Hydraulic oil cooling device for construction machinery

Abstract

To provide a hydraulic oil cooling device for construction machinery capable of improving cooling efficiency of hydraulic oil in an idling rotation state of an engine.SOLUTION: A discharge side oil passage 48 of a first hydraulic pump 40 which is a fixed capacity type one is provided with a hydraulic motor 38 for driving a cooling fan 37 of an oil cooler 31, and it is also provided with a flow rate ratio regulation valve 51 that receives a command of a controller 47 and then can distribute hydraulic oil flow to flow toward a hydraulic motor and flow that directly flows toward a merging section 45 while bypassing the hydraulic motor. The controller, referring to a table which stores oil temperature and cooling fan speed for each rotation speed of an engine in association with each other, gives a command for adjusting distribution of a flow rate of the hydraulic oil to the flow rate ratio regulation valve if the oil temperature is a threshold or below and an engine returns to an idling rotation state with minimum hydraulic load on the engine from a rated rotation state, and performs control to keep the cooling fan rotation speed constant before and after returning to the idling rotation state.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to a hydraulic oil cooling device for a construction machine, and more particularly to a hydraulic oil cooling device for a construction machine that cools hydraulic oil by controlling the rotation speed of a hydraulic motor for driving a cooling fan. [Background technology]

[0002] Construction machinery such as pile drivers, earth drills, and cranes have an engine housing house (engine room) installed on one side of a rotating body, which houses various equipment such as an engine, a hydraulic pump driven by the engine, a radiator for engine cooling water, an intercooler for cooling the intake air, an oil cooler for cooling the hydraulic oil, and a cooling fan for blowing cooling air, and is configured so that cooling air taken in through a cooling air intake port in the wall of the house is sent to each of the heat exchangers of the radiator, intercooler, and oil cooler arranged side by side on the front and rear or left and right sides (see, for example, Patent Document 1).

[0003] The cooling fans installed in this type of construction machine are often driven by the power transmitted from the engine output shaft, but because they are configured to cool the engine and hydraulic equipment simultaneously, they have the disadvantage of being poor in cooling efficiency and prone to overheating. In addition, there is also the disadvantage that it takes extra time to warm up the machine, for example, immediately after starting the engine, because cooling air is sent to the oil cooler even when the temperature of the hydraulic oil (hereinafter also referred to as the oil temperature) has not yet reached a warm-up temperature suitable for machine operation. As a prior art that solves this problem, a system is known that includes a hydraulic motor for driving the cooling fan, the rotation of which is controlled independently of the engine, and increases or decreases the rotation speed of the cooling fan according to the oil temperature (see, for example, Patent Document 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2010-138656 A [Patent Document 2] JP 2006-37872 A Summary of the Invention [Problem to be solved by the invention]

[0005] In the hydraulic oil cooling device of this type described in Patent Document 2, when the hydraulic actuator is not operating (when the hydraulic load on the engine is minimized), the engine speed is adjusted to an idle speed lower than when the hydraulic actuator is operating, in order to improve fuel efficiency and reduce noise. However, in this idle speed state, the discharge flow rate from the hydraulic pump is limited to a low flow rate, so that both the flow rate of the hydraulic oil passing through the oil cooler and the flow rate of the hydraulic motor for driving the cooling fan are reduced, resulting in a decrease in the cooling efficiency of the hydraulic oil in the oil cooler. In particular, when the engine speed is operated at the maximum rated engine speed, there is a problem that transitioning to the idle speed state does not directly contribute to the prevention of overheating of the hydraulic oil.

