JP4799127B2 - Positioning device - Google Patents

Description

The present invention includes a screw transmission mechanism including a screw shaft, a nut member , and a ball disposed between the screw shaft and the nut member , and a speed reduction mechanism disposed coaxially with the screw shaft. The present invention relates to a positioning device configured to convert a rotational motion transmitted from the motor into a linear motion by a screw transmission mechanism.

In general, this type of positioning device is used as a precision positioning device such as a table for a machine tool or a steering device for an automobile. For example, as shown in Patent Document 1, a rear wheel steering device is used for the purpose of improving the turning ability at the time of low-speed driving of an automobile and the stability of driving at the time of high-speed driving. The device is used. This positioning device includes an electric motor as a power source, a speed reduction mechanism that decelerates the output of the electric motor, and a screw transmission mechanism that converts rotational motion as output of the speed reduction mechanism into linear motion. The output is transmitted as a linear displacement amount by the screw shaft of the screw transmission mechanism through each of these mechanisms, and the wheels linked to both ends of the screw shaft are precisely positioned and controlled at a predetermined steering angle. .
JP 7-215226 A

  In the positioning device described in Patent Document 1, the electric motor, the speed reduction mechanism, and the screw transmission mechanism are arranged coaxially with the screw shaft as the positioning output shaft. Since each element is provided side by side in the axial direction, the length is increased in the axial direction, and there is a problem in mountability in a limited space.

  Furthermore, since the positioning device described in Patent Document 1 uses a planetary gear as a speed reduction mechanism and uses two sets of planetary gears to obtain a predetermined speed reduction ratio, the axial length does not have to be even longer. It was something that I did not get. Therefore, in order to shorten the length in the axial direction, it is possible to shorten the amount by reducing the planetary gears as a reduction mechanism to one set. However, both the required reduction ratio and the reduction in the radial direction are compatible. It becomes difficult.

  In other words, in the planetary gear system, the reduction ratio is basically governed by the ratio of the number of teeth between the sun gear and the ring gear, that is, the ratio of the pitch circle. In order to obtain a high reduction ratio, the sun gear diameter must be reduced and the ring gear diameter increased. There is. When the diameter of the sun gear is reduced, it is necessary to reduce the diameter of the screw shaft as the output shaft located on the inner periphery of the sun gear, which causes a problem in strength. In order to increase the diameter of the screw shaft as the output shaft, it is necessary to increase the diameter of the sun gear, and accordingly, the diameter of the ring gear also increases, and the compactness that is the greatest advantage of the coaxial positioning device is lost. Therefore, it is very difficult to lay out in a limited space.

  Therefore, the positioning device described in Patent Document 1 cannot be downsized in both the radial direction and the axial direction while ensuring a predetermined high reduction ratio.

  The present invention has been made paying attention to such a point, and an object thereof is to provide a positioning device capable of miniaturization in both the radial direction and the axial direction while ensuring a high reduction ratio.

According to a first aspect of the present invention for solving the above problems, a ball screw transmission mechanism comprising a screw shaft, a nut member , and a ball disposed between the screw shaft and the nut member , and the screw shaft. A positioning mechanism configured to decelerate the output of the power source with the reduction mechanism and transmit it to the screw transmission mechanism to position the positioned member at a predetermined position.
The speed reduction mechanism includes a hollow input shaft driven by a power source, a hollow rotating body rotatably supported at an inclined portion formed on the input shaft, and an output shaft linked to the ball screw transmission mechanism. A second gear having n2 teeth meshing with the first gear having n1 teeth fixed to the case, and a fourth gear having n4 teeth formed on the output shaft. mate to form a third gear tooth number n3, the rotating body is configured as a swing-type speed reduction mechanism for changing the engagement position between the gears while swinging motion by the rotation of the input shaft, rotation of the speed reduction mechanism The bearing means for supporting the body is configured as a ball bearing or a roller bearing, and the ball or roller of the bearing has an outer periphery or rotation of the inclined portion of the input shaft on at least one of the inner periphery and the outer periphery thereof. Is positioned directly on the inner surface of the body, also characterized in that the nut member of the ball screw transmission mechanism is coaxially polymerized disposed radially inward of the input-shaft and the circumferential the inclined portion of the speed reduction mechanism And

