JP2850276B2 - Control device for machine tool with two spindles - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for a machine tool having two main spindles, such as a lathe, and more particularly to a speed command for efficiently and accurately processing a workpiece.

[0002]

2. Description of the Related Art For example, when processing a long and narrow work with a lathe or the like, it is necessary to support both ends of the work via respective spindles, and to drive the two spindles synchronously while rotating the work. is there. FIG.
FIG. 2 is a block diagram schematically showing a control device for a machine tool having two main spindles. In the figure, reference numeral 10 denotes a first spindle, and 14 denotes a first spindle motor. The first spindle 10 and the first spindle motor 14 are connected via gears or belts 12 and 13. Reference numeral 20 denotes a second spindle, 24 denotes a second spindle motor, and the second spindle 20 is driven by gears or belts 22 and 23.
And the second spindle motor 24 are connected. Reference numeral 1 denotes a work, which is held by a chuck 11 attached to the first spindle 10 and a chuck 21 attached to the second spindle 20. The first spindle 10 is provided with a pulse encoder 15 for position feedback. Similarly, a pulse concoder 25 is attached to the second main wheel 20 for position feedback. A first spindle amplifier 16 drives the first spindle motor 14, and a second spindle amplifier 26 drives the second spindle motor 24. Here, the first spindle amplifier 16 and the second spindle amplifier 26 are constituted by a microprocessor, a speed control circuit having a memory and the like, a position control circuit, a power drive circuit having a power transistor and the like. Numeral 2 is a numerical controller (CNC), and numeral 6 is an acceleration / deceleration time constant circuit for smoothing a speed command issued inside the numerical controller (CNC) 2.
3 is the speed command output from the acceleration / deceleration time constant circuit 6 as the first
_First to convert to position command θ ₁ ^* given to spindle amplifier 16
This is a spindle position command creation circuit. Similarly, reference numeral 4 denotes a second spindle position command generation circuit for converting a speed command output from the acceleration / deceleration time constant circuit 6 into a position command θ ₂ ^* to be given to the second spindle amplifier 26.

Next, the operation will be described. The first spindle amplifier 16 and the second spindle amplifier 26 are switched to position control, and the first spindle 1 and the second spindle amplifier 26 are respectively controlled by the numerical controller (CNC) 2.
0 and the position command to the second spindle 20 is positioned synchronous theta ₁ ^*
And θ ₂ ^* are ^converted to the first spindle amplifier 16 and the second spindle amplifier 2
Give to 6. The first spindle amplifier 16 performs position control based on the output signal (first spindle position feedback) θ ₁ of the pulse encoder 15 so as to follow the position command θ ₁ ^* . Similarly, the second spindle amplifier 26 performs position control based on the output signal (second spindle position feedback) θ ₂ of the pulse encoder 25 so as to follow the position command θ ₂ ^* .

Next, the operation when the position commands θ ₁ ^* and θ ₂ ^* are output from the numerical controller (CNC) 2 will be described. When a desired speed command W _r ^* is input, the acceleration / deceleration time constant circuit 6 smoothes the speed command W _r ^* to create and output a new speed command. The first spindle position command creation circuit 3
A position command θ ₁ using a speed command which is an output signal of the acceleration / deceleration time constant circuit 6 so that the first spindle 10 has a desired speed.
^Is created and output to the first spindle amplifier 16. Similarly, the second spindle position command creation circuit 4 creates a position command θ ₂ ^* so that the second spindle 20 has a desired speed, and generates the second spindle amplifier 2.
Output to 6.

Here, the time constant set by the acceleration / deceleration time constant circuit 6 will be described. 6 is an output characteristic diagram of a commonly used spindle motor, and FIG. 7 is a torque characteristic diagram thereof. In both cases, the horizontal axis is the motor speed, the vertical axis is the motor output P in FIG. 6, and FIG. Motor torque T. FIG. 8 is an acceleration / deceleration characteristic diagram of the motor speed control obtained from these output characteristics. The vertical axis represents the motor speed, and the horizontal axis represents the acceleration / deceleration time. Now, in the case of position control, FIG.
It is necessary to make the acceleration / deceleration characteristics gentler than the acceleration / deceleration characteristics. For example, the maximum speed for position synchronization is N _C (rp
If m), the slope must be gentler than the slope of the tangent line A at that speed. In other words, the acceleration / deceleration characteristic has a constant time constant such as a straight line B. Therefore, the acceleration time is as shown in FIG.
If the speed control according to the acceleration characteristic becomes a t _c, t _p next acceleration or deceleration time is longer when the position synchronization control according to acceleration and deceleration characteristics of the straight line B.

