JP2005207447A - Ball screw - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a ball screw that prevents occurrence of noise by reducing a relative clearance between a screw shaft and a nut by adding a simple mechanism to a general ball screw having a relative clearance. <P>SOLUTION: The ball screw 1 comprises the screw shaft 2, the nut 3, and a plurality of balls 4. The ball screw 1 has an elastic member 5. The nut 3 is moved in the initial restoration direction of the elastic member 5 by an elastic force of the elastic member 5, thereby reducing the relative clearance between the screw shaft 2 and the nut 3. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a ball screw, and more particularly to a ball screw used for an automobile such as a variable valve mechanism of an internal combustion engine or a general industrial machine.

2. Description of the Related Art Conventionally, a variable valve mechanism for an internal combustion engine that uses a ball screw as a drive mechanism for a control shaft that controls the variable action of a valve section is known. (For example, refer to Patent Document 1). The variable valve mechanism shown in Patent Document 1 converts the rotational motion of a drive motor into a linear motion by a ball screw to rotationally drive a control shaft, and the fulcrum of each link is acted upon by the action of a control cam fixed to the control shaft. And finally the camshaft timing is adjusted. Thus, the use of the ball screw for rotationally driving the control shaft is optimal as a means for using the energy of the drive motor without waste.
Japanese Patent Laid-Open No. 2002-256832 (5th page, FIG. 1)

  By the way, in the variable valve mechanism as disclosed in Patent Document 1, a high-frequency force generated by rotation of the camshaft that switches between the normal and reverse two directions is transmitted to the control shaft and further coupled to the control shaft. It is also transmitted to the ball screw. This force transmitted to the ball screw is transmitted to the inside of the ball screw and acts as a vibration load on the internal gap of the ball screw. For this reason, inside the ball screw, there has been a problem that the screw shaft, the nut and the ball constituting the ball screw constantly collide to generate noise and noise.

  The noise and noise caused by the internal clearance of such a ball screw can be achieved by finishing the ball rolling surfaces of the screw shaft and nut with high precision by grinding, etc., and inserting a ball according to these ball rolling surfaces. This can be prevented by setting the value to zero or minus. However, in general, in ball screws that are produced in large quantities at a low cost such as those for automobiles, the relative clearance between the screw shaft, nut, and balls must be relatively large, so that low cost and mass productivity can be achieved. It was difficult to prevent noise and noise while maintaining.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to substantially eliminate the internal gap by adding a simple mechanism to a general ball screw having an internal gap, thereby reducing noise. An object of the present invention is to provide a low-cost ball screw capable of preventing the occurrence.

The above object of the present invention can be achieved by the following constitution.
(1) A ball screw including a screw shaft, a nut screwed to the screw shaft, and a plurality of balls disposed between the screw shaft and the nut,
An elastic member that urges the nut in a predetermined direction; and the elastic force of the elastic member moves the nut in an initial restoring direction of the elastic member to reduce a relative clearance between the screw shaft and the nut. Ball screw characterized by
(2) The screw shaft is supported by the housing via a bearing,
The ball screw according to (1), wherein the elastic member is mounted between the nut and the housing.
(3) The screw shaft is supported by the housing via a bearing,
The ball screw according to (1), wherein the elastic member is mounted between the nut and an inner ring of the bearing or a spacer attached to an end surface of the inner ring.
(4) The ball screw according to any one of (1) to (3), wherein the elastic member is separable from the nut according to a position of the nut.
(5) The end of the nut is provided with a holder having a protrusion formed on the inner peripheral surface thereof to be screwed into the thread groove of the screw shaft.
The ball screw according to (1), wherein the elastic member is mounted between the nut and the holder.
(6) The elastic member is a torsion coil spring having a body portion penetrated by a coupling pin that connects the driven member that slides in the axial direction together with the nut and the nut,
One end of the torsion coil spring is locked to the outer peripheral surface of the nut, and the other end is locked to the driven member. The elastic force of the torsion coil spring is applied to the nut from the radial direction. The ball screw according to (1), wherein a relative gap between the screw shaft and the nut is reduced.
(7) The elastic member is a torsion coil spring having a body portion penetrated by a coupling pin that connects the driven member that slides in the axial direction together with the nut and the nut,
One end of the torsion coil spring is locked to the side end surface of the nut, and the other end is locked to the driven member. The elastic force of the torsion coil spring is applied to the nut from the axial direction. The ball screw according to (1), wherein a relative gap between the screw shaft and the nut is reduced.

