JPH1179685A - Balancer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a balancer which quickly winds up or extends a cable according to changes in tension of the cable caused by the movement of a material to be supported and has a simple structure in the wind-up type balancer having a long cable wound around a rotating drum. SOLUTION: This balancer is provided with a drive shaft 1 which is provided with a screw groove 101 having a prescribed lead angle, a nut 2 which is threadly engaged with the screw groove, a drum 3 for winding a cable 4 which is coaxially fixed to the nut 2 and supported by the circumference of the drive shaft 1, and an elastic member which applies a pressing force f2 against the thrusting force f1 in the axial direction of the nut 2 to the end face of the nut, when the drum is relatively rotated about the drive shaft 1 in the direction for extending the cable, and when the thrusting force f1 by the tension of the cable 4 is larger than the pressing force f2, the drum 3 is smoothly rotated about the drive shaft 1 in the direction for extending the cable 4, and in the reverse case, the drum 3 is rotated in the direction for winding up the cable 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a balancer that immediately takes up or unwinds a long cord wound around a rotary drum in response to a change in the tension of the cord.

[0002]

2. Description of the Related Art There is a demand that an object having a certain weight be supported in the air and stopped at an arbitrary height, and that the supporting height can be easily changed by applying a small external force. A mechanism that meets such a request will be referred to herein as a “balancer”.

There are various types of balancer mechanisms. For example, those using a spring, those using a counterweight, those using a crane using hydraulic pressure or pneumatic pressure, those using a winch type using a motor or the like can be used. Both methods have a common point in that the weight of the supported object is supported and balanced by a spring, a counterweight, or the like, and a movement in the direction of the force is given according to a force applied to the supported object from the outside. .

[0004] As an application of the balancer, in addition to a large supporting weight (several tens of kg to 100 kg) and an extremely wide movable range, there is a demand for quick follow-up. For example, this is a case where a work robot is supported on a wide wall surface having a height of several tens of meters. Such a robot can move up, down, left, and right on the wall while supporting its own weight with a moving function equipped with a suction cup.However, in rare cases, it may fail to adsorb to the wall and move at high speed over a wide range. Can not.
In this case, the balancer can support the entire weight of the robot as needed and can be lifted and lowered at high speed, and while the robot is attached to the wall and moving by itself, it applies a certain tension to the rope. In addition, it is required that the robot can quickly follow the movement so that no excessive force is applied to the robot.

[0005] When such a wide movable range and a large supporting weight are required, a winch-type roll-up balancer is a candidate. The winch-type one generally has a strong and heavy mechanism itself, and the rope tension is high. The time delay from the change to the response operation becomes a problem. The drive shaft input control method using a relay circuit or a mechanical clutch cannot expect such a quick response as is problematic here. Of course, it is possible to adopt precision control by electronic control circuit and servo motor,
Expensive.

[0006]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a hoist-type balancer having a long cable wound around a rotary drum. An object of the present invention is to provide a balancer that can immediately perform a winding or unwinding operation of a cord according to a change in tension and that has a simple structure.

[0007]

The above object can be attained by a balancer whose structure is schematically explained with reference to FIG. 1 attached to the present specification. FIG. 1 is a partially cutaway elevational view showing a configuration of a main part of a balancer, wherein reference numeral 1 denotes a drive shaft, 101 denotes a thread groove provided on the drive shaft 1, 2 denotes a nut,
Is a drum for winding the rope, 4 is a rope, f1 is an axial thrust generated in the nut 2 when the drum 3 rotates in the direction in which the rope 4 is fed, and f2 is f1 on an end face of the nut 2 by an elastic member (not shown). Is the pressing force applied in the opposite direction. A hatch symbol at the left end of the pressing force f2 schematically shows a stationary member that becomes a fulcrum of the elastic member. Further, arrows indicating f1 and f2 do not indicate the magnitude of the force, but simply indicate the direction of the force.

