JP2000303909A - Gas fuel supply system of vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To quickly detect a gas leakage to take a measure to the leakage by providing a control part for determining the gas leakage when a pressure drop rate is larger than a predetermined pressure drop rate threshold. SOLUTION: During the operation of an engine, a first cutoff valve 50 and a second cutoff valve 65 are opened, and according to a command of an injector driver 35, an injector 15 is opened and closed repeatedly. When the first cutoff valve 50 and the second cutoff valve 65 are closed, compressive natural gas is confined in a high pressure pipe 13 and a low pressure pipe 14. When no gas leakage is caused in he pipe, the pressure of the compressive natural gas is substantially constant and little drops. If gas leakage is caused, the pressure drops gradually or suddenly. Accordingly, leakage between the first cutoff valve 50 and the second cutoff valve 65 can be monitored by a first pressure sensor 31 at a control part, and a leakage between the second cutoff valve 65 and an injector 15 can be monitored by a second pressure sensor 33.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for determining gas leakage in a vehicle gas fuel supply system.

[0002]

2. Description of the Related Art In recent years, natural gas (NG) has been adopted as one of alternative fuels for gasoline and light oil, and when this natural gas is used as fuel for vehicles, particularly passenger vehicles, a high-pressure container is installed on the vehicle body. (Cylinder) and 20
Natural gas compressed to about 0 kg / cm ² is filled, and this natural gas is converted into low-pressure gas by a pressure reducing valve and supplied to the combustion chamber of the engine. Natural gas compressed at such a high pressure is called compressed natural gas (CNG).

Research on vehicles using compressed natural gas has been advanced. For example, Japanese Unexamined Patent Publication No. 7-189731 discloses a "remaining fuel display device for a gas-fueled vehicle" which measures pressure fluctuations and temperature fluctuations caused by a compressible fluid. The present invention proposes a technique for displaying the remaining amount of fuel more accurately by making a correction.

In the above publication, reference numeral 1 in FIG. 2 denotes a CNG tank,
2 is a high-pressure pipe, 13 is a first solenoid shut-off valve, 14 is a second solenoid shut-off valve.
4 can be closed.

[0005]

Since the compressed natural gas line from the CNG tank to the engine is for storing and flowing high-pressure natural gas, there must be no leakage in piping and valves. However, an object of the present invention is to detect a gas leak in a gas fuel supply system for a vehicle due to external influences such as vibration, acceleration, temperature change, etc. peculiar to a vehicle, to quickly detect the gas leak and take a countermeasure. To provide techniques that can be taken.

[0006]

To achieve the above object, a first aspect of the present invention is to provide a gas fuel supply for a vehicle in which a shutoff valve, a pressure sensor, and a shutoff valve are arranged in this order on a pipe for supplying gaseous fuel to a gas engine. The system includes a gas leak diagnosis timer, and closes the two open shut-off valves based on a gas leak diagnosis signal generated on condition of a fuel cut signal, and then measures a pressure drop amount with a pressure sensor. A control unit that calculates a pressure drop rate based on the pressure information and the time information from the diagnosis timer, and determines that there is a gas leak when the pressure drop rate is greater than a predetermined pressure drop rate threshold. It is characterized by having.

[0007] A pair of shut-off valves, a pressure sensor disposed therebetween, and a control unit detect gas leakage. As a result, even if a gas leak occurs in the vehicular gas fuel supply system even during traveling, it is possible to quickly detect the occurrence and take measures.

[0008]

Embodiments of the present invention will be described below with reference to the accompanying drawings. In the following description, first, second,... Or primary, secondary,... Are identification names given along the flow of gaseous fuel. FIG. 1 is a schematic view of a vehicle according to the present invention. This vehicle 10 has a CNG tank 12 filled with compressed natural gas as a gas fuel mounted on a rear portion of a vehicle body 11, and a compressed natural gas in the CNG tank 12. Is provided to the combustion chamber of the gas engine 16 mounted on the front of the vehicle body 11 via the high-pressure pipe 13, the pressure control unit 60, the low-pressure pipe 14, and the injector 15. The description of the other symbols will be described later.

