JP2001240200A - Liquid quantity detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably detect such a state that the liquid surface level in a tank becomes a predetermined level or less, by the pressure sensor attached to the pipeline system between the tank and a pump regardless of the operation state of the pump. SOLUTION: The pressure sensor 11 for changing over an output signal, corresponding to such a state that the pressure of the pipeline system 5 changing corresponding to the liquid surface level L in the tank T becomes set pressure or less, is connected on the way of the pipeline system 5, which connects the tank T storing a liquid and the suction port of the pump P, through a throttle.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid level detecting device for detecting, by a pressure sensor, that a liquid level in a tank such as a fuel tank falls below a predetermined level.

[0002]

2. Description of the Related Art Conventionally, in order to notify that the liquid level in a tank for storing kerosene used for a domestic boiler or the like has fallen below a predetermined level, a pressure sensor has been directly attached to a lower portion of the tank. is there.

[0003]

However, a control unit which stops the operation of the pump in response to a signal from the pressure sensor or activates a notification means for prompting the replenishment of liquid such as kerosene into the tank. In order to place the pressure sensor close to the control unit when the pressure sensor is away from the tank, or to avoid changing the structure of the tank due to the mounting of the pressure sensor, the inlet of the tank and the pump The pressure sensor may be installed in the middle of the pipeline system connecting the two. However, simply installing a pressure sensor in the middle of the pipeline system causes the pressure in the pipeline system to act directly on the pressure sensor. In response, the pressure sensor switches the output signal, and the detection of the liquid level may become unstable.

The present invention has been made in view of such circumstances, and detects that the liquid level in a tank has fallen below a predetermined level by attaching a pressure sensor to a pipe system between the tank and the pump. In doing so, an object of the present invention is to provide a liquid amount detection device capable of performing stable detection regardless of the operation state of a pump.

[0005]

According to one aspect of the present invention, there is provided a tank for storing a liquid,
In the middle of a pipe system connecting the suction port of the pump capable of discharging the liquid, an output is output in accordance with the pressure of the pipe system, which changes according to the liquid level in the tank, being equal to or lower than a set pressure. A pressure sensor for switching a signal is connected via a throttle.

According to the structure of the first aspect of the present invention, the pressure of the pipeline system changes according to the change in the liquid level in the tank, and the pressure of the pipeline system is set. Since the pressure sensor switches and outputs an output signal when the pressure becomes equal to or less than the pressure, even if the pressure sensor is not directly attached to the tank, it is detected that the liquid level in the tank has reached a predetermined level or less. be able to. In addition, since the pressure sensor is connected in the middle of the pipeline through the throttle, the pressure change in the pipeline due to the operation of the pump does not directly reach the pressure sensor, and the pressure change is reduced by the throttle. Therefore, the fact that the liquid level in the tank has fallen below the predetermined level can be stably detected regardless of the operating state of the pump.

[0007] The invention according to claim 2 provides the above-described claim 1.
In addition to the configuration of the invention described in the above, the pipe system includes a first pipe connected to the tank and a second pipe connected to the suction side of the pump.
A pipe, and a substantially T-shaped joint member that connects the first and second pipes and can connect the pressure sensor, the joint member having a large-diameter hole communicating with the first pipe, A small-diameter hole on the second conduit side coaxially connected to the large-diameter hole via an annular step facing the first conduit side is provided coaxially,
A connection passage communicating with the inside of the pressure sensor is provided so as to open an inner end on an inner surface of the large-diameter hole, and an annular throttle interposed between the first conduit and the connection passage is connected to an inner surface of the large-diameter hole. A cylindrical tubular body formed between the first and second conduits and fixedly connected to the joint member so that one end of the cylindrical body is fitted into the small-diameter hole is provided. For example, by forming a large-diameter hole in a conventional substantially T-shaped joint member and performing a slight process of fitting and fixing the cylindrical body to the small-diameter hole, a diaphragm is formed in the joint member. be able to. Moreover, since the annular throttle opens into the joint member on the first conduit side, that is, on the side opposite to the pump, the influence of the pressure change in the joint member at the time of starting the pump on the throttle is further reduced, and the time of starting the pump is reduced. Detection by the pressure sensor can be further stabilized.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described based on one embodiment of the present invention shown in the attached drawings.