[0006] SUMMARY OF THE PRESENT EMBODIMENTS The present invention has an object to provide a hydraulic oil cooling device for a construction machine that is capable of increasing the efficiency of cooling the hydraulic oil when the engine is idling. [Means for solving the problem]

[0007] In order to achieve the above object, the hydraulic oil cooling device for a construction machine of the present invention comprises a plurality of hydraulic pumps including a variable displacement hydraulic pump and a fixed displacement hydraulic pump, an engine which serves as a power source for all of the hydraulic pumps, a return oil passage through which hydraulic oil flows and returns to a hydraulic oil tank via a control valve of a hydraulic actuator, an oil cooler provided in the return oil passage, a cooling fan which takes in outside air and sends it to the oil cooler, a hydraulic motor which drives the cooling fan, an oil temperature sensor which detects the temperature of the hydraulic oil, a controller which sets the rotation speed of the cooling fan to the increased side in response to an increase in the oil temperature detected by the oil temperature sensor, and a table which is referenced by the controller and which stores the oil temperature in correspondence with the rotation speed of the cooling fan for each rotation speed of the engine, The hydraulic system includes a second hydraulic pump that supplies hydraulic oil to the hydraulic actuator, and a junction section that is provided in the return oil passage upstream of the oil cooler and that joins hydraulic oil from the first hydraulic pump and the second hydraulic pump, the hydraulic motor is provided in the discharge side oil passage of the first hydraulic pump, and a flow ratio adjustment valve that is capable of distributing a flow of hydraulic oil to a flow toward the hydraulic motor and a flow that bypasses the hydraulic motor and goes directly to the junction section in response to a command from the controller, and the controller, when the oil temperature is equal to or lower than a threshold value and the engine returns to an idle rotation state in which a hydraulic load on the engine is minimized, issues a command to the flow ratio adjustment valve to adjust the flow distribution of the hydraulic oil, thereby controlling the rotation speed of the cooling fan to be constant before and after the engine returns to the idle rotation state.

[0008] The present invention is further characterized in that an upper rotating body is rotatably mounted on a lower running body, the engine is provided on one widthwise side of the upper rotating body, and the oil cooler is provided integrally with the cooling fan and the hydraulic motor on the other widthwise side of the upper rotating body.

[0009] The hydraulic system further comprises a third fixed displacement hydraulic pump that supplies hydraulic oil to the oil cooler. Effect of the Invention

[0010] According to the hydraulic oil cooling device for construction machinery of the present invention, a hydraulic motor for driving a cooling fan is provided in the discharge side oil passage of a first fixed displacement hydraulic pump, and a flow ratio adjustment valve is also provided. When the oil temperature is below a threshold value and the engine returns from a rated rotation state to an idle rotation state, the controller issues a command to the flow ratio adjustment valve to adjust the flow distribution of the hydraulic oil, thereby controlling the cooling fan speed to be constant before and after the return to the idle rotation state. This makes it possible to control the rotation of the cooling fan in response only to changes in oil temperature, regardless of the engine speed, and enables operation that ensures cooling of the hydraulic oil in the oil cooler while achieving low fuel consumption and low noise.

[0011] In addition, even if the oil temperature rises after returning to the idle rotation state, the rotation speed of the cooling fan can be increased to accelerate the rotation from low speed to medium speed. Moreover, even if the oil temperature rises above the maximum threshold, the required flow rate of hydraulic oil can be secured and the rotation of the cooling fan can be maintained at the rotation speed corresponding to medium speed. In other words, even in a variety of operating environments for construction machinery, operation can be performed while ensuring the cooling performance of the hydraulic oil in the oil cooler.

[0012] Furthermore, since the hydraulic oil after driving the hydraulic motor passes directly through the oil cooler in a self-cooling circuit, the cooling efficiency of the hydraulic oil in the oil cooler can be further improved.In addition, since the engine is provided on one side of the upper rotating body in the width direction, and the oil cooler is provided integrally with the cooling fan and hydraulic motor on the other side of the upper rotating body in the width direction, it is possible to reduce the thermal effects caused by the overcrowding of various parts housed in the house, and model changes and new development of construction machinery that require compliance with strict exhaust gas regulations can be smoothly carried out. [Brief description of the drawings]

