Fluid mattress

Abstract

To provide a fluid mattress capable of approximating pressure in a cell to an optimal value.SOLUTION: A fluid mattress includes: fluid supply means; a fluid channel; a plurality of first cells mutually connected; a plurality of second cells mutually connected; a first electromagnetic valve connected to the plurality of first cells and the fluid channel; a second electromagnetic valve connected to the plurality of second cells and the fluid channel; an external electromagnetic valve connected to an outside and the fluid channel; a pressure sensor; and a control part. The control part stops the fluid supply means, closes the first electromagnetic valve, opens the second electromagnetic valve and the external electromagnetic valve, determines the first pressure on the basis of a time changing from a third pressure in which a measurement value of the pressure sensor is lower than a first pressure and higher than a second pressure to a fourth pressure lower than the third pressure and higher than the second pressure, and sets the first pressure higher the longer the time.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] SUMMARY OF THE INVENTION Embodiments of the present invention relate to a fluid mattress. [Background technology]

[0002] In hospitals and other medical institutions, air mattresses are sometimes placed on beds. Air mattresses contain multiple air cells, and controlling the pressure inside the air cells can keep the user comfortable. However, the optimal pressure inside the air cells varies depending on the user's physique and even for the same user, it varies depending on the user's posture, making it difficult to always maintain the optimal pressure inside the air cells. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-049435 Summary of the Invention [Problem to be solved by the invention]

[0004] An object of an embodiment of the present invention is to provide a fluid mattress that allows the pressure in the cells to approach an optimum value. [Means for solving the problem]

[0005] A fluid mattress according to an embodiment of the present invention includes a fluid supply means capable of supplying a fluid, a fluid passage to which the fluid is supplied from the fluid supply means, a plurality of interconnected first cells, a plurality of interconnected second cells, a first solenoid valve having a first end connected to the plurality of first cells and a second end connected to the fluid passage, a second solenoid valve having a first end connected to the plurality of second cells and a second end connected to the fluid passage, an external solenoid valve having a first end connected to the outside and a second end connected to the fluid passage, a pressure sensor for measuring the pressure of the fluid in the fluid passage, and a control unit that receives the measurement result of the pressure sensor and controls the fluid supply means, the first solenoid valve, the second solenoid valve, and the external solenoid valve. The control unit is capable of realizing a first mode in which the pressure in the second cell is set to a first pressure and the pressure in the first cell is set to a second pressure lower than the first pressure, and a second mode in which the pressure in the first cell is set to the first pressure and the pressure in the second cell is set to the second pressure or lower. When transitioning from the first mode to the second mode, the control unit stops the fluid supply means, closes the first solenoid valve, and opens the second solenoid valve and the external solenoid valve, and determines the first pressure based on the time it takes for the measurement value of the pressure sensor to change from a third pressure that is lower than the first pressure and higher than the second pressure to a fourth pressure that is lower than the third pressure and higher than the second pressure, and increases the first pressure as the time increases. [Effects of the Invention]

[0006] According to an embodiment of the present invention, a fluid mattress can be realized that allows the pressure in the cells to approach an optimum value. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a diagram showing a fluid mattress according to a first embodiment. [Figure 2] FIG. 2 is a flowchart showing the operation of the fluid mattress according to the first embodiment. [Figure 3]3(a) to 3(c) are graphs showing the change in pressure in each air cell, with the horizontal axis representing time and the vertical axis representing the pressure in each air cell. [Figure 4] FIG. 4 is a flowchart showing a method for calculating the correction coefficient. [Figure 5] FIG. 5 is a graph showing pressure changes during exhaust, with the horizontal axis representing time and the vertical axis representing pressure inside the air cell. [Figure 6] FIG. 6 is a flowchart showing a method for calculating an estimated value of the first pressure. [Figure 7] FIG. 7 is a graph showing a method for estimating the physique-converted value, with the horizontal axis representing the discharge time and the vertical axis representing the user's physique-converted value. [Figure 8] FIG. 8 is a graph showing a method for determining the first pressure, with the horizontal axis representing the converted value for body size and the vertical axis representing the set value of the first pressure. [Figure 9] FIG. 9 is a diagram showing a fluid mattress according to a second embodiment. [Figure 10] FIG. 10 is a flowchart showing the operation of the fluid mattress according to the third embodiment. [Figure 11] FIG. 11 is a graph showing pressure changes during exhaust, with the horizontal axis representing time and the vertical axis representing pressure within the air cell. [Figure 12] FIG. 12 is a flowchart showing a method for determining the posture of a user. [Figure 13] FIG. 13 is a diagram showing a method for determining the posture of a user. DETAILED DESCRIPTION OF THE INVENTION

[0008] First Embodiment FIG. 1 is a diagram showing a fluid mattress according to this embodiment. As shown in FIG. 1, the fluid mattress 1 according to this embodiment is used by being placed on a medical bed 100, for example. A user sits on the fluid mattress 1. The fluid mattress 1 may also be used by being placed on a nursing care bed. Nursing care beds are used not only in medical institutions such as hospitals, but also in nursing care facilities and the user's own home. The user of the fluid mattress 1 is, for example, a patient or a person requiring nursing care.

[0009] The fluid mattress 1 is provided with a blower 10, a fluid passage 20, air cells 31-33, solenoid valves 41-44, a pressure sensor 50, and a control unit 60. The blower 10 is a fluid supply means capable of supplying air as a fluid. The blower 10 may be, for example, a pump. The fluid passage 20 is connected to the blower 10, and air is supplied from the blower 10. In this specification, "connected" means that a fluid can flow.

