Construction machine

Abstract

To improve durability and reliability of a hydraulic actuator and a hydraulic pump by correctly detecting a property of hydraulic oil by an oil sensor.SOLUTION: In a hydraulic shovel 1, separately from a supply pipeline 13 and a return pipeline 14 for circulating a hydraulic oil between a hydraulic oil tank 7 and a hydraulic cylinder 5A and the like of a work device 5, a first drain pipeline 15 is provided for returning the hydraulic oil discharged from a first hydraulic pump 10 to the hydraulic oil tank 7. The first drain pipeline 15 includes: an upstream side rising pipe part 15C to which the first hydraulic pump 10 is located upstream of the hydraulic oil flow, and which rises so as to be convex upward; and a low position pipe part 15D provided downstream of the upstream side rising pipe part 15C in the hydraulic oil flow, and arranged at the position lower than the upstream side rising pipe part 15C. Further, an oil sensor 20 for detecting a property of the hydraulic oil is mounted on the low position pipe part 15D.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a construction machine, such as a hydraulic excavator, that is provided with a configuration for circulating hydraulic oil between a hydraulic oil tank and a hydraulic actuator. [Background technology]

[0002] Generally, a hydraulic excavator as a construction machine includes a self-propelled lower traveling body, an upper rotating body rotatably mounted on the lower traveling body, and a working device rotatably mounted on the front part of the upper rotating body. The hydraulic excavator also includes a hydraulic actuator for moving the lower traveling body, a hydraulic actuator for rotating the upper rotating body, and a hydraulic actuator for rotating the working device.

[0003] The upper rotating body is equipped with a rotating frame rotatably supported on the lower traveling body, a hydraulic oil tank provided on the rotating frame for storing hydraulic oil, a prime mover such as an engine provided on the rotating frame, and a hydraulic pump that is driven by the prime mover to supply pressurized hydraulic oil (pressurized oil) to each hydraulic actuator. In addition, the upper rotating body is provided with supply piping that connects the hydraulic oil tank, the hydraulic pump, and each hydraulic actuator to supply the hydraulic oil in the hydraulic oil tank to the hydraulic actuators, and return piping that returns the hydraulic oil discharged from the hydraulic actuators via the oil cooler into the hydraulic oil tank.

[0004] In addition, hydraulic excavators are equipped with operation sensors that detect operation data including the engine exhaust temperature, exhaust pressure, lubricating oil temperature, hydraulic oil temperature, pressure, etc. in order to grasp the operating condition (Patent Document 1).

[0005] Furthermore, some other hydraulic excavators are equipped with an oil sensor for detecting the properties of the hydraulic oil, located in the return pipe between the oil cooler downstream of the hydraulic actuator and the hydraulic oil tank (Patent Document 2). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2000-259729 A [Patent Document 2] JP 2020-133320 A Summary of the Invention [Problem to be solved by the invention]

[0007] As in Patent Document 2, by using an oil sensor to grasp the properties of the hydraulic oil, such as deterioration of the hydraulic oil or the inclusion of foreign matter, it is possible to suppress deterioration in the performance of each hydraulic actuator and hydraulic pump. However, in order to accurately detect the properties of the hydraulic oil, it is necessary to install the oil sensor in a position where the flow of the hydraulic oil is stable and can be detected normally.

[0008] In contrast, in Patent Document 2, an oil sensor is installed in the return pipe. This return pipe is a pipe through which a large amount of hydraulic oil flows when the hydraulic oil is discharged from the hydraulic actuator, and the flow of the hydraulic oil is not stable. For this reason, Patent Document 2 has a problem in that it may not be possible to accurately detect the properties of the hydraulic oil.

