Water level change detection system

Abstract

To provide a water level change detection system capable of accurately detecting a change in the water level of a bathtub.SOLUTION: A water level change detection system 1 includes: a circulation pump 6 which is installed in a circulation passage 3 connected to a bathtub 2 in such a manner that water of the bathtub 2 circulates therethrough, and which circulates the water of the bathtub 2; a pressure sensor 5 for detecting a pressure at a pressure detection position 5a inside the circulation passage 3; correction value calculating means for calculating a correction value which gets larger as a flow rate in the circulation passage 3 increases; pressure correcting means for calculating a correction pressure by subtracting or adding the correction value from or to the pressure detected by the pressure sensor 5 during operation of the circulation pump 6; water level change detection means for detecting the change in the water level of the bathtub 2 on the basis of the correction pressure; and bathing-in / out determination means for determining bathing-in or bathing-out when the correction pressure calculated by the pressure correcting means changes by a bathing-in reference value or more.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to a water level change detection system. [Background technology]

[0002] Conventionally, there are water heaters in which a bathtub and a heater are connected by piping to form a circulation path, and bathtub water is circulated by a circulation pump, drawn into the circulation path, heated by the heater, and returned to the bathtub. In such water heaters, there are water level detection systems that install a pressure sensor in the circulation path to detect the water pressure in the circulation path and estimate the water level in the bathtub from the detected value. For example, Patent Document 1 discloses a technology that determines whether the pressure sensor value is a detection value in an inappropriate state where air has been drawn into the circulation path, since an accurate water level cannot be measured if air is drawn into the circulation path when measuring the water level from the water pressure in the circulation path. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 9-273808 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in conventional bathtub water level detection systems using pressure sensors, while bathtub water is circulating in the circulation path, the circulation pump operates to cause water to flow through the pipes, resulting in a loss of pressure in the pipes and a change in the pressure sensor value compared to when water is not circulating, making it impossible to detect the water level accurately.

[0005] The present disclosure has been made to solve the above-mentioned problems, and aims to provide a water level change detection system that is placed in a circulation path that circulates water in a bathtub and detects changes in the water level, and that can accurately detect changes in the water level in the bathtub even while the water is circulating. [Means for solving the problem]

[0006] A circulation pump that is connected to the bathtub and installed in a circulation path through which the bathtub water circulates, and that circulates the bathtub water; and a pressure sensor that detects pressure at a pressure detection position inside the circulation path. a flow rate detection means for detecting the flow rate of water flowing through the circulation path by the circulation pump; The larger the flow rate in the circulation path, the larger the correction value. , calculated by multiplying the square of the flow rate detected by the flow rate detection means by a correction constant. a correction value calculation means; Calculate the corrected pressure using the pressure detected by the pressure sensor and the correction value. The bathtub water level change detection means detects a change in the bathtub water level based on the corrected pressure, and a bathing entry / exit determination means determines that a bather has started bathing or exited the bath when the corrected pressure calculated by the pressure correction means has changed by more than a bathing reference value. The correction value calculation means acquires the non-circulating pressure detected by the pressure sensor when the circulation pump is not operating, acquires the circulating pressure detected by the pressure sensor when the circulation pump is operating and the circulating flow rate detected by the flow rate detection means, and calculates the correction constant by the formula (P1-P0) / (V1×V1), where P0 is the non-circulating pressure, P1 is the circulating pressure, and V1 is the circulating flow rate. Water level change detection system. Also, a circulation pump that is connected to the bathtub and installed in a circulation path through which the bathtub water circulates, and circulates the bathtub water; and a pressure sensor that detects pressure at a pressure detection position inside the circulation path. a rotation speed detection means for detecting the rotation speed of the motor of the circulation pump; The larger the flow rate in the circulation path, the larger the correction value. , calculated by multiplying the square of the rotation speed of the circulation pump detected by the rotation speed detection means by a correction constant. a correction value calculation means; Calculate the corrected pressure using the pressure detected by the pressure sensor and the correction value. The bathtub water level change detection means detects a change in the bathtub water level based on the corrected pressure, and a bathing entry / exit determination means determines that a bather has started bathing or exited the bath when the corrected pressure calculated by the pressure correction means has changed by more than a bathing reference value. The correction value calculation means acquires the non-circulating pressure detected by the pressure sensor when the circulation pump is not operating, acquires the circulating pressure detected by the pressure sensor when the circulation pump is operating and the rotation speed of the circulation pump detected by the rotation speed detection means, and calculates the correction constant by the formula (P1-P0) / (R1×R1), where P0 is the non-circulating pressure, P1 is the circulating pressure, and R1 is the rotation speed of the circulation pump. Water level change detection system. [Effects of the Invention]

[0007] According to the present disclosure, in a water level change detection system that is placed in a circulation path that circulates water in a bathtub and detects changes in the water level, it is possible to provide a water level change detection system that can accurately detect changes in the water level in the bathtub even while water is circulating by correcting the measurement value of the pressure sensor according to the flow rate of the circulation path. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a configuration diagram of a water level change detection system according to a first embodiment. [Figure 2]10 is a modified example of the configuration diagram of the water level change detection system according to the first embodiment. [Figure 3] FIG. 2 is a configuration diagram of a calculation unit according to the first embodiment. [Figure 4] 4 is a flowchart illustrating a method for calculating a correction constant according to the first embodiment. [Figure 5] 10 is a flowchart showing calculation of a corrected pressure and bathing entry / exit determination. [Figure 6] 10 is a graph showing fluctuations in corrected pressure during bathing. [Figure 7] 10 is a graph showing the relationship between the rotation speed of a circulation pump and the passage of time. [Figure 8] 1 is a graph showing the relationship between the rotation speed of a circulation pump and the passage of time (when the rotation speed changes stepwise). [Figure 9] FIG. 10 is a configuration diagram of a water level change detection system according to a second embodiment. [Figure 10] FIG. 10 is a configuration diagram of a calculation unit according to a second embodiment. [Figure 11] 10 is a flowchart illustrating a method for calculating a correction constant according to the second embodiment. [Figure 12] 10 is a flowchart showing calculation of a corrected pressure and bathing entry / exit determination according to the second embodiment. [Figure 13] FIG. 10 is a configuration diagram of a water level change detection system according to a third embodiment. [Figure 14] FIG. 11 is a configuration diagram of a calculation unit according to a third embodiment. [Figure 15] 10 is a flowchart illustrating a method for calculating a correction constant according to the fourth embodiment. [Figure 16] 10 is a flowchart showing calculation of a corrected pressure and bathing entry / exit determination according to the fourth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] The following description will discuss embodiments of the present disclosure with reference to the accompanying drawings. In each drawing, identical or corresponding parts are designated by the same reference numerals, and redundant descriptions are appropriately simplified or omitted. The present disclosure is not limited to the following embodiments, and any of the components of the embodiments may be modified, combined, or omitted without departing from the spirit of the present disclosure.

[0010] Embodiment 1 FIG. 1 is a configuration diagram of a water level change detection system according to a first embodiment of the present disclosure. The water level change detection system 1 includes a circulation path 3 through which bath water 4 circulates in a bathtub 2, a pressure sensor 5, and a circulation pump 6. The bathtub 2 and the circulation path 3 are connected by an inlet 8 that draws bath water 4 into the circulation path 3 and an outlet 9 through which water that has passed through the circulation path 3 returns to the bathtub 2. The system also includes a flow sensor 7, which is a flow rate detection means for detecting the flow rate of the circulation path 3. A heater 11 may be provided in the circulation path 3. The heater 11 heats the bath water 4 circulated through the circulation path 3. By driving the circulation pump 6, the cooled bath water 4 is drawn into the circulation path 3 through the inlet 8, heated by the heater 11, and returned to the bathtub 2, enabling reheating operation. The heater 11 may be, for example, an electric heater, a gas boiler, or a heat pump unit. Furthermore, a portion of the circulation path 3 may branch off, and an on-off valve 13 may be provided at the connection point where it is connected to a hot water storage tank or a water pipe, so that hot water can be supplied to the bathtub 2 through the circulation path 3. A control unit 12 may also be provided to control the operation of the circulation pump 6, heater 11, and on-off valve 13. The water level change detection system 1 of this embodiment is applicable to, for example, a storage-type hot water heater or an instantaneous hot water heater equipped with a hot water storage tank.

[0011] Pressure sensor 5 measures the water pressure at pressure detection position 5a, which is a point inside circulation path 3. The position in circulation path 3 where pressure sensor 5 measures the pressure is referred to as pressure detection position 5a. Pressure sensor 5 is, for example, a semiconductor pressure sensor. When water is not circulating in circulation path 3, the water pressure at pressure detection position 5a changes depending on the water level in bathtub 2. Therefore, the water level in bathtub 2 can be estimated from the pressure detected by pressure sensor 5. Furthermore, by detecting a change in the value of pressure sensor 5, it is possible to detect a change in the water level in bathtub 2.

[0012] Even if the water level in the bathtub 2 does not change, while water in the bathtub 2 is circulating through the circulation path 3, the value of the pressure sensor 5 is different from when it is not circulating. This is because the operation of the circulation pump 6 causes water to flow through the piping, resulting in a loss of pressure in the piping. Therefore, while the circulation pump 6 is operating, an accurate water level cannot be detected from the value of the pressure sensor 5. When changes in the water level in the bathtub 2 are used to determine whether a user has entered or left the bath, the increase or decrease in pressure due to changes in the water level caused by entering or leaving the bath is greatly affected by the loss of pressure in the piping, making it impossible to accurately determine whether a user has entered or left the bath.

