Liquid level detection device

Abstract

This liquid level detection device (21) is provided with a ventilation tube (27) provided so as to penetrate through a side surface section (22A) of a housing (22), said ventilation tube (27) being located on the upper side (the other side) of the housing (22) than a water passage hole (25) and an ultrasonic sensor (23). An external vent hole (28) that opens to the outside of the housing (22) and an internal vent hole (29) that opens to the upper side (the other side) of the housing (22) inside the housing (22) and communicates with the external vent hole (28) are formed in the vent tube (27).

Description

Technical Field

[0001] The present invention relates to a liquid level detection device arranged in a liquid tank storing liquid such as urea water for purifying exhaust gas. Background Art

[0002] Generally speaking, construction machinery and the like are equipped with a diesel engine as a prime mover. Recently, in order to remove nitrogen oxides (NOx) in the exhaust gas discharged by the diesel engine, an exhaust gas purification device using urea water (urea aqueous solution) as a reducing agent is installed in the construction machinery and the like. Therefore, a urea water tank for storing urea water is provided in the construction machinery and the like.

[0003] The urea water tank is provided with a liquid level detection device for detecting the remaining amount of urea water, that is, the liquid level position of the urea water. As such a liquid level detection device, there is known a device having the following components: a cylindrical housing, which is provided inside the urea water tank so as to extend in the up-down direction; an ultrasonic sensor, which is provided at the lower part of the housing and reflects the upward oscillating ultrasonic wave to the liquid level of the urea water to detect the liquid level position; a water outlet, which is provided at the lower side of the housing and allows the urea water to flow in and out between the inside and outside of the housing; and a vent, which is provided at the housing so as to be located above the liquid level of the urea water and allows air to flow in and out between the inside and outside of the housing (Patent Document 1).

[0004] Here, in the urea water tank, when the construction machine is traveling or working, the urea water fluctuates and generates bubbles. If the urea water contains bubbles, the bubbles reflect the ultrasonic waves oscillating from the ultrasonic sensor, so there is a concern that the correct liquid level position cannot be detected. Therefore, in Patent Document 1, the water port is covered with a porous membrane to prevent bubbles from entering the housing.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: International Publication No. 2020 / 036648 Summary of the invention

[0008] As described above, in Patent Document 1, the water vent is covered with a porous membrane to prevent bubbles from entering the housing. However, construction machinery sometimes operates on wasteland, uneven ground, slopes, etc. In such a site, it is believed that urea water rises and falls greatly and reaches the vent on the upper side. Then, urea water containing bubbles enters from the vent, and there is a problem that the bubbles affect the detection of the liquid level position of the urea water, thereby reducing reliability.

[0009] In this case, as with the water port, it is considered that the air vent is covered with a porous membrane to prevent bubbles from entering the housing. However, the porous membrane not only creates ventilation resistance, but also becomes clogged even if only splashes of urea water hit it, thereby reducing ventilation and failing to maintain uniform pressure.

[0010] The present invention is completed in view of the above-mentioned problems of the prior art, and an object of the present invention is to provide a liquid level detection device, which prevents liquid containing bubbles from penetrating into the shell through the vent hole, thereby improving the reliability of detection of the liquid level position.

[0011] The liquid level detection device of the present invention comprises: a cylindrical shell, which has a water hole for allowing liquid to flow into the inside; and an ultrasonic sensor, which is arranged on one side of the above-mentioned shell and oscillates and receives ultrasonic waves. In the above-mentioned liquid level detection device, there is a vent cylinder arranged at a position on the other side of the above-mentioned shell closer to the above-mentioned water hole and the above-mentioned ultrasonic sensor so as to penetrate the side surface of the above-mentioned shell, and the above-mentioned vent cylinder is formed with an external vent hole opening on the outside of the above-mentioned shell and an internal vent hole opening on the other side of the above-mentioned shell inside the above-mentioned shell and connected to the above-mentioned external vent hole.

