Working machinery

Abstract

The present invention provides a machine capable of removing dust accumulated in a heat exchanger while suppressing the temperature rise of the fluid passing through the heat exchanger. [Solution] The machine calculates the heat transfer rate, which represents the efficiency of heat exchange in the heat exchanger, based on the detection results of the flow sensor, the first temperature difference sensor, and the second temperature difference sensor, stores it in memory, compares the past heat transfer rate stored in memory with the latest heat transfer rate, determines the reverse rotation time for the cooling fan, and rotates the cooling fan in reverse for the determined reverse rotation time.

Description

Technical Field

[0001] The present invention relates to a working machine provided with a cooling fan capable of forward and reverse rotation.

Background Art

[0002] Working machines may be used in environments where dust (such as wood chips, earth and sand, dust, etc.) scatters. In working machines used in such environments, there is a problem that dust in the air taken into the engine room by the cooling fan accumulates on the surface of the heat exchanger, reducing the cooling performance of the heat exchanger.

[0003] Therefore, Patent Document 1 discloses a technique for removing dust deposited on a heat exchanger by rotating a cooling fan in the reverse direction. Further, Patent Document 2 discloses a technique for rotating one of two cooling fans in the forward direction and the other in the reverse direction.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, when the cooling fan is rotated in the reverse direction as in Patent Document 1, there is a problem that the temperature of the fluid passing through the heat exchanger increases because the high-temperature air around the engine passes through the heat exchanger. Further, in order to solve the problem of Patent Document 1, when adjacent cooling fans rotate in opposite directions as in Patent Document 2, a new problem occurs that the air flow is disturbed and the bidirectional airflows cancel each other out.

[0006] The present invention has been made in view of the above circumstances, and its purpose is to provide a work machine capable of removing dust accumulated in a heat exchanger while suppressing the temperature rise of the fluid passing through the heat exchanger. [Means for solving the problem]

[0007] To achieve the above objective, the present invention provides a machine that supports a building, a drive source housed in the building that generates a driving force to operate the machine, a heat exchanger housed in the building that exchanges heat between cooling air and a high-temperature fluid, a cooling fan housed in the building between the drive source and the heat exchanger that generates the cooling air flowing from the heat exchanger to the drive source and is capable of forward rotation and reverse rotation in the opposite direction to the forward rotation, a flow sensor that detects the flow rate of the high-temperature fluid or the cooling air, and a first temperature difference sensor that detects the temperature difference of the high-temperature fluid before and after heat exchange with the cooling air. A work machine comprising a second temperature difference sensor for detecting the temperature difference of the cooling air before and after heat exchange with the high-temperature fluid, and a controller having a memory, wherein the controller calculates a heat transfer rate representing the efficiency of heat exchange in the heat exchanger based on the detection results of the flow sensor, the first temperature difference sensor, and the second temperature difference sensor, stores it in the memory, compares the past heat transfer rates stored in the memory with the latest heat transfer rates, determines the reverse rotation time of the cooling fan, and reverses the rotation of the cooling fan for the determined reverse rotation time. [Effects of the Invention]

[0008] According to the present invention, it is possible to remove dust accumulated in a heat exchanger while suppressing the temperature rise of the fluid passing through the heat exchanger. Other problems, configurations, and effects will be clarified by the following description of embodiments. [Brief explanation of the drawing]

[0009] [Figure 1] This is a side view of a hydraulic excavator. [Figure 2] This is a perspective view of the upper rotating body from the left rear. [Figure 3] This is a cross-sectional view of the engine building. [Figure 4] This is a hardware configuration diagram for a hydraulic excavator. [Figure 5] This is a functional block diagram of the controller. [Figure 6] This is a flowchart for determining the reverse rotation time. [Figure 7] This is an example of information stored in memory for each control cycle. [Figure 8] This figure shows an example of the distribution of average flow rate and average heat transfer coefficient. [Figure 9] This is an example of a reverse rotation time table. [Figure 10] This is a flowchart for reversing the fan's rotation. [Modes for carrying out the invention]

[0010] [Configuration of Hydraulic Excavator 1] An embodiment of the hydraulic excavator 1 according to the present invention will be described with reference to the drawings. The hydraulic excavator 1 according to this embodiment is an example of a work machine. Specific examples of work machines are not limited to the hydraulic excavator 1, but may also include wheel loaders, dump trucks, cranes, etc. Furthermore, unless otherwise specified, the terms front, back, left, and right in this specification refer to the viewpoint of the operator riding and operating the hydraulic excavator 1.

[0011] Figure 1 is a side view of a hydraulic excavator 1. As shown in Figure 1, the hydraulic excavator 1 comprises a lower traveling body 2 and an upper rotating body 3 supported by the lower traveling body 2. The lower traveling body 2 and the upper rotating body 3 are examples of the machine body.

[0012] The lower vehicle 2 is equipped with a pair of crawlers 4 on the left and right sides, which are continuous tracks. Driven by the travel motor 5, the pair of crawlers 4 rotate independently. As a result, the hydraulic excavator 1 moves. However, the lower vehicle 2 may be wheeled instead of having crawlers 4.

[0013] The upper revolving body 3 is supported by the lower traveling body 2 so as to be rotatable. Then, when the swing motor 6 rotates, the upper revolving body 3 rotates with respect to the lower traveling body 2. The upper revolving body 3 mainly includes a revolving frame 7 serving as a base, a cab (driver's seat) 8 arranged on the front left side of the revolving frame 7, a counterweight 9 arranged at the rear part of the revolving frame 7, a front working machine 10 (working device) pivotally attached to the front center of the revolving frame 7 in the vertical direction, and an engine house 20 (house).