  According to the ball screw of the present invention, the ball screw includes a screw shaft, a nut, and a plurality of balls, and includes an elastic member that urges the nut in a predetermined direction, and the nut is elasticized by the elastic force of the elastic member. The relative clearance between the screw shaft and the nut is reduced by moving the member in the initial restoring direction. Thereby, even when a vibration load is applied from the outside, it is possible to prevent the generation of noise and abnormal noise, and it is possible to obtain a ball screw that is low in cost and rich in mass productivity.

  Hereinafter, each embodiment of a ball screw concerning the present invention is described in detail with reference to drawings.

(First embodiment)
First, a first embodiment of a ball screw according to the present invention will be described with reference to FIG.

  As shown in FIG. 1, the ball screw 1 of this embodiment includes a screw shaft 2, a nut 3, a plurality of balls 4, and a coil spring 5 that is an elastic member of the present invention. The screw shaft 2 has a spiral thread groove 2b formed on the outer peripheral surface of the axial center portion 2a over the entire length. Both ends 2 c and 2 d of the screw shaft 2 are formed to have a diameter smaller than that of the central portion 2 a and are fitted to an inner ring 8 of a rolling bearing 7 disposed in the housing 6. As a result, the screw shaft 2 is rotatably supported by the housing 6 via the rolling bearing 7. One end 2c of the screw shaft 2 is connected to a rotating shaft 10 of a motor 9 which is a driving portion by a coupling 11, and the screw shaft 2 is rotationally driven by the rotation of the motor 9.

  A spiral thread groove 3 a having the same direction and the same pitch as the thread groove 2 b of the screw shaft 2 is formed on the inner peripheral surface of the nut 3. Then, a plurality of balls 4 are rotatably disposed between the screw groove 2 b of the screw shaft 2 and the screw groove 3 a of the nut 3, and the nut 3 is interposed between the screw shaft 2 via the plurality of balls 4. Are screwed together.

  A ball circulation member 12 is provided on the outer periphery of the nut 3 to repeatedly circulate the ball 4 that has passed between the screw grooves 2b and 3a. Further, a connecting member 14 that is a driven member is connected to the nut 3 by a connecting pin 13, and the connecting member 14 performs a linear motion in conjunction with the nut 3.

  The coil spring 5 is disposed between the nut 3 and the housing 6 in a compressed state. One end 5a abuts on a side end surface (right end surface in FIG. 1) 3b of the nut 3 and the other end 5b. Is fitted and fixed to the outer peripheral surface of the cylindrical portion 6a extending from the housing 6 in the nut 3 direction. The nut 3 is biased in the initial restoring direction (left direction in FIG. 1) of the coil spring 5 by the elastic force of the coil spring 5, and moves to the left by an internal gap in the axial direction with respect to the screw shaft 2. Thereby, the relative clearance between the screw shaft 2 and the nut 3 is reduced, and the internal clearance of the ball screw is substantially eliminated.

  The free length of the coil spring 5 fixed to the housing 6 is such that the elastic force acts on the nut 3 at the position of the nut 3 where noise is generated, and the coil spring 5 is separated from the nut 3 at the position of the nut 3 where noise is not generated. Therefore, the elastic force is not applied. Further, at the position of the nut 3 where noise is generated, the elastic force of the coil spring 5 is more than the vibration component transmitted to the nut 3 from the mechanism connected via the connecting member 14, for example, the control shaft of the internal combustion engine. It is set large and smaller than the normal operating force of the ball screw 1. By setting the elastic force in this way, the ball screw 1 is stably operated while the internal clearance of the ball screw 1 is substantially maintained.

  In the ball screw 1 configured as described above, when the screw shaft 2 is rotated by the rotational movement of the motor 9, the ball 4 rolls between the screw groove 2 b of the screw shaft 2 and the screw groove 3 a of the nut 3. 3 is slid in the axial direction, and at the same time, the connecting member 14 connected to the nut 3 is slid in the axial direction. Accordingly, the rotational motion of the motor 9 is converted into a linear motion via the ball screw 1.

