JP7080146B2 - Linear motion mechanism - Google Patents

Description

The present invention relates to a linear motion mechanism.

A linear motion mechanism equipped with a screw shaft and a nut fitted so as to be able to rotate relative to the screw shaft is widely used as a motion conversion mechanism that converts the rotary motion of a rotary drive source such as a motor into a linear motion. (For example, Patent Document 1).

The above linear motion mechanism is roughly classified into a screw shaft rotation type in which the screw shaft is on the rotary side and the nut is on the linear motion side, and a nut rotation type in which the screw shaft is on the linear motion side and the nut is on the rotary side. .. In order to prevent the screw shaft and the nut from being separated from each other, these linear motion mechanisms are provided with a regulating means for restricting the axial movement of the member on the linear motion side more than necessary. As the regulating means, for example, an electric one that manages the movement range of the linear motion side member by using a stroke sensor or the like, or a cylindrical engaging member that is fixed to the outer peripheral surface of the screw shaft and engages with the nut. (Stopper) or the like can be adopted, but the latter, which can avoid complicated linear motion mechanism and high cost, tends to be heavily used.

As the stopper, for example, a linear motion regulation type that regulates the linear motion of the linear motion side member by engaging with the nut in the axial direction, or a linear motion regulation type that regulates the rotation of the rotary side member by engaging with the nut in the rotation direction. This makes it possible to adopt a rotation regulation type that regulates the linear motion of the linear motion side member. However, if the nut and the stopper collide with each other when the linear motion restriction type stopper is adopted, the nut may bite into the end face of the stopper, and the linear motion mechanism may fall into an inoperable locked state. Therefore, in order to improve the reliability of the linear motion mechanism, it is preferable to use a rotation restriction type stopper.

Here, FIG. 8 shows an example of a linear motion mechanism using a rotation restriction type stopper. The linear motion mechanism 100 shown in the figure includes a screw shaft 101 on the rotating side, a nut 102 on the linear motion side fitted to the outer periphery of the screw shaft 101, and an outer peripheral surface of the screw shaft 101 on the axially outer side of the nut 102. It is a screw shaft rotation type equipped with a fixed cylindrical stopper 103. The nut 102 is provided with an engaging surface 102a, and the stopper 103 engages with the engaging surface 102a of the nut 102 in the rotation direction (rotational direction of the screw shaft 101) when the nut 102 reaches a predetermined movement limit. A mating engaged surface 103a is provided. In this case, the axial engagement allowance W between the engaging surface 102a and the engaged surface 103a cannot be made larger than the lead L of the male screw 101a provided on the outer peripheral surface of the screw shaft 101. Therefore, if the fixed position (phase) of the stopper 103 with respect to the screw shaft 101 deviates from the normal position, the engagement allowance W between the engaging surface 102a and the engaged surface 103a becomes small as shown in FIG. 9, and the screw There is a possibility that the relative rotation of the shaft 101 and the nut 102 (the axial movement of the nut 102) cannot be reliably regulated.

Therefore, in order to realize the state shown in FIG. 8, when the nut 102 reaches the movement limit, the engagement allowance W between the engaging surface 102a and the engaged surface 103a of the stopper 103 is the dimension of the lead L. It is necessary to fix the stopper 103 to the screw shaft 101 so that the size is substantially the same. Therefore, when the stopper 103 is attached and fixed to the screw shaft 101, it is necessary to align the phase of the screw shaft 101 (male screw 101a) and the stopper 103 (engaged surface 103a). In order to easily and accurately perform this phase alignment, for example, as shown in FIG. 10, a keyway 101b is provided at a predetermined position on the outer peripheral surface of the screw shaft 101 on the outer side in the axial direction of the male screw 101a, and the stopper 103 is provided. It is conceivable that a notch 103b is provided on the inner peripheral surface, and a key member (not shown) is fitted into a key fitting portion formed by the cooperation of the key groove 101b and the notch 103b.

Japanese Unexamined Patent Publication No. 2017-67197

By the way, the male screw 101a to be provided on the outer peripheral surface of the screw shaft 101 can be formed by cutting or rolling. Threading is more advantageous than cutting in terms of cost because it can suppress the occurrence of material loss due to work, and the wear resistance of the male screw 101a is increased by increasing the hardness of the work surface due to work hardening. And has the advantage of being able to increase fatigue resistance.

