WO2023042321A1

WO2023042321A1 - Backlash eliminating mechanism and rotation angle detecting device

Info

Publication number: WO2023042321A1
Application number: PCT/JP2021/034005
Authority: WO
Inventors: 卓也村北
Original assignee: 村北ロボテクス株式会社
Priority date: 2021-09-15
Filing date: 2021-09-15
Publication date: 2023-03-23
Also published as: JP7130296B1; JPWO2023042321A1

Abstract

[Problem] To provide a backlash eliminating mechanism and a rotation angle detecting device using the backlash eliminating mechanism. [Solution] Provided is a backlash eliminating mechanism characterized by comprising a base material 1, a large gear 2, a first small gear 3, a second small gear 4, a planetary gear 5, and a biasing mechanism 6, wherein the biasing mechanism 6 is a one-degree-of-freedom mechanism that moves on a surface parallel to the rotation surface of the large gear 2, the movement is provided with a restoring force, and the planetary gear 5 is biased to eliminate backlash.

Description

Backlash removal mechanism and rotation angle detector

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a backlash removal mechanism and a rotation angle detection device using the mechanism.

Devices for detecting the rotation angle of rotational motion are widely known, and for example, the magnetic type described in Document 1, the capacitance type described in Document 2, and the optical type are known.

In any method, in order to measure multiple rotations exceeding one rotation, it is necessary to measure the number of rotations in addition to the angle. Since rpm data is normally lost when the device is powered off, an auxiliary power source is required to store it.

Since it is not easy to maintain the auxiliary power supply, so-called batteryless devices have also been invented. For example, Documents 3 to 5 use two gears with different numbers of teeth to enable multi-rotation measurement based on the so-called vernier principle.

However, since the backlash of the gear deteriorates the detection accuracy, its removal has been a long-standing problem (for example, Document 6).

Patent No. 6626476 U.S. Patent Application Publication No. 2002/000129 JP 2000-283704 JP 2004-354075 JP 2007-155698 Patent No. 3882167 JP 2004-044620

Therefore, a backlash removal mechanism and a rotation angle detection device using the same are provided.

Accordingly, the present invention provides, in summary, the following.
[1] A substrate, a large gear, a first small gear, a second small gear, a planetary gear, and an urging mechanism, wherein the large gear is rotatably held by the substrate; The small gear is rotatably held by the base while meshing with the large gear, the second small gear is rotatably held by the base while meshing with the large gear, and the planetary gears are the first small gear and the second While meshing with both of the small gears, the first small gear, the second small gear, and the planetary gear are rotatably held by the biasing mechanism at a position where the respective rotation axes of the first and second small gears and the planetary gears are aligned approximately on the same plane. A backlash eliminating mechanism, wherein the mechanism is a one degree of freedom mechanism that moves in a plane parallel to the plane of rotation of the gear, the motion having a restoring force and urging the planetary gears to eliminate backlash.
[2] The planetary gear is a stepped planetary gear, further comprising a first stepped gear and a second stepped gear, the large gear being rotatably held by a base material, and the first stage gear The lower stage of the stepped gear is rotatably held by the base material while meshing with the large gear, the lower stage of the second stepped gear is rotatably held by the base material while meshing with the large gear, and the first small gear is The second pinion is rotatably held by the base material while meshing with the upper stage of the first stepped gear, and the second pinion is rotatably held by the base material while meshing with the upper stage of the second stepped gear. The number of teeth of the upper stage of the stepped gear is the same as the number of teeth of the upper stage of the second stepped gear, and the ratio of the number of teeth of the lower stage to the number of teeth of the upper stage of the stepped planetary gear is equal to the number of teeth of the first stage. equal to the ratio of the number of teeth of the lower stage of the second stepped gear to the number of teeth of the lower stage of the stepped gear, said stepped planetary gear having its lower stage meshing with the first pinion and its upper stage meshing with the second pinion. While meshing with the gears, the first small gear, the second small gear, and the stepped planetary gear are rotatably held by an urging mechanism at a position where the respective rotation axes of the first small gear and the second small gear and the stepped planetary gear are aligned approximately on the same plane. ].
[3] A first stepped gear is a first stepped gear train that connects the large gear and the first pinion, and a second stepped gear is the gear that connects the large gear and the second pinion. a second stepped gear train coupled to the pinion gears, all gears in these gear trains being rotatably retained on respective substrates to urge said stepped planetary gears to The backlash removing mechanism according to [1] or [2], which removes all backlash between rows.
[4] The backlash removing mechanism according to any one of [1] to [3], wherein the first pinion and the second pinion each include an absolute encoder.
[5] A rotation angle detection device comprising the backlash removing mechanism according to any one of [1] to [4].
[6] A reduction gear comprising the backlash removing mechanism according to any one of [1] to [4].
[7] A method of determining the rotation speed and rotation angle of the first pinion described in this specification based on the following procedures 1-4.
(1) An initial state in which the tooth angles of the first pinion (the number of teeth is Z) and the second pinion (the number of teeth is Y) are set to 0 is appropriately determined.
(2) Measure the tooth angle A of the first pinion and the tooth angle B of the second pinion in an arbitrary rotating state.
(3) Subtract the tooth angle A of the first pinion from the tooth angle B of the second pinion to obtain the reference tooth angle C.
(4) From the relationship C=Z×N mod Y, the rotation speed N of the first pinion with respect to the reference tooth angle C is obtained.