[0013] [Figure 1] 1 is a side view of a pile driver to which a hydraulic oil cooling device showing a first embodiment of the present invention is applied. [Diagram 2] FIG. [Diagram 3] FIG. [Figure 4] FIG. 11 is a side view of a main part of the equipment housing house. [Diagram 5] FIG. 5 is a cross-sectional view of FIG. 4 . [Figure 6] FIG. 4 is a control circuit diagram of the hydraulic oil cooling device. [Figure 7] 13 is a graph showing the relationship between engine speed, oil temperature, fan speed, and motor flow rate. [Figure 8] FIG. 4 is a control circuit diagram of a hydraulic oil cooling device showing a second embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] 1 to 7 show a first embodiment of the present invention applied to a pile driver, which is an example of a construction machine. As shown in Figs. 1 to 5, the pile driver 11 includes a base machine 15 including a lower track body 12 equipped with left and right crawler devices 12a and an upper rotating body 14 rotatably mounted on the lower track body 12 via a swivel bearing 13, a leader 16 erected at the front of the upper rotating body 14, and a hoisting cylinder 17 supporting the leader 16 from the rear. A leader support 18 is provided at the front of the upper rotating body 14 to support the leader 16 so that it can be hoisted. Stabilizing jacks 19 are provided at four locations on the front, rear, left and right of the upper rotating body 14, and a counterweight 20 is mounted at the rear end of the upper rotating body 14 to balance the pile driver 11.

[0015] The leader 16 is divided into a rotatable basic leader 21 pivotally supported by the leader support 18, an upper leader 22 connected to the upper part of the basic leader 21, and a lower leader 23 connected to the lower part of the basic leader 21. The upper leader 22 is further divided into a plurality of leader members, and a top sheave 24 is attached to the upper end. In addition, a hydraulically driven auger (not shown) is attached to the front of the leader 16 so that it can be raised and lowered.

[0016] The upper rotating body 14 has a machine frame in which a rectangular box-shaped main frame 25, on whose underside the rotating bearing 13 is attached, and floor frames 26 (opposite side not shown) framed on both sides in the width direction of the main frame 25 are integrally connected. An operator's cab 27 for an operator is provided at the front of the right floor frame. An engine housing house 28 is provided on the left floor frame 26, which houses an engine power unit and associated equipment such as an exhaust gas purification device. Meanwhile, an equipment housing house 29 is provided at the rear of the right floor frame, which houses hydraulic equipment such as a hydraulic oil tank 30 and an oil cooler 31, which are components of a hydraulic oil cooling device described later.

[0017] The engine power unit is configured to include a diesel engine (hereinafter referred to as engine) 32 mounted in a vibration-proof state on the floor frame 26, and a hydraulic pump device 34 attached in a cantilevered manner to the rear side of the engine 32, opposite the side where the cooling fan 33 is present. In addition, on the front side of the engine 32 on the floor frame 26, that is, on the upstream side in the direction of the flow of cooling air by the cooling fan 33, an engine-related heat exchanger 35 such as a radiator and intercooler arranged facing the cooling fan 33 is provided.

[0018] The hydraulic pump unit 34 is configured by adding multiple gear pumps, which are fixed displacement hydraulic pumps, to a so-called tandem hydraulic pump unit in which two swash plate pumps, which are variable displacement hydraulic pumps, are connected in series, and is connected by hydraulic circuits to various hydraulic actuators associated with each of them via control valves, for example, in the case of the swash plate pump, to various hydraulic motors for the undercarriage 12, auger, and winch, which are driven under high load. Note that the swash plate pump keeps the tilt angle of the swash plate at a minimum when no operation signal is input, and in this state, hydraulic oil is not discharged at a predetermined amount or more. On the other hand, the flow rate of hydraulic oil discharged from the gear pump is proportional to the rotation speed of the engine 32.

[0019] Each of the houses 28, 29 is formed in a substantially rectangular box shape, with multiple inspection doors 28a, 29a provided on the outer wall surface, and with air intakes and exhaust ports made of punched metal or the like provided at positions on the front, rear, and inner wall surfaces that take ventilation into consideration. As a result, in the engine housing house 28, it is possible for the rotation of the cooling fan 33 to introduce outside air from the air intake port, pass it through the heat exchanger 35 of the engine system, and discharge the cooled air (exhaust air) to the outside from the exhaust port.

