Optical level detection device

Abstract

To identify a fault of an optical detection body used for detecting the liquid level of a liquid.SOLUTION: Provided is an optical level detection device 1 comprising a sensor unit 100 having a plurality of optical detection bodies 110, and a control unit 120. Each of the plurality of optical detection bodies 110 includes a luminous body 111, a light reception body 112, and a prism 113. The prism 113 is constituted to pass light from the luminous body 111 through in a liquid, and to reflect light from the luminous body 111 and guide it to the light reception body 112 in the outside of the liquid. The control unit 120 causes the luminous body 111 included in each of the plurality of optical detection bodies 110 to emit light, compares the voltage outputted from the light reception body 112 included in each of the optical detection bodies 110 with a first threshold Vth1, detects the presence of the liquid, causes the luminous body 111 included in each of the plurality of optical detection bodies 110 to not emit light, compares the voltage outputted from the light reception body 112 corresponding to the luminous body 111 that does not emit light with the first threshold Vth1, and identifies a fault of the light reception body 112.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an optical level detection device that detects the level of a liquid using a plurality of optical detectors, and more particularly to an optical level detection device capable of discriminating a failure of any one of the plurality of optical detectors.

Background Art

[0002] A level detection device for detecting the level (liquid level height) of a liquid such as fuel stored in a container is known. In this level detection device, a plurality of optical detectors each composed of a light emitter, a light receiver, and a prism are provided in the vertical direction, and the liquid level height is detected based on the difference between light reflection and transmission in the prism. This type of optical level detection device is described in Patent Document 1.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The optical level detection device described in Patent Document 1 is configured by providing a plurality of optical detectors each using a light emitter, a light receiver, and a prism in the vertical direction. When the optical detector is located in the liquid, the light irradiated from the light emitter travels from the surface in contact with the 90° angle of the prism toward the liquid. Therefore, the light irradiated from the light emitter does not reach the light receiver. On the other hand, when the optical detector is not located in the liquid but outside the liquid, the light irradiated from the light emitter is reflected at the 90° angle of the prism and travels toward the light receiver. Therefore, the light irradiated from the light emitter reaches the light receiver. In this way, the liquid level height can be detected based on the presence or absence of the sensor output signal in each of the plurality of optical detectors.

[0005] On one hand, in any of the plurality of optical detectors, due to a failure of the light emitter or the light receiver, a correct sensor output signal may not be output from the light receiver. In this case, in the case of a failure of the light emitter or an open failure in which the light receiver becomes insulated, the sensor output signal from the light receiver becomes the same state as when the optical detector is located in the liquid. For this reason, it is impossible to distinguish between whether it is in the liquid or a failure. Also, in the case of a short circuit failure in which the light receiver is in a short circuit state, the sensor output signal from the light receiver becomes the same state as when the optical detector is located outside the liquid (in the gas). For this reason, it is impossible to distinguish between whether it is outside the liquid or a failure.

[0006] Therefore, in the optical level detection device, it has been desired to be able to determine a failure of the optical detector. The present invention has been made to solve the above problems, and an object thereof is to provide an optical level detection device capable of determining a failure of an optical detector used for detecting the liquid level height of a liquid.

Means for Solving the Problems

[0007] The optical level detection device according to the present invention is an optical level detection device including a sensor unit having a plurality of optical detectors and a control unit, wherein each of the plurality of optical detectors includes a light emitter, a light receiver, and a prism, the prism is configured to transmit light from the light emitter in the liquid and reflect light from the light emitter outside the liquid and guide it to the light receiver, the control unit causes the light emitters included in each of the plurality of optical detectors to emit light, compares the voltage output from the light receivers included in each of the plurality of optical detectors with a first threshold value to detect the presence or absence of the liquid, does not cause the light emitters included in each of the plurality of optical detectors to emit light, and compares the voltage output from the light receiver corresponding to the light emitter that does not emit light with the first threshold value to determine a failure of the light receiver.

[0008] In the optical level detection device according to the present invention, each of the plurality of optical detectors is connected to a control unit, and the control unit controls whether or not to apply a light emission drive voltage to the light emitter included in each of the plurality of optical detectors, discriminates whether or not the light emission drive voltage is applied, and compares the voltage output from the light receiver corresponding to the light emitter for which it is discriminated that the light emission drive voltage is not applied with a first threshold value to determine a failure.

[0009] In the optical level detection device according to the present invention, the voltage output from the light receiver is in one of the following states: a first voltage output from the light receiver that receives the light from the light emitter reflected by the prism when the light emitters of the plurality of optical detectors emit light and each of the plurality of optical detectors is located outside the liquid; a second voltage output from the light receiver that does not receive the light from the light emitter when the light emitters of the plurality of optical detectors emit light and each of the plurality of optical detectors is located in the liquid; a third voltage output from a normal light receiver without causing the light emitters of each of the plurality of optical detectors to emit light; and a fourth voltage output from a light receiver in a short circuit failure state without causing the light emitters of each of the plurality of optical detectors to emit light.

[0010] In the optical level detection device according to the present invention, the control unit compares the first voltage, the second voltage, the third voltage, and the fourth voltage with the first threshold value, determines that the first voltage and the fourth voltage are in a first signal state, and determines that the second voltage and the third voltage are in a second signal state different from the first signal state.

[0011] In the optical level detection device according to the present invention, each of the plurality of optical detectors further includes a light guide unit configured to guide a part of the light from the light emitter to the light receiver, and the control unit causes the light emitters included in each of the plurality of optical detectors to emit light and compares the voltage output from the light receivers included in each of the plurality of optical detectors with a second threshold value for determining a failure of the optical detector.

[0012] In the optical level detection device according to the present invention, the light guide unit is configured to guide an amount of light from the light emitter to the light receiver that is less than the light reflected by the prism.

[0013] In the optical level detection device according to the present invention, a light shielding portion is provided between a light emitter and a light receiver, the light guiding portion includes a light transmitting portion, and the light transmitting portion is provided at any position of the light shielding portion.

[0014] In the optical level detection device according to the present invention, the light guiding portion includes a reflecting portion, and the reflecting portion is configured to reflect a part of the light from the light emitter that is about to pass through the prism and guide it to the light receiver.

[0015] In the optical level detection device according to the present invention, the voltage output from the light receiver is in any one of the following states: a first voltage output from the light receiver that receives the light from the light emitter reflected by the prism when the light emitters of a plurality of optical detectors emit light and each of the plurality of optical detectors is located outside the liquid; a fifth voltage output from the light receiver that receives the light from the light emitter guided by the light guiding portion when the light emitters of the plurality of optical detectors emit light and each of the plurality of optical detectors is located in the liquid; and a sixth voltage output from the light receiver when the light emitters of the plurality of optical detectors emit light and there is a failure in the light emitter or the light receiver. The control unit compares the first voltage, the fifth voltage, and the sixth voltage with a first threshold value and a second threshold value to detect the presence or absence of the liquid and discriminate the failure.

[0016] In the optical level detection device according to the present invention, the control unit determines that the first voltage is in a first signal state, determines that the sixth voltage is in a second signal state different from the first signal state, and determines that the fifth voltage is at a third level intermediate between the first signal state and the second signal state.

Effect of the Invention

[0017] In the optical level detection device according to the present invention, without causing the light emitters included in each of the plurality of optical detectors to emit light, the voltage output from the light receivers corresponding to the non-emitting light emitters is compared with a first threshold value for detecting the presence or absence of a liquid, thereby making it possible to determine a failure of the light receivers. Further, a part of the light from the light emitters is configured to be guided to the light receivers, the light emitters included in each of the plurality of optical detectors are caused to emit light, and the voltages output from the light receivers included in each of the plurality of optical detectors are compared with a first threshold value for detecting the presence or absence of a liquid and a second threshold value for determining a failure of the optical detector, thereby making it possible to determine a failure of the optical detector.

