JPS6251880B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a gravity balance device for reducing or canceling out the gravitational moment acting on a swinging working arm (hereinafter referred to as an arm), and particularly for an arm of a working machine such as an articulated robot. The present invention relates to a gravity balance device suitable for use in.

A gravitational moment due to its own weight acts on the arm of an articulated robot. This gravitational moment changes in a cosine wave shape depending on the rotation angle of the arm, resulting in variations in positioning accuracy. Furthermore, since the gravitational moment acts downward, the response when the arm is tilted upward is slower than when it is tilted downward, which is not good in terms of control characteristics. Additionally, there are various methods for teaching a robot, but considering the method in which the operator directly operates the robot by holding the robot's tip, this requires a great deal of time and effort since the operator must move the heavy robot arm. , is inefficient.

Conventionally, methods of using balance weights or suspending robot arms with springs have been adopted to reduce the gravitational moment. However, in the case of balance weights, there are problems in that control characteristics are degraded due to an increase in inertial load, and the device cannot be made compact due to its structure. On the other hand, the method of balancing using a spring allows the device to be made compact, but it is difficult to maintain good balance over the entire rotational angle of the arm. The reason for this will be explained using the drawings as a result of studies conducted by the present inventor. First, FIG. 1 shows a structural diagram of a robot equipped with a conventional spring balance device. That is, the box part 510 placed on the floor 500
A pivot base 520 is provided on the upper surface of the box portion 510 so as to be pivotable. A first arm 530 is rotatably supported on the swing base 520, and a second arm 540 is also rotatably supported at the tip of the first arm 530. A hand 550 is attached to the tip. First arm 530 and second arm 540 and rotating base 52
0, there are a first arm drive cylinder 532 and a second arm drive cylinder 542, respectively, which position the respective arms. The first arm balance spring 570 is the first arm 530
and a rotating base 520 at both ends, and the first
A moment is applied to the arm 530 to resist gravity. Second arm balance spring 572
is locked at one end to the second arm 540 and at the other end to a triangular plate 562, which is connected to the first arm 530 and the parallel link 532.
, so that even if the first arm rotates, it will not tilt.

FIG. 2 is a schematic diagram showing a generalized version of the gravity balance device shown in FIG. Main body 10 and arm 2
A tension spring 40 is locked between the two ends. The angle formed by the arm side reference line 2 with respect to the horizontal reference line 1 is the rotation angle θ, the spring end installation angle on the arm side is α, the spring end installation angle on the main body side is β, and the spring end installation length on the arm side is m, and the installation length of the spring end on the main body side is n. Also, the spring constant of the tension spring 40 is k, and the free length is l ₀
shall be. At this time, the value of the spring force moment Ms based on the restoring force of the spring is calculated using the following formula.

As an example, in equation (1), k=1Kg/
mm, l ₀ = 480mm, m = 120mm, n = 600mm, β-α
Figure 3 shows a graph of the spring force moment obtained as a result of calculation by substituting =0°.

Incidentally, a gravity balance device needs to generate a force that resists the gravitational moment with a very high degree of approximation over the entire rotational angle of the arm (for example, in the case of articulated robots, it is often around 90 degrees). To this end, the gravity balance device must meet the following conditions:

(a) The spring force moment must be a cosine function within the rotation range of the arm.

(b) The amplitude of the spring force moment can be varied.

(c) The curve of the spring force moment can be moved parallel to the θ-axis direction.

Here, the conventional gravity balance device is used under the above conditions.
Consider whether or not (a), (b), and (c) are satisfied. (1)
As you can see from the form of the equation, the conventional balance device is
By appropriately setting the value of (β-α), the graph can be translated in parallel in the θ-axis direction. Furthermore, by changing the value of the spring constant k, the amplitude of the graph can be changed. Therefore, conditions (b) and (c) are satisfied. However, as shown in FIG. 3, the spring force moment is larger than that of a 360 degree period sinusoidal function curve (not shown). Here, the spring force moment is a sine function curve, which is
This is because β−α=0°. As already mentioned, since this balance device satisfies condition (c), the spring force moment can also be made into a cosine function.
Although it is possible to change the distortion somewhat by changing the values of m, n, and l ₀ , condition (a) cannot be satisfied. In other words, in conventional gravity balance devices, when using a spring in which the relationship between deflection and axial force is proportional, the free length of the spring, the spring constant, the spring end support position on the main body side, and the spring end support position on the arm side are No matter how you choose the variables that can be selected during design, the gravitational moment, which varies in a cosine manner with respect to the arm's rotation angle with respect to the horizontal plane, can be completely canceled out for all values of the arm's rotation angle. It is impossible to generate such a moment.