[0020] The equipment housing house 29 has a similar structure, but as shown in Figs. 4 and 5, a mesh-shaped exhaust port 29b is provided on the upper side wall surface. Fig. 4 shows the state seen from the direction facing the inspection door 29a of the equipment housing house 29, and the side where the hydraulic oil tank 30 is located (the left side in Fig. 4) is the rear side of the upper rotating body 14. A heat exchanger 39 of a hydraulic equipment system that unitizes an oil cooler 31 for cooling the hydraulic oil (return oil), a cooling fan 37, and a hydraulic motor 38 for driving the cooling fan is attached to the upper part of a stand 36 installed on a floor frame. The oil cooler 31 has a cooling core made of a tube to which a fin for heat dissipation is attached, and the hydraulic oil flows as a cooled fluid in the tube. Then, the outside air is taken into the house 29 from below by the rotation of the cooling fan 37, and passes through it as cooling air while cooling the hydraulic oil in the cooling core, and is exhausted to the outside from the exhaust port 29b.

[0021] The control circuit and control method of the hydraulic oil cooling device will be described below with reference to Figures 6 and 7. As shown in Figure 6, the hydraulic oil cooling device includes a fixed displacement first hydraulic pump (gear pump) 40 that supplies hydraulic oil to an oil cooler 31, a fixed displacement second hydraulic pump (gear pump) 41 that supplies hydraulic oil to a hydraulic actuator (e.g., a hydraulic motor that rotates the upper rotating body 14), an engine 32 (see Figure 2) that serves as a power source for all hydraulic pumps 40, 41 (hydraulic pump device 34), a return oil passage (T line) 44 through which hydraulic oil flows to return to the hydraulic oil tank 30 via a first control valve (8-valve) 42 and a second control valve (3-valve) 43 corresponding to various hydraulic actuators, and a return oil passage (T line) 44 through which the return oil flows. The control circuit includes an oil cooler 31 provided in the return oil passage 44, a junction 45 provided in the return oil passage 44 upstream of the oil cooler 31 and junctioning the hydraulic oil from the first hydraulic pump 40 and the second hydraulic pump 41, a cooling fan 37 that takes in outside air and sends it to the oil cooler 31, a hydraulic motor 38 that drives the cooling fan 37, an oil temperature sensor 46 that detects the temperature of the hydraulic oil, and a controller (control unit) 47 that sets the rotation speed of the cooling fan 37 to an increased side according to an increase in the oil temperature detected by the oil temperature sensor 46 and to a decreased side according to a decrease in the oil temperature. The various devices are provided at appropriate positions on the control circuit, and for example, the oil temperature sensor 46 is disposed near the surface of the hydraulic oil tank 30 in a manner that it is attached to the hydraulic oil tank 30.

[0022] The discharge oil passage 48 of the first hydraulic pump 40 is provided with the hydraulic motor 38, and is provided with a flow ratio adjustment valve (electromagnetic proportional flow control valve) 51 that receives a command from the controller 47 and distributes the flow of hydraulic oil to a flow (supply oil passage 49) toward the hydraulic motor 38 and a flow (bypass oil passage 50) that bypasses the hydraulic motor 38 and directly toward the junction 45. A circulation oil passage (suction line) 52 for supplying a part of the hydraulic oil to the first hydraulic pump 40 is connected to the return oil passage 44 downstream of the oil cooler 31. Here, the discharge oil passage 48 is provided with a relief valve 53 and a check valve 54 for the purpose of protecting the hydraulic circuit, and a check valve 56 is further provided as a back pressure countermeasure for the outflow oil passage 55 of the hydraulic motor 38. Meanwhile, the return oil passage 44 is provided with a check valve 57 in parallel with the oil cooler 31 in consideration of changes in the flow resistance of the hydraulic oil, and measures are taken when providing the oil cooler 31.

