JP4506065B2 - Machine Tools - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a machine tool.
[0002]
[Prior art]
Conventionally, a machine tool has a built-in electric circuit for energizing a sensor for monitoring an operation state of the machine tool and an actuator for operating the machine tool.
In this electrical circuit, a ground side path in which one of a high potential path connected to the high potential side of the DC power supply and a low potential path connected to the low potential side is normally connected to the ground position. The other is a non-grounded path that is not connected to the grounding position. The non-ground side path is provided with an overcurrent protection device such as a fuse. When the non-ground side path is short-circuited to the ground side path or a ground position (for example, a housing), the fuse is blown. By disconnecting the ungrounded path, the electric circuit is protected from the short-circuit current.
[0003]
[Problems to be solved by the invention]
However, the fuse provided in the non-ground side path has a sufficiently large rating so that the fuse is not blown while the machine tool is normally operating. Such a fuse takes time to blow even when a short-circuit current flows, and the short-circuit current flows in the electric circuit until the non-grounded path is cut.
[0004]
In this way, when the short-circuit current is flowing, if the short-circuit (contact state) between the non-ground side path and the ground-side path or ground position is resolved (isolated) due to vibration or the like, a spark is generated between them. There was a thing. In addition, even when the circuit path of the electric circuit generates heat due to a short circuit current and melts, sparks may occur at the melted portion. In a machine tool, a large amount of oil mist is usually generated during processing of a workpiece. Therefore, if a spark is generated in a place where the oil mist is filled, there is a risk of ignition, which is very dangerous.
[0005]
An object of the present invention is to provide a machine tool capable of preventing a spark from being generated even when a short-circuit current flows.
[0008]
  To solve the above problemClaim1The machine tool described in
  A high-potential path connected to the high-potential side of the DC power supply and a low-potential path connected to the low-potential side of the DC power supply, and either the high-potential path or the low-potential path is at the ground position A machine tool comprising an electrical circuit that is connected to a ground path and the other is a non-ground path that is not connected to a ground position,
  A short circuit current that flows from the non-ground side path to the connection path when the non-ground side path and the ground position are short-circuited in the connection path that connects the ground side path and the ground position. It has a limiting resistor that limits the current to a predetermined current value
  It is characterized by that.
[0009]
According to the machine tool configured as described above, even when the non-ground side path and the ground position are short-circuited, the limiting resistance limits the short-circuit current flowing from the non-ground side path to the connection path to a predetermined current value. To do. Therefore, the resistance of the limiting resistor is set so that the current value is (= e / z) of the short-circuit current determined by the voltage value e of the DC power supply and the resistance value z of the limiting resistor becomes a current value that does not cause a spark. If the value is determined, no spark is generated even when a short-circuit current flows.
[0010]
  Also,thisMachine ToolsIn
  Electric circuitIs,
  A short-circuit current that flows from the non-ground side path to the connection path when the non-ground side path and the ground position are short-circuited in the connection path that connects the ground side path and the ground position is a predetermined current value. Limiting resistor to limit toWhen,
  Short-circuit detecting means for detecting that a short-circuit current has flowed through the limiting resistor;
  Path disconnecting means for electrically disconnecting a part of one or both of the high potential path and the low potential path when the short circuit current is detected by the short circuit detecting means,
  The short-circuit detecting means does not turn on at a potential difference generated at both ends of the limiting resistor in a normal operation state, and turns on at a potential difference generated at both ends of the limiting resistor in a short-circuit state in which a short-circuit current flows through the limiting resistor. It is a photocoupler that detects the short-circuit current flowing through the resistor.
[0011]
According to the machine tool configured as described above, when the short-circuit detecting unit detects that a short-circuit current flows through the limiting resistor, the path cutting unit detects one or both of the high-potential path and the low-potential path. The electrical circuit can be protected from a short circuit current.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the present invention will be described with examples.
[First Embodiment]
[overall structure]
As shown in FIG. 1, the machine tool 1 includes a DC power supply 10, an input / output board 20, a three-wire sensor (hereinafter simply referred to as a sensor) 30, an actuator 32, and the like in a housing 40.
