Explosion-proof system

Abstract

Provided is an explosion-proof system 1 for easily establishing an explosion-proof structure. The explosion-proof system 1 includes a position storage device 12 for a motor shaft present in an explosive atmosphere, wherein the position storage device 12 holds position data without an external supply of power.

Description

Explosion-proof system

[0001] The present disclosure relates to explosion protection systems.

[0002] A technique has been proposed for safely using an encoder that detects the rotation speed of a motor in an explosion-proof environment (Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 2006-329695

[0004] The problem to be solved by the present disclosure is to facilitate the establishment of an explosion-proof structure. The present disclosure has an object to provide an explosion-proof system that allows for easy establishment of an explosion-proof structure.

[0005] The explosion-proof system of the present disclosure includes a position storage device for a motor shaft that exists in an explosive atmosphere, and the position storage device retains position data without receiving an external power supply.

[0006] According to the explosion-proof system of the present disclosure, an explosion-proof system that can easily establish an explosion-proof structure can be provided.

[0007] Fig. 1 is a diagram illustrating an explosion-proof system according to an embodiment of the present disclosure; Fig. 2 is a diagram illustrating a conventional explosion-proof system; Fig. 3 is a diagram for explaining the difference between the explosion-proof system according to the embodiment of the present disclosure and a conventional explosion-proof system; Fig. 4 is a diagram illustrating a robot in which the position storage device of the present disclosure is used.

[0008] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] The present disclosure will be described with reference to the accompanying drawings. The present disclosure is not limited to the following embodiments. The present disclosure can be appropriately modified and implemented without departing from the spirit and scope of the present disclosure.

[0009] (Explosion-proof System) The explosion-proof system 1 of the present disclosure will be described using a painting robot as an example. Note that the painting robot is merely an example. The explosion-proof system 1 of the present disclosure can be applied to various industrial machines, etc.

[0010] FIG. 1 is a diagram illustrating an overview of an explosion-proof system 1 according to an embodiment of the present disclosure. The explosion-proof system 1 includes a first printed wiring board (PCB1) 10 and a second printed wiring board (PCB2) 20. The first printed wiring board 10 corresponds to a robot (painting unit) in a painting robot. In particular, the first printed wiring board 10 corresponds to a position detection circuit (pulse coder). The second printed wiring board 20 includes an electric circuit and corresponds to a control device in the painting robot. In particular, the second printed wiring board 20 includes an amplifier circuit and the like.

[0011] (First Printed Wiring Board (PCB1)) The first printed wiring board 10 includes a communication circuit (CC) 11 and a position memory device (PMD) 12. The communication circuit (CC) 11 is a circuit that communicates with the second printed wiring board 20. The communication circuit 11 includes a power supply unit (PS) 13 and a communication unit (CL) 14.

[0012] (Power Supply Unit (PS)) The power supply unit 13 is a part that receives power from a power supply circuit (PC) 21 included in the second printed wiring board 20. Power is supplied from the power supply circuit 21 to the power supply unit 13 via a power line L1.

[0013] (Communication Unit (CP)) The communication unit 14 is a part that communicates with a communication circuit (CC) 22 included in the second printed wiring board 20. Communication between the communication unit 14 and the communication circuit 22 is performed via a first communication line L2 and a second communication line L3.

[0014] Before describing the position memory device (PMD) 12, the second printed wiring board 20 will be described.

[0015] (Second Printed Wiring Board (PCB2)) The second printed wiring board 20 includes a power supply circuit (PC) 21 and a communication circuit (CC) 22. The power supply circuit 21 is a circuit that supplies power to the power supply unit 13 of the first printed wiring board 10. As described above, the power supply circuit 21 is electrically connected to the power supply unit 13 via the power line L1.

[0016] The communication circuit 22 is a circuit that communicates position data of the motor shaft and the like with the communication unit 14 of the first printed wiring board 10. As described above, the communication circuit 22 is connected to the communication unit 14 of the first printed wiring board 10 via the first communication line L2 and the second communication line L3.

