JPH0265987A - robot power transmission device - Google Patents

Abstract

PURPOSE:To absorb the error in the distance between 1st and 2nd link plates due to the working error of a part and the assembly error by making a link freely movable in the axial direction to the link axis by at least either one end at a link pivotally supporting part. CONSTITUTION:Both ends of two links 21, 22 are pivotally supported by bearings so that the phase difference in two links becomes at about 90 deg. and in parallel to a driving axis by a pair of 2 sets of the columns whose distance from the respective rotary center is equally provided on a 1st link plate 13 and 2nd link plate 14 in the length equal to the interaxial distance of the driving axis and a terminal arm axis, and also the two links 21, 22 make the column and bearing or bearing link relatively movable in the supporting axial direction at one end thereof at least. As a result, even if the distance between the 1st link plate 13 and 2nd link plate 14 differs from designed dimension by working error and assembly error, no excessive bending moment is generated on the pivotally supporting part by sliding the inner rings of bearings 19a, 19c, 20a, 20c and link axes 15, 16.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a power transmission device for a robot having rotating joints.

(Prior Art) In order to reduce the weight and improve the mobility of the arm, some conventional arm opening devices perform rotation transmission drive using a drive transmission means without directly connecting the actuator to the arm rotation axis.

Drive transmission means include timing belt, steel belt,
There are parallel links. Steel belts and parallel links are considered to be more effective than timing belts, which can cause looseness due to the recent shift to direct drive motors and the high precision demands of robots.

However, steel belts have problems with durability,
In addition, a tension device was required, making it difficult to maintain the appropriate tension.

On the other hand, the parallel link system has good durability but the rotation range is 1
There was a small defect of about 40 degrees.

As a solution to this drawback, Japanese Patent Application Laid-Open No. 63-77674
There is a double link method presented in the issue. According to this method, since the two links rotate with a phase difference of 90', the rotation range of the arm can be 300 degrees or more.

(Problem to be solved by the invention) In robots using conventional harmonic reduction gears, the reduction gear itself has low rigidity, so the low rigidity of the arm and drive transmission system has not been a problem, and the reduction gear Since it is interposed between the motor and the load such as the arm, it acts as a damper and reduces the occurrence of resonance between the servo system and the mechanism.

However, when a direct drive (hereinafter referred to as DD) motor is used as the drive source, if the arm rigidity is low, resonance will occur because the load of the arm etc. is directly connected to the output shaft of the motor, which will increase the servo gain. In extreme cases, the arm could not be driven due to the low servo gain (in the case of DD robots, in order to prevent resonance and increase the servo gain, the robot's natural frequency must be It is said that a value of 1007 or more is desirable, and this is 50I (resonance will occur if it is less than z. Incidentally, in the case of a robot using a harmonic reduction gear, the natural frequency is about 15 to 207).

In addition to the stiffness of the arm itself, the stiffness of the ball bearings used in the joints determines the stiffness of the arm. Since ball bearings are usually considered to be spring-based, it is necessary to apply preload to increase their rigidity.

However, in the double link system as shown in the above-mentioned Japanese Patent Application Laid-Open No. 63-77674, it is possible to apply preload to the ball bearing of the link shaft support, but instead of increasing the rigidity of the drive transmission system by preload, the two Link installation error (
(particularly in the axial direction), an excessive bending moment is generated in the link shaft support, leading to an increase in friction torque and a reduction in bearing life.Furthermore, fluctuations in friction torque when the link rotates and deterioration in robot position accuracy. There was a fear that

(Means for Solving the Problems) The present invention has been made in view of the above-mentioned circumstances, and includes fixing a drive shaft connected to a direct drive motor to a first link plate disposed inside the rear part of the base arm. , a tip arm shaft is pivotally supported on the front part of the base arm via a bearing in parallel with the drive shaft, the tip arm is fixed to the tip arm shaft, a second link plate is fixed to the tip arm shaft, and the drive shaft is fixed to the tip arm shaft. With a length equal to the distance between the shaft and the tip arm shaft, both ends of the two links are connected to the first link plate and the second link plate by a pair of supports provided at equal distances from the center of rotation. The book is supported by bearings so that the phase difference between the links is approximately 90 degrees and parallel to the drive shaft, and the two links have at least one end where the support and the bearing or the bearing and the link are aligned in the direction of the support axis. It is characterized by being relatively movable.

