JP2009236281A - Feed screw mechanism and rear wheel toe angle variable control device for vehicle using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a feed screw mechanism, smoothly operated, freely settable in a lead angle to the minimum, and improved in a self locking performance. <P>SOLUTION: This feed screw mechanism 20 includes a male screw member 14, which is formed with a male screw 14a and rotatably supported by housings 10 and 11 connected to a vehicle body, and an output rod 15, which has a female screw 15a to be screwed to the male screw 14a and supported by the housings 10 and 11 freely to move in the axial direction and coupled to a rear wheel 5 side. The diameter d of a valley of the female screw 15a of the output rod 15 is formed larger than the outer diameter D of the male screw 14a of the male screw member 14, and the output rod 15 is arranged so that the axis 15A thereof is offset in parallel with the axis 14A of the male screw member. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a feed screw mechanism and a vehicle rear wheel toe angle variable control device using the same, and more particularly to a technique for preventing a feed screw from reversely operating due to an external force.

  In general, a vehicle having four wheels on the front, rear, left and right has a toe angle set on the front wheels to ensure steering stability, and the left and right front wheels are steered when changing the traveling direction. In recent years, the toe angle of the rear wheels can be controlled to improve stability during braking and responsiveness during acceleration, or to prevent diagonal running during high-speed turning and to make a small turn during low-speed turning. Automobiles equipped with variable angle control devices have been developed.

  As such a toe angle variable control device, a lateral link in the suspension device that supports the left and right rear wheels, or an electric actuator that linearly displaces at the connecting portion of the trailing link with the vehicle body, and by extending and retracting this, A configuration in which the toe angles of the left and right wheels can be individually changed is known (see Patent Document 1).

  As a linear displacement actuator, a linear displacement actuator using an electric motor and a feed screw mechanism is known. In this type of linear displacement actuator, the rotational motion of the electric motor is converted into linear motion (hereinafter referred to as “normal operation”), and the lead angle of the screw is set smaller than the friction angle. Even if there is a self-locking function, even if an external force acting in the axial direction is applied, the linear motion is not converted into a rotational motion (hereinafter referred to as “reverse operation”).

However, when a linear displacement actuator such as the above-described variable toe angle control device is applied to a vehicle, an external force in the axial direction may rotate the electric motor due to the influence of traveling vibration or the like, and the linear displacement actuator may reversely operate. . Even in such a case, as a screw mechanism that prevents reverse operation (no loosening), a thread is formed so that a section having a loose lead angle and a section having a steep lead angle are alternately repeated. A screw mechanism has been proposed (see Patent Document 2).
Japanese Patent Laid-Open No. 9-30438 JP 2007-16797 A

  However, in the screw mechanism described in Patent Document 2, for example, if the lead angle in the loose section is 0 degree, the external force acting in the axial direction does not generate rotational torque, but the lead angle follows the spiral. Therefore, the nut member operates in the axial direction in stages, and the actuator cannot be operated smoothly so as to be proportional to the rotational speed or rotational speed of the motor. On the other hand, it is conceivable to increase the reliability of self-locking by making the lead angle extremely small. However, such a limitation has various design features such as the motor rotation speed, the gear ratio of the speed reducer, and the rated output of the electric motor. This is not preferable because it restricts the origin.

  The present invention has been made in view of such a background. A feed screw mechanism that can operate smoothly, can set a lead angle as freely as possible, and has improved self-locking, and a rear wheel using the same. An object is to provide a variable toe angle control device.

  In order to solve the above-described problems, according to the present invention, one of a male screw member and a female screw member that are screwed together is rotatably supported by a housing, and the other is supported by the housing so as to be axially movable. In the feed screw mechanism, the male screw member has a diameter smaller than the diameter of the female screw member, and is arranged so that its axis is offset parallel to the axis of the female screw member.

  A male screw member connected to one of the vehicle body side member and the rear wheel side member, and a female screw member screwed to the male screw member and connected to either the vehicle body side member or the rear wheel side member In a vehicular rear wheel toe angle variable control device that individually changes the toe angle of the left and right rear wheels by extending and contracting a pair of left and right screw type linear actuators respectively provided with the male screw member and the female screw member Either one is rotatably supported by the housing, and the other is supported by the housing so as to be axially movable. The male screw member has a diameter smaller than the diameter of the female screw member, and the axis thereof is the female screw member. It arranges so that it may be offset in parallel to the axis line.

  According to the feed screw mechanism of the present invention, when an external force in the axial direction is input to the male screw member or the female screw member, the load is transmitted only to one side with which the screw is engaged, so that a moment is generated in the male screw member and a twist occurs. Therefore, at the time of input to the contraction side, the tops of the threads of the external thread or the internal thread come into contact with the bottoms of the internal threads of the internal thread or the external thread with a radial force, or the flank of the external thread is a radial force against the flank of the internal thread. The frictional resistance between the male screw and the female screw is increased. On the other hand, at the time of input to the extension side, the frictional resistance of the screw portion on the opposite side increases. Therefore, the self-locking property at the time of reverse operation is enhanced, and the possibility that the feed screw mechanism reversely operates can be reduced even if an external force in the axial direction is input to the male screw member or the female screw member.