[0012] According to the present invention, it is possible to prevent liquid containing bubbles from entering the housing through the vent hole, and to improve the reliability of the detection of the liquid level position. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a left side view showing a wheel loader provided with the liquid level detection device according to the first embodiment of the present invention.

[0014] Figure 2 It is a cross-sectional view showing the urea water tank, the liquid level detection device, etc.

[0015] Figure 3 It is shown Figure 2 A three-dimensional diagram of the liquid level detection device in FIG.

[0016] Figure 4 It is a perspective view showing a liquid level detection device according to a second embodiment.

[0017] Figure 5 It is a perspective view showing a liquid level detection device according to a third embodiment. DETAILED DESCRIPTION

[0018] Hereinafter, a liquid level detection device according to an embodiment of the present invention will be described in detail with reference to the drawings, taking a case where the liquid level detection device is provided in a urea water tank of a wheel loader as a construction machine as an example.

[0019] Figures 1 to 3 A first embodiment is shown. Figure 1In the figure, a wheel loader 1 as a construction machine is constructed to include a rear body 2, a front body 3 connected to the front side of the rear body 2 so as to be swingable in the left-right direction, rear wheels 4 provided on both sides of the rear body 2 in the left-right direction, front wheels 5 provided on both sides of the front body 3 in the left-right direction (only the left side is shown), and a working device 6 provided on the front side of the front body 3 so as to be able to perform a pitching action.

[0020] The rear vehicle body 2 is equipped with an engine 7 as a driving source, a torque converter 8, a transmission 9, a hydraulic pump (not shown), etc. The engine 7 is a diesel engine. An exhaust gas purification device 13 described below is provided on the exhaust side of the engine 7.

[0021] A cab 10 for an operator to sit in is provided on the upper side of the rear vehicle body 2. The transmission 9 is connected to a rear axle device 11 via a propeller shaft 9A extending in the front-rear direction. Furthermore, the transmission 9 is connected to a front axle device 12 via a propeller shaft 9B.

[0022] The exhaust gas purification device 13 is provided on the exhaust side of the engine 7 to purify the exhaust gas discharged by the engine 7. The exhaust gas purification device 13 is formed as a NOx purification device that purifies nitrogen oxides (NOx) in the exhaust gas using urea water (urea aqueous solution) 15 described below. The exhaust gas purification device 13 has a storage cylinder 13A connected to the exhaust side of the engine 7, and a urea selective reduction catalyst, an oxidation catalyst, and a urea water injection valve (none of which are shown in the figure) are provided in the storage cylinder 13A. Urea water 15 is supplied to the urea water injection valve from a urea water tank 14 described below via a urea water pipe (not shown in the figure).

[0023] Thus, the exhaust gas purification device 13 injects urea water 15 into the exhaust gas using the urea water injection valve, and uses ammonia generated from the urea water 15 by the urea selective reduction catalyst to reduce NOx in the exhaust gas and decompose it into water and nitrogen. Then, the ammonia in the exhaust gas is reduced by the oxidation catalyst.

[0024] The urea water tank 14 as a liquid tank is provided, for example, at the rear side of the rear vehicle body 2. Figure 2 As shown, the urea water tank 14 stores urea water 15 as a reducing agent to be supplied to the urea water injection valve of the exhaust gas purification device 13. The urea water tank 14 is provided with a liquid level detection device 21 described below. In addition, the urea water tank 14 is provided with a pipe connecting the urea water tank 14 and the urea water injection valve, a quality sensor for detecting the quality of the urea water 15, etc. (all not shown).

[0025] Here, the urea water tank 14 may sway greatly when the wheel loader 1 is traveling or working. In this case, the urea water 15 sways and bubbles (including microbubbles) 15A are generated in the urea water tank 14 .

[0026] Next, refer to Figure 2 , Figure 3 , the structure of the liquid level detection device 21 which is the characteristic portion of the first embodiment is described in detail.