Since the formation position of the key groove 101b with respect to the male screw 101a directly affects the phase of the stopper 103 (engaged surface 103a) with respect to the screw shaft 101, it is necessary to control it with high accuracy. Therefore, when the keyway 101b is provided on the screw shaft 101, the keyway 101b is formed together with the male screw 101a by cutting that facilitates high-precision machining (particularly, automatic cutting by numerical control, which is also called NC machining). Will be done. When the male screw 101a is formed by threading, the male screw 101a and the key groove 101b are machined in a separate process. Therefore, compared to the case where the male screw 101a and the key groove 101b are formed at once by NC machining. This is because the accuracy of phase matching between the screw shaft 101 and the stopper 103 is inferior.

Therefore, when the structure shown in FIG. 10 is adopted, the male screw 101a cannot be formed by threading (the screw shaft 101 is so-called), considering the accuracy of the phase matching between the screw shaft 101 and the stopper 103, which should be given the highest priority. It cannot be a rolled screw), and it is not possible to enjoy various merits that can be enjoyed when the male screw 101a is formed by a rolling process.

In view of the above circumstances, the present invention is a linear motion mechanism in which a rotation-restricted type stopper is fixed to a screw shaft, and while using a rolled screw for the screw shaft, the phase alignment between the screw shaft and the stopper is easily and accurately performed. The purpose is to enable good performance and to provide a highly reliable linear motion mechanism at low cost.

The present invention, which was devised to achieve the above object, is fixed to a screw shaft having a male screw formed on the outer peripheral surface, a nut fitted so as to be rotatable relative to the screw shaft, and the outer peripheral surface of the screw shaft. It is equipped with a tubular stopper, and as one of the screw shaft and the nut rotates, the other moves forward and backward in the axial direction, and the engaging surface provided on the nut and the engaged engagement provided on the stopper. In a linear motion mechanism in which the relative axial movement of the screw shaft and nut is restricted by engaging the surface in the rotational direction, the male screw guides the relative movement of the nut with respect to the screw shaft, and the stopper It is characterized by having a fixed portion to which the stopper is fixed by being plastically deformed by receiving a compressive force in the diameter reduction direction and having at least a part of the female screw provided on the inner peripheral surface of the stopper in close contact with the female screw.

According to the above configuration, the nut moves relative to the screw shaft in the axial direction and the stopper is fixed (crimped and fixed) within the range of the male screw provided on the outer peripheral surface of the screw shaft. It can be formed by rolling. As a result, it is possible to obtain a high-quality, high-strength screw shaft in which the shape accuracy of the male screw does not vary among individuals and the hardness of the male screw is increased by work hardening at low cost.

Further, since a female screw is provided on the inner peripheral surface of the stopper, when fixing the stopper to the screw shaft, the stopper outerly fitted to the screw shaft is rotated by a predetermined amount with respect to the male screw of the screw shaft. By tightening the female screw of the stopper to a predetermined axial position and phase, the relative position (axial position and phase) of the stopper with respect to the screw shaft can be set with high accuracy. Further, since the stopper is fixed to the fixing portion of the male screw by having at least a part of the female screw provided on the inner peripheral surface of the stopper in close contact with the fixing portion, the stopper is properly aligned with respect to the screw shaft. It is fixed (non-rotated) to the screw shaft in the state where it is made. As a result, when the engaging surface of the nut and the engaged surface of the stopper are engaged in the rotational direction, they can be engaged with each other with a predetermined engagement allowance W (see FIG. 8), so that the screw shaft and the screw shaft can be engaged with each other. The relative movement of the nut can be reliably regulated.

In the above configuration, the guide portion and the fixed portion can be provided separately in the axial direction. By doing so, even if a compressive load is applied to the fixed portion of the male screw as the stopper is plastically deformed, the load is less likely to reach the guide portion. As a result, it is possible to prevent unwanted deformation of the guide portion of the male screw as much as possible, and to ensure smooth relative movement of the screw shaft and the nut.