FIG. 1 shows the principle of the present invention, comprising a substrate 1, a large gear 2, a first pinion 3, a second pinion 4, a planetary gear 5 and a biasing mechanism 6. , the large gear 2 is rotatably held by the base material 1, the first small gear 3 is rotatably held by the base material 1 while meshing with the large gear 2, and the second small gear 4 is meshed with the large gear 2. While being rotatably held by the base material 1, the planetary gear 5 meshes with both the first small gear 3 and the second small gear 4, and the first small gear 3 and the second small gear 4 and the planets The rotation axes of the gears 5 are rotatably held by the biasing mechanism 6 at a position in which the rotation axes of the gears 5 are aligned approximately on the same plane. A backlash removing mechanism characterized in that the movement has a restoring force and urges the planetary gear 5 to remove backlash.

The biasing mechanism 6 may be, for example, a known invention such as a spring-biased swing arm (Reference 7), and as shown in FIG. 6d, the block 6a rotatably retains the planetary gear 5 and slides along a path defined by a guide 6b fixed to the substrate 1, a compression spring 6c biases the block 6a, and an anchor 6d. A biasing mechanism that is fixed to the base material 1 and supports the reaction force of the compression spring 6c may be used.

According to this configuration, when the planetary gear 5 is urged in the direction toward the rotation axis of the large gear 2, the first small gear 3 produces counterclockwise torque and the second small gear 4 produces clockwise torque. of torque is applied. Since the small gear 3 and the small gear 4 are torqued in opposite directions, the forces are balanced without rotating the large gear 2 . At this time, the first pinion 3 contacts only the tooth flank that contacts when the large gear 2 is rotated clockwise, and conversely, the second pinion 4 contacts when the large gear 2 is rotated counterclockwise. contact only with the tooth flank that is in contact with This action eliminates the backlash. Note that the biasing mechanism may not only push, but also pull, in which case the contacting tooth flanks are reversed.

Since the gear train is meshed with each other, the planetary gear 5 or the biasing mechanism 6 is displaced only in a very small range, but within that range the

pinion gears

3 and 4 and the planetary gear 5 form a differential mechanism. It eliminates backlash caused by static errors during gear manufacturing and dynamic errors such as wear and thermal expansion.

In order for the

pinion gears

3 and 4 and the planetary gears 5 to form a differential mechanism, it is necessary to hold the rotation of the planetary gears 5 at a position where their respective rotation axes are aligned approximately on the same plane. The reason why the positions of the rotation axes of the planetary gears 5 are approximated is that the spur gears are robust against variations in the distance between the axes to some extent. Therefore, the biasing mechanism 6 does not necessarily have to be a linear motion mechanism, and as described above, it may be approximately linearly moved by a rotating mechanism such as a swing arm. In this specification, the term "gear" refers to a mechanism that transmits power through meshing of teeth. The tooth profile may be involute, cycloid, trochoid, or the like.

As shown in FIG. 2, the backlash removing mechanism includes a case where the large gear 2 is an internal gear, and a rack as a special case where the number of teeth of the large gear 2 is infinite. If the gear 2 is regarded as a rack, its motion can be regarded as linear motion rather than rotary motion. Further, the large gear 2 does not necessarily have to be circular, and may be provided with teeth on a free curve as long as it can be properly meshed with the

small gears

3 and 4 .