  Here, even when the vibration load transmitted from the connecting member 14 is transmitted to the nut 3, the nut 3 reduces the relative clearance with the screw shaft 2 by the coil spring 5, that is, the internal clearance of the ball screw 1. The nut 3 will not vibrate because it is urged to make substantially zero. Therefore, no noise or abnormal noise is generated due to interference between the screw shaft 2, the nut 3, and the ball 4, and the ball screw 1 can be operated quietly and stably.

  Therefore, according to the ball screw 1 of the present embodiment, the ball screw 1 includes the screw shaft 2, the nut 3, and the plurality of balls 4, and the coil spring 5 that urges the nut 3 in a predetermined direction. Since the nut 3 is moved in the initial restoring direction of the coil spring 5 by the elastic force of the coil spring 5 to reduce the relative clearance between the screw shaft 2 and the nut 3, a vibration load is applied from the connecting member side. Even in this case, it is possible to prevent the generation of noise and abnormal noise, and to obtain a highly accurate linear motion. In addition, the above effect is achieved by adding a coil spring 5 between the nut 3 and the housing 6 to a general ball screw, so that a low-cost and highly productive ball screw can be obtained. it can.

  Further, the coil spring 5 fixed to the cylindrical portion 6a of the housing 6 is set to such a length as to be separated from the nut 3 at a nut position where noise is not generated. Noise can be efficiently prevented by applying a predetermined elastic force of the coil spring 5 only at the position 3 and not applying an elastic force at the position of the nut 3 where no noise is generated.

(Second Embodiment)
Next, a second embodiment of the ball screw according to the present invention will be described with reference to FIG. In addition, about the equivalent part to the ball screw 1 of 1st Embodiment, the same code | symbol is attached | subjected and description is abbreviate | omitted or simplified.

  As shown in FIG. 2, in the ball screw 20 of the second embodiment, a cylindrical spacer 21 is disposed on the side surface of the inner ring 8 of the rolling bearing 7 that faces the nut 3. The coil spring 5 is compressed between the nut 3 and the spacer 21 in a compressed state with one end 5a abutting on the side end surface 3a of the nut 3 and the other end 5b fitted to the outer peripheral surface of the spacer 21. It is arranged. Further, the spacer 21 has an inner peripheral surface provided close to and opposed to the outer peripheral surface of the screw shaft 2, and the diameter of the coil spring 5 fitted to the outer peripheral surface is a small diameter.

  The ball screw 20 configured in this manner causes the elastic force of the coil spring 5 to act on the nut 3 while rotating the coil spring 5 together with the spacer 21, and causes the nut 3 to move relative to the screw shaft 2 by the axial internal clearance. It moves to the left in the figure, and the relative clearance between the screw shaft 2 and the nut 3 is reduced. As a result, even when a vibration load is applied from the connecting member 14 side, the nut 3 does not vibrate, and noise and noise due to interference between the screw shaft 2, the nut 3, and the ball 4 are prevented.

  In the embodiment shown in FIG. 2, the coil spring 5 is described as being fitted to the spacer 21, but the other end 5 b of the coil spring 5 is directly applied to the side surface of the inner ring 8 without using the spacer 21. The mechanism may be further simplified by making contact.

  Therefore, according to the ball screw 20 of the present embodiment, similarly to the first embodiment, the nut 3 is moved in the initial restoring direction of the coil spring 5 by the elastic force of the coil spring 5, and the screw shaft 2 and the nut 3 are moved. Since the relative gap is reduced, even when a vibration load is applied from the connecting member side, generation of noise and noise can be prevented, and highly accurate linear motion can be obtained. The above effect is achieved by adding a coil spring 5 between the nut 3 and the inner ring 8 of the rolling bearing 7 or the spacer 21 attached to the end face of the inner ring 8 to a general ball screw. Therefore, it is possible to obtain a ball screw which is low in cost and rich in mass productivity.

  Further, since the coil spring 5 is mounted between the nut 3 and the inner ring 8 of the rolling bearing 7 or the spacer 21 attached to the end face of the inner ring 8, the diameter of the coil spring 5 can be reduced. The ball screw 20 can be made compact.