When the stopper is plastically deformed (fixed to the screw shaft) by applying a compressive force in the radial direction to two points on the outer peripheral surface of the stopper that are 180 ° out of phase, the inner peripheral surface of the stopper Of these, it is preferable to provide notches opened on both end faces of the stopper at positions that are 90 ° out of phase with the compressive force applying portion. By doing so, the deformability of the stopper is increased, so that the stopper can be accurately and firmly fixed to the screw shaft even if the compressive force in the radial direction to be applied to the stopper is reduced. If the compressive force can be reduced, the compressive load applied to the screw shaft via the stopper can be reduced, which is advantageous in preventing unwanted deformation of the screw shaft as much as possible.

The present invention can be applied to a linear motion mechanism in which a female screw screwed with a guide portion of a male screw is provided on the inner peripheral surface of the nut, and a spiral groove is provided on the inner peripheral surface of the nut, and this spiral is provided. It can also be applied to a linear motion mechanism in which a large number of balls are interposed between a spiral groove and a spiral groove defined in a guide portion of a male screw. That is, the present invention can be applied not only to a linear motion mechanism including a so-called sliding screw mechanism but also to a linear motion mechanism including a so-called ball screw mechanism.

From the above, according to the present invention, in the linear motion mechanism in which the rotation-restricted type stopper is fixed to the screw shaft, the phase alignment between the screw shaft and the stopper can be easily performed while using the threaded screw for the screw shaft. It can be done with high accuracy. As a result, a highly reliable linear motion mechanism can be provided at low cost.

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) is a side view of a shaft material processed into a screw shaft shown in FIG. 3, and (b) is a side view of a shaft material on which a male screw is formed. It is a perspective view of the stopper before being fixed to a screw shaft. It is a figure which shows the assembly process of a linear motion mechanism. FIG. , It is a side view which shows the fixing step of the other stopper. It is a partially enlarged sectional view of the linear motion mechanism which concerns on other embodiment of this invention. It is a figure which shows the preferable engagement state of a stopper and a nut. It is a figure which shows an example of the unfavorable engagement state of a stopper and a nut. It is a partial perspective view of the conventional linear motion mechanism.

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

FIG. 1 is a perspective view of a linear motion mechanism 1 according to an embodiment of the present invention, and FIG. 2 is a side view of the linear motion mechanism 1 [Detailedly, the nut 3 is on one side in the axial direction (in FIG. 2). Side view of the state where the movement limit (on the left side of the paper) has been reached]. The linear motion mechanism 1 is arranged on both sides of the screw shaft 2 in the axial direction, a cylindrical nut 3 fitted to the outer periphery of the screw shaft 2 so as to be rotatable relative to the screw shaft 2, and a screw. A tubular (short cylindrical) stopper 4 fixed to the outer peripheral surface of the shaft 2 is provided. In the linear motion mechanism 1 of the present embodiment, the nut 3 does not rotate around the axis as the screw shaft 2 rotates around the axis under the driving force of a rotational drive source (not shown) such as an electric motor. It is a screw shaft rotation type linear motion mechanism that moves forward and backward in the axial direction. Therefore, the nut 3 is restricted from rotating around the axis of the screw shaft 2 by a rotation restricting portion (not shown).

As shown in FIG. 3, a male screw 21 is formed on the outer peripheral surface of the screw shaft 2. The male screw 21 has a guide portion 22 for guiding the advancing / retreating movement of the nut 3 fitted so as to be relatively rotatable with respect to the screw shaft 2, and a pair of fixing portions 23 provided on the outer side in the axial direction of the guide portion 22. .. At least in the state before fixing the stopper 4 (FIG. 3), the pitch, the valley diameter (minimum diameter) and the outer diameter (maximum diameter) of the guide portion 22 and the fixing portion 23 are the same. An annular groove 24 is provided between the guide portion 22 and the fixed portion 23, and the guide portion 22 and the fixed portion 23 are separated from each other in the axial direction by the annular groove 24. The annular groove 24 is composed of a cylindrical surface having a diameter smaller than the valley diameter of the guide portion 22 and the fixing portion 23 of the male screw 21.

The screw shaft 2 is rotatably supported in the radial direction with respect to a stationary member (not shown) by bearings (rolling bearings or sliding bearings) (not shown) arranged at both ends in the axial direction. Therefore, both ends of the screw shaft 2 in the axial direction are provided with a cylindrical surface 25 having a constant diameter into which the bearing is fitted. The cylindrical surface 25 of the present embodiment is formed to have a smaller diameter than the annular groove 24.

