JP2011184911A - Driving circuit for cooling fan - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a driving circuit constituted further compactly in a simple structure for a cooling fan for supplying cooling air to a cooler such as a radiator or an oil cooler provided at an industrial vehicle such as a construction machine. <P>SOLUTION: The driving circuit for the cooling fan includes: a hydraulic motor 13 with the cooling fan 12 fixed to an output shaft; a variable displacement hydraulic pump 5 including a discharge quantity control part 5a controlling the discharge quantity of an operating fluid, and sucking the operating fluid from the operating fluid tank 15 to discharge the operating fluid; a pump discharge passage 31 reaching the hydraulic motor 13 from the hydraulic pump 5; a return passage 34 reaching the operating fluid tank 15 from the hydraulic motor 13; a branch passage 41 formed branching from the pump discharge passage 31 and reaching the operating fluid tank 15; a throttle 51 and a pressure control valve 52 provided in the branch passage 41; and a discharge quantity control pressure supply passage 42 connected between the throttle 51 and the pressure control valve 52 of the branch passage 41 to supply discharge quantity control pressure to the discharge quantity control part 5a. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a drive circuit for a hydraulically driven cooling fan provided in an industrial vehicle such as a construction machine such as a wheel loader or a hydraulic excavator or an agricultural vehicle such as a tractor.

  Conventionally, in industrial vehicles such as wheel loaders, hydraulic excavators and other agricultural machines such as construction machines and tractors, coolers (heat exchangers) such as radiators that cool engine coolant and oil coolers that cool hydraulic fluid ) Is cooled by cooling air supplied from a cooling fan. Generally, this cooling fan is attached to the output shaft of a hydraulic motor, and is configured to rotate by rotational driving of this hydraulic motor.

  For example, a cooling fan drive circuit disclosed in Patent Document 1 includes a hydraulic motor that drives the cooling fan, and a variable displacement hydraulic pump that controls the rotational speed of the hydraulic motor, and includes a cooling water temperature and a hydraulic oil temperature. The rotation speed of the cooling fan is continuously controlled according to the engine speed. The number of revolutions of the cooling fan is controlled by the discharge amount of the hydraulic pump, and the hydraulic pump includes a servo valve that controls the discharge amount of the hydraulic oil. This servo valve is based on the cooling water temperature, hydraulic oil temperature, and engine speed from the controller from the electromagnetic proportional valve that receives the control pressure from the pressure reducing valve of the work machine circuit that drives the work machine attached to the construction machine. The pilot pressure corresponding to the command current value is received, and the tilt angle of the hydraulic pump is controlled based on the pilot pressure.

  Further, for example, a cooling fan drive circuit disclosed in Patent Document 2 includes a hydraulic motor that rotationally drives the cooling fan, a switching valve that switches a rotation direction of the hydraulic motor, and a hydraulic pump that supplies hydraulic oil to the hydraulic motor. And a variable relief valve that changes the circuit pressure of the drive circuit so as to increase or decrease the amount of hydraulic pressure supplied from the hydraulic pump to the hydraulic motor, and is configured to rotate the cooling fan forward and backward. In this drive circuit, the rotational pressure of the hydraulic motor that rotates the cooling fan is variably controlled by changing the circuit pressure of the drive circuit using a variable relief valve.

JP 2001-182535 A JP 2006-45808 A

  As described above, the cooling fan drive circuit described in Patent Document 1 is configured to control the number of revolutions of the cooling fan by changing the discharge amount of the hydraulic pump. In addition, the controller performs predetermined calculations based on outputs from multiple devices, such as detecting the temperature of hydraulic fluid and using the pilot pressure and the control pressure from the work machine circuit. Since the hydraulic pump is controlled based on the result, the control of the discharge amount of the hydraulic pump is complicated.

  On the other hand, in the cooling fan drive circuit described in Patent Document 2, the valve opening degree of the variable relief valve is controlled in order to control the number of rotations of the cooling fan. It is necessary to select a proportionally larger one. Increasing the size of the valve not only requires a large space for the valve, but also increases the cost of the valve. Furthermore, the greater the flow rate of the valve, the greater the load, and the greater the flow rate escaped from the variable relief valve, resulting in increased energy loss.