[0009] The present invention has been made in consideration of the problems with the prior art described above, and an object of the present invention is to provide a construction machine that can accurately detect the properties of hydraulic oil using an oil sensor, thereby improving the durability and reliability of hydraulic actuators and hydraulic pumps. [Means for solving the problem]

[0010] The present invention relates to a hydraulic system comprising a self-propelled lower traveling body, an upper rotating body rotatably provided on the lower traveling body, and a working device rotatably provided at a front part of the upper rotating body, the upper rotating body being provided with a rotating frame rotatably supported on the lower traveling body, a hydraulic oil tank provided on the rotating frame and storing hydraulic oil, a prime mover provided on the rotating frame, and a hydraulic pump driven by the prime mover for supplying hydraulic oil to a hydraulic actuator for traveling the lower traveling body, a hydraulic actuator for rotating the upper rotating body, and a hydraulic actuator for rotating the working device. In a construction machine comprising a hydraulic pump, a hydraulic actuator, and an oil sensor for detecting the properties of the hydraulic oil, a drain pipe for returning the hydraulic oil discharged from the hydraulic pump to the hydraulic oil tank is provided in addition to a supply pipe and a return pipe for circulating the hydraulic oil between the hydraulic oil tank and the hydraulic actuator, and the drain pipe is provided with a riser pipe section that rises upwardly so as to be convex, with the hydraulic pump located upstream of the hydraulic oil flow, and a low-position pipe section that is located downstream of the riser pipe section in the hydraulic oil flow and at a lower position than the riser pipe section, and the oil sensor is attached to the low-position pipe section. Effect of the Invention

[0011] According to the present invention, the properties of the hydraulic oil can be accurately detected by the oil sensor, and the durability and reliability of the hydraulic actuator and hydraulic pump can be improved. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a left side view showing a hydraulic excavator according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a configuration diagram showing a flow path of hydraulic oil. [Diagram 3] FIG. 2 is a front view showing a hydraulic oil tank, a hydraulic pump, an oil sensor, etc. [Figure 4] FIG. 4 is an enlarged view showing a main part in FIG. [Diagram 5] FIG. 11 is a configuration diagram showing a flow path of hydraulic oil according to a modified example. [Figure 6]FIG. 13 is a front view showing a hydraulic oil tank, a hydraulic pump, an oil sensor, etc. according to a modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, a hydraulic excavator will be taken as an example and described in detail with reference to Figs. 1 to 4 as a representative example of a construction machine according to an embodiment of the present invention.

[0014] In Fig. 1, a hydraulic excavator 1, which is a representative example of a construction machine, is called an ultra-large hydraulic excavator and has an operating weight exceeding 800 tons, for example. The hydraulic excavator 1 is equipped with a first engine 8 and a second engine 9, which will be described later. The hydraulic excavator 1 is equipped with a self-propelled crawler-type lower traveling body 2, an upper rotating body 4 rotatably mounted on the lower traveling body 2 via a rotating device 3, and a working device 5 rotatably provided at the front of the upper rotating body 4.

[0015] The lower traveling structure 2 has a hydraulic motor for traveling, and the swivel device 3 has a hydraulic motor for swing (neither shown). These hydraulic motors constitute hydraulic actuators. The working device 5 is provided in front of a swing frame 6, which will be described later. The working device 5 has a plurality of hydraulic cylinders 5A as hydraulic actuators.

[0016] The upper rotating body 4 is equipped with a rotating frame 6, a hydraulic oil tank 7, a first engine 8, a second engine 9, a first hydraulic pump 10, a second hydraulic pump 11, a supply pipe 13, a return pipe 14, a first drain pipe 15, an oil sensor 20, etc., which will be described later. The rotating frame 6 is supported so as to be capable of rotating on the lower traveling body 2. The rotating frame 6 forms a support structure, and a working device 5 is rotatably attached to the front part of the rotating frame 6.

[0017] As shown in Figures 2 and 3, the hydraulic oil tank 7 is provided on the revolving frame 6 and stores hydraulic oil. The hydraulic oil tank 7 is formed, for example, as a rectangular parallelepiped can structure. A supply pipe 13 and a return pipe 14, which will be described later, are connected to the hydraulic oil tank 7. In addition, a downstream rising pipe portion 15E of a first drain pipe 15, which will be described later, is connected to an upper portion of the hydraulic oil tank 7.

