Construction machinery

Abstract

This construction machine prevents a decrease in the cooling efficiency of the heat exchanger unit by switching the forward and reverse rotation of the cooling fan at the appropriate timing. [Solution] In a construction machine (1) comprising a heat exchanger (3), a cooling fan (4) that supplies cooling air to the heat exchanger when it is rotating forward, and a controller (2) that controls the operation of the cooling fan, the controller calculates the amount of cooling air passing through the heat exchanger when the cooling fan is rotating forward by the product of the wind speed of the cooling fan and the cross-sectional area of ​​the heat exchanger, multiplies the calculated amount of air passing through by the time the cooling fan is rotating forward to obtain an integrated value of the amount of air passing through, and when the integrated value of the amount of air passing through reaches a predetermined threshold, controls the cooling fan to reverse for a predetermined time, and resets the integrated value when the reverse rotation of the cooling fan ends.

Description

Technical Field

[0001] The present invention relates to construction machinery, and particularly to the control of a cooling fan for cooling a heat exchanger.

Background Art

[0002] Generally, in the engine room of construction machinery such as hydraulic excavators, a heat exchanger unit and a cooling fan for supplying cooling air to the heat exchanger unit are provided. The heat exchanger unit is composed of a plurality of heat exchangers such as a radiator and an oil cooler. Then, the cooling air generated by the cooling fan cools various fluids passing through each of the plurality of heat exchangers, passes through the engine room, and is discharged outside the vehicle body of the construction machinery.

[0003] Many construction machinery work sites have poor environments, and there may be a large amount of dust such as dust and fine wood chips floating. When construction machinery is operating at such a work site, dust may be carried by the cooling air of the cooling fan, and dust may accumulate on the heat exchanger unit, which may deteriorate the cooling efficiency of the heat exchanger. Therefore, in order to prevent the deterioration of the cooling efficiency of the heat exchanger unit, there is a device that can blow off and remove the accumulated dust on the heat exchanger unit by reversing the cooling fan.

[0004] For example, Patent Document 1 describes a configuration in which "the normal rotation time of the cooling fan is recorded by a timer, when the first predetermined time is reached, the cooling fan is reversed for the second predetermined time, and when the reverse rotation ends, the timer is reset".

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, in Patent Document 1, the timing for reversing the cooling fan is determined solely by recording a predetermined forward rotation time with a timer. Therefore, the amount of dust accumulated on the heat exchanger unit may change due to the change in the airflow rate caused by the forward rotation of the cooling fan. Consequently, in Patent Document 1, if the airflow rate of the cooling fan is high within the predetermined forward rotation time, it may not be possible to remove the accumulated dust within the predetermined reversal time. On the other hand, if the airflow rate of the cooling fan is low within the predetermined forward rotation time, it is thought that the accumulated dust can be removed in less time than the predetermined reversal time because the amount of dust is small.

[0007] Therefore, in Patent Document 1, the forward and reverse rotation of the cooling fan cannot be switched at the appropriate timing. As a result, if the airflow through the cooling fan is large, dust and debris that accumulates in the heat exchanger unit during reverse rotation may not be completely removed, potentially leading to a decrease in the cooling efficiency of the heat exchanger unit.

[0008] This invention has been made in view of the above-described circumstances, and its purpose is to provide a construction machine that can prevent a decrease in the cooling efficiency of a heat exchanger unit by switching the forward rotation and reverse rotation of the cooling fan at an appropriate timing. [Means for solving the problem]

[0009] To achieve the above objective, one aspect of the present invention provides a construction machine comprising a heat exchanger, a cooling fan that supplies cooling air to the heat exchanger when it is rotating forward, and a controller that controls the operation of the cooling fan, wherein the controller calculates the amount of cooling air passing through the heat exchanger when the cooling fan is rotating forward by multiplying the wind speed of the cooling fan by the cross-sectional area of ​​the heat exchanger, obtains an integrated value of the amount of air passing through by multiplying the calculated amount of air passing through by the time the cooling fan is rotating forward, controls the cooling fan to reverse for a predetermined time when the integrated value of the amount of air passing through reaches a predetermined threshold, and resets the integrated value when the reverse rotation of the cooling fan ends. [Effects of the Invention]

[0010] According to the construction machine of the present invention, a decrease in the cooling efficiency of the heat exchanger unit can be prevented by switching between the forward and reverse rotation of the cooling fan at an appropriate timing. Other issues, configurations, and effects not mentioned above will be clarified by the following description of the embodiments. [Brief explanation of the drawing]