  The present invention has been made in order to solve the above-described problems, and a hydraulic fan is provided with a cooling fan for supplying cooling air to a radiator, an oil cooler or the like included in an industrial vehicle such as a construction machine. An object of the present invention is to provide a cooling fan drive circuit that can be rotationally driven with a simple mechanism that can realize a more compact configuration.

  The cooling fan drive circuit according to the present invention includes a hydraulic motor that drives the cooling fan and a discharge amount control unit that controls the discharge amount of the hydraulic oil. A hydraulic pump, a pump discharge path for hydraulic oil from the hydraulic pump to the hydraulic motor, a return path for hydraulic oil from the hydraulic motor to the hydraulic oil tank, and a branch formed in the pump discharge path to form the hydraulic oil A branch path to the tank; a throttle provided in the branch path; a pressure control valve provided downstream of the throttle in the branch path; and between the throttle and the pressure control valve in the branch path And a discharge amount control pressure supply path for supplying a discharge amount control pressure for controlling the discharge amount of the hydraulic pump to the discharge amount control unit.

  According to the above configuration, the pressure on the downstream side of the throttle provided in the branch path can be used as a pressure necessary for controlling the discharge amount of the hydraulic pump. The flow rate required to control the discharge amount of the hydraulic pump is sufficiently smaller than the flow rate of the hydraulic oil flowing through the pump discharge path. Therefore, the pressure control valve provided on the downstream side of the throttle can be a small valve as compared with the case where no throttle is provided. By controlling the discharge amount of the hydraulic pump with such a small flow rate, the flow rate of hydraulic oil that escapes from the pressure control valve is reduced, and energy loss can be reduced. Furthermore, by using a small pressure control valve, the space occupied by the pressure control valve can be reduced, the drive circuit can be made compact, and the cost for the valve can be reduced. In addition, since the pump discharge path and the discharge amount control pressure supply path communicate with each other via a throttle, a change in the discharge pressure of the hydraulic pump is immediately reflected in the discharge amount control pressure. Therefore, the load sensing control is performed so that the differential pressure between the discharge pressure of the hydraulic pump and the discharge amount control pressure is constant, so that the discharge amount of the hydraulic pump and thus the rotation speed of the cooling fan can be controlled with good accuracy. Can do. Furthermore, in order to obtain the above-described effect, it is only necessary to provide the circuit with a simple aperture of the mechanism without requiring complicated control, so that the structure of the drive circuit is not complicated.

  In the cooling fan drive circuit, the pressure control valve may be a variable relief valve. Thereby, the discharge amount control pressure can be arbitrarily set.

  Furthermore, in the cooling fan drive circuit, the variable relief valve may be an inverse proportional relief valve. As a result, when the controller that controls the pressure control valve becomes uncontrollable due to a failure or the like, the discharge amount control pressure is maximized and the cooling fan is driven to rotate at the maximum number of rotations, so that no overheating occurs.

  According to the present invention, by providing a throttle in the branch path, the pressure control valve provided on the downstream side of the throttle can be reduced in size compared to the case where no throttle is provided, and the pump discharge amount can be controlled with a small flow rate. Thus, the cooling fan drive circuit can be configured more compactly with a simple mechanism, and energy loss can be reduced.

It is a drive circuit diagram of the cooling fan which concerns on embodiment of this invention.

  Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings. The cooling fan drive circuit according to the present invention can be employed in industrial vehicles including construction machines such as wheel loaders and hydraulic excavators.