The screw shaft 2 having the above configuration can be manufactured, for example, as follows. First, as shown in FIG. 4A, a shaft material 2 is provided with cylindrical surfaces 25 at both ends in the axial direction, and a large diameter portion 26 having a diameter larger than that of the cylindrical surface 25 is provided between both cylindrical surfaces 25. 'Prepare. The shaft material 2'is produced, for example, by forging or cutting a steel bar.

Next, as shown in FIG. 4B, a male screw 21 is formed on the large diameter portion 26 of the shaft material 2'. The male screw 21 formed at this stage is different from the male screw 21 provided on the screw shaft 2 (see FIG. 3) in the finished product state, and the guide portion 22 and the fixing portions 23 provided on both sides thereof in the axial direction are continuous in the axial direction. It has a morphology. Although detailed illustration is omitted, the male screw 21 is formed by threading the large diameter portion 26 of the shaft material 2'and has a uniform pitch, valley diameter and outer diameter over the entire axial direction. The method of threading is not particularly limited, and is known, for example, a method using a pair of flat dies provided so as to be relatively parallel movable, a method using a plurality of roller dies provided so as to be relatively rotatable, and the like. Can be adopted.

Next, the annular groove 24 is formed at a predetermined position in the axial direction of the male screw 21. As a result, the screw shaft 2 having the shape of the finished product shown in FIG. 3 can be obtained. The annular groove 24 is not required to have the shape accuracy required for the male screw 21. Therefore, the method of forming the annular groove 24 is arbitrary, but here it is formed by cutting.

After the annular groove 24 is formed, at least the formed region of the male screw 21 of the screw shaft 2 is subjected to quench hardening treatment. As a result, the surface hardness of the male screw 21 can be increased, so that the wear resistance and fatigue resistance of the male screw 21 can be increased. The quench hardening treatment may be so-called soaking quenching in which the entire screw shaft 2 is quenched, or surface quenching in which only the surface layer portion of the male screw 21 forming region of the screw shaft 2 is quenched. However, when the screws are soaked, it is preferable to perform a tempering treatment after the quenching and hardening treatment. Since the male screw 21 is formed by threading, the formation region of the male screw 21 in the surface layer portion of the screw shaft 2 is hardened by work hardening. Therefore, if the surface hardening treatment is performed as necessary. Sufficient, you can omit it.

As shown in FIG. 2, a female screw 3a screwed with a male screw 21 (guide portion 22) provided on the outer peripheral surface of the screw shaft 2 is formed on the inner peripheral surface of the nut 3. Therefore, the linear motion mechanism 1 of the present embodiment is a so-called sliding screw mechanism. An engaging surface 3b that engages with the stopper 4 (engaged surface 4b provided on the left side of the paper surface) in the rotation direction of the screw shaft 2 is provided on the end surface of the nut 3 on one side in the axial direction (left side of the paper surface). Further, on the end surface of the nut 3 on the other side in the axial direction (right side of the paper surface), an engagement surface 3b that engages with the stopper 4 (engaged surface 4b provided on the right side of the paper surface) on the right side of the paper surface in the rotation direction of the screw shaft 2 is provided. Has been done. In the illustrated example, a spirally inclined inclined surface 3c is provided on the end surface of the nut 3, and a stepped surface formed at the end of the inclined surface 3c constitutes an engaging surface 3b.

As shown in FIGS. 2 and 5, a female screw 4a is formed on the inner peripheral surface of the stopper 4 having a short cylindrical shape. The female screw 4a of the stopper 4 (see FIG. 5) before being fixed to the screw shaft 2 is formed so as to be screwed into the fixing portion 23 of the male screw 21 provided on the screw shaft 2. Therefore, the pitch, valley diameter (maximum diameter), and inner diameter (minimum diameter) of the female screw 4a provided on the stopper 4 before being fixed to the screw shaft 2 are formed on the inner peripheral surface of the nut 3, respectively. It has the same size as the pitch, valley diameter and inner diameter of the female screw 3a.

