JP2016045055A - Speed reducer built-in torque detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a speed reducer built-in torque detector short in the rotation axis direction in which a wave motion gear speed reducer that is mechanically connected to a motor and decelerates the power is integrated with a torque detector for detecting a rotation torque of the output of the speed reducer.SOLUTION: A rotary transformer for non-contact power feeding for supplying power to a wheatstone bridge circuit including a strain gauge disposed in a rotation shaft and a torque measurement signal transmission circuit is disposed in a cylinder outer-periphery of a flex spline of a wave motion gear speed reducer. By installing a secondary-side coil and core in the cylinder outer-periphery along a gear unit in which the flex spline engages with a circular spline, the length in the axial direction can be shortened, and a small-sized and easy-to-assemble speed reducer built-in torque detector can be obtained.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a speed reducer-integrated torque detector capable of detecting torque and integrated with a speed reducer.

  Conventionally, as shown in FIG. 2, as a means for detecting torque and controlling torque while transmitting the power of the motor 104 to a load device, a reduction gear 103 is connected to the output shaft of the motor 104 to reduce the rotational speed. At the same time, it is common to increase the torque and connect the torque detector 20 that can measure the torque via a shaft coupling such as the coupling 105, and connect the rotary shaft 2 that is the output of the torque detector 20 to the load device. Met. With this configuration, each unit is independent, and maintenance such as replacement of parts is advantageous. However, since the length in the axial direction becomes long, it is difficult to use for a robot or the like, and there is a limited application.

  As an improvement on this, an invention is disclosed in which a motor, a speed reducer, and a torque detector are configured in an integral structure.

  In Patent Document 1, since the motor, the wave gear reducer, and the torque detection unit are arranged in series and are hollow shafts, wiring from the torque detection unit integrated with the rotation output shaft is easy. I have to. However, the lead wire from the strain gauge of the torque detector can be wired only when it is a hollow shaft, and its application range is limited. And, a device for shortening the length in the axial direction is not particularly made and is general.

  In Patent Document 2, the flex spline of the wave gear reducer is arranged in the gap between the armature of the motor and the rotor, and although the axial length can be slightly shortened, it is a complicated structure that covers the motor and is assembled. There was a difficulty in sex. In torque detection, there is no description of a detailed embodiment, and it is assumed that means for measuring the magnetostriction of the rotating shaft is used. In this case, the torsional fatigue durability and corrosion resistance of the magnetostrictive plating film become problems, and when the load is continuously applied to the rotating shaft, the shaft itself causes creep deformation with time, so that high-precision measurement should be maintained. Is difficult.

  Patent Document 3 discloses a wave gear device with a torque detection mechanism that detects torque by attaching a strain gauge to a flex spline of a wave gear reducer. Here, the strain gauge is attached to a fixed member instead of a rotating member, and the torque of the rotating body is indirectly measured in the vicinity of the bending portion in the speed reducer, so the responsiveness is poor. There was a difficulty in measurement accuracy. The strain gauge is attached to a part called a boss provided in a part of the flex spline, and this shape determines the accuracy of strain detection, and it can be said that the degree of freedom to design an optimum one is small. Since the wiring from the strain gauge is close to the motor and measures against noise are required, a signal is taken out by a shielded wire or the like, resulting in an increase in cost. Furthermore, although a Wheatstone bridge circuit that detects a change in resistance value of the strain gauge is required, there is no description of the circuit board that constitutes this, and the function of torque detection is not completed within the housing of the embodiment. A separate space for installing the circuit was required.

JP 2013-215081 A Japanese Patent No. 4581543 Japanese Patent No. 3512160

  When the motor 104 and the speed reducer 103 are separated and the speed reducer 103 and the torque detector 20 are configured as an integral type with the basic unit shown in FIG. 2 as the basic form, the structure shown in FIG. Conceivable. In other words, the rotary shaft 2 is connected to the flex spline 13 that is the output of the speed reducer to transmit power to the load device, and at the same time, a plurality of strain gauges are affixed to the strain generating portion 2a provided on the rotary shaft 2. The rotational torque of the shaft 2 can be measured, and the torque is detected by wireless transmission of data from the rotating side substrate 4 to the fixed side substrate 10 which is electrically connected to the strain gauge and constitutes a circuit.

