JP2008239068A - Shock absorber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce shock generated when a nut collides with a stopper such as a bush. <P>SOLUTION: A damper device has a screw mechanism 30 converting linear movement into rotational movement by a ball screw. In the male screw part 32a of a screw shaft 32, the screw lead L1 formed in a neutral area A1 is formed to have the same lead as a female screw part 34a, and the screw lead L2 formed in a braking area A2 other than the neutral area is formed smaller than the screw lead L1 formed in the neutral area A1 (L2<L1). Thereby, when the nut 34 is displaced in the braking area A2, since frictional resistance between the nut 34 and the screw shaft 32 is increased in comparison with a case where the nut is displaced in the neutral area A1, the nut 34 is prevented from being largely displaced when the nut is displaced from the neutral area A1 of the male screw part 32a to the braking area A2 thereof. Therefore, the shock generated when the nut 34 collides with the bush 52 can be reduced. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a shock absorber.

  As a shock absorber for a vehicle, for example, in the invention described in Patent Document 1, a screw mechanism that converts linear motion including a bolt portion and a nut portion into rotational motion, an electric generator that attenuates rotational motion of the bolt portion, and the like It is comprised.

The generator is composed of a stator and a rotary electric motor having a rotor that rotates within the stator, and this attenuator uses a magnetic rotational resistance for rotating the rotor. To generate a damping force.
JP 2006-117209 A

  By the way, generally, stoppers made of an elastic member such as rubber are arranged on both ends in the axial direction of the rotating shaft, and the nut portion is displaced more than a predetermined amount in the rotating shaft direction by this stopper. Is regulated. However, when there is a sudden input to the shock absorber, the nut portion may violently collide with the stopper, and the stopper may be greatly damaged.

  An object of this invention is to provide the buffering device which can reduce the impact which arises when a nut part collides with a stopper in view of the said point.

  The shock absorber according to claim 1, which has been made to achieve the above object, includes a bolt portion in which a male screw portion is formed, and a nut portion in which a female screw portion that is screw-coupled to the male screw portion is formed, Screw mechanism that converts linear motion input from the outside into rotational motion, damping force imparting means that imparts damping force to attenuate the rotational motion converted by the screw mechanism, and both ends of the bolt portion in the rotational axis direction And a stopper that restricts the nut portion from being displaced by a predetermined amount or more in the rotation axis direction.

  And the pitch of the screw formed in the neutral region excluding both end sides in the rotation axis direction of the male screw portion is the same as the pitch of the female screw portion, and is formed in the male screw portion other than the neutral region. The screw pitch is different from the screw pitch formed in the neutral region.

  Thus, when the nut portion displaces one end side or the other end side (region other than the neutral region) of the male screw portion, the friction between the nut portion (female screw portion) and the bolt portion (male screw portion). Since the resistance becomes larger than when the neutral region is displaced, the nut portion is reduced from being largely displaced when the male screw portion is displaced from the neutral region to a region other than the neutral region.

  For this reason, even when there is a sudden input to the shock absorber from the outside, the speed when the nut part is displaced in a region other than the neutral region is compared to the case where the pitch of the male screw part is the same throughout the region. Since it becomes late | slow, the impact which arises when a nut part reaches | attains the edge part of an external thread part and collides with a stopper can be fully suppressed. Therefore, the impact generated when the nut portion collides with the stopper can be reduced.

In the second aspect of the present invention, a power transmission unit that transmits the rotational motion of the bolt unit to the damping force application unit is disposed between the bolt unit and the damping force application unit. It is characterized by being composed of a super elastic member whose elastic coefficient becomes smaller as it becomes larger.

  Thus, only when the external input due to vibration or the like changes abruptly, the power transmission unit is greatly distorted, so the rotation angle of the damping force applying means is smaller than the rotation angle of the bolt unit. Therefore, since the transmission rate of the rotational motion transmitted from the bolt portion to the damping force applying means can be reduced, the load applied to the damping force applying means can be reduced.