(Third embodiment)
Next, a third embodiment of the ball screw according to the present invention will be described with reference to FIG. In addition, about the equivalent part to the ball screw 1 of 1st Embodiment, the same code | symbol is attached | subjected and description is abbreviate | omitted or simplified.

  As shown in FIG. 3, in the ball screw 30 of the third embodiment, the coil spring 5 is mounted between a side end surface 3 b of the nut 3 and a holder 31 provided on the side end surface 3 b of the nut 3. The holder 31 is a ring-shaped member having substantially the same outer dimensions as the nut 3, and a protrusion 31 a having the same shape as the thread groove 2 b of the screw shaft 2 is formed on the inner peripheral surface. Further, an inner diameter on one end side is enlarged on the inner peripheral surface of the holder 31, and a spring accommodating chamber 31 b for accommodating the coil spring 5 is formed. Furthermore, a locking hole 31c penetrating in the axial direction is formed on the outer side of the holder 31 in the radial direction. The holder 31 is disposed adjacent to the nut 3 such that the protrusion 31 a is screwed into the screw groove 2 b of the screw shaft 2 and the spring accommodating chamber 31 b is opposed to the side end surface 3 b of the nut 3.

  A pin hole 3 c is formed on the radially outer side of the nut 3 in parallel with the screw shaft 2, and a rotation stop pin 32 is inserted into the pin hole 3 c and the locking hole 31 c of the boulder 31. The rotation stop pin 32 prevents relative rotation between the nut 3 and the holder 31 and enables relative movement between the nut 3 and the holder 31 in the axial direction. The coil spring 5 is housed in the spring housing chamber 31b in a compressed state, and its one end 5a abuts against the side end surface 3b of the nut 3 to press the nut 3 leftward in FIG. As a result, the nut 3 moves to the left by the axial internal gap between the screw shaft 2 and the relative gap between the screw shaft 2 and the nut 3 is reduced.

  In the ball screw 30 configured as described above, when the nut 3 slides in the axial direction with respect to the rotation of the screw shaft 2, the holder 31 in which the protruding portion 31a is screwed into the screw groove 2b of the screw shaft 2 is also provided. Slide and move in the same direction as the nut 3 at the same speed. That is, the distance between the nut 3 and the holder 31 is always a constant distance regardless of the position of the nut 3. Therefore, the magnitude of the elastic force of the coil spring 4 acting on the nut 3 is always constant, and the state where there is no internal gap between the screw shaft 2 and the nut 3 can be stably maintained. Therefore, even when a vibration load is applied from the connecting member 14 side, the nut 3 does not vibrate, and noise and noise due to interference between the screw shaft 2, the nut 3, and the ball 4 are prevented. In addition, since a constant elastic force always acts on the nut 3, a stable operation can be obtained regardless of the position of the nut 3.

  Therefore, according to the ball screw 30 of the present embodiment, as in the first embodiment, the nut 3 is moved in the initial restoring direction of the coil spring 5 by the elastic force of the coil spring 5, and the screw shaft 2 and the nut 3 are moved. Since the relative gap is reduced, even when a vibration load is applied from the connecting member side, generation of noise and noise can be prevented, and highly accurate linear motion can be obtained. The above effect is achieved by adding a coil spring 5 mounted between an end surface 3b of the nut 3 and a holder 31 disposed on the end surface 3b of the nut 3 to a general ball screw. It is possible to obtain a ball screw with high mass productivity at low cost.

  In addition, since the coil spring 5 is mounted between the nut 3 and the holder 31 disposed on the end face of the nut 3, the relative position between the nut 3 and the holder 31 is kept constant. In this state, the screw shaft 2 can be slid. Thereby, regardless of the position of the nut 3, a constant elastic force can be applied to the nut 3, and a state in which there is substantially no internal gap can be stably obtained.

(Fourth embodiment)
Next, a fourth embodiment of the ball screw according to the present invention will be described with reference to FIGS. In addition, about the equivalent part to the ball screw 1 of 1st Embodiment, the same code | symbol is attached | subjected and description is abbreviate | omitted or simplified.