[0014] The cab 8 is arranged adjacent to the front working machine 10 in the left - right direction (the width direction of the vehicle body). More specifically, the cab 8 is arranged on the left side (one side in the left - right direction) of the front working machine 10. However, the arrangement of the cab 8 is not limited to the above example, and the cab 8 may be arranged on one side of the front working machine 10 in the left - right direction.

[0015] A space for an operator to board and operate the hydraulic excavator 1 is formed in the cab 8. Inside the cab 8, a seat for the operator to sit on and an operating device 33 (see FIG. 4) operated by the operator sitting on the seat are arranged. The operating device 33 receives the operation of the operator to operate the hydraulic excavator 1. When the operating device 33 is operated by the operator, the lower traveling body 2 travels, the upper revolving body 3 rotates, and the front working machine 10 operates. Specific examples of the operating device 33 include a lever, a steering wheel, a pedal, a switch, etc.

[0016] The front working machine 10 includes a boom 11 pivotally supported by the upper revolving body 3, an arm 12 pivotally supported at the tip of the boom 11, a bucket 13 (attachment) pivotally supported at the tip of the arm 12, a boom cylinder 14 for rotating the boom 11 with respect to the upper revolving body 3, an arm cylinder 15 for rotating the arm 12 with respect to the boom 11, and a bucket cylinder 16 for rotating the bucket 13 with respect to the arm 12. The counterweight 9 is for taking the weight balance with the front working machine 10 and is a heavy object having an arc shape in top view.

[0017] Figure 2 is a perspective view of the upper revolving structure 3 seen from the left rear. Figure 3 is a sectional view of the engine house 20. As shown in Figure 2, the upper revolving structure 3 supports a fuel tank 17 for storing fuel (e.g., light oil) and a hydraulic oil tank 18 for storing hydraulic oil. The fuel tank 17 and the hydraulic oil tank 18 are arranged in front of the engine house 20.

[0018] The engine house 20 is arranged behind the cab 8, the front working machine 10, the fuel tank 17, and the hydraulic oil tank 18, and in front of the counterweight 9. Also, as shown in Figure 3, the engine house 20 has an internal space for accommodating the engine 21, the hydraulic pump 22, the heat exchanger 23, the cooling fan 24, and the fan motor 25.

[0019] The engine 21 is an example of a drive source that burns the fuel stored in the fuel tank 17 to generate a driving force for operating the hydraulic excavator 1. Therefore, the surrounding of the engine 21 becomes high temperature. However, the specific example of the drive source is not limited to the engine 21, and an electric motor or the like may also be used.

[0020] The hydraulic pump 22 is accommodated in the engine house 20 to the right of the engine 21. The hydraulic pump 22 rotates by the driving force of the engine 21 and discharges the hydraulic oil stored in the hydraulic oil tank 18. The hydraulic oil discharged from the hydraulic pump 22 is supplied to hydraulic actuators (travel motor 5, swing motor 6, boom cylinder 14, arm cylinder 15, bucket cylinder 16) via a valve (not shown). Thereby, the hydraulic actuators operate.

[0021] The heat exchanger 23 is housed in the engine building 20 to the left of the engine 21 and the cooling fan 24. The heat exchanger 23 exchanges heat between the cooling air generated by the cooling fan 24 and a fluid (e.g., coolant, hydraulic oil, air). The heat exchanger 23 includes, for example, a radiator that exchanges heat between the coolant cooling the engine 21 and the cooling air, an oil cooler that exchanges heat between the hydraulic oil and the cooling air, and part or all of an intercooler that cools the air compressed by the supercharger mounted on the engine 21.

[0022] The cooling fan 24 is housed in the engine building 20, between the engine 21 and the heat exchanger 23 in the left-right direction. The cooling fan 24 rotates in both forward and reverse directions, driven by the fan motor 25. Forward rotation is the direction in which cooling air is generated within the engine building 20, from the heat exchanger 23 side towards the engine 21 side. Reverse rotation is the direction opposite to forward rotation (more specifically, the direction in which cleaning air is generated from the engine 21 side towards the heat exchanger 23 side).

[0023] In other words, the engine 21 is positioned downstream of the cooling airflow (in other words, upstream of the cleaning airflow) of the heat exchanger 23 and the cooling fan 24. Also, the heat exchanger 23 is positioned upstream of the cooling airflow (in other words, downstream of the cleaning airflow) of the engine 21 and the cooling fan 24.

[0024] Furthermore, openings 20L and 20R are formed in the outer wall of the engine building 20. Opening 20L penetrates the left wall of the engine building 20 in the thickness direction. Opening 20R penetrates the right wall of the engine building 20 in the thickness direction. Openings 20L and 20R allow air to circulate between the inside and outside of the engine building 20. However, the air flowing into the engine building 20 through openings 20L and 20R contains dust (e.g., wood chips, soil, dirt, etc.).

[0025] When the cooling fan 24 rotates forward, the air (cooling air) that flows into the engine building 20 through the opening 20L exchanges heat with the fluid flowing inside the heat exchanger 23, and then passes around the cooling fan 24, the engine 21, and the hydraulic pump 22 before being discharged from the engine building 20 through the opening 20R. In addition, dust contained in the air that flows in through the opening 20L accumulates on the surface (left side) of the heat exchanger 23. The cooling air generated by the forward-rotating cooling fan 24 is a "low-temperature fluid," while the fluid passing inside the heat exchanger 23 is a "high-temperature fluid."