FIG. 2 is a diagram showing the principle of a gas fuel supply system according to the present invention. The gas fuel supply system 20 compresses a CNG tank 12 from the outside through a filling port 21, a filling pipe 22, and a check valve 40. Compressed natural gas that can be filled with natural gas and stored in CNG tank 12
The first shutoff valve 50, the high pressure pipe 13, the joint box 23 interposed in the high pressure pipe 13, the manual on / off valve 24, the filter 25, the pressure control unit 60, the low pressure pipe 14, and the low pressure pipe 14 can be sent to the intake port 26 via the injector 15. It is a system that can do it.

In addition, in this system, the joint box 23 includes a first pressure sensor 31 and a first temperature sensor 3.
2, a second pressure sensor 33 at the outlet of the pressure control unit 60, and a second temperature sensor 34 at the injector 15.
And a control unit 36 for controlling the opening and closing of a first shut-off valve 50 and a second shut-off valve (to be described later in detail) incorporated in the pressure control unit 60.

That is, the pressure P of the compressed natural gas in the high-pressure pipe 13 is determined by the first pressure sensor 31 and the first temperature sensor 32.
0, the temperature T0 is measured, the information is input to the control unit 36, and the pressure P2 and the temperature T2 of the compressed natural gas in the low-pressure pipe 14 are measured by the second pressure sensor 33 and the second temperature sensor 34, and the information is measured. Input to the control unit 36, and based on the input information, the control unit 36
0 or the second shutoff valve 65 built in the pressure control unit 60 is controlled.

Since compressed natural gas is a gas and a compressible fluid, Boyle-Charles' law (PV / T = constant. P: absolute pressure, V: volume or volume, T: absolute temperature)
Compliant. Here, since the volume of the flow path is constant, V does not change, and if the temperature rises and falls, the pressure rises and falls in proportion, and the pressure may constantly change, which hinders control.
Therefore, the temperature of the pressure P0 is corrected at the temperature T0. Similarly, the pressure P2 is corrected by the temperature T2. If the temperature is corrected, any pressure becomes a pressure based on 0 ° C., and it is possible to make a relative comparison.

FIG. 3 is an enlarged sectional view of a part 3 of FIG. 2, in which the check valve 40 and the first shutoff valve 50 are assembled in a common valve box 41,
This valve box 41 is characterized by being screwed to the opening of the CNG tank 12, and in particular, the first shut-off valve 50 is called an in-tank shut-off valve because a main part is in the CNG tank 12. The structures of the check valve 40 and the first shutoff valve 50 will be described in order.

In the check valve 40, a sleeve 42 is screwed into the valve box 41, a valve body 43 is brought into contact with a lower opening of the sleeve 42, and the valve body 43 is pushed toward the valve closing side by a spring 44. This valve has a structure in which it is supported by another sleeve 45 and a rod 46, and a flow path 47 and a throttle portion 48 are formed in the rod 46. The operation of the check valve 40 is shown in FIG.
This will be described in (a). Reference numeral 49 denotes a stopper, which is open in the figure, but can be turned over with a hexagon wrench or the like to close the upper opening 41a. This is used when the filling tube 22 is to be inspected for maintenance.

The first shut-off valve 50 has a solenoid 5
Screw the cylindrical solenoid holder 52 that supports 1
A rod 53 is passed through the solenoid holder 52, a valve element 55 is stopped at a tip of the rod 53 via a pin 54, and the valve element 55 is opposed to a valve seat on the valve box 41 side, and when the solenoid 51 is energized. The rod 53 is retracted by the suction action of the solenoid 51 to open the valve, and when the power supply to the solenoid 51 is stopped, the suction action is lost and the spring 5
6 is a solenoid type shut-off valve which is brought into a valve closed state by the pushing action. 57 is a port opened in the solenoid holder 52. The operation of the first shut-off valve 50 will be described with reference to FIG. Reference numeral 58 denotes a stopper plug, which is open in the figure. However, the upper opening 41b can be closed by turning it with a hexagon wrench or the like.

