JP2019190506A - Ball screw device - Google Patents

Abstract

A ball screw device capable of optimizing the shape of a communication path provided in a deflector to suppress the occurrence of ball clogging in an unloaded path and further smoothing relative rotation of a screw shaft with respect to a nut member. I will provide a. A load is formed in a cylindrical shape having a screw shaft having a spiral rolling groove formed on an outer peripheral surface thereof, and a through hole through which the screw shaft is inserted, and the load is opposed to the rolling groove. A nut member having rolling grooves formed on the inner peripheral surface, a large number of balls rolling in a load passage formed by the rolling groove and the load rolling groove facing each other, and an end and a start end of the load passage. A ball screw device having a connecting path for connecting the ball and returning the ball by one turn of the load path, and a deflector fitted to the peripheral wall of the nut member. The passage has a pair of introduction straight portions that the ball enters from the load passage and directly faces the rolling groove of the screw shaft. [Selection diagram]

Description

  The present invention relates to a ball screw device capable of mutually converting rotational motion and linear motion.

  A ball screw device is a machine element that can convert rotational motion and linear motion to each other. The purpose of converting rotational motion generated by a servo motor to linear motion in various machine tools, conveyors, industrial robots, etc. It is often used in. In the ball screw device, a screw shaft and a cylindrical nut member are screwed together via a large number of balls, and a helical rolling groove on which the ball rolls is formed on the outer peripheral surface of the screw shaft. On the other hand, a load rolling groove facing the rolling groove of the screw shaft is formed on the inner peripheral surface of the nut member. The rolling groove of the screw shaft and the load rolling groove of the nut member constitute a spiral load passage facing each other, and the ball rolls the load passage while rolling the screw shaft and the nut member. Load between. The nut member includes a no-load passage that rolls in a state where the ball is released from the load. The no-load passage connects both ends of the load passage to form an infinite circulation path of the ball, and the ball is returned from the end of the load passage to the starting end by the no-load passage.

  The structure of the infinite circulation path is classified into several types. As one of them, for example, as shown in Patent Document 1, a piece member called a deflector is fitted to the peripheral wall of the nut member. A structure in which the balls are returned by one turn of the load passage is known. The deflector is formed with a communication path serving as the no-load path corresponding to the inner peripheral surface of the nut member. The communication path receives the ball that has reached the end of the load path and shifts it from a loaded state to a no-load state, and changes the traveling direction of the ball to release the ball from the rolling groove of the screw shaft. The ball rolls over the communication path, gets over the threaded portion of the screw shaft, and is returned to the starting end of the load passage.

JP, 2006-180469, A

  The ball that has entered the connecting path of the deflector from the load passage is released from the load state and transitions to a no-load state, and further changes the traveling direction that has been rolling around the screw shaft in a spiral manner. Get over the thread on the screw shaft. Since the communication path is open toward the outer peripheral surface of the screw shaft, and the ball rolls along the communication path while being in contact with the screw shaft, the load on the ball is sufficiently unloaded. When the traveling direction of the ball changes in a state where the ball is not in the state, the gap between the ball and the communication path is narrowed, and there is a problem that the ball is easily clogged in the no-load path.

  When the ball is easily clogged in the no-load passage, smooth conversion between the rotational motion and the linear motion by the ball screw device is hindered.For example, when the screw shaft is rotated by an electric motor, the rotational torque is increased with a larger rotational torque. There is a problem that it is necessary to rotate the screw shaft, leading to an increase in the size of the electric motor and an increase in power consumption.

  The present invention has been made in view of such a problem, and the object of the present invention is to optimize the shape of the connecting path provided in the deflector to suppress the occurrence of ball clogging in the no-load path and An object of the present invention is to provide a ball screw device capable of further smoothing relative rotation of a screw shaft.

  That is, the present invention is formed in a cylindrical shape having a screw shaft having a spiral rolling groove formed on the outer peripheral surface and a through hole through which the screw shaft is inserted, and is opposed to the rolling groove. A nut member having an inner peripheral surface formed with a load rolling groove, a plurality of balls rolling on the load path formed by the rolling groove and the load rolling groove facing each other, and an end of the load path And a deflector that is connected to a peripheral wall of the nut member, and has a connecting path for returning the ball by one turn of the load path by connecting the start end and the deflector, and the deflector The communication path includes a pair of introduction straight portions that face the ball from the load passage and face the rolling groove of the screw shaft.