According to the first aspect of the present invention, a so-called oscillating speed reducing mechanism is used as the speed reducing mechanism, and in order to effectively utilize the structural features of the oscillating speed reducing mechanism, the screw transmission mechanism is provided in the hollow portion of the hollow rotating body. Since the nut member and the input shaft of the speed reduction mechanism are coaxially arranged, it is possible to reduce the overall size while ensuring a high speed reduction ratio and a necessary shaft diameter. Also, since at least one of the inner race or outer race of the so-called bearing as the bearing member can be omitted, the size of the rotating body in the radial direction can be reduced correspondingly, contributing to the downsizing of the positioning device. . The omission of the inner race or the like also leads to expansion of the accommodation space inside the rotating body, and can be utilized as a dimension absorption allowance for the radial dimension expansion due to the overlapping arrangement of the input shaft and the nut member. Furthermore, since the overlapping length of the input shaft and the nut member can be sufficiently secured and the supporting rigidity can be increased, the bending rigidity of the entire apparatus can be improved.

According to a second aspect of the present invention , in the first aspect , the power source is a hollow electric motor and is provided in the axial direction coaxially with the speed reduction mechanism. According to this configuration, it is possible to reduce the size of the positioning device as one unit including the electric motor as the power source.

According to a third aspect of the present invention , in the first or second aspect, the bearing means for supporting the output shaft is configured as a ball bearing or a roller bearing, and the ball or roller is at least one of the inner periphery or the outer periphery thereof. It is characterized by being positioned directly on the outer periphery of the output shaft or the inner surface of the case.

  According to this configuration, since at least one of a so-called bearing inner race or outer race as a bearing member can be omitted in the same manner as described above, the outer diameter of the case can be reduced accordingly, and the positioning device Contributes to downsizing. In addition, the omission of the inner race or the like can increase the outer diameter of the output shaft, which is advantageous in the case of high output specifications. If both the inner race and the outer race are omitted, as a matter of course, the degree of freedom of design is increased as compared with only one, but only one is more advantageous in consideration of assembling properties.

  Since the positioning device of the present invention is configured as described above, it is possible to reduce the size of the positioning device while ensuring a high reduction ratio and high strength.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the positioning device according to the present invention, an electric motor 2, a speed reduction mechanism 3 and a screw transmission mechanism 4 are arranged coaxially with the axis of the case 1. The screw shaft 4a as a final output shaft of the positioning device is used as a steering shaft of a rear wheel steering device of an automobile, for example. The output of the electric motor 2 is decelerated by the speed reduction mechanism 3, and the rotational motion thereof is screw transmission. It is converted into a linear motion by the mechanism 4 and transmitted to the left and right rear wheels (not shown) linked to both ends of the screw shaft 4a as a rear wheel steering amount. In this case, by switching the driving direction of the electric motor 2, the screw shaft 4a as the steering shaft is displaced in both axial directions, and the wheel is steered at a predetermined angle in an arbitrary direction.

  The electric motor 2 is configured as a hollow motor, is disposed coaxially with the hollow drive shaft 5, and includes a stator 2 a fixed to the case 1 and a rotor 2 b fixed to the outer periphery of the drive shaft 5. . In this embodiment, a normal electric motor in which a winding is wound around an iron core as a core is used, but a so-called coreless motor in which the winding is hardened with resin or the like and the core is omitted can be used. By using the coreless motor, it is possible to compress the radial dimension of the positioning device.