From the above considerations, the gravity balance device has a curve of the spring force moment that is θ so that the spring force moment can be approximated to a cosine function (corresponding to the gravitational moment) in the rotation angle range of the arm.
It was found that a function to expand and contract in the axial direction was necessary.

The purpose of the present invention is to reduce the gravitational moment acting on the arm over the entire range in which the arm can rotate.
The object of the present invention is to provide a gravity balance device that can perform cancellation with an extremely high degree of approximation.

A feature of the present invention is that in a gravity balance device for a work machine that balances the gravitational moment due to the weight of an arm rotatably supported on a support member, a conversion means for converting the rotation angle of the arm is provided, and the conversion means and the A force generating means for resisting the gravitational moment of the arm transmitted through the converting means is interposed between the support members, and the converting means is connected to the rotation axis of the arm and is integrally formed with the arm. A first gear constituting a speed change gear train provided so as to be rotatable; and a gear ratio that is mechanically engaged with the first gear and has a different number of teeth than the first gear. and a second gear constituting the speed change gear train, and the force generating means is set to rotate together with the second gear of the speed change gear train and have an arbitrary relative angle with respect to the arm. The force generating means is arranged to connect the tip of the sub-arm attached to the second gear and a proper position of the support member, and both connecting portions of the force generating means are connected to the sub-arm and the support member. A gravity balance device for a work machine that is rotatably supported by a shaft, which expands and contracts the curve of the moment that resists gravity in the direction of the axis of rotation of the arm, thereby creating a gravitational moment that acts on the arm due to the gravity. This almost cancels out the loss and improves the controllability of the work machine.

Embodiments of the present invention will be described below with reference to the drawings. In FIG. 4, the upper part of the main body 10 has an A-axis 1
There are 2. The arm 20 is supported by the A-axis 12 and is rotatable about the A-axis 12 as a rotation axis. Further, the A-axis 12 also supports the A-gear 102, and the A-gear 102 is also rotatable about the A-axis 12 as a rotation axis. Since the arm 20 and the A gear 102 are connected by the A coupling pin 22, the arm 20 and the A gear 102 rotate together. A B-shaft 14 is attached to the main body 10 below the A-shaft 12. The sub-arm 30 is supported by the B-axis 14 and is rotatable about the B-axis 14 as a rotation axis. Further, the B shaft 14 also supports a B gear 104, and the B gear 104 is also rotatable with the B shaft 14 as a rotation axis. Since the sub-arm 30 and the B gear 104 are connected by the B coupling pin 34, the sub-arm 30 and the B gear 104 rotate together. A gear 102 and B gear 104
are interlocked with each other, and arm 20 and sub arm 3
0 rotates synchronously while maintaining a constant ratio of each rotation amount. There is a tension spring 40 between the C pin 32 fixed to the sub-arm 30 and the D pin 16 fixed to the lower part of the main body, and both ends of this tension spring 40 are rotatable to the C pin 32 and the D pin 16, respectively. is supported by

When the rotation angle of the arm 20 is changed, the A gear 1
The rotation angle of the sub-arm 30 changes via the 02 and B gears 104, and the amount of deflection of the tension spring 40 changes. As a result, the spring force of the tension spring 40 and the distance from the B-axis 14 to the line of action of this spring force both change, so the spring force causes the sub-arm 30 to
The value of the moment acting on changes. In the end, the sub-arm 30 changes according to the change in the rotation angle of the arm 20.
The moment due to the spring force acting on changes. The moment due to this spring force is the B gear 104.
It is transmitted to the arm 20 via a transmission mechanism using the A gear 102 and the A gear 102. However, if the gear ratio between the B gear 104 and the A gear 102 is set appropriately, the arm 2
The arm 20
The moment of gravity acting on the spring force and the moment due to the spring force can be canceled out with a high degree of approximation. The reason for this will be explained below. However, the size relationship of the pair of internal gears in FIG. 4 does not necessarily represent an appropriate design result.

