JPS6348417A - Multiple rotation type absolute encoder - Google Patents

Abstract

PURPOSE:To detect a rotational quantity over a wide range by connecting a driven shaft to a main shaft through a planetary differential speed reducer and providing absolute rotational quantity detection parts to the main shaft and drive shaft respectively, and thus obtaining a large speed reduction rate. CONSTITUTION:The main shaft 2, planetary differential speed reducer 3, driven shaft 4, etc., are put and arranged in a cylindrical case 1. The absolute rotational quantity detection parts 5 and 6 are provided to the main shaft 2 and driven shaft 4 respectively. The main shaft 2 is supported by a bearing 8 provided to a front plate 7. Then when the main shaft 2 is rotated, its rotational quantity is transmitted to the speed reducer 3 and an operating shaft 18 and a cylindrical body 25 rotate in one body to rotate an eccentric cylinder 22 eccentrically. This eccentric rotation is transmitted through the gear system composed of external gears 27 and 28 and internal gears 29 and 30 through the cylindrical body 25 and a visco-elastic material 26 the this gear system enters specific speed reducing operating to outputs a rotational quantity based upon the speed reduction ratio from the drive shaft 4. Consequently, the rotational quantity is detected over a wide range.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a multi-rotation type absolute encoder that detects the absolute rotation amount of a main shaft over multiple rotations.

<Prior art> Conventionally, multi-rotation type absolute encoders include those in which multiple absolute encoders are sequentially linked via a gear mechanism (Japanese Patent Application Laid-open No. 106691/1983), and two resolvers using a harmonic drive. A structure arranged coaxially (Japanese Patent Application Laid-Open No. 154319/1983) has been proposed.

<Problems to be Solved by the Invention> However, in the former type, since a plurality of absolute encoders cannot be connected coaxially, there is a drawback that the entire device inevitably becomes larger.

On the other hand, while the latter type makes the entire device more compact,
There is a problem in that the manufacturing cost of the harmonic drive is high because it is difficult, and the cost motion of the harmonic drive causes a decrease in detection accuracy.

This invention is intended to solve the above problem,
We focused on the feature of the planetary differential type reducer, namely its ability to obtain a large reduction ratio with a simple structure, and by incorporating this type of reducer into the mechanism, we reduced the size and cost.

Furthermore, it is an object of the present invention to provide a new multi-rotation type absolute encoder with improved accuracy.

Means for Solving the Problems> In order to achieve the above object, the present invention connects the driven shaft to the main shaft via a planetary differential type reducer, and also sets the absolute rotation amount to each of the main shaft and the driven shaft. Effects of configuring a multi-rotation type absolute encoder by providing a detection section> When rotation is applied to the main shaft, the amount of rotation is transmitted to the planetary differential type reducer, and the amount of rotation is transmitted to the planetary differential type reducer. A predetermined deceleration operation is performed, and the driven shaft outputs a rotation amount according to the deceleration ratio. The respective rotation amounts of the main shaft and the driven shaft are detected by respective absolute rotation amount detection sections, and the absolute rotation amounts over multiple rotations of the main shaft are determined using the detected values directly in an arithmetic circuit or the like.

<Embodiment> FIG. 1 shows the internal structure of a multi-rotation type absolute encoder according to an embodiment of the present invention.

The illustrated example includes a main shaft 2, a planetary differential type reducer 3. The driven shaft 4 and the like are housed and arranged, and the main shaft 2 and the driven shaft 4 are each provided with an absolute rotation amount detection section 5.6, and the main shaft 2 is supported by a bearing 8 provided on the front plate 7.
Its tip protrudes from the front.

The one absolute rotation amount detection section 5 is for detecting the absolute rotation amount of the main spindle 2, and a rotating disk 9 on which a detection pattern for the absolute rotation amount has been applied is attached to the main spindle 2, and this rotating disk A light emitting element group 10 made up of a plurality of light emitting diodes and a light receiving element group 11 made up of a plurality of phototransistors are disposed facing each other with a light emitting element 9 sandwiched therebetween.