[0013] The circulation pump 6 is, for example, a centrifugal pump or a diffuser pump that includes a motor and gears. When the motor of the circulation pump 6 rotates, water circulates in the circulation path 3, and bath water 4 is sucked in through the suction port 8. When the motor of the circulation pump 6 is operated, the motor rotation speed is constant. Alternatively, the motor rotation speed can be changed in stages.

[0014] A flow sensor 7, which is a flow rate detection means, is provided on the piping of the circulation path 3. The flow sensor 7 detects the flow rate of water flowing through the circulation path 3 by the circulation pump 6. The detected value of the flow sensor 7 is sent to the calculation unit 20. The flow sensor 7 is, for example, a flow meter such as a thermal flow meter or an electromagnetic flow meter.

[0015] FIG. 3 is a block diagram of the calculation unit 20 according to the first embodiment. The calculation unit 20 includes at least one processor and at least one memory. The calculation unit 20 includes a correction value calculation unit 21, which calculates a correction value that increases as the flow rate in the circulation path 3 increases, and a pressure correction unit 22, which calculates a corrected pressure by adding or subtracting the correction value to the pressure detected by the pressure sensor 5. The calculation unit 20 also includes a bathing / exit determination unit 23, which uses the corrected pressure to detect changes in the water level and determine whether the user has entered or exited the bath. The bathing / exit determination unit 23 functions as a water level change detection unit that detects changes in the water level in the bathtub 2 using the corrected pressure. The correction value calculation unit 21, the pressure correction unit 22, and the bathing / exit determination unit 23 are components comprised of software, firmware, or a combination of software and firmware. The processor is also referred to as a CPU (Central Processing Unit), processing device, arithmetic unit, microprocessor, microcomputer, or DSP. The memory may be composed of, for example, non-volatile or volatile semiconductor memory such as RAM, ROM, flash memory, EPROM, or EEPROM. The calculation unit 20 is communicatively connected to the pressure sensor 5 and acquires the pressure detected by the pressure sensor 5. The calculation unit 20 is communicatively connected to the circulation pump 6 and acquires the operating status of the circulation pump 6. The calculation unit 20 is communicatively connected to the flow sensor 7 and acquires the flow rate of water flowing through the circulation path 3 detected by the flow sensor 7. The calculation unit 20 is connected to the control unit 12, which controls the operation of the circulation pump 6, the heater 11, and the on-off valve 13, and may be configured to transmit the corrected pressure calculated by the pressure correction unit 22 and the bathing entry / exit determination results by the bathing entry / exit determination unit 23 to the control unit 12. Alternatively, the calculation unit 20 may be integrated with the control unit 12, with the calculation unit 20 being part of the control unit 12.

[0016] The pressure correction unit 22, which serves as a pressure correction means, adds or subtracts a correction value from the pressure detected by the pressure sensor 5 while the circulation pump 6 is operating to obtain the corrected pressure. The corrected pressure is a pressure corrected by taking into account the change in the value of the pressure sensor 5 due to the flow of bath water through the circulation path 3 caused by the operation of the circulation pump 6. In other words, the corrected pressure can be considered to be equal to the pressure detected by the pressure sensor 5 when bath water 4 is not circulating through the circulation path 3. The pressure detected by the pressure sensor 5 when bath water 4 is not circulating through the circulation path 3 changes depending on the water level in the bathtub 2. Therefore, the water level in the bathtub 2 can be determined from the pressure detected by the pressure sensor 5 when bath water 4 is not circulating through the circulation path 3 or the corrected pressure. The correction value corresponds to the piping pressure loss caused by water flowing through the circulation path 3, and becomes larger as the circulation flow rate increases. The correction value is calculated by the correction value calculation unit 21. The calculation method will be described later.

[0017] As shown in FIG. 1 , when the circulation pump 6 is located upstream of the pressure detection position 5a where the pressure sensor 5 detects the pressure in the direction of water flow from the bathtub, the water pressure at the pressure detection position 5a increases by the amount of the piping pressure loss from the pressure detection position 5a to the outlet 9 of the bathtub 2, compared to when the water is not circulating. Therefore, the pressure correction unit 22 subtracts a correction value from the pressure detected by the pressure sensor 5 to obtain the corrected pressure. Also, FIG. 2 shows a modified configuration of the water level change detection system according to the first embodiment. In FIG. 2 , when the suction port 8 is the starting point, the circulation pump 6 is located downstream of the position where the pressure sensor 5 detects the pressure in the direction of water flow from the bathtub. When the suction port 8 is the starting point, when the pressure sensor 5 is located upstream of the circulation pump 6, the water pressure at the pressure detection position 5a decreases by the amount of the piping pressure loss from the suction port 8 of the bathtub 2 to the pressure sensor 5, compared to when the water is not circulating. Therefore, the pressure correction unit 22 adds a correction value to the pressure detected by the pressure sensor 5 to obtain the corrected pressure.

[0018] Correction value calculation unit 21, which is a means for calculating a correction value, calculates a correction value from the flow rate of bath water 4 flowing through circulation path 3 detected by flow rate sensor 7. It is known that the correction value, which corresponds to the pipe pressure loss, is proportional to the square of the flow rate. Equation 1 is a calculation formula for the corrected pressure when, as shown in Figure 1, suction port 8 is the starting point and circulation pump 6 is located upstream of pressure detection position 5a where pressure sensor 5 detects pressure in the direction of water flow from the bathtub. In this case, the corrected pressure is found by subtracting the correction value from the detection value Pa of pressure sensor 5. In Equation 1, the corrected pressure is Pc, the pressure detected by pressure sensor 5 is Pa, and the flow rate of bath water flowing through circulation path 3 when Pa is detected is V. The correction value is k x V 2 The correction value k is a correction constant that is a proportional constant of the correction value. The correction constant k is a value that changes depending on the length and shape of the piping from the pressure detection position 5a to the outlet 9 of the bathtub 2. An appropriate value for the correction constant k is set in advance in the correction value calculation unit 21. Alternatively, the correction constant k is calculated in advance by a method described below and set in the correction value calculation unit 21.

[0019]

number

[0020] FIG. 4 is a flowchart showing a method for calculating the correction constant k. The correction constant k is calculated in advance before detecting a change in the water level and set in the correction value calculation unit 21. The correction constant calculation method will be explained using FIG. 4. Calculation of the correction constant k begins when bath water is present in the bathtub 2 and the circulation path 3 is filled with water. First, in step S101, when the circulation pump 6 is not operating, i.e., when water is not flowing in the circulation path 3, the correction value calculation unit 21 acquires the non-circulation pressure P0 detected by the pressure sensor 5 when bath water is not circulating in the circulation path 3. Next, the process proceeds to step S102.

[0021] In step S102, the correction value calculation unit 21 drives the circulation pump 6 to circulate the bath water through the circulation path 3. Next, the process proceeds to step S103.

[0022] In step S103, the correction value calculation unit 21 acquires the circulation pressure P1 detected by the pressure sensor 5. At this time, taking into consideration the start-up time of the circulation pump 6 driven in step S103, the circulation pressure P1 may be acquired after a certain period of time has elapsed. Next, the process proceeds to step S104.

[0023] In step S104, the correction value calculation unit 21 acquires the flow rate V1 of the water flowing through the circulation path 3 detected by the flow rate sensor 7. Next, the process proceeds to step S105.

[0024] In step S105, the correction value calculation unit 21 calculates the correction constant k using the non-circulating pressure P0 detected by the pressure sensor 5 when bath water is not circulating in the circulation path 3, the circulating pressure P1 detected by the pressure sensor 5 when bath water is not circulating in the circulation path 3, and the flow rate V1 in the circulation path 3 when P1 is detected. The correction constant k can be calculated using Equation 2. The calculated correction constant k is saved in the memory (not shown) of the calculation unit 20, and is read and used when the pressure correction unit 22 performs pressure correction. This completes the calculation process for the correction constant k.

[0025]

number

[0026] By actually operating the water level change detection system 1 as shown in FIG. 4 and calculating the correction constant k, it is possible to determine the correction constant k, which differs depending on the installation environment, and to calculate a highly accurate correction value.

[0027] Correction constant k is a value that varies depending on the length and shape of the piping from pressure detection position 5a to outlet 9 of bathtub 2, and also on factors such as clogging of the piping over time. Therefore, it is desirable to perform the flow of Fig. 4 every time a certain period of time (e.g., one year) has passed, calculate correction constant k, and update the value of correction constant k stored in the memory (not shown) of calculation unit 20. Alternatively, calculation unit 20 may count the number of times circulating pump 6 is driven, and when the number exceeds a certain number of times (e.g., 1,000 times), perform the flow of Fig. 4 to calculate correction constant k and update the value of correction constant k stored in the memory (not shown) of calculation unit 20.

