JP3598697B2 - LPG cylinder remaining fuel detector - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an apparatus for detecting the amount of fuel remaining in an LPG cylinder, and more particularly to an apparatus for detecting the amount of fuel remaining in an LPG cylinder mounted on an industrial vehicle or the like.
[0002]
[Prior art]
As shown in FIG. 5, there is an industrial vehicle such as a forklift that has an LPG cylinder 1 mounted on a rear portion of a vehicle body and operates using LPG as fuel. In such a vehicle, the remaining fuel amount in the LPG cylinder 1 is monitored by the fuel remaining amount warning system, and when the remaining fuel amount becomes equal to or less than a predetermined value, the LPG cylinder 1 is replaced to supply fuel. As shown in FIG. 6, a fuel remaining amount warning system includes a fuel remaining amount detecting device 3 provided in a fuel supply pipe 2 for supplying fuel from an LPG cylinder 1 to an engine (not shown). It comprises a power supply 4 and a warning lamp 5 electrically connected to the device 3.
[0003]
The fuel remaining amount detection device 3 detects the vapor pressure of the LPG flowing from the LPG cylinder 1 through the fuel supply pipe 2, and when the vapor pressure is equal to or higher than the set value, the pair of terminals is open. When it is less than the above, the pair of terminals is short-circuited. A power supply 4 and a warning lamp 5 are connected in series between a pair of terminals of the fuel remaining amount detection device 3. When the remaining fuel in the LPG cylinder 1 is sufficient, the terminals of the remaining fuel detecting device 3 are opened because the vapor pressure of the LPG is higher than the set value, and the warning lamp 5 does not light. On the other hand, when the remaining fuel in the LPG cylinder 1 decreases and the vapor pressure of the LPG drops below the set value, the terminals of the remaining fuel detecting device 3 are short-circuited and the warning lamp 5 is turned on. By arranging the warning lamp 5 on an instrument panel or the like, it is possible to inform the driver of the need for refueling.
[0004]
FIG. 7 shows a configuration of a conventional fuel remaining amount detection device 3. A cantilever 7 made of a conductor is provided in the main body 6, a movable contact 8 is formed at a free end of the cantilever 7, and a fixed end is electrically connected to a terminal 9 provided outside the main body 6. I have. A fixed contact 10 is fixed to the main body 6 so as to face the moving contact 8, and the fixed contact 10 is electrically connected to a terminal 11 provided outside the main body 6. The upper surface of the central portion of the cantilever 7 is pressed downward by a spring 12, and the upper surface of the diaphragm button 13 contacts the lower surface. The lower end of the diaphragm button 13 is in contact with the upper surface of a diaphragm 15 stretched by an O-ring 14 in the main body 6. A gas chamber 17 that communicates with the fuel supply pipe 2 via a mounting pipe 16 is defined on the lower surface side of the diaphragm 15.
[0005]
When the vapor pressure of the LPG filled in the gas chamber 17 from the fuel supply pipe 2 is high, the diaphragm 15 is pressed upward against the elastic force of the spring 12, and the cantilever 7 is lifted upward via the diaphragm button 13. Can be As a result, as shown in FIG. 7, a gap is generated between the movable contact 8 formed at the free end of the cantilever 7 and the fixed contact 10, so that the terminals 9 and 11 are open. On the other hand, when the vapor pressure of the LPG in the gas chamber 17 decreases, the diaphragm 15 gradually lowers due to the elastic force of the spring 12, and the cantilever 7 also lowers accordingly. In this way, when the vapor pressure in the gas chamber 17 becomes lower than the set value, the moving contact 8 formed at the free end of the cantilever 7 comes into contact with the fixed contact 10 as shown in FIG. 11 is short-circuited.
