JP5963296B2 - Flow switch - Google Patents

Description

  The present invention relates to a flow switch for detecting a flow presence / absence state of a fluid such as a gas flowing in a pipeline.

  FIG. 9 shows a conventional flow switch 910 disclosed in Patent Document 1. In the flow switch 910, a piston 901 having an orifice 905 provided in the center is accommodated in a cylinder 906 constituting a pipe so as to be slidable. At both ends of the cylinder 906, an inlet 907 for taking a fluid such as water into the cylinder 906 and an outlet 908 for discharging the fluid from the cylinder 906 are provided. The inlet 907 and the outlet 908 are connected to the end of another pipe 909.

  A magnet portion 902 is provided on the outer peripheral surface of the piston 901. A compression coil spring 904 is disposed in the cylinder 906, and the piston 901 is constantly urged toward the inlet 907 side of the cylinder 906 by the compression coil spring 904. Further, a magnetically sensitive switch element 903 that operates in response to the magnetic force of the magnet portion 902 is attached to the outer surface of the cylinder 906.

  In the flow switch 910, when no fluid flows in the pipe 909, the fluid pressures P1 and P2 acting on the piston 901 are balanced with each other before and after the orifice 905 of the piston 901. Since only the urging force of the compression coil spring 904 is acting on the piston 901, the piston 901 is in a position moved toward the inlet 907 in the cylinder 906. When the piston 901 is in this position, the magnet part 902 of the piston 901 is separated from the magnetically sensitive switch element 903, and the magnetically sensitive switch element 903 is not affected by the magnetic force of the magnet part 902 and its contact point. Is in the off state.

  Further, when a fluid flows in the pipe 909, the fluid flow enters the inside of the cylinder 906 from the inlet 907, passes through the orifice 905 of the piston 901, and goes to the outlet 908. Since the fluid is throttled when passing through the orifice 905 having a small cross-sectional area, the pressure P1 on the inlet 907 side of the cylinder 906 is larger than the pressure P2 on the outlet 908 side before and after the orifice 905 due to the flow resistance. Become. Due to these differential pressures ΔP (= P1−P2), the piston 901 is pushed to the outlet side of the cylinder 906, and the urging force of the compression coil spring 904 is set smaller than the force pushing the piston by this differential pressure ΔP. As a result, the piston 901 moves toward the outlet 908 of the cylinder 906 against the urging force of the compression coil spring 904. Then, the movement of the piston 901 causes the magnet portion 902 of the piston 901 to approach the magnetically sensitive switch element 903, and the magnetically sensitive switch element 903 detects (sensitive) the magnetic force of the magnet portion 902, and contacts Is closed and turned on. In this way, the flow switch 910 detects the fluid flow presence / absence state by switching the magnetically sensitive switch element 903 between the on state and the off state according to the presence / absence of the fluid flow.

JP-A-8-235983

  However, in the above-described flow switch 910, when the fluid flowing in the pipe 909 has a high pressure such as liquefied gas, the cylinder 906 is made of a metal material so as to withstand such a high pressure. However, since a metal material generally has a large frictional force, if a metal material is used for the cylinder 906, a large frictional force is generated between the piston 901 and a minute flow of fluid. There was a problem that it could not be detected.

  The present invention aims to solve the above problems. That is, an object of the present invention is to provide a flow switch that can detect a minute flow of a fluid even when the pressure of the fluid is high.

In order to achieve the above object, a first aspect of the present invention provides a flow switch that operates according to a flow state of a fluid flowing in a metal pipe, and is fixedly accommodated in the pipe. A cylindrical cylinder, a piston housed in the cylinder movably between a no-flow position near the inlet end of the cylinder and a position with flow near the outlet end, and the piston in the no-flow position. An urging member that urges toward the position, and a position detection unit that outputs a position signal corresponding to the position of the piston, and both the cylinder and the piston are made of a plastic sliding material, The flow switch is characterized in that the inner peripheral surface of the pipe and the outer peripheral surface of the cylinder are densely overlapped when housed fixed in the pipe.

  The invention described in claim 2 is the invention described in claim 1, wherein the piston has a cylindrical peripheral wall portion, a plate-shaped main body portion provided so as to close the inside of the peripheral wall portion, and the And a bottom wall portion provided with a flow hole penetrating the main body portion.

  According to a third aspect of the present invention, in the second aspect of the invention, there is provided a protrusion that fits into the flow hole so as to close the flow hole when the piston is in the no-flow position. It has a valve seat.

  The invention described in claim 4 is the invention described in claim 3, wherein the piston is provided with a magnet, the pipe is made of a non-magnetic material, and the outer peripheral surface thereof is The piston is moved to the no-flow position when current flows in the direction, and the piston is moved to the flow-position when current flows in the other direction opposite to the one direction. A coil that exerts a magnetic force on the magnet is provided.

  According to a fifth aspect of the present invention, in the invention according to the fourth aspect of the present invention, the position detecting means includes a magnet of the piston when the piston is in the position with the flow and when in the position without the flow. It is comprised by the magnetic force sensitive type sensor element provided so that the sensitive state with respect to the magnetic force of this may output the position signal according to the said sensitive state.

  According to the first aspect of the present invention, since both the cylinder and the piston are made of a plastic sliding material, the plastic sliding material has a very small frictional force compared to a metal material, and therefore slides on each other. The frictional force between the inner peripheral surface of the cylinder and the outer peripheral surface of the piston can be made very small. Further, since the cylinder is formed so that the inner peripheral surface of the pipe and the outer peripheral surface of the cylinder overlap closely when housed fixedly in the pipe, the plastic sliding material is made of a metal material. Compared to this, if high-pressure fluid flows into the cylinder, it may expand and break from the inside, but in the present invention, the cylinder is supported by a pipe line and the piston is surrounded by the pipe. It is supported by the cylinder and can receive the force in the direction of expansion, so that the pressure resistance against a high-pressure fluid can be ensured. Therefore, even when the pressure of the fluid is high, the minute flow of the fluid can be detected.

  According to the invention described in claim 2, the piston includes a cylindrical peripheral wall portion, a plate-like main body portion provided so as to close the inner side of the peripheral wall portion, and a circulation hole penetrating the main body portion. The bottom wall portion of the piston functions as an orifice plate, so that when the fluid flows, pressure loss is surely caused by passage of the fluid through-hole, The piston can be stably moved by the fluid without causing a chattering or the like because a pressure difference is stably generated between one surface side and the other surface side of the bottom wall portion. Further, since the inside of the cylinder is closed by the piston and the path through which the fluid flows is only the flow hole, the fluid flow can be reliably captured.

  According to the third aspect of the present invention, the cylinder has the valve seat provided with the protruding portion that fits the flow hole so as to close the flow hole when the piston is in the no-flow position. When the fluid flows in from the outlet end side, the piston moves to the no-flow position by this fluid. At this time, the protrusion of the valve seat fits into the flow hole provided in the bottom wall and the flow The hole is blocked, thus preventing fluid flow. In other words, a check valve having a piston as a valve body can be configured by sharing the members constituting the flow switch, and in a device that requires a flow switch and a check valve, the device is not provided separately. Can be downsized.

  According to the fourth aspect of the present invention, the piston is provided with a magnet, the pipe is made of a non-magnetic material, and the outer peripheral surface thereof is provided with a piston when a current flows in one direction. A coil that applies a magnetic force to the magnet of the piston is provided so that the piston moves to the position with flow when it is moved to the position without flow and current flows in the opposite direction. By moving the piston to the no-flow position and closing the flow hole with the protrusion to restrict the flow of the fluid, or moving the piston to the flow position to open the flow hole and allow the fluid flow, In other words, the components that make up the flow switch can be shared, and the solenoid valve can be constructed with the piston as the valve body. In devices that require a flow switch, check valve, and solenoid valve, each is separately The device can be miniaturized without kicking.

  According to the fifth aspect of the present invention, the position detection means is provided so that the state of sensitivity of the piston to the magnetic force of the piston changes depending on whether the piston is in the position with flow or in the position without the flow. In addition, since it is composed of a magnetic force sensitive sensor element that outputs a position signal corresponding to the sensitive state, it is not necessary to separately provide a magnet for specifying the position of the piston, and the size can be further reduced.