[0011] [Figure 1] This is a side view of a hydraulic excavator according to an embodiment of the present invention. [Figure 2] This is a block diagram showing the configuration around a heat exchanger unit. [Figure 3] This is a block diagram showing the configuration around the oil cooler. [Figure 4] This is a block diagram showing the configuration around the capacitor. [Figure 5] This figure shows an example of a performance curve used to calculate the airflow rate. [Figure 6] This is a flowchart showing the control procedure for the cooling fan. [Figure 7] This is a flowchart showing the control procedure for the cooling fan. [Figure 8] This diagram shows the timing of the cooling fan's reverse operation in automatic mode. [Figure 9] This figure compares the timing of the cooling fan's reverse operation in automatic mode between the present invention and the prior art. [Modes for carrying out the invention]

[0012] The embodiments of the construction machinery according to the present invention will be described below with reference to the drawings. Figure 1 is a side view of a hydraulic excavator 1, which is one embodiment of the construction machinery. Note that the present invention is not limited to hydraulic excavators and can be applied to any construction machinery, such as wheel loaders.

[0013] As shown in Fig. 1, the hydraulic excavator 1 includes a crawler-type lower traveling body 101 that constitutes the vehicle body, an upper revolving body 102 that is provided above the lower traveling body 101 so as to be rotatable and constitutes the vehicle body, and a hydraulic-driven working device 103 that is attached to the upper revolving body 102 and performs various operations.

[0014] The upper revolving body 102 is rotationally driven with respect to the lower traveling body 101 by the driving force of a slewing device 105. The upper revolving body 102 mainly includes a slewing frame 102a that is a base frame, a cab 107 on which an operator rides and various operations are performed, and a machine room 102b that houses a motor (see Fig. 2), a hydraulic pump (see Fig. 3), etc. that are driving sources.

[0015] The working device 103 includes a boom 103a whose base end is rotatably attached to the slewing frame 102a, an arm 103b that is rotatably attached to the tip of the boom 103a, and a bucket 103c that is rotatably attached to the tip of the arm 103b.

[0016] The boom 103a is driven by a boom cylinder 104a. Specifically, one end side of the boom cylinder 104a is connected to the slewing frame 102a, and the other end side is connected to the boom 103a. By the supply and discharge of hydraulic oil, the rod expands and contracts, thereby rotating (pitching) the boom 103a in the vertical direction with respect to the upper revolving body 102.

[0017] The arm 103b is driven by an arm cylinder 104b. Specifically, one end side of the arm cylinder 104b is connected to the boom 103a, and the other end side is connected to the arm 103b. By the supply and discharge of hydraulic oil, the rod expands and contracts, thereby rotating the arm 103b in the front-rear direction with respect to the boom 103a.

[0018] The bucket 103c is driven by a bucket cylinder 104c. Specifically, one end side of the bucket cylinder 104c is connected to the arm 103b, and the other end side is connected to the bucket 103c. By the supply and discharge of hydraulic oil, the rod expands and contracts, thereby rotating the bucket 103c in the front-rear direction with respect to the arm 103b.

[0019] Bucket 103c is a working tool used for operations such as scooping up loads such as earth and sand, minerals, etc. and dropping the loads at a predetermined position, or leveling the ground. Note that this bucket 103c can be exchanged for various attachments such as a grapple for grasping wood, rock, waste, etc., or a breaker for crushing bedrock.

[0020] Next, the outline of the internal structure of the hydraulic excavator 1 will be described with reference to FIG. 2. FIG. 2 is a block diagram showing the configuration around the heat exchanger unit 3. In FIG. 2, the hydraulic excavator 1 includes a heat exchanger unit 3, a cooling fan 4 that supplies cooling air to the heat exchanger unit 3 during normal rotation, and a filter 7 disposed on the upstream side of the heat exchanger unit 3 when the cooling fan 4 is rotating forward.

[0021] The heat exchanger unit 3 of the illustrated embodiment includes a radiator 8 as a heat exchanger, an oil cooler 9, and a condenser 10. The radiator 8 is for cooling the cooling water that cools power sources and main machines such as the battery 6, an inverter (not shown), and a motor (not shown).

[0022] The oil cooler 9 is for cooling the hydraulic oil for operating hydraulic actuators 104a to 104c such as hydraulic cylinders and hydraulic motors. For example, as shown in FIG. 3, the hydraulic oil stored in the hydraulic oil tank 20 is supplied to the hydraulic actuators 104a to 104c via a hydraulic pump 21 and a valve (direction control valve) 22, and then introduced into the oil cooler 9 via the hydraulic oil pipe 30. When the hydraulic oil flows through the oil cooler 9, it is heat-exchanged with the cooling air generated by the cooling fan 4 and cooled, and then returned to the hydraulic oil tank.

