JPH06155217A - Numerically controlled machine - Google Patents

Abstract

PURPOSE:To provide a numerically controlled machine of which loads of respective parts of the machine and a drive device are lightened, thermal displacement is restrained, and driven members can be fed at high speed. CONSTITUTION:In addition to a first control system to control a servo motor 7, a second control system to control a pneumatic cylinder 12 is further provided. The direction and the magnitude of force applied on a table 1 in the moving direction are detected with the load sensor 3 of the second control system, a thrust control part 15 controls proportional pressure control valves 13a, 13b and adjusts the pressure of the pneumatic cylinder 12 so as to maintain the magnitude of the force detected with the load sensor 3 to be zero, and the thrusts in the normal and reverse both moving directions are given to the table 1 independently of the servo motor 7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a numerically controlled machine represented by a numerically controlled machine tool, and in particular, in addition to a conventional control system for feeding a driven member, a force is applied in a moving direction of the driven member. The present invention relates to a numerical control machine provided with a second control system for giving.

[0002]

2. Description of the Related Art Conventionally, in a numerical control machine, only one driving device is provided for one moving shaft of one driven member. This will be explained by taking a numerically controlled machine tool typified by a machining center as an example. The driven members of the machining center are the spindle head and the X-
It is a Y table. When these driven members move in accordance with commands from the numerical control device, various forces act in the moving line direction. Energy is supplied to the driving device for driving the driven member in order to overcome the various forces and move the driven member as instructed by the numerical control device. The force acting on the driven member is the inertial force of the driven member, the gravity acting on the driven member itself, the cutting resistance,
These are frictional resistance in the guide portion of the driven member, frictional torque of the ball screw device, and the like, and these forces change variously in accordance with changes in the command of the numerical control device, changes in the machining state of the workpiece, and the like. In a numerical control machine, especially a machining center, it is common to use a servo motor as a drive device for moving the driven member. The rotary motion of the output shaft of the servo motor is linearly reciprocated. A ball screw device or the like is used as a motion transmitting device for converting to a driven member and the screw part of the ball screw device is rotatably supported by the machine frame, and the nut part is fixed to the driven member. There is. The output shaft of the servomotor is connected to the screw portion. A sensor for detecting the moving position of the driven member is provided at an appropriate position from the output shaft of the servo motor to the driven member, and provides the numerical control device with information regarding the moving position of the driven member. ing. The conventional machining center does not have a means for directly detecting the force acting on the driven member described above, and the servo control device uses the command of the numerical control device and the information from the sensor described above to detect the force. A new command is sent to match the current position of the driving member with the command position, and energy is supplied to the servo motor. That is, in a conventional machining center, even with respect to the force acting on the driven member, all of them are controlled by only one control system using only the information on the position, speed, acceleration, etc. of the driven member. Only one servo motor in the system was responsible for all the tasks.

[0003]

[Problems to be Solved by the Invention] In recent years, numerical control machines have been required to have high performance, resulting in ever-increasing speed.
Higher precision and higher efficiency are required. However,
Since each of these requirements conflicts, it is very difficult to improve all of them at the same time. Furthermore, in addition to the above technical problems, there is an economic demand for cost reduction in addition to the above technical problems. Even if we consider only the speedup, in order to move a substance of a certain mass with twice the acceleration as before, it is simple as is clear from the formula of (force) = (mass) x (acceleration). It requires twice as much power. That is, if it is a motor, a motor having a double output must be used. Also, in the case of doubling the speed, as is clear from the formula of (work rate) = (force) × (speed), a motor with double output is still required. A recent numerical control machine employs a servo motor to drive a driven member, but a high output servo motor is very expensive. Further, even if an expensive high-output servomotor is used to increase the speed, the amount of heat generated by the servomotor and the amount of heat generated by each part of the machine such as the ball screw portion and the guide member of the driven member increase. The heat displacement increases, the accuracy of the machine decreases, and the efficiency of the machine also deteriorates due to heat loss due to heat generation. That is, it is technically very difficult to realize high precision and high efficiency while achieving high speed. The present invention has been made to solve the above-mentioned problems, and an object thereof is to provide a numerical control machine capable of sending a driven member at high speed while reducing the load on each part of the machine and the drive device and suppressing thermal displacement. To provide.

