JP4092459B2 - Torque detection device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a torque detection device, and more particularly to a technique for detecting torque by detecting thrust force due to reaction torque.
[0002]
[Prior art]
The power switching machine may be provided with a rotary switch (tap) for switching a plurality of contacts. The rotary switch is rotationally driven by a motor, and switches contacts according to the operating status. In the rotary switch, the rotational resistance between the contacts increases due to deterioration over time, and the contact switching may not be performed smoothly. For this reason, the maintenance which engages a torque detector with a rotary switch from the exterior of an electric power switching machine, and detects the load torque of a rotary switch regularly is needed.
[0003]
There is a reaction type torque meter as a torque detection device, which is low in price, but has a drawback that it is weak in structure because it needs to support a large weight including a reduction motor with a delicate sensor. In addition, output signal interference due to the bending moment of the shaft also occurs.
[0004]
On the other hand, Japanese Patent Laid-Open No. 9-250958 discloses a torque detection device that uses the thrust displacement of a helical gear. A displacement detector that expands and contracts by a thrust force is provided on a passive gear of a helical gear, and torque is detected by the displacement. The torque applied to the drive shaft gives a thrust force in the axial direction of the passive gear from the drive gear of the helical gear fixed to the drive shaft, and this thrust force causes displacement in the displacement detector. The torque can be easily detected by examining the relative relationship between the drive torque and the displacement in advance.
[0005]
[Problems to be solved by the invention]
However, when a helical gear is used, the driving shaft and the driven shaft are in a parallel relationship, and unless the gear rotates, no thrust force is generated and the displacement detector does not move. Therefore, there is a problem that it is impossible to detect the load torque from when the torque is applied to the rotary switch until the rotation starts from the stationary state. Furthermore, since the thrust force greatly depends on the dynamic friction coefficient and the lead angle of the gear, there is a problem that it is difficult to detect stable torque.
[0006]
The present invention has been made in view of the above-described problems of the prior art, and an object of the present invention is to provide a device that can maintain strength in structure and can stably detect torque with high accuracy. is there.
[0007]
[Means for Solving the Problems]
The present invention includes a worm gear that engages a drive shaft and a driven shaft, and a sensor that detects a horizontal thrust force acting on the worm gear in accordance with a load torque of the driven shaft. A load cell of a robust mechanism, wherein the lower end of the load cell is fixed to a base, the upper end of the load cell is fixed to a bearing of a worm on the drive shaft side, and the upper end is horizontally displaceable in the direction of the thrust force A strain generating hole is formed in the direction, and the strain due to the displacement in the thrust direction is detected .
[0008]
The present invention also includes a hypoid gear that engages the drive shaft and the driven shaft, and a sensor that detects a horizontal thrust force acting on the hypoid gear according to a load torque of the driven shaft, sensor is a load cell of Roberval mechanism, the lower end of the load cell is fixed to the base, so that the upper top end of the load cell is fixed to the bearing of the drive shaft side of the gear is displaceable in the direction of the thrust force A strain generating hole is formed in the horizontal direction, and the strain due to the displacement in the thrust direction is detected .
[0012]
Thus, in the torque detection device of the present invention, the load torque is detected using the thrust force applied to the worm gear or the hypoid gear. The worm gear or the hypoid gear is characterized in that the two axes are orthogonal to each other and the axis center is offset. Therefore, for example, in the case of a worm gear, a driven shaft is connected to a load such as a rotary switch, a worm wheel is connected to the driven shaft, and a worm is connected to the driving shaft, so that a thrust force is applied to the worm by the load torque. Will be. Usually, the worm is provided with a thrust bearing and receives a thrust force. In the present invention, the thrust force is received by a sensor, for example, a load cell, and a strain generated in the load cell is detected. The amount of strain detected by the load cell is proportional to the thrust force, and the thrust force is proportional to the load torque. Accordingly, if the relationship between the strain amount and the load torque is verified in advance, the load torque can be detected with high accuracy. Further, since the shaft center has an offset, even if the gear is not rotating, a thrust force is generated by the load torque, and the torque for starting the rotation from a stationary state can also be detected.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings, taking as an example a case where load torque necessary for rotating a power switching tap is detected.
