A digital signal output device that outputs a digital signal corresponding to an operation switch

Abstract

The present invention relates to a digital signal output device that outputs a digital signal corresponding to an operation switch. The digital signal output device (1) comprises: an operation switch (11) having a first terminal (21-1) to which a first voltage is applied and a second terminal (21-2) that outputs the first voltage when the contact is closed; a voltage switching unit (12) that selects a second voltage from a plurality of constant voltages; a voltage determination unit 13 that determines whether the output voltage of the voltage switching unit (12) has changed from the second voltage in a predetermined cycle; and a digital signal generating unit (14) that generates a digital signal indicating a first state when the first voltage is output from the second terminal (21-2) in each cycle when the voltage determination unit (13) determines that the output voltage has not changed from the second voltage, and generates a digital signal indicating a second state when the first voltage is not output.

Description

Technical Field

[0001] The present invention relates to a digital signal output device which outputs a digital signal corresponding to an operation switch. Background Art

[0002] As an interface for converting the operation state of an operation switch provided on a machine tool or a robot into a digital signal that can be processed by a control device for controlling the machine tool or the robot, a digital signal output device that outputs a digital signal corresponding to the operation switch is included. Such a digital signal is also referred to as, for example, a digital input signal or a DI signal. Here, the control device for controlling a machine tool or a robot includes, for example, a numerical control device for controlling a machine tool or a robot controller for controlling a robot.

[0003] The digital signal output device outputs a conductive digital signal (high or 1) when the contact of the operating switch is closed, and outputs a disconnected digital signal (low or 0) when the contact of the operating switch is disconnected. The control device for controlling the machine tool or robot can grasp the operating state (opening and closing state) of the operating switch through the conductive and disconnected digital signals output from the digital signal output device, and perform various processes according to the state.

[0004] In a digital signal output device, a common voltage shared with a machine tool, a robot or its control device is applied to one end of an operating switch, i.e., a "common terminal". When the contacts of the operating switch are closed, a voltage equivalent to the common voltage is output from the other end of the operating switch, i.e., the "output terminal". On the other hand, when the contacts of the operating switch are disconnected, a voltage different from the voltage equivalent to the common voltage is output from the output terminal of the operating switch. In a digital signal output device, a digital signal of on / off is generated and output according to the voltage output from the output terminal of the operating switch. Under such an operating principle, in order to properly generate a digital signal of on / off, the voltage output from the output terminal of the operating switch must be different values ​​according to the opening and closing of the contacts of the operating switch. Therefore, a voltage different from the common voltage is applied to the output terminal of the operating switch via a resistor (a pull-up resistor or a pull-down resistor).

[0005] For example, as described in Japanese Patent Gazette No. 2015-180061, there is known an electronic circuit having the following structure, which comprises: a first input terminal and a second input terminal; an input circuit including a first input and a second input; a plurality of input switches which are controlled by one or more clock signals and include a first input switch electrically connected between the first input terminal and the first input of the input circuit and a second input switch electrically connected between the second input terminal and the second input of the input circuit; and a charge compensation circuit having a first output and a second output, the charge compensation circuit being used to compensate for charges injected by the plurality of input switches accompanying a transition of at least one of the one or more clock signals.

[0006] For example, as described in Japanese Patent Gazette No. 2015-099412, there is known a digital output device having a computing device and a detection device, wherein the computing device has a plurality of digital circuits for outputting digital signals to the outside, and the detection device determines through a logic circuit whether the logic value of an object signal to be detected in the digital signal meets predetermined conditions, and when the conditions are met, determines that the object signal is illegal.

[0007] For example, as described in Japanese Patent Gazette No. 2009-055656, there is known an inverter device that can input a digital signal corresponding to the opening and closing state of a switch unit connected to the outside in a source input form and a synchronous input form, characterized in that the inverter device comprises: an input terminal connected to one end of each of the above-mentioned switch units, respectively; a common terminal commonly connected to the other end of each of the above-mentioned switch units; a first switching unit that connects the above-mentioned common terminal to any one of a first common potential corresponding to the source input form and a second common potential corresponding to the synchronous input form; a first and a second input circuit that are provided for each of the above-mentioned input terminals and input digital signals in the source input form and the synchronous input form, respectively; and a second switching unit that is linked to the above-mentioned first switching unit and connects the above-mentioned input terminal to any one of the above-mentioned first and second input circuits according to each of the above-mentioned input forms.

[0008] For example, as described in Japanese Patent Gazette No. 11-161391, there is known an interface circuit having an input terminal for receiving an input signal such as a contact input or a logic input, characterized in that the interface circuit comprises: a switching unit for switching between a connection state in which a pull-up resistor is connected to the input terminal and a connection state in which a pull-down resistor is connected to the input terminal; a discrimination unit for discriminating whether it is a synchronous input or a source input by discriminating the switched connection state of the switching unit; and a signal switching unit for switching between a signal output state in which a signal obtained by inverting the input signal and a signal output state in which the input signal is directly output based on the discrimination result of the discrimination unit. Summary of the invention

[0009] Generally, in machines such as machine tools, robots or their control devices, a common voltage is set for each machine. That is, the common voltage is different for different machines. For example, there are machines with a common voltage of 0 [V] and machines with a common voltage of 24 [V]. Therefore, in a digital signal output device, in order to improve versatility so as to be able to correspond to a variety of common voltages, a switching switch capable of selectively applying a variety of voltages via a resistor (pull-up resistor or pull-down resistor) is provided on the output terminal of the operating switch. For example, in order to appropriately generate a digital signal for on and off regardless of whether the operating switch is set on a machine with a common voltage of 0 [V] or a machine with a common voltage of 24 [V], a switching switch for switching to any one of the voltages of 24 [V] and 0 [V] is provided in the digital signal output device. The designer or operator of a machine such as a machine tool, a robot or its control device switches the switching switch to 24 [V] voltage when the common voltage of the machine provided with an operating switch is 0 [V], and switches the switching switch to 0 [V] voltage when the common voltage of the machine provided with a switch is 24 [V]. However, when an abnormality occurs in the switching switch, such as poor contact caused by rust or mixing of foreign matter, or displacement of the switching position caused by vibration or impact of the machine, a voltage different from the common voltage cannot be applied to the output terminal of the operating switch via a resistor. As a result, the digital signal output device will perform an erroneous operation and cannot properly generate a digital signal for on and off. When the switching switch in the digital signal output device has an abnormality and cannot generate an appropriate digital signal, the machine tool or robot may perform a dangerous operation different from the original operation. Therefore, a high-safety technology is needed that can avoid the danger of the machine provided with an operating switch even if an abnormality occurs in the digital signal output device that outputs the digital signal corresponding to the operating switch.