(Structure) A detailed description will be given below based on the illustrated embodiment. A flange 2 is fixed to the upper part of a fixed base 1. A stator portion 3a of a direct (hereinafter referred to as DD) motor 3 for driving a base arm is fixed to the fixed base 1. The DD Momo
A spacer 4 is fixed to the upper part of the rotor -3, and a rear (base) part 5a of a base arm 5 is fixed to the spacer 4.

On the other hand, on the opposite side of the base arm 5 tip 5b from the base arm drive DD motor 3, a support member 6 has an elongated hole so that its position can be adjusted in the longitudinal direction of the arm in a direction perpendicular to the output shaft of the base arm drive DD motor 3. The base arm 5 is fastened to the base arm 5 by bolts. A press plate 7 is attached to the support member 6.
The cross roller bearing 8 is fixed by the cross roller bearing 8, and the cross roller bearing 8 supports the tip arm shaft 9 in parallel with the output shaft of the DD motor 3 for driving the base arm. 10 is a tip arm connected to the tip arm shaft at its rear.

Further, a tip arm knocking shaft 11 is coaxially supported on the spacer 4 by bearings 12a and 12b, and coaxially with the output shaft of a DD motor for driving the base arm. A first link plate 13 is connected to the protruding end of the tip arm sliding shaft 11 in the base arm 5 by fitting a fitting hole 13a into a fitting shaft 11a of the tip arm sliding shaft 11. In addition, the tip arm shaft 9
A second link plate 14 is also connected to the base arm 5 side by fitting the fitting hole 14a to the fitting shaft 9a of the distal arm shaft 9. Fitting holes 15, 16° and 17.18 are provided in the opposing surfaces of the first link plate 13 and the second link plate 14 at distances r, r,, r, and r2' from the center of rotation of the link plate. It's open. This fitting hole 15° 16, 17, 18 and the fitting hole 13a,
14a is manufactured by simultaneously machining the first link plate 13 and the second link plate 14, so the distance from the rotation center of each is r machin = r1 r.

= r2, and the angle α = β. Fitting hole 15,1
A pair of link shafts 15a, 16a and 17a, 18a having different lengths are attached to the tip arm sliding shaft 11, respectively.

Long link shaft 15a, short link shaft 17a, short link shaft 16
a and the long link shaft 18a are bearings 19a, 20a, 19b.
, 20b, 19c, 20c, 19d, 20d by links 21.22, respectively. The links 21 and 22 have different rotation surfaces so that they do not interfere with each other even when the link plates 13, 14 rotate.

Furthermore, the links 21 and 22 are made equal in distance 811e between their axes by simultaneous machining. Also e□t
The design dimension of e is set equal to the distance between the axes of the base arm 5.

In addition, link 21, . Disc springs 23 and 24 are inserted between the two bearings in each shaft support of 22, and the retaining plate 25 is used to connect the outer ring of the bearing, the ball, the inner ring of the bearing, the disc spring, the inner ring of the bearing, the ball, and the outer ring of the bearing. The preload is set over the entire range. 26 is a screw that fastens the presser plate 25 to the link 21.22.

The shaft supports at both ends of each link 21 and 22 are preloaded as shown in Fig. 7, but at least one shaft support is aligned in the axial direction, so the link shaft and the link (bearing inner ring) are not axially aligned. In other words, the inner ring of the bearing and the link shafts 15, 16 are fitted with precise clearance, and the inner ring of the bearing is fitted with the link shafts 15, 16.
A gap is provided to allow some movement in the axial direction.

There is also a method shown in FIG. 8 as another embodiment of this part. This is done by adding preload to the short link shaft 102 fixed to the first link plate 101 by means of a bearing nut 106 screwed into the short link shaft 102 into the inner ring of a pair of angular bearings 104 and 105 having a collar 103 in the outer ring. , while fixing one end of the link 107 to the outer ring of the angular bearing 104, 105,
A long link shaft 11 fixed to a second link plate 111 is attached to the inner ring of a pair of angular bearings 109 and 110 having a collar 108 in the outer ring at the other end of the link 107.
A sleeve 113 is slidably fitted into the angular bearing 109, 110, and a bearing nut 114 screwed into a threaded portion formed at one end of the sleeve 113 applies preload to the inner ring of the angular bearing 109, 110. Short link shaft 115 fixed to link plate 111 and long link shaft 116 fixed to first link plate 101
At both ends of the link 117 connecting the link 1
Similar to 07, there is a collar 11 on the outer ring on the short link shaft 115 side.
A pair of angular bearings containing 6 117.118
At the same time, a bearing nut 119 is screwed into the threaded part formed at the tip of the short link shaft to apply preload to the angular bearing, and a collar 120 is inserted into the outer ring on the long link shaft 116 side. A sleeve 123 that is slidably fitted to the long link shaft 116 is fitted to the inner rings of a pair of angular bearings 121 and 122, and a bearing nut 124 that is screwed into a threaded portion formed at one end of the sleeve 123 is inserted into the angular bearing. Preload is applied to the inner rings of bearings 121 and 122.