[0023] The controller 47 is mainly composed of a CPU, and stores a reference table in a storage unit (not shown). This table basically has the structure shown in Table 1 below, and stores the oil temperature and the rotation speed of the cooling fan 37 for each rotation speed of the engine 32 in association with each other. As an example, when the rated rotation speed of the engine 32 is 2000 min -1 , Idle speed 800 min -1In this case, the rotation operation of the cooling fan 37 is stopped when the oil temperature range is set to 40° C. or lower by setting thresholds in stages, and is set to low speed when the oil temperature is 40 to 55° C., medium speed when the oil temperature is 55 to 65° C., and high speed when the oil temperature is 65° C. or higher. Here, 40° C. is set as the minimum threshold, 55° C. is set as the intermediate threshold, and 65° C. is set as the maximum threshold. When the cooling fan 37 is operated (medium speed / low speed) when the oil temperature is 65° C. or lower, the rotation speed is fixed to a constant speed corresponding to the oil temperature regardless of the rotation speed of the engine 32. That is, the first hydraulic pump 40 is used to have a capacity capable of supplying a sufficient flow rate of hydraulic oil to the hydraulic motor (fan motor) 38 so that the engine 32 can operate at medium speed even when the engine 32 is idling (for example, rated: 97.4 L / min, idling: 39.0 L / min). The rated rotation speed of the engine 32 is the rotation speed at which the maximum output of the engine 32 can be obtained, and is obtained, for example, at the maximum accelerator opening when the accelerator pedal is fully depressed during driving.

[0024] [Table 1]

[0025] The graph in Figure 7 shows the relationship between engine speed, oil temperature, fan speed, and motor flow rate in the control method of the hydraulic oil cooling device that references the above table. For example, when the auger is started in an environment with high outside air temperature and the auger is driven continuously, the hydraulic oil circulating in the hydraulic circuit generates heat and rises in temperature. At this time, the engine speed is set to the rated 2000 min -1 The oil pressure load of the engine 32 remains high. When the oil temperature exceeds 50° C., the cooling fan 37 operates at a low speed (fan rotation speed: 1000 min -1 The hydraulic oil passing through the oil cooler 31 is cooled by the first hydraulic pump 40 (motor flow rate: 25 L / min). In this case, the flow ratio adjustment valve 51 allocates, for example, 25 L / min (approximately 25%) of the hydraulic oil flow rate (97.4 L / min) discharged from the first hydraulic pump 40 to the hydraulic motor 38.

[0026] At time t1, when the auger is stopped, the engine speed is rated at 2000 min -1 From idling for 800 min -1 The oil temperature drops to 53°C, and the engine 32 that drives the hydraulic pump unit 34 is in a state close to no load. At this time, the oil temperature has risen to 53°C, but remains within the range (40 to 55°C) for low-speed operation of the cooling fan 37, with the upper limit being the intermediate threshold value of 55°C. Therefore, the controller 47 controls the engine 32 to operate at the rated speed (2000 min-1) when the oil temperature is equal to or lower than the intermediate threshold value of 55°C. -1 ) to the idle speed state (800 min) with the hydraulic load of the engine 32 at a minimum. -1 When the engine returns to the idle speed state, a command is given to the flow ratio control valve 51 to increase the ratio of hydraulic oil directed to the hydraulic motor 38 in order to maintain the flow rate of hydraulic oil directed to the hydraulic motor 38, and the rotation speed of the cooling fan 37 is controlled to be constant before and after the engine returns to the idle speed state. In other words, the cooling fan 37 is operated at a low speed (fan rotation speed: 1000 min -1 In this case, the flow ratio adjustment valve 51 allocates, for example, 25 L / min (approximately 64%) of the hydraulic oil flow rate (39.0 L / min) discharged from the first hydraulic pump 40 to the hydraulic motor 38.