[0010] According to one embodiment disclosed in the present invention, a digital signal output device comprises: an operating switch having a first terminal to which a first voltage is applied and a second terminal that outputs the first voltage when the contact is closed; a voltage switching unit that selects and outputs a second voltage different from the first voltage from a plurality of constant voltages; a voltage determination unit that determines, at each predetermined cycle, whether the voltage output from the voltage switching unit has changed from the second voltage; and a digital signal generating unit that, when the voltage determination unit determines that the voltage has not changed from the second voltage, generates, at each cycle, a digital signal representing a first state when the first voltage is output from the second terminal, and generates a digital signal representing a second state different from the first state when the first voltage is not output from the second terminal. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The present invention can be more clearly understood by referring to the following drawings.

[0012] Figure 1 This is a schematic diagram showing the structure of a digital signal output device according to one embodiment disclosed in the present invention.

[0013] Figure 2 This is a diagram showing a structure when a digital signal output device according to an embodiment of the present invention is applied when a common voltage is 0 [V].

[0014] Figure 3 Yes means Figure 2 A diagram showing a situation when an abnormality occurs in a voltage switching unit in a digital signal output device.

[0015] Figure 4A Yes means Figure 2 A diagram showing the relationship between the open / closed state of an operation switch in a digital signal output device and a digital signal output from a digital signal generating unit, which shows a situation when there is no abnormality in the switching switch in the voltage switching unit.

[0016] Figure 4B Yes means Figure 2 A diagram showing the relationship between the open / closed state of an operation switch in a digital signal output device and a digital signal output from a digital signal generating unit, which shows a situation when an abnormality occurs in a switching switch in a voltage switching unit.

[0017] Figure 5A This is a diagram showing a configuration when a conventional digital signal output device is applied when a common voltage is 0 [V], and shows a situation when there is no abnormality in a switching switch in a voltage switching unit.

[0018] Figure 5B This is a diagram showing the structure of a conventional digital signal output device when the common voltage is 0 [V], and shows a situation when an abnormality occurs in a switching switch in a voltage switching unit.

[0019] Fig. 6A Yes means Figure 5A and Figure 5B The diagram shows the relationship between the open and closed state of the operating switch in the conventional digital signal output device and the digital signal output from the digital signal generating unit, which shows the situation when there is no abnormality in the switching switch in the voltage switching unit.

[0020] Figure 6B Yes means Figure 5A and Figure 5B A diagram showing the relationship between the open / closed state of an operating switch in a conventional digital signal output device and a digital signal output from a digital signal generating unit shows a situation when an abnormality occurs in a switching switch in a voltage switching unit.

[0021] Figure 7 This is a diagram showing a configuration when a digital signal output device according to an embodiment of the present invention is applied when a common voltage is 24 [V].

[0022] Figure 8 Yes means Figure 7 A diagram showing a situation when an abnormality occurs in a voltage switching unit in a digital signal output device.

[0023] Fig. 9A Yes means Figure 7 A diagram showing the relationship between the open / closed state of an operation switch in a digital signal output device and a digital signal output from a digital signal generating unit, which shows a situation when there is no abnormality in the switching switch in the voltage switching unit.

[0024] Fig. 9B Yes means Figure 7 A diagram showing the relationship between the open / closed state of an operation switch in a digital signal output device and a digital signal output from a digital signal generating unit, which shows a situation when an abnormality occurs in a switching switch in a voltage switching unit.

[0025] Fig. 10A This is a diagram for explaining the timing of signal processing in a digital signal output device according to one embodiment of the present invention, and shows a situation when there is no abnormality in a switching switch in a voltage switching unit.

[0026] Fig. 10B This is a diagram for explaining the timing of signal processing in the digital signal output device according to one embodiment of the present invention, and shows a situation when an abnormality occurs in a switching switch in a voltage switching unit.

[0027] Fig.11 This is a schematic diagram showing the structure of a digital signal output device according to a first aspect of another embodiment disclosed in the present invention.

[0028] Fig.12This is a diagram for explaining the signal processing timing of the digital signal output device according to the first aspect and the second aspect of another embodiment disclosed in the present invention.

[0029] Fig.13 This is a schematic diagram showing the structure of a digital signal output device according to a third aspect which is another embodiment disclosed in the present invention. DETAILED DESCRIPTION

[0030] The digital signal output device for outputting a digital signal corresponding to an operation switch is described with reference to the following drawings. For ease of understanding, the scales of these drawings are appropriately changed. The method shown in the drawings is only an example for implementation and is not limited to the illustrated implementation method.

[0031] First, the structure of a digital signal output device according to an embodiment of the present invention will be described. Figure 1 This is a schematic diagram showing the structure of a digital signal output device according to one embodiment of the present invention.

[0032] The digital signal output device 1 includes an operation switch 11 , a voltage switching unit 12 , a voltage determination unit 13 , and a digital signal generation unit 14 .

[0033] The digital signal representing the first state and the digital signal representing the second state to be described below are on-off digital signals. That is, one of the digital signal representing the first state and the digital signal representing the second state is an on signal (high or 1), and the other is an off signal (low or 0). Preferably, the digital signal representing the first state is an on signal (high or 1), and the digital signal representing the second state is an off signal (low or 0).