[0018] The first engine 8 and the second engine 9 serving as prime movers are provided on the revolving frame 6. An internal combustion engine such as a diesel engine is used as the prime mover, but a hybrid prime mover combining an internal combustion engine and an electric motor or an electric motor alone may be used. A plurality of first hydraulic pumps 10, which will be described later, are attached to the first engine 8, and a plurality of second hydraulic pumps 11 are attached to the second engine 9. As a result, the hydraulic excavator 1 is provided with two sets of engines: the first engine 8 equipped with a plurality of first hydraulic pumps 10, and the second engine 9 equipped with a plurality of second hydraulic pumps 11. A configuration in which one first hydraulic pump 10 is provided to the first engine 8, and one second hydraulic pump 11 is provided to the second engine 9 may be used.

[0019] A first hydraulic pump 10 serving as a hydraulic pump is configured as a hydraulic pump group attached to the first engine 8. A second hydraulic pump 11 serving as a hydraulic pump is configured as a hydraulic pump group attached to the second engine 9. The first hydraulic pump 10 is driven by the first engine 8, and the second hydraulic pump 11 is driven by the second engine 9, thereby supplying pressurized hydraulic oil (pressurized oil) to a traveling hydraulic motor serving as a hydraulic actuator for traveling the lower traveling body 2, a swing hydraulic motor serving as a hydraulic actuator for swinging the upper swing body 4, and a hydraulic cylinder 5A serving as a hydraulic actuator for swinging the working device 5.

[0020] An example of the flow of pressure oil supplied from the first hydraulic pump 10 and the second hydraulic pump 11 will now be described with reference to Fig. 2. The hydraulic oil (pressurized oil) discharged from the first hydraulic pump 10 and the second hydraulic pump 11 flows through a supply pipe 13 and is supplied to the hydraulic cylinder 5A via a control valve 12. On the other hand, the hydraulic oil discharged from the hydraulic cylinder 5A flows through a return pipe 14 and is returned to the hydraulic oil tank 7 via the control valve 12.

[0021] Furthermore, when the first hydraulic pump 10 and the second hydraulic pump 11 are variable displacement piston pumps, hydraulic oil is supplied as a lubricating oil to lubricate and cool the sliding parts between the cylinder and the piston, the sliding parts of the tilt angle variable part, etc. Then, the hydraulic oil discharged after lubricating each sliding part is returned to the hydraulic oil tank 7 through a first drain pipe 15 and a second drain pipe 16 described below.

[0022] Furthermore, there is a risk that the discharge efficiency of the hydraulic oil may decrease if air gets into the hydraulic oil flow path of the first hydraulic pump 10 and the second hydraulic pump 11. For this reason, a first exhaust pipe 17 (described later) is connected to the top of the first hydraulic pump 10, and a second exhaust pipe 18 (described later) is connected to the top of the second hydraulic pump 11. This allows the first hydraulic pump 10 and the second hydraulic pump 11 to bleed internal air through the exhaust pipes 17, 18.

[0023] The supply pipe 13 is provided between the hydraulic oil tank 7 and the hydraulic cylinder 5A. The supply pipe 13 connects the hydraulic oil tank 7 with the first hydraulic pump 10, the second hydraulic pump 11, the control valve 12, and the hydraulic cylinder 5A. This allows the supply pipe 13 to supply the hydraulic oil discharged from the first hydraulic pump 10 and the second hydraulic pump 11 to the hydraulic cylinder 5A.

[0024] The return pipe 14 is provided between the hydraulic cylinder 5A and the hydraulic oil tank 7. The return pipe 14 connects the hydraulic cylinder 5A, the control valve 12, and the hydraulic oil tank 7. This enables the return pipe 14 to return the hydraulic oil discharged from the hydraulic cylinder 5A to the hydraulic oil tank 7.

[0025] The first drain pipe 15 as a drain pipe is a pipe that returns the hydraulic oil discharged from the first hydraulic pump 10 attached to the first engine 8 to the hydraulic oil tank 7. In other words, the first drain pipe 15 is a pipe separate from the supply pipe 13 and the return pipe 14 that circulate the hydraulic oil between the hydraulic oil tank 7 and the hydraulic cylinder 5A. The first drain pipe 15 lubricates and cools the sliding parts inside the first hydraulic pump 10 and returns the discharged hydraulic oil to the hydraulic oil tank 7, and in this hydraulic oil flow (flow direction of the hydraulic oil), the first hydraulic pump 10 side is the upstream side and the hydraulic oil tank 7 side is the downstream side.

