Communication device

Abstract

Network congestion may cause liveness monitoring to mistakenly identify active communication devices as lost. [Solution] The outdoor control unit 39 determines that indoor units 20a to 20c have disappeared in the data link layer L1 if it does not receive the first packet P1 during the first period T1. The outdoor control unit 39 determines that indoor units 20a to 20c have disappeared in the application layer L2 if it does not receive the first response RES1 to the first request REQ1 during the second period T2. The first period T1 is shorter than the second period T2. If the outdoor control unit 39 determines that indoor units 20a to 20c have disappeared in the data link layer L1, it stops the periodic retransmission of the second packet P2, which includes the first request REQ1.

Description

Technical Field

[0004]

[0001] It relates to a communication device.

Background Art

[0002] As shown in Patent Document 1 (International Publication No. 2011 / 074454), there is a technique for performing retransmission control of packets.

Summary of the Invention

Problems to be Solved by the Invention

[0003] In Patent Document 1, since network congestion due to packet retransmission control is not considered, there is a risk that in a survival monitoring, communication cannot be established with a live communication device, and a live communication device may be erroneously determined to have disappeared.

Means for Solving the Problems

[0004] The communication device in the first perspective communicates with multiple communication devices via a first network. The multiple communication devices include the first communication device. The communication device includes a control unit. The control unit periodically receives a first packet from the first communication device in the first layer of multiple layers in which the communication function is divided. If the control unit does not receive a first packet during a first period, it determines that the first communication device has disappeared in the first layer. Alternatively, if the control unit does not receive a first packet for a first consecutive number of times, it determines that the first communication device has disappeared in the first layer. In the second layer, which is higher than the first layer, the control unit periodically sends a first request to the first communication device. The control unit receives a first response to the first request from the first communication device. In the first layer, the control unit sends the first request to the first communication device as a second packet. The second packet includes the first request. The control unit periodically retransmits the second packet to the first communication device until it receives an acknowledgment packet for the second packet from the first communication device. If the control unit does not receive the first response during the second period, it determines that the first communication device has disappeared at Layer 2. Alternatively, if the control unit does not receive the first response for two consecutive times, it determines that the first communication device has disappeared at Layer 2. The first period is shorter than the second period. Or, the first number of attempts is less than the second number of attempts. If the control unit determines that the first communication device has disappeared at Layer 1, it stops the periodic retransmission of the second packet.

[0005] The communication device in the first perspective determines that the first communication device has been lost in the first layer before determining that the first communication device has been lost in the second layer, because the first period is shorter than the second period, and stops the periodic retransmission of the second packet. As a result, the communication device can prevent mistakenly determining that a live first communication device has been lost in the second layer due to the resolution of congestion in the first network.

[0006] The communication device in the second perspective is the communication device in the first perspective, and the control unit periodically sends a third packet to multiple communication devices at the first layer, prompting them to join the first network. If the control unit determines that the first communication device has disappeared at the first layer, and then receives a fourth packet from the first communication device requesting to join the first network before determining that the first communication device has disappeared at the second layer, the control unit cancels the determination that the first communication device has disappeared at the first layer.

[0007] The third-perspective communication device is a first-perspective or second-perspective communication device, and the control unit, if it determines in the second layer that the first communication device has disappeared, increases the transmission interval of the first request.

[0008] The third-party communication device, with this configuration, can prevent congestion in the first network.

[0009] The communication device in the fourth perspective is a communication device from any one of the first, second, or third perspectives, and the communication device and multiple communication equipment are air conditioners. [Brief explanation of the drawing]

[0010] [Figure 1] This is a schematic diagram of the air conditioner's configuration. [Figure 2A] This diagram illustrates the availability monitoring at the data link layer. [Figure 2B] This diagram illustrates the availability monitoring at the data link layer. [Figure 3A] This diagram illustrates health monitoring in the application layer. [Figure 3B] This diagram illustrates health monitoring in the application layer. [Figure 4] This flowchart illustrates the health monitoring process when the first period is longer than the second period. [Figure 5] This flowchart illustrates the health monitoring process when the first period is shorter than the second period. [Modes for carrying out the invention]

[0011] (1) Overall configuration of the air conditioner Air conditioner 2 constitutes a vapor compression type refrigeration cycle and provides air conditioning for one or more target spaces within a building. Air conditioner 2 is a so-called multi-type air conditioning system for buildings.