[0034] The operation switch 11 has a first terminal 21-1 and a second terminal 21-2. The operation switch 11 is, for example, a mechanical switch. The first terminal is a common terminal, to which a first voltage, i.e., a common voltage, is applied. The second terminal is connected to the digital signal generating unit 14. When the operator operates the operation switch 11 so that the contact is closed, the first terminal 21-1 and the second terminal 21-2 are connected, and the first voltage, i.e., the common voltage, is output from the second terminal 21-2.

[0035] The voltage switching unit 12 has a voltage selection function capable of selecting and outputting a second voltage different from the first voltage from a plurality of constant voltages. The voltage switching unit 12 has a plurality of input terminals 31 - 1 , 31 - 2 , . . . , 31 - n (n is a natural number), an output terminal 32 , and a switch 33 .

[0036] Different constant voltages V1, V2, ..., V are applied to the input terminals 31-1, 31-2, ..., 31-n, respectively. n . Constant voltage V1, V2, ..., Vn The candidate that can become the second voltage different from the first voltage, that is, the common voltage is included.

[0037] The switch 33 selectively switches the electrical connection destination of the output terminal 32 from among the plurality of input terminals 31-1, 31-2, ..., 31-n. The operator operates the switch 33 to select one of the electrical connection destinations of the output terminal 32 from among the plurality of input terminals 31-1, 31-2, ..., 31-n, and thereby the constant voltage applied to the selected input terminal is output from the output terminal 32. As described above, the constant voltages V1, V2, ..., V2 applied to the input terminals 31-1, 31-2, ..., 31-n are n The input terminal 32 to which the second voltage is applied is selected as the connection destination of the output terminal 32 because the second voltage different from the common voltage should be output from the output terminal 32 .

[0038] The voltage determination unit 13 periodically monitors the voltage output from the output terminal of the voltage switching unit 12. The voltage monitoring cycle of the voltage determination unit 13 is, for example, about several milliseconds. The voltage determination unit 13 determines whether the voltage output from the voltage switching unit 12 has changed from the second voltage in each cycle. The determination result of the voltage determination unit 13 is notified to the digital signal generation unit 14.

[0039] As described above, in the switch 33 in the voltage switching unit 12, the input terminal to which the second voltage different from the common voltage is applied is selected as the connection destination of the output terminal 32. Therefore, if there is no abnormality in the switch 33, the voltage determination unit 13 detects that the second voltage is output from the output terminal 32 of the voltage switching unit 12 in each cycle. However, when an abnormality occurs in the switch 33 in the voltage switching unit 12 later, such as poor contact due to rust or mixing of foreign matter, or a shift in the switching position due to vibration or impact of the machine, the second voltage cannot be output from the output terminal 32 of the voltage switching unit 12 from the time when the abnormality occurs. That is, when the voltage determination unit 13 detects that the voltage output from the output terminal 32 of the voltage switching unit 12 has changed from the second voltage, it means that some abnormality has occurred in the switch 33 in the voltage switching unit 12. The voltage determination unit 13 determines whether the voltage output from the output terminal 32 of the voltage switching unit 12 has changed from the second voltage in each predetermined cycle, and notifies the digital signal generation unit 14 of the determination result.

[0040] The digital signal generating unit 14 generates and outputs one of a digital signal indicating a first state and a digital signal indicating a second state different from the first state, based on the voltage output from the second terminal of the operating switch 11 and the determination result of the voltage determining unit 13. More specifically, the digital signal generating unit 14 performs digital signal generation and output processing at each predetermined cycle.

[0041] When the voltage determination unit 13 determines that the voltage output from the output terminal 32 of the voltage switching unit 12 has not changed from the second voltage, when the common voltage (first voltage) is output from the second terminal 21-2 of the operation switch 11, the digital signal generation unit 14 generates and outputs a digital signal representing the first state. At this time, since the voltage output from the output terminal 32 of the voltage switching unit 12 has not changed from the second voltage, it can be known that the switch 33 has no abnormality, and the contact of the operation switch 11 is closed, so that the first terminal 21-1 and the second terminal 21-2 are connected, and the first voltage applied to the first terminal 21-1, that is, the common voltage, is output from the second terminal 21-2. In this way, when the switch 33 in the voltage switching unit 12 has no abnormality, the digital signal output device 1 outputs a digital signal representing the first state corresponding to the closed state of the contact of the operation switch 11. Since the digital signal generation and output processing of the digital signal generation unit 14 are performed in accordance with each predetermined cycle, as long as the switch 33 in the voltage switching unit 12 has no abnormality, if the contact of the operation switch 11 continues to be closed, the digital signal output device 1 continues to output a digital signal representing the first state.

[0042] In addition, when the voltage determination unit 13 determines that the voltage output from the output terminal 32 of the voltage switching unit 12 has not changed from the second voltage, when the common voltage (first voltage) is not output from the second terminal 21-2 of the operating switch 11, the digital signal generation unit 14 generates and outputs a digital signal representing the second state. At this time, since the voltage output from the output terminal 32 of the voltage switching unit 12 has not changed from the second voltage, it can be known that the switching switch 33 has no abnormality, and the contact of the operating switch 11 is disconnected, so that there is no conduction between the first terminal 21-1 and the second terminal 21-2, and the first voltage applied to the first terminal 21-1, that is, the common voltage, is not output from the second terminal 21-2. In this way, when there is no abnormality in the switching switch 33 in the voltage switching unit 12, the digital signal output device 1 outputs a digital signal representing the second state corresponding to the disconnected state of the contact of the operating switch 11. Since the digital signal generation and output processing of the digital signal generating unit 14 is performed in each predetermined cycle, as long as there is no abnormality in the switching switch 33 in the voltage switching unit 12 and the contact of the operating switch 11 continues to be disconnected, the digital signal output device 1 continues to output the digital signal representing the second state.

