JPH10122323A - Load sensing type direct acting continuously variable transmission - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a load sensing type direct acting continuously variable transmission which can continuously vary deceleration ratio by sensing a load given in accordance with an operating environment corresponding to external force or the like also convert a rotary motion into a linear motion by high transmitting efficiency. SOLUTION: In a screw shaft 2 constituted by screwing helical screw parts 4, 3 having a prescribed pitch P and a nut 1, a diameter D0 of the screw part 3 in the nut 1 is formed a little larger than a diameter d of the screw part 4 of the screw shaft 2 screwed thereto, also the nut 1 is supported turnably relating to a support member 5, this support member 5 is energized by a prescribed spring load Fs in a diametric direction of the screw shaft 2, so as to bring the nut 1 into eccentric contact with the screw shaft 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a load-responsive linearly-operated continuously variable transmission that can be used in a wide variety of fields such as robots, transporting machines, and jacks.

[0002]

2. Description of the Related Art In all fields of the industrial world, as a conversion device for converting a rotary motion of an electric motor or the like into a linear motion,
Screws or ball screws are widely used. However, since those gear ratios were fixed, a large reduction gear ratio had to be selected so that operation was possible even under the condition of generating the maximum thrust in the use conditions. For this reason, there is a major problem that driving can be performed only at low speed even when the load is light. Therefore, a drive system having a load-responsive speed change function capable of changing the speed ratio according to the load has been required, but at present, there is virtually no drive system. For example, there has been a mechanism for switching a gear train from driving an electric motor to driving a ball screw.However, in order to switch a gear ratio according to a load, control is performed by detecting a load and performing a switching operation. Since a mechanism is required, the device becomes a large-scale device, and the speed cannot be continuously changed. Although a method using a load-sensitive torque converter such as that employed in vehicles and the like is also conceivable as this transmission mechanism, this method is also not a device that can be used in a wide range due to an increase in the size of the device.

Conventionally, as shown in FIG. 6, a bearing having a radius slightly larger than the pitch circle radius with respect to a screw shaft is rotatably supported with respect to a support member, and the bearing has a diameter of the screw shaft. Transmissions configured to contact eccentrically in the direction are already commercially available. In this device, the difference in radius from the center axis of each of the screw shaft and the bearing to the eccentric contact point generates a translational movement according to the rotation of the screw shaft, and the feature is a complicated structure like a ball screw. Instead of a screw shaft and a bearing, the structure is simple, light and inexpensive. In addition, since rolling motion can be converted to linear motion by rolling contact without friction, there is little friction loss and high conversion efficiency. There are advantages.

[0004]

However, in the example of FIG. 6 described above, the amount of eccentricity of the bearing with respect to the screw shaft is set to a predetermined constant value by means of an adjusting screw or the like, so that the gear shifting is performed. The ratio was constant.

Accordingly, the present invention solves the above-mentioned problems in the conventional transmission, and can change the speed reduction ratio steplessly in response to a load applied in accordance with an operating environment corresponding to an external force and the like. Provided is a load-responsive linearly-operated continuously variable transmission that can convert rotational motion into linear motion with high transmission efficiency.

[0006]

SUMMARY OF THE INVENTION Therefore, according to the present invention, in a screw shaft and a nut formed by screwing helical screw portions having a predetermined pitch, the diameter of the screw portion of the nut is screwed to the screw shaft. The nut is formed to be slightly larger than the diameter of the screw portion of the screw shaft, the nut is rotatably supported by a support member, and the support member is urged in a diameter direction of the screw shaft by a predetermined spring load. Are eccentrically contacted with the screw shaft. Further, the present invention provides a flank shape of the screw surface of the screw shaft or the nut that gives a relationship between the amount of eccentricity and the contact angle of the eccentric contact surface of the screw shaft and the nut, and the nut in a diametrical direction with respect to the screw shaft. By adjusting the mutual relationship between the displacement and the load characteristics of the spring biasing the nut, the amount of eccentricity of the nut with respect to the screw shaft becomes a desired ratio as the axial load applied to the screw shaft or the nut increases. And the reduction ratio increases at a desired ratio, and the amount of eccentricity of the nut with respect to the screw shaft at the desired ratio as the axial load acting on the screw shaft or the nut decreases. The present invention is characterized in that it has a characteristic of increasing and reducing a reduction ratio at a desired ratio, and these are used as means for solving the problem.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows the basic principle of one embodiment of a load-responsive linear motion continuously variable transmission according to the present invention.
FIG. 1A is a longitudinal sectional view of a linearly-operated continuously variable transmission when the linear speed of the nut increases at a low load load and a small reduction ratio, and FIG. FIG. 1C is a longitudinal sectional view of the dynamic continuously variable transmission. FIG. 1C shows a state in which the nut and the screw shaft mesh with each other from a low load (FIG. 1A) to a high load (FIG. 1B). It is the cross-sectional view shown in steps. FIG.
As shown in (A), the load-sensitive linearly-operated continuously variable transmission having a conversion device for converting a rotary motion into a linear motion according to the present invention has a screw portion 4 composed of a spiral trapezoidal screw having a predetermined pitch P or the like. Is screwed to the inner peripheral side of a nut 1 having a screw portion 3 similarly formed of a spiral trapezoidal screw having a predetermined pitch P.