1 to 6 show an embodiment of the present invention. FIG. 1 is a view showing a pipeline system between a tank and a boiler. FIG. 2 is an enlarged vertical sectional view of a joint member and a pressure sensor. 3 is a sectional view taken along line 3-3 in FIG. 2, FIG. 4 is a view taken in the direction of arrow 4 in FIG. 2, FIG. 5 is an explanatory view of the operation state of the snap action mechanism and the relationship between forces, and FIG. It is a graph for explaining the amount of displacement.

First, in FIG. 1, a tank T stores a liquid, for example, a liquid fuel such as kerosene.
A tank P is provided at a suction port of a pump P for supplying fuel from the tank T to a burner such as a burner 6 attached to the tank T.
Are connected via a pipeline system 5.

The pipe system 5 includes a first line connected to a lower portion of the tank T.
The first pipe 8 includes a pipe 8, a second pipe 9 connected to the suction side of the pump P, and a joint member 10 connecting the first and second pipes 8 and 9. Is provided with an on-off valve V, and a strainer S is provided in the second pipe 9.

Referring to FIGS. 2 to 4 together, a joint member 10 in the pipeline system 5 includes a main pipeline section 10a connecting the first and second pipelines 8 and 9, and a main pipeline section 10a of the main pipeline section 10a. It is formed in a substantially T-shape integrally with a branch pipe section 10b continuously provided so as to be orthogonal to the intermediate section, and the pipe system changes according to the liquid level L in the tank T. A pressure sensor 11 that switches an output signal in accordance with the pressure in 5 becoming equal to or less than a set pressure is connected to the branch pipe section 10b.

The casing 12 of the pressure sensor 11 comprises a diaphragm case 13, a casing main body 14, and an insulating plate 15 sandwiched between the casings 13, 14.
The diaphragm case 13, the casing main body 14, and the insulating plate 15 are fastened by a plurality of, for example, a pair of screw members 16, 16 inserted through the insulating plate 15.

The diaphragm case 13 is composed of first and second case halves 17 and 18 formed in a dish shape by a thin plate made of, for example, stainless steel. The periphery is their 1
The gasket 19, the peripheral portion of the diaphragm 20, and the peripheral portion of the diaphragm retainer 21, which are sequentially stacked from the first case half 17 side between the peripheral portions of the casings 7 and 18, are caulked and connected to each other.

The diaphragm 20 is formed, for example, by processing a thin disk of stainless steel into a concentric corrugated shape, and the diaphragm retainer 21 is formed, for example, of stainless steel into a dish-like shape with a greater wall thickness than the diaphragm 20. You.

At the center of the first case half 17, a connecting cylinder 17a is integrally formed.
The nut 22 rotatably mounted on the joint member 10
Is screwed into a male screw 23 engraved on the outer surface of the distal end of the branch pipeline 10b, and a gasket 24 is sandwiched between the connection cylinder 17a and the branch pipeline 10b.

First case half 17 and diaphragm 2
Between 0, the pressure chamber 2 facing one side of the diaphragm 20
The pressure chamber 25 communicates with the lower portion of the tank T via the joint member 10 and the first pipe 8 when the on-off valve V is opened. A pressure corresponding to the liquid level L (see FIG. 1) acts.

Immediately after the start of the pump P and the consumption of liquid fuel such as kerosene by the burner 6 starts, the pressure in the pipeline system 5 may drop suddenly for a moment. At this time, if the sudden decrease in the pressure directly acts on the pressure chamber 25, the pressure sensor 11 may malfunction. Therefore, the pressure sensor 11 is connected to the middle of the pipeline system 5 via the throttle 47.

In the main conduit portion 10a of the joint member 10,
A second hole coaxially connected to the large-diameter hole 48 through a large-diameter hole 48 communicating with the first conduit 8 and an annular step 50 facing the first conduit 8 side;
A small-diameter hole 49 on the pipe line 9 side is provided coaxially, and a connection passage 51 communicating with the pressure chamber 25 of the pressure sensor 11 is formed in the branch pipe section 10b of the joint member 10 inside the large-diameter hole 48. It is provided so as to open the end.

