational force generated by the helical gear C is converted into a linear reciprocating motion of a movable plate constituting a linear reciprocating motion mechanism via a pin fixed to the helical gear C at a position displaced from the center of the helical gear C. . This linearly reciprocating direction is a direction parallel to the motor shaft axis. The movable plate is generally configured in a U shape so that the tension arm and the compression arm extend in the same direction and in parallel from the movable plate base. Long and narrow first and second slits (long holes) are arranged in directions perpendicular to each other in the base and the pull arm of the movable plate.

  The first slit has its length direction arranged in a direction orthogonal to the motor shaft axis, and its center position in the length direction is located on a line that passes through the center of the final stage gear and is parallel to the motor shaft axis. . On both sides of this line through the center of the final gear, there will be a tension arm on the side far from the motor shaft axis and a compression arm on the near side. In the 1st slit, the pin provided in the helical gear C is arrange | positioned so that a movement is possible. A sleeve that can slide and rotate is added to the outer periphery of the pin, and the friction force is reduced by rotating the pin as it moves in the first slit. The reciprocating motion axis of the movable plate at the center of the width of the tension arm is offset from the line passing through the center of the final gear in the direction away from the motor shaft (shown as “offset distance A”). Thus, by shifting (offset) the center of the movable plate (reciprocating motion axis), it becomes possible not only to reduce the width of the unit, but also the weakest tensile force point as will be described in detail later. It is possible to convert the force at the straight line into a straight reciprocating motion with little loss.

  The second slit is arranged with its length direction in the motor shaft axial direction with the reciprocating motion axis of the pulling arm of the movable plate as the center in the width direction. The second slit is provided in order to escape a rotating shaft provided in common to the helical gear A and the helical gear B. As a guide function of the movable plate, a groove is provided in the frame or the frame lid, and the movable plate is inserted into the groove to enable reciprocating motion, while the movable plate is regulated from both sides. Further, the second slit functions as a positioning of the movable plate in the direction orthogonal to the motor shaft and an additional guide for the movable plate.

  As a result, the second slit is also offset in the direction away from the longitudinal center of the first slit (hence, the center of the helical gear C), and the offset direction is away from the motor shaft (in the figure). Down). The offset distance A between the slits coincides with the offset distance between the rotational centers of the helical gears A and B and the rotational center of the helical gear C.

  An elastic member having one end supported is provided at the tip of the compression arm of the movable plate. The other end of the elastic member is supported by a fixed part such as a frame or a frame lid. As the elastic member, a hydraulic damper or an air cylinder can be used in addition to the coil spring as shown. By providing this elastic member, as will be described in detail later, it is possible to increase the pulling force and reduce the return operation speed for noise reduction. A compact design is possible by arranging the tension arm and the compression arm on the opposite side with respect to the center of the movable plate.

  With this configuration, the rotation of the motor is converted into the linear reciprocation of the movable plate by moving the pin in the first slit provided in the movable plate base. An output member attaching portion for attaching an output member (wire or bar) (not shown) is provided at the tip of the pulling arm of the movable plate that reciprocates so as to coincide with the reciprocating motion axis. The other end of the output member (not shown) is coupled to an external load, for example, a seat lock simple release device, and is driven in a direction of pulling or pushing it.

  FIG. 3 is a diagram for explaining the action of the movable plate. A distance obtained by shifting the center position of the pulling arm of the movable plate (and the corresponding second slit position) from the rotation center of the helical gear C (final gear) is indicated as “offset distance A” in the drawing. The illustrated direct acting actuator has a structure in which the rotation shaft (hence, the second slit) common to the helical gears A and B is arranged on the shifted axis line so that the rotation shaft can penetrate the second slit. Thus, by shifting the center, it becomes possible to convert the force at the weakest tensile force point into a straight reciprocating motion with little loss.

  As pin positions provided on the helical gear C, in FIG. 3, three points of a start point / end point, an intermediate point, and a maximum movable position are illustrated. When the helical gear C makes one clockwise rotation from the start point position, as shown in FIG. 4, it is driven in the direction of pulling the movable plate from the start point position to the maximum movable position and pushed out from the maximum movable position to the end point position. Will be driven to. FIG. 4 shows the output characteristics of the linear actuator. The broken line shows the output by the motor driving force, the alternate long and short dash line shows the reaction force of the spring, and the solid line shows the resultant force of both. The resultant force during the pulling action acts so that the spring force when the compressed spring is extended is added to the motor driving force. Conversely, when acting in the pushing direction, the spring is compressed, so that the resultant force obtained by subtracting the spring force from the motor driving force acts on the movable plate. Further, in both cases of tension and extrusion, the force at the intermediate point is minimized as shown in FIG.

  As shown in FIG. 3, the second slit position (pull arm center) is close to the shaft orthogonal direction with respect to the pin position at the intermediate point during pulling driving. When driven by pulling at a position far away from the center of the pull arm (reciprocating direction axis) in the direction perpendicular to the shaft, the driving force is distributed not only in the reciprocating direction but also in the orthogonal direction, resulting in poor efficiency. As in the configuration, the pull driving force can be prevented from being lowered at the intermediate point by bringing the center of the pull arm closer to the pin position at the intermediate point where the minimum tensile force is obtained in the direction perpendicular to the shaft. However, at the intermediate point when the pin has passed the maximum movable position and the pushing force is acting, the pin position is further away from the center of the pull arm, the loss is further increased, and the pushing driving force is further reduced. However, this type of linear actuator usually returns to the end point position without any load after operating the load such as the seat lock release device at the maximum movable position or immediately before it. In addition, a decrease in the pushing driving force is not a problem. Rather, it is necessary to further reduce the pushing driving force, and a coil spring is provided as a configuration for that purpose.