[0004]

In order to achieve this object, in a numerical control machine of the present invention, a driven member that is movable along at least one axis or in both forward and reverse directions around one rotation axis, Providing information about driving means for moving the driven member directly or via motion transmitting means, and information on at least one or more of the driven member's position, moving direction, moving speed, and acceleration. An information providing unit for controlling the driving unit based on an instruction input by the manual data input device or an instruction of a program created in advance and the information provided by the information providing unit. A first control system including: a force applying means for applying a force to the driven member in both forward and backward movement directions separately from the driving means; and a method of moving the driven member. Force detecting means for detecting the direction and magnitude of the force acting on the force, and second control means for controlling the force applying means so as to maintain the magnitude of the force detected by the force detecting means at a predetermined value. And a second control system consisting of In still another aspect of the numerical control machine of the present invention, a driven member that is movable along at least one axis or in both forward and reverse directions around one rotation axis,
Providing information about driving means for moving the driven member directly or via motion transmitting means, and information on at least one or more of the driven member's position, moving direction, moving speed, and acceleration. An information providing unit for controlling the driving unit based on an instruction input by the manual data input device or an instruction of a program created in advance and the information provided by the information providing unit. And a pneumatic or hydraulic actuator for applying a force in both forward and reverse movement directions to the driven member separately from the driving means, and adjusting the pressure in the actuator. A pressure regulator,
Force detecting means for detecting the direction and magnitude of the force acting in the moving direction of the driven member, and controlling the pressure adjusting device so as to maintain the magnitude of the force detected by the force detecting means at a predetermined value. And a second control system including a second control means for performing the operation.

[0005]

According to the present invention having the above-mentioned structure, the second control system is provided in addition to the first control system having the same structure as the conventional structure, and the force detecting means is provided in the second control system. Detects the direction and magnitude of the force acting in the moving direction of the driven member, and controls the force applying means so that the second control means maintains the magnitude of the force detected by the force detecting means at a predetermined value. Then, the force applying means applies a force to the driven member in both forward and reverse movement directions separately from the driving means of the first control system. In yet another aspect of the numerical control machine of the present invention, a second control system is provided in addition to the first control system having a configuration substantially similar to the conventional configuration, and the force detection means is provided in the second control system. The pressure adjusting device detects the direction and magnitude of the force acting in the moving direction of the driven member, and the second control means maintains the magnitude of the force detected by the force detecting means at a predetermined value by the pneumatic control. Alternatively, the pressure of the hydraulic actuator is adjusted to apply a force in both forward and reverse movement directions to the driven member separately from the driving means of the first control system.

[0006]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows the configuration of the first embodiment of the present invention. As a driven member, the table 1 is guided so as to be movable in the left-right direction of the paper (hereinafter referred to as the X direction). A through hole 1a is provided in the lower portion of the table 1. The ball screw device 2 comprises a screw shaft 2a and a nut 2b, and the screw shaft 2a and the nut 2b are screwed together. The ball screw device 2 is inserted into the through hole 1a described above,
A nut 2b is fixed to the lower portion of the table 1 via a ring-shaped load sensor 3. The screw shaft 2a is supported rotatably with respect to the machine base 5 via a bearing 4 and is immovable in the X direction. One end of the screw shaft 2a has a coupling 6
Is connected to the output shaft 7a of the servomotor 7 fixed to the machine base 5 via. Output shaft 7 of this servo motor 7
When a is rotated, the table 1 moves in the X direction by the screwing action of the screw shaft 2a of the ball screw device 2 and the nut 2b. On the other hand, a resolver 8 is provided at one end of the servomotor 7, and sends the rotation amount of the output shaft 7a of the servomotor 7, that is, the movement amount of the table 1 in the X direction to the motor control unit 9.