[0014]
FIG. 1 shows a conceptual configuration diagram of the present embodiment. The torque detection device 1 includes a drive motor 2, a gear mechanism 3, a sensor 4, and a processing unit 5, and a drive shaft of the motor 2 and a load 6 are engaged by the gear mechanism 3. Specifically, the gear mechanism is a worm gear. The gear mechanism 3 is provided with a sensor 4 to detect a thrust force acting on the gear mechanism. The detected thrust force is supplied to the processing unit 5. The processing unit 5 processes a signal from the sensor and outputs it as a torque value. Specifically, the correspondence relationship between the sensor detection value and the torque value is stored in advance in a memory, and a torque value corresponding to the input sensor value is output. The load 6 is a power switching tap.
[0015]
2 is a front view of the torque detection device 1 according to the present embodiment, and FIG. 3 is a cross-sectional view taken along line XX of FIG. The torque detection device 1 has a DC motor 10 with a speed reducer, and drives the drive shaft 13 with the DC motor 10. It is desirable that the DC motor 10 does not move in the thrust direction. The DC motor 10 and the drive shaft 13 are coupled by a coupler 12. The coupler 12 desirably has low rigidity in the thrust direction or is free. The drive shaft 13 is provided with a worm gear worm 14a, which meshes with the worm wheel 14b to rotationally drive the driven shaft 18.
[0016]
At both ends of the worm 14a, a load cell 16 of a robust type is provided. A ball bearing 15 is provided at an upper end portion of the load cell 16, and the drive shaft 13 is rotatably supported by the ball bearing 15. The lower end of the load cell 16 is fixed to the base, and the upper end is constituted by a Roverval mechanism so that it can move along the drive shaft 13, and a strain generating hole 16b is formed at the center. The hole 16b is formed considering that the load application axis of the load cell 16 and the thrust direction are parallel. A strain sensor 16a is provided at a predetermined position (strain generating portion) of the load cell 16, and when the worm 14a receives a force in the direction of the arrow (thrust direction) in FIG. 1, the load cell 16 is distorted in the thrust direction, and this strain is electrically Convert to signal and output externally.
[0017]
A driven shaft 18 is provided on the worm wheel 14b that meshes with the worm 14a. That is, the worm wheel 14b is pivotally supported with the driven shaft 18 as the center of rotation. The driven shaft is also supported on the base via the ball bearing 17. The end of the driven shaft 18 is connected to a tap (not shown).
[0018]
During normal operation of the power switching machine, the tap is driven to rotate by the motor, and the contact is switched. On the other hand, at the time of maintenance, the driven shaft 18 of the torque detection device 1 of the present embodiment is connected to the tap. Then, the DC motor 10 is driven and torque is applied to the tap. When the end of the driven shaft 18 is not connected to the tap, no thrust force is generated in the worm 14a. However, when the tap is connected, a thrust force proportional to the load torque is generated in the worm 14a.
[0019]
FIG. 4 shows how the load cell 16 is deformed. 4A shows a state where the load torque is zero, and FIG. 4B shows a state where the load torque is present and a thrust force is applied. The load cell 16 of the Roverval mechanism is distorted in the thrust direction. In FIG. 4B, distortion is exaggerated for convenience of explanation. A sensor 16a provided in the strain generating section outputs an electrical signal corresponding to the strain. The electric signal is supplied to the processing unit 5 and output as a torque value. It is also preferable to provide a display in the torque detection device 1 and display the detected torque value as a numerical value on the display. The detected load torque is compared with a predetermined threshold value, and if it is equal to or less than the predetermined threshold value, an OK sign can be displayed, and if the threshold value is exceeded, an NG sign can also be displayed.