  If the screw mechanism is constituted by a ball screw as described in claim 3, the absolute frictional resistance is made smaller than that of a general screw mechanism constituted by a male screw and a female screw. Therefore, the loss when the nut portion displaces the male screw portion of the bolt portion can be reduced.

  Further, when the screw mechanism is configured by a ball screw, the pitch of the screw formed in the male screw portion other than the neutral region is the same as that of the screw formed in the neutral region. It is better to make it smaller than the pitch.

  In this way, in the state where the nut has entered the region other than the neutral region from the neutral region of the male screw portion, the force acting from the ball of the ball screw works in a direction to widen the groove of the male screw portion, It works in the direction of shrinking between the grooves of the nut (female thread).

  Therefore, since it can suppress that a nut part loses earlier than a bolt part, the replacement time of a nut part can be made later than the replacement time of a bolt part.

In the present embodiment, the shock absorber according to the present invention is applied to a suspension of a four-wheeled vehicle, and the present embodiment will be described below with reference to the drawings.
1. Overall Configuration of Suspension FIG. 1 is a configuration diagram illustrating the configuration of a suspension according to the present embodiment. The suspension according to the present embodiment includes a coil spring 10 and a damper that absorbs vibration of the coil spring 10 as illustrated in FIG. It is comprised by the apparatus 20 grade | etc.,.

The damper device 20 includes mechanical parts such as a screw mechanism 30, a damping force applying mechanism 40, a power transmission member 50 and a bush 52, and electrical parts such as a control unit 70.
The mechanical portion of the damper device 20 is disposed in the coil spring 10 so that the damper device 20 and the coil spring 10 are integrated (unitized), and the suspension according to the present embodiment is integrated in this way. In this state, it is assembled to the vehicle body (not shown).

  The screw mechanism 30 includes a screw shaft 32 having a male screw portion 32a and a nut 34 having a female screw portion 34a that is screw-coupled to the male screw portion 32a via a plurality of balls 34b. It is a screw.

  The nut 34 is fixed to the inner wall side of a first housing (inner tube) 54 formed in a substantially cylindrical shape. The first housing 54 is a second housing (outer tube) formed in a substantially cylindrical shape. ) 56 is assembled to be displaceable on one end side in the longitudinal direction (lower end side in FIG. 1). And the longitudinal direction one end side (lower end side of FIG. 1) of the 1st housing 54 is assembled | attached to the wheel (illustration omitted) side.

  For this reason, when the wheel is linearly moved up and down (linearly) by a road surface step or the like, the first housing 54 is displaced in the second housing 56 in the axial direction in response to the external input, and the nut 34 is directly moved. Because of the dynamic motion, the screw shaft 32 rotates according to the linear motion.

That is, in this embodiment, the linear motion of the wheel input via the nut 34 is converted into a rotational motion by the screw mechanism 30 and transmitted to the rotor 44 of the damping force generation mechanism 40 described later.
Note that a sliding contact portion 54A that is slidably in contact with the inner peripheral surface of the second housing 56 is provided on the outer peripheral portion of the other end in the longitudinal direction of the first housing 54 (the upper end side in FIG. 1). The linear motion of the first housing 54 is guided by the sliding contact portion 54A.

  A third housing 60 is fixed to the other end in the longitudinal direction of the second housing 56 (upper end in FIG. 1), and a bearing that rotatably supports the screw shaft 32 is supported on the third housing 60. 58 is assembled.

  Further, as shown in FIG. 2, the male screw portion 32a formed on the screw shaft 32 includes a screw lead (pitch) L1 at the central portion in the rotation shaft 32b direction of the screw shaft 32 and a screw at both end portions in the rotation shaft 32b direction. Is different from the lead L2.