  As shown in FIGS. 4 and 5, a torsion coil spring 41 that is an elastic member is used in the ball screw 40 of the fourth embodiment. The torsion coil spring 41 is formed such that one end 41b and the other end 41c protrude in a radial direction from a main body portion 41a in which a spring wire is wound in a coil shape, and the main body portion 41a connects the nut 3 and the connecting member 14 together. It is supported by being inserted through a coupling pin 13 that is connected so as to be relatively swingable. One end 41b of the torsion coil spring 41 is bent at a substantially right angle and locked to the outer peripheral surface of the nut 3, and the other end 41c is bent at a substantially right angle so that the torsion coil spring 41 is twisted and engaged with the connecting member 14. It has been stopped. Thereby, the elastic force (torsion restoring force) of the torsion coil spring 41 acts on the outer peripheral surface of the nut 3 from the radial direction.

  In the ball screw 40 configured in this way, the elastic force of the torsion coil spring 41 acting on the nut 3 acts from the radial direction of the nut 3, so that the nut 3 rotates around the coupling pin 13. It is assumed that there is substantially no radial internal gap between the screw shaft 2 and the nut 3. Therefore, even when a vibration load is applied from the connecting member 14 side, the nut 3 does not vibrate, and noise and noise due to interference between the screw shaft 2, the nut 3, and the ball 4 are prevented.

  According to the ball screw 40 of the present embodiment, the relative clearance between the screw shaft 2 and the nut 3 is reduced by moving the nut 3 in the initial restoring direction of the torsion coil spring 41 by the elastic force of the torsion coil spring 41. Therefore, even when a vibration load is applied from the connecting member side, generation of noise and abnormal noise can be prevented, and highly accurate linear motion can be obtained. Further, the above effect is achieved by adding a torsion coil spring 41 attached to the coupling pin 13 of the connecting member 14 to the general ball screw 1, thereby obtaining a low-cost and highly productive ball screw. be able to.

  In particular, the torsion coil spring 41 penetrates the body 41a through the coupling pin 13 that connects the nut 3 and the connecting member 14 so as to be relatively swingable, and one end 41b is locked to the outer peripheral surface of the nut 3. Since the other end 41c is engaged with the connecting member 14 and the elastic force of the torsion coil spring 41 is applied to the nut 3 from the radial direction, the relative clearance between the screw shaft 2 and the nut 3 can be reduced. . In addition, since the torsion coil spring 41 moves together with the nut 3, regardless of the position of the nut 3, a constant elastic force can be applied to the nut 3, and a state without an internal gap can be stably obtained.

(Fifth embodiment)
Next, a fifth embodiment of the ball screw according to the present invention will be described with reference to FIGS. In addition, about the equivalent part to the ball screw 40 of 4th Embodiment, the same code | symbol is attached | subjected and description is abbreviate | omitted or simplified.

  In the ball screw 50 of the present embodiment, the torsion coil spring 51, which is an elastic member, has a main body 51a in which a spring wire is wound in a coil shape a plurality of times, like the torsion coil spring 41 of the fourth embodiment. One end 51b and the other end 51c project in a radial direction from 51a. The torsion coil spring 51 is supported by inserting the main body 51a through the coupling pin 13. One end 51b is locked to the side end surface 3c on the motor side of the nut 3, and the other end 51c is twisted by the torsion coil spring 51. In this state, it is locked to the connecting member 14. Therefore, the elastic force (torsion restoring force) of the torsion coil spring 51 acts on the nut 3 from the axial direction.

  In the ball screw 50 configured as described above, the elastic force of the torsion coil spring 51 acting on the nut 3 acts from the axial direction of the nut 3, so that the nut 3 is shown in the drawing by an axial clearance relative to the screw shaft 2. Moving to the right, the relative gap between the screw shaft 2 and the nut 3 is reduced. Therefore, even when a vibration load is applied from the connecting member 14 side, the nut 3 does not vibrate, and noise and noise due to interference between the screw shaft 2, the nut 3, and the ball 4 are prevented.