[0028] FIG. 5 is a flowchart of the calculation of the corrected pressure and the bathing entry / exit determination. An example of a method for calculating the corrected pressure by the pressure correction unit 22 and for determining bathing entry / exit using the corrected pressure by the bathing entry / exit determination unit 23 will be described using FIG. 5. When the bathing entry / exit determination process starts, the calculation unit 20 first determines in step S201 whether a certain period of time has elapsed. For this purpose, the calculation unit 20 has a timer (not shown). Alternatively, the calculation unit 20 is connected to the timer so that it can communicate with the timer. The reason for determining in step S201 whether a certain period of time has elapsed is to perform the process of calculating the corrected pressure and the process of determining bathing entry / exit from the corrected pressure at regular time intervals. Once the certain period of time has elapsed, the process proceeds to step S202.

[0029] In step S202, the calculation unit 20 acquires the pressure Pa at the pressure detection position 5a detected by the pressure sensor 5. Next, the process proceeds to step S203.

[0030] In step S203, the calculation unit 20 acquires the flow rate V of water flowing through the circulation path 3 detected by the flow rate sensor 7. Next, the process proceeds to step S204.

[0031] In step S204, correction value calculation unit 21 of calculation unit 20 calculates a correction value using the flow rate V, and pressure correction unit 22 calculates a corrected pressure Pc using the correction value. The calculation of the correction value and the corrected pressure is performed using Equation 1. At this time, if the flow rate V is 0, that is, if the circulation pump 6 is not operating and water is not flowing in the circulation path 3, the corrected pressure Pc is set to the pressure P detected by pressure sensor 5. Note that, due to an error in the flow rate sensor 7, the flow rate V detected by the flow rate sensor 7 may not be 0 when the circulation pump 6 is not operating. Therefore, if the flow rate V is equal to or less than a threshold value, the corrected pressure Pc may be set to the pressure P detected by pressure sensor 5. Next, proceed to step S205.

[0032] In step S205, the bathing entry / exit determination unit 23 of the calculation unit 20 determines whether the previous pressure value Pf is stored in the memory of the calculation unit 20. The previous pressure value Pf is the value of the corrected pressure when the corrected pressure was calculated the last time in association with the bathing entry / exit determination process. If there is no previous pressure value Pf, it means that this is the first time the bathing entry / exit determination process has been performed at regular intervals. Since the bathing entry / exit determination process is performed according to changes in pressure, if there is no previous pressure value Pf, bathing entry / exit determination cannot be made. If it is determined that there is no previous pressure value Pf, proceed to step S210. If it is determined that there is a previous pressure value Pf, proceed to step S206.

[0033] In step S206, the bathing entry / exit determination unit 23 of the calculation unit 20 determines whether the value obtained by subtracting the corrected pressure Pc from the previous pressure value Pf is greater than the bathing reference value. The bathing reference value is a preset value corresponding to the change in pressure detected by the pressure sensor 5 when a person bathes in the bath water 4 in the bathtub 2 while the circulation pump 6 is not operating, and is stored in the memory of the calculation unit 20. The bathing reference value varies depending on the shape of the bathtub 2. If the value obtained by subtracting the corrected pressure Pc from the previous pressure value Pf is not greater than the bathing reference value, proceed to step S208. If the value obtained by subtracting the corrected pressure Pc from the previous pressure value Pf is greater than the bathing reference value, proceed to step S207, where the bathing flag is set to ON. The bathing flag is a variable stored in the bathing entry / exit determination unit 23. It is set to ON when the bathing entry / exit determination process determines that the person is bathing, and to OFF when the person is not bathing. At this time, the calculation unit 20 may also store the time when the bathing flag was set to ON. Next, the process proceeds to step S208.

[0034] In step S208, the bathing entry / exit determination unit 23 of the calculation unit 20 determines whether the value obtained by subtracting the previous pressure value Pf from the corrected pressure Pc is greater than the bathing reference value. If the value obtained by subtracting the previous pressure value Pf from the corrected pressure Pc is not greater than the bathing reference value, the process proceeds to step S210. If the value obtained by subtracting the previous pressure value Pf from the corrected pressure Pc is greater than the bathing reference value, the process proceeds to step S209, where the bathing flag is turned OFF. At this time, the calculation unit 20 may store the time when the bathing flag was turned OFF. Next, the process proceeds to step S210.

[0035] In step S210, the bathing entry / exit determination unit 23 of the calculation unit 20 substitutes the current corrected pressure value Pc for the previous pressure value Pf. Next, the process returns to step S201, and the bathing entry / exit determination process is repeated at regular intervals.

[0036] By following the above flow, the corrected pressure can be calculated even when the circulation pump 6 is operating. The corrected pressure can be considered to be equal to the pressure detected by the pressure sensor 5 when bath water is not circulating in the circulation path 3. Therefore, the corrected pressure can be used to detect changes in the water level in the bathtub 2.

[0037] Furthermore, because the correction pressure changes in response to changes in the water level in the bathtub 2, the correction pressure can be used to determine whether a user is entering or leaving the bath, even when the circulation pump 6 is operating. The results of the bathing entry / exit determination can be used to notify notification means, such as a remote control or external communication terminal, that cooperates with the water level change detection system of the present disclosure, which can be used, for example, to monitor bathing by elderly people or children. Furthermore, by having the determination results used as information by control means that controls other devices via an external communication network, the results can be used as an information source for coordinated operations that trigger the start or stop of other devices, the implementation of special operations, or the detection of dangerous conditions and the like and reporting them to third parties.

[0038] Furthermore, bathing entry / exit determination unit 23 may use the average value of the corrected pressure calculated over a certain period of time (hereinafter referred to as the averaging time) to determine whether or not a bather has entered or left the bath. Because the value detected by pressure sensor 5 during circulation fluctuates due to air bubbles in circulation path 3 and variations in the operation of circulation pump 6, using the average value of the corrected pressure over the averaging time can reduce the effects of pressure fluctuations other than water level fluctuations. In step S201 of FIG. 5, it is determined whether a certain period of time has elapsed so that the process of calculating the corrected pressure is performed at regular intervals. When using the average value of the corrected pressure over the averaging time to determine whether or not a bather has entered or left the bath, the averaging time should be set sufficiently longer than the regular interval for calculating the corrected pressure. For example, if the corrected pressure is calculated every minute, the averaging time should be set to five minutes, and the average value of five calculated corrected pressures should be calculated.

[0039] Figure 6 is a graph showing the fluctuations in corrected pressure during bathing. In Figure 6, T1, T2, T3, and T4 represent the averaging times. P1, P2, P3, and P4 are the average corrected pressures at T1, T2, T3, and T4, respectively. Time t represents the time when bathing began. At T1 and T2, before bathing began, the average corrected pressures P1 and P2 are nearly equal. In the example in Figure 6, bathing began midway through T3. During the averaging time T3, which includes the time t when bathing began, the average corrected pressure P3 approaches either the corrected pressure before bathing or the corrected pressure during bathing, as shown in Figure 6(a) or (b), depending on the timing of bathing. When determining whether or not a person has started bathing, if the difference between the average corrected pressure for the previous averaging time and the average corrected pressure for the current averaging time exceeds the bathing reference value, it is determined that the person has started bathing. In this case, the bathing reference value should be set to half the amount of pressure change detected by the pressure sensor 5 when one person is bathing. As a result, in the case of (a) in Figure 6, bathing is determined based on the difference between P4 and P3, and in the case of (b) in Figure 6, bathing is determined based on the difference between P3 and P2.

[0040] Alternatively, the bathing reference value may be set based on the amount of change in pressure detected by pressure sensor 5 when one person is bathing, and it may be determined that a person has started bathing when the difference between the average corrected pressure for the two previous average calculation times and the average corrected pressure for the current average calculation time exceeds the bathing reference value. As a result, in both cases of Figure 6(a) and (b), it is determined that a person has started bathing when the difference between P2 and P4 exceeds the bathing reference value.

[0041] The bathing entry / exit determination unit 23 may refrain from bathing entry / exit determination for a certain period of time after the rotation speed of the circulation pump 6 motor reaches or exceeds a predetermined rated rotation speed, or after the circulation flow rate reaches or exceeds the flow rate when the circulation pump 6 reaches the rated rotation speed. Figure 7 is a graph showing the relationship between the rotation speed of the circulation pump 6 and the passage of time. When the circulation pump 6 receives an operation start signal from the control unit 12 to start operation of the circulation pump 6, it operates at the rated rotation speed. However, when the circulation pump 6 receives the operation start signal at time t0 in Figure 7, it takes time to reach the rated rotation speed, as shown by time t1. The measurement value of the pressure sensor 5 becomes unstable while the rotation speed of the circulation pump 6 is changing (between time t0 and time t1 in Figure 7) and immediately after the rotation speed of the circulation pump 6 reaches the rated rotation speed (between time t1 and time t2 in Figure 7). Therefore, the calculation unit 20 does not perform bathing entry / exit determination for a certain period of time after the circulation pump 6 receives an operation start signal from the control unit 12 and the rotation speed reaches or exceeds the rated rotation speed, or the circulation flow rate reaches or exceeds the flow rate when the circulation pump 6 reaches the rated rotation speed. This prevents erroneous bathing entry / exit determination. Alternatively, the time until the circulation pump 6 reaches the rated rotation speed after receiving the operation start signal from the control unit 12 (between time t0 and time t1 in FIG. 7) and the time until the value of the pressure sensor 5 stabilizes (between time t1 and time t2 in FIG. 7) can be set as the certain period of time, and the calculation unit 20 may not perform bathing entry / exit determination for a certain period of time after the circulation pump 6 receives an operation start signal from the control unit 12.

