JP2012225787A - Differential pressure measuring unit and liquid quantity estimation system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a differential pressure measuring unit in which the quantity of liquids in a liquid tank divided into a plurality of accommodation chambers can be estimated by a single unit, and a liquid quantity estimation system including the differential pressure measuring unit.SOLUTION: A liquid quantity estimation apparatus 7 of a vehicle fuel system 1 includes a vapor-phase diaphragm section 40 which outputs a pressure Pa of a vapor-phase part TA and a first pressure P1 in proportion to an area S(0) of a diaphragm 42, a plurality of liquid-phase diaphragm sections 50 each outputting a total pressure Pc applied to a bottom wall 10b of a plurality of accommodation chambers 11 inside a fuel tank 10 and a second pressure P2 in proportion to an area S of a diaphragm 52, and a differential pressure sensor 30 to which the vapor-phase diaphragm section 40 and the plurality of liquid-phase diaphragm sections 50(1)-50(3) are connected.

Description

  The present invention relates to, for example, a differential pressure measuring unit used for estimating a liquid amount of a liquid such as gasoline or liquefied gas contained in a liquid tank such as a fuel tank of a vehicle, and a liquid amount estimating system including the differential pressure measuring unit. It is about.

  2. Description of the Related Art Conventionally, a fuel remaining amount detection device as a liquid amount estimation device mounted on a vehicle has a liquid level detection unit that detects a liquid level (that is, a liquid level) of fuel in a fuel tank as a liquid tank. As this liquid level detecting means, for example, a pressure type liquid level measuring device disclosed in Patent Document 1 has been used.

  As shown in FIG. 3, a pressure type liquid level measuring device 801 disclosed in Patent Document 1 includes a back pressure box 810 having movable volume chambers X and Y partitioned by a movable partition wall 812, and a liquid at the bottom of the tank. It has a differential pressure sensor A provided in the phase part and a differential pressure sensor B provided in the gas phase part of the upper space in the tank.

  In the differential pressure sensor A, a liquid phase pressure P1 at the tank bottom is guided to one pressure receiving portion, and a pressure guiding tube 823 is connected to a back pressure portion which is the other pressure receiving portion. In the differential pressure sensor B, the gas phase pressure P2 in the tank is guided to one pressure receiving portion, and a pressure guiding tube 824 is connected to the back pressure portion which is the other pressure receiving portion. The pressure guiding pipe 823 and the pressure guiding pipe 824 are connected to each other and connected to the movable volume chamber X of the back pressure box 810. Further, the gas phase portion of the tank is connected to the movable volume chamber Y by a pressure guiding tube 825.

  The liquid pressure P corresponding to the amount of liquid in the liquid phase part is obtained by subtracting the gas phase pressure P2 from the liquid phase pressure P1. The differential pressure sensor A measures the differential pressure between the liquid phase pressure P1 and the pressure P3 in the movable volume chamber X, and the differential pressure sensor B measures the differential pressure between the gas phase pressure P2 and the pressure P3 in the movable volume chamber X. The pressure P3 was canceled by subtracting the differential pressure measured by the differential pressure sensor B from the differential pressure measured by the differential pressure sensor A, and the hydraulic pressure P could be obtained. A control unit (not shown) detects the liquid level in the tank based on the fluid pressure P.

  However, the above-described pressure type liquid level measuring device 801 has a problem that the structure is complicated and the manufacturing cost is high, such as a back pressure box 810 and a plurality of differential pressure sensors A and B partitioned by a movable partition wall 812. It was. In order to solve such a problem, there is a liquid amount estimation device described below.

  As shown in FIG. 4, the liquid amount estimation device 920 includes a differential pressure measurement unit 925 including a differential pressure sensor 930, a gas phase diaphragm unit 940, and a liquid phase diaphragm unit 950, and a control unit (not shown). ing.

  The differential pressure sensor 930 includes a box-shaped sensor case 931, a differential pressure detection diaphragm 932 that partitions the inside of the sensor case 931 into a first pressure receiving chamber 931a and a second pressure receiving chamber 931b, and a first pressure receiving pressure of the differential pressure detecting diaphragm 932. A differential pressure signal output unit (not shown) that outputs a differential pressure signal corresponding to the difference between the pressure received by the surface 932a on the chamber 931a side and the pressure received on the surface 932b on the second pressure receiving chamber 931b side to the control unit. is doing.

  The gas phase diaphragm portion 940 includes a case 941 provided with an opening 941a and a thin film diaphragm 942 provided so as to close the opening 941a. The case 941 is connected to the first pressure receiving chamber 931a via the pressure guiding tube 945. The case 941, the pressure guiding tube 945, and the first pressure receiving chamber 931a are filled with a pressure transmission solution such as silicone oil. The gas phase diaphragm 940 is disposed on the inner surface of the upper wall 910a of the liquid tank 910 with the diaphragm 942 facing the bottom wall 910b. When the diaphragm 942 receives pressure, the first pressure P1 corresponding to the pressure is transmitted to the first pressure receiving chamber 931a via the pressure transmission solution.

  The liquid phase diaphragm unit 950 is configured in the same manner as the gas phase diaphragm unit 940 and includes a case 951 and a diaphragm 952. The area of the diaphragm 952 is formed to be the same area as the diaphragm 942. The case 951 is connected to the second pressure receiving chamber 931b through the pressure guiding tube 955. The case 951, the pressure guiding tube 955, and the second pressure receiving chamber 931b are filled with a pressure transmission solution such as silicone oil. The liquid phase diaphragm portion 950 is disposed on the inner surface of the bottom wall 910b of the liquid tank 910 with the diaphragm 952 facing the upper wall 910a. When the diaphragm 952 receives pressure, the second pressure P2 corresponding to the pressure is transmitted to the second pressure receiving chamber 931b through the pressure transmission solution.

  Since the gas phase diaphragm 940 is disposed on the upper wall 910a of the liquid tank 910, the diaphragm 942 receives the pressure Pa of the gas phase TA, and the first pressure corresponding to the pressure Pa and the area of the diaphragm 942 is obtained. P1 is transmitted to the first pressure receiving chamber 931a. Since the liquid phase diaphragm portion 950 is disposed on the bottom wall 910b of the liquid tank 910, the diaphragm 952 has a total pressure Pc of the pressure Pa of the gas phase portion TA and the liquid pressure Pb of the liquid stored in the liquid tank 910. In response, the second pressure P2 corresponding to the total pressure Pc and the area of the diaphragm 952 is transmitted to the second pressure receiving chamber 931b.

  The higher the height (depth) of the liquid stored in the liquid tank 910, that is, the larger the liquid amount, the higher the fluid pressure Pb, that is, the fluid pressure Pb becomes a pressure corresponding to the fluid amount. The second pressure P2 includes a gas phase pressure component P2a corresponding to the pressure Pa of the gas phase portion TA and the area of the diaphragm 952, and a fluid pressure component P2b corresponding to the fluid pressure Pb and the area of the diaphragm 952. Therefore, when the difference between the first pressure P1 and the second pressure P2 is obtained, the gas phase pressure component P2a included in the first pressure P1 and the second pressure P2 is offset, and the hydraulic pressure component P2b is Output as a differential pressure signal. A control unit (not shown) estimates the amount of liquid in the liquid tank 910 based on this differential pressure signal.