FIGS. 4A and 4B are operational diagrams of the check valve and the first shut-off valve according to the present invention. In (a), when high-pressure compressed natural gas is supplied as indicated by a white arrow, the valve element 43 moves to the valve opening side by the pressure. As a result, the compressed natural gas reaches the CNG tank 12 via the throttle section 48 as shown by the arrow. When the supply of the compressed natural gas is stopped, the valve body 43 returns by the action of the spring 45 to prevent backflow. In (b), when the solenoid 51 is energized, the valve element 55 is retracted to open the valve, and the compressed natural gas inside the CNG tank 12 flows through the port 57 as shown by the arrow. When the energization of the solenoid 51 is stopped, the valve is closed by the action of the spring 56.

FIG. 5 is an enlarged sectional view of a portion 5 in FIG. 2. The operation will be described with reference to FIG. 7, so that the outline of the structure will be described. The pressure control unit 60 includes a second shutoff valve 65 and a primary pressure reducing valve 70.
, The safety valve 77 and the secondary pressure reducing valve 80 are grouped together, and detailed description of the structure is omitted.
Is a solenoid type shut-off valve driven by a solenoid 66, and a primary pressure reducing valve 70 is a pressure regulator having a diaphragm 71, a pressure adjusting spring 72, a back pressure chamber 73, a back pressure inlet 74, and a pressure adjusting screw 75. The safety valve 77 is a valve including a valve body 78 and a spring 79,
The secondary pressure reducing valve 80 includes a diaphragm 81 and a pressure adjusting spring 8.
2. Back pressure chamber 83, back pressure inlet 84, pressure adjusting screw 85
It is a pressure regulator provided with.

FIG. 6 is a bottom view of the pressure control unit shown in FIG. 5. The compressed natural gas entering the pressure control unit 60 as shown by the arrow is supplied to the inner filter 86 and the second shut-off valve 6.
It flows as indicated by the arrow via 5. Returning to FIG. 5, the flow indicated by the arrow passes through the primary pressure reducing valve 70, and moves upward as indicated by the arrow to reach the secondary pressure reducing valve 80.

FIG. 7 is a diagram showing the principle of operation of the pressure control unit employed in the present invention. The primary pressure reducing valve 70 reduces the pressure P0 to the pressure P1. For details, see Diaphragm 7
1, the pressure P0 acts on the upper surface of the drawing, the pressure P1 acts on the lower surface of the diaphragm 71, and the pressing force of the spring 72 acts. Natural gas flows with the balance of these three acting forces and the valve opening determined. However, if the pressure P1 rises above the set pressure, the pressure in the back pressure chamber 73 rises, pushing up the diaphragm 71 to narrow the valve, and as a result, the pressure P1 decreases. If the pressure P1 is lower than the set pressure, the valve opening increases to increase the pressure P1. In this way, the primary pressure reducing valve 70 can maintain the pressure P1 at a predetermined set pressure. In this embodiment, the pressure P0 is 10 to 260 kg / cm ² , and the pressure P1 is 6 k
g / cm ² , and a constant pressure P1 can be obtained even if the pressure P0 changes significantly.

The secondary pressure reducing valve 80 reduces the pressure P1 to the pressure P2, and its basic operation is the same as that of the primary pressure reducing valve 70, and will not be described. Pressure P1 is 6 kg / cm ² , pressure P
2 is 2.6 kg / cm ² , but it goes without saying that even if the pressure P1 fluctuates, the pressure P2 can be kept at a predetermined set pressure. The pressure P2 is detected by the second pressure sensor 33. The pressure values described above are merely examples, and the present invention is not limited to these values.

When the solenoid 66 is energized, the second shut-off valve 65 is opened and natural gas flows as indicated by the arrow. When the energization is stopped, the spring 67 closes the valve. The safety valve 77 has a pressure P1 due to a trouble occurring in the primary pressure reducing valve 70.
Is opened to protect the low-pressure pipe 14 including the secondary pressure reducing valve 80 at the time when the pressure rises significantly.