The lead means the distance that the nut 34 moves in the axial direction with one rotation of the screw shaft 32 (see JIS B 1191 etc.), and is equivalent to a so-called screw pitch.
Specifically, a screw lead L2 formed in a region A2 (hereinafter referred to as a braking region A2) other than the neutral region A1 in the male screw portion 32a of the screw shaft 32 is a screw formed in the neutral region A1. Is set to be smaller than the lead (pitch) L1 (L2 <L1).

  On the other hand, the female thread portion 34a of the nut 34 is set to the same lead as the lead L1 in the entire neutral region A1. Therefore, as will be described later, in the neutral region A1, the screw shaft 32 is rotationally displaced according to the linear movement displacement of the first housing 54, whereas in the braking region A2, the displacement relative to the displacement of the first housing 54 is achieved. Resistance is generated.

  Here, the neutral region A1 refers to a region in which the nut 34 can normally move in the male screw portion 32a, that is, a region in which the damper device 20 can be normally operated. From the male screw portion 32a to the braking region A2 Refers to the area excluding.

  The braking region A2 includes, for example, a region (T + α) obtained by adding a predetermined length α to the dimension T in the rotation shaft 32b direction of the nut 34 from one end to the other end side of the male screw portion 32a, and the male screw portion 32a. A region (T + α) obtained by adding a predetermined length α to the dimension T from the other end toward the one end side.

  The damping force applying mechanism 40 is a damping force applying means that applies a damping force for attenuating the rotational motion of the screw shaft 32 to the screw shaft 32. The damping force applying mechanism 40 is the embodiment. Then, it is the same as a known motor including the stator coil 42, the magnet rotor 44, and the housing 46 for housing these 42 and 44.

  The damping force applying mechanism 40 is assembled to the third housing 60, and the third housing 60 is provided with a fixture 62 for fixing the suspension to the vehicle.

  The rotor shaft (rotating shaft) 44a of the magnet rotor 44 is arranged coaxially with the rotating shaft 32b of the screw shaft 32, and the torque transmitted to the screw shaft 32 between the magnet rotor 44 and the screw shaft 32a. A power transmission member 50 for transmitting (rotational motion of the screw shaft 32) to the damping force applying mechanism 40 (magnet rotor 44) is disposed.

Further, the power transmission member 50 is made of a super elastic member (NiTi alloy in this embodiment) whose longitudinal elastic modulus (Young's modulus) decreases as the stress increases.
For this reason, when the torque transmitted to the power transmission member 50 increases, the stress generated in the power transmission member 50 increases, and the distortion generated in the power transmission member 50 increases nonlinearly. For this reason, as shown in FIG. 3, the rotation angle of the magnet rotor 44 per unit time becomes smaller than the rotation angle of the screw shaft 32 per unit time as the torque transmitted to the power transmission member 50 increases.

  In this embodiment, for example, when the temperature is 337 K and the stress generated by the power transmission member 50 is the smallest, the longitudinal elastic modulus is about 400 [MPa]. When the generated stress is the largest, the longitudinal elastic modulus is about 10 [MPa].

  The bushes 52 are disposed on both ends of the male screw portion 32a in the direction of the rotation shaft 32b, and are stoppers that restrict the nut 34 from being displaced more than a predetermined amount (beyond the male screw portion 32a) in the direction of the rotation shaft 32b. In the present embodiment, the bush 52 is formed of an elastic member such as rubber.

  The control unit 70 is a control unit that controls the damping force applied to the screw shaft 32 by the damping force application mechanism 40, and the control unit 70 according to the present embodiment controls the amount of current supplied to the stator coil 42. Thus, the damping force generated by the damping force applying mechanism 40 is controlled.

  Specifically, as shown in FIG. 4, a rotation speed detection sensor 72 that detects the rotation speed of the magnet rotor 44 is provided, and the control unit 70 causes the wheels to move linearly and rotate the magnet rotor 44. Based on the detection signal output from the rotational speed detection sensor 72, the amount of current supplied to the stator coil 42 is adjusted to control the damping force.

