Maintenance system

Abstract

To provide a maintenance system capable of securing a power supply for an adapter device without requiring new installation work.SOLUTION: A maintenance system comprises a limit switch that is provided for an object in a plant and switches between an on state and an off state depending on the state of the object, a power device including a current detection circuit for detecting the on state and off state of the limit switch, and an adapter device inserted into wiring between the power device and the limit switch, wherein the adapter device includes a detection unit that detects a state of the object of the limit switch and transmits the detection result to a maintenance monitoring device, and a power supply unit that supplies at least a portion of power from the power device to the limit switch and also supplies at least a portion of the power from the power device to the detection unit.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a security system. [Background technology]

[0002] Valves and control valves are widely used in petrochemical plants. Valves always have mechanical moving and sliding parts, so maintenance work is essential for safe and accurate operation. In order to perform that maintenance work appropriately, it is desirable to obtain preventive maintenance data during operation.

[0003] Limit switches are installed on valves to ensure that the fluid control parts inside the valve move to the fully closed or fully open position during operation. During plant operation, the operating status of the valve is monitored based on the status of the limit switches.

[0004] A technology for monitoring valves is disclosed in Patent Document 1. In Patent Document 1, a current detection circuit using a photocoupler detects the current that flows when the contact of a limit switch is on. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2005-064929 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, it is difficult to predict whether there is an abnormality in the movement of a valve using only the monitoring functions for plant operation such as limit switches. Therefore, it is desirable to add a preventive maintenance device to analyze the detailed behavior of the valve, for example. The same can be said not only for valves, but also for various objects used in plants. Valves and other objects that can be monitored are also called objects.

[0007] A preventive maintenance device is an additional device installed to maintain an object, and is hereafter also referred to as an "adapter device." By using the adapter device to collect and monitor the movement of the object in more detail, it is expected that sudden failures that lead to huge losses can be avoided. When adding the adapter device to an existing plant facility and operating it, it is necessary to lay cables to supply power, etc.

[0008] Therefore, it is conceivable that the installation work can be eliminated by using a primary battery as the power source for the adapter device instead of the power wiring. However, since batteries have a limited lifespan, maintenance work such as replacement would be necessary, which is not desirable.

[0009] The present invention has been made in view of the above, and an object of the present invention is to provide a maintenance system that can ensure power supply for an adapter device without requiring new installation work. [Means for solving the problem]

[0010] A maintenance system according to one aspect includes a limit switch that is provided for an object in a plant and switches between an on state and an off state depending on the state of the object, a power supply device including a current detection circuit for detecting the on state and off state of the limit switch, and an adapter device inserted into wiring between the power supply device and the limit switch, wherein the adapter device includes a detection unit that detects the state of the object of the limit switch and transmits the detection result to a maintenance monitoring device, and a power supply unit that supplies at least a portion of the power from the power supply device to the limit switch and also supplies at least a portion of the power from the power supply device to the detection unit. Effect of the Invention

[0011] According to the present invention, the power supply unit included in the adapter device supplies at least a portion of the power from the power supply unit to the detection unit that transmits the detection result of the state of the target object to the maintenance monitoring device, thereby making it possible to secure the power supply for the adapter device without requiring new installation work. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a block diagram showing an example of a schematic configuration of a system according to a comparative example. [Diagram 2] FIG. 2 is a block diagram showing an example of a schematic configuration of the maintenance system 100 according to the first embodiment. [Diagram 3] FIG. 3 is a diagram showing an example of determining whether or not there is an abnormality in the valve 3. In FIG. [Figure 4] FIG. 4 is a block diagram showing an example of a schematic configuration of the power supply system A100. [Diagram 5] FIG. 5 is a block diagram showing an example of a schematic configuration of the power supply system A100. [Figure 6] FIG. 6 is a block diagram showing an example of a schematic configuration of the power supply system A100. [Figure 7] FIG. 7 is a diagram showing the relationship between the terminal voltage and the terminal current of the power supply terminals T1, T2 when the power adaptor device A2 is not inserted. [Figure 8] FIG. 8 is a diagram showing the relationship between the terminal voltage and terminal current between the power supply terminals T1, T2 when the power adapter device A2 is inserted between the limit switch SW and the power supply device A1 and the limit switch SW is in the on state. [Figure 9] FIG. 9 is a simplified circuit diagram showing the first current path when the limit switch SW is in the on state. [Figure 10] FIG. 10 is a diagram illustrating the power that can be extracted when the limit switch SW is in the on state. [Figure 11] FIG. 11 is a diagram showing the relationship between the terminal voltage and terminal current of the power supply terminals T1, T2 when the limit switch SW is in the off state with the power adaptor device A2 inserted. [Figure 12] FIG. 12 is a diagram showing the input control circuit A22 and its peripheral circuits when the limit switch SW is in the off state. [Figure 13]FIG. 13 is a diagram illustrating the power that can be extracted when the limit switch SW is in the OFF state. [Figure 14] FIG. 14 is a diagram showing the relationship between the power before and after conversion by the voltage-current conversion circuit A23 of the power adaptor device 2 when the limit switch SW is in the OFF state. [Figure 15] FIG. 15 is a diagram showing an example of a specific configuration of the adapter device 2 and the valve 3. As shown in FIG. [Figure 16] FIG. 16 is a block diagram showing an example of a schematic configuration of a maintenance system 100a according to the second embodiment. [Figure 17] FIG. 17 is a block diagram showing an example of a schematic configuration of a maintenance system 100b according to the third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, the embodiments of the present invention will be described in detail with reference to the drawings. In the following description of each embodiment, the same or equivalent components as those in other embodiments are given the same reference numerals, and their description will be simplified or omitted. The present invention is not limited to each embodiment. In addition, the components of each embodiment include those that are replaceable and easy for a person skilled in the art, or those that are substantially the same. The configurations described below can be appropriately combined. In addition, the configurations can be omitted, replaced, or modified within the scope of the gist of the invention.

[0014] In this specification, in order to facilitate understanding of the contents of the present disclosure, the technical background of the plant and the like will be described first before describing the present embodiment.

[0015] <Plant power supply> Large production facilities such as petrochemical plants can operate for nearly 100 years to produce materials essential to life. In response to modern demands, additional instrumentation equipment is often installed on-site at facilities that have been in operation for many years, with the aim of improving safety, quality, and production efficiency. However, installing power wiring for the additional equipment requires the equipment to be shut down, which not only incurs construction costs but also has a significant impact on the operation of the production facility.

[0016] 1 is a block diagram showing an example of a schematic configuration of a system according to a comparative example. The system according to the comparative example includes a limit switch SW and a power supply device 1. The power supply device 1 also includes a current detection circuit 12 for detecting the state of the limit switch SW, i.e., the on state and the off state.

[0017] The power supply device 1 supplies the limit switch SW with a current required for the operation of the limit switch SW. This current is called the operating current I. The operating current I is a loop current flowing through the power supply device 1 and the limit switch SW. The limit switch SW is operated by the operating current I from the power supply device 1. The limit switch SW is provided (attached) to an object in a plant. The limit switch SW switches between an on state and an off state depending on the state of the object. The value of the operating current I changes depending on the state of the limit switch SW, and therefore the operating current I can also be called a signal corresponding to the state of the limit switch SW. This signal is also called a signal ST.

[0018] An example of the object is a valve that controls the flow rate of a fluid. In this case, the state of the object includes the open state and the closed state of the valve. The valve may have any structure, such as a ball valve, a butterfly valve, or a gate valve. For example, a limit switch SW is in an on state when the valve is in an open state, and in an off state when the valve is in a closed state. However, conversely, the limit switch SW may be in an on state when the valve is in a closed state, and in an off state when the valve is in an open state.