[0043] Furthermore, when the voltage determination unit 13 determines that the voltage output from the output terminal 32 of the voltage switching unit 12 has changed from the second voltage, the digital signal generation unit 14 generates a digital signal indicating the second state. At this time, since the voltage output from the output terminal 32 of the voltage switching unit 12 has changed from the second voltage, it means that some abnormality has occurred in the switching switch 33 at the time of this change. In this way, when an abnormality occurs in the switching switch 33 in the voltage switching unit 12, the digital signal output device 1 outputs a digital signal indicating the second state regardless of whether the contact of the operation switch 11 is in an open state or a closed state. Since the digital signal generation and output processing of the digital signal generation unit 14 are performed in accordance with each predetermined cycle, when an abnormality occurs in the switching switch 33 in the voltage switching unit 12 subsequently, the digital signal output device 1 continues to output a digital signal indicating the second state from the time when the abnormality occurs.

[0044] Thus, according to the present embodiment, when the switch 33 in the voltage switching unit 12 is normal, the digital signal output device 1 outputs a digital signal indicating the first state corresponding to the closed state of the contact of the operation switch 11, and outputs a digital signal indicating the second state corresponding to the open state of the contact of the operation switch 11. In addition, when the switch 33 in the voltage switching unit 12 is abnormal, the digital signal output device 1 outputs a digital signal indicating the second state.

[0045] The reason why the digital signal output device 1 outputs the digital signal indicating the second state when the switching switch 33 in the voltage switching unit 12 is abnormal is as follows. Usually, the operation switch is operated to close the contact when a machine tool or robot provided with the operation switch performs a certain action, and when the operation switch is not operated and the contact is open, the machine tool or robot usually remains in a stopped state. Therefore, in the digital signal output device 1 of the present embodiment, in order to stop the machine tool or robot when the switching switch 33 in the voltage switching unit 12 is abnormal, the digital signal indicating the second state is output as when the contact of the operation switch 11 is in an open state. Thus, even if the switching switch 33 in the voltage switching unit 12 is abnormal, the danger of the machine provided with the operation switch 11 can be avoided.

[0046] Next, several application examples of the digital signal output device 1 of the present embodiment are given. Here, as an example, the case where the common voltage is 0 [V] and 24 [V] is described, but the magnitude of the common voltage given is only an example and may be a value other than this. In addition, in the example to be described below, as an example, the digital signal representing the first state is set to a conduction signal (high or 1), and the digital signal representing the second state is set to a disconnection signal (low or 0). Even if the digital signal representing the first state is set to a disconnection signal (low or 0), and the digital signal representing the second state is set to a conduction signal (high or 1), the following description may also be applied.

[0047] Figure 2 This is a diagram showing a structure when a digital signal output device according to an embodiment of the present invention is applied when a common voltage is 0 [V]. Figure 3 Yes means Figure 2 A diagram showing a situation when an abnormality occurs in a voltage switching unit in a digital signal output device. Figure 4A Yes means Figure 2 A diagram showing the relationship between the open / closed state of an operation switch in a digital signal output device and a digital signal output from a digital signal generating unit, which shows a situation when there is no abnormality in the switching switch in the voltage switching unit. Figure 4B Yes means Figure 2 A diagram showing the relationship between the open / closed state of an operation switch in a digital signal output device and a digital signal output from a digital signal generating unit, which shows a situation when an abnormality occurs in a switching switch in a voltage switching unit.

[0048] exist Figure 2 and Figure 3 In the example shown, as an example, the digital signal output device 1 has a structure in which, for example, 24 [V] and 0 [V] are applied to the input terminals 31-1 and 31-2 of the voltage switching unit 12, respectively, in order to improve versatility so as to be able to cope with a variety of common voltages. The 0 [V] common voltage is applied to the common terminal, i.e., the first terminal 21-1, of the operation switch 11. Therefore, in order to output 24 [V] different from the common voltage from the output terminal 32 of the voltage switching unit 12, the operator operates the switching unit 33 to switch the connection destination of the output terminal 32 to the input terminal 31-1. As a result, 24 [V] is output from the output terminal 32 of the voltage switching unit 12.

[0049] The second terminal 21-2 of the operating switch 11 is connected to the digital signal generating unit 14 via the point P1. The resistor 42 is connected to the point P1, and one end of the resistor 42 on the opposite side of the point P1 is grounded. The output terminal 32 of the voltage switching unit 12 is connected to the resistor 41 via the point P2. One end of the resistor 41 on the opposite side of the point P2 is connected to the point P1. In addition, the resistor 43 and the voltage determining unit 13 are connected to the point P2. One end of the resistor 43 on the opposite side of the point P2 is grounded. The resistance value of the resistor 41 is set to R1 [Ω], the resistance value of the resistor 42 is set to R2 [Ω], and the resistance value of the resistor 43 is set to R3 [Ω].

[0050] like Figure 2 and Figure 4A As shown, when there is no abnormality in the switching switch 33 in the voltage switching unit 12, the output terminal 32 and the input terminal 31-1 are electrically connected through the switching switch 33, and therefore, the second voltage different from the common voltage (first voltage), that is, 24 [V] is output from the output terminal 32 of the voltage switching unit 12. The voltage determination unit 13 that periodically monitors the voltage output from the output terminal 32 of the voltage switching unit 12 continues to detect 24 [V] regardless of the open / closed state of the operation switch 11, and determines that the voltage output from the output terminal 32 of the voltage switching unit 12 has not changed from 24 [V].

[0051] like Figure 2 and Figure 4A As shown, when there is no abnormality in the switching switch 33 in the voltage switching unit 12, if the contact of the operating switch 11 is closed, the first terminal 21-1 and the second terminal 21-2 are connected, and the common voltage (first voltage) applied to the first terminal 21-1, that is, 0 [V], is output from the second terminal 21-2. As a result, the digital signal generating unit 14 generates and outputs a digital signal representing the first state, that is, a conduction signal. In addition, as shown in Figure 2 and Figure 4A As shown, when there is no abnormality in the switching switch 33 in the voltage switching unit 12, if the contact of the operating switch 11 is disconnected, there is no conduction between the first terminal 21-1 and the second terminal 21-2. Since 24V is output from the output terminal of the voltage switching unit 12, a voltage of 24×R2 / (R1+R2)[V] appears at point P1, and this voltage is input to the digital signal generating unit 14. This 24×R2 / (R1+R2)[V] is a voltage different from the common voltage, that is, 0[V]. As a result, the digital signal generating unit 14 generates and outputs a digital signal representing the second state, that is, a disconnection signal.

