Work machine

Abstract

To provide a work machine capable of supplying an appropriate amount of cooling air to a plurality of heat exchangers while suppressing an increase in power consumption.SOLUTION: A work machine comprises: an engine; a first heat exchanger; a second heat exchanger placed adjacently to the first heat exchanger; a first cooling fan placed facing the first heat exchanger; a second cooling fan placed facing the second heat exchanger; a rotation speed sensor detecting an engine rotation speed; a temperature detection device detecting temperature of a first fluid passing through the first heat exchanger and temperature of a second fluid passing through the second heat exchanger; and a controller executing first acceleration control to increase a rotation speed of the second cooling fan when the first cooling fan is driven for a first predetermined time at the upper limit rotation speed of the first cooling fan.SELECTED DRAWING: Figure 7

Description

[Technical field]

[0001] The present invention relates to a work machine equipped with a plurality of heat exchangers and a plurality of cooling fans. [Background technology]

[0002] 2. Description of the Related Art Conventionally, work machines such as hydraulic excavators are equipped with a number of heat exchangers, such as a radiator that cools the engine's cooling water, an oil cooler that cools the working oil in the hydraulic system, and an intercooler that cools the air compressed by a turbocharger.

[0003] For example, Patent Document 1 discloses a work machine equipped with multiple heat exchangers arranged adjacent to each other and multiple cooling fans arranged facing each of the multiple heat exchangers and driven by electricity. This work machine controls the rotation speed of each of the multiple cooling fans individually in accordance with the temperature of the fluid in the corresponding heat exchanger. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6702819 Summary of the Invention [Problem to be solved by the invention]

[0005] However, there are cases where dust accumulates on the surface of a heat exchanger, reducing the heat exchange efficiency (hereinafter referred to as "clogging"). In this case, if one of adjacent heat exchangers becomes clogged, the rotation speed of the cooling fan corresponding to that heat exchanger increases. The higher the rotation speed of the cooling fan, the greater the increase in power consumption of the fan motor that drives the cooling fan, which poses a problem of increased power consumption by the work machine.

[0006] The present invention has been made in consideration of the above-mentioned circumstances, and its object is to provide a work machine that can supply an appropriate volume of cooling air to multiple heat exchangers while suppressing an increase in power consumption. [Means for solving the problem]

[0007] In order to achieve the above object, the present invention provides a work machine including an engine, a first heat exchanger, a second heat exchanger arranged adjacent to the first heat exchanger, a first cooling fan arranged facing the first heat exchanger, a second cooling fan arranged facing the second heat exchanger, a rotation speed sensor that detects a rotation speed of the engine, a temperature detection device that detects a temperature of a first fluid passing through the first heat exchanger and a temperature of a second fluid passing through the second heat exchanger, and a controller that determines upper limit rotation speeds of the first cooling fan and the second cooling fan based on the engine rotation speed detected by the rotation speed sensor, and controls the rotation speeds of the first cooling fan and the second cooling fan based on the temperatures of the first fluid and the second fluid detected by the temperature detection device below the respective determined upper limit rotation speeds, wherein the controller executes a first acceleration control to increase the rotation speed of the second cooling fan when the first cooling fan has been driven at the upper limit rotation speed of the first cooling fan for a first predetermined time. Effect of the Invention

[0008] According to the present invention, it is possible to supply an appropriate amount of cooling air to a plurality of heat exchangers while suppressing an increase in power consumption. Note that problems, configurations, and effects other than those described above will become apparent from the description of the following embodiments. [Brief description of the drawings]

[0009] [Figure 1] FIG. 2 is a side view of the hydraulic excavator. [Diagram 2] FIG. [Diagram 3] FIG. [Figure 4]FIG. 2 is a control block diagram of a hydraulic excavator. [Diagram 5] FIG. 2 is a block diagram of a controller. [Figure 6] FIG. 4 is a diagram showing the relationship between fluid temperature and set rotation speed (A), and the relationship between engine rotation speed and upper limit rotation speed (B). [Figure 7] 4 is a flowchart of a fan control process. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] An embodiment of a hydraulic excavator 1 (working machine) according to the present invention will be described with reference to the drawings. Note that specific examples of the working machine are not limited to the hydraulic excavator 1, and may be a wheel loader, a crane, a dump truck, etc. Furthermore, unless otherwise specified, the terms front, back, left, and right in this specification are based on the viewpoint of an operator who is on board and operating the hydraulic excavator 1.

[0011] FIG. 1 is a side view of a hydraulic excavator 1. As shown in FIG. 1, the hydraulic excavator 1 includes 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 an example of a vehicle body. The lower traveling body 2 includes a pair of left and right crawlers 4 which are endless tracks. The pair of left and right crawlers 4 are rotated independently by driving a traveling motor 5. As a result, the hydraulic excavator 1 travels. However, the lower traveling body 2 may be of a wheeled type instead of the crawlers 4.

[0012] The upper rotating body 3 is supported on the lower traveling body 2 so as to be rotatable by a rotating motor 6. The upper rotating body 3 mainly comprises a rotating frame 7 serving as a base, a cab (operator's seat) 8 disposed on the front left side of the rotating frame 7, a counterweight 9 disposed at the rear of the rotating frame 7, and a front work machine 10 (work device) attached to the front center of the rotating frame 7 so as to be rotatable in the vertical direction.