It is a side view of the flow switch of the present invention. It is sectional drawing which follows an axial direction when the piston of the flow switch of FIG. 1 exists in a no-flow position. It is sectional drawing in alignment with the axial direction when the piston of the flow switch of FIG. 1 exists in a position with a flow. It is a block diagram which shows the vehicle fuel system which has the flow switch of FIG. It is a functional block diagram of the control part of the vehicle fuel system of FIG. It is a graph which shows an example of the equilibrium pressure relationship information stored in the memory of the control part of FIG. It is a figure which shows typically the storage state of the some equilibrium pressure relation information to the memory of the control part of FIG. It is a flowchart which shows an example of the process (liquid amount estimation process 1) which CPU of the control part of FIG. 5 performs. It is sectional drawing of the conventional flow switch.

  First, a flow switch of the present invention will be described, and then a vehicle fuel system as a liquid amount estimation system having the flow switch will be described.

  An embodiment of the flow switch of the present invention will be described with reference to FIGS. The flow switch of the present invention is used to detect whether or not a fluid such as liquefied petroleum gas (LPG) used as fuel for a vehicle is flowing. This LPG is known to change in pressure from about 0.1 MPa to 3 MPa depending on environmental conditions such as ambient temperature.

  As shown in each figure, the flow switch 70 includes a casing 71 as a pipe line, a cylinder 75, a piston 81, a spring 85 as a biasing member, a substrate 87, and a winding coil 91. doing.

  The casing 71 is formed in a substantially cylindrical shape using, for example, a nonmagnetic metal such as an aluminum alloy having rigidity capable of withstanding the pressure of LPG. A first flow path 72 having a circular cross section is provided in a portion near the one end 71a of the housing 71, and the first flow path connected coaxially with the first flow path 72 in a portion near the other end 71b. A second flow path 73 having a narrower circular cross section is provided. The casing 71 is penetrated from one end 71a to the other end 71b by the first flow path 72 and the second flow path 73 that are communicated with each other. Normally, the fluid flows into the casing 71 from one end 71a, flows through the casing 71, and then flows out from the other end 71b.

  A step portion 71 c is formed at a connecting portion between the first flow path 72 and the second flow path 73 in the housing 71. The stepped portion 71c is provided with a cylindrical projection 71d formed so as to protrude toward the first flow path 72. The cylindrical protrusion 71 d has the same inner diameter as the second flow path 73 and is arranged coaxially with the second flow path 73.

  The peripheral surface 72a of the first flow path 72 (that is, the inner peripheral surface of the casing 71) is threaded to form a female screw at a location near the one end 71a of the casing 71. One end of the path is screwed and fixed to each other. Further, the outer peripheral surface 71e of the casing 71 is threaded to form a male screw at a location near the other end 71b, and one end of another pipe line (not shown) is screwed and fixed to each other. A substrate housing chamber 71 f for housing a substrate 87 described later is provided on the outer peripheral surface 71 e of the housing 71.

  The cylinder 75 is made of, for example, a plastic sliding material such as POM (polyacetal), and has a cylindrical body portion 76 and a valve seat portion 77 provided so as to close the inlet end 76a of the body portion 76. Are formed in a bottomed cylindrical shape (cup type). The body portion 76 has an outer diameter that is the same as the diameter of the first flow path 72 (that is, the inner diameter of the casing 71). The valve seat portion 77 is provided around a disc-shaped main body portion 77a, a substantially conical protrusion portion 77b that protrudes coaxially with the body portion 76 from the center of the inner surface 77d of the main body portion 77a, and the protrusion portion 77b. And a plurality of communication holes 77c penetrating the main body 77a.

  The cylinder 75 is inserted into the housing 71 from the one end 71 a side, and is inserted into the casing 75 by a compressed fall-off prevention spring 78 and a pressing plate 79 fixed in the first flow path 72. The portion 77 is biased toward the other end 71 b side of the casing 71 and is fixedly accommodated in the first flow path 72. The pressing plate 79 is formed in a disc shape, and a communication hole 79a is provided in the center. When the cylinder 75 is accommodated in the first flow path 72, the outlet end 76 b of the trunk portion 76 contacts the stepped portion 71 c of the housing 71, and the outer circumferential surface 76 c of the trunk portion 76 (that is, the outer circumference of the cylinder 75). Surface) abuts on a portion of the peripheral surface 72a of the first flow path 72 where the thread is not cut. That is, the cylinder 75 is fixedly accommodated in the housing 71 so that the peripheral surface 72a of the first flow path 72 and the outer peripheral surface 76c of the body 76 of the cylinder 75 overlap closely. In addition, an O-ring 96 having the same diameter as the first flow path 72 is disposed in the step portion 71 c of the housing 71, and this O-ring 96 is connected to the step portion 71 c and the outlet end 76 b of the trunk portion 76 of the cylinder 75. The fluid is prevented from passing between the peripheral surface 72a of the first flow path 72 and the outer peripheral surface 76c of the body portion 76 of the cylinder 75.

  The piston 81 is made of, for example, a plastic sliding material such as POM (polyacetal), and has a cylindrical peripheral wall portion 82 and a bottom wall portion provided so as to close the inside of one end 82a of the peripheral wall portion 82. 83, and is formed in a bottomed cylindrical shape. The peripheral wall portion 82 has an outer diameter that is the same as the inner diameter of the body portion 76 of the cylinder 75, and the length thereof is shorter than the length of the body portion 76 of the cylinder 75. The bottom wall portion 83 includes a disk-shaped main body portion 83a and a flow hole 83b penetrating the center of the main body portion 83a. The circulation hole 83b is formed in a mortar shape along the outer shape of the protrusion 77b so that the end of the main body 83a near the outer surface 83c can be fitted with the protrusion 77b. The bottom wall portion 83 constitutes an orifice plate with the main body portion 83a and the flow hole 83b.

  A disc-shaped magnet 84 having the same diameter as the inner diameter of the peripheral wall portion 82 is accommodated inside the piston 81. The magnet 84 is inserted from the other end 82 b of the peripheral wall portion 82, one end surface of the magnet 84 is in contact with the inner side surface 83 d of the main body portion 83 a of the bottom wall portion 83, and the edge portion of the other end surface is the peripheral wall portion 82. It is locked by a locking claw 82d provided on the inner peripheral surface 82c of the piston 81 and fixed so as not to drop off from the piston 81. The magnet 84 is provided with a flow hole 84b penetrating through the center thereof, and the flow hole 84b is disposed coaxially with the flow hole 83b of the bottom wall portion 83.

  The piston 81 is accommodated coaxially in the body portion 76 of the cylinder 75 such that the outer side surface 83c of the main body portion 83a of the bottom wall portion 83 and the inner side surface 77d of the main body portion 77a of the valve seat portion 77 face each other. ing. When the piston 81 is accommodated in the cylinder 75, the outer peripheral surface 82 e of the peripheral wall portion 82 (that is, the outer peripheral surface of the piston 81) is the inner peripheral surface 76 d of the trunk portion 76 of the cylinder 75 (that is, the inner periphery of the cylinder 75). Surface) and closely overlap each other.

  Since the piston 81 and the cylinder 75 are made of a plastic sliding material, the frictional force between the outer peripheral surface 82e of the peripheral wall portion 82 of the piston 81 and the inner peripheral surface 76d of the barrel portion 76 of the cylinder 75 is very high. Get smaller. That is, the piston 81 is located between the no-flow position Qa near the inlet end 76a of the cylinder 75 shown in FIG. 2 and the position with flow Qb near the outlet end 76b of the cylinder 75 shown in FIG. It is slidably accommodated along the P direction. When the piston 81 is in the no-flow position Qa, there is a slight gap between the outer side surface 83c of the main body portion 83a of the bottom wall portion 83 of the piston 81 and the inner side surface 77d of the main body portion 77a of the valve seat portion 77 of the cylinder 75. A gap is provided.

