JPS63175B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for detecting the position of a moving object, and in particular, in machine tools and industrial machines, the present invention detects when the relative position of a workpiece and a tool has reached a predetermined position, and By directly or indirectly replacing the unit movement amount of a moving object with a digital pulse signal suitable for switching the control of
The present invention relates to an improvement in a method for detecting the position of a moving object.

In general, in machine tools and industrial machinery, it is extremely important to accurately detect the position of the tool, etc. in order to control the feed rate of the tool, etc. according to the relative position of the workpiece and the tool, that is, the progress of machining. It is. Therefore, conventionally, for example, as shown in FIG.
A fixedly arranged slide base 14 for processing the workpiece 12 fixed on the top of the slide base 14, and a slide table 18 on which a spindle 16 is supported and moves back and forth on the slide base 14.
, a DC motor 24 that moves the slide table 18 forward or backward by rotating a feed shaft 22 screwed into a feed nut 20 fixed to the lower surface of the slide table 18; and a rotation direction of the DC motor 24. and a DC motor drive circuit 26 that controls the rotational speed, and the DC motor drive circuit 26
A speed switching setting circuit 28 outputs an appropriate feed speed setting value according to the forward position of the spindle 16.
and a machine sequence 30 for controlling the DC motor drive circuit 26, in which a dog 32 is provided at a predetermined location on the side surface of the slide table 18, and a dog 32 is provided at a predetermined location on the slide base 14. A mechanical limit switch 34 is provided which is turned on and off by the dog 32.
Detects the pre-collection position of the slide table 18, that is, the spindle 16 by being turned on and off by the controller, and thereby controls the DC motor drive circuit 26 via the mechanical sequence circuit 30.
The feeding state of the slide table 18 was controlled. In the figure, 35 is a bearing, 36 is
The stopper 37 is fixed to the front end surface of the slide table 18, and the stopper CR1 and CR2 are fixed to the inner wall surface of the slide base 14.
The forward/reverse switching contacts LS1 to LS4 for switching the rotation direction of the DC motor 24 are speed switching contacts for switching the feed speed according to the processing situation.

This method is very simple and requires a number of mechanical limit switches 34 and dogs 32 in the positions required for control switching approximately equal to the number of signal outputs required.
However, mechanical limit switches have weak mechanical strength and
Furthermore, since there is insufficient protection against the factory atmosphere such as oil, water, and dust, malfunctions are likely to occur due to chips, dust, cooling water, etc., and reliability is lacking. or,
The relative positional relationship between the limit switch and the dog tends to deteriorate over time, making it difficult to adjust the dog.
Furthermore, there are few problems with single-function machines that process a single workpiece using a single spindle, but in recent years, there has been a demand for multiple processes on a single or multiple workpieces. In the case of a general-purpose machine, the position of the dog and limit switch must be changed every time the workpiece or spindle is replaced.
The problem is that it lacks versatility. These problems also apply when a proximity switch is used instead of a limit switch.

On the other hand, in recent numerically controlled machine tools, digital servo mechanisms equipped with position feedback systems are often used. As shown in FIG. 2, this includes a pulse generator 40 that directly or indirectly converts the amount of movement of a moving object 38 such as a slide table into a digital pulse signal;
A reversible counter 42 that reversibly counts 0-output pulse signals corresponding to the position of the moving object 38 and outputs the deviation from a preset command pulse.
, a digital-analog converter 44 that converts the output of the reversible counter 42 into an analog signal, and a servo motor 48 that amplifies the output of the digital-analog converter 44 to control the position of the moving object 38. It consists of a servo amplifier 46 for output. According to such a digital mechanism, since the position of the moving object 38 can be monitored from moment to moment, highly accurate feed control should be possible under ideal conditions. However, in reality, not only are there many parts, the configuration is complex, and extremely expensive, but the reliability of each element is low, and bumps in the transmission system cause instability in the operation of the servo mechanism. ing. Moreover, installing a servo mechanism having this position feedback system in a conventional machine tool requires considerable modification.