[0020]
Thus, in this embodiment, the worm gear is provided for the engagement between the drive shaft 13 and the driven shaft 18. In the worm gear, the drive shaft 13 and the driven shaft 18 are orthogonal to each other, and there is an offset between the two shaft centers. Therefore, even if the worm gear does not rotate, the load torque gives a force in the thrust direction to the worm 14a, and the load cell 16 can detect the thrust force. Thereby, it is also possible to detect the load torque amount required to start the rotation from the static state of the tap.
[0021]
Furthermore, in the case of helical gears, the thrust force changes depending on the lead angle, but in the case of worm gears, the thrust force is determined regardless of the lead angle, so it is stable regardless of gear molding accuracy and changes over time. Can be detected.
[0022]
In this embodiment, the drive shaft 13 and the driven shaft 18 are engaged with each other by a worm gear. However, like the worm gear, the other rotation axes are orthogonal to each other and the rotation center is offset. It would also be possible to use a member. An example of such an engaging member is a hypoid gear.
[0023]
The hypoid gear is mainly used as a substitute for a worm gear, and is composed of a conical small gear and a large gear meshing with the small gear. A small gear is provided on the drive shaft 13 and a load cell 16 is connected to the bearing. A large gear is provided on the driven shaft 18. Even when a hypoid gear is used, a thrust force is applied to the small gear by the load torque, and the load torque can be detected with high accuracy by detecting this with the load cell 16.
[0024]
As mentioned above, although embodiment of this invention was described, this invention is not limited to this, A various change is possible.
[0025]
For example, in the present embodiment, the load cell is used to detect the thrust force of the gear, but any sensor that can detect the thrust force of the gear can be used. For example, the thrust force may be detected by providing an elastic member on the bearing of the worm 14a and detecting the amount of displacement of the elastic member due to the thrust force.
[0026]
In the present embodiment, the drive shaft and the driven shaft are engaged by the worm gear and the hypoid gear, but any engagement mechanism equivalent to these can be used. The conditions that such an engagement function should have are that the two axes are orthogonal to each other, and that the centers of the two axes do not coincide and have an offset. Therefore, it is not preferable to use a bevel gear mechanism in which two axes are orthogonal to each other but the axis centers coincide with each other.
[0027]
【The invention's effect】
As described above, according to the present invention, torque can be detected with high accuracy.
[Brief description of the drawings]
FIG. 1 is a conceptual configuration diagram of an embodiment.
FIG. 2 is a plan view of the torque detection device according to the embodiment.
FIG. 3 is a sectional view taken along line XX of the torque detection device according to the embodiment.
FIG. 4 is an explanatory diagram of a load cell.
[Explanation of symbols]
10 DC motor, 12 coupler, 13 drive shaft, 14a worm, 14b worm wheel, 15, 17 ball bearing, 16 load cell, 18 driven shaft.

Claims (3)

A worm gear that engages the drive shaft and the driven shaft;
A sensor for detecting a horizontal thrust force acting on the worm gear according to a load torque of the driven shaft;
Have
The sensor is a load cell of a robust mechanism, the lower end of the load cell is fixed to a base, the upper end of the load cell is fixed to a bearing of a worm on the drive shaft side, and the upper end can be displaced in the direction of the thrust force. Thus, a strain generating hole is formed in the horizontal direction, and the torque detection device is configured to detect strain due to displacement in the thrust direction . A hypoid gear that engages the drive shaft and the driven shaft;
A sensor for detecting a horizontal thrust force acting on the hypoid gear according to a load torque of the driven shaft;
Have
The sensor is a load cell of a robust mechanism, the lower end of the load cell is fixed to a base, the upper end of the load cell is fixed to a bearing of a gear on the drive shaft side, and the upper end can be displaced in the direction of the thrust force. Thus, a strain generating hole is formed in the horizontal direction, and the torque detection device is configured to detect strain due to displacement in the thrust direction . The apparatus according to claim 1,
A load is connected to the driven shaft;
The correspondence relationship between the thrust force and the load torque is stored in the memory in advance, and the load torque from the stationary state of the load to the start of rotation is detected from the thrust force detected by the sensor and detected. A processing device for detecting an abnormality of the load by comparing the measured load torque with a predetermined threshold;
A torque detection device comprising:

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