Of the stoppers 4, the end surface facing the end surface (inclined surface 3c) of the nut 3 in the axial direction is the engaged surface 4b that engages with the engagement surface 3b provided on the nut 3 in the rotation direction of the screw shaft 2. Is provided. In the present embodiment, a spirally inclined inclined surface 4c is provided on the end surface of the stopper 4, and a stepped surface formed at the end of the inclined surface 4c constitutes an engaged surface 4b.

Although the details will be described later, the stopper 4 is fixed (tightened and fixed) to the screw shaft 2 by being plastically deformed by receiving a compressive force in the radial direction applied to the outer peripheral surface thereof. In order to facilitate the deformation of the stopper 4 at this time, notches 4d opened on both end surfaces of the stopper 4 are formed on the inner peripheral surface of the stopper 4. The notches 4d are formed at two locations (more specifically, two locations whose phases are 180 ° out of phase) separated in the circumferential direction.

An example of the assembly procedure of the linear motion mechanism 1 having the above configuration will be described with reference to FIGS. 6 (a) to 6 (c).

First, as shown in FIG. 6A, one of the pair of stoppers 4 (here, the stopper 4 arranged on the left side of the paper surface of FIG. 2) is fixed to the screw shaft 2. Specifically, the stopper 4 is externally fitted to one end of the screw shaft 2 in the axial direction, and then the stopper 4 and the screw shaft 2 are rotated relative to each other by a predetermined amount with respect to the male screw 21 of the screw shaft 2. Tighten the female screw 4a of the stopper 4 to a predetermined axial position and phase. Here, the stopper 4 is tightened so that the inclined surface 4c of the stopper 4 is located within the range of the annular groove 24 provided between the guide portion 22 and the fixing portion 23 on one side in the axial direction.

Next, as shown by the black arrow in FIG. 6A, the stopper 4 is plastically deformed by applying a compressive force A in the radial direction to the stopper 4, and the female screw 4a formed on the inner peripheral surface of the stopper 4 is formed. The stopper 4 is fixed (tightened and fixed) to the screw shaft 2 by bringing at least a part of the screw shaft 2 into close contact with the fixing portion 23 of the male screw 21 of the screw shaft 2. In the present embodiment, the compressive force A in the diameter reduction direction is applied to two points on the outer peripheral surface of the stopper 4 having a phase difference of 180 °. More specifically, of the outer peripheral surface of the stopper 4, the compressive force A is applied to the imparting portion B (see FIG. 5) at a position 90 ° out of phase with the notch 4d formed on the inner peripheral surface of the stopper 4. Is given. As a result, the deformability of the stopper 4 is increased, and the compressive force A required when the stopper 4 is plastically deformed (the stopper 4 is crimped and fixed to the screw shaft 2) can be reduced, so that the compressive force can be reduced. As a result of reducing the compressive load applied to the outer peripheral surface of the screw shaft 2 with the addition of A, it is possible to effectively prevent unwanted deformation of the male screw 21.

Further, in the present embodiment, an annular groove 24 is provided between the fixing portion 23 constituting the male screw 21 of the screw shaft 2 and the guide portion 22, and the fixing portion 23 and the guide portion 22 are separated in the axial direction. Even when a compressive load is applied to the fixing portion 23 of the male screw 21 as the stopper 4 is plastically deformed, the load is less likely to reach the guide portion 22. As a result, it is possible to more effectively prevent the guide portion 22 of the male screw 21 from being deformed undesirably.

As described above, after the stopper 4 is crimped and fixed to the fixing portion 23 on one side in the axial direction constituting the male screw 21 of the screw shaft 2, as shown in FIG. 6B, the male screw of the screw shaft 2 is screwed. The female screw 3a of the nut 3 is screwed into the guide portion 22 constituting the 21.

Finally, as shown in FIG. 6 (c), the other of the pair of stoppers 4 (here, the stopper 4 arranged on the right side of the paper surface of FIG. 2) is fixed to the screw shaft 2. This fixing operation is performed in the same procedure as the fixing procedure of one stopper 4 described with reference to FIG. 6A. As a result, the linear motion mechanism 1 shown in FIGS. 1 and 2 is completed.

The above assembly procedure is merely an example. For example, before fixing the stopper 4 to the screw shaft 2, the nut 3 is externally fitted to the screw shaft 2 (the guide portion 22 of the male screw 21 of the screw shaft 2). The female screw 3a of the nut 3 may be screwed).