A cylindrical cylinder 52 having one end fitted into the small diameter hole 49 and communicating between the first and second pipelines 8 and 9 is fixed to the main pipeline 10a. 52 between the first pipe line 8 and the connection passage 51 between the outer surface of the large diameter hole 48 and the inner surface of the large-diameter hole 48.
7 is formed.

The pressure sensor 11 is provided by such a throttle 47.
Can be reduced, and a rapid pressure drop in the pressure chamber 25 at the time of starting the pump P can be sufficiently suppressed.

The casing main body 14 is formed of a synthetic resin, and an operating chamber 26 is formed between the casing main body 14 and the insulating plate 15 sandwiched between the casing main body 14 and the diaphragm case 13. The diaphragm holder 21 regulates the displacement end of the diaphragm 20 to the side where the volume of the pressure chamber 25 is increased, and the center of the diaphragm holder 21 is supported by one end of a guide cylinder 27. Is in contact with and supported by the center of the second case half 18 and the insulating plate 1.
5 penetrates into the working chamber 26 through the central portion.

An operating shaft 28 is provided at the center of the diaphragm 20.
The operating shaft 28 extends in a direction opposite to the pressure chamber 25 and is fitted to the guide cylinder 27 so as to be slidable in the axial direction. Thus, the operating shaft 2
The other end of 8 protrudes from the other end of the guide cylinder 27 to the working chamber 26 side.

A snap action mechanism is provided in the working chamber 26 for snapping when the amount of axial movement of the working shaft 28 accompanying the displacement of the diaphragm 20 exceeds the set amount of movement from any side in the axial direction. 30 are accommodated.

The snap action mechanism 30 includes a single tension spring 31 whose one end is fixed to the inner surface of the casing main body 14 of the casing 12, and a pair of compression springs whose one ends are supported by a receiving member 33 supported by the casing main body 14. Springs 32 and 32 are provided.

The tension spring 31 and the compression springs 32, 3
2 is formed by processing a single thin plate spring material such that the compression springs 32, 32 are arranged on both sides of the tension spring 31. The tension spring 31 and the two compression springs 3 are formed.
The other ends of 2, 32 are commonly connected.

The receiving member 33 has a flat mounting surface 17 formed on the inner surface of the casing main body 14 facing the working chamber 26.
a flat plate-like mounted portion 33a fixed to one end of the tension spring 31 with a rivet 34, and the mounted portion 33 so as to be disposed on both sides of the tension spring 31.
A pair of arms 33b, 33b extending from a, and support portions 33c, 33c, one end of which is provided substantially at right angles to the ends of both arms 33b, 33b and extends to the opposite side to insulating plate 15.
And a flat pressure receiving portion 33d integrally connecting the other ends of the support portions 33c and 33c, and is formed of a thin metal plate.

The support portions 33c of the receiving member 33 are
A tension spring 3 is provided between the supporting portions 33c and 33c.
One of the compression springs 32 is in contact with and supported by an intermediate portion between the support portions 33c, 33c.

One end of a contact rod 35 made of ceramics or the like is coaxially fitted to the other end of the operating shaft 28 having one end connected to the diaphragm 20, and the other end of the contact rod 35 is The tension spring 31 is in contact with an intermediate portion. That is, the operating shaft 28 is connected to the snap action mechanism 30 via the contact rod 35.

The snap action mechanism 30 is in a state as shown in FIG. 2 in a state where no pressure is applied to the pressure chamber 25, and in this state, the other end of the tension spring 31 and the compression springs 32, 32. Sliding contact surface 14b for contacting
Is formed on the inner surface of the casing main body 14, and the reed switch 36 is fixedly disposed on the sliding contact support surface 14b.

A tension spring 31 and both compression springs 3
A magnet 37 is fixed to the other end of each of the pressure chambers 25 and 32 so as to be close to the reed switch 36 in a natural state where no pressure is applied to the pressure chamber 25, and is opposed to the sliding contact support surface 14b. At the position where the
A stopper 38, which is a screw member, is attached so that the axial advance / retreat position can be adjusted. The stopper 38 comes into contact with the magnet 37 and regulates a moving end of the magnet 37 in a direction away from the reed switch 36.