Japanese Patent Laid-Open No. 7-243893

  However, for example, in a case where the liquid stored in the liquid tank is a high-pressure liquefied gas such as liquefied petroleum gas (LPG), a vehicle that is required to improve the pressure resistance of the liquid tank or to make the space in the vehicle more efficient. In order to mount the liquid tank (fuel tank) using a gap in the case, the liquid tank 910 may be partitioned into a plurality of storage chambers 911 (1) to (3) as shown in FIG. In such a case, since it is necessary to estimate the liquid level (liquid amount) for each storage chamber by providing the differential pressure measurement units 925 (1) to (3) for each storage chamber, the liquid amount estimation device 920 is provided. In this case, a plurality of differential pressure measurement units 925 corresponding to the number of the storage chambers are required, resulting in an increase in manufacturing cost.

  The present invention aims to solve the above problems. That is, the present invention provides a differential pressure measurement unit that enables estimation of the amount of liquid in a liquid tank partitioned into a plurality of storage chambers with a smaller number of units than the number of storage chambers, and a liquid having the differential pressure measurement unit. It aims to provide a quantity estimation system.

  In order to achieve the above object, a first aspect of the present invention provides a differential pressure measurement unit used for estimating the amount of liquid in a liquid tank partitioned into a plurality of storage chambers whose gas phase portions communicate with each other. And a differential pressure signal output that outputs a differential pressure signal corresponding to a difference between the pressure received by the first pressure receiving portion, the second pressure receiving portion, and the pressure received by the second pressure receiving portion. And a differential pressure sensor provided in the gas phase portion, connected to the first pressure receiving portion so as to output a first pressure corresponding to the pressure of the gas phase portion and to transmit the first pressure The gas phase diaphragm portion and the bottom walls of each of the plurality of storage chambers are provided at or near the bottom walls, respectively, and a second pressure corresponding to the pressure applied to the bottom walls is output and a plurality of the second pressures are combined. Connected to the second pressure receiving part so that pressure is transmitted. A differential pressure measuring unit, characterized in that it has a number of liquid phase diaphragm portion.

  The invention described in claim 2 is the invention described in claim 1, wherein the amount of change in the combined pressure when the amount of liquid in any one of the plurality of storage chambers changes by a predetermined amount, and Each of the plurality of liquid phase diaphragm portions is formed so that the amount of change in the combined pressure when the amount of liquid in any other storage chamber changes by the predetermined amount is equal. To do.

  The invention described in claim 3 is the invention described in claim 2, wherein each of the plurality of storage chambers of the liquid tank is formed in a vertical cylindrical shape, and each of the diaphragms of the plurality of liquid phase diaphragm portions. And the area ratio is equal to the area ratio of the bottom wall of the storage chamber in which they are provided.

  The invention described in claim 4 is the invention described in any one of claims 1 to 3, wherein the amount of change in the first pressure when the pressure in the gas phase changes by a predetermined amount; Each of the gas phase diaphragm portion and the plurality of liquid phase diaphragm portions is formed so that the amount of change in the combined pressure when the pressure in the gas phase portion changes by the predetermined amount is equal. It is what.

  The invention described in claim 5 is the invention described in claim 4, wherein the thickness of the diaphragm of the gas phase diaphragm portion and the thickness of each of the plurality of liquid phase diaphragm portions are the same, and The gas phase diaphragm portion and the plurality of liquid phase diaphragm portions are formed so that the diaphragm area of the gas phase diaphragm portion and the total area of the diaphragms of the plurality of liquid phase diaphragm portions are equal to each other. It is characterized by being.

  In order to achieve the above object, the invention described in claim 6 is based on the differential pressure measurement unit according to any one of claims 1 to 5 and the differential pressure signal output by the differential pressure measurement unit. A liquid amount estimating device for estimating the amount of liquid in the liquid tank, and a liquid partitioned into a plurality of storage chambers provided with the liquid amount estimating device and having a gas phase portion communicating with each other. A liquid amount estimation system including a tank.

  According to the first and sixth aspects of the present invention, the pressure applied to the bottom walls of the gas phase diaphragm portion that outputs the first pressure corresponding to the pressure of the gas phase portion and the plurality of storage chambers in the liquid tank. And a plurality of liquid phase diaphragm portions that respectively output a second pressure corresponding to the pressure, and a differential pressure sensor to which the gas phase diaphragm portion and the liquid phase diaphragm portion are connected. The first pressure output from the gas phase diaphragm unit is transmitted to the first pressure receiving unit of the differential pressure sensor, and the plurality of second pressures output from the plurality of liquid phase diaphragm units are combined with each other to become a combined pressure. It is transmitted to the second pressure receiving part of the pressure sensor. The combined pressure corresponds to the total pressure of the gas phase pressure component corresponding to the pressure in the gas phase portion and the amount of liquid stored in each storage chamber (that is, the total liquid in the liquid tank). And a hydraulic component. Therefore, the liquid pressure of the entire liquid in the liquid tank can be obtained from the differential pressure signal corresponding to the difference between the first pressure and the combined pressure output by the differential pressure sensor. The liquid pressure has a relationship with the liquid amount of the entire liquid in the liquid tank, and the liquid amount in the liquid tank can be estimated based on the liquid pressure.

  According to the second aspect of the present invention, the amount of change in the combined pressure when the amount of liquid in any one of the plurality of storage chambers changes by a predetermined amount, and the amount of liquid in any other storage chamber Since each of the plurality of liquid phase diaphragm portions is formed so that the amount of change in the combined pressure when the predetermined amount changes is equal to the amount of liquid, the amount of liquid does not change regardless of the amount of liquid in any storage chamber. If the amount of change is the same, the amount of change in the combined pressure (i.e., the fluid pressure component) will be the same. Therefore, the combined pressure changes according to the change in the amount of liquid in the liquid tank.

  According to the invention described in claim 3, each of the plurality of storage chambers of the liquid tank is formed in a vertical cylindrical shape, the thickness of each of the plurality of liquid phase diaphragm portions is the same, and the area ratio is Since it is formed so as to be equal to the area ratio of the bottom wall of the storage chamber in which they are provided, the change in the combined pressure when the liquid amount in any one of the storage chambers changes by a predetermined amount A plurality of liquid phase diaphragm portions in which the amount and the amount of change in the combined pressure when the amount of liquid in any other storage chamber changes by the predetermined amount can be easily formed by adjusting the area of the diaphragm .

  According to the fourth aspect of the present invention, the amount of change in the first pressure when the pressure in the gas phase changes by a predetermined amount, and the amount of change in the combined pressure when the pressure in the gas phase changes by the predetermined amount. Since the gas phase diaphragm portion and the plurality of liquid phase diaphragm portions are formed so as to be equal to each other, the first pressure and the combined pressure (that is, the gas phase diaphragm portion) are changed according to the pressure change of the gas phase portion. Pressure component) changes equally.