[0052] like Figure 3 and Figure 4BAs shown, when the switching switch 33 in the voltage switching unit 12 generates an abnormality, the output terminal 32 and the input terminal 31-1 are not electrically connected. Therefore, after the abnormality occurs, the second voltage, i.e., 24 [V], is not output from the output terminal 32 of the voltage switching unit 12, and the ground side voltage of the resistor 42, i.e., 0 [V], appears at point P2. The voltage determination unit 13 that periodically monitors the voltage output from the output terminal 32 of the voltage switching unit 12 detects 0 [V] instead of 24 [V] after the abnormality occurs, regardless of the open / closed state of the operating switch 11. Therefore, the voltage determination unit 13 determines that the voltage output from the output terminal 32 of the voltage switching unit 12 has changed from 24 [V] to 0 [V]. As a result, the digital signal output device 1 outputs a digital signal indicating the second state, i.e., an off signal, regardless of the open / closed state of the contact of the operating switch 11. In addition, when an abnormality occurs in the switching switch 33 in the voltage switching unit 12, the ground side voltage of the resistor 42, i.e., 0 [V], appears at point P1, and thus 0 [V] is input to the digital signal generating unit 14. However, since the digital signal output device 1 originally outputs a disconnection signal based on the judgment that the voltage output from the output terminal 32 of the voltage switching unit 12 has changed from 24 [V] to 0 [V], the input of 0 [V] to the digital signal generating unit 14 itself does not have any special impact.

[0053] Figure 5A This is a diagram showing a configuration when a conventional digital signal output device is applied when a common voltage is 0 [V], and shows a situation when there is no abnormality in a switching switch in a voltage switching unit. Figure 5B This is a diagram showing the structure of a conventional digital signal output device when the common voltage is 0 [V], and shows the situation when the switching switch in the voltage switching unit is abnormal. Fig. 6A Yes means Figure 5A and Figure 5B A diagram showing the relationship between the open / closed state of the operating switch in the conventional digital signal output device and the digital signal output from the digital signal generating unit, which shows the situation when there is no abnormality in the switching switch in the voltage switching unit. In addition, Figure 6B Yes means Figure 5A and Figure 5B A diagram showing the relationship between the open / closed state of an operating switch in a conventional digital signal output device and a digital signal output from a digital signal generating unit shows a situation when an abnormality occurs in a switching switch in a voltage switching unit.

[0054] In the conventional digital signal output device 101, a 0 [V] common voltage is applied to the first terminal 121-1, which is the common terminal of the operation switch 111. Therefore, in order to output 24 [V] different from the common voltage from the output terminal 132 of the voltage switching unit 112, the operator operates the switching unit 133 to switch the connection destination of the output terminal 132 to the input terminal 131-1. As a result, 24 [V] is output from the output terminal 132 of the voltage switching unit 112.

[0055] The second terminal 121-2 of the operation switch 111 is connected to the digital signal generation unit 114 via the point P1. The resistor 142 is connected to the point P1, and the end of the resistor 142 opposite to the point P1 is grounded. The output terminal 132 of the voltage switching unit 112 is connected to the resistor 141, and the resistor 141 is further connected to the point P1. The resistance value of the resistor 141 is set to R1 [Ω], and the resistance value of the resistor 142 is set to R2 [Ω]. Figure 5A and Fig. 6A As shown, when there is no abnormality in the switching switch 133 in the voltage switching unit 112, the output terminal 132 and the input terminal 131-1 are electrically connected through the switching switch 133. Therefore, a second voltage different from the common voltage (first voltage), i.e., 24 [V], is output from the output terminal 132 of the voltage switching unit 112.

[0056] like Figure 5A and Fig. 6A As shown, when there is no abnormality in the switching switch 133 in the voltage switching unit 112, if the contact of the operating switch 111 is closed, the first terminal 121-1 and the second terminal 121-2 are connected, and the common voltage (first voltage) applied to the first terminal 121-1, that is, 0 [V], is output from the second terminal 121-2. As a result, the digital signal generating unit 114 generates and outputs a conduction signal. In addition, if the contact of the operating switch 111 is disconnected, there is no conduction between the first terminal 121-1 and the second terminal 121-2. Since 24V is output from the output terminal 132 of the voltage switching unit 112, a voltage of 24×R2 / (R1+R2)[V] appears at point P1, and this voltage is input to the digital signal generating unit 14. This 24×R2 / (R1+R2)[V] is a voltage different from the common voltage, that is, 0 [V]. As a result, the digital signal generating unit 14 generates and outputs a disconnection signal.

[0057] like Figure 5B and Figure 6BAs shown, when the switch 133 in the voltage switching unit 112 is abnormal, the output terminal 132 and the input terminal 131-1 are not electrically connected. Therefore, 24 [V] is not output from the output terminal 132 of the voltage switching unit 112, and the ground side voltage of the resistor 142, that is, 0 [V], appears at point P1. When there is no abnormality in the switch 133 in the voltage switching unit 112, the voltage 0 [V] that appears at point P1 is the same as the voltage that appears at point P1 when the contact of the operating switch 111 is closed. Therefore, when the switch 133 in the voltage switching unit 112 is abnormal, the digital signal output device 1 generates and outputs a conduction signal regardless of whether the contact of the operating switch 111 is in an open state or a closed state. That is, when the switch 133 in the voltage switching unit 112 is abnormal, the voltage that appears at point P1 is 0 [V], not the voltage of 24 × R2 / (R1 + R2) [V] that appears when the contact of the operating switch 111 is open. Therefore, the digital signal output device 1 should originally generate an OFF signal based on the voltage of 24×R2 / (R1+R2) [V] appearing at the point P1, but generates an ON signal based on the voltage of 0 [V] appearing at the point P1.