Brief Description of the Drawings

[0018]

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Mode for Carrying Out the Invention

[0019] Hereinafter, embodiments of the optical level detection device of the present invention will be described with reference to the drawings. In each figure, the same parts are denoted by the same reference numerals.

[0020] Embodiment 1. First, the basic configuration of the optical level detection device 1 in Embodiment 1 will be described with reference to FIGS. 1 to 3. FIG. 1 is a configuration diagram showing the configuration of the optical level detection device 1 according to Embodiment 1. FIG. 2 is a configuration diagram showing the overall configuration of the optical level detection device 1 according to Embodiment 1. FIG. 3 is a circuit diagram showing the connection between the light emitter and the light receiver of the optical level detection device 1 according to Embodiment 1.

[0021] [Configuration of Embodiment 1] The optical level detection device 1 mainly includes a sensor unit 100 and a control unit 120. The sensor unit 100 is provided with a case 101, a substrate 105, and a plurality of optical detectors 110. Here, as shown in FIG. 2, a case where 16 optical detectors 110A to 110P are provided in the sensor unit 100 is shown as a specific example. The control unit 120 may be mounted on the substrate 105. The case 101 has a waterproof function so that liquid 400 or the like does not enter the sensor unit 100. The substrate 105 is provided with wirings for supplying drive signals to the plurality of optical detectors 110 and supplying the detection signals obtained from the plurality of optical detectors 110 to the control unit 120. In FIG. 1, among the plurality of optical detectors 110A to 110P, the optical detectors 110A, 110B, 110C, 110O, and 110P are shown enlarged. Each of the plurality of optical detectors 110A to 110P includes a light emitter 111, a light receiver 112, a prism 113, and light shielding portions 114 to 116.

[0022] As the prism 113, a so-called right-angled prism having a 90° angle as a reflection angle can be used. Note that as the prism 113, it only needs to have a 90° angle located in a liquid or in a gas (outside the liquid), and it may be a triangular prism having angles of 90°, 45°, and 45°, or a pentagonal prism having angles of 90°, 135°, 135°, 90°, and 90°. Also, by adjusting the directions of the light emitter 111 and the light receiver 112, it is possible to set the reflection angle of the prism 113 located in a liquid or in a gas to other than 90°. For example, as the configuration and arrangement of the light emitter 111, the light receiver 112, and the prism 113, it is possible to use the configurations and arrangements of various prisms, light-emitting elements, and light-receiving elements described in Japanese Patent Application Laid-Open No. 2021-148590 by the applicant of the present application.

[0023] In the first embodiment, as a specific example, the prism 113 has a reflection angle of 90° (hereinafter simply referred to as the "reflection angle"), and the reflection angle of the prism 113 is arranged to be located in a liquid or a gas. The light emitter 111 and the light receiver 112 are provided facing the surface facing the reflection angle of the prism 113. The light emitter 111 irradiates light from the surface facing the reflection angle of the prism 113 toward one surface in contact with the reflection angle of the prism 113. The light receiver 112 receives the light reflected by the two surfaces in contact with the reflection angle of the prism 113. In this specification, when it is said that "reflected by the reflection angle", it means "reflected by the two surfaces in contact with the reflection angle". Similarly, when a prism 113 having a reflection angle other than 90° is used, it may be read as being reflected by the two surfaces in contact with the reflection angle.

[0024] The light shielding portion 114 blocks the leakage of light from the light emitter 111 so that the light from the light emitter 111 does not reach the light receiver 112 of the adjacent optical detector. The light shielding portion 115 is provided between the light emitter 111 and the light receiver 112, and blocks the leakage of light from the light emitter 111 so that the light from the light emitter 111 does not directly reach the light receiver 112. The light shielding portion 116 blocks the leakage of light from the adjacent optical detector 110 so that the light from the light emitter 111 of the adjacent optical detector does not reach the light receiver 112.

[0025] As shown in FIG. 2, the optical level detection device 1 uses the reflection or transmission of light by the prism 113 in each of the plurality of optical detectors 110A to 110P included in the sensor unit 100, and is used to detect the height of the liquid surface 401 in the container 300 as the liquid level height of the liquid 400.

[0026] In the optical level detection device 1, the light emitter 111 and the light receiver 112 in each of the plurality of optical detectors 110A to 110P are connected to the control unit 120 as photosensors PS_A to PS_P as shown in FIG. 3. The control unit 120 may be provided inside the substrate 105 or outside the substrate 105. Here, the light emitter 111 is composed of a photodiode, and the light receiver 112 is composed of a phototransistor. And the pair of the light emitter 111 and the light receiver 112 constitutes a photosensor PS. The control unit 120 controls the application of the light emission drive voltage from the terminal OUT to the light emitter 111 provided in each of the photosensors PS_A to PS_P. The control unit 120 takes in the sensor output signal of the light receiver 112 provided in each of the photosensors PS_A to PS_P corresponding to the application of the light emission drive voltage from the terminal IN. The control unit 120 detects the liquid level height of the liquid 400 by comparing the voltage of the sensor output signal taken in from the light receiver 112 provided in each of the photosensors PS_A to PS_P with a first threshold value Vth1 as a liquid level threshold value. The first threshold value Vth1 will be described later. Further, the control unit 120 discriminates the presence or absence of the application of the light emission drive voltage to the light emitter 111, and compares the voltage of the sensor output signal output from the light receiver 112 corresponding to the light emitter 111 for which it is discriminated that the light emission drive voltage is not applied with the first threshold value Vth1 to perform failure discrimination. The failure discriminated in this case is a short circuit failure in which the inside of the light receiver 112 is in a short circuit state.

[0027] [Failure Discrimination of Embodiment 1] Hereinafter, the detection of the liquid level height of the liquid 400 and the discrimination of the failure of each of the plurality of optical detectors 110A to 110P in the optical level detection device 1 will be described with reference to FIGS. 4 to 7. FIG. 4 is a characteristic diagram showing the characteristics of the sensor output signal during the liquid level height detection by the normal optical detectors 110A to 110P. FIG. 5 is a characteristic diagram showing the characteristics of the sensor output signal during the liquid level height detection in a comparative example where any one of the optical detectors 110A to 110P has failed. FIG. 6 is a characteristic diagram showing the characteristics of the sensor output signal during the failure determination of the optical level detection device 1 according to the first embodiment. The above FIGS. 4 to 6 show the states corresponding to the liquid level height of the liquid 400 shown in FIG. 2. FIG. 7 is an explanatory diagram for explaining the difference between the comparative example and the embodiment. Note that the sensor output signals in the characteristic diagrams of FIGS. 4 to 6 show a specific example in which the phototransistor constituting the light receiver 112 shown in FIG. 3 is constituted by an NPN-type transistor and the power supply voltage Vcc is +5V. When the phototransistor constituting the light receiver 112 is constituted by a PNP-type transistor, the characteristics of 0V and 5V in the characteristic diagrams of FIGS. 4 to 6 are inverted. Also, by changing the power supply voltage Vcc, a sensor output signal of an arbitrary voltage can be obtained.