[0019] The object may be a valve that controls the flow of a fluid in two positions, fully open (i.e., open state) and fully closed (i.e., closed state), or a valve that controls the flow of a fluid in a series of positions from fully open to fully closed. In addition, the object is not limited to a valve. The object may include various objects that are installed in a plant and whose state may change. An example of an object other than a valve is a damper for regulating the amount of gas passing through a duct, which is an air passage. However, unless otherwise specified, the object will be described below as being a valve. To the extent that there is no contradiction, a valve may be appropriately interpreted as an object.

[0020] The limit switch SW may be a plurality of limit switches SW, for example, two limit switches SW. In this case, one limit switch SW may be in an on state when the valve is in an open state, and in an off state when the valve is in a closed state. The other limit switch SW may be in an on state when the valve is in a closed state, and in an off state when the valve is in an open state. By using two limit switches SW whose states can be switched exclusively to each other, the open / closed state of the valve can be grasped more accurately.

[0021] Depending on the state of the limit switch SW, the current value of the operating current I (loop current), i.e., the magnitude of the signal ST, changes. This signal ST is detected by the current detection circuit 12 of the power supply device 1, and thus the open / closed state of the valve is detected. Note that, to the extent that there is no contradiction, detection may be interpreted as meaning detection, and detection and detection may be interpreted appropriately.

[0022] The limit switch SW is originally installed in production equipment such as a plant. The power supply unit 1 supplies power to each part in the plant. Therefore, if an adapter device that extracts power from the power supply unit 1 is installed, the extracted power can be used to detect the state of the detection target, for example, the open / closed state of a valve. There is no need to prepare a new power source for this purpose.

[0023] First Embodiment 2 is a block diagram showing an example of a schematic configuration of a maintenance system 100 according to the first embodiment. A valve that is an object of maintenance is illustrated and called a valve 3. The maintenance system 100 is used, for example, to determine whether or not there is an abnormality in the valve 3 before it leads to a breakdown.

[0024] The maintenance system 100 according to the first embodiment is different from the system according to the comparative example (FIG. 1) in that it further includes an adapter device 2. More specifically, in this example, The maintenance system 100 includes a power supply device 1 , an adapter device 2 , a valve 3 , and a maintenance monitoring device 9 .

[0025] As described above, the power supply device 1 is configured to include a current detection circuit 12. The adapter device 2 is connected to the wiring between the power supply device 1 and the valve 3. A limit switch SW is attached to the valve 3. Furthermore, a drive unit 30 is illustrated with a reference symbol as a component of the valve 3. The drive unit 30 drives the valve 3 to open and close the valve 3. Examples of the drive unit 30 include a valve body, a valve shaft, etc. that rotate as the valve opens and closes. Another example of the drive unit 30 is a cylinder, etc. that performs a linear reciprocating motion as the valve opens and closes.

[0026] An operating current is supplied from the power supply device 1 to the limit switch SW via the adapter device 2. The operating current supplied to the limit switch SW is referred to as operating current I" and is illustrated in the figure. Depending on the state of the limit switch SW, the current value of the operating current I" also changes, and therefore the current value of the current supplied from the power supply device 1 to the adapter device 2 also changes. This change is detected by the current detection circuit 12 of the power supply device 1, and the open / closed state of the valve 3 is detected.

[0027] The current detection circuit 12 of the power supply device 1 is used to detect a current flowing from the power supply device 1 to the adapter device 2 or a current flowing from the adapter device 2 to the power supply device 1. A predetermined threshold is set for the current value (detected current value) detected by this current detection circuit 12. The predetermined threshold includes two types of thresholds: an on-definite current and an off-definite current.

[0028] The on-definite current is a value that determines that the limit switch SW is on. When the limit switch SW is on, the current detection circuit 12 detects a current value equal to or greater than the on-definite current. If the current detection circuit 12 detects a current value equal to or greater than the on-definite current, it is detected that the limit switch SW is on.

[0029] The OFF-definite current is a value that determines that the limit switch SW is in the OFF state. The current value detected by the current detection circuit 12 when the limit switch SW is in the OFF state is equal to or less than the OFF-definite current value. If the current value detected by the current detection circuit 12 is equal to or less than the OFF-definite current, it is detected that the limit switch SW is in the OFF state.

[0030] Further description will be given of the adapter device 2. In the example shown in Fig. 2, the adapter device 2 includes a power supply unit 4, a detection unit 5, and a charge / discharge unit 6.

[0031] The power supply unit 4 is connected between the power supply device 1 and the limit switch SW. The power supply unit 4 supplies at least a portion of the power from the power supply device 1 to the limit switch SW, and also supplies at least a portion of the power from the power supply device 1 to the detection unit 5.

[0032] The power supply unit 4 includes a regulator circuit 42. When the limit switch SW is in the on state, the regulator circuit 42 stops operating and supplies a current diverted from the loop current (i.e., operating current I) flowing through the power supply device 1 and the limit switch SW to the detection unit 5. A portion of the current from the power supply device 1 is supplied directly to the limit switch SW. The current flowing from the power supply unit 4 to the detection unit 5 is referred to as current I' and is illustrated. When the limit switch SW is in the off state, the regulator circuit 42 supplies to the detection unit 5 a current obtained by voltage-current conversion of the current from the power supply device 1 using an internal switching regulator.

[0033] The detection unit 5 detects the state of the valve 3, and transmits the detection result to the maintenance monitoring device 9. In this example, the detection unit 5 includes a sensor unit 51 and a communication unit 52.

[0034] In this example, the sensor unit 51 detects the state of the valve 3 based on the state of the drive unit 30 of the valve 3. An example of the state of the valve 3 is the opening degree of the valve 3 (valve opening degree). For example, if the drive unit 30 is a rotating valve element or the like, the valve opening degree is detected based on the rotation angle. If the drive unit 30 is a cylinder or the like that performs linear reciprocating motion, the valve opening degree is detected based on the position.

[0035] 2, a signal indicating the state of the drive unit 30 is transmitted from the drive unit 30 to the sensor unit 51. The sensor unit 51 detects the state of the drive unit 30, and therefore the state of the valve 3, based on the signal received from the drive unit 30.

[0036] The communication unit 52 transmits data including the detection result of the sensor unit 51 to the maintenance monitoring device 9. The transmission may be wireless transmission, wired transmission, or a combination of wireless transmission and wired transmission.

[0037] In one embodiment, the communication unit 52 compresses data indicating the detection result of the sensor unit 51 and transmits the data to the maintenance monitoring device 9. In this example, the communication unit 52 includes a data compression unit 520 and a storage unit 521. The data compression unit 520 has a function of compressing data to be transmitted. The storage unit 521 stores the data to be transmitted. The data compressed by the data compression unit 520 is stored in the storage unit 521. The communication unit 52 transmits the data stored in the storage unit 521 to the maintenance monitoring device 9.

[0038] When the communication unit 52 transmits data, it may require a lot of power. For example, when transmitting data wirelessly, a lot of power is consumed during transmission. In such a case, the data may be transmitted using the power stored in the charge / discharge unit 6.

[0039] The communication unit 52 may transmit the above data intermittently (intermittent transmission). For example, the communication unit 52 may transmit the data periodically. The communication unit 52 may transmit the data at a constant cycle, or may change the transmission cycle.

[0040] For example, when the valve 3 is stationary and there is no change, there is no need to transmit data frequently. In such a case, it is preferable to lengthen the transmission cycle, which can reduce power consumption. Alternatively, data may be stored and accumulated in the memory unit 521, and a predetermined amount of data may be transmitted at once.

[0041] On the other hand, when the stationary valve 3 starts to move, that is, when the opening degree of the valve 3 starts to change, it is preferable to transmit data at short intervals. For example, when the valve 3 that should have been set to an open state starts to close, or when the valve 3 that should have been set to a closed state starts to open, data is acquired from the actuator 30 at short intervals and then transmitted at short intervals, so that the detailed behavior of the valve 3 can be confirmed in the maintenance monitoring device 9.