  However, in such a configuration, the cup-shaped flex spline 13 is elastically deformed at an intermediate portion between the portion where the gear portion of the flex spline 13 is engaged with the circular spline 12 and the portion connected to the rotary shaft 2 side. It can be seen that the axial space here is not effectively utilized only by the region being bent. On the other hand, the outer periphery of the secondary side coil 5 and the secondary side core 6 is only in a region where the primary side core 7, the primary side coil 8, and the fixed side substrate 10 are limited, and the other part is an empty space. You can see that

  An object of the present invention is to obtain a speed reducer-integrated torque detector having a short outer shape in the axial direction by paying attention to a portion that is not effectively utilized and an empty space.

The speed reducer integrated torque detector according to the present invention is a wave gear reducer that is mechanically connected to a motor to reduce power, and a speed reducer integrated torque detector that detects rotational torque of an output portion of the wave gear reducer. In
A flex spline of a wave gear reducer is provided with a cylindrical outer peripheral portion and a rotary transformer that is opposed to the cylindrical outer peripheral portion and feeds power in a non-contact manner.

  It is preferable that the detection of the rotational torque is performed by an electric circuit including a strain gauge.

FIG. 3 is a cross-sectional structural view of a reduction gear integrated torque detector showing an embodiment of the present invention. A diagram showing the configuration of a conventional torque detector, reducer, and motor Cross-sectional structure diagram of a conventional speed reducer integrated torque detector

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a sectional structural view showing an embodiment of the present invention. This reduction gear integrated type torque detector is formed by integrating a torque detector and a reduction gear portion.

  The rotating shaft 2 is rotatably supported, transmits power decelerated by a speed reducer, and also includes a strain generating portion 2a for detecting rotational torque. The strain generating portion 2a has a small outer diameter at the central portion in the axial direction of the rotating shaft 2, and has a strength in the axial direction of the rotating shaft 2 and does not deform, but deforms in the torsional direction. A strain gauge is affixed to the surface, and a torsion occurring in the strain generating portion 2a is detected from a change in the resistance value of the strain gauge resistor to detect a rotational torque. The shape of the strain generating portion 2a is not limited to a cylindrical shape, and an optimal one is selected depending on the amount of rotational torque to be measured. On the load side of the rotary shaft 2, it is mechanically connected to a load device (not shown), and the rotational torque is detected while rotating together with the load device.

  On the other hand, the motor shaft 101 is rotatably supported by a bearing 102 provided in a motor housing (not shown), and is connected to a wave generator 14 on the input side of the speed reduction mechanism to transmit rotational power to the rotary shaft 2. Is done.

  The bearing 3 is, for example, a cross roller bearing that receives a load by line contact with a cylindrical roller, and its outer ring is fixed to a connection portion 17 that also serves as a housing, and rotatably supports the rotary shaft 2. It is provided as follows. Accordingly, the bearing 3a is an outer ring, and the bearing 3b facing the bearing 3a is an inner ring, and the rotary shaft 2 is rotatable by being fixed to the rotary shaft 2 with screws.

  The primary side core 7 and the primary side coil 8, and the secondary side core 6 and the secondary side coil 5 form a rotary transformer structure that supplies power without contact. The rotating shaft 2 includes rotating-side substrates 4a and 4b that rotate together with the rotating shaft 2. The rotating-side substrates 4a and 4b include a Wheatstone bridge circuit that includes a strain gauge attached to the cylindrical surface of the strain generating portion 2a. It is mounted and power is supplied to this circuit without contact.

  Hereinafter, the flow of electric power and electric signals in this circuit will be described. The fixed-side substrate 10 is supplied with power from an external DC power supply device, converts this DC to AC, and is used to supply power to an electric circuit provided on the rotating shaft 2 and rotating together. A circuit is provided.