[0027] Figure 2 In the embodiment, the liquid level detection device 21 is provided in the urea water tank 14. The liquid level detection device 21 detects the liquid level position, that is, the remaining amount, of the urea water 15 stored in the urea water tank 14. The liquid level detection device 21 is configured to include a housing 22, an ultrasonic sensor 23, a water hole 25, a vent 27, an external vent 28, and an internal vent 29 as described below.

[0028] The housing 22 is provided inside the urea water tank 14 so as to extend in the vertical direction. For example, the upper side of the housing 22 protrudes upward from the top surface 14A on the other side, and the lower side on one side is located near the bottom surface 14B of the urea water tank 14. Figure 3 As shown, the housing 22 is formed into a square tube shape with the upper side blocked, for example. Specifically, the housing 22 is composed of four side portions 22A arranged in a quadrilateral manner and an upper surface portion 22B blocking the upper side of the four side portions 22A. The lower side of the housing 22 is blocked by the ultrasonic sensor 23 described below. In addition, the housing can also be configured such that the lower side is blocked by the lower surface portion, and the ultrasonic sensor is built into the lower surface portion. In addition, the housing can also be formed into a polygonal cylinder other than a cylindrical body or a quadrangular cylinder.

[0029] Furthermore, the housing 22 has cylinder mounting holes 22C formed on the upper sides of the side surfaces 22A facing each other. The two cylinder mounting holes 22C are arranged at a position higher than the liquid level of the full tank urea water 15. The breather cylinder 27 described below is inserted and mounted in the two cylinder mounting holes 22C.

[0030] The ultrasonic sensor 23 is provided on the lower side of one side of the housing 22. The ultrasonic sensor 23 includes an oscillating / receiving unit 23A having an ultrasonic vibrator (piezoelectric element) on the upper surface. The ultrasonic sensor 23 can make the sound waves oscillated from the oscillating / receiving unit 23A reflect on the liquid surface of the urea water 15 and be received by the oscillating / receiving unit 23A. In addition, the ultrasonic sensor 23 is connected to the controller 24.

[0031] The ultrasonic sensor 23 transmits the time from when the oscillator / receiver 23A oscillates the sound wave to when the oscillator / receiver 23A receives the sound wave to the controller 24. The controller 24 detects (calculates) the liquid level of the urea water 15 based on the time from oscillation to reception.

[0032] The water through hole 25 is provided on the lower side of the side surface portion 22A of the housing 22 which is located near the ultrasonic sensor 23. The water through hole 25 constitutes a passage for allowing the urea water 15 to enter and exit between the inside and the outside of the housing 22.

[0033] The membrane 26 is provided to cover the water through hole 25. The membrane 26 is formed of a porous membrane having many micropores. When the urea water 15 in the urea water tank 14 flows into the housing 22 through the water through hole 25, the membrane 26 prevents the infiltration of bubbles (microbubbles) 15A and allows only the urea water 15 to flow in. Thus, the membrane 26 prevents erroneous detection caused by the sound waves of the ultrasonic sensor 23 hitting the bubbles 15A.

[0034] The breather cylinder 27 is arranged at an upper position of the housing 22 which is higher than the liquid level of the urea water 15 in a full tank state. Specifically, the breather cylinder 27 is inserted and installed in the cylinder installation hole 22C in a manner of extending in the horizontal direction through the mutually facing side portions 22A of the housing 22. The breather cylinder 27 is formed as a circular cylinder extending along a straight line and having openings at both ends. In other words, the breather cylinder 27 is arranged so that the two ends which are connected to each other are located outside the housing 22. On this basis, the breather cylinder 27 protrudes from the side portion 22A of the housing 22 to the outside of the housing 22, so that the external vent hole 28 described below opens at a position away from the side portion 22A. In addition, in addition to a circular cylinder, the breather cylinder can also be an elliptical cylinder or a square cylinder.