[0010] A plurality of air cells 31 to 33 are provided, and are repeatedly arranged in a direction from the head side to the foot side of the medical bed 100. The air cells 31 to 33 are made of a soft sheet material and can be filled with air. For example, the air cells 31, 32, and 33 have the same size and shape.

[0011] Each of the solenoid valves 41 to 44 has a first end and a second end, and can switch between permitting and prohibiting the flow of air between the first end and the second end. The plurality of air cells 31 (first cells) are connected to each other and are connected to a first end of the solenoid valve 41 (first solenoid valve). The plurality of air cells 32 (second cells) are connected to each other and are connected to a first end of the solenoid valve 42 (second solenoid valve). The plurality of air cells 33 (third cells) are connected to each other and are connected to a first end of the solenoid valve 43 (third solenoid valve).

[0012] That is, in the fluid mattress 1, a plurality of air cells that are the same size and shape and arranged in a row are divided into three flow paths by solenoid valves 41 to 43. A first end of solenoid valve 44 (external solenoid valve) is connected to the outside of the fluid mattress 1 and can draw in or discharge atmospheric air as air. Second ends of solenoid valves 41 to 44 are connected to the fluid passage 20.

[0013] The pressure sensor 50 measures the pressure of air in the fluid passage 20. The control unit 60 receives the measurement results of the pressure sensor 50 and controls the air blower 10 and the solenoid valves 41 to 44. The control unit 60 can perform a bedsore prevention operation. When the control unit 60 performs a bedsore prevention operation, it repeatedly executes a first mode, a second mode, and a third mode, which will be described later. The control unit 60 also calculates and stores a correction coefficient k, which indicates the ease with which exhaust gas escapes, such as the degree of opening of the solenoid valve 44 connected to the outside. The control unit 60 also stores the correlations shown in FIGS. 6 to 8. These correlations will also be described later.

[0014] Next, the operation of the fluid mattress 1 according to this embodiment will be described. First, the general operation of the fluid mattress 1 will be described. FIG. 2 is a flowchart showing the operation of the fluid mattress according to this embodiment. 3(a) to (c) are graphs showing the change in pressure in each air cell, with time on the horizontal axis and pressure in each air cell on the vertical axis. FIG. 3(a) shows the change in pressure in air cell 31, FIG. 3(b) shows the change in pressure in air cell 32, and FIG. 3(c) shows the change in pressure in air cell 33.

[0015] As shown in step S1 of FIG. 2 and FIGS. 3(a) to 3(c), the control unit 60 realizes an initial state T0. In the initial state T0, the control unit 60 sets the internal pressure of all of the air cells 31 to 33 to a first pressure P1. The first pressure P1 is a pressure that maintains all of the air cells 31 to 33 in a moderately inflated state when a user is lying on the fluid mattress 1, and enables the air cells 31 to 33 to comfortably support the user. For example, the first pressure P1 is a pressure that maximizes the contact area between the air cells 31 to 33 and the user. In the initial state T0, the first pressure P1 is a preset value.

[0016] 2, the control unit 60 calculates a correction coefficient k that indicates the degree of opening of the solenoid valve 44 connected to the outside. The method for calculating the correction coefficient k will be described later. Next, the control unit 60 determines whether the bedsore prevention operation is on or off, as shown in step S3 of Fig. 2. If the bedsore prevention function is on, the process proceeds to step S4.

[0017] In step S4, the first mode T1 is executed. As shown in FIG. 1 and FIGS. 3(a) to 3(c), in the first mode T1, the pressure in the air cells 32 and 33 is set to a first pressure P1, and the pressure in the air cell 31 is set to a second pressure P2 or less. The second pressure P2 is lower than the first pressure P1. The pressure in the air cell 31 is set to, for example, a pressure close to atmospheric pressure. As a result, the user is supported by the air cells 32 and 33, but not by the air cell 31. The duration of the first mode T1 is, for example, 5 minutes.

[0018] Next, the process proceeds to step S5, where the second mode T2 is executed. In the second mode T2, the pressure in the air cell 31 is returned to the first pressure P1, and the pressure in the air cell 32 is set to a second pressure P2 or less. The pressure in the air cell 32 is set to, for example, a pressure close to atmospheric pressure. As a result, the user is supported by the air cells 31 and 33, but not by the air cell 32. The duration of the second mode T2 is, for example, five minutes. Note that FIG. 1 shows the second mode T2.

[0019] Next, the process proceeds to step S6, where the third mode T3 is executed. In the third mode T3, the pressure in the air cell 32 is returned to the first pressure P1, and the pressure in the air cell 33 is set to a pressure close to atmospheric pressure, for example. As a result, the user is supported by the air cells 31 and 32, but not by the air cell 33. The duration of the third mode T3 is, for example, five minutes.

[0020] Next, returning to step S3, if the bedsore prevention operation is ON, proceed again to step S4, and repeat the first mode T1, second mode T2, and third mode T3. If the bedsore prevention operation is OFF, proceed to step S7, and realize the initial state T0, after which the control unit 60 ends operation. Even after the control unit 60 ends operation, the internal pressure of the air cells 31-33 maintains the first pressure P1.