  According to the present invention, the connecting path of the deflector includes a pair of introduction straight portions into which a ball enters from a load passage of the nut member, and these introduction straight portions are opposed to the rolling grooves of the screw shaft so that the ball travels The ball is led to an unloaded state without changing the direction. Thereby, the shape of the communication path is optimized, the occurrence of ball clogging in the no-load path is suppressed, and the relative rotation of the screw shaft with respect to the nut member can be further smoothed.

It is a perspective view showing an example of a ball screw device to which the present invention is applied. It is a side view which shows the nut member of the ball screw apparatus shown in FIG. It is a perspective view which shows an example of the deflector to which this invention is applied. It is a principal part enlarged view which shows the connection part of the load rolling groove of a nut member, and the connecting path of a deflector. It is a principal part enlarged view which shows the mode of rolling of the ball | bowl in the connecting path of a deflector. It is the top view which observed a mode that the deflector was fitted in the mounting hole of the nut member from the inside of the nut member concerned.

  Hereinafter, a ball screw device of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 shows an example of a ball screw device to which the present invention is applied. This ball screw device 1 includes a screw shaft 2 in which a ball rolling groove 20 is formed in a spiral shape on the outer peripheral surface, and a cylindrical nut member 3 that is screwed around the screw shaft 20 via a large number of balls. It consists of and. The nut member 3 is provided with an infinite circulation path for the balls. The ball is interposed between the screw shaft 2 and the nut member 3. For example, when the screw shaft 2 is rotated with respect to the nut member 3, the nut member 3 is moved in the axial direction of the screw shaft 2. Or by rotating the nut member 3 with respect to the screw shaft 2, the screw shaft 2 moves in the axial direction of the nut member 3.

  One or more rolling grooves are formed on the outer peripheral surface of the screw shaft 2, and the rolling grooves 20 exist at a predetermined pitch along the axial direction of the screw shaft 2. Further, between the adjacent rolling grooves 20 is a thread portion 21, and the thread portion 21 indicates the outer diameter of the screw shaft 2.

  The nut member 3 has a through hole through which the screw shaft 2 is inserted, and is formed in a cylindrical shape. At one end in the axial direction, a flange portion 30 for connecting the nut member 3 to another mechanical device. Is provided. The flange part 30 is provided with a plurality of attachment holes 31 for inserting fixing bolts. On the inner peripheral surface of the nut member 3, a spiral load rolling groove is formed by the same lead as the rolling groove 20 of the screw shaft 2. The load rolling groove and the rolling groove 20 are opposed to each other to form a load path of the ball, and the ball loads a load between the screw shaft 2 and the nut member 3 while rolling the load path. To load.

  A plurality of deflectors 4 are mounted on the body portion 32 of the nut member 3. Each deflector 4 has a communication path for returning the ball from the end of the load path to the start, and by attaching the deflector 4 to the nut member 3, the ball is infinitely circulated around the screw shaft 2. The road is completed.

  FIG. 2 is a side view of the nut member 3 showing a state where the screw shaft 2 and the deflector 4 are removed from the nut member 3. A plurality of mounting holes 33 for fitting the deflector 4 are provided in the body portion 32 of the nut member 3. These mounting holes 33 are arranged in a balanced manner at equal intervals along the circumferential direction of the nut member 3. Each deflector 4 corresponds to one circuit of the infinite circuit, and the nut member 3 is provided with an infinite circuit having the same number of circuits as the number of the mounting holes 33 in the axial direction.

  FIG. 3 is a perspective view showing the deflector 4. The deflector 4 is formed in a substantially rectangular shape, and has a distal end surface 40 that is curved corresponding to the inner peripheral surface of the nut member 3, and the distal end surface with respect to the mounting hole 33 of the nut member 3. 40 is inserted. The deflector 4 is provided with a pair of locking portions 41. When the deflector 4 is inserted into the mounting hole 33 from the outside of the nut member 3, the pair of locking portions 41 are formed on the step portion 34 (see FIG. 2) provided inside the mounting hole 33. As a result, the position of the deflector 4 with respect to the radial direction of the nut member 3 is determined, and the tip surface 40 is positioned with respect to the inner peripheral surface of the nut member 3.