The load-responsive linearly-operated continuously variable transmission according to the present invention comprises a screw for screwing the diameter D0 of the nut 1 to the screw shaft 2 in the structure comprising the nut 1 and the screw shaft 2. The nut 1 is formed to be slightly larger than the diameter d of the screw portion 4 of the shaft 2 (the pitch circle radius of the nut 1 is formed slightly larger than the pitch circle radius of the screw shaft 2), and the nut 1 is fixed to the support member 5 by a bearing 6 or the like. So that the nut 1 is eccentrically brought into contact with the screw shaft 2 by being urged by a spring 7 or the like by a predetermined spring load Fs in the diameter direction of the screw shaft 2. It is what was constituted. The principle of movement is that the rotating screw shaft 2
And the nut 1 which is screwed to the nuts. That is, screw shaft 2
If only the rotation is impossible and the shaft cannot be moved, the nut 1 goes straight in the axial direction by a pitch corresponding to the relative rotation difference.

With the above construction, the flank of the screw surface of the screw shaft 2 or the nut 1 which gives the relationship between the eccentric amount X and the contact angle of the eccentric contact surfaces of the screw shaft 2 and the screw portions 3 and 4 of the nut 1. By adjusting the shape and the correlation between the displacement and the characteristics of the load in the spring 7 that urges the screw shaft 2 in the diametric direction, the axial load applied to the screw shaft 2 or the nut 1 increases. Therefore, the nut 1 has such a characteristic that the eccentricity X of the nut 1 with respect to the screw shaft 2 decreases at a desired ratio and the reduction ratio increases at a desired ratio, and the axial load acting on the screw shaft 2 or the nut 1 As the load F1 decreases, the eccentric amount X of the nut 1 with respect to the screw shaft 2 increases at a desired rate and the reduction ratio decreases at a desired rate. , And the it can be used in a wide industry in general.

More specifically, the relationship between the diameter D0 of the screw portion 3 of the nut 1 and the diameter d of the screw portion 4 of the screw shaft 2 screwed to the nut 1 is that the diameter D0 of the nut 1 is screwed thereto. The screw shaft 2 is formed to have a diameter slightly larger than the diameter d of the screw portion 4, and when a high load F1 is applied to the screw shaft 2 downward in the drawing as shown in FIG. When the load F1 (dotted arrow) acts, the axis l of the screw shaft 2 is given a small amount of eccentricity X with respect to the axis L of the nut 1; The reduction ratio between the nut 1 and the screw shaft 2 is selected to be close to infinity by selecting the engagement diameter D (X) ≒ d. That is, the axial speed of the nut 1 with respect to the rotation of the screw shaft 2 is selected to be close to zero. However, when X = 0, only nut 1 idles,
Since thrust is not generated, use in which X = 0 is avoided, and operation is performed within a finite value range.