[0021] In this way, when the bedsore prevention operation is on, the control unit 60 sequentially reduces the internal pressure of the plurality of air cells 31, the plurality of air cells 32, and the plurality of air cells 33 to below the second pressure P2. This causes the user's body to move little by little relative to the fluid mattress 1, and also causes parts of the user's body that are not pressed by the air cells to move little by little, thereby suppressing the occurrence of bedsores.

[0022] Next, each operation will be described in detail. First, a method for realizing the initial state T0 shown in step S1 of FIG. 2 will be described. As shown in FIGS. 1 and 3(a)-(c), in the initial state T0, the control unit 60 drives the blower 10 with the solenoid valves 41-43 open and the solenoid valve 44 closed. This causes air to be injected from the blower 10 into the air cells 31-33 via the fluid passage 20 and the solenoid valves 41-43. Then, when the measurement value of the pressure sensor 50 reaches a first pressure P1, the blower 10 is stopped. By opening the solenoid valves 41-43, the air cells 31-33 are interconnected and reach the same pressure. In this way, the pressure in all of the air cells 31-33 becomes the first pressure P1.

[0023] Next, a method for calculating the correction coefficient k shown in step S2 of FIG. 2 will be described. FIG. 4 is a flowchart showing a method for calculating the correction coefficient. 4, the control unit 60 drives the blower 10 and closes the solenoid valves 41 to 44. In this state, the pressure sensor 50 measures the pressure in the fluid passage 20 to obtain a first measured value P-close.

[0024] Next, as shown in step S22 of Fig. 4, the control unit 60 opens only the solenoid valve 44. The solenoid valves 41 to 43 remain closed. The blower 10 continues to operate. In this state, the pressure sensor 50 measures the pressure in the fluid passage 20, and after the measured value stabilizes, the second measured value P-open is acquired.

[0025] 4, a correction coefficient k that represents the flow state of the solenoid valve 44 is calculated based on the ratio (P-close / P-open) between the first measurement value P-close and the second measurement value P-open. The first measurement value P-close is determined mainly by the performance of the blower 10.

[0026] The second measurement value P-open is determined mainly by the performance of the blower 10 and the degree of opening of the solenoid valve 44. The greater the degree of opening of the solenoid valve 44, the lower the resistance when air passes through the solenoid valve 44, and the lower the second measurement value P-open. Therefore, the ratio (P-close / P-open) becomes larger and the correction coefficient k becomes higher. Conversely, the smaller the degree of opening of the solenoid valve 44, the higher the resistance when air passes through the solenoid valve 44, and the higher the second measurement value P-open. Therefore, the ratio (P-close / P-open) becomes smaller and the correction coefficient k becomes lower. The control unit 60 stores the correction coefficient k.

[0027] Next, a method for determining the set value of the first pressure P1 will be described. In this embodiment, the control unit 60 calculates a first estimated value of the first pressure P1 when transitioning from the initial state T0 or the third mode T3 to the first mode T1, calculates a second estimated value of the first pressure P1 when transitioning from the first mode T1 to the second mode T2, and calculates a third estimated value of the first pressure P1 when transitioning from the second mode T2 to the third mode T3. The control unit 60 then sets the average of the first, second, and third estimated values ​​as the set value of the first pressure P1. Note that the control unit 60 may also set the median of the first, second, and third estimated values ​​as the set value of the first pressure P1. In this manner, the set value of the first pressure P1 is determined for each cycle consisting of the first mode T1, the second mode T2, and the third mode T3.

[0028] The first, second, and third estimated values ​​are calculated using the same method. The method for calculating the second estimated value will be described below as an example. FIG. 5 is a graph showing pressure changes during exhaust, with the horizontal axis representing time and the vertical axis representing pressure inside the air cell. FIG. 6 is a flowchart showing a method for calculating an estimated value of the first pressure. FIG. 7 is a graph showing a method for estimating the physique-converted value, with the horizontal axis representing the discharge time and the vertical axis representing the user's physique-converted value. FIG. 8 is a graph showing a method for determining the first pressure, with the horizontal axis representing the converted value for body size and the vertical axis representing the set value of the first pressure.

[0029] When transitioning from first mode T1 to second mode T2, the control unit 60 stops the blower 10, closes the solenoid valves 41 and 43, and opens the solenoid valves 42 and 44. This connects the air cell 32 to the outside. At this time, the user crushes the air cell 32, causing air to be discharged from the air cell 32 to the outside.

[0030] As shown in Figure 5, as air is discharged from the air cell 32 to the outside, the pressure inside the air cell 32 decreases. The rate at which the pressure decreases depends on the user's physique and the first pressure P1 of the air cells 31 and 33. The larger the user's physique, the longer it takes for the air to be discharged. This is because, while the solenoid valve 44 limits the air passing speed, the larger the user's physique, the greater the amount of air that is discharged between the third pressure P3 and the fourth pressure P4, and the longer it takes to discharge the air.

[0031] 5, if the first pressure P1 of the air cells 31 and 33 is lower than the appropriate value and the air cells 31 and 33 are too soft, the amount of air discharged when the pressure in the air cells 32 changes from the third pressure P3 to the fourth pressure P4 increases, and the time required for discharge becomes longer. Conversely, if the first pressure P1 of the air cells 31 and 33 is higher than the appropriate value and the air cells 31 and 33 are too hard, the amount of air discharged when the pressure in the air cells 32 changes from the third pressure P3 to the fourth pressure P4 decreases, and the time required for discharge becomes shorter.

