JP4548773B2 - Ball screw with position holding mechanism - Google Patents

Description

  The present invention relates to a ball screw used for a variable valve system of an automobile, and in particular, even when a reaction force acts on a screw shaft, the ball is prevented from rolling to prevent a nut from rotating. The present invention relates to a ball screw with a position holding mechanism that can hold a position in a direction.

  2. Description of the Related Art As a valve operating apparatus for an internal combustion engine, a variable valve operating apparatus capable of changing valve operating characteristics such as a lift amount and a working angle of an intake / exhaust valve of the engine is known. Such a variable valve device is realized, for example, by using a three-dimensional cam in which the profile of a cam that drives opening and closing of the valve changes when the camshaft changes in the axial direction, and oscillates the rotational motion of the cam that rotates with the camshaft. 2. Description of the Related Art There is known a variable valve operating apparatus that transmits to an intake / exhaust valve via a cam and changes the operation modes of the cam, the intake / exhaust valve, and the swing cam by an axial displacement of a control shaft.

  As a displacement mechanism in the axial direction of the shaft for changing the valve operating characteristic, a mechanism using an electric actuator using an electric motor has been proposed. This electric actuator is excellent in controllability and responsiveness because the position of the camshaft and the control shaft in the axial direction can be controlled through a power supply mode to the electric actuator. However, in order to maintain the position of the shaft in the axial direction in order to maintain the valve operating characteristics of the intake / exhaust valve as desired, it is necessary to continuously energize the electric actuator, which requires a large amount of power consumption.

  As a solution to such a problem, a variable valve operating apparatus for an internal combustion engine as shown in FIG. 5 is known. In this variable valve operating apparatus, a camshaft 51 having a three-dimensional cam 50 drives the reciprocating motion of a valve 52 that opens and closes a port that communicates with a combustion chamber of an internal combustion engine. The electric actuator 53 has an output shaft 54 that is displaced in the axial direction, and the camshaft 51 that is connected via a bearing 55 is displaced in the axial direction to vary the valve operating characteristics of the valve 52. The electric actuator 53 has an excitation coil 57 mounted in a frame 56 and a rotor 58 that is rotatably supported on the inner peripheral side thereof. The rotor 58 rotates in response to energization of the exciting coil 57, displaces the screw shaft 61 of the ball screw 59 in the axial direction, and selectively restrains the movement of the ball 63 of the ball screw 59. 60.

  As shown in an enlarged view in FIG. 6, the restraining mechanism 60 is provided on the ball screw 59, and a stopper 64 that prevents the movement of the ball 63 between the screw shaft 61 and the nut 62 screwed to the screw shaft 61. And a stopper hooking portion 65 that operates in response to the protruding operation of the stopper 64. A screw groove 62a that forms a rolling path of the ball 63 together with a helical thread groove 61a formed on the screw shaft 61 is formed on the inner peripheral surface of the nut 62, and a piece member 66 that uses the rolling path as a revolving path. Is installed. As a result, the ball 63 can move along the outer periphery of the screw shaft 61 without stopping from the screw groove 61a and the piece member 66 without dropping from the nut 62, and the screw shaft 61 is rotated with the rotation of the nut 62. Moves in the axial direction.

The stopper 64 includes an electromagnet 67, an elastic member 68, and a protruding member 69, and the protruding member 69 is inserted into a hole 70 provided in a portion corresponding to the thread groove 62 a of the nut 62. In order to switch the blocking operation of the ball 63 by the projecting member 69, the elastic member 68 constantly urges the projecting member 69 toward the screw shaft 61, while the electromagnet 67 responds to the exciting current of the coil. The protruding member 69 is sucked and pulled out from the screw groove 61a. That is, when the electromagnet 67 is energized, the protruding member 69 is attracted and pulled up by the electromagnet 67, and the ball 63 on the screw shaft 61 can roll along the screw groove 61a. For this reason, the rotor 58 can rotate corresponding to the excitation state of the excitation coil 57, and the axial displacement of the screw shaft 61 is allowed. When the energization of the electromagnet 67 is interrupted, the protruding member 69 protrudes into the thread groove 61a and prevents the ball 63 from rolling. For this reason, the rotor 58 is restrained and cannot rotate, and the axial position of the screw shaft 61 is maintained.
JP 2004-19631 A