[0017] (Connection between the first printed wiring board and the second printed wiring board) In the explosion-proof system 1 of this embodiment, the power supply line L1, the first communication line L2, and the second communication line L3 are not provided with switches or circuits such as disconnection circuits. The power supply unit 13 and the power supply circuit 21 are directly electrically connected via the power supply line L1. The communication unit 14 and the communication circuit 22 are directly electrically connected via the first communication line L2 and the second communication line L3. In other words, the first printed wiring board 10 and the second printed wiring board 20 are directly electrically connected without the intervention of switches or circuits.

[0018] The reason why the first printed wiring board 10 and the second printed wiring board 20 can be electrically connected without an isolation circuit or the like is because the position storage device can retain position data without receiving an external power supply.

[0019] (Position Memory Device (PMD)) The position memory device 12 will be described. As described above, the first printed wiring board 10 includes the position memory device 12. The position memory device 12 is part of the position detection circuit included in the first printed wiring board 10. The position detection circuit is a circuit that detects the position of each axis of the motor that constitutes the robot. The position detection circuit includes, for example, a pulse coder. The position memory device 12 is a circuit that holds the position data of each axis of the motor detected by the position detection circuit.

[0020] The position storage device 12 of this embodiment can store the position of the motor shaft without receiving an external power supply, i.e., the position storage device 12 can store position data without receiving an external power supply.

[0021] (Mechanical (MM) Encoder) The reason why the position memory device 12 can retain position data without receiving a power supply is because the position detection circuit (pulse coder) is configured as a battery-less encoder. Since the position memory device 12 can retain position data without receiving a power supply, an external battery for the position memory device 12 to retain its position is not required. This is because when the power supply from the second printed wiring board 20 to the first printed wiring board 10 is turned off or when the power supply of the control device is turned off, there is no need to supply power from the battery to the position memory device 12.

[0022] In this embodiment, the position detection circuit is a so-called battery-less type encoder. The battery-less encoder may be, for example, a mechanical (MM) type, more specifically, a gear type (gear type) encoder.

[0023] The battery-less encoder is not limited to a mechanical type, and various types can be used as long as they can retain position data without receiving an external power supply, such as magnetic types, types using nonvolatile memory, and self-power generation types.

[0024] (Motor position data acquisition device, motor position data storage device, motor control device) An example of the functions of each part of the explosion-proof system 1 when the explosion-proof system 1 is a painting robot will be described. In the painting robot, the first printed wiring board 10 can function as a motor position acquisition device and a motor position data storage device. The second printed wiring board 20 can function as a motor control device. The motor position acquisition device acquires the current position of the motor. In other words, the motor position acquisition device functions as a position detection circuit. When communication is established between the first printed wiring board 10 and the second printed wiring board 20, information regarding the position is sent from the first printed wiring board 10 to the second printed wiring board 20, i.e., the motor control device.

[0025] The second printed wiring board 20 serves as a motor control device and outputs a control command to the first printed wiring board 10 in accordance with the motor position and a command value.

[0026] In the explosion-proof system 1 of this embodiment, even when the power supply to the communication circuit between the first printed wiring board 10 and the second printed wiring board 20 is turned off, the position memory device 12 can store position data without an external power supply.

[0027] The explosion-proof structure of the explosion-proof system 1 will now be described. The explosion-proof structure includes an internal pressure explosion-proof structure and an intrinsically safe explosion-proof structure. (Internal Pressure Explosion-Proof Structure) First, the internal pressure explosion-proof structure will be described. The explosion-proof system 1 is a system that includes a robot or machine used in an explosive atmosphere, such as a painting robot. Therefore, the explosion-proof system 1 is equipped with an internal pressure explosion-proof structure 40.

[0028] 1, the pressurized explosion-proof structure 40 of this embodiment covers the first printed wiring board 10. In other words, the first printed wiring board 10 is disposed inside the pressurized explosion-proof structure 40.

[0029] The pressurized explosion-proof structure 40 includes an inlet 41 and a scavenging port 42. Protective gas is introduced into the pressurized explosion-proof structure 40 from the inlet 41 as shown by arrow A41. The protective gas is a gas used for preventing the internal pressure explosion. The protective gas is, for example, air or nitrogen.