  The piston 81 is connected to the outer surface 83c of the main body portion 83a of the bottom wall portion 83 by a spring 85 as a biasing member having one end attached to the cylindrical protrusion 71d and the other end attached to the other end surface of the magnet 84. The valve seat 77 is biased in a direction in which the inner surface 77d of the main body 77a approaches each other. That is, the spring 85 urges the piston 81 toward the no-flow position Qa. The urging force of the spring 85 is such that the piston 81 moves to the no-flow position Qa when the fluid is not flowing and the fluid is flowing, and when the fluid is flowing and the piston 81 is the fluid-flowing position. It is set to move to Qb.

  When the piston 81 is in the no-flow position Qa, the projection 77b of the cylinder 75 is fitted into the flow hole 83b of the bottom wall 83, and the flow hole 83b is closed. An O-ring 97 having the same diameter as the inner diameter of the body 76 of the cylinder 75 is disposed on the inner surface 77d of the main body 77a of the valve seat 77. The O-ring 97 has a position where the piston 81 does not flow. When in Qa, it is sandwiched between the bottom wall portion 83 and the valve seat portion 77, and a fluid flows between the outer peripheral surface 82 e of the peripheral wall portion 82 of the piston 81 and the inner peripheral surface 76 d of the trunk portion 76 of the cylinder 75. Is prevented from passing.

  The board 87 is configured by mounting various electronic components on a well-known printed board provided with a wiring pattern. The substrate 87 is accommodated in a substrate accommodating chamber 71f provided near the longitudinal center of the outer peripheral surface 71e of the housing 71. A reed switch 88 as a magnetically sensitive sensor element is mounted on the substrate 87.

  The reed switch 88 is a known magnetic force sensitive sensor element that opens and closes contacts in response to magnetic force, and detects the magnetic force of the magnet 84 provided on the piston 81 when the piston 81 is in the no-flow position Qa ( The contact is closed (closed operation), and when the piston 81 is in the flow position Qb, the magnetic force of the magnet 84 is not detected and the contact is opened (open operation). In this embodiment, the reed switch 88 is connected to an output signal line with one end pulled up, and the other end is grounded (ground connection), and outputs an L level signal when it is closed by detecting a magnetic force. When the opening operation is performed without detecting the magnetic force, an H level signal is output. The reed switch 88 corresponds to the position detection means in the claims, and these L level signal and H level signal correspond to the position signals in the claims.

  The reed switch 88 is not limited to the above, and detects the magnetic force of the magnet 84 to close the contact when the piston 81 is in the position with flow Qb, and closes the contact when the piston 81 is in the position without flow Qa. For example, the reed switch 88 may be provided at a location near the other end 71b of the outer peripheral surface 71e of the housing 71 so that the magnetic force 84 is not detected and the contact is opened. In place of such a reed switch 88, for example, other types of magnetically sensitive sensor elements such as a Hall element may be used as long as the object of the present invention is not violated. In response to the magnetic force of the magnet of the piston, a magnetically sensitive type is provided so that the sensitive state changes between when the piston is in the position Qb with flow and when it is in the position Qa without flow. It may be any capacitors element.

  For example, the winding coil 91 is configured by winding an electric wire such as an enamel wire a plurality of times, and functions as an electromagnet that generates a magnetic force when a current is applied. The winding coil 91 is provided in the vicinity of the outlet end 76b of the cylinder 75 on the outer peripheral surface 71e of the casing 71 so as to be wound in parallel in the circumferential direction. The winding coil 91 moves the piston 81 to the no-flow position Qa when current flows in one direction (positive direction), and when current flows in the other direction (negative direction) opposite to this one direction. It is provided to exert a magnetic force on the magnet 84 of the piston 81 so as to move the piston 81 to the position Qb with flow. The winding coil 91 is connected to the substrate 87, and the current is supplied from the substrate 87.

  Each operation (flow switch operation, check valve operation, and electromagnetic valve operation) of the flow switch 70 described above will be described. Hereinafter, the fluid pressure on the one end 71a side of the casing 71 is referred to as upstream pressure, and the fluid pressure on the other end 71b side is referred to as downstream pressure.

(1) Operation as a flow switch and check valve When operating as a flow switch and check valve, if the coil coil 91 is energized, the reed switch 88 does not operate according to the position of the piston 81. Since the detection result becomes invalid, the winding coil 91 is not energized when operated as a flow switch and a check valve.

(1-1) When the upstream pressure and the downstream pressure are the same When the upstream pressure and the downstream pressure are the same, no force is generated to cause the fluid to flow, and the piston 81 is attached to the spring 85. It is positioned at the no-flow position Qa by the force. The reed switch 88 detects the magnetic force of the magnet 84 of the piston 81 at the no-flow position Qa, closes the contact, and outputs a no-flow state signal (L level signal) corresponding thereto.

(1-2) When the upstream side pressure is higher than the downstream side pressure When the upstream side pressure is higher than the downstream side pressure, the force that causes the fluid to flow from the one end 71a side to the other end 71b side of the casing 71 work. This force is transmitted to the fluid filled in the casing 71 and applied to the outer side surface 83 c of the bottom wall portion 83 of the piston 81. Then, the piston 81 moves away from the valve seat 77 against the urging force of the spring 85, and moves from the no-flow position Qa toward the flow-present position Qb. Thereby, the fitting between the flow hole 83b and the protrusion 77b of the valve seat 77 is released, the flow hole 83b is opened, and the fluid flows into the first flow path 72 from the one end 71a side, The gas passes through the communication hole 79a and the plurality of communication holes 77c of the valve seat 77 in order, and further passes through the flow hole 83b and flows out from the second flow path 73 to the other end 71b of the casing 71. Further, a pressure loss is caused by the fluid flowing through the flow hole 83b. A force due to the pressure loss is generated in the piston 81, and the piston 81 moves to the position Qb with flow. When the piston 81 moves away from the no-flow position Qa to the position with flow Qb, the reed switch 88 does not detect the magnetic force of the magnet 84 of the piston 81, opens its contact, and there is a flow according to this. A status signal (H level signal) is output. As described above, the flow switch 70 detects the flow of the fluid from the one end 71 a side to the other end 71 b side of the casing 71.

(1-3) When the upstream side pressure is lower than the downstream side pressure When the upstream side pressure is lower than the downstream side pressure, the force that causes the fluid to flow from the other end 71b side of the housing 71 toward the one end 71a side is work. This force is transmitted through the fluid filled in the casing 71 and applied to the inner side surface 83 d of the bottom wall portion 83 of the piston 81 via the magnet 84. Then, by this force, the piston 81 approaches the valve seat portion 77 and moves to the no-flow position Qa and is pressed against the valve seat portion 77. As a result, the protrusion 77b of the valve seat 77 and the flow hole 83b of the piston 81 are fitted to close the flow hole 83b, thereby preventing fluid flow. Thus, the flow switch 70 operates as a check valve that prevents the flow of fluid from the other end 71b side of the housing 71 toward the one end 71a side with the piston 81 as a valve body. In this case, the reed switch 88 detects the magnetic force of the magnet 84 of the piston 81 at the no-flow position Qa, closes the contact, and outputs a no-flow signal (L level signal) corresponding thereto.

(2) Operation as a solenoid valve By energizing the winding coil 91, the piston 81 can be moved to the no-flow position Qa and the flow-present position Qb regardless of the upstream pressure and the downstream pressure. Specifically, when the current in one direction is passed through the winding coil 91, a magnetic force repelling the magnet 84 of the piston 81 is generated, and a force separating the piston 81 from the winding coil 91 is generated. It moves to the no-flow position Qa and is fixed. As a result, the projection 77b of the valve seat 77 and the flow hole 83b of the piston 81 are fitted to close the flow hole 83b, thereby restricting the flow of fluid. Further, when a current in the other direction is passed through the winding coil 91, a magnetic force that attracts the magnet 84 of the piston 81 is generated, and a force that causes the piston 81 to approach the winding coil 91 is generated, and the piston 81 is in a position Qb with flow. Move to and be fixed. Thereby, the fitting between the projection 77b of the valve seat 77 and the flow hole 83b of the piston 81 is released, the flow hole 83b is opened, and the fluid flow is permitted. Thus, the flow switch 70 operates as an electromagnetic valve having the piston 81 as a valve body.