A motor controller 9 is provided to control the amount of movement of the table 1, and a numerical controller 10 and a keyboard 11 are provided to give commands to the motor controller 9. The command to the motor control unit 9 is determined by a program stored in advance in the numerical control device 10 or a command manually input to the keyboard 11. Based on this command, the motor control unit 9 sends a command to the servo motor 7. Power for moving the table 1 is supplied. In response to this, a position signal for recognizing the movement amount of the table 1 is fed back from the resolver 8 to the motor control unit 9.

On the other hand, a pneumatic cylinder 12 is fixed to the end of the machine base 5 facing the servo motor 7, and the pneumatic cylinder 1
One end of the second rod 12c is fixed to the table 1. The left and right pressure chambers 12a and 12b of the pneumatic cylinder 12 are
The proportional pressure control valves 13a and 13b are respectively connected to the proportional pressure control valves 13a and 13b.
It is connected to the. 2 for the proportional pressure control valves 13a and 13b
The pressure on the secondary side is increased / decreased according to an input signal from the outside, and the left and right pressure chambers 12a, 12b of the pneumatic cylinder 12 can be adjusted to arbitrary pressures by the proportional pressure control valves 13a, 13b. it can. That is, the proportional pressure control valve 13
a to the pressure chamber 12a to increase the pressure in the pressure chamber 12a, and at the same time, the proportional pressure control valve 13b is opened to open the pressure chamber 12a.
By depressurizing the inside of b, a thrust force is applied to the table 1 in the right direction (+ X direction) of the drawing through the rod 12c, and conversely, air is sent from the proportional pressure control valve 13b to the pressure chamber 12b to increase the pressure. By opening the proportional pressure control valve 13a and lowering the air pressure in the pressure chamber 12a, thrust can be applied to the table 1 in the left direction (-X direction) of the drawing via the rod 12c. Although the pneumatic cylinder 12 and the proportional pressure control valves 13a and 13b are used in this embodiment, the cylinder is not limited to pneumatic pressure or hydraulic pressure, and the two proportional pressure control valves 13a and 13b are not limited to the cylinders. Alternatively, a combination of an electromagnetic switching valve and a pressure control valve may be used.

In order to control this thrust, the thrust controller 15
Is provided, and a pressure signal is sent from the thrust control unit 15 to the two proportional pressure control valves 13a and 13b. On the other hand, a load signal applied to the X direction of the table 1 is fed back from the load sensor 3 attached to the table 1 to the thrust control unit 15. Next, the operation will be described. When the numerical control device 10 gives a movement command to the motor control unit 9, power is supplied to the servo motor 7, and the servo motor 7 rotates the output shaft 7a,
Try to move table 1. However, moving the table 1 involves various loads. This load means the friction torque between the nut 2b of the ball screw device 2 and the screw shaft 2a, the friction torque of the bearing 4, the friction resistance of the guide portion (not shown) that guides the table 1, the inertial force of the table 1 during acceleration. The cutting resistance during cutting, and the influence of gravity applied to the table 1 when the moving direction is the vertical direction (Z direction).

In this embodiment, as described above, the load sensor 3 is provided between the nut 2b of the ball screw device 2 and the table 1 to detect the loads in the moving axis direction due to the various loads described above. Pneumatic cylinder 1 with appropriate thrust
Give by 2. This thrust is controlled in a closed loop so that the value of the load sensor 3 becomes 0 as the target value of the thrust controller 15. Most of the above-mentioned various loads applied to the servo motor 7 and each part of the machine are canceled by this thrust, and the axial load applied to the ball screw device 2 and the bearing 4 is significantly reduced.