[0028] When detecting the liquid level height of the liquid 400 shown in FIG. 2, if all of the optical detectors 110A to 110P are normal, the sensor output signal shown in FIG. 4 can be obtained from the light receivers 112 of the plurality of optical detectors 110A to 110P. In the optical detectors 110I to 110P located outside the liquid, the light from the light emitter 111 is reflected by the prism 113 and reaches the light receiver 112. Therefore, a current flows in the light receiver 112 of the optical detectors 110I to 110P corresponding to the light from the light emitter 111, and a first voltage E1 near 0V is output as the sensor output signal. On the other hand, in the optical detectors 110A to 110H located in the liquid, the light from the light emitter 111 travels through the liquid from the prism 113. Therefore, the light receiver 112 of the optical detectors 110A to 110H does not receive the light from the light emitter 111, and no current flows. Thus, a second voltage E2 near 5V is output as the sensor output signal. The control unit 120 compares the sensor output signals of the first voltage E1 and the second voltage E2 as described above with a first threshold value Vth1 which is a liquid level threshold value set in the middle of the first voltage E1 and the second voltage E2. By setting the first threshold value Vth1 in the middle of the first voltage E1 and the second voltage E2, it becomes possible to detect the liquid level height of the liquid 400 by comparing the sensor output signal from the photoreceptor 112 with the first threshold value Vth1. That is, the control unit 120 determines that the optical detectors 110I to 110P are in a first signal state which is a low level below the first threshold value Vth1, determines that the optical detectors 110A to 110H are in a second signal state which is a high level exceeding the first threshold value Vth1, and can detect that the liquid level height of the liquid 400 is the height of the optical detector 110H.

[0029] Here, among the plurality of optical detectors 110A to 110P, assume that there is a short circuit failure in which the photoreceptors 112 of the optical detectors 110E, 110H, and 110M are short-circuited, and the light emitters 111 and the photoreceptors 112 are normal otherwise. The sensor output signals from the optical detectors 110A to 110P at this time are shown in FIG. 5.

[0030] In the normal optical detectors 110I to 110L, and 110N to 110P located outside the liquid, the light from the light emitter 111 is reflected by the prism 113 and reaches the photoreceptor 112. For this reason, an electric current flows in the photoreceptors 112 of the optical detectors 110I to 110L, and 110N to 110P corresponding to the light from the light emitter 111, and a first voltage E1 around 0V is output as a sensor output signal. In the normal optical detectors 110A to 110D, and 110F to 110G located in the liquid, the light from the light emitter 111 travels through the liquid from the prism 113 and does not reach the photoreceptor 112. For this reason, the photoreceptors 112 of the optical detectors 110A to 110D, and 110F to 110G output a second voltage E2 around 5V as a sensor output signal.

[0031] In the optical detectors 110E, 110H, and 110M, due to a short circuit fault in the photoreceptor 112, the sensor output signal becomes the same state as the first voltage E1 near 0V from the photoreceptor 112. For this reason, the optical detectors 110E, 110H, and 110M are in the same state as being located outside the liquid. In the optical detector 110E, as shown in [E] of FIG. 5, due to a short circuit fault in the photoreceptor 112, the sensor output signal becomes the first voltage E1, and it is misjudged as being outside the liquid (in the gas) (see the comparative example in FIG. 7, in the liquid). However, since the adjacent optical detectors 110D and 110F show the second voltage E2 in the liquid, and it can be estimated that the optical detector 110E is located in the liquid, it can be determined that it is a short circuit fault of the photoreceptor 112. In the optical detector 110H, as shown in [H] of FIG. 5, due to a short circuit fault in the photoreceptor 112, the sensor output signal becomes the first voltage E1, and it is misjudged as being outside the liquid (in the gas) (see the comparative example in FIG. 7, in the liquid). Note that the adjacent optical detectors 110G and 110I show the second voltage E2 and the first voltage E1 respectively, and it is unclear whether it is located in the liquid or is faulty, and it cannot be determined that it is a fault. In the optical detector 110M, as shown in [M] of FIG. 5, due to a short circuit fault in the photoreceptor 112, the sensor output signal becomes the first voltage E1, but the adjacent optical detectors 110L and 110N show the first voltage E1 respectively, and it is unclear whether it is located outside the liquid or is faulty, and it cannot be determined that it is a fault (see the comparative example in FIG. 7, outside the liquid (in the gas)). And when the sensor output signals of the first voltage E1 and the second voltage E2 as described above are compared with the first threshold Vth1 as the liquid level threshold, the liquid level height of the liquid 400 is erroneously detected as being the height of the optical detector 110G instead of the height of the original optical detector 110H.

[0032] Hereinafter, with reference to FIG. 6, the determination of the short circuit fault of the photoreceptor 112 included in the optical detector 110 will be described. Here, as in FIG. 5, it is assumed that the photoreceptor 112 in the optical detectors 110E, 110H, and 110M has a short circuit fault. The control unit 120 controls the light emitters 111 provided in each of the plurality of optical detectors 110 to be in a non-light-emitting state. The voltage output from the photoreceptor 112 corresponding to the non-light-emitting light emitter 111 is compared with a first threshold value Vth1 to determine a failure of the photoreceptor 112. Specifically, the control unit 120 identifies whether or not a light emission drive voltage is applied to the light emitter 111, and compares the voltage output from the photoreceptor 112 corresponding to the light emitter 111 for which it is identified that no light emission drive voltage is applied with the first threshold value Vth1 to determine a failure.

[0033] That is, the photoreceptors 112 of the normal optical detectors 110A to 110D, 110F to 110G, 110I to 110L, and 110N to 110P do not receive any light, and thus output a third voltage E3 of around 5V as a sensor output signal. On the other hand, in the optical detectors 110E, 110H, and 110M, due to a short circuit failure of the photoreceptor 112, current flows through the phototransistor of the photoreceptor 112 that does not receive any light, and a fourth voltage E4 of around 0V is output. The control unit 120 compares the third voltage E3 output as a sensor output signal from the photoreceptors 112 of the optical detectors 110A to 110D, 110F to 110G, 110I to 110L, and 110N to 110P with the first threshold value Vth1. The third voltage E3 is in a high-level second signal state exceeding the first threshold value Vth1. The control unit 120 determines that the photoreceptors 112 of the optical detectors 110A to 110D and 110F to 110G are normal. The control unit 120 compares the fourth voltage E4 output as a sensor output signal from the photoreceptors 112 of the optical detectors 110E and 110H with the first threshold value Vth1. The fourth voltage E4 is in a low-level first signal state less than the first threshold value Vth1. The control unit 120 identifies that no light emission drive voltage is applied to the photoreceptors 112 of the optical detectors 110E and 110H, and determines that there is a photoreceptor short circuit failure because the sensor output signal is in the first signal state less than the first threshold value Vth1 (refer to Embodiment 1 in liquid in FIG. 7). The control unit 120 compares the fourth voltage E4 output as a sensor output signal from the light receiver 112 of the optical detector 110M with a first threshold value Vth1. The fourth voltage E4 is in a first signal state less than the first threshold value Vth1. The control unit 120 identifies that no light emission drive voltage is applied to the light receiver 112 of the optical detector M, and determines that there is a short circuit failure in the light receiver since the sensor output signal is in the first signal state less than the first threshold value Vth1 (refer to Embodiment 1 in FIG. 7, outside the liquid (in gas)).

[0034] That is, in Embodiment 1, the voltage of the sensor output signal output from the light receiver 112 is · The first voltage E1 near 0V output from the light receiver 112 that receives the light from the light emitter 111 reflected by the prism 113 when the optical detector 110 is located outside the liquid, · The second voltage E2 near 5V output from the light receiver 112 that does not receive the light from the light emitter 111 when the optical detector 110 is located in the liquid, · The third voltage E3 near 5V output from the light receiver 112 that is not short-circuited, to which no light emission drive voltage is applied, the light emitter 111 does not emit light, and the light receiver 112 does not receive the light from the light emitter 111, · The fourth voltage E4 near 0V output from the light receiver 112 to which no light emission drive voltage is applied, the light emitter 111 does not emit light, and due to the short circuit failure of the light receiver 112, current flows through the phototransistor of the light receiver 112 although no light is received, and is one of the above.