[0023] The condenser 10 is for cooling the refrigerant for the air conditioner (hereinafter abbreviated as refrigerant). The hydraulic excavator 1 is equipped with an air conditioner for heating and cooling the cab 107. The air conditioner includes an outdoor unit located outside the cab 107 and an indoor unit located inside the cab 107. For example, as shown in Figure 4, the outdoor unit has a compressor 24 for compressing the refrigerant, a condenser 10 for condensing the refrigerant compressed by the compressor 24, and a receiver (not shown) for storing the refrigerant condensed by the condenser 10. On the other hand, the indoor unit has an expansion valve 25 for expanding the refrigerant sent from the receiver, and an evaporator 23 for evaporating the refrigerant expanded by the expansion valve 25. The air conditioner is operated or stopped by an air conditioner switch (not shown) located inside the cab 107.

[0024] In this embodiment, the equipment cooled by the radiator 8 is described for a hydraulic excavator 1 whose power source is a battery 6, but it may also be used for construction machinery equipped with an engine, and the heat exchanger unit 3 may include an aftercooler through which compressed air from a supercharger passes, and a fuel cooler through which fuel passes, etc.

[0025] Furthermore, in this embodiment, power sources such as the battery 6, inverter, and motor, as well as the main engine, are cooled by a single heat exchanger, the radiator 8. However, if the cooling circuits for the battery 6, inverter, and motor are separated, multiple heat exchangers may be used to cool the cooling water in each cooling circuit. Also, although the heat exchanger unit 3 is described as a unit that includes the radiator 8, oil cooler 9, and condenser 10, it is not necessary to include all of these heat exchangers. Depending on the specifications of the hydraulic excavator 1, it may include at least one of the above heat exchangers, or it may consist of the above heat exchangers and other heat exchangers. In addition, the multiple heat exchangers can be arranged at any location within the heat exchanger unit 3.

[0026] As shown in Figure 2, the hydraulic excavator 1 is equipped with a coolant temperature sensor 11 for detecting the temperature of the main engine coolant, a hydraulic oil temperature sensor 12 for detecting the temperature of the hydraulic oil, and a refrigerant pressure sensor 13 for detecting the pressure of the refrigerant compressed by the air conditioner compressor 24. Although not shown, the coolant temperature sensor 11 is located upstream of the radiator 8, the hydraulic oil temperature sensor 12 is located downstream of the hydraulic oil tank which is located downstream of the oil cooler 9, and the refrigerant pressure sensor 13 is located between the condenser 10 and the expansion valve 25.

[0027] The cooling fan 4 is driven by an appropriate drive source 5, such as an electric motor or a hydraulic motor, as shown in Figure 2. When the cooling fan 4 rotates forward, an airflow is generated in the direction indicated by arrow F1 in Figure 2, and cooling air is supplied to the heat exchanger unit 3. Through heat exchange with the cooling air, the various fluids passing through each heat exchanger in the heat exchanger unit 3 are cooled, and the cooling air is discharged outside the vehicle body. When the cooling fan 4 rotates backward, an airflow is generated in the direction indicated by arrow F2 in Figure 2. Although a single cooling fan 4 is shown in this figure, multiple cooling fans 4 may be provided.

[0028] The battery 6 in Figure 2 is the power source for the hydraulic excavator 1. When the battery 6 is activated and high-voltage power is available, it becomes possible to operate the main inverter and motor. When using the cooling fan 4, the high-voltage power available from the battery 6 is converted to a low voltage using a voltage converter (not shown), which allows the aforementioned drive source 5 to be driven and cooling air to be supplied to the heat exchanger unit 3.

[0029] Furthermore, if the cooling fan 4 is to be used when the battery 6 is not activated, the aforementioned drive source 5 can be driven by a low-voltage lead-acid battery (not shown) provided in the hydraulic excavator 1, thereby supplying cooling air to the heat exchanger unit 3.

[0030] As is clear from Figure 2, the filter 7 is positioned upstream of the heat exchanger unit 3 when the cooling fan 4 is rotating forward, and it collects dust and debris such as wood chips to prevent the accumulation of debris on the fins of the heat exchanger, such as the radiator 8. The debris collected by the filter 7 is then blown away and removed by the reverse rotation of the cooling fan 4. With such a filter 7 positioned upstream of the heat exchanger unit 3, if the operator needs to remove any remaining debris that is not removed by the reverse rotation of the cooling fan 4, it is not necessary to clean the fins of each heat exchanger in the heat exchanger unit 3, and only the filter 7 needs to be cleaned, thus improving the ease of maintenance.