[0012] Figure 1 is a schematic diagram of the air conditioner 2. As shown in Figure 1, the air conditioner 2 has one outdoor unit 30 (communication device) and multiple indoor units 20 (communication equipment). The outdoor unit 30 and the multiple indoor units 20 are connected by liquid refrigerant communication piping and gas refrigerant communication piping, forming a refrigerant circuit. The outdoor unit 30 and the multiple indoor units 20 are daisy-chained together by communication lines 90 (first network). The outdoor unit 30 communicates with the multiple indoor units 20 via the communication lines 90. The multiple indoor units 20 include indoor units 20a to 20c (first communication equipment).

[0013] (2) Detailed configuration of the air conditioner (2-1) Outdoor unit The outdoor unit 30 is installed, for example, on the roof of a building. The outdoor unit 30 mainly comprises a compressor, a flow path switching valve, an outdoor heat exchanger, an outdoor expansion valve, an outdoor fan, and an outdoor control unit 39 (control unit).

[0014] The compressor draws in low-pressure refrigerant from the suction pipe, compresses the refrigerant using a compression mechanism, and discharges the compressed refrigerant through the discharge pipe. The compressor's compression mechanism is driven by a compressor motor. The flow path switching valve is a mechanism that switches the refrigerant flow path between a first state and a second state. During cooling operation, the flow path switching valve sets the refrigerant flow path to the first state. At this time, the refrigerant discharged from the compressor flows through the refrigerant circuit in the order of outdoor heat exchanger, outdoor expansion valve, indoor expansion valve, and indoor heat exchanger, before returning to the compressor. In the first state, the outdoor heat exchanger functions as a condenser, and the indoor heat exchanger functions as an evaporator. During heating operation, the flow path switching valve sets the refrigerant flow path to the second state. At this time, the refrigerant discharged from the compressor flows through the refrigerant circuit in the order of indoor heat exchanger, indoor expansion valve, outdoor expansion valve, and outdoor heat exchanger, before returning to the compressor. In the second state, the outdoor heat exchanger functions as an evaporator, and the indoor heat exchanger functions as a condenser. The outdoor heat exchanger facilitates heat exchange between the refrigerant flowing through it and the outdoor air of the building. The outdoor expansion valve is a mechanism for regulating the pressure and flow rate of the refrigerant flowing through the refrigerant circuit. The outdoor fan supplies outdoor air to the outdoor heat exchanger. The outdoor fan is driven by an outdoor fan motor.

[0015] The outdoor control unit 39 controls the operation of each component of the outdoor unit 30. The outdoor control unit 39 is communicatively connected to the compressor motor, flow path switching valve, outdoor expansion valve, and outdoor fan motor. The outdoor control unit 39 has a control calculation device, a memory device, and a network interface device. The control calculation device is a processor such as a CPU or GPU. The memory device is a storage medium such as RAM, ROM, or flash memory. The control calculation device reads a program stored in the memory device and controls the operation of each component of the outdoor unit 30 by performing predetermined calculation processing according to the program. The control calculation device can also write calculation results to the memory device or read information stored in the memory device according to the program. The outdoor control unit 39 exchanges various information, such as control signals or signals related to various settings, with the indoor control units 29a to 29c of the indoor units 20a to 20c via the communication line 90.

[0016] The outdoor control unit 39 has a plurality of layers in which the communication function is divided. In the present embodiment, the plurality of layers in which the communication function is divided are the plurality of layers in the OSI reference model. The plurality of layers in which the communication function is divided may be, for example, the plurality of layers in the TCP / IP model.

[0017] The plurality of layers in which the communication function is divided mainly includes a data link layer L1 (layer 1) and an application layer L2 (layer 2) higher than the data link layer L1.