  However, in this conventional restraint mechanism 60, it is sufficient that the projecting member 69 can project between the balls 63 and 63 on the thread groove 61a in a timely manner. However, if the projecting member 69 projects on the ball 63, the position holding operation fails. There is a fear and there is a problem in terms of reliability. Further, since it is necessary to open the hole 70 on the thread groove 62a of the nut 62, when the ball 63 rolls over the hole 70, the behavior of the ball 63 is not stabilized and noise and vibration are generated. There is a problem. Further, the ball 63 rolls over the hole 70, so that excessive stress is generated at the edge portion of the hole 70, which may lead to a short life of the ball screw 59.

  The present invention has been made in view of such circumstances. Even when a reaction force acts on the screw shaft, the ball is prevented from rolling to prevent the nut from rotating, and the screw shaft can be displaced in the axial direction. An object of the present invention is to provide a ball screw with a position holding mechanism that can be mechanically held at an arbitrary position.

In order to achieve such an object, the invention according to claim 1 of the present invention includes a screw shaft having a spiral thread groove formed on the outer peripheral surface thereof, and is externally fitted to the screw shaft and spirally formed on the inner peripheral surface. And a plurality of balls accommodated in a rolling path formed by opposing screw grooves, and a piece window drilled in a body portion of the nut, and the rolling A ball screw with a position holding mechanism that holds the position of the screw shaft in the axial direction by preventing rolling of the ball and a piece member formed with a connecting groove having a moving path as a circulation path. The mechanism is embedded at a position corresponding to the piece member of the nut, an opening is formed in a part of the connecting groove of the piece member, and the position holding mechanism is configured in the opening , and the tip thereof is the Formed on the arc surface or inclined surface along the shape of the connecting groove, the most protruding By retractable projecting member which forms part of the coupling groove in state, the control rolling of the ball by opening and closing the opening of the coupling groove, selectively the axial position of the screw shaft A configuration was adopted that was held.

As described above, in the ball screw with a position holding mechanism that holds the position of the screw shaft in the axial direction against the reaction force applied, the position holding mechanism is embedded at a position corresponding to the piece member of the nut. An opening is formed in a part of the connecting groove, and a position holding mechanism is formed in the opening , and the tip is formed in an arc surface or an inclined surface along the shape of the connecting groove, and the protrusion is in the most protruding state. by retractable projecting member which forms part of the coupling groove, to control the rolling of the ball Lumpur by opening and closing the opening of the coupling groove, to selectively retain the axial position of the screw shaft Therefore, regardless of the projecting timing of the projecting member, the ball can be prevented from rolling, and the reliability can be remarkably improved. Further, since it is not necessary to open a hole or the like on the screw groove of the nut, it does not affect the behavior of the ball, and it is possible to prevent noise and vibration and to secure a desired life in the ball screw.

  Further, as in the invention described in claim 2, the position holding mechanism includes an annular exciting coil, a rod-shaped protruding member made of a magnetic material inserted into the exciting coil, and a predetermined protruding member. An elastic member that biases in the direction, and by applying a predetermined applied voltage to the exciting coil, the protruding member is sucked against the elastic member and driven in the longitudinal direction. According to a third aspect of the present invention, the piezoelectric device includes a piezoelectric element, a rod-shaped projecting member that engages with the piezoelectric element, and an elastic member that biases the projecting member in a predetermined direction. A configuration may be adopted in which the projecting member is driven in the longitudinal direction against the elastic member by applying a predetermined applied voltage to the element.

  Further, as in the invention according to claim 4, the position holding mechanism is embedded in a mounting hole drilled along an axial direction from one end surface of the nut, and the protruding member is formed on a side surface of the connecting groove. It may be arranged in the formed opening, or, as in the invention according to claim 5, is embedded in the piece window drilled along the radial direction from the outer peripheral surface of the nut, and the protruding member May be disposed in an opening formed in the bottom of the connecting groove.