That is, the balancer of the present invention (hereinafter referred to as “the machine”) has a thread groove 101 having a predetermined lead angle.
And a nut 2 screwed into the screw groove 101
And a drum 4 for winding the rope 4 which is coaxially fixed to the nut 2 and supported around the drive shaft 1, and when the drum 3 is rotated relative to the drive shaft 1 in a direction in which the rope 4 is extended. An elastic member that applies a pressing force f2 opposing the axial propulsion force f1 of the nut 2 to the end face of the nut 2, and if the axial propulsion force f1 of the nut 2 due to the tension of the cable 4 is greater than the pressing force f2, It is characterized in that the drum 3 smoothly rotates relative to the drive shaft 1 in the direction in which the thread 4 is extended, and in the opposite case, in the direction in which the cable 4 is wound.

Since this machine is provided with the drum 3 on which the long cord 4 is wound, the object to be supported can be lifted and lowered at high speed in a wide range as required. In a state where the weight of the supported object is supported and balanced by another means (for example, a suction cup of a robot), for example, a force generated by the self-motion of the supported object is generated through the relative rotation of the drum 3 and the drive shaft 1. Absorbed by elastic members. That is, when the axial propulsion force f1 of the nut 2 generated by the tension of the cable 4 applied to the drum 3 and the pressing force f2 of the elastic member against the end face of the nut 2 are balanced, the drum 3 moves with respect to the drive shaft 1. At rest, if these two forces are not equal, the drum 3 and the drive shaft 1 rotate relatively.

The initial load of the machine is adjusted by adjusting the strength of the elastic member while the drive shaft 1 is stationary, so that the drum 3 is driven in a state where a predetermined tension is applied to the cable 4. Nut 2 on the side which is stationary with respect to and on which the pressing force f2 acts
In such a manner that the end surface of the nut comes to the middle point of the moving range (stroke) of the nut 2. Note that the predetermined tension may be a magnitude that balances with the weight of the supported object or may be smaller. The case where the tension is balanced with the weight of the supported object corresponds to the case where the supported object has no ability to support its own weight, and the case where the tension is smaller than that corresponds to the case where the own weight supporting capacity of the supported object can be expected to some extent. Any of these cases can be dealt with by appropriately selecting the elastic constant of the elastic member. In this machine whose load has been adjusted in this way, the nut 2 reciprocates before and after the midpoint of the stroke in accordance with the relative swing between the drum 3 and the drive shaft 1 irrespective of the stop or rotation of the drive shaft 1. Perform balance while exercising.

In this state, it is assumed that a downward force acts due to, for example, the movement of the supported object. This force increases the tension of the rope 4, so that the axial thrust f1 of the nut 2 becomes larger than the pressing force f2, and as a result, the drum 3 immediately rotates relative to the drive shaft 1. The rope 4 is extended. Conversely, when the force acts upward and the tension of the rope 4 decreases, the drum 3 immediately rotates relative to the direction in which the drum 4 takes up the rope. Therefore, the apparatus follows the movement of the supported object very quickly, and does not apply an excessive force to the supported object.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As a preferred embodiment of the present invention,
The sliding friction coefficient between the screw groove 101 and the nut 2 when the lead angle of the screw groove 101 is about 45 ° and the axial propulsion force f1 of the nut 2 is larger than the pressing force f2 or vice versa. Is set within an angle range that is equal to or less than a practically allowable value.

The “lead angle” in the present machine is the angle between the tangent of the thread groove 101 provided on the drive shaft 1 and the cross section of the drive shaft 1. When a rotational force is applied to the nut 2 by the tension of the cable 4 being applied to the drum 3, there is no problem even if the lead angle is, for example, about 30 °. On the other hand, when the pressing force applied to the end face of the nut 2 generates a rotational force of the nut 2, if the lead angle has the above value, the thread groove 10
The coefficient of sliding friction between the nut 1 and the nut 2 becomes excessive, preventing smooth rotation. In this case, the lead angle is, for example, 60 °.
The above values would be desirable. However, with such a large lead angle, the rotation of the drum 3 due to the tension of the cable 4 may interfere. Therefore, in order to satisfy both cases, it is conceivable to set the lead angle to around 45 °.