[0018] (2-2) Indoor unit The indoor units 20a to 20c are installed, for example, on the ceiling of the target space. Each of the indoor units 20a to 20c mainly has an indoor heat exchanger, an indoor fan, an indoor expansion valve, and indoor control units 29a to 29c.

[0019] The indoor heat exchanger causes heat exchange between the refrigerant flowing through the indoor heat exchanger and the air in the target space. The indoor fan sucks the air in the target space into the indoor units 20a to 20c, causes the sucked air to exchange heat with the refrigerant in the indoor heat exchanger, and supplies it to the target space. The indoor fan is driven by an indoor fan motor. The indoor expansion valve is a mechanism for adjusting the pressure and flow rate of the refrigerant flowing through the refrigerant circuit.

[0020] The indoor control units 29a to 29c control the operations of the respective parts constituting the indoor units 20a to 20c. The indoor control units 29a to 29c are communicably connected to an indoor fan motor and an indoor expansion valve. The indoor control units 29a to 29c include a control arithmetic unit, a storage device, and a network interface device. The control arithmetic unit is a processor such as a CPU or a GPU. The storage device is a storage medium such as a RAM, a ROM, or a flash memory. The control arithmetic unit reads out a program stored in the storage device and performs predetermined arithmetic processing according to the program, thereby controlling the operations of the respective parts constituting the indoor units 20a to 20c. Further, the control arithmetic unit can write an arithmetic result into the storage device or read out information stored in the storage device according to the program. The indoor control units 29a to 29c are configured to be able to receive various signals transmitted from an operation remote controller corresponding to the indoor units 20a to 2jc. Further, the indoor control units 29a to 29c exchange various information such as control signals or signals regarding various settings with the outdoor control unit 39 of the outdoor unit 30 via a communication line 90.

[0021] Similar to the outdoor control unit 39, the indoor control units 29a to 29c have a plurality of layers in which the communication function is divided. The plurality of layers in which the communication function is divided mainly include a data link layer L1 and an application layer L2.

[0022] (2-3) Life and death monitoring The outdoor control unit 39 performs life and death monitoring of the indoor units 20a to 20c in each of the data link layer L1 and the application layer L2. Hereinafter, for example, the fact that the indoor unit 20a is dead may be described as the indoor unit 20a has disappeared.

[0023] As a premise, the outdoor control unit 39 has a first list indicating the addresses and life and death states in the data link layer L1 of the indoor units 20a to 20c, which is used during communication between the data link layers L1. Further, the outdoor control unit 39 has a second list indicating the addresses and life and death states in the application layer L2 of the indoor units 20a to 20c, which is used during communication between the application layers L2.

[0024] Table 1 below is an example of the second list in the application layer L2 status monitoring, where the outdoor control unit 39 determines that indoor units 20a to 20c are operational. In Table 1, the "Status" of indoor units 20a to 20c is "Operational," indicating that indoor units 20a to 20c are operational. [Table 1]

[0025] Table 2 below is an example of the first list when the outdoor control unit 39 determines that indoor units 20a to 20c are active during the status monitoring at the data link layer L1. Table 2 shows the correspondence between the address at the application layer L2 and the address at the data link layer L1 for each of the indoor units 20a to 20c. Unlike Table 1, Table 2 shows that indoor units 20a to 20c are active because there is a record corresponding to each of them. [Table 2]

[0026] (2-3-1) Liveness monitoring at the data link layer Figures 2A and 2B illustrate the status monitoring at the data link layer L1. As shown in Figures 2A and 2B, the outdoor control unit 39 periodically receives the first packet P1 from the indoor units 20a to 20c at the data link layer L1 (transmission interval T3). While the outdoor control unit 39 is periodically receiving the first packet P1, it determines that the indoor units 20a to 20c are alive.

[0027] On the other hand, if the outdoor control unit 39 does not receive the first packet P1 during the first period T1, it determines that the indoor units 20a to 20c have disappeared at the data link layer L1. For example, if the outdoor control unit 39 determines that the indoor unit 20a has disappeared at the data link layer L1 because the power to the indoor unit 20a has been turned off, it deletes the record corresponding to the indoor unit 20a in the first list.