[0031] However, the presence of a filter 7 on the hydraulic excavator 1 is not mandatory but optional. If the hydraulic excavator 1 is not equipped with a filter 7, most of the dust accumulated on the heat exchanger unit 3 will be blown away and removed by the reverse rotation of the cooling fan 4, so even without a filter 7, dust will not remain accumulated on the heat exchanger unit 3.

[0032] Furthermore, the hydraulic excavator 1 is equipped with a controller 2 that controls the operation of the cooling fan 4, and a reverse switch 14 that reverses the cooling fan 4 in response to manual operation by the operator. The reverse switch 14 outputs a signal to reverse the cooling fan 4. The controller 2 is composed of a computer and includes a CPU, RAM, ROM, HDD, input I / F, and output I / F. In this hardware configuration, the CPU reads the control program (software) stored on a recording medium such as ROM, HDD, or optical disc, expands it onto RAM, and executes the expanded control program, thereby enabling the control program and hardware to work together to realize the functions of the controller 2.

[0033] If the drive source 5 for the cooling fan 4 is an electric motor, the drive source 5 and the controller 2 are electrically connected, and the controller 2 controls the operation of the cooling fan 4 by outputting a forward rotation signal or a reverse rotation signal to the drive source 5 (electric motor). If the drive source 5 is a hydraulic motor, the controller 2 is electrically connected to an electromagnetic control valve (not shown) that controls the supply of hydraulic fluid to the drive source 5, and the controller 2 outputs a forward rotation signal or a reverse rotation signal to the electromagnetic control valve, switching the oil passage of the electromagnetic control valve, thereby causing the drive source 5 to rotate in the forward or reverse direction and controlling the operation of the cooling fan 4.

[0034] As shown in Figure 2, the controller 2 is electrically connected to each of the sensors 11, 12, and 13, and is configured to receive the temperature and pressure of each fluid detected by each sensor 11, 12, and 13 as input. The controller 2 controls the rotation speed of the cooling fan 4 based on the temperature and pressure input from each of the sensors 11, 12, and 13.

[0035] The reverse switch 14 is located inside the cab and is electrically connected to the controller 2. The type of reverse switch 14 is arbitrary; for example, a touch panel type, push button type, dial type, or seesaw type may be used.

[0036] In the hydraulic excavator 1 described above, when the battery 6, which is the power source, is started and the power from the battery 6 is available, if the operating conditions (operating conditions to prevent overcooling of various fluids) are met, such as the temperature and pressure of the cooling water circulating in the main engine cooling circuit including the battery 6, inverter and motor, the hydraulic oil circulating in the hydraulic circuit, and the refrigerant circulating in the air conditioner's refrigerant circuit being above a predetermined value, the controller 2 outputs a forward rotation signal to the drive source 5 or the electromagnetic control valve, causing the cooling fan 4 to rotate forward and cooling air to be supplied to the heat exchanger unit 3.

[0037] The controller 2 then outputs a reverse signal to the drive source 5 or electromagnetic control valve when the cumulative value of the airflow passing through the heat exchanger unit 3 during the forward rotation of the cooling fan 4 reaches a threshold S (for example, 1000 m3), causing the cooling fan 4 to reverse for a predetermined time tr (for example, 30 seconds), and resets the threshold S when the reverse rotation of the cooling fan 4 is completed.

[0038] The airflow rate passing through the heat exchanger unit 3 can be derived from the performance curve of the cooling fan 4 (see Figure 5) by multiplying the airflow velocity corresponding to the output of the cooling fan 4 (for example, 40 m / s) by the cross-sectional area of ​​the heat exchanger unit 3 that the cooling fan 4 passes through when supplying cooling air to the heat exchanger unit 3 (for example, 1 m²). Note that the value of the cross-sectional area of ​​the heat exchanger unit 3 is, for example, a design value.

[0039] The cumulative value of the airflow can be derived by calculating the product of the airflow, which is the product of the air velocity corresponding to the output of the cooling fan 4 and the cross-sectional area of ​​the heat exchanger unit 3, and the time (for example, every second) during which the cooling fan 4 is in forward rotation.