[0058] In this way, the conventional digital signal output device 101 will perform the following erroneous action, that is, when an abnormality occurs in the switching switch 133 in the voltage switching unit 112, when the contact of the operating switch 111 is disconnected, the output from the digital signal output device 101 is not a disconnection signal but an inverted conduction signal. If the conventional digital signal output device 101 performs such an erroneous action, the machine tool or robot installed with the digital signal output device 101 may perform a dangerous action different from the original action. Generally, a certain action is performed on the machine tool or robot based on the conduction signal output from the digital signal output device 101 when the operating switch 111 is operated to close the contact, and when the operating switch 111 is not operated and the contact is disconnected, the machine tool or robot usually remains in a stopped state based on the conduction signal output from the digital signal output device 101. However, in the conventional digital signal output device 101, when the switch 133 in the voltage switching unit 112 is abnormal, even if the operating switch 111 is not operated and the contact is disconnected, the on signal is output instead of the off signal as described above, causing the machine tool or robot that should have stopped to operate. Such unexpected operation of the machine tool or robot is very dangerous.

[0059] In contrast, in the digital signal output device 1 of the present embodiment, in order to stop the operation of the machine tool or robot even when an abnormality occurs in the changeover switch 33 in the voltage switching unit 12, the digital signal indicating the second state is outputted as when the contact of the operation switch 11 is in the open state, just as when the contact of the operation switch 11 is in the open state. Thus, even if an abnormality occurs in the changeover switch 33 in the voltage switching unit 12, the danger of the machine provided with the operation switch 11 can be avoided.

[0060] Figure 7 This is a diagram showing the structure of a digital signal output device according to an embodiment of the present invention when the common voltage is 24 [V]. Figure 8 Yes means Figure 7 FIG. 1 is a diagram showing a situation in which an abnormality occurs in a voltage switching unit in a digital signal output device. Fig. 9A Yes means Figure 7 A diagram showing the relationship between the open and closed state of the operating switch in the digital signal output device and the digital signal output from the digital signal generating unit, which shows the situation when there is no abnormality in the switching switch in the voltage switching unit. In addition, Fig. 9B Yes means Figure 7 A diagram showing the relationship between the open / closed state of an operation switch in a digital signal output device and a digital signal output from a digital signal generating unit, which shows a situation when an abnormality occurs in a switching switch in a voltage switching unit.

[0061] exist Figure 7 and Figure 8 In the example shown, as an example, the digital signal output device 1 has a structure in which, for example, 24 [V] and 0 [V] are applied to the input terminals 31-1 and 31-2 of the voltage switching unit 12, respectively, in order to improve versatility so as to be able to cope with a variety of common voltages. The 24 [V] common voltage is applied to the common terminal, i.e., the first terminal 21-1, of the operation switch 11. Therefore, in order to output 0 [V] different from the common voltage from the output terminal 32 of the voltage switching unit 12, the operator operates the switching unit 33 to switch the connection destination of the output terminal 32 to the input terminal 31-2. As a result, 0 [V] is output from the output terminal 32 of the voltage switching unit 12.

[0062] The second terminal 21-2 of the operating switch 11 is connected to the digital signal generating unit 14 via the point P1. The resistor 42 is connected to the point P1, and one end of the resistor 42 on the opposite side of the point P1 is grounded. The output terminal 32 of the voltage switching unit 12 is connected to the resistor 41 via the point P2. One end of the resistor 41 on the opposite side of the point P2 is connected to the point P1. In addition, the resistor 43 and the voltage determining unit 13 are connected to the point P2. One end of the resistor 43 on the opposite side of the point P2 is grounded. The resistance value of the resistor 41 is set to R1 [Ω], the resistance value of the resistor 42 is set to R2 [Ω], and the resistance value of the resistor 43 is set to R3 [Ω].

[0063] like Figure 7 and Fig. 9A As shown, when there is no abnormality in the switching switch 33 in the voltage switching unit 12, the output terminal 32 and the input terminal 31-2 are electrically connected through the switching switch 33, so that the second voltage different from the common voltage (first voltage), that is, 0 [V], is output from the output terminal 32 of the voltage switching unit 12. The voltage determination unit 13 that periodically monitors the voltage output from the output terminal 32 of the voltage switching unit 12 continuously detects 24 [V] regardless of the open / close state of the operation switch 11, and determines that the voltage output from the output terminal 32 of the voltage switching unit 12 has not changed from 0 [V].

[0064] like Figure 7 and Fig. 9A As shown, when there is no abnormality in the switch 33 in the voltage switching unit 12, if the contact of the operating switch 11 is closed, the first terminal 21-1 and the second terminal 21-2 are connected, and the common voltage (first voltage) applied to the first terminal 21-1, that is, 24 [V], is output from the second terminal 21-2. As a result, the digital signal generating unit 14 generates and outputs a digital signal representing the first state, that is, a conduction signal. In addition, as shown in Figure 7 and Fig. 9A As shown, when there is no abnormality in the switching switch 33 in the voltage switching unit 12, if the contact of the operating switch 11 is disconnected, there is no conduction between the first terminal 21-1 and the second terminal 21-2. Since 24V is output from the output terminal of the voltage switching unit 12, the ground side voltage of the resistor 42, i.e., 0 [V], appears at point P1, and this voltage is input to the digital signal generating unit 14. This 0 [V] is a voltage different from the common voltage, i.e., 24 [V]. As a result, the digital signal generating unit 14 generates and outputs a digital signal indicating the second state, i.e., an off signal.