[0026] 3, in this embodiment, the first drain pipe 15 is arranged so that it extends downward from each of the multiple first hydraulic pumps 10, merges, then repeatedly rises and falls to form an S-shaped crank shape, and then rises toward the upper part of the hydraulic oil tank 7. Specifically, the first drain pipe 15 has discharge pipes 15A extending downward from the multiple first hydraulic pumps 10, and a junction pipe 15B connected to the discharge pipes 15A and extending horizontally.

[0027] The first drain pipe 15 has the first hydraulic pump 10 located upstream of the hydraulic oil flow, and is provided downstream of the first hydraulic pump 10 (junction pipe 15B) in the hydraulic oil flow, and has an upstream side riser pipe section 15C which is a U-shaped (inverted U-shaped) riser pipe section with a convex upward direction of the machine body. The upstream side riser pipe section 15C has a riser pipe 15C1 rising from the downstream end of the junction pipe 15B, a horizontal pipe 15C2 connected to the upper end of the riser pipe 15C1 and extending horizontally, and a faller pipe 15C3 falling from the downstream end of the horizontal pipe 15C2. In this embodiment, a low-position pipe section 15D is connected to the lower end of the faller pipe 15C3.

[0028] In addition, the first drain pipe 15 has a low-position pipe section 15D that is connected downstream of the upstream riser pipe section 15C in the hydraulic oil flow, in this embodiment, to a position downstream of the upstream riser pipe section 15C, i.e., to the lower end of the downdraft pipe 15C3, and is positioned lower than the upstream riser pipe section 15C.

[0029] Furthermore, the first drain pipe 15 has a downstream side rising pipe section 15E, which is a rising pipe section common to a second drain pipe 16 described later, that is provided downstream of the hydraulic oil flow from the low position pipe section 15D and rises toward the upper part of the hydraulic oil tank 7. The common downstream side rising pipe section 15E also serves as a part of the second drain pipe 16 described later, and is connected to the downstream side of the low position pipe section 16D.

[0030] The low-position pipe section 15D is disposed between the upstream side rising pipe section 15C and the downstream side rising pipe section 15E. The low-position pipe section 15D is disposed at a lower position than the convex portion (horizontal pipe 15C2) of the upstream side rising pipe section 15C. In this embodiment, the low-position pipe section 15D is disposed at a lower position than the entire upstream side rising pipe section 15C. As shown in FIG. 4, the low-position pipe section 15D is composed of an upstream side horizontal pipe section 15D1 connected to the downstream end of the upstream side rising pipe section 15C and extending horizontally, a straight pipe section 15D2 connected to the downstream end of the horizontal pipe section 15D1, and a connecting pipe section 15D3 bent from the downstream end of the straight pipe section 15D2 to the hydraulic oil tank 7 side. The low-position pipe section 15D is disposed at a height position equivalent to the bottom position of the hydraulic oil tank 7, for example.

[0031] The straight pipe section 15D2 is made of a linear pipe and is inclined so that the downstream side of the downstream rising pipe section 15E is higher than the upstream side of the upstream rising pipe section 15C, that is, so that the hydraulic oil flow becomes higher toward the downstream side (for example, inclined at an angle of 5 to 30 degrees with respect to the horizontal plane, preferably at an angle of about 10 degrees). In addition, the straight pipe section 15D2 is provided with an oil sensor 20 (sensor mounting port 19) described later on the downstream side of the connecting pipe section 15D3. Moreover, the straight pipe section 15D2 made of a linear pipe is less likely to accumulate air and other impurities (for example, metal powder generated by wear of the hydraulic pumps 10, 11), so it becomes an environment in which the detection accuracy of the oil sensor 20 is stable.

[0032] The connecting pipe section 15D3 is connected to the downstream rising pipe section 15E at a position lower than the position at which the second drain pipe 16 (lower position pipe section 16D) constituting the other drain pipe is connected to the common downstream rising pipe section 15E.