[0042] Furthermore, the measurement value of the pressure sensor 5 becomes unstable even when the circulation pump 6 is in the process of stopping its operation. Assume that the circulation pump 6 receives a stop signal from the control unit 12 at t3 in FIG. 7 to stop the operation of the circulation pump 6. The measurement value of the pressure sensor 5 becomes unstable until the circulation pump 6 stops rotating (between time t3 and time t4 in FIG. 7) and immediately after the circulation pump 6 stops rotating (between time t4 and time t5 in FIG. 7). Therefore, the calculation unit 20 does not perform bathing entry / exit determination for a certain period of time after the circulation pump 6 receives the stop signal from the control unit 12 and stops rotating, or after the circulation flow rate becomes zero. This prevents erroneous bathing entry / exit determination. In addition, the time from when the circulation pump 6 receives the operation stop signal from the control unit 12 until the circulation pump 6 stops (between time t3 and time t4 in Figure 7) to when the value of the pressure sensor 5 stabilizes (between time t4 and time t5 in Figure 7) can be set as a fixed time, and the calculation unit 20 may not perform bathing entry / exit judgment for a fixed time after the circulation pump 6 receives the operation stop signal from the control unit 12.

[0043] In addition, multiple rated rotation speeds may be set for the circulation pump 6. Figure 8 is a graph showing the relationship between the rotation speed of the circulation pump and the passage of time (when the rotation speed changes stepwise). Assume that at time t0 in Figure 8, the circulation pump 6 receives a rotation speed control signal from the control unit 12 to control the rotation speed of the circulation pump 6 to a first rated rotation speed. While the rotation speed of the circulation pump 6 is changing (between time t0 and time t1 in Figure 8) or immediately after the rotation speed of the circulation pump 6 reaches the rated rotation speed (between time t1 and time t2 in Figure 8), the measurement value of the pressure sensor 5 becomes unstable. Therefore, the calculation unit 20 does not perform bathing entry / exit determination for a certain period of time after the rotation speed of the circulation pump 6 receives an operation start signal from the control unit 12 and becomes equal to or greater than the rated rotation speed, or the circulation flow rate becomes equal to or greater than the flow rate when the circulation pump 6 reaches the rated rotation speed. This prevents erroneous bathing entry / exit determination. In addition, the time from when the circulation pump 6 receives the rotation speed control signal from the control unit 12 until the circulation pump 6 reaches the rotation speed specified by the rotation speed control signal (between time t0 and time t1 in Figure 8) and the time until the value of the pressure sensor 5 stabilizes (between time t1 and time t2 in Figure 8) can be set as a fixed time, and the calculation unit 20 may not perform bathing entry / exit judgment for a fixed time after the circulation pump 6 receives the rotation speed control signal from the control unit 12.

[0044] As described above, the water level change detection system 1 of this embodiment is connected to the bathtub 2 and installed in the circulation path 3 through which the water in the bathtub 2 circulates. It includes: a circulation pump 6 that circulates the water in the bathtub 2; a pressure sensor 5 that detects the pressure at a pressure detection position 5a inside the circulation path 3; a correction value calculation means that calculates a correction value that increases as the flow rate in the circulation path 3 increases; a pressure correction means that calculates a corrected pressure by subtracting the correction value from the pressure detected by the pressure sensor 5 while the circulation pump 6 is operating if the circulation pump 6 is installed upstream of the pressure detection position 5a in the direction of water flow from the bathtub 2 in the circulation path 3; or by adding the correction value to the pressure detected by the pressure sensor 5 while the circulation pump 6 is operating if the circulation pump 6 is installed downstream of the pressure detection position 5a in the direction of water flow from the bathtub 2 in the circulation path 3; a water level change detection means that detects changes in the water level in the bathtub 2 based on the corrected pressure; and a bathing entry / exit determination means that determines whether a bather has started bathing or left the bath when the corrected pressure calculated by the pressure correction means has changed by more than a bathing reference value.

[0045] In this way, the correction value calculation means calculates a correction value that becomes larger the greater the flow rate in the circulation path 3 while the circulation pump 6 is operating, and the pressure correction means calculates the corrected pressure from the pressure detected by the pressure sensor 5 and the correction value, thereby making it possible to accurately detect changes in the water level of the bathtub 2 even when the circulation pump 6 is operating and bath water is flowing in the circulation path 3.

[0046] The bathing entry / exit determination means acquires the corrected pressure calculated by the pressure correction means at regular intervals, and determines that bathing has started if the corrected pressure is greater than the previously acquired corrected pressure by at least the bathing reference value, and determines that bathing has ended if the corrected pressure is less than the previously acquired corrected pressure by at least the bathing reference value. This allows bathing entry / exit determination to be made using the corrected pressure even when bath water is flowing in the circulation path 3.

[0047] The water level change detection system 1 further includes a flow rate detection means for detecting the flow rate of water flowing in the circulation path 3 by the circulation pump 6, and the correction value calculation means calculates a correction value based on the flow rate detected by the flow rate detection means. This makes it possible to calculate a correction value corresponding to the piping pressure loss caused by the water circulating in the circulation path 3.

[0048] The correction value is the product of the square of the flow rate detected by the flow rate detection means and the correction constant. Since the piping pressure loss caused by the water circulating in the circulation path 3 is proportional to the square of the flow rate, the correction value can be calculated with high accuracy by multiplying the square of the flow rate in the circulation path 3 detected by the flow rate detection means and the correction constant.

[0049] Furthermore, the correction constant increases as the difference between the non-circulating pressure detected by the pressure sensor 5 when the circulation pump 6 is not operating and the circulating pressure detected by the pressure sensor 5 when the circulation pump 6 is operating increases. This characteristic allows the correction constant, which is the proportionality constant of the correction value, to be set with high precision.

[0050] Furthermore, the pressure correction means acquires the non-circulating pressure detected by the pressure sensor 5 when the circulation pump 6 is not operating, acquires the circulating pressure detected by the pressure sensor 5 when the circulation pump 6 is operating and the circulating flow rate detected by the flow rate detection means, and calculates a correction constant using the formula (P1-P0) / (V1×V1) where P0 is the non-circulating pressure, P1 is the circulating pressure, and V1 is the circulating flow rate. In this way, the water level change detection system 1 can accurately calculate the correction value by calculating the correction constant before detecting a water level change.

[0051] The pressure correction means updates the correction constant at regular intervals, so that even if the correction constant changes due to clogging of the piping that forms the circulation path 3 over time, the new correction constant can be set.

[0052] The bathing entry / exit determination means may also determine whether a bather has started bathing by calculating the average value of the corrected pressure during each predetermined averaging time, determining that a bather has started bathing when the average value of the corrected pressure is greater than the previous average value of the corrected pressure by at least the bathing reference value, and determining that a bather has left bathing when the average value of the corrected pressure is smaller than the previous average value of the corrected pressure by at least the bathing reference value. By using the average value of the corrected pressure during the averaging time, the effects of pressure fluctuations other than water level fluctuations can be suppressed.

[0053] The water level change detection system 1 further includes a control unit 12 that controls the operation of the circulation pump 6, and the bathing entry / exit determination means does not make a bathing entry / exit determination for a certain period of time after the circulation pump 6 receives an operation start signal or operation stop signal from the control unit 12. This prevents erroneous bathing entry / exit determination.

[0054] The water level change detection system 1 further includes a control unit 12 that controls the operation of the circulation pump 6, and the bathing entry / exit determination means does not make a bathing entry / exit determination for a certain period of time after the circulation pump 6 receives a rotation speed control signal from the control unit 12. This prevents erroneous bathing entry / exit determination.

[0055] Embodiment 2 FIG. 9 is a configuration diagram of a water level change detection system according to a second embodiment of the present disclosure. In the water level change detection system according to the first embodiment, the correction value is calculated using the measurement value of the flow rate sensor 7. In the second embodiment, the flow rate sensor 7 is not included. Note that a description of the same parts of the present embodiment as those of the first embodiment will be omitted. The correction value used to calculate the corrected pressure increases as the flow rate in the circulation path 3 increases. The flow rate is determined by the rotation speed of the circulation pump 6. Therefore, in this embodiment, the correction value is calculated from the rotation speed of the circulation pump.

[0056] The flow rate V1 of bath water flowing through circulation path 3 is proportional to the rotation speed R of circulation pump 6. Since the correction value corresponding to the piping pressure loss is proportional to the square of the flow rate, it can be said that the correction value is proportional to the square of the rotation speed R of circulation pump 6. Equation 3 is a calculation formula for the corrected pressure when circulation pump 6 is located upstream of pressure detection position 5a where pressure sensor 5 detects pressure in the direction of water flow from the bathtub, with suction port 8 as the starting point, as shown in Figure 9. In this case, the corrected pressure is calculated by subtracting the correction value from the circulation pressure P1. In equation 3, the correction pressure is Pc, the non-circulation pressure detected by pressure sensor 5 when bath water is not circulating in circulation path 3 is P0, the circulation pressure detected by pressure sensor 5 when bath water is circulating in circulation path 3 is P1, and the rotation speed of circulation pump 6 when P1 is detected is R. The correction value is k x R 2 The correction value k is a correction constant that varies depending on the length and shape of the piping from pressure detection position 5a to outlet 9 of bathtub 2. An appropriate value for correction constant k may be set in advance in correction value calculation unit 21. Correction constant k may also be calculated by operating water level change detection system 1 during initial setup of water level change detection system 1, for example.