[0013]
The input / output board 20 includes a sensor input circuit 22 that supplies the power supplied from the DC power supply 10 to the sensor 30, an actuator output circuit 24 that supplies the actuator 32, and the like. The input / output board 20 is connected to the housing 40 in a path connected to the negative electrode side of the DC power supply 10.
[0014]
The housing 40 is divided into a control chamber 42 in which the DC power supply 10 and the input / output substrate 20 are disposed, and a processing chamber 44 in which the sensor 30 and the actuator 32 are disposed. The housing 40 is grounded to the outside by a grounding point 46.
[Sensor input circuit 22]
First, the sensor input circuit 22 constituting the input / output board 20 will be described with reference to FIG.
[0015]
The sensor input circuit 22 has a high potential path LH from the positive side of the DC power supply 10 to the sensor 30 and a low potential path LL from the negative side of the DC power supply 10 to the sensor 30 as paths for supplying power to the sensor 30. I have. The high potential path LH is connected to the positive electrode side of the DC power supply 10 via a relay (path disconnecting means in the present invention) RY, a first limiting resistor R1, and a second limiting resistor R2 provided in series. The first limiting resistor is provided with a short-circuit detection circuit (short-circuit detection means in the present invention) 50 in parallel. The sensor input circuit 22 includes an operation load RA that is activated by a detection signal output from the sensor 30.
[0016]
The relay RY has a coil portion connected to the short circuit detection circuit 50. If the output of the short circuit detection circuit 50 is L level (0 V), the high potential path LH is opened and the output of the short circuit detection circuit 50 is H level. If (+ 5V), the high potential path LH is closed.
[0017]
The upper limit zmax of the combined resistance value z of the limiting resistors R1 and R2 is determined based on the voltage value v1 and current value i1 necessary for normal operation of the sensor 30 and the voltage value e of the DC power supply 10 (zmax = (e -V1) / i1). The lower limit zmin of the combined resistance value z is a high potential when the high potential path LH from the second limiting resistor R2 to the sensor 30 and the low potential path LL from the negative electrode of the DC power supply 10 to the sensor 30 are short-circuited. This is determined by how much the short-circuit current flowing from the path LH toward the low potential path LL is limited. Here, when the short-circuit current is limited to the current value i2, the lower limit zmin is determined based on the current value i2 and the voltage value e of the DC power supply 10 (zmin = e / i2). Thus, the limiting resistors R1 and R2 are selected so that the combined resistance value z is between zmin and zmax. For example, when the voltage value necessary for normal operation of the sensor 30 is 12 V, the current value is 10 mA, and the voltage value of the DC power supply 10 is 24 V, the upper limit zmax of the combined resistance value is 1.2 KΩ (= (24 −12) /0.01). When the current value of the short circuit current is limited to 0.5 A, the lower limit zmin of the combined resistance value z is 48Ω (= 24 / 0.5).
[0018]
The short circuit detection circuit 50 detects a short circuit current flowing through the first limiting resistor R1, and as shown in FIG. 3, the grounded emitter first switching circuit 52 using the pnp transistor Tr1, This is composed of a grounded-emitter-type second switching circuit 54 using an npn transistor Tr2 and a flip-flop (hereinafter referred to as FF) 56.
[0019]
The first switching circuit 52 outputs the output point P1 without the transistor Tr1 being turned on (the emitter-collector is energized) in the potential difference generated between both ends of the first limiting resistor R1 in the normal operation state where the power is supplied to the sensor 30. The output from the output point P1 becomes L level (0V), and on the other hand, in the short-circuit state in which a short-circuit current flows through the first limiting resistor R1, the transistor Tr1 is turned on by the potential difference generated at both ends of the first limiting resistor R1. It is configured to be at the H level (value determined by the resistance value of the load resistance (R13) and the collector current of the transistor Tr1). For example, when the resistance value of the first limiting resistor R1 is 8Ω, the resistance value of the second limiting resistor R2 is 40Ω, and the voltage value of the DC power supply 10 is 24V, 4V ( = 24 × 8 / (40 + 8)) potential difference occurs. That is, the first switching circuit 52 has characteristics of the transistor Tr1 to be used and the resistors R11, R12, and R13 to be used so that the transistor Tr1 is turned on when the potential difference between both ends of the first limiting resistor R1 becomes 4V. It is sufficient to determine the resistance value.
