JP2019157952A - Linear motion mechanism and its manufacturing method - Google Patents

Abstract

To exactly and easily fix a stopper to a prescribed position with respect to a screw shaft, in a linear motion mechanism for regulating the axial movement of a linear motion member by making a stopper fixed to the screw shaft engaged with a nut in a rotation direction.SOLUTION: A linear motion mechanism 1 comprises: a screw shaft 2 at which a nut male screw 2a is formed at an external periphery, a nut 3 at which a female screw 3a screwed with the nut male screw 2a is formed at an internal peripheral face; and a stopper 4 fixed to the screw shaft 2. The linear motion mechanism regulates the relative axial movement of the screw shaft 2 and the nut 3 by making the stopper 4 and the nut 3 engaged with each other in a rotation direction. A stopper male screw 2b is arranged at an external peripheral face of the screw shaft 2, a female screw 4a having a lead different from a lead of the stopper male screw 2b is arranged at an internal peripheral face of the stopper 4, and the stopper 4 is fixed to the screw shaft 2 by screwing the female screw 4a of the stopper 4 and the stopper male screw 2b of the screw shaft 2 to each other.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a linear motion mechanism that converts a rotational motion of one of a screw shaft and a nut into a linear motion of the other and a manufacturing method thereof.

  The linear motion mechanism is roughly classified into a screw shaft rotation type that rotates the screw shaft to directly move the nut, and a nut rotation type that rotates the nut to directly move the screw shaft. In these linear motion mechanisms, in order to prevent separation between the screw shaft and the nut, it is necessary to restrict the axial movement of the linear motion member (the nut for the screw shaft rotation type and the screw shaft for the nut rotation type) at a predetermined position. is there. For example, it is conceivable to restrict the axial movement of the linear motion member by bringing the linear motion member into contact with the regulation member provided in the housing in the axial direction. However, when the linear motion member screwed with the rotary member is brought into contact with the end surface of the regulating member in the axial direction, the linear motion member bites into the end surface of the regulating member and the thread groove of the rotary member and is locked. In some cases, the linear member cannot be moved backward by rotating the rotating member backward.

  For example, in the ball screw mechanism disclosed in Patent Document 1 below, the linear movement member is moved in the axial direction by engaging a stopper provided on the screw shaft and a protrusion provided on the nut in the rotational direction. It is regulated at a predetermined position. In this way, by bringing the stopper portion and the protrusion of the nut into contact with each other in the rotational direction, it is possible to prevent a situation where both of them bite into and are locked.

JP, 2006-70281, A

  For example, the linear motion mechanism 100 shown in FIG. 6 rotates the screw shaft 101 to move the nut 102 directly, and a stopper 103 is fixed to the screw shaft 101. When the screw shaft 101 is rotated and the nut 102 reaches the end in the axial direction, the locking surface 103a of the stopper 103 and the locking surface 102a of the nut 102 are engaged in the rotation direction, whereby rotation of the screw shaft 101 is performed. It is restricted and the axial movement of the nut 102 is restricted.

  As described above, when the locking surface 103a of the stopper 103 and the locking surface 102a of the nut 102 are engaged in the rotational direction, the axial width W of the contact portion between the locking surfaces 103a and 102a is set to the screw shaft 101. Cannot be larger than the lead L of the male screw 101a. For this reason, when the fixing position (phase) of the stopper 103 with respect to the screw shaft 101 deviates from the normal position, as shown in FIG. 7, the axial width W ′ of the contact portions of both the locking surfaces 103a and 102a becomes small. There is a risk that the rotation of the nut 102 cannot be reliably regulated. Therefore, it is necessary to fix the stopper 103 at an accurate position (phase) with respect to the screw shaft 101 in order to sufficiently secure the axial width of the contact portion between the both locking surfaces 103a and 102a.

