JP2505520B2 - Position detection device for eccentric planetary differential reducer - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a position detection device for an eccentric planetary differential reducer, and more specifically, to an accurate rotation angle (corresponding to the rotation position) on the output side of a reduction mechanism. The present invention relates to a position detection device that can detect well.

(Prior Art) Recently, with the advent of industrial robots in various industries, in order to drive the arm member of the robot based on a predetermined program in cooperation with the motor and delicately control its operation, Various speed reducers having a reduction ratio have been devised.

An eccentric planetary differential type speed reducer is a typical example of such a speed reducer, and a cyclo trademark speed reducer or the like is included therein.

In controlling a robot using this type of speed reducer,
Usually, a position detector (for example, an encoder) is provided on the input side of the speed reducer, and the input rotation angle is detected by this to perform feedback control of the machining of the work or the like.

(Problems to be Solved by the Invention) However, in such a conventional position detector, since the rotational position on the input side of the decelerator is detected, the detection accuracy is not always good. .

That is, since the rotational position on the input side is detected and the position on the output side via the deceleration mechanism is predicted from this detection result, errors and delays associated with deceleration are involved, and there is a limit to accuracy improvement.
Therefore, as the rotational position of the speed reducer, it is ideal to actually detect the position on the output side close to the work, but this type of good quality has not yet been put to practical use.

Further, for example, an encoder may be installed on the output side, but in this case, there are problems such as restrictions on the mounting position and an increase in size.

(Object of the invention) Therefore, an object of the present invention is to provide a position detecting device for an eccentric planetary differential type speed reducer capable of accurately detecting the rotational position on the output side of the speed reducer with a simple configuration.

(Means for Solving the Problem) In order to achieve the above object, a position detecting device for an eccentric planetary differential type speed reducer according to the present invention reduces the rotation of an input shaft through an eccentric planetary differential type gear mechanism to output a shaft. A displacement sensor that detects the displacement in the radial direction of the output gear of the gear mechanism that rotates the same as the output shaft of the speed reducer that transmits to the output shaft of the gear mechanism, and obtain the rotation angle of the output gear of the gear mechanism from the output of the displacement sensor. Position detecting means for detecting the position of the output rotation with respect to the input rotation of the reduction gear based on the angle.

(Operation) In the present invention, the rotation of the input shaft is reduced in speed through the eccentric planetary differential type gear mechanism and is transmitted to the output shaft. The displacement is detected by the displacement sensor, the rotation angle of the output gear of the gear mechanism is obtained from the output of the displacement sensor, and the position of the output rotation with respect to the input rotation of the speed reducer is detected based on this rotation angle.

Therefore, the output rotational position is directly detected from the displacement of the output side gear of the reduction gear, and the output rotational position can be accurately detected with a simple configuration and at low cost.

(Example) Hereinafter, the present invention will be described with reference to the drawings.

1 to 5 are views showing an embodiment of a position detecting device for an eccentric planetary differential type speed reducer according to the present invention. First, the configuration will be described. FIG. 1 is a diagram showing the overall circuit configuration of the position detector. Although a half section of a main part of the speed reducer is shown in the figure, the structure of the speed reducer will be described first for convenience of understanding. 2 and 3 are views showing the speed reducer, and for convenience of description, show a state before the proximity sensor is attached. In these figures, 1 is a motor provided in a housing 2 of the speed reducer, and an output shaft 1a of the motor 1 is provided with a small gear 3. The small gear 3 meshes with the large gears 5 fixed to the right end shaft portions of the three sets of cam shafts 4 provided radially outward of the output shaft 1a. Cam shaft 4
An eccentric cam 6 is formed in the middle part of each of the left end shaft part of the cam shaft 4 and the shaft part between the large gear 5 and the eccentric cam 6, and the three parts formed on the block member 7 and the block member 7 respectively. It is rotatably supported by the disk member 8 that abuts the block member 7 via the protrusion 7a. Reference numeral 9 denotes an external gear having a large number of wavy tooth-shaped portions 9a formed at equal intervals on the outer periphery thereof. The cam shaft 4 penetrates through the eccentric cam 6 to engage the protruding portion 7a of the block member 7. Penetrate and play together. Radially outward of the external gear 9, the number of the toothed portions 9a of the external gear 9 is one more than the number n of the external gear 9, that is, n + 1 pins 10 are planted at equal intervals, and An internal gear 11 that engages with the external gear 9 is provided. On the other hand, on the left side of the block member 7 in the figure, a flange portion 12a that is integrally formed coaxially with the low speed side output shaft 12 is provided coaxially with the block member 7 and the disk member 8, and the flange 13 Part 12a,
The block member 7 and the disc member 8 are integrally connected. The low speed side output shaft 12 is rotatably supported by the housing 2 of the reduction gear via a bearing (not shown), and the internal gear
11 is fixedly provided to the housing 2.