A ball screw with a position holding mechanism according to the present invention includes a screw shaft having a helical thread groove formed on the outer peripheral surface, and a nut that is fitted on the screw shaft and has a helical screw groove formed on the inner peripheral surface. And a plurality of balls accommodated in a rolling path formed by opposing screw grooves and a piece window drilled in a body portion of the nut, and a connection having the rolling path as a circulation path A ball screw with a position holding mechanism that prevents rolling of the ball and holds the axial position of the screw shaft, wherein the position holding mechanism is the piece member of the nut. The opening is formed in a part of the connecting groove of the piece member, and the position holding mechanism is formed in the opening , and the tip of the arc is formed along the shape of the connecting groove. The connecting groove is formed on the surface or inclined surface and protrudes most By retractable projecting member forming a part, said control rolling of the ball by opening and closing the opening of the connecting groove. Thus selectively retaining the axial position of the screw shaft Regardless of the projecting timing of the projecting member, the ball can be prevented from rolling and the reliability can be remarkably improved. Further, since it is not necessary to open a hole or the like on the screw groove of the nut, it does not affect the behavior of the ball, and it is possible to prevent noise and vibration and to secure a desired life in the ball screw.

  A screw shaft having a spiral thread groove formed on the outer peripheral surface, a nut externally fitted to the screw shaft and having a spiral thread groove formed on the inner peripheral surface, and a roller formed by both opposing screw grooves. A plurality of balls housed in a movement path, and a piece member fitted to a piece window formed in the trunk portion of the nut and having a connection groove having the rolling path as a circulation path, In a ball screw with a position holding mechanism for preventing the ball from rolling and holding the axial position of the screw shaft, the position holding mechanism includes an annular excitation coil and a magnetic material fitted in the excitation coil. And a resilient member that biases the projecting member in a predetermined direction, and is embedded in the axial direction at a position corresponding to the piece member of the nut, and is connected to one of the connecting grooves of the piece member. An opening is formed in the excitation coil, and a predetermined applied voltage is applied to the exciting coil. To control the rolling of the ball by sucking the projecting member against the elastic member and driving it in the axial direction so as to project and retract in the opening, and the axial position of the screw shaft. Was kept selectively.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
Fig.1 (a) is a top view which shows 1st Embodiment of the ball screw with a position holding mechanism based on this invention, (b) is the side view.
This ball screw with a position holding mechanism includes a screw shaft 1 having a helical thread groove 1a formed on the outer periphery, and a helical screw groove that is fitted on the screw shaft 1 and corresponds to the screw groove 1a on the inner periphery. A nut 2 formed with 2a, a large number of balls 3 accommodated between the screw grooves 1a and 2a, and a position holding mechanism 4 attached to the nut 2 are provided.

  The cross-sectional shape of each thread groove 1a, 2a may be a circular arc shape or a Gothic arc shape, but here a Gothic arc shape with a large contact angle with the ball 3 and a small axial clearance can be set. Is formed. Thereby, the rigidity with respect to an axial load becomes high, and vibration can be suppressed.

  An elliptical piece window 5 penetrating the inner and outer peripheral surfaces and notching a part of the thread groove 2a is formed in the barrel portion of the cylindrical nut 2, and an elliptical piece member 6 is formed in the piece window 5. Is fitted. An inner part of the piece member 6 connects adjacent ones of the screw grooves 2a to form a connection groove 7 curved in an S-shape, and a portion of the connection groove 7 and the screw groove 2a that is substantially one turn. And constitutes a rolling path of the ball 3. A large number of balls 3 interposed between the inner and outer screw grooves 1a and 2a in the rolling path roll along the screw grooves 1a and 2a, and are guided by the connecting grooves 7 of the piece member 6 to be threaded. And then returns to the adjacent screw groove 1a and rolls along the screw grooves 1a and 2a again. The depth of the connecting groove 7 is set to a depth at which the ball 3 can exceed the thread of the screw groove 1 a in the screw shaft 1 in the connecting groove 7.