However, the lead angle in this machine is not limited to 45 °, and the optimum values are the materials of the screw 101 and the nut 2, the lubrication method, the structure (for example, ball screw), the diameter of the screw 101 and the diameter of the drum 3. It changes depending on design conditions such as the ratio. Therefore, according to these design conditions, the sliding friction coefficient between the screw groove 101 and the nut 2 is suppressed to a value that is practically allowable or less, and the lead angle at which the nut 2 can smoothly rotate with respect to the screw groove 101 is reduced. It is desirable to choose.

As another embodiment of the present invention, the elastic member may be a coil spring inserted between a stationary member including a bearing for supporting the drive shaft 1 and an end face of the nut 2. In order for the coil spring to effectively apply a pressing force to the entire stroke of the nut 2, it is desirable that the coil spring has a natural length greater than the stroke of the nut 2 and its strength can be adjusted. In order to realize smooth rotation of the nut 2, it is also important to slide between the tip of the coil spring and the end face of the nut 2, so that a bearing or the like may be interposed between them.

As still another preferred embodiment of the present invention, starting, stopping, rotation direction and speed of a prime mover for driving a drive shaft are controlled by sensors provided near both ends of the stroke of the nut 2. Can be.

As described above, in this machine, the force generated by the self-motion of the supported object is transferred to the drum 3 and the drive shaft without waiting for the change in the tension of the cable 4 to be converted into the change in the input to the drive shaft 1. It is absorbed by the elastic member through the relative rotation with respect to 1. However, the effective operation of the elastic member is limited to within the stroke of the nut 2, so when the nut 2 reaches its stroke limit, the tension state of the cable 4 at that time is reflected in the input to the drive shaft 1. Then, it is necessary to cope with the situation by changing the rotation state of the drive shaft 1. That is, in this state, if the drive shaft 1 is stopped, it is necessary to start the prime mover to rotate the drive shaft 1 in a desired direction, or to change the speed if the drive shaft 1 is rotating.

The above control operation can be realized by providing at least one position sensor in the vicinity of the stroke limit point of the nut 2 and guiding its output signal to a control circuit including an appropriate logic circuit. For example, when an inverter-controlled AC motor is used as a prime mover and a limit switch or the like is used as a position sensor, all of the detection and control operations can be performed by electric signals, which is convenient. In consideration of the delay time of the control, it is desirable that the mounting position of the sensor is set slightly inside of the stroke limit point of the nut.

When the apparatus is fixedly installed at a predetermined position, the drum 3 reciprocates in the axial direction of the drive shaft 1 with the balance operation, and the rope 4 is extended from the drum 3. Also, since the hanging position of the cable 4 moves when it is wound up, the direction of the cable 4 connecting the machine and the supported object is inclined from the vertical, so that a horizontal component force harmful to the supported object is released. It can happen. A similar phenomenon occurs when the supported object moves in a horizontal direction. Therefore, in order to avoid this, for example, it is conceivable to provide a rail parallel to the drive shaft 1 and mount the machine on the rail via a pulley so as to be slidable in the horizontal direction.

[0020]

An embodiment of the present invention will be described with reference to FIGS. 2A and 2B. FIG. 2A shows a balancer 100 according to the present embodiment.
FIG. 2B is a partially cutaway plan view showing the overall configuration of FIG. 2, and FIG. 2B is a detailed view of the sensor unit. The same components as those in FIG. 1 are denoted by the same reference numerals.

2A and 2B, reference numeral 5 denotes a coil spring for generating the pressing force f2, 6 denotes a bolt for adjusting the strength of the coil spring 5, and 7 denotes a bearing for supporting the drive shaft 1 and one end of the coil spring 5. 8 is a thrust bearing inserted between the other end of the coil spring 5 and the end face of the nut 2, 9 is a movable plate (see FIG. 2B) provided at a floating end of the adjusting bolt 6, and 10 is movable. A sensor for detecting the position of the plate 9 (the same), 11 is an AC motor as a prime mover, 12 is a gear train connecting the AC motor 11 and the drive shaft 1, 13 is a roll for sliding the cable 4, and 14 is A drive shaft rotation angle detection sensor for displaying the extension length of the cable 4, 15 is a protective cover, and 16 is a base plate. An even number of coil springs 5 are evenly arranged around the drive shaft 1 so that the pressing force applied to the end face of the nut 2 is not eccentric.