[0006]

Since the conventional control device for a machine tool having two main spindles is constructed as described above, when the rotation speed of the two main spindles rotating by the same command is changed. In particular, it takes time to accelerate or decelerate, or if the time constant is shortened to shorten the processing time, an excessive force will be applied to the work and twisting will occur. Therefore, there is a problem that the processing time cannot be reduced.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and has a control device for a machine tool having two main spindles capable of shortening a machining time while maintaining machining accuracy. The purpose is to obtain.

[0008]

A control device for a machine tool having two spindles according to the present invention includes a first spindle motor for driving a first spindle, and a second spindle motor disposed opposite to the first spindle. A second spindle motor for driving the spindle, and a first spindle motor and a second spindle motor based on a position command from a position command circuit.
In the control device for a machine tool having two main spindles for driving a main spindle motor and controlling a position of a first main spindle and a second main spindle to process a work interposed between the first main spindle and the second main spindle, respectively. , Has a time constant corresponding to each of the constant torque region, the constant output region, and the reduced output region according to the rotation speed, and inputs a command rotation speed .
An acceleration / deceleration time constant circuit is provided which adjusts the inclination with respect to the interval by a corresponding time constant and outputs the adjusted time constant to the position command circuit.

According to another aspect of the present invention, there is provided a machine tool control device having two main spindles, the first main spindle motor driving a first main spindle and the second main spindle arranged opposite to the first main spindle. A first spindle motor and a second spindle motor based on a position command from a position command circuit to control the position of the first spindle and the second spindle, respectively. In a control device for a machine tool having two main spindles for processing a work interposed between a main spindle and a second main spindle, the control apparatus is adapted to a constant torque area, a constant output area, and a reduced output area according to a rotation speed. for time has constant respectively, enter the command rotational speed, the time of the command rotational speed
A circuit for adjusting the inclination by a corresponding time constant and outputting the adjusted signal to a position command circuit, wherein a plurality of acceleration / deceleration time constant circuits having respectively different time constants, and torques of a first spindle and a second spindle are respectively provided. Means for switching back and forth, and switching the acceleration / deceleration time constant circuit so that the two torques do not reach the limit value.

A control device for a machine tool having two other spindles according to the present invention has a first-order time delay filter circuit provided between an acceleration / deceleration time constant circuit and a position command circuit of the control device.

[0011]

According to the present invention, when the speed command changes,
Since it is output to the position command circuit via an acceleration / deceleration time constant circuit having a different acceleration / deceleration time constant according to each speed region, it is delayed by an appropriate time constant according to the speed command, and the command rotation speed is Slope with respect to time (: acceleration)
Is adjusted by the corresponding time constant and becomes smaller. As a result, the acceleration / deceleration time can be shortened while maintaining the accuracy of the position synchronization control of the first spindle and the second spindle.

Further, in the present invention, a plurality of acceleration / deceleration time constant circuits are prepared, and the torques of the first main spindle and the second main spindle are monitored, and the acceleration / deceleration time constants are set so that both torques do not reach the limit value. Switch the constant circuit. For example, when both torques exceed the specified torque, an acceleration / deceleration time constant circuit having a large time constant is selected. Thus, the acceleration / deceleration time constant circuit according to the work can be selected, and appropriate control can be performed.

Further, in the present invention, the first-order lag filter circuit 7 eliminates the inflection point of the acceleration / deceleration time constant of the acceleration / deceleration time constant circuit, or smoothes the acceleration / deceleration time constant. The switching point of the time constant when switching to the time constant circuit is smoothed. As a result, the speed inflection point of the acceleration / deceleration pattern in the position control is eliminated to form a smooth curve, and the position error between the spindles is reduced.

[0014]

[Embodiment 1] FIG. 1 is a block diagram schematically showing a control device for a machine tool having two spindles according to an embodiment of the present invention. In the figure, reference numerals 10 to 16 and 20 to 26 are the same as those of the conventional apparatus shown in FIG. 5, and a description thereof will be omitted. Reference numeral 2 denotes a numerical controller (CNC), and reference numeral 5 denotes a three-stage acceleration / deceleration time constant circuit for smoothing a speed command inside the numerical controller (CNC) 2. Reference numeral 3 denotes a first spindle position command generation circuit for converting an output signal (speed command) of the three-stage acceleration / deceleration time constant circuit 5 into a position command θ ₁ ^* to be given to the first spindle amplifier 16; Position command θ ₂ ^* for giving an output signal (speed command) from constant circuit 5 to second spindle amplifier 26
This is a second spindle position command creation circuit that converts the data into.