  The piece member 6 is made of a sintered alloy prepared by adjusting a metal powder into a plastic shape and molded by an injection molding machine. In this injection molding, first, metal powder and a binder made of plastic and wax are kneaded by a kneader, and the kneaded product is granulated into pellets. The granulated pellet is supplied to a hopper of an injection molding machine and molded by being pushed into a mold in a heated and melted state. The metal powder is preferably a material that can be subsequently carburized and quenched. For example, C (carbon) is 0.3 wt%, Ni (nickel) is 1 to 2 wt%, and the remainder is Fe (iron). . The material of the piece member 6 is not limited to this, and may be formed of, for example, an injection-moldable thermoplastic resin such as PA (polyamide) 66.

  The ball 3 is assembled by attaching the piece member 6 to the piece window 5 of the nut 2 from the inner diameter side of the nut 2 and then applying the nut 2 from the shaft end of the screw shaft 1 to place the ball 3 between the screw grooves 1a and 2a. The nut 2 is rotated while being sequentially inserted, and the nut 2 is moved to the screw shaft 1. In addition, after the piece member 6 is mounted on the piece window 5 of the nut 2, the ball 3 may be similarly inserted using a temporary shaft (not shown).

  The position holding mechanism 4 includes an exciting coil 8, an elastic member 9 including a coil spring and the like, and a protruding member 10, and is embedded in a mounting hole 11 drilled from one end surface of the nut 2 along the axial direction. . The projecting member 10 is made of a magnetic material, and includes a movable iron core portion 10a fitted into the annular exciting coil 8, a flange portion 10b serving as a seating surface of the elastic member 9, and an open / close pin extending from the flange portion 10b in the axial direction. 10c and formed in a rod shape as a whole. The position holding mechanism 4 constitutes a so-called plunger-type linear electromagnetic solenoid that applies a voltage to the exciting coil 8 to give a linear motion to the protruding member 10 by its magnetic force. A plate-like cover 12 for sealing the mounting hole 11 is fastened to the end face of the nut 2 via a fixing screw 13.

  The position holding mechanism 4 is mounted at a position corresponding to the piece member 6. An opening 7a is formed in a part of the connecting groove 7 of the piece member 6, and an opening / closing pin 10c is inserted into the opening 7a so as to be able to protrude and retract. Moreover, the front-end | tip of the opening-and-closing pin 10c is formed in the circular arc surface or inclined surface along the shape of the connection groove | channel 7, and has comprised a part of connection groove | channel 7 in the state which protruded most. That is, due to the axial movement of the opening / closing pin 10c, the opening 7a of the connecting groove 7 is closed, and a continuous S-shaped connecting groove 7 is formed.

Next, the operation of the ball screw with a position holding mechanism according to the present invention will be described with reference to FIGS. FIG. 2 shows a state in which the screw shaft 1 in the ball screw can be freely displaced in the axial direction without being restrained by the position holding mechanism 4.
Here, the elastic member 9 is attached in a stretched state between the bottom surface 11a of the mounting hole 11 and the flange portion 10b. When no voltage is applied to the exciting coil 8, that is, in a natural state, the protruding member The ten open / close pins 10 c are projected to the maximum by the urging force of the elastic member 9 (right side in the figure), and close the opening 7 a of the connecting groove 7 in the piece member 6. In this state, the ball 3 can smoothly roll in the connecting groove 7 of the piece member 6, and the screw shaft 1 can be freely displaced in the axial direction without being restrained by the position holding mechanism 4.

  On the other hand, when an applied voltage is applied to the exciting coil 8 in response to the displacement signal, the attractive force acts on the movable core portion 10a, and the protruding member 10 is pulled out against the urging force of the elastic member 9. That is, the opening / closing pin 10c moves to the left side in the drawing, the opening 7a of the connecting groove 7 is opened, and the connecting groove 7 is partially opened. In this state, a part of the ball 3 enters the opening 7 a of the connecting groove 7, and the centers of the balls 3 and 3 are shifted from the predetermined rolling trajectory R along the connecting groove 7 to be in a so-called staggered state. Rolling is prevented. Therefore, as a result, the screw shaft 1 is restrained by the position holding mechanism 4 and cannot be displaced in the axial direction, and the rotation of the nut 2 is prevented and the position is held.