125.126.127.128 are each color 10
Set screws 129 and 130 fix the sleeves 123 and 113 to the long link shafts 116 and 112, respectively.

Note that 27 and 28 are lids attached to the base arm 5 and used during assembly.

Further, the diameters of the fitting holes 13a and 14a, 15a and 17a, 16a and 18a, and the bearing holes of the links 21 and 22 are the same.

On the other hand, inside the fixed base 1, a stator 27a of a DD motor 27 for driving the tip arm is fixed to the bottom 1a of the fixed base 1. The output shaft (rotor) 27b of the tip arm drive DD motor 27 is connected to the tip arm drive shaft 11.
It is installed so that it is coaxial with the Tip arm active D
The output shaft 27b of the D motor 27 is the tip arm drive shaft 11
It is fastened to a flange 28 connected to the lower end 11b of.

A gap is provided between the flange 28 and the flange 2. Further, a hollow shaft portion 4a is formed in the lower part of the spacer 4, passing through between the hollow portion 3d of the DD motor 3 for driving the base arm and the tip arm driving shaft 11,
A downwardly protruding portion 4a of the flange 2 of the hollow shaft portion 4a
A block 3o is connected within the gap. The block 30 is pivotally supported by the flange 28 via a bearing 32. 23 and 24 are disc springs that apply preload to the bearing 32.

A mechanical stopper for restricting rotation of the base arm is formed on the block 30 and comes into contact with a fixed stopper 33 fixed to the flange 2. Further, the block 3o is provided with a dog 34, and the flange 2
The origin is fixed to the bracket 35 provided on the base arm for detecting the rotation angle of the base arm, and the proximity switches 36, 37, and 38 for overrun detection are used to detect the rotation angle of the base arm.

A relay box 40 having a connector 39 connected to a controller (not shown) is provided on the back side of the fixed base 1.

Furthermore, a support column 41 for wiring is attached to the upper surface of the fixing table between the relay box 40 and the flange 2. A flexible conduit tube (hereinafter referred to as a conduit tube) 4 is connected to the upper end of the wiring support 41 via a rotary connector 42.
One end of 3 is connected.

The other end of the conduit tube 43 is provided at the rear upper part of the distal arm 1o so as to be approximately coaxial with the distal arm axis 9, and is connected to the distal arm 10 via a rotary connector 45 provided on the upper part of the cover 44. ing.

Inside the tip arm 10 , an AC motor 47 for driving the rotation of the work shaft and an AC motor 48 for driving the work shaft positioning stopper are provided on the parallel tip arm shaft 9 and are provided with a speed reducer 46 . The AC motor 47 is provided to be substantially coaxial with the tip arm shaft 9, and a timing pulley 48 is provided on the output shaft 46a of the reducer 46, and a timing pulley is provided on the output shaft 48a of the AC motor 48, which will be described later. 49 are connected.

On the other hand, the front part 10b of the tip arm 10 has spline bearings 51, 51' so that a pair of working axes 50.50' formed by splines are parallel to the tip arm axis 9.
, 52.52', radial bearing 53.53'
54 and 54', it is slidably and rotatably supported in the axial direction.

The spline bearings 51.51' and 52.52' are connected to the timing pulley 56 through sleeves 55.55'.
．． 56'. The timing pulley 56
．． 56' and the timing pulley 48 are rotationally connected by a timing belt 57.

The upper end portions 50a, 50a' of one working shaft 50.50' are the rods 58 of a pair of air cylinders 58°58' provided at the upper front part of the tip arm 10 in parallel with the working shaft 50.50'.
It is provided so as to be rotatable and integral in the axial direction by bearings 60 and 60' provided in joints 59 and 59' connected to the joints 59 and 58a'.