Further, a pair of connection terminals 39, 39 connected to both ends of the reed switch 36 are attached to the casing main body 14 such that a part thereof protrudes from the surface 14c of the casing main body 14 on the side opposite to the diaphragm case 13. These connection terminals 39, 39 are connected to alarm means (not shown) or the like, and output signals that are switched according to a change in the switching mode of the reed switch 36 are output from the connection terminals 39, 39.

The relationship between the operating state of the snap action mechanism 30 and the force will be described with reference to FIG. 5. When the diaphragm 20 is in a natural state, that is, as shown in FIG. The tension spring 31 via the operating shaft 28 and the contact rod 35
When the force FP acting on the compression springs 32 is “0”, the tension springs 31 and the compression springs 32...
, And the other ends of the tension springs 31 and the compression springs 32.
It is pressed against the sliding contact support surface 14b by the force F0.

When the diaphragm 20 is displaced to the side where the volume of the pressure chamber 25 is increased in accordance with the increase in the pressure of the pressure chamber 25, the operating shaft 28 is moved in the axial direction and the tension spring 31 is moved.
Is displaced, the spring force F1 of the compression springs 32 and the spring force F2 of the tension spring 31 gradually increase, so that the axial movement amount of the operating shaft 28 reaches the set movement amount and the tension spring 3
As shown in FIG. 5 (b), when the displacement amount of 1 is a conceivable point, the spring force F1 of the compression springs 32 and the spring force F2 of the tension spring 31 are balanced, and the tension springs 31 and the compression springs 32. The force F0 exerted by the other end of is “0”. At this time, during the transition from the state of FIG. 5A to the state of FIG. 5B, the other ends of the tension springs 31 and the compression springs 32 move while sliding on the sliding contact support surface 14b. 3
The spring force F1 of 2 ... becomes stronger.

When the pressure in the pressure chamber 25 further increases and the operating shaft 28 moves in the axial direction beyond the set amount of operation, and the tension spring 31 is displaced past the thought point, FIG.
As shown in (c), the tension spring 31 and the compression spring 32
.. Operate sharply in a direction away from the sliding contact support surface 14b, and the magnet 37 is quickly separated from the reed switch 36 and pressed against the stopper 38 by the force F0.

When the force FP from the operating shaft 28 gradually decreases, the snap action mechanism 30 moves from the state of FIG. 5C to the state of FIG. It returns to the state of a).

The set operation amount of the operation shaft 28 for causing the snap action mechanism 30 to perform the snap operation and the idea of the tension spring 31 can be adjusted by operating the adjustment means 40 from outside the casing 12.

The adjusting means 40 includes a screw shaft 41 screwed to the casing main body 14 such that an inner end thereof abuts against a pressure receiving portion 33d of the receiving member 33 so as to be able to change an axial advance / retreat position. A knob 42 fixed to the projecting end of the screw shaft 41 from the main body 14.

The knob 42 is formed by integrally molding a metal cylinder 43 for fitting the outer end of the screw shaft 41 to a synthetic resin covering portion 44 covering the cylinder 43. A screw member 45 inserted from the outside into the covering portion 44 is screwed into the cylindrical body 43, and the tip of the screw member 45 is screwed into the screw shaft 41.
The knob 42 is fixed to the outer end of the screw shaft 41 by being strongly pressed against the outer surface of the screw shaft 41.

A projection 42a is provided at one position in the circumferential direction of the knob 42, and a projection 42a is provided on the outer surface of the knob 42. The surface 42c of the casing main body 14 on the side opposite to the diaphragm case 13 has the projection 42a. A sheet-like graduation plate 46 provided with graduations (not shown) for allowing the axial position of the screw shaft 41 to be recognized by contrasting the portions 42a is attached.

Incidentally, the spring constant of the diaphragm 20 is set stronger than that of a conventional one in which a movable contact is attached to a snap action mechanism. This allows
As shown in FIG. 6, the displacement of the diaphragm 20 due to the pressure change in the pressure chamber 25 is relatively large in the prior art, whereas in the present embodiment, the displacement in the pressure chamber 25 according to the pressure change is relatively large. The displacement of the diaphragm 20 is relatively small.