Next, a gas leak detection technique in the gas fuel supply system of the present invention described above will be described. FIG. 8 is a diagram showing a gas fuel supply system for explaining the failure determination technique of the present invention. In order to supplement the control flow described below, a start switch 90 is added to a drawing that is an essential part of FIG. It is. Start switch 90 is ACC-OF
F contact 91, ACC-ON contact 92, IG-ON contact 9
3 and the ST-ON contact 94, and if the ACC-OFF contact 91 is selected, the accessory is turned off and the ACC
If the ON contact 92 is selected, the accessory is turned on, and if the IG-ON contact 93 is selected, the ignition O is turned on.
The state becomes N, and starter rotation is started at the ST-ON contact 94.

Since the other reference numerals have already been described, they will not be described again.
1 and the second shut-off valve 65 "are a first group for gas leak detection, and the second shut-off valve 65 and the second pressure sensor 33
And the injector 15 "form a second group of gas leak detection. This is because the injector 15 exhibits the function of the shut-off valve when receiving the fuel cut signal.

FIG. 9 is a time chart of the gas leak detection technology according to the present invention. (A) shows a time zone in which the fuel cut signal is on. This ON signal is a requirement for gas leak diagnosis. At (b), a gas leak diagnosis signal is detected.
In (c) and (d), the first shutoff valve and the second shutoff valve are closed. In (e), the diagnosis timer is reset based on the gas leak diagnosis signal, and the counting is started. The set time of this diagnostic timer is t0. The above is the case where the diagnosis is completed when the diagnosis timer expires. In addition to the above, according to the present invention, as indicated by the broken line in FIG.
The diagnosis can be completed based on this signal.
Details will be described later with reference to FIG.

Returning to FIG. 8, during operation of the engine, the first shut-off valve 50 and the second shut-off valve 65 are open, and the injector 15 is controlled based on a command from the injector driver 35.
Is opening and closing repeatedly. When the fuel cut signal is received, the injector 15 closes.
The supply pressure of the NG tank 12 acts. Therefore, when the first shutoff valve 50 and the second shutoff valve 65 are closed, the compressed natural gas is confined in the high-pressure pipe 13 and the low-pressure pipe 14. If there is no gas leakage from the pipes, the pressure of the compressed natural gas contained should be almost constant, that is, hardly drop.
If there is a gas leak, the pressure will drop slowly or sharply. Therefore, the first pressure sensor 31 can monitor the leak between the first shutoff valve 50 and the second shutoff valve 65, and the second
The leak between the second shut-off valve 65 and the injector 15 can be monitored by the pressure sensor 33.

FIG. 9F shows this state. That is, the horizontal axis represents time, and the vertical axis represents the output of the first pressure sensor. If there is no gas leakage, the pressure hardly drops even after the lapse of time t0, and the solid line shows. If there is a gas leak, the pressure drops as indicated by the broken line. Therefore, the pressure drop rate threshold value ΔP0 after the lapse of the determination time t0 may be determined in advance by actually measuring using an actual engine and a gas fuel supply system, and obtaining the data. This is called that the pressure decrease rate threshold value ΔP0 is predetermined. The pressure drop rate obtained from the determination time t0 and the output of the first pressure sensor 31 is equal to the pressure drop rate threshold ΔP
If it is smaller than 0, it is normal (no gas leakage), and if the pressure decrease rate is greater than the pressure decrease rate threshold value ΔP0, it can be determined that there is gas leakage between the first shutoff valve 50 and the second shutoff valve 65.

Similarly, the pressure drop rate threshold value ΔP2 is determined in advance, and as shown in FIG. 9 (g), the pressure drop rate obtained from the determination time t0 and the output of the second pressure sensor 33 becomes the pressure drop rate. If it is smaller than the threshold value ΔP2 (this threshold value is also stored in the control unit in advance), it is normal (no gas leakage),
If the pressure decrease rate is greater than the pressure decrease rate threshold value ΔP2, it can be determined that there is gas leakage between the second shut-off valve 65 and the injector 15.

An example of a control flow based on the above time chart will be described below. FIG. 10 is a flowchart (part 1) of the gas leak detection according to the present invention, where STxx indicates a step number. ST01: First, it is checked whether the fuel cut signal is in the ON state, that is, whether or not the fuel cut signal is detected. If No, the process jumps to (C) in another figure, and if Yes, the process proceeds to the next ST02. In the vehicle, for example, the fuel cut signal is output for a relatively long time in the deceleration mode.
N. ST02: "1" is given to the flag FL / FC corresponding to the ON state of the fuel cut signal. ST03: The first and second shut-off valves are both closed. ST04: Take in pressure information from the first pressure sensor and store it. This pressure information is the initial value of the pressure P0,
Called (1). Similarly, pressure information is taken from the second pressure sensor and stored. This pressure information is an initial value of the pressure P2 and is referred to as a pressure P2 (1).

