JP2023072507A - ball screw - Google Patents

Abstract

To provide a ball screw that can obtain high positional accuracy and a desired seal clearance at low costs while simplifying the assembling work of a seal member to a nut.SOLUTION: In a ball screw 100, a spigot portion 70 coaxial with a screw shaft 100 is configured by an end portion inner peripheral surface of a nut 20 and a fixed portion outer peripheral surface of a seal member 50. A tongue portion 53 for deciding a phase projecting out in an outer diametrical direction is formed at only one place on an outer periphery of the seal member 50, and the tongue portion 53 is inserted in a fitting recessed portion 34 formed along an axial direction at an end portion of the nut 20, thereby fixing a position in a circumferential direction of the seal member 50 while regulated in a predetermined phase.SELECTED DRAWING: Figure 1

Description

The present invention relates to a ball screw provided with a seal member attached to the nut end.

The ball screw has a plurality of balls interposed between a spiral thread groove provided on the outer peripheral surface of the screw shaft and a spiral thread groove provided on the inner peripheral surface of the nut. In this type of ball screw, a seal member is attached to the end of the nut (see Patent Document 1, for example).

JP-A-2003-97668

In this type of ball screw, in order to prevent leakage of lubricant such as grease filled inside the nut and intrusion of foreign matter from the outside, when the seal member is assembled, the thread groove shape of the screw shaft and the inner circumference of the seal member It is necessary to match the phase with the lip part of

At that time, if the sealing member is not mounted at the mounting position where the desired clearance is obtained due to poor positioning of the sealing member, the sealing performance is degraded. Therefore, in order to obtain good dust resistance and sealing performance, it is necessary to precisely adjust the phase between the lip portion of the seal member and the thread groove shape of the screw shaft while aligning the central axes of the screw shaft and the seal member. .

Conventionally, in this phase alignment work, an assembly worker assembles seal members by actual alignment while visually confirming phases one by one.
However, in the case of the assembling method by fitting, two adjustment operations are required, namely, adjusting the phase of the lip portion of the sealing member and the thread groove shape of the screw shaft with high accuracy while aligning the central axes of the screw shaft and the sealing member. It is difficult to carry out the above at the same time, requiring a great deal of labor and time for the operator, as well as raising assembly costs and lowering productivity.

Accordingly, the present invention has been made by paying attention to such problems, and while simplifying the work of assembling the seal member to the nut, it is possible to achieve high positioning accuracy and seal clearance at a desired phase at low cost. An object of the present invention is to provide an obtained ball screw.

In order to solve the above problems, a ball screw according to an aspect of the present invention includes a screw shaft having a helical thread groove on its outer peripheral surface, and a screw shaft fitted on the screw shaft and having a helical thread groove on its inner peripheral surface. a nut having a thread groove; a plurality of balls interposed between the thread grooves of the screw shaft and the nut; and fixing means for fixing the seal member to the nut, wherein at least one end of the nut is provided with an outer peripheral surface of the seal member and the end The inner peripheral surface of the sealing member constitutes a spigot portion that is fitted at a position coaxial with the screw shaft, and a tongue portion that protrudes in the outer radial direction at only one location on the outer peripheral surface of the sealing member, and the end portion A fitting recess into which the tongue portion can be inserted along the axial direction is formed only at one place on the inner peripheral side of the screw shaft. position.

According to the present invention, the lip portion of the seal member and the thread groove shape of the screw shaft can be aligned simply by fitting the tongue portion of the seal member into the fitting recess while aligning the central axes of the screw shaft and the seal member with the spigot portion. The phase can be easily set with high accuracy. Therefore, it is possible to obtain a high positioning accuracy and a seal clearance at a desired phase at a low cost while simplifying the assembly work of the seal.

