JPS626944B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an intermittent rotating body used in automated machine tools such as numerical control (hereinafter referred to as NC) machine tools, that is, a so-called indexing table. Regarding a control device. In particular, lathes, milling machines, machining
For indexing table control devices for various NC machine tools such as centers and other automated machine tools, the unit distance code method, which has many advantages, is used as the encoding method, such as the Gray code method. This invention relates to an improvement in the difficulty of detecting malfunctions in the indexing table control device, which is a disadvantage thereof.

[Conventional technology]

The operations to be performed by an automated machine tool, such as an NC machine tool, encode a series of steps such as mounting a workpiece, positioning the workpiece, selecting a tool, executing machining, and removing the workpiece. It is well known that the process is executed sequentially based on a given command, but it is generally executed on each side of a polygonal rotating body (turret in a lathe, index table in a milling machine or machining center, etc.). You can select the required tool by attaching different tools and intermittently rotate the rotating body by a specific angle as necessary, or if the workpiece is rotated intermittently by a specific unit angle. Control of the indexing table to fix it at a desired position suitable for machining is also one of the important operations that must be performed by an automated machine tool. In other words, there are various types of automated machine tools, including NC machine tools, limited-purpose controlled machine tools, special-purpose machine tools with limited uses, and semi-automatic machine tools, but all of them use intermittent rotating bodies that rotate intermittently. Generally, one of the important operations is so-called indexing table control, in which the device is rotated to a desired angle and positioned.

As an example, a conventional indexing table control system based on an NC control system will be described with reference to FIGS. 1 and 2. In the figure, 1 is the command device.
It is an NC device, and this NC including indexing table control
It encodes and outputs all operation commands that the machine tool should execute. Regarding the indexing table control, a signal TF instructing that the intermittent rotating body 2 such as the turret, index table, and workpiece mounting device should start rotating in a desired direction is sent to the control circuit 3 and the verification circuit 8 described later. Output towards. In response to this signal, the control circuit 3 gives an instruction to start driving to the drive device 4 that drives the intermittent rotating body 2 in a desired direction, whereby the intermittent rotating body 2 starts rotating. The intermittent rotating body 2 rotates integrally with a code plate 5 as shown in FIGS. 1 and 2, and each time the intermittent rotating body 2 rotates by a unit angle, a group of weighted limit switches is activated.
LS _1~ 4 6 and strobe signal limit switch
Limit switch for LSs parity check LSp
6' is operated, and as the intermittent rotating body 2 rotates, a tool mounted at a specific angular position is selected, or a workpiece is fixed at a desired position,
A code signal corresponding to the angular position is sequentially output. On the other hand, the NC device 1 outputs a code command T to the verification circuit 8, which indicates the angular position at which the intermittent rotating body 2 should stop rotating. Note that the signal TF applied to the verification circuit 8 also serves as a strobe signal for the code command T, and the code command T applied to the verification circuit 8 is valid only during the period in which the strobe signal TF is issued. The code signal indicating the momentary angular position of the intermittent rotating body 2 is converted by the code conversion circuit 7 into the same encoding method as the encoding method of the code command T output from the NC device 1, and then sent to the verification circuit 8. When the code command T issued from the NC device 1 instructs the angular position at which the intermittent rotating body 2 should stop rotating, a command is sent to the control circuit 3 to stop the driving of the intermittent rotating body 2. output a command to stop the drive device 4 and stop the intermittent rotating body 2 at that angular position, and
The indexing table control completion signal FIN is output to the device 1, and the next process, that is, the machining process performed using another tool, the machining process performed at another machining position, or the other workpiece Start the machining process etc. for the part.