  The operation (action) according to the present invention of the flow switch 70 described above will be described.

  For example, when the cylinder 75 and the piston 81 are configured using a metal material or the like, the frictional force between them becomes large, and this frictional force hinders the movement of the piston 81 due to the pressure of the fluid. As a result, a minute flow of gas or the like may not be detected. However, in the above-described flow switch 70, both the cylinder 75 and the piston 81 are made of a plastic sliding material, so that the frictional force between them can be made very small compared to a metal material or the like.

  In addition, the plastic sliding material has lower rigidity than a metal material or the like. Therefore, when a cylinder 75 or a piston 81 is formed using a plastic sliding material and a fluid such as high pressure LPG is flowed inside thereof, pressure is generated in a direction in which the cylinder 75 or piston 81 expands from the inside to the outside. The piston 81 may be damaged by pressure. However, the cylinder 75 can be supported from the periphery by the casing 71 made of a highly rigid metal, and the piston 81 can be supported from the periphery by the cylinder 75 to withstand the pressure.

  As described above, according to the present invention, since both the cylinder 75 and the piston are made of a plastic sliding material, the plastic sliding material has a very small frictional force compared to a metal material, and therefore slides on each other. The frictional force between the inner peripheral surface 76d of the cylinder 75 and the outer peripheral surface 82e of the piston 81 can be made very small. Further, when the cylinder 75 is fixedly accommodated in the first flow path 72 of the housing 71, the peripheral surface 72 a of the first flow path 72 and the outer peripheral surface 76 c of the body portion 76 of the cylinder 75 overlap closely. Therefore, the plastic sliding material has a lower rigidity than the metal material, and when a high-pressure fluid flows into the cylinder 75 or the piston 81, the plastic sliding material may expand and break from the inside. Then, the cylinder 75 is supported by the casing 71 around the cylinder 75, and the piston is supported by the cylinder 75 around the cylinder 75, so that the force in the expanding direction can be received. Therefore, the pressure resistance against a high-pressure fluid is ensured. it can. Therefore, even when the pressure of the fluid is high, the minute flow of the fluid can be detected.

  The piston 81 includes a cylindrical peripheral wall portion 82, a main body portion 83a that closes one end 82a of the peripheral wall portion 82, and a bottom wall portion 83 that includes a flow hole 83b that passes through the main body portion 83a. Therefore, the bottom wall portion 83 of the piston 81 functions as an orifice plate. Therefore, when the fluid flows, the pressure loss is surely caused by the passage of the fluid through the flow hole 83b, and the bottom wall portion 83 side of the bottom wall portion 83 The piston 81 can be stably moved by the fluid without causing a chattering or the like due to a stable pressure difference between the inner surface 83d side and the inner surface 83d. Further, the cylinder 75 is closed by the piston 81, and the flow path of the fluid is only the flow hole 83b, so that the fluid flow can be reliably captured.

  Moreover, since the piston 81 has the valve seat part 77 provided with the projection part 77b fitted to the flow hole 83b so as to close the flow hole 83b when the piston 81 is in the no-flow position Qa, When the fluid flows from the other end 71b side (that is, the outlet end 76b side of the cylinder 75), the piston 81 is moved to the no-flow position Qa by this fluid. At this time, the projection 77b of the valve seat portion 77 is moved. The flow hole 83b is fitted into the flow hole 83b provided in the bottom wall portion 83 to close the flow hole 83b. That is, a check valve using the piston 81 as a valve body can be configured by sharing the members constituting the flow switch 70. In a device that requires a flow switch and a check valve, the check valve is not provided separately. The device can be miniaturized.

  The piston 81 is provided with a magnet 84, the casing 71 is made of a non-magnetic material, and the piston 81 is moved to the no-flow position Qa when current flows in one direction on the outer peripheral surface 71e. Since a winding coil 91 is provided that exerts a magnetic force on the magnet 84 of the piston 81 so that the piston 81 is moved to the position with flow Qb when a current flows in the opposite direction. By causing a current to flow through 91, the piston 81 is moved to the no-flow position Qa and the flow hole 83b is blocked by the projection 77b to restrict the flow of fluid, or the piston 81 is moved to the flow position Qb to move the flow hole. 83b can be opened to permit fluid flow, that is, the members constituting the flow switch 70 can be shared, and the solenoid valve can be configured with the piston 81 as a valve body. In such over switch and the check valve and the solenoid valve and the necessary equipment can be miniaturized the apparatus without providing each separately.

  The reed switch 88 is closed when the magnetic force of the magnet 84 of the piston 81 is detected when the piston 81 is in the no-flow position Qa, and when the piston 81 is in the no-flow position Qb, Since the magnetic force is not detected and the opening operation is performed, it is possible to share the magnet 84 without further providing a magnet for detecting the position of the piston 81, and to further reduce the size.

  In the present embodiment, the cylinder 75 and the piston 81 are made of POM (polyacetal) as a plastic sliding material. However, the present invention is not limited to this. This plastic sliding material is, for example, a material used for sliding parts such as a sliding bearing, and when sliding, such as the above-mentioned POM (polyacetal), PA (polyamide), PTFE (polytetrafluoroethylene), etc. This is a plastic (synthetic resin) material suitable for use in the sliding portion, having a property that the frictional force is much smaller than that of a metal material such as an aluminum alloy. And if it is such a plastic sliding material, unless it is contrary to the objective of this invention, the kind of the said plastic sliding material used for the cylinder 75 and the piston 81 is arbitrary. Further, if the frictional force at the time of sliding is reduced, the cylinder 75 and the piston 81 may be configured using different types of plastic sliding materials.

  In the present embodiment, the valve seat 77 is provided with a protrusion 77b that closes the flow hole 83b of the piston 81 and functions as a check valve. However, the protrusion 77b is not provided as a flow switch. It may be one that only functions. In addition, the flow switch 70 is provided with the winding coil 91 and functions as an electromagnetic valve. However, the flow switch 70 may function only as a flow switch and a check valve without providing the winding coil 91. .

  In the present embodiment, a reed switch 88, which is a magnetically sensitive sensor element as a position detecting means, is provided to detect the position of the piston 81 by detecting the magnetic force generated by the magnet 84 of the piston 81. However, the present invention is not limited to this. For example, a light emitting element and a light receiving element are provided. When the piston 81 is in the no-flow position Qa, light from the light emitting element is blocked and does not reach the light receiving element. The position of the piston 81 may be detected by using an optical sensor unit as a position detection unit in which both elements are arranged to face each other across the inside of the cylinder 75 so that the light reaches the light receiving element. . Alternatively, the position of the piston 81 is detected by using a mechanical switch such as a push button switch that is pressed when the piston 81 is in the no-flow position Qa and is not pressed when the piston 81 is in the position with flow. May be. That is, the position detection means used for detecting the position of the piston 81 is arbitrary as long as the object of the present invention is not violated.

  Next, a liquid amount estimation apparatus having the above-described flow switch 70 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 that stores liquefied petroleum gas (LPG) as fuel F of the vehicle, and that estimates the amount of fuel F in the fuel tank. It is.

  As shown in FIG. 4, the vehicle fuel system (indicated by reference numeral 1 in the figure) includes a fuel tank 10 as a liquid tank, a liquid amount estimation device 7 that estimates the amount of fuel F in the fuel tank 10, have.