BRIEF DESCRIPTION OF THE DRAWINGS It is explanatory drawing of one Embodiment of the ball screw which concerns on one aspect|mode of this invention, The same figure (a) is a front view, (b) is sectional drawing along an axis, and the ball is abbreviate|omitting illustration. 1 is a perspective view illustrating an embodiment of a ball screw according to an aspect of the present invention, in which the screw shaft and balls are omitted in FIG. b) is an exploded perspective view of the seal portion of FIG. 1(a). BRIEF DESCRIPTION OF THE DRAWINGS It is explanatory drawing of one Embodiment of the ball screw based on one aspect|mode of this invention, (a) is sectional drawing along the axis line of the nut in FIG. 1, and the sealing part of the edge part, (b) is a front view seen from the seal portion side. FIG. 2 is a diagram (a diagram along the ZZ cross section in FIG. 1) for explaining the relationship between the gap between the lip portion of the seal member and the outer periphery of the screw shaft with respect to changes in the mounting posture of the seal member, and FIG. The members are shown installed in correct phase, and (b) shows a hypothetical situation where the seal member is installed in incorrect phase. FIG. 5 is a schematic vertical cross-sectional view for explaining a modification of fixing means for the sealing member; FIG. 5 is a schematic vertical cross-sectional view for explaining a modification of fixing means for the sealing member; FIG. 5 is a schematic vertical cross-sectional view for explaining a modification of fixing means for the sealing member; It is explanatory drawing of the modification of the fixing means of a sealing member, The same figure (a) is the schematic longitudinal cross-sectional view, (b) is a schematic front view of a fixing means. FIG. 5 is a schematic vertical cross-sectional view for explaining a modification of fixing means for the sealing member; FIG. 5 is a schematic vertical cross-sectional view for explaining a modification of fixing means for the sealing member; FIG. 11 is an exploded perspective view illustrating a modification of one embodiment of the ball screw according to one aspect of the present invention; FIG. 5 is a schematic diagram illustrating a modified example of the shape of the tongue portion and the fitting recess and the combination thereof in the ball screw according to one aspect of the present invention.

An embodiment of the present invention will be described below with appropriate reference to the drawings. Note that the drawings are schematic. Therefore, it should be noted that the relationship, ratio, etc. between the thickness and the planar dimensions are different from the actual ones, and the drawings include portions where the relationship and ratio of the dimensions are different from each other.
Further, the embodiments shown below are examples of devices and methods for embodying the technical idea of the present invention. etc. are not specified in the following embodiments.

As shown in FIG. 1 , a ball screw 100 according to this embodiment has a screw shaft 10 and a nut 20 fitted on the outer periphery of the screw shaft 10 . A helical thread groove 11 is formed on the outer peripheral surface of the screw shaft 10 , and a helical thread groove 21 facing the thread groove 11 of the screw shaft 10 is formed on the inner peripheral surface of the nut 20 . A plurality of balls 40 are interposed between the thread grooves 11 and 21, and the plurality of balls 40 roll between the thread grooves 11 and 21 as the screw shaft 10 and the nut 20 rotate relative to each other.

The ball screw 100 according to this embodiment is an example of an internal circulation system, the screw shaft 10 is a single thread, and the inner peripheral surface of the nut 20 has one or more circulation circuits, As shown in FIGS. 1 to 3, each circulation circuit is provided with a ball reversing portion 22 which is a substantially S-shaped groove formed to a position deeper than the screw groove 21 of the nut 20 .
As a result, when the ball 40 that has rolled in each circulation circuit reaches the end point of the thread groove 21, it passes through the ball reversing portion 22 on the nut side and returns to the starting point of the thread groove 21 in the same circulation circuit. The circulation of rolling between the grooves 11 and 21 is repeated.

The ball screw 100 of the present embodiment is a suitable example for an electric actuator that constitutes, for example, a steering mechanism of a vehicle. It has a cylindrical portion 30 projecting outwardly, and a ball rolling groove for an inner ring of a bearing constituting the electric actuator is integrally formed on the outer peripheral surface of the cylindrical portion 30 .

In this embodiment, the cylindrical portion 30 is formed coaxially with the screw shaft 10 at one axial end of the nut 20, as shown in FIGS. In this embodiment, the nut end surface 23 on the inner diameter side of the cylindrical portion 30 is a surface perpendicular to the axial direction. An annular seal mounting groove 31 is formed on the inner surface of the cylindrical portion 30 . A C-shaped snap ring 60, which is fixing means for fixing the seal member 50, is axially fitted into the seal mounting groove 31 using a dedicated tool.