[0040] For example, the PQ performance curve shown in Figure 5(a) and the heat exchanger pressure drop curve shown in Figure 5(b) can be used as the performance curves for the cooling fan 4. First, the ratio of airflow to the rotational speed or output of the cooling fan 4 is calculated from the value obtained by dividing the forward rotational speed of the cooling fan 4 by the maximum rotational speed of the cooling fan 4 (i.e., fan forward rotational speed / fan maximum rotational speed), or from the value obtained by dividing the output of the cooling fan 4 by the maximum output of the cooling fan 4 and cubing that value (i.e., (fan output / fan maximum output)^3). Then, a curve corresponding to the airflow ratio is selected from the PQ performance curve of the cooling fan 4 (see Figure 5(a)). Next, the airflow that matches the PQ curve obtained from Figure 5(a) is selected by referring to the heat exchanger pressure drop curve shown in Figure 5(b). For example, if the above-mentioned airflow ratio is 60%, the 60% curve shown in Figure 5(a) (dotted line in the figure) is applied to Figure 5(b), and the airflow Q1 at the intersection of the 60% curve and the pressure drop curve is selected. Then, the integrated value [m3] is calculated from the airflow rate [m3 / s] and the forward rotation time [s]. In this way, the integrated value of the airflow rate passing through the cooling fan 4 can be determined. Note that the heat exchanger pressure loss curve in Figure 5(b) is a curve obtained experimentally.

[0041] By integrating the product of the airflow rate and time, the cumulative value of the airflow rate from the start of forward rotation of the cooling fan 4 can be derived. Note that the value of the airflow rate is never constant because the wind speed changes according to the output of the cooling fan 4, so the product of the airflow rate and time also changes as the value of the airflow rate changes. Furthermore, if the drive source 5 for the cooling fan 4 is not driven and no cooling air is supplied, the wind speed, airflow rate, and the cumulative value of the airflow rate will be 0, so in this case, it is not counted in the cumulative value of the airflow rate.

[0042] The value of the threshold S is preferably determined experimentally based on the cooling specifications of the cooling fan 4 and the heat exchanger unit, in combination with the vehicle specifications of the hydraulic excavator 1. Here, it is preferable that multiple threshold S values ​​are pre-stored in the controller 2 and can be arbitrarily selected, but it may also be a single fixed value. Furthermore, it is preferable that the predetermined time tr during the reverse operation can be arbitrarily changed according to the value of the threshold S. In addition, an automatic reverse mode ON / OFF switch may be provided in the cab to start or stop the mode in which the controller 2 periodically reverses the cooling fan 4 (hereinafter referred to as "automatic mode").

[0043] Furthermore, even if the cumulative value of the airflow passing through the heat exchanger unit 3 does not reach the threshold S, the controller 2 is configured to output a reverse signal to the drive source 5 or the electromagnetic control valve when the reverse switch 14 is operated by the operator in the cab and a reverse signal is output from the reverse switch 14, thereby reversing the cooling fan 4 for a predetermined time tr, and resetting the threshold S when the reversal of the cooling fan 4 is completed.

[0044] Furthermore, in automatic mode, conditions for reversing the cooling fan 4 may include conditions other than the airflow rate passing through the heat exchanger unit 3 reaching the threshold S. Also, in conditions for reversing the cooling fan 4 due to the operation of the reverse switch 14, conditions other than the operation of the reverse switch 14 may be included.

[0045] As another example of the conditions for reversing the cooling fan 4 in automatic mode, for example, the rate of increase of the cooling water temperature, hydraulic oil temperature, and refrigerant pressure when the air conditioner is in use may be recorded, and the cooling fan 4 may be reversed if the rate of increase of the temperature and pressure exceeds a threshold. Alternatively, the cooling fan 4 may be automatically reversed when the ambient temperature is low and the cooling water temperature, hydraulic oil temperature, and refrigerant pressure are all low (i.e., low temperature and low pressure).

[0046] Next, a specific example of the reversal process of the cooling fan 4, which is performed by the controller 2 of the hydraulic excavator 1, will be described. Figures 6 and 7 are flowcharts showing the control procedure of the cooling fan 4.

[0047] As shown in Figure 6, the controller 2 determines whether the automatic mode is activated (step S1) and whether a reverse signal is output from the reverse switch 14 (step S15). If the automatic mode is activated (determination in step S1 is Yes) and no reverse signal is output from the reverse switch 14 (determination in step S15 is No), the process proceeds to step S2. On the other hand, regardless of whether the determination in step S1 is Yes or No, if the determination in step S15 is Yes, the process proceeds to step S16.

[0048] In step S2, the accumulation of the airflow volume passing through the heat exchanger unit 3 when the cooling fan 4 is rotating in the forward direction begins. As mentioned above, the airflow volume can be derived by multiplying the air velocity of the cooling fan 4 by the cross-sectional area of ​​the heat exchanger unit 3. Furthermore, the accumulation of the airflow volume can be derived by multiplying the airflow volume by time.