ST05: Since the pressure P0 is the internal pressure of the high-pressure pipe and the pressure P2 is the internal pressure of the low-pressure pipe, if P0 ≦ P2, it is considered that there is some abnormality in the first and second pressure sensors. FL · PS is a pressure sensor flag, and gives “1” if abnormal, and gives “0” if normal. ST06: Then, if ST05 is Yes, PL · PS =
Let it be 1. ST07: If No in ST05, PL · PS = 0. (A) indicates that the process proceeds to the next step.

FIG. 11 is a flowchart (part 2) of the gas leak detection according to the present invention, which is a flow following (A) in the previous figure. For convenience, the step numbers start from ST11. . ST11: Check whether PL · PS = 1. ST12: If Yes in ST11, a pressure sensor abnormality display is displayed on a warning display section (announcer panel, instrument panel) by a lamp or the like. When this display appears, the driver may quickly bring the vehicle into a repair shop or the like and take measures to resolve the failure.

ST13: If No in ST11, that is, if there is no abnormality, the diagnostic timer is turned on and counting is started. ST14: Take in pressure P0 (n) and pressure P2 (n). (n) means the nth, which means that pressure information at that time is read. ST15: Wait for the diagnosis timer to expire at tf (n) ≧ t0. That is, the accumulated time tf (n) of the diagnostic timer is equal to the predetermined determination time (elapsed time required for the determination) t0.
Pressure P0 (n), P2 until equal to or exceeds
Continue sampling in (n). Pressure P0 every time
(n) and P2 (n) have new values. When tf (n) ≧ t0 is satisfied, the process proceeds to the next step. How to determine the determination time t0 will be described later. ST16: If Yes in ST15, tf (n) = t0
And proceed to the next step. ST17: Take in pressures P0 (n) and P2 (n) as final values. (B) indicates that the process proceeds to the next step.

FIG. 12 is a flowchart (part 3) of the gas leak detection according to the present invention, which is a flow following (B) in the preceding figure. The step numbers are assigned from 21 for convenience. ST21: The pressure P0 (n) at the point of time tf (n) is subtracted from the initial value P0 (1) of the pressure P0, and the obtained pressure drop amount (P0 (1) -P
0 (n)) divided by the diagnosis time tf (n) is the pressure decrease rate at this time. This pressure decrease rate is compared with a pressure decrease rate threshold value ΔP0. ST22: Yes in ST21, meaning that P0 (n) has decreased, and it can be considered that there is a leak in the high-pressure pipe.
Give 1 to ak0 (1 is leaky). ST23: If No in ST21, FL·leak0
To 0 (0 is leaking).

ST24: From initial value P2 (1) of pressure P2 to t
The pressure P2 (n) at the time of f (n) is subtracted, and the obtained pressure drop amount (P2 (1) -P2 (n)) is divided by the diagnosis time tf (n). It becomes a falling rate. This pressure drop rate is compared with a pressure drop rate threshold value ΔP2. ST25: Yes in ST24, that is, P2 (n) has decreased, and it can be considered that there is a leak in the low-pressure pipe, and thus FL·le indicating a leak in the low-pressure pipe.
ak2 is given 1 (1 is leaky). ST26: If No in ST24, FLleak2
To 0 (0 is leaking).

ST27: FL·leak0 = 0 and F
It is determined whether or not L·leak2 = 0. If Yes, there is no gas leak in either the high-pressure pipe or the low-pressure pipe, so the flow ends. ST28: If No in ST27, it can be considered that the gas is in a gas leak state, so that the gas leak is displayed on a warning display section (announcer panel, instrument panel) with a lamp or the like. When this display appears, the driver may quickly bring the vehicle into a repair shop or the like and take measures to resolve the failure.