The inner diameter of the seal mounting groove 31 is formed to have substantially the same size as the outer diameter of the fixing portion 51 of the seal member 50, and the opening edge of the seal mounting groove 31 has one fitting recess 34 recessed toward the outer diameter side. formed only in The seal mounting groove 31 is formed coaxially with the screw shaft 10 at a position deeper than the opening edge of the cylindrical portion 30 .
An annular seal member 50 is attached to a position on the inner peripheral side of the cylindrical portion 30 and near the nut end surface. The seal member 50 of this embodiment is made of elastomer, and the fixing portion 51 and the lip portion 52 are integrally formed.

Specifically, in this embodiment, as shown in FIG. and a substantially elliptical lip portion 52 that conforms to the helical shape.
The lip portion 52 of the present embodiment is formed in an arc shape along the helical shape of the thread groove 11, and the portion of the screw shaft 10 that faces the inside of the thread groove 11 and the remaining angle range of the screw shaft 10. and the portion facing the land surface 12 are combined to form a substantially elliptical shape. The inside of the nut is filled with a lubricant such as grease, and when the seal member 50 is mounted, the lip portion 52 faces the thread groove 11 with a small gap therebetween to form a non-contact seal.

The outer peripheral surface 54 of the fixing portion 51 is a cylindrical surface having a diameter slightly smaller than or substantially the same as the inner peripheral surface of the seal mounting groove 31, and the surface of the fixing portion 51 facing the nut 20 in the axial direction is It is a vertical torus. In this embodiment, the seal mounting groove 31 of the cylindrical portion 30 and the outer peripheral surface 54 of the seal member 50 constitute the spigot portion 70 .

Here, in the present embodiment, as shown in FIGS. 1 to 3, the outer peripheral surface 54 of the fixed portion 51 of the seal member 50 has a tongue portion 53 that protrudes in the radial direction only at one location. It is set up. The tip of the tongue portion 53 is arcuate.
In the seal mounting structure of the present embodiment, the tongue portion 53 is fitted into the fitting recess 34 formed in the end portion on the inner peripheral side of the cylindrical portion 30 , and the seal member 50 is positioned on the nut 20 . Thereafter, the sealing member 50 is fixed inside the cylindrical portion 30 relative to the C-shaped retaining ring 8 by axially inserting the C-shaped retaining ring 8 into the annular fixing groove 32 .

In particular, in the present embodiment, as shown in FIG. 1(b), the nut end face 23 is used as a reference plane, and the center position (the deepest groove) of the ball reversing portion 22 in the axial direction is positioned at a predetermined dimension in the axial direction. position) is set. Based on the position and phase of the ball reversing portion 22 at the axial dimension A, the axial position B (and the position C from the end) of the seal mounting groove 31 in the axial direction of the seal mounting groove 31 serving as the seal mounting reference, and The phase at which the tongue portion 53 of the seal member 50 is to be attached, that is, the center position of the fitting recess 34 in the circumferential direction (right above position in the figure) is determined.

In the present embodiment, when manufacturing the seal member 50, the circumferential direction of the tongue portion 53 and the fitting recess 34 is adjusted so that the central portion of the tongue portion 53 is arranged at a position corresponding to the theoretical fixed angle calculated in advance. is formed.

It should be noted that manufacturing errors may occur in the screw shaft 10 and the nut 20 . The angular adjustment of the tongue portion 53 and the fitting recess 34 within the error range can be performed by the gap between the tongue portion 53 and the fitting recess 34 in the circumferential direction.
Therefore, when the seal member 50 is used for a specific ball screw, the gap between the tongue portion 53 and the fitting recess portion 34 in the circumferential direction is determined according to the manufacturing error of the screw shaft 10 and the nut 20. do. That is, if the manufacturing error is small, the gap is narrowed, and if the error is large, the gap is widened.

Next, the method of assembling the seal member 50 in the ball screw 100 of the present embodiment and the effects thereof will be described. As for the method of assembling the other constituent parts, since they are assembled in the same manner as in the conventional art, the explanation thereof will be omitted as appropriate.