[0033] Here, the hydraulic oil supplied to lubricate and cool the first hydraulic pump 10 and the second hydraulic pump 11 is supplied at a constant flow rate. Therefore, the hydraulic oil discharged from the first hydraulic pump 10 and the second hydraulic pump 11 and circulating in the first drain pipe 15 has a constant and stable flow rate. As a result, the first drain pipe 15 has a smaller fluctuation range in the hydraulic oil pressure and less rapid changes in the hydraulic oil temperature than the supply pipe 13 and the return pipe 14. Moreover, the low-position pipe section 15D of the first drain pipe 15 is disposed at a lower position than the upstream side riser pipe section 15C and the downstream side riser pipe section 15E, so that the structure is such that air is less likely to accumulate. Therefore, the oil sensor 20 provided in the low-position pipe section 15D can accurately detect the properties of the hydraulic oil.

[0034] The second drain pipe 16 as another drain pipe is a pipe that returns the hydraulic oil discharged from the multiple second hydraulic pumps 11 attached to the second engine 9 to the hydraulic oil tank 7. Like the first drain pipe 15, the second drain pipe 16 is a pipe separate from the supply pipe 13 and the return pipe 14 that circulate the hydraulic oil between the hydraulic oil tank 7 and the hydraulic cylinder 5A. The second drain pipe 16 returns the hydraulic oil discharged from the second hydraulic pump 11 to the hydraulic oil tank 7, and the second hydraulic pump 11 side is the upstream side and the hydraulic oil tank 7 side is the downstream side in the flow direction of the hydraulic oil.

[0035] The second drain pipe 16 includes a discharge pipe 16A, a junction pipe 16B, an upstream side rising pipe section 16C, and a low position pipe section 16D, similar to the first drain pipe 15. In addition, the downstream side of the low position pipe section 16D is connected to the common downstream side rising pipe section 15E constituting the first drain pipe 15.

[0036] Here, the low-position pipe section 16D located downstream of the second drain pipe 16 is connected to the downstream-side rising pipe section 15E at a position higher than the position at which the low-position pipe section 15D of the first drain pipe 15 is connected to the common downstream-side rising pipe section 15E. This makes it possible to prevent air from flowing into the first drain pipe 15 (low-position pipe section 15D) even if air flows from the second drain pipe 16 into the downstream-side rising pipe section 15E.

[0037] The first exhaust pipe 17 as an exhaust pipe is for discharging air generated inside the first hydraulic pump 10 attached to the first engine 8. A first end of the first exhaust pipe 17 is connected to an upper part inside the first hydraulic pump 10. Meanwhile, a second end of the first exhaust pipe 17 is connected to an upper part of the riser pipe 15C1 of the upstream riser pipe section 15C of the first drain pipe 15. This enables the first exhaust pipe 17 to discharge air generated inside the first hydraulic pump 10 to the first drain pipe 15.

[0038] The second exhaust pipe 18 as an exhaust pipe is for discharging air generated inside the second hydraulic pump 11 attached to the second engine 9. Similar to the first exhaust pipe 17, the second exhaust pipe 18 has a first end connected to an upper part inside the second hydraulic pump 11 and a second end connected to an upper part of the upstream riser pipe section 16C of the second drain pipe 16. This enables the second exhaust pipe 18 to discharge air generated inside the second hydraulic pump 11 to the second drain pipe 16.

[0039] The sensor mounting port 19 is provided in the low-position pipe section 15D of the first drain pipe 15. The sensor mounting port 19 is made of a cylinder with a female thread engraved on the inner circumference side, and is fixed to the low-position pipe section 15D by means of welding, adhesive, or the like. The sensor mounting port 19 is disposed on the downstream side (high side) of the straight pipe section 15D2 of the low-position pipe section 15D. More specifically, if the center line of the sensor mounting port 19 is the axis O1-O1 and the center line of the straight pipe section 15D2 is the axis O2-O2, the sensor mounting port 19 is attached to the straight pipe section 15D2 so that its axis O1-O1 is perpendicular to the axis O2-O2 of the straight pipe section 15D2.