[0027] Here, if the oil temperature continues to rise after returning to the idle rotation state, the cooling capacity of the hydraulic oil will become insufficient. Therefore, at time t2, when the oil temperature reaches the intermediate threshold value of 55° C., the rotation speed of the cooling fan 37 is reduced to a low speed (1000 min -1 ) to medium speed (1560min -1 ) to accelerate the rotation. In this case, the flow ratio adjustment valve 51 allocates, for example, the entire flow rate (100%) of the hydraulic oil flow rate (39.0 L / min) discharged from the first hydraulic pump 40 to the hydraulic motor 38. This allows the hydraulic oil passing through the oil cooler 31 to be efficiently cooled, and the rise in oil temperature is suppressed.

[0028] In this way, according to the first configuration of the hydraulic oil cooling system for a construction machine of the present invention, the hydraulic motor 38 for driving the cooling fan is provided in the discharge side oil passage 48 of the fixed displacement first hydraulic pump 40, and a flow ratio adjustment valve 51 is provided. In the controller 47, when the oil temperature is equal to or lower than a threshold value (e.g., 65°C) and the engine 32 is in a rated rotation state (e.g., 2000 min -1 ) to idle speed (e.g. 800 min -1 When returning to the idle speed state, a command is given to the flow ratio adjustment valve 51 to adjust the flow distribution of the hydraulic oil, so that the rotation speed of the cooling fan 37 is kept constant (for example, 1000 min -1 ), it is possible to control the rotation of the cooling fan 37 in response to changes in oil temperature alone, without depending on the rotation speed of the engine 32, thereby enabling operation that ensures cooling of the hydraulic oil in the oil cooler 31 while achieving low fuel consumption and low noise.

[0029] In addition, even if the oil temperature rises after returning to the idling state, the rotation speed of the cooling fan 37 is increased to a low speed (for example, 1000 min -1 ) to medium speed (e.g. 1560min -1 ) to rotate at an increased speed. Moreover, even if the oil temperature rises above a maximum threshold value (e.g., 65°C), the flow rate of hydraulic oil can be ensured at a required amount (e.g., 39.0 L / min) and the rotation of the cooling fan 37 can be maintained at a rotation speed corresponding to medium speed. In other words, even in a variety of operating environments for construction machinery, operation can be performed while ensuring the cooling performance of the hydraulic oil in the oil cooler 31.

[0030] Furthermore, a self-cooling circuit is formed in which the hydraulic oil after driving the hydraulic motor 38 passes directly through the oil cooler 31, thereby further improving the cooling efficiency of the hydraulic oil in the oil cooler 31. In addition, since the engine 32 is provided on one side in the width direction of the upper rotating body 14, and the oil cooler 31 is provided integrally with the cooling fan 37 and the hydraulic motor 38 on the other side in the width direction of the upper rotating body 14, it is possible to reduce the thermal effects caused by the overcrowding of the various parts housed in the houses 28, 29, and model changes and new model development of construction machinery that must comply with strict exhaust gas regulations can be smoothly carried out.

[0031] 8 shows a second embodiment of the hydraulic oil cooling device for a construction machine according to the present invention. In the following description, the same components as those shown in the first embodiment are given the same reference numerals and detailed description thereof will be omitted.

[0032] The second embodiment has the characteristic configuration (control circuit) of the hydraulic oil cooling device as it is, and further has a fixed displacement third hydraulic pump (gear pump) 58 that supplies hydraulic oil to the oil cooler 31, a discharge side oil passage 59 of the third hydraulic pump 58, and a junction 60 that is provided in the return oil passage 44 upstream of the oil cooler 31 and joins the hydraulic oil from the second hydraulic pump 41 and the third hydraulic pump 58. In addition, a check valve 61 is provided in the return oil passage 44 upstream of the junction 60 to prevent the hydraulic oil from the third hydraulic pump 58 from flowing back to the second control valve 43. The third hydraulic pump 58 is provided in the hydraulic pump device 34 by adding a gear pump.

[0033] With this second configuration, the same effects as with the first configuration can be achieved, and furthermore, in the case of this embodiment, since a fixed displacement third hydraulic pump 58 is provided as a dedicated component for the oil cooler 31, adjustment of the set passing flow rate can be easily and inexpensively performed even for an oil cooler 31 with a relatively large capacity, thereby expanding the range of applications as a hydraulic oil cooling device for construction machinery.