[0032] The "physique" of the user is a concept that represents the force acting on the air cells when the user is on the fluid mattress 1. The physique is largely dependent on the weight of the user, but is not a concept that is determined solely by weight. The physique also depends on the weight of the bedding and the contact area between the fluid mattress 1 and the user. The contact area depends on the user's posture and the state of the medical bed 100. The user's posture may be, for example, a supine position or a sitting position. The state of the medical bed 100 may be a flat position, a raised back position, a raised leg position, etc. The discharge time also depends on the opening degree of the solenoid valve 44. In other words, it also depends on the correction coefficient k mentioned above.

[0033] As shown in FIG. 5, in this embodiment, a third pressure P3 and a fourth pressure P4 are set. The third pressure P3 is lower than the first pressure P1 and higher than the second pressure P2. The fourth pressure P4 is lower than the third pressure P3 and higher than the second pressure P2. That is, P1>P3>P4>P2. In one example, the first pressure P1 is atmospheric pressure plus approximately 3 kPa (kilopascals), the third pressure P3 is atmospheric pressure plus 2 kPa, the fourth pressure P4 is atmospheric pressure plus 0.7 kPa, and the second pressure P2 is atmospheric pressure plus 0.4 kPa. The atmospheric pressure is approximately 101 kPa.

[0034] 5 and 6, the control unit 60 stores the time t0 when the measurement value of the pressure sensor 50 reaches the third pressure P3. Next, as shown in step S52, the control unit 60 stores the time t1 when the measurement value of the pressure sensor 50 reaches the fourth pressure P4. Then, as shown in step S53, the control unit 60 calculates the time (t1 - t0) until the pressure in the air cell 32 changes from the third pressure P3 to the fourth pressure P4.

[0035] As shown in step S54 of FIG. 6, the control unit 60 estimates a physique conversion value W based on time (t1-t0). The "physique conversion value W" is a numerical value representing the user's physique. FIG. 7 shows the correlation between the time (t1-t0) until the pressure in the air cell 31 changes from the third pressure P3 to the fourth pressure P4 and the physique conversion value W. As shown in FIG. 7, the control unit 60 estimates that the physique conversion value W increases as the time (t1-t0) increases. As described above, this correlation also depends on the hardness of the air cells 31 and 33, i.e., the first pressure P1. This correlation also depends on the correction coefficient k. The control unit 60 stores this correlation in association with the first pressure P1 and the correction coefficient k. The control unit 60 may also store the results of multiple regression analysis of the time (t1-t0), the first pressure P1, the correction coefficient k, and the physique conversion value W. In this way, the control unit 60 estimates the physique equivalent value W based on the first pressure P1 and the correction coefficient k in addition to the time (t1-t0).

[0036] FIG. 8 shows the correlation between the physique conversion value W and the set value of the first pressure P1. The control unit 60 stores this correlation. As shown in step S55 of FIG. 6 and in FIG. 8, the control unit 60 calculates the set value of the first pressure P1 from the physique conversion value W. The larger the physique conversion value W, the larger the set value of the first pressure P1. Therefore, the longer the time difference (t1-t0), the higher the set value of the first pressure P1. In this way, a second estimated value of the first pressure P1 is calculated in the second mode T2.

[0037] Similarly, the control unit 60 calculates the first estimated value in the first mode T1. That is, when transitioning from the initial state T0 or the third mode T3 to the first mode T1, the control unit 60 stops the blower 10, closes the solenoid valves 42 and 43, and opens the solenoid valves 41 and 44, and calculates the first estimated value of the first pressure P1 based on the time (t1-t0) over which the measurement value of the pressure sensor 50 changes from the third pressure P3 to the fourth pressure P4.

[0038] Furthermore, in the third mode T3, a third estimated value is calculated. That is, when transitioning from the second mode T2 to the third mode T3, the blower 10 is stopped, the solenoid valves 41 and 42 are closed, and the solenoid valves 43 and 44 are opened. The third estimated value of the first pressure P1 is calculated based on the time (t1-t0) it takes for the measurement value of the pressure sensor 50 to change from the third pressure P3 to the fourth pressure P4. The control unit 60 then sets the average value of the first, second, and third estimated values ​​as the set value for the first pressure P1. In subsequent operations, the first pressure P1 is realized according to this set value. Furthermore, in step S7 of FIG. 2, the pressure in the air cells 31-33 is set to the last set first pressure P1.

[0039] Next, the effects of this embodiment will be described. In this embodiment, the external force acting on the air cell is evaluated based on the exhaust time from the air cell using a concept of a body size equivalent value, and the first pressure is set based on this body size equivalent value. Therefore, the first pressure can be set to an optimal value. This allows the pressure inside the air cell to approach the optimal value.

[0040] In response to this, it is also possible to determine the set value of the first pressure based on the weight of the user. However, as described above, the optimal value of the first pressure depends not only on the weight but also on the weight of the bedding, the user's posture, the state of the medical bed, and the like. Therefore, if the first pressure is set based only on the weight, it will deviate from the optimal value. Furthermore, it is necessary to reset the first pressure every time the user changes.

[0041] Furthermore, according to this embodiment, the optimal value of the first pressure is estimated using the bedsore prevention operation. Therefore, there is no need to perform a dedicated operation to determine the set value of the first pressure. Furthermore, because the set value of the first pressure can be determined for each cycle of the bedsore prevention operation, even if the user's posture or the state of the medical bed changes, the first pressure can be adjusted accordingly. Therefore, the state of the air cell can always be maintained close to the optimum state.

