JPH04348884A - Industrial robot - Google Patents

Abstract

PURPOSE:To provide a robot suitable for assembly by providing such an arrangement that the vertical motion of a hand attached to a rotary member may be stopped at an arbitrary position. CONSTITUTION:A rotational power is transmitted to a bevel gear 60a from a d.c. servomotor 23 installed in the root section of a second arm 12, through a shaft 53 and a coupling 54, and the rotation of the bevel gear 60a is transmitted in a direction turned by an angle of 90 deg. by means of a bevel gear 60b, and is then transmitted to a spur gear 61a and a pinion 61b, successively, so as to vertically move a rack 62. Accordingly, upper and lower bases 64a, 64b are vertically moved so as to vertically move a hand 13. Since the hand 13 is moved up and down by the d.c. servomotor 23 through the intermediary of the rack 62 and the pinion 61b, it may be freely moved up and down, and may be stopped at an arbitray position.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to industrial robots.

0002

BACKGROUND OF THE INVENTION In recent years, automation of assembly work has been rapidly progressing through the introduction of robots in production processes. An example of a conventional industrial robot used for this purpose is shown in FIG.

This robot has a two-joint horizontal structure with a first arm 1 and a second arm 2. A DC servo motor 3 is provided at the base of the first arm 1 to directly drive the first arm 1, and a DC motor 3' is provided at the base of the second arm 2 which is pivotally supported at the tip of the first arm to drive the second arm. 2 is configured to directly drive the motor. 2nd arm 2
An air cylinder 4 is provided at the tip of the piston rod, a vertical shaft 5 is attached to the tip of the piston rod, and a hand 6 is pivotally supported at the lower end of the vertical shaft 5. Therefore, the hand 6 is moved up and down by the expansion and contraction of the air cylinder 4. Further, a stepping motor 8 fixed to the base 7 causes timing belts 9, 9', 9'' and pulleys 10, 10',
The rotational force is transmitted to the hand 6 through 10''10''' to perform a twisting motion.

The above-mentioned robot (FIG. 1) has two degrees of freedom in the horizontal plane by the first arm 1 and the second arm 2, and one degree of freedom in the vertical direction.
4 degrees of freedom and 1 degree of freedom for twisting the hand
It has a degree of freedom and is used for assembling parts from above.

[0005]

The conventional industrial robot described above has the following two drawbacks.

The first drawback is that since the vertical movement of the hand is driven by an air cylinder, arbitrary positioning in the vertical direction is not possible. If a mechanical stopper is provided, the stop position can be accurately set at the end of the stroke of vertical movement, but if the stop position is to be changed, the stopper position must be corrected, so it is not possible to immediately respond to changes in the movement pattern. The second drawback is that the twisting shaft of the hand is driven by a drive system equivalent to direct connection to a stepping motor, which tends to cause the stepping motor to step out, making control difficult.

An object of the present invention is to eliminate the drawbacks of the conventional robots described above, and to provide an industrial robot that can stop the vertical movement of the hand at any position with high precision. It's about doing.

[0008]

[Means for Solving the Problems] In order to achieve the above object, the present invention includes a base, a first support member supported on the base so as to be able to swing about a first vertical axis, an arm, a second arm supported so as to be swingable about a second vertical axis provided at a swing end of the first arm, and a tip of the second arm that can move up and down; a vertically movable member supported as such, a rotating member formed to be able to move vertically together with the vertically movable member and rotate about a third vertical axis, and provided on the second arm; and a vertical movement drive motor connected to the vertical movement member via means for converting rotational motion into linear movement to move the vertical movement member and the rotation member up and down, and a vertical movement drive motor provided on the base and the rotation member. An industrial robot comprising: a rotary drive motor connected to rotate the rotating member about the third vertical axis; and a hand attached to a lower end of the rotating member.