FIG. 13 is a flowchart (part 4) of the gas leak detection according to the present invention, which is a flow from FIG. 10 (C). The step numbers are assigned from 31 for convenience. FIG.
In (a), before the time t0, the fuel cut signal becomes (OF).
When F) is reached, the flow of FIG. 13 proceeds. ST31: If No in ST01 shown in FIG. 10, "0" is given to the flag FL / FC. FL / FC = 0
This means that the fuel cut signal is OFF. ST32: Then, it is checked whether or not the previous FL / FC was “1”. The last time corresponds to the (n-1) th.
If No, the diagnosis is not performed because the fuel cut signal was not ON last time.

ST33 to ST40: If Yes in ST32, ST33 to ST40 in which (n) of ST21 to ST28 in FIG. 12 is replaced with (n-1) are executed, and when it is recognized that the gas is leaking, In ST40, a gas leak is displayed. If “Yes” in ST39, it is not in the gas leakage state, so the flow proceeds to next ST41. ST41: Open both the first and second shut-off valves. ST42: The diagnostic timer is turned off and reset to prepare for the next diagnosis. Since the steps ST31 to ST42 can be executed, a pipe leak diagnosis can be made based on the fuel cut signal (OFF) even before the expiration of the diagnosis timer.

The type of the gas fuel described in claim 1 is not limited as long as it is a gas fuel such as compressed natural gas, hydrogen gas, and coal gas. Further, the numbers of the shutoff valves and the pressure sensors are not limited to the embodiment.

[0038]

According to the present invention, the following effects are exhibited by the above configuration. According to the first aspect, gas leakage is detected by the pair of shut-off valves, the pressure sensor disposed therebetween, and the control unit. As a result, even if a gas leak occurs in the vehicular gas fuel supply system even during traveling, it is possible to quickly detect the gas leak and take a countermeasure.

[Brief description of the drawings]

FIG. 1 is a schematic view of a vehicle according to the present invention.

FIG. 2 is a principle diagram of a gas fuel supply system according to the present invention.

FIG. 3 is an enlarged sectional view of a part 3 in FIG. 2;

FIG. 4 is an operation diagram of a check valve and a first shut-off valve according to the present invention.

FIG. 5 is an enlarged sectional view of a part 5 in FIG. 2;

FIG. 6 is a bottom view of the pressure control unit of FIG. 5;

FIG. 7 is an operation principle diagram of a pressure control unit employed in the present invention.

FIG. 8 is a diagram of a gas fuel supply system for explaining a gas leak detection technique of the present invention.

FIG. 9 is a time chart of a gas leak diagnosis according to the present invention.

FIG. 10 is a flowchart (part 1) of gas leak detection according to the present invention.

FIG. 11 is a flowchart (part 2) of gas leak detection according to the present invention.

FIG. 12 is a flowchart (part 3) of gas leak detection according to the present invention.

FIG. 13 is a flowchart of gas leak detection according to the present invention (part 4).

[Explanation of symbols]

10: vehicle, 13: pipe (high pressure pipe), 14: pipe (low pressure pipe), 16: gas engine, 20: gas fuel supply system, 31: pressure sensor (first pressure sensor), 36: control unit.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Akifumi Otaka 1-4-1 Chuo, Wako-shi, Saitama Pref. Honda Technical Research Institute, Inc. (72) Inventor Hiroyuki Goto 1-4-1 Chuo, Wako-shi, Saitama No. F-term in Honda R & D Co., Ltd. (reference) 2G067 AA14 BB11 CC04 DD02

Claims (1)

[Claims] 1. A vehicle gas fuel supply system in which a shutoff valve, a pressure sensor, and a shutoff valve are arranged in this order in a pipe for supplying gaseous fuel to a gas engine, comprising: a gas leak diagnosis timer; The shut-off valve is closed based on a gas leak diagnosis signal generated under the condition of a fuel cut signal, and then a pressure sensor measures the amount of pressure drop, and the pressure information and time information from the diagnosis timer are used to determine the pressure. A gas fuel supply system for a vehicle, comprising: a control unit that calculates a descending rate and determines that there is a gas leak when the pressure decreasing rate is greater than a predetermined pressure decreasing rate threshold value.