A schematic diagram of a gravity balance device based on the present invention is shown in FIG. A tension spring 40 is locked between the main body 10 and the sub-arm 30, and the sub-arm 30 and the arm 20 have an A gear 102 and a B gear 10, respectively.
4 is fixed, and the A gear 102 and the B gear 104 are meshed. The angle formed by the arm-side reference line 2 with respect to the horizontal reference line 1 passing through the rotation center of the arm 20 is θ.
When this θ becomes zero, that is, when the arm 20 rotates to the position where the arm-side reference line 2 coincides with the horizontal reference line 1, the center line 4 of the sub-arm 30 is used as a reference, and this reference line 4 and the sub-arm 30 are Let η be the angle formed by the sub-arm center line 3 after the displacement. With respect to the position where the tension spring 40 has the smallest deflection (that is, the position where the sub-arm tip spring mounting position is on the line connecting the sub-arm rotation center and the tension spring mounting position on the main body 10 side), θ=0. Let the angle formed by the corresponding sub-arm position 4 be ξ. Furthermore, the length of the spring end attached to the sub-arm side is m, and the length of the spring end attached to the main body side is n. In addition, the gear ratio of the A gear 102 and the B gear 104 is i:
Set to 1. Further, the angle formed by the sub-arm position 4 with respect to the horizontal line passing through the rotation center of the sub-arm is θ ₀ . Also, the rotation angle from the center line passing through the rotation center of the sub-arm to the sub-arm center line 3 is θ
Define as ₁ . Furthermore, β is an angle formed by a straight line connecting this rotation center and the support point of the tension spring 40 on the main body 10 side with respect to a horizontal line passing through the rotation center of the sub-arm 30, and α is an angle between the sub-arm side reference line 3 and the horizontal line passing through the rotation center of the sub-arm 30. It is the angle formed by the straight line connecting the rotation center of No. 30 and the support point of the tension spring on the sub-arm.
In the example shown, the tension spring support point on the sub-arm is
Since it is on the center line of the sub-arm 30, α=0.

At this time, from the definition of each angle, θ ₁ , η, ξ,
The following relationship holds between β, α, and _θ0 .

Therefore, θ ₁ −(β−α)=ξ+η. By substituting this result into equation (1), the spring force moment Ms acting on the sub-arm can be found as follows. However, l ₀ is the free length of the tension spring 40.

This moment Ms acts on the arm 20 via a gear transmission mechanism. Rotation angle η of sub-arm
and the rotation angle θ of the arm 20, η=−iθ
There is a function. Further, the moment acting on the arm 20 is 1/i in magnitude and opposite in direction to the spring force moment Ms acting on the sub-arm 30. Therefore, the moment acting on arm 20 is
If Ma, then after all becomes. As can be seen from the form of equation (4), by setting the value of ξ appropriately, the graph can be moved in parallel in the θ-axis direction, and by changing the value of k, the amplitude of the graph can be changed. Is possible.
Furthermore, by changing the values of m, n, and l ₀ , it is possible to change the distortion of the graph with respect to the sine function curve to some extent. The above effects can also be obtained with conventionally used gravity balance devices, but in the gravity balance device based on the present invention, by changing the value of i in equation (4), the graph can be adjusted in the θ-axis direction. It can be expanded and contracted. As an example, in equation (4), k = 1Kg/mm, l ₀ = 480mm, m = 120mm, n
The moment Ms acting on the sub-arm when = 600 mm and ξ = 115.3 degrees becomes a graph as shown in Fig. 6 versus η. On the other hand, i=0.75
Then, the moment Ma acting on the arm 20 is
The shapes of the curves are the same, but the values of the coordinate axes are different, and they can be expressed with respect to θ as shown in FIG. At this time, the amplitude also changes, but this can be compensated for by modifying the value of k.