  For example, in Patent Document 1 described above, the screw shaft and the stopper portion are splined together to prevent relative rotation between the two. In this case, in order to fix the stopper at an accurate position with respect to the screw shaft, it is necessary to process the male screw and the spline groove provided on the outer peripheral surface of the screw shaft with high accuracy. However, since the male screw and the spline groove are usually processed in different processes, it is not easy to set their relative positions with high accuracy.

  Therefore, the problem to be solved by the present invention is that in the linear motion mechanism that restricts the axial movement of the linear motion member by engaging the stopper fixed to the screw shaft in the rotational direction with the nut, the stopper is fixed to the screw shaft. It is to fix accurately and easily at a predetermined position.

  In order to solve the above-mentioned problems, the present invention provides a screw shaft in which a male screw for nut is formed on an outer peripheral surface, a nut in which a female screw to be screwed with the male screw for nut is formed on an inner peripheral surface, and the screw shaft A stopper fixed to the screw shaft, converting a rotational motion of one of the screw shaft and the nut into a linear motion of the other, and engaging the stopper and the nut in a rotational direction to In the linear motion mechanism that restricts relative axial movement with the nut, a stopper male screw is provided on the outer peripheral surface of the screw shaft, and a lead different from the lead of the stopper male screw is provided on the inner peripheral surface of the stopper. A linear motion mechanism is provided in which a female screw having a stopper is fixed to the screw shaft by screwing a female screw of the stopper and a male screw for stopper of the screw shaft.

  As described above, by forcibly tightening the female screw of the stopper having a different lead from the male screw for stopper provided on the outer peripheral surface of the screw shaft, one or both of the male screw for stopper and the female screw of the stopper are fixed. The stopper can be fixed to the screw shaft by plastic deformation. In this case, since the male screw for nut and the male screw for stopper of the screw shaft can be formed in one step (ie, one chuck), the relative position (especially phase) between the male screw for nut and the male screw for stopper is highly accurate. Therefore, it is possible to accurately and easily match the phases of the nut and the stopper screwed into these.

  In the above-described linear motion device, when the lead of the male screw for nut of the screw shaft and the lead of the male screw for stopper are equal, it is easy to process them in one step.

  If the male screw for stopper of the screw shaft and the female screw of the stopper have the same hardness, both of them are crushed when tightened, and there is a possibility that the fixing force of both is insufficient. Since the male screw on the outer peripheral surface of the screw shaft is usually hardened by heat treatment, the female screw for the stopper is formed of a material whose hardness is lower than that of the male screw for the stopper of the screw shaft. Is preferably positively plastically deformed to secure a fixing force between the screw shaft and the nut.

  An annular groove is preferably provided between the male screw for nut and the male screw for stopper of the screw shaft. As a result, the male screw for nut and the male screw for stopper are separated by the annular groove, so that when the female screw of the stopper is forcibly tightened to the male screw for stopper of the screw shaft, the load is applied to the male screw for nut of the screw shaft. In addition, the nut male thread can be prevented from being deformed.

  As described above, the stopper can be accurately and easily fixed to the screw shaft in a predetermined position by forcibly tightening and fixing the female screw with a different lead provided on the stopper to the male screw for stopper of the screw shaft. can do.

It is a perspective view of the linear motion mechanism which concerns on one Embodiment of this invention. It is a side view of the linear motion mechanism of FIG. It is a side view of a screw shaft. (A) And (B) is a side view which shows the manufacturing process of a screw shaft. It is a perspective view of a stopper. It is a side view of the linear motion mechanism which concerns on a comparative example. It is a side view of the linear motion mechanism which concerns on a comparative example.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  As shown in FIGS. 1 and 2, a linear motion mechanism 1 according to an embodiment of the present invention includes a screw shaft 2, a nut 3 screwed into the screw shaft 2, and a stopper 4 fixed to the screw shaft 2. Is provided. In the illustrated example, a pair of stoppers 4 are provided near both axial ends of the screw shaft 2. The linear motion mechanism 1 of the present embodiment is a screw shaft rotation type linear motion mechanism in which a screw shaft 2 is rotated by a driving means (electric motor or the like) (not shown) to reciprocate a nut 3 in the axial direction.