  According to the invention described in claim 5, the diaphragm thickness of the gas phase diaphragm part and the thickness of each diaphragm of the plurality of liquid phase diaphragm parts are the same, and the area of the diaphragm of the gas phase diaphragm part, Since the gas phase diaphragm part and the plurality of liquid phase diaphragm parts are formed so that the total area of each diaphragm of the plurality of liquid phase diaphragm parts is equal, when the pressure of the gas phase part changes by a predetermined amount Each of the gas phase diaphragm portion and the plurality of liquid phase diaphragm portions having the same amount of change in the first pressure and the amount of change in the combined pressure when the pressure in the gas phase portion changes by the predetermined amount is defined as the area of the diaphragm. It can be easily formed by adjusting.

  As described above, according to the first and sixth aspects of the present invention, the differential pressure between the first pressure from the gas phase diaphragm portion and the combined pressure from the plurality of liquid phase diaphragm portions, which is output by the differential pressure sensor. Since the liquid pressure of the entire liquid in the liquid tank can be obtained from the corresponding differential pressure signal, in the estimation of the liquid amount of the liquid tank partitioned into the plurality of storage chambers, the same number of differential pressures as the storage chambers The liquid pressure of the entire liquid in the liquid tank can be obtained by using only one unit or a unit smaller than the number of storage chambers without providing a measurement unit. Therefore, based on this liquid pressure, the liquid tank liquid can be obtained at low cost. The amount can be estimated.

  According to the second aspect of the present invention, if the amount of change in the liquid amount is the same regardless of the amount of liquid in any storage chamber of the liquid tank, the amount of change in the combined pressure (that is, the above-described hydraulic pressure component) is also increased. Since the combined pressure changes according to the change in the liquid volume in the liquid tank, the total liquid pressure in the liquid tank obtained from the differential pressure signal output from the differential pressure sensor is also the liquid volume in the liquid tank. Therefore, the amount of liquid in the liquid tank can be estimated easily and accurately based on the liquid pressure.

  According to the invention described in claim 3, the amount of change in the combined pressure when the amount of liquid in any one of the plurality of storage chambers changes by a predetermined amount, and the amount of liquid in any other storage chamber Since a plurality of liquid phase diaphragm portions that are equal to the amount of change in the combined pressure when the pressure changes by the predetermined amount can be easily formed by adjusting the area of the diaphragm, the manufacturing cost can be reduced.

  According to the fourth aspect of the present invention, the first pressure and the combined pressure (that is, the gas phase pressure component) change equally according to the pressure change in the gas phase portion, so that it is output by the differential pressure sensor. In the differential pressure signal between the first pressure and the combined pressure, the change in the first pressure due to the change in the pressure in the gas phase portion and the change in the gas phase pressure component included in the combined pressure are offset. It is possible to prevent a change in pressure in the gas phase caused by a change in ambient temperature from affecting the output of the differential pressure sensor and improve the measurement accuracy.

  According to the fifth aspect of the present invention, the amount of change in the first pressure when the pressure in the gas phase changes by a predetermined amount, and the amount of change in the combined pressure when the pressure in the gas phase changes by the predetermined amount. Since each of the gas phase diaphragm portion and the plurality of liquid phase diaphragm portions that are equal to each other can be easily formed, the manufacturing cost can be reduced.

It is a figure which shows schematic structure of the vehicle fuel system which is one Embodiment of the liquid quantity estimation system of this invention. It is a figure which shows the structure of the modification of the vehicle fuel system of FIG. It is a figure which shows the conventional pressure type liquid level measuring device. It is a figure which shows the structure of the conventional liquid quantity estimation apparatus. FIG. 5 is a diagram illustrating a configuration in which a plurality of liquid amount estimation apparatuses in FIG. 4 are arranged in a liquid tank partitioned into a plurality of storage chambers.

  Hereinafter, a vehicle fuel system, which is an embodiment of the liquid amount estimation system of the present invention, will be described with reference to FIGS.

  A vehicle fuel system described below includes a fuel tank that is mounted on a vehicle and stores liquefied petroleum gas (LPG) as fuel F of the vehicle, and is divided into a plurality of storage chambers that communicate with each other in gas phase portions. And a system for estimating the liquid amount of the fuel F in the fuel tank. In this vehicle fuel system, the amount of fuel F is estimated based on the pressure in the gas phase portion of the fuel tank and the pressures in the liquid phase portions of the plurality of storage chambers.

  In a fuel tank that contains liquefied gas such as LPG as fuel F, the fuel tank is at a high pressure (about 0.1 MPa to 3 MPa). In order to prevent the unevenness of the fuel tank, the fuel tank may be divided into a plurality of storage chambers. The above-described conventional liquid amount estimation apparatus requires a plurality of the above-described conventional differential pressure measurement units in order to estimate the liquid amount in the fuel tank partitioned into the plurality of storage chambers. The differential pressure sensor used for the differential pressure measurement unit is expensive, and the cost increases as the number of differential pressure measurement units increases. The conventional liquid amount measurement device and the differential pressure measurement unit are different from the liquid amount of the fuel tank. It was unsuitable for use in the estimation of. The vehicle fuel system, the liquid amount estimating device, and the differential pressure sensor unit described below are suitable for estimating the liquid amount in the fuel tank partitioned into a plurality of storage chambers.

  As shown in FIG. 1, the vehicle fuel system 1 includes a fuel tank 10 as a liquid tank that contains fuel F, and a liquid that estimates the amount of fuel F (ie, LPG remaining amount) contained in the fuel tank 10. A quantity estimation device 20.

  The fuel tank 10 is a well-known vehicle component that is disposed, for example, under the floor of a vehicle and accommodates the fuel F of the vehicle. The fuel tank 10 is connected to a fuel filling port of a vehicle to which fuel F is supplied from a fuel supply stand or the like through an inflow pipe (not shown). The fuel tank 10 is connected to an injection device for supplying fuel F to an internal combustion engine of the vehicle through an outflow pipe (not shown).

  In the present embodiment, the entire fuel tank 10 is formed in a rectangular parallelepiped box shape, and a plurality of partition walls 10c and 10d that are vertically erected from the inner surface of the bottom wall 10b to about half the height of the fuel tank 10 are provided. , And are provided at intervals in the width direction (left-right direction in FIG. 1). The fuel tank 10 is formed by the partition walls 10c and 10d in the first storage chamber 11 (1), the second storage chamber 11 (2), and the third storage chamber 11 (3) as shown by a dotted line in FIG. It is divided into a plurality of storage rooms. In the present embodiment, each of the storage chambers 11 (1) to 11 (1) to (1) to (1) to (1), the second storage chamber 11 (2), and the third storage chamber 11 (3) are sequentially reduced in volume. 3), and each of the storage chambers 11 (1) to 11 (3) has a cylindrical shape having the same cross-sectional area in the width direction from the top wall 10a to the bottom wall 10b (that is, the axial direction is the vertical direction ( It is formed in a vertical cylinder shape parallel to the vertical direction in FIG. That is, the volume ratio of the storage chambers 11 (1) to (3) is equal to the area ratio of the bottom walls 10b (1) to (3) of the storage chambers 11 (1) to (3). Each of the storage chambers 11 (1) to (3) is formed.