  The fuel tank 10 is, for example, a well-known vehicle component that is disposed under the floor of a vehicle and accommodates the fuel F of the vehicle. In the present embodiment, the fuel tank 10 is formed in a rectangular parallelepiped box shape with a volume of 100 L. ing. The fuel tank 10 is connected to a fuel filling port of a vehicle (not shown), and an inflow pipe 11 for allowing the fuel F supplied from a fuel supply stand or the like to flow into the fuel tank 10 and the inflow pipe 11 are opened and closed. An inflow valve 12 configured by an electromagnetic valve is provided. The inflow pipe 11 is provided with a shut-off valve (not shown) that needs to be attached for safety. Further, the fuel tank 10 is connected to an injection device or the like for supplying fuel F to an internal combustion engine (not shown), and an outflow pipe 13 for flowing the fuel F in the fuel tank 10 toward the injection device or the like, An outflow valve 14 configured by an electromagnetic valve for opening and closing the outflow pipe 13 is provided. The configuration of the fuel tank 10 and the like shown in FIG. 4 is an example, and for example, the connection locations of the inflow pipe 11 and the outflow pipe 13 to the fuel tank 10 are appropriately determined according to the system configuration and the like. In the fuel tank 10, there are a gas phase portion 17 in which the vaporized fuel F and the like are accommodated, and a liquid phase portion 18 in which the liquid fuel F is accommodated. In the fuel tank 10, only the gas phase portion 17 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 17 exists.

  The liquid amount estimation device 7 includes an airtight tank 31, a pipe 39 as another pipe, the above-described flow switch 70, a heater 46 as a heating unit, and a gas phase pressure as a gas phase pressure information measuring unit. A sensor 58, an airtight tank temperature sensor 59 as an airtight tank temperature measuring means, and a control unit 60 are provided.

  The airtight tank 31 is provided separately from the fuel tank 10 and is disposed close to the fuel tank 10. In the present embodiment, the airtight tank 31 is formed in a rectangular parallelepiped box shape with a volume of 1.0 L. ing. The airtight tank 31 is connected to the fuel tank 10 by a pipe 39. One end 39 a of the pipe 39 is connected to the upper end of the side wall 10 b of the fuel tank 10, and the other end 39 b is connected to the lower wall 31 c of the airtight tank 31. That is, the airtight tank 31 is provided separately from the fuel tank 10 and is connected to the upper portion of the fuel tank 10, that is, the gas phase portion 17 in the fuel tank 10. As a result, the airtight tank 31 is filled with the same gas as the gas phase portion 17.

  The flow switch 70 is configured so that one end 71 a of the casing 71 is connected to the airtight tank 31 via the pipe 39 and the other end 71 b of the casing 71 is connected to the fuel tank 10 via the pipe 39. It is provided in the middle part. As described above, the flow switch 70 includes: (1) a flow switch that detects the flow of fluid from the one end 71a side to the other end 71b side of the casing 71; and (2) the piston 81 as a valve body. It functions as a check valve that prevents the flow of fluid from the other end 71b toward the one end 71a, and (3) an electromagnetic valve that operates to open or close the piping 39 by opening and closing the piston 81 as a valve body. . Further, the bottom wall 83 of the piston 81 (that is, the main body 83a and the flow hole 83b) functions as an orifice plate.

  The flow switch 70 detects a flow state in which gas is flowing from the airtight tank 31 toward the gas phase portion 17 in the pipe 39 and a flow state in which no gas is flowing. Specifically, the reed switch 88 of the flow switch 70 is electrically connected to the control unit 60 described later via the substrate 87, and the reed switch 88 detects whether or not the gas in the pipe 39 flows. Thus, the electric signals (the above-described flow state signal and the no flow state signal) corresponding to the flow state and the no flow state are output to the control unit 60.

  The bottom wall portion 83 of the piston 81 of the flow switch 70 functions as an orifice plate and is provided so as to be perpendicular to the flow direction of gas as a fluid (that is, the direction of the axis P). The bottom wall 83 regulates the flow rate of the gas flowing through the pipe 39 by causing the gas to flow through the flow hole 83b. In the present embodiment, the bottom wall portion 83 is adjusted so that the regulated flow rate is 100 ccm (the flow rate is 100 cc / min at a pressure difference of 1 atm). In addition, about the structure of the bottom wall part 83, it determines suitably according to an apparatus structure.

  Further, the flow switch 70 functions as a check valve and prevents the flow of fluid from the gas phase portion 17 toward the airtight tank 31. For example, when the airtight tank 31 is damaged due to a strong impact or the like, there is a risk that high pressure LPG may leak into the atmosphere from this damaged portion. Can be prevented.

  The flow switch 70 functions as an electromagnetic valve, and opens or closes the connection between the gas phase portion 17 and the airtight tank 31 by closing or opening the flow hole 83b of the bottom wall portion 83 of the piston 81. Is provided. Specifically, the winding coil 91 of the flow switch 70 is electrically connected to the control unit 60 described later via the substrate 87, and the magnetic force generated by the winding coil 91 by the current supplied from the control unit 60. Is controlled so that the flow hole 83b of the piston 81 is closed or opened.

  The heater 46 is a known heater for heating an object by generating and releasing heat from electric energy such as a heating wire, a halogen heater, or a carbon heater. Of course, in addition to electricity, heat may be released by burning various fuels. The heater 46 is provided in close contact with the four side walls 31b of the hermetic tank 31, and heats the gas in the hermetic tank 31 through each side wall 31b to raise its temperature (that is, raise the temperature).

  Further, in order to efficiently heat the gas in the airtight tank 31 by the heater 46 and prevent the piping 39 and the fuel tank 10 from being affected by the heat of the heater 46, a heat insulating material made of glass wool or the like (not shown), etc. Thus, a heat insulation process such as covering the heater 46 is performed. As a result, the pressure and temperature of the airtight tank 31 and the gas phase portion 17 are stable in a state where there is no heating by the heater 46 and no gas is pushed into the gas phase portion 17. “Pressure and temperature are stable” includes a case where there is no change in value and a case where there is a small fluctuation range that does not hinder the estimation of the liquid amount. The heater 46 is electrically connected to a control unit 60 described later, and is controlled by a control signal from the control unit 60.

  In the present embodiment, the airtight tank 31 is formed in a rectangular parallelepiped box shape, and the heater 46 is provided in close contact with the four side walls 31b of the airtight tank 31, but is not limited thereto. Instead, for example, the gas-tight tank 31 is formed in a long tubular shape, and the gas in the gas-tight tank 31 can be heated, such as a configuration in which a heating wire as the heater 46 is wound around the outer peripheral surface. If present, these configurations are arbitrary.

  In order to equalize the pressures in the airtight tank 31 and the gas phase portion 17, first, the winding coil 91 of the flow switch 70 is energized in the other direction to generate a magnetic force that brings the piston 81 close to the winding coil 91. Is moved to the flow position Qb to open the circulation hole 83b, the gas phase portion 17 and the airtight tank 31 are connected through the pipe 39, and the respective pressures become the same. After that, when the winding coil 91 is energized in one direction to generate a magnetic force that separates the piston 81 from the winding coil 91, the piston 81 is moved to the no-flow position Qa and the circulation hole 83b is closed. When the gas in the airtight tank 31 is heated by the heater 46 in this state, the pressure in the airtight tank 31 becomes higher than the pressure in the gas phase portion 17. Then, when the energization of the winding coil 91 is stopped, the piston 81 is pushed toward the flow position Qb by the pressure difference between the gas phase portion 17 and the airtight tank 31, and the flow hole 83b is opened. Gas flows from the airtight tank 31 to the gas phase portion 17 so as to eliminate the pressure difference between the airtight tank 17 and the airtight tank 31. That is, the gas in the airtight tank 31 is pushed into the gas phase unit 17.

  The airtight tank temperature sensor 59 is constituted by, for example, a thermistor or a thermocouple, and is provided on the upper wall 31a of the airtight tank 31, and measures the temperature in the airtight tank 31. The airtight tank temperature sensor 59 is electrically connected to a control unit 60 described later, and outputs an electrical signal corresponding to the measured temperature in the airtight tank 31 to the control unit 60.

  As shown in FIG. 5, the control unit 60 includes a microcomputer 61 for a known embedded device. The microcomputer 61 includes a central processing unit (CPU) 62 and a ROM (Read Only Memory). 63, a RAM (Random Access Memory) 64, a memory 65, and a timer 66.

