State monitoring device

Abstract

To protect an external apparatus even when an external apparatus different from an IEPE sensor is connected to a state monitoring device and a switch fails, in a state monitoring device including a power supply node constituting a power supply for the IEPE sensor and a switch for switching electrical connection / disconnection between the external apparatus and the power supply node.SOLUTION: A state monitoring device 80 includes: a connection terminal 102; a power source node 110 for an IEPE sensor; switches U1, U2; a constant current element 112; a signal generation circuit 115; and a fuse 119. The connection terminal 102 is connectable to one of the IEPE sensor and an analog signal output apparatus. The signal generation circuit 115 generates a control signal SG for complementarily controlling the switches U1, U2. The fuse 119 is connected between power lines PL1, PL2 and limits a short-circuit current flowing from the power source node 110 toward a ground node 118.SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] The present disclosure relates to a condition monitoring device.

Background Art

[0002] Japanese Patent No. 4995134 (Patent Document 1) discloses a monitoring device for a wind turbine. A sensor is attached to the monitoring unit of this monitoring device. The measurement data of this sensor is used to monitor the state of the wind turbine.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] A condition monitoring device for monitoring the state of an object such as a wind turbine generally includes connection terminals to which external devices such as sensors are connected. An IEPE (Integrated Electronics Piezo Electric) sensor is used to measure the dynamic acceleration of an object and operates by receiving a constant current. The condition monitoring device may have connection terminals to which the IEPE sensor can be connected as an external device. In this case, the condition monitoring device further includes a power supply node for the IEPE sensor and a constant current element for supplying a constant current to the IEPE sensor.

[0005] In order to reduce the manufacturing cost and size of the condition monitoring device, the connection terminal preferably serves as both a connection terminal for an IEPE sensor (first device) as an external device and a connection terminal for a device different from the IEPE sensor (second device). On the other hand, when the second device is connected to the connection terminal, from the viewpoint of protection, the situation where the power supply generated by the power supply node is applied to the second device is not preferable. Therefore, the condition monitoring device preferably includes a switch that switches the electrical connection / disconnection between the external device and the power supply node, and a signal generation circuit that generates a control signal for turning on the switch when the first device is connected and turning off the switch when the second device is connected. However, if the switch fails, the switch may not be turned off according to the control signal when the second device is connected, and the power supply node may be electrically connected to the second device unintentionally. As a result, the power supply may be applied to the second device, and the second device may not be protected.

[0006] The present disclosure has been made to solve the above problems, and an object thereof is to protect an external device different from an IEPE sensor even when the external device is connected to a condition monitoring device including a power supply node constituting a power supply for the IEPE sensor and a switch that switches the electrical connection / disconnection between the external device and the power supply node and the switch fails.

Means for Solving the Problem

[0007] The state monitoring device of the present disclosure is configured to monitor the state of an object. The state monitoring device includes a connection terminal, a power supply node, a first switch, a second switch, a constant current element, a signal generation circuit, and a current limiting element. The connection terminal is connectable to an IEPE sensor as a first device and one of a second device different from the IEPE sensor. The power supply node is configured to constitute a power supply for the IEPE sensor. The first switch is connected between the power supply node and the first power line. The second switch is connected between the second power line and the ground node. The constant current element is connected between a branch line branched from the second power line at a branch point of the second power line and the connection terminal. The signal generation circuit generates a control signal for complementarily controlling the first switch and the second switch. The current limiting element is connected between the first power line and the second power line. The control signal includes a first signal and a second signal. The first signal is generated to turn on the first switch and turn off the second switch when the IEPE sensor is connected to the connection terminal. The second signal is generated to turn off the first switch and turn on the second switch when the second device is connected to the connection terminal. The current limiting element is configured to limit a short-circuit current flowing from the power supply node toward the ground node.

[0008] When a failure of the first switch (such as an open failure or a short - circuit failure) occurs, the first switch may not be controlled according to the control signal. In particular, when the first switch has a short - circuit failure, even though the second signal is being generated when the second device is connected to the connection terminal, the power supply node and the second device may be electrically connected. As a result, the power supply for the IEPE sensor is unintentionally applied to the second device through the first switch, the first power line, the branch line, and the constant - current element. This is not preferable from the perspective of protecting the second device. With the above configuration, when the second signal is generated and the first switch has a short - circuit failure, the power supply node and the ground node are short - circuited and a short - circuit current flows. Thereby, the current - limiting element operates (for example, cuts off the circuit of this current or reduces this current to a level that can be practically ignored). As a result, it is possible to suppress the power supply for the IEPE sensor from being applied to the second device. Therefore, even when the first switch has a short - circuit failure, the second device can be protected. In addition, according to the above configuration, the connection terminal is configured to be connectable to one of the first device and the second device. Therefore, the condition monitoring device does not separately require a connection terminal for connecting to the first device and a connection terminal for connecting to the second device. Thus, the cost and size of the condition monitoring device can be reduced. When the first switch has an open failure, since the power supply node is disconnected from the connection terminal regardless of the control signal, the power supply of the IEPE sensor is not applied to the second device. Therefore, even when the first switch has an open failure, the second device is protected.

[0009] The condition monitoring device may further include a first rectifying element connected between the branch point and the connection terminal. The first rectifying element may be configured to suppress the current flowing from the connection terminal toward the branch point.