As described above, in the linear motion mechanism 1 according to the present invention, the male screw 21 provided on the outer peripheral surface of the screw shaft 2 has a guide portion 22 for guiding the relative movement of the nut 3 with respect to the screw shaft 2, and a stopper 4. It has a fixing portion 23 to which the stopper 4 is fixed by being plastically deformed by receiving a compressive force A in the diameter reduction direction and having at least a part of the female screw 4a provided on the inner peripheral surface of the stopper 4 in close contact with the screw.

According to this configuration, the nut 3 moves relative to the screw shaft 2 and the stopper 4 is fixed (crimped and fixed) within the range of the male screw 21 provided on the outer peripheral surface of the screw shaft 2. , The male screw 21 can be formed by threading. As a result, it is possible to obtain a high-quality, high-strength screw shaft 2 at low cost, in which the shape accuracy of the male screw 21 does not vary among individuals and the hardness of the male screw 21 is increased by work hardening.

Further, since the female screw 4a (screwed into the fixing portion 23 of the male screw 21) is provided on the inner peripheral surface of the stopper 4, the screw shaft 2 is used when fixing the stopper 4 to the screw shaft 2. The stopper 4 fitted to the outside is rotated by a predetermined amount, and the female screw 4a of the stopper 4 is tightened to a predetermined axial position and phase with respect to the male screw 21 (fixing portion 23) of the screw shaft 2 to the screw shaft 2. The relative position (axial position and phase) of the stopper 4 can be set with high accuracy. Further, since the stopper 4 is fixed to the fixing portion 23 of the male screw 21 by having at least a part of the female screw 4a provided on the inner peripheral surface of the stopper 4 in close contact with the fixing portion 23, the stopper 4 is relative to the screw shaft 2. It is fixed to the screw shaft 2 in a non-rotating state with proper alignment. Therefore, as the screw shaft 2 is rotationally driven, the nut 3 reaches a predetermined movement limit, and the engaging surface 3b of the nut 3 and the engaged surface 4b of the stopper 4 are in the rotation direction of the screw shaft 2. When engaged (see FIG. 2), the two can be engaged with a predetermined engagement allowance W (see FIG. 8). As a result, it is possible to reliably restrict the nut 3 from moving to a position beyond the predetermined movement range.

From the above, according to the present invention, in the linear motion mechanism 1 in which the rotation restriction type stopper 4 is fixed to the screw shaft 2, the screw shaft 2 and the stopper 4 are used while the threaded screw is used for the screw shaft 2. Phase matching can be performed easily and accurately. As a result, it is possible to reliably regulate the relative movement of the screw shaft 2 and the stopper 4 more than necessary, and it is possible to provide a highly reliable linear motion mechanism 1 at low cost.

Further, in the present embodiment, an annular groove 24 is provided between the guide portion 22 and the fixing portion 23 constituting the male screw 21, the guide portion 22 and the fixing portion 23 are separated in the axial direction, and the inner circumference of the stopper 4 is formed. Of the surfaces, notches 4d opened on both end faces of the stopper 4 are provided at positions that are 90 ° out of phase with the part where the compressive force A in the radial direction applied to the outer peripheral surface of the stopper 4 is applied. When the stopper 4 is fixed to the screw shaft 2, it is possible to effectively prevent the guide portion 22 of the male screw 21 from being deformed undesirably. Therefore, it is possible to realize a linear motion mechanism 1 in which smooth relative movement of the screw shaft 2 and the nut 3 is guaranteed, that is, a linear motion mechanism 1 having excellent operability.

Although the linear motion mechanism 1 and the method for manufacturing the linear motion mechanism 1 according to the embodiment of the present invention have been described above, the linear motion mechanism 1 can be appropriately modified without departing from the gist of the present invention.

For example, in the embodiment described above, the annular groove 24 is provided between the guide portion 22 and the fixing portion 23 formed on the outer peripheral surface of the screw shaft 2, but the annular groove 24 does not necessarily have to be provided and is omitted. It doesn't matter. That is, the male screw 21 may have the guide portion 22 and the fixing portion 23 continuous in the axial direction, as in the shaft material 2'shown in FIG. 4 (b). In particular, a stopper 4 provided with the notch 4d in the embodiment shown in FIG. 5 is used, and a compressive force in the diameter reduction direction is used at a position on the outer peripheral surface of the stopper 4 whose phase is 90 ° out of phase with the notch 4d. By applying A, when the stopper 4 is crimped and fixed to the screw shaft 2, as described above, it is possible to prevent unwanted deformation of the guide portion 22 as much as possible. A male screw 21 in which the portion 22 and the fixing portion 23 are continuous in the axial direction can be adopted.