[0035] When detecting the liquid level height of the liquid 400, the control unit 120 compares the first voltage E1 and the second voltage E2 shown in FIG. 4 with the first threshold value Vth1. On the other hand, when determining the short circuit failure of the light receiver 112, the control unit 120 compares the third voltage E3 and the fourth voltage E4 with the first threshold value Vth1. As described above, the control unit 120 can reliably and quickly detect the liquid level height of the liquid 400 and determine the short circuit failure of the light receiver 112. The control unit 120 outputs the liquid level height of the liquid 400 detected by the optical level detection device 1 to the outside, and outputs, as failure information, those among the plurality of optical detectors 110A to 110P that are determined to have failed to the outside. The short circuit failure determination of the light receiver 112 in the first embodiment may be executed as a failure diagnosis when the optical level detection device 1 is started up, at the start of measurement, during a temporary pause in measurement, or at the end of measurement.

[0036] [Effects Obtained by the First Embodiment] The optical level detection device 1 described in the first embodiment above includes a sensor unit 100 having a plurality of optical detectors 110 and a control unit 120. Each of the plurality of optical detectors 110 includes a light emitter 111, a light receiver 112, and a prism 113. The prism 113 is configured to transmit the light from the light emitter 111 in the liquid and reflect the light from the light emitter 111 outside the liquid and guide it to the light receiver 112. The control unit 120 causes the light emitter 111 included in each of the plurality of optical detectors 110 to emit light, compares the voltage output from the light receiver 112 included in each of the plurality of optical detectors 110 with a first threshold value Vth1, and detects the presence or absence of the liquid. The control unit 120 does not cause the light emitter 111 included in each of the plurality of optical detectors 110 to emit light, compares the voltage output from the light receiver 112 corresponding to the non-emitting light emitter 111 with the first threshold value Vth1, and determines the failure of the light receiver 112. Here, when the light emitter 111 does not emit light, no current flows through the normal light receiver 112, but when the light emitter 111 does not emit light, current flows through the light receiver 112 with a short circuit failure. Therefore, by comparing the voltage output from the light receiver 112 corresponding to the non-emitting light emitter 111 with the first threshold value Vth1, it is possible to reliably and quickly determine the short circuit failure of the light receiver 112 included in the optical detector.

[0037] In the optical level detection device 1 described in the above Embodiment 1, each of the plurality of optical detectors 110 is connected to the control unit 120. The control unit 120 controls whether or not to apply a light emission driving voltage to the light emitter 111 included in each of the plurality of optical detectors 110, discriminates whether or not a light emission driving voltage is applied to the light emitter 111, and compares the voltage output from the light receiver 112 corresponding to the light emitter 111 for which it is discriminated that no light emission driving voltage is applied with a first threshold value Vth1 to determine a failure. Therefore, by discriminating that no light emission driving voltage is applied and comparing the voltage output from the light receiver 112 corresponding to the discriminated light emitter 111 with the first threshold value Vth1, it is possible to surely and quickly determine a short circuit failure of the light receiver 112.

[0038] In the optical level detection device 1 described in the above Embodiment 1, the voltage output from the light receiver 112 is · a first voltage E1 output from the light receiver 112 that emits light from the light emitters 111 of the plurality of optical detectors 110 and receives the light from the light emitter 111 reflected by the prism 113 when each of the plurality of optical detectors 110 is located outside the liquid, · a second voltage E2 output from the light receiver 112 that emits light from the light emitters 111 of the plurality of optical detectors 110 and does not receive the light from the light emitter 111 when each of the plurality of optical detectors 110 is located in the liquid, · a third voltage E3 output from the light receiver 112 that does not emit light from the light emitters 111 of each of the plurality of optical detectors 110 and has no short circuit failure, · a fourth voltage E4 output from the light receiver 112 that does not emit light from the light emitters 111 of each of the plurality of optical detectors 110 and is in a short circuit failure state, and is in any one of these states. Therefore, since the liquid level height of the liquid 400 is detected from the first voltage E1 and the second voltage E2, and a short circuit failure of the light receiver 112 is determined from the third voltage E3 and the fourth voltage E4, it is possible to surely perform the liquid level height detection of the liquid 400 and the determination of the short circuit failure of the light receiver 112.

[0039] In the optical level detection device 1 described in the above Embodiment 1, the control unit 120 compares the first voltage E1, the second voltage E2, the third voltage E3, and the fourth voltage E4 with a first threshold value Vth1 that is a liquid level threshold value, determines that the first voltage E1 and the fourth voltage E4 are in a first signal state, and determines that the second voltage E2 and the third voltage E3 are in a second signal state different from the first signal state. Thereby, it is possible to surely perform the detection of the liquid level height of the liquid 400 and the determination of the short circuit failure of the light receiver 112 by the determination using the common first threshold value Vth1.

[0040] Embodiment 2. The basic configuration of the optical level detection device 1 in Embodiment 2 will be described with reference to FIGS. 8 and 9. FIG. 8 is a configuration diagram showing the configuration of the optical level detection device 1 according to Embodiment 2. FIG. 9 is an explanatory diagram showing the configuration of the main part of the optical level detection device 1 according to Embodiment 2. In these FIGS. 8 and 9, the same components as those described in Embodiment 1 are denoted by the same reference numerals, and redundant explanations are omitted, and the description will be centered on the different parts.

[0041] [Configuration of Embodiment 2] The optical level detection device 1 mainly includes a sensor unit 100 and a control unit 120. The sensor unit 100 is provided with a case 101, a substrate 105, and a plurality of optical detectors 110. Here, as in Embodiment 1, a case where 16 optical detectors 110A to 110P are provided in the sensor unit 100 is shown as a specific example. In FIG. 8, among the plurality of optical detectors 110A to 110P, the optical detector 110A, the optical detector 110B, the optical detector 110C, the optical detector 110O, and the optical detector 110P are shown enlarged. In FIG. 9, the optical detector 110H and the optical detector 110I are shown further enlarged.

[0042] Each of the plurality of optical detectors 110A to 110P includes a light emitter 111, a light receiver 112, a prism 113, light shielding portions 114 to 116, and a light guide portion 117. The light emitter 111 irradiates light from the surface facing the reflection angle of the prism 113 toward one surface in contact with the reflection angle of the prism 113. The light receiver 112 receives the light reflected by the two surfaces in contact with the reflection angle of the prism 113.

[0043] The light shielding portion 114 blocks the leakage of light from the light emitter 111 so that the light from the light emitter 111 does not reach the light receiver 112 of the adjacent optical detector. The light shielding portion 115 is provided between the light emitter 111 and the light receiver 112. The light shielding portion 115 blocks the leakage of light from the light emitter 111 so that the light from the light emitter 111 does not directly reach the light receiver 112, except in the case of the light guide portion 117. The light shielding portion 116 blocks the leakage of light from the adjacent optical detector 110 so that the light from the light emitter 111 of the adjacent optical detector does not reach the light receiver 112.

[0044] The light guide portion 117 is configured to guide a part of the light from the light emitter 111 to the light receiver 112 within the same optical detector. The light guide portion 117 is configured to guide an amount of light less than the light reflected by the reflection angle of the prism 113 from the light emitter 111 to the light receiver 112 within the same optical detector. As shown in FIG. 9, the light guide portion 117 can be configured as a light transmission portion 117a at any position of the light shielding portion 115. Note that it is also possible to configure the entire light shielding portion 115 with a translucent member having a predetermined density or light transmittance and having the same light transmission characteristics as the light transmission portion 117a.