[0010] When the potential of the connection terminal is higher than the potential of the ground node and the second signal is being generated (the second switch is on), current may flow from the connection terminal to the ground node through the constant current element and the second switch. As a result, the potential of the connection terminal may decrease, which may affect the output value of the second device or damage the second device. Such a situation is not preferable. With the above configuration, even when the potential of the connection terminal is higher than the potential of the ground node, due to the rectifying action of the first rectifying element, the situation where current flows from the connection terminal to the ground node is avoided. Thereby, it is possible to prevent the output value of the second device from being affected or the second device from being damaged.

[0011] The first rectifying element may be connected between the branch point and the constant current element. The IEPE sensor is driven by a constant current supplied from the constant current element and outputs a low-impedance voltage signal on the same line as the power supply node. In order to operate the IEPE sensor accurately, it is necessary to supply a stable constant current to the IEPE sensor regardless of the output of the IEPE sensor. If the first rectifying element is connected between the constant current element and the connection terminal (provided on the downstream side of the constant current element), the constant current supplied to the IEPE sensor may change due to element characteristics such as the parasitic capacitance or frequency response of the first rectifying element. Such a situation is not preferable. With the above configuration, since the first rectifying element is provided on the upstream side of the constant current element, the influence of the element characteristics of the first rectifying element can be reduced by the constant current element. As a result, the IEPE sensor can be operated accurately.

[0012] The condition monitoring device may further include a second rectifying element connected between the branch point and the ground node. The second rectifying element may be configured to suppress the current flowing from the ground node towards the branch point.

[0013] When the potential of the connection terminal is lower than the potential of the ground node and the second signal is being generated (the second switch is turned on), current flows from the ground node through the second switch and the constant current element to the connection terminal. As a result, the potential of the connection terminal rises, which may affect the output value of the second device or damage the second device. Such a situation is not preferable. With the above configuration, even when the potential of the connection terminal is lower than the potential of the ground node, due to the rectifying action of the second rectifying element, the situation where current flows from the ground node to the connection terminal is avoided. Thereby, it is possible to prevent the output value of the second device from being affected or the second device from being damaged.

[0014] The second rectifying element may be connected between the branch point and the second switch. If the second rectifying element is connected between the second switch and the ground node, the second switch is not directly connected to the ground node, and there is a possibility that the second switch may not operate stably. Such a situation is not preferable. With the above configuration, the second switch is directly connected to the ground node. Therefore, stable operation of the second switch can be enabled.

[0015] Each of the first switch and the second switch may be formed by a semiconductor switching element.

[0016] Generally, semiconductor switching elements have advantages over mechanical switches in terms of size and cost. With the above configuration, while enjoying such advantages, it is possible to appropriately deal with a short - circuit fault of the first switch (semiconductor switching element).

[0017] The current - limiting element may include a fuse configured to cut off the short - circuit current path.

[0018] With the above configuration, when a short-circuit current (overcurrent) flows from the power supply node to the ground node while the second signal is being generated, the fuse blows. As a result, the power supply node is electrically disconnected from the second device. Consequently, a situation where the power supply of the IEPE sensor is applied to the second device is avoided. Therefore, even when the second device is connected to the connection terminal and a short-circuit failure of the first switch occurs, the second device can be effectively protected.

[0019] The second device may include an analog signal output device that outputs an analog signal to the connection terminal.

[0020] The analog signal output circuit may be designed to operate at a low voltage. In this case, the operating voltage of this circuit is lower than the above-mentioned power supply voltage. From the perspective of protecting this circuit, it is not preferable for a relatively high voltage such as the power supply for the IEPE sensor to be applied to this circuit. With the above configuration, even when the analog signal output circuit is connected to the connection terminal and a short-circuit failure of the first switch occurs, the analog signal output circuit as the second device can be protected.

Advantages of the Invention

[0021] According to the present disclosure, in a condition monitoring device including a power supply node constituting a power supply for an IEPE sensor and a switch that switches between electrical connection / disconnection between an external device and the power supply node, an external device different from the IEPE sensor can be protected even in the event of a switch failure.

Brief Description of the Drawings

[0022]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Embodiments for Carrying Out the Invention

[0023] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. The same or corresponding parts in the drawings are denoted by the same reference numerals and their description will not be repeated. Each of the embodiments and its modification examples may be combined with each other as appropriate.

[0024] In the present disclosure, when it is described that a certain element (first element) is "connected to" another element (second element), the first element may be connected to the second element with a third element intervening between the first element and the second element, or the first element may be directly connected to the second element without the third element.

[0025] In the present disclosure, when an element (first element) is described as being "connected" between another element (second element) and still another element (third element), a fourth element may be interposed between the first element and the second element, or between the first element and the third element, or the first element may be directly connected to the second element or the third element without the fourth element.

[0026] FIG. 1 is a diagram schematically showing the configuration of a wind power generation device including a state monitoring device according to an embodiment of the present disclosure. Referring to FIG. 1, the wind power generation device 10 includes a main shaft 20, blades 30, a speed increaser 40, and a generator 50. The wind power generation device 10 further includes a main shaft bearing (hereinafter simply referred to as "bearing") 60, vibration detection equipment 70, and a state monitoring device 80. The speed increaser 40, the generator 50, the bearing 60, the vibration detection equipment 70, and the state monitoring device 80 are stored in the nacelle 90. The nacelle 90 is supported by a tower 100.