[0013] The cab 8 defines a space for an operator to ride in and operate the hydraulic excavator 1. Inside the cab 8, a seat for the operator to sit in, an operating device to be operated by the operator seated on the seat, and a display 8a (see FIG. 2) are arranged.

[0014] The operating device receives operations by an operator for operating the hydraulic excavator 1. When the operator operates the operating device, the lower traveling body 2 travels, the upper rotating body 3 rotates, and the front working implement 10 operates. Specific examples of the operating device include a lever, a steering wheel, a pedal, a switch, etc.

[0015] The display 8a is an example of a notification device that notifies information to an operator in the cab 8. Note that specific examples of the notification device are not limited to the display 8a, and may be an LED lamp, a speaker, or a combination of these.

[0016] The front working implement 10 includes a boom 11 supported on the upper rotating body 3 so as to be able to rise and fall, an arm 12 supported rotatably at the end of the boom 11, a bucket 13 supported rotatably at the end of the arm 12, a boom cylinder 14 that drives the boom 11, an arm cylinder 15 that drives the arm 12, and a bucket cylinder 16 that drives the bucket 13. The counterweight 9 is used to balance the weight of the front working implement 10, and is a heavy object that has an arc shape when viewed from above.

[0017] The upper rotating body 3 also supports an engine building 20 (building). The engine building 20 is supported by the rotating frame 7 behind the cab 8 and the front work machine 10 and in front of the counterweight 9. The engine building 20 has a space for accommodating components for operating the hydraulic excavator 1.

[0018] Fig. 2 is a plan view of the upper rotating body 3. As shown in Fig. 2, an engine building 20 houses an engine 21, a hydraulic pump 22, a heat exchanger assembly 23, and the like as components for operating the hydraulic excavator 1.

[0019] The engine 21 is disposed to the right of the heat exchanger assembly 23 and to the left of the hydraulic pump 22. The engine 21 generates driving force for operating the hydraulic excavator 1 by mixing and burning fossil fuel and air. The rotation speed of the engine 21 is set by an engine rotation speed setting dial (not shown) or the like.

[0020] The hydraulic pump 22 is disposed to the right of the engine 21 and the heat exchanger assembly 23. The hydraulic pump 22 is connected to the output shaft of the engine 21 and rotates to pump hydraulic oil stored in a hydraulic oil tank (not shown) toward the hydraulic actuators (the travel motor 5, the swing motor 6, the boom cylinder 14, the arm cylinder 15, and the bucket cylinder 16).

[0021] Fig. 3 is a perspective view of the heat exchanger Assy 23. The heat exchanger Assy 23 is a unit that cools multiple fluids. As shown in Fig. 2 and Fig. 3, the heat exchanger Assy 23 according to this embodiment includes multiple heat exchangers 24o, 24r, and 24i, and multiple cooling fans 25o, 25r, and 25i.

[0022] The heat exchanger 24o is an oil cooler that exchanges heat between the hydraulic oil (fluid) that operates the hydraulic actuator and cooling air. The heat exchanger 24r is a radiator that exchanges heat between the cooling liquid (fluid) that cools the engine 21 and cooling air. The heat exchanger 24i is an intercooler that cools the air (fluid) compressed by a supercharger mounted on the engine 21.

[0023] The cooling fans 25o, 25r, and 25i take in air from outside the vehicle body as cooling wind, and generate cooling wind that flows from left to right (from upstream to downstream) inside the engine building 20. The cooling fans 25o, 25r, and 25i are rotated by the driving force of the corresponding fan motors 26o, 26r, and 26i (see FIG. 4). The fan motors 26o, 26r, and 26i are electric motors that rotate when supplied with electric power.

[0024] The hydraulic excavator 1 includes, for example, a generator (not shown) connected to the output shaft of the engine 21 to generate electricity, and a battery (not shown) that stores the electricity generated by the generator. The fan motors 26o, 26r, and 26i are driven to rotate by the electricity stored in the battery. That is, the cooling fans 25o, 25r, and 25i are driven by the electricity to generate cooling air.

[0025] The cooling fans 25o, 25r, and 25i are configured to be able to change their rotation speeds independently under the control of the controller 30 (see FIG. 4). More specifically, the rotation speeds of the fan motors 26o, 26r, and 26i are controlled by control signals from the controller 30, thereby increasing or decreasing the rotation speeds of the cooling fans 25o, 25r, and 25i. As the rotation speeds of the cooling fans 25o, 25r, and 25i increase and the amount of cooling air generated increases (i.e., the rotation speed becomes faster), the power consumption of the fan motors 26o, 26r, and 26i that drive the cooling fans 25o, 25r, and 25i also increases.

[0026] 2 and 3, the heat exchanger assembly 23 includes an outer wall 23a and a partition wall 23b. The outer wall 23a houses the heat exchangers 24o, 24r, and 24i and the cooling fans 25o, 25r, and 25i. However, the face on the upstream side of the flow of cooling air (i.e., the left face) and the face on the downstream side of the flow of cooling air (i.e., the right face) are open. That is, the cooling air generated by the cooling fans 25o, 25r, and 25i flows in from the left face of the heat exchanger assembly 23 and flows out from the right face. The partition wall 23b divides the internal space of the outer wall 23a.