[0035] The external vent holes 28 are provided to be open at both ends of the vent cylinder 27 that is the outside of the housing 22. The external vent holes 28 constitute one of the vent holes that are located above the liquid level of the urea water 15 and allow air to enter and exit between the inside and the outside of the housing 22. The external vent holes 28 are arranged at a position away from the side surface 22A of the housing 22 to the outside. Thus, the external vent holes 28 can be spaced apart from the internal vent holes 29 described below. Therefore, even if the urea water 15 enters the vent cylinder 27, the urea water 15 can fall to a lower position in the vent cylinder 27 before reaching the vicinity of the internal vent holes 29. In other words, the urea water 15 can be allowed to leave the internal vent holes 29 in the vent cylinder 27. Furthermore, even if the urea water 15 attached to the side surface 22A flows down to the lower side, the external vent holes 28 can be prevented from entering the external vent holes 28.

[0036] The internal vent hole 29 is provided in the housing 22 so as to be opened at the upper side of the breather 27. The internal vent hole 29 constitutes the other side of the vent hole that allows air to enter and exit between the inside and the outside of the housing 22. The internal vent hole 29 is opened at the upper side of the breather 27, thereby preventing the urea water 15 from flowing out into the housing 22 even if the urea water 15 enters the breather 27 from the external vent hole 28.

[0037] The liquid level detection device 21 of the first embodiment has the above-described configuration. Next, an operation for detecting the liquid level position of the urea water 15 in the urea water tank 14 will be described.

[0038] First, since the urea water 15 in the urea water tank 14 enters and exits the housing 22 through the water through hole 25, the liquid level position of the urea water 15 in the housing 22 is the same as the liquid level position of the urea water 15 outside the housing 22 (inside the urea water tank 14). In this case, since the membrane body 26 composed of a porous membrane is provided on the housing 22 so as to cover the water through hole 25, when the urea water 15 in the urea water tank 14 flows into the housing 22, it is possible to prevent the bubbles (micro bubbles) 15A from entering.

[0039] Furthermore, if the urea water 15 increases or decreases in the housing 22 (the liquid level position is displaced in the up-down direction), in order to keep the pressure inside and outside the housing 22 equal, it is necessary to allow the air accumulated in the upper part of the housing 22 to enter and exit. In this case, since the upper space in the housing 22 is connected to the urea water tank 14 through the external vent hole 28 and the internal vent hole 29 provided in the breather 27, the air can be freely allowed to enter and exit according to the increase or decrease of the urea water 15 without generating ventilation resistance. That is, the pressure inside and outside the housing 22 can be kept equal.

[0040] Furthermore, the ultrasonic sensor 23 oscillates sound waves upward from the oscillating / receiving part 23A. At this time, since the urea water 15 in the housing 22 does not contain the bubbles 15A, the sound waves oscillated from the oscillating / receiving part 23A are reflected on the liquid surface of the urea water 15 and received by the oscillating / receiving part 23A. The detection data is sent to the controller 24, and the controller 24 detects (calculates) the liquid surface position of the urea water 15 based on the time from oscillation to reception, and displays the remaining amount of the urea water 15 on a monitor (not shown) in the cab 10.

[0041] However, the wheel loader 1 is operated on wasteland, uneven ground, slopes, etc., based on repeated travel and stopping. Figure 2 As shown, the urea water 15 in the urea water tank 14 greatly surges, and there is a concern that the urea water 15 including the air bubbles 15A may reach the external vent hole 28 .

[0042] However, according to the first embodiment, the liquid level detection device 21 is provided with a vent 27 which is provided in a position on the upper side (the other side) of the housing 22 relative to the water passing hole 25 and the ultrasonic sensor 23 so as to penetrate the side surface portion 22A of the housing 22. Furthermore, the vent 27 is provided with an external vent 28 which opens to the outside of the housing 22 and an internal vent 29 which opens to the upper side (the other side) of the housing 22 and communicates with the external vent 28.