  When the energization of the exciting coil 8 is interrupted, the attractive force acting on the movable core portion 10a is released, and the protruding member 10 protrudes toward the piece member 6 by the urging force of the elastic member 9, and the connecting groove 7 The ball 3 can smoothly roll again in the connecting groove 7 by closing the opening 7a.

  In this example, the position holding mechanism 4 is configured to apply an applied voltage to the exciting coil 8 and draw the protruding member 10 against the urging force of the elastic member 9 by the attraction force. Not limited to the configuration and operation described above, although not shown, the elastic member 9 is attached in a compressed state, and the exciting coil 8 is energized to resist the urging force of the elastic member 9 so that the projecting member 10 is removed. You may make it protrude to the member 6 side.

  In the present embodiment, unlike the conventional restraining mechanism, the protruding member is protruded into the thread groove of the nut to prevent the ball from rolling, and an opening is formed in a part of the connecting groove 7 of the piece member 6. 7a is formed, and the opening and closing pin 10c constituting the projecting member 10 is projected and retracted in the opening 7a to control the rolling of the ball 3 so that the axial position of the screw shaft 1 is selectively held. Therefore, the ball 3 can be prevented from rolling regardless of the projecting timing of the projecting member 10, and the reliability can be remarkably improved. In addition, since it is not necessary to open a hole or the like on the screw groove 2a of the nut 2, it does not affect the behavior of the ball 3 and prevents the generation of noise and vibration to ensure the desired life of the ball screw. Can do.

  FIG. 4 is an enlarged cross-sectional view of a main part showing a second embodiment of the ball screw with a position holding mechanism according to the present invention. In this embodiment, only the configuration and arrangement of the position holding mechanism are different from those of the above-described embodiment. The same reference numerals are assigned to the same parts of the same parts, and the detailed description thereof is omitted.

  This ball screw with a position holding mechanism includes a screw shaft 1 having a helical thread groove 1a formed on the outer periphery, and a helical screw groove that is fitted on the screw shaft 1 and corresponds to the screw groove 1a on the inner periphery. The nut 14 in which 14a was formed, the many ball | bowl 3 accommodated between these screw grooves 1a and 14a, and the position holding mechanism 15 with which the nut 14 was mounted | worn are provided.

  An elliptical piece window 5 penetrating the inner and outer peripheral surfaces and notching a part of the screw groove 14a is formed in the barrel portion of the cylindrical nut 14, and an elliptical piece member 16 is formed in the piece window 5. Is fitted. A connecting groove 17 curved in an S shape is formed on the inner side of the piece member 16 by connecting adjacent ones of the screw grooves 14a, and a portion of the connecting groove 17 and the screw groove 14a that is substantially one round. And constitutes a rolling path of the ball 3. A large number of balls 3 interposed between the inner and outer screw grooves 1 a and 14 a in the rolling path roll along the screw grooves 1 a and 14 a, and are guided by the connecting groove 17 of the piece member 16 to be screw shaft 1. And then returns to the adjacent screw groove 1a and rolls along the screw grooves 1a and 14a again. Further, the depth of the connecting groove 17 is set to such a depth that the ball 3 can exceed the thread of the screw groove 1 a in the screw shaft 1 in the connecting groove 17.

  The position holding mechanism 15 includes a projecting member 18, a piezoelectric element 19 engaged with one end of the projecting member 18, and an elastic member 20 made of a disc spring or the like, and extends radially from the outer peripheral surface of the nut 14. It is embedded in the piece window 5 drilled. The projecting member 18 includes a flange portion 18a serving as a seating surface of the elastic member 20, and an opening / closing pin 18b extending in the longitudinal direction from the flange portion 18a, and is formed in a rod shape as a whole. The position holding mechanism 15 constitutes a plunger-type linear electromagnetic solenoid that applies a voltage to the piezoelectric element 19 to give a linear motion to the protruding member 10 by its extension force.