[0027] The heat exchangers 24o, 24r, and 24i are arranged in a direction perpendicular to the flow direction of the cooling air (front-rear direction). In other words, the heat exchangers 24o, 24r, and 24i are arranged adjacent to each other in the front-rear direction. The cooling fans 25o, 25r, and 25i are arranged in a direction perpendicular to the flow direction of the cooling air (front-rear direction) downstream of the heat exchangers 24o, 24r, and 24i in the flow direction of the cooling air. Furthermore, the cooling fans 25o, 25r, and 25i are arranged facing the corresponding heat exchangers 24o, 24r, and 24i in the flow direction of the cooling air.

[0028] The heat exchanger 24o and the cooling fan 25o are disposed in a space on one side (front side) of the internal space of the outer wall 23a, which is partitioned by the partition wall 23b. That is, only the cooling air generated by the cooling fan 25o is supplied to the heat exchanger 24o. In other words, the heat exchanger 24o exchanges heat between the hydraulic oil and only the cooling air generated by the cooling fan 25o.

[0029] The heat exchangers 24r, 24i and the cooling fans 25r, 25i are disposed in the other (rear) side of the internal space of the outer wall 23a, separated by the partition wall 23b. That is, the outer wall 23a and the partition wall 23b constitute an example of a flow path member that defines a common cooling air flow path 27 through which the cooling air generated by the cooling fans 25r, 25i passes.

[0030] Therefore, the heat exchanger 24r is mainly supplied with the cooling air generated by the cooling fan 25r, but is also supplied with some of the cooling air generated by the cooling fan 25i. Similarly, the heat exchanger 24i is mainly supplied with the cooling air generated by the cooling fan 25i, but is also supplied with some of the cooling air generated by the cooling fan 25r. In other words, the heat exchangers 24r and 24i exchange heat between the cooling air passing through the common cooling air flow passage 27 and the fluid (cooling liquid, air).

[0031] In this embodiment, the heat exchanger 24r is an example of a first heat exchanger, the heat exchanger 24i is an example of a second heat exchanger, the cooling fan 25r is an example of a first cooling fan, the cooling fan 25i is an example of a second cooling fan, the coolant of the engine 21 is an example of a first fluid, and the air compressed by the turbocharger is an example of a second fluid. However, the heat exchanger 24i may be the first heat exchanger, and the heat exchanger 24r may be the second heat exchanger.

[0032] 1, an air intake port 28 is formed on the left side surface of the engine building 20. Furthermore, an exhaust port (not shown) is formed on the right side surface of the engine building 20. Then, as the cooling fans 25o, 25r, and 25i rotate, air (cooling air) that has flowed into the engine building 20 from the air intake port 28 passes through the heat exchanger assembly 23 and is discharged to the outside of the engine building 20 from the exhaust port.

[0033] Fig. 4 is a control block diagram of the hydraulic excavator 1. As shown in Fig. 4, the hydraulic excavator 1 includes a controller 30 having a CPU 31 (Central Processing Unit) and a memory 32. The memory 32 is configured, for example, with a ROM (Read Only Memory), a RAM (Random Access Memory), an HDD (Hard Disk Drive), or a combination of these. The controller 30 realizes the processing described below by the CPU 31 reading and executing program codes stored in the memory 32.

[0034] However, the specific configuration of the controller 30 is not limited to this, and may be realized by hardware such as an application specific integrated circuit (ASIC) or a field programmable gate array (FPGA).

[0035] The controller 30 is connected to a rotation speed sensor 33 and temperature sensors 34o, 34r, 34i (temperature detection devices). The rotation speed sensor 33 detects the engine rotation speed E of the engine 21 and outputs a rotation speed signal indicating the detected engine rotation speed E to the controller 30. The temperature sensors 34o, 34r, 34i detect the temperatures of the fluids (hydraulic oil, coolant, air) of the corresponding heat exchangers 24o, 24r, 24i and output a temperature signal indicating the detected temperatures to the controller 30. The temperature sensor 34r is an example of a first temperature sensor, and the temperature sensor 34i is an example of a second temperature sensor.

[0036] The controller 30 also controls the operations of the engine 21, the fan motors 26o, 26r, and 26i, and the display 8a. More specifically, the controller 30 controls the rotation speed of the engine 21 so that the rotation speed is set by an engine rotation speed setting dial or the like. The controller 30 also controls the rotation speeds of the fan motors 26o, 26r, and 26i based on the engine rotation speed E detected by the rotation speed sensor 33 and the temperatures To, Tr, and Ti detected by the temperature sensors 34o, 34r, and 34i. The controller 30 also notifies the operator in the cab 8 of information through the display 8a.

[0037] Fig. 5 is a block diagram of the controller 30. Fig. 6 is a diagram showing (A) the relationship between the temperature Tr held by the set rotation speed determination unit 41r and the set rotation speed Fr0 of the cooling fan 25r, and (B) the relationship between the engine rotation speed E held by the upper limit rotation speed determination unit 42r and the upper limit rotation speed Fr-max.

[0038] 5(A), the controller 30 includes, as functional blocks for controlling the rotation speed Fr of the cooling fan 25r, a set rotation speed determination unit 41r, an upper limit rotation speed determination unit 42r, a minimum value output unit 43r, switches 44r and 45r, and a maximum value output unit 46r. Each of the blocks 41r to 46r shown in FIG. 5(A) may be realized by hardware (e.g., an electric circuit) or software (i.e., the CPU 31 executes a program stored in the memory 32).