[0006]
[Problems to be solved by the invention]
However, as shown in FIG. 9, it is known that the vapor pressure of LPG greatly changes depending on the temperature, and is low at low temperatures and high at high temperatures. In FIG. 9, curve A shows a mixed gas of 100% propane, curve B shows a mixed gas of 100% butane, and curve C shows a mixed gas of 50% propane + 50% butane. For this reason, when working in a cold or cold environment, the vapor pressure of the LPG in the gas chamber 17 of the fuel remaining amount detection device 3 is set to the set value even if the fuel remains sufficiently in the LPG cylinder 1. The fuel level warning system is activated when the value becomes less than the threshold, and the warning lamp 5 is lit.
[0007]
The present invention has been made in order to solve such a problem, and an object of the present invention is to provide an LPG cylinder fuel remaining amount detecting device capable of detecting the remaining fuel amount with high accuracy even when the temperature fluctuates. And
[0008]
[Means for Solving the Problems]
An apparatus for detecting a remaining fuel amount of an LPG cylinder according to the present invention includes a main body, a gas chamber communicating with the LPG cylinder in the main body, a diaphragm that is displaced in accordance with the vapor pressure of the LPG in the gas chamber, and a gas chamber that includes the diaphragm. , A fixed contact, and a movable contact that is disposed to face the fixed contact and that moves with the displacement of the diaphragm when the vapor pressure of the LPG in the gas chamber decreases and contacts the fixed contact. A temperature correction means for adjusting a biasing force of a spring or an interval between the fixed contact and the movable contact so that the movable contact comes into contact with the fixed contact at a lower vapor pressure of LPG than at a high temperature.
[0009]
A temperature correction means, a wax case that holds one end of the spring and is provided so as to be able to advance and retreat in the length direction of the spring, and a wax that is enclosed in the wax case and moves the wax case forward and backward by a volume change accompanying a temperature change. , The urging force of the spring can be reduced at low temperatures compared to at high temperatures. Further, the temperature correction means is constituted by a cantilever made of a bimetal having one end fixed to the main body, a center portion sandwiched between the diaphragm and the spring, and a moving contact formed at the other end, and the moving contact is fixed at a low temperature. It can also be curved away from the contacts.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
FIG. 1 shows a configuration of an apparatus for detecting a remaining fuel amount of an LPG cylinder according to an embodiment of the present invention. The main body 21 has a cylindrical portion 22 and a mounting tube 23 that project in opposite directions along the central axis of the main body 21. A cantilever 24 made of a conductor is provided in the main body 21 so as to cross the center axis of the main body 21. One end of the cantilever 24 is fixed to the main body 21 as a fixed end, and a terminal 25 provided outside the main body 21 is provided. Is electrically connected to The other end of the cantilever 24 is a free end, and a moving contact 26 is formed at this free end. A fixed contact 27 is fixed to the main body 21 so as to face the moving contact 26, and the fixed contact 27 is electrically connected to a terminal 28 provided outside the main body 21. The upper surface of the central portion of the cantilever 24 is pressed downward by the lower end of a spring 29 disposed in the cylindrical portion 22, and the upper surface of the diaphragm button 30 contacts the lower surface. The lower end of the diaphragm button 30 is in contact with the upper surface of a diaphragm 32 stretched by an O-ring 31 in the main body 21. A gas chamber 33 communicating with the mounting pipe 23 is defined in the main body 21 on the lower surface side of the diaphragm 32 by the diaphragm 32.
[0011]
A shaft 34 is provided on the central axis of the main body 21 and at the upper end of the tubular portion 22 such that the tip portion projects downward into the tubular portion 22. A wax case 35 is provided so as to cover the tip of the shaft 34, and the upper end of the spring 29 is held at the lower end of the wax case 35. The wax case 35 includes a case body 36 having an open upper part, and a lid 37 that covers the upper part of the case body 36 and through which the shaft 34 slidably penetrates. Thereby, the wax case 35 is provided so as to be able to advance and retreat along the shaft 34 while the inside is sealed. Inside the wax case 35, a sleeve 38 made of an elastic material such as synthetic rubber is provided around the shaft 34, and a wax 39 is sealed between the outer peripheral portion of the sleeve 38 and the inner wall portion of the case body 36. .
