Liquid level sensor

Abstract

A liquid level sensor 100 according to an embodiment of the present invention uses a float to measure a liquid level in a container, and comprises a base member 10, an arm 20 that can be connected to the float, a holder 30 which has a holding portion 32 for holding a held portion 222 of the arm and which is attached to the base member 10 so as to be rotatable about a first axis AX1, and a detecting mechanism for detecting rotation of the holder 30, wherein the arm 20 includes a projecting portion 223 that projects from the holder 30 in an extension direction (V1-V2 direction) of the held portion 222, and the base member 10 includes an engaging portion 111 for engaging the projecting portion 223 to stop the rotation of the holder 30 in a predetermined position, as a result of which the liquid level sensor is resistant to the effects of disturbances such as vibration of the container.

Description

Technical Field

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[0001] The present invention relates to a liquid level sensor that measures the liquid level in a container using a float.

Background Art

[0002] Patent Document 1 and Patent Document 2 disclose liquid level sensors that measure the liquid level in a container using a float. In these liquid level sensors, when the float is displaced based on a change in the liquid level in the container, the arm connected to the float is also displaced. Since the arm is held by the holding portion of the holder that rotates with respect to the base member at its held portion, the displacement of the arm becomes a rotation with respect to the base member of the holder. By measuring this rotation angle, the liquid level is measured.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

[0006] In particular, in structures such as those described in Patent Document 2, where a protruding portion extending from the held portion has a bent portion, and the tip located at the end of the bent portion is locked to the base member, if the rod-shaped arm in the held portion rotates around its axis (rotates), the position of the tip shifts (swinging phenomenon), causing the measured liquid level to be offset or the measurement range to shift. As mentioned above, in the case of a liquid level sensor intended for measuring the capacity of a gasoline tank, a shift in the lower limit of the measurement range for the tank capacity can cause serious problems, such as unexpected engine stoppage during operation.

[0007] Against this backdrop, the present invention aims to provide a liquid level sensor having a structure that is less susceptible to external disturbances such as vibration of the container. [Means for solving the problem]

[0008] To solve the above problems, the present invention provides a liquid level sensor for measuring the liquid level in a container using a float, in one aspect (first aspect), comprising: a base member connectable to a container; an arm connectable to a float; a holder having a holding portion for holding the portion of the arm, and rotatably mounted on the base member around a first axis; and a detection mechanism for detecting the rotation of the holder. In such a liquid level sensor, the arm has a protruding portion that extends from the holder along the extending direction of the portion to be held, and the base member has a locking portion that locks the protruding portion and stops the rotation of the holder at a predetermined position.

[0009] In the above liquid level sensor, the protruding portion extends along the extending direction of the held portion, that is, there is no bend between the protruding portion and the held portion, thus reducing the possibility that the rotation of the arm may be measured as the rotation of the holder relative to the base member. Furthermore, from the viewpoint of stabilizing the holding of the arm, the holding portion of the holder is set so that the held portion has a predetermined length along the direction in which the arm extends. This sets the extending direction of the held portion.

[0010] A liquid level sensor provided by the present invention as another embodiment (second embodiment) is a liquid level sensor that measures the liquid level in a container using a float, comprising: a base member connectable to a container; a holder having a holding portion for holding a portion of an arm connectable to a float, and rotatably mounted on the base member around a first axis; and a detection mechanism for detecting the rotation of the holder, wherein the base member has a locking portion for locking a protruding portion of the arm that protrudes from the holder, thereby stopping the rotation of the holder at a predetermined position, and when the holder is in the predetermined position, the receiving surface of the locking portion is positioned along the extending direction of the receiving surface of the holding portion.

[0011] Because the receiving surface of the locking part (the contact surface with the protruding part when the protruding part is locked to the locking part) is positioned along the extending direction of the receiving surface of the holding part (the contact surface of the arm with the held part), even if the held part of the arm that contacts the receiving surface of the holding part experiences a positional displacement relative to the holding part, the protruding part that contacts the receiving surface of the locking part will also experience a similar positional displacement relative to the locking part. Therefore, the positional displacement of the held part relative to the holding part is less likely to be detected by the detection mechanism as a change in the rotation angle of the holder's base member. Consequently, even if vibrations of the float caused by container vibrations are transmitted to the arm and cause a positional displacement between the holding part and the held part, this positional displacement is less likely to affect the rotation detection by the detection mechanism. If the receiving surface of the locking part is located on the extension of the receiving surface of the holding part, the effect of positional displacement can be suppressed more stably.

[0012] A liquid level sensor provided by the present invention as another embodiment (third embodiment) is a liquid level sensor that measures the liquid level in a container using a float, comprising: a base member connectable to a container; an arm connectable to a float; a holder having a holding portion for holding a portion of the arm, and rotatably mounted on the base member around a first axis; and a detection mechanism for detecting the rotation of the holder, wherein the base member has a locking portion that engages with a protruding portion of the arm which protrudes from the holder, thereby stopping the rotation of the holder at a predetermined position, and the holder comprises a plurality of holding portions, each of which is provided on the holder such that the portion to be held intersects with the first axis and stops the rotation of the holder at a position different from the other.

[0013] The liquid level sensor disclosed in Patent Document 2 is provided with multiple insertion holes for inserting the tip of an arm, and the measurement range of the rotation angle can be changed by selecting one of these insertion holes. The fixed body corresponding to the base member is provided with a restricting part that restricts the movement of the tip of the arm inserted into the insertion hole, and the measurement range is set by this restricting part. However, in the structure disclosed in Patent Document 2, two restricting parts are provided for each insertion hole, so by changing the insertion hole into which the arm is inserted, both measurement limits of the measurement range are changed. When both measurement limits of the measurement range are changed in this way, it is necessary to reconfigure the method for calculating the rotation angle from the measurement data. This increases the computational load on the calculation unit that calculates the rotation angle.

[0014] The liquid level sensor holder according to the third embodiment described above has multiple holding parts, so by selecting a holding part, the rotational stopping position of the holder relative to the base member can be moved, and the measurement range can be changed, as in the liquid level sensor disclosed in Patent Document 2. Here, selecting a holding part and moving the rotational stopping position changes only one of the measurement limits of the measurement range, and the other measurement limit of the measurement range remains constant regardless of which holding part is selected. Thus, in the liquid level sensor according to the third embodiment, no matter which holding part is selected, one of the two measurement limits set by the measurement range is common, so the method for calculating the rotation angle (relative position of the holder relative to the base member) from the data measured by the detection mechanism can be common, and the computational load on the calculation unit that calculates the rotation angle does not increase easily.

[0015] A liquid level sensor provided by the present invention as yet another embodiment (fourth embodiment) is a liquid level sensor that measures the liquid level in a container using a float, comprising: a base member connectable to a container; an arm connectable to a float; a holder having a holding part for holding the arm and rotatably mounted on the base member around a first axis; a detection mechanism for detecting the rotation of the holder; and a shaft body along the first axis, wherein the shaft body has a connecting part for setting its relative position to the arm and is interlocked with the holder via the arm.

[0016] The rotation mechanism that enables the holder to rotate relative to the base member may have a shaft along the first axis. This shaft requires high machining precision and preferably has excellent wear resistance. In the liquid level sensor according to the fourth embodiment described above, since the shaft is made of a separate material from the other members, it is possible to manufacture the shaft independently. In this case, if the shaft is made of a different material from the other members, for example, a metallic material, it may be easier to improve the machining precision and durability of the bearing structure.

[0017] In the liquid level sensor described above, the connecting portion may have an insertion hole into which an arm extending in a direction intersecting the first axis is inserted. This insertion hole may also be a through hole. It is preferable that the receiving surface of the arm in the insertion hole (through hole) is located on the extension of the receiving surface of the holder's holding portion. In this case, the shaft and the holder can be substantially integrated via the arm.

[0018] The liquid level sensor according to the first or second embodiment described above may have a holder comprising a plurality of holding parts, and each of the plurality of holding parts may be provided on the holder such that the part to be held intersects with the first axis and stops the rotation of the holder at a position different from that of the other.

[0019] In the liquid level sensor according to each of the above embodiments, the base member and the holder may have a stopper that stops the rotation of the holder at a predetermined position. This stopper has the function of stopping the rotation of the holder in the same way as a locking part by directly contacting the base member and the holder. A specific example of the stopper is a case in which one of the base member and the holder has a projection and the other has a recess. The projection provided on either one may contact the other.

[0020] In the liquid level sensor according to the first to third embodiments, it is preferable to have the above-mentioned stopper, and that the stopping position based on the stopper is different from the stopping position based on the locking portion. In addition to the structure that stops the rotation of the holder using a protruding portion, by having a structure that stops the rotation by contact between the base member and the holder, it becomes easy to set multiple measurement ranges for the rotation of the holder.

[0021] The above-mentioned stopper may stop the rotation of the holder in the direction in which the protrusion moves away from the locking portion, or it may stop the rotation in the direction in which the protrusion comes into contact with the locking portion, or it may be capable of stopping both types of rotation.

[0022] When stopping the rotation in the direction in which the protrusion moves away from the locking portion, the range between the stop position based on the locking portion and the stop position based on the stopper is the rotatable range of the holder, and this range is the measurement range of the rotation angle in the detection mechanism. Specifically, of the two measurement limit values in the measurement range of the rotation angle, one measurement limit value is set by the stop position based on the locking portion, and the other measurement limit value is set by the stop position based on the stopper. Even when a plurality of one measurement limit values are set because the holder has a plurality of holding portions as in the liquid level sensor according to the third aspect, the other measurement limit value set by the stop position based on the stopper is common, so the calculation load of the rotation angle is not likely to increase.

[0023] When stopping the rotation in the direction in which the protrusion abuts against the locking portion, separately from the rotation stop of the holder by the protrusion, since it has a structure for stopping the rotation in the same direction, it becomes easy to set a plurality of measurement ranges of the rotation of the holder. In this case, the stopper may be composed of a protrusion protruding in the radial direction on the holder and the locking portion.

[0024] In the above liquid level sensor, the detection mechanism may include a magnetic generator provided on one of the holder and the base member, and a magnetic measurement unit provided on the other of the holder and the base member for measuring the magnetic field from the magnetic generator. In this case, if the magnetic measurement unit has a magnetoresistive effect element and the arrangement direction of the magnetic generator and the magnetoresistive effect element is non-parallel to the first axis, specifically, a direction orthogonal to the direction along the first axis, there may be a case where the height (thickness) in the direction along the first axis of the liquid level sensor can be reduced.

[0025] The above magnetic measurement unit may include two full-bridge circuits having magnetoresistive effect elements. In this case, for the two full-bridge circuits, it is preferable that the sensitivity axes of the magnetoresistive effect elements are set such that when one midpoint output outputs a sine wave, the other midpoint output outputs a sine wave with a 90° phase shift from the sine wave. By setting it in this way, when obtaining the rotation angle from the output data, the change in the resistance value of the magnetoresistive effect element based on the change in the measurement temperature is canceled. Therefore, the rotation angle measured by the detection mechanism is not affected by the measurement temperature, and the measurement accuracy is less likely to decrease.

[0026] In the above liquid level sensor, the holder may be provided at a position different from the holding portion and may further include an auxiliary holding portion for holding the arm. By providing the auxiliary holding portion in addition to the holding portion, the holding of the arm by the holder can be stabilized.

[0027] In this case, it is preferable that the receiving surface of the auxiliary holding portion is located outside the extension of the receiving surface of the holding portion. If the arm has a bent portion between the portion held by the holding portion and the portion held by the auxiliary holding portion, it can easily cope with a structure in which the receiving surface of the auxiliary holding portion is not located on the extension of the receiving surface of the holding portion. In the case of this structure, even if the arm tries to rotate (spin) in the held portion held by the holding portion, the auxiliary holding portion suppresses the rotation, and the rotation of the arm is less likely to occur.

[0028] The protruding portion of the above liquid level sensor may be located on the side of the arm where the float is connected across the held portion, or may be located on the opposite side. In the latter case, even if the arm swings due to the vibration from the float, the movement is relaxed in the held portion held by the holder, so it is difficult to be transmitted to the protruding portion side. Therefore, the latter configuration is more likely to stabilize the contact between the protruding portion and the locking portion, and may be preferable.

[0029] In the above-described liquid level sensor, the specific configuration of the detection mechanism is not limited. One specific example is a case in which a resistor is provided on one of the holder and the base member, and a sliding contact is provided on the other of the holder and the base member that contacts the resistor. Other specific examples include a case in which a transmitter is provided on one of the holder and the base member, and a receiver is provided on the other of the holder and the base member that receives a signal from the transmitter, or a case in which a transmitter is provided on one of the holder and the base member, a receiver that receives a signal from the transmitter, and a reflector provided on the other of the holder and the base member that reflects the signal from the transmitter back to the receiver. In these cases, the signal may be an electromagnetic wave such as light or radio waves, or it may be an acoustic signal. [Effects of the Invention]

[0030] According to the present invention, a liquid level sensor is provided that has a structure that is less susceptible to external disturbances such as vibration of the container. [Brief explanation of the drawing]

[0031] [Figure 1] This is an explanatory diagram (perspective view) showing a first example of a liquid level sensor according to the first embodiment of the present invention. [Figure 2] This is an explanatory diagram (perspective view) of a liquid level sensor according to the first example of the first embodiment, exploded in the Z1-Z2 direction. [Figure 3] This is an explanatory diagram showing a cross-section (YZ plane) along the line A-A' in Figure 1. [Figure 4] This is an explanatory diagram (perspective view) of the holder for the liquid level sensor according to the first embodiment. [Figure 5] This is an explanatory diagram (perspective view) of the holder for the liquid level sensor according to the first embodiment. [Figure 6] This is an explanatory diagram (side view) of the holder of the liquid level sensor according to the first embodiment. [Figure 7] This is an explanatory diagram (perspective view) showing the liquid level sensor according to the first example of the first embodiment, with the arm held in the holder. [Figure 8]This is an explanatory diagram showing the cross-section (VZ plane) along the line B-B' in Figure 7. [Figure 9] This is an explanatory diagram showing the cross-section (VW plane) along the line C-C' in Figure 7. [Figure 10] This is an explanatory diagram (plan view) of the operation of a liquid level sensor according to the first example of the first embodiment. [Figure 11] This is an explanatory diagram (perspective view) of the operation of a liquid level sensor according to the first example of the first embodiment. [Figure 12] This is an explanatory diagram (perspective view) of the locking part of the liquid level sensor according to the first example of the first embodiment. [Figure 13] This is an explanatory diagram (side view) of the locking part of the liquid level sensor according to the first example of the first embodiment. [Figure 14] This is an explanatory diagram of the normal operation of the locking part of a liquid level sensor having a structure related to the conventional technology. [Figure 15] This is an explanatory diagram illustrating the oscillation phenomenon that occurs when the locking part of a liquid level sensor having a structure related to the conventional technology occurs. [Figure 16] This is an explanatory diagram (plan view) of the operation of a liquid level sensor according to a second example of the first embodiment. [Figure 17] This is an explanatory diagram (plan view) of the operation of a liquid level sensor according to a third example of the first embodiment. [Figure 18] This is a circuit diagram illustrating the magnetic measuring unit of the liquid level sensor according to the first embodiment. [Figure 19] This is an explanatory diagram of the data output from the magnetic measurement unit of the liquid level sensor according to the first embodiment. [Figure 20] This diagram illustrates the positional relationship between the magnetic generator and the magnetic measuring unit of the liquid level sensor according to the first embodiment. [Figure 21] This graph shows the relationship between the angle of the magnetic field reaching the measurement circuit from the magnetic generator in the liquid level sensor according to the first embodiment and the rotation angle of the holder. [Figure 22] This graph shows the relationship between the angle of the magnetic field from the magnetic generator and the measurement range of the detection mechanism in the liquid level sensor according to the first embodiment. [Figure 23] This is an explanatory diagram (perspective view) showing a first example of a liquid level sensor according to the second embodiment of the present invention. [Figure 24] This is an explanatory diagram (plan view) of the operation of the liquid level sensor according to the first example of the second embodiment. [Figure 25] This is an explanatory diagram (plan view) of the operation of the liquid level sensor according to the second example of the second embodiment. [Figure 26] This is an explanatory diagram (plan view) of the operation of the liquid level sensor according to the third example of the second embodiment. [Figure 27] This is an explanatory diagram (plan view) of the operation of the liquid level sensor according to the fourth example of the second embodiment. [Figure 28] This is an explanatory diagram (perspective view) of the operation of the liquid level sensor according to the fourth example of the second embodiment. [Best Mode for Carrying Out the Invention]

[0032] Embodiments of the present invention will be described below with reference to the drawings. In the following description, the same reference numerals will be used for identical components, and components that have already been described will be omitted from the description as appropriate.

[0033] (First Embodiment) [Example 1] Figure 1 is an explanatory diagram (perspective view) showing a first example of a liquid level sensor according to the first embodiment of the present invention. Figure 2 is an explanatory diagram (perspective view) of the liquid level sensor according to the first example of the first embodiment, exploded in the Z1-Z2 direction. Figure 3 is an explanatory diagram showing a cross-section (YZ plane) along the line A-A' in Figure 1.

[0034] The liquid level sensor 100 according to the first example of the first embodiment is for measuring the liquid level in a container using a float (not shown). The liquid level sensor 100 includes a base member 10 connectable to a container (not shown), an arm 20 connectable to a float, a holder 30 having a holding part 32 that holds the held part 222 of the arm 20, and a holder 30 rotatably mounted on the base member 10 around a first axis AX1, and a detection mechanism for detecting the rotation of the holder 30. When the float is displaced due to a change in the liquid level in the container, the arm 20 connected to the float is also displaced. When the arm 20 is displaced, the holder 30 that holds the arm 20 rotates around the first axis AX1. A starting point and an ending point are set in the rotation range of the holder 30 to define a rotatable range, and the liquid level is measured by detecting the rotation angle of the holder 30 within this rotatable range with the detection mechanism.

[0035] The base member 10 comprises a holder receiving portion 12 through which the first axis AX1 passes and on which the holder 30 is positioned, a box-shaped base body portion 11 located on the Y1 side in the Y1-Y2 direction of the holder receiving portion 12, and a container connecting portion 13 located on the Y2 side in the Y1-Y2 direction of the holder receiving portion 12 for fixing to the container.

[0036] The holder receiving portion 12 has a flat plate-shaped portion that aligns with the XY plane, and the holder 30 is located on the Z1 side in the Z1-Z2 direction of this portion. The holder receiving portion 12 is provided with a base through-hole 121 through which the shaft 40, which is interlocked with the holder 30, passes.

[0037] The box-shaped base body 11 is hollow inside, and a circuit board 60 is placed inside it. A magnetic detection unit 61 and a control device 62 for the magnetic detection unit 61 are mounted on the circuit board 60. Wiring 70, which has metal wiring 71 covered by a covering part 72, is connected to the circuit board 60, and measurement data detected by the magnetic detection unit 61 and processed by the control device 62 is output to the outside from the wiring 70.

[0038] The magnetic detection unit 61 is positioned non-parallel to the first axis AX1, and in this example, to the side (specifically, on the Y1-Y2 direction Y1 side, which is perpendicular to the Z1-Z2 direction along the first axis AX1), relative to the magnetic generator 50 housed inside the holder 30. This makes it possible to reduce the length (thickness) of the liquid level sensor 100 in the direction of the first axis AX1. Such an arrangement may be easier if the magnetic detection unit 61 has a magnetoresistive element. Details of the detection method of the magnetic detection unit 61 will be described later.

[0039] The specific structure of the container connection part 13 is not limited. It may have holes for screwing it to the container, or it may have adhesive surfaces for bonding it to the container.

[0040] In this embodiment, the arm 20 is machined from a rod-shaped member with a circular cross-section, and comprises a first arm portion 21 to which the float is connected, and a second arm portion 22 where the held portion 222, which is the part held by the holder 30, is located, with the bent portion 23 in between. In this embodiment, the second arm portion 22 does not have any particular bends and is a straight shaft body with a central axis AX2 extending in a certain direction. The second arm portion 22 has a protruding portion 223 that protrudes from the holder 30.

[0041] The protruding portion 223 can be locked to a locking portion 111 provided on the base body portion 11. Since the arm 20 is held by the holder 30 in the held portion 222 connected to the protruding portion 223, the locking portion 111 of the base member 10 can lock the protruding portion 223, thereby stopping the rotation of the holder 30 at a predetermined position.

[0042] In this specification, the rotation direction in which the projection 223 abuts against the locking portion 111 during rotation of the holder 30 around the first axis AX1 is referred to as the "first rotation direction," and the rotation direction opposite to this, i.e., the rotation in which the projection 223 moves away from the locking portion 111 (clockwise in this example), is referred to as the "second rotation direction." The stopping position defined by the projection 223 protruding from the holder 30 sets the measurement limit value of the rotation range of the detection mechanism in the first rotation direction.

[0043] The holder 30 has a holder body portion 301 which has a ring-shaped general form and a bottom surface whose normal extends in the Z1-Z2 direction. The holder body portion 301 has a hollow opening on the Z2 side in the Z1-Z2 direction, and a magnetic generator 50 is housed inside it. In this example, the magnetic generator 50 is a ring-shaped permanent magnet that is magnetized in the radial direction. The permanent magnet, which is the magnetic generator 50, is provided with a chamfered portion 51 so that its relative position around the first axis AX1 with respect to the holder body portion 301 is fixed.

[0044] The detailed structure of the holder 30 and shaft 40 will be described below, with reference to Figures 4 to 6. Figures 4 and 5 are explanatory diagrams (perspective views) of the holder of the liquid level sensor according to the first embodiment. Figure 6 is an explanatory diagram (side view) of the holder of the liquid level sensor according to the first embodiment. The definition of the V1-V2 direction shown in Figure 6 will be described later.

[0045] The holder 30 is provided with a holder through-hole 31 through which the shaft body 41, which extends in the Z1-Z2 direction in the shaft body 40, is inserted. On the Z2 side of the shaft body 41 in the Z1-Z2 direction of the shaft body 40, there is a base portion 42 with a larger outer diameter than the shaft body 41, and this base portion 42 abuts against the holder receiving portion 12 of the base member 10. As a result, the shaft body 40 can rotate around the first axis AX1 while its relative position with respect to the base member 10 is defined in the X1-X2 direction, Y1-Y2 direction, and Z1-Z2 direction. During this rotation of the shaft body 40 around the first axis AX1, the inner surface of the base through-hole 121 slides against the outer surface of the shaft body 40.

[0046] On the Z1 side of the shaft body 41 in the Z1-Z2 direction of the shaft body 40, there is a shaft body through hole 411 which penetrates in a direction intersecting the first axis AX1 and into which the arm 20 is inserted. In this example, the through axis of the shaft body through hole 411 is aligned with the in-plane direction of the XY plane. The shaft body through hole 411 is a connecting part that connects the arm 20 and the shaft body 40, and the relative position of the shaft body 40 with respect to the arm 20 is set by inserting the second arm portion 22 of the arm 20 through the shaft body through hole 411. In this example, the diameter of the shaft body through hole 411 is set to match the shaft diameter of the arm 20, so the shaft body contact portion 221 of the second arm portion 22 fits into the shaft body through hole 411, thereby fixing the relative position of the shaft body 40 with respect to the arm 20. Furthermore, in this example, the position (height) of the shaft through hole 411 in the direction along the first axis AX1 (Z1-Z2 direction) coincides with the height of the first holder insertion hole 321h provided in the first holding portion 321 of the holder 30. Therefore, when the second arm portion 22 of the arm 20 is inserted, the second arm portion 22 is prevented from coming out of the holder 30 via the shaft 40. As a result, the arm 20 is integrated with the holder 30 and the shaft 40, and stable interlocking with the base member 10 is achieved.

[0047] Then, since the arm 20 is fitted into a through hole provided in the holding portion 32 of the holder 30 at the held portion 222, the shaft body 40 is linked to the holder 30 via the arm 20. Specifically, based on the movement of the arm 20, when the shaft body 40, which is capable of rotating around the first axis AX1 relative to the base member 10, rotates around the first axis AX1, the holder 30 is linked to it via the arm 20 and rotates around the first axis AX1.

[0048] In this embodiment, the holding portion 32 provided on the Z1 side in the Z1-Z2 direction of the holder body portion 301 consists of a first holding portion 321 having a first holder insertion hole 321h and a second holding portion 322 having a second holder insertion hole 322h, and both holding portions (first holding portion 321, second holding portion 322) are set so that the held portion 222 of the arm 20 intersects with the first axis AX1.

[0049] Furthermore, the stopping positions based on each holding part 32 (first holding part 321, second holding part 322) are set to be different from each other. Specifically, using the first holding part 321 as a reference, the second holding part 322 is set so that the protruding part 223 protrudes from the holder 30 at a position shifted by 30° in the second rotation direction (clockwise), so the measurement limit value of the rotation angle measurement range of the detection mechanism in the first rotation direction is also increased by 30°.

[0050] As described above, the holder 30 is provided with multiple holding structures for the arm 20, allowing for the selection of the shape of the arm 20 to set multiple measurement ranges for the rotation angle. This point will be discussed later as another example of this embodiment.

[0051] The arrangement of the holder 30 and the arm 20 will be described in detail below, with reference to Figures 7 to 9. Figure 7 is an explanatory diagram (perspective view) showing the state in which the arm is held in the holder for the liquid level sensor according to the first example of the first embodiment. Figure 8 is an explanatory diagram showing a cross-section (VZ plane) along the line B-B' in Figure 7. Figure 9 is an explanatory diagram showing a cross-section (VW plane) along the line C-C' in Figure 7.

[0052] As described above, the second arm portion 22 has a held portion 222 that is held by the holding portion 32 (first holding portion 321 in this example), a protruding portion 223 that protrudes from the holder 30, and a shaft contact portion 221 that passes through the shaft through hole 411 between the bent portion 23 and the held portion 222. Here, when the holder 30 rotates in the first rotational direction (counterclockwise), the surface that receives the held portion 222 inside the first holder insertion hole 321h of the first holding portion 321 is defined as the receiving surface of the first holding portion 321 (first holding receiving surface 321A). The direction in which the first holding receiving surface 321A extends along the second arm portion 22 of the arm 20 is defined as the holding portion extension direction, and is shown as the V1-V2 direction in the figure. In this example, as a specific example, the second arm portion 22 has a rod-like shape with a uniform circular cross-section, and its central axis AX2 is included in the in-plane direction of the XY plane. Therefore, the V1-V2 direction, which indicates the extension direction of the holding portion, is included in the in-plane direction of the XY plane, and the central axis AX2 of the second arm portion 22 aligns with the V1-V2 direction. The direction perpendicular to the V1-V2 direction in the XY plane is called the W1-W2 direction.

[0053] In this example, the projection direction of the projection 223 protruding from the holder 30 is aligned with the extension direction of the holding portion (V1-V2 direction). Because the projection 223 is aligned with the extension direction of the holding portion, even if the second arm portion 22 is displaced relative to the holder 30 due to the vibration of the container being transmitted through the first arm portion 21 to the second arm portion 22, the projection 223 will be displaced relative to the locking portion 111 in response to this displacement, making it less likely for the holder 30 to rotate.

[0054] In other words, rotation of the holder 30 due to vibration of the container is less likely to occur, and therefore deviations in the measurement range of the rotation angle due to this vibration are less likely to occur. Furthermore, since the base member 10 into which the shaft 40 that is linked to the holder 30 is fitted and held is also fixed to the container at the container connection part 13, vibrations of the container in this path are transmitted to the holder 30. However, this vibration is not the same as the vibration transmitted to the arm 20 when the float picks up the liquid level fluctuation caused by the vibration of the container, so an external force based on vibration is always applied between the holder 30 and the arm 20. This external force can cause a relative positional displacement between the second arm part 22 and the holder 30.

[0055] Figure 10 is a plan view illustrating the operation of the liquid level sensor according to the first example of the first embodiment. Figure 11 is a perspective view illustrating the operation of the liquid level sensor according to the first example of the first embodiment. In Figures 10 and 11, the protruding portion 223 is locked to the locking portion 111 provided on the X1 side in the X1-X2 direction of the base body portion 11, so the holder 30 is in the stop position, which is the limit position of rotation in the first rotation direction. This stop position sets the measurement limit value of the rotation range of the detection mechanism in the first rotation direction.

[0056] When the holder 30 is in the stopped position, the receiving surface of the locking portion 111 located on the Z1 side in the Z1-Z2 direction (first locking receiving surface 111A), that is, the contact surface with the protrusion 223 on the locking portion 111, is located along the extending direction (holding portion extending direction, V1-V2 direction) of the receiving surface (first holding receiving surface 321A) of the first holding portion 321 of the holder 30. In this example, when the held portion 222 of the second arm portion 22 is cylindrical, the first holding receiving surface 321A consists of a part of the inner surface of an annular body, and the axis of rotation of the annular body is in the holding portion extending direction (V1-V2 direction). On the other hand, the first locking receiving surface 111A is planar, and the holding portion extending direction (V1-V2 direction) is one of the in-plane directions. Therefore, the first locking receiving surface 111A is located along the extending direction (V1-V2 direction) of the first holding receiving surface 321A.

[0057] Therefore, even if the second arm portion 22 experiences a relative displacement with respect to the holder 30 due to the vibration of the container being transmitted through the first arm portion 21 to the second arm portion 22, it is unlikely that the protruding portion 223 will experience a displacement that would cause the holder 30 to rotate. For example, if the held portion 222 experiences a displacement that moves in the V1-V2 direction relative to the first holding surface 321A, the protruding portion 223 will move in the V1-V2 direction relative to the first locking surface 111A. However, even if the protruding portion 223 is displaced in this way, the holder 30 will not experience a rotational movement around the first axis AX1. Furthermore, when the rod-shaped second arm portion 22 rotates (spins) around its central axis AX2, and the held portion 222 slides against the first holding surface 321A, a displacement occurs in the protruding portion 223 that causes it to slide against the first locking surface 111A. However, this displacement of the protruding portion 223 does not cause the holder 30 to rotate around the first axis AX1. In this example, since the second arm portion 22 is rod-shaped with a circular cross-section, the first locking surface 111A is located on the extension of the first holding surface 321A. This relationship holds when the second arm portion 22 is rod-shaped and the cross-sections of the held portion 222 and the protruding portion 223 have a certain shape, not necessarily a circle.

[0058] The locking portion of this example will be explained in detail below, with reference to Figures 12 to 15, in comparison with the prior art. Figure 12 is an explanatory diagram (perspective view) of the locking portion of a liquid level sensor according to the first example of the first embodiment. Figure 13 is an explanatory diagram (side view) of the locking portion of a liquid level sensor according to the first example of the first embodiment. Note that Figure 13 is a view from the direction of extension of the holding portion (V1-V2 direction). In this example, as a specific example, the position (height) of the first holding receiving surface 321A of the holder 30 and the protruding portion 223 of the second arm portion 22 are equal in the direction along the first axis AX (Z1-Z2 direction). Therefore, even if the rod-shaped second arm portion 22 rotates around its central axis AX2, the height of the first holding receiving surface 321A of the holder 30 and the first locking receiving surface 111A of the locking portion 111 of the base body portion 11 are equal, and the relative position of the protruding portion 223 with respect to the locking portion 111 does not change. Therefore, no rotation occurs around the first axis AX1 of the holder 30.

[0059] Figure 14 is an explanatory diagram of the locking part of a liquid level sensor having a structure according to the prior art when it is functioning normally. Figure 15 is an explanatory diagram of the locking part of a liquid level sensor having a structure according to the prior art when a swaying phenomenon occurs. In a liquid level detection device disclosed in Patent Document 2, which is an example of a liquid level sensor having a structure according to the prior art, the liquid level is measured by measuring the rotation angle of a rotating body (corresponding to the holder 30 in this example) that is rotatably supported by a fixed body (corresponding to the base member 10 in this example). In this liquid level detection device, the liquid level measurement range is set as follows. An arm connected to a float is held by the rotating body, and the end of the arm not connected to the float has a protruding part that extends from the rotating body. The position at which the rotation of the rotating body stops when this protruding part comes into contact with the regulating part of the fixed part (corresponding to the locking part 111 in this example) is the limit position of the measurement range.

[0060] In the liquid level detection device of Patent Document 2, unlike the liquid level sensor 100 in this example, the restricting portion corresponding to the locking portion 111 is located below the position where the arm is held by the rotating body. This arrangement is due to the fact that in the liquid level detection device of Patent Document 2, in order to set multiple measurement ranges for rotation angles, the fixed body is provided with a hollow portion that opens toward the rotating body, and multiple restricting portions corresponding to multiple measurement ranges are provided on the inner wall of this hollow portion. To prevent the arm from contacting the restricting portion for setting other measurement ranges when one measurement range for rotation angle is selected, the protruding portion of the arm is provided with a bent portion, and only the very tip of the bent portion is inserted into the opening of the fixed body, allowing it to contact the predetermined restricting portion. Thus, in the liquid level detection device of Patent Document 2, while it is possible to measure rotation angles in multiple ranges, in order to avoid interference between the arm and the restricting portions of other measurement ranges, the structure is such that only the tip of the bent portion on the protruding portion of the arm contacts the restricting portion of the fixed body.

[0061] Figure 14 conceptually illustrates the structure of the locking mechanism of this liquid level detection device, and is a view of the portion of the arm 620 held by the rotating body from the extension direction. As shown in Figure 14, the projection 623 of the arm 620 has a bent portion 623B, and the tip portion 623C located at the end of the bent portion 623B has a structure that locks into the regulating portion 611 of the fixed body. As shown in Figure 14, in this structure, when the projection 623 is properly positioned (normal), the central axis (tip central axis OX2) of the tip portion 623C located at the end of the bent portion 623B is parallel to the rotation axis OX1 of the rotating body that is interlocked with the arm 620. In Figure 14, viewed from the extension direction of the arm 620, the rotation axis OX1 and the tip central axis OX2 overlap.

[0062] In this structure, when the arm 620 rotates (spins) around the extension direction described above, the tip central axis OX2 tilts with respect to the rotation axis OX1, as shown in Figure 15, causing a swaying phenomenon in the tip portion 623C. When this swaying phenomenon occurs, in one example, the tip portion 623C moves ahead of its intended position (displaced to the right in Figure 15). As a result, the protruding portion 623 engages with the restricting portion 611 while the rotating body is ahead of its intended stopping position (to the left in Figure 15), and the rotation of the rotating body stops. Therefore, in the liquid level detection device in the state shown in Figure 15, the liquid level measurement range becomes narrower than in normal conditions. The liquid level sensor 100 according to this example can avoid such changes in the measurement range caused by the rotation of the arm 20.

[0063] The holder 30 is provided at a different position from the holding portion 32 (first holding portion 321 in this example) and further includes an auxiliary holding portion 34 for holding the first arm portion 21 of the arm 20. In this example, the auxiliary holding portion 34 consists of a first auxiliary holding portion 341 that has a snap-fit ​​structure and grips the first arm portion 21, and a second auxiliary holding portion 342 that contacts the snap-fitted first arm portion 21 and supports the first arm portion 21.

[0064] Although the second arm portion 22 is fitted into the shaft through hole 411 and the first holding portion 321, in this example the second arm portion 22 is a rod-shaped structure with a uniform circular cross-section, and therefore can rotate (spin) around its central axis AX2. However, since the arm 20 has a bent portion 23 between the first arm portion 21 and the second arm portion 22, the receiving surface of the second auxiliary holding portion 342 (auxiliary holding receiving surface 342A), that is, the portion of the second auxiliary holding portion 342 that the first arm portion 21 contacts, is located off-center from the extension of the receiving surface of the holding portion 32 (first holding receiving surface 321A). Therefore, the auxiliary holding portion 34 can suppress the rotation (spin) of the second arm portion 22 around its central axis AX2 by holding the first arm portion 21.

[0065] In this embodiment, the holder 30 has a plurality of projections that protrude radially from the outer surface of the holder body 301. Of these projections, when viewed along the first axis AX1 (in the Z1-Z2 direction), the projection proximal to the projection 223 is designated as the first projection 331, and the projection distal to the projection 223 is designated as the second projection 332. These projections have different roles, and the second projection 332 will be described first below.

[0066] When the holder 30 rotates in the second rotational direction (clockwise), the second rotational direction side surface of the second projection 332 (second projection surface 332A) comes into contact with the Y1-Y2 direction Y1 side surface (base contact surface 112A) of the contact portion (base contact portion 112) provided on the X2 side in the X1-X2 direction of the base body portion 11, thereby stopping the rotation of the holder 30 in the second rotational direction (clockwise). In other words, the base member 10 and the holder 30 have the base contact portion 112 and the second projection 332 as stoppers that stop the rotation of the holder 30 (in this example, rotation in the second rotational direction) at a predetermined position without the arm 20. Since the base contact portion 112 is provided on the opposite side (X2 side) in the X1-X2 direction compared to the locking portion 111, the measurement limit value of the second rotational direction of the rotational range of the detection mechanism is set by the stopping position based on this stopper.

[0067] As described above, in the first example of the first embodiment, when the holder 30 rotates counterclockwise (first rotation direction), the rotation of the holder 30 stops when the projection 223 comes into contact with the locking portion 111. On the other hand, when the holder 30 rotates clockwise (first rotation direction), the rotation of the holder 30 stops when the second projection 332 comes into contact with the base contact portion 112. Therefore, for example, if the state in which the second projection 332 is in contact with the base contact portion 112 is used as the starting point for measuring the rotation angle of the holder 30, when the holder 30 starts rotating counterclockwise (first rotation direction), the second projection 332 moves away from the base contact portion 112, and the rotation angle of the holder 30 is measured. Then, when the holder 30 rotates 60° counterclockwise (first rotation direction), the second projection 332 comes into contact with the base contact portion 112, and the counterclockwise rotation (first rotation direction) of the holder 30 stops. Figure 10 shows this timing, at which point the holder 30 has reached the end of the rotation angle measurement range. Therefore, as shown in Figure 10, in this example (first example of the first embodiment), the rotation angle measurement range of the holder 30 is 60°. In Figure 10, the rotation range of the projection 223 is shown on the right side by a double-headed arrow on a dashed line, and the rotation range of the second projection 332 is shown on the left side by a double-headed arrow on a dashed line.

[0068] [Example 2] Figure 16 is an explanatory diagram (plan view) of the operation of a liquid level sensor according to a second example of the first embodiment. In Figure 16, as in Figure 10, the protruding portion 223 is locked to the locking portion 111 provided on the X1 side in the X1-X2 direction of the base body portion 11, so the holder 30 is in the stop position, which is the limit position of rotation in the first rotation direction. This stop position sets the measurement limit value of the rotation range of the detection mechanism in the first rotation direction.

[0069] The liquid level sensor 100A according to the second example of the first embodiment differs in the shape of its arm from the liquid level sensor 100 according to the first example of the first embodiment. In the liquid level sensor 100, the first arm portion 21 and the second arm portion 22 of the arm 20 are at a 90° angle due to the bent portion 23, whereas in the liquid level sensor 100A, the bending angle of the bent portion 23 of the arm 201 is different, and the first arm portion 21 and the second arm portion 22 are at a 60° angle.

[0070] Therefore, the held portion 222 of the second arm portion 22 is held by the second holding portion 322, which is positioned 30° in the second rotational direction compared to the first holding portion 321. In this way, because different holding portions are used, the extension direction of the holding portion (V1-V2 direction) is the direction in which the receiving surface (second holding receiving surface 322A) of the second holding portion 322 extends.

[0071] Therefore, as shown in Figure 16, the distance between the base contact surface 112A and the second projection surface 332A in the liquid level sensor 100A is greater than the distance between the base contact surface 112A and the second projection surface 332A in the liquid level sensor 100. As a result, the rotation angle measurement range of the liquid level sensor 100A is wider than that of the liquid level sensor 100. Specifically, the measurement range for the liquid level sensor 100 is 60°, but for the liquid level sensor 100A it is 90°, an increase of 30° (see Figure 16). In Figure 16, the rotation range of the projection 223 is shown on the right side by a double-headed arrow, and the rotation range of the second projection 332 is shown on the left side by a double-headed arrow.

[0072] Thus, in the liquid level sensors 100 and 100A according to the first embodiment, the multiple holding parts 32 (first holding part 321, second holding part 322) are provided on the holder 30 such that the held part 222 intersects with the first axis AX1 and that different stopping positions are set for each of them. Therefore, by changing the shape of the arm 20 held by the holder 30, the measurement range of the rotation angle of the holder 30 can be easily changed. Here, the base contact part 112, which gives a common measurement limit value in multiple measurement ranges, may be used as the starting point in liquid level measurement, i.e., the lower limit of the liquid level measurement range. In this case, when the tank capacity is small, the liquid level sensor 100 with a measurement range of 60° should be used, and when the tank capacity is large, the liquid level sensor 100A with a measurement range of 90° should be used.

[0073] [Example 3] Figure 17 is an explanatory diagram (plan view) of the operation of a liquid level sensor according to the third example of the first embodiment. The liquid level sensor 100B according to the third example of the first embodiment differs in the shape of its arm from the liquid level sensor 100 according to the first example of the first embodiment. The arm 20 of the liquid level sensor 100 has a protrusion 223 on the second arm portion 22, but the arm 201 of the liquid level sensor 100B has a relatively shorter second arm portion 22, and as a result does not have a protrusion 223.

[0074] Therefore, when the holder 30 rotates in the first rotational direction, a part of the arm 201 does not engage with the locking portion 111, and the surface of the first projection 331 on the first rotational direction side (first projection surface 331A) comes into contact with the receiving surface of the locking portion 111 located on the Z2 side in the Z1-Z2 direction (second locking receiving surface 111B, see Figure 15), thereby stopping the rotation of the holder 30 in the first rotational direction.

[0075] In other words, in the third example of the first embodiment, unlike the first example and the second example of the first embodiment, both the stopping position in the first rotation direction and the stopping position in the second rotation direction are stopping positions set by the stopper between the base member 10 and the holder 30. The stopping position in the first rotation direction is shifted by 60° in the second rotation direction relative to the stopping position in the first example of the first embodiment, and as a result, the measurement range of the rotation angle of the liquid level sensor 100B according to the third example of the first embodiment becomes 120° (see Figure 17). In Figure 17, the rotation range of the first projection 331 is shown on the right side by a double-headed arrow on a dashed line, and the rotation range of the second projection 332 is shown on the left side by a double-headed arrow on a dashed line.

[0076] In the liquid level sensors 100, 100A, and 100B according to this embodiment, when a part of the arm 20 (the protruding portion 223) is extended from the holder 30, the protruding portion 223 contacts the first locking receiving surface 111A of the locking portion 111, stopping the rotation of the holder 30. At this time, the rotatable angle of the holder 30 can be changed by changing the protruding position of the protruding portion 223, specifically by selecting whether to use the first holding portion 321 or the second holding portion 322. Furthermore, when the arm 20 is not extended from the holder 30, the first projection 331 provided on the holder 30 contacts the second locking receiving surface 111B, which is a portion closer to the holder receiving portion 12 in the direction along the first axis AX1 (Z1-Z2 direction) than the first locking receiving surface 111A, i.e., a portion with a lower height, stopping the rotation of the holder 30. Thus, in the liquid level sensors 100, 100A, and 100B according to this embodiment, by combining whether or not to extend the arm 20 with the selection of the mounting angle of the arm 20, it is possible to set a wider variety of measurement ranges.

[0077] [Measurement principle] The principle of measuring the rotation angle in the liquid level sensor according to the first embodiment will be explained below with reference to Figures 18 to 22. Figure 18 is a circuit diagram illustrating the magnetic measuring unit of the liquid level sensor according to the first embodiment. Figure 19 is an explanatory diagram of the data output from the magnetic measuring unit of the liquid level sensor according to the first embodiment. Figure 20 is a diagram illustrating the positional relationship between the magnetic generator and the magnetic measuring unit of the liquid level sensor according to the first embodiment. Figure 21 is a graph showing the relationship between the angle of the magnetic field from the magnetic generator and the rotation angle of the holder in the liquid level sensor according to the first embodiment. Figure 22 is a graph showing the relationship between the angle of the magnetic field from the magnetic generator and the measurement range of the detection mechanism in the liquid level sensor according to the first embodiment. In Figures 21 and 22, the horizontal axis is the rotation angle of the holder 30, and the vertical axis is the angle of the magnetic field from the magnetic generator 50.

[0078] In this embodiment, the mechanism for detecting the rotation angle of the holder 30 relative to the base member 10 comprises, as described above, a permanent magnet (magnetic generator 50) disposed inside the holder body 301 and a magnetic detection unit 61. The magnetic detection unit 61 has a measurement circuit 63 consisting of a plurality of bridge circuits having magnetoresistive elements. When the holder 30 rotates, the permanent magnet (magnetic generator 50) inside the holder 30 rotates. As a result, the relative angle between the magnetic poles of the permanent magnet (magnetic generator 50) and the magnetoresistive elements in the measurement circuit 63 changes, and the magnetization direction of the free magnetic layer of the magnetoresistive element changes according to the direction of the magnetic field from the permanent magnet (magnetic generator 50). On the other hand, since the magnetization direction of the fixed magnetic layer of the magnetoresistive element is not affected by the external magnetic field, the relative angle between the free magnetic layer and the fixed magnetic layer changes, and the resistance value of the magnetoresistive element changes. Based on this change in resistance value, the output signal from the bridge circuit changes, and this signal is output from the measurement circuit 63.

[0079] As shown in Figure 18, in the measurement circuit 63, a first full-bridge circuit FB1 and a second full-bridge circuit FB2 are arranged in parallel between the power supply side terminal VDD and the ground side terminal GND. The first full-bridge circuit FB1 consists of a first half-bridge, which is formed by connecting magnetoresistive elements S11 and S21 in series, and a second half-bridge, which is formed by connecting magnetoresistive elements S22 and S12 in series, arranged in parallel between the power supply side terminal VDD and the ground side terminal GND. The potential difference between the midpoint output OP1 of the first half-bridge and the midpoint output OP2 of the second half-bridge is measured as the first measurement potential data VD1.

[0080] The second full-bridge circuit FB2 consists of a third half-bridge, formed by connecting magnetoresistive elements S31 and S41 in series, and a fourth half-bridge, formed by connecting magnetoresistive elements S42 and S32 in series, arranged in parallel between the power supply side (VDD) and the ground side (GND). The potential difference between the midpoint output OP3 of the third half-bridge and the midpoint output OP4 of the fourth half-bridge is measured as the second measured potential data VD2.

[0081] Here, magnetoresistive elements S11 and S12 have the same direction and orientation of their sensitivity axes. Magnetoresistive elements S21 and S22 have the same direction and orientation of their sensitivity axes, and in relation to magnetoresistive element S11, the direction of their sensitivity axes is the same but the orientation is opposite. Magnetoresistive elements S31 and S32 have the same direction and orientation of their sensitivity axes, and in relation to magnetoresistive element S11, the direction of their sensitivity axes is orthogonal. Magnetoresistive elements S41 and S42 have the same direction and orientation of their sensitivity axes, and in relation to magnetoresistive element S31, the direction of their sensitivity axes is the same but the orientation is opposite.

[0082] Because the sensitivity axis of the magnetoresistive element in the measurement circuit 63 is set in this way, when one midpoint output (for example, the midpoint output OP1 of the first full-bridge circuit FB1) outputs a sine wave as the first measurement potential data VD1, the other midpoint output (the midpoint output OP2 of the second full-bridge circuit FB2) outputs a sine wave that is 90° out of phase with the sine wave output by midpoint output OP1 as the second measurement potential data VD2. Figure 19 illustrates this relationship.

[0083] Thus, in the ideal state where sine waves with a 90° phase difference are output, the rotation angle RA is expressed by the following equation (1). RA = arctan(VD2 / VD1) (1)

[0084] Here, the magnetoresistive element may be either a giant magnetoresistive element (GMR element) or a tunnel magnetoresistive element (TMR element), and in either case, it consists of a laminate in which multiple films (fixed magnetic layer, non-magnetic material layer, free magnetic layer, etc.) are stacked. If the composition and thickness of each film constituting this laminate differ, the element characteristics (sensitivity, temperature characteristics, etc.) will differ. Therefore, it is preferable that the eight magnetoresistive elements in the measurement circuit 63 have the same film configuration (common laminated structure). In this case, the characteristics of the eight magnetoresistive elements, especially the temperature characteristics, tend to be similar. When the temperature characteristics of the eight magnetoresistive elements in the measurement circuit 63 are similar, the temperature dependence of the first measurement potential data VD1 and the temperature dependence of the second measurement potential data VD2 tend to have the same trend. In the above equation (1), the ratio of the first measurement potential data VD1 and the second measurement potential data VD2 is taken in the calculation of the rotation angle RA, so this calculation cancels out the respective temperature dependencies, and the calculated rotation angle RA is constant and unaffected by temperature.

[0085] Furthermore, from the viewpoint of making the rotation angle RA less susceptible to temperature influences, it is preferable that the eight magnetoresistive elements are manufactured using a common film deposition process, and it is even more preferable that the film deposition substrate used in the film deposition process is common.

[0086] In this embodiment, the magnetic generator 50 consists of a ring-shaped permanent magnet magnetized in the radial direction, and as the holder 30 rotates, its magnetization direction rotates in the XY plane. The measurement circuit 63, which serves as the measurement point, is located at a predetermined distance D from the first axis AX1, which is the rotation axis of the holder 30, within the XY plane formed by the rotation of the magnetization direction of the holder 30 (see Figure 20). Therefore, as shown in Figure 21, the relationship between the angle of the magnetic field emitted from the magnetic generator 50 (permanent magnet) and reaching the measurement circuit 63 and the rotation angle of the holder 30 is not linear (straight), but rather a waveform in which sinusoidal waves are superimposed and undulate.

[0087] Therefore, the output signal from the magnetic detection unit 61 in the liquid level sensor 100 according to the first embodiment deviates from the ideal state shown in Figure 20 and becomes a waveform in which the sine wave is modulated. Since the modulation to the first measured potential data VD1 and the modulation to the second measured potential data VD2 are not the same, when comparing the waveforms of each other, the difference is larger than a simple phase shift. Even if the above equation (1) is applied in this state, the rotation angle RA cannot be accurately determined.

[0088] Therefore, the first measured potential data VD1 and the second measured potential data VD2 output from the magnetic detection unit 61 are input to the control device 62 for waveform correction. The liquid level sensors 100, 100A, and 100B in each example of this embodiment have different measurement ranges for rotation angles, but the measurement limit value on one side (the second rotation direction side) is the stopping position based on the second projection surface 332A of the second projection 332 contacting the base contact surface 112A of the base body 11. Accordingly, when the measurement ranges of each liquid level sensor are superimposed on Figure 21, as shown in Figure 22, the liquid level sensors 100 and 100A in the other examples are included within the measurement range of the liquid level sensor 100B in the third example of the first embodiment, and the common angle in all measurement ranges is used as one of the measurement limit values ​​(30° in Figure 22). Although the measured value of the liquid level sensor does not change linearly with respect to the rotation angle of the holder 30, the liquid level sensors 100, 100A, and 100B according to this embodiment share a common starting point for the measurement range. Therefore, if the control device 62 prepares a waveform correction program for the liquid level sensor 100B according to the third example of the first embodiment, the liquid level sensors 100 and 100A according to the other examples can use that correction program as is.

[0089] In contrast, for example, the liquid level sensor in Patent Document 2 has multiple measurement ranges for rotation angle, but if the measurement limits of each measurement range differ from one another, the starting point will differ for each measurement range. Therefore, multiple correction programs must be prepared to match each measurement range. Consequently, the computational load of a device having similar functions to the control device 62 will be higher than that of the liquid level sensors 100, 100A, and 100B according to this embodiment.

[0090] (Second Embodiment) Figure 23 is an explanatory diagram (perspective view) showing a first example of a liquid level sensor according to the second embodiment of the present invention. Figure 24 is an explanatory diagram (plan view) of the operation of a liquid level sensor according to the first example of the second embodiment. Figure 25 is an explanatory diagram (plan view) of the operation of a liquid level sensor according to the second example of the second embodiment. Figure 26 is an explanatory diagram (plan view) of the operation of a liquid level sensor according to the third example of the second embodiment. Figure 27 is an explanatory diagram (plan view) of the operation of a liquid level sensor according to the fourth example of the second embodiment. Figure 28 is an explanatory diagram (perspective view) of the operation of a liquid level sensor according to the fourth example of the second embodiment. Since the basic structure of the liquid level sensors 101, 101A, 101B, and 101C according to the second embodiment of the present invention is the same as that of the liquid level sensors 100, 100A, and 100B according to the first embodiment, only the differences will be explained.

[0091] In the first embodiment, the holder 30 of the liquid level sensors 100, 100A, and 100B had a holding portion 32 that consisted of a first holding portion 321 and a second holding portion 322. However, in the second embodiment, the holder 30 of the liquid level sensors 101, 101A, 101B, and 101C has a holding portion 32 that consists of a first holding portion 321, a second holding portion 322, and a third holding portion 323. Similar to the first embodiment, the holding portion 32 is provided on the holder 30 such that the held portion 222 intersects with the first axis AX1 and that different stopping positions are set for each portion. As a result, the liquid level sensors 101, 101A, 101B, and 101C in the second embodiment can use the protruding portion 223 to set three different measurement ranges for the rotation angle of the holder 30.

[0092] As shown in Figures 23 and 24, in the liquid level sensor 101 according to the first example of the second embodiment, an arm 20 with a bending angle of 90° at the bent portion 23 is used, similar to the liquid level sensor 100, and the second arm portion 22 of the arm 20 is held by the first holding portion 321. In this case, the measurement range of the rotation angle of the holder 30 is 60°, as shown in Figure 24. In Figure 24, the rotation range of the protrusion 223 on the right is indicated by a double-headed arrow on a dashed line, and the rotation range of the second projection 332 on the left is indicated by a double-headed arrow on a dashed line.

[0093] As shown in Figure 25, in the liquid level sensor 101A according to the second example of the second embodiment, an arm 201 with a bending angle of 60° at the bent portion 23 is used, similar to the liquid level sensor 100A, and the second arm portion 22 of the arm 201 is held by the second holding portion 322. In this case, the measurement range of the rotation angle of the holder 30 is 90°, as shown in Figure 25. In Figure 25, the rotation range of the protrusion 223 is shown on the right side by a double-headed arrow on a dashed line, and the rotation range of the second projection 332 is shown on the left side by a double-headed arrow on a dashed line.

[0094] As shown in Figure 26, in the liquid level sensor 101B according to the third example of the second embodiment, an arm 203 with a bending angle of 30° at the bent portion 23 is used, and the second arm portion 22 of the arm 203 is held by a third holding portion 323 having a third holding receiving surface 323A. In this case, the measurement range of the rotation angle of the holder 30 is 120°, as shown in Figure 26. In Figure 26, the rotation range of the protrusion 223 on the right is indicated by a double-headed arrow on a dashed line, and the rotation range of the second projection 332 on the left is indicated by a double-headed arrow on a dashed line.

[0095] In the first embodiment, the holder 30 of the liquid level sensors 100, 100A, and 100B had a first projection 331 and a second projection 332, but in the second embodiment, the holder 30 of the liquid level sensors 101, 101A, 101B, and 101C has only the second projection 332. The second projection surface 332A of this second projection 332 contacts the base contact surface 112A of the base contact portion 112, similar to the liquid level sensors 100, 100A, and 100B in the first embodiment, stopping the holder 30 from rotating in the second rotational direction (clockwise) (stop position based on the stopper). In addition, the holder receiving portion 12 of the base member 10 of the liquid level sensors 101, 101A, 101B, and 101C in the second embodiment is provided with a protrusion 122 that projects toward the Z1 side in the Z1-Z2 direction.

[0096] As shown in Figures 27 and 28, in the liquid level sensor 101C according to the fourth example of the second embodiment, an arm 202 without a protrusion 223 is used, similar to the liquid level sensor 100B according to the third example of the first embodiment. Therefore, in the liquid level sensor 100B, the surface of the second projection 332 on the first rotational direction side (second projection second surface 332B) contacts the surface of the convex portion 122 provided on the holder receiving portion 12 on the second rotational direction side (convex portion contact surface 122A), stopping the rotation of the holder 30 in the first rotational direction (stop position based on stopper). In this case, the measurement range of the rotation angle of the holder 30 is 150°, as shown in Figure 27. In this example, since the measurement range of the rotation angle of the holder 30 is set by the second projection 332, unlike other examples, in Figure 27, only the rotation range of the second projection 332 is indicated by a double-headed arrow.

[0097] (modified version) The following describes some modifications of the liquid level sensors 100, 100A, and 100B according to the first embodiment, and the liquid level sensors 101, 101A, 101B, and 101C according to the second embodiment.

[0098] In each embodiment, the arms 20, 201, 202, and 203 used had a second arm portion 22 that was rod-shaped with a circular cross-section, but this is not limited to this. For example, although the cross-section is circular in all cases, the radius of the circle of the projection portion 223 may differ from that of the held portion 222. Specifically, the radius of the circle in the cross-section of the projection portion 223 may be larger or smaller than the radius of the circle in the cross-section of the held portion 222. The cross-sectional shape of the second arm portion 22 is not limited to a circle, but may be an ellipse, polygon, irregular shape, etc. Also, the cross-sectional shape of the projection portion 223 and the cross-sectional shape of the held portion 222 may be different.

[0099] In each of the embodiments described above, the protrusion 223 is located on the arms 20, 201, 202, and 203 on the side opposite to the side to which the float is connected, with the held portion 222 in between. However, the invention is not limited to this, and the float may be connected to the end of the portion where the protrusion 223 is provided, as viewed from the held portion 222. However, in this case, vibrations from the float are transmitted to the protrusion 223 before they are mitigated in the held portion 222, so there is a concern that the stability of the stopping position set by the locking portion 223 engaging with the locking portion 111 will decrease. Therefore, as in each of the embodiments described above, it is preferable that the protrusion 223 is located on the arms 20, 201, 202, and 203 on the side opposite to the side to which the float is connected, with the held portion 222 in between.

[0100] In each of the embodiments described above, the holding portion 32 of the holder 30 was composed of a through hole through which the second arm portion 22 was inserted, but it is not limited to this. For example, it may have a snap-fit ​​structure, such as the auxiliary holding portion 34. Alternatively, the holding portion 32 may have a hollow portion that opens toward the Z1 side in the Z1-Z2 direction, and after the second arm portion 22 is placed in this hollow portion, the second arm portion 22 may be held by a member that presses the second arm portion 22 from the Z1 side in the Z1-Z2 direction.

[0101] In each of the embodiments described above, the stopper formed by the base member 10 and the holder 30 is constructed by projections (first projection 331, second projection 332) provided on the holder 30 contacting the base member 10, but is not limited to this. For example, the holder 30 may have a recess on its outer surface that is recessed in the direction along the first axis AX1 (Z1-Z2 direction), and the base member 10 may have a protrusion that projects radially into the recess of the holder 30. Alternatively, if the stopper has a portion that protrudes toward the mating member, the direction of that protrusion may be along the Z1-Z2 direction.

[0102] In each of the embodiments described above, the shaft 40 had a shaft through-hole 411 through which the second arm portion 22 was inserted as a connecting portion, but the shape of the connecting portion is not limited. Similar to the modified form of the holding portion 32 of the holder 30, the arm 20 and the shaft 40 may be connected by a snap-fit ​​structure or by using an open hollow portion and a retaining member. Also, in each of the embodiments described above, the shaft contact portion 221 of the second arm portion 22 was fitted into the shaft through-hole 411, but the shaft contact portion 221 may be loosely fitted into the shaft through-hole 411 as long as the held portion 222 is properly held by the holder 30.

[0103] In each of the embodiments described above, the detection mechanism included a magnetic generator 50 made of a radially magnetized permanent magnet and a magnetic detection unit 61 equipped with a measurement circuit 63 having a magnetoresistive element, but is not limited thereto. The magnetic generator 50 does not have to be a permanent magnet, and the magnetization direction may be axial. In this case, it is preferable that the magnetic detection unit 61 has a Hall element. Alternatively, the magnetic detection unit 61 may be provided on the holder 30 side, and the magnetic generator 50 may be provided on the base member 10. Or, the magnetic generator 50 and the magnetic detection unit 61 may be provided on the base member 10, and a yoke may be arranged on the holder 30, forming a magnetic circuit passing through the yoke based on the magnetic generator 50. In this case, the magnetic flux density passing through the magnetic circuit changes as the holder 30 rotates, and the magnetic detection unit 61 may detect this change in magnetic flux density.

[0104] In the above embodiment, the detection mechanism detects magnetism, but is not limited to this. For example, the detection mechanism may include a resistor provided on one of the holder 30 and the base member 10, and a sliding contact provided on the other of the holder 30 and the base member 10 that contacts the resistor. As an example of another detection mechanism, it may include a transmitter provided on one of the holder 30 and the base member 10, and a receiver provided on the other of the holder 30 and the base member 10 that receives a signal from the transmitter. Examples of signal sources emitted by the transmitter in this case include light, electromagnetic waves such as radio waves, and sound. As another example of a detection mechanism, it may include a transmitter provided on one of the holder 30 and the base member 10 and a receiver that receives a signal from this transmitter, and a reflector provided on the other of the holder 30 and the base member 10 that reflects the signal from the transmitter back to the receiver. Examples of signal sources emitted by the transmitter in this case include light, electromagnetic waves such as radio waves.

[0105] In the above embodiment, a specific example was given where the base contact portion 112, which provides a common measurement limit value across multiple measurement ranges, is used as the starting point (lower limit of the liquid level measurement range) in liquid level measurement. However, the embodiment is not limited to this. The base contact portion 112 may also be used as the endpoint (upper limit of the liquid level measurement range) in liquid level measurement.

[0106] The embodiments described above are provided to facilitate understanding of the present invention and are not intended to limit it. Accordingly, each element disclosed in the above embodiments is intended to include all design modifications and equivalents that fall within the technical scope of the present invention. [Explanation of symbols]

[0107] 100, 100A, 100B, 101, 101A, 101B, 101C: Liquid level sensor 10: Base component 11: Base body 12: Holder receiving part 13: Container connection part 20, 201, 202, 203: Arm 21: First arm section 22: Second arm section 23: Bending section 30: Holder 31: Holder through hole 32: Holding part 34:Auxiliary holding part 40: Axis 41: Shaft body 42: Base 50: Magnetic generator 51: Chamfered section 60: Circuit board 61: Magnetic detection unit 62: Control device 63: Measurement circuit 70: Wiring 71: Metal wiring 72: Covering part 111: Locking part 111A: First locking receiving surface 111B: Second locking receiving surface 112: Base contact area 112A: Base contact surface 121: Base through hole 122: Convex part 122A: Convex contact surface 221: Shaft contact part 222 :Holded part 223:Protrusion 301: Holder body 321: 1st holding part 321A: First holding surface 321h: First holder insertion hole 322:Second holding part 322A: Second holding surface 322h: Second holder insertion hole 323: Third holding part 323A: Third holding surface 331: First projection (stopper) 331A: 1st protrusion surface 332: Second projection (stopper) 332A: 2nd protruding surface 332B: 2nd protrusion 2nd surface 341: 1st auxiliary holding part 342:Second auxiliary holding part 342A: Auxiliary holding surface 411: Shaft through hole (connection part) 611: Regulatory Department 620: Arm 623:Protrusion 623B: Bent section 623C: Tip AX1: 1st axis AX2: Central axis D: Distance FB1: First full-bridge circuit FB2: Second full-bridge circuit GND: Ground side end OP1: Midpoint output OP2: Midpoint output OP3: Midpoint output OP4: Midpoint output RA: Rotation angle S11~S42: Magnetoresistive element VD1: First measured potential data VD2: Second measured potential data VDD: Power supply side end OX1: Rotation axis OX2: Tip center axis

Claims

1. A liquid level sensor that measures the liquid level inside a container using a float, Base member and An arm that can be connected to the float, A holder that holds the arm and is mounted to the base member so as to be rotatable around a first axis, A detection mechanism for detecting the rotation of the holder, Equipped with, The arm has a bent portion, a second arm portion that extends along a second axis perpendicular to the first axis and whose end protrudes from the holder, and a first arm portion that extends along a third axis intersecting the second axis and whose end is connected to the float. The holder has a holding portion that holds the portion of the second arm along the second axis, and an auxiliary holding portion that holds the first arm along the third axis. The base member has a locking portion that engages the protruding portion extending along the second axis, thereby stopping the rotation of the holder at a predetermined position. A liquid level sensor characterized by the following features.

2. The liquid level sensor according to claim 1, wherein when the holder is in the predetermined position, the receiving surface of the locking portion is positioned along the extending direction of the receiving surface of the holding portion.

3. The holder comprises a plurality of the holding parts, The multiple holding parts are, In all cases, the part to be held intersects with the first axis, To stop the rotation of the holder at different positions, The liquid level sensor according to claim 1, provided in the holder.

4. The system further comprises a shaft body along the first axis, The liquid level sensor according to claim 1, wherein the shaft has a connecting portion for setting its relative position to the arm and is interlocked with the holder via the arm.

5. The liquid level sensor according to claim 4, wherein the connecting portion has an insertion hole into which the arm extending in a direction intersecting the first axis is inserted.

6. The liquid level sensor according to any one of claims 1 to 4, wherein the base member and the holder have a stopper that stops the rotation of the holder at a predetermined position.

7. The base member and the holder each have a stopper that stops the rotation of the holder at a predetermined position. The liquid level sensor according to any one of claims 1 to 3, wherein the stopping position based on the stopper is a different position from the stopping position based on the locking portion.

8. The liquid level sensor according to claim 7, wherein the stopper stops the rotation of the holder in the direction in which the protruding portion moves away from the locking portion.

9. The liquid level sensor according to claim 7, wherein the stopper stops the rotation of the holder in the direction in which the protruding portion comes into contact with the locking portion.

10. The liquid level sensor according to claim 9, wherein the stopper comprises a projection that protrudes radially in the holder and the locking portion.

11. The liquid level sensor according to any one of claims 1 to 4, wherein the detection mechanism comprises a magnetic generator provided on one of the holder and the base member, and a magnetic measuring unit provided on the other of the holder and the base member for measuring the magnetic field from the magnetic generator.

12. The liquid level sensor according to claim 11, wherein the magnetic measuring unit has a magnetoresistive element, and the direction in which the magnetic generator and the magnetoresistive element are aligned is non-parallel to the first axis.

13. The magnetic measuring unit comprises two full-bridge circuits having the magnetoresistive elements. The liquid level sensor according to claim 12, wherein, with respect to two full-bridge circuits, the sensitivity axis of the magnetoresistive element is set such that when the midpoint output of one outputs a sine wave, the midpoint output of the other outputs a sine wave that is 90° out of phase with the sine wave.

14. The liquid level sensor according to any one of claims 1 to 4, wherein the detection mechanism comprises a resistor provided on one of the holder and the base member, and a sliding contact provided on the other of the holder and the base member that contacts the resistor.

15. The liquid level sensor according to any one of claims 1 to 4, wherein the detection mechanism comprises a transmitter provided on one of the holder and the base member, and a receiver provided on the other of the holder and the base member for receiving a signal from the transmitter.

16. The liquid level sensor according to any one of claims 1 to 4, wherein the detection mechanism comprises a transmitter provided on one of the holder and the base member and a receiver that receives a signal from the transmitter, and a reflector provided on the other of the holder and the base member that reflects the signal from the transmitter back to the receiver.

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