[0020]
In the second switching circuit 54, the output point P1 of the first switching circuit 52 is an input point, and when the output of the first switching circuit 52 is L level (normal operation state), the transistor Tr2 is not turned ON. When the output from the output point P2 is H level (+ 5V), and the output level of the first switching circuit 52 is H level (short circuit state), the transistor Tr2 is turned on and the output from the output point P2 is L. It becomes level (0V).
[0021]
In the FF 56, the input to the input terminal D is always at the H level (+ 5V), and the output point P2 of the second switching circuit 54 is connected to the negative logic clock terminal CK. Here, when the output of the second switching circuit 54 is H level (normal operation state), the output of the non-inverting output terminal Q1 is L level (0V) and the output of the inverting output terminal Q2 is H level (+ 5V). Become. On the other hand, when the output level of the second switching circuit 54 is L level (short circuit state), the output of the non-inverted output terminal Q1 is H level (+ 5V) and the output of the inverted output terminal Q2 is L level (0V). The FF 56 has a non-inverted output terminal Q1 output at L level (0V) and an inverted output terminal Q2 output at H level (+ 5V) in response to a reset pulse input from the reset terminal CLR at the same time when the machine tool 1 is turned on. ).
[0022]
Thus, in the short circuit detection circuit 50, the output of the first switching circuit 52 becomes H level, the output level of the second switching circuit 54 becomes L level, and the output of the non-inverting output terminal Q1 of the FF 56 becomes H level and inverted output. It can be detected that the output of the terminal Q2 has become L level as a short-circuit current flowing through the first limiting resistor R1. The non-inverted output terminal Q1 of the FF 56 is connected to a microcomputer provided in a controller (not shown) provided outside the housing 40, and a short-circuit current flows to the first limiting resistor R1 by the short-circuit detection circuit 50. When detected, the microcomputer displays a message notifying that a short-circuit current has flowed on the display screen of the controller. Further, the inverting output terminal Q2 of the FF 56 is connected to the coil portion of the relay RY, and when the short-circuit detection circuit 50 does not detect that a short-circuit current flows through the first limiting resistor R1, the inverting output terminal Q2 Since the output of Q2 is at the H level, the relay RY is activated and the high potential path LH is closed. On the other hand, when the short-circuit detection circuit 50 detects that a short-circuit current flows through the first limiting resistor R1, the output of the inverting output terminal Q2 becomes L level, so that the operation of the relay RY stops and the high potential path LH Will be open.
[0023]
[Actuator output circuit 24]
Next, the actuator output circuit 24 included in the input / output substrate 20 will be described with reference to FIG. In this actuator output circuit 24, the same reference numerals are given to the same configurations as those of the sensor input circuit 22 described above, and only differences from the sensor input circuit 22 will be described in detail.
[0024]
The actuator output circuit 24 includes, as paths for supplying power to the actuator 32, a high potential path LH from the positive electrode side of the DC power supply 10 to the actuator 32 and a low potential path LL from the negative electrode side of the DC power supply 10 to the actuator 32. I have. The high potential path LH is connected to the positive electrode side of the DC power supply 10 via the relay RY, the first limiting resistor R1, the second limiting resistor R2, and the switching element SW provided in series, and of these, the first limiting A short circuit detection circuit 50 is provided in parallel with the resistor.
[0025]
The switching element SW controls the operation of the actuator 32 by opening and closing the high potential path LH.