FIGS. 2a and 2b show in more detail the structure of the code plate 5, the limit switch groups _LS1-46 , the strobe signal limit switch LSs, and the parity check limit switch LSp6'.
In the figure, a code plate 5 that rotates integrally with the intermittent rotating body 2 on which a tool is mounted or a workpiece is mounted at a specific angular position is provided with a code plate 5 representing each angular position at each specific angular position. A group of limit switches is provided opposite each protrusion.
LS _1~ 4 6 and strobe signal limit switch
Limit switch LSp for LSs/parity check
6' is provided. Each protrusion is weighted "1", "2", "4", and "8" from the outer circumference to the inner circumference, so for example, the corner position I is 1, the corner position I is 2,
3, 4, 5, 6, 7, 8
correspond to each. In this example, these four signals are transmitted via four separate wires.
However, these limit switches do not need to be of the contact type, and may be of any type, such as a proximity switch, a light receiving element, or an electromagnetic switch. Therefore, the object that operates these limit switches does not have to be a protrusion, and may be any kind of light emitting element, magnetic material, wire ring, etc. In this example, a strobe signal limit switch LSs and a parity check limit switch LSp6' are provided, and perform the function of detecting malfunction by emitting the respective signals.

[Problem that the invention seeks to solve]

Incidentally, there are three types of codes: serial codes, parallel codes, and serial-parallel codes, and it is well known that the serial-parallel code system is currently most widely used. In addition, the encoding method uses binary code,
It is also well known that there are three types of code: BCD code (binary coded decimal code) and unit distance code, which is a higher-level concept such as Gray code, and each has its advantages and disadvantages. The biggest difference between the former two and the latter is that while in the former two there is an opportunity for the signal value to change at two or more places at the same time, in the latter there is always an opportunity for it to change at only one place. be. Therefore, when the first two methods are applied to a parallel coding system or a serial coding system, there is a possibility of malfunction due to a slight time difference between the arrival of parallel signals, so the initial part of the signal is truncated and only the central part of the signal is processed. A method has been adopted to use
In order to determine that this is the central portion of the signal, a strobe signal whose signal start is slightly delayed from other parallel signals is required. Therefore, as a coding method for the position detection signal obtained from the limit switch group for position detection of the intermittent rotating body, binary
When using a code or BCD code, there is an additional burden of providing this strobe signal system, which not only increases the number of limit switches but also requires an additional circuit for malfunction detection using the signals generated by these. In particular, it is troublesome to adjust the relative setting positions of each limit switch for position detection and the corresponding limit switch for strobe signal, and furthermore, if the adjustment is incorrect, it may cause malfunction and incorrect machining. , tool damage;
It has the disadvantage that it tends to cause confusion in the system. On the other hand, since the unit distance code including the Gray code always changes at only one location when the signal value changes, malfunctions in the above sense cannot occur. Therefore, it can be said that unit distance codes are superior in terms of signal processing. However, as long as there is a change in the signal, it is recognized as a correct signal.
In particular, if only one signal that changes erroneously does not change, the signal will not be recognized forever, so it has a fundamental drawback that it is difficult to detect an error in the signal.

If there is a malfunction in the indexing table control of an automated machine tool such as an NC machine tool, it will not only result in the production of defective products due to incorrect machining, but also damage to tools, system confusion, etc. In addition, it is necessary to confirm the absence of malfunctions more frequently if possible. Therefore, in the prior art,
As in the above example, it was common to use a binary code or BCD code, which makes it easy to detect malfunctions, and to use this together with a malfunction detection system using parity checks and strobe signals. As a result, malfunction detection systems such as parity check systems and strobe signal systems are additionally required, which not only increases the number of limit switches as described above, but also requires additional circuit systems for malfunction detection. In particular, the relative adjustment between the strobe signal limit switch and the index limit switch is extremely troublesome, and if the adjustment is incorrect, malfunctions may occur, resulting in incorrect machining and tool damage. , there were drawbacks such as system confusion.

[Means for solving problems]

An object of the present invention is to use a unit distance code, for example, a gray code, which is an encoding system for a position detection signal of an intermittent rotating body, which is easy to adjust because signal processing is inherently easy, and has a large cost benefit. The present invention is characterized in that it uses a code to eliminate the need for a strobe signal system, and moreover, it is possible to reliably detect malfunctions due to signal failure, etc. The first object of the present invention is to provide a positioning device for an intermittent rotating body used in an automated machine tool such as an NC machine tool, that is, an indexing table control device. (a) A state change detection circuit 26 that reliably detects the number of state changes of the signal output by the limit switches LS _{1 to 4} 16 attached to the code plate 15, that is, the number of unit angular positions that the intermittent rotating body 12 passes. (b) An intermittent rotating body 12
A counter 23 is provided which has a step number corresponding to the number of angular positions at which it can stop;
A code signal indicating the angular position where the intermittent rotating body 12 currently exists at the time of initial setting (for example, when the power is turned on, or when the operation is temporarily stopped due to a malfunction but restarted after the accident handling is completed). After that, addition and subtraction pulses given from the state change detection circuit 26 are sequentially accumulated, and the content (count number) recorded in this counter 23 is used as the actual value of the intermittent rotating body 12. (c) The content (count number) of this counter 23 and the command device 11 such as an NC device
A number representative of the code command T that indicates the angular position that the intermittent rotating body 12 should reach is given by The second method is to make it be determined that it is an indexing malfunction.
(d) The content of the counter 23 is compared with the code signal indicating the position of the rotating body 12 at every moment, and if a malfunction occurs even if the indexing is not completed, it can be detected immediately.