  In each of the first storage chamber 11 (1), the second storage chamber 11 (2), and the third storage chamber 11 (3), a gas phase portion TA that stores vaporized fuel F and the like, and a liquid state And a liquid phase portion TL in which the fuel F is accommodated. In the first storage chamber 11 (1), the second storage chamber 11 (2), and the third storage chamber 11 (3), the partition walls 10 c and 10 d are about half the height of the fuel tank 10. Since each upper part is connected, the gaseous-phase part TA of each storage chamber 11 (1)-(3) is each connected. In the fuel tank 10, only the gas phase portion TA exists when the fuel F is empty, and a slight space is provided even when the fuel F is full, that is, the gas phase portion TA exists.

  The liquid amount estimation apparatus 20 includes a differential pressure measurement unit 25 including a differential pressure sensor 30, a gas phase diaphragm unit 40, and a plurality of liquid phase diaphragm units 50, and a control unit 60.

  The differential pressure sensor 30 is provided in a sensor case 31 formed in a box shape, a differential pressure detection diaphragm 32 that partitions the sensor case 31 into a first pressure receiving chamber 31a and a second pressure receiving chamber 31b, and a differential pressure detection diaphragm 32. And a strain gauge (not shown) that outputs a signal corresponding to the deformation amount of the differential pressure detection diaphragm 32 (that is, a differential pressure signal). In the differential pressure detection diaphragm 32, one pressure receiving surface 32a faces the first pressure receiving chamber 31a, and the other pressure receiving surface 32b faces the second pressure receiving chamber 31b. The pressure in the first pressure receiving chamber 31a The pressure receiving chamber 31b is deformed in accordance with the pressure balance (that is, the difference between them). The strain gauge outputs a differential pressure signal in accordance with the deformation amount of the differential pressure detection diaphragm 32. The differential pressure sensor 30 is provided on the outer surface of the upper wall 10a of the fuel tank 10, and its strain gauge is connected to a control unit 60 described later. One pressure receiving surface 32a corresponds to the first pressure receiving portion in the claims, the other pressure receiving surface 32b corresponds to the second pressure receiving portion in the claims, and the strain gauge is the differential pressure in the claims. It corresponds to the signal output unit.

  The gas phase diaphragm unit 40 includes a case 41 and a diaphragm 42. The case 41 is formed in a flat box shape having rigidity that does not deform due to pressure in the fuel tank 10 using a metal material such as stainless steel, for example, and an opening 41a is provided in one plane portion. The diaphragm 42 is formed in a thin film shape using, for example, a metal material such as stainless steel, and is disposed so as to close the opening 41 a of the case 41 so that the inside of the case 41 becomes a sealed space. When a pressure is applied to the outer surface of the diaphragm 42 thus provided, a first pressure P1 corresponding to the pressure is output to a pressure guiding tube 45 connected to the case 41 via a pressure transmission solution described later. . The first pressure P <b> 1 has a magnitude proportional to the pressure applied to the outer surface of the diaphragm 42 and the area of the diaphragm 42.

  The gas phase diaphragm portion 40 is disposed on the inner surface of the upper wall 10a of the fuel tank 10 so that the opening 41a (that is, the diaphragm 42) of the case 41 faces the bottom wall 10b of the fuel tank 10. The case 41 of the gas phase diaphragm section 40 is connected to the first pressure receiving chamber 31 a of the differential pressure sensor 30 via the pressure guiding tube 45. That is, the gas phase diaphragm 40, the pressure guiding tube 45, and the first pressure receiving chamber 31a are in communication with each other.

  The plurality of liquid phase diaphragm portions 50 are configured in the same manner as the gas phase diaphragm portion 40, and include a case 51 and a diaphragm 52. The case 51 is formed into a flat box shape having rigidity that does not deform due to the pressure in the fuel tank 10 using, for example, a metal material such as stainless steel, and an opening 51a is provided in one flat portion. The diaphragm 52 is formed into a thin film having the same thickness as the diaphragm 42 of the gas-phase diaphragm section 40 using, for example, a metal material such as stainless steel, so that the inside of the case 51 is a sealed space. It arrange | positions so that the opening 51a may be plugged up. When a pressure is applied to the outer surface of the diaphragm 52 thus provided, a second pressure P2 corresponding to the pressure is output to a pressure guiding tube 55 connected to the case 51 via a pressure transmission solution described later. . The second pressure P <b> 2 has a magnitude proportional to the pressure applied to the outer surface of the diaphragm 52 and the area of the diaphragm 52.

  Each of the plurality of liquid phase diaphragm portions 50 has the bottom wall 10b (1) of each of the storage chambers 11 (1) to (3) such that the opening 51a (that is, the diaphragm 52) faces the upper wall 10a of the fuel tank 10. ) To (3) are arranged on the inner surface. Of course, the present invention is not limited to this. For example, each of the plurality of liquid phase diaphragm portions 50 has a slight gap between the diaphragm 52 and the bottom wall 10b so that the opening 51a faces the bottom wall 10b. The pressure applied to the bottom wall 10b (including a pressure equivalent to the pressure to the extent that it does not contradict the purpose of the present invention, that is, the total pressure Pc described later) is applied to the diaphragm 52. The bottom wall 10b or the vicinity thereof may be provided. In particular, by directing the diaphragm 52 toward the bottom wall 10b, it is possible to prevent the liquid from remaining on the diaphragm 52 when the liquid level falls below the diaphragm 52, and to prevent the influence of the vibration of the liquid. Occurrence can be prevented. That is, the liquid phase diaphragm portion 50 may be disposed with the diaphragm 52 in either the upper or lower direction, but is desirably disposed downward for an automobile application in which vibration during driving occurs.

  Hereinafter, when distinguishing the plurality of liquid phase diaphragm portions 50 provided in each of the storage chambers 11 (1) to (3) and their constituent members, it corresponds to each of the storage chambers 11 (1) to (3). In addition, (1) to (3) are attached to the end of the code. Each of the case 51 (1) to (3) of each liquid phase diaphragm portion 50 (1) to (3) is connected to the second pressure receiving chamber 31 b of the differential pressure sensor 30 via the pressure guiding tube 55. That is, the plurality of diaphragm portions 50 (1) to (3), the pressure guiding tube 55, and the second pressure receiving chamber 31b are in communication with each other.