The other absolute rotation detecting section 6 is for detecting the absolute rotation amount of the driven shaft 4, and similarly to the absolute rotation amount detecting section 5 of the main shaft 2, it includes a rotating disk 12, a light emitting element group 13, and a light receiving element group 14. It consists of

The planetary differential type reducer 3 is for decelerating the rotation of the main shaft 2 and transmitting it to the driven shaft 4. The operating shaft 18 is rotatably supported at the center of the housing 15 by bearings 16 and 17. The tip of the operating shaft 18 projects from the cover plate 19 and is integrally connected to the main shaft 2, and the driven shaft 4 is inserted into the housing 15 and supported by bearings 20 and 21. An eccentric cylinder 22 is fitted on the operating shaft 18 so as to be able to rotate integrally therewith, and a bearing 2 is mounted on the eccentric cylinder 22.
3 and 24, the cylindrical body 25 is arranged to freely rotate independently.

A cylindrical viscoelastic material 26 made of rubber or the like is integrally fitted onto the cylindrical body 25, and external gears 27 and 28 are mounted on this viscoelastic material 26 so as to be integrally rotatable. External gears 27 and 28 are located on the outer periphery of the gears 27 and 28, respectively.
An internal gear 29, 30 is provided in which the eccentric portion of the gear meshes.

One internal gear 29 is supported and fixed to the housing 15 and the cover plate 19, and the other internal gear 30 is integrally connected and fixed to the driven shaft 4.

In the figure, numerals 31 to 34 are circuit boards, among which circuit boards 31 and 32 are equipped with circuits necessary to configure the absolute rotation amount detection section 5.6, and circuit boards 33 and 34 are equipped with circuits necessary to configure the absolute rotation amount detection section 5.6. A circuit is incorporated for converting the detection signal from the absolute rotation amount detection section 5.6 into a predetermined signal code and for calculating the absolute rotation amount of the main shaft 2 over multiple rotations.

FIG. 2 shows another embodiment of the present invention, in which the planetary differential type reducer 3 is a reducer using eccentric planetary differential rollers. In the same figure, the external gear 27.2
8 to the outer roller 35.36, and the internal gear 29.3
0 is replaced with inner rollers 37 and 38, respectively, and the other configurations are the same as in the first embodiment. Therefore, by assigning corresponding symbols to corresponding configurations, individual explanations will be omitted here.

When the main shaft 2 is rotated, the amount of rotation is transmitted to the planetary differential speed reducer 3, and the operating shaft 18 rotates integrally with the main shaft 2, causing the eccentric cylinder 22 to eccentrically rotate. This eccentric rotation is transmitted to the external gear 27 via the cylindrical body 25 and the viscoelastic material 26.
．． 28 and internal gears 29 and 30, and a predetermined deceleration operation in this gear system causes the driven shaft 4 to output a rotation amount according to the reduction ratio.

Now, the number of teeth of the external gear 27 is Zl, and the number of teeth of the internal gear 29 is Z2.
．． The number of teeth of the external gear 28 is Z3 + The number of teeth of the internal gear 30 is Z4
Also, the distance between the shafts of the external gear 27 and the internal gear 29 is aI
+Assuming that the distance between the axes of the external gear 28 and the internal gear 30 is a2, the number of teeth of each of these gears satisfies the following conditions.

ZI < Zz, Z3 < Z4 Z+Za≠Zt Zs a, =a2 =A (A is a constant) Next, spindle 2
If the amount of rotation of the driven shaft 4 is θ, the amount of rotation θ2 of the driven shaft 4 can be expressed by the following equation.

ZI Z4 Also, the detection resolution of the main shaft 2 is n1/1 rotation, and the detection resolution of the driven shaft 4 is n z / 1 rotation (however, R2 is ZI Z
a / (ZI Z4Zt Z3) or an integral multiple thereof, and ZI 24/ (ZI
Z4 Zt Z3 ) is also an integer), then the detected value R of the driven shaft 4 when the main shaft 2 rotates once
21 is given by Huggi's 0 formula.