As shown in FIG. 3, when it is desired to increase the number of teeth and the diameter of the planetary gear 5, the tooth width of the small gear 3 and the small gear 4 is increased, and the engagement position between the small gear 3 and the small gear 4 and the planetary gear 5 is adjusted. may be shifted in the tooth trace direction to avoid interference.

The

small gears

3 and 4 do not necessarily have the same number of teeth. Rather, if different numbers of teeth are selected and absolute encoders are provided for each, they can be used as a multi-rotation rotation angle detector. An absolute encoder means a device that can measure the absolute value of the rotation angle within the range of one rotation.

Since the rotation angle of the first pinion 3 and the rotation angle of the second pinion 4 show a unique combination within the range of the least common multiple of the number of teeth, it is possible to measure multiple rotations within that range. Become. For example, if the number of teeth of the first pinion is 19 and the number of teeth of the second pinion is 17, it is possible to measure up to 323 teeth. At this time, if the number of teeth of the large gear is 323, the second small gear can measure the rotation angle of the large gear with 19 times the resolution.

Furthermore, if the number of teeth of the pinion is a product of suitable prime numbers, various sizes can be selected for the large gear. For example, if the number of teeth of the first pinion is 2×7=14 and the number of teeth of the second pinion is 3×5=15, up to 210 teeth can be measured. At that time, if the number of teeth of the large gear is 210 (= 2 x 3 x 5 x 7), 1 rotation, if it is 105 (= 3 x 5 x 7), 2 rotations, 70 (= 2 x 5 x 3 rotations if 7), 5 rotations if 42 (2 x 3 x 7), 6 rotations if 35 (= 5 x 7), 30 (= 2 x 3 x 5) is 7 rotations, and if 21 (=3×7), the number of rotations of the large gear can be measured up to 10 rotations.

Here, when the number of teeth of the pinion is 14 and 15, the prime factors are selected from the sequence of

prime numbers

2, 3, 5, and 7, which are selected in order from the smallest prime number, without duplication. has a special meaning in terms of design at the point where the is the minimum and at the point where the number of teeth is approximately equal. If the number of teeth is too small, they may be multiplied by any common natural number, ie the ratio of the number of teeth is 14:15.

As shown in FIG. 4, the backlash removing mechanism includes a base material 1, a large gear 2, a first small gear 3, a second small gear 4, a stepped planetary gear 5, and an urging mechanism 6. , a first stepped gear 7 and a second stepped gear 8, the large gear 2 is rotatably held on the base material 1, and the lower stage of the first stepped gear 7 meshes with the large gear 2. The lower stage of the second stepped gear 8 is rotatably held by the base 1 while meshing with the large gear 2, and the first small gear 3 is held by the first stepped gear. The second small gear 4 is rotatably held by the base material 1 while meshing with the upper stage of the second stepped gear 8 , and the stepped planetary gear 5 While the lower stage meshes with the first small gear 3 and the upper stage meshes with the second small gear 4, the rotation axes of the first small gear 3, the second small gear 4 and the stepped planetary gear 5 are approximately the same. It is rotatably held by an urging mechanism 6 at a position aligned on a plane, and the urging mechanism 6 is a mechanism with one degree of freedom that moves on a plane parallel to the rotation plane of the large gear 2, and the movement is a restoring force. and urging the stepped planetary gear 5 to remove the backlash. Here, the gears located on the far side of the paper are the lower gears, and the gears on the front side of the paper are the upper gears.

This configuration has the effect of increasing the number of teeth of the pinion gears 3 and 4 in the configuration of FIG. can be done. However, the reduction ratio of the gear train from the planetary gear 5 to the large gear 2 must be selected so as to match between the first and second trains. Therefore, planetary gears generally need to be stepped gears (including special cases in which the number of teeth of the upper and lower stages are the same and become ordinary spur gears).