[0028] Table 3 below is an example of the first list when the outdoor control unit 39 determines that the indoor unit 20a has disappeared at the data link layer L1. In Table 3, compared to Table 1, the record corresponding to the indoor unit 20a has been deleted. [Table 3]

[0029] The outdoor control unit 39 periodically transmits (broadcasts) a third packet P3 to multiple indoor units 20 at the data link layer L1, prompting them to join the communication line 90.

[0030] In this embodiment, the first period T1 in which the data link layer L1 determines that indoor units 20a to 20c have disappeared is shorter than the second period T2 in the application layer L2, which will be described later, in which the application layer L2 determines that indoor units 20a to 20c have disappeared. If the outdoor control unit 39 receives a fourth packet P4 from indoor unit 20a requesting to join the communication line 90 between the time it determines that indoor unit 20a has disappeared in the data link layer L1 and the time it determines that indoor unit 20a has disappeared in the application layer L2, it cancels the determination that indoor unit 20a has disappeared in the data link layer L1. When the outdoor control unit 39 cancels the determination that indoor unit 20a has disappeared in the data link layer L1, it adds a record corresponding to indoor unit 20a in the first list.

[0031] Table 4 below is an example of the first list when the outdoor control unit 39 cancels the determination that the indoor unit 20a has disappeared at the data link layer L1. In Table 4, a record corresponding to the indoor unit 20a has been added compared to Table 3. [Table 4]

[0032] (2-3-2) Health monitoring at the application layer Figures 3A and 3B illustrate the status monitoring at the application layer L2. As shown in Figures 3A and 3B, the outdoor control unit 39 periodically (transmission interval T4) sends a first request REQ1 to the indoor units 20a to 20c at the application layer L2. At this time, the outdoor control unit 39 sends the first request REQ1 to the indoor units 20a to 20c as a second packet P2 at the data link layer L1. The second packet P2 contains the first request REQ1. Specifically, for example, when the outdoor control unit 39 sends the first request REQ1 to indoor unit 20a, the outdoor control unit 39 sends the first request REQ1 at the application layer L2 with the destination address set to "aaa" according to Table 1. Next, the outdoor control unit 39 sends the second packet P2, which encapsulates the first request REQ1, at the data link layer L1 with the destination address set to "111" according to Table 2.

[0033] The outdoor control unit 39 receives an acknowledgment packet ACK for the second packet P2 from the indoor units 20a to 20c. The outdoor control unit 39 periodically retransmits the second packet P2 to the indoor units 20a to 20c until it receives an acknowledgment packet ACK for the second packet P2 from the indoor units 20a to 20c.

[0034] The outdoor control unit 39 receives a first response RES1 to the first request REQ1 from the indoor units 20a to 20c. At this time, the indoor units 20a to 20c transmit the first response RES1 to the outdoor control unit 39 as a fifth packet P5 encapsulating the first response RES1 at the data link layer L1. The outdoor control unit 39 sends an acknowledgment packet ACK to the indoor units 20a to 20c for the fifth packet P5. The outdoor control unit 39 determines that the indoor units 20a to 20c are alive as long as it is periodically receiving the first response RES1.

[0035] On the other hand, if the outdoor control unit 39 does not receive the first response RES1 during the second period T2 after sending the first request REQ1, it determines in the application layer L2 that the indoor units 20a to 20c have disappeared. The first period T1 is shorter than the second period T2. For example, if the outdoor control unit 39 determines in the application layer L2 that indoor unit 20a has disappeared, it changes the "status" of the record corresponding to indoor unit 20a in the second list to "disappeared".

[0036] Table 5 below is an example of the second list when the outdoor control unit 39 determines that the indoor unit 20a has disappeared at the application layer L2. In Table 5, compared to Table 1, the "Status" of the record corresponding to the indoor unit 20a has been changed to "Disappeared". [Table 5]

[0037] If the outdoor control unit 39 determines that the indoor unit 20a has disappeared at the data link layer L1 (because the first period T1 is shorter than the second period T2), it stops the periodic retransmission of the second packet P2 to the indoor unit 20a because the address of the indoor unit 20a at the data link layer L1 is unknown.