[0026] On the other hand, when the cooling fan 24 rotates in reverse, the air (cleaning air) that flows into the engine building 20 through the opening 20R is heated as it passes around the engine 21 before passing through the heat exchanger 23. This removes the dust accumulated on the left side of the heat exchanger 23. Meanwhile, the high-temperature fluid flowing inside the heat exchanger 23 is hardly cooled, or even becomes hotter, by exchanging heat with the air heated by the engine 21.

[0027] [Hardware configuration of hydraulic excavator 1] Figure 4 is a hardware configuration diagram of the hydraulic excavator 1. As shown in Figure 4, the hydraulic excavator 1 includes a controller 30 having a CPU 31 (Central Processing Unit) and memory 32. The memory 32 is composed of, for example, ROM (Read Only Memory), RAM (Random Access Memory), HDD (Hard Disk Drive), or a combination thereof. The controller 30 performs the processing described later by having the CPU 31 read and execute the program code stored in the memory 32.

[0028] However, the specific configuration of the controller 30 is not limited to this and may be implemented using hardware such as an ASIC (Application Specific Integrated Circuit) or FPGA (Field-Programmable Gate Array).

[0029] The controller 30 controls the operation of the entire hydraulic excavator 1. Based on various signals output from the operating device 33, reverse rotation switch 34, high-temperature side flow sensor 35, low-temperature side flow sensor 36, first high-temperature side temperature sensor 37, second high-temperature side temperature sensor 38, first low-temperature side temperature sensor 39, and second low-temperature side temperature sensor 40, the controller 30 controls the operation of the engine 21, hydraulic pump 22, and fan motor 25, and displays various information on the display 41.

[0030] The operating device 33 receives operator input to instruct the operation of the hydraulic excavator 1 (more specifically, the hydraulic actuator) and outputs an operation signal corresponding to the operator's input to the controller 30. The controller 30 controls the operation of the engine 21, hydraulic pump 22, and fan motor 25 according to the operation signal output from the operating device 33.

[0031] The reverse rotation switch 34 receives an operator's command to reverse the rotation of the cooling fan 24 and outputs a reverse rotation signal to the controller 30. The controller 30, in principle, rotates the cooling fan 24 in the forward direction while the engine 21 is running. On the other hand, when the controller 30 receives a reverse rotation signal from the reverse rotation switch 34, it rotates the cooling fan 24 in the reverse direction for the reverse rotation time determined by the reverse rotation time determination process (Figure 6). Then, after the reverse rotation time has elapsed since the start of the reverse rotation of the cooling fan 24, the controller 30 starts rotating the cooling fan 24 in the forward direction again.

[0032] The high-temperature side flow sensor 35 is installed, for example, in a pipeline through which high-temperature fluid connected to the heat exchanger 23 flows. It detects the flow rate Wh [kg / sec] of the high-temperature fluid flowing through the heat exchanger 23 per unit time and outputs a flow rate signal indicating the detected flow rate Wh to the controller 30. The low-temperature side flow sensor 36 is, for example, an airflow sensor installed on the front (opening 20L side) or back (opening 20R side) of the heat exchanger 23. It detects the flow rate Wc [kg / sec] of the low-temperature fluid passing through the heat exchanger 23 per unit time and outputs a flow rate signal indicating the detected flow rate Wc to the controller 30. The low-temperature side flow sensor 36 may also be a rotation speed sensor for the cooling fan 24. The flow rate Wc may be detected by multiplying the rotation speed of the cooling fan 24 detected by the rotation speed sensor by a predetermined flow rate of cooling air per rotation. Furthermore, the hydraulic excavator 1 may be equipped with only one of the high-temperature side flow sensor 35 and the low-temperature side flow sensor 36, and the other may be omitted.

[0033] The first high-temperature side temperature sensor 37 detects the temperature Th1 of the high-temperature fluid before it flows into the heat exchanger 23 (i.e., before heat exchange with the cooling air) and outputs a temperature signal indicating the detected temperature Th1 to the controller 30. The second high-temperature side temperature sensor 38 detects the temperature Th2 of the high-temperature fluid after it flows out of the heat exchanger 23 (i.e., after heat exchange with the cooling air) and outputs a temperature signal indicating the detected temperature Th2 to the controller 30.

[0034] As an example, if the high-temperature fluid is the coolant for the engine 21, the first high-temperature side temperature sensor 37 detects the temperature Th1 of the coolant after it has cooled the engine 21 and before it flows into the heat exchanger 23. The second high-temperature side temperature sensor 38 detects the temperature Th2 of the coolant after it has flowed out of the heat exchanger 23 and before it cools the engine 21. As another example, if the high-temperature fluid is hydraulic oil, the first high-temperature side temperature sensor 37 detects the temperature Th1 of the hydraulic oil after it has flowed out of the hydraulic actuator and before it flows into the heat exchanger 23. The second high-temperature side temperature sensor 38 detects the temperature Th2 of the hydraulic oil after it has flowed out of the heat exchanger 23 and before it returns to the hydraulic oil tank 18. As yet another example, if the high-temperature fluid is compressed air, the first high-temperature side temperature sensor 37 detects the temperature Th1 of the compressed air after it has been compressed by the supercharger and before it flows into the heat exchanger 23. Furthermore, the second high-temperature side temperature sensor 38 detects the temperature Th2 of the compressed air after it has flowed out of the heat exchanger 23 and before it is supplied to the engine 21.