[0042] The charging / discharging unit 6 charges with power from the power supply unit 4 and also discharges the charged power to the detection unit 5. In this example, the charging / discharging unit 6 is charged by at least a part of the current I' output from the power supply unit 4. The charging / discharging unit 6 may function as a power source for the detection unit 5, in which case at least a part of the operating power of the detection unit 5 is covered by the discharging power of the charging / discharging unit 6. It can also be said that the operating power of the detection unit 5 includes the discharging power of the charging / discharging unit 6. For example, when the communication unit 52 requires power temporarily when transmitting data to the maintenance monitoring device 9, the charging / discharging unit 6 discharges to the detection unit 5. The charging / discharging unit 6 is configured to include, for example, a secondary battery, a supercapacitor, etc.

[0043] The maintenance monitoring device 9 executes processing for maintaining the valve 3 based on the data from the detection unit 5 of the adapter device 2. For example, the maintenance monitoring device 9 determines whether the valve 3 is normal or abnormal, that is, whether the valve 3 is abnormal, based on the data from the detection unit 5.

[0044] The maintenance monitoring device 9 is realized by using, for example, a computer including a processor such as a CPU, a storage device, an input / output interface, a communication interface, and the like. For example, data is received from the communication unit 52 via the communication interface. Based on the received data, the processor analyzes the movement of the valve 3, and determines the presence or absence of an abnormality in the valve 3 based on the analysis result. Examples of the analysis result include whether the opening and closing operation of the valve is fast, slow, or not smooth (gets stuck), which may be caused by deterioration of the drive unit 30 of the valve 3, and the like. Description will be made with reference to FIG. 3 as well.

[0045] 3 is a diagram showing an example of determining whether or not there is an abnormality in the valve 3. The horizontal axis of the graph indicates time, and the vertical axis of the graph indicates the valve opening. The graph shows the change over time (behavior) of the valve opening when the valve 3 transitions from a closed state to an open state.

[0046] The solid line in the graph represents actual measurement data, and corresponds to the data transmitted from the communication unit 52 of the detection unit 5 to the maintenance monitoring device 9. For example, such time-series data is transmitted from the communication unit 52 of the detection unit 5 to the maintenance monitoring device 9, and the presence or absence of an abnormality in the valve 3 is determined based on the data.

[0047] The dashed dotted line in the graph is reference data, and indicates the change over time in the valve opening degree of a normal valve 3. The reference data is prepared in advance based on, for example, design data, experimental data, etc. of the valve 3.

[0048] In the example shown in FIG. 3(A), while the valve 3 is opening, there is a time period during which the valve opening degree of the actual measurement data is smaller than the valve opening degree of the reference data. It is presumed that some abnormality exists in the valve 3, which prevents the valve 3 from opening smoothly. In the example shown in FIG. 3(B), the valve opening degree of the actual measurement data does not reach 100%. It is presumed that some abnormality exists in the valve 3, which prevents the valve 3 from opening completely. For example, when such actual measurement data is obtained, the maintenance monitoring device 9 determines that there is an abnormality in the valve 3. Note that, although not shown, when the actual measurement data almost matches the reference data or there is no significant deviation, the maintenance monitoring device 9 determines that there is no abnormality in the valve 3 (the valve 3 is normal).

[0049] Returning to FIG. 2, for example, in the manner described above, the maintenance monitoring device 9 determines whether or not there is an abnormality in the valve 3 based on data from the communication unit 52 of the detection unit 5. The determination result of the maintenance monitoring device 9 is notified to a user of the maintenance system 100 (such as a plant manager). The notification method is not particularly limited, and for example, an alarm notification, an email notification, or the like may be used. By being notified of an abnormality in the valve 3 early, maintenance work such as repair or replacement can be performed, for example, before the valve 3 completely breaks down. This makes it possible to maintain the valve 3.

[0050] By using the adapter device 2, it is possible to extract power from the wiring leading from the power supply device 1 to the limit switch SW, and use the extracted power as a power source for the detection unit 5. Therefore, it is possible to ensure a power source for the adapter device 2 without requiring new installation work. Such a power supply unit 4 of the adapter device 2 can be said to constitute a power supply system. The power supply system will be described with reference to Figs. 4 to 14.

[0051] 4 to 6 are block diagrams showing an example of a schematic configuration of a power supply system A100. The illustrated power supply system A100 includes a power supply device A1, a power adapter device A2, and a limit switch SW provided for a valve A3. The power supply device A1 corresponds to the power supply device 1 (see FIG. 2) described above. The power adapter device A2 corresponds to the power supply unit 4 (see FIG. 2) of the adapter device 2 described above.

[0052] The power supply device A1 has a terminal T11 and a terminal T12. The power adapter device A2 has a terminal T13, a terminal T14, a terminal T15, a terminal T16, a terminal T21, and a terminal T22. The terminal T13 is connected to the terminal T11. The terminal T14 is connected to the terminal T12. The terminals T15 and T16 are connected to the terminals of the limit switch SW.

[0053] An external accessory device A4 can be connected to the power adapter device A2. The external accessory device A4 corresponds to the detection unit 5 (see FIG. 2) of the adapter device 2 described above. The external accessory device A4 has a terminal T41 and a terminal T42. When the external accessory device A4 is connected to the power adapter device A2, the terminal T41 is connected to the terminal T21, and the terminal T42 is connected to the terminal T22. A charging / discharging unit A41 provided for the external accessory device A4 is also shown. The charging / discharging unit A41 corresponds to the charging / discharging unit 6 (see FIG. 2) described above.

[0054] The power supply device A1 has a protection circuit A13 and a current detection circuit A12. The current detection circuit A12 corresponds to the current detection circuit 12 described above. The power adapter device A2 has an input control circuit A22, a voltage-current conversion circuit A23, and a switching circuit A24. The switching circuit A24 has a bypass circuit 240. The switching circuit A24 is connected to a terminal T42 of the external accessory device A4 via a terminal T22.

[0055] <Switching circuit> The bypass circuit 240 in the switching circuit A24 has a Zener diode Dz2. This Zener diode Dz2 and the external accessory A4 are connected in parallel. By connecting them in parallel, the voltage applied to the external accessory A4 becomes equal to the voltage applied to the Zener diode Dz2.

[0056] When the external accessory A4 is not connected, the current corresponding to the signal ST returns to the power supply A1 through the bypass circuit A240. That is, when the external accessory A4 is not connected and the limit switch SW is in the on state, the switching circuit A24 sends the signal ST, i.e., the current flowing through the limit switch SW, to the power supply A1.

[0057] When the external accessory device A4 is not connected and the limit switch SW is in the off state, the current passes through the Zener diode Dz2. This current passes through the bypass circuit A240. That is, when the external accessory device A4 is not connected and the limit switch SW is in the off state, the switching circuit A24 sends the current converted by the voltage-current conversion circuit A23 to the power supply device A1.

[0058] When the external accessory device A4 is connected, a current flows through the external accessory device A4, and no current flows through the bypass circuit 240. However, when the external accessory device A4 is not operating, such as when the power supply of the external accessory device A4 is off, no current flows through the external accessory device A4. In this case, a current flows through the bypass circuit 240 of the switching circuit A24.

[0059] When the limit switch SW is on, the current supplied from the power supply device A1 does not flow to the voltage-current conversion circuit A23, but flows to the limit switch SW. The power adapter device A2 takes in the current returning from the limit switch SW and supplies this current to the external accessory device A4 via the switching circuit A24.

[0060] When the limit switch SW is in the OFF state, the current supplied from the power supply device A1 does not flow to the limit switch SW, but flows to the voltage-current conversion circuit A23.

