WO2006008875A1 - Hydraulic circuit for working vehicle - Google Patents

Abstract

A hydraulic circuit for a working vehicle, increasing efficiency and suitable for driving a cooling fan and a working machine. The circuit has a working machine actuator, an actuator for driving the cooling fan, a common variable displacement hydraulic pump for supplying pressurized oil to both the working machine actuator and the actuator for driving the cooling fan, and a control device for controlling the flow rate of the pressurized oil to the working machine actuator and the flow rate of the pressurized oil to the actuator for driving the cooling fan. The maximum discharge capacity of the variable displacement hydraulic pump is less than the sum of the maximum flow rate required for driving the working machine and the maximum flow rate required for driving the cooling fan. When the flow rate from the hydraulic pump is less than the sum of the maximum flow rate required for driving the working machine and the maximum flow rate required for driving the cooling fan, the control device supplies a flow rate required for driving the working machine and the remaining flow rate to the actuator for driving the cooling fan.

Description

 Specification

 Hydraulic circuit of work vehicle

 Technical field

 [0001] The present invention relates to a hydraulic circuit of a work vehicle.

 Background art

 Conventionally, there is a work vehicle in which a cooling fan for cooling a radiator air cooler is driven by a hydraulic motor. For example, in Patent Document 1, pressure oil discharged from a fixed displacement hydraulic pump force is divided by a flow control valve with pressure compensation, and a part thereof is supplied to a fixed displacement hydraulic motor that drives a cooling fan. A hydraulic circuit that supplies the remaining pressure oil to the work machine is disclosed.

 [0003] Further, in the hydraulic circuit disclosed in Patent Document 2, the oil discharged from the variable displacement hydraulic pump is related to an engine mounted on a vehicle such as a railway vehicle and a device for driving a cooling fan of the hydraulic device. Is supplied to a fixed capacity hydraulic motor for driving a cooling fan via a diaphragm having a variable diaphragm type diaphragm mechanism. Then, the differential pressure before and after the throttle, that is, the discharge amount of the variable displacement hydraulic pump is controlled according to the engine speed, and the opening area of the throttle is controlled according to the cooling water temperature. The rotational speed of the hydraulic motor for driving the fan is kept constant.

 Patent Document 1: Japanese Patent Application Laid-Open No. 5-24445 (Page 2, Figure 1-2)

 Patent Document 2: JP-A-9 317465 (Page 3-4, Fig. 1)

 Disclosure of the invention

 Problems to be solved by the invention

However, according to the hydraulic circuit described in Patent Document 1, there are the following problems. Since the work machine drive and the cooling fan drive are shared by a single fixed displacement hydraulic pump, the hydraulic oil discharged from the fixed displacement hydraulic pump is supplied to the hydraulic motor for driving the cooling fan. The rest is constantly supplied to the work machine drive circuit. However, in this work machine drive circuit, even when the work machine is not operated, the pressure oil is drained to the tank via the neutral circuit of the direction switching valve for driving the work machine. The problem is is there.

 [0005] In the hydraulic circuit described in Patent Document 2, a variable displacement hydraulic pump is used to drive the cooling fan, but there is no description regarding the work machine drive circuit.

 [0006] The present invention has been made paying attention to the above-mentioned problems, and an object of the present invention is to provide a hydraulic circuit for a work vehicle that improves efficiency and is suitable for driving a cooling fan and a work implement. Means for solving the problem

 [0007] In order to achieve the above object, according to a first aspect of the present invention, in the hydraulic circuit of the work vehicle, the work machine actuator, the cooling fan drive actuator, the work machine activator, and the cooling fan drive actuator A common variable displacement hydraulic pump that supplies pressure oil and a control device that controls the flow rate of the pressure oil to the working machine actuator and the flow rate of the pressure oil to the cooling fan drive actuator are configured.

 [0008] In a second invention according to the first invention, the maximum discharge amount of the variable displacement hydraulic pump is greater than the flow rate obtained by adding the maximum flow rate required for driving the work machine and the maximum flow rate required for driving the cooling fan. If the discharge amount of the hydraulic pump is insufficient for the flow rate required for driving the work implement and the flow rate required for driving the cooling fan, the control device is necessary for the work implement. Supply the flow rate, and supply the remaining flow rate to the cooling fan drive actuator.

 [0009]

 The invention's effect

 According to the first invention, the number of pumps can be reduced by using a common pump for supplying pressure oil to the working machine actuator and the cooling fan driving actuator. In addition, this pump has a variable displacement type and has a control device that controls the flow rate of the pressure oil to the work machine actuator and the flow rate of the pressure oil to the cooling fan drive actuator so that the required flow rate is always supplied from the pump. Since only the liquid is discharged, the efficiency can be improved.