[0049] In step S3, the controller 2 determines whether the cumulative value of the airflow rate passing through the heat exchanger unit 3, calculated in step S2, is equal to or greater than the threshold S. If the cumulative value of the airflow rate is equal to or greater than the threshold S, the determination in step S3 is Yes, and the process proceeds to step S4. If the determination in step S3 is No, step S3 is repeated until the determination in step S3 becomes Yes.

[0050] In step S4, the controller 2 stops accumulating the airflow rate and proceeds to step S5.

[0051] In step S5, the controller 2 determines whether the coolant temperature detected by the coolant temperature sensor 11 is below a threshold. If the determination in step S5 is Yes, the controller 2 determines whether the hydraulic oil temperature detected by the hydraulic oil temperature sensor 12 is below a threshold (step S6). If the determination in step S6 is Yes, the controller 2 determines whether the refrigerant pressure of the air conditioner detected by the refrigerant pressure sensor 13 is below a threshold (step S7).

[0052] Then, if the determination in step S7 is Yes, the controller 2 outputs a reverse signal, and the cooling fan 4 starts to reverse (step S8). As a result, dust and debris collected by the filter 7 are blown away and removed from the filter 7. Alternatively, if there is no filter 7, dust and debris accumulated on the heat exchanger unit 3 are blown away and removed from the heat exchanger unit 3.

[0053] Furthermore, in step S8, it is preferable that the air conditioner's compressor 24 is stopped by the controller 2 at the same time as the cooling fan 4 starts to reverse. When the cooling fan 4 is reversed, the air heated by passing around the battery 6 passes through the condenser 10, causing the refrigerant to be heated. If the refrigerant is excessively heated while the air conditioner is running, it may place an excessive load on the air conditioner system and cause the air conditioner to malfunction.

[0054] Therefore, when reversing the cooling fan 4, it is necessary to stop the air conditioner. However, stopping the air conditioner every time before starting to reverse the cooling fan 4 is troublesome for the operator, and the operator may forget to stop the air conditioner. Accordingly, in step S8, it is preferable to stop the air conditioner's compressor and stop the flow of refrigerant at the same time as starting to reverse the cooling fan 4, thereby preventing excessive load on the air conditioner.

[0055] Referring to Figure 7, after step S8 is performed, the controller 2 determines whether the coolant temperature is below a threshold (step S9), whether the hydraulic oil temperature is below a threshold (step S10), and whether the refrigerant pressure of the air conditioner is below a threshold (step S11). If each of the determinations from steps S9 to S11 is Yes, the controller 2 determines whether a predetermined time tr has elapsed since the cooling fan 4 started to reverse (step S12).

[0056] The controller 2 then continues to reverse the cooling fan 4 until a predetermined time tr has elapsed, and repeatedly performs each of the checks from steps S9 to S11. Once the predetermined time tr has elapsed since the cooling fan 4 started to reverse, the controller 2 returns the cooling fan 4 to forward rotation and resets the accumulated value of the airflow. In the example shown in Figures 6 and 7, the controller 2 also releases the stop of the air conditioner's compressor 24 (step S23).

[0057] In automatic mode, if any of the judgments from steps S9 to S11 is No, the controller 2 interrupts the reverse operation of the cooling fan 4 and returns the cooling fan 4 to forward operation (step S13). After step S13 is executed, the controller 2 does not reset all of the accumulated values ​​(accumulated amount S) of the airflow rate passing through the heat exchanger unit 3, but restarts accumulation from accumulated amount S'. Specifically, if t0 is the time that the reverse operation actually occurred up to step S13, and tc is the remaining predetermined time obtained by subtracting the time t0 that the reverse operation actually occurred from the predetermined time tr during the reverse operation, the controller 2 calculates the accumulated amount S' (the formula is S'=S(tc / tr)), which is the product of the ratio of the remaining predetermined time tc to the predetermined time tr and the accumulated amount S, and restarts accumulation of the airflow rate passing through the heat exchanger unit 3 from this accumulated amount S' (step S14).

[0058] The reason for restarting the accumulation from the accumulated amount S' in step S14 is explained below. In step S14, the cooling fan 4 has only reversed for a predetermined time of less than tr, so it is possible that some dust and debris that could not be removed by this reverse operation remain in the heat exchanger unit 3. If the accumulated amount S' were reset upon returning to step S14, the time required for forward rotation to reach the accumulated amount S would be longer, making it easier for more dust and debris to accumulate in the heat exchanger unit 3, which could result in a decrease in the cooling efficiency of the heat exchanger unit 3. Therefore, the controller 2 does not reset the accumulated amount S', but instead controls the time until the cooling fan 4 reverses operation again to be shortened.