[0045] [Fault discrimination in Embodiment 2] Hereinafter, regarding the optical level detection device 1 of Embodiment 2, the detection of the liquid level height of the liquid 400 and the discrimination of faults will be described with reference to FIGS. 10 to 16 using a plurality of optical detectors 110A to 110P. FIG. 10 is an explanatory diagram showing a liquid level height detection state in a comparative example without the light guide unit 117. FIG. 11 is an explanatory diagram showing a liquid level height detection state of the optical level detection device 1 according to the second embodiment. FIG. 12 is a characteristic diagram showing the characteristics of the sensor output signal during liquid level height detection by the normal optical detectors 110A to 110P. FIG. 13 is a characteristic diagram showing the characteristics of the sensor output signal during liquid level height detection in a comparative example where any one of the optical detectors 110A to 110P has failed. FIG. 14 is a characteristic diagram showing the characteristics of the sensor output signal during liquid level height detection of the optical level detection device 1 according to the second embodiment. FIG. 15 is a characteristic diagram showing the characteristics of the sensor output signal during failure determination of the optical level detection device 1 according to the second embodiment. FIG. 16 is an explanatory diagram explaining the difference between the comparative example and the second embodiment.

[0046] Note that the sensor output signals in the characteristic diagrams of FIGS. 12 to 15 show a specific example when the phototransistor is constituted by an NPN-type transistor and the power supply voltage Vcc is +5V in the connection with the control unit 120 described in FIG. 3.

[0047] When detecting the liquid level height of the liquid 400 using the plurality of optical detectors 110A to 110P, when the liquid level height of the liquid 400 is at the position of the optical detector 110H and all of the optical detectors 110A to 110P are normal, the sensor output signal of FIG. 12 can be obtained. Hereinafter, description will be made with reference to FIG. 12. In the optical detectors 110I to 110P located outside the liquid, the light from the light emitter 111 is reflected by the prism 113 and reaches the light receiver 112. Therefore, a current flows in the light receiver 112 of the optical detectors 110I to 110P corresponding to the light from the light emitter 111, and a first voltage E1 near 0V is output as the sensor output signal.

[0048] In the optical detectors 110A to 110H located in the liquid, the light from the light emitter 111 travels from the prism 113 into the liquid. Therefore, the light receiver 112 of the optical detectors 110A to 110H does not receive the light from the light emitter 111, no current flows, and a second voltage E2 near 5V is output as the sensor output signal. The control unit 120 compares the sensor output signals of the first voltage E1 and the second voltage E2 as described above with a first threshold value Vth1, which is a liquid level threshold value set between the first voltage E1 and the second voltage E2. The control unit 120 determines that the optical detectors 110I to 110P are in a first signal state, which is a low level below the first threshold value Vth1, and determines that the optical detectors 110A to 110H are in a second signal state, which is a high level exceeding the first threshold value Vth1, and can detect that the liquid level height of the liquid 400 is the height of the optical detector 110H.

[0049] · Comparative example: FIG. 10 shows an enlarged view of the optical detectors 110D and 110H to 110L, omitting the optical detectors 110A to 110C, 110E to 110G, and 110M to 110P among the plurality of optical detectors 110A to 110P used in the comparative example. Here, it is assumed that there is a failure of the light emitter 111 or an open failure of the light receiver 112 in the optical detectors 110D, 110I, and 110K. As an example, FIG. 10 shows a state in which the light emitter 111 does not emit light due to a failure in the optical detectors 110D, 110I, and 110K. In the optical detectors 110H and 110L, although the light from the light emitter 111 reaches the light receiver 112, it is assumed that a normal sensor output signal cannot be output due to a short failure of the light receiver 112. Among the plurality of optical detectors 110A to 110P, it is assumed that those other than the optical detectors 110D, 110H, 110I, 110K, and 110L are normal.

[0050] The sensor output signals from the optical detectors 110A to 110P in the comparative example as described above are shown in FIG. 13. (Comparative example: Normal optical detector) In the normal optical detectors 110A to 110C and 110E to 110G located in the liquid, the light from the light emitter 111 travels through the prism 113 into the liquid and does not reach the light receiver 112. For this reason, no current flows through the light receivers 112 of the optical detectors 110A to 110C and 110E to 110G, and a second voltage E2 of around 5V is output as a sensor output signal. In the normal optical detectors 110J and 110M to 110P located outside the liquid, the light from the light emitter 111 is reflected by the prism 113 and reaches the light receiver 112. Therefore, in the light receivers 112 of the optical detectors 110J and 110M to 110P, a current flows corresponding to the light from the light emitter 111, and a first voltage near 0V is output as a sensor output signal.

[0051] (Comparative Example: Faulty Optical Detector in Liquid) In the optical detector 110D, due to at least one of a failure of the light emitter 111 or an open failure of the light receiver 112, no current flows through the light receiver 112. Therefore, in the optical detector 110D, the sensor output signal indicates a second voltage E2 near 5V, and it is unknown whether it is normally located in the liquid or is faulty, and it cannot be determined that it is faulty (refer to the comparative example in Fig. 16, light emitter failure · light receiver open failure, column in liquid). Since the light receiver 112 of the optical detector 110H has a short circuit failure, a current flows through the light receiver 112 regardless of light reception. Therefore, in the optical detector 110H, the sensor output signal becomes the first voltage E1 near 0V ((H) in Fig. 13), but it is misjudged as being outside the liquid, and it cannot be determined that it is faulty (refer to the comparative example in Fig. 16, light receiver short circuit failure, column in liquid).

[0052] (Comparative Example: Faulty Optical Detector outside Liquid) In the optical detectors 110I and 110K, due to at least one of a failure of the light emitter 111 or an open failure of the light receiver 112, no current flows through the light receiver 112. Therefore, the optical detectors 110I and 110K indicate a second voltage E2 near 5V for the sensor output signal ((I) and (K) in Fig. 13), and are misjudged as being in the liquid regardless of being outside the liquid, and it cannot be determined that they are faulty (refer to the comparative example in Fig. 16, light emitter failure · light receiver open failure, column outside liquid (in gas)). Since the optical detector 110L has a short circuit fault in the light receiver 112, current flows through the light receiver 112 regardless of whether light is received. For this reason, in the optical detector 110L, the sensor output signal becomes the first voltage E1 (in (L) of FIG. 13) near 0V, but it is not known whether it is normal and located outside the liquid or is faulty, and it is impossible to determine that it is faulty (see the comparative example, light receiver short circuit fault, outside the liquid (in gas) column in FIG. 16).

[0053] · Embodiment 2: FIG. 11 omits the optical detectors 110A to 110C, 110E to 110G, and 110M to 110P among the plurality of optical detectors 110A to 110P in the optical level detection device 1 according to Embodiment 2, and enlarges and shows the optical detectors 110D and 110H to 110L. Here, assume that there is a fault in the light emitter 111 or an open circuit fault in the light receiver 112 in the optical detectors 110D, 110I, and 110K among the plurality of optical detectors 110A to 110P. As an example, FIG. 10 shows a state in which the light emitters 111 in the optical detectors 110D, 110I, and 110K do not emit light due to a fault. In the optical detectors 110H and 110L, although the light from the light emitter 111 reaches the light receiver 112, it is assumed that a normal sensor output signal cannot be output due to a short circuit fault in the light receiver 112. And assume that among the plurality of optical detectors 110A to 110P, those other than the optical detectors 110D, 110H, 110I, 110K, and 110L are normal.