[0027] The main shaft 20 enters the nacelle 90 and is connected to the input shaft of the speed increaser 40, and is rotatably supported by the bearing 60. The main shaft 20 transmits the rotational torque generated by the blades 30 receiving wind power to the input shaft of the speed increaser 40. The blades 30 are provided at the tip of the main shaft 20, convert wind power into rotational torque, and transmit it to the main shaft 20.

[0028] The speed increaser 40 is provided between the main shaft 20 and the generator 50, increases the rotational speed of the main shaft 20, and outputs it to the generator 50. As an example, the speed increaser 40 is composed of a planetary gear and a gear speed increasing mechanism including an intermediate shaft, a high-speed shaft, etc. The generator 50 is connected to the output shaft of the speed increaser 40 and generates electricity by the rotational torque received from the speed increaser 40. The generator 50 is composed of an induction generator.

[0029] The bearing 60 is fixedly installed in the nacelle 90 and rotatably supports the main shaft 20. The bearing 60 is composed of a rolling bearing, and specifically, is composed of an automatic aligning roller bearing, a tapered roller bearing, a cylindrical roller bearing, a ball bearing, or the like. These bearings may be single-row or multi-row.

[0030] The vibration detection device 70 is installed on the bearing 60 and detects the vibration of the bearing 60. This detection result is used to determine the vibration state of the wind power generation device 10. The vibration detection device 70 includes an IEPE sensor. The IEPE sensor has a built-in amplifier and is different from a PE sensor (Piezo Electric) in that it is suitable for measuring dynamic acceleration and the like. The IEPE sensor generates the output of the amplifier as a signal indicating the measured value. In order for the IEPE sensor to generate the signal, it needs to receive the operating power of the amplifier from the outside. In this example, the IEPE sensor is an IEPE acceleration sensor. This sensor measures the acceleration to detect the vibration of the bearing 60 and outputs the measured value to the condition monitoring device 80.

[0031] Figure 2 is a diagram for explaining in detail the configuration of the condition monitoring device 80 and the IEPE acceleration sensor. Referring to Figure 2, the condition monitoring device 80 monitors the state of the object based on the measured value of the IEPE acceleration sensor. The object is, in this example, the wind power generation device 10. The condition monitoring device 80 includes a connection terminal 102, a power supply circuit 105, power lines 114, 116, an AFE (Analog Front End) 126, a CPU (Central Processing Unit) 128, and a memory 129.

[0032] An external device is connected to the connection terminal 102. The external device is a device provided outside the condition monitoring device 80. In this example, the external device is the vibration detection device 70 (IEPE acceleration sensor 71) as the first device. The detailed configuration of the vibration detection device 70 will be described later.

[0033] The power supply circuit 105 is a circuit that functions as the power supply for the IEPE acceleration sensor 71 and includes a power supply node 110 and a constant current element 112. The power supply node 110 constitutes the power supply for the IEPE acceleration sensor 71 and is configured to generate the power supply voltage for the IEPE acceleration sensor 71. In this example, the power supply voltage is 24V.

[0034] The constant current element 112 is connected to the connection terminal 102 through the power line 114. The constant current element 112 is connected to the AFE 126 through the power line 116. The constant current element 112 is configured to supply a constant current to the connection terminal 102 by receiving the current supplied from the power supply node 110 and changing its resistance value and the potential difference across both ends. Thereby, the power supply circuit 105 can function as a constant current source. The constant current element 112 is, for example, a constant current diode. The connection terminal 102, the power supply circuit 105, and the power lines 114 and 116 are also referred to as "unit 120". A more detailed configuration of the power supply circuit 105 will be described later.

[0035] The AFE 126 receives a signal indicating its measurement value from the IEPE acceleration sensor 71 through the power lines 114 and 116. The AFE 126 converts this signal into a digital signal by a predetermined conversion process and transmits the digital signal to the CPU 128.

[0036] The CPU 128 executes various arithmetic processes. The memory 129 includes a ROM 129a and a RAM 129b. The ROM 129a stores programs executed by the CPU 128. The RAM 129b functions as a working memory.

[0037] The vibration detection device 70 includes an IEPE acceleration sensor 71, a cable 76, and a connector 77. The IEPE acceleration sensor 71 is connected to the connection terminal 102 through the cable 76 and the connector 77. The IEPE acceleration sensor 71 includes a piezoelectric element 72 and a FET (Field Effect Transistor) 74. The piezoelectric element 72 outputs electric charge depending on the vibration acceleration of the measurement object. The FET 74 operates as an amplifier that amplifies the output of the piezoelectric element 72. The FET 74 operates by receiving a constant current (operating power) supplied from the constant current element 112 through the power line 114, the connection terminal 102, the connector 77, and the cable 76.

[0038] Specifically, a constant current is supplied from the power supply circuit 105 (constant current source) to the FET 74 through the power line 114, and the FET 74 adjusts the voltage level of the power line 114 to a predetermined bias voltage. The gate voltage of the FET 74 changes depending on the output of the piezoelectric element 72. The change in the gate voltage of the FET 74 causes a voltage change from the bias voltage of the power lines 114 and 116. The AFE 126 generates a digital signal based on this voltage change and transmits it to the CPU 128.