〔Example〕

Hereinafter, with reference to the drawings, the circuit configurations and operations of two preferred embodiments of the invention according to the present application will be explained, and the configuration and unique effects of the present invention will be clarified. FIG. 3 shows a preferred embodiment of the first invention according to the present application. In the figure, 11 is an NC device as a command device, which encodes all operation commands to be executed by this machine tool, including index control, and converts them into binary code or BCD code in this embodiment. Output using .
Regarding indexing table control, intermittent rotating bodies 1 such as turrets, index tables, workpiece mounting tools, etc.
In response to a code command T that instructs that the intermittent rotating body 2 should start rotating in a desired direction and also indicates the angular position at which the intermittent rotating body 12 should stop, a signal TF having a strobe function is sent to the control circuit 13 and the first A code command T indicating the angular position at which the intermittent rotating body 12 should stop is output to the first matching circuit 18 and the second matching circuit 25. Reference numeral 12 denotes an intermittent rotating body such as a turret, index table, workpiece mounting device, etc., which in this embodiment has 12 independent angular positions with symbols .about.XII. That is, 12 different tools can be mounted and the workpiece can be fixed at a desired position offset by 30 degrees. 13 is a control circuit, and the NC device 11 is a command device.
The signal TF received from the intermittent rotating body 12
starts rotating in a desired direction, and gives a command to the drive device 14 to start driving based on the signal TF, which also serves as a strobe signal for the signal T described above. A code plate 15 rotates integrally with the intermittent rotating body 12 and operates the limit switch groups LS 1 to LS ₄ 16, each of which is weighted. The configuration of the limit switch group LS _{1 to LS 4} 16 is as shown in FIGS. Outputs a signal indicating. Reference numeral 17 encodes the unit distance code signal outputted by the limit switch group LS _{1 to 4} 16 into a code command T that instructs the rotation stop angle position of the intermittent rotating body 12 issued from the NC device 11 as a command device. This is a code conversion circuit that converts the code into a binary code or BCD code system so as to match the code system, and is connected to the first verification circuit 18 so that it is verified against the code command T issued by the NC device 11 as a command device. There is. In addition,
As mentioned above, the signal TF issued by the NC device 11 serving as a command device functions as a strobe signal for the code command T indicating the angular position at which the intermittent rotating body 12 should stop rotating. As in the case of the prior art described above, the code command T given to the NC
It is valid only during the period when the signal TF emitted from the device 11 is emitted. When the first matching circuit 18 recognizes that the signals match, a matching signal is given to the control circuit 13, the drive device 14 is stopped, and the intermittent rotating body 12 is stopped at a desired specific angular position.