[0054] The sensor output signals from the optical detectors 110A to 110P in Embodiment 2 as described above are shown in FIG. 14. In the description of FIG. 14, the voltage near 0V will be referred to as the first voltage E1, the voltage near 4V will be referred to as the fifth voltage E5, and the voltage near 5V will be referred to as the sixth voltage E6. (Embodiment 2: Normal optical detector) In the normal optical detectors 110J and 110M to 110P located outside the liquid, the light from the light emitter 111 is reflected by the prism 113 and reaches the light receiver 112. Therefore, an electric current flows through the light receiver 112 of the optical detectors 110J and 110M to 110P in response to the light from the light emitter 111, and a first voltage E1 around 0V is output as a sensor output signal. In the normal optical detectors 110A to 110C and 110E to 110G located in the liquid, most of the light from the light emitter 111 travels from the prism 113 into the liquid, but a part of the light from the light emitter 111 reaches the light receiver 112 through the light guide portion 117. Therefore, an electric current flows through the light receiver 112 of the optical detectors 110A to 110C and 110E to 110G in response to a part of the light from the light emitter 111, and a fifth voltage E5 around 4V is output as a sensor output signal. Note that the voltage value of the fifth voltage E5 can be adjusted in the range of 3V to 4V between the first voltage E1 around 0V and the sixth voltage E6 around 5V according to the amount of light reaching the light receiver 112 through the light guide portion 117.

[0055] (Embodiment 2: Optical Detector with Light Emitter Failure and Light Receiver Open Failure) In the optical detector 110D in the liquid, which is a failure of the light emitter 111 or an open failure of the light receiver 112, due to the failure of at least one of the light emitter 111 or the light receiver 112, no current flows through the light receiver 112, and a sixth voltage E6 around 5V is output as a sensor output signal (refer to [D] in Fig. 14, the embodiment in Fig. 16, light emitter failure and light receiver open failure, and in the liquid). In the optical detectors 110I and 110K outside the liquid, which are a failure of the light emitter 111 or an open failure of the light receiver 112, due to the failure of at least one of the light emitter 111 or the light receiver 112, no current flows through the light receiver 112, and a sixth voltage E6 around 5V is output as a sensor output signal (refer to [I] and [K] in Fig. 14, the embodiment in Fig. 16, light emitter failure and light receiver open failure, and the column of outside the liquid (in gas)).

[0056] That is, the voltage of the sensor output signal output from the light receiver 112 of the normal optical detector 110 or the light receiver 112 of the optical detector 110 with a light emitter failure or a light receiver open failure is · The first voltage E1 near 0V output from the light receiver 112 that receives the light from the light emitter 111 reflected by the prism 113 when the normal optical detector 110 is located outside the liquid, · The fifth voltage E5 near 4V output from the light receiver 112 that receives the light from the light emitter 111 guided by the light guide portion 117 when the normal optical detector 110 is located in the liquid, · The sixth voltage E6 near 5V output from the light receiver 112 when there is a failure of the light emitter 111 or an open failure of the light receiver 112, and it becomes any one of them.

[0057] As shown in FIG. 14, the control unit 120 preliminarily determines a first threshold value Vth1 as a liquid level threshold value in the middle of the first voltage E1 and the fifth voltage E5, and preliminarily determines a second threshold value Vth2 as a failure determination threshold value in the middle of the fifth voltage E5 and the sixth voltage E6. Then, the control unit 120 compares any one of the first voltage E1, the fifth voltage E5, and the sixth voltage E6 output from each light receiver 112 with the first threshold value Vth1 and the second threshold value Vth2, so that when detecting the liquid level height of the liquid 400 using a plurality of optical detectors 110, the failure of the optical detector 110 can be determined.

[0058] In the optical detector 110D, as shown in [D] of FIG. 14, the sensor output signal becomes the sixth voltage E6 due to a failure of the light emitter 111 or an open failure of the light receiver 112. This sixth voltage E6 can be discriminated from the fifth voltage E5 of the normal sensor output signal when located in the liquid by comparison with the second threshold value Vth2. Therefore, the control unit 120 can determine that the optical detector 110D has failed. In the optical detector 110I, as shown in [I] of FIG. 14, due to a failure of the light emitter 111 or an open failure of the light receiver 112, the sensor output signal becomes the sixth voltage E6. This sixth voltage E6 can be discriminated from the fifth voltage E5 of the normal sensor output signal when located in the liquid by comparison with the second threshold Vth2. Therefore, the control unit 120 can determine that the optical detector 110I has failed. In the optical detector 110K, as shown in [K] of FIG. 14, due to a failure of the light emitter 111 or an open failure of the light receiver 112, the sensor output signal becomes the sixth voltage E6. This sixth voltage E6 can be determined to be a failure by comparison with the second threshold Vth2. For this reason, comparison with the adjacent optical detectors 110J and 110L becomes unnecessary, the failure determination process is simplified, and the failure can be determined more quickly than in the comparative example.

[0059] Note that according to the above failure determination, for the short-circuited light receivers 112 in the optical detectors 110H and 110L, the sensor output signal is near 0V, and it is unknown whether it is normal and located outside the liquid or a failure, and it cannot be determined that it is a failure. Therefore, the light receiver short-circuit failure determination described below is executed.

[0060] (Embodiment 2: Optical Detector with Light Receiver Short-Circuit Failure) Hereinafter, with reference to FIG. 15, the determination of the short-circuit failure of the light receiver 112 included in the optical detector 110 will be described. Here, as in FIGS. 13 to 14, it is assumed that the light receivers 112 in the optical detectors 110H and 110L have a short-circuit failure. In this light receiver short-circuit failure determination process, the control unit 120 controls the light emitters 111 included in each of the plurality of optical detectors 110 to be in a non-light-emitting state. The voltage output from the light receiver 112 corresponding to the non-light-emitting light emitter 111 is compared with the first threshold Vth1 to determine the failure of the light receiver 112. Specifically, the control unit 120 identifies the presence or absence of the application of the light emission drive voltage to the light emitter 111, and compares the voltage output from the light receiver 112 corresponding to the light emitter 111 for which it is identified that the light emission drive voltage is not applied with the first threshold Vth1 to determine the failure.

[0061] Since the photoreceptors 112 of the optical detectors 110A to 110G, 110I to 110K, and 110M to 110P are not short-circuited, and the photoreceptors 112 do not receive any light, a third voltage E3 around 5V is output as a sensor output signal. The control unit 120 compares the third voltage E3 output as a sensor output signal from the photoreceptors 112 of the optical detectors 110A to 110G, 110I to 110K, and 110M to 110P with the first threshold value Vth1. The third voltage E3 is in a high-level second signal state exceeding the first threshold value Vth1. The control unit 120 determines that the photoreceptors 112 of the optical detectors 110A to 110G, 110I to 110K, and 110M to 110P are normal.

[0062] In the optical detector 110H, since the photoreceptor 112 is short-circuited, current flows through the phototransistor of the photoreceptor 112 that does not receive any light, and a fourth voltage E4 around 0V is output. The control unit 120 compares the fourth voltage E4 output as a sensor output signal from the photoreceptor 112 of the optical detector 110H with the first threshold value Vth1. The fourth voltage E4 is in a low-level first signal state less than the first threshold value Vth1. The control unit 120 identifies that the light emission drive voltage is not applied to the photoreceptor 112 of the optical detector 110H, and since the sensor output signal is in the first signal state less than the first threshold value Vth1, the control unit 120 determines that the photoreceptor 112 of the optical detector 110H has a photoreceptor short-circuit failure (refer to (H) in FIG. 15, the embodiment in FIG. 16, photoreceptor short-circuit failure, and the column in the liquid).

[0063] In the optical detector 110L, since the photoreceptor 112 is short-circuited, current flows through the phototransistor of the photoreceptor 112 that does not receive any light, and a fourth voltage E4 around 0V is output. The control unit 120 compares the fourth voltage E4 output as a sensor output signal from the light receiver 112 of the optical detector 110L with the first threshold value Vth1. The fourth voltage E4 is in a first signal state at a low level below the first threshold value Vth1. The control unit 120 identifies that the light emission drive voltage is not applied to the light receiver 112 of the optical detector 110L, and since the sensor output signal is in the first signal state below the first threshold value Vth1, it determines that the light receiver 112 of the optical detector 110L has a short circuit failure of the light receiver (refer to (L) in FIG. 15, the embodiment in FIG. 16, short circuit failure of the light receiver, outside the liquid (in gas)).