The reason why the spring constant of the diaphragm 20 can be set relatively strong is that the snap action mechanism 3
This is because the magnet 37 is moved toward and away from the reed switch 36 by the snap operation of 0, and the spring constant of the diaphragm 20 is set relatively high in the conventional device in which the movable contact is attached to the snap action mechanism. In this case, since the fluctuation of the displacement amount of the diaphragm 20 affects the contact pressure of the movable contact and the fixed contact,
The contact pressure changes due to fluctuations in the liquid level caused by the tank sway, etc., and the detection of the liquid level becomes unstable.

Next, the operation of this embodiment will be described.
A reed switch 36 is fixed inside the reed switch 36, and the reed switch 36 is
A magnet 37 for switching the approach / separation to / from is attached to the snap action mechanism 30. Therefore, when the pressure in the pressure chamber 25 changes according to the change in the liquid level L in the tank T, the diaphragm 20 is displaced and the operating shaft 28
Is moved in the axial direction, and the snap action mechanism 30 snaps in response to the axial movement amount of the operating shaft 28 being greater than or equal to the set movement amount from any side in the axial direction. When the liquid level L in the tank T reaches the predetermined level, the switching mode of the reed switch 36 is changed to detect that the liquid level L has reached the predetermined level. can do.

Furthermore, the reed switch 36 performs a switching operation by a change in the magnetic field due to the approach / separation of the magnet 37. Even if the position of the magnet 37 slightly changes, the switching mode does not change. Stable detection is possible even if the liquid level L fluctuates due to shaking or the like, and accurate detection can be performed without causing dust that has entered the casing 12 or poor conduction due to condensation formed inside the casing 12. It is.

Since the set movement amount of the operating shaft 28 can be adjusted by operating the adjusting means 40 from outside the casing 12, the liquid level at which the snap action mechanism 30 performs the snap operation, that is, the setting to be detected. The level can be changed and the same pressure sensor 1
It is possible to deal with various tanks T having different liquid levels to be detected in step 1.

Furthermore, the use of the reed switch 36 and the magnet 37 makes it possible to set the spring constant of the diaphragm 20 to a relatively high value, and in combination with the provision of the adjusting means 40, the range of the liquid level to be detected. Can be greatly expanded as compared with the conventional one. For example, the range of the liquid level that can be detected by the conventional device using the movable contact and the fixed contact is, for example, 80 to 240.
While the range in which the pressure of mmAq acts on the pressure chamber 25 is relatively narrow, by setting the elasticity of the diaphragm 20 to be relatively strong, for example, 80 to 3000 m
It is possible to make the range in which the pressure of mAq acts on the pressure chamber 25 relatively wide. Since the range of the liquid level to be detected can be expanded in this way, the types of tanks T to which the pressure sensor 11 can be applied can be expanded.

Further, since the pressure sensor 11 is connected in the middle of the pipe system 5 connecting the tank T and the suction port of the pump P, the liquid in the tank T is not required even if the pressure sensor 11 is not directly mounted on the tank T. It can be detected that the surface level L has become equal to or lower than a predetermined level. Moreover, since the pressure sensor 11 is connected in the middle of the pipeline system 5 through the throttle 47, the pressure change in the pipeline system 5 due to the operation of the pump P does not directly reach the pressure sensor 11, and Stop change 4
Since the pressure is reduced by the pressure sensor 11 and applied to the pressure sensor 11, it is possible to stably detect that the liquid level L in the tank T has fallen below the predetermined level regardless of the operating state of the pump P.