When a predetermined load Fx is applied in the axial direction of the screw shaft 2, a spring load F for urging the nut 1 is set.
This illustrates a state in which the axis L of the nut 1 is eccentric from the axis l of the screw shaft 2 by a predetermined eccentric amount X in the diametric direction against s. In this state, the spring load Fs applied to the nut 1 is balanced with the force in the nut diameter direction exerted on the nut 1 by the load load Fx by the cam action of the screw slope. The spring load Fs tends to increase in inverse proportion to the amount of eccentricity X (when the amount of eccentricity X is large, the pressing force is small because the spring 7 is extended, and when the amount of eccentricity X is small, the spring load Fs is small). 7 is compressed and exerts a large pressing force.) Therefore, when the axial load increases, the spring 7 is largely compressed so that the eccentric amount X decreases, and when the axial load decreases, the spring 7 is eccentric by the spring force. The quantity X increases. That is,
Considering the case where a predetermined load Fx acts on the screw shaft 2 downward in the drawing, the screw shaft 2 that gives the relationship between the eccentric amount X and the contact angle of the eccentric contact surface between the screw shaft 2 and the nut 1 is considered.
Alternatively, the correlation between the flank shape of the screw surface of the nut 1 and the displacement and load characteristics of the spring 7 that urges the screw shaft 2 in the diameter direction is automatically adjusted.
As the axial load acting on the screw shaft 2 or the nut 1 increases, the amount of eccentricity of the nut with respect to the screw shaft decreases at a desired ratio and the reduction ratio increases at a desired ratio. As the axial load acting on the screw shaft or the nut decreases, the characteristic that the amount of eccentricity of the nut with respect to the screw shaft increases at a desired ratio and the reduction ratio decreases at a desired ratio can be obtained. At this time, the contact point Q between the screw portion 4 of the screw shaft 2 and the screw portion 3 of the nut 1 forms a meshing portion between them, and the rotation diameter of the screw shaft 2 at that time is d, and the rotation of the nut 1 is The diameter is D (X) = D0-2 (aX) (a is the maximum amount of eccentricity when there is no load). Therefore, assuming that the angular velocity of the screw shaft 2 is ω, the angular velocity W of the nut 1 at that time is
Is given by W = (d / D) from πdω = πD (x) W derived from the fact that the circumferential distances passing through both contact points Q are equal.
(X)) ω = (d / (D0−2 (a−X)) ω.
The angular velocity reduction ratio R (x) is W / ω = d / D (x).

As described above, according to the present invention, by adding a simple structure of biasing by a spring load to the eccentric support portion between the nut 1 and the screw shaft 2, a load-sensitive stepless step which has not been provided in the past is provided. The shift had an extremely important effect. This is because the axial load of the screw shaft 2 (or relatively the nut 1), which is a load, is maintained in a state where the nut 1 is supported by the spring load so as to have a large eccentricity with respect to the screw shaft 2. When increasing, the flank shape of each of the screw portions 3 and 4 of the nut 1 and the screw shaft 2 is usually trapezoidal, so that the screw shaft 2 tends to move to the center of the nut 1. Thus, since the difference in radius from the respective axes l, L of the screw shaft 2 and the nut 1 to the eccentric contact point Q has generated an orthogonal movement in the axial direction, a large shift effect is obtained when the difference is reduced. The action of being generated and generating a strong thrust while slowing down is naturally generated. Ultimately, when the axes l and L of the screw shaft 2 and the nut 1 match, the screw shaft 2 and the nut 1
There is no difference in radius from the respective axes l and L to the eccentric contact point Q, and the nut 1 does not axially move even if the screw shaft 2 rotates. That is, the reduction ratio becomes infinite, and an infinite thrust can be generated. However, at this time, in the extreme state, when the screw shaft 2 rotates, the nut 1 freely rotates coaxially, so that the actual thrust drops to zero. Therefore, the thrust according to the applied load increases gradually as the eccentricity approaches zero from a large eccentricity state, reaches a maximum at a certain eccentricity, and shows a fluctuation such that the eccentricity is zero and the thrust becomes zero. it is conceivable that. Therefore, it is assumed that the actual operating range of the eccentric amount is changed so as to vary from a certain value to a value close to zero but to a finite small value. FIG. 3 shows the relationship between the amount of eccentricity X and the output shaft speed (the orthogonal speed of the nut 1).