  As shown in FIG. 3, a nut male screw 2 a and stopper male screws 2 b provided on both sides in the axial direction are formed on the outer peripheral surface of the screw shaft 2. The lead of the nut male screw 2a is equal to the lead of the stopper male screw 2b. In the present embodiment, an annular groove 2c is provided between the nut male screw 2a and the stopper male screw 2b in the axial direction. The annular groove 2c is formed of a cylindrical surface having a smaller diameter than the groove bottoms (minimum diameter portion) of the nut male screw 2a and the stopper male screw 2b. Cylindrical surfaces 2 d are provided at both axial ends of the outer peripheral surface of the screw shaft 2. The cylindrical surface 2d is attached to the housing via a bearing, whereby the screw shaft 2 is supported so as to be rotatable in the radial direction (not shown). As the bearing that supports the screw shaft 2 in the radial direction, a sliding bearing or a rolling bearing can be used. For example, a metallic sliding bearing that slide-supports the cylindrical surface 2d can be used.

  The screw shaft 2 is manufactured by the following procedure. First, a shaft material 2 ′ as shown in FIG. 4A is formed by forging or cutting. Cylindrical surfaces 2d are provided at both axial ends of the shaft material 2 ', and large-diameter portions 2e having a diameter larger than that of the cylindrical surface 2d are provided at intermediate portions in the axial direction.

  Next, with the shaft material 2 'chucked, a male screw 2f is formed on the large diameter portion 2e of the shaft material 2' as shown in FIG. 4B. The male screw 2f is formed by rolling or cutting, and is formed by rolling in this embodiment. The male screw 2 f includes a nut male screw 2 a and a stopper male screw 2 b and is continuously formed in the axial direction. That is, both the nut male screw 2a and the stopper male screw 2b are formed on the large-diameter portion 2e of the shaft material 2 'while maintaining the chuck of the shaft material 2' without releasing it (that is, with one chuck). The male screw 2f has a uniform lead throughout the axial direction.

  Next, the threaded shaft 2 shown in FIG. 3 is completed by forming an annular groove 2c at a predetermined location of the male thread 2f of the shaft material 2 '. The annular groove 2c is formed by cutting, for example. The annular groove 2c may be formed and the cylindrical surface 2d may be subjected to cutting finishing. In the present embodiment, surface hardening treatment is applied to the nut male screw 2 a and the stopper male screw 2 b of the screw shaft 2. Specifically, the entire surface of the screw shaft 2 can be subjected to a surface hardening process such as a quenching process, or only the nut male screw 2a and the stopper male screw 2b can be subjected to a surface hardening process using high-frequency heating or the like. If there is no particular need, the surface hardening process of the screw shaft 2 may be omitted.

  As shown in FIG. 1, the nut 3 has a cylindrical shape, and the screw shaft 2 is inserted into the inner periphery. As shown in FIG. 2, a female screw 3 a that is screwed with a nut male screw 2 a of the screw shaft 2 is formed on the inner peripheral surface of the nut 3. The nut 3 is restricted from rotating around the screw shaft 2. In the present embodiment, the end of a swing arm (not shown) is connected to the nut 3, thereby restricting the rotation of the nut 3. When the screw shaft 2 rotates, the nut 3 moves in the axial direction without rotating, and the swing arm connected to the nut 3 swings.