[0035] The first low-temperature side temperature sensor 39 detects the temperature Tc1 of the low-temperature fluid (cooling air) before it passes through the heat exchanger 23 (i.e., before heat exchange with the high-temperature fluid) and outputs a temperature signal indicating the detected temperature Tc1 to the controller 30. The second low-temperature side temperature sensor 40 detects the temperature Tc2 of the low-temperature fluid (cooling air) after it passes through the heat exchanger 23 (i.e., after heat exchange with the high-temperature fluid) and outputs a temperature signal indicating the detected temperature Tc2 to the controller 30. For example, in the internal space of the engine building 20, the first low-temperature side temperature sensor 39 is located to the left of the heat exchanger 23, and the second low-temperature side temperature sensor 40 is located between the heat exchanger 23 and the cooling fan 24.

[0036] The difference between temperatures Th1 and Th2 corresponds to the temperature difference ΔTh of the high-temperature fluid before and after heat exchange with the cooling air. In other words, the first high-temperature side temperature sensor 37 and the second high-temperature side temperature sensor 38 are examples of first temperature difference sensors that detect the temperature difference of the high-temperature fluid before and after heat exchange with the cooling air. The difference between temperatures Tc1 and Tc2 corresponds to the temperature difference ΔTc of the cooling air before and after heat exchange with the high-temperature fluid. In other words, the first low-temperature side temperature sensor 39 and the second low-temperature side temperature sensor 40 are examples of second temperature difference sensors that detect the temperature difference of the cooling air before and after heat exchange with the high-temperature fluid.

[0037] Display 41 is an example of a notification device that informs the operator in cab 8 of information. However, the specific example of a notification device is not limited to display 41; it could also be an indicator with a changing number of lit LEDs, a speaker that outputs sound, etc.

[0038] [Functional blocks of controller 30] Figure 5 is a functional block diagram of the controller 30. As shown in Figure 5, the controller 30 comprises a heat transfer coefficient calculation unit 51, a cooling performance diagnostic unit 52, a reverse rotation time determination unit 53, and a fan rotation control unit 54. The controller 30 functions as the heat transfer coefficient calculation unit 51, the cooling performance diagnostic unit 52, the reverse rotation time determination unit 53, and the fan rotation control unit 54, for example, by the CPU 31 executing a program stored in the memory 32.

[0039] The heat transfer coefficient calculation unit 51 calculates the heat transfer coefficient K [W / m²] based on the detection results from the high-temperature side flow sensor 35 (or low-temperature side flow sensor 36), the first high-temperature side temperature sensor 37, the second high-temperature side temperature sensor 38, the first low-temperature side temperature sensor 39, and the second low-temperature side temperature sensor 40. 2 The heat transfer coefficient K is calculated. The heat transfer coefficient K is a numerical value that represents the efficiency of heat exchange in the heat exchanger 23. In other words, the value of the heat transfer coefficient K decreases as the cooling performance of the heat exchanger 23 decreases (for example, as the amount of dust accumulating on the surface of the heat exchanger 23 increases). The heat transfer coefficient K is calculated, for example, based on equations 1 to 4 described later.

[0040] The cooling performance diagnostic unit 52 diagnoses the cooling performance of the heat exchanger 23 based on multiple heat transfer coefficients K repeatedly calculated by the heat transfer coefficient calculation unit 51. More specifically, the cooling performance diagnostic unit 52 diagnoses the cooling performance of the heat exchanger 23 by comparing past heat transfer coefficients K with the latest heat transfer coefficient K. Even more specifically, the cooling performance diagnostic unit 52 calculates the percentage decrease R[%] of the heat transfer coefficient K as an indicator of the cooling performance of the heat exchanger 23. The specific method for diagnosing the cooling performance will be described later with reference to Figures 6 to 8.

[0041] The reverse rotation time determination unit 53 determines the reverse rotation time t [sec] according to the cooling performance of the heat exchanger 23 (more specifically, the rate of decrease R) diagnosed by the cooling performance diagnosis unit 52. The reverse rotation time t is the time for which the cooling fan 24 is rotated in reverse. More specifically, the reverse rotation time t is the time for which the cooling fan 24 is rotated in reverse in order to restore the cooling performance of the heat exchanger 23 to a predetermined level (in other words, to remove dust accumulated on the surface of the heat exchanger 23). The reverse rotation time determination unit 53 determines the reverse rotation time t, for example, using the reverse rotation time table (Figure 9) described later.

[0042] The fan rotation control unit 54 reverses the rotation of the cooling fan 24 for a reverse rotation time t determined by the reverse rotation time determination unit 53. The fan rotation control unit 54 may also display the reverse rotation time t or the remaining reverse rotation time on the display 41 while the cooling fan 24 is rotating in reverse. Furthermore, the fan rotation control unit 54 may suppress the rotation speed of the engine 21 to below a predetermined rotation speed while the cooling fan 24 is rotating in reverse.

[0043] [Reverse rotation time determination process] Figure 6 is a flowchart of the reverse rotation time determination process. Figure 7 is an example of information stored in memory 32 for each control cycle. Figure 8 is a diagram showing an example of the distribution of average flow rate Wa and average heat transfer coefficient Ka. Figure 9 is an example of a reverse rotation time table. The reverse rotation time determination process is a process that determines the reverse rotation time t based on the cooling performance of the heat exchanger 23 (i.e., the rate of decrease R of the heat transfer coefficient K). The controller 30 repeatedly executes the reverse rotation time determination process at predetermined control cycles P (e.g., 1 second) while the engine 21 is running.