[0011] According to the second invention, the variable displacement hydraulic pump has a maximum discharge amount that is simply the sum of the maximum flow rate required for driving the conventional work machine and the maximum flow rate required for driving the cooling fan. The size can be reduced, and the manufacturing cost can be reduced. Also, the discharge rate of the hydraulic pump is less than the sum of the flow rate required to drive the work machine and the flow rate required to drive the cooling fan. In this case, the necessary flow rate is preferentially supplied to the work machine, and the remaining flow rate is supplied to the cooling fan drive, so that the work efficiency of the work machine can be reduced. Therefore, it is particularly preferable for a work vehicle such as a bulldozer or the like that has a short working machine operation time because the cooling capacity of the cooling fan is not greatly reduced.

 BEST MODE FOR CARRYING OUT THE INVENTION

 Hereinafter, an embodiment of a hydraulic circuit for a work vehicle according to the present invention will be described with reference to the drawings. In the following, a bulldozer will be described as an example of an application machine of the present invention.

 As shown in FIGS. 2 and 3, a bulldozer 1 to which the present invention is applied includes a pair of left and right crawler type traveling devices 3, 3 at the lower part of a body frame 2, and an upper rear side of the body frame 2. Is equipped with an operation room 4. The engine 19 and a cooling device 17 such as a radiator and an oil cooler are provided at the inner front of the vehicle body frame 2, and a cooling fan 18 is provided in the vicinity of the cooling device 17 on the leeward side of the cooling air. The cooling fan 18 is driven to rotate by the hydraulic motor 10. Further, the U-shaped work implement support frame 6 in a top view is attached so that the opening side thereof is directed to the rear of the vehicle, and end portions on the opening side are swingable up and down on the left and right sides of the body frame 2. Then, the blade 5 tilts back and forth around the vertical axis through the universal connection portion 6a to the front end portion of the front projecting portion 6e formed on the front left side of the work equipment support frame 6 facing the front of the vehicle. (Hereafter, Angle

 That's it. ) Freely and tilted left and right (hereinafter referred to as tilt) around the longitudinal axis.

[0014] A pair of left and right lift cylinders 7 and 7 are mounted between the left and right upper surface portions on the opening side of the work implement support frame 6 and the left and right side portions of the vehicle body frame 2 to drive the work implement support frame 6 up and down. To do. An angle cylinder 8 that drives the blade 5 at an angle is attached between the front projecting portion 6 e of the work machine support frame 6 and the right end portion of the back surface of the blade 5. In addition, the bracket 6b provided on the upper part of the forward projecting portion 6e of the work implement support frame 6 and the blade 5 are connected by a link 6c via a self-connecting portion 6d located above the universal connecting portion 6a. It has been. A tilt cylinder 9 that tilts and drives the blade 5 is attached between one end of the link 6c and the opening-side left portion of the work implement support frame 6. FIG. 1 is a block diagram of a hydraulic circuit of a bulldozer according to an embodiment. The hydraulic motor 10, which is a cooling fan driving actuator, is controlled in its flow rate and direction by a direction switching valve 13. Similarly, the working fluid actuators of the lift cylinders 7 and 7, the tilt cylinder 9 and the angle cylinder 8 are controlled by the direction switching valves 14, 15 and 16, respectively. These directional control valves 1 3, 14, 15 and 16 are composed of pilot operated directional control valves.

 [0016] The electromagnetic pilot operation valves 21a and 21b are configured to input a control signal from the controller 20 to the solenoid portion and output a pilot pressure corresponding to the magnitude of the control signal. The output pilot pressure of the electromagnetic pilot operation valves 21a and 21b is input to the pilot operation portion of the direction switching valve 13 through the pilot pipe lines 31a and 31b. Also, pilot operation valves 22a, 22b, 23a, 23b, 24a, 24bi¾, which output pilot pressure according to the operation amount of the lift operation Reno 41, Chino re operation 42, and the angle operation lever 43, respectively. The pilot valves 32a, 32b, 33a, 33b, 34a, 34b are connected to the pilot operating portions of the direction switching valves 14, 15, 16, respectively.

 [0017] In addition, the above-mentioned norot pipes 32a, 32b, 33a, 33b, 34a, 34b are provided. Pressure sensors 25a, 25b, 26a, 26b, 27a, 27b are provided for detecting the norot pressure. The detection signals from these pressure sensors 25a, 25b, 26a, 26b, 27a, and 27b are input to the controller 20 as operation amount signals for the lift operation lever 41, tilt operation lever 42, and angle operation lever 43, respectively. Being!