[0012]
The shaft 34 is screwed to the upper end of the cylindrical portion 22 by a thread formed on the outer periphery of the upper end, and the shaft 34 is rotated using a groove formed on the upper end of the shaft 34. Thereby, the protruding length of the shaft 34 into the tubular portion 22 can be adjusted. In addition, the shaft 34, the wax case 35, the sleeve 38, and the wax 39 form the temperature correcting means of the present invention.
[0013]
Next, the operation of the remaining fuel amount detection device according to this embodiment will be described. As shown in FIG. 6, the fuel remaining amount detecting device shown in FIG. 1 is attached to a fuel supply pipe connecting the LPG cylinder and the engine via an attachment pipe 23 in advance. At this time, the gas chamber 33 partitioned in the main body 21 by the diaphragm 32 communicates with the fuel supply pipe via the mounting pipe 23, and the gas chamber 33 is filled with LPG from the LPG cylinder.
[0014]
When the fuel remaining in the LPG cylinder is sufficient, the vapor pressure of the LPG taken into the gas chamber 33 is high, and the gas pressure presses the diaphragm 32 upward against the elastic force of the spring 29, and the diaphragm 32 is pressed. The cantilever 24 is lifted upward via the button 30. Thereby, as shown in FIG. 1, a gap is generated between the movable contact 26 formed at the free end of the cantilever 24 and the fixed contact 27, and the space between the terminals 25 and 28 is opened. On the other hand, when the remaining amount of fuel in the LPG cylinder decreases, the vapor pressure of LPG in the gas chamber 33 decreases, and the diaphragm 32 gradually lowers due to the elastic force of the spring 29, so that the cantilever 24 also lowers. Thus, when the vapor pressure in the gas chamber 33 becomes lower than the set value, the moving contact 26 formed at the free end of the cantilever 24 comes into contact with the fixed contact 27, and the terminals 25 and 28 are short-circuited. . Therefore, if a power supply and a warning lamp are connected in series between the terminals 25 and 28, the driver can be notified of the necessity of refueling by turning on the warning lamp.
[0015]
As shown in FIG. 9, in a high-temperature environment, the vapor pressure of LPG increases, so that the diaphragm 32 moves upward from the LPG in the gas chamber 33 even if the remaining amount of fuel in the LPG cylinder is constant. Receives greater gas pressure that is directed. However, at a high temperature, as shown in FIG. 2, the wax 39 sealed in the wax case 35 expands to compress the sleeve 38 made of an elastic material and push the shaft 34 out of the wax case 35. I do. Actually, since the shaft 34 is fixed to the main body 21, the wax case 35 moves downward so as to come off the shaft 34. As a result, the spring 29 is compressed, and the urging force for pressing the diaphragm 32 toward the gas chamber 33 increases. As described above, when the temperature is high, the gas pressure in the gas chamber 33 increases, but at the same time, the force of pressing the diaphragm 32 toward the gas chamber 33 by the spring 29 also increases.
[0016]
Conversely, in a low-temperature environment, the vapor pressure of the LPG drops, so that the upwardly acting gas acting on the diaphragm 32 from the LPG in the gas chamber 33 even if the remaining amount of fuel in the LPG cylinder is constant. The pressure decreases. However, when the temperature is low, the wax 39 sealed in the wax case 35 contracts, the sleeve 38 made of an elastic material relaxes, and the wax case 35 is moved by the elastic force of the spring 29 so that the shaft 34 is inserted further deeply. It will move upward. As a result, the biasing force of the spring 29 extending and pressing the diaphragm 32 toward the gas chamber 33 is reduced. As described above, at low temperatures, the gas pressure in the gas chamber 33 decreases, but at the same time, the force of the spring 29 pressing the diaphragm 32 toward the gas chamber 33 also decreases.