Further, for example, although not particularly mentioned in the embodiment described above, as the stopper 4, a stopper 4 made of a steel material (raw material) that has not been subjected to a hardening treatment such as quenching can be used. By doing so, the deformability of the stopper 4 is increased as compared with the case of using the stopper 4 made of a hardened steel material, so that the compressive force A in the diameter reduction direction to be applied to the stopper 4 is increased. Even if it is reduced, the stopper 4 can be accurately and firmly fixed to the screw shaft 2. If the compressive force A can be reduced, the compressive load applied to the screw shaft 2 via the stopper 4 can be reduced, so that it is possible to effectively prevent unwanted deformation of the screw shaft 2.

Further, the linear motion mechanism 1 described above is a so-called screw shaft rotation type linear motion mechanism in which the screw shaft 2 is on the rotation side and the nut 3 is on the linear motion side. It can also be applied to a so-called nut rotation type linear motion mechanism in which the linear motion side is set and the nut 3 is the rotating side.

Further, the linear motion mechanism 1 described above is a linear motion mechanism in which a female screw 3a screwed with a guide portion 22 of a male screw 21 provided on the outer peripheral surface of the screw shaft 2 is provided on the inner peripheral surface of the nut 3. However, in the present invention, as shown in FIG. 7, a spiral groove 6 is provided on the inner peripheral surface of the nut 3, and the spiral groove 6 and the spiral defined in the guide portion 22 of the male screw 21 of the screw shaft 2 are defined. It can also be applied to a linear motion mechanism in which a large number of balls 7 are interposed between the groove 5 and the groove 5. That is, the present invention has not only the linear motion mechanism 1 composed of a so-called sliding screw mechanism as shown in FIGS. 1 and 2, but also the linear motion mechanism composed of a so-called ball screw mechanism as schematically shown in FIG. It can also be applied to 1.

The present invention is not limited to the above-described embodiments, and it is needless to say that the present invention can be carried out in various forms without departing from the gist of the present invention. Indicated by the scope of the claim and further include the equal meanings set forth in the claims, and all modifications within the scope.

1 Linear mechanism 2 Thread shaft 3 Nut 3a Female thread 3b Engagement surface 4 Stopper 4a Female thread 4b Engagement surface 21 Male thread 22 Guide part 23 Fixed part 24 Circular groove A Compressive force

Claims (5)

The screw shaft is provided with a screw shaft having a male screw formed on the outer peripheral surface, a nut fitted so as to be rotatable relative to the screw shaft, and a cylindrical stopper fixed to the outer peripheral surface of the screw shaft. And as one of the nuts rotates, the other moves back and forth in the axial direction, and the engaging surface provided on the nut and the engaged surface provided on the stopper engage in the rotational direction. By doing so, in a linear motion mechanism in which the relative axial movement of the screw shaft and the nut is restricted.
The male screw has a guide portion that guides the relative movement of the nut with respect to the screw shaft, and the stopper is plastically deformed by receiving a compressive force in the radial direction, and the female screw provided on the inner peripheral surface of the stopper. It has a fixed portion to which the stopper is fixed by at least a part of the stopper being brought into close contact with the stopper.
A linear motion mechanism characterized in that the guide portion and the fixed portion are provided separately in the axial direction . The linear motion mechanism according to claim 1 , wherein the male screw is formed by threading. The stopper is plastically deformed by applying a compressive force in the radial direction to two points on the outer peripheral surface having a phase difference of 180 °.
2 . Linear motion mechanism. The linear motion mechanism according to any one of claims 1 to 3 , wherein a female screw screwed with the guide portion of the male screw is provided on the inner peripheral surface of the nut. Claims 1 to 3 in which a spiral groove is provided on the inner peripheral surface of the nut, and a large number of balls are interposed between the spiral groove and the spiral groove defined in the guide portion of the male screw. The linear motion mechanism described in any one of the above.

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