On the other hand, 19 is an RS flip-flop circuit with a T terminal, and limit switches LS _{1 to 4} 16
There are the same number of Reference numeral 20 denotes an OR gate, which operates at a specific desired time prior to the start of a series of machining operations, in other words, at the time of initial setup, for example, at the same time as the power is turned on, or after completion of troubleshooting in the event of a malfunction. First, an initial reset signal is received from the control circuit 13 and applied to the T terminal of each RS flip-flop circuit RSFF19, and the setting state of these RS flip-flop circuits RSFF19 is adjusted to the angular position of the rotating body 12 at that time. Match the operating state of the corresponding limit switch LS _{1 to 4} 16. The other input signal of this OR gate 20 is connected to be given from the output terminal of an OR gate 22 which is connected to the output terminal of the exclusive OR gate 21, and the intermittent rotating body 12 rotates by a unit angle to switch the limit switch LS. When any one of _{1 to 4} 16 changes its state and outputs a signal different from the signal recorded by the RS flip-flop circuit RSFF19 corresponding to the limit switch LS _{1 to 4} 16 that changed its state, The corresponding exclusive OR gate 21 outputs the OR gate 20
Corresponding RS flip-flop circuit via
By changing the settings of RSFF 19, the set of RS flip-flop circuits RSFF 19 is made representative of the angular position where the constantly rotating body 12 is present. 22 is an OR gate, which allows the output of any exclusive OR gate 21 to pass through. The RS flip-flop circuit RSFF that can be explained above
19, OR gate 20, exclusive OR gate 21,
The circuit in the range surrounded by the dashed line in the figure, which consists of the OR gate 22, is the state change detection circuit 26 according to the gist of the present invention.
When the intermittent rotating body 12 rotates by a predetermined unit angle, for example, 30 degrees, the limit switch is activated.
If any of the limit switches LS _{1 to} 4 16 changes its state, one addition pulse is output, but even if the intermittent rotating body 12 rotates by a predetermined unit angle, the limit switches LS _{1 to 4} 16 A function is achieved in which the addition pulse is not output from the OR gate 22 unless there is a change in state. 23 is a counter (in this example, a decimal counter) having a step number corresponding to the number of angular positions at which the intermittent rotating body 12 can stop (12 in this example);
During the initial set specified by the control circuit 13 (for example, when the power is turned on, when a malfunction occurs and the operation is temporarily stopped, but after the accident handling is completed and the operation is resumed, etc.), the intermittent rotation is performed. The angular position (for example 1) where the body 12 currently exists is input, and from then on,
Each time the intermittent rotating body 12 rotates by a unit angle, it advances by 1, and unless there is a malfunction, the number corresponding to the angular position where the intermittent rotating body 12 currently exists is always expressed. It can be easily constructed by combining flop circuits. In this example, in order to satisfy the condition that the initial setting value is read only at the time of initial setting, the AND circuit 24
is used, a signal is given from the control circuit 13 to the AND circuit 24 only at the time of initial setting, and during the period when this signal is given, the code conversion circuit 1
7, a number representing the angular position where the intermittent rotating body 12 is present at that time (for example, a number represented by a BCD code, in this example, a number from 1 to 12) is written to the counter 2.
3 (in this example, a decimal counter). After the initial setting is completed, each time the count is output from the OR gate 22, it increments by one. In this way, the function of the state change detection circuit 26 allows the intermittent rotating body 12 to rotate by a unit angle.
Only when one of the limit switches LS _{1 to} LS 4 16 operates reliably, a count is given to the counter 23 and the counter 23 increments. It will match the number that represents the position. Next, the content (count number) recorded by the counter 23 is input to the second verification circuit 25, where a code command is issued from the NC device 11, which is a command device, to instruct the rotation stop angle position of the intermittent rotating body 12. It is compared with the count number representing T, and if they match, a signal indicating the coincidence of the signals is outputted to the control circuit 13, and furthermore, it is sent to the NC device 11, which is a command device, indicating that the indexing operation has been completed normally. A signal FIN indicating this is output, and the next process is started. On the other hand, limit switch LS _1~4 16
When the device that outputs the equal unit distance code signal does not function normally, the drive device 14 stops based on the coincidence signal given to the control device 13 from the first verification circuit 18, and the intermittent rotating body 1
2 stops, at this time, none of the RSFFs 19 of the state change detection circuit 26 changes state, so the OR circuit 22 does not output a count, and the contents of the counter 23 (count number) does not change, so the count number representing the code command T given to the matching circuit 25 does not match the content (count number) of the counter 23, so the second matching circuit 25 does not output a matching signal.
Therefore, this condition is used to issue an alarm for indexing malfunction.