Next, the effects of the present invention will be explained using specific examples. FIG. 7 is a graph showing the moment due to gravity and the moment Ma due to the balance device relative to the arm 20. θ is an angle from a horizontal line passing through the center of rotation of the arm 20, that is, a horizontal reference line 1, to a straight line connecting the center of gravity of the arm 20 and the center of rotation, that is, an arm-side reference line 2, and is referred to as a rotation angle. In FIG. 7, the arm 20 can be rotated within a rotation angle of -100° to 5°. The value -Mg, which is the inverted sign of the moment of gravity acting on the arm 20, changes according to a cosine function curve with respect to a change in the rotation angle θ of the arm 20 with respect to the horizontal plane. On the other hand, if the gravity balance device based on the present invention is used to obtain a moment with a graph extending in the θ-axis direction, the graph will look like Ma in Fig. 7,
A very close approximation to the gravitational moment can be obtained. However, Ma is k=
1.84Kg/mm, l ₀ = 640mm, m = 200mm, n = 800mm,
It was calculated as follows: ξ=115.3°, i=0.719, −100°≦θ≦5°.

The graph of curve Ms ₁ in FIG. 7 is an example of a moment obtained by a conventional gravity balance device. However, this graph shows that in equation (1), k = 1.3Kg/mm, l ₀ = 640mm, m = 200mm, n =
800mm, β-α=95°, -100°≦θ≦5°, which is calculated by changing the various parameters and selecting the one that most closely approximates the gravitational moment curve. This is what I chose.
Comparing the graphs Ms ₁ and Ma, it can be seen that the effects of the present invention are remarkable.

In the above embodiment, the tension spring 4 is used as the force generating means.
0 is used, but as in the example in Figure 8,
A compression spring 42 may be attached to a sub-arm 30 disposed on the opposite side of the arm 20. However, the size relationship of the gears in the gear train in FIG. 8 and subsequent figures does not necessarily represent an appropriate design result.

Further, as in the example shown in FIG. 9, a hydraulic cylinder 50 to which a constant hydraulic pressure is applied to one side may be used as the force generating means. In order to apply a constant hydraulic pressure to one side of the hydraulic cylinder 50, the hydraulic pressure source 52, the check valve 5
4. The relief valve 56 and the oil tank 58 may constitute a hydraulic circuit.

In order to consider the characteristics in this case, consider the case in which a cylinder 50 is used in place of the tension spring 40 in FIG. When the contraction force of the hydraulic cylinder is F, equation (1) can be replaced with the following equation (5).

In this case, the obtained moment is also greatly distorted compared to the cosine function. In FIG. 5, when a cylinder 50 is used in place of the tension spring 40, equation 3 is replaced by the following equation (6).

Equation (4) can be replaced with the following equation (7).

When a hydraulic cylinder is used, the moment is distorted differently than when a spring is used, but in this case as well, the graph can be expanded or contracted in the θ-axis direction by changing the value of i.

Below, an example in which the above-described gravity balance device is actually applied to a robot will be described. FIG. 10 is a schematic diagram of the mechanism of a robot to which the gravity balance device according to the present invention is applied. A main body column 222 is supported on the upper surface of the box part 210 placed on the floor 200 so as to be rotatable with respect to the box part 200, and a first arm 23 is rotatably supported with respect to the main body column 222.
A second arm 240 is also rotatably supported at the tip of the first arm 230, and a hand 25 is supported at the tip of the second arm 240.
0 is attached. the first arm 230
A first arm drive cylinder 232 whose both ends are locked to the main body column 222 positions the first arm. The second arm drive cylinder 242 has one end locked to the main body column 222 and the other end locked to an L-shaped plate A264, and the second arm 240 is positioned via this L-shaped plate A264 and the parallel link 260. conduct. The hand 250 is
Hand support link B294, L-shaped plate B290
and is supported by the main body column 222 via a hand support link A292.