[0042] Furthermore, in this embodiment, in step S2 of Fig. 2, the control unit 60 calculates a correction coefficient k that represents the degree of opening of the solenoid valve 44, and selects the correlation shown in Fig. 7 based on this correction coefficient k. Therefore, even if there is variation in the degree of opening of the solenoid valve 44, the first pressure can be set with high accuracy.

[0043] Furthermore, in this embodiment, a first estimated value is calculated when switching to the first mode, a second estimated value is calculated when switching to the second mode, and a third estimated value is calculated when switching to the third mode, and the average of these is used as the setting value for the first pressure. This allows the first pressure to be set accurately, even if there is local variation in the pressure applied to the air cell, by dispersing the effect of this variation.

[0044] In this embodiment, an example has been described in which the physique conversion value W is estimated based on the time (t1-t0), the first pressure P1, and the correction coefficient k in the process shown in step S54 of FIG. 6, but at least one of the first pressure P1 and the correction coefficient k does not need to be taken into consideration.

[0045] <Second embodiment> FIG. 9 is a diagram showing a fluid mattress according to this embodiment. As shown in Fig. 9, in the fluid mattress 2 according to this embodiment, each air cell is divided into two stages, an upper stage and an lower stage. Furthermore, the fluid mattress 2 is provided with a solenoid valve 45 (fourth solenoid valve).

[0046] Specifically, each air cell 31 includes a lower subcell 31a and an upper subcell 31b. For example, one lower subcell 31a and one upper subcell 31b are joined via a diaphragm 31c. Similarly, each air cell 32 includes a lower subcell 32a, an upper subcell 32b, and a diaphragm 32c, and each air cell 33 includes a lower subcell 33a, an upper subcell 33b, and a diaphragm 33c.

[0047] The solenoid valve 41 is connected to the upper sub-cell 31b of the air cell 31. The solenoid valve 42 is connected to the upper sub-cell 32b of the air cell 32. The solenoid valve 43 is connected to the upper sub-cell 33b of the air cell 33. A first end of the solenoid valve 45 is connected in common to all of the lower sub-cells 31a, 32a, and 33a. A second end of the solenoid valve 45 is connected to the fluid passage 20. This makes it possible to independently control the pressure in the upper and lower stages for each air cell.

[0048] The pressure in the lower sub-cells 31a, 32a, and 33a is always set to the first pressure P1. In the bedsore prevention operation, the pressure in the upper sub-cells 31b, 32b, and 33b is successively set to a pressure equal to or lower than the second pressure P2.

[0049] According to this embodiment, the lower subcells 31a, 32a, and 33a can be kept inflated at all times, so that even if the upper subcell collapses, the user is supported by the lower subcells. This prevents the user from coming into contact with the bottom of the medical bed 100, providing the user with a more comfortable sleeping experience. The configuration, operation, and effects of this embodiment other than those described above are the same as those of the first embodiment. Note that, although this embodiment has shown an example in which the lower subcell is disposed directly below the upper subcell, the lower subcell may also be disposed directly below the space between adjacent upper subcells.

[0050] <Third embodiment> This embodiment is an example that solves the problems of the first and second embodiments described above.

[0051] First, this problem will be explained. When a user is on the fluid mattress 1 or 2 and is in a sitting position or the medical bed 100 is raised, the weight of the user is concentrated on a small number of air cells. As a result, in the operation described in the first embodiment, when the pressure in the air cells or the upper sub-cells is reduced from the first pressure P1 to the second pressure P2, the total amount of air discharged from the air cells is smaller than when the user is in a lying position. In addition, in the case of a patient with kyphosis or contracture, the weight of the user is concentrated on a small number of air cells.

[0052] Therefore, in the algorithm for determining the set value of the first pressure P1, the time (t1-t0) becomes shorter, the body size equivalent value W is estimated to be smaller, and the first pressure P1 is set lower. As a result, for example, in the second mode T2, the pressure in the air cells 31 and 33 decreases, the upper and lower surfaces of the air cells come into contact, and the user cannot be supported. Hereinafter, contact between the upper and lower surfaces of the air cells or sub-cells is referred to as "bottoming out."

[0053] For example, when the fluid mattress 2 according to the second embodiment is used, the upper sub-cells 31b and 33b bottom out, and the user is supported by the lower sub-cells 31a, 32a, and 33a. In this case, pressure is no longer applied to the upper sub-cell 32b, and therefore, the discharge of air from the upper sub-cell 32b essentially stops. When the fluid mattress 1 according to the first embodiment is used, the air cells 31 and 33 bottom out, and the user abuts against the bottom of the medical bed 100. In this case, pressure is no longer applied to the air cell 32, and therefore, the discharge of air from the air cell 32 essentially stops.

[0054] As the air discharge stops, the time (t1-t0) becomes shorter, the body size equivalent value W becomes smaller, and the set value of the first pressure P1 becomes lower. As the first pressure P1 becomes lower, the amount of air discharged decreases. As this cycle is repeated, the set value of the first pressure P1 decreases, and eventually the lower sub-cells 31a, 32a, 33a of the fluid mattress 2 hit the bottom and can no longer support the user, causing the user to come into contact with the bottom of the medical bed 100.

[0055] Therefore, in this embodiment, the control unit 60 determines the posture of the user, and if the user is not in a supine position, increases the first pressure P1 by a fixed amount, thereby avoiding the above-mentioned cycle and continuing to set an appropriate first pressure P1.