The diaphragms 52 (1) to (3) of the liquid phase diaphragm portions 50 (1) to (3) have respective area ratios, and the respective housings in which the liquid phase diaphragm portions 50 (1) to (3) are provided. It is formed to be equal to the area ratio of the bottom walls 10b (1) to (3) of the chambers 11 (1) to (3). That is, the areas of the diaphragms 52 (1) to (3) are sequentially set to S (1), S (2), and S (3), and the areas of the bottom walls 10b (1) to (3) are sequentially set to T. When (1), T (2), and T (3) are set, the diaphragms 52 (1) to (3) are formed so that the following equation (i) is established.
S (1): S (2): S (3) = T (1): T (2): T (3) (i)

Further, each of the gas phase diaphragm unit 40 and each of the liquid phase diaphragm units 50 (1) to (3) includes an area of the diaphragm 42 of the gas phase diaphragm unit 40 and each of the liquid phase diaphragm units 50 (1) to (3). ) Of the diaphragms 52 (1) to (3) are equal to each other. That is, when the area of the diaphragm 42 is S (0) and the areas of the diaphragms 52 (1) to (3) are sequentially S (1), S (2), and S (3), the following (ii) The vapor phase diaphragm 40 and the liquid phase diaphragms 50 (1) to 50 (3) are formed so that the formula
S (0) = S (1) + S (2) + S (3) (ii)

  For example, a pressure transmission solution such as silicon oil is sealed in the gas phase diaphragm 40, the pressure guiding tube 45, and the first pressure receiving chamber 31a. When the diaphragm 42 receives pressure, the gas-phase diaphragm unit 40 outputs a first pressure P1 proportional to the pressure and the area S (0) of the diaphragm 42. The first pressure P1 is transmitted to the first pressure receiving chamber 31a via the pressure transmission solution. In addition, the same pressure transmission solution as described above is sealed in each of the liquid phase diaphragm portions 50 (1) to (3), the pressure guiding tube 55, and the second pressure receiving chamber 31b. When each diaphragm 52 (1)-(3) receives pressure, each liquid phase diaphragm 50 (1)-(3) is proportional to the pressure and the area S (1)-(3) of the diaphragm 52. 2 pressures P2 (1) to (3) are output. The second pressures P2 (1) to (3) are combined with each other to become a combined pressure P2g, and the combined pressure P2g is transmitted to the second pressure receiving chamber 31b through the pressure transmission solution.

Since the gas phase diaphragm portion 40 is provided on the inner surface of the upper wall 10a of the fuel tank 10, the pressure Pa of the gas phase portion TA is applied to the diaphragm 42. Therefore, the first pressure P1 output from the gas phase diaphragm section 40 is proportional to the pressure Pa of the gas phase section TA and the area S (0) of the diaphragm 42. This relationship is shown in equation (iii).
P1 = Pa × S (0) × α0 (iii)
(However, α0 is a constant)

Moreover, since the liquid phase diaphragm part 50 (1) is provided in the inner surface of the bottom wall 10b (1), the pressure added to the bottom wall 10b (1) is added to the diaphragm 52 (1). This pressure is the total pressure Pc (1) of the pressure Pa of the gas phase portion TA and the hydraulic pressure Pb (1) due to the weight of the fuel F in the storage chamber 11 (1). Therefore, the second pressure P2 (1) output from the liquid phase diaphragm unit 50 (1) is proportional to the total pressure Pc (1) of the pressure Pa and the hydraulic pressure Pb (1) and the area S (1) of the diaphragm 52. To do. This relationship is shown in equation (iv).
P2 (1) = (Pa + Pb (1)) × S (1) × α1 (iv)
(However, α1 is a constant)

In addition, the second pressure P2 (2) output from the liquid phase diaphragm 50 (2) is similar to the above in that the pressure Pa of the gas phase TA and the pressure of the fuel F in the storage chamber 11 (2) are self-weighted. The second pressure P2 (3), which is proportional to the total pressure Pc (2) with Pb (2) and the area S (2) of the diaphragm 52 and output from the liquid phase diaphragm 50 (3), is similar to the above. It is proportional to the total pressure Pc (3) of the pressure Pa of the gas phase TA and the hydraulic pressure Pb (3) due to the dead weight of the fuel F in the storage chamber 11 (3) and the area S (3) of the diaphragm 52. These relationships are shown in equations (v) and (vi).
P2 (2) = (Pa + Pb (2)) × S (2) × α2 (v)
P2 (3) = (Pa + Pb (3)) × S (3) × α3 (vi)
(However, α2 and α3 are constants)

  The constants α0 to α3 included in the expressions (iii) to (vi) are determined according to the configuration such as the thickness (rigidity) of each diaphragm and the thickness of the pressure guiding tube. In the present embodiment, each diaphragm portion, the pressure guiding tube, and the differential pressure sensor are configured so that these constants α0 to α3 are equal and have the same constant α.

The combined pressure P2g obtained by combining the second pressures P2 (1) to (3) is the sum of the above P2 (1) to (3) and the following (vii) derived in consideration of the above equation (ii). ).
P2g = P2 (1) + P2 (2) + P2 (3)
= (S (1) + S (2) + S (3)) × Pa × α
+ (Pb (1) × S (1) + Pb (2) × S (2) + Pb (3) × S (3)) × α
= S (0) × Pa × α
+ (Pb (1) × S (1) + Pb (2) × S (2) + Pb (3) × S (3)) × α
... (vii)

Here, the hydraulic pressure Pb (1) can be obtained by multiplying the depth h (1) of the fuel F (liquid), the specific gravity ρ of the fuel F, and the gravitational acceleration g.
Pb (1) = h (1) × ρ × g (viii)
In addition, since the storage chamber 11 (1) is formed in a vertical cylinder shape, the liquid amount V (1) in the storage chamber 11 (1) is determined based on the liquid depth h (1) and the bottom wall 10b (1). Can be obtained by multiplying by the area S (1).
V (1) = h (1) × S (1) (ix)

From these (viii) and (ix) equations, the liquid volume V (1) in the storage chamber 11 (1) is
Pb (1) = (V (1) / S (1)) × ρ × g
V (1) = (Pb (1) × S (1)) / (ρ × g) (x)
Similarly, the liquid amount V (2) in the storage chamber 11 (2) and the liquid amount V (3) in the storage chamber 11 (3) are
V (2) = (Pb (2) × S (2)) / (ρ × g) (xi)
V (3) = (Pb (3) × S (3)) / (ρ × g) (xii)
It becomes.

Then, the following equation (xiii) is derived from the above equations (vii) and (x) to (xii) as a constant α ′ = (ρ × g) × α.
P2g = (S (0) × Pa × α) + ((V (1) + V (2) + V (3)) × α ′)
... (xiii)
In the above formula (xiii), the first term on the right side represents the gas phase pressure component P2a corresponding to the pressure Pa of the gas phase part TA, and the second term on the right side represents the fluid pressure of the entire fuel F in the fuel tank 10. The hydraulic component P2b is shown. The total value of the liquid amounts V (1) to (3) indicates the liquid amount of the entire fuel F accommodated in the fuel tank 10.

The first pressure P1 is applied to one pressure receiving surface 32a of the differential pressure detection diaphragm 32 of the differential pressure sensor 30, and the combined pressure P2g is applied to the other pressure receiving surface 32b. The differential pressure detection diaphragm 32 is deformed according to the first pressure P1 and the combined pressure P2g, and outputs a differential pressure signal according to the difference ΔP between the first pressure P1 and the combined pressure P2g. The difference ΔP between the first pressure P1 and the combined pressure P2g is obtained from the above equations (iii) and (xiii).
ΔP = P2g−P1
= (S (0) × Pa × α) + ((V (1) + V (2) + V (3)) × α ′)
− (S (0) × Pa × α)
= (V (1) + V (2) + V (3)) × α ′ (xiv)
The difference ΔP is a hydraulic pressure component P2b corresponding to the hydraulic pressure of the entire fuel F in the fuel tank 10, that is, a value indicating the total amount of the fuel F accommodated in the fuel tank 10.