  The deflector 4 is provided with the communication path 42. The connecting path 42 is formed in a groove shape with respect to the deflector 4 and is open to the distal end surface 40 over the entire length. Both ends of the communication path 42 are open to a pair of side planes 43. The pair of side planes 43 are provided in parallel to each other, and the communication path 42 is provided so as to connect between the pair of side planes 43. The connecting path 42 is bent with a combination of a straight portion and a curved portion, and the opening 44 with respect to one side plane 43 and the opening 44 with respect to the other side plane 43 are related to the axial direction of the screw shaft 2. The rolling groove 20 is provided by being displaced by one pitch. The depth of the communication path 42 with respect to the distal end surface 40 is set to be the deepest at an intermediate position of the path connecting the pair of openings 44, and is set to be the shallowest at both ends opened to the pair of side planes 43. .

  FIG. 4 is a view showing a connection state between the load rolling groove 35 of the nut member 3 and the connecting path 42 of the deflector 4. The load rolling groove 35 has a Gothic arch-shaped cross section, and is formed by a pair of rolling surfaces 35a formed with a curvature larger than the curvature of the ball spherical surface. The ball rolls in the load rolling groove 35 while applying a load between the screw shaft 2 and the nut member 3. The inner diameter of the connecting path 42 of the deflector 4 is set larger than the groove width of the load rolling groove 35. For this reason, when the ball enters the communication path 42 from the load rolling groove 35, the ball is released from the load and becomes unloaded. On the other hand, when the ball enters the load rolling groove 35 from the communication path 42, the ball shifts from the unloaded state to the loaded state. Further, as shown in FIG. 4, a slight step 36 is generated at the connection portion between the communication path 42 and the load rolling groove 35.

  FIG. 5 is a view showing a state in which the ball 5 rolls inside the connecting path 42 of the deflector 4. The deflector 4 is cut out to show the connecting path 42, and the nut member 3 is omitted. It is. Similar to the load rolling groove 35 of the nut member 3, the rolling groove 20 of the screw shaft has a Gothic arch-shaped cross section, and is formed with a pair of curvatures larger than the curvature of the spherical surface of the ball 5. The rolling surfaces 20a are formed to intersect. The connecting path 42 of the deflector 4 is positioned so as to straddle the two adjacent rolling grooves 20. When the ball 5 enters the unloaded passage where the rolling groove 20 and the communication path 42 face each other, the ball 5 is brought to one rolling surface 20a of the rolling groove 20 by the communication path 42, and the rolling surface It lifts to the top of the thread 21 of the screw shaft 2 while in contact with 20a. Further, when the ball 5 gets over the thread portion 21, the ball 5 rolls down to the deepest portion of the rolling groove 20 while being in contact with the rolling surface 20 a of the adjacent rolling groove 20.

  FIG. 6 is a plan view showing the positional relationship between the connecting path 42 of the deflector 4 and the load rolling groove 35 of the nut member 3, and the front end surface 40 of the deflector 4 is observed from the inside of the through hole of the nut member 3. It shows how it was done. The communication path 42 includes a pair of introduction straight portions 42 a that open to the side plane of the deflector, an intermediate straight portion 42 b that faces the screw thread portion 21 of the screw shaft 2 and crosses the screw thread portion 21, and these It has a pair of transition curve part 42c which connects an introductory straight part and an intermediate | middle straight part.

  The introduction straight portion 42a has a role of shifting the ball 5 that has entered the communication path 42 from a loaded state to a no-load state or from a no-load state to a loaded state. It faces the running groove 20 and covers the rolling groove 20. That is, the ball 5 that has entered the introduction straight portion 42a rolls straight on the rolling groove 20 without being brought to one of the rolling surfaces of the rolling groove 20, and during that time, the load is removed from the load state. Transition to the state.

  The intermediate straight portion 42b intersects the load rolling groove 35 at a constant angle θ, and the ball 5 gets over the thread portion 21 while rolling the intermediate straight portion 42b in an unloaded state. On the other hand, the transition curve portion 42c gradually changes the traveling direction of the ball 5 between the introduction straight portion 42a and the intermediate straight portion 42b, and delivers the ball between these straight passages. The ball 5 is brought toward one rolling surface 20a of the rolling groove 20 by the transition curve portion 42c, and gradually begins to lift from the rolling groove 20 so as to scoop up the rolling surface 20a.

