JP4300165B2 - Position detector and liquid level sensor using the same - Google Patents

Description

  The present invention relates to a position detector and a liquid level sensor using the position detector, for example, based on a position detector that detects the position and moving direction or passage of a magnet by closing a contact point of a reed switch when the magnet approaches. The present invention relates to a liquid level sensor that detects a level of a liquid level.

  The liquid level sensor is composed of a float with a magnet built in the liquid level, and a reed switch that is vertically spaced apart by a predetermined interval, and floats whenever the liquid level rises or falls. Moves up and down, and the reed switch is closed by the magnetic force of the magnet to detect the position of the liquid level or the rise and fall of the liquid level.

  FIG. 6 is a diagram for explaining the operation of a conventional reed switch, which is described in Japanese Patent Publication No. 50-11072 (Patent Document 1). The reed switch L is configured by incorporating contact points 21 and 22 facing each other in a glass tube, and a bias magnet 1 is disposed in the vicinity of the reed switch L facing the reed switch L.

  The bias magnet 1 cannot turn on the contacts 21 and 22 of the reed switch L with a single magnetic force so that a reverse magnetic field is applied to the reed switch L when the magnetic force and float of the magnet 3 in the float rise and fall. Since the magnet 3 is disposed, the contacts 21 and 22 of the reed switch L are turned on and off.

  That is, in the state shown in FIG. 6A, the N pole of the bias magnet 1 is disposed in the vicinity of the contact 21, and the S pole is disposed in the vicinity of the contact 22. An intermediate magnetic flux is applied to the contact 21 from the N pole of the bias magnet 1, and an intermediate magnetic flux is applied to the contact 22 from the S pole. The north pole of the magnet 3 in the float approaches from the left side of FIG. 6A, but at this time, the contacts 21 and 22 are open.

  When the magnet 3 moves further to the right side, as shown in FIG. 6B, the N pole of the magnet 3 and the N pole of the bias magnet 1 approach each other, so that the magnetic path of the bias magnet 1 passing through the contacts 21 and 22 Magnetic flux from the N pole to the S pole of the magnet 3 is applied, and the contacts 21 and 22 are attracted and turned on. Further, even if the magnet 3 moves further to the right side, the contacts 21 and 22 are kept on and self-held by the magnetic flux from the bias magnet 1.

  When the magnet 3 moves to the left and moves from the position shown in FIG. 6B to the position shown in FIG. 6A, the N pole of the magnet 3 and the S pole of the bias magnet 1 approach each other. , 22 disappears, and at the same time, the two magnetic poles are strongly attracted to each other, so that the magnetic flux passing through the contacts 21, 22 is remarkably reduced, and the contacts 21, 22 are turned off.

In this way, the contacts 3 and 22 can be turned on and off by moving the magnet 3, and the state can be maintained by moving the magnet 3 away. If a plurality of combinations of the reed switch L and the bias magnet 1 shown in FIG. 6 are arranged in a vertical direction at a predetermined interval in a tank (not shown), the reed switch L is turned on when the liquid level rises and falls. A liquid level sensor that detects the liquid level or the rise or fall of the liquid level by detecting OFF can be configured.
Japanese Patent Publication No. 50-11072

  In order to detect the liquid level with the reed switch L shown in FIG. 6, the magnetic force and installation position of the bias magnet 1, the magnetic characteristics of the reed switch L, the magnetic force of the magnet 3 in the float and the reverse magnetic field due to the rise and fall It is necessary to configure such that a number of factors maintain appropriate conditions, such as arranging the magnet 3 so as to give to the reed switch L. For this reason, if the condition of any factor is not satisfied, the liquid level cannot be accurately detected as the liquid level sensor.

  In addition, when the reed switch L is self-holding, since the contacts 21 and 22 are only turned on only by the magnetic flux from the bias magnet 1, the instability of being turned off from being turned on due to external vibration or the like and malfunctioning. Will have both.

  Accordingly, the present invention provides a position detector that can detect the position and moving direction of a magnet or whether or not a magnet has passed by detecting on / off of a switch without being affected by external vibration and the like, and a liquid level sensor using the position detector Is to provide.