[0017]
Therefore, when the temperature fluctuates, the amount of the wax 39 sealed is set such that the change in the upward pressing force due to the gas pressure in the gas chamber 33 is substantially equal to the change in the downward pressing force due to the spring 29. If the length of protrusion of the shaft 34 into the cylindrical portion 22 is adjusted in advance, even if the vapor pressure of the LPG changes due to temperature fluctuation, as long as the remaining fuel amount in the LPG cylinder is constant, The distance between the moving contact 26 and the fixed contact 27 does not change, thereby preventing malfunction. That is, at a low temperature, the moving contact comes into contact with the fixed contact at a lower LPG vapor pressure than at a high temperature, and the remaining fuel amount in the LPG cylinder can be accurately detected.
[0018]
FIG. 3 shows a configuration of a remaining fuel amount detection device according to another embodiment of the present invention. The main body 41 has a tubular portion 42 and a mounting tube 23 that project in opposite directions along the central axis of the main body 41. A cantilever 44 made of bimetal is provided in the main body 41 so as to cross the central axis of the main body 41. One end of the cantilever 44 is fixed to the main body 41 as a fixed end, and moves to the other end of the cantilever 44 which is a free end. A contact 26 is formed. The upper end of the spring 29 is fixed to the upper end of the tubular portion 42. Other members are the same as those of the fuel remaining amount detecting device shown in FIG. That is, in the fuel remaining amount detecting device according to this embodiment, in the fuel remaining amount detecting device shown in FIG. And a cantilever 44 made of bimetal is used in place of the cantilever 44.
[0019]
The cantilever 44 is made of a bimetal formed by bonding two pieces of metal having different coefficients of thermal expansion from each other. The free end curves downward so that the moving contact 26 approaches the fixed contact 27 at a high temperature, and at a low temperature. The free end curves upward so that the moving contact 26 is separated from the fixed contact 27. The cantilever 44 forms the temperature correcting means in this embodiment.
[0020]
Next, the operation of the remaining fuel amount detection device according to this embodiment will be described. When the fuel remaining amount detection device shown in FIG. 3 is attached to the fuel supply pipe connecting the LPG cylinder and the engine via the attachment pipe 23, the inside of the gas chamber 33 partitioned in the main body 41 by the diaphragm 32 is LPG from the LPG cylinder. Is charged with.
[0021]
When the fuel remaining in the LPG cylinder is sufficient, the vapor pressure of the LPG taken into the gas chamber 33 is high, and the gas pressure presses the diaphragm 32 upward against the elastic force of the spring 29, and the diaphragm 32 is pressed. The cantilever 44 is lifted upward via the button 30. As a result, as shown in FIG. 3, a gap is formed between the movable contact 26 formed at the free end of the cantilever 44 and the fixed contact 27, and the two terminals 25 and 28 are opened. On the other hand, when the remaining amount of fuel in the LPG cylinder decreases, the vapor pressure of the LPG in the gas chamber 33 decreases, and the diaphragm 32 gradually lowers due to the elastic force of the spring 29, and accordingly, the cantilever 44 also lowers. Thus, when the vapor pressure in the gas chamber 33 becomes lower than the set value, the movable contact 26 formed at the free end of the cantilever 44 comes into contact with the fixed contact 27, and the terminals 25 and 28 are short-circuited. .
[0022]
Here, in a high-temperature environment, the vapor pressure of LPG rises, so that the diaphragm 32 receives a larger gas pressure from the LPG in the gas chamber 33 even if the remaining amount of fuel in the LPG cylinder is constant. The center of the cantilever 44 is also displaced upward. However, at a high temperature, the free end of the bimetallic cantilever 44 curves downward due to the difference in the coefficient of thermal expansion between the two metal pieces. As described above, at a high temperature, the central portion of the cantilever 44 is displaced upward, but at the same time, the free end of the cantilever 44 is curved downward.
[0023]
Conversely, in a low-temperature environment, the vapor pressure of the LPG drops, so that the upwardly acting gas acting on the diaphragm 32 from the LPG in the gas chamber 33 even if the remaining amount of fuel in the LPG cylinder is constant. As the pressure decreases, the center of the cantilever 44 is displaced downward together with the diaphragm 32, as shown in FIG. However, at low temperatures, the free end of the bimetallic cantilever 44 curves upward. Thus, at low temperatures, the central portion of the cantilever 44 is displaced downward, but at the same time, the free end of the cantilever 44 curves upward.