  Therefore, when the ball 5 that has contacted the load rolling groove 35 and rolled around the screw shaft 2 while applying a load enters the introduction straight portion 42a of the communication path 42, the ball 5 is released from the load. Thus, a no-load state is established, and the traveling direction is changed by the transition curve portion 42c following the introduction straight portion 42a. The ball 5 whose traveling direction has changed at the transition curve portion 42c enters the intermediate straight portion 42b as it is, and rolls straight without changing the traveling direction at the intermediate straight portion 42b. After getting over 21, the vehicle enters the transition curve portion 42c existing on the opposite side. The ball 5 that has entered the transition curve portion 42c on the opposite side changes its traveling direction again, passes through the introduction straight portion 42a that follows the transition curve portion 42c, and then enters the load rolling groove 35a again. When the ball 5 enters the load rolling groove 35a from the introduction straight portion 42a, the ball 5 shifts from a no-load state to a load state.

  When the connecting path 42 of the deflector 4 is configured in this way, the ball 5 is completely released from the load at the introduction straight portion 42a and then enters the transition curve portion 42 to change the traveling direction. The traveling direction of the ball does not change when the ball is not fully unloaded. That is, since the transition curve portion 42 brings the ball 5 to one rolling surface 20a after the ball 5 is in an unloaded state, the clearance between the ball 5 and the deflector 4 is excessive in the transition curve portion 42. It does not become narrow, and the occurrence of a phenomenon that the ball 5 is clogged in the no-load passage can be avoided.

  In order to shift the ball 5 from the loaded state to the no-load state in the introduction straight portion 42a, or to quickly shift from the no-load state to the load state, the length X of the introduction straight portion 42a is at least the ball. 5 has a length corresponding to a half of the diameter of the ball 5, that is, a length corresponding to the radius of the ball 5. If the length of the introduction straight portion 42a is set in this way, when the maximum diameter portion of the ball 5 passes through the step 36 (see FIG. 4) between the load rolling groove 35 and the connecting path 42 of the deflector. The ball 5 has not yet entered the transition curve portion 42c, and the ball 5 can enter the transition curve portion 42c after waiting for the ball 5 to be completely released from the load.

  In addition, the pair of side planes 43 of the deflector 4 are orthogonal to the load rolling groove 35 in order to ensure a sufficient length X of the introduction straight portion while reducing the size of the deflector. Yes. Thus, when the pair of side planes 43 are orthogonal to the load rolling groove 35, the opening 44 of the connecting path 42 faces the load rolling groove without inclining. It is possible to maximize the length of the introduction straight portion 42a. Further, since the opening 44 faces the load rolling groove without being inclined, the opening 44 can be accurately formed in the deflector, and the load rolling groove 35 and the communication path can be formed. The step 36 of the connecting portion 42 can be formed uniformly along the peripheral wall of the connecting path 42, so that smooth rolling of the ball 5 can be expected.

  As described above, in the ball screw device of this embodiment, the shape of the connecting path provided in the deflector is changed from the load state of the ball load to the no load state, or from the no load state to the load state. It is optimized based on the transition, and it is possible to suppress the occurrence of ball clogging in the no-load passage and further smooth the relative rotation of the screw shaft with respect to the nut member.

DESCRIPTION OF SYMBOLS 1 ... Ball screw apparatus, 2 ... Screw shaft, 3 ... Nut member, 4 ... Ball, 20 ... Rolling groove, 31 ... Circulation groove, 32 ... Load part, 33 ... Unload part, 40 ... Infinite circuit

Claims (4)

A screw shaft having a spiral rolling groove formed on the outer peripheral surface;
A nut member having a through-hole through which the screw shaft is inserted and formed in a cylindrical shape, and a load rolling groove facing the rolling groove is formed on an inner peripheral surface;
A number of balls rolling in a load passage formed by the rolling groove and the load rolling groove facing each other;
A connecting path for connecting the terminal end and the starting end of the load path to return the ball by one turn of the load path, and a deflector fitted to the peripheral wall of the nut member;
With
The connecting path of the deflector is provided with a pair of introduction straight portions that allow a ball to enter from the load passage and face the rolling groove of the screw shaft.   The connecting path is provided at both ends of the intermediate straight portion connecting the pair of introduction straight portions and crossing the thread portion of the screw shaft, and connecting the intermediate straight portion and the pair of introduction straight portions. The ball screw device according to claim 1, further comprising a pair of transition curve portions.   3. The ball screw device according to claim 1, wherein the pair of introduction straight portions provided in the communication path has a length corresponding to at least the radius of the ball. The deflector has a pair of side planes in which an introduction straight part of the communication passage opens, and the side planes are provided in parallel to each other and are orthogonal to the load rolling groove. The ball screw device according to any one of claims 1 to 3.

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