  The CPU 62 controls various controls in the vehicle fuel system 1 and executes various processes including control according to the present embodiment in accordance with various control programs stored in the ROM 63. The ROM 63 stores various information such as the control program and parameters referred to by the control program. In particular, the ROM 63 stores a control program for causing the CPU 62 to function as various means such as gas pushing control means, equilibrium pressure detection means, and liquid amount estimation means. And CPU62 functions as various means mentioned above by running this control program. The RAM 64 appropriately stores data, programs, and the like necessary for the CPU 62 to execute various processes. The memory 65 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 memory 65 stores various types of information such as mathematical formulas and parameters (such as a pressure adjustment time described later) used in a liquid amount estimation process described later. The timer 66 is a well-known time measuring mechanism used for the CPU 62 to measure an arbitrary time. In the present embodiment, the time unit (minimum time unit) of the timer 66 is 1 msec. By using the higher speed microcomputer 61, the time unit can be made smaller, that is, the time resolution can be easily increased. The timer 66 corresponds to a flow duration measuring means.

  In the memory 65 provided in the microcomputer 61 of the control unit 60, as shown in FIG. 6, the gas in the airtight tank 31 is predetermined by the heater 46 at a predetermined pressure (pressure before pushing) in the gas phase unit 17. A flow duration T indicating the duration of the state in which the gas is flowing from the airtight tank 31 to the gas phase section 17 after the flow hole 83b of the piston 81 is opened by being heated to the temperature, and thereafter the flow is lost and the gas phase is lost. Equilibrium pressure relationship information H indicating the relationship between the pressure Pm3 (equilibrium pressure) of the gas phase unit 17 when the pressure of the unit 17 and the pressure of the airtight tank 31 are in equilibrium is stored. The equilibrium pressure relation information H is, for example, a function (regression equation) or a data table showing a graph obtained by preliminary measurement, simulation, or the like, and there are a plurality of pieces of pressure for each pressure before the gas is pushed into the gas phase portion 17. Is provided. In this embodiment, as schematically shown in FIG. 7, the pressure before the gas is pushed into the gas phase portion 17 (pressure before pushing) is a plurality of equilibrations every 0.01 MPa from 0.10 MPa to 3.00 MPa. Pressure related information H is stored.

  In the gas phase portion 17 and the airtight tank 31, the gas phase portion 17 and the airtight tank 31 are set to the same initial pressure P1, respectively, and then the airtight tank 31 is sealed by closing the flow hole 83b of the piston 81. These gases are heated to change the pressure in the airtight tank 31 from the initial pressure P1 to the pressure P2 after the change, and then the flow hole 83b of the piston 81 is opened to connect the gas phase portion 17 and the airtight tank 31. Gas flows between them so as to eliminate the pressure difference between the gas phase portion 17 and the airtight tank 31. When the gas flow is eliminated and the pressure difference is eliminated, the pressure in the gas phase portion 17 and the airtight tank 31 becomes the equilibrium pressure P3.

  There is a correlation between the total amount of gas flow at this time and the volume of the gas phase portion 17. That is, after the gas phase portion 17 and the airtight tank 31 are communicated with each other, the pressure difference between the pressure in the gas phase portion 17 and the pressure in the airtight tank 31 gradually decreases toward the equilibrium pressure P3. As the volume of the part 17 increases, the pressure change amount (pressure difference between the initial pressure P1 and the equilibrium pressure P3) toward the equilibrium pressure P3 in the gas phase part 17 decreases, and the pressure toward the equilibrium pressure P3 in the airtight tank 31 increases. The amount of change (the pressure difference between the post-change pressure P2 and the equilibrium pressure P3) increases, so that the total amount of gas flow increases, and the flow duration T during which the gas flows according to the total amount of gas flow is also To increase. From this, the larger the volume of the gas phase portion 17, the lower the equilibrium pressure P3, and the longer the flow duration T, that is, the longer the flow duration T, as shown in FIG. That is, the pressure Pm3) of the gas phase portion 17 is lowered. That is, there is also a correlation between the flow duration T and the equilibrium pressure P3. Further, the higher the initial pressure (pressure before pushing) of the gas phase portion 17 is, the higher the gas density is, and the more difficult the gas flows, so the flow duration T becomes longer (the graph in FIG. 6 moves upward as a whole). Tend to).

  The interface unit (not shown) included in the microcomputer 61 connects the flow switch 70, the heater 46, the gas phase pressure sensor 58, and the airtight tank temperature sensor 59 to the CPU 62. It is possible to send and receive various signals.

  Next, an example of the process (liquid amount estimation process 1) executed by the CPU 62 described above will be described with reference to the flowchart shown in FIG.

  When the ignition switch of the vehicle is turned on, power is supplied to the vehicle fuel system 1 and the CPU 62 of the control unit 60 starts to operate, and the CPU 62 executes a predetermined initialization process. Then, after the initialization process is completed, the CPU 62 proceeds to step T100 shown in the flowchart of FIG. 8 at a predetermined timing such as a constant cycle, for example.

  In step T100, the piston 81 of the flow switch 70 is moved to the position Qb with flow, and the flow hole 83b of the piston 81 is opened. Specifically, when a current in the other direction is passed through the winding coil 91 of the flow switch 70, the piston 81 of the flow switch 70 moves to the position Qb with flow, and the flow hole 83b of the piston 81 and the valve seat portion. 77 is disengaged from the protrusion 77b, and the flow hole 83b of the piston 81 is opened. Thereby, the connection between the gas phase section 17 and the airtight tank 31 is opened, and these are communicated with each other. Then, the process proceeds to Step T105.

  In step T105, the process waits until a predetermined pressure adjustment time elapses. This pressure adjustment time is a waiting time until the pressure in the gas phase unit 17 and the pressure in the airtight tank 31 become the same. Then, after the pressure adjustment time has elapsed, the process proceeds to step T110. “The pressure is the same” includes a case where the pressure is exactly the same and a case where there is a small difference that does not hinder the estimation of the liquid amount.

  Alternatively, instead of such processing, a pressure sensor may be provided in each of the gas phase unit 17 and the airtight tank 31, and the process may wait until the pressures measured by these sensors become the same. What is necessary is just to perform the process which controls opening and closing of the flow hole 83b of piston 81 so that the pressure in each of the part 17 and the airtight tank 31 may become the same, respectively.

  In step T110, based on the electrical signal output from the gas phase pressure sensor 58, the pressure Pm1 (initial pressure P1) of the gas phase portion 17 measured by the gas phase pressure sensor 58 is detected, and the airtight tank temperature sensor is detected. Based on the electric signal output from 59, the temperature Ts1 in the airtight tank 31 measured by the airtight tank temperature sensor 59 is detected. Then, the process proceeds to Step T115.

  In step T115, the piston 81 of the flow switch 70 is moved to the no-flow position Qa, and the flow hole 83b of the piston 81 is closed. Specifically, when a current in one direction flows through the winding coil 91 of the flow switch 70, the piston 81 of the flow switch 70 moves to the no-flow position Qa, and the flow hole 83b of the piston 81 and the valve seat portion. 77 projections 77b are fitted, and the flow hole 83b is closed. Thereby, the connection between the gas phase portion 17 and the airtight tank 31 is closed, and the airtight tank 31 is sealed. Then, the process proceeds to Step T120.

  In step T120, a control signal for driving the heater 46 is sent to the heater 46 so as to heat the gas in the airtight tank 31 until the gas reaches a predetermined target temperature. Thereby, the heater 46 heats the gas in the airtight tank 31 and raises the temperature to the target temperature Tt. In the present embodiment, the target temperature Tt is determined so that the ratio between the temperature Ts1 in the airtight tank 31 measured in step T110 and the target temperature Tt becomes a predetermined value (Tt: Ts1 = 6: 5). It has been. The above-described equilibrium pressure relationship information H is prepared by performing preliminary measurement or the like in a state where the ratio of the temperature Ts1 in the airtight tank 31 and the target temperature Tt is the same as the predetermined value. Of course, other target temperatures may be set. Since the gas in the airtight tank 31 is about to expand due to the heating by the heater 46, the pressure in the airtight tank 31 is increased because the gas is in a sealed state. However, the temperature is not limited to this. For example, using a temperature sensitive member such as bimetal, the temperature is set to be turned off at a predetermined energization temperature lower than the target temperature and turned on at the target temperature or higher. A switch is connected in series to the power supply line of the heater 41 and disposed in the airtight tank 20, and a control signal for driving the heater 46 so as to continue heating the gas in the airtight tank 31 to the target temperature is The control method of the heater 46 for heating the gas in the airtight tank 31 such as sending to the heater 46 is arbitrary. Then, the process proceeds to Step T130.