  The present invention is a position detector for detecting the position and moving direction of a moving object having a magnet or the presence or absence of movement, and at least two contact points arranged at predetermined intervals in the moving direction of the magnet. And at least one switch unit including two switches, and determination means for determining the position and moving direction of the moving object or the presence or absence of movement according to the opening / closing state of each contact in the switch unit according to the movement of the magnet.

  In this invention, it is possible to determine the moving direction of the magnet or the presence or absence of movement by detecting which of the contacts included in at least one switch unit is closed first. The possibility of malfunction due to vibrations can be eliminated.

  Preferably, the switch unit is housed in a holder and unitized. It becomes easy to install the switch unit at an arbitrary position by unitizing.

  Another aspect of the present invention is a liquid level sensor for detecting the level of a liquid level and the rise and fall of the float, which has a built-in magnet, and floats up and down in response to the rise and fall of the liquid level. A plurality of switch units including at least two switches in which the respective contacts are arranged at predetermined intervals along the descending path, and the respective contact points of the plurality of switch units according to the rise and fall of the float. Judgment means for judging the level of the liquid level and the rise and fall according to the open / close state.

  According to the present invention, the liquid level can be detected without using a conventional self-holding type reed switch, and the possibility of malfunction due to external vibration or the like can be eliminated.

  FIG. 1 is a layout diagram of a reed switch constituting a position detector according to an embodiment of the present invention, and FIG. 2 is a block diagram showing an overall structure of the position detector according to an embodiment of the present invention.

  In the following description, a case where the position detector of the present invention is used as a level sensor will be described. In FIG. 1, at the detection positions (1) to (5), reed switches L11 and L12, L21 and L22, L31 and L32, L41 and L42, and L51 and L52 that make a pair are on the liquid level. They are arranged at a predetermined constant interval D in the vertical direction, which is the moving direction. The reed switches L11 and L12, L21 and L22, L31 and L32, L41 and L42, and L51 and L52, which are paired with each other, are arranged with their positions slightly shifted in the vertical direction, which is the moving direction.

  One contact of each of the reed switches L11, L12 to L51, L52 is grounded, and the other contact is connected to the input port of the CPU 10 shown in FIG. 2 and simultaneously through the resistors R11, R12 to R51, R52. A power supply voltage is supplied. These reed switches L11 and L12, L21 and L22, L31 and L32, L41 and L42, and L51 and L52 are housed in, for example, a holder (not shown) and unitized into units U1 to U5. Thus, it becomes easy to install each reed switch in an arbitrary position by unitizing.

  The units U1 to U5 are each composed of a pair of reed switches, but each unit U1 to U5 may incorporate more reed switches. For example, if two pairs of reed switches connected in parallel are arranged with their positions slightly shifted in the vertical direction, even if one reed switch becomes defective, it can be duplicated by the other reed switch. Further, three reed switches may be incorporated.

  A magnet 3 is arranged in the float 4. The float 4 rises and falls according to the rise and fall of the liquid level, and the contacts are arranged in the order of the reed switches L 11, L 12 to L 51, L 52 by the magnetic flux from the magnet 3. Turn on / off. For example, if the liquid level is equal to or lower than the detection position (1), the reed switches L11, L12 to L51, L52 are all off. When the liquid level rises and the magnet 3 approaches the detection position (1), the reed switch L11 is turned on. When the liquid level further rises, the reed switch L12 is turned on while the reed switch L11 is kept on.

  When the liquid level further rises, the magnet 3 moves away from the reed switch L11, so that the reed switch L11 is turned off, and then the reed switch L12 is turned off. Hereinafter, as the liquid level rises, the reed switches L21 to L52 are turned on and turned off when the magnet 3 is separated. Accordingly, in this embodiment, the reed switches L11, L12 to L51, L52 are not provided with a self-holding function.

  The CPU 10 shown in FIG. 2 detects the on / off of each of the reed switches L11, L12 to L51, L52 based on a change in potential, and determines the moving direction or passage of the magnet 3 and is applied to a liquid level sensor. In this case, the rise or fall of the liquid level is judged.