Here, even after the intermittent rotating body 12 has stopped, the units such as limit switches LS _{1 to LS 4} 16, etc.
The mechanism by which the second matching circuit 25 does not output a matching signal when the device that outputs the distance code signal does not function normally will be described with reference to the drawings. FIG. 5 shows a gray code chart made using the code plate 15 shown in FIG. 4. To simplify the explanation, it is assumed that the intermittent rotating body 12 rotates only in the counterclockwise direction, and that the limit switch
Assume that LS ₄ does not close due to poor contact. First, let us assume that the intermittent rotating body 12 exists at the angular position "" and is given a command T to reach the angular position "".
Limit switch LS ₄ does not close during the period when it passes through the corner position of . However, the intermittent rotating body continues to rotate until the code value of "" occurs, that is, only limit switch LS ₁ is closed and the other limit switches LS _{1 to 3} are open.
It progresses as follows: “”, “”, “”…. However,
Since the above stopping condition is satisfied at the angular position "XII", the intermittent rotating body 12 stops at the commanded angular position "XII" rather than at the commanded angular position "". However, since the limit switch LS ₄ is inactive and does not change its state, no pulse is input to the counter 23 when the angular position moves from "" to "".
The content recorded by the counter 23 is "XI", which does not match the "" of the command value T. Therefore, an alarm of index malfunction is issued.

As explained above, according to the first invention, there is no need for a strobe signal or the like to detect the position of an intermittent rotating body, and the unit distance code, such as a gray code, is used for easy signal processing. In an indexing table control device such as a positioning device for an intermittent rotating body used in a machine, etc., a state change detection circuit 2 surrounded by a dashed line in FIG.
6, one addition pulse is emitted only when it is confirmed that the code signal to be emitted every time the intermittent rotating body rotates by a unit angle, and the counter 23 cumulatively records this addition pulse. and the number (T
It is possible to detect whether the intermittent rotating body has stopped at the correct angular position by comparing it with the command). As a result, since a unit distance code such as a gray code, which is easy to process, is used, there is no need for additional malfunction detection systems such as a parity check system or strobe signal system, and of course there is no need for additional limit switches. It does not require a malfunction detection circuit or a malfunction detection circuit, and eliminates the need for troublesome work such as adjusting limit switches, and detects index malfunctions easily and reliably. It is possible to provide an indexing table control device that can effectively prevent this.

In the first invention described above, the correctness or wrongness of the indexing operation is determined after the intermittent rotating body 12 stops, that is, at the time when each indexing operation is completed. In the second invention, as shown in part of the circuit in FIG. 6, the output of the code conversion circuit 17 is directly input to the collation circuit 25,
This is compared with the contents of the counter 23, and errors can be detected without waiting for the intermittent rotating body 12 to stop. i.e. limit switch LS _1~4
As long as the drive unit 16 is operating normally, the signal of the code conversion circuit 17 and the contents of the counter 23 should always match, and a mismatch occurs the moment a malfunction occurs. All you have to do is stop it and issue an alarm.

Further, as long as there is no malfunction, the contents of the counter 23 should match the number representing the momentary angular position of the intermittent rotating body 12, but once a malfunction occurs, these do not match. Therefore, the initial reset time at which the counter 23 can be reset is not only when the power is turned on, but also at a specific desired time after the accident handling is completed, but if desired, it can be done at other times. Of course, it is also possible to reset the data.

〔Effect of the invention〕

As explained above, according to the present invention, signal processing is essentially easy, so adjustment is easy;
The basic benefits of this encoding system can be fully enjoyed by using a unit distance code, such as a Gray code, which also has a large cost benefit.On the other hand, its drawback, which is the difficulty of detecting malfunctions, is difficult to detect when detecting state changes. This is effectively solved by a combination of a circuit, a counter, and a second verification circuit. For example, it is possible to reliably detect malfunctions caused by a limit switch signal not being generated, etc., and prevent the production of defective products or damage to tools due to incorrect machining. It is possible to provide an indexing control device for an automated machine tool such as an NC machine tool, which can effectively prevent system confusion.