  In step T130, based on the electrical signal output from the airtight tank temperature sensor 59, the temperature Ts2 in the airtight tank 31 measured by the airtight tank temperature sensor 59 is detected. Then, the process proceeds to Step T140.

  In Step T140, it is determined whether or not the temperature Ts2 in the airtight tank 31 detected in Step T130 has reached the target temperature Tt. When the target temperature Tt has not been reached, the process returns to step T130 (N at T140), and when the target temperature Tt has been reached, the process proceeds to step T150 (Y at T140).

  In step T150, after heating until the temperature in the airtight tank 31 reaches the target temperature, the energization to the winding coil 91 of the flow switch 70 is stopped, and the piston 81 moves in the cylinder 75 according to the pressure applied thereto. Enable. At this time, since the pressure of the airtight tank 31 is higher than the pressure of the gas phase portion 17 due to the heating by the heater 46, the piston 81 due to the difference between these pressures tries to move from the non-flow position Qa to the flow position Qb. The force overcomes the biasing force of the spring 85, the piston 81 moves to the position Qb with flow, and the flow hole 83b of the piston 81 is opened. As a result, the connection between the gas phase portion 17 and the airtight tank 31 is opened, and these are communicated with each other. The gas in the airtight tank 31 is expanded and pushed into the gas phase portion 17. Further, in step T150, a control signal for driving the heater 46 is sent to the heater 46 so that the temperature in the airtight tank 31 maintains the target temperature Tt even after the circulation hole 83b is opened. Then, the process proceeds to Step T160.

  Note that the CPU 62 detects the fuel consumption based on various electrical signals indicating the injector opening, the fuel flow rate, and the like, and changes the amount of the fuel F when the fuel consumption exceeds a predetermined reference value. The above steps T100 to T140 are executed in advance when the fuel consumption is large, and this step T150 is executed when the fluctuation of the remaining amount of fuel of the fuel F is small, such as when the fuel consumption is below a predetermined reference value. You may make it do. Thereby, in a state that is not suitable for the estimation of the liquid amount, such as when the liquid amount in the fuel tank 10 is fluctuated due to the inflow or outflow of the fuel F, the connection between the airtight tank 31 and the gas phase portion 17 is closed, The gas in the airtight tank 31 is heated to increase the pressure, and the gastight tank 31 and the gas phase unit 17 are connected in a state suitable for estimation of the liquid amount, such as when the fluctuation of the liquid amount has subsided. By opening and expanding the gas in the airtight tank 31 and pushing it into the gas phase part 17 at a time, the time required for estimating the liquid amount can be shortened.

  In step T160, based on the electrical signal output from the reed switch 88 of the flow switch 70, the flow state of the gas in the pipe 39 detected by the flow switch 70 is detected, and waits until the flow presence state is detected. Then, the timer 66 starts measuring the flow duration T that indicates the duration of the state in which the gas is flowing. Then, the process proceeds to Step T170.

  In step T170, the flow state of the gas in the pipe 39 detected by the flow switch 70 is detected based on the electrical signal output from the reed switch 88 of the flow switch 70. The detection of the flow state is continued (Y in T170), and when no flow state is detected, that is, when the pressure in the gas phase portion 17 and the airtight tank 31 is balanced, the process proceeds to step T180.

  In step T180, the counting of the flow duration time T by the timer 66 is stopped. Then, the process proceeds to Step T190.

  In step T190, after the pressure in the gas phase unit 17 and the airtight tank 31 is balanced based on the pressure Pm1 of the gas phase unit 17 detected in step T110 and the flow duration time T measured in step T180. The pressure Pm3 (equilibrium pressure P3) of the gas phase portion 17 is acquired (detected).

  Specifically, the equilibrium pressure relation information H specified by the pressure Pm1 (pressure before pushing) of the gas phase part 17 before the gas is pushed into the gas phase part 17 by opening the flow hole 83b of the piston 81, By applying the flow continuation time T, the pressure Pm3 of the gas phase part 17 is acquired from the equilibrium pressure relation information H.

  An example of the acquisition of the pressure Pm3 in the gas phase part is as follows. When the pressure Pm1 before the gas is pushed into the gas phase part 17 is 1.00 MPa, the graph of FIG. If the flow duration T is 48 seconds, the pressure Pm3 of the gas phase portion 17 is acquired as 1.01000 MPa from the above graph. Then, the process proceeds to Step T200.

  In step T200, the pressure Pm1 of the gas phase section 17 detected in step T110 and the temperature Ts1 in the airtight tank 31, the temperature Ts2 in the airtight tank 31 detected in step T130, and the gas phase acquired in step T190. Based on the pressure Pm3 of the part 17, the volume VA of the part corresponding to the gas phase part 17 in the volume VT of the fuel tank 10 (hereinafter referred to as the gas phase part volume VA) is calculated.

  Derivation of the formula used for this calculation is shown below. The volume of the gas phase portion 17 is VA, the volume of the airtight tank 31 is Vs, the pressure of the gas phase portion 17 before the gas is pushed into the gas phase portion 17 by opening the flow hole 83b of the piston 81 (ie, the airtight tank 31). Pm1 (initial pressure P1), the temperature of the airtight tank 31 before heating by the heater 46 is Ts1, the temperature of the airtight tank 31 after heating is Ts2, and the pressure of the airtight tank 31 after heating is Ps2 (pressure after change) P2) After the flow hole 83b of the piston 81 is opened, the pressure of the gas phase part 17 after the pressure of the gas phase part 17 and the airtight tank 31 is balanced is Pm3 (equilibrium pressure P3), and the flow hole 83b of the piston 81 is Let T be the time from opening to pressure equilibrium (flow duration).

When the temperature rises from Ts1 to Ts2 by heating the gas in the airtight tank 31, the volume Vs of the airtight tank does not change.
Ps2 = (Ts2 / Ts1) × Pm1 (2.1)
It becomes.

Since the flow hole 83b of the piston 81 is closed, the pressure in the gas phase portion 17 remains Pm1, and a pressure difference is generated between the gas phase portion 17 and the airtight tank 31, and then the flow hole 83b in the piston 81. Is opened, the gas flows from the airtight tank 31 to the gas phase portion 17 during the flow duration T until the pressure of the gas phase portion 17 equilibrates to Pm3. And the pressure Pm3 of the gas phase part 17 after the equilibrium is calculated according to Boyle's law.
Pm3 × (Vs + VA) = Pm1 × ((Ts2 / Ts1) × Vs + VA)
Pm3 = Pm1 ((Ts2 / Ts1) × Vs + VA) / (Vs + VA)
... (2.2)
When this equation (2.2) is transformed,
VA = ((Pm3− (Ts2 / Ts1) Pm1) × Vs) / (Pm1−Pm3)
... (2.3)
Is calculated, and the gas phase volume VA is calculated using the equation (2.3). Then, the process proceeds to Step T210.

  Here, from the above equation (2.2), as the volume VA of the gas phase part 17 is larger, the equilibrium is achieved in a state where the pressure Pm3 of the gas phase part 17 is lower, so that the flow duration T of the gas flow may become longer. I can expect. That is, the larger the volume VA of the gas phase portion 17, the lower the pressure Pm3 of the gas phase portion 17 after equilibration, and the lower the pressure Pm3, the pressure change amount (pressure) of the gas phase portion 17 accompanying the gas flow Since Pm1 → pressure Pm3) is small and the pressure change amount (pressure Ps2 → pressure Pm3) of the hermetic tank is large, the total flow amount of gas is increased and the flow duration time T is lengthened.