[0065] like Figure 8 and Fig. 9BAs shown, when an abnormality occurs in the switching switch 33 in the voltage switching unit 12, the output terminal 32 and the input terminal 31-2 are not electrically connected. Therefore, after the abnormality occurs, the second voltage, i.e., 0 [V], is not output from the output terminal 32 of the voltage switching unit 12, and a voltage of 24×R3 / (R1+R3) [V] appears at point P2. The voltage determination unit 13 that periodically monitors the voltage output from the output terminal 32 of the voltage switching unit 12 detects 24×R3 / (R1+R3) [V] instead of 0 [V] after the abnormality occurs, regardless of the open / closed state of the operating switch 11. Therefore, the voltage determination unit 13 determines that the voltage output from the output terminal 32 of the voltage switching unit 12 has changed from 0 [V] to 24×R3 / (R1+R3) [V]. As a result, the digital signal output device 1 outputs a digital signal indicating the second state, i.e., an off signal, regardless of the open / closed state of the contact of the operating switch 11.

[0066] Next, several examples of implementations of a digital signal output device according to another embodiment of the present invention will be given.

[0067] Fig. 10A This is a diagram for explaining the timing of signal processing in a digital signal output device according to one embodiment of the present invention, and shows a situation when there is no abnormality in a switching switch in a voltage switching unit. Fig. 10B This is a diagram for explaining the timing of signal processing in a digital signal output device according to an embodiment of the present invention, and shows a situation when a switching switch in a voltage switching unit is abnormal. Fig. 10A and Fig. 10B As an example, the reference Figure 2 , Figure 3 , Figure 4A as well as Figure 4B The digital signal output device 1 will be described when the common voltage is 0 [V].

[0068] like Fig. 10A As shown, when there is no abnormality in the switching switch 33 in the voltage switching unit 12, a second voltage different from the common voltage (first voltage), that is, 24 [V], is output from the output terminal 32 of the voltage switching unit 12. The voltage determination unit 13 that periodically monitors the voltage output from the output terminal 32 of the voltage switching unit 12 continues to detect 24 [V] regardless of the open / closed state of the operating switch 11, and determines that the voltage output from the output terminal 32 of the voltage switching unit 12 has not changed from 24 [V]. When the contact of the operating switch 11 is switched from the closed state to the open state at time t1, the voltage ( Figure 2The voltage at the midpoint P1) changes from 0 [V] to 24 × R2 / (R1 + R2) [V]. After receiving this change, the digital signal generation unit 14 switches the output from the on signal to the off signal. Here, the time required for the digital signal generation unit 14 to switch the digital signal to be output after receiving the change in input voltage is set as "t2-t1".

[0069] like Fig. 10B As shown, it is assumed that at time t1, an abnormality occurs in the switch 33 in the voltage switching unit 12, and at the same time, the contact of the operating switch 11 is switched from the closed state to the open state. In this case, after time t1, the second voltage, i.e., 24 [V], is not output from the output terminal 32 of the voltage switching unit 12, and the ground side voltage of the resistor 42, i.e., 0 [V], appears at point P2. The voltage determination unit 13 that periodically monitors the voltage output from the output terminal 32 of the voltage switching unit 12 detects that 0 [V] is not 24 [V] after time t1. On the other hand, the voltage ( Figure 2 The voltage at the midpoint P1 remains unchanged at 0 [V] after time t1. Therefore, the digital signal generation unit 14 switches the output from the on signal to the off signal. Fig. 10A As described in the above, the time required for the digital signal generator 14 to switch the digital signal to be output after receiving the change of the input voltage has been set to "t2-t1", so the digital signal generator 14 outputs the disconnection signal after time t2. In this way, when the switch 33 in the voltage switching unit 12 is abnormal and the contact of the operating switch 11 is switched from closed to open at the same time ( Fig. 10B When the moment t1 in the voltage switching section 12 occurs, it is impossible to distinguish whether the switching from the on signal to the off signal by the digital signal generating section 14 is caused by an abnormality in the switching switch 33 or caused by the switching of the contacts of the operating switch 11 from closed to open. In addition, it can be considered that if an abnormality occurs in the switching switch 33 in the voltage switching section 12, it is safer to output the off signal immediately at the moment of the abnormality. Therefore, in the first mode and the second mode of another embodiment of the present invention, during one period of the processing cycle of the voltage determining section 13 and the digital signal generating section 14, the determination result of the voltage determining section 13 is given priority in the generation process of the digital signal generating section 14. Below, several examples of this embodiment are given.

[0070] In a first mode of another embodiment disclosed in the present invention, a filter circuit is provided between the second terminal 21 - 2 of the operation switch 11 and the digital signal generator 14 , thereby giving priority to the determination result of the voltage determination unit 13 in the generation process of the digital signal generator 14 . Fig.11This is a schematic diagram showing the structure of a digital signal output device according to a first aspect of another embodiment disclosed in the present invention.

[0071] like Fig.11 As shown, the filter circuit 15 is provided at the point P3 of the preceding stage of the digital signal generating unit 14. As described above, the determination process of the voltage determination unit 13 and the generation process of the digital signal generating unit 14 are repeatedly performed in the same cycle. By providing the filter circuit 15, during one period of the processing cycle of the voltage determination unit 13 and the digital signal generating unit 14, the timing at which the digital signal generating unit 14 obtains the voltage of the second terminal 21-2 of the operation switch 11 will be later than the timing at which the voltage determination unit 13 obtains the voltage of the output terminal 32 of the voltage switching unit 12.

[0072] In a second mode of another embodiment of the present invention, during one period of the processing cycle of the voltage determination unit 13 and the digital signal generation unit 14, the timing at which the voltage determination unit 13 obtains the voltage output from the output terminal 32 of the voltage switching unit 12 is set earlier than the timing at which the digital signal generation unit 14 obtains the voltage of the second terminal 21-2 of the operation switch 11, so that the determination result of the voltage determination unit 13 has priority in the generation process of the digital signal generation unit 14. During one period of the processing cycle of the voltage determination unit 13 and the digital signal generation unit 14, the timing at which the voltage determination unit 13 obtains the voltage output from the output terminal 32 of the voltage switching unit 12 is set earlier than the timing at which the digital signal generation unit 14 obtains the voltage of the second terminal 21-2 of the operation switch 11. As a result, when an abnormality occurs in the switching switch 33 in the voltage switching unit 12, the digital signal generation unit 14 that receives the determination result of the voltage determination unit 13 immediately generates and outputs a disconnection signal.