[Effect of the first embodiment]
According to the machine tool 1 configured as described above, even when the high potential path LH and the low potential path LL are short-circuited, the short-circuit current flowing from the high potential path LH to the low potential path LL is limited by the limiting resistor R1, R2 limits to a predetermined current value. Therefore, the current value i2 (= e / z) of the short circuit current determined by the voltage value e of the DC power supply 10 and the combined resistance value z of the limiting resistors R1 and R2 is a current value that does not cause a spark. If the combined resistance value z of the limiting resistors R1 and R2 is determined, no spark is generated even when a short-circuit current flows.
[0026]
Moreover, since the relay RY electrically disconnects the high potential path LH when the short circuit detection circuit 50 detects that a short circuit current flows through the first limiting resistor R1, it is possible to protect the electric circuit from the short circuit current. it can.
[Second Embodiment]
[overall structure]
As shown in FIG. 4, the machine tool 2 includes a DC power supply 10, an input / output board 20, a three-wire sensor (hereinafter simply referred to as a sensor) 30, an actuator 32, and the like in a housing 40. In addition, in the machine tool 2, the same code | symbol shall be attached | subjected about the structure similar to the machine tool 1 of 1st Embodiment, and only the difference with the machine tool 1 of 1st Embodiment is explained in full detail.
[0027]
The input / output board 20 includes a sensor input circuit 26 that supplies the power supplied from the DC power supply 10 to the sensor 30, an actuator output circuit 28 that supplies the actuator 32, and the like.
[Sensor input circuit 26]
First, the sensor input circuit 26 provided in the input / output board 20 will be described with reference to FIG.
[0028]
The sensor input circuit 26 supplies a high potential path LH from the positive side of the DC power supply 10 to the sensor 30 and a low potential path LL from the negative side of the DC power supply 10 to the sensor 30 as paths for supplying power to the sensor 30. I have. The high potential path LH is connected to the positive electrode side of the DC power supply 10 via a relay (path cutting means in the present invention) RY provided in series. The sensor input circuit 26 includes a ground side path LG that connects the low potential path LL to the housing 40, a third limiting resistor R3 and a fourth limiting resistor R4 that are provided in series with the ground side path LG, and a fourth limiting resistance R4. A short-circuit detection circuit (short-circuit detection means in the present invention) 60 provided in parallel with the limiting resistor R4, an operational load RA that operates according to a detection signal output from the sensor 30, and the like are provided. In the sensor input circuit 26, the high potential path LH with respect to the ground side path corresponds to the non-ground side path in the present invention.
[0029]
The relay RY has a coil portion connected to the short circuit detection circuit 60. If the output of the short circuit detection circuit 60 is L level (0 V), the high potential path LH is opened and the output of the short circuit detection circuit 50 is H level. If (+ 5V), the high potential path LH is closed.
[0030]
When the combined resistance value z of the limiting resistors R3 and R4 is short-circuited (ground fault) between the high potential path LH from the relay RY to the sensor 30 and the casing 40, the casing 40 is connected from the high potential path LH. This is determined by how much current value the short-circuit current flowing to the negative electrode side of the DC power supply 10 is limited. Here, when the short-circuit current is limited to the current value i3, the combined resistance value z is determined based on the current value i3 and the voltage value e of the DC power supply 10 (z = e / i3). For example, when the current value i3 of the short circuit current is limited to 0.5 A or less, the combined resistance value z is 48Ω or more (= 24 / 0.5).
[0031]
The short circuit detection circuit 60 is a circuit that detects that a short circuit current has flown through the fourth limiting resistor R4. As shown in FIG. 6, the photocoupler CP and a flip-flop (hereinafter referred to as FF) 56 are provided. It consists of and.
The photocoupler CP is ON in a normal operation state where the power is supplied to the sensor 30 and the potential difference generated between both ends of the fourth limiting resistor R4 (a state in which the emitter-collector on the phototransistor side is energized by light emission on the light-emitting diode side). ), The output from the output point P3 becomes H level (+ 5V). On the other hand, the potential difference generated at both ends of the fourth limiting resistor R4 in the short-circuit state where the short-circuit current flows in the fourth limiting resistor R4 is turned ON and the output point P3 Becomes an L level (0 V).