  In step T210, by subtracting the gas phase portion volume VA calculated in step T200 from the volume VT in the fuel tank 10, the volume VL of the portion corresponding to the liquid phase portion 18 in the volume VT of the fuel tank 10 (hereinafter, referred to as the volume phase VA). The liquid phase portion volume VL is calculated, and this liquid phase portion volume VL is set as the liquid amount VL of the fuel F in the fuel tank 10. Then, a signal for displaying the liquid amount VL is sent to a fuel gauge (not shown) mounted on the vehicle. And the process of this flowchart is complete | finished.

  Steps T120 to T150 described above correspond to gas push-in control means, step T190 corresponds to equilibrium pressure detection means, and steps T110, T200, and T210 correspond to liquid amount estimation means.

  Next, an operation example in the vehicle fuel system 1 described above will be described.

  When the ignition switch of the vehicle is turned on, the vehicle fuel system 1 starts operation and estimates the amount of the fuel F in the fuel tank 10 periodically (for example, every 3 minutes). In the estimation of the liquid amount VL, first, the flow hole 83b of the piston 81 of the flow switch 70 is opened (T100), and the passage of the pressure adjustment time at which the pressures of the gas phase portion 17 and the airtight tank 31 are equal (waits) ( Thereafter, the pressure Pm1 of the gas phase portion 17 and the temperature Ts1 in the airtight tank 31 are detected (T110). Then, the circulation hole 83b of the piston 81 is closed to close the airtight tank 31 (T115), the temperature Ts2 in the airtight tank 31 is detected while heating the gas in the airtight tank 31 by the heater 46, and this temperature is detected. After heating until Ts2 reaches a predetermined target temperature Tt, if the movement of the piston 81 according to the pressure applied to the piston 81 is enabled, the flow hole 83b of the piston 81 is opened, and the gas phase portion 17 and the airtight tank 31 is communicated (T120 to T150). As a result, a pressure difference is generated between the gas phase portion 17 and the airtight tank 31, and the gas is pushed into the gas phase portion 17 from the airtight tank 31, and the gas is pushed in based on the output of the flow switch 70. A flow duration T indicating the duration of the state in which the gas is flowing from the gas phase portion 17 to the airtight tank 31 is counted (T160 to T180).

  Then, the pressure Pm3 of the gas phase portion 17 in the equilibrium state is obtained from the equilibrium pressure relation information H using the pressure Pm1 of the gas phase portion 17 before the gas is pushed into the gas phase portion 17 and the measured flow duration T. (T190). And the pressure Pm1 of the gas phase part 17, the pressure Pm3 of the gas phase part 17 in the equilibrium state, the temperature Ts1 in the airtight tank 31 before heating the gas in the airtight tank 31, and the gas in the airtight tank 31 The gas phase volume VA of the fuel tank 10 is calculated from Boyle's law using the temperature Ts2 in the airtight tank 31 after heating to the target temperature Tt and before the circulation hole 83b of the piston 81 is opened. (T200), the liquid phase portion volume VL is calculated by subtracting the gas phase portion volume VA from the volume VT of the fuel tank 10, and this liquid phase portion volume VL is used as the liquid amount of the fuel F in the fuel tank 10. Obtained as VL and displayed on the fuel gauge (T210).

  Next, an estimation example of the liquid amount VL of the fuel F in the fuel tank 10 in the vehicle fuel system 1 will be shown.

  The volume VT of the fuel tank 10 is 100 L and the volume of the airtight tank 31 is 1.0 L. In the liquid amount estimation process described above, the pressure Pm1 of the gas phase part 17 before the gas is pushed becomes 1.00 MPa, and heating is performed. The temperature Ts1 in the previous airtight tank 31 becomes 300K, the temperature Ts2 in the airtight tank 31 after heating becomes 360K, and the gas flows from the gas phase portion 17 to the airtight tank 31 after the flow hole 83b of the piston 81 is opened. It is assumed that the flow continuation time T indicating the continuation time of the current state is 28 seconds.

  At this time, since the pressure Pm1 of the gas phase portion 17 before the gas is pushed into the gas phase portion 17 is 1.00 MPa, the graph shown in FIG. When 28 seconds, which is the flow duration time T, is applied to this graph, 1.01818 MPa is acquired as the pressure Pm3 of the gas phase portion 17.

The gas phase volume VA is calculated from the above equation (2.3).
VA = ((1.01818− (360/300) × 1.00) × 1.0)
/(1.00-1.01818)
= 10.0L
When this gas phase volume VA is subtracted from the volume VT of the fuel tank 10, the liquid phase volume VL, that is, the liquid amount VL of the fuel F in the fuel tank 10 is
VL = 100-10.0 = 90.0L
It becomes. In this way, the liquid amount VL of the fuel F in the fuel tank 10 is estimated.

  By using the above-described flow switch 70 in such a vehicle fuel system 1 (that is, the liquid amount estimation device 7), there is no need to separately provide a flow switch, an orifice, a check valve, and a solenoid valve, Therefore, the liquid amount estimation device 7 and the vehicle fuel system 1 can be reduced in size.

  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 that contains kerosene, gasoline, various chemicals, and the like 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 the present invention, a plastic sliding material is used for the cylinder and the piston. However, if an operating force can be secured in relation to a fluid or a spring, the cylinder and the piston are made of a nonmagnetic metal such as aluminum or stainless steel. A configuration using can also be considered.

  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)
7 Liquid quantity estimation device 10 Fuel tank (liquid tank)
17 Gas phase part in fuel tank (gas phase part)
18 Liquid phase part in fuel tank 39 Piping 46 Heater (heating means)
58 Gas Phase Pressure Sensor (Gas Phase Pressure Information Measuring Means)
59 Airtight tank temperature sensor (Airtight tank temperature measuring means)
60 control unit 62 CPU (gas push-in control means, equilibrium pressure detection means, liquid amount estimation means)
66 timer (flow duration measuring means)
70 Flow switch 71 Case (pipe)
75 Cylinder 77 Valve seat (valve seat)
77b Projection part 81 Piston 82 Peripheral wall part 83 Bottom wall part 83a Main body part 83b Flow hole 84 Magnet 85 Spring (biasing member)
88 Reed switch (position detecting means, magnetic force sensitive sensor element)
91 Winding coil (coil)

Claims (5)

A flow switch that operates according to a flow state of a fluid flowing in a pipe made of metal ,
A cylindrical cylinder that is fixedly accommodated in the conduit,
A piston housed in the cylinder movably between a no-flow position near the inlet end of the cylinder and a position with flow near the outlet end;
A biasing member that biases the piston toward the no-flow position;
Position detecting means for outputting a position signal corresponding to the position of the piston,
Both the cylinder and the piston are made of plastic sliding material,
The flow switch according to claim 1, wherein the cylinder is formed so that an inner peripheral surface of the pipe line and an outer peripheral surface of the cylinder closely overlap each other when the cylinder is fixedly accommodated in the pipe line.   The piston has a cylindrical peripheral wall portion, a plate-like main body portion provided so as to close the inner side of the peripheral wall portion, and a bottom wall portion provided with a flow hole penetrating the main body portion. The flow switch according to claim 1.   The flow according to claim 2, further comprising: a valve seat provided with a protrusion that fits into the flow hole so as to close the flow hole when the piston is in the no-flow position. switch. The piston is provided with a magnet,
The pipe is made of a non-magnetic material, and on the outer circumferential surface thereof, when current flows in one direction, the piston is moved to the no-flow position, and the current flows in the other direction opposite to the one direction. The flow switch according to claim 3, wherein a coil that exerts a magnetic force on a magnet of the piston is provided so as to move the piston to the position with the flow when the gas flows.   The position detecting means is provided so that the sensitive state with respect to the magnetic force of the magnet of the piston changes depending on whether the piston is in the position with the flow or the position without the flow. The flow switch according to claim 4, wherein the flow switch is configured by a magnetic force sensitive sensor element that outputs a position signal.

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