[0056] The driving method of this embodiment will be specifically described below. In this embodiment, the fluid mattress 2 described in the second embodiment is used as the fluid mattress.

[0057] FIG. 10 is a flowchart showing the operation of the fluid mattress according to this embodiment. FIG. 11 is a graph showing pressure changes during exhaust, with the horizontal axis representing time and the vertical axis representing pressure within the air cell. FIG. 12 is a flowchart showing a method for determining the posture of a user. FIG. 13 is a diagram showing a method for determining the posture of a user.

[0058] As shown in step S11 of FIG. 10, the control unit 60 determines the posture of the user on the fluid mattress. As shown in Figure 11, when any one of the upper subcells 31b, 32b, and 33b is connected to the outside, the shape of the pressure change curve when air is exhausted from that upper subcell to the outside varies depending on the user's posture. Specifically, when the user is in a seated position or with their back raised (hereinafter collectively referred to as "seated position"), the load is concentrated on a specific upper subcell compared to when the user is in a lying position, causing air to escape from that upper subcell in a short period of time, resulting in bottoming out. When the upper subcell bottoms out, the pressure change in the upper subcell suddenly decreases, and the slope of the pressure change curve becomes smaller. Therefore, by detecting whether or not such an inflection point exists in the pressure change curve, it is possible to determine whether the upper subcell has bottomed out.

[0059] In this embodiment, the shape of the pressure change curve is quantified and this quantification is compared with a threshold value to determine whether or not the pressure has bottomed out and identify the user's posture. Specifically, a fifth pressure P5 is set between the third pressure P3 and the fourth pressure P4. That is, P1>P3>P5>P4>P2.

[0060] For example, with the user sitting on the fluid mattress 2, the control unit 60 stops the blower 10, opens the solenoid valves 41 and 44, and closes the solenoid valves 42, 43, and 45. This connects the upper sub-cell 31b of the air cell 31 to the outside, and air begins to escape. The pressure sensor 50 measures the pressure in the fluid passage 20 and periodically outputs the result to the control unit 60.

[0061] As shown in step S91 in FIGS. 11 and 12, the control unit 60 stores the time t0 when the pressure in the upper subcell 31b reaches the third pressure P3. Next, as shown in step S92, the control unit 60 stores the time t2 when the pressure in the upper subcell 31b reaches the fifth pressure P5. Next, as shown in step S93, the control unit 60 stores the time t1 when the pressure in the upper subcell 31b reaches the fourth pressure P4.

[0062] Next, as shown in step S94, the control unit 60 calculates the first time (t2-t0) during which the pressure in the upper subcell 31b changes from the third pressure P3 to the fifth pressure P5 and the second time (t1-t2) during which the pressure changes from the fifth pressure P5 to the fourth pressure P4, and calculates the ratio R of the first time to the second time, R=(t2-t0) / (t1-t2).

[0063] Next, as shown in step S95 of Fig. 12 and Fig. 13, the ratio value R is compared with a threshold value A. If the ratio value R is higher than the threshold value A, the user's posture is determined to be a lying position, and if the ratio value R is lower than the threshold value A, the user's posture is determined to be a sitting position.

[0064] Next, the process proceeds to step S12 in Fig. 10, and if the user is not in a sitting position, the process ends. If the user is in a sitting position, the process proceeds to step S13, and the value (P1 + Padd) obtained by adding the additional pressure Padd to the already set first pressure P1 is set as a new first pressure P1. The process then ends.

[0065] If the user's posture returns to the lying position, step S13 in Fig. 10 is not executed, and the set value of the first pressure P1 returns to a value to which the additional pressure Padd is not added. Note that the operation shown in Fig. 10 may be performed when determining the set value of the first pressure P1, or may be performed independently.

[0066] According to this embodiment, the control unit 60 determines the user's posture, and if the user is sitting (including with their back raised), the first pressure P1 is increased. This allows the user to be properly supported even when the load is concentrated on some of the upper sub-cells, and also prevents the first pressure P1 from being erroneously set too low. As a result, the first pressure P1 can be kept set appropriately.

[0067] Furthermore, according to this embodiment, since the fluid mattress 2 is used, even if the upper sub-cell hits the bottom, the user can be supported by the lower sub-cell. This prevents the user from feeling uncomfortable. Note that if the user's discomfort can be eliminated by some means, the fluid mattress 1 according to the first embodiment may be used in this embodiment. Other configurations, operations, and effects of this embodiment are the same as those of the first embodiment.

[0068] The above-described embodiments are examples of realizing the present invention, and the present invention is not limited to these embodiments. For example, the present invention also includes embodiments in which some components or steps are added, deleted, or modified in the above-described embodiments.

[0069] For example, while the above-described embodiments have shown examples in which three systems of air cells are provided, this is not limiting. Two systems, or four or more systems of air cells may also be provided. Furthermore, while the above-described embodiments have shown examples in which multiple air cells are arranged in one direction from the head to the foot of the medical bed, this is not limiting and they may also be arranged in the left-right direction. Furthermore, while the above-described embodiments have shown examples in which air is used as the fluid driving the cells, this is not limiting. For example, water, gel, or oil may also be used as the fluid. Furthermore, the size of each air cell is selected appropriately depending on the location on the bed where it is to be placed and the desired function, and multiple air cells of different sizes may be combined and used within a single fluid mattress.