  The electric motor 2 is configured to be rotationally controlled by a control device (not shown), and the rotor 2b rotates by a predetermined rotation angle in response to a control signal from the control device to drive the drive shaft 5. The drive shaft 5 is fitted on the outer periphery of a fixed cylinder 8 fixed to the case 1, and a bearing 7 is interposed between an encoder 6 as a rotation sensor provided at the shaft end and the electric motor 2. It is rotatably supported on the inner periphery of the case 1. A neutral spring 11 is interposed in the fixed cylinder 8 so as to be compressed between flange-shaped stoppers 9 and 10 provided on the outer periphery of the screw shaft 4a. When the control system of the electric motor 2 fails, the neutral spring 11 returns the screw shaft 4a to the neutral position with the spring force, and forcibly returns the rear wheel from the steering position to the intended position (straight forward position). It has become.

  Further, an electromagnetic brake 12 having a disk 12a fixed to the drive shaft 5 and a friction plate 12c that presses and separates the disk 12a by the action of the electromagnetic solenoid 12b is interposed between the encoder 6 and the electric motor 2. The positioning device is locked so that the external force from the member to be positioned is not transmitted to the positioning device.

  The speed reduction mechanism 3 includes a hollow input shaft 3a driven by an electric motor 2 serving as a power source, a hollow rotating body 3c rotatably supported on an inclined portion 3b formed on the input shaft 3a, A second gear A2 having a number of teeth n2 that meshes with a first gear A1 having a number of teeth n1 fixed to the case 1 at an axial end of the rotating body 3c. And the third gear A3 having the number of teeth n3 that meshes with the fourth gear A4 having the number of teeth n4 formed on the output shaft 3d, and the rotating body by the eccentric motion of the inclined portion 3b accompanying the rotation of the input shaft. 3c is configured as an oscillating speed reduction mechanism that changes the meshing position between the gears while oscillating.

  The input shaft 3a is configured as a part of the drive shaft 5 as a motor output shaft, and an inclined portion 3b is formed at one end thereof. The inclined portion 3b includes an inner peripheral surface that is coaxial with the shaft center X and an outer peripheral surface of the shaft center Y that is inclined at a predetermined angle with respect to the shaft center X, and screw transmission via needle bearings 3e and 3e on the inner peripheral surface. It is supported on the outer peripheral surface of the nut member 4b of the mechanism 4, and the rotating body 3c is rotatably supported on the outer peripheral surface via balls 3g as bearing means. That is, the three members of the rotating body 3c, the input shaft 3a, and the nut member 4b of the screw transmission mechanism 4 are superposed in the radial direction around the inclined portion 3b of the input shaft 3a.

  The rotating body 3c is formed in a thin hollow ring shape having a large internal space, and bevel gears as the second gear A2 and the third gear A3 are formed on the axial end surfaces thereof. The second gear A2 and the third gear A3 mesh with the first gear A1 as a fixed gear and the fourth gear A4 as an output gear that face each other in the axial direction. The first and fourth gears are similarly formed as bevel gears. The tooth shapes of the first to fourth gears are formed in a concave shape with a predetermined arc, and a roller 3q as a needle roller is interposed in one concave portion of each meshing portion, and meshing transmission is performed via this roller 3q. Will come to be. That is, the first and fourth gears are configured as convex teeth by the concave portions and the rollers 3q located in the concave portions, and the second and third gears are configured as concave teeth that mesh with the convex teeth.

  The oscillating speed reduction mechanism configured as described above operates according to the following principle. That is, the rotating body 3c performs a swinging motion with respect to the rotation of the inclined portion 3b, and the second gear A2 and the third gear A3 formed on the end surfaces thereof are moved with respect to the shaft centers of the first gear A1 and the fourth gear A4. Thus, the first and second gears and the third and fourth gears are displaced in the circumferential direction.

  At this time, the circumferential relative displacement between the first gear A1 and the second gear A2 is only a value corresponding to the number of teeth difference between the first gear A1 and the second gear A2, that is, if the number of teeth difference is 1. The rotational movement of the rotating body 3c is shifted by one tooth, and when the difference in the number of teeth is 2, two teeth are shifted. The same movement is performed between the third gear A3 and the fourth gear A4.