[0038] If the outdoor control unit 39 determines at the application layer L2 that the indoor unit 20a has disappeared, it lengthens the transmission interval T4 of the first request REQ1 and broadcasts the second packet P2 to the indoor units 20a to 20c.

[0039] (2-3-3) Challenges of health monitoring when the first period is longer than the second period The following describes the challenges of monitoring the operational status when the first period T1 is longer than the second period T2, using the flowchart in Figure 4. In Figure 4, the case where the power to indoor units 20a and 20b is turned off while the power to indoor unit 20c remains ON (when indoor units 20a and 20b disappear) is explained, and therefore indoor units 20a, 20b and indoor unit 20c are shown separately.

[0040] As a prerequisite, the outdoor control unit 39 determines that the indoor units 20a to 20c are active at both the data link layer L1 and the application layer L2, respectively. In other words, the first list represents the state shown in Table 2, and the second list represents the state shown in Table 1.

[0041] The power to indoor units 20a and 20b is turned OFF (Step S1).

[0042] After the power to the indoor units 20a and 20b is turned OFF, the outdoor control unit 39 sends a first request REQ1 to the indoor units 20a and 20b (step S2), and at the time the first request REQ1 is sent, it starts counting the second period T2 for the indoor units 20a and 20b (step S3).

[0043] However, since the outdoor control unit 39 cannot receive an acknowledgment packet ACK for the second packet P2 from the indoor units 20a and 20b, it periodically retransmits the second packet P2 to the indoor units 20a and 20b until it receives an acknowledgment packet ACK for the second packet P2 from the indoor units 20a and 20b (step S4). This causes congestion on the communication line 90.

[0044] Furthermore, after the power to the indoor units 20a and 20b is turned OFF, the outdoor control unit 39 cannot receive the first packet P1 from the indoor units 20a and 20b, so it starts counting for the first period T1 for the indoor units 20a and 20b at the same time as the start of counting for the second period T2 (step S5).

[0045] Meanwhile, the outdoor control unit 39 sends a first request REQ1 to the indoor unit 20c (step S6), and at the time of sending the first request REQ1, it starts counting the second period T2 for the indoor unit 20c (step S7). However, due to congestion on the communication line 90, it cannot receive an acknowledgment packet ACK for the second packet P2 from the indoor unit 20c. Therefore, the outdoor control unit 39 periodically retransmits the second packet P2 to the indoor unit 20c until it receives an acknowledgment packet ACK for the second packet P2 from the indoor unit 20c (step S8). This causes further congestion on the communication line 90.

[0046] Furthermore, because the communication line 90 is congested, the outdoor control unit 39 cannot receive the first packet P1 from the indoor unit 20c (step S9). Therefore, at the same time as the start of the counting of the second period T2, it starts counting the first period T1 for the indoor unit 20c (step S10).

[0047] Because the power to indoor units 20a and 20b is OFF, the outdoor control unit 39 does not receive the first response RES1 from indoor units 20a and 20b, and the second period T2 elapses. Therefore, the outdoor control unit 39 determines that indoor units 20a and 20b have disappeared at the application layer L2 (step S11).

[0048] Due to congestion on the communication line 90, the outdoor control unit 39 does not receive the first response RES1 from the indoor unit 20c, and the second period T2 elapses. Therefore, the outdoor control unit 39 determines at the application layer L2 that the indoor unit 20c has disappeared (step S12).

[0049] As a result, if the first period T1 is longer than the second period T2, the outdoor control unit 39 may mistakenly determine that a functioning indoor unit 20c has disappeared at the application layer L2 due to continued congestion on the communication line 90.

[0050] Table 6 below shows the second list at this stage. In Table 6, compared to Table 1, the "Status" of the records corresponding to indoor units 20a to 20c has been changed to "Disappeared". [Table 6]

[0051] (2-3-4) Health monitoring when the first period is shorter than the second period In this embodiment, in order to solve the above-mentioned problems, the first period T1 is shorter than the second period T2. Below, the fact that the above-mentioned problems do not occur when the first period T1 is shorter than the second period T2 will be explained using the flowchart in Figure 5. Steps S1 to S9 in Figure 5 are the same as in Figure 4, except that the first period T1 is shorter than the second period T2.