A large diameter hole 48 communicating with the first pipeline 8 is provided in the joint member 10 which forms the pipeline system 5 together with the first pipeline 8 on the tank T side and the second pipeline 9 on the pump P side. First
A small-diameter hole 49 on the second conduit 9 side coaxially connected to the large-diameter hole 48 is provided coaxially with the large-diameter hole 48 through an annular step 50 facing the conduit 8 side, and a connection passage 51 communicating with the pressure sensor 11.
Is provided on the inner surface of the large-diameter hole 48 so as to open the inner end, and an annular throttle 47 interposed between the first conduit 8 and the connection passage 51 is provided between the inner surface of the large-diameter hole 48. A cylindrical tubular body 52 formed and communicating between the first and second conduits 8 and 9 is fixed to the joint member 10 such that one end of the cylindrical tubular body 52 fits into the small-diameter hole 49. Therefore, the large-diameter hole 48 is formed in the generally T-shaped joint member 10 which has been conventionally commercially available, and the small-diameter hole 47 is fitted and fixed to the small-diameter hole 49. 1
0 can be formed.

Further, since the annular throttle 47 opens into the joint member 10 on the first conduit 8 side, that is, on the side opposite to the pump P, a change in pressure in the joint member 10 when the pump P starts is applied to the throttle 47. Therefore, the influence of the pressure sensor 11 when the pump P is started can be further stabilized.

Although the embodiments of the present invention have been described in detail, the present invention is not limited to the above embodiments, and various design changes can be made without departing from the present invention described in the appended claims. It is possible to do.

In the above embodiment, the case where the present invention is applied to the tank T for storing liquid fuel such as kerosene has been described. However, the present invention is widely applied to a tank for storing liquid other than liquid fuel. It is possible.

[0052]

As described above, according to the first aspect of the present invention, it is possible to detect that the liquid level in the tank has fallen below a predetermined level even if the pressure sensor is not directly attached to the tank. Thus, it is possible to stably detect that the liquid level in the tank has become equal to or lower than the predetermined level regardless of the operation state of the pump.

According to the second aspect of the present invention, the throttle can be formed in the joint member by only slightly processing the joint member, and the detection by the pressure sensor at the start of the pump is further stabilized. be able to.

[Brief description of the drawings]

FIG. 1 is a diagram showing a pipeline system between a tank and a boiler.

FIG. 2 is an enlarged vertical sectional view of a joint member and a pressure sensor.

FIG. 3 is a sectional view taken along line 3-3 of FIG. 2;

FIG. 4 is a view taken in the direction of arrow 4 in FIG. 2;

FIG. 5 is an explanatory diagram of a relationship between an operation state and a force of a snap action mechanism.

FIG. 6 is a graph for explaining a displacement amount of a diaphragm according to a pressure.

[Explanation of symbols]

 Reference numeral 5: Pipe system 8: First pipe 9: Second pipe 10: Joint member 11: Pressure sensor 47: Restrictor 48: Large diameter hole 49・ Small diameter hole 50 ・ ・ ・ Step 51 51 ・ ・ ・ Connection passage 52 ・ ・ ・ Cylinder L ・ ・ ・ Liquid level P ・ ・ ・ Pump T ・ ・ ・ Tank

Claims (2)

[Claims] A liquid in the tank (T) is provided in a pipe system (5) connecting a tank (T) for storing the liquid and a suction port of a pump (P) capable of discharging the liquid. A pressure sensor (11) that switches an output signal according to a pressure of the pipeline system (5) that changes according to the surface level (L) becomes equal to or less than a set pressure is connected via a throttle (47). A liquid amount detection device characterized by the above-mentioned. 2. The pipe system (5) includes a tank (T).
, A second pipe (9) connected to the suction side of the pump (P), and first and second pipes (8, 8).
9) a substantially T-shaped joint member (10) which can connect the pressure sensor (11) and connect the pressure sensor (11), and the joint member (10) has a large diameter communicating with the first conduit (8). Hole (48) and an annular step (5) facing the first conduit (8) side.
0), a small-diameter hole (49) on the second conduit (9) side coaxially connected to the large-diameter hole (48) is provided coaxially, and a connection passage (5) communicating with the pressure sensor (11).
1) is provided on the inner surface of the large-diameter hole (48) so as to open the inner end, and an annular throttle (47) interposed between the first conduit (8) and the connection passage (51) is enlarged. Diameter hole (4
A cylindrical body (52) formed between the inner surface of (8) and communicating between the first and second conduits (8, 9) has one end fitted into the small-diameter hole (49). 2. The liquid amount detecting device according to claim 1, wherein the liquid amount detecting device is fixed to the joint member.