The balancer 100 of this embodiment has a drive shaft 1 provided with a screw groove 101 having a predetermined lead angle, a nut 2 screwed into the screw groove 101, and a drive shaft 1 fixed coaxially to the nut 2. Drum 4 for winding four ropes supported around
And a coil spring 5 for applying to the end face of the nut 2 a pressing force f2 that opposes the axial propulsion force f1 of the nut 2 when the drum 3 is rotated relative to the drive shaft 1 in the direction in which the cable 4 is extended. When the axial propulsion force f1 of the nut 2 due to the tension of the rope 4 is larger than the pressing force f2, the drum 3 is driven in the direction in which the rope 4 is extended, and in the opposite case, in the direction in which the rope 4 is wound up. It is characterized by relative rotation with respect to 1. In this case, a thrust bearing 8 is inserted between the tip of the coil spring 5 and the end face of the nut 2,
Since the lead angle is set to 45 °, the drum 3 rotates smoothly relative to the drive shaft 1 in any of the above directions.

The balancer 100 is provided with a drum 3 on which a long cable 4 is wound, and on a wide wall having a height of several tens of meters, for example, a heavy (several tens kg to 1) like a working robot.
00kg) The object to be supported can be lifted and lowered at high speed as needed. In a state where the weight of the supported object is supported and balanced by other means (for example, a suction cup of the robot), for example, a force generated by the self-motion of the robot is transmitted through a coil spring via the relative rotation between the drum 3 and the drive shaft 1. Absorbed by 5. That is, when the axial propulsion force f1 of the nut 2 caused by the tension of the cable 4 applied to the drum 3 and the pressing force f2 of the coil spring 5 against the end face of the nut 2 are balanced, the drum 3 moves with respect to the drive shaft 1. When the two forces are not equal, the drum 3 and the drive shaft 1 rotate relatively.

The initial load of the balancer 100 is adjusted by turning the bolt 6 and adjusting the strength of the coil spring 5 while the drive shaft 1 is stationary. That is,
When a predetermined tension (for example, 10 kg) is applied to the cable 4, the drum 3 is stationary with respect to the drive shaft 1, and the end face of the nut 2 on the side on which the pressing force f <b> 2 acts is the moving range (stroke) of the nut 2. At the midpoint of. The balancer 100 thus adjusted in load responds to the relative swing between the drum 3 and the drive shaft 1 regardless of whether the drive shaft 1 is stopped or rotated.
The nut 2 performs a balance operation while reciprocating before and after the midpoint of the stroke. At this time, the head of the bolt 6 reciprocates in a direction perpendicular to the surface of the stationary member 7.

In this state, it is assumed that a downward force acts on the object to be supported, for example. This force increases the tension of the rope 4, so that the axial thrust f1 of the nut 2 becomes larger than the pressing force f2, and as a result, the drum 3 immediately rotates relative to the drive shaft 1. The rope 4 is extended. Conversely, when the force acts upward and the tension of the rope 4 decreases, the drum 3 immediately rotates relative to the direction in which the drum 4 takes up the rope. Therefore, the balancer 100 follows the movement of the supported object very quickly,
Does not give excessive force to the supported object. The cable 4 is smoothly fed out or wound up via a roll 13 provided adjacent to the drum 3.

As described above, in the balancer 100, the force generated by the self-movement of the supported object is applied to the drum 3 and the drive shaft 1 without waiting for the change in the tension of the cable 4 to be converted into the change in the input to the drive shaft 1. Absorbed by the coil spring 5 via the relative rotation of However, the effective operation of the coil spring 5 is limited to the stroke of the nut 2. Therefore, when the nut 2 reaches the stroke limit, the tension state of the cable 4 at that time is input to the drive shaft 1. The reflection must be taken into account by changing the rotation state of the drive shaft 1. That is, in this state, if the drive shaft 1 is stopped, it is necessary to start the prime mover to rotate the drive shaft 1 in a desired direction, or to change the speed if the drive shaft 1 is rotating.