[0057]

number

[0058] Fig. 10 is a configuration diagram of the calculation unit 20 according to the second embodiment. The same components as those in Fig. 3, which is a configuration diagram of the calculation unit 20 according to the first embodiment, are assigned the same reference numerals. In Fig. 10, the calculation unit 20 further includes a rotation speed acquisition unit 24 as a rotation speed acquisition means for acquiring the rotation speed of the circulation pump 6. The rotation speed acquisition unit 24 is configured to be able to acquire the rotation speed of the circulation pump 6 from the circulation pump 6. Alternatively, the calculation unit 20 may be configured to be able to acquire the rotation speed R of the circulation pump 6 from the control unit 12 that controls the circulation pump 6.

[0059] FIG. 11 is a flowchart showing a method for calculating the correction constant k according to the second embodiment. The method for calculating the correction constant according to the second embodiment will be described with reference to FIG. 11. Calculation of the correction constant k begins when bath water is present in the bathtub 2 and the circulation path 3 is filled with water. First, in step S301, when the circulation pump 6 is not operating, i.e., when water is not flowing in the circulation path 3, the correction value calculation unit 21 acquires the non-circulating pressure P0 detected by the pressure sensor 5 when bath water is not circulating in the circulation path 3. Next, the process proceeds to step S302.

[0060] In step S302, the correction value calculation unit 21 drives the circulation pump 6 to circulate the bath water through the circulation path 3. Next, the process proceeds to step S303.

[0061] In step S303, the correction value calculation unit 21 acquires the circulation pressure P1 detected by the pressure sensor 5. At this time, taking into consideration the start-up time of the circulation pump 6 driven in step S303, the circulation pressure P1 may be acquired after a certain period of time has elapsed. Next, the process proceeds to step S304.

[0062] In step S304, correction value calculation unit 21 acquires the rotation speed R of circulation pump 6. In this embodiment, calculation unit 20 has a rotation speed acquisition means, and is configured so that calculation unit 20 can acquire the rotation speed R of circulation pump 6 from circulation pump 6. Alternatively, calculation unit 20 may be configured so that it can acquire the rotation speed R of circulation pump 6 from control unit 12 that controls circulation pump 6. Next, proceed to step S305.

[0063] In step S305, the correction value calculation unit 21 calculates the correction constant k using the non-circulation pressure P0, the circulation pressure P1, and the rotation speed R of the circulation pump 6. The flow rate V1 of the circulation path 3 is proportional to the rotation speed R of the circulation pump 6. Therefore, the correction constant k can be calculated using Equation 4. The calculated correction constant k is saved in the memory (not shown) of the calculation unit 20, and is read and used when the pressure correction unit 22 performs pressure correction. This completes the calculation process of the correction constant k.

[0064]

number

[0065] By actually operating the water level change detection system 1 as shown in FIG. 11 and calculating the correction constant k, it is possible to determine the correction constant k that differs depending on the installation environment, and to calculate a highly accurate correction value.

[0066] FIG. 12 is a flowchart of the calculation of the corrected pressure and the bathing entry / exit determination according to the second embodiment. An example of a method for calculating the corrected pressure by the pressure correction unit 22 and for determining whether the user has entered or left the bath using the corrected pressure by the bathing entry / exit determination unit 23 will be described using FIG. 12. In FIG. 12, the same steps as those in FIG. 5, which is a flowchart of the calculation of the corrected pressure and the bathing entry / exit determination according to the first embodiment, are denoted by the same reference numerals. Some of the explanations for the steps similar to those in FIG. 5 will be omitted. This embodiment differs from FIG. 5 in that the rotation speed of the circulation pump 6 is used to calculate the corrected pressure Pc.

[0067] First, the calculation unit 20 determines whether or not a certain time has elapsed in step S201. If the certain time has elapsed, the process proceeds to step S202.

[0068] In step S202, the calculation unit 20 acquires the pressure P at the pressure detection position 5a detected by the pressure sensor 5. Next, the process proceeds to step S403.

[0069] In step S403, the calculation unit 20 acquires the rotation speed R of the circulation pump 6. Next, the process proceeds to step S404.

[0070] In step S404, correction value calculation unit 21 of calculation unit 20 calculates a correction value using the rotation speed R of circulation pump 6, and pressure correction unit 22 calculates the corrected pressure Pc using the correction value. The calculation of the correction value and the corrected pressure is performed using Equation 3. At this time, if the rotation speed R of circulation pump 6 is 0, that is, if the circulation pump 6 is not operating and water is not flowing in the circulation path 3, the corrected pressure Pc is set to the pressure P detected by pressure sensor 5. Next, proceed to step S205.

[0071] In step S205, the bathing entry / exit determination unit 23 of the calculation unit 20 determines whether the previous pressure value Pf is stored in the memory of the calculation unit 20. If it is determined that the previous pressure value Pf is not stored, the process proceeds to step S210. If it is determined that the previous pressure value Pf is stored, the process proceeds to step S206.

[0072] In step S206, the bathing entry / exit determination unit 23 of the calculation unit 20 determines whether the value obtained by subtracting the corrected pressure Pc from the previous pressure value Pf is greater than the bathing reference value. If the value obtained by subtracting the corrected pressure Pc from the previous pressure value Pf is not greater than the bathing reference value, the process proceeds to step S208. If the value obtained by subtracting the corrected pressure Pc from the previous pressure value Pf is greater than the bathing reference value, the process proceeds to step S207, where the bathing flag is turned ON. At this time, the calculation unit 20 may store the time when the bathing flag was turned ON. Next, the process proceeds to step S208.

[0073] In step S208, the bathing entry / exit determination unit 23 of the calculation unit 20 determines whether the value obtained by subtracting the previous pressure value Pf from the corrected pressure Pc is greater than the bathing reference value. If the value obtained by subtracting the previous pressure value Pf from the corrected pressure Pc is not greater than the bathing reference value, the process proceeds to step S210. If the value obtained by subtracting the previous pressure value Pf from the corrected pressure Pc is greater than the bathing reference value, the process proceeds to step S209, where the bathing flag is turned OFF. At this time, the calculation unit 20 may store the time when the bathing flag was turned OFF. Next, the process proceeds to step S210.

[0074] In step S208, the bathing entry / exit determination unit 23 of the calculation unit 20 substitutes the current corrected pressure value Pc for the previous pressure value Pf. Next, the process returns to step S201, and the bathing entry / exit determination process is repeated at regular intervals.

[0075] By performing the above flow, the corrected pressure can be calculated using the rotation speed of the circulation pump 6 in the bathing entry / exit determination process of Figure 12. Therefore, the water level change detection system 1 according to this embodiment does not require the installation of a flow rate sensor 7, reducing costs, and the bathing entry / exit determination can be made using the corrected pressure even if bath water is circulating in the circulation path 3.

[0076] As described above, the water level change detection system 1 of this embodiment is connected to the bathtub 2 and installed in the circulation path 3 through which the water in the bathtub 2 circulates. The system comprises: a circulation pump 6 that circulates the water in the bathtub 2; a pressure sensor 5 that detects the pressure at a pressure detection position 5a inside the circulation path; a correction value calculation means that calculates a correction value that increases as the flow rate in the circulation path 3 increases; a pressure correction means that calculates a corrected pressure by subtracting the correction value from the pressure detected by the pressure sensor 5 while the circulation pump 6 is operating if the circulation pump is installed upstream of the pressure detection position 5a in the direction in which the water flows from the bathtub; or by adding the correction value to the pressure detected by the pressure sensor 5 while the circulation pump 6 is operating if the circulation pump 6 is installed downstream of the pressure detection position 5a in the direction in which the water flows from the bathtub 2; and a water level change detection means that detects changes in the water level in the bathtub based on the corrected pressure. The system further comprises a rotation speed detection means that detects the rotation speed of the motor of the circulation pump 6, and the correction value calculation means calculates the correction value based on the rotation speed of the circulation pump 6 detected by the rotation speed detection means.

[0077] In this way, by calculating the correction value from the rotation speed of the motor of the circulation pump 6, the water level change detection system 1 of this embodiment does not need to install a flow sensor 7, reducing costs and allowing the correction pressure to be calculated even if bath water is circulating in the circulation path 3.

[0078] The correction value is the product of the square of the rotation speed of the circulation pump 6 detected by the rotation speed detection means and the correction constant. The piping pressure loss caused by the circulation of water through the circulation path 3 is proportional to the square of the flow rate. Since the rotation speed of the motor of the circulation pump 6 is proportional to the flow rate, the correction value can be calculated with high accuracy by multiplying the square of the rotation speed of the circulation pump 6 and the correction constant.

[0079] Furthermore, the pressure correction means acquires the non-circulating pressure detected by the pressure sensor 5 when the circulation pump 6 is not operating, acquires the circulating pressure detected by the pressure sensor when the circulation pump 6 is operating and the rotation speed of the circulation pump 6 detected by the rotation speed detection means, and calculates a correction constant using the formula (P1-P0) / (R1×R1), where P0 is the non-circulating pressure, P1 is the circulating pressure, and R1 is the rotation speed of the circulation pump. In this way, the water level change detection system 1 can accurately calculate the correction value by calculating the correction constant before detecting a water level change.