Next, the operation will be described. The first spindle position command creation circuit 3 inputs a speed command and converts it into a position command θ.
_After being converted to ₁ ^* and supplied to the first spindle amplifier 16, the first
The main spindle amplifier 16 and the first main spindle 10 operate in the same manner as in the prior art, and the second main spindle position command creation circuit 4 inputs a speed command, converts it into a position command θ ₂ ^* , and After being supplied to the second spindle amplifier 26 and the second spindle 2
0 performs the same operation as in the prior art.
The operation until ₁ ^* and θ ₂ ^* are output will be described. When the desired speed command _Wr ^* is input to the three-stage acceleration / deceleration time constant circuit 5, the three-stage acceleration / deceleration time constant circuit 5 outputs the speed command _Wr.
^* Is smoothed to create and output a speed command pattern described later. The first spindle position command creation circuit 3 and the second spindle position command circuit 4 create position commands θ ₁ ^* and θ ₂ ^* using these output signals and output them to the first spindle amplifier 16 and the second spindle amplifier 26. .

Next, the three-stage acceleration / deceleration time constant circuit 5 will be described. Here, FIGS. 6 to 8 again described in the conventional example.
This will be described with reference to FIG. As described above, FIG. 6 is an output characteristic diagram of a general spindle motor, and FIG. 7 is a torque characteristic diagram thereof. Constant torque region between motor speed 0 to N _B [rpm] which is controlled to be constant torque, the motor speed N _B to N
_C [rpm] is a constant output area where the output is controlled to be constant, and motor speeds N _{C to} N _max [rpm] are a reduced output area where the output is inversely proportional to the speed. FIG. 8 is an acceleration / deceleration characteristic diagram at the time of motor speed control obtained from the output characteristics of these motors as described above. Basic relational expression P = ωT, T = J · dω / dt (P: output [kw], ω: angular velocity [rad / s], T: torque [N
[M], J: Inertia [kg · m ² ]), the relationship between the motor speed and the acceleration / deceleration time is as follows. Motor speed 0 to N _B [rpm] deceleration time t at constant torque region of into a linearly proportional to the motor speed N, the motor speed N _B ~
In the constant output region of N _C [rpm], the acceleration / deceleration time t becomes a quadratic curve proportional to the square of the motor speed N ^2, and in the constant speed output region of the motor speed N _{C to} N _max [rpm], the acceleration / deceleration time t Is a cubic curve proportional to the third power N ³ of the motor speed.

FIG. 2 is an explanatory diagram of the acceleration / deceleration pattern in the position control according to the present invention, and corresponds to FIG. This will be further described with reference to FIG. Conventionally, only one stage is used for the acceleration / deceleration time constant in the case of position synchronization. For example, the motor maximum speed during position synchronization control is N _max [rpm].
In this case, since the control must be performed within the range of the output shown in FIG. 6, it is necessary to set the acceleration / deceleration time constant (straight line C ₂ ) of the inclination of the tangent C at the speed _Nmax . Therefore, when accelerating to the motor speed N _C , the acceleration / deceleration time constant (straight line B ₂ ) of the inclination of the tangent line B should be originally, but when the position synchronization control is performed with this time constant, the straight line C ₂ is obtained. Therefore, the acceleration / deceleration time becomes longer. Therefore, in this embodiment, three stages of acceleration / deceleration time constants can be set based on the output characteristics of the motor. When setting the acceleration / deceleration time constant at each stage, the acceleration / deceleration time constant is determined based on the gentlest slope in each characteristic region (constant torque region, constant output region, reduction region) of the motor output characteristics. Since the point of the maximum speed in each characteristic region has the gentlest slope in that region, the motor speed N _B [r
pm], the straight line A ₁ , the motor speed N _C [rp
m], the straight line B ₁ , the motor speed N _max [rp
By setting the three acceleration and deceleration time constant becomes linearly C ₁ by the tangent C of m], so that it is acceleration or deceleration operation in a short time efficiently from low-speed rotation of the motor up to speed. However, since the acceleration / deceleration pattern in the speed control is a pattern at the time of the maximum torque output, in order to improve the accuracy during the position synchronization between the two spindles, the acceleration / deceleration pattern is set with a time constant having a margin more than the set value. Also, the spindle amplifier 16 of the first spindle,
The spindle amplifier 26 of the second spindle, the first spindle motor 10, the second
There is no problem if the spindle motor 20, load inertia and the like have the same specifications, but if they are different, they are set according to the longer spindle characteristics of the acceleration / deceleration pattern.