  The primary core 7 is a ferrite having a U-shaped cross section with protrusions at both ends, and is attached to the fixed substrate 10 via a core holder 9. A primary coil 8 formed by winding a copper wire is provided between both protrusions of the primary core 7. The primary side coil 8 is electrically connected to the fixed side substrate 10, and power is supplied from a switching circuit in the fixed side substrate 10.

  On the other hand, the secondary side of the transformer is configured on the flex spline 13 so as to face the primary side core 7 and the primary side coil 8 at a predetermined interval. A secondary side core 6 made of a ferrite sheet is provided on a cylindrical outer peripheral surface of the flex spline 13, and a secondary side coil 5 formed by winding a copper wire is provided on the outer periphery of the secondary side core 6. . The secondary core 6 is composed of a strip-shaped ferrite sheet, and can be formed by winding it around the flex spline 13 with a double-sided tape or an adhesive. The wire drawn from the secondary coil 5 is electrically connected to the rotation side substrates 4a and 4b.

  Accordingly, when power is supplied from the external DC power supply device to the fixed side substrate 10 and the current converted to AC by the switching circuit on the fixed side substrate 10 is passed through the primary side coil 8, an AC magnetic field is generated. An alternating current magnetic field permeates through the secondary side core 6 on the rotating shaft 2 side to induce a current in the secondary side coil 5. The induced current is supplied to a strain gauge constituting a Wheatstone bridge circuit through a rectification circuit and a stabilization circuit in the rotation side substrates 4a and 4b.

  In actual torque detection, when torque is applied to the rotating shaft 2, the strain generating portion 2a of the rotating shaft 2 is distorted according to the magnitude of the torque, and the magnitude of this distortion changes the resistance value of the resistor of the strain gauge. Is detected as the size of. Detection is performed by a detection circuit provided in the rotation side substrates 4a and 4b, and the detected analog signal is digitized and modulated by A / D conversion.

  This digitized signal is transmitted by the LED that performs infrared communication provided on the rotation side substrates 4a and 4b, and is received by the light receiving element provided on the fixed side substrate 10, and is digital corresponding to the torque value. A signal can be obtained. The fixed board 10 is provided with a demodulation circuit so that a voltage signal corresponding to the detected torque value can be output. The output voltage signal is displayed on a display or the like by known means and used for controlling the motor.

  The rotation-side substrates 4a and 4b are fixed to the flange portion 2b of the rotation shaft 2 by the substrate fixing column 19, have a ring shape, and the placement positions of the electronic components are the substrate so as to maintain the balance during rotation. Considered above. In the present embodiment, the rotation-side substrates 4a and 4b are composed of two substrates. However, depending on the diameter size of the rotation shaft 2, the substrate area can be widened and may be composed of one substrate. In this case, the reduction gear integrated torque detector is further shortened in the axial direction.

  On the other hand, a wave gear reducer is connected to the drive side with respect to the rotating shaft 2. The wave gear reducer includes a flex spline 13 having a thin cup shape and gear teeth on the outer periphery of the opening, and a circular spline having gear teeth on the inner peripheral surface corresponding to the outer peripheral gear teeth of the flex spline 13. 12 and a wave generator 14 which is located on the inner periphery of the flex spline 13 and which is coupled to the motor shaft 101.

  The wave generator 14 is a component in which a thin ball bearing is combined on the outer periphery of an elliptical cam. The inner ring of the bearing is fixed to the cam, and the outer ring is elastically deformed via the ball. The flex spline 13 is a thin cup-shaped metal elastic body, and the bottom of the thin cup of the flex spline 13 is called a diaphragm and functions as a reduction gear output. The circular spline 12 is a rigid ring-shaped part, and has an internal tooth structure having two more teeth than the flex spline 13.