[0039] The set rotation speed determination unit 41r determines the set rotation speed Fr0 based on the temperature Tr detected by the temperature sensor 34r. The set rotation speed determination unit 41r determines the set rotation speed Fr0 corresponding to the temperature Tr, for example, using the correspondence relationship shown in Fig. 6(A). Then, the set rotation speed determination unit 41r outputs the determined set rotation speed Fr0 to the minimum value output unit 43r.

[0040] The set rotation speed Fr0 is the minimum rotation speed for maintaining the temperature Tr of the cooling liquid passing through the heat exchanger 24r below a predetermined first threshold temperature T1. As shown in FIG. 6(A), the set rotation speed Fr0 is a value that increases as the temperature Tr increases. The correspondence relationship shown in FIG. 6(A) is calculated in advance by experiment or simulation and stored in the memory 32. Note that the relationship between the temperature Tr and the set rotation speed Fr0 is not limited to the linear relationship shown in FIG. 6(A), and may be a positive correlation such as a quadratic curve, an exponential curve, a logarithmic curve, or a stepwise relationship.

[0041] The upper limit rotation speed determination unit 42r determines the upper limit rotation speed Fr-max based on the engine rotation speed E detected by the rotation speed sensor 33. The upper limit rotation speed determination unit 42r determines the upper limit rotation speed Fr-max corresponding to the engine rotation speed E, for example, by using the correspondence relationship shown in Fig. 6(B). Then, the upper limit rotation speed determination unit 42r outputs the determined upper limit rotation speed Fr-max to the minimum value output unit 43r and the switch 44r.

[0042] The upper limit rotation speed Fr-max is the minimum rotation speed required to maintain the temperature Tr of the coolant passing through the heat exchanger 24r at the first threshold temperature T1 (i.e., to satisfy the heat balance). As shown in FIG. 6(B), the upper limit rotation speed Fr-max is a value that increases as the engine speed E increases. The correspondence relationship shown in FIG. 6(B) is calculated in advance by experiment or simulation, and is stored in the memory 32. Note that the relationship between the engine speed E and the upper limit rotation speed Fr-max is not limited to the linear relationship shown in FIG. 6(B), and may be a positive correlation such as a quadratic curve, an exponential curve, a logarithmic curve, or a stepwise relationship.

[0043] The minimum value output unit 43r outputs the smaller (slower) value of the set rotation speed Fr0 output from the set rotation speed determination unit 41r and the upper limit rotation speed Fr-max output from the upper limit rotation speed determination unit 42r to the maximum value output unit 46r. When the temperature Tr is lower than the first threshold temperature T1, the set rotation speed Fr0 is smaller (slower) than the upper limit rotation speed Fr-max. When the temperature Tr is equal to the first threshold temperature T1, the set rotation speed Fr0 and the upper limit rotation speed Fr-max are equal. When the temperature Tr is higher than the first threshold temperature T1, the set rotation speed Fr0 is larger (faster) than the upper limit rotation speed Fr-max.

[0044] The switch 44r is configured to be switchable between an ON state in which the upper limit rotation speed Fr-max output from the upper limit rotation speed determination unit 42r is output to the maximum value output unit 46r and an OFF state in which the upper limit rotation speed Fr-lim is not output to the maximum value output unit 46r. The switch 45r is configured to be switchable between an ON state in which a predetermined limit rotation speed Fr-lim is output to the maximum value output unit 46r and an OFF state in which the predetermined limit rotation speed Fr-lim is not output to the maximum value output unit 46r.

[0045] The limit rotation speed Fr-lim is the maximum rotation speed of the cooling fan 25r that does not exceed the power generation capacity of the hydraulic excavator 1. In other words, the limit rotation speed Fr-lim is a limit value on the hardware. That is, the limit rotation speed Fr-lim is set to a value faster (larger) than the upper limit rotation speed Fr-max.

[0046] The maximum value output unit 46r outputs the maximum value among the value output from the minimum value output unit 43r, the upper limit rotation speed Fr-max output from the switch 44r in the ON state, and the limit rotation speed Fr-lim output from the switch 45r in the ON state as the rotation speed Fr of the cooling fan 25r.

[0047] When both switches 44r and 45r are in the OFF state, maximum value output unit 46r outputs the value output from minimum value output unit 43r (i.e., a value equal to or less than the upper limit rotation speed Fr-max) as the rotation speed Fr of cooling fan 25r. When switch 44r is in the ON state and switch 45r is in the OFF state, maximum value output unit 46r outputs the upper limit rotation speed Fr-max (i.e., a fixed value) output from switch 44r as the rotation speed Fr of cooling fan 25r. When switch 45r is in the ON state, maximum value output unit 46r outputs the limit rotation speed Fr-lim (i.e., a fixed value) output from switch 45r as the rotation speed Fr of cooling fan 25r.

[0048] As shown in Fig. 5(B), the controller 30 includes a set rotation speed determination unit 41i, an upper limit rotation speed determination unit 42i, a minimum value output unit 43i, switches 44i and 45i, and a maximum value output unit 46i as functional blocks for controlling the rotation speed Fi of the cooling fan 25i. The roles of the blocks 41i to 46i shown in Fig. 5(B) are the same as those of the blocks 41r to 46r shown in Fig. 5(A), so repeated explanations will be omitted.

[0049] The set rotation speed Fi0 is the minimum rotation speed for maintaining the temperature Ti of the air passing through the heat exchanger 24i below a predetermined second threshold temperature T2. There is a positive correlation between the temperature Ti and the set rotation speed Fi0, as in Fig. 6(A). However, the specific values ​​of the set rotation speeds Fr0 and Fi0 do not need to be the same.