  From this equation (xiv), when the pressure Pa of the gas phase portion TA changes, both the first pressure P1 and the combined pressure P2g change. However, when the difference ΔP is obtained, the gas pressure of the first pressure P1 and the combined pressure P2g The component P2a is canceled out, that is, the change amount of the first pressure Pa when the pressure Pa of the gas phase portion TA changes by a predetermined amount and the change amount of the pressure Pa of the gas phase portion TA when the predetermined amount changes. The amount of change in the combined pressure P2g becomes equal.

  Moreover, each liquid phase diaphragm part 50 (1)-(3) outputs 2nd pressure P2 (1)-(3) proportional to the area of each diaphragm 52 (1)-(3). And from the said (i) type | formula, the area ratio of the area S (1)-(3) of each diaphragm 52 (1)-(3) is the bottom wall 10b of each storage chamber 11 (1)-(3) ( 1) to (3) are equal to the area ratio of the areas T (1) to (3), and the respective storage chambers 11 (1) to (3) are formed in a vertical cylindrical shape, so that the respective volume ratios are also It becomes equal to the area ratio of the areas T (1) to (3). Therefore, when the liquid volumes V (1) to (3) in the storage chambers 11 (1) to (3) are the same, the second pressure output from each liquid phase diaphragm section 50 (1) to (3). P2 (1) to (3) are the same. That is, the amount of change in the combined pressure P2g when the amount of liquid in any one of the plurality of storage chambers 11 (1) to (3) changes by a predetermined amount, and in any other storage chamber 11 The amount of change in the combined pressure P2g when the amount of liquid changes by the predetermined amount becomes equal.

  The control unit 60 is composed of, for example, a known microcomputer and controls the entire liquid amount estimation apparatus 20. The microcomputer of the control unit 60 includes a central processing unit (CPU), a ROM, a RAM, a data memory, an external interface, and the like.

  The CPU manages various controls in the vehicle fuel system 1 and executes various processes including controls according to the present embodiment in accordance with various control programs stored in the ROM. The ROM stores various information such as the control program and parameters referred to by the control program. In particular, the ROM stores a control program for causing the CPU to function as various means such as a liquid amount estimating means. And CPU functions as various means mentioned above by running this control program. The RAM appropriately stores data, programs and the like necessary for the CPU to execute various processes. The data memory is composed of a nonvolatile memory that can retain data even when the power is cut off, such as an EEPROM (Electrically Erasable Programmable ROM) or a flash memory. The data memory stores various information such as mathematical formulas and parameters used in the liquid amount estimation process. In particular, this data memory stores a data table indicating the relationship between the differential pressure signal and the amount of liquid in the entire fuel F stored in the fuel tank 10. The above-mentioned differential pressure sensor 30 is connected to the external interface, and a differential pressure signal from the differential pressure sensor 30 is input to the CPU through the external interface. Further, the external interface is connected to a vehicle network (not shown) so as to be able to communicate with other electronic equipment (ECU).

  When the differential pressure signal from the differential pressure sensor 30 is input, the CPU refers to the data table stored in the data memory, acquires the liquid amount corresponding to the differential pressure signal, and according to the liquid amount The display signal is generated, and the display signal is transmitted to a combination meter (meter ECU) (not shown) through the vehicle network. When the combination meter receives this display signal, the combination meter displays the amount of liquid indicated by the display signal on the fuel gauge of the combination meter. In order to avoid the influence of the weight of the pressure transmission solution on the differential pressure measurement value, it is preferable to correct the differential pressure signal in the CPU or to create a data table in consideration of the influence in advance. The CPU (control unit 60) corresponds to the liquid amount estimating means in the claims.

  According to the present embodiment, the liquid amount estimation device 7 of the vehicle fuel system 1 outputs the first pressure P1 proportional to the pressure Pa of the gas phase portion TA and the area S (0) of the diaphragm 42. And the second pressure P2 proportional to the pressure (total pressure Pc (1)) applied to the bottom wall 10b (1) of the storage chamber 11 (1) in the fuel tank 10 and the area S (1) of the diaphragm 52 (1). The liquid phase diaphragm 50 (1) for outputting (1), the pressure (total pressure Pc (2)) applied to the bottom wall 10b (2) of the storage chamber 11 (2) in the fuel tank 10 and the diaphragm 52 (2 ) Is applied to the liquid phase diaphragm portion 50 (2) that outputs the second pressure P2 (2) proportional to the area S (2) and the bottom wall 10b (3) of the storage chamber 11 (3) in the fuel tank 10. Pressure (total pressure Pc (3)) and diaphragm 5 The liquid phase diaphragm portion 50 (3) that outputs the second pressure P2 (3) proportional to the area S (3) of (3), the gas phase diaphragm portion 40, and the plurality of liquid phase diaphragm portions 50 (1) to 50 (1). (3) is connected to the differential pressure sensor 30.

  The first pressure P1 output from the gas phase diaphragm unit 40 is transmitted to one pressure receiving surface 32a of the differential pressure sensor 30. The plurality of second pressures P2 (1) to (3) output from each of the plurality of liquid phase diaphragm portions 50 (1) to (3) are combined with each other to become a combined pressure P2g, and the other pressure received by the differential pressure sensor 30. It is transmitted to the surface 32b. The combined pressure P2g is proportional to the gas pressure P2a proportional to the pressure Pa of the gas phase TA and the total area of the diaphragms 52 (1) to (3), and to the hydraulic pressure of the entire fuel F in the fuel tank 10. Hydraulic component P2b. Therefore, the hydraulic pressure (hydraulic pressure component P2b) of the entire fuel F in the fuel tank 10 is obtained from the differential pressure signal corresponding to the difference ΔP between the first pressure P1 and the combined pressure P2g output by the differential pressure sensor 30. Can do. The liquid pressure has a relationship with the liquid amount in the fuel tank 10, and the liquid amount in the fuel tank 10 can be estimated based on the liquid pressure. Therefore, in the estimation of the liquid amount in the fuel tank 10 partitioned into the plurality of storage chambers 11 (1) to (3), one differential pressure measurement is performed without providing a plurality of differential pressure measurement units (that is, differential pressure sensors). The liquid pressure of the entire liquid in the fuel tank 10 can be obtained by using only the unit 25, and therefore the liquid amount in the fuel tank 10 can be estimated at low cost based on this liquid pressure.