[0044] First, the heat transfer coefficient calculation unit 51 obtains the temperature Th1 detected by the first high-temperature side temperature sensor 37, the temperature Th2 detected by the second high-temperature side temperature sensor 38, the temperature Tc1 detected by the first low-temperature side temperature sensor 39, the temperature Tc2 detected by the second low-temperature side temperature sensor 40, and the flow rate Wh detected by the high-temperature side flow rate sensor 35 (S11). The heat transfer coefficient calculation unit 51 may also obtain the flow rate Wc detected by the low-temperature side flow rate sensor 36 instead of the flow rate Wh, or in addition to the flow rate Wh.

[0045] Next, the heat transfer coefficient calculation unit 51 calculates the heat transfer coefficient K by substituting the values ​​obtained in step S11 into the following equation 4. Q[W] is the amount of heat transferred per unit time from the high-temperature fluid to the low-temperature fluid. A[m 2 ] is the heat transfer area between the high-temperature fluid and the low-temperature fluid (i.e., the surface area of ​​the heat exchanger 23). ΔT[K] is the logarithmic mean temperature difference of the heat exchanger 23, which is calculated by Equation 2. ch[kJ / kg·K] is the specific heat of the high-temperature fluid. F is a correction coefficient obtained from a predetermined calculation diagram. Solving Equations 1 to 3 for the heat transfer coefficient K yields Equation 4. Note that in Equation 3, the flow rate Wc of the low-temperature fluid, the specific heat cc, and the temperature difference ΔTc may be used instead of the flow rate Wh of the high-temperature fluid, the specific heat ch, and the temperature difference ΔTh. Q =K×A×ΔT (Formula 1) ΔT=F×(ΔTh-ΔTc) / ln(ΔTh / ΔTc) (Formula 2) Q =Wh×ch×ΔTh (Formula 3) K = (Wh×ch×ΔTh) / (A×ΔT) (Equation 4)

[0046] Next, as shown in Figure 7, the heat transfer coefficient calculation unit 51 stores the flow rate Wh obtained in step S11 and the heat transfer coefficient K calculated in step S12 using the flow rate Wh in the memory 32 (S13). More specifically, the heat transfer coefficient calculation unit 51 stores the flow rate Wh and heat transfer coefficient K for the same control period P in the memory 32, associating them with a value indicating the control period P (for example, time). Furthermore, as the reverse rotation time determination process is repeatedly executed, multiple sets of flow rate Wh and heat transfer coefficient K are stored in the memory 32, as shown in Figure 7. Note that the flow rate stored in the memory 32 may be either the flow rate Wh or Wc, or both.

[0047] Next, the heat transfer coefficient calculation unit 51 determines whether the fluctuation of the flow rate Wh over a predetermined period (for example, 10 cycles) going back from the present is less than a predetermined value (S14). For example, if the current time is control cycle P20, the heat transfer coefficient calculation unit 51 extracts the maximum and minimum values ​​of the flow rates Wh11 to Wh20 during control cycles P11 to P20. Next, the heat transfer coefficient calculation unit 51 compares the difference (= fluctuation) between the extracted maximum and minimum values ​​with a predetermined value. The predetermined value is set to a value that can be evaluated as stable, for example, the flow rate of the high-temperature fluid flowing through the heat exchanger 23.

[0048] Next, if the heat transfer coefficient calculation unit 51 determines that the fluctuation of the flow rate Wh is less than a predetermined value (S14: Yes), it calculates the average value of the flow rates Wh11 to Wh20 (average flow rate Wa20) and the average value of the heat transfer coefficients K11 to K20 (average heat transfer coefficient Ka20) over a predetermined period (for example, control cycles P11 to P20), and stores them in the memory 32 (S15). In other words, each time the heat transfer coefficient K is calculated, the heat transfer coefficient calculation unit 51 calculates the average flow rate Wa and the average heat transfer coefficient Ka and stores them in the memory 32.

[0049] Furthermore, if the past flow rates Wh and heat transfer coefficients K stored in the memory 32 are less than a predetermined number (i.e., less than a predetermined period has passed since the start of storing the flow rates Wh and heat transfer coefficients K), the heat transfer coefficient calculation unit 51 should use all the flow rates Wh and heat transfer coefficients K stored in the memory 32 to calculate the average flow rate Wa and average heat transfer coefficient Ka. For example, the average flow rate Wa3 is calculated using flow rates Wh1 to Wh3, and the average heat transfer coefficient Ka3 is calculated using heat transfer coefficients K1 to K3.

[0050] On the other hand, if the heat transfer coefficient calculation unit 51 determines that the fluctuation of the flow rate Wh is greater than or equal to a predetermined value (S14: No), it terminates the reverse rotation time determination process without executing the processes from step S15 onward. In other words, the heat transfer coefficient calculation unit 51 does not store in the memory 32 the average flow rate Wa and average heat transfer coefficient Ka for the period in which the fluctuation of the flow rate Wh exceeds a predetermined value, such as the control cycles P11 to P12 in Figure 7. Furthermore, old flow rates Wh and heat transfer coefficients K that are not used to calculate the average flow rate Wa and average heat transfer coefficient Ka (i.e., flow rates Wh and heat transfer coefficients K from 11 cycles prior) may be deleted from the memory 32.