The load applied to the ball screw device 2 and the bearing 4 will now be described in more detail. A preload is generally applied to the ball screw device 2 and the bearing 4 in order to prevent looseness and improve rigidity. This preload is canceled when a load about 3 times the preload is applied from the outside (preload release), and when this preload release occurs in the cutting state, vibration is likely to occur, so generally the maximum axial load is applied. Assuming that, the preload corresponding to it is set. for that reason,
In the conventional method of feeding the table 1 only by the servo motor, assuming that the maximum axial load such as cutting resistance at the time of cutting is large, it is necessary to increase the preload to cope with this. However, if the preload is increased, the friction torque is also increased, and a large preload also increases the internal load.As a result, the amount of heat generated increases, causing thermal deformation in each part of the machine and lowering the accuracy. Also has an adverse effect on life. Further, since the ball screw device 2 and the bearing 4 having a large preload are fed, the load on the servomotor 7 also increases, which also causes thermal deformation. Further, the heat loss increases energy loss.

In this embodiment, the thrust generated by the pneumatic cylinder 12 largely cancels the various loads described above, and the axial load on the ball screw 2 and the bearing 4 is greatly reduced. Therefore, since a large load is not applied to both, it is possible to significantly reduce the preload, and it is possible to suppress thermal deformation of each part of the machine.

On the other hand, due to the decrease in the axial load and the decrease in the preload described above, the ball screw device 2 and the bearing 4 are
The friction torque is reduced, and the load on the servo motor 7 is also significantly reduced. Therefore, the amount of heat generated from the servo motor 7 is also reduced, and thermal deformation due to this is also suppressed. Also,
Since the load on the servomotor 7 is reduced, even a servomotor 7 smaller than the conventional one can sufficiently cope with the speedup, so that the speedup can be realized at a low cost.

As described above, the pneumatic cylinder 12
Is controlled by the thrust control unit 15 so that the axial force detected by the sensor 3 always maintains a value close to zero. By being controlled in this way, the force applied to the table 1 in the direction of the moving axis is mainly borne by the pneumatic cylinder 12, and the load of the servo motor 7 and
The load on the ball screw device 2 transmitting the motion is reduced. Here, since there are two completely different control systems, a control delay occurs between them, but even if a minute time difference occurs in the force control, a load of an amount corresponding to that minute time is servo-controlled. The control system of the pneumatic cylinder 12 takes charge of the axial load applied to the table 1 immediately after the lapse of the minute time by only bearing the load on the motor 7. Therefore, in the present embodiment, both the maximum axial load and the average axial load that the servo motor 7 and the ball screw device 2 bear can be made significantly lower than the conventional values in terms of the entire operating time.

In this embodiment, the control system on the pneumatic cylinder 12 side is a closed loop, and the servomotor 7
It was provided independently of the control system on the side. In devising the configuration of this embodiment, the pneumatic cylinder 12 is subordinate to the control system on the servomotor 7 side, and a subordinate control method is used to provide the pneumatic cylinder 12 with an output proportional to the output given to the servomotor 7. Was also examined. However, in this embodiment, most of the thrust required to move the table 1 on the pneumatic cylinder 12 side is generated, and the servo motor 7 is mainly used for positioning. Then, it was determined that the assist by the pneumatic cylinder 12 was limited. That is, the fluctuation of the load applied to the table 1 during operation is large, and the pneumatic cylinder 12
In order to follow the output of the table 1, it is necessary to predict the load fluctuation when sending the table 1. However, this fluctuation is difficult to predict because it changes from moment to moment, and the predicted data must therefore be unreliable. For the above reason, in this embodiment, the independent control system is provided without using the dependent control method.

Further, in the conventional numerical control machine, the table 1
There was no concept of directly detecting the force applied to the (driven member). On the other hand, in the present embodiment, the force applied to the table 1 is directly detected, and the independent control system performs the closed loop control so as to reduce the force to 0.
It has become possible to bear most of the thrust required to feed the table 1 to the pneumatic cylinder 12. In the above-described embodiment, the load of the servomotor 7 can be set by setting the thrust generated by the pneumatic cylinder 12 so that the force applied to the table 1 in the moving axis direction is maintained close to zero. Although it was made as small as possible, this set value is a value that can be appropriately selected. In addition, in this embodiment, the thrust is applied to the X-direction feed of the table 1 for feeding the workpiece.
It can be applied not only in the direction but also in the feed of the table 1 in the Y direction, and it is also possible to add thrust by this method to the spindle head for feeding the tool.