[0059] After step S14 is executed, the controller 2, as described above, continues to accumulate the airflow rate until the accumulated value of the airflow rate in step S3 is equal to or greater than the threshold S, and repeats step S3 until the determination in step S3 is Yes. In this embodiment, in automatic mode, if any of the determinations from step S9 to S11 is No, the process proceeds to steps S13 and S14. However, steps S13 and S14 may be set to arbitrary conditions, and if any of the determinations from step S9 to S11 is No, the controller 2 may issue a warning to the operator (step S24) and proceed to determine whether the cooling fan 4 is reversed (step S25).

[0060] Next, we will explain the case where the determination in step S15 is Yes and the process proceeds to step S16. In step S16, the controller 2 determines whether the coolant temperature detected by the coolant temperature sensor 11 is below a threshold. If the determination in step S16 is Yes, the controller 2 determines whether the hydraulic oil temperature detected by the hydraulic oil temperature sensor 12 is below a threshold (step S17). If the determination in step S17 is Yes, the controller 2 determines whether the refrigerant pressure of the air conditioner detected by the refrigerant pressure sensor 13 is below a threshold (step S18).

[0061] Then, if the determination in step S18 is Yes, the controller 2 outputs a reverse signal to start the cooling fan 4 in reverse and stops the air conditioner compressor 24 (step S19).

[0062] After step S19 is performed, the controller 2 determines whether the coolant temperature is below a threshold (step S20), whether the hydraulic oil temperature is below a threshold (step S21), and whether the air conditioner refrigerant pressure is below a threshold (step S22). If each of the determinations from steps S20 to S22 is Yes, the controller 2 determines whether a predetermined time tr has elapsed since the cooling fan 4 started to reverse (step S23).

[0063] The controller 2 then continues to rotate the cooling fan 4 in the reverse direction until a predetermined time tr has elapsed, and repeatedly performs the checks from steps S20 to S22. Once the predetermined time tr has elapsed since the cooling fan 4 started rotating in the reverse direction, the controller 2 returns the cooling fan 4 to the forward direction, resets the accumulated value of the airflow, and releases the stop of the air conditioner's compressor 24 (step S23).

[0064] If such a reversal switch 14 is operated and any of the determinations in steps S16 to S18 or steps S20 to S22 are No, the controller 2 issues a warning to the operator (step S24) and determines whether the cooling fan 4 is reversed or not (step S25). If the cooling fan 4 is reversed, the controller 2 executes step S23; otherwise, the process ends.

[0065] Thus, in this embodiment, when the cumulative value of the airflow rate passing through the heat exchanger unit 3 reaches a threshold S, the controller 2 reverses the cooling fan 4 for a predetermined time tr. Figure 8 is a timing chart showing the operation timing of the cooling fan 4 in automatic mode. The horizontal axis in Figure 8 is the time axis.

[0066] In Figure 8, point a indicates the starting point of the cooling fan 4's operation. When the cooling fan 4 is rotated at a low speed during forward rotation, the amount of air passing through the heat exchanger unit 3 is small, resulting in a longer cumulative time until the cumulative value reaches the threshold S (point b). Upon reaching point b, the cooling fan 4 switches from forward rotation to reverse rotation (STEP 1).

[0067] Next, the cooling fan 4 continues to operate in reverse for a predetermined time tr (between points b and c), and when the reverse operation ends (point c), the value of the accumulated amount S is reset and it returns to forward rotation (STEP 2). From the point when the accumulated value of the airflow through reaches 0 (point d), the accumulation of the airflow through begins again until the threshold S is reached.

[0068] Conversely to STEP 1, when the cooling fan 4 is rotated at high speed while rotating in the forward direction, the amount of air passing through the heat exchanger unit 3 increases, resulting in a shorter accumulation time until the accumulated value reaches the threshold S again (point e). Upon reaching point e, the cooling fan 4 switches from forward rotation to reverse rotation, similar to STEP 1 (STEP 4). After that, similar to STEP 2, it continues reverse rotation for a predetermined time tr (between points ef), and when the reverse rotation ends (point f), the accumulated value S is reset, and it returns to forward rotation. Then, from the point where the accumulated value becomes 0 (point g), accumulation of the amount of air passing through begins again until the threshold S is reached once more.

[0069] In automatic mode, after STEP 4, the cooling fan 4 continues to accumulate the airflow rate until it reaches a threshold S according to its output, and once the threshold S is reached, it reverses direction for a predetermined time tr, repeating this process. Therefore, by switching between forward and reverse rotation of the cooling fan 4 at appropriate timings, a decrease in the cooling efficiency of the heat exchanger unit 3 can be reliably prevented.