  FIG. 1 is a drive circuit diagram of a cooling fan. The cooling fan drive circuit includes a hydraulic motor 13 that drives the cooling fan 12, a variable displacement hydraulic pump 5 that sucks and discharges hydraulic oil from the hydraulic oil tank 15, and an operation that extends from the hydraulic pump 5 to the hydraulic motor 13. An oil pump discharge path 31 and a hydraulic oil return path 34 from the hydraulic motor 13 to the hydraulic oil tank 15 are provided. A branch passage 41 leading to the hydraulic oil tank 15 is formed in the pump discharge passage 31. A throttle 51 and a pressure control valve 52 are provided in this branch passage 41 in order from the upstream side. The hydraulic pump 5 includes a discharge amount control unit 5a that changes the discharge amount of hydraulic oil. A discharge amount control pressure supply path 42 that supplies a discharge amount control pressure to the discharge amount control unit 5a is a branch path 41. A branch is formed between the throttle 51 and the pressure control valve 52. Hereinafter, the driving circuit of the cooling fan will be described in detail.

  The hydraulic motor 13 that rotationally drives the cooling fan 12 is a fixed capacity hydraulic motor that rotates by receiving pressure oil supplied from the hydraulic pump 5. Between the hydraulic pump 5 and the hydraulic motor 13, there is a hydraulic oil discharge path 31 from the hydraulic pump 5 to the hydraulic motor 13 and a hydraulic oil return path 34 from the hydraulic motor 13 to the hydraulic oil tank 15. Each is formed as a conduit.

  The hydraulic pump 5 according to the present embodiment includes a regulator as the discharge amount control unit 5a. This regulator is a control device that controls the discharge capacity of the hydraulic pump 5, and includes a servo piston connected to a swash plate that changes the discharge amount of the hydraulic pump 5, and according to the hydraulic pressure applied to the servo piston. By changing the tilt angle of the swash plate, the discharge capacity is controlled so that the applied pressure and the discharge pressure are constant. The hydraulic pump 5 and the discharge amount control unit 5 a included in the hydraulic pump 5 can employ a known general variable displacement hydraulic pump as the hydraulic pump 5.

  In order to take out the hydraulic pressure (discharge amount control pressure) to be applied to the discharge amount control unit 5 a of the hydraulic pump 5, the branch passage 41 leading to the hydraulic oil tank 15 between the hydraulic pump 5 and the hydraulic motor 13 in the pump discharge passage 31. Is branched. The branch path 41 includes a throttle 51 and a pressure control valve 52 in order from the upstream side until reaching the hydraulic oil tank 15. A discharge amount control pressure supply passage 42 for supplying a discharge amount control pressure to the discharge amount control unit 5a is branched between the throttle 51 of the branch passage 41 and the pressure control valve 52. Note that both the branch path 41 and the discharge amount control pressure supply path 42 can be formed by pipes, and the branch path 41 can also be formed by a hydraulic block.

  The throttle 51 is provided for the purpose of taking out hydraulic oil at a pressure required to control the discharge amount of the hydraulic pump 5 from the hydraulic oil discharged from the hydraulic pump 5. Accordingly, the throttle 51 has a minimum flow rate sufficient for operating the discharge amount control unit 5a, and has a sufficiently small diameter (for example, φ = 1 mm).

  The pressure control valve 52 is a valve for controlling the hydraulic pressure downstream of the throttle 51 of the branch passage 41, that is, the discharge amount control pressure supplied to the discharge amount control unit 5a. The pressure control valve 52 may be a fixed relief valve having a constant flow rate, but is preferably a variable relief valve because the discharge amount control pressure can be arbitrarily set. In the present embodiment, an electromagnetic proportional valve whose valve opening degree is controlled by the controller 17 described later is used as the pressure control valve 52. The electromagnetic proportional valve is more preferably an inverse proportional valve that is set to a maximum pressure when no current flows. As a result, even if the controller 17 breaks down and the pressure control valve 52 becomes uncontrollable, the maximum discharge amount control pressure is supplied to the discharge amount control unit 5a, so the hydraulic motor 13 rotates at the maximum rotation speed. Will continue. That is, since the cooling fan 12 continues to rotate at the maximum rotational speed even when the controller 17 fails, an industrial vehicle to which the cooling fan driving circuit according to the present embodiment such as a wheel loader is applied without causing overheating. Work can be continued.