  Further, if the feed screw mechanism having the above configuration is applied to the screw type linear actuator constituting the rear wheel toe angle variable control device of the vehicle, the linear actuator can be expanded and contracted during normal operation, but a lateral force acts on the rear wheel. Even in such a case, the linear actuator exhibits the self-locking function more reliably by the increased frictional resistance. Therefore, it is possible to reduce the possibility that the actuator reversely operates even with vibrations caused by kickback from the road surface and repeated input of expansion and contraction during meandering.

<< Configuration of Embodiment >>
Hereinafter, an embodiment of a rear wheel toe angle variable control device according to the present invention will be described in detail with reference to the drawings. FIG. 1 is a perspective view of the left rear suspension. A double wishbone type rear suspension 1 changes a toe angle of a knuckle 2 that rotatably supports a rear wheel 5, an upper arm 3 and a lower arm 4 that connect the knuckle 2 to a vehicle body so as to be movable up and down, and a rear wheel 5. Accordingly, the electric actuator 10 is connected to the knuckle 2 and the vehicle body, and the damper 6 with a suspension spring for buffering the vertical movement of the rear wheel 5 is provided.

  The upper arm 3 and the lower arm 4 have base ends connected to the vehicle body via rubber bush joints 3a and 4a, respectively, and tip ends connected to the upper and lower portions of the knuckle 2 via ball joints 3b and 4b, respectively. The electric actuator 10 has a base end connected to the vehicle body via a rubber bush joint 10a and a tip connected to the rear portion of the knuckle 2 via a rubber bush joint 10b. The damper 6 with suspension spring has an upper end connected to the vehicle body and a lower end connected to the upper portion of the knuckle 2 via a rubber bush joint 6a.

  By adopting such a configuration, when the electric actuator 10 is driven to extend, the knuckle 2 rotates rearward in the vehicle width direction so that the toe angle of the rear wheel 5 is set in the vehicle traveling direction inside (toe-in side). When the electric actuator 10 is driven to contract, the knuckle 2 turns rearward inward in the vehicle width direction to change the toe angle of the rear wheel 5 outward in the vehicle traveling direction (toe-out side). As described above, the electric wheel actuators 10 provided to the left and right rear wheels 5 are extended and retracted, whereby the rear wheel toe angle variable control device can individually control the toe angles of the left and right rear wheels 5. .

  Next, the electric actuator 10 will be described with reference to FIG. FIG. 2 is a longitudinal sectional view of the electric actuator 10. The electric actuator 10 includes a first housing 11 in which a rubber bush joint 10 a on the vehicle body is formed, a second housing 12 fastened to the first housing 11 with a plurality of bolts 13, and a telescopic support supported by the second housing 12. And an output rod 15 (female screw member) in which a rubber bush joint 10b on the knuckle 2 side is formed. A DC motor 16 with a brush as a driving source is accommodated in the first housing 11 and fastened to the first housing 11 with a bolt 17. A planetary gear type speed reducer 18, an elastic coupling 19, and a feed screw mechanism 20 using a trapezoidal screw are accommodated in the second housing 12.

  The DC motor 16 has a cup-shaped stator yoke 16b, two magnets 16c arranged at equal intervals on the inner peripheral surface of the stator yoke 16b, and a plurality of magnetic poles, and close to the inner peripheral side of the magnet 16c. A rotor 16d provided and a rotating shaft 16a provided integrally at the center of the rotor 16d are provided. In the DC motor 16, the flange portion 16 e of the stator yoke 16 b is fixed to the first housing 11 with a plurality of bolts 17, and the rotating shaft 16 a rotated by energization rotates the male screw member 14 via the speed reducer 18.

  The speed reducer 18 is configured by combining two stages of a first planetary gear mechanism 18a and a second planetary gear mechanism 18b. The speed reducer 18 decelerates the rotation of the rotating shaft 16a of the brushed DC motor 16 in two stages and outputs it. It transmits to the carrier 18c which is a member. The carrier 18 c is connected via a coupling 19 to an input flange 20 a that is an input member of the feed screw mechanism 20. The coupling 19 includes two outer elastic bushes, an inner elastic bush, and the like. The coupling 19 exhibits an automatic alignment function that absorbs a slight axial deviation between the carrier 18c and the input flange 20a, and suddenly changes torque. It absorbs and enables smooth power transmission.

  The output rod 15 is slidably and non-rotatably supported by two slide bearings 21 fixed to the inner peripheral surface of the second housing 12. A single spiral female screw 15a having a trapezoidal cross section formed on the hollow inner peripheral surface of the output rod 15 is a single spiral coil having a trapezoidal cross section of the male screw member 14 fastened to the input flange 20a. The feed screw mechanism 20 is configured by screwing into the male screw 14a.

  The trough diameter d of the female screw 15a of the output rod 15 is larger than the outer diameter D of the male screw 14a of the male screw member 14, and the axis 15A of the output rod 15 is offset in parallel to the axis 14A of the male screw member 14. (See FIGS. 3 and 4). As a result, the output rod 15 is in a state in which the female screw 15a is screwed into the male screw 14a of the male screw member 14 only on one side (the lower side in FIG. 2) with respect to the axis 15A. The rotary motion of 20a is converted into a thrust motion and moved linearly.