In addition, in the above explanation, a contact type limit switch is used and is operated by a protrusion provided on the code board, but this is just an example.
Proximity switch, combination of light emitting element and light receiving element,
It goes without saying that a non-contact type such as a combination of a wire ring and an electromagnetic switch is also acceptable.
Further, although the description has been made using a parallel coding system as the coding system for the signals from the limit switches LS _{1 to LS 4} 16, it is also possible to use a serial coding system or a series-parallel coding system by introducing a clock system.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a conventional indexing table control device, and FIG.
These are a plan view and an AA sectional view of a code plate used therein. FIG. 3 is a block diagram of an indexing table control device according to the first invention of the present application. FIGS. 4a and 4b are a plan view and a BB sectional view of a code plate used in the indexing table control device according to the present application. FIG. 5 is a unit distance code chart for explaining the operation of the invention of the present application. FIG. 6 is a part of a block diagram of an indexing table control device according to the second invention of the present application. DESCRIPTION OF SYMBOLS 11... Command device, 12... Intermittent rotating body, 13... Control circuit, 14... Drive device, 15... Code plate, 16
...Limit switch, 17...Code conversion circuit, 1
8...First verification circuit, 19...RS flip-flop circuit with T terminal, 20...OR gate, 21
...exclusive OR gate, 22...OR gate, 23...counter, 24...AND gate, 25...second matching circuit, 26...state change detection circuit.

Claims (1)

[Claims] 1. (a) A plurality of predetermined angular positions ~XII
(b) a code command T indicating the angular position at which the intermittent rotor 12 should stop; and a strobe signal for reading the code command.
a command device 11 that emits TF; and (c) the command device 1.
(iv) a control circuit 13 that issues a command to start rotating the intermittent rotating body 12 in a desired direction in response to a strobe signal TF issued by the control circuit 1;
(e) a driving device 14 that rotates the intermittent rotating body 12 in a desired direction in response to a command issued by the controller; (f) a device 16 for emitting a unit distance code signal indicating the angular position existing at that moment; (g) a first matching circuit 18 that matches these two code signals; and (h) the control circuit 13 receiving the matching signal from the first matching circuit 18. In an indexing table control device that stops the drive device 14 and stops the intermittent rotating body 12 at an angular position specified by the code command T, (i) the intermittent rotating body 12 a state change detection circuit 26 that generates one addition pulse each time it is confirmed that the unit distance code signal that should be generated every time the unit angle rotates; and (v) the intermittent rotation. The intermittent rotating body 12 has a step number corresponding to the number of angular positions at which the body 12 can stop, and at the time of initial setting, the intermittent rotating body 12
A number representative of the code signal indicating the angular position at which is currently present is recorded, and the state change detection circuit 2
a counter 23 in which the addition pulses given from 6 are sequentially cumulatively recorded; and (e) the intermittent rotating body 12 is stopped based on the matching signal issued by the first matching circuit 18. An indexing table control device characterized in that, if the second collation circuit 25 issues a mismatch signal in a state where the indexing table is in a state where the indexing table is in a state where the indexing table is in a state where the second matching circuit 25 generates a discrepancy signal, it is determined that the indexing table control is malfunctioning. 2 (a) Multiple predetermined angular positions ~XII
(b) a code command T indicating the angular position at which the intermittent rotor 12 should stop; and a strobe signal for reading the code command.
a command device 11 that emits TF; and (c) the command device 1.
(iv) a control circuit 13 that issues a command to start rotating the intermittent rotating body 12 in a desired direction in response to a strobe signal TF issued by the control circuit 1;
(e) a driving device 14 that rotates the intermittent rotating body 12 in a desired direction in response to a command issued by the controller; (f) a device 16 for emitting a unit distance code signal indicating the angular position existing at that moment; (g) a first matching circuit 18 that matches these two code signals; and (h) the control circuit 13 receiving the matching signal from the first matching circuit 18. In an indexing table control device that stops the drive device 14 and stops the intermittent rotating body 12 at an angular position specified by the code command T, (i) the intermittent rotating body 12 a state change detection circuit 26 that generates one addition pulse each time it is confirmed that the unit distance code signal that should be generated every time the unit angle rotates; and (v) the intermittent rotation. The intermittent rotating body 12 has a step number corresponding to the number of angular positions at which the body 12 can stop, and at the time of initial setting, the intermittent rotating body 12
A number representative of the code signal indicating the angular position at which is currently present is recorded, and the state change detection circuit 2
(l) a second collation circuit 25 that collates the content (count number) recorded in the counter 23 with the output of the code conversion circuit 17; (e) If the second verification circuit 25 issues a discrepancy signal, it is determined that the indexing base control is malfunctioning.