[0061] As described later, the voltage-current conversion circuit A23 includes a transistor and an inductor. When the transistor in the voltage-current conversion circuit A23 is on, the voltage-current conversion circuit A23 stores power based on the current taken in in the internal inductor. When the transistor in the voltage-current conversion circuit A23 is off, the voltage-current conversion circuit A23 releases the power stored in the inductor as a current, and the current that flows is supplied as power to the external accessory device A4 via the switching circuit A24. The voltage-current conversion circuit A23 converts voltage and current under a constant power so that the voltage is required for the operation of the external accessory device A4. The on-off operation of the transistor in the voltage-current conversion circuit A23 is, for example, 100 kHz or more.

[0062] When power is being supplied to the external accessory device A4, the current detection circuit A12 in the power supply device A1 must also be operated at the same time. When the limit switch SW is in the on state, a current flows that is determined by the voltage applied to the bypass circuit 240 in the switching circuit A24 in the power adapter device A2, specifically the Zener diode described below, the resistance in the current detection circuit A12, and the voltage of the DC power supply A11. The current value of this current must be equal to or greater than the on-confirmed current at which the current detection circuit A12 identifies that the limit switch SW is in the on state.

[0063] On the other hand, when the limit switch SW is in the off state, a current flows that is determined by the voltage applied to the input control circuit A22 of the power adapter device A2, the resistance value of the current detection circuit A12, and the voltage of the DC power supply A11. The current value of this current must be equal to or less than the off-state current at which the current detection circuit A12 identifies that the limit switch SW is in the off state.

[0064] <Example> Hereinafter, an embodiment of the power supply system of the present disclosure will be described with a specific configuration example. Here, the flow of current when the limit switch SW is in the on state and the off state will be described. FIG. 4 shows the path of the current when the limit switch SW is in the on state. As shown in FIG. 4, when the limit switch SW is in the on state, the current flowing from the power supply device A1 to the power adapter device A2 flows in the direction of the arrows Y11 and Y12, passes through the limit switch SW, and flows in the direction of the arrows Y13 and Y14 into the external accessory device A4. Furthermore, the current flowing into the external accessory device A4 passes through the external accessory device A4 as shown by the arrow Y15, and flows in the direction of the arrows Y16 and Y17 to return to the power supply device A1. The current path from the arrow Y11 to the arrow Y17 is called the first current path.

[0065] The input control circuit A22 of the power adaptor A2 includes resistors R1, R2, and R3, and a Zener diode Dz1. The voltage-to-current conversion circuit A23 includes a switching regulator A211, diodes D1 and D2, and an inductor L.

[0066] The resistors R1 and R2 of the input control circuit A22 form a voltage dividing resistor circuit. The input control circuit A22 outputs a voltage value corresponding to the ratio of the resistance value of the resistor R2 to the total resistance value of the resistors R1 and R2 from the connection point between the resistors R1 and R2. The input control circuit A22 also generates a constant reference voltage based on the resistance value of the resistor R3 and the Zener voltage of the Zener diode Dz1.

[0067] The switching regulator A211 has a comparator A211A, a drive circuit (DRV) A211B, and a transistor Tr1. The switching regulator A211 has a feedback terminal FB, an output terminal OUT, and a ground terminal G. The ground terminal G is electrically connected to the negative side of the DC power supply A11. The feedback terminal FB corresponds to the positive terminal (+) and the negative terminal (-) of the comparator A211A.

[0068] A reference voltage determined by the Zener voltage of the Zener diode Dz1 and the resistor R3 is input to the negative terminal (-) of the comparator A211A. A voltage value divided by the resistors R1 and R2 is input to the positive terminal (+) of the comparator A211A.

[0069] The drive circuit A211B is operated by the output voltage of the comparator A211A to operate the transistor Tr1. When the transistor Tr1 is in an on state, a current based on the output of the drive circuit A211B is output from the output terminal OUT.

[0070] One end of an inductor L is connected to the output terminal OUT. The other end of the inductor L is connected to the anode of a diode D1. The cathode of the diode D1 is connected to a terminal T42 of the external accessory device A4 via a terminal T22. In addition, the output terminal OUT is connected to the cathode of a diode D2. The anode of the diode D2 is connected to a terminal T41 of the external accessory device A4 via a terminal T21.

[0071] <Connection to external accessories> The terminal T21 of the power adapter device A2 is electrically connected to the terminal T41 of the external accessory device A4. The terminal T22 is electrically connected to the terminal T42 of the external accessory device A4. Power is supplied from the power adapter device A2 to the external accessory device A4 through these terminals T21 and T41, and terminals T22 and T42.

[0072] In addition, the terminals T21 and T41 are detachable, and the terminals T22 and T42 are detachable. Therefore, the external accessory device A4 can be removed from the power adapter device A2. Even when the external accessory device A4 is removed, the power adapter device A2 can still operate.

[0073] When the limit switch SW is on, the voltage-current conversion circuit A23 does not operate. When the limit switch SW is on, the terminals T15 and T16 are shorted, and a current flows through the limit switch SW but does not flow through the voltage-current conversion circuit A23. The voltage applied to the voltage-current conversion circuit A23 falls below a reference voltage that is predetermined by the comparator A211A.

[0074] The comparator A211A compares the voltage applied to the positive terminal (+) with the voltage applied to the negative terminal (-). When the voltage applied to the positive terminal (+) is higher than the voltage applied to the negative terminal (-), the comparator A211A sends a Hi signal to the drive circuit A211B. This turns on the transistor Tr1, causing a current to flow from the output terminal OUT.

[0075] On the other hand, when the voltage applied to the positive terminal (+) is lower than the voltage applied to the negative terminal (-), the comparator A211A sends a Low signal to the drive circuit A211B. This turns off the transistor Tr1, and no current flows from the output terminal OUT. When the limit switch SW is in the on state, the voltage falls below the voltage at the negative terminal (-) of the comparator A211A, and the switching regulator A211 stops operating. The current flowing from the limit switch SW through the first current path returns to the power supply device A1 through the external accessory device A4.

[0076] On the other hand, when the limit switch SW is in the OFF state, no current flows through the limit switch SW, but flows through the voltage-current conversion circuit A23. Fig. 5 shows the path of the current when the limit switch SW is in the OFF state.

[0077] When the limit switch SW is in the off state, the current flowing from the power supply device A1 to the power adapter device A2 flows as indicated by the arrows Y21 and Y22 and flows into the voltage-current conversion circuit A23. If the transistor Tr1 of the switching regulator A211 of the voltage-current conversion circuit A23 is on, the current flows in the directions of the arrows Y23, Y24, and Y25 and flows into the external accessory device A4. That is, when the limit switch SW is in the off state, the current converted by the voltage-current conversion circuit A23 is supplied to the external accessory device A4. Furthermore, the current flowing into the external accessory device A4 passes through the external accessory device A4 as indicated by the arrow Y26, flows in the directions of the arrows Y27 and Y28, and returns to the power supply device A1. The current path from the arrow Y21 to the arrow Y28 is called the second current path. In the case of the second current path, the power adapter device A2 stores the power to be supplied to the external accessory device A4 in the inductor L and supplies the stored power to the external accessory device A4.

[0078] FIG. 6 shows the current path when the limit switch SW is in the off state. When the limit switch SW is in the off state and the transistor Tr1 of the switching regulator A211 of the voltage-current conversion circuit A23 is off, the power stored in the inductor L is discharged as a current as shown by the arrow Y31. This current passes through the diode D1 and flows in the directions of the arrows Y32 and Y33 to the external accessory device A4. That is, when the limit switch SW is in the off state, the power stored in the inductor L is supplied to the external accessory device A4. Furthermore, the current that has flowed into the external accessory device A4 passes through the external accessory device A4 as shown by the arrow Y34, flows in the directions of the arrows Y35, Y36, and Y37, and returns to the inductor L through the diode D2. The current path from the arrow Y31 to the arrow Y37 is called the third current path. In the case of the third current path, the power adapter device A2 is in a state in which it discharges the power stored in the inductor L and supplies it as a current to the external accessory device A4.