[0030] As the protective gas is fed into the interior of the pressurized explosion-proof structure 40, the gas that filled the interior of the pressurized explosion-proof structure 40 is scavenged as shown by arrow A42 through the scavenging port 42. As the feeding and scavenging progress, the gas inside the pressurized explosion-proof structure 40 is largely replaced by the protective gas.

[0031] (Purge unit (PU) and switch unit (SU)) In order to control the process of purging the gas inside the pressurized explosion-proof structure 40 and replacing it with a protective gas, the explosion-proof system 1 includes a purge unit (PU) 30 and a switch unit (SU) 37.

[0032] The switch unit 37 is disposed in the pressurized explosion-proof structure 40. The switch unit 37 includes an air flow sensor (AS) 31, a scavenging switch (SW) 32, and a pressure monitor (PM) 33. The air flow sensor 31 is a sensor that measures the air flow rate of gas, for example, at the inlet 41 or the scavenging port 42. The scavenging switch 32 is a switch that switches the supply of protective gas on and off and opens and closes the scavenging port 42. The pressure monitor 33 is a component that monitors the pressure inside the pressurized explosion-proof structure 40.

[0033] The purge unit 30 and the switch unit 37 are connected by a wiring L30. The purge unit 30 controls the replacement of the protective gas inside the pressurized explosion-proof structure 40 with a protective gas. The monitoring result of the pressure monitor 33 is transmitted to the purge unit 30 via the wiring L30. The purge unit 30 may control the replacement of the protective gas in the pressurized explosion-proof structure 40 based on the received monitoring result.

[0034] The purge unit 30 is connected to an intrinsically safe explosion-proof related device 35 and a power supply 36 via a wiring L32. The intrinsically safe explosion-proof related device refers to all of the devices related to intrinsic safety explosion-proof, including intrinsically safe explosion-proof circuits, etc. The intrinsically safe explosion-proof related device is also called intrinsically safe related device.

[0035] (Main Power Switch) The purge unit 30 is connected to a main power switch 34 via a line L31. The main power switch 34 is a switch that switches on and off the power supply to the first printed wiring board 10 and the second printed wiring board 20. The purge unit 30 can switch the main power switch 34.

[0036] (Explosion-Proof Control) The establishment of explosion-proof safety in the explosion-proof system 1 of this embodiment will be described. Boundary line L10 shown in FIG. 1 indicates the boundary line between the non-hazardous area (N-HR) and the hazardous area (HR). The side of arrow A1 relative to boundary line L10 is the non-hazardous area. The side of arrow A2 relative to boundary line L10 is the hazardous area. For example, in the above-mentioned painting robot, the side where the robot (painting unit) is located is an explosive environment, which is the hazardous area. The first printed wiring board 10 is located in the hazardous area. On the other hand, the second printed wiring board 20 is located in the non-hazardous area.

[0037] In the explosion-proof system 1 of this embodiment, first, scavenging of the pressurized explosion-proof structure 40 is performed with the main power switch 34 turned off. Then, after the interior of the pressurized explosion-proof structure 40 has been scavenged, the main power switch 34 is turned on. This ensures explosion-proof safety.

[0038] When the main power switch 34 is not turned on, the explosion protection of the first printed wiring board 10 placed in an explosive environment is ensured because the first printed wiring board 10 is not connected to an external battery and is not exposed to electrical energy in the explosive atmosphere.

[0039] Then, with the main power switch 34 not turned on, scavenging of the internal pressure explosion-proof structure 40 is performed. When scavenging of the internal pressure explosion-proof structure 40 is completed, the internal pressure explosion-proof state of the first printed wiring board 10 is established.

[0040] With the internal pressure explosion-proof state of the first printed wiring board 10 established, the main power switch 34 is turned on. By the above procedure, explosion-proof safety can be easily established in the explosion-proof system 1 without providing a disconnection circuit or the like between the first printed wiring board 10 and the second printed wiring board 20.