Next, a second embodiment of the present invention will be described with reference to FIG. 2 showing this essential part. Note that illustration and description of the configuration that is substantially the same as that of the first embodiment will be omitted.
In the first embodiment, the ring-shaped load sensor 3 is arranged between the nut 2b of the ball screw device 2 and the table 1 in order to detect the axial force applied to the table 1.
In the second embodiment, the load sensor 16 is provided between the bearing support member 16 that supports the bearing 4 and the machine base 5. With this configuration, similarly to the first embodiment described above, the magnitude and direction of the axial force applied to the table can be accurately detected, and based on this, an appropriate thrust can be applied to the table by the pneumatic cylinder (not shown). it can.

Next, a third embodiment of the present invention will be described with reference to FIG. 3 showing this essential part. In the first embodiment, the load sensor 3 is used to detect the axial force applied to the table 1, but in the third embodiment, the rotational torque sensor 18 is provided between the servo motor 7 and the machine base 5. Place and
The rotational torque sensor 18 detects the axial force applied to the table and its direction. Then, based on the detected force, a pneumatic cylinder (not shown) is driven to feed the table.

The present invention can also be applied to a numerical control machine of a rotary coordinate system, or a numerical control machine that directly drives a driven member by the output of a servomotor without going through a ball screw or the like. Hereinafter, a fourth embodiment in which the present invention is applied to a machine having a rotary coordinate system will be described with reference to FIGS. FIG. 4 shows the overall configuration of a robot 40 according to the fourth embodiment of the present invention. This robot 40 is
It has six joints B, C, D, E and F, and is configured so that the hand 41 can be freely positioned with six degrees of freedom.

FIG. 5 shows the structure of the B joint of the robot 40 shown in FIG. 4, and FIG. 6 is a sectional view taken along line GG of the B joint of the robot shown in FIG. A pinion 29 is disposed on the rotary shaft 20 that is integrally formed with the arm 42 that is a driven member, and is rotatably attached to the machine base 22 via a bearing 21. One end of the rotary shaft 20 is connected to an output shaft 25a of a servomotor 25 fixed to the machine base 22 via a coupling 23. A resolver 26 for confirming the rotation amount of the output shaft 25a and a rotation torque sensor 24 for detecting a load applied to the servo motor 25 are provided at one end of the servo motor 25. On the other hand, as shown in FIG. 6, a pneumatic cylinder 27 is fixedly installed on the machine base 22.
A rack 28 is coupled to the rod 27a of the. Here, when the pneumatic cylinder 27 is driven and a thrust force in the vertical direction of the paper surface in FIG. 6 is applied to the rack 28, a pinion 29 provided coaxially with the rack 28 and the rotating shaft 20 described above.
By the engaging action of, the clockwise and counterclockwise rotational force can be applied to the arm 42. The configurations of the control unit on the servo motor 25 side and the control unit of the pneumatic cylinder 27 are substantially the same as those of the first embodiment described above, and therefore, illustration and description thereof are omitted here.

In the fourth embodiment, the load of the servo motor 25 can be reduced by the thrust of the pneumatic cylinder 27, and the heat generation from the servo motor 25 can be reduced to suppress the thermal deformation. You can Furthermore,
By reducing the load on the servo motor 25, it becomes possible to speed up the numerical control machine by using the servo motor 25 having a small capacity.

In the description of this embodiment, the robot 4
Although the B joint of No. 0 has been described, the other five joints of this robot are also controlled in the same manner. Although the pneumatic cylinder 27, the rack 28, and the pinion 29 are used in this embodiment, it is also suitable to use a rotary pneumatic or hydraulic actuator instead.