[0043] Therefore, even if the urea water 15 containing the bubbles 15A enters the breather 27 from the external vent hole 28, the urea water 15 containing the bubbles 15A flows out into the urea water tank 14 (outside the housing 22) through the breather 27 because the internal vent hole 29 opens at the upper side of the breather 27. As a result, the urea water 15 containing the bubbles 15A can be prevented from entering the housing 22 from the external vent hole 28 and the internal vent hole 29. In other words, the bubbles 15A can be prevented from being mixed into the urea water 15 in the housing 22. As a result, the ultrasonic sensor 23 can function correctly, and the reliability of the detection of the liquid level position of the urea water 15 can be improved.

[0044] The breather 27 is provided with two ends that are connected to each other being located outside the housing 22. On this basis, external vent holes 28 are provided at both ends of the breather 27. Thus, when the vehicle body of the wheel loader 1 is tilted while operating on wasteland, uneven ground, or a slope, the urea water 15 containing the bubbles 15A can reliably flow out from the external vent holes 28 provided at the lower end of the two ends.

[0045] The breather 27 protrudes from the side surface 22A of the housing 22, and the external vent hole 28 is arranged at a position away from the side surface 22A of the housing 22 to the outside. Therefore, the external vent hole 28 is far away from the internal vent hole 29. Therefore, even if the urea water 15 enters the breather 27 from the external vent hole 28, the breather 27 can make the urea water 15 fall to the lower position in the breather 27 before reaching the vicinity of the internal vent hole 29. In addition, even if the urea water 15 attached to the side surface 22A flows downward, the breather 27 can prevent the urea water 15 from entering the external vent hole 28.

[0046] The breather 27 is formed of a cylindrical pipe member whose both ends serve as external vent holes 28. The breather 27 is provided to penetrate the side surfaces 22A of the housing 22 that face each other. Thus, the breather 27 can be easily formed using a linear pipe member.

[0047] Next, Figure 4 A second embodiment of the present invention is shown. The second embodiment is characterized in that the vent cylinder penetrating the side portion of the shell is formed as a cylinder having an open end outside the shell and a closed end inside the shell. In addition, in the second embodiment, the same symbols are marked for the same components as the first embodiment, and their descriptions are omitted.

[0048] Figure 4In the second embodiment, the liquid level detection device 31 includes a housing 32. The housing 32 includes four side surfaces 32A and an upper surface 32B, and a cylinder mounting hole 32C is provided in one side surface 32A at a position higher than the liquid level of the urea water 15 in the full tank state. In addition, the housing may be formed into a polygonal cylinder other than a cylindrical body or a quadrangular cylinder.

[0049] The breather cylinder 33 is inserted and installed in the cylinder installation hole 32C in a manner that extends in the horizontal direction through the side portion 32A of the housing 32. The breather cylinder 33 is formed as a covered circular cylinder with an open end outside the housing 32 extending in a straight line and an end inside the housing 32 blocked by a cover portion 33A. In addition, the breather cylinder 33 is the same as the breather cylinder 27 of the first embodiment, and the end outside the housing 32 protrudes from the side portion 32A.

[0050] The external vent hole 34 opens at the end of the breather cylinder 33 outside the housing 32. The internal vent hole 35 communicates with the external vent hole 34 through the breather cylinder 33 and opens at the upper side of the breather cylinder 33 inside the housing 32.

[0051] Thus, the liquid level detection device 31 of the second embodiment thus constructed can also obtain the same operation and effect as the first embodiment. In particular, the liquid level detection device 31 of the second embodiment has the breather 33 inserted and mounted only on one side portion 32A, so the structure can be simplified.

[0052] Next, Figure 5 The third embodiment of the present invention is shown. The third embodiment is characterized in that a bent vent is provided through adjacent side surfaces of the housing. In the third embodiment, the same components as those of the first embodiment are denoted by the same reference numerals, and their description is omitted.