[0024]
Therefore, when the temperature fluctuates, the material and size of the bimetal constituting the cantilever 44 may be determined so that the amount of displacement of the central portion of the cantilever 44 and the amount of bending of the free end of the cantilever 44 become substantially equal. Even if the vapor pressure of the LPG changes due to the temperature fluctuation, the distance between the moving contact 26 and the fixed contact 27 does not change as long as the remaining fuel in the LPG cylinder is constant, thereby preventing malfunction. That is, at a low temperature, the moving contact comes into contact with the fixed contact at a lower LPG vapor pressure than at a high temperature, and the remaining fuel amount in the LPG cylinder can be accurately detected.
[0025]
【The invention's effect】
As described above, according to the present invention, even if the vapor pressure of LPG changes due to temperature fluctuation, malfunction can be prevented, and the remaining fuel amount of the LPG cylinder can be detected with high accuracy. It becomes. Therefore, even in a severe environment such as a high temperature or a low temperature, the fuel remaining amount warning system operates accurately, and the reliability of the operation by the industrial vehicle equipped with the LPG cylinder is improved.
[Brief description of the drawings]
FIG. 1 is a sectional view showing an apparatus for detecting a remaining fuel amount of an LPG cylinder according to an embodiment of the present invention.
FIG. 2 is a cross-sectional view illustrating the fuel remaining amount detection device according to the embodiment at a high temperature.
FIG. 3 is a cross-sectional view illustrating a fuel remaining amount detection device according to another embodiment.
FIG. 4 is a cross-sectional view showing a fuel remaining amount detection device according to another embodiment at a low temperature.
FIG. 5 is a side view showing a forklift equipped with an LPG cylinder.
FIG. 6 is a diagram showing a configuration of a fuel remaining amount warning system.
FIG. 7 is a cross-sectional view showing a conventional fuel remaining amount detection device.
FIG. 8 is a sectional view showing a conventional fuel remaining amount detection device when the remaining fuel amount is small.
FIG. 9 is a characteristic diagram showing a relationship between temperature and vapor pressure of LPG.
[Explanation of symbols]
21, 41 Main body 22, 42 Tubular portion 23 Mounting tube 24, 44 Cantilever 25, 28 Terminal 26 Moving contact 27 Fixed contact 29 Spring 30 Diaphragm button 31 O-ring 32 Diaphragm 33 Gas chamber 34 Shaft 35 Wax case 36 Case body 37 Cover Body 38 Sleeve 39 Wax

Claims (3)

Body and
A diaphragm defining a gas chamber communicating with the LPG cylinder in the main body and displacing according to the vapor pressure of the LPG in the gas chamber;
A spring for urging the diaphragm in the direction of the gas chamber,
Fixed contacts,
A moving contact that is arranged to face the fixed contact and moves with the displacement of the diaphragm to contact the fixed contact when the vapor pressure of the LPG in the gas chamber decreases;
Temperature correction means for adjusting the biasing force of the spring or the interval between the fixed contact and the movable contact so that the movable contact comes into contact with the fixed contact at a low LPG vapor pressure at a low temperature than at a high temperature. An LPG cylinder fuel remaining amount detection device, characterized in that: The temperature correction means includes a wax case that holds one end of the spring and is provided to be able to advance and retreat in the length direction of the spring, and the wax case that is sealed in the wax case and changes in volume due to a temperature change. 2. The device according to claim 1, comprising a wax that moves forward and backward, and at a low temperature, the biasing force of the spring is lower than at a high temperature. The temperature correction means is a cantilever made of a bimetal having one end fixed to the main body, a center portion sandwiched between the diaphragm and the spring, and the other end formed with the moving contact, and the temperature correction means moves at a low temperature. The device of claim 1, wherein the contacts are curved away from the fixed contacts.

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