[0079] When the limit switch SW is in the off state, the current flowing through the voltage-current conversion circuit A23 alternates between the second current path and the third current path, that is, alternates between a state in which power is stored in the inductor L via the second current path and supplied to the external accessory device A4, and a state in which the power stored in the inductor L is released via the third current path and supplied to the external accessory device A4.

[0080] Hereinafter, the operation of the power adaptor A2 will be described in more detail with reference to FIGS.

[0081] In the switching regulator A211, the comparator A211A compares the voltage applied to the positive terminal (+) with the voltage applied to the negative terminal (-). When the voltage applied to the positive terminal (+) is higher than the voltage applied to the negative terminal (-), the comparator A211A sends a Hi signal to the drive circuit A211B, turning on the transistor Tr1. When the transistor Tr1 turns on, a current is output from the output terminal OUT.

[0082] On the other hand, when the voltage applied to the positive terminal (+) of the comparator A211A is lower than the voltage applied to the negative terminal (-), the comparator A211A sends a low signal to the drive circuit A211B, turning off the transistor Tr1. When the transistor Tr1 is turned off, no current is output from the output terminal OUT.

[0083] That is, the drive circuit A211B operates according to the output voltage of the comparator A211A to turn the transistor Tr1 on or off. The switching regulator A211 turns the transistor Tr1 on and off to adjust the current output from the output terminal OUT so that the voltage at the positive terminal (+) of the comparator A211A becomes equal to the reference voltage input to the negative terminal (-) of the comparator A211A.

[0084] Here, it is assumed that the transistor Tr1 is on and a current flows through the second current path. At that time, while power is stored in the inductor L, a current also flows through the external accessory device A4. When a current flows through the second current path, the voltage between the terminals T13 and T14, which is equal to the voltage between the terminals T11 and T12 of the power supply device A1, drops due to the resistance of the power adapter device A2, that is, the terminal voltage of the power adapter device A2. Then, with the drop in the terminal voltage, the voltage divided by the resistors R1 and R2, which is the voltage applied to the positive terminal (+) of the comparator A211A, drops. Since this voltage becomes lower than the reference voltage applied to the negative terminal (-) of the comparator A211A, the output of the drive circuit A211B becomes a Low signal, the transistor Tr1 is turned off, and the current through the second current path stops flowing. When the current through the second current path stops flowing, the power stored in the inductor L is released as a current and is supplied to the external accessory device A4 through the third current path.

[0085] Since no current flows through the second current path in the transistor Tr1, the terminal voltage of the power adapter device A2 rises. When the terminal voltage rises, the voltage divided by the resistors R1 and R2, which is the voltage applied to the positive terminal (+) of the comparator A211A, rises and becomes greater than the reference voltage applied to the negative terminal of the comparator, so that the output of the drive circuit A211B becomes a Hi signal, the transistor Tr1 turns on, and a current flows through the second current path. In this way, when the limit switch SW is in the off state, the voltage-to-current conversion circuit A23 repeatedly stores power in the inductor L through the second current path and releases the power stored in the inductor L through a third current path different from the second current path.

[0086] Next, the operation of storing power in the inductor L and the operation of releasing the stored power will be described. One end of the inductor L is connected to the output terminal OUT. As shown in FIG. 5, when the transistor Tr1 is on and a current flows through the second current path, the inductor L stores electric energy. When the external accessory device A4 is connected to the power adapter device A2, power is supplied to the external accessory device A4. The switching circuit A24 has a Zener diode Dz2. The Zener diode Dz2 and the external accessory device A4 are connected in parallel. This switching circuit A24 is a so-called shunt regulator, and the same voltage as the voltage applied to the Zener diode Dz2 is applied to the external accessory device A4. When the limit switch SW is in the on state, the switching circuit A24 supplies the current flowing through the limit switch SW by the first current path to the external accessory device A4. When the limit switch SW is in the off state, the switching circuit A24 supplies the current converted by the voltage-current conversion circuit A23 to the external accessory device A4.

[0087] Diodes D1 and D2 are connected to the inductor L. The diodes D1 and D2 are provided to prevent a reverse current flow. The anode of the diode D1 is connected to the other end of the inductor L. The cathode of the diode D1 is connected to the terminal T42 of the external accessory device A4 via the terminal T22. The cathode of the diode D2 is connected to the output terminal OUT. The anode of the diode D2 is connected to the terminal T41 of the external accessory device A4 via the terminal T21.

[0088] 6, when the transistor Tr1 is off, the current discharged from the inductor L flows through the diode D1 to the switching circuit A24, passes through the external accessory device A4, passes through the diode D2, and returns to the inductor L. In other words, the current discharged from the inductor L flows through the third current path.

[0089] At this time, voltage-current conversion is performed under a constant power condition, that is, voltage-current conversion is performed to convert power, which is the product of the current of the second current path when the transistor Tr1 is on and the terminal voltage between the terminals T11 and T12 of the power supply device A1 corresponding to the second current path, into a current whose value is obtained by dividing the power by the voltage applied to the Zener diode Dz2.

[0090] The Zener diode Dz2 of the bypass circuit A240 passes the current when the external accessory A4 is not connected. When the limit switch SW is in the on state, if the external accessory A4 is not connected, the current flows along the first current path from the arrow Y11 to the arrow Y13 shown in FIG. 4, and then passes through the Zener diode Dz2 and flows in the direction of the arrow Y17. At this time, the current passes through the bypass circuit A240 and returns to the DC power supply A11. If the external accessory A4 is not connected and the limit switch SW is in the off state, the current passes through the Zener diode Dz2. That is, the current passes through the bypass circuit A240.

[0091] The bypass circuit A240 also includes a Zener diode Dz2 and a capacitor C. In the bypass circuit A240, the capacitor C is connected in parallel to the Zener diode Dz2.

[0092] So far, the operation of power supply voltage conversion by the power adapter device A2 has been described. Even if the power adapter device A2 is inserted between the power supply device A1 and the limit switch SW, the current detection circuit A12 needs to detect the on / off state of the limit switch SW. The input control circuit A22 has a function of adjusting the operation of the voltage-current conversion circuit A23 and at the same time, has a function of adjusting the operation of the current detection circuit A12 that detects the on / off state of the limit switch SW. Hereafter, the conditions required for detecting the on / off state of the limit switch SW will be described.

[0093] <Operation without power adapter> First, the operation when the power adapter device A2 is not used will be described.

[0094] The characteristics of the current detection circuit A12 are determined in advance regardless of whether the power adapter device A2 is inserted or not. Specifically, the resistance value of the resistor of the current detection circuit A12 in the power supply device A1, the magnitude of the OFF-definition current Ioff that determines that the limit switch SW is in the OFF state, the magnitude of the ON-definition current Ion that determines that the limit switch SW is in the ON state, and the magnitude of the voltage Vd of the DC power supply A11 of the power supply device A1 are determined in advance.

[0095] Hereinafter, it is assumed that the protection circuit A13 and the current detection circuit A12 in the power supply device A1 can be approximated by resistance characteristics in which the voltage and the current are in a proportional relationship.

[0096] Fig. 7 is a diagram showing the relationship between the inter-terminal voltage and inter-terminal current of power terminals T1, T2 when power adapter device A2 is not inserted. In Fig. 7, the vertical axis represents the inter-terminal voltage between terminals T11, T12 of power supply device A1, the horizontal axis represents the inter-terminal current between terminals T11, T12 of power supply device A1, and solid line J1 represents the characteristics between terminals T11, T12 of power supply device A1.

[0097] The current Ioff in Fig. 7 is a current that determines that the limit switch SW is in the off state (hereinafter referred to as the off-determined current Ioff). The area to the left of the off-determined current Ioff in Fig. 7 is the area in which the limit switch SW is considered to be in the off state.