[0051] Next, the cooling performance diagnostic unit 52 calculates the percentage decrease R of the average heat transfer coefficient Ka using the average flow rate Wa and average heat transfer coefficient Ka stored in the memory 32 (S16). The cooling performance diagnostic unit 52 plots the average flow rate Wa and average heat transfer coefficient Ka stored in the memory 32 on a two-dimensional plane with the average flow rate Wa on the horizontal axis and the average heat transfer coefficient Ka on the vertical axis, for example, as shown in Figure 8. Here, plots "●" correspond to values ​​from past control cycles, and plots "〇" correspond to values ​​from the latest control cycle (for example, P20).

[0052] Next, the cooling performance diagnostic unit 52 extracts the maximum average heat transfer coefficient Ka (for example, Ka7) from among the average heat transfer coefficients Ka of plots within a predetermined flow rate width ΔW range that includes the latest average flow rate Wa20 (i.e., the average heat transfer coefficient Ka stored in memory 32 in association with average flow rates Wa whose difference from the latest average flow rate Wa20 is less than the predetermined width). Then, the cooling performance diagnostic unit 52 calculates the decrease ratio R (=1-Ka20 / Ka7) of the latest average heat transfer coefficient Ka20 relative to the maximum average heat transfer coefficient Ka7. The decrease ratio R is a value that increases as the cooling performance of the heat exchanger 23 deteriorates, for example.

[0053] As shown in Figure 8, there is a positive correlation between the average heat transfer coefficient Ka and the average flow rate Wa. Furthermore, the maximum average heat transfer coefficient Ka7 within a predetermined flow rate width ΔW that includes the average flow rate Wa20 represents the maximum performance of the heat exchanger 23 at that average flow rate Wa20 (i.e., the cooling performance of the heat exchanger 23 with dust removed from its surface). Moreover, the predetermined flow rate width ΔW is specified, for example, by the average flow rate Wa20 ± α. α is adjusted as appropriate depending on the relationship between the accuracy of specifying the maximum performance of the heat exchanger 23 and the number of plots.

[0054] Next, the cooling performance diagnostic unit 52 compares the reduction rate R calculated in step S16 with a predetermined threshold Rth (S17). The threshold Rth is set, for example, to a value within an acceptable range for the reduction in the cooling performance of the heat exchanger 23.

[0055] Next, if the cooling performance diagnostic unit 52 determines that the reduction ratio R calculated in step S16 is equal to or greater than the threshold Rth (S17: Yes), the reverse rotation time determination unit 53 determines the reverse rotation time t using the reverse rotation time table shown in Figure 9 and stores the determined reverse rotation time t in the memory 32 (S18). If a reverse rotation time t is already stored in the memory 32, the reverse rotation time determination unit 53 overwrites the reverse rotation time t already stored in the memory 32 with the latest reverse rotation time t.

[0056] The reverse rotation time table shown in Figure 9 holds multiple reverse rotation times t11 to t66, associated with combinations of the rate of decrease R of the average heat transfer coefficient Ka and the average flow rate Wa. The reverse rotation time t held in the reverse rotation time table increases as, for example, the rate of decrease R increases (i.e., the cooling performance of the heat exchanger 23 decreases). The reverse rotation time t corresponding to the rate of decrease R and the average flow rate Wa is predetermined by experiment or simulation. However, it is sufficient that the reverse rotation time table associates at least the rate of decrease R with the reverse rotation time t.

[0057] In other words, the reverse rotation time determination unit 53 simply needs to extract the reverse rotation time t, which is associated with the average flow rate Wa calculated in the most recent step S15 and the reduction rate R calculated in the most recent step S16, from the reverse rotation time table and store it in the memory 32.

[0058] On the other hand, if the cooling performance diagnostic unit 52 determines that the reduction ratio R calculated in step S16 is less than the threshold Rth (S17: No), the reverse rotation time determination unit 53 terminates the reverse rotation time determination process without executing the process in step S18. In other words, if the cooling performance diagnostic unit 52 determines that the reduction ratio R calculated in step S16 is less than the threshold Rth (S17: No), the reverse rotation time determination unit 53 does not store (overwrite) a new reverse rotation time t in the memory 32.

[0059] [Fan reverse rotation processing] Figure 10 is a flowchart of the fan reverse rotation process. The fan reverse rotation process is the process of reversing the rotation of the cooling fan 24. The controller 30 repeatedly executes the fan reverse rotation process at predetermined control cycles P while the engine 21 is running, for example.

[0060] The fan rotation control unit 54 determines whether or not the reverse rotation switch 34 has been operated (S21). If the fan rotation control unit 54 determines that the reverse rotation switch 34 has not been operated (S21: No), it terminates the fan reverse rotation process without executing the processes from step S22 onward. The reverse rotation switch 34 may, for example, be configured so that it cannot be operated when the rotation speed of the engine 21 is above a threshold, and can be operated when the rotation speed of the engine 21 is below a threshold. The operator can then operate the reverse rotation switch 34 while the hydraulic excavator 1 is stopped (i.e., idle).

[0061] On the other hand, if the fan rotation control unit 54 determines that the reverse rotation switch 34 has been operated (S21: Yes), it determines whether or not the reverse rotation time t is stored in the memory 32 (S22). If the fan rotation control unit 54 determines that the reverse rotation time t is stored in the memory 32 (S22: Yes), it controls the fan motor 25 to reverse the rotation of the cooling fan 24 for the reverse rotation time t (S23). In addition, as the reverse rotation time t has elapsed since the start of the reverse rotation of the cooling fan 24, the fan rotation control unit 54 rotates the cooling fan 24 in the forward direction and deletes the reverse rotation time t from the memory 32 (S24). Furthermore, the fan rotation control unit 54 deletes all the information shown in Figure 7 from the memory 32.