  The flex spline 13 is bent into an elliptical shape by the wave generator 14, and the teeth are engaged with the circular spline 12 at the major axis of the ellipse, and the teeth are not meshed at the minor axis. When the circular spline 12 is fixed and the wave generator 14 is rotated clockwise, the flex spline 13 is elastically deformed, and the meshing position of the teeth with the circular spline 12 is sequentially moved. When the wave generator 14 rotates once, the flex spline 13 moves counterclockwise by the difference in the number of teeth. Accordingly, the diaphragm of the flex spline 13 of the wave gear reducer serves as an output unit, and the speed is reduced by the reduction ratio of the wave gear reducer.

  The rotating shaft 2 is fastened to the diaphragm portion of the flex spline 13, that is, the reduction gear output portion by screws. An oil seal 11 is provided in the middle of the meshing portion of the flex spline 13 and the secondary core 6 and the secondary coil 5 in the axial direction for the purpose of preventing oil on the reduction gear side. The oil seal 11 is inserted into the cover 16 and comes into contact with the cylindrical surface of the flex spline 13 for sealing.

  On the other hand, the rotating shaft 2 is fixed to the bearing inner ring 3b by a flange portion 2b projecting in the radial direction. The bearing outer ring 3a provided so as to face the bearing inner ring 3b is fixed to the connection portion 17 that also serves as an exterior portion.

  As described above, in the present invention, a rotary transformer for non-contact power feeding is provided so as to be aligned in the axial direction with the meshing gear of the flex spline 13 of the wave gear reducer, and the rotation that rotates together with the flex spline 13 is provided. Since electric power is supplied to the rotation side substrates 4a and 4b provided on the shaft 2, a reduction gear integrated torque detector that is short in the axial direction can be realized. That is, since the rotary transformer is installed here using the empty space in the cylindrical portion of the flex spline 13, the space can be effectively used and shortened in the axial direction. The flex spline 13 is elastically deformed during driving and slightly distorted during driving. However, the flex spline 13 is not at a level that causes a decrease in performance of the rotary transformer for non-contact power feeding.

  Further, according to this arrangement, not only miniaturization can be realized, but also the degree of freedom in design and ease of assembly can be improved. This is because, when the secondary coil 5 is present on the rotating shaft 2 side as shown in FIG. 3 in the prior art, the rotating-side substrates 4a and 4b must have an inner diameter so as to escape when assembled. The secondary coil 5 needs a required number of turns, and the rotation-side substrates 4a and 4b have to be designed in consideration of the variation in height. On the other hand, in the present invention, the secondary coil 5 is not provided on the rotating shaft 2, and it is not necessary to consider the dimensional variation of the portion through which the rotating side substrates 4a and 4b pass during assembly, and the degree of freedom in design. The assembly is easy.

  As an application example of the present invention, the present invention can be applied to a robot or the like as an actuator that generates power while controlling torque.

DESCRIPTION OF SYMBOLS 1 Reduction gear integrated type torque detector 2 Rotating shaft 2a Strain generating part 2b Collar part 3 Bearing 3a Bearing outer ring 3b Bearing inner ring 4a, 4b Rotation side substrate 5 Secondary side coil 6 Secondary side core 7 Primary side core 8 Primary Side coil 9 Core holder 10 Fixed side substrate 11 Oil seal 12 Circular spline 13 Flex spline 14 Wave generator 15 Shaft cover 16 Cover 17 Connection portion 19 Substrate fixing column 20 Torque detector 101 Motor shaft 102 Bearing 103 Reducer 104 Motor 105 Coupling

Claims (2)

In a wave gear reducer that is mechanically connected to a motor to reduce power, and a speed reducer integrated torque detector that detects rotational torque of an output part of the wave gear reducer,
A speed reducer comprising: a cylindrical outer peripheral portion of a flex spline of the wave gear reducer; and a rotary transformer that is opposed to the cylindrical outer peripheral portion and that supplies power in a non-contact manner. Body torque detector. The speed reducer-integrated torque detector according to claim 1, wherein the rotational torque is detected by an electric circuit including a strain gauge.