On the other hand, a sleeve 63 is rotatably supported in parallel to the working shaft 50.50' through bearings 61 and 62 at an intermediate portion of the working shaft 50.50' at the front of the tip arm 10. A timing pulley 64 is formed on the sleeve 63 above the bearing 61, and is rotatably connected to the timing pulley 49 by a timing belt 65, and a sliding stopper 6 having a thread formed on the outer periphery is attached above the timing pulley 64.
A bearing 67 having a female thread that fits into the male thread of No. 6 is fixed. Reference numeral 68 denotes a stopper portion formed on the top of the sliding stopper 66, and is guided in a slidable but non-rotatable manner by a guide 69 fixed inside the distal arm 10 in parallel to the axis of the sleeve 63. Reference numeral 70 is a cover provided at the front part of the tip arm 10.

Note that the inside of the robot, including the cover 70, the cover 44, the relay box 40, the lids 27 and 28, and the support member 6, is sealed from the outside.

70.7-1.71' is a proximity switch for the origin and overrun detection of the tip arm rotation angle detection device.

Further, 72 is a mechanical stopper for the tip arm fixed to the rear part 5a of the base arm 5, and is adapted to come into contact with the first link plate when the tip arm overruns.

In the present invention, a mechanical stopper 72 for the tip arm and a mechanical stopper 33 for the base arm are provided inside the robot. Therefore, safety is improved, and even if the robot overruns and contacts the mechanical stopper, the dust generated by the contact will not be released to the outside, so it can be used in environments that require cleanliness.

Although a block 30 with a mechanical stopper and a fixed stopper 33 are provided in the gap between the flange 2 and the flange 28, the output shaft 27b of the DD motor 27 for driving the tip arm and the hollow shaft portion 4a are used instead of the stopper.
A brake for stopping the rotation may be provided on the flange 2 or the fixed base. Further, in this case, it may be possible to stop the output shaft 27b of the distal arm drive DD motor and the hollow shaft portion 4a at once using one brake means.

Note that a work tool (not shown) is attached to the lower ends 50b, 50b' of the work shafts 50, 50'.

Further, 73 is a cable that is inserted into the conduit tube 43 and connects the relay box 40 and the distal arm 10. Since no electrical components are installed inside the base arm 5, there is no risk of cable breakage even if the links 21 and 22 rotate.

Of the two sets of parallelogram link mechanisms, links 18 and 19
Length ex, +3. are processed at the same time, so they are equal.

Also, the rotation center of the link plate 10.11 and the link 18
．． Distance between shafts of 19 shaft supports r1+ ri, rzt
Since rz' is also processed at the same time, they are equal.

In addition, since the support member 5 is structured so that its position can be adjusted during assembly, the distance between the axes of the base arm can be adjusted to L=e1(e2
), the rotation of the distal arm late movement shaft 3 is transmitted to the distal arm shaft.

Note that it is possible to simultaneously machine the two links and the base arm so that the distances between the axes e, e2, and L between the links 18 and 19 and the base arm 2 are equal, but the size of the link and the base arm, Since the machined hole diameters are extremely different, it is actually impossible to machine them simultaneously.

Also, the lids 27 and 28 are located at the rear of the base arm 5 (
These two holes are provided to seal the holes formed in the upper part of the base part and the lower part of the front (tip) part, but these two holes are working holes for assembling the links 21, 22, etc. into the base arm 5. However, since the base arm has a closed structure except for this hole and the pivot point facing the hole, high arm rigidity can be obtained (usually, an arm with a built-in link has a structure in which one side of the arm is completely closed). The rigidity was low because it became .

).

Further, an exhaust tube may be provided in the conduit tube 43 to suck in dust generated inside the robot from the outside. Since the conduit tube 43 is connected at one end to the approximate center of rotation of the distal arm 10 by a rotating connector, it can easily follow the rapid movement of the arm (conventionally, the resistance caused by bending or twisting the wiring attached to the arm (There was a problem with accuracy deterioration due to this.)

Next, we will discuss the effect.

Even if the distance between the first link plate 13 and the second link plate 14 differs from the design dimensions due to processing errors or assembly errors, in the case of FIG. 7, the bearings 19a, 19c, 20a,
Since the inner ring 20c and the link shaft 15, 16 slide, no excessive bending moment is generated in the shaft support.

In addition, even in the case of FIG. 8, the sleeves 113 and 12 are
3 to the long link shafts 112 and 116 to absorb the error in the distance between the first link plate 13 and the second link plate 14, and then remove the set screw 129.
．． At 130, the sleeve 113°123 is attached to the long link shaft 112
．． 116.