[0039] In the above, although the IEPE acceleration sensor 71 (first device) is connected to the connection terminal 102, a second device different from the IEPE acceleration sensor 71 may be connected. In this example, the second device is an analog signal output device. Thus, the connection terminal 102 can be connected to either the IEPE acceleration sensor 71 (first device) or the analog signal output device (second device) (in other words, it serves as both a connection terminal for the first device and a connection terminal for the second device). Therefore, the condition monitoring device 80 does not separately require a connection terminal for connecting to the IEPE acceleration sensor 71 and a connection terminal for connecting to the analog signal output device. If these connection terminals were separately required, the number of required connection terminals would increase. As a result, the cost and size of the condition monitoring device 80 could increase. On the other hand, in the embodiment, as described above, the connection terminal 102 can be connected to the IEPE acceleration sensor 71 or, instead of the IEPE acceleration sensor 71, to the analog signal output device. As a result, an increase in the number of required connection terminals can be avoided. Therefore, the cost and size of the condition monitoring device 80 can be reduced.

[0040] FIG. 3 is a diagram showing a state where an analog signal output device is connected to the connection terminal 102. Referring to FIG. 3, the analog signal output device 91 includes an analog signal output circuit 92, a cable 96, and a connector 97. The analog signal output circuit 92 generates an analog signal and outputs the signal to the connection terminal 102 through the cable 96 and the connector 97. The analog signal output circuit 92 is designed to operate at a low voltage (in this example, 0V to 5V). That is, the operating voltage of the analog signal output circuit 92 is lower than the voltage (24V) of the power supply node 110.

[0041] Before explaining the detailed configuration of the power supply circuit 105 of the embodiment below, the configuration of the power supply circuit of the IEPE acceleration sensor 71 in the comparative example will be explained.

[0042] FIG. 4 is a diagram for explaining the configuration of the power supply circuit in the comparative example. FIG. 5 is a diagram for explaining the problems that can be caused in the comparative example.

[0043] Referring to FIG. 4, the condition monitoring device 80C is different from the condition monitoring device 80 of the embodiment in that it includes a power supply circuit 105C, but is basically the same as the condition monitoring device 80 in other respects. The connection terminal 102 is connected to an external device 95.

[0044] The power supply circuit 105C is different from the power supply circuit 105 of the embodiment in that it is used as the power supply circuit of the IEPE acceleration sensor 71 in the comparative example. The power supply circuit 105C includes a power supply line PSL, a switch U, a signal generation circuit 115, a signal line SL1, and a power line PL in addition to the power supply node 110 and the constant current element 112.

[0045] The power supply line PSL is connected to the power supply node 110. The switch U is connected between the power supply line PSL and the power line PL.

[0046] The signal generation circuit 115 generates a control signal SG for controlling the on / off of the switch U. The control signal SG is transmitted to the switch U through the signal line SL1. The control signal SG is either of the signals SG1 and SG2. The signal SG1 is a high-level signal (logical high) and is generated to turn on the switch U. The signal SG2 is a low-level signal (logical low) and is generated to turn off the switch U. In other words, the switch U is turned on in response to the high-level signal and turned off in response to the low-level signal. The signal generation circuit 115 (on / off of the switch U) is controlled by the CPU 128. The power line PL is connected to the constant current element 112.

[0047] When the external device 95 is the IEPE acceleration sensor 71, power supply from the power supply node 110 to the IEPE acceleration sensor 71 is required. Therefore, when the IEPE acceleration sensor 71 is connected, the signal generation circuit 115 generates the signal SG1 as the control signal SG. As a result, the switch U is turned on, and operating power (constant current) is supplied from the power supply node 110 to the IEPE acceleration sensor 71 through the switch U, the constant current element 112, and the connection terminal 102. As a result, a signal indicating the measured value is transmitted from the IEPE acceleration sensor 71 to the CPU 128 through the power lines 114 and 116 and the AFE 126. This measured value is used for state monitoring of the wind power generation device 10.

[0048] When the external device 95 is the analog signal output device 91, it is not preferable from the viewpoint of protection that a relatively high voltage such as the voltage (24V) of the power supply node 110 is applied to the analog signal output circuit 92 (operating voltage: 0 to 5V). Therefore, when the analog signal output device 91 is connected, the signal generation circuit 115 generates the signal SG2 as the control signal SG. As a result, the switch U is turned off, and the power supply node 110 is electrically disconnected from the analog signal output circuit 92. As a result, the situation where the voltage of the power supply node 110 is applied to the analog signal output circuit 92 is avoided, and the analog signal from this circuit is transmitted to the CPU 128 through the power lines 114 and 116 and the AFE 126. This analog signal is used for state monitoring of the wind power generation device 10.

[0049] Referring to FIG. 5, when the switch U has a short circuit failure in the power supply circuit 105C, the switch U becomes conductive even though the signal SG2 is generated. As a result, the power supply node 110 is electrically connected to the analog signal output device 91. As a result, the voltage of the power supply node 110 is unintentionally applied to the analog signal output device 91. Thus, when the analog signal output device 91 is connected to the state monitoring device 80C including the power supply circuit 105C of the comparative example, there is a possibility that the analog signal output device 91 cannot be protected.