[0034] The present invention is not limited to the above-mentioned embodiments, and the configuration of the control circuit can be changed as appropriate according to the specifications of the construction machine. The reference table structure (engine and cooling fan rotation settings, oil temperature settings) is also optional. Furthermore, although a pile driver has been exemplified as a construction machine, the present invention is not limited to this, and can be applied to various construction machines equipped with an engine power unit as a power source for excavation equipment and loading equipment, such as earth drills and cranes. In particular, among construction machines, pile drivers that bury piles and improve ground are particularly effective as a measure to improve heat balance, since they leave the jack on the ground at the construction site and stay there for a long time. [Explanation of symbols]

[0035] 11...pile driver, 12...lower running body, 12a...crawler device, 13...swivel bearing, 14...upper rotating body, 15...base machine, 16...leader, 17...derailing cylinder, 18...leader support, 19...jack, 20...counterweight, 21...basic leader, 22...upper leader, 23...lower leader, 24...top sheave, 25...main frame, 26...floor frame, 27...operator's cab, 28...engine housing, 28a...inspection door, 29...equipment housing, 29a...inspection door, 29b...exhaust port, 30...hydraulic oil tank, 31...oil cooler, 32...diesel engine , 33...cooling fan, 34...hydraulic pump device, 35...heat exchanger, 36...frame, 37...cooling fan, 38...hydraulic motor, 39...heat exchanger, 40...first hydraulic pump, 41...second hydraulic pump, 42...first control valve, 43...second control valve, 44...return oil passage, 45...junction, 46...oil temperature sensor, 47...controller, 48...discharge side oil passage, 49...supply oil passage, 50...bypass oil passage, 51...flow ratio control valve, 52...circulation oil passage, 53...relief valve, 54...check valve, 55...outflow side oil passage, 56, 57...check valve, 58...third hydraulic pump, 59...discharge side oil passage, 60...junction, 61...check valve

Claims

1. a hydraulic oil cooling device for a construction machine comprising: a plurality of hydraulic pumps including a variable displacement hydraulic pump and a fixed displacement hydraulic pump; an engine serving as a power source for all of the hydraulic pumps; a return oil passage through which hydraulic oil flows and returns to a hydraulic oil tank via a control valve of a hydraulic actuator; an oil cooler provided in the return oil passage; a cooling fan that takes in outside air and sends it to the oil cooler; a hydraulic motor that drives the cooling fan; an oil temperature sensor that detects the temperature of the hydraulic oil; a fixed displacement first hydraulic pump that supplies hydraulic oil to the oil cooler, a second hydraulic pump that supplies hydraulic oil to the hydraulic actuator, and a junction portion that is provided in the return oil passage upstream of the oil cooler and that joins hydraulic oil from the first hydraulic pump and the second hydraulic pump, The hydraulic motor is provided in the discharge side oil passage of the first hydraulic pump, and a flow ratio control valve is provided that can distribute the flow of hydraulic oil to a flow toward the hydraulic motor and a flow that bypasses the hydraulic motor and directly toward the junction in response to a command from the controller. The hydraulic oil cooling device for a construction machine is characterized in that, when the oil temperature is below a threshold value and the engine returns from a rated rotation state to an idle rotation state in which the hydraulic load on the engine is minimized, the controller gives a command to the flow ratio control valve to adjust the flow distribution of the hydraulic oil, thereby controlling the rotation speed of the cooling fan to be constant before and after the engine returns to the idle rotation state.

2. 2. The hydraulic oil cooling device for a construction machine as described in claim 1, characterized in that an upper rotating body is rotatably mounted on a lower running body, the engine is provided on one widthwise side of the upper rotating body, and the oil cooler is provided integrally with the cooling fan and the hydraulic motor on the other widthwise side of the upper rotating body.

3. 3. The hydraulic oil cooling system for a construction machine according to claim 1, further comprising a third fixed displacement hydraulic pump which supplies hydraulic oil to the oil cooler.

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