[0070] The present invention includes the following aspects.

[0071] (Appendix 1) a fluid supply means capable of supplying a fluid; a fluid passage through which the fluid is supplied from the fluid supply means; a plurality of interconnected first cells; a plurality of interconnected second cells; a first solenoid valve having a first end connected to the plurality of first cells and a second end connected to the fluid passage; a second solenoid valve having a first end connected to the plurality of second cells and a second end connected to the fluid passage; an external solenoid valve having a first end connected to the outside and a second end connected to the fluid passage; a pressure sensor for measuring the pressure of the fluid in the fluid passage; a control unit that receives the measurement results of the pressure sensor and controls the fluid supply means, the first solenoid valve, the second solenoid valve, and the external solenoid valve; Equipped with The control unit a first mode in which the pressure in the second cell is a first pressure and the pressure in the first cell is a second pressure lower than the first pressure; a second mode in which the pressure in the first cell is set to the first pressure and the pressure in the second cell is set to the second pressure or less; is feasible, When transitioning from the first mode to the second mode, the control unit stops the fluid supply means, closes the first solenoid valve, and opens the second solenoid valve and the external solenoid valve, and determines the first pressure based on the time it takes for the measurement value of the pressure sensor to change from a third pressure that is lower than the first pressure and higher than the second pressure to a fourth pressure that is lower than the third pressure and higher than the second pressure, and the longer the time, the higher the first pressure becomes.

[0072] (Appendix 2) a plurality of interconnected third cells; a third solenoid valve having a first end connected to the plurality of third cells and a second end connected to the fluid passage; Furthermore, The control unit a third mode can be realized in which the pressure in the first cell and the pressure in the second cell are set to the first pressure and the pressure in the third cell is set to the second pressure or less; A fluid mattress as described in Appendix 1, wherein in the first mode and the second mode, the pressure in the third cell is the first pressure.

[0073] (Appendix 3) The control unit when transitioning to the first mode, stopping the fluid supply means, closing the second solenoid valve and the third solenoid valve, and opening the first solenoid valve and the external solenoid valve, and calculating a first estimated value of the first pressure based on the time it takes for the measurement value of the pressure sensor to change from the third pressure to the fourth pressure; when transitioning to the second mode, stopping the fluid supply means, closing the first solenoid valve and the third solenoid valve, and opening the second solenoid valve and the external solenoid valve, and calculating a second estimated value of the first pressure based on the time it takes for the measurement value of the pressure sensor to change from the third pressure to the fourth pressure; when transitioning to the third mode, stopping the fluid supply means, closing the first solenoid valve and the second solenoid valve, and opening the third solenoid valve and the external solenoid valve, and calculating a third estimated value of the first pressure based on the time it takes for the measurement value of the pressure sensor to change from the third pressure to the fourth pressure; A fluid mattress as described in Appendix 2, wherein the first pressure is the average value of the first estimated value, the second estimated value, and the third estimated value.

[0074] (Appendix 4) placed on the bed, A fluid mattress as described in Appendix 2 or 3, wherein the first cells, the second cells, and the third cells are repeatedly arranged from the head side to the foot side of the bed.

[0075] (Appendix 5) Further comprising a fourth solenoid valve; The first cell is a first lower cell connected to a first end of the fourth solenoid valve; a first upper cell disposed on the first lower cell and connected to a first end of the first solenoid valve; and The second cell is a second lower cell connected to a first end of the fourth solenoid valve; a second upper cell disposed on the second lower cell and connected to a first end of the second solenoid valve; and The third cell is a third lower cell connected to a first end of the fourth solenoid valve; a third upper cell disposed on the third lower cell and connected to a first end of the third solenoid valve; and 5. The fluid mattress according to any one of claims 2 to 4, wherein the second end of the fourth solenoid valve is connected to the fluid passage.

[0076] (Appendix 6) 6. The fluid mattress according to any one of claims 2 to 5, wherein the control unit repeatedly realizes the first mode, the second mode, and the third mode.

[0077] (Appendix 7) A fluid mattress described in any one of Appendices 1 to 6, wherein the control unit determines the first pressure based on the pressure in the first cell when transitioning from the first mode to the second mode.

[0078] (Appendix 8) The control unit driving the fluid supply means to close the first solenoid valve, the second solenoid valve, and the external solenoid valve, and causing the pressure sensor to acquire a first measurement value; driving the fluid supply means to close the first solenoid valve and the second solenoid valve, and to open the external solenoid valve, and causing the pressure sensor to acquire a second measurement value; calculating a correction coefficient representing a flow state of the external solenoid valve based on a ratio between the first measurement value and the second measurement value; 8. The fluid mattress according to any one of claims 1 to 7, wherein the first pressure is determined based on the correction coefficient.

[0079] (Appendix 9) The control unit determining the posture of the user based on a ratio between a first time period during which the measurement value of the pressure sensor changes from the third pressure to a fifth pressure that is lower than the third pressure and higher than the fourth pressure, and a second time period during which the measurement value of the pressure sensor changes from the fifth pressure to the fourth pressure; 9. The fluid mattress according to any one of claims 1 to 8, wherein the first pressure is increased when the user is in a sitting position.