  Further, the amount of change in the combined pressure P2g when the amount of liquid in any one of the plurality of storage chambers 11 (1) to (3) changes by a predetermined amount, and in any other storage chamber 11 Since each of the plurality of liquid phase diaphragm portions 50 (1) to (3) is formed so that the amount of change of the combined pressure P2g when the amount of liquid changes by the predetermined amount is equal, Even if the amount of liquid in the storage chambers 11 (1) to (3) changes, if the amount of change in the amount of liquid is the same, the amount of change in the combined pressure P2g (that is, the fluid pressure component P2b) will be the same. The synthetic pressure P2g changes in proportion to the change in the amount of liquid in the tank 10. Therefore, the hydraulic pressure of the entire fuel F in the fuel tank 10 obtained from the differential pressure signal output from the differential pressure sensor 30 also changes in proportion to the amount of liquid in the fuel tank 10, and therefore, based on this hydraulic pressure. The amount of liquid in the fuel tank 10 can be estimated easily and accurately.

  In addition, each of the plurality of storage chambers 11 (1) to (3) of the fuel tank 10 is formed in a vertical cylindrical shape, and each of the diaphragms 52 (1) of the plurality of liquid phase diaphragm portions 50 (1) to (3). ) To (3) are formed so as to be equal to the area ratio of the bottom walls 10b (1) to (3) of the storage chamber 11 in which they are provided. ) To (3), the amount of change in the combined pressure P2g when the amount of liquid in any one storage chamber 11 changes by a predetermined amount, and the amount of liquid in any other storage chamber 11 changes by the predetermined amount. Adjust the areas S (1) to (3) of the diaphragms 52 (1) to (3) and the plurality of liquid phase diaphragms 50 (1) to (3) that have the same amount of change in the combined pressure P2g. By doing so, it can be formed easily. Therefore, the manufacturing cost can be reduced.

  Further, the amount of change in the first pressure P1 when the pressure Pa of the gas phase portion TA changes by a predetermined amount is equal to the amount of change of the combined pressure P2g when the pressure Pa of the gas phase portion TA changes by the predetermined amount. Since each of the gas-phase diaphragm section 40 and the plurality of liquid-phase diaphragm sections 50 (1) to (3) is formed, the first pressure P1 is combined with the pressure change in the gas-phase section TA. The pressure P2g (that is, the gas phase pressure component P2a) changes equally. Therefore, in the differential pressure signal between the first pressure P1 and the synthesized pressure P2g output by the differential pressure sensor 30, the change in the first pressure P1 due to the change in the pressure Pa of the gas phase portion TA and the gas contained in the synthesized pressure P2g. The change in the phase pressure component P <b> 2 a is canceled out, and therefore, the change in the pressure Pa of the gas phase portion TA due to the change in the ambient temperature of the fuel tank 10 is prevented from affecting the output of the differential pressure sensor 30. Measurement accuracy can be improved.

  Further, the thickness of the diaphragm 42 of the gas phase diaphragm section 40 is the same as the thickness of each of the diaphragms 52 (1) to (3) of the plurality of liquid phase diaphragm sections 50 (1) to (3), and the diaphragm 42. Of the gas phase diaphragm section 40 and the plurality of liquid phases so that the area S (0) of the gas and the total area S (1) + S (2) + S (3) of the diaphragms 52 (1) to (3) are equal. Since the diaphragm portions 50 (1) to (3) are formed, the change amount of the first pressure P1 when the pressure Pa of the gas phase portion TA is changed by a predetermined amount and the pressure Pa of the gas phase portion TA are The gas phase diaphragm portion 40 and the plurality of liquid phase diaphragm portions 50 (1) to (3) having the same amount of change in the combined pressure P2g when quantitatively changed are respectively connected to the diaphragms 42, 52 (1) to (3). ) Area S (0) to (3 It can be easily formed by adjusting the. Therefore, the manufacturing cost can be reduced.

  Moreover, since each of the gas-phase diaphragm section 40 and the plurality of liquid-phase diaphragm sections 50 (1) to (3) is configured by sealing silicon oil as a pressure transmission solution, for example, the thickness is the same. In a plurality of diaphragms having different areas, the rigidity tends to be higher as the diaphragm area is smaller. Therefore, the smaller the diaphragm area in each of the diaphragm portions 40, 50 (1) to (3), the output pressure corresponding to the applied pressure. However, when the pressure transmission solution is sealed, the diaphragm is less likely to be deformed than when the gas is sealed as the pressure transmission medium. Therefore, the diaphragms 42, 52 (1) to (3) The difference in rigidity (deformation amount) is the first pressure P1 and the second pressure P2 (the second pressure P2 output from each diaphragm section 40, 50 (1) to (3)). ) Impact on to (3) becomes smaller. Therefore, the measurement accuracy of the difference ΔP can be improved, and the estimation accuracy of the liquid amount in the fuel tank 10 can be improved.

  In the present embodiment, in the differential pressure measurement unit 25, the gas phase diaphragm section 40 outputs a first pressure P1 proportional to the pressure Pa of the gas phase section TA received by the diaphragm 42 and the area S (0) of the diaphragm 42, The liquid phase diaphragm portions 50 (1) to (3) are proportional to the total pressures Pc (1) to (3) received by the diaphragms 52 (1) to (3) and the areas S (1) to (3) of the diaphragm 52. The second pressures P2 (1) to (3) are output, but the present invention is not limited to this.

  For example, the area of each of the diaphragms 42 and 52 (1) to (3) is made the same and the thickness (rigidity) is adjusted according to the areas T (0) to (3), respectively. The first pressure P1 proportional to the pressure Pa of the gas phase TA received by the diaphragm 42 and the area T (0) of the upper wall 10a is output, and the liquid phase diaphragms 50 (1) to (3) are connected to the diaphragm 52 (1 ) To (3) are proportional to the total pressure Pc (1) to (3) and the area T (1) to (3) of the bottom wall 10b (that is, the volume of each storage chamber 11 (1) to (3)). The second pressures P2 (1) to (3) may be output. Since the fuel tank 10 is a rectangular parallelepiped, the area T (0) of the upper wall 10a is equal to the total area of the areas T (1) to (3) of the bottom wall 10b. That is, by adjusting the thickness of each of the diaphragms 42, 52 (1) to (3), the liquid amount in any one of the plurality of storage chambers 11 (1) to (3) has changed by a predetermined amount. The plurality of liquid phase diaphragm portions 50 (1) so that the amount of change in the combined pressure P2g at the time and the amount of change in the combined pressure P2g when the amount of liquid in any other storage chamber changes by the predetermined amount are equal. ) To (3) are formed, and further, the amount of change in the first pressure P1 when the pressure of the gas phase portion TA changes by a predetermined amount and the composition when the pressure of the gas phase portion TA changes by the predetermined amount. Each of the gas phase diaphragm portion 40 and the plurality of liquid phase diaphragm portions 50 (1) to (3) is formed so that the amount of change in the pressure P2g is equal.

  Alternatively, in the configuration in which the area or thickness of each of the diaphragms 42 and 52 (1) to (3) is not particularly considered (for example, the configuration in which the area or thickness is not adjusted to be the same), the gas-phase diaphragm unit 40 The first pressure P1 output from the gas phase is a value corresponding to at least the pressure Pa of the gas phase TA, and the second pressures P2 (1) to (3) output from the liquid phase diaphragms 50 (1) to (3). ) Includes a gas phase pressure component P2a having a value corresponding to at least the pressure Pa of the gas phase part TA. For example, in the initialization process of the differential pressure sensor 30, the first pressure P1 and By adjusting the zero point so that the gas phase pressure component P2a of the combined pressure P2g is offset, the amount of liquid in the fuel tank 10 can be estimated.