[0073] Fig.12 This is a diagram for explaining the signal processing timing of the digital signal output device according to the first aspect and the second aspect of another embodiment disclosed in the present invention.

[0074] like Fig.12 As shown, at time t1, an abnormality occurs in the switching switch 33 in the voltage switching unit 12, and at the same time, the contact of the operating switch 11 switches from a closed state to an open state. In this case, after time t1, the second voltage, i.e., 24 [V], is not output from the output terminal 32 of the voltage switching unit 12, and the ground side voltage of the resistor 42, i.e., 0 [V], appears at point P2. The voltage determination unit 13, which periodically monitors the voltage output from the output terminal 32 of the voltage switching unit 12, detects 0 [V] instead of 24 [V] after time t1. Therefore, at the time point of time t1, the digital signal generation unit 14 switches the output from the on signal to the off signal. In this way, through the first and second methods of another embodiment disclosed in the present invention, Fig. 10BCompared with the case where an abnormality occurs in the switching switch 33 in the voltage switching unit 12, the output of the disconnection signal can be made earlier.

[0075] Furthermore, in the first and second aspects of another embodiment disclosed in the present invention, the case where the common voltage is 0 [V] is described as an example, but the first and second aspects can also be applied to other large common voltages.

[0076] A third mode of another embodiment disclosed in the present invention is a mode in which, when an abnormality occurs in the switch 33 in the voltage switching unit 12 , in addition to outputting a disconnection signal through the digital signal generating unit 14 , an alarm signal is also generated. Fig.13 This is a schematic diagram showing the structure of a digital signal output device according to a third aspect which is another embodiment disclosed in the present invention.

[0077] like Fig.13 As shown, through the third mode of another embodiment disclosed in the present invention, the digital signal output device 1 is further provided with an alarm signal generating unit 16, which generates an alarm signal indicating an abnormality of the voltage switching unit 12 when the voltage determination unit 13 determines that the voltage has changed from the second voltage, that is, when the switching switch 33 of the voltage switching unit 12 has an abnormality. The alarm signal generated by the alarm signal generating unit 16 is sent to the control device of the machine tool or robot provided with the digital signal output device 1. The control device receiving the alarm signal can perform, for example, an alarm stop or a protective action on the machine tool or robot. In this way, when an abnormality occurs in the switching switch 33 of the voltage switching unit 12, in addition to outputting a disconnection signal (a digital signal indicating the second state) through the digital signal generating unit 14, an alarm signal is also output through the alarm signal generating unit 16, thereby reliably avoiding the danger of the machine provided with the operating switch.

[0078] In addition, the voltage determination unit 13, the digital signal generation unit 14, and the alarm signal generation unit 16 can be constructed in the form of a software program, for example, or can be constructed by a combination of various electronic circuits and software programs. For example, when these components are constructed in the form of a software program, the functions of the above-mentioned components can be realized by causing the operation processing device to operate according to the software program. Alternatively, the voltage determination unit 13, the digital signal generation unit 14, and the alarm signal generation unit 16 can be realized as a semiconductor integrated circuit in which a software program for realizing the functions of each component is written. The operation processing device that executes the software program for realizing the functions of the voltage determination unit 13, the digital signal generation unit 14, and the alarm signal generation unit 16 can be composed of a single integrated circuit (IC), or can be set in an operation processing device in a machine tool, a robot, or its control device. In addition, the filter circuit 15 can be constructed by an analog electronic circuit, or can be constructed in the form of a software program and realized by causing the operation processing device to operate. The functions of the above-mentioned components are thereby realized.

[0079] According to one embodiment of the present invention, a digital signal output device with high safety can be realized, and even if an abnormality occurs in the digital signal output device that outputs a digital signal corresponding to an operation switch, the danger of a machine provided with an operation switch can be avoided.

Claims

1. A digital signal output device, characterized in that: have: an operating switch having a first terminal to which a first voltage is applied and a second terminal for outputting the first voltage when a contact is closed; a voltage switching unit that selects and outputs a second voltage different from the first voltage from a plurality of constant voltages; a voltage determination unit that determines, at each predetermined period, whether the voltage output from the voltage switching unit has changed from the second voltage; as well as A digital signal generating unit, which generates a digital signal indicating a first state when the first voltage is output from the second terminal in each of the above-mentioned cycles when the voltage judging unit judges that there is no change from the second voltage, and generates a digital signal indicating a second state different from the first state when the first voltage is not output from the second terminal.

2. The digital signal output device according to claim 1, characterized in that: The digital signal generating unit generates a digital signal indicating the second state when the voltage determining unit determines that the voltage has changed from the second voltage.

3. The digital signal output device according to claim 1 or 2, characterized in that: The first voltage is a common voltage.

4. The digital signal output device according to any one of claims 1 to 3, characterized in that: One of the digital signal indicating the first state and the digital signal indicating the second state is an on signal, and the other is an off signal.

5. The digital signal output device according to any one of claims 1 to 4, characterized in that: The voltage switching unit includes a plurality of input terminals to which the constant voltages applied are different, an output terminal, and a switch for selectively switching a connection destination of the output terminal from among the plurality of input terminals. The voltages applied to the plurality of input terminals include the second voltage.

6. The digital signal output device according to any one of claims 1 to 5, characterized in that: The digital signal output device further includes a filter circuit (15) provided between the operation switch and the digital signal generating unit.

7. The digital signal output device according to any one of claims 1 to 6, characterized in that: In one period of the cycle, the timing at which the voltage determination unit acquires the voltage output from the voltage switching unit is set earlier than the timing at which the digital signal generation unit acquires the voltage of the second terminal.

8. The digital signal output device according to any one of claims 1 to 7, characterized in that: The digital signal output device further includes an alarm signal generating unit that generates an alarm signal indicating abnormality of the voltage switching unit when the voltage determining unit determines that the voltage has changed from the second voltage.

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