[0023]

As is apparent from the above description,
According to the numerical control machine of the present invention, in order to maintain the magnitude of the force applied in the moving direction detected by the force detection means provided on the driven member at a predetermined value, in addition to the conventional drive means,
Further, a thrust was applied to the driven member by the force applying means. As a result, the load on the conventional drive means can be reduced, and the force applied to the motion transmission means for transmitting the force generated by the drive means to the driven member can be significantly reduced. As a result, it is not necessary to increase the size of a drive device such as a servomotor for increasing the speed of the numerical control machine, and a high-speed numerical control machine can be constructed at low cost. Further, the force applied to the motion transmitting means such as a ball screw is also small, and the amount of heat generated by the ball screw or the like is small. Therefore, speeding up does not deteriorate accuracy, and efficiency deterioration due to heat generation can be avoided. Further, even in a numerical control machine having a speed comparable to that of a conventional one, by applying the configuration of the present invention, the preload applied to the nut portion of the ball screw can be reduced, so that the thermal displacement of the ball screw device can be reduced. However, the life can be extended and the rigidity can be further improved. It is also possible to use a servomotor having a small capacity.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a numerical control machine according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view of essential parts of a numerical control machine according to a second embodiment of the present invention.

FIG. 3 is a sectional view of essential parts of a numerical control machine according to a third embodiment of the present invention.

FIG. 4 is a configuration diagram of a robot according to a fourth exemplary embodiment of the present invention.

5 is a configuration diagram showing a joint portion of FIG. 4. FIG.

6 is a sectional view taken along line GG of the joint portion of FIG.

[Explanation of symbols]

 1 Table 2 Ball Screw Device 3 Load Sensor 7 Servo Motor 8 Resolver 9 Motor Control Unit 10 Numerical Control Device 12 Pneumatic Cylinder 13a Proportional Pressure Control Valve 13b Proportional Pressure Control Valve 17 Load Sensor 18 Rotation Torque Sensor 24 Rotation Torque Sensor 25 Servo Motor 26 Resolver 27 Pneumatic cylinder

[Procedure amendment]

[Submission date] January 18, 1993

[Procedure Amendment 1]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 1

[Correction method] Change

[Correction content]

[Figure 1]

Claims (5)

[Claims] 1. A driven member that is movable along at least one axis or in both forward and reverse directions around a rotation axis,
Providing information about driving means for moving the driven member directly or via motion transmitting means, and information on at least one or more of the driven member's position, moving direction, moving speed, and acceleration. An information providing unit for controlling the driving unit based on an instruction input by the manual data input device or an instruction of a program created in advance and the information provided by the information providing unit. A numerical control machine having a first control system comprising: force applying means for applying a force in both forward and reverse movement directions to the driven member separately from the driving means; Force detecting means for detecting the direction and magnitude of the force acting in the moving direction, and controlling the force applying means so as to maintain the magnitude of the force detected by the force detecting means at a predetermined value. The first of the eye 2
A numerical control machine comprising a second control system including a control means. 2. A driven member which is movable along at least one axis or in both forward and reverse directions around one rotation axis,
Providing information about driving means for moving the driven member directly or via motion transmitting means, and information on at least one or more of the driven member's position, moving direction, moving speed, and acceleration. An information providing unit for controlling the driving unit based on an instruction input by the manual data input device or an instruction of a program created in advance and the information provided by the information providing unit. A numerical control machine having a first control system including: a pneumatic or hydraulic actuator for applying a force in both forward and reverse movement directions to the driven member separately from the driving means; A pressure adjusting device for adjusting the pressure of the force, force detecting means for detecting the direction and magnitude of the force acting in the moving direction of the driven member, and the force detecting means. A numerical control machine comprising a second control system including a second control means for controlling the pressure adjusting device so as to maintain the magnitude of the detected force at a predetermined value. 3. The numerical control machine according to claim 1, wherein the second control system is a closed loop control. 4. The motion transmitting means is constituted by a set of ball screw devices, and the force detecting means is provided between the ball screw device and a driven member or a machine frame supporting the ball screw device. The numerical control machine according to claim 1, wherein the numerical control machine is a force sensor. 5. The numerical value according to claim 1, wherein the driving means is composed of a servo motor, and the force detecting means is a rotational torque sensor for detecting a rotational torque applied to an output shaft of the servo motor. Control machine.