With such a configuration, the load applied to the robot leg, the transport arm, or the like according to the operating environment corresponding to the external force or the like in the robot, the transport machine, and the jack is the configuration of the present invention. Acts as a load acting in the axial direction between the screw shaft 2 and the nut 1, and according to the load, the input rotation of the screw shaft 2 is changed from the maximum nut direct speed to the maximum load maximum reduction ratio at the no-load minimum reduction ratio. Thus, the speed can be changed in a stepless manner up to the time when the nut direct speed is minimum, and the speed can be output as the axial direct speed of the nut 1. Moreover,
According to the present invention, the component can also function as a conversion device for converting power from rotary motion to linear motion, and does not require an electric control device or the like unlike the conventional one, and is mechanically A simple structure can be achieved and the cost can be reduced. Further, according to the load-responsive linear motion continuously variable transmission of the present invention, the nut 1 moves quickly on the screw shaft 2 although the force is small at a low load, and the linear speed decreases at a high load. It is possible to move on the screw shaft 2 with a large thrust.

FIG. 2 shows a state in which the load-responsive linearly-operated continuously variable transmission according to the present invention is unitized and housed in a housing 5 which is a supporting member. The rotatable nut 1 and the screw shaft 2 formed by screwing together the threaded portions are formed into a cylindrical housing 5 as a support member by a pair of bearings 6 mounted on the outer periphery of the nut 1. Are fitted and supported on the inner periphery of the. As shown in FIG. 2B, the housing 5 is urged by a spring 7 with a predetermined spring load in a diametrical direction.
As shown in FIG. 2 (C), it is configured so as to be non-rotatable and slidably perpendicular to the rail-shaped regulation guide 8. In the embodiment shown in this figure, as shown in FIG. 2 (A), a triple configuration is used in which three components of a load-responsive linear motion continuously variable transmission including a nut 1 and a screw shaft 2 are connected. A more effective conversion function and a continuously variable transmission function are realized by reliable and smooth transmission of the driving force.

FIG. 4 shows the relationship between the amount of eccentricity and the output shaft speed when the flank of the screw thread has a convex shape as the flank cross-sectional shape of the nut 1. It is understood that the output shaft speed has a relatively gradually increasing characteristic. FIG. 5 shows the relationship between the amount of eccentricity and the output shaft speed when the flank of the screw thread has a slightly concave shape as the flank cross-sectional shape of the nut 1. It has a characteristic that increases rapidly. As described above, in the robot, the transporting machine, and the jack, etc. that employ the load-responsive linear motion continuously variable transmission of the present invention, the behavior characteristics of their legs and arms that should be adapted to the operating environment corresponding to the external force, etc. As shown, an appropriate flank shape is determined for the screw shaft and nut arrangement.

The embodiments of the present invention have been described above. However, within the scope of the present invention, the shapes of the screw shaft and the nut, their materials, the cross-sectional shape and the screwing form of the screw portion, and the support of the nut The supporting mode of the member, the biasing mode of the supporting member by a spring, and the like can be appropriately adopted. Further, in the above-described embodiment, the support member for supporting the nut is configured to be urged in the screw shaft diametric direction by a predetermined spring load. However, in some cases, the screw shaft itself is mounted on the nut side by a predetermined spring load. It is also possible to configure so as to be energized.

[0017]

As described above in detail, according to the present invention, a robot or a transport machine or a jack or the like acts on a leg or a transport arm of a robot according to an operating environment corresponding to an external force or the like. The load acts as a load acting in the axial direction between the screw shaft and the nut,
In accordance with the load, the input rotation of the screw shaft is steplessly shifted from the maximum speed of the nut at a non-load minimum reduction ratio to the minimum speed of the nut at a maximum load reduction ratio at a no-load minimum reduction ratio, and is set as a linear speed of the nut in the axial direction. Can be output. In addition, according to the present invention, the component can also function as a conversion device for converting power from rotary motion to linear motion, and a driving mechanism and an electrical control device for shifting as in the conventional device. Since it is not accompanied by a mechanical mechanism, the structure can be made extremely simple only by employing a mechanical mechanism, and the structure can be made robust, lightweight, compact, and low in cost. In addition, according to the load-responsive linearly-operated continuously variable transmission of the present invention, while having a simple mechanical structure, at low load, the force is small but the nut quickly moves on the screw shaft, The linear speed decreases when a load is applied, but the nut can move on the screw shaft with a large force, and the legs and arms of a robot or transport machine equipped with a load-sensitive linear motion continuously variable transmission respond to external forces, etc. This has a tremendous effect of exhibiting behavior characteristics that should be reasonably adapted to the operating environment that has been set.