[0098] The current Ion in Fig. 7 is a current that determines that the limit switch SW is in the on state (hereinafter referred to as the on-determined current Ion). The area to the right of the on-determined current Ion in Fig. 7 is the area in which the limit switch SW is considered to be in the on state.

[0099] Even when the power adapter device A2 is inserted, it is necessary that the current flowing is within the range regarded as the on state or off state.

[0100] In Figure 7, point OFF1 indicates that no current is flowing, and therefore the limit switch SW is in the off state. At this time, the voltage between the terminals is at its maximum value, and the current between the terminals is at its minimum value (0). Point ON1 indicates that the limit switch SW is in the on state. At this time, the voltage between the terminals is at its minimum value (0), and the current between the terminals is at its maximum value. In this way, the voltage between the power supply terminals T1 and T2 is at its maximum value when the limit switch SW is in the off state, and the more current flows, the lower it becomes.

[0101] <Operation when using a power adapter device> Next, the power consumption during operation when the power adapter A2 is used will be described. Fig. 8 is a diagram showing the relationship between the terminal voltage and terminal current between the power terminals T1 and T2 when the power adapter A2 is inserted between the limit switch SW and the power supply A1 and the limit switch SW is in the on state.

[0102] When the limit switch SW is on using the power adapter A2, part of the power is consumed by the circuit in the power adapter A2. Therefore, when the limit switch SW is on, it is in the state of point ON2 in Figure 8. The power adapter A2 needs to be designed so that the terminal current and terminal voltage at this point ON2 satisfy the specifications of the current detection circuit A12 of the power supply A1. In other words, when the limit switch SW is on, the terminal current needs to be equal to or greater than the on-determined current Ion.

[0103] 9 is a simplified circuit diagram showing the first current path when the limit switch SW is in the on state. Using FIG. 9, a condition in which the inter-terminal current is equal to or greater than the on-definite current Ion for determining that the current detection circuit A12 is in the on state will be specifically described.

[0104] In FIG. 9, if the voltage of the DC power supply A11 of the power supply device A1 is Vd, the voltage applied to the Zener diode Dz2 in the switching circuit A24 is Vt, and the resistance value of the resistor R12 of the current detection circuit A12 is Rs, the on-definite current Ion can be expressed by the following equation (1). (Vd-Vt) / Rs≧Ion …(1) The Zener voltage of the Zener diode Dz2 needs to be selected so that it becomes the voltage Vt that satisfies the formula (1).

[0105] Fig. 10 is a diagram for explaining the power that can be extracted when the limit switch SW is in the on state. In Fig. 10, the horizontal axis represents the current between the terminals of the power supply device A1, and the vertical axis represents the voltage between the terminals of the power supply device A1.

[0106] In Fig. 10, when focusing on point ON2 on solid line J1, the area of ​​hatched range M1 including point ON2 is calculated as the product of terminal voltage and terminal current, and therefore represents power. That is, hatched range M1 shown in Fig. 10 is the power that can be extracted when limit switch SW is in the on state. Hereinafter, for convenience of explanation, range M1 may be referred to as power M1.

[0107] Fig. 11 is a diagram showing the relationship between the terminal voltage and terminal current of the power supply terminals T1, T2 when the limit switch SW is in the off state with the power adapter device A2 inserted. In Fig. 11, the horizontal axis represents the terminal current of the power supply device A1, and the vertical axis represents the terminal voltage of the power supply device A1.

[0108] In Fig. 11, since the limit switch SW is in the OFF state, point ON2 (see Fig. 8) on the solid line J1 moves to point OFF2 as indicated by arrow Y4. Point OFF2 indicates that the limit switch SW is in the OFF state. The power adapter A2 needs to be designed so that the terminal current and terminal voltage satisfy the specifications of the current detection circuit A12 of the power supply A1. In other words, when the limit switch SW is in the OFF state, the current value of the current returning from the power adapter A2 to the power supply A1 needs to be equal to or less than the off-determined current Ioff.

[0109] Fig. 12 is a diagram showing the input control circuit A22 and its peripheral circuits when the limit switch SW is in the off state. In Fig. 12, the resistance value of the resistor R12 of the current detection circuit A12 is indicated as Rs.

[0110] In FIG. 12, when the limit switch SW is in the off state, the voltage-current conversion circuit A23 repeatedly stores power and releases the stored power by turning on and off the transistor Tr1. This causes a high-speed switching between a state in which a current flows and a state in which a current does not flow. For this reason, the current flowing through the resistor R12 (resistance value Rs) of the current detection circuit A12 is treated as the average current of these. The resistance value of the input control circuit A22 is set so that the current flowing through the resistor R12 (resistance value Rs) of the current detection circuit A12 is equal to or less than the off-definite current Ioff. More specifically, the resistance values ​​of the resistors R1, R2, and R3 of the input control circuit A22 are set so that the current flowing through the resistor R12 of the current detection circuit A12 is equal to or less than the off-definite current Ioff. Hereinafter, for convenience of explanation, the resistance value of the resistor R1 may be written as "R1" and the resistance value of the resistor R2 may be written as "R2".

[0111] In the input control circuit A22, if the voltage applied to the series circuit of the resistors R1 and R2 is Vx and the voltage applied to the Zener diode Dz1 is Vz, the voltage Vx can be expressed by the following equation (2). Vx = Vz * (R1 + R2) / R2 … (2)

[0112] In addition, in formula (2), "*" indicates multiplication. The same applies to the following explanations.

[0113] The inter-terminal current flowing between terminals T11 and T12 of power supply device A1 must satisfy the relationship expressed by the following equation (3), where Vd is the power supply voltage and Rs is the resistance value of resistor R12 of current detection circuit A12. (Vd-Vx) / Rs =(Vd-Vz*(R1+R2) / R2) / Rs≦Ioff …(3)

[0114] That is, when the limit switch SW is in the off state, it is necessary to set the resistance values ​​of the resistors R1 and R2 of the input control circuit A22 so as to satisfy the condition of equation (3) regarding the operation of the voltage-current conversion circuit A23.

[0115] Fig. 13 is a diagram for explaining the power that can be extracted when the limit switch SW is in the OFF state. In Fig. 13, the horizontal axis represents the current between the terminals of the power supply device A1, and the vertical axis represents the voltage between the terminals of the power supply device A1.

[0116] In FIG. 13, when focusing on point OFF2 on solid line J1, the area of ​​hatched range M2 including point OFF2 is calculated as the product of terminal voltage and terminal current, and therefore represents power. That is, hatched range M2 shown in FIG. 13 is the power that can be extracted when limit switch SW is in the OFF state. According to range M2 shown in FIG. 13, the terminal voltage is higher than range M1 shown in FIG. 10. Also, according to range M2, the terminal current is lower than range M1 shown in FIG. 10. Hereinafter, for convenience of explanation, range M2 may be referred to as power M2.

[0117] FIG. 14 is a diagram showing the relationship between the power before and after conversion by the voltage-current conversion circuit A23 of the power adaptor device 2 when the limit switch SW is in the OFF state.

[0118] The voltage and current converted under a constant power condition will be described below. The voltage applied to the external accessory device A4 connected to the power adapter device A2 is the voltage Vt applied to the Zener diode Dz2 of the switching circuit A24. Before being converted by the voltage-current conversion circuit A23, the product of the voltage V1 and the current I1 is a value that falls within a range M2. In FIG. 14, the range M2 is a rectangular range with four vertices: the intersection of the vertical and horizontal axes, the point of the terminal voltage V1 on the vertical axis, the point of the terminal current I1 on the horizontal axis, and the point OFF2.