[0040] The oil sensor 20 is attached to the low-position pipe section 15D of the first drain pipe 15 via a sensor attachment port 19. The oil sensor 20 detects the properties of the hydraulic oil, such as the viscosity, concentration, non-conductivity, temperature, and the presence or absence of foreign matter of the hydraulic oil, and outputs the detected properties to a controller 21 described later.

[0041] The oil sensor 20 is disposed in the low-position pipe section 15D on the downstream side (higher side) of the straight pipe section 15D2 by being screwed into the sensor mounting port 19. The oil sensor 20 is disposed coaxially with the sensor mounting port 19, so the oil sensor 20 is perpendicular to the axis O2-O2 of the straight pipe section 15D2. This allows the detection part at the tip of the oil sensor 20 to be correctly applied to the hydraulic oil flowing straight through the straight pipe section 15D2.

[0042] The controller 21 is provided, for example, on the upper rotating body 4, and is connected wirelessly or by wire to the oil sensor 20, etc. When data on the viscosity, concentration, non-conductivity, temperature, presence or absence of foreign matter, etc. of the hydraulic oil is input from the oil sensor 20, the controller 21 inspects the properties of the hydraulic oil based on the detection results, and notifies the time for replacement, etc.

[0043] The server 22 is connected to the controller 21 via a wireless or wired network, and is configured to be able to transmit and receive data to and from the controller 21. The server 22 provides the controller 21 with various types of information.

[0044] The cab 23 is provided at the left front portion of the upper rotating body 4. A driver's seat, an operating lever for traveling, an operating lever for work, etc. (none of which are shown) are provided inside the cab 23.

[0045] The hydraulic excavator 1 according to this embodiment has the above-mentioned configuration, and its operation will now be described.

[0046] First, the operator gets into the cab 23 and starts the first engine 8 and the second engine 9. Then, the operator can travel the hydraulic excavator 1 by operating the operating lever for travel arranged inside the cab 23, and can operate the rotating device 3 and the working device 5 by operating the operating lever for work, thereby performing work such as excavating earth and sand.

[0047] Here, when the first engine 8 and the second engine 9 are operated, the hydraulic oil in the hydraulic oil tank 7 is supplied as pressurized oil by the first hydraulic pump 10 and the second hydraulic pump 11 to the control valve 12 through the supply piping 13. In this state, for example, when an operator in the cab 23 operates an operation lever for work, the hydraulic oil is supplied to the hydraulic cylinder 5A, causing the work device 5 to rotate. Meanwhile, the pressurized oil discharged from the hydraulic cylinder 5A is returned to the hydraulic oil tank 7 through the return piping 14.

[0048] In addition, when the first hydraulic pump 10 and the second hydraulic pump 11 are operated, hydraulic oil is supplied as a lubricating oil to lubricate and cool the sliding parts, etc., and the hydraulic oil discharged after lubricating the sliding parts is returned to the hydraulic oil tank 7 through the first drain pipe 15 and the second drain pipe 16.

[0049] In addition, the oil sensor 20 detects the viscosity, concentration, non-conductivity, temperature, etc. of the hydraulic oil flowing through the first drain pipe 15 and outputs the results to the controller 21. As a result, the controller 21 inspects the properties of the hydraulic oil based on, for example, the detection result of the oil sensor 20 and data from the server 22, and notifies the user of the time to replace the hydraulic oil, etc.

[0050] Thus, in this embodiment, the hydraulic excavator 1 is provided with a first drain pipe 15 for returning hydraulic oil discharged from the first hydraulic pump 10 to the hydraulic oil tank 7, in addition to the supply pipe 13 and return pipe 14 for circulating hydraulic oil between the hydraulic oil tank 7 and the traveling hydraulic motor of the lower traveling body 2, the swing hydraulic motor of the swing device 3, and the hydraulic cylinder 5A of the working device 5. The first drain pipe 15 is provided with an upstream side riser pipe section 15C that rises upwardly so as to be convex, with the first hydraulic pump 10 located upstream of the hydraulic oil flow, and a low-position pipe section 15D that is provided downstream of the upstream side riser pipe section 15C in the hydraulic oil flow and located at a lower position than the upstream side riser pipe section 15C. In addition, an oil sensor 20 for detecting the properties of the hydraulic oil is attached to the low-position pipe section 15D.