ZIZa Therefore, the main shaft 2 detected by one absolute rotation amount detection section 5
If the detected value of the driven shaft 4 detected by the other absolute rotation amount detection unit 6 is R2, then the absolute rotation amount N of the main shaft 2 when the main shaft 2 rotates multiple times is expressed by the following equation 0. Given.

N-R+ + [Rz / Rz+ko xn,,,
,,■However, for calculated values in [ ], decimal places are rounded down.

Thus, the circuit assembled on the circuit boards 33 and 34 performs the calculation of the above equation 0, and converts the calculation result into a predetermined output code and outputs it.

In the above embodiment, the eccentricity X of the eccentric cylinder 22 is set to be larger than the constant A related to the distance between the shafts of the gear system by a predetermined length, so that the external gear 27 and the internal gear 29
Buff crush between external gear 28 and internal gear 30
This is done so that the backlash between the In this case, the viscoelastic material 26 is attached to the cylindrical body 25 and the external gear 27 in order to prevent contact pressure from being applied as a preload between the tooth surfaces due to the assembly error and impairing the smoothness of rotation. It is interposed between 28 and 28. Thus, the viscosity of the viscoelastic material 26 absorbs gear machining errors and assembly precision errors, and also absorbs sound, vibration, etc., resulting in smooth rotation without backlash. .

Regarding the second embodiment shown in FIG. 2, the diameter of the outer roller 35 is dl, the diameter of the inner roller 37 is dl, and the diameter of the outer rotor 36 is d3. Assuming that the diameter of the inner roller 38 is d4, the distance between the axes of the outer roller 35 and the inner roller 37 is al+, and the distance between the axes of the outer roller 36 and the inner roller 38 is a2, the diameter of each of these rollers satisfies the following conditions. Satisfied.

d,<dl,d,<d4 d,d4 ≠d2 d3 a, ! az = A (However, A is a constant) Next, main axis 2
If the amount of rotation of the driven shaft 4 is θ1, the amount of rotation θ2 of the driven shaft 4 can be expressed by the following equation 0.

d, d4 Therefore, ZI, Zz, and Z3 in the above example.

Z4 to d,, dl, d3. By replacing d4 with the calculation in 2 above, it is possible to calculate the absolute rotation amount N over multiple rotations of the main shaft 2, and the calculation result can be converted into a predetermined output code and output.

<Effects of the Invention> As described above, in this invention, the driven shaft is connected to the main shaft via a planetary differential type reducer, and an absolute rotation amount detection section is provided for each of the main shaft and the driven shaft. By taking advantage of the features of the planetary differential type reducer, namely the ability to obtain a large reduction ratio with a simple structure, it is possible to make the multi-rotation type absolute encoder more compact and to detect a wide range of rotation amounts. becomes. Furthermore, since the backlash removal mechanism can be easily incorporated into the planetary differential type speed reducer, the detection accuracy can be improved, and other remarkable effects are achieved in achieving the object of the invention.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the internal structure of a multi-rotation type absolute encoder according to one embodiment of the present invention, and FIG. 2 is a sectional view showing the internal structure of another embodiment. 2... Main shaft 3... Planetary differential type reducer 4... Driven shaft

Claims (3)

[Claims] (1) A multi-rotation type absolute encoder in which a driven shaft is connected to the main shaft via a planetary differential type reducer, and an absolute rotation amount detection unit is provided on each of the main shaft and the driven shaft. (2) Claims in which the planetary differential type reducer is provided with a backlash removal mechanism made of a viscoelastic material for setting the backlash between the external gear and the internal gear to zero or less. The multi-rotation type absolute encoder according to item 1. (3) The absolute rotation amount detection unit has a rotary disk on which an absolute rotation amount detection pattern is applied, which is fixed to the shaft, and a light emitting element group and a light receiving element group are arranged facing each other with this rotating disk in between. A multi-rotation type absolute encoder according to claim 1.