[0064] That is, the voltage of the sensor output signal output from the light receiver 112 in Embodiment 2 is · The first voltage E1 near 0V output from the light receiver 112 that receives the light from the light emitter 111 reflected by the prism 113 when the optical detector 110 is located outside the liquid, · The third voltage E3 near 5V output from the light receiver 112 that does not have the light emission drive voltage applied, the light emitter 111 does not emit light, there is no short circuit failure, and the light from the light emitter 111 is not received, · The fourth voltage E4 near 0V output from the light receiver 112 that does not have the light emission drive voltage applied, the light emitter 111 does not emit light, due to the short circuit failure of the light receiver 112, current flows through the phototransistor of the light receiver 112 although no light is received, · The fifth voltage E5 near 4V output from the light receiver 112 that receives the light from the light emitter 111 guided by the light guide unit 117 when the optical detector 110 is located in the liquid, · The sixth voltage E6 near 5V output from the light receiver 112 in the event of a failure of the light emitter 111 or an open circuit failure of the light receiver 112, and is one of these.

[0065] The control unit 120 compares the first voltage E1 and the fifth voltage E5 with the first threshold value Vth1 to detect the liquid level height of the liquid 400. The control unit 120 compares the fifth voltage E5 and the sixth voltage E6 with the second threshold value Vth2 to detect a failure of the light emitter 111 or an open failure of the light receiver 112. The control unit 120 compares the third voltage E3 and the fourth voltage E4 with the first threshold value Vth1 to detect a short failure of the light receiver 112. As described above, the control unit 120 can surely and quickly detect the liquid level height of the liquid 400, determine a failure of the light emitter 111 or an open failure of the light receiver 112, and determine a short failure of the light receiver 112. The control unit 120 outputs the liquid level height of the liquid 400 detected by the optical level detection device 1 to the outside, and outputs the one determined to be a failure among the plurality of optical detection elements 110A to 110P to the outside as failure information. The failure determination between the light emitter 111 and the light receiver 112 in the second embodiment may be executed as a failure diagnosis at the time of starting the optical level detection device 1, at the start of measurement, during a temporary pause in measurement, or at the end of measurement.

[0066] · Modification Example of the Second Embodiment Here, a modification example of the optical level detection device 1 according to the second embodiment will be described with reference to FIG. 17. FIG. 17 is an explanatory diagram showing the configuration of a modification example of the optical level detection device 1 according to the second embodiment. In FIG. 17, among the plurality of optical detection elements 110A to 110P, the optical detection element 110H and the optical detection element 110I are shown enlarged. It is assumed that the optical detection elements 110A to 110G and 110J to 110P not shown here also have the same configuration. In the optical detection element 110H and the optical detection element 110I shown in FIG. 17, a reflection portion 117b as a light guide portion 117 is provided in a partial region of the prism 113. The reflection portion 117b reflects a part of the light from the light emitter 111 that is about to pass through the prism 113 and guides it to the light receiver 112. Here, a partial region of the prism 113 refers to any region of the surface that sandwiches the reflection angle located inside or outside the liquid. As a result, the reflecting portion 117b can guide a smaller amount of light from the light emitter 111 to the light receiver 112 than the light reflected by the reflection angle of the prism 113 within the same optical detector. Note that the reflecting portion 117b can be separated into a pair of reflecting portions so as to sandwich the reflection angle of the prism 113 and perform similar reflection. As the light guiding portion 117, it is also possible to use a mixture of the light transmitting portion 117a described in the second embodiment and the reflecting portion 117b described in the modification of the second embodiment. Further, as the light guiding portion 117, it is also possible to use the light transmitting portion 117a and the reflecting portion 117b in combination.

[0067] [Effects Obtained by the Second Embodiment] The optical level detection device 1 described in the above second embodiment includes a sensor unit 100 having a plurality of optical detectors 110 and a control unit 120. Each of the plurality of optical detectors 110 includes a light emitter 111, a prism 113, a light guiding portion 117, and a light receiver 112. The prism 113 is configured to transmit light from the light emitter 111 in the liquid and reflect light from the light emitter 111 outside the liquid and guide it to the light receiver 112. The light guiding portion 117 is configured to guide a part of the light from the light emitter 111 to the light receiver 112. The control unit 120 causes the light emitter 111 included in each of the plurality of optical detectors 110 to emit light, and compares the voltage of the sensor output signal output from the light receiver 112 included in each of the plurality of optical detectors 110 with a first threshold for detecting the presence or absence of the liquid and a second threshold for diagnosing a failure of the optical detector 110. Thereby, when detecting the liquid level height of the liquid 400 using the plurality of optical detectors 110, it is possible to discriminate a failure of the light emitter 111 or an open failure of the light receiver 112 included in the optical detector 110.

[0068] In the optical level detection device 1 described in the above second embodiment, the light guiding portion 117 guides a smaller amount of light from the light emitter 111 to the light receiver 112 than the light reflected by the prism 113. This makes it possible to set the voltages of the sensor output signals output from the photoreceptor 112 to different voltages, and when detecting the liquid level height of the liquid 400 using a plurality of optical detectors 110, it becomes possible to reliably determine the failure of the optical detector 110.

[0069] In the optical level detection device 1 described in the above Embodiment 2, a light shielding portion 115 is provided between the light emitter 111 and the photoreceptor 112. A light transmission portion 117a is provided as a light guide portion 117 at any position of the light shielding portion 115. Thereby, the light guide portion 117 can surely guide a smaller amount of light from the light emitter 111 to the photoreceptor 112 than the light reflected by the prism 113, and when detecting the liquid level height of the liquid 400 using a plurality of optical detectors 110, it becomes possible to surely determine the failure of the optical detector 110.

[0070] In the optical level detection device 1 described in the above Embodiment 2, the light guide portion 117 includes a reflection portion 117b. The reflection portion 117b reflects a part of the light from the light emitter 111 that is about to pass through the prism 113 by the reflection portion 117b and guides it to the photoreceptor 112. Thereby, the light guide portion 117 can surely guide a smaller amount of light from the light emitter 111 to the photoreceptor 112 than the light reflected by the prism 113 outside the liquid, and when detecting the liquid level height of the liquid 400 using a plurality of optical detectors 110, it becomes possible to surely determine the failure of the optical detector 110.

[0071] In the optical level detection device 1 described in the above Embodiment 2, the voltage of the sensor output signal output from the photoreceptor 112 is · The first voltage E1 output from the photoreceptor 112 that receives the light from the light emitter 111 reflected by the prism 113 when the light emitters 111 of the plurality of optical detectors 110 are made to emit light and each of the plurality of optical detectors 110 is located outside the liquid, and · Cause the light emitters 111 of the plurality of optical detectors 110 to emit light, and when each of the plurality of optical detectors 110 is positioned in the liquid, the fifth voltage E5 output from the light receivers 112 that receive the light from the light emitters 111 guided by the light guide portion 117, and · The sixth voltage E6 output from the light receiver 112 when there is an open failure in the light emitter 111 or the light receiver 112 of each of the plurality of optical detectors 110, and is in either of the states. The control unit 120 compares any one of the first voltage E1, the fifth voltage E5, and the sixth voltage E6 output from each light receiver 112 with the first threshold value Vth1 and the second threshold value Vth2. Thereby, when detecting the liquid level height of the liquid 400 using the plurality of optical detectors 110, it is possible to reliably and quickly determine the failure of the optical detector 110.