[0009]

[Function] With the above structure, the rotational motion of the vertical motion drive motor is converted into linear motion, and is then decelerated and transmitted to the vertical motion member, so that it moves up and down together with the vertical motion member and rotates around the fourth axis. Since the hand attached to the rotating member can be accurately positioned in the vertical direction and the rotating member can be rotated by a predetermined amount, a wrist mechanism most suitable for assembly work can be obtained.

0010

Embodiment An embodiment of the present invention will be described below with reference to FIGS. 2 to 7.

FIG. 2 is a side view of an embodiment of the industrial robot according to the present invention, and FIGS. 3 and 4 are side views similarly cut at the center.

This robot has a three-degree-of-freedom configuration including a two-joint structure consisting of a first arm 11 and a second arm 12, and a hand mechanism that moves up and down at the tip of the second arm 12.
The rotation of the hand 13 is not controlled, and the hand 13 has a mechanism that keeps the posture (angle with respect to the ground) constant. Note that a four-degree-of-freedom configuration that also controls the rotation of the hand 13 will be described later.

The first arm 11 has a two-part structure, and the lower first arm 11' is directly driven via a speed reducer 31 by a DC servo motor 21 installed on a base 20 coaxial with its pivot shaft. The upper first arm 11' is rotatably supported around its pivot axis, and the lower first arm 11' and the first arm 11'' are rotatably supported with respect to the first arm 11 between their tips. The second freely pivoted
An arm 12 is sandwiched between them, and they are connected by a shaft 15.

The second arm 12 is configured to transmit the output of a DC servo motor 22 installed on a base 20 coaxially with the pivot shaft of the first arm 11 to a double crank 42 via a speed reducer 32. Here, the output shaft 18 of the double crank 42 is
It is rotatably supported on the first upper arm 11'. The above double crank 42 has an output shaft 18 as shown in FIG.
Two crank pins 42a and 42b having a phase difference of 90° on the same diameter are provided. In response to this, the second
Also at the base of the arm 12 are two crank pins 1 having a phase difference of 90° on the same diameter with respect to the second shaft 15 that pivots the arm.
2a and 12b are provided. The front crank pin 42a and the front crank pin 12a are connected by a connecting rod 52a, and the front crank pin 42b and the front crank pin 12b are connected by a connecting rod 52b to form a double link mechanism.

The wrist mechanism includes a vertically movable member consisting of bases 64a, 64b and a rack 62, a rotating bracket 74a,
74b, a rotating member consisting of a spline shaft 65, and a hand 1
3, and its outline consists of a pair of upper and lower bases 6
4a and 64b are connected via a rack 62, and a spline shaft 65 is rotatably supported by the pair of bases 64a and 64b as described below, and the hand 13 is attached to the lower end of the spline shaft 65 to form a tool holding shaft. .

Rotating brackets 74a and 74b (rotating members) are rotatably supported on the pair of upper and lower bases 64a and 64b, respectively, and the upper end of a spline shaft 65 (rotating member)
The lower ends are fixed to the rotating brackets 74a and 74b, respectively. Thereby, the spline shaft 65 is rotatably supported around the fourth axis (fourth vertical axis) AA. Further, a bearing holder 67 is fixed to the tip of the second arm 12 so as to rotatably support a spline bearing 66 for slidingly guiding the spline shaft 65 about the fourth shaft AA. A sprocket 45 that penetrates the spline shaft 65 is fixed to the spline bearing 66. As a result, the hand 13
A hand mechanism supporting the second arm 12 is rotatably supported at the tip of the second arm 12, and as will be described in detail next, the hand 13 can be moved up and down via a rack 62 provided on a third vertical axis. Configure. The rack 62 and spline shaft 65 are covered with bellows 68 to prevent dust.