The present invention was made to eliminate the above-mentioned conventional drawbacks, and is capable of reliably detecting the position of a moving object without using unreliable mechanical limit switches or complicated servo mechanisms, and can be incorporated into machine tools, etc. It is an object of the present invention to provide a method for detecting the position of a moving object that is extremely easy and inexpensive.

In order to achieve the above object, the configuration of the present invention outputs a pulse signal having a pulse corresponding to the unit movement amount of a reciprocating moving object, and is arranged at a specific position in the moving range of the moving object. A reference number is determined corresponding to the reference position by setting the position where the moving object contacts and presses the stopper that does not move during contact pressing, and determines the moving direction of the moving object based on the pulse signal and the movement. A count number of the pulse signal is obtained by adding or subtracting the number of pulses of the pulse signal to the reference number according to the direction, and a count number of the pulse signal is determined in advance based on the reference number and corresponding to a predetermined position in the movement range of the moving object. In the method for detecting the position of a moving object, the moving object is pressed against the stopper by detecting a match between the set pulse number and the count number to detect that the moving object has reached the predetermined position. When the pulse signal is no longer output, the count number of the pulse signal is reset to the reference number. According to the above configuration of the present invention, when the moving object reaches a predetermined position, the count number of the pulse signal and the set pulse number match, so that
It is possible to detect that a moving object has reached a predetermined position. Also, when a moving object comes into contact with the stopper and is pressed, the pulse signal is no longer output.
Since the number of pulses of the pulse signal is reset to the reference number, even if the moving position and the count number do not match while the moving object is moving, the error will not be accumulated. In addition, by making it possible to output an abnormal signal when the number of pulse signals counted when the moving object is pressed against the stopper and the pulse signal is no longer output is outside the preset tolerance range. , failure detection can be facilitated.

Embodiments of the present invention will be described in detail below with reference to the drawings. In this embodiment, the present invention is applied to the conventional machine tool shown in FIG. 1, and as shown in FIG. A rotary encoder 50 detects the rotation amount of the slide table 18 from the gear coupling 49, and a limit detection circuit 52 detects the feed position of the slide table 18 according to the output of the rotary encoder 50 and outputs it to the mechanical sequence circuit 30. It is prepared. The other points are the same as those of the conventional example shown in FIG. 1, so the explanation will be omitted.

The rotary encoder 50 is composed of a pair of photoelectric elements disposed around the gear of the gear coupling 49 of the DC motor 24 with a phase difference of 90°, for example, and rotates in the direction of rotation of the feed shaft 22, i.e. , two pulse signals as shown in FIG. 4 are outputted to the limit detection circuit 52, and have different phase differences depending on the direction in which the slide table 18 is fed.

The limit detection circuit 52 includes an encoder input circuit 54 to which the output of the rotary encoder 50 is input, an input circuit 56 to which the operating command of the output of the mechanical sequence circuit 30 is input, an output circuit 58, and a display circuit 60. and a programmable peripheral interface (hereinafter referred to as PPI) 62
and a central processing unit (hereinafter referred to as CPU) 64
, read-only memory (hereinafter referred to as ROM) 66, and random access memory (hereinafter referred to as ROM) 66, and random access memory (hereinafter referred to as ROM) 66
(referred to as RAM) 68, and a bus 70 connecting these. This limit detection circuit 52
The set pulse numbers P ₁ to _{P 4} corresponding to the control switching positions P ₁ to P ₄ are written and stored in the internal RAM 68 by a separately prepared program module.

The operation will be explained below with reference to FIGS. 5 and 6. The DC motor 24 rotates the feed shaft 22 via a gear coupling 49 to advance and retreat the slide table 18 to which the feed nut 20 is fixed. For example, as shown in FIG. 5, the slide table 18 is fast-forwarded from point _P1 to point _P2 in response to limit signals _LS1 to _LS4 obtained by the limit detection circuit 52, and from point _P2 to _{point P3} . The first delay is sent until
The second delay is carried out from P ₃ to P ₄ , and finally from P ₄ to P 4.
P Fast-rewinds to ₁ point. These feed rates are
The speeds are set in advance in the speed switching setting circuit 28, and one of these speeds is selected by opening and closing the relay in the mechanical sequence circuit 30.