[0032]
Therefore, in the limiting resistor R4 described above, the potential difference v2 generated at both ends in a normal operation state including the influence of noise or the like is smaller than the potential difference v3 necessary for turning on the photocoupler CP (v2 <v3), and It is necessary to set the resistance value so that the potential difference v4 generated at both ends in the short-circuit state is larger than the potential difference v3 necessary for turning on the photocoupler CP (v4> v3). For example, the voltage (potential difference v3) necessary for surely turning on the photocoupler CP is 1.2 V, the current flowing to the light emitting diode side of the photocoupler CP is 0.01 A, and the photocoupler CP is surely turned off. The voltage (potential difference v2) is 0.5V, the voltage value of the DC power supply 10 is 24V, the current assumed to flow through the fourth limiting resistor R4 due to the occurrence of noise, etc. is 0.001A, and the photocoupler CP Exemplifies a case where it can be reliably detected that a short-circuit current of 0.02 A or more has flowed. In this case, in order to make the potential difference generated across the fourth limiting resistor R4 having the resistance value r4 in the normal operation state smaller than the voltage at which the photocoupler CP is surely turned off, an expression of 0.5> r4 × 0.001 Therefore, the resistance value r4 of the fourth limiting resistor R4 needs to be smaller than 500Ω (<0.5 / 0.001). On the other hand, in order for the potential difference generated at both ends of the fourth limiting resistor R4 in the short-circuit state to be larger than the voltage necessary to turn on the photocoupler CP, 1.2 <(0.02-0.01) × r4 Based on this, the resistance value r4 of the fourth limiting resistor R4 needs to be larger than 120Ω (> 1.2 / 0.01). Therefore, the resistance value r4 of the fourth limiting resistor R4 may be selected between 120Ω and 500Ω.
[0033]
Further, when it is desired to limit the short-circuit current to 0.5 A or less, if the voltage (potential difference v3) necessary for surely turning on the photocoupler CP is 1.2 V, the resistance value of the third limiting resistor R3 is 0. Based on the equation 5> (24-1.2) / r4, it should be greater than 45.6 Ω (> 22.8 / 0.5). Furthermore, in order for the photocoupler CP to detect that a short-circuit current has flowed, a short-circuit current of 0.02 A or more needs to flow, and thus the resistance value of the third limiting resistor R3 is 0.02 <(24-1 .2) Based on the equation of / r3, it needs to be smaller than 1140Ω (<22.8 / 0.02). Therefore, the resistance value r3 of the third limiting resistor R3 may be selected between 45.6Ω and 1140Ω.
[0034]
In the FF 56, the input to the input terminal D is always H level (+ 5V), and the output point P3 of the photocoupler CP is connected to the negative logic clock terminal CK. Here, when the output level of the photocoupler CP is H level (normal operation state), the output of the non-inverting output terminal Q1 is L level (0V) and the output of the inverting output terminal Q2 is H level (+ 5V). . On the other hand, when the output level of the photocoupler CP is L level (short circuit state), the output of the non-inverting output terminal Q1 is H level (+ 5V), and the output of the inverting output terminal Q2 is L level (0V). The FF 56 has a non-inverted output terminal Q1 output at L level (0V) and an inverted output terminal Q2 output at H level (+ 5V) in response to a reset pulse input from the reset terminal CLR at the same time when the machine tool 1 is turned on. ).
[0035]
Thus, the short circuit detection circuit 60 indicates that the output of the photocoupler CP is at L level, the output of the non-inverting output terminal Q1 of the FF 56 is H level, and the output of the inverting output terminal Q2 is L level. It can be detected as a short-circuit current flowing through R4. The non-inverted output terminal Q1 of the FF 56 is connected to a microcomputer provided in a controller (not shown) provided outside the housing 40, and a short-circuit current flows through the fourth limiting resistor R4 by the short-circuit detection circuit 60. When detected, the microcomputer displays a message notifying that a short-circuit current has flowed on the display screen of the controller. Further, the inverting output terminal Q2 of the FF 56 is connected to the coil portion of the relay RY. When the short-circuit detection circuit 60 does not detect that a short-circuit current flows through the fourth limiting resistor R4, the inverting output terminal Q2 Since the output of Q2 is at the H level, the relay RY is activated and the high potential path LH is closed. On the other hand, when the short circuit detection circuit 60 detects that a short circuit current flows through the fourth limiting resistor R4, the output of the inverting output terminal Q2 becomes L level, so that the operation of the relay RY stops and the high potential path LH. Will be open.