[0052] Because the power to indoor units 20a and 20b is OFF, the outdoor control unit 39 does not receive the first packet P1 from indoor units 20a and 20b, and the first period T1 elapses. Therefore, the outdoor control unit 39 determines that indoor units 20a and 20b have disappeared at the data link layer L1 (step S13).

[0053] Due to congestion on communication line 90, the outdoor control unit 39 does not receive the first packet P1 from the indoor unit 20c, and the first period T1 elapses. Therefore, the outdoor control unit 39 determines that the indoor unit 20c has disappeared at the data link layer L1 (step S14).

[0054] Tables 7 and 8 below show the first and second lists at this stage, respectively. In particular, in Table 8, the records corresponding to indoor units 20a to 20c have been deleted compared to Table 2. [Table 7] [Table 8]

[0055] The outdoor control unit 39 determines that indoor units 20a to 20c have disappeared at the data link layer L1, and therefore stops the periodic retransmission of the second packet P2 to indoor units 20a to 20c (step S15). This resolves the congestion on the communication line 90.

[0056] The outdoor control unit 39 periodically transmits (broadcasts) the third packet P3 to the indoor units 20a to 20c at the data link layer L1 (step S16).

[0057] In step S15, the periodic retransmission of the second packet P2 to indoor units 20a to 20c is stopped, and the congestion on the communication line 90 is resolved. Therefore, after the outdoor control unit 39 determines that indoor units 20a to 20c have disappeared at the data link layer L1, it receives the fourth packet P4 from indoor unit 20c before determining that indoor units 20a to 20c have disappeared at the application layer L2 (step S17). However, because the power to indoor units 20a and 20b is OFF, the outdoor control unit 39 does not receive the fourth packet P4 from indoor units 20a and 20b after determining that indoor units 20a to 20c have disappeared at the data link layer L1, but before determining that indoor units 20a to 20c have disappeared at the application layer L2.

[0058] The outdoor control unit 39 receives the fourth packet P4 from the indoor unit 20c and therefore cancels the determination that the indoor unit 20c has disappeared at the data link layer L1 (step S18).

[0059] Tables 9 and 10 below show the first and second lists at this stage, respectively. In particular, Table 10 includes additional records corresponding to indoor unit 20c compared to Table 8. [Table 9] [Table 10]

[0060] Because the power to indoor units 20a and 20b is OFF, the outdoor control unit 39 does not receive the first response RES1 from indoor units 20a and 20b, and the second period T2 elapses. Therefore, the outdoor control unit 39 determines that indoor units 20a and 20b have disappeared at the application layer L2 (step S19).

[0061] Tables 11 and 12 below show the first and second lists, respectively, at this stage. In particular, in Table 11, compared to Table 9, the "Status" of the records corresponding to indoor units 20a and 20b has been changed to "Disappeared". [Table 11] [Table 12]

[0062] If the first period T1 is shorter than the second period T2, the indoor unit 20c is determined to have disappeared at the data link layer L1 before the application layer L2 determines that the indoor unit 20c has disappeared, and the periodic retransmission of the second packet P2 is stopped. As a result, the outdoor control unit 39 can prevent mistakenly determining that a still-functioning indoor unit 20c has disappeared at the application layer L2 due to the resolution of congestion on the communication line 90.

[0063] Furthermore, as shown in Tables 1,7-12, if the first period T1 is shorter than the second period T2, the outdoor control unit 39 can create the first and second lists that reflect the actual situation while maintaining the state in the application layer L2 that the indoor unit 20c is "alive".

[0064] If the outdoor control unit 39 determines at the application layer L2 that indoor units 20a and 20b have disappeared, it lengthens the transmission interval T4 of the first request REQ1 and broadcasts the second packet P2 to indoor units 20a to 20c (step S20).

[0065] (3) Features (3-1) Conventional technologies exist for controlling packet retransmission. However, these conventional technologies do not take into account network congestion caused by packet retransmission control. As a result, in health monitoring, they may be unable to communicate with active communication devices, potentially leading to the incorrect identification of active communication devices as lost.