After assembly, when operating the robot, use the DD motor 3 for driving the base arm and the DD motor 27 for driving the tip arm.
By rotating the base arm 5 and the distal arm 10
rotates to position the work shaft 50, 50' in a plane, and also performs rotational positioning of the work shaft by the AC motor 47 for driving the rotation of the work shaft. At the same time, the stopper part 6 is moved by the AC motor 48 for active positioning of the work axis positioning stopper.
Position 8.

Next, either of the air cylinders 58, 58' is actuated to lower the working shaft 50, 50'.

Rod 58 of air cylinder 58.58' at desired height
a and 58a' come into contact with the stopper portion 68 and stop.

(Effects) As described above, according to the present invention, a drive shaft connected to a direct drive motor is fixed to the first link plate disposed inside the rear part of the base arm, and a bearing is attached to the front part of the base arm. The tip arm shaft is pivotally supported in parallel with the active shaft, the tip arm is fixed to the tip arm shaft, the second link plate is fixed to the tip arm shaft, and the distance between the drive shaft and the tip arm shaft is fixed. The phase difference between the two links is approximately 90 by using two pairs of supports, each of which has the same length as the first link plate and the second link plate at both ends of the two links, and which are provided at equal distances from the center of rotation. The two links are supported by bearings at the same time and parallel to the drive shaft, and at least one end of the two links is such that the support and the bearing or the bearing and the link are movable relative to each other in the direction of the support shaft. Therefore, in the link shaft support, the link can move in the axial direction with respect to the link shaft at least at one end, so the distance between the first and second link plates due to processing errors and assembly errors of the five parts Since errors can be absorbed, an accurate double link mechanism can be realized.

This prevents excessive bending moment from occurring in the link shaft support, making it precise and reasonable.

And stable rotation transmission is possible. At the same time as this.

Since a preload can be applied to the bearing, the natural frequency of the shaft support becomes high, and even when a DD motor is used as the rotational power source, the servo gain can be made sufficiently high, so the dynamic characteristics of the robot are improved.

In other words, according to the present invention, it can be said that the structure is optimal for a robot using a DD momo.

In addition, in the first embodiment (Fig. 7), by using angular bearings that are aligned face-to-face, it is possible to apply a larger preload and also absorb errors even if there is some degree of parallelism between the link shafts. can.

Further, by supporting the other end of the link in the same manner as the short link shaft of the second embodiment (FIG. 8), the rigidity can be further increased.

In the second embodiment (FIG. 8), since the sleeve is fixed to the link shaft with a set screw, the number of parts increases, but the rigidity can be further increased.

In addition, in the above-mentioned embodiment, the outer ring of the bearing is fixed to the link,
Although it is preferable to adjust the axial position on the inner ring side, it is also possible to fix the inner ring to the shaft and adjust the axial position of the outer ring (or a sleeve fitted to the outer ring) with respect to the link.

It can also be applied to quick-acting transmission means using simple parallel or non-parallel links other than double links, and can be applied to other structures in which the link plates are not arranged facing each other, such as Japanese Patent Laid-Open No. 63-7767
It is also possible to use two sets of two link plates like 4.

[Brief explanation of the drawing]

Fig. 1 is a front sectional view of an embodiment of the present invention, Figs. 2 and 3 are enlarged views of main parts of Fig. 1, Fig. 4 is an external side view of Fig. 1, and Fig. 5 is a plan view of the same. , FIG. 6 is a plan view of the link shown in FIG. 1, FIG. 7 is a front sectional view of the shaft support of the link shown in FIG. 6, and FIG. 8 is a front sectional view of the second embodiment of the link. 1... Fixed base 3... Direct motor for driving base arm 5...
Base arm 9...Tip arm shaft 10...Tip arm 11...Tip arm movement shaft 13...First link plate 14...Second link plate 21.22...Link 27...・Direct motor 27b for tip arm sleep
・・・Output shaft

Claims (1)

[Claims] A drive shaft connected to a direct drive motor is fixed to a first link plate disposed in the rear part of the base arm, and a tip arm shaft is pivotally supported in parallel to the drive shaft via a bearing in the front part of the base arm. , fix the tip arm to the tip arm shaft, fix the second link plate to the tip arm shaft, and connect both ends of the two links to the first link plate with a length equal to the distance between the drive shaft and the tip arm shaft. The link plate and the second link plate are each provided with a pair of supports provided at equal distances from the center of rotation.
The book is supported by bearings so that the phase difference between the links is approximately 90 degrees and parallel to the drive shaft, and the two links have at least one end where the support and the bearing or the bearing and the link are aligned in the direction of the support axis. A power transmission device for a robot, characterized in that it is capable of relative movement.