[0080] Embodiment 3 FIG. 13 is a configuration diagram of a water level change detection system according to a third embodiment of the present disclosure. In the water level change detection system according to the first embodiment, the correction value was calculated using the measurement value of the flow rate sensor 7. In the second embodiment, the correction value was calculated using the rotation speed of the circulation pump 6. In the third embodiment, in addition to the pressure sensor 5 that measures the water pressure at the pressure detection position 5a, which is a point inside the circulation path 3, a second pressure sensor 5c is provided. In this embodiment, the calculation unit 20 calculates the flow rate V1 of the circulation path 3 using the measurement values ​​of the pressure sensor 5 and the second pressure sensor 5c. Note that a description of the same parts of this embodiment as those of the first embodiment will be omitted.

[0081] The second pressure sensor 5c measures the water pressure at a second pressure detection position 5b, which is a point located downstream of the pressure detection position 5a in the circulation path 3 in the direction of water flow from the bathtub, different from the pressure detection position 5a inside the circulation path 3. The second pressure sensor 5c is, for example, a semiconductor pressure sensor. The calculation unit 20 is communicatively connected to the second pressure sensor 5c and acquires the pressure detected by the second pressure sensor 5c.

[0082] The correction value used to calculate the corrected pressure increases as the flow rate in the circulation path 3 increases. Furthermore, the piping pressure loss is proportional to the square of the flow rate. The difference between the measurement value of the pressure sensor 5 and the measurement value of the second pressure sensor 5c corresponds to the piping pressure loss from the pressure detection position 5a to the second pressure detection position 5b in the circulation path 3. Therefore, in this embodiment, the flow rate in the circulation path 3 is calculated from the difference between the measurement value of the pressure sensor 5 and the measurement value of the second pressure sensor 5c, and the correction value is calculated.

[0083] Fig. 14 is a configuration diagram of a calculation unit 20 according to a third embodiment of the present disclosure. The same components as those in Fig. 3, which is a configuration diagram of the calculation unit 20 according to the first embodiment, are assigned the same reference numerals. In Fig. 14, the calculation unit 20 further includes a flow rate calculation unit 25 that calculates the flow rate from the measurements of the pressure sensor 5 and the second pressure sensor 5c. In this embodiment, the pressure sensor 5, the second pressure sensor 5c, and the flow rate calculation unit 25 function as a flow rate detection means.

[0084] A method for calculating the flow rate of the circulation path 3 from the measured value Pa of the pressure sensor 5 and the measured value Pb of the second pressure sensor 5c will be described. The piping pressure loss dP from the pressure detection position 5a to the second pressure detection position 5b is (Pa - Pb). In this case, no components that generate head, such as a pump, are placed between the pressure detection position 5a and the second pressure detection position 5b. If the flow rate of the circulation path 3 is V, the piping pressure loss dP is V 2 × m, where m is a coefficient determined by the length and shape of the piping from pressure detection position 5a to second pressure detection position 5b. m is experimentally determined in advance using the piping that constitutes circulation path 3 and is set in calculation unit 20. As a result, flow rate V can be calculated using the measurement value Pa of pressure sensor 5, the measurement value Pb of second pressure sensor 5c, and coefficient m, as shown in Equation 5.

[0085]

number

[0086] In this embodiment, the correction constant k is calculated using the same flow as in the flowchart of Fig. 4 in embodiment 1. The difference is that when the flow rate V1 is acquired in step S104, the flow rate calculation unit 25 of the calculation unit 20 calculates the flow rate according to Equation 5 using the measured value Pa of the pressure sensor 5, the measured value Pb of the second pressure sensor 5c, and the coefficient m.

[0087] In this embodiment, the calculation of the corrected pressure and the bathing entry / exit determination are performed in the same manner as in the flowchart of Fig. 5 in embodiment 1. The difference is that when the flow rate V is obtained in step S203, the flow rate calculation unit 25 of the calculation unit 20 calculates the flow rate according to Equation 5 using the measured value Pa of the pressure sensor 5, the measured value Pb of the second pressure sensor 5c, and the coefficient m.

[0088] As described above, the water level change detection system 1 according to this embodiment can calculate the corrected pressure using the measurements from the pressure sensor 5 and the second pressure sensor 5c and determine whether the bather has entered or left the bath without installing the flow rate sensor 7. Furthermore, installing the second pressure sensor 5c has the effect of preventing errors in water level change detection due to measurement errors from the pressure sensor 5 by using the measurements from the pressure sensor 5 and the second pressure sensor 5c to detect water level changes when water is not circulating. Therefore, by effectively utilizing the second pressure sensor 5c, which is installed to increase the accuracy of the water level change detection system 1, it becomes possible to detect water level changes when bath water is circulating in the circulation path 3.

[0089] As explained above, the water level change detection system 1 according to this embodiment is installed in the circulation path 3 connected to the bathtub 2 and through which the water in the bathtub 2 circulates, and includes the circulation pump 6 that circulates the water in the bathtub 2, the pressure sensor 5 that detects the pressure at the pressure detection position 5a inside the circulation path 3, a correction value calculation means that calculates a correction value that increases as the flow rate in the circulation path 3 while the circulation pump 6 is operating, a pressure correction means that calculates a corrected pressure by subtracting the correction value from the pressure detected by the pressure sensor 5 while the circulation pump 6 is operating if the circulation pump 6 is installed upstream of the pressure detection position 5a in the direction of water flow from the bathtub 2 in the circulation path 3, or by adding the correction value to the pressure detected by the pressure sensor 5 while the circulation pump 6 is operating if the circulation pump 6 is installed behind the pressure detection position in the direction of water flow from the bathtub 2 in the circulation path 3, and a bath level change detection system based on the corrected pressure. The device is equipped with a water level change detection means that detects changes in the water level of the tub 2, and further includes a flow rate detection means that detects the flow rate of water flowing in the circulation path 3 by the circulation pump 6, and the pressure correction means calculates a correction value based on the flow rate detected by the flow rate detection means, and further includes a second pressure sensor 5c that detects the pressure at a second pressure detection position 5b located downstream of the pressure detection position 5a in the direction in which water flows from the bathtub 2 in the circulation path, and a flow rate calculation means that calculates the flow rate based on the difference between the pressure detected by the pressure sensor and the pressure detected by the second pressure sensor, and the circulation pump 6 is installed upstream of the pressure detection position 5a or downstream of the second pressure detection position 5b in the direction in which water flows from the bathtub 2 in the circulation path 3, and the pressure sensor 5c, the second pressure sensor 5c, and the flow rate calculation means function as the flow rate detection means.

[0090] In this way, by installing two pressure sensors in the circulation path 3 and calculating the flow rate based on the difference between the pressure sensor 5 and the second pressure sensor 5c, the corrected pressure can be calculated without installing a flow rate sensor.

[0091] Embodiment 4 In the third embodiment, the flow rate V1 in the circulation path 3 was calculated using the measured values ​​of the pressure sensor 5 and the second pressure sensor 5c. In the present embodiment, a correction value is calculated from the piping pressure loss between the pressure detection position 5a and the second pressure detection position 5b, which is the difference between the measured values ​​of the pressure sensor 5 and the second pressure sensor 5c. In the present embodiment, the configuration of the water level change detection system 1 is the same as that shown in FIG. 13 of the third embodiment, so the diagram and description of the configuration will be omitted.

[0092] The corrected pressure Pc is expressed as in Equation 6 using a correction constant n. Pa is the measurement value of the pressure sensor 5, and Pb is the measurement value of the second pressure sensor 5c. Pa - Pb is the piping pressure loss between the pressure detection position 5a and the second pressure detection position 5b. The correction value is proportional to the piping pressure loss. The correction constant n is calculated in advance using a method described below.

[0093]

number

[0094] FIG. 15 is a flowchart showing a method for calculating the correction constant n according to the embodiment. The correction constant n is calculated in advance before detecting a change in the water level and set in the correction value calculation unit 21. The correction constant calculation method will be explained using FIG. 15. Calculation of the correction constant n begins when bath water is present in the bathtub 2 and the circulation path 3 is filled with water. First, in step S501, when the circulation pump 6 is not operating, i.e., when water is not flowing in the circulation path 3, the correction value calculation unit 21 acquires the non-circulation pressure Pa0 detected by the pressure sensor 5 when bath water is not circulating in the circulation path 3. Next, the process proceeds to step S502.

[0095] In step S502, the correction value calculation unit 21 drives the circulation pump 6 to circulate the bath water through the circulation path 3. Next, the process proceeds to step S503.

[0096] In step S503, the correction value calculation unit 21 acquires the circulation pressure Pa1 detected by the pressure sensor 5 and the circulation pressure Pb1 detected by the second pressure sensor 5c. At this time, taking into account the start-up time of the circulation pump 6 driven in step S503, the circulation pressures Pa1 and Pb1 may be acquired after a certain period of time has elapsed. Next, the process proceeds to step S504.

[0097] In step S504, the correction value calculation unit 21 calculates the correction constant n using the non-circulation pressure Pa0, the circulation pressure Pa1, and Pb1. The correction constant n can be calculated using Equation 7. The calculated correction constant n is stored in the memory (not shown) of the calculation unit 20, and is read and used when the pressure correction unit 22 performs pressure correction. This completes the calculation process of the correction constant n.