Here, in this type of ball screw, if the sealing member is not mounted at the mounting position where the desired clearance is obtained due to poor positioning of the sealing member, the sealing performance is degraded. Therefore, relatively high positioning accuracy and clearance control are required. In general, the positioning of the sealing member is performed by fitting. At this time, in order to obtain good dust resistance and sealing performance, it is necessary to adjust the phases of the seal member and the screw shaft with high accuracy while aligning the central axes of the screw shaft and the seal member.

On the other hand, in the ball screw 100 of the present embodiment, the nut 20 has, as described above, the cylindrical portion 30 which is one end, the outer peripheral surface 54 of the seal member 50 and the inner peripheral surface of the cylindrical portion 30. A spigot portion 70 is configured in which the formed seal mounting groove 31 is fitted at a position coaxial with the screw shaft 10 .

Furthermore, in the ball screw 100 of the present embodiment, the tongue portion 53 protrudes radially outward only at one location on the outer peripheral surface 54 of the seal member 50, and the inner peripheral side of the nut end surface 23 of the cylindrical portion 30. A fitting recess 34, which is formed only at one location and into which the tongue portion 53 can be inserted along the axial direction, matches the phase of the sealing shape by the lip portion 52 of the sealing member 50 and the outer peripheral shape of the screw shaft 10. It is formed so as to be positioned at the mounting position (Invention 1).

As a result, in the ball screw 100 of the present embodiment, when the seal member 50 is attached to the nut 20, the pre-formed tongue portion 53 is simply fitted into the fitting recess portion 34 along the axial direction. Can be automatically mounted at a fixed angle.
Therefore, when the seal member 50 is attached to the nut 20, the position in the circumferential direction is uniquely determined at a preset position without checking the phase with the screw shaft 10, so the mounting position can be determined visually. Incorrect assembly is prevented, unlike positioning methods that use special markings or the like.

If the seal is fixed by plastic deformation at the time of assembly, it is difficult to easily position the phase at the time of installation. It can be said that the configuration in which the phase can be uniquely and automatically determined by fitting into 34 along the axial direction is excellent. Therefore, it is preferable that the tongue portion 53 is not deformed plastically, but is formed in advance only in one place so as not to be deformed before and after assembly or to be attached by deformation up to the range of elastic deformation. .

Furthermore, in the ball screw 100 of the present embodiment, the seal mounting groove 31 is located on the inner side of the opening edge of the cylindrical portion 30, and the spigot portion 70 is formed coaxially with the screw shaft 10. Not only the phase of the member 50 in the circumferential direction, but also the position of the center axis and the axial position can be regulated at the same time. As a result, when the ball screw 100 is assembled, there is no need to align the center axes of the screw shaft 10 and the seal member 50 .

In addition, since the spigot portion 70 is formed, the central shaft is also mounted at the desired position at the same time. are arranged facing each other with a gap between them.
Therefore, the lip portion 52 can be opposed over the entire circumference of the screw shaft 10 with a substantially uniform gap therebetween. Therefore, the desired sealing performance can be exhibited without generating extra torque or, conversely, generating a gap larger than desired.
In addition, since the mounting posture of the seal member 50 is maintained stably over time, foreign matter can be effectively prevented from entering from the contact surface between the nut 20 and the seal member 50, and initial sealing performance can be maintained over a long period of time. and maintainable.

As shown in FIG. 4(b), if the seal member 50 is not assembled in the desired phase (in the example shown in FIG. ), contacting portions are generated, and gaps are larger than expected. Even if the central axis of the sealing member 50 is misaligned when it is attached, the same is true.

As described above, according to the ball screw 100 of the present embodiment, it is possible to extremely easily set the center axis and the phase when the seal member 50 is mounted, and fix the seal member 50 after that.
In particular, in the ball screw 100 of the present embodiment, one tongue portion 53 is fitted into one fitting recess 34 formed on the inner peripheral side of the cylindrical portion 30 to position the seal member 50 on the nut 20. .

In other words, since the fitting recess 34 is formed only in one place in the opening edge so as to communicate with the seal mounting groove 31, the fitting recess 34 can be easily processed, and during assembly, it can be Since it is impossible to assemble in the position (phase) of , the risk of erroneous assembly is completely eliminated. Furthermore, it is excellent in that the fitting state of the tongue portion 53 can be reliably confirmed visually before and after attachment.