[0066] In this embodiment, the outdoor unit 30 (communication device) communicates with a plurality of indoor units 20 (communication devices) via a communication line 90 (first network). The plurality of indoor units 20 include indoor units 20a to 20c (first communication devices). The outdoor unit 30 includes an outdoor control unit 39. The outdoor control unit 39 periodically receives a first packet P1 from the indoor units 20a to 20c in the data link layer L1 (first layer), one of the multiple layers in which the communication function is divided. If the outdoor control unit 39 does not receive a first packet P1 during the first period T1, it determines in the data link layer L1 that the indoor units 20a to 20c have disappeared. The outdoor control unit 39 periodically sends a first request REQ1 to the indoor units 20a to 20c in the application layer L2 (second layer), which is higher than the data link layer L1. The outdoor control unit 39 receives a first response RES1 to the first request REQ1 from the indoor units 20a to 20c. At the data link layer L1, the outdoor control unit 39 sends the first request REQ1 to the indoor units 20a to 20c as a second packet P2. The second packet P2 contains the first request REQ1. The outdoor control unit 39 periodically retransmits the second packet P2 to the indoor units 20a to 20c until it receives an acknowledgment packet ACK for the second packet P2 from the indoor units 20a to 20c. At the application layer L2, if the outdoor control unit 39 does not receive the first response RES1 during the second period T2, it determines that the indoor units 20a to 20c have disappeared. The first period T1 is shorter than the second period T2. At the data link layer L1, if the outdoor control unit 39 determines that the indoor units 20a to 20c have disappeared, it stops periodically retransmitting the second packet P2.

[0067] In this embodiment, because the first period T1 is shorter than the second period T2, the outdoor unit 30 determines at the data link layer L1 that indoor units 20a to 20c have disappeared before the application layer L2 determines that indoor units 20a to 20c have disappeared, and stops the periodic retransmission of the second packet P2. As a result, for example, even if the power to indoor unit 20c remains ON while the power to indoor units 20a and 20b are turned OFF, the outdoor unit 30 can prevent it from mistakenly determining at the application layer L2 that the still-functioning indoor unit 20c has disappeared due to the resolution of congestion on the communication line 90.

[0068] (3-2) In the outdoor unit 30 of this embodiment, the outdoor control unit 39 periodically sends a third packet P3 to multiple indoor units 20 at the data link layer L1 to prompt them to join the communication line 90. After the outdoor control unit 39 determines that indoor units 20a to 20c have disappeared at the data link layer L1, if it receives a fourth packet P4 from indoor units 20a to 20c requesting to join the communication line 90 before determining that indoor units 20a to 20c have disappeared at the application layer L2, the outdoor control unit 39 cancels the determination that indoor units 20a to 20c have disappeared at the data link layer L1.

[0069] (3-3) In the outdoor unit 30 of this embodiment, if the outdoor control unit 39 determines in the application layer L2 that the indoor units 20a to 20c have disappeared, it lengthens the transmission interval T4 of the first request REQ1.

[0070] As a result, the outdoor unit 30 can prevent congestion of the communication line 90.

[0071] (3-4) In this embodiment, the outdoor unit 30 and the multiple indoor units 20 constitute an air conditioner 2.

[0072] (4) Variations (4-1) Variation 1A In this embodiment, the communication device and the first communication equipment were air conditioners 2. However, the communication device and the first communication equipment are not limited to air conditioners 2.

[0073] (4-2) Modification 1B In this embodiment, the first network was a communication line 90. However, the first network is not limited to a wired network, but may also be a wireless network.

[0074] (4-3) Modification 1C In this embodiment, the air conditioner 2 had three indoor units 20a to 20c as multiple communication devices. However, the number of indoor units that the air conditioner 2 has as multiple communication devices is not limited to three.

[0075] In this embodiment, the air conditioner 2 had one refrigerant system. However, the air conditioner 2 may have multiple refrigerant systems.