[0041] In the explosion-proof system 1 of this embodiment, there is a period when the main power switch 34 is turned off and power is not supplied to the first printed wiring board 10. However, the position memory device 12 can retain position data even when not receiving external power supply. Therefore, there is no need to acquire position data again when the main power switch 34 is turned on.

[0042] The advantages of the explosion-proof system 1 of this embodiment will be described below in comparison with a conventional explosion-proof system 101. FIG. 2 is a diagram showing the conventional explosion-proof system 101. The position memory device 121 provided in the conventional explosion-proof system 101 requires a power supply to store position data. Therefore, in the conventional explosion-proof system 101, the position memory device (PMD) 121 is provided with a power supply unit (PS) 15. The conventional explosion-proof system 101 also includes an external battery 52 for retaining position data and intrinsically safe explosion-proof related equipment 51 for the battery 52. ​​The power supply unit 15 is connected to the intrinsically safe explosion-proof related equipment 51 and the battery 52 via wiring L50. The intrinsically safe explosion-proof related equipment 51 is also connected to the first printed wiring board 10 via wiring L51.

[0043] In the conventional explosion-proof system 101, the position storage device 121 receives power from the battery 52 while the main power switch 34 is turned off. This power supply allows the position storage device 121 to hold the position data.

[0044] (Disconnection Circuit) In the conventional explosion-proof system 101, a disconnection circuit 50 is provided in the power supply line L1, the first communication line L2, and the second communication line L3 that connect the first printed wiring board 10 and the second printed wiring board 20. The disconnection circuit 50 is a circuit that cuts off the connection between the first printed wiring board 10 and the second printed wiring board 20. The disconnection circuit 50 is necessary to cut off the connection between the first printed wiring board 10 and the second printed wiring board 20 during a period when an intrinsically safe explosion-proof structure is required. The period during which an intrinsically safe explosion-proof structure is required is the period until scavenging of the pressurized explosion-proof structure in which the first printed wiring board 10 is placed is completed.

[0045] This section explains intrinsically safe explosion-proof structures. Intrinsically safe explosion-proof structures are structures that prevent explosions by limiting electrical energy below a certain level so that ignition cannot be caused by sparks or temperature rises. For example, current is limited by resistors and fuses, and voltage is limited by Zener diodes.

[0046] In an intrinsically safe explosion-proof structure, the maximum output voltage Uo and maximum output current Io are specified for the intrinsically safe explosion-proof related equipment. The maximum external inductance Lo and maximum external capacitance Co that can be connected to the intrinsically safe explosion-proof related equipment are specified from Uo and Io.

[0047] The inductance of the first printed wiring board 10 is L1, and the capacitance is C1. The inductance of the second printed wiring board 20 is L2, and the capacitance is C2. The first printed wiring board 10 and the second printed wiring board 20 are connected by a non-insulated communication wiring. Therefore, when considering an intrinsically safe explosion-proof circuit, the first printed wiring board 10 and the second printed wiring board 20 are considered to be electrically integrated. Therefore, the inductance is L1 + L2, and the capacitance is C1 + C2.

[0048] To establish an intrinsically safe explosion-proof circuit, it is necessary that Lo≧L1+L2 and Co≧C1+C2. If Lo<L1+L2 or Co<C1+C2, the intrinsically safe explosion-proof circuit does not hold.

[0049] Therefore, in order to reliably establish an intrinsically safe explosion-proof circuit, the first printed wiring board 10 and the second printed wiring board 20 are electrically separated. When the first printed wiring board 10 and the second printed wiring board 20 are electrically separated, Lo≧L1 and Co≧C1 are realized, and the intrinsically safe explosion-proof circuit can be established.

[0050] In order to electrically separate the first printed wiring board 10 and the second printed wiring board 20, a separation circuit 50 is provided between the first printed wiring board 10 and the second printed wiring board 20. The first printed wiring board 10 and the second printed wiring board 20 are then electrically separated from each other. This establishes an intrinsically safe explosion-proof circuit.