In the above-described embodiment, the method of setting the acceleration / deceleration time constant in three stages has been described. However, the above-mentioned regions (constant torque region, low output region ) are set so as to be closer to the acceleration / deceleration pattern.
By setting the time constant is divided into a number of stages range and reduced power range) to a further, it is possible to deceleration operation by the position synchronization control close to the speed control. Further, the time constant is a straight line proportional to the motor speed N in the constant torque region, a quadratic curve proportional to the square of the motor speed N ² in the constant output region, and proportional to the cube N ³ of the motor speed in the reduced output region. Cubic curve
The acceleration / deceleration pattern in the position control may be in accordance with the acceleration / deceleration pattern in the speed control.

Embodiment 2 FIG. FIG. 3 is a block diagram schematically showing a control device for a machine tool having two spindles according to another embodiment of the present invention. FIG.
In the figure, reference numeral 7 denotes a first-order lag filter circuit for applying a first-order lag element to the output of the three-stage acceleration / deceleration time constant circuit 5, which is different from the above embodiment in that the first-order lag filter circuit 7 is provided. The first-order lag filter circuit 7 smoothes the inflection point of the acceleration / deceleration time constant of the three-stage acceleration / deceleration time constant circuit 5 (for example, the switching point of the time constants of the motor speeds N _B , N _C and N _max in FIG. 2). Thus, the speed inflection point of the acceleration / deceleration pattern during the position synchronization control is eliminated to obtain a smooth curve. By using the first-order lag filter circuit 7, the position control error between the two spindles, which is considered to occur in the transitional mode of the inflection point, is reduced, and the control accuracy is increased. In particular, this embodiment has a remarkable effect when a spindle amplifier, a spindle motor, a load inertia, and the like having different characteristics are used.

Embodiment 3 FIG. FIG. 4 is a block diagram schematically showing a control device for a machine tool having two spindles according to still another embodiment of the present invention. In FIG. 4, reference numeral 8 denotes a torque feedback signal (% output) τ from the first spindle amplifier 16.
_{Based on 1} and the torque feedback signal (% output) τ ₂ from the second spindle amplifier 26, it is determined whether the torque feedback value is equal to or greater than a specified torque (for example, 80%),
A torque judging circuit for outputting a signal for switching to a slower acceleration / deceleration time constant if the torque is equal to or more than a specified torque, 9 is a three-step (or more multi-step) acceleration / deceleration time constant based on an output signal of the torque judgment circuit 8. This is a changeover switch circuit that switches circuits.

In this embodiment, for example, two types of three-stage acceleration / deceleration time constant circuits 5a and 5b are set in advance.
One has a standard time constant, the other has a sufficient time constant (for example, twice), and if the work is relatively light, use the standard time constant. For example, when a heavy workpiece is gripped and replaced, the time constant is automatically switched to another time constant without setting the time constant again.
That is, the torque determination circuit 8 inputs the torque feedback signals τ ₁ and τ ₂ and determines whether the torque feedback signals are equal to or greater than the specified torque. If the work is relatively light, it is determined that the torque feedback signals τ ₁ and τ ₂ are less than the specified torque, and the changeover switch circuit 9 is switched to a three-stage acceleration / deceleration time constant circuit 5a.
And control based on the standard time constant. When the work is heavy, the torque feedback signals τ ₁ , τ
₂ is determined to be equal to or greater than the specified torque, and the changeover switch circuit 9 is switched to the three-stage acceleration / deceleration time constant circuit 5b to switch the standard
Control based on double time constant. Also in this embodiment, a first-order lag filter circuit 7 is provided.
Not only the inflection point of the deceleration time constant of the step acceleration / deceleration time constant circuits 5a and 5b, but also the time constant of the time constant when switching from one three-step acceleration / deceleration time constant circuit to the other three-step acceleration / deceleration time constant circuit The switching point is smoothed to eliminate the speed inflection point of the acceleration / deceleration pattern during the position synchronization control, thereby forming a smooth curve.