[0050] The upper limit rotation speed Fi-max is the minimum rotation speed required to maintain the temperature Ti of the air passing through the heat exchanger 24i at the second threshold temperature T2 (i.e., to satisfy the heat balance). There is a positive correlation between the engine speed E and the upper limit rotation speed Fi-max, as in FIG. 6(B). However, the specific values ​​of the upper limit rotation speeds Fr-max and Fi-max do not need to be the same.

[0051] The limit rotation speed Fi-lim is the maximum rotation speed of the cooling fan 25i that does not exceed the power generation capacity of the hydraulic excavator 1. In other words, the limit rotation speed Fi-lim is set to a value faster (larger) than the upper limit rotation speed Fi-max. However, the specific values ​​of the limit rotation speeds Fr-lim and Fi-lim do not need to be the same.

[0052] 5(A) as a functional block for controlling the rotation speed Fo of the cooling fan 25o. These functional blocks determine the rotation speed Fo of the cooling fan 25o based on the temperature To of the hydraulic oil passing through the heat exchanger 24o, the engine speed E, and the limit rotation speed Fo-lim of the cooling fan 25o.

[0053] The set rotation speed Fr0 is an example of a first set rotation speed, the upper limit rotation speed Fr-max is an example of a first upper limit rotation speed, and the limit rotation speed Fr-lim is an example of a first limit rotation speed. The set rotation speed Fi0 is an example of a second set rotation speed, the upper limit rotation speed Fi-max is an example of a second upper limit rotation speed, and the limit rotation speed Fi-lim is an example of a second limit rotation speed.

[0054] Dust that has entered the engine building 20 through the air intake 28 accumulates on the surfaces (left surfaces) of the heat exchangers 24r and 24i. This reduces the heat exchange efficiency of the heat exchangers 24r and 24i (i.e., clogging). However, the amount of dust that accumulates on the surfaces of the heat exchangers 24r and 24i may become unbalanced due to various reasons such as the layout and surface condition of the heat exchangers 24r and 24i. Therefore, the controller 30 repeatedly executes the fan control process shown in FIG. 7 at predetermined time intervals while the engine 21 is rotating. FIG. 7 is a flowchart of the fan control process.

[0055] The fan control process is a process for supplying an appropriate amount of cooling air to the heat exchangers 24r and 24i while suppressing an increase in power consumption of the entire hydraulic excavator 1. In this embodiment, the fan control process will be described on the premise that the temperature Ti of the air passing through the heat exchanger 24i is always less than the second threshold temperature. In other words, the following description is based on the premise that the amount of dust accumulated on the surface of the heat exchanger 24r is greater than that of the heat exchanger 24i.

[0056] First, when the temperature Tr is less than the first threshold temperature T1 and the temperature Ti is less than the second threshold temperature T2 (S11: No), the controller 30 executes normal control (S12). The first threshold temperature T1 is set to a value that indicates that the acceleration control described below is required. The first threshold temperature T1 may be a fixed value or may be a value that changes depending on the engine speed E, etc. (for example, the faster the engine speed E, the higher the first threshold temperature T1).

[0057] In normal control, cooling fan 25r is rotated at rotation speed Fr corresponding to temperature Tr, and cooling fan 25i is rotated at rotation speed Fi corresponding to temperature Ti. More specifically, controller 30 turns switches 44r, 44i, 45r, and 45i to the OFF state. As a result, controller 30 determines set rotation speeds Fr0 and Fi0 determined by set rotation speed determination units 41r and 41i as rotation speeds Fr and Fi. Then, controller 30 transmits control signals corresponding to the determined rotation speeds Fr and Fi to fan motors 26r and 26i.

[0058] That is, in step S12, the controller 30 controls the rotation speed of each of the cooling fans 25r, 25i based on the temperatures Tr, Ti to be equal to or lower than the upper limit rotation speeds Fr-max, Fi-max.

[0059] On the other hand, when the temperature Tr remains equal to or higher than the first threshold temperature T1 for a first predetermined time and the temperature Ti is lower than the second threshold temperature T2 (S11: Yes & S13: No), the controller 30 executes the transitional control (S14). The transitional control is a control for rotating the cooling fan 25r at the upper limit rotation speed Fr-max corresponding to the first threshold temperature T1 and rotating the cooling fan 25i at the rotation speed Fi corresponding to the temperature Ti.

[0060] The states of the switches 44r, 44i, 45r, and 45i in the transitional control are the same as those in the normal control. However, the set rotation speed Fr0 determined by the set rotation speed determination unit 41r when the temperature is equal to or higher than the first threshold temperature T1 is equal to or higher than the upper limit rotation speed Fr-max, so the minimum value output unit 43r outputs the upper limit rotation speed Fr-max, which is a smaller value. As a result, the controller 30 determines the upper limit rotation speed Fr-max determined by the upper limit rotation speed determination unit 42r as the rotation speed Fr, and determines the set rotation speed Fi0 determined by the set rotation speed determination unit 41i as the rotation speed Fi. Then, the controller 30 transmits control signals corresponding to the determined rotation speeds Fr and Fi to the fan motors 26r and 26i.

[0061] Next, when the temperature Tr becomes less than the first threshold temperature T1 and the temperature Ti becomes less than the second threshold temperature T2 (S11: No) during the execution of the transitional control (S14), the controller 30 cancels the transitional control and executes the normal control again (S12).