[0098]

number

[0099] By actually operating the water level change detection system 1 as shown in FIG. 15 and calculating the correction constant n, it is possible to determine the correction constant n, which differs depending on the installation environment, and to calculate a highly accurate correction value.

[0100] Correction constant n is a value that varies depending on the length and shape of the piping from pressure detection position 5a to outlet 9 of bathtub 2, and also on factors such as clogging of the piping over time. Therefore, it is desirable to perform the flow of FIG. 15 every time a certain period of time (e.g., one year) has passed, calculate correction constant n, and update the value of correction constant n stored in the memory (not shown) of calculation unit 20. Alternatively, calculation unit 20 may count the number of times circulating pump 6 is driven, and when the number exceeds a certain number of times (e.g., 1,000 times), perform the flow of FIG. 15 to calculate correction constant n and update the value of correction constant n stored in the memory (not shown) of calculation unit 20.

[0101] FIG. 16 is a flowchart of the calculation of the corrected pressure and the bathing entry / exit determination according to the fourth embodiment. Using FIG. 16, an example of a method for calculating the corrected pressure by the pressure correction unit 22 and determining whether the user has entered or left the bath using the corrected pressure by the bathing entry / exit determination unit 23 will be described. In FIG. 16, the same steps as those in FIG. 5, which is a flowchart of the calculation of the corrected pressure and the bathing entry / exit determination according to the first embodiment, are denoted by the same reference numerals. Some of the explanations for the steps similar to those in FIG. 5 will be omitted. This embodiment differs from FIG. 5 in that the measured values ​​of the pressure sensor 5 and the second pressure sensor 5c are used to calculate the corrected pressure Pc.

[0102] First, the calculation unit 20 determines whether or not a certain time has elapsed in step S201. If the certain time has elapsed, the process proceeds to step S202.

[0103] In step S602, the calculation unit 20 acquires the pressure Pa at the pressure detection position 5a detected by the pressure sensor 5 and the pressure Pb at the second pressure detection position 5b detected by the second pressure sensor 5c. Next, the process proceeds to step S604.

[0104] In step S604, correction value calculation unit 21 of calculation unit 20 calculates a correction value using pressure Pa and pressure Pb, and pressure correction unit 22 calculates a corrected pressure Pc using the correction value. The calculation of the correction value and corrected pressure is performed using Equation 6. At this time, if the difference between pressure Pa and pressure Pb is 0, that is, if circulation pump 6 is not operating and water is not flowing in circulation path 3, the corrected pressure Pc is set to the pressure Pa detected by pressure sensor 5. Note that, due to measurement errors of pressure sensor 5 and second pressure sensor 5c, the difference between pressure Pa and pressure Pb may not be 0 when circulation pump 6 is not operating. Therefore, if the difference between pressure Pa and pressure Pb is equal to or less than a threshold, the corrected pressure Pc may be set to the pressure Pa detected by pressure sensor 5. Next, proceed to step S205.

[0105] In step S205, the bathing entry / exit determination unit 23 of the calculation unit 20 determines whether the previous pressure value Pf is stored in the memory of the calculation unit 20. If it is determined that the previous pressure value Pf is not stored, the process proceeds to step S210. If it is determined that the previous pressure value Pf is stored, the process proceeds to step S206.

[0106] In step S206, the bathing entry / exit determination unit 23 of the calculation unit 20 determines whether the value obtained by subtracting the corrected pressure Pc from the previous pressure value Pf is greater than the bathing reference value. If the value obtained by subtracting the corrected pressure Pc from the previous pressure value Pf is not greater than the bathing reference value, the process proceeds to step S208. If the value obtained by subtracting the corrected pressure Pc from the previous pressure value Pf is greater than the bathing reference value, the process proceeds to step S207, where the bathing flag is turned ON. At this time, the calculation unit 20 may store the time when the bathing flag was turned ON. Next, the process proceeds to step S208.

[0107] In step S208, the bathing entry / exit determination unit 23 of the calculation unit 20 determines whether the value obtained by subtracting the previous pressure value Pf from the corrected pressure Pc is greater than the bathing reference value. If the value obtained by subtracting the previous pressure value Pf from the corrected pressure Pc is not greater than the bathing reference value, the process proceeds to step S210. If the value obtained by subtracting the previous pressure value Pf from the corrected pressure Pc is greater than the bathing reference value, the process proceeds to step S209, where the bathing flag is turned OFF. At this time, the calculation unit 20 may store the time when the bathing flag was turned OFF. Next, the process proceeds to step S210.

[0108] In step S208, the bathing entry / exit determination unit 23 of the calculation unit 20 substitutes the current corrected pressure value Pc for the previous pressure value Pf. Next, the process returns to step S201, and the bathing entry / exit determination process is repeated at regular intervals.

[0109] By following the above flow chart, it is possible to calculate the corrected pressure using the measurements from pressure sensor 5 and second pressure sensor 5c and determine whether the bather is entering or leaving the bath without installing flow sensor 7. Therefore, by effectively utilizing second pressure sensor 5c, which is installed to improve the accuracy of water level change detection system 1, it becomes possible to detect water level changes while bath water is circulating in circulation path 3.

[0110] As explained above, the water level change detection system 1 according to this embodiment is installed in the circulation path 3 connected to the bathtub 2 and through which the water in the bathtub 2 circulates, and includes the circulation pump 6 that circulates the water in the bathtub 2, the pressure sensor 5 that detects the pressure at the pressure detection position 5a inside the circulation path 3, a correction value calculation means that calculates a correction value that increases as the flow rate in the circulation path 3 increases, and a correction value calculation means that subtracts the correction value from the pressure detected by the pressure sensor 5 while the circulation pump 6 is operating when the circulation pump 6 is installed upstream of the pressure detection position 5a in the direction of water flow from the bathtub 2 in the circulation path 3, or subtracts the correction value from the pressure detected by the pressure sensor 5 while the circulation pump 6 is operating when the circulation pump 6 is installed downstream of the pressure detection position 5a in the direction of water flow from the bathtub 2 in the circulation path 3. The circulation pump 6 is equipped with a pressure correction means that calculates a corrected pressure by adding a correction value to the pressure detected by pressure sensor 5 while pump 6 is operating, and a water level change detection means that detects changes in the water level in bathtub 2 based on the corrected pressure.It further includes a second pressure sensor 5c that detects the pressure at second pressure detection position 5b located downstream of pressure detection position 5a in the direction in which water flows from bathtub 2 in circulation path 3.In the direction in which water flows from bathtub 2 in circulation path 3, circulation pump 6 is installed upstream of pressure detection position 5a or downstream of second pressure detection position 5b.The correction value calculation means calculates a correction value based on the difference between the pressure detected by pressure sensor 5 and the pressure detected by second pressure sensor 5c.

[0111] The configurations shown in the above embodiments are examples of the content of the present invention, and may be combined with other known technologies, and some of the configurations may be omitted or modified within the scope of the gist of the present invention.