  As described above, the pressure control valve 52 that controls the discharge amount control pressure of the hydraulic pump 5 can be controlled with a smaller flow rate than the case where the throttle 51 is not provided, and a small valve can be employed. By controlling the pressure with such a small flow rate, the flow rate of the hydraulic oil that is released from the pressure control valve 52 to the hydraulic oil tank 15 is reduced, and energy loss can be reduced. By adopting the small pressure control valve 52, the exclusive space of the pressure control valve 52 can be reduced, the circuit can be made compact, and the cost for the valve can be reduced. Furthermore, since it is only necessary to provide the diaphragm 51 that does not require complicated control, the structure of the drive circuit is simple and the cost can be reduced.

  The temperature detection means 23 is connected to the controller 17 that controls the valve opening degree of the pressure control valve 52. The temperature detection means 23 is configured to detect the temperature of the engine coolant, the temperature of the hydraulic oil, the temperature of the torque converter oil, and the like and output the detection signal to the controller 17. The controller 17 is configured to output a control signal to the pressure control valve 52 to perform drive control of the hydraulic motor 13 based on an input signal from the temperature detecting means 23.

  In parallel with the control of the controller 17 described above, the hydraulic pump 5 performs load sensing control by the discharge amount control unit 5a. In this load sensing control, the discharge amount of the hydraulic pump 5 is controlled so that the differential pressure between the discharge pressure of the hydraulic pump 5 and the discharge amount control pressure is constant. In this drive circuit, the pump discharge passage 31 and the discharge amount control pressure supply passage 42 communicate with each other, so that a slight time lag occurs when passing through the throttle 51, but the hydraulic pump 5 corresponds to the discharge amount control pressure. Since the discharge amount immediately changes, load sensing control with high accuracy can be performed, and the rotation speed of the cooling fan 12 can be controlled with high accuracy.

  Here, the operation of the drive circuit of the cooling fan 12 will be described. The controller 17 receives the detection signal from the temperature detection means 23 and detects the detected temperature (cooling water temperature, hydraulic oil temperature, torque converter oil temperature, air conditioner refrigerant pressure, axle oil temperature, and air cooler. The number of revolutions of the cooling fan 12 suitable for this is determined, a control current value serving as a discharge amount control pressure corresponding to this number of revolutions is determined, and this is controlled by pressure control. Output to the valve 52. In this manner, the cooling air is supplied to the radiator 10 and the oil cooler 11 by the cooling fan 12 whose rotational speed changes so as to rotate at a higher speed as the temperature detected by the temperature detecting means 23 becomes higher.

  The present invention is not limited to a construction machine such as a wheel loader, and includes a cooling fan mounted with an engine and driven to rotate by a hydraulic motor that operates with pressure oil from a hydraulic pump that rotates by receiving the power of the engine. It can be widely applied to other industrial vehicles.

DESCRIPTION OF SYMBOLS 10 Radiator 11 Oil cooler 12 Cooling fan 13 Hydraulic motor 15 Hydraulic oil tank 17 Controller 18 Relief valve 23 Temperature detection means 31 Pump discharge path 34 Return path 35 Relief path 41 Branch path 42 Oil path 51 Restriction 52 Pressure control valve

Claims (3)

A hydraulic motor that drives the cooling fan;
A variable displacement hydraulic pump that includes a discharge amount control unit that controls the discharge amount of the hydraulic oil and sucks and discharges the hydraulic oil from the hydraulic oil tank;
A pump discharge path for hydraulic oil from the hydraulic pump to the hydraulic motor;
A return path of hydraulic oil from the hydraulic motor to the hydraulic oil tank;
A branch path formed in the pump discharge path to reach the hydraulic oil tank;
An aperture provided in the branch path;
A pressure control valve provided downstream of the throttle in the branch path;
A discharge amount control pressure supply path connected between the throttle of the branch passage and the pressure control valve to supply a discharge amount control pressure for controlling the discharge amount of the hydraulic pump to the discharge amount control unit; A cooling fan drive circuit.   The cooling fan drive circuit according to claim 1, wherein the pressure control valve is a variable relief valve.   The cooling fan drive circuit according to claim 2, wherein the variable relief valve is an inversely proportional relief valve.

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