In the balancer 100, an AC motor 11 controlled by an inverter is used as a prime mover, and its rotational force is transmitted to the drive shaft 1 via a gear train 12. A movable plate 9 is attached to the head of a bolt 6 that moves with the expansion and contraction of the coil spring 5, and the position of the movable plate is determined by a sensor 10.
To control the rotation of the AC motor 11 by guiding the output signal of the sensor 10 to a control circuit (not shown) including an appropriate logic circuit. For example, an optical sensor is used as the sensor 10, and two sensors 1 are provided near the limit of the movable range of the movable plate 9 corresponding to the stroke of the nut 2.
0 is provided. Of the four sensors in total, the inner two inform the control circuit that they are approaching the limit, and the outer two inform them that they have reached the limit. By providing two sensors 10 near the limit point in this way,
Since the moving speed of the nut 2 can be detected, the detected speed is reflected in the speed control of the AC motor 11, so that the driving of the drum 3 from the driving by the coil spring 5 to the driving by the AC motor 11 can be performed more smoothly. As a result, the shock to the supported object can be reduced.

In the balancer 100, a rotation angle sensor 14 is provided at one end of the drive shaft 1, and by processing an output signal thereof, the extension length of the cable 4 can be displayed. The above components are assembled on a base plate 16, and the gear train 12 and the sensors are connected to the protective cover 1.
5 protected.

[0029]

As described above, according to the present invention, a supported object having a large supporting weight can be lifted and lowered at high speed in a wide range, and the weight of the supported object can be reduced. Is supported by other means and is balanced, the force generated by the self-movement of the supported object is absorbed by the elastic member through the relative rotation between the drum and the drive shaft. Therefore, without waiting for the change in the tension of the cable to be converted into a change in the input to the drive shaft, the drum is immediately rotated relative to the direction in which the change in the tension is canceled, so that the cable is fed or wound up. The ability to follow an object's self-motion is extremely high.

[Brief description of the drawings]

FIG. 1 is a partially broken elevational view showing a configuration of a main part of a balancer according to the present invention.

FIG. 2A is a partially cutaway plan view showing an entire configuration of a balancer according to one embodiment of the present invention, and FIG. 2B is a detailed view of a sensor unit.

[Explanation of symbols]

f1: axial propulsion force of nut f2: pressing force by coil spring 1: drive shaft 101: screw groove 2: nut 3: drum 4: cable 5: coil spring 6: bolt 7: stationary member 8: thrust bearing 9: Movable plate 10: Position sensor 11: AC motor 12: Gear train 13: Roll 14: Rotation angle sensor 15: Protective cover 16: Base plate 100: Balancer

Claims (5)

[Claims] 1. A drive shaft provided with a screw groove having a predetermined lead angle, a nut screwed into the screw groove, and a cable winding fixed coaxially to the nut and supported around the drive shaft. And a resilient member for applying a pressing force to the end face of the nut opposite to an axial propulsion force of the nut when the drum is relatively rotated in a direction in which the rope is extended with respect to the drive shaft, the tension of the rope. When the thrust force is larger than the pressing force, the drum rotates smoothly relative to the drive shaft in the direction in which the rope is extended, and in the reverse case, in the direction in which the rope is wound up. Balancer. 2. An angle at which the coefficient of sliding friction between the thread groove and the nut becomes less than a value practically allowable when the drum rotates relative to the drive shaft in any of the above directions. The balancer according to claim 1, wherein the balancer is set within a range. 3. The balancer according to claim 2, wherein said lead angle is substantially 45 °. 4. The apparatus according to claim 1, wherein the elastic member is a coil spring inserted between a stationary member including a bearing for supporting the drive shaft and an end face of the nut. The balancer described. 5. The balancer according to claim 1, wherein a rotation direction and a speed of a motor driving the drive shaft are controlled by a position sensor provided near a stroke limit of the nut. .