[0112] Examples of aspects that may be included in the present disclosure are set forth below as appendices. (Appendix 1) a circulation pump that is connected to the bathtub and installed in a circulation path through which the water in the bathtub circulates, and that circulates the water in the bathtub; a pressure sensor for detecting pressure at a pressure detection position inside the circulation path; a correction value calculation means for calculating a correction value that increases as the flow rate in the circulation path increases; a pressure correction means for calculating a corrected pressure by subtracting the correction value from the pressure detected by the pressure sensor while the circulation pump is operating when the circulation pump is installed upstream of the pressure detection position in the direction in which water flows from the bathtub in the circulation path, or by adding the correction value to the pressure detected by the pressure sensor while the circulation pump is operating when the circulation pump is installed downstream of the pressure detection position in the direction in which water flows from the bathtub in the circulation path; a water level change detection means for detecting a change in the water level of the bathtub based on the corrected pressure; a bathing entry / exit determination means for determining whether a bather has started or exited the bath when the corrected pressure calculated by the pressure correction means has changed by more than a bathing reference value; A water level change detection system comprising: (Appendix 2) The water level change detection system described in Appendix 1 is characterized in that the bathing entry / exit determination means acquires the corrected pressure calculated by the pressure correction means at regular intervals, determines that bathing has started if the corrected pressure is greater than the previously acquired corrected pressure by a bathing standard value or more, and determines that the user has left the bath if the corrected pressure is smaller than the previously acquired corrected pressure by a bathing standard value or more. (Appendix 3) a flow rate detection unit for detecting the flow rate of water flowing through the circulation path by the circulation pump; 3. The water level change detection system according to claim 1, wherein the correction value calculation means calculates the correction value based on the flow rate detected by the flow rate detection means. (Appendix 4) The circulation pump further includes a rotation speed detection means for detecting the rotation speed of the motor of the circulation pump, The water level change detection system according to claim 1 or 2, wherein the correction value calculation means calculates the correction value based on the rotation speed of the circulation pump detected by the rotation speed detection means. (Appendix 5) a second pressure sensor that detects the pressure at a second pressure detection position that is located downstream of the pressure detection position in the direction in which water flows from the bathtub in the circulation path; a flow rate calculation means for calculating the flow rate based on a difference between a pressure detected by the pressure sensor and a pressure detected by the second pressure sensor, The circulation pump is installed in the circulation path upstream of the pressure detection position or downstream of the second pressure detection position in the direction in which water flows from the bathtub, 4. The water level change detection system according to claim 3, wherein the pressure sensor, the second pressure sensor, and the flow rate calculation means function as the flow rate detection means. (Appendix 6) a second pressure sensor that detects pressure at a second pressure detection position that is located downstream of the pressure detection position in the direction in which water flows from the bathtub in the circulation path; the circulation pump is installed upstream of the pressure detection position or downstream of the second pressure detection position in the circulation path in the direction in which water flows from the bathtub; The water level change detection system described in Appendix 1 or 2, characterized in that the correction value calculation means calculates the correction value based on the difference between the pressure detected by the pressure sensor and the pressure detected by the second pressure sensor. (Appendix 7) The water level change detection system according to claim 3, wherein the correction value is a product of the square of the flow rate detected by the flow rate detection means and a correction constant. (Appendix 8) The water level change detection system described in Appendix 4, characterized in that the correction value is the product of the square of the rotation speed of the circulation pump detected by the rotation speed detection means and a correction constant. (Appendix 9) The water level change detection system described in Appendix 7 or 8, characterized in that the correction constant becomes larger as the difference between the non-circulating pressure detected by the pressure sensor when the circulation pump is not operating and the circulating pressure detected by the pressure sensor when the circulation pump is operating becomes larger. (Appendix 10) The water level change detection system described in Appendix 7 is characterized in that the pressure correction means acquires the non-circulating pressure detected by the pressure sensor when the circulation pump is not operating, acquires the circulating pressure detected by the pressure sensor and the circulating flow rate detected by the flow detection means when the circulation pump is operating, and calculates the correction constant using the formula (P1-P0) / (V1×V1) when the non-circulating pressure is P0, the circulating pressure is P1, and the circulating flow rate is V1. (Appendix 11) The water level change detection system described in claim 8, characterized in that the pressure correction means acquires the non-circulating pressure detected by the pressure sensor when the circulation pump is not operating, acquires the circulating pressure detected by the pressure sensor when the circulation pump is operating and the circulation pump rotation speed detected by the rotation speed detection means, and calculates the correction constant using the formula (P1-P0) / (R1×R1) when the non-circulating pressure is P0, the circulating pressure is P1, and the circulation pump rotation speed is R1. (Appendix 12) 12. The water level change detection system according to claim 7, wherein the pressure correction means updates the correction constant at regular intervals. (Appendix 13) The water level change detection system described in Appendix 1 is characterized in that the bathing entry / exit determination means calculates the average value of the corrected pressure within each predetermined average calculation time, and determines that bathing has started when the average value of the corrected pressure is greater than the previous average value of the corrected pressure by more than the bathing standard value, and determines that bathing has occurred when the average value of the corrected pressure is smaller than the previous average value of the corrected pressure by more than the bathing standard value. (Appendix 14) Further, a control unit is provided to control the operation of the circulation pump. The water level change detection system described in Appendix 2 or 13, characterized in that the bathing entry / exit determination means does not make the bathing entry / exit determination for a certain period of time after the circulation pump receives an operation start signal or operation stop signal from the control unit. (Appendix 15) Further, a control unit is provided to control the operation of the circulation pump. The water level change detection system described in Appendix 2, 13 or 14, characterized in that the bathing entry / exit determination means does not make the bathing entry / exit determination for a certain period of time after the circulation pump receives a rotation speed control signal from the control unit. [Explanation of symbols]

[0113] 1 Water level change detection system, 2 Bathtub, 3 Circulation path, 4 Bath water, 5 Pressure sensor, 5a Pressure detection position, 5b Second pressure detection position, 5c Second pressure sensor, 6 Circulation pump, 7 Flow rate sensor, 8 Intake port, 9 Discharge port, 11 Heater, 12 Control unit, 13 Opening / closing valve, 20 Calculation unit, 21 Correction value calculation unit, 22 Pressure correction unit, 23 Bath entry / exit determination unit, 24 Rotation speed acquisition unit, 25 Flow rate calculation unit.

Claims

1. a circulation pump connected to the bathtub and installed in a circulation path through which the water in the bathtub circulates, for circulating the water in the bathtub; a pressure sensor for detecting pressure at a pressure detection position inside the circulation path; a flow rate detection means for detecting the flow rate of water flowing through the circulation path by the circulation pump; a correction value calculation means for calculating a correction value that increases as the flow rate in the circulation path increases by multiplying the square of the flow rate detected by the flow rate detection means by a correction constant; a pressure correction means for calculating a corrected pressure using the pressure detected by the pressure sensor and the correction value; a water level change detection means for detecting a change in the water level of the bathtub based on the corrected pressure; and a bathing entry / exit determination means for determining whether a bather has started or exited the bath when the corrected pressure calculated by the pressure correction means has changed by more than a bathing reference value, The correction value calculation means acquires the non-circulating pressure detected by the pressure sensor when the circulation pump is not operating, acquires the circulating pressure detected by the pressure sensor and the circulating flow rate detected by the flow detection means when the circulation pump is operating, and calculates the correction constant using the formula (P1-P0) / (V1xV1) when the non-circulating pressure is P0, the circulating pressure is P1, and the circulating flow rate is V1. This water level change detection system is characterized by the above.

2. a circulation pump connected to the bathtub and installed in a circulation path through which the water in the bathtub circulates, for circulating the water in the bathtub; a pressure sensor for detecting pressure at a pressure detection position inside the circulation path; a rotation speed detection means for detecting the rotation speed of the motor of the circulation pump; a correction value calculation means for calculating a correction value that increases as the flow rate in the circulation path increases by multiplying the square of the rotation speed of the circulation pump detected by the rotation speed detection means by a correction constant; a pressure correction means for calculating a corrected pressure using the pressure detected by the pressure sensor and the correction value; a water level change detection means for detecting a change in the water level of the bathtub based on the corrected pressure; and a bathing entry / exit determination means for determining whether a bather has started or exited the bath when the corrected pressure calculated by the pressure correction means has changed by more than a bathing reference value, The correction value calculation means acquires the non-circulating pressure detected by the pressure sensor when the circulation pump is not operating, acquires the circulating pressure detected by the pressure sensor when the circulation pump is operating and the rotation speed of the circulation pump detected by the rotation speed detection means, and calculates the correction constant using the formula (P1-P0) / (R1xR1) when the non-circulating pressure is P0, the circulating pressure is P1, and the rotation speed of the circulation pump is R1.This water level change detection system is characterized by the above.

3. The water level change detection system described in claim 1 or 2, characterized in that the bathing entry / exit determination means acquires the corrected pressure calculated by the pressure correction means at regular intervals, determines that bathing has started if the corrected pressure is greater than the previously acquired corrected pressure by more than the bathing standard value, and determines that bathing has started if the corrected pressure is smaller than the previously acquired corrected pressure by more than the bathing standard value.

4. a second pressure sensor that detects the pressure at a second pressure detection position that is located downstream of the pressure detection position in the direction in which water flows from the bathtub in the circulation path; a flow rate calculation means for calculating the flow rate based on a difference between the pressure detected by the pressure sensor and the pressure detected by the second pressure sensor, The circulation pump is installed in the circulation path upstream of the pressure detection position or downstream of the second pressure detection position in the direction in which water flows from the bathtub, 2. The water level change detection system according to claim 1, wherein the pressure sensor, the second pressure sensor, and the flow rate calculation means function as the flow rate detection means.

5. a second pressure sensor that detects pressure at a second pressure detection position that is located downstream of the pressure detection position in the direction in which water flows from the bathtub in the circulation path; the circulation pump is installed upstream of the pressure detection position or downstream of the second pressure detection position in the circulation path in the direction in which water flows from the bathtub; The water level change detection system according to claim 1 or 2, characterized in that the correction value calculation means calculates the correction value based on the difference between the pressure detected by the pressure sensor and the pressure detected by the second pressure sensor.

6. A water level change detection system as described in claim 1 or 2, characterized in that the correction constant becomes larger as the difference between the non-circulating pressure detected by the pressure sensor when the circulation pump is not operating and the circulating pressure detected by the pressure sensor when the circulation pump is operating becomes larger.

7. 3. The water level change detection system according to claim 1, wherein the pressure correction means updates the correction constant at regular intervals.

8. The water level change detection system described in claim 1 or 2, characterized in that the bathing entry / exit determination means calculates the average value of the corrected pressure within a predetermined average calculation time, and determines that bathing has started when the average value of the corrected pressure is greater than the previous average value of the corrected pressure by more than the bathing standard value, and determines that bathing has started when the average value of the corrected pressure is smaller than the previous average value of the corrected pressure by more than the bathing standard value.

9. Further, a control unit is provided to control the operation of the circulation pump. The water level change detection system described in claim 3, characterized in that the bathing entry / exit determination means does not make the bathing entry / exit determination for a certain period of time after the circulation pump receives an operation start signal or operation stop signal from the control unit.

10. Further, a control unit is provided to control the operation of the circulation pump. The water level change detection system according to claim 3, characterized in that the bathing entry / exit determination means does not make the bathing entry / exit determination for a certain period of time after the circulation pump receives a rotation speed control signal from the control unit.

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