  The linear motion actuator of the present invention can be configured to drive the external load in the direction of pushing out the external load using a bar as an output member. For example, the external load of the simple device for releasing the seat lock is pulled using a wire. When configured to drive in the direction, the coil spring is incorporated so as to act in the pulling direction of the movable plate. As a result, the tensile force can be increased by the return force of the coil spring without changing the motor specifications. The load current value can be reduced by increasing the tensile force. Thus, the noise is reduced by acting in the direction of compressing the spring and decelerating the return operation speed at the same time when the movable plate enters the return operation from the maximum tension position.

  FIG. 5 shows the motor load current characteristics during one reciprocation of the movable plate. Compared with no spring, with a spring, the current is low and the pulling operation time is short. After the starting current flows at the start, the peak current can be suppressed with the assistance of the spring while the movable plate is being pulled and driven. Also, the return operation time is longer. However, after passing the maximum movable position, a motor load current for compressing the spring flows.

  FIG. 6 is a diagram illustrating a circuit configuration for driving the linear motion actuator shown in FIG. From the DC power source + terminal, current is supplied to the-terminal through the motor via the switch SW or the sliding contact mechanism. As shown in FIG. 2, the sliding contact mechanism is composed of a conductive member arranged so as to have a predetermined pattern on the insulating frame, and a contact (brush) that makes sliding contact with the conductive member. The conductive member is fixed below the helical gear C and concentrically therewith. The contact is fixed to the back side of the rotating helical gear C at a position displaced from the center of rotation, and rotates once while contacting the conductive member when the helical gear C rotates once.

  The conductive member illustrated in FIG. 6 is electrically separated (insulated) into the inner peripheral side (region B) and the outer peripheral side (region A). Each of the regions A and B is a start point / end point position, and has a lead-out portion from the brush sliding portion, and one end of the wiring is connected to the tip thereof. The contact has a configuration in which an inner peripheral brush that is in sliding contact with the region B and an outer peripheral brush that is in sliding contact with the region A are integrally connected.

  Here, the switch SW is disposed outside the unit, and this switch is turned ON / OFF by a human operation (manual). The contact position shown in FIG. 6 is the start point / end point position. At this time, both the inner and outer brushes of the contacts are on the region B, and the connection with the outer region A is cut off. When the switch SW is turned on, a current flows from the + terminal to the − terminal through the motor, and the motor rotates. When the motor rotates, the contact that moves with the rotation of the helical gear C short-circuits the region B and the region A, and a power supply circuit to the motor that passes through this contact is formed. Thus, even if the switch is released and turned off, the motor continues to rotate because the motor supplies power via the sliding contact mechanism. Then, returning to the illustrated start / end positions, the electrical connection between the region B and the region A is turned off and the motor stops. In this way, the series resistor for motor deceleration is not required, and the motor power supply circuit during pulling driving and returning is the same, so only one polyswitch is inserted to prevent burning.

It is a top view which shows the whole structure of the linear motion actuator which embodies this invention. It is the longitudinal cross-sectional view which cut | disconnected the linear motion actuator shown in FIG. 1 in the center of a movable plate. It is a figure explaining the effect | action of a movable plate. It is a figure which shows the output characteristic of a linear motion actuator. It is a figure which shows the motor load current characteristic during a movable plate reciprocating once. It is a figure which illustrates the circuit structure for driving the linear motion actuator shown in FIG. It is a figure which shows the structure of the conventional linear motion actuator.

Claims (6)

In a linear actuator having a motor, a reduction mechanism coupled to the motor shaft, and a linear reciprocation mechanism that converts rotation of the final gear of the reduction mechanism into linear reciprocation.
The final gear has a pin provided to be deviated from the rotation center thereof,
The rectilinear reciprocation mechanism has a movable plate configured by providing a slit having a predetermined width and length and allowing the pin to move in the slit.
The movable plate has its reciprocating motion axis offset to one side from a line passing through the center of the final stage gear, and an elastic member acting on the movable plate is disposed.
A linear actuator consisting of The linear motion actuator according to claim 1, wherein the elastic member is constituted by a coil spring that acts to assist a tensile driving force in a pulling direction of the movable plate and to act as a load in a pushing direction. The speed reduction mechanism has a worm gear fixed to the motor shaft and a worm wheel arranged to mesh with the worm gear, and the first arm of the movable plate has its reciprocating motion axis in the width direction. The linear motion actuator according to claim 2, wherein a separate slit is provided at the center to allow the rotation axis of the worm wheel to escape. The linear motion actuator according to claim 3, wherein a helical gear provided on the same axis is provided on a rotation axis of the worm wheel, and the final gear is arranged so as to mesh with the helical gear. The linear motion actuator according to claim 4, wherein an output member mounting portion for mounting a load is provided at an end portion of the first arm so as to coincide with a reciprocating motion axis of the movable plate. A sliding contact mechanism is provided for reciprocating the movable plate once when the switch is turned on. The sliding contact mechanism includes a conductive member disposed on the insulating frame so as to have a predetermined pattern, and a conductive member disposed on the conductive member. The conductive member is fixed concentrically therewith below the final gear, while the contact is rotated at a position deviated from the center of rotation. The linear motion actuator according to claim 5, wherein the linear actuator is fixed to the back surface side and rotates once while contacting the top of the conductive member when the final stage gear rotates once.

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