[0051] The effects of the explosion-proof system 1 of this embodiment over the conventional explosion-proof system 101 will be described with reference to Fig. 3. Fig. 3 is a diagram for explaining the difference between the explosion-proof system 1 of the embodiment of the present disclosure and the conventional explosion-proof system 101.

[0052] The explosion-proof system 1 according to the embodiment of the present disclosure and the conventional explosion-proof system 101 mainly differ in points A to D shown in Fig. 3, which will be described in order below.

[0053] (A) In the explosion-proof system 1 of this embodiment, as shown by arrow A20, the position memory device 121 is replaced with a mechanical (MM) position memory device 12. The mechanical position memory device 12 can retain position data without receiving an external power supply. Therefore, the position memory device 12 does not need to be equipped with a power supply unit 15.

[0054] (B) Since the position storage device 12 can store position data without receiving an external power supply, an external battery 52 for storing position data is not required, as shown by the X mark A21.

[0055] (C) Since the external battery 52 is no longer required, as shown by the X mark A22, the intrinsically safe explosion-proof related device 51 for the battery 52 is no longer required. In addition, as shown by the X mark A24, the wiring L50 and wiring L51 connecting the intrinsically safe explosion-proof related device 51 and the first printed wiring board 10 are no longer required.

[0056] (D) By eliminating the need for the external battery 52, the disconnection circuit 50 is also unnecessary, as shown by the X mark A23 in FIG.

[0057] By eliminating the need for battery 52, there is no need to make battery supply lines such as wiring L50 and wiring L51 intrinsically safe because electrical energy is not exposed to an explosive atmosphere. Therefore, an intrinsically safe explosion-proof circuit can be established without separating first printed wiring board 10 and second printed wiring board 20. As a result, there is no need for disconnection circuit 50.

[0058] (Communication Failure) In a typical ideal communication circuit, especially in the case of differential communication, it is preferable to use a shielded twisted pair from the sending end to the receiving end. However, including a disconnection circuit, such as a contact, along the wiring increases concerns about the following (1) to (5): (1) signal quality degradation due to the contact (deterioration of communication waveform, impedance mismatch, etc.), (2) communication failure due to poor contact or malfunction of the contact, (3) reduced noise resistance in the contact circuit, (4) reduced noise resistance due to areas that are not shielded or cannot be twisted compared to an ideal configuration, and (5) communication failure due to reduced noise resistance.

[0059] Regarding the above-mentioned concerns, the explosion-proof system 1 of this embodiment is not provided with the disconnection circuit 50. Therefore, in the explosion-proof system 1 of this embodiment, the above-mentioned concerns are alleviated, and communication performance is more likely to be ensured.

[0060] (Other Forms) The use of a position memory device capable of retaining position data without receiving an external power supply has been described above using a painting robot as an example. Position memory devices capable of retaining position data without receiving an external power supply can also be used in robots other than painting robots. For example, it would be useful to use a position memory device capable of retaining position data without receiving an external power supply in a robot used in a non-explosive atmosphere.

[0061] 4 is a diagram showing a robot 110 using the position storage device 12 of the present disclosure. An example of the first printed wiring board 10 is a battery-less position detection circuit (battery-less encoder) provided in the robot. An example of the second printed wiring board 20 is a robot controller.

[0062] The robot 110 shown in FIG. 4 is a robot used in a non-explosive atmosphere, and is therefore not provided with an internal pressurized explosion-proof structure.

[0063] By using a battery-less position memory device 12, such as a mechanical one, in a robot 110 used in a non-explosive environment, the hassle of battery replacement and the complexity of the device due to the provision of electrical circuits can be reduced. In particular, a large number of robots 110 are used in manufacturing processes, etc. Therefore, eliminating the need to manage batteries can significantly reduce the burden on process management.

[0064] As described above, the explosion-proof system 1 of the present disclosure can be, for example, a painting robot that uses a battery-less pulse coder. The explosion-proof system 1 of the present disclosure uses a position detector (pulse coder) that does not require a power supply to retain position data, thereby realizing a painting robot system with improved communication performance between the position detector and the amplifier.

