JPH043232Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to a liquid level detection device that detects a liquid level using induced electromotive force.

[Prior Art] FIG. 3 shows a longitudinal section of a conventional induced liquid level sensor 12, which includes a first coil 122 wound around a synthetic resin core 120, and a first coil 122 wound around a synthetic resin core 120.
It consists of a second coil 124 wound around the outer circumference of a plastic case 123 that houses the float, a float 125 that moves up and down depending on the liquid level, and a shot ring 126 that is a coil and is installed approximately in the center of the float 125. ing.

The first coil 122 consists of an upper coil 1221 wound on the upper part of the core 120 and a lower coil 1222 wound on the lower part.
1a, the coil 122 is connected in series adjacent to the coil 122, and the frequency becomes sparse from the top toward the middle point along the direction of change in the liquid level.
1a and an upper unevenly wound coil 1221b that generates magnetic flux in the same direction. The lower coil 1222 has a winding density that increases from sparse to dense from the middle point downward along the direction of change in the liquid level;
and a lower non-uniformly wound coil 1222b which generates magnetic flux in the opposite direction to the coil 1221b, and a lower non-uniformly wound coil 1222b which is connected in series adjacent to the coil 1222b and which generates magnetic flux in the opposite direction to the coil 1221b.
b and a lower multiple-turn coil 1222a with multiple turns that generates magnetic flux in the same direction.

The upper coil 1221 is connected to the lower coil 1222.
It is connected in series to the AC signal source 11 (see FIG. 4), which will be described later. The second coil 124 is wound around the outer periphery of a plastic case 125 that houses the first coil 122 with substantially uniform density along the direction of change in the liquid level, and is magnetically coupled to the first coil 122. There is. In addition,
Upper and lower uneven winding coils 1221b, 12
22b and the second coil 124 are wound over the entire liquid level detection range, and the upper and lower unevenly wound coils 1221a and 1222a are wound around the upper and lower unevenly wound coils 1221b outside the liquid level detection range. , 1222b.

The shot ring 126 is connected to the float 12.
5 through the first and second coils 122,1
The first and second coils 122, 124 are arranged coaxially with respect to the coil axis of 24.
It is magnetically coupled to the tank, and in that state it moves up and down depending on the liquid level.

FIG. 5 shows a circuit configuration diagram of the liquid level detection device. In the figure, 11 is an AC signal source that sends an AC signal to the first coil 122 of the inductive liquid level sensor 12, and 13 is the AC signal source. This is a detection control signal generation circuit that outputs a pulsed detection control signal for a half cycle period. 14 is a detection circuit, which includes an amplifier 141 that amplifies the alternating current voltage induced in the second coil 124 of the induction sensor 12, and a switch that is closed during the period when the detection control signal generation circuit 13 outputs the detection control signal. an analog switch 142 that outputs the signal output from the amplifier 141;
It is composed of. 15 is a smoothing circuit that smoothes the signal output from the analog switch 142;
16 is a voltage detection circuit that detects the voltage of the signal smoothed by the smoothing circuit 15; 17 is a detection circuit 16;
This is a display circuit that displays the liquid level according to the detected voltage.

The frequency of the AC signal output from the AC signal power source 11 is set to a low enough level that circuit elements such as operational amplifiers constituting the amplifier circuit 141 etc. can exhibit the desired characteristics, and that resonance phenomena due to stray capacitance do not occur. Any value can be set; for example, in this embodiment, it is set to 10KHz.

Now, when an AC signal flows to the first coil 122 by the AC signal power source 11, the second coil 12
The AC voltage induced from 4 is output. on the other hand,
A detection control signal is output from the detection control signal generation circuit 13, and this closes the analog switch 142 of the detection circuit 14 for a half cycle of the AC signal, so that the AC voltage output from the second coil 124 is transmitted to the detection circuit. 14, only a half-cycle voltage is output from the detection circuit 14. The detected half-cycle voltage is smoothed into a DC voltage by the smoothing circuit 15, and this DC voltage is detected by the voltage detection circuit 16.

By the way, the DC voltage and shot ring 12
6, that is, the relationship with the liquid level is approximately linear as shown in FIG. Therefore, based on this relationship, the display circuit 17 displays the liquid level based on the voltage detected by the voltage detection circuit 16.

However, in such a conventional liquid level detection device, as shown in FIG. 5, as a measure to bring the S-shaped detection characteristic closer to a linear shape, upper and lower multi-turn coils 1221a and 1222a are used. Upper and lower uneven winding coils 1221b, 122
2b, as well as the number of turns and the 2
This is accommodated by increasing the number of turns at the upper and lower ends of the coil 124, that is, the detection coil. For this reason, the diameter of the bobbin after winding becomes thicker at both ends, and the upper and lower multi-turn coils become larger, reducing the degree of freedom in designing the float. However, there were some problems that made it impossible to create a new design.

[Purpose of the invention] The present invention has been developed by focusing on these conventional problems, and it increases the number of turns at both the upper and lower ends of the excitation coil compared to the center, and increases the number of turns at the detection side coil. The object of the present invention is to provide a liquid level detector that can improve the linearity of the above characteristics without increasing the size by reducing the number of turns of both coils and making the total number of turns approximately constant. be.

[Embodiments of the invention] The invention will be described in detail below based on the embodiments shown in FIGS. 1 and 2.