[0119] As described above, the current value increases by converting the voltage to a current. After conversion by the voltage-to-current conversion circuit A23, the product of the voltage V2 and the current I2 becomes a value that falls within the range M3 including the point OFF3. In FIG. 14, the range M3 is a rectangular range having four vertices: the intersection of the vertical and horizontal axes, the point of the inter-terminal voltage V2 on the vertical axis, the point of the inter-terminal current I2 on the horizontal axis, and the point OFF3. The area of ​​the range M3 is the same as the area of ​​the range M2.

[0120] Below, a first example and a second example will be explained together with specific numerical values.

[0121] <Example 1> As a first example, when the power adapter device A2 is not inserted, the voltage Vd of the DC power supply A11 of the power supply device A1 is 24 (V), the resistance value Rs of the resistor R12 of the current detection circuit A12 is 4 (kΩ), the on-definite current Ion of the current detection circuit A12 is 4 (mA), and the off-definite current Ioff is 3 (mA).

[0122] Here, reference is made again to Fig. 7. In Fig. 7, the voltage at point OFF1 is 24 (V), and the current at point ON1 is 6 (mA).

[0123] Next, consider the case where the power adapter device A2 is inserted. The voltage across the external accessory device A4, that is, the voltage Vt across the Zener diode Dz2 of the switching circuit A24, is assumed to be 3 (V). When the limit switch SW is in the on state, the current between the terminals of the power supply device A1 can be expressed by equation (4). (Vd-Vt) / Rs =(24-3) / 4000=5.25mA≧Ion=4mA …(4)

[0124] In the above formula (4), the current between the terminals of the power supply device A1 becomes larger than the on-definite current Ion of 4 (mA), and satisfies the condition of formula (1). At this time, the power M1 that can be supplied to the external accessory device A4 can be expressed by formula (5). M1 = 3V * 5.25mA = 15.75mW … (5)

[0125] When the limit switch SW is in the off state, if the voltage Vx applied to the resistors R1 and R2 of the input control circuit A22 is 15 (V), the off-definite current Ioff can be expressed by equation (6). (Vd-Vx) / Rs =(24-15) / 4000=2.25mA≦Ioff=3mA …(6) In the above formula (6), the current between the terminals of the power supply device A1 is smaller than the off-definite current Ioff of 3 (mA), and therefore satisfies the condition.

[0126] At this time, the power M2 that can be supplied to the external accessory device A4 can be expressed by the formula (7). M2 = 15V * 2.25mA = 33.75mW … (7) It can be seen that the power M2 is greater than the power M1, and that the power M2 can be approximately twice the power M1. This shows that the voltage-current conversion circuit A23 can supply more power to the external accessory device A4 when the limit switch SW is in the OFF state than when the limit switch SW is in the ON state. The power M2 corresponds to M2 in FIG. 14.

[0127] Since the voltage applied to the external accessory device A4 is 3 (V), the current that can be passed through the external accessory device A4 can be expressed by equation (8). 33.75 / 3=11.25mA …(8)

[0128] As can be seen from the above formula (8), the current that can be passed through the external accessory device A4 is about 10 (mA). This allows the sensor to be operated and radio waves to be sent and received by short-range wireless communication. Therefore, it can be seen that the current obtained by the power adapter device A2 is sufficient to operate the external accessory device A4.

[0129] <Second Example> Next, as a second example, when the limit switch SW is in the off state and the current flowing through the second current path is the average current due to the on / off of transistor Tr1, we will explain the resistance of the input control circuit A22 when it is not turned on by the current detection circuit A12.

[0130] When the power adapter device A2 is not inserted, the voltage Vd of the DC power supply A11 is 24 (V), and the current between the terminals of the DC power supply A11 when the limit switch SW is on is 5 (mA). In this case, the resistance value Rs of the resistor R12 of the current detection circuit A12 can be expressed by the following equation (9). Rs = 24 V / 5 mA = 4.8 kΩ … (9)

[0131] When the power adapter device A2 is inserted and the average current between the terminals of the DC power supply A11 becomes 2 (mA), the voltage between the terminals of the DC power supply A11, i.e., the voltage Vx across both ends of the resistors R1 and R2 of the input control circuit A22, can be expressed by the following equation (10). Vx=24V*(5mA-2mA) / 5mA=14.4V …(10)

[0132] In this case, the power M2 is M2 = 14.4 V * 2 mA = 28.8 mW. Since the voltage applied to the external accessory device A4 is 3 (V), the current flowing to the external accessory device can be expressed by the following equation (11). 28.8mW / 3V=9.6mA …(11) In addition, in this trial calculation, the current flowing through resistors R1 and R3 is ignored, the self-consumption current of the switching regulator A211 is assumed to be zero, and the conversion efficiency of the voltage-to-current conversion circuit A23, which is composed of transistor Tr1, inductor L, etc., is assumed to be 100%. Considering these points, the power that can be extracted when the limit switch SW is in the off state, in particular, is actually lower than the value expressed by equation (11).

[0133] The reference voltage in the comparator A211A is determined in advance, and each resistance value of the input control circuit A22 is determined so as to be equal to the reference voltage. Specifically, if the voltage Vx applied to the resistors R1 and R2 of the input control circuit A22 is Vx=14.4 (V) and the voltage applied to the Zener diode Dz1 of the input control circuit A22 is Vz, the resistance values ​​of the resistors R1 and R2 of the input control circuit A22 are determined so as to satisfy the formulas (12) and (13). (Vd-Vx) / Rs=(Vd-Vz*(R1+R2) / R2) / Rs =(24-Vz*(R1+R2) / R2)≦Ioff …(12) (R1+R2) / R2=14.4 / Vz …(13)

[0134] Although the resistance values ​​of resistors R1 and R2 of the input control circuit A22 can be calculated appropriately as described in equations (12) and (13), fine adjustment of the resistance values ​​is performed on-site where the power adapter device A2 is installed. Therefore, it is preferable to use resistors such as variable resistors whose resistance values ​​can be adjusted for the input control circuit A22. For example, the resistance value Rs of resistor R12 of the current detection circuit A12, the value of the on-definition current Ion of the current detection circuit A12, and the value of the off-definition current Ioff are determined by the specifications of the current detection circuit A12. Therefore, each value is adjusted on-site where the power adapter device A2 is installed.

[0135] For example, by using the power adapter device A2 and external accessory device A4 as described above as the power supply unit 4 and detection unit 5 (Figure 2) of the adapter device 2 in the maintenance system 100, power can be extracted from the wiring leading from the power supply device 1 to the limit switch SW, and the extracted power can be used as a power source for the detection unit 5.

[0136] <Example of adapter device and valve configuration> 15 is a diagram showing an example of a specific configuration of the adapter device 2 and the valve 3. The adapter device 2 is inserted into the wiring L1 and L2 extending from the power supply device 1 to the limit switch SW.

[0137] The valve 3 is opened or closed to control the flow rate of the fluid. The valve 3 may have any structure, such as a ball valve, a butterfly valve, or a gate valve. As mentioned above, the valve is not limited to a valve that is opened or closed, and may be a damper for adjusting the amount of gas passing through a duct, which is an air passage.

[0138] The valve 3 includes a hollow portion 31 and flanges 32a and 32b. The valve 3 is a valve that controls the flow of a fluid at two positions, a fully open position (i.e., an open state) and a fully closed position (i.e., a closed state). The hollow portion 31 is a portion through which a fluid (not shown) flows. The flanges 32a and 32b are connection portions for connecting the valve 3 to a pipe (not shown). The fluid may be either a liquid or a gas, or may be a powder or granules.

[0139] When the valve 3 is in an open state, the valve 3 allows a fluid (not shown) to flow through the hollow portion 31. When the valve 3 is in a closed state, the valve 3 stops the flow of the fluid through the hollow portion 31.

[0140] Here, the direction of axis J is the Z direction, the direction perpendicular to the Z direction, the length direction of hollow portion 31 is the X direction, and the direction perpendicular to both the X direction and the Z direction is the Y direction.