[0062] That is, in steps S11 to S14, the controller 30 controls the cooling fan 25r at the smaller of the set rotation speed Fr0 and the upper limit rotation speed Fr-max. When the temperature Tr is equal to or higher than the first threshold temperature T1, the controller 30 drives the cooling fan 25r at the upper limit rotation speed Fr-max. Similarly, in steps S11 to S14, the controller 30 controls the cooling fan 25i at the smaller of the set rotation speed Fi0 and the upper limit rotation speed Fi-max. When the temperature Ti is equal to or higher than the first threshold temperature T1, the controller 30 drives the cooling fan 25i at the upper limit rotation speed Fi-max.

[0063] On the other hand, when the state in which the temperature Tr is equal to or higher than the first threshold temperature T1 continues for the first predetermined time and the temperature Ti is lower than the second threshold temperature (S11: Yes & S13: Yes), the controller 30 adds 1 to the variable N (S15). The variable N indicates the number of times that the start condition of the first speed increase control (steps S11 & S13) is satisfied. The variable N is initialized (N=0) when the cleaning of the heat exchangers 24o, 24r, 24i is performed (for example, step S23 described later).

[0064] Next, the controller 30 compares the variable N with a threshold number of times Nth (S16). The threshold number of times Nth is set to a value that allows the heat exchanger 24r to be evaluated as being clogged to such an extent that the temperature of the heat exchanger 24r cannot be maintained below the first threshold temperature T1 even if the speed-up control (S17) described later is executed. Then, when the variable N is less than the threshold number of times Nth (S16: No), the controller 30 executes the next stage of speed-up control (S17). In this embodiment, three stages of speed-up control are implemented, but the number of speed-up controls is not limited to this.

[0065] When steps S11 and S13 are satisfied (in other words, when the transitional control is being executed), the next stage of the speed increase control is the first speed increase control, which maintains the rotation speed Fr of the cooling fan 25r at the upper limit rotation speed Fr-max and increases the rotation speed Fi of the cooling fan 25i to the upper limit rotation speed Fi-max corresponding to the second threshold temperature T2.

[0066] That is, the controller 30 turns the switch 44i to the ON state from the transitional control state. As a result, the controller 30 determines the upper limit rotation speed Fi-max as the rotation speed Fi, regardless of the value of the set rotation speed Fi0 determined by the set rotation speed determination unit 41i. Meanwhile, the rotation speed Fr of the heat exchanger 24r does not change from the upper limit rotation speed Fr-max during the transitional control. Then, the controller 30 transmits control signals corresponding to the determined rotation speeds Fr and Fi to the fan motors 26r and 26i.

[0067] That is, in the first speed-up control, when the cooling fan 25r is driven at the upper limit rotation speed Fr-max for a first predetermined time, the controller 30 increases the rotation speed of the cooling fan 25i. More specifically, in the first speed-up control, when the cooling fan 25r is driven at the upper limit rotation speed Fr-max for a first predetermined time while the cooling fan 25i is driven at the set rotation speed Fi0, the controller 30 increases the rotation speed of the cooling fan 25i from the set rotation speed Fi0. More specifically, in the first speed-up control, when the cooling fan 25r is driven at the upper limit rotation speed Fr-max for a first predetermined time while the cooling fan 25i is driven at the set rotation speed Fi0, the controller 30 increases the rotation speed of the cooling fan 25i from the set rotation speed Fi0 to the upper limit rotation speed Fi-max.

[0068] Next, while executing the first acceleration control (S17), the controller 30 compares the temperature Tr with the release threshold temperature TC (S18) until a second predetermined time has elapsed since the start of the first acceleration control (S19: No). The release threshold temperature TC is set to a value that allows evaluation that the acceleration control may be released. The release threshold temperature TC is set to a value lower than the first threshold temperature T1.

[0069] Then, during the execution of the first acceleration control, if the temperature Tr is less than the release threshold temperature TC and the temperature Ti is less than the second threshold temperature T2 (S18: No) before the second predetermined time has elapsed (S19: No), the controller 30 cancels the first acceleration control (S20) and executes normal control (S12). However, even if the acceleration control is cancelled in step S20, the variable N is not initialized.

[0070] On the other hand, if the state in which the temperature Tr is equal to or higher than the release threshold temperature TC continues for the second predetermined time and the temperature Ti is lower than the second threshold temperature (S18: Yes & S19: Yes), the controller 30 judges whether or not the final stage of the speed increase control is being executed (S21). If the controller 30 judges that the final stage of the speed increase control is not being executed (S21: No), it executes the processes from step S17 onwards again.

[0071] When the conditions of steps S18 & S19 are satisfied during the execution of the first acceleration control (S18: Yes & S19: Yes), the controller 30 executes the second acceleration control (S17). The second acceleration control is a control for increasing the rotation speed Fr of the cooling fan 25r to the limit rotation speed Fr-lim and maintaining the rotation speed Fi of the cooling fan 25i at the upper limit rotation speed Fi-max.

[0072] That is, the controller 30 switches the switch 45r to the ON state from the state of the first acceleration control. As a result, the controller 30 outputs the limit rotation speed Fr-lim as the rotation speed Fr. Meanwhile, the rotation speed Fi of the heat exchanger 24i does not change from the upper limit rotation speed Fi-max in the first acceleration control. Then, the controller 30 transmits control signals corresponding to the determined rotation speeds Fr, Fi to the fan motors 26r, 26i. Note that steps S18 to S20 during the execution of the second acceleration control are the same as those in the first acceleration control.