FIG. 1 shows the sensor structure of the liquid level detector according to this embodiment, and this sensor is similar to the sensor in the liquid level detecting device shown in the conventional example.
Plastic case 123 formed into a cylindrical shape
The case 123 has a core 120 made of synthetic resin located at the center of the interior of the case 123.
An upper coil 1221 is formed on the outer circumferential surface of the case so that the winding density gradually becomes sparse from dense to sparse from the upper longitudinal direction of the case toward the midpoint, and an upper coil 1221 is formed so that the winding density gradually becomes sparse from the midpoint to the lower end of the case. The first coil consists of a lower coil 1222 formed from sparse to dense.
A coil 122 (detection coil) is wound around the first coil 122, and a multi-turn detection coil 12 is formed by a multi-turn coil following the upper and lower ends of the first coil 122.
21a and 1222a are located. Further, a second coil 124 (excitation coil) is wound around the outer peripheral surface of the core 120 located in the case 123, and in this embodiment, the second coil 124 (excitation coil)
The middle part of the coil is uniformly wound, but the multiple winding detection coils 1221a and 12 at both ends thereof are uniformly wound.
Supplementary coils 12 are installed at both upper and lower ends near 22a.
4a and 124b are wound continuously with the second coil 124. In addition, in order to prevent the external size of the liquid level sensor from increasing, the detection coils 1221a and 1222 are wound as many times as the number of turns wound around the supplementary coils 124a and 124b.
The number of turns of a was reduced, and the total number of turns of the supplementary coil and the multi-turn coil was set to be approximately constant.

In this way, in this embodiment, the multi-turn coils 1221a and 1222a and the supplementary coil 1
The ratio of the number of turns with 24a and 124b is A, B, C.
As a result of changing it in three ways, as shown in FIG. 2, the characteristics of the output voltage corresponding to the height of the shot ring were as shown in the figure.

That is, as shown by line C, when the number of turns of the multi-turn coil is 185 and the number of turns of the supplementary coil is 370, the output peak value of the characteristic line is located outside the usage range, and its linearity is This is the best, and the effect of widening the usage range L can be obtained. Furthermore, according to the C curve shown in Fig. 2, since the slope (rise) at both ends of the sensor becomes steep, the amount of change in the output voltage with respect to the displacement of the shot ring height also becomes large, and as a result, when there is a small amount of fuel, This also has the effect of improving resolution. In addition, according to this embodiment, the sum of the multi-turn coil and the supplementary coil can be kept almost constant, so the outer diameter of the sensor as a whole does not have to be increased, and therefore the sensor can be made smaller and more flexible in float design. There are some effects that can be improved.

[Summary of the invention] As described above, the invention provides an upper coil 1221 that is formed so that the winding density gradually becomes sparse from the top toward the middle point along the direction of change in the liquid level.
and a lower coil 1222 formed in such a way that the winding density gradually becomes denser from sparse downwards from the intermediate point and generates a magnetic flux in the opposite direction to that of the upper coil 1221, in series or in parallel. Become the first
a second coil 122, which is magnetically coupled to the first coil 122 and formed so that the winding density at both the upper and lower ends is denser than that at the center along the direction of change in the liquid level. A coil 124, a resin core 120 around which the first and second coils 122, 124 are wound, and the first or second coil 12.
A shot ring 1 is disposed coaxially with the coil shaft of 2,124 and moves up and down according to the liquid level.
Inductive liquid level sensor 12 consisting of 26, 126'
The first or second coil 122, 12
4 by connecting the AC signal source 11 to either one of the first or second coils 122, 124.
A liquid level detection device characterized in that an induced electromotive force is obtained from the other one of the two, and the effective value of a waveform obtained by detecting the induced electromotive force every half cycle of the AC signal source 11 is used as a detection output. It is.

[Effect of the invention] Therefore, according to the liquid level detector of this invention, at both ends of the second coil 124 of the sensor,
It is formed so that its winding density is dense, and as a result, the output voltage characteristic corresponding to the height of the shot ring becomes a linear characteristic. Since the change in output voltage with respect to the displacement of the shot ring height is also large, effects such as improved resolution when a small amount of fuel is available can be obtained.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram showing an embodiment of the liquid level sensor according to the present invention, Fig. 2 is a characteristic diagram showing the relationship between shot ring height and output voltage of the sensor, and Fig. 3 shows a conventional sensor. Explanatory diagram, 4th
The figure is its operating circuit diagram, and FIG. 5 is its characteristic diagram. 1221a, 1222a...Multi-turn coil, 1
24a, 124b...Supplementary coils.

Claims (1)

[Scope of utility model registration request] The upper coil 1221 is formed so that the winding density gradually becomes sparse from above toward the middle point along the direction of change in the liquid level, and the winding density gradually becomes sparse from the middle point downward. A first coil 122 is formed in series or in parallel with a lower coil 1222 which is densely packed and is formed to generate magnetic flux in the opposite direction to that of the upper coil 1221. a second coil 124 that is coupled and formed so that the winding density at both upper and lower ends is denser than that at the center along the direction of change in liquid level; and the first and second coils 122. ，
124 wound around the resin core 120, and shot rings 126, 126' which are disposed coaxially with the coil axis of the first or second coil 122, 124 and move up and down according to the liquid level. By connecting the AC signal source 11 to either the first or second coil 122, 124, the first or second coil
An induced electromotive force is obtained from the other of the coils 122 and 124, and the induced electromotive force is applied to the AC signal source 11.
A liquid level detection device characterized in that the detection output is an effective value of a waveform obtained by detecting the waveform every half cycle.