[0062] Furthermore, the fan rotation control unit 54 may, while step S23 is being executed, display the determined reverse rotation time t, or the remaining reverse rotation time (i.e., the value obtained by subtracting the elapsed reverse rotation time from the reverse rotation time t), on the display 41. Note that the method of notifying the reverse rotation time t or remaining time is not limited to display on the display 41, and may also be notified through an indicator or speaker. In addition, the controller 30 may disable the operation of the operating device 33 (i.e., ignore the operation signal and not operate the hydraulic actuator) while the cooling fan 24 is rotating in reverse.

[0063] On the other hand, if the fan rotation control unit 54 determines that the reverse rotation time t is not stored in the memory 32 (S22: No), it controls the fan motor 25 to reverse the cooling fan 24 for a predetermined time (S25). Furthermore, the fan rotation control unit 54 reverses the cooling fan 24 to forward rotation once the predetermined time has elapsed. As another example, if the fan rotation control unit 54 determines that the reverse rotation time t is not stored in the memory 32 (S22: No), it may omit the processing in step S25 and not reverse the cooling fan 24.

[0064] [Effects of the Embodiment] According to the above embodiment, the cooling performance of the heat exchanger 23 is diagnosed by comparing the past average heat transfer coefficient Ka7 with the latest average heat transfer coefficient Ka20, and the cooling fan 24 is reversed for a reverse rotation time t determined according to the degree of deterioration in cooling performance (i.e., the rate of deterioration R). This allows the cooling fan 24 to be reversed for the minimum time necessary to remove the dust accumulated on the surface of the heat exchanger 23, thereby suppressing the temperature rise of the high-temperature fluid flowing inside the heat exchanger 23 while removing the dust accumulated on the heat exchanger 23.

[0065] Furthermore, according to the above embodiment, if it is determined that the fluctuation of the flow rate Wh is greater than a predetermined value, the average flow rate Wa and the average heat transfer coefficient Ka are not stored in the memory 32. This prevents the cooling performance of the heat exchanger 23 from being diagnosed based on the unstable average heat transfer coefficient Ka during periods when the rotational speed of the engine 21 is rapidly increasing. This makes it possible to determine an appropriate reverse rotation time t.

[0066] Furthermore, according to the above embodiment, an appropriate reverse rotation time t can be determined by comparing the maximum average heat transfer coefficient Ka7 included within a predetermined flow rate width ΔW with the latest average heat transfer coefficient Ka20, thereby diagnosing the cooling performance of the heat exchanger 23.

[0067] Furthermore, according to the above embodiment, the reverse rotation time t corresponding to the rate of decrease R of the average heat transfer coefficient Ka is set in advance in the reverse rotation time table, and the reverse rotation time t is determined based on the latest rate of decrease R, so that the cooling fan 24 can be reversed for the minimum necessary time.

[0068] Furthermore, according to the above embodiment, by notifying the reverse rotation time t and the remaining time for reverse rotation, the operator can be made aware of the waiting time until work by the hydraulic excavator 1 can be resumed.

[0069] [Differentiation] Furthermore, the method is not limited to diagnosing the decrease in the cooling performance of the heat exchanger 23 (i.e., calculating the decrease rate R) using a plot with a predetermined flow rate width ΔW. As another example, the cooling performance of the heat exchanger 23 may be diagnosed (i.e., the decrease rate R may be calculated) by comparing the largest average heat transfer coefficient Ka among all past plots "●" in Figure 8 with the latest average heat transfer coefficient Ka. Alternatively, the method is not limited to the largest average heat transfer coefficient Ka, but may also be used to diagnose the cooling performance of the heat exchanger 23 (i.e., calculate the decrease rate R) using past average heat transfer coefficients Ka (for example, the average heat transfer coefficient Ka1 initially stored in memory 32).

[0070] Furthermore, the calculation of the reduction rate R is not limited to the average flow rate Wa and the average heat transfer coefficient Ka; the flow rate Wh (or flow rate Wc) and the heat transfer coefficient K may also be used. In this case, the process involves replacing the average flow rate Wa with the flow rate Wh (or flow rate Wc), replacing the average heat transfer coefficient Ka with the heat transfer coefficient K, and moving step S13 in Figure 6 to the position of step S15.

[0071] Furthermore, the indicator used to diagnose the cooling performance of the heat exchanger 23 is not limited to the rate of decrease R (e.g., 1-Ka20 / Ka7). As another example, the cooling performance of the heat exchanger 23 may be diagnosed using the value obtained by subtracting the latest average heat transfer coefficient Ka20 from the maximum average heat transfer coefficient Ka7 (the decrease in average heat transfer coefficient Ka).

[0072] Furthermore, the volume held in the table in Figure 9 is not limited to the reverse rotation time t, but may also be the volume of cleaning air. The fan rotation control unit 54 then reverses the cooling fan 24 until cleaning air of the volume extracted from the table is generated. More specifically, the volume of cleaning air is determined by multiplying the airflow per rotation of the cooling fan 24 by the rotational speed of the cooling fan 24.

[0073] Furthermore, the reverse rotation time determination process may be performed for each of the radiator, oil cooler, and intercooler, or for just one of them. Also, when the reverse rotation time determination process is performed for each of the radiator, oil cooler, and intercooler, the display 41 may show which heat exchanger 23 has reduced cooling performance.