[0073] That is, during execution of the first acceleration control, when the temperature Tr remains equal to or higher than the release threshold temperature TC for a second predetermined time or longer and the temperature Ti is lower than the second threshold temperature T2, the controller 30 executes a second acceleration control to increase the rotation speed of the cooling fan 25r to the limit rotation speed Fr-lim and maintain the rotation speed of the cooling fan 25i at the upper limit rotation speed Fi-max.

[0074] Furthermore, when the conditions of steps S18 & S19 are satisfied during the execution of the second acceleration control (S18: Yes & S19: Yes), the controller 30 executes the third acceleration control (S17). The third acceleration control is a control for maintaining the rotation speed Fr of the cooling fan 25r at the limit rotation speed Fr-lim and increasing the rotation speed Fi of the cooling fan 25i to the limit rotation speed Fi-lim.

[0075] That is, the controller 30 switches the switch 45i to the ON state from the state of the second acceleration control. As a result, the controller 30 outputs the limit rotation speed Fi-lim as the rotation speed Fi. Meanwhile, the rotation speed Fr of the heat exchanger 24r does not change from the limit rotation speed Fr-lim in the second acceleration control. Then, the controller 30 transmits control signals corresponding to the determined rotation speeds Fr, Fi to the fan motors 26r, 26i. Note that steps S18 to S20 during the execution of the third acceleration control are the same as those in the first acceleration control.

[0076] That is, during execution of the second acceleration control, when the temperature Tr remains equal to or higher than the release threshold temperature TC for a second predetermined time and the temperature Ti is less than the second threshold temperature T2, the controller 30 executes a third acceleration control in which the rotation speed of the cooling fan 25r is maintained at the limit rotation speed Fr-lim and the rotation speed of the cooling fan 25i is increased to the limit rotation speed Fi-lim.

[0077] Furthermore, when the conditions of steps S18 & S19 are satisfied during the execution of the third speed increase control (S18: Yes & S19: Yes), the controller 30 determines that the final stage of the speed increase control is being executed (S21: Yes). Then, the controller 30 displays a message on the display 8a to prompt the operator to clean the heat exchanger 24r (in other words, to warn of clogging of the heat exchanger 24r) (S22). Note that the method is not limited to displaying a message on the display 8a, and may be lighting an LED or outputting a warning sound from a speaker, as long as the method allows the operator to recognize the need to clean the heat exchanger 24r. That is, when the third speed increase control is continuously executed, the controller 30 issues a notice through the notification device to prompt the operator to clean the heat exchanger 24r.

[0078] Next, the controller 30 cancels the third acceleration control, initializes the variable N (=0), and executes normal control (S12). If the variable N reaches the threshold number of times Nth (S16: Yes), the controller 30 executes the processes of steps S17 to S21 (i.e., does not execute the first acceleration control) and executes the processes of step S22 and after.

[0079] According to the above embodiment, for example, the following advantageous effects are achieved.

[0080] According to the above embodiment, when the heat exchanger 24r is clogged and the coolant temperature Tr rises (S11: Yes & S13: Yes), the first speed increase control is executed to increase the speed of the cooling fan 25i facing the other heat exchanger 24i, not the cooling fan 25r facing the heat exchanger 24r. This makes it possible to supply sufficient cooling air into the cooling air flow path 27 while leveling out the rotation speeds of the cooling fans 25r and 25i.

[0081] Furthermore, according to the above embodiment, when the temperature Tr does not fall below the release threshold temperature TC even after the first acceleration control is executed (S18: Yes & S19: Yes), the second control is executed to increase the rotation speed of the cooling fan 25r. Furthermore, when the temperature Tr does not fall below the release threshold temperature TC even after the second acceleration control is executed, the third control is executed to increase the rotation speed of the cooling fan 25i. In this way, by alternately increasing the rotation speed of the cooling fans 25r, 25i, sufficient cooling air can be supplied to the cooling air flow path 27 while leveling out the rotation speeds of the cooling fans 25r, 25i.

[0082] Here, the faster the rotation speed of the cooling fans 25r, 25i, the greater the increase in the power consumption of the fan motors 26r, 26i. Therefore, even if the cooling air supplied to the cooling air flow path 27 is the same, the power consumption is smaller when the rotation speeds of the cooling fans 25r, 25i are equalized than when there is a large difference in the rotation speeds of the cooling fans 25r, 25i. Therefore, according to the first to third acceleration controls, the increase in power consumption of the hydraulic excavator 1 as a whole can be suppressed.

[0083] Furthermore, according to the above embodiment, when the temperature Tr does not fall below the release threshold temperature TC even after the third acceleration control is executed (S18: Yes & S19: Yes & S21: Yes), the display 8a notifies the operator to clean the heat exchanger 24r. This allows the operator to unclog the heat exchanger 24r.

[0084] Furthermore, according to the above embodiment, when the variable N reaches the threshold number of times Nth (S16: Yes), the first speed-up control is not executed, and the cleaning of the heat exchanger 24r is notified through the display 8a. This allows the operator to unclog the heat exchanger 24r when switching between the normal control and the speed-up control is being performed repeatedly.

[0085] Furthermore, according to the above embodiment, when the temperature Tr falls below the release threshold temperature TC (S18: No), the speed increase control is released and the control returns to normal control (S20→S12). In this way, by minimizing the execution of the speed increase control, it is possible to suppress an increase in power consumption due to the continuation of the speed increase control.