[0065] In conventional technology, an external battery was required to maintain the position data of each motor axis that makes up the robot when the power to the control device was turned off. This external battery was connected to a circuit board exposed to an explosive atmosphere. Therefore, the external battery was treated as an intrinsically safe explosion-proof structure that limits the electrical energy from the battery below a certain level and places restrictions on the capacitive and inductive loads that can be connected.

[0066] To minimize these loads, a method has been used in which the circuit is physically disconnected during periods when a certain amount of explosive material is present, but disconnecting the circuit can result in a decrease in communication performance.

[0067] The explosion-proof system 1 of the present disclosure does not include a disconnection circuit, and therefore, the explosion-proof system 1 of the present disclosure suppresses degradation of communication performance.

[0068] The present disclosure is not limited to the above-described embodiments and modifications, and includes modifications and improvements within the scope of achieving the object of the present disclosure.

[0069] The following supplementary notes are further disclosed regarding the above-described embodiment: (Supplementary Note 1) In an explosion-proof system (1) including a position storage device (12) for a motor shaft present in an explosive atmosphere, the position storage device (12) retains position data without receiving an external power supply.

[0070] (Supplementary Note 2) The explosion-proof system (1) comprises a position detection circuit (10) including the position storage device (12), the position detection circuit (10) is disposed inside the pressurized explosion-proof structure (40), and the position detection circuit (10) comprises a battery-less encoder that maintains the position of the motor shaft without receiving an external power supply.

[0071] (Supplementary Note 3) In the explosion-proof system (1), the battery-less encoder is mechanical.

[0072] (Supplementary Note 4) The explosion-proof system (1) comprises a position detection circuit (10) including the position memory device (12), the position detection circuit (10) is disposed inside the pressurized explosion-proof structure (40), the position detection circuit (10) is electrically connected to an electric circuit (20) installed outside the pressurized explosion-proof structure (40), and before applying internal pressure to the pressurized explosion-proof structure (40), the position memory device (12) retains position data without receiving an external power supply.

[0073] (Supplementary Note 5) In the explosion-proof system (1), the position detection circuit (10) is electrically connected to the electric circuit (20) without a disconnection circuit (50).

[0074] 1 Explosion-proof system 10 First printed wiring board (PCB1, position detection circuit) 11 Communication circuit (CC) 12 Position memory device (PMD) 13 Power supply unit (PS) 14 Communication unit (CP) 15 Power supply unit (PS) 20 Second printed wiring board (PCB2, control device, electric circuit) 21 Power supply circuit (PC) 22 Communication circuit (CC) 30 Purge unit (PU) 31 Air flow sensor (AS) 32 Scavenging switch (SW) 33 Pressure monitor (PM) 34 Main power switch 35 Intrinsically safe explosion-proof related equipment 36 Power supply 37 Switch unit (SU) 40 Internal pressurized explosion-proof structure 41 Inlet 42 Scavenging port 50 Disconnection circuit 51 Intrinsically safe explosion-proof related equipment 52 Battery 101 Conventional explosion-proof system 110 Robot 121 Conventional Position Memory Device (PMD) N-HR Non-hazardous area HR Hazardous area

Claims

1. In an explosion-proof system including a position memory device for a motor shaft existing in an explosive atmosphere, the position memory device holds position data without receiving an external power supply. An explosion-proof system.

2. It includes a position detection circuit including the position memory device. The position detection circuit is arranged inside an internal pressure explosion-proof structure. The position detection circuit includes a battery-less encoder that holds the position of the motor shaft without receiving an external power supply. The explosion-proof system according to claim 1.

3. The battery-less encoder is mechanical. The explosion-proof system according to claim 2.

4. It includes a position detection circuit including the position memory device. The position detection circuit is arranged inside an internal pressure explosion-proof structure. The position detection circuit is electrically connected to an electric circuit installed outside the internal pressure explosion-proof structure. Before applying internal pressure to the internal pressure explosion-proof structure, the position memory device holds position data without receiving an external power supply. The explosion-proof system according to claim 1 or 2.

5. The position detection circuit is electrically connected to the electric circuit without passing through a disconnection circuit. The explosion-proof system according to claim 4.

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