When the feed shaft 22 is rotated by the DC motor 24, since the rotary encoder 50 is coupled to the gear coupling 49, the rotary encoder 50 outputs two signals having different phase differences depending on the direction of rotation. , a pulse output as shown in FIG. 4 is obtained, which is input to the encoder input circuit 54 of the limit detection circuit 52.

As shown in FIG. 6, the limit detection circuit 52 receives an operating command signal from the machine sequence circuit 30 through an input circuit 56, and is in a dormant state when it is not operating. When the mechanical sequence circuit 30 output is in operation, the direction of the two pulse signals with a 90° phase difference from the rotary encoder 50 is determined, and the forward direction (encoder forward rotation) or backward direction (encoder reverse rotation) is determined. ). The encoder is in forward rotation,
When the slide table 18 is in the forward movement state, the abnormal output (described later) of the limit detection circuit 52 is cleared, and the pulse signals output from the rotary encoder 50 are added and counted. On the other hand, when the encoder is outputting a reversal signal and the slide table 18 is in the backward state, the encoder output that is output as the slide table 18 moves back is determined from the pulse signals that have been counted up to that time. Subtract and count the number of pulses. These count values and predetermined positions input into the RAM 68 in advance
The CPU 64 compares and verifies whether the set pulse numbers P ₁ to P ₄ correspond to P ₁ to _{P 4} , and if they match, changes the on/off state of the limit signals LS ₁ to _{LS 4} and outputs the signals via the PPI 62. It is output to the output circuit 58.
Thereby, the mechanical sequence circuit 30 is controlled according to the position of the slide table 18. As the machining of the workpiece 12 progresses and the stopper 36 on the slide table 18 side reaches the origin position where it comes into contact with the dead stopper 37 fixed to the end surface of the slide base 14, the slide table will move regardless of the rotational torque of the DC motor 24. 18 becomes impossible to move forward, and no pulse output can be obtained from the rotary encoder 50. Therefore, the state in which the output of the rotary encoder 50 disappears for a certain period of time is determined to be the origin position, and the counter is reset. At this time, before performing the reset, it is determined whether the count value of the counter at the time of return to the origin is around a predetermined value (for example, zero) corresponding to the origin position. That is, when the count value is greater than or equal to the lower limit discriminant value and less than the upper limit discriminant value, it is determined that the operation has been performed normally, the count value of the counter is reset to a predetermined value, and fast reversal is performed to proceed to the next processing. On the other hand, if the count value of the counter is less than the lower limit discrimination value or exceeds the upper limit discrimination value, it may be due to an abnormality in either the mechanical system or the electrical system.
The counter count value is the actual slide table 18
It is considered that the display circuit 60 has shifted from the position of the display circuit 60.
In addition to displaying an abnormal state, an abnormal output is output to the machine sequence circuit 30, and the machining is stopped.

The limit signal (control switching signal point) can be easily changed by modifying the data (corresponding to the distance from the origin) in the RAM 68 in the limit detection circuit 52 using a separately prepared program module. It can be done.

In this embodiment, instead of immediately determining the moment when the stopper 36 on the slide table 18 side contacts the dead stopper 37 as the origin, the stopper 36 exerts a substantially constant force against the dead stopper 37 due to the rotational torque of the DC motor 24. Since the point continuously pressed for a predetermined period of time is determined to be the origin, there are few errors due to backlash, return, etc. In this embodiment, the reference position is the machining end position at the most forward position of the slide table, but the reference position is not limited to this, and may also be the return completion position at the rearmost position of the slide table. It is. Furthermore, in this embodiment, the reference position was the movement end position (i.e., stroke end) of the slide table 18;
The reference position is not limited to this, but may be an intermediate position or
It is also possible to set it as an intermediate processing position where a certain processing ends.