[0036]
[Actuator output circuit 28]
Next, the actuator output circuit 28 provided in the input / output substrate 20 will be described with reference to FIG. In this actuator output circuit 28, the same reference numerals are given to the same configurations as those of the sensor input circuit 26 described above, and only differences from the sensor input circuit 26 will be described in detail.
[0037]
The actuator output circuit 28 has, as paths for supplying power to the actuator 32, a high potential path LH from the positive electrode side of the DC power supply 10 to the actuator 32 and a low potential path LL from the negative electrode side of the DC power supply 10 to the actuator 32. I have. High potential path LH is connected to the positive electrode side of DC power supply 10 via relay RY and switching element SW provided in series. The actuator output circuit 28 includes a ground side path LG that connects the low potential path LL to the housing 40, a third limiting resistor R3 and a fourth limiting resistor R4 provided in series with the ground side path LG, A short circuit detection circuit 60 provided in parallel with the limiting resistor R4 is provided.
[0038]
The switching element SW controls the operation of the actuator 32 by opening and closing the high potential path LH.
[Effects of Second Embodiment]
According to the machine tool 2 configured in this way, even if the high potential path LH and the housing 40 are short-circuited, a short circuit that flows from the high potential path LH through the housing 40 to the negative electrode side of the DC power supply 10. The limiting resistors R3 and R4 limit the current to a predetermined current value. Therefore, the current value i3 (= e / z) of the short circuit current determined by the voltage value e of the DC power supply 10 and the combined resistance value z of the limiting resistors R3 and R4 is a current value that does not cause a spark. If the resistance value of the combined resistance value z of the limiting resistors R3 and R4 is determined, no spark is generated even when a short-circuit current flows.
[0039]
Moreover, since the relay RY electrically disconnects the high potential path LH when the short circuit detection circuit 60 detects that a short circuit current has flown through the fourth limiting resistor R4, the electrical circuit can be protected from the short circuit current. it can.
[Modification]
As mentioned above, although embodiment of this invention was described, this invention is not limited to said specific one Embodiment, In addition, it can implement with a various form.
[0040]
For example, in the first and second embodiments, a sensor that uses a three-wire sensor as the sensor 30 is illustrated, but as the sensor, as shown in FIG. 7, the operation load RA is serially connected to the low potential path LL. By providing, a two-wire sensor 34 such as an optical switch or a limit switch can be used.
[0041]
In the present embodiment, one sensor input circuit 22, 26 is provided with one sensor 30, but a plurality of sensors 30 are provided with respect to one sensor input circuit 22, 26. May be provided.
In the present embodiment, one actuator 32 is provided for one actuator output circuit 24, 28, but a plurality of actuators 32 are provided for one actuator output circuit 24, 28. It may be provided.
[0042]
In the first embodiment, the limiting resistors R1 and R2 are illustrated as being provided in series with the high potential path LH. However, even if both the limiting resistors R1 and R2 are provided in series with the low potential path LL. Good. Further, one of the limiting resistors R1 and R2 may be provided in series with the high potential path LH and the other in series with the low potential path LL.
[0043]
Moreover, the electric circuit comprised with the relay RY and the short circuit detection circuit 50 in 1st Embodiment, and the electric circuit comprised with the relay RY and the short circuit detection circuit 60 in 2nd Embodiment were shown in FIG. As described above, the same sensor input circuit or actuator output circuit may be used.
[0044]
In addition, the specific configuration of the short-circuit detection circuit 50 in the first embodiment is not particularly limited as long as the short-circuit detection circuit 50 can detect that a short-circuit current flows through the first limiting resistor R1.