[0053] Figure 5 In the third embodiment, the liquid level detection device 41 includes a housing 42. The housing 42 includes four side surfaces 42A and an upper surface 42B, and a cylinder mounting hole 42C is provided in two adjacent side surfaces 42A at a position higher than the liquid level of the urea water 15 in the full tank state. In addition, the housing may be formed into a polygonal cylinder other than a cylindrical body or a quadrangular cylinder.

[0054] The air cylinder 43 is formed into an L-shaped cylinder body with the middle portion in the longitudinal direction being bent as a bent portion 43A. The L-shaped air cylinder 43 is inserted and installed in the cylinder installation hole 42C in a manner extending in the horizontal direction so as to penetrate the adjacent side portions 42A of the housing 42. In addition, the air cylinder 43 is the same as the air cylinder 27 of the first embodiment, and the end portion outside the housing 42 protrudes from the side portion 42A.

[0055] External vent holes 44 are arranged at both ends of breather cylinder 43 outside housing 42. Internal vent holes 45 communicate with external vent holes 44 through breather cylinder 43 and are arranged above bent portion 43A of breather cylinder 43 inside housing 42.

[0056] In this way, also in the liquid level detection device 41 of the third embodiment configured as above, the same operation and effects as those of the first embodiment can be obtained.

[0057] In addition, in the first embodiment, the case where the breather 27 penetrates the two side portions 22A of the housing 22 is described as an example, and in the second embodiment, the case where the breather 33 penetrates the one side portion 32A of the housing 32 is described as an example. However, the present invention is not limited to this, and the breather may be configured to be a T-shaped or Y-shaped trident shape so that it penetrates the three side portions. In addition, the breather may be configured to be a cross shape so that it penetrates the four side portions.

[0058] In the first embodiment, the case where the liquid level detection device 21 is provided in the urea water tank 14 of the wheel loader 1 as a construction machine is described as an example. However, the present invention is not limited to this, and the liquid level detection device can also be configured to be provided in the urea water tank of other construction machines such as a hydraulic excavator. In addition, the liquid level detection device can also be used to detect the liquid level position of liquids other than urea water (fuel, water, etc.). The above structure can also be applied to other embodiments in the same manner.

[0059] Explanation of symbols

[0060] 15—urea water (liquid), 15A—bubble, 21, 31, 41—liquid level detection device, 22, 32, 42—housing, 22A, 32A, 42A—side portion, 23—ultrasonic sensor, 25—water hole, 27, 33, 43—vent cylinder, 28, 34, 44—external vent, 29, 35, 45—internal vent.

Claims

1. A liquid level detection device, comprising: A cylindrical housing having a water hole for allowing liquid to flow into the interior; and The ultrasonic sensor is disposed on one side of the housing and oscillates and receives ultrasonic waves. The above-mentioned liquid level detection device is characterized in that: A vent cylinder is provided at a position on the other side of the housing relative to the water through hole and the ultrasonic sensor so as to penetrate the side surface of the housing, The breather cylinder is formed with an external vent hole opened outside the housing and an internal vent hole opened inside the housing at the other side of the housing and communicating with the external vent hole.

2. The liquid level detection device according to claim 1, characterized in that: The vent cylinder is configured such that a plurality of ends that are interconnected are located outside the housing. The external ventilation holes are formed at the plurality of end portions.

3. The liquid level detection device according to claim 1, characterized in that: The vent cylinder protrudes outward from the side surface of the housing. The external ventilation hole is formed at a position away from the side surface portion of the housing toward the outside.

4. The liquid level detection device according to claim 1, characterized in that: The breather cylinder is formed of a cylindrical pipe member whose both ends serve as the external breather holes.

5. The liquid level detection device according to claim 3, characterized in that: The vent is provided through the side surfaces of the housing facing each other.

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