The number of teeth of the upper and lower stages of the stepped planetary gear 5 can be derived from a simple calculation of the reduction ratio. The product of the number of teeth of the upper stage of the second stepped gear 8 is the number of teeth of the upper stage of the stepped planetary gear 5 , the number of teeth of the lower stage of the second stepped gear 7 , and the first stepped gear 8 . and the number of teeth of the upper stage of . Under this condition, when the number of teeth of the upper stage of the stepped gear 7 and the number of teeth of the upper stage of the stepped gear 8 are matched with an arbitrary number of teeth, The ratio of the number of teeth of the lower stage of the planetary gear 5 matches the ratio of the number of teeth of the lower stage of the stepped gear 8 to the number of teeth of the lower stage of the stepped gear 7 .

For example, the number of teeth of the lower stage of the first stepped gear 7 is 15, the number of teeth of the first pinion 3 is 11, the number of teeth of the second stepped gear 8 is 14, and the number of teeth of the second pinion 4 is 14. is 13, and the number of teeth of the upper stage of the stepped gear 7 and the stepped gear 8 is the same arbitrary number of teeth (for example, when the number of teeth of each is 10), the upper part of the stepped planetary gear 5 The number of teeth of the lower stage should be 15 and 14, respectively. In this case, the ratio between the number of revolutions of the first pinion and the number of revolutions of the second pinion is the number of teeth of the first pinion (15×11=165) in the configuration of FIG. It is equal to the ratio when the number of teeth of the pinion is (14×13=182), and the number of teeth up to 30030, which is the least common multiple of both numbers of teeth, can be measured.

The prime factors of 11, 13, 14, and 15 teeth shown in the example are selected from the sequence of

prime numbers

2, 3, 5, 7, 11, and 13, which are selected in order from the smallest prime number, so as not to overlap, and in the sense of the least common multiple The point with the smallest number of teeth and the point with approximately the same number of teeth have special significance in terms of design. If the number of teeth is too small, they may be multiplied by any common natural number, ie the ratio of the number of teeth should be 11:13:14:15 regardless of the order. Similarly suitable combinations include 13:14:15:17, 14:15:17:19, 17:19:21:22, 19:21:22:23.

In any of the configurations described above, any gear may be driven, and in that case, it can be used as a speed reducer while measuring the rotation angle. For example, in the configuration shown in FIG. 4, it is easy to drive the second pinion 4 rotatably fixed to the base material.

If any one gear of the first backlash removing mechanism and one of the gears of the second backlash removing mechanism are properly connected on the same rotating shaft, a multi-stage speed reducer can be constructed, as shown in FIG. 4 are the stepped gear train 10 and the stepped gear train 11 that connect the large gear 2, the small gear 3 and the small gear 4, respectively, and A reduction gear with a large reduction ratio can be obtained by using a backlash removing mechanism characterized in that each gear in the row is rotatably held on the base material 1 . This configuration is effective because it is possible to remove the backlash of all the gears with a single biasing mechanism. Since the stepped gear train can be replaced with a virtual stepped gear with the same reduction ratio in terms of the reduction ratio, multi-rotation measurement is possible on the same principle as the configuration of FIG.

In this specification, the value expressed by the number of advanced teeth is referred to as the tooth angle. For example, when a gear with 182 teeth is rotated by 90 degrees, the tooth angle is 182×90/360=45.5, and when it is rotated by 180 degrees, the tooth angle is 182×180/360=91.

As in the above example, when the numbers of teeth of the first pinion and the second pinion are set to 165 and 182, respectively, when the first pinion rotates N (N is a non-negative integer), the second The tooth angle C of the pinion can be easily calculated from the remainder of the division, and becomes C=165×N mod 182. Thus, the tooth angle of the second gear when the tooth angle of the first gear is aligned with 0 is specifically called the reference tooth angle. Since the reference tooth angle C indicates 182 unique numerical values that do not overlap with respect to the number of rotations N, the number of rotations and the angle of rotation of the first gear can be known by reading these combinations. In this case, it is desirable to create a lookup table such as that shown in FIG.

According to the above method, the rotation speed and rotation angle of the first pinion can be calculated based on the following procedure. However, as in the example above, the ratio of the number of rotations of the first and second gears is changed from 11:13 to 165:182 by the action of the stepped gear, as if the first and second gears Since the number of teeth may be 165 and 182, respectively, when using a stepped gear or stepped gear train, the following first and second gears are these virtual gears. shall point to
(1) An initial state in which the tooth angles of the first pinion (the number of teeth is Z) and the second pinion (the number of teeth is Y) are set to 0 is appropriately determined.
(2) Measure the tooth angle A of the first pinion and the tooth angle B of the second pinion in an arbitrary rotating state.
(3) Subtract the tooth angle A of the first pinion from the tooth angle B of the second pinion to obtain the reference tooth angle C.
(4) From the relationship C=Z×N mod Y, the rotation speed N of the first pinion with respect to the reference tooth angle C is obtained.