  As shown in FIG. 5, the stopper 4 is formed in a hollow disk shape. A female screw 4 a is formed on the inner peripheral surface of the stopper 4. The female screw 4a is different in lead from the male screw 2b for stopper of the screw shaft 2. For example, the lead of the male screw 2b for stopper is set to a value of about 95 to 65% with respect to the lead of the female screw 4a. Specifically, when the lead of the female screw 4a is 4 mm, the lead of the male screw for stopper 2b is set within a range of 3.8 to 2.6 mm, for example. As shown in FIG. 2, by forcibly tightening the female screw 4a of the stopper 4 to the male screw 2b for the stopper of the screw shaft 2 having a different lead, at least one of the female screw 4a and the male screw 2b for stopper is plastically deformed. As a result, the female screw 4a and the male screw 2b for stopper bite each other, and the stopper 4 is fixed to the outer periphery of the screw shaft 2. The lead of the male screw for stopper 2b may be larger than the lead of the female screw 4a. For example, the lead of the male screw for stopper 2b may be set to a value of about 105 to 135% with respect to the lead of the female screw 4a. Good.

  In this embodiment, the hardness of the female screw 4a of the stopper 4 is lower than the hardness of the male screw 2b for stopper. Specifically, the female screw 4a of the stopper 4 is formed of a steel material (raw material) that has not been subjected to surface hardening treatment such as quenching, and the screw shaft 2 is heat-treated at least on the male screw 2a for nut and the male screw 2b for stopper. (Surface hardening treatment) is performed. Thus, when the female screw 4a of the stopper 4 is forcibly tightened to the male screw 2b for stopper of the screw shaft 2, the female screw 4a of the stopper 4 is preferentially plastically deformed, so that the male screw 4b for stopper bites into the female screw 4a. Thus, both can be firmly fixed.

  In the present embodiment, the annular groove 2c is provided between the nut male screw 2a and the stopper male screw 2b of the screw shaft 2, thereby separating the two in the axial direction. Thereby, even if the female screw 4a of the stopper 4 is forcibly tightened to the male screw 2b for stopper and the male screw 2b for stopper is plastically deformed, the influence does not reach the male screw 2a for nut. Thereby, since the deformation | transformation of the male screw 2a for nuts is avoided, the male screw 2a for nuts and the female screw of the nut 3 can be screwed normally, and the nut 3 can be moved smoothly.

  As shown in FIGS. 1 and 2, locking surfaces 3 b and 4 b that engage with each other in the rotational direction of the screw shaft 2 are provided on end surfaces of the nut 3 and the stopper 4 that face each other in the axial direction. In the illustrated example, an inclined surface 3c that is spirally inclined is provided on the end surface of the nut 3, and a step surface formed between both ends in the circumferential direction of the inclined surface 3c is the locking surface 3b. Further, as shown in FIG. 5, an inclined surface 4 c that is spirally inclined is provided on the outer peripheral portion of the end surface of the stopper 4, and the step surface formed between the circumferential ends of the inclined surface 4 c is a locking surface. 4b.

  An end face 4d on the outer side in the axial direction of the stopper 4 (end face on the side not facing the nut 3 in the axial direction) is attached to the housing via a bearing, whereby the screw shaft 2 is rotatably supported in the thrust direction (illustrated). (Omitted). As the bearing that supports the screw shaft 2 in the thrust direction, a sliding bearing or a rolling bearing can be used, and for example, a needle roller bearing can be used.

  In the linear motion mechanism 1 described above, when the screw shaft 2 is rotationally driven in the forward direction by a drive means (not shown), the nut 3 moves to one side in the axial direction, and a swing arm (not shown) connected to the nut 3 Swing to the side. When the nut 3 reaches one end in the axial direction, the locking surface 3b on one end surface in the axial direction of the nut 3 and the locking surface 4b on the end surface of the stopper 4 on one side in the axial direction are engaged in the rotational direction. Accordingly, further axial movement of the nut 3 is restricted. Similarly, when the screw shaft 2 is rotationally driven in the reverse direction, the nut 3 moves to the other side in the axial direction, and the swing arm swings to the other side. Further, the engagement surface 3b of the other end surface in the axial direction of the nut 3 and the engagement surface 4b of the end surface of the stopper 4 on the other side in the axial direction are engaged in the rotation direction, so that the axial direction of the nut 3 is further increased. Movement is restricted. As described above, when the locking surface 3b of the nut 3 and the locking surface 4b of the stopper 4 are engaged in the rotation direction, the end surface (inclined surface 3c) of the nut 3 and the end surface of the stopper 4 (inclined surface 4c). ) Is not in axial contact.