  That is, the differential pressure measurement unit 25 is provided at least in the differential pressure sensor 30 and the gas phase portion TA, and outputs the first pressure P1 corresponding to the pressure Pa of the gas phase portion TA and the first pressure P1 is transmitted. The gas-phase diaphragm 40 connected to one pressure receiving surface 32a of the differential pressure sensor 30 and the bottom walls 10b (1) to (3) of the plurality of storage chambers 11 (1) to (3) as shown in FIG. The second pressures P2 (1) to (3) are output according to the total pressures Pc (1) to (3) applied to the bottom walls 10b (1) to (3), respectively, and a plurality of the second pressures are output. A plurality of liquid phase diaphragm portions 50 (1) to (3) respectively connected to the other pressure receiving surface 32b of the differential pressure sensor 30 so that the combined pressure P2g of P2 (1) to (3) is transmitted. If so, for example, the above formulas (i) and (ii) are not satisfied. At best, it not limited to the configuration of the present embodiment described above, unless contrary to the object of the present invention, the configuration of the differential pressure measuring unit 25 is arbitrary.

  In the present embodiment, the gas phase diaphragm section 40, the pressure guiding tube 45, and the first pressure receiving chamber 31a are filled with a pressure transmission solution such as silicon oil, and similarly, each liquid phase diaphragm section 50 (1). (3) The pressure transmission tube 55 and the second pressure receiving chamber 31b are filled with the same pressure transmission solution as described above. However, the pressure transmission solution is not limited to this and is replaced with the pressure transmission solution. In addition, a gas may be enclosed as a pressure transmission medium. Thus, by using gas as the pressure transmission medium, the influence of the pressure transmission medium's own weight on the differential pressure measurement value can be reduced, and the differential pressure measurement accuracy can be improved. In particular, the fuel tank is deep and the pressure guiding tube is deep. The effect becomes remarkable when it becomes long in the vertical direction.

  Further, in the present embodiment, the fuel tank 10 is formed in a rectangular parallelepiped box shape, but is not limited to this, and for example, as shown in FIG. 2, the height, width, and depth are different. A fuel tank 10 configured by combining a plurality of storage chambers 11 may be used. Further, the storage chamber is not limited to a vertical cylindrical shape. That is, the shape of the fuel tank 10 is arbitrary as long as it does not contradict the purpose of the present invention.

  Although the above-described embodiment describes a vehicle fuel system that is mounted on a vehicle and accommodates liquefied gas and estimates the amount of liquid, the present invention is not limited to this. For example, it may be a liquid amount estimation system that is installed in a factory or home, and contains various liquid fuels or various chemicals and estimates the amount of the liquid. The apparatus and system to apply are arbitrary. In addition, the liquid whose liquid amount is to be estimated is not limited to liquefied petroleum gas, for example, liquefied gas for industrial use such as nitrogen, oxygen and ammonia, or fuel that is liquid at normal temperature and pressure (kerosene, gasoline) Etc.), various chemicals, etc., as long as they do not contradict the purpose of the present invention.

  In addition, embodiment mentioned above only showed the typical form of this invention, and this invention is not limited to embodiment. That is, various modifications can be made without departing from the scope of the present invention.

1 Vehicle fuel system (liquid level estimation system)
10 Fuel tank (liquid tank)
10b Bottom wall of fuel tank (bottom wall of containment chamber)
DESCRIPTION OF SYMBOLS 11 Several storage chambers 20 Liquid quantity estimation apparatus 25 Differential pressure measurement unit 30 Differential pressure sensor 32 Differential pressure detection diaphragm 32a One pressure receiving surface (1st pressure receiving part)
32b The other pressure receiving surface (second pressure receiving portion)
40 Gas Phase Diaphragm Unit 41 Case 42 Diaphragm 50 Multiple Liquid Phase Diaphragm Units 51 Case 52 Diaphragm 60 Control Unit (Liquid Volume Estimating Unit)
TA gas phase TL liquid phase Pa gas phase pressure Pc total pressure (pressure applied to the bottom wall of the storage chamber)
P1 1st pressure P2 2nd pressure P2g Composite pressure

Claims (6)

A differential pressure measurement unit used for estimating the amount of liquid in a liquid tank partitioned into a plurality of storage chambers in which gas phase portions are communicated with each other,
A first pressure receiving unit, a second pressure receiving unit, and a differential pressure signal output unit that outputs a differential pressure signal according to a difference between the pressure received by the first pressure receiving unit and the pressure received by the second pressure receiving unit; Having a differential pressure sensor;
A gas phase diaphragm portion provided in the gas phase portion, connected to the first pressure receiving portion so as to output a first pressure corresponding to the pressure of the gas phase portion and transmit the first pressure;
Each of the plurality of storage chambers is provided at or near the bottom wall, and outputs a second pressure corresponding to the pressure applied to the bottom wall, and transmits the combined pressure of the plurality of second pressures. And a plurality of liquid phase diaphragm portions respectively connected to the second pressure receiving portion.   The amount of change in the combined pressure when the liquid amount in any one of the plurality of storage chambers changes by a predetermined amount, and the combination when the amount of liquid in any other storage chamber changes by the predetermined amount 2. The differential pressure measurement unit according to claim 1, wherein each of the plurality of liquid phase diaphragm portions is formed so that the amount of change in pressure is equal. Each of the plurality of storage chambers of the liquid tank is formed in a vertical cylindrical shape,
The diaphragms of the plurality of liquid phase diaphragm portions are formed to have the same thickness and an area ratio equal to an area ratio of a bottom wall of the storage chamber in which the diaphragms are provided. 2. The differential pressure measurement unit according to 2.   The amount of change in the first pressure when the pressure in the gas phase changes by a predetermined amount is equal to the amount of change in the combined pressure when the pressure in the gas phase changes by the predetermined amount. The differential pressure measuring unit according to any one of claims 1 to 3, wherein each of the gas phase diaphragm portion and the plurality of liquid phase diaphragm portions is formed.   The thickness of the diaphragm of the gas phase diaphragm part and the thickness of each of the plurality of liquid phase diaphragm parts are the same, and the area of the diaphragm of the gas phase diaphragm part, and each of the plurality of liquid phase diaphragm parts The differential pressure measuring unit according to claim 4, wherein the gas phase diaphragm portion and the plurality of liquid phase diaphragm portions are formed so that a total area of the diaphragms is equal. A differential pressure measuring unit according to any one of claims 1 to 5, and a liquid amount estimating means for estimating a liquid amount in a liquid tank based on a differential pressure signal output from the differential pressure measuring unit. A liquid amount estimation device;
A liquid amount estimation system comprising: a liquid tank provided with the liquid amount estimation device and partitioned into a plurality of storage chambers in which gas phase portions are communicated with each other.

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