[0051] Here, the hydraulic oil that lubricates and cools the first hydraulic pump 10 flows at a constant flow rate through the first drain pipe 15 to which the oil sensor 20 is attached. Therefore, the first drain pipe 15 has smaller fluctuations in the hydraulic oil pressure and flow rate and less sudden changes in the hydraulic oil temperature than the supply pipe 13 and the return pipe 14. Moreover, the low-position pipe section 15D of the first drain pipe 15 is located at a lower position than the upstream side riser pipe section 15C and the downstream side riser pipe section 15E, so the structure is such that air is less likely to accumulate.

[0052] Therefore, since the oil sensor 20 is provided in the low pipe section 15D of the first drain piping 15 where the hydraulic oil flows stably and air is unlikely to accumulate, the properties of the hydraulic oil can be accurately detected. As a result, the durability and reliability of the traveling hydraulic motor of the lower traveling body 2, the swing hydraulic motor of the swing device 3, the hydraulic cylinder 5A of the working device 5, the first hydraulic pump 10, and the second hydraulic pump 11, which constitute the hydraulic actuator, can be improved.

[0053] In addition, the low-position pipe section 15D has a straight pipe section 15D2 that becomes higher toward the downstream of the hydraulic oil flow. In addition, the oil sensor 20 is attached to the straight pipe section 15D2 of the low-position pipe section 15D. This creates an environment around the detection section of the oil sensor 20 where air and impurities are unlikely to accumulate, so the detection accuracy of the oil sensor 20 can be stabilized.

[0054] On the other hand, the hydraulic pump includes a first hydraulic pump 10 and a second hydraulic pump 11. Two prime movers are provided: a first engine 8 to which the first hydraulic pump 10 is attached, and a second engine 9 to which the second hydraulic pump 11 is attached. In addition, the drain piping includes a first drain piping 15 connected to the first hydraulic pump 10, which includes an upstream side rising pipe section 15C and a low position pipe section 15D, and to which an oil sensor 20 is attached, and a second drain piping 16 connected to the second hydraulic pump 11. The first drain pipe 15 and the second drain pipe 16 are located downstream of the hydraulic oil flow from the low-position pipe section 15D of the first drain pipe 15, and the first drain pipe 15 and the second drain pipe 16 have a common downstream rising pipe section 15E, and the second drain pipe 16 is connected to the common downstream rising pipe section 15E at a position higher than the position at which the low-position pipe section 15D of the first drain pipe 15 is connected to the common downstream rising pipe section 15E.

[0055] As a result, even if air flows from the second drain pipe 16 into the downstream rising pipe section 15E, it is possible to prevent the air from flowing into the first drain pipe 15 (low-position pipe section 15D) which is located at a lower position. This also makes it possible to stabilize the detection accuracy of the oil sensor 20.

[0056] Further, a first end of a first exhaust pipe 17 for discharging air generated in the first hydraulic pump 10 is connected to the first hydraulic pump 10. Further, a first end of a second exhaust pipe 18 for discharging air generated in the second hydraulic pump 11 is connected to the second hydraulic pump 11. A second end of the first exhaust pipe 17 is connected to the upstream riser pipe section 15C of the first drain pipe 15, and a second end of the second exhaust pipe 18 is connected to the upstream riser pipe section 16C of the second drain pipe 16. As a result, the first exhaust pipe 17 can discharge air generated inside the first hydraulic pump 10 to the first drain pipe 15. Further, the second exhaust pipe 18 can discharge air generated inside the second hydraulic pump 11 to the second drain pipe 16.

[0057] In the embodiment, an example is described in which two first engines 8 and two second engines 9 and two systems of first drain pipes 15 and second drain pipes 16 are provided, and the oil sensor 20 is attached to the first drain pipe 15. However, the present invention is not limited to this configuration, and may be configured as in the modified examples shown in Figures 5 and 6, for example. That is, a single first engine 8 and one system of first drain pipes 15 may be provided, and the oil sensor 20 may be attached to the first drain pipe 15.