  Therefore, when configured as a speed reduction mechanism, assuming that the speed reduction ratio is R (the number of rotations of the output shaft 3d when the input shaft 3a makes one revolution), R = 1− (n1 × n3) / (n2 × n4) Represented as:

  Here, n1: number of teeth of the first gear A1, n2: number of teeth of the second gear A2, n3: number of teeth of the third gear A3, n4: number of teeth of the fourth gear A4, n1 = 99, n2 = When 100, n3 = 101, and n4 = 100, the reduction ratio is R = 1 / 10,000 (forward rotation).

  That is, since the number of teeth of the first gear A1 is 99 and the number of teeth of the second gear A2 is 100, when the input shaft 3a rotates forward once, the second gear A2 is 1/100 of the first gear A1. Only forward rotation. The movement of the second gear A2 is directly transmitted to the third gear A3, and the same meshing is performed between the third gear A3 and the fourth gear A4. In this case, if the number of teeth of the third gear A3 is 101 and the number of teeth of the fourth gear A4 is 100, the fourth gear A4 rotates reversely by 1/100 with respect to the third gear A3. Accordingly, one-stage deceleration is also performed between the third gear A3 and the fourth gear A4. That is, when the rotational movement of the input shaft 3a is transmitted to the output side, two-stage deceleration is performed between the first and second gears A1 and A2 and between the third and fourth gears A3 and A4. Will be done.

  Further, when the second gear A2 and the third gear A3 are engaged with the first gear A1 and the fourth gear A4, respectively, while the second gear A2 and the third gear A3 are oscillating, they slide on the meshing surfaces as long as they are meshed between the fixed teeth. Is produced. In order to prevent seizure due to noise, vibration and heat generated by this sliding, the roller 3q is interposed in the meshing portion of each gear as described above.

Therefore, as shown in FIG. 2, when the rotating body 3a swings in the circumferential direction, the meshing position of the first gear A1 and the second gear A2 (meshing position of the third gear A3 and the fourth gear A4) is It moves in the circumferential direction and meshes the concave teeth with the convex teeth. And the slide which arises between each concave tooth and convex tooth is absorbed by rotation of roller 3q. Therefore, not only the setting of the backlash is unnecessary, but also a precise engagement can be performed by applying a preload between the gears. (More details of this kind of reduction gear are described in Japanese Patent Publication No. 7-56324 according to the invention of the present inventor)
The output shaft 3d provided with the fourth gear is rotatably supported on the inner surface of the case 1 via a ball 3h as a bearing member, and is bolted to the nut member 4b of the screw transmission mechanism 4 at one end. It is fixed integrally. Therefore, the rotational output of the speed reduction mechanism 3 is transmitted to the screw transmission mechanism 4 as the final output member of the positioning device, and is transmitted as a linear displacement to the screw shaft 4a. Incidentally, the screw transmission mechanism 4 is configured as a ball screw transmission mechanism ball 4 d is interposed between the screw shaft 4a and the nut member 4b.

  The nut member 4b includes a flange portion 4c fixed by a bolt at the rear end of the output shaft 3d of the speed reduction mechanism 3 and a cylindrical portion 4e in which a storage portion for storing the ball 4d is formed. However, it extends inward in the axial direction so as to overlap with the input shaft and the rotating body on the inner periphery of the input shaft as described above. The cylindrical portion 4e includes a threaded portion and a threaded portion that cooperate with the screw shaft 4a via a ball 4d, and an inner end thereof extends to the inner peripheral portion of the electric motor.

  The components of the speed reduction mechanism 3 configured as described above are rotatably supported by balls 3f, 3g, and 3h as bearing members. The balls 3f, 3g, and 3h are supported by the speed reduction mechanism 3. Positioning is performed by annular positioning grooves 3i, 3j, 3k, 3l, 3m, and 3n formed directly in the component, and the component member and the ball in which the positioning groove is formed constitute a so-called ball bearing. The components on the outer periphery also serve as the outer race of the bearing, and the components on the inner periphery also serve as the inner race of the bearing.