In the present embodiment, the electric power generated by the damping force applying mechanism 40 is converted into an appropriate voltage by a regulator and regenerated by the battery 74 mounted on the vehicle.
2. Characteristic Operation and Characteristics of Suspension When the nut 34 is present in the neutral region A1 of the male screw portion 32 (see FIG. 1), if there is a sudden input from the wheel to the suspension, the nut 34 is neutral. As shown in FIGS. 5 (a) and 5 (b), the region A1 moves beyond the region A1 to the braking region A2 (one end side or the other end side of the male screw portion 32a).

  At this time, in the male screw portion 32a, the screw lead L1 formed in the neutral region A1 is the same as the lead of the female screw portion 34a, and the screw lead L2 formed in the braking region A2 is the neutral region A1. When the nut 34 is displaced in the braking region A2, the nut 34 (female screw portion 34a) and the screw shaft 32 (male screw portion 32a) The frictional resistance between is increased compared to when the neutral region A1 is displaced.

For this reason, when the nut 34 is displaced from the neutral region A1 to the braking region A2 of the male screw portion 32a, it is reduced that the nut 34 is greatly displaced. The speed at which the nut 34 is displaced in the braking region A2 becomes slower than the case where the lead of the male screw portion 32a is the same throughout, and the impact when the nut 34 collides with the bush 52 can be sufficiently suppressed.

Therefore, the impact generated when the nut 34 collides with the bush 52 can be reduced.
In the present embodiment, when there is a sudden input from the wheel to the suspension, a large torque is applied to the power transmission member 50 via the male screw portion 32a, and a large stress is generated in the power transmission member 50.

  Here, since the power transmission member 50 is composed of a superelastic member whose longitudinal elastic modulus decreases as the stress increases, when a large torque is applied to the power transmission member 50, the power transmission member 50 is greatly distorted and unit. The rotation angle of the magnet rotor 44 per unit time is smaller than the rotation angle of the screw shaft 32 per time.

  For this reason, since the transmission rate of the rotational motion transmitted from the screw shaft 32 to the magnet rotor 44 can be reduced, the peak of the rotational speed of the magnet rotor 44 can be reduced, which is necessary for the damping force applying mechanism 40. It is possible to prevent the above power from being generated (overpower).

  Therefore, it is possible to prevent over-rotation of the magnet rotor 44 and over-output of the damping force applying mechanism 40, so that the stator coil 42 can be prevented from being burned and damaged, and the withstand voltage of the regulator can be reduced. It is possible to prevent it from exceeding.

  Moreover, in this embodiment, since the screw mechanism 30 is comprised with the ball screw, absolute frictional resistance can be made smaller than the general screw mechanism comprised with a screw and a female screw. Therefore, the loss when the nut 34 displaces the male screw portion 32a of the screw shaft 32 can be reduced.

  Further, in the present embodiment, the screw lead L2 formed in the braking region A2 of the male screw portion 32a is smaller than the screw lead L1 formed in the neutral region A1 (L2 <L1). 6 enters the braking region A2 from the neutral region A1, as shown in FIG. 6, the ball 34b of the screw mechanism 30 is opposite to the direction in which the nut 34 is displaced in the groove of the female screw portion 34. And the ball 34b presses the portion P2 in the direction in which the nut 34 is displaced in the groove of the male screw portion 34a.

  For this reason, since the ball 34b provides a force for compressing the female screw portion 34a and a force for pulling the male screw portion 32a, the nut 34 can be prevented from being lost earlier than the screw shaft 32. The replacement time of the nut 34 can be made later than the replacement time of the screw shaft 32.

3. Correspondence between Invention Specific Items and Embodiments In this embodiment, the screw shaft 32 corresponds to a bolt portion described in the claims, and the nut 34 corresponds to a nut portion described in the claims. The bush 52 corresponds to the stopper described in the claims, the damping force application mechanism 40 corresponds to the damping force application means described in the claims, and the power transmission member 50 corresponds to the claims. It corresponds to the described power transmission unit.