[0050] The power supply circuit 105 of the state monitoring device 80 according to the embodiment has a configuration for dealing with such a problem. This will be described below.

[0051] FIG. 6 is a diagram for explaining the detailed configuration of the power supply circuit 105 of the embodiment. Referring to FIG. 6, the power supply circuit 105 is different from the power supply circuit 105C of the comparative example in that it includes switches U1 and U2 instead of the switch U, and includes power lines PL1 and PL2 instead of the power line PL. The power supply circuit 105 is also different from the power supply circuit 105C in that it further includes a branch line BL, a signal line SL2, a NOT gate 117, a ground line EL, a ground node 118, and a fuse 119.

[0052] Switch U1 is connected between power supply node 110 (power supply line PSL) and power line PL1. Switch U2 is connected between power line PL2 and ground node 118 (ground line EL). Each of switches U1 and U2, similar to switch U, is turned on when receiving a high-level signal as input and turned off when receiving a low-level signal as input. Each of switches U1 and U2 is provided to switch the electrical connection / disconnection between external device 95 and power supply node 110.

[0053] Each of switches U1 and U2 is a semiconductor switching element. The semiconductor switching element may be, for example, any of a bipolar transistor, an insulated gate bipolar transistor (IGBT), a metal-oxide-semiconductor field-effect transistor (MOSFET), or a junction field effect transistor (JFET).

[0054] Power line PL2 includes power lines PL2a and PL2b. Power line PL2a is the portion of power line PL2 above the branch point BP in the figure (power supply side). Power line PL2b is the portion of power line PL2 below the branch point BP in the figure (ground side).

[0055] Branch line BL branches from branch point BP of power line PL2. Constant current element 112 is connected between branch line BL and connection terminal 102 (power line 114). Signal line SL2 branches from signal line SL1.

[0056] The NOT gate 117 is connected between the signal line SL2 and the switch U2. When receiving the control signal SG as an input, the NOT gate 117 generates the inversion of the input as an output. For example, when the NOT gate 117 receives a high-level signal (signal SG1) as an input, it generates a low-level signal as an output. As a result, the switch U2 is turned off. When the NOT gate 117 receives a low-level signal (signal SG2) as an input, it generates a high-level signal as an output. As a result, the switch U2 is turned on.

[0057] The control signal SG transmitted through the signal line SL2 is inverted via the NOT gate 117, and the inverted signal is input to the switch U2. Note that the control signal SG transmitted through the signal line SL1 is input to the switch U1 without being inverted.

[0058] Due to the inversion operation of the NOT gate 117, the signal SG1 is generated as a signal for turning on the switch U1 and turning off the switch U2. Similarly, the signal SG2 is generated as a signal for turning off the switch U1 and turning on the switch U2. Thus, in the embodiment, the control signal SG corresponds to a signal for complementarily controlling the switch U1 and the switch U2.

[0059] The ground line EL is connected to the ground node 118. The ground node 118 is connected to the earth (ground). In this example, it is assumed that the potential of the ground node 118 (ground potential) is lower than the potential of the connection terminal 102.

[0060] The fuse 119 is connected between the power line PL1 and the power line PL2. The fuse 119 is configured to cut off the circuit when a current (overcurrent) greater than a predetermined threshold value flows. Instead of the fuse 119, an overcurrent protection IC or a polyswitch may be used (details will be described later), but the fuse 119 is superior to them in terms of cut-off speed and cost. In this example, the fuse 119 is configured to cut off the circuit when a short-circuit current flows from the power supply node 110 toward the ground node 118. Specifically, the fusible body of the fuse 119 is configured to melt when this short-circuit current flows. The above short-circuit current flows, for example, when the switch U1 has a short-circuit failure during the generation of the signal SG2 for turning off the switch U1 and turning on the switch U2. This point will be described in detail later.

[0061] FIG. 7 is a diagram for explaining the state when the signal SG1 is being generated in the embodiment. In this example, each of the switches U1 and U2 is not faulty and operates normally according to the control signal SG.

[0062] Referring to FIG. 7, since the IEPE acceleration sensor 71 is connected to the connection terminal 102, the signal generation circuit 115 generates the signal SG1. As a result, the switch U1 is turned on and the switch U2 is turned off. As a result, operating power (constant current) is supplied from the power supply node 110 to the IEPE acceleration sensor 71 through the constant current element 112 and the connection terminal 102. In this case, it is assumed that the current flowing through the fuse 119 is not large enough to melt the fuse 119 (not an overcurrent).

[0063] FIG. 8 is a diagram for explaining the state when the signal SG2 is being generated in the embodiment. Also in this example, each of the switches U1 and U2 is not faulty and operates normally according to the control signal SG.

[0064] Referring to FIG. 8, since the analog signal output device 91 is connected to the connection terminal 102, the signal generation circuit 115 generates the signal SG2. As a result, the switch U1 is turned off and the switch U2 is turned on. Consequently, the power supply node 110 is disconnected from the analog signal output device 91. In this case, a situation where the voltage (24V) of the power supply node 110 is applied to the analog signal output device 91 is avoided. Therefore, the analog signal output device 91 is protected.