Furthermore, the ball screw 100 of the present embodiment is of an internal circulation type in which the plurality of balls 40 circulate through the ball reversing portion 22 formed on the inner peripheral surface of the nut 20, and from the outside it looks like a no-load region. When the position of the ball reversing portion 22 is unknown, the no-load region can be easily confirmed by forming the tongue portion 53 of the seal member 50 based on the axial position of the ball reversing portion 22 (Invention 2).

In other words, according to the ball screw 100 of the present embodiment, the distance from the position of the ball reversing portion 22 to the position B of the nut 20 and the specifications (lead and BCD) of the screw are different for mass-produced products of the same design. For this reason, the cross section of the thread groove 21 in the cross section of the nut 20 at the position B is the same for all products, and the phase of the substantially elliptical lip portion 52 of the seal member 50 is also kept the same. The phases of the reversing portion 22 and the fitting recess 34 are determined, the fitting recess 34 is provided in the nut 20 in advance, the phase of the lip portion 52 of the sealing member 50 and the position of the tongue portion 53 are determined, and these are combined. Thus, the phase of the lip portion 52 can be kept the same, the phase of the thread groove 11 of the screw shaft 10 incorporated in the nut 20 and the lip portion 52 can also be kept the same, and the sealing performance can be made the same for all products. can do.
Also, the position of the ball reversing portion 22 can be clearly recognized from the position of the tongue portion 53 even in the completed state of the ball screw 100 . Therefore, if the circulation circuit is a single circuit, it becomes easier to assemble so as not to place the no-load region in the required phase as the load region in the built-in product, and subsequent confirmation can be easily performed. Therefore, it contributes to improving the stability and reliability of the performance of the finished product, as well as improving the embedability in the finished product.

In particular, according to the ball screw 100 of this embodiment, the nut 20 has the cylindrical portion 30 that surrounds the screw shaft 10 and protrudes radially outward from the end portion in the axial direction. Furthermore, since the ball rolling groove for the inner ring of the bearing that constitutes the electric actuator is integrally formed, it is suitable for use in the electric actuator that constitutes the steering mechanism of the vehicle (Invention 3).

In other words, it is particularly suitable for mass production due to its good buildability. Further, in the ball screw 100 of this embodiment, the position of the ball reversing portion 22 can be determined from the position of the tongue portion 53 . Therefore, it is possible to prevent erroneous assembly when assembling the ball reversing portion 22, which is a no-load region with respect to the tongue portion 53, into the electric actuator at a desired phase. As a result, it is possible to assemble while confirming that the positions of the ball reversing portion 22 and the portion where the stress due to the moment load generated by the driving reaction force of the electric actuator and generated through the screw shaft 10 do not coincide with each other.

Furthermore, since the cylindrical portion 30 is formed so as to protrude radially outward from the end portion in the axial direction, the thickness is increased and the rigidity is improved. Since the fitting recess 34 and the seal mounting groove 31 are provided in a highly rigid portion, even if the nut 20 receives a moment load generated by the drive reaction force of the electric actuator through the screw shaft 10, the nut 20 is not deformed. The position of the sealing member 50 and the screw shaft 10 is stabilized by being suppressed, and the sealing performance can be maintained.

As the steering mechanism for the vehicle, a steer-by-wire (SBW) system in which the steering unit and the steering unit are electrically connected without being mechanically connected to change the steering angle of the steering unit via an electric signal. Alternatively, it can be applied to an electric power steering (EPS) in which a steering unit and a steering unit are mechanically connected.
When incorporated into these steering mechanisms, the nut 20 is connected to the driving side and rotates, and the ball screw 100 converts the rotation into linear motion, and the screw shaft 10 is linearly moved to drive the steering mechanism. It is suitable as a rotation-to-linear motion conversion mechanism.

Further, according to the ball screw 100 of this embodiment, the fixing means is the C-shaped retaining ring 8, and the sealing member 50 can be axially fixed to the end of the nut 20 by the C-shaped retaining ring 8. After mounting the sealing member 50, the C-shaped snap ring 8 can be inserted into the fixing groove 32 from the coaxial direction to fix the sealing member 50. As shown in FIG. Therefore, according to the ball screw 100 of the present embodiment, the seal assembly work can be continuously and efficiently performed from the same side in the axial direction during the assembly work (Invention 4).