For example, Z = 165, Y = 182, using a 10-bit (indicating an integer value from 0 to 1023) absolute encoder, the reading of the first pinion is 99, the reading of the second pinion is 298, the tooth angles in (2) above are A=165×99/1024=15.
95, and B=182×298/1024=52.96. In order to read the lookup table, it is necessary to align the tooth angle of the first pinion to zero. .96=37. In FIG. 9, it can be seen that N=137 when reading the number of revolutions corresponding to the reference tooth angles in the ones place 7 and the tens place 30. Therefore, it can be seen that the first gear is advanced by the number of teeth A=15.95 after N=137 revolutions. By calculation, the number of teeth advanced by the first gear is 137 x 165 + 15.95 = 22620.95. Since both are connected by a large gear and advance by the same number of teeth, the tooth angle of the second gear is 22620. .95 mod 182=52.95, which agrees with the above calculation considering the encoder error. If the number of revolutions becomes negative, 182 should be added to the number of revolutions. For example, the state of N=-3 can be treated equally to the state of N=182-3=179.

The number of rotations of the large gear can be easily calculated according to the reduction ratio with the first gear, but if the large gear is also provided with a third encoder, the measurable number of rotations can be further increased. . Since the number of teeth of the first and second small gears can be measured up to 30,030, they can be regarded as gears with 30,030 teeth. Since the relationship between the virtual gear and the large gear is the same as the relationship between the first and second small gears, based on the above procedure, the number of teeth of the large gear and the number of teeth of the least common multiple of 30030 are calculated. can be measured. For example, if the number of teeth of the large gear is a prime number such as 17, 19, or 23 that does not overlap with a prime factor of 30,030, then up to 30,030 revolutions can be measured.

A common method for removing gear backlash is the so-called scissor gear, but it must be used for all gear stages, and the biasing mechanism itself rotates, making it difficult to adjust and assemble. was the problem. According to this backlash removing mechanism, the backlash of the gear train can be removed centrally, and the biasing force can be varied as needed, which is a great advantage.

The backlash elimination mechanism can also be used as a speed reducer, or can constitute a multi-rotation goniometer using its constituent elements. In practical implementation, the goniometer and speed reducer are often used together, so it is highly effective in that they can be realized using the components of the backlash elimination mechanism.

It is the figure which showed the principle of a backlash removal mechanism. It is the figure which showed the backlash removal mechanism in case a large gear is an internal gear. It is the figure which showed the state which a large gear and a planetary gear do not interfere. It is the figure which showed the example which provided the stepped gear between the large gear and the small gear. 5 is a diagram showing an example in which the stepped gear in FIG. 4 is a stepped gear train; FIG. FIG. 4 is a diagram showing an embodiment of a rotation angle detection device to which a backlash removal mechanism is applied; FIG. 7 is an exploded view of the detection portion of FIG. 6; It is the figure which extracted and showed the biasing mechanism of FIG. FIG. 4 is a diagram showing an example of a lookup table;

FIG. 6 shows an example in which the present invention is implemented as a rotation angle detection device, and FIG. , a second small gear 4, a planetary gear 5, and an urging mechanism 6. The large gear 2 is rotatably held by a base (not shown but coupled to the base 1a). , the first small gear 3 is rotatably held on the base 1 while meshing with the large gear 2, the second small gear 4 is rotatably held on the base 1 while meshing with the large gear 2, and the planetary gear 5 While meshing with both the first pinion 3 and the second pinion 4, the respective rotation axes of the first pinion 3 and the second pinion 4 and the planetary gear 5 are aligned approximately on the same plane. position, it is rotatably held by a biasing mechanism 6, the biasing mechanism 6 being a one-degree-of-freedom mechanism that moves on a plane parallel to the plane of rotation of the gear wheel 2, the motion having a restoring force, The rotation angle detection device is characterized in that the planetary gear 5 is energized to eliminate backlash.