In the above embodiment, the rotary encoder 50 outputs two pulse signals having a phase difference of 90 degrees, but the type of output signal of the rotary encoder is not limited to this. When using a rotary encoder that outputs only a single pulse train as an output signal, forward and backward signals may also be input as command information from the machine sequence circuit 30 to determine direction, or It is also possible to generate different pulse signals separately when the rotary encoder itself rotates forward or reverse. In this case, the operation of the limit detection circuit is further simplified.

Further, in the above embodiment, the limit signal is incorporated into a mechanical sequence circuit consisting of a relay sequence circuit, but it is of course possible to incorporate it into a sequencer, which has become increasingly popular in recent years.

In the above embodiments, the present invention was applied to a machine tool in which the slide table was controlled to be fed by a DC motor, but the scope of application of the present invention is not limited to this. The feed is controlled by the cylinder,
The present invention can be similarly applied to general machine tools in which the feed rate is changed by changing the flow rate of the oil or air.

As described above, according to the present invention, the position of a moving object can be detected without contact with high precision over a long period of time without using a mechanical limit switch. Furthermore, since a complicated servo system is not required, the structure can be made compact and inexpensive. Furthermore, the control switching point can be easily changed, and the same equipment can handle many types of control. Furthermore, even if an error occurs due to a phase shift between the mechanical system that moves the moving object and the electrical system that counts the pulse signals, this error can be corrected electrically, making it extremely easy. It has excellent effects such as being easy to implement and increasing reliability.

[Brief explanation of the drawing]

Figure 1 is a block diagram showing the configuration of an example of a feed control device for a machine tool using a conventional mechanical limit switch, and Figure 2 is a configuration of an example of a servo mechanism equipped with a conventional position feedback system. FIG. 3 is a block diagram showing the configuration of a feed control device for a machine tool in which an embodiment of the method for detecting the position of a moving object according to the present invention is adopted, and FIG. 5 is a diagram showing the output waveform of the rotary encoder in the embodiment, FIG. 5 is a diagram showing the feed speed control state of the slide table in the embodiment, and FIG. 6 is a diagram showing the operation of the limit detection circuit in the embodiment. This is a flowchart. 12... Workpiece, 14... Slide base, 16
...Spindle, 18...Slide table, 20...
Feed nut, 22...Feed shaft, 24...DC motor,
26... DC motor drive circuit, 28... Speed switching setting circuit, 30... Mechanical sequence circuit, 36... Stopper, 37... Dead stopper, 50... Rotary encoder, 52... Limit detection circuit, 54... Encoder input circuit, 56... Input circuit, 58...Output circuit, 60...Display circuit, 62...PPI, 64...CPU,
66...ROM, 68...RAM, 70...bus.

Claims (1)

[Claims] 1. A pulse signal having a pulse corresponding to the unit movement amount of a reciprocating moving object is output, and a stopper that is disposed at a specific position in the moving range of the moving object and does not move when pressed in contact. A reference number is determined corresponding to the reference position by setting the position where the moving object contacts and presses the object as a reference position, and determines the moving direction of the moving object based on the pulse signal, and also determines the pulse according to the moving direction. The number of pulses of the signal is added or subtracted from the reference number to obtain the count number of the pulse signal, and the number of pulses set in advance is determined based on the reference number and corresponds to a predetermined position in the movement range of the moving object. In the method for detecting the position of a moving object, which detects that the moving object has reached the predetermined position by detecting a match with a count number, the moving object is pressed against the stopper and the pulse signal is output. A method for detecting the position of a moving object, characterized in that, when the pulse signal disappears, the count number of the pulse signal is reset to the reference number. 2. An abnormal signal is output when the number of pulse signals counted when the moving object is pressed against the stopper and the pulse signal is no longer output is outside a preset tolerance range. A method for detecting the position of a moving object according to claim 1.