In the above-described embodiment, the description has been given of the machine tool in the case where the work is rotated by rotating the main shaft. However, for example, when the boring of a long cylindrical material is performed, the cutter is used. The present invention is also applied to a machine tool which is mounted on two spindles and rotates a cutter to process a workpiece.

[0023]

As described above, according to the present invention, when the command speed changes, the command speed is output to the position command circuit via the acceleration / deceleration time constant circuit having a different acceleration / deceleration time constant according to each speed range. Therefore, the device is not complicated, and the time of the command rotation speed is delayed by an appropriate time constant according to the speed command (the motor maximum output can be used effectively).
Is adjusted, and the acceleration / deceleration time can be shortened while maintaining the accuracy of the position synchronization control of the first spindle and the second spindle.

Further, according to the present invention, a plurality of acceleration / deceleration time constant circuits are prepared, and the torques of the first main spindle and the second main spindle are monitored, and the acceleration / deceleration time is controlled so that both torques do not reach the limit value. Since the constant circuit is switched, an acceleration / deceleration time constant circuit according to the work can be selected in this manner, and appropriate control can be performed.

Further, according to the present invention, the inflection point of the deceleration time constant of the acceleration / deceleration time constant circuit is eliminated to make it smooth, or one of the acceleration / deceleration time constant circuits is switched to the other. The switching point of the time constant at the time of turning is smoothed, so that there is no speed inflection point of the acceleration / deceleration pattern in the position control, and a smooth curve is obtained. As a result, the position error between the spindles is reduced. I have.

[Brief description of the drawings]

FIG. 1 is a block diagram schematically showing a control device for a machine tool having two spindles according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of an acceleration / deceleration pattern in position control according to the present invention.

FIG. 3 is a block diagram schematically showing a control device for a machine tool having two spindles according to another embodiment of the present invention.

FIG. 4 is a block diagram schematically showing a control device for a machine tool having two spindles according to still another embodiment of the present invention.

FIG. 5 is a block diagram schematically showing a conventional control device for a machine tool having two main spindles.

FIG. 6 is an output characteristic diagram of a commonly used spindle motor.

FIG. 7 is a torque characteristic diagram of a spindle motor.

FIG. 8 is an acceleration / deceleration characteristic diagram in speed control of a spindle motor.

[Explanation of symbols]

 Reference Signs List 1 work 5 three-stage acceleration / deceleration time constant circuit 7 primary delay filter circuit 8 torque judgment circuit 9 time constant switching circuit 10 first spindle 14 first spindle motor 16 first spindle amplifier 20 second spindle 24 second spindle motor 26 second Main shaft amplifier The same reference numerals in the drawings indicate the same or corresponding parts.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI G05B 19/416 G05D 3/00 Q G05D 3/00 G05B 19/407 K

Claims (3)

(57) [Claims] A first spindle motor for driving a first spindle;
A second spindle motor for driving a second spindle disposed opposite to the first spindle. The first spindle motor and the second spindle motor are driven based on a position command from a position command circuit. In the control device for a machine tool having two main spindles for driving and controlling the position of the first main spindle and the second main spindle, and processing a work interposed between the first main spindle and the second main spindle. , Has a time constant corresponding to each area of a constant torque area, a constant output area, and a reduced output area according to the rotation speed, inputs a command rotation speed , and slopes the command rotation speed with respect to time.
The control device of a machine tool having two main shaft and having a deceleration time constant circuit for outputting prior Symbol position command circuits after adjusting the time constant corresponding. 2. A first spindle motor for driving a first spindle,
A second spindle motor for driving a second spindle disposed opposite to the first spindle. The first spindle motor and the second spindle motor are driven based on a position command from a position command circuit. In the control device for a machine tool having two main spindles for driving and controlling the position of the first main spindle and the second main spindle, and processing a work interposed between the first main spindle and the second main spindle. , Has a time constant corresponding to each area of a constant torque area, a constant output area, and a reduced output area according to the rotation speed, inputs a command rotation speed , and slopes the command rotation speed with respect to time.
The a circuit for outputting the position command circuit after adjusting the time constant corresponding, a plurality of acceleration and deceleration time constant circuit constants are different when the corresponding, the first spindle and the torque of the second spindle And a means for switching the acceleration / deceleration time constant circuit so that the two torques do not reach the limit values. 3. The machine tool having two spindles according to claim 1, further comprising a first-order time delay filter circuit provided between said acceleration / deceleration time constant circuit and said position command circuit. Control device.