[0065] FIGS. 9 and 10 are diagrams for explaining the state when the switch U1 has a short-circuit failure during the generation of the signal SG2 in the embodiment. FIG. 11 is a diagram for explaining the state when the switch U1 has an open-circuit failure during the generation of the signal SG2 in the embodiment.

[0066] Referring to FIG. 9, when the switch U1 has a short-circuit failure during the generation of the signal SG2, a short-circuit current flows from the power supply node 110 toward the ground node 118 due to the potential difference between the potential of the power supply node 110 and the ground potential. Although an overcurrent is required to operate (blow) the fuse 119, since this short-circuit current is large, the fuse 119 operates thereby to cut off the circuit of the short-circuit current (see FIG. 10). Since the fuse 119 is provided on the power supply node 110 side with respect to the branch point BP, when the fuse operates as described above, the power supply node 110 is electrically disconnected from the analog signal output device 91. Therefore, a situation where the voltage of the power supply node 110 is applied to the analog signal output device 91 is avoided. Therefore, even when the switch U1 has a short-circuit failure, the analog signal output device 91 can be protected.

[0067] In addition, when an open-circuit failure of the switch U1 is caused even though the signal SG1 (switch U1: on, switch U2: off) is being generated, both of the switches U1 and U2 are in an open state, and the power supply node 110 is electrically disconnected from the analog signal output device 91 (see FIG. 11). As a result, the voltage of the power supply node 110 is not applied to the analog signal output device 91. Therefore, even when the switch U1 has an open-circuit failure, the analog signal output device 91 is protected.

[0068] As described above, according to the state monitoring device 80 of the embodiment, when the switch U1 experiences a short-circuit failure while the signal SG2G is being generated, a short-circuit current flows from the power supply node 110 to the ground node 118. As a result, the fuse 119 operates (blows) to cut off the circuit of the short-circuit current. Consequently, the voltage of the power supply node 110 is electrically disconnected from the analog signal output device 91, and a situation where the voltage of the power supply node 110 is applied to the analog signal output device 91 can be avoided. Therefore, unlike the state monitoring device 80C of the comparative example (FIGS. 4 and 5), the analog signal output device 91 can be protected even when a short-circuit failure occurs in the switch U1. Furthermore, the analog signal output device 91 is protected even when an open-circuit failure occurs in the switch U1. Therefore, the analog signal output device 91 can be protected both when an open-circuit failure or a short-circuit failure occurs in the switch U1.

[0069] Each of the switches U1 and U2 is a semiconductor switching element. Generally, semiconductor switching elements have advantages over mechanical switches in terms of size and cost. According to the embodiment, while enjoying such advantages, it is possible to appropriately handle open-circuit failures and short-circuit failures of semiconductor switching elements.

[0070] [Modifications of the Embodiment] Referring to FIG. 8 again, when the potential of the connection terminal 102 (the potential of the output signal of an external device 95 such as the analog signal output device 91) is higher than the ground potential and the signal SG2 is being generated, there is a possibility that current may flow from the connection terminal 102 through the constant current element 112 and the switch U2 to the ground node 118. As a result, the potential of the connection terminal 102 may decrease, and there is a possibility that the output value of the external device 95 (for example, the analog signal output device 91) may be affected or the external device 95 may be damaged (the first problem).

[0071] When the potential of the connection terminal 102 is lower than the ground potential and the signal SG2 is generated, current may flow from the ground node 118 to the connection terminal 102 through the switch U2 and the constant current element 112. As a result, the potential of the connection terminal 102 may rise, which may affect the output value of the external device 95 or damage the external device 95 (second problem).

[0072] The state monitoring device according to this modification has a configuration for addressing the first and second problems. This will be described in detail below.

[0073] FIG. 12 is a diagram for explaining the configuration of the state monitoring device according to this modification. Referring to FIG. 12, the state monitoring device 80A differs from the state monitoring device 80 of the embodiment in that it further includes diodes D1 and D2. In other respects, the state monitoring device 80A is basically the same as the state monitoring device 80 unless otherwise specified.

[0074] The diode D1 is connected between the branch point BP and the connection terminal 102. The forward direction of the diode D1 is the direction from the branch point BP to the connection terminal 102, and it is configured to suppress the current flowing from the connection terminal 102 to the branch point BP.

[0075] With such a configuration, even when the potential of the connection terminal 102 (output signal of the external device 95) is higher than the ground potential, due to the rectifying action of the diode D1, the situation where current flows from the connection terminal 102 to the ground node 118 is avoided. Thereby, it is possible to prevent the output value of the external device 95 from being affected or the external device 95 from being damaged. Therefore, the first problem can be solved.

[0076] The diode D1 may be connected between the constant current element 112 and the connection terminal 102 in the power supply circuit 105 (provided on the downstream side of the constant current element 112), but as in this example, it is preferably connected between the branch point BP and the constant current element 112 (provided on the branch line BL on the upstream side of the constant current element 112).

[0077] If the diode D1 is provided on the downstream side of the constant current element 112, the constant current supplied to the IEPE acceleration sensor 71 may change due to element characteristics such as the parasitic capacitance or frequency response of the diode D1. When the external device 95 is the IEPE acceleration sensor 71, the IEPE acceleration sensor 71 operates by receiving the constant current supplied from the constant current element 112 through the connection terminal 102. Therefore, when the constant current changes as described above, the operating state of the IEPE acceleration sensor 71 may be affected. As a result, the accuracy of the measured value of the IEPE acceleration sensor 71 may decrease. Such a situation is not preferable.