[0080] (Appendix 10) The fluid mattress described in Appendix 9, wherein the control unit determines that the user's posture is supine when the ratio of the first time to the second time is higher than a threshold value, and determines that the user's posture is sitting when the ratio is lower than the threshold value. [Explanation of symbols]

[0081] 1, 2 Fluid mattress 10. Blower 20 Fluid passage 31, 32, 33 Air Cell 31a, 32a, 33a Lower subcells 31b, 32b, 33b Upper subcells 31c, 32c, 33c septum 41, 42, 43, 44, 45 Solenoid valves 50 Pressure Sensor 60 Control Unit 100 medical beds

Claims

1. a fluid supply means capable of supplying a fluid; a fluid passage through which the fluid is supplied from the fluid supply means; a plurality of interconnected first cells; a plurality of interconnected second cells; a first solenoid valve having a first end connected to the plurality of first cells and a second end connected to the fluid passage; a second solenoid valve having a first end connected to the plurality of second cells and a second end connected to the fluid passage; an external solenoid valve having a first end connected to the outside and a second end connected to the fluid passage; a pressure sensor for measuring the pressure of the fluid in the fluid passage; a control unit that receives the measurement result of the pressure sensor and controls the fluid supply means, the first solenoid valve, the second solenoid valve, and the external solenoid valve; Equipped with The control unit a first mode in which the pressure in the second cell is a first pressure and the pressure in the first cell is equal to or lower than a second pressure lower than the first pressure; a second mode in which the pressure in the first cell is set to the first pressure and the pressure in the second cell is set to the second pressure or less; is feasible, When transitioning from the first mode to the second mode, the control unit stops the fluid supply means, closes the first solenoid valve, and opens the second solenoid valve and the external solenoid valve, and determines the first pressure based on the time it takes for the measurement value of the pressure sensor to change from a third pressure that is lower than the first pressure and higher than the second pressure to a fourth pressure that is lower than the third pressure and higher than the second pressure, and the longer the time, the higher the first pressure becomes.

2. a plurality of interconnected third cells; a third solenoid valve having a first end connected to the plurality of third cells and a second end connected to the fluid passage; Furthermore, The control unit a third mode can be realized in which the pressure in the first cell and the pressure in the second cell are set to the first pressure and the pressure in the third cell is set to the second pressure or less; The fluid mattress of claim 1 , wherein the pressure in the third cell is the first pressure in the first mode and the second mode.

3. The control unit When transitioning to the first mode, the fluid supply means is stopped, the second solenoid valve and the third solenoid valve are closed, the first solenoid valve and the external solenoid valve are opened, and a first estimated value of the first pressure is calculated based on the time it takes for the measurement value of the pressure sensor to change from the third pressure to the fourth pressure, When transitioning to the second mode, the fluid supply means is stopped, the first solenoid valve and the third solenoid valve are closed, the second solenoid valve and the external solenoid valve are opened, and a second estimated value of the first pressure is calculated based on the time it takes for the measurement value of the pressure sensor to change from the third pressure to the fourth pressure, When transitioning to the third mode, the fluid supply means is stopped, the first solenoid valve and the second solenoid valve are closed, the third solenoid valve and the external solenoid valve are opened, and a third estimated value of the first pressure is calculated based on the time it takes for the measurement value of the pressure sensor to change from the third pressure to the fourth pressure, The fluid mattress according to claim 2 , wherein the first pressure is an average value of the first estimated value, the second estimated value, and the third estimated value.

4. placed on the bed, The fluid mattress according to claim 2 , wherein the first cells, the second cells, and the third cells are repeatedly arranged from the head side to the foot side of the bed.

5. Further provided with a fourth solenoid valve; The first cell is a first lower cell connected to a first end of the fourth solenoid valve; a first upper cell disposed on the first lower cell and connected to a first end of the first solenoid valve; and The second cell is a second lower cell connected to a first end of the fourth solenoid valve; a second upper cell disposed on the second lower cell and connected to a first end of the second solenoid valve; and The third cell is a third lower cell connected to a first end of the fourth solenoid valve; a third upper cell disposed on the third lower cell and connected to a first end of the third solenoid valve; and 3. The fluid mattress of claim 2, wherein the second end of the fourth solenoid valve is connected to the fluid passage.

6. The fluid mattress according to any one of claims 2 to 5, wherein the control unit repeatedly realizes the first mode, the second mode, and the third mode.

7. The fluid mattress according to claim 1 , wherein the control unit determines the first pressure based on the pressure in the first cell when transitioning from the first mode to the second mode.

8. The control unit driving the fluid supply means to close the first solenoid valve, the second solenoid valve, and the external solenoid valve, and causing the pressure sensor to acquire a first measurement value; driving the fluid supply means to close the first solenoid valve and the second solenoid valve and to open the external solenoid valve, and causing the pressure sensor to acquire a second measurement value; calculating a correction coefficient representing a flow state of the external solenoid valve based on a ratio between the first measurement value and the second measurement value; The fluid mattress of claim 1 , wherein the first pressure is determined based on the correction factor.

9. The control unit determining the posture of the user based on a ratio between a first time period during which the measurement value of the pressure sensor changes from the third pressure to a fifth pressure that is lower than the third pressure and higher than the fourth pressure, and a second time period during which the measurement value of the pressure sensor changes from the fifth pressure to the fourth pressure; The fluid mattress of claim 1 , wherein the first pressure is increased when the user is in a sitting position.

10. The fluid mattress of claim 9, wherein the control unit determines that the user's posture is lying down when the ratio of the first time to the second time is higher than a threshold value, and determines that the user's posture is sitting down when the ratio is lower than the threshold value.

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