Returning to FIG. 1, a proximity sensor (displacement sensor) 20 is provided at a predetermined position of the internal gear 11 of the speed reducer, and the tip of the proximity sensor 20 faces the tooth profile 9a of the external gear 9. There is.
The proximity sensor 20 has a tooth profile 9a based on the eccentric oscillation of the external gear 9.
Is used to detect the displacement, and for example, a device that converts the displacement into an electric signal (displacement-voltage conversion element) is used. In addition,
The proximity sensor 20 may be other than this, as long as it detects a displacement of a member and extracts it as a physical quantity capable of signal processing at a subsequent stage such as an electric or magnetic signal.

The output of the proximity sensor 20 is extracted as an analog voltage signal, and this signal is amplified by the buffer amplifier 21 and then input to the A / D converter 22. The A / D converter 22 A / D converts the voltage signal from the buffer amplifier 21 at every predetermined timing and outputs it to the detection circuit 23 as a digital value. Data from the memory 24 is further input to the detection circuit 23, and the memory 24 is displaced in the tooth profile portion 9a due to the rotation of the external gear 9 (sinusoidally changes with time as described later). The relationship with the rotational angle position of is stored in advance in a map or the like as data. This data is created in advance by, for example, an experiment.

The detection circuit 23 finds the displacement of the tooth profile 9a by comparing the digital value with the memory data, and detects the rotational position of the external gear 9 based on this displacement. Buffer amplifier 21, A /
The D converter 22, the detection circuit 23, and the memory 24 constitute a position detection means 25 as a whole.

 Next, the operation will be described.

When the motor 1 is started, the cam shaft 4 as an input shaft is rotationally driven via the small gear 3, and the three eccentric cams 6 respectively rotate in synchronization with, for example, the clockwise rotation direction in FIG. Along with this, the external gear 9 is moved to the axial center O of the internal gear 11.
Eccentricity of the eccentric cam 6 is eccentric outwardly, and the tooth profile 9a of the external gear 9 is sequentially rotated in the clockwise direction in the pin 10 of the internal gear 11.
Deeply engage. Then, the pin 10 of the internal gear 11 is sequentially inserted into the recess of the tooth profile 9a of the external gear 9, and the external gear 9 is driven counterclockwise by the difference in pitch between the tooth profile 9a and the pin 10. It Further, the block member 7 and the disc portion 8
Rotates around the axis O together with the cam shaft 4, and the low speed side output shaft
12 is rotationally driven via the flange portion 12a. At this time, the ratio of the rotation speed of the low speed side output shaft 12 to the rotation speed of the cam shaft 4,
That is, the reduction ratio of the external gear 9 and the internal gear 11 (the input / output reduction ratio is Therefore, if the number of tooth profile portions 9a and the number of pins 10 are set to be large, an extremely large reduction ratio can be obtained together with the reduction ratio generated between the pinion gear 3 and the cam shaft 4. It is also possible to control the operation.

Here, focusing on the tooth profile 9a of the external gear 9,
9a is displaced according to the eccentric oscillation of the external gear 9 as the output shaft, and this eccentric oscillation is expressed by the concept of the revolution and rotation of the external gear if the viewpoint is changed. Revolution means external gear 9
Means to draw a minimal circular locus around the axis O without changing its own direction, and to rotate means to rotate the external gear 9 itself around the axis O. Therefore, the outer peripheral portion (corresponding to the tooth profile portion 9a) of the external gear 9 does not rotate during revolution, but the outer peripheral portion rotates only by rotation. Around it, the pin 10 is rotated while the external gear 9 revolves once.
The external gear 9 rotates about one pitch, and the radial displacement of the tooth profile 9a in this case is shown in FIG. In FIG. 4, the time T corresponds to the revolution period, which corresponds to the displacement of the tooth profile 9a for one pitch. Further, among the displacements, the crests are the displacement portions of the tooth profile 9a outward of the radiation, and the valleys are the displacements of the tooth profile portion 9a in the radial direction. These peaks and troughs are separated by a distance a with respect to the intermediate displacement of the tooth profile 9a. The value of a is uniquely determined by the specifications of the speed reducer that is the detection target.