In addition, according to the ball screw 100 of the present embodiment, since the tongue portion 53 has an arc-shaped end portion projecting in the outer diameter direction, the tongue portion 53 can be easily and efficiently processed by an end mill ( Invention 5).

As described above, according to the ball screw 100 of the present embodiment, the central axes of the screw shaft 10 and the seal member 50 are automatically aligned, and the phases of the seal member 50 and the screw shaft 10 are adjusted to a desired phase. Can be installed automatically. Therefore, while simplifying the work of assembling the seal member 50 to the nut 20, high positioning accuracy and desired seal clearance can be obtained at low cost.
Furthermore, since the position in the circumferential direction is reliably regulated by fitting the tongue portion 53 into the fitting recess portion 34, the phase of the seal member 50 does not change during use, and the seal clearance can be kept constant. Stable rotational torque and sealing performance can be maintained for a long period of time.

It should be noted that the ball screw according to the present invention is not limited to the above embodiments, and various modifications are possible without departing from the gist of the present invention.
For example, in the embodiment shown in FIG. 1, the edge on the inner diameter side of the cylindrical portion 30 is formed as an inclined surface or a curved surface that expands outward in diameter, thereby preventing the seal member 50 from being caught when it is fitted. can.

Further, for example, the lip portion 52 is not limited to a non-contact type seal, and may be a contact type seal. The planar shape of the lip portion 52 can of course be changed in various ways according to the cross section of the screw shaft 10 . For example, in the case of a contact seal, the number of sliding contact portions varies depending on how many thread grooves 11 appear in the cross section perpendicular to the axial direction of the screw shaft 10 .

Moreover, since the cross-sectional shapes and phases of the thread grooves 11 and 21 differ depending on the type of the ball screw 100, it is of course possible to appropriately vary the fixing angle of the seal member 50 in the circumferential direction accordingly. .
From the design conditions such as the cross-sectional shapes and phases of the thread grooves 11 and 21, it is possible to calculate the theoretical fixed angle (phase) at which the lip portion 52 of the seal member 50 slides against the screw shaft 10 without gaps over the entire circumference. The formation position of the tongue portion 53 is provided only at one predetermined position in the circumferential direction according to these.

In the above embodiment, no particular reference was made to the shape of the front and back of the sealing member 50, but if it is necessary to distinguish between the front and back of the sealing member 50, various identification marks and identification shapes can be incorporated.
Specifically, the seal member 50 is designed so that the phase of the seal shape of the seal member 50 and the outer peripheral shape of the screw shaft 10 are matched regardless of whether the seal member 50 is assembled from the front or back side. A seal shape can be formed. As a result, if the sealing member 50 can be made bilaterally symmetrical, it can be mounted on either the front or the back (Invention 6).

Also, for example, a projecting portion is provided only on one side of the sealing member 50, and a projecting fitting portion is provided on the bottom surface of the seal mounting groove 31 of the opposing nut 20 so that when the sealing member 50 is attached to the seal mounting groove 31, the projecting portion By adopting a structure in which the protruding fitting portion is fitted, it is possible to check the front and back of the seal member 50 in advance, and furthermore, even if it is assembled by mistake, it is possible to correct the incorrect assembly of the seal before mounting the screw shaft 10. Attachment can be easily confirmed visually.
In the examples shown in FIGS. 1 and 11 , the axial depth of the fitting recess 34 is also formed to a position deeper than the bottom surface of the seal mounting groove 31 . Regardless of this, it is preferable to provide a projecting fitting portion at a position different from the fitting recess 34 to incorporate a foolproof structure into the seal member 50 (Invention 7).