[0058] In the embodiment, the low-position pipe section 15D of the first drain pipe 15 is illustrated as including a horizontal pipe section 15D1 and an inclined straight pipe section 15D2. However, the present invention is not limited to this. For example, the low-position pipe section may be formed only of a horizontal pipe. It may also be formed as a curved pipe.

[0059] Furthermore, in the embodiment, the hydraulic excavator 1 equipped with a backhoe-type working implement 5 has been taken as an example of the construction machine. However, the present invention is not limited to this, and can be widely applied to other construction machines such as hydraulic excavators equipped with a loading shovel-type working implement. [Explanation of symbols]

[0060] 1. Hydraulic excavator (construction machinery) 2 Undercarriage 3 Swivel device 4. Upper rotating body 5. Working Equipment 5A Hydraulic Cylinder (Hydraulic Actuator) 6 Swivel Frame 7 Hydraulic Oil Tank 8. First engine (first prime mover) 9. Second engine (second prime mover) 10 First hydraulic pump (hydraulic pump) 11 Second hydraulic pump (hydraulic pump) 13 Supply piping 14 Return pipe 15 First drain pipe (drain pipe) 15C Upstream riser pipe section 15C1 riser pipe 15C2 horizontal pipe 15C3 Downpipe 15D Low position pipe section 15D2 Straight pipe section 15E Downstream rising pipe section 16 Second drain pipe (other drain pipe) 17 First exhaust pipe (exhaust pipe) 18 Second exhaust pipe (exhaust pipe) 19 Sensor mounting port 20 Oil Sensor

Claims

1. The vehicle comprises a self-propelled lower traveling body, an upper rotating body rotatably provided on the lower traveling body, and a working device rotatably provided on a front part of the upper rotating body, The upper rotating body is A rotating frame supported on the lower traveling body so as to be capable of rotating; a hydraulic oil tank provided on the rotating frame and configured to store hydraulic oil; A prime mover provided on the rotating frame; a hydraulic pump that is driven by the prime mover to supply hydraulic oil to a hydraulic actuator that travels the lower traveling body, a hydraulic actuator that rotates the upper rotating body, and a hydraulic actuator that rotates the working device; an oil sensor for detecting the properties of hydraulic oil; In a construction machine comprising: a drain pipe for returning the hydraulic oil discharged from the hydraulic pump to the hydraulic oil tank, in addition to a supply pipe and a return pipe for circulating the hydraulic oil between the hydraulic oil tank and the hydraulic actuator; The drain piping includes a riser pipe section that rises upward so as to be convex with the hydraulic pump positioned upstream of the hydraulic oil flow, and a low-position pipe section that is provided downstream of the riser pipe section in the hydraulic oil flow and is positioned lower than the riser pipe section, A construction machine characterized in that the oil sensor is attached to the low-position pipe portion.

2. 2. The construction machine according to claim 1, The low-position pipe portion has a straight pipe portion that becomes higher toward the downstream of the hydraulic oil flow, A construction machine characterized in that the oil sensor is attached to the straight pipe section of the low-position pipe section.

3. 2. The construction machine according to claim 1, The hydraulic pump includes a first hydraulic pump and a second hydraulic pump, The prime mover includes a first prime mover to which the first hydraulic pump is attached and a second prime mover to which the second hydraulic pump is attached, the drain piping includes a first drain piping connected to the first hydraulic pump, the first drain piping including the riser pipe section and the low position pipe section and having the oil sensor attached thereto, and a second drain piping connected to the second hydraulic pump; The first drain pipe and the second drain pipe are provided downstream of the low-position pipe portion of the first drain pipe in a hydraulic oil flow direction, and the first drain pipe and the second drain pipe have a common rising pipe portion, A construction machine characterized in that the second drain piping is connected to the common riser pipe section at a position higher than the position at which the low-position pipe section of the first drain piping is connected to the common riser pipe section.

4. 2. The construction machine according to claim 1, a first end of an exhaust pipe for discharging air generated in the hydraulic pump is connected to the hydraulic pump; A construction machine characterized in that a second end of the exhaust piping is connected to the riser pipe portion.

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