[0078] In the embodiment, the diode D1 is provided on the upstream side of the constant current element 112. Thereby, the situation in which the IEPE acceleration sensor 71 is affected by the element characteristics of the diode D1 is avoided by the constant current element 112. As a result, when the IEPE acceleration sensor 71 is connected to the connection terminal 102, a constant current can be stably supplied to the IEPE acceleration sensor 71 through the connection terminal 102. Therefore, the IEPE acceleration sensor 71 can be appropriately operated, and a decrease in the accuracy of the measured value of this sensor can be avoided.

[0079] The diode D2 is connected between the branch point BP and the ground node 118. The forward direction of the diode D2 is the direction from the branch point BP toward the ground node 118, and it is configured to suppress the current flowing from the ground node 118 toward the branch point BP.

[0080] By adopting such a configuration, even when the potential of the connection terminal 102 is lower than the ground potential, the situation in which current flows from the ground node 118 to the connection terminal 102 is avoided due to the rectifying action of the diode D2. Thereby, it is possible to prevent the output value of the external device 95 (for example, the analog signal output device 91) from being affected or the external device 95 from being damaged. Therefore, the second problem can be solved.

[0081] Diode D2 may be connected between switch U2 and the ground node 118 in the power supply circuit 105 (provided on the ground wire EL), but as in this example, it is preferably connected between the branch point BP and switch U2 (provided on the power line PL2b).

[0082] If diode D2 is connected between switch U2 and the ground node 118, switch U2 is not directly connected to the ground node 118. In this case, switch U2 may not operate stably. On the other hand, according to the embodiment, switch U2 is directly connected to the ground node 118. Therefore, stable operation of switch U2 can be enabled.

[0083] The state monitoring device 80A may include only one of diodes D1 and D2. For example, if it is assumed that the potential of the connection terminal 102 (output signal of the external device 95) is always higher than the ground battery, it is not assumed that current flows from the ground node 118 to the connection terminal 102. In this case, since diode D2 is not necessarily required, the state monitoring device 80A may include only diode D1 among diodes D1 and D2. On the other hand, if it is assumed that the potential of the connection terminal 102 is always lower than the ground battery, it is not assumed that current flows from the connection terminal 102 to the ground node 118. In this case, since diode D1 is not necessarily required, the state monitoring device 80A may include only diode D2 among diodes D1 and D2.

[0084] Each of diodes D1 and D2 is a Schottky barrier diode for power supply. Since this diode can apply a large voltage and has a large allowable current, it is suitable for the power supply circuit 105C. Each of diodes D1 and D2 may be a silicon diode or an ideal diode. It is preferable that each of diodes D1 and D2 has a small reverse current so that the reverse current does not affect the external device 95.

[0085] As described above, according to this modification example, it is possible to avoid a situation where current unintentionally flows from the ground node 118 to the external device 95 or from the external device 95 to the ground node 118. Therefore, it is possible to prevent the operating state of the external device 95 from unintentionally changing or to more effectively protect the external device 95.

[0086] [Other Modification Examples] The IEPE sensor of the vibration detection device 70 is not limited to an IEPE acceleration sensor, and may be another type of IEPE sensor that measures physical quantities such as the load or pressure of an object.

[0087] The device (second device) different from the IEPE sensor (first device) was assumed to be an analog signal output device 91, but it may be an analog output sensor such as a current sensor, a digital output sensor such as a proximity sensor, a digital signal output device such as the I / O of a PLC (Programmable Logic Controller), or a device equipped with an A / D converter or a comparator and a digital bus output such as I / 2C.

[0088] Although the condition monitoring device 80 (80A) was assumed to be provided in the wind power generation device 10, it may be provided in an industrial machine having a rotating system or a machine tool. In this case, the condition monitoring device 80 (80A) monitors the condition (including the vibration condition) of the industrial machine or the machine tool.

[0089] The state monitoring device 80 (80A) may include a plurality of units 120. In this case, since each unit 120 can be connected to an external device 95, the state monitoring device 80 (80A) is configured to be connectable to a plurality of external devices 95. The AFE 126 receives, as inputs, a plurality of analog signals from a plurality of external devices 95, respectively, through the plurality of units 120. The CPU 128 controls (generates a control signal SG) the signal generation circuit 115 for each power supply circuit 105 of the unit 120. In other words, for each external device 95, the CPU 128 determines whether to apply a voltage to the power supply node 110 of the unit 120 to which the external device 95 is connected, and based on the result of the determination, controls the on / off of the switches U1 and U2 of the unit 120. From a practical perspective, it is common for the state monitoring device 80 (80A) to receive signal inputs from a plurality of external devices 95. If the state monitoring device 80 (80A) requires a dedicated connection terminal for the first device to acquire the output signal of the first device and a dedicated connection terminal for the second device to acquire the output signal of the second device, the types of external devices connectable to each connection terminal are limited. As a result, the usability of the state monitoring device 80 decreases. To prevent a decrease in usability, mounting a large number of dedicated connection terminals for the first device and a large number of dedicated connection terminals for the second device on the state monitoring device 80 would lead to an increase in the cost and size of the state monitoring device 80. On the other hand, in this modification, the connection terminal 102 of each unit 120 serves as both a connection terminal for the first device and a connection terminal for the second device. Therefore, it is possible to improve usability and avoid an increase in size and cost as described above.