A DC servo motor 2 is installed at the base of the second arm 12.
3 (first driving means), and transmits its rotational output to the bevel gear 60a via the shaft 53 and the coupling 54, and the rotation direction of the bevel gear 60a is changed by 90 degrees by the bevel gear 60b, It is configured to be transmitted sequentially to the gear 61a and pinion 61b to drive the rack 62 up and down. The vertical movement of the rack 62 is guided by a spline shaft 65 and a spline bearing 66, the roller 63a is configured to prevent the rack 62 from rotating around the fourth axis AA, and the roller 63b is configured to support the rack 62 against engagement with the pinion 61b. It has been done. As a result, the rack 62 is moved up and down, the upper and lower bases 64a and 64b fixed to the rack 62 are moved up and down, and the hand 13 is driven up and down. The vertical movement of hand 13 is done by rack 6.
Since it is driven by the DC servo motor 23 via the pinion 61b and the pinion 61b, it can be moved up and down freely and stopped accurately at any position. Any means such as a feed screw provided on the third vertical shaft and a nut combined therewith may be used as a means for converting the above-mentioned rotational motion into linear motion.

Next, the rotation mechanism of the hand 13 will be explained. A sprocket 45' which is fixed to the base 20 and is rotatably provided to the first shaft 16 via a chain 54'' to a sprocket 45' which is rotatably provided to the shaft 15 which is coaxial with the second shaft 17. Then add sprocket 4
5' is connected to a sprocket 45 via a chain 54'. Since the sprocket 45 is fixed to the spline bearing 66, the hand 13 can be rotated via the spline shaft 65 by rotating the sprocket 45. Here, sprocket 45" is the base 2
Since it is fixed at 0, the rotation of the hand 13 cannot be controlled, but the mechanism is such that it always maintains a constant angle with respect to the base 20 regardless of the rotation of the first arm 11 and the second arm 12.

If the assembly parts have no directionality, a three-degree-of-freedom robot like the one described above is sufficient;
If it becomes necessary to control the robot as well, it can be easily constructed into a four-degree-of-freedom robot as described below.

As shown in FIG. 7, a DC servo motor 24 (rotary drive motor) is installed on the base 20, its rotation is reduced by a reducer 34, and the rotation is reduced to the base 20 via a sprocket 44 and a chain 54'. Free the sprocket 45'' that was fixed to the
A sprocket 44' is added to the sprocket 44' so that it can rotate and perform the twisting motion of the hand.The reason why a chain is used as the power transmission element for this twisting motion is to ease maintenance. Endless parts such as belts require disassembly of the shaft part when assembling and removing them.However, since chains are not endless, the chain can be assembled and removed without leaving the shaft part as it is. Can be done.

Finally, the features of the link mechanism will be explained.

In FIG. 6, the double crank 42 rotated by the DC servo motor 22 has two transmission paths with a phase difference of 90 degrees, that is, the crank pin 42.
a, the second arm 12 is driven via the connecting rod 52a, the crank pin 12a and the crank pin 42b, the connecting rod 52b, and the crank pin 12b. Therefore, the second arm 12 can be rotated over a wide range without having to worry about problems unlike in the case of a single crank. In this embodiment, rotational drive of approximately 300° is possible.

Furthermore, the double link mechanism moves so that the crank pins 42a, 42b, 12b, 12a are always located at the vertices of the parallelogram. Therefore, when the first arm 11 is rotated while the double crank 42 remains stationary, the second arm 12 moves in parallel along the second arm 17, which is the central support axis.

As described above, since the second arm 12 moves in parallel and the drive motor is installed on the base 20, the moment of inertia of the rotating portion of this robot is significantly smaller than that of conventional robots. Next, the principle is shown in Figures 8 and 9.
Explain using.

FIG. 8 shows the first robot of the conventional type shown in FIG.
This is a schematic representation of the case where arm 1 rotates by an angle θ, where 2 is the second arm, a1 is the concentrated mass of the first arm 1, and a2 is the first
The mass of the arm drive motor 23, a3 is the concentrated mass of the second arm 2,
a4 is the concentrated mass of the hand mechanism. The lengths of the first arm 1 and the second arm 2 are both 2a.

When the first arm 1 is rotated by an angle θ, the second arm 2
is also rotated by an angle θ. Therefore, the moment of inertia J of the first arm 1 is J=a1r12+a2r22+a3r32+a4
It becomes r42. However, r1 is the radius of rotation of a1, r2 is the radius of rotation of a2, r3 is the radius of rotation of a3, and r4 is the radius of rotation of a4.