[0076] If a single refrigerant system has one outdoor unit and multiple indoor units, the communication device may be one outdoor unit belonging to a specific refrigerant system among the multiple refrigerant systems, and the multiple communication devices may be multiple indoor units belonging to that specific refrigerant system.

[0077] If a refrigerant system has one outdoor unit and multiple indoor units, the communication device may be the outdoor unit of each of the multiple refrigerant systems, and the multiple communication devices may be the multiple indoor units of each of the multiple refrigerant systems. In this case, each outdoor unit may be configured to periodically send a first request REQ1 to multiple indoor units of the same refrigerant system, and a specific outdoor unit among all the refrigerant systems may be configured to periodically receive a first packet P1 from all the indoor units within all the refrigerant systems.

[0078] (4-4) Modification 1D In this embodiment, the outdoor control unit 39 determined that indoor units 20a to 20c had disappeared at the data link layer L1 if it did not receive the first packet P1 during the first period T1. However, the outdoor control unit 39 may also determine that indoor units 20a to 20c have disappeared at the data link layer L1 if it does not receive the first packet P1 for a first consecutive number of times.

[0079] Furthermore, in this embodiment, the outdoor control unit 39 determined that the indoor units 20a to 20c had disappeared in the application layer L2 if it did not receive the first response RES1 during the second period T2 after sending the first request REQ1. However, the outdoor control unit 39 may also determine that the indoor units 20a to 20c have disappeared in the application layer L2 if it does not receive the first response RES1 for a second consecutive time after sending the first request REQ1.

[0080] In this case, the first count is less than the second count.

[0081] (4-5) While embodiments of this disclosure have been described above, it should be understood that various modifications to the form and details are possible without departing from the spirit and scope of this disclosure as described in the claims. [Explanation of Symbols]

[0082] 2. Air conditioner 20 Indoor unit (communication equipment) 20a~20c Indoor unit (1st communication equipment) 30 Outdoor unit (communication device) 39 Outdoor Control Unit (Control Unit) 90 Communication lines (Network 1) ACK (Acknowledgment) packet L1 Data Link Layer (Layer 1) L2 Application Layer (Layer 2) P1~P4 Packet 1~Packet 4 REQ1 First Request RES1 First Response T1 Period 1 T2 Second Period T4 First request transmission interval [Prior art documents] [Patent Documents]

[0083] [Patent Document 1] International Publication No. 2011 / 074454

Claims

1. A communication device (30) that communicates with a plurality of communication devices (20), including first communication devices (20a to 20c), via a first network (90), It includes a control unit (39), The control unit, In the first layer (L1) of the multiple layers in which the communication function is divided, a first packet (P1) is periodically received from the first communication device. If the first packet is not received during the first period (T1), or if the first packet is not received for a first consecutive number of times, the first communication device is determined to have disappeared at the first layer. In the second layer (L2) above the first layer, a first request (REF1) is periodically transmitted to the first communication device, and a first response (RES1) to the first request is received from the first communication device. In the first layer, the first request is transmitted to the first communication device as a second packet (P2) containing the first request, and the second packet is periodically retransmitted to the first communication device until an acknowledgment packet (ACK) for the second packet is received from the first communication device. If the first response is not received during the second period (T2), or if the first response is not received for a second consecutive time, the second layer determines that the first communication device has disappeared. The first period is shorter than the second period, or the first number of occurrences is fewer than the second number of occurrences. If the control unit determines that the first communication device has been lost in the first layer, it stops the periodic retransmission of the second packet. Communication device (30).

2. The control unit, In the first layer, a third packet (P3) prompting the plurality of communication devices to join the first network is periodically transmitted. If, after determining that the first communication device has been lost in the first layer, a fourth packet (P4) requesting participation in the first network is received from the first communication device before determining that the first communication device has been lost in the second layer, the determination that the first communication device has been lost in the first layer is revoked. The communication device (30) according to claim 1.

3. If the control unit determines in the second layer that the first communication device has disappeared, it increases the transmission interval (T4) of the first request. A communication device (30) according to claim 1 or 2.

4. The aforementioned communication device and the plurality of communication devices are air conditioners (2). A communication device (30) according to claim 1 or 2.

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