  The position holding mechanism 15 is mounted at a position corresponding to the piece member 16. An opening 17a is formed at the bottom of the connecting groove 17 of the piece member 16, and an opening / closing pin 18b is inserted into the opening 17a so as to be freely retractable. Further, the tip of the opening / closing pin 18b is formed in an arc surface or an inclined surface along the shape of the connection groove 17, and forms a part of the connection groove 17 in the most protruding state. That is, due to the radial movement of the opening / closing pin 18b, the opening 17a of the connecting groove 17 is closed, and a continuous S-shaped connecting groove 17 is formed.

  Here, when no voltage is applied to the piezoelectric element 19, the open / close pin 18 b of the protruding member 18 is sunk by the urging force of the elastic member 20 (upper part in the figure), and the opening 7 a of the connecting groove 17 in the piece member 16. Is opened, and the connecting groove 17 is partially opened. In this state, a part of the ball 3 enters the opening 17 a of the connecting groove 17, and the centers of the balls 3 and 3 are deviated from a predetermined rolling trajectory R along the connecting groove 17 to become a staggered state. Is blocked (indicated by a broken line in the figure). Therefore, the screw shaft 1 is restrained by the position holding mechanism 15 and cannot be displaced in the axial direction, and the rotation of the nut 14 is prevented and the position is held.

  On the other hand, when an applied voltage is applied to the piezoelectric element 19 in response to the displacement signal, the piezoelectric element 19 expands and the protruding member 18 protrudes against the urging force of the elastic member 20. That is, the open / close pin 18b moves radially inward (lower part in the figure) to close the opening 17a of the connecting groove 17. In this state, the ball 3 can smoothly roll in the connecting groove 17 of the piece member 16, and the screw shaft 1 can be freely displaced in the axial direction without being restrained by the position holding mechanism 15.

  Further, when the energization to the piezoelectric element 20 is interrupted, the force acting on the projecting member 15 is released, and the projecting member 18 is submerged by the urging force of the elastic member 20 (upper part in the figure). The opening 17a is opened and the ball 3 is locked.

  Also in this embodiment, an opening 17a is formed in a part of the coupling groove 17 of the piece member 16, and the opening / closing pin 18b protrudes and retracts in the opening 17a due to expansion / contraction of the piezoelectric element 20 as in the above-described embodiment. Thus, the rolling of the ball 3 is controlled and the axial position of the screw shaft 1 is selectively held, so that the rolling of the ball 3 can be prevented regardless of the projecting timing of the projecting member 18. And the reliability can be greatly improved. Further, since the position holding mechanism 15 is embedded in the piece window 5 in which the piece member 16 is mounted, it is not necessary to open a hole or the like on the screw groove 14a of the nut 14. Therefore, the number of processing steps can be reduced and the cost can be reduced, and the generation of noise and vibration can be prevented and the desired life of the ball screw can be ensured.

  The embodiment of the present invention has been described above, but the present invention is not limited to such an embodiment, and is merely an example, and various modifications can be made without departing from the scope of the present invention. Of course, the scope of the present invention is indicated by the description of the scope of claims, and further, the equivalent meanings described in the scope of claims and all modifications within the scope of the scope of the present invention are included. Including.

  The ball screw with a position holding mechanism according to the present invention is used in an electric actuator such as a variable valve device of an internal combustion engine, and is a position holding that controls the axial displacement of the screw shaft against a reaction force applied to the screw shaft. It can be applied to a ball screw provided with a mechanism.