In addition, the specific configuration of the short-circuit detection circuit 60 in the second embodiment is not particularly limited as long as the short-circuit detection circuit 60 can detect that a short-circuit current flows through the fourth limiting resistor R4.
[0045]
Further, in the present embodiment, an example in which the high potential path LH is opened by the relay RY when a short circuit current is detected by the short circuit detection circuits 50 and 60 is illustrated, but the high potential path LH is opened. For example, as shown in FIG. 9, the switching circuit 70 using a field effect transistor (hereinafter referred to as FET) Tr4 may be used to open the high potential path LH as shown in FIG. Good. In this case, the time required to open the high-potential path LH by the relay is several ms, whereas the time required to open the high-potential path LH by the FET is several tens of μs. LH can be released. Alternatively, the high potential path LH may be configured to be opened by a switching element other than those described above.
[0046]
In the first embodiment, the low potential path LL is connected to the casing 40 by connecting the connection path between the low potential path LL and the negative electrode side of the DC power supply 10 to the ground side path, and the high potential path LH is connected to the non-ground side. Although illustrated as a path, the high potential path LH is connected to the casing 40 by connecting the connection path between the high potential path LH and the positive side of the DC power supply 10 to the casing 40, and the low potential path LL is connected to the non-ground side. A route may be used.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a machine tool (first embodiment).
FIG. 2 is a diagram showing a sensor input circuit (a) and an actuator output circuit (b).
FIG. 3 shows a short circuit detection circuit.
FIG. 4 is a block diagram showing the configuration of a machine tool (second embodiment).
FIG. 5 is a diagram showing a sensor input circuit (a) and an actuator output circuit (b).
FIG. 6 shows a short circuit detection circuit.
FIG. 7 is a diagram showing a part of a sensor input circuit according to another embodiment.
FIG. 8 is a diagram showing a part of a circuit included in a control board in another embodiment;
FIG. 9 is a diagram showing a switching circuit that opens a high potential path by a field effect transistor in another embodiment;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Machine tool, 2 ... Machine tool, 10 ... DC power supply, 20 ... Input / output board, 22 ... Sensor input circuit, 24 ... Actuator output circuit, 26 ... Sensor Input circuit, 28 ... Actuator output circuit, 30 ... Sensor, 32 ... Actuator, 40 ... Housing, 42 ... Control room, 44 ... Processing room, 46 ... Grounding point , 50 ... short circuit detection circuit, 52 ... first switching circuit, 54 ... second switching circuit, 56 ... flip-flop, 60 ... short circuit detection circuit, LG ... ground side path, LH: High potential path, LL: Low potential path, R1: First limiting resistor, R2: Second limiting resistor, R3: Third limiting resistor, R4: Fourth limiting Resistance, RA ... Operating load, RY ... Relay, SW ... Switch Quenching element.

Claims (1)

A high-potential path connected to the high-potential side of the DC power supply and a low-potential path connected to the low-potential side of the DC power supply, and either the high-potential path or the low-potential path is at the ground position A machine tool comprising an electrical circuit that is connected to a ground path and the other is a non-ground path that is not connected to a ground position,
The electrical circuit is
A short-circuit current that flows from the non-ground side path to the connection path when the non-ground side path and the ground position are short-circuited in the connection path that connects the ground side path and the ground position is a predetermined current value. and limiting resistor be limited to,
Short-circuit detecting means for detecting that a short-circuit current has flowed through the limiting resistor;
Path disconnecting means for electrically disconnecting a part of one or both of the high potential path and the low potential path when the short circuit current is detected by the short circuit detecting means,
The short-circuit detecting means does not turn on at a potential difference generated at both ends of the limiting resistor in a normal operation state, and turns on at a potential difference generated at both ends of the limiting resistor in a short-circuit state in which a short-circuit current flows through the limiting resistor. A machine tool that is a photocoupler that detects a short-circuit current flowing through a resistor .

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