  That is, the ball 3f as a bearing member for supporting the input shaft 3a is positioned by the positioning groove 3j formed on the outer periphery of the input shaft 3a on the inner periphery thereof, and forms a part of the case 1 on the outer periphery thereof. Positioning is performed by positioning grooves 3i formed on the inner periphery of the boss portion of one gear A1. The positioning groove 3j on the input shaft side is formed over a part of the outer periphery of the lock nut 3o. The ball 3g that supports the rotating body 3c is positioned by the positioning groove 3l formed on the outer periphery of the input shaft 3a on the inner periphery thereof, and the positioning groove 3k formed on the inner periphery of the rotating body 3c on the outer periphery thereof. It is positioned by. In this case, the annular positioning grooves 3l and 3k are formed in a direction perpendicular to the axis Y of the inclined portion. Similar to the positioning groove 3j of the ball 3f, the positioning groove 3l on the input shaft side is formed over a part of the outer periphery of the lock nut 3p. Further, the ball 3h for supporting the output shaft 3d is positioned by the positioning groove 3n formed on the inner periphery of the output shaft 3d and the outer periphery of the flange portion 4c of the nut member 4b, and the inner periphery of the case 1 on the outer periphery. Positioning is performed by positioning grooves 3m formed on the circumference.

  Therefore, the omission by sharing the basic components of the inner race and the outer race contributes to the improvement of the degree of freedom of design, such as downsizing and increasing the strength. That is, the thickness of the inner and outer races directly contributes to the downsizing, and the increase in the diameter of the balls 3f, 3g, 3h as the bearings or the input shaft 3a, the output shaft 3d, and the screw transmission mechanism as to the strength increase. The diameter of each component shaft such as the nut member 4b and the screw shaft 4a can be increased. A plurality of the balls 4f, 4g, 4h are integrally linked by a retainer.

  Since the positioning device according to the above embodiment is configured as described above, it has the following characteristics.

  The oscillating speed reduction mechanism 3 not only provides a high reduction ratio as described above, but also allows each gear to mesh with each other in the axial direction at the radially outer end of the meshing position of the first to fourth gears. Therefore, a sufficient hollow space can be secured inward in the radial direction, which means that the degree of freedom in designing the basic component as the positioning device is expanded. Therefore, the screw transmission mechanism 4 as the output member of the positioning device can be arranged in a coaxial manner with the input shaft 3a of the speed reduction mechanism 3 while maintaining the required diameter, and the entire device can be downsized.

  Furthermore, the reduction ratio of the oscillating speed reduction mechanism is governed by the difference in the number of teeth between the first and second gears and the difference in the number of teeth between the third and fourth gears. This also contributes greatly to downsizing. That is, since the maximum reduction ratio can be obtained with the difference between the pitch circles of the respective gears being minimized, not only the internal space of the gear component can be secured, but also the outer diameter can be compressed.

  Further, since the nut member 4b of the transmission mechanism 4 is disposed inside the input shaft 3a so as to pass through the rotating body 3c of the speed reduction mechanism 3 toward the inside in the axial direction of the apparatus, the rotation of the output shaft 3d Is transmitted to the nut member 4b in the radial direction of the speed reduction mechanism, and not only the power transmission path becomes very compact, but also the extension portion can be extended to the vicinity of the electric motor. The support rigidity of the nut member 4b and the support rigidity of the output shaft of the speed reduction mechanism can be sufficiently ensured.

  Further, the inner and outer circumferences of the balls 3f, 3g, and 3h as bearing members are directly positioned by the constituent elements of the speed reduction mechanism 3, and the inner and outer races are omitted. The number of parts can be reduced. And the degree of freedom of dimension setting of each part of the speed reduction mechanism increases as much as the inner and outer races as a single unit are eliminated. In particular, the increase in the degree of freedom in setting the dimensions of the inner periphery of the rotating body contributes to the increase in the degree of freedom in the superposition of the screw transmission mechanism 4.