The base material 1 includes a lower case 1a, an upper case 1b, a set screw 1c, and a bearing 1f. It connects with the upper case 1b.

The first small gear 3 has a main body 3a and a permanent magnet 3b, and the second small gear 4 also has a main body 4a and a permanent magnet 4b, which are rotatably held on the base material 1 via bearings 1f. .

A circuit board 9 is fixed to the screw hole 1e, and has a magnetic encoder 9a on its back surface to read the rotation angles of the

permanent magnets

3b and 4b.

FIG. 8 is an extracted view of the biasing mechanism. A convex block 6a is provided with a rotating shaft 6f, which rotatably holds the planetary gear 5 and guides it into the same shaped slot of the substrate 1. The leaf spring 6c slides against the apex of the leaf spring 6c, and the end of the leaf spring 6c has a smooth arc shape and slides in contact with the base material 1, and the restoring force due to the deflection of the leaf spring 6c slides down the block 6a. An urging mechanism characterized by urging.

Claims

A substrate, a large gear, a first pinion, a second pinion, a planetary gear, and a biasing mechanism, wherein the large gear is rotatably held by the substrate and the first pinion is rotatably held on the base while meshing with the large gear; a second pinion is rotatably held on the base while meshing with the large gear; planetary gears are the first pinion and the second pinion; While meshing with both, the first small gear, the second small gear, and the planetary gear are rotatably held by the biasing mechanism at a position where the respective rotation axes are aligned approximately on the same plane, and the biasing mechanism is a large A backlash elimination mechanism, a one degree of freedom mechanism for motion in a plane parallel to the plane of rotation of the gear, the motion having a restoring force to urge the planetary gear to eliminate backlash.
The planetary gear is a stepped planetary gear, further comprising a first stepped gear and a second stepped gear, wherein the large gear is rotatably held by a base material and the first stepped gear The lower stage is rotatably held by the base material while meshing with the large gear, the lower stage of the second stepped gear is rotatably held by the base material while meshing with the large gear, and the first pinion is held by the first gear. The second pinion is rotatably held by the base while meshing with the upper stage of the stepped gear, the second pinion is rotatably held by the base while meshing with the upper stage of the second stepped gear, and the first stepped gear The number of teeth of the upper stage is the same as the number of teeth of the upper stage of the second stepped gear, and the ratio of the number of teeth of the lower stage to the number of teeth of the upper stage of the stepped planetary gear is equal to that of the first stepped gear. equal to the ratio of the number of teeth of the lower stage of the second step gear to the number of teeth of the lower stage, said stepped planetary gear having its lower stage meshing with the first pinion and its upper stage meshing with the second pinion 2. The urging mechanism according to claim 1, wherein the rotation axes of the first pinion, the second pinion, and the stepped planetary gear are rotatably held by the biasing mechanism in a position where the rotation axes of the first pinion, the second pinion, and the stepped planetary gear are aligned approximately on the same plane. backlash elimination mechanism.
A first stepped gear is a first stepped gear train connecting the large gear and the first small gear, and a second stepped gear is the large gear and the second small gear. wherein all the gears in these gear trains are each rotatably supported on a substrate to urge the stepped planetary gears to move between the gear trains 3. A backlash elimination mechanism according to claim 1 or 2, which eliminates all backlash.
4. The backlash removing mechanism according to claim 1, wherein each of the first pinion and the second pinion has an absolute encoder.
A rotation angle detection device comprising the backlash removing mechanism according to any one of claims 1 to 4.
A speed reducer comprising the backlash removing mechanism according to any one of claims 1 to 4.
A method for determining the rotation speed and rotation angle of the first pinion according to any one of claims 1 to 4 based on the following procedures 1 to 4.
(1) An initial state in which the tooth angles of the first pinion (the number of teeth is Z) and the second pinion (the number of teeth is Y) are set to 0 is appropriately determined.
(2) Measure the tooth angle A of the first pinion and the tooth angle B of the second pinion in an arbitrary rotating state.
(3) Subtract the tooth angle A of the first pinion from the tooth angle B of the second pinion to obtain the reference tooth angle C.
(4) From the relationship C=Z×N mod Y, the rotation speed N of the first pinion with respect to the reference tooth angle C is obtained.