(Other embodiments)
In the above embodiment, a ball screw is used as the screw mechanism 30. However, the present invention is not limited to this, and a general screw mechanism including a male screw and a female screw is used instead of the ball screw. Also good.

  In the above embodiment, the screw lead L2 formed in the braking region A2 in the male screw portion 32a is smaller than the screw lead L1 formed in the neutral region A1 (L2 <L1). The present invention is not limited to this, and the screw lead L2 formed in the braking region A2 of the male screw portion 26b may be larger than the screw lead L1 formed in the neutral region A1. Good (L1 <L2).

  In the above-described embodiment, the damping force is electrically controlled. However, the present invention is not limited to this, and the damping force may be generated by a so-called oil damper using a fluid resistance. .

  In the above-described embodiment, the external force from the wheel is transmitted to the nut 34. However, the present invention is not limited to this, and the external force from the wheel is transmitted to the screw shaft 32. It may be.

  In the above-described embodiment, the rotational force of the screw shaft 32 is indirectly transmitted to the damping force generation mechanism 40 via the power transmission member 50 made of a superelastic member. However, the present invention is limited to this. For example, the power transmission member 50 may be formed of a normal elastic member such as rubber, or the screw shaft 32 and the damping force generation mechanism 40 may be directly connected.

Moreover, in the said embodiment, although this invention was applied to the suspension of a four-wheel vehicle, this invention is not limited to this, For example, you may apply to a rail vehicle or a two-wheeled vehicle.
Further, the present invention is not limited to the above-described embodiment as long as it matches the gist of the invention described in the claims.

It is a block diagram showing the structure of the suspension of this embodiment. It is explanatory drawing explaining the pitch of an external thread part and an internal thread part. It is explanatory drawing explaining the characteristic of a power transmission member. It is explanatory drawing explaining the electrical structure of the suspension of this embodiment. It is explanatory drawing explaining the action | operation of the suspension of this embodiment. It is explanatory drawing explaining the effect of the suspension of this embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Coil spring, 20 ... Damper device, 30 ... Screw mechanism, 32 ... Screw shaft, 32a ... Male screw part, 32b ... Rotating shaft, 34 ... Nut, 34a ... Female screw part, 34b ... Ball, 40 ... Giving damping force Mechanism, 42 ... Stator, 44 ... Magnet rotor, 44a ... Rotor shaft, 50 ... Power transmission member, 52 ... Bush, 54 ... First housing, 56 ... Second housing, 58 ... Bearing, 60 ... Third housing, 62 ... Fixing tool, 70 ... control unit, 72 ... rotational speed detection sensor, 74 ... battery, A1 ... neutral area, A2 ... braking area.

Claims (4)

A screw mechanism that has a bolt portion formed with a male screw portion and a nut portion formed with a female screw portion that is screw-coupled to the male screw portion, and converts a linear motion input from the outside into a rotational motion;
Damping force applying means for applying a damping force for damping the rotational motion converted by the screw mechanism;
A stopper that is disposed at both ends of the bolt portion in the rotation axis direction and restricts the nut portion from being displaced by a predetermined amount or more in the rotation axis direction;
Of the male screw portion, the pitch of the screw formed in the neutral region excluding both end sides in the rotation axis direction is the same as the pitch of the female screw portion,
The shock absorber according to claim 1, wherein a pitch of screws formed outside the neutral region in the male screw portion is different from a pitch of screws formed in the neutral region. Between the bolt part and the damping force applying means, a power transmission part for transmitting the rotational movement of the bolt part to the damping force applying means is arranged,
2. The shock absorber according to claim 1, wherein the power transmission unit is configured by a super elastic member having a smaller elastic coefficient as the stress increases.   The shock absorber according to claim 1, wherein the screw mechanism is configured by a ball screw.   4. The shock absorber according to claim 3, wherein a pitch of screws formed outside the neutral region in the male screw portion is smaller than a pitch of screws formed in the neutral region.

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