Further, for example, the ball screw 100 of the above-described embodiment has shown an example of an internal circulation system in which the ball reversing portion 22 is provided on the inner circumference of the nut, but the present invention is not limited to this.
For example, the structure of the ball reversing part includes a return tube type provided on the outer circumference of the nut, a piece type in which a piece member is provided on the inner circumference of the nut and connects adjacent screw grooves with a piece member to reverse the ball, as well as a An end deflector type or the like can be adopted in which the ball is reversed and passed through the through hole of the nut provided at the end portion and extending in the axial direction. In the case of an end deflector type, the seal member may be integrated with the end deflector holder. Also, when using a separate member such as a return tube type, bridge type, end deflector type, etc. for the structure of the ball reversing portion, the axial dimension A is defined by a part of the outer shape of the separate member or the nut 20 with the nut end surface 23 as a reference plane. A part of the surface of the mounting portion on which another member is mounted may be used as a reference.
In the ball screw seal mounting structure according to the present invention, the phase of the seal member 50 can be mounted at the desired phase regardless of the presence or absence of the screw shaft 10. Therefore, depending on the circulation system of the ball screw, Since pre-assembly of the seal is also possible, the ball assembly process may vary in assembly procedure depending on the specification.

Further, in the above-described embodiment, an example in which one sealing member 50 is attached to one end portion of the nut 20 in the axial direction is shown, but the present invention is not limited to this, and the mounting structure of the sealing member according to the present invention is It can also be applied to a case where one or a plurality of sealing members are superimposed on each end of the nut in the axial direction.

Further, the fixing means for fixing the seal member 50 is not limited to the C-shaped snap ring as long as it can prevent slippage in the axial direction, and various modifications are possible. In other words, when using a retaining ring other than a C-type retaining ring, a corresponding mounting structure can be provided on the end surface of the nut.

Also, the sealing member 50 may be an elastic body other than an elastomer, or may be made of metal such as steel plate or resin. Moreover, in order to maintain the shape of the seal member 50 and increase its strength, the fixed portion 51 may include a metal core. Modifications of this type are shown in FIGS. 5 to 10 below. In addition, the same code|symbol is attached|subjected to the structure which is the same as that of the said embodiment, or respond|corresponds, and the description is abbreviate|omitted suitably.

For example, in the example shown in FIG. 5, a snap ring 60 other than the C-shaped snap ring is used as the fixing means. Moreover, in the example shown in FIG. 6, the seal member 50 itself is fitted into the seal mounting groove 31 by utilizing the elastic deformation of the seal member 50 itself as the fixing means. Therefore, it can be said that the seal mounting groove 31 also serves as the fixing groove 32 .
In the example shown in FIG. 6, the spigot fitting clearance and the axial clearance of the seal mounting grooves 31, (32) are controlled so that the position and holding state of the seal member 50 are stabilized. Further, in the example shown in the figure, the guide surface 33 is provided with a conical surface that expands outward in diameter so as to facilitate insertion.

In the example shown in FIG. 7, as the fixing means, the seal member 50 is formed by two-color molding in which a substantially L-shaped seal main body portion 51b and a core metal portion (for example, iron) 51a are combined. The outer surface is formed so as to constitute a spigot portion 70 and is press-fitted and held in the seal mounting grooves 31, (32). In the example shown in the figure, the seal mounting grooves 31 (32) are configured by a stepped portion that also serves as the guide surface 33. As shown in FIG. If the seal member 50 is a non-contact type seal, the seal member 50 may be formed only of metal and its outer peripheral surface may be press-fitted and held in the spigot portion 70 having a similar structure.

In addition, in the example shown in FIG. 8, as a fixing means, the seal member 50 itself is fitted into the spigot joint portion 70 by utilizing the elastic deformation of the seal member 50 itself. In the example shown in the figure, a plurality of chrysanthemum washer-like slits 51s are provided radially in the circumferential direction, as shown in the figure (b), so that the elastic deformation and holding state of the seal member 50 itself are stabilized. Further, in the example shown in the figure, the guide surface 33 is provided with a conical surface whose diameter expands outward so that the seal member 50 can be easily inserted.

In addition, in the example shown in FIG. 9, the sealing member 50 is made of a steel plate as a fixing means, and is fitted into the spigot portion 70 by utilizing its own elastic deformation. In the example shown in the figure, the end portion corresponding to the outer peripheral surface 54 of the seal member 50 is rounded into a pipe shape, and the fixing portion 51, which is the intermediate portion, is turned outward so that the elastic deformation and holding state of the seal member 50 itself are stabilized. It is a slope that projects diagonally toward the

In the example shown in FIG. 10, as a fixing means, the seal member 50 is formed by two-color molding in which a seal body portion 52, which is a metal core portion (for example, iron), and an elastic body portion (for example, rubber) 51 are adhered together. A pawl portion corresponding to the seal mounting groove 31 is formed on the outer peripheral surface 54 of the body portion 51 so as to constitute a spigot portion 70 and is engaged and held.