  The CPU 10 determines that the contacts of the reed switches L11, L12 to L51, and L52 are turned on when the contacts of the reed switches L11, L12 to L51, and L52 are closed by the magnetic flux from the magnet 3, and determines that the contacts are off if the power supply potential. Further, the CPU 10 has a memory 11 for storing a program based on flowcharts shown in FIGS. 3 and 4 described later. The output port of the CPU 10 is connected to the output circuit 12. The output circuit 12 includes, for example, an alarm circuit that issues an alarm when the liquid level reaches a predetermined position, or a circuit that notifies an error when the CPU 10 determines an error.

  3 and 4 are flowcharts for explaining the operation of the position detector in one embodiment of the present invention. 3 shows the confirmation operation of each contact when the magnet is between the lowest point and the highest point, and FIG. 4 shows the confirmation operation of the contact at each position (1) to (5) shown in FIG. .

  In the description of FIG. 3 and FIG. 4, a pair of reed switches from the lowest point to the highest point of each detection position (1) to (5) is referred to as a contact 1 to 5, and each detection position ( The lower reed switches L11, L21, L31, L41, and L51 in 1) to (5) are referred to as SW1, and the upper reed switches L12, L22, L32, L42, and L52 are referred to as SW2.

  The CPU 10 confirms the contacts 1 to 5 at the detection positions (1) to (5) in steps (abbreviated as SP in the drawing) SP1 to SP5 shown in FIG. In step SP1, it is determined whether or not the reed switches L11 and L12, which are the contacts 1 at the detection position (1), are turned off or on by the processing of FIG. 4, and the respective results are held. That is, in step SP11 shown in FIG. 4, it is determined whether or not SW2 is off. If SW2 is off, it is determined in step SP12 whether or not the corresponding SW1 is off. For example, if the reed switch L12 is off, it is determined whether or not the corresponding reed switch L11 is off. If any of the reed switches L11 and L12 is off, there is no input and it is determined that the state is A. And each discrimination | determination result is hold | maintained.

  If the reed switch L11 that is SW1 is turned on in step SP12, it is determined that the state is an input B, and the result is held. If the reed switch L12 that is SW2 is turned on in step SP11, it is determined whether or not the reed switch L11 that is SW1 is turned on in step SP13. If SW1 is on, it is determined and held as an input state C, and if SW1 is off, it is determined and held as an input state D.

  In steps SP2 to SP5, the CPU 10 discriminates and holds the state A to D for each of the reed switches L21, L22 to L51, and L52 that are the contacts 2 to 5 in the same manner as described above. . In step SP6, processing is performed based on the states A to D that are the determination results of the reed switches L11, L12 to L51, and L52.

  Based on the determination results of the states A to D of the contacts 1 to 5, if the state changes in the order of A → B → C → D → A at each position (1) to (5), the liquid level Is rising, and it is determined that the magnet 3 is passing upward. Further, if the state changes as A → D → C → B → A, it is determined that the liquid level is lowered and the magnet 3 is passing down. If the state changes as A → B → C → B → A, it is determined that the liquid level has changed from rising to lowering and has not passed through the switch unit located above the magnet 3, and the state has changed to A → If it has changed as D-> C-> D-> A, it is determined that the liquid level has changed from falling to rising and has not passed through the switch unit located below the magnet 3.

Based on the determination result, the CPU 10 performs processing as follows.
(A) If ON of SW1 or SW2 of a plurality of switch units is detected, an error is determined.
(B) In all switch units, if SW1 and SW2 are not detected to be on, the position of the switch unit that has been determined to pass immediately before is set as the liquid level.
(C) If the switch unit SW1, SW2 or both of the switch units are turned on, the switch unit position is set to the liquid level.
(D) When it is detected that SW2 at the adjacent switch unit position (1) and SW1 at position (2) are turned on, the position (2) is set to the liquid level if it rises by judgment, and the position if it falls by judgment. Let (1) be the liquid level.