  In the feed screw mechanism 20, the lead angle of the screw is set to be smaller than the friction angle of the male screw 14a with respect to the female screw 15a, so that when the load is applied to the output rod 15, the male screw member 14 is controlled regardless of the magnitude of the load. It has a self-locking function that does not rotate.

<< Effects of Embodiment >>
Next, with reference to FIGS. 1-4, the effect of the toe angle variable control apparatus which concerns on embodiment is demonstrated. 3 is a schematic view of the feed screw mechanism 20, and FIG. 4 is a cross-sectional view taken along the line IV-IV in FIG. 3. The right side shows the male screw member 14a and the left side shows the output rod 15.

  When the automobile travels, the load acting on the rear wheel 5 is input to the electric actuator 10 via the knuckle 2 while changing the magnitude and direction. In particular, during high-speed turning, a large lateral load is input to the output rod 15. However, as described above, the feed screw mechanism 20 of the electric actuator 10 has a self-lock function, so The male screw 14 does not rotate. However, when the kickback from the road surface and the external force in the expansion / contraction direction are alternately input, or when the friction coefficient of the flank is reduced due to long-term use, the male screw 14 may be slightly rotated.

  However, as shown in FIGS. 3 and 4, according to the feed screw mechanism 20 according to the present embodiment, when an external force F in the contraction-side axial direction is input to the output rod 15, the male screw 14 a and the female screw 15 a Since the load is transmitted only through the contact region 22 on one side (the lower side in FIG. 3) where the two engage with each other, a moment M is generated in the male screw member 14 around the input flange 20a, and the feed screw mechanism 20 is twisted. Occurs. That is, the top of one side of the male screw 14a and the bottom of the valley on one side of the female screw 15a abut against each other with a radial force, and the top of the mountain on one side of the female screw 15a and the bottom of the one side of the male screw 14a have a diameter. Contact with direction force. Therefore, the frictional resistance between the male screw 14 and the female screw 14 increases, and the self-locking function of the electric actuator 10 acts more reliably.

  On the other hand, when an external force in the axial direction on the extension side is input to the output rod 15, a moment is generated in the male screw member 14 about the input flange 20 a to rotate upward in the figure, thereby causing the male screw 14 and the female screw 14 to move. The frictional resistance increases, and the self-locking function of the electric actuator 10 acts more reliably. Thereby, even if an external force in the axial direction is input to the output rod 15, a strong self-locking function works, and the possibility that the electric actuator 10 is reversely operated is reduced.

  Therefore, in the rear wheel toe angle variable control device of the vehicle according to the present embodiment, the electric actuator 10 operates in reverse to the rear wheel 5 even with respect to vibration caused by kickback from the road surface or repeated input of expansion and contraction during meandering. The possibility that the toe angle will change is reduced.

  Although the description of the specific embodiment is finished as above, the present invention is not limited to the above embodiment and can be widely modified. For example, in the rear wheel toe angle variable control device, the internal thread member may not be slidable with respect to the housing, but the external thread member may be slidable, and the internal thread member is connected to the vehicle body side member. May be. Further, the male screw and the female screw need not be trapezoidal screws as long as they constitute feed screws, and may be triangular screws or square screws.

  In the above embodiment, the female screw member has a helical shape. However, depending on the difference in diameter between the male screw member and the female screw member, the lead angle of the screw, the angle of the thread, etc., the female screw is divided on the non-threaded side. It is good also as a form to do. Furthermore, in addition to these changes, changes can be made as appropriate without departing from the spirit of the present invention.

Rear view of rear suspension Vertical section of electric actuator Schematic diagram of the feed screw mechanism IV-IV sectional view in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Electric actuator 11 1st housing 12 2nd housing 14 Male thread member 14a Male thread 15 Output rod (Female thread member)
15a Female screw 16 Brushed DC motor 20 Feed screw mechanism d Output rod valley diameter D Male screw member outer diameter F External force M Moment

Claims (2)

One of a male screw member and a female screw member that are screwed together is rotatably supported by the housing, and the other is a feed screw mechanism that is supported by the housing so as to be axially movable.
The feed screw mechanism, wherein the male screw member has a diameter smaller than that of the female screw member, and is arranged so that an axis thereof is offset in parallel to an axis of the female screw member. A male screw member connected to one of the vehicle body side member and the rear wheel side member, and a female screw member screwed to the male screw member and connected to either the vehicle body side member or the rear wheel side member. A vehicle rear wheel toe angle variable control device that individually changes the toe angle of the left and right rear wheels by extending and retracting a pair of left and right screw type linear actuators respectively provided,
One of the male screw member and the female screw member is rotatably supported by the housing, and the other is supported by the housing so as to be axially movable.
The rear wheel toe angle variable control device characterized in that the male screw member has a diameter smaller than the diameter of the female screw member and is arranged so that its axis is offset in parallel to the axis of the female screw member.

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