[0018] In the control circuit of the variable displacement hydraulic pump 11 that is rotationally driven by the engine 19 (see FIG. 2), the swash plate angle (corresponding to the discharge amount) of the hydraulic pump 11 is set to each direction switching valve 13,. It is a so-called load sensing circuit that is controlled according to the opening amount (ie, required flow rate) of 14, 15, 1 6 (however, the load sensing circuit is not shown in detail in the block diagram of FIG. 1) .) In other words, the swash plate angle of the hydraulic pump 11 is set so that the differential pressure between the pump discharge pressure and the load pressure (differential pressure before and after each directional control valve 13, 14, 15, 16) is the same regardless of the load pressure. The swash plate drive cylinder 12a to be adjusted is controlled. Opening force of each directional control valve 13, 14, 15, 16 Otherwise, only a small flow rate is required to generate the same differential pressure. Conversely, if the opening is large, the same differential pressure is generated. It requires a large flow rate to make it happen. Therefore, on Road

 By the sensing circuit, the swash plate angle of the hydraulic pump 11 is automatically adjusted so that the flow rate corresponding to the opening amount of each direction switching valve 13, 14, 15, 16 is always discharged. It should be noted that the control of the swash plate angle of the hydraulic pump 11 by port sensing is a force that can use a method such as a hydraulic servo, an electric servo, an electric hydraulic servo, etc. Since these techniques are well known, a detailed description is omitted. . Here, the entire configuration including each hydraulic device such as the hydraulic servo, electric servo, and electrohydraulic servo for controlling the hydraulic circuit and the controller 20 is referred to as a control device 50.

 [0019] Further, the hydraulic pump 11 has a maximum discharge amount Qmax force, a maximum flow rate Q Wmax required for driving the work machine (when the operation amounts of the lift operation lever 41, the tilt operation lever 42, and the angle operation lever 43 are all maximum). The discharge rate is smaller than the sum of the flow rate and the maximum flow rate QFmax required to drive the cooling fan at the maximum speed. That is, the maximum discharge amount Qmax is selected so as to satisfy, for example, the following expression “Qmax = QWmax + QFmax Xa, where α = 0.2 to 0.5”.

 [0020] The controller 20 is composed of, for example, a computing device such as a microcomputer, and the detection signals of the pressure sensors 25a, 25b, 26a, 26b, 27a, 27b, that is, the lift operation lever 41, the tilt operation lever 42, and the angle Based on the operation amount of the operation lever 43, the supply flow rate to the work machine actuators of the lift cylinders 7, 7, the tilt cylinder 9 and the angle cylinder 8 is obtained, and the total flow rate required to drive the work machine (hereinafter referred to as the work machine flow rate). ) Calculate QW by calculation. The controller 20 stores the detected pressure values of the pressure sensors 25a, 25b, 26a, 26b, 27a, 27b and the flow rates supplied to the diff cylinder 7, 7, the chino cylinder 9, and the angle cylinder 8 in the storage device. Suppose you have a data table or an arithmetic expression that shows the correspondence between

[0021] Further, the controller 20 inputs the engine water temperature, the hydraulic oil temperature, and the engine speed detected by the engine water temperature sensor 36, the hydraulic oil temperature sensor 37, and the engine speed sensor 38, respectively, and according to these input values. The target rotational speed of the cooling fan 18 is obtained by calculation so that the engine water temperature and hydraulic oil temperature are below the allowable values, and the flow rate to the hydraulic motor 10 corresponding to the target rotational speed (hereinafter referred to as fan flow rate). Ask for QF. And said work that we asked The total flow rate of the machine flow rate QW and fan flow rate QF is compared with the preset maximum discharge rate Qmax of the hydraulic pump 11, and based on the comparison result! /, The electromagnetic performance is as follows. A control signal is output to the pilot operation valves 21a and 21b to control the opening amount of the direction switching valve 13, that is, the fan flow rate.

 [0022] (l) When QW + QF≤Qmax

 The controller 20 controls the opening amount of the direction switching valve 13 via the electromagnetic pilot operation valves 21a and 21b so as to supply the obtained fan flow rate QF to the hydraulic motor 10.