  After performing the above processing in step SP6, the CPU 10 outputs a signal to the output circuit 12 in step SP7. That is, if the processing content is (A), the CPU 10 holds the liquid level at the position detected immediately before, and if the processing content is (A), the CPU 10 outputs an error signal from the output circuit 12, and the processing content is If (c) and (d), the liquid level is updated to the newly detected position.

  According to this embodiment, the distance between a pair of contact points is set to a constant distance D, and if the time for which each contact point is closed is counted by the CPU 10, the rising and falling speeds of the liquid level are measured. It becomes possible to do.

  Further, when there is an abnormality in the reed switch, it is possible to determine which reed switch is abnormal when the liquid level reaches the position of the abnormal reed switch. Conventionally, as shown in FIG. 5A, when the self-holding type reed switches L1 to L5 provided with the bias magnet shown in FIG. 6 are arranged in the vertical direction, for example, the reed switch L2 is turned on. Thus, when the reed switch L3 is not turned on and the reed switch L4 is turned on, it is understood that the reed switch L3 is abnormal.

  On the other hand, in this embodiment, as shown in FIG. 5B, when the reed switches L21 and L22 indicate that they are raised, the reed switch L31 is not turned on and the reed switch L32 is not turned on. When turned on, it can be seen that the reed switch L31 is abnormal. That is, in the prior art, if the liquid level did not rise to the position of the reed switch L4, the abnormality of the reed switch L3 could not be determined. In this embodiment, however, the liquid level reached the position of the reed switch L32. An abnormality of the reed switch L31 can be determined.

  In the above description, the example in which the present invention is applied to the liquid level sensor has been described. However, the present invention is not limited to this, and the reed switches L11, L12 to L51, L52 are arranged in the horizontal direction, and the magnet 3 is arranged in the horizontal direction. The movement direction of the magnet 3 may be determined.

  As mentioned above, although embodiment of this invention was described with reference to drawings, this invention is not limited to the thing of embodiment shown in figure. Various modifications and variations can be made to the illustrated embodiment within the same range or equivalent range as the present invention.

  The present invention can be used for a liquid level sensor that detects the level of the liquid level in the tank and the rise and fall without providing a self-holding function for each reed switch.

It is a layout view of the reed switch that constitutes the position detector in one embodiment of this invention. It is a block diagram which shows the whole structure of the position detector in one Embodiment of this invention. It is a flowchart for demonstrating operation | movement of the position detector in one Embodiment of this invention, and shows the confirmation operation | movement of the contact in the lowest point-the highest point. 2 is a flowchart for explaining the operation of the position detector in one embodiment of the present invention, which detects the on / off of each reed switch at each position (1) to (5) in FIG. The operation | movement which discriminate | determines presence or absence is shown. It is a figure for contrasting and explaining the effect of a conventional example and the embodiment of this invention. It is a figure for demonstrating operation | movement of the conventional reed switch.

Explanation of symbols

  3 magnet, 10 CPU, 11 memory, 12 output circuit, L11, L12, L21, L22, L31, L32, L41, L42, L51, L52 Reed switch, R11, R12, R21, R22, R31, R32, R41, R42 , R51, R52 resistors, U1-U5 units.

Claims (3)

A position detector for detecting the moving direction or presence / absence of movement of a moving object having a magnet,
At least one switch unit including at least two switches in which the respective contacts are arranged at a predetermined interval in the moving direction of the magnet;
A position detector comprising determination means for determining the position and moving direction of the moving object or the presence or absence of movement based on the order of opening and closing of the contacts in the switch unit according to the movement of the magnet.   The position detector according to claim 1, wherein the at least one switch unit is housed in a holder and unitized. A liquid level sensor that detects the level of liquid level and the rise and fall of the liquid level,
A float with a built-in magnet that moves up and down as the liquid level rises and falls;
A plurality of switch units including at least two switches in which the respective contacts are arranged at predetermined intervals along the ascent and descent paths of the float;
A liquid level sensor comprising: a determination means for determining the level of the liquid level and the rise and fall based on the order of opening and closing of the contacts in the plurality of switch units in accordance with the rise and fall of the float.

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