[0086] The above-described embodiments are illustrative examples of the present invention, and are not intended to limit the scope of the present invention to these embodiments. Those skilled in the art can implement the present invention in various other forms without departing from the gist of the present invention. [Explanation of symbols]

[0087] 1: Hydraulic excavator (working machine) 2: Lower running body 3: Upper rotating body 4: Crawler 5: Driving motor 6: Swing motor 7: Swivel frame 8: Cab 8a: Display 9: Counterweight 10: Front work machine 11: Boom 12: Arm 13: Bucket 14: Boom cylinder 15: Arm cylinder 16: Bucket cylinder 20: Engine building 21: Engine 22: Hydraulic pump 23:Heat exchanger assembly 23a: Exterior wall 23b: Bulkhead 24i,24o,24r: Heat exchanger 25i, 25o, 25r: Cooling fan 26i, 26o, 26r: Fan motor 27: Cooling air flow path 28:Air supply port 30: Controller 31 :CPU 32: Memory 33: Rotational speed sensor 34i, 34o, 34r: Temperature sensor 41i, 41r: Set rotation speed determination section 42i, 42r: Upper limit rotation speed determination section 43i, 43r: Minimum value output section 44i, 44r, 45i, 45r: Switch 46i, 46r: Maximum value output section

Claims

1. The engine, A first heat exchanger; a second heat exchanger disposed adjacent to the first heat exchanger; a first cooling fan disposed facing the first heat exchanger; a second cooling fan disposed opposite the second heat exchanger; A rotation speed sensor for detecting a rotation speed of the engine; a temperature detection device for detecting a temperature of a first fluid passing through the first heat exchanger and a temperature of a second fluid passing through the second heat exchanger; a controller that determines upper limit rotation speeds of the first cooling fan and the second cooling fan based on the engine rotation speed detected by the rotation speed sensor, and controls the rotation speeds of the first cooling fan and the second cooling fan based on the temperatures of the first fluid and the second fluid detected by the temperature detection device below the determined upper limit rotation speeds, the controller executes a first speed increase control to increase the rotation speed of the second cooling fan when the first cooling fan has been driven at the upper limit rotation speed of the first cooling fan for a first predetermined time.

2. 2. The work machine according to claim 1, the temperature detection device includes a first temperature sensor that detects a temperature of the first fluid passing through the first heat exchanger and a second temperature sensor that detects a temperature of the second fluid passing through the second heat exchanger; the controller controls the first cooling fan at a smaller rotation speed of a first upper limit rotation speed of the first cooling fan determined based on a rotation speed of the engine and a first set rotation speed determined based on a temperature of the first fluid detected by the first temperature sensor, and controls the second cooling fan at a smaller rotation speed of a second upper limit rotation speed of the second cooling fan determined based on a rotation speed of the engine and a second set rotation speed determined based on the temperature of the second fluid detected by the second temperature sensor, the first acceleration control by the controller is control for increasing the rotation speed of the second cooling fan from the second set rotation speed when the first cooling fan is driven at the first upper limit rotation speed for the first predetermined time while the controller is driving the second cooling fan at the second set rotation speed.

3. 3. The work machine according to claim 2, the first acceleration control by the controller is control for increasing the rotation speed of the second cooling fan from the second set rotation speed to the second upper limit rotation speed when the first cooling fan is driven at the first upper limit rotation speed for the first predetermined time while the controller is driving the second cooling fan at the second set rotation speed.

4. 3. The work machine according to claim 2, the controller drives the first cooling fan at the first upper limit rotation speed when the temperature of the first fluid detected by the first temperature sensor is equal to or higher than a first threshold temperature, and drives the second cooling fan at the second upper limit rotation speed when the temperature of the second fluid detected by the second temperature sensor is equal to or higher than a second threshold temperature.

5. 5. The working machine according to claim 4, the controller, during execution of the first acceleration control, when the temperature of the first fluid detected by the first temperature sensor remains at or above a release threshold temperature set lower than the first threshold temperature for a second predetermined time or more and the temperature of the second fluid detected by the second temperature sensor is lower than the second threshold temperature, executes a second acceleration control to increase the rotation speed of the first cooling fan to a first limit rotation speed that is faster than the first upper limit rotation speed and maintain the rotation speed of the second cooling fan at the second upper limit rotation speed.

6. 6. The working machine according to claim 5, the controller, during execution of the second acceleration control, when the temperature of the first fluid detected by the first temperature sensor remains equal to or higher than the release threshold temperature for the second predetermined period and the temperature of the second fluid detected by the second temperature sensor is lower than the second threshold temperature, executes a third acceleration control to maintain the rotation speed of the first cooling fan at the first limit rotation speed and to increase the rotation speed of the second cooling fan to a second limit rotation speed that is faster than the second upper limit rotation speed.

7. 7. The work machine according to claim 6, A notification device is provided for notifying information, The working machine according to claim 1, wherein the controller issues a notification via the notification device, when the third speed increase control is continuously executed, urging the user to clean the first heat exchanger.

8. 5. The working machine according to claim 4, the controller cancels the first speed increase control when the temperature of the first fluid detected by the first temperature sensor is less than a release threshold temperature and the temperature of the second fluid detected by the second temperature sensor is less than the second threshold temperature during execution of the first speed increase control.

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