Therefore, the output X of the proximity sensor 20 is the sinusoidal electric signal X = a sin θ as shown in FIG.
(Θ is the rotation angle of the cam shaft 4) and then passed through the buffer amplifier 21 and A / D converted by the A / D converter 22.

Now, if the output X of the proximity sensor 20 has a value A shown in FIG. 5, this is A / D converted and then compared with the memory data in the detection circuit 23. By comparison with memory data, when A is found that corresponds to the theta _A becomes the rotation angle, theta _A is detected as the rotational position of the external gear 9 which is an output shaft. In the figure, θ _P represents the rotation angle of the pin 10 for one pitch. Thus, X = a sin [theta is changed by theta _P every time the external gear 9 revolves once, the change in theta _P is the external gear 9 is repeated by n is rotates once. Therefore, by counting the value of X and the number of repetitions of θ _P , the rotational position of the external gear 9 can be detected extremely accurately. The detection result is used as sensor information for feedback control, for example, in a work processing device in which a speed reducer is applied to a robot, and the control accuracy is improved.

From the above, this embodiment has the following effects as compared with the conventional sensor.

(I) While the conventional sensor detects the rotational position on the input side of the speed reducer, in the present embodiment, the rotational position is detected from the gear displacement on the output side. The rotation position can be detected with extremely high accuracy without intervention.

(II) Since the value of a is determined by the specifications of the speed reducer, only the voltage level needs to be detected, and the proximity sensor 20 and the signal processing system in the subsequent stage may have a simple configuration, and there are few failures and low cost. Become.

(III) The mounting position can be saved and the size can be reduced.

Although the above embodiment is an example in which one proximity sensor is configured, the embodiment of the present invention is not limited to this, and a plurality of proximity sensors may be provided, and the following example is shown.

Example of providing two sensors Two proximity sensors are arranged on the internal gear 11 with a phase difference of 90 ° in the circumferential direction, and X = a sin θ Y = a cos θ from each sensor, where a: proportional to the amount of eccentricity Voltage θ: Two voltage signals representing the rotation angle of the cam shaft 4 are extracted.

Then from these two signals By determining, the rotation angle θ can be easily detected from the values of Z and a. In this example, the detection accuracy can be improved as compared with the above examples.

Example of providing four sensors Two pairs of the above sensors are used as a pair.
In the four examples, they are arranged at intervals of °. Then, the output of each set is Z = a tan θ, and by obtaining the output and the average value, it is possible to always perform the “0” point compensation of the detection device, and the detection accuracy is further improved.

(Effect) According to the present invention, since the output rotation position is detected from the gear displacement on the output side of the speed reducer, the output rotation position can be detected very accurately with a simple structure and at low cost. It is possible to realize a small-sized device without restriction on the mounting position of the sensor.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 to FIG. 5 are views showing an embodiment of a position detecting device for an eccentric planetary differential type speed reducer according to the present invention, and FIG. The figure is a front sectional view of the speed reducer, FIG. 3 is a sectional view taken along the line III-III of FIG. 2, FIG. 4 is a diagram showing a continuous output waveform of the proximity sensor, and FIG. It is a figure which shows the output waveform of 1 pitch. 4 ... Cam shaft (input shaft), 9 ... External gear, 10 ... Pin, 11 ... Internal gear, 12 ... Output shaft, 20 ... Proximity sensor, 21 ... Buffer amplifier, 22 ... A / D converter, 23 ... Detection circuit, 24 ... Memory, 25 ... Position detection means.

Claims (1)

(57) [Claims] 1. A radial displacement of an output gear of the gear mechanism rotating the same as an output shaft of a speed reducer for decelerating the rotation of an input shaft via an eccentric planetary differential type gear mechanism and transmitting it to an output shaft. A displacement sensor that detects the rotation angle of the output gear of the gear mechanism from the output of the displacement sensor, and position detection means that detects the position of the output rotation with respect to the input rotation of the speed reducer based on this rotation angle. A position detecting device for an eccentric planetary differential type speed reducer.