[0070] Next, we will explain the difference in timing of the cooling fan reverse operation between the present invention and the prior art described in Patent Document 1.

[0071] Figure 9 shows the difference in timing of cooling fan reverse operation in automatic mode between the present invention and the prior art (Patent Document 1), with the horizontal axis representing time. In the prior art (Patent Document 1, hereinafter referred to as the prior art), when the cooling fan output is both low and high rotation speeds, the cooling fan is rotated forward for a fixed first predetermined time and reversed for a fixed second predetermined time, making it impossible to reverse the cooling fan at the appropriate timing. On the other hand, as explained in Figure 8, in the present invention, it is possible to select the timing of the start of reverse operation based on the output of the cooling fan 4, so it can be seen that the heat exchanger unit 3 can be cleaned by reversing the cooling fan 4 at an appropriate timing compared to the prior art.

[0072] Furthermore, in the illustrated embodiment, even if the cumulative value of the airflow rate passing through the heat exchanger unit 3 does not reach the threshold S, when a reverse signal is output from the reverse switch 14, the controller 2 reverses the cooling fan 4 for a predetermined time tr. Therefore, in workplaces with a relatively large amount of dust, the operator can operate the reverse switch 14 at an appropriate time to reverse the cooling fan 4 and clean the heat exchanger unit 3.

[0073] Furthermore, in the illustrated embodiment, the controller 2 resets the accumulated amount S of the airflow when the cooling fan 4 reverses, not only when the cooling fan 4 reverses due to the cumulative value of the airflow passing through the heat exchanger unit 3 during forward rotation reaching a threshold S, but also when the cooling fan 4 reverses due to the operator operating the reverse switch 14. Therefore, the cooling fan 4 does not reverse at unnecessarily short intervals.

[0074] In the example of the cooling fan 4's reverse rotation process described above, the conditions for the cooling fan 4 to start and continue reverse rotation were explained as the various fluid temperatures being below a threshold; however, these can be any conditions.

[0075] The present invention is not limited to the embodiments described above, and includes various modifications that do not depart from the spirit of the invention. For example, the present invention is not limited to having all the configurations described in the embodiments described above, but also includes configurations in which some of those configurations are omitted. Furthermore, it is possible to add or replace some of the configurations of one embodiment with the configurations of another embodiment. Other embodiments that can be conceivable within the scope of the technical idea of ​​the present invention are also included within the scope of the present invention. [Explanation of Symbols]

[0076] 1: Hydraulic excavator (construction machinery) 2: Controller 3: Heat exchanger unit 4: Cooling fan 7: Filter 8: Radiator (heat exchanger) 9: Oil cooler (heat exchanger) 10: Capacitor (heat exchanger) 14: Reverse switch (switch) 24: Compressor

Claims

1. Heat exchanger, A cooling fan that supplies cooling air to the heat exchanger when it is rotating in the forward direction, A construction machine comprising a controller that controls the operation of the cooling fan, The aforementioned controller, The amount of cooling air passing through the heat exchanger when the cooling fan is rotating forward is calculated by the product of the cooling fan's wind speed and the heat exchanger's cross-sectional area, and the calculated amount of air passing through is multiplied by the time the cooling fan is rotating forward to obtain the integrated value of the air passing through. When the cumulative value of the airflow reaches a predetermined threshold, the cooling fan is controlled to reverse for a predetermined period of time. The accumulated value is reset when the cooling fan stops reversing. A construction machine characterized by the following features.

2. In the construction machine described in claim 1, A cockpit for the operator, The control room is provided with a switch that outputs a signal to the controller to reverse the cooling fan when operated by the operator, The aforementioned controller, Even if the accumulated value has not reached the threshold, if the signal is input, the cooling fan is controlled to reverse for the predetermined time, and the accumulated value is reset when the cooling fan finishes reversing. A construction machine characterized by the following features.

3. In the construction machine described in claim 1, A cockpit for the operator, The vehicle includes an air conditioner for providing air conditioning to the driver's cab, The aforementioned air conditioner is, It includes a compressor for compressing a refrigerant, and a condenser, which acts as a heat exchanger, for condensing the refrigerant compressed by the compressor, The aforementioned controller, The system controls the operation of the compressor to stop when the cooling fan is reversed. A construction machine characterized by the following features.

4. In the construction machine described in claim 3, The aforementioned controller, When the pressure of the refrigerant exceeds a predetermined value, the system controls the cooling fan to interrupt its reverse rotation and return to forward rotation, while not resetting the accumulated value. A construction machine characterized by the following features.

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