[0074] Furthermore, the fan rotation control unit 54 may prompt the operator to operate the reverse rotation switch 34 by notifying the operator through a notification device that the reverse rotation time t is stored in the memory 32. Also, the fan rotation control unit 54 is not limited to reversing the rotation of the cooling fan 24 by operating the reverse rotation switch 34, but may automatically execute the processes of steps S23 to S24 at a predetermined timing (for example, when the reverse rotation time t is stored in the memory 32 and the rotational speed of the engine 21 falls below a predetermined value).

[0075] Furthermore, the reverse rotation table shown in Figure 9 may be modifiable. For example, the appropriate reverse rotation time t may change in accordance with the aging deterioration of the hydraulic excavator 1 (more specifically, the heat exchanger 23). Another example is that the appropriate reverse rotation time t may change according to the operating environment of the hydraulic excavator 1. Therefore, the controller 30 may modify the reverse rotation table shown in Figure 9 (more specifically, the reverse rotation time t corresponding to the average flow rate Wa and the rate of decrease R).

[0076] The controller 30 may modify the reverse rotation table at its own discretion. For example, the controller 30 may shorten the reverse rotation time t the longer the interval at which the cooling fan 24 is reversed (the interval at which step S23 is executed), and lengthen the reverse rotation time t the shorter the interval at which the cooling fan 24 is reversed (the interval at which step S23 is executed). Alternatively, the controller 30 may modify the reverse rotation time t according to the operator's input through the control device 33.

[0077] The embodiments described above are illustrative for explaining the present invention and are not intended to limit the scope of the invention to those embodiments only. Those skilled in the art can implement the present invention in various other forms without departing from the spirit of the invention. [Explanation of symbols]

[0078] 1: Hydraulic excavator 2: Lower running body 3: Upper rotating body 4: Crawler 5: Driving motor 6: Swivel motor 7: Swivel Frame 8: Cab 9: Counterweight 10: Front work machine 11: Boom 12: Arm 13: Bucket 14: Boom Cylinder 15: Arm Cylinder 16: Bucket Cylinder 17: Fuel tank 18: Hydraulic oil tank 20: Engine building 20L,20R: Opening 21: Engine 22: Hydraulic pump 23: Heat exchanger 24: Cooling fan 25: Fan motor 30: Controller 31: CPU 32: Memory 33: Operating device 34: Reverse rotation switch 35: High-temperature side flow sensor 36: Low-temperature flow sensor 37: First high-temperature side temperature sensor 38: Second high-temperature side temperature sensor 39: First low-temperature sensor 40: Second low-temperature sensor 41: Display 51: Heat transfer rate calculation section 52: Cooling Performance Diagnostic Unit 53: Reverse rotation time determination unit 54: Fan rotation control unit

Claims

1. The aircraft supporting the building, A drive source housed in the aforementioned building generates the driving force to operate the machine, A heat exchanger housed in the aforementioned building, which exchanges heat between cooling air and a high-temperature fluid, A cooling fan, housed in the building between the drive source and the heat exchanger, is capable of forward rotation and reverse rotation in the opposite direction to the forward rotation, generating the cooling air flowing from the heat exchanger to the drive source. A flow sensor for detecting the flow rate of the high-temperature fluid or the cooling air, A first temperature difference sensor detects the temperature difference of the high-temperature fluid before and after heat exchange with the cooling air, A second temperature difference sensor detects the temperature difference of the cooling air before and after heat exchange with the high-temperature fluid. In a work machine equipped with a controller having memory, The aforementioned controller, Based on the detection results of the flow sensor, the first temperature difference sensor, and the second temperature difference sensor, the heat transfer coefficient representing the heat exchange efficiency in the heat exchanger is calculated and stored in the memory. The past heat transfer rate stored in the memory and the latest heat transfer rate are compared to determine the reverse rotation time of the cooling fan. A work machine characterized by rotating the cooling fan in the reverse direction for the determined reverse rotation time.

2. In the work machine described in claim 1, The controller is characterized in that it does not store in the memory the heat transfer coefficient for a period during which the fluctuation of the flow rate detected by the flow sensor exceeds a predetermined value.

3. In the work machine described in claim 1, The aforementioned controller, The flow rate detected by the flow sensor and the heat transfer coefficient calculated using the said flow rate are stored in the memory in association with each other. From among the heat transfer coefficients stored in the memory in association with the flow rates within a predetermined flow rate range including the most recent flow rate, the maximum heat transfer coefficient is extracted. A working machine characterized by determining the reverse rotation time by comparing the maximum heat transfer rate with the latest heat transfer rate.

4. In the work machine described in claim 3, The memory stores a table that associates the reduction rate with the reverse rotation time, such that the greater the reduction rate of the heat transfer coefficient, the longer the reverse rotation time. The controller is characterized in that it determines the reverse rotation time held on the table in correspondence with the rate of decrease of the latest heat transfer rate relative to the maximum heat transfer rate.

5. In the work machine described in claim 1, Equipped with a notification device to broadcast information, The controller is characterized in that, while the cooling fan is rotating in reverse, it notifies the time of the reverse rotation or the remaining time of the reverse rotation through the notification device.

6. In the work machine described in claim 4, The controller is characterized by modifying the table stored in the memory.

7. In the work machine described in claim 1, The aforementioned controller, Each time the heat transfer coefficient is calculated, the average heat transfer coefficient is calculated by averaging multiple heat transfer coefficients over a predetermined period going back in time, and stored in the memory. A work machine characterized by determining the reverse rotation time by comparing the average heat transfer coefficient of the past with the average heat transfer coefficient of the latest.

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