The transmission efficiency of a transmission mechanism using friction at the contact surface of a normal screw shaft and nut structure is at most about 20 to 30%, whereas the load-sensitive type direct current of the present invention is attained. According to the continuously variable transmission, since it operates by the rolling contact without slipping on the eccentric contact surface between the screw shaft and the nut, there is almost no loss due to friction and a transmission efficiency of about 70 to 80% can be obtained. (As for the value of the transmission efficiency, since the eccentric contact point in the load-responsive linear motion continuously variable transmission according to the present invention is in contact with a finite surface, there is a relative speed difference between the surfaces. The effect is not described in detail. Can be calculated using a Hertzian stress equation or the like.) The transmission efficiency of the ball screw is 90%.
It is noteworthy that the above-mentioned transmission efficiency was achieved with a structure much simpler than that of the ball screw, though not so much as compared with the above. Furthermore, since a large gear ratio can be generated by a very small movement of the nut in the diameter direction of the screw shaft, a gear shift in response to the load is performed by a very small movement of the nut that can hardly be recognized by the naked eye. The response speed is remarkably high, and the wear of the mechanism is very small. Furthermore, although the screw shaft and the nut are in eccentric contact, the load is dispersed to these contact portions by the number of contact points as many as the screw portion ridges, so that a large load is supported. It is possible and robust.

[Brief description of the drawings]

FIG. 1 shows the basic principle of an embodiment of a load-responsive linear motion continuously variable transmission according to the present invention. FIG. 1 (A) shows a state in which a nut direct speed is increased at a low load small load reduction ratio. FIG. 1B is a longitudinal sectional view of the linearly-operated continuously variable transmission, and FIG. 1B is a longitudinally sectional view of the linearly-operated continuously variable transmission when the speed at which the nut goes straight at a low speed with a large load and large reduction ratio;
(C) is a cross-sectional view of the meshing state of the nut and the screw shaft from the time of low load to the time of high load.

FIG. 2 is an explanatory view of an assembled state of a unitized load-responsive linear motion continuously variable transmission according to the present invention.

FIG. 3 is a diagram showing the relationship between the amount of eccentricity and the output shaft speed in the load-responsive linear motion continuously variable transmission according to the present invention.

FIG. 4 is a diagram showing an example of the relationship between the amount of eccentricity and the output shaft speed in the load-responsive linear motion continuously variable transmission according to the present invention.

FIG. 5 is a diagram showing another example of the relationship between the amount of eccentricity and the output shaft speed in the load-responsive linear motion continuously variable transmission according to the present invention.

FIG. 6 is a longitudinal sectional view showing a main part of a conventional screw shaft and nut.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Nut 2 Screw shaft 3 Nut screw part 4 Screw shaft screw part 5 Housing (support member) 6 Bearing 7 Spring 8 Restriction guide a Maximum eccentricity D0 Diameter of screw part in nut d Diameter of screw part of screw shaft F Load load F _S Spring load L Nut shaft center l Screw shaft center P Thread pitch Q Contact point X Eccentric amount

Claims (2)

[Claims] In a screw shaft and a nut formed by screwing helical screw portions having a predetermined pitch, the diameter of the screw portion of the nut is slightly larger than the diameter of the screw portion of the screw shaft screwed thereto. While forming, the nut is rotatably supported with respect to a support member, and the support member is urged by a predetermined spring load in the screw shaft diametric direction so that the nut is eccentrically contacted with the screw shaft. A load-sensitive linearly-operated continuously variable transmission characterized by having a configuration. 2. The eccentric contact surface between the screw shaft and the nut, the flank shape of the screw surface of the screw shaft or the nut that gives a relationship between the amount of eccentricity and the contact angle, and the nut in the diametric direction with respect to the screw shaft. By adjusting the mutual relationship between the displacement and the load characteristics of the spring biasing the nut, the amount of eccentricity of the nut with respect to the screw shaft becomes a desired ratio as the axial load applied to the screw shaft or the nut increases. And the reduction ratio increases at a desired ratio, and the amount of eccentricity of the nut with respect to the screw shaft at the desired ratio as the axial load acting on the screw shaft or the nut decreases. 2. The load-responsive linearly-operated continuously variable transmission according to claim 1, wherein the transmission has a characteristic of increasing and reducing the reduction ratio at a desired ratio.