In the above-described embodiment, the tongue portion 53 of the seal member 50 has an arc-shaped end portion that protrudes in the outer diameter direction by processing with an end mill or the like. Of course, it is not limited to this, and it may be machined into a keyway-like shape with another tool.
For example, in the example shown in FIG. 11, the tongue portion 53 of the seal member 50 is a rectangular end portion. Also, the axial depth of the fitting recess 34 may be deeper than the axial position of the seal mounting groove 31 .

Also, the shape of the tongue portion 53, the shape of the fitting recess 34, and combinations thereof are not limited to the examples of the above embodiment, and various modifications are possible. For example, as shown in FIG. 12A, a combination of a tongue portion 53 having an arcuate end portion and a fitting recess portion 34 formed of a groove penetrating in the radial direction may be used.
Further, as shown in FIG. 2B, a combination of a tongue portion 53 having a rectangular end portion and a fitting recess portion 34 formed of a groove penetrating in the radial direction may be used. Alternatively, as shown in FIG. 4(c), a combination of a tongue portion 53 having a rectangular end portion and a fitting recess portion 34 formed of an arc-shaped groove that does not penetrate in the radial direction may be used.

10 screw shaft 11 (screw shaft) thread groove 12 land surface 20 nut 21 (nut) thread groove 22 ball reversing portion 23 nut end surface 30 cylindrical portion 31 seal mounting groove 32 fixed groove 33 guide surface 34 fitting recess 40 ball 50 Seal member 51 Fixed portion 52 Lip portion 53 Tongue portion 54 Outer peripheral surface 60 C-shaped retaining ring (fixing means)
70 spigot part 100 ball screw

Claims (7)

A screw shaft having a helical thread groove on its outer peripheral surface, a nut fitted on the screw shaft and having a helical thread groove on its inner peripheral surface, and between the thread grooves of the screw shaft and the nut. A plurality of interposed balls, an annular sealing member for sealing between the outer periphery of the screw shaft and the inner periphery of the nut along the outer peripheral shape of the screw shaft, and the sealing member being fixed to the nut. A ball screw comprising a fixing means for
forming a spigot portion in which an outer peripheral surface of the seal member and an inner peripheral surface of the end portion are fitted to at least one end portion of the nut at a position coaxial with the screw shaft;
A tongue projecting radially outward at only one location on the outer peripheral surface of the seal member, and a tongue formed at only one location on the inner peripheral side of the end portion and inserted along the axial direction. A possible fitting recess is formed so as to be located at a mounting position where the sealing shape of the sealing member and the outer peripheral shape of the screw shaft are in phase.
A ball screw characterized by: The ball screw is an internal circulation type in which the plurality of balls circulate through a ball reversing portion formed on the inner peripheral surface of the nut,
2. The ball screw according to claim 1, wherein the mounting positions of the spigot portion and the tongue portion of the sealing member are formed based on the axial position and phase of the ball reversing portion. The ball screw is used for an electric actuator constituting a steering mechanism of a vehicle,
The nut has a cylindrical portion projecting radially outward from the end, and
3. The ball screw according to claim 2, wherein a ball rolling groove for an inner ring of a bearing constituting said electric actuator is integrally formed on an outer peripheral surface of said cylindrical portion. The fixing means is a C-shaped retaining ring,
The ball screw according to any one of claims 1 to 3, wherein the seal member is axially fixed to the end of the nut by the C-shaped retaining ring. The ball screw according to any one of claims 1 to 4, wherein the tongue portion has an arc-shaped peripheral edge at the end projecting in the radial direction. The seal shape of the seal member is formed so that the phase of the seal shape of the seal member and the outer peripheral shape of the screw shaft are matched regardless of whether the seal member is assembled from the front or back side. The ball screw according to any one of claims 1 to 4. The ball screw according to any one of claims 1 to 4, wherein the seal member is provided with a foolproof structure that makes assembly impossible from the opposite side of the seal member.

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