  As described above, since the positioning device according to the present invention can reduce the size of the positioning device while ensuring a high reduction ratio and high strength, it can be applied to the positioning device of the rear wheel steering device of an automobile as follows. It has the following features.

  First, because the swing reduction mechanism can set a high reduction ratio and increase the control resolution as an actuator, it is possible to position and control a very small steering angle with high accuracy, especially during high-speed running. Travel stability is greatly improved. In addition, when the minute steering angle fluctuates due to external force from the wheel, running stability is impaired. However, for external force from the wheel, the positioning device is locked by the operation of the electromagnetic brake, and the transmission efficiency from the wheel is reduced. Becomes zero, and the rear wheels are accurately maintained at a predetermined minute steering angle. In this embodiment, a ball screw type transmission mechanism is used as the screw transmission mechanism, but it is also possible to use a screw transmission mechanism that does not use a ball. In this case, the transmission efficiency from the wheels can be set to zero without using the electromagnetic brake.

  In addition, because the high-strength design of each part of the positioning device is possible, sufficient rigidity and strength can be ensured against the action of excessive external force from the wheels, and the rear wheel steering mechanism as an important safety part for automobiles can be secured. Reliability can be improved. In addition, since it is possible to reduce the size in both the radial direction and the axial direction, the mountability of the limited space below the vehicle body is excellent.

  The present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the gist of the present invention.

  In each of the embodiments described above, the deceleration operation by the deceleration mechanism has been described with respect to the example of the two-stage deceleration. However, the first, the fourth, It can also be limited to a one-stage deceleration action between two gears, and can be arbitrarily set as required.

  In the above-described embodiment, the rotating body of the speed reduction mechanism is supported by a single bearing member, but a plurality of them can be provided in the axial direction. Further, the bearing as the bearing member is not limited to the ball bearing but may be a roller bearing.

Sectional drawing of the positioning device concerning this invention. Explanatory drawing of a deceleration mechanism meshing part.

DESCRIPTION OF SYMBOLS 1 Case 2 Electric motor 3 Deceleration mechanism 3a Input shaft 3b Inclined part 3c Rotating body 3d Output shaft 4 Screw transmission mechanism 4a Screw shaft 4b Nut member

Claims (3)

A ball screw transmission mechanism including a screw shaft, a nut member , and a ball disposed between the screw shaft and the nut member; and a speed reduction mechanism disposed coaxially with the screw shaft; In a positioning device configured to decelerate by a deceleration mechanism and transmit it to a ball screw transmission mechanism and position a member to be positioned at a predetermined position,
The speed reduction mechanism includes a hollow input shaft driven by a power source, a hollow rotating body rotatably supported at an inclined portion formed on the input shaft, and an output shaft linked to the ball screw transmission mechanism. A second gear having n2 teeth meshing with the first gear having n1 teeth fixed to the case, and a fourth gear having n4 teeth formed on the output shaft. Forming a third gear having n3 meshing teeth, and configured as an oscillating speed reduction mechanism that changes the meshing position between the gears while the rotating body oscillates by the rotation of the input shaft,
The bearing means for supporting the rotating body of the speed reduction mechanism is configured as a ball bearing or a roller bearing, and the ball or roller of the bearing has an outer periphery of the inclined portion of the input shaft or a rotating body on at least one of an inner periphery and an outer periphery thereof. Positioned directly on the inner surface,
The positioning apparatus nut member of the ball screw transmission mechanism, characterized in that it is coaxially polymerized disposed radially inward of the input-shaft and the circumferential the inclined portion of the decelerating mechanism. The positioning apparatus according to claim 1 , wherein the power source is a hollow electric motor and is provided in the axial direction coaxially with the speed reduction mechanism. The bearing means for supporting the output shaft is configured as a ball bearing or a roller bearing, and the ball or roller of the bearing is positioned on the outer periphery of the output shaft or the inner surface of the case on at least one of the inner periphery and the outer periphery thereof. The positioning device according to claim 1, wherein:

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