(A) is a top view which shows 1st Embodiment of the ball screw with a position holding mechanism based on this invention. (B) is a side view of the same as above. It is explanatory drawing which shows operation | movement of the ball screw with a position holding mechanism which concerns on this invention, and has shown the state which can be freely displaced to an axial direction, without the screw axis | shaft in a ball screw being restrained by a position holding mechanism. It is explanatory drawing which shows operation | movement of the ball screw with a position holding mechanism which concerns on this invention, and has shown the state by which the screw axis | shaft in a ball screw was restrained by the position holding mechanism, and the position was hold | maintained. It is a principal part expanded sectional view which shows 2nd Embodiment of the ball screw with a position holding mechanism which concerns on this invention. It is a fragmentary sectional view which shows the conventional variable valve apparatus of an internal combustion engine. It is principal part sectional drawing which shows the restraint mechanism provided in a variable valve apparatus same as the above.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Screw shaft 1a, 2a, 14a ... Screw groove 2, 14 ... Nut 3 ... Ball 4, 15 ... ... Position holding mechanism 5 ... Frame windows 6, 16 ... Frame members 7, 17 ... Connection grooves 7a, 17a ... ... Opening 8 ... Excitation coils 9, 20, ... Elastic members 10,18 ... Projecting members 10a ... Movable core 10b, 18a ... Flange 10c, 18b ... Opening / closing pin 11 ... Mounting hole 11a ... Bottom 12 ... ... Cover 13 ... Fixing screw 19 ... Piezoelectric element 50 ... Three-dimensional cam 51 ...・ Camshaft 52・ ・ Valve 53 ・ ・ ・ ・ ・ ・ Electric actuator 54 ・ ・ ・ ・ ・ ・ ・ ・ ・ Output shaft 55 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Bearing 56 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Frame 57・ ・ ・ ・ ・ ・ ・ ・ ・ Excitation coil 58 ・ ・ ・ ・ ・ ・ ・ ・ ・ Rotor 59 ・ ・ ・ ・ ・ ・ ・ ・ ・ Ball screw 60 ・ ・ ・ ・ ・ ・ ・ ・ ・ Restraining mechanism 61 ・ ・············ Screw shafts 61a, 62a ··· Screw grooves 62 ·············································· Stopper 65 ······· Stopper latching portion 66 ················································ 69 ... Projecting member 70 ... Hole R ... Rolling raceway

Claims (5)

A screw shaft having a helical thread groove formed on the outer peripheral surface;
A nut externally fitted to the screw shaft and having a spiral thread groove formed on the inner peripheral surface;
A plurality of balls housed in a rolling path formed by opposing screw grooves;
A piece member fitted with a piece window drilled in the trunk portion of the nut and formed with a connecting groove having the rolling path as a circulation path;
In the ball screw with a position holding mechanism that prevents the ball from rolling and holds the axial position of the screw shaft,
The position holding mechanism is embedded at a position corresponding to the piece member of the nut, an opening is formed in a part of the connecting groove of the piece member, and the position holding mechanism is configured in the opening , Opening and closing the opening of the connecting groove by projecting and projecting a protruding member that forms a part of the connecting groove in a state where the distal end is formed in an arc surface or an inclined surface along the shape of the connecting groove and protrudes most. The ball screw with a position holding mechanism is characterized in that the rolling of the ball is controlled and the axial position of the screw shaft is selectively held.   The position holding mechanism includes an annular excitation coil, a rod-shaped projecting member made of a magnetic material fitted in the excitation coil, and an elastic member that biases the projecting member in a predetermined direction. The ball screw with a position holding mechanism according to claim 1, wherein a predetermined applied voltage is applied to the coil to suck the protruding member against the elastic member and drive the protruding member in the longitudinal direction thereof.   The position holding mechanism includes a piezoelectric element, a rod-like protruding member that engages with the piezoelectric element, and an elastic member that biases the protruding member in a predetermined direction, and applies a predetermined applied voltage to the piezoelectric element. The ball screw with a position holding mechanism according to claim 1, wherein the protruding member is driven in the longitudinal direction against the elastic member.   The position holding mechanism is embedded in a mounting hole drilled along an axial direction from one end surface of the nut, and the projecting member is disposed in an opening formed in a side surface of the connecting groove. A ball screw with a position holding mechanism according to any one of claims 1 to 3. The position holding mechanism is embedded in the piece window drilled along the radial direction from the outer peripheral surface of the nut, and the protruding member is disposed in an opening formed in the bottom of the connecting groove. A ball screw with a position holding mechanism according to any one of 1 to 3.

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