 [0023] (2) When QW + QF> Qmax,

 When the total flow rate of the work machine flow rate QW and the fan flow rate QF is larger than the maximum discharge rate Qmax of the variable displacement hydraulic pump 11, that is, the controller 20 sets the fan flow rate as "Qmax- “QW” is obtained by calculation, and the opening amount of the direction switching valve 13 is controlled via the electromagnetic pilot operated valves 21a and 2 lb so as to supply the hydraulic motor 10 with a flow rate equal to “Qmax−QW”. As a result, the supply of the work machine flow rate QW is prioritized, and the cooling fan 18 rotates at a rotation speed corresponding to the flow rate “Qmax—QW” smaller than the required fan flow rate QF.

 [0024] In any of the cases (1) and (2), the opening amounts of the direction switching valves 14, 15, and 16 for driving the work machine actuator are respectively determined by the pilot operation valves 22a, 22b, Since the pressure is automatically adjusted according to the operation pilot pressures 23a, 23b, 24a, and 24b, the work implement flow rate QW is always supplied to the work implement.

 [0025] According to the above embodiment, since the pressure oil supplied to the work machine actuator and the pressure oil supplied to the cooling fan drive actuator are discharged by the common variable displacement hydraulic pump 11, the number of hydraulic pumps Less. The discharge volume of the variable displacement hydraulic pump 11 is automatically controlled to discharge a flow rate corresponding to the opening amount of the directional control valves 13, 14, 15, 16 for driving the cooling fan and driving the work equipment. Yes. As a result, when the work implement is not operated, the discharge amount of the variable displacement hydraulic pump 11 is only the fan flow rate, so that the loss can be extremely reduced and the efficiency can be improved.

[0026] Then, when the maximum discharge amount Qmax of the variable displacement hydraulic pump 11 is less than the total flow rate of the work machine flow rate QW and the fan flow rate QF, the controller 20 Priority is given to the supply of W, and the opening amount of the direction switching valve 13 for driving the cooling fan is controlled so that the fan flow rate becomes “Qmax-QW”. As a result, the work machine drive is given priority, and the number of rotations of the cooling fan 18 is reduced. Therefore, even if the flow for driving the cooling fan is temporarily reduced, the influence on the overall cooling capacity is small. The variable displacement hydraulic pump 11 has its maximum discharge amount Qmax force. The maximum flow rate QWmax required to drive the work implement and the maximum flow rate QFmax required to drive the cooling fan 18 at the maximum rotation speed Therefore, a small hydraulic pump can be used.

 The embodiments of the present invention have been described above, but these are examples for explaining the present invention, and are not intended to limit the scope of the invention to these embodiments alone. Therefore, the present invention can be implemented in various other forms without departing from the gist thereof.

 [0028] For example, the example of the hydraulic circuit configured to operate the pilot operated valve with the work implement operating levers 41, 42, and 43 has been described. However, the present invention is not limited to this, and the work implement operating lever is configured with an electric lever. Even if the controller 20 inputs the operation amount signal to the controller 20, and the controller 20 outputs a command to the electromagnetic pilot operation valve in accordance with the operation amount signal to control the direction switching valve for driving the work implement, The present invention is applicable.

 [0029] The work implement flow rate QW is calculated by calculation based on the pilot pressure of each work implement operation, but each work implement operation lever 41, 42, 43 (including the case of the electric lever described above). Let's calculate it based on the operation stroke.

 [0030] Further, the hydraulic pump 11 is not limited to be driven to rotate by an engine, and may be configured to be driven to rotate by an electric motor.

 [0031] The present invention is not limited to a bulldozer but can be applied to a wheel loader and other work vehicles.

 Brief Description of Drawings

FIG. 1 is a block diagram of a hydraulic circuit according to an embodiment.

 FIG. 2 is a side view of a bulldozer to which the present invention is applied.

FIG. 3 is a plan view of a bulldozer to which the present invention is applied. Explanation of symbols

Claims

The scope of the claims  [1] In the hydraulic circuit of a work vehicle,  A work machine actuator,  An actuator for driving the cooling fan;  A common variable displacement hydraulic pump that supplies hydraulic oil to both the work machine actuator and the cooling fan drive actuator;  A control device for controlling the flow rate of the pressure oil to the working machine actuator and the flow rate of the pressure oil to the cooling fan driving actuator.  A hydraulic circuit for a work vehicle.  [2] The maximum discharge amount of the variable displacement hydraulic pump is less than the flow rate obtained by adding the maximum flow rate required for driving the work implement and the maximum flow rate required for driving the cooling fan,  When the discharge amount of the hydraulic pump is insufficient for the flow rate required for driving the work implement and the flow rate required for the cooling fan drive, the control device supplies the flow rate required for the work implement, Supply the remaining flow to the cooling fan actuator  A hydraulic circuit for a work vehicle according to claim 1, wherein