[0090] The state monitoring device 80 (80A) may further include a failure lamp. This lamp is configured to light up when a short-circuit current flows from the power supply node 110 to the ground node 118 (when the fuse 119 blows). By adopting such a configuration, it is possible to notify the user of the state monitoring device 80 (80A) of a short-circuit failure of the switch U1.

[0091] Each of switches U1 and U2 may be an electronic switch different from a semiconductor element switching element such as an analog switch or a relay. Alternatively, each of switches U1 and U2 may be a mechanical switch such as a slide switch, a DIP (Dual In-line Package) switch, or a toggle switch. Each of switches U1 and U2 needs to operate complementarily with each other (otherwise, even if there is no short-circuit failure, a short-circuit current may flow and fuse 119 may blow). Therefore, when these switches are electronic switches, for example, a NOT circuit that inverts a control signal for the other switch is connected to an input of one of these switches. Alternatively, one of these switches may be an a-contact relay (normally off) and the other may be a b-contact relay (normally on). When switches U1 and U2 are mechanical switches, these switches are integrated so as to operate complementarily.

[0092] Constant current element 112 may include a constant current diode and a temperature compensation resistor connected in parallel thereto. Constant current element 112 may be replaced by a constant current circuit including a current source IC (Integration Circuit) or an operational amplifier.

[0093] Fuse 119 may be replaced by an overcurrent protection IC. The overcurrent protection IC is an element that stops its output when an overcurrent flows through it. Alternatively, fuse 119 may be replaced by a polyswitch. The polyswitch is an element that reduces the output current when an overcurrent flows through it. In this example, the polyswitch is configured such that the output current becomes small enough to be practically negligible. With such a configuration, even when signal SG2 is generated and switch U1 has a short-circuit failure, the current flowing through analog signal output device 91 from state monitoring device 80 (80A) through connection terminal 102 is small enough to be practically negligible. Thereby, the influence on analog signal output device 91 received from this current can be reduced to a negligible level. As a result, analog signal output device 91 can be protected.

[0094] Thus, the element connected between the power lines PL1 and PL2 of the state monitoring device 80 (80A) is not limited to the fuse 119, and any “current limiting element” that limits the short-circuit current flowing from the power supply node 110 to the ground node 118 may be used. “Limiting the short-circuit current” includes interrupting the current path when a short-circuit current flows and supplying, as an output, a current reduced to a practically negligible level in response to the short-circuit current to the power line PL2a. In other words, the “current limiting element” of the present disclosure is a concept that includes any of the fuse 119, the overcurrent protection IC, or the polyswitch.

[0095] The embodiments disclosed this time should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is shown not by the above description but by the claims, and it is intended that all modifications within the meaning and scope equivalent to the claims be included.

Explanation of Reference Numerals

[0096] 10 Wind power generation device, 71 IEPE acceleration sensor, 80, 80A, 80C State monitoring device, 91 Analog signal output device, 95 External device, 102 Connection terminal, 105, 105C Power supply circuit, 110 Power supply node, 112 Constant current element, 115 Signal generation circuit, 118 Ground node, 119 Fuse (current limiting element), D1, D2 Diode.

Claims

1. A state monitoring device configured to monitor the state of an object, comprising: an IEPE sensor as a first device, and a connection terminal connectable to one of a second device different from the IEPE sensor; a power supply node configured to constitute a power supply for the IEPE sensor; a first switch connected between the power supply node and a first power line; a second switch connected between a second power line and a ground node; a constant current element connected between a branch line branched from the second power line at a branch point of the second power line and the connection terminal; a signal generation circuit that generates a control signal for complementarily controlling the first switch and the second switch; a current limiting element connected between the first power line and the second power line, wherein the control signal includes a first signal for turning on the first switch and turning off the second switch when the IEPE sensor is connected to the connection terminal; and a second signal for turning off the first switch and turning on the second switch when the second device is connected to the connection terminal, and the current limiting element is configured to limit a short-circuit current flowing from the power supply node toward the ground node. The state monitoring device.

2. further comprising a first rectifying element connected between the branch point and the connection terminal, wherein the first rectifying element is configured to suppress a current flowing from the connection terminal toward the branch point. The state monitoring device according to claim 1.

3. The state monitoring device according to claim 2, wherein the first rectifying element is connected between the branch point and the constant current element.

4. further comprising a second rectifying element connected between the branch point and the ground node, wherein the second rectifying element is configured to suppress a current flowing from the ground node toward the branch point. The state monitoring device according to claim 1.

5. The state monitoring device according to claim 4, wherein the second rectifying element is connected between the branch point and the second switch.

6. Each of the first switch and the second switch is formed of a semiconductor switching element. The state monitoring device according to claim 1.

7. The state monitoring device according to any one of claims 1 to 6, wherein the current limiting element includes a fuse configured to cut off a circuit of the short-circuit current.

8. The state monitoring device according to claim 1, wherein the second device includes an analog signal output device that outputs an analog signal to the connection terminal.

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