  According to the ball screw 50 of the present embodiment, the relative clearance between the screw shaft 2 and the nut 3 is reduced by moving the nut 3 in the initial restoring direction of the torsion coil spring 51 by the elastic force of the torsion coil spring 51. Therefore, even when a vibration load is applied from the connecting member side, generation of noise and abnormal noise can be prevented, and highly accurate linear motion can be obtained. Further, the above effect is achieved by adding a torsion coil spring 51 attached to the coupling pin 13 of the connecting member 14 to the general ball screw 1 to obtain a low-cost and highly productive ball screw. be able to.

  In particular, the torsion coil spring 51 penetrates the main body 51a through the coupling pin 13 that couples the nut 3 and the coupling member 14 so as to be relatively swingable, and one end 41b is locked to the side end surface 3c of the nut 3. At the same time, the other end 51c is locked to the connecting member 14, and the elastic force of the torsion coil spring 51 is applied to the nut 3 from the axial direction, so that the relative clearance between the screw shaft 2 and the nut 3 can be reduced. it can. Further, since the torsion coil spring 51 moves together with the nut 3, a constant elastic force can be applied to the nut 3 regardless of the position of the nut 3, and a state without an internal gap can be stably obtained.

Note that the present invention is not limited to the above-described embodiments and examples, and modifications, improvements, and the like can be made as appropriate.
For example, although this embodiment demonstrated the mechanism in which a nut slides to an axial direction with respect to rotation of a screw shaft, even if it is a mechanism in which a screw shaft slides with respect to rotation of a nut, it can implement. There is an effect.
In the present embodiment, the elastic member is described as being disposed on the right side of the nut. However, the present invention is not limited to this, and the same effect can be obtained even when the elastic member is disposed on the left side of the nut.

It is a side view of the ball screw which is a 1st embodiment of the present invention. It is a side view of the ball screw which is 2nd Embodiment of this invention. It is a side view of the ball screw which is 3rd Embodiment of this invention. It is a side view of the ball screw which is 4th Embodiment of this invention. It is a VV arrow transverse cross section in FIG. It is a side view of the ball screw which is 5th Embodiment of this invention. It is a VII-VII arrow cross-sectional view in FIG.

Explanation of symbols

1, 20, 30, 40 Ball screw 2 Screw shaft 2b Thread groove 3 Nut 4 Ball 5 Coil spring (elastic member)
6 Housing 7 Rolling bearing (bearing)
8 Inner ring 9 Motor 13 Connecting pin 14 Connecting member 21 Spacer 31 Holder 31a Protruding portion 41 Torsion coil spring (elastic member)

Claims (7)

A ball screw comprising a screw shaft, a nut screwed to the screw shaft, and a plurality of balls disposed between the screw shaft and the nut,
An elastic member that urges the nut in a predetermined direction; and the elastic force of the elastic member moves the nut in an initial restoring direction of the elastic member to reduce a relative clearance between the screw shaft and the nut. Ball screw characterized by The screw shaft is supported by the housing via a bearing,
The ball screw according to claim 1, wherein the elastic member is mounted between the nut and the housing. The screw shaft is supported by the housing via a bearing,
The ball screw according to claim 1, wherein the elastic member is mounted between the nut and an inner ring of the bearing or a spacer attached to an end surface of the inner ring.   The ball screw according to claim 1, wherein the elastic member is separable from the nut according to a position of the nut. The end of the nut is provided with a holder having a protrusion formed on the inner peripheral surface thereof to be screwed with the thread groove of the screw shaft,
The ball screw according to claim 1, wherein the elastic member is mounted between the nut and the holder. The elastic member is a torsion coil spring having a body portion penetrated by a coupling pin that connects the nut and a driven member that slides in the axial direction together with the nut,
One end of the torsion coil spring is locked to the outer peripheral surface of the nut, and the other end is locked to the driven member. The elastic force of the torsion coil spring is applied to the nut from the radial direction. The ball screw according to claim 1, wherein a relative gap between the screw shaft and the nut is reduced. The elastic member is a torsion coil spring having a body portion penetrated by a coupling pin that connects the nut and a driven member that slides in the axial direction together with the nut,
One end of the torsion coil spring is locked to the side end surface of the nut, and the other end is locked to the driven member. The elastic force of the torsion coil spring is applied to the nut from the axial direction. The ball screw according to claim 1, wherein a relative gap between the screw shaft and the nut is reduced.

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