In a robot with such a mechanism, even if the rotation angle φ of the first arm 230 changes, the rotation angle ξ of the second arm 240 does not change, so the value of the gravitational moment acting on the second arm 240 is It is a function only of ξ. Further, since the moment of gravity acting on the second arm 240 is supported via the parallel link 260, only the weight of the second arm is loaded on the first arm 230 side, and the moment of gravity acting on the first arm 230 The value of is a function only of the rotation angle φ of the first arm 230 measured from the horizontal reference line. Therefore, the gravity balance device according to the invention can be applied independently to each arm.

The 11th diagram shows the configuration when the gravity balance device based on the present invention is applied to the first arm.
It is a diagram. A D gear 300 is fixed to the first arm 230 with a fixing pin 320.
00 is the E gear 302 that acts as an idle gear
The F gear 304 is rotated via the . A sub-arm 310 is integrated into this F gear 304, and a first arm balance spring 270 is locked between this sub-arm 310 and the main body column 222.

Next, FIG. 12 is a diagram showing a configuration when the gravity balance device based on the present invention is applied to the second arm. The G gear 400 has a fixed pin 420
is fixed to the L-shaped plate A264, and the second
Arm 240 is engaged to L-shaped plate A264 via parallel link 260. Said G gear 4
00 is the H gear 402 that acts as an idle gear
The I gear 404 is rotated via. This I gear 404 is integrated with a sub-arm 410, and a second arm balance spring 472 is locked between this sub-arm 410 and the main body column 222.

However, the structure of the robot is not limited to that shown in FIG. For example, in order to apply the present invention to the second arm having the structure shown in FIG.
The rotation of
The arm balance spring 572 may be connected.

As described in detail above, according to the present invention, a gravity balance device can be obtained that can cancel out the gravitational moment acting on the arm with an extremely high degree of approximation over the entire range in which the arm rotates.

[Brief explanation of the drawing]

Figure 1 is a structural diagram of an articulated robot to which a conventional gravity balance device is applied, Figure 2 is a generalized schematic diagram of the conventional gravity balance device, and Figure 3 is a schematic diagram of a conventional gravity balance device. Figure 4 shows an example of a graph of the spring force moment obtained by
5 and 5 are schematic diagrams showing an embodiment of the present invention,
Fig. 6 is a diagram showing an example of a graph of the spring force moment acting on the arm and sub-arm, Fig. 7 is a diagram showing the relationship between the gravitational moment and the spring force moment due to the gravity balance device, and Figs. Figures showing other embodiments of the invention, Figure 10 is a structural diagram of an articulated robot to which the invention is applied, Figures 11 and 12 are diagrams showing the application of a gravity balance device to the first arm and second arm, respectively. FIG. 10...Main body, 12...A axis, 14...B axis, 20...
Arm, 30...Sub arm, 40...Tension spring, 4
2... Compression spring, 102... A gear, 104... B gear, 222... Main body column, 230... First arm,
240...Second arm, 264...L-shaped plate A,
270...First arm balance spring, 300...D gear, 302...E gear, 304...F gear, 310,
410...Sub arm, 400...G gear, 402...
H gear, 404...I gear, 472...2nd arm balance spring.

Claims (1)

[Scope of Claims] 1. A gravity balance device for a work machine that balances the gravitational moment due to the weight of an arm rotatably supported on a support member, comprising a conversion means for converting the rotation angle of the arm, the conversion means and A force generating means for resisting the gravitational moment of the arm transmitted through the converting means is interposed between the supporting members, and the converting means is connected to the rotation axis of the arm and is integral with the arm. a first gear constituting a transmission gear train provided so as to be able to rotate; and a first gear mechanically engaged with the first gear and set to a predetermined gear ratio having a different number of teeth from the first gear. and a second gear constituting the transmission gear train,
The force generating means rotates together with the second gear of the speed change gear train, and includes a tip of a sub-arm attached to the second gear and the support so as to be settable at an arbitrary relative angle with respect to the arm. A working machine characterized in that the force generating means is arranged so as to be connected to a proper position of the member, and both connecting parts of the force generating means are rotatably supported by the sub-arm and the supporting member. gravity balance device. 2. The gravity balance device according to claim 1, wherein the force generating means comprises a spring. 3. The gravity balance device according to claim 1, wherein the force generating means comprises a hydraulic cylinder that supplies a constant hydraulic pressure to either the head side or the rod side.