FIG. 9 is a diagram schematically showing the case where the first arm 11 of the above embodiment rotates by an angle θ.

As explained with reference to FIG. 6, in the assembly robot according to the present invention, when the first arm rotates by an angle θ, the second arm
The arm translates along the second axis. Therefore, the radius of rotation of the second arm is not the sum of the length of the first arm. Therefore, the moment of inertia J' of the first arm 11 is J'=(m1+
m5) r12+m3r'32+m4r'42. m
5 is the mass of the link 10.

[0029] Here, both the length of the first arm and the second arm are 2a.
Comparing the moments of inertia in Figures 8 and 9, J=m1a2m2(2a)2+m3(3a)2+m4(
4a) 2=(m1+4m2+9m3+16m4)a2J
'=(m1+m5)a2+m3(2a)2+m4(2a
) 2 = (m1 + 4m3 + 4m4 + m5) a2 Design Since m2 > m5 is considered common sense, it is clear that J >>J'
becomes.

For example, m1=5Kg, m2=3Kg, m
3=4Kg, m4=3Kg, m5=1Kg, 2a=0.
When calculated as 4m, J = 4.04Kgm2, J
' = 1.36Kgm2, and by applying the present invention, the moment of inertia of the first arm is approximately 1/1 compared to that of the conventional robot.
It becomes 3.

As a result, when the present invention is applied, the drive motor for the first arm can be made to have a significantly smaller capacity at the same operating speed as the conventional one. Furthermore, if the drive motor for the first arm is made comparable to the conventional one, the operating speed will be significantly faster.

[0032]

[Effects of the Invention] As explained above, according to the present invention,
The vertical movement of the hand attached to the rotating member can be stopped at a desired position with high precision, resulting in an excellent practical effect of providing a robot most suitable for assembly work.

[Brief explanation of drawings]

[Figure 1] Front view of a two-jointed industrial robot commonly used in the past.

FIG. 2 is a front view of the industrial robot according to the present invention;

[Figure 3
] A central sectional view of the industrial robot in Figure 2,

[Fig. 4] A central sectional view of the industrial robot in Fig. 2;

[Fig. 5] Plan view of the tool holding shaft drive part,

[Fig. 6] Plan view of the double link part,

[Fig. 7] Front view of the tool holding shaft rotation drive motor section,

[Figure 8
] Schematic diagram showing a conventional industrial robot mechanism,

FIG. 9 is a schematic diagram showing a link mechanism of an industrial robot according to an embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 11... First arm, 12... Second arm, 20... Base, 21, 22, 23, 24... Drive motor, 42... Double crank, 52a, 52b... Connection rod of double link mechanism, 54, 5
4f, 54″...Chain, 60a, 60b...Bevel gear, 61a, 61b...Spur gear, 62...Rack, 65...Spline shaft, 66...Spline bearing.

Claims (1)

[Claims] 1. a base; a first arm supported so as to be swingable about a first vertical axis on the base; and a second vertical axis provided at a swinging end of the first arm. a second arm supported so as to be able to swing around; a wrist mechanism that is provided to be slidable in the vertical direction via a third vertical shaft provided at a swinging end of the second arm; , a drive motor that supplies a driving force for vertically sliding the wrist mechanism provided on the second arm, and a rotational movement of the drive motor on the third vertical axis; a conversion mechanism in which a rotary movement member is arranged on the second arm and a linear movement generating member is arranged on the wrist mechanism so as to convert the movement into a linear movement; A rotating member disposed in the mechanism and formed to be able to rotate around a fourth vertical axis, and sliding the rotating member in the vertical direction by transmitting the motion of the linear motion generating member to the rotating member. and a connecting member that connects the linear motion generating member and the rotating member so as to rotatably support the rotating member, and a connecting member that connects the rotating member to rotate about the fourth vertical axis. An industrial robot characterized by having a rotary drive motor.