  As described above, the nut 3 and the stopper 4 are engaged in the rotational direction to restrict the axial movement of the nut 3, thereby preventing the nut 3, the stopper 4, and the screw shaft 2 from biting. Then, the nut 3 can be smoothly retracted by rotating the screw shaft 2 in the opposite direction.

  The present invention is not limited to the above embodiment. For example, in the above-described embodiment, the case where the annular groove 2c is provided between the nut male screw 2a and the stopper male screw 2b of the screw shaft 2 is shown, but not limited thereto, the nut male screw 2a and the stopper male screw are provided. 2b may be formed continuously in the axial direction. For example, a shaft material 2 ′ shown in FIG. 4 (B) may be used as the screw shaft 2.

  In the above-described embodiment, the screw shaft rotation type linear motion mechanism 1 that converts the rotational motion of the screw shaft 2 into the linear motion of the nut 3 has been described. The present invention may be applied to a nut rotation type linear motion mechanism that converts to linear motion. Further, the present invention provides either a sliding screw mechanism in which a female screw of a nut and a male screw of a screw shaft are directly screwed together, or a ball screw mechanism in which a female screw of a nut and a male screw of a screw shaft are screwed through a large number of balls. It is also applicable to.

DESCRIPTION OF SYMBOLS 1 Linear motion mechanism 2 Screw shaft 2a Male screw for nut 2b Male screw for stopper 2c Annular groove 3 Nut 3a Female screw 3b Locking surface 4 Stopper 4a Female screw 4b Locking surface

Claims (5)

A screw shaft having a male screw for a nut formed on an outer peripheral surface; a nut having a female screw threadedly engaged with the male screw for the nut formed on an inner peripheral surface; and a stopper fixed to the screw shaft. And the rotational movement of one of the nuts is converted into the other linear movement, and the relative axial movement of the screw shaft and the nut is restricted by engaging the stopper and the nut in the rotational direction. In the linear motion mechanism that
A male screw for stopper is provided on the outer peripheral surface of the screw shaft, and a female screw having a lead different from the lead of the male screw for stopper is provided on the inner peripheral surface of the stopper, and the female screw of the stopper and the male screw for stopper of the screw shaft are provided. A linear motion mechanism in which the stopper is fixed to the screw shaft by screwing together.   The linear motion mechanism according to claim 1, wherein the lead of the male screw for nut of the screw shaft and the lead of the male screw for stopper are equal.   The linear motion mechanism according to claim 1 or 2, wherein the hardness of the female screw of the stopper is lower than the hardness of the male screw for stopper of the screw shaft.   The linear motion mechanism according to any one of claims 1 to 3, wherein an annular groove is provided between the male screw for nut and the male screw for stopper of the screw shaft. A screw shaft having a male screw for a nut formed on an outer peripheral surface; a nut having a female screw threadedly engaged with the male screw for the nut formed on an inner peripheral surface; and a stopper fixed to the screw shaft. And the rotational movement of one of the nuts is converted into the other linear movement, and the relative axial movement of the screw shaft and the nut is restricted by engaging the stopper and the nut in the rotational direction. In the manufacturing method of the linear motion mechanism to
Processing the male screw for nut and the male screw for stopper on the outer periphery of the screw shaft with one chuck;
Forming an internal thread having a lead different from the external thread of the stopper on the inner peripheral surface of the stopper;
And a step of engaging a female screw of the nut with a male screw for a nut of the screw shaft and fixing the stopper to the screw shaft by screwing a female screw of the stopper with a male screw for a stopper of the screw shaft. Mechanism manufacturing method.

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