[0141] The axis J passes through the actuator 33. The actuator 33 is provided on the axis J. The actuator 33 drives the axis J. The actuator 33 operates according to a control signal from the outside. The actuator 33 rotates the axis J in a clockwise or counterclockwise direction around the Z direction to open or close the valve 3.

[0142] The detection unit 5 includes a cam CM, a pin PJ, and a detection lever SWL1 in addition to the sensor unit 51 described above. The shaft J rotates clockwise or counterclockwise about the Z axis by opening and closing the valve 3. The cam CM is provided at the end of the shaft J.

[0143] The cam CM fixed to the shaft J moves clockwise or counterclockwise as the shaft J rotates. When the cam CM moves as the shaft J rotates, the position of the pin PJ changes. The change in the position of the pin PJ changes the angle of the detection lever SWL1. For example, at least a part of this detection lever SWL1 or its surrounding portion (for example, the portion up to the actuator 33) may correspond to the drive unit 30 (FIG. 2) described above.

[0144] In this example, the sensor unit 51 detects the angle of the detection lever SWL1. The sensor unit 51 outputs a signal corresponding to the angle of the detection lever SWL1. Therefore, the detection unit 5 can detect the open or closed state of the valve, i.e., the valve opening degree. Data including this detection result is transmitted from the communication unit 52 to the maintenance monitoring device 9.

[0145] <Second embodiment> FIG. 16 is a block diagram showing an example of a schematic configuration of a maintenance system 100a according to the second embodiment. The maintenance system 100a according to the second embodiment differs from the maintenance system 100 according to the first embodiment (FIG. 2) in that the sensor unit 51 includes a camera. This camera captures an image of the valve 3, more specifically, the drive unit 30 of the valve 3. In this sense, image data of the valve 3 is obtained. The state of the valve 3 can be ascertained from the image, and in this sense, the image data of the valve 3 can also be data indicating the detection result of the valve 3. Note that the terms "capture" and "image" may be interpreted to include "filming" and "video."

[0146] For example, when the drive unit 30 rotates, a pattern is drawn on a disk at the rotating part. From the position of the pattern in the image of the drive unit 30, the rotational position of the axis J (see FIG. 15) of the valve 3, i.e., the valve opening degree, is detected. Instead of the pattern, a scale indicating the rotation angle may be provided on the axis J, and the scale portion may be imaged by the sensor unit 51. Note that the camera portion of the sensor unit 51 may be provided outside the adapter device 2. In that case, image data of the drive unit 30 captured by the camera is transmitted from the camera to the sensor unit 51 and acquired.

[0147] The communication unit 52 transmits image data of the valve 3 acquired by the sensor unit 51 to the maintenance monitoring device 9. The maintenance monitoring device 9 analyzes the image data to grasp (calculate, etc.) the state of the valve 3, for example, the valve opening degree, and determines whether or not there is an abnormality in the valve 3.

[0148] The maintenance system 100a according to the second embodiment also enables maintenance of the valve 3, similarly to the maintenance system 100 according to the first embodiment described above. Furthermore, by using the adapter device 2, it is possible to extract power from the wiring leading from the power supply device 1 to the limit switch SW, and use the extracted power as the power source for the detection unit 5. Therefore, it is possible to ensure the power source for the adapter device 2 without requiring new installation work.

[0149] <Third embodiment> Fig. 17 is a block diagram showing an example of a schematic configuration of a maintenance system 100b according to the third embodiment. The maintenance system 100b according to the third embodiment differs from the maintenance system 100 (Fig. 2) according to the first embodiment in that it includes a warning light 8. The warning light 8 emits light when the limit switch SW is turned on (when the valve 3 is opened or closed). A sound may be output together with the light emission. By providing such a warning light 8, it becomes easier to know that the limit switch SW is turned on, i.e., the valve 3 is opened or closed.

[0150] The maintenance system 100b according to the third embodiment also enables maintenance of the valve 3, similarly to the maintenance system 100 according to the first embodiment described above. Furthermore, by using the adapter device 2, it is possible to extract power from the wiring leading from the power supply device 1 to the limit switch SW, and use the extracted power as the power source for the detection unit 5. Therefore, it is possible to ensure the power source for the adapter device 2 without requiring new installation work. Furthermore, by providing a warning light 8, it becomes easy to monitor the open or closed state of the valve 3. [Explanation of symbols]

[0151] 1 Power supply 2 Adapter device 3 Valve 4 Power supply section 5. Detection unit 6 Charge / discharge section 8 warning light 9 Maintenance monitoring equipment 12 Current detection circuit 30 Drive unit 31 Hollow part 32a, 32b flange 33 Actuator 42 Regulator circuit 51 Sensor section 52 Communications Department 100, 100a, 100b Maintenance Systems 520 Data Compression Unit 521 Storage section CM Cam PJ Pin SWL1 Detection lever A1 Power supply A2 Power Adapter Device A3 Valve A4 External accessories A11 DC power supply A12 Current detection circuit A13 Protection circuit A22 Input control circuit A23 Voltage-to-current conversion circuit A24 Switching circuit A41 Charge / discharge section A100 Power Supply System A211 Switching Regulator A211A Comparator A211B Drive circuit C Capacitor D1, D2 Diodes Dz1, Dz2 Zener diode L Inductor L1, L2 wiring SW Limit switch

Claims

1. a limit switch provided for an object in a plant and switching between an on state and an off state depending on a state of the object; A power supply device including a current detection circuit for detecting an on state and an off state of the limit switch; an adapter device that is inserted into wiring between the power supply device and the limit switch; Equipped with The adapter device comprises: A detection unit that detects a state of the object and transmits a detection result to a maintenance monitoring device; A power supply unit that supplies at least a portion of the power from the power supply device to the limit switch and also supplies at least a portion of the power from the power supply device to the detection unit; Including, Conservation system.

2. the current detection circuit is used to detect a current flowing from the power supply device to the adapter device or a current flowing from the adapter device to the power supply device; The detected current value of the current detection circuit when the limit switch is in the on state is equal to or greater than an on-confirmation current that determines that the limit switch is in the on state, The detected current value of the current detection circuit when the limit switch is in the off state is equal to or less than an off-determined current that determines that the limit switch is in the off state; The security system of claim 1 .

3. the power supply unit includes a regulator circuit, The regulator circuit includes: When the limit switch is in an on state, the operation is stopped, and a current diverted from the loop current flowing through the power supply device and the limit switch is supplied to the detection unit, When the limit switch is in an off state, the current obtained by converting the current from the power supply device into a voltage-current by an internal switching regulator is supplied to the detection unit.

3. A security system according to claim 1 or 2.

4. The detection unit is A sensor unit for detecting a state of the object; a communication unit that transmits data indicating a detection result of the sensor unit to the maintenance monitoring device; Including, 3. A security system according to claim 1 or 2.

5. the sensor unit includes a camera that captures an image of the object; The communication unit transmits data of the image of the object to the maintenance monitoring device.

5. The security system of claim 4.

6. The communication unit compresses data indicating a detection result of the sensor unit and intermittently transmits the compressed data to the maintenance monitoring device.

5. The security system of claim 4.

7. the adapter device includes a charge / discharge unit that charges the power from the power supply unit and discharges the power to the detection unit, The operating power of the detection unit includes the discharge power of the charge / discharge unit.

3. A security system according to claim 1 or 2.

8. The charging / discharging unit discharges electricity to the detection unit when the detection unit transmits the detection result to the maintenance monitoring device.

8. The security system of claim 7.

9. The maintenance monitoring device determines whether or not there is an abnormality in the object based on the detection result from the detection unit.

3. A security system according to claim 1 or 2.

10. the object includes a valve for controlling a flow rate of a fluid; The state of the object includes an open state and a closed state of the valve.

3. A security system according to claim 1 or 2.

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