[0072] In the optical level detection device 1 described in the above Embodiment 2, the control unit 120 determines that the first voltage E1 is in the first signal state, determines that the sixth voltage E6 is in the second signal state different from the first signal state, and determines that the fifth voltage E5 is at the third level intermediate between the first signal state and the second signal state. Thereby, when detecting the liquid level height of the liquid 400 using the plurality of optical detectors 110, it is possible to reliably and quickly determine the failure of the optical detector 110.

[0073] In the optical level detection device 1 described in the above Embodiment 2, the control unit 120 does not cause the light emitters 111 included in each of the plurality of optical detectors 110 to emit light, and compares the voltage output from the light receiver 112 corresponding to the non-emitting light emitter 111 with the first threshold value Vth1 to determine the failure of the light receiver 112. Here, when the light emitter 111 does not emit light, no current flows through the normal light receiver 112, but when the light emitter 111 does not emit light, current flows through the short-circuited light receiver 112. Therefore, by comparing the voltage output from the light receiver 112 corresponding to the non-emitting light emitter 111 with the first threshold value Vth1, it is possible to reliably and quickly determine the short-circuit failure of the light receiver 112 included in the optical detector.

[0074] In the optical level detection device 1 described in the above Embodiment 2, the voltage output from the light receiver 112 is · a third voltage E3 output from the light receiver 112 that is not short-circuited, with the light emitters 111 of each of the plurality of optical detectors 110 not emitting light, and · a fourth voltage E4 output from the light receiver 112 in a short-circuit failure state, with the light emitters 111 of each of the plurality of optical detectors 110 not emitting light, and further includes any one of the states. Therefore, in order to determine a short-circuit failure of the light receiver 112 from the third voltage E3 and the fourth voltage E4, it is possible to reliably and quickly determine a short-circuit failure of the light receiver 112.

[0075] In the optical level detection device 1 described in the above Embodiment 2, the control unit 120 can reliably and quickly determine a short-circuit failure of the light receiver 112 included in the optical detector by comparing the third voltage E3 and the fourth voltage E4 with a first threshold value Vth1 that is a liquid level threshold value.

[0076] In the optical level detection device 1 described in the above Embodiment 2, the control unit 120 determines the first voltage E1 and the fourth voltage E4 as a first signal state, and determines the second voltage E2 and the third voltage E3 as a second signal state different from the first signal state. Thereby, it is possible to reliably and quickly perform detection of the liquid level height of the liquid 400 and determination of a short-circuit failure of the light receiver 112 by determination using a common first threshold value Vth1.

Explanation of Reference Numerals

[0077] 1 Optical level detection device, 100 Sensor unit, 101 Case, 105 Substrate, 110, 110A to 110P Optical detectors, 111 Light emitter, 112 Light receiver, 113 Prism, 114, 115, 116 Light shielding part, 117 Light guide part, 117a Light transmission part, 117b Reflection part, 120 Control unit, 300 Container, 400 Liquid, 401 Liquid level, PS_A to PS_P Photo sensors.

Claims

1. An optical level detection device (1) comprising a sensor unit (100) having a plurality of optical detectors (110) and a control unit (120), wherein each of the plurality of optical detectors (110) comprises a light emitter (111), a light receiver (112), and a prism (113), the prism (113) is configured to transmit light from the light emitter (111) in a liquid and reflect light from the light emitter (111) outside the liquid to guide it to the light receiver (112), and the control unit (120) causes the light emitter (111) provided in each of the plurality of optical detectors (110) to emit light, compares a voltage output from the light receiver (112) provided in each of the plurality of optical detectors (110) with a first threshold value (Vth1), and detects the presence or absence of the liquid, does not cause the light emitter (111) provided in each of the plurality of optical detectors (110) to emit light, compares a voltage output from the light receiver (112) corresponding to the non-emitting light emitter (111) with the first threshold value (Vth1), and discriminates a failure of the light receiver (112). Optical level detection device.

2. Each of the plurality of optical detectors (110) is connected to the control unit (120), and the control unit (120) controls the application or non-application of a light emission drive voltage to the light emitter (111) provided in each of the plurality of optical detectors (110), identifies the application or non-application of the light emission drive voltage to the light emitter (111), and compares a voltage output from the light receiver (112) corresponding to the light emitter (111) for which it is identified that the light emission drive voltage is not applied with the first threshold value (Vth1) to discriminate the failure. The optical level detection device according to Claim 1.

3. The voltage output from the light receiver (112) is a first voltage (E1) output from the light receiver (112) that receives light from the light emitter (111) reflected by the prism (113) when the light emitter (111) of the plurality of optical detectors (110) emits light and each of the plurality of optical detectors (110) is located outside the liquid, and a second voltage (E2) output from the light receiver (112) that does not receive light from the light emitter (111) when the light emitter (111) of the plurality of optical detectors (110) emits light and each of the plurality of optical detectors (110) is located in the liquid. Without causing the light emitter (111) of each of the plurality of optical detectors (110) to emit light, the third voltage (E3) output from the normal light receiver (112), and Without causing the light emitter (111) of each of the plurality of optical detectors (110) to emit light, the fourth voltage (E4) output from the light receiver (112) in a short-circuit failure state, and being in any of the states of The optical level detection device according to claim 1.

4. The control unit (120) compares the first voltage (E1), the second voltage (E2), the third voltage (E3), and the fourth voltage (E4) with the first threshold value (Vth1), determines that the first voltage (E1) and the fourth voltage (E4) are in a first signal state, and determines that the second voltage (E2) and the third voltage (E3) are in a second signal state different from the first signal state. The optical level detection device according to claim 3.

5. Each of the plurality of optical detectors (110) further includes a light guide unit (117) configured to guide a part of the light from the light emitter (111) to the light receiver (112), the control unit (120) causes the light emitter (111) included in each of the plurality of optical detectors (110) to emit light, and compares the voltage output from the light receiver (112) included in each of the plurality of optical detectors (110) with a second threshold value (Vth2) for determining a failure of the optical detector (110), The optical level detection device according to claim 1.

6. The light guide unit (117) is configured to guide a smaller amount of light from the light emitter (111) to the light receiver (112) than the light reflected by the prism (113), The optical level detection device according to claim 5.

7. A light shielding part (115) is provided between the light emitter (111) and the light receiver (112), the light guide unit (117) includes a light transmission part (117a), and the light transmission part (117a) is provided at any position of the light shielding part (115). The optical level detection device according to claim 6.

8. The light guide unit (117) includes a reflection part (117b), and the reflection part (117b) is configured to reflect a part of the light from the light emitter (111) that is about to pass through the prism (113) and guide it to the light receiver (112). The optical level detection device according to claim 6.

9. The voltage output from the light receiver (112) Causing the light emitter (111) of the plurality of optical detectors (110) to emit light, and when each of the plurality of optical detectors (110) is located outside the liquid, the first voltage (E1) output from the light receiver (112) that receives the light from the light emitter (111) reflected by the prism (113), Causing the light emitter (111) of the plurality of optical detectors (110) to emit light, and when each of the plurality of optical detectors (110) is located in the liquid, the fifth voltage (E5) output from the light receiver (112) that receives the light from the light emitter (111) guided by the light guide portion (117), Causing the light emitter (111) of the plurality of optical detectors (110) to emit light, and the sixth voltage (E6) output from the light receiver (112) when a failure occurs in the light emitter (111) or the light receiver (112), in any one of the states, The control unit (120) compares the first voltage, the fifth voltage, and the sixth voltage with the first threshold value (Vth1) and the second threshold value (Vth2) to detect the presence or absence of the liquid and determine the failure. The optical level detection device according to any one of claims 5 to 8.

10. The control unit (120) is, determines that the first voltage (E1) is in a first signal state, determines that the sixth voltage (E6) is in a second signal state different from the first signal state, determines that the